专业外语英语加汉语Unit2classification_of_material.doc

Unit2 Classification of Materials材料的分类 Basic Classifications and Engineering Materials基本分类、工程材料Solid materials have been conveniently grouped into three basic classifications： metals，ceramics and polymers固体材料便利的被分为三个基本类型:金属、陶瓷和聚合物.This scheme is based primarily on chemical makeup and atomic structure, and most materials fall into one distinct grouping or another， although there are some intermediates. 这个方案,是主要基于化学结构和原子的结构,和大多数材料属于一个或另一个截然不同的分组,虽然有一些中间体。In addition，there are three other groups of important engineering materials-composites， semiconductor， and biomaterials除此之外,还有其他三组重要的工程材料- - - - - - -复合材料、半导体、生物材料等。 Composites consist of combinations of two or more different materials， whereas semiconductors are utilized because of their unusual electrical characteristics；biomaterials are implanted into the human body brief explanation of the material types and representative characteristics is offered next复合材料由两种或者两种以上不同的材料组成，然而半导体由于它们非同寻常的电学性质而得到使用；生物材料被移植进入人类的身体中。关于材料类型和他们特殊的特征的一个简单的解释将在后面给出。 Metals： Metallic materials are normally combinations of metallic elements They have large numbers of nonlocalized electrons；that is，these electrons are not bound to particular atoms. Many properties of metals are directly attributable to these electrons金属材料通常由金属元素组成。它们有大量无规则运动的电子。也就是说，这些电子不是被约束于某个特定的原子。金属的许多性质直接归属这些不规则运动的电子。 Metals are extremely good conductors of electricity and heat，and are not transparent to visible light：a polished metal surface has a lustrous appearance Furthermore， metals are quite strong，yet deformable， which accounts for their extensive use in structural applications金属是十分好的电和热的导体，它们对可见光不透明；一个抛光的金属表面有光辉的外表。除此之外，金属是十分硬的，也是可变形的，这个性质解释了它们广泛使用在结构方面的应用。 Ceramics： Ceramics are compounds between metallic and nonmetallic elements： they are most frequently oxides, nitrides，and carbidesThe wide range of materials that falls within this classification includes ceramics that are composed of clay minerals， cement， and glass. 陶瓷是介于金属和非金属元素之间的化合物；它们通常是氧化物，氮化物和碳化物。落在这个分类种类中的宽的材料范围包括陶瓷，它们由粘土矿物，水泥和玻璃组成。 These materials are typically insulative to the passage of electricity and heat， and are more resistant to high temperatures and harsh environments than metals and polymersWith regard to mechanical behavior，ceramics are hard but very brittle这些材料是典型的电和热的绝缘体，并且它们比金属和聚合物更加耐高温和耐苛刻的环境。至于机械性能，陶瓷是硬的但是却很脆。 Polymers：Polymers include the familiar plastic and rubber materials Many of them are organic compounds that are chemically based on carbon，hydrogen， and other nonmetallic elements； furthermore，they have very large molecular structuresThese materials typically have low densities and may be extremely flexible聚合物包括常见的塑料和橡胶材料。它们中的大多数是有机化合物，这些化合物是以化学的方法把碳、氢和其他非金属元素组合而成。因此，它们有非常大的分子结构。这些材料通常有低的密度并且可能十分柔软。 Composites： A number of composite materials have been engineered that consist of more than one material typeFiberglass is a familiar example，in which glass fibers are embedded within a polymeric material. 许多复合材料被作用工程使用，它们由至少一种类型的材料组成。玻璃丝是一个熟悉的例子，玻璃纤维被埋入聚合物材料中A composite is designed to display a combination of the best characteristics of each of the component materials Fiberglass acquires strength from the glass and flexibility from the polymer Many of the recent material developments have involved composite materials为了联合显示每一种组分材料最好的特性，一种复合材料被设计出来。玻璃丝从玻璃中获得强度并且从聚合物中获得柔软性。最近发展中的绝大多数材料包含了复合材料 Semiconductors： Semiconductors have electrical properties that are intermediate between the electrical conductors and insulators Furthermore，the electrical characteristics of these materials are extremely sensitive to the presence of minute concentrations of impurity atoms，which concentrations may be controlled over very small spatial regions半导体有电的性质，它们是介于电导体和绝缘体之间的中间物。除此之外，这些材料的电学性质对微量杂质原子的存在十分敏感，杂质原子浓度可能只是在一个十分小的区域内可以控制。The semiconductors have made possible the advent of integrated circuitry that has totally revolutionized the electronics and computer industries over the past two decades这些半导体使得集成电路的出现变得可能，在过去20多年间，这些集成电路革新了电子装置和计算机工业（更不用说我们的生活）。 Biomaterials: Biomaterials are employed in components implanted into the human body for replacement of diseased or damaged body partsThese materials must not produce toxic substances and must be compatible with body tissue(iemust not cause adverse biological reactions)生物材料被应用于移植进入人类身体以取代病变的或者损坏的身体部件。这些材料不能产生有毒物质而且必须同人身体器官要相容（比如，不能导致相反的生物反应）。All of the above materials-metals，ceramics，polymers，composites and semiconductors-may be used as biomaterialsFor example，some of the biomaterials such as CFC(carbon fiberscarbon)and CFPS (polysulfone) are utilized in artificial hip replacements所有以上材料金属，陶瓷，聚合物，复合材料和半导体材料可能用作生物材料。比如，如CF/C和CF/PS（聚砜）这些生物材料被用作人工关节的取代物。Advanced Materials Materials that are utilized in high-technology (or high-tech) applications are sometimes termed advanced materialsBy high technology we mean a device or product that operates or functions using relatively intricate and sophisticated principles；examples include electronic equipment(VCRs，CD players，etc)，computers，fiberoptic systems，spacecraft，aircraft，and military rocketry用在高科技中的材料有时被称作先进材料。借助于高科技，我们预定一个装置或者产品，这些产品用相对复杂和熟练的原理运转或者起作用；这些例子包括电子设备（ VCRs, CD 播放器），计算机，光纤系统，宇宙飞船，航天飞机和军事火箭。These advanced materials are typically either traditional materials whose properties have been enhanced or newly developed，highperformance materialsFurthermore，they may be of all material types(egmetals，ceramics，polymers)，and are normally relatively expensive这些高级材料或是典型的传统材料，它们的性质被提高，最近开发出来的，高性能材料。除此之外，它们可能是所有材料类型（比如，金属、陶瓷和聚合物），通常相对较贵。Modern Materials Needs In spite of the tremendous progress that has been made in the discipline of materials science and engineering within the past few years，there still remain technological challenges，including the development of even more sophisticated and specialized materials，as well as consideration of the environmental impact of materials productionSome comment is appropriate relative to these issues so as to round out this perspective在过去几年内，尽管材料科学与工程的规律取得了巨大的进步，仍然有一些技术挑战，包括开发更加熟练的专业化的材料，还有考虑材料生产对环境导致的影响。针对这个问题，一些评论是十分相关的。 Nuclear energy holds some promise，but the solutions to the many problems that remain will necessarily involve materials from fuels to containment structures and facilities for the disposal of radioactive waste核能还是非常有前途的，但是许多需要解决的问题仍然存在，从燃料到保护结构以及放置这些放射性废料的装置材料都是有必要改善的。 Significant quantities of energy are involved in transportationReducing the weight of transportation vehicles(automobiles，aircraft，trains，etc)，as well as increasing engine operating temperatures，will enhance fuel efficiencyNew high strength，lowdensity structural materials remain to be developed，as well as materials that have highertemperature capabilities，for use in engine components相当数量的能源用在交通上。减少交通工具（汽车，飞机，火车等）的重量，和提高引擎操作温度，将提高燃料的使用效率。新的高强，低密度结构材料仍在发展，用作引擎部位能耐高温材料也在发展中。Furthermore，there is a recognized need to find new，economical sources of energy，and to use the present resources more efficientlyMaterials will undoubtedly play a significant role in these developments除此之外，寻找新的、经济的能源资源，并且更加有效的使用目前现存的资源是公认为必须的。材料将毫无疑问的在这些发展过程中扮演重要的角色。For example，the direct conversion of solar energy into electrical energy uses silicon materialsTo ensure a viable technology，materials that are highly efficient in this conversion process yet less costly must be developed比如，用硅材料把太阳能直接转化为电能。为了保证技术的可行，在这个转化过程中的高效但不贵的材料必须被发展。Additionally，environmental quality depends on our ability to control air and water pollutionPollution control techniques employ various materials In addition, materials Processing and refinement methods need to be improved so that they produce less environmental degradation，that is，less pollution and less despoilage of the landscape from mining of raw materials除此之外，环境质量取决于我们控制大气和水污染的能力。污染控制技术使用了各种材料。再者，材料加工和精制的方法需要改善以便它们产生很少的环境退化，也就是说，在材料加工过程中，带来更少的污染和更少的对自然环境的破坏 Also， in some materials manufacturing processes，toxic substances are Produced，and the ecological impact of their disposal must be considered. 也，在一些材料生产过程中，有毒物质产生了，并且它们的处置对生态产生的影响必须加以考虑。Many materials that we use are derived from resources that are nonrenewable，that is not capable of being regeneratedThese include polymers， for which the prime raw material