共查询到19条相似文献,搜索用时 109 毫秒
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溶胶—凝胶法制备莫来石晶须 总被引:3,自引:0,他引:3
用正硅酸乙酯,硝酸铝为原料,采用溶胶-凝胶工艺制备了Al2O3-SiO2干凝胶,通过高温热处理制得了直径为0.5-2.5μm,长径比为5-40的莫来石晶须。采用XRD,SEM,TEM和SADP等手段研究了莫来石晶须的晶相组成,形貌与生长方向,发现莫来石晶须是沿其c轴方向生长的。 相似文献
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分别采用CuTi、CuTi+B和CuTi+TiB2钎料,在钎焊温度为930℃,保温时间为10min条件下,钎焊连接Al2O3和TC4合金。通过扫描电子显微镜、透射电子显微镜和压剪试验等方法,研究了接头中生成的TiB晶须对接头组织结构及力学性能的影响。结果表明:B或TiB2粉的添加均可在钎焊接头中原位自生TiB晶须。当钎料中添加B粉时,接头中原位自生的TiB晶须比添加TiB2时的尺寸小。原位自生的TiB晶须可将Al2O3/TC4合金钎焊接头界面分为5个区域,各区分布满足延性–刚性–延性结构,此结构有助于减小降低接头残余应力,提高接头抗剪强度。采用CuTi+TiB2钎料时,Al2O3/TC4合金钎焊接头的抗剪强度最大为143 MPa,比用CuTi钎料时所获接头强度提高了239%。 相似文献
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磷石膏制备硫酸钙晶须的初步研究 总被引:1,自引:0,他引:1
以磷石膏为原料,直接采用水热法制备硫酸钙晶须,为磷石膏制备硫酸钙晶须的工业化生产提供重要理论依据。实验考察反应温度、料浆初始pH、反应时间、料浆浓度及磷石膏粒度对生成硫酸钙晶须的影响,用扫描电镜观察硫酸钙晶须的形貌,并通过偏光显微镜和图像分析软件分析不同反应条件下制备的硫酸钙晶须的直径和长度。结果表明:反应温度为130~140℃,料浆初始pH为4.0,反应时间为4 h,料浆质量分数为5%,原料粒度为50~75μm是生成硫酸钙晶须的最佳反应条件,在此条件下可制备出平均直径为2μm,长径比为42的硫酸钙晶须产品。 相似文献
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以页岩提钒中和渣为原料,采用水热法制备硫酸钙晶须,并进行稳定-改性处理,最终制备用于填充塑料的硫酸钙晶须填料。研究了反应温度、反应时间、料浆浓度及助晶剂用量对硫酸钙晶须长径比的影响以及改性剂用量、初始料浆浓度、改性温度及改性时间对硫酸钙晶须改性效果的影响。结果表明,在反应温度为130℃、反应时间为6 h、料浆质量分数为3%、助晶剂六水氯化镁用量为10%的条件下,制备出的硫酸钙晶须长径比达90,但晶须在空气中易水化变粗,长径比降至20以下。在硬脂酸用量为4%、初始料浆质量分数为8%、改性温度为90℃、改性时间为20 min的条件下,制备的硫酸钙晶须填料活性指数达0.72,吸油值为0.278 8 g/g,制得的硫酸钙晶须填料呈棒状或纤维状,表面光滑,结晶度较好,长径比稳定在40~50。结合XRD、SEM、FT-IR分析可知,硬脂酸能有效抑制晶须水化过程,保持晶须晶型及形貌稳定,硬脂酸通过与晶须表面发生化学键链接封闭其亲水活性点而抑制晶须水化。 相似文献
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通过溶胶─凝胶工艺制备了莫来石前驱体,加入适当矿化剂经高温煅烧合成了高纯、单相莫来石晶须。XRD及SEM分析结果显示:晶须直径为50~100nm,长度为3~8μm,晶须尺寸均匀性好,表面光洁,直晶率高。运用所制备的晶须制备了多孔基板试样,并与普通粒子堆积法烧成样品显微结构与性能进行比较,进而分析了低维晶须材料与普通粒子的堆积成孔方式的异同。在此基础上,对莫来石晶须在其它方面的应用进行了展望。 相似文献
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SiC晶须表面涂覆Al2O3的溶胶—凝胶工艺及机理 总被引:4,自引:4,他引:4
用异丙醇铝为先驱体通过溶胶-凝胶工艺成功地在SiC晶须表面涂覆了5—30nm的Al_2O_2涂层。认为SiC表面与Al(OC_2H_7)_2(OH)形成配位键并构成胶团是形成涂层的重要机制。研究了溶胶浓度、晶须预处理,晶须直径和反复涂层对涂层效果的影响。 相似文献
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Mullite whiskers were synthesized by a vapor-solid reaction. Mullite composition xerogels were fired at 900° to 1600°C with AlF3 in an airtight container. An average whisker increased in length from 7 μm at 1100°C to 10 μm at 1600°C, whereas an average whisker decreased in aspect ratio from 25 to 10 with increased firing temperature. The whiskers elongated to the c -axis and the side planes were the {110}. A clear lattice image corresponding to (110) lattice spacing up to the edges of the whiskers was observed with high-resolution electron microscopy, and no droplet was observed on the tips of the whiskers. The chemical composition of the whiskers synthesized below 1100°C showed an apparent Al2 O3 -rich composition of about 72 mol%. Composites reinforced by 15 vol% of mullite whiskers in the matrix of 75 vol% mullite/25 vol% Y-TZP enhanced the fracture toughness compared with those materials without mullite whiskers. 相似文献
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《Ceramics International》2022,48(10):14224-14230
A SiC whisker-bonded mullite foamed ceramic was prepared by using white clay, industrial alumina and silicon powder as raw materials without solid carbon sources. The XRD, SEM, EDS, and Factsage® software were used to investigate the effect of sintering temperature on the phase composition, microstructure, compressive strength, and Young's modulus of foamed ceramics. Additionally, the synthesis reaction of in-situ SiC whiskers and the effect of their formation on the properties of ceramics were studied. The results showed that the in-situ SiC whiskers with dendrite shapes were formed after firing above 1300 °C at the expense of Si/SiO vapors as well as CO vapor, though there were no solid carbon sources in raw materials, which provided a new idea for the synthesis of SiC whiskers. The formation of SiC whiskers was helpful for improving the compressive strength and Young's modulus of mullite foamed ceramics remarkably. Furthermore, the reinforcement mechanism has been investigated systematically. 相似文献
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Zhaoyang Liu Jingkun Yu Xiangnan Wang Jiakang Wang Ling Zhang Tianpeng Wen Danbin Jia Zhengguo Yan Lei Yuan Beiyue Ma 《International Journal of Applied Ceramic Technology》2022,19(3):1405-1414
Using recyclable industrial waste Si/SiC and Al2(SO4)3 as starting materials, urchin-like mullite whiskers were successfully synthesized via the molten salt method. The characterizations were focused on the phase transformations and morphology evolution of mullite whiskers. The circular oxidation-dissolution-precipitation mechanism was proposed for the growth of urchin-like mullite whiskers. Then, the pressing-sintering process was used for fabricating porous whisker-structured mullite ceramics for oil-water separation applications. Physical properties of porous ceramic, including bulk density, apparent porosity, mechanical and thermal shock resistance were measured. It was found that excessive reaction temperature could decompose the mullite, and a suitable temperature for pure urchin-like mullite whiskers was found to be 900°C. To achieve oil-water separation, bionic surface grafting technology was used for coating a hydrophobic and lipophilic material (octadecylamine, ODA) on mullite ceramic. Oil adsorption capacities of the ceramic/ODA for various oils, that is, .27 and .24 g/g for cooking and motor oil, respectively, were successfully achieved. 相似文献
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Microstructural evolution and densification behavior of porous kaolin-based mullite ceramic added with MoO3 were investigated. The results indicated that MoO3 addition not only lowered the secondary mullitization temperature to below 950?°C, but also facilitated effectively the anisotropic growth of mullite grains. Fine mullite whiskers grew and interlocked with one another in the pre-existing pore regions, in-situ forming a stiff 3D skeleton structure of mullite whiskers, which arrested further densification of the sample. On the other hand, due to the great capillary attraction of small pores, the liquid phase tended to spread over small grains, which favored the growth from small mullite grains into whiskers at the expense of the liquid phase. Consequently, competitive mechanisms of sintering and crystal growth of mullite functioned, which further limited the sample densification. As a result, the total linear shrinkage of the sample added with MoO3 after firing at 1400?°C was only ??2.75%, and its porosity was retained at as high as 67%. 相似文献
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《Journal of the European Ceramic Society》2022,42(13):5984-5994
Mullite fibers/whiskers hierarchical structure materials (MFWs) were prepared via the three-stage method, i.e. seeds breeding, precursors introducing and whiskers growth. The mechanism of low-temperature in-situ synthesis of mullite whiskers during gas-phase reaction process has been discussed in detail. The seeds bred on mullite fibers (MFs) are the growth points and can effectively reduce the subsequent growth temperature of mullite whiskers (MWs). The precursors composed of aluminum source, silicon source and catalyst provided raw materials for whiskers growth. Under the heat treatment temperature of 800 °C, mullite seed grains were guided to in-situ transform into MWs. Moreover, MFWs fabricated via low-temperature in-situ growth mechanism on the MFs present low density (0.103–0.147 g/cm3) and ultralow thermal conductivity (0.0426–0.0514 W·m?1·K?1). Due to the lower whiskers growth temperature in this work than the ones in the most recent literatures, the three-stage method can be regarded as a viable strategy for low-temperature in-situ growth whiskers. 相似文献
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Self-reinforced porous mullite ceramics were fabricated by a starch consolidation method with flyash, different aluminium sources (Al(OH)3 and Al2O3) and the additive AlF3 as raw materials. The reinforcement mechanism of needle-like mullite whiskers through in situ synthesis in ceramic body was investigated. The bulk density, apparent porosity and bending strength of the samples were tested. Phase compositions and microstructures of the sintered samples were measured by XRD and SEM, respectively. It showed that AlF3 as additive was helpful to the formation of mullite whiskers at a low temperature. As the aluminium sources, Al(OH)3 was more suitable for the preparation of mullite whiskers than Al2O3. The in situ synthesized mullite whiskers formed an interlocking structure, which enhanced the mechanical strength of the porous mullite ceramics. Porous mullite ceramics with bending strength of about 100 MPa and apparent porosity of about 55% were made at 1550 °C. 相似文献