Silicon Carbide Nanopowders Research Articles

Polycarbosilane-grafted silicon carbide nanoparticles as a high-yielding non-oxide ceramic precursor

Silicon carbide (SiC) is a multifunctional material with a myriad of potential applications, from high-power electronics to friction applications to power generation. Grafting preceramic polymers (PCPs) from SiC nanoparticles would create a platform for forming SiC via a polymer derived route that would have advantages over simple particle-PCP slurries and may enable new additive manufacturing inks or spreadable coatings with controlled rheology. Grafting PCPs directly on SiC powders would greatly improve dispersion of these particles and yield a single component system. Moreover, PCP-grafted-SiC would be a new addition to the burgeoning field of polymer grafted nanoparticles (PGNPs). Herein, SiC nanoparticles were surface-modified in a grafting-from polymerization reaction to create polycarbosilane (PCS) grafted SiC. Surface grafting was verified through a number of analytical techniques and the synthesized materials were pyrolyzed at 1600 °C. The PCS-grafted SiC retained 66 % of its pre-pyrolysis mass, representing a significant improvement over PCS-grafted silica nanoparticles from our previous work (20 wt% yield). In addition to an increased ceramic yield, the grafting of PCS to SiC also resulted in the formation of a SiC phase not present in the simple physical mixture of SiC nanopowder in PCS. This study demonstrated that PCP-grafted nanoparticles (GNPs) can be synthesized utilizing non-oxide nanoparticle cores with desirable rheology, opening possibilities for future ceramic inks and coatings.

Al-5052/SiC + CeO2 hybrid surface composites: Achieving improved microstructural and mechanical behaviour via friction stir processing

In the present work, hybrid surface composites (HSCs) were fabricated using aluminium 5052 alloy as base matrix and silicon carbide (SiC) and cerium oxide (CeO2) as reinforcement particles via friction stir processing (FSP) technique. Varying reinforcement ratios of SiC and CeO2 nano-powders, viz 100:0, 75:25, 50:50, 25:75, and 0:100 was used. Multi-pass FSP was employed to obtain improved dispersion of reinforcement particles. Results revealed the collaborative impact of SiC and CeO2 particles on the mechanical properties of the SCs, shedding light on the optimal ratios for achieving superior mechanical performance. The hybrid ratio of (SiC: CeO2) 75:25 was predominant in tensile strength enhancements with an ultimate tensile strength of 283 MPa compared to 269 MPa of BM while the percentage elongation increased to 21.6 as compared to 18.8 in BM. The average microhardness also improved to 92 HV compared to 85 HV. These results emphasised on the importance of HSC fabricated using 75:25 ratio of SiC:CeO2 reinforcing particles.

The synergistic and reinforcement mechanism of SiC nanostructures on the ablation properties of silicone rubber composites

With improvements to the performance of ramjets, the ablation environment in afterburning chambers has become more severe, leading to an urgent demand for high-performance thermal protection materials (TPMs). In this study, the reinforcing effects of silicon carbide (SiC) nanowhiskers and nanopowders on silicone rubber composites and their synergistic effects were investigated. Both SiC nanowhiskers and nanopowders improved the thermal stability of the TPMs. SiC nanowhiskers enhanced the thermal conductivity of the TPMs by forming thermal conductivity pathways. Furthermore, SiC nanofillers can reinforce the ablation resistance of the TPM. The best performance was demonstrated by the TPM formulated with five parts SiC nanowhiskers and five parts SiC nanopowders. The ablation rate was reduced by 72.7% relative to the TPM with a basic formulation, and the back temperature increased by only 27.1%. In this study, the SiC nanofiller improved the ablation resistance of composites by densifying the pore structure and strengthening the skeleton of the char layer. Furthermore, the more compact char layer improved the thermal conductivity of the composites. The increase in the thermal conductivities of the composites and the char layer led to a decrease in the thermal insulation properties of the composites.

Development of novel nanocomposite radiation shielding blocks as gamma rays barrier

This work is focused on developing new types of radiation shielding materials using the stereolithography 3D printing technique, which enables the creation of gamma radiation shielding materials in two different sizes. Six different square nanocomposite radiation shielding blocks with an additive ratio of 0.5 wt% were prepared using aluminum nano-powder (nano-Al), copper nano-powder (nano-Cu), calcium nano-powder (nano-Ca), silicon carbide nano-powder (nano-SiC), graphene nano-platelets (GnPs), and eggshell nano-powder (nano-Es). Then, blocks prepared in two different thicknesses (5 mm and 10 mm) were analyzed with Mössbauer spectroscopy utilizing the Co-57 source for γ-ray shielding. The radiation attenuation properties of the developed materials for γ-rays were evaluated. The nano-Cu doped composite block was determined to have the greatest performance in gamma-ray shielding among the specimens mentioned in this investigation. The findings indicate that it is possible to reduce the shield thickness by about 19% compared to neat resin for γ-rays using the determined nano-powders. These experimental findings suggest that the nano-Cu, nano-Ca, and nano-Al reinforced resin nanocomposites are potentially valuable new radiation shielding materials.

Synthesis and investigation of the physicochemical properties of polymorphic 3C–SiC

Silicon carbide (SiC) nanopowders were synthesized under Ar atmosphere via the carbonization reaction method using silicon powders and expanded graphite as initial materials, and ferric nitrate as catalyst precursor. The effects of heat treatment temperature and the C/Si molar ratio on SiC products were studied. The microstructure, phase composition and chemical state of the products were analyzed by XRD, SEM, XPS, TEM and Raman. The photoluminescence (PL) properties of SiC nanopowders were tested. The results showed that the content of the 3C–SiC product is higher after heat treatment at 1400 °C for 3 h with a molar ratio of C/Si of 1:1. 3C–SiC exists in the form of particles and wires. The formation process of 3C–SiC can be explained by a two-step method, nucleation under catalysis and growth under Vapor-Solid (VS) mechanism. Two ultraviolet light emission peaks are observed at about 318 and 380 nm. The main PL spectra of 3C–SiC nanopowders exhibit larger blueshifts. The blueshift is attributed to the stacking fault, oxygen defects, morphology and quantum confinement effect. It has potential application prospects in ultraviolet detectors, optoelectronic devices and light emitters.

Investigation of the effect of silicon carbide nanoadditives on the structure and properties of microfine corundum during electroconsolidation

The effect of nanodisperse powders on the microstructure and properties of corundum was studied. The microstructures of composites under different modes of electroconsolidation are considered. The phase composition and some mechanical properties of the composite materials obtained by the electrosintering method were determined. A comparative assessment of the properties is provided and recommendations are formulated for further improvement of the physical and mechanical properties of Al2O3–SiC composites, where silicon carbide nanopowders are used as additives.

The effect of the amount and size of alumina sintering aid particles on some mechanical properties and microstructure of silicon carbide bulky pieces via spark plasma sintering

Abstract In this paper, for sintering silicon carbide nanopowders via the spark plasma sintering method, nano-and micro-sized alumina sintering aids were used separately at 3 vol.%, 5 vol.%, and 7 vol.%. The sintering process was undertaken at 1900 °C for 10 min. To investigate some mechanical and physical properties of the resulting samples, density was obtained via the Archimedean method, and hardness was taken by the Vickers indenter method. The microstructure of the samples was examined through scanning electron microscopy. The results indicated that in the samples containing nano-alumina, the largest percentage of density and hardness was related to the sample containing 5 vol.% nano-alumina as a sintering aid and were obtained as 99% of theoretical density and 31.3 GPa, respectively. For the samples containing micro-alumina, the highest percentage of density and hardness was related to the sample containing 7 vol.% micro-alumina and obtained 93% of theoretical density and 20.1 GPa, respectively. By investigating the fractured surfaces of the samples and via the linear intercept method, the largest mean grain size was associated with the densest sample at 3.7 µm.

Machining performance of Nano SiC and graphite powder mixed aluminum matrix composites fabricated by powder metallurgy using EDM

Currently, aluminum MMCs are increasingly being used for different engineering applications due to their lot advantages. In this experiment, MMCs were machined using electrical discharge machining (EDM) to get high-performance results. Powder Metallurgy method was used to add different percentages of Graphite (3 %, 5 % & 7 %) and Silicon Carbide (5 %, 10 % & 15 %) Nano-powders to pure Aluminum powders. Different Compaction loads and Sintering temperatures were taken at 150, 200 & 250 KN, and 500, 550 & 600 °C respectively. The process parameters have been designed using the Taguchi L9 orthogonal array. With input parameters such as current (I), pulse on time (Ton), pulse off time (Toff), and voltage, the EDM technique was chosen for machining composite materials. The addition of silicon carbide particulates with aluminum metal matrix increases the Surface Roughness (Ra) and Hardness but decreases the Metal removal rate (MRR), and a suitable amount of graphite particulates with aluminum metal matrix increases MRR, SR, and Hardness also of the composite material. The Taguchi technique is used to assess the best P/M process parameter setting for a given signal-to-noise (S/N) ratio order.

Special features of manufacturing cutting inserts from nanocomposite material Al2O3-SiC

The article examines the cutting characteristics of the developed composite material based on aluminum oxide micropowders with silicon carbide nanopowder additives obtained with the help of electric sintering. The influence of thermal conductivity of the developed composite Al2O3-SiC based material on the wear and durability of the material in application of cutting tool is examined, and a comparison with the traditional cutting ceramic tool materials is made. Considering that the process of cutting with ceramic inserts is carried out without the cutting fluids, the heat removal improvement from the cutting zone makes it possible to increase the tool life. It is proposed to use the thermomechanical parameter B for a comparative assessment of cutting ceramic composite material characteristics.

Investigation of the formation of defects under fast neutrons and gamma irradiation in 3C–SiC nano powder

In this work cubic phase, silicon carbide nano-powders were irradiated at the high-flux pulsed reactor IBR–2 (Dubna, Russia). The 3C–SiC powder was irradiated with neutron doses up to 1015 n/cm2. The irradiated samples were then analyzed using X-ray diffraction, Raman spectroscopy, Positron annihilation spectroscopy, and Fourier Transform Infrared Spectroscopy. The XRD analysis showed a slight decrease in the lattice parameters with the increase in neutron fluences. The results obtained from positron annihilation measurements were compared to the theoretical calculations, to recognizing the type of structural defect in the samples. A positron lifetime component 355 ps associated with the calculated values for clusters containing of 13–21 vacancies was identified. The concentration of these defects was estimated to be in the region of 5 ppm, and was very similar to the one identified on the unirradiated sample. The results also indicate high irradiation resistivity of the 3C–SiC after irradiation.

Development of an Antireflection Layer Using a LDS Based on β-SiC Nanoparticles

The main objective of this work is to use β-SiC (also called 3C-SiC) silicon carbide nanoparticles to formulate composite layer for wavelength conversion. Silicon Carbide nanopowders (npβ-SiC) were successfully synthesized by sol-gel method and followed by carbothermal reduction. Composite thin layers based on np-β-SiC incorporated into polyvinyl alcohol, (PVA) as matrix, where prepared. We have investigated the composite layers deposited silicon solar cell as a luminescent down shifting layer (LDS) to convert UV wavelengths. The texturation of the substrates by making pyramids, pyramids with nanowires was investigated in order to decrease the surface reflectance of silicon surface. An improvement in the spectral response of the obtained solar cells was very remarkable. In order to confirm this property, electro-optical characterizations were carried out on the solar cell with the developed composite layer and also on that without β-SiC/PVA coating, as reference. The morphological quality of the used substrates was examined by SEM images. EQE measurements have shown a noticeable increase showing the ability to use the prepared composite layer as lightweight encapsulation material for photovoltaic devices.

Synthesis and sintering of nanocrystalline SiC ceramic powders

This paper reports a simple route to synthesize nanocrystalline silicon carbide (SiC) ceramic powders via the direct reaction of silicon powders with carbon black in a temperature-programmed muffle furnace. The mixing powders of silicon and carbon black were loaded in a alumina crucible, and then the crucible was sealed with some materials to prevent oxidization. The effect of reaction temperature on the phase of the product powders was investigated. FESEM and TEM images showed that the SiC nanopowders were spherical and had an average particle size of 48.56 nm. The sintering activities of the SiC nanopowders and commercial SiC fine powders were also investigated by hot-pressing sintering. SiC nanoceramic sintered at 1850 °C exhibited a high relative density (up to 99.2%) and a high flexural strength of 580 MPa, which exhibits better sintering activity of synthesized SiC nanopowders.

Effect of heat-treatment temperature on mechanical properties and microstructure of alumina–SiC nanocomposite

In this investigation, 90 vol. % alumina and 10 vol. % silicon carbide nanopowders were combined. Initial samples were fabricated by the hot press method under 20-MPa pressure of 1650 °C. Then, the nanocomposites were heat-treated at 1200, 1400, 1500, and 1600 °C for several hours. After the heat-treatment, XRD (X-ray diffraction), SEM (scanning electron microscope), and FE-SEM (field emission scanning electron microscope) analyses were used to explore the nanocomposite specifications and microstructure. The flexural strength, apparent density, crack healing, and fracture toughness were measured to study the physical and mechanical properties of nanocomposite specimens. The best result for flexural strength was achieved for specimens heat-treated at 1500 °C for 2 h, exhibiting a 34% increase in the flexural strength. Furthermore, with heat-treatment at 1600 °C for 2 h, the fracture toughness for nanocomposite reached 5.563 MPa m1/2.

Experience of ceramic production from silicon carbide with the addition of SiC nanopowder

The effect of silicon carbide nanopowder additives on the properties of armor ceramics from this compound has been investigated, and the results are presented. The study reveals that the powder introduction in an amount from 5 to 10 wt. % leads to an increase in hardness and crack resistance when density is maintained. It enabled us to obtain the material which can be used in structural and armored ceramics.

Carbon forms, carbide yield and impurity-driven nonstoichiometry of plasma-generated β-silicon carbide nanopowders

Silicon carbide nanopowders are chemically complex materials containing various carbon forms and impurities. The current study quantifies the chemical complexity of these nanopowders in terms of their carbide phase nonstoichiometry and yield. The investigated samples include a range of β-silicon carbide nanopowders (BET surface area = 30–160 m2 g−1) produced from thermal plasma processes. The samples were characterized as to their carbon forms (temperature-programmed oxidation, Raman spectroscopy, HRTEM), total carbon content (combustion analysis), oxygen and nitrogen contents (inert gas fusion), surface elemental composition and bonding (XPS), crystallographic phases (XRD). The nanopowders contain widely varying amounts (0.5–19%) of carbon in noncarbidic forms (free and organic). However, the carbide phase of the nanopowders is invariably carbon deficient with the C:Si atomic ratio ranging from 0.89 to 0.95. The extent of carbon deficiency is linked to the level of oxygen and nitrogen impurities that substitute for carbon in the carbide structure. The substitution scenarios involve high temperature dissolution of nitrogen into the carbide lattice and room-temperature oxidation of particle surfaces to form an amorphous oxycarbide. Uncontrolled surface oxidation and contamination by carbonaceous deposits reduce the SiC yield of the nanopowders (76–91%) from those of ultrafine and micrometer-sized counterparts. Since the majority of contamination occurs on the nanopowder surface, the yield tends to decrease with decreasing particle size. The obtained results emphasize the importance of explicit control over the chemical impurities and particle surface conditions for fabricating the stoichiometrically balanced SiC nanopowders in high yield.

Pyrolysis of a mixture of monosilane and alkanes in a compression reactor to produce nanodispersed silicon carbide

The method of producing of nano-dimensional silicon carbide by compressing in a cyclic chemical reactor is proposed. Pyrolysis is initiated in mixtures of monosilane and hydrocarbon with argon. The resulting product is examined by X-ray diffraction and electron microscopy. It is established that the powder contains crystallites of silicon carbide with an average size of 5–12 nm. It is shown that at certain ratios of precursor concentrations in argon, the formation of carbon nanoparticles and/or graphene coating on the surface of SiC particles is also possible. The method is technological and efficient, it can be used in the production of high purity silicon carbide nanopowders and other compounds.

The effect of electron beam on nanocrystallites size, strain and structural parameters of the silicon carbide nanopowder

The effect of high-energy electron beam on the silicon carbide nanopowder’s structural parameters, strain and powder size was studied. The sample was irradiated with [Formula: see text]2-MeV electron beam energy under different fluencies such as 1.13 ⋅ 10[Formula: see text], 1.89 ⋅ 10[Formula: see text], 2.79 ⋅ 10[Formula: see text] and 3.69 ⋅ 10[Formula: see text] cm[Formula: see text] at the linear electronic accelerator. Initial and irradiated samples at various doses have been analyzed in the XRD. The nanostructural effects within FullProf are treated using the pseudo-Voigt profile function. The dependences of maximum strain and nanocrystallite size on irradiation dose were obtained and analyzed.

Thermal conductivity estimation of fully ceramic microencapsulated pellets with ZrO2 as simulated particles

Fully ceramic microencapsulated (FCM) fuel is manufactured by replacing the graphite matrix of conventional high-temperature gas-cooled reactor tristructural isotropic (TRISO) fuel compact with silicon carbide (SiC) matrix, because of the tremendous merits of SiC. Most of the previous studies on FCM fuel thermal conductivity focused on the parameters of the SiC matrix and particle volume fraction. The present work deals with the estimation of fuel thermal conductivity of the FCM, considering not only the particle size and volume fraction but also the matrix-particles interaction such as the interfacial layer and gap formation between the matrix and particle. ZrO2-3mol%Y2O3 particles were used to simulate the TRISO-coated particle and SiC nanopowder as the matrix. An estimation of thermal conductivity was performed with the Maxwell-Eucken model and Hasselman-Johnson model, and further correction was done employing the Knudsen effect. The calculation result showed that correction with the Knudsen effect provided the values that were closest to the measured thermal conductivity.

Dopamine sensor in real sample based on thermal plasma silicon carbide nanopowders

Silicon carbide nanopowders (SiC_PL) were prepared via thermal plasma synthesis. The electrocatalytic activity of the SiC_PL coated glassy carbon electrode (GCE) towards the electrochemical oxidation of dopamine (DA), ascorbic acid (AA), and uric acid (UA), was characterized by cyclic voltammetry (CV), in 0.1 M phosphate buffer solution (PBS) at pH 7. The peaks of oxidation for DA, AA, and UA result well separated on the modified electrode in contrast with the behavior shown on bare GCE. A low limit of detection (LOD) of 0.043 μM was found at the SiC_PL coated GCE. In a real sample, the recovery rates of the added compound were 98.8%, 106.5% and 100.7%, indicating a potential for the SiC_PL electrode to determine DA in real conditions. The results of the characterization as supercapacitor electrode show that the specific capacitance for SiC_PL is of 151.2 F/g at 0.12 A/g. After 2.5 × 105 cycles SiC electrode still retains about 90% of its initial capacitance showing good stability.

Assessment of tool wear and mechanical properties of Al 7075 nanocomposite in friction stir processing (FSP)

The aim of this study is to investigate the tool wear on friction stir processing of Al7075 base nanocomposite. The silicon carbide nanopowder was used as a reinforcing phase. The effects of input parameters including rotation speed, traverse speed and the pass number on the tool wear, microhardness and the topography were studied through the response surface methodology. Each of the input process parameters was selected in five levels, and other parameters were considered constant. The friction stir tools were examined under a scanning electron microscope, and wear mechanisms were investigated at different conditions. The analysis of variance revealed that quadratic polynomial models are fitting to predict tool wear and microhardness. In addition, the results showed that tool wear also varied between 12 and 116 mm under different parameters. Furthermore, the rotation speed and pass number of 52.9% and 13.1%, respectively, have the greatest impact on tool wear. Traverse speed with more than 55% had the most effect on microhardness comparatively. Also, energy-dispersive spectroscopy analysis showed that with the highest percentage of Fe in rotation speed 900 rpm, traverse speed 50 mm/min and with three passes, the microhardness reached the highest level of 127.24 Vickers.