SiC的添加对AlN/Mo/SiC复合陶瓷的制备和性能影响探究

以氮化铝(AlN),钼(Mo),碳化硅(SiC)为原料,采用放电等离子烧结的方式,在1700℃,30 MPa制备出致密度高达98.5％的SiC添加的AlN/Mo复合陶瓷.采用XRD,FESEM,Agilent4284型LCR自动测试仪,网络分析仪及激光导热仪对样品的微观形貌,导电性能,介电性能和热导率进行了测试分析.研究结果表明:采用放电等离子烧结工艺,在较低的温度下可以制备出组织致密均匀的AlN/Mo/SiC复合材料,但随着SiC添加含量的增加,当SiC的体积含量占到总体的60％时,复合材料的致密度又会出现明显的下降.添加SiC后,相对于AlN/Mo复合陶瓷,复合材料的电阻率得以进行有效的控制,不会出现非线性突变-渗流现象,而是在一定的范围内缓慢下降.在26.5～40.0 GHz下复合材料的介电常数和介电损耗均随着SiC含量的增加而增加.复合材料的热导率随着SiC含量的增加而下降:当致密度高于某临界值时,其热导率主要受SiC含量及其分布状态的影响,随着SiC含量的增加呈缓慢下降的趋势;而当致密度低于临界值后,致密度成为热导率的决定性因素,使得复合材料的热导率随着致密度的降低快速下降.     

Mo/AlN/Mo功能梯度材料的制备

实验选用细粉AlN和Mo粉末为原料,采用放电等离子烧结(SPS)技术进行Mo/AlN/Mo功能梯度电极材料的制备与表征,采用X射线衍射(XRD)法确定SPS烧结块体的相组成,用扫描电子显微镜(SEM)观察块体断口的显微结构,用阿基米德法和HXD-1000型显微硬度仪对块体的硬度和密度进行测试。研究发现:金属Mo与AlN混合烧结后并没有发生化学反应,只是简单的复合,Mo/AlN/Mo块体抛光截面层对称结构清晰,中间层为AlN层,最外层为金属Mo,过渡层均匀且结合良好,没有发现裂纹等缺陷,符合梯度设计要求。当Mo含量为70%时,Mo/AlN复合材料的硬度值下降缓慢,由于高韧性金属Mo的加入提高了AlN的韧性而同时缓和了其硬度,这使金属Mo层和AlN陶瓷层之间的结合稳定,这种过渡利于Mo/AlN/Mo功能梯度材料的内部结合;当Mo/AlN复合材料的Mo含量达到70%时致密度曲线有明显的上扬达到99.3%,随后致密度曲线随着Mo含量的增加而下降,这由于随着Mo含量的增加烧结后晶粒尺寸逐渐长大造成的。在Mo含量小于19%之前,介电常数有指数增长的趋势,Mo/AlN复合材料的导通阀值为Mo含量大于19%。     

热压烧结AlN-TiB2复合材料导热性能的研究

采用热压烧结工艺制备了AlN-TiB2复合材料。通过XRD、SEM和激光导热仪研究了TiB2含量和烧结温度对材料导热性能的影响。结果表明:随着TiB2含量的增加,复合材料的热导率逐渐下降,当TiB2含量增至50%时,热导率由102.9 W/(m.K)下降到36.6 W/(m.K)。另外,在TiB2含量10%时,随着烧结温度的升高,热导率呈逐渐上升的趋势。并对A1N-TiB2的相组成和显微结构进行了观察分析。     

电子封装用注射成形Mo/Cu合金烧结工艺的研究

本文采用粉末注射成形工艺制备电子封装用Mo/Cu合金 ,重点研究了烧结工艺 ,分析了烧结过程中的烧结温度、时间对烧结密度、微观组织和热导率的影响规律。研究表明 ,随着烧结温度的升高 ,材料密度不断增加 ,但当温度大于 14 5 0℃时 ,密度反而下降。材料经 14 5 0℃ 3h烧结达到了 98%的相对密度 ,热导率为 15 8W /(m·K)。     

Mo替代Ni对TiC基金属陶瓷组织结构和性能的影响

采用粉末冶金工艺制备了不同含量的Mo替代Ni的TiC基金属陶瓷材料,其中TiC基体和粘结相Co的质量分数分别为75%、5%,Mo和Ni的总质量分数为20%;分析了金属陶瓷的显微结构、抗弯强度、致密度和电学性能。结果表明,当TiC基金属陶瓷中Mo替代Ni的含量变化时,陶瓷各项性能发生变化。当Mo的质量分数为4%时,TiC基金属陶瓷的综合性能最佳,其抗弯强度为149.18 MPa,电阻率为1.45×10~(-5)Ω·m,而致密度达到94%。     

多元陶瓷增强Cu基复合材料的导热性能研究

以Cu基预合金粉为基体,加入SiC、Si_3N_4、B4C多元陶瓷作为颗粒增强相,利用粉末冶金法通过真空热压烧结工艺制备了SiC、Si_3N_4、B4C多元陶瓷/Cu基复合材料,并用激光脉冲法测试其室温条件下的导热性能。研究发现,随着SiC、Si_3N_4、B4C多元陶瓷含量的增加,复合材料的热导率逐渐减小,特别是当SiC、Si_3N_4、B4C多元陶瓷总质量分数大于15.0%以后,热导率急剧下降。复合材料内部的孔隙以及晶界、晶格畸变、位错等缺陷是影响热导率的主要因素。要获得导热性能良好的复合材料,应严格控制SiC、Si_3N_4、B4C多元陶瓷的质量分数在15.0%以内,并且可以考虑通过退火以及二次挤压等方法进一步提高致密度,减少烧结体内的位错、孔隙等缺陷,从而提高导热性能。     

热压烧结AIN-TiB2复合材料导热性能的研究

采用热压烧结工艺制备了AIN-TiB,复合材料.通过XRD、SEM和激光导热仪研究了TiB2含量和烧结温度对材料导热性能的影响.结果表明:随着TiB2含量的增加,复合材料的热导率逐渐下降,当TiB2含量增至50%时,热导率由102.9W/(m·K)下降到36.6 W/(m·K).另外,在TiB2含量10%时,随着烧结温度的升高,热导率呈逐渐上升的趋势.并对A1N-TiB2的相组成和显微结构进行了观察分析.     

AlN-TiC复相陶瓷导热性能的研究

采用热压烧结工艺制备了AlN-TiC复相陶瓷。通过XRD、SEM和激光导热仪研究了TiC含量和烧结温度对复相陶瓷导热性能的影响,并对A1N-TiC的相组成和显微结构进行了观察分析。结果表明,随着TiC质量分数增至50%时,热导率由102.9W/(m·K)下降到46.6W/(m·K);在TiC含量为10%时,随着温度的升高,热导率从59.8W/(m·K)增加到83.6W/(m·K)。     

CaO掺杂对10NiO-NiFe2O4复合陶瓷致密化及导电性能的影响

研究了CaO的添加量和烧结温度对10NiO-NiFe2O4复合陶瓷的物相组成、致密度和导电性能的影响.结果表明:0%～4% (质量比,下同)CaO含量范围内,烧结样品的XRD图谱仅有NiO和NiFe2O4的衍射峰.CaO掺杂对10NiO-NiFe2O4复合陶瓷具有明显的助烧作用.材料在烧结温度为1 200 ℃,CaO掺杂量为2%时,致密度达到最大为98.75%,比相同温度下未掺杂CaO的样品提高20%左右.CaO掺杂量对1 200℃烧结的10NiO-NiFe2O4复合陶瓷的电导率影响显著.当CaO掺杂量为0%～1%时,材料电导率在500～650℃区间出现1～2个数量级的突降;当CaO质量分数为2%和4%时,材料电导率在30～960℃范围内随着测试温度的升高而增大;其中,添加2?O样品的电导率在960℃下可达到最大为16.29 S/cm.     

Mo含量对(Ti,W,Ta)C-Ni系金属陶瓷组织与性能的影响

以(Ti,W,Ta)C固溶体粉末、金属Mo粉和Ni粉为原料,采用真空液相烧结法制备(Ti,W,Ta)C-x Mo-1%Ni金属陶瓷(x为质量分数,x=0~20%),研究Mo含量对(Ti,W,Ta)C-Ni系金属陶瓷的显微组织、物相组成、致密度和力学性能的影响。结果表明,随Mo含量增加,金属陶瓷的组织逐渐细化;Mo对(Ti,W,Ta)C-Ni系金属陶瓷的致密化具有较强的促进作用,使得金属陶瓷的烧结收缩率增加,孔隙减少;随Mo含量增加,(Ti,W,Ta)C-Ni系金属陶瓷的硬度提高,而抗弯强度先升高后降低。当Mo含量为15%时,(Ti,W,Ta)C-Ni系金属陶瓷的力学性能最优,硬度HRA和抗弯强度分别为90.2和1 661 MPa。     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

焦炭热性能指标意义浅析

通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。     

Results of treatment of cancer of the cardia

Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients.     

Effect of antibiotics of chemotaxis of human leukocytes

The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed.     

Quality of life of relatives of mental patients

Usage of quality of life of psychiatric patients' relatives as the parameter of estimation of the quality of psychiatric care is considered. By means of standard questionnaire elaborated by the authors as well as by means of both individual and group conversations the quality of life was analyzed in 40 relatives which lived together with psychiatric patients. Different spheres of their life and difficulties (financial, social-psychologic, production) were examined in families with such patients. The defects of psychiatric care that had direct influence on the quality of life of the psychiatric patients' relatives are outlined.     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)