氨解法制备纳米Ti0.4Cr0.6OxNy粉体

以共沉淀法制备的钛和铬的摩尔比为4：6的TiO2／Cr2O3纳米复合粉体为前驱体,氨气为氮化剂,制备了钛铬双金属氧氮化物纳米粉体。采用Auger电子能谱、X射线衍射、透射电子显微镜、BET比表面积、电子探针等技术对氧化物复合粉体和合成氧氮化物粉体进行了表征。结果表明：前驱体组成均匀、比表面积大、反应活性高,800℃氮化8h可以合成X射线衍射纯立方相钛铬双金属氧氮化物纳米粉体e粉体呈球形,晶粒尺寸在20～35nm,比表面积达35．62m^2／g,基本无团聚。氮化前后粉体的氧含量和氮含量发生了明显变化,粉体的组成可以用Ti0.4Cr0.6OxNy表示。     

氮化物结合碳化硅耐火材料的研究现状

分别概述了以氮化硅、赛隆和氧氮化硅作为结合相 的SiC材料的结构特点、理化性能、生产工艺和应用情况,详细 介绍了国内这3种材料的研究现状,并对今后氮化物结合SiC 材料的研究内容提出了自己的观点。     

抚顺页岩油中碱性氮化物的高分辨质谱表征

页岩油的加工和利用越来越受到人们的重视。文章利用电喷雾-傅立叶变换离子回旋共振高分辨质谱仪(ESI FT-ICR MS)对抚顺页岩油中的氮化物进行了详细的表征。结果表明,抚顺页岩油中的碱性氮化物以N1类氮化物(化合物分子中含有1个氮原子)居多,N2类氮化物(分子中含有2个氮原子的化合物)次之。N1类碱性氮化物主要是带烷基侧链的吡啶类衍生物和带一个环烷环的吡啶类衍生物。N2类碱性氮化物则同时含有两个氮杂环,一个环为碱性环(含N六元环),而另一个为非碱性环(含N五元环)。     

金属-氮化物结合滑板的研制与应用

以刚玉为骨料,金属铝为主要基质,利用粉末冶金工艺,氮化烧成,制成了具有金属陶瓷性能的金属-氮化物结合滑板.金属铝以细粉、颗粒和铝纤维三种形式引入,加入量为10%～20%,同时在配料中引入一种氨盐作添加剂,确定氮化温度低于1100℃.研制的滑板具有优良的抗氧化性、抗侵蚀性和高温结构强度,尤其适合于高氧钢及钙处理钢的浇铸,其理化指标为w(Al2O3)96.6%,w(T.C)3.23%,常温耐压强度147～224 MPa,常温抗折强度51.6～59.4 MPa,体积密度3.15～3.26g@cm-3,显气孔率8%～10%,线膨胀率1.2%(1200℃).     

金属-氮化物结合刚玉滑板的制备与性能研究

以板状刚玉和金属铝粉为主要原料制备了金属-氮化物结合刚玉滑板,借助XRD和SEM等研究了铝粉加入量、加入粒度、氮化温度以及莫来石钛酸铝复相原料对滑板材料性能的影响.结果表明:(1)以板状刚玉和金属铝粉为主要原料,可以制得金属-氮化物结合刚玉滑板材料;(2)金属铝粉加入量为12%时综合性能较好;(3)铝粉以两种粒度混合引入,滑板具有好的综合性能,氮化温度1000 ℃即可;(4)引入适量的莫来石-钛酸铝复相材料可提高滑板材料的热震稳定性.     

氧化锆氧传感器铂电极的制备与表征

采用陶瓷注射成型技术制备了氧化锆(ZrO2)固体电解质基体,在烧成的ZrO2基体上涂制铂(Pt)电极浆料,将电极在不同温度下烧结.用扫描电镜表征所制备的Pt电极和进行时效实验电极表面的微观形貌,结果表明:电极烧结温度和时效时间对电极微观形貌影响很大.用电化学阻抗谱研究了Pt电极的电化学性能,结果显示:所制备的Pt电极显示出优良的电化学催化性能.     

氮化物陶瓷粉体的制备技术及发展趋势

氮化物陶瓷具有优异的耐高温、抗腐蚀、耐磨损性能,是一类应用广泛的结构功能材料。采用烧结方式制备结构与性能满足要求的氮化物陶瓷材料,有必要首先合成符合一定纯度和烧结活性的氮化合物粉体。本文综述了传统产业化氮化物陶瓷粉体的制备技术,以及新型合成技术的研究进展;对现有技术中存在的问题做了归纳总结,并依据国家政策层面的需求和支持提出该领域的发展趋势。     

水热合成镧掺杂钛酸铋粉体的初步研究

初步研究了镧掺杂钛酸铋粉体的水热合成工艺,借助XRD及TEM对粉体的组成、结构、晶粒度及粉体形貌进行了研究。结果表明:合成该粉体的最佳工艺条件为240℃保温6h;粉体的微观形貌呈片状;镧的掺杂抑制了钛酸铋晶体的生长。     

水热法制备钛酸铋粉体的研究

以TiCl4乙醇溶液和Bi（NO3）3·5H2O为原料．NaOH为矿化剂，其摩尔配比的关系为TiCl：Bi（NO3）3·5H2O：NaOH=0．1：0．75：1．5．用水热法合成钙钛矿结构的钛酸铋粉体。讨论了水热合成条件（前驱物和粉体处理、晶化时间、填充率）对钛酸铋粉体结构和形貌的影响。XRD、SEM分析表明，在240℃，晶化时间16h，填充比为60％的条件下，可制备平均晶粒粒径为9～12nm，团聚较轻，颗粒边界明显．球形的钛酸铋粉体。     

磷酸锂粉体的制备与表征

以LiOH·H₂O和NH₄H₂PO₄为原料,采用微波水热法在200℃下合成磷酸锂。研究了微波水热反应对磷酸锂颗粒形貌的影响,并对其物相组成、形貌以及晶体结构进行了分析。结果表明,利用微波和水热合成的优势制备的磷酸锂物相较纯、形状较规则,结晶性较好。     

氧氮化物玻璃

氧氮化物玻璃是一种特种玻璃。与氧化物玻璃相比，其性能和结构上都存在较大差异。本文分析了几种与氮化硅有关的氧氮化物玻璃的形成范围及其网络结构特征。同时，对氧氮化物玻璃的密度、显微硬度、杨氏模量、断裂韧性、粘度及转变温度和析晶性与含N量之间的关系进行了探讨。     

氧氮玻璃的研究进展

氧氮玻璃具有比氧化物玻璃更高的密度、折射率、杨氏模量、玻璃转变温度、软化温度和导电性能,更优异的化学稳定性,在陶瓷焊接,核废料固化,陶瓷增韧等方面都有广泛的应用前景.本文介绍了氧氮玻璃的系统、氧氮玻璃的制备方法、氧氮玻璃的结构、性能和氧氮玻璃的应用.     

Y—La—Si—O—N系统氧氮玻璃形成与性能

本研究利用溶胶－凝胶技术制备Ｙ－Ｌａ－Ｓｉ－Ｏ－Ｎ氧氮玻璃配合料，在１大气压Ｎ２气氛中１６００℃左右温度熔制，制备出表观呈灰黑色透明的Ｙ－Ｌａ－Ｓｉ－Ｏ－Ｎ系统氧氮玻璃。实验结果表明氧氮玻璃含氮量为６．７－１０．９ａｔ％；显微硬度Ｈｖ为３．５－６．４７ＧＰａ；断裂韧性为０．６４－１．３８ＭＰａｍ＾１／２，Ｔｇ在１０００℃以上，膨胀系数为１．０５×１０＾－６℃＾－１．     

Alkali Durability of Oxynitride Glass Fibers

Oxynitride glass fibers were drawn from the melt in N₂ atmospheres. The fibers were tested for their alkali durability in 10% NaOH at 96°C for 6 h. The durability is reported as weight loss in mg/cm². The photomicrographs of the fibers before and after testing are presented. Calcium silicate oxynitride fibers have good durability because of a protective surface layer of Ca(OH)₂. Yttria-containing glasses have the best durability among the compositions reported here.     

Aqueous Slip Casting of Transparent Aluminum Oxynitride

Highly transparent Aluminum oxynitride (AlON) body has been produced using aqueous slip casting technique. High‐purity alumina and AlN were used as raw materials for the synthesis of single‐phase AlON powder. As‐synthesized AlON powder was surface modified to enable the AlON powders resistant to hydrolysis in water during aqueous slip casting. High solid loaded aqueous AlON slip was prepared for casting followed by drying and sintering to produce transparent AlON. Phase formation and stability was characterized by XRD, pH, and viscosity measurements. AlON powders before and after surface treatments were characterized. Sintered transparent AlON samples were characterized for their mechanical, microstructural, and optical properties. Sintered and polished AlON produced in this study has shown inline transparency up to 80% between 0.22 and 6 μm wavelength region.     

Superplastic Deformation in Silicon Nitride–Silicon Oxynitride In Situ Composites

Starting with a mixture of ultrafine β-Si₃N₄ and a SiO₂-containing additive, a superplastic Si₃N₄-based composite was developed, using the concept of a transient liquid phase. Significant deformation-induced phase and microstructure evolutions occurred in the nonequilibrium, fine-grained Si₃N₄ material, which led to the in situ development of a Si₃N₄–22-vol%-Si₂N₂O composite and strong texture formation. The unusual ductility of the composites with elongated Si₂N₂O grains was attributed to the fine-grained microstructure, the presence of a transient liquid phase, and the alignment of the elongated Si₂N₂O grains. The mechanical properties of the resultant composite were enhanced rather than impaired by superplastic deformation and subsequent heat treatment; the resultant composite exhibited both high strength (957 MPa) and high fracture toughness (4.8 MPa·m^1/2).     

Reaction and Formation of Crystalline Silicon Oxynitride in Si–O–N Systems under Solid High Pressure

Oxidized amorphous Si₃N₄ and SiO₂ powders were pressed alone or as a mixture under high pressure (1.0–5.0 GPa) at high temperatures (800–1700°C). Formation of crystalline silicon oxynitride (Si₂ON₂) was observed from amorphous silicon nitride (Si₃N₄) powders containing 5.8 wt% oxygen at 1.0 GPa and 1400°C. The Si₂ON₂ coexisted with β-Si₃N₄ with a weight fraction of 40 wt%, suggesting that all oxygen in the powders participated in the reaction to form Si₂ON₂. Pressing a mixture of amorphous Si₃N₄ of lower oxygen (1.5 wt%) and SiO₂ under 1.0–5.0 GPa between 1000° and 1350°C did not give Si₂ON₂ phase, but yielded a mixture of α,β-Si₃N₄, quartz, and coesite (a high-pressure form of SiO₂). The formation of Si₂ON₂ from oxidized amorphous Si₃N₄ seemed to be assisted by formation of a Si–O–N melt in the system that was enhanced under the high pressure.     

Processing, Mechanical Properties, and Oxidation Behavior of Silicon Oxynitride Ceramics

Silicon oxynitride ceramics were prepared by hot-pressing an equimolar Si₃N₄+ SiO₂ mixture with 3 mol% CeO₂. The Ce₂O₃/SiO₂ ratio of intergranular phase (liquid phase) increased as the formation of Si₂N₂O proceeded. The intergranular liquid remained as a glass on cooling until the Ce₂O₃/SiO₂ ratio exceeded a certain value, at which point the liquid crystallized. There were great differences in thermal and mechanical properties and oxideation behavior between the specimen containing intergranular glassy phase and the one containing intergranular crystalline phase (Ce₅(SiO₄)₃N–Ce_4.67(SiO₄)₃O). The specimen containing the intergranular glassy phase showed excellent hightemperature strength and oxidation resistance.     

Texture Development in Silicon Nitride–Silicon Oxynitride In Situ Composites via Superplastic Deformation

Silicon nitride–silicon oxynitride (Si₃N₄–Si₂N₂O) in situ composites have been fabricated via either the annealing or the superplastic deformation of sintered Si₃N₄ that has been doped with a silica-containing additive. In this study, quantitative texture measurements, including pole figures and X-ray diffraction patterns, are used in conjunction with scanning electron microscopy and transmission electron microscopy techniques to examine the degree of preferred orientation and texture-development mechanisms in these materials. The results indicate that (i) only superplastic deformation can produce strong textures in the β-Si₃N₄ matrix, as well as Si₂N₂O grains that are formed in situ ; (ii) texture development in the β-Si₃N₄ matrix mainly results from grain rotation via grain-boundary sliding; and (iii) for Si₂N₂O, a very strong strain-dependent texture occurs in two stages, namely, preferred nucleation and anisotropic grain growth.     

Reaction Sintering and Properties of Silicon Oxynitride Densified by Hot Isostatic Pressing

Silicon oxynitride ceramics were reaction sintered and fully densified by hot isostatic pressing in the temperature range 1700°C to 1950°C from an equimolar mixture of silicon nitride and silica powders without additives. Conversion to Si₂N₂O increases steeply from a level around 5% of the crystalline phases at 1700°C to 80% at 1800°C, and increases a few percent further at higher temperatures. α -Si₃N₄ is the major residual crystalline phase below 1900°C. The hardness level for materials containing 85% Si₂N₂O is approximately 19 GPa, comparable with the hardness of Si₃N₄ hot isostatically pressed with 2.5 wt% Y₂O₃, while the fracture toughness level is around 3.1 MPa. m^1/2, being approximately 0.8 MPa.m^1/2 lower. The three-point bending strength increased with HIP temperature from approximately 300 to 500 MPa.