- 1、本文档共27页,可阅读全部内容。
- 2、有哪些信誉好的足球投注网站(book118)网站文档一经付费(服务费),不意味着购买了该文档的版权,仅供个人/单位学习、研究之用,不得用于商业用途,未经授权,严禁复制、发行、汇编、翻译或者网络传播等,侵权必究。
- 3、本站所有内容均由合作方或网友上传,本站不对文档的完整性、权威性及其观点立场正确性做任何保证或承诺!文档内容仅供研究参考,付费前请自行鉴别。如您付费,意味着您自己接受本站规则且自行承担风险,本站不退款、不进行额外附加服务;查看《如何避免下载的几个坑》。如果您已付费下载过本站文档,您可以点击 这里二次下载。
- 4、如文档侵犯商业秘密、侵犯著作权、侵犯人身权等,请点击“版权申诉”(推荐),也可以打举报电话:400-050-0827(电话支持时间:9:00-18:30)。
查看更多
TEXT ONE
William Illiam Morris (the wallpaper designer, rather than the carmaker) suggested that nothing should have a place that is not known to be useful or believed to be beautiful. Opals, though, might be both. A group of researchers from the University of Southampton, in England, and the German Plastics Institute in Darmstadt, led by Jeremy Baumberg, have discovered how to create a plastic with the gemstones iridescent properties. Their invention could be used to make a sparkling substitute for paint, banknotes that are hard to counterfeit and chemical sensors that can act as visible sell-by dates.
Opals get their milky sheen and rainbow sparkle from the way light is scattered by the tiny crystals that form them. These crystals are stacked in what is known as a face-centred cubic structure. This means that the constituent atoms are arranged in a lattice of cubes, with one extra atom sitting at the centre of each cubes six faces. Light entering this lattice gets bounced around in ways that generate colour by reinforcing the peaks of some wavelengths and cancelling out those of others.
For many years researchers have been trying to develop a synthetic material with the same light-scattering properties as an opal, by etching patterns into various materials. That approach has failed. Instead, Dr Baumberg has built his opalescent material from scratch. He and his team grew tiny polystyrene spheres until they were some 200 nanometres across, before hardening them with a blast of heat. They then coated the spheres with a sticky polymer before heating them again. As the mixture was baked, the spheres moved naturally into a face-centred cubic structure.
The result is a flexible film of crystals with opalescent properties that can be used to coat malleable surfaces, producing attractive iridescent hues. The size of the spheres can be tailored to scatter particular wavelengths of light—a useful property for security applications in which it is important that materials ca
为中小学学生教育成长提供学习参考资料,学习课堂帮助学生教师更好更方便的进行学习及授课,提高趣味性,鼓励孩子自主进行学习,资料齐全,内容丰富。
文档评论(0)