Phase Analysis of the Binary System of Cryolite (Na3AlF6) and Sodium Metasilicate (Na2SiO3)

The phase analysis of cryolite (Na₃AlF₆) and sodium metasilicate (Na₂SiO₃) was performed by thermal analysis. The eutectic system with a region of two immiscible substances at a concentration of Na₂SiO₃ between 42.8 and 46.3 mol‐% was identified and the eutectic temperature determined to (886±2) °C. Based on the results of mass‐loss measurements, it was assumed that the introduced Na₂SiO₃ reacts with Na₃AlF₆ due to the formation of some nonvolatile stable compounds. The stable reaction products were identified by X‐ray diffraction analysis and IR spectroscopy of the spontaneously cooled samples, which established the formation of NaF and stable amorphous aluminosilicate compounds.     

Effect of sodium metasilicate on natural flotability of coal

The effect of the quantity of sodium metasilicate and conditioning time in one set of experiments, and the effect of the solution concentration of sodium metasilicate, added at the same dosage and conditioning time to coal slurry, on flotability of a typical Indian coal in another set of experiments are studied. Two sets of 3² full factorial experiments are carried out to assess the effects of the aforementioned variables. The generated data are analyzed quantitatively and explained qualitatively. At 0.1% (w/v) solution concentration of solution added (0.02 g/kg) and 8 min conditioning time, sodium metasilicate acted as activator for kaolinite, whereas at 1.0% (w/v) solution concentration (0.2 g/kg), it acted as dispersant. The best observed condition of depressant is obtained at an added concentration of 10.0% (w/v, 0.2 g/kg) and 8 min conditioning time. The desired effect of the sodium metasilicate can be achieved by controlling its quantity, solution concentration added, and conditioning time.     

橙红色荧光粉Ca_(1-x-y)Sm_xBi_ySiO_3的制备及其发光性能

以Sm3+作为激活剂,Bi3+作为辅助激活剂,采用水热法合成Ca1-x-ySmxBiySi O3前驱体,然后在1 100℃焙烧得到系列橙红色荧光粉。用X-射线衍射仪、扫描电镜和荧光分光光度计和傅里叶变换红外光谱等手段对样品的组成、结构和形貌及其发光性质进行分析和表征。分析结果表明:产物都为三斜晶系结构的Ca1-x-ySmxBiySi O3和四方结构的方石英Si O2共熔体。在405 nm近紫外光激发下,产物的发射光谱由3个峰组成,发射峰值位于566、606和650 nm处,分别归属于Sm3+的4G5/2→6HJ/2(J=5,7,9)跃迁。产物的激发光谱在405 nm有很强的发射带,与近紫外LED芯片匹配。随着Sm3+掺量的增加,样品发光强度先增强后减弱,当Sm3+的物质的量分数为3%时发光强度达到最大,浓度猝灭机理为电偶极-电偶极相互作用。当Bi3+的物质的量分数在0.3%~1.5%时,对产物Ca0.97Sm0.03Si O3的荧光强度起敏化作用。Sm3+和Bi3+的最佳物质的量分数分别为3%和0.5%。     

A Novel White Light Emitting Long-lasting Phosphor

A novel white light emitting long-lasting phosphor Cd1-xDyxSiO3 is reported in this letterThe Dy^3 doped CdSiO3 phosphor emits white light. The phosphorescence can be seen with the naked eye in the dark clearly even after the 254nm UV irradiation have been removed for about 30min. In the emission spectrum of 5% Dy^3 doped CdSiO3 phosphor, there are two emission peaks of Dy^3 , 580nm (^4F9/2→^6H13/2) and 486nm (^4F9/2→^6H15/2), as well as a broad band emission located at about 410nm. All the three emissions form a white light with CIE chromaticity coordinates x=0.3874, y=0.3760 and the color temperature is 4000 K under 254 nm excitation. It indicated that this phosphor is a promising new luminescent material for practice application.     

Electrostatic Filter Ash from Silane Production as Silicate Substitute in Zeolite Chemistry

This paper is a case study of complete substitution of sodium‐metasilicate in zeolite Na‐A synthesis by an electrostatic filter ash (FA) arising in high amounts during silane waste incineration process. The silicate abundant FA is a suitable material for reinsertion in zeolite chemistry. This is shown in the presented investigation by the development of a model reaction process at low temperatures (50–60 °C) and short times (1.5–4 h). The experiments were performed under addition of NaAlO₂ and variation of the alkalinity and the reaction period. Characterization and fine tuning of the process was mainly done by studying the kinetics of FA digestion and zeolite crystallization by XRD and chemical analyses (ICP‐OES) of solutions and solids. It could be shown that pure FA was mostly dissolved (98 %) in 8 M NaOH already after 1 h. Addition of NaAlO₂ and crystallization for further 60 min under optimized conditions at 50 °C yielded to a suitable product. It consists of zeolite Na‐A (92 % by mass) beside some hydrosodalite (8 % by mass). According to this low temperature short time process this study is a contribution for the development of energy efficient recycling solutions.     

Li2SiO3 fast microwave-assisted hydrothermal synthesis and evaluation of its water vapor and CO2 absorption properties

A series of lithium metasilicate (Li₂SiO₃) powder materials has been successfully synthesized by the microwave-assisted hydrothermal route using lithium hydroxide and tetraethyl-orthosilicate-derived sol precursors. Ceramic powders were obtained under hydrothermal conditions of autogenous pressure in the presence of a nonionic surfactant. The production of pure and well-crystallized Li₂SiO₃ using very short reaction times at low temperatures was shown by X-ray diffraction, scanning electron microscopy, and N₂ adsorption-desorption analyses. Synthesized Li₂SiO₃ particles were nanocrystalline and exhibited different morphologies and specific surface areas depending on the synthesis conditions. Additionally, the capability of selected Li₂SiO₃ samples to absorb H₂O and CO₂ was evaluated via thermogravimetric analyses by varying the temperature, carrier gas, and water vapor concentration. Li₂SiO₃ particles exhibited interesting textural and morphological characteristics that make them suitable for use as a CO₂ absorbent and which suggest that they also have the potential to be used in other applications.     

Surfactant-assisted hydrothermal crystallization of nanostructured lithium metasilicate (Li2SiO3) hollow spheres: II—Textural analysis and CO2-H2O sorption evaluation

In a previous work, the synthesis and structural-microstructural characterization of different nanocrystalline lithium metasilicate (Li₂SiO₃) samples were performed. Then, in this work, initially, a textural analysis was performed over the same samples. Li₂SiO₃ samples prepared with a non-ionic surfactant (TRITON X-114) presented the best textural properties. Therefore, this sample was selected to evaluate its water vapor (H₂O) and carbon dioxide (CO₂) sorption properties. Sorption experiments were performed at low temperatures (30-80 °C) in presence of water vapor using N₂ or CO₂ as carrier gases. Results clearly evidenced that CO₂ sorption on these materials is highly improved by H₂O vapor, and of course, textural properties enhanced the H₂O-CO₂ sorption efficiency, in comparison with the solid-state reference sample.     

Bi3+敏化的SrSiO3:Eu3+,Bi3+发光体的合成与发光

本文采用高温固相扩散法合成出一种新的发光体ＳｒＳｉＯ３：ｅＵ＾３＾＋，Ｂｉ＾３＾＋。研究了激活剂Ｅｕ＾３＾＋与敏化剂Ｂｉ＾３＾＋浓度变化与发光强度的关系。实验发现，组成为Ｓｒ０．８１７Ｌｉ０．０９１５ＳｉＯ３：Ｅｕ＾３＾＋０．０７５，Ｂｉ＾３＾＋的发光体其发光强度最大。给出了发光体ＳｒＳｉＯ３：Ｅｕ＾３＾＋，ＳｒＳｉＯ３：Ｅｕ＾３＾＋，Ｂｉ＾３＾＋的激发光谱与发光光谱；测定了发光体的Ｘ射线粉...     

橙红色荧光粉Ca1-x-ySmxBiySiO3的制备及其发光性能

以Sm³⁺作为激活剂,Bi³⁺作为辅助激活剂,采用水热法合成Ca_1-x-ySm_xBi_ySiO₃前驱体,然后在1 100 ℃焙烧得到系列橙红色荧光粉.用X-射线衍射仪、扫描电镜和荧光分光光度计和傅里叶变换红外光谱等手段对样品的组成、结构和形貌及其发光性质进行分析和表征.分析结果表明：产物都为三斜晶系结构的Ca_1-x-ySm_xBi_ySiO₃和四方结构的方石英SiO₂共熔体.在405 nm近紫外光激发下,产物的发射光谱由3个峰组成,发射峰值位于566、606和650 nm处,分别归属于Sm³⁺的⁴G_5/2→⁶H_J/2(J=5,7,9)跃迁.产物的激发光谱在405 nm有很强的发射带,与近紫外LED芯片匹配.随着Sm³⁺掺量的增加,样品发光强度先增强后减弱,当Sm³⁺的物质的量分数为3%时发光强度达到最大,浓度猝灭机理为电偶极-电偶极相互作用.当Bi³⁺的物质的量分数在0.3%~1.5%时,对产物Ca_0.97Sm_0.03SiO₃的荧光强度起敏化作用.Sm³⁺和Bi³⁺的最佳物质的量分数分别为3%和0.5%.     

偏硅酸镉的自激活发光

利用高温固相法合成了一种具有自激活发光行为的CdSiO3基质.对样品进行了X射线衍射分析和光谱分析.光谱分析结果表明,在偏硅酸镉的发射光谱中存在三个自激活发光峰,它们分别位于380,467和560nm处,另外,通过热释光谱技术讨论了偏硅酸镉中的缺陷及相关机理.在热释光谱中有两个明显的热释峰,分别位于448和563K,它们的陷阱深度分别为0 58和0 61eV,表明了在偏硅酸镉中存在着不同的陷阱,这些陷阱的存在导致了偏硅酸镉的自激活发光.