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《超硬材料工程》2017,(5)
以氮化锂(Li_3N)为触媒和六方氮化硼(hBN)为原料,在静态高温高压条件下加入籽晶批量合成出了≥50目的立方氮化硼(cBN)单晶。通过X射线衍射仪(XRD)和红外线光谱仪(FTIR)对合成后的触媒层内物相组成进行了分层表征;采用K值法、绝热法和RIR值等理论方法,计算出了触媒层内各物相的质量分数,分析了各物相在触媒层中的变化规律。采用扫描电子显微镜(SEM)对cBN单晶形貌和cBN单晶/触媒的界面形貌进行了观察,分析了触媒层的形貌对cBN单晶合成效果的影响。结果表明,触媒层内主要存在不规则的cBN微晶、hBN和Li3BN2等物相。触媒层的中间层是hBN发生固相直接转变生成cBN微晶的主要区域,触媒层中Li3BN2和cBN微晶的含量直接影响cBN单晶的合成效果。 相似文献
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立方氮化硼( cubic boron nitride,cBN)具有优异的物理力学性能和极高的化学稳定性,可以胜任铁系金属的加工,在高性能切削刀具等领域有着广泛的应用前景.cBN涂层在复杂刀具应用中有着不可替代的作用,由于气相生长高纯度和结合性能的cBN刀具涂层仍存在着较多的技术难题,因此仍然难以得到广泛的应用.本文综述了近20年来气相沉积cBN涂层的研究进展,阐述了物理气相沉积与化学气相沉积cBN涂层的方法与机理,分析了cBN刀具涂层制备与应用的关键问题,结合研究现状指出了cBN刀具涂层研究的发展方向. 相似文献
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《超硬材料工程》2020,(1)
研究立足于国产六面顶压机,在8.0 GPa的压力、1 800℃~2 350℃温度、300 s时间条件下采用2μm的纯立方氮化硼(cBN)微粉进行分米级尺寸纯相聚晶立方氮化硼(PcBN)材料的制备。利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、维氏硬度计对纯相PcBN微观组织及物相进行定性分析,研究纯相PcBN和传统PcBN在不同加工条件下切削淬火钢的表面粗糙度和刀具磨损性能特征,并对其结果进行了比较。结果表明:在8.0 GPa压力条件下随着温度的升高,纯相PcBN形成了更为致密组织结构,其自身硬度也随之升高,当温度超过2 300℃时硬度出现一定程度的降低,原因可能是部分晶粒长大后颗粒形成了空隙,空隙减弱了颗粒间的键合。测试中发现在8 GPa,温度低于2 000℃时cBN向w-BN(纤锌矿结构氮化硼)发生转化现象。与传统cBN工具相比,纯相PcBN具有更为优异的耐磨性。切割一段时间后,采用纯相PcBN材料工具加工的物性表面粗糙度R_a仍然低于30 nm。可见该材料在金属加工领域具有广阔应用前景。 相似文献
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通过高温高压合成了无硬质合金衬底的立方氮化硼聚晶(PcBN)。该cBN聚晶厚度1~5mm,具有导电性、可以被电火花切割。与传统立方氮化硼复合片(带有硬质合金衬底)进行对比,该立方氮化硼聚晶无中间钴的过渡层、具有比传统复合片长10%~20%的切削寿命。 相似文献
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《中国陶瓷》2019,(7)
将立方氮化硼微粉和TiN、Al微粉按一定的质量比进行混料,在高温和超高压条件下合成聚晶立方氮化硼(PCBN)复合片,对复合片进行了物相分析、硬度测试以及表面显微结构分析,同时分析了切削淬火钢时cBN含量对PCBN刀具磨损的影响,研究了PCBN刀具切削时的磨损机理。烧结后PCBN复合层中的物相由除了cBN、TiN添加相以外,还出现了新相AlN和TiB_2,说明添加粘接剂与cBN发生反应,并且Al已完全反应,说明复合层中的cBN颗粒通过反应生成新物相,并被粘接剂固结。当cBN含量为80 wt%时,复合片的维氏硬度达到了4512 HV。PCBN后刀面的磨损成一个规则倒三角形,刀具的失效主要是粘结磨损和氧化磨损共同作用的结果。 相似文献
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An overview of the application of crystal growth fundamentals in the high pressure–high temperature production of diamond by solvent/catalyst technique is presented. The process, also called temperature gradient process, makes use of a molten catalyst to dissolve carbon from a source (graphite or diamond powder) and transport the dissolved carbon to a growth site where they precipitate on a diamond seed. The pressure and temperature requirements for the process are generally around 5.0–6.5 GPa and 1300–1700 °C, depending on the chemistry of the solvent used and the desired crystal geometry. In spite of major progress in the science and technology of diamond growth, large scale commercial production of diamonds single crystals for jewelry or electronic applications has not been feasible until recently. This has been mainly due to the substantial cost associated with the presses needed, and the difficulties in controlling the growth parameters and catalyst chemistry. The recent developments in the commercial production of diamond single crystals utilizing the Split Sphere pressurization apparatus are discussed. 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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与采用低温费托合成主产油品技术相比,产品更为多元化和高值化的高温费托合成技术在目前市场环境下显示出非常明显的优势。本文综述了高温费托合成技术的发展历程及其最新进展,重点介绍了高温费托合成过程中的核心问题,主要包括高温费托合成工艺、固定流化床反应器、费托合成催化剂;介绍了高温费托合成产物分布与特性,讨论了高温费托合成产物的加工路线,并对高温费托合成煤间接液化的工业应用前景和产业化方向进行了展望。结果表明:高温费托合成技术具有产物附加值高、兼顾油品和化学品、技术发展成熟等优势,产物中轻组分含量高、碳数分布较窄、高附加值的α-烯烃含量高;精细化、高端化、差异化加工是实现高温费托合成产物高值化利用的关键。 相似文献
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Xue Sun Tianbiao Yu Xuezhi Wang Maoqiang Xu Wanshan Wang 《Ceramics International》2018,44(14):16307-16313
Vitrified bond CBN composites, with different amounts of TiO2 doping, were prepared by conventional sintering and high magnetic field sintering processes. Mechanical properties, cross-sectional morphology, refractoriness, fluidity and structural characterization have been carried out to understand the role of TiO2 addition and sintering conditions. Results show that TiO2 addition significantly affected bending strength, refractoriness and fluidity of vitrified bonds. In addition, high magnetic field sintering improved bending strength and the microstructure of vitrified bond CBN composites. Due to high magnetic field sintering, CBN grains were completely covered by vitrified bond and exhibited fewer pores. In addition, high magnetic field promoted the growth of specific grains, such as SiO2, whereas suppressed grain growth of other crystal phases, such as NaAlSi3O8. 相似文献
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《Carbon》2014
Here, we report the synthesis of high quality single crystal graphene on polycrystalline Cu foil using solid waste plastic as carbon source in an ambient pressure (AP) chemical vapor deposition (CVD) process. Gas chromatography analysis shows that the waste plastic is rich in polyethylene and polystyrene based polymer components. The growth of individual crystal strongly influenced by the injection rate of decomposed polymeric components generated during pyrolysis of waste plastic. Synthesis of large hexagonal and round shape single crystal graphene are achieved with a controlled rate of pyrolysis for the waste plastic. Raman studies confirm high quality of the graphene crystals independent of hexagonal and round shapes. Again, nucleation of bilayer or few-layer graphene crystals are observed with a higher injection rate of decomposed polymeric components. The evolution of hexagonal graphene crystals synthesized by AP-CVD process from waste plastic can be significant to obtain large single crystal graphene and stacked bi-layer structure. Our findings shows that solid waste plastic can be directly use as a feedstock for high quality graphene growth and thereby converting to a significantly value added product. 相似文献