固定化MexOy-TiO2/活性炭催化剂的应用研究

袁 昊，顾依文，赵丽娜(上海第二工业大学城市建设与环境工程学院，上海 201209)

固定化MexOy-TiO2/活性炭催化剂的应用研究

袁 昊，顾依文，赵丽娜
(上海第二工业大学城市建设与环境工程学院，上海 201209)

为了研究既能有效降解水中有机污染物，又能从处理过的废水中方便地回收光催化剂，利用工业偏钛酸为原料，制备了MexOy-TiO2/AC复合光催化剂（Me为Ag、Zn、La），并采用XRD、SEM等对复合光催化剂进行了表征。将MexOy-TiO2/AC催化剂涂在光催化反应器壁上，以O, O-二甲基-S-（N-甲基氨基甲酰甲基）二硫代磷酸酯（dimethoate）水溶液为目标污染物，研究了复合光催化剂的光催化活性。结果表明，MexOy的掺入可使TiO2/AC复合光催化剂的光催化活性增强，其中制备的Ag2O-TiO2/AC复合光催化剂的光催化活性最高。

光催化活性；二氧化钛；掺杂；降解

0 引言

在众多半导体光催化剂中，二氧化钛因其光催化活性高、稳定性好而倍受关注。目前，降解水中污染物时通常采用TiO2悬浮体系（P25）。此体系中纳米TiO2与污染物充分接触，能有效地光催化、氧化水中的有机污染物[1]。长期以来，光催化技术的处理效率始终难以达到实际应用的水平。这是因为该技术存在一些缺陷：（1）悬浮态的二氧化钛对有机物吸附性差，污染物在其周围聚集的浓度低，影响催化降解效果；（2）悬浮相TiO2光催化剂回收困难，难以二次利用，限制了光催化技术的广泛应用；（3）TiO2半导体只能吸收紫外光区的光能，而这部分光能仅占太阳能光强的4 %，对自然光的利用率低。

经研究发现，活性炭（AC）可以将溶液中的目标污染物富集到TiO2催化剂表面，在TiO2表面产生一个底物富集环境，从而提高污染物的矿化速度，而且中间产物也被吸附在催化剂表面并被分解，避免了二次污染的产生[2]。为了有效地解决催化剂技术存在的缺陷，本文以活性炭作为催化剂载体，将金属氧化物掺杂到二氧化钛催化剂中制备复合光催化剂，改变粒子结构与表面性质，促进光生电子——空穴对的有效分离，提高光催化剂的光催化活性[3]；再将TiO2复合光催化剂负载到反应器壁上，在TiO2表面产生一个底物富集环境，从而解决了上面提到的问题。

1 试验方法

1.1 催化剂制备

在373 K温度下，将颗粒状活性炭（AC, 40 ～ 60 mesh）用浓HNO3煮沸1 h活化生成羟基，然后用去离子水洗净，干燥后放入石英反应器中，用干燥N2在373 K下干燥25分钟。

取偏钛酸（硫酸法钛白粉中间体）加入浓硫酸，在373 K条件下搅拌2.5 h，得到透明澄清的溶液。然后边搅拌边滴加已配制好的AC以及掺杂改性盐碱性溶液，老化、抽滤，最后在氮气保护下煅烧3 h[4]，研磨即得MexOy-TiO2/AC复合光催化剂（Me为Ag、Zn、La），将制备好的催化剂用丙烯酸粘胶剂固定在反应器壁上。

1.2 催化剂制备的表征

TiO2的晶型通过XRD在D /max-RA 转靶X射线多晶衍射仪上测定，其Cu Kα射线λ＝0.154 18 nm，扫描范围2θ= 20° ～ 70°。用SEM分析TiO2的形貌和颗粒大小。

1.3 光降解试验

将一定浓度的dimethoate（乐果O, O-二甲基-S-[2-(甲胺基)-2-氧代乙基]硫代磷酸酯）设定为实验目标污染物。在自制的实验装置中，以紫外杀菌灯（功率8 W，主发射波长253.7 nm）作为光催化反应的光源。两个灯管平行放置，置于溶液上方，距离液面7 cm。由磁力搅拌向系统提供反应所需的溶解氧，并促进反应物和产物的传质。实验进行3 h，每隔0.5 h取样，经滤纸过滤后，再取样后测其吸光度，测定溶液中dimethoate的残余浓度，以评价其催化性能。通过Apollo TOC 9000测定总有机碳（TOC）。用UV-2450紫外-可见分光光度仪测定Dimethoate浓度（λmax=800 nm）。

Dimethoate降解率定义为

式中C0为Dimethoate的初始浓度，Ct为反应时间t时的Dimethoate浓度。

2 结果与讨论

2.1 催化剂的表征

图1为MexOy-TiO2/AC 的SEM照片。通过SEM照片可以看出沉积物质颗粒约为15 nm ～ 25 nm，较大的颗粒达到了近50 nm，颗粒均匀分散且颗粒间的边界清晰。图2的TEM照片显示TiO2粒子分布得比较均匀，形状多为椭球形。由此表明，掺杂活性炭可以改善TiO2的分散性，抑制晶粒的生长，使其形成较小颗粒，且粒径能够均匀分布。

在XRD谱图中（如图3），掺杂改性后的MexOy-TiO2/AC（Me是Ag）的X射线衍射谱图主要表现在对应于层间隙最大距离d 001的差异，表明产物层间距大小的（001）面衍射峰有向大角度移动的趋势，层间距的变化显示出有形成MexOy-TiO2/AC复合物的可能。TiO2的晶型对光催化剂活性有很大的影响，锐钛矿型（α-TiO2, Anatase）的光催化活性比较高。从图中可以看出，样品主要表现为锐钛矿型，在衍射角2θ= 25.3°, 37.8°, 48.0°, 53.9°, 55.1°, 62.7°, 68.9°和70.4°处有明显的衍射峰，各峰对应的面间距d值与JCPDS卡中21-1272号锐钛矿型TiO2的d值完全一致。同时可以观察到少量的金红石相出现，在衍射角2θ=27.4°处有金红石相的特征衍射。

图1 Ag掺杂样品SEM图Fig. 1 SEM image of the sample

图2 Ag掺杂样品TEM图Fig. 2 TEM image of the sample

2.2 Dimethoate初始浓度的影响

在pH＝10.0，其他条件不变的情况下，不同dimethoate初始浓度下的光催化降解率随时间的变化如图4所示。

图3 样品 XRD 图Fig.3 X-ray diffraction patterns of the sample

图4 Dimethoate初始浓度对光降解率的影响Fig.3 The effect of Photoability concentration on the initial Dimethoate

由图可看出，随着dimethoate初始浓度的增加，其降解率大幅度降低。60 min内，初始浓度为0.4×10-4mol/L的dimethoate溶液，其降解率为86.27 %；而初始浓度为10.0×10-4mol/L时，其降解率仅为10.05 %。光催化降解机理认为，TiO2表面上光致电子-空穴对复合可在10-9s内完成。反应物必须先吸附于催化剂表面才能被有效降解，因此界面吸附过程是有机物降解率的重要控制因素。当dimethoate的浓度增大，催化剂用量不变（即总吸附位不变）时，TiO2表面吸附的dimethoate增大，此时dimethoate的降解率虽然下降，但dimethoate的降解速率增大，体系的酸性增强，从而降低复合光催化剂的催化效果；当dimethoate的初始浓度达到一定浓度后，TiO2表面达到吸附饱和，单位时间内dimethoate的降解率将基本保持不变。在较低的初始浓度下，体系的酸性变化相对缓慢一些，有利于保持催化剂的高活性。这样虽然对于催化剂表面的吸附不利，但由于采用了活性碳作为催化剂的载体，因此，在一定的浓度范围内可以减缓这方面的副作用，使得高浓度降解率远低于低浓度反应。

2.3 反应液初始pH值的影响

Dimethoate初始浓度为1.0×10-4mol/L时，60 min内反应液初始pH值对光催化的影响如图5所示。从图中可看出，60 min内，pH = 2.0，6.5和11.5时，dimethoate的降解率分别为13.66 %，35.61 %和82.71 %，dimethoate的降解率随pH值的升高而明显增加。这是因为TiO2在酸性和碱性溶液中，催化降解的效果是不一样的。TiO2的等电点约为pH=6.0[4]，在pH ＞ 6.0时的溶液中，OH-可以充当光致空穴的俘获剂（h++ OH-→ •OH），在TiO2表面容易生成光致羟基自由基，加强氧化效果。在酸性条件下[5]，氧化物主要为光致空穴，其氧化能力比羟基自由基小，所以在酸性条件下TiO2的氧化能力比碱性条件下低。当初始溶液是碱性时，OH-充当光致空穴的俘获剂（h++ OH-→ •OH），在TiO2表面容易生成光致羟基自由基，Dimethoate中的有机硫产生硫酸、有机磷氧化产生磷酸、有机氮经进一步氧化为，这使得随着MexOy-TiO2/AC复合光催化剂对dimethoate的降解，溶液中的酸根离子增加，溶液慢慢地变成酸性。此时，氧化物主要为光致空穴，其氧化能力比羟基自由基小，氧化能力下降，dimethoate的降解速率下降，pH值的变化也越来越小。pH值测定结果也表明，酸性条件下，溶液的pH变化较小，而在碱性条件下，溶液的pH由降解前的11.5大幅度地降低到4.27，说明dimethoate在碱性条件下更能有效地降解污染物及其产生的中间体。

图5 反应液起始pH值对Dimethoate光降解的影响Fig.5 The effect of initial pH value

2.4 氧化剂对复合光催化剂催化性能的影响

本试验在其他条件不变的情况下，分别加入一系列不同浓度的H2O2氧化剂，其浓度为0 ～ 9.0 mmol/L，经过1 h的光催化降解，其结果如图6。

图6 氧化剂H2O2浓度的影响Fig.6 Photocatalytic degradation by H2O2

从图6中可以看出，H2O2的浓度在0 ～ 3.00 mmol/L范围内，dimethoate的降解率随H2O2浓度的增加而急剧增加；再增加H2O2的浓度，dimethoate的降解率增加得并不明显；当H2O2浓度大于6 mmol/L时，降解率又开始呈缓慢下降的趋势，意味着H2O2利用效率的下降。由于H2O2是很强的氧化剂，不仅能俘获光致电子，还能有效地降低光催化剂表面电子-空穴对的复合。在H2O2浓度较低时，光催化性能的提高归因于·OH形成量的增加；体系中的H2O2浓度过高时，吸附于光催化剂表面的过氧化氢不仅可能造成H2O2与有机污染物在催化剂表面的竞争、阻止了dimethoate在其表面的吸附，而且会减少生成于光催化剂表面上的·OH或俘获光致空穴，进而抑制·OH的形成，影响光催化的效果，导致降解率又呈下降趋势。

2.5 废水中有机碳降解的对比

在其他条件相同的情况下，图7为AgO-TiO2/AC复合光催化剂、TiO2/AC以及P25催化剂对污染物矿化的情况。图7显示，AgO-TiO2/AC对有机碳的降解效果要好于另外两种催化剂，表明AgO-TiO2/AC可以更有效地分解有机物和产生的中间产物。这是因为掺杂后TiO2的晶粒尺寸变小，比表面积增大。而晶粒尺寸越小，光生载流子到达光催化剂表面的路程就越短[6]，光生电子和空穴的复合几率也就越小，更多的光生载流子迁移到催化剂表面参与氧化还原的反应，从而有利于TiO2光催化活性的提高；而且，晶粒尺寸变小时能隙变宽，导带电位变得更负，价带电位变得更正，氧化还原能力更强。催化剂的比表面积是影响其催化活性的一个重要参数，比表面积越大，表面原子在整个粒子中所占比例相应地增加，粒子对光的吸收效率提高，光的利用率增加；而比表面积越大，催化剂表面存在的活性中心相应地就越多，可以增大催化剂的吸附速率，有利于有机物质在催化剂表面的预吸附，从而有助于减少光生电子与空穴在催化剂表面上的复合，提高光催化活性。从掺杂离子本身的性质来看，一般认为，Ag+、Zn2+、La3+具有全充满的电子构型，会使得捕获的电子容易释放出来，形成浅势捕获，从而延长光生电子与空穴的寿命，提高TiO2的光量子产率[7]。UV-Vis吸收光谱显示，掺杂改性后的TiO2的吸收带边位置没有发生大的移动，但在紫外-可见光区的吸收效率有一定的增强，提高了催化剂的活性。这些都使得MexOy-TiO2/AC复合光催化剂能够更有效地分解有机物和产生的中间产物。

图7 对废水中TOC去处效果的比较Fig.7 Photoability of the composites

3 结论

本文制备的MexOy-TiO2/AC复合光催化剂在紫外光源和太阳光的照射下均具有很高的光催化活性。将制备的MexOy-TiO2/AC复合光催化剂（Me为Ag, Zn, La）固定到光催化反应器壁上，解决了催化剂的回收问题，同时可以有效降解污水中的污染物。

我们对dimethoate水溶液降解进行了研究，发现MexOy-TiO2/AC复合光催化剂对dimethoate水溶液的光催化降解率随起始pH值的增大而增大；降解率随反应物浓度的增大而降低。

通过对比试验，MexOy-TiO2/AC复合光催化剂比粉末P25和TiO2/AC可以更彻底地降解有机废水及其产生的中间体。

[1] 高濂, 郑珊, 张青红. 纳米二氧化钛光催化材料及应用[M]. 北京： 化学工业出版社, 2002： 1-13, 39-42.

[2] 刘守新, 陈广胜, 孙承林. 活性炭的光催化再生机理[J]. 环境化学, 2005, 24(4)： 405-408.

[3] FERNÀNDEZ A, LASSAKETTA G, JIMÉNEZ V M, et al. Preparation and characterization of TiO2photocatalysts supported on various rigid supports (glass, quartz and stainless steel)[J]. Appl. Catal. B., 1995, 7： 49-63.

[4] 赵秀峰, 张志红, 孟宪锋, 等. B掺杂TiO2/AC光催化剂的制备及活性[J]. 分子催化, 2003, 17(4)： 292-296.

[5] SUN Z S, CHEN Y X, KE Q, et al. Photocatalytic degradation of azo bye TiO2/bentonite nancomposite[J]. Acta Sientiae Circumtantiae (China), 2002, 149(1-3)： 169-174.

[6] 丁士文, 李梅, 王利勇. 铁掺杂纳米二氧化钛介孔材料的合成、结构与性能[J]. 西安交通大学学报, 2008, 42(9)： 1184-1188.

[7] 王铁, 王日燕, 韩志杰. 铁和镧共掺杂二氧化钛的光催化活性[J]. 应用化工, 2008, 37(8)： 913-916.

Abstract: TiO2films were deposited on AZ31 magnesium alloy substrates by r.f. magnetron sputtering technique. The surface properties of the films were investigated, including thermal stability, surface micro-hardness and corrosion in Hank’s simulated body fluid (SBF). The scanning electronic microscope observations reveal the dense structure characteristics of the as-deposited TiO2films. Under 200 ℃heat treatment for 30 minutes or 4 times’ heat cycles at 85 ℃ for one hour, no structural defects such as cracks were observed on the surface of the films, indicating the good thermal stability of the films. Nano-indentation experiment shows that the average micro-hardness of TiO2film reaches 1.51 GPa. Finally, the 7 days’ corrosion experiments in SBF initially reveal that TiO2films help to prevent the magnesium alloy from corroding in SBF in certain time.

Keywords: magnesium alloy; surface properties; TiO2films; magnetron sputtering

0 Introduction

As excellent light metals and structural materials, magnesium alloys have been widely used in industrial fields such as transportation, building, electronic products, etc[1-4]. Moreover, due to non-toxic properties and biocompatibility, magnesium alloys are bringing forth wonderful expectations on the application of medical field[5-6]. However, conventional magnesium alloys usually present poor surface properties such as poor corrosion resistance, temperature stability, which would greatly limit their further applications[7-10]. Thus the surface modification becomes critical to the application of magnesium alloys.

Multiple approaches have been explored to the surface modification of magnesium alloys, including anodic or microarc oxidation[1,3,11], magnetron sputtering[2,4,9], cathodic arc deposition[8], etc. Except magnetron sputtering, the mechanism of most of the above approaches is to form relatively dense oxidation layer on the surface of magnesium alloys via complex chemical or electrochemical reaction. So the quality of modification is related to the contents of metal elements of magnesium alloys and deposition conditions[1,3,11]. Comparatively, magnetron sputtering is one kind of physical vapor deposition technique to grow films on substrates, which is convenient and economy for operation and causing less environmental pollution. Usually the films are deposited by magnetron sputtering present good uniformity and expectable properties[2].

Due to high hardness and non-toxic properties, TiN film coating becomes an attractive choice for surface modification of magnesium alloy[7]. Furthermore, Al film presents charm for corrosion resistance[2,9]. Many studies on structural and mechanical properties of Al film and TiN film deposited on magnesium alloys have been reported. However, considering the biocompatibility of the coating materials in the filed of medical application, TiO2film might be also an desirable choice for the modification of magnesium alloy and then the study on the surface properties of TiO2film on magnesium alloy is significant[6].

AZ31 is one kind of widely used wrought magnesium alloy. In this paper, we report the deposition of TiO2films on AZ31 magnesium alloy substrates by r.f. magnetron sputtering and investigate the surface properties of TiO2films, including thermal stability, surface micro-hardness and corrosion in simulated body fluid. These researches are important for the application of TiO2films on the modification of magnesium alloys.

1 Experimental

Some 1 cm×1 cm as-casted AZ31 magnesium alloy chips about 2 mm thick, provided with by Jiaxing Engineering Technology Centre of Light Alloys Metals, Chinese Academy of Sciences, were used as substrates of the samples. The chips were firstly ground with SiC abrasive paper and then polished by one mechanical polishing equipment using corundum abrasive. The polished chips were cleaned in acetone by one ultrasonic cleaner, washed by deionized water and finally dried in air.

During the process of magnetron sputtering, the dried AZ31 chips were fixed onto the sample holder in the cavity of the magnetron sputtering equipment. The base pressure of the cavity was 5 × 10-4Pa. The sputtering atmosphere was the mixture of Ar and O2with working pressure 0.5 Pa. The sputtering target was 99.95 % TiO2ceramic disc purchased from Jiangxi Hai Te Advanced Material Co., LTD. During the sputtering, the substrates were not heated. The r.f. sputtering power and time reached 115 W and 50 minutes, respectively.

The as-deposited samples were marked with TiO21#, TiO22#, TiO23#, and TiO24#, respectively, for characterizations of different properties. Firstly for each as-deposited sample, the surface morphology was observed by one Hitachi S-4800 scanning electronic microscope (SEM). Secondly, TiO22# and TiO23# samples were used for two techniques of heat treatment experiments. For TiO22#, the heat treatment technique 1 was that, the sample was kept in the oven under 200 ℃ for 30 minutes and then removed from the oven and cooled in the air. For TiO22#, the heat treatment technique 2 was that, the sample was kept in the oven under 85 ℃ for one hour and then removed from the oven and cooled for 15 minutes in the air. These steps were repeated for three times. After the above heat treatment techniques, the surface morphologies of the samples were observed by SEM. The reason for choosing these two heat treatment techniques is to investigate the thermal stability of TiO2films.

Thirdly, the TiO24# sample was used for characterizing the surface micro-hardness of TiO2film by one MTS XP nano-indenter.

Finally, the TiO21# sample was chosen for the study of corrosion behavior in Hank’s simulated body fluid (SBF). The sample was first put into one bottle of SBF. The composition of SBF was NaCl (8.00g) + KCl (0.40g) + CaCl2(0.14g) + NaHCO3(0.35g) + MgCl2·6H2O (0.1g) + MgSO4·7H2O (0.06g) + KH2PO4(0.06g) + Na2HPO4·12H2O (0.06g) + H2O (1L)[5]。 After 7 days’ corrosion, the sample was removed from the bottle and washed by cleaning solution mixed with CrO3and AgNO3. The surface and profile morphologies of the corrosion sample were also observed by SEM.

2 Results and discussion

Before the SEM observation, the as-deposited TiO2films were characterized by X-ray diffraction for investigating their crystallization. The X-ray diffraction patterns present the films are polycrystalline with typical anatase structure but not rutile structure, which might be ascribed to low deposition temperature[12].

Fig.1 exhibits the surface and profile morphology images of as-deposited TiO21# sample. The surface morphology image displays that the as-deposited TiO2film is composed of uniformly distributed grains. The surface seems dense and no defects such as cracks are observed. The profile image indicates the thickness of the TiO2film, about 2～3 µm. The dense structural characteristics might result from the low deposition temperature and similar thermal expansion between the magnesium alloy substrate and the film[2].

The surface morphologies of TiO22# film before and after heat treatment under technique 1 are shown in Fig. 2. Before heat treatment, the as-deposited TiO22# film presents similar structural characteristics to the as-deposited TiO21# film. After heat treatment under 200 ℃ for 30 minutes, the size of grains hardly changed, implying that recrystallization would not occur below this temperature. Although the film was cooled in the air, no defects such as cracks are observed on the surface of the film and the surface keeps dense.

Fig. 1. The SEM morphology images of as- dSeposited films TiO21# sample (left： surface, right： profile)

Fig. 2. The surface morphology images of TiO2 2# film observed by SEM (Left： as-deposited, right： heated under technique1)

The surface morphologies of TiO23# film before and after heat treatment under technique 2 are shown in Fig. 3. Unlike technique 1, technique 2 means temperature shocking to some degree. From Fig. 3, it could be observed that the surface structural characteristics of the TiO2film would also hardly change and the surface of the film keeps dense.

Fig. 3. The surface morphology images of TiO2 3# film observed by SEM (Left： as-deposited, right： heated under technique2)

The above heat treatment experiment results reveal the good thermal stability of the TiO2films on AZ31 magnesium alloys. This kind of thermal stability further demonstrates the similar thermal expansion between the magnesium alloy substrate and the film.

The nano-indentation data of TiO24# film are listed in Table 1. Considering the thickness of the film is estimated as 2-3 µm according to Fig. 1, the indentation depth was chosen as 300 nm. For investigating the micro-hardness properties of the whole surface of the film, 16 indentation points were adopted. From Table 1, the micro-hardnessvalues vary from 1.135 GPa to 2.07 GPa. The worse uniformity of micro-hardness data might be related to the nano-sized effect. The arithmetic mean of the hardness of the 16 points is calculated as 1.510 GPa. The micro-hardness data of TiO2film is similar to that of Al film but much lower than that of TiN film, meaning that TiO2film has lower wear resistance than TiN film[2,13,14].

Tab. 1 Surface micro-hardness data (unit： GPa) of TiO24# film

The surface and profile morphologies of TiO21# film after corrosion experiment in SBF are shown in Fig.4. From the surface morphology image, it could be noticed that, after 7 days’ corrosion in SBF, the dense film was destroyed. Holes and corrosion products appear on the surface of the sample. The diameter of the corrosion holes ranges from 0.2 µm to 0.5 µm. At the same time, according to the profile morphology image, the depth of the corrosion hole is beneath 1 µm, indicating that the magnesium alloy substrate was not corroded. The corrosion behavior should be strongly related to the surface quality of the films[15]. These experiment results reveal that TiO2film helps to prevent the magnesium alloy from corroding in SBF in 7 days’ time.

Fig. 4. The morphology images of TiO2 1# film observed by SEM after corrosion experiment in SBF(left： surface, right： profile)

The corrosion behavior of surface-modified magnesium alloy could be understood as degradation behavior. The above studies of corrosion behavior of the TiO2films on magnesium alloy substrates initially reveal that TiO2films are valuable for controlling the degradation rate of magnesium alloys, which is vital to the clinical application. Certainly detailed corrosion or degradation mechanism should be further explored.

3 Conclusions

The as-deposited TiO2films on AZ31 magnesium alloy substrates prepared by r.f. magnetron sputtering present dense structure characteristics. Under 200 ℃ heat treatment for 30 minutes or 4 times heat treatment at 85 ℃ for one hour, no structural defects such as cracks are observed on the surface of the films, revealing good heat stability of the films. Nano-indentation experiment shows that the average micro-hardness of TiO2film reaches 1.510 GPa. Finally, the corrosion experiments in simulated body fluid initially reveal that TiO2films would help to control the corrosion or degradation rate of magnesium alloy in SBF.

Acknowledgements: The authors would like to appreciate the financial support from the Leading Academic Discipline Project of Shanghai Municipal Education Commission (No. J51803).

References:

[1] PARK S, JANG Y S, KIM Y K, et al. Surface characteristics of AZ91D alloy anodized with various conditions[J]. Surf. Interface Anal., 2008, 40：1270-1277.

[2] WU S K, YEN S C, CHOU T S. A study of r.f.-sputtered Al and Ni thin films on AZ91D magnesium alloy[J]. Surf. Coat. Tech., 2006, 200：2769-2774.

[3] LIU Y, WEI Z L, YANG F W, et al. Environmental friendly anodizing of AZ91D magnesium alloy in alkaline borate-benzoate electrolyte[J]. J. Alloys Compd., 2011, 509： 6440-6446.

[4] WU G S, ZENG X Q, LI G Y, et al. Preparation and characterization of ceramic/metal duplex coatings deposited on AZ31 magnesium alloy by multi-magnetron sputtering[J]. Mater. Lett., 2006, 60： 674-678.

[5] ZHANG J, ZONG Y, YUAN G Y, et al. Degradable behavior of new-type medical Mg-Nd-Zn-Zr magnesium alloy in simulated body fluid[J]. Chinese J. Nonferrous Met., 2010, 20： 1989-1997.

[6] YANG J X, CUI F, LEE I S, et al. Plasma surface modification of magnesium alloy for biomedical application[J]. Surf. Coat. Tech., 2010, 205：s182-s187.

[7] WU G S, WANG X M, DING K J, et al. Corrosion behavior of Ti-Al-N/Ti-Al duplex coating on AZ31magnesium alloy in NaCl aqueous solution[J]. Mater. Charact., 2009, 60： 803-807.

[8] ALTUN H, SINIC H. Corrosion behaviour of magnesium alloys coated with TiN by cathodic arc deposition in NaCl and Na2SO4solutions[J]. Mater. Charact., 2008, 59： 266-270.

[9] ZHANG J, YANG D H, OU X B. Microstructures and properties of aluminum film and its effect on corrosion resistance of AZ31B substrate[J]. Trans. Nonferrous Met. Soc. China, 2008, 18： s312-s317.

[10] JR S F, MERINO M C, ARRABAL R, et al. XPS study of the effect of aluminium on the atmospheric corrosion of the AZ31magnesium alloy[J]. Surf. Interface Anal., 2009, 41： 143-150.

[11] HUANG Y S, LIU H W. TEM analysis on micro-arc oxide coating on the surface of magnesium alloy[J]. J. Mater. Eng. Perform., 2011, 20：463-467.

[12] CHEN L F, CHENG C X. Study on nano TiO2films deposited by DC magnetron sputtering[J]. Journal of Luoyang Institute of Science and Technology： Natural Science Edition, 2009, 19： 5-7.

[13] BARSHILIA H C, JAIN A, RAJAM K S. Structure, hardness and thermal stability of nanolayered TiN/CrN multilayer coatings[J]. Vacuum, 2004, 72： 241-248.

[14] YU L H, DONG S R, XU J H, et al. Superhardness effect of TaN/TiN and NbN/TiN nanostructure multilayers and its mechanism[J]. Acta Phys. Sin.- Ch. Ed., 2008, 57： 7063-7066.

[15] HOCHE H, ROSENKRANZ C, DELP A, et al. Investigation of the macroscopic and microscopic electrochemicalcorrosion behaviour of PVD-coated magnesium die cast alloy AZ91[J]. Surf. Coat. Tech., 2005, 193： 178-184.

摘 要：利用射频磁控溅射工艺在AZ31镁合金表面溅射了TiO2薄膜，并对薄膜的特性进行了研究。扫描电镜观察显示制备态的TiO2薄膜结构致密，表面无缺陷。对薄膜经过200 ℃保温30分钟、常温冷却或者85 ℃保持一小时后放到常温保持15分钟，连续实施4次该操作的两种热处理工艺后，观察到薄膜表面致密结构没有发生变化，表面也没有缺陷生成。这表明了薄膜具有热稳定性。薄膜表面硬度特性研究表明薄膜表面的显微硬度为1.51 GPa。最后，研究了表面镀有TiO2薄膜的AZ31镁合金在模拟人体体液环境下的腐蚀（降解）特性。结果表明，在7天腐蚀过程中，AZ31镁合金基底没有被腐蚀，因此TiO2薄膜对AZ31镁合金基底具有很好的保护作用。

关键词：镁合金；表面特性；TiO2薄膜；磁控溅射

Study on the Application of Stabilized MexOy-TiO2/AC Photocatalysts

YUAN Hao, GU Yi-wen, ZHAO Li-na
( School of Urban Development and Environmental Engineering, Shanghai Second Polytechnic University, Shanghai 201209, P.R.China )

MexOy-TiO2/AC photocatalyts were prepared by using metatitanic acid（Me is Ag, Zn or La） to effectively degrade pollutants in water and to avoid the recovery of the photocatalysts. The photocatalysts that prepared were analyzed by XRD and SEM. The MexOy-TiO2/AC catalysts were stabilized on the inner surface of photocatalytic reactor and their photocatalytic activity for the photocatalytic degradation of methyl orange and dimethoate were studied. It was found that photocatalytic activity of MexOy-TiO2/AC catalytic doped with MexOy were higher than that of TiO2/AC photocatalyts. The photocatalytic activity of Ag2O- TiO2/AC mutiplex photocatalyts is the highest of all the studied samples.

photocatalytic activity; TiO2; dope; degradation

Surface Properties of TiO2Films Deposited on AZ31 Magnesium Alloys by r.f. Magnetron Sputtering

ZHU Xiang-rong1, BING Nai-ci1, SHEN Jiao-wen1, CHEN Qiu-rong2
(1.School of Urban Development and Environmental Engineering, Shanghai Second Polytechnic University, Shanghai 201209, P. R. China; 2. Jiaxing Engineering Technology Centre of Light Alloy Metals, Chinese Academy of Sciences, Jiaxing 314051, Zhejiang, P. R. China)

AZ31镁合金表面磁控溅射TiO2薄膜的表面特性的研究

祝向荣1，邴乃慈1，沈娇雯1，陈秋荣2
(1. 上海第二工业大学城市建设与环境工程学院，上海 201209；中国科学院嘉兴轻合金工程中心，浙江嘉兴 314051)

O643

A

文献标志码：A

1001-4543(2012)01-0037-06

2011-06-28;

2012-03-13

袁昊（1979－），男，湖北应城人，博士，主要研究方向为功能材料研究，电子邮箱yuanhao@eed.sspu.cn。

文章编号： 1001-4543(2012)01-0043-05

收稿日期： 2011-12-21; 修回日期： 2012-02-09

作者简介： 祝向荣（1971－），男，江西人，博士，主要研究方向为信息及环境友好功能材料，电子邮箱xrzhu@eed.sspu.cn。

上海市教育委员会重点学科建设项目（No. J51803）