半导体量子点在白光LED中涂覆厚度的确定

在蓝光LED上涂覆黄光量子点是合成白光LED的重要方法之一,确定量子点的涂覆厚度是合成白光的一个关键步骤。引入厚度系数来模拟厚度,证明了一定厚度范围内,厚度系数与厚度的线性关系。根据光谱的线性叠加以及能量守恒定律,建立数学模型,编程计算,结合实验,确定量子点厚度。按照模拟计算得到的厚度涂覆LED芯片,即可获得白光LED。本方法可以为实际生产提供指导,提高生产效率。     

Heaven on Earth

‘By 2050 we will have probed the universe even further, peeling back time as we strive for some sense of creation and meaning.’ The world's first neurologist in space, Roberta L Bondar , who conducted international experiments on space mission STS 42 and has subsequently undertaken neurological research with NASA, urges us to look up and into space, which is set to remain a rich area of exploration, scientific investigation and wonder, with the discovery of new planets, light, patterns and materials on the not-so-distant horizon.     

Structure and physicomechanical properties of NbN-based protective nanocomposite coatings: A review

This review summarizes the present-day achievements in the study of the structure and properties of protective nanocomposite coatings based on NbN, NbAlN, and NbSiN prepared by a variety of modern deposition techniques. It is shown that a change in deposition parameters has a significant effect on the phase composition of the coatings. Depending on the magnitude of negative potential on the substrate, the pressure of nitrogen or a nitrogen–argon mixture in the chamber, and the substrate temperature, it is possible to obtain coatings containing different phases, such as NbN and SiN_x (Si₃N₄), AlN, and NbAl₂N. It is found that, in the case of formation of the ε-NbN phase, the coatings become very hard; their hardness achieves values on the order of 53 GPa. At the same time, they remain thermally stable at temperatures of up to 600°C, chemically inert, and resistant to wear. The effect of the nanograin size, the volume fraction of boundaries and interfaces, and the point defect concentration on the physicomechanical properties of these coatings is described. Niobium nitride-based coatings can be used in superconducting systems and single-photon detectors; they are capable of operating under the action of strong magnetic fields of up to 20 T; they can be used in integrated logic circuits and applied as protective coatings of machine parts, edges of cutting tools, etc.     

Phase Diagram and Enhanced Piezoelectric Response of Lead‐Free BaTiO3–CaTiO3–BaHfO3 System

Three composition groups in the BaTiO₃–CaTiO₃–BaHfO₃ ternary system, (1 ? x)Ba(Hf_yTi_1?y)O₃–x(Ba_1?zCa_z)TiO₃ (abbreviated as BH_yT–xBC_zT with x = 0–1.0, y = 0.16, z = 0.20; x = 0–1.0, y = 0.16, z = 0.30; x = 0–1.0, y = 0.20, z = 0.30, respectively), have been designed for investigating the variation of the intermediate O‐phase region and its effect on the electrical properties. The temperature‐composition phase diagram of each group has been proposed based on the X‐ray diffraction patterns and the temperature‐dependent dielectric behaviors. The enhanced piezoelectric properties are achieved in the O–T phase boundary compositions of the three groups, which are BH_0.16T–0.58BC_0.20T, BH_0.16T–0.48BC_0.30T and BH_0.20T–0.53BC_0.30T, respectively. Piezoelectric coefficient d₃₃ of 448 pC/N is obtained in BH_0.20T–0.53BC_0.30T, which is higher than those of the other two phase boundary compositions. The O‐phase zone in BH_0.20T–xBC_0.30T is narrower than those in the BH_0.16T–xBC_0.20T and BH_0.16T–xBC_0.30T. In spite of its small O‐phase volume occupancy, the O‐phase plays a key role in the properties of the system. Our work confirms that the enhancement in piezoelectric properties is not only related to the O–T phase boundary near room temperature (RT), but also related to the shift of T_R‐O toward RT. In addition, a quantitative relation between the phase boundary composition and atomic mole ratio of Hf to Ca (R_m) is proposed, which the R_m value corresponding to the phase boundary is about 0.58. The results clearly demonstrate that in this system high piezoelectric properties are achieved by tuning the specific R_m value. Such a work may provide new clues for designing lead‐free piezoelectric materials with enhanced piezoelectric property.     

Toughening effects of nucleating agent on impact polypropylene copolymer

In this study, the impact polypropylene copolymer (IPC) blended with the sorbitol‐based nucleating agent (NA) NX8000 was prepared and then characterized using a wide range of instrumentations. The results showed that the NA formed a fibril network which resulted in the increased viscosity of system and the decreased size of ethylene–propylene random copolymer (EPR) phase. The results of mechanical tests revealed “the brittle–ductile transition (BDT)” occurred while the ethylene content was between 3.5 wt % and 6 wt % and indicated that the impact strength of IPC was greatly improved by the addition of NX8000 when the EPR content was right over the critical value of BDT. The investigations provided valuable information for the further development of IPC materials and boarded its potential industrial applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40705.     

一种具有表面活性的双尾疏水缔合丙烯酰胺共聚物

文章以自制双尾疏水丙烯酰胺单体丙烯酰胺(N-苄基-N-辛基丙烯酰胺,N-benzyl-N-octylacrylamide,BOAM)和表面活性单体(辛基酚聚氧乙烯醚丙烯酸酯,OP-10-AC)与丙烯酰胺(acrylamide,AM)水溶液共聚合成新型疏水缔合共聚物(AM-Na A-OP10AC-BOAM)。实验结果表明,当聚合物浓度大600mg/L时,表观黏度迅速增加,表现出明显的缔合行为;共聚合物溶液具有良好的黏弹性和表面活性,SEM扫描电镜照片显示共聚物溶液中存在网状的缔合微观形貌特征。     

室温固化环氧树脂胶粘剂的制备及性能研究

以腰果酚、甲醛和三乙烯四胺为原料,采用一步法制备了环氧树脂(EP)用腰果酚醛三乙烯四胺新型固化剂;然后以双酚A型EP为基体树脂、腰果酚醛三乙烯四胺为固化剂和聚乙烯醇缩丁醛(PVB)为增韧改性剂,制备了室温固化EP胶粘剂。研究结果表明:当w(PVB)=10%(相对于EP质量而言)时,胶粘剂的拉伸强度(30.58 MPa)、冲击强度(6.30 kJ/m2)和剪切强度(17.71 MPa)相对最大;此时改性EP胶粘剂的热稳定性相对最好,并且其断裂方式由脆性断裂变为韧性断裂。     

锂盐在铝电解中的作用

报道了锂盐在铝电解中的作用.阐述了其提高熔体的电导率,降低电解质的熔点,减少铝的溶解损失,减小极化电压,降低电解质的蒸气压及延长阴极寿命等优点.提出锂盐与其它添加剂的有机结合,可获得更大经济效益和社会效益的构想.     

加利福尼亚Ojai流域河流穿越管道的设计与施工

加利福尼亚州Ojai流域废水管输系统的文图拉河段因河床退化及洪水的冲击,部分管段已不能正常运行。OjaiValleySanitary地区比较了几个可选方案的预算资金成本、运行和维护费用、环境因素,以及体系的可靠性,确定了应用水平方向钻进的方法在河底安装反向虹吸管。文章详细描述了新管道建设所面临的困难和解决措施,包括项目审批;承包商投标;地理勘查、施工设计和工程进度安排;表面套管、管道的安装和管道的清洗;以及风险评估和业主、承包商、顾问间的合作。