Silicon Raw Material Research Articles

A Hydrothermal Synthesis Process of ZSM-5 Zeolite for VOCs Adsorption Using Desilication Solution

ZSM-5 zeolite is a kind of high-value-added porous aluminosilicate zeolite. The use of the coal gasification slag utilization process by-product desilication liquid as a silicon raw material to replace the current raw materials such as water glass will help reduce production costs and achieve high-value utilization of solid waste. ZSM-5 zeolites for volatile organic compounds (VOCs) adsorption were prepared by a one-step hydrothermal method using the desilication solution prepared from coal gasification slag as the main silicon source and sodium source. The effects of crystallization reaction time, the crystallization temperature, the Na2O/SiO2 molar ratio, and the SiO2/Al2O3 molar ratio on the relative crystallinity and the specific surface area of the ZSM-5 zeolite were investigated and optimized. The optical reaction conditions were as follows: a crystallization time of 12 h, a crystallization temperature of 170 °C, a Na2O/SiO2 molar ratio of 0.2, and a SiO2/Al2O3 molar ratio of 200. The optimal ZSM-5 zeolite synthesized is hexagonal, with regular grains, a relative crystallinity of 101.48%, a specific surface area of 337.48 m2·g−1, and a pore volume of 0.190 cm3·g−1. And the optimal ZSM-5 zeolite was composed of SiO2 content of 97.52 wt%, Al2O3 content of 1.58 wt%, Na2O content of 0.33 wt%, and SiO2/Al2O3 molar ratio of 104.93. Na2O/SiO2 molar ratio is 0.0033. The results of static adsorption experiments show that the static adsorption capacities of ZSM-5 zeolite for p-xylene, benzene, toluene, and butyl acetate were 118.85, 69.98, 68.74, and 95.85 mg·g−1, respectively, which can effectively adsorb VOCs. The synthetic process of the ZSM-5 zeolite is a simple preparation process and short in synthesis time. The results of this study not only help to realize the high-value utilization of silicon components in solid waste, but also provide an economical and effective way to synthesize VOCs adsorption materials.

Numerical analysis in Ar-H<sub>2</sub> coupled-coil inductively coupled thermal plasma with Si feedstock for stable operation

<span lang="EN-US">In nanopowder synthesis, the starting powder to be evaporated is infused in a plasma torch through the upper coil and the lower coil in the coupled model of inductively coupled thermal plasma (coupled-coil inductively coupled thermal plasma (ICTP)). Mixing these evaporated materials to form the coupled ICTP significantly influences the thermodynamic and transport properties. It is essential to understand these complex interactions between coupled ICTP and feedstock evaporation. This research investigated the thermal interactions between silicon raw material powder (Si) with ICTP in coupled 99%Ar/1%H<sub>2</sub> through the numerical model developed for the synthesis of Si nanopowder. The feed rate of the Si raw material was set at 0.05, 0.1, and 0.5 g/min. This implies that the increased Si feed is too heavy to vaporize all the injected feed.</span>

DIATOMITES AND OPOKA FROM WESTERN KAZAKHSTAN DEPOSITS: LITHOGEOCHEMISTRY, STRUCTURAL AND TEXTURAL PARAMETERS, POTENTIAL OF USE

Link for citation: Smirnov P.V., Zhakipbayev B.E., Staroselets D.A., Deryagina O.I., Batalin G.A., Gareev B.I., Vergunov A.V. Diatomites and opoka from Western Kazakhstan deposits: lithogeochemistry, structural and textural parameters, potential of use. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 187-201. In Rus. The relevance. In recent decades, individual studies in the Republic of Kazakhstan have been aimed at expanding the potential of using rocks of large and industrial exploitation of silicite deposits for revising their physicochemical, mineralogical parameters, and assessing the prospects for expanding their use in new industries and technologies in the construction and technical industries, materials science based on deep chemical processing of mineral raw materials. The article presents new data on the chemical-mineralogical and structural parameters of diatomites from the Utesai deposit and opoka from the Taskala deposit of the Republic of Kazakhstan. The main aim: comprehensive analysis of the chemical-mineral composition and structural and textural features of rocks from two largest deposits of silicon raw materials in the Western part of Kazakhstan – the Utesai diatomite deposit and the Taskala opoka deposit. Objects: diatomites of the Utesai deposit and opoka of the Taskala deposits in the western part of the Republic of Kazakhstan. Methods: field research, lithological and petrographic analysis of thin sections, X-ray diffraction analysis, differential thermal analysis, scanning electron microscopy, X-ray fluorescence analysis. Results. The studied diatomites and opoka are characterized by a high degree of homogeneity; they are represented by typical phases for silicic rocks of the region – opal-CT, clay minerals with an admixture of quartz and feldspars. From the mineralogical point of view, the most obvious difference between the studied diatomites and the Trans-Urals is the significant content of kaolinite – over 10 %, while in the diatomites of the Trans-Urals, the main clay component is smectite and mixed-layer illite-smectite formations. The rocks under consideration are clayey diatomites and clayey flasks, the total content of basic oxides allows us to characterize raw materials as medium quality, most suitable for the production of foam glass materials, and, in particular, glass fiber, in the production of which alumina is an important functional component. At the same time, the significant content of clay and other impurities does not allow us to recommend such raw materials for the production of filter and sorbing materials.

Excellent yellow emission of Si3N4:Eu nanorods derived from waster silicon with better thermal stability for white LEDs

The core issue of light emitting diodes (LEDs) for actual application is the thermal stability of phosphors. Silicon nitride (Si 3 N 4 ) is generally recognized as especially important structural material due to its excellent mechanical properties at extreme high temperature. In this work, Si 3 N 4 : Eu was demonstrated to be an excellent luminescence functional material for LEDs. The discarded corner-waster silicon raw material was utilized to act as the precursor. The Si 3 N 4 :Eu phosphor was synthesized by a facile nitriding process at elevated temperature. The pure α-Si 3 N 4 :Eu nanorods were successfully obtained by adjusting the doping concentration of Eu. It is coexistence with mixed-valence (divalent and trivalent) for Eu in α-Si 3 N 4 according to X-ray photoelectron spectroscopy. The synthesized α-Si 3 N 4 :Eu nanorods showed bright yellow under the excitation of 365 nm (UV) and white luminescence by 460 nm chip (Blue). The Si 3 N 4 :Eu nanorods possess excellent thermal stability, maintains nearly 70% of the origin intensity even at temperatures over 300 °C. The Si 3 N 4 :Eu nanorods demonstrated comparable performance to commercial YAG:Ce 3+ (YAG). Moreover, the long-term thermal stability of Si 3 N 4 :Eu nanorods is superior to commercial YAG, revealing the enhanced service performance. This work not only presents a facile Si 3 N 4 :Eu nanorods green synthesis route from waste utilization, but also offers an enhanced service performance for the high temperature LEDs application.

Cycling Performance of Different Nano Sized Silicon Particles in a Carbon Matrix

Silicon is among the most promising material for next generation anode battery material, with over ten times higher capacity than graphite and the second most abundant element on earth crust after oxygen. However silicon faces a host of well known (but not well understood) problems that prevent it’s widespread commercialization. The pulverization of silicon particles due to volume expansion related stress is well know. 150nm is postulated as the maximum size below which particles can withstand this stress and maintain mechanical integrity (The success story of graphite as a lithium-ion anode material – fundamentals, remaining challenges, and recent developments including silicon (oxide) composites (rsc.org)). Real world materials don’t have a single particle size though, they have a particle size distribution. In this study the cycling performance of a silicon raw material with different particle size is evaluated as part of a silicon graphite composite material. Different silicon submicron to nano sized particles in a carbon matrix containing graphite and binders were produced. Through both powder characteristics and electrochemical testing, we can show that the sizes will have an impact on columbic efficiency and is crucial for the cycling life.

In Situ Synthesis and Dual Functionalization of Nano Silicon Enabled by a Semisolid Lithium Rechargeable Flow Battery.

Nanosized silicon has attracted considerable attentions as a new-generation anode material for lithium-ion batteries (LIBs) due to its exceptional theoretical capacity and reasonable cyclic stability. However, serious side reactions often take place at the nanosized silicon/electrolyte interface in LIBs, where critical electrochemical properties such as initial Coulombic efficiency (ICE) are compromised. On the basis of this feature, a new method is developed to synthesize nanosilicon-based particles in a facile, scalable way, which are endowed with the function of prelithiation and storage stability in air. A semisolid lithium rechargeable flow battery (SSFB) technology is used for the first time to convert the micrometer-sized silicon raw material into an amorphous-nanosilicon-based material (ANSBM), as a result of the pulverization process induced by the repeated lithiation/delithiation cycles. The particle size is successfully reduced from 1-4 μm to around 30 nm after cycles in the flow battery. Bulk functionalization of the nano silicon is introduced by the unbalanced lithiation/delithiation cyclic process, which endows ANSBM with a unique prelithiation capability universally applicable to different anode systems such as nanosized Si, SiOx, and graphite, as evidenced by the significantly improved ICEs. Superior air stability (10% relative humidity) is exhibited by ANSBM due to surface functionalization by the stable interfacial layer encapsulated by electron-conductive carbon. The outcome of this work provides a promising way to synthesize dual-functionalized nano silicon with good electrochemical performance in terms of improved capacity and increased initial Coulombic efficiency when it is composited with other typical anode materials.

3D numerical simulation with experimental validation of a traveling magnetic field stirring generated by a Bitter coil for silicon directional solidification process

Silicon is the most widely used raw material in photovoltaic industry; however, the quality of the silicon photovoltaic solar cells depends on the quality of the raw material (i.e. metallurgical silicon or poly-silicon) and the solidification methods used for the production of the silicon ingot from which the solar cells are produced. This study is related to how improve the quality of the final ingot in the directional solidification process; it is necessary to control the impurity segregation of silicon raw material during the processing. This control can be accomplished by adding an electromagnetic Bitter coil which can generate an external traveling magnetic field (TMF) stirring to control the hydrodynamic flow of silicon melt during the solidification process without contaminating it. To carry out this study, we used a Bridgman vertical directional solidification furnace, equipped with a cylindrical Bitter coil stirrer used in order to have the control of the silicon melt convection on the principal parameters of the solidification process, such as the growth rate, the thermal gradient and the natural convection of silicon melt. For the electromagnetic, heat exchange and silicon melt flow modelling, we used 3D numerical Multiphysics coupled models. Parallel to the numerical results we carried out experimental investigations relating to the characterization of the electromagnetic parameters. This study shows a promising effect of the applied traveling magnetic field on the final ingot quality; indeed, we have the ability to control the silicon melt flow which can affect the thermal configuration, the solidification interface shape and the segregation of impurities by changing the electric current input configuration of the Bitter coil stirrer.

Recovery of porous silicon from waste crystalline silicon solar panels for high-performance lithium-ion battery anodes.

A low-cost and easy-available silicon (Si) feedstock is of great significance for developing high-performance lithium-ion battery (LIB) anode materials. Herein, we employ waste crystalline Si solar panels as silicon raw materials, and transform micro-sized Si (m-Si) into porous Si (p-Si) by an alloying/dealloying approach in molten salt where Li+ was first reduced and simultaneously alloyed with m-Si to generate Li-Si alloy at the cathode. Subsequently, the as-prepared Li-Si alloy served as the anode in the same molten salt to release Li+ into the molten salt, resulting in the production of p-Si by taking advantage of the volume expansion/contraction effect. In the whole process, Li+ was shuttled between the electrodes in molten LiCl-KCl, without consuming Li salt. The obtained p-Si was applied as an anode in a half-type LIBs that delivered a capacity of 2427.7 mAh g-1 at 1 A g-1 after 200 cycles with a capacity retention rate of 91.5% (1383.3 mAh g-1 after 500 cycles). Overall, this work offers a straightforward way to convent waste Si panels to high-performance Si anodes for LIBs, giving retired Si a second life and alleviating greenhouse gas emissions caused by Si production.

New Approach in Research of Quartzes and Quartzites for Ferroalloys and Silicon Production

This article deals with material research of selected types of quartz and quartzites in order to determine the priority of their use in the production of ferrosilicon and pure silicon, respectively. The highest quality quartzes and quartzites are commonly used in metallurgy, but not all types of these silicon raw materials are suitable for the production of ferrosilicon and pure silicon, despite their similar chemical composition. Behavior differences can be observed in the process conditions of heating and carbothermic production of ferrosilicon and silicon. These differences depend, in particular, on the nature and content of impurities, and the granularity (lumpiness) and microstructure of individual grains. The research focused primarily on determining the physicochemical and metallurgical properties of silicon raw materials. An integral part of the research was also the creation of a new methodology for determining the reducibility of quartzes (or quartzites), which could be used for real industrial processes and should be very reliable. The results of the laboratory experiments and evaluation of the physicochemical and metallurgical properties of the individual quartzes (or quartzites) are presented in the discussion. Based on comparison of the tested samples’ properties, their priority of use was determined. This research revealed the highest quality in quartzite from Sweden (Dalbo deposit) and Ukraine (Ovruč deposit) and quartz from Slovakia (Švedlár deposit). The use of these raw materials in industrial conditions is expected to result in the achievement of better production parameters, such as higher yield and product quality and lower electricity consumption.

Preparation of a Composite Calcium Silicate Board with Carbide Slag and Coal-Based Solid Waste Activated by Different Alkali Activators.

Overall performance of composite calcium silicate boards (CCSBs) was investigated to further promote their application. The alkali activators were used to fully hydrate the calcium and silicon raw materials, which further improved the comprehensive performance of the CCSBs made of four pure industrial solid wastes. Within the range of dosage in this study, single doping of different proportions of the alkali activator improved the flexural strength of the CCSB. Based on this, the mechanical properties of the CCSB were further improved as the compounded alkali activator was optimized. Flexural strength is improved when the average pore diameter was refined. The freeze–thaw cycle test shows that a compound-doped alkali activator can effectively reduce the mass loss and strength loss, thereby improving the frost resistance of this material. This research discussed an economically affordable approach to prepare the CCSB material made of industrial solid waste.

CO2 and water vapor adsorption properties of framework hybrid W-ZSM-5/silicalite-1 prepared from RHA.

Framework hybrid W-ZSM-5 and W-silicalite-1 zeolites were synthesized by hydrothermal methods using rice husk ash (RHA) as a silicon raw material. RHA is a low-cost precursor material, and its use can also alleviate the environmental and human health related problems that may occur when it is stacked in open fields. A series of comparative samples were characterized by XRD, FTIR, ICP-OES, SEM, N2 adsorption–desorption and pore size analysis in order to examine their crystal structure, hybrid state, morphology and textural properties. The maximum CO2 adsorption capacities of W-ZSM-5 and W-silicalite-1 are 81.69 and 69.96 cm3 g−1, respectively, measured at 15 bar. The isotherms of CO2, N2 and O2 are perfectly fitted by the Toth model, and it is noted that the presence of Al atoms increases the heterogeneity. It can be seen that the greater the heterogeneity of the adsorbent, the larger the CO2 adsorption capacity achieved. The incorporation of tungsten into the framework does not affect the crystallization of the zeolite, but it prevents the formation of silanol and O–H groups at the adsorption sites. Therefore, the CO2/H2O selectivity of W-ZSM-5 is slightly higher than that of ZSM-5, and that of W-silicalite-1 is three times that of silicalite-1. W-ZSM-5/silicalite-1 are promising adsorbents for separating CO2 under humid industrial conditions.

ПЕРСПЕКТИВИ ВІДКЛАДІВ НАДЗАПЛАВНИХ ТЕРАС ДНІСТРА НА ЗОЛОТУ МІНЕРАЛІЗАЦІЮ

The article clarifies the stratigraphic binding and origin of silicon nodules, which served as the main raw material for the manufacture of tools for mammoth hunters of the Mezhyrich Late Paleolithic site. In archaeological publications, these nodules are often mentioned to be confined to the "Vyrzhikovsky layer" (the Albian layer of the Lower Cretaceous), which was formed under continental conditions and consists of sand-clay (kaolin, in particular) deposits. The analysis of the necessary conditions and possible mechanisms for the formation of silicon nodules indicates the erroneousness of such ideas. Most likely, the source of silicon raw materials was the marine deposits of the Cenomanian (Upper Cretaceous), or, in accordance with the modern stratigraphic division of the Mesozoic-Cenozoic sequence, deposits of the Burim suite (upper Albian – lower Cenomanian). The paleogeographic setting, sedimentological conditions and lithological composition of the "Vyrzhikovsky layer" did not ensure the formation of silicon nodules in it in the form of inclusions. The latter are diagenetic in origin and could only form in the thickness of carbonate rocks, free of clay minerals. The region of Kaniv dislocations was the optimal region from the silicon production point of view, which was determined: firstly, by the tectonic dislocation of the sedimentary sequence, which contributed to the removal of deposits containing silicon nodules in the thickness of younger rocks; secondly,the erosion activity of temporary streams, which brought these deposits to the level of the denudation cut-off. The most convenient place for collecting flints was not the outcrop of bedrock in ravines but the cones of their removal, which overlook the floodplains of the Dnipro and Ros'. The possibility of collecting flint in the immediate vicinity of the Mezhirich site, in the ravines and gullies between the Ros and Rosava rivers, does not find confirmation, since the chalk deposits here lie much lower than the local erosion base and are not exposed by ravines. Therefore, the leading role in the formation of the raw material supply of the Late Paleolithic site of Mezhirich was played by the region adjacent to the Kaniv mountains of the alluvial-proluvial plain.Despite long-term geological study of the Dniester River basin, we still have no clear evidences about gold-bearing potentiality of this area as well as origin of gold. The leading role of geological, geochemical and mineralogical criteria is proved for defining the prospects of substantial gold deposits finding within the Dniester river basin. Gold was found here in the crystalline basement and in the sedimentary cover rocks. Study of mineralogy and lithology of the terraces above the flood-plain and typomorphic peculiarities of native gold shows that palaeogeographic conditions and alimentation zones of debris vary at the different tectonic stages of this area development. Gold-bearing potential of the Pliocene-Quaternary sediments in the Dniester River basin is related to the Pliocene (VI-IX terraces above the flood-plain) and Quaternary (I-V terraces above the flood-plain) terraces complex of the Dniester river, as well as this river and its inflows recent alluvia. Our study of the Mid-flow part of the Dniester river basin allow to conclude that native gold was found in geologocal strata of all ages, from Proterozoic up to the recent alluvium. This fact points the necessity of further prospecting to find the mother lodes of gold. Our field study, samples analyses made as well as publications observation allow highlighting the principal directions of further prospecting and evaluation works. The main among that are: 1) comprehensive study of river Dniester alluvia and its terraces complex (previously VI–VII terraces), that will allow to specify their material composition, to assess real gold-bearing potential and to define the history of denudation areas changes; 2) lithogeochemical prospecting of primary and secondary dispersion haloes to clear the principal gold-bearing regularities; 3) definition of prospect plots within the area described; 4) modern analytical approach study of typomorphic peculiarities of native gold from alluvia and terrace deposits to define its ore formational affinity and mineral type.

ПРО ВІК І ПОХОДЖЕННЯ КРЕМ'ЯНОЇ СИРОВИНИ ІНВЕНТАРЮ ГЕОАРХЕОЛОГІЧНОЇ ПАМ'ЯТКИ МЕЖИРІЧ (КАНІВСЬКЕ ПРИДНІПРОВ'Я)

The article clarifies the stratigraphic binding and origin of silicon nodules, which served as the main raw material for the manufacture of tools for mammoth hunters of the Mezhyrich Late Paleolithic site. In archaeological publications, these nodules are often mentioned to be confined to the "Vyrzhikovsky layer" (the Albian layer of the Lower Cretaceous), which was formed under continental conditions and consists of sand-clay (kaolin, in particular) deposits. The analysis of the necessary conditions and possible mechanisms for the formation of silicon nodules indicates the erroneousness of such ideas. Most likely, the source of silicon raw materials was the marine deposits of the Cenomanian (Upper Cretaceous), or, in accordance with the modern stratigraphic division of the Mesozoic-Cenozoic sequence, deposits of the Burim suite (upper Albian – lower Cenomanian). The paleogeographic setting, sedimentological conditions and lithological composition of the "Vyrzhikovsky layer" did not ensure the formation of silicon nodules in it in the form of inclusions. The latter are diagenetic in origin and could only form in the thickness of carbonate rocks, free of clay minerals. The region of Kaniv dislocations was the optimal region from the silicon production point of view, which was determined: firstly, by the tectonic dislocation of the sedimentary sequence, which contributed to the removal of deposits containing silicon nodules in the thickness of younger rocks; secondly,the erosion activity of temporary streams, which brought these deposits to the level of the denudation cut-off. The most convenient place for collecting flints was not the outcrop of bedrock in ravines but the cones of their removal, which overlook the floodplains of the Dnipro and Ros'. The possibility of collecting flint in the immediate vicinity of the Mezhirich site, in the ravines and gullies between the Ros and Rosava rivers, does not find confirmation, since the chalk deposits here lie much lower than the local erosion base and are not exposed by ravines. Therefore, the leading role in the formation of the raw material supply of the Late Paleolithic site of Mezhirich was played by the region adjacent to the Kaniv mountains of the alluvial-proluvial plain.

Dual-carbon enhanced silicon-based composite as superior anode material for lithium ion batteries

Dual-carbon enhanced Si-based composite (Si/C/G) has been prepared via employing the widely distributed, low-cost and environmentally friendly Diatomite mineral as silicon raw material. The preparation processes are very simple, non-toxic and easy to scale up. Electrochemical tests as anode material for lithium ion batteries (LIBs) demonstrate that this Si/C/G composite exhibits much improved Li-storage properties in terms of superior high-rate capabilities and excellent cycle stability compared to the pristine Si material as well as both single-carbon modified composites. Specifically for the Si/C/G composite, it can still deliver a high specific capacity of about 470 mAh g−1 at an ultrahigh current density of 5 A g−1, and exhibit a high capacity of 938 mAh g−1 at 0.1 A g−1 with excellent capacity retention in the following 300 cycles. The significantly enhanced Li-storage properties should be attributed to the co-existence of both highly conductive graphite and amorphous carbon in the Si/C/G composite. While the former can enhance the electrical conductivity of the obtained composite, the latter acts as the adhesives to connect the porous Si particulates and conductive graphite flakes to form robust and stable conductive network.

Research on distribution of aluminum in electron beam melted silicon ingot

The purification of metallurgical grade silicon, especially the removal of aluminum, was investigated by electron beam melting and solidification. Small amounts of silicon raw materials were melted in an electron beam furnace with same melting time and different solidification time to obtain the distribution of Al in silicon ingot. The removal mechanisms in different stages were also discussed. The results show that the removal of Al during melting process only depends on evaporation and that during solidification process depends on both segregation and evaporation. The distribution of Al shows an obvious increasing trend from the bottom to the top of the silicon ingot when solidification time is 600 s. The removal efficiency in most area is close to that in the ingot solidified instantaneously, but the energy consumption is less, which is considered to be an effective way for the purification of silicon.

Characterisation of single crystalline silicon grown by Czochralski method

The conversion efficiency of solar cells made from single crystalline Si is generally about 3–4% higher than those made from Si multicrystal by the casting method. In this paper, the single crystalline Si obtained by the Czochralski method using metallurgical grade silicon raw materials was characterised by minority carrier lifetime, optical microscopy, the concentration of impurities and the conversion efficiency. The influence of crystalline defects and impurity elements on the electrical property has been investigated. We can conclude that both defects and impurity elements play important roles in the deterioration of the minority carrier lifetime. The conversion efficiency of solar cell using the middle wafer can reach 11·39%.

Applying Data Envelopment Analysis to Evaluation of Taiwanese Solar Cell Industry Operational Performance

In the Taiwanese solar power industry, the upstream industry’s lack of silicon raw materials and the downstream’s underdevelopedsystematic manufacturingstatus have led industrial development to continue concentrating on cell and module research and development manufact uring and production. Taiwan’s solar power industry has developed midstream cell manufacturersholding a share of the global market. The research period for this study was between 20 10 and 2011. This study constructed a performance evaluation model by using data envelopment analysis for the solar cell industry to assist relevant manufacturers in the Taiwanese solarpower industry in formulating operational strategies ; guidelines on future development in the industryhave been recommended .

Catalyst-assisted synthesis and growth mechanism of ultra-long single crystal α-Si3N4 nanobelts with strong violet–blue luminescent properties

Ultra-long single crystal α-Si3N4 nanobelts were prepared by thermal chemical vapour deposition (CVD) method. Silicon vapour from the original solid silicon raw material was allowed to react with flowing nitrogen at 1450 °C on the carbon felt deposited with Ni(NO3)2. The as-prepared α-Si3N4 nanobelts were 40–60 nm thick, 200–300 nm wide, and up to several millimetres long. Their growth process was governed by the VLS base-growth and the VS tip-growth mechanisms. The former was responsible for the initial nucleation and proto-nanobelt (template) formation of α-Si3N4 and the subsequent growth along the [101] or [100] direction, and the latter for the additional growth at the tips. The synergistic function from these two growth mechanisms resulted in the formation of a large quantity of ultra-long α-Si3N4 nanobelts. An intense violet–blue visible photoluminescence (PL) of the as-synthesized α-Si3N4 nanobelts was observed at room temperature, which could be highly valuable for the future potential applications in optoelectronic nanodevices.

Recent Patenting Activities in Low-Cost Silicon Raw Materials for Silicon Solar Cells

Recent Patenting Activities in Low-Cost Silicon Raw Materials for Silicon Solar Cells

Recent Patenting Activities in Low-Cost Silicon Raw Materials for Silicon Solar Cells

For the last decades, numerous researches and patents are focused on developing novel refining processes of low-cost silicon. In this paper, patents that reveal different refining methods including chemical routes, metallurgical routes and other promising routes are reviewed respectively, and the detailed processes together with their pros and cons are demonstrated according to their basic principles. Based on different processes used for silicon production, the corresponding techniques of fabricating silicon ingots and solar cells are also introduced. Keywords: Low-cost silicon, refining, impurity, chemical route, metallurgical route, solar cell, fabricating silicon, fossil fuels, solar energy, pn junction, photovoltaic effect, p-type semiconductor, n-type semiconductor, Earth's crust, solar grade (SOG) silicon, electronic grade polysilicon, solar cell fabrication, halogen silane, chemical vapor deposition (CVD), Siemens process, fluidized bed reactor, Union Carbide, Ethyl Corporation's processes, material recycling, Czochralski (Cz) growth, directional solidification, crucible, surface area, gas reactant, vapor-to-liquid deposition, high purity graphite reactor, polysilicon, orthoethylsilicate or tetraethoxysilane, carbothermic reduction, hydrometallurgical refining, slagging, Elkem's slag-based pyro-metallurgical refinement technique, Elkem's products, Zone melting, zone refining, electromagnetic induction, vacuum evaporation, wet hydrogen atmosphere, efficiency, solidification, horizontal zone melt refining technique, solid-liquid interface, segregation coefficients, rejection' principle, crystallization front, surface oxidization, Al-Si alloy, Electrometallurgy, aluminothermic, electrolysis, exothermic chemical reactions, Calisolar, silicon wafers, casting growth, Cz-silicon ingots, mass ratio, gallium, photovoltaic, surface damage gettering, nitridation/oxidation treatment, ohmic contact, epitaxial silicon film, silane-related compound