电子束蒸发制备PbI2膜及其光学性能研究

采用电子束蒸发法制备PbI2膜,研究不同工艺参数对制备样品光学性质的影响.结果表明,制备样品属于六方相多晶结构,随衬底温度的升高,样品中的I元素含量降低并趋于理想化学配比.随着衬底温度的升高,PbI2膜的光谱透过性能逐渐改善,吸收边沿低能一侧的拖尾逐步消除,源自样品结晶质量的提高.根据紫外-可见透过谱,计算了不同条件下制备样品的厚度、折射率、吸收系数和光学带隙.结果发现,随衬底温度的升高,制备样品的折射率和光学带隙出现波动变化,但吸收系数单调增大.在相同的衬底温度下,35 cm的源-衬间距下制备的样品具有最大的光吸收系数,归因于该系列样品较高的致密度.     

稀土高氯酸盐-甘氨酸配合物[Sm2(Gly)6(H2O)4](ClO4)6.5H2O单晶体的低温热容及标准生成焓

合成了稀土高氯酸盐-甘氨酸配合物晶体。经热重、差热、化学化析及有关文献对比,确定其组成是[Sm2(Gly)6(H2O)4](ClO4)6·5H2O,单晶结构,纯度是99.0%.熔点分析仪分析知其没有固定熔点,在79～370K温区,用高精密全自动绝热量仪对单晶配合物进行了热容测定,发现该配合物在低温段没有反常热容。348.07K附近是该配合物的分解温区,配合物的分解温度、分解熵和分解焓分别是346.89K,44.669kJ/mol和128.77J/K·mol。计算机拟合了热容对温度的多项式方程,在79～318K温区,Cp=1294.56+624.17K-11.893X^2+75.075X^3+23.762X^4.在常压,298.15K下用具有恒温环境的反应热量计测定了配合物的标准生成焓值为-8022.405kJ/mol。     

Theoretical investigation on the electronic structure,elastic properties,and intrinsic hardness of Si₂N₂O

According to the density functional theory we systematically study the electronic structure, the mechanical prop- erties and the intrinsic hardness of Si2N2O polymorphs using the first-principles method. The elastic constants of four Si2N2O structures are obtained using the stress-strain method. The mechanical moduli (bulk modulus, Young’s mod- ulus, and shear modulus) are evaluated using the Voigt-Reuss-Hill approach. It is found that the tetragonal Si2N2O exhibits a larger mechanical modulus than the other phases. Some empirical methods are used to calculate the Vickers hardnesses of the Si2N2O structures. We further estimate the Vickers hardnesses of the four Si2N2O crystal structures, suggesting all Si2N2O phases are not the superhard compounds. The results imply that the tetragonal Si2N2O is the hardest phase. The hardness of tetragonal Si2N2O is 31.52 GPa which is close to values of β-Si3N4 and γ-Si3N4.     

由热重数据计算动力学参数

热重法(TG)是一种动态测量技术,可在程序升温或降温情况下对给定物质或体系提供一个连续的,以温度或时间为函数的重量变化曲线,所以由它跟踪反应能给出反应动力学的有关信息。这种非等温法与早期使用的等温法相比,有快速、连续和需要较少实验数据等优点,近年来在动力学研究方面得到广泛应用,但还只限于研究下列几种类型的简单     

溶胶-凝胶法制备ZnO薄膜及其微结构特性研究

采用溶胶-凝胶法(Sol-Gel)制备氧化锌(ZnO)薄膜,研究镀膜层数和退火温度对ZnO薄膜晶体结构、光谱性质及表面形貌的影响.X射线衍射谱测试表明,退火温度为600℃、镀膜层数为10层时制备样品的晶粒尺寸最大,结晶度最好.紫外-可见透过谱发现,样品退火后其透过率曲线变得陡直,光学带隙随退火温度升高而逐渐减小.光致发光谱测试显示,ZnO薄膜的发光谱包含388 nm和394 nm附近的两个主要发光峰,分别对应于本征发射和缺陷发射,其强度随退火温度升高呈现相反的变化.原子力显微照片则显示了随退火温度的升高制备样品表面晶粒的分布趋于均匀而致密.     

CdSe晶体光参量振荡器的热透镜效应仿真研究

在CdSe晶体光参量振荡器(OPO)中,泵浦激光经过晶体后产生大量废热,使CdSe晶体出现明显热透镜效应,从而导致泵浦激光的光斑半径在晶体内部不断变小,最终降低了晶体的损伤阈值和OPO的输出功率。本文利用COMSOL软件对高重频脉冲激光泵浦CdSe晶体进行多物理场建模,完成了CdSe晶体热透镜效应仿真,通过参数优化,发现对流系数与晶体最大温度成反比,与晶体后端面和焦点的光斑半径成正比,聚焦位置随对流系数增加趋于稳定。单脉冲能量和重复频率与晶体最大温度和焦点的光斑半径成正比,与晶体后端面光斑半径和聚焦位置成反比。准直激光光斑半径与晶体最大温度成反比,与晶体后端面光斑半径、聚焦位置和焦点光斑半径成正比。该研究解决了CdSe OPO中晶体后端面光斑半径难以直接测量的问题,为优化CdSe晶体热透镜效应提供了理论依据。     

Theoretical investigation on the electronic structure,elastic properties, and intrinsic hardness of Si2N20

According to the density functional theory we systematically study the electronic structure, the mechanical prop- erties and the intrinsic hardness of Si2N2O polymorphs using the first-principles method. The elastic constants of four Si2N2O structures are obtained using the stress-strain method. The mechanical moduli （bulk modulus, Young’s mod-ulus, and shear modulus） are evaluated using the Voigt-Reuss-Hill approach. It is found that the tetragonal Si2N2O exhibits a larger mechanical modulus than the other phases. Some empirical methods are used to calculate the Vickers hardnesses of the Si2N2O structures. We further estimate the Vickers hardnesses of the four Si2N2O crystal structures, suggesting all Si2N2O phases are not the superhard compounds. The results imply that the tetragonal Si2N2O is the hardest phase. The hardness of tetragonal Si2N2O is 31.52 GPa which is close to values of β-Si3N4 and γ-Si3N4.     

PbI2多晶膜的制备及其晶体结构

采用电子束蒸发法制备PbI2多晶膜,研究了制备条件对沉积速率和晶体结构的影响.结果表明,源-衬间距和衬底温度对沉积速率的影响不具单调性,沉积速率随源-衬间距增大、衬底温度升高呈波动起伏.不同条件下制备的PbI2膜均属六方结构,但结晶质量和择优生长晶面存在差异.实验发现,随着膜层厚度增大,样品的结晶质量提高,当膜厚超出某一临界值,其结晶质量出现明显的下降.同时,随着衬底温度升高,PbI2膜的择优生长方向由80 ℃的(110)晶面转变为120 ℃的(001)晶面,且高级次(002)、(003)、(004)晶面的衍射峰逐渐增强,样品的c轴择优取向生长更加明显.综合以上,在电子枪束流25 mA、电压6.5 kV,源-衬间距30 cm、衬底温度160 ℃的条件下,采用电子束蒸发制备的PbI2多晶膜具有最佳的结晶性能.     

Theoretical investigation on the electronic structure, elastic properties, and intrinsic hardness of Si2N2O

According to the density functional theory we systematically study the electronic structure, the mechanical prop- erties and the intrinsic hardness of Si2N2O polymorphs using the first-principles method. The elastic constants of four Si2N2O structures are obtained using the stress-strain method. The mechanical moduli (bulk modulus, Young’s mod- ulus, and shear modulus) are evaluated using the Voigt-Reuss-Hill approach. It is found that the tetragonal Si2N2O exhibits a larger mechanical modulus than the other phases. Some empirical methods are used to calculate the Vickers hardnesses of the Si2N2O structures. We further estimate the Vickers hardnesses of the four Si2N2O crystal structures, suggesting all Si2N2O phases are not the superhard compounds. The results imply that the tetragonal Si2N2O is the hardest phase. The hardness of tetragonal Si2N2O is 31.52 GPa which is close to values of β-Si3N4 and γ-Si3N4.