Silicon Carbide-silicon Research Articles

Novel Synthesis of SiC-SiO2 Nanotubes from Cinachyrella sp. and Its Improvement of the Corrosion Resistance of Low Carbon Steel in 3.5% NaCl Water Solution

Coat synthesis of silicon carbide and composites of Si derivatives is a challenge for high-quality thin film applications, including corrosion resistance industries. A novel fabrication process of silicon carbide-silicon dioxide nanotube composites (SCDNTs) was developed by a solid reaction of silicon-carbon (marine sponge Cinachyrella sp.) resources. Trimetallic catalyst (Fe/Ni/Zr) supported on different Al2O3 media with heating in an argon flow was used to prepare SCDNTs composite. A higher crystallinity degree of the nanocomposites is attained at a heating temperature of 1200 °C as a suitable starting temperature to have a reasonable degree of crystallinity. XRD analysis of the prepared composite showed the presence of polycrystalline silicon dioxide and two phases of silicon carbide; 3C-SiC and 6H-SiC. TEM analysis showed the presence of silicon carbide's cubic and hexagonal structures embedded into silicon dioxide nanotubes. FTIR analysis confirmed the XRD and TEM analyses through the presence of the functional groups related to Si-Si, Si-O and Si-C. The SCDNTs spin coating process on LWS was optimized at 1000 rpm. Varying thin coatings of up to 5 layers of SCDNTs were prepared low steel substrate to evaluate its corrosion behavior in a 3.5% NaCl solution. Five-layer SCDNTs composite coating on LCS was the favorable coating as obtained from the electrochemical measurements ensured a corrosion inhibition efficiency of 92.5% and corrosion rate of 63.98 mm/y. XRD spectra and stereomicroscope were used to evaluate the surface of LWS coated with SCDNTs before and after corrosion test.Graphical

Reliability Assessment of Hybrid Silicon-Silicon Carbide IGBT Implemented on an Inverter for Photo Voltaic Applications

Reliability Assessment of Hybrid Silicon-Silicon Carbide IGBT Implemented on an Inverter for Photo Voltaic Applications

Novel heat flux sensor for SiC-SiC ceramic matrix composite engine components

Silicon carbide-silicon carbide ceramic matrix composites (SiC-SiC CMC’s) are being used in gas turbine engine hot sections due to their refractory nature and excellent toughness at high temperatures. A novel heat flux sensor was developed for SiC-SiC CMC based engine components, which can survive temperatures up to 550 °C. The heat flux sensor consists of platinum thin films that forms a thermocouple junction with the SiC-SiC CMC which utilizes the bulk thermoelectric properties of the SiC-SiC CMC for its operation. This novel Pt:SiC-SiC CMC heat flux sensor generates a thermoelectric voltage that is directly proportional to the temperature gradient along the through thickness direction of the CMC component onto which it was deposited and has a calibration factor of 0.0266 µV/(W/m2). Fabrication details, experimental results and implementation challenges are discussed.

Composite material for high‐temperature thermochemical energy storage using calcium hydroxide and ceramic foam

AbstractThermochemical energy storage using a calcium oxide/calcium hydroxide/water (CaO/Ca(OH)2/H2O) reaction system is a promising technology for thermal energy storage at high‐temperatures (400°C‐600°C). The purpose of this study is to develop a practical composite material by enhancing heat transfer through the reaction bed and mitigating problems of pure CaO/Ca(OH)2 materials, such as formation of centimeter‐scale agglomerates and change in the bulk volume during repetitive reactions. The present study focused on a novel composite material using a silicon carbide/silicon (SiC/Si) foam. In the literature, performance of thermochemical energy storage of the composite using the ceramic foam remains unclear. In this study, we evaluated the performance of the composite material (~63 g) by a 100‐W‐scale packed bed reactor. The volumetric heat output rate (for the first 5 minutes, under maximum hydration pressure) of the composite was 1.3 kW L‐bed−1, which was 1.4 times higher than that previously reported for a bed of pure Ca(OH)2 pellets. The composite material, in which the CaO/Ca(OH)2 samples were subdivided inside pores with a mean diameter of 400 μm, retained high reactivity during cycle reactions, and maintained its bulk volume. Therefore, the composite material developed in this study shows promising application for high‐temperature thermochemical energy storage.

Effect of Electrolysis Modes on Physico-Mechanical Properties of Composite Coatings Based on Nickel

The receiving method and some properties of the composite nickel containing galvanic coating on base nickel-cobalt-oxide silicon-carbide silicon system were discussed. Chloride electrolyte for the application of the composite electroplating coating with firmness to wear and corrosion properties of nickel-cobalt-oxide silicon-carbide silicon system was elaborated. Influence of electrolysis and electrolyte composition on physico-mechanical properties (firmness to wear, corrosion resistance, hardness, internal tensions, porosity, adhesion) of the composite electrolytic coating of nickel-cobalt-silicon oxide system, electroplated from chloride electrolyte, and on the properties of electrolyte (diffusing ability, output current draught) were investigated. The possibility of using for composite electroplating of nickel-cobalt-silicon oxide-carbide silicon system as a firmness to wear coating in instead of chrome was showed.

Chemical compatibility between UO2 fuel and SiC cladding for LWRs. Application to ATF (Accident-Tolerant Fuels)

Silicon carbide-silicon carbide (SiC/SiC) composites are considered to replace the current zirconium-based cladding materials thanks to their good behavior under irradiation and their resistance under oxidative environments at high temperature. In the present work, a thermodynamic analysis of the UO2±x/SiC system is performed. Moreover, using two different experimental methods, the chemical compatibility of SiC towards uranium dioxide, with various oxygen contents (UO2±x) is investigated in the 1500–1970 K temperature range. The reaction leads to the formation of mainly uranium silicides and carbides phases along with CO and SiO gas release. Knudsen Cell Mass Spectrometry is used to measure the gas release occurring during the reaction between UO2+x and SiC powders as function of time and temperature. These experimental conditions are representative of an open system. Diffusion couple experiments with pellets are also performed to study the reaction kinetics in closed system conditions. In both cases, a limited chemical reaction is observed below 1700 K, whereas the reaction is enhanced at higher temperature due to the decomposition of SiC leading to Si vaporization. The temperature of formation of the liquid phase is found to lie between 1850 < T < 1950 K.

Self-Propagating High-Temperature Synthesis of Si-SiC Composite Powder

Silicon-silicon carbide (Si-SiC) composite powders were synthesized by in-situ self- propagating high-temperature synthesis using rice husk ash (RHA)/carbon/Mg as precursors in argon atmosphere. The as-SHS powders were leached by two leaching steps. The microstructure and chemical composition of the obtained Si-SiC composite powders were examined using scanning electron microscope (SEM) and x-ray diffractometer (XRD), respectively.

High, Low, and Zero Field Spin Dependent Recombination in 4H SiC Metal Oxide Semiconductor Field Effect and Bipolar Junction Transistors

Silicon carbide based transistors have great promise in high temperature and high power applications. In particular, the great promise of silicon carbide based metal oxide semiconductor field effect transistors (MOSFETs) has been somewhat limited by materials physics problems in the region near the silicon carbide-silicon dioxide interface. Materials physics problems in SiC bipolar junction transistors (BJTs) are also topics of current interest. Studies involving a combination of high, low, and zero field electrically detected magnetic resonance via spin dependent recombination provide a powerful approach for the understanding of SiC transistor materials physics problems. In this paper, we will review our group’s work on multi-field spin dependent recombination of 4H SiC based MOSFETs and BJTs. We emphasize the physical principles involved in the measurements in part because they could potentially be quite useful if they were to be applied to other wide band gap semiconductor device systems.

High, Low, and Zero Field Spin Dependent Recombination in 4H SiC Mosfets

Silicon carbide metal oxide semiconductor field effect transistors (MOSFETs) have great promise in high power and high temperature applications. Among the many polytypes, 4H is the most promising for MOSFET applications. Unfortunately, the effective channel mobility in these devices remains disappointingly low and the devices frequently exhibit as yet poorly understood bias temperature instabilities. The underlying causes of the low effective channel mobility and the bias temperature instabilities are as yet not fully understood but clearly involve the presence of electrically active point defects very close to the silicon carbide-silicon dioxide interface. Electron paramagnetic resonance (EPR) has unrivaled sensitivity and analytical power in the identification of point defects in semiconductors and insulators. However, the detection limit of conventional EPR in solids is about ten billion defects under near ideal circumstances. Thus, conventional EPR lacks the sensitivity to detect these defects in a transistor even remotely approaching technological relevance. The electrically detected magnetic resonance (EDMR) technique called spin dependent recombination (SDR) provides a sensitivity at least ten million times higher than that of conventional EPR. SDR/EDMR can also provide information about the physical location and energy levels of defects, with the additional advantage that it is readily made sensitive to only those defects which actually affect the performance of the device under observation. In this study, we utilize SDR/EDMR measurements carried out over a wide range of magnetic fields, frequencies, and temperatures utilizing multiple electronic measurement platforms (spin dependent charge pumping, spin dependent gated diode recombination current measurements, and bipolar amplification effect spin dependent recombination measurements) to identify defects on both sides of the silicon carbide-silicon dioxide interface. Our measurements identify multiple defect centers, some in the silicon dioxide near the interface, others in the silicon carbide near the interface. The silicon dioxide centers include simple oxygen vacancy centers and hydrogen complexed oxygen vacancy centers. The silicon carbide centers include silicon vacancies and, as yet only partially identified hydrogen complexed defects. Of particular interest are defect centers which are either created or activated by bias temperature stressing.We show that the presence of one near interface silicon carbide defect is strongly correlated with the interface trap density in as processed devices, the silicon vacancy. We also show that the amlitudes of several SDR/EDMR spectra, those associated with oxygen vacancy centers in the oxide and at least one hydrogen complexed center are correlated with bias temperature instability response.We believe our work will be useful to SiC device process designers in particular. We also believe that the work will be of interest to a broader audience, including those involved in research dealing with other wide band gap semiconductors because the novel low to near zero field SDR measurements we utilize can likely be readily adapted to devices based upon virtually any wide band gap material.

First-order phase transition through an intermediate state

The theory of first-order phase transitions in systems where the direct formation of nuclei of a new phase is inhibited for any reason, for example, because of the extremely high elastic energy, has been constructed using the example of the silicon-silicon carbide phase transition due to the chemical reaction with carbon monoxide. It has been shown that, in this case, the phase transition occurs through an intermediate state, which significantly promotes the formation of new-phase nuclei. For the silicon-silicon carbide phase transition, such an intermediate state is the “pre-carbide” state of silicon saturated with dilatation dipoles, i.e., pairs formed by a carbon atom and a silicon vacancy that are strongly attracted to each other. The model dependence of the potential energy of systems with an intermediate phase on the reaction coordinates has been investigated. The kinetics of transformation of the intermediate state into a new phase has been described.

Characterization of silicon-silicon carbide ceramic derived from carbon-carbon silicon carbide composites

Abstract The main objective of the present work is to process porous silicon–silicon carbide (Si–SiC) ceramic by the oxidation of carbon–carbon silicon carbide (C/C–SiC) composites. Phase studies are performed on the oxidized porous composite to examine the changes due to the high temperature oxidation. Further, various characterization techniques are performed on Si–SiC ceramics in order to study the material's microstructure. The effects of various parameters such as fiber alignment (twill weave and short/chopped fiber) and phenolic resin type (resol and novolak) are characterized.

Over‐infiltration mechanisms in selective laser sintered Si/SiC preforms

PurposeThe paper aims to evaluate mechanisms for silicon overfilling including volume expansion of silicon on solidification for composite silicon/silicon carbide (SiC) objects generated using post‐process infiltration of selective laser sintered (SLS) SiC preforms.Design/methodology/approachOverfilling was characterized through geometrical means and microscopy, and results were used for further study and discussion of overfilling mechanisms.FindingsSilicon overfilling in silicon infiltrated SLS SiC parts is attributed primarily to its infiltrant silicon volume expansion on solidification. Si/SiC composites were found to be thermally stable with good material bonding.Research limitations/implicationsSilicon as an infiltrant is unusual as it expands on solidification, whereas most infiltrants contract. Overfilling during infiltration of SLS porous performs is therefore not considered to be prevalent.Originality/valueThis paper provides an examination of the value of silicon as an infiltrant material for SLS SiC preforms. Various mechanisms are presented for volume change during post‐process infiltration of indirect SLS non‐metallic performs.

Interfacial Properties of SiO&lt;sub&gt;2&lt;/sub&gt; Grown on 4H-SiC: Comparison between N&lt;sub&gt;2&lt;/sub&gt;O and Wet O&lt;sub&gt;2&lt;/sub&gt; Oxidation Ambient

Many investigations have been conducted on the growth conditions of SiO2 on SiC to improve the oxide quality and the properties of the silicon carbide-silicon dioxide interface. In this work a comparison between a wet oxidation and an oxidation in N2O ambient diluted in N2 is proposed. The interface state density Dit near the conduction-band edge of SiC has been evaluated by conventional C-V measurements obtaining results similar or better than the literature data. Furthermore, the slow trapping phenomena have been studied and preliminary results are reported.

Erratum: “Charge transport in hydrogenated boron-doped nanocrystalline silicon-silicon carbide alloys”[J. Appl. Phys. 98, 054311 (2005)

Erratum: “Charge transport in hydrogenated boron-doped nanocrystalline silicon-silicon carbide alloys” †J. Appl. Phys. 98, 054311 „2005...‡ Seung Yeop Myong and Koeng Su Lim Department of Electrical Engineering and Computer Science, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 Republic of Korea Received 25 February 2006; accepted 3 March 2006; published online 23 May 2006

Effect of hydrogen dilution on carrier transport in hydrogenated boron-doped nanocrystalline silicon-silicon carbide alloys

The effect of the hydrogen dilution ratio on characteristics of hydrogenated boron-doped nanocrystalline silicon-silicon carbide alloy (p-nc-Si–SiC:H) films is investigated. Hydrogen coverage near the growing surface causes nanocrystallization by retarding the reactions of the precursors. It was found that p-nc-Si–SiC:H alloys have two different kinds of carrier transport mechanisms: one is the thermally activated hopping conduction between neighboring crystallites near room temperature and the other is the band tail hopping conduction below 150K. However, the film at the onset of the nanocrystalline growth exhibits a different behavior due to a large band tail disorder.

Charge transport in hydrogenated boron-doped nanocrystalline silicon-silicon carbide alloys

We have investigated the carrier transport mechanism of mixed-phased hydrogenated boron-doped nanocrystalline silicon–silicon carbide alloy (p-nc-Si-SiC:H) films. From temperature-dependent dark conductivity measurements, we found that the p-nc-Si-SiC:H alloys have two different carrier transport mechanisms: one is the thermally activated hopping between neighboring crystallites near the room-temperature region and the other is the band tail hopping below 150 K.

Process Development of Silicon-Silicon Carbide Hybrid Micro-Engine Structures

AbstractA MEMS-based gas turbine engine is being developed for use as a button-sized portable power generator or micro-aircraft propulsion source. Power densities expected for the micro- engine require high combustor exit temperatures (1300-1700K) and very high rotor peripheral speeds (300-600m/s). These harsh operating conditions induce high stress levels in the engine structure, and thus require refractory materials with high strength. Silicon carbide has been chosen as the most promising material for use in the near future due to its high strength and chemical inertness at elevated temperatures. However, techniques for microfabricating single- crystal silicon carbide to the level of high precision needed for the micro-engine are not currently available. To circumvent this limitation and to take advantage of the well-established precise silicon microfabrication technologies, silicon-silicon carbide (SiC) hybrid turbine structures are being developed using chemical vapor deposition of poly-SiC on silicon wafers and wafer bonding processes. Residual stress control of SiC coatings is of critical importance to all the silicon-silicon carbide hybrid structure fabrication steps since a high level of residual stresses causes wafer cracking during the planarization, as well as excessive wafer bow, which is detrimental to the subsequent planarization and bonding processes. The origins of the residual stresses in CVD SiC layers have been studied. SiC layers (as thick as 30µm) with low residual stresses (on the order of several tens of MPa) have been produced by controlling CVD process parameters such as temperature and gas ratio. Wafer-level SiC planarization has been accomplished by mechanical polishing using diamond grit and bonding processes are currently under development using interlayer materials such as silicon dioxide or poly-silicon. These process development efforts will be reviewed in the context of the overall micro-engine development program.

Effects of additive amount on microstructure and mechanical properties of silicon carbide-silicon nitride composites

Powder mixtures of β-SiC-α-Si3N4 in a weight ratio of 1 : 1 containing 5–20 wt% Y-Mg-Si-Al-O-N oxynitride as a sintering additive were liquid-phase sintered at 1800°C for 3 h by hot-pressing. These materials had a microstructure of “in situ-toughened composites” as a result of the α → β phase transformation of Si3N4 during sintering. The introduction of larger amount of additives accelerated the grain growth of elongated β-Si3N4 grains with higher aspect ratio, resulting in the improved fracture toughness and strength. Typical flexural strength and fracture toughness of SiC-Si3N4 composites containing 15 wt% oxynitride glass were 860 MPa and 5.7 MPa · m1/2, respectively.

Heterogeneous effect in carbonized porous silicon

The spectra of photoluminescence from carbonized porous silicon were measured upon the anodic polarization of samples in an oxidative electrolyte. A significant increase in the intensity of a blue-green emission band was observed and attributed to a change in parameters of the silicon-silicon carbide heterostructure. In addition, the carbonized porous silicon exhibits effective electroluminescence in an oxidizing electrolyte.

The structure of ceramic foams produced using polymeric precursors

During the last decade porous ceramic materials have been finding increasing applications due to their favorable properties such as high temperature stability, high permeability, low mass, low specific heat capacity and low thermal conductivity. These characteristics are essential for many technological applications such as catalyst supports, filters for molten metals and hot gases, refractory linings, thermal and fire insulators and porous implants [1, 2]. Ceramic foams can be produced by different methods, principally impregnation of polymer foams with slurries containing appropriate binders and ceramic particles followed by pressureless sintering at elevated temperatures [2–5]. This involves coating an open-cell polymeric sponge with a ceramic slurry several times, pyrolysis of the polymer to form a ceramic skeleton followed by sintering. Ceramic foams produced by this method are generally of low strength as their struts are thin and can contain a hole in the center [2, 6–8]. Recently, a new method to produce silicon carbide (SiC) foams using polymeric precursor solutions was developed by Bao et al. [9] where a polyurethane foam was immersed in a polymeric precursor solution to form a pre-foam which was pyrolyzed in nitrogen. The main advantages of this new approach are the simplicity and ease of control of structure of the final product. This new process was exploited further to prepare silicon carbide-silicon nitride (SiC-Si3N4) composite foams [10]. In this letter we provide microstructural evidence of the improvements in structure of the ceramic foams produced by our method. The polysilane precursor discussed in this study was synthesized by the alkali dechlorination of a combination of chlorinated silane monomers in refluxing toluene/tetrahydrofuran with molten sodium as described previously [11, 12]. The structure of the SiC polysilane precursor synthesized is given below. Ph indicates a phenyl group.