Fouling behaviour of zwitterionic DLC surfaces

在拟议的项目中，应通过实验研究以下两个关于在化学工艺工程中应用的涂层表面上形成污垢沉积物的假设的有效性，并将所得结果纳入综合模型：1）改性类金刚石碳涂层（DLC）的表面显示出异常有利的结垢行为，即，如果在使用条件下，这些表面提供相同和显著密度的带正电荷和带负电荷的表面官能团（所谓的两性离子表面），则从过饱和水溶液中对蛋白质和盐的吸附特别低。2.）具有这种表面的涂层不仅可通过沉积后的基于等离子体的改性（如已知的）获得，而且可通过在沉积期间引入合适的元素或化合物（例如氧和氮或二氧化硫和氮）获得。为了评估这些假设，将通过等离子体活化化学气相沉积制备DLC涂层。在使用条件下电离的功能性表面基团，即，在通常为6 < pH < 8的水溶液中，将通过在由低级烃的膜沉积过程中加入合适的气体或蒸气将杂原子（O、N、S）引入生长的膜中来制备。因此获得的表面将其特征在于物理化学;特别是zeta电位和LW-AB组件的表面自由能将进行研究。涂层组合物将使用XPS和在一定程度上EPMA，污垢相关的表面官能团主要通过FTIR-ATR光谱进行研究。在适当调节后，将表面分别暴露于典型的清洁和污染条件下，使用乳清蛋白分离物（WPI）和牛奶盐（模拟牛奶超滤液，SMUF）作为污染系统。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、污垢存款和清洁机制之间的相互作用，将有助于改进定制表面设计的机会以及适应的清洁策略。

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.