微波烧结制备WC-12Co硬质合金

以88%WC+12%Co混合料粉为原料,采用微波烧结制备WC-12Co硬质合金,研究烧结温度与保温时间对合金密度和硬度以及显微组织的影响。结果表明,在1400～1475℃范围内,随烧结温度升高,WC晶粒长大不明显,合金密度和硬度增大。在1475℃的烧结温度下保温0min,烧结周期1.5～2h,烧结合金的相对密度达99.8%,硬度为87.5HRA,烧结样品显微组织结构均匀,但保温时间超过30min后由于晶粒异常长大以及钴相分布不均匀,导致合金的密度和硬度急剧下降。采用辅助加热材料和保温材料以及设计合理的样品摆放,可降低样品中不同部位的温度梯度,从而获得形状良好的合金样品。     

水热法和氢气还原法制备纳米Mo–40Cu复合粉末及其烧结性能研究

结合水热法和氢气还原法制备纳米Mo–40Cu复合粉末,利用X射线衍射仪、扫描电子显微镜、透射电镜等手段研究了氢气气氛下烧结工艺对Mo–40Cu复合材料组织和力学性能的影响。结果表明,最佳制粉工艺为水热温度400 ℃和氢气还原温度700 ℃,获得了均匀的Mo–40Cu复合粉末,粉末粒径为70~90 nm;在氢气气氛下最佳烧结工艺为1300 ℃保温2 h,合金的相对密度、抗弯强度、硬度、电导率和热导率分别为98.1%、1060 MPa、HRA 51、20.8 MS·m-1和191.7 W·m-1·K-1,热膨胀系数在500~700 ℃约为10.8×10-6 K-1,合金中组织均匀,晶粒细小,尺寸约为3~4 μm。     

烧结温度对SiC_p/Al复合材料组织与性能的影响

借助于直热法粉末触变成形,通过控制加电方式,压制成形并烧结制备SiC_p/Al复合材料,并对复合材料进行微观组织分析及热物理性能与力学性能测试,研究烧结温度对复合材料微观组织、热膨胀系数、热导率及抗弯强度的影响。结果表明:随烧结温度升高,复合材料内气孔减少,热膨胀系数先减小后增大,热导率逐渐增大,抗弯强度先增大后减小。最佳烧结温度为600℃,此温度下制备的含SiC_p体积分数60%的SiC_p/Al复合材料中,SiC_p颗粒分布均匀,材料组织致密;室温至250℃平均热膨胀系数小于5.0×10-6℃-1,其室温热导率为165W/(m·℃),密度为3.01 g/cm3,复合材料的抗弯强度为340 MPa。     

Al-50Si合金电子封装材料的热压法制备及性能表征

本文采用热压法制备了一种性能优良的Al-50Si合金电子封装材料。通过比较不同烧结工艺下烧结体的密度,获得了制备该合金的最佳烧结工艺:低温(460℃)压制压力100MPa、烧结温度800℃、烧结时间2h,热等静压工艺参数:温度540℃、压力200MPa,保温保压4h。对在最佳烧结工艺条件下,经过热等静压处理后的材料进行了性能表征,具体性能:相对密度达到99%,抗弯强度223MPa,硬度153HB,热膨胀系数在0～200℃达到9.3×10-6/K,热导率达到142W/(m.K)。     

烧结温度及热处理对注射成形4605低合金钢组织与性能的影响

以4605母合金粉末为原料,采用注射成形工艺,在1 320～1 380℃烧结温度下制备4605低合金钢,并采用3种不同工艺进行热处理,研究烧结温度及热处理工艺对合金钢显微组织与硬度、抗拉强度等性能的影响。结果表明:4605低合金钢的烧结密度随烧结温度升高而增大;其显微组织由板条状马氏体和多边形铁素体组成;合金钢的硬度和抗拉强度均随烧结温度升高而升高,在1 380℃下烧结的低合金钢,致密度达96.38%,抗拉强度为613 MPa;塑性随烧结温度升高先上升后下降,在1 360℃烧结的合金钢伸长率最大,达13.5%。烧结温度为1 380℃的合金钢,经过800℃保温0.5 h,油冷,然后在200℃保温2 h的热处理后,得到马氏体组织,抗拉强度和硬度最高,分别为708 MPa和78.8 HRA;烧结温度为1 360℃的合金钢,在800℃保温1 h,油冷,然后在600℃保温2 h的热处理后,得到回火索氏体组织,伸长率最大,达到18.76%。     

TiH2粉末注射成形坯烧结工艺研究

本文以低成本的TiH2粉末为原料,采用粉末注射成形技术(MIM)制备纯Ti材料,研究了烧结温度、烧结时间和烧结气氛对样品的致密度、显微组织的影响;探究了烧结气氛对烧结试样中碳、氧含量的影响,并测定了真空烧结试样的力学性能。结果表明:TiH2粉末通过MIM工艺可以获得接近全致密的烧结Ti制品;随烧结温度提高和烧结时间延长,制品孔隙度减小,致密度提高;在1 150℃烧结3h,致密度为93.88%,烧结温度提高到1 300℃,致密度可达98.52%;在1 300℃的烧结温度下,烧结时间从2h延长到3h,致密度可从96.69%增加到98.52%;在其它工艺相同的条件下,烧结气氛对制品的性能有显著影响,真空条件下致密度最高,晶粒尺寸最大,碳、氧含量最低;在真空度为5×10-3 Pa下,于1 300℃烧结3h制品的显微硬度为388HV,抗拉强度为325MPa,延伸率为4.43%。     

高热导率低热膨胀系数Cu-ZrW_2O_8复合材料的制备与性能

以负热膨胀材料ZrW2O8与金属Cu为原料,分别采用常规烧结法和热压法制备具有高热导率低膨胀系数的新型Cu基复合材料Cu-ZrW2O8,研究ZrW2O8体积分数与烧结方法对该复合材料致密度、热导率及热膨胀系数的影响.结果表明:热压法制备的Cu-50%ZrW2O8复合材料的热导率达173.3 W/(m·K),致密度为91.6%,均明显高于常规烧结样品;热压样品的热膨胀系数为11.2×10-6K-1,稍高于常规烧结样品:在150～300℃温度范围内热处理后该样品的平均热膨胀系数降低到10.87×10 -6K-1,较纯Cu的平均热膨胀系数17×10-6K-1低很多,有望成为一种新型的电子封装材料.     

碳含量及烧结温度对MIM 4340合金钢组织及力学性能的影响

采用注射成形工艺制备4340低合金钢,研究碳含量与烧结温度及热处理工艺对合金钢显微组织和力学性能的影响。结果表明:通过添加德国巴斯夫还原型羰基铁粉(CN)及改进型羰基铁粉(OM)的方式,分别配制不同碳含量的混合粉末,并经1 280～1 320℃保温2 h烧结后,质量分数为0.50%碳含量的样品最接近标准碳含量。烧结密度随碳含量的升高先减小后增大,随烧结温度升高而增大。烧结态显微组织由铁素体(α-Fe)、珠光体(铁素体+渗碳体Fe_3C)和贝氏体组成,抗拉强度和伸长率为762.16～1 032.03 MPa和5.25%～8.62%。0.50%碳含量、1 300℃烧结态4340合金钢样品经850℃保温0.5 h油冷及400℃保温2 h回火热处理后得到最佳力学性能,抗拉强度和伸长率达到1 510.24 MPa和4.30%,硬度为40.0 HRC。     

细晶W-15Cu材料的制备研究

利用机械合金化工艺制备了颗粒尺寸为0．5μm、W晶粒尺寸为10am的纳米晶W-Cu粉末，研究了其烧结致密化行为、烧结合金显微组织及其性能，并考察了其晶粒长大特性。结果表明：烧结温度和时间的增加有利于致密化，1300℃烧结30min，合金取得了99％的相对密度；硬度随烧结温度、时间的增加而增加，在1375℃烧结30min，硬度为HB321。W晶粒随着烧结温度的升高而增大，1200℃烧结30min获得了相对密度为98％以上、硬度为HB264、晶粒尺寸约为350am的细晶W-Cu合金。     

烧结温度对Fe-Cu-Mo-C合金组织和性能的影响

采用机械球磨混粉和真空烧结相结合的方法制备了Fe-Cu-Mo-C合金,研究了不同烧结温度对粉末冶金Fe-Cu-Mo-C合金材料的显微组织、密度、抗拉强度和摩擦磨损性能的影响。结果表明:随着烧结温度由1 000℃升高到1 100℃,Fe-Cu-Mo-C合金烧结体组织孔隙数量减少、孔隙尺寸明显降低;当烧结温度提高到1 150℃时,烧结体组织中孔隙尺寸增大。随着烧结温度升高,烧结体的密度、硬度、抗拉强度和伸长率先增大后减小,磨损量先降低后升高。最佳烧结温度为1 100℃,此时烧结体的密度为6.90 g/cm3,抗拉强度为319 MPa,洛氏硬度为34.7 HRC,磨损量为0.087 g。     

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。     

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。     

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.     

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.