共查询到19条相似文献,搜索用时 218 毫秒
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采用在铸造过程中添加改性超细陶瓷粉体的强韧化技术,研究了2种不同种类的改性超细陶瓷粉体对HT250耐磨性的影响。结果表明:添加改性超细陶瓷粉体的试样中,A型石墨得到了明显细化,分布更均匀,长度适中且端部变钝;与此同时,珠光体层片距变小,组织致密;共晶团数量明显增多。耐磨试验中,当载荷为130 N时,添加#1和#2粉体试样的耐磨性分别比未加粉体试样的耐磨性提高29.3%和50.7%;当载荷为150 N时,添加粉体试样的耐磨性分别比未加粉体试样的提高38.7%和59.2%;与此同时,两种载荷下,3种试样的磨损增长率分别为83.7%(不添加粉体)、57.5%和38.6%。 相似文献
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研究了在HT250中加入0.1%纳米陶瓷粉体对其显微组织和热疲劳的影响,结果表明:(1)纳米陶瓷粉体作为液态HT250的外来异质形核的核心,起到孕育作用,促进石墨化,使石墨变得细小且分布均匀,长度减小,对基体的割裂作用减弱;珠光体体积分数增加且得到细化,片间距减小,基体连续性得到改善;(2)添加0.1%纳米陶瓷粉体后,HT250的导热系数下降,平均下降4.6%;(3)与未添加纳米陶瓷粉体的HT250相比,添加0.1%纳米陶瓷粉体后,热膨胀系数下降,平均下降8.6%;(4)添加0.1%纳米陶瓷粉体后,HT250的热疲劳性能提高17%。 相似文献
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陶瓷粉体在高分子粘结剂中的分散性以及注射喂料的流动性是陶瓷粉末注射成型的关键因素.由于高分子的分子结构和物理形态与陶瓷粉体不同,导致两者相容性差.并且陶瓷粉体表面自由能较高,与高分子粘结剂混合过程中会有团聚的倾向.本研究采用硬脂酸对氧化锆粉进行表面改性,降低了粉体的表面自由能,提高了喂料的均匀性.改性后的陶瓷粉体表面由亲水性变为亲油性,提高了粉体与粘结剂的相容性,降低了喂料体系的粘度. 相似文献
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高导热高绝缘导热硅脂的制备及性能表征 总被引:1,自引:0,他引:1
高导热硅脂作为一种热界面材料,可以显著地减小因接触空隙而产生的热阻,提高散热效果。通过采用自制的氮化硅、氮化铝、氧化铝等陶瓷粉体来代替传统的金属粉体作为导热填料,制备出高绝缘高导热的导热硅脂。研究了陶瓷粉体种类、添加量以及表面改性剂对导热硅脂热导率的影响规律。采用热阻测试仪、AMD、Inter主板测试平台、耐压测试仪等表征了导热硅脂的导热和绝缘性能。并对实验结果进行了理论分析。 相似文献
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采用高能球磨掺杂氧化物粉体和压敏陶瓷粉体2种不同制备技术制备ZnO-Bi2O3压敏陶瓷,通过扫描电镜和X-射线衍射对其显微组织和相成分进行分析,探讨不同高能球磨制备技术对氧化锌压敏陶瓷电性能和显微组织的影响。结果表明:压敏陶瓷粉体高能球磨是制备高性能氧化锌压敏陶瓷的一种优异的技术,在1000°C下烧结3h,压敏陶瓷的电位梯度为617V/mm,非线性系数为57;压敏陶瓷的致密度高达95%,显微组织均匀、致密;高能球磨压敏陶瓷粉体可细化晶粒,增强烧结驱动力,加速烧结过程,降低烧结温度。 相似文献
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为降低热应力造成多层结构浸入式水口开裂的可能性,采用有限单元法研究了内面层厚度和材料物理性能参数对其热应力的影响,以及内面层厚度和导热系数对其内壁温度的影响.结果表明,当内面层厚度由0mm增至10mm时,浸入式水口所受最大拉应力先升后降;当其厚度在2~4 mm之间时,拉应力较小.随着内面层弹性模量、热膨胀系数和导热系数的降低,最大拉应力减小.增加外面层厚度,减小其导热系数,预热后浸入式水口内壁温度的降低幅度减小. 相似文献
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以硝酸钙、硝酸镁、正硅酸乙酯为先驱体,利用溶胶-凝胶法合成CaO-MgO-SiO2纳米陶瓷粉体,研究了溶胶系统pH值、去离子水添加量、先驱体浓度、溶胶静置温度以及分散剂等因素对煅烧后粉体形貌的影响.结果表明:当pH值处于2.5~4.5、C[H2O]/C[Si]为2:1~4:1、先驱体浓度为0.8 mol/L、水浴温度为60℃、添加适量分散剂时,凝胶在煅烧后能获得具有良好分散性的纳米粉体.通过严格控制上述溶胶-凝胶过程中的原位工艺条件,制得了粒子直径为50~100 nm、分散性非常好的CaO-MgO-SiO2纳米陶瓷粉体. 相似文献
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通过单道次压缩及连续冷却实验,研究了变形温度(810-720℃)对具有超细原始奥氏体晶粒的含Nb双相钢显微组织的影响.实验结果表明:实验钢最终组织为铁索体加马氏体的双相组织.压缩过程中,实验钢应力-应变曲线上出现峰值,且峰值应力随变形温度的降低先增大后减小;随着变形温度的降低,铁索体的含量先增大再减小,但增减幅度不大,在最低变形温度(720℃)时,铁素体品粒尺寸降低到2.8 μm,弥散分布于铁素体晶界上的马氏体含量达到22.7%;随着变形温度的增加,铁索体晶粒硬度减小,最低可降至230 GPa;EBSD取向分析显示,随着变形温度的降低,组织中小角度晶界增多. 相似文献
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目的探究SiO_2气凝胶在复合隔热涂料中的应用,从隔热机理出发,通过降低复合隔热涂层的导热系数,提高反射率、辐射率等方式,使涂层达到隔热降温的目的。方法首先通过单掺实验确定各填料的含量,并采用紫外/可见光/近红外分光光度计、红外辐射率测量仪和自制的测试隔热装置等,分析涂层的发射率、辐射率和隔热性能,最后通过正交实验方法得到最优涂层配方。结果 SiO_2气凝胶能显著降低涂层的导热系数,在此基础上,添加钛白粉、空心玻璃微珠、红外陶瓷粉等颜填料,能有效提高涂层的反射率和辐射率,从而进一步增强了涂层的隔热效果。分别添加质量分数为5%的SiO_2气凝胶、5%的钛白粉、5%的空心玻璃微珠和10%的红外陶瓷粉时,复合隔热涂层具有最优的隔热性能。SiO_2气凝胶复合型隔热涂层的干膜厚度为60μm时,与未涂覆的空白样板对比,温度最高可降低14.8℃。结论 SiO_2气凝胶复合型隔热涂层具有优异的隔热性能,并且具有薄层、轻质、环保等优点,具有一定的实际应用价值。 相似文献
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采用激光脉冲试验法研究不同淬火和回火工艺对高速列车制动盘用Cr-Mo-V钢在50~800℃时的比热容、热扩散系数和导热系数。结果表明,当试验温度低于700℃时,随着试验温度的提高,试验料热扩散系数和导热系数逐渐降低,比热容逐渐提高;当试验温度超过700℃时,试验料热扩散系数和导热系数又随之提高,比热容随之下降。当试验温度低于700℃时,随着回火温度或淬火温度的提高,试验料在不同试验温度条件下热扩散系数和导热系数均稍有提高,比热容稍有降低;当试验温度为800℃时,几组试验料的比热容、热扩散系数和导热系数基本相当。 相似文献
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研究了Te和铌铁的加入量对冷硬铸铁轧辊组织和性能的影响,结果表明:(1)在冷硬铸铁中加入微量的Te和铌铁,能够显著增加白口深度、提高显微组织硬度;(2)加铌铁对灰口组织的抗拉强度影响不明显,但是能够改善灰口组织的抗弯强度;(3)加Te会降低灰口组织的强度,所以Te的加入量越低越好。 相似文献
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The crack-healing behaviors and microstructure evolution of pure tungsten produced by laser powder bed fusion (LPBF) were studied and compared before and after post hot isostatic pressing (post-HIP) treatment. An average thermal conductivity of 133 W·m−1·K−1 at room temperature (RT) was obtained after HIP, which was 16% higher than that of as-built sample (115 W·m−1·K−1). Although the HIP process had little effect on density, it resulted in a large grain size of >300 μm accompanied by a decrease in dislocation density and crack healing, which led to a substantial improvement of thermal conductivity of pure tungsten. The positive correlation between relative density and thermal conductivity of as-built tungsten was reported. 相似文献
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添加熔融石英对MgO材料抗热震性的影响 总被引:1,自引:0,他引:1
研究了不同粒度的熔融石英对MgO材料抗热震性的影响,采用XRD和SEM进行了矿物组成和显微结构分析,同时比较了热震前后试样孔径分布的变化。结果表明,加入熔融石英颗粒的试样,热震后抗折强度和耐压强度保留率明显大于未添加试样和添加熔融石英细粉试样的强度保留率。添加熔融石英后试样的热膨胀系数变小,高温下熔融石英粉易与MgO反应生成镁橄榄石,促进了试样烧结使致密度提高,由于热膨胀系数不匹配因而在熔融石英颗粒周边形成明显的微裂纹圈。因为微裂纹吸收热应力的作用,所以,加入熔融石英颗粒和细粉可以提高MgO材料的抗热震性,相比之下,添加熔融石英颗粒时效果更明显。 相似文献
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《中国铸造》2015,(6)
In this study, three kinds of modified ultra-fine ceramic powders marked A, B and C, which were prepared by each of three different modifiers mixing with a commercial SiC, were added to HT250 cast iron, respectively, and the effects of the modified ultra-fine ceramic powders on microstructure, mechanical properties and wear resistance were studied. Metallographic examination, tensile test, scanning electron microscopy, and three-dimensional surface topography were applied to analyze and compare the samples containing modified powder with the original samples. The results showed that the most obvious modification effect among the powders was seen in the sample containing powder A, with the graphite and eutectic cells being refined, the tensile strength being increased by 36.9%, and the wear resistance being improved by 45.5% and 47.2% under loads of 150 N and 300 N, respectively. The improvements of mechanical properties and wear resistance in the HT250 cast iron with the modified ultra-fine ceramic powders were attributed to the synergistic effect of the grain refinement with the powder acting as a hard particle phase and the lubrication by the graphite. 相似文献
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A new theoretical model of gray cast iron taking into account a locally interconnected structure of flake graphite was designed, and the corresponding effective thermal conductivity was calculated using the thermal resistance network method. The calculated results are obviously higher than that of the effective medium approximation assuming that graphite is distributed in isolation. It is suggested that the interconnected structure significantly enhances the overall thermal conductivity. Moreover, it is shown that high anisotropy of graphite thermal conductivity, high volume fraction of graphite, and small aspect ratio of flake graphite will cause the connectivity effects of graphite to more obviously improve the overall thermal conductivity. Higher graphite volume fraction, lower aspect ratio and higher matrix thermal conductivity are beneficial to obtain a high thermal conductivity gray cast iron. This work can provide guidance and reference for the development of high thermal conductivity gray cast iron and the design of high thermal conductivity composites with similar locally interconnected structures. 相似文献
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Molds made of gray cast iron for casting pig iron ingots are subjected to severe temperature fluctuations. The main life-
limiting factor for mold damage is the formation of surface cracks arising from thermal fa-tigue. Various flame and plasma
sprayed coatings were investigated to extend the life of these molds. Coating materials studied include plasma sprayed ceramic
coatings with bond coats as well as flame sprayed oxidation- resistant alloy powders. The results of cyclic furnace tests
from room temperature to 1100 °C in air, simulating the thermal cycle in casting, indicated that failure occurred along the
interface between the bond coat and the gray iron substrate because of iron oxidation, and not at the interface between the
ceramic top coat-ing and the bond coating for a superalloy substrate. The field test results indicated that plasma sprayed
alumina coatings with 200 μm top coating thickness are the most promising materials for pig iron casting. 相似文献