Search results for: eutectic silicon

Authors: Igor Bilenko, Artem Shitikov, Michael Gorodetsky

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Optical whispering gallery mode (WGM) resonators combine very high optical quality factor (Q) with small size. Resonators made from low loss crystalline fluorites (CaF2, MgF2) may have Q as high as 1010 that make them unique devices for modern applications including ultrasensitive sensors, frequency control, and precision spectroscopy. While silicon is a promising material transparent from near infrared to terahertz frequencies, fundamental limit for Si WGM quality factor was not reached yet. In our paper, we presented experimental results on the preparation and testing of resonators at 1550 nm wavelength made from crystalline silicon grown and treated by different techniques. Q as high as 3x107 was demonstrated. Future steps need to reach a higher value and possible applications are discussed.

Keywords: optical quality factor, silicon optical losses, silicon optical resonator, whispering gallery modes

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Authors: Lotfi Hedi Khezami, Mohamed Ben Rabha, N. Sboui, Mounir Gaidi, B. Bessais

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Metal-nano particle-assisted Chemical Etching is an extraordinary developed wet etching method of producing uniform semiconductor nano structure (nano wires) from patterned metallic film on crystalline silicon surface. The metal films facilitate the etching in HF and H2O2 solution and produce silicon nanowires (SiNWs). Creation of different SiNWs morphologies by changing the etching time and its effects on optical and opto electronic properties was investigated. Combination effect of formed SiNWs and stain etching treatment in acid (HF/HNO3/H2O) solution on the surface morphology of Si wafers as well as on the optical and opto electronic properties are presented in this paper.

Keywords: stain etching, porous silicon, silicon nanowires, reflectivity, lifetime, solar cells

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Authors: T. Zaki, Fathi S. Soliman

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Desulfurization process is required by most, if not all refineries, to achieve ultra-low sulfur fuel, that contains less than 10 ppm sulfur. A lot of research works and many effective technologies have been studied to achieve deep desulfurization process in moderate reaction environment, such as adsorption desulfurization (ADS), oxidative desulfurization (ODS), biodesulfurization and extraction desulfurization (EDS). Extraction desulfurization using deep eutectic solvents (DESs) is considered as simple, cheap, highly efficient and environmentally friend process. In this work, four DESs were designed and synthesized. Choline chloride (ChCl) was selected as typical hydrogen bond acceptors (HBA), and ethylene glycol (EG), glycerol (Gl), urea (Ur) and thiourea (Tu) were selected as hydrogen bond donors (HBD), from which a series of deep eutectic solvents were synthesized. The experimental data showed that the synthesized DESs showed desulfurization affinities towards the thiophene species in cyclohexane solvent. Ethylene glycol molecules showed more affinity to create hydrogen bond with thiophene instead of choline chloride. Accordingly, ethylene glycol choline chloride DES has the highest extraction efficiency.

Keywords: DES, desulfurization, green solvent, extraction

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Authors: Ubeyd Toçoğlu, Miraç Alaf, Hatem Akbulut

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We present a work which was conducted in order to improve the cycle life of silicon based lithium ion battery anodes by utilizing novel composite structure. In this study, carbon coated nano sized (50-100 nm) silicon particles were embedded into Graphene/MWCNT silicon matrix to produce free standing silicon based electrodes. Also, conventional Si powder anodes were produced from Si powder slurry on copper current collectors in order to make comparison of composite and conventional anode structures. Free –standing composite anodes (binder-free) were produced via vacuum filtration from a well dispersion of Graphene, MWCNT and carbon coated silicon powders. Carbon coating process of silicon powders was carried out via microwave reaction system. The certain amount of silicon powder and glucose was mixed under ultrasonication and then coating was conducted at 200 °C for two hours in Teflon lined autoclave reaction chamber. Graphene which was used in this study was synthesized from well-known Hummers method and hydrazine reduction of graphene oxide. X-Ray diffraction analysis and RAMAN spectroscopy techniques were used for phase characterization of anodes. Scanning electron microscopy analyses were conducted for morphological characterization. The electrochemical performance tests were carried out by means of galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy.

Keywords: graphene, Li-Ion, MWCNT, silicon

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Authors: V. Swarnalatha, A. V. Narasimha Rao, P. Pal

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The present research reports the investigation of fast etching of silicon for the fabrication of microelectromechanical systems (MEMS) structures using silicon wet bulk micromachining. Low concentration tetramethyl-ammonium hydroxide (TMAH) and hydroxylamine (NH₂OH) are used as main etchant and additive, respectively. The concentration of NH₂OH is varied to optimize the composition to achieve best etching characteristics such as high etch rate, significantly high undercutting at convex corner for the fast release of the microstructures from the substrate, and improved etched surface morphology. These etching characteristics are studied on Si{100} and Si{110} wafers as they are most widely used in the fabrication of MEMS structures as wells diode, transistors and integrated circuits.

Keywords: KOH, MEMS, micromachining, silicon, TMAH, wet anisotropic etching

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Authors: Gilbert Omorodion Osayemwenre, Edson Meyer, R. T. Taziwa

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The electrical analysis of single junction amorphous silicon solar modules is carried out using outdoor monitoring technique. Like crystalline silicon PV modules, the electrical characterisation and performance of single junction amorphous silicon modules are best described by its current-voltage (IV) characteristic. However, IV curve has a direct dependence on the type of PV technology and material properties used. The analysis reveals discrepancies in the modules performance parameter even though they are of similar technology. The aim of this work is to compare the electrical performance output of each module, using electrical parameters with the aid of PVPM 100040C IV tracer. These results demonstrated the relevance of standardising the performance parameter for effective degradation analysis of a-Si:H.

Keywords: PVPM 100040C IV tracer, SolarWatt part, single junction amorphous silicon module (a-Si:H), Staebler-Wronski (S-W) degradation effect

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Authors: Taoufik Bettaieb, Sihem Soufi

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As a bioactive metalloid, silicon (Si) is an essential element for plant growth and development. It also plays a crucial role in enhancing plants’ resilience to different abiotic and biotic stresses. The morpho-physiological, biochemical, and molecular background of Si-mediated stress tolerance in plants were unraveled. Cold stress is a severe abiotic stress response to the decrease of plant growth and yield by affecting various physiological activities in plants. Several approaches have been used to alleviate the adverse effects generated from cold stress exposure, but the cost-effective, environmentally friendly, and defensible approach is the supply of silicon. Silicon has the ability to neutralize the harmful impacts of cold stress. Therefore, based on these hypotheses, this study was designed in order to investigate the morphological and physiological background of silicon effects applied at different concentrations on cold stress mitigation during early growth of a turfgrass, namely Paspalum vaginatum Sw. Results show that silicon applied at different concentrations improved the morphological development of Paspalum subjected to cold stress. It is also effective on the photosynthetic apparatus by maintaining stability the photochemical efficiency. As the primary component of cellular membranes, lipids play a critical function in maintaining the structural integrity of plant cells. Silicon application decreased membrane lipid peroxidation and kept on membrane frontline barrier relatively stable under cold stress.

Keywords: crops, cold stress, silicon, abiotic stress

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Authors: Ricky Saputra, Rashmi Walvekar, Mohammad Khalid, Kaveh Shahbaz, Suganti Ramarad

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This particular study of interest aims to study the effect of coupling ultrasonic treatment with eutectic solvents in devulcanization process of waste rubber tyre. Specifically, three different types of Deep Eutectic Solvents (DES) were utilized, namely ChCl:Urea (1:2), ChCl:ZnCl₂ (1:2) and ZnCl₂:urea (2:7) in which their physicochemical properties were analysed and proven to have permissible water content that is less than 3.0 wt%, degradation temperature below 200ᵒC and freezing point below 60ᵒC. The mass ratio of rubber to DES was varied from 1:20-1:40, sonicated for 1 hour at 37 kHz and heated at variable time of 5-30 min at 180ᵒC. Energy dispersive x-rays (EDX) results revealed that the first two DESs give the highest degree of sulphur removal at 74.44 and 76.69% respectively with optimum heating time at 15 minutes whereby if prolonged, reformation of crosslink network would be experienced. Such is supported by the evidence shown by both FTIR and FESEM results where di-sulfide peak reappears at 30 minutes and morphological structures from 15 to 30 minutes change from smooth with high voidage to rigid with low voidage respectively. Furthermore, TGA curve reveals similar phenomena whereby at 15 minutes thermal decomposition temperature is at the lowest due to the decrease of molecular weight as a result of sulphur removal but increases back at 30 minutes. Type of bond change was also analysed whereby it was found that only di-sulphide bond was cleaved and which indicates partial-devulcanization. Overall, the results show that DES has a great potential to be used as devulcanizing solvent.

Keywords: crosslink network, devulcanization, eutectic solvents, reformation, ultrasonic

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Authors: Shoumodip Roy, Ankit Singhania, Santanu Mallick, Abhiram Jha, M. K. Agarwal, R. V. Ramna, Uttam Singh

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The quality of hot metal at any blast furnace is judged by the silicon content in it. Lower hot metal silicon not only enhances process efficiency at steel melting shops but also reduces hot metal costs. The Hot metal produced at G-Blast furnace Tata Steel Jamshedpur has a significantly higher Si content than Benchmark Blast furnaces. The higher content of hot metal Si is mainly due to inferior raw material quality than those used in benchmark blast furnaces. With minimum control over raw material quality, the only option left to control hot metal Si is via optimizing the furnace parameters. Therefore, in order to identify the levers to reduce hot metal Si, Data mining was carried out, and multiple regression models were developed. The statistical analysis revealed that Slag B3{(CaO+MgO)/SiO2}, Slag Alumina and Hot metal temperature are key controllable parameters affecting hot metal silicon. Contour Plots were used to determine the optimum range of levels identified through statistical analysis. A trial plan was formulated to operate relevant parameters, at G blast furnace, in the identified range to reduce hot metal silicon. This paper details out the process followed and subsequent reduction in hot metal silicon by 15% at G blast furnace.

Keywords: blast furnace, optimization, silicon, statistical tools

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Authors: S. Y. Park, S. M. Lee, S. H. Lee, K. M. Lim

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In this research analyzed the effects that phase formation reaction change in the grey cast iron makes on characteristics of microstructures, liquidity, and mechanical properties through cooling curve when adding rare earth elements (R.E). This research was analyzed with comparison between the case of not adding the rare earth elements (R.E) into the grey cast iron with the standard composition (as 3.3%C-2.1%Si-0.7%Mn-0.1%S) and the case of adding 0.3% rare earth elements (R.E). The thermal analysis parameters have been drawn through eutectic temperature theoretically calculated, recalescence temperature, and undercooling temperature measured from start of eutectic reaction to end of solidification in the cooling curve obtained by thermal analysis to analyze formation behavior of graphite, and the effects by addition of rare earth elements on this have been reviewed. When adding rare earth elements (R.E), the cause of liquidity slowdown was analyzed trough the solidification starting temperature and change of solidification ending temperature. The strength and hardness have been measured to evaluate the mechanical properties, and the sound tensile strength has been evaluated through quality coefficient after measuring relative hardness and normality degree of tensile strength by calculating theoretical tensile strength and theoretical hardness. The change of Pearlite Inter-lamellar Spacing of matrix microstructure and eutectic cell count of macrostructure was measured to analyze the effects of the rare earth elements on the sound tensile strength. The change of eutectic cell count has been clarified through activation of the eutectic reaction, and the cause of pearlite inter-lamellar spacing clarified through eutectoid reaction temperature.

Keywords: cooling curve, element, grey cast iron, thermal analysis, rare earth element

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Authors: Samira Naghdi, Kyong Yop Rhee

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Transfer-free synthesis of graphene on dielectric substrates is highly desirable but remains challenging. Here, by using a thin sacrificial platinum layer as a catalyst, graphene was deposited on a silicon substrate through a simple and transfer-free synthesis method. During graphene growth, the platinum layer evaporated, resulting in direct deposition of graphene on the silicon substrate. In this work, different growth conditions of graphene were optimized. Raman spectra of the produced graphene indicated that the obtained graphene was bilayer. The sheet resistance obtained from four-point probe measurements demonstrated that the deposited graphene had high conductivity. Reflectance spectroscopy of graphene-coated silicon showed a decrease in reflectance across the wavelength range of 200-800 nm, indicating that the graphene coating on the silicon surface had antireflection capabilities.

Keywords: antireflection coating, chemical vapor deposition, graphene, the sheet resistance

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Authors: Birute Bugelyte, Ingrida Jurkute, Vida Vickackaite

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The most complicated step of the determination of volatile compounds in complex matrices is the separation of analytes from the matrix. Traditional analyte separation methods (liquid extraction, Soxhlet extraction) require a lot of time and labour; moreover, there is a risk to lose the volatile analytes. In recent years, headspace gas chromatography has been used to determine volatile compounds. To date, traditional extraction solvents have been used in headspace gas chromatography. As a rule, such solvents are rather volatile; therefore, a large amount of solvent vapour enters into the headspace together with the analyte. Because of that, the determination sensitivity of the analyte is reduced, a huge solvent peak in the chromatogram can overlap with the peaks of the analyts. The sensitivity is also limited by the fact that the sample can’t be heated at a higher temperature than the solvent boiling point. In 2018 it was suggested to replace traditional headspace gas chromatographic solvents with non-volatile, eco-friendly, biodegradable, inexpensive, and easy to prepare deep eutectic solvents (DESs). Generally, deep eutectic solvents have low vapour pressure, a relatively wide liquid range, much lower melting point than that of any of their individual components. Those features make DESs very attractive as matrix media for application in headspace gas chromatography. Also, DESs are polar compounds, so they can be applied for microwave assisted extraction. The aim of this work was to investigate the possibility of applying deep eutectic solvents for microwave assisted extraction and headspace gas chromatographic determination of hexanal in fat-rich food. Hexanal is considered one of the most suitable indicators of lipid oxidation degree as it is the main secondary oxidation product of linoleic acid, which is one of the principal fatty acids of many edible oils. Eight hydrophilic and hydrophobic deep eutectic solvents have been synthesized, and the influence of the temperature and microwaves on their headspace gas chromatographic behaviour has been investigated. Using the most suitable DES, microwave assisted extraction conditions and headspace gas chromatographic conditions have been optimized for the determination of hexanal in potato chips. Under optimized conditions, the quality parameters of the prepared technique have been determined. The suggested technique was applied for the determination of hexanal in potato chips and other fat-rich food.

Keywords: deep eutectic solvents, headspace gas chromatography, hexanal, microwave assisted extraction

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Authors: B. Bouktif, M. Gaidi, M. Benrabha

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Metal-nano particle-assisted chemical etching is an extraordinary developed wet etching method of producing uniform semiconductor nanostructure (nanowires) from the patterned metallic film on the crystalline silicon surface. The metal films facilitate the etching in HF and H2O2 solution and produce silicon nanowires (SiNWs). Creation of different SiNWs morphologies by changing the etching time and its effects on optical and optoelectronic properties was investigated. Combination effect of formed SiNWs and stain etching treatment in acid (HF/HNO3/H2O) solution on the surface morphology of Si wafers as well as on the optical and optoelectronic properties are presented in this paper.

Keywords: semiconductor nanostructure, chemical etching, optoelectronic property, silicon surface

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Authors: Qi Lu, Jian Deng, Daishun Huang, Chao Guo

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The lead cooled fast reactor is considered as one of the most potential Generation IV nuclear systems due to the low working pressure, the appreciable neutron economy, and the considerable passive characteristics. Meanwhile, the lead bismuth eutectic (LBE) has the related advantages of lead with the weaker corrosiveness, which has been paid much attention by recent decades. Moreover, the sub-channel code is a necessary analysis tool for the reactor thermal-hydraulic design and safety analysis, which has been developed combined with the accumulation of LBE experimental data and the understanding of physical phenomena. In this study, a sub-channel code available for LBE was developed, and the corresponding geometric characterization method of typical sub-channels was described in detail, especially for for the fuel assembly with wire spacer. As for this sub-channel code, the transversal thermal conduction through gap was taken into account. In addition, the physical properties, the heat transfer model, the flow resistance model and the turbulent mixing model were analyzed. Finally, the thermal-hydraulic experiments of LBE conducted on THEADES (THErmal-hydraulics and Ads DESign) were selected as the evaluation data of this sub-channel code, including 19 rods with wire spacer, and the calculated results were in good agreement with the experimental results.

Keywords: lead bismuth eutectic, sub-channel code, wire spacer, transversal thermal conduction

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Authors: Zekun Lin, Xun Li

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Silicon photonics has gained much interest and extensive research for a promising aspect for fabricating compact, high-speed and low-cost photonic devices compatible with complementary metal-oxide-semiconductor (CMOS) process. Despite the remarkable progress made on the development of silicon photonics, high-performance, cost-effective, and reliable silicon laser sources are still missing. In this work, we present a 1550 nm III-V/silicon laser design with stable single-mode lasing property and robust and high-efficiency vertical coupling. The InP cavity consists of two uniform Bragg grating sections at sides for mode selection and feedback, as well as a central second-order grating for surface emission. A grating coupler is etched on the SOI waveguide by which the light coupling between the parallel III-V and SOI is reached vertically rather than by evanescent wave coupling. Laser characteristic is simulated and optimized by the traveling-wave model (TWM) and a Green’s function analysis as well as a 2D finite difference time domain (FDTD) method for the coupling process. The simulation results show that single-mode lasing with SMSR better than 48dB is achievable, and the threshold current is less than 15mA with a slope efficiency of around 0.13W/A. The coupling efficiency is larger than 42% and possesses a high tolerance with less than 10% reduction for 10 um horizontal or 15 um vertical dislocation. The design can be realized by standard flip-chip bonding techniques without co-fabrication of III-V and silicon or precise alignment.

Keywords: III-V/silicon integration, silicon photonics, single mode laser, vertical coupling

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Authors: Kwang-Ho Kim, Kwan-Hong Min, Pyungwoo Jang, Chisup Jung, Kyu Seomoon

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By restricting the dimensions of silicon to less than Bohr radius of bulk crystalline silicon (∼5 nm), quantum confinement causes its effective bandgap to increase. Therefore, silicon quantum wells (QWs) using these quantum phenomena could be a good candidate to achieve high performance silicon solar cells. The Al2O3/Si QW structures were fabricated by using the successive deposition technique, as a quantum confinement device to increase the effective energy bandgap and passivation effect in Si surface for the 3rd generation solar cell applications. In Si/Al2O3 QWs, the thicknesses of Si layers and Al2O3 layers were varied between 1 to 5 nm, respectively. The roughness of deposited Si on Al2O3 was less than 4 Å in the thickness of 2 nm. By using the Al2O3/Si QW structures on Si surfaces, the lifetime measured by u-PCD technique increased as a result of passivated surface effects. The discussion about the other properties such as electrical and optical properties of the QWs structures as well as the fabricated solar cells will be presented in this paper.

Keywords: Al2O3/Si quantum well, quantum confinement, solar cells, third generation, successive deposition technique

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Authors: B. Oji, O. Olaniran

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The prospect of improving the corrosion property of Al 6063 alloy based hybrid composites reinforced with cassava peel ash (CPA) and silicon carbide (SiC) is the target of this research. It seeks to determine the viability of using locally sourced material (CPA) as a complimentary reinforcement for SiC to produce low cost high performance aluminum matrix composite. The CPA was mixed with the SiC in the ratios 0:1, 1:3, 1:1, 3:1 and 1:0 for 8 wt % reinforcement in the produced composites by double stir-casting method. The microstructures of the composites were studied before and after corrosion using the scanning electron microscopy which reveals the matrix (dark region) and eutectic phase (lamellar region). The corrosion rate was studied in accordance with ASTM G59-97 (2014) using an AutoLab potentiostat (Versa STAT 400) with versaSTUDIO electrochemical software which analyses the results obtained. The result showed that Al 6063 alloy exhibited good corrosion resistance in 0.3M H₂SO₄ and 3.5 wt. % NaCl solutions with sample C containing the 25% wt CPA showing the highest resistance to corrosion with corrosion rate of 0.0046 mmpy as compared to the control sample which has a value of 13.233 mmpy. Sample B, D, E, and F also showed a corrosion rate of 3.9502, 2.6903, 2.1223, and 5.7344 mmpy which indicated a better corrosion rate than the control in the acidic environment. The corrosion rate in the saline medium shows that sample E with 75% wt CPA has the lowest corrosion rate of 0.0422 mmpy as compared to the control sample with 0.0873 mmpy corrosion rate.

Keywords: Al-Mg-Si alloy, AutoLab potentiostat, Cassava Peel Ash, CPA, hybrid composite, stir-cast method

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Authors: Satyendra Mourya, Jyoti Jaiswal, Gaurav Malik, Brijesh Kumar, Ramesh Chandra

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Present work describes the fabrication and sensing characteristics of the Pd-Pt decorated nanostructured silicon carbide (SiC) thin films on anodized porous silicon (PSi) substrate by RF magnetron sputtering. The gas sensing performance of Pd-Pt/SiC/PSi sensing electrode towards H2 gas under low (10–400 ppm) detection limit and high operating temperature regime (25–600 °C) were studied in detail. The chemiresistive sensor exhibited high selectivity, good sensing response, fast response/recovery time with excellent stability towards H2 at high temperature. The selectivity measurement of the sensing electrode was done towards different oxidizing and reducing gases and proposed sensing mechanism discussed in detail. Therefore, the investigated Pd-Pt/SiC/PSi structure may be a highly sensitive and selective hydrogen gas sensing electrode for deployment in extreme environment applications.

Keywords: RF Sputtering, silicon carbide, porous silicon, hydrogen gas sensor

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Authors: Sami Iqbal, Azam Hussain, Weiping Wu, Guo Xinli, Tong Zhang

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A novel octagonal upright micro-pyramid structure was generated by wet chemical anisotropic etching on a monocrystalline silicon wafer (100). The primary objectives are to reduce front surface reflectance of silicon wafers, improve wettability, enhance surface morphology, and maximize the area coverage by generated octagonal pyramids. Under rigorous control and observation, the etching process' response time was maintained precisely. The experimental outcomes show a significant decrease in the optical surface reflectance of silicon wafers, with the lowest reflectance of 8.98%, as well as enhanced surface structure, periodicity, and surface area coverage of more than 85%. The octagonal silicon pyramid was formed with a high etch rate of 0.41 um/min and a much shorter reaction time with the addition of hydrofluoric acid coupled with magnetic stirring (mechanical agitation) at 300 rpm.

Keywords: octagonal pyramids, rapid etching, solar cells, surface engineering, surface reflectance

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Authors: Khamael M. Abualnaja, Lidija Šiller, Ben R. Horrocks

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The structural characterization of silicon nano crystals (SiNCs) have been carried out using transmission electron microscope (TEM) and atomic force microscopy (AFM). SiNCs are crystalline with an average diameter of 65 nm. Erbium trichloride was added to silicon nano crystals using a simple chemical procedure. Erbium is useful in this context because it has a narrow emission band at ⋍1536 nm which corresponds to a standard optical telecommunication wavelength. The optical properties of SiNCs and erbium-mixed SiNCs samples have been characterized using UV-vis spectroscopy, confocal Raman spectroscopy and photoluminescence spectroscopy (PL). SiNCs and erbium-mixed SiNCs samples exhibit an orange PL emission peak at around 595 nm that arise from radiative recombination of Si. Erbium-mixed SiNCs also shows a weak PL emission peak at ⋍1536 nm that attributed to the intra-4f transition in erbium ions. The intensity of the PL peak of Si in erbium-mixed SiNCs is increased in the intensity up to ×3 as compared to pure SiNCs. It was observed that intensity of 1536 nm peak decreased dramatically in the presence of silicon nano crystals and the PL emission peak of silicon nano crystals is increased. Therefore, the resulted data present that the energy transfer from erbium ions to SiNCs due to the chemical mixing method which used in this work.

Keywords: Silicon Nanocrystals (SiNCs), Erbium Ion, photoluminescence, energy transfer

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Authors: D. Miroud, H. Mokaddem, M. Tata, N. Foucha

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The body of PDC (polycrystalline diamond compact) drill bit can be manufactured from two different materials, steel and tungsten carbide matrix. Commonly the steel body is produced by machining, thermal spraying a bonding layer and hardfacing of Ni-based matrix reinforced with fused eutectic tungsten carbide (WC/W2C). The matrix body bit is manufactured by infiltrating tungsten carbide particles, with a Copper binary or ternary alloy. By erosion-corrosion mechanisms, the PDC drill bits matrix undergoes severe damage, occurring particularly around the PDC inserts and near injection nozzles. In this study, we investigated the possibility to repair the damaged matrix regions by hardfacing technic. Ni-based hardfacing alloy reinforced with fused eutectic tungsten carbide is deposited on infiltrated WC-W-Ni substrate by oxyacetylene welding (OAW). The microstructure at the hardfacing / matrix interface is characterized by SEM- EDS, XRD and micro hardness Hv0.1. The hardfacing conditions greatly affect the dilution phenomenon and the distribution of carbides at the interface, without formation of transition zone. During OAW welding deposition, interdiffusion of atoms occurs: Cu and Sn diffuse from infiltrated matrix substrate into hardfacing and simultaneously Cr and Si alloy elements from hardfacing diffuse towards the substrate. The dilution zone consists of a nickel-rich phase with a heterogeneous distribution of eutectic spherical (Ni-based hardfacing alloy) and irregular (matrix) WC/W2C carbides and a secondary phase rich in Cr-W-Si. Hardfacing conditions cause the dissolution of banding around both spherical and irregular carbides. The micro-hardness of interface is significantly improved by the presence of secondary phase in the inter-dendritic structure.

Keywords: dilution, dissolution, hardfacing, infiltrated matrix, PDC drill bits

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Authors: Glemarie C. Hermosa, Sheng-Jie You, Chien Chih Hu

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Efficient separation technologies are required for the removal of carbon dioxide from natural gas streams. Membrane-based natural gas separation has emerged as one of the fastest growing technologies, due to the compactness, higher energy efficiency and economic advantages which can be reaped. The removal of Carbon dioxide from gas streams using membrane technology will also give the advantage like environmental friendly process compared to the other technologies used in gas separation. In this study, Polyimide membranes, which are mostly used in the separation of gases, are blended with a new kind of solvent: Deep Eutectic Solvents or simply DES. The three types of DES are used are choline chloride based mixed with three different hydrogen bond donors: Lactic acid, N-methylurea and Urea. The blending of the DESs to Polyimide gave out high permeability performance. The Gas Separation performance for all the membranes involving CO2/CH4 showed low performance while for CO2/N2 surpassed the performance of some studies. Among the three types of DES used the solvent Choline Chloride/Lactic acid exhibited the highest performance for both Gas Separation applications. The values are 10.5 for CO2/CH4 selectivity and 60.5 for CO2/N2. The separation results for CO2/CH4 may be due to the viscosity of the DESs affecting the morphology of the fabricated membrane thus also impacts the performance. DES/blended Polyimide membranes fabricated are novel and have the potential of a low-cost and environmental friendly application for gas separation.

Keywords: deep eutectic solvents, gas separation, polyimide blends, polyimide membranes

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Authors: Woei-Shyan Lee, Shuo-Ling Chang

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The nanoindentation behaviour and phase transformation of annealed single-crystal silicon wafers are examined. The silicon specimens are annealed at temperatures of 250, 350 and 450ºC, respectively, for 15 minutes and are then indented to maximum loads of 30, 50 and 70 mN. The phase changes induced in the indented specimens are observed using transmission electron microscopy (TEM) and micro-Raman scattering spectroscopy (RSS). For all annealing temperatures, an elbow feature is observed in the unloading curve following indentation to a maximum load of 30 mN. Under higher loads of 50 mN and 70 mN, respectively, the elbow feature is replaced by a pop-out event. The elbow feature reveals a complete amorphous phase transformation within the indented zone, whereas the pop-out event indicates the formation of Si XII and Si III phases. The experimental results show that the formation of these crystalline silicon phases increases with an increasing annealing temperature and indentation load. The hardness and Young’s modulus both decrease as the annealing temperature and indentation load are increased.

Keywords: nanoindentation, silicon, phase transformation, amorphous, annealing

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Authors: Adjmal Ghaur, Christoph Peschel, Iris Dienwiebel, Lukas Haneke, Leilei Du , Laurin Profanter, Tobias Placke, Martin Winter

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In recent years, lithium-ion batteries (LIBs)are widely used in electric vehicles (EVs) and mobile energy storage devices (ESDs), which has led to higher requirements for energy density. To fulfill these requirements, tremendous attention has been paid to design advanced LIBs with various siliconactive materials as alternative negative electrodes to replace graphite (372 mAh g⁻¹)due to their high theoretical gravimetric capacity (4200mAh g⁻¹). However, silicon as potential anode material suffers from huge volume changes during charging and discharging and has poor electronicconductivity which negatively impacts the long-term performance and preventshigh silicon contents from practical application. Additionally, an unstable crystalline silicon structure tends to pulverization during the (de)lithiation process. To compensate for the volume changes, alleviate pulverization, and maintain high electronicconductivity, silicon-doped graphite composites with protecting coating layers are a promising approach. In this context, phosphazene compounds are investigated concerning their silicon protecting properties in silicon-doped graphite composites. In detail, electrochemical performance measurements in pouch full-cells(NCM523||SiOx/C), supressing gas formation properties, and post-mortem analyzes were carried out to characterize phosphazene compounds as additive materials. The introduction of the dual-additive approach in state-of-the-art electrolytes leads to synergistic effects between FEC and phosphazene compounds which accelerate the durability of silicon particles and results in enhanced electrochemical performance.

Keywords: silicon, phosphazene, solid electrolyte interphase, electrolyte, gasmeasurements

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Authors: Lintle Mohase, Ninikoe Lebusa, Mpho Stephen Mafa

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Wheat is an economically important cereal crop. However, the changing climatic conditions that intensify drought in production areas, and additional pest infestation, such as the Russian wheat aphid (RWA, Diuraphis noxia), severely hamper its production. Drought and pest management require an additional water supply through irrigation and applying inorganic nutrients (including silicon) as alternative strategies to mitigate the stress effects. Therefore, other approaches are needed to enhance wheat productivity during drought stress and aphid abundance. Two wheat cultivars were raised under greenhouse conditions, exposed to drought stress, and treated with silicon before infestation with the South African RWA biotype 2 (RWASA2). The morphological evaluations showed that severe drought or a combination of drought and infestation significantly reduced the plant height of wheat cultivars. Silicon treatment did not alleviate the growth reduction. The biochemical responses were measured using spectrophotometric assays with specific substrates. An evaluation of the enzyme activities associated with oxidative stress and defence responses indicated that drought stress increased NADPH oxidase activity, while silicon treatment significantly reduced it in drought-stressed and infested plants. At 48 and 72 hours sampling periods, a combination of silicon, drought and infestation treatment significantly increased peroxidase activity compared to drought and infestation treatment. The treatment also increased β-1,3-glucanase activity 72 hours after infestation. In addition, silicon and drought treatment increased glucose but reduced sucrose accumulation. Furthermore, silicon, drought, and infestation treatment combinations reduced the sucrose content. Finally, silicon significantly increased the trehalose content under severe drought and infestation, evident at 48 and 72-hour sampling periods. Our findings shed light on silicon’s ability to induce protective biochemical responses during drought and aphid infestation.

Keywords: drought, enzyme activity, silicon, soluble sugars, Russian wheat aphid, wheat

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Authors: Nam Chol Yu, Kyong Il Chu

Abstract:

Using DLTS measurement techniques, we determined the dominant recombination center levels (defects of both A and B) in gold and platinum doped n-type silicon. Also, the injection and temperature dependence of the Shockley-Read-Hall (SRH) carrier lifetime was studied under low-level injection and high-level injection. Here measurements show that the dominant level under low-level injection located at EC-0.25eV(A) correlated to the Pt+G1 and the dominant level under high-level injection located at EC-0.54eV(B) correlated to the Au+G4. Finally, A and B are the same dominant levels for controlling the lifetime in gold-platinum doped n-silicon.

Keywords: recombination center level, lifetime, carrier lifetime control, gold, platinum, silicon

Procedia PDF Downloads 124

Authors: Latifa Sabri, Mohammed Benzirar, Mimoun Zazoui

Abstract:

The installation of photovoltaic systems is one of future sources to generate electricity without emitting pollutants. The photovoltaic cells used in these systems have demonstrated enormous efficiencies and advantages. Several researches have discussed the maximum efficiency of these technologies, but only a few experiences have succeeded to right weather conditions to get these results. In this paper, two types of cells were selected: crystalline and amorphous silicon. Using the method of genetic algorithm, the results show that for an ambient temperature of 25°C and direct irradiation of 625 W/m², the efficiency of crystalline silicon is 12% and 5% for amorphous silicon.

Keywords: PV, maximum efficiency, solar cell, genetic algorithm

Procedia PDF Downloads 398

Authors: Nam Chol Yu, GyongIl Chu, HoJong Ri

Abstract:

Using DLTS (Deep-level transient spectroscopy) measurement techniques, we determined the dominant recombination center levels (defects of both A and B) in gold and platinum doped n-type silicon. Also, the injection and temperature dependence of the Shockley-Read-Hall (SRH) carrier lifetime was studied under low-level injection and high-level injection. Here measurements show that the dominant level under low-level injection located at EC-0.25 eV (A) correlated to the Pt+G1 and the dominant level under high-level injection located at EC-0.54 eV (B) correlated to the Au+G4. Finally, A and B are the same dominant levels for controlling the lifetime in gold-platinum doped n-silicon.

Keywords: recombination center level, lifetime, carrier lifetime control, Gold, Platinum, Silicon

Procedia PDF Downloads 35

Authors: Alexey P. Antropov, Alexander V. Ragutkin, Nicolay A. Yashtulov

Abstract:

The original controlled technology for power active nanocomposite membrane-electrode assembly engineering on the basis of porous silicon is presented. The functional nanocomposites were studied by electron microscopy and cyclic voltammetry methods. The application possibility of the obtained nanocomposites as high performance renewable energy sources for micro-power electronic devices is demonstrated.

Keywords: cyclic voltammetry, electron microscopy, nanotechnology, platinum-palladium nanocomposites, porous silicon, power activity, renewable energy sources

Procedia PDF Downloads 319

Authors: Aynur Aker, Hasan Kaya

Abstract:

Al-12.6wt.%Si-%2wt.Co alloy was prepared in a graphite crucible under vacuum atmosphere. The samples were directionally solidified upwards with different growth rate at constant temperature gradient using by Bridgman–type growth apparatus. The values of microstructures (λ) was measured from transverse sections of the samples. The microhardness (HV), ultimate tensile strength (σ) and electrical resistivity (ρ) of the directional solidification samples were also measured. Influence of the growth rate and spacings on microhardness, ultimate tensile strength and electrical resistivity were investigated and the relationships between them were experimentally obtained by using regression analysis. The results obtained in present work were compared with the previous similar experimental results obtained for binary and ternary alloys.

Keywords: directional solidification, Al-Si-Co alloy, mechanical properties, electrical properties

Procedia PDF Downloads 255