材料导论第一章答案.doc

Chaper 1 Introduction 第一章　导论 P17-18 Problems 1-1~1-4：略 1-5 Environmental and Other Effect 1-5. Steel is often coated with a thin layer of zinc if it is to be used outside. What characteristics do you think the zinc provides to this coated, or galvanized, steel? What precautions should be considered in producing this product? How will the recyclability of the product be affected? 问题大意：钢铁表面的镀锌有什么作用？镀锌时应注意哪些问题？镀锌后钢铁的回收会受到什么影响？ The zinc provides corrosion resistance to the iron in two ways. If the iron is completely coated with zinc, the zinc provides a barrier between the iron and the surrounding environment, therefore protecting the underlying iron. If the zinc coating is scratched to expose the iron, the zinc continues to protect the iron because the zinc corrodes preferentially to the iron (see Chapter 22). To be effective, the zinc should bond well to the iron so that it does not permit reactions to occur at the interface with the iron and so that the zinc remains intact during any forming of the galvanized material. When the material is recycled, the zinc will be lost by oxidation and vaporization, often producing a “zinc dust” that may pose an environmental hazard. Special equipment may be required to collect and either recycle or dispose of the zinc dust. 答案大意：镀锌层可以防止钢铁腐蚀，机理如下：1、在钢铁与外部环境间产生阻隔；2、在钢铁暴露后，锌仍能以牺牲阳极的方式保护钢铁。镀锌时应注意锌层与钢铁间的结合并防止发生在锌与钢铁界面间的反应。在镀锌钢铁回收时，锌会形成“锌尘”对环境产生危害。 1-6. We would like to produce a transparent canopy for an aircraft. If we were to use a ceramic (that is, traditional window glass) canopy, rocks or birds might cause it to shatter. Design a material that would minimize damage or at least keep the canopy from breaking into pieces. 问题大意：用单纯的玻璃制造的飞机座舱罩易碎，如何改进才能减少其破坏造成的损失或防止其破碎？ We might sandwich a thin sheet of a transparent polymer between two layers of the glass. This approach, used for windshields of automobiles , will prevent the “safety” glass from completely disintegrating when it fails, with the polymer holding the broken pieces of gla