A contribution to the production of zero‐defect materials is the development of carbon‐bonded alumina foam filters for removing nonmetallic inclusions from molten metals. Herein, such filters containing various mixtures of Carbores P, lactose, and tannin as binder are investigated by Raman spectroscopy. The filter samples differ in whether or not they are fired and whether or not n‐Si is added to them. Raman measurements are also performed on samples of the individual binder substances, which have been preannealed at temperatures up to 1400 °C. The variation of the sp2 carbon cluster sizes due to the heat treatment is estimated using the intensity ratio of the D and G bands as determined from these measurements. The conversion of the samples from hydrogen‐rich amorphous carbon systems to nanocrystalline graphite is observed. The results show no significant differences between the binders in regard to the material properties that can be studied with Raman spectroscopy.
The aim of this study is the investigation of a technological synthesis of MgAlON, which is a prospective coating material on ceramic foam filters for the filtration of magnesium, aluminum, and other metal melts. Thermodynamic calculations are performed, and the synthesis is carried out at 1500 °C in nitrogen atmosphere using samples consisting of different fractions of Al2O3, MgO, and AlN as starting materials. The effect of the quantity of these components on the conversion degree of the educts is evaluated. Furthermore, the effect of the holding time at the synthesis temperature, as well as the composition points or regions showing the highest conversion degree, are determined. XRD analysis is performed to evaluate the phase fractions and lattice parameters of the spinel after the respective reaction, and the nitrogen content of selected samples is evaluated. Sessile drop tests using AlSi7Mg are performed at 950 °C on selected sintered samples, determining their wettability, and therefore, applicability of the material in light metal melt filtration.
We observe coherent acoustic phonon superoscillations at subterahertz frequencies. The superoscillations result from the interference of optically excited coherent longitudinal acoustic phonon modes in a GaAs/AlGaAs superlattice. The superoscillations are seen in local temporal regions and their frequency is up to 60% larger than the highest-frequency excited and detected phonon mode. Such superoscillatory phonon pulses may potentially be used for high-resolution acoustic measurement in strong scattering media.
Lactose and tannin are eco‐friendly alternatives to commonly used binders for carbon‐bonded alumina filters that are applied in steel melt filtration. The investigation of binder pyrolysis is a contribution to understand the production process of these filters. In this work, lactose and the tannins gallic acid, ellagic acid, and tannic acid were investigated by Raman spectroscopy. The tannins were measured in situ in an argon‐filled heating chamber. The transformation of the tannin molecules to a system of amorphous disordered carbon could be observed in the Raman spectra. In addition, the condensed pyrolysis products of the tannins were measured and identified. The Raman spectra were supported by peak positions calculated with density functional theory.
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.