13 PREPARATION OF LEAD DIOXIDE ELECTRODE (A REVIEW)
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二氧化铅论文:二氧化铅的制备及其超级电容器性能研究【中文摘要】超级电容器是近年来出现的一种介于电池和传统电容器之间的新型储能器件,它具有传统电池无法比拟的高功率密度、长循环寿命、环境友好等优点,随着新型绿色环保电动汽车的兴起以及各种电子通讯技术的发展,能源危机和环境保护成为人类可持续发展的战略核心,对于能源储存与转换元器件的要求越来越高,也使得超级容器的发展被提升到了一个新的高度。
高能量、大功率的超级电容器更显示了其前所未有的应用前景,现已成为世界各国的研究热点。
本论文根据大量的文献调研,紧跟该领域的国际前沿,从活性碳材料和金属氧化物材料着手,通过改进材料的制备方法,优化电极制作技术,研制出超级电容器用活性碳电极和二氧化铅薄膜电极,并组装成混合超级电容器。
将材料的表征手段和电化学研究手段相结合,对材料的相关性能进行了测试,为研制混合超级电容器提供了实验依据和理论基础。
主要研究内容如下:1、采用活性碳作为超级电容器的电极材料,组装成对称双电层超级电容器,研究其活性碳电极在5.3 mol L-1 H2SO4(1.28 g cm-3)、2 mol L-1 KCl和2 mol L-1 LiNO3不同电解液中的电化学性能,测试其比电容大小,利用恒流充放电和电化学阻抗谱等手段,测试对称活性碳双电层超级电容器在5.3 mol L-1 H2SO4电解液条件下的电容特性,在100 mAg-1的电流密度下能达到32.4 Fg-1。
2、采用石墨片作为正极集流体,采用恒电流法在石墨片上沉积二氧化铅电极,并通过SEM和XRD研究了二氧化铅电极的形貌和结构特性。
以二氧化铅电极为正极,活性碳电极为负极,5.3 mol L-1 H2SO4作为电解液,组装成混合超级电容器,并进行了恒流充放电和交流阻抗等电化学测试。
结果表明:沉积电流对电极的电化学性能影响很大,在25 mA cm-2电流密度下沉积的二氧化铅电极不仅具有高比电容而且具有较好的循环稳定性,其与活性碳电极组装成混合超级电容器时,在150 mAg-1电流密度下比电容能达到128.4 Fg-1,恒流充放电循环3700次后其容量保持率仍能达到70%。
山东农业大学应用化学专业申报山东省教育厅2007年度高等学校特色专业申报书附件目录附件一、教师发表专业研究论文………………………….附件二、教师发表教研论文……………………………….附件三、教师科研课题……………………………………附件四、教师教学研究课题………………………………附件五、教师教研奖励及部分获奖证书…………………附件六、近几年编写教材统计……………………………附件七、本科学生承担的科技创新项目和SRT项目……附件八、本科学生在SRT项目和科技创新项目研究及毕业论文中发表和已投稿论文目录……………………………………..附件一化学与材料科学学院2003.5-2008.5教师发表专业研究论文1.艾仕云(1). Study on production of hydroxyl free radical and its reaction with salicylic acid at lead dioxide electrode. J.Electroanal. Chem., 2005, 578, 223-2292. 艾仕云(1).Electrochemical deposition and properties of nanometer-structure Ce-dopedlead dioxide film electrodes. Chin. J. Chem.2005, 23, 71-753.艾仕云(1).Preparation of fluorine-doped lead dioxide modified electrodes forelectroanalytical applications. Electroanalysis, 2003, 15, 1403-14074.艾仕云(1). Study on lead dioxide modified electrode and its application in detection of phenols. Chin. J. of Chem. 2003, 21, 157-1615. 艾仕云(1).P reparation of Ce-PbO2 modified electrode and its application in detection ofanilines. 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Semiconductor Manufacturing Technology半导体制造技术Instructor’s ManualMichael QuirkJulian SerdaCopyright Prentice HallTable of Contents目录OverviewI. Chapter1. Semiconductor industry overview2. Semiconductor materials3. Device technologies—IC families4. Silicon and wafer preparation5. Chemicals in the industry6. Contamination control7. Process metrology8. Process gas controls9. IC fabrication overview10. Oxidation11. Deposition12. Metallization13. Photoresist14. Exposure15. Develop16. Etch17. Ion implant18. Polish19. Test20. Assembly and packagingII. Answers to End-of-Chapter Review QuestionsIII. Test Bank (supplied on diskette)IV. Chapter illustrations, tables, bulleted lists and major topics (supplied on CD-ROM)Notes to Instructors:1)The chapter overview provides a concise summary of the main topics in each chapter.2)The correct answer for each test bank question is highlighted in bold. Test bankquestions are based on the end-of-chapter questions. If a student studies the end-of-chapter questions (which are linked to the italicized words in each chapter), then they will be successful on the test bank questions.2Chapter 1Introduction to the Semiconductor Industry Die:管芯 defective:有缺陷的Development of an Industry•The roots of the electronic industry are based on the vacuum tube and early use of silicon for signal transmission prior to World War II. The first electronic computer, the ENIAC, wasdeveloped at the University of Pennsylvania during World War II.•William Shockley, John Bardeen and Walter Brattain invented the solid-state transistor at Bell Telephone Laboratories on December 16, 1947. The semiconductor industry grew rapidly in the 1950s to commercialize the new transistor technology, with many early pioneers working inSilicon Valley in Northern California.Circuit Integration•The first integrated circuit, or IC, was independently co-invented by Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor in 1959. An IC integrates multiple electronic components on one substrate of silicon.•Circuit integration eras are: small scale integration (SSI) with 2 - 50 components, medium scale integration (MSI) with 50 – 5k components, large scale integration (LSI) with 5k to 100kcomponents, very large scale integration (VLSI) with 100k to 1M components, and ultra large scale integration (ULSI) with > 1M components.1IC Fabrication•Chips (or die) are fabricated on a thin slice of silicon, known as a wafer (or substrate). Wafers are fabricated in a facility known as a wafer fab, or simply fab.•The five stages of IC fabrication are:Wafer preparation: silicon is purified and prepared into wafers.Wafer fabrication: microchips are fabricated in a wafer fab by either a merchant chip supplier, captive chip producer, fabless company or foundry.Wafer test: Each individual die is probed and electrically tested to sort for good or bad chips.Assembly and packaging: Each individual die is assembled into its electronic package.Final test: Each packaged IC undergoes final electrical test.•Key semiconductor trends are:Increase in chip performance through reduced critical dimensions (CD), more components per chip (Moore’s law, which predicts the doubling of components every 18-24 months) andreduced power consumption.Increase in chip reliability during usage.Reduction in chip price, with an estimated price reduction of 100 million times for the 50 years prior to 1996.The Electronic Era•The 1950s saw the development of many different types of transistor technology, and lead to the development of the silicon age.•The 1960s were an era of process development to begin the integration of ICs, with many new chip-manufacturing companies.•The 1970s were the era of medium-scale integration and saw increased competition in the industry, the development of the microprocessor and the development of equipment technology. •The 1980s introduced automation into the wafer fab and improvements in manufacturing efficiency and product quality.•The 1990s were the ULSI integration era with the volume production of a wide range of ICs with sub-micron geometries.Career paths•There are a wide range of career paths in semiconductor manufacturing, including technician, engineer and management.2Chapter 2 Characteristics of Semiconductor MaterialsAtomic Structure•The atomic model has three types of particles: neutral neutrons(不带电的中子), positively charged protons(带正电的质子)in the nucleus and negatively charged electrons(带负电的核外电子) that orbit the nucleus. Outermost electrons are in the valence shell, and influence the chemical and physical properties of the atom. Ions form when an atom gains or loses one or more electrons.The Periodic Table•The periodic table lists all known elements. The group number of the periodic table represents the number of valence shell electrons of the element. We are primarily concerned with group numbers IA through VIIIA.•Ionic bonds are formed when valence shell electrons are transferred from the atoms of one element to another. Unstable atoms (e.g., group VIIIA atoms because they lack one electron) easily form ionic bonds.•Covalent bonds have atoms of different elements that share valence shell electrons.3Classifying Materials•There are three difference classes of materials:ConductorsInsulatorsSemiconductors•Conductor materials have low resistance to current flow, such as copper. Insulators have high resistance to current flow. Capacitance is the storage of electrical charge on two conductive plates separated by a dielectric material. The quality of the insulation material between the plates is the dielectric constant. Semiconductor materials can function as either a conductor or insulator.Silicon•Silicon is an elemental semiconductor material because of four valence shell electrons. It occurs in nature as silica and is refined and purified to make wafers.•Pure silicon is intrinsic silicon. The silicon atoms bond together in covalent bonds, which defines many of silicon’s properties. Silicon atoms bond together in set, repeatable patterns, referred to asa crystal.•Germanium was the first semiconductor material used to make chips, but it was soon replaced by silicon. The reasons for this change are:Abundance of siliconHigher melting temperature for wider processing rangeWide temperature range during semiconductor usageNatural growth of silicon dioxide•Silicon dioxide (SiO2) is a high quality, stable electrical insulator material that also serves as a good chemical barrier to protect silicon from external contaminants. The ability to grow stable, thin SiO2 is fundamental to the fabrication of Metal-Oxide-Semiconductor (MOS) devices. •Doping increases silicon conductivity by adding small amounts of other elements. Common dopant elements are from trivalent, p-type Group IIIA (boron) and pentavalent, n-type Group VA (phosphorus, arsenic and antimony).•It is the junction between the n-type and p-type doped regions (referred to as a pn junction) that permit silicon to function as a semiconductor.4Alternative Semiconductor Materials•The alternative semiconductor materials are primarily the compound semiconductors. They are formed from Group IIIA and Group VA (referred to as III-V compounds). An example is gallium arsenide (GaAs).•Some alternative semiconductors come from Group IIA and VIA, referred to as II-VI compounds. •GaAs is the most common III-V compound semiconductor material. GaAs ICs have greater electron mobility, and therefore are faster than ICs made with silicon. GaAs ICs also have higher radiation hardness than silicon, which is better for space and military applications. The primary disadvantage of GaAs is the lack of a natural oxide.5Chapter 3Device TechnologiesCircuit Types•There are two basic types of circuits: analog and digital. Analog circuits have electrical data that varies continuously over a range of voltage, current and power values. Digital circuits have operating signals that vary about two distinct voltage levels – a high and a low.Passive Component Structures•Passive components such as resistors and capacitors conduct electrical current regardless of how the component is connected. IC resistors are a passive component. They can have unwanted resistance known as parasitic resistance. IC capacitor structures can also have unintentional capacitanceActive Component Structures•Active components, such as diodes and transistors can be used to control the direction of current flow. PN junction diodes are formed when there is a region of n-type semiconductor adjacent to a region of p-type semiconductor. A difference in charge at the pn junction creates a depletion region that results in a barrier voltage that must be overcome before a diode can be operated. A bias voltage can be configured to have a reverse bias, with little or no conduction through the diode, or with a forward bias, which permits current flow.•The bipolar junction transistor (BJT) has three electrodes and two pn junctions. A BJT is configured as an npn or pnp transistor and biased for conduction mode. It is a current-amplifying device.6• A schottky diode is formed when metal is brought in contact with a lightly doped n-type semiconductor material. This diode is used in faster and more power efficient BJT circuits.•The field-effect transistor (FET), a voltage-amplifying device, is more compact and power efficient than BJT devices. A thin gate oxide located between the other two electrodes of the transistor insulates the gate on the MOSFET. There are two categories of MOSFETs, nMOS (n-channel) and pMOS (p-channel), each which is defined by its majority current carriers. There is a biasing scheme for operating each type of MOSFET in conduction mode.•For many years, nMOS transistors have been the choice of most IC manufacturers. CMOS, with both nMOS and pMOS transistors in the same IC, has been the most popular device technology since the early 1980s.•BiCMOS technology makes use of the best features of both CMOS and bipolar technology in the same IC device.•Another way to categorize FETs is in terms of enhancement mode and depletion mode. The major different is in the way the channels are doped: enhancement-mode channels are doped opposite in polarity to the source and drain regions, whereas depletion mode channels are doped the same as their respective source and drain regions.Latchup in CMOS Devices•Parasitic transistors can create a latchup condition(???????) in CMOS ICs that causes transistors to unintentionally(无心的) turn on. To control latchup, an epitaxial layer is grown on the wafer surface and an isolation barrier(隔离阻障)is placed between the transistors. An isolation layer can also be buried deep below the transistors.Integrated Circuit Productsz There are a wide range of semiconductor ICs found in electrical and electronic products. This includes the linear IC family, which operates primarily with anal3og circuit applications, and the digital IC family, which includes devices that operate with binary bits of data signals.7Chapter 4Silicon and Wafer Preparation8z Semiconductor-Grade Silicon•The highly refined silicon used for wafer fabrication is termed semiconductor-grade silicon (SGS), and sometimes referred to as electronic-grade silicon. The ultra-high purity of semiconductor-grade silicon is obtained from a multi-step process referred to as the Siemens process.Crystal Structure• A crystal is a solid material with an ordered, 3-dimensional pattern over a long range. This is different from an amorphous material that lacks a repetitive structure.•The unit cell is the most fundamental entity for the long-range order found in crystals. The silicon unit cell is a face-centered cubic diamond structure. Unit cells can be organized in a non-regular arrangement, known as a polycrystal. A monocrystal are neatly arranged unit cells.Crystal Orientation•The orientation of unit cells in a crystal is described by a set of numbers known as Miller indices.The most common crystal planes on a wafer are (100), (110), and (111). Wafers with a (100) crystal plane orientation are most common for MOS devices, whereas (111) is most common for bipolar devices.Monocrystal Silicon Growth•Silicon monocrystal ingots are grown with the Czochralski (CZ) method to achieve the correct crystal orientation and doping. A CZ crystal puller is used to grow the silicon ingots. Chunks of silicon are heated in a crucible in the furnace of the puller, while a perfect silicon crystal seed is used to start the new crystal structure.• A pull process serves to precisely replicate the seed structure. The main parameters during the ingot growth are pull rate and crystal rotation. More homogeneous crystals are achieved with a magnetic field around the silicon melt, known as magnetic CZ.•Dopant material is added to the melt to dope the silicon ingot to the desired electrical resistivity.Impurities are controlled during ingot growth. A float-zone crystal growth method is used toachieve high-purity silicon with lower oxygen content.•Large-diameter ingots are grown today, with a transition underway to produce 300-mm ingot diameters. There are cost benefits for larger diameter wafers, including more die produced on a single wafer.Crystal Defects in Silicon•Crystal defects are interruptions in the repetitive nature of the unit cell. Defect density is the number of defects per square centimeter of wafer surface.•Three general types of crystal defects are: 1) point defects, 2) dislocations, and 3) gross defects.Point defects are vacancies (or voids), interstitial (an atom located in a void) and Frenkel defects, where an atom leaves its lattice site and positions itself in a void. A form of dislocation is astacking fault, which is due to layer stacking errors. Oxygen-induced stacking faults are induced following thermal oxidation. Gross defects are related to the crystal structure (often occurring during crystal growth).Wafer Preparation•The cylindrical, single-crystal ingot undergoes a series of process steps to create wafers, including machining operations, chemical operations, surface polishing and quality checks.•The first wafer preparation steps are the shaping operations: end removal, diameter grinding, and wafer flat or notch. Once these are complete, the ingot undergoes wafer slicing, followed by wafer lapping to remove mechanical damage and an edge contour. Wafer etching is done to chemically remove damage and contamination, followed by polishing. The final steps are cleaning, wafer evaluation and packaging.Quality Measures•Wafer suppliers must produce wafers to stringent quality requirements, including: Physical dimensions: actual dimensions of the wafer (e.g., thickness, etc.).Flatness: linear thickness variation across the wafer.Microroughness: peaks and valleys found on the wafer surface.Oxygen content: excessive oxygen can affect mechanical and electrical properties.Crystal defects: must be minimized for optimum wafer quality.Particles: controlled to minimize yield loss during wafer fabrication.Bulk resistivity(电阻系数): uniform resistivity from doping during crystal growth is critical. Epitaxial Layer•An epitaxial layer (or epi layer) is grown on the wafer surface to achieve the same single crystal structure of the wafer with control over doping type of the epi layer. Epitaxy minimizes latch-up problems as device geometries continue to shrink.Chapter 5Chemicals in Semiconductor FabricationEquipment Service Chase Production BayChemical Supply Room Chemical Distribution Center Holding tank Chemical drumsProcess equipmentControl unit Pump Filter Raised and perforated floorElectronic control cablesSupply air ductDual-wall piping for leak confinement PumpFilterChemical control and leak detection Valve boxes for leak containment Exhaust air ductStates of Matter• Matter in the universe exists in 3 basic states (宇宙万物存在着三种基本形态): solid, liquid andgas. A fourth state is plasma.Properties of Materials• Material properties are the physical and chemical characteristics that describe its unique identity.• Different properties for chemicals in semiconductor manufacturing are: temperature, pressure andvacuum, condensation, vapor pressure, sublimation and deposition, density, surface tension, thermal expansion and stress.Temperature is a measure of how hot or cold a substance is relative to another substance. Pressure is the force exerted per unit area. Vacuum is the removal of gas molecules.Condensation is the process of changing a gas into a liquid. Vaporization is changing a liquidinto a gas.Vapor pressure is the pressure exerted by a vapor in a closed container at equilibrium.Sublimation is the process of changing a solid directly into a gas. Deposition is changing a gas into a solid.Density is the mass of a substance divided by its volume.Surface tension of a liquid is the energy required to increase the surface area of contact.Thermal expansion is the increase in an object’s dimension due to heating.Stress occurs when an object is exposed to a force.Process Chemicals•Semiconductor manufacturing requires extensive chemicals.• A chemical solution is a chemical mixture. The solvent is the component of the solution present in larger amount. The dissolved substances are the solutes.•Acids are solutions that contain hydrogen and dissociate in water to yield hydronium ions. A base is a substance that contains the OH chemical group and dissociates in water to yield the hydroxide ion, OH-.•The pH scale is used to assess the strength of a solution as an acid or base. The pH scale varies from 0 to 14, with 7 being the neutral point. Acids have pH below 7 and bases have pH values above 7.• A solvent is a substance capable of dissolving another substance to form a solution.• A bulk chemical distribution (BCD) system is often used to deliver liquid chemicals to the process tools. Some chemicals are not suitable for BCD and instead use point-of-use (POU) delivery, which means they are stored and used at the process station.•Gases are generally categorized as bulk gases or specialty gases. Bulk gases are the relatively simple gases to manufacture and are traditionally oxygen, nitrogen, hydrogen, helium and argon.The specialty gases, or process gases, are other important gases used in a wafer fab, and usually supplied in low volume.•Specialty gases are usually transported to the fab in metal cylinders.•The local gas distribution system requires a gas purge to flush out undesirable residual gas. Gas delivery systems have special piping and connections systems. A gas stick controls the incoming gas at the process tool.•Specialty gases may be classified as hydrides, fluorinated compounds or acid gases.Chapter 6Contamination Control in Wafer FabsIntroduction•Modern semiconductor manufacturing is performed in a cleanroom, isolated from the outside environment and contaminants.Types of contamination•Cleanroom contamination has five categories: particles, metallic impurities, organic contamination, native oxides and electrostatic discharge. Killer defects are those causes of failure where the chip fails during electrical test.Particles: objects that adhere to a wafer surface and cause yield loss. A particle is a killer defect if it is greater than one-half the minimum device feature size.Metallic impurities: the alkali metals found in common chemicals. Metallic ions are highly mobile and referred to as mobile ionic contaminants (MICs).Organic contamination: contains carbon, such as lubricants and bacteria.Native oxides: thin layer of oxide growth on the wafer surface due to exposure to air.Electrostatic discharge (ESD): uncontrolled transfer of static charge that can damage the microchip.Sources and Control of Contamination•The sources of contamination in a wafer fab are: air, humans, facility, water, process chemicals, process gases and production equipment.Air: class number designates the air quality inside a cleanroom by defining the particle size and density.Humans: a human is a particle generator. Humans wear a cleanroom garment and follow cleanroom protocol to minimize contamination.Facility: the layout is generally done as a ballroom (open space) or bay and chase design.Laminar airflow with air filtering is used to minimize particles. Electrostatic discharge iscontrolled by static-dissipative materials, grounding and air ionization.Ultrapure deiniozed (DI) water: Unacceptable contaminants are removed from DI water through filtration to maintain a resistivity of 18 megohm-cm. The zeta potential represents a charge on fine particles in water, which are trapped by a special filter. UV lamps are used for bacterial sterilization.Process chemicals: filtered to be free of contamination, either by particle filtration, microfiltration (membrane filter), ultrafiltration and reverse osmosis (or hyperfiltration).Process gases: filtered to achieve ultraclean gas.Production equipment: a significant source of particles in a fab.Workstation design: a common layout is bulkhead equipment, where the major equipment is located behind the production bay in the service chase. Wafer handling is done with robotic wafer handlers. A minienvironment is a localized environment where wafers are transferred on a pod and isolated from contamination.Wafer Wet Cleaning•The predominant wafer surface cleaning process is with wet chemistry. The industry standard wet-clean process is the RCA clean, consisting of standard clean 1 (SC-1) and standard clean 2 (SC-2).•SC-1 is a mixture of ammonium hydroxide, hydrogen peroxide and DI water and capable of removing particles and organic materials. For particles, removal is primarily through oxidation of the particle or electric repulsion.•SC-2 is a mixture of hydrochloric acid, hydrogen peroxide and DI water and used to remove metals from the wafer surface.•RCA clean has been modified with diluted cleaning chemistries. The piranha cleaning mixture combines sulfuric acid and hydrogen peroxide to remove organic and metallic impurities. Many cleaning steps include an HF last step to remove native oxide.•Megasonics(兆声清洗) is widely used for wet cleaning. It has ultrasonic energy with frequencies near 1 MHz. Spray cleaning will spray wet-cleaning chemicals onto the wafer. Scrubbing is an effective method for removing particles from the wafer surface.•Wafer rinse is done with overflow rinse, dump rinse and spray rinse. Wafer drying is done with spin dryer or IPA(异丙醇) vapor dry (isopropyl alcohol).•Some alternatives to RCA clean are dry cleaning, such as with plasma-based cleaning, ozone and cryogenic aerosol cleaning.Chapter 7Metrology and Defect InspectionIC Metrology•In a wafer fab, metrology refers to the techniques and procedures for determining physical and electrical properties of the wafer.•In-process data has traditionally been collected on monitor wafers. Measurement equipment is either stand-alone or integrated.•Yield is the percent of good parts produced out of the total group of parts started. It is an indicator of the health of the fabrication process.Quality Measures•Semiconductor quality measures define the requirements for specific aspects of wafer fabrication to ensure acceptable device performance.•Film thickness is generally divided into the measurement of opaque film or transparent film. Sheet resistance measured with a four-point probe is a common method of measuring opaque films (e.g., metal film). A contour map shows sheet resistance deviations across the wafer surface.•Ellipsometry is a nondestructive, noncontact measurement technique for transparent films. It works based on linearly polarized light that reflects off the sample and is elliptically polarized.•Reflectometry is used to measure a film thickness based on how light reflects off the top and bottom surface of the film layer. X-ray and photoacoustic technology are also used to measure film thickness.•Film stress is measured by analyzing changes in the radius of curvature of the wafer. Variations in the refractive index are used to highlight contamination in the film.•Dopant concentration is traditionally measured with a four-point probe. The latest technology is the thermal-wave system, which measures the lattice damage in the implanted wafer after ion implantation. Another method for measuring dopant concentration is spreading resistance probe. •Brightfield detection is the traditional light source for microscope equipment. An optical microscope uses light reflection to detect surface defects. Darkfield detection examines light scattered off defects on the wafer surface. Light scattering uses darkfield detection to detectsurface particles by illuminating the surface with laser light and then using optical imaging.•Critical dimensions (CDs) are measured to achieve precise control over feature size dimensions.The scanning electron microscope is often used to measure CDs.•Conformal step coverage is measured with a surface profiler that has a stylus tip.•Overlay registration measures the ability to accurately print photoresist patterns over a previously etched pattern.•Capacitance-voltage (C-V) test is used to verify acceptable charge conditions and cleanliness at the gate structure in a MOS device.Analytical Equipment•The secondary-ion mass spectrometry (SIMS) is a method of eroding a wafer surface with accelerated ions in a magnetic field to analyze the surface material composition.•The atomic force microscope (AFM) is a surface profiler that scans a small, counterbalanced tip probe over the wafer to create a 3-D surface map.•Auger electron spectroscopy (AES) measures composition on the wafer surface by measuring the energy of the auger electrons. It identifies elements to a depth of about 2 nm. Another instrument used to identify surface chemical species is X-ray photoelectron spectroscopy (XPS).•Transmission electron microscopy (TEM) uses a beam of electrons that is transmitted through a thin slice of the wafer. It is capable of quantifying very small features on a wafer, such as silicon crystal point defects.•Energy-dispersive spectrometer (EDX) is a widely used X-ray detection method for identifying elements. It is often used in conjunction with the SEM.• A focused ion beam (FIB) system is a destructive technique that focuses a beam of ions on the wafer to carve a thin cross section from any wafer area. This permits analysis of the wafermaterial.Chapter 8Gas Control in Process ChambersEtch process chambers••The process chamber is a controlled vacuum environment where intended chemical reactions take place under controlled conditions. Process chambers are often configured as a cluster tool. Vacuum•Vacuum ranges are low (rough) vacuum, medium vacuum, high vacuum and ultrahigh vacuum (UHV). When pressure is lowered in a vacuum, the mean free path(平均自由行程) increases, which is important for how gases flow through the system and for creating a plasma.Vacuum Pumps•Roughing pumps are used to achieve a low to medium vacuum and to exhaust a high vacuum pump. High vacuum pumps achieve a high to ultrahigh vacuum.•Roughing pumps are dry mechanical pumps or a blower pump (also referred to as a booster). Two common high vacuum pumps are a turbomolecular (turbo) pump and cryopump. The turbo pump is a reliable, clean pump that works on the principle of mechanical compression. The cryopump isa capture pump that removes gases from the process chamber by freezing them.。
Positive ElectrodeKR Bullock,Coolohm,Inc.,Blue Bell,PA,USA &2009Elsevier B.V.All rights reserved.Positive Plate ConstructionPositive electrodes are classified as Plante´,Faure´or pasted,and tubular.Bipolar plates have a positive elec-trode on one side and a negative electrode on the other side,with an electronic conductor between the two plates.Plante´plates are made by cycling a high-surface-area lead electrode in acid to form a thick corrosion layer of lead dioxide acting as active mass on the surface.These designs are used exclusively in industrial applications where very long life is desired and a high specific energy is not required.Tubular positive plates are generally used in com-bination with pasted negative plates.The tubular struc-ture has good deep cycle life,but this design is not as versatile as the pasted plate.Tubular plates and bipolar designs are covered in the article entitled Secondary Batteries–Lead–Acid Sys-tems:Electrode Design and Bipolar Batteries in this encyclopedia.Most lead–acid batteries(LABs)sold today have pasted electrodes.They are made by applying a paste onto a current collector called a‘grid’.There are four ways of making the grid:(1)casting molten lead or lead alloy in a book mold,(2)slitting and expanding,(3)punching a lead sheet,and(4)continuous casting of grids as a rolled sheet. Because pure lead is a very soft material,antimony has been added since the1880s to strengthen the lead and reduce grid growth.Unfortunately,antimony also accel-erates water loss by poisoning the negative plate.Lead–calcium alloys were developed by H.E.Haring and U.B. Thomas in1935to minimize gassing and grid corrosion. The use of lead–calcium alloys led to the introduction,in the1970s,of low-maintenance batteries that do not re-quire water addition.Valve-regulated LABs sometimes use pure lead alloyed with a small amount of tin to keep gas formation at a minimum.This lead is soft enough to permit the construction of cylindrical cells.These cells are made by winding a stack of pasted positive and negative plate strips,separated by a porous,absorptive glass mat, into a jelly-roll configuration while the plates are still wet.The lead paste applied to the grid is prepared by mixingfinely divided lead and lead oxide–called‘leady litharge’or‘gray oxide’or‘battery oxide’–withfibers,water,and diluted sulfuric acid.This mixture is then‘hydro set’at high temperatures and humidities.This process forms a hardened porous structure composed of lead oxide particles and basic lead sulfates formed by the reaction of sulfuric acid with the oxide.When the positive plate is charged or‘formed’in sulfuric acid,active material is oxidized to lead dioxide(PbO2).Lead paste is resistive to the current applied during thisfirst charge because lead sulfate is an insulator and the lead oxides and basic lead oxides are semiconductors.‘Red lead’,a lead oxide mixture that contains both lead(II)oxide(PbO)and lead tetraoxide (Pb3O4),is frequently used in the paste mix to enhance its conductivity and thereby accelerate paste oxidation.Pasted plates are used where low-cost,high specific energy or power,or special grid or plate structures are required. They are the most common plate designs used in auto-motive batteries,which is the largest market for LABs.Traditional grids are rectilinear designs with a corner tab that attaches to the top lead connectors in the cell or battery.Although lead is a good conductor,the thickness of the lead is limited by its weight.The thinner the lead becomes,however,the shorter will be the operating time up to a point where the grid is no longer functional. These considerations result in a wide variety of grid designs and thicknesses that accommodate the required discharge rate and the charging conditions in a specific application.For example,automotive batteries typically have thin grids,allowing more plates to be put in the battery to accommodate high discharge rates.Radial grid wires from the tab to the opposite sides of the plate shorten the current path to improve the current-carrying capacity of the battery.Standby power batteries,on the contrary,are generally made with thick grids to tolerate long times onfloat charge.Operating PrinciplesCharge and Discharge Reactions and Half-Cell PotentialsThe cathode or positive electrode of a fully charged lead–acid cell is composed mainly of a porous lead di-oxide material in contact with a current collector that is typically made of lead metal.On discharge,the lead di-oxide reacts with aqueous sulfuric acid to form lead sulfate and water:PbO2þ3HþþHSO4Àþ2eÀ"PbSO4þ2H2O½I590The reaction is reversible on charge.Charge and dis-charge processes have a dissolution/precipitation mech-anism.The Pb2þions dissolve and reprecipitate on the surface of the electrode.Since the Pb2þions are only slightly soluble in sulfuric acid,the product maintains the porous structure of the plate over many cycles.The solubility of lead sulfate decreases with acid concentration and increases with temperature.Table1 shows the concentrations of lead sulfate dissolved in saturated sulfuric acid solutions as a function of these variables.The thermodynamics of the positive plate reaction are well characterized.The standard potential for the posi-tive electrode versus a hydrogen electrode is1.690V.The half-cell potentials for the lead dioxide,lead sulfate electrode vary with temperature and acid concentration, given in moles sulfuric acid per1000g water.Half-cell potentials have been reported at varying acid concen-trations from0.1to8molal(m)at temperatures from0to 551C.This cell is written asCell I:ðPtÞH2j H2SO4ðmÞj PbSO4j b-PbO2ðPtÞThe mercurous sulfate–mercury electrode is frequently used as the reference electrode to study the half-cell reactions in the LAB.The standard potential for this cell is0.6125.This reference electrode is written asCell II:ðPtÞH2j H2SO4ðmÞjj Hg2SO4jðHgÞIts half-cell potentials have been reported for acid con-centrations from0.1to7.199m and temperatures from5 to551C.Tables2and3show the potentials for Cells I and II,respectively.When the positive half-cell potential is measured using a mercurous sulfate–mercury refer-ence electrode,the open-circuit voltage(OCV)equals the potential of Cell I minus the potential of Cell II at the appropriate acid concentration and temperature for each cell.Although cadmium rods are sometimes used toTable1Solubility of lead sulfate in saturated sulfuric acidsolutionsMass%H2SO4Mass%PbSO4Â100001C251C351C501C10.000.120.160.380.9620.000.050.120.280.8030.000.040.120.200.4640.000.040.120.180.23Reproduced from Crockford HD and Brawley DJ(1934)Journal of theAmerican Chemical Society56:2600.Table2The potentials(V)of the lead dioxide electrode(Cell1)Acid concentration278.16K283.16K293.16K298.16K308.16K318.16K328.16K 0.1000m 1.57410 1.57173 1.56730 1.56509 1.56086 1.55683 1.55284 0.1996m 1.59097 1.58893 1.58480 1.58284 1.57887 1.57510 1.57146 0.2917m 1.60031 1.59833 1.59450 1.59266 1.58896 1.58544 1.581970.4717m 1.61237 1.61065 1.60720 1.60550 1.60232 1.59924 1.596171.129m 1.63738 1.63606 1.63336 1.63195 1.62948 1.62701 1.624552.217m 1.66364 1.66259 1.66045 1.65943 1.65720 1.65518 1.653203.900m 1.69856 1.69743 1.69524 1.69420 1.69212 1.69013 1.688264.973m 1.71984 1.71864 1.71603 1.71491 1.71260 1.71056 1.708786.095m 1.74035 1.73891 1.73640 1.73516 1.73285 1.73073 1.728567.199m 1.75965 1.75820 1.75560 1.75425 1.75187 1.74964 1.74740Reproduced from Beck WH,Dobson JV,and Wynne-Jones WFK(1960)The potentials of the mercurous sulphate/mercury electrode.Transactions of the Faraday Society56:1172.Table3The potentials(V)of the mercurous sulfate–mercury electrode(Cell II)Acid concentration278.16K288.16K298.16K308.16K318.16K328.16K 0.1003m0.738660.738200.737750.737290.736780.73629 0.1745m0.725470.724610.723860.723010.722090.72116 0.3877m0.705890.704580.703200.701800.700250.69850 0.5530m0.697030.695360.693680.692010.690070.688580.9776m0.680990.679120.676760.674530.672410.670281.872m0.658370.655820.653450.650650.647760.64491 3.911m0.619770.617250.614300.611550.608570.60633 5.767m0.595380.587170.584740.582030.579200.57614 7.972m0.559850.557310.554900.552660.550420.54842 Reproduced from Beck WH,Singh KP,and Wynne–Jones WFK(1959)The behaviour of the lead dioxide electrode.Part6–The potentials of the lead dioxide/lead sulphate electrode.Transactions of the Faraday Society55:331.Secondary Batteries–Lead–Acid Systems|Positive Electrode591measure the half-cell potentials of the LAB,they are not recommended for precise work.The standard potential of the lead–acid cell is2.048V at251C.A third-order polynomial equation has been fitted to the data to get the following relationship be-tween the OCV V and the acid molality m at251C:m¼517:8557À729:8575Vþ331:772V2À47:832189V3 To obtain accurate values,OCV must be measured on a well-equilibrated cell using a voltmeter with a high input impedance.Variations in acid concentration and tem-perature can change the voltages at the electrode sur-faces.The half-cell potential of the positive electrode changes more with acid concentration than that of the negative electrode.In addition,water formed during positive plate discharge decreases the voltage by diluting the acid concentration at the positive plate,especially at high discharge rates.Chemical Reactions that Limit Shelf LifeThe self-discharge reactions that limit shelf life have been defined in both traditionalflooded and valve-regulated lead–acid(VRLA)batteries.They are the same in both battery types.The only exception is the oxidation of additives such as antimony from the lead alloy in some flooded batteries.Low-maintenance and VRLA batteries use lead alloys that contain stable materials such as tin and sometimes calcium.Oxygen evolution:PbO2þH2SO4-PbSO4þ12O2ðgÞþH2O½II Oxidation of organics,R:2PbO2þRþ2H2SO4-2PbSO4þCO2ðgÞþ2H2OþR0½III Sulfation of residual lead(II)oxide(primarily in newly formed cells):PbOþH2SO4-PbSO4þH2O½IV Corrosion of the lead current collector:PbO2þPbþ2H2SO4-2PbSO4þ2H2O½V Oxidation of alloying metals in the lead current collector, for example antimony:5PbO2þ2Sbþ6H2SO4-5PbSO4þðSbO2ÞSO4þ6H2O½VI The reduction of lead dioxide by hydrogen is negligible on open circuit,but it can occur at very high voltages and temperatures.Overcharge ReactionsAs the battery approaches the end of charge,the recharge reaction becomes less efficient and the positive electrode begins to evolve oxygen:H2O-2Hþþ12O2ðgÞþ2eÀ½VII Organic materials that dissolve from the negative plate expander materials or the separators will oxidize to carbon dioxide:Organics-CO2þH2OþneÀ½VIII where n is the number of electrons and eÀthe electronic charge.Lead carbonates and basic lead carbonates that form during battery processing may be oxidized:PbCO3þH2O-PbO2þCO2þ2Hþþ2eÀ½IX Lead oxides,lead sulfates,and basic lead sulfates that were not converted to lead dioxide during the initial battery formation charge may oxidize to lead dioxide. Examples of these reactions arePbOþH2O-PbO2þ2Hþþ2eÀ½X PbSO4þ2H2O-PbO2þ2HþþH2SO4þ2eÀ½XI Basic lead sulfates may also be oxidized.Water is lost on overcharge in aflooded cell,because hydrogen that forms at the negative plate will vent from the cell.The charge voltage is typically reduced to a low ‘tapered’current to terminate the charge and reduce water loss.Adequate ventilation is an important safety consideration during overcharge.When a VRLA cell is overcharged at a constant voltage,oxygen recombination at the negative plate will keep the positive plate at a higher voltage than in a flooded cell under the same conditions.The higher positive plate voltage will produce more oxygen for re-combination,which will cause the internal temperature of the cell to rise.As the temperature rises,increasing vapor pressure of the acid as well as the oxygen and hydrogen formed at the plates may cause the pressure-relief valves on the battery to vent.This can be controlled by reducing the voltage or using a low‘tapered’current to charge the cell.It is also important to have a reliable pressure-relief valve on the cell that will reseal after opening.Manufacturers provide instructions for proper charging of their products under various conditions.Positive Plate Failure ModesThe following failure modes that limit the life of the positive plate are discussed in this section:•corrosion of the positive plate current collector with the formation of a resistive barrier layer between the grid and active material;592Secondary Batteries–Lead–Acid Systems|Positive Electrode•grid growth owing to excessive corrosion;•shedding of the active lead dioxide material from thepositive plate;•formation of a short between the positive and negativeplates;•loss of positive plate surface area,porosity,or chem-ical conductivity;and •contamination of the lead grid,electrolyte,or oxidematerial.Various battery designs and improved materials have overcome these sources of degradation and,consequently, have pushed cycle life farther.With each new advance-ment or application,a new primary failure mode must be understood and overcome.Positive Grid CorrosionThe lead grid will also slowly corrode,as discussed under failure modes.Grid corrosion can occur at any potential on the positive plate.The products of corrosion depend on the ionic environment at the grid surface and inside the corrosionfilm,as well as the potential.Lead oxide forms on the lead when conditions are basic,and lead sulfate forms when conditions are acidic and sulfate ion is available:PbþH2O-PbOþ2Hþþ2eÀ½XIIPbþH2SO4-PbSO4þ2Hþþ2eÀ½XIII Basic lead sulfates may also form.Table4lists the compounds that have been found in the positive plate environment.Lead sulfate forms a semipermeable membrane at the surface of the corrosion layer,where acid is available. Lead oxide forms underneath the lead sulfatefilm next to the grid by oxidation of lead in a solid-state process. Impediments to the diffusion of sulfate,hydrogen,and oxygen ions within thefilm cause variations in the cor-rosion products across thefilm.Figure1shows which product is formed at the lowest potential under each set of conditions and at what po-tential that compound is oxidized.Below pH1.9,the equilibria involve HSO4À.Above this pH,the equilibria for SO42Àare used.pS is defined as the negative of the log activity of the dominant sulfate ion at a given pH.The conditions at thefilm/solution interface are on the left face of the three-dimensional cube shown in Figure1.As the positive plate discharges,the acid concentration and voltage decrease.At the corrosion film/solution interface at pH0,the compound lead(II) sulfate(PbSO4),or lead dioxide will be stable,depending on the potential.This agrees with the normal charge and discharge reactions in the LAB.The negative electrode potential will become more positive and the total cell voltage will decrease as the sulfate ion concentration decreases.The right-hand face of the cube in Figure1shows what can happen within the corrosionfilm on the positive plate.At the low potentials seen at the negative plate and shown at the bottom of the diagram,the lead grid is stable.However,at the potentials of the positive plate,the lead grid will slowly oxidize to form the sulfate and oxide species shown in Table4.Which lead(II)species form is controlled by both the hydrogen and the sulfate ion activities in the corrosion film.Tetrabasic lead sulfate,4PbOÁPbSO4,is not stable at room temperature.The lead hydroxide(Pb(OH)2), region of the diagram represents all three lead(II)species shown in Table4.Two lead(II)species,lead(II)hy-droxide and3PbOÁPbSO4ÁH2O,will oxidize under basic conditions to lead tetraoxide at a slightly lower potentialTable4Compounds in the Pb/H2SO4/H2O systemLead PbBasic lead sulfates PbOÁPbSO43PbOÁPbSO4ÁH2O4PbOÁPbSO4Lead(II)oxides Pb(OH)2PbO(red)Higher valence oxides Pb2O3¼PbOÁPbO2Pb3O4¼2PbOÁPbO2PbO2Reproduced with permission from Bullock KR(1980)Effect of anion activity on electrochemical equilibria:Three-dimensional potential-pH diagram for Pb/H2SO4/H2O system.Journal of the Electrochemical Society127:662.−−E(V)3O4Figure1Potential(E)of lead compounds in the positive plate of a lead–acid battery(LAB)as a function of hydrogen and sulfate ion concentrations.Reproduced with permission from Bullock KR(1980)Effect of anion activity on electrochemical equilibria:Three-dimensional potential-pH diagram for Pb/H2SO4/H2O system.Journal of the Electrochemical Society127: 662.Secondary Batteries–Lead–Acid Systems|Positive Electrode593than they will oxidize to lead dioxide.A very small sta-bility region for lead tetraoxide is shown in Figure1. The compound Pb2O3has a very small stability region within the lead tetraoxide region,which is not shown because its equilibrium properties are not well understood.Temperature,acid concentration,and half-cell po-tential all have an effect on the corrosion rate and the materials formed.The highest corrosion rates are at overcharge and open-circuit potentials.Grid Growth and ShortingThe corrosion products shown above are all larger than lead.As they form on the grid,the volume expands and stresses the softer lead underneath.These mechanical stresses deform and expand the grid,causing the active material to lose contact with the current collector.When grid growth becomes excessive,some of the material may fall off the grid.Plate growth sometimes causes shorting if the positive plate expands enough to touch a negative component.The grid may also force the lead connections upward until the top of the battery case breaks.Softer materials such as pure lead or lead–calcium alloys will deform more than the harder lead–antimony alloys.This failure mode is generally found in batteries on a prolongedfloat or trickle current charge,where the grid corrodes at a low level for a very long time.It has been overcome in standby power batteries by grid designs that grow uniformly inward toward the active material rather than away from the material and toward the battery case. This grid design concept wasfirst accomplished in a cylindrical design that was suspended horizontally in the AT&T Round Cell.The grid concept was later extended to a rectangular design by engineers at Bell Laboratories. Shedding of the Positive Active Material and Shorting of the PlatesShedding is a common failure mode in deep discharge cycling applications such as vehicle propulsion or utility load leveling.It is also common in automotive batteries where high discharge rates produce variations in the material usage,acid concentrations,and potentials across the plates.The positive active material increases in size during discharge when lead sulfate is formed and de-creases in size during charge when lead dioxide is formed.These volumetric changes cause mechanical stresses in the plate.The materials gradually break apart and shed off the plate.In aflooded battery,the particles will fall to the bottom of the cell and build up as a layer of lead sulfate. Gas evolution during overcharge or mechanical stirring may cause some of the particles to move to the top and settle on the tops of the plates.If the particles touch the negative plate,they will be reduced to lead and may gradually build a conductive bridge or‘short’between the positive and negative plates.This can lead to rapid discharge and cell failure.Extra space is often designed at the bottom of cells in automotive or deep-cycling applications to prevent shorting by this mechanism.A nonconductive shield is also sometimes placed on top of the plate stack to keep the shed material from settling on the plates.Another cause of material shedding is acid stratifi-cation,with higher concentrations at the bottom of the cell.This generally occurs when aflooded cell is deep cycled with minimal overcharge.The active material in the more concentrated acid at the bottom of the cell will soften and shed,even though the material at the top may remain in good condition.Overcharge to produce gas bubbles that stir the electrolyte can prevent stratification but will accelerate other failure modes,such as grid corrosion,and reduce the energy efficiency of the battery. Moreover,the gas bubbles that form on the plates during overcharge exert large pressures on a microscale that can cause some breakup of the active material.Mechanical circulation of the acid is effective,but increases the cell volume and is therefore not practical in most applications.The most effective way to reduce shedding and shorting is to compress a glass mat or other soft separator material against the positive plate to hold the material in place.Valve-regulated lead–acid batteries that have electrodes tightly compressed against a glass mat separ-ator do not shed,but may have some softening of the active material because of acid stratification.Valve-regulated lead–acid batteries with gelled electrolyte also have less shedding,because the gelled electrolyte reduces acid stratification.Flooded batteries have much better cycle life when good separator systems are used to compress the active material.Loss of Positive Plate Surface Area,Porosity,or Chemical ConductivityShedding and softening of the active material is one source of the loss of positive active material and capacity, as discussed above.Another cause for capacity loss is the formation of large lead sulfate crystals that are difficult to recharge,called‘sulfation’.This failure can occur on either plate.It is caused by discharging the plate to form lead sulfate,and then letting the battery sit in a state of discharge for a time that varies with the temperature. Lead sulfate is an insulator that will recrystallize to form large crystals that do not easily recharge.When the current cannot reach the active material,the plates be-come covered with white lead sulfate crystals,and the porosity of the plate decreases.Long periods of time on open circuit also cause sulfation.594Secondary Batteries–Lead–Acid Systems|Positive ElectrodeBoth mechanisms are accelerated by high tempera-tures.Charging the battery soon after use and periodically recharging it during storage at high ambient temperatures is the best method of preventing this failure mode.Various approaches to recharging this‘hard sulfate’have been proposed.One method is a low current trickle charge with a high voltage cutoff.This allows the voltage to increase to a level that overcomes the plate resistance and slowly recharge the sulfate.This method takes many days to accomplish and will not work if the crystals get too large.Contamination of the Lead Grid,Acid,or Active MaterialMetallic ions and organic materials that accelerate failure sometimes contaminate aflooded battery when water is added to it.Contaminants generally accelerate corrosion, self-discharge,or gas evolution and water loss.Failure by contamination is less of a problem in low-maintenance or VRLA designs if manufacturers maintain good quality control over the materials they use in their manu-facturing processes.Unlikeflooded batteries,water can-not be added to these designs to replace the water lost by gas evolution.Specifications for battery acid and water should be carefully followed.Metal ions such as arsenic and antimony can be re-leased from the lead grid by corrosion processes.They increase cycle life in deep discharge applications,but also accelerate self-discharge and gas evolution with water loss as the battery ages.The concentrations of these materials are usually controlled in VRLA batteries and low-maintenance batteries,which are sensitive to me-tallic impurities that increase gassing rates.Additives Used in Positive Plates and GridsA variety of conductive and nonconductive materials have been suggested as additives to the positive active material to reduce cell weight or extend life.Fillers for plastic–metal composite grids,protectivefilms that would protect the grid from corrosion,and porous,conductive, carbon-foam plates that replace the grid are all under development.These materials must have good stability and conductivity and adhere well to the active materials. The brittleness of the lead dioxide and volumetric changes in its structure during cycling must be con-sidered when new materials are evaluated.The materials must also be electrochemically stable at positive plates in a strong acid environment.Conductive AdditivesLead is a metallic conductor,and lead dioxide is a semiconductor with conductivity up to1000siemens per centimeter(S cmÀ1)at room temperature.Thirty-five percent sulfuric acid has a conductivity of0.8S cmÀ1. Because of the high conductivity of these materials,a fully charged LAB has a resistance of only a few milliohms.Unfortunately,the lead(II)compounds are not so conductive.Lead sulfate is an insulator,and the lead(II) oxides and basic lead sulfates are semiconductors.Before the cell is given itsfirst charge,called‘formation’,battery pastes are mixtures of these materials.Plate formation cannot proceed until a conductive pathway is formed.D.Pavlov and coworkers have shown that in acid solutions,the materials next to the current collector are first converted to conductive lead and lead dioxide. Formation then proceeds toward the center of each pellet.Lead sulfate is the last material to be converted in the formation process.The rate of formation is thus limited by the nonconductive nature of the lead oxide in the positive plate.The capacity of a discharged positive plate that is covered with an insulating layer of lead sulfate crystals is limited by the rate of diffusion of acid to the underlying lead dioxide.The total capacity of the lead dioxide is also limited by the need to maintain a stable,conductive structure in the plate to conduct current from the re-action site to the current collector.If the plate becomes too heavily sulfated,it will be impossible to recharge.Conductive additives that are stable in the positive plate are used to overcome this problem.The ideal additive has a conductivity that is at least as high as carbon,a long-range order to minimize the amount of material needed,and stability within the positive plate during formation.It must also not contaminate or de-grade the battery during subsequent use.Many con-ductive materials oxidize in the positive plate because of its high potentials and the strongly oxidizing properties of lead dioxide and sulfuric acid.A traditional way to enhance the conductivity of the positive plate during formation is to use25–100wt%of red lead which contains lead tetraoxide.When sulfuric acid is added to this oxide to make a paste,the red lead reacts to form lead dioxide and lead sulfate.Plates made of red lead have poor cycle life unless the positive active material is highly compressed.This has limited the use of red lead inflat-plate designs,such as those used for automotive batteries.An alternative is to oxidize the surface to conductive lead oxide with ozone gas or so-lutions of persulfates or peroxides.Much lower quantities of lead dioxide are needed with this approach than when red lead is added to the plate,and the normal battery paste can be used.Carbon is added to the negative plate and has been tested in the positive plate,but it is not generally used in positive plates because it oxidizes to carbon dioxide. Conductive polymers doped with anions or intrinsicallySecondary Batteries–Lead–Acid Systems|Positive Electrode595。
Unit 1 Production of DrugsDepending on their production or origin pharmaceutical agents can be split into three groups:I .Totally synthetic materials (synthetics),Ⅱ.Natural products,andⅢ.Products from partial syntheses (semi-synthetic products).The emphasis of the present book is on the most important compounds of groups I and Ⅲ一thus Drug synthesis. This does not mean,however,that natural products or other agents are less important. They can serve as valuable lead structures,and they are frequently needed as starting materials or as intermediates for important synthetic products.Table 1 gives an overview of the different methods for obtaining pharmaceutical agents.1单元生产的药品其生产或出身不同药剂可以分为三类:1。
完全(合成纤维)合成材料,Ⅱ。
天然产物,和Ⅲ。
产品从(半合成产品)的部分合成。
本书的重点是团体的最重要的化合物Ⅰ和Ⅲ一所以药物合成。
这并不意味着,但是,天然产品或其他代理人并不太重要。
它们可以作为有价值的领导结构,他们常常为原料,或作为重要的合成中间体产品的需要。
常见化学专业词汇英文翻译1. The Ideal-Gas Equation 理想气体状态方程2. Partial Pressures 分压3. Real Gases: Deviation from Ideal Behavior 真实气体:对理想气体行为的偏离4. The van der Waals Equation 范德华方程5. System and Surroundings 系统与环境6. State and State Functions 状态与状态函数7. Process 过程8. Phase 相9. The First Law of Thermodynamics 热力学第一定律10. Heat and Work 热与功11. Endothermic and Exothermic Processes 吸热与发热过程12. Enthalpies of Reactions 反应热13. Hess’s Law 盖斯定律14. Enthalpies of Formation 生成焓15. Reaction Rates 反应速率16. Reaction Order 反应级数17. Rate Constants 速率常数18. Activation Energy 活化能19. The Arrhenius Equation 阿累尼乌斯方程20. Reaction Mechanisms 反应机理21. Homogeneous Catalysis 均相催化剂22. Heterogeneous Catalysis 非均相催化剂23. Enzymes 酶24. The Equilibrium Constant 平衡常数25. the Direction of Reaction 反应方向26. Le Chatelier’s Principle 列·沙特列原理27. Effects of Volume, Pressure, Temperature Changes and Catalystsi. 体积,压力,温度变化以及催化剂的影响28. Spontaneous Processes 自发过程29. Entropy (Standard Entropy) 熵(标准熵)30. The Second Law of Thermodynamics 热力学第二定律31. Entropy Changes 熵变32. Standard Free-Energy Changes 标准自由能变33. Acid-Bases 酸碱34. The Dissociation of Water 水离解35. The Proton in Water 水合质子36. The pH Scales pH值37. Bronsted-Lowry Acids and Bases Bronsted-Lowry 酸和碱38. Proton-Transfer Reactions 质子转移反应39. Conjugate Acid-Base Pairs 共轭酸碱对40. Relative Strength of Acids and Bases 酸碱的相对强度41. Lewis Acids and Bases 路易斯酸碱42. Hydrolysis of Metal Ions 金属离子的水解43. Buffer Solutions 缓冲溶液44. The Common-Ion Effects 同离子效应45. Buffer Capacity 缓冲容量46. Formation of Complex Ions 配离子的形成47. Solubility 溶解度48. The Solubility-Product Constant Ksp 溶度积常数49. Precipitation and separation of Ions 离子的沉淀与分离50. Selective Precipitation of Ions 离子的选择沉淀51. Oxidation-Reduction Reactions 氧化还原反应52. Oxidation Number 氧化数53. Balancing Oxidation-Reduction Equations 氧化还原反应方程的配平54. Half-Reaction 半反应55. Galvani Cell 原电池56. Voltaic Cell 伏特电池57. Cell EMF 电池电动势58. Standard Electrode Potentials 标准电极电势59. Oxidizing and Reducing Agents 氧化剂和还原剂60. The Nernst Equation 能斯特方程61. Electrolysis 电解62. The Wave Behavior of Electrons 电子的波动性63. Bohr’s Model of The Hydrogen Atom 氢原子的波尔模型64. Line Spectra 线光谱65. Quantum Numbers 量子数66. Electron Spin 电子自旋67. Atomic Orbital 原子轨道68. The s (p, d, f) Orbital s(p,d,f)轨道69. Many-Electron Atoms 多电子原子70. Energies of Orbital 轨道能量71. The Pauli Exclusion Principle 泡林不相容原理72. Electron Configurations 电子构型73. The Periodic Table 周期表74. Row 行75. Group 族76. Isotopes, Atomic Numbers, and Mass Numbers 同位素,原子数,质量数77. Periodic Properties of the Elements 元素的周期律78. Radius of Atoms 原子半径79. Ionization Energy 电离能80. Electronegativity 电负性81. Effective Nuclear Charge 有效核电荷82. Electron Affinities 亲电性83. Metals 金属84. Nonmetals 非金属85. Valence Bond Theory 价键理论86. Covalence Bond 共价键87. Orbital Overlap 轨道重叠88. Multiple Bonds 重键89. Hybrid Orbital 杂化轨道90. The VSEPR Model 价层电子对互斥理论91. Molecular Geometries 分子空间构型92. Molecular Orbital 分子轨道93. Diatomic Molecules 双原子分子94. Bond Length 键长95. Bond Order 键级96. Bond Angles 键角97. Bond Enthalpies 键能98. Bond Polarity 键矩99. Dipole Moments 偶极矩100. Polarity Molecules 极性分子101. Polyatomic Molecules 多原子分子102. Crystal Structure 晶体结构103. Non-Crystal 非晶体104. Close Packing of Spheres 球密堆积105. Metallic Solids 金属晶体106. Metallic Bond 金属键107. Alloys 合金108. Ionic Solids 离子晶体109. Ion-Dipole Forces 离子偶极力110. Molecular Forces 分子间力111. Intermolecular Forces 分子间作用力112. Hydrogen Bonding 氢键113. Covalent-Network Solids 原子晶体114. Compounds 化合物115. The Nomenclature, Composition and Structure of Complexes 配合物的命名,组成和结构116. Charges, Coordination Numbers, and Geometries 电荷数、配位数、及几何构型117. Chelates 螯合物118. Isomerism 异构现象119. Structural Isomerism 结构异构120. Stereoisomerism 立体异构121. Magnetism 磁性122. Electron Configurations in Octahedral Complexes 八面体构型配合物的电子分布123. Tetrahedral and Square-planar Complexes 四面体和平面四边形配合物124. General Characteristics 共性125. s-Block Elements s区元素126. Alkali Metals 碱金属127. Alkaline Earth Metals 碱土金属128. Hydrides 氢化物129. Oxides 氧化物130. Peroxides and Superoxides 过氧化物和超氧化物131. Hydroxides 氢氧化物132. Salts 盐133. p-Block Elements p区元素134. Boron Group (Boron, Aluminium, Gallium, Indium, Thallium) 硼族(硼,铝,镓,铟,铊)135. Borane 硼烷136. Carbon Group (Carbon, Silicon, Germanium, Tin, Lead) 碳族(碳,硅,锗,锡,铅)137. Graphite, Carbon Monoxide, Carbon Dioxide 石墨,一氧化碳,二氧化碳138. Carbonic Acid, Carbonates and Carbides 碳酸,碳酸盐,碳化物139. Occurrence and Preparation of Silicon 硅的存在和制备140. Silicic Acid,Silicates 硅酸,硅酸盐141. Nitrogen Group (Phosphorus, Arsenic, Antimony, and Bismuth) 氮族(磷,砷,锑,铋)142. Ammonia, Nitric Acid, Phosphoric Acid 氨,硝酸,磷酸143. Phosphorates, phosphorus Halides 磷酸盐,卤化磷144. Oxygen Group (Oxygen, Sulfur, Selenium, and Tellurium) 氧族元素(氧,硫,硒,碲)145. Ozone, Hydrogen Peroxide 臭氧,过氧化氢146. Sulfides 硫化物147. Halogens (Fluorine, Chlorine, Bromine, Iodine) 卤素(氟,氯,溴,碘)148. Halides, Chloride 卤化物,氯化物149. The Noble Gases 稀有气体150. Noble-Gas Compounds 稀有气体化合物151. d-Block elements d区元素152. Transition Metals 过渡金属153. Potassium Dichromate 重铬酸钾154. Potassium Permanganate 高锰酸钾155. Iron Copper Zinc Mercury 铁,铜,锌,汞156. f-Block Elements f区元素157. Lanthanides 镧系元素158. Radioactivity 放射性159. Nuclear Chemistry 核化学160. Nuclear Fission 核裂变161. Nuclear Fusion 核聚变162. analytical chemistry 分析化学163. qualitative analysis 定性分析164. quantitative analysis 定量分析165. chemical analysis 化学分析166. instrumental analys is 仪器分析167. titrimetry 滴定分析168. gravimetric analysis 重量分析法169. regent 试剂170. chromatographic analysis 色谱分析171. product 产物172. electrochemical analysis 电化学分析173. on-line analysis 在线分析174. macro analysis 常量分析175. characteristic 表征176. micro analysis 微量分析177. deformation analysis 形态分析178. semimicro analysis 半微量分析179. systematical error 系统误差180. routine analys is 常规分析181. random error 偶然误差182. arbitration analysis 仲裁分析183. gross error 过失误差184. normal distribution 正态分布185. accuracy 准确度186. deviation偏差187. precision 精密度188. relative standard deviation 相对标准偏差(RSD)189. coefficient variation 变异系数(CV)190. confidence level 置信水平191. confidence interval 置信区间192. significant test 显著性检验193. significant figure 有效数字194. standard solution 标准溶液195. titration 滴定196. stoichiometric point 化学计量点197. end point滴定终点198. titration error 滴定误差199. primary standard 基准物质200. amount of substance 物质的量201. standardization 标定202. chemical reaction 化学反应203. concentration浓度204. chemical equilibrium 化学平衡205. titer 滴定度206. general equation for a chemical reaction化学反应的通式207. proton theory of acid-base 酸碱质子理论208. acid-base titration 酸碱滴定法209. dissociation constant 解离常数210. conjugate acid-base pair 共轭酸碱对211. acetic acid 乙酸212. hydronium ion水合氢离子213. electrolyte 电解质214. ion-product constant of water 水的离子积215. ionization 电离216. proton condition 质子平衡217. zero level零水准218. buffer solution缓冲溶液219. methyl orange 甲基橙220. acid-base indicator 酸碱指示剂221. phenolphthalein 酚酞222. coordination compound 配位化合物223. center ion 中心离子224. cumulative stability constant 累积稳定常数225. alpha coefficient 酸效应系数226. overall stability constant 总稳定常数227. ligand 配位体228. ethylenediamine tetraacetic acid 乙二胺四乙酸229. side reaction coefficient 副反应系数230. coordination atom 配位原子231. coordination number 配位数232. lone pair electron 孤对电子233. chelate compound 螯合物234. metal indicator 金属指示剂235. chelating agent 螯合剂236. masking 掩蔽237. demasking 解蔽238. electron 电子239. catalysis 催化240. oxidation氧化241. catalyst 催化剂242. reduction 还原243. catalytic reaction 催化反应244. reaction rate 反应速率245. electrode potential 电极电势246. activation energy 反应的活化能247. redox couple 氧化还原电对248. potassium permanganate 高锰酸钾249. iodimetry碘量法250. potassium dichromate 重铬酸钾251. cerimetry 铈量法252. redox indicator 氧化还原指示253. oxygen consuming 耗氧量(OC)254. chemical oxygen demanded 化学需氧量(COD) 255. dissolved oxygen 溶解氧(DO)256. precipitation 沉淀反应257. argentimetry 银量法258. heterogeneous equilibrium of ions 多相离子平衡259. aging 陈化260. postprecipitation 继沉淀261. coprecipitation 共沉淀262. ignition 灼烧263. fitration 过滤264. decantation 倾泻法265. chemical factor 化学因数266. spectrophotometry 分光光度法267. colorimetry 比色分析268. transmittance 透光率269. absorptivity 吸光率270. calibration curve 校正曲线271. standard curve 标准曲线272. monochromator 单色器273. source 光源274. wavelength dispersion 色散275. absorption cell吸收池276. detector 检测系统277. bathochromic shift 红移278. Molar absorptivity 摩尔吸光系数279. hypochromic shift 紫移280. acetylene 乙炔281. ethylene 乙烯282. acetylating agent 乙酰化剂283. acetic acid 乙酸284. adiethyl ether 乙醚285. ethyl alcohol 乙醇286. acetaldehtde 乙醛287. β-dicarbontl compound β–二羰基化合物288. bimolecular elimination 双分子消除反应289. bimolecular nucleophilic substitution 双分子亲核取代反应290. open chain compound 开链族化合物291. molecular orbital theory 分子轨道理论292. chiral molecule 手性分子293. tautomerism 互变异构现象294. reaction mechanism 反应历程295. chemical shift 化学位移296. Walden inversio 瓦尔登反转n297. Enantiomorph 对映体298. addition rea ction 加成反应299. dextro- 右旋300. levo- 左旋301. stereochemistry 立体化学302. stereo isomer 立体异构体303. Lucas reagent 卢卡斯试剂304. covalent bond 共价键305. conjugated diene 共轭二烯烃306. conjugated double bond 共轭双键307. conjugated system 共轭体系308. conjugated effect 共轭效应309. isomer 同分异构体310. isomerism 同分异构现象311. organic chemistry 有机化学312. hybridization 杂化313. hybrid orbital 杂化轨道314. heterocyclic compound 杂环化合物315. peroxide effect 过氧化物效应t316. valence bond theory 价键理论317. sequence rule 次序规则318. electron-attracting grou p 吸电子基319. Huckel rule 休克尔规则320. Hinsberg test 兴斯堡试验321. infrared spectrum 红外光谱322. Michael reacton 麦克尔反应323. halogenated hydrocarbon 卤代烃324. haloform reaction 卤仿反应325. systematic nomenclatur 系统命名法e326. Newman projection 纽曼投影式327. aromatic compound 芳香族化合物328. aromatic character 芳香性r329. Claisen condensation reaction克莱森酯缩合反应330. Claisen rearrangement 克莱森重排331. Diels-Alder reation 狄尔斯-阿尔得反应332. Clemmensen reduction 克莱门森还原333. Cannizzaro reaction 坎尼扎罗反应334. positional isomers 位置异构体335. unimolecular elimination reaction 单分子消除反应336. unimolecular nucleophilic substitution 单分子亲核取代反应337. benzene 苯338. functional grou 官能团p339. configuration 构型340. conformation 构象341. confomational isome 构象异构体342. electrophilic addition 亲电加成343. electrophilic reagent 亲电试剂344. nucleophilic addition 亲核加成345. nucleophilic reagent 亲核试剂346. nucleophilic substitution reaction亲核取代反应347. active intermediate 活性中间体348. Saytzeff rule 查依采夫规则349. cis-trans isomerism 顺反异构350. inductive effect 诱导效应t351. Fehling’s reagent 费林试剂352. phase transfer catalysis 相转移催化作用353. aliphatic compound 脂肪族化合物354. elimination reaction 消除反应355. Grignard reagent 格利雅试剂356. nuclear magnetic resonance 核磁共振357. alkene 烯烃358. allyl cation 烯丙基正离子359. leaving group 离去基团360. optical activity 旋光性361. boat confomation 船型构象362. silver mirror reaction 银镜反应363. Fischer projection 菲舍尔投影式364. Kekule structure 凯库勒结构式365. Friedel-Crafts reaction 傅列德尔-克拉夫茨反应366. Ketone 酮367. carboxylic acid 羧酸368. carboxylic acid derivative 羧酸衍生物369. hydroboration 硼氢化反应370. bond oength 键长371. bond energy 键能372. bond angle 键角373. carbohydrate 碳水化合物374. carbocation 碳正离子375. carbanion 碳负离子376. alcohol 醇377. Gofmann rule 霍夫曼规则378. Aldehyde 醛379. Ether 醚380. Polymer 聚合物。
第46卷第20期2018年10月广 州 化 工Guangzhou Chemical Industry Vol.46No.20 Oct.2018新型二氧化铅电极的研究进展孙鹏哲1,2(1深圳市深港产学研环保工程技术股份有限公司,广东 深圳 518000;2重庆市环境保护设计工程设计研究院有限公司,重庆 404200)摘 要:概述了近年来国内采用压塑法制备复合二氧化铅电极的研究进展,主要涉及塑片复合二氧化铅电极的制备方法(包括原料的制备方法㊁压制的方法)㊁掺杂改性(改性材料有石墨粉㊁活性炭粉㊁金属粉以及金属氧化物粉)及在污水处理方面的应用㊂研究采用改性材料和二氧化铅粉末混合掺杂,从而优化电极;并指出塑片二氧化铅电极现存的问题,并展望了塑片二氧化铅电极的发展方向㊂关键词:二氧化铅;压塑法;塑片电极;改性材料 中图分类号:O646 文献标志码:A文章编号:1001-9677(2018)20-0024-03 Research Progress on New Lead Dioxide ElectrodeSUN Peng-zhe1,2(1IERE Environment Protection Engineering Technique Co.,Ltd.,Guangdong Shenzhen518000;2Chongqing Environment Engineering Acaoemu Co.,Ltd,Chongqing404200,China)Abstract:In recent years,research progress on plastic piece of lead dioxide composite electrodes,which were prepared by the high pressure molding technique,was summarized.The new preparation method of lead dioxide electrode mainly involved the methods for preparation of plastic piece of lead dioxide electrode,which included preparation of raw material,high pressing method,doping modified materials with graphite powder,activated carbon powder,metal powder or metal oxides powder,and application in wastewater treatment.Experimental research mixed modified materials and lead dioxide powder,so as to optimize electrode.The problems existing in plastic piece of lead dioxide electrode were pointed out.And the development trend was forecasted.Key words:lead dioxide;high pressure molding technique;plastic piece electrode;modified materials二氧化铅良好的导电性及稳定的化学惰性,早在20世纪30年代二氧化铅就被作为不溶性阳极用在化工工业生产中[1]㊂最初PbO2电极没有基体,是通过机械加压,粉末成型的方式制备二氧化铅电极,这种无基体二氧化铅电极机械性能不好,使用寿命短,因此,不受科研工作者的青睐,难以推广[2-3]㊂自1967年Beer发明钛基体氧化钌活性涂层电极以来,科研工作者对DSA电极(dimensionally stable anodes)进行了大量的研究工作,并在氯碱㊁氯酸盐㊁硫酸㊁电镀㊁冶金㊁电解水㊁污水处理㊁有机合成等工业领域获得应用[4-6]㊂近年来,大量科研工作者深入研究钛基体二氧化铅电极,大幅提升了钛基体二氧化铅电极的催化性能㊁使用寿命㊂该种电极并不是没有缺陷的,由于基体和活性层之间存在结构差异,结合不够紧密,同时在使用过程中由于基体钝化,电极不可避免造成镀层易脱落[7]㊂此外钛基体二氧化铅电极还存在有耐腐蚀性差,稳定性较差,成本高,使寿命相对较短等缺点,不利于推广应用[3]㊂因此,研究人员致力于开发性能良好的新型电极㊂近些年,研究人员重新采用高压塑片法制备二氧化铅电极,在二氧化铅粉末掺杂一定配比的有机黏结剂(有机微粉㊁PTFE乳液等)压制出的二氧化铅电极机械性能良好,提升了耐腐蚀性,延长了使用寿命㊂但由于该方法制备的二氧化铅电极的电阻率过高,催化活性较差,试验效果不好㊂目前,塑片二氧化铅电极在持续进行改性研究,逐步取得成效[8]㊂1 电极的制备1.1 β-PbO2粉末的制备二氧化铅是棕褐色粉末,有较好导电性[9]㊂PbO2有很多晶型,主要研究斜方晶型(α-PbO2)㊁四方晶型(β-PbO2)[10]㊂与α-PbO2的电阻率(650μΩ㊃cm)比相比,β-PbO2的电阻率(96μΩ㊃cm)较低,稳定性良好[11]㊂通常二氧化铅电极的活性层是有β-PbO2组成,是由于β-PbO2的析出氧电位较高[2]㊂β-PbO2粉末可以通过电化学沉积获得,也可以由α-PbO2通过热转化而来[9]㊂而现阶段在研究塑片二氧化铅电极时,通常采用庄京等[12]的制备工艺:将10g醋酸铅溶于20mL水中,调节pH值在9.0~10.0之间,添加80mL的NaClO溶液,混合后置于90℃恒温水浴锅中加热6h,最终的反应液过滤,所得滤饼冲洗,干燥,研磨,即制备得到深棕色的β-PbO2棒状晶体㊂1.2 塑片电极的制备工艺直接用β-PbO2粉末压制出的电极机械强度低,容易破碎,不适合应用在污水处理方面㊂研究发现在β-PbO2粉末中添加第46卷第20期孙鹏哲:新型二氧化铅电极的研究进展25一些有机黏结剂(有机微粉㊁聚四氟乙烯乳液等),改善粉末的成形状态,在高压下,可以制得机械性好,表面致密的塑片电极㊂现阶段实验室内制备塑片电极,主要的步骤是:首先把自制的β-PbO2粉末㊁改性物质及有机粘结混匀,其次将干燥的混合粉体装入模具,保持一定的高压几分钟即得塑片二氧化铅电极㊂2 掺杂的改性材料为了提高新型塑片二氧化铅电极的电催化活性,延长使用寿命等,因此制备过程会添加一定配比的物质去改善塑片电极的电化学性质㊂今年来,研究发现掺杂的某些必要物质(有机微粉㊁聚四氟乙烯乳液等)以及改性物质(软锰矿㊁纳米氧化钛㊁氧化铈粉末㊁镧粉㊁镍金属㊁粉活性炭㊁石墨粉等)均有利于电极的电催化氧化性能的提高㊂(1)聚四氟乙烯乳液在制片过程中,聚四氟乙烯乳液(PTFE)是作为黏结剂使用的㊂当然也可以使用其他物质,例如一些有机微粉㊂在DSA 电极的研究过程中,发现PTFE可以增加电极的疏水性和稳定性,提高电极催化活性[13]㊂而在压塑工艺中,添加聚四氟乙烯的电极的最大作用首先是使用寿命得到增加,增强电极的机械性能㊂其次,PTFE是具有疏水性的有机分子,有助于在电极表面上吸引汇集有机物类型的污染物,同时PTFE可塑性良好,且不参与反应㊂最后,PTFE会引起混合粉体的团聚现象,以致于制备出表面分布不均的电极,可能会产生表面凹凸,甚至是微孔,有助于增大电极表面积[14]㊂(2)石墨粉和活性炭[13]活性炭具有比表面比较大,吸附性能高的特点,所以常用于电极的表面改性处理㊂在塑片电极制备中,掺杂活性炭可以提升电极的吸附性能㊂石墨粉可以增强电极的致密㊁坚硬的特性,还可以提高电极的耐腐蚀性㊁导电性,提升电极的电流效率㊂因此,掺杂石墨粉或活性炭可以提高电极的电催化活性㊂(3)其他活性成分金属粉:镧和镍㊂镍是具有铁磁性的金属元素,抗腐蚀性能好,有良好导电率性,在复合材料的制备常会用到[15]㊂此外在DSA电极研究中,镍也会用于修饰二氧化铅电极的研究[16]㊂单志国等[17]通过添加镍金属粉制备电极,金属镍粉可以提升电极的导电性,从而增强电极的电催化氧化活性;镍金属粉还可以提升电极的硬度,使电极表面产生微孔,增加了电极的比表面积㊂在DSA电极研究中,镧也被作为改性物质用于电极的改性实验,可以提高电极的催化氧化能力掺杂镧粉制备电极,镧粉可以提高电极的导电性及析氧电位㊂金属化合物:二氧化钛㊁二氧化铈和软锰矿㊂在DSA电极研究中TiO2具有光催化性,可以增加电极的特性[21-22]㊂邵春雷等[10,23]加入纳米二氧化钛制备电极,其中与纯塑片电极(β-PbO2-PTFE)相比,添加的纳米二氧化钛的电极具有更好的电催化氧化能力,可能是因为掺杂二氧化钛的电极表面容易产生空穴,有利于生成羟基自由基,同时二氧化钛还提升电极的比表面积㊂但是,TiO2电阻率较高,会增电极电阻率㊂添加锰的化合物,会增加电极的粗糙度机械强度㊁耐磨性㊁耐蚀性㊁催化活性等,尤其粗糙度,衡量电极催化活性的重要指标[24-26]㊂李云霞等[27]加入锰矿粉制备复合电极,锰矿粉有助于延长电极的使用寿命,提高电极催化氧化能力㊂在DSA电极研究中发现CeO2增加催化降解有机物的能力[21,28-30]㊂孙鹏哲等[8]掺杂氧化铈及石墨粉制备塑片二氧化铅电极,氧化铈和石墨加入提高了电极的析氧电位,极大的提高了塑片电极的催化氧化能力㊂非金属化合物:二氧化硼㊂谢婷婷等[31]掺杂碳化硼和石墨制备二氧化铅塑片电极,该种二氧化铅电极具有较强的耐腐蚀性,较高的机械强度,较好的导电性,研究发现在处理偶氮染料染料废水时,碳化硼/石墨改性二氧化铅电极脱色效果优于β-PbO2电极㊂3 污水处理中的应用塑片PbO2电极可以用于处理难生物降解有机污染物,且对含盐有机废水效果显著㊂邵春雷等[10]采用压塑法制备β-PbO2电极,该种电极用于处理模拟240mg/L硝基苯废水, COD去除率较好㊂在同样的实验条件下,塑片电极的催化降解效果比石墨电极好㊂房豪杰等[32]采用压塑法制备β-PbO2电极,该种电极用于处理模拟中性枣红染料废水,在PbO2与FDPF-1(黏结剂)质量比为7/1时,该种配比的电极处理废水的效果最好㊂徐莺等[33]采用压塑法制备β-PbO2电极,该种电极处理模拟20mg/L染料废水(中性枣红),研究发现,在磷酸二氢钾或氯化钠作为电解质时候,能取得良好的预处理效果㊂曹长青[34]等人采用压塑法制备β-PbO2电极,该种电极处理模拟废水染料废水(茜素红),实验研究了pH值㊁电解质浓度㊁极板距离等因素对处理效果的影响㊂曹长青[23]等人将少量纳米二氧化钛粉末㊁β-PbO2粉末和FDPF-1有机粘合剂均匀混合后采用压塑法制备电极,该种改性β-PbO2/TiO2电极处理模拟240mg/L㊁0.05mol/L Na2SO4的硝基苯废水以及茜素红废水,发现不同电极的电催化活性的排序:β-PbO2/TiO2>β-PbO2>石墨,其中β-PbO2/TiO2(2%)电极的电催化活性最好㊂李云霞等[27]利用压塑法制备β-PbO2电极,掺杂锰矿粉的β-PbO2复合电极,研究发现当软锰矿粉掺杂量(质量百分比)达到17.6%时,该种电极的性能最好㊂在处理模拟30mg/L染料废水(弱酸性桃红-BS)㊁0.05mol/L电解质KNO3实验条件下,催化降解30min后,COD的去除率达到83%㊂同时,该实验还做了添加叔丁醇的实验(羟基自由基的验证实验),结果表明有羟基自由基的生成㊂单治国等[35-36]采用掺杂锰矿粉的β-PbO2复合电极处理模拟硝基苯废水,在电解质为10g/L的氯化钠实验条件下,催化降解120min后,COD的去除率达到99.43%,同时研究发现该降解过程符合一级反应动力学㊂朱艳等[37]利用压塑法制备掺杂活性炭㊁石墨混合粉体的二氧化铅粉末多孔电极,研究发现当掺杂量活性炭㊁石墨混合粉体质量百分比为20%时,该种电极处理效果较好㊂在氯化钠电解质体系下模拟处理氨氮废水,由于氯离子的协同作用,处理氨氮的处理效果较好㊂张弛等[38]利用压塑法制备了掺杂活性炭粉体㊁镧粉的改性二氧化铅电极,当掺杂量物质质量百分比为20%时,复合电极的电催化降解活性较好,在氯化钠电解质体系下,模拟处理100mg/L的染料废水(亚甲蓝),染料的脱色率效果明显,但COD的去除率不高㊂4 结 语高压塑片法制备二氧化铅的工艺简单,操作方便,原料成本相对低㊂新型塑片二氧化铅电极通过掺杂改性,使得电极的电催化氧化活性得到了极大的提高,同时还具有使用寿命长,耐腐蚀性强的优点,由此验证了压塑法制备二氧化铅电极的可能性㊂整体来看,对高压塑片法制备二氧化铅的研究时间较短,研究内容较少,研究深度不够㊂同时,该种新型电极的制备工艺有待进一步优化,需要进一步的探究对该种塑片电极的反复塑造影响㊁反应动力学㊁催化氧化反应机理㊁添加改性材26 广 州 化 工2018年10月料(如纳米氧化钛㊁镧粉㊁软锰矿)作用机理㊁表面多孔性与光滑性研究等方面㊂目前,在塑片电极改性研究中添加改性物质已有活性炭㊁石墨粉㊁镧粉㊁软锰矿㊁纳米氧化钛㊁氧化铈粉末㊁镍金属粉等等㊂还有很多材料可以尝试添加,如金属化合物系:金刚石颗粒㊁碳化物㊁碳化硼,碳系:石墨烯㊁碳纳米管㊂同时还可以考虑对掺杂物质的掺杂比例㊁掺杂种类的混合等当面的细化规范研究㊂此外对该种电极降解机理,耐腐蚀性检测,使用寿命,电化学测试方面等验证测试方面研究有限㊂压片机制备塑片电极过程中,制备压力,保持时间等因素对电极的使用寿命㊁催化活性具有重要的影响㊂关于塑片电极应用方面的研究要结合它本身的优缺点,还需要进一步的探讨,例如,关于电极的压制形状与三维电极应用方面结合研究;塑片电极可以考虑作为惰性电极或者金属冶炼等方面进行结合研究㊂参考文献[1] Schümann U,Gründler P.Electrochemical degradation of organicsubstances at PbO2anodes:monitoring by continuous CO2 measurements[J].Water Research,1998,32(9):2835. 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Unit 1 Production of DrugsDepending on their production or origin pharmaceutical agents can be split into three groups:I .Totally synthetic materials (synthetics),Ⅱ.Natural products,andⅢ.Products from partial syntheses (semi-synthetic products).The emphasis of the present book is on the most important compounds of groups I and Ⅲ一thus Drug synthesis. This does not mean,however,that natural products or other agents are less important. They can serve as valuable lead structures,and they are frequently needed as starting materials or as intermediates for important synthetic products.Table 1 gives an overview of the different methods for obtaining pharmaceutical agents.1单元生产的药品其生产或出身不同药剂可以分为三类:1。
完全(合成纤维)合成材料,Ⅱ。
天然产物,和Ⅲ。
产品从(半合成产品)的部分合成。
本书的重点是团体的最重要的化合物Ⅰ和Ⅲ一所以药物合成。
这并不意味着,但是,天然产品或其他代理人并不太重要。
它们可以作为有价值的领导结构,他们常常为原料,或作为重要的合成中间体产品的需要。
13PREPARATION OF LEAD DIOXIDE ELECTRODE (A REVIEW)W.T. Mason(Dept. of Chem., Leeds Univ., Leeds, UK)IntroductionCurrent technological developments, for instance in electro-chemical power sources, are creating fresh interest in the fundamental properties of solid oxide electrodes. Of these, lead dioxide has attracted considerable attention owing to its use as the active material in the positive plate of the lead-acid cell, and there exists a considerable amount of literature concerning the behaviour of this electrod[1-5].For measurements on any solid electrodes the experimental requirements are severe. In the present case lead dioxide should be carefully prepared and manipulated, both mechanically and electrochemically; a rigorous standard of electrolyte cleanliness is necessary and consequently special techniques of measurement are required.In most of the earlier reported preparations of lead dioxide no attention was paid to the polymorphic form of the product. However, in some more recent papers details of preparations are given in which careful control of the product morphology has been achieved. The various methods[6-10] for the preparation of lead dioxide that have been proposed from time to time may be subdivided into chemical and electrolytic preparations.Lead dioxide has been prepared chemically by methods in whichPb(II) compounds are oxidized to lead dioxide in the solution phase or in melts or by heating at elevated temperatures in oxygen. It was reported that lead dioxide could be prepared by the thermal oxidation of PbO[6] or Pb3O4[7]; however, White and Roy[8] examined the products by X-ray diffraction and found that the oxide produced corresponded to an oxide with an active oxygen content of PbO[1.582]; i.e., it was not possible to produce an oxide by this method with oxygen in excess of Pb12O19. Lead dioxide may also be prepared by the hydrolysis of lead[IV] salts[8]; for example, lead tetrachloride may be hydrolyzed in cold hydrochloric acid solution[9], or a saturated solution of lead tetraacetate may be hydrolyzed in glacial acetic acid. The majority of preparation, however, involve theoxidation of lead(II) salts. Chemical oxidations of sodium plumbite solution in alkali are readily achieved with chlorine, bromine, and hydrogen peroxide[10] and simple lead(II) salts may be oxidized with 37 M nitric acid[10]. Anodic oxidations may be carried out with alkaline solutions of nitrates, perchlorates, fluoroborates, or fluorosilicates. The anodic oxidation of lead sulphate is well known[10].Pure Lead DioxideThe use of lead dioxide in electrolytic systems, particularly for thermodynamic measurements, has indicated that irreproducible results are often obtained, and this imposes stringent purity requirements on the materials involved.1 For example, in the work of Hamer, who studied the galvanic cell.H2 (1 atm), Pt / H2SO4 (1M), PbSO4 , / lead dioxide, PtMethods for preparing lead dioxide in a suitably stable form were studied since commercial samples gave erratic emf results no matter how they were treated before use.Hamer suggested that the electrolysis of an aqueous solution containing lead nitrate and concentrated nitric acid, maintained at 93o C with use of a platinum gauze anode, produced the most consistent potential values.Conformation of Lead Dioxide to PbO2A considerable amount of effort has been made into forcing lead dioxide to conform to exact stoichiometry. The methods used include chemical oxidation[12], direct oxidation at high temperatures using high oxygen pressures[13], and the crystal growth of stoichiometric lead dioxide in the solution phase[14].Electrolytic PreparationsOf various inert materials available as anodes for the electrodeposition of lead dioxide, Pt and Au are the most suitable. Various eletrolytes have been employed. A nearly saturated solution of lead perchlorate in perchloric acid-water[14] was electrolyzed at anode current densities of 1 and 2 mA/cm2, using a platinum anode and a graphite cathode at temperatures near -50o C. Analysis of the product gave 96.4% of the theoretical active oxygen for lead dioxide, with no significant difference between materials prepared at the different current densities.The effect of hydrogen ion concentration on the lead dioxide electrodeposit was investigated by Diusman and Giaque[10] using lead nitrate-nitric acid solutions in water. At the highest acidities, the active oxygen content of the product declined; however, there was no clear evidence that a solution of 0.1M HNO3 engendered a different product than one with 1.0 M HNO2. It was suspected that NO2- ions, formed at the cathode by reduction, may have an adverse effect on the oxygen content of the sample. This possibility was investigated and eliminated through the use of a solution of lead nitrate and copper nitrate as electrolyte, since Collat and Lingane[15] have shown that electrolytic reduction of nitrate ions proceeds all the way to NH4+ in the presence of Cu2+. No change in the active oxygen content of the samples produced was observed. Duisman and Giaque [10] also examined the effect of rotating on the anode at different speeds. It was observed that at high speeds the porosity of the sample was slightly decreased. The products, prepared at speeds higher than 100 ppm, all had essentially the same active oxygen content. Current density has no significant effect on the active oxygen content of the lead dioxide deposit. However, the samples prepared at low current densities had a more crystalline appearance and are generally of much better mechanical strength.The existence of the two polymorphs, a -and b -lead dioxide, has been studied in great detail[14]. The following methods have been used successfully for the production of the two polymorphs.1. a -Lead Dioxidea) Oxidation of yellow lead monoxide by a fused sodiumchlorate-sodium nitrate mixture[14]; b) Oxidation of sodium plumbite by chlorine dioxide[15]; c) Oxidation of lead acetate by ammonium persulfate[16]; d) Other methodsOther methods include alkaline formation of lead battery positive plates (Voss and Freundlich[17]) and electrooxidation of lead acetate in an alkaline solution (Zaslavskii[18]).2. b -Lead Dioxideb -Lead dioxide can be prepared by (i) acid formation of lead battery positive plates[13] or (ii) electrooxidation of lead perchlorate[14]. In the latter method lead monoxide (195g) was added to 500 ml of 2Mperchloric acid solution and a current of density 2.5mA cm-2 was passed.The deposit was removed, ground, andwashed with water.Another preparation (iii) iselectrooxidation of lead acetate in acid solution[14]. Lead acetate (100g) was dissolved in 0.5 M acetic acid solution. A platinum anode and lead cathode were suspended in the solution and a current of density 1.0 mA cm-2 was passed. The deposit was ground and washed with water.Reference(1) G.W.Vinal, Storage Batteries, Wiley, New York, 1965.(2) P.Ness, Rev. Pure Applied Chem., 12, 161 (1967).(3) C.k.Morehouse, R.Glicksman, Bull.Chem.Soc.Japan, 46,1462 (1958)(4) J.P.Hoare, The Electrochemistry of Oxygen, Instersicience, NewYork,1969(5) J. Burbank, A.C.Simon, Advan. Electrochem. Eng., 8, 157 (1971).(6) R. de Levie, Can.J. Chem., 6, 329 (1967).(7) N.V. Sidgwick, The Chemical Elements and Their Compounds, Oxford Univ. Press. London, 1950, p 118(8) J. A. Darbyshire, J. Chem. Soc., 134, 211 (1932).(9) W. B. White and R. Roy, J. Amer. Ceram. Soc., 47, 242 (1964)(10) J. A. Duisman and W. F. Giaque, J. Phys. Chem., 72, 562 (1968)(11) M. Fleischmann and H. R. Thirsk, J. Appl. Electrochem, 110, 688 (1963).(12) W. J. Hamere, J. Amer. Chem. Soc., 57, 9 (1935).(13) W. C. Vosburgh and D. N. Craig, ibid., 51, 2009 (1929).(14) N. E. Bagshaw, R. L. Clarke, and B. Galiwell, J. Appl. Chem., 16, 18 (1966).(15) N. E. Bagshqw and K. D. Wilson, Electrochim. Acta, 10, 876 (1965).(16) N. G. Bakhchisaraits yan E. and A. Dzhafarov, Nekot., et.al.,J.Colloid.Interface Sci.,10, 251,(1963)(17) N. G. Bakchisaraits, E., A. Dzhafqrov, and G. A. Kokarev, J.Inorg.& Nucl.Chem., 32, 243 (1961).(18) N.G. Bakchiraist; Yan E.and A. Dafrov, et.al.,Microchem. J., 17, 785 (1961)。