不同工艺对真空气雾化Ni粉粒度的影响研究

采用真空紧耦合气雾化生产Ni粉,考察了雾化压力、漏嘴内径以及出炉温度对粉末粒度的影响。结果表明,随着雾化压力和出炉温度的增加以及漏嘴内径的减小,雾化后粉末粒度减小,细粉出粉率增加;制备细粉的最佳工艺条件为雾化压力5 MPa、漏嘴内径4.5 mm、出炉温度1 600℃,此条件下生产的Ni粉主要为球形。     

雾化压力对电极感应熔炼气雾化TC4粉末形貌与性能的影响

采用电极感应熔炼气雾化工艺,在3.5~7.0 MPa压力下制备高品质球形TC4合金粉末,利用激光粒度仪、扫描电镜、霍尔流速计、真实密度仪等,研究雾化压力对粒度53μm的细粉收得率、平均粒径、微观形貌、空心粉以及松装密度和流动性的影响。结果表明:在3.5~6.0 MPa压力范围内,随雾化压力增大,粉末的平均粒径逐渐减小,细粉收得率增加。当雾化压力为3.5 MPa时,粉末球形度较好,卫星球较少,平均粒径为69.4μm,细粉收率为23.0%,相对密度为99.1%,松装密度为2.40 g/cm~3,流动性为22.4 s/50 g。当雾化压力提高到6.0 MPa时,TC4合金粉末的平均粒径为48.6μm,细粉收得率为40.8%。进一步增大雾化压力时,粉末的平均粒径反而变大,细粉收得率降低,卫星球颗粒逐渐增多,球形度变差。粉末松装密度和流动性都随雾化压力增大而降低。     

气雾化参数对316L不锈钢粉末粒度的影响

利用自行研制的超音速气雾化喷嘴制备316L不锈钢粉末,研究雾化压力、金属熔体质量流量及熔体过热度对粉末粒度的影响。结果表明,实验制备的316L不锈钢粉末粒度主要分布在5～70μm之间,平均粒径为19.4～26.9μm。提高雾化压力,减小金属熔体质量流量或增大熔体过热度均使粉末平均粒径减小,细粉收得率增加;最佳雾化参数为雾化压力5.5 MPa,金属熔体质量流量4.28 kg/min,熔体过热度300 K。在此条件下得到的粉末形貌主要为球形和近球形,部分粉末表面有卫星球或凹坑出现。     

超高压水雾化工艺参数对金刚石胎体用预合金粉末粒度与形貌的影响

采用超高压水雾化工艺制备金刚石制品用预合金粉末,利用激光粒度分析仪和扫描电镜对粉末粒径和颗粒形貌进行表征,研究雾化水压、金属熔体过热度与导流管内径对粉末形貌与平均粒径的影响。结果表明,随雾化水压增大、金属熔体过热度提高或导流管内径减小,粉末的平均粒径均减小,当雾化水压大于60 MPa,金属熔体过热度大于250℃时,提高雾化水压和金属熔体过热度对粉末粒径的影响已不明显。导流管内径小于2.0 mm时,导流管出现频繁堵塞现象;随雾化水压增大或导流管内径减小,颗粒形貌从球形向类球形和不规则形转变,但随熔体过热度增大,粉末颗粒形貌从不规则形态向类球形和球形转变。     

高压水雾化法制备MIM不锈钢粉末工艺研究

利用水雾化法制备不锈钢粉末,并研究了漏嘴内径和雾化压力对粉末形貌、氧含量、粉末粒度分布以及振实密度的影响。采用激光粒度分析仪、扫描电子显微镜对样品进行表征。结果表明:当水雾化压力为115 MPa、漏嘴内径为3.5 mm时,可制备出平均粒径较小且分布均匀(D50为8.83μm,D90为20.80μm),氧含量较低,振实密度高的不锈钢细粉。     

雾化气体压力对Sn_(0.3)Ag_(0.7)Cu焊锡粉末特性的影响

利用超音速气雾化装置制备了Sn0.3Ag0.7Cu无铅焊锡粉末,用扫描电子显微镜和激光粒度分析仪对粉末的微观形貌和粒度分布进行表征,并提出一种反应质量差法计算粉末的氧含量,分析了雾化气体压力对粉末有效雾化率、微观形貌、粒度分布以及氧化程度的影响。结果表明:雾化气体压力对粉末的有效雾化率、微观形貌、粒度分布影响较大。粉末的有效雾化率随雾化气体压力的增加而不断提高;相对高的气压下粉末球形度好,0.6 MPa压力下雾化粉末的球形度好且无团聚;随着雾化气体压力的增大,粉末不断细化,且随着雾化压力的提高,粉末粒度减小幅度逐渐变缓;粉末中的氧含量随雾化气体压力的增大略有增加,高的氧含量使粉末表面粗糙度增大。     

紧耦合气雾化技术制备选区激光熔化用18Ni300合金粉末的研究

基于紧耦合气雾化技术制备符合选区激光熔化用18Ni300合金粉末, 重点研究了雾化压力对粉末粒度(中值粒径, D₅₀)、粒度分布、球形度、氧含量、流动性和松装密度等特性的影响。结果表明: 雾化压力对上述粉末特性影响显著, 当雾化压力在3.5 MPa到4.5 MPa范围时, 随着压力的提高, 粉末粒度降低、表面形貌改善、流动性变好、松装密度增加。当雾化压力为4.5 MPa时, 所制备的粉末综合特性最优, 粉末粒度(D₅₀)为34 μm, 球形度为0.77, 氧含量为0.02%(质量分数), 流动性为17.4[s·(50g)-1], 松装密度为4.32g·cm-3, 15~53 μm粒径范围粉末收得率为38.1%, 满足选区激光熔化技术对金属粉末性能的要求。     

雾化器导液管内径对无铅焊锡粉末形貌及粒度分布的影响

本试验利用自行设计的超音速雾化制粉装置,研究了导液管内径对SnAgCu系无铅焊锡粉末有效雾化率、粒度分布、球形度及氧含量的影响.研究结果表明:在过热度为250℃,导液管外径为7mm,喷头突出为4 mm,雾化压力为0.7MPa,雾化介质为氮气条件下,导液管内径为3mm,雾化粉末具有最佳的球形度、表面光滑度及粒度分布,同时具有较高的有效雾化率和较低的氧含量;随着导液管内径减小,粉末明显细化,有效雾化率升高,但粒度分布的离散度变大;随着导液管内径增大,粉末有效雾化率急剧降低,粒度分布变差,且表面更粗糙,形状更不规则.     

EIGA雾化法制备激光3D打印用TC4合金粉末工艺研究

采用电极感应熔炼气雾化法(EIGA)制备激光3D打印用TC4合金粉末(15～45μm)。采用扫描电镜(SEM)、X射线衍射分析仪(XRD)、激光粒度分析仪(LPS)、粉体特性综合测试仪等设备,对粉末的形貌、物相组成、粒度分布、松装密度及流动性进行表征,同时研究了雾化气体压力和熔体温度对激光3D打印TC4合金粉末收得率影响。结果表明:采用EIGA制备得到TC4合金粉末形貌为近规则球形,粉末表面存在少量"卫星球",粉末由α′-Ti相组成。TC4合金粉末收得率随着雾化气体压力和熔体温度的升高先增加后减小。最佳雾化工艺参数为:雾化气体压力5 MPa,熔体温度1 800℃,此条件下平均粒径D_(50)为81.2μm,15～45μmTC4钛合金粉末收得率为22.3%,流动性为42.5 s,松装密度为2.83 g/cm~3,氧含量1 260×10~(-6),符合激光3D打印用TC4钛合金粉末特征要求。     

工艺条件对溶液雾化氧化法制备Co_3O_4粉末的影响

以CoCl2·6H2O为原料,采用溶液雾化氧化法制备Co3O4粉末,对反应温度、溶液浓度、载气压力等工艺条件对产物粒子形貌及粒度分布的影响进行系统研究.结果表明,反应温度对Co3O4粉末的形貌和粒度都有影响,高温下粉末粒度较小,球形度较好,但温度过高会导致粒子团聚;COCl2·6H2O溶液的浓度对Co3O4粉末粒度也有影响,高浓度下所得Co3O4粉末的粒径较大;雾化压力增大,有利于得到颗粒分布均匀、分散性好的Co3O4粉末,但粉末粒度随之增大.在反应温度为850℃、CoCl2·6H2O溶液浓度为1.5 mol/L、雾化压力为1.5×10 5Pa的条件下,反应较完全,可制备物相单一的Co3O4粉末,产物为均匀分布的球形粉末,且粒度分布较窄.     

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.