Application of microwave discharges for treatment of polymer surfaces
In this paper we analyze application of a simple microwave cavity discharge on the surface modification of polymers. Electrons and radicals from the low pressure plasma as well as the metastable excited oxygen species react intensively with many engineering plastic materials leading to the increased adhesion of polymers. This is of importance to achieve better bondability by gluing, painting, varnishing, stamping, printing or metalizing. The change of the wetting contact angle is discussed with respect to the treatment time and the polymer used. The creation of reactive functional groups of the hydroxyl and carboxyl acid type on the polymer surface is mainly responsible for the better adhesion. The lifetime of the bondability of polycarbonate, polymethyl methacrylate and polyether ketone was investigated. The surface modification of plastic materials may be performed in the vacuum chambers operated by low cost standar d microwave oven components or at a higher expense by rf generators at 13.6 MHz.
Microwave plasma: its characteristics and applications in thin film technology
Abstract Microwave plasmas differ significantly from other plasmas, exhibit many interesting properties and so offer new possibilities for the plasma processing of thin films. Plasma properties strongly depend on the conditions and methods used to excite the gas. Due to the existence of a direct connection between the properties of plasma-prepared thin films and plasma micro-parameters a perfect knowledge of the plasma generation is a basic requirement for mastering a plasma deposition process. Therefore, different methods of generating microwave isotropic and anisotropic plasmas are discussed. Special attention is devoted to the mechanisms of plasma excitation and to the generation of a dense and homogeneous plasma in large volumes. Some applications of microwave plasma in thin film technology are also presented.
Nonprofit Communication and Fundraising in China: Exploring the Theory of Situational Support in an International Context
Using a survey of 586 college students from Beijing, China, this study tested the theory of situational support by exploring Chinese students’ motivations to participate in nonprofit fundraising events. This study also compared theory variables between Chinese and U.S. college students by looking at similar data from a survey previously conducted with 514 U.S. students. There were differences between the two groups regarding constraint recognition, subjective norms, attitudes toward fundraising, and other variables, perhaps because of Confucianism, collectivism, and other differences between China and the United States. The findings generate a range of theoretical and practical implications including how nonprofit practitioners in China might develop better communication and messaging strategies to segment publics, motivate potential donors, and advance future fundraising efforts.