Liquid Infiltration Technique Research Articles

Mechanical characteristics of Si/SiC graded ceramic lattice structures with a triply periodic minimal surface fabricated by laser powder bed fusion

SiC graded ceramic lattice structures (GCLSs) have attracted rising attention owing to outperformed merits including ultra-lightweight and excellent specific strength compared with uniform ceramic lattice structures (UCLSs). In this study, Si/SiC Gyroid GCLSs with variable relative densities (35 % and 45 %) and different gradient directions were designed and fabricated via laser powder bed fusion combined with liquid silicon infiltration techniques. 35 % and 45 % UCLSs were also prepared as a reference. The manufacturing precision and mechanical responses of these CLSs were systematically investigated through compressive tests and micro-computed tomography analysis. The mechanical performances of 35 % GCLSs are lower than that of 35 % UCLSs. The weaker load-bearing capacity in the upper portion and the stress concentration in the inclined load-bearing surface lead to the knockdown of mechanical properties for 35 % GCLSs. The nonlinear superposition of mechanical properties in 45 % GCLSs is the main reason for the superior mechanical performance of 45 % GCLSs compared to 45 % UCLSs. Besides, various theoretical models and finite element simulations were implemented to evaluate the mechanical properties of SiC CLSs. The comparison of compressive strength with other ceramic porous structures emphasized the exceptional mechanical properties (16.07 MPa for 35 % UCLSs and 22.91 MPa for 45 % GCLSs) of Si/SiC CLSs.

Magnesium Strengthening in 3D Printed TCP Scaffold Composites

This study reports the production of a Mg/15%β-tricalcium phosphate Ca3(PO4)2 composite by combining direct ink writing for the β-TCP preform and liquid infiltration technique to obtain a continuous metal matrix composite. The influence of the volume fraction of β-TCP and the in situ reaction between ceramic and metal on the microstructure and mechanical properties were investigated in detail. The β-TCP preform was uniformly distributed in the matrix, forming a continuous three-dimensional (3D) network. The obtained composite was characterized by means of relative density (He pycnometry), X-ray diffractometry (XRD), scanning electron microscopy (SEM), and electron spectroscopy (EDX). The results suggested that a highly densified composite was processed. Three phases were identified as products generated by an exothermic reaction (Mg2Ca, CaO, and MgO); based on this, the chemical reaction mechanism for MgO formation was proposed. The compression and hardness tests showed that the Mg/15%β-tricalcium phosphate Ca3 (PO4)2 composite significantly improved its mechanical properties, i.e., 27% and 15% higher than pure Mg in compressive strength and yield strength, respectively. This behavior was attributed to the high densification of the resulting composite, strong chemical interfacial bonding, phase dispersion hardening (in situ phase formation), and the geometry and continuity of the reinforcement. These provided good load transfer from the Mg matrix to the reinforcement and contributed as strengthening mechanisms. The results reported in this investigation can help to design Mg/calcium phosphate continuous composites for biomedical applications.

Frequency Characteristics of High Strain Rate Compressions of Cf-MWCNTs/SiC Composites

The incorporation of ductile reinforcements into ceramics helps restrain crack deflection, which can enhance ceramics’ toughness and overcome the matrix’s brittleness. In this paper, we produced a ceramic composite reinforced by carbon fibers coated by multi-wall carbon nanotubes (shortened by Cf-MWCNT/SiC composites) for enhanced impact resistance at a high strain rate that commonly occurs in composite materials used in astronautics, marine, and other engineering fields. The fabrication process involves growing multi-wall carbon nanotubes (MWCNTs) on a carbon fiber woven fabric (Cf) to create the fibril/fabric hybrid reinforcement. It is then impregnated by polymer solution (precursor of the ceramics), forming composites after the pyrolysis process, known as the liquid polymer infiltration and pyrolysis (PIP) technique. To assess the impact resistance of the Cf-MWCNT/SiC under high-strain rate compressions, the split Hopkinson pressure bar (SHPB) technique is employed. Since the failure behavior of the Cf-MWCNT/SiC composites in the absence of the ductile phase is not well understood, the study employs the Hilbert–Huang transform (HHT) to analyze the stress–time curves obtained from the SHPB experiments. By applying the HHT, we obtained the frequency–time spectrum and the marginal Hilbert spectrum of the stress signals. These analyses reveal the frequency characteristics of the Cf-MWCNT/SiC composite and provide insights into the relationship between transformed signal frequency and fracture behavior. By understanding the dynamic fracture behavior and frequency response of the Cf-MWCNT/SiC, it becomes possible to enhance its impact resistance and tailor its performance for specific protective requirements. Therefore, the findings of this study can guide the future design and optimization of Cf-MWCNT/SiC structures for various protective applications, such as body armor, civil structures, and protections for vehicles and aircraft.

On the hydrodynamics of macroporous structures: Experimental, CFD and artificial neural network analysis

Porous metallic structures play a critical role in mass and heat transfer processes due to their high surface areas, fixed porosity, and high stiffness – so understanding their fluid flow behaviour is crucial in designing materials that perform efficiently in mass and heat transfer. In view of this, a multi-disciplinary approach is employed to study the hydrodynamics of aluminium foams produced by a liquid melt infiltration technique using experimental, computational fluid dynamics (CFD) modelling and simulation, as well as artificial neural network (ANN) machine learning backpropagation. X-ray computed tomography datasets were used to characterize pore-structure-related properties of replicated materials, followed by three-dimensional advanced imaging of workable representative volume elements. Hydraulic flow information was acquired for the porous matrices using the constant-head permeameter technique. Experiments showed the permeability and Forchheimer coefficient dependence on pore-structure-related properties for fluid-flowing within the pre-Forchheimer and fully developed Forchheimer regimes. Flow permeability of 8.479 × 10−09m2 was highest in the material with the widest mean pore openings (0.212 mm) and lowest (1.291 × 10−09m2) in the material with the narrowest mean pore openings (0.106 mm). Conversely, Forchheimer coefficients were higher for materials with lower porosities and lower for materials with higher porosities. CFD calculations accurately predicted the fluid properties of metallic foams, as well as the influence of intrinsic foam properties on permeability and the Forchheimer coefficient. The ANN model framework was also able to provide valuable information about the hydrodynamics of these materials. Convolution and non-linearity of the ANN model were improved by adding supplementary neurons to the hidden layers allowing deviations within 0.3 and 9.0 percent to be attained.

Investigation of Microstructural Features and Mechanical Characteristics of the Pressureless Sintered B4C/C(Graphite) Composites and the B4C-SiC-Si Composites Fabricated by the Silicon Infiltration Process.

The B4C/C(graphite) composites were fabricated by employing a pressureless sintering process. The pressureless sintered B4C/C(graphite) composites exhibited extremely low mechanical characteristics. The liquid silicon infiltration technique was employed for enhancing the mechanical property of B4C/C(graphite) composites. Since the porosity of the B4C/C(graphite) composites was about 25–38%, the liquid silicon was able to infiltrate into the interior composites, thereby reacting with B4C and graphite to generate silicon carbide. Thus, boron carbide, silicon carbide, and residual silicon were sintered together forming B4C-SiC-Si composites. The pressureless sintered B4C/C(graphite) composites were transformed into the B4C-SiC-Si composites following the silicon infiltration process. This work comprises an investigation of the microstructure, phase composition, and mechanical characteristics of the pressureless sintered B4C/C(graphite) composites and B4C-SiC-Si composites. The XRD data demonstrated that the pressureless sintered bulks were composed of the B4C phase and graphite phase. The pressureless sintered B4C/C(graphite) composites exhibited a porous microstructure, an extremely low mechanical property, and low wear resistance. The XRD data of the B4C-SiC-Si specimens showed that silicon infiltrated specimens comprised a B4C phase, SiC phase, and residual Si. The B4C-SiC-Si composites manifested a compact and homogenous microstructure. The mechanical property of the B4C-SiC-Si composites was substantially enhanced in comparison to the pressureless sintered B4C/C(graphite) composites. The density, relative density, fracture strength, fracture toughness, elastic modulus, and Vickers hardness of the B4C-SiC-Si composites were notably enhanced as compared to the pressureless sintered B4C/C(graphite) composites. The B4C-SiC-Si composites also manifested outstanding resistance to wear as a consequence of silicon infiltration. The B4C-SiC-Si composites demonstrated excellent wear resistance and superior mechanical characteristics.

Microstructure Evolution and Performance Improvement of Silicon Carbide Ceramics via Impregnation Method.

The high topological silicon carbide (SiC) ceramics can be prepared by stereolithography (SLA) combined with liquid silicon infiltration (LSI) techniques. This paper aims to enhance the performance of SiC ceramics prepared by SLA and LSI techniques via the cyclic impregnation/carbonization of the precursor of carbon source solution before LSI. The effects of impregnation/carbonization cycles on the microstructure and properties of C/SiC preform and sintered body were analyzed in detail. The results show that, with the increase of impregnation/carbonization cycles, the porosity in the C/SiC preform decreases obviously and the content of secondary SiC in the sintered body increases effectively. Especially, when the impregnation/carbonization cycle was performed twice, the sintered body had the optimal mechanical properties. The value of flexural strength, bulk density and elastic modulus were 258.63 ± 8.33 MPa, 2.95 ± 0.02 g/cm3 and 425.16 ± 14.15 GPa, respectively. In addition, the thermal dimensional stability of sintered body was also improved by this method. This method proves that SiC ceramics prepared by SLA combined with LSI have the potential of applications in space optical mirrors.

Fabrication of SiCf/SiC composites through hybrid processing via chemical vapor infiltration, electrophoretic deposition, and liquid silicon infiltration

ABSTRACT The present work demonstrates the effectiveness of a novel hybrid process comprising chemical vapor infiltration (CVI), electrophoretic deposition (EPD), and liquid silicon infiltration (LSI) techniques for the successful fabrication of low-porosity SiCf/SiC composites. For this purpose, fiber/matrix interphase dual coating layers of BN and SiC were coated onto SiC fabrics using CVI. A ceramic matrix consisting of SiC and carbon black nanoparticles was then infiltrated into the fine voids of the fabrics using EPD. Finally, LSI was performed to obtain dense microstructures with low porosities by filling the remaining small gaps and reacting Si with C to form SiC. Microstructural results observed by scanning electron microscopy revealed a dense structure with no damage to the fibers. The experimental density was found to be 2.62 g/cc, with an open porosity of 0.55. The room-temperature flexural strength was evaluated to be 111 MPa, and the composites displayed little fiber pull-out.

Dual pump broadband fiber-optic parametric amplifier based on near-zero dispersion photonic crystal fiber with single zero dispersion wavelength

A broadband fiber-optic parametric amplifier (FOPA) based on near-zero dispersion profile with single zero dispersion wavelength (ZDW) by selective liquid infiltration technique is numerically investigated. Here, the gain and bandwidth for an FOPA incorporating “dual pumping” scheme are thoroughly investigated by varying the fiber length, operating wavelength (central wavelength), and pump power. The structure is engineered in such a way that the dispersion profile is having near-zero dispersion value (negative β2) for a wide wavelength range and small positive β4 around the pump wavelength; thereby, the phase mismatch term remains within the favorable value for a wide wavelength leading to wider FOPA sources. The structure also supports reasonable high nonlinearity and low propagation loss. Our numerical investigation results in an FOPA with optimized bandwidth of around 180 nm close to communication wavelength. Finally, a detailed comparative study of the single pump scheme and dual pump scheme for FOPA/amplifier gain and spectrum bandwidth has been performed for identical fiber parameters. It has been observed that dual pump scheme provides smoother/flatter spectrum (lesser gain fluctuation) around the center of the optimized profile with slightly lesser bandwidth compared to single pump operation. Additionally, it was observed that the dual pump FOPA supports higher pump power thereby enabling higher FOPA unaltered peak gain (3 dB) throughout the bandwidth (the peak and dip of the gain spectrum difference remaining within 3 dB) than that of single pump scheme.

Effect of CNT impregnation on the mechanical and thermal properties of C/C-SiC composites

The present study investigates the effect of additional carbon source, in the form of carbon nanotubes (CNTs), on mechanical and thermal properties of carbon fiber reinforced silicon carbide (C/C-SiC) ceramic matrix composites (CMC) produced by liquid silicon infiltration (LSI) technique. The CNTs used in this study were impregnated into the C/C preforms before the liquid silicon infiltration stage. The results showed that the addition of excess carbon to the C/C preforms in the form of CNTs enhanced Si infiltration efficiency significantly resulting in C/C-SiC composites with higher density and microstructural uniformity. Accordingly, the addition of CNTs improved the flexural strength of the composites by 40% with respect to no-CNT-containing composites due to a lower amount of residual porosity and additional reinforcement effect of the unreacted CNTs. The thermal conductivity of the resulting C/C-SiC composites has been also increased by 31% and 18% parallel and perpendicular to the carbon fiber–woven fabric surface, respectively, by CNT addition.

Effect of HOD parameters on gain and bandwidth of parametric amplifiers for near-zero ultra-flat dispersion profile

Higher order dispersion (HOD) parameters play an important role in the overall performance of fiber optic parametric amplifier (FOPA). Effect of HOD parameters on gain spectrum and bandwidth for an engineered dispersion profile has been investigated revealing some interesting outcomes. Here, we have optimized a near-zero ultra flat dispersion profile around the communication wavelength based on selective liquid infiltration technique. The performance of FOPA in terms of gain and bandwidth based on the optimized dispersion profile is thoroughly investigated incorporating different HOD parameters. Considering upto 6th order of HOD terms, we could observe one additional sharp gain peak (on both sides of the central gain maxima) which otherwise is absent when considering other lesser values of HOD parameters. The spectral shift and width of the additional peaks are found to vary significantly due to the incorporation of these different HOD terms. The effect of HOD parameters are found to be extremely significant for the generation of new frequencies as well as modification of the peak widths for the communication band application.

Tensile Fracture Behavior of Carbon Fiber/Al Composites Produced by the Liquid Extrusion Infiltration Technique

The liquid extrusion infiltration technique was used to fabricate two 2D CF/Al composites with T700 and T300 carbon fiber fabrics. Microstructure examination demonstrated their different macroscopic infiltration morphology, but the infiltration effect was perfect. The coefficient of thermal expansion of those two composites was shown to be much lower than that of the matrix alloy below 673 K (400°C). At a temperature higher than 673 K (400°C), this value for a T300 CF/Al composite was equivalent to only 22.6%, which was much smaller than that of the matrix alloy. The ultimate tensile strength of T700 CF/Al and T300 CF/Al composites was improved by factors of 2.007 and 2.467 than that of the matrix alloy, respectively. The differences in the thermal expansion coefficient and ultimate tensile strength stem from carbon fiber volume fractions and its grades of the two different fabrics. The fracture morphology of tensile specimens was also influenced by the fiber orientation in fabrics. A T300 CF/Al composite displayed better tensile and thermal expansion properties than a T700 CF/Al composite, which were prepared and designed for further industrial applications.

Robocasting of reaction bonded silicon carbide structures

A novel shaping method for the fabrication of reaction bonded silicon carbide structures was investigated in this work. A paste consisting of silicon carbide as inert filler and carbon powder was developed and printed by robocasting technology. Layer by layer deposition of the ceramic paste facilitates the printing of complex shaped structures. Different structures such as lattices, hollow cylinders, bending bars and gyroids were printed using nozzles with diameter of 0.5 mm and 1.5 mm. After pyrolysis at 700 °C and further heat treatment at 1850 °C the samples were infiltrated using the liquid silicon infiltration technique to obtain dense near-net shape RBSC structures. The robocasted structures showed a hardness of approximately 20 GPa, a thermal conductivity of ∼112 W/m*K, Young’s modulus of ∼356 GPa, flexural strength of ∼224 MPa and an amount of residual silicon of approximately 23%. These measured properties are comparable with those of traditionally fabricated RBSC.

Dry sliding wear behavior of infiltrated particulate reinforced Ni/TiC composites

Nickel-Titanium carbide composites are promising candidates for abrasive applications where high electrical and thermal conductivity and good wear resistance are needed. This paper describes the dry sliding wear behavior of a Ni/TiC composite material. The composite with 60 vol% reinforcement was prepared by a liquid infiltration technique, obtaining a continuous matrix material and homogeneous distribution of the reinforcement. The wear behavior of the composite with residual porosity of 1.4% and hardness 49 HRC was investigated under two-body abrasion conditions using a pin-on-ring device with a counterpart ring made of M2 hard steel. An increase in the wear rate was observed when increasing the applied load and the sliding distance, while decreasing at a higher sliding speed. The first part of the wear process is characterized by a tribochemical reaction mechanism by oxidation of the matrix.At higher speed the increase in temperature between the surfaces favors the formation of stable and adherent oxides of the type NiO and likely TiO2 that act as lubricants. Iron oxide is also likely to form due to wear of M2 ring, most likely Fe3O4. The characteristics of the worn surfaces at higher load and lower speed suggest a dominant mechanism of adhesion wear, showing a significant amount of material displaced plastically towards the margin of the wear track. The TiC particles exposed on the composite surface reduce the load to the matrix, decreasing the wear rate of the ductile material.

A Study on Fatigue Characteristics of Al-SiC Metal Matrix Composites Processed Through Microwave Energy

Aluminium based Metal Matrix Composites are the very promising light materials with enhanced mechanical properties. Aluminium Metal Matrix composites (AMC) are identified as one of the very good materials for aerospace and automobile applications because of their lightweight, cost effectiveness and high stiffness. Metal Matrix Composites can be produced by various methods such as liquid infiltration, stir casting, spray deposition and powder metallurgy technique. Microwave processing of metals is a rapid developing technology which will offer significant time saving and can be cost effective. It is a volumetric process and very efficient to obtain high heating rates due to the interaction of microwave with the material in molecular level. The present work is an attempt made to study the fatigue characteristics of microwave processed Al-SiCP metal matrix composite. Sintering of the compacted Aluminium powder with 4% SiC is carried out using microwave energy. The sintered metal matrix composite is subjected to secondary processing of Extrusion. The fatigue characteristics and micro hardness properties are investigated.

Designing broadband fiber optic parametric amplifier based on near-zero single ZDW PCF with ultra-flat nature

We propose a broadband fiber optic parametric amplifier (FOPA) based on a near-zero ultra-flat dispersion profile with a single zero-dispersion wavelength (ZDW) by using a selective liquid infiltration technique. The amplifier gain and bandwidth is investigated for a variety of fiber lengths, pump power, and operating wavelengths. It is observed that sufficient peak gains and broader bandwidths can be achieved with a small negative anomalous dispersion (β2≤0) and a positive value of the 4th-order dispersion parameter (+ β4) around the pump. We can optimize an FOPA with a bandwidth of more than 220 nm around the communications wavelength.

Effect of Carbon Black Content and Molding Pressure on the Thermal Conductivity of SiC/Si Ceramic Composites

SiC/Si ceramic composites have been considered as promising candidate materials for heat exchanger due to their good thermal conductivity and corrosion resistance. In this work, the SiC/Si ceramic composites were fabricated by liquid silicon infiltration technique, and the effect of carbon black content and molding pressure on thermal conductivity of the composites was studied. With carbon black content increasing from 5 wt. % to 25 wt. %, the thermal conductivity increased from 42.36 W/(m·K) to 65.60 W/(m·K) when molding pressure was fixed as 50 MPa. With molding pressure increasing from 30 MPa to 110 MPa, the thermal conductivity of SiC/Si ceramic composites with 20 wt. % carbon black content increased firstly, and then decreased, obtaining a maximum thermal conductivity of 71.62 W/(m·K) under 90 MPa. The SiC/Si ceramic composites with an optimal thermal conductivity of 76.55 W/(m·K) at room temperature were obtained when carbon black content and molding pressure were 25 wt. %, 90 MPa, respectively.

Densification Behavior and Hardness Evaluation of Consolidated W-25Cu Composite Powder by Re-Compaction Method

In this work, one stage and two stages compaction technique were used to fabricate the tungsten-copper composite powder. Liquid infiltration technique was used to consolidate the W-Cu green compact and a low concentration iron powder was added as activation material to enhance the sintering behavior. In addition, two-steps compaction process was developed for improving mechanical properties of W-Cu composite as well as segregation of Fe around W grain. The green compact was directly infiltrated at 1250 °C for about 2 hours under vacuum conditions. The microstructure, inter-boundary layer and the contamination levels of the infiltrated compacts were characterized using the scanning electron microscope (SEM) and the energy dispersive X-ray analysis (EDX). Relative sintering density varied in the range of 97.1 to 99.3 % of theoretical density, and it was highly depended on Fe concentration and method of compaction. In contrast to one stage compaction, the experimental results showed that the composites fabricated by the two stages of compact ion had better homogeneous structure, high densification and a clear segregation of inter-boundary layer of Fe-W around W grains.

A New Design for All-Normal Near Zero Dispersion Photonic Crystal Fiber with Selective Liquid Infiltration for Broadband Supercontinuum Generation at 1.55 μm

A new design of all-normal and near zero flattened dispersion based on all-silica photonic crystal fibers (PCFs) using selectively liquid infiltration technique has been proposed to realize smooth broadband supercontinuum generation (SCG). The investigation gives the details of the effect of different geometrical parameters along with the infiltrating liquids on the dispersion characteristics of the fiber. Numerical investigations establish a dispersion value of −0.48 ps/nm/km around the wavelength of 1.55 μm. The optimized design has been found to be suitable for SCG around the C band of wavelength with flat broadband wavelength band (375 nm bandwidth) and smooth spectrum with only a meter long of the PCF. The proposed structure also demonstrates good tunable properties that can help correct possible fabrication mismatch towards a better optimization design for various optical communication systems.

Development of Carbon- and Ceramic-Based Composites through Liquid Routes and Their Mechanical Properties

Carbon- and silicon carbide (SiC)-based materials, especially in the form of composites, have attracted more attention from reactor technologists than have other ceramics because they better fulfill the prime requirements of reactor materials, such as high-temperature stability and low susceptibility to irradiation and nonbrittle fracture. These composites are fabricated through different routes and may vary in their properties. Therefore, sufficient data need to be generated on the microstructure and mechanical properties of these composites. In the studies reported here, carbon- and SiC-based fibrous ceramic composites were prepared using a liquid-infiltration sol-gel technique with carbon fibers as reinforcement and hybrid sol and pitch as matrix precursors. To some compositions, SiC nanoparticles were added. The composites were heated to 1000°C and 1500°C. The sol-gel route results in an amorphous mixed oxycarbide, silica, and carbon matrix, which on heat treatment at 1500°C is converted to a semicrystalline SiC matrix composite. Scanning electron microscope examination of carbon fiber/carbon and carbon fiber/SiC composites showed good wetting of fibers by matrix resin, forming good bonding at the interface. The carbon fiber/SiC composites with SiC nanoparticles as additional reinforcement showed higher density as well as a 34% increase in flexural strength compared with those without nanoparticles. The addition of just 1 wt% of SiC nanoparticles decreased oxidation by 4 wt%.

Comparison of Liquid Phase Sintering and Cu-Melt Infiltration Methods to Consolidate 80W-Cu Composite Using Nickel as Sintering Activator

In this article, studies were conducted to evaluate the densification of W-Cu sintered compacts produced using two methods; liquid phase sintering (LPS) and combination of liquid phase sintering and liquid infiltration technique (LPS+LI) named Cu-melt infiltration (Cu-MI). Low concentration of nickel (1wt.%) was used to activate the sintering process in both methods. Isothermal sintering was carried out in alumina tube furnace at temperatures of 1150°C for 2 hr. under H2/Ar. as protective gas. The infiltration (Cu-MI) method proved to be effective in the densification, microstructure and hardness enhancement of the 80W-Cu compact as opposed to the other conventionally liquid phase sintered compacts. The relative densities of 80W-Cu-1Ni composites prepared by using insert method (Cu-melt infiltration) achieved 96.22% of theoretical density.