固相反应法制备Nd:YAG透明陶瓷

以Y(NO₃)₃和NH₃·H₂O为原料,并在Y(NO3)3溶液中添加少量(NH₄)₂SO₄,采用沉淀法制备出化学组成为Y₂(OH)₅(NO₃)·nH₂O的先驱沉淀物.先驱沉淀物在1100℃下煅烧4h,得到了平均粒径为60nm的氧化钇原料粉体.Y₂O₃粉体与Al₂O₃、Nd₂O₃超细粉球磨混合后,采用固相反应工艺,经1700℃真空烧结5h,制备出透明的Nd:YAG陶瓷,同时对Nd:YAG透明陶瓷的光学性能进行了研究.     

原位氮化法制备纳米TiN-Al2O3复合粉体

以化学共沉淀法制备的纳米ＴｉＯ_２－Ａｌ_２Ｏ_３复合粉体为原料,采用原位选择性氮化的方法制备了纳米ＴｉＮ－Ａｌ_２Ｏ_３复合粉体．应用化学热力学原理分析、计算了氮化反应的条件和机理,研究了氮化条件对氮化反应的影响．实验结果表明,氮化反应在７００℃时开始进行,在９００℃保温５ｈ,氮化反应进行完全,ＴＥＭ照片显示纳米ＴｉＮ 颗粒均匀分布于Ａｌ_２Ｏ₃基体中,粒径为５０～７０ｕｍ．     

高透光率Nd:YAG透明陶瓷的制备与性能研究

以Y(NO₃)₃·6H₂O、Al (NO₃)₃·9H₂O、(NH₄)₂SO₄和Nd(NO₃)₃为原料, NH₄HCO₃为沉淀剂, 以TEOS作为添加剂, 采用共沉淀法制备出Nd:YAG前驱体粉体; 前驱体经过1200℃煅烧5h后, 得到分散性好, 颗粒近似球型、纯YAG立方相的Nd:YAG纳米粉体, 其平均粒径约为100nm. 煅烧后的粉体压制成素坯, 在1700～1800℃煅烧10h, 可获得透光性良好的Nd:YAG激光透明陶瓷, YAG晶粒的平均尺寸为15μm, 晶界处和晶粒内没有杂质、气孔存在, 无散射中心. 1.5mm厚的样品在近红外波长为1064nm处透过率为83.5%, 基本接近于透明Nd:YAG晶体的理论值.     

微波均相合成YAG纳米粉体及其可烧结性研究

采用微波辐照尿素法均相合成技术制备了具有良好分散性的纳米级单相YAG粉体,分析了YAG前驱体的化学组成及其物相变化过程,并对YAG粉体的粒度和形貌进行了表征,结果表明在尿素与钇铝离子的摩尔比为15:1的低尿素用量条件下,合成的无定形前驱物经900℃煅烧直接结晶生成YAG单相粉体,在反应体系中添加适量(NH₄)₂SO₄可使YAG粉体的粒度分布和可烧结性明显改善,添加8%的(NH₄)₂SO₄得到的YAG粉体具有良好的可烧结性,在1500℃烧结即可实现致密化.     

微波法快速制备高稳定性纳米羟基磷灰石

以Ca(NO₃)₂·4H₂O和(NH₄)₂HPO₄为前驱物,采用微波法快速制备出由30nm左右的小颗粒自组装成短捧状的纳米羟基磷灰石粉末,并分析了其自组装的原因。采用XRD,IR,TG-DTA,TEM对其进行了测试,并探讨了不同的微波辐射时间、微波功率、低温煅烧对羟基磷灰石粉体的热稳定性的影响。研究结果证实:随微波辐射反应溶液时间的延长,HAP的热稳定性提高,微波辐射反应溶液的最佳时间是1h;随微波功率的升高,HAP的热稳定性提高;微波辐射反应溶液时间为1h、微波功率为700W、500℃保温HAP3h,HAP在1200℃稳定存在。     

氨解法制备纳米氮化铬粉体

以沉淀法制备的纳米Cr₂O₃为原料,采用氨解法在800-900℃、氮化4-8h制备了纳米氮化铬粉体.对不同氨解温度、氨解时间合成的CrN粉体用X射线衍射(XRD)、透射电镜(TEM)等方法进行了表征.研究了氨解温度、氨解时间对CrN粉体性能的影响.结果表明:该方法所需设备简单,氮化温度低,反应时间短,产品纯度高.在800℃氮化8h可得到粒度为40-80nm的纯立方相CrN纳米粉体.     

水热盐溶液卸压法制备氧化物粉体

本文采用一种新的水热粉体制备方法-水热盐溶液卸压法,制得了α-Al₂O₃粉体、AlO（OH）纤维以及ZrO₂和AlO（OH）复合氧化物粉体．发现以1mol／LAl（NO₃）₃溶液作为前驱物,0．2mol／LFe（NO₃）₃为添加剂,在300℃可制得α－Al₂O₃粉体．以1mol／LAl（NO₃）₃溶液为前驱物;1mol／LKBr为添加剂,在350℃可制得长径比为13：1的AlO（OH）纤维．当采用AlCl₃、ZrOCl₂溶液为前驱物,Zr/Al的比例为1：3时,在240℃可制得纤维状AlO(OH)颗粒和球形ZrO₂颗粒的复合氧化物粉体．     

氮化铁纳米晶的溶剂热合成

以氯化亚铁（FeCl₂·4H₂O）为铁源, 氯化铵（NH₄Cl）和叠氮化钠（NaN₃）为混合氮源, 通过溶剂热合成法制备了具有包覆结构的氮化铁纳米晶. 分别采用X射线衍射（XRD)、 透射电镜（TEM)和高分辨透射电镜（HRTEM)对最终产物的形貌特征和物相组成进行了表征, 结合处理前后产物的XRD检测, 探讨了氮化铁纳米晶复合结构形成的机理. 对影响实验的因素,如反应温度、反应时间、加料次序和磁性质等进行了研究. 结果表明：通过严格控制加料次序, 在有机溶剂二甲苯中400℃反应12h可以合成氮化铁复合结构纳米晶. 由于核壳结构的影响, 氮化铁纳米晶最大比饱和磁化强度比文献值低.     

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.     

新型氨基储氢材料CaCl2的性能研究

研究了工作温度、起始氨压和球磨处理对无水CaCl₂的吸放氨性能的影响. 结果发现, 球磨2h样品在温度20℃和氨压0.55MPa的条件下, 15min内即可完全氨化, 形成CaCl₂(NH₃)₈, 其吸氨量可达55.1wt%, 相当于储氢量9.72wt%. CaCl₂(NH₃)₈在20～300℃的范围内可通过三步反应实现完全脱氨, 脱氨反应受温度和压力控制, 其中6个NH₃分子在常温、常压下即可脱附. 如果与NH₃分解催化剂联用, 可能是一种较好的以NH₃为介质的高容量储氢材料. 进一步研究表明, 较高的工作温度和起始氨压可以提高CaCl₂的吸氨动力学性能, 而球磨时间的增加可以显著降低其放氨工作温度, 提高其放氨动力学性能.     

Synthesis of Vanadium Nitride by a One Step Method

Vanadium nitrides were prepared via one step method of carbothermal reduction and nitridation of vanadium trioxide. Thermalgravimetric analysis （TGA） and X-ray diffraction were used to determine the reaction paths of vanadium carbide, namely the following sequential reaction： V2O3→V8C7 in higher temperature stage, the rule of vanadium nitride synthesized was established, and defined conditions of temperature for the production of the carbides and nitrides were determined. Vanadium oxycarbide may consist in the front process of carbothermal reduction of vanadium trioxide. In one step method for vanadium nitride by carbothermal reduction and nitridation of vanadium trioxide, the nitridation process is simultaneous with the carbothermal reduction. A one-step mechanism of the carbothermal reduction with simultaneous nitridation leaded to a lower terminal temperature in nitridation process for vanadium nitride produced, compared with that of carbothermal reduction process without nitridation. The grain size and shape of vanadium nitride were uniform, and had the shape of a cube. The one step method combined vacuum carborization and nitridation （namely two step method） into one process. It simplified the technological process and decreased the costs.     

ECR等离子体对硅表面的低温大面积氮化

利用电子回旋共振微波放电氮等离子体对单晶硅表面进行了低温大面积氮化的探索 ,通过样品表征和等离子体成分探测 ,分析讨论了氮化机理。结果表明 ,这种方法可以用于硅表面的低温氮化处理 ,获得大面积的均匀氮化硅表层。     

静态氮气氛中合成金属氮化物

提出了在高温和静态氮气氛下利用金属与氮气直接反应制取金属氮化物的合成方法.通过选择不同的反应条件,用该方法合成了从活泼金属(如Li、Mg、La、Ce和Al)到过渡金属(如Ti、Zr、V、Nb和Cr)等10种二元氮化物.时所得氮化物进行XRD物相分析表明,所得产物均以二元氮化物为主相,杂相含量很少.用扫描电镜(SEM)观察了AIN、TiN和VN样品的表面形貌,EDX分析表明,它们的化学组成与名义成分基本一致.与其它氮化物合成方法相比,静态氮气中直接氮化的合成方法具有节省资源和环境友好的优点.     

纳米氮化硼增强金属基复合材料的研究进展

在金属中添加陶瓷增强相是调控和改善金属材料结构和性能的重要途径。传统硬质陶瓷增强相难以满足金属材料日益严苛的应用需求。以氮化硼纳米片（boron nitride nanosheet,BNNS）和氮化硼纳米管（boron nitridenanotube,BNNT）为代表的纳米氮化硼具有极大的比表面积和优异的力学性能、热稳定性、化学稳定性等,是制备性能优异的金属基复合材料的理想增强相。系统总结了纳米氮化硼的种类和特征,综述了纳米氮化硼增强金属基复合材料的制备方法,归纳了纳米氮化硼增强Cu、Al、Ti复合材料的研究成果,总结了纳米氮化硼/金属复合材料的力学和摩擦学性能,并揭示了复合材料性能改善的机理。最后,展望了纳米氮化硼/金属复合材料的发展趋势。     

Structure of ceramics produced through high-temperature nitridation of hafnium foil

The high-temperature hafnium nitridation process, with HfN_x formation, comprises two stages. With increasing nitridation temperature and time, the lattice parameter of the nitride decreases. The observed discrete nucleation of nitride microcrystals on the surface is a consequence of metal diffusion through an amorphous carboxynitride. No structural defects were detected by high-resolution transmission electron microscopy in selected areas.     

Mechanical properties optimization of tungsten nitride thin films grown by reactive sputtering and laser ablation

Transition metal nitrides coatings are used as protective coatings against wear and corrosion. Their mechanical properties can be tailored by tuning the nitrogen content during film synthesis. The relationship between thin film preparation conditions and mechanical properties for tungsten nitride films is not as well understood as other transition metal nitrides, like titanium nitride. We report the synthesis of tungsten nitride films grown by reactive sputtering and laser ablation in the ambient of N₂ or N₂/Ar mixture at various pressures on stainless steel substrates at 400  C. The composition of the films was determined by XPS. The optimal mechanical properties were found by nanoindentation based on the determination of the proper deposition conditions. As nitrogen pressure was increased during processing, the stoichiometry and hardness changed from W₉N to W₄N and 30.8-38.7 GPa, respectively, for films deposited by reactive sputtering, and from W₆N to W₂N and 19.5-27.7 GPa, respectively, for those deposited by laser ablation.     

原位选择性氮化法制备t-ZrO2-TiN复合粉料

研究以固溶反应为基础的粉粒制备技术，应用热力学原理分析计算了（Zr,Ti）O2固溶系统的选择性的氮化条件，确定了反应温度对该系统氮化后相组成的影响。采用碳热还原法，在高纯氮气氛下原位反应生成氮化钛，同时保持氮化锆组成和结构不变，利用X射线衍射和X射线荧光光谱对氮化后粉料的物相和氮化效果进行分析，采用扫描电镜对复合粉料的形貌进行观察。     

Synthesis of boron nitride from ferroboron Part 1 – Nitriding

Abstract

Thermodynamic calculations and nitriding experiments have been carried out to convert ferroboron precursor to boron nitride in a mixture of NH₃ with N₂ gases under ambient pressure. The results show that complete nitridation can be achieved at 673 K with 20 vol.-%NH₃ in the gas mixture. The nitrided product consists of amorphous boron nitride, iron, and metastable iron nitrides. The measured weight gain follows a two stage, near parabolic kinetics accompanied by volume expansion, which causes spalling of the outer nitrided layer and facilitates further nitriding. An alternative reaction route using 100 vol.-%N₂ is also possible, but a higher reaction temperature (≥～1700 K) is needed. The product from the high temperature route contains partially crystallised (hexagonal) boron nitride, iron, and virtually no metastable iron nitride.     

Nitride synthesis using ammonia and hydrazine—a thermodynamic panorama

Because of the wide variety of projected applications of ultrapure nitrides in advanced technologies, there is interest in developing new cost-effective methods of synthesis. Explored in this study is the use of ammonia and hydrazine for the synthesis of nitrides from oxides, sulfides and chlorides. Even when the standard Gibbs energy change for the nitridation reactions involved are moderately positive, the reaction can be made to proceed by lowering the partial pressure of the product gas below its equilibrium value. Use of a metastable form of precursor in the nanometric size range is an alternative method to facilitate nitridation. Ellingham-Richardson-Jeffes diagrams are used for a panoramic presentation of the driving force for each set of reactions as a function of temperature. Oxides are the least promising precursors for nitride synthesis; sulfides offer a larger synthetic window for many useful nitrides such as BN, AlN, InN, VN, TiN, ThN and Si₃N₄. The standard Gibbs free energy changes for reactions involving chlorides with either ammonia or hydrazine are much more negative. Hydrazine is a more powerful nitriding agent than ammonia. The metastability of hydrazine requires that it be introduced into a reactor through a water-cooled lance. The use of volatile halides with ammonia or hydrazine offers the potential for synthesis of pure and doped nanocrystalline nitrides. Nitride thin films can also be prepared by suitable adaptations of the chloride route.     

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。