1.Synthesis And Mechanism Of Copper Aluminum Borate Whiskers 2.Study Of Lithium Collaborative Exploitation From Jiezechaka And Longmucuo Salt-lakes Of Tibet

The inorganic whiskers were widely used in metal, ceramic and polymer matrix composite because of their high-strength. As a new kind of inorganic whisker, Cu2Al6B4O17 was hopeful to stengthen and toughen matrix, such as metal, ceramic or polymer. High-temperature flux method was used to synthesis Cu2Al6B4O17 whiskers in this paper. The technological conditions and growth mechanism of Cu2Al6B4O17 whisker were studied. The main results of these experiments are shown as follows:(1) Through single factor experiments, influencing factors and controls parameters of Cu2Al6B4O17 whiskers’ preparation were obtained: boric acid, copper sulfate and aluminum sulfate as reagents, potassium sulfate as flux, corundum crucible as container; the molor ratio of nCu: nAl: nB was 2: 6: 8, the mass ratio of reagents and flux was 13:7; the rate of heating was 5 oC/min, the rate of cooling was 1 oC/min, calcination temperature was 870 oC.(2) The prepared products were analyzed and characterized by XRD, SEM, TEM and TG etc. The results showed that the products were tetragonal Cu2Al6B4O17 whiskers with diameters from 100 nm to 1 μm, lengths from 5 to 200 μm, and preferential growth was c-axis. But for that, the whiskers have excellent stability against erosion of acid and alkali and better surface hydrophilic performace. The TG-DSC results shown that the whiskers were decomposed as Al18B4O33 whiskers and amorphous Cu3B4O9 from 1064 to 1200 oC.(3) The reaction process and growth mechanism of Cu2Al6B4O17 whiskers have been preliminarily studied by the analyses of the intermediate products and final products. The intermediate product was Al4B2O9. The growth process of Cu2Al6B4O17 whisker was explained via the anisotropic growth mechanism.The separation of magnesium and lithium from sulfate type salt-lake containing high ratio of magnesium to lithium is still an international technical problem in the development of salt-lake brine. In addition, lithium can’t be enriched highly with increasing of the concentration of carbonate ions because of lower solubility of lithium carbonate in water during exploiting lithium from carbonate subtype salt-lakes.In this paper, lithium was exploited following three steps:(1) Preparation of Lithium-enriched brine:After mixing the two different types of brines, concentrations of magnesium and carbonate can be reduce to 1 g/L and 3 g/L respectively. Then, lithium was concentrated to 8 ~ 12 g/L by evaporating the mixed brine. Influence parameters on mixing result and crystallization behavior of magnesium carbonate, such as density, mixing ratio, reacting temperature and aging time, etc., were investigated.(2) Preparation of carbonate-enriched brine: The carbonate-enriched brine can be obtained via evaporating Jiezechaka brine directly or freezing and evaporating of Jiezechaka brine. The results showed that frozen proportion of SO42-, CO32- were 95.49% and 75.13% respectively while using Li2CO3 saturated Jiezechaka brine. The concentration of carbonate was enriched up to 124.979 g/L while concentration of carbonate was reducing gradually. But for that, separation of sulfate and carbonate from frozen solid of Jiezechaka brine was researched. Sulfate and carbonate were separated by freezing lithium carbonate saturated brine at-10 oC and-20 oC successively. Sulfate and carbonate in frozen solid from Jiezechaka brine also can be separated by melting and freezing at-10 oC.(3) Precipitation of lithium carbonate: lithium carbonate was precipitated by mixing prepared lithium-enriched brine and carbonate-enriched brine with molar ratio of CO32- : 2Li+ being 1.3:1 at room temperature(15 ~ 25 oC). After precipitating, the contents of Li2CO3 were from 67.84 to 78.01% and the yields of lithium were from 50.10 to 56.87% in the raw precipitated lithium carbonate salts(unwashed by dilute water) with few contaminations of K+, Na+, B2O3, Cl- and SO42-. The results proved that the process of lithium collaborative extraction from Jiezechaka and Longmucuo salt-lakes was feasible.(4) Pilotscale experiment was carried out in pilot plant of Lhasa under guidance of previous experiment parameters. Finally, 1653 kg lithium-enriched brine with lithium concentration as 9.326 g/L, 1629 kg carbonate-enriched brine with carbonate concentration as 60.442 g/L and 50 kg lithium carbonate products with purity of being 59.10 to 61.46% were obtained. The result of pilotscale experiment was repeatable.