SiC Rod Research Articles

Characterisation of Molten Lithium Carbonate Corrosion on SiC Heating Elements Using Raman Spectroscopy

The synthesis of lithium battery materials involves the use of muffle furnaces operating with SiC type heating elements. Usually, the industrial SiC heating element is protected by passive oxidation forming a protective silica film on the surface of the element. However, this strategy is not suitable for heating elements that operate in a Li-rich environment. A preliminary study has recently been completed to develop an understanding on the degradation of silicon carbide heating elements under the exposure to lithia. After basic characterisation of the SiC rod and its oxidation in air, its reaction products in the presence of Li was studied. The SiC rod was reacted with a likely Li source, Li2CO3, in three different % Li concentration environments through vapour-phase, wetting and full-immersion studies, particularly at the temperature just above the Li2CO3 melting point in delivering accelerated ageing. The characterisation was achieved via an integrative data analysis through the coordination of Raman, XRD, and Energy dispersive X-ray analysis (EDX) techniques. We found that molten Li2CO3 reacts with the silica surface layer of the element forming three main lithium silicates (LixSiyOx/2+2y). The degradation of surface silica into non-adherent lithium silicate leads to a speeding-up of the SiC oxidation process. Both processes eventually lead to a complete structural failure of the SiC rod. We performed a long-term vapour phase lithium attack experiment characterising the SiC after regular time intervals solely by Raman spectroscopy. Initially, a library of Raman spectra for the commonly encountered compounds in the Si-Li-O system was obtained from specifically synthesised stoichiometric compounds. In doing so, the reaction products at different reaction time intervals can be clearly identified, demonstrating the utility of Raman characterisation in corrosion studies.

Optimization and analysis of machining performance for the milling process during milling of W-Al-Si-C alloy material

This study determined the optimum HSS cutting tool technique parameters for milling W-Al-Si-C rods using Taguchi methodology. This paper explains the empirical results of the selection of appropriate cutting settings that assure lower power consumption in high-end Computer Numerical Control (CNC) machines. An experiment employing the Taguchi methodology on an extruded W-Al- Si-C rod was performed on a CNC lathe with cutting speed, feed rate, and depth of cut as the process parameters. The performance characteristics (energy usage) were quantified by a data collection system. Minor energy process parameters were selected after data analysis. Experimental results are presented to demonstrate the worth of the chosen methodology. A total of 350[Formula: see text]rpm, 0.37[Formula: see text]mm/rev feed rate, and 1[Formula: see text]mm of cut depth produced the best MRR result. The maximum material removal rate (MRR) is obtained at lower levels of spindle speed and depth of cut, i.e., 1.452[Formula: see text]g/sec.

Structure and photochemistry of a potential precursor of circumstellar dust: The optical spectrum of Si4C2+

Mixed silicon carbide clusters are important components of circumstellar shells and their optical properties are fundamental for modelling the chemistry involved in the evolution of dust particles. Herein, we report the ultraviolet photodissociation (UVPD) spectrum of mass-selected Si4C2+ cations obtained in the 208–330 nm range (3.8–6.0 eV) in a quadrupole/time-of-flight tandem mass spectrometer coupled to a laser desorption source operating with a SiC rod and a broadly tuneable optical parametric oscillator laser. The UVPD spectrum is observed in the two lowest-energy fragment channels, corresponding to dominant loss of atomic Si at low energy and the rather stable Si2C molecule at high energy. The UVPD spectrum is analyzed by quantum chemical calculations at two levels of density functional theory (CAM-B3LYP, M11) to determine the structures, energies, electronic spectra, and fragmentation energies of the lowest-energy isomers. To locate these isomers on the multidimensional potential energy surface, basin hopping is employed as global optimization approach. The UVPD spectrum is consistent with the optical absorption spectrum computed for the two lowest-energy isomers, one of which is reported for the first time.

Electrodeposition of Si in Molten CaCl2 Above 1300K

Metallic Si is produced by carbon reduction of SiO2 in an arc furnace above 2000K, and the energy consumption and CO2 exhaustion in the process are very large. The authors reported that TiO2 could dissolve in molten CaCl2 containing CaO above 1300K, and that Ti metal was electrodeposited in the bath. This result implies the possibility of electrolytic production of liquid metallic Si in molten CaCl2-CaO-SiO2 above its melting point, which can lead the innovative production process of metallic Si with lower energy consumption and lower CO2 exhaustion. To realize this process, the electrochemical behavior of Si in molten CaCl2-CaO-SiO2 at a very high temperature has to be studied in detail. In this study, the cathodic reaction has been investigated in molten CaCl2-CaSiO3 above 1300K, and the electrodesipotion of metallic Si has been attempted. Based on our previous studies on Ti electrolysis, calcium silicate was used instead of CaO and SiO2. Calcium chloride containing 0~10 mol% CaSiO3 in a Mo crucible was fused in an air-tight furnace, and electrolysis was carried out at 1373 ~ 1573 K under a pure Ar flow. The working electrode was mainly a Mo wire with an Al2O3 sheath, and a SiC rod was also used. Another Mo wire electrode was used as quasi-reference electrode, and its potential was calibrated with Mo dissolution potential in the bath. Cyclic voltammetry was performed to investigate the electrode reactions in the bath, and then potentio-static electrolysis was carried out to obtain electrodeposit. The electrode surfaces after electrolysis as well as the electrodeposit were analyzed by XRD and SEM-EDX. The cathodic current obviously enlarged with the CaSiO3 addition, and the CaSiO3 solubility seemed to increase with the bath temperature. A sharp cathodic current peak appeared around -1.1 V (vs. Mo dissolution potential) at the Mo electrode, while no cathodic current peak was observed at the SiC electrode. Electrodeposit as shown in Fig.1 was obtained at the Mo electrode, and metallic Si was detected in it. Although a MoSi2 layer was also formed on the surface by electrolysis as shown in Fig. 2, the amount of Si in the layer was limited considering the quantity of electricity during the electrolysis. Since CaSi2 was sometimes found in the deposit, the suitable electrolytic potential needs to be revealed. It was shown that metallic Si was obtained by electrolysis in molten CaCl2-CaSiO3 under the proper condition. However, the amount of metallic Si on the electrode could not be determined yet because of the powdery morphology of deposit. It should be desirable to obtain liquid metallic Si by electrolysis above its melting point. Figure 1

Influence on the recovered spectrum caused by thermal optics effect of the collimation lens used in static Fourier transform infrared spectrometer

In a stepped-mirror-based static Fourier transform infrared spectrometer, the collimation lens is located adjacent to the light source and the thermal radiation would lead to the partial temperature increase, and the refractive index of the infrared material unavoidably changes. Then the light beam passing through the collimation lens will induce a divergence angle, directly affecting the resolution of the recovered spectrum. Meanwhile, the angular divergence results in a displacement in the interference signal, making increasing difficulties in the interferogram processing and the spectrum recovery. In this paper, the distribution of temperature in different areas of the collimation lens is studied under the working condition, and the defocusing value of the collimation lens is 0.153 mm that is caused by the refractive index gradient of the infrared material along with the temperature. In addition, the divergence angle induced by defocusing is calculated, its distribution being nonuniform but symmetrical within the sample area. Moreover, the divergence angle brings about additional optical path difference, its effect on the recovered spectrum is analyzed. Compared with the ideal recovered spectrum, much noise emerges and the peak value is reduced in the real recovered spectrum. The spectrum-construction error of the real recovered spectrum is 18.72%, indicating that the recovered spectrum is seriously distorted, and the resolution at the center wavelength in the ideal recovered spectrum and the real spectrum are 4.71 cm-1 and 5.57 cm-1, respectively. This indicates that the spectrum resolving power is weakened. Furthermore, the reasonable temperature range is obtained by analyzing the curve of spectrum-construction error versus temperature of the collimation lens. When a spectrum-construction error of less than 5% is demanded, the temperature difference between the front len of collimation and the ambient must be less than 8 ℃. Finally, experiments are performed using a SiC rod as the light source, and interferograms are made by four steps including dark current electric noise elimination, spatial gain correction, image signal averaging, and spectrum recovery. Results show that the spectrum-construction errors (SCE) from the cold light source and non-cold light source are 8.48% and 21.51%, respectively. Although they are all larger than the theoretical value, the SCE of cold light source decreases by 13.03% compared to cooling-free light source. Hence, it is necessary to reduced the thermal radiation influence on collimation lens from the light source. This result is helpful in solving the analogous problems.

레이저 화학증착을 이용한 3차원 쾌속조형에 관한 실험적 연구

Laser chemical vapor deposition can be an effective technique for a rapid prototyping with ceramic materials, in particular. The objective of the study is to fabricate several 3-dimensional objects by stacking multi-layers as well as to find out some basic aspects of a rapid prototyping with laser chemical vapor deposition such as deposition characteristics with traversing speed of the laser, possible problems in stacking multi-layers etc. The limit speed of the laser that can grow a tilted SiC rod was found in this study, and laser directing writing that occurs over the limit speed was also investigated. Finally, a zigzag-shaped rod, a spiral-shaped rod, as wall and a square duct were successfully fabricated with laser chemical vapor deposition of tetramethylsilane.

Nd-Yag 레이저 화학증착을 이용한 SiC 로드 성장에 관한 실험적 연구

Laser chemical vapor deposition can be used as a new approach for a rapid prototyping technique. The purpose of the study is to fabricate several 3-dimensional objects that are relatively simple as well as to find the characteristics of SiC rod growth that is the first step in developing a new rapid prototyping technique with laser chemical vapor deposition. In the study, SiC rods were generated with varying precursor pressure for 5. minutes. Deposition rates with varying precursor pressure, shapes of rods, surface roughness and component organization were investigated, in particular. Finally, several simple objects like a branch or a propeller were successfully fabricated using laser chemical vapor deposition.

Aligned small α-SiC nanorods on β-SiC particles grown in an arc-discharge

Aligned α-SiC nanorods, several nanometers in diameter and with lengths up to 200 nm, were grown on the facets of simultaneously formed β-SiC particles by using an SiC rod as the anode to arc-discharge in a helium atmosphere. SEM, TEM and XRD were employed to characterize the prepared nanostructures. The small α-SiC nanorods exhibit excellent elastic deformation ability and have a strong bond to the β-SiC substrate. The possible growth mechanism of the nanostructures is discussed.

Large-scale synthesis of β-SiC nanorods in the arc-discharge

SiC nanorods sheathed in amorphous SiO 2 were synthesized in mass by an arc-discharging approach, using a SiC rod containing iron impurity as the anode, and were characterized by SEM, TEM, EDX and XRD. The prepared nanorods possess a β-SiC crystal core with a uniform diameter of 5–20 nm and an amorphous SiO 2 wrapping layer tens of nanometers in thickness, and their lengths range from hundreds of nanometers to several micrometers. A possible growth mechanism is discussed.

Fabrication and characterization of SiC rod-particulate-reinforced reaction-bonded Si3N4 composites

Reaction-bonded Si3N4 composites reinforced by whisker-like SiC rod particulates have been fabricated by nitriding SiCrod-containing Si powder compacts, which were presintered to a controlled density by spark plasma sintering (SPS). The effects of processing parameters, including presintered density, SiCrod content, nitriding temperature, atmosphere pressure and heating rate on the nitridation reaction were investigated. It was found that the addition of SiCrod to Si powders led to easier control of complete nitridation compared to the case of pure Si powder compacts, probably because the SiCrod not only acted as diluting filler to suppress the rapid rise in temperature resulting from an SHS-like reaction between Si and N2, but also provided paths for diffusion of reactant gases. The density of the reaction-bonded Si3N4–50 vol% SiCrod composites was increased up to near 90% which is quite a lot higher than that of conventional reaction-bonded Si3N4 ceramics, by using SPS to improve the density prior to nitridation. The relative density increased from ∼70 to 90% after the nitridation without appreciable dimensional change, being characteristic of reaction-sintering. As the reinforcement in the reaction products, the SiCrod improved Young's modulus and bending strength both at ambient and elevated temperatures, as well as thermal and electric conductivity.

Synthesis of one-dimensional nanostructures—β-SiC nanorods with and without amorphous SiO2 wrapping layers

Synthesis of one-dimensional nanostructures—β-SiC nanorods with and without amorphous SiO2 wrapping layers–was achieved by controlling carbothermal reduction of sol-gel derived silica xerogels with carbon nanoparticles embedded in the network. The β-SiC nanorods with amorphous SiO2 wrapping layers were obtained by carboreduction at 1650 °C for 1.5 hours and then heating at 1800 °C for 30 minutes. The composite nanorods are typically up to 20 µm in length. The diameters of the center, thinner β-SiC nanorods are in the range of 10 to 30 nm while the outside diameters of the corresponding amorphous SiO2 wrapping layers are between 20 and 70 nm. Monolithic β-SiC nanorods were produced by only carbothermal reduction at 1650 °C for 2.5 hours. The diameters of the monolithic β-SiC nanorods are in agreement with those at the center of the thinner β-SiC nanorods wrapped up in amorphous SiO2 layers. The large quantities of SiC rod nuclei and the nan-ometer-sized nucleus sites on carbon nanoparticles are favorable to the formation of much thinner β-SiC nanorods. The formation of the outside amorphous SiO2 wrapping layer is due to the combination reaction of decomposed SiO vapor and O2 during cooling. The monolithic β-SiC nanorods may be used as reinforcing and toughening elements in ceramic, metal, and polymer matrix nanocomposites. The β-SiC nanorods with amorphous SiO2 wrapping layers might offer opportunities for both fundamental research and technological applications.

Preparation of β–SiC Nanorods with and Without Amorphous SiO2 Wrapping Layers

Preparation of β–SiC nanorods with and without amorphous SiO2 wrapping layers was achieved by carbothermal reduction of sol-gel derived silica xerogels containing carbon nanoparticles. The β–SiC nanorods with amorphous SiO2 wrapping layers were obtained by carboreduction at 1650 °C for 1.5 h, and at the end of 1.5 h the temperature was steeply raised to 1800 °C and held for 30 min; they are typically up to 20 µm in length. The diameters of the center thinner β–SiC nanorods within the amorphous SiO2 wrapping layers are in the range 10–30 nm, while the outer diameters of the corresponding amorphous SiO2 wrapping layers are between 20 and 70 nm. The β–SiC nanorods without amorphous SiO2 wrapping layers were produced by carbothermal reduction only at 1650 °C for 2.5 h, and their diameters are in agreement with those of the center thinner β–SiC nanorods wrapped in amorphous SiO2 layers. Large quantities of SiC rod nuclei and the nanometer-sized nucleus sites on carbon nanoparticles are both favorable to the formation of much thinner β–SiC nanorods. The formation of the outer amorphous SiO2 wrapping layer is from the combination reaction of decomposed SiO vapor and O2.

Synthesis of “A β-SiC nanorod within a SiO 2 nanorod” one dimensional composite nanostructures

“A β-SiC nanorod within a SiO 2 nanorod” one dimensional composite nanostructures were synthesized by the combination of a low temperature (1650°C) carbothermal reduction and a high temperature (1800°C) heating of sol-gel derived silica xerogels containing carbon nanoparticles. The composite nanostructures are more than 20 μm in length. The diameters of the center thinner β-SiC nanorods are typically in the range 10–30 nm, while the outside diameters of the corresponding thicker amorphous SiO 2 nanorods are between 20 and 70 nm. Large quantities of SiC rod nuclei and the nanometer-sized nucleus sites on carbon nanoparticles are both favor-able to the formation of much thinner β-SiC nanorods. The formation of the outer coaxial thicker amorphous SiO 2 nanorods is from the combination reaction of decomposed SiO vapor and O 2 during cooling.

Application of SiC‐Si functionally gradient material to thermoelectric energy conversion device

AbstractBecause of its high–temperature chemical stability, SiC ceramic is a promising material for high‐temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC‐Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction.An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC.The microstructure of the FGM is classified into three regions: the SiC‐Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC‐Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC‐Si FGM at the cold junction, at room temperature, was 108 times higher than that of a nongradient SiC ceramic.

Calculation of Heating Patterns in Microwave Sintering using a 3D Finite-Difference Code

ABSTRACTAnalysis of heating patterns in microwave sintering experiments provide information on the contributions of the various heat transfer components to the overall temperature pattern. Measured temperature patterns provide limited information on overall effects. Numerical simulations provide a cost effective way from which the effect of geometry, material properties and the presence of stimulus such as SiC rods or sheets on the heating pattern can be studied separately. Parametric studies allow us to identify the most significant properties and provide guidelines for the routine successful utilization of microwave sintering experiments. These guidelines may also facilitate the scale up and commercialization of microwave sintering.In this paper we describe a thermal model that calculates the temperature distribution in ceramic samples and insulation under realistic microwave sintering conditions. The calculation process involves a two-step procedure. The first step is to calculate the microwave power deposition in the sample and surrounding insulation. 3D FDTD calculations, described in a companion paper[1,2], are used for this purpose. The other step involves calculation of the temperature distribution using a 3D finite-difference heat-transfer program developed in our Departments[3]. Results illustrating the effect of thickness of insulation and the placement of SiC rod susceptors in picket-fence arrangement are presented.

Inert‐Atmosphere Dilatometer for Use to 2000°C

Journal of the American Ceramic SocietyVolume 46, Issue 2 p. 104-106 Inert-Atmosphere Dilatometer for Use to 2000°C PETER T. B. SHAFFER, PETER T. B. SHAFFERSearch for more papers by this authorSTANLEY D. MARK, STANLEY D. MARKSearch for more papers by this author PETER T. B. SHAFFER, PETER T. B. SHAFFERSearch for more papers by this authorSTANLEY D. MARK, STANLEY D. MARKSearch for more papers by this author First published: February 1963 https://doi.org/10.1111/j.1151-2916.1963.tb11688.xCitations: 7 The writers are, respectively, senior research associate, Applied Research Branch, Research and Development Division, and manager, Technical Branch, Bonded Abrasives Division, The Carborundum Company, Niagara Falls, N. Y. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume46, Issue2February 1963Pages 104-106 RelatedInformation