Liquid Infiltration Process Research Articles

A novel porous carbon synthesized to serve in the preparation of highly dense and high-strength SiC/SiC by reactive melt infiltration

SiC/SiC composites, prepared by reactive melt infiltration (RMI), exhibit exceptional properties. However, the presence of residual Si in the composite matrix can significantly compromise their high-temperature mechanical properties. Addressing the issue of high-content residual Si aggregation remains a crucial focus of research in order to fully unlock the application potential of SiC/SiC composites prepared by RMI. In this work, a special porous carbon (Cg) is successfully synthesized and introduced into the porous 2D SiC/SiC composites prepared by CVI. The unique pore structure of the SiC/SiC-Cg is thoroughly analyzed, along with its liquid Si infiltration process. The difference in coefficient of thermal expansion (CTE) between SiC and Cg can cause thermal stress, which can destory the Cg structure. Consequently, the C particles detach from the Cg skeleton and react with liquid Si to create SiC. This process effectively separates residual Si and helps alleviate the negative effects of residual Si aggregation. The microstructure and phase distribution of SiC/SiC composites obtained by liquid Si infiltrating different C structures are investigated and compared, and it demonstrates the positive effect of Cg on the uniform phase distribution of matrix in the composites. The as-received SiC/SiC composites possess a density of 2.94 g/cm3 with open porosity of 1.23 %, and a flexural strength of 808.7 ± 10.2 MPa, a fracture toughness of 25.5 ± 1.8 MPa·m1/2, a tensile strength of 317.4 ± 12.4 MPa and a proportional ultimate stress of 157.33 ± 4.1 MPa. Acoustic emission (AE) and digital image correlation (DIC) technology are used to study the special mechanical behavior of composites.

Application of SiO2-coated SiC powder in stereolithography and sintering densification of SiC ceramic composites

Stereolithography additive manufacturing of SiC ceramic composites has received much attention. However, the forming efficiency and mechanical properties of their products need to be improved. This study aimed to prepare SiC ceramic composites with complex shapes and high flexural strength using a combination of digital light processing (DLP) and reactive solution infiltration process (RMI). A low-absorbance SiO2 cladding layer was formed on the surface of SiC powder through a non-homogeneous precipitation process. With the densification of the cladding layer at high temperatures, SiO2-coated SiC composite powder was used to formulate a photosensitive ceramic slurry with a solid content of 44 vol%. The resulting slurry exhibited a considerable improvement in curing thickness and rate and was used to mold ceramic green body with a single-layer slicing thickness of 100 μm using DLP. The ceramic blanks were then sintered and densified using a carbon thermal reduction combined with liquid silica infiltration (LSI) process, resulting in SiC ceramic composites with a density of 2.87 g/cm3 and an average flexural strength of 267.52 ± 2.5 MPa. Therefore, the proposed approach can reduce the manufacturing cycle and cost of SiC ceramic composites.

Additive manufacturing of carbon fiber reinforced ceramic matrix composites based on fused filament fabrication

For the first time, carbon fiber reinforced ceramic matrix composites (CMC) were successfully fabricated by additive manufacturing (AM) using the fused filament fabrication (FFF) technology, filaments (“CF-PEEK”) with thermoplastic polyetheretherketone (PEEK) as the matrix and C-precursor, and carbon short-fibers (< 250 μm) as reinforcements. In order to prevent a re-melting of the as-printed CFRPs (C-fiber reinforced plastics) during pyrolysis at 1000 °C in N2ensuring the freedom of design and complex parts, a prior crosslinking step at 325 °C with a dwell time of 48 h in air was introduced to stabilize and crosslink the CFRP. Due to the stabilization and the printing of degassing channels for the pyrolysis, near net shape and complex CMC parts with different C-fiber orientations (0°; ±45°; 90°) were obtained by the liquid siliconization infiltration process (LSI). The manufactured C/C-SiC parts were characterized regarding their microstructure and mechanical properties. The reinforcing C-fibers were successfully protected during the LSI-process and flexural strengths of almost 60 MPa were obtained.

Antimicrobial Activity of MgB2 Powders Produced via Reactive Liquid Infiltration Method.

We report for the first time on the antimicrobial activity of MgB2 powders produced via the Reactive Liquid Infiltration (RLI) process. Samples with MgB2 wt.% ranging from 2% to 99% were obtained and characterized, observing different levels of grain aggregation and of impurity phases. Their antimicrobial activity was tested against Staphylococcus aureus ATCC BAA 1026, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. A general correlation is observed between the antibacterial activity and the MgB2 wt.%, but the sample microstructure also appears to be very important. RLI-MgB2 powders show better performances compared to commercial powders against microbial strains in the planktonic form, and their activity against biofilms is also very similar.

Thermal analysis of hybrid aluminium metal matrix composites

In this work the thermal properties of hybrid metal matrix composites are analyzed. Thermal analysis of composite materials is essential for electronic devices. Thermal analysis of hybrid metal matrix composites is applied in electronic packaging. The property proposed to be assessed within are increased endurance limit, increased productivity, energizing, low maintenance cost and benefit to the surroundings such as less noise, less airborne emissions. Packaging material should have considerable aspects such as deplorably low thermal coefficient of expansion, high thermal conductivity, and low cost, low density with good mechanical properties. The hybrid composites are fabricated by liquid in filtration process and subjected to thermal studies such as thermal diffusivity, thermal coefficient of expansion and melting point.

Pore-scale modeling of wettability effects on infiltration behavior in liquid composite molding

The effect of wettability on the infiltration behavior in the liquid composite molding process has not been fully studied, and the available evidence appears to be conflicting. Based on the three-dimensional microcomputed tomography images of porous media, a series of immiscible displacement simulations under a wide range of wettability conditions was established by the phase field method. Interestingly, we found that increasing the affinity of the porous matrix for the invading fluid can increase the displacement efficiency and reduce the void content until the critical wetting transition is reached, beyond which the displacement efficiency decreases sharply. The nonmonotonic behavior of the wettability effect can be explained by the competition among complex and intriguing pore-scale displacement events, mainly involving the Haines jump, cooperative pore filling, and corner flow. These novel findings provide a theoretical basis for extracting the optimal wettability range, thus minimizing the void content formed during the liquid infiltration process.

Comparative study of interphase evolution in polysiloxane resin-derived matrix containing carbon micro and nanofibers during thermal treatment

The work presents the results of research on composite materials made of silicon-containing polymer-derived ceramic matrix composites (PDC-Cs) and nanocomposites (PDC-NCs). Carbon micro and nanofibers (CFs and CNFs) were used as reinforcements. The interactions between carbon micro and nanofibers and polysiloxane matrix, as well as interphase evolution mechanism in composite samples during their heating to 1000 °C were studied. CF/resin and CNF/resin composites were prepared via liquid precursor infiltration process of unidirectionally aligned fibers. After heating to 700 °C–800 °C, decomposition of the resin in the presence of CNFs led to the formation of fiber/organic-inorganic composites with pseudo-plastic properties and improved oxidation resistance compared to as-prepared fiber/resin composites. The most favourable mechanical properties and oxidation resistance were obtained for composites and nanocomposites containing the maximum amount of carbon nanoparticles precipitated in the SiOC matrix during the heat treatment at 800 °C. The precipitated carbon phase improves fiber/matrix adhesion of composites.

Effect of the Aluminum Matrix on Tensile Properties of Carbon Fiber/Al Composites Prepared by Liquid Extrusion Infiltration

Two-dimensional T300 carbon fiber-reinforced aluminum alloy matrix (2D CF/Al) composites were prepared by the liquid extrusion infiltration (LEI) process with the matrices of 6061Al and ZL102 alloys. Scanning electron microscopy (SEM) detected a satisfactory infiltration effect for both composites. The fiber distribution was uniform, and casting microdefects were not revealed. Transmission electron microscopy (TEM) analysis disclosed the matrix-carbon fibers interface reaction, the brittle Al4C3 phase. Al4C3 sizes were found to be about 150 and 400 nm in 2D CF/6061Al and 2D CF/ZL102 composites, respectively, the interface reaction of a ZL102 matrix was more pronounced. As compared to pure cast alloys, the ultimate tensile strength increased by 134.5. SEM analysis of the tensile specimen fracture demonstrated that the fracture of a 2D CF/6061Al composite was reasonable and for a 2D CF/ZL102 composite it was via the brittle mode, these were caused by the interface bonding.

An innovative process for dispersion of graphene nanoparticles and nickel spheres in A356 alloy using pressure infiltration technique

AbstractIn this paper, a unique, innovative liquid metal infiltration process for the dispersion of graphene in the aluminum (Al) matrix in the presence of nickel spheres is introduced. The nickel spheres impart a reaction that induces wettability with molten Al, hence facilitating the infiltration of Al encapsulating graphene. Raman spectroscopy shows the two‐dimensional bands, thereby confirming the presence of graphene in the infiltrated composite. The microstructure of the infiltrated composite shows the dispersion of graphene, Al‐silicon eutectic, and a reaction product between nickel and Al around nickel spheres. The sample of composite tested in this study exhibits a high contact angle and hydrophobicity, possibly due to the dispersion of graphene particles on the surface of the samples. This presence of graphene on the surface causes a reduction of wetting by water and a decrease in corrosion rate which is demonstrated by polarization testing results.

Low-Energy Ablation and Low Thermal Diffusivity of a CFRC Composite Modified by SiC

The use of materials for aerospace devices, such as rocket nozzles and thermal shields, depends primarily on their thermal and structural characteristics. Ceramic materials and carbon composites have been studied for this purpose. This work measures and investigates the ablation and thermal diffusivity of hybrid matrix composites of carbon–silicon carbide matrix reinforced by carbon fiber (C/C-SiC). Silicon powder was added to a phenolic thermoset matrix with proportions of 5, 10, and 20 %. In addition, the liquid polymer infiltration (LPI) process using a silicone polymer was used to produce the same composites. A thermal plasma torch was used to obtain the ablation and effective thermal diffusivity characteristics of the materials. The morphologies, microstructures, and chemical compositions of the samples were investigated by scanning electron microscopy and energy-dispersive spectrometry (SEM/EDS) and X-ray diffraction (XRD). The thermal diffusivities of the composites were found to be in the range of 0.2–1.5 × 10−6 m2·s−1 from 700 °C to 1000 °C, respectively. The void volume fraction of the composites was approximately 20 % and decreased the thermal diffusivity.

Magnetic Shielding Capability of MgB2 Cup Made by Liquid Infiltration Process

With the development of weak magnetic detection methods, the sensors, like superconducting quantum interference device (SQUID), become more and more sensitive. The magnetic shielding takes a more important part in weak signal detection systems than before. Traditional magnetic shielding methods are expensive, not flexible, and hard to prevent the low-frequency magnetic field clearly. For the superconducting magnetic shield, the operating temperature of a low critical temperature superconducting magnetic shield has high demand on refrigerating system. The high critical temperature superconducting magnetic shielding would introduce thermal magnetic noise. Due to the excellent superconductive property, the medium-temperature superconductor MgB2 has a huge potential to build the magnetic shielding system. In this article, we fabricate an MgB2 superconducting magnetic shielding cup with Mg Liquid Infiltration method. The highest TC of the sample is 39.4 K. The highest JC is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K. The shielding effect of the cup has been tested at axial dc weak magnetic field and the shielding factor exceeds 2000.

Relaxation Phenomena in a Long MgB2 Tube Subjected to Transverse Magnetic Field, at 4.2 K

The use of bulk MgB 2 as a magnetic shield may have interesting applications in the accelerator field as magnetic protection of the particle beams. Many of these applications will require a low-temperature environment due to the high magnetic fields involved; therefore, the stability of superconducting bulk materials, at these low temperatures, must be carefully controlled. Critical stability issues of the bulk superconducting materials include macro- and micro-flux jumps, which are related, respectively, to the sudden loosing of the shielding effect and to the initial reduction of the shielding characteristic, which initiates the long-term relaxation phenomena. We have tested the shielding characteristics at 4.2 K of a bulk MgB 2 tube (L = 450 mm, OD/ID = 49/32.4 mm), produced by the reactive liquid infiltration process that is capable to reduce to a minimum the macro-flux jumps. Applying step-wise increasing transverse magnetic fields up to about 3 T on the surface of the tube, we measured the dynamics of the superconducting currents that, with their displacements, give rise to the relaxation phenomena. These effects have been modeled by the superposition of two exponential decay functions. This parametrization can help in the prediction of the magnetic behavior of this material, but in a limited time lapse.

Observation of liquid infiltration process into closed-end holes by droplet train impingement

Observation of liquid infiltration process into closed-end holes by droplet train impingement

Enhancing copper infiltration into alumina using spark plasma sintering to achieve high performance Al2O3/Cu composites

Al2O3/Cu (with 30wt% of Cu) composites were prepared using a combined liquid infiltration and spark plasma sintering (SPS) method using pre-processed composite powders. Crystalline structures, morphology and physical/mechanical properties of the sintered composites were studied and compared with those obtained from similar composites prepared using a standard liquid infiltration process without any external pressure. Results showed that densities of the Al2O3/Cu composites prepared without applying pressure were quite low. Whereas the composites sintered using the SPS (with a high pressure during sintering in 10min) showed dense structures, and Cu phases were homogenously infiltrated and dispersed with a network from inside the Al2O3 skeleton structures. Fracture toughness of Al2O3/Cu composites prepared without using external pressure (with a sintering time of 1.5h) was 4.2MPam1/2, whereas that using the SPS process was 6.5MPam1/2. These toughness readings were increased by 18% and 82%, respectively, compared with that of pure alumina. Hardness, density and electrical resistivity of the samples prepared without pressure were 693 HV, 82.5% and 0.01Ωm, whereas those using the SPS process were 842 HV, 99.1%, 0.002Ωm, respectively. The enhancement in these properties using the SPS process are mainly due to the efficient pressurized infiltration of Cu phases into the network of Al2O3 skeleton structures, and also due to high intensity discharge plasma which produces fully densified composites in a short time.

Fluidized Bed Production of Surface Functionalized Powders for Solid Oxide Fuel Cell Cathodes

Solid oxide fuel cells (SOFC's) offer significant energy benefits, due to their high efficiency and capability to utilize either hydrogen or hydrocarbon fuels. Presently, there is considerable incentive to develop medium temperature (600 C to 800 C) SOFC's, in order to reduce material compatibility issues and to reduce the engineering challenges associated with high operating temperatures. Developing cathode materials with both high electrical conductivity and high catalytic activity at intermediate temperatures is one of the key challenges for SOFC development. La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is the present state of the art material for intermediate temperature SOFC cathodes. While monolithic LSCF cathodes have sufficient electrical conductivity, overall fuel cell efficiency can decrease at intermediate temperatures due to reduced electrochemical kinetics. One approach to enhance intermediate temperature reaction kinetics is to use "surface functionalized" cathode materials, in which a thin layer of a high catalytic activity material, such as La0.8Sr0.2MnO3 (LSM), is deposited on the surface of a high conductivity material such as LSCF. Prior works have demonstrated the benefits of surface functionalized cathode materials [1,2]. These studies used liquid infiltration from a nitrate solution to deposit LSM onto the surface of post-sintered LSCF cathodes. An optimum surface loading of LSM on LSCF was identified, beyond which cathode performance was reduced. This effect was attributed to decreased conductivity of the surface layer, as the LSM thickness increased. Despite the demonstrated benefits of surface functionalized cathode material, the liquid infiltration process has not been widely implemented in SOFC production, mainly due to concerns about cost and manufacturing complexity. This presentation will describe a technique for producing surface functionalized cathode powders by fluidized bed chemical vapor deposition (FBCVD). The FBCVD process combines two well established technologies, fluidized bed processing and chemical vapor deposition of oxide films. The starting material in this study was a commercial LSCF cathode powder (0.7 μm average diameter). Various LSM surface loadings were deposited by FBCVD, using the metal organic precursors La(thd)3, Sr(thd)2 and Mn(thd)3 along with an O2/Ar gas mixture. The resulting LSM coated LSCF powders were screen printed onto scandia stabilized zirconia electrolyte disks, and sintered to prepare symmetric half cells. A similar cell was prepared using uncoated LSCF powder for comparison. Electrochemical impedance spectroscopy was done to characterize performance of the half cells under open circuit potential, at 600 C, 700 C and 800 C in air. In each case, the LSM coated powders outperformed the uncoated LSCF, as indicated by a lower polarization resistance. An optimum surface loading was observed at 0.19 moles of LSM per kg of LSCF powder, which resulted in minimum polarization resistance, for each temperature tested. High resolution transmission electron microscopy shows the LSM surface functionalized layer to consist of uniformly dispersed fine particles on the LSCF surface. The FBCVD process is economical, and can be easily scaled to high volume production. The resulting surface functionalized cathode powders represent a drop-in replacement for conventional cathode powders in SOFC manufacturing. The FBCVD process is shown to be an effective and economical technique to produce surface coatings on powders for solid oxide fuel cells, and many other applications. 1. Ze Liu, Mingfei Liu, Lei Yang, Meilin Liu, Journal of Energy Chemistry, Vol. 22, 555 (2013). 2. M.E. Lynch, L. Yang, W. Qin, J.-J. Choi, M. Liu, K. Blinn, M. Liu, Energy & Environmental Science, Vol. 4(6), 2249 (2011).

High temperature corrosion of carbon/carbon composites in Zr–Ti melts during liquid metal infiltration

The carbon/carbon composites with Zr–Ti–C were prepared by liquid metal infiltration (LMI) process. The chemical corrosion and thermal stress damage of carbon matrices in Zr–Ti melts were investigated. A corrosion mechanism and a method of rehabilitating defective materials were proposed. The results indicated that the internal carbon matrices of composites were not corroded by the Zr–Ti melts and their vapours. However, the superficial matrices contacting the melts were severely consumed. In addition, the release of thermal stress produced the defects. The flexural strength of the samples after LMI could be improved via a new deposition of pyrocarbon in the defects.

MgB2 cylindrical superconducting shielding for cryogenic measurement applications: a case study on DC current transformers

A method for designing cylindrical hollow superconductingshields for cryogenic measurement devices operating in background fields of1 T is proposed. The shield design is based on MgB2 composite,manufactured by the reactive Mg liquid infiltration process [1]. TheMgB2 composite allows low-cost shields with good mechanical resistanceto be realized easily. The geometrical design is benchmarked by theexperimental characterization at 4.2 K. A design case study for the shieldof a cryogenic DC current transformer is reported. Design results show ashielding efficiency of 70% for both the axial and radial components,with prospective measurement accuracy up to 10 ppm on 100 kA.

Effects of copper on microstructure and mechanical properties of Cf/ZrC composites fabricated by low-temperature liquid metal infiltration

Carbon fiber-reinforced zirconium carbide matrix (Cf/ZrC) composites were fabricated by a liquid metal infiltration process at 1200°C, using low melting Zr7Cu10, ZrCu and Zr2Cu alloys as infiltrators. The effects of Cu on microstructure and mechanical properties of the composites were investigated. The results indicated that the products were composed of either single- or polycrystalline ZrC, C and Cu. With increasing Cu content in the infiltrators, the yield of ZrC decreased from 43.7vol% to 27.9vol%. When ZrCu was used as an infiltrator, the obtained composites exhibited a better bending strength of 98.2±3.1MPa. What is more, the use of Zr2Cu could provide the highest fracture toughness of the composites with a moderate debonding.

Fabrication and characterization of 3-D Cf/ZrC composites by low-temperature liquid metal infiltration

Three-dimensional braided carbon fiber-reinforced ZrC matrix composite, 3-D Cf/ZrC, were prepared by liquid metal infiltration process at 1200°C using a Zr2Cu intermetallic compound as infiltrator. The microstructure and properties of the composites were investigated. The results indicated that ZrC with a yield of 35.2±1.8vol.% was certified as the major phase of the composites. The formation of ZrC was controlled by a solution-precipitation mechanism. The obtained composites exhibited good mechanical properties, with a flexural strength of 293.0±12.1MPa, a flexural modulus of 82.7±6.4GPa and a fracture toughness of 9.8±0.9MPam1/2. The mass and linear ablation rates of the composites exposed to oxyacetylene torch were 0.0013±0.0005gs−1 and −0.0009±0.0003mms−1, respectively. The formation of a dense ZrO2 protective layer and the evaporation of residual Cu contributed mainly to the excellent ablation resistance.

G0305 先端を封じた細管内の液体浸入特性(GS3 気泡・界面・マイクロ流)

In a semiconductor devise fabrication process, cleaning process has shifted to single-wafer spin cleaning from bath method. For the single-wafer cleaning, effective liquid infiltration into micro scale pores is important. In this study, we theoretically and experimentally investigate the liquid infiltration process into closed end tubes. From the estimation of force balance, we found that the surface tension force is not enough for the infiltration of order of 100 ?m tubes and it is necessary external pressure to fill the tube. In addition we experimentally observed the relationship between external applied pressure and air volume in the tubes. As a result, it is found that the air compressibility is the dominant factor for the liquid infiltration and dissolution has a low impact.