Centimeter-sized Cs_(3)Cu_(2)I_(5)single crystals grown by oleic acid assisted inverse temperature crystallization strategy and their films for high-quality X-ray imaging

Low-dimensional halide perovskites have become the most promising candidates for X-ray imaging,yet the issues of the poor chemical stability of hybrid halide perovskite,the high poisonousness of lead halides and the relatively low detectivity of the lead-free halide perovskites which seriously restrain its commercialization.Here,we developed a solution inverse temperature crystal growth(ITCG)method to bring-up high quality Cs_(3)Cu_(2)I_(5)crystals with large size of centimeter order,in which the oleic acid(OA)is introduced as an antioxidative ligand to inhibit the oxidation of cuprous ions effieiently,as well as to decelerate the crystallization rate remarkalby.Based on these fine crystals,the vapor deposition technique is empolyed to prepare high quality Cs_(3)Cu_(2)I_(5)films for efficient X-ray imaging.Smooth surface morphology,high light yields and short decay time endow the Cs_(3)Cu_(2)I_(5)films with strong radioluminescence,high resolution(12 lp/mm),low detection limits(53 nGyair/s)and desirable stability.Subsequently,the Cs_(3)Cu_(2)I_(5)films have been applied to the practical radiography which exhibit superior X-ray imaging performance.Our work provides a paradigm to fabricate nonpoisonous and chemically stable inorganic halide perovskite for X-ray imaging.

Dual-phase coexistence enables to alleviate resistance drift in phase-change films

The amorphous phase-change materials with spontaneous structural relaxation leads to the resistance drift with the time for phase-change neuron synaptic devices. Here, we modify the phase change properties of the conventional Ge_2Sb_2Te_5(GST) material by introducing an SnS phase. It is found that the resistance drift coefficient of SnS-doped GST was decreased from 0.06 to 0.01. It can be proposed that the origin originates from the precipitation of GST nanocrystals accompanied by the precipitation of SnS crystals compared to single-phase GST compound systems. We also found that the decrease in resistance drift can be attributed to the narrowed bandgap from 0.65 to 0.43 eV after SnS-doping. Thus, this study reveals the quantitative relationship between the resistance drift and the band gap and proposes a new idea for alleviating the resistance drift by composition optimization, which is of great significance for finding a promising phase change material.

X-RAY STUDY ON TITANIUM NITRIDE FILMS DEPOSITED BY VCAD METHOD

TiN films deposited by the VCAD method at the substrate of stainless steel and superhigh speed tool steels are uniform and dense.Their colour,orientation and lattice parameter depend on deposited condition The lattice structure of deposited film,the change of the lattice parameter and its preferred orientation were studied by the XRD method,different behaviours of TiNx film were analysed.The lattice parameter of TiNx films is increased with the nitrogen content and The colour of TiNx film is strongly related to the content of Nitrogen also.The change of preferred orientation depends mainly on the Bias.

Influence of reducing anneal on the ferromagnetism in single crystalline Co-doped ZnO thin films

This paper reports that the high-quality Co-doped ZnO single crystalline films have been grown on a-plane sapphire substrates by using molecular-beam epitaxy. The as-grown films show high resistivity and non-ferromagnetism at room temperature, while they become more conductive and ferromagnetic after annealing in the reducing atmosphere either in the presence or absence of Zn vapour. The x-ray absorption studies indicate that all Co ions in these samples actually substituted into the ZnO lattice without formatting any detectable secondary phase. Compared with weak ferromagnetism （0.16 μB/Co2＋） in the Zno.95 Co0.05 O single crystalline film with reducing annealing in the absence of Zn vapour, the films annealed in the reducing atmosphere with Zn vapour are found to have much stronger ferromagnetism （0.65 μB/Co2＋） at room temperature. This experimental studies clearly indicate that Zn interstitials are more effective than oxygen vacancies to activate the high-temperature ferromagnetism in Co-doped ZnO films, and the corresponding ferromagnetic mechanism is discussed.

Physical and Chemical Properties of GdN: A Critical Comparison between Single Crystals and Thin Films, Theory and Experiment

Since about 10 years, there is a controversy about physics and chemistry of GdN between stoichiometric (tested) large single crystals and off-stoichiometric thin films. GdN single crystals are anti-ferromagnetic for applied magnetic fields of only 10 Oe, become ferromagnetic for excess electrons and larger magnetic fields. They are semimetallic. Thin films are ferromagnetic and semiconductors. Over the time, many experiments have been performed on both systems and the physics in each system is consistent. Band structure computations either yield ferromagnetic semimetals or ferromagnetic semiconducting thin films. There seems to be two incompatible worlds, those of single crystals and those of thin films. In the present work, the author compares directly the various measurements and calculations and gives reasons for their different results.

Structural Analysis of ZnO Film Deposited by Means of Metal Organic Decomposition Method

ZnO films were deposited on glass substrates by means of a metal organic decomposition (MOD) method. We investigated the effect of annealing temperature, time and the number of laminated layers on the film structure on the basis of X-ray diffraction measurements. We found the optimum conditions of the temperature and the time to be 600°C and 40 minutes for the preparation, respectively. In addition, the layer-by-layer forming was not found to degrade the film from viewpoint of X-ray line width.

溶液空间限域法制备有机-无机杂化卤化铅钙钛矿单晶薄膜及其器件应用研究进展

近年来,有机-无机杂化卤化铅钙钛矿材料因其出色的光电特性在国际上备受瞩目,并已成功应用于太阳能光伏、光电探测、电致发光等多个领域。目前绝大部分器件研究都集中在钙钛矿多晶材料上,但钙钛矿单晶材料拥有更低的缺陷态密度、更高的载流子迁移率、更长的载流子复合寿命、更宽的光吸收范围,以及更高的稳定性等优异的性质,可有效减少载流子传输过程中的散射损失,以及在晶界处的非辐射复合,并抑制离子迁移所引起的迟滞效应。采用钙钛矿单晶薄膜作为器件有源层有望制备性能更高效且更稳定的钙钛矿光电器件。目前,已报道的多种钙钛矿单晶薄膜制备方法包括溶液空间限域法、化学气相沉积法、自上而下加工法等,其中溶液空间限域法的发展和应用最为广泛。本文聚焦利用溶液空间限域法制备高质量钙钛矿单晶薄膜的相关方法,以及钙钛矿单晶薄膜在光电探测器、太阳能电池、场效应晶体管和发光二极管等相关器件应用中的研究进展,并对钙钛矿单晶薄膜及其光电器件的未来发展趋势进行了展望。

基于模板剥离法制备高性能钙钛矿单晶薄膜光电探测器

近年来,杂化钙钛矿半导体材料由于其带隙可调、吸收系数高、载流子迁移率高、成本低廉等诸多优点,在光电器件领域备受青睐,如太阳能电池、电致发光器件、光电探测器等。其中,钙钛矿单晶薄膜因其无晶界、杂质和缺陷含量低等特点,展现出更为优异的光学、电学特性,成为制备高性能光电器件的理想材料体系。然而,钙钛矿单晶薄膜常采用空间限域法直接生长在空穴传输层上,不可避免地将导致界面缺陷和载流子层间输运等问题,严重制约了钙钛矿单晶薄膜光电探测器的性能。为此,本文通过引入模板剥离法工艺技术,在钙钛矿单晶薄膜两侧分别蒸镀功能层材料,制备了结构为Cu/BCP/C_(60)/MAPbBr_(3)/MoO_(3)/Ag的钙钛矿单晶薄膜光电探测器。基于模板剥离法,两侧蒸镀的功能层与钙钛矿单晶薄膜接触紧密,将有效改善载流子的注入和传输;同时,优化的器件结构以及考虑能带匹配等因素可实现高灵敏、响应快速的钙钛矿单晶薄膜光电探测器。改进后器件的开关比高达3.1×10^(3),响应度可达7.15 A/W,探测率为5.39×10^(12)Jones,外量子效率达到1794%。该工作为进一步改善和提升钙钛矿单晶薄膜光电探测器的探测性能提供了一种可行性技术方案。

BaTiO_(3)纳米单晶薄膜在外加电场作用下畴结构演化的相场研究

铁电薄膜的工作电场加载频率及基底失配应变可影响微观畴结构形态和材料宏观铁电性能。本文利用相场模拟方法分别研究了在-0.1%、-0.7%的失配应变下,0.1~100 kHz频率范围内BaTiO_(3)纳米单晶薄膜的铁电性能变化规律。研究发现,随着外加电场频率的增大,薄膜电滞回线由四方形向椭圆形转变,标准蝶形曲线向腰果形曲线发生改变。在50 kHz以下的低频段,矫顽场随频率增加而快速升高,但剩余极化强度变化幅度不大;而在50 kHz以上的高频段,矫顽场随频率增加略有升高,剩余极化强度则呈下降趋势。在低频段下铁电性能的频率依赖性受失配应变的影响较大,而在高频段下则对失配应变不敏感。同时发现,压缩失配应变可导致剩余极化及矫顽场显著升高,而拉伸应变的效果相反。分析表明,BaTiO_(3)纳米单晶薄膜铁电性能的频率依赖性源自内部微结构演化速度与外电场施加速率的相互竞争。本研究可为铁电功能薄膜材料的实验设计提供理论基础,为其在高频电子器件中的应用提供有力支撑。

氧化镓单晶在酸碱条件下的腐蚀坑形貌研究

氧化镓晶体材料由于其优异的性能以及可以用熔体法生长的优势,在功率器件、光电领域有着巨大的潜力。近年来,国内外众多专家也随之开展对氧化镓单晶材料的研究工作,高质量低缺陷的氧化镓单晶材料对后续的外延、器件的制备极其重要。目前,国际上主流的生长方法是导模法,导模法具有生长周期短、尺寸大及生长稳定等优点,然而在晶体缺陷控制方面还有很大的进步空间。本文围绕氧化镓单晶的腐蚀坑形貌,对导模法生长的氧化镓单晶进行加工制样,进行了不同酸碱条件下的腐蚀实验。详细介绍了观察到的不同腐蚀坑形貌,分析了晶体缺陷对腐蚀坑形貌的影响,对今后氧化镓单晶生长机理和晶体缺陷的研究具有重要意义。

应对未来战争的“光学盾牌”——超大尺寸蓝宝石单晶板材

蓝宝石单晶具有优良的力学性能和光学性能,是目前透明装甲的优选材料。导模法能够制备出形状和尺寸都接近目标要求的晶体,可以大幅度降低晶体的生产成本。我们通过自主设计的晶体生长设备,优化晶体生长工艺和热场,成功制备了尺寸为480 mm×1200 mm×12 mm的蓝宝石单晶板材,晶坯形状规则,加工去掉表面气泡层后在20 mW He-Ne激光照射下检测,整体无散射。

镍基单晶铸造气膜孔低周疲劳断裂特征研究

气膜孔结构作为一种重要的热防护技术广泛应用于涡轮叶片中。气膜孔的存在会引入制造缺陷、应力集中等不利因素,成为疲劳失效的主要诱因之一。本研究开展不同温度下镍基单晶铸造气膜孔低周疲劳试验,分析熔模铸造直接成型的气膜孔疲劳断裂特征。结果表明:不同温度下疲劳寿命取决于应力幅值;随温度降低,疲劳断裂路径由Mode-I型转换为晶体学平面断裂,断口形貌呈现出从类解理至韧性断裂特征。气膜孔周围微结构分析表明,在1000℃及循环应力作用下,氧化膜发生破裂形成氧化裂纹;在700℃条件下,疲劳裂纹形核主要由滑移累积导致;在850℃条件下,疲劳损伤由氧化损伤和滑移累积共同作用。晶体塑性有限元分析揭示铸造气膜孔疲劳断裂特征主要受气膜孔附近应力分布的影响。

应对未来战争的“光学盾牌”——蓝宝石基透明装甲

本文采用自主设计开发的大尺寸导模(EFG)炉成功制备了尺寸为485 mm×985 mm×12 mm的蓝宝石单晶板材,将其切割、研磨后与玻璃、聚碳酸酯复合为透明装甲样品,其中尺寸为352 mm×341 mm×33 mm样品面密度为79.27 kg/m^(2),尺寸为351 mm×342 mm×33 mm的样品面密度为79.38 kg/m^(2)。分别采用直径为7.62 mm和12.7 mm的穿甲燃烧弹对其进行打靶测试,实验结果显示,蓝宝石基透明装甲在100 m 0°法线角射击中,具有优异的抗冲击性能。

高良姜素纳米胶束制备及其体内药动学研究

目的制备高良姜素纳米胶束,并考察其体内药动学。方法薄膜水化法制备纳米胶束,测定其粒径、Zeta电位、稳定性、体外释药。以水化体积、水化温度、聚乙二醇聚己内酯用量为影响因素,包封率、载药量、沉降率为评价指标,单因素试验优化处方工艺。18只大鼠随机分为3组,分别灌胃给予高良姜素、高良姜素自微乳、高良姜素纳米胶束的0.5%CMC-Na混悬液(40 mg/kg),于不同时间点采血,HPLC法测定高良姜素血药浓度,计算主要药动学参数。结果最佳处方为水化体积20 mL,水化温度45℃,聚乙二醇聚己内酯用量220 mg,包封率为(95.42±1.14)%,载药量为(7.92±0.15)%,沉降率为(0.85±0.18)%,粒径为(78.76±5.94)nm,Zeta电位为-(33.40±1.28)mV。纳米胶束冻干粉在60 d内粒径、包封率无明显变化,模拟胃液、模拟肠液中其48 h内累积释放度高于原料药。与原料药、自微乳比较,纳米胶束t_(max)、t_(1/2)延长(P<0.05,P<0.01),C_(max)、AUC_(0~t)、AUC_(0-∞)升高(P<0.05,P<0.01),相对生物利用度增加至3.64倍。结论纳米胶束可有效促进高良姜素口服吸收,改善其生物利用度。

高效铌酸锂薄膜波导模斑转换器设计

铌酸锂薄膜光子集成技术在高速光电子领域不断凸显,被广泛用于各种片上功能实现,如电光调制、光频梳、滤波器、非线性光学频率转换器、非线性量子光源、激光器等。在铌酸锂薄膜光子集成技术发展过程中,目前面临的一个重要的技术瓶颈就是铌酸锂薄膜纳米波导与单模光纤的高效耦合。针对这一问题,设计了一种基于SiO_(2)、SiON锥形结构以及双层铌酸锂锥形结构的模斑转换器,实现铌酸锂薄膜纳米波导与单模光纤之间模式和能量的高效传递与转换。采用三维有限差分光束传播法对器件结构进行了模拟仿真,并优化了结构参数,可实现与铌酸锂薄膜波导与单模光纤的高效耦合,耦合效率在82.2%~89.0%之间,同时,得到了±1.8μm光纤耦合对准容差,可为下一步制备出高效耦合的铌酸锂薄膜光子器件提供参考。

Machining of a film-cooling hole in a single-crystal superalloy by high-speed electrochemical discharge drilling

Single-crystal superalloys are typical advanced materials used for manufacturing aero- engine turbine blades. Their unique characteristics of high hardness and strength make them exceedingly difficult to machine. However, a key structure of a turbine blade, the film-cooling hole, needs to be machined in a single-crystal superalloy; such machining is challenging, especially considering the increasing levels of machining efficiency and quality demanded by the aeroengine industry. Tube electrode high-speed electrochemical discharge drilling （TSECDD）, a hybrid technique of high-speed electrical discharge drilling and electrochemical machining, provides high machining efficiency and accuracy, as well as eliminating the recast layer. In this study, TSECDD is used to machine a film-cooling hole in a nickel-based single-crystal superalloy （DD6）. The Tagu- chi methods of experiment are used to optimise the machining parameters. Experimental results show that TSECDD can effectively drill the film-cooling hole; the optimum parameters that give the best performance are as follows： pulse duration： 12μs, pulse interval： 30 gs, peak current： 6 A, and salt solution conductivity： 3 mS/cm. Finally, a hole is machined by TSECDD, and the results are compared with those obtained by electrical discharge machining. TSECDD is found to be promising for improving the surface quality and eliminating the recast layer.

水热法制备陶瓷材料研究进展

本文综述了水热法在单晶生长、粉体制备、薄膜、纤维制备、材料合成与处理等方面的研究进展。

薄膜水化法制备长春西汀胶束的工艺研究

目的:制备以聚乙二醇-聚乳酸(PEG-PLA)为载体的长春西汀胶束。方法:采用薄膜水化法制备长春西汀胶束,考察投药量、有机溶剂种类、有机溶剂用量、水化温度、水化转速、水化水用量、水化时间等7个单因素对长春西汀胶束的载药量、包封率、产率、粒径及多分散性指数(PDI)的影响,得出制备长春西汀胶束的最佳工艺。采用动态光散射法(DLS)测定胶束粒径和PDI,紫外分光光度法(UV)测定胶束的载药量、包封率和产率。结果:制得的长春西汀胶束载药量为20.35%,粒径为118.3 nm。结论:该制备以PEG-PLA为载体的长春西汀胶束工艺简单可行,为其进一步研究奠定了基础。

树状聚酰胺—胺对模拟乳液破乳的影响

应用单滴法考察了合成的树状高分子聚酰胺-胺对油滴液膜的破乳效果,并分析了其破乳机理。结果表明:随着该聚合物的文化代数及质量浓度的增加,油滴液膜排液时间缩短,半生命期减小,破裂速率常数增大,破乳性能提高;树状高分子聚酰胺-胺对水包油型原油乳状液的破乳性能强与该分子具有三维球形结构和表面高密度的酰胺官能团有关。

柔性碳纳米管透明导电薄膜国内外研究进展

综述了碳纳米管透明导电薄膜(CNTs-TCF)的主要制备方法以及存在的优缺点,介绍了碳纳米管(CNTs)的制备、金属性/半导体性、纯度与石墨化以及均匀分散CNTs溶液制备过程对CNTs-TCF电学性能产生的影响及相应的改进方法。最后简单介绍了CNTs-TCF在平板显示器、太阳能电池和触控面板上的应用情况,并对CNTs-TCF下一步研究进行了展望。