凝胶注模法制备多孔碳化硅支撑体

以大颗粒碳化硅(SiC)为陶瓷骨料,采用凝胶注模法制备支撑体生坯,原位反应烧结制备大孔径、高渗透性的多孔SiC陶瓷支撑体,主要考察了有机单体含量和烧结制度对高温气固分离用陶瓷膜支撑体性能的影响.研究结果表明:适宜的有机单体含量有助于SiC颗粒稳定分散在悬浮液中,提高烧结温度和延长保温时间均可增加SiC颗粒的氧化程度,在1 550℃时,XRD图谱显示莫来石相生成,支撑体的抗弯强度有一定程度的提高.采用凝胶注模法制备的生坯在1 550℃,保温4h烧结后具有良好的性能:抗弯强度为20.4 MPa,孔隙率为37%,平均孔径为23μm,气体渗透率为2.01×10-12 m2.     

原位反应烧结法制备SiC多孔木材陶瓷

以香杉木粉、硅粉和环氧树脂为原料,先低温制成木材陶瓷,然后利用高温原位反应烧结工艺制成了具有原木微观结构的SiC多孔木材陶瓷。TGA研究了木粉和环氧树脂的热分解行为,用XRD和SEM研究SiC多孔木材陶瓷的物相组成和微观结构,用阿基米德法测定SiC多孔木材陶瓷的显气孔率,系统研究了烧结温度和成分配比对SiC多孔木材陶瓷的摩擦学性能的影响。结果显示：SiC多孔木材陶瓷具有类似于原始木材的微观管胞结构;显气孔率随着烧结温度的升高而降低,但随着Si含量的升高而升高;在1600℃下制备的SiC多孔木材陶瓷具有良好的摩擦学性能,后期析出的碳颗粒可以有效降低磨损量。     

SiC /AZ61镁基复合材料蠕变性能的研究

采用搅熔铸造法制备碳化硅颗粒增强镁基复合材料SiC/AZ61,通过动态机械热分析、显微组织观察和XRD衍射分析了其蠕变性能.结果表明:碳化硅颗粒的加入细化了晶粒,SiC大多分布在晶界处,颗粒镁基复合材料的蠕变性能与AZ61合金相比得到了显著的改善.蠕变性能的提高主要因为高温时具有高的热稳定性的SiC颗粒取代晶界处高温下易软化的β相(Mg17Al12)钉扎晶界,阻止了晶界的交滑移和位错的攀移.     

以硅藻土为硅源制备SiC/堇青石复合多孔陶瓷的性能研究

以硅藻土为主要硅源,同时配合SiC、Al_2O_3、滑石粉末为主要原料,通过反应烧结技术制备SiC/堇青石复相多孔陶瓷,研究了不同原料配比对SiC/堇青石复相多孔陶瓷的相组成、显微结构、抗弯强度、气孔率的影响,同时在得出最优配比组的基础上,研究石墨造孔剂的含量、碳化硅颗粒粒径、孔径分布等因素对SiC/堇青石复相多孔陶瓷的影响。结果表明:当SiC与其余物料理论质量比为8∶2时,在1250℃下保温3h制备的样品综合性能最佳,其气孔率为37.721%,抗弯强度达到49.1887 MPa。     

烧结温度对SiC多孔陶瓷性能的影响

采用反应烧结工艺,通过改变烧结温度,制备出了一系列不同烧结温度下（1 600,1 630,1 660和1 690℃）的SiC多孔陶瓷粉体。通过XRD、SEM、气孔测试、压缩强度测试和油水分离测试等,对SiC多孔陶瓷的物相结构、微观形貌、孔隙率、力学性能等进行了表征。结果表明,随着烧结温度的升高,SiO₂的特征衍射峰强度逐渐升高,在1 690℃时SiO₂的特征衍射峰强度最高;SiC多孔陶瓷的气孔随温度升高呈现出先降低后增加的趋势,在1 660℃时气孔率最低为32.1%;SEM分析发现,1 600和1 630℃下烧结的SiC多孔陶瓷中的小颗粒较多,且SiC多孔陶瓷的颗粒较为分散,随着烧结温度的升高,小颗粒相逐渐减少,SiC多孔陶瓷整体逐渐收缩紧密,晶粒逐渐长大。力学性能分析表明,随着烧结温度的升高,SiC多孔陶瓷的压缩强度先升高后轻微下降,在1 660℃时压缩强度达到了最大值25.6 MPa。油水分离测试发现,随着烧结温度的升高,SiC陶瓷的膜通量出现了先降低后有略微升高的趋势,截留率出现了先升高后轻微降低的趋势,在烧结温度为1 660℃时,膜通...     

纳米碳含量对碳/碳化硅陶瓷的机械加工性及与玻璃熔体润湿性的影响

采用无压烧结法制备纳米碳颗粒(nano-Cp)改性碳化硅陶瓷 (C_p/SiC), 研究了不同纳米碳含量对C_p/SiC陶瓷的机械加工性及与玻璃熔体润湿性的影响。通过XRD和SEM对C_p/SiC陶瓷进行物相和显微分析。研究结果表明: 随着可加工相纳米碳含量的增加, C_p/SiC陶瓷的机械加工性能得到明显改善。根据陶瓷材料的机械加工指数(M)综合评价, M₁₅=0.921＞M₂₅=0.547＞M₅=0.056＞M₀=0.021(下标数字代表碳含量), 且15wt%C_p/SiC中的碳颗粒预先被氧化, 抑制了C_p/SiC陶瓷基体表面形成SiO₂, 阻止了C_p/SiC陶瓷与玻璃熔体的润湿, 使夹具材料与玻璃熔体不发生粘接, 适合用作玻璃夹具材料。     

原位反应结合碳化硅多孔陶瓷的制备与性能

以碳化硅(SiC)和氧化铝(Al₂O₃)为起始原料、石墨为造孔剂, 通过原位反应结合工艺制备SiC多孔陶瓷. XRD分析表明多孔陶瓷的主相是SiC, 结合相是莫来石与方石英; SEM观察到多孔陶瓷具有相互连通的开孔结构. 坯体在烧结前后具有很小的尺寸变化, 线收缩率约在±1.5%内. 多孔陶瓷的开口孔隙率随烧结温度和成型压力的增大而减小, 随石墨加入量的增加而增大; 而体密度具有相反的变化趋势. 随着石墨粒径的增大, 多孔陶瓷的孔径分布呈现双峰分布. 抗弯强度随烧结温度和成型压力的增大而增大, 随石墨加入量的增大而减小. 于1450℃保温4h烧成的样品在0～800℃的平均热膨胀系数为6.4×10^-6/K. 多孔陶瓷还表现出良好的透气性、抗高温氧化和耐酸腐蚀性, 但耐碱腐蚀性相对较差.     

4 μm SiC颗粒表面化学镀铜工艺

为了增强微米级SiC陶瓷颗粒与金属基体的结合力,采用化学镀铜法对SiC颗粒表面进行了改性处理,使SiC颗粒在金属基体液中分散更均匀、镀覆更好。通过正交试验法优化了化学镀铜工艺的主要参数,研究了其主要工艺条件对化学镀铜的影响;分别通过JSM7500F,S-3400N扫描电镜(SEM)对微米级SiC颗粒镀铜前后的表观形貌进行了观察分析,利用X射线衍射仪(XRD)对其镀铜前后的组成进行了表征,并测试了镀铜层与SiC颗粒的结合力;同时对比了微米级SiC颗粒镀铜前后对锌基复合材料微观形貌的影响;讨论了镀液中配位剂、pH值、还原剂等对铜镀层的影响。结果表明:随着镀液中配位剂、还原剂含量的增加,单位时间内微米级SiC颗粒表面镀铜层的质量先增加后降低,pH值的升高显著降低了镀铜的诱导时间;可实现微米级SiC颗粒表面化学镀铜层的均匀镀覆,且结合良好。     

新型多孔碳化硅陶瓷膜管的制备与性能表征

以SiC为骨料,选用低共熔混合物作为烧结助剂,用液相烧结技术制备出单通道多孔陶瓷支撑体,采用悬浮粒子浸涂法对支撑体涂覆氧化铝膜.考察了氧化铝膜、烧成温度对支撑体孔径分布和空气渗透通量等性能的影响.结果表明:涂膜后膜管的孔径分布变窄,空气渗透通量略有下降;随着烧结温度的提高,结合剂的高温特性使得支撑体的开孔率和空气渗透通量分别下降了1.9%和17.9 m3/(m2·h),孔径分布变宽,平均孔径增大.     

造孔剂含量对多孔BiScO3-PbTiO3高温压电陶瓷性能的影响

为研究造孔剂含量对多孔BiScO_3-PbTiO_3(记作BS-PT)高温压电陶瓷性能的影响,采用炭黑作为造孔剂,通过传统固相烧结法对不同初始固相体积分数的准同型相界附近的BS-PT/炭黑混合物制备出多孔高温压电陶瓷.利用X射线衍射仪对多孔陶瓷进行物相分析,通过扫描电子显微镜观察样品的新鲜断面和抛光热腐蚀后的表面显微结构,并对其压电、介电和水声性能进行研究.结果表明:制备的不同初始BS-PT体积分数多孔压电陶瓷均为立方钙钛矿相结构,孔隙通道密实化清晰可见,没有显著的缺陷,气孔的形状是长条形的,长度从几微米到几十甚至上百微米不一,气孔之间是孤立的;随着造孔剂炭黑的体积分数从20%增加至50%,气孔率线性地从8.3%增加至22.1%,εr、d33及d31逐渐下降,静水压优值(HFOM)逐渐增大.多孔压电陶瓷的性能强烈依赖于孔隙空间结构,如气孔率、孔径、孔隙形态及连接方式.     

含前驱体SiC粉体低压成型低温烧结SiC多孔陶瓷

采用聚碳硅烷和SiC粉体为原料低压成型低温烧结制备SiC多孔陶瓷,研究了聚碳硅烷含量对SiC多孔陶瓷性能的影响。SEM分析表明,聚碳硅烷裂解产物将SiC颗粒粘结起来,多孔陶瓷具有相互连通的开孔结构。烧成SiC多孔陶瓷的孔隙孔径为单峰分布、分布窄,室温至800℃之间多孔陶瓷的平均热膨胀系数为4.2×10-6 K-1。随着聚碳硅烷含量的增大,SiC多孔陶瓷的孔隙率降低、三点弯折强度增大,当聚碳硅烷质量分数为10%时分别为44.3%和31.7MPa。     

Low-temperature processing of porous SiC ceramics

Porous silicon carbide ceramics were fabricated from SiC, polysiloxane, and polymer microbead (as a pore former) at a temperature as low as 800 °C by a simple pressing and heat-treatment process. The effects of polysiloxane and template contents on the porosity and strength of the ceramics were investigated. During heat treatment, the polysiloxane transformed to an amorphous SiOC phase, which acted as the bonding material between SiC particles, and the polymer microbeads decomposed into gases and left pores. The porosity of porous SiC ceramics could be controlled within a range of 26–56 % with the present set of processing variables. The porous SiC ceramics showed a maximal porosity of 56 % when 10 μm SiC particles and 16 % polysiloxane were used with 20 % polymer microbeads. Flexural strength generally increased with increasing polysiloxane content and decreased with increasing polymer microbead content. Typical flexural strength of the porous SiC ceramics was 53 MPa at 42 % porosity.     

Mechanical and microstructural properties of cordierite-bonded porous SiC ceramics processed by infiltration technique using various pore formers

Cordierite-bonded porous SiC ceramics were prepared by air sintering of cordierite sol infiltrated porous powder compacts of SiC with graphite and polymer microbeads as pore-forming agents. The effect of sintering temperature, type of pore former and its morphology on microstructure, mechanical strength, phase composition, porosity and pore size distribution pattern of porous SiC ceramics were investigated. Depending on type and size of pore former, the average pore diameter, porosities and flexural strength of the final ceramics sintered at 1400 °C varied in the range of ~ 7.6 to 10.1 µm, 34–49 vol% and 34–15 MPa, respectively. The strength–porosity relationship was explained by the minimum solid area (MSA) model. After mechanical stress was applied to the porous SiC ceramics, microstructures of fracture surface appeared without affecting dense struts of thickness ~ 2 to 10 µm showing restriction in crack propagation through interfacial zone of SiC particles. The effect of corrosion on oxide bond phases was investigated in strong acid and basic salt medium at 90 °C. The residual mechanical strength, SEM micrographs and EDX analyses were conducted on the corroded samples and explained the corrosion mechanisms.     

含先驱体聚合物浆料浇注成型制备SiC多孔陶瓷

采用SiC粉体与聚碳硅烷(PCS)为原料浇注成型低温烧结制备SiC多孔陶瓷,研究了PCS含量对SiC多孔陶瓷性能的影响。结果表明,PCS含量大于2wt%时可浇注成型,PCS经烧结后生成裂解产物将SiC颗粒粘结起来。所得SiC多孔陶瓷孔径呈单峰分布、孔径分布窄、热膨胀系数低、烧结过程中线收缩率小。随着PCS含量的增大烧成SiC多孔陶瓷的孔隙率降低,但强度显著提高。PCS含量为6wt%时多孔陶瓷的孔隙率、弯折强度和线收缩率分别为36.2%、33.8MPa和0.42%。     

固相烧结SiC陶瓷

实验采用α-SiC,β-SiC和（1％αSiC＋99％β-SiC作为起始粉末,以B,C为添加剂,热压烧结SiC陶瓷,其烧结过程中尽管发生多型体之转的转变,但其现现形式为α-SiC的6H→4H,和β-SiC的3C→6H两种形式,尽管有大量的长柱颗粒生成,但是由于没有弱的界面结合,不能原位增强。     

原位增强SiC陶瓷

实验采用β-SiC为起始原料,Y₂O₃、A1₂O₃为烧结助剂,通过适当的烧结控制,获得了具有长柱状晶粒结构的α－SiC陶瓷,材料以液相烧结机制密化,在烧结过程中发生了与柱状晶形成有关的SiC晶粒3C→4H相变．材料的力学性能与晶粒的形态即长径比存在一定的依从关系,并显示出原位增强的特性．在较佳工艺条件下,材料的强度和韧性最大值分别达到620MPa、6．1MPa.m^1/2．压痕裂纹扩展的途径表明,裂纹偏转和晶粒桥联是主要的增韧机理,这得益于其弱的界面结合．     

微孔碳陶瓷化反应机理的研究

研究了微孔碳制备SiC陶瓷的反应过程及反应机理.SiC陶瓷的最终组织受C/Si质量比及渗硅时间的影响.较低C/Si质量比时试样中心未被硅化,较高C/Si质量比时制得由SiC、Si及极少量未反应C组成的复相陶瓷.随渗硅时间延长,复相陶瓷中SiC颗粒的形状由长条状向无规则状转变,颗粒分布则由局部有序向无序转变.反应过程为：液硅因毛细作用自发的渗入微孔碳孔道,同时与溶解的碳壁发生反应生成SiC.因孔道及碳壁尺寸的不同造成液硅渗入深度和碳壁被溶解厚度的差异,结果出现被SiC包裹的小颗粒碳.随后被包裹的碳通过SiC层扩散到液硅中,沉积在先形成的SiC上促使大量先形成SiC的合并以及部分硅被SiC包裹,进而改变SiC陶瓷的显微组织.     

Preparation and properties of mullite-bonded porous SiC ceramics using porous alumina as oxide

Mullite-bonded porous silicon carbide ceramics were prepared by an in situ reaction bonding technique and sintering in air with SiC, porous Al₂O₃, and graphite as starting materials. The pores in the ceramics were formed by burning graphite and by stacking particles of SiC and Al₂O₃. The surface of SiC was oxidized to SiO₂ at high temperature. With a further increase in temperature, SiO₂ reacted with Al₂O₃ to form mullite. The reaction-bonding characteristics, phase composition, open porosity, mechanical strength as well as the microstructure of porous SiC ceramics were investigated.     

Fabrication and characterization of highly porous mullite ceramics

Highly porous mullite ceramics were fabricated by a reaction-bonding technique from a powder mixture of Al₂O₃ and SiC, with graphite particles as the pore-forming agent. The effects of sintering temperature on porosity and strength as well as pore size and surface area were investigated. It has been shown that the strength and pore size increase but the porosity and surface area decrease with the increase in sintering temperature. Due to the formation of a fine-grained microstructure with well-developed necks, an average strength up to 106 MPa was achieved at a porosity of 32.4%. On the other hand, a relatively high surface area of 12.4 m² g⁻¹ was obtained for a 61% porous mullite ceramic, which was observed to have a good thermal-shock resistance to crack propagation.