scholarly journals Seeded Mineralization in Silk Fibroin Hydrogel Matrices Leads to Continuous Rhombohedral CaCO3 Films

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 166
Author(s):  
Dan Wang ◽  
Yu-xuan Feng ◽  
Ming Li ◽  
Shengdi Guo ◽  
Yuan Jiang
Keyword(s):  
Silk Fibroin ◽  
Solid Content ◽  
Self Organized ◽  
Diffusion Limited ◽  
Transmission Electron ◽  
Significant Strength ◽  
Hierarchical Architectures ◽  
Partially Occluded ◽  
Limited Process ◽  
Seed Layers

As many biominerals are formed in gel-like media, hydrogel-mediated mineralization is deemed as paradigms of biomineralization and ideal approaches to synthetic minerals with hierarchical architectures and related functions. Nevertheless, the long diffusion distance in hydrogels makes mineralization a diffusion-limited process, leading to isolated crystals instead of uniform hierarchical architectures. In the current study, seeded mineralization in silk fibroin hydrogel matrices is successful in delivering continuous rhombohedral CaCO3 films. Though the coverage of hydrogel matrices makes mineralization a diffusion-limited process, the presence of seed layers promotes the growth of uniform overlayers in proper conditions. The regulation of the solid content of hydrogels provides a rational route to rhombohedral architectures with tunable morphologies and thickness. In the course of mineralization, the hydrogel matrices are partially occluded in rhombohedral films as inter- and intra-crystalline constituents, as confirmed by scanning and transmission electron microscopy. Our study confirms the availability of synthesizing continuous mineralized films with hierarchical architectures and the structural gradient in hydrogel matrices via self-organized mineralization. These films with the occlusion of hydrogel constituents may exhibit significant strength and resilience, and their formation can deepen our mechanistic understanding of biomineralization proceeding in gel-like media.

Formation of Palladium Silicide and Germanide in the Pd/a-Si/Si., Pd/a-Ge/Si, and Pd/a-GeSi/Si Systems During Thermal Treatment

1990 ◽  
Vol 205 ◽  
Author(s):  
F. Edelman ◽  
C. Cytermann ◽  
R. Brener ◽  
M. Eizenberg ◽  
R. Weil ◽  
...  
Keyword(s):  
Crystallization Process ◽  
X Ray Diffraction ◽  
Globular Structure ◽  
X Ray ◽  
Si Substrates ◽  
Diffusion Limited ◽  
Transmission Electron ◽  
Palladium Silicide ◽  
Kinetics Of ◽  
Limited Process

AbstractX-ray diffraction and transmission electron microscopy have been used to study the kinetics of phase transformations and the structure of Pd/a-Si, Pd/a-Ge and Pd/a-GeSi thin films deposited on Si substrates. Different kinds of amorphouis structures were used: a-Si:H:D, a-Si.:F, a-Ge:H:D, and a-GeSi:H:D. The first stage of phase transformation during heat treatment was palladium silicide (Pd2Si) and palladium germanide (Pd2Ge) formation at temperatures above 200°C. Annealing studies demonstrated that the presence of F in a-Si promotes the Pd2Si formation. The study of the Pd2Si crystallization process showed that: a) when the Pd layer and the a-Si layer are thin, then c-PdSi grows in a fractal-]ike form; b) when the Pd and a-Si both are thick, then c-Pd2Si grows in a globular structure; c) in both above mentioned cases a well-oriented [0011 texture forms. The growth of the silicide and germanide layers in the temperature range of 200-300°C was found to be controlled by a diffusion limited process. It was found that c-Pd2Ge transforms to c-PdGe above 200°C. The a-Ge,.,Si,. 5 alloy behaved similarly to a-Si forming only [001] textured c-Pd2(Ge,Si).

Preparation of α-Ni(OH)2 with Flowerlike Hierarchical Architectures via Homogeneous Precipitation Method

2011 ◽  
Vol 284-286 ◽  
pp. 684-687
Author(s):  
Chang Yu Li ◽  
Li Li Liu ◽  
Shou Xin Liu
Keyword(s):  
Electron Microscopy ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
X Ray ◽  
Homogeneous Precipitation Method ◽  
Α Phase ◽  
Transmission Electron ◽  
Hierarchical Architectures ◽  
Flowerlike Structure ◽  
Adsorption Desorption

Without using any templates or surfactants, flowerlike α-nickel hydroxide (Ni(OH)2) was successfully synthesized by homogeneous precipitation method. The prepared products were characterized by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and N2 adsorption-desorption. The prepared Ni(OH)2 is α-phase with specific surface area of 245.0 m2/g and shows flowerlike structure with 4-6 um in diameter.

Studies of Compositional Variations in Germanium Quantum Dots Grown on Silicon

2000 ◽  
Vol 638 ◽  
Author(s):  
Alan D.F. Dunbar ◽  
Matthew P. Halsall ◽  
Uschi Bangert ◽  
Alan Harvey ◽  
Philip Dawson ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
The Self ◽  
Asymmetric Distribution ◽  
Scanning Transmission Electron ◽  
Self Organized ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Uk

AbstractWe report optical and scanning transmission electron microscopy studies of germanium dots grown on silicon. In an attempt to control the self-organized growth process and promote dot size uniformity the dot layers were grown on a 4.5nm Si0.6Ge0.4 alloy template layer. Photoluminescence results indicate the formation of carrier confining Ge rich islands, whilst Raman scattering results indicate the presence of an alloy throughout the structures formed. The samples were studied in the UK high resolution scanning transmission electron microscopy facility at Liverpool, UK. Energy dispersive analysis of individual line scans through the sample show that the structures are composed of an alloy throughout with an asymmetric distribution of Germanium in the dots and in the wetting layer close to the dots. We discuss the results in the light of the proposed growth mode for these dots and conclude that attempts to manipulate the composition of these dots during growth may be problematic due to the self-organized nature of their formation.

scholarly journals In situ wide-field visualization of palladium hydrogenation

2020 ◽  
Author(s):  
Chongjun Jin ◽  
Nicholas Fang ◽  
Xiaoyi She ◽  
Huifeng Du ◽  
Yang Shen ◽  
...  
Keyword(s):  
Real Time ◽  
Hydrogen Diffusion ◽  
Fast Response ◽  
Wide Field ◽  
Ion Diffusion ◽  
Optical Contrast ◽  
Self Organized ◽  
Transmission Electron ◽  
Kinetics Of

Abstract Visualizing hydrogenation processes in metals in real-time is important to various hydrogen-involved applications. However, observing hydrogen diffusion was limited by transmission electron microscopy, and the kinetics of hydrogenation in the interior of the metals was not reported. Here we proposed an optical microscopy-based visualization of palladium hydrogenation from diffusion surface to the interior by introducing a fast-response mechanical platform that transforms the hydrogen diffusion into self-organized ordered wrinkles with sharp optical contrast. This platform is an Au/Pd double layer on elastomer which results in directional hydrogenation from sidewall to the interior. The kinetics of hydrogenation in the interior of the palladium along the diffusion direction was monitored in real-time. This platform will enable in-situ visualization of atom/ion diffusion on metals that are crucial in energy storage and hydrogen detection.

Self-Organized Composition Modulation In Omvpe Ga1−xInxAsySb1−y/GaSb Epitaxial Heterostructures

1999 ◽  
Vol 583 ◽  
Author(s):  
Y-C. Chen ◽  
V. Bucklen ◽  
K. Rajan ◽  
C. A. Wang ◽  
G. W. Charache ◽  
...  
Keyword(s):  
Cross Section ◽  
Three Dimensional ◽  
Component Composition ◽  
Organometallic Vapor Phase Epitaxy ◽  
Composition Modulation ◽  
Self Organized ◽  
Transmission Electron ◽  
Epitaxial Heterostructures ◽  
20 Nm ◽  
Lattice Matched

AbstractMicrostructures of lattice-matched Ga1−xInxAsySb1−y grown by organometallic vapor phase epitaxy (OMVPE) on (100) 6°→ (111)B GaSb substrates have been examined in detail by transmission electron microscopy. A three-dimensional self-organized composition modulation (SOCM) microstructure was found with an orientation inclined 10 degrees to the surface orientation when viewed in (011) cross-section. The periodicity of the SOCM increased from ˜13 nm to 20 nm, as x increased from 0.1 to 0.2 while the orientation of the SOCM remained the same. The fact that the orientation was not sensitive to the component composition indicated that substrate misorientation plays a major role in deciding this SOCM orientation. This may open fabrication opportunities for three-dimensional natural superlattices by engineering on the substrate misorientation.

Self-Organized Lead(II) Sulfide Quantum Dots Superlattice

MRS Advances ◽  
2017 ◽  
Vol 2 (15) ◽  
pp. 841-846 ◽  
Author(s):  
José Maria C. da Silva Filho ◽  
Victor A. Ermakov ◽  
Luiz G. Bonato ◽  
Ana F. Nogueira ◽  
Francisco C. Marques
Keyword(s):  
Quantum Dots ◽  
Interplanar Spacing ◽  
Face Centered Cubic ◽  
X Ray ◽  
Self Organized ◽  
Transmission Electron ◽  
The Mean ◽  
Face Centered ◽  
Pbs Quantum Dots ◽  
Deposited Films

ABSTRACTWe show that superlattice (SL) of PbS quantum dots (QD) can be easily prepared by drop casting of colloidal QD solution onto glass substrate and the ordering level can be controlled by the substrate temperature. A QD solution was dropped on glass and dried at 25, 40, 70 and 100°C resulting in formation of different SL structures. X-ray diffractograms (XRD) of deposited films show a set of sharp and intense peaks that are higher order satellites of a unique peak at 1.8 degrees (two theta), which corresponds, using the Bragg’s Law, to an interplanar spacing of 5.3 nm. The mean particles diameter, calculated through the broadening of the (111) peak of PbS using the Scherrer’s formula, were in agreement with the interplanar spacing. Transmission electron microscopy (TEM) measurements were also used to study the SL structure, which showed mainly a face centered cubic (FCC) arrangement of the QD. The photoluminescence (PL) spectrum of QD in the SL showed a shift toward lower energy compared to one in solution. It can be attributed to the fluorescence resonant energy transfer (FRET) between neighbors QD´s. Moreover, we observed greater redshift of PL peak for film with lower drying temperature, suggesting that it has a more organized structure.

Sb-rich nanoinclusions in an AlGaAsSb metamaterial

MRS Advances ◽  
2019 ◽  
Vol 4 (5-6) ◽  
pp. 277-284
Author(s):  
Nikolay A. Bert ◽  
Vladimir V. Chaldyshev ◽  
Nikolay A. Cherkashin ◽  
Vladimir N. Nevedomskiy ◽  
Valery V. Preobrazhenskii ◽  
...  
Keyword(s):  
Molecular Beam ◽  
Filling Factor ◽  
Local Thermodynamic Equilibrium ◽  
Average Diameter ◽  
Formation Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Self Organized ◽  
Transmission Electron ◽  
The Matrix

ABSTRACTWe studied the microstructure of Al0.28Ga0.72As0.972Sb0.028 metamaterials containing a developed array of AsSb nanoinclusions. The AlGaAsSb films were grown by low-temperature molecular-beam epitaxy followed by high-temperature annealing at 750°C. The process resulted in an array of self-organized AsSb nanonclusions with an average diameter of 15 nm. The volume filling factor was about 0.003. Using transmission electron microscopy and x-ray diffraction we showed that the nanoinclusions have A7-type rhombohedral atomic structure with the following orientation in the matrix (0003)p || {111}m and [-2110]p || 〈220〉m, where p and m indices indicate the AsSb precipitate and AlGaAsSb matrix, correspondingly. The nanoinclusions appeared to be strongly enriched by antimony (more than 90 atomic %), whereas the Sb content in the AlGaAsSb matrix was 2.8 atomic %. The strong enrichment of the inclusion with Sb resulted from the local thermodynamic equilibrium between the solid AlGaAsSb matrix and AsSb inclusions which became liquid at a formation temperature of 750°C.

scholarly journals Hydrogen desorption in SiGe films: A diffusion limited process

1997 ◽  
Vol 70 (24) ◽  
pp. 3287-3289 ◽  
Author(s):  
J. Vizoso ◽  
F. Martín ◽  
J. Suñé ◽  
M. Nafría
Keyword(s):  
Hydrogen Desorption ◽  
Diffusion Limited ◽  
Limited Process

Evaluation of the Strain Field Inside and Around Growth Islands by Means of X-Ray Diffuse Scattering

1999 ◽  
Vol 583 ◽  
Author(s):  
Martin Schmidbauer ◽  
Thomas Wiebach ◽  
Helmut Raidt ◽  
Peter Schäfer ◽  
Michael hanke ◽  
...  
Keyword(s):  
Strain Field ◽  
Reciprocal Space ◽  
X Ray Diffraction ◽  
Abrupt Increase ◽  
X Ray ◽  
Force Microscopy ◽  
Self Organized ◽  
Atomic Force ◽  
Transmission Electron ◽  
Highly Strained

AbstractThe strain distribution inside and in the vicinity of coherently strained self-organized islands has been investigated by high-resolution x-ray diffraction (HRXRD). Finite element method (FEM) calculations were carried out in order to calculate the strain field, which was then used to simulate x-ray reciprocal space maps on the basis of kinematical scattering theory. For Si0 75Ge0.25 islands an abrupt increase in the Ge-concentration at about one third of the island height has been found. This behavior can be attributed to different nucleation stages during growth. Highly strained buried CdSe quantum dots (QDs) strongly influence the surrounding ZnSe matrix. From reciprocal space maps and FEM simulations we were able to estimate the shape and size of the islands. The results are in agreement with transmission electron microscopy (TEM) and UHV atomic force microscopy (AFM) data.

Effect of a-SiC:H Film Composition on the Performance of Large Area Optical Sensors

2001 ◽  
Vol 685 ◽  
Author(s):  
P. Louro ◽  
Yu. Vygranenko ◽  
M. Fernandes ◽  
M. Vieira ◽  
M. Schubert
Keyword(s):  
Optical Sensors ◽  
Carrier Transport ◽  
Energy Band Diagram ◽  
Large Area ◽  
Conduction Band Offset ◽  
Sensor Performance ◽  
Diffusion Limited ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
Limited Process

AbstractA series of large area single layers and heterojunction cells in the assembly glass/ZnO:Al/p (SixC1-x:H)/i (Si:H)/n (SixC1-x:H)/Al (0<x<1) were produced by PE-CVD at low temperature. Junction properties, carrier transport and photogeneration are investigated from dark and illuminated current-voltage and capacitance-voltage characteristics. For the heterojunction cells Atypical J-V characteristics under different illumination conditions are observed leading to poor fill factors. High serial resistances around 106 Ω are also measured. These experimental results were used as a basis for the numerical simulation of the energy band diagram, and the electrical field distribution of the whole structures. Further comparison with the sensor performance gave satisfactory agreement.Results show that the conduction band offset is the most limiting parameter for the optimal collection of the photogenerated carriers. As the optical gap increases and the conductivity of the doped layers decreases, the transport mechanism changes from a drift to a diffusion-limited process.

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