Papers by Keyword: Wollastonite

Abstract: Studies have shown that using nonferrous metallurgy waste in the ceramic mixture for the making of roof tiles improves the final product quality; one can use the clayey portion of the zircon-ilmenite ore gravity tailings as the clay, pyrite cinders as leaners and sintering intensifier, and wollastonite as an agent to reduce shrinkage and prevent deformation-related buckling. The common method of linear regression was used to study the dependency of the basic physico-mechanical properties of tiles on how much clay from the zircon-ilmenite ore gravity tailings, pyrite cinders, and wollastonite is used in manufacture. The resultant mathematical model takes into account the combined effects these components have on the physico-mechanical properties of tiles; it matches well the experimental data.

Abstract: Micro-fillers based on natural mineral wollastonite, modifying fine-grained concrete and improving its physical and mechanical characteristics, are developed and studied. The influence of the most common stabilizers on the aggregate stability of wollastonite-based microdispersed systems in the aquatic dispersion environment is considered. The optimal parameters, ensuring the production of micro-fillers in the form of stable suspensions, are developed. The application efficiency of the wollastonite-based filler due to its micro-reinforcing properties is revealed. These properties are specified by the formation of needle-shaped crystals by the ultrasonic dispersion in the aquatic environment, chemically related to cement-containing raw materials and contributing to the active selective adsorption of the binder hydration products. It has a significant influence on the rheological parameters of cement composites, on structure formation, as well as on their strength and deformation properties.

Abstract: The paper presents the results of the study dealing with improving the physical and mechanical properties of building ceramics samples: mean density, compressive strength, wear resistance, impact resistance, water absorption, thermal conductivity coefficient, and frost resistance. In the study the organic-mineral additive based on industrial wollastonite with the superplasticizer S-3 was used. The most functional amount of the applied additive, as well as the optimal volume of water in the molding mixture and the firing temperature were determined with the method of experiment mathematical planning. In the course of the studies the specifics of the organic-mineral additive influence on the properties and structure of building ceramics are revealed. The findings are attested by electron microscopy data. The application of the organic-mineral additive improves the performance characteristics of building ceramics samples.

Abstract: The effective highly-dispersed additive on the basis of the natural mineral wollastonite has been developed and studied. It enables obtaining fine concrete with the bending strength of up to 21.6 MPa and the strength of compression of up to 55 MPa, and the content of 0.5% (in terms of dry matter). The additive is a suspension of wollastonite after mechanical, and then ultrasonic processing in the aquatic environment of the anionic stabilizer of naphthalene-formaldehyde type. Due to the laser granulometry it has been ascertained that grinding wollastonite together with the anionic stabilizer leads to a change in the specific surface from 20 400 to 32 600 cm²/cm³ and to forming the particles with a modal diameter of 10.31 μm. After ultrasonic processing in the aquatic stabilizer environment the wollastonite particle size reduces to 0.4 μm. The positive heat and humidity effect on the structure and strength of the concrete with highly-dispersed wollastonite-based additive under the mode 3+4+3 h at the isothermal hardening temperature of 80^оС is shown. The application of the developed additive in the fine concrete composition makes it possible to save up to 15% of cement due to the strength increase.

Abstract: Two different approaches are proposed in this study to enhance the bioactivity of hydroxyapatite-based scaffolds for bone tissue regeneration. The first method consists in a structural modification of Hydroxyapatite (HA) through doping it with Magnesium (1,3% wt) while the second one in using HA in combination with a calcium silicate, i.e. Wollastonite (WS), to form a composite bioceramic. Scaffolds with high and strongly interconnected porosity (pores ranging from 300 to 800 µm) were produced throughout both procedures. Higher mechanical properties in compression were obtained when the composite Ws/HA bioceramic was adopted. That one showed a weight loss after 6 months in physiological solution seven times higher than doped HA. Preliminary in vitro tests highlighted that both kinds of scaffold allowed the adhesion of MG63, without significant differences in terms of vitality, indicating a good biocompatibility of both used biomaterials.

Abstract: Mortar can be defined as a material which is used to hold building blocks that include bricks, stone or concrete together. In this paper, a special type of mortar which is mixed with Wollastonite and also micro-silica is considered and the goal was predicting the compressive strength of mortar in terms of artificial neural networks. For this purpose, the input parameters were assumed to be: the weight of microsilica, wollastonite, ordinary Portland cement, high-range water reducer, and also age of the mortar. Finally based on a sensitivity analysis, the relative importance of input parameters were determined.

Abstract: This paper focuses on the carbonation of non-hydraulic binders based primarily on wollastonite (CaSiO₃) in order to study the relationship between clinker composition, curing conditions and compaction on carbonation reaction rate. Decoupled carbonation and drying experiments are carried out using cements at different CaO/SiO₂ ratio, at 60 °C, 1 bar of CO₂ and multiple RH (relative humidity) and compaction degrees. Solid analysis include mass gain or loss, TGA, XRF and Carbon/Hydrogen (CH) to determine respectively the bound H₂O content, CO₂ content and the mineralogical assemblage. Relative humidity strongly influences carbonation intrinsic reaction rate, while compaction seems to be a second order mechanism. Testing procedure can be used to discriminate the reactivity of clinkers with various initial phase assemblage.

Abstract: In the ceramic industry, color is of great importance to product development. Parameters such as hue, brightness and color intensity influence the visual appearance of the ceramic surface and its market value. Research on the development of new pigments is ongoing, with focus on cost reduction, environmental suitability and color innovation. Different studies have shown the feasibility of using industrial by-products to obtain pigments. Many of these waste products have calcium carbonate and nickel oxides in their composition. This study investigates the synthesis of ceramic pigment with the structure of wollastonite - CaSiO₃, with the use of nickel as chromophore ion. In order to evaluate the effect of adding nickel to the formation of crystalline phases X-ray diffraction was used. Particle size analysis was performed by Laser diffraction technique and a colorimetric study was conducted through the analysis of the pigment applied to a commercial enamel, by determining colorimetric parameters L*, a* and b*. The results showed that wollastonite combined with nickel acts as pigment and that its presence may interfere with the performance of new pigments depending on the nickel content and synthesis temperature.

Abstract: Investigations of wollastonite and calcium phosphate biocoatings with Zn-and Cu-incorporation produced by a microarc oxidation method were presented. Dependences of coating properties on the microarc oxidation parameters were revealed. A variation of the process parameters allowed us to produce wollastonite-calcium phosphate coatings with a plate-like structure, thickness of 25–30 μm, roughness of 2.5–5.0 μm, and enhanced strength properties. Coatings based on substituted hydroxyapatite deposited under voltages of 200–250 V have an X-ray amorphous structure. An increase of oxidation voltage to 300 V leads to the formation of crystalline phases in the coating, such as CaHPO₄ and β-Ca₂P₂O₇. The maximum content of 0.4 at% zinc and 0.1 at% copper was obtained for coatings based on Zn-and Cu-substituted hydroxyapatites, consequently, deposited under oxidation voltage of 250 V.

Abstract: Naturally occurring volcanic glass in the form of the expanded perlite consist of 72.59wt% silica was used as a starting material together with the calcined eggshell in order to explore the wollastonite formation via solid state reaction. The molar mixing ratios of CaO:SiO₂ were carried out from 1:0.8 to 1:1.4, calcined in the range of 600 - 1100°C for 2 - 5 hours. The XRD results confirm the formation of wollastonite (CaSiO₃) started at 800°C, and increasing of calcination temperature favoured the formation of gelehnite (Ca₂Al₂SiO₇) associated with wollastonite. The morphology characterized by SEM clearly show tiny needle-like shape of primary wollastonite on the surface of agglomerate particles. The CaO:SiO₂ ratio of 1:1.4 which calcined at 1100 °C for 2-5 hours was found to be the most appropriate molar ratio in the case of using the calcined eggshell and expanded perlite as starting materials.