优质细颗粒金刚石单晶的高温高压合成与表征

文章利用国产六面顶高温高压设备,根据对金刚石合成不同区域的生长特点,通过对合成工艺的调整,实现了对体系中金刚石成核率与生长速率的控制,并成功合成出了具有完整晶形,尺寸大约在2~10μm的优质细颗粒金刚石单晶。通过热重-差热分析以及Raman光谱测试发现,合成具备完整晶面的细粒度金刚石单晶抗氧化强度大于表面粗糙的同粒度的金刚石微粉破碎料,且合成的晶体内部存在较小的残余应力。     

Li基多元触媒体系中深色cBN的合成研究

文章以Li基多元化合物为触媒,在引入添加剂的条件下合成出了深色的cBN单晶.研究发现,随着添加剂含量的增加,cBN的颜色由浅至深并逐渐变成黑色.晶体的形貌完整,粒度均一.用电子显微镜对晶体微观形貌进行了分析,发现随着添加剂含量的变化,晶体的缺陷也相应地发生了变化.     

Ti（OC4H9）4高温水解气相合成TiO2超细颗粒

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。     

添加剂硼对合成细颗粒金刚石单晶的影响

实验在国产六面顶压机上利用高温高压方法,在铁基粉末触媒中添加硼粉,合成出了细颗粒金刚石单晶,找到了合成含硼细颗粒金刚石单晶的最佳添加比例.实验结果表明:随着硼添加量的增加,晶体的颜色逐渐加深,合成细颗粒金刚石单晶的最低压力点呈动态变化趋势.在铁基粉末触媒中添加硼粉,合成的金刚石单晶容易出现包裹体,且颗粒细化后依旧没有大的改善,原因与硼的电子结构有关.     

涂覆类cBN磨料性能研究

对比了几种涂覆类cBN磨料的性能及其应用于陶瓷结合剂磨具的性能,通过扫描电子显微镜(SEM)、差热—热重分析仪(DSC-TG)及力学性能测试仪对其进行表征,结果发现:刚玉涂覆cBN磨料的力学性能和热稳定性没有劣化,但与陶瓷结合剂制成磨具抗折强度降低;钛涂覆cBN磨料陶瓷结合剂磨具抗折强度提高,但钛涂覆后cBN磨料力学性能和热稳定性变差;玻璃涂覆cBN磨料的力学性能和热稳定性有所提高,其与陶瓷结合剂在界面处结合紧密,增强了二者之间的把持力,提高了其磨削性能.     

细颗粒石墨材料的试制研究

以20μm以下骨料粒度为主体，生产细颗粒石墨材料的试制研究情况。对试制中的一些问题进行了分析和讨论。     

细颗粒硫化锌的制备及其研究进展

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。     

超高速陶瓷cBN砂轮的关键技术

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.     

不同晶形粗颗粒（0．8mm）金刚石单晶的高温高压合成

优质粗颗粒金刚石单晶(尺寸达0.8mm)在制备金刚石工具方面具有重要的应用,其合成条件相对于普通工业金刚石单晶更为苛刻.文章介绍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优质粗颗粒金刚石单晶的合成研究.通过采用先进的旁热式组装和粉末触媒技术,并优化了合成工艺,在高温高压条件下(5.4GPa,1300℃～1435℃)成功合成出尺寸为0.8mm(20目)三种不同晶形的粗颗粒金刚石单晶.     

水力旋流器分离细颗粒的试验研究

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。     

优质板状Ⅰb型宝石级金刚石大单晶的合成

高温高压下合成Ⅰb型宝石级金刚石大单晶,需要较长的合成时间。由于低温板状晶体合成区间很窄,因此较中温和高温晶体的合成相对困难。文章对板状Ⅰb型宝石级金刚石大单晶的合成进行了研究,并实现了不同尺寸优质板状晶体的可重复性合成。     

影响立方氮化硼单晶合成效果的工艺探讨

通过对立方氮化硼单晶生产工艺的改进,六方氮化硼的转化率提高了一倍,单产有了较大幅度的提高,合成电流较为平稳,较好地保护了导电钢圈,因而顶锤消耗明显降低,达到了高产低成本的效果.     

The influence of Li-based catalysts/additives on cBN crystal morphologies synthesized under HPHT

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.     

HPHT synthesis of large single crystal diamond doped with high nitrogen concentration

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.     

Mechanical properties of nano-polycrystalline cBN synthesized by direct conversion sintering under HPHT

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.     

高温高压温度梯度法合成板状宝石级金刚石单晶

板状宝石级金刚石单晶具有重要的应用价值.它可以作为红外透明窗口和高功率激光器的散热片等.文章研究了温度梯度法合成宝石级金刚石与籽晶的生长面以及合成温度之间的关系,在低温区用籽晶(100)面合成了4mm的优质板状晶体.     

Real indentation hardness of nano-polycrystalline cBN synthesized by direct conversion sintering under HPHT

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.     

优质毫米级粗颗粒金刚石单晶的高温高压合成

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.     

超高压烧结制备cBN/Sialon复合材料及烧结过程中的失效分析

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.