Hydrothermal method is the most commonly used for preparing magnesium lithium silicate layered silicate minerals and other methods, the reaction temperature, reaction time and affect the pH value is prepared by hydrothermal method hectorite three main parameters [BergayaF, . ThengBKG, LagalyG Handbook of clay science [M] Elsevier Science & Technology, 2006:. 116-120]. A lot of work has shown that, at lower reaction temperatures can not be successfully synthetic clay mineral, and therefore most of the clay synthesis reaction temperature was set at 100 ~ 500 °. the pH of the hydrothermal synthesis reaction system directly affects the type of clay minerals: under acidic conditions of pH 2 to 6, such as a suitable synthetic kaolinite class: 1 layered silicate, pH 7 to 10:00 adapted Synthesis 2: hectorite a layered structure, montmorillonite, higher alkaline conditions conducive to the preparation of zeolites. Hydrothermal reaction time determines the yield and crystallinity of synthetic clay, the longer the reaction time, the higher the yield, the better the degree of crystallinity.
For ceramic matrix composites based on SiC fibers in a magnesium lithium silicate matrix, the vitroceramic matrix has been found two-phased, made of cordierite and spodumene. This morphology evolves during heat treatment and/or creep tests. The morphological characteristics - volume fraction, specific perimeter, specific surface area nand mean chord length in number and in weight - of the cordierite phase in this matrix have been investigated and quantified, using automatic image analysis and more specially the P(l) function and granulometry in grey tone levels. Evidence is given on a demixtion in the cordierite phase followed by a coarsening at temperatures above 1300K.
The stimulated emission of Yb/sup 3+/ in a magnesium lithium silicate glass that was made to oscillate at a wavelength of 1.0l5 mu at liquid N temperature and lower is described. A Xe-filled helical flashtube was used as the optical pumping source. The lifetime for spontaneous mission apparently is at least as long as the rise time of the source. Variation-of the emission with temperature was noted, and the peak power density was about 12 w/cm/aup 2/. absorption bands at 914, 946, and 976 m mu apparently give most of the laser action, although bands at 310 and 220 m mu were present. The overall emission bandwidth was about 6 m mu with a shortest wavelength line at 1.0125 mu , while the longest wavelength line was at 1.0184 mu . (D.C.W.)