Artificial patination is mostly based on empirical recipes for which the result is difficult to forecast. Little is known about the final corrosion compound formed on the patinated object. Therefore, different patinas based on copper nitrate -an ingredient recurrent in numerous references -were realized according to traditional recipes. Their characteristics of morphology and molecular composition were studied using various methods such as scanning electron microscopy (SEM)-energy dispersive X-ray analysis (EDX), X-ray diffraction analysis (XRD) and Raman spectroscopy (RS). A better understanding of artificial patinas will not only allow developing appropriate methods of conservation and restoration, but also differentiating between natural and artificial patinas. An example of a patina present on an ancient artifact is discussed and compared with the studied artificial patinas.
Shaping metal−organic frameworks (MOFs) into robust particles with a controllable size is of large interest to the field of adsorption. Therefore, a method is presented here to produce robust MOF beads of different sizes, ranging from 250 μm to several millimeters, which, moreover, preserve the adsorption properties of the unformulated MOF. A simple, mild, and flexible method is demonstrated with the zeolitic imidazolate framework-8 (ZIF-8)/polyvinyl formal composite material. The properties of the composite material are determined via optical imaging, scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, X-ray diffraction, mercury intrusion, argon porosimetry and pycnometry as well as thermogravimetric analysis/ differential scanning calorimetry, crush strength tests, and immersion experiments. The proposed method allows the production of resistant particles with a high MOF loading (up to 85 wt %) and remarkable structural and textural properties required for adsorptive separation processes, including a preserved ZIF-8 crystalline structure, microporosity, and a narrow macropore size distribution (1.27 μm average). The particles show a spherical shape with an average aspect ratio of 0.85. The stability tests demonstrated that the composite MOF material exhibits a high mechanical strength (3.09 N/Pc crushing strength) almost equivalent to that of a widely used commercial zeolite material. Furthermore, the material remains stable up to 200°C and in most solvents. The adsorption properties are explored via static and dynamic experiments in the vapor and liquid phases. The results show that the adsorption capacities are only reduced in proportion to the binder content compared with the pristine material, indicating no binder intrusion in the ZIF-8 pores. Fixed-bed experiments demonstrate the remarkable separation performance in the vapor phase, whereas mass transfer limitations arise in the liquid phase with increasing flow rate. The mass transfer limitations are attributed to the diffusion in the macropores or through the ZIF-8 crystal outer layer.
A fixed-bed method is proposed to test materials for HCl removal from hydrogen gas.• Zeolite X was the best performing material among screened zeolites.• Ion-exchanged X zeolites were successfully produced, characterized and evaluated.• HCl removal from hydrogen gas occurred through reaction with the zeolite cations.• Cation type and hydration significantly influenced the HCl removal performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.