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介绍非金属的英语作文英文回答：Non-metals are a type of chemical element that lacksthe properties of metals. They are generally poorconductors of heat and electricity, and they do not exhibit the luster or malleability that is characteristic of metals. Non-metals are typically gases or solids at room temperature, and they are more reactive than metals.Some of the most common non-metals include hydrogen, oxygen, nitrogen, and chlorine. Hydrogen and oxygen are gases that make up the majority of the Earth's atmosphere. Nitrogen is a gas that is essential for plant growth, and chlorine is a gas that is used in the production of bleach and other chemicals.Non-metals play an important role in many chemical reactions. They are often used as oxidizing agents,reducing agents, or catalysts. Oxidizing agents aresubstances that cause other substances to lose electrons, while reducing agents are substances that cause other substances to gain electrons. Catalysts are substances that speed up chemical reactions without being consumed.Non-metals are also used in a variety of industrial applications. For example, hydrogen is used in the production of fertilizers and plastics, oxygen is used in the production of steel and glass, and nitrogen is used in the production of fertilizers and explosives.中文回答：非金属是指不具有金属特性的化学元素。
回收贵金属的利弊英语作文Pros and Cons of Recycling Precious Metals。
Recycling precious metals has become a popular way tonot only reduce waste but also to recover valuable resources. However, like any other practice, there are both advantages and disadvantages to consider. In this essay, we will explore the pros and cons of recycling precious metals.Pros:1. Environmental Benefits: One of the most significant advantages of recycling precious metals is the positive impact it has on the environment. By reusing these materials, we can reduce the need for mining and extraction, which can be harmful to the environment. Additionally, recycling precious metals reduces the amount of waste that ends up in landfills, further reducing the environmental impact.2. Conservation of Resources: Precious metals arefinite resources, and recycling them allows us to conserve these valuable materials for future generations. By reusing and repurposing these metals, we can extend their lifespan and reduce the need for new mining and extraction.3. Economic Benefits: Recycling precious metals can also have economic benefits. By recovering and reusing these materials, we can reduce the demand for newly mined metals, which can help stabilize prices. Additionally, recycling can create jobs in the recycling and refining industries, contributing to the economy.4. Energy Savings: Recycling precious metals requires less energy than mining and refining new materials. This can lead to significant energy savings and reduced greenhouse gas emissions, further benefiting the environment.Cons:1. Cost and Complexity: While recycling precious metalscan be beneficial, it is also a complex and costly process. Recovering and refining these materials requiresspecialized equipment and expertise, which can be expensive. Additionally, the process of separating and purifying the metals can be complicated and time-consuming.2. Contamination: Precious metals can become contaminated during the recycling process, reducing their purity and value. Contamination can occur from impuritiesin the materials being recycled or from the use of improper recycling techniques. This can make it more difficult to reuse the metals in high-value applications.3. Limited Supply: While recycling can help conserve precious metals, it is not a limitless source. Eventually, the supply of recycled metals may not be enough to meet demand, leading to the need for new mining and extraction.4. Environmental Impact: While recycling preciousmetals can have environmental benefits, the process itself can also have negative environmental impacts. The use of chemicals and the generation of waste during the refiningprocess can contribute to pollution and environmental degradation.In conclusion, recycling precious metals has both advantages and disadvantages. While it can have significant environmental and economic benefits, it also comes with costs and complexities. As the demand for these valuable resources continues to grow, it is important to carefully consider the pros and cons of recycling precious metals and work towards finding sustainable solutions for their recovery and reuse.。
专八作文垃圾回收Every year, millions of tons of waste are generated worldwide, and much of this waste ends up in landfills, causing pollution and environmental damage.每年，全球产生数百万吨废物，其中大部分废物最终被填埋，导致污染和环境破坏。
One way to address this issue is through the recycling of materials such as paper, glass, plastic, and metal. Recycling helps reduce the amount of waste that goes to landfills and conserves natural resources.解决这个问题的一个方法是通过回收纸张、玻璃、塑料和金属等材料。
回收有助于减少填埋的废物量，并保护自然资源。
However, despite the environmental benefits of recycling, many people still do not fully participate in recycling efforts. Some people may lack access to recycling facilities, while others may not understand the importance of recycling or may simply not care.然而，尽管回收的环保好处，许多人仍然不完全参与回收工作。
一些人可能无法接触到回收设施，而其他人可能不了解回收的重要性，或者根本不在乎。
Furthermore, the process of recycling can be complex and require effort, which may discourage some individuals from actively participating in recycling programs. Sorting and cleaning recyclables, transporting them to recycling centers, and ensuring that items are properly recycled can be time-consuming and inconvenient.此外，回收的过程可能会很复杂，并需要付出努力，这可能会阻止一些人积极参与回收计划。
无机非金属材料英语作文1. Non-metallic materials are everywhere in our daily lives. From plastic bottles to ceramic dishes, these materials play a crucial role in shaping our modern world.2. Unlike metals, non-metallic materials do not conduct electricity. This property makes them ideal for use in electrical insulation, such as in the coating of wires and cables.3. Many non-metallic materials are transparent, allowing light to pass through them. This makes themperfect for use in windows, eyeglasses, and even smartphone screens.4. Non-metallic materials are also known for their high resistance to corrosion. This makes them suitable for usein outdoor structures, such as bridges and buildings, where exposure to the elements is inevitable.5. In addition to their practical applications, non-metallic materials are also valued for their aesthetic qualities. For example, ceramics are often used in decorative art and pottery due to their unique colors and textures.6. The versatility of non-metallic materials is truly remarkable. From the flexibility of rubber to the hardness of diamond, these materials come in a wide range of forms and properties, making them indispensable in various industries.。
第一课It is known that metals are very important in our life. Metals have the greatest importance for industry. All machines and other engineering constructions have metal parts; some of them consist only of metal parts.众所周知，金属在我们的生活中是非常重要的，金属对于工业而言是有巨大的重要性，所有机器和其他工程构造都有金属零部件，其中一些还只能由金属组成。
There are two large groups of metals:1) Simple metal- more or less pure chemical elements2) Alloys- materials consisting of a simple metal combined with some other elements.有两大类金属：（1）纯金属——或多或少的金属元素（2）合金——组成纯金属的原料结合其他元素。
About two thirds of all elements found in the earth are metals, but not all metals may be used in industry. Those metals which are used in industry are called engineering metals. The most important engineering metal is iron, which in the form of alloys with carbon and other elements, finds greater use than any other metal. Metals consisting of iron combined with some other elements are known as ferrous metals; all the other metals are called nonferrous metals. The most important nonferrous metal are copper, aluminum, lead, zinc, tin, but all these metals are used much less than ferrous metals, because the ferrous metals are much cheaper.在地球上发现的所有元素中，大约三分之二是金属元素，但是并不是所有的金属都能够用于工业上。
八年级英语环保措施单选题80题(含答案)1.We should use ______ bags instead of plastic ones.A.paperB.glassC.metalD.wood答案：A。
解析：环保活动中提倡使用纸袋代替塑料袋。
选项B 玻璃材质的袋子不常见；选项 C 金属材质的袋子不适合日常使用；选项D 木质袋子也不常用。
2.For saving energy, we can turn off ______ when not in use.A.lightsputersC.televisionsD.all of the above答案：D。
解析：灯、电脑和电视在不使用的时候都可以关闭以节约能源。
3.______ can be recycled to make new products.A.NewspapersB.ClothesC.Food wasteD.Dirty water答案：A。
解析：报纸可以回收利用制作新产品。
衣服通常有其他处理方式但不是回收制作新产品；食物垃圾和脏水不能回收制作新产品。
4.One way to protect the environment is to plant more ______.A.flowersB.treesC.grassD.weeds答案：B。
解析：种树可以保护环境。
花、草也有一定作用但不如树的作用明显；杂草不是用来保护环境的。
5.______ pollution is a big problem for the environment.A.AirB.WaterC.NoiseD.All of the above答案：D。
解析：空气污染、水污染和噪音污染都是环境面临的大问题。
6.We can use ______ to reduce waste.A.reusable containersB.single-use cupsC.plastic forksD.paper napkins答案：A。
介绍非金属元素英语作文Non-metal elements are a diverse group of elements that have distinct properties and characteristics. They can be found in various forms and are essential for our daily lives. Let's explore some of these fascinating non-metal elements.First up, we have hydrogen. It is the lightest and most abundant element in the universe. Hydrogen is highly flammable and is commonly used as a fuel source for rockets and in the production of ammonia. It is also used in the petroleum industry to remove impurities from crude oil and in the production of margarine.Next, we have carbon. It is a versatile element that forms the basis of all organic compounds. Carbon can exist in different forms, such as diamond, graphite, and coal. Diamonds are known for their hardness and are used in jewelry. Graphite, on the other hand, is a soft andslippery material that is used in pencils and as alubricant.Moving on, we come to nitrogen. It is an essential element for all living organisms as it is a key component of proteins and nucleic acids. Nitrogen gas makes up about 78% of the Earth's atmosphere and is used in various industries, such as the production of fertilizers, explosives, and as a coolant in the food industry.Another interesting non-metal element is sulfur. It is known for its distinctive smell and yellow color. Sulfur is used in the production of sulfuric acid, which is widely used in the chemical industry. It is also used in the manufacturing of rubber, detergents, and fertilizers.Phosphorus is another essential non-metal element. It is found in our bones and teeth and is crucial for energy transfer in our cells. Phosphorus is used in the production of fertilizers, detergents, and matches. It is also an important component in the manufacturing of fireworks.Lastly, we have chlorine. It is a highly reactive non-metal element that is commonly used as a disinfectant in swimming pools and drinking water. Chlorine is also used in the production of PVC, a versatile plastic used in various applications such as pipes, window frames, and flooring.In conclusion, non-metal elements play a crucial role in our daily lives. From hydrogen and carbon to nitrogen, sulfur, phosphorus, and chlorine, each element has its own unique properties and applications. Understanding these elements helps us appreciate the diversity and importance of non-metals in our world.。
U1 How to be happy1、吵闹的邻居的确对我们家庭不和有很大影响。
Noisy neighbors are one of the major causes of domestic upset.2、在职场上，如果一个同事对我们表示威吓的话，会造成难以言表的抑郁情绪。
A colleague at work who bullies or dismisses us creates untold wretchedness.3、我们不可能适应这种敌对关系，这种不良的人际关系会损害身心健康。
We can never fully adapt to hostile relationships, which inevitably damage our wellbeing.4、如果这种坏情绪长时间留在人们的心里，会让人陷入无法解决的恶性心理困境。
If this bad mood stays inside our mind, it will lead us to an unresolved destructive depression.5、我们不应当回避这些问题，而是要正确面对它们。
We should not avoid these problems but face them instead.U21、随着大量市民被迫迁到遥远的效外，汽车的需求量正在飞涨。
The demand for cars is soaring as growing numbers of citizens are pushed into distant suburbs.2、生态城市将把传统设计要素同最先进的绿色技术相结合。
The eco-city will combine elements of traditional design with the latest green technologies.3、预计到2010年将有一千辆燃料电池车投入使用，而到2012年将增至一万辆。
高三英语材料科学单选题60题1. In the field of materials science, the "atom" is considered as the basic ______.A. unitB. elementC. particleD. molecule答案：A。
本题考查名词词义辨析。
选项A“unit”有“单位；单元”的意思，“atom”（ 原子）被视为材料科学中的基本“单位”，符合语境。
选项B“element”指化学元素；选项C“particle”侧重于粒子；选项D“molecule”指分子。
在材料科学中，原子通常被描述为基本单位，其他选项不符合。
2. The study of materials science often involves the analysis of various ______.A. substancesB. compoundsC. mixturesD. materials答案：D。
此题考查名词的含义。
选项A“substances”指物质；选项B“compounds”指化合物；选项C“mixtures”指混合物；选项D“materials”指材料。
材料科学的研究对象主要是各种“材料”，其他选项虽然也与物质相关，但不如“materials”直接和准确。
3. When testing the properties of a new material, the ______ of heat transfer is an important factor.A. processB. methodC. wayD. means答案：A。
本题考查名词的用法。
选项A“process”强调过程；选项B“method”侧重方法；选项C“way”比较常用，指方式、道路；选项D“means”意为手段、工具。
在测试新材料性能时，热传递的“过程”是重要因素，A 选项最符合题意。
介绍非金属的英语作文Title: Exploring the World of Non-Metals。
Non-metals, often overlooked in the shadow of their metallic counterparts, play a crucial role in the composition of our world. From the air we breathe to the materials we use daily, non-metals are ubiquitous. In this essay, we'll delve into the characteristics, importance, and various applications of non-metals.Firstly, what distinguishes non-metals from metals? Unlike metals, which generally exhibit properties like conductivity, malleability, and lustre, non-metalstypically lack these characteristics. Instead, non-metals tend to be poor conductors of electricity and heat, brittle in nature, and often have lower melting and boiling points compared to metals.One of the most abundant non-metals in our atmosphere is nitrogen (N2). Comprising approximately 78% of Earth'satmosphere, nitrogen is essential for life as it is a primary component of proteins and nucleic acids. Oxygen (O2) is another vital non-metal, constituting about 21% of the atmosphere and supporting respiration in most living organisms.Carbon (C), another non-metal, is the backbone of organic chemistry and life itself. It exists in various forms, including graphite, diamond, and amorphous carbon. Carbon compounds form the basis of all known life forms, making it an indispensable element.Moving beyond the elements that constitute our atmosphere and living organisms, non-metals find extensive applications in various industries. Silicon (Si), for instance, is a crucial component in semiconductor devices, powering much of modern technology, from computers to smartphones. Similarly, sulfur (S) is used in theproduction of sulfuric acid, a vital industrial chemicalwith numerous applications, including in fertilizers, detergents, and batteries.Phosphorus (P) is another essential non-metal, particularly in agriculture. It is a key component of fertilizers, promoting healthy plant growth and maximizing crop yields. Without phosphorus, agricultural productivity would significantly decline, posing a threat to global food security.Non-metals also play a significant role inenvironmental protection and sustainability efforts. Chlorine (Cl), for instance, is used in water treatment processes to disinfect and purify drinking water, safeguarding public health. Additionally, non-metallic materials such as plastics, made predominantly from carbon and hydrogen, have revolutionized industries and daily life, offering lightweight, durable, and versatile solutions for packaging, construction, and consumer goods.Despite their importance, non-metals often receive less attention than their metallic counterparts. However, their significance cannot be overstated, as they are essentialfor sustaining life, driving technological innovation, and addressing global challenges.In conclusion, non-metals are integral to the functioning of our world, from the air we breathe to the technologies we rely on. Understanding their properties, applications, and significance is crucial for appreciating the complexity and interconnectedness of the natural world. As we continue to explore and harness the potential of non-metals, we pave the way for advancements in science, technology, and sustainable development.。
Influence of nonmetals recycled from waste printed circuit boards on flexural properties and fracture behavior of polypropylene compositesYanhong Zheng,Zhigang Shen *,Chujiang Cai,Shulin Ma,Yushan XingBeijing Key Laboratory for Powder Technology Research and Development,Beijing University of Aeronautics and Astronautics,Beijing 100191,People’s Republic of Chinaa r t i c l e i n f o Article history:Received 20May 2008Accepted 1July 2008Available online 10July 2008Keywords:Composites (A)Fracture (E)Scanning electron microscopy (G)a b s t r a c tFlexural strength and flexural modulus of the composites can be successfully improved by filling nonmet-als recycled from waste printed circuit boards (PCBs)into polypropylene (PP).By using scanning electron microscopy (SEM),the influence of nonmetals on fracture behavior of PP composites is investigated by in situ flexural test.Observation results show that the particles can effectively lead to mass micro cracks instead of the breaking crack.The process of the crack initiation,propagation and fiber breakage dissipate a great amount of energy.As a result,the flexural properties of the composites can be reinforced signif-icantly.Results of the in situ SEM observation and analysis to the dynamic flexural process supply effec-tive test evidence for the reinforcing mechanism of the nonmetals/PP composites on the basis of the energy dissipation theory.Ó2008Elsevier Ltd.All rights reserved.1.IntroductionNonmetals,an industrial solid-waste byproduct,are produced in large quantities during the recycling of waste printed circuit boards (PCBs)by physical method.Thousands of millions of tons of nonmetals are generated in the world each year.A huge source of pollution,nonmetals can also be a huge resource.The storage and disposal of nonmetals,designed to avoid environmental pollu-tion,have become a worldwide problem,and the reuse of nonmet-als is becoming increasingly important.Traditionally,the nonmetals are landfilled or incinerated,which will cause resource waste and potential environment problems.Recently,many researchers have used nonmetals as fillers for paints,adhesives,decorating agents and building materials,polyester composite and phenolic molding compound [1–6].But so far,according to author’s knowledge little work has been reported on the use of nonmetals as fillers for polypropylene (PP).PP as one of the most important commodity polymers is widely used in the packaging,textile and automobile industries because of its good processibility and great recyclability [7–10].Its application as an engineering thermoplastic is somewhat limited because of its poor fracture behavior.In fact if it is reinforced using filler or fiber it can be used instead of other commodity thermoplastic and even engineering thermoplastics [8–12].Nonmetals recycled fromwaste PCBs contain 50–70%glass fibers having high length diame-ter ratio,high elastic modulus and low elongation.Therefore,non-metals recycled from waste PCBs represent a potential substitute for traditional mineral fillers or pure glass fibers and can highly im-prove the strength of plastic products.They have more advantages than traditional fillers.Although the nonmetals recycled from waste PCBs can be successfully reused as reinforcing fillers in PP composites,influ-ence of them on fracture behavior of the composites cannot be neglected.Up to now,the research of particles reinforcing of polymer was mostly going on at the end of the experiment and was based on the results of the experiment,while the pro-cess of the particles reinforcing was unclear.Despite the impor-tance of fracture behavior of polymer materials,there are limited studies dealing with the fracture behavior in GF/PP,CaCO 3/PP,and GB/PPO composites [9,10,13–15].These research works have mostly been focused on the fracture behavior of composites via tensile test or notched flexural test.But according to author’s knowledge there is no evidence to show that investigation of fracture behavior of composites via unnotched flexural test has been performed.In this article,the objective of the research is to study the dy-namic process of nonmetals particles reinforcing of PP polymer.In nonmetals/PP composites,the dynamic process of the crack ini-tiation,propagation and fiber breakage are watched under scan-ning electron microscope (SEM)in situ unnotched flexural tests.These changes caused by nonmetals supply effective test evidence for the reinforcing mechanism of the nonmetals/PP composites on the basis of the energy dissipation theory.0261-3069/$-see front matter Ó2008Elsevier Ltd.All rights reserved.doi:10.1016/j.matdes.2008.07.004*Corresponding author.Tel./fax:+861082317516.E-mail address:shenzhg@ (Z.Shen).Materials and Design 30(2009)958–963Contents lists available at ScienceDirectMaterials and Designj o u r n a l h o m e p a g e :w w w.e l s e vier.c om/loc ate/matdes2.Experimental2.1.Material and fabrication procedure of compositesNonmetals,an industrial solid-waste byproduct,are produced in large quantities during physical recycling waste PCBs.The waste PCBs consist of a wovenfiberglass(modified,50–70%)mat impreg-nated with thermoset resins(epoxy resin or phenolic resin,etc., 30–50%).By vibrating screen classification,large quantities of non-metals with different particle size can be obtained.The nonmetals, with particle size of less than150meshes,were selected for mak-ing composites.Microscopic observation shows that most of them are single glassfibers and thermosetting resin powders(see Fig.1). They contain about70wt%single glassfibers.These glassfibers possess many excellent characteristics,such as high length diame-ter ratio(L/D ratio),high elastic modulus,low elongation and low thermal conductivity.To improve the dispersion of nonmetals particles in PP matrix and the compatibility between the nonmetals and matrix,all the nonmetals are modified with1.0wt%content of silane coupling agent KH-550(c-Aminopropyltriethoxysilane,Nanjing Shuguang Chemical Group Co.,Ltd.,China)through silanization for30min at80°C with high speed mixer(SHR-5A,Zhangjiagang Qiangda Plastics Machinery Co.,Ltd.,China)at1800rpm.Before the silan-ization,40vol%content of KH-550is mixed and hydrolyzed in the solvent(ethanol–water,volume ratio7:3)for30min at room temperature(23°C)and500rpm in a stirrer.PP powder S1003 [Beijing Yanshan Petrochemical Co.,Ltd.,China,meltflow rate 3.6g/10min(ASTM D1238,230°C,and2.16kg)]is used as the ma-trix polymer.The PP powders and the modified nonmetals particles are dried at80°C for2h.Then,the dried nonmetals particles and PP powers are stirred and mixed by using high speed mixer.The nonmetals/PP blends are extruded into thread with a screw extru-der(TE-35,Coperion Keya(Nanjing)Machinery Co.,Ltd.,China)at 210°C and220rpm.The extrudate is pelletized,dried for2h at 90°C.Then standardflexural specimens were made through injec-tion molding using an injection machine(CJ108M3V,Chen De Plas-tics Machinery Co.,Ltd.)at200°C.2.2.Flexural testFlexural test was carried out according to ISO178:1993stan-dards using an electronic universal testing machine(DXLL-10000, No.4Chemical Machinery Plant of Shanghai Chemical Equipment Co.,Ltd.,China)at a cross head speed of2mm/min.Five specimens for each type of composite were tested at room temperature (23°C),and the mean values were reported.2.3.Differential scanning calorimetry(DSC)measurementDSC measurements of PP composites with and without nonmet-als recycled from waste PCBs were carried out with DSC-SP equip-ment(Rheometric Scientific,Ltd.,USA)in aflowing nitrogen atmosphere.The temperature range utilized was from room tem-perature to300°C at a heating rate of10°C/min.Endothermic reactions as a function of the temperature were plotted as negative heatflow.2.4.In situ SEM experimental setup and observation inflexural testTo determine fracture behavior of pure PP and PP composites with nonmetals,a specially designed small load frame(see Fig.2)was built and utilized to apply three-pointflexural loading. The small load frame with a specimen is under a SEM(S-570,Hit-achi,Ltd.,Japan).Specimen dimension was6mm wide and2mm thick in gauge section.One side surfaces of specimens were pol-ished and coated with a thin layer of gold prior to microscopy to avoid charge build up.The dynamic fracture process of pure PP and PP composites was observed in the system of in situ SEM unnotchedflexural test when external load are imposed on the composites.3.Results and discussion3.1.Flexural propertiesFig.3shows theflexural properties of pure PP and nonmetals/ PP composites byfilling the nonmetals particles(0–30wt%)at room temperature.The content of the coupling agent was1wt%. The particle sizes of thefillers are less than150meshes.Theflex-ural strength of pure PP is35.53MPa,and theflexural strength of PP composite is greatly increased to46.81MPa byfilling10wt% nonmetals.Theflexural strength of PP composite increases quickly as the nonmetals contents increase and are56.08MPa with addi-tion of20wt%nonmetals.As the nonmetals contents increase to 30wt%,theflexural strength is further improved and reaches 66.25MPa in the experiment.The increases of theflexural moduli of composites are greater than that fromflexural strengths.The flexural modulus of pure PP is1.64GPa,and theflexural modulus of PP composite is greatly increased to2.49byfilling10wt%non-Fig.1.SEM micrograph of nonmetals recycled from wastePCBs.Fig.2.A load frame built for SEM observation.Y.Zheng et al./Materials and Design30(2009)958–963959metals.The flexural modulus of PP composite increases quickly as the nonmetals contents increase and are 3.13GPa with addition of 20wt%nonmetals.As the nonmetals contents increase to 30wt%,the flexural modulus of the composite is further improved and reach 3.82GPa.In other words,the flexural properties of the nonmetals/PP composites are increased with increasing the nonmetals contents from 10to 30wt%.The maximum increment of the flexural strength and flexural modulus is 86.5%and 133.0%,respectively.It is evident that the presence of nonmetals recycled from waste PCBs is an important factor in influence on flexural properties of the nonmetals/PP composites.3.2.DSC analysisDSC offers a convenient means of studying the reaction rates and mechanisms under controlled conditions.This value is partic-ularly important for conversion of the material into product for their potential practical application.Table 1summarizes the results of the DSC tests of pure PP and nonmetals/PP composites by filling the nonmetals particles (0–30wt%).The endothermic peak (T m )of pure PP is 168.4°C and the heat of fusion (D H m )is 77.5J/g.The T m of the nonmetals/PP composites are 165.1,165.5,166.8°C and the D H m of the compos-ites are 57.5,52.3,50.4J/g with the addition of 10,20,and 30wt%nonmetals,respectively.This indicates that addition of the filler into PP changes little in the T m of the composite,but that the D H m decreases by 27.1J/g with the addition of 30wt%nonmetals.Reduction of the T m is caused because of no nucleating effect of the nonmetals.And reduction of the D H m can be attributed to substi-tution of PP by nonmetals possessing low thermal conductivity.In a word,the addition of the nonmetals into PP leads to a decrease in the T m and D H m of the composites.Table 1also shows that the T m of pure PP and nonmetals/PP composite range from 165.1to 168.4°C,and this indicated that PP,both in the pure state and in the composite,exhibited onlythe crystal form a because the melting temperature of a crystals is 160–176°C [16].3.3.In situ SEM observation and analysisThe flexural properties results show that strength and rigidity of the composites are significantly improved by filling the non-metals into PP.With such millions of glass fibers and good com-patibility between the nonmetals and matrix,there are mass excellent supporting bodies,and appropriate interfacial adhesives are formed between the particles and matrix.Every dispersed particle triggers effective stress concentrations and lead to mass crazes so that the big cracks cannot be formed in the nonmet-als/PP composites.The process of the crack initiation,propagation and fiber breakage dissipate a great amount of energy.Thus,the matrix properties are improved with the addition of nonmetals particles into PP.In this study,the effect of particles on fracture behavior of PP composites is observed and analyzed during in situ SEM observation in three-point flexural test.All results are summarized as follows.Fig.4shows the SEM micrographs for the in situ observation of pure PP under the three-point flexural loading.The loading direc-tion is horizontal.The surface of the specimen of the pure PP is smooth without loading as shown in Fig.4a.At the beginning of the flexural loading,there is no change.When up to a certain load-ing it triggers many initial cracks,and the size of the crack is usu-ally big,nearly parallel to the load direction as shown in Fig.4b.Subsequently,more cracks appear following crazes thickening (Fig.4c),and extend to the dominant crack rapidly.Then the pure PP specimen gets flexural failure (Fig.4d).Fig.5shows the SEM micrographs for the in situ observation of the PP composite filled with nonmetals recycled from waste PCBs (30wt%)under the three-point flexural loading.The loading direc-tion is horizontal.For in situ SEM observation,the nonmetals/PP composite get polishing treatment,and many single fibers are ex-posed on the surface of the composite (Fig.5a).But the resin pow-ders particle size is smaller than glass fibers and they are intimately mixed in the PP matrix,which cannot be easily distin-guished in the composite.Furthermore,the particles are dispersed well in the matrix and the nonmetals are well wetted with PP material because of good compatibility between nonmetals and matrix (Fig.5b).And the glass fibers in the matrix are nearly per-pendicular to the load direction.That is mainly because the speci-men was made through injection molding using an injection machine.The glass fibers isotropy induced by fiber orientation is beneficial to flexural properties of the nonmetals/PP composites.Fig.5a shows the initial condition of the composite specimen with-out the flexural loading.At the beginning of the flexural loading,the SEM micrograph of the specimen shows no change,just as pure PP.When up to a certain loading,it triggers an initial micro crack,and craze is propagated by moving towards the interface of the particle and matrix.Then the crack is either terminated when it meets another particle or branched into mass finer crazing instead of the breaking crack directly (Fig.5b).Meanwhile,the partial interfacial debonding between the fiber ends and matrix can be seen at the bright place in Fig.5b and c.As the flexural loading in-creases,it breaks the single glass fiber (Fig.5c).When the loading further increases,mass broken fibers appear (Fig.5d).That is mainly because the glass fibers possess high elastic modulus and low elongation,they first undertake the loading when external load is imposed on the composite.Meanwhile,the strength of the loading is far greater than that of the single glass fiber,and there is strong adhesion and good compatibility between the fiber and the matrix,so the glass fibers are first broken compared with the PP matrix.Subsequently,the PP composite specimen gets flex-uralfailure.Fig.3.Flexural properties of the pure PP and nonmetals/PP composites.Table 1DSC data of the pure PP and nonmetals/PP composite PP content (wt%)Nonmetals content (wt%)T m (°C)D H m (J/g)1000168.4377.529010165.1457.518020165.5152.337030166.8250.36960Y.Zheng et al./Materials and Design 30(2009)958–963Results show that the pure PP matrix can initiate big cracks in the flexural test by in situ SEM observation.On increasing the load-ing,the bigger one of the cracks is extended into the dominant crack rapidly and then the pure PP specimen gets flexural failure rapidly.It means that the main energy absorption is in the crack initiation.While nonmetals recycled from waste PCBs are filled into PP matrix,mass micro cracks are triggered in the composite specimen.The crack is either terminated when it meets another particle or branched into mass finer crazing instead of the breaking crack directly.Since glass fiber acts like a barrier,craze cannot pass easily.In this condition,the crazes should turn glass fiber,move to-ward interface or break the glass fibers.The process of the crack initiation,propagation and fiber breakage dissipate a great amount of energy.Meanwhile,in the process of the flexural loading,partial interfacial debonding can slowdown the propagation of the crack and promote crack termination.These factors cause improvement of the flexural properties of the nonmetals/PP composites by filling the nonmetals particles recycled from waste PCBs evidently.The results of the in situ observation and analysis to the dynamic pro-cess supply effective test evidence for the reinforcing mechanismof the nonmetals/PP composites on the basis of the energy dissipa-tion theory.4.ConclusionsFlexural strength and flexural modulus of the composites can be successfully improved by filling nonmetals recycled from waste PCBs into PP.And the T m and D H m of the composites decrease with the addition of the nonmetals.The dynamic flexural process of the pure PP and nonmetals/PP composites are observed with SEM.Results show that the pure PP matrix can initiate big cracks under the flexural loading,and it extends to the dominant crack rapidly as the flexural loading in-creases.It means that the main energy absorption is in the crack initiation.While nonmetals are filled into PP matrix,mass micro cracks are triggered and consume tremendous energy.The glass fi-ber acts like a barrier,craze cannot pass easily.Therefore,the crazes should turn glass fiber,move toward interface or break the glass fibers.The process of the crack propagation and fiber breakage dissipate a great amount of energy.Meanwhile,intheFig.4.SEM micrograph for the in situ observation of the pure PP.(a)Initial condition;(b)triggering initial crack;(c)appearance of more cracks;and (d)flexural failure.The loading direction is horizontal.Y.Zheng et al./Materials and Design 30(2009)958–963961process of the flexural loading,partial interfacial debonding can slowdown the propagation of the crack and promote crack termi-nation.All of these factors can prevent and delay the nonmetals/PP composites getting flexural failure,and cause the improvement of the flexural properties evidently.In situ SEM observation and analysis experimental results show that energy dissipation is the major factor of reinforcing mecha-nism.In situ observation and analysis to the dynamic process sup-ply effective test evidence for the reinforcing mechanism of the nonmetals/PP composites on the basis of the energy dissipation theory.AcknowledgementsThe authors acknowledge with gratitude the financial support of the National Natural Science Foundation of China (Grant No.50774003),China Postdoctoral Science Foundation funded project (Grant No.20070420286)and the Joint Building Project of Beijing Education Committee.References[1]Yokoyama S,Iji M.Recycling of thermosetting plastics waste from electroniccomponent production processed.In:Proceedings of the IEEE international symposium on electronics and the environment.Orlando:IEEE;1995.[2]Iji M.Recycling of epoxy resin compounds for moulding electroniccomponents.J Mater Sci 1998;33:45–53.[3]Hong SG,Su SH.The use of recycled printed circuit boards as 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