非晶态介孔 FeAlP 催化剂用于合成 1,5-苯二氮类化合物

 A simple and versatile method for the synthesis of 1,5-benzodiazepines from o-phenylenediamine and ketones in the presence of solvents and under solvent-free conditions that used an amorphous mesoporous iron aluminophosphate as catalyst was developed. High yields with excellent selectivity were obtained with a wide variety of ketones under mild reaction conditions. The catalyst had the advantages of ease of preparation, ease of handling, simple recovery, reusability, non toxicity, and being inexpensive.     

聚乙二醇介质中纳米铁基催化剂上的费托合成

 采用化学还原法在纯水中制备了纳米铁基催化剂, 将其直接分散到液态聚乙二醇 (PEG) 中进行费托合成 (FTS) 反应. 透射电子显微镜、X 射线衍射、穆斯堡尔谱和 X 射线光电子能谱等结果表明, 还原态催化剂粒径在 30~65 nm, 主要由无定形的 Fe-B 和α-Fe 组成, 其中 B 部分电子向 Fe 转移. 反应过程中, 无定形的 Fe-B 首先快速转变为 α-Fe, 而 α-Fe 很容易发生碳化或氧化, 最终转变为 Fe3O4 和碳化铁. PEG 能有效抑制纳米粒子的聚集长大, 反应后催化剂粒径减小为 20~55 nm. 在 3.0 MPa, V( H2)/V(CO) = 2 和 200 oC 的反应条件下, 该催化剂表现出优异的 FTS 低温活性和较高的稳定性, 反应后产物和催化体系很容易实现分离.     

Photoluminescence analyses of hydrogenated amorphous silicon nitride thin films

Silicon-rich hydrogenated amorphous silicon nitride (a-SiN_x:H) films were grown by plasma enhanced chemical vapor deposition (PECVD) with different r=NH₃/SiH₄ gas flow ratios. The optical absorption characteristics were analyzed by Fourier transform infrared (FTIR) and UV-visible transmittance spectroscopies. The recombination properties were investigated via photoluminescence (PL) measurements. As r was increased from 2 to 9, the PL emission color could be adjusted from red to blue with the emission intensity high enough to be perceived by naked eye at room temperature. The behaviors of the PL peak energy and the PL band broadness with respect to the optical constants were discussed in the frame of electron-phonon coupling and band tail recombination models. A semiquantitative analysis supported the band tail recombination model, where the recombination was found to be favored when the carriers thermalize to an energy level at which the band tail density of states (DOS) reduces to some fraction of the relevant band edge DOS. For the PL efficiency comparison of the samples with different nitrogen contents, the PL intensity was corrected for the absorbed intensity fraction of the incident PL excitation source. The resulted correlation between the PL efficiency and the subgap absorption tail width further supported the band tail recombination model.     

强流脉冲电子束作用下20钢的微观结构状态

 为了研究金属材料的超快变形行为,利用强流脉冲电子束（HCPEB）装置对20钢进行轰击,采用X射线衍射、光学显微镜及透射电镜等技术分析了受轰击样品的变形组织与结构。实验结果表明,强流脉冲电子束能够在材料表层诱发幅值为1 GPa量级的应力,快速的加热和冷却过程在近表层诱发了强烈的塑性变形,并在材料表层内形成了复杂的位错缠结结构和位错胞结构,同时还伴随位错圈等空位簇缺陷的形成,多次轰击导致局部区域形成纳米和非晶结构。HCPBE轰击诱发的幅值极大的应力和极高的应变速率而导致的整个原子平面的位移可能是非晶结构形成的关键原因。     

Mechanical, vibrational, and dynamical properties of amorphous systems near jamming

Amorphous systems undergo the jamming transition when the density increases, temperature drops, or external shear stress decreases, as described by the jamming phase diagram which was proposed to unify different processes such as the glass transition, random close packing, and yielding under shear stress. At zero temperature and shear stress, the jamming transition occurs at a critical density at Point J. In this paper, we review recent studies of the material properties of marginally jammed solids and the glassy dynamics in the vicinity of Point J. As the only singular point in the jamming phase diagram, Point J exhibits special criticality in both mechanical and vibrational quantities. Dynamics approaching the glass transition in the vicinity of Point J show critical scalings, suggesting that the molecular glass transition and the colloidal glass transition are equivalent in the hard sphere limit. All these studies shed light on the long-standing puzzles of the glass transition and unusual properties of amorphous solids.     

Synthesis and magnetic properties of Fe100-xMox alloy nanowire arrays

The Fe100-xMox(13≤x≤25) alloy nanowire arrays are synthesized by electrodeposition of Fe 2+ and Mo 2+ with different ionic ratios into the anodic aluminum oxide templates.The crystals of Fe100-xMox alloy nanowires gradually change from polycrystalline phase to amorphous phase with the increase of the Mo content and the nanowires are of amorphous structure when the Mo content reaches 25 at%,which are revealed by the X-ray diffraction and the selected area electron diffraction patterns.As the Mo content increases,the magnetic hysteresis loops of Fe100-xMox alloy nanowires in parallel to the nanowire axis are not rectangular and the slopes of magnetic hysteresis loops increase.Those results indicate that the magnetostatic interactions between nanowires and the magnetocrystalline anisotropy both have significant influences on the magnetization reversal process of the nanowire arrays.     

Open-circuit voltage analysis of p-i-n type amorphous silicon solar cells deposited at low temperature

This paper identifies the contributions of p-a-SiC:H layers and i-a-Si:H layers to the open circuit voltage of p-i-n type a-Si:H solar cells deposited at a low temperature of 125 C.We find that poor quality p-a-SiC:H films under regular conditions lead to a restriction of open circuit voltage although the band gap of the i-layer varies widely.A significant improvement in open circuit voltage has been obtained by using high quality p-a-SiC:H films optimized at the "low-power regime" under low silane flow rates and high hydrogen dilution conditions.     

退火处理Fe43Co43Hf7B6Cu1非晶合金的正电子湮没研究

对熔体急冷法制备的Fe₄₃Co₄₃Hf₇B₆Cu₁非晶合金进行了200,300,400和500 ℃保温30 min的退火处理,用正电子湮没寿命谱、X射线衍射、穆斯堡尔谱等方法研究了退火后试样的结构及结构缺陷变化.结果表明,在非晶合金的制备态,正电子主要在非晶基体相空位尺寸的自由体积中湮没,湮没寿命τ₁为158.4 ps,强度I₁关键词： 43Co₄₃Hf₇B₆Cu₁非晶')" href="#">Fe₄₃Co₄₃Hf₇B₆Cu₁非晶 退火处理 正电子湮没寿命 结构与结构缺陷     

磁过滤器电流对非晶碳薄膜摩擦学特性影响的研究

研究了过滤阴极真空电弧技术中,不同的磁过滤器电流下(5—13 A),制备的四面体非晶碳(ta-C)薄膜对摩擦学特性的影响.通过对薄膜厚度,薄膜结构以及薄膜表面粗糙度随磁过滤电流的变化结果进行了测试,结果表明,随着磁过滤器电流的增大,薄膜的sp³键含量逐渐减少,表面粗糙度从0.13增大到0.38.磁过滤器电流在5 A时,薄膜的摩擦系数最小约为0.08,当电流增大到7 A时,摩擦系数显著增大,磁过滤器电流从7 A增大到13 A时,薄膜的摩擦系数再次减小约为0.1. 关键词： 四面体非晶碳 过滤阴极真空电弧 磁过滤器电流 摩擦系数     

The role that conduction band tail states play in determining the optical response of hydrogenated amorphous silicon

We aim to explore the role that conduction band tail states play in shaping the optical response of hydrogenated amorphous silicon. We do so within the framework of an empirical model for the valence band and conduction band density of states functions, one that considers valence band band, valence band tail, conduction band band, and conduction band tail states. We examine the sensitivity of the joint density of states function to variations in the conduction band tail breadth, all other parameters being held fixed at their nominal hydrogenated amorphous silicon values. We find that when the conduction band tail is narrower than the valence band tail, its role in shaping the corresponding spectral dependence of the joint density of states function is relatively minor. This justifies the use of a simplified empirical model for the density of states functions that neglects the presence of the conduction band tail states in the characterization of the optical response of this material. Experimental data corresponding to hydrogenated amorphous silicon, demonstrating that the conduction band tail breadth is always less than the valence band tail breadth for this material, is then presented. Finally, fundamental reasons for the observed asymmetry in the band tail breadths are reviewed.