Study On The Preparation Of Thermal Ceramics With Al₂O₃Based

Aiming at the heat dissipation of LED lamp holder, the experiment choosesAlN+Al2O3+cordierite composite ceramics as the research object. AlN has high thermalconductivity which can reach310W·m-1·K-1at room temperature. But because of theworking temperature(115℃) of the lamp holder and the thermal conductivity of Al2O3which can reach30W·m-1·K-1at100℃, Al2O3is added by considering the preparation costand the work environment of the lamp holder. The addition of cordierite aims to reduce thesintering temperature.The cordierite used in the experiment is in situ synthesis. Mix the material accordingto the mole ratio, and sinter the powder in1350℃～1450℃. Achieve different powderwhich has different synthesis temperature. Determine the best temperature through XRDdiffraction analysis. Aiming at the temperature of dislodging the plasticizer, thecomposition and the sintering temperature the experiment begins. Weigh powder inaccordance. Pour PVB ethanol solution into barrel, turn on the blender in low speed andadd powder one by one and then increase the speed, after running for six hours the slurry isdried in vacuum oven, and dry powder is milled and sifted. Using mould press the powderis pressed round flake with diameter of40mm, the forming parameter is40MPa keeping5seconds. First the green body is heated to dislodge plasticizer in450℃～550℃, and thensintered in1350℃～1550℃respectively, during sintering the keeping time is one hour.Observe the microstructure of the fracture of the ceramic using scanning electronmicroscope and its energy spectroscopy, and phase analysis by x-ray diffraction.The study found that:1. Synthesis temperature of cordierite is1380℃; PVB has beenburned completed when the green body sintering in450℃.2. Composite ceramics havegood sintering good properties and density when the addition of cordierite is10％.3. Thecomposite ceramic can be burnt at about1500℃when the addition of aluminum nitride is40％; The number of large size grain increases with the increase of the addition ofaluminum nitride.4. During the sintering process, Al6O3N4, Al7O3N5, Al8O3N6, Al5O6Nand Al9O3N7are formed which are wurtzite structure.5. AlN has been kept down and thelattice ofAlN doesn’t receive too much pollution.