Advances in engineering rely on the development of new materials. The materials must have improved properties, capable of being tailored to a specific application need, to fulfil the requirements of designers of the future. Ceramic fibres are playing a major part in enabling the development of new composite materials capable of withstanding the forces and temperatures exerted on components in industries as diverse as aerospace and sports goods. However, the currently available fibres have limitations or problems associated with their manufacture and use, and can be expensive. Commercial Fibre ProductionSeveral types of ceramic fibres are currently available for use in a variety of applications. These can be divided into two main categories. Oxide Fibres主要基于氧化铝，氧化物纤维都遇到了谷物生长问题，这些问题破坏了纤维的完整性，并且在加热和冷却周期上的1100°C以上的相变问题。它们由三种不同的技术制造。浆液旋转涉及在有机聚合物或氧化铝前体聚合物中的亚微米结晶陶瓷颗粒的分散，干燥成纤维。欧洲杯猜球平台 The sol-gel method produces microscopic gels by the spinning of viscous solutions of inorganic metal alkoxide polymers and silicon alkoxide, which are then heated to drive off any volatile materials to produce porous fibres with a non-uniform cross-section. Finally, single crystal fibres can be made from the film edge defined growth process, an expensive technique which produces alumina, and yttria-stabilised alumina filaments. Non-Oxide Fibres两种主要制造方法用于生产非氧化物纤维。一条聚合物途径涉及有机硅卤化物的还原和热重排，然后融化到非常细的纤维（7-14µm）上。还可以使用化学蒸气沉积（CVD），从而将细碳或钨丝暴露于有机硅气体中，从而导致化学反应并产生陶瓷纤维。CVD过程还使纤维的涂层能够防止反应或提供修改的特性，但这是最终光纤生产的额外步骤，因此增加了成本。 Ceramic Fibre Usage各种复合材料使将陶瓷纤维纳入结构中受益。欧洲杯足球竞彩 Organic Matrix CompositesOrganic matrix composites are generally reinforced by either glass or carbon fibres, which increase stiffness and fatigue life, and decrease the dielectric constant, improving the compressive strength. Glass matrix composites have been developed for use in gas turbine or military applications. In general, these are either lithium or magnesium alumino-silicates reinforced by silicon carbide fibres, or glassy carbon systems made from phenolic resins, reinforced by various non-oxide fibres. Metal Matrix Composites金属基质复合材料由于其高刚度，强度，温度性能，疲劳寿命和耐蠕变性而非常受欢迎。欧洲杯足球竞彩在金属矩阵中使用陶瓷纤维的主要缺点是合金元素与陶瓷纤维优先反应，破坏其增强完整性。为了防止这种情况，将需要用另一种材料覆盖纤维，该材料将充当基质及其增强纤维之间的接口。 Ceramic Matrix CompositesCeramic matrix composites can also benefit from the use of ceramic reinforcing fibres, but again, reaction between the fibre and the body ceramic can cause degradation. Bicomponent Extrusion双成分挤出是一种旋转技术，可以通过干燥或熔体旋转通过相同的孔口同时挤出两个不同的陶瓷前体。这主要产生具有核心和护套组件结构的陶瓷纤维，尽管可以使用基质 - 纤维和其他组件的其他排列。 可以简单地将双成分挤压视为两台在另一个内部工作的旋转机。需要两组电动机，齿轮箱，驱动轴和泵，它们使用两组压力换能器通过毛细管通过双储水箱喂食。但是，可以采用中央温度测量系统。从储层中的毛细血管以90°的角度馈入中心搅拌机头，使核心前体可以直接进料到核心旋转旋钮，而鞘毛毛细管则通过插管分成两个毛细管，将其分成两个毛细管圆形的两侧。毛细管。挤出后，可以使用与用于治疗整体（单个成分）纤维的技术相似的技术，包括加热，氧化，辐射和化学方法。 Production VariablesThe innovative production apparatus, has a maximum extrusion capability of one litre per hour from both the precursor reservoirs, giving a theoretical annual production capacity of 250kg of bicomponent fibre, an excellent rate for a laboratory scale machine. With industrial modifications, such as multiple extrusion nozzles and larger pumps, the process could produce the fibres at a phenomenal rate. Fibres with a 7-14 µm core and a 1-2 µm sheath can be produced at speeds of up to 200-300 metres per minute using the laboratory machine, figure 1. The final diameter and speed of extrusion are controlled by several factors: •初始聚合物的分子量和溶剂的最小水平，允许丝形成。 •The core/sheath spinerette ratio, and the ratio of the wall thickness of the core spinerette to the total diameter of the spinerette orifice. •The draw down ratio, or the reduction in diameter due to extrusion required to extract enough solvent to allow solid filament formation. •聚合物晶体尺寸的均匀性。 •The length of the chamber, and the direction of gas flow.
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Figure 1.Bicomponent extrusion using the monomeric precursors a and b. |
The control of the pyrolysis regime is also of importance to the final product, and in particular the factors of time, temperature and atmospheric gases. Contained within the patents for the bicomponent extrusion process are methods to control stoichiometry, and to control pyrolysis speed to match extrusion output, allowing a continuous process, rather than the batch processes currently used. Advantages of Bicomponent Extrusion
The bicomponent process, by generating ceramic fibres with a core-sheath structure, can eliminate many problems experienced when using monolithic ceramic fibres in composite materials. The sheath can act as an interfacial barrier, preventing reaction between the core and the metal matrix in metal matrix composites, for example, and allowing the production of a wide variety of systems, table 1. Other advantages include: •降低了由于一通处理而导致的成本 •Tailored properties for individual applications •Enhanced strength through lower oxygen content. 表格1。Metal and ceramic matrix composites incorporating ceramic fibres produced by the bicomponent extrusion process.
|
Silica/Al2O3 |
C/BN |
Al |
SiC |
TiB2 |
Al/Ti |
SiC |
C |
毫克 |
SiC |
C |
SiC |
SiC |
BN |
聚合物B-SIC |
TiN |
BN |
C |
Yttrium- Al2O3 |
C/BN/PSZ |
Al2O3 |
SiC |
BN |
C |
Present and Future Applications随着物业范围的扩展，陶瓷纤维的市场看起来会增长。它们已经在金属基质复合材料中，在机床中用于改善耐磨性的机床，用于僵硬的跑步产品，以及在喷气发动机组件和汽车组件中，以减轻重量并提高燃油效率，并且可以使用双色组件类型来生产。陶瓷纤维增强的柴油发动机活塞由重力铸造。 Future applications of ceramic matrix composites are also numerous, and include reducing the weight and therefore the launch costs of satellites, heat shields for space planes, rocket engine components, advanced organic matrix composite tooling (removing the need for stainless steel moulds), high precision machine tools, body armour and military hardware applications, biomedical implants, and biomimetics. 目前，陶瓷纤维的用途受其可操作的温度的限制，但预计将来会随着新设计的纤维（例如双成分类型）的利用而上升。研究感兴趣的另一个领域可能是从3GNM的当前值提高拉伸强度-2to 9GNm-2, although the theoretical maximum of 27GNm-2is unlikely to be achieved! Other ceramic fibre formulations are also under consideration, with titanium silicide showing promise. |