升华再结晶法制备AIN晶须及其生长特性

以ＡｌＮ粉体为原料，加入适量的ＣａＯ－Ｂ２Ｏ３矿化剂，采用升华再结晶法制备ＡｌＮ晶须，初步探讨了反应器及其合成温度对产物的种类的影响，研究了晶须的结构特征及其生长机理，结果表明，初期的合成产物包括ＡＬＮ晶柱、晶须和非晶ＡｌＮ纤维，以ＶＬＳ机制生长；后期产物为ＡｌＮ晶须，表现为ＶＳ生长机制：ＸＲＤ及ＴＥＭ分析表明，晶须大多呈现沿（２１１０）、（１０１ｌ）和（０００１），ｌ＝０、１、２、３的晶面生长，     

添加Y2O3-Dy2O3的AlN陶瓷的烧结特性及显微结构

本文探索了以自蔓延高温（ＳＨＳ）法合成并经抗水化处理的ＡｌＮ粉为原料,以Ｙ２Ｏ３－Ｄｙ２Ｏ３作为助烧结剂的ＡｌＮ陶瓷的烧结特性及显微结构,结果表明,晶界处存在Ｄｙ４Ａｌ２Ｏ９、Ｙ３Ａｌ２Ｏ９、ＤｙＡｌＯ３、Ｄｙ２Ｏ３和ＤｙＮ等第二相物质,随烧结温度变化,第二相的种类、数量和分布不同,显微结构也随之变化,从而影响ＡｌＮ的热导率,在１８５０℃下,可获得热导率为１４８Ｗ／ｍ·Ｋ的ＡｌＮ陶瓷。     

CaO-Y2O3添加剂对AlN陶瓷显微结构及性能的影响

研究了掺杂ＣａＯ－Ｙ２Ｏ３热压烧结和常压烧结ＡｌＮ陶瓷的性能和显微结构．结果表明：热压烧结ＡｌＮ陶瓷的第二相为Ｙ３Ａｌ５Ｏ１２，常压烧结ＡｌＮ陶瓷的第二相为Ｙ３Ａｌ５Ｏ１２和Ｃａ３Ｙ２Ｏ６；热压烧结ＡｌＮ的第二相体积百分数和晶格氧含量均低于常压烧结；热压烧结ＡｌＮ陶瓷的微观结构良好，其热导率达到２００Ｗ／ｍ·Ｋ．     

低温共烧多层AlN陶瓷基片

介绍由高热导率ＡｌＮ陶瓷与金属Ｗ制备的低温共烧多层ＡｌＮ基片，研究了以Ｄｙ２Ｏ３为主的添加系统对低温烧结ＡｌＮ性能，显微结构的影响。     

SiC－AlN－Y_2O_3复相陶瓷的制备与性能

通过热压烧结技术，ＳｉＣ、ＡｌＮ和Ｙ２Ｏ３粉末混合作在１９２０～２０５０℃、Ａｒ气氛下形成了致密的复相陶瓷．在室温下ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相材料的抗弯强度和断裂韧性分别达到６００ＭＰａ和７ＭＰａ·ｍ１／２以上运用ＸＲＤ、ＳＥＭ和ＴＥＭ分析致密样品的断裂裂纹、形貌和组成．ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相陶瓷在１３７０℃氧化试验３０ｈ，其氧化产物为莫来石．     

流延法制备低温烧结的高热导率AlN基片

本文研究了流延法制备低温烧结的高热导率ＡｌＮ基片过程中影响流延浆料粘度的主要因素，结果表明，溶剂比例的增加会导致浆料粘度下降。增塑剂的减少则使粘度上升，本文还研究了添加剂对ＡｌＮ陶瓷烧结及热导性能的影响，实验表明Ｂ２Ｏ３能以过渡液相的形式促进烧结，而Ｄｙ２ｏ３在低温下人较好的去除ＡｌＮ晶格氧的能力，通过添加Ｄｙ２Ｏ３、Ｂ２Ｏ３等组成的混合助烧结剂。在１６５０℃下烧结４ｈ，获得了热导率高达１３０Ｗ／     

SiC—AlN—Y2O3复相陶瓷的制备与性能

通过热压烧结技术，ＳｉＣ、ＡｌＮ和Ｙ２Ｏ３粉末混合体在１９２０￣２０５０℃、Ａｒ气氛下形成了致密的复相陶瓷。在室温下ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相材料的抗弯强度和断裂韧性分别达到６００ＭＰａ和７ＭＰａ·ｍ＾１／２以上。运用ＸＲＤ、ＳＥＭ和ＴＥＭ分析致密样品的断裂裂纹、形貌和组成。ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相陶瓷在１３７０℃氧化试验３０ｈ，其氧化产物为莫来石。     

溶胶法涂覆碳化硅昌须的工艺研究

以Ａｌ（ＮＯ３）３为原料用溶胶法成功地在ＳｉＣ晶须表面涂覆了一层厚２－１０ｎｍ的Ａｌ２Ｏ３结果表明，溶胶浓度，ＰＨ值，涂覆方式以及有机分散剂对涂覆效果有显著影响，涂覆使ＳｉＣ晶须的抗氧化能力明显增强，涂层与晶须结合较为牢固。     

CaO-Y2O3添加剂对AlN陶瓷显微结构及性能的影响

研究了掺杂ＣａＯ－Ｙ_２Ｏ_３热压烧结和常压烧结ＡｌＮ陶瓷的性能和显微结构．结果表明：热压烧结ＡｌＮ陶瓷的第二相为Ｙ_３Ａｌ_５Ｏ_１２,常压烧结ＡｌＮ陶瓷的第二相为Ｙ_３Ａｌ_５Ｏ_１2和Ｃａ_３Ｙ_２Ｏ_６;热压烧结ＡｌＮ的第二相体积百分数和晶格氧含量均低于常压烧结;热压烧结ＡｌＮ陶瓷的微观结构良好,其热导率达到２００Ｗ／ｍ·Ｋ．     

溶胶法涂覆碳化硅晶须的工艺研究

以Ａｌ（ＮＯ３）３为原料用溶胶法成功地在ＳｉＣ晶须表面涂覆了一层厚２－１０ｎｍ的Ａｌ２Ｏ３。结果表明，溶胶浓度，ＰＨ值，涂覆方式以及有机分散剂对涂覆效果有显著影响。涂覆使ＳｉＣ晶须的抗氧化能力明显增强，涂层与晶须结合较为牢固。     

升华再结晶法制备AIN晶须及其生长特性

以AIN粉体为原料，加入适量的CaO-B2O3矿化剂，采用升华再结晶法制备AIN晶须．初步探讨了反应器及其合成温度对产物种类的影响，研究了晶须的结构特征及其生长机理．结果表明，初期的合成产物包括AIN晶柱、晶须和非晶AIN纤维，以VLS机制生长：后期产物为AIN晶须，表现为VS生长机制：XRD及TEM分析表明，晶须大多呈现沿｛2110｝、｛101l｝和｛0001｝，l＝0、1、2、3的晶面生长．多数晶须宏观生长轴向平行于这些晶面的法线，而部分晶须由于发生斜生长，导致宏观生长轴向与这些晶面的法线斜交．     

碳热还原法合成AIN晶须及其生长机理

以Al2O3和石墨为原料，采用碳热还原法制备AIN晶须.研究了矿化剂的种类及温度等工艺对AIN晶须合成的影响结果表明，以CaF2和B2O3为矿化剂的AIN品须是以VLS机制生长的，高温下VLS机制可以转变为VS机制，同时存在两维成核及螺位错生长过程，晶须生长方向大多呈{101n}，（n=0，1，2，3）及{121m}，（m=0，1；2）的晶面生长     

碳热还原法生成AlN晶须的形貌及结晶方向

在用碳热还原法制备ＡｌＮ粉未过程中，发现大量白色ＡｌＮ晶须存在于ＡｌＮ粉末坯体表面某形貌有直板状、锯齿状及抿曲状，电子衍射花斑显示结晶方向均为（０００２），其生长机理可能为ＶＳ机制。     

铝粉在高压氮气中自蔓延燃烧合成氮化铝

利用铝粉在高压氮气中的自蔓延燃烧合成（SHS）方法,制备了氮含量较高（33．5wt％）的AIN,研究了稀释剂含量、添加剂含量、氮气压力、反应物的相对密度、反应物厚度对燃烧产物氮含量的影响,并对后燃烧现象进行了分析,产物中发现氮化铝晶须和棒晶．     

Mechanical properties of monolithic AIN and SiCw/AIN composites

Flexural, tensile, and high cycle fatigue test data are presented for pressureless sintered aluminium nitride (AIN) and hot-pressed aluminium nitride reinforced with silicon carbide whiskers (SiC_w/AIN). Tests were conducted at ambient temperature. The SiC_w/AIN composites consisting of 30wt% SiC_w produced significant increases in flexural strength, tensile strength, and tensile fatigue strength compared to monolithic AIN. Increases were nearly double in all cases. Corresponding strain-to-failures measured in tensile tests increased from 0.04% in monolithic AIN to 0.10% in the SiC_w reinforced composite. Fracture surfaces showed evidence of whisker-toughening mechanisms due to additions of SiC_w whiskers. High-cycle fatigue results indicated that both materials have the ability to sustain higher stress levels in the cyclic tests compared to the tensile experiments. The improved performance under cyclic testing is explained in terms of strain-rate effects. The times at or near peak stress are considerably less under high-cycle fatigue testing (20 Hz) compared to tensile tests (strain rate = 0.5%min^–1).     

Controlling of the electrical resistivity of GaN layer using AIN nucleation layer

The sheet resistance (Rs) of undoped GaN films on AIN/c-plane sapphire substrate was investigated. The Rs was strongly dependent on the AIN layer thickness and semi-insulating behavior was observed. To clarify the effect of crystalline property on Rs, the crystal structure of the GaN films has been studied using X-ray scattering and transmission electron microscopy. A compressive strain was introduced by the presence of AIN nucleation layer (NL) and was gradually relaxed as increasing AIN NL thickness. This relaxation produced more threading dislocations (TD) of edge-type. Moreover, the surface morphology of the GaN film was changed at thicker AIN layer condition, which was originated by the crossover from planar to island grains of AIN. Thus, rough surface might produce more dislocations. The edge and mixed dislocations propagating from the interface between the GaN film and the AIN buffer layer affected the electric resistance of GaN film.     

Reactive gas condensation synthesis of aluminum nitride nanoparticles

Aluminum Nitride (AIN) nanoparticles were synthesized using a Reactive Gas Condensation (RGC) technique in which a mixture of ammonia (NH3) and nitrogen (N2) gases were used for the nitridation of aluminum. NH3 served as the reactive gas, while N2 served as both a carrier gas and the inert source for particle condensation. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that at reactive gas compositions greater than 10% NH3 in N2, samples were composed entirely of hexagonal AIN nanoparticles. Electron diffraction patterns showed single crystal hexagonal AIN structure. The particle size was controlled by varying the pressure of the gas mixture. AIN nanoparticles were dispersed in a liquid matrix to enhance thermal conductivity. Results showed that a minimal addition of AIN increased the thermal conductivity of hydrocarbon pump oil by approximately 27%. The thermal conductivity became constant after reaching a maximum above 0.01 wt% AIN. Temporal stability of AIN was studied by XRD. Samples exposed to air for extended periods of time and analyzed by XRD show no degradation of crystalline AIN nanoparticles.     

Computational investigation on structural and physical properties of AIN nanosheets and nanoribbons

Through first-principles computations, we investigated the structural, electronic and magnetic properties of two-dimensional AIN single layer and one-dimensional AIN nanoribbons. AIN single layer and nanoribbons quit the Wurtzite configuration and adopt a graphitic-like structure after geometry optimization. Both hydrogen-terminated zigzag and armchair AIN nanoribbons have a direct band gap, which increases monotonically with increasing ribbon width. Bare zigzag AIN nanoribbons have a spin-polarized ground state and are magnetic semiconductors. The results may promote the experimental preparation of AIN nanosheets and nanoribbons and their applications to nanotechnology.     

Hydrophobing of aluminium nitride powders

The hydrophobing of AIN powders through adsorption of capric acid, stearic acid and cetyl alcohol on the particle surface was investigated by statistical analysis. Stearic acid as surface adsorbent and cyclohexane as solvent were identified as the best combination for achieving highly effective hydrophobicity of AIN. The adsorption data obtained for this combination indicated a Langmuir chemisorption isotherm. Even after 96 h leaching in water, no crystalline phase other than AIN could be detected by X-ray diffraction (XRD).     

Nitriding in the high temperature oxidation of Fe-31Mn-9AI-6Cr alloy

An alloy, of Fe-31.3Mn-8.92AI-5.96Cr-0.86C composition, was heated from 800 to 1000° C in atmospheres of oxygen, nitrogen and dry air respectively. A needle-like structure was observed between the alloy matrix and the external oxidation layer in the nitrogen-containing atmosphere at temperatures higher than 800° C. The needle-like phase was identified as AIN by both X-ray and STEM diffraction methods. Nitriding first occurred in the austenitic grains adjacent to the free surface, with subsequent AIN growth towards the alloy matrix. The ferrite phase, formed due to the precipitation of chromium carbide, prevented the growth of AIN. For the alloy oxidized in air, AIN formed and the growth front of AIN was ahead of the oxides. The aluminium content of the alloy matrix in the nitrided region was depleted by the formation of AIN. Due to the rapid nitriding of AI, the formation of a protective oxide layer was retarded and the oxidation resistance became less promising.Will be on leave to the Department of Materials Science and Engineering, Cornell University, as visiting scientist, after 1 October 1987.