固定化MexOy-TiO2/活性炭催化劑的應(yīng)用研究

袁 昊，顧依文，趙麗娜(上海第二工業(yè)大學(xué)城市建設(shè)與環(huán)境工程學(xué)院，上海 201209)

固定化MexOy-TiO2/活性炭催化劑的應(yīng)用研究

袁 昊，顧依文，趙麗娜
(上海第二工業(yè)大學(xué)城市建設(shè)與環(huán)境工程學(xué)院，上海 201209)

為了研究既能有效降解水中有機(jī)污染物，又能從處理過的廢水中方便地回收光催化劑，利用工業(yè)偏鈦酸為原料，制備了MexOy-TiO2/AC復(fù)合光催化劑（Me為Ag、Zn、La），并采用XRD、SEM等對(duì)復(fù)合光催化劑進(jìn)行了表征。將MexOy-TiO2/AC催化劑涂在光催化反應(yīng)器壁上，以O(shè), O-二甲基-S-（N-甲基氨基甲酰甲基）二硫代磷酸酯（dimethoate）水溶液為目標(biāo)污染物，研究了復(fù)合光催化劑的光催化活性。結(jié)果表明，MexOy的摻入可使TiO2/AC復(fù)合光催化劑的光催化活性增強(qiáng)，其中制備的Ag2O-TiO2/AC復(fù)合光催化劑的光催化活性最高。

光催化活性；二氧化鈦；摻雜；降解

0 引言

在眾多半導(dǎo)體光催化劑中，二氧化鈦因其光催化活性高、穩(wěn)定性好而倍受關(guān)注。目前，降解水中污染物時(shí)通常采用TiO2懸浮體系（P25）。此體系中納米TiO2與污染物充分接觸，能有效地光催化、氧化水中的有機(jī)污染物[1]。長(zhǎng)期以來，光催化技術(shù)的處理效率始終難以達(dá)到實(shí)際應(yīng)用的水平。這是因?yàn)樵摷夹g(shù)存在一些缺陷：（1）懸浮態(tài)的二氧化鈦對(duì)有機(jī)物吸附性差，污染物在其周圍聚集的濃度低，影響催化降解效果；（2）懸浮相TiO2光催化劑回收困難，難以二次利用，限制了光催化技術(shù)的廣泛應(yīng)用；（3）TiO2半導(dǎo)體只能吸收紫外光區(qū)的光能，而這部分光能僅占太陽能光強(qiáng)的4 %，對(duì)自然光的利用率低。

經(jīng)研究發(fā)現(xiàn)，活性炭（AC）可以將溶液中的目標(biāo)污染物富集到TiO2催化劑表面，在TiO2表面產(chǎn)生一個(gè)底物富集環(huán)境，從而提高污染物的礦化速度，而且中間產(chǎn)物也被吸附在催化劑表面并被分解，避免了二次污染的產(chǎn)生[2]。為了有效地解決催化劑技術(shù)存在的缺陷，本文以活性炭作為催化劑載體，將金屬氧化物摻雜到二氧化鈦催化劑中制備復(fù)合光催化劑，改變粒子結(jié)構(gòu)與表面性質(zhì)，促進(jìn)光生電子——空穴對(duì)的有效分離，提高光催化劑的光催化活性[3]；再將TiO2復(fù)合光催化劑負(fù)載到反應(yīng)器壁上，在TiO2表面產(chǎn)生一個(gè)底物富集環(huán)境，從而解決了上面提到的問題。

1 試驗(yàn)方法

1.1 催化劑制備

在373 K溫度下，將顆粒狀活性炭（AC, 40 ～ 60 mesh）用濃HNO3煮沸1 h活化生成羥基，然后用去離子水洗凈，干燥后放入石英反應(yīng)器中，用干燥N2在373 K下干燥25分鐘。

取偏鈦酸（硫酸法鈦白粉中間體）加入濃硫酸，在373 K條件下攪拌2.5 h，得到透明澄清的溶液。然后邊攪拌邊滴加已配制好的AC以及摻雜改性鹽堿性溶液，老化、抽濾，最后在氮?dú)獗Ｗo(hù)下煅燒3 h[4]，研磨即得MexOy-TiO2/AC復(fù)合光催化劑（Me為Ag、Zn、La），將制備好的催化劑用丙烯酸粘膠劑固定在反應(yīng)器壁上。

1.2 催化劑制備的表征

TiO2的晶型通過XRD在D /max-RA 轉(zhuǎn)靶X射線多晶衍射儀上測(cè)定，其Cu Kα射線λ＝0.154 18 nm，掃描范圍2θ= 20° ～ 70°。用SEM分析TiO2的形貌和顆粒大小。

1.3 光降解試驗(yàn)

將一定濃度的dimethoate（樂果O, O-二甲基-S-[2-(甲胺基)-2-氧代乙基]硫代磷酸酯）設(shè)定為實(shí)驗(yàn)?zāi)繕?biāo)污染物。在自制的實(shí)驗(yàn)裝置中，以紫外殺菌燈（功率8 W，主發(fā)射波長(zhǎng)253.7 nm）作為光催化反應(yīng)的光源。兩個(gè)燈管平行放置，置于溶液上方，距離液面7 cm。由磁力攪拌向系統(tǒng)提供反應(yīng)所需的溶解氧，并促進(jìn)反應(yīng)物和產(chǎn)物的傳質(zhì)。實(shí)驗(yàn)進(jìn)行3 h，每隔0.5 h取樣，經(jīng)濾紙過濾后，再取樣后測(cè)其吸光度，測(cè)定溶液中dimethoate的殘余濃度，以評(píng)價(jià)其催化性能。通過Apollo TOC 9000測(cè)定總有機(jī)碳（TOC）。用UV-2450紫外-可見分光光度儀測(cè)定Dimethoate濃度（λmax=800 nm）。

Dimethoate降解率定義為

式中C0為Dimethoate的初始濃度，Ct為反應(yīng)時(shí)間t時(shí)的Dimethoate濃度。

2 結(jié)果與討論

2.1 催化劑的表征

圖1為MexOy-TiO2/AC 的SEM照片。通過SEM照片可以看出沉積物質(zhì)顆粒約為15 nm ～ 25 nm，較大的顆粒達(dá)到了近50 nm，顆粒均勻分散且顆粒間的邊界清晰。圖2的TEM照片顯示TiO2粒子分布得比較均勻，形狀多為橢球形。由此表明，摻雜活性炭可以改善TiO2的分散性，抑制晶粒的生長(zhǎng)，使其形成較小顆粒，且粒徑能夠均勻分布。

在XRD譜圖中（如圖3），摻雜改性后的MexOy-TiO2/AC（Me是Ag）的X射線衍射譜圖主要表現(xiàn)在對(duì)應(yīng)于層間隙最大距離d 001的差異，表明產(chǎn)物層間距大小的（001）面衍射峰有向大角度移動(dòng)的趨勢(shì)，層間距的變化顯示出有形成MexOy-TiO2/AC復(fù)合物的可能。TiO2的晶型對(duì)光催化劑活性有很大的影響，銳鈦礦型（α-TiO2, Anatase）的光催化活性比較高。從圖中可以看出，樣品主要表現(xiàn)為銳鈦礦型，在衍射角2θ= 25.3°, 37.8°, 48.0°, 53.9°, 55.1°, 62.7°, 68.9°和70.4°處有明顯的衍射峰，各峰對(duì)應(yīng)的面間距d值與JCPDS卡中21-1272號(hào)銳鈦礦型TiO2的d值完全一致。同時(shí)可以觀察到少量的金紅石相出現(xiàn)，在衍射角2θ=27.4°處有金紅石相的特征衍射。

圖1 Ag摻雜樣品SEM圖Fig. 1 SEM image of the sample

圖2 Ag摻雜樣品TEM圖Fig. 2 TEM image of the sample

2.2 Dimethoate初始濃度的影響

在pH＝10.0，其他條件不變的情況下，不同dimethoate初始濃度下的光催化降解率隨時(shí)間的變化如圖4所示。

圖3 樣品 XRD 圖Fig.3 X-ray diffraction patterns of the sample

圖4 Dimethoate初始濃度對(duì)光降解率的影響Fig.3 The effect of Photoability concentration on the initial Dimethoate

由圖可看出，隨著dimethoate初始濃度的增加，其降解率大幅度降低。60 min內(nèi)，初始濃度為0.4×10-4mol/L的dimethoate溶液，其降解率為86.27 %；而初始濃度為10.0×10-4mol/L時(shí)，其降解率僅為10.05 %。光催化降解機(jī)理認(rèn)為，TiO2表面上光致電子-空穴對(duì)復(fù)合可在10-9s內(nèi)完成。反應(yīng)物必須先吸附于催化劑表面才能被有效降解，因此界面吸附過程是有機(jī)物降解率的重要控制因素。當(dāng)dimethoate的濃度增大，催化劑用量不變（即總吸附位不變）時(shí)，TiO2表面吸附的dimethoate增大，此時(shí)dimethoate的降解率雖然下降，但dimethoate的降解速率增大，體系的酸性增強(qiáng)，從而降低復(fù)合光催化劑的催化效果；當(dāng)dimethoate的初始濃度達(dá)到一定濃度后，TiO2表面達(dá)到吸附飽和，單位時(shí)間內(nèi)dimethoate的降解率將基本保持不變。在較低的初始濃度下，體系的酸性變化相對(duì)緩慢一些，有利于保持催化劑的高活性。這樣雖然對(duì)于催化劑表面的吸附不利，但由于采用了活性碳作為催化劑的載體，因此，在一定的濃度范圍內(nèi)可以減緩這方面的副作用，使得高濃度降解率遠(yuǎn)低于低濃度反應(yīng)。

2.3 反應(yīng)液初始pH值的影響

Dimethoate初始濃度為1.0×10-4mol/L時(shí)，60 min內(nèi)反應(yīng)液初始pH值對(duì)光催化的影響如圖5所示。從圖中可看出，60 min內(nèi)，pH = 2.0，6.5和11.5時(shí)，dimethoate的降解率分別為13.66 %，35.61 %和82.71 %，dimethoate的降解率隨pH值的升高而明顯增加。這是因?yàn)門iO2在酸性和堿性溶液中，催化降解的效果是不一樣的。TiO2的等電點(diǎn)約為pH=6.0[4]，在pH ＞ 6.0時(shí)的溶液中，OH-可以充當(dāng)光致空穴的俘獲劑（h++ OH-→ ?OH），在TiO2表面容易生成光致羥基自由基，加強(qiáng)氧化效果。在酸性條件下[5]，氧化物主要為光致空穴，其氧化能力比羥基自由基小，所以在酸性條件下TiO2的氧化能力比堿性條件下低。當(dāng)初始溶液是堿性時(shí)，OH-充當(dāng)光致空穴的俘獲劑（h++ OH-→ ?OH），在TiO2表面容易生成光致羥基自由基，Dimethoate中的有機(jī)硫產(chǎn)生硫酸、有機(jī)磷氧化產(chǎn)生磷酸、有機(jī)氮經(jīng)進(jìn)一步氧化為，這使得隨著MexOy-TiO2/AC復(fù)合光催化劑對(duì)dimethoate的降解，溶液中的酸根離子增加，溶液慢慢地變成酸性。此時(shí)，氧化物主要為光致空穴，其氧化能力比羥基自由基小，氧化能力下降，dimethoate的降解速率下降，pH值的變化也越來越小。pH值測(cè)定結(jié)果也表明，酸性條件下，溶液的pH變化較小，而在堿性條件下，溶液的pH由降解前的11.5大幅度地降低到4.27，說明dimethoate在堿性條件下更能有效地降解污染物及其產(chǎn)生的中間體。

圖5 反應(yīng)液起始pH值對(duì)Dimethoate光降解的影響Fig.5 The effect of initial pH value

2.4 氧化劑對(duì)復(fù)合光催化劑催化性能的影響

本試驗(yàn)在其他條件不變的情況下，分別加入一系列不同濃度的H2O2氧化劑，其濃度為0 ～ 9.0 mmol/L，經(jīng)過1 h的光催化降解，其結(jié)果如圖6。

圖6 氧化劑H2O2濃度的影響Fig.6 Photocatalytic degradation by H2O2

從圖6中可以看出，H2O2的濃度在0 ～ 3.00 mmol/L范圍內(nèi)，dimethoate的降解率隨H2O2濃度的增加而急劇增加；再增加H2O2的濃度，dimethoate的降解率增加得并不明顯；當(dāng)H2O2濃度大于6 mmol/L時(shí)，降解率又開始呈緩慢下降的趨勢(shì)，意味著H2O2利用效率的下降。由于H2O2是很強(qiáng)的氧化劑，不僅能俘獲光致電子，還能有效地降低光催化劑表面電子-空穴對(duì)的復(fù)合。在H2O2濃度較低時(shí)，光催化性能的提高歸因于·OH形成量的增加；體系中的H2O2濃度過高時(shí)，吸附于光催化劑表面的過氧化氫不僅可能造成H2O2與有機(jī)污染物在催化劑表面的競(jìng)爭(zhēng)、阻止了dimethoate在其表面的吸附，而且會(huì)減少生成于光催化劑表面上的·OH或俘獲光致空穴，進(jìn)而抑制·OH的形成，影響光催化的效果，導(dǎo)致降解率又呈下降趨勢(shì)。

2.5 廢水中有機(jī)碳降解的對(duì)比

在其他條件相同的情況下，圖7為AgO-TiO2/AC復(fù)合光催化劑、TiO2/AC以及P25催化劑對(duì)污染物礦化的情況。圖7顯示，AgO-TiO2/AC對(duì)有機(jī)碳的降解效果要好于另外兩種催化劑，表明AgO-TiO2/AC可以更有效地分解有機(jī)物和產(chǎn)生的中間產(chǎn)物。這是因?yàn)閾诫s后TiO2的晶粒尺寸變小，比表面積增大。而晶粒尺寸越小，光生載流子到達(dá)光催化劑表面的路程就越短[6]，光生電子和空穴的復(fù)合幾率也就越小，更多的光生載流子遷移到催化劑表面參與氧化還原的反應(yīng)，從而有利于TiO2光催化活性的提高；而且，晶粒尺寸變小時(shí)能隙變寬，導(dǎo)帶電位變得更負(fù)，價(jià)帶電位變得更正，氧化還原能力更強(qiáng)。催化劑的比表面積是影響其催化活性的一個(gè)重要參數(shù)，比表面積越大，表面原子在整個(gè)粒子中所占比例相應(yīng)地增加，粒子對(duì)光的吸收效率提高，光的利用率增加；而比表面積越大，催化劑表面存在的活性中心相應(yīng)地就越多，可以增大催化劑的吸附速率，有利于有機(jī)物質(zhì)在催化劑表面的預(yù)吸附，從而有助于減少光生電子與空穴在催化劑表面上的復(fù)合，提高光催化活性。從摻雜離子本身的性質(zhì)來看，一般認(rèn)為，Ag+、Zn2+、La3+具有全充滿的電子構(gòu)型，會(huì)使得捕獲的電子容易釋放出來，形成淺勢(shì)捕獲，從而延長(zhǎng)光生電子與空穴的壽命，提高TiO2的光量子產(chǎn)率[7]。UV-Vis吸收光譜顯示，摻雜改性后的TiO2的吸收帶邊位置沒有發(fā)生大的移動(dòng)，但在紫外-可見光區(qū)的吸收效率有一定的增強(qiáng)，提高了催化劑的活性。這些都使得MexOy-TiO2/AC復(fù)合光催化劑能夠更有效地分解有機(jī)物和產(chǎn)生的中間產(chǎn)物。

圖7 對(duì)廢水中TOC去處效果的比較Fig.7 Photoability of the composites

3 結(jié)論

本文制備的MexOy-TiO2/AC復(fù)合光催化劑在紫外光源和太陽光的照射下均具有很高的光催化活性。將制備的MexOy-TiO2/AC復(fù)合光催化劑（Me為Ag, Zn, La）固定到光催化反應(yīng)器壁上，解決了催化劑的回收問題，同時(shí)可以有效降解污水中的污染物。

我們對(duì)dimethoate水溶液降解進(jìn)行了研究，發(fā)現(xiàn)MexOy-TiO2/AC復(fù)合光催化劑對(duì)dimethoate水溶液的光催化降解率隨起始pH值的增大而增大；降解率隨反應(yīng)物濃度的增大而降低。

通過對(duì)比試驗(yàn)，MexOy-TiO2/AC復(fù)合光催化劑比粉末P25和TiO2/AC可以更徹底地降解有機(jī)廢水及其產(chǎn)生的中間體。

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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).

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摘 要：利用射頻磁控濺射工藝在AZ31鎂合金表面濺射了TiO2薄膜，并對(duì)薄膜的特性進(jìn)行了研究。掃描電鏡觀察顯示制備態(tài)的TiO2薄膜結(jié)構(gòu)致密，表面無缺陷。對(duì)薄膜經(jīng)過200 ℃保溫30分鐘、常溫冷卻或者85 ℃保持一小時(shí)后放到常溫保持15分鐘，連續(xù)實(shí)施4次該操作的兩種熱處理工藝后，觀察到薄膜表面致密結(jié)構(gòu)沒有發(fā)生變化，表面也沒有缺陷生成。這表明了薄膜具有熱穩(wěn)定性。薄膜表面硬度特性研究表明薄膜表面的顯微硬度為1.51 GPa。最后，研究了表面鍍有TiO2薄膜的AZ31鎂合金在模擬人體體液環(huán)境下的腐蝕（降解）特性。結(jié)果表明，在7天腐蝕過程中，AZ31鎂合金基底沒有被腐蝕，因此TiO2薄膜對(duì)AZ31鎂合金基底具有很好的保護(hù)作用。

關(guān)鍵詞：鎂合金；表面特性；TiO2薄膜；磁控濺射

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鎂合金表面磁控濺射TiO2薄膜的表面特性的研究

祝向榮1，邴乃慈1，沈嬌雯1，陳秋榮2
(1. 上海第二工業(yè)大學(xué)城市建設(shè)與環(huán)境工程學(xué)院，上海 201209；中國科學(xué)院嘉興輕合金工程中心，浙江嘉興 314051)

O643

A

文獻(xiàn)標(biāo)志碼：A

1001-4543(2012)01-0037-06

2011-06-28;

2012-03-13

袁昊（1979－），男，湖北應(yīng)城人，博士，主要研究方向?yàn)楣δ懿牧涎芯?，電子郵箱yuanhao@eed.sspu.cn。

文章編號(hào)： 1001-4543(2012)01-0043-05

收稿日期： 2011-12-21; 修回日期： 2012-02-09

作者簡(jiǎn)介： 祝向榮（1971－），男，江西人，博士，主要研究方向?yàn)樾畔⒓碍h(huán)境友好功能材料，電子郵箱xrzhu@eed.sspu.cn。

上海市教育委員會(huì)重點(diǎn)學(xué)科建設(shè)項(xiàng)目（No. J51803）