Monday, October 30, 2017

Structural diversity, single-crystal to single-crystal transformation and photocatalytic properties of Cu(II)-metal-organic frameworks based on 1,4-phenylenedipropionic acid

Highlights

Four Cu(II)-MOFs containing 1,4-phenylenedipropionic acid have been reported.
The effect of N,N′-donor coligand is critical in the arrangement of polymeric structure.
The 3D framework of 3 is transformed to 4 upon heating in a single-crystal-to-single-crystal manner.
All compounds are photo-catalytically active for the decomposition of MB.

Abstract

A series of four new copper(II) based metal-organic frameworks containing 1,4-phenylenedipropionic acid and different N,N′-donor coligands, namely, [Cu(ppa)(bpy)]n(1), {[Cu(ppa)(azp)(H2O)](H2O)}n (2), {[Cu(ppa)(tdp)(H2O)](H2O)2}n (3), and {[Cu(ppa)(tdp)](H2O)}n (4), (H2ppa = 1,4-phenylenedipropionic acid, bpy = 4,4′-bipyridine, azp = 4,4′-azobipyridine, tdp = 4,4′-thiodipyridine) have been successfully synthesized and structurally characterized by elemental analysis, IR, UV–vis, TGA, XRPD and single-crystal X-ray diffraction. Compound 1 containing a short and rigid bpy coligand displays a 2D square lattice (sql) topology while 2 and 3 which contain more flexible and longer azp and tdp coligands possess two-fold interpenetrating diamond-like (dia) 3D framework. Finally, the thermal-induced compound 4 is transformed from compound 3 by heating, through single-crystal-to-single-crystal transformation, adopting a CdSO4-like (cds) 3D framework. Additionally, the solid stated compounds 14 exhibit the energy band gaps of 3.50, 3.16, 3.53 and 3.31 eV, respectively. Thus, the photocatalytic properties of 14have been investigated. Approximately 84.9% for 1, 93.3% for 2, 82.0% for 3 and 85.4% for 4 of methylene blue were decomposed within 105 min.

Graphical abstract
Four new Cu(II)-MOFs have been synthesized in the presence of 1,4-phenylenedipropionic acid (ppa) and different N,N′-donor ancillary ligands. The structural diversity indicates that the effect of N,N′-donor ancillary ligand is critical in construction of polymeric arrangement.

Image for unlabelled figure

Keywords








Sunday, October 22, 2017

Solar-Tectic LLC Develops Inexpensive Sapphire Glass with MOHS 8

In 2015 Solar-Tectic LLC ("ST") announced plans to develop sapphire glass. And recently ST announced that it has succeeded in developing this sapphire glass using its patent pending technique which was reported on in Materials Letters, a peer reviewed journal

(Solar-Tectic/ LEDinside)

The new sapphire glass technique involves the deposition of a highly transparent crystalline Al2O3 (aluminum oxide) thin-film on ordinary soda-lime glass, via a thin buffer layer, using a simple and common deposition technique (e-beam evaporation), thus achieving a breakthrough material which is much less expensive and much lighter than single crystal sapphire, and easily scalable for manufacturing and commercialization.
 
The sapphire film is extremely thin which is important for cost reduction in manufacturing. In recent years Apple Inc. and others have tried without success in making cost effective sapphire glass for smartphone covers.
 
In addition to anti-scratch, ceramic glass products are an important part of ST solar technology since they can be used for the deposition of highly textured (oriented), good quality semiconductor films on inexpensive substrates for efficient photovoltaic, display, and LED electronics. 
 
ST ceramic glass can also be conducting, as in the case of titanium nitride (TiN) for example. A distinguishing feature of ST's approach is to make films that have "texture" or preferential orientation which means the crystals in the films are aligned -- greatly improving the electronic properties of materials.
 
Remarkably, the new sapphire glass has a MOHS 8 (verified by a 3rd party independent institution).  Single crystal sapphire has a MOHS 9.  Therefore, the ST sapphire glass is close to single crystal sapphire in hardness. This is the first time this hardness has ever been achieved on ordinary soda-lime glass. Al2O3 is one of the hardest materials known, second only to diamond.
 
ST is also developing this approach using laser instead of e-beam.  ST will be optimizing the films with the aim of achieving MOHS 9, and all kinds of glass substrates can be used in the process, including quartz.

Keywords:LED,sapphire,glassanti-scratch,Solar-Tectic,

Source:LEDinside

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Plastic yield criterion and hardening of porous single crystals

Abstract

This article presents an assessment of the yield criterion for porous plastic single crystal, proposed by Paux et al. (2015), for face-centred cubic and hexagonal close-packed crystalline structures. Comparisons with reference FFT full-field computations on single voided cubic unit cells, presenting different crystal orientations, show an overall agreement for the different plastic anisotropies considered at low and high triaxiality. An extension of the criterion to hardenable crystals, which takes into account the spatial heterogeneity of the approximate plastic strain field, is further proposed and compared with FE results from the literature for body-centred cubic crystals.

Keywords

Plasticity
Single crystal
Porosity
Micromechanics

Source:ScienceDirect
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