共查询到19条相似文献,搜索用时 390 毫秒
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采用冷压陶瓷技术开发具有一级相变、居里温度(TC)低于室温的(Ba0.91La0.09)Ti1-0.09/4O3(BL9T)单相陶瓷。该陶瓷用于国产X射线衍射仪低温粉末XRD测量时的温度准确性验证。考虑晶体结构随温度的弛豫后,由介电温谱和变温拉曼光谱技术综合确定的砭最高为-62℃,以确保BL9T在%以上始终处于立方结构。以BL9T的单胞体积(圪)与温度的线性膨胀关系为依据,验证了在低于室温进行粉末×RD测量时变温样品室具有较高的温度准确性。在-30℃到-60℃温度范围内,变温样品室内热电偶的监控温度(瓦)与陶瓷粉末样品表面的实际温度(t)的偏差非常小(〈2℃)。 相似文献
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蒸压釜变温应力及变形的分析与计算 总被引:1,自引:1,他引:0
本文通过对蒸压釜釜体变形的分析,推导出釜体变温应力和变温弯曲变形的计算公式,给出了实验处理的计算方法;讨论了变温应力和变温弯曲变形对釜体安全的影响,并提出了改善釜体受力情况的措施。 相似文献
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为了制备高性能无铅压电陶瓷,采用固相合成法和水热法合成了(KxNa1-x)NbO3 (KNN)无铅压电陶瓷粉体.利用压制成型法在不同压力下成型,对不同粉体的烧结性能进行了对比,研究了粘结剂(PVA)添加量和陶瓷密度之间的关系,测量了用不同电压极化后陶瓷的压电特性,以及介电常数与温度之间的关系.结果表明:与固相合成法相比,水热合成的粉体有更好的烧结性,添加K会降低陶瓷的烧结性,陶瓷的密度对烧结温度非常敏感.1 050 ℃保温2 h得到的K0.5Na0.5NbO3陶瓷具有较高的压电常数d33 (90 pC/N),该陶瓷的居里温度为410 ℃. 相似文献
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分析了温度对三线阵测绘相机传递函数和交会角的影响,通过热光学计算确定了测绘相机的热控指标.首先,在设定测绘相机热载荷状态的基础上,用有限元方法分析了温度场及热弹性变形;利用Zernike多项式进行波面拟合,代入光学软件考察温度对光学系统传递函数的影响,得到测绘相机光学传递函数在假定温度场作用下的下降系数.然后,进行了测绘基座的热尺寸稳定性分析.并在此基础上考察了温度对测绘相机交会角的影响.实验显示,上述分析避免了热控设计的过设计或设计不足,为制定合理的热控设计指标提供了数据依据. 相似文献
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The analytic solution for the model of electron beam heating a moderately thick STEM/SEM specimen was used to calculate the steady state temperature profiles developed in the bulk of the specimen. For thin specimens one maximum in the temperature profile was found near the surface. The location of this maximum shifted away from the surface with increasing sample thickness. For specimens of thickness approaching the electron range two maxima were found: one close to the surface (as in thin samples) due to a ‘self-insulating’ effect, and another maximum near the sample-substrate interface—a result of very rapid increase in the energy loss by the electrons near their penetration range. These results are of particular interest for X-ray microanalysis where high beam currents are used, resulting in potentially large temperature rises in the bulk of the specimen. 相似文献
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Recently, an electron backscatter diffraction (EBSD) system was developed that uses a 1024 × 1024 CCD camera coupled to a thin phosphor. This camera has been shown to produce excellent EBSD patterns. In this system, crystallographic information is determined from the EBSD pattern and coupled with the elemental information from energy or wavelength dispersive X-ray spectrometry. Identification of the crystalline phase of a sample is then made through a link to a commercial diffraction database. To date, this system has been applied almost exclusively to conventional, bulk samples that have been polished to a flat surface. In this investigation, we report on the application of the EBSD system to the phase identification analysis of individual micrometre and submicrometre particles rather than flat surfaces. 相似文献
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HIP-Si3N4陶瓷/45#钢副干摩擦和水润滑下摩擦学性能 总被引:2,自引:0,他引:2
利用MPX-2000型盘销式摩擦磨损试验机考察了HIP—Si3N4陶瓷/45^#钢副在干摩擦和水润滑下的摩擦磨损性能;用扫描电子显微镜观察了试件表面的磨损状态;采用X射线电子能谱仪分析了摩擦表面的化学成分:结果表明:干摩擦条件下,HIP—Si3N4陶瓷的磨损速率比45^#钢小,45^#钢发生粘着磨损,HIP—Si3N4陶瓷发生了脆性断裂和脱落;水润滑条件下,摩擦表面产生了Si(OH)4反应膜,降低了磨损,主要是化学腐蚀磨损。 相似文献
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Jian Kong Dangsheng Xiong Jianliang Li Qunxing Yuan Rajnesh Tyagi 《Tribology Letters》2009,35(3):151-158
The tribological properties of Cu-based and Zr-based bulk metallic glasses (BMGs) sliding against Si3N4 under dry and water lubrication were studied on a pin-on-disc tribometer. The wear mechanisms of bulk metallic glasses were
investigated based on the calculated flash temperature. The friction coefficients if fully amorphous alloy are about 0.7,
while those of BMGs with nanocrytalline are a little higher. The wear rates of Cu-based BMG (V101) are about one order of
magnitude lower than those of Zr-based BMG (Vit1) under dry friction, even two orders of magnitude lower under water lubrication.
The wear resistance of bulk metallic glasses was influenced by the flash temperature. The calculated flash temperature (3,337 K)
on the friction surface of Zr-based amorphous alloy exceeds its glass transition temperature, even its melting temperature.
The high flash temperature leads to glass transition accompanied with viscous flow and material transfer, which is responsible
for the poor wear resistance of Zr-based BMGs. 相似文献
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This paper is one of a series dealing with the surface temperature conditions in disks and gears. It attempts to apply and extend the theory proposed in an earlier paper which predicted the behavior of the surface temperature of machine elements subjected to repeated frictional contacts. In considering the critical temperature hypothesis proposed by Blok as a criterion for failure by scuffing, it is essential that the operating surface temperature is taken into account in addition to the well known “flash temperature.” There have been many papers referrinq to this “flash temperature,” but little is known of the factors which affect the operating surface temperature, commonly called the bulk temperature. This paper demonstrates that the bulk temperature growth under loaded conditions can be predicted theoretically, and that by observing the behavior of the surface temperature the heat transfer coefficient and friction conditions can be calculated. Finally full details of the thermocouple used by the authors in their tests are given. 相似文献
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针对内燃机活塞表面温度变化迅速的特点,研制了一种瞬态温度传感器用于测量活塞表面温度。采用直流脉冲磁控溅射的方法将NiCr薄膜直接溅射沉积在高温烧结后嵌有NiCr、NiSi丝的陶瓷元件端面,NiCr薄膜外侧溅射Si3N4保护膜。传感器外壁选用带螺纹的304不锈钢作为铠装套筒。采用自行研制的薄膜热电偶静动态标定系统对所研制的瞬态温度传感器进行标定,结果表明:所研制的传感器在50~400℃范围内具有良好的线性和热稳定性,其塞贝克系数在39~41μV/K之间,非线性误差小于0.34%,重复性好;热接点薄膜厚度为355nm时,传感器的响应时间为41.7μs,且响应时间随着薄膜厚度的增大而增加;该瞬态温度传感器可以满足曲轴转速为1800r/min的内燃机活塞表面瞬态温度测试的需求。 相似文献
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Zhengguang Zhu Lihua Yuan Guanhua Wu Wei Wu Jiacheng Wang 《Russian Journal of Nondestructive Testing》2018,54(8):610-617
The geometric model of thermal barrier coatings (TBCs) was established. Two cases based on the standard thickness of the ceramic layer existed. These were the steps of TBCs thickness were being higher than the standard layer and those of lower than standard layer. The heat transfer processes of these two cases were simulated with the ANSYS software. The change process of thermal effusivity was analyzed in the two cases and the coating thickness differences effect on the surface temperature distributions of TBCs was analyzed through the time course curves of temperature difference. Moreover, the difficulty of detection for these two cases with infrared nondestructive testing was discussed according to maximum temperature difference and the maximum temperature contrast ratio. The result demonstrated that all curves of thermal effusivity with various thickness differences coincided with each other at the initial and longer times, where the ceramic layer thickness was lower than the standard layer. This was more easily detectable compared to the higher thickness and the maximum temperature contrast ratio or the maximum temperature difference increased as the coating thickness difference increased. 相似文献