The suitability of a clay for studies of the absorption/adsorption of organic molecules by multinuclear NMR spectroscopy can be judged from EPR spectra. The binding of triethyl phosphate to a montmorillonite, low in paramagnetic metal ions, has been studied by solid-state 31P and 13C NMR spectroscopy; magic angle spinning NMR spectroscopy has been used to observe mobile phases within such solids. A number of mobile and immobile phases have been detected; one important mechanism in sorption probably involves coordination to the interlamellar cation. The results are discussed in terms of the utility of clays in a variety of applications.
In this work, the effect of processing parameters on the resulting microstructure and mechanical properties of magnesium alloy WE43 processed via Additive Friction Stir Deposition (AFSD), a nascent solid-state additive manufacturing (AM) process, is investigated. In particular, a parameterization study was carried out, using multiple four-layer deposits, to identify a suitable process window for a structural 68-layers bulk WE43 deposition. The parametric study identified an acceptable set of parameters with minimal surface defects and excellent consolidation for the fabrication of a bulk WE43 deposition. Microstructural, tensile, and fatigue life characterization was conducted on the bulk WE43 deposition and compared to commercially available wrought material to elucidate the process-structure-property-performance (PSPP) relationship of the AFSD process. This study shows that the bulk WE43 deposit exhibited a refined homogenous microstructure and a texture shift relative to the wrought material. However, a reduction in hardness and tensile behavior was observed in the as-deposited WE43 compared to the wrought control. Additionally, fatigue specimens extracted from the bulk deposition exhibited a decrease in life in the low-cycle regime but performed comparably to the wrought plate in the high-cycle regime. The outcomes of this study illustrate the potential of the AFSD process in additively manufactured structural load-bearing components made with magnesium alloy WE43 in the as-built condition.
Additive Friction Stir-Deposition (AFS-D) is a transformative, metallic additive manufacturing (AM) process capable of producing near-net shape components with a wide variety of material systems. The solid-state nature of the process permits many of these materials to be successfully deposited without the deleterious phase and thermally activated defects commonly observed in other metallic AM technologies. This work is the first to investigate the as-deposited microstructure and mechanical performance of a free-standing AA5083 deposition. An initial process parameterization was conducted to down-select optimal parameters for a large deposition to examine build direction properties. Microscopy revealed that constitutive particles were dispersed evenly throughout the matrix when compared to the rolled feedstock. Electron backscatter diffraction revealed a significant grain refinement from the inherent dynamic recrystallization from the AFS-D process. Tensile experiments determined a drop in yield strength, but an improvement in tensile strength in the longitudinal direction. However, a substantial reduction in tensile strength was observed in the build direction of the structure. Subsequent fractographic analysis revealed that the recommended lubrication applied to the feedstock rods, necessary for successful depositions via AFS-D, was ineffectively dispersed into the structure. As a result, lubrication contamination became entrapped at layer boundaries, preventing adequate bonding between layers.
Amorphous silica and glass fibres have been derivatised at the surface with fluorinated aromatic molecules. The resultant materials have been analysed by various techniques including thermogravimetry (TG), dynamic contact-angle analysis and, to a large extent, mass spectrometry. The last method was found to be particularly useful for the analysis of the surface of silica materials. Two different experimental routes were used to produce a -CH,C6F, modified surface. Further modifications to these materials involved attempted nucleophilic replacement of fluorine of the pentafluorobenzyl group with phenolate and benzoate anions. The materials were relatively hydrophobic and have potential use in glass-fibre composites by prevention of water ingress along the interface of the material.
The binding of triethyl phosphate (TEP) to smectites containing Bu,N+, Mg2+ or A$+ as the counter-ion has been studied. Solid-state 31P and 13C CPMAS and SPE-MAS NMR were used to observe both mobile and motion-restricted phases. Magnesium complexes of TEP and dimethylmethyl phosphonate (DMMP) have been prepared and used as models for the complexes formed in the clay matrix. These compounds were also investigated by solid-state 31P NMR and FTIR spectroscopies. TG, XRD and FTIR spectroscopy have also been used to study the sorbed TEP species. A number of sorption sites have been detected; one important mechanism of sorption involves coordination to the interlamellar cation.
E-glass fibres have been treated with aqueous fluorides under mild conditions. The fluorinated fibres were analysed by ESCA, SEM and contact-angle measurements. There is good evidence to show that low fluoride salt concentrations impart a degree of water repellency without the formation of salts on the fibre surface.
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.