锆刚玉莫来石—氮化硼系复合材料抗热震性的研究

对以锆刚玉莫来石为基引入１０％－３０％ＢＮ和以ＢＮ为基引入１０％－３０％锆刚玉莫来石的两类试样进行了抗热震性的研究。结果表明；在氧化物基料中引入ＢＮ，可以明显提高材料的抗热震性，认为这主要是ＢＮ的热膨胀系数的各向异性而引起的大量微裂纹所致。     

SiC微粉对低耐火浇注料强度和抗热震性的影响

在采用硅灰和高产减水剂的低水泥烧注料中掺加ＳｉＣ微粉后显著改善了浇米料的抗热震性，但降低了１４５０℃烧后抗压强度，虽然ＳｉＣ氧化使材料的气孔率增大，延缓了烧结进程，例题本实验范围内ＳｉＣ微粉不同掺量的试要１４５０℃烧后抗压强度大致相同，因此有，理由认为莫来石成对强度的有利影响一定程度上补偿了因气孔经增大造成的强度损失。     

改进抗热震性的碳化硅窑具材料

本文针对粘土结合碳化硅窑具材料热稳定性尚不十分理想的现状、改变结合剂的组成和材料的结构特性，从而提高了这种材料的抗热震性和扩大其应用范围。     

锆石/SiC复合物的抗热震性

测试锆石/碳化硅(30%)复合试样的抗热震性需要在高于1 000℃的温度下进行,并与气孔率值几乎相同的纯锆石试样相比较.结果证实了淬火试样的断裂应力未受到合成SiC微粒对淬火温度升高的影响.另一方面,发现重要的温差△T在复合物中要高于纯锆石试样,低于它时材料保持其初始强度.X-射线衍射分析显示了复合试样表面层的锆石分解并生成了由内核和外壳组成的试样.     

锆刚玉莫来石－氮化硼系复合材料抗热震性的研究

对以锆刚玉莫来石为基引入１０％～３０％（以质量计，下同）ＢＮ和以ＢＮ为基引入１０％～３０％锆刚玉莫来石的两类试样进行了抗热震性的研究。结果表明：在氧化物基料中引入ＢＮ，可以明显提高材料的抗热震性，认为这主要是ＢＮ的热膨胀系数的各向异性而引起的大量微裂纹所致。在ＢＮ基料中引入不超过２０％锆刚玉莫来石时，材料仍保持其优良的抗热震性。ＢＮ的编织状结构可以缓冲热震应力，阻碍热震裂纹的扩展。     

Al2O3/TiC纳米陶瓷刀具材料的抗热震性能及断裂机理研究

用强度衰减法对Al2O3/TiC纳米陶瓷刀具材料的抗热震性能进行了详细的研究.热震实验表明该种材料的临界热震温差为340℃.当温差达到350℃时,强度有明显的下降.与微米级的材料相比,纳米材料的抗热震性能反而有所降低.通过对热震后试样表面的显微观察和表面热应力的估算发现,材料在烧结后冷却过程和热震过程中产生的热应力导致试样表面产生裂纹,从而导致了材料强度的下降.     

多孔碳化硅陶瓷的抗热震性研究

本文考察了多了孔碳化硅陶瓷的抗热震性,并探讨了不同制造工艺对多孔碳化硅陶瓷抗热震性的影响。同时研究了ＳｉＣ陶瓷在热处理过程中ＳｉＣ颗粒表面氧化形成的ＳｉＯ２在不同热处理温度的状态变化及其对试样抗热震性的影响。     

碳化钛烧结复合材料的抗热震性

利用残余强度方法研究了碳化钛烧结金属陶瓷复合材料的抗热震性。发现抗热震性及残余强度变化系数与材料中金属结合的化学成分及碳化物相的体积比之间存在着强烈的依存关系。     

陶瓷材料抗热震断裂性和抗热震损伤性统一的理论

从裂纹体出发，基于能量守恒原理，论述了ＨａｓｓｅＩｍａｎ关于抗热震断裂性和损伤性统一理论的建立、意义和应用。解释了材料在热震破坏过程中不同阶段显示的不同抗热震主导机制，明确裂纹在抗热震方面的重要作用，提出营造裂纹的原理及途径。     

窑具材料抗热震性的研究进展

介绍了陶瓷材料的抗热震性评价理论,并在此基础上总结了窑具材料抗热震性的有关研究进展情况,从热震破坏产生的原因着手,探讨了提高窑具材料抗热震性的措施。     

Thermal Shock Resistance of Nano SiC-BN Composites

Nano SiC-BN composite powders were prepared by dissolving analytically pure H3BO3 and CO(NH2)2 with the mole ratio of 1:2.5 in the absolute alcohol, adding 80% β-SiC with 0.2 μm average grain size while stirring, firing at 850 ℃ in nitrogen (purity: 99.99%, pressure: 0.92-0.93 MPa) for 15 h. Nano SiC-BN composite specimens were prepared by hot-pressed sintering the nano SiC-BN composite powder in N2 atmosphere with 0.92-0.93 MPa and at 30 MPa axial pressure for 0.5-1 h at 1 750-1 800 ℃. The thermal shock re...     

Thermal shock resistance of rare-earth doped in-situ SiAlON reinforced h-BN matrix ceramics under vacuum thermal cycling

In-situ SiAlON reinforced BN-matrix ceramics were prepared by hot pressing sintering, and the effects of different rare earth oxides on the thermal shock resistance of the materials were investigated. The effects of rare earth oxides on the phase composition, microstructure, bending strength, thermal properties and thermal shock resistance of the composites were studied. The results show that the phase composition and bending strength of ceramics with different rare earth oxides had no obvious change. However, the influence on the thermal expansion coefficient of the material was notable. The thermal expansion coefficient of the ceramics with CeO₂ increased by 24.6% compared with Sm₂O₃ in the test temperature range. After 50 cycles of thermal shock at Δt = 1150 °C, the residual strength of ceramics with CeO₂ was down to 157.1 MPa, decreased by 40.6% compared with the one tested in room temperature. And the Sm₂O₃-added ceramics reduced by 34.7%–167.1 MPa after thermal shock. The decrease of the residual strength of ceramics is mainly caused by the internal stress generated by the mismatch between the growth of quartz and SiAlON phase in the matrix and the thermal expansion coefficient of the matrix. However, no macro cracks were observed on the surface of the samples after thermal shock.     

低碳MgO-C材料的抗热震性研究

以电熔大结晶镁砂、天然鳞片石墨、纳米炭黑、酚醛树脂、铝粉等为主要原料制备w(C)=3%的低碳MgO-C材料,以其抗热震性为考核指标,选取颗粒级配、复合抗氧化剂、石墨粒度和复合结合剂4个因素,进行了四因素三水平正交试验。结果表明:在本试验范围内,颗粒级配是影响低碳MgO-C材料抗热震性的主要因素,复合抗氧化剂次之,石墨粒度和复合结合剂的影响基本相当;通过极差分析确定,镁砂颗粒级配(3～1、1～0.088和≤0.088mm的镁砂的质量比)采用50:23:27,复合抗氧化剂采用Al2.5+Mg-Al0.5+B4C0.5,石墨粒度采用10μm的,复合结合剂采用炭黑N220+沥青+酚醛树脂,可制备出抗热震性最佳的低碳MgO-C材料。     

氮化硅陶瓷材料高温抗热震性能及其衰减规律研究

氮化硅陶瓷作为先进陶瓷材料具有耐高温、抗腐蚀等优异性能,因此被广泛应用于航空航天领域的强热冲击环境。热压烧结制备的Si3N4复合材料的抗弯强度较高,但抗热震性能随温度升高显著降低,热压烧结工艺在提升抗热震性能方面尚有不足。本文提出了使用二次热处理烧结方式来提高Si3N4陶瓷的抗热震性能,通过热压烧结-气压烧结二次热处理的烧结方式获得更致密、抗热震性能更好的Si3N4陶瓷材料。测试结果显示,常规热压方式制备的氮化硅陶瓷,随着热震温度的升高、次数的增加,材料内部产生微裂纹的概率增大,热震后试样抗弯强度逐渐降低,1200℃时平均强度下降率达23.48%。而经过二次热处理后氮化硅陶瓷抗弯强度略有降低,但抗热震性能得到明显改善,随着热处理时间增加,二次热处理后氮化硅陶瓷显微结构更加致密,抗热震性能将明显提高,热震后强度下降率明显减小,1200℃热震10次后强度下降率为12.25%。本文提出了提高Si3N4陶瓷的抗热震性的方法,探讨了氮化硅陶瓷在1200℃高温下的抗热震性能及其衰减规律,为改善氮化硅陶瓷器件高温性能提供了参考。     

莫来石加入量对SiC-莫来石材料性能的影响

以SiC颗粒(2～1mm、≤1mm)、SiC细粉(≤0.066mm)、莫来石细粉(≤0.074mm)和SiO2微粉(≤0.045mm)为原料,在w(SiC细粉)=40%的基础配方中分别以质量分数为5%、10%、15%、20%和25%的莫来石细粉取代相应量的SiC细粉,并外加2%的SiO2微粉,成型后分别在1300℃和1500℃的大气气氛中煅烧3h,测定试样煅烧前后的质量变化率以及烧后试样的显气孔率、常温抗折强度和抗热震性,并用扫描电镜观察试样的显微结构。结果表明:在SiC自保护氧化的作用下,试样的抗氧化性较强,而且随着莫来石加入量的增大,1300℃烧后试样的氧化程度减小,1500℃烧后试样的氧化程度先减小,至15%后又增大;1300℃烧后试样比1500℃具有较高的抗热震性,并且随着试样中莫来石加入量的增大,烧后试样的抗热震性提高。     

Thermal shock resistance of Al2O3/SiO2 composites by sol-gel

In this paper, the SiO₂ ceramic matrix composites were reinforced by the two-dimensional (2D) braided Al₂O₃ fibers by sol-gel. To develop the high performance aeroengine with excellent resistance to thermal shock for advanced aerospace application, two different thermal shock temperatures (1100?°C and 1300?°C) and three different thermal shock cycles (10, 20 and 30 cycles) were tested and compared in this paper; besides, the thermal shock resistance of Al₂O₃/SiO₂ composites was investigated in air. Our results suggested that, the flexural strength of the untreated composites was 78.157?MPa, while the residual strength of Al₂O₃/SiO₂ composites under diverse thermal shock cycles and temperatures had accounted for about 95% and 50% of the untreated composites, respectively. Meanwhile, the density and porosity of the composites were gradually increased with the increase in test temperature. Moreover, the changes in fracture morphology and micro-structural evolution of the composites were also observed. Our observations indicated that, the fracture morphology of the composites mainly exhibited ductile fracture at the thermal shock temperature of 1100?°C, whereas brittle fracture at the thermal shock temperature of 1300?°C. Additionally, Al₂O₃/SiO₂ composites belonged to the Oxide/Oxide CMCs, so no new phase was formed after thermal shock tests. Above all, findings of this paper showed that Al₂O₃/SiO₂ composites had displayed outstanding thermal shock resistance.     

反应烧结碳化硅材料的抗热震性能研究

通过对比不同温差热震后材料的残余强度 ,对反应烧结碳化硅材料的抗热震性能进行了研究。结果表明 :反应烧结碳化硅材料的抗热震性能与显微组织密切相关 ,低游离硅含量与小粒径的反应烧结碳化硅材料具有较好的抗热震断裂性能 ,而高游离硅含量或大碳化硅粒径的材料具有相对优异的抗热震损伤性。对反应烧结碳化硅材料的抗热震性与显微组织的关系进行了探讨。     

MgO-SiC-C复合材料力学性能和抗热震性能研究

对MgO-SiC-C复合材料的力学性能和抗热震性能的研究结果表明SiC含量增加,材料的强度和抗热震性能提高。升温过程中结合剂结构的变化对MgO-SiC-C复合材料强度变化起重要作用。     

炭/陶复合材料的抗热震性能研究

对含石墨的炭／陶复合材料优良的抗热震性能进行了讨论。这种性质与石墨的导热系数大、断裂功高、热膨胀和弹性模量小密切相关。     

Enhanced mechanical properties,thermal shock resistance and ablation resistance of Si2BC3N ceramics with nano ZrB2 addition

The mechanical properties, thermal shock resistance, and ablation resistance of nano ZrB₂ modified Si₂BC₃N ceramics were investigated. The results show that ZrB₂ stimulated microstructure evolution obviously. Therefore, the maximum strength and fracture toughness reach 559.6 MPa and 6.77 MPa·m^1/2, which are improved by 61.0% and 29.4%, respectively. Furthermore, the residual strengths of 10 wt% ZrB₂ containing composites tested at 1000 ℃ retain 363.6 MPa, which is much higher than 97.7 MPa of pristine Si₂BC₃N ceramics. Besides, the ablation resistance of ZrB₂ modified Si₂BC₃N ceramics at 3000 ℃ is enhanced remarkably and the linear and mass ablation rates of ZrB₂-10 are only 0.009 mm/s and 1.91 mg/s, respectively. The ablation in the ultra-high temperature zone is totally dominated by the ZrB₂ component, and the thermochemical erosion is determined by the oxidation resistance of ZrB₂ in the thermal affected zone.