Processing of Nanostructured Ceramics

纳米晶陶瓷的吸引力来自于它们提供不同寻常的物理和机械性能的潜力，根据材料的不同，这些性能可以包括高温超塑性，正常不透明材料的光学透明度和一系列其他电、光和磁性能，以及潜在的更高的强度、韧性和硬度。尽管一些商业纳米粉末现在已经被大量生产，但需要通过工业上可行的路线将其固结成致密的纳米结构部件，以充分利用所提供的潜力。如果能够实现这一点，就有可能将这些材料用于非常广泛的应用。先进陶瓷是许多电子器件、燃料电池、磁铁、传感器和生物材料以及非常广泛的结构部件中的活性材料。这意味着它们被用于几乎所有类型的工业，包括发电、航空航天、运输和军事应用以及其他材料的制造。这类应用对于保持全球竞争力、降低能源消耗和最大限度地减少污染至关重要。据估计，2000年全球市场规模为200亿美元，年增长率为7.2%。其中，电子行业的市场占有率约为65%，其余的属于化学加工、涂料和先进结构力学行业。这项研究提案的主要目标是开发拉夫堡大学的一些最新发展。这是在EPSRC以前的拨款下已经实现的。具体地说：*虽然现在可以从纳米悬浮液中注浆浇注非常均匀和高密度的压坯，但目前烘干那些由高固含量悬浮液制成的压坯(可以产生最好的坯体)存在一个主要问题-即使使用湿度干燥器也可能需要几天时间。这些物体的结构需要了解作为所使用的加工条件的函数，特别是悬浮液的固体含量。这让我们有机会控制这种情况，或许还可以改善这种情况，以便在不牺牲身体性能的情况下，干燥时间可以快得多。*类似地，现在可以从通过喷雾冷冻干燥纳米悬浮液形成的粉末中干燥均匀和高密度的压坯(与制作速溶咖啡颗粒的过程相同)。然而，高固含量悬浮液(产生最高密度)又一次带来了问题，这一次是坚硬的凝聚体不会破碎。需要进行与上述非常类似的工作，才能让我们了解为什么会发生这种情况，以及可以采取什么措施。*这两种类型的压坯都需要在熔炉中烧成，以生产完全致密的陶瓷，同时保持极细的、低于100纳米的平均颗粒尺寸。虽然现在也可以使用一种新的无压力(因此成本较低)的工艺来实现这一点，但对这一工艺如何工作的理解仍然不是完美的，我们还需要扩大规模以制造更大的部件。*最后，随着我们接近可以将这些开发用于商业开发的点，我们确实需要更好地了解行业的需求。我们离开发他们可以在工厂车间使用的工艺路线还有多远？他们对哪些陶瓷系统最感兴趣？哪些公司真的准备好接受新的“纳米技术”，哪些公司热衷于再袖手旁观一段时间。这些问题以及其他问题都将在该方案的最后任务中得到解决。

The appeal of nanocrystalline ceramics arises from their potential to offer unusual physical and mechanical properties, which, depending on the material, can include superplasticity at elevated temperatures, optical transparency for normally opaque materials and a range of other electrical, optical and magnetic properties as well as potentially higher strengths, toughnesses and hardness.Although some commercial nanopowders are now produced in relatively large quantities, consolidation into dense nanostructured components by industrially-viable routes is needed to take full advantage of the potential offered. If this can be achieved there is the potential to use the materials for a very wide range of applications. Advanced ceramics are the active material in many electronics devices, fuel cells, magnets, sensors and biomaterials, as well as a very wide range of structural components. This means that they are used in almost every type of industry, including power generation, aerospace, transportation and military applications as well as in the manufacture of other materials. Such applications are vital to maintaining global competitiveness, decreasing energy consumption and minimising pollution. Their estimated world market was >$20B in 2000, with an annual growth rate of 7.2%. Of this, the electronics sector was ~65% of the market, the rest falling into the chemical processing, coatings and advanced structural mechanics sectors.The primary objective of this research proposal is to develop a number of recent developments at Loughborough Univ. that have been achieved under previous EPSRC grants. Specifically:* Whilst it is now possible to slip cast very homogeneous and high density compacts from nanosuspensions, there is currently a major problem with drying those made from high solids content suspensions (which yield the best bodies) - it can take several days even using a humidity drier. The structure of these bodies need understanding as a function of the processing conditions used, particularly the solids content of the suspension. This then gives us a chance to control the situation and perhaps improve it so that drying times can be much faster without sacrificing the properties of the body.* Similarly, it is now possible to dry press homogeneous and high density compacts from powders that have been formed by spray-freeze drying the nanosuspensions (the same process used to make instant coffee granules). Once again, however, the high solids content suspensions (which yield the highest densities) provide problems, this time with hard agglomerates that don't crush. Very similar work needs performing as above to allow us to understand why this is happening and what can be done about it.* Both types of compact need firing in furnaces to produce fully dense ceramics whilst retaining an extremely fine, sub 100 nm, average grain size. Whilst this can now also be done using a novel pressureless (and hence low cost) process, the understanding of how this process works is still not perfect and we also need to scale up to make larger components.* Finally, as we near the point where we can exploit these developments commercially, we really need to develop a better understanding of industry's requirements. Just how close are we to developing process routes that they can use on their factory floors? Which ceramic systems are they most interested in? Which companies are really ready to embrace the new 'nanotechnology' and which are keen to sit on the sidelines for a bit longer yet. These issues, and others, will all be addressed in the final task of the programme.