原位形成氧氮玻璃中间层连接Si3N4陶瓷

用Si3N4-Al2O3-Y2O3-SiO2混合粉制备用于连接氮化硅陶瓷的焊料,原位形成以氧氮玻璃为中间层的氮化硅陶瓷接头.研究了连接过程中温度、压力及气氛对陶瓷接头微观组织及性能的影响.结果表明:在0.1 MPa氩气条件下,接头内含有一定量气孔,氮化硅母材有少量分解;氮气气氛、0.1 MPa条件下可保证陶瓷母材稳定、接头致密,在氧氮玻璃中间层均匀分布有β-SiAlON陶瓷相;当氮气气压增大到0.5 MPa时,陶瓷接头无法实现有效连接.在较低温度下,当连接压力由0.6 MPa增大到1.5 MPa时,接头弯曲强度提高;升高温度,接头强度出现峰值,在1550℃时达到最高,连接压力对接头的影响减小;继续增大压力将使液相焊料流出,甚至母材自身发生变形.     

Al2O3/Al2O3扩散连接机理的研究

采用热压方式进行氧化铝陶瓷材料的扩散连接，并深入探讨了其连接机理，结果表明：采用适当的连接工艺，可使此种材料产生塑性形变，接触面积增加，空洞收缩和闭合，扩散进行充分，1420℃，15MPa热压60min条件下，获得的最高强度为357MPa，超过母材强度平均连接强度为250MPa，是母材平均强度的85％。     

Si3N4／Si3N4陶瓷连接的研究进展

本文综述了Ｓｉ３Ｎ４／Ｓｉ３Ｎ４陶瓷连接的研究现状，论述不同连接工艺对接头强度的影响。     

Si3N4／Si3N4陶瓷连接的研究进展

连接技术是Ｓｉ３Ｎ４陶瓷实用过程中必须解决的难题之一。本文综述了Ｓｉ３Ｎ４／Ｓｉ３Ｎ４陶瓷连接的研究现状以及不同连接工艺对连接强度的影响。     

RE-Si-Al-O-N(RE=Y或Lu)连接Si_3N_4陶瓷接头的微观组织与性能

通过添加稀土Y或Lu,设计Si3N4–Al2O3–RE2O3–Si O2(RE-Si-Al-O-N,RE=Y或Lu)混合粉末焊料,原位形成以RE-Si-Al氧氮玻璃为中间层的氮化硅陶瓷接头。研究了连接过程中陶瓷接头微观组织与性能随连接温度、保温时间、稀土类型的变化,并分析了接头高温氧化行为。结果表明,采用Y-Si-Al-O-N焊料时,保温时间延长有利于接头内组织均匀化、焊缝致密化及焊料与母材间的相互扩散,形成良好连接。接头强度随保温时间延长先升高后降低,保温30 min时,接头强度出现峰值(218 MPa)。接头经1 200℃氧化20 h后仍保持原始强度的82%。采用Lu-Si-Al-O-N玻璃连接氮化硅,随连接温度升高,焊缝致密化程度提高,?-sialon相增加,连接强度呈现升高趋势。     

ZrSiO4对Si3N4结合SiC制品强度和抗氧化性的影响

研究了硅酸锆 (ZrSiO4)添加物对氮化硅结合碳化硅制品性能尤其是强度和抗氧化性能的影响 ,分析了其作用机理。研究结果表明 ,硅酸锆可显著提高氮化硅结合碳化硅制品的抗氧化性能 ,但提高制品强度的作用较小。     

烧结工艺对Si3N4泡沫陶瓷性能的影响

本文在有机泡沫浸渍法制备多孔氮化硅陶瓷的过程中,讨论了升温速度、烧结助剂的添加量和烧结温度对氮化硅网眼多孔陶瓷显微组织、物相和力学性能的影响.研究结果表明,随Y2O3和Al2O3的含量的增加,烧结体的强度明显增加,且含量为20%时较优.通过分析聚氨酯海绵的DSC-TDA曲线,得出在150～475 ℃温度区间,要缓慢升温.烧结温度在1700 ℃左右较优,且相变较完全.     

Al和Si对MgO-Si3 N4复合材料强度和显微结构的影响

以电熔镁砂、氮化硅与Al或Si为原料,制备的试样经1400℃烧后制成了MgO-Si3N4复合材料,研究了金属Al或Si对MgO-Si3N4复合材料强度的影响.发现Al或Si的加入均可显著提高MgO-Si3N4复合材料的常温耐压强度和高温抗折强度(1400℃).然后借助SEM和EDAX等手段研究了加入4%Al或Si的MgO-Si3N4复合材料的显微结构,揭示了金属Al和Si的增强作用机理体系中的Al转化为晶须状的氮氧化物,起纤维增韧作用;体系中的Si转化为粒状或絮状的氮化硅,起颗粒增强作用.     

Si3N4结合SiC制品中SiO2含量的测定

氮化硅结合碳化硅制品具有耐磨损,抗侵蚀,高温强度大,抗热震性好等优点,近年来其应用领域不断扩大,用量正在迅速增加。其中杂质SiO2直接影响氮化硅结合碳化硅制品的抗碱蚀能力,其含量是氮化硅结合碳化硅制品的重要质量指标之一。目前,这类材料中SiO2的测定方法还没有国家标准。     

Si3N4陶瓷注射成形研究进展

氮化硅陶瓷具有高强度、高硬度、耐高温、耐腐蚀、导热性好、摩擦系数小、热膨胀系数小、抗热震性好等优点,是耐高温、耐磨的理想结构材料之一。由于氮化硅硬度大．难以用传统的加工方法进行加工,限制了其在一些领域的广泛应用。陶瓷注射成形的出现为氮化硅陶瓷再添生机,氮化硅注射成形不仅可净尺寸成形各种形状复杂的异形件．而且成形产品具有较高的表面光洁度和尺寸精度。本文较详细介绍了陶瓷注射成形的工艺过程及Si3N4陶瓷注射成的研究讲展．最后对Si3N4陶脊沣射成形枯术讲行了展望．     

A Crystalline Si3N4/Amorphous Si3N4 Composite

A composite consisting of elongated α-Si₃N₄ crystallites (5–50 (Am in diameter) embedded in an amorphous Si₃N₄ matrix was synthesized by chemical vapor deposition. The hardness and indentation fracture toughness of the amorphous matrix and of the composite have been evaluated at temperatures from ambient to 1200°C. It was found that the crystallites have relatively little influence on the hardness and indentation fracture toughness when the surrounding matrix is amorphous. However, a 1400°C heat treatment of the material results in a matrix consisting of small crystals (100 nm in diameter) surrounded by carbon-containing regions which appear to be amorphous in the TEM; TEM and EELS in nearby triple points revealed the presence of amorphous carbon. After heat treatment, the indentation fracture toughness at ambient and at 1200°C is increased due to extensive microcracking. The Vickers hardness at 1200°C also increased significantly as a result of the heat treatment. The relationship between the mechanical properties and the microstructure is discussed.     

氮化硅及其微粉的制备

介绍了氮化硅的性能、应用范围以及其微粉的制备方法。     

氮化硅及其微粉的制备

本文介绍了氮化硅的性能、应用范围以及其微粉的制备方法。     

Formation mechanism of Si3N4 in reaction-bonded Si3N4-SiC composites

The formation mechanism and thermodynamics of Si₃N₄ in reaction-bonded Si₃N₄-SiC materials were analyzed. There are two kinds of Si₃N₄, fibroid α-Si₃N₄ and columnar β-Si₃N₄, which are formed by different processes in Si₃N₄-SiC materials. Silicon reacts with oxygen, forming gaseous SiO and reducing oxygen partial pressure. SiO(g) diffuses from central to peripheral sections of blocks and reacts with nitrogen, thus forming Si₃N₄, mainly in peripheral sections. The reaction between silicon and oxygen causes the consumption of oxygen and leads to low oxygen partial pressure in the sintering system, which allows silicon to react with nitrogen directly generating Si₃N₄in situ. SiO(g) reacts with nitrogen forming Si₃N₄ at both central and peripheral sections of block. The non-uniform distribution of Si₃N₄ and uneven microstructure is caused by the generation process, indicating that it is unavoidable in Si₃N₄-SiC composites.     

Fabrication of Si3N4 preforms from Si3N4 produced via CRN technique

Ceramic preforms with randomly distributed particles as reticulated porous structure which are generally used for metal infiltration as reinforcement, membranes, catalyst supports etc. Preforms are characterized by open porosity making possible their infiltration by liquid metal alloys. In this work, quartz powders using carbon black as a reducing agent were used for alpha Si₃N₄ powders synthesis through a carbothermal reduction and nitridation (CRN) process. The CRN process was carried out under nitrogen flow at 1,450 °C for 4 h. At high temperatures, carbon as reducing agent reacts with the oxygen of SiO₂, and the resulting metallic silicon compounds with nitrogen gas to obtain silicon nitride powder. The reacted powders were used to obtain reticulated ceramic by replica method. The powders containing various bentonite ratios were mixed in water to prepare slurry. The slurry was infiltrated into a polyurethane sponge. A high porous ceramic foam (preform) structure was achieved after burn out of the sponge. All ceramic preforms were sintered to increase stiffness (in the temperature range 900–1,350 °C). The sintered ceramic foams were subjected to compressive tests. The scanning electron microscopy was used to examine the reticulated ceramic foam structure, and X-ray diffraction analysis was performed to determine phases.     

Si3N4含量对Si3N4-SiC材料腐蚀性能的影响

利用Si3N4—SiC材料在冰晶石静态融盐电解质中的腐蚀实验研究材料的腐蚀性能,对腐蚀增重率进行记录分析,Si3N4的含量是影响材料腐蚀性能的重要因素,根据实验测定得出Si3N4的含量越高,Si3N4-SiC材料腐蚀程度越严重。     

Preparation and mechanical properties of Si3N4 nanocomposites reinforced by Si3N4@rGO particles

A new type of reduced graphene oxide-encapsulated silicon nitride (Si₃N₄@rGO) particle was synthesized via an electrostatic interaction between amino-functionalized Si₃N₄ particles and graphene oxide (GO). Subsequently, the Si₃N₄@rGO particles were incorporated into a Si₃N₄ matrix as a reinforcing phase to prepare nanocomposites, and their influence on the microstructure and mechanical properties of the Si₃N₄ ceramics was investigated in detail. The microstructure analysis showed that the rGO sheets were uniformly distributed throughout the matrix and firmly bonded to the Si₃N₄ grains to form a three-dimensional carbon network structure. This unique structure effectively increased the contact area and load transfer efficiency between the rGO sheets and the matrix, which in turn had a significant impact on the mechanical properties of the nanocomposites. The results showed that the nanocomposites with 2.25 wt.% rGO sheets exhibited mechanical properties that were superior to monolithic Si₃N₄; the flexural strength increased by 83.5% and reached a maximum value of 1116.4 MPa, and the fracture toughness increased by 67.7% to 10.35 MPa·m^1/2.     

Sn/Si3N4复合镀层中纳米Si3N4含量测定方法的比较

采用电熔解法溶解Sn/Si3N4复合镀层,以紫外可见分光光度法测定了镀层中纳米Si3N4的含量,并与传统酸溶解及重量法对比。结果表明,电解法在10 min内使镀层完全溶解且在测定波长448 nm处纳米Si3N4溶液的吸光度值与其浓度在10～200 mg/L范围保持良好的线性关系,该方法简单,省时,误差小,回收率98.5%～100%。     

低成本氮化硅陶瓷

1 前言氮化硅陶瓷是典型的高温高强结构陶瓷，具有良好的室温及高温机械性能，强度高，耐磨性强，抗热震性能好，是结构陶瓷研究中最为广泛深入的材料，同时也是陶瓷发动机、陶瓷刀具、耐磨件及其它高温结构件的首选材料。但长期以来，制造氮化硅陶瓷的原材料和生产工艺的费用一直非常高，从而导致了氮化硅陶瓷生产的高成本和氮化硅陶瓷制品价格的昂贵。基于此原因，氮化硅陶瓷一直来仅在一些尖端高科技领域得以应用。最近，研究人员已研究开发了一项新的低成本氮化硅陶瓷生产技术，该技术能在很大程度上降低氮化硅陶瓷的生产成本。该技术的…     

纳米氮化硅粉体的制备

本文用碳热还原法制备了纳米氮化硅粉体,研究了纳米氮化硅颗粒的表面形貌及其电子自旋共振谱。