Silicon Carbide Components Research Articles

Preparation of high-density green body based on binder jetting 3D printing using spheroidized SiC powder

Silicon carbide (SiC) ceramic stands as a critical material in the realm of high-performance engineering ceramics. However, Crafting SiC ceramics with intricate structures and superior mechanical properties presents notable challenges in shaping, sintering, and processing. Binder jetting (BJ) additive manufacturing has the outstanding advantages of high forming efficiency and no thermal deformation, especially suitable for printing complex structure SiC components.; however, BJ printed green bodies often exhibit low density, resulting in high residual silicon content and diminished strength of the final components. In this work, we introduce a novel strategy to fabricate high-strength SiC components with complex geometries by improving the density of printed SiC green bodies. This method involves modifying the morphology of SiC powder through the molten salt method to increase the density of BJ 3D printed green bodies from 1.24 ± 0.13 g/cm³ to 2.01 ± 0.03 g/cm³, followed by a reactive melt infiltration process. The resulting RB-SiC ceramics display exceptional flexural strength, averaging 280.60 ± 33.05 MPa, and an elastic modulus of 294.67 ± 4.90 GPa. These values represent some of the highest for flexural strength and elastic modulus reported among 3D-printed SiC composites. With its robust mechanical performance and streamlined fabrication process, this strategy holds substantial promise for the production of structural SiC ceramics.

Preparation of low residual silicon content Si-SiC ceramics by binder jetting additive manufacturing and liquid silicon infiltration

Complex silicon carbide (SiC) ceramic components are difficult to fabricate due to their strong covalent bonds. Binder jetting (BJ) additive manufacturing has the outstanding advantages of high forming efficiency and no thermal deformation, especially suitable for printing complex structure SiC components. This study tried to obtain low silicon content silicon carbide ceramics by binder jetting followed by phenolic resin impregnation and pyrolysis (PRIP) and liquid silicon infiltration (LSI). BJ was used for the SiC green parts fabrication, and the highest compressive strength (7.7 ± 0.3 MPa) and lowest dimensional deviations (1.2–1.6 mm) were obtained with the printing layer thickness of 0.15 mm. Subsequently, PRIP treatments were introduced to increase the carbon content for the following LSI process. As the number of PRIP cycles increased, the carbon density of SiC/C preform increased and the porosity decreased. After the LSI treatment, the final Si-SiC composites processed with 2 PIRP cycles reached the highest flexural strength (257 ± 14.26 MPa) and the best wear resistance. This was attributed to the low residual silicon content (10.2 vol%) and almost no residual carbon. Furthermore, several complex structural components were fabricated using these methods. The preparation of complex components verifies the feasibility of BJ and LSI for manufacturing high-strength and high-precision SiC ceramics. Besides, this work hopes to provide technical guidance for the preparation of complex SiC composites in the future.

Power Transmission and Control in Microturbines’ Electronics: A Review

When the shaft rotates in microturbines, the rotational movement is converted to electrical power. This is achieved through a permanent magnet synchronous machine (PMSM) housed on the shaft and the power electronics components. To the best of the authors’ knowledge, articles that comprehensively describe the power transmission and control in the electrical part of microturbines have yet to be introduced, namely, the PMSM and power electronics. This review paper presents a detailed review of power conversion in each component of the electrical part of microturbines. The paper also reviews the existing literature on microturbines’ electrical performance, noting areas where progress has already been made as well as those where more research is still needed. Furthermore, the paper explains the control system in the electrical part of microturbines, outlining the grid synchronisation control approach for grid-connected microturbines and reviews the possibility of employing control strategies that engage the PMSM and power electronics as controllers for certain variables in microturbines, such as the shaft rotational speed and torque. Such control methods are more crucial in externally fired microturbines since traditional control strategies used in internally fired microturbines, such as thermal input regulation, are no longer an option in externally fired microturbines for controlling the shaft speed. The significance of higher switching frequencies in power electronics is also discussed. The higher switching frequency, the faster response to load variations and, therefore, the more reliable the control system. A greater switching frequency allows for reduced power loss, cost, and unit size. In this context, it is recommended in this review paper that future research consider using silicon carbide switching devices rather than silicon ones, which is the current practice, to build up the microturbines converters’ topology. The recommendation was motivated by looking at the existing literature that compares the switching frequency, size, cost, thermal endurance, and power losses of silicon and silicon carbide components in applications other than microturbines since initiatives of using silicon carbide in microturbine power electronics have not been reported in the literature, as far as the authors are aware. The electrical components of microturbines account for a third of the entire size and cost of the unit. This means that reducing the size and cost of the electronics contributes effectively to reducing the total size and cost. In applications other than microturbines, silicon carbide exhibited promising results compared to silicon in terms of size and long-term cost. Investigating silicon carbide in microturbines is worthwhile to see if it provides such promising benefits to the microturbine unit.

STUDY ON COOLING OF HIGH PERFORMANCE SIC FEATURES

High-performance electronic parts are vital features in almost all modern motorized machines. These silicon components are significantly minimised, especially in transportation branch. Concentration of performance requires perfect cooling conditions. A fluid flow cooling by an active cooling circuit with heat sinks is a commonly used principle. Sufficient cooling and uniform temperature field on heat transfer area are crucial parameters for the sustainable function of Silicon-Carbide components. Producer of electric vehicles induces research in the field of coolers due to the requirements of installed SiC features. This study uses advanced CFD methods to analyse the current state of commonly manufactured heat exchangers and provides new approaches by CFD optimisation in combination with 3D printed replacement parts. Approach based on 3D print also allows design inspiration in natural principles. Biomimetic inspiration shows a wide range of thousands of years lasting optimisation made by nature. Research in this field can help us with the evolution of enhanced heat transfer surfaces. Developed coolers were examined by CFD techniques. Simulations of heat transfer are verified by laboratory measurement of prototype heatsinks. These techniques are presented on the unique design of a heat sink which was simulated, manufactured, and measured. The study shows CFD approaches, describes details of prototype measurement, and also deals with negative issues of metal 3D print.

Co-printing of silicon carbide components using vibration assisted printing and fused filament fabrication

Co-printing of silicon carbide components using vibration assisted printing and fused filament fabrication

Preparation of silicon carbide ceramic slurry for stereolithography based additive manufacturing

Stereolithography-based additive manufacturing of ceramics has received tremendous attention in academic and industrial communities. In order to fabricate silicon carbide (SiC) components with complex shapes by stereolithography, a high SiC loaded ceramic slurry with low viscosity and excellent curing ability is required. However, it is challenging to meet these slurry requirements. In this work, the effects of resin formulation, dispersant, particle size, solid content and ball milling time on the properties of SiC ceramic slurry were systematically studied. The SiC slurries were prepared by using four precursor SiC powders having different particle sizes and modified by high temperature oxidation to reduce its UV absorbance. Additionally, the suitable SiC slurries for stereolithography were prepared by ball milling under appropriate processing parameters, and the geometrically complex SiC green bodies were subsequently fabricated.

Comprehensive Analysis of Short circuit Protections for Silicon-Carbide MOSFET

Silicon carbide (SIC) Metal-Oside-Semi-conductor Field-Effect Transistor (MOSFET) have excellent performance compared to traditional silicon components. The short circuit protection of SIC MOSFET plays an important role in ensuring the reliability and performance of SIC MOSFET. Due to the high internal heat flux and short short-circuit endurance time of SIC components, the short-circuit stability of SIC components is lower than that of silicon components. The paper briefly introduces two main types of SIC short circuit: hard switch short circuit and load short circuit and their characteristics, discusses the main types of contact and non-contact short circuit protection methods such as desaturation detection, parasitic inductance detection, gate voltage detection, shunt detection, instantaneous power consumption detection and Rogowski coil detection and compares their advantages and disadvantages. The desaturation detection method is the most widely used short-circuit protection method. Although the cost is low and the structure is simple, The desaturation detection has the inherent disadvantage of detecting the blind spot. The other detection methods overcome the defect of detection blind area, and the detection speed and accuracy are obvious advantages, but they also have their own limitations to limit their popularization.

New insights on the ablation mechanism of silicon carbide in dissociated air plasmas

Thermal protection system (TPS) applied in space vehicle is mainly composed of silicon carbide (SiC) and related components. When exposed in re-entry flows, the SiC based TPS may suffer from severe ablation if the surface temperature is beyond a critical threshold (generally ≥1600°C). Unveiling the ablation mechanism of SiC is thus vitally important to define the borders of service and to help optimize the TPS structures in re-entry environments. Motivated by this, this work uses an inductively coupled plasma wind tunnel to generate the dissociated air plasmas and explores the ablation behaviors of several SiC materials (including SiC ceramic and SiC fiber reinforced SiC matrix composites). Some new insights are acquired based on the detailed analysis of the surface characteristics prior to and after ablations. First, the role of surface roughness on the critical ablation temperature of the SiC based composite is put forward. Second, a ‘from-point-to-surface’ ablation process due to the surface roughness during the short ‘temperature jump’ is proposed, which is an important supplementary to the existing ablation model of SiC; Finally, a smoother surface with less defects is concluded to efficiently enhance the ablation resistance of the SiC based TPS in re-entry environments.

Research on optimization method of process parameters for SiC components robotic bonnet polishing

Silicon carbide (SiC) materials are widely used in the fields of advanced optics, such as SiC mirrors. To improve the polishing efficiency and surface quality of SiC components, reduce the cost of polishing equipment and shorten the production cycle, a robotic bonnet polishing (RBP) technology based on industrial robots was proposed. To obtain the global optimal parameters, a regression orthogonal experiment was designed by using the response surface methodology (RSM). The material removal model capturing the main process parameters was established successfully. The predicted optimal process parameters were verified by experiments. Under the optimal process parameters, the predicted material removal rate (MRR) is 0.0543 mm³/min , with an error of 9.8%. The relationship between main process parameters and surface roughness (RMS) was established by the support vector machine (SVM), and the predicted optimal value is 8.58 nm, with an error of 10.26%. Thus, the precise and controllable polishing of SiC components can be realized by RBP technology.

Research and applications of additive manufacturing technology of SiC ceramics

<p indent="0mm">Silicon carbide (SiC) ceramic material shows significant application prospects in engineering and technical fields, such as aerospace, nuclear energy, and automobile industry engineering, due to its excellent mechanical, thermal, and optical properties. It is also key to the breakthrough of national scientific research and important strategic equipment. In recent years, the requirement of high-performance SiC ceramic components with complicated shapes, such as lightweight space optical mirrors, is becoming increasingly stringent, pushing the need for ceramic processing techniques. Traditional manufacturing techniques for SiC ceramic components include slip casting, isostatic pressing, and injection molding, etc. However, these processing methods have certain restrictions, including the requirement of molds and tools, time-consuming steps, high cost, and incapability to prepare SiC ceramic parts with complex shapes and arbitrary geometries. Additive manufacturing (AM) technology has provided a new development direction for the preparation of SiC ceramic. Different from the conventional processing methods, AM is performed in a layer-by-layer fashion to fabricate the components from a computer-aided design model. It theoretically allows the production of complex-shaped SiC ceramic parts without the requirement of molds, thus overcoming the shortcomings of the conventional methods in fabricating complicated ceramic components. The AM technique has become an effective way to achieve lightweight SiC ceramic formation and integration of complex SiC ceramic components. Currently, the AM of SiC ceramics has become a research hotspot in this field. In this review, the recent advances in the research and applications of SiC ceramics prepared by AM are systematically summarized and discussed, including the material design and fabrication methods, processes and equipment, post-processing technology, finite element simulation, performance evaluation, and desired applications. After briefly introducing the general research ideas and expected results of SiC ceramics via additive manufacturing, the design and preparation methods of AM-based SiC materials, including SiC powder, slurry/paste, filament, and laminate, are described in detail. Subsequently, the common AM process of SiC ceramics is introduced, including selective laser sintering, three-dimensional printing, stereolithography, direct ink writing, fused deposition modeling, and laminated object manufacturing. Further, post-treatment processes of the green body for AM-based SiC ceramics are presented, including carbonization, liquid/gas silicon infiltration, chemical vapor infiltration, and precursor impregnation and pyrolysis. In addition, this paper summarizes the finite element simulation of AM and post-treatment process for SiC ceramics and illustrates the performance evaluation methods of SiC ceramic components, including their mechanical, thermal, and optical performances. Typical applications of AM-based SiC ceramic components are elaborated as well. Finally, the outstanding challenges, future directions, and potential perspectives related to AM-prepared SiC ceramics are proposed. In the future, the AM-prepared SiC components will develop toward the advanced directions, such as the SiC ceramics with micro- or macroscale structures, lightweight SiC ceramics, the application of SiC composite material, and the material-structure-function combination for SiC ceramics. The purpose of this paper is to provide a significant reference for the research of complex SiC ceramic components fabricated via AM.

Fabrication of dense SiSiC ceramics by a hybrid additive manufacturing process

AbstractIn this work, we report the fabrication of Silicon infiltrated Silicon Carbide (SiSiC) components by a hybrid additive manufacturing process. Selective laser sintering of polyamide powders was used to 3D print a polymeric preform with controlled relative density, which allows manufacturing geometrically complex parts with small features. Preceramic polymer infiltration with a silicon carbide precursor followed by pyrolysis (PIP) was used to convert the preform into an amorphous SiC ceramic, and five PIP cycles were performed to increase the relative density of the part. The final densification was achieved via liquid silicon infiltration (LSI) at 1500°C, obtaining a SiSiC ceramic component without change of size and shape distortion. The crystallization of the previously generated SiC phase, with associated volume change, allowed to fully infiltrate the part leading to an almost fully dense material consisting of β‐SiC and Si in the volume fraction of 45% and 55% respectively. The advantage of this approach is the possibility of manufacturing SiSiC ceramics directly from the preceramic precursor, without the need of adding ceramic powder to the infiltrating solution. This can be seen as an alternative AM approach to Binder jetting and direct ink writing for the production of templates to be further processed by silicon infiltration.

An integrated approach for the modelling of silicon carbide components laser milling process

The paper deals with characterisation and modelling of laser milling process on silicon carbide hard ceramic. To this end, a Yb:YAG pulsed fiber laser was adopted to mill silicon carbide bars. Square pockets, 5×5 mm2 in plane dimension, were machined at the maximum nominal average power (30W), under different laser process parameters: pulse frequency, scan speed, hatching distance, repetitions and scanning strategy. After machining, the achieved depth and the roughness parameters were measured by way of digital microscopy and 3D surface profiling, respectively. In addition, the material removal rate was calculated as the ratio between the removed volume/process time. Analysis of variance (ANOVA) was adopted to assess the effect of the process parameters on the achieved depth, the material removal rate (MRR) and roughness parameters, while response surface methodology (RSM) and artificial neuronal networks (ANNs) were adopted to model the process behaviours. Results show that both RSM and ANNs fault in MRR and RSm roughness parameters modelling. Thus, an integrated approach was developed to overcome the issue; the approach is based on the use of the RSM model to obtain a hybrid Training dataset for the ANNs. The results show that the approach can allow improvement in model accuracy.Graphical abstract

Embedded sensors in additively manufactured silicon carbide

Silicon carbide (SiC) components are being considered for a wide range of nuclear applications due to their high-temperature strength retention, low neutron absorption, chemical inertness, and dimensional stability under neutron irradiation. However, machining and joining of SiC components have traditionally limited its application to relatively simple geometries. Recent work has demonstrated additive manufacturing of complex, high-purity, crystalline SiC components using a combination of binder jet printing and densification via chemical vapor infiltration (CVI). The process lends itself to embedding of fuel, absorbers, moderators, and sensors at strategic locations within a component. The latter could allow for enhanced in situ performance monitoring of limiting fuel temperatures, self-shielded neutron flux, and potentially spatially distributed strain within complex SiC components if sensors can be successfully embedded during CVI. This work describes (1) methods for embedding sensors; (2) thermodynamic analyses and material compatibility testing for identifying sensors capable of surviving high temperatures and exposure to hydrogen and hydrogen chloride during CVI; and (3) nuclear applications for embedded sensors, including potential failure modes during fabrication and during reactor operation. Molybdenum-sheathed thermocouples were successfully embedded in a complex SiC component, whereas niobium-sheathed high-temperature irradiation-resistant thermocouples started to drift as soon as the reactant gases were introduced and ultimately failed during CVI due to severe constrained expansion, potentially resulting from niobium hydride formation in the low-temperature region of the CVI system. Optical fibers were successfully embedded in SiC, but further work is needed to protect the fragile fiber leads after their protective coatings are removed during CVI.

Additive manufacturing of silicon carbide by selective laser sintering of PA12 powders and polymer infiltration and pyrolysis

In this work, we propose a novel hybrid additive manufacturing technique, which combines selective laser sintering (SLS) of polyamide powders and subsequent preceramic polymer infiltration and pyrolysis to manufacture Silicon Carbide components for complex architectures. By controlling the porosity of the sintered polymeric preform we are able to control the shrinkage upon the first infiltration and pyrolysis. This enabled the manufacturing of smaller features than those achievable with other manufacturing techniques. The mechanical strength of the resulting ceramic increased with the number of reinfiltration cycles up to 24 MPa, inversely the residual porosity decreased to 10 vol%. The microstructure showed two distinct phases of SiOC and SiC. The first was attributed to the interaction between the porous polyamide and the ceramic precursor during the first infiltration. SiC derived from the pyrolysis of the preceramic precursor alone.

Effect of SiC powder on the properties of SiC slurry for stereolithography

Silicon carbide (SiC) is a kind of structural ceramics with excellent properties and it is widely used in industrial fields. Stereolithography (SL) is a potential additive manufacturing technique to fabricate fine complex SiC components, the resin-based SiC slurry with superior rheological and photo-polymerization properties is important for SL. In this paper, we investigated the influence of SiC powder on the properties of the SiC slurries for SL. The physical characteristics of SiC powder such as particle size, size distribution and appearance were tested and observed, and their influence on the dispersion, sedimentation and photo-polymerization property of the SiC slurry were investigated and discussed in detail based on their correlative theory, we finally prepared SiC slurry with superior rheological and photo-polymerization properties, and fabricated the fine complex SiC green body with low defects, high accuracy and high bending strength successfully. The SiC slurry with the solid content of 40 vol% was fabricated by the SiC powder with the median diameter D50 ≈ 10.0 μm and a narrow particle size distribution, it is Bingham fluid with good fluidity and the viscosity of it is 464.40 mPa s under the shear rate of 51.08 s−1, the cured SiC parts with Z – axis dimension change of 0.75% was finally fabricated, the three points bending strength of it is 50.18 MPa. Our research work provides some fundamental understanding of the SL technique for fabricating fine complex SiC components, explored a suitable way to fabricate high quality SiC green parts through SL, and offers some valuable references for preparing SiC slurry with superior rheological and photo-polymerization properties.

Joining of sintered SiC ceramics at a lower temperature using borosilicate glass with laser cladding Si modification layer

The silicon carbide whose surface had been modified by laser cladding silicon layer was soldered by borosilicate glass. And the borosilicate glass solder had a thermal expansion coefficient similar to that of the silicon carbide substrate. The laser cladding silicon layer significantly improved the wettability between molten glass solder and silicon carbide and could reduce the soldering temperature. A sandwich-like joining structure (SiC/Si/solder/Si/SiC) was made after the borosilicate glass slurry put on the laser cladding silicon layers. The microstructure, compositions, and interfacial properties were studied. Results showed that good adhesion between silicon carbide and the glass soldering layer was achieved. The flexural strength of the connection structure prepared at 900 °C in the air reached 110 MPa. This research provides an effective technical solution for realizing local heat treatment soldering of large silicon carbide components.

Characterizing the Tensile Strength of Metastable Grain Boundaries in Silicon Carbide Using Machine Learning

The local atomic structure, local chemistry, and stoichiometry of grain boundaries control in part the strength and fracture toughness of silicon carbide components. The predictions of the structure and properties of these grain boundaries are generally limited to their ground-state configurations. We investigated the tensile strength behavior of metastable grain boundaries in silicon carbide using high-throughput atomistic simulations combined with machine learning techniques. We analyzed and compared the ∑5 ⟨100⟩{120} and ∑9 ⟨110⟩{122} tilt grain boundary metastable configurations to identify structural and chemical attributes that dominate their tensile strength. We characterized these metastable grain boundaries using a set of microscopic descriptors representing the local grain boundary atomic structure and the local grain boundary stoichiometry and chemical-bound types. We used a boosted regression tree surrogate model for the successful prediction of metastable grain boundary strength as a function of these descriptors. Our results show that the tensile strength of generic (i.e., any random grain boundary from the entire grain boundary population), metastable grain boundaries is primarily dominated by the grain boundary excess free volume, closely followed by the type of structure composing the boundary and the amount of C–C bonds. The 5% strongest metastable grain boundaries have particular characteristics with a low amount of free volume and the highest density of C–C bonds. Our results reveal that the 5% strongest and weakest metastable grain boundaries are most sensitive to the local stoichiometry, regardless of the local atomic structure composing the grain boundary as compared to any other generic metastable grain boundaries. We show that the strongest and weakest metastable grain boundary configurations can be identified as specific regions in a low-dimensional-representation space of their microscopic descriptors. Taken together, these findings showcase the effectiveness and validity of using a low-dimensional representation of the grain boundary structure and machine-learned surrogate models to rapidly assess metastable grain boundary strength without the need to perform actual tensile simulations.

Comparison of Si and SiC EMI and Efficiency in a Two-Level Aerospace Motor Drive Application

Power electronics are crucial elements in more-electric aircraft (MEA) applications. Existing hardware is almost exclusively silicon (Si)-based. However, recent advances in semiconductor technology yielded silicon carbide (SiC) components with current ratings suitable for aerospace applications. These devices have much strength that can increase power density and improve performance over Si-based hardware. High switching speeds are characteristic of SiC devices, and there is much concern about their impact on electromagnetic interference (EMI). This may necessitate larger EMI filters to comply with EMI standards, which would decrease power density and negate some of SiC’s benefits. The following research explores the tradeoff between efficiency and EMI. It compares the performance of two high-power three-phase converters: one built from SiC MOSFETs and the other from Si IGBTs. The test setup consists of a 250-kW drive stand capable of sourcing and regeneratively sinking power as well as a 40-kVA aerospace rated machine. Experimental results are obtained at a bus voltage of 270-Vdc with power levels exceeding 1.5 p.u. The findings demonstrate comparable EMI performance for Si and SiC under MIL-STD-461 with the SiC converter achieving higher efficiency.

炭化ケイ素セラミック成形体の光造形アディティブ・マニュファクチュアリング

炭化ケイ素セラミック成形体の光造形アディティブ・マニュファクチュアリング

Comparison of graphene films grown on 6H-SiC and 4H-SiC substrates

Atomic force microscopy, Kelvin-probe microscopy and Raman spectroscopy have been used to examine graphene films grown by thermal decomposition of the Si face of semi-insulating substrates of 6H-SiC and 4H-SiC polytypes in the atmosphere of argon. It was demonstrated that the quality of graphene grown on substrates of various polytypes at identical technological growth regimes is about the same. A conclusion was made that the differences in crystal structure between 6H-SiC and 4H-SiC does not lead to significant dissimilarities in the mechanism of sublimation of silicon carbide components from the surface of a crystal and in that of graphene crystallization.