高温高压下白色硬玉质翡翠的合成与表征

以硅酸铝和硅酸钠为原料制备出玻璃料,利用高温高压法确定了白色硬玉质翡翠的最佳合成条件,并通过XRD、FTIR和SEM等方法对样品进行表征.结果表明:5.0 GPa、1450℃条件下合成样品的主要成分为NaAlSi2 O6,分子结构为硅氧四面体结构,具有柱状纤维编织形貌,与天然硬玉结构相同.我们的研究对于揭示天然翡翠的形成机制提供有力的参考.     

4.0～5.5GPa压力下硬玉翡翠的合成与表征

模拟天然硬玉成矿原理,采用优化的合成工艺,以硅酸铝和硅酸钠为原料制备出玻璃料,在高温高压下将非晶质的硬玉成分粉末转化为晶态硬玉.合成硬玉质地温润细腻、色泽均匀,具有高档硬玉的品质.XRD和SEM分析结果表明合成样品结晶矿物为硬玉(NaAlSi2O6),且结晶程度较好,晶粒细密,具有与天然硬玉相似的柱状纤维编织结构.在4.0～5.5 GPa压力条件下研究发现,随着压力的增加,硬玉合成温度随之增加;温度对合成硬玉晶粒的成长和编织情况有很大的影响;利用FTIR检测合成硬玉,其红外特征峰与天然硬玉一致,表明其分子结构为硅氧四面体结构;检测合成硬玉的硬度和密度等常规宝玉石参数与天然硬玉接近.     

溶剂热法制备金属酞菁晶体的研究进展

金属酞菁是一类以异吲哚为组成单元的人工合成的平面大环配合物,它们不仅是高品质的颜料和染料,也是太阳能电池、液晶材料、信息存储、环境催化等领域的新兴材料。传统的金属酞菁制备往往需要高沸点溶剂的回流反应以及使用浓硫酸纯化产物,普遍存在毒性高、效率低、耗时长等缺点。从绿色化学的发展和新型金属酞菁材料的制备要求来看,采用环境友好、成本低廉、易于操作的新方法制备与纯化金属酞菁是未来的发展趋势。本文综述了溶剂热法一步制备金属酞菁晶体的研究进展,总结了能够通过该方法制备的金属酞菁晶体种类及其相应的反应条件和产物结构,综合评价了该方法的技术优势,并对应用溶剂热法制备的金属酞菁晶体的未来发展进行了展望。     

一种翡翠仿制品-透辉石微晶玻璃显微结构及晶体化学特征的研究

利用偏光显微镜、电子探针仪及X射线粉晶衍射仪,对一种翡翠的仿制品-人造透辉石微晶玻璃的显微结构、析晶特征、化学成分及物相组成进行了研究.该微晶玻璃外观具有明显的放射状晶花,偏光显微镜下观察及BSE图像反映出透辉石微晶玻璃具有显微斑状结构,且含特征的骸晶.电子探针测试得到该材料内玻璃质基质、主晶相透辉石及少量石英的化学成分,其中透辉石内的镍含量明显高于天然翡翠.X射线粉晶衍射分析确定其主要物相为透辉石和玻璃质,与天然翡翠以硬玉、纳铬辉石等为主要矿物组成不同.     

6.0GPa下NaAlSi2O6翡翠的合成与表征

通过模拟天然翡翠的形成机理,对高温高压技术和玻璃料制取工艺的优化,以Na2SiO3·9H2O和Al2(SiO3)3为原料并添加少量致色剂CrO3,在超高压6.0 GPa下实现玻璃料由非晶态向晶态转化.通过XRD、FTIR和SEM等方法对样品进行表征,实验结果表明:6.0 GPa、1530℃条件下合成样品呈现翠绿色,质地温润,具有较高的润度和透明度;样品主要成分为NaAlSi2 O6,结晶度较高,分子结构为硅氧四面体结构,晶粒细密,致密有序;合成翡翠的硬度和密度等常规宝玉石参数也与天然翡翠接近,我们的研究对于探究翡翠在超高压下形成提供了数据参考.     

硼协同掺杂金刚石单晶的高温高压合成

金刚石是一种具有优异性能的极限性超硬多功能材料。人工合成的金刚石可通过掺杂的方式使其具有各种独特的性质。掺硼金刚石兼具p型半导体的导电特性和金刚石自身优良的物理和化学性能,在国防、医疗、勘探、科研等领域具有极高的应用价值。本文基于本课题组高温高压(HPHT)法合成的系列掺硼金刚石以及硼协同掺杂金刚石单晶,进行了硼掺杂金刚石、硼氢协同掺杂金刚石以及硼氮协同掺杂金刚石的合成和性能特征等方面的研究。通过表征合成样品在光学、电学方面的性能,探讨了不同掺杂添加剂对合成金刚石性能的影响,为合成高性能的半导体金刚石提供了思路。     

ZnSe红外窗口材料的性能及其制备

ZnSe是一种优秀的红外窗口材料,得到广泛的关注.在本文叙述了ZnSe红外窗口材料的光学特性和力学特性,以及详细地描述ZnSe体单晶熔体法、气相法、溶液法和固相再结晶制备技术及其影响因素.     

工艺因素对非水解溶胶-凝胶法制备钛酸铝纳米粉体的影响

以无水三氯化铝和四氯化钛为前驱体,正丁醇为氧供体,选择聚乙二醇(PEG)为分散剂,采用非水解溶胶-凝胶法(NHSG),低温合成钛酸铝纳米粉体.借助XRD、FT-IR、TEM等测试技术研究了反应前驱体浓度、凝胶化工艺以及PEG的加入顺序对钛酸铝纳米粉体合成及分散效果的影响.结果表明:随着前驱体浓度的减小,氯化醇盐之间的异质聚合反应变弱,导致钛酸铝合成效果的变差,但粉体团聚程度有减小的趋势,优选的前驱体浓度为2.25mol/L;与直接干燥、回流、容弹三种凝胶化工艺相比,回流结合容弹的凝胶化工艺因有助于形成更多的Al-O-Ti异质键合,因此具有更好的合成效果;在回流后加入PEG1000,既可保证钛酸铝的低温合成,又可抑制粉体的团聚,有利于制备分散性好、合成率高的钛酸铝纳米粉体.     

玻璃晶化法制备氧化物透明陶瓷研究进展

透明陶瓷是一种具有广阔应用前景的无机非金属材料,但以粉末烧结为主的传统制备策略存在依赖高质量原料粉体、需要长时间高温处理、设备和工艺复杂、生产成本高等技术限制。玻璃晶化法是通过调控晶化过程实现玻璃全部结晶并且获得透明陶瓷的新方法,因其可以克服与传统透明陶瓷加工相关的技术困难,并在合成高致密度、无气孔、非立方相、纳米结构透明陶瓷等方面具有独特的优势,而受到人们的广泛关注。本文首先从玻璃晶化法制备氧化物透明陶瓷的工艺方法和组分体系两方面入手,详细概述了该方法的发展历程和研究现状。接着,指出了目前研究中存在的问题,并对其未来发展前景进行了展望,以期该方法能够广泛应用于制备下一代高性能透明陶瓷材料。     

Eu2Zr2O7纳米晶体的制备及其烧结致密化

以共沉淀法和水热法合成了Eu2Zr2O7纳米晶,在真空烧结条件下分别制备出Eu2Zr2O7陶瓷.用XRD和SEM测试手段对样品进行了表征,用Archimedes法获得样品的相对密度.分析了两种方法得到Eu2Zr2O7粉体的物相变化、合成条件、微观形貌及烧结致密化,结果表明:共沉淀法合成粉体粒径约80 nm,分散性较好,水热法合成粉体粒径约30 nm;经烧结前者样品的相对密度94.6;,烧结后为97;,提高了2.4;,且后者烧结温度比前者低100℃,可见水热法合成的粉体晶粒细小并活性较高对烧结致密化起到促进作用.     

碳化硅单晶生长用高纯碳化硅粉体的研究进展

碳化硅(SiC)以其宽带隙、高临界击穿场强、高热导率、高载流子饱和迁移率等优点,被认为是目前较具发展前景的半导体材料之一.近年来,物理气相传输(PVT)法在制备大尺寸、高质量SiC单晶衬底方面取得了重大突破,进一步推动了SiC在高压、高频、高温电子器件领域的应用.SiC粉体是PVT法生长SiC单晶的原料,其纯度会直接影...     

MOCVD of titanium dioxide on the basis of new precursors

Thin films with a considerably higher dielectric constant than silicon dioxide, for example titanium dioxide or titanium containing barium strontium titanate, can be used for dielectrics in ultralarge scale integration devices. TiO₂ shows, besides its high dielectric constant, a sufficiently low leakage current and high breakdown field strength. MOCVD is the most promising method for depositing those dielectrics because of its obvious advantages like homogeneity of films, good step coverage and ultrathin film deposition. In this work, three new precursor chemicals have been developed and tested in a low pressure horizontal cold wall-type furnace. For the synthesis of the novel precursors, commercial titaniumisopropylate is brought to an reaction with an alcoholic compound at 150 °C and distilled under vacuum. The motivation for the development of new Ti precursors lies in an improvement of the handling and deposition characteristics as for example the hydrolytic stability. For the three precursors the deposition parameters temperature, pressure, gas flow and activation energy is presented. The electrical properties dielectric constant and leakage current were compared to commercially available titaniumisopropylate.     

Facile synthesis of silver‐nanobeadwire transparent conductive film by organic‐precursor paint reduction

A new facile process has been developed to synthesize silver nanowire transparent conductive films by reducing high‐aspect‐ratio, needle‐shaped silver carboxylates, prepared as the precursor, while retaining their morphology. Nanowire precursors are simply obtained by ultrasound irradiation when silver (I) oxide and carboxylic acids are used as starting materials. The aspect ratio of the precursors is increased when the ultrasound irradiation is followed by microwave irradiation. Silver nanowires can be easily obtained by reducing these precursors with hydrazine gas or irradiating them with Ar plasma for a short time. The morphology of the resulting nanowires is different from that of typical nanowires that have been reported. The nanowires have porous morphology, where small nanoparticles are connected to form nanobeadwire. The nanobeadwire is considered to increase the transparency of the film because of its rough morphology. This new method can synthesize silver nanobeadwires and fabricate the transparent conductive film simultaneously, in one‐step, so that it can significantly simplify manufacturing processes.     

高温溶液法生长SiC单晶的研究进展

碳化硅(SiC)作为第三代半导体材料,不仅禁带宽度较大,还兼具热导率高、饱和电子漂移速率高、抗辐射性能强、热稳定性和化学稳定性好等优良特性,在高温、高频、高功率电力电子器件和射频器件中有很好的应用潜力。高质量、大尺寸、低成本SiC单晶衬底的制备是实现SiC器件大规模应用的前提。受技术与工艺水平限制,目前SiC单晶衬底供应仍面临缺陷密度高、成品率低和成本高等问题。高温溶液生长(high temperature solution growth, HTSG)法生长SiC单晶具有晶体结晶质量高、易扩径、易实现p型掺杂等独特的优势,有望成为大规模量产SiC单晶的主要方法之一,目前该方法的主流技术模式是顶部籽晶溶液生长(top seeded solution growth, TSSG)法。本文首先回顾总结了TSSG法生长SiC单晶的发展历程,接着介绍和分析了该方法的基本原理和生长过程,然后从晶体生长热力学和动力学两方面总结了该方法的研究进展,并归纳了该方法的优势,最后分析了TSSG法生长SiC单晶技术在未来的研究重点和发展方向。     

Germanium: Epitaxy and its applications

This paper reviews the most important properties of germanium, gives an insight into the newer techniques and technology for the growth of epitaxial Ge thin layers and focuses on some applications of this material, with a special emphasis on recent achievements in electronics and photovoltaics. We will highlight the recent development of Ge research and will give an account of the most important Ge applications that emerged in the last two decades.Germanium is a key material in modern material science and society: it is used as a dopant in fiber optic glasses and in semiconductor devices, both in activating conduction in layers and also as a substrate for III–V epitaxy. Ge is also widely used in infrared (IR) detection and imaging and as a polymerization catalyst for polyethylene terephthalate (PET). Moreover, high-speed electronics for cell phone communications relies heavily on SiGe alloys. Ge electronics is nowadays gaining new interest because of the enhanced electronic properties of this material compared to standard silicon devices, but the lack of a suitable gate oxide still limits its development. High efficiency solar cells, mainly for space use but also for terrestrial solar concentration have surpassed 40% efficiency and Ge has a lead role in achieving this goal.The main focus of the paper is on Ge epitaxy. Since epitaxy starts from the surface of the substrate, different studies on substrate pre-epitaxy, surface analysis and preparations are reviewed, covering the most common substrates for Ge deposition such as Ge, Si and GaAs. The most used Ge precursors such as GeH₄ and GeCl₄ are described, but several novel precursors, mostly metal-organic, have recently been developed and are becoming more common in epitaxial Ge deposition. Epitaxial growth of Ge by means of the most common methods, including Chemical Vapour Deposition and Molecular Beam Epitaxy is discussed, along with some recent advances in Ge deposition, such as Atomic Layer Deposition and Low Energy Plasma-Enhanced Chemical Vapour Deposition.Several Ge applications are finally discussed, with the aim of providing insights into the potential of this material for the development of novel devices that are able to surpass the current limits of standard device design. Ge in microelectronics is becoming more and more important, thanks to the possibilities offered by bandgap engineering of strained SiGe/Si. However, lack of a good Ge oxide is posing several problems in device improvement. In the field of photovoltaics Ge is mainly used as a substrate for high efficiency III–V solar cells and for the development of thermophotovoltaic devices instead of the most expensive and scarcer GaSb. In this field, Ge epitaxy is very rare but the development of an epitaxial Ge process may help in developing new solar cells concepts and to improve the efficiency of thermophotovoltaic converters. Ge may play a role even in new spintronics devices, since a GeMn alloy was found to have a higher Curie temperature than GaAsMn.     

Controllable one‐step synthesis of CuO,Cu2O and Cu

In the present report, CuO, Cu₂O and Cu have been successfully synthesized through a facile, one‐step hydrothermal method at a relative low temperature by controlling only the concentration of citric acid. Compared with other synthetic methods, the present method is mild, high‐efficient and nontoxic. The crystal structure and morphology of the as prepared samples were characterized by X‐ray diffraction and scanning electron microscopy, respectively. The mechanism for the crystal phase and morphological changes with different citric acid concentrations were discussed. The possible reaction process of the synthesis was also studied on the basis of the experimental results. We hope that this facile, one‐step hydrothermal method could be used in controlling synthesis of other metals and metal oxides under appropriate experimental conditions.     

高纯硒化镉(CdSe)多晶原料的合成研究

硒化镉(CdSe)是一种重要的Ⅱ-Ⅵ族半导体材料,在核辐射探测、非线性频率转换等方面都有着重要的应用.高纯原料是生长优质CdSe单晶,实现上述应用的基础,但目前合成方法存在效率低、纯度不高等缺点.为此实验室对传统高温元素合成法进行优化,利用理论计算的反应温度点为指导,辅以外部加压,控制内外压差,有效实现原料的批量、安全合成,单次可合成200 g,经粉末衍射(XRD)、综合热分析(TG/DTA)、等离子发射光谱仪(ICP)等测试,合成的原料质量较好,能生长出较大尺寸单晶.文中对合成过程可能的纯度影响因素及控制措施也进行了相应讨论.     

Precursors for sol-gel preparations

Precursors used for the synthesis of oxide systems by the sol-gel method are reviewed and their role in the various stages of the process is discussed. Emphasis is given to alkoxide precursors and to their physical and chemical properties. In particular, the following topics are discussed: degree of oligomerization, volatility, viscosity, reactions with alcohol, molecular association between alkoxides, hydrolysis, stabilization against hydrolysis. Some information about preparation methods, commercial products and availability is also given. Among non-alkoxide precursors, nitrates, carboxylates, acetylacetonates, chlorides and other inorganics are described from the point of view of their use in sol-gel preparations. They are compared, when possible, with the corresponding alkoxides.     

金刚石辐射伏特效应同位素电池器件研究进展

微机电系统、深空、深海探测任务等对于长效、便携电源提出了更高的要求。同位素电池由于其能量密度高、功率输出稳定,可以在高低温、无太阳光照等极端环境下持续不断地为月球车、海底探测器等提供能量。作为同位素电池中的主要类型,辐射伏特效应同位素电池由于其理论能量转换效率高、易于微型化被广泛研究,并已经成功应用于心脏起搏器。宽禁带的半导体换能结器件制作的同位素电池能够获得更高的能量转换效率。宽禁带半导体中的代表金刚石具有5.5 eV的禁带宽度与耐辐射的特性,使其成为制作辐射伏特效应同位素电池换能结器件的最佳选择。随着化学气相沉积技术的发展,金刚石晶体的外延技术突飞猛进,为金刚石半导体器件的发展打下了材料基础。本文对比了常见的同位素电池换能结用半导体材料和辐射源材料的特性,介绍了辐射伏特效应的基本原理,接着对辐射伏特效应同位素电池的关键参数进行了分析,并汇总了有关金刚石辐射伏特效应同位素电池研究的文献,通过各个参数,如开路电压、转换效率等的对比,指出了目前金刚石同位素电池发展的状态与存在的问题。通过分析金刚石与其他n型半导体材料组成的异质pn结目前的性能与应用情况,给出了基于金刚石异质pn结的高性能同位素电池的结构设计,并进行了总结与展望。     

化学气相沉积单层VIB族过渡金属硫化物的研究进展

2004年以来,石墨烯因其优异的光学、电学性质而被广泛地研究,但由于其零带隙的特性极大地限制了它的应用前景.单层的VIB族过渡金属硫化物(TMDs)拥有类似石墨烯的晶体结构及可控的能带结构,是一类理想的二维直接带隙半导体材料,不仅可用于探索如谷极化等一些基础和前沿的物理问题,也可以广泛应用于纳米器件、光电子学和光催化的研究.近年来,化学气相沉积(CVD)技术作为一种相较于传统化学合成或物理剥离更加有效的制备方法被引入此类材料的生长,能够合成出拥有大面积连续的、厚薄均匀和较高晶体质量的单层TMDs.基于此,重点介绍了利用CVD技术生长单层TMDs所取得的进展,讨论了各工艺条件(如反应温度、载流气体、衬底、前驱物与衬底之间的距离等)对单层TMDs的生长及性质的影响.最后,探讨了利用CVD技术实现调控单层TMDs的尺寸、覆盖度和层厚均匀性的途径和方法.