无压自浸渗法制备SiCp／AI复合材料的概况

概述了无压自浸渗法制备SiCp／AI复合材料的理论及现状，介绍了利用无压自浸渗法制备SiCp／AI复合材料最佳工艺条件，并就过程中工艺参数对浸渗和材料性能的影响进行了分析。     

SiCp/Al复合材料的自发熔渗机理

以Mg为助渗剂,采用液态铝自发熔渗经氧化处理的SiC粉体压坯的方法,制备出高增强体含量的SiCp/Al复合材料.通过考察铝液在SiC粉体压坯中的渗入高度与温度、时间的关系来研究铝液的熔渗机理,并对SiCp/Al复合材料进行X射线衍射、能量散射谱和金相分析.结果表明:在熔渗前沿发生的液-固界面化学反应促进两相润湿,毛细管力导致铝液自发渗入到SiC多孔陶瓷中;熔渗高度与时间呈抛物线关系.熔渗激活能为166 kJ/mol,这表明渗透过程受界面反应控制.经氧化处理的SiC粉体均匀地分布在金属基体中,其轮廓清晰.在SiCp/Al复合材料中未发现Al4C3的存在.     

界面SiO2层对SiC/Al电子封装材料热膨胀系数的影响

用无压浸渗的方法制备了高体积分数的SiC/Al复合材料.通过改变SiC预制样品的烧结工艺来改变SiC和Al的界面状况,分析了SiC表面SiO2层的变化对SiC/Al复合材料的热膨胀系数的影响.用无压浸渗的方法可得到常温下热膨胀系数为(5.68～7.12)×10-6/K的SiC/Al复合材料.颗粒大小一定时,复合材料的热膨胀系数随着SiO2界面层的厚度增加而减小.当界面SiO2层厚度从45 nm增加到2100 nm时,常温下热膨胀系数从7.12×10-6/K减小到5.68×10-6/K.     

高体分SiCp/Al复合材料新型制备工艺研究

系统简要地介绍了低成本无压浸渗近净形制备加工高体分SiCp/Al复合材料的新技术。以碳化硅颗粒体分约为45％的制备态材料为例，对其基本力学性能、热物理性能及阻尼性能进行了测试。通过对比和分析，揭示了这种技术的优势所在，以及该结构／功能一体化复合材料最具前景的几个应用方向。     

SiCp/Al复合材料的应用及无压渗透法制备

综合介绍了SiCp／Al复合材料的性能、应用及其制备方法。着重介绍了无压渗透法,指出了该工艺的优缺点。对SiCp／Al系统的润湿性及改善润湿性的方法作了论述。     

镁含量对无压浸渗SiC/Al复合材料性能的影响

以SiC粉及铝合金(3%Mg(质量分数)、5%Mg、7%Mg、10%Mg)为主要原料,采用无压浸渗工艺制备得到了SiC/Al复合材料。表征了SiC/Al复合材料的物相组成、显微结构、力学性能及热导率,研究了合金中Mg含量对SiC/Al复合材料结构组成、力学及热学性能的影响。结果表明:制备得到的SiC/Al复合材料主晶相均为SiC与Al。适量Mg的引入有助于改善铝合金与SiC颗粒间的浸渗性能,能有效促进SiC/Al复合材料的界面反应。其中引入5%Mg样品的显微结构较为致密,综合性能较优,其气孔率为0.13%,体积密度为2.94 g/cm³,抗弯强度为(366.36±14.37) MPa,断裂韧性为(9.2±0.27) MPa·m^1/2,热导率为178.81 W/(m·K)。     

镁含量对无压浸渗SiC/Al复合材料性能的影响EI北大核心CSCD

以SiC粉及铝合金(3%Mg(质量分数)、5%Mg、7%Mg、10%Mg)为主要原料,采用无压浸渗工艺制备得到了SiC/Al复合材料。表征了SiC/Al复合材料的物相组成、显微结构、力学性能及热导率,研究了合金中Mg含量对SiC/Al复合材料结构组成、力学及热学性能的影响。结果表明:制备得到的SiC/Al复合材料主晶相均为SiC与Al。适量Mg的引入有助于改善铝合金与SiC颗粒间的浸渗性能,能有效促进SiC/Al复合材料的界面反应。其中引入5%Mg样品的显微结构较为致密,综合性能较优,其气孔率为0.13%,体积密度为2.94 g/cm3,抗弯强度为(366.36±14.37)MPa,断裂韧性为(9.2±0.27)MPa·m1/2,热导率为178.81 W/(m·K)。     

无压浸渗法制备碳化硅颗粒增强铝基复合材料工艺研究

用有预制型的无压浸渗法制备了体积分数高达75%的碳化硅颗粒增强铝基复合材料.研究了各工艺参数对复合材料制备过程与性能的影响.结果表明:SiO2氧化膜、N2气氛和充分的保温时间有利于浸渗;浸渗温度选择1000℃比较合适;Mg的质量分数为10%时浸渗能顺利进行.     

SiC／Al复合材料的组织与力学性能研究

采用无压浸渗法制备了SiC／Al复合材料．研究不同颗粒大小的复合材料的抗弯强度、金相组织和断裂机理。结果表明：颗粒尺寸为20um的SiC／Al复合材料抗弯强度最高：小颗粒复合材料的断裂以沿晶断裂为主，局部有韧性撕裂的特征，而大颗粒还伴有穿晶解理特征。     

Lanxide~(TM)法制备SICp/AI复合材料

LanxideTM技术是制备铝基复合材料的一种新方法,适于制备低孔隙率的 MMC。本文对利用该技术制备 SiCp/Al复合材料进行了综述,阐述了 Al对 SiCp的润湿、渗透及界面反应等问题,并介绍了增强 SiCp/Al的润湿、渗透及控制界面反应的方法。     

Kinetic Study of Cobalt Silicide Infiltration into Silicon Carbide Preforms

Infiltrations of titanium-doped cobalt silicide into silicon carbide preforms were performed using an indirect infiltration method. The infiltration was found to proceed in two stages. In the early stage a melt spread over the pore surfaces and coated the solid particles, and in the final stage the melt filled the intervals between coated particles. The degree of infiltration is linearly dependent upon infiltration time in the early stage and slows down in the final stage. The Washburn equation and Darcy's law do not fit the infiltration process. A model involving melt spreading and coating during infiltration is proposed to explain the linear dependence between the degree of infiltration and the infiltration time.     

Finite element modeling of reactive liquid silicon infiltration

The LSI process, i.e. the infiltration of molten silicon into porous structures, is one of the most economical techniques for the production of C/C-SiC and C/SiC ceramics. However, despite decades of development, the infiltration behavior affected by phenomena at the infiltration front has not been understood sufficiently. In the present work, a numerical model, based on the finite element method, was developed to simulate the infiltration process. The 3D model includes the penetration of silicon into the porous preform as well as the exothermal reactions at the infiltration front caused by the growth of SiC layers. For model validation, a special measuring furnace was used, enabling in situ optical inspection and weight measurement during liquid silicon infiltration into C/C-preforms in a controlled atmosphere. For the first time, a numerical model could be established which provides a tool to simulate the infiltration kinetics as well as the thermal processes during the LSI process in three dimensions. The model enables the optimization of melt infiltration processes with complex components within reasonable computer times.     

Wood-derived ultra-high temperature carbides and their composites: A review

Wood gains much attention owing to its unique characters such as cellular pore structures, low density etc. Wood-derived carbides have great potential applications as the high-temperature filters for gas or liquid, catalyst carrier, fluid/gas reservoir devices, biocatalyst supports, etc. In this paper, we review recent progress in comprehensively understanding the processing techniques, properties and applications of wood-derived carbides. The key techniques for producing wood-derived carbides involves the infiltration techniques which are categorized into six parts (slurry infiltration, polymer precursor infiltration, melting infiltration, molten salt infiltration, sol-gel infiltration, and chemical or physical vapor infiltration). The advantages and disadvantages of these techniques are discussed in details, and the according solutions for solving the problems of each technique are further proposed. The infiltration kinetics of processing carbides are also discussed in details. The investigated properties of wood-derived carbides are summarized, which includes the mechanical properties and thermal properties. The potential applications of wood-derived carbides are explored, along with an overview of the existing challenges and practical limitations. In the end, we provide future perspectives to highlight the future directions of research in this growing area.     

Factors Affecting the Significance of Gravity on the Infiltration of a Liquid into a Porous Solid

A mathematical model is formulated to illustrate the significance of gravity on the infiltration of a liquid in a porous solid. The result indicates that the relative significance of gravity on the infiltration depth depends on the infiltration time as well as the properties of the permeating liquid and the porous solid. The effect of gravity can be neglected for a short infiltration time, and for infiltration systems with the infiltrating liquid having a large value of surface energy, a small value of wetting angle on the solid, and a low density, and the porous solid having a small equivalent capillary radius and a small tortuosity.     

Improvement in mechanical properties of three‐dimensional printing parts made from natural polymers reinforced by acrylate resin for biomedical applications: a double infiltration approach

This study demonstrates that a double infiltration technique, when compared to traditional single infiltration, can increase the mechanical properties of natural polymers fabricated by three‐dimensional printing using a water‐based binder. Double infiltration decreases the water absorption and amount of water‐soluble matter, and significantly increases flexural modulus and strength in wet conditions compared to single infiltration. These improvements can be related to the greater remaining load‐bearing area and lower degree of plasticization of the structure. However, no improvements over single infiltration were observed for testing in dry conditions. Copyright © 2006 Society of Chemical Industry     

Reactive melt infiltration fabrication of C/C-SiC composite: Wetting and infiltration

Reactive melt infiltration is a fast and economical fabrication process for high performance C/C-SiC composite. In order to help understanding reactive melt infiltration production of C/C-SiC composite by liquid silicon, wetting and infiltration of the porous C/C composite preform by liquid silicon were investigated using a sessile drop technique. The contact angle decreased with the increase of time while the drop base diameter increased. According to the variation of drop base diameter and contact angle as a function of time, four different stages corresponding to the interfacial reaction and infiltration of liquid silicon were identified during wetting of the porous C/C composite preform by the liquid silicon. The infiltration height based on wetting curve linearly increased with time, much smaller than that calculated according to Washburn equation, which strongly indicated the reaction control of silicon infiltration.     

反应熔渗法制备C/C-SiC复合材料及其反应机理和动力学的研究进展

对反应熔渗法制备C/C-SiC复合材料过程中Si的渗入行为以及Si/C的反应机理和动力学进行了综合评述.分析了高温下Si的密度、粘度、表面张力及Si/C润湿角对渗入能力的影响.概括了Washburn公式及其改进模型在液Si渗入行为方面的研究进展,给出了渗入时间、SiC生成速率与渗入高度之间的关系.对控制Si/C反应的溶解-沉淀机理和扩散机理进行了阐述,总结分析得出：不同阶段Si/C反应发生的区域不同,因而控制反应的机理也不同.最终的SiC相是由不同反应机理共同作用形成的.     

熔融渗硅对石墨氧化行为的影响

分别在500 ℃、700 ℃、900 ℃及1 100 ℃空气条件下,对石墨及渗硅石墨进行氧化实验,以分析熔融渗硅对等静压石墨氧化行为的影响。采用扫描电镜(SEM)分析了样品表面及内部形貌,通过压汞法表征了样品的孔隙结构,并对材料的力学性能进行了测试分析。结果表明:500 ℃条件下,石墨和渗硅石墨均未发生明显的氧化失重现象;温度为700 ℃时,石墨的氧化失重率随时间延长明显增加,而该温度下渗硅石墨的氧化失重率变化较小。而且,渗硅石墨在700 ℃时仍能保持较好的强度,而此温度下,石墨随氧化时间的延长,强度明显降低,甚至被氧化成粉末状。因此,熔融渗硅在提高材料抗氧化性能的同时能够显著提升材料的强度。     

Capillary infiltration studies of liquids into 3D-stitched C–C preforms: Part A: Internal pore characterization by solvent infiltration,mercury porosimetry,and permeability studies

Mathematical modeling of silicon infiltration in porous carbon–carbon (C–C) preforms is the key to fabricate liquid silicon infiltration based carbon–silicon carbide (C–SiC) composite components. Existing models for silicon infiltration are based on straight capillaries. For interconnected capillary systems, e.g. as in 3D-stitched C–C preforms these show large deviations when compared with experimental observations. The aim of the present study is to develop a mathematical model suitable for silicon infiltration in 3D-stitched C–C preforms. The work is being presented in two parts: A and B. This part (Part A) describes the experimental details pertaining to the fabrication of the C–C preforms and their pore structure characterization by mercury porosimetry, infiltration of solvents by capillary rise, and by permeability studies. A two-pore capillary infiltration model termed as modified Washburn equation has been proposed. It has been validated by experimental data of solvent infiltration. The same model correlates silicon infiltration observations as well (Part B).