红外辐射场下镧锰氧化物红外发射率特性研究

发布时间：2018-05-20 23:07

本文选题：镧锰氧化物 + 锶掺杂　；参考：《安徽工业大学》2017年硕士论文

【摘要】：掺杂型镧锰氧化物由于具有金属-绝缘相转变现象,使其发射率呈现自主变化特性,从而受到研究者们的广泛关注。金属-绝缘相变属于二级相变,不伴随热量的吸收与释放,其发射率的自主变化需要借助外场能量发生。然而遗憾的是,至今未见有将外场作用于镧锰氧化物研究其发射率变化的报道。基于此,本文选择锶掺杂的镧锰氧化物作为研究对象,采用红外辐射场与镧锰氧化物相互作用,利用X射线衍射分析、扫描电镜、红外吸收光谱、电子自旋共振等现代分析手段,探索了镧锰氧化物的组成、结构与发射率之间的对应关系,揭示了其发射率与红外辐射场的响应特性与规律。得出结论如下:1.为了克服辐射场引起的发射率测试结果偏差,在现有发射率测试系统的基础上设置了辐射场系统和温度控制系统。本装置结构简单、成本低廉,能够显著降低样品与标准体的温差,从而有效降低发射率测试结果偏差。2.无外场作用下,掺Sr后样品的晶体沿a、b轴收缩,沿c轴膨胀,使得样品表现出(104)晶面择优取向,这可能是样品发射率降低的原因之一。不同形貌样品发射率的大小顺序为:块状球状片状。随着Sr的掺杂,样品晶体完整性增强,晶格振动需要更高的能量,其Mn O键吸收峰向短波方向偏移,且x=0.3样品的吸收峰明显弱于其他样品,发射率表现出最小值。3.红外辐射场作用下,样品晶格结构对称性随温度升高而提高,稳定性增强;且x=0.2样品有向立方相转变的趋势,其铁磁性也增强。由于Mn-O、MnO-Mn和La位表面振动,与2.5~500μm波段辐射场形成共振,因此样品在2.5~500μm辐射场下的温度高于0.76~2.5μm下的温度。且相同条件下的发射率与波长成正比,因此样品在2.5~500μm下的发射率也较高。而x=0.2样品在照射时间20s时,2.5~500μm下的发射率却较低;且在0.76~2.5μm下的发射率基本不变,在2.5~500μm下的发射率增长幅度较大,达到23%。导致这一现象的原因,可能与晶格振动与辐射波的共振吸收,以及掺杂样品x=0.2时的金属绝缘相变发生的温度位置有关。样品发射率在辐射场和同温度场下均呈现升高趋势。然而,样品在辐射场下的发射率大于在温度场下的发射率。原因可能是辐射场下发射率上升是由两个因素导致的:一是辐射导致的温度升高;二是辐射导致的样品内部晶格振动变化。4.晶格振动和能级跃迁对辐射场下样品发射率的影响较为显著,而传播过程的影响相对较小。样品晶格结构不同,共振吸收的波段发生变化,从而影响发射率。样品内部的能级跃迁,影响对光能的吸收,从而与晶格振动共同作用,影响发射率。辐射距离相等条件下,辐射波段对样品发射率的影响不大。
[Abstract]:Doping lanthanum manganese oxide has been widely concerned by researchers because of its metal-insulating phase transition, which makes its emissivity change independently. The metal-insulating phase transition is a second-order phase transition, which is not accompanied by the absorption and release of heat. The independent change of emissivity needs to be generated by external field energy. However, unfortunately, there are no reports of the external field acting on lanthanum manganese oxide to study the emissivity of lanthanum manganese oxide. In this paper, strontium doped lanthanum manganese oxide is chosen as the object of study. The infrared radiation field and lanthanum manganese oxide interaction are adopted, and X-ray diffraction analysis, scanning electron microscope and infrared absorption spectrum are used. The relationship between the composition, structure and emissivity of lanthanum manganese oxide has been explored by means of electron spin resonance, and the response characteristics and laws of its emissivity and infrared radiation field have been revealed. The conclusion is as follows: 1. In order to overcome the emissivity error caused by radiation field, the radiation field system and temperature control system are set up on the basis of the existing emissivity measurement system. The device is simple in structure and low in cost, and can significantly reduce the temperature difference between the sample and the standard body, thus effectively reducing the deviation of the emissivity test results. Without external field, the crystal of Sr-doped sample shrinks along the aqb axis and expands along the c-axis, which makes the sample exhibit a preferred orientation of the crystal plane of 104), which may be one of the reasons for the decrease of the emissivity of the sample. The order of emissivity of different morphologies is as follows: block globular flake. With Sr doping, the crystal integrity of the sample is enhanced, and the lattice vibration needs higher energy. The absorption peak of mn / O bond shifts to the shortwave direction, and the absorption peak of xn0.3 sample is obviously weaker than that of other samples, and the emissivity shows the minimum value of .3. Under the action of infrared radiation field, the symmetry of lattice structure increases with the increase of temperature, and the stability of the sample is enhanced, and the ferromagnetism of the sample x0. 2 has the tendency of transition to cubic phase. Due to the surface vibration of Mn-O _ (-O) -MnO-Mn and La sites, which resonates with the radiation field at 2.5 渭 m band, the temperature of the sample is higher than the temperature of 0.76 ~ (2.5 渭 m) at 2.5 ~ 500 渭 m radiation field. Under the same conditions, the emissivity is proportional to the wavelength, so the emissivity of the sample at 2.5 渭 m is higher. However, the emissivity of XG 0.2 sample is low at 2.5 渭 m for 20 s, and the emissivity at 2.5 渭 m at 0.76 渭 m is almost unchanged, and the emissivity increases greatly at 2.5 渭 m, reaching 23%. The reason for this phenomenon may be related to the resonance absorption of lattice vibration and radiation wave, and the temperature position of the metal insulation phase transition of doped sample x = 0.2. The emissivity of the sample increases under both the radiation field and the same temperature field. However, the emissivity of the sample in the radiation field is greater than that in the temperature field. The reason may be that the rise of emissivity under radiation field is caused by two factors: one is the temperature rise caused by radiation and the other is the lattice vibration change of sample induced by radiation. The effect of lattice vibration and energy level transition on the emissivity of the sample under radiation field is significant, but the influence of the propagation process is relatively small. The band of resonance absorption varies with the lattice structure of the sample, which affects the emissivity. The energy level transition in the sample affects the absorption of light energy, which, together with the lattice vibration, affects the emissivity. When the radiation distance is equal, the radiation band has little effect on the emissivity of the sample.
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O611.62

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