Nanosized SiC Powders Research Articles

Microstructural characterization and enhanced tensile and tribological properties of Cu–SiC nanocomposites developed by high-pressure torsion

In this study, an attempt has been made to fabricate Cu–SiC nanocomposites by flake powder metallurgy and high-pressure torsion processing techniques at room temperature. Pure Cu and a mixture of Cu and nano-sized SiC powders were mechanically milled separately for 3 h and then green compacts were prepared by uniaxial pressing under 1 GPa pressure. The green compacts experienced 6-turn high-pressure torsion under a pressure of 6 GPa to prepare bulk Cu and Cu–SiC samples. The microstructures of the consolidated samples were characterized using an X-ray diffractometer and a high resolution scanning/transmission electron microscope, and the mechanical properties were evaluated by microhardness, tensile and wear tests. The results show that almost full density samples with ultrafine-grained (UFG) microstructure and well-dispersed nanoparticles in the metal matrix were obtained by the method used. The addition of the nanoparticles reduced the grain size and microstructural gradient between the center and edges of the disk samples. SiC nanoparticles improved copper microhardness by 35%, yield strength by 23% and tensile strength by 9% by implementing various strengthening mechanisms. The produced material showed a reduced coefficient of friction and high wear resistance. Delamination was determined as the major wear mechanism in HPTed Cu–SiC nanocomposite.

Nanosized SiC particle reinforced Ti6Al4V matrix composites manufactured by laser melting deposition

In this work, in-situ (TiC+Ti5Si3)/Ti6Al4V matrix composites (TMCs) with enhanced hardness and wear performance were manufactured by laser melting deposition (LMD) via the addition of nanosized SiC powder. The microstructures of single tracks were investigated to determine the optimal parameters for LMD. Besides, the influence of the SiC content on the microstructural evolutions and mechanical properties was explored. Results demonstrate that the in-situ reaction occurs between SiC and titanium during the LMD process. In-situ TiC and Ti5Si3 were distributed uniformly at grain boundaries and titanium matrix with a full-columnar grains for 0.5 wt.% and 1.0 wt.% SiC addition. The morphology of the composites consists of equiaxed grains with a three-dimensional quasi-continuous network structure when the content of SiC increases to 1.5 wt.% and 3.0 wt.%. The hardness of the composites is 321.1, 342.3, 347.8, and 442.1 Hv with the increasing formation of reinforcements. Meanwhile, the average coefficient of friction decreases from 0.39 to 0.32 with the wear mechanism changing from abrasion to adhesive wear.

Effect of Nano-Sized SiC Powder Filler on Additive Manufactured Properties of Precursor-Derived Ceramics

Effect of Nano-Sized SiC Powder Filler on Additive Manufactured Properties of Precursor-Derived Ceramics

Multiple thermal resistance induced extremely low thermal conductivity in porous SiC-SiO2 ceramics with hierarchical porosity

Maximizing interfaces for blocking heat conduction in porous ceramic structures is an efficient approach for achieving maximum thermal resistance. Here, we adopted three strategies simultaneously for maximizing thermal resistance in porous SiC-based ceramics: (1) addition of nano-sized silica into nano-sized SiC powder for generating SiC/SiO2 interfaces, (2) addition of nano-sized carbon into nano-sized SiC powder as the template, and (3) sintering in air, which leads to the partial oxidation of the nano-sized SiC particles and burn-out of nano-sized carbon, giving rise to the generation of the SiC-core/SiO2-shell structure and formation of micro-, meso-, and macro-sized pores. The thermal conductivity, compressive strength, porosity, and specific compressive strength of porous SiC-SiO2 ceramics processed at 600 °C with the above strategies were 0.066 Wm−1 K−1, 2.7 MPa, ∼72 %, and 3.9 MPa·cm3/g, respectively.

The Influence of Deformation Modes on the Structure and Properties of Al–Mg–X Powder Composites. III. The Influence of Nanosized SiC Powder Content and Deformation Processing on the Properties of AMg5 Alloy Powder Composites

The structure and mechanical properties of a powder composite with an AMg5 alloy metallic matrix reinforced with SiC particles have been examined. The composite with 3% reinforcing phase shows the best combination of strength, ductility, and damping capacity. Additional deformation processing of the composite improves its strength but reduces ductility because of planar pores observed on the fracture surface of severely deformed samples. It is shown that 30% strain hardening in the rolling process is not accompanied by reduction in ductility.

Conversion of Bagasse Ash Waste to Nanosized SiC Powder

In this work, sugarcane bagasse ash (BA) was used as a low-cost starting material for synthesizing nanosized SiC powder as an alternative to existing techniques for utilizing ever increasing amounts of industrial BA wastes. Fine SiC powder was SHS-produced from BA–C–Mg mixtures and characterized by XRD and SEM. The product powder was found to contain SiC, MgO, and a minor amount of Mg2SiO4. Unwanted MgO and Mg2SiO4 were leached out with acid solutions. The leached product represented the agglomerated powder of nanoparticles with a mean size of about 50 nm. Our approach can help not only to diminish harmful effects caused by ash disposal but also to suggest a cost-effective process for production of fine SiC powder.

Production of Al2O3–SiC nano-composites by spark plasma sintering

In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600°C for 10min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5h. The milled powders were sintered in a SPS machine. After sintering process, phase studies, densification and mechanical properties of Al2O3–SiC composites were examined. Results showed that the specimens containing micro-sized SiC have an important effect on bulk density, hardness and strength. The highest relative density, hardness and strength were 99.7%, 324.6 HV and 2329MPa, respectively, in Al2O3–20wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale.

Effect of MoSi2 addition and particle size of SiC on pressureless sintering behavior and mechanical properties of ZrB2–SiC–MoSi2 composites

In the present paper, ZrB2–SiC–MoSi2 composites were prepared by pressureless sintering at temperatures of 2050, 2100 and 2150°C for 1h under argon atmosphere. In order to prepare composite samples, ZrB2 powder was milled for 2h, then the reinforcing particles including of micron and nano-sized SiC powder were added. MoSi2 was added to ZrB2 from 0 to 5wt.% as sintering aid. The mixtures were formed and, after the pyrolysis, they were sintered. Densification, microstructure and mechanical properties of ZrB2–SiC composites were investigated. The shrinkage of samples was measured, and the microstructure of samples was examined using scanning electron microscopy (SEM), equipped with EDS spectroscopy. In order to examine the oxidation behavior, the samples were heat treated at 1500°C in air and then their weight changes were measured. Room temperature mechanical properties were examined. Mass fraction of MoSi2, particle size of SiC powder and sintering temperature have a great effect on relative density, porosity, shrinkage, hardness, fracture toughness, oxidation resistance and microstructure of these composites. The highest relative density, hardness, fracture toughness and weight changes of 98.7%, 16.17GPa, 3MPam1/2 and 0.28%, respectively, were obtained in ZrB2–10wt.%SiCnano–4wt.%MoSi2 composites sintered at 2150°C.

Effects of Micro and Nano Sized SiC Powder on the Rheological Properties of Al Based Feedstocks for Low Pressure Injection Molding

This study investigates the effects of micro- and nano-sized SiC powder on the rheological behavior of Al based feedstocks for powder injection molding (PIM). Different compositions of Al feedstocks with additions of micro and nano-SiC powder were prepared and their rheological properties were measured with a rotational rheometer. The effects of SiC content and shear rate were investigated and activation energies were compared amongst the feedstocks. The results showed that nano-SiC powder has a prominent effect on the viscosity and yield stress whereas micro-SiC does not have an effective role and the base micro-Al powder determines the overall rheological behavior of the feedstock. It was found that the feedstocks reveal pseudoplastic behavior at low shear rates and dilatancy at high shear rates. The critical shear rate (γcrit) was 100 s-1 for changing the rheological behavior. The activation energy of a given feedstock was found to increase with micro-SiC content while the reverse trend was observed for nano-SiC.

Influence of the vol% SiC on properties of pressureless Al2O3/SiC nanocomposites

Al2O3/SiC nanocomposites were prepared by pressureless sintering with micron-sized Al2O3 powders whose average ranged 5 µm in d50 and nano-sized SiC powders whose average ranged 80 nm in d50 as raw materials. The combined powders were then ball-milled in iso-propanol alcohol and then, the slurry was freeze granulated. Compressed samples were prepared by cold isostatic pressing of the granules. Pressureless sintering was carried out in an argon atmosphere at 1750℃ for 4 h. The physical and mechanical properties, including density, hardness and fracture toughness of specimens as well as microstructural investigations were analyzed. The results showed that by increasing vol% of SiC up to 5, hardness and fracture toughness were improved, whereas by increasing more than 5 vol% of SiC, hardness increased but fracture toughness decreased. The scanning electron microscope micrographs showed that, SiC nanoparticles inhibited the grain growth of Al2O3 and reduced the matrix grain size accordingly.

Pressureless sintering behavior and mechanical properties of ZrB2–SiC composites: effect of SiC content and particle size

In the present paper, ZrB2–SiC composites were prepared by pressureless sintering at temperatures of 2000–2200°C for 1h under argon atmosphere. In order to prepare composite samples, ZrB2 powder was milled for 2h, then the reinforcing particles including of micron and nano-sized SiC powder were added. The mixtures were formed and, after the pyrolysis, they were sintered. Densification, microstructural and mechanical properties of ZrB2–SiC composites were investigated. The shrinkage of samples was measured both before and after the sintering, and the microstructure of samples was examined using scanning electron microscopy (SEM), equipped with EDS spectroscopy. Both mass fraction and size of SiC powder have a great effect on relative density, porosity, shrinkage, hardness and microstructure of these composites. The highest relative density and hardness were 98.12% and 15.02GPa, respectively, in ZrB2–10wt% SiCnano composite sintered at 2200°C.

Composite fabrication in cast Al A206 via friction stir processing

Using friction stir processing (FSP) in forming localised or surface composites in castings can be very advantageous and has significant potential for many applications. Consequently, this study was initiated at ACRC to investigate the feasibility of fabricating composites in Al alloy castings via FSP. The study started with the Al A206 alloy matrix via an ex-situ technique, using a pre-machined groove with emplaced reinforcements. Three reinforcement materials (nanosized tantalum powders, nanosized SiC powders, and discontinuous reinforced aluminium) and several key processing parameters (number of FSP passes, the amount of the reinforced materials) were investigated and localised composites were produced successfully. This paper will present the experimental set-up, procedure, the microstructure and properties of the resulting composites, and a discussion of the formation mechanism of the composite and the influences of materials and process on the microstructure and properties.

A Study of Preparation and Characterization of Nano-Sized SiC Powder Using High Energy Ball Milling

This study investigated the preparation of nanosized crystalline SiC powders from micro sized Silicon Carbide powder at room temperature through high energy ball milling. Silicon carbide was milled with hardened steel balls and ball milling media under identical conditions of ball mass to powder mass ratio 10:1 and target milling times of 60 h. The sample was taken out after every 20 hours of milling and it was characterized for its crystalline size, lattice strain, and percentage of crystalline by using X-Ray Diffractometer (XRD). It was found that for the 60 hours The size, shape and texture of the fresh as well as nanostructured Silicon carbide powder were studied using Scanning Electron Microscopy (SEM). The raw Silicon carbide powder particles were mostly angular in shape. The shape of the 60h milled particles is irregular and the surface morphology is rough.

Preparation of optimal feedstock for low-pressure injection molding of Al/SiC nanocomposite

Abstract This study aims to prepare optimal feedstock for fabrication of Al/SiC nanocomposites by the low-pressure injection molding technique. For this purpose, micron-sized aluminum and nanosized SiC powders were mixed with different amounts of the binder consisting of 89 wt% paraffin wax, 9 wt% bees wax, and 2 wt% stearic acid. Rheometry analyses as well as the Weir model were utilized to determine the optimal feedstock with the desired rheological properties and high homogeneity. Considering powder to binder ratios, shear sensitivity, flow activation energy, and homogeneity within the rheometry analyses, the feedstock of 78 wt% powder loading is selected as the optimal sample for injection molding. Investigation of optimal feedstock by the scanning electron microscopy technique also verified the high homogeneity of this feedstock. In addition, it was observed that all of the feedstocks had thixotrop behavior.

Effect of milling on dielectric and microwave absorption properties of SiC based composites

The electromagnetic and microwave absorption properties of SiC-epoxy composites with the variation in particle size of SiC and dispersion of different metals in SiC have been studied. The micronsized SiC powder was reduced to nanosized SiC powder using high energy planetary ball mill. The results show the significant influence of particle size on the electromagnetic and microwave absorption properties. With the reduction in particle size, complex permittivity and microwave absorption of the epoxy composites have increased to a good extent. For further improvement in microwave absorption, different metal particles were dispersed in the SiC powder and as a result the microwave absorption properties were improved significantly. The values of RL for as-received SiC are improved from −16.23 dB at 10.888 GHz to −37.08 dB at 10.888 GHz with Cr-metal powder dispersion and −43.35 dB at 10.300 GHz with Mn-metal powder dispersion in SiC with 10 h milling. The corresponding 10 dB absorption bandwidth increased from 1.932 GHz to 3.024 GHz for Cr and Mn-metal powder dispersion. This study suggests that the reduction in particle size and metal dispersion in the SiC matrix are effective means to improve microwave absorption.

Synthesis of Nanosized Silicon Carbide Through Non-Transferred Arc Thermal Plasma

A thermal plasma system was used for the preparation of nanosized SiC powder. First SiC was synthesized by solid-state reaction using waste silicon and activated carbon powders and then plasma processing was carried out to form nanosized SiC. Phase and structural analysis was carried out by X-ray diffraction which confirmed the formation of SiC in both cases. Plasma treatment did not show any kind of change in structure and phase of SiC; except little free silicon. Morphological investigation showed the formation of 20–30 nm spherical SiC particles after plasma treatment which was initially 1–5 μm. It was found that DC current played an important role in the reduction of particle size. It was proposed that nanosized SiC was formed due to the dissociation of grains from their grain boundary due to strong plasma gas stream.

Wear Assessment of Ti/SiC Surface Nano-Composite Layer and its Associated CP-Ti Substrate

In the present investigation, the surface of a commercially pure titanium (CP-Ti) substrate was modified to Ti/SiC nanocomposite layer employing friction stir processing technique; nanosized SiC powder was introduced into the stir zone provided by a rotating and advancing tool. The fabricated nanocomposite surface layer exhibited a micro hardness value of ~535HV which is much greater than 160HV of the substrate material using Vickers micro hardness testing. In addition, the un-treated CP-Ti substrate showed sever wear regime in the pin-on-disc test against the hardened AISI 52100 steel. It suffers extensive typical adhesive wear dominated by plastic deformation as evidenced by scanning electron microscopy. Also, deep grooves were formed, i.e. evidence of abrasive wear. Contrary to this, enhanced wear properties were detected for the Ti/SiC nanocomposite surface layer, i.e. lower coefficient of friction and weight loss. The nanocomposite surface layer was found to be adherent to the underlying substrate during the pin-on-disc test. The superior wear behavior of the nanocomposite surface layer is attributed to its improved micro hardness value due to the presence of hard nanosize SiC particles in a refined titanium matrix.

Wear Assessment of Ti/SiC Surface Nano-Composite Layer and its Associated CP-Ti Substrate

In the present investigation, the surface of a commercially pure titanium (CP-Ti) substrate was modified to Ti/SiC nanocomposite layer employing friction stir processing technique; nanosized SiC powder was introduced into the stir zone provided by a rotating and advancing tool. The fabricated nanocomposite surface layer exhibited a micro hardness value of ~535HV which is much greater than 160HV of the substrate material using Vickers micro hardness testing. In addition, the un-treated CP-Ti substrate showed sever wear regime in the pin-on-disc test against the hardened AISI 52100 steel. It suffers extensive typical adhesive wear dominated by plastic deformation as evidenced by scanning electron microscopy. Also, deep grooves were formed, i.e. evidence of abrasive wear. Contrary to this, enhanced wear properties were detected for the Ti/SiC nanocomposite surface layer, i.e. lower coefficient of friction and weight loss. The nanocomposite surface layer was found to be adherent to the underlying substrate during the pin-on-disc test. The superior wear behavior of the nanocomposite surface layer is attributed to its improved micro hardness value due to the presence of hard nanosize SiC particles in a refined titanium matrix.

The effects of friction-stir process parameters on the fabrication of Ti/SiC nano-composite surface layer

Sound friction-stir processed layers were fabricated on a commercially pure titanium substrate with or without introduction of nano-sized SiC powder to the stir zone under an argon shrouding system using tool rotation and substrate advancing speeds in the range 800–1250 rpm and 35–55 mm/s, respectively. Surface layers exhibited finer grain sizes and greater hardness values compared to those of the as-received substrate. Superior surface enhancements were resulted by uniform dispersion of nano-sized SiC powder in the fabricated surface composite layer after four friction stir process passes. The fabricated Ti/SiC nano-composite surface layer showed a matrix of dynamically restorated ultra fine grains/subgrains with a mean size of ~ 400 nm and a hardness value of ~ 534 HV; this is about 3.3 times greater than that of the as-received substrate.

Electron microscopy observations of MgB2 wire prepared by an internal Mg diffusion method

Microstructure in a high-density MgB2 wire fabricated by an internal Mg diffusion (IMD) process has been investigated by electron microscopy imaging and analysis at different scales. In the IMD process, a pure Mg rod was used as Mg source, and nanosized SiC powders were mixed with amorphous B powders. In the case of a heat treatment at 640°C for 1h carried out after rolling and drawing processes, the wire has two microstructural features that degrade critical current density: uncrystallized zones composed mainly of unreacted B and SiC powders, and cracks partly filled with course Mg2Si crystals. Those cracks were formed in the uncrystallized zones as well as in crystallized MgB2 zones. It indicate that the cracks formed by the mechanical milling and drawing remain after the heat treatment.