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根据γ-Fe_2O_3属立方晶系是亚铁磁性物质,α-Fe_2O_3属正交晶系是反铁磁性物质的原理,我们利用热天平外加一个恒定磁场,通过测定γ-Fe_2O_3在升温过程中磁力的变化来研究γ-Fe_2O_3转变为α-Fe_2O_3的相变过程。结果表明,热分析方法简便可行,可准确地测出相变点温位,为生产工艺提供可靠的参数依据,还可观察到γ-Fe_2O_3磁性随温度变化的规律。我们发现γ-Fe_2O_3磁性随温度变化不是呈单阶线性的。从50℃到350℃,其磁性随温度升高呈线性增加,但斜率较小,在近300度的范围内磁性仅增强19.96%。从350℃到520℃,其磁性与温度的关系为非线性,DTA 曲线上对应该区间出现了平漫的二重放热峰。从520℃到580℃,磁性与温度又呈线性关系,但斜率较大,当温度达到576℃时,磁性增强了92.84%.测出了我所采用新工艺研制成的γ-Fe_2O_3磁粉转变为α-Fe_2O_3的相变点温位是699.5℃。
According to the fact that the cubic system of γ-Fe_2O_3 is a ferrimagnetic material and the α-Fe_2O_3 belongs to the orthorhombic system of antiferromagnetic materials, we use the thermobalance to add a constant magnetic field. By measuring the magnetic force of γ-Fe_2O_3 during the heating process Changes to study the γ-Fe_2O_3 into α-Fe_2O_3 phase transformation process. The results show that the thermal analysis method is simple and feasible, the temperature of phase transition point can be accurately measured, and the reliable parameters for the production process can be provided. The variation of magnetic properties of γ-Fe_2O_3 with temperature can be observed. We found that the magnetic properties of γ-Fe_2O_3 do not exhibit single-order linearity with temperature. From 50 ℃ to 350 ℃, the magnetic properties increase linearly with the increase of temperature, but the slope is small. Only about 19.96% of magnetism is enhanced in the range of nearly 300 degrees. From 350 ℃ to 520 ℃, the relationship between magnetic and temperature is non-linear, and on the DTA curve, there appears a flat diffuse exothermic peak. From 520 ℃ to 580 ℃, the magnetism has a linear relationship with the temperature, but the slope is relatively large, and the magnetism increases by 92.84% when the temperature reaches 576 ℃ .It is measured that the γ-Fe 2 O 3 magnetic powder developed by our new technology transforms into α-Fe_2O_3 phase transition temperature is 699.5 ℃.