Janina Setina

The use of shale ash in dry mix construction materials

The research was made to determine the use of shale ash usage in dry mix construction materials by replacing part of cement amount. Cement mortar ZM produced by SIA Sakret and two types of shale ashes from Narva Power plant (cyclone ash and electrostatic precipitator ash) were used. Fresh mortar properties, hardened mortar bulk density, thermal conductivity (?10, dry) (table value) were tested in mortar ZM samples and mortar samples in which 20% of the amount of cement was replaced by ash. Compressive strenght, frost resistance and resistance to sulphate salt solutions were checked. It was stated that the use of electrostatic precipitator ash had a little change of the material properties, but the cyclone ash significantly reduced the mechanical strength of the material.

Effect of Siliceous Pozzolanic Additives on the Hydration Process of Cement

The given study investigates the influence of pozzolanic admixtures both micro- and nanosize silica and biomass ashes on microstructure and properties of hydration process of cement paste. The investigations were carried out by - XRD, SEM and FTIR. Pozzolanic activity of the concrete admixtures strongly depends on their chemical composition, content of reactive silica as well as the specific surface area. The micro- and nanosilica pozzolanic additives demonstrated the higher values of pozzolanic activity. Those activate the process of mineralization and are acting both as the cementitious admixture as well as the fine filler.

Characterization of Iron Oxide Nanoparticles for Sol-Gel Dip-Coating Method Prepared Thin Films

The paper describes two methods of syntheses of iron oxides, microstructure and morphology of magnetite nanoparticles. Nanocomposite thin films of SiO2/Fe3O4 have been prepared with sol-gel dip coating technique: dip-coating from SiO2/Fe3O4 sol and encapsulation magnetite between two SiO2 layers. Structural and morphological characteristics of iron oxides particles and prepared film were analyzed by X-Ray Diffraction, SEM, FTIR, DTA, AFM. AFM topography of surface and measurements of roughness has shown that using iron oxide encapsulation between two SiO2 layers to provide the even distribution of iron oxide, results as high quality films with low Rq values 1.5 2.7 nm.

Amorphous Compositions for Production of Thick Films

The article gives an overview of suitability of three kinds of phosphorus-containing glass systems: phosphate, alumosilicate phosphate and fluorophosphate for production of thick-films. Amorphous compositions based on metaphosphate glasses characterize high electric resistivity, thermal expansion coefficients matching with substrate, appropriate viscosity-temperature relationship, and suitable chemical reactivity, that they can be applied in thick-film technology for screen printed resistors on alumina substrate as an alternative of lead borosilicate glasses. Alumosilicate phosphate glasses are the base for the wide range of glass-crystalline high temperature materials (operating up to 10000C) for sealing of the silicon chip in microelectronics. Perfect adhesion of glass ceramics with substrate (the transition zone 5-7.5 μm) is provided by the formation of chemical bond with the oxidized surface of silicon and by the occurrence of analogous structural elements on the silicon surface and in the glass-ceramics. Due to the unique optical properties, low melting temperature of fluorine containing borophosphate glasses (FBP) can be used as brazing material (optical glue) for SiO2 glass optical fiber construction knots.

Correlation of Surface Characteristics and Thermal Conductivity of High Silica Glass Fibre Materials

The new generation of high silica materials with high thermal resistance was created by leaching of chopped glass fibre. These materials with low thermal conductivity are inert to the majority of chemical reagents, resistant to organic and mineral acids, weak alkali, water and highpressure steam. High silica chopped strand mats are non-woven fabrics designed for using in a wide range of insulation and protection applications at temperature till 11000C. The technology and quality of leaching process of initial Si-Al-Na glass widely depends on quality of fibre surface characteristics, i.e., roughness of surface of glass filaments. The surface roughness of the fibre before leaching is a function of chemical durability, therefore it depend on content of Al2O3. The thermal conductivity (within 20…10000C) of chopped strand mats directly depends on the surface roughness. The morphology and compositional profiles of surface of glass fibre before and after leaching were investigated using AFM, SEM, X-ray microanalysis and X-ray powder diffractometer. The different defects for fibre with content of Al2O3 <2.5% and high roughness namely cracking and crystalline deposits of Na2SO4 on top and into pores of fiber after leaching have been identified. The presence of sodium ions on surface of fibre decreases the heat insulation properties of mats. The structure of glass filaments surface was investigated in order to clarify the influence of surface characteristics on thermal conductivity of high silica glass fibre non-woven fabrics.

Preparation of Synthetic Cordierite by Solide-State-Reaction with Addition of Dolomite

Cordierite was obtained from the mixture of aluminum hydroxide, sand, different magnesium compounds by a solid-state reaction method. The effect of dolomite doping on phase-transformation kinetics and microstructure has been investigated during thermal treatment by keeping a stoichiometric cordierite compound. Adding of dolomite has been used as a flux for preparation of a cordierite precursor by a coprecipitation process. Subsequently, DTA and XRD analyses were conducted to identify the phases formed in the sintered products. Morphological changes of the ground mixtures and sintered product were observed using SEM. The crystallization process of metastable quartz like μ-cordierite can be obtained at 1250…13000C. In this range of temperature form other compounds, such as spinel, quartz. Increase of sintering temperature and prolonged holding times promote the formation of only one phase – indialite or α-cordierite, the hexagonal form of cordierite. Experimental observation shows two steps in the solid-state reaction. First step – formation of volatiles compounds and pores, second – formation and growing of crystalline phases. Evolution of CO, CO2 and H2O that occurred during the thermal treatment of compositions is very important fact in the nucleation process. The intensity of crystallization depends on the gas volume and amount of pore in the sample. The experiments indicated that the intrinsic concentration of volatiles like CO, CO2, H2O influence the appearance of the cordierite phase. SEM photographs sowed that crystallization of cordierite start on the surface of pore. Growth of α-cordierite inside of pores is considerably affected by the time of thermal treatment and amount of adding of dolomite. A remarkable change in peak intensity of XRD patterns of the compositions was observed. Up to 20 wt. % addition of dolomite to the precursor allowed the fabrication of synthetic cordierite at lower temperature.

Easily melting glass for assembly of optical fiber into connectors

The easily melting fluorine containing borophosphate glasses for construction knots have been obtained and investigated. The unique optical properties i.e. low refractive index - nD equals 1.41-1.45, wide spectral transparency region from 200 to 2000 nm as well as extended temperature application range from - 70 to +300 degree(s)C, thermostability and mechanical properties determine possibility to use fluorine containing borophosphate glass as optical glue. The process of structure formation within temperature range 20-1000 degree(s)C has been investigated in details. It has been determined by IR and X-ray methods that the development of glass network begins with decomposition of components at 500 degree(s)C with further formation of glass elements within temperature range 625-675 degree(s)C. The stable glassforming area is determined by P-O-B groups. The role of fluorine in structure development depends on its depolymerizator behavior, on the other hand it has some glassforming ability. Latter is based on ability of fluorine to move from boron to phosphorus coordination sphere. For the compositions under research the formation of monofluorophosphate groups at higher temperatures have been determined. The ratio P:B equals 1, 2:2 defines obtaining of stable glass without devitrification within the temperature range from 300 to 700 degree(s)C. The interfacial processes between fluorine containing melts and quartz fiber have been investigated.