Improving the Efficiency of Multicrystalline Silicon by Adding an ARC Layer in the Front Device

High efficiency multicrystalline solar cells must improve performance while replacing higher cost monocrystalline silicon with lower cost multicrystalline silicon. Composite silicon dioxide-titanium dioxide (SiO₂?TiO₂) films are deposited on a large area of 15.6×15.6 cm² textured multicrystalline silicon solar cells to increase the incident light trapped within the device. This is being achieved through new cell device structures that improve light trapping and energy conversion capability. These new structures depend on passivated thick and thin layers of silicon dioxide and titanum dioxide grown via wet and dry thermal oxidation. By replacing dry oxidation with wet oxidation the temperatures process can be lowered from 1050^°C to 850^°C to reduce both cycle time and wafer damage.     

Fabrication of a miniature twin-fuel-cell on silicon wafer

The fabrication and performance evaluation of a miniature twin-fuel-cell on silicon wafers are presented in this paper. The miniature twin-fuel-cell was fabricated in series using two membrane-electrode-assemblies sandwiched between two silicon substrates in which electric current, reactant, and product flow. The novel structure of the miniature twin-fuel-cell is that the electricity interconnect from the cathode of one cell to the anode of another cell is made on the same plane. The interconnect was fabricated by sputtering a layer of copper over a layer of gold on the top of the silicon wafer. Silicon dioxide was deposited on the silicon wafer adjacent to the copper layer to prevent short-circuiting between the twin cells. The feed holes and channels in the silicon wafers were prepared by anisotropic silicon etching from the back and front of the wafer with silicon dioxide acting as intrinsic etch-stop layer. Operating on dry H₂/O₂ at 25 °C and atmospheric pressure, the measured peak power density was 190.4 mW/cm² at 270 mA/cm² for the miniature twin-fuel-cell using a Nafion 112 membrane. Based on the polarization curves of the twin-fuel-cell and the two single cells, the interconnect resistance between the twin cells was calculated to be in the range from 0.0113 Ω (at 10 mA/cm²) to 0.0150 Ω (at 300 mA/cm²), which is relatively low.     

Adsorption of fluoride from aqueous solution by magnesia‐amended silicon dioxide granules

BACKGROUND: A new kind of adsorbent, magnesia‐amended silicon dioxide granules (MAS), has been prepared by wet impregnation of silicon dioxide with magnesium chloride solution. The physicochemical properties were characterized using X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) and Brunauer, Emmett, Teller (BET) studies. The porous structure and high surface area of these granules make them suitable for sorption. The aim of this study was to show the possibility of defluoridation of water using MAS and to demonstrate the advantage of its use compared with silicon dioxide. RESULTS: XRD and FT‐IR analysis showed that amorphous magnesia was loaded on silicon dioxide after treating with magnesium chloride solution and calcining at 500 °C. Batch sorption experiments indicated that MAS is more effective than silicon dioxide for fluoride adsorption. The sorption capacities of MAS decreased as the solution pH rose. At pH 3, the maximum defluoridation capacity of MAS was 12.6 mg g^?1. The adsorption process fitted the Dubinin–Radushkevich isotherm and kinetic studies revealed that the adsorption followed second‐order rate kinetics. CONCLUSION: The results indicate that it is feasible to modify both the physical and chemical properties of silicon dioxide with magnesia so that it can be used as a potential adsorbent to adsorb fluoride from aqueous solution. Copyright © 2009 Society of Chemical Industry     

Geometric analysis of dielectric failures in polyimide/silicon dioxide nanocomposites

Polyimide/silicon dioxide nanocomposites were tested for their dielectric strength against nanofiller concentrations between 0% and 14%. The sol–gel process was used for in situ generation of silicon dioxide nanoparticles in a polyamic acid host matrix. Spin‐coated and imidized samples with approximately 15 μm in thickness were then subjected to dielectric breakdown measurements in accordance with ASTM standards. Results showed two distinct regimes of dielectric strength. Higher dielectric withstand capability of nearly 275 kV mm^?1 was exhibited by samples with 0% and 2% silicon dioxide. Higher concentration samples were dielectrically weaker by approximately 45% at 150 kV mm^?1. Broken‐down specimens were examined under optical and electron microscopes. An inverse relationship between nanoparticle concentration and breakdown perforation diameter was observed. Hole sizes decreased gradually from 140 to 40 μm as silicon dioxide content increased from 0% to 6% and ultimately settled near 30 μm with higher concentrations. The testing results, examined through failure analysis, were explained by breakdown behaviors and mechanisms at different size scales. The findings from this project, in context with previous works and theories, can help establish connections of dielectric strength, perforation diameter, and nanofiller concentration for future polymer nanocomposite research. POLYM. ENG. SCI., 59:1897–1904, 2019. © 2019 Society of Plastics Engineers     

Silicon Fuel in High Performance Explosives

In an effort to improve the insensitive munition (IM) response but maintain performance of aluminized formulations, silicon was investigated as a possible replacement for aluminum. An RDX‐based silicon explosive was developed in which nearly 90 % reaction of silicon to silicon dioxide was realized by 7 volume expansions as measured by the 2.54 cm diameter copper cylinder expansion test. In spite of the low nitramine loading in the formulation (79 wt.‐%), the corresponding Gurney constant for the explosive was 2.81±0.02 km s⁻¹, which is superior to Composition A‐3 under the same experimental conditions (91 % RDX, 2.69±0.02 km s⁻¹). Energy calculations from detonation calorimetry also indicate reaction of the silicon, which was further confirmed by both silicon metal and silicon dioxide in the analyzed residue. The energy release, despite it being equivalent to a highly loaded explosive, was found to lag behind the rate of A‐3. This indicates silicon oxidation may occur sometime after lighter gas reactions in the reaction front, but is fast enough to impart work in the copper cylinder test.     

超声水热法制备单分散球形二氧化硅及因素分析

采用超声水热法在醇水氨体系制备了单分散球形二氧化硅,其中氨作为催化剂提供强亲核剂,通过设计正交实验研究了超声波功率、反应温度、搅拌强度和反应物摩尔配比对单分散球形二氧化硅粒度的影响。研究表明随超声功率和反应物摩尔配比增加,二氧化硅粒度明显增加;随温度和搅拌强度增加二氧化硅粒度增加,但幅度较小。二氧化硅形成过程可分为水解和缩合两步,其中水解是关键步骤。采用XRD、SEM和IR对制备的样品进行表征,结果表明单分散球形二氧化硅为非晶态颗粒,粒度均匀,外形规则,且样品中含有大量羟基。     

Particle Sizes of Fumed Silica

Fumed silica is a synthetic amorphous silicon dioxide produced by burning silicon tetrachloride in an oxygen-hydrogen flame. Surface areas range from 50–400 m²/g. Using particle sizing techniques, fumed silica shows micron sized particles leading to surface areas markedly lower than expected. Fumed silica appears as a fluffy solid with bulk densities down to 0.03 g/cm³, being invariant over the wide range of surface areas. Attempts to relate the variation of the surface area directly to the performance of fumed silica in technical applications, such as its thickening efficiency in fluids, mainly fail and remain ambiguous.     

采用细粒无机填料提高轮胎胶料粘合性能

介绍主要成分为二氧化硅的矽美粉和主要成分为碳酸钙的LDR2500两种细粒子无机填料在载重斜交轮胎胎体帘布胶中的应用情况。试验结果表明，合理使用细粒子无机填料可收到既明显提高胶料与锦纶纤维的粘合强度又大幅降低配方成本的双重效果。     

Environment Friendly Nano Silicon Dioxide Accelerated Zinc Phosphate Coating on Mild Steel Using a Series of Surfactants as Additives

Mild steel panels were subjected to zinc phosphate conversion coating accelerated by environment friendly nano silicon dioxide using a series of cationic surfactants as additives. Four cationic surfactants have been synthesized in the absence of solvent using triethylamine and four different long chain alkyl halides. From ¹H NMR and ¹³C NMR spectra the chemical structures of the synthesized surfactants were confirmed. The nano silicon dioxide accelerator provided a highly porous phosphate coating ensuring good adhesion to the consecutive top coating. The incorporation of cationic surfactants as additives led to fine-grained coatings which enhanced adherence and excellent corrosion resistance property to the phosphate coating. The performance of the surfactants as a corrosion inhibitor increases with the increase in the hydrophobicity of the side-chain length. Accelerator and additive incorporation effectively reduced the extent of zinc dissolution during phosphating and exhibited the highest polarization resistance. The good dispersability of additives and increased hydrophobicity yielded coatings with improved protection against corrosion. The corrosion inhibition performance of the coated steel has been studied by Open Circuit Potential (OCP), Potentiodynamic Polarization Curve, Electrochemical Impedance Spectroscopy (EIS) and salt spray test.     

氨水沉淀法由含钛滤液提取二氧化钛

以含钛高炉渣为原料,经硫酸铵熔融法得到含钛滤液,然后以氨水为沉淀剂,控制pH值使钛水解,水解产物经600℃煅烧2 h得到二氧化钛。考察了螯合剂的加入量、溶液pH值和反应时间对钛沉淀率的影响,实验结果表明:反应过程中铁与钛发生共沉淀,造成二氧化钛产物中的铁含量过高。EDTA几乎完全抑制了铁的沉淀,明显降低了二氧化钛产物的全铁含量;2-羟基丙烷-1,2,3-三羧酸的加入降低了产物中二氧化硅的含量,提高了产物中二氧化钛的含量。当2-羟基丙烷-1,2,3-三羧酸与硅的摩尔比为1,EDTA与铁的摩尔比为3,pH值为2.0,反应时间为90 min时产物中二氧化钛的含量为96.35%。     

Fluorescent Amines as a New Tool for Study of Siliceous Sponges

Siliceous sponges (Hexactinellida and Demospongiae classes) are aquatic invertebrates which are important both for marine and freshwater ecology and also as the source of biologically active compounds. The sponge skeleton consists of spicules - needle-like or branched composite structures based on silicon dioxide. Mechanisms of silicon assimilation and synthesis of high-ordered glass-like structures at ambient temperatures by sponges are intriguing for biologists, chemists and nanotechnologists. Fluorescent amines are in-vivo dyes that stain growing siliceous frustules of diatom algae so the use of these agents for the sponge study was attempted. We found that cultivation of the Lubomirskia baicalensis (Pallas, 1773) sponge in the presence of fluorescent tracers of biosilica - N¹,N³,N³-trimethyl-N¹-(7-nitro-2,1,3- benzoxadiazol-4-yl)propane-1,3-diamine and N¹,N³-dime thyl-N¹-[3-(dimethylamino)propyl]-N³-(7-nitro-2,1,3-benz oxadiazo-4yl)propane-1,3-diamine results in the staining of growing siliceous spicules. This finding shows that amine dyes accompany silicon from the environment to sponges spicules which opens a new way to study of silicon assimilation by sponges. Fluorescent staining of the growing spicules following with the confocal microscopy can be a powerful tool for morphological studies, revealing information about the dynamics of spiculogenesis and for bio-fabrication of new fluorescent materials.     

Simultaneous preparation of TiO2 and ammonium alum,and microporous SiO2 during the mineral carbonation of titanium-bearing blast furnace slag

In this study, a route for simultaneous mineralization of CO₂ and production of titanium dioxide and ammonium alum, and microporous silicon dioxide from titanium-bearing blast furnace slag (TBBF slag) was proposed, which is comprised of (NH₄)₂SO₄ roasting, acid leaching, ammonium alum crystallization, silicic acid flocculation and Ti hydrolysis. The effects of relevant process parameters were systematically investigated. The results showed that under the optimal roasting and leaching conditions about 85% of titanium and 84.6% of aluminum could be extracted while only 30% of silicon entered the leachate. 84% of Al³⁺ was crystallized from the leachate in the form of ammonium aluminum sulfate dodecahydrate with a purity up to 99.5 wt%. About 85% of the soluble silicic acid was flocculated with the aid of secondary alcohol polyoxyethylene ether 9 (AEO-9) to yield a microporous SiO₂ material (97.4 wt%) from the crystallized mother liquor. The Al- and Si-depleted solution was then hydrolyzed to generate a titanium dioxide (99.1 wt%) with uniform particle size distribution. It was figured out that approximately 146 kg TiO₂ could be produced from 1000 kg of TBBF slag. Therefore, the improved process is a promising method for industrial application.     

Macroporous silicon for high-capacitance devices using metal electrodes

In this paper, high-capacity energy storage devices based on macroporous silicon are demonstrated. Small footprint devices with large specific capacitances up to 100 nF/mm², and an absolute capacitance above 15 μF, have been successfully fabricated using standard microelectronics and MEMS techniques. The fabricated devices are suitable for high-density system integration. The use of 3-D silicon structures allows achieving a large surface to volume ratio. The macroporous silicon structures are fabricated by electrochemical etching of silicon. This technique allows creating large structures of tubes with either straight or modulated radial profiles in depth. Furthermore, a very large aspect ratio is possible with this fabrication method. Macroporous silicon grown this way permits well-controlled structure definition with excellent repeatability and surface quality. Additionally, structure geometry can be accurately controlled to meet designer specifications. Macroporous silicon is used as one of the electrodes over which a silicon dioxide insulating layer is grown. Several insulator thicknesses have been tested. The second capacitor electrode is a solid nickel filling of the pores prepared by electroplating in a low-temperature industry standard process. The use of high-conductivity materials allows reaching small equivalent series resistance near 1 Ω. Thanks to these improvements, the presented devices are capable of operating up to 10 kHz.

PACS

84.32.Tt; 81.15.Pq; 81.05.Rm     

Forms of extraction of silicon compounds in rice husks

The forms of extraction of silicon compounds in rice husk, proposed as a source of silicon dioxide, were examined. A model in which the silica particles distributed in the plant cells of rice husk are separated by organic layers from mineralizer impurities was proposed. Crystallization of silicon dioxide begins after elimination of the layers of carbon formed at the site.     

Hypercrosslinked microporous organic polymer networks derived from silole-containing building blocks

Three silole-containing hypercrosslinked microporous organic polymer networks were designed and synthesized via Friedel–Crafts alkylation promoted by anhydrous FeCl₃. The results demonstrated that the substitution of methyl group connected with silicon atom by benzene has negligible effect on the surface area and gas uptake ability of the polymer networks. The network-1 produced from 1,1-dimethyl-2,3,4,5-tetraphenylsilole shows a surface area up to 1236 m² g⁻¹ with the hydrogen uptake ability of 1.33 wt% (77.3 K/1.13 bar) and a carbon dioxide capture capacity of 2.94 mmol g⁻¹ at 273 K/1.13 bar. The isosteric heats of carbon dioxide sorption for all of the polymer networks exceed 25 kJ/mol at the zero coverage because the introduction of silicon atom into the polymer skeleton enhanced the binding affinity between the adsorbent and CO₂ molecules. In addition, the selectivity of the polymer networks for CO₂/N₂ and CO₂/CH₄ were found to be around 35 and 6 at 273 K, respectively. These results show that these materials are potential candidates for applications in post-combustion CO₂ capture and separation.     

Graphitic carbon growth on crystalline and amorphous oxide substrates using molecular beam epitaxy

We report graphitic carbon growth on crystalline and amorphous oxide substrates by using carbon molecular beam epitaxy. The films are characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The formations of nanocrystalline graphite are observed on silicon dioxide and glass, while mainly sp² amorphous carbons are formed on strontium titanate and yttria-stabilized zirconia. Interestingly, flat carbon layers with high degree of graphitization are formed even on amorphous oxides. Our results provide a progress toward direct graphene growth on oxide materials.PACS: 81.05.uf; 81.15.Hi; 78.30.Ly.     

Self-Assembled Monolayers of Vinyltriethoxysilane and Vinyltrichlorosilane Deposited on Silicon Dioxide Surfaces

Abstract

This study was aimed at deposition of self-assembled monolayers (SAMs) using vinyltriethoxysilane (VTES) and vinyltrichlorosilane (VTCS) molecules chemisorbed on silicon dioxide surfaces. The kinetics of SAM formation on planar glass substrates and silicon wafers was characterized by contact angle measurements. The surface free energy and its dispersion and polar components enabled to estimate the time of immersion required to deposit compact SAMs. Adsorption of organosilane molecules as a function of immersion time was characterized by X-ray photoelectron spectroscopy. The SAM thickness was evaluated by spectroscopic ellipsometry. Surface topography of deposited layers was investigated by atomic force microscopy (AFM). The VTCS/glass combination exhibited the fastest kinetics but the deposit was not uniform and included local agglomerates. The hydrophobic vinyl groups at deposit surface resulted in a surface free energy of 32 mJ/m².     

我国气相法二氧化硅的生产状况及其应用

气相法二氧化硅是高科技纳米材料。介绍其赋予材料的与众不同的性能,论述发展气相法二氧化硅的重要性,重点分析国内气相法二氧化硅的生产状况、技术状况、存在的问题和市场情况。     

Influence of spray-drying operating conditions on Rhamnus purshiana (Cáscara sagrada) extract powder physical properties

The aim of this work was to study Rhamnus purshiana (Cáscara sagrada) extract spray-drying in order to obtain powders with good rheological properties for direct compression (DC) and stability attributes.The experiments were carried out in a Büchi B-290 Mini Spray Dryer using colloidal silicon dioxide as carrier agent. A 2^5 − 1 fractional factorial statistical design was used to find adequate spray-drying operating conditions to produce Cáscara sagrada powders with good flow, good compactability properties, high process yield, low moisture content, low hygroscopicity, and caking tendency. Morphology, size, structural and thermal properties of the particles were also evaluated. The operating variables studied were air inlet temperature, atomization air flow rate, pump feed rate, aspiration capacity, and feed solids concentration.The 2^5 − 1 factorial experimental design used was a good strategy to establish spray-drying operating conditions to produce Cáscara sagrada extract powders with good properties for direct compression and high process yields. Colloidal silicon dioxide was an effective drying adjuvant. Its use in relatively high concentrations together with low atomization air flow rates improved powder flowability, increased the product's glass transition temperature, and decreased its moisture content and hygroscopicity.     

Thermal regeneration of spent coal‐based activated carbon using carbon dioxide: process optimisation,Methylene Blue decolorisation isotherms and kinetics

Spent coal‐based activated carbon from the silicon industry has been used as raw material for the regeneration of activated carbon, with carbon dioxide as the regenerating agent. The regeneration process was optimised using response surface methodology and the optimum regeneration conditions were: regeneration temperature 985 °C; regeneration time 120 min; and carbon dioxide flow rate of 600 ml/min. The iodine number and yield of the activated carbon obtained under the optimum regeneration conditions were 1071 mg/g and 67%, with a Brunauer–Emmet–Teller surface area of 1270 m²/g and pore volume of 0.91 cm³/g. The regenerated carbon was tested for the removal of Methylene Blue dyes. The maximum adsorption capacity was found to be 395 mg/g and the equilibrium data fitted to the Langmuir isotherm model. The kinetic data indicated that the best fit corresponds to the pseudo‐second‐order kinetic model.