Vapor Infiltration Research Articles

MODELING AND EXPERIMENTAL STUDIES OF THE CHEMICAL VAPOR INFILTRATION PROCESS OF TUNGSTEN SELF-COMPOSITES

The numerical modeling using the COMSOL Multiphysics software of the process of chemical vapor infiltration of tungsten powder in order to establish the dependences between the residual porosity of the self-composite and the synthesis parameters was carried out. The influence of the parameters of the chemical vapor infiltration process of tungsten powder on the depth of its impregnation and the density of the resulting selfcomposites was experimentally studied also. It has been established that the main factor determining the maximum depth of infiltration is the rate of deposition of tungsten from the gas phase.

Characterization of C/C Composites Produced Using 3D-preforms by CVD/CVI Method for Biomedical Applications

In this study, carbon/carbon (C/C) composite structures were produced by depositing a pyrolytic carbon matrix around carbon fibers found in a three-dimensional (3D) preform using the Chemical Vapor Infiltration (CVI) method. The preforms used as starting materials were in orthogonal fiber geometry and 3D carbon fiber knitting structure. The CVI process performed in the CVD (Chemical Vapor Deposition) device was carried out at 1250 ℃, under 2 mbar pressure, with a methane gas flow rate of 2.0 lt/min, for a total period of 312 hours gradually applied in an inert atmosphere consisting of argon and nitrogen gases. The produced block piece was processed to obtain small test samples; tensile and three-point bending tests were applied to the pieces, and their densities were measured. Samples were subjected to in-vitro biodegradation tests in 0.9 % isotonic sodium chloride solution by weight at 37 °C for a total of 21 days. The density and apparent porosity of the produced samples were measured to be 1.395 g/cm³ and 13.424%, respectively. The tensile strength and bending strength of the produced C/C composites were determined to be 252.5±6.20 MPa and 236.6±25.7 MPa, respectively. At the end of 21 days, the biodegradation ratio of C/C composites was calculated as 0.0095%.

Effects of heat treatment on mechanical and thermophysical properties of KD‐SA SiCf/SiC composites

AbstractThe mechanical and thermophysical properties of KD‐SA SiCf/SiC composites manufactured by the hybrid chemical vapor infiltration (CVI)–precursor impregnation and pyrolysis (PIP) technique were systematically studied at 1400, 1600, and 1800°C, respectively, under argon atmosphere for 1 h. The results show that Si element in SiC fiber escapes and diffuses to pyrolytic carbon (PyC) interphase after 1400°C heat treatment, forming a Si‐rich line in PyC interphase. With a further increase of heat treatment temperature, the Si sublimation in the Si‐rich line leads to the cracking of the PyC interphase as well as the increase of the order degree of the PyC interphase, resulting in a significant decrease in the interfacial shear strength of the composite. Due to the decomposition of PIP SiC matrix and Si sublimation of SiC fiber, the flexural strength of the composite decreases after heat treatment at 1400°C. When the heat treatment temperature increases to 1600 and 1800°C, the flexural strength of the composite is slightly increased compared with 1400°C. Moreover, the thermal conductivity of the composites has been improved significantly by raising temperatures due to an increase of the crystallinity of the PIP SiC matrix.

Challenges and innovative solutions in fabrication of ceramic matrix composite for ultra high-temperature application

Ceramic Matrix Composites (CMCs) are transformational materials with outstanding thermal stability, mechanical strength, and resilience to severe conditions, making them important in aerospace, energy, and defence applications. This paper examines the novel approaches and problems of creating CMCs for ultra-high-temperature settings, emphasizing material selection, reinforcing strategies, and advanced production techniques. Recent improvements include using silicon carbide (SiC) and zirconium oxide (ZrO?) as matrix materials and reinforcements, such as continuous fibers and whiskers, to improve performance. Advanced processing methods, such as Polymer Infiltration Pyrolysis (PIP) and Chemical Vapor Infiltration (CVI), provide precise microstructure customization for high-demand applications. Despite these gains, challenges such as oxidation resistance, surface degradation, and cost-effective scaling persist. Integrating non-destructive evaluation techniques and adhering to high-quality standards is essential for boosting reliability. This review emphasizes the promise of CMCs in satisfying critical technological objectives while underlining the need for continuous research into processing advancements and environmental durability to enhance their application in ultra-high-temperature sectors.

Low viscosity high stability silicon carbide slurry for densification of SiC ceramic matrix composites

Low viscosity high stability silicon carbide slurry for densification of SiC ceramic matrix composites

Enhancing Zirconia-Toughened Alumina with Polyethylene Glycol (PEG) and Empty Fruit Bunch-Derived Solid Carbon

Zirconia-toughened alumina (ZTA) is a widely utilized oxide ceramic known for its exceptional toughness, wear resistance, and corrosion resistance, making it suitable for applications such as cutting tools and biomedical devices. Despite its advantages, the burnout of binders like polyethylene glycol (PEG) at high temperatures leaves porous structures in ZTA composites, potentially hindering densification and material performance. This study aims to enhance ZTA composite properties by using PEG to create pores that facilitate carbon (C) infiltration through the chemical vapor infiltration process, utilizing biomass-derived carbon from empty fruit bunches (EFB). The ZTA composites were impregnated with different amounts of PEG, ranging from 0 to 5 wt%, to increase the porosity of their microstructures, as the composites had to be porous to facilitate efficient C deposition, and achieve optimal strength. Empty fruit bunches (EFBs) were used as the C source. The scanning electron microscopy (SEM) results revealed that the PEG formed pores on the surface of the ZTA composites, possibly, because the higher PEG concentration decreased the density of the ZTA composites. However, the density of the ZTA composites increased post C infiltration as the C filled the pore spaces. The C-infiltrated ZTA composite containing 3 wt.% of PEG had the highest density (4.145 g/cm3) as well as the highest hardness (1911 HV) and fracture toughness (6.98 MPa.m1/2). It also required the lowest Raman spectra intensity ratio (ID/IG, 1.26), which indicated that it contained a high percentage of sp2 hybridised C atoms and a higher degree of graphitising C. Our findings had proved that during the sintering process, the binder evaporated, leaving pores that were later filled with C. This improved fracture resistance, hardness, and density because fewer pores remained, and porosity was reduced. However, as the PEG content increased to 4 wt.%, mechanical properties declined. This was due to agglomeration, which created more pores in the microstructure, making it easier for cracks to spread.

The influence of the fluoride process of tungsten deposition parameters on the properties of tungsten self-composites obtained by chemical vapor infiltration

The influence of the parameters of the chemical vapor infiltration process of tungsten powder on the depth of its impregnation, mechanical properties and density of the obtained blanks is studied. It was found that the depth of infiltration depends on the rate of chemical vapor deposition of tungsten, and the maximum bend strength is achieved the sample, obtained at temperature of 450 °C and a gas pressure of 133 mbar. The method of chemical vapor infiltration is promising for the development of technology of additive manufacture of the items made of tungsten and composites based on it.

Efficiency of in-wall weave patterns on the mechanical properties of integrally woven carbon/carbon honeycomb structures

Combining honeycomb structures with carbon/carbon (C/C) composites provides significant benefits, such as enhanced load-bearing strength, reduced weight, minimal thermal expansion, and no moisture absorption. These characteristics make such structures particularly suited for space applications. Carbon fiber reinforced composites, with their versatile design capabilities, emerge as an ideal material for satellite bearing platforms. In this study, three continuous carbon fiber woven structures are designed, and an integrally woven ortho-hexagonal C/C honeycomb structure was fabricated through performing Chemical Vapor Infiltration (CVI) process on honeycomb preform. A multiscale damage model is used to analyze and compare the properties related to out-of-plane compression, shear in the L-direction, and shear in the W-direction across these three C/C honeycomb structures. Results indicate that the plain-woven C/C honeycomb structure demonstrates the most favorable mechanical properties, with the highest compressive modulus and shear strength under various loading conditions. Damage initially occurred in single-layer honeycomb walls with void defects, with ultimate failure appearing predominantly in the middle regions of all walls. These findings establish the plain-woven structure as the preferred choice for satellite bearing platforms due to its outstanding mechanical characteristics, providing stability and strength crucial for space applications.

Effects of Temperature and Water Vapor Content on Microstructure, Mechanical Properties and Corrosion Behavior of C/C-SiC Composites.

Carbon-fiber-reinforced carbon and silicon carbide (C/C-SiC) composites were prepared using chemical vapor infiltration (CVI) combined with reactive melt infiltration (RMI). The microstructure and flexural properties of C/C-SiC composites after oxidation in different temperature water vapor environments were studied. The results indicate that the difficulty of oxidation in water vapor can be ranked from easy to difficult in the following order: carbon fiber (CF), pyrolytic carbon (PyC), and ceramic phase. The surface CFs become cone-shaped under corrosion. PyC has a slower oxidation rate and lower degree of oxidation compared to CF. The SiO2 layer formed by the oxidation of SiC and residual Si was insufficient to fully cover the surface of CFs and PyC. As the temperature increased, the oxide film thickened, but the corrosion degree of CF and PyC intensified, and the flexural performance continuously deteriorated. The flexural strength of C/C-SiC composites was 271.86 MPa at room temperature. Their strength retention rates were all higher than 92.19% after water vapor corrosion at 1000 °C, still maintaining the "pseudoplastic" fracture characteristics. After water vapor corrosion at 1200 °C, the CFs inside the composites sustained more severe damage, with a strength retention rate as low as 48.75%. The fracture mode was also more inclined towards brittle fracture.

Tensile properties of 3D stitched C/C–SiC composites prepared by a hybrid chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP) process

Tensile properties of 3D stitched C/C–SiC composites prepared by a hybrid chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP) process

Inverse Identification of Constituent Elastic Parameters of Ceramic Matrix Composites Based on Macro–Micro Combined Finite Element Model

Accurate material performance parameters are the prerequisite for conducting composite material structural analysis and design. However, the complex multiscale structure of ceramic matrix composites (CMCs) makes it extremely difficult to accurately obtain their mechanical performance parameters. To address this issue, a CMC micro-scale constituents (fiber bundles and matrix) elastic parameter inversion method was proposed based on the integration of macro–micro finite element models. This model was established based on the μCT scan data of a plain-woven CMC tensile specimen using the chemical vapor infiltration (CVI) process, which could reflect the real microstructure and surface morphology characteristics of the material. A BP neural network was used to predict the multiscale stiffness, considering the influence of the porous structure on the macroscopic stiffness of the material. The inversion process of the constituent elastic parameters was established using the trust-region algorithm combined with an improved error function. The inversion results showed that this method could accurately invert the CMC constituent elastic parameters with excellent robustness and anti-noise performance. Under four different degrees of deviation in the initial iteration conditions, the inversion error of all parameters was within 1%, and the maximum inversion error was only 2.16% under a 10% high noise level.

Ti3SiC2 MAX phase modified SiCf/SiC composites with high strength and thermal conductivity prepared by low-temperature reactive melt infiltration

Ti3SiC2 MAX phase modified SiCf/SiC composites with high strength and thermal conductivity prepared by low-temperature reactive melt infiltration

Mechanical and broadband absorption properties of Nextel 610/SiOC composites synergistically enhanced by the interfacial structure design

Mechanical and broadband absorption properties of Nextel 610/SiOC composites synergistically enhanced by the interfacial structure design

Ultrahigh room and high − temperature mechanical properties of SiCf/SiC composites prepared by hybrid CVI and PIP methods: Effects of PIP temperature

Ultrahigh room and high − temperature mechanical properties of SiCf/SiC composites prepared by hybrid CVI and PIP methods: Effects of PIP temperature

Design and Manufacture of SiC/SiC Nozzle Guide Vanes With Environmental Barrier Coatings for High-Pressure Turbines

Abstract Increasing the efficiency of jet engines is essential to meet the demanded climate targets. Ceramic matrix composites (CMCs) are strong candidates for aircraft applications because they withstand high temperatures, while their density is two-thirds lower than that of conventional nickel-based alloys. This leads to cooling air savings and a lower overall engine weight, resulting in a potential reduction of emissions. To investigate the potential benefits and manufacturing techniques required for the introduction of CMC to the high-pressure turbine (HPT) of a modern jet engine, the geometry of a nozzle guide vane of an existing turbine was redesigned considering ceramic specific constraints. Then, the liquid silicon infiltration (LSI) process was used to manufacture silicon carbide fiber-reinforced silicon carbide (SiC/SiC) nozzle guide vanes (NGV). Hi-Nicalon S woven fabric was used together with a chemical vapor infiltration (CVI)-based fiber coating. The outer surface of the vane was ground to meet the requirements for surface roughness, and geometric and positional tolerances. Cylindrical, laser-drilled cooling holes were introduced for trailing edge cooling. In the final step, an environmental barrier coating (EBC) system consisting of yttrium disilicate (Y-DS) and yttrium monosilicate (Y-MS) layers was applied using physical vapor deposition (PVD) processing. Wind tunnel testing under technology readiness level (TRL) 4 will be performed and vane performance will be evaluated.

Investigation of Titanium Nitride as an Effective Interphase for Carbon-Fiber-Reinforced Silicon Carbide Ceramic Matrix Composites.

Ceramic matrix composites (CMCs) have played a significant role in increasing the efficiency of gas turbine engines. CMCs combine the high temperature resistance of ceramics with the high mechanical strength of ceramic fibers into a single unit. Interphase layers are a crucial component in CMCs, as they prevent ceramic fibers from oxidation and introduce strengthening mechanisms into the composite. Hexagonal boron nitride and pyrolytic carbon are the most commonly used interphase layers in the aerospace industry. Other than that, very few materials have been evaluated as interphase layers. In this study, we explore the possibilities of using titanium nitride as an interphase layer in single-tow CMCs (mini composite) representative of a unidirectional composite at a smaller scale. T-300 carbon fibers were coated with TiN by atmospheric pressure chemical vapor infiltration using TiCl4, N2, and H2. The deposition temperature, precursor flow rate ratio, total precursor flow rate, and deposition time were optimized to obtain high-quality coatings. The best coating was produced at 800 °C, 4:1 H2 [TiCl4]/N2 ratio, 125 standard cubic centimeters per minute (N2 + H2 [TiCl4]) total flow precursor flow rate, and 2 h of deposition time. At these conditions, the coatings displayed good fiber coverage, good fiber adhesion, minimum fiber linkage, and minimum surface roughness. There was minimum fiber degradation after TiN coating, with a retention of 95% of the initial Young's modulus and 26% of the ultimate tensile strength of the carbon fiber. Adding the TiN interphase coating to the Cf/SiC CMC increased the ultimate tensile strength of the composite by 1122% and Young's modulus by 150%.

Preparation and mechanical behavior of Yb2Si2O7 interphase in SiCf/SiC minicomposites

AbstractIn this work, the Yb2Si2O7 interphase was prepared on SiC fibers using the sol–gel method. The influence of sol concentration on the morphology of the interphase was discussed. After heat treatment in argon at 1200°C for 1 h, the Yb2Si2O7 was grown in situ on the fiber surface, forming an interphase layer. Then, SiCf/Yb2Si2O7/SiC minicomposites were prepared by chemical vapor infiltration (CVI). The Yb2Si2O7 interphase exhibited no changes throughout the high‐temperature preparation process and maintained stability and compatibility with the fiber and matrix. The tensile strength of SiCf/Yb2Si2O7/SiC minicomposites with Yb2Si2O7 interphase was significantly higher than SiCf/SiC minicomposites without interphase. The crack deflection, interfacial debonding, and fiber pullout were observed in the tensile fracture of the SiCf/Yb2Si2O7/SiC minicomposites.

Improved densification of SiCf/SiC composites by microwave-assisted chemical vapor infiltration process based on multifrequency solid-state sources excitation

Improved densification of SiCf/SiC composites by microwave-assisted chemical vapor infiltration process based on multifrequency solid-state sources excitation

Understanding fiber preform effects on tensile strengths of SiC/SiC composites prepared by chemical vapor infiltration based on a unified fiber bundle bending view

Understanding fiber preform effects on tensile strengths of SiC/SiC composites prepared by chemical vapor infiltration based on a unified fiber bundle bending view

Preparation of Si3N4f/Si3N4 wave-transparent composites by vat photopolymerization combined with chemical vapor infiltration

Preparation of Si3N4f/Si3N4 wave-transparent composites by vat photopolymerization combined with chemical vapor infiltration