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121.
《Angewandte Chemie (International ed. in English)》2017,56(41):12471-12475
Lead‐based perovskite nanocrystals (NCs) have outstanding optical properties and cheap synthesis conferring them a tremendous potential in the field of optoelectronic devices. However, two critical problems are still unresolved and hindering their commercial applications: one is the fact of being lead‐based and the other is the poor stability. Lead‐free all‐inorganic perovskite Cs3Bi2X9 (X=Cl, Br, I) NCs are synthesized with emission wavelength ranging from 400 to 560 nm synthesized by a facile room temperature reaction. The ligand‐free Cs3Bi2Br9 NCs exhibit blue emission with photoluminescence quantum efficiency (PLQE) about 0.2 %. The PLQE can be increased to 4.5 % when extra surfactant (oleic acid) is added during the synthesis processes. This improvement stems from passivation of the fast trapping process (2–20 ps). Notably, the trap states can also be passivated under humid conditions, and the NCs exhibited high stability towards air exposure exceeding 30 days. 相似文献
122.
Sikandar Azam Muhammad Imran Amin Ur Rahman Asif Nadeem Riadh Neffati 《International journal of quantum chemistry》2023,123(3):e27025
The optical properties, electronic charge density, electronic structure of the new layered selenides materials, BaGdCuSe3, CsUCuSe3, CsZrCuSe3, and CsGdZnSe3 compounds have been calculated by using the full potential and linear augmented plane wave (FP-LAPW) methods as applied in the WIEN2k package, which is based on the density functional theory. The ALnMSe3 compound's structure of these was (A = Cs, Ba; Ln = Zr, Gd, U; M = Cu, Zn) is composed of (n = 1, 2) layers, which might be separated by A atoms. It is to be observed that there is strong hybridization between the s, p, and d states of Zr, Gd, and Cu atoms. Around the gadolinium atom, the charge density contours are completely circular, but the Gadolinium “Gd” atom shows an ionic nature. To calculate the refractive index, we used Kramer's Kronig correlations with the imaginary part dielectric function. The decrease in the refractive index is due to the lack of probability for direct excitation of the electrons, resulting in a loss of energy. The value of the static refractive index for all reference compounds is about 1.75–2.25, which is indication that the material used in optoelectronic devices. 相似文献
123.
层状复合氢氧化物(LDHs)因其化学组成可调、比表面积大、生物相容性好等特点,目前在环境、能源和生物医药等领域广受关注.然而, LDHs在合成过程中由于其分子内作用力易发生团聚而导致其在基体中的分散不均匀,极大地限制了LDHs在实际中的应用.有机改性是改善LDHs分散性的有效方法,从表面改性和插层改性两个方面综述了近年来LDHs的有机改性方法,并介绍了其在阻燃、吸附、催化、气体阻隔、发光、储能和生物医药材料等领域的应用.最后对改性后LDHs未来的研究方向和应用领域进行了展望. 相似文献
124.
采用毒性小、环境友好的乙二醇甲醚(ethylene glycol monomethyl ether,EGME)与水混合的双溶剂(体积比为1∶1)溶解CsBr,通过提高CsBr的溶解度,减少了后续CsBr的甲醇溶液的旋涂遍数,简化了电池制备流程。通过优化CsBr的甲醇溶液的旋涂遍数发现,在旋涂1遍200 mg·mL-1 CsBr的水/EGME溶液的基础上旋涂2遍15 mg·mL-1 CsBr的甲醇溶液,所制备的CsPb-Br3钙钛矿太阳能电池(perovskite solar cells,PSCs)拥有最佳的性能,实现了1.44 V的开路电压(open-circuit voltage,VOC),6.26mA·cm-2的短路电流密度(short circuit current density,JSC),74.57%的填充因子(fill factor,FF)及最高6.72%的光电转换效率(pho-toelectric conversion efficiency,PCE)。 相似文献
125.
126.
N. A. Abrosimov 《Mechanics of Composite Materials》1999,35(6):495-506
Nonlinear three-dimensional problems of dynamic deformation, buckling, and posteritical behavior of composite shell structures under pulsed loads are analyzed. The structure is assumed to be made of rigidly joined plates and shells of revolution along the lines coinciding with the coordinate directions of the joined elements. Individual structural elements can be made of both composite and conventional isotropic materials. The kinematic model of deformation of the structural elements is based on Timoshenko-type hypotheses. This approach is oriented to the calculation of nonstationary deformation processes in composite structures under small deformations but large displacements and rotation angles, and is implemented in the context of a simplified version of the geometrically nonlinear theory of shells. The physical relations in the composite structural elements are based on the theory of effective moduli for individual layers or for the package as a whole, whereas in the metallic elements this is done in the framework of the theory of plastic flow. The equations of motion of a composite shell structure are derived based on the principle of virtual displacements with some additional conditions allowing for the joint operation of structural elements. To solve the initial boundary-value problem formulated, an efficient numerical method is developed based on the finite-difference discretization of variational equations of motion in space variables and an explicit second-order time-integration scheme. The permissible time-integration step is determined using Neumann's spectral criterion. The above method is especially efficient in calculating thin-walled shells, as well as in the case of local loads acting on the structural element, when the discretization grid has to be condensed in the zones of rapidly changing solutions in space variables. The results of analyzing the nonstationary deformation processes and critical loads are presented for composite and isotropic cylindrical shells reinforced with a set of discrete ribs in the case of pulsed axial compression and external pressure.Scientific Research Institute of Mechanics, Lobachevskii Nizhegorodsk State University, N. Novgorod, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 6, pp. 757–776, November–December, 1999. 相似文献
127.
实验研究了La2/3CamMnO3样品零磁场下的电阻率和低磁场下的磁化强度随温度的变化行为.结果表明,除了居里温度(Tc)外还存在另一特征温度Tonset,高于Tonset的样品为典型的顺磁绝缘体,而低于Tc的样品为典型的铁磁金属,但在Lonset和Tc之间,样品的磁化率大大偏离居里一外斯定律,同时其导电特性显示出明显的反常.对观察到的不寻常导电特性,根据铁磁金属集团在顺磁绝缘体背景上随机分布的假设,进行了分析与探讨。 相似文献
128.
129.
针对桩与连续梁组合这一基础形式,研究了梁—桩—土竖向耦合振动特性. 首先,将桩假设为一维黏弹性杆件,采用平面应变模型模拟桩侧成层土对桩的动力作用. 同时,桩顶对梁的支撑简化为竖向点支撑. 然后,分别根据一维杆件纵向振动理论和Timoshenko梁理论给出桩和梁的竖向振动控制方程并求解,进而借助离散傅里叶逆变换获得在梁上瞬时激振下梁和土层以上桩段的时域响应半解析解. 通过与有限元模拟结果对比,验证了解的合理性. 在此基础上,讨论了梁几何参数和桩身缺陷对梁—桩—土竖向耦合振动特性的影响. 相似文献
130.
This paper is concerned with the problem of heat conduction from an inclusion in a heat transfer layered medium. Making use of the boundary integral equation method, the well-posedness of the forward problem is established by the Fredholm theory. Then an inverse boundary value problem, i.e. identifying the inclusion from the measurements of the temperature and heat flux on the accessible exterior boundary of the medium is considered in the framework of the linear sampling method. Based on a careful analysis of the Dirichlet-to-Neumann map, the mathematical fundamentals of the linear sampling method for reconstructing the inclusion are proved rigorously. 相似文献