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This study presents the general characteristics of binders used in precision casting of Nickel-based superalloys. Three groups of binders were described: resins, organic compounds, and materials containing nanoparticles in alcohol or aqueous systems. This study also includes literature reports on materials commonly used and those recently replaced by water-soluble binders, i.e., ethyl silicate (ES) and hydrolysed ethyl silicate (HES). The appearance of new and interesting solutions containing nano-alumina is described, as well as other solutions at the initial stage of scientific research, such as those containing biopolymers, biodegradable polycaprolactone (PCL), or modified starch. Special attention is paid to four binders containing nano-SiO 2 intended for the first layers (Ludox AM, Ludox SK) and structural layers (EHT, Remasol) of shell moulds. Their morphology, viscosity, density, reactions, and electrokinetic potential were investigated. The binders were characterized by a high solid-phase content (>28%), viscosity, and density close to that of water (1-2 mPa·s) and good electrokinetic stability. The nanoparticles contained in the binders were approximately spherically shaped with an average particle size of 16-25 nm.

This study compares the consolidation efficiency and compatibility of three selected alkoxysilanes on two porous carbonate and silicate substrates. Emphasis was given to artificially induced microstructural defects and subsequent restoration of mechanical and physical properties. Two newly engineered formulations (1) a TiO₂ modified tetraethyl-orthosilicate in isopropanol with 70% active content and (2) a TiO₂ modified alkyl-trialkoxysilane in isopropanol with 75% active content were compared to a commercial product (3), a solvent free tetraethyl-orthosilicate with 99% active content. Treatments were evaluated by scanning electron microscopy, mercury intrusion porosimetry, colour impact and their effect on dynamic modulus of elasticity, splitting tensile- and flexural strengths, capillary water absorption and water vapour permeability. A key outcome was that mechanical strength gain induced by treatments is primarily governed by a stone's texture and microstructure, and secondarily by the gel deposition rate of consolidants. Likewise, the kinetics of the gel-forming reaction during curing is dependent not only on the product but also on the substrate. Therefore, the moisture related properties and the visual impact develop during time. There is no general trend on how it evolves in time, which can lead to incorrect interpretations of treatment compatibility. The results prove that wide-ranging treatment performance is obtained when applying the same products on different substrates., Competing Interests: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Reversed-phase liquid chromatography coupled with electrospray ionization mass spectrometry was used to study the molecular structures of components and molar mass distributions in ethyl silicate-40, a versatile liquid precursor for silicon-based materials. Identity testing by standard spectroscopic techniques showed that a commercial sample of ethyl silicate-40 was composed of linear/branched ethoxysiloxane oligomers with the silicon atoms ranging from 2 to 12 together with minor monocyclic species. Analysis of the sample by liquid chromatography coupled with evaporative light scattering detection resulted in an elution profile consisting of a series of peak clusters. Peak identification showed that the linear/branched homologous series of oligomers were eluted in the order of increasing number of silicon atoms in the molecules and the time duration (width) of the resulting peak clusters increased in the same fashion corresponding to increasing number of geometric isomers. In addition, small amounts of monocyclic oligomers present in the sample were found to be less retained than each linear/branched counterpart. Finally, the molar mass distribution parameters for ethyl silicate-40 determined by the developed method were in good agreement with the literature values. Overall, this work demonstrates that reversed-phase liquid chromatography coupled with electrospray ionization mass spectrometry is an indispensable tool for the comprehensive characterization of complex mixtures of this type., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)