Infiltration Temperature Research Articles

再结晶碳化硅及其复合材料的研究进展与应用

Recrystallized silicon carbide (RSiC), a high-purity material sintered by using evaporation-condensation without additives, is one of the most important materials in high-temperature structural applications. However, its low density and porous structure, caused by the sintering mechanism in the absence of shrinkage, restrict the engineering applications of RSiC. This paper reviews research and related technologies on the preparation of high-density RSiC, porous RSiC, and RSiC composites. The fluidity of SiC slurries can be improved by electrostatic stabilization or steric stabilization, which has been achieved by modifying the surfaces of fine SiC raw powders with grafted polymers based on silane coupling agents; the resultant slurry had high solid content, and when sintered produced RSiC with a relatively high density (2.75 g/cm3). Using the interconnected pores of RSiC as a modification path, its density has been further increased (2.99 g/cm3) by combining polymer impregnation-pyrolysis of polycarbosilane (PIP, 1400℃) and recrystallization (2400℃). SiC has excellent chemical stability, thermal stability, and mechanical properties, and its sintering mechanism does not produce shrinkage. Because of these advantages, various porous RSiC elements have been manufactured with relative ease. These elements can be gradually substituted for those made from conventional materials, such as Al2O3, cordierite, reaction-bonded SiC, and mullite, in ceramic membranes used for concentrating hot corrosive solutions, filtering diesel particulate, and filtering fine particles from hot gases, as well as in volumetric honeycombs used to collect and convert solar energy. Because SiC is compatible with many metallic elements, RSiC-(inter)metallic composites have been prepared by infiltrating molten liquid through the interconnected pore structure of RSiC. Dense RSiC-MoSi2 composites directly infiltrated at 2050~2100℃ with molten MoSi2 exhibited excellent oxidation resistance, relatively low resistivity (~10-1 W cm) and a ~40% improvement in flexural strength compared to RSiC. The interface between SiC and MoSi2 has been modified by PIP pre-treatment of polycarbosilanes (PCS) (or phenolic resin), which either directly forms a SiC layer (with PCS) or reacts with Si while infiltrating the MoSi2-Si-X (X=Ti, Cr, Al) alloy, further improving strength (171.4 MPa) while decreasing the resistivity (10-3 W cm) and infiltration temperature (1800℃ for MoSi2-Si-X). This modified material can be used as structural material and as a high-temperature electrothermal material, substituting for MoSi2. Using molten infiltration assisted by gas pressure, a RSiC-Al composite with very high thermal conductivity (250 W/(m K)) and low thermal expansion coefficient has also been fabricated, a material which could meet the requirements of electronic packaging materials for high-power electronic components.

Impregnation of porous mullite with Na2SO4 phase change material for thermal energy storage

The porous mullite/Na2SO4 composites with both novel structure and improved heat storage properties were successfully prepared by infiltration of the molten Na2SO4 into the porous mullite matrix, which was fabricated by TBA-based freezing casting method. The effects of fabrication parameters on pore structure of the porous mullite matrix, the infiltration ratio of molten Na2SO4 and heat storage properties of the composites were investigated extensively. The results show that the infiltration ratio of the molten Na2SO4 decreases with decreasing the porosity and increasing the infiltration temperature and the average pore size of the porous mullite matrix. While it increases initially with increases of the infiltration time, and tends to remain constant thereafter. The optimal infiltration temperature and infiltration time are 950°C and 1h, respectively. The unidirectionally aligned open pores in the porous mullite matrix benefit the infiltration process, and the higher infiltration ratio of the molten Na2SO4 and the relatively larger specific heat capacity of the mullite powders both contribute to the higher heat storage density of the composites.

Growth of Polymer Nanorods with Different Core–Shell Dynamics via Capillary Force in Nanopores

The dynamics of poly(n-butyl methacrylate) confined in porous anodic aluminum oxide (AAO) templates are investigated using differential scanning calorimetry (DSC) and fluorescence nonradiative energy transfer (NRET). Two glass transition temperatures (Tg,low and Tg,high) are obtained at higher infiltration temperatures via capillary force followed by slow cooling. Tg,low resembles the Tg of the bulk phase and represents the transition of the core layer. Tg,high represents the transition of the adsorbed layer in the confined polymer glass. The temperature threshold to form one or two glass transitions is determined by adjusting the infiltration temperatures and the pore diameters. It is shown that the adsorbed layer has increased interchain proximity relative to the bulk. In addition, the glass transition behavior is hypothesized to be mediated by the counterbalance of the size and interfacial effects in the confined space. The easily synthesized core–shell nanofibers with one glassy and one rubbery component without the need for block polymers have promising potential for use in several processing strategies.

Synthesis of biomorphic paper-derived anatase

Biomorphic anatase-based plates were obtained using paper as template for fixing TiO2. Ceramics with a microstructure similar to paper were produced by infiltration in TiCl4 and hydrolysis in NH4OH at temperatures between −25 and 25°C, followed by air drying and calcination up to 1000°C. After thermal treatment, the samples were characterized by XRD, TG/DTA, BET, SEM and EDX. Plates manufactured by infiltration in TiCl4 and hydrolysis in NH4OH at 0°C presented anatase as major phase, whose amount decreases with increasing calcination temperature. The results showed that by decreasing the infiltration and hydrolysis temperature, the surface area decreased, crystallite size increased and the anatase-to-rutile transformation was inhibited.

Formation of novel photoluminescent hybrid materials by sequential vapor infiltration into polyethylene terephthalate fibers

Abstract

Optimisation of high thermal conductivity Al/diamond composites produced by gas pressure infiltration by controlling infiltration temperature and pressure

In this study, Al/diamond composites were fabricated by the gas pressure infiltration method. The infiltration temperature and pressure were varied to study their influence on the interfacial microstructures and thermal conductivities of composites. The results show that the infiltration temperature and pressure dramatically affect the reaction between the Al matrix and the diamond particles. The appropriate conditions activate the reaction on the {111} faces of diamond which possesses a higher chemical stability than the {100} faces. The course of the reaction can lead to the structural and chemical modification of the interface, which strongly affects the thermal conductivity of the final composites. Using our optimised parameters of 800 degrees C and 0.8 MPa, a superior thermal conductivity above 760 W m(-1) K-1 was obtained. Controlling the fabrication parameters to optimise the reaction on the {100} and {111} faces can result in a superior Al/diamond material with greater thermal conductivity.

화학침착법과 고분자함침 열분해법의 복합공정으로 제조한 SiCf/SiC 복합체의 제조 공정에 따른 파괴거동

SiC f /SiC composites were prepared using the hybrid process of chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP). Before the application of PIP, partially matrix-filled preform composites with different densities were fabricated by control of chemical vapor infiltration time and temperature. The changes of the final density of the SiC f /SiC composites had a tendency similar to that of preform composites partially filled by CVI. Composites with lower density after the CVI process had a larger increment of density during the PIP process. Three types of microstructures were observed on the fractured surface of the composite: 1) well pulled-out fibers and lower density, 2) slightly pulled-out fibers and higher density, and 3) only bulk SiC. The different fractions and distributions of the microstructures could have an effect on the mechanical properties of the composites. In this study, SiC f /SiC composites prepared using a hybrid process of CVI and PIP had density values in the range of 1.05 ~ 1.44 g/㎤, tensile strength values in the range of 76.4 ~ 130.7 MPa, and fracture toughness values in the range of 11.2 ~ 13.5MPa·m 1/2 .

Pre-review study of the aluminum/alumina master alloy made through pressure infiltration

The work is focused to prepare Al based master-alloy pellet with 50 vol.% of Al2O3 for subsequent manufacturing of aluminum matrix composites with desired amount of reinforcement (5–20%). Since master-alloy is manufactured via pressure infiltration and proper interface between particles and melt is required for uniform particle distribution within the melt, fundamental correlation between parameters of pressure infiltration and quality of the Al/Al2O3 interface is revealed in this study. Standard observation techniques as 3-D computed tomography (CT), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) are used for structural characterization. Drop test was used to estimate effect of time, temperature, annealing of Al2O3 and its type on the wettability of Al2O3 with Al. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to study changes within the Al2O3 prior infiltration. Stir casting was used to prepare the final composite and dynamical mechanical analysis (DMA) was used to estimate the Young’s modulus of as-cast composite. The proper infiltration parameters was defined in this work and it were shown that the infiltration temperature and pressure have direct correlation on the interface between particle and aluminum.

Cf/C composites: correlation between CVI process parameters and Pyrolytic Carbon microstructure

Chemical Vapour Infiltration (CVI) technique has been long used to produce carbon/carbon composites. The Pyrolytic Carbon (Py-C) matrix infiltrated by CVI could have different microstructures, i.e. Rough Laminar (RL), Smooth Laminar (SL) or Isotropic (ISO). These matrix microstructures, characterized by different properties, influence the mechanical behaviour of the obtained composites. Tailoring the process parameters, it is possible to direct the infiltration towards a specific Py-C type. However, the factors, influencing the production of a specific matrix microstructure, are numerous and interconnected, e.g. temperature, pressure, flow rates etc. Due to the complexity of the physical and chemical phenomena involved in CVI process, up to now it has not been possible to obtain a general correlation between CVI process parameters and Py–C microstructure. This study is aimed at investigating the relationship between infiltration temperature and the microstructure of obtained Py-C, for a pilot - sized CVI/CVD reactor. Fixing the other process parameters and varying only the temperature, from 1100°C to 1300°C, the Py-C infiltration was performed on fibrous preforms. Polarized light microscopy, with quantitative measurements of average extinction angle (Ae), and Raman spectroscopy were used to characterize the obtained Py-C microstructures.

Influence of infiltration temperature on the microstructure and oxidation behavior of SiC–ZrC ceramic coating on C/C composites prepared by reactive melt infiltration

SiC–ZrC ceramic coating on C/C composites was prepared by reactive melt infiltration (RMI) using a powder mixture composed of Zr, Si and C as the infiltrator. The phase composition and microstructure of the ceramic coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The oxidation resistance of the as-prepared composites was tested at 1550°C in static air. The results indicate that the infiltration temperature has remarkable effects on the phase composition and microstructure of the ceramic coating, as well as on the oxidation resistance of the composites. The SiC–ZrC coated C/C composites prepared at 2000°C exhibit an excellent oxidation resistance. They gain weight about 5.9wt% after oxidation at 1550°C in static air for 5h, whereas the SiC–ZrC coated C/C composites prepared at 1800°C lose weight about 3.2wt%. As a comparison, SiC coated C/C composites prepared at 2000°C by RMI show an inferior oxidation resistance. After 5h oxidation, SiC coated C/C composites are severely damaged and their weight loss reaches up to 44.3wt%. The outstanding oxidation resistance of the SiC–ZrC coated C/C composites prepared at 2000°C can be attributed to the rapid formation of a continuous glass-like layer composed of ZrO2, ZrSiO4 and SiO2, which covers the surface of the composites and retards the oxygen diffusion and the attack on the underlying C/C substrate. For SiC coated C/C composites, the large SiC particles formed on the surface of the composites are difficult to oxidize rapidly and so a continuous and dense SiO2 layer cannot be formed in time to significantly hinder fast oxygen diffusion leading to the consequent severe oxidation of the C/C substrate.

Microstructure and graphitization behavior of diamond/SiC composites fabricated by vacuum vapor reactive infiltration

To inhibit the graphitization of diamond under high temperature and low pressure, diamond/SiC composites were firstly fabricated by a rapid gaseous Si vacuum reactive infiltration process. The microstructure and graphitization behavior of diamond in the composites under various infiltration temperatures and holding time were investigated. The thermal conductivity of the resultant materials was discussed. The results show that the diamond-to-graphite transition is effectively inhibited at temperature of as high as 1600 °C under vacuum, and the substantial graphitization starts at 1700 °C. The microstructure of those ungraphitized samples is uniform and fully densified. The inhibition mechanisms of graphitization include the isolation of the catalysts from diamond by a series of protective layers, high pressure stress applied on diamond by the reaction-bonded SiC, and the moderate gas–solid reaction. For the graphitized samples, the boundary between diamond and SiC is coarse and loose. The graphitization mechanism is considered to be an initial detachment of the bilayers from the diamond surfaces, and subsequently flattening to form graphite. The ungraphitized samples present higher thermal conductivity of about 410 W·m−1·K−1 due to the fine interfacial structure. For the graphitized samples, the thermal conductivity decreases significantly to 285 W·m−1·K−1 as a result of high interfacial thermal resistance.

The Role of Infiltration Temperature in the Reaction Bonding of Boron Carbide by Silicon Infiltration

The present paper is concerned on the effect of infiltration temperature on the components, microstructure, and mechanical properties of reaction‐bonded boron carbide (RBBC) ceramics. RBBC ceramics were fabricated by reactive infiltration of molten silicon (Si) into porous preforms containing boron carbide (B4C) and free carbon. It has been found that infiltration temperatures have significant influence on the infiltration reactions involved and therefore the evolution of different phases formed in the RBBC ceramics. An increase in grain size of boron carbide particles through the coalescence of neighboring grains was observed at certain infiltration temperatures. The morphology of silicon carbide (SiC) phases developed from discontinuous and cloud‐like SiC to continuous and integrated SiC zones with the increase of infiltration temperatures. With increasing temperatures up to 1600°C, the hardness, flexural strength, and fracture toughness all increased. When the temperatures exceeded 1600°C, while the hardness and flexural strength decreased, the fracture toughness continued to increase.

Chemical vapor infiltration of activated carbon with tetramethylsilane

Chemical vapor infiltration of activated carbon with tetramethylsilane (TMS) at 200hPa total pressure and a gas phase concentration of 15 (mol-)% TMS in nitrogen is studied. The influence of temperature on the infiltration process is discussed in detail. Up to 873K, the infiltration is performed in the kinetically controlled regime resulting in high loadings up to around 42 (wt.-)%. The modified materials show high values for BET-surface and pore volume indicating a sufficient adoption of the infiltrated silicon layer to the surface morphology of the carbon substrates. Low oxidation resistance of the infiltrated material and EDX measurements give rise to the assumption that the infiltrated material is silicon. At higher infiltration temperatures above 873K, particles are formed which have the shape of cylindrical nanostructures. EDX measurements reveal that silicon carbide is produced at these temperatures.

Application of Pressureless Infiltration Technique for Processing and Characterizing Properties of 3-3 Al(Mg)/ZrO2 Composites

3-3 Al(Mg)/ZrO2 composites based on Al–Mg alloy reinforced by ceramic interpenetrating network structure were fabricated via pressureless infiltration technology. Infiltration temperature and infiltration atmosphere are the key parameters distinctly effecting on infiltration processes. The composites were produced at atmospheric pressure by infiltrating 2–10 wt% magnesium content Al–Mg alloys into 25 % dense ZrO2 foams with highly interconnected porosity. The processing parameters of temperature ≥ 890 °C, and atmosphere, flowing N2–Ar, were investigated to determine the processing window. Moreover, the increasing of Mg content (2–10 wt%) resulted in an increased amount of infiltration. The observation of the process shows that infiltration is faster at higher temperatures and N2 partial pressures. Both optical and scanning electron microscopy have been used to characterize the composites. Electrical conductivity of composite reduces with increasing of Mg content in matrix and volume fraction of reinforcement. The use of ZrO2 preform with low cell size in composite results in the increase in hardness of Al–Mg/ZrO2 composite.

The Numerical and Experimental Analysis of Heat Transport and Water Infiltration in a Granular Packed Bed Due to Supplied Hot Water

The characteristics of heat transport and water infiltration in a granular packed bed due to supplied hot water are investigated experimentally and numerically. The distributions of water saturation and temperature are focused on one-dimensional models assuming the local thermal equilibrium between water and particles at any specific space in a vertical granular packed bed column. This study describes the dynamics of heat transport and water infiltration in various testing condition. The calculated water saturation, temperature distribution, and infiltration depth are compared with the experimental results. Experimentally and numerically, the influence of particle sizes and supplied water flux on heat transport during unsaturated flow are clarified in detail. The results showed that the granular packed bed with a larger particle size results in a faster infiltration rate and forms a wider infiltration depth. However, an extension of the heated layer is not as much as that of the infiltration layer because the temperature of water infiltration gradually drops due to upstream heat transport. It is found that a greater supplied water flux corresponds to a higher water saturation and temperature along a granular packed bed for each time increment. The numerical results closely match the experimental results.

Preparation of Anti-Static Ceramics by Fe-Infiltration on Sintered Zirconia Body

Anti-static materials are widely used in the fields of textile, petrochemical processing, aerospace and electronics. An innovative processing method for fabricating anti-static ceramics has been developed based on Fe-infiltration on the sintered zirconia body. The sintered zirconia ceramics infiltrated by metal Fe in the inner atmosphere showed both perfect anti-resistive and mechanical properties. In this study, infiltration temperature and time was optimized to control the surface resistivity. It was shown that the lower surface resistivity could be obtained at higher infiltration temperature and longer infiltration time. However, the surface hardness was decreased. The surface resistivity reached 5.6×107Ω/ at 1300°C for 12 hours. The phase transformation and microstructure changes were characterized by XRD and SEM. The existence state of Fe was analyzed by EDS.

Ti3Si(Al)C2-based ceramics fabricated by reactive melt infiltration with Al70Si30 alloy

Abstract Dense Ti3Si(Al)C2-based ceramics were synthesized using reactive melt infiltration (RMI) of Al70Si30 alloy into the porous TiC preforms. The effects of the infiltration temperature on the microstructure and mechanical properties of the synthesized composites were investigated. All the composites infiltrated at different temperatures were composed of Ti3Si(Al)C2, TiC, SiC, Ti(Al, Si)3 and Al. With the increase of infiltration temperature from 1050 °C to 1500 °C, the Ti3Si(Al)C2 content increased to 52 vol.% and the TiC content decreased to 15 vol.%, and the Vickers hardness, flexural strength and fracture toughness of Ti3Si(Al)C2-based composite reached to 9.95 GPa, 328 MPa and 4.8 MPa m1/2, respectively.

Preparation of Antistatic Ceramics Employing Fe-infiltration in Sintered Zirconia Body

Antistatic ceramic with good mechanical performance has wide application in fields of aerospace, petrochemical engineering, electronics and textile. Antistatic ceramic ZrO2 was fabricated via an innovative surface modification method based on embedding Fe-infiltration into the 3Y-TZP ceramic at high temperature, which showed good antistatic and mechanical properties. In addition, microstructure and morphology of as-prepared samples were characterized by XRD, SEM and XPS. Furthermore, the antistatic mechanism of ZrO2 ceramics was investigated. The effects of infiltration temperature and infiltration time on vickers hardness and surface resistivity of specimen were evaluated. Experimental results showed that the surface resistivity and hardness decreased with the increase of infiltration temperature and infiltration time, in which the surface resistivity decreased from more than 10 Ω/□ to 8.3×10 Ω/□, and the hardness of ZrO2 ceramics decreased from 12.7 GPa to 11.23 GPa after infiltration at 1000°C for 4 h. Analysis results indicated that there was a phase transformation of ZrO2 from t-ZrO2 to m-ZrO2 in the infiltration process. It was also found that Fe, Fe3O4 and FeO located in the interface of infiltration layer, which were attributed to the antistatic property of ZrO2 ceramics.

Optimization of Mechanical Properties of Hybrid Al2O3/SiCp Reinforced Composites Produced by Pressure-Assisted Aluminum Infiltration

This study investigates Al2O3/SiCp-Al composites fabricated by pressure-assisted liquid–metal infiltration techniques and modified alumina/SiC particle preforms. The infiltration was achieved successfully; microstructure and mechanical properties of the composites were examined. An experimental design based on the Taguchi technique was used to acquire the data and investigate the mechanical properties of the hybrid composites. An orthogonal array and analysis of variance were employed to investigate the influence of test parameters such as infiltration temperature and infiltration pressure. It was found that the infiltration temperature was the most effective factor in increasing the mechanical properties of hybrid Al2O3/SiCp composite.

The Study on Preparation of a B<sub>4</sub>C/Al Composite Fabricated by the Sponge Impregnant Method

In this work, B4C porous ceramics reinforced alumium composite was fabricated by the sponge impregnant method and pressureless infiltration technique. The wettability of aluminum on B4C, the component and the wear resistance of the composite were studied .The result indicates that the infiltration temperature is determined 1200 centigrade and there are mainly Al, B4C, Al3BC , no AL4C3in the experimental composite, the wear resistance of B4C/AL composite is 25 to 30 times higher than that of the alumium.