scholarly journals Superelasticity of a photo-actuating chiral salicylideneamine crystal

2022 ◽  
Vol 5 (1) ◽  
Author(s):  
Takuya Taniguchi ◽  
Kazuki Ishizaki ◽  
Daisuke Takagi ◽  
Kazuki Nishimura ◽  
Hiroki Shigemune ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
External Force ◽  
Molecular Crystal ◽  
Light Irradiation ◽  
Elastic Response ◽  
Layer Model ◽  
Induced Stress ◽  
External Stimuli

AbstractSuperelasticity is a type of elastic response to an applied external force, caused by a phase transformation. Actuation of materials is also an elastic response to external stimuli such as light and heat. Although both superelasticity and actuation are deformations resulting from stimulus-induced stress, there is a phenomenological difference between the two with respect to whether force is an input or an output. Here, we report that a molecular crystal manifests superelasticity during photo-actuation under light irradiation. The crystal exhibits stepwise twisted actuation due to two effects, photoisomerization and photo-triggered phase transition, and the actuation behavior is simulated based on a dynamic multi-layer model. The simulation, in turn, reveals how the photoisomerization and phase transition progress in the crystal, indicating superelasticity induced by modest stress due to the formation of photoproducts. This work provides not only a successful simulation of stepwise twisted actuation, but also to the best of our knowledge the first indication of superelasticity induced by light.

scholarly journals Control of a thermosalient phase transition by solid solutions

2014 ◽  
Vol 70 (a1) ◽  
pp. C985-C985
Author(s):  
Elisa Nauha ◽  
Matteo Lusi ◽  
Pance Naumov
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Energy Conversion ◽  
Solid Solutions ◽  
Thermal Energy ◽  
Molecular Crystal ◽  
Mechanical Performance ◽  
Mixed Crystals ◽  
Macro Scale ◽  
Scale Motion

Thermosalient crystals that exhibit macro-scale motion upon phase transition could be useful as actuators that are capable of converting thermal energy into motion or mechanical work in macroscopic devices.[1] The application capability of these miniature actuators for energy conversion depends on the temperature range and dynamics of transition. While the thermo-mechanical performance cannot be systematically varied with a pure molecular crystal, solid solutions could present a way to intentionally tune both the dynamics and the temperature of the transition in a continuous manner (Figure 1). To verify this hypothesis, Zn(2,2'-bpy)Br2,[2] was selected as a thermosalient material which could form solid solutions (or mixed complexes) with Zn(2,2'-bpy)Cl2. Only one form (isomorphous to one of the two Zn(2,2'-bpy)Br2forms) has been reported for the chloride.[3] The results indicate that indeed, the two complexes form solid solutions in varying ratios. The mixed crystals undergo the same phase transformation as the pure Zn(2,2'-bpy)Br2at a Cl/Br-ratio-dependent temperature. The temperature and dynamics of the thermosalient phenomenon correlates with the Cl/Br-ratio.

scholarly journals Pressure-Induced Structural Phase Transition and Metallization in Ga2Se3 up to 40.2 GPa under Non-Hydrostatic and Hydrostatic Environments

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 746
Author(s):  
Meiling Hong ◽  
Lidong Dai ◽  
Haiying Hu ◽  
Xinyu Zhang
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
High Pressure ◽  
Phase Transformation ◽  
Transport Properties ◽  
Electrical Transport ◽  
Structural Phase ◽  
Structure Evolution ◽  
Systematic Research ◽  
Electrical Transport Properties

A series of investigations on the structural, vibrational, and electrical transport characterizations for Ga2Se3 were conducted up to 40.2 GPa under different hydrostatic environments by virtue of Raman scattering, electrical conductivity, high-resolution transmission electron microscopy, and atomic force microscopy. Upon compression, Ga2Se3 underwent a phase transformation from the zinc-blende to NaCl-type structure at 10.6 GPa under non-hydrostatic conditions, which was manifested by the disappearance of an A mode and the noticeable discontinuities in the pressure-dependent Raman full width at half maximum (FWHMs) and electrical conductivity. Further increasing the pressure to 18.8 GPa, the semiconductor-to-metal phase transition occurred in Ga2Se3, which was evidenced by the high-pressure variable-temperature electrical conductivity measurements. However, the higher structural transition pressure point of 13.2 GPa was detected for Ga2Se3 under hydrostatic conditions, which was possibly related to the protective influence of the pressure medium. Upon decompression, the phase transformation and metallization were found to be reversible but existed in the large pressure hysteresis effect under different hydrostatic environments. Systematic research on the high-pressure structural and electrical transport properties for Ga2Se3 would be helpful to further explore the crystal structure evolution and electrical transport properties for other A2B3-type compounds.

scholarly journals Solid Form and Phase Transformation Properties of Fexofenadine Hydrochloride during Wet Granulation Process

Pharmaceutics ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 802
Author(s):  
Suye Li ◽  
Hengqian Wu ◽  
Yanna Zhao ◽  
Ruiyan Zhang ◽  
Zhengping Wang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Water Content ◽  
Scale Up ◽  
Small Scale ◽  
Dissolution Behavior ◽  
Wet Granulation ◽  
Water Addition ◽  
Granulation Process ◽  
And Performance

The quality control of drug products during manufacturing processes is important, particularly the presence of different polymorphic forms in active pharmaceutical ingredients (APIs) during production, which could affect the performance of the formulated products. The objective of this study was to investigate the phase transformation of fexofenadine hydrochloride (FXD) and its influence on the quality and performance of the drug. Water addition was key controlling factor for the polymorphic conversion from Form I to Form II (hydrate) during the wet granulation process of FXD. Water-induced phase transformation of FXD was studied and quantified with XRD and thermal analysis. When FXD was mixed with water, it rapidly converted to Form II, while the conversion is retarded when FXD is formulated with excipients. In addition, the conversion was totally inhibited when the water content was <15% w/w. The relationship between phase transformation and water content was studied at the small scale, and it was also applicable for the scale-up during wet granulation. The effect of phase transition on the FXD tablet performance was investigated by evaluating granule characterization and dissolution behavior. It was shown that, during the transition, the dissolved FXD acted as a binder to improve the properties of granules, such as density and flowability. However, if the water was over added, it can lead to the incomplete release of the FXD during dissolution. In order to balance the quality attributes and the dissolution of granules, the phase transition of FXD and the water amount added should be controlled during wet granulation.

scholarly journals Effects of deformation on the microstructure of a Ti-V microalloyed steel in the phase transition region

2004 ◽  
Vol 57 (4) ◽  
pp. 303-311
Author(s):  
Wiliam Regone ◽  
Sérgio Tonini Button
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Transition Region ◽  
Microstructural Evolution ◽  
Microalloyed Steel ◽  
Hot Forging ◽  
Microalloyed Steels ◽  
Air Cooling ◽  
Water Cooling ◽  
Phase Transition Region

Microalloyed steels are used in the forging of many automotive parts like crankshafts and connecting rods. They are hot worked in a sequence of stages that includes the heating to the soaking temperature, followed by forging steps, and finally the controlled cooling to define the microstructure and mechanical properties. In this work it was investigated the thermomechanical behavior and the microstructural evolution of a Ti-V microalloyed steel in the phase transition region. Torsion tests were done with multiple steps with true strain equal to 0.26 in each step. After each torsion step the samples were continuous cooled for 15 seconds to simulate hot forging conditions. These tests provided results for the temperature at the beginning of the phase transformation, and allowed to analyze the microstructural changes. Also, workability tests were held to analyze the microstructural evolution by optical and scanning electron microscopy. Results from the torsion tests showed that the temperature for the beginning of phase transformation is about 700 ºC. Workability tests held at 700 ºC followed by water-cooling presented microstructures with different regions: strain hardened, and static and dynamic recrystallized. Workability tests at 700 ºC followed by air-cooling showed a complex microstructure with ferrite, bainite and martensite, while tests at 650 and 600 ºC followed by water-cooling showed a microstructure with allotriomorphic ferrite present in the grain boundaries of the previous austenite.

scholarly journals Switching Between Enantiomers by Combining Chromoselective Photocatalysis and Biocatalysis

2021 ◽  
Author(s):  
Luca Schmermund ◽  
Susanne Reischauer ◽  
Sarah Bierbaumer ◽  
Christoph Winkler ◽  
Alba Diaz-Rodriguez ◽  
...  
Keyword(s):  
Photocatalytic Oxidation ◽  
Green Light ◽  
Light Irradiation ◽  
Thermal Processes ◽  
Rhodococcus Ruber ◽  
Oxidation Potentials ◽  
Enzymatic Cascades ◽  
Electron Holes ◽  
External Stimuli ◽  
Generate Electron

<a></a><a></a><a></a><a></a><a></a><a>Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible-light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN-OA-m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo-chemo-enzymatic cascades that give either the (<i>S</i>)- or the (<i>R</i>)-enantiomer of phenylethanol. In combination with an unspecific peroxygenase from <i>Agrocybe aegerita,</i> green light irradiation of CN-OA-m led to the enantioselective hydroxylation of ethylbenzene to (<i>R</i>)-1-phenylethanol (99% <i>ee</i>). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from <i>Rhodococcus ruber </i>to form<i> </i>(<i>S</i>)-1-phenylethanol (93% <i>ee</i>).</a><a></a>

Drastic photoluminescence modulation of an organic molecular crystal with high pressure

2019 ◽  
Vol 3 (8) ◽  
pp. 1510-1517 ◽  
Author(s):  
Junjie Guan ◽  
Chunfang Zhang ◽  
Dexiang Gao ◽  
Xingyu Tang ◽  
Xiao Dong ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Molecular Crystal ◽  
Near Infrared ◽  
Infrared Region ◽  
Photoluminescence Spectra ◽  
Organic Molecular Crystal ◽  
Greenish Yellow ◽  
Near Infrared Region

The pressure-induced phase transition of diphenylfluorenone leads to a drastic redshift of the photoluminescence spectra from greenish-yellow to the near-infrared region.

Dynamic surface-assisted assembly behaviours mediated by external stimuli

Soft Matter ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 54-63 ◽  
Author(s):  
Xuan Peng ◽  
Fengying Zhao ◽  
Yang Peng ◽  
Jing Li ◽  
Qingdao Zeng
Keyword(s):  
Electric Field ◽  
Irradiation Temperature ◽  
Light Irradiation ◽  
Dynamic Surface ◽  
Guest Species ◽  
External Stimuli

In this review, STM investigations reveal that surface-assisted assembly nanostructures can be well mediated by external stimuli, including guest species, light irradiation, temperature and electric field.

Effect of Deposition Conditions on Intrinsic Stress, Phase Transformation and Stress Relaxation in Tantalum Thin Films

1991 ◽  
Vol 239 ◽  
Author(s):  
A. Mutscheller ◽  
L. A. Clevenger ◽  
J.M.E. Harper ◽  
C. Cabrai ◽  
K. Barmakt
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Phase Transformation ◽  
Stress Relaxation ◽  
Compressive Stress ◽  
Stress Relief ◽  
Beta Phase ◽  
Alpha Phase ◽  
Intrinsic Stress

AbstractWe demonstrate that the high temperature polymorphic tantalum phase transition from the tetragonal beta phase to the cubic alpha phase causes complete stress relaxation and a large decrease in the resistance of tantalum thin films. 100 nm beta tantalum thin films were deposited onto thermally oxidized <100> silicon wafers by dc magnetron sputtering with argon. In situ stress and resistance at temperature were measured during temperature-ramped annealing in purified He. Upon heating, films that were initially compressively stressed showed increasing compressive stress due to thermo-elastic deformation from 25 to 550°C, slight stress relief due to plastic deformation from 550 to 700°C and complete stress relief due to the beta to alpha phase transformation at approximately 700–800°C. Incomplete compressive stress relaxation was observed at high temperatures if the film was initially deposited in the alpha phase or if the beta phase did not completely transform into alpha by 800°C. This incomplete beta to alpha phase transition was most commonly observed on samples that had radio frequency substrate bias greater than -100 V. We conclude that the main stress relief mechanism for tantalum thin films is the beta to alpha phase transformation that occurs at 700 to 800°C.

Phenomena And Mechanism On Phase Transformation Twinning In Nanocrystalline BaTiO3

2010 ◽  
Vol 1256 ◽  
Author(s):  
Sujata Mazumder ◽  
Jiten Ghosh
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
High Temperature ◽  
Intermediate Phase ◽  
High Vacuum ◽  
Point Group ◽  
Atomic Scale ◽  
Twin Structure ◽  
High Temperature Xrd ◽  
Low Symmetry

AbstractThe detailed structure of nanocrystalline BaTiO3 powder during ball milling has been studied using XRD & TEM. The study illustrates important advances in understanding atomic scale properties of this material. Ferroelectric BaTiO3 powder undergoes phase transformation along the sequence Cubic(Pm3m)-tetragonal(P4mm)-orthohombic (Amm2)-rhombohedral(R3m) structure when pressureless sintered samples are cooled from high temperature to low temperature. The high to low symmetry phases are not related to group subgroup symmetry as transformation is discontinuous and first order in nature and the twin relationship in the low symmetry is forbidden by Landau theory. In case of ball milled BaTiO3 powder a continuous and diffusionless phase transition occur via second order to and from a metastable intermediate phase. In this pathway crystallites in the aggregation are twinned and the twin structure is related to crystal point group m3m which in the present case is illustrated as having 6mm symmetry formed under low driving force. The unit cell evolution due to phase transition and the crystallographic relationship are established. The phase transformation, coalescence and twin structure of thermally annealed BaTiO3 nanocrystals under high vacuum has been investigated using in situ high temperature XRD. The structure analysis is performed with the use of the method of computer modelling of disorder structure and simulation of corresponding diffraction pattern.

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