高能球磨-放电等离子烧结法制备双晶分布钛

以平均粒径约150μm的球形钛粉为原料,采用高能球磨结合放电等离子烧结技术制备由双尺度晶粒组成的高致密纯钛块体材料,研究高能球磨过程中钛粉的形貌、尺寸及显微组织的变化,分析球磨钛粉放电等离子烧结时的致密化行为和显微组织的演变规律,测试烧结钛块体材料的室温压缩性能。结果表明:钛粉在球磨初期发生剧烈的塑性变形并相互焊合,形成层片状团聚粉末。球磨10 h时,钛粉的部分晶粒细化至40~100 nm。放电等离子烧结过程中,随烧结温度升高和烧结时间延长,烧结钛的密度逐渐增大。在烧结温度为800℃、保温时间为4 min、烧结压力为50 MPa的条件下,烧结钛的密度达到4.489 g/cm3,接近全致密,其显微组织由双尺度的等轴晶组成,细晶区晶粒尺寸为1~2μm,粗晶区晶粒尺寸为5~20μm,二者呈层状交替分布;该试样在室温压缩条件下的综合力学性能与铸锻Ti-6Al-4V合金相当。     

球磨时间对W-30Cu复合粉末中W晶粒度及烧结致密化行为的影响

研究了高能球磨时间对W-30Cu复合粉末晶粒度及烧结行为的影响.结果表明,当球磨时间从16h提高到33h时,复合粉的晶粒度由25nm减小到10nm,并发生机械合金化现象;在温度为1275℃烧结60min,经18h高能球磨的复合粉末烧结就可以达到全致密.研究还发现,高能球磨W-30Cu复合粉末具有较好的热稳定性,经950℃退火处理,晶粒尺寸没有发生异常长大现象;经烧结材料的硬度明显高于普通的W-30Cu复合材料.经1 275℃烧结30 min后合金其晶粒尺寸在300～550 nm.     

纤维状WC晶粒硬质合金的制备

以高能球磨方法处理制备的纳米晶复合粉末为原料，通过真空烧结制备硬质合金块体，研究该纳米晶复合粉末的烧结致密化行为和显微结构特征。结果表明：该纳米晶粉末的烧结致密化可依烧结温度从低至高分为、3个阶段，而在高于1250℃的液相烧结阶段，将温度提高至1375℃烧结30min，可获得密度为14．46g／cm^3、烧结收缩率为27．2％的致密硬质合金。此时，WC晶粒呈纤维状，随机分布在烧结体中，其长度约为1．2μm，径向尺寸约为100nm；采用高能球磨处理工艺可以获得原位生成的纤维状WC晶粒增强的硬质合金。     

稀土氧化物粒子对钼合金粉末冶金过程及力学性能的影响

试验研究了掺杂La2O3、Y2O3、CeO2稀土氧化物颗粒对钼合金的粉末物性、烧结进程、制品的烧结致密度及压力加工丝材的室温力学性能的影响规律。试验结果表明,掺杂稀土氧化物粒子细化了钼粉的粒度,降低了松装密度和粒度分布范围,同时导致粉末团聚现象增多;稀土氧化物粒子延迟了钼合金的烧结进程,降低了烧结制品的致密度,同时细化了烧结体晶粒尺寸。稀土氧化物粒子以弥散强化和细晶强化的形式,提高了钼合金丝的室温强度。CeO2显著提高了钼合金丝的室温韧性,La2O3、Y2O3则降低了钼合金丝的室温韧性。     

La_2O_3对超细钨复合粉末烧结性能与钨合金显微组织的影响

采用溶胶喷雾干燥-煅烧还原方法制备超细/纳米W-La2O3复合粉末,将粉末压制成形后在1 950℃烧结,制备La2O3弥散强化钨合金,检测合金的密度与强度,并采用SEM对超细粉末形貌、合金的组织结构、断口形貌进行分析,结果表明:随La2O3加入量增加,粉末颗粒显著细化,W-0.7%La2O3复合粉末的粒径仅为0.1μm;制备的W-La2O3超细/纳米复合粉末具有很高的烧结活性,烧结后,合金最高相对密度达到99.1%;La2O3均匀弥散分布于钨晶界,抑制钨合金的晶粒长大,提高材料的强度,W-0.7%La2O3合金中钨平均晶粒尺寸仅为8.7μm,抗弯强度达到548 MPa;合金的断裂形式表现为穿晶-沿晶共有的复合断裂形式。     

烧结温度与混粉比例对双尺度钛合金组织与性能的影响

采用高能球磨-放电等离子烧结技术制备具有双尺度显微组织的Ti-6Al-4V合金,并研究烧结温度和加入未球磨粉末的比例对烧结试样显微组织及力学性能的影响。实验结果表明:当球磨时间为6 h时,由于球磨粉末内部的应变量不均匀,球磨粉末烧结试样的显微组织均由粗晶网篮组织和细晶等轴组织组成。随烧结温度升高,烧结试样的密度逐渐提高,细晶区的晶粒尺寸逐渐增大,材料强度呈先上升后下降的趋势。在球磨粉末中加入一定比例的未球磨粉末可显著提高烧结材料的塑性,并且保持较高的强度。当球磨粉末与未球磨粉末按质量比4:1混合、SPS烧结温度为850℃、保温时间为4min时,烧结材料相对密度达到99.0%,细晶区晶粒尺寸为1~2μm,烧结试样获得最佳强度-塑性组合,其拉伸屈服强度为1012 MPa,断裂强度为1056 MPa,伸长率为10%。     

热机械合金化法制备纳米晶W-Cu复合粉末

采用热机械合金化制备纳米晶W-Cu复合粉末。通过XRD、SEM、激光粒度测试等方法对球磨后的粉末进行表征。结果表明:随球磨时间延长,W的晶粒尺寸不断减小,球磨30 h后W的平均晶粒尺寸为41 nm左右;球磨初期,粉末迅速细化;随球磨时间延长,粉末粒度有所增加;进一步增加球磨时间,粉末粒度减小。球磨粉末还原后有较高的烧结活性,1 200℃烧结后相对密度可达97%以上。烧结材料的组织非常均匀,且晶粒细小。     

细晶Mo-18Cu合金烧结工艺的研究

采用溶胶-喷雾干燥-煅烧-氢还原方法制备了晶粒尺寸为30~50nm的超细Mo-18Cu复合粉末,并利用该复合粉末制备出了高性能细晶Mo-18Cu合金。研究了烧结工艺对烧结体致密化的影响、合金的力学性能和显微组织特征。结果表明:在1 350℃烧结,Mo-18Cu合金的相对密度可达98%以上,抗拉强度和伸长率分别达到545MPa和3.85%;合金的显微组织均匀,晶粒细小。     

细晶钨铜复合材料制备工艺的研究

将W-20％Cu混合粉末在行星式高能球磨机中机械合金化(MA)。经过一定时问球磨后可以得到W晶块尺寸30nm左右的纳米粉末。测定了粉末晶粒尺寸、粉末的粒度、比表面、松装密度和振实密度等性能。粉末的晶块尺寸用XRD分析得出。研究了MA W-2096Cu粉末烧结后的显微组织。研究表明，球磨后粉末在1200～1300℃下烧结即可达到近全致密，相对密度在99．596以上，拉伸强度达到780MPa以上，伸长率大于3．5％，钨晶粒尺寸在1～2μm左右。     

高能球磨制备Al2O3/Cu复合材料

采用高能球磨法制备Al2O3/Cu复合粉末,通过X射线衍射仪(XRD)和扫描电镜(SEM)研究高能球磨时间对复合粉末的物相、晶粒尺寸和表面形貌的影响。结果表明,随球磨时间的增加,基体Cu的晶粒不断被细化,在球磨初期,晶粒尺寸减小很快,当晶粒尺寸小于20 nm时,细化速率变缓而趋于稳定;Cu颗粒形貌由树枝状变为层状,并向椭球体转变;纳米Al2O3颗粒逐渐嵌入Cu颗粒体内,且分散均匀,从而获得纳米Al2O3颗粒弥散分布的Cu基复合粉末。并探讨了高能球磨对放电等离子体烧结Al2O3/Cu复合材料导电性能和力学性能的影响,研究认为高能球磨可以促进基体的晶界强化和弥散强化,而晶界的增加并不会导致电阻率的显著增大,影响电阻率的主要因素为Al2O3的体积分数、孔隙和杂质的固溶。     

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)     

Comparison of rates of infection of two methods of emergency ventricular drainage

The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.     

浅析《野草》的版画特征

鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美".     

四辊破碎机车刀架的改造

针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。     

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。     

Comparison of the results of surgical and conservative treatment of fractures of the diaphysis of the tibia

In this paper is treated the fundamental problematic of the fracture of the diaphysis of the tibia and the therapeutic results after the conservative and operative treatment are confronted. Among 518 patients with 433 open fractures and 35 with closed fractures of the diaphysis of the tibia, successful treatment of more 2/3 was obtained in the period from 1968 to 1972. Following our casuistics and literature, whose results are similar, we find out that the average total treatment of the osteosynthesis of the fracture of the diaphysis was shortened for 2,5 months depending upon the type and the localisation of the fracture. Apolied methods of the operative and conservative and conservative treatment in relation to the velocity of the medical cure as well as to the extreme anatomical-functional results are analised. We noticed that osteosynthesis, made by the intermedullary nail and the extension of the canals or by a small AO table, by the achieved stability makes conditions of immediate motions and an early rehabilitation. Because of that it gives the best functional results.     

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.     

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。     

参与式农业基地建设行动方案设计

为了编制实用性强的基地建设行动方案,首先,确定参与式发展的主体,搭建一个"决策框架";其次,针对行动目标,提出不同参与主体,如管理者、农民、消费者等团队与个人的目标及行动内容;最后,工作应向重塑伙伴式合作关系,挖掘农民自我发展潜力,完成三大角色的转换,打造农业基地文化等方向推进.