Plasma Enhanced Glass Surface Modification: Structure and Properties
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PLASMA ENHANCED GLASS SURFACE MODIFICATION: STRUCTURE AND PROPERTIES XIAOBO ZHOU, R. A. CONDRATE, SR. AND P. F. JOHNSON College of Ceramics, Alfred University, NY 14802
ABSTRACT Soda-lime-silica glasses were treated by an argon plasma, that was generated by an inductively-coupled rf power supply. The surface composition of the treated glasses
were profiled using SIMS, and the glass structure was probed using diffuse reflectance FTIR spectroscopy. A Buehler Micromet II (micro hardness tester) was used to measure hardness. The effects of various process parameters such as temperature, gas pressure and treatment time on glass surface composition, structure and properties are discussed. The results show that the surfaces of the treated samples were dealkalized to some depths
as great as 0.5 1L.The surface structure of the treated glasses is close to that of pure silica glass and surface hardness is improved after plasma treatment.
INTRODUCTION Plasma treatment as a modification technique involves a variety of physical and chemical interactions with a solid. Metallurgists and electronic materials specialists have long made use of plasmas to modify surfaces I1-3]. Direct plasma reaction has been developed for nitriding glass surfaces [N. In recent years, plasma sputtering has also been widely used in the glass industry to clean glass surfacesN1 . However, little attention, to our knowledge, has been paid to the effects of plasma treatment on glass surface structure, composition and properties. Many investi ators, however have found that electron bombardment I"] and ion bombardment [8-12f can cause alkali depletion of glass surfaces. McCaughan [11(predicted that ion migration may result from plasma reaction with glass. The purpose of the present work is to investigate the effects of plasma treatment on glass surface. Plasma treatments are very complex and involve a significant number of process variable in addition to the standard time, temperature and atmosphere variables common to all thermal processing techniques. Details of plasma composition are strongly influenced by the power, the reactor design and the gas composition. To simplify our study, only one gas component (Ar) will be used in this study. EXPERIMENTAL A schematic diagram of the plasma unit is shown in fig. 1. It consists of an amorphous silica reaction chamber of diameter 3 cm. A 4-turn, water-cooled, 1/4 inch copper
tube induction coil, powered by a LECO 13.56 MHz RF generator of lkw maximum capacity, is used for generating the plasma. Samples were prepared to an approximate size of 10xlOxO.9 mm from soda-lime-silica microscope slides purchased from VWR
Scientific Inc. Table 1 shows the composition of the samples. The sample was placed on an amorphous silica stage which is located on the axis of the chamber and at the lowest coil level to keep the sample immersed in the plasma but at a relatively low tempera-
ture. The chamber was evacuated to 3 Pa using a mechanical vacuum pump, and filled to the desired pressure with an inert gas. The inert gas (
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