Synthesis And Research Of Al/ZrMgMo₃O₁₂ And BaFe₁₂O₁₉/ZrMgMo₃O₁₂

In nature, most of the materials have the characteristic of thermal expansion and contraction. With change of the temperature, deformation and thermal stress will appear due to thermal expansion and contraction. This characteristic can easily lead to reduced sensitivity and poor performance of the device, or even directly result in device failure. Negative thermal expansion materials are different from commonly used materials, and their thermal expansion coefficients are negative. Compositing with the expansion material, the composite materials of near-zero coefficient of thermal expansion or controllable expansion can be obtained. Equipment, which is made of materials of near-zero coefficient of thermal expansion or controllable expansion, won’t produce deformation and thermal stress due to changes of temperature. It can not only improve the stability and precision of instruments and equipment, but also extend the services’ life. Nearly twenty years, explorations and researches of negative thermal expansion materials have caused numerous domestic and foreign scientists’ attention. A lot of new negative thermal expansion materials have been discovered. However, for the newly discovered negative thermal expansion materials, because of the short available time, developments of their applications and processing are still in the laboratory stage. In this work, our group prepared Zr Mg Mo3O12, a new negative thermal expansion material, and then composited it with common materials. We hope to improve the thermal expansion coefficient, and thus make a composite material with adjustable coefficient of thermal expansion.This thesis is divided into four parts, as follows:The first part gives a systematic introduction of the definition and classification of negative thermal expansion. Also it introduces the status quo of negative thermal expansion materials, negative thermal expansion phenomenon, and the advantages and disadvantages of various types of negative thermal expansion materials.The second part describes the experimental apparatus required in tests and the characterization methods of negative thermal expansion materials.In the third part, Zr Mg Mo3O12 was prepared by solid phase materials. Preparecomposite materials according to the mass ratio of Zr Mg Mo3O12 and Al the metal powder, and tested their relative performance. The results show that, AlZr Mg Mo3O12 composite has no any other impurity phases, but Al and Zr Mg Mo3O12 two phases; composite material has good thermal stability, and its compactness increases with increasing of Al content; thermal expansion coefficient of the composite material can be adjusted by changing the mass ratio of Al to Zr Mg Mo3O12;composites’ Al- Zr Mg Mo3O12 conductive properties has a conductive percolation characteristic, that is when the quality of the Al content reaches a certain percentage,capacitance characteristic instantaneously converts to resistance.In the fourth part, Zr Mg Mo3O12, materials prepared by solid phase was composited with Ba Fe12O19 with Nan scale according to their mass ratio. The X-ray diffraction(XRD) analysis of the samples show that Ba Fe12O19 will be decomposed into Fe2O3 and Fe3O4; thermal analysis of samples prepared shows the samples have good thermal stability, without absorbing heat phenomenon; sample materials are strong magnetic, which can interfere with the scanning electron microscope imaging;in a certain extent, the coefficient of thermal expansion can be adjusted by changing the ratio of Zr Mg Mo3O12- Ba Fe12O19 in the samples.