Fouling behaviour of zwitterionic DLC surfaces

在拟议的项目中，应通过实验研究以下两个假设在化学过程工程中应用的涂层表面上形成污垢沉积物的正确性，并将所获得的结果纳入一个综合模型中。改性类金刚石碳涂层(DLC)的表面表现出异常良好的污垢行为，即，如果在使用条件下，这些表面提供相同和显著密度的正负电荷表面官能团(所谓的两性离子表面)，则这些表面对过饱和水溶液中的蛋白质和盐类的吸附特别低。2.)如已知的那样，具有这种表面的涂层不仅可以在沉积后通过等离子改性获得，还可以在沉积过程中加入合适的元素或化合物，如氧气和氮气或二氧化硫和氮气。为了验证这些假设，将采用等离子体激活化学气相沉积的方法制备类金刚石涂层。在使用条件下，即在通常为6&lt；pH&lt；8的水溶液中，通过在生长的薄膜中加入杂原子(O、N、S)，在从低碳氢化合物沉积薄膜的过程中添加适当的气体或蒸汽，可以制备出在使用条件下被电离的功能表面基团。这样得到的表面将被物理化学表征；特别是表面自由能的Zeta势和LW-AB分量将被研究。涂层成分将使用XPS和一定程度上的EPMA来研究，主要通过FTIR-ATR光谱来研究与污垢相关的表面官能团。经过适当的处理后，表面将分别暴露在典型的清洁和污垢条件下，使用乳清分离蛋白(WPI)和奶盐(模拟牛奶超滤液，SMUF)作为污垢系统。在实验中获得的数据和见解将被用作数学模型描述的基础。深入了解表面、污垢沉积和清洗机制之间的相互作用将增加定制表面设计和适应清洗策略的机会。

In the proposed project the validity of the following two hypotheses about the formation of fouling deposits on coated surfaces for applications in chemical process engineering shall be studied experimentally and the obtained results shall be incorporated in a comprehensive model: 1.) Surfaces of modified diamond-like carbon coatings (DLC) show an exceptionally favourable fouling behaviour, i.e., especially low adsorption of proteins and salts from supersaturated aqueous solutions, if, under conditions of use, these surfaces furnish identical and significant densities of positively and negatively charged surface functional groups (so-called zwitterionic surfaces). 2.) Coatings with such surfaces are not only accessible - as already known - by plasma-based modification after deposition, but also by the incorporation of suitable elements or compounds during deposition, such as oxygen and nitrogen or sulfur dioxide and nitrogen. In order to evaluate these hypotheses DLC coatings will be prepared by plasma-activated chemical vapour deposition. Functional surface groups which are ionized under conditions of use, i.e., in aqueous solutions with typically 6 < pH < 8, will be prepared by incorporation of hetero-atoms (O, N, S) into the growing film by the addition of suitable gases or vapours during film deposition from low hydrocarbons. Thus obtained surfaces will be characterised physico-chemically; particularly zeta potentials und LW-AB components of surface free energies will be studied. Coating compositions will be investigated using XPS and to some extent EPMA, fouling-relevant surface functional groups primarily by FTIR-ATR spectroscopy. After suitable conditioning the surfaces will be exposed to typical cleaning and fouling conditions, respectively, using whey protein isolates (WPI) and milk salts (simulated milk ultra filtrate, SMUF) as fouling systems. The data and insights obtained in the experiments will be used as the basis for a description in terms of a mathematical model. An in-depth understanding of the interactions between surface, fouling deposit, and cleaning mechanisms will enable improved opportunities of tailor-made surface design as well as an adapted cleaning strategy.