scholarly journals Patterned crystal growth and heat wave generation in hydrogels

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Thomas B. H. Schroeder ◽  
Joanna Aizenberg
Keyword(s):  
Crystal Growth ◽  
Sodium Acetate ◽  
Phase Change Materials ◽  
Heat Waves ◽  
Growth Front ◽  
Polyacrylamide Hydrogel ◽  
Stored Energy ◽  
Metastable Liquid ◽  
Downstream Processes ◽  
Crystal Growth Front

AbstractThe crystallization of metastable liquid phase change materials releases stored energy as latent heat upon nucleation and may therefore provide a triggerable means of activating downstream processes that respond to changes in temperature. In this work, we describe a strategy for controlling the fast, exothermic crystallization of sodium acetate from a metastable aqueous solution into trihydrate crystals within a polyacrylamide hydrogel whose polymerization state has been patterned using photomasks. A comprehensive experimental study of crystal shapes, crystal growth front velocities and evolving thermal profiles showed that rapid growth of long needle-like crystals through unpolymerized solutions produced peak temperatures of up to 45˚C, while slower-crystallizing polymerized solutions produced polycrystalline composites and peaked at 30˚C due to lower rates of heat release relative to dissipation in these regions. This temperature difference in the propagating heat waves, which we describe using a proposed analytical model, enables the use of this strategy to selectively activate thermoresponsive processes in predefined areas.

Prefered molecular orientation at crystal growth front in Ca(PO3)2 glass

1985 ◽  
Vol 4 (2) ◽  
pp. 244-246 ◽  
Author(s):  
Hideo Hosono ◽  
Sukezo Kawamura ◽  
Yoshihiro Abe
Keyword(s):  
Crystal Growth ◽  
Molecular Orientation ◽  
Growth Front ◽  
Crystal Growth Front

Aspects of Dislocation Behavior in SiC

2008 ◽  
Vol 600-603 ◽  
pp. 261-266 ◽  
Author(s):  
Michael Dudley ◽  
Yi Chen ◽  
Xian Rong Huang ◽  
Rong Hui Ma
Keyword(s):  
Crystal Growth ◽  
Thermal Stresses ◽  
Growth Front ◽  
Growth Defect ◽  
Formation Mechanisms ◽  
Dislocation Glide ◽  
Electrical Stress ◽  
Dislocation Behavior ◽  
Homoepitaxial Layers ◽  
Crystal Growth Front

A review is presented of the current understanding of the dislocation configurations observed in PVT-grown 4H- and 6H-SiC boules and CVD-grown 4H-SiC homoepitaxial layers. In both PVT-grown boules and CVD-grown epilayers, dislocation configurations are classified according to whether they are growth dislocations, i.e., formed during growth via the replication of dislocations which thread the moving crystal growth front, or result from deformation processes (under either mechanical or electrical stress) immediately following growth, during post growth cooling, i.e., behind the crystal growth front or during device operation. Possible formation mechanisms of growth defects in the PVT grown boules, such as axial screw dislocations and threading edge dislocation walls are proposed. Similarly, possible origins of growth defect configurations in CVD-grown epilayers, such as Frank faults bounded by Frank partials, BPDs and TEDs, are also discussed. In a similar way, the origins of BPD configurations resulting from relaxation of thermal stresses during post-growth cooling of the PVT boules are discussed. Finally, the susceptibility of BPD configurations replicated into CVD grown epilayers from the substrate towards Recombination Enhanced Dislocation Glide (REDG) is discussed.

Analysis on the Ceasing Mechanism of the YBCO Crystal Growth during Melting Growth Process by Unidirectional Solidification

2007 ◽  
Vol 546-549 ◽  
pp. 2091-2096
Author(s):  
Hai Tao Cao ◽  
Rui Hu ◽  
Hong Chao Kou ◽  
Jin Shan Li ◽  
En Zhi Gao ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Liquid Phase ◽  
Growth Process ◽  
Growth Characteristic ◽  
Growth Front ◽  
Zone Melting ◽  
Unidirectional Solidification ◽  
Continuous Growth ◽  
Crystal Growth Front ◽  
Solidification Technology

The unidirectional solidification technology by a zone melting method was performed to obtain the large single domain YBCO. The interface morphology and chemical composition at the growth front of the YBCO crystal were investigated in order to make clear the growth characteristic of the YBCO crystal during melting growth by unidirectional solidification. It was found that YBCO crystal would cease growing when yttrium was depleted in the liquid phase at the YBCO crystal growth front. For maintaining the continuous growth of YBCO crystal, compositions of Y, Ba and Cu in raw samples have to be adjusted so as to make yttrium rich in the liquid phase at the YBCO crystal growth front during the melting growth process. It is very useful for the study on the mechanism of the YBCO crystal growth.

High SiC Growth Rate Obtained by Vapour-Liquid-Solid Mechanism

2007 ◽  
Vol 556-557 ◽  
pp. 105-108 ◽  
Author(s):  
N. Boutarek ◽  
Didier Chaussende ◽  
Roland Madar
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
High Temperature ◽  
Growth Rates ◽  
Growth Front ◽  
Bulk Crystals ◽  
Deposition Rates ◽  
Liquid Handling ◽  
Homoepitaxial Layers ◽  
Crystal Growth Front

The growth of 3C-SiC polycrystal and 6H-SiC homoepitaxial layers from Metal-Si alloys is carried out as function of temperature and propane partial pressure. Based on the vapourliquid- solid mechanism, we present a new configuration for the growth of SiC which could allow first to simplify the liquid handling at high temperature and second to precisely control the crystal growth front. 3C-SiC crystals exhibiting well-faceted morphology are obtained at 1100-1200°C with outstanding deposition rates, varying from 1 to 1.5 mm/h in Ti-Si melt. At 1200-1300°C, thick homoepitaxial 6H-SiC layers were successfully obtained in Co-Si melts, with growth rates up to 200 ,m/h. Details on the experiments will be given and the potentialities of such process for the growth of bulk crystals will be discussed..

Control of Void Formation in 4H-SiC Solution Growth

2012 ◽  
Vol 717-720 ◽  
pp. 57-60 ◽  
Author(s):  
Takeshi Mitani ◽  
Masayuki Okamura ◽  
Tetsuo Takahashi ◽  
Naoyoshi Komatsu ◽  
Tomohisa Kato ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Crystal Growth ◽  
Secondary Ion Mass Spectrometry ◽  
Void Formation ◽  
Growth Front ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Ar Gas ◽  
Secondary Ion ◽  
Crystal Growth Front

Void formation in 4H-SiC crystals grown from solution has been investigated by secondary ion mass spectrometry and Raman scattering. It becomes clear that ambient Ar gas is filled in voids and the solvent (Si) partially remains. The result indicates that Ar dissolved in the solvent vaporizes and forms bubbles. The trapped bubbles at the crystal growth front are considered to be incorporated in the growing crystal as voids. We also have developed following methods for suppression of the void formation; (1) dipping seed crystals so that the growth front faces upward, (2) growth under He atmosphere, and (3) the high temperature treatment of the solvent before crystal growth.

Montmorillonite Dendrites

1974 ◽  
Vol 32 ◽  
pp. 454-455
Author(s):  
Necip Güven ◽  
Rodney W. Pease
Keyword(s):  
Crystal Growth ◽  
Growth Mechanism ◽  
Growth Front ◽  
Morphological Features ◽  
Dendritic Crystal ◽  
Crystal Growth Mechanism

Morphological features of montmorillonite aggregates in a large number of samples suggest that they may be formed by a dendritic crystal growth mechanism (i.e., tree-like growth by branching of a growth front).

scholarly journals Thermal Characterization of Medium-Temperature Phase Change Materials (PCMs) for Thermal Energy Storage Using the T-History Method

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7371
Author(s):  
Paulina Rolka ◽  
Roman Kwidzinski ◽  
Tomasz Przybylinski ◽  
Adam Tomaszewski
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Thermophysical Properties ◽  
Phase Change Materials ◽  
Experimental Tests ◽  
Stored Energy ◽  
Medium Temperature ◽  
Heating Systems ◽  
Selection Of

To reduce energy consumption and increase energy efficiency in the building sector, thermal energy storage with phase change materials (PCMs) is used. The knowledge of the thermophysical properties and the characteristics of PCMs (like their enthalpy changes and the distribution of stored energy over a specified temperature range) is essential for proper selection of the PCM and optimal design of the latent thermal energy store (LHTES). This paper presents experimental tests of the thermophysical properties of three medium-temperature PCMs: OM65, OM55, RT55, which can be used in domestic hot water installations and heating systems. Self-made test chambers with temperature control using Peltier cells were used to perform measurements according to the T-history method. In this way the temperature range of the phase transition, latent heat, specific heat capacity, enthalpy and the distributions of stored energy of the three PCMs were determined. The paper also presents measurements of the thermal conductivity of these PCMs in liquid and solid state using a self-made pipe Poensgen apparatus. The presented experimental tests results are in good agreement with the manufacturers’ data and the results of other researchers obtained with the use of specialized instruments. The presented research results are intended to help designers in the selection of the right PCM for the future LHTES co-working with renewable energy systems, waste heat recovery systems and building heating systems.

Electrical Initiation of Solidification and Preservation of Supercooled State for Sodium Acetate Trihydrate

2010 ◽  
Author(s):  
Tetsuo Munakata ◽  
Shinichi Nagata
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Sodium Acetate ◽  
Growth Direction ◽  
Crystal Growth Rate ◽  
Sodium Acetate Trihydrate ◽  
Supercooled State ◽  
Acetate Trihydrate ◽  
Thermal Energy Storage Material ◽  
Bottom To Top

Electrical initiation of solidification from supercooled state and preservation of supercooled state of sodium acetate trihydrate solution, which is considered as a promising thermal energy storage material, are experimentally investigated with varying the configuration of electrodes and confirmed that the initiation of solidification and preservation of supercooled state are both possible by using the electric field. Further, effect of crystal growth direction on crystal growth rate is also investigated by using the newly developed electrical nucleation method. The result shows that the crystal growth rate, which growth direction is bottom to top, is slightly decreased compared with the direction of top to bottom at certain supercooling temperature range.

Lattice-plane curvature and small-angle grain boundaries in SiC bulk crystals

2006 ◽  
Vol 39 (1) ◽  
pp. 17-23 ◽  
Author(s):  
Christoph Seitz ◽  
Ziad G. Herro ◽  
Boris M. Epelbaum ◽  
Rainer Hock ◽  
Andreas Magerl
Keyword(s):  
Grain Boundaries ◽  
Small Angle ◽  
Growth Front ◽  
Large Radius ◽  
Lattice Plane ◽  
Bulk Crystals ◽  
Rocking Curve ◽  
One Dimensional ◽  
Lattice Planes ◽  
Crystal Growth Front

SiC crystals grown by the physical vapour transport process along the [001] direction show a curvature of the crystal growth front in correspondence with the shape of the isotherms. A large radius for the curvature of the isotherms enhances the formation of an extended facet. Under the facet, the lattice planes are flat with a high crystal quality as expressed by rocking-curve half widths of 0.022°. In the non-faceted region, the lattice planes become bent, following the shape of the isotherms with a radius of typically 0.5 to 0.8 m and an increased rocking-curve half width of 0.3°. A reduction of the growth rate from 300 µm h−1to 70 µm h−1does not affect this behaviour significantly. The lattice-plane curvature and the development of the facet are predominantly affected by the shape of the isotherms. For crystals grown in the [015] direction, the lattice planes adjust only in a one-dimensional manner to the isotherms. In all cases, the lattice-plane curvature results from the formation of a high density of small-angle grain boundaries. They are generated by the condensation of dislocations with Burgers vectors in theabplane.

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