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非整数电荷态英文IntroductionIn the world of chemistry, atoms can exist in different electronic states or configurations. One of these states is known as non-integer or non-whole-number electronic charge state. In this article, we will discuss the concept of non-integer electronic charge state, its properties, and its importance in chemistry.Properties of non-integer electronic charge stateWhen an atom has a non-integer electronic charge state, it means that the number of electrons in the atom is not a whole number. This can occur in several ways. For example, an atom can gain or lose an electron fractionally, or it can obtain an electron from an external source that is not a whole number. In such cases, the electronic charge of the atom will be fractional. For instance, an atom with 6.5 electrons will have an electronic charge of -6.5.Non-integer electronic charge states are unique in that they can have fractional atomic radii and fractional oxidation states. This occurs because the behavior of electrons in non-integer charge states is difficult to predict. However, atomic radii and oxidation states are critical properties in chemistry, and understanding the fractional values in these properties is crucial for accurate chemical analysis.Applications of non-integer electronic charge stateNon-integer electronic charge state is not only important in theoretical aspects of chemistry, but it also has important practical applications. It is particularly useful inanalyzing oxidized metal ions in minerals and soils, determining the reactivity and corrosivity of chemicals, and predicting the behavior of dissolved organic matter in soils and water.For example, non-integer electronic charge state is used to determine the oxidation state of metal ions in minerals suchas pyrite, which contributes to the formation of acid mine drainage. It is also used to determine the reactivity of chemicals in industrial processes. In environmental chemistry, the study of fractional electron states is crucial in predicting the behavior of organic matter in soils and water, which influences nutrient dynamics and water quality.ConclusionNon-integer electronic charge states are a fascinating and important aspect of chemistry. They play a significant rolein determining atomic radii, oxidation states, and chemical behavior. Understanding non-integer electronic charge statesis critical to accurate chemical analysis and has important practical applications in various fields, including environmental, mineralogical, and industrial chemistry.。
附录A 外文翻译译文：非牛顿流体电学：综述3.在非牛顿流体电泳在第二节讨论了关于电渗流带电表面，如果我们通过想象改变参考系统，带电表面的流体应该是静止的，然后将带电面以速度大小相等但与以前面讨论的亥姆霍兹Smoluchowski的速度方向相反移动。
这种情况下有效地代表了电泳具有很薄的EDL的粒子在一个无限大的非运动牛顿流体范围[17,18,26,34] 。
显然，先前讨论电渗的亥姆霍兹Smoluchowski速度当然也可适用于分析在无限大非牛顿流体域具有薄EDL颗粒的电泳速度，仅仅与它的符号相反，并改变了充电通道壁与带电粒子的潜力。
事实上，支付给非牛顿液体粒子电泳最早的关注可以追溯到30年前Somlyody [ 68 ]提起的一项有关采用非牛顿液体以提供优越的阈值特性的电泳显示器的专利。
在1985年， Vidybida和Serikov [ 69 ]提出关于球形颗粒的非牛顿电泳研究第一个理论解决方案。
他们展示了一个粒子在非牛顿净电泳运动流体可通过以交替的电场来诱导一个有趣的且违反直觉的效果。
最近才被Hsu课题组填补这方面20年的研究空白。
在2003年，Lee[70]等人通过一个球形腔的低zeta电位假设封闭andweak施加电场分析了电泳刚性球形颗粒在非牛顿的Carreau流体的运动。
他们特别重视电泳球形粒子位于中心的空腔特征。
之后，该分析被扩展来研究电泳位于内侧的球面的任意位置的球形颗粒的腔体[71] 。
除了单个粒子电泳外， Hsu[72]等人假设粒子分散潜力在卡罗流体zeta进行了集中的电泳调查分析，并分析了由Lee[73]完成的其它任意潜力。
为了研究在边界上非牛顿流体电泳的影响，Lee[74]等人分析了电泳球状粒子在卡罗体液从带电荷到不带电荷的平面表面，发现平面表面的存在增强了剪切变稀效果，对电泳迁移率产生影响。
类似的分析后来由Hsu等 [75]进行了扩展。
为了更紧密地模拟真实的应用环境，Hsu等人[76]分析了球形粒子的电泳由一个圆柱形的微细界卡罗流体低zeta电位到弱外加电场的条件。
conductivities 电导率elemental semiconductor 元素半导体periodic table 元素周期表compound semiconductor 化合物半导体combinations 化合Amorphous 非晶polycrystalline多晶single crystal 单晶ordered region 有序化区域grains 晶粒grain boundaries 晶界periodic table 周期表inert elements 惰性元素valence electrons 价带电子positively charged 带正电ionic bond 离子键Atomic bonding 原子价键)colsed-valence energy shells 满价带能量壳层covalent bond 共价键lowest energy shell 最低能量壳层valence shell 价电子层thermal vibration 热振动thermal energy 热能lattice vibrations 晶格振动point defect 点缺陷lattice point 晶格点vacancy 空位interstitial 间隙line defect 线缺陷line dislocation 线位错interstitial impurities 间隙杂质substitutional impurities 替位杂质doping 掺杂Doping diffusion 杂质扩散ion implantation 离子注入Growth from melt 熔体法生长Czochralski method 丘克拉斯基法，提拉法seed 籽晶solidification 结晶solid-liquid interface 固液界面.Epitaxial Growth 外延生长single-crystal substrate 单晶衬底homoepitaxy 同质外延heteroepitaxy 异质外延ternary alloy 三元合金Principle of Quantum Mechanics 量子力学Energy Quanta 能量子monochromatic light 单色光photoelectric effect 光电效应incident intensity 入射光强度kinetic energy 动能limiting frequency 截止频率photon 光子work function 功函数Wave-Particle Duality Principle 波粒二象性matter waves 物质波particle-like behavior 粒子性wave-like properties 波动性electromagnetic waves 电磁波classical laws of physics 经典力学wave mechanics 波动力学wave theory 波动理论Schrödinger’s wave equation 薛定谔波动方程The one-electron atom 单电子原子，氢potential 势能principal quantum number 主量子数mass of the electron 电子质量bound 束缚nucleus 原子核quantized 量子化quantum numbers 量子数quantum state 量子态Pauli exclusion principle 泡利不相容原理discrete energy levels 分立能级energy level 能级outermost electrons 最外层电子band of allowed energies 允带band of forbidden energies 禁带allowed and forbidden bands 允带和禁带valence electrons 价带电子absolute zero 绝对零度)bandgap energy 带隙能量valence band 价带conduction band 导带forbidden energy band 禁带Carrier generation 载流子产生Carrier recombination 载流子复合Carrier transport 载流子输运intrinsic carrier concentration 本征载流子浓度free carriers 自由载流子intrinsic semiconductor 本征半导体Doping 掺杂majority carrier 多数载流子minority carrier 少数载流子electron hole pair 电子空穴对meta-stable state 亚稳态Radiative recombination 辐射复合Auger recombination 俄歇复合Light-emitting diodes发光二极管defects缺陷forbidden region 禁带区域heavily doped 重掺杂heavily excited重激发net movement 净流动net carrier flow 净载流子流动thermal velocity 热运动速度electric field 电场constant velocity 恒定速度acceleration 加速度Transport 输运drift transport漂移运动solar cells太阳能电池photodiodes 光电二极管bipolar junction transistors (BJTs) 双极晶体管depletion region耗尽区majority carrier 多子minority carrier 少子diffusion current 扩散电流drift current 漂移电流net current 净电流Forward Bias正向偏压Reverse Bias 反向偏压net electric field 净电场built-in field 内建电场minority carrier injection 少数载流子注入external circuit 外电路n-channel n沟four-terminal 四端MOS capacitor MOS电容gate 栅source 源drain 漏channel region 沟道区positive gate voltage 正栅压vertical electric field 垂直电场inversion layer 反型层channel region 沟道区drain-to-source voltage 漏源电压channel 沟道field-effect场效应transistor action晶体管效应n-channel MOSFET n沟MOSFET threshold voltage 阈值电压inversion layer 反型层drain current 漏电流gate voltages 栅压capacitor 电容器polycrystalline silicon 多晶硅parallel-plate capacitor 平行板电容器semiconductor substrate 半导体衬底) metal gate 金属栅accumulation layer of hole 空穴堆积层inversion layer of electrons 电子反型层NMOS devices NMOS器件n-channel enhancement mode MOSFET n沟道增强型MOSFETpositive gate voltage 正栅压electron inversion layer 电子反型层n-channel depletion mode MOSFET n沟道耗尽型MOSFET threshold voltage 阈值电压p-channel enhancement-mode MOSFET p沟增强型MOSFETp-channel depletion mode MOSFET p沟耗尽型MOSFET negative gate voltage 负栅压inversion layer of holes 空穴反型层channel stop 沟道截断active device region 有源器件区photoresist 光刻胶silicon dioxide 二氧化硅silicon nitride 氮化硅gate oxide 栅氧化物threshold voltage 阈值电压ion implantation 离子注入polysilicon layer 多晶硅层photolithography 光刻metallization 镀金属.complementary metal-oxide-semiconductor (CMOS) inverter 互补型金属氧化物半导体反相器p-well process p阱工艺p-channel MOSFET p沟MOSFETp well p阱potential 电势reverse biased 反向偏压的The integrated circuit IC, 集成电路interconnect lines 互连线chip 芯片gate insulator 栅绝缘层native oxide 天然氧化物diffusion coefficient 扩散系数quartz tube 石英管Impurity doping 杂质掺杂Diffusion 扩散ion implantation 离子注入epitaxial growth 外延生长infinite source 无限源limited source 有限源predeposition 预淀积drive-in diffusion 主扩散implant ions 注入离子photoresist 光刻胶oxides 氧化物Photomasks 光掩膜版Photolithography 光刻plasma 等离子体Plasma etching 等离子刻蚀cathode 阴极anode 阳极Metallization 镀电极Bonding 键合Packaging 封装vapor deposition technique 气相沉积技术。
编号：毕业设计(论文)外文翻译（原文）学院：国防生学院专业：机械设计制造及其自动化学生姓名：学号：指导教师单位：姓名：职称：2014年3 月9 日A METHODOLOGY FOR THE DESIGN OF EFFECTIVE COOLING SYSTEM IN INJECTION MOULDINGInt J Mater Form (2010) V ol. 3 Suppl 1:13– 16DOI10.1007/s12289-010-0695-2Springer-VerlagFrance2010ABSTRACTIn thermoplastic injection molding, part quality and cycle time depend strongly on the cooling stage. Numerous strategies have been investigated in order to determine the cooling conditions which minimize undesired defects such as war page and differential shrinkage. In this paper we propose a methodology for the optimal design of the cooling system. Based on geometrical analysis, the cooling line is defined by using conformal cooling concept. It defines the locations of the cooling channels. We only focus on the distribution and intensity of the fluid temperature along the cooling line which is here fixed. We formulate the determination of this temperature distribution, as the minimization of an objective function composed of two terms. It is shown how this two antagonist terms have to be weighted to make the best compromise. The expected result is an improvement of the part quality in terms of shrinkage and war page.KEYWORDS: Inverse problem；heat transfer；injection molding；Cooling design1.INTRODUCTIONIn the field of plastic industry, thermoplastic injection molding is widely used. The process is composed of four essential stages: mould cavity filling, melt packing, solidification of the part and ejection. Around seventy per cent of the total time of the process is dedicated to the cooling of the part. Moreover this phase impacts directly on the quality of the part [1] [2]. As a consequence, the part must be cooled as uniformly as possible so that undesired defects such as sink marks, warpage, shrinkage, thermal residual stresses are minimized. The most influent parameters to achieve these objectives are the cooling time, the number, the location and the size of the channels, the temperature of the coolant fluid and the heat transfer coefficient between the fluid and the inner surface of the channels. The cooling system design was primarily based on the experience of the designer but the development of new rapid prototyping process makes possible to manufacture very complex channel shapes what makesthis empirical former method inadequate. So the design of the cooling system must be formulated as an optimization problem.1.1 HEAT TRANSFER ANALYSISThe study of heat transfer conduction in injection tools is a non linear problem due to the dependence of parameters to the temperature. However thermo physical parameters of the mould such as thermal conductivity and heat capacity remain constant in the considered temperature range. In addition the effect of polymer crystallization is often neglected and thermal contact resistance between the mould and the part is considered more often as constant. The evolution of the temperature field is obtained by solving the F ourier’s equation with periodic boundary conditions. This evolution can be split in two parts: a cyclic part and an average transitory part. The cyclic part is often ignored because the depth of thermal penetration does not affect significantly the temperature field [3].Many authors used an average cyclic analysis which simplifies the calculus, but the fluctuations around the average can be comprised between 15% and 40% [3].The closer of the part the channels are, the higher the fluctuations around the average are. Hence in that configuration it becomes very important to model the transient heat transfer even in stationary periodic state. In this study, the periodic transient analysis of temperature will be preferred to the average cycle time analysis. It should be noticed that in practice the design of the cooling system is the last step for the tool design. Nevertheless cooling being of primary importance for the quality of the part, the thermal design should be one of the first stages of the design of the tools.1.2 OPTIMIZATION TECHNIQUES IN MOULDINGIn the literature, various optimization procedures have been used but all focused on the same objectives. Tang et al. [4] used an optimization process to obtain a uniform temperature distribution in the part which gives the smallest gradient and the minimal cooling time.Huang[5] tried to obtain uniform temperature distribution in the part and high production efficiencyi.e. a minimal cooling time. Lin [6] summarized the objectives of the mould designer in 3 facts. Cool the part the most uniformly, achieve a desired mould temperature so that the next part can be injected and minimize the cycle time.The optimal cooling system configuration is a compromise between uniformity and cycle time. Indeed the longer the distance between the mould surface cavity and the cooling channels is, the higher the uniformity of the temperature distribution will be [6]. Inversely, the shorter the distance is, the faster the heat is removed from the polymer. However non uniform temperatures at the mould surface can lead to defects in the part. The control parameters to getthese objectives are then the location and the size of the channels, the coolant fluid flow rate and the fluid temperature. Two kinds of methodology are employed. The first one consists in finding the optimal location of the channels in order to minimize an objective function [4] [7]. The second approach is based on a conformal cooling line.Lin [6] defines a cooling line representing the envelop of the part where the cooling channels are located. Optimal conditions (location on the cooling and size of the channels) are searched on this cooling line. Xu et al. [8] go further and cut the part in cooling cells and perform the optimization on each cooling cell.1.3 COMPUTATIONAL ALGORITHMSTo compute the solution, numerical methods are needed. The heat transfer analysis is performed either by boundary elements [7] or finite elements method [4].The main advantage of the first one is that the number of unknowns to be computed is lower than with finite elements. Only the boundaries of the problem are meshed hence the time spent to compute the solution is shorter than with finite elements. However this method only provides results on the boundaries of the problem. In this study a finite element method is preferred because temperatures history inside the part is needed to formulate the optimal problem. To compute optimal parameters which minimize the objective function Tang et al. [4] use the Powell’s conjugate direction search method. Mathey et al. [7] use the Sequential Quadratic Programming which is a method based on gradients. It can be found not only deterministic methods but also evolutionary methods.Huang et al. [5] use a genetic algorithm to reach the solution. This last kind of algorithm is very time consuming because it tries a lot of range of solution. In practice time spent for mould design must be minimized hence a deterministic method (conjugate gradient) which reaches an acceptable local solution more rapidly is preferred.2 METHODOLOGY2.1 GOALSThe methodology described in this paper is applied to optimize the cooling system design of a T-shaped part (Figure 1). This shape is encountered in many papers so comparison can easily be done in particularly with Tang et al. [4].Based on a morphological analysis of the part, two surfaces Γ1 and Γ3 are introduced respectively as the erosion and the dilation (cooling line) of the part (Figure 1). The boundary condition of the heat conduction problem along the cooling line Γ3 is a third kind conditionwith infinite temperatures fixed as fluid temperatures. The optimization consists in finding these fluid temperatures. Using a cooling line prevents to choose the number and size of cooling channels before optimization is carried out. This represents an important advantage in case of complex parts where the location of channels is not intuitive. The location of the erosion line in the part corresponds to the minimum solidified thickness of polymer at the end of cooling stage so that ejectors can remove the part from the mould without damages.Figure 1 : Half T-shaped geometry2.2 OBJECTIVE FUNCTIONIn cooling system optimization, the part quality should be of primarily importance. Because the minimum cooling time of the process is imposed by the thickness and the material properties of the part, it is important to reach the optimal quality in the given time. The fluid temperature impacts directly the temperature of the mould and the part, and for turbulent fluid flow the only control parameter is the cooling fluid temperature. In the following, the parameter to be optimized is the fluid temperature and the determination of the optimal distribution around the part is formulated as the minimization of an objective function S composed of two terms computed at the end of the cooling period (Equation (1)). The goal of the first term S1 is to reach a temperature level along the erosion of the part.3 CONCLUSIONSIn this paper, an optimization method was developed to determine the temperature distribution on a cooling line to obtain a uniform temperature field in the part which leads to the smallest gradient and the minimal cooling time. The methodology was compared with those found in the literature and showed its efficiency and benefits. Notably it does not require specifying a priori the number of cooling channels. Further work will consist in deciding a posteriori the minimal number of channels needed to match the solution given by the optimal fluid temperature profile.An integrated framework for die and mold cost estimation using design features and tooling parametersReceived: 5 August 2003 / Accepted: 6 January 2004 / Published online: 2 February 2005Springer-Vela London Limited 2005AbstractTooling is an essential element of near net shape manufacturing processes such as injection molding and die casting, where it may account for over 25% of the total product cost and development time, especially when order quantity is small. Development of rapid and low cost tooling, combined with a scientist approach to mold cost estimation and control, has therefore become essential. This paper presents an integrated methodology for die and mold cost estimation, based on the concept of cost drivers and cost moodier. Cost drivers include the geometric features of cavity and core, handled by analytical cost estimation approach to estimate the basic mold cost. Cost moodier include tooling parameters such as parting line, presence of side core(s), surface texture, ejector mechanism and die material, contributing to the total mold cost. The methodology has been implemented and tested using 13 industrial examples. The average deviation was 0.40%. The model is edible and can be easily implemented for estimating the cost of a variety of molds and dies by customizing the cost moodier using quality function deployment approach, which is also described in this paper. Keywords：Cost estimation; Die casting; Injection molding; Quality function deployment。
Chapter 2:Source transformation 电源变换A voltage in series with a resister 电压串联电阻A current source in parallel with a resister 电流并联电阻Bilateral 双边的Superposition 叠加Chapter 3:Cumbersome 麻烦的，笨重的Simultaneous 同时发生的Terminology 术语Planar 二维的Ammeter 安培表Fictitious 编造的Manipulation 操纵（作）Pertinent 相关的（pertain v.）Chapter 4:The operational amplifier 运算放大器Diode 二极管Transistor 晶体管Penchant 喜好Judicious 明智的Invoke 求助于Replica 复制品Comparator 比较器Chapter 5:Charge in motion 运动中的电荷Quantitative relationship 定量关系Insulator 绝缘体Dielectric material 电介质材料Time-varying electric field 时变电场Displacement current 位移电流Conduction current 传导电流Passive element 无源元件Be measured in 单位是Graphically 图形上Coiled wire 线圈Short current 短路Change instantaneously 跃变Arcing 电弧Differential 微分Algebraic 代数的Power is the time rate of expending energy 功率是消耗能量对时间的倒数Letter C 字母CConductive plate 金属板Natural response 固有响应；零输入响应Step response 阶跃响应；零状态响应Coefficient 系数First-order circuit 一阶电路Exponent 指数Reciprocal 倒数Transient response 瞬间响应Steady-state response 稳态响应Oscilloscope 示波器Analogous 类比的Exponential decay of the initial voltage 初始电压的指数衰减The rate of decay 衰减率Elementary calculus 基本微积分Chapter 6:Oscillation 等幅震荡Derivation 衍生物Characteristic roots 特征根Resonant radian frequency 谐振角频率Dimension 量纲Complex frequency 复频率Over damp 过阻尼Under damp 欠阻尼Critically damp 临界阻尼Chapter 7:Sinusoidal 正弦的Allude to 提及的Distribution circuit 配线电路Spell out 详述Realm 领域Interval 间隔时间Reciprocal 相互的Amplitude 波幅Phase angle 相位角Trigonometry 平面三角学Rms value 均方根Dc voltage 直流电压Transient component 暂态分量Infinitesimal 无穷小Forfeit 丧失Phasor 向量Argument 括号Notation 符号Phasor transform 向量变换Time domain 时域Complex-number domain 复数域Boldface letter 黑体字Polar form 极坐标Postulate 假设Subscript 下脚标Nonsensical 无意义的Nomenclature 术语，命名法Passive elements 无源元件Active elements 有源元件Impedance 阻抗Reactance 电抗Instantaneous power 瞬时功率Average power 有功功率；平均功率Reactive power 无功功率Apparent power 视在功率Chapter 8：Via 通过A lagB by 120° A滞后B120°A leadB by 120°Phase sequence 相序Periphery 圆柱体表面Stator 定子Winding 线圈Generator 发电机Line-to-line voltage 线电压Line-to-neutral voltage 相电压Chapter 9:Reactive components 动态元件Filter 滤波器Audible 听得见的Frequency-selective circuits 选频电路Attenuate 衰减Graphic equalizer 图式均衡器Low pass filters 低通high pass filters 高通Band pass filters 带通Band reject filters 带阻滤波器Preliminary 初步Passband 通带Stopband 阻带Frequency response plot 频率响应曲线Magnitude plot 幅频特性曲线Phase angle plot 相频特性曲线Cutoff frequency 截止频率--------------from 张一超。
Absorption coefficient 吸收常数：垂直于光束方向的水层元内单位厚度的吸收量Acceptor impurity 受主杂质：lll族杂质在Si、Ge中能够接受电子而产生导电空穴并形成负电中心acceptor ionization 受主电离：空穴挣脱受主杂质束缚的过程Antiferromagnetism 反铁磁性：材料中相邻原子或离子的磁矩作反向平行排列使得总磁矩为零的性质。
Birefringence 双折射：光入射到各向异性的晶体分解为两束光而沿不同方向折射的现象Conduction bands 导带：一部分被电子填充，另一部分能级空着的允带Crystallization 结晶：液态金属转变为固态金属形成晶体的过程Current density 电流密度：描述电路中某点电流强弱和流动方向的物理量currie temperature 居里温度：自发极化急剧消失的温度Diamagnetism 抗磁性：外加磁场使材料中电子轨道运动发生变化，感应出很小的磁矩且该磁矩与外磁场方向相反的性质Dielectric breakdown 介电体击穿：介电体在高电场下电流急剧增大，并在某一电场强度下完全丧失绝缘性能的现象dielectric loss 介电损耗：将电介质在电场作用下，单位时间内消耗的电能Dielectric medium 电介质：能够被电极化的介质Dipolar turning polarization 偶极子转向极化：极性介电体的分子偶极矩在外电场作用下，沿外施电场方向转向而产生宏观偶极矩的极化Disperse phase 分散相：被分散的物质Dispersion of refractive index 折射率的色散：材料的折射率m随入射光频率减小而减小的现象Donor impurity level 施主能级：将被施主杂质束缚的电子能量状态称施主能级Donor impurity 施主杂质：V族杂志在硅、锗中电力时，能够释放电子而产生导电导子并形成整点中心，称其位施主杂质或n型杂志donor ionization 施主电离：施主杂质释放电子的过程Electirical polarization 电子极化：电场作用下，构成原子外围的电子云相对原子核发生位移形成的极化Electrical field 电场：由电荷及变化磁场周围空间里存在的一种特殊物质Electrical resistivity 电阻率：某种材料制成的长1米、横截面积是1平方米的在常温下（20℃时）导线的电阻，叫做这种材料的电阻率。
minerals 英文解释Minerals: Definition, Classification, and Importance.Minerals are naturally occurring solid substances that have a defined chemical composition and an ordered internal structure. Unlike organic matter, which is composed of carbon-based compounds and often has a living origin, minerals are inorganic and do not result from the activity of living organisms. The study of minerals is known as mineralogy, and it is a branch of geology that deals with the formation, composition, distribution, and properties of minerals.Classification of Minerals.Minerals can be classified based on their chemical composition, physical properties, and mode of formation. Based on their chemical composition, minerals are primarily divided into two categories: silicates and non-silicates. Silicates are the most abundant group of minerals and arecharacterized by the presence of silicon and oxygen atomsin their structure. Non-silicate minerals, on the other hand, do not contain silicon and are further classified based on their main constituent elements.Properties of Minerals.Minerals exhibit a wide range of physical properties, including color, luster, hardness, cleavage, and fracture. Color, for instance, can range from transparent to opaque, and it is often influenced by the presence of impurities or trace elements within the mineral. Luster refers to the way light reflects from the mineral's surface, and it can be metallic, vitreous (glassy), or dull. Hardness is measured using the Mohs scale, which ranges from 1 (softest) to 10 (hardest), with diamond being the hardest naturally occurring material. Minerals also exhibit specific cleavage or fracture patterns when they are broken, which is a diagnostic feature for identifying different minerals.Formation of Minerals.Minerals form through a variety of geological processes, including crystallization from magma or dissolved solutions, precipitation from aqueous solutions, and metasomatic replacement of pre-existing rocks. Magmatic minerals crystallize directly from molten magma as it cools and solidifies. Hydrothermal minerals, on the other hand, form from hot water solutions that can be associated withvolcanic activity or deep-seated geothermal systems. Sedimentary minerals are deposited from aqueous solutions carried by wind, water, or ice, and they often form layers within sedimentary rocks. Metasomatic replacement occurs when fluids interact with pre-existing rocks, causing the rocks to dissolve and be replaced by new minerals.Importance of Minerals.Minerals play a crucial role in both the natural environment and human society. In the natural environment, minerals are essential for the structure and function of rocks and soils. They also influence the cycling ofnutrients and trace elements within ecosystems, and theyare involved in many geochemical processes that shape theEarth's crust.For humans, minerals are essential for maintaining good health and normal bodily functions. Minerals such as calcium, phosphorus, and magnesium are integral components of bones and teeth, while iron is crucial for the transport of oxygen in the blood. Other minerals, such as potassium, sodium, and chloride, are important for regulating fluid balance and nerve conduction within the body. Minerals are obtained primarily through the diet, and they are present in a wide range of foods, including fruits, vegetables, grains, and dairy products.Economic Importance of Minerals.In addition to their importance in maintaining human health, minerals are also crucial for the global economy. Many minerals are mined and processed for use in a wide range of industries, including construction, electronics, automotive manufacturing, and more. Metals such as iron, copper, and aluminum are essential for the production of steel, wiring, and packaging materials, respectively.Precious metals like gold and platinum are used in jewelry and high-tech applications due to their unique physical and chemical properties. Industrial minerals like sand, gravel, and limestone are also widely used in construction and road building.The extraction and use of minerals can have environmental impacts, including land degradation, water pollution, and social and economic disparities between mining communities and the rest of society. Therefore, itis crucial to ensure that mining activities are conducted responsibly and with consideration for the long-term sustainability of both the environment and local communities.In conclusion, minerals are an integral part of our lives, playing crucial roles in the natural environment, human health, and the global economy. Understanding the formation, properties, and uses of minerals is essentialfor appreciating their importance and for ensuring that we make responsible use of these natural resources.。
a r X i v :c o n d -m a t /0005011v 1 [c o n d -m a t .s t r -e l ] 30 A p r 2000Non-linear conduction in charge-ordered Pr 0.63Ca 0.37MnO 3:Effect of magnetic fieldsAyan Guha and A.K.RaychaudhuriDepartment of Physics,Indian Institute of Science,Bangalore 560012,IndiaA.R.Raju and C.N.R.RaoChemistry and Physics of Materials Unit,Jawaharlal Nehru Center for Advanced Scientific Research,Jakkur,P.O.,Bangalore 560064,India Non-linear conduction in a single crystal of charge-ordered Pr 0.63Ca 0.37MnO 3has been investigated in an applied magnetic field.In zero field,the non-linear conduction,which starts at T <T CO can give rise to a region of negative differential resistance (NDR)which shows up below the N´e el temperature.Application of a magnetic field inhibits the appearance of NDR and makes the non-linear conduction strongly hysteritic on cycling of the bias current.This is most severe in the temperature range where the charge ordered state melts in an applied magnetic field.Our experiment strongly suggests that application of a magnetic field in the CO regime causes a coexistance two phases.Rare earth manganites with general chemical formula Re 1−x Ae x MnO 3have attracted current interest because of rich variety of phenomena like colossal magnetoresis-tance (CMR)and charge ordering (CO)[1,2].For certain values of x,close to 0.5,these compounds undergo a first order charge-ordering (CO)transition where the Mn 3+and Mn 4+species arrange themselves alternately in the lattice.This transition leading to charge localization oc-curs on cooling below a temperature T CO ,refrerred to as the charge ordering temperature.Orbital ordering also accompanies the charge ordering and a long range AFM order sets in at lower temperature (T N <T CO ).(For some systems,like Nd 0.5Sr 0.5MnO 3T N =T CO [1].)The system studied by us,Pr 1−x Ca x MnO 3(x =0.37),hap-pens to be an unique charge ordered system in which the charge ordered state remains insulating for all values of x due to its low tolerance factor.It shows both charge and orbital order below T CO =240K and the AFM order occurs at T N =175K.A fascinating aspect of the charge ordered/orbital or-dered state is that the charge ordered insulator (COI)phase is unstable to a number of external perturbations (like magnetic field [1],electric field [3,4],optical radi-ation [5,6]etc.)and can be melted by them.An ap-plication of the magnetic field leads to a collapse of the charge ordering gap(∆CO )and there is an insulator -metal transition (melting )of the COI state to an FMM state [7,8].Optical radiation seems to create conducting filaments which at low temperatures leads to non-lineartransport and even at much lower temperatures a regionof negative differential resistance (with V ∼I −n with 0<n <1)[5,6].Application of an electric field also gives riseto non-linear conduction,which seems to have a thresh-old field associated with it and a broad band noise ofsubstantial magnitude with a power spectrum ∼1/fre-quency [9].A schematic of the phase diagram of the material inthe H-T plane studied is shown in the inset of figure 1.In a given field H,the COI state melts into the FMMphase at the melting temperature T MH (marked in the figure).We designate the region T MH <T <T CO with H =0(shaded in inset)as the ”mixed charge ordered”(MCO)region to distinguish it from the COI (H =0,T <T CO )state as well as from the FMM state (H =0,T <T MH ).We call it MCO region because we will show below that thie region has co-existence of two phases.In this paper we address the specific question of the nature of non-linear electronic transport in the COI as well as MCO region for T <T MH ).We have performed experi-ments along a constant H line.In particular,we observe that in the COI state,transport is strongly non-linear with a negative differential resistance (NDR)developing for T <T N while in the MCO state,the NDR is strongly inhibited.In addition,in the MCO state there is a large hysteresis in the I-V characteristics seen on cycling of the bias current.We ascribe this to creation of a coexisting two phase region in the mixed state.(Hysteresis seen in the I-V curve on cycling the bias current is distinct from the hysteresis in resistivity seen on H field cycling in most past experiments)Our sample was a (4X 2X 0.3mm 3)single crystal of Pr 0.63Ca 0.37MnO 3grown by the floating zone technique.Four linear contact pads of Ag-In alloy was soldered on to the sample in linear four-probe configuration with sep-aration ≈0.25mm.I-V data were taken with current bi-asing and with a temperature control better than 10mK.To avoid any memory effects,the sample was heated well above T CO ,before recording the I-V data at each temper-ature and magnetic field.We have also measured elec-trical noise by digitizing the voltage across the sample voltage probes.The power spectrum was obtained by fourier transform of the time autocorrelation function of the voltage after subtracting out the mean.The magnetic field measurements were done using cryogen-free super-conducting magnet capable of producing field upto 15T.In this communication,to limit the scope of data being presented,we report data only for a field of 8T,which in the temparature range of investigation encompasses allthe phases that we need to study.Fig.1shows the resistivity(ρ)as a function of tem-perature for various magneticfields.For H=0,T CO≈240K.In afield of8T,the T CO≈210K and the CO state completely melts to the FMM state at80K.We identify this temperature as T MH for8Tfield.A magneticfield of12T arrests the formation of CO state and the sam-ple remains metallic at all temperatures.The observed data are in agreement with previous studies done on the Pr1−x Ca x MnO3system[7].[Note:Magnetic suscepti-bility shows a transition near T≈240K T N≈175K.] Fig.2shows the I-V characteristics at different tempera-tures in zero magneticfield.The I-V characteristics are linear for T>260K(>T CO)and at all T<T CO(i.e,in the COI state),non-linear conduction is observed.One can identify a threshold electricfield or a current density beyond which the conduction is strongly non-linear as reported earlier infilms of Nd0.5Ca0.5MnO3[9].In the inset offig.2,we show the noise power measured at6Hz as a function of biasing current I.At the onset of the non-linear conduction the noise increases rather rapidly.The noise has a1/f character for0.02Hz<f<20Hz.Ap-pearance of a strong noise component is a characteristics of the melting process.At T<170K,a new component gets added to the non-linearity and a region of negative differential resistance (dV/dI<0)is observed when the bias current I exceeds a current threshold(I T H).I T H decreases as T decreases and at T=85K,I T H≈1.2mA corresponding to a cur-rent density≈0.5A/cm2.In the region of negative dif-ferential resistance(NDR),for I>I T H,V∝I−n,where0 <n<1.The I-V characteristics are symmetric and ex-hibits no hysteresis on current cycling except for T close to T co.The observed data are highly reproducible.In-terestingly,there are several similarities of NDR state created by current and that created by optical radiation using a laser[5].Wefind that the exponent n,which is a measure of the NDR(dlnV/dlnI=-n),has a strong temperature dependence.Infig.3we show n as a func-tion of temperature T scaled by T N.Wefind that n→0as T/T N→1and for T/T N≫1,n→constant(≈0.5).A likely explanation for occurence of NDR can be that for I>I T H metallicfilaments open up.These filaments being of lower resistance will provide parallel paths of conduction.This extra current path will de-crease the voltage drop across the sample for a given current.As the current increases presumably more such channels open up leading up to a further decrease in V. This will manifest itself in the I-V curve with a region of NDR.Non-linear conduction can also occur due to de-pinning of CO domains above a threshold appliedfield as has been reported earlier[9].But in the region of NDR, we assume conduction through metallicfilaments to be the dominant mechanism for non-linear conduction.The formation of the conductingfilament is not a breakdown as the I-V curve is reproducible on cycling.A similar mechanism is proposed for optically produced NDR[6]. In an optically melted CO state in the NDR regime,I∝V−n with n≈2/3at T=10K[6].Given the similarity, it is expected that both have the same origin.We have measured the temperature rise of the sam-ple with respect to the base(∆T)by attaching directly a thermometer to the sample.∆T≤20K at the lowest tem-perature(≈80K)and at the highest power dissipation level(0.1W).At150K,∆<10K and its is negligible for T≥180K.The power dissipation level where the NDR sets in at the lowest temperature leads to a∆T≈5K. We also investigated whether the NDR is caused by this heating effect and rule out heating as the cause for the NDR.However,the heating can have some influence on the value of n at the highest measuring current.It appears that a strong correlation exists between the onset of the NDR regime and the magnetic order at T N .We illustrate this infigure3where we plot the temper-ature dependence of the intensity of the(0.5.0.5.0)line as obtained from the neutron diffraction[10]in a sample of Pr0.65Ca0.35MnO3.The temperature dependence of the intensity of this line is a measure of the growth of the AFM order below T N.It is clearly seen from thefigure that not only n→0at T=T N,it also follows a tem-perature dependence which closely matches that of the growth of the AFM order as observed through neutron diffraction.There may be two likely reasons for the ap-pearance of NDR below T N.One reason can be that for T<T N there may be incommensurate to commensurate transition of the CO or orbital order as has been reported in a closely related composition Pr0.5Ca0.5MnO3[11]. The incommensuration which is due to disorder in orbital ordering can inhibit formatiom of such conductingfila-ments as are needed for the NDR.Alternatively,the AFM order in these materials being of pseudo-CE type[12], there is a FM coupling between the planes which contain zig-zag AFM chains.It may be that below T N,this inter-plane FM coupling enhances the formation of the metallic filaments which can be made up of FMM phases.If the later hypothesis is true we will not see formation of NDR region in CO systems with CE-type AFM order which has only AFM coupling between planes.Figure4shows the I-V characteristics at different tem-peratures in a8T magneticfield.In the MCO state,the non-linear conduction persists and is qualitatively similar to that found in COI.For both T>T CO and T<T MH the I-V behaviour is linear,but the two states haveρdiffering by two orders of magnitude.(All the data were taken afterfield cooling(FC)in H=8T from T=300K. At each temperature,the sample was freshly prepared as a FC sample after warming it upto room temperature to avoid any memory effect.)There is a distinct memory of the previously appliedfield when thefield is changed in the COI state and on warming up beyond T CO one can erase the memory.Experiments were also carried out under zero-field cooled(ZFC)condition.The I-V charac-teristics for both FC and ZFC are qualitatively similar,Chemistry,JNCASR,forfinancial support. and the ZFC curve consistently showing higher V(fora given I)than the corresponding FC curve at each T.Given the limited scope of this paper we donot discussthe details here.The inset offigure4shows a comparison of the I-Vcurves of the COI and the MCO states at a representa-tive temperature.The COI and the MCO state differsignificantly in two aspects,there is no NDR at any tem-perature in the MCO state at8T and there is stronghysteresis in the I-V curve in the MCO region.An important observation of this investigation is thatthe melting of the CO state either by temperature(T≈T CO)or by a magneticfield is accompanied bystrong hysteresis behaviour in the I-V curve(i.e,the I-Vcurves do not follow each other during current rampingup and down the cycle.This is different from the hys-teresis seen on H cycling).This can be seen infigures4and5.The hysteresis does not depend on the speed withwhich the current is ramped up and down.Typically inour experiment one cycle is taken over40minutes.Thearea under the hysteresis curve is defined as the hatchedregion infigure5.We plot the area under the hystere-sis curve as a function of T in the inset offig5.It isclearly seen that in the COI state,the hysteresis is ob-served only for∆T≈10K below T CO.In contrast,inthe MCO state,hysteresis persists over an extensive tem-perature range above T MH.In the inset(b)offig.5,weshow an example of the hysteresis in the MCO state asT→T MH from above.The appearance of hysteresis in the I-V curves canbe interpreted as due to the coexistance of two phasesin the MCO region.There is evidence of such co-existing phases in the TEM data taken near T CO in(La,Ca)MnO3and(Pr,Ca)MnO3systems near the melt-ing transition(T≈T co)[13].In this material under study,it has been seen that the ferromagnetic spin correlationspersist below T CO[10].This is stabilized by the appliedfield and thus can be the nucleus of the FMM phase.Inthe MCO state these nuclei get stabilized on cooling andthen grow as the second phase.Eventually as T→T MH,the MCO state collapses to the FMM phase.Existenceof such coexisting phases will prevent the formation ofthe metallicfilaments needed for the occurence of NDR.As a result the NDR will be strongly suppressed in thisregion.To summarize,we have carried out a systematic in-vestigation of non-linear transport in a CO system in amagneticfield.Wefind that a negative differential re-sistance region shows up below T N which is inhibitedby application of a magneticfield.In the region T co<T<T MH,application of a magneticfield creates a re-gion of coexisting phases leading to a strong hystereticI-V curve which become substantial in the temperatureregions close to T co and T MH.A.Guha thanks the CSIR Center of Excellence inFIGURE CAPTIONS(1)FIG.1.Resistivity as a function of T in different magneticfields for the sample Pr0.63Ca0.37MnO3.The inset shows the schematic phase diagram.(2)FIG.2.The I-V curves showing non-linear conduc-tion and negative differential resistance.The inset shows the appearance of large noise at the onset of nonlinear conduction.(3)FIG.3.Temperature dependence of the exponent n.The line shows the temperature dependence of the in-tensity of the(1/2,0/1/2)line obtained from the neutron experiment[10].(4)FIG.4.The non-linear transport in a magnetic field of8T.The inset shows a comparison of the I-V data at T=90K in zerofield and in H=8T.(5)FIG5.Hysteresis observed in the I-V curves on cycling of the bias current.The inset(a)shows the tem-perature dependence of the area under hysteresis close to T co.The inset(b)shows the hysteresis in I-V curve in a magneticfield.。
