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Search Results: 1 - 10 of 3623 matches for " silicon sources. "
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Estudo e caracteriza??o da zeólita OFF Tipo T empregando diferentes fontes de silício
Caovilla, Alessandra;Rigo, Reus T.;Penha, Fábio G.;Pergher, Sibele B. C.;
Química Nova , 2009, DOI: 10.1590/S0100-40422009000700025
Abstract: offretite t zeolite was synthesized using different source of si (ludox as-30, ludox ls-30 and aerosil 200 degussa). the obtained materials were characterized by different complementary techniques: xrd, textural analysis by n2 adsorption, iv, sem and chemistry analysis. this zeolite has an intermediary structure between offretite and erionite zeolites. in all experiments offretite t phase was obtained. offretite phase presenting better crystalility are obtained in synthesis with stirring and employing aerosil as silicon source. this zeolite presents a potencial application as catalyst for hydroisodewaxing process.
Extratores de silício disponível em escórias e fertilizantes
Pereira, H. S.;Kornd?rfer, G. H.;Moura, W. F.;Corrêa, G. F.;
Revista Brasileira de Ciência do Solo , 2003, DOI: 10.1590/S0100-06832003000200007
Abstract: methods to quantify available silicon (si) in fertilizers and slags are not yet sufficiently trustworthy. in this study, si extracted from several sources was analyzed, using the extractors: na2co3 + nh4no3 in varying concentration, time of agitation and of reaction; water; hcl 0,5 mol dm-3; 50 g dm-3 of na2co3; 50 g dm-3 of citric acid; 0,5 mol dm-3 of acetic acid; acid cation exchange resin (amberlite irc-50, pk 6.1); and the leaching column method. a greenhouse experiment, where 125 kg ha-1 of total si from 12 different sources was applied on irrigated rice, was also conducted. for the determination of si, shaking duration was not essential, although 3 h of shaking entailed a statistically superior result. the concentrations of 10 + 16 g dm-3 and 30 + 48 g dm-3 of na2co3 + nh4no3 proved to be the most promising for si extraction. the smaller concentration (10 + 16 g dm-3) was therefore chosen to evaluate si sources in relation to settling time. all si sources increased solubility during the rest time period. the best correlation between si uptake by the rice plants and si detected in the various analyzed sources was found in the period between day 5 and 9. according to the results, extractor na2co3 + nh4no3 evaluates si in fertilizers adequately and can be used as method to determine the potential si release in the soil and its availability for plants. the most efficient source for si solubilization for rice was rhodia, followed by wollastonita, while the sources mb-4 and blast furnace slag provided less available si. the acid extractors were more efficient at extracting si from blast furnace slags and less efficient with wollastonita. water was the extractor that presented the lowest si recovery rate. the best correlation between si contents and uptake by the rice crop were achieved by the extractors resin amberlite and na2co3 10 g dm-3 + nh4no3 16 g dm-3, followed by the column-method.
Soluble tissue sugar content and leaf blast severity in response to the application of calcinated serpentinite as a silicon source in irrigated rice
Prabhu, Anne Sitarama;Santos, Alberto Baêta dos;Didonet, Agostinho Dirceu;
Summa Phytopathologica , 2007, DOI: 10.1590/S0100-54052007000400014
Abstract: a field experiment conducted with the irrigated rice cultivar brs formoso, to assess the efficiency of calcinated serpentinite as a silicon source on grain yield was utilized to study its effect on leaf blast severity and tissue sugar levels. the treatments consisted of five rates of calcinated serpentinite (0, 2, 4, 6, 8 mg.ha-1) incorporated into the soil prior to planting. the leaf blast severity was reduced at the rate of 2.96% per ton of calcinated serpentinite. the total tissue sugar content decreased significantly as the rates of serpentinite applied increased (r2 = 0.83). the relationship between the tissue sugar content and leaf blast severity was linear and positive (r2 = 0.81). the decrease in leaf blast severity with increased rates of calcinated serpentinite was also linear (r2= 0.96) and can be ascribed to reduced sugar level.
Preparation and kinetic analysis of Li4SiO4 sorbents with different silicon sources for high temperature CO2 capture
ShaoYun Shan,QingMing Jia,LiHong Jiang,QinChao Li,YaMing Wang,JinHui Peng
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-012-5188-x
Abstract: Using diatomite and analytical pure SiO2 as silicon sources, Li4SiO4 sorbents for high temperature CO2 capture were prepared through solid-state reaction method. Phase composition was analyzed by X-ray diffraction, and the CO2 absorption capacity and absorptoin-desorption performance were studied by the simultaneous thermal thermogravimetric analyzer (TG-DSC). The results showed that silicon source had an important influence on CO2 absorption properties. The kinetic parameters for the chemisorption and diffusion processes were obtained by the isothermal study for different silicon sources. The results showed that the activation energies for these two processes were estimated to be 105.427 and 35.928 kJ/mol for the sample with analytical pure SiO2 (AS). While for the sample with diatomite (DS), the activation energies for these two processes were estimated to be 78.500 and 20.439 kJ/mol, respectively.


红外与毫米波学报 , 1991,
Abstract: 用傅里叶红外吸收谱对不同热处理条件下的SOI样品进行了系统的分析,结果表明:对于190keV,1.8×10~(18)/cm~2N~+注入的样品,在低于1100℃的温度下退火可保持氮化硅埋层的无定形态,而~1200℃热退火则导致氮化硅埋层的结晶成核现象。对于200keV,1.8×10~(18)/cm~2O~+注入的样品,氧化硅埋层的形成是连续渐变的,注入的氧化硅埋层向常规的热氧化非晶态SiO_2转变的激活能为0.13eV。
The Effect of the MeV Si-Ion Irradiation on the Photoluminescence of Silicon Nanocrystals  [PDF]
Alejandra López-Suárez
World Journal of Condensed Matter Physics (WJCMP) , 2013, DOI: 10.4236/wjcmp.2013.32019

Silicon nanocrystals embedded in silicon nitride films were irradiated with Si-ions at 8 MeV in order to modify their optical response. The samples were characterized by means of Rutherford Backscattering Spectrometry, Elastic Recoil Detection Analysis, High-Resolution Transmission Electronic Microscopy and Photoluminescence analysis. It was found a blue-shift in the photoluminescence emission from the as-grown films after they were irradiated with high energetic silicon ions. According to the quantum confinement theory, this fact is related to a decrease in size of the silicon nanocrystals, which means that a higher silicon fluence irradiation is related with a diminishing in silicon nanocrystal size.

An Explorative Study on Major Stressors and Its Connection to Depression and Chronic Stress among German Elite Athletes  [PDF]
Insa Nixdorf, Raphael Frank, Jürgen Beckmann
Advances in Physical Education (APE) , 2015, DOI: 10.4236/ape.2015.54030
Abstract: Although research shows that chronic stress and specific stressful events (e.g. injury, failure) are associated with depressive symptoms in athletes, connections between chronic, major stressors and depressive symptoms are yet unknown. Therefore, the goal of the study was to gain new findings between major stressors and their relations to depressive symptoms and chronic stress. A total of 134 elite athletes provided data in an online survey. In addition to quantitative measurements (current depressive symptoms, and level of chronic stress), possible stressors were assessed qualitatively with an open ended question. By using content analysis to explore stressors, three different types of stressors were categorized: Double burden, sport specific demands, and conditions. Further statistical analysis found these stressors to be associated with dropout intentions, depression and chronic stress. Athletes, who reported sport specific demands (such as high training loads) as major stressors indicated higher levels of chronic stress and depressive symptoms than athletes without major stressors. Further research investigating sources of stress and its association to depressive syndromes in athletes could benefit from considering sport specific factors.
Assessment of Groundwater Quality in Central India  [PDF]
Shabya Choudhary, Shobhana Ramteke, Keshaw Prakash Rajhans, Pravin Kumar Sahu, Suryakant Chakradhari, Khageshwar Singh Patel, Laurent Matini
Journal of Water Resource and Protection (JWARP) , 2016, DOI: 10.4236/jwarp.2016.81002
Abstract: The groundwater is widely used for irrigation of rice crops. The overuse of groundwater causes depletion of the water quality (i.e. enormous increase in conductivity, hardness and ion and metal contents, etc.) in several regions of the country and world. In this work, the quality of the groundwater in the densestrice cropping area, Saraipali, Chhattisgarh, Central India is discussed. The water is sodic in nature with extremely high electrical conductivity. The mean concentration (n = 30) of F-, Cl-, NO3-, SO42-, NH4+, Na+, K+, Mg2+, Ca2+ and Fe in the water was 1.2 ± 0.2, 98 ± 31, 46 ± 15, 56 ± 9, 19 ± 4, 206 ± 25, 9.2 ± 2.3, 39 ± 6, 114 ± 19 and 1.7 ± 0.6 mg/L, respectively. The sources of the contaminants are apportioned by using the factor analysis model. The suitability of the groundwater for the drinking and irrigation purposes is assessed.
Comparison of Silicon Nitride Nanofibers Synthesized Using Silica Nanopowders and Silica Gel  [PDF]
Sanket Deshmukh, Kei-Peng Jen, Sridhar Santhanam
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.38074
Abstract: Nanofibers of alpha silicon nitride were grown by a vapor-solid mechanism at 1450?C, through the carbothermal reduction process. Two different precursor silica sources were used: silica nanopowders and silica gel. The effect of processing geometry, particularly the stacking orientations of the graphite substrates, silica pellets, and crucibles, on the density of nanofiber growth was also explored. The silicon nitride nanofibers appear with a predominantly rectangular cross section from silica nanopowder precursors and with a circular cross section for silica gel precursors. Silica gel precursors produce nanofiber products that are smaller in cross section but greater in length than the products from silica nanopowder precursors. The processing geometry must be suitably designed such that the vapor-solid mechanism that is responsible for the formation of the nanofibers is not disrupted.
Porous Silicon as Soft Material in Low-Frequency MEMS (MicroElectro-Mechanical Systems) Resonators  [PDF]
C. Malhaire, A. Danescu, V. Lysenko, A. Sabac
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.811031
Abstract: This study focuses on the mechanical response of silicon on porous silicon bilayer cantilevers ended with a seismic mass. The porous silicon is intended to provide an alternative to decrease the cantilever stiffness for low-frequency MEMS applications. The first eigenfrequency of the cantilever is obtained using static deflection obtained under classical Euler-Bernoulli assumptions and Rayleigh method. In order to estimate the errors due to small-strain approximation and Euler-Bernoulli theory, the analytical results were validated through 3D finite element simulations for different cantilever geometries and porosities. Both bulk silicon and silicon on porous silicon bilayer cantilevers ended with a seismic mass were fabricated and we measured the first eigenfrequency (f0) and quality factor (Q) by using a laser Doppler vibrometer. In agreement with the theoretical predictions we found that, when compared to bulk silicon cantilevers, the first eigenfrequency of a bilayer cantilever containing 6% porous silicon (at 50% porosity) on 94% bulk silicon is lowered by 5%, from (5447 ± 120) Hz to 5198 Hz. This decrease is also accompanied by a reduction of the quality factor by two.
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