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1、Unit 2 Classification of MaterialsSolid materials have been conveniently grouped into three basic classifications: metals, ceramics, and polymers. This scheme is based primarily on chemical makeup and atomic structure, and most materials fall into one distinct grouping or another, although there are
2、 some intermediates. In addition, there are three other groups of important engineering materialscomposites, semiconductors, and biomaterials.译文：固体材料被便利的分为三个基本的类型：金属，陶瓷和聚合物。这个分类是首先基于化学组成和原子结构来分的，大多数材料落在明显的一个类别里面，尽管有许多中间品。除此之外， 有三类其他重要的工程材料复合材料，半导体材料和生物材料。Composites consist of combinations of two or
3、more different materials, whereas semiconductors are utilized because of their unusual electrical characteristics; biomaterials are implanted into the human body. A brief explanation of the material types and representative characteristics is offered next.译文：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
4、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。METALSMetallic materials are normally combinations of metallic elements. They have large numbers of nonlocalized electrons; that is, these electrons are not bound to particularatoms. Many properties of metals are directly able to these electrons.be bo
5、und to 被约束于。be attribute to 归属于。归因于。译文：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 str
6、ong, yet deformable, which accounts for their extensive use in structural applications.科技英语在讲述科学真理的时候通常用主动语态。如： Metals are extremely good conductors of electricity Deformable ？译文：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。CERAMICSCeramics are compounds between
7、metallic and nonmetallic elements; they are most frequently oxides, nitrides, and carbides. The wide range of materials that falls within this classification includes ceramics that are composed of clay minerals, cement, and glass.that引导的定语从句译文：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
8、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 polymers. With regard to mechanical behavior, ceramics are hard but very brittle.more. Than.with regard to.译文：这些材料是典型的
9、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。POLYMERSPolymers 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 structures. These materi
10、als typically have low densities and may be extremely flexible.译文：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。COMPOSITESA number of composite materials have been engineered that consist of more than one material type. Fiberglass is a familiar example
11、, in which glass fibers are embedded within a polymeric material.more than译文：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 flexibi
12、lity from the polymer. Many of the recent material developments have involved composite materials. 译文：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。SEMICONDUCTORSSemiconductors have electrical properties that are intermediate between the electrical conductors and insulat
13、ors. 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. be sensitive to 对敏感的译文：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
14、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 (not to mention ourlives) over the past two decades.译文：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
15、Biomaterials are employed in components implanted into the human body for replacement of diseased or damaged body parts. These materials must not produce toxic substances and must be compatible with body tissues (i.e., must not cause adverse biological reactions).译文：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
16、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 materialsmetals, ceramics, polymers,composites, and semiconductorsmay be used as biomaterials. For example, some of the biomaterials such as CF/C (carbon fibers/carbon) and CF/PS (polysulfone) are utilized in artificial hip replacements.译文：所有
17、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肾的取代物。ADVANCED MATERIALSMaterials that are utilized in high-technology (or high-tech) applications are sometimes termed advanced materials. By high technology we mean a device or product that operates or functions using relatively intrica
18、te and sophisticated principles; examples include electronic equipment (VCRs, CD players, etc.), computers, fiberoptic systems, spacecraft, aircraft, and military rocketry.译文：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 advance
19、d materials are typically either traditional materials whose properties have been enhanced or newly developed, high-performance materials. Furthermore, they may be of all material types (e.g., metals, ceramics, polymers), and are normally relatively expensive.译文：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
20、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。In subsequent chapters are discussed the properties and applications of a number of advanced materialsfor example, materials that are used for lasers, integrated circuits, magnetic information storage, liquid crystal displays (LCDs),fiber optics, and the therm
21、al protection system for the Space Shuttle Orbiter.译文： 在下面的章节将讨论众多先进材料的性质和应用比如被用作激光，集成电路，磁信息存储，液晶显示器，光纤和空间舱轨道的热保护系统的材料。MODERN MATERIALS NEEDSIn 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 tec
22、hnological challenges, including the development of even more sophisticated and specialized materials, as well as consideration of the environmental impact of materials production. Some comment is appropriate relative to these issues so as to round outthis perspective.译文：在过去几年内，不论材料科学与工程的规律取得了巨大的进步，
23、仍然有一些技术挑战，包括开发更加熟练的专业化的材料，并且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 to facilities for the disposal of radioactive waste.译文：核能还保持着一些承诺，但是解决许多仍然存在的问题，
24、将有必要把材料包括在里，从燃料到保护结构以便方便处置这些放射性废料。Significant quantities of energy are involved in transportation. Reducing the weight of transportation vehicles (automobiles, aircraft, trains, etc.), as well as increasing engine operating temperatures, will enhance fuel efficiency. New high strength,low-density st
25、ructural materials remain to be developed, as well as materials that have higher-temperature capabilities, for use in engine components.译文：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
26、 of energy, and to use the present resources more efficiently. Materials will undoubtedly play a significant role in these developments.译文：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 into electrical energy has been demonstrated. Solar
27、 cells employ some rather complex and expensive materials. To ensure a viable technology, materials that are highly efficient in this conversion process yet less costly must be developed.译文：比如，太阳能直接转化为电能已经被证实了。太阳能电池使用相当复杂并且昂贵的材料。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。Furthermore, environmental quality dep
28、ends on our ability to control air and water pollution. Pollution control techniques employ various materials. In addition, materials processing and refinement methods need to be improved so that theyproduce less environmental degradation, that is, less pollution and less despoilage of the landscape
29、 from the mining of raw materials.译文：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，在生材料加工过程中，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 theirdisposal must be considered.Many materials
30、that we use are derived from resources that are nonrenewable, that is, not capable of being regenerated.These include polymers, for which the prime raw material is oil, and some metals. These nonrenewable resources aregradually becoming depleted.译文：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。我们使用的许多材
31、料来源于不可再生的资源，不可再生也就是说不能再次生成的。这些材料包括聚合物，最初的原生材料是油和一些金属。这些不可再生的资源逐渐变得枯竭which necessitates: 1) the discovery of additional reserves, 2) the development of new materials having comparable properties with less adverse environmental impact, and/or 3) increased recycling efforts and the development of new r
32、ecycling technologies.译文：下面是必须的：1）发现另外的储藏，2）开发拥有较少负环境影响的新材料，3)增加循环的努力并且开发新的循环技术。As a consequence of the economics of not only production but also environmental impact and ecological factors, it isbecoming increasingly important to consider the cradle-to-grave life cycle of materials relative to the overall manufacturing process.译文：结果，不仅是生产，而且环境影响和生态因子，和材料整个生产过程紧密相关的材料“一生”的生命周期的考虑变得越来越重要。