一种微孔介质预置纳米催化剂的新工艺
发布时间：2018-11-23 07:05
【摘要】：固体能源装置如SOFCs、SOECs等具有高能量转化效率、低污染等特性,在能源、环保等领域受到重视。电子导体—离子导体混合物材料是固体能源装置常用的材料,金属Ni、Fe等被用作催化剂和电子导体,而结构纳米化是该领域的重要方向。金属催化剂纳米化具有提高三相界面密度等优势和巨大的研究价值,而浸渍等传统方法具有效率低、重复性差等缺点。本文针对固体能源装置常用的微孔介质预置纳米催化剂,基于等离子渗N等成熟的热处理方法,提出和发展一种以金属等离子体预置纳米催化剂的新方法并研究其机制。通过轰击金属靶形成的金属等离子体在微孔介质上表现为沉积和扩散效应,并形成纳米颗粒物。实验和理论计算证明该预置过程中,在微孔介质表面及微孔口附近,金属催化剂等离子体发生扩散和吸附沉积,在微孔较大深度处金属催化剂以表面扩散为主要预置方式并形成纳米颗粒物。该工艺可以在微孔介质较大的深度范围内制备优质的纳米催化剂结构,具有制备微孔内纳米催化剂的可行性、应用价值和发展潜力。本论文基于实验观察与基本理论讨论预置纳米催化剂的机制,沉积系数与表面扩散系数是镀渗工艺的主要控制因素,通过实验与理论计算比较,证明本文提出的等离子体镀渗微观机制的合理性。并且通过不同工艺参数的实验,本文讨论了基体骨架材料与结构特性、温度、时间和气氛成分等预置工艺的主要影响因素,初步研究了预置工艺的动力学和热力学。金属粒子在微孔内壁以沉积区为扩散源形成表面扩散,其扩散系数小于在晶面上的扩散系数。金属等离子体沉积过程中,浓度或颗粒粒径逐渐增长而趋于稳定;表面扩散过程中,扩散前沿颗扩散阻力较大,而随时间增加和扩散距离增加,整体上浓度梯度的扩散驱动力减小,表面扩散趋势减小,扩散深度和浓度场而趋于稳定。工艺下温度选择800℃~1000℃为宜,过高温度不利于颗粒保持纳米尺度,微孔封闭与介质致密化趋势明显增加,而工艺适宜气氛为H2和Ar混合气氛。1000℃×4h 0.03L/min H2+0.03L/min Ar和800℃×24h 0.03L/min H2+0.03L/min Ar被认为是对直孔2μm×20μm的Ni O-YSZ微孔介质的较好预置金属Ni工艺。
[Abstract]:Solid energy devices such as SOFCs,SOECs have the characteristics of high energy conversion efficiency and low pollution. The mixture of electronic conductors and ionic conductors is a common material in solid energy devices. Metal Ni,Fe is used as catalysts and electronic conductors. Nanocrystalline structure is an important direction in this field. Nanocrystalline metal catalysts have the advantages of increasing the density of three-phase interface and great research value, while the traditional methods such as impregnation have the disadvantages of low efficiency and poor repeatability. In this paper, a new method and mechanism of metal plasma preset nanocrystalline catalyst is proposed and developed based on the matured heat treatment method such as plasma nitriding, aiming at the microporous medium preset nanocatalyst commonly used in solid energy plant. Metal plasmas formed by bombarding metal targets exhibit deposition and diffusion effects in microporous media and form nanoparticles. Experimental and theoretical calculations show that the metal catalyst plasma diffuses and adsorbs deposition on the surface of the microporous medium and near the pore orifice during the presetting process. The surface diffusion was used as the main presetting method to form nanoparticles in the metal catalyst at large depth of micropore. This process can be used to prepare high quality nanometer catalyst structure in the large depth range of microporous medium, which has the feasibility, application value and development potential of preparing nanometer catalyst in micropore. In this paper, the mechanism of preset nano-catalyst is discussed based on experimental observation and basic theory. Deposition coefficient and surface diffusion coefficient are the main controlling factors of plating process. It is proved that the mechanism proposed in this paper is reasonable. Based on the experiments of different process parameters, the main factors affecting the preset process, such as matrix material and structure, temperature, time and atmosphere composition, are discussed, and the kinetics and thermodynamics of the preset process are preliminarily studied. The diffusion coefficient of metal particles on the inner wall of micropores is smaller than that on the crystal plane. In the process of metal plasma deposition, the concentration or particle size increases gradually and tends to be stable. In the process of surface diffusion, the diffusion resistance of particles at the diffusion front is large, but with the increase of time and diffusion distance, the diffusion driving force of the concentration gradient decreases, the surface diffusion trend decreases, and the diffusion depth and concentration field tend to be stable. The optimum temperature is 800 鈩，
本文编号：2350718
[Abstract]:Solid energy devices such as SOFCs,SOECs have the characteristics of high energy conversion efficiency and low pollution. The mixture of electronic conductors and ionic conductors is a common material in solid energy devices. Metal Ni,Fe is used as catalysts and electronic conductors. Nanocrystalline structure is an important direction in this field. Nanocrystalline metal catalysts have the advantages of increasing the density of three-phase interface and great research value, while the traditional methods such as impregnation have the disadvantages of low efficiency and poor repeatability. In this paper, a new method and mechanism of metal plasma preset nanocrystalline catalyst is proposed and developed based on the matured heat treatment method such as plasma nitriding, aiming at the microporous medium preset nanocatalyst commonly used in solid energy plant. Metal plasmas formed by bombarding metal targets exhibit deposition and diffusion effects in microporous media and form nanoparticles. Experimental and theoretical calculations show that the metal catalyst plasma diffuses and adsorbs deposition on the surface of the microporous medium and near the pore orifice during the presetting process. The surface diffusion was used as the main presetting method to form nanoparticles in the metal catalyst at large depth of micropore. This process can be used to prepare high quality nanometer catalyst structure in the large depth range of microporous medium, which has the feasibility, application value and development potential of preparing nanometer catalyst in micropore. In this paper, the mechanism of preset nano-catalyst is discussed based on experimental observation and basic theory. Deposition coefficient and surface diffusion coefficient are the main controlling factors of plating process. It is proved that the mechanism proposed in this paper is reasonable. Based on the experiments of different process parameters, the main factors affecting the preset process, such as matrix material and structure, temperature, time and atmosphere composition, are discussed, and the kinetics and thermodynamics of the preset process are preliminarily studied. The diffusion coefficient of metal particles on the inner wall of micropores is smaller than that on the crystal plane. In the process of metal plasma deposition, the concentration or particle size increases gradually and tends to be stable. In the process of surface diffusion, the diffusion resistance of particles at the diffusion front is large, but with the increase of time and diffusion distance, the diffusion driving force of the concentration gradient decreases, the surface diffusion trend decreases, and the diffusion depth and concentration field tend to be stable. The optimum temperature is 800 鈩，
本文编号：2350718
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