Effect of some parameters on the diffusion coefficient and metastable zone of lithium metaborate dihydrate

Working areas related to boron compounds are rapidly diversed and this resulted in increasing the importance of industrial production conditions' determination of these compounds. Therefore, determination of parameters of lithium metaborate dehydrate, in industrial applications of which, it is wide used in rechargeable batteries, in the production of lithium-ion batteries, in the silicate analysis and in the glass and ceramics industry, draws the major attention of the present researchers. In this study, the production conditions of lithium metaborate dihydrate compund were determined by using the crystallization method in 45 oC, 50 oC and 60 oC temperatures. In the first, the diffusion coefficient depends on various parameters and the diffusion step affecting crystal growth of lithium metaborate dihydrate was determined. The diaphragm cell technique was basically used to determinate the diffusion coefficient. In the study also, by using polythermal method, the metastable zone widths of lithium metaborate dihydrate were determined in the conditions of 45 oC, 50 oC and 60 oC temperatures and saturated solutions independently with 1, 3, 5, 7 °C/hr cooling rates. Then, the effects of calcium (Ca) and ethyl alcohol impurity on the metastable zone width of the saturated solution of the compound were determined in the given temperature conditions. To determine the surface tension value between the solution and the nuclei occured in the supersaturated solution, the induction period method is used. The experimental results show that, the nucleation of lithium metaborate dihydrate is controlled by homogeneous nucleation as well as heterogeneous nucleation in 62.35 oC temperature and the surface tension value for homogeneous nucleation was determined as 0.00770 mj/m2 while the surface tension value for heterogeneous nucleation was determined as 0.00205 mj/m2. Experimental datas show that with increasing of the temperature, the nucleation rate constant values were decreased and the metastable zone width was found to increase. Evaluating these nucleation rate constants to Arhenius equation, the necessary activation energy for nucleation was determined as -214.49 kJ/moles. Moreover, it is concluded that the impurities such as Ca (II) and alcohol in different concentrations were found to be highly effective on the solution saturation temperatures, and these impurities were found to have a narrowing effect on metastable zone width.