Papers by Keyword: Magnesium Carbonate

Abstract: The interaction of magnesium carbonate with polyphenylsiloxane under the conditions of mechanochemical activation with subsequent heating has been investigated. Based on the TGA and DTA data, it has been shown that, upon heating up to 420°C, the reaction proceeded completely with the release of carbon dioxide. The polymer was dissolved in DMFA and purified by repeated precipitation with water. The polymer yield was 64%. The residue insoluble in organic solvents has been obtained by evaporation of an aqueous solution. The composition and structure of the synthesis products have been analyzed by means of element analysis, IR spectroscopy, and diffractometry. It has been demonstrated that the fraction soluble in DMFA had a silicon-to-magnesium ratio equal to 4.2, while the fraction isolated from water had this ratio equal to 1.0. The IR and XRD data enabled one to conclude that, regardless of the different compositions, the structures of all fractions were similar and corresponded to mesomorphic layered polymers produced by the ion exchange method.

Abstract: The kinetics of crystallization of magnesium carbonate (nesquehonite) at room temperature (27°C) has been examined using an electrical conductivity method during process of nucleation. Magnesium carbonate hydrate from a reaction of magnesium chloride (MgCl₂) and sodium carbonate (Na₂CO₃) in supersaturated condition was analyzed. Variations of batch reactor experimental are magnesium chloride initial concentration (500-3.000 mg/L) and operating pH (8-14). In this paper, we studied the crystallization kinetics of magnesium carbonate via an electrical conductivity method, a concentration monitoring method. By monitoring electrical conductivity during the solution reaction process, changes in [Mg²⁺] can be measured and an induction period of nucleation could be determined. Crystal has been formed was confirmed with powder X-ray Diffractometer (XRD) analyses. The results show that magnesium carbonate is formed during operating condition pH 10 with magnesium chloride initial concentration 3.000 mg/L. The nucleation process of magnesium carbonate crystallization can be represented by second-order reaction equation with R² is 0.8. The induction period of magnesium carbonate crystallization is 50 second.

Abstract: The accelerated carbonation with different pressure steaming conditions was used to process the steel slag, so the slag could turn into a primary cementitious product with carbonation activity. XRD, FTIR, TG, N₂ absorption BET surface area analyzer and SEM were used to characterize the mineral and chemical compositions and microstructure of each sample before and after the carbonation. The results show that: the carbonation products with different morphologies are formed under different temperature conditions. The optimum temperature for the accelerated carbonation for processing the steel slag is selected to be 90 °C, which results in the compressive strength of 32.8 MPa. The BET specific surface area of the steel slag reduces after carbonation, the sample density increased after carbonation.

Abstract: Magnesium carbonate is important material used in certain industries. It is used as raw materials for drug making in pharmacy, as filler in painting industry, as raw material for magnesium metal making, as nutrient element in fertilizer, etc. Natural source of magnesium carbonate in Indonesia is mainly in the form of dolomite mineral. The larger deposit of dolomite in Indonesia is located in East Java. Through a series of unit process that consist of roasting, carbonation, and nucleation, the dolomite from East Java Indonesia has been converted into ultra fine grain magnesium carbonate. Since the process does not utilize harmful compound and does not produce harmful waste, it can be classified as environmental friendly process. Roasting process was operated at temperature range of 600 – 1000 °C. It is found that dolomite can be converted to magnesium and calcium oxide at this range of temperature. The mean particle size of magnesium carbonate obtained through this process is around 1.073 micron.

Abstract: In this study, magnesium removal through reaction of alkaline liquors and magnesium cation in liquors of laterite leaching was investigated. Basic magnesium carbonate and magnesium carbonate with high filtration properties were obtained at 70°C or above, whereas magnesium hydrate colloid existed in the products at temperatures below 70°C, resulting in the difficulty of product filtration. When the molar ratio of Na₂CO₃ to Mg²⁺ was 2.25:1, the reaction temperature was 90-100°C and the reaction time was 30min, nearly 100% magnesium was removed from liquors.

Abstract: As a novel material, Mg-based foam material not only has fantastic physical characteristics, such as low density, high specific surface area, high specific strength and stiffness, and good biocompatibility, but also has special functional properties, for example, electromagnetic wave shielding, vibration reduction, sound absorption, and so on. It can be widely applied to aeronautical and aerospace, military, shipbuilding, transportation, automotive and medical industries. Mg-based foam material was prepared by direct foaming in magnesium alloy liquid in this study, and the effect of technological parameters on the products, such as addition amount of and granularity of SiC particles and MgCO₃ particles, stirring temperature, stirring time, stirring velocity, foaming temperature and foaming time, was investigated. The aim of this research was to develop a new technology which could fabricate large scale Mg-based foam material in air condition. The results showed that variations of technological parameters may affect preparation of the foam materials in some extent and resulted in the changes of the products in apparent density, porosity and structural uniformity. The light weight Mg-based foam with homogeneous pores could be obtained by suitable combination of the technological parameters.

Abstract: Petaliform magnesium oxide nanomaterials were prepared by which the basic magnesium carbonate made from light burning powder of low grade magnesite were used as precursor. The XRD results indicated that aqueous magnesium carbonate changed to basic magnesium carbonate (4MgCO₃•Mg(OH)₂ •4H₂O) when heating temperature reached 95°C, the SEM confirmed that the morpholo_Zgy of basic magnesium carbonate (4MgCO₃•Mg(OH)₂•4H₂O) were petaliform, after calcinations the magnesium oxide with the same morphologies as precursors’ were obtained, simultaneously , the products with high activity (iodine value of 197mgI₂/g).

Abstract: Hollow carbon hemispheres (HCHs) were synthesized at 500 oC in the magnesium carbonate-metallic Li system with the help of CHBr3. The product was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM). XRD and electron diffraction (ED) pattern results showed that HCHs were graphite phase and polycrystalline. By FESEM and TEM observation, the diameters of the HCHs were in the range of 200-900 nm. The shell of the HCHs was single-layer and their thickness was about 31 nm. The formation mechanism of HCHs with the help of CHBr3 was discussed. Besides, the effect of reaction temperature and dosage of CHBr3 on the morphology of HCHs was studied.

Abstract: Magnesium carbonate precipitation by the reaction of MgCl₂ with Na₂CO₃, using sodium tartrate as an additive was studied. The effects of sodium tartrate concentration, reaction temperature, and stirring speed on the precipitation were investigated comprehensively. Scanning electron microscopy (SEM) and X-ray powder diffraction methods were used to characterize the carbonate precipitate products. Sodium tartrate concentration, reaction temperature, and stirring speed have significant effects on the morphology of the carbonate products. Sodium tartrate has an inhibitive effect on the precipitation. The product weight decreases with the increase in the amount of sodium tartrate added, and with the increase in reaction temperature, but is almost irrelevant to the stirring speed. The products obtained at 25 and 50°C were all identified as nesquehonite. The experimental results show that the use of an additive would be an effective method to adjust the morphology of magnesium carbonate.

Abstract: It is the easy and widely used way to make light calcium carbonate and magnesium carbonate from dolomite by carbonizing process. During this process, the dolomite is calcined at different temperature, from 700°C to 950°C to get the mixture including either calcium carbonate and magnesia or calcia and magnesia. Then the mixture is blended with water in different temperature from room temperature to 80°C. As a result, it is supposed to get calcium hydroxide and magnesium hydroxide, but XRD analysis reveals that it is not accord with the theory. Magnesium hydroxide can not be obtained during this reaction. After the carbonization process, the calcium carbonate and a kind of mixture which is composed with different crystal phase of Mg5(CO3)4(OH)2[H2O]4 have been produced, instead of magnesium carbonate. The magnesia is gotten when the mixture is calcined at 450~750°C.