氮化锌粉末的结构和化学键状态

将Zn粉末置于流量为500ml／min的NH3气流中，在600℃氮化120min，制备出高质量的Zn3N2粉末。X射线衍射（XRD）表明Zn3N2粉末具有立方结构，其晶格常数为0．9788nm。扫描电子显微镜（SEM）和透射电子显微镜（TEM）观察发现Zn3N2粉末晶粒形状具有多样性。X射线光电子谱（XPS）表明Zn3N2的化学键状态与ZnO及金属Zn明显不同，表明N-Zn键的形成。用计算机模拟了Zn3N2晶体的立体结构，用高分辨电子显微镜（HRTEM）观察了Zn3N2粉末的内部结构，观察结果与Partin等提出的Zn3N2结构模型相符合。     

Mg-5Al-10.3Ti纳米复合材料的力学性能及微观组织

通过机械化学研磨法将Mg、Al、Ti粉末混以聚乙烯乙二醇进行研磨，合成了Mg-5Al-10．3Ti纳米复合材料。与常规粉末冶金法相比，该法合成的材料的力学性能呈现出反常的应变软化现象。透射电子显微镜分析表明，合金中镁晶粒尺寸大多为20～30nm，个别晶粒的尺寸约为90nm；此外，观察到许多直径约3～7nm的纳米管。     

Mg-Al合金中AlN颗粒的原位合成机制研究

采用在合金熔体中通入氮气的方法在镁铝合金中原位生成了AlN颗粒增强相。合金微观组织的研究分析表明,AlN相不仅可通过间接氮化反应（3Mg+N2→Mg3N2,Mg3N2+2Al → 2AlN+3Mg)形成,而且可在熔体中由Al和N2直接反应形成。控制氮化反应温度在750℃,且合金熔体凝固后的快速重熔可在合金中获得分布均匀的AlN相。     

Mg掺杂InxGa1-xN薄膜的磁控溅射法制备和表征

本文采用磁控溅射法用In2O3靶、Ga2O3靶、Mg靶在Si片上制备出InxGa1-xN薄膜和Mg掺杂的InxGa1-xN薄膜。薄膜中的In组分随着Mg的掺杂而减少,因为Mg的掺杂抑制了In-N键的形成,并增加了Ga进入薄膜的机会。通过EDS对Mg掺杂的InxGa1-xN薄膜的分析表明,有1.4%的Mg组分被成功地注入进InxGa1-xN薄膜。电学性能分析表明 In0.84Ga0.16N 和Mg掺杂的 In0.1Ga0.9N薄膜导电类型由n型转变为p型,而且Mg掺杂的 In0.1Ga0.9N薄膜的空穴浓度和电子迁移率分别为 2.65×1018 cm?3 和3.9 cm2/Vs。     

Mg掺杂In_xGa_(1-x)N薄膜的磁控溅射法制备和表征（英文）

采用磁控溅射法,用In_2O_3靶、Ga_2O_3靶、Mg靶在Si片上制备出In_xGa_(1-x)N薄膜和Mg掺杂的In_xGa_(1-x)N薄膜。薄膜中的In组分随着Mg的掺杂而减少,因为Mg的掺杂抑制了In-N键的形成,并增加了Ga进入薄膜的机会。通过EDS对Mg掺杂的In_xGa_(1-x)N薄膜的分析表明,有1.4%的Mg组分被成功地掺入In_xGa_(1-x)N薄膜。电学性能分析表明In_(0.84)Ga_(0.16)N和Mg掺杂的In_(0.1)Ga_(0.9)N薄膜导电类型由n型转变为p型,而且Mg掺杂的In_(0.1)Ga_(0.9)N薄膜的空穴浓度和电子迁移率分别为2.65×10~(18) cm~(-3)和3.9 cm~2/(V·s)。     

掺Pd改性纳米晶Mg2Ni吸放氢氘特性研究

采用机械合金化法制备了Mg2Ni-1．0％Pd（质量分数，下同）合金粉末，用XRD及AFM等分析表征了球磨20h后粉末的相结构和微观形貌，测定了Mg2Ni-1．0％Pd合金吸放氢氘的P-C-T曲线和动力学曲线。结果表明，机械合金化制备的Mg2Ni-1．0％Pd合金粉末粒度在10nm～50nm之间；同熔炼法制备的Mg2Ni合金相比，纳米Mg2Ni-1．0%Pd合金吸氢时的焓变值减小，放氢时焓变值增大，可逆贮氢容量为1．06（H／M,原子比，下同）；与吸放氢相比，在相同温度下合金吸放氘的坪台压升高，焓变值减小，具有显著的同位素效应。纳米Mg2Ni-1．0％Pd合金的吸氢速率和吸氘速率与温度的关系在573K附近发生变化。     

Mg3MNi2（M=Ti，Al）的晶体结构

Al和Ti对Mg2Ni结构中部分Mg的取代,得到与Mg2Ni晶体结构不同的新型合金．多晶X射线结构分析表明,其化学式为Mg3MNi2(M=Ti,Al),立方晶系,空间群Fd3m,Z=16,48个Mg坐落在48(y),16个M(M=Al,Ti)坐落在16(d)位,32个Ni坐落在32(e)位,Mg3AlNi2的晶胞参数a=1．15474(2)nm,Mg3TiNi2的a=1．16178(2)nm．与Mg2Ni相比,Mg3MNi2合金的晶体密度更大,Mg-Ni键长更长,吸放氢温度降低,循环寿命延长．     

AgPbmSbTem＋2纳米粉末的水热合成、表征及无压烧结

以AgNO3、Pb（NO3）2、Sb（NO3）3和Te粉为原料，采用水热法成功合成了无规则形状和球形的AgPbmSbTem＋2（LAST-m，m=10，12，14，16，18）系列纳米粉末。TEM和XRD分析表明，LAST-m粉末均呈NaCl型晶体结构，颗粒尺寸约为40nm；选区电子衍射图分析表明LAST-m肼为单晶材料。以无规则粉末为例，采用无压烧结法制备了LAST-18的复合块体材料，并测试了其室温到473K的热电性能。     

Mg-Al合金中AlN颗粒的原位合成机制研究（英文）

采用在合金熔体中通入氮气的方法在镁铝合金中原位生成了Al N颗粒增强相。合金微观组织的研究分析表明,Al N相不仅可通过间接氮化反应(3Mg+N_2→Mg_3N_2,Mg_3N_2+2Al→2AlN+3Mg)形成,而且可在熔体中由Al和N2直接反应形成。控制氮化反应温度在750℃,且合金熔体凝固后的快速重熔可在合金中获得分布均匀的Al N相。     

温和条件下碲化铅纳米颗粒的制备

以Pb(CH_3COO)_2·3H_2O和TeO_2为原料,硼氢化钾为还原剂,在常压下,室温至70 ℃碱性水溶液中成功地制得了PbTe纳米粉末.粉末X射线衍射分析表明制备的粉末为NaCl结构,透射电子显微镜观察表明颗粒粒径随反应温度升高而增大,从8 nm (室温) 增加至40 nm (70 ℃).能谱(EDS)分析表明产物的组成元素为Pb和Te.还对PbTe纳米颗粒的形成机理做了探讨.     

固化球磨纳米晶粉末制备块体超细晶Mg-3Al-Zn合金(英文)

采用粉末冶金技术制备块体超细晶Mg-3Al-Zn合金。首先采用球磨Mg、Al、Zn混合粉末来制备纳米晶粉末,所得的粉末的平均晶粒尺寸为45nm。随后将球磨好的粉末封入铝包套内,分别在室温和633K温度下,在真空烧结炉内进行真空热压。然后将烧结后的样品在423K下挤压以进行进一步的致密化处理。结果表明:致密后的冷压样品的晶粒尺寸为180nm,而热压坯的晶粒尺寸为600nm,冷压样品的屈服强度达464MPa;超细晶镁合金的强化机制主要是细晶强化,这主要是由于HCP结构的材料晶粒尺寸对材料的影响更为明显。固化后冷压样品的最终密度为(1.777±0.006)g/cm3,而热压样品的最终密度为(1.800±0.006)g/cm3。     

Zn元素对直接氮化法制备AlN粉体的影响

为解决直接氮化法制备AlN粉体过程中存在的问题,采用具有高饱和蒸气压的Zn元素作为原料铝合金的合金元素,研究了Zn元素对Al-Zn以及Al-Mg-Zn合金直接氮化制备AlN粉体的影响。结果表明:Zn元素的挥发可以在反应初期破坏合金熔体氮化形成的氮化膜,避免熔体结块,提高转化率;另一方面,试验及热力学分析表明Zn元素的脱氧作用较差,而Mg元素可以在氮化过程中脱去气氛中的氧,避免Al2O3的形成。因此,采用Al-Mg-Zn三元合金进行直接氮化能够得到低含氧量、低金属杂质残留的纯相AlN。     

Influence factors and microstructure evolution during preparation of nanocrystalline (Ti, W, Mo, V)(C, N)–Ni composite powders

Nanocrystalline (Ti, W, Mo, V)(C, N)–Ni composite powders with crystalline size of about 35 nm were synthesized at 1300 °C from oxides by a simple and cost-effective route which combines traditional low-energy milling plus carbothermal reduction–nitridation techniques. Influence of main technological parameters was investigated by X-ray diffraction, and microstructure of the milled powders and reaction products was studied by scanning electron microscopy. The results show that the phase evolution of TiO₂ follows TiO₂ → Ti₃O₅ → Ti(C, N), and (Ti, W, Mo, V)(C, N)–Ni composite powders with higher nitrogen content and smaller crystalline size can be produced by introducing high nitrogen pressure. By contrast with high nitrogen pressure, high synthesizing temperature and long isothermal time can contribute to dissolution of W, Mo and V atoms into Ti(C, N). In addition, synthesizing temperature has a significant effect on the microstructure evolution of (Ti, W, Mo, V)(C, N)–Ni composite powders.     

微波加热制备氮化钒工艺

以五氧化二钒或偏钒酸铵为原料,炭黑为还原剂,采用微波法研究氮化钒的制备工艺.探讨在还原时间为60 min,还原最高温度为933 K时,混合物配碳比、氮化温度、氮化时间、氮气的流量、混合物成形压力等因素对产物氮含量的影响.由一步法结果表明:在混合物成形压力为20 MPa,配碳比为35%,氮化时间为120 min,氮化温度为1723 K,氮流量为2 L/min,产物氮化钒的氮含量为12.6%,钒含量79.2%,碳含量4.6%,密度为4.5 g/cm3.经 XRD检测产物为纯氮化钒.同时与传统的电阻炉加热方式相比,微波加热缩短了反应和冷却时间,节省能耗,简化工艺,降低成本.     

Effect of urea on synthesis of aluminum nitride powders from aluminum nitrate and glucose

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Nanocrystalline Mg and Mg alloy powders by hydriding-dehydriding processing

The process of mechanically assisted hydriding and subsequent thermal dehydriding was proposed to produce nanocrystalline Mg and Mg alloy powders using pure Mg and Mg-5.5%Zn-0.6%Zr(mass fraction)(ZK60 Mg) alloy as the starting materal.The hydriding was achieved by room-temperature reaction milling in hydrogen.The dehydriding was carried out by vacuum annealing of the as-milled powders.The microstructure and morphology of both the as-milled and subsequently dehydrided powders were characterized by X-ray diffraction analysis(XRD) ,transmission electron microscopy(TEM) ,and scanning electron microscopy(SEM) ,respectively.The results show that,by reaction milling in hydrogen,both Mg and ZK60 Mg alloy can be fully hydrided to form nanocrystalline MgH2 with an average grain size of 10 nm.After subsequent thermal dehydriding at 300℃,the MgH2 can be turned into Mg again,and the newly formed Mg grains are nanocrystallines,with an average grain size of 25 nm.     

Synthesis of (Ti,W, Mo,V)(C,N) nanocomposite powder from novel precursors

(Ti, W, Mo, V)(C, N) nanocomposite powders with globular-like particle of ∼10–100 nm were synthesized by a novel method, namely carbothermal reduction–nitridation (CRN) of complex oxide–carbon mixture, which was made initially from salt solution containing titanium, tungsten, molybdenum, vanadium and carbon elements by air drying and subsequent calcining at 300 °C for 0.5 h. Phase composition of reaction products was discussed by X-ray diffraction (XRD), and microstructure of the calcined powders and final products was studied by scanning electron microscopy (SEM) and transmission electron microscope (TEM), respectively. The results show that the synthesizing temperature of (Ti, W, Mo, V)(C, N) powders was reduced greatly by the novel precursor method. Thus, the preparation of (Ti, 15W, 5Mo, 0.2V)(C, N) is at only 1200 °C for 2 h. The lowering of synthesizing temperature is mainly due to the homogeneous chemical composition of the complex oxide–carbon mixture and its unusual honeycombed structure.     

纳米Si_2N_2O-Sialon陶瓷超塑性挤压试验与模拟研究

文章以Y2O3和Al2O3纳米粉体作为烧结助剂,真空热压烧结非晶纳米Si3N4粉体和纳米AlN混合粉体,制备具有超塑性的平均晶粒直径小于100nm的Si2N2O-Sialon复相陶瓷,研究纳米复相陶瓷的超塑性挤压性能。在1550℃的低温下,纳米Si2N2O-Sialon复相陶瓷实现了以1mm/s的高速率、3.57大挤压比的挤压变形,成形出良好的制件。采用有限元技术模拟Si2N2O-Sialon陶瓷的超塑性挤压过程,得出了不同温度挤压变形的力和行程曲线,以及挤压成形过程中应力和应变的分布情况,与实验结果进行比较,分析了纳米陶瓷超塑性变形的基本规律。研究表明,纳米Si2N2O-Sialon陶瓷具有较好的超塑性,可实现大挤压比挤压变形,可以进行工程陶瓷零件的超塑性成形。     

Synthesis of Ti3SiC2 by spark plasma sintering(SPS)of elemental powders

Ti3SiC2 materials have been fabricated by spark plasma sintering of the elemental powders with the addition of Al.At the heating rate of 80℃/min and under the pressure of 30MPa,the ideal synthesis temperature of Ti3SiC2 is in the range of 1150-1250℃.The addition of Al is in favor of the formation of Ti3SiC2.The synthesized compound has the molecular of Ti3Si0.8Al0.2C2 and lattice parameters of α=0.3069nm,c=1.7670nm.Its grain is plane-shape with a size of about 50μm in the elongated dimension.The prepared material has Vickers hardness of 3.5-5.5GPa(at 1N and 15s) and is as readily machinable as graphite‘s.     

Fabrication of nanocrystalline WC and nanocomposite WC–MgO refractory materials at room temperature

Reactant material powders of pure WO₃, Mg and graphite have been milled at room temperature using a high-energy ball mill. After a few kiloseconds of milling (11 ks), numerous fresh surfaces of the reactant materials are created as a result of the repeated impact and shear forces generated by the balls. After 86 ks of milling, a mechanical solid state reduction is successfully achieved between the fresh Mg and WO₃ particles to form a product of nanocrystalline mixture of MgO and W. A typical mechanical solid state reaction takes place between the W particles and graphite powders to obtain fine grains of nanocrystalline WC. Towards the end-stage of ball-milling (173 ks), the nanocrystalline MgO grains (10 nm) are embedded into the fine matrix of WC to form fine nanocomposite powders (1 μm in diameter) of WC–18% MgO material with spherical-like morphology. This composite powder was then consolidated under vacuum at 1963 K, with a pressure ranging from 19.6 to 38.2 MPa for 0.3 ks, using a plasma activated sintering method. In addition, pure nanocrystalline WC powders (7 nm in diameter) obtained by removing the MgO from the milled powders, using a simple leaching technique have been also consolidated by the same consolidation technique. The consolidation step does not lead to a dramatic grain growth and the compacted samples that are fully dense still maintain their unique nanocrystalline characteristics. The elastic properties and the hardness of both consolidated samples have been investigated. A model for fabrication of refractory nanocrystalline WC and nanocomposite WC–18% MgO materials at room temperature is proposed.