Synthesis Of One-dimensional Magnesium Borate Nanomaterials

One-dimensional （1D） magnesium borate nanomaterial is an importantfunctional magnesium material. Because of its excellent physical and chemicalproperties, such as low weight, high elastic modulus and hardness, resistance tocorrosion, high temperature, good electrical insulating, etc., it is expected to have abroad application prospect. It could be used as composite reinforced materials,friction materials, insulation materials and heat-resistant materials, etc.Aiming to solve problems such as energy conservations, product performancesand application requirements, by using brine as a main raw material and employingthe hydrothermal precursor method, the preparation process of the precursor wasoptimized. And parameters which could affect the composition and morphology of theprecursor were investigated. Meanwhile, research about the effects of differentroasting conditions on the quality of1D magnesium borate nanomaterial wasperformed. Test methods, such as XRD, SEM, TG, FT-IR and nitrogen adsorptionisotherm were employed to characterize the chemical composition, morphology,thermal behavior and structural feature of the products. The main contents and resultswere shown as following:1. The1D precursor, basic magnesium borate, was prepared by using ahydrothermal method with brine, Na2B4O7·10H2O and NH3·H2O. The results showedthat the composition of the precursor was MgBO₂（OH）;2. The effects of operating parameters such as n（Mg）/n（B）, Mg2+concentration,pH value, hydrothermal temperature and hydrothermal time on the composition andmorphology of the precursors were investigated. The results showed that n（Mg）/n（B）and Mg2+concentration had great effect on the composition of the precursors, whereas the effect of hydrothermal time was little, and pH value and hydrothermal temperatureonly affected the morphology of the precursors;3. The optimized hydrothermal parameters were: without addition of anysurfactant the concentration of Mg2+, Na2B4O7·10H2O and NH3·H2O was1.80mol·L^-1,0.30mol·L^-1and6.30mol·L^-1, respectively. pH value was10, hydrothermaltemperature was190℃and hydrothermal time was10h. The precursor had gooddispersibility, with an aspect ratio of5^-15, a diameter about80nm, a length of0.4^-1.0μm;4. The effects of the calcination temperature and existence of the byproduct,inorganic salts, on the composition and morphology were investigated. Within thescope of the study, the results showed that the calcination temperature and thepresence of inorganic salts did not affect the crystal type and the composition of theproduct. And the morphology of product was gradually improved as the calcinationtemperature increased. When the calcination temperature rose to800°C, the aspectratio of the product did not continue to increase. The morphology of the product waswith a more uniform aspect ratio, and the BET specific surface area, pore volume andaverage pore diameter were reduced when the product was roasted with inorganicsalts;5. The optimized calcination condition was: without washing, calcinationtemperature was700℃.1D magnesium borate （Mg₂B₂O₅） nanomaterial with adiameter about80nm, a length of0.6^-1.0μm and an aspect ratio of10^-15wasobtained by the optimized calcination process due to the water loss. The product had asmall BET specific surface area (9.52m2·g^-1), pore volume (0.0513cm³·g^-1) andaverage pore diameter （17.15nm）;6. The indicators of the resin were proportional to the amount of fillers afteradding the modified materials into the resin, the the amount of fillers was0vol.%-30vol.%, respectively. Within the scope of the study, when the amount offillers was20vol.%, the resin had the highest compressive strength （79.764MPa） and compression modulus of elasticity （1.978GPa）, which increased by17%and53%,respectively.