Studies various factors effecting the synthesis of submicron silicon dioxide particles by leaching from waste dumps of the Balaklavskoe deposit

The paper presents the results of studies of the main parameters of synthesis of silicon dioxide powder from Balaklava deposit sludge with silicon dioxide content of 24%. During the study caustic soda solution is used as a leaching agent and sulfuric acid was used as a precipitant. At the leaching stage the concentration of leaching agent, the ratio of liquid phase to solid phase, the optimum temperature of leaching as well as the mode of pulp agitation are investigated. At the precipitation stage, the following parameters are considered: concentration of precipitating agent and temperature of the precipitation process. As a result of using the optimal parameters the high efficiency of obtaining silica powder of 98.56% is achieved. Average particle size is 200-800 nm, and agglomerate size is more than 800 nm.

Study of Thermal and Mechanical Properties of LLDPE/Sugarcane bagasse/Eggshell Hybrid Biocomposites

Thermal and mechanical properties of neat linear low-density polyethylene (LLDPE) hybrid biocomposite with sugarcane bagasse and eggshell as a reinforcing filler were investigated. Hybrid biocomposites with sugarcane bagasse/eggshell was varied in the range of 6/4, 12/8, 17/13, 20/20, 13/17, 8/12, and 4/6 wt.%, were prepared and examined. The sugarcane bagasse fiber (Sb) was surface-treated using a silane coupling agent (3-(trimethoxysilyl) propyl methacrylate) and eggshell (Es) was treated using titanium (IV) isopropoxide. The results showed that high calcium oxide content was 99 % by weight in eggshell and silicon dioxide content was 50 % by weight in sugarcane bagasse. The tensile and flexural modulus and hardness of the composites with treated Sb/Es were higher than that of the untreated. These values of the LLDPE/Sb/Es composites increased with Sb/Es content. Differential scanning calorimetry (DSC) results show interesting trends in term of the influence of Sb/Es content, both with untreated and treated Sb/Es on the crystallization behavior of the composites but the melting and cold crystallization temperature of its composites did not obviously change. Thermogravimetric analysis (TGA) indicated their thermal stability of the composites, both untreated and surface-treated Sb/Es were lower than that of neat LLDPE. The sample molded from the biocomposite with surface-treated Sb/Es particles showed better dispersion of the materials inside.

Sintering, Microstructure and Dielectric Properties of Ca-Al-B-Si-O Glass/Al2O3 Composites with Various SiO2 Content

The effects of silicon dioxide addition on the sintering, microstructure and microwave dielectric properties of Ca-Al-B-Si-O glass/Al2O3 composites were investigated. Results show that: Increasing the silicon dioxide content in the glass leads to the corresponding rise of bulk density, dielectric constant of the LTCC materials and the decrease of its dielectric loss and porosity. A bulk density of 2.92 g·cm-3, a porosity of 0.2%, aεr value of 7.11 and a tan δ value of 0.00096(measured at 10 MHz) are obtained for 68 wt% silicon dioxide of the samples sintered at 875°C for 30 min.

Preparation and Properties of High-Density Polyethylene/Silica Composites

High-density polyethylene (HDPE)/silica composites with different silicon dioxide fraction were prepared by the melting blend method. The effects of silicon dioxide content on the thermal properties and mechanical properties were mainly investigated. The results show that the thermal degradation of the composites shifts towards higher temperatures as the concentration of silicon dioxide is increased. With increasing silica dioxide content, the tension yield strength of HDPE/silicon composites increased, but its breaking elongation decreased. When silicon dioxide content is 5 %, the tension yield strength and its breaking elongation are 29.33 MPa and 102.82 %, respectively.