Etching Morphology of Vitreous Silicon Dioxide
in HF-Bad Solution
Zhufeng Shao1,a*, Shuzhong Tian2,b,Hui Wang1,c, Zaikui Xiang1,d
1China Building Materials Academy, Chaoyang district, Beijing, China
2Shandong Agriculture and Engineering University, Jinan, Shandong, China
a ,
b ,
c wanghui@cbmamail.
com,d
Key words: Quartz glass; Hydrofluoric Acid; Etching.
Abstract.The surface morphology of quartz glass etched in HF acid is influenced by many factors, such
as the quality of polishing, types of the quartz glass, metal ion in HF acid, etc. This paper conducted an analysis on the factors and tried to make improvements. Meanwhile, this experiment approved of the model of both destructive layer and the varying of clod micro-cracks in the process of etching. Besides, the changing law of both ditch-like and pit-like flaws was investigated in this experiment, and conclusions could be drawn as follows: at the concave curvature, the bigger the radius of curvature is, the faster the etching will be; The etching rate with protruding curvature is higher than that of concave curvature; The etching rate with concave curvature is lower than that on the plane surface.
Introduction
Vitreous Silicon Dioxide, a special type of technology glass compod of single SiO2, is a
new-technic and increasingly ud material, such as quartz glass pot ud for miconductor, quartz glass photoelectric transfer fiber, quartz glass for space navigation, quartz glass for nsor, etc. Quartz glass has become an esntial material for modern technology and industry. However, as a typical fragile material, quartz glass has poor machinability. Most quartz glass devices demand smooth surface, which should be achieved by preci polishing[1]. But many quartz glass has to be 元旦节的来历简介
procesd into complicated forms, like quartz glass ud for nsor [2]. Traditional machining will cau remnant stress and vere damage on sub-surface. Wet chemical etching of quartz glass can remove remnant stress and avoid damage on sub-surface with a high processing efficiency. Therefore, it is quite meaningful to conduct a systematical study on the influences of both internal and external structure upon the etching morphology of quartz glass, so as to improve the performance of quartz glass devices and broaden its practical application.
In 1771, Scheele prepared hydrofluoric acid for the first time and probably discovered that it etches silicate glass [3]. HF2-,(HF)2 are part of the component of hydrofluoric acid, and the reaction mechanism activates due to the mucleophilic substitution HF2-,(HF)2 for Si atom [4].
The equation of the reaction is
SiO2 + 4HF=SiF4 + 2H2O. (1)
SiF4 demonstrates gaous state under usual conditions, and can react with hydrofluoric acid before volatilization[5]. The equation is
4SiF 4 + 3H 2O + 2HF=3H 2SiF 6 + H 2SiO 3. (2)
When a smooth, polished surface is etched, the surface lo its smooth appearance and cusp-like structures are formed. Ying Su considered as acid concentration and etching temperature are two obvious influence factors of etching morphology[6]. However some other factors can also affect the morphology, in this picture if the reaction temperature and concentration of hydrofluoric acid are constant, the etching morphology will be effected by the factors like the quality of polishing, the internal flaw of quartz glass, the content of contamination metallic ions in solution, etc. It is necessary to do some study on the affect factures. Experiment
This study is bad on the type four quartz glass manufactured by China Building Material Academy. In this experiment, quartz glass were sliced and grinded with carborundum, who radius was 3.5 µm, then polished with 0.5 µm radius CeO 2 powder. After that, the polished slices were etched in a 15mol/L aqueous HF solution kept at the temperature of 37℃. The last process was to obrve the surface morphology with optical microscope. Model Building
Due to the glass ’s brittleness, lots of micro-cracks were buried in the sub-surface after the process of grinding and polishing. In the process of polishing, becau of the randomness of quartz glass ’ subsurface, the subsurface layer shows the performance of fluidity under the pressure of polishing tray, which result in the micro-cracks were concealed by the subsurface
layer(Fig. 1 (a)). Therefore, the micro-cracks can ’t be obrved even with optical microscope. Becau the circumambience all around the micro-cracks has a loo atomic structure, hydrofluoric
acid can infiltrate into the flaws easily, causing a faster reaction in the flaws than that in the complete surface. So the flaws will extend into ditches and pits rapidly if the slices were put into the hydrofluoric acid (Fig. 1 (b), (c), (d) ).The morphology of micro-cracks opened lightly ware shown in Fig.2 from overhead and lateral view.
The influence of polishing quality on etching morphology
The process of grinding and polishing can result in the creation, development and intercrossing of cracks on the surface of the glass, leading to the emergence and the removal of a destructive layer. The removal of the destructive layer is coinciding with the removal of some cracks. However, the process of mechanical actions can not only create new cracks but also stretch the existing cracks. Therefore, with the process of grinding and polishing going on, the clod micro-cracks would Fig.1 Transformation of a surface with clod microcracks or flaws into a cusp-likeglass surface by wet chemical
etching[6]
time and etched for the same duration. The morphology of the glass will be shown in Fig.4. With the process of polishing continuing, clod cracks gradually became shallower and fewer, leading to
a more smooth surface.
Fig.2 The Morphology of extending micro-cracks after being etched
(a) (b) overhead view (c) (d) lateral view[6]
Fig. 3 Transformation of clod microcracks with polishing
b a
c
d
Fig. 4 Influence of the duration of polishing upon the surface morphology (a) one hour after being
polished (b) three hours after being polished (c) five hours after being polished
掌舵人(d) eight hours after being polished
后奥运Table 1 Etching rate, time and increment of flaws Surface Etching Rate
62µm/h
Picture Lable a b c d e f g h i Etching Time(h) 0.90 1.35 1.93 3.20 4.40 5.84 8.03 10.19 15.27 Increment ditch
0 1.30 2.33 4.29 5.67 7.46 9.39 11.02 14.34 pit 0
2.22
4.38
7.88
10.30
13.64
18.36
20.76
27.48
The changes of surface flaws in the process of etching
Clod micro-cracks, remanent during the process of the polishing, as well as the interior flaws extended raplidly in HF acid, formed ditches and pits. Fig.6 tracked the etching changes of one ditch and pit in HF acid. a
c d
b
etching time Fig.5 Changes of ditch-like and pit-like flaws in the HF acid solution
Fig.5 showed that in the process of etching the quartz glass, the tip of the crack was gradually passivated and the radius of curvature incread, Table 1 showed the specific number. Besides, the
whole ditch-like flaw
became broadened and round, forming a circinal flaw finally. It
also showed that the extending rate of protruding curvature(Fig.5 A point)
三角函数倍角公式was higher than that of concave curvature Fig.5 B point). Fig.6 showed the increment of
ditch-like and pit-like flaws with
etching time. As the picture showed, the extending rate of pit-like flaw
g h
i
d e
f
a b
c
A B
the ditch-like one. Therefore, it could be concluded that, in the places where there is a concave curvature, the bigger the radius of curvature is, the faster the etching will be. In Fig.5 there was another phenomena that both of the ditch-like and pit-like flaws would gradually become shallower in the process of etching, showing that the etching rate with concave curvature is lower than that on the plane surface.海南热带飞禽世界
Conclusion擂鼓
1.The quality of polishing influences the surface morphology of quartz glass after being etched
greatly. The longer the polishing lasts, more smooth the surface morphology of quartz glass after being etched will be.
2.Flaws of various shapes in the quartz glass will gradually become shallower and circular
during the process of etching.
Acknowledgement
This article was funded by the Special National International Technology Cooperation of China (No.2012DFA51310).
Reference
Reference an article:肚子隐隐作痛
[1] H. G. Gao, B. Chen, J. L. Cao, Machining Technique of Superslick Optic Surface, Optics and
Precision Engineering. 1995,4:7-14.
五公主
[2] L. Zhuang, F. Yuan, Study of Arts flow of Pendulous Reed, Journal of Harbin Institute of
Technology. 1993,2:18-24.
[3] A. B.Burg, In Fluorine Chemistry, J. H. Simons, Academic Press: New York, 1950, V ol. I, p
150.
[4] D. M. Knotter. Etching Mechanism of Vitreous Silicon Dioxide in HF-Bad Solutions, J. Am.
Chem. Soc. 2000, 122, 4345-4351.
[5] Y. Su ,Y. H. Zhou, W. Huang, Study on Reaction Kinetics Between Silica Glass and
Hydrofluoric Acid, Journal of The Chine Ceramic Society. 2004, 3:227-293.
[6] G. A. C. M. Spierings, Wet Chemical Etching of Silicate Glass in Hydrofluoric Acid Bad
Solutions, Journal of Materials science. 28 (1993) 6261-6273.
[7] Y. Su, X. Y. He, G. Yu, Effect of Bulk and Surface Defects on Etched Surface Topography of
Silica Glass, Science and Technology of Overas Building Materials. 2007, 4:46-48.
