SiC Si Research Articles

Characteristics of a 1200 V Hybrid Power Switch Comprising a Si IGBT and a SiC MOSFET

Hybrid Power Switches (HPS) combine the advantages of SiC unipolar and Si bipolar devices and therefore can bridge the gap between these technologies. In this paper, the performance of a hybrid power switch configuration based on the latest SiC MOSFET and Si IGBT technologies is presented. The device is evaluated through experimental measurements of its characteristics under various conditions. The results show the HPS can achieve switching losses as low as a SiC MOSFET while offering the high current capability of the IGBT without significant increase in costs.

Solid-State Contactor With Si Thyristor and SiC FET Hybrid Module for High-Efficiency Motor Control

Solid-State Contactor With Si Thyristor and SiC FET Hybrid Module for High-Efficiency Motor Control

Comparison of Si CMOS and SiC CMOS Operational Amplifiers

In this study, we numerically compare the characteristics of Si and SiC CMOS operational amplifiers (OpAmp) using LTspice. According to prior researches, we set the device parameters for Si and SiC MOSFETs. The OpAmp consists of three stages: the input stage, the gain stage, and the output stage. We established three criteria for the OpAmp's operation: (1) a unity gain frequency of 1MHz, (2) an open-loop gain of at least 75dB, and (3) a phase margin of more than 60° when a load capacitance is 300pF. To achieve a unity gain frequency of 1MHz, we adjusted the values of the resistor and capacitor used for phase compensation. The supply voltage was set to be ±5V for the Si OpAmp and ±15V for the SiC one. Our numerical analysis of the frequency response shows that the Si OpAmp met all three criteria. In contrast, the SiC OpAmp, when faced with a load capacitor of 300pF, had a phase margin of 43.4°, falling below the 60° mark. For the SiC OpAmp, the frequency response declined rapidly when the supply voltage dropped to 10V or below.

Superior ablation resistance of plasma sprayed SiC based coating by structural optimized powders

Pristine SiC coating prepared by plasma spraying is difficult to achieve good ablation resistance at high temperature due to its weak SiO2 scale. Besides incorporation by ultra-high temperature ceramics, the modification of the SiC coating from its feedstock powder is necessary. In the current work, the mixed powders of SiC, Si and C, where the SiC was encapsulated and then carbonized by polydopamine, denoted as SiC@C–Si, were employed as the feedstocks, compared with the mixed case, i.e. SiC–Si–C. The SiC@C–Si coating exhibited superior anti-ablation properties, with a linear ablation rate of 0.62 μm/s, 57 % lower than the SiC–Si–C coating. This is attributed to the fact that nano-carbon formed by carbonization of polydopamine is more prone to reacting with Si than micron-sized C powder, thereby forming a dense microstructure after ablation. Besides, in-situ formed SiC by the depletion reaction increases the flow resistance and decelerates the failure of SiO2 film, thus improving the ablation resistance.

Observation of enhanced heat transfer between a nanotip and substrate at nanoscale distances via direct temperature probing with Raman spectroscopy

Nanoscale heat transfer between two nanostructured surfaces holds paramount significance in the realms of extreme manufacturing and high-density data storage. However, experimental probing of heat transfer encounters significant challenges, primarily due to limitations in current instrumentation. Here, we report a method based on Raman spectroscopy to directly probe the temperature difference between a Si nanotip and SiC substrate. Results indicate a decrease in substrate temperature, while the temperature of the nanotip remains relatively stable as the nanotip moves away from the substrate from approximately 82.5 to 1320 nm. We trace this enhanced heat transfer to a significant augmentation, by one order of magnitude, in air conduction and thermal radiation energy exchange theoretically, with air conduction being the dominant mode over thermal radiation. This work advances the direct observation of surface temperatures with gaps smaller than 1 μm, utilizing a noncontact and nondestructive Raman technique, which can be extended to studying near-field heat transfer across various Raman-active surfaces.

Comparison of Si and SiC MOSFETs responses to electrical stress and the observation of parameter recovery in SiC MOSFET by stress superposition

In this study we examined the effects of room temperature DC and AC electrical stress on Si and SiC n-channel metal-oxide-semiconductor field effect transistors (MOSFETs). Measurement of threshold voltage, transconductance, subthreshold swing, charge pumping, and gate oxide breakdown are used to compare the impact of stress on Si MOSFETs and SiC MOSFETS, as well as to understand the processes of carrier injection and trapping at oxide and interface defects. DC stress is observed to promote negative charge buildup in the gate oxide and interface in Si MOSFETs. However, in SiC MOSFETs the net charge buildup sign alternates between negative and positive as the DC stress polarity is changed from positive to negative, respectively. For the same stress level, relative degradation in parameters of SiC MOSFETs are significantly smaller than those in Si MOSFETs, where in the latter interface state density, conductance, and subthreshold swing have degraded by up to 400%.The change of charge buildup sign explains our observation that degradation in SiC MOSFETs subjected to AC bipolar stress is insignificantly small, whereas AC stressing of Si MOSFETs is observed to be much more severe. Also, the superposition of alternating DC stress polarity eliminates the stress induced degradation in SiC MOSFETs thus enabling a straightforward process for parameter reconfiguration and recovery.

Ultra-precision diamond finishing of reaction-sintered silicon carbide enhanced by vibration-assisted photocatalytic oxidation

RS-SiC faces limitations in surface accuracy with conventional finishing processes due to its high mechanical hardness and multiphase nature. In this study, vibration-assisted photocatalytic oxidation is introduced to enhance the efficiency and precision of RS-SiC diamond polishing. By utilizing the photocatalytic reaction, the hard heterogeneous SiC phase and Si phase on the RS-SiC surface are transformed into a "softer" homogeneous oxide layer that can be removed easily. The introduction of vibration increases the relative velocity between the workpiece and the abrasive and prevents the aggregation of the photocatalyst, thus improving polishing efficiency. By reducing the abrasive size to the nanometer scale, the boundary between the Si phase and SiC phase can be smoothed out to further improve the workpiece surface finish. Using TiO2 as the photocatalyst, H2O2 as the oxidant, 25 nm diamond as the abrasive, and introducing vibration, an ultra-smooth surface with a surface roughness of 0.195 nm in Ra is obtained by the finishing method proposed in this paper. The proposed photocatalysis/vibration-assisted finishing approach offers a novel method for ultra-smooth polishing reaction-sintered silicon carbide.

Enhanced mechanical and wave‐absorption properties of SiC–Si3N4–FeSi porous ceramics by introducing Al

Enhanced mechanical and wave‐absorption properties of SiC–Si₃N₄–FeSi porous ceramics by introducing Al

Transient turn-on characteristics of Si RBDT and SiC MOSFET under nanosecond current pulse range

With the development of pulse power supplies, solid-state semiconductor switches are required to have fast switching speeds and low losses. Both Reverse blocking diode thyristor (RBDT) and silicon carbide metal oxide semiconductor field effect transistor (SiC MOSFET) have fast turn-on speed, making them suitable candidates for short pulse generator. In this paper, the transient turn-on characteristics of Si RBDT and SiC MOSFET are analyzed theoretically and validated experimentally. Si RBDT and commercial 1.2 kV/81A SiC MOSFET are comparatively investigated in switching current pulse with a rise time of several hundreds of nanoseconds. (1) The anode current of RBDT could rise exponentially because of the latch-up effect of Si RBDT, while the drain current of SiC MOSFET tends to be saturated. (2) Utilizing the current rise time (Trise) to represent the switching speed, SiC MOSFET can switch faster when the current is lower than 400A. With the increase of the current, Si RBDT presents faster turn-on speed and lower switching loss due to the regenerative action of the two coupled transistors. (3) The transient characteristics of Si RBDT include a voltage-controlled inductance, while SiC MOSFET contains a current-controlled inductance based on the current rise time, respectively. With the increasing of the main voltage, the equivalent inductance of Si RBDT decreases and tends to be saturated when the main voltage is higher than half of the breakdown voltage of Si RBDT. For SiC MOSFET, the equivalent inductance increases until the drain current remains stable for a given gate voltage. This paper confirms the advantages of Si RBDT and SiC MOSFET in different situations.

Resilient Si@C architecture fabricated by mechanochemical conjugation and thermal reduction for lithium storage: Simulation on interfacial state evolution

Synchronal comminution via high-energy bead milling not only efficiently pulverizes Si particles and exfoliates graphene oxide (GO) sheets but also facilitates Si surface functionalization and intensify Si-C conjugation. After a thermal reduction, a well-wrapped Si@C anode material can be fabricated for lithium storage. The discharge specific capacities of this Si@C composite sustain at 1110.3 mAh g−1 after 300 cycles at 1 A g−1 and 316.4 mAh g−1 for 800 cycles at 5 A g−1, which are respectively 1.35 and 2.07 times that of its random blended Si/C counterpart. By employing molecular dynamics (MD) simulations with ReaxFF reactive force field to investigate the mechanochemical reactions between Si and GO amidst high-energy milling, an atomic scale portrayal of Si crystal fragmentation and Si-C bonding can be depicted. Analyses focusing on the differential forces exerted on various Si crystal planes, coupled with potential energy (PE) trends, reveal a higher propensity for cleavage in (111) plane, with (311) plane followed. Radial distribution function (RDF) outcomes indicate that ball milling leads to substantial disruption of crystalline order in Si particles, generating a plethora of Si dangling bonds. This disruption stimulates the formation of SiOOC, SiOC and SiC bonds at the Si/C interface, thus enhancing the integration of GO with Si substrate. Subsequent thermal reduction processes not only restore the structural order of Si and GO but also consolidate Si/C bonding.

Synthesis of Ag2CO3/TiO2/SiC with pH stability and chloride ion boosted for efficient photodegrading tetracycline under visible light

The increasing issue of antibiotic contamination in water has sparked significant interest in seeking effective solutions. In this research, a dual Z-scheme ternary photocatalyst Ag2CO3/TiO2/SiC (ATS) was synthesized by a mechanochemical-coprecipitation method. The experimental results demonstrated that the 15 %Ag2CO3/TiO2/SiC (ATS-15) reached a remarkable tetracycline (TC) degradation efficiency of 95.87 % (k = 0.1063 min−1) after a 30 min exposure to visible light, which was 46.22 and 13.63 times more effective than SiC (k = 0.0023 min−1) and TiO2/SiC (k = 0.0078 min−1), respectively. The synergistic effect of ATS ternary structure to promote Si electron transfer and SiC surface oxidation. The photocatalytic performance of ATS-15 was greatly enhanced due to the synergistic effect of Cl− and CO3•−, achieving 95 % of TC degradation within 5 min. In the ATS-15 system, Cl− converts a portion of Ag2CO3 into AgCl and establishes a quaternary electron transfer scheme with ATS-15, thereby enhancing the performance of the photocatalyst. ATS-15 photocatalyst can maintain TC degradation rate above 90 % among pH 3 to 9. The ATS-15 system also exhibits excellent adaptability to various water environment, achieving 94.01 % TC degradation rate in natural river water, with only a 1 % reduction. A novel treatment scheme for antibiotic pollution in a complex water environment was proposed by ATS-15 photocatalyst with high pH stability and water applicability.

Oxidation mechanism of Al–Si–SiC composite at elevated temperature

Resin-bonded Al–Si–SiC composite was sintered in the air, and the oxidation mechanism was investigated utilizing industrial CT, XRD, and SEM, combined with thermodynamic calculations, as well as a reaction model, was established. The generation of Al4C3 is avoided by constructing the Al-Sialloy(l) intermediate phase. Simultaneously, AlN exists as a solid solution, which improves the stability of the composite. With temperature increasing, the antioxidant properties of the Al–Si–SiC composite are enhanced by forming a dense layer, and the oxidation mechanism varies at different temperatures. At 1100 °C, the outer layer of Al and Si oxidized to generate Al2O3 and SiO2, respectively, while the inner layer generated irregular granular AlN–SiC solid solution; At 1300 °C, the outer pores were filled densely with Al2O3 and SiO2, while the high temperature and low Po2/Pθ induced active oxidation of SiC in the inner layer so that Po2/Pθ was further reduced and the AlN–SiC solid solution particles grew up; At 1500 °C, Al-Sialloy(l) rapidly seals the outer pore channels, accompanied by the in-situ formation of mullite and dense layers, where only N2(g) is free to diffuse inward, followed by the continuous dissolution of C and N in a form of atoms in the Al-Sialloy(l) to generate hexagonal granular AlN–SiC solid solution.

High‐strength Si–SiC lattices prepared by powder bed fusion, infiltration‐pyrolysis, and reactive silicon infiltration

AbstractThis study focuses on the design, additive manufacturing, and characterization of silicon carbide‐based components with complex geometries. These parts were produced using a novel hybrid technique, previously developed: powder bed fusion of polyamide was used to 3D print two different templates with complex architectures. Preceramic polymer infiltrations and pyrolysis with polycarbosilane and furan resin were performed to obtain the ceramic parts. The final densification was achieved with reactive or nonreactive silicon infiltrations according to four different strategies, producing ceramics comprised of crystalline βSiC, reaction‐bonded βSiC, and low residual silicon. The final gyroid samples (∼70 vol% macroporosity) exhibited a maximum compressive strength of 24.7 ± 2.2 MPa, with a skeleton density of 3.173 ± 0.022 g/cm3, and a relative density of 0.935 ± 0.016. These findings underscore the potential of this manufacturing approach and showcase its effectiveness in fabricating intricate ceramic structures for engineering applications as heat exchangers and catalytic supports.

Boron carbide based composites densified via Ti3SiC2 boronizing with excellent mechanical properties and amorphization tolerance

Consolidated boron carbide (B4C) composites are extremely hard but have been shown to undergo stress-induced amorphization when subjected to high velocity impact. This localized amorphization has been related to the sudden loss of their strength and poor ballistic protection. In this work, dense B4C based composites were spark plasma sintered through in-situ reactions involving with Ti3SiC2 and boron. Hierarchical structures composed of TiB2–SiC–Si reinforcement and B4C matrix were finally built and the degree of amorphization was markedly reduced as the increment of boron amounts. As-generated composites with tough and hard reinforcement possess enhanced amorphization resistance without compromising their mechanical properties. Due to the co-doping of Si and B in boron carbide, the amorphization degree yields a reduction of up to 73 %. The dominant amorphous tolerance is associated with the chain retention and atomic-level local lattice distortion in boron carbide. Therefore, Ti3SiC2 boronizing route may present itself a promising strategy to design boron carbide based composites with better ballistic performance.

Reliability comparisons between additively manufactured and conventional SiC–Si ceramic composites

AbstractAn additively manufactured reaction‐bonded silicon carbide ceramic composite is fabricated using a bimodal powder feedstock and the binder‐jetting printing technique. On fabricating, the ceramic is investigated to report its composition, mechanical, and thermal properties at room temperature and high temperatures (up to 750). The ceramic has a density of 2.76 g/cc, and shows a hardness of 21.74 GPa, and a flexure strength of 207.5 MPa at room temperature. The mechanical property of flexure strength is used to estimate its failure probability under applied stress, using a Weibull distribution. The mechanical properties and failure probabilities are compared with those of conventionally fabricated reaction‐bonded silicon carbide ceramics reported in the literature. These ceramics were fabricated using methods such as slip‐casting, compacting, and tape‐casting. The comparison is used to elucidate the advantages and areas of improvement of the present additive manufacturing technique for reaction‐bonded ceramics.

The ablation behaviors of ZrB2-based UHTC coating with La2O3-modified SiC bond coat

Ultra-high temperature ceramic (UHTC) has been developed to protect C/C composites exposed to high-temperature oxidizing environment. In this study, the effect of additive for the ablation behavior of ZrB2-based coating was investigated. The SiC–La2O3 bond coat was firstly prepared on the C/C composites by the method of pack cementation (PC). ZrB2–SiC–Si (ZSS) and ZrB2–SiC–Al2O3 (ZSA) coatings with dense microstructure and excellent interfacial bonding then were prepared on the surface of C/C composites coated with SiC–La2O3 layer by the method of atmospheric plasma spraying (APS). The ablation experiments of all coated samples were conducted under oxyacetylene torch with a heat flux of 4.18 MW/m2. The microstructure, phase compositions, interfacial bonding, ablation and oxidation behaviors of coating were investigated. After ablation test, the ZrO2 sketon with prorous structure was formed in the central region of ZSS coating. However, denser structure still can be observed at ZSA coating due to the formation of liquid phase. The SiC–La2O3–C/C interface are still without cracks. Furthermore, the diffusion of La element into ZSS and ZSA coatings from the SiC–La2O3 layer was beneficial for the improvement of ablation resistance. The result indicated that SiC–La2O3/ZSA could effectively provide protection for C/C composites.

Thermal oxidation polishing of pressureless sintered silicon carbide

Pressureless sintered silicon carbide (PS–SiC) is a promising material for mirrors used in short-wavelength optical systems. However, due to its intrinsic hardness and multiphase nature, achieving atomic and close-to-atomic scale (ACS) polishing to meet the stringent requirements of the optical systems is challenging. In this study, a thermal oxidation polishing method is employed to achieve ACS polishing of PS-SiC. This method converts the hard heterogeneous SiC phase and Si phase into the “softer” homogeneous SiO2 via thermal oxidation, followed by polishing using silica sol, resulting in a finished surface roughness of 0.55 nm in Ra within 15 min. Molecular dynamics simulations are also conducted to study the thermal oxidation process of PS-SiC. The results show that SiC and Si phases oxidize at different rates, leading to roughness deterioration after thermal oxidation. This also causes unevenness in the SiC and Si phases beneath the oxidized layer. Therefore, it is necessary to control the polishing time to avoid over-polishing and potential exposure of the underlying uneven SiC and Si phases.

Optimizing processing performance of Fe-6.5 wt%Si–SiC magnetic abrasive particles by in-situ formation of FexSiy interlayer

The Magnetic Abrasive Finishing (MAF) technology has demonstrated significant potential for precision machining due to its adaptable processing characteristics. However, the current methods for preparing Magnetic Abrasive Particles (MAPs) suffer from issues such as high cost, uneven particle size distribution, and unsatisfactory structure. In this paper, a two-step ball milling method is proposed to address these problems and produce MAPs with a uniform core-shell structure. During the ball milling process, nanoscale iron powder (NIP) is added and forms a coated intermediate bonding layer on the Fe-6.5 Si powder core, increasing the adhesion between the ferromagnetic phase core and the abrasive hard phase. The study found that the addition of 10 wt% NIP as a mass percentage can optimize the MAP structure. During the sintering process at 1169.7 °C, the NIP interface transforms into a metallic interface layer, namely FexSiy (Fe5Si3 and Fe3Si), between the hard phase and the ferromagnetic phase. This intermediate layer combines the hard phase with the ferromagnetic phase, enhancing the magnetic saturation intensity while reducing the coercivity. The developed MAPs were applied to the polishing of Zr alloy tubes and effectively removed localized defects on the outer surface of the tubes. After six polishing cycles, the surface roughness decreased from 0.361 µm to 0.085 µm. This study establishes the correlation between interface behavior and magnetic properties and proposes a new strategy for the preparation of high-performance MAPs.

Formation of silicon carbide nanowire coatings on C/C composites using an in situ catalytic strategy for improved oxidation resistance

A low-cost in situ catalytic reaction strategy was employed to successfully prepare SiC–Si coatings on the C/C matrix. The addition of catalysts enabled the fabrication of SiC nanowire coatings at lower temperatures. The effect of catalyst amount (Fe(NO3)3·9H2O) and preparation temperature on the interface microstructure and oxidation resistance of SiC–Si coated C/C composites was systematically investigated. Results demonstrated that the nanowires with a addition of Fe(NO3)3–9H2O at 2 wt% showed maximum density and yield. Additionally, it was observed that the oxidation resistance of the coatings exhibited an initial rise followed by a subsequent decline as the sintering temperature increased. The superior oxidation resistance of the coatings obtained at 1300 °C can be attributed to the in-situ formation of a substantial silicon oxide layer on the surface. This layer effectively fills the cracks and pores within the coating. Furthermore, the failure of the coating was mainly attributed to oxygen diffusion through the microcracks and pores.

Enhanced mechanical properties of nanocrystalline B4C–SiC composites by in-situ high pressure reactive sintering

A unique optimized of core–shell structural B4C nanopowder, sintering aid additive of Si, and high-pressure sintering technique has been used to process nanocrystalline B4C–SiC ceramics with enhanced mechanical properties. C-coated B4C nanopowder was initially uniformly mixed with micron Si of different content by ball-milling. B4C–SiC composites with a homogenous distribution of SiC in B4C matrix were subsequently obtained by sintering the mixed powders at 6 GPa and 1600 °C. The added Si reacted with submicron amorphous carbon layer and amorphous carbon nanoshell to form dispersed SiC nanocrystals and Si–C phase filled at B4C grain boundaries and pores, respectively. The prepared composite had the most outstanding mechanical properties when the Si content in the precursor was 15 wt%, with a hardness reaching 37.8 GPa and a fracture toughness reaching 7.3 MPa·m1/2. Microstructural characterizations indicated that the multi deflection of nanoscale crack caused by intergranular fracture, the covalent bonding of Si–C phase at the grain boundary, and the abundant nanotwin substructure were jointly responsible for the superior performance in hardness and fracture toughness.