共查询到19条相似文献,搜索用时 62 毫秒
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Ti(OC4H9)4高温水解气相合成TiO2超细颗粒 总被引:3,自引:0,他引:3
本文探讨了Ti(OC_4H_9)_4高温气相水解合成TiO_2超细颗粒的新工艺,实验研究了反应物浓度、反应温度和停留时间对粒子性能的影响;将反应界面层模型运用到CVD反应器中,有效地解释了实验规律。 相似文献
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细颗粒硫化锌的制备及其研究进展 总被引:7,自引:0,他引:7
细颗粒硫化锌作为一种复合半导体材料和它所具有的特异光电性能,其制备研究越来越引起人们极大的重视。本文详细介绍了细颗粒硫化锌的制备方法及其研究进展。 相似文献
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超高速陶瓷cBN砂轮的关键技术 总被引:1,自引:0,他引:1
超高速磨削技术已经是现代磨削技术发展的热点.实现超高速磨削加工,必须要有线速度高的砂轮,基于陶瓷cBN砂轮的优点多,陶瓷cBN砂轮广泛应用在高速磨削加工,文章就实现超高速陶瓷cBN砂轮的关键技术进行了简单介绍. 相似文献
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水力旋流器分离细颗粒的试验研究 总被引:12,自引:1,他引:11
介绍了用于细颗粒分离的水力旋流器的基本结构形式及主要结构参数。并针对旋流器雷诺数、分流比、旋数等无因次参数对压力特性的影响进行了细致的试验研究,找出了这些参数与欧拉数和压降比的相互关系。所有试验均在不含气的条件下进行。结果表明,随着雷诺数、分流比和旋数的分别加大,水力旋流器的压力降呈增加趋势,压降比则呈下降趋势。另外,针对当量直径45μm尿素复合颗粒进行了分离特性研究。结果表明,随着雷诺数的加大,分离效率逐步提高,但并非雷诺数越大越好;对于分流比,则只在低雷诺数时有利于分离效果的改善;旋数分别为9、16和29的实验结果表明,旋数16的总体效果为最优。 相似文献
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Dapeng YangXiaorui Ji Hongshi LiuYing-ai Li Tiechen ZhangPinwen Zhu 《Diamond and Related Materials》2011,20(2):174-177
In this paper, various cubic boron nitride (cBN) crystal morphologies were synthesized using hexagonal boron nitride (hBN) as raw materials and Li3N, LiH, and LiNH2 as catalysts/additives under high pressure and high temperature (HPHT).These crystal shapes contain thick-plate, spherical, octahedral or hex-octahedral, flat cone and flaky hexagonal morphologies. The reasons of various crystal shapes synthesized can be summarized as follows: various catalysts/additives take on distinct properties under HPHT, which have crucial effects on the cBN crystal morphologies synthesized. Catalyst Li3N tends to grow cBN with thick-plate morphology, catalyst LiH would induce the growth of cBN tending to integrated octahedral morphology, and catalyst LiNH2 would play diverse roles for cBN crystal morphologies in various systems. 相似文献
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Yafei Zhang Chuanyi Zang Hongan Ma Zhongzhu Liang Lin Zhou Shangsheng Li Xiaopeng Jia 《Diamond and Related Materials》2008,17(2):209-211
Large green single crystal diamond with high nitrogen concentration is firstly synthesized by temperature gradient method under high pressure and high temperature (HPHT). Sodium azide (NaN3) is added as the source of nitrogen to the synthesis system of high pure graphite and kovar alloy (Fe59Co25Ni17). The HPHT synthesis condition is 5.4 GPa and 1480 K. The maximum crystal size is 3.2 mm. The infrared absorption spectra indicate that the nitrogen concentration in the green large single crystal diamond reaches 1520 ppm in the form of single substitution, which is close to that in nature diamond, and several times higher than that in the man-made Ib large single crystal diamond previously. 相似文献
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Using hBN and pBN as starting materials, various types of binderless polycrystalline cBN (BL-PcBN) were synthesized in the pressure range of 8–20 GPa and temperature range of 1300–2400 °C, and their mechanical properties were evaluated. In the synthesis pressure range of 10 GPa and higher, the hardness of BL-PcBN showed a correlation not with the synthesis pressure, but with the synthesis temperature. Binderless polycrystalline cBN synthesized at about 2200 °C exhibited the highest mechanical properties, for both starting materials. Specifically, BL-PcBN(h) (100–300 nm grain size) synthesized from hBN at 10 GPa and 2200 °C showed a hardness of 45 GPa, transverse rupture strength of 1.6 GPa. In contrast, BL-PcBN(p) synthesized from pBN at the same temperature had finer grain size (50–100 nm) and exhibited the same level of hardness but lower strength properties (transverse rupture strength of approx. 1.3 GPa) than BL-PcBN(h). Consequently, the material that exhibited the best mechanical properties was BL-PcBN(h) synthesized at 10 GPa and 2200 °C. A prototype micro ball end mill made of this material was examined in a mirror-like (polished-like) finishing test using high-strength hardened steel. This ball end mill achieved a fine finishing surface with a surface roughness (Ra) of 20 nm or better. The test revealed the high potential of this material for use as a high-precision cutting tool for high strength ferrous materials. 相似文献
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The hardness characteristic of nano-polycrystalline cBN synthesized by direct conversion sintering was thoroughly investigated using Vickers and Knoop indenters. It was found that nano-polycrystals consisting of smaller cBN grains increase the elastic recovery of indentations during unloading of the indenters and the diagonal of Vickers indentations and the minor diagonal of Knoop indentations significantly decrease in length. Thus, if a Vickers indenter is used, the apparent hardness value increases, making it impossible to perform an accurate evaluation, e.g. incorrect Vickers hardness values in excess of 80 GPa were obtained from nano-polycrystalline cBN with a grain size of 50 nm or less. On the other hand, it was verified that a Knoop indenter ensures an accurate hardness evaluation even if the constituent grains are fine because its major diagonal length which is used for measurement is less susceptible to elastic recovery. In an accurate evaluation of the hardness of different types of nano-polycrystalline cBN using a Knoop indenter, the hardness of each type of cBN was around 45 GPa, and there was no clear Hall–Petch relationship between hardness and grain size without a slight bell-like correlation. These results suggest that reported hardness values higher than 80 GPa of similar nano-polycrystalline cBN evaluated using a Vickers indenter are incorrect values caused by elastic recovery occurring at the indentation. 相似文献
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粗颗粒工业金刚石的合成与普通工业金刚石相比,需要较长的生长时间,而且其合成条件相对于普通工业金刚石单晶更为苛刻.文章总结了在具有高精密化控制系统的国产SPD 6×1670T型六面顶压机上进行的优质粗颗粒金刚石单晶的合成研究.在粉末触媒合成金刚石工艺的基础上,提高了压力和温度控制系统的精密化程度,引入了旁热式组装,改良了合成工艺,通过精密地控制金刚石的成核量与生长速度,以及采用最佳粒度的触媒,在高温高压条件下(~5.4GPa,~1360℃)成功合成出尺寸达到1.0mm的(18目)粗颗粒金刚石单晶,并分析了晶体的形貌和表面特征. 相似文献
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在使用六面顶压机合成cBN/Sialon复合材料的实验过程中,当石墨杯内径为18.8mm时,烧结过程一切正常.当石墨杯内径扩展为22.0mm后,电流突降、电阻突升的情况开始出现.阐述了电阻突升可能造成的危害,从加热系统的各部分结构与组装方式入手,分析了电阻突升的原因,结果表明,烧结过程中发生较大体积收缩的Si3N4导致了加热电流回路的崩溃.改进组装方式后顺利合成了具有良好机械性能的cBN/Sialon复合材料,随着保温时间的增加,Sialon的Z值增加,发育良好的棒状β-Sialon晶体均匀分布于烧结体中. 相似文献