This paper discussed impact of temperature on the size distribution in preparing ultrafine silica from rice husk.The samples prepared were analyzed with infrared spectrum,and the relation between the particle size and...This paper discussed impact of temperature on the size distribution in preparing ultrafine silica from rice husk.The samples prepared were analyzed with infrared spectrum,and the relation between the particle size and intensity of characteristic absorption peak of IR at center around 1 100 cm-1 was disscussed with the baseline method.Results show that when the temperature is 650 ℃ and roasting time is 11 h,at optimal reaction conditions,the size distribution of the ultrafine silica powder prepared is relatively concentrated,and the average particle size is 199.5 nm.Moreover,the characteristic absorption band of IR is broadening gradually along with particle size decreasing.展开更多
首先对羰基铁进行点腐蚀得到多孔羰基铁,然后采用St?ber法和原位聚合法将SiO_2和导电高分子聚吡咯包覆在多孔羰基铁表面,制备多孔羰基铁/SiO_2/聚吡咯电磁复合吸波材料。采用XRD、SEM、TEM、FT-IR对样品结构、微观形貌进行了表征,在网...首先对羰基铁进行点腐蚀得到多孔羰基铁,然后采用St?ber法和原位聚合法将SiO_2和导电高分子聚吡咯包覆在多孔羰基铁表面,制备多孔羰基铁/SiO_2/聚吡咯电磁复合吸波材料。采用XRD、SEM、TEM、FT-IR对样品结构、微观形貌进行了表征,在网络分析仪中采用同轴法测试样品电磁参数,并根据传输线理论研究了2~18 GHz微波频段内吡咯含量及涂层厚度对样品吸波性能的影响。实验结果表明:制备的多孔羰基铁/SiO_2/聚吡咯复合电磁吸波材料具有核壳结构;随着吡咯加入量的增加,吸波材料吸收峰逐渐向低频方向移动;当涂层厚度为3.5 mm、吡咯加入量为6%(w/w)时,在9.44~17.56 GHz范围内反射率均低于-10 d B,频带宽度为8.12 GHz,损耗反射率达到-23 d B。良好的吸波性能归因于复合物有效的阻抗匹配特性及多重界面极化效应,多孔羰基铁/SiO_2/聚吡咯是一种轻质、宽频、强吸收的吸波材料。展开更多
The SiO2/TiO2 composite powders including mineral tourmaline powders (T/SiO2/TiO2) were prepared from a sol made by a two-step hydrolysis method, using metasilicate ester as precursor. The powders were characterized b...The SiO2/TiO2 composite powders including mineral tourmaline powders (T/SiO2/TiO2) were prepared from a sol made by a two-step hydrolysis method, using metasilicate ester as precursor. The powders were characterized by scanning electron microscopy (SEM). The photocatalytic activity of the sample was evaluated by the photocatalytic degradation of methyl orange. The effects of heat-treatment on the photocatalytic activity were discussed. It is found that the T/SiO2/TiO2 composite powders show higher photocatalytic activity when including 10% SiO2 and 4% tourmaline. Moreover, the photocatalytic mechanism of tourmaline on the powders was proposed.展开更多
Under certain conditions of proper temperature and pH value, sodium silicate was hydrolyzed in liquid ammonia chloride, and spherical microfine SiO2 powder in micrometer-size was prepared. In this experiment, the rela...Under certain conditions of proper temperature and pH value, sodium silicate was hydrolyzed in liquid ammonia chloride, and spherical microfine SiO2 powder in micrometer-size was prepared. In this experiment, the relationship between needed time and proper pH value, temperature, density of the solution, and its current capacity were found .The optimum conditions are pH 8.5, 70 ~C, and the concentration of sodium silicate is 0.6 mol/L for the density of the solution. The structure of spherical microfine silicon was characterized by SEM and XRD.展开更多
The purpose of the present research is the different morphologies production of crystalline and amorphous-silica powder. It’s a basic material for many pharmaceutical and environmental applications as well. And, it’...The purpose of the present research is the different morphologies production of crystalline and amorphous-silica powder. It’s a basic material for many pharmaceutical and environmental applications as well. And, it’s produced using the combination of the alkali chemical etching process and the ultra-sonication technique. The critical preparation conditions are KOH concentration (weight %) and the sonication time (hour). The paper presents the chemical mechanism of the silica particle formation as well as the different morphology. The results show the formation of crystalline and amorphous-porous-silica particles in the micrometer range with the porous order network that has pore sizes range in micrometer too. This synthetic uses commercial silicon, which could be useful for large-scale production. Also, the nano-sphere and nano-cubic shapes of silica powder are formed starting by commercial silicon powder.展开更多
文摘This paper discussed impact of temperature on the size distribution in preparing ultrafine silica from rice husk.The samples prepared were analyzed with infrared spectrum,and the relation between the particle size and intensity of characteristic absorption peak of IR at center around 1 100 cm-1 was disscussed with the baseline method.Results show that when the temperature is 650 ℃ and roasting time is 11 h,at optimal reaction conditions,the size distribution of the ultrafine silica powder prepared is relatively concentrated,and the average particle size is 199.5 nm.Moreover,the characteristic absorption band of IR is broadening gradually along with particle size decreasing.
文摘首先对羰基铁进行点腐蚀得到多孔羰基铁,然后采用St?ber法和原位聚合法将SiO_2和导电高分子聚吡咯包覆在多孔羰基铁表面,制备多孔羰基铁/SiO_2/聚吡咯电磁复合吸波材料。采用XRD、SEM、TEM、FT-IR对样品结构、微观形貌进行了表征,在网络分析仪中采用同轴法测试样品电磁参数,并根据传输线理论研究了2~18 GHz微波频段内吡咯含量及涂层厚度对样品吸波性能的影响。实验结果表明:制备的多孔羰基铁/SiO_2/聚吡咯复合电磁吸波材料具有核壳结构;随着吡咯加入量的增加,吸波材料吸收峰逐渐向低频方向移动;当涂层厚度为3.5 mm、吡咯加入量为6%(w/w)时,在9.44~17.56 GHz范围内反射率均低于-10 d B,频带宽度为8.12 GHz,损耗反射率达到-23 d B。良好的吸波性能归因于复合物有效的阻抗匹配特性及多重界面极化效应,多孔羰基铁/SiO_2/聚吡咯是一种轻质、宽频、强吸收的吸波材料。
基金Project(E2004000033) supported by the Natural Science Foundation of Hebei Province, China
文摘The SiO2/TiO2 composite powders including mineral tourmaline powders (T/SiO2/TiO2) were prepared from a sol made by a two-step hydrolysis method, using metasilicate ester as precursor. The powders were characterized by scanning electron microscopy (SEM). The photocatalytic activity of the sample was evaluated by the photocatalytic degradation of methyl orange. The effects of heat-treatment on the photocatalytic activity were discussed. It is found that the T/SiO2/TiO2 composite powders show higher photocatalytic activity when including 10% SiO2 and 4% tourmaline. Moreover, the photocatalytic mechanism of tourmaline on the powders was proposed.
基金the National Innovation Foundation of China (No. 04C26225120227)
文摘Under certain conditions of proper temperature and pH value, sodium silicate was hydrolyzed in liquid ammonia chloride, and spherical microfine SiO2 powder in micrometer-size was prepared. In this experiment, the relationship between needed time and proper pH value, temperature, density of the solution, and its current capacity were found .The optimum conditions are pH 8.5, 70 ~C, and the concentration of sodium silicate is 0.6 mol/L for the density of the solution. The structure of spherical microfine silicon was characterized by SEM and XRD.
文摘The purpose of the present research is the different morphologies production of crystalline and amorphous-silica powder. It’s a basic material for many pharmaceutical and environmental applications as well. And, it’s produced using the combination of the alkali chemical etching process and the ultra-sonication technique. The critical preparation conditions are KOH concentration (weight %) and the sonication time (hour). The paper presents the chemical mechanism of the silica particle formation as well as the different morphology. The results show the formation of crystalline and amorphous-porous-silica particles in the micrometer range with the porous order network that has pore sizes range in micrometer too. This synthetic uses commercial silicon, which could be useful for large-scale production. Also, the nano-sphere and nano-cubic shapes of silica powder are formed starting by commercial silicon powder.
