等离子体化学气相沉积法合成石英玻璃_英文_

朱洪波等：矿渣粉、高钙灰及其改性材料对水泥早期水化进程的影响· 531 ·第36卷第4期等离子体化学气相沉积法合成石英玻璃宋学富1，孙元成2，钟海2，王宏杰2，顾真安2(1. 哈尔滨工业大学材料科学与工程学院，哈尔滨 150001；2. 中国建筑材料科学研究总院，北京 100024)摘要：用高频等离子体作为热源，采用化学气相沉积法合成了石英玻璃样品。

实验分别使用O2和空气作为等离子体电离气体和冷却保护气体，改变等离子体电离工作气体种类时，等离子体火焰长度和石英玻璃沉积温度变化较大，而灯具冷却保护气体的改变对等离子火焰长度和石英玻璃沉积温度的影响不大。

当等离子体电离气体和灯具保护气体均为O2时，等离子体火焰长度为12cm，石英基体温度为1300℃，当等离子体电离气体和灯具保护气体均为空气时，等离子体火焰长度可达24cm，石英基体温度升高到1840℃，可确保气相沉积过程进行，合成的石英玻璃在波长190nm处光透过率达84%，羟基含量3.5×10–6，可达到全光谱透过的要求。

关键词：等离子火焰；化学气相沉积；石英玻璃中图分类号：TQ171；O643 文献标识码：A 文章编号：0454–5648(2008)04–0531–04SYNTHESIS OF SILICA GLASS BY PLASMA CHEMICAL V APOR DEPOSITION METHODSONG Xuefu1，SUN Yuancheng2，ZHONG Hai2，WANG Hongjie2，GU Zhen’an2(1. School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001;2. China Building Materials Academy, Beijing 100024, China)Abstract: Silica glass was synthesized by plasma chemical vapor deposition method, which uses inductively coupled plasma as the heat source. Air and oxygen were separately used as ionized gas and protecting gas. The influence of ionized gases on the length of plasma flame and the temperature of substrate is more significant than that of the protecting gases. A length of 24cm plasma flame and a deposition temperature of 1300℃were obtained when oxygen was used as both ionized gases and protecting gases, but in the case of air, the length of plasma flame was 24cm and the deposition temperature was 1840℃. Both of the longer plasma flame and the higher deposition temperature offered a good condition to deposit high quality silica glass. The silica glass has 84% transmittance at a wavelength of 190nm and 3.5 10–6 of the hydroxyl group, which is the glass of full-spectrum transmittance.Key words: plasma flame; chemical vapor deposition; silica glassSilica glass has the low thermal expansion coefficient, low conductivity, good thermal shock resistance, corro-sion resistance and excellent spectrum transmittance, because of the high bond energy and compactness of the network structure. Thus it has become the fundamental material of the high-tech field and has been widely used in optics, photoelectrons and dielectric materials.[1–2] Higher properties of silica glass are required with the development of space technology, and the silica glass prepared by common chemical vapor deposition (CVD) method does not meet these requirements, because it contains a large quantity of hydroxy groups. Recently, the plasma chemical vapor deposition (PCVD) method has been widely used to prepare optical fiber, nanomaterials and thin films, and in heat treatment of materials.[3–4] The cleanliness of its heat source ensures the purity of materials and avoids secondary pollutant. In this paper, silica glass was synthesized by PCVD.1 Experimental procedureA high frequency current was obtained by a modified收稿日期：2007–10–01。

修改稿收到日期：2008–01–30。

第一作者：宋学富(1978—)，男，博士研究生。

通讯作者：顾真安(1936—)，男，中国工程院院士。

Received date:2007–10–01. Approved date: 2008–01–30.First author: SONG Xuefu (1978–), male, postgraduate student for doctor degree.E-mail: songxuefu@Correspondent author: GU Zhen’an (1936–), male, academician of theChinese Academy of Engineering.E-mail: guzha@第36卷第4期2008年4月硅酸盐学报JOURNAL OF THE CHINESE CERAMIC SOCIETYVol. 36，No. 4April，2008硅 酸 盐 学 报· 532 ·2008年oscillator coupled with gas in the burner by a water- cooled copper induction coil. The gas was ionized and generated a plasma torch,[5–7] which was used to heat the silica substrate. Gaseous SiCl 4 was ejected into the flame carried by the carrier gas, and the chemical reaction took place as follows:SiCl 4+O 2=SiO 2+2Cl 2 (1) The reaction product, SiO 2, was deposited onto the silica substrate and silica glass was prepared. The ex-perimental facility is shown in Fig.1.Fig.1 Experimental equipment schematic of PCVDpreparation silica glassDifferent kinds of gas were used respectively as working gases 1 and 2, and the influence of gas on the plasma flame was analyzed. Working gases 1 and 2 were O 2 and O 2, O 2 and air, air and O 2, and air and air, respec-tively. The length of flame and the substrate temperature were both measured under the above conditions. The gases were controlled by a glass rotameter, and the gas-flow rates of working gases 1 and 2 were 5 m 3/h and 9 m 3/h separately. During temperature measurement, the silica substrate was 80 mm away from the induction coil, meanwhile, the flow of SiCl 4 was turned off and the input power of the plasma generator was 100 kw. Silica glass 1 was synthesized using O 2 as working gases 1 and 2 for 15 h, and silica glass 2 was synthesized using air as working gases 1 and 2 for 19 h. The transmittance prop-erty of the prepared silica glass was tested by a UV3101- PC UV-Visible-IR spectrophotometer.2 Results and discussion2.1 Influence of working gasIn this experiment, the induction coil received energy from the oscillator and generated a high frequency elec-tromagnetic field, which ionized the gas in the burner. Finally inductively coupled plasma was obtained. Plasma generated by different gases under the same conditions had different properties as a result of the different ioniza-tion energy. The length of the plasma torch changed when changing working gases 1 and 2, because the place andflow state of them were different. The length of the plasma flame and temperature of the silica glass substratewere measured and shown in Figs.2 and 3.Fig.2Length of plasma flame with different working gasesFig.3 Temperature of silica substrates with different workinggases宋学富 等：等离子体化学气相沉积法合成石英玻璃· 533 ·第36卷第4期According to Fig.2, the flame length of experiments was 12–24 cm. The influence of working gas 2 on flame length was slight compared with working gas 1, and the flame length was the longest when working gas 1 and 2 were both air. The variation of plasma flame indicates the different degree of ionization. Air is a mixed gas. Besides its main gases N 2 and O 2, there are other trace gases. The first ionization energies of these gases are shown in Table 1. The dewpoint of air and O 2 is –67 ℃, so the influences of water is the same. The first ionization energy of O 2 was lower than Ar, and the length of the Ar plasma flame was longer than the O 2 plasma flame. So it is not accurate to judge the discharge ability of gas in plasma according to the first ionization energy alone. This is because dia-tomic molecules will break up into atoms before ioniza-tion and absorb energy. In air plasma flames, the raregases, which are monoatomic molecules, will be ionized first, and the electrons generated will collide with other molecules, and then more gas molecules will be ionized. As a result, when gas was used as both working gases 1 and 2, the degree of ionization was the highest and the plasma flame was the longest. Working gas 1 mainly per-formed as ionization gas, while working gas 2 took the function of cooling the burner and kept it from being fused. So the influence of working gas 1 on the plasma flame was greater than that of working gas 2. The surface temperature of silica glass substrate rose from 1 300 ℃ to 1 840 ℃ when the working gases were changed from O 2 to air, which ensured good condition for vapor deposi-tion.Table 1 First ionization energies of gas-phase molecules in airGas Ar H 2O He N 2O 2 CO CO 2 Xe Ne Kr RnFirst ionization energy/eV 15.75 11.35 24.59 15.05 12.07 14.01 13.77 12.13 21.56 14.00 10.752.2 Spectrum analysisThe appearances of silica glasses 1 and 2 are shown in Fig.4. Silica glass 1 was deposited at a lower temperature, and the reaction product SiO 2 could not be deposited onto the substrate uniformly and form high quality silica glass,so only subtransparent glass was prepared. Silica glass 2Fig.4 Appearance of silica glasseswas deposited at a higher temperature, and SiO 2 could be deposited onto the substrate in a fused state, so transpar-ent silica glass of high quality was obtained. The spectra transmittance curves of silica glass 2 are shown in Fig.5. According to Fig.5, the transmittance of light with a wavelength of 190nm was 84%(Fig.5(a)). And there wasFig.5 Spectra transmittance curves of silica glass硅 酸 盐 学 报· 534 ·2008年an absorption peak at a wavelength of 2 730 nm(Fig.5(b)), which took place due to the vibration of O —H radicals in the structure network, and its content can be calculated as follow:0196.5lg I C d I ⎛⎞=⎜⎟⎝⎠ (2)Where, C is the content of hydroxyl group content; d is the thickness of the silica glass sample;0I is the distance from the base line at 2 730 nm to the zero line;I is the distance from the peak at 2 730 nm to the zero line.According to Formula(2), the hydroxyl group content was 3.5×10–6, which meets the requirements for full- spectrum transmittance.3 Conclusions(1) The plasma torch length reached 24cm and the silica glass substrate temperature was 1 840 ℃with air used as working gases 1 and 2. In these conditions, the vapor deposition proceeded well and silica glass with high quality was prepared.(2) Using air as both working gases, the deposited sil-ica glass has a transmittance of 84% at 190 nm wave-length light, and the hydroxyl group content is 3.5×10–6, which meets the requirements of space technology.References:[1] WEN Guangwu, LEI Tingquan, ZHOU Yu. Progress in research onfused silica matrix composites [J]. J Mater Eng, 2002, 1: 40–43. [2] XUE Siwen, PROULX Pierre, BOULOS M I. Effect of the coil anglein an inductively coupled plasma torch: a novel tow-dimensional model [J]. Plasma Chem Plasma Process, 2003, 23(2): 245–263. [3] TSANTILIS S, BRIESEN H, -PRA TSINIS.S.E.Sintering time for silicaparticle growth.Aerosol Sci and Tech [J]. 2001, 34: 237–246.[4] CANNAS M, COSTA S, BOSCAINO R, et al. Post UV irradiationannealing of E’ centers in silica controlled by H 2 diffusion [J]. J Non- Crystal Solids, 2004, 337(1): 9–14.[5] WANG Yufen, ZHONG Hai, SONG Xuefu, et al. 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