关键词： 固体力学   材料科学   材料微结构  

摘要： 首先列举事实说明现在研究固体力学行为时,越来越有必要来考虑材料的微结构,目前固体力学工作者考虑材料微结构的主要流派,它们的共同点和存在的问题,概率微结构理论及其困难,对前景的展望.

关键词： 耐火材料   刚玉   莫来石   碳   氧化锆  

摘要： 本文研究了反应烧结含ZrO_2的刚玉-莫来石材料及其碳结合材料的相组成,显微结构和力学性能。结果表明,对刚玉-莫来石材料由于加入氧化锆引起的微裂纹,中、低温强度趋于下降;但在1300℃以上,强度和抗蠕变性能都有明显上升。这可能是因为微裂纹得到一定弥合,同时氧化锆和莫来石之间形成晶界固溶。对碳结合刚玉-莫来石-氧化锆材料,在所有试验温度下,强度都随石墨加入量增加而下降。强度-温度曲线呈现两个特征:(1)由600℃至800℃强度下降,而由800℃至1000℃强度均有回升;(2)由1300℃至1400℃强度略有回升。这与金属粉添加剂在不同温度下的行为有密切关系。形成针状或纤维状的碳化物有利于提高强度。

关键词： 复合材料   显微结构   力学性能  

摘要： 本文通过XRD和SEM分析了热压Si_3N_4/TiC的显微组织特征,研究了添加TiC粒子对Si_3N_4陶瓷力学性能的影响。结果表明:在Si_3N_4/TiC颗粒复合材料中,TiC与裂纹前端的交互作用使裂纹发生偏转,增加了裂纹扩展阻力,使断裂韧性值提高,断口形貌趋于复杂;同时TiC与Si_3N_4的弱界面结合以及TiC团聚体的存在使Si_3N_4/TiC在韧性增加的同时强度降低。K_(IC)增加越显著,强度下降越明显。

关键词： Advanced materials   Damage   X-rays   Cross section (Physics)   Resolution (Optics)   Fracture (Materials)   Electronics   Fiber reinforced composites   Computerized tomography   Imaging   Dimensions   Nondestructive evaluation   Ceramics  

摘要： Quality assessment of advanced materials like high strength ceramics and fibre reinforced composites requires detection and characterization of early damage and defects like cracks and pores even with linear dimensions of only 10 μm. Structures of the same size must be distinguishable in components of precision mechanics and electronics. This paper discusses some applications of microfocal X-ray radiography and high resolution computed tomography in nondestructive evaluation of such components. The latter can be looked at as a nondestructive microscopic technique imaging cross sections of an object. Results of investigations using a tomographic unit with a resolution capability of the order of magnitude of 20 μm are presented. ?1990 The American Society of Mechanical Engineers

关键词： 半导体   硅   中子嬗变   掺杂   微结构  

摘要： NTD Si材料与原始单晶硅相比,其缺陷和位错有所增加,特别是EPR缺陷增加显著,电阻率增加20%左右,150(?)·cm以上的电阻率曲线还存在一个较弱的吸收峰值。辐照处理后的NTD Si材料,其点阵常数普遍增大,[111]方向的缺陷明显增多。中照50小时后,局部出现辐照损伤。

关键词： 氧化镁   碳   复合材料   耐火材料   结构  

关键词： Aorta   Basement membrane   Coarctation hypertension  

摘要： To determine the effect of elevated blood pressure on the ultrastructure of rat aorta, hypertension (average mean pressure 163 .+-. 17 mm Hg) was produced by suprarenal aortic coarctation. After 3 weeks, the subendothelium of the hypertensive thoracic aorta showed significantly increased volume measurements for mononuclear leukocytes and basement membrane-like material compared with the sham-operated control group. Focal areas of rarefaction of the subendothelial extracellular material were associated with the nearby presence of mononuclear leukocytes. None of these alterations were found in the normotensive abdominal aorta. The tunica media of hypertensive thoracic aorta also contained significantly increased basement membrane-like material. This new finding in an animal hypertension model is the direct result of the quantitative morphological approach employed in this study. In some rats, the partially constricting aortic ligature compromised the right renal artery leading to ischemic atrophy of the right kidney and hyperreninemia in addition to hypertension. In this group, excluded from the previous analysis and evaluated separately, subendothelial thickening and accumulation of basement membrane-like material in the thoracic aorta were greatly increased compared with the control group and other hypertensive rats. This result could not be attributed to an effect of blood pressure alone and might have been caused in part by humoral factors. Basement membrane accumulation appears to be an important early response of the arterial wall to hypertension or other factors in this rat model.

关键词： ZR   玻璃窑   ZAS   显微结构   窑炉   物理化学  

摘要： 由陕西省硅酸盐学会和机械电子工业部成阳四四○○厂共同组织的《四四○○厂屏玻璃窑用ZAS、ZR系列耐火材料使用后显微结构物理化学及窑炉相关技术研究》应用理论研究课题,于1989年12月22日通过成果鉴定。四四○○厂屏玻璃窑是由日本引进的大型玻璃熔炼设备,自投产共运行了六年零四个月。为了逐步减少屏玻璃窑用耐火材料的进口量,提高耐火材料的国产化程度。陕西省硅酸盐学会同四四○○厂于1987年8月27日签订了立题协议。学会利用多学科、多部门、人才集中、设备配套横向联合攻关的优势,组织力量,对我国第一座引进的大型屏

关键词： 水泥   熟料   显微结构   硅酸盐  

摘要： 本文研究了用TAS Plus图像分析仪对水泥熟料显微结构矿相进行定量分析的方法,提出用蒸馏水作水泥熟料光片的浸蚀剂,并找出了不同矿相的浸蚀条件。浸蚀出来的光片试样能较好地满足各矿相分别定量的要求。根据水泥熟料纤维结构特征编写矿相定量分析程序,可获得准确的分析数据。