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Anomalous behavior and phase transformation of α-GaOOH nanocrystals under static compression 下载免费PDF全文
The structural compression mechanism and compressibility of gallium oxyhydroxide, α-GaOOH, are investigated by in situ synchrotron radiation x-ray diffraction at pressures up to 31.0 GPa by using the diamond anvil cell technique. Theα-GaOOH sustains its orthorhombic structure when the pressure is lower than 23.8 GPa. The compression is anisotropic under hydrostatic conditions, with the a-axis being most compressible. The compression proceeds mainly by shrinkage of the void channels formed by the coordination GaO_3(OH)_3 octahedra of the crystal structure. Anomaly is found in the compression behavior to occur at 14.6GPa, which is concomitant with the equatorial distortion of the GaO_3(OH)_3 octahedra. A kink occurs at 14.6 GPa in the plot of finite strain f versus normalized stress F, indicating the change in the bulk compression behavior. The fittings of a second order Birch–Murnaghan equation of state to the P–V data in different pressure ranges result in the bulk moduli B_0= 199(1) GPa for P 14.6 GPa and B_0= 167(2) GPa for P 14.6 GPa. As the pressure is increased to about 25.8 GPa, a first-order phase transformation takes place, which is evidenced by the abrupt decrease in the unit cell volume and b and c lattice parameters. 相似文献
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The photoluminescence(PL) properties of Y2O3:Eu3+nanophosphors were systematically investigated with the goal of improving the color quality and quantum efficiency of Y2O3:Eu3+nanophosphors for potential applications in nanoscale devices. The emission spectra, excitation spectra and fluorescence decay curves were employed to trace the energy transfer process from Eu3+at C3isite to Eu3+at C2site. The experimental results show that the energy transfer process becomes more and more efficient with the increase in the Eu3+concentration. The emission of Eu3+at C2site is favorable because it has high radiative efficiency and better color quality. The successful suppress of the emission Eu3+at C3iis especially important for its applications in general illumination or display technology. The quantum efficiency and color quality of Y2O3:Eu3+can be improved by controlling the energy transfer between the Eu3+at S6site and Eu3+at C2site. 相似文献
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利用原位高压同步辐射X射线衍射方法,对尺寸为11 nm的CaF2纳米晶粒进行高压结构相变和压缩特性研究。当压力为12 GPa时,观察到由萤石结构向α-PbCl2结构转变的一次相变,该相变压力点远高于体材料,但略低于粒径更小的CaF2纳米晶体。相比体材料,纳米尺寸的CaF2样品的体弹模量更大,说明其更难被压缩。当压力释放至常压时,11 nm的CaF2纳米晶粒的α-PbCl2型亚稳相结构被保留下来,相变不可逆。分析了影响11 nm CaF2纳米晶粒独特高压行为的原因,判定尺寸效应为主要因素,该尺寸下较高的表面能导致结构稳定性增强和体积模量增加。 相似文献
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以手性色谱柱为分离柱,串联蒸发光散射检测器(ESLD),采用反相高效液相色谱法测定普瑞巴林原料药中普瑞巴林R-异构体的含量。色谱条件如下:CHIRALPAK ZWIX(+)(4.0mm×150mm,3μm)为手性分离柱,柱温为25℃;甲醇-乙腈-水-甲酸-二乙胺(450+450+100+2.0+2.5)为流动相,流量为0.5 mL·min^(-1);ESLD漂移管温度为70℃,载气流量为2.0L·min^(-1)。普瑞巴林R-对映异构体的线性范围为0.80~4.5mg·L^(-1),检出限为0.30mg·L^(-1),测定下限为0.80mg·L^(-1)。加标回收率为93.8%~94.5%,测定值的相对标准偏差(n=6)小于2.5%。 相似文献
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高压对米曲霉理化性质影响及诱变的研究 总被引:1,自引:0,他引:1
在100~400 MPa压力、保压20 min的条件下处理酱油酿造菌种——米曲霉,研究高压对米曲霉存活率、形态特征、生理性质、蛋白酶、淀粉酶活性等的影响,并诱变筛选优良菌株。结果表明:高压对米曲霉的存活率、形态特征有明显的影响;压力对蛋白酶及淀粉酶活性的影响也有特异的规律,即在一定压力范围内(0.1~200 MPa)蛋白酶的活性随着压力的增加而减小,但随着压力的进一步升高(200~400 MPa)蛋白酶的活性又逐渐增强,在300 MPa时超过对照组,400 MPa时蛋白酶的活性达到最高值;淀粉酶在0.1~100 MPa时活性下降,在200 MPa时其平均的糊化和糖化活性最强、活力最高,当压力升高活性又开始降低,400 MPa时几乎又回到对照值。另外,高压处理后获得一株理想的变异菌株HP300a:生长速度快、孢子数量多、蛋白酶活力高,且不易被杂菌污染。其成曲的几项主要指标均优于对照株,酿出酱油的几项主要指标也明显优于对照株。为利用高压诱变筛选米曲霉优良菌种、提高酿造酱油产品的产量及质量提供了理论依据,并发现了高压处理米曲霉引起其蛋白酶及淀粉酶活性改变的特殊规律。 相似文献
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