Size Effect on the Radiation Stability Silicon Dioxide Sphere Particles

The effect of protons(E = 100 keV,F = 5×10^(15) cm^(-2)) exposure on the diffuse reflectance spectra of the SiO_(2 )with different size particles in wavelength range from 250 to 2500 nm have been investigated.Particles were nanosphere,submicrosphere,microsphere and submacrosphere,as well as solid micro-and nanocrystals.The synthesis of the particles was carried out by the formation of silica shells and dissolution of the polystyrene core particles.The surface morphology,surface area and crystal structure of the particles have been investigated.When evaluating the changes of the solar absorptance,it was found that the radiation stability of the micro-and submacro-hollow particles is higher than that of the other nanostructured particles,except for solid microcrystals.The low radiation stability of the hollow microparticles is due to the large void inside the hollow particles where radiation defects are not formed.

Preparation and photocatalytic activity of neodymium doping titania loaded to silicon dioxide

Neodymium doping titania was loaded to silicon dioxide to prepare Nd/TiO2-SiO2 by sol-gel method and Nd/TiO2-SiO2 was characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, Fourier transform-infrared spectroscopy （FT-IR） and diffuse reflectance spectra （DRS）. Photocatalytic activities of Nd/TiO2-SiO2 with different neodymium contents were evaluated by degradation of methyl orange. The light absorption of Nd/TiO2-SiO2 increased with increasing doping neodymium in a visible light range of 388-619 nm, and Nd doping was in favor of decreasing the recombination of photo-generated electrons with holes. Nd and SiO2 improved the photocatalytic activity of TiO2. The optimal molar fraction of Nd to Ti was 0.1%, and the optimum calcination temperature was 600 ℃. The highest degradation rate of methyl orange was 82.9% after irradiation for 1 h.

Effect of TMS(nanostructured silicon dioxide) on growth of Changbai larch seedlings

The roots of 200 one-year-old Changbai Larch (Larix olgensis) seedlings were soaked for 6 hours at the TMS concentrations of 2000, 1000, 500, 250, 125, and 62 μL·L?1. Mean seedling height, root collar diameter, main root length and number of lateral roots were measured every 15 days during growing season from May 30 to Oct. 20. Experimental results showed that TMS treatments greatly promoted seedling growth and improved seedling quality. The treatment by 500 μL·L?1 TMS produced the best result, for which the mean height, root collar diameter, main root length, and the number of lateral roots of seedlings were increased by 42.5%, 30.7%, 14.0%, and 31.6%, respectively, compared to that of the control seedlings. As to seedling quality, grade-I seedling and grade-II seedlings were fifty-fifty, and no grade-III seedlings was found. The treatment by 500 μL·L?1 TMS resulted in the highest chlorophyll concentration. Keywords Changbai Larch - Larix olgensis - Seedling production - Nanostructured silicon dioxide CLC number S143.8 Document code B Foundation item: This study is supported by Jilin Forestry Group Co.Biography: LIN Baoshan (1955-), male, Associate professor at the college of forestry, Beihua University, Jilin City 132011, Jilin Province, P.R China.Responsible editor: Chai Ruihai.

Polymer grafting modification of the surface of nano silicon dioxide

Based on the composite modification technology of the surface of nano Silicondioxide by non-soap emulsion polymerization, it is verified that there are polymer grafted on thesurface of nano silicon dioxide. The modification mechanism and the bonding status on the surface ofnano silicon dioxide after modification were suggested via the results of the infrared spectrum,transmission electronic microscope photograph and X-ray photoelectron spectrum. The hydroxyl formedby hydrolyzing of silane coupling agent reacts with hydroxyl on the surface of nano silicon dioxideto form Si-O-Si bonds by losing water molecules and hence the double bonds are introduced onto thesurface of nano silicon dioxide. The surface of nano silicon dioxide is grafted with polymer throughfree radical polymerization between the double bonds on the surface of nano silicon dioxide andstyrene under the action of initiating agent. The dispersibility of nano silicon dioxide and thecontrollability of surface modification of nano silicon dioxide can be greatly improved by themodification process.

Rain Erosion Behavior of Silicon Dioxide Films Prepared on Sapphire

Silicon dioxide （SiO2） films were prepared on sapphire （α-Al2O3） by radio frequency magnetron reactive sputtering in order to increase both transmission and rain erosion resistant performance of infrared domes of sapphire. Composition and structure of SiO2 films were analyzed by X-ray photoelectron spectroscopy （XPS） and X-ray diffraction （XRD）, respectively. The transmittance of uncoated and coated sapphire was measured using a Fourier transform infrared （FTIR） spectrometer. Rain erosion tests of the uncoated and coated sapphire were performed at 211 m/s impact velocity with an exposure time ranging from 1 to 8 min on a whirling arm rig. Results show that the deposited films can greatly increase the transmission of sapphire in mid-wave IR. After rain erosion test, decreases in normalized transmission were less than 1% for designed SiO2 films and the SiO2 coating was strongly bonded to the sapphire substrate. In addition, sapphires coated with SiO2 films had a higher transmittance than uncoated ones after rain erosion.

Removal of Chromium from Aqueous Solution Using Hybrid Membrane of Chitosan and Silicon Dioxide

Adsorption experiment from aqueous solutions containing known amount of chromium （Cr） using hybrid membrane of chitosan and silicon dioxide was explored to evaluate the efficiency of the membrane as sorbent for Cr（VI）. Some variable parameters such as pH, contact time and the dosage of the membrane were optimized. Adsorption isotherms of Cr（VI） onto the hybrid membrane were measured with varying initial concentrations under optimized condition. Furthermore, the sorption mechanism of Cr by the membrane was investigated by applying Langmuir and Freundlich isotherm equations to the data obtained. The surface morphology of the membrane was determined by SEM （scanning electron microscope） for material characterization. The concentrations of Cr in solution are determined by ICP-MS （inductively coupled plasma mass spectrometry）. Hybrid membrane of chitosan and silicon dioxide can be an efficient sorbent for Cr（VI）.

Chemical Analysis Method for Magnesia and Magnesia-Alumina Refractories——Gravimetric-Molybdenum Blue Photometric Method for Determination of Silicon Dioxide Content

This standard specifies the gravimetric-molybdenum blue photometric method for determination of silicon dioxide content.

Ginseng ameliorates pulmonary toxicity induced by silicon dioxide nanoparticles in rats

Objective:To investigate the protective and therapeutic role of ginseng against silicon dioxide nanoparticles(SiO2NPs)-induced toxicity in the lungs.Methods:Sixty male rats were divided into five groups(n=12/group);group 1 was used as a control,group 2 received ginseng,group 3 was treated with SiO2NPs,and group 4 was pretreated with ginseng one week before SiO2NPs,while group 5 was given SiO2NPs one week before supplementation with ginseng.Animals were treated with both ginseng and SiO2NPs orally for five weeks.Real-time PCR was used to measure gene expression.Besides,DNA damage and cell cycle changes were determined by comet assay and flow cytometry,respectively.Histological study was also done to assess the effect of ginseng on SiO2NPs-induced toxicity.Results:SiO2NPs increased lipid peroxidation and decreased the activities of antioxidant enzymes.SiO2NPs induced apoptosis in lung tissues as revealed by upregulation of Bax and caspase 3 and downregulation of Bcl-2 as well as the induction of DNA damage.SiO2NPs also caused inflammation as indicated by upregulation of the inflammation-related genes[interleukin 1 beta(IL-1β),tumor necrosis factor-alpha(TNF-α),nuclear factor kappa B(NF-κB),cyclooxygenase 2(COX2),and transforming growth factor-beta 1(TGFβ1)]as well as cell cycle arrest in the G0/G1 phase of lung cells.Moreover,histopathological examination proved the biochemical and molecular perturbations that occurred due to SiO2NPs toxicity.However,ginseng alleviated SiO2NPs-induced toxicity in rat lung.Conclusions:Ginseng has a potent preventive and therapeutic effect and could be used in the treatment of SiO2NPs-induced pulmonary toxicity.

Preparation and Characterization of CA-MA Eutectic/Silicon Dioxide Nanoscale Composite Phase Change Material from Water Glass via Sol-Gel Method

This work mainly involved the preparation of a nano-scale form-stable phase change material（PCM） consisting of capric and myristic acid（CA-MA） binary eutectic acting as thermal absorbing material and nano silicon dioxide（nano-SiO_2） serving as the supporting material. Industrial water glass for preparation of the nano silicon dioxide matrix and CA-MA eutectic mixture were compounded by single-step sol-gel method with the silane coupling agent. The morphology, chemical characterization and form stability property of the composite PCM were investigated by transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, Fourier-transform infrared（FT-IR） spectroscopy and polarizing microscopy（POM）. It was indicated that the average diameter of the composite PCM particle ranged from 30-100 nm. The CA-MA eutectic was immobilized in the network pores constructed by the Si-O bonds so that the composite PCM was allowed no liquid leakage above the melting temperature of the CA-MA eutectic. Differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA） measurement were conducted to investigate the thermal properties and stability of the composite PCM. From the measurement results, the mass fraction of the CA-MA eutectic in the composite PCM was about 40%. The phase change temperature and latent heat of the composite were determined to be 21.15 ℃ and 55.67 J/g, respectively. Meanwhile, thermal conductivity of the composite was measured to be 0.208 W·m^（-1）·K^（-1） by using the transient hot-wire method. The composite PCM was able to maintain the surrounding temperature close to its phase change temperature and behaved well in thermalregulated performance which was verified by the heat storage-release experiment. This kind of form-stable PCM was supposed to complete thermal insulation even temperature regulation by the dual effect of relatively low thermal conductivity and phase change thermal storage-release properties. So it can be formulated that the nanoscale CA-MA/SiO_2 composite PCM with the form-stable property, good thermal storage capacity and relatively low thermal conductivity can be applied for energy conservation as a kind of thermal functional material.

Toxicity of silicon dioxide nanoparticles with varying sizes on the cornea and protein corona as a strategy for therapy

The human cornea is exposed directly to particulate matter （PM） in polluted air. This exposure can cause eye discomfort and corneal injury. Ultrafine PM （diameter ~100 nm） is thought to be particularly harmful to health, but there is limited research investigating its toxicity to the eye. In this study, we evaluated toxiciW differences among 30-, 40-, 100- and 150-nm silicon dioxide nanoparticles （Si02 NPs） on the cornea. A 24-hour in vitro exposure of primary human corneal epithelial cells （hCECs） to ultrafine （30 and 40 nm） SiO2 NPs produced toxicity, as evidenced by cell membrane damage, reduced cell viability, increased cell death and mitochondrial dysfunction. In vivo exposure to the same nanoparticles produced observable corneal injury. These effects were more severe with ultrafine than with fine （100 and 150 nm） Si02 NPs. Common antioxidant compounds, e.g., glutathione, did not protect the cornea from SiO2 NP-induced damage. However, foetal bovine serum （FBS） did significantly reduce toxicity, likely by forming a protective protein corona around the nanoparticles. This finding suggests that FBS （or its derivatives） may be a useful clinical therapy for corneal toxicity caused by ultrafine particulates.

Detection of Gain Enhancement in Laser-Induced Fluorescence of Rhodamine B Lasing Dye by Silicon Dioxide Nanostructures-Coated Cavity

In this work, nanostructured silicon dioxide films are deposited by closed-field unbalanced direct-current （DC） reactive magnetron sputterin technique on two sides of quartz cells containing rhodamine B dye dissolved in ethanol with 10-5 M concentration as a random gain medium. The preparation conditions are optimized to prepare highly pure SiO2 nanostructures with a minimum particle size of about 20nm. The effect of SiO2 films as external cavity for the random gain medium is determined by the laser-induced fluorescence of this medium, and an increase of about 200% in intensity is observed after the deposition of nanostructured SiO2 thin films on two sides of the dye cell.

Enhanced etching of silicon didioxide guided by carbon nanotubes in HF solution

This paper describes a new method to create nanoscale SiO2 pits or channels using single-walled carbon nanotubes （SWNTs） in an HF solution at room temperature within a few seconds. Using aligned SWNT arrays, a pattern of nanoscale SiO2 channels can be prepared. The nanoscale SiO2 patterns can also be created on the surface of three- dimensional （3D） SiO2 substrate and even the nanoscale trenches can be constructed with arbitrary shapes. A possible mechanism for this enhanced etching of SiO2 has been qualitatively analysed using defects in SWNTs, combined with H3O＋ electric double layers around SWNTs in an HF solution.

An effective catalyst carrier SiO_(2):Enhancing catalytic and combustion properties of CuFe_(2)O_(4)on energetic components

To enhance the catalytic activity of copper ferrite(CuFe_(2)O_(4))nanoparticle and promote its application as combustion catalyst,a low-cost silicon dioxide(SiO_(2))carrier was employed to construct a novel CuFe_(2)O_(4)/SiO_(2)binary composites via solvothermal method.The phase structure,morphology and catalytic activity of CuFe_(2)O_(4)/SiO_(2)composites were studied firstly,and thermal decomposition,combustion and safety performance of ammonium perchlorate(AP)and 1,3,5-trinitroperhydro-1,3,5-triazine(RDX)with it affecting were then systematically analyzed.The results show that CuFe_(2)O_(4)/SiO_(2)composite can remarkably either advance the decomposition peak temperature of AP and RDX,or reduce the apparent activation energy at their main decomposition zone.Moreover,the flame propagation rate of RDX was promoted by about 2.73 times with SiO_(2)content of 3 wt%,and safety property of energetic component was also improved greatly,in which depressing the electrostatic discharge sensitivity of pure RDX by about 1.89 times.In addition,the effective range of SiO_(2)carrier content in the binary catalyst is found to be 3 to 5 wt%.Therefore,SiO_(2)opens a new insight on the design of combustion catalyst carrier and will promote the application of CuFe_(2)O_(4)catalyst in solid propellant.

Performance and Emission Characteristics of a CRDI Diesel Engine Fuelled by SiO_(2) Nanoparticle-Waste Fat Biodiesel Blends

This study investigates the use of waste fat biodiesel(WFB)from the leather industry as a substitute for diesel fuel.Specifically,it examines the diesel engine performance of WFB,a blend of WFB and diesel(B50),and different blends of WFB and silicon dioxide(SiO_(2))nanoparticles(B50SiO_(2)40,B50SiO_(2)80,and B50SiO_(2)120μg/g).The results indicate that the B50SiO_(2)120 blend increases brake thermal efficiency by 10.03%compared to pure biodiesel but falls 1.93%short of neat diesel.Furthermore,the B50SiO_(2)120 mixture reduces smoke,hydrocarbon,and carbon monoxide emissions by 31.87%,34.14%,and 43.97%respectively,compared to diesel.However,the B50SiO_(2)120 blend shows a 4.91%increase in nitrogen oxide emissions compared to diesel.

Desiliconization kinetics of nickeliferous laterite ores in molten sodium hydroxide system

A novel process was proposed for treating nickeliferous laterite ores with molten sodium hydroxide.The effect on silicon extraction caused by the factors,such as stirring speed,reaction temperature,particle size and NaOH-to-ore mass ratio,was investigated.The results show that increasing stirring speed,reaction temperature and NaOH-to-ore mass ratio while decreasing particle size increases silicon extraction rate.The desiliconization kinetics of nickeliferous laterite ores in molten sodium hydroxide system was described successfully by chemical reaction control model.The activation energy of the desiliconization process was found to be 44.01 kJ/mol,and the reaction rate based on a chemical reaction-controlled process can be expressed as:1-(1-α) 1/3 = 27.67exp[-44 010/(RT)]t.

Preparation of high-purity straight silicon nanowires by molten salt electrolysis

Silicon nanowires of high purity and regular morphology are of prime importance to ensure high specific capacities of lithium-ion batteries and reproducible electrode assembly process.Using nickel formate as a metal catalyst precursor,straight silicon nanowires(65–150 nm in diameter)were directly prepared by electrolysis from the Ni/SiO2 porous pellets with 0.8 wt%nickel content in molten CaCl2 at 900℃.Benefiting from their straight appearance and high purity,the silicon nanowires therefore offered an initial coulombic efficiency of 90.53% and specific capacity of 3377 m Ah/g.In addition,the silicon nanowire/carbon composite exhibited excellent cycle performance,retaining 90.38%of the initial capacity after 100 cycles.Whilst further study on the charge storage performance is still ongoing,these preliminary results demonstrate that nickel formate is an efficient and effective metal catalyst precursor for catalytic preparation of high purity straight silicon nanowires via the molten salt electrolysis,which is suitable for large-scale production.

New insights into the effects of silicon content on the oxidation process in silicon-containing steels

Simultaneous thermal analysis（STA） was used to investigate the effects of silicon content on the oxidation kinetics of silicon-containing steels under an atmosphere and heating procedures similar to those used in industrial reheating furnaces for the production of hot-rolled strips. Our results show that when the heating temperature was greater than the melting point of Fe2SiO4, the oxidation rates of steels with different silicon contents were the same; the total mass gain decreased with increasing silicon content, whereas it increased with increasing oxygen content. The oxidation rates for steels with different silicon contents were constant with respect to time under isothermal conditions. In addition, the starting oxidation temperature, the intense oxidation temperature, and the finishing oxidation temperature increased with increasing silicon content; the intense oxidation temperature had no correlation with the melting of Fe2SiO4. Moreover, the silicon distributed in two forms： as Fe2SiO4 at the interface between the innermost layer of oxide scale and the iron matrix, and as particles containing silicon in grains and grain boundaries in the iron matrix.

Possibilities and prospects for producing silumins with different silicon contents using amorphous microsilica

The main objective of this work is to research complex physical-chemical processes of Al(l)-SiO2 interface and develop a new technology for producing foundry silumins based on amorphous microsilica obtained from silicon production waste. Effective methods for producing hypoeutectic, eutectic, and hypereutectic silumins using amorphous microsilica were developed. Alloys with a silicon content of 7 wt.% were obtained by blowing preheated amorphous microsilica into the aluminum melt(t=900 ℃) along with the stream of argon followed by intense mixing. Alloys with a silicon content of 21 wt.% were manufactured by induction melting of a silicon-containing mixture(60% Si O2, 40%Al + 20%3 Na F·2 Al F3) subjected to the presintering when the amorphous microsilica was reduced to crystalline silicon. It is found that crystalline silicon, which is formed during the roasting of the tableted burden, is smoothly absorbed by the aluminum melt. Aluminum oxide, obtained during the redox reaction, dissolves in cryolite, after which aluminum and silicon are fused together and transferred to the melt. The calculation of the economic efficiency of producing silumins using amorphous microsilica demonstrates a quick project payback period, as well as a high level of its profitability.

Study of He-induced nano-cavities as sinks of oxygen for forming silicon-on-insulator

In the present work, a Cz-Silicon wafer is implanted with helium ions to produce a buried porous layer, and then thermally annealed in a dry oxygen atmosphere to make oxygen transport into the cavities. The formation of the buried oxide layer in the case of internal oxidation （ITOX） of the buried porous layer of cavities in the silicon sample is studied by positron beam annihilation （PBA）. The cavities are formed by 15 keV He implantation at a fluence of 2×10^16 cm^-2 and followed by thermal annealing at 673 K for 30 min in vacuum. The internal oxidation is carried out at temperatures ranging from 1073 to 1473 K for 2 h in a dry oxygen atmosphere. The layered structures evolved in the silicon are detected by using the PBA and the thicknesses of their layers and nature are also investigated. It is found that rather high temperatures must be chosen to establish a sufficient flux of oxygen into the cavity layer. On the other hand high temperatures lead to coarsening the cavities and removing the cavity layer finally.

Fabrication of Silicon Quantum Wires by Conventional Silicon Processing

Ultra fine silicon quantum wires with the Si/SiO2 heterointerface have been fabricated successfully by using reactive ion etching, anisotropic wet chemical etching and subsequent thermal oxidation. The cross-sectional image of scanning electron microscope shows the silicon quantum wires of high quality with the linewidth down to 20nm. The present method has many remarkable advantages, which is important to the study of low-dimension quantum physics and devices.