Untersuchungen zur Physisorption und Chemisorption von Wasser auf Zinkoxid‐Oberflächen

Abstract

Summary. The investigation of different zinc oxide samples by means of thermogravimetry and infrared spectroscopy has shown that the surface of the samples is covered by an approximately monoatomic layer of hydroxide groups. Furthermore, varying amounts of carbonate groups are found which are due to the presence of zinc hydroxide carbonate I1 [Zn,(OH),(CO,),]. Below relative water vapour pressures of p/po = 0.2 (25"C), two hydrogen bridges connect one physisorbed water molecule with two chemisorbed surface hydroxide groups. In addition, about the same amount of water is physically adsorbed between vapour pressures of p/po 0.2 and 0.8. ,4t still higher relative humidity, a multiinolccular layer is built up which reaches a thickness of about 200 water molecules at p/po = 1.0.All samples show in the v-OH region of the IR. spectrum a broad absorption with four bands, A , B, C, and D. The position of the bands and the change of their intcnsities when rising the temperature of the samples up to 600°C indicate that both bands of longer wave lengths, C and D, arise from physically adsorbed water molecules, while the bands A and B are due to hydroxide groups located on the crystallographic faces (0001) and (OOOX), respectively.

Coagulation in a shear field generated by stirring in a cylindrical vessel

“…The ZnO was found, in agreement with data reported by other investigators on similar samples (5)(6)(7)(8)(9)(10)(11)(12), to contain both "water" and "CO2. "…”

Nature and Estimation of Functional Groups on Solid Surfaces

“…Thus, the two bands observed for BeO at 3735 and 3630 cm -1 are assigned to these free OR groups. In the case of ZnO, Tsyganenko and Filimonov [62] disagree with the previously mentioned assignment of Atherton et al [83] and Mattmann et al [84] of the reported two sharp bands of isolated OR groups at 3680 and 3620 cm -1 to type I and type III hydroxy Is, respectively. They argue, that Zn 2 + ions due to their relatively large ionic radius, may have a higher coordination number with respect to oxygen in the surface than in bulk ZnO.…”

“…Each of these two faces provides one possible configuration for surface OH groups, a singly coordinated OH in the (0001) plane and a triply bridging group in the (0001) plane as shown in Figure 4. The observed narrow bands of isolated OH groups at 3660-3685 cm-1 and 3610-3630 cm-1 were therefore attributed to these two configurations [83,84]. Tsyganenko and Filimonov [62] have generalized this approach to explain the frequently observed multiplicity ofOH stretching bands by the assumption Reproduced with permission from ref.…”

In situ electrochemical Scanning Kelvin Probe Blister-Test studies of the de-adhesion kinetics at polymer/zinc oxide/zinc interfaces

“…If the interfacial water activity reaches a critical low value, it should converge more and more towards ice-like structures with a high degree of order. Mattmann et al [42] investigated water adsorption isotherms on zinc oxide. He reported that for around 80% r.h. two water monolayers will be strongly adsorbed on ZnO and that a change from 97 to 82% r.h. will lead to the evaporation of the additionally physisorbed liquid-like H 2 O multilayers.…”