Improved surface properties of polymer materials by multiple ion beam treatment
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Ion beam treatment studies have been carried out to investigate the potential for improvements in surface-sensitive properties of polymers. Kapton, Teflon, Tefzel, and Mylar have been implanted with boron, nitrogen, carbon, silicon, and iron ions, singly or simultaneously with dual or triple beams. The implanted materials were characterized by optical microscopy, transmission electron microscopy, nano-hardness indentation, wear testing, scanning tunneling microscopy, x-ray analysis, nuclear reaction analysis, Fourier transform infrared spectroscopy, and Raman spectroscopy. Although the polymers showed a color change and varying degrees of measurable surface depression in the bombarded area, the implanted surface revealed substantial improvements in surface smoothness, hardness, and wear resistance. In particular, B, N, C triple-beam implanted Kapton showed over 30 times larger hardness than unimplanted material, making it more than three times harder than stainless steel. Sliding wear properties were characterized using an oscillating nylon or high carbon steel wear ball. Severe wear tracks were observed in virgin Kapton, but no appreciable wear was observed in ion implanted Kapton. Mechanisms underlying the improved surface properties are addressed.
I. INTRODUCTION
Polymeric solids have risen in importance at an astonishing rate in recent years. Polymer materials have many unique advantages, including their light weight, moldability, ability to form intricate shapes, corrosion resistance, versatile electronic properties, and low manufacturing cost. Their increased use spans applications ranging from materials for everyday life to both low- and high-technology engineering applications. The usage of polymers has been, however, generally limited to relatively mild service applications because of their inherent softness. A qualitative change in the severity of intended applications depends upon improving mechanical properties. In particular, surface-sensitive properties such as hardness and resistance to wear, abrasion, erosion, and fatigue, especially at somewhat elevated temperatures, must be improved. Applications include automobile, marine and aircraft exterior structural components, various utensils, high-speed moving parts, and load-bearing components subject to wear and severe stress histories. High performance organic coatings are used in aircraft to improve the impact resistance against rain, seawater, dust, gravel, stones, de-icing salts, and exhaust chemicals during take-off and landing; yet the demand for wear resistant polymers is increasing.1 The rapid growth in importance of the field of polymer science and engineering within the field of materials science and engineering attests to the high level of demand in this general area. 610
Highly crosslinked polymers have good resistance to thermal degradation, and crosslinking induced by y-irradiation has been applied for this purpose. Literature regarding ion implanted polymers relates mostly to changes in electrical or optical properties.2"7 Few papers d
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