博士学位论文
摘要
表面薄膜赋予材料表面耐磨、耐蚀、耐热、耐疲劳以及特殊的光、热、电和磁等多种功能，在现代高新技术中受到了越来越多的重视，成为材料科学中最活跃的研究领域之一。薄膜材料和薄膜技术为机械、能源和交通等部门，以及现代军事提供了具有优异性能的新材料和器件，极大地促进了光电子技术、计算机技术、航空航天技术等现代高新技术的发展，在高新技术产业中具有举足轻重的作用。本文研究了三种无机薄膜的制备工艺及其力学和耐蚀性能，获得了一些有意义的结果。
采用磁控溅射方法在硅和玻璃基体上沉积了BaTiO3(BTO)薄膜，通过原位测试不同厚度BTO薄膜的应力、介电常数和铁电性能随温度的变化规律，系统研究了薄膜的铁电性能与厚度和应力的关系，并用两种方法确定BTO薄膜的双轴杨氏模量和热膨胀系数。实验结果表明，BTO薄膜中的应力为张应力。膜中张应力随薄膜厚度的减小而增大，导致居里温度下降，剩余极化减小，矫顽场增大。特别是当厚度较小(35~250nm)时，这种变化更加明显。张应力对薄膜居里温度的影响主要位于300-450Mpa应力区间，在该区间内，应力增大导致薄膜居里温度线性下降（0.16℃/Mpa）。根据温度升高过程中BTO薄膜应力曲线的斜率变化、介电常数峰值、电滞回线收缩等确定的居里温度一致。由于薄膜中张应力的存在，BTO薄膜相变温度比体材料的相变温度低。电滞回线表明铁电-顺电相变开始于BTO薄膜的居里温度，并持续
工作经验总结
到接近BTO体材料的居里温度。说明BTO薄膜中存在多种畴。BTO薄膜的铁电性能主要由膜内畴决定，而表面畴的影响相对很小。另外，根据升温过程中铁电-顺电相变时晶胞体积和应变的变化，以及不同基体上BTO薄膜应力随温度变化率的计算结果表明，BTO薄膜双轴杨氏模量比体材料的稍大，而热膨胀系数比体材料的偏小。
上升天秤薄膜应力的存在和变化对薄膜与基体的粘结强度有很大影响。为了制备高质量的类金刚石（DLC）薄膜，并改善DLC薄膜和基体之间的粘接强度，采用双离子束轰击混合（DIBM）技术+离子束沉积(IBD)技术在钢基体上沉积DLC膜，研究了DLC膜的力学性能和耐蚀性能。实验结果表明，利用DIBM + IBD沉积技术可以明显提高DLC膜和钢基的复合硬度，而且还使硬度峰值向低能方向偏移；同时显著地提高了DLC膜/基的粘结强度（当DIBM技术中所用中能Ar+束能量为30 keV时，其沉积的DLC膜临界载荷P c为IBD工艺沉积膜P c的2倍以上）。钢表面类金刚石膜改性后，不仅具有减摩作用，而且表现出良好的耐磨性。失重试验结
无机表面薄膜力学及耐蚀性能研究
果表明，类金刚石膜可显著降低钢基体在腐蚀介质中的腐蚀速率，提高基体试样抗均匀腐蚀的能力。从电化学实验和金相显微分析可知，钢基体上沉积的DLC膜对腐蚀介质具有物理阻滞作用，可以有效地防止腐蚀介质渗入钢基体表面，提高钢基体在腐蚀介质中的稳定性；同时还能增大阳极极化过程的阻力，降低电极催化活性，提高其耐蚀能力，特别是改善了钢基体抗点蚀等局部腐蚀的能力。
投诉建议
另外，用重量法和电化学方法研究了镀液成分和工艺参数对化学镀Fe-P合金沉积速率和镀层耐蚀性能的影响。实验中，采用了铜基体偶接铝的方法。实验表明，偶接铝使施镀体系的电极电位负移，降低了体系的阴、阳极极化阻抗，诱导了Fe-P合金的化学沉积。从镀液组分的反应级数可知，镀液中还原剂NaH2PO2浓度变化对化学沉积速率的影响最大，其次为FeSO4和氢离子浓度。计算出反应活化热为4.425 Kcal/mol。由于氢析出等副反应的发生，用电化学方法确定的镀层沉积速率大于重量法确定的沉积速率。用电化学方法和重量法两种方法确定镀层在腐蚀介质中的腐蚀速率，和中性腐蚀介质相比，镀层在酸性腐蚀介质中的腐蚀速率较大。化学镀层在1M NaOH介质中的极化曲线上出现若干个阳极电流峰，表明多个阳极反应的存在。循环伏安曲线中阴、阳极峰电流的不同以及不同扫描速度下峰电位的变化，说明反应为不可逆反应。
关键词：无机薄膜；相变；铁电性能；耐蚀性；力学性能；DIBM
博士学位论文
Abstract
The coating technology is very important and applied widely in industry due to the excellent performance of film, such as good resistance to wear, corrosion, heat, and excellent optical, thermal, magnetism and electrics properties. The advances made in thin film drive the expansion of photoele有关长城的诗句
教堂英语ctronics, computer, microelectronics, nsors and information industry and provide high-tech materials and devices for mechanics, energy sources, traffic and national defence department. In this thesis, the film deposition technique, the mechanical and anti-corrosion behaviors of films are studied by analyzing the BTO, DLC and Fe-P films. Some interesting results are obtained.
瀛奎律髓Thin BTO films were deposited by magnetron sputtering on Si and glass substrates. The thickness of the BTO layer was varied between 35 nm and 1 μm. The stress, dielectric permittivity, and ferroelectric hysteresis loop were measured after deposition and during heating. The combined effect of film thickness and stress on BTO ferroelectric behavior was studied. The thermal expansion and bilayer-modulus were calculated by two methods. It is found that the BTO films are under tensile stress at the Curie temperature. The tensile stress in BTO films increas with decreasing film thickness leading to a shift of the Curie point to a lower temperature, a decrea of remanent polarization, and an increa of the coercive field, especially obvious as the film thickness lower than 250 nm. The effect of tensile stress on the Curie temperature is dominant within a restricted range of stress between 300 and 450 mega Pascals(MPa), where the Curie temperature decreas linearly by about 0.16℃/Mpa. A good correlation is found among the stress, dielectric and ferroelectric measurements with respect to the temperature of the Curie point, which is determined bad on iden
tifying changes in the slope of film stress versus temperature plot, the peak characteristic of dielectric permittivity and the shrinkage of hysteresis loop during heating. The ferroelectric hysteresis loop shows that the ferroelectric-paraelectric pha transition starts at the Curie temperature of the BTO films and continues within a range of temperatures until about the Curie temperature of the bulk BTO material. The ferroelectric behavior indicates the prence of various types of domains. The ferroelectric domains within the interior part of the BTO film have a dominant effect
无机表面薄膜力学及耐蚀性能研究
on its ferroelectric behavior, while the contribution of surface domains is relatively small. The biaxial modulus and expansion coefficient of BTO films were determined bad on the change of stress in BTO films and of the volume of BTO unit cell due to pha transition or the stress slope of BTO films on Si and glass substrates versus temperature plot. The biaxial modulus of BTO film is little higher than that of bulk BTO materials, while the expansion coefficient of BTO films is little lower than that of bulk BTO materials.
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To improve the adhesion strength of film on substrate, a dual ion-beam bombardment and mixing (DIBM) technique was developed and employed to prepare diamond-like carbon (DLC) films on steel
substrates. The mechanical performance and anti-corrosion behavior of DLC films were studied. The results show that DIBM technology not only increas the compound hardness of DLC film and steel substrate, but also leads to an energy shift corresponding to the maximum microhardness to lower ion energy. By implanting with medium energy Ar ion beam and introducing a mixed interface, DIBM technology improves the anti-wear performance and adhesion strength of DLC film, the critic load of DLC films prepared by DIBM + IBD increas by more than a factor of two than that by IBD. Also, the DLC films increa the stability and reduce corrosion rate of substrates in corrosive solution by functioning as a physical barrier and restraining from anodizing. In addition, the DLC films improve the steel substrate resistance to pitting corrosion remarkably. Thus, the DLC film provides a favorable protection for steel to be applied in corrosion environments.
Also studied in the thesis was the effect of bath composition and process on the deposition rate and corrosion behavior of electroless Fe-P deposits by weight and electrochemical method. During the deposition process, the copper substrate was coupled with aluminum foil, which shifted the potential negatively and decread the resistance for cathodic and anodic reaction, thus induced the Fe-P deposition. The reaction orders of bath composition and the activation energy were determined by plotting the logarithm of deposition rate versus the logarithm of concentration of bath and reciprocal
of temperature, respectively. And the reaction orders of NaH2PO2、FeSO4、H+ and the activation energy are 0.34、0.18、0.13 and 4.425 Kcal/mol, respectively. The deposition rate determined by electrochemical method is higher than that by weight method due to the other reactions, such as hydrogen evolution. Compared with the corrosion rate in NaCl solution, the corrosion rate in acid solution
胆汁酸偏高博士学位论文
is large. In the polarization curve of Fe-P deposits in NaOH solution, there are veral current peaks, suggesting the appearance of new reaction or the change of surface state. The cycle voltammetric behavior at different scan rate of the deposits in NaOH solution shows that the oxidation reaction is irreversible.
Key words: Thin films；Pha transition；Ferroelectric；Corrosion resistance；Mechanical; DIBM
