Effect Of SiC Nanowires Research Articles

Effect of SiC nanowires on ablation property of Cu-doped C/C-ZrC composites

In-situ SiC nanowires were prepared by sol-gel method, followed by the fabrication of C/C-ZrC composites using low-temperature reaction melt infiltration using Zr-Cu alloy. Thermal physical test results verify that the growth of in-situ SiC nanowires can improve thermal conductivity and minimize interlayer thermal expansion of composites. Addition of SiC nanowires can effectively reduce surface temperature and ablation rates. Thermodynamic calculations revealed the ablative process in the Zr, Si and Cu ternary system, yielding SiO2 and ZrO2 as oxidation products. The presence of Si promotes the formation of ZrO2 oxide layer, while Cu evaporates directly in center region.

Effect of SiC nanowires on adhesion and wear resistance of hydroxyapatite coating on AZ31 magnesium alloy

Hydroxyapatite (HA) coatings doped with different contents of SiC nanowire (SiCnws) were prepared on the surface of AZ31 magnesium alloy by electrophoretic deposition to solve the problems of low adhesion and poor wear resistance of pure HA coatings. Performance tests were conducted on the coating, including corrosion resistance, adhesion and wear performance. The results showed that the prepared coating was intact. The adhesion and wear resistance of the coating were significantly improved when the doping amount of SiCnws was 3%. Among them, the adhesion increased by 37.06% and the scratch depth decreased by 86.67%. At the same time, the corrosion resistance of the coating still maintained a high level. It showed that the performance of doping 3% SiCnws modified coating was balanced and excellent in all aspects.

Effect of Reinforcement Size on Mechanical Behavior of SiC-Nanowires-Reinforced 6061Al Composites

In the present study, the effects of SiC nanowires (SiCnws) with diameters of 100 nm, 250 nm and 450 nm on the microstructure and mechanical behavior of 20 vol.% SiCnws/6061Al composites prepared by pressure infiltration were studied. It was found that the interface between SiCnws and Al matrix was well bonded, and no interface product was found. The thicker SiCnws are beneficial to improve the density. In addition, the bamboo-like and bone-like morphologies of SiCnws produce a strong interlocking effect between SiCnws and Al, which helps to improve the strength and plasticity of the material. The tensile strength of the composite prepared by SiCnws with a diameter of 450 nm reached 544 MPa. With a decrease in the diameter of SiCnws, the strengthening effect of SiCnws increases. The yield strength of SiCnws/6061Al composites prepared by 100 nm is 13.4% and 28.5% higher than that of 250 nm and 450 nm, respectively. This shows that, in nano-reinforced composites, the small-size reinforcement has an excellent improvement effect on the properties of the composites. This result has a guiding effect on the subsequent composite structure design.

Oxidation and ablation behaviours of a SiCnw@SiC–Si coating fabricated for carbon-fibre-reinforced carbon-matrix composites via thermal evaporation and gaseous silicon infiltration

A SiC-nanowire-modified SiC–Si (SiCnw@SiC–Si) coating was prepared for carbon-fibre-reinforced carbon-matrix (C/C) composites using a two-step method based on thermal evaporation and gaseous silicon infiltration, and the effects of SiC nanowires on the oxidation and ablation behaviours of the coated samples were studied. Oxidation tests conducted at 1500 °C revealed that the weight loss of the SiC–Si-coated C/C composite was 15.85% after 6 h, whereas the SiCnw@SiC–Si-coated C/C composite experienced a significantly lower weight loss of 1.27% after 50 h. Ablation tests suggested that the mass and linear ablation rates of the SiCnw@SiC–Si-coated C/C composite were 0.05 mg/s and 0.09 μm/s, respectively; they were reduced by 78.26 and 92.74%, respectively, compared with those of the SiC–Si-coated C/C composite. Careful characterisation suggested that the network structure of the SiC nanowires in the SiC–Si phase can suppress crack propagation and firmly attach to the coating surface to enhance the interfacial adhesion between the coating and substrate, leading to improved anti-oxidation and anti-ablation properties. The SiCnw@SiC–Si coating could offer a technological foundation for preventing the oxidation and ablation of C/C composites in aerospace engineering.

Influence of SiC nanowires on the microstructures and properties of Ag–Cu–Ti filler metals and brazed joints

Ag–26.7Cu–4.5Ti filler metals with different contents of SiC nanowires were prepared to analyze the effect of SiC nanowires on the microstructures, melting temperature, wettability, shear strength and fracture morphology of brazed joints. The results indicate that a small amount of SiC nanowires ([Formula: see text]0.1%) can refine the matrix microstructure and reduce the Cu–Ti intermetallic compounds, which can induce the increase of shear strength of brazed joints with 46.7% maximum amplitude, the ductile pattern is the main fracture mode for Ag–Cu–Ti–1.0 SiC brazed joints. Moreover, the SiC nanowires can improve the spreading are of Ag–Cu–Ti filler metals on steel substrate with a 9.4% increase amplitude, when the content of SiC nanowires is more than 0.1%, the wettability can be reduced obviously. The addition of SiC nanowires can show little effect on the melting temperature, which results in the same brazing temperature for Ag–Cu–Ti–[Formula: see text]SiC filler metals. With the optimization content of SiC nanowires, the optimal content of SiC is 0.05–0.1%, excessive SiC addition with agglomeration can decrease the wettability and shear strength.

Effect of SiC nanowires on the mechanical properties and thermal conductivity of 3D-SiCf/SiC composites prepared via precursor infiltration pyrolysis

In this study, SiC nanowires (SiCNWS) were grown in situ on the surface of PyC interface through chemical vapor infiltration (CVI) to improve the mechanical characteristics and thermal conductivity of three-dimensional SiCf/SiC composites fabricated via precursor infiltration pyrolysis (PIP). The effect of SiCNWS on the properties of the obtained composites was investigated by comparing them with conventional SiCf/PyC/SiC composites. After the deposition of SiCNWS, the flexural strength of the SiCf/SiC composites was found to increase by 46 %, and the thermal conductivity showed an obvious increase at 25−1000 °C. The energy release of the composites in the damage evolution process was analysed by acoustic emission. The results indicated that the damage evolution process was delayed owing to the decrease in porosity, the crack deflection and bridging of the SiCNWS. Furthermore, the excellent thermal conductivity was attributed to the thermally conductive pathways formed by the SiCNWS in the dense structure.

Effects of SiC nanowires on reliability of Sn58Bi-0.05GNSs/Cu solder joints

In this work, SiC nanowires (SiC NWs) reinforced SBG (Sn-58Bi-0.05GNSs) composite solder was prepared using powder metallurgy route. The effect of SiC NWs on melting temperature, wetting behavior, shear properties, microstructure of the prepared solder joints and interfacial reaction were studied in detail. Results reveal that incorporating SiC NWs can develop the wetting behavior and shear properties of solder joint but has a little effect on melting temperature. The microstructure of solder is refined markedly with the addition of SiC NWs, which is one of the reasons for the increase in the shear strength of the solder joints. Additionally, the dimension of Cu6Sn5IMC grains diminishes with the doping of SiC NWs, which resulted in the thinning of Cu6Sn5IMC layer. Thence, the addition of SiC NWs may be an effective way to improve the reliability of solder joints.

Mechanical properties and strengthening mechanism of SiCf/SiC mini-composites modified by SiC nanowires

The effects of the SiC nanowires (SiCNWs) and PyC interface layers on the mechanical and anti-oxidation properties of SiC fiber (SiCf)/SiC composites were investigated. To achieve this, the PyC layer was coated on the SiCf using a chemical vapour infiltration (CVI) method. Then, SiCNWs were successfully coated on the surface of SiCf/PyC using the electrophoretic deposition method. Finally, a thin PyC layer was coated on the surface of SiCf/PyC/SiCNWs. Three mini-composites, SiCf/PyC/SiC, SiCf/PyC/SiCNWs/SiC, and SiCf/PyC/SiCNWs/PyC/SiC, were fabricated using the typical precursor infiltration and pyrolysis method. The morphologies of the samples were examined using scanning electron microscopy and energy dispersive X-ray spectrometry. Tensile and single-fibre push-out tests were carried out to investigate the mechanical performance and interfacial shear strength of the composites before and after oxidization at 1200 °C. The results revealed that the SiCf/PyC/SiCNWs/SiC composites showed the best mechanical and anti-oxidation performance among all the composites investigated. The strengthening and toughening is mainly achieved by SiCNWs optimization of the interfacial bonding strength of the composite and its own nano-toughening. On the basis of the results, the effects of SiCNWs on the oxidation process and retardation mechanism of the SiCf/SiC mini-composites were investigated.

Effect of SiC nanowires on compression and thermal properties of SiC nanowires/lightweight carbon foam composites

Commonly, the lightweight carbon foam (LCF) derived from polymer foams possesses inherent large pores which significantly limit its application in thermal insulation. In this study, the SiC nanowires/lightweight carbon foam composites (SnwLCF) were prepared experimentally by depositing SiC nanowires on the three-dimensional skeletons of LCF through chemical vapor infiltration (CVI) process. The microstructure, compression property and thermal conductivity of the SnwLCF were investigated systematically. The results indicated that the macro-pores of LCF were divided by SiC nanowires, and many smaller pores were formed inside them. The divided pores were considered to be the key to improve the thermal insulation performance of LCF. Furthermore, the contents of SiC nanowires played an important role in the compression and thermal properties of the SnwLCF. Hence, this study had reference significance for the design and optimization of the porous thermal insulation materials.

Effect of SiC nanowires on the high-temperature microwave absorption properties of SiCf/SiC composites

SiC-nanowire-reinforced SiCf/SiC composites were successfully fabricated through an in situ growth of SiC nanowires on SiC fibres via chemical vapour infiltration. The dielectric and microwave absorption properties of the composites were investigated within the frequency range of 8.2–12.4 GHz at 25–600 °C. The electric conductivity and complex permittivity of the composites displayed evident temperature-dependent behaviour and were enhanced with increasing temperature. The composites exhibited superior microwave absorption abilities with a minimum reflection loss value of −47.5 dB at 11.4 GHz and an effective bandwidth of 2.8 GHz at 600 °C. Apart from the contribution of the interconnected SiC nanowire network and multiple reflections, the excellent microwave absorption performance was attributed to dielectric loss that originated from SiC nanowires with abundant stacking faults and heterostructure interfaces. Results suggested that the composites are promising candidates for high-temperature microwave absorbing materials.

Strengthening behavior in high content SiC nanowires reinforced Al composite

Recently, it has been found that the larger surface areas of SiC nanowires have significant effect on the microstructure and performance of composites. The strengthening effect of SiC nanowires is preceded to the traditional micron-scale reinforcements. However, the strengthening behavior and corresponding model of the SiCnw/6061Al composite has not been understood yet. Therefore, in the present work, SiCnw/6061Al composites with different fractions (10, 15 and 20vol%) have been prepared by pressure infiltration method. The effect of SiC nanowires' amount on the microstructure and the mechanical properties of SiCnw/Al composites has been investigated. The interface between SiC nanowires and Al matrix was well bonded and free of interfacial reaction products regardless of heat treatments. The tensile strength of annealed SiCnw/6061Al composites was increased with the content of SiC nanowires. However, the tensile strength of aged SiCnw/6061Al composite was reached to its maximum at 15vol%, which should be attributed to the higher porosity of the composites. The yield strength was increased with the content of SiC nanowires, and the strengthening behavior of SiCnw/6061Al composites could be described by the modified shear-lag model. The strengthening factor (the slope of σcy–Vr curves) of SiCnw/6061Al composites is much higher than that of Al composite reinforced with particulates and short whiskers.

Enhancement of the oxidation resistance of C/C composites by depositing SiC nanowires onto carbon fibers by electrophoretic deposition

SiC nanowires (SiCNWs) were introduced into carbon fiber (CF) cloth laminated preform by electrophoretic deposition (EPD) and they were used to modify carbon/carbon (C/C) composites. The effects of SiCNWs on the oxidation kinetics and retardation mechanism of C/C composites were investigated. Compared with C/C composites, SiC nanowire reinforced C/C (SiCNW–C/C) composites have a better oxidation resistance since SiCNWs can act as connecting bridges between the adjacent carbon cloth layers, strengthen the adhesion of interlayer matrix, thus inhibit the formation of rapid oxidation channels such as annular matrix cracks and interlamination interface debonding.

Effect of SiC nanowires on the thermal shock resistance of joint between carbon/carbon composites and Li2O–Al2O3–SiO2 glass ceramics

Abstract In order to improve the bonding property of joint between SiC modified carbon/carbon (C/C) composites and Li2O–Al2O3–SiO2 (LAS) glass ceramics, SiC nanowires were attempted as the reinforcement materials in the interface region of SiC transition layer and Li2O–MgO–Al2O3–SiO2 (LMAS) gradient joining interlayer. The C/C–LAS joint with SiC nanowire-reinforced interface layer was prepared by a three-step technique of pack cementation, in situ reaction and hot-pressing. The microstructure and thermal shock resistance of the as-prepared joints were examined. The average shear strength of the joined samples with SiC nanowires increased from 24.9 MPa to 31.6 MPa after 40 thermal cycles between 1000 °C and room temperature, while that of the joined samples without SiC nanowires dropped from 21.4 MPa to 8.3 MPa. The increase of thermal shock resistance of the C/C–LAS joints was mainly attributed to the toughening mechanism of SiC nanowires by pullout, bridging and crack deflection.

Effect of in situ grown SiC nanowires on microstructure and mechanical properties of C/SiC composites

Hexagonal-shaped SiC nanowires were in situ formed in C/SiC composites with ferrocene as catalyst in the densification process of polymer impregnation and pyrolysis. The effect of SiC nanowires on microstructure and properties of the composites were studied. The results show that the in situ formed SiC nanowires were hexagonal, mostly with diamer of about 250nm, and grew by the vapor–liquid–solid (VLS) mechanism. The C/SiC composite with nanowires shows higher bulk density and flexural strength than the one with no SiC nanowires, and the high temperature flexural strength behavior of C/SiC composites with SiC nanowires was evaluated.

Novel method to synthesize SiC nanowires and effect of SiC nanowires on flexural strength of Cf/SiC composite

The graphite fiber toughened silicon carbide (Cf/SiC) composite was annealed at 1500, 1600, 1700, 1750, 1800 and 1850°C for 30min and the flexural strength increased first and then decreased as annealing temperature increased. The maximum flexural strength was obtained for the sample annealed at 1750°C. The microstructure observation indicated that the amount and length of in situ formed SiC nanowires increased as the annealing treatment time increased, which was very favorable to the improvement of flexural strength. The formation of SiC nanowires was attributed to the presence of the metal La and Al. The vapor–liquid–solid growth mechanism of the SiC nanowires along 〈111〉 direction is proposed. Furthermore, the purpose of this paper is to report novel method to synthesize SiC nanowires.

The effect of SiC nanowires on the flexural properties of CVI-SiC/SiC composites

Single crystal SiC nanowires with volume fractions of 0%, 1.6%, 5.7% and 6.1% were incorporated in the matrices of several CVI-Tyranno-SA/SiC composites, to study the effects of the nanowires on the flexural properties of the composites. The results show that the SiC nanowires are very effective reinforcements for SiC/SiC composites. The flexural modulus, proportional limit stress and ultimate strength increase linearly with the increasing nanowires volume fraction. Specifically, the flexural properties depend on the thickness of carbon coating on the nanowires.