Size SiC Research Articles

Microstructure Evolution and Creep Properties of AZ61 Magnesium Matrix Composites Reinforced with Bimodal-Sized SiC Particles

In the scope of this exploration, AZ61 magnesium matrix composites fortified with bimodal size SiC particles were synthesized using ultrasonic-assisted mixing in the semi-solid state, which exhibited optimal grain refinement and exceptional creep resistance. We examined the impact of bimodal SiC particles on the microscopic structure and creep deformation of the resulting composites. Our findings indicated that incorporating bimodal SiC particles resulted in the refinement of the matrix grains and alteration of the morphology of the Mg17Al12 phase. Furthermore, the micron-sized SiC particles exhibited a typical necklace-like particle distribution around the grain boundaries of the bimodal SiC particle/AZ61 composites, while the nano-sized SiC particles were mainly located around the micron-sized particles. As the volumetric percentage of micron SiC particles increased, the quantity of nano-sized particle clusters diminished noticeably. Creep analysis at 200 °C and 50 MPa revealed that the creep life of M−6+N−1 composite was increased by 111.9% compared to the AZ61 alloy. Additionally, the M−6+N−1 combination exhibited a significantly lower steady-state creep rate compared to the matrix alloy, with a reduction of approximately 11 times. These results indicate that the bimodal SiC particle/AZ61 composites have superior creep resistance, which is a consequence of the grain refinement and grain boundary pinning effects of SiC particles.

Enhancing the performance of SiC-based varistors through the use of SPS processing and fluxes

SiC varistors, which are used as surge arrestors in high power/high energy applications, often contain high levels of porosity (∼25 %) which can degrade varistor performance. Starting with SiC-clay varistors (∼43 µm grain size SiC) we employed spark plasma sintering (SPS) and flux additions (to enable liquid phase sintering) to reduce the level of porosity and understand its impact on the microstructure and the electrical properties. Sintering by SPS at 1200 °C for 5 min increased the density to 94 % theoretical, increasing energy density capability by almost a factor of 10 (to ∼1100 J cm−3), but the non-linear coefficient (α) fell by 40 % (to 3.5) and breakdown field (Eb) fell by 75 % (to ∼200 V cm−1). Varistors prepared with nepheline syenite as a flux (replacing clay) which were pressureless sintered at 1200 °C had maximum densities of 80 %. The samples in which all the clay was replaced by the flux exhibited exceptional energy density performance (over 10,000 J cm−3) but suffered reductions in other parameters. Using small grain size SiC (∼3 µm) and 40 % syenite flux yielded consistently superior properties: low power range α value 12.2, high power range α value 32.5, breakdown field ∼5880 (V cm−1) and very low leakage currents ∼10−3 (mA/cm2).

Synthesis of controllable particle size SiC nanoparticles based on domain theory

The study indicated that the phenolic resin pyrolysis carbon showed a gradual decrease in microdomain and domain sizes, as well as inter-domain compactness with increasing carbonization temperature (1200–1600 °C) and time (1–3 h). We determined that with an increase in carbonization temperature and time, the reduction and disappearance of organic groups such as CC, CH2, and C–O–C led to a gradual transformation of carbon microcrystals from structures of a larger size, with a certain curvature of more defects to smaller short straight shapes with fewer defects. This also led to a tendency of assimilation within the domains, an increase of inter-domain differences, and difficulty of further merging and growing smaller microdomains and domains. The β-SiC nanoparticles with a controllable particle size in the range of 30–200 nm, as well as controllable dispersibility, were successfully synthesized by reacting the coke with silicon. With further heat treatment at 600 °C for 6 h in air, the wrapped 2.0–3.6 nm amorphous phase homogeneous structure silicon oxide film was prepared on the SiC nanoparticles surface, which improved the oxidation resistance of the SiC nanoparticles. We determined that the reduction in microdomain and domain sizes, and an increase in inter-domain grain boundary defects, was one of the main reasons for promoting the exfoliation of microdomain and domain structures during the synthesis process to generate dispersed single smaller SiC nanoparticles.

Formation of grain boundaries in nanocrystalline SiC ceramics examined by powder diffraction supported by MD simulations

Atomic structure of nanocrystalline SiC powder sintered under high-pressure high-temperature conditions was examined with use of powder diffraction technique supported by molecular dynamics simulation. Shape and atomic structure of grain surfaces was identified based on real space PDF analysis of experimental diffraction data and theoretical calculations performed for atomic models of nanograins relaxed by MD simulation. It is shown that in presence of about 5 % of excess carbon in the initial 11 nm size SiC powder HPHT sintering leads to formation of (100) and (110) grain boundaries formed by single C planes and (111) boundaries formed by double C planes. Under pressure 3 GPa and 1600°C sphere-like grains tend to transform to dodecahedrons terminated by single C atomic planes. Under 8 GPa the grains adopt the shape of cube-octahedrons terminated by (100) single C planes and (111) planes terminated by single and double C planes.

Eklemeli İmalat ile Üretilen PLA Parçaların Yapıştırılmasında Yapıştırma Parametrelerinin Mekanik Dayanımına Etkisinin İncelenmesi

Geçmişten günümüze plastik malzemeler şekillendirme kabiliyetleri sayesinde endüstrinin her alanında yoğun olarak kullanılmaktadırlar. Özellikle son 10 yılda eklemeli imalat sektöründe masa tipi 3B yazıcıların yaygınlaşmasıyla termoplastikler en çok kullanılan plastik malzeme çeşidi olmuştur. Bununla beraber bu yöntemle üretilen parçaların montajı da bir o kadar önem kazanmıştır. Plastik malzemeler düşük yüzey enerjisine sahip oldukları için yapışkanlı birleştirme işleminin gerçekleştirilmesinde zorluklar vardır. Bu hususta en önemli işlem parametreleri yapıştırıcı tipi, parça yüzey temizliği ve yapıştırma kalınlığıdır. Bu çalışmada; eklemeli imalat yöntemi ile PLA levhalar üretilmiş ve iki farklı yapıştırıcı (Loctite 9492 ve Terason 9225) ile birleştirilmiştir. Yüzey hazırlığı için 320 ve 600 SiC zımpara kullanılarak mekanik zımparalama yapılmıştır. Üç farklı yapıştırıcı kalınlığı (0,3 0,18 ve 0,1mm) ile PLA-PLA malzeme çiftinden yapıştırma bağlantıları oluşturulmuştur. Bağlantılar çekme testine tabi tutularak mekanik özellikleri incelenmiştir. Sonuçlar, 3B baskıda farklı doluluk oranlarında (%100, %80, %60, %40 ve %20) yapılan baskı sonucunda, doluluk oranının yüksekmesiyle birlikte parça mukavemeti artış göstermiştir. Sonuçlar yapıştırma bağlantı mukavemetinin yapıştırıcı çeşidine bağlı olarak yapıştırma kalınlığının değişiminden ters korelasyonlu olarak etkilendiğini ortaya koymuştur. Yapıştırıcı kalınlığının artması Loctite EA 9492 bağlantılarının mukavemetini arttırırken, Teroson PU 9225 bağlantılarında ise tam tersi etki yaratmaktadır.

Plasma sprayed TiC–Ti5Si3–Ti3SiC2 composite coatings from Ti–SiC-graphite powders with different SiC particle size

The TiC–Ti5Si3–Ti3SiC2 coating was successfully prepared by reactive plasma spraying with agglomerated Ti–SiC-graphite powders as raw material. The effect of SiC particle size on the microstructure and properties of plasma sprayed TiC–Ti5Si3–Ti3SiC2 coating was studied. The results were that, as the size of SiC particles decreased, the TiC content of the reaction product phase increased, while the content of Ti5Si3 and Ti3SiC2 decreased. Compared to coarse SiC, the coating prepared with fine SiC as the raw material had a reduced surface roughness, the highest density, (porosity:11.76%), and highest hardness, (1132 HV0.2). In addition, the coating prepared with small size SiC exhibited more uniform elemental distribution. Moreover, it had the best wear resistance with a weight loss of 0.4 mg, which was ∼1/40 of 45 steel substrate.

Stress simulation of 6-inch SiC single crystal

With the size of SiC boule increasing, the problem of crystal creaking becomes more and more serious. In this work, residual stress in SiC boule is calculated by conducting stress simulation based on COMSOL and STR-VR software. A direct diagram comparing on crystal stress distribution is given. Besides, we provide relevant indications for the complete realization of large size SiC bulk with low stress for growing mainstream 6-inch SiC bulk with competitive thickness (40–50 mm) and low residual stress. And a 6-inch stress-free SiC bulk with improved quality was successfully fabricated based on our theoretical investigations.

Effect of particle size on additive manufacturing of complex architecture of silicon carbide

The high-temperature stability, chemical inertness, and enhanced mechanical strength of SiC are utilized for the fabrication of space components. Here, environment-friendly water-based SiC ceramic inks were developed using different size SiC powders. The relation between the SiC particle size and rheological properties is established. The additive manufacturing conditions for SiC are optimized which shows the compressive strength of ∼1.21 MPa. This strength was obtained in the green state for SiC having an average particle size of ∼0.5 μm. As the milling time increases, particle size decreases which make better dispersion in the ink system and it shows good shear-thinning characteristics. The optimum sintering temperature (1400 °C) results in improved compressive strength of ∼80 MPa with a relative density of ∼81%. The current printing method can produce complex ceramic components which can be utilized for manufacturing complex aerospace components.

Impact of nano sized SiC and Gr on mechanical properties of aerospace grade Al7075 composites

Aluminum composites exhibit high resistance to wear and corrosion, possess high strength, offer durability and more such properties. In this study, Al7075, reinforced with nano size SiC - Gr was produced by a stir casting technique and its microstructure and mechanical behavior were evaluated. Reinforcements were added in the range of 0 - 3 wt. %. The microstructure study, tensile and compression strength of the developed hybrid Metal Matrix Composites have been analyzed and examined. From the investigational study, it was found that the reinforcements are evenly dispersed in the base material. The porosity and density of the developed composites were found to be enhanced. The mechanical properties such as ultimate tensile and compressive strength of the developed MMCs could be improved by addition of SiC particulates compared to base material. Further, the strength of developed hybrid composites was found to be decreased by adding of solid lubricant such as graphite (Gr) particulates along with hard ceramic particulates. Finally, fractured surface of the tensile test specimens were analysed using a SEM analysis.

200 mm silicon carbide bulk growth optimisation: mass transport controlled by a designed gas deflector

200 mm silicon carbide bulk growth would be the mainstream in industrial production, but the difficulty of multiple physical fields control is increased with the larger diameter. In this study, a resistance heating based physical vapour transport system was established and explored for its appropriate parameters of multiple physical fields (such as thermal, velocity, flux and reaction components fields) by the COMSOL simulation. A combination of pressure at 5 torr and seed temperature of 2340 K was gained by taking the rate and homogeneity of in-plane growth into consideration. Furthermore, a gas deflector was designed to decrease the convection and to improve the homogeneity of mass transport. This gas deflector had the ability to enhance the quality and yield of 200 mm SiC crystal bulk. A high yield of 90.1% was achieved for the 200 mm part within the crystal thanks to this deflector (without the usage of the deflector was 38.5%). This work provides a useful tool and insights into the steps required for the optimisation of 200 mm or larger size SiC bulk growth.

The preparation of SiC ceramic photosensitive slurry for rapid stereolithography

Stereolithography is one of the most widely used additive manufacturing techniques for preparing high precision and complex ceramic components. Due to the high optical absorbance and refractive index of SiC powder, the rapid stereolithography of SiC ceramics components has become a key challenge. Here, we innovatively use graded silica to improve the curing thickness, rheological and settling performance of the slurry. And we presented a preparation method of SiC ceramic slurry for stereolithography with high solid content, low viscosity, low sedimentation rate and high curing thickness. The printable precision of the slurry is more than 75 μm, the dynamic viscosity is less than 2 Pa·s, and the 24 h sedimentation height is less than 5%. This strategy demonstrates a tantalizing possibility and promising prospect to rapid stereolithography of large size SiC ceramic green body.

Study on Mechanical Properties of AA6061/SiC/B<sub>4</sub>C Hybrid Nano Metal Matrix Composites

The present work investigates the mechanical characterization of aluminium alloy (AA) 6061 based hybrid nanometal matrix composites (MMCs) fabricated using conventional stir casting process. Two compositions viz., AA6061+1.5 wt.% B4C+0.5 wt.% SiC (Hybrid A) and AA6061+1.5 wt.% B4C+1.5 wt.% SiC (Hybrid B) was prepared and its mechanical properties such as microhardness, tensile, compressive, flexural and impact strength were investigated to compare with unreinforced AA6061. SiC and B4C ceramic particles (purity 99.89%) of average particle size of 50 nm were used as reinforcements. Significant enhancement in microhardness of 30.2% and 31.02% for hybrid A and B are observed respectively. The ultimate tensile strength (UTS) increased by 10.72% and 16.55% for hybrid A and B respectively. Improved interaction because of the enhanced surface to volume ratio at the interface resulted in improvement of mechanical properties. Field emission scanning electron microscopy (FESEM) of the fractured surface shows brittle fracture because of the incorporation of the ceramic reinforcements in the matrix material. The developed AA6061/SiC/B­4C hybrid nanocomposites show improved mechanical properties for high-performance structural applications.

Influence of Hot Extrusion on the Microstructure, Tensile and Wear Properties of Mg–5Sb–xSiC Hybrid Composites

The structure, hardness, tensile and wear behavior of Mg–5Sb–xSiC hybrid composites experimented where the amount of SiC particles were 1, 3, and 5 wt% SiCp before and after applying hot extrusion process. Micron size SiC particles were added to Mg–5Sb alloy via stir casting technique to form both Mg3Sb2 and SiC particles in the as-cast microstructures. Although SiC addition reduced the grain size of the Mg–5%Sb in-situ metal matrix composite (MMC), no improvement was observed on ultimate tensile strength (UTS) and the ductility (EL.%) in the as-cast state. The use of the extrusion process led to a remarkable fracturing of Mg3Sb2 intermetallic along the extrusion direction, grain refinement, and reduction in the size of SiC clusters. The optimal amount of SiC was found to be 3 wt%, which reduced the grain size from ~ 827 to ~ 4 µm and promoted the UTS amounts from 120 to 244 MPa for as-cast and hot extruded composites. Besides, the enhancement of yield strength of extruded MMCs was rationalized depending on the grain size compared to the as-cast condition. The fractography of the as-cast composites revealed more cleavage planes in contrast with hot extruded composites, which proved much more dimples. It was also found that the use of hard SiC particles in hybrid composite improved wear properties just in the extruded state. According to observations, in various sliding test conditions, the abrasive, oxidation and delamination are mostly operated in combination.

Processing and characterization of Al-Si alloy/SiC foam interpenetrating phase composite

Interpenetrating phase composites (IPCs) are a class of composites consisting of two or more topologically co-continuous phases and have three-dimensionally percolating interconnected structure. The co-continuous and interconnected architecture of the IPCs can provide superior properties compared to the conventional particulate reinforced composites at room and elevated temperatures. IPCs having metal/ceramic phases are finding applications in various fields like (thermal management materials, aerospace, automobile industries, light-weight armor materials, etc.). In the present work, Al-Si alloy/SiC foam IPC was fabricated by infiltrating the alloy melt into SiC foam via the squeeze-casting process. Open porous SiC foams, fabricated via the replication method, and having two different pore sizes (10 and 20 PPI) were used for IPC fabrication. The SiC foams had both macropores between the SiC foam struts and micropores within the strut walls. Results show that the Brinell hardness of the composite fabricated using a small pore size (20 PPI) SiC foam is higher than the composite fabricated with a large pore size SiC foam (10 PPI). Thorough structural characterization via scanning electron microscope and localized study of hardness distribution in different regions of the composite using nanoindentation were carried out.

Synthesis and development of size hybrid nano SiC- Al7075 composites by advanced stir casting

In the present study, micron size SiC particles are ball milled for 45-hours in wet milling arrangement of a planetary type ball mill and synthesized nano SiC particles are dispersed in an aluminium alloy by stir casting technique. The amount of addition of milled SiC particles varies from 0.5 to 2.5 wt% in steps of 0.5%. DLS-Particle size analysis of milled particles has been conducted. FESEM and TEM images of the synthesized particles reveals that ball milled nano SiC particles having irregular laminar in shape and SAED pattern shows a number of sharp ring spots coinciding with the ring confirm that the microstructure is predominantly nanocrystalline. The density of Al 7075-SiC nanocomposites found increases with an increase in the addition of milled SiC powder. The hardness and strength of the composites synthesized by addition of a different amount of milled powder mix shows that presence of nano-SiC particles has significantly improved the strength and slight reduction in ductility as compared with the matrix alloy. Fractured specimens reveal that dimples of different size and has ductile intergranular mode of fracture.

Effects of HfB2 addition on pressureless sintering behavior and microstructure of ZrB2-SiC composites

In this study the effects of HfB2 addition were investigated on the sintering behavior, densification and microstructure of ZrB2-SiC in the presence of B4C and MoSi2 as a sintering catalyst. 5, 10, 15 and 20 wt% of HfB2 was substituted with ZrB2 in ultra-high temperature ceramic composites of ZrB2-SiC. Additionally, the effect of using nano-scale against common micron size SiC was compared. All compositions were sintered for 1 h in 2100 °C and 2150 °C. Relative and bulk density and open porosity percentage of samples were calculated by Archimedes method. Dimensional changes of pellets and their weight reduction after pyrolysis and sintering proved that increasing of HfB2 leads to increasing of density and samples with MoSi2 gain higher density in comparison to others containing B4C. Phase studies specified by X-Ray diffraction showed the formation of ZrB2-HfB2 solid solution. Characterization and microstructure studies done by scanning electron microscopy revealed that microstructural properties improved by adding HfB2 up to 20 wt%.

The effect of heat treatment on the mechanical and tribological properties of dual size SiC reinforced A357 matrix composites

In the present work, the effect of aging temperature and particle size ratio of SiC particles on the mechanical and tribological properties of A357 composites reinforced with dual particle size SiC were investigated. The composites were prepared by melt-stirring assisted permanent mold casting technique with different weight fractions (3% coarse +3% fine, 4% coarse +2% fine, and 2% coarse +4% fine) of large and small size SiC particles. These three prepared composites are referred as DPS1, DPS2 and DPS3 composites. The solutionizing temperature was maintained constant at 540°C for 9h while the aging was done at 160°C, 180°C and 200°C (T6 treatment) for 6h. Optical and scanning electron microscopy studies showed fairly uniform dispersion of dual size SiC particles in A357 matrix with good interfacial bonding. High-resolution transmission electron microscopy images showed formation of uniformly dispersed needle-like β″ phase and spherical shaped β-Mg2Si precipitates under peak aging conditions. Compared to T6 treated A357 alloy, the T6 treated DPS A357 composites showed improved yield strength, tensile strength, hardness and wear resistance. Among the three composites, hardness and wear resistance of T6 treated DPS2 composite was found to be significantly higher when compared to the other two composites (DPS1 and DPS3). Ratio of large particles to small particles also seems to effect the mechanical and tribological properties. Presence of more small particles was found to be good for strength and ductility whereas more large particles were found to be good for hardness and wear resistance.

Dual matrix and reinforcement particle size (SPS and DPS) composites: influence on mechanical behavior of particulate aluminum-SiC-Gr metal matrix composites

Aluminum powder reinforcing with ceramic particles makes an attractive composite material among Metal Matrix Composites (MMC). In the present research, powder reinforced composites were prepared by conventional powder metallurgy (PM) method, which comprises of powder blending, isostatic pressing and sintering process with different Silicon carbide particle sizes with varying percentages. Composite specimens were produced to net near shape for hardness, compression and tensile test as per the ASTM standard. Samples were sintered at 610°C for 120 minutes under argon atmosphere. The mechanical behavior of unreinforced Al5052 and Al7075 samples and dual amalgamation of Al5052 + Al7075 matrix along with SiC and Graphite reinforced composites prepared up to 18 weight %. These composite samples were produced using single or dual sized SiC powder particles. The study done to discern in which conditions the superlative properties would be attained. The most enhanced strength was obtained with the Specimen sample from batch 7 (Al5052+Al7075 blended with SiC 37µm of 18 weight % + Gr 6 weight %). Batch 7 constitutes of smaller size SiC particles with increasing percentage showed the most superlative result. The effective manufacture of aluminum based powder samples has influenced intensely by aluminum grade, SiC powder size and weight fraction. The overall results revealed that the Al-SiC-Gr considered as an exceptional composite combination where high strength to weight ratio are of a key significance

Experimental inspection of aluminium matrix composites reinforced with SiC particles fabricated through ultrasonic assisted stir casting process

Al-SiC composite has improved mechanical properties which can be used in automobile sector to make different automobile parts. In the present study Al-SiC composites with different wt% of micron SiC particles have been fabricated by stir casting and the ultrasonic assisted stir casting process. The effect of ultrasonication for uniform mixing of the micron size SiC particles on the mechanical properties has been studied. The various mechanical properties like Tensile strength, Compressive strength, density, hardness etc. have been measured.

Tribological behavior of composites fabricated by reactive SPS sintering in Ti‐Si‐C system

AbstractIn this study, wear and friction behavior of two based‐composites from the Ti‐Si‐C system, (40 wt% TiC; 28 wt% Ti5Si3; 17 wt% Ti3SiC2) and (18 wt% TiC; 26 wt% Ti5Si3; 41 wt% Ti3SiC2) reinforced by 15 wt% of large size SiC (100‐150 µm) particles were investigated. The four‐phase composites exhibited approximatively the same friction coefficient (µ ~ 0.9) under high loads (10 N and 7 N). The composite with high Ti3SiC2 showed higher wear rate values by one order of magnitude. However, under 1 N, the composite with high TiC content showed a higher running‐in period and a lower steady state µ value (0.37 after 1000 m sliding distance). Scanning electron microscopy, Energy Dispersive X‐Ray and Raman spectroscopy analysis of the worn surfaces of the two composites revealed that oxidation was the dominant wear mechanism. The oxidation process and the removal kinetics of the oxides during sliding controlled the tribological behavior of the composites. The influence of processing variables on microstructures development and wear mechanisms of the composites is discussed.