SiC—TiB2系复合材料的某些性能

本文研究了在超高压力器中用准液体静力热压法制取含有粒度极小的相组成的ＳｉＣ－ＴｉＢ２系致密复合材料的可能性。对所制成的材料的某些物理机械性能及耐热性能做了研究。     

原位生成TiB2颗粒增韧SiC基复相陶瓷研究

提出一种新的方法制备ＳｉＣ－ＴｉＢ２颗粒复相陶瓷。通过Ｔｉ，Ｓｉ与Ｂ４Ｃ之间的化学反应在ＳｉＣ基体中原位生成ＴｉＢ２颗粒，获得的ＴｉＢ２颗粒一般在５μｍ以下，但发现有ＴｉＢ２颗粒团聚现象。其中ＳｉＣ－ＴｉＢ２３０％（ｖｏｌ）复相陶瓷的断裂韧性和三点弯曲强度分别比ＳｉＣ基体提高约１倍，达到４．５ＭＰａ·ｍ＾１／２和４００ＭＰａ。认为ＴｉＢ２颗粒与ＳｉＣ基体之间热膨胀系数不同导致的残余应力场引起的裂纹     

Integrated high strength and high toughness induced by elongated TiB2 grains in reactive sintered TiB2–TiC–SiC ceramics

Although the addition of other phases into TiB₂ matrix to form ceramic composites has been widely used to improve the mechanical properties of monolithic TiB₂ ceramics, it is still difficult to greatly enhance the flexural strength and fracture toughness simultaneously. In this work, TiB₂–TiC–SiC composites were successfully prepared by reactive spark plasma sintering of Ti₃SiC₂–B₄C–Ti powder mixtures. During the sintering process, TiB₂ grains grew into an elongated morphology, endowing the composites with integrated high strength and high toughness. The growth mechanism of TiB₂ grains was attributed to the evaporation–condensation kinetics induced by the presence of B₂O₃. These findings can accelerate the exploration of ceramic composites with excellent comprehensive properties.     

Wear resistance of αSiC–TiB2 composites prepared by reactive sintering

The relative wear resistance of αSiC–TiB₂ composites prepared by reactive sintering was investigated on a pin on flat tribometer, in air and in presence of water. Experimental results show that the composite materials are less worn than monolithic SiC. The wear mechanisms in air and water are identified.In air, a protective oxidised debris layer is formed on the composites, whereas roller formation was observed with SiC. In water, the surface of the composites is polished, whereas SiC is worn by fragile ruptures (cleavages).     

Reaction Synthesis and Mechanical Properties of TiB2–AlN–SiC Composites

TiB₂–AlN–SiC (TAS) ternary composites were prepared by reactive hot pressing at 2000°C for 60 min in an Ar atmosphere using TiH₂, Si, Al, B₄C, BN and C as raw powders. The phase composition was determined to be TiB₂, AlN and β-SiC by XRD. The distribution of elements Al and Si were not homogeneous, which shows that to obtain a homogeneous solid solution of AlN and SiC in the composites by the proposed reaction temperatures higher than 2000°C or time duration longer than 60 min are needed. The higher fracture toughness (6·35±0·74 MPa·m^1/2 and 6·49±0·73 MPa·m^1/2) was obtained in samples with equal molar contents of AlN and SiC (TAS-2 and TAS-5) in the TAS composites. The highest fracture strength (470±16 MPa) was obtained in TAS-3 sample, in which the volume ratio of TiB₂/(AlN+SiC) was the nearest to 1 and there was finer co-continuous microstructure. ©     

Effects of graphite nano-flakes on thermal and microstructural properties of TiB2–SiC composites

In the last decades, the production of ultra-high temperature composites with improved thermo-mechanical properties has attracted much attention. This study focuses on the effect of graphite nano-flakes addition on the microstructure, densification, and thermal characteristics of TiB₂–25 vol% SiC composite. The samples were manufactured through spark plasma sintering process under the sintering conditions of 1800 °C/7 min/40 MPa. Scanning electron microscopy images demonstrated a homogenous dispersion of graphite flakes within the TiB₂–SiC composite causing a betterment in the densification process. The thermal diffusivity of the specimens was gained via the laser flash technique. The addition of graphite nano-flakes as a dopant in TiB₂–SiC did not change the thermal diffusivity. Consequently, the remarkable thermal conductivity of TiB₂–SiC remained intact. It seems that the finer grains and more interfaces obstruct the heat flow in TiB₂–SiC–graphite composites. Adding a small amount of graphite nano-flakes enhances the densification of the mentioned composite by preventing the grain growth.     

(SiC,TiB2)/B4C复合材料的微观结构及性能

以B4C与Si3N4和少量SiC,TiC为原料,Al2O3和Y2O3为烧结助剂,烧结温度为1 800～1 880℃,压力为30 MPa的热压条件下制备(SiC,TiB2)/B4C复合材料.用透射电子显微镜、扫描电子显微镜和能谱分析进行显微结构分析.结果表明:在烧结过程中反应生成了SiC,TiB2和少量的BN.复合材料的主晶相之间有长棒状架构弥散相和束状弥散相,在部分B4C晶粒内部出现了内晶结构.结合对复合材料性能的分析表明:新形成相、均匀细晶和棒状结构对提高材料的性能具有重要作用.通过对材料断口形貌和裂纹扩展模式分析认为,复合材料的断裂机制主要为裂纹偏转.     

TiB2表面镀铜工艺

利用化学镀覆技术成功在TiB2颗粒表面均匀化学镀覆铜。透射电子显微镜观察表明：通过严格的镀前预处理工艺的优化设计以增加活化点,对传统镀液配方的调整以降低镀速,能够成功地在TiB2颗粒表面镀覆一层铜,从而培强了其和铜基体之间的界面结合力,为TiB2在复合材料领域之中的应用打下了坚实基础。     

Development of spark plasma sintered conductive SiC–TiB2 composites for electrical discharge machining applications

Highly dense electrically conductive silicon carbide (SiC)–(0, 10, 20, and 30 vol%) titanium boride (TiB₂) composites with 10 vol% of Y₂O₃–AlN additives were fabricated at a relatively low temperature of 1800°C by spark plasma sintering in nitrogen atmosphere. Phase analysis of sintered composites reveals suppressed β→α phase transformation due to low sintering temperature, nitride additives, and nitrogen sintering atmosphere. With increase in TiB₂ content, hardness increased from 20.6 to 23.7 GPa and fracture toughness increased from 3.6 to 5.5 MPa m^1/2. The electrical conductivity increased to a remarkable 2.72 × 10³ (Ω cm)^–1 for SiC–30 vol% TiB₂ composites due to large amount of conductive reinforcement, additive composition, and sintering in nitrogen atmosphere. The successful electrical discharge machining illustrates potential of the sintered SiC–TiB₂ composites toward extending the application regime of conventional SiC-based ceramics.     

SiC晶须对Al2O3／TiB2／SiCw陶瓷刀具材料高温断裂韧性的影响

研究了不同ＳｉＣ晶须含量的Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ陶瓷刀具材料的断裂韧性随温度的变化规律。结果表明：Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ陶瓷材料的Ｋ１Ｃ在１０００℃内随温度的升高而增大；晶须含量越大，通过计算分析表明，随温度的升高粘裂时拔出的晶须大大增多，当晶须体积含量（下同）为２０％时，Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ陶瓷在室温时只有长径比小于２．８７的晶须在断裂时才有可能产生拔出，而在９００℃时     

碳相含量对C—SiC—TiB2复合材料结构和力学性能的影响

研究了碳相含量对原位合成的碳／陶复合材料（Ｃ－ＳｉＣ－ＴｉＣ－ＴｉＢ２）的结构和性能的影响。结果表明：随着碳含量的增加,材料的抗弯强度下降。材料的烧结温度应随着碳含量增加相应的提高,才能获得致密的碳／陶复合材料     

TiB2 陶瓷材料氧化动力学研究

采用Ф函数法,计算了TiB2陶瓷在空气中氧化时的ΔG°R值。计算表明,在700~1 100℃的温度区间内,TiB2陶瓷将会发生氧化。在硅碳棒高温炉中进行了TiB2陶瓷的氧化试验,并推导了TiB2陶瓷的氧化动力学公式。研究表明,TiB2陶瓷在空气中中温氧化时,其氧化行为表现为氧化增重随时间的变化服从抛物线规律;在研究的温度范围内,TiB2陶瓷的氧化活化能为44 982.8 J/mol;TiB2陶瓷材料的氧化主要由氧通过氧化层的向内扩散所控制。     

ZrB2质与TiB2质耐火材料

介绍了ZrB2 与TiB2 以及其他一些非氧化物高温材料的性质 ;ZrB2 与TiB2 在高温工业中的应用与预期发展 ;ZrB2 与TiB2 原料与制品的生产 ,包括自蔓延高温合成ZrB2 与TiB2 ;ZrB2 质与TiB2 质复合材料 ,如ZrB2 -SiC ,TiB2-SiC ,ZrB2 -BN ,TiB2 -BN ,ZrB2 -MoSi2 ,TiB2 -MoSi2 ,ZrB2-C ,TiB2 -C ,ZrB2 -B4C ,TiB2 -B4C等。     

TiB2基陶瓷复合材料研究进展

本文综述了近年来TiB2基复相陶瓷和金属陶瓷的研究进展，对TiB2基复合陶瓷的组成体系、制备工艺与材料性能特别是力学性能的关系进行了较详细的分析和介绍。     

TiB2及其复合材料的研究进展

本文评述了近十几年来ＴｉＢ２陶瓷及其复合材料的研究进展,从原料制备,烧结工艺,显微结构及复合材料的发展方向等方面进行了分析和讨论。指出了目前限制陶瓷及其复合材料快速发展的主要问题在于：原料价格昂贵,难以烧结致密化,同时材料的性能有待进一步的提高。最后,本文提出了解决上述问题的可行的办法。     

High-performance B4C–TiB2–SiC composites with tuneable properties fabricated by reactive hot pressing

In this work, we systematically studied the effects of powder characteristics (B₄C, TiC and Si powders) on the existential form of toughening phases (SiC and TiB₂) as well as the overall microstructure and properties of B₄C–TiB₂–SiC composites fabricated by reactive hot pressing. The particle size of the TiC powder plays a largely determining role in the development of novel toughening phases, the TiB₂–SiC composite structure, that are formed in the B₄C matrix, while the Si particle size affects the agglomerate level of the SiC phase. The TiB₂–SiC composite structure and SiC agglomerates enhance the fracture toughness, but decrease the flexural strength. Both the microstructure and mechanical properties of B₄C–TiB₂–SiC composites can be effectively tuned by regulating the combinations of the particle sizes of the starting powders. The B₄C–TiB₂–SiC composites demonstrate flexural strength, fracture toughness and Vickers hardness in the respective range of 567–632 MPa, 5.11–6.38 MPa m^1/2, and 34.8–35.6 GPa.     

碳相含量对C—SiC—TiC—TiB2复合材料结构和性能的影响

本文研究了碳相含量在１０～４０ｖｏｌ％范围内变动时对原位合成的碳／陶复合材料（Ｃ－ＳｉＣ－ＴｉＣ－ＴｉＢ２）的结构和性能的影响。结果表明：随着碳含量的增加，材料的抗弯强度下降。当碳相含量小于２０ｖｏｌ％时，材料的抗弯强度可达到４００Ｍｐａ以上。随着碳相含量的增加，应相应提高烧结温度。对材料在６００°Ｃ、８００°Ｃ、１０００°Ｃ、１２００°Ｃ下的抗氧化性能进行了研究。研究发现了在试验温度下，材料表现出优良的抗氧化能力。碳含量较少的试样表现为氧化增重，碳含量较多的试样表现为氧化失重。     

TiB2涂层的制备技术进展

介绍并比较了多种制备ＴｉＢ２涂层的方法，并对制备过程中存在的几个主要问题进行了总结。