High performance nanotube fibres

纳米粒子可以表现出与块体不同的性质，在各种应用中具有潜在的优势。例如，半导体的纳米颗粒具有高度可定义的颜色，因此对安全墨水很有用，而用于医学示踪分析的放射性核苷酸原子可以保存在巴基小球中，并与身体化学分开。在机械方面，碳纳米管的尺寸并不比聚合物分子大很多，它具有特殊的轴向强度和刚性，单个纳米管的强度至少是任何已知纤维的~10倍。挑战是使纳米管保持一致，然后将其构建成纤维，以便将它们的一些出色的机械性能转化为有用的工程材料。最近，剑桥大学的团队展示了一种在一次操作中制造碳纳米管纤维的工艺。这一工艺(在《科学》杂志上宣布)制造高性能纤维的潜力引起了全世界的极大兴趣，无论是对现有的纤维行业来说，它代表着一种颠覆性的技术，还是纤维用户。然而，技术拉动如此之大，以至于我们在基础层面上对这一过程的洞察需要迎头赶上。我们需要能够生产预定尺寸的纳米管，作为迈向具有高度一致性能的纤维产品的第一阶段。所看到的特殊性质的原因还不完全清楚，工艺参数和所得到的结构之间的关系也不完全清楚。更深入的了解也是扩大战略的基础，这将是估计产品可能的工业成本以及未来风险的关键。到目前为止制造的纤维的强度和硬度至少将与目前的碳纤维和芳纶纤维产品相媲美，而在骨折时的能量吸收是这些材料的几倍，这是对防弹衣和车辆强化市场新兴材料的赞誉。然而，这一过程内在的、一步到位的简单性表明，这种产品应该比目前可用的任何同类产品便宜得多。事实上，这一过程可能被视为制造碳黑的高度精炼版本，碳黑是一种售价约为碳纤维成本五分之一的大宗商品。如果这种新的更便宜的纤维在复合材料中获得成功，它可能会降低运输车辆的成本，使F1结构技术能够接触到家庭汽车。该项目的第一阶段将是建立一个完全仪表化的生产平台，以更多地了解纳米管的生长和缺陷的来源，这些缺陷是测量性能不一致的来源。将进行关键实验，以确定扩大规模的最佳方法，特别是将建造第二个反应堆，以评估将该过程小型化作为扩大战略。有太多东西需要我们去理解。将生产千米长的纤维，以便对应用进行外部评估。碳纳米颗粒为医学提供了机会：药物输送和癌症治疗就是两个例子。然而，药理学家和肿瘤学家的热情被毒物学家的警示说明所平衡。使纳米颗粒独一无二的特性会在体内产生有益或有害的影响。就纳米管而言，最新的毒理学研究表明，它们的毒性并不比(比方说)激光打印机中的颗粒更大，然而，人们认识到，从长远来看，人体可能难以消除纳米管。从商业角度来看，任何纳米颗粒的恐慌，无论是否有充分的理由，都可能阻碍发展，在最糟糕的情况下，会使投资面临风险。随着这项工作的推进，剑桥大学的材料研究人员将与纳皮尔大学和国际移民组织的毒物学家密切合作。

Nanoscale particles can show properties which are different from the bulk, and are potentially advantageous for various applications. For example, nanoparticles of semiconductors have highly definable colours and hence are useful for security inks, while atoms of radionucleotides, used for tracer analysis in medicine can be held within bucky balls and kept separate from body chemistry. On the mechanical front, carbon nanotubes, which are not much larger in size than polymer molecules, show exceptionally axial strength and stiffness, the strength of an individual nanotube being at least ~10 times higher than that of any known fibre. The challenge is to make the nanotubes consistently and then to build them into fibres so that some of their brilliant mechanical properties can be translated into useful engineering materials. A process to make carbon nanotube fibres in a single operation has recently been demonstrated by the Cambridge team. The potential of the process (announced in Science ) for making high performance fibres has led to considerable interest worldwide, both from the existing fibre industry, for whom it represents a disruptive technology, and from fibre users. However, the 'technology pull' is such that our insight into the process at a basic level needs to catch up. We need to be able to produce nanotubes of predetermined dimensions as the first stage towards a fibre product with highly consistent properties. The reason for the exceptional properties seen is not fully understood, nor is the relation between process parameters and the resultant structure. A deeper understanding is also necessary as a basis for scale-up strategies, which will be critical in estimating the likely industrial cost of the product, and thus the future risk. The fibres made so far promise strengths and stiffnesses which will at least rival current carbon and aramid fibre products, while the energy absorption on fracture is several times that of these materials, commending the material for the burgeoning markets in body armour and vehicle 'hardening'. However, the intrinsic, one-step simplicity of the process indicates that the product should be very much cheaper than any equivalent currently available. Indeed, the process might be viewed as a highly refined version of that used to make carbon black, a commodity which sells for about 1/50th of the cost of carbon fibre. If this new cheaper fibre is successful in composites, it could bring down the cost of transport vehicles, enabling F1 structural technology to reach the family car. The first stage of the project will be to build a fully instrumented production rig, to learn more about the nanotube growth and the origin of defects which are a source of inconsistency in measured properties. Key experiments will be undertaken to determine the best approach to scale-up, in particular a second reactor will be built to evaluate to miniaturise the process as a scale-up strategy. There is so much yet to be understood. Kilometre lengths of fibre will be produced so that the applications can be externally assessed. Carbon nanoparticles provide opportunities for medicine: drug delivery and cancer treatment being two examples. However, the enthusiasm of pharmacologists and oncologists is balanced by cautionary notes from toxicologists. The properties which make nanoparticles unique lead to effects in vivo which may either be beneficial or detrimental. In the case of nanotubes, the latest toxicological studies indicate that they are no more toxic than particles from (say) a laser printer, however, it is recognised that the human body may have difficulty in eliminating nanotubes in the long term. From the business angle, any nanoparticle scare, whether well founded or not, may hold development back and at worst put investment at risk. As we take this work forward the materials researchers at Cambridge will work closely with toxicologists at Napier University and the IOM.