Preparation And Crystallization Kinetics Of Magnesium Hydroxide Sulfate Hydrate Nanowires

Nanowires have attracted great interests because of their unique one-dimensional structures,good assembly properties and unique physicochemical properties.Inorganic salt nanowires which are of high flexibility,multi-surface active sites and low cost can be used as adsorbents,filter materials and reinforcing and toughening materials in the fields such as machinery,textile,plastic and environmental protection etc.It is of great scientific significance and has potential application value to explore a simple method to prepare nanowire with high yield and low cost.Magnesium hydroxide sulfate hydrate?MOS?nanowires wre prepared by using magnesium sulfate and sodium hydroxide as the raw materials and potassium hydrogen phthalate?KHpht?as the complexing agent.The complexation and adsorption of KHpht and the crystallization kinetics of MOS nanowires were studied.The main contents include the following aspects.Influences of hydrothermal synthesis reaction conditions on morphology and structure of MOS nanowires were studied by single factor experiment.By analyzing the morphologies and structures of samples,the optimum synthesis conditions for MOS nanowires were obtained.Using anhydrous ethanol as the dispersant,the concentration of MgSO₄ was 0.3 mol/L,the molar ratios of KHpht to MgSO₄ and NaOH to MgSO₄ were 1.1 and 2.5,respectively,at the hydrothermal reaction temperature of 160°C for 10 h.The as-synthesized MOS nanowires have uniform morphology and few impurities,with 20-100 nm diameters and 20-60?m lengths.The complexation of pht^2-with Mg²⁺was analyzed by potentiometric titration and the adsorption effect of pht^2-was studied through instrumental analysis and characterization.The results show that the complexation reaction between pht^2-and Mg²⁺lower the concentration of dissociative Mg²⁺and the supersaturation of the system.The chemical bonding of Mg-pht exists on the surface of MOS crystals.Due to the different lattice arrangement of each crystal plane,the adsorption ratio of pht^2-on the lateral growth of MOS crystals was higher than that on the longitudinal growth plane.Therefore,the growth of a-axis and c-axis was inhibited and the growth of MOS nanocrystals along the b-axis is promoted consequently.The crystallization kinetics parameters of MOS nanowires were determined by MATLAB software combining with crystallization kinetics equation.According to several possible growth mechanism models,the kinetics models of low-temperature and high-temperature reaction were really different.The MA-1 kinetics models at140°C and 160°C shows that the multi-nucleus controlled crystal surface growth and MC-1 kinetics models at 180°C and 200°C reveals the linear controlled crystal surface growth.