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对0Cr18Ni9Ti不锈钢先后进行渗Zr、渗C、预氧化等表面处理,研究了经不同工艺阶段处理后,试样在1 000~1 150℃空气中的高温氧化行为。结果表明,各试样单位面积氧化增重与氧化时间的关系基本上均遵循抛物线规律,且氧化速率常数皆随温度升高而增大。经过渗Zr、渗C、预氧化工艺阶段处理后,试样的氧化激活能均有所提高,恒温氧化速率明显减小,即试样的抗高温氧化性能提高。 相似文献
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H13模具钢表面处理和热疲劳—热熔损性能 总被引:6,自引:0,他引:6
对H13钢进行了硫氮碳(SNC)共渗加氧化处理,稀土(RE)-SNC共渗及稀土(RE)-SNC共渗加氧化处理等表面处理工艺试验,并对处理试样分别进行了热疲劳性能和在合金铝液中的热熔损性能试验,结果表明,在空气氧化条件下,添加稀土的SNC共渗加氧化复合处理试验的渗层热疲劳性能比未添加稀土(RE)的SNC共渗加氧化得事处理及随后未经氧化处理的RE-SNC共渗的试样高,在本试验条件下,加稀土进行处理的试 相似文献
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在基础固体渗硼剂(碳化硼和碳化硅)中分别添加氟硼酸钾、氧化铪、氧化锆和氧化镧(4%,质量分数)对TC4钛合金渗硼层的表面形貌、渗层厚度、硬度及渗层组织的影响进行了研究,并对其各自的作用机制进行了探讨,最终优选出最佳的催渗剂。结果表明:添加氟硼酸钾的渗层表面凹凸不平且腐蚀严重,与渗硼之前的试样相比,试样厚度明显减少,因此不能作为TC4钛合金固体渗硼的催渗剂;添加氧化铪的试样渗层表面形貌良好,但渗层疏松且薄,与基础渗硼剂的相比,厚度不仅未增加,反而有所减少(减幅为90.7%),因此也不能作为TC4钛合金的催渗剂;添加氧化锆、氧化镧的渗层表面形貌良好,与基础渗硼剂的相比,厚度与硬度得到显著提高(添加氧化锆增幅分别为30.1%和30.3%,添加氧化镧增幅分别为49.7%和90.2%),具有明显的催渗作用,因此能作为TC4钛合金固体渗硼的催渗剂;与添加氧化锆的渗层相比,添加氧化镧的渗层组织均匀致密,渗层更厚更硬(分别提高了15.1%和46.0%),具有更显著的催渗效果,是最佳的TC4钛合金固体渗硼的催渗剂。 相似文献
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稀土对45钢硼铝共渗渗层生长初期的影响 总被引:6,自引:0,他引:6
本文研究了稀土对45钢硼铝共渗层生长初期的影响,建立了渗层生核长大模型。试验结果表明:稀土硼铝共渗试样在保温8分钟时表面就已形成较完整渗层,而硼铝共渗试样表面则24分钟才完成这一过程。由此认为,稀土促进了渗剂的分解,并促使活性元素大量吸附在试样表面,提高了硼化物的成核速度和成核率。 相似文献
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对原位反应合成的C-SiC-TiC-TiB_2复合材料在600~1200℃空气中的抗氧化性能进行了研究。在不同材料组成和试验温度下,试样分别出现氧化增重和失重,这主要取决于碳相和陶瓷相的氧化速率及氧化层的结构特征。在600℃该材料几乎不被氧化;800℃时TiB_2被优先氧化,形成B_2O_3液相;在1000℃以上B_2O_3与SiO_2生成硼硅酸盐玻璃,形成一致密氧化层。氧化过程中液相的出现和致密氧化层的形成显著降低了氧化速率,使材料进入钝氧化,表现出优良的抗氧化能力。 相似文献
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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。 相似文献
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K Ohta M Nishi M Ueda S Ohyama T Matsubara T Takahashi T Nakajima 《Canadian Metallurgical Quarterly》1998,99(9):589-594
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. 相似文献
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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) 相似文献
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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. 相似文献
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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". 相似文献
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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。 相似文献
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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. 相似文献