直接氮化法制备氮化铝纳米线

在氮、氢混合气气流中(氢气10%,体积比),以铝和氯化铵混合粉体为原料,在水平管式炉中采用直接氮化法合成了氮化铝纳米线。使用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和透射电子显微镜(TEM)对纳米线的形貌和结构进行了检测与分析;研究了铝和氯化铵的比例(质量比)、反应温度、升温速度等因素对生成物的种类、形貌和氮化铝纳米线产量的影响。研究发现,所获得的AlN纳米线为单晶六方纤锌矿结构,表面不光滑且有非晶层,而AlN纳米线依照Vapor-Solid(VS,气-固)生长机制生长。获得了较为优化的制备氮化铝纳米线的工艺条件,利用VS生长机制和气相过饱和度概念对上述影响氮化铝纳米线生长的条件进行了初步的机理分析。     

直接氮化法制备纳米晶TiN薄膜

首先采用溶胶-凝胶法在Al2O3基体上制备了TiO2纳米晶薄膜，然后在管式气氛炉中，用氨气作为还原剂，直接氮化制备TiO2纳米晶薄膜；从而成功地的α-Al2O3陶瓷基片上制备了纳米晶TiN薄膜。利用XRD、XPS、FE-SEM等分析技术，研究了制备的纳米晶TiN薄膜的相组成及形貌。结果表明最佳工艺条件为：氮化温度为700℃，氮化时间为1h。     

氮化法制备氮化锌粉末的结构和光致发光性质

将Zn粉末置于流量为500mL/min的NH3气流中,在600℃氮化温度下氮化120min的条件下,制备出高质量的Zn3N2粉末.用X射线衍射(XRD)测量了Zn3N2粉末的结构,Zn3N2粉末是具有立方结构的晶体,其晶格常数a为0.9788nm.用扫描电子显微镜(SEM)观察了Zn3N2粉末的表面形貌,发现Zn3N2粉末具有非常丰富的晶粒表面形貌.用透射电子显微镜(TEM)验证了晶粒形状的多样性.用高分辨电子显微镜(HRTEM)观察了Zn3N2粉末的内部结构.用波长为325nm的He-Cd激光器为激发光源,测量了Zn3N2粉末的光致发光谱,观察到在385nm处有强的光致发光峰.     

铝合金直接氨化生长氮化铝反应机制研究

针对铝合金直接氮化生长ＡＩＮ过程中的晶体生长过程进行分析,通过Ｘ－ｒａｙ衍射和ＳＥＭ观察,获得了不同生长阶段ＡＩＮ晶体的生长特征,研究了铝合金直接氨化生长氮化铝的反应机制．提出了一种气－液－固－固）晶体生长机制,简称ＶＬＳＳ机制,并着重对ＶＬＳＳ机制的实现条件、实现过程以及与传统的ＶＬＳ晶体生长机制的相同点和差异进行了讨论．     

AlN陶瓷粉末制备方法特点和进展

本文就国内外AlN粉开合成的研究情况,综述了直接氮化法、Al2O3碳热还原法、自蔓延高温合成法、等离子体法、气溶胶法等主要的几种AlN粉末制备方法的特点和研究进展,分析了制备AlN粉末的主要发展方向。     

基于非水解sol-gel法的碳热还原氮化合成氮化铝超细粉体

以无水氯化铝和异丙醚为原料,采用非水解溶胶-凝胶法制备出氧化铝凝胶。其经800℃煅烧才析出少量γ-Al2O3晶体,γ-Al2O3向α-Al2O3晶型转变在1200℃附近,经900℃煅烧后比表面积仍高达145m2/g,具有介孔结构。以该高活性氧化铝凝胶作为铝源,采用碳热还原氮化工艺合成氮化铝粉体。结果表明,氧化铝凝胶经300℃预煅烧,按n(C)/n(Al)=7.8与碳黑混合,在流量80mL/min高纯N2中,于1450℃还原氮化2h便可合成出平均粒径在400nm的高纯六方相AlN粉体。     

还原扩散法直接制备金属间化合物粉末

结合以往的工作对直接制备金属间化合物的还原扩散法类型和特点作了概括介绍。     

氮化铝粉末制备工艺的研究

本文介绍了氮化铝(AlN)陶瓷的特性,并以金属铝直接氮化法和氧化物高温碳还原氮化法为重点,阐述了AlN粉末的各种制备工艺及反应机理、主要工艺参数的影响,对各种方法的优缺点进行了评述。提出:还原法和直接氮化法是目前较成熟的方法,而气相反应法具有较好的推广应用前景。     

电弧放电等离子体法合成立方相氮化铬纳米粉

采用电弧放电等离子体方法,通过金属铬和氮气的直接反应合成了粒度小于10nm的纯立方相氮化铬（CrN）纳米粉.利用X射线衍射分析（XRD）、透射电镜(TEM)和傅立叶变换红外光谱（FT-IR）对不同氮气压下形成的产物进行了表征.研究了氮气压和氨气的加入对形成立方相CrN纳米晶的影响.研究结果表明：相对较低的N₂气压(5~20kPa) 有利于金属Cr向立方CrN的转化,可以使更多的氮原子结合到金属Cr的格子中去;活性氮源（氨气）的加入降低了金属Cr的氮化.     

Characterization of Tin-catalyzed silicon nanowires synthesized by the hydrogen radical-assisted deposition method

Tin-catalyzed silicon nanowires (SiNWs) were synthesized at various hydrogen gas flow rates using the hydrogen radical-assisted deposition method. Large quantities of SiNWs with various crystal phases were synthesized and their characteristics were estimated. Tin-capped SiNWs were straightly grown and their structures were changed with increasing hydrogen gas flow rates. Their diameters on the bottom side were increased ranging from approximately 50 to 200 nm and their lengths extended up to ~ 2 µm with increasing hydrogen gas flow rates.     

Structural characterization of β-SiC nanowires synthesized by direct heating method

Crystal structure of β-SiC nanowires was investigated using Raman spectroscopy, FT-IR, XRD, transmission electron microscopy and selected area electron diffraction. Cubic β-SiC nanowires were synthesized by heating NiO catalyzed Si substrates with WO₃ and graphite mixed powders in the growth temperature of 1000–1100 °C. HRTEM image showed atomic arrangements of the grown SiC nanowires with a main growth direction of [111]. Raman spectra showed two characteristic peaks at 796 cm^− 1 and 968 cm^− 1, which are corresponding to transversal optic mode and longitudinal optic mode of β-SiC, respectively. Also, FT-IR absorption spectroscopy showed a SiC characteristic absorption band at ∼792 cm^− 1.     

化学气相反应制备碳化硅纳米线

用硅粉、二氧化硅和石墨粉作原料，在无催化剂的条件下，在1400℃下用高温化学气相反应法制备了碳化硅纳米线，并用高分辨扫描电镜观察了所得碳化硅纳米线的形貌。所得碳化硅纳米线直径为100-500nm，长度可达几百微米。还提出了描述碳化硅纳米线的生长机理。     

Fabrication of single-crystalline gallium nitride nanowires by using alginate as template

Hexagonal gallium nitride nanowires were synthesized successfully by solvothermal method with alginate as template. The microstructure, morphologies and compositions of the as-prepared product were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), and energy dispersive X-ray (EDX). Results suggested that the rod-like nanowires were hexagonal single-crystalline GaN growing along [001] direction. The photoluminescence spectra (PL) of the GaN revealed that the as-synthesized sample possesses excellent optical properties.     

Photoluminescence and field-emission characteristics of ZnO nanowires synthesized by two-step method

ZnO nanowires with excellent photoluminescence (PL) and field-emission properties were synthesized by a two-step method, and the ZnO nanowires grew along (0 0 2) direction. PL measurements showed that the ZnO nanowires have stronger ultraviolet emission properties at 376 nm and there is 3 nm blue shift after the nanowires were immersed in thiourea (TU) solution compared with those of without immersion. The immersed-ZnO nanowires show a turn-on field of 2.3 V/μm at a current density of 0.1 μA/cm and emission current density up to 1 mA/cm² at an applied field of 6.8 V/μm, which demonstrate that the immersed-ZnO nanowires posses efficient field-emission properties in contrast with those not immersed. The ZnO nanowires may be ideal candidates for making luminescent devices and field-emission displays.     

Ni/Cu双金属纳米线非模板法制备研究

在外加磁场作用下,制备出Ni纳米线,再以Ni纳米线为载体,利用Ni置换溶液中的Cu2+制备出Ni/Cu双金属纳米线,并进行扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、能谱(EDS)等表征。结果显示样品线性较好、尺寸均匀,约为200 nm,组成为Ni单质和Cu单质,均为面心立方结构,其含量分别为62.34%与36.37%(质量分数)。     

Fabrication of bismuth oxide-tin oxide nanowires by direct thermal oxidation of Bi-Sn eutectic nanowires

Bismuth oxide-tin oxide (BiO_x-SnO_x) heterostructure nanowires with a diameter of 70 nm were fabricated by directly annealing Bi-Sn eutectic nanowires synthesized by the vacuum hydraulic pressure injection process. After removal of AAO (Anodic Aluminum Oxide) template with an etching solution, a spontaneous oxide was formed on nanowires to enclose the Bi-Sn eutectic alloys. While these nanowires went through the annealing process with the proper heating rate of 50 °C/min, the well-annealed oxide nanowires remain solid, straight and segmental. The results of cathodoluminescence (CL) spectrum and photoresponse proved that the products consisted of bismuth oxide and tin oxide. This fabrication methodology provides a simple way to produce one-dimensional oxide nanomaterials.     

Erosion mechanisms of aluminium nitride ceramics at different impact angles

In this paper, erosion wear behaviour of aluminium nitride (AlN) ceramics is studied. The influence of particle hardness and shape on erosion of the AlN surface is examined. The effect of varying the impingement angle on the weight loss and the roughness parameters of AlN ceramics testing sample is also determined. Therefore, erosive wear behaviour of AlN ceramics was investigated using SiC and SiO₂ particles as erodents, at following impact angles: 30°, 45°, 60°, 75° and 90°. Scanning electron microscopy (SEM) was used to analyze the eroded surfaces in order to determine erosion mechanisms. The roughness parameters (R_a, R_z and R_max), before and after erosion with SiO₂ and SiC particles at 30° and 90° angles of impingement, respectively, were determined using a profilometer. It was found that the impact angle is influencing the erosion wear of the AlN ceramics and maximum erosion takes place at impact angle of 90°. The results indicate that hard, angular SiC particles cause more damage than softer, more rounded SiO₂ particles.     

Large-scale SnO2 nanowires synthesized by direct sublimation method and their enhanced dielectric responses

In this paper, we developed a direct sublimation method to synthesize large-scale rutile SnO₂ nanowires on 6H–SiC substrate using SnO₂ nanoparticles as starting material. The structural properties of these straight nanowires were investigated in detail. These nanowires grow along [121], and the average diameter and length of these nanowires are 80 nm and 5 μm, respectively. In addition, the dielectric measurement indicates that the dielectric response of the SnO₂ nanowires is significantly enhanced in the low-frequency range. It is suggested that both the rotation direction polarization (RDP) and the space charge polarization (SCP) process should be responsible for the enhancement of ε_r of these SnO₂ nanowires.     

超细金属Zn纳米线的水热合成

用水热合成法制备了纤锌矿结构的超细金属Zn纳米线,X射线衍射结果分析表明所制备的金属Zn纳米线是单一的纤锌矿结构.扫描电子显微镜照片显示合成的纳米线长度达几微米,直径10～20nm,每一根纳米线都有一个锥形的顶部.进一步研究表明反应温度对合成产物的形貌有重要的影响,最后对纳米线的生长机制进行了初步分析.