Peelable clay/PE nanocomposite seals with ultra-wide peelable heat seal temperature window

AbstractIn a narrow temperature window in going from the isotropic to highly chiral orders, cholesteric liquid crystals exhibit so-called blue phases, consisting of different morphologies of long, space-filling double twisted cylinders. Those of cubic spatial symmetry have attracted considerable attention in recent years as templates for soft photonic materials. The latter often requires the creation of monodomains of predefined orientation and size, but their engineering is complicated by a lack of comprehensive understanding of how blue phases nucleate and transform into each other at a submicrometer length scale. In this work, we accomplish this by intercepting nucleation processes at intermediate stages with fast cross-linking of a stabilizing polymer matrix. We reveal using transmission electron microscopy, synchrotron small-angle X-ray diffraction, and angle-resolved microspectroscopy that the grid of double-twisted cylinders undergoes highly coordinated, diffusionless transformations. In light of our findings, the implementation of several applications is discussed, such as temperature-switchable QR codes, micro-area lasing, and fabrication of blue phase liquid crystals with large domain sizes.

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Stabilization of Ferroelectric Phase in Highly Oriented Quinuclidinium Perrhenate (HQReO4) Thin Films

Materials ◽

10.3390/ma14092126 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2126

Author(s):

Junyoung Lee ◽

Woojun Seol ◽

Gopinathan Anoop ◽

Shibnath Samanta ◽

Sanjith Unithrattil ◽

...

Keyword(s):

Thin Films ◽

Solution Process ◽

Intermediate Temperature ◽

Perovskite Oxide ◽

Temperature Phase ◽

Polar Phase ◽

Practical Applications ◽

Temperature Range ◽

Potential Alternative ◽

Temperature Window

The low-temperature processability of molecular ferroelectric (FE) crystals makes them a potential alternative for perovskite oxide-based ferroelectric thin films. Quinuclidinium perrhenate (HQReO4) is one such molecular FE crystal that exhibits ferroelectricity when crystallized in an intermediate temperature phase (ITP). However, bulk HQReO4 crystals exhibit ferroelectricity only for a narrow temperature window (22 K), above and below which the polar phase transforms to a non-FE phase. The FE phase or ITP of HQReO4 should be stabilized in a much wider temperature range for practical applications. Here, to stabilize the FE phase (ITP) in a wider temperature range, highly oriented thin films of HQReO4 were prepared using a simple solution process. A slow evaporation method was adapted for drying the HQReO4 thin films to control the morphology and the temperature window. The temperature window of the intermediate temperature FE phase was successfully widened up to 35 K by merely varying the film drying temperature between 333 and 353 K. The strategy of stabilizing the FE phase in a wider temperature range can be adapted to other molecular FE materials to realize flexible electronic devices.

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Selective catalytic reduction of NO by Co-Mn based nanocatalysts

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2020-0240 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Vahid Zabihi ◽

Mohammad Hasan Eikani ◽

Mehdi Ardjmand ◽

Seyed Mahdi Latifi ◽

Alireza Salehirad

Keyword(s):

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Energy Dispersive ◽

Diffraction Field ◽

X Ray Diffraction ◽

X Ray ◽

Analysis Techniques ◽

Acidic Sites ◽

Temperature Window ◽

Temperature Programmed

Abstract One of the most significant aspects in selective catalytic reduction (SCR) of nitrogen oxides (NOx) is developing suitable catalysts by which the process occurs in a favorable way. At the present work SCR reaction by ammonia (NH3-SCR) was conducted using Co-Mn spinel and its composite with Fe-Mn spinel, as nanocatalysts. The nanocatalysts were fabricated through liquid routes and then their physicochemical properties such as phase composition, degree of agglomeration, particle size distribution, specific surface area and also surface acidic sites have been investigated by X-ray diffraction, Field Emission Scanning Electron Microscope, Energy-dispersive X-ray spectroscopy, energy dispersive spectroscopy mapping, Brunauer–Emmett–Teller, temperature-programmed reduction (H2-TPR) and temperature-programmed desorption of ammonia (NH3-TPD) analysis techniques. The catalytic activity tests in a temperature window of 150–400 °C and gas hourly space velocities of 10,000, 18,000 and 30,000 h−1 revealed that almost in all studied conditions, CoMn2O4/FeMn2O4 nanocomposite exhibited better performance in SCR reaction than CoMn2O4 spinel.

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Tailored activity of Ce–Ni bimetallic modified V2O5/TiO2 catalyst for NH3-SCR with promising wide temperature window

Vacuum ◽

10.1016/j.vacuum.2021.110384 ◽

2021 ◽

pp. 110384

Author(s):

Junqiang Xu ◽

Xianlin Zou ◽

Guorong Chen ◽

Yanrong Zhang ◽

Qiang Zhang ◽

...

Keyword(s):

Tio2 Catalyst ◽

Nh3 Scr ◽

Temperature Window

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Synthesis of Bulk Zr48Cu36Al8Ag8 Metallic Glass by Hot Pressing of Amorphous Powders

Journal of Manufacturing and Materials Processing ◽

10.3390/jmmp5010023 ◽

2021 ◽

Vol 5 (1) ◽

pp. 23

Author(s):

Tianbing He ◽

Nevaf Ciftci ◽

Volker Uhlenwinkel ◽

Sergio Scudino

Keyword(s):

Metallic Glass ◽

Metallic Glasses ◽

Flow Behavior ◽

Matrix Composites ◽

Powder Consolidation ◽

Low Viscosity ◽

Flash Annealing ◽

Amorphous Powders ◽

Temperature Window ◽

Glass Matrix Composites

The critical cooling rate necessary for glass formation via melt solidification poses inherent constraints on sample size using conventional casting techniques. This drawback can be overcome by pressure-assisted sintering of metallic glass powders at temperatures above the glass transition, where the material shows viscous-flow behavior. Partial crystallization during sintering usually exacerbates the inherent brittleness of metallic glasses and thus needs to be avoided. In order to achieve high density of the bulk specimens while avoiding (or minimizing) crystallization, the optimal combination between low viscosity and long incubation time for crystallization must be identified. Here, by carefully selecting the time–temperature window for powder consolidation, we synthesized highly dense Zr48Cu36Ag8Al8 bulk metallic glass (BMG) with mechanical properties comparable with its cast counterpart. The larger ZrCu-based BMG specimens fabricated in this work could then be post-processed by flash-annealing, offering the possibility to fabricate monolithic metallic glasses and glass–matrix composites with enhanced room-temperature plastic deformation.

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(Ti,Al)O2 Whiskers Grown during Glow Discharge Nitriding of Ti-6Al-7Nb Alloy

Materials ◽

10.3390/ma14102658 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2658

Author(s):

Krzysztof Szymkiewicz ◽

Jerzy Morgiel ◽

Łukasz Maj ◽

Małgorzata Pomorska

Keyword(s):

Surface Hardening ◽

Surface Defects ◽

Plasma Nitriding ◽

Surface Roughening ◽

Effective Surface ◽

Plan View ◽

Gas Nitriding ◽

Transmission Electron ◽

Temperature Window ◽

20 Nm

Plasma nitriding of titanium alloys is capable of effective surface hardening at temperatures significantly lower than gas nitriding, but at a cost of much stronger surface roughening. Especially interesting are treatments performed at the lower end of the temperature window used in such cases, as they are least damaging to highly polished parts. Therefore identifying the most characteristic defects is of high importance. The present work was aimed at identifying the nature of pin-point bumps formed at the glow discharged plasma nitrided Ti-6Al-7Nb alloy using plan-view scanning and cross-section transmission electron microscopy methods. It helped to establish that these main surface defects developed at the treated surface are (Ti,Al)O2 nano-whiskers of diameter from 20 nm to 40 nm, and length up to several hundreds of nanometers. The performed investigation confirmed that the surface imperfection introduced by plasma nitriding at the specified range should be of minor consequences to the mechanical properties of the treated material.

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