發(fā)布時間：2018-11-23 07:05

【摘要】：固體能源裝置如SOFCs、SOECs等具有高能量轉(zhuǎn)化效率、低污染等特性,在能源、環(huán)保等領域受到重視。電子導體—離子導體混合物材料是固體能源裝置常用的材料,金屬Ni、Fe等被用作催化劑和電子導體,而結(jié)構(gòu)納米化是該領域的重要方向。金屬催化劑納米化具有提高三相界面密度等優(yōu)勢和巨大的研究價值,而浸漬等傳統(tǒng)方法具有效率低、重復性差等缺點。本文針對固體能源裝置常用的微孔介質(zhì)預置納米催化劑,基于等離子滲N等成熟的熱處理方法,提出和發(fā)展一種以金屬等離子體預置納米催化劑的新方法并研究其機制。通過轟擊金屬靶形成的金屬等離子體在微孔介質(zhì)上表現(xiàn)為沉積和擴散效應,并形成納米顆粒物。實驗和理論計算證明該預置過程中,在微孔介質(zhì)表面及微孔口附近,金屬催化劑等離子體發(fā)生擴散和吸附沉積,在微孔較大深度處金屬催化劑以表面擴散為主要預置方式并形成納米顆粒物。該工藝可以在微孔介質(zhì)較大的深度范圍內(nèi)制備優(yōu)質(zhì)的納米催化劑結(jié)構(gòu),具有制備微孔內(nèi)納米催化劑的可行性、應用價值和發(fā)展?jié)摿Α１菊撐幕趯嶒炗^察與基本理論討論預置納米催化劑的機制,沉積系數(shù)與表面擴散系數(shù)是鍍滲工藝的主要控制因素,通過實驗與理論計算比較,證明本文提出的等離子體鍍滲微觀機制的合理性。并且通過不同工藝參數(shù)的實驗,本文討論了基體骨架材料與結(jié)構(gòu)特性、溫度、時間和氣氛成分等預置工藝的主要影響因素,初步研究了預置工藝的動力學和熱力學。金屬粒子在微孔內(nèi)壁以沉積區(qū)為擴散源形成表面擴散,其擴散系數(shù)小于在晶面上的擴散系數(shù)。金屬等離子體沉積過程中,濃度或顆粒粒徑逐漸增長而趨于穩(wěn)定;表面擴散過程中,擴散前沿顆擴散阻力較大,而隨時間增加和擴散距離增加,整體上濃度梯度的擴散驅(qū)動力減小,表面擴散趨勢減小,擴散深度和濃度場而趨于穩(wěn)定。工藝下溫度選擇800℃~1000℃為宜,過高溫度不利于顆粒保持納米尺度,微孔封閉與介質(zhì)致密化趨勢明顯增加,而工藝適宜氣氛為H2和Ar混合氣氛。1000℃×4h 0.03L/min H2+0.03L/min Ar和800℃×24h 0.03L/min H2+0.03L/min Ar被認為是對直孔2μm×20μm的Ni O-YSZ微孔介質(zhì)的較好預置金屬Ni工藝。
[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，

本文編號：2350718