Crystal structures of spinel-type Na2MoO4and Na2WO4 revisited using neutron powder diffraction

Time-of-flight neutron powder diffraction data have been collected from Na2MoO4 and Na2WO4 to a resolution of sin ([theta])/[lambda] = 1.25 Å-1, which is substanti­ally better than the previous analyses using Mo K[alpha] X-rays, providing roughly triple the number of measured reflections with respect to the previous studies [Okada et al. (1974). Acta Cryst. B30, 1872-1873; Bramnik & Ehrenberg (2004). Z. Anorg. Allg. Chem. 630, 1336-1341]. The unit-cell parameters are in excellent agreement with literature data [Swanson et al. (1962). NBS Monograph No. 25, sect. 1, pp. 46-47] and the structural parameters for the molybdate agree very well with those of Bramnik & Ehrenberg (2004). However, the tungstate structure refinement of Okada et al. (1974) stands apart as being conspicuously inaccurate, giving significantly longer W-O distances, 1.819 (8) Å, and shorter Na-O distances, 2.378 (8) Å, than are reported here or in other simple tungstates. As such, this work represents an order-of-magnitude improvement in precision for sodium molybdate and an equally substantial improvement in both accuracy and precision for sodium tungstate. Both compounds adopt the spinel structure type. The Na+ ions have site symmetry .-3m and are in octa­hedral coordination while the transition metal atoms have site symmetry -43m and are in tetra­hedral coordination

Modification of Oligomers and Reinforced Polymeric Composites by Carbon Nanotubes and Ultrasonic

An abridged version of the book chapter is presented in the archive. Full version on the publisher's site: https://link.springer.com/chapter/10.1007/978-3-030-26672-1_3Розглядається широке коло питань щодо розроблених напрямів модифікації епоксидних олігомерів і армованих полімерних композитів на їх основі вуглецевими нанотрубками і ультразвуком. Аналізується перспективність створення гібридних полімерних композитів функціонального призначення.This chapter analyzes the physical (in the form of ultrasound) and chemical modification of liquid polymer media and reinforced polymeric composites. The main emphasis is made on the analysis of ultrasonic cavitation processing as the most effective one for solving one of the main technological problems in the production of nanomodified polymer composites