Study On Synthesis Mechanism,preparation And Microstructure Of A New Thermal Battery Anode Li-b Alloy

The goal of this thesis is to understand reaction synthesis mechanism of Li ?B alloy that is used as anode of thermal battery, explore a special process that can prepare Li ?B alloy steadily and determine the microstructure of Li ?13 alloys and the crystal structure of Li ?B compound in the alloys.According to physical phenomenon appeared and phase composition in the course of the reaction synthesis as well as the effects of different process parameters on reaction products, a model of all reactions in Li ?B synthesis is proposed. In the model, the first reaction can be divided as three stages, i. e. surface instantaneous reaction, diffusion reaction and solving reaction. The second reaction consists of nucleation pregnant and exploded reaction stages.Based on the reaction synthesis theoretical model, a technique obtaming excellent Li ?B alloy, i. e. pretreatment of amorphous boron powder, adding boron in batches, strengthening stir and mechanical heat treatment is invented. It decreases cost of raw materials, difficult of temperature control, increases material?s thermal stability and apparent quality. The max discharge capacity of the produced lithium boron alloy film reaches to 6552C/g, yield strength 16. 4Mpa, tensile strength 18. 7Mpa, elongation rate 9. 5 %, temperature of thermal stability above6OO~C . The materials s properties has reached to international advancedlevel.By means of XRD, SEN~I, electron density function and valence bond theory, the morphology, crystal structure and bond characteristics of compound Li13 are found. The re~ults firstly show that the crystal structure of LiB belongs to hexagonal system with space group No. 194 P63/mmc. In unit cell, B atoms occupy (2b) site: (0,0,1/4) and Li atoms (2c) site: (1/3,2/3,1/4). Lattice constants: aO.4022nm, c0. 2796nm, theoretical density: 1. 50 g/cm3. And compound LiB belongs to polyanionic compound, Zintle compound, in which bend covalent bond chain B B B lies in <001> direciion. The morphology of compound LiB is fibrous growing along <001> direction, and the fibers align along rolling direction after rolling.