Ultrasound cavitation and exfoliation dynamics of 2D materials re-vealed in operando by X-ray free electron laser megahertz imaging

Ultrasonic liquid phase exfoliation is a promising method for the production of two-dimensional (2D) layered materials. A large number of studies have been made in investigating the underlying ultrasound exfoliation mechanisms. However, due to the experimental challenges for capturing the highly transient and dynamic phenomena in real-time at sub-microsecond time and micrometer length scales simultaneously, most theories reported to date still remain elusive. Here, using the ultra-short X-ray Free Electron Laser pulses (~25ps) with a unique pulse train structure, we applied MHz X-ray Microscopy and machine-learning technique to reveal unambiguously the full cycles of the ultrasound cavitation and graphite layer exfoliation dynamics with sub-microsecond and micrometer resolution. Cyclic fatigue shock wave impacts produced by ultrasound cloud implosion were identified as the dominant mechanism to deflect and exfoliate graphite layers mechanically. For the graphite flakes, exfoliation rate as high as ~5 angstroms per shock wave impact was observed. For the HOPG graphite, the highest exfoliation rate was ~0.15 angstroms per impact. These new findings are scientifically and technologically important for developing industrial upscaling strategies for ultrasonic exfoliation of 2D materials

Solution of the problem of negative value of the linear technological size

The calculation of the linear technological sizes is one of necessary design stages of technological processes of machining. A problem is that with performance of calculation of the linear technological sizes negative value of the technological size sometimes turns out. In the article consideedr an example of calculation, in which appears negative value of the technological size. The calculation is carried out on the technique with use of the chart of processing and the computer program which is carrying out automatic construction and the decision of the equations of dimension chains. As a result of the study, it was found that the appearance of a negative value when calculating the technological dimensions is not an error, this is due to the uncertainty of the positions of the technological size boundaries before calculation

Solution of the problem of negative value of the linear technological size

The calculation of the linear technological sizes is one of necessary design stages of technological processes of machining. A problem is that with performance of calculation of the linear technological sizes negative value of the technological size sometimes turns out. In the article consideedr an example of calculation, in which appears negative value of the technological size. The calculation is carried out on the technique with use of the chart of processing and the computer program which is carrying out automatic construction and the decision of the equations of dimension chains. As a result of the study, it was found that the appearance of a negative value when calculating the technological dimensions is not an error, this is due to the uncertainty of the positions of the technological size boundaries before calculation

Modification of Chitin with Kraft Lignin and Development of New Biosorbents for Removal of Cadmium(II) and Nickel(II) Ions

Novel, functional materials based on chitin of marine origin and lignin were prepared. The synthesized materials were subjected to physicochemical, dispersive-morphological and electrokinetic analysis. The results confirm the effectiveness of the proposed method of synthesis of functional chitin/lignin materials. Mechanism of chitin modification by lignin is based on formation of hydrogen bonds between chitin and lignin. Additionally, the chitin/lignin materials were studied from the perspective of waste water treatment. The synthetic method presented in this work shows an attractive and facile route for producing low-cost chitin/lignin biosorbents with high efficiency of nickel and cadmium adsorption (88.0% and 98.4%, respectively). The discovery of this facile method of synthesis of functional chitin/lignin materials will also have a significant impact on the problematic issue of the utilization of chitinous waste from the seafood industry, as well as lignin by-products from the pulp and paper industry

Isolation and identification of chitin from heavy mineralized skeleton of Suberea clavata (Verongida: Demospongiae: Porifera) marine demosponge

WOS: 000412959500037PubMed: 28185932Since the discovery of chitin in skeletal structures of sponges (Porifera) in 2007, studies on search of novel species which possess this structural aminopolysaccharide continue up today. The most potential source of chitin is suggested to be localized in the four families of sponges related to the order Verongida (Demospongiae) which nevertheless require further clarification. Here, we report for the first time the isolation and identification of alpha-chitin from the Suberea clavata demosponge (Aplysinidae: Verongida). Raman spectroscopy, Calcofluor White staining, chitinase test and ESI-MS techniques were used to identify chitin. We suggest that the presence of chitin within fibrous skeletons of diverse species of Verongida order, and, especially in all species of the Aplysinidae family, may be useful for the identification of novel, previously unidentified marine demosponges. (C) 2017 Elsevier B.V. All rights reserved.DFG (Germany) [EH 394-3]; PUT research grant (Poland) [03/32/DSPB/0706/2017]This work was supported by DFG Grant EH 394-3 (Germany) and PUT research grant 03/32/DSPB/0706/2017 (Poland). The authors thank Prof. Dr. Yixin Zhang for the use of the ESI-MS instrument and Rob van Soest for his support and comments

Photoluminescence of HgCdTe nanostructures grown by molecular beam epitaxy on GaAs

AbstractPhotoluminescence (PL) of HgCdTe-based hetero-epitaxial nanostructures with 50 to 1100 nm-wide potential wells was studied. The nanostructures were grown by molecular beam epitaxy on GaAs substrates. A strong degree of alloy disorder was found in the material, which led to the broadening of the PL spectra and a considerable Stokes shift that could be traced up to temperature T∼230 K. Annealing of the structures improved the ordering and led to the increase in the PL intensity. A remarkable feature of the PL was an unexpectedly small decrease of its intensity with temperature increasing from 84 to 300 K. This effect can be related to localization of carriers at potential fluctuations and to the specific character of Auger-type processes in HgCdTe-based nanostructures.</jats:p