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Neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells 下载免费PDF全文
Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China's Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi(Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa) are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm~3. 相似文献
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首次报道了一种新型的基于铰链式六面顶压机的二级6-8模大腔体静高压装置的内置加热元件的设计与温度标定。此加热组装结构简单,升温快,保温效果好,并有效地解决了国外基于两面顶压机构架下的二级6-8模内加热组装中热电偶在施加压力时易断的问题。以低成本的碳管为加热元件,采用直接和间接两种加热方式,用双铂铑(Pt6%Rh-Pt30%Rt)B型热电偶进行温度测量,并根据实验过程中加热功率与腔内实际温度的关系,对不同压力下腔体内的温度进行了标定。实验结果表明:此加热系统的油压达到40 MPa(腔体压力约10 GPa)时,温度可以达到1 700 ℃以上;在油压为30 MPa、样品室温度为1 000 ℃时,保温时间可达2 h,甚至更长;实验中获得样品的直径可达3 mm,高度可达7 mm,实现了在高温超高压条件下大样品的制备,满足了实验对产生高温超高压条件的需要。 相似文献
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以氧化镁(MgO)和氧化钴(CoO)为初始材料,利用固相反应方法,经8h的混料、200MPa的预压以及在空气氛围下1 200℃的烧结等步骤,成功制备出钴的摩尔分数为9%的氧化镁传压介质(MgO+9%CoO)。采用X射线粉末衍射仪、扫描电子显微镜以及热重分析仪对样品进行表征,结果表明:在烧结过程中混合粉料之间发生了反应,金属离子相互交换,钴离子取代MgO晶格中的部分镁离子,从而形成MgO-CoO固溶体。与目前国产MgO传压介质(MgO+10%Na4SiO4(质量分数))相比,实验制备的钴掺杂MgO传压介质不含杂质,高温高压下更稳定,并且温度发生效率更高。 相似文献
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Neutron powder diffraction and high-pressure synchrotron x-ray diffraction study of tantalum nitrides 下载免费PDF全文
Tantalum nitride(TaN) compact with a Vickers hardness of 26 GPa is prepared by a high-pressure and hightemperature(HPHT) method. The crystal structure and atom occupations of WC-type TaN have been investigated by neutron powder diffraction, and the compressibility of WC-type TaN has been investigated by using in-situ high-pressure synchrotron x-ray diffraction. The third-order Birch–Murnaghan equation of state fitted to the x-ray diffraction pressure–volume(P–V) sets of data, collected up to 41 GPa, yields ambient pressure isothermal bulk moduli of B'_0= 369(2) GPa with pressure derivatives of B 0= 4 for the WC-type TaN. The bulk modulus of WC-type TaN is not in good agreement with the previous result(B_0= 351 GPa), which is close to the recent theoretical calculation result(B_0= 378 GPa). An analysis of the experiment results shows that crystal structure of WC-type TaN can be viewed as alternate stacking of Ta and N layers along the c direction, and the covalent Ta–N bonds between Ta and N layers along the c axis in the crystal structure play an important role in the incompressibility and hardness of WC-type TaN. 相似文献
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本文基于高压研究及超硬材料生产所用的静高压立方大腔体(六面顶)压机的需要,制备了源于南非叶腊石矿的两种(A和B)叶腊石粉压块,并与同工艺国产(北京门头沟)黄色叶腊石粉压块进行比较,以此建立评估叶腊石传压及密封性能的实验方法与物理判据.采用Bi,Tl,Ba等标压物质原位标定了以上3种叶腊石压腔中心位置及密封边处的压力;同时,采用银熔点法分别获得了3种叶腊石作传压密封材料时高温下腔体压力与系统加载的对应关系.结果表明,在相同加载油压下南非叶腊石B粉压块和国内叶腊石粉压块中心位置的压力差值不超过0.1 GPa,在升压和降压过程中叶腊石块中心位置与密封边位置的压力差值也更为相近.相比于南非叶蜡石A粉压块,B粉压块在高温传压和密封性能上更接近国产叶腊石粉压块. 相似文献
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研究了Pd40Ni40P20合金在重力(1g)及微重力(μg)条件下凝固组织的差异,微重力条件下的样品中组织细化,1次枝晶短且方向性差,当冷速v为0.056K/s时,其1次枝晶间距L值远小于同样冷速条件下地面获得的组织中的L值,而与地面冷速为0.67K/s的L值相当。在此基础上推算了空间与地面不同冷速下固液界面前沿液相中溶质输运系数的差异。 相似文献