碳热还原合成Ti(C,N)晶须的相转变行为及生长机理

以TiO2和碳黑为主要原料,NaCl为卤化剂,NiCl2作为晶须生长的添加剂,在N2气氛下采用碳热还原法,在不同温度下合成Ti（C,N）晶须。采用X射线衍射研究合成样品的相组成及合成过程中原料的相转变行为,采用扫描电镜观察合成样品的形貌,探讨晶须的生长机理并建立生长模型。结果表明：在1 200℃合成时,主要发生TiO2与碳黑、氮气之间的直接还原反应,形成TiN;在温度为1 250-1 400℃时,NaCl分解产生的Cl原子起卤化作用,从NiCl2中分解出的Ni起催化作用,合成出Ti（C,N）晶须,晶须长度在10-30μm之间,直径大约1μm;合成的晶须表面光滑,顶端残留有催化剂颗粒,具有典型的气-液-固晶须生长机制特征。     

平衡气量控制法合成四针状氧化锌晶须的形貌和发光性能

以金属锌为原料不添加任何催化剂,在700°C时通过平衡气量控制法合成四针状氧化锌晶须。研究了成长时间对样品微结构和发光性能的影响。结果表明,制备的样品是由四针状氧化锌组成的;四针状氧化锌针的长度和直径随成长时间的延长而增加;在样品的室温发光谱中,在385~391nm处出现强的紫外光发射,但没有任何深水平发射,且紫外发射的强度随样品成长时间的延长而增强。     

镀层表面锡晶须自发生长现象的研究进展

镀层表面锡晶须自发生长是材料科学中一个受到长期关注的科学现象.随着近年来电子器件无铅化的发展,锡晶须问题日益突出.对于高密度电子封装技术,由晶须自发生长引起的短路和电子故障问题对电子产品的可靠性构成了潜在的威胁.因此,研究锡晶须的生长规律,阐明锡晶须的生长机理,探寻抑制锡晶须生长的技术手段成为当前研究的热点.总结了近年来国内外对锡晶须生长现象的一些相关研究,主要包括锡晶须的生长行为、各种影响锡晶须生长的因素、近年来晶须生长机制方面的新进展、锡晶须生长趋势的评估方法以及工业上抑制晶须生长的一些技术措施等.     

激光照射原位生成SiC晶须的晶须形态

利用冷等静压法将掺有粘结剂的SiC纳米颗粒压制成块体并经大功率CO2激光器照射,在激光照射区域获得SiC晶须,利用扫描电镜对晶须进行观察,分析照射层不同区域和不同气氛环境下晶须形态的变化。结果表明:不同气氛环境下晶须形态有显著区别,分别表现为放射状团簇特征、螺旋状团簇特征和密排短棒状团簇特征;同一照射层内,不同区域晶须形态也不一致,沿光束入射方向,可见以较大晶粒为核心的团簇状小长径比晶须和数量丰富、形态良好的大长径比晶须;不同的气氛组分和光强梯度分布是造成晶须形态不同的主要原因。     

有机前驱体热解合成Si3N4纳米带及其生长机制的研究

通过催化剂辅助有机前驱体热解，合成了单晶Si3N4纳米带。其工艺主要包括3个步骤：有机前驱体低温交联固化、高能球磨粉碎和高温热解。采用SEM、XRD、EDS、TEM和HRTEM等分析手段对Si3N4纳米带进行了详细的表征，对Si3N4纳米带的生长机制进行了深入的探讨。     

原位反应铜基复合材料的研究现状

简介了四种原位合成铜基复合材料的国内外研究现状，分析比较了各种工艺的优劣，指出液-液、液-固原位合成法具有更好的发展前景，生产成本低，更易于实现工业上的规模化生产。     

原位反应铜基复合材料的研究现状

简介了四种原位合成铜基复合材料的国内外研究现状,分析比较了各种工艺的优劣,指出液-液、液-固原位合成法具有更好的发展前景,生产成本低,更易于实现工业上的规模化生产。     

以CuSe纳米粒子为催化剂制备超长ZnSe纳米线

采用化学气相沉积的方法,以Zn粉末为原料,CuSe纳米粒子为催化剂,在Si衬底上成功制备了毫米级ZnSe纳米线。用X射线衍射、EDS和SEM对产物的结构、成分和形貌进行了测试与表征。结果表明：生长的ZnSe纳米线为立方闪锌矿结构,长度达0.35～0.7mm,Zn和Se的摩尔比为1？0.97,其室温光致发光谱显示在325nm波长激发下,ZnSe纳米线在439nm处呈现自由激子的强烈发射,表明生长的ZnSe纳米线具有高的结晶质量。纳米线生长符合氧化还原反应下的气液固生长机制,并证明Cu3Zn合金充当了实际的ZnSe纳米线生长催化剂。     

碱式氯化镁晶须的水热制备及热分解机理研究

采用水热法以氯化镁溶液、氢氧化钠为原料制备了碱式氯化镁晶须。通过SEM和SAED观察样品的显微形貌及晶体结构,晶须长度150μm以上,直径0.5~1μm,为单晶物质。通过XRD测定样品的晶相结构,产物为碱式氯化镁9Mg(OH)_2·MgCl_2·5H_2O。通过红外光谱考察了不同镁离子浓度产物官能团的不同。升温速率为2~5℃/min,高温程序煅烧前驱体碱式氯化镁,制备出氧化镁晶须,很好的保持了碱式氯化镁晶须的形貌,仍为单晶物质,并推测了其可能的热分解的机理过程。     

Hydrothermal synthesis and conductive properties of Al-doped ZnO rod-like whiskers

The Al-doped ZnO rod-like whiskers were synthesized by a simple hydrothermal method. The resistivity of Al-doped ZnO whisker (AZO_w) samples significantly decreased with the increase of Al³⁺ concentration, and showed a minimum when Al³⁺ doping concentration was 2.0%. If Al³⁺ concentration continued to increase, namely more than 2.0%, the resistivity of Al-doped ZnO samples would increase. So, in this study the optimum Al doping concentration was 2.0%, and the lowest electric resistivity (3.959 × 10⁴ Ω cm) was obtained.     

Growth of ZnO Nanostructures on Metal-Filled Porous Silicons

在多孔Si上使用不同催化剂成功生长ZnO纳米结构。结果表明,Au作催化剂在Si衬底上得到末端呈六角形的ZnO纳米棒,Cu作催化剂在Si(100)和(111)分别上生长出带状和棒状纳米ZnO,Zn作催化剂在Si衬底上则获得ZnO纳米线。Zn催化制备的ZnO纳米线晶面间距为0.283nm,生长方向是[0110],具有结晶较好的六角纤锌矿晶体结构。比较了不同催化剂制备ZnO的光学性能,发现得到Zn催化制备的ZnO纳米线缺陷绿光峰最弱,因此Zn催化生长制备的纳米ZnO结构质量较好。空气中退火后,3种催化剂生长的纳米ZnO的缺陷发光峰位置不变,而强度变弱。     

Synthesis of tetrapod-shaped ZnO whiskers and microrods in one crucible by thermal evaporation of Zn/C mixtures

Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst. The digital camera, optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction techniques were used to study the morphologies and crystal structures of these tetrapod-shaped ZnO microcrystals. The results show that these two types of ZnO tetrapods are grown at different heights within the same crucible. The legs of these tetrapod-shaped ZnO crystals are hexagonally faceted. Some tetrapod-shaped ZnO whiskers show hierarchical structures. A short button-like hexagonal ZnO microcrystal is observed at the triple junctions of some tetrapod-shaped ZnO whiskers. The tetrapod-shaped ZnO microrods are capped by two sets of hexagonal pyramids with two different groups of crystal planes for the surfaces. These two types of tetrapod-shaped ZnO microcrystals have different side faces and aspect ratio, which are believed to be the result of their different growth behaviors. The octa-twin model was used to discuss the different growth behaviors of these two types of ZnO tetrapods. The crystal planes of the legs and the pyramids were determined.     

Synthesis and characterization of multipod zinc oxide whiskers synthesized via a modified self-propagating high-temperature synthesis method

A self-propagating high-temperature synthesis (SHS) method, which features a 2-step heating process carried out in a closed chamber, was developed to prepare multipod ZnO whiskers (mZnOw). A compacted Zn powder was first heated at 370 °C in air to form a refractory layer of ZnO on the surface of Zn particles. Next, the SHS reaction was ignited by rapidly heating to ∼750 °C under different oxygen gauge pressures (PO₂) to obtain a loose white product mainly composed of mZnOw. It was found that the PO₂ strongly affected the reaction conversion and morphological features, along with the Zn-to-O ratio, of the as-synthesized products, which, in turn, might influence their photoluminescence and microwave absorption properties. A possible explanation for the effects of PO₂ on these characteristics was also proposed.     

ZnO纳米片状晶体的生长及其表征

采用高温碳热还原反应工艺．以氧化锌和碳粉为主要原料，在N2／H2O气氛中制备成功ZnO纳米片状晶体.所制薄片直径在100nm．厚度约50nm.采用场发射扫描电子显做镜（FESEM）、高分辨透射电子显做镜（HETEM）、X射线衍射分析仪（XRD）、拉曼（RAMAN）光谱等测试手段对产物进行表征。结果表明产物为ZnO，呈单一六角晶系纤锌矿结构，在相同的反应时间内，提高反应温度可使纳米片生长为六角塔状晶体，证填ZnO纳米片是六角平板状结构。     

Sn-9Zn/Cu无铅焊点ZnO须自发生长

研究了Sn-9Zn/Cu无铅焊点ZnO须自发生长行为.结果表明,在室温条件下Sn-9Zn/Cu无铅焊点因为富锌相的氧化,在富锌相表面自发生长出大量的ZnO须,ZnO须呈现针状、块状、花朵状等不同形态;对ZnO须进行FIB测试,发现在富锌相中出现明显的空洞,主要是因为Zn元素扩散导致的.另外,证实在Zn元素扩散与氧发生反应的过程中,富锌相发生体积收缩,诱使结构中出现明显的拉应力,拉应力为ZnO须生长提供驱动力.     

Growth of uniform ZnO nanoparticles by a microwave plasma process

ZnO nanoparticle coatings with a controlled size distribution have been grown on quartz substrates by a novel microwave plasma assisted spray (MPAS) technique. This study presents the analysis of structure, photoluminescence, and magnetic properties of particle coatings with two distinctly different mean particle sizes (400 nm and 200 nm). X-ray diffraction patterns show a typical wurtzite structure without any impurity phases for the nanoparticle coatings. SEM and TEM investigations have shown the grown nanoparticles to be spherical and well separated with a narrow size distribution. Nanoparticles are polycrystalline with smaller grain sizes associated with the smaller particle sizes. Photoluminescence (PL) spectra reveal the presence of oxygen vacancy related defects in the 400 nm nanoparticles, which become less pronounced in the 200 nm nanoparticles. The 400 nm nanoparticles are found to exhibit room-temperature ferromagnetism with a clear hysteretic behavior, while the 200 nm nanoparticles are diamagnetic even down to 10 K. These results suggest the oxygen vacancies were the cause for defect-induced ferromagnetism in the 400 nm nanoparticles.     

六钛酸钾晶须制备新工艺

用喷雾干燥-烧结法一次煅烧直接合成了长径比大于10,形貌优良的六钛酸钾晶须,研究了钛钾比、煅烧温度以及保温时间对晶须生长的影响.得出制备六钛酸钾晶须的最佳条件:TiO2与K2CO3的摩尔比为5.5,煅烧温度为1150℃,保温时间为10 h.     

ZnO温度响应凝胶注模成型的流变性能和干燥机制

为解决坯体干燥问题,将含大单体支链的温度响应凝胶体系应用于ZnO的凝胶注模成型,研究大单体支链PIPAAm的加入量与支链长度、总有机物含量和固相体积分数对悬浮液流变性能的影响,并分析坯体的干燥机理。研究表明：添加该凝胶体系的 ZnO 悬浮液仍表现为剪切变稀流变行为,但其黏度随着 PIPAAm 支链的加入量与相对分子质量以及总有机物含量的增加而升高。大单体支链的引入抑制甚至消除ZnO温度响应凝胶注模坯体表面“密实层”的形成,加快坯体干燥,促进坯体收缩。