一种自焙炭块的导热系数

利用激光脉冲法、铜卡量热计法和浸渍法分别测定了不同石墨化度的自焙炭块的热扩散系数α、恒压比热容ｃｐ和体积密度Ｄｂ，并据λ＝Ｄｂｃｐα求出２００～１１００℃该炭块的导热系数λ。结果表明：原始自焙炭块的λ值随温度升高而增大，这可能是由于测试过程中石墨化度随温度升高而明显增加，且λ值与石墨化度成正比所致；恒温下，λ值随石墨化度增加而增大；在石墨化度较高时，λ值随温度升高而稍有降低。当石墨化度在０．７以上时，国产自焙炭块的λ值接近美国ＵＣＡＲ炭砖的值     

热处理温度对炭/炭复合材料性能的影响

利用热梯度化学气相沉积工艺制备了炭／炭复合材料，研究了热处理温度对炭／炭复合材料石墨化度、硬度、抗弯强度和摩擦性能的影响。结果表明：石墨化度随着热处理温度的升高而增大，炭，炭复合材料石墨化的能垒在2200℃附近；炭／炭复合材料的抗弯强度随着热处理温度的升高，先升高后降低，当热处理温度是2000℃时，所得材料的抗弯强度最高；炭／炭复合材料的硬度和摩擦系数随着热处理温度的升高而降低。     

不同热处理温度下炭/炭复合材料的制动摩擦性能

在MM - 10 0 0摩擦试验机上 ,对一种针刺毡结构的炭 /炭 (C/C)复合材料在不同热处理温度下的摩擦磨损性能进行了测试 ,并对摩擦表面进行了光学形貌观察 ;采用X射线衍射技术测试了其在不同热处理温度下的石墨化度 ,并对石墨化度与材料的摩擦性能之间的关系进行了探讨。结果表明 :随着热处理温度升高 ,针刺毡结构的炭 /炭复合材料的石墨化度提高 ,摩擦磨损性能也相应发生变化 ,即摩擦因数开始随热处理温度升高而增大 ,到 2 30 0℃时出现峰值 ,线性磨损和质量磨损则在 2 2 0 0℃时出现峰值 ,氧化磨损则随热处理温度升高而下降。石墨化度对材料的摩擦磨损性能有一定影响 ,合理控制石墨化度可以得到理想性能的材料 ,对本研究所用的C/C复合材料其最佳的热处理温度为 2 30 0℃。     

硼酸对炭纤维及C/C复合材料导热性能的影响

在预制体炭纤维预石墨化前对其进行硼酸处理，研究硼酸对炭纤维性能，C／C复合材料导热率的影响及其作用机理。结果表明：硼酸通过高温热处理过程所分解的硼对炭纤维起到了有效的催化石墨化作用，显著提高炭纤维的石墨化性能，改善炭纤维的表面状态，从而有效地促进CVI过程中炭纤维表面沉积较高织构热解炭。通过对炭纤维以及热解炭微观炭结构的调整，硼酸的添加可有效地提高C／C复合材料的导热性能。     

炭/炭复合材料热膨胀性能的研究

利用热膨胀仪测定了炭/炭复合材料从室温到1300℃的热膨胀系数,研究了热处理温度、炭纤维取向和环境温度对炭/炭复合材料热膨胀性能的影响。结果表明由于热解炭是以层状的方式围绕炭纤维生长,所以其热膨胀各向异性,垂直于纤维方向的热膨胀大于平行于纤维方向的热膨胀。随着热处理温度的升高,炭/炭复合材料中具有乱层石墨结构的晶体有序度增加,石墨化度增大,石墨片层间的范德华作用力增强,热膨胀系数减小。随着环境温度的升高热膨胀系数先增大后减小,在1200℃有最大值。     

基于一维稳态纵向导热法对几种铸铁材料热物理性能的研究

采用KY-DRX-JH金属高温导热系数测试仪,测定不同合金成分铸铁材料的导热系数。结果表明:在100～550℃,灰铸铁的导热系数随温度的升高呈下降趋势,蠕铁在100℃的导热系数低于灰铁,其导热系数范围为33.33～42.47 W/m·K;合金蠕铁的导热系数随温度的升高先升后降,峰值点在300℃左右。100℃时合金蠕铁的导热系数随基体中铁素体量的增加而提高。     

WC/Co-B_4C复合材料的组织结构及力学性能

在Ｂ４Ｃ基体中掺入不同含量的 ＷＣ／Ｃｏ（其中 ＷＣ的质量分数为 ９４％;Ｃｏ为６％）;采用热压烧结法得到了高致密度的复合材料．当ＷＣ／Ｃｏ的体积分数达到４０％时,在１９００℃,３５ ｍｉｎ;３５ＭＰａ的条件下,复合材料的相对密度＞９８％,弯曲强度和断裂韧性分别为４５３ＭＰａ和 ８．７ ＭＰａ·ｍ１／２．利用ＸＲＤ; ＳＥＭ; ＴＥＭ分析了复合材料的物相组成及显微组织．研究了不同含量的 ＷＣ／Ｃｏ对复合材料力学性能的影响,并探讨了复合材料的增韧机制分析认为,复合材料致密度的提高是强度提高的主要原因;热膨胀系数失配产生的残余应力场是赋予材料高韧性的主要增韧机制,同时微裂纹的存在也是材料韧性提高的原因．     

添加少量Ni,Ti,C对溅射钨涂层氧化行为的影响

葡萄牙的科研人员采用反应磁控溅射工艺进行研究,具体工艺多数为：功率密度１０Ｗ／ｃｍ２,负偏压为７０Ｖ,靶材分别用Ｗ、Ｗ－１０％Ｔｉ、Ｗ－１０％Ｎｉ（质量百分比）,ＣＨ４／Ａｒ分压比为１／５,真空室压力为１０－４Ｐａ．涂前基体表面用离子轰击清洗．开始时,表面加热到４５０℃,然后用Ａｒ~＋轰击８ｍｉｎ（离子枪在２０Ａ,４０Ｖ下调节,基体偏压为－１２０Ｖ）,沉积时间选择在涂层厚度达到４μｍ为止．然后对获得的Ｗ－Ｃ－Ｍ（Ｍ＝Ｎｉ,Ｔｉ）涂层的化学成分、结构、形貌及抗氧化性能进行了研究． 结果表明,Ｗ－Ｃ－…     

在高压氮气氛下加热W＋C混合粉合成W（C,N）粉末

目前，钨的氯化物及碳氯化物并末商业化，其原因是ＷＮ不能在常压氮气氛下加热而得到，当温度达到９００Ｋ时，从热力学角度讲ＷＮ已不能稳定存在． 日本东京大学及工业科学院科研人员预言：（ｌ）化学反应Ｗ＋（ｌ／２）Ｎ２→ＷＮ和Ｗ＋Ｃｘ＋（１／２－Ｘ／２） Ｎ２→Ｗ（ＣｘＮ１－ｘ）｛ｘ<１简写为Ｗ（Ｃ３Ｎ）｝随着氮气压力 Ｐ（Ｎ２）的用高可能发生。因而通过在高压氮气中加热Ｗ和Ｗ＋Ｃ粉末就可能合成钨的氯化物及碳氢化物，并且随着ｐ（Ｎ２）的升高在Ｗ（Ｃ，Ｎ）中Ｎ含量也随之增大．（２）Ｗ（Ｃ，Ｎ）较ＷＮ稳定，并且可能…     

连续旋转CVI快速制备C／C复合材料

连续旋转化学气相浸渗是在ＣＶＩ原理基础上发展的一种快速制备Ｃ／Ｃ复合材料的新工艺。通过底部发热体加热使石墨衬底及缠绕其上的二维Ｃ布获得了具有低、中高三个温度区域的合理温度场,使微观孔隙与宏观孔隙分别在不同温度区进行致密化。在沉积过程中反应物气体渗故的深度仅为一层（或几层）Ｃ布,突破了一般ＣＶＩ法中“瓶颈”效应对沉积温度的制约,使沉积速度显著提高。通过实验研究了沉积温度、反应物气体中Ｃ３Ｈ６浓度和衬     

Rapid chemical vapor infiltration of C/C composites

With liquid petrol gas (LPG) as carbon source, carbon felt as porous perform and hydrogen as diluent, C/C composites were fast fabricated by using a multi-physics field chemical vapor infiltration (MFCVI) process in a self-made furnace. A set of orthogonal experiments were carried out to optimize parameters in terms of indices of density and graphitization degree. The results show the optimal indices can be achieved under the conditions of temperature 650 °C, LPG concentration 80%, gas flux 60 mL/s, total pressure 20 kPa, infiltration time 15 h. The verification experiment proves the effectiveness of the orthogonal experiments. Under the optimal conditions, the graphitization degree of 75% and bulk density of 1.69 g/cm are achieved with a uniform density distribution. At the same time, a new structure is obtained.     

溶胶浸渍抗氧化涂层对C/C复合材料摩擦特性的影响

采用溶胶浸渍技术对4种C／C复合材料进行抗氧化处理。在M2000型摩擦实验机上测试了4种C／C材料的摩擦特性。结果表明：在相同载荷下，光滑层CVI（SL）的C／C材料浸渍后试样与未浸渍试样的摩擦因数值最接近：树脂炭（RC）的C／C材料中，浸渍后试样的摩擦因数均低于未浸渍的试样且相差最大；粗糙层CVI（RL）的C／C材料中，中高载荷下浸渍溶胶试样的摩擦因数低于未浸渍溶胶的试样：而具有粗糙层／光滑层／树脂炭（RL／SL／RC）的C／C材料中，中高载荷下浸渍溶胶后试样的摩擦因数变化比未浸渍试样的高。随载荷增加，SL炭材料未浸渍和己浸渍试样摩擦因数的变化幅度均最低，RC炭材料未浸渍试样和己浸渍试样的摩擦因数变化幅度最大，RL／SL／RC、RL结构的试样是否浸渍溶胶对其摩擦因数的影响无明显规律。石墨化度高的材料的摩擦行为受浸渍溶胶的影响高于石墨化度低的材料。     

炭/炭复合材料石墨化度的XRD均峰位法测定

采用XRD平均峰位法测定了4种C／C复合材料的石墨化度。研究结果表明：用平均峰位法测定C／C复合材料的石墨化度具有简便可靠、区分度高的优点。当C／C复合材料中炭纤维的含量低于基体炭含量时，难石墨化的炭纤维对C／C复合材料XRD谱线低角度一侧的线形有一定影响，但对最终的测量结果影响不大。     

热梯度CVI C/C材料的结构与性能

以炭纤维整体毡为预制体，采用热梯度CVI工艺制备了两种不同结构基体炭的C／C材料，即RL结构和SL结构材料。采用光学金相仪，X射线衍射仪，硬度计，激光导热仪等设备研究了沉积态和热处理态C／C材料的显微结构及热物理性能。对比研究了两种结构材料的力学性能及摩擦摩损性能。结果表明：当密度超过一定值后，密度对C／C材料的力学性能和摩擦性能的影响远不如CVD炭结构的影响大；不管是沉积态还是热处理态，RL结构材料的刹车性能曲线明显优于SL结构材料的刹车性能曲线，这意味着CVD炭的微观结构不同是造成C／C材料摩擦性能差异的根本原因。     

Effects of cryogenic treatment on the thermal physical properties of Cu<Subscript>76.12</Subscript>Al<Subscript>23.88</Subscript> alloy

The thermal diffusion coefficient,heat capacity,thermal conductivity,and thermal expansion coefficient of Cu76.12Al23.88 alloy before and after cryogenic treatment in the heating temperature range of 25°C to 600°C were measured by thermal constant tester and thermal expansion instrument.The effects of cryogenic treatment on the thermal physical properties of Cu76.12Al23.88 alloy were investigated by comparing the variation of the thermal parameters before and after cryogenic treatment.The results show that the variation trend of the thermal diffusion coefficient,heat capacity,thermal conductivity,and thermal expansion coefficient of Cu76.12Al23.88 alloy after cryogenic treatment was the same as before.The cryogenic treatment can increase the thermal diffusion coefficient,thermal conductivity,and thermal expansion coefficient of Cu76.12Al23.88 alloy and decrease its heat capacity.The maximum difference in the thermal diffusion coefficient between the before and after cryogenic treatment appeared at 400°C.Similarly,thermal conductivity was observed at 200°C.     

Influence of load on sliding tribology of C/C composite with 40Cr steel couple coated by Cr

With the 40Cr steel couple coated by Cr, the sliding tribology behavior of two kinds of C/C composites with different matrix was tested using a M2000 wear tester. The results show that with the increasing of load, the friction coefficients of the composite with resin carbon matrix（RC） decrease quickly from 0.156 under 60 N to 0.123 under 150 N, while those of the composite with rough lamination/smooth lamination/resin carbon （RL/SL/RC） change only between 0.122 and 0.101. The wear volume loss of the two composites increases except for under 100 N. The SEM morphology shows that with the increasing of load, the worn surface of the composite with RC becomes more and more integrated while the size of the debris becomes less and less. The Raman spectrum shows that the graphitization on the worn surface of the fibers draws down after 100 N, the graphitization of the boundary between the fiber and the matrix carbon rises up to 150 N, but the graphitization of the matrix carbon draws down all the while. With the increasing of load, the graphitization on the worn surface of all the worn areas becomes closer and closer, which indicates the worn surface of the different component has the similar friction ability. The composites with RL/SL/RC have better tribological characteristic than the composite with RC.     

Impact of Impurity Content on the Sintering Resistance and Phase Stability of Dysprosia- and Yttria-Stabilized Zirconia Thermal Barrier Coatings

Dysprosia-stabilized zirconia (DySZ) is a promising candidate to replace yttria-stabilized zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high-temperature sintering behavior. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and YSZ coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 h at a temperature of 1150 °C. Samples were measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes. Phase analysis utilizing x-ray diffraction was used to determine differences in phase degradation of the coatings after heat treatment.     

制动过程中热应力对C/C复合材料磨损表面形貌的影响

以炭纤维针刺整体毡为预制体,经化学气相渗透和树脂浸渍增密方式得到C/C复合材料。采用有限元分析软件,模拟飞机在正常着陆条件下,刹车盘在制动过程中的热应力分布,并研究热应力对C/C复合材料磨损表面形貌的影响。结果表明:热应力是由于摩擦热的不均匀分布引起的。在摩擦表面外径处温度较高,产生的热应力较大,最大值约为3.15 MPa;而在靠近内径处温度较低,热应力较小,约为1.78 MPa。内、外径处热应力的差异导致磨损表面具有两种不同的组织形貌;靠近外径处的磨损表面比较粗糙,摩擦膜不完整,颜色暗淡,为暗带的组织形貌,摩擦性能较差;而靠近内径处的磨损表面光滑,摩擦膜连续稳定,颜色明亮,为亮带的组织形貌,摩擦性能较好。     

Friction and wear properties of pitch／resin densified carbon—carbon composites used for airbrakes

By use of X-ray diffractometry and scanning electron microscope(SEM),the friction and wear results obtained from MM-1000 dynamometer tests of CVI pitch/resin C/C composites were analyzed.By investigating the factors that affected the friction and wear properties,such as matrix carbon,applcation environment,graphitization degree and brake pressure,etc,friction and wear mechanism of carbon materials were probed.The results indicate that pitch densified CVI initially treated composite is more graphitizable with its graphitization degree up 59 62%,and which results in uniform small debris easier to generate,more smooth friction curves with the coefficient of 0.3-0.4 and relatively higher wear and mass loss,compared with CVI/resin C/C composites.It was further proved by SEM observation that tribological behavior of C/C composite was system dependent.Factors determining the friction and wear properties such as the size of debris and its influence on friction and wear,brake pressure,graphization degree and debris bilm formation interacted and affected each other.The friction and wear mechanism of C/C composites under different high temperature treatments needs further research.     

Research on graphite powders used for HTR-PM fuel elements

Different batches of natural graphite powders and electrographite powders were characterized by impurity, degree of graphitization, particle size distribution, specific surface area, and shape characteristics. The graphite balls consist of proper mix-ratio of natural graphite, electrographite and phenolic resin were manufactured and characterized by thermal conductivity, anisotropy of thermal expansion, crush strength, and drop strength. Results show that some types of graphite powders possess very high purity, degree of graphitization, and sound size distribution and apparent density, which can serve for matrix graphite of HTR-PM. The graphite balls manufactured with reasonable mix-ratio of graphite powders and process method show very good properties. It is indicated that the properties of graphite balls can meet the design criterion of HTR-PM. We can provide a powerful candidate material for the future manufacture of HTR-PM fuel elements.