such as the aramids.
这些复合材料表现出来的机械强度主要是由强化玻璃纤维决定的，尽管结构缺陷会使强度减弱。工程学研究正提供重要的信息说明材料结构是如何受到玻璃树脂的界面性质、构造空隙和类似缺陷的影响以及这些微缺陷是如何扩散产生构造裂缝的。这些复合材料以及从对它们的研究中获得的信息使人类进入到生产第二代聚合复合材料的阶段，即以高强度纤维如芳香族聚酰胺为基础的复合材料。
3. Advanced Ceramics
For most people, the word ―ceramics‖ conjures up the notion of things like china, pottery, tiles, and bricks. Advanced ceramics differ from these conventional ceramics by their composition, processing, and microstructure. For example: 3．现代陶瓷
对大多数人来说，“陶瓷”这个词会让人联想到瓷器、陶器、砖、瓦这些东西。现代陶瓷以它们的组成、加工过程和微细结构区别于这些传统的陶瓷。例如：
?Conventional ceramics are made from natural raw materials such as clay or silica; advanced ceramics require extremely pure man-made starting materials such as silicon carbide, silicon nitride, zirconium oxide, or aluminum oxide and may also incorporate sophisticated additives to produce specific microstructures.
?传统的陶瓷是用天然的原料如粘土或硅石制成的。现代陶瓷则要求非常纯的人造原料如碳化硅、氮化硅、氧化锆或氧化铝，可能还要渗入一些复杂的添加剂来产生特殊的微结构。
?Conventional ceramics initially take shape on a potter‘s wheel or by slip casting and are fired (sintered) in kilns; advanced ceramics are formed and sintered in more complex processes such as hot isostatic pressing.
?传统陶瓷是先在陶工轮上或粉浆浇注成型，然后在窑里烧结定型。现代陶瓷是用更为复杂的工艺过程如高温静压成型法来定型的。
?The microstructure of conventional ceramics contains flaws readily visible under optical microscopes; the microstructure of advanced ceramics is far more uniform and typically is examined for defects under electron microscopes capable of magnifications of 50,000 times or more.
?传统陶瓷的微结构容易形成在光学显微镜下就可以看见的裂痕。而现代陶瓷的微结构则要均匀得多，一般要在5万倍或更大倍数的电子显微镜下才能检查出瑕疵来。
Advanced ceramics have a wide range of application. In many cases, they do not constitute a final product in themselves, but are assembled into components critical to the successful performance of some other complex system. Commercial applications of advanced ceramics can be seen in cutting tools, engine nozzles, components of turbines and turbochargers, tiles for space vehicles, cylinders to store atomic and chemical waste, gas and oil drilling valves, motor plates and shields, and electrodes for corrosive liquids.
现代陶瓷的应用范围更为广泛。在很多情况下，现代陶瓷并未直接成为最终产品，而是组合在一些复杂的系统中成为优良性能的关键部分。现代陶瓷的商业应用可以在切削工具、发动机喷嘴、涡轮和涡轮增压器的元件、太空舱的瓦面、储藏原子和化学废物的圆柱体、气体和
石油钻探阀、电动极板和防护罩以及腐蚀性液体中的电极等等方面看见。
4. Ceramic Composites
Like polymer composites, ceramic composites consist of high-strength of high-modulus fibers embedded in a continuous matrix. Fibers may be in the form of ―whiskers‖ of substances such as silicon carbide or aluminum oxide that are grown as single crystals and that therefore have fewer defects than the same substances in a bulk ceramic. Fibers in a ceramic composite serve to block crack propagation; a growing crack may be deflected to a fiber or might pull the fiber from the matrix. Both processes absorb energy, slowing the propagation of the crack. The strength, stiffness, and toughness of a ceramic composite is principally a function of the reinforcing fibers, but the matrix makes its own contribution to these properties. The ability of the composite material to conduct heat and current is strongly influenced by the inductivity of the matrix. The interaction between the fiber and the matrix is also important to the mechanical properties of the composite material and is mediated by the chemical compatibility between fiber and matrix at the fiber surface. A prerequisite for adhesion between these two materials is that the matrix, in its fluid form, be capable of wetting the fibers. Chemical bonding between the two components can then take place.
4．陶瓷合成材料
像聚合复合材料一样，陶瓷复合材料也包括在连续的基质上嵌入高强度或高模数的纤维。纤维可以是碳化硅或氧化铝以“晶须”的形式出现，然后生长为单个晶体。这与同样的物质直接嵌入在大块陶瓷上相比较所产生裂纹较少。陶瓷复合体上的纤维可以阻碍裂纹的扩散。正在生长的裂纹会向纤维处偏移或使纤维脱离基质。这两个过程都要吸收能量，从而减慢了裂纹的扩散。陶瓷复合材料的强度、硬度和韧性主要取决于强化纤维，但是基质也会对这些性质产生影响。复合材料的导热和导电性能受基质传导系数的影响很大。纤维和基质之间的相互作用对复合材料机械性能的影响也很大，并可通过纤维表面纤维和基质间的化学兼容性进行调整，这两种物质粘合在一起的前提就是基质以流体形态存在时能润湿纤维。两种组分间形成了化学键。
As with advanced ceramics, chemical reactions play a crucial role in the fabrication of ceramic composites. Both defect-free ceramic fibers and optimal chemical bonds between fiber and matrix are required for these composites to exhibit the desired mechanical properties in use. Engineering these chemical reactions in reliable manufacturing processes requires the expertise of chemical engineers.
与现代陶瓷的产生一样，化学反应在陶瓷复合材料的加工制造中也充当了关键的角色。这些复合材料要求无瑕疵的陶瓷纤维、纤维和母体间有最适当的作用力，这才能在使用中展现所预想的机械性能。在实际的制造过程中设计这样的化学反应要求化学工程师具备专业的知识。
5. Composite Liquids
A final important class of composite materials is the composite liquids. Composite liquids are highly structured fluids based either on particles or droplets in suspension, surfactants, liquid crystalline phases, or other macromolecules. A number of composite liquids are essential to the needs of modern industry and society because they exhibit properties important to special end uses.
Examples include lubricants, hydraulic traction fluids, cutting fluids, and oil-drilling muds. Paints, coatings, and adhesives may also be composite liquids. Indeed, composite liquids are valuable in any case where a well-designed liquid state is absolutely essential for proper delivery and action. 5．复合液体
最后一类重要的复合材料是复合液体。复合液体是高结构液体，以悬浮液、表面活性剂、液晶相或其它大分子与固体微粒或液滴组成。许多复合液体对现代工业和社会都是必不可少的，因为它们表现出来的性质对一些特殊用途是非常重要的。这些用途包括润滑剂、水力牵引液体以及油田钻井泥浆，油漆、涂料和粘合剂也可能是合成液体。确实，在任何情况下，如果好的液体状态对某种传递和反应是重要的，那么合成液体就是有价值的。
Chemical engineers have long been involved with materials science and engineering. This involvement will increase as new materials are developed whose properties depend strongly on their microstructure and processing history. Chemical engineers will probe the nature of microstructure—how it is formed in materials and what factors are involved in controlling it. They will provide a new fusion between the traditionally separate areas of materials synthesis and materials processing. And they will bring new approaches to the problems of fabricating and repairing complex materials systems.
化学工程师长期涉足材料科学和工程学研究工作。随着新材料的开发，其性质越来越依赖微结构和加工过程，研究程度也将深入。化学工程师将探索微结构的本质—它是如何在材料中形成的， 哪些因素可以用来控制它。他们将采用新的方式把传统的分离开来的材料合成和材料加工融合起来。他们还将用新方法解决构造的问题，修复复杂的材料系统。
Unit 21 Chemical Industry and Environment 化学工业与环境
How can we reduce the amount of waste that is produced? And how we close the loop by redirecting spent materials and products into programs of recycling? All of these questions must be answered through careful research in the coming years as we strive to keep civilization in balance with nature.
我们怎样才能减少产生废物的数量？我们怎样才能使废弃物质和商品纳入循环使用的程序？所有这些问题必须要在未来的几年里通过仔细的研究得到解决，这样我们才能保持文明与自然的平衡。
1. Atmospheric Chemistry
Coal-burning power plants, as well as some natural processes, deliver sulfur compounds to the stratosphere, where oxidation produces sulfuric acid particles that reflect away some of the incoming visible solar radiation. In the troposphere, nitrogen oxides produced by the combustion of fossil fuels combine with many organic molecules under the influence of sunlight to produce urban smog. The volatile hydrocarbon isoprene, well known as a building block of synthetic rubber, is also produced naturally in forests. And the chlorofluorocarbons, better known as CFCs, are inert in automobile air conditioners and home refrigerators but come apart under ultraviolet bombardment in the mid-stratosphere with devastating effect on the earth‘s stratospheric ozone layer. The globally averaged atmospheric concentration of stratospheric ozone itself is only 3 parts in 10 million, but it has played a crucial protective role in the development of all biological life
through its absorption of potentially harmful shout-wavelength solar ultraviolet radiation. 1．大气化学
燃煤发电厂像一些自然过程一样，也会释放硫化合物到大气层中，在那里氧化作用产生硫酸颗粒能反射入射进来的可见太阳辐射。在对流层，化石燃料燃烧所产生的氮氧化物在阳光的影响下与许多有机物分子结合产生都市烟雾。挥发的碳氢化合物异戊二烯，也就是众所周知的合成橡胶的结构单元，可以在森林中天然产生含氯氟烃。我们所熟悉的CFCs，在汽车空调和家用冰箱里是惰性的，但在中平流层内在紫外线的照射下回发生分解从而对地球大气臭氧层造成破坏，全球大气层中臭氧的平均浓度只有3ppm，但它对所有生命体的生长发育都起了关键的保护作用，因为是它吸收了太阳光线中有害的短波紫外辐射。
During the past 20 years, public attention has been focused on ways that mankind has caused changes in the atmosphere: acid rain, stratospheric zone depletion, greenhouse warming, and the increased oxidizing capacity of the atmosphere. We have known for generations that human activity has affected the nearby surroundings, but only gradually have we noticed such effects as acid rain on a regional then on an intercontinental scale. With the problem of ozone depletion and concerns about global warming, we have now truly entered an era of global change, but the underlying scientific facts have not yet been fully established.
在过去的二十年中，公众的注意力集中在人类对大气层的改变：酸雨、平流层臭氧空洞、温室现象，以及大气的氧化能力增强，前几代人已经知道，人类的活动会对邻近的环境造成影响，但意识到像酸雨这样的效应将由局部扩展到洲际范围则是慢慢发现的。随着臭氧空洞问题的出现，考虑到对全球的威胁，我们已真正进入到全球话改变的时代，但是基本的科学论据还没有完全建立。
2. Life Cycle Analysis
Every stage of a product‘s life cycle has an environmental impact, starting with extraction of raw materials, continuing through processing, manufacturing, and transportation, and concluding with consumption and disposal or recovery. Technology and chemical science are challenged at every stage. Redesigning products and processes to minimize environmental impact requires a new philosophy of production and a different level of understanding of chemical transformations. Environmentally friendly products require novel materials that are reusable, recyclable, or biodegradable; properties of the materials are determined by the chemical composition and structure. To minimize waste and polluting by-products, new kinds of chemical process schemes will have to be developed. Improved chemical separation techniques are needed to enhance efficiency and to remove residual pollutants, which in turn will require new chemical treatment methods in order to render them harmless. Pollutants such as radioactive elements and toxic heavy metals that cannot be readily converted into harmless materials will need to be immobilized in inert materials so that they can be safely stored. Finally, the leftover pollution of an earlier, less environmentally aware era demands improved chemical and biological remediation techniques. 2．生命周期分析
产品生命循环周期的每一个阶段都会对环境造成影响。从原材料的提取，到加工、制造和运输的过程，最后到被消耗和丢弃或回收，每一个阶段都对工艺学和化学提出了挑战。重新设计产品和过程以减少对环境的影响需要新的生产原理和在不同的水平层面上理解化学变化，对环境友善的产品要求有新的原料，它们应是可再使用的，可循环的，或者可生物降解的。物质的性质是由其化学组成和结构决定的，要减少废品和有污染的副产品，就要开发新的化
学工艺线路，已开发的化学分离技术需要有效地提高以分离出剩余的污染物，这反过来又要求新的化学处理方法使它们变得无害。而诸如放射性元素和那些不容易转化为无害物质的重金属污染物则需要把它们固定为惰性物质以便能安全地储放。还有最后一点，早期的污染残留物，对环境污染程度尚未很意识到的一些物质要求进一步用化学和生物的修复技术进行处理。
Knowledge of chemical transformations can also help in the discovery of previously unknown environmental problems. The threat to the ozone layer posed by CFCs was correctly anticipated through fundamental studies of atmospheric chemistry, eventually leading to international agreements for phasing out the production of these otherwise useful chemicals in favor of equally functional but environmentally more compatible alternatives. On the other hand, the appearance of the ozone hole over the Antarctic came as a surprise to scientists and only subsequently was traced to previously unknown chlorine reactions occurring at the surface of nitric acid crystals in the frigid Antarctic stratosphere. Thus it is critically important to improve our understanding of the chemical processes in nature, whether they occur in fresh water, saltwater, soil, subterranean environments, or the atmosphere.
了解化学反应的机理可以帮助我们发现以前不知道的环境问题，CFCs对臭氧层造成的威胁能够正确地预防要得益于大气化学的基础研究。由此导致了国际上一致同意逐步取消这些产品的生产。而代之以作用相同但对环境更为友善的其它产品。另一方面，南极上空臭氧空洞的出现使科学家们大为震惊，随后才发现了以前所不了解的南极寒冷的平流层内硝酸晶体表面所发生的氯原子的反应。这对我们进一步了解自然界中所发生的化学反应过程是非常重要的。不管这些反应是发生在淡水中，海水中，土壤里，地下环境或是大气中。
3. Manufacturing with Minimal Environmental Impact
Discharge of waste chemicals to the air, water, or ground not only has a direct environmental impact, but also constitutes a potential waste of natural resources. Early efforts to lessen the environmental impact of chemical processes tended to focus on the removal of harmful materials from a plant‘s waste stream before it was discharged into the environment. But this approach addresses only half of the problem; for an ideal chemical process, no harmful by-products would be formed in the first place. Any discharges would be at least as clean as the air and water that were originally taken into the plant, and such a process would be ―environmentally benign‖. 3．对环境影响最小的生产 把废物排放到空气、水或土壤中不仅对环境造成了直接的影响，还是对自然资源的一个潜在的浪费。早期减少化学过程对环境影响的工作主要集中在工厂废气排放如环境之前有害物质的分离，但这种思路只考虑了问题的一半。因为一个理想的化学过程，也就是没有有害的副产品产生的过程应在一开始就建立好，任何排放物至少应像进入到工厂内的空气和水一样干净。这样的过程才可以称是“与环境友善的”。
Increasing concern over adverse health effects has put a high priority on eliminating or reducing the amounts of potentially hazardous chemicals used in industrial processes. The best course of action is to find replacement chemicals that work as well but are less hazardous. If a substitute cannot be found for a hazardous chemical, then a promising alternative strategy is to develop a process for generating it on-site and only in the amount needed at the time. 对健康有害影响的关注逐渐升级，人们首先考虑到如何消除或减少工业过程中所用有害化学