scholarly journals Influence of Growth Conditions on Mechanical Properties of K2NiXCo(1−X) (SO4)2·6H2O Crystals

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1550
Author(s):  
Natalia A. Vasilyeva ◽  
Elena B. Rudneva ◽  
Vera L. Manomenova ◽  
Marina V. Koldaeva ◽  
Alexey E. Voloshin
Keyword(s):  
Crack Length ◽  
Crack Resistance ◽  
Optical Filters ◽  
Growth Conditions ◽  
Visible Spectral Region ◽  
Structural Defects ◽  
Optical Elements ◽  
Ultraviolet Range ◽  
Solar Blind ◽  
Comprehensive Study

K2NiXCo(1−X) (SO4)2·6H2O (KCNSH) mixed crystal is a promising material for solar blind optical filters, combining high transparency in the ultraviolet range with effective suppression of the visible spectral region. Increasing the mechanical strength of these crystals is important to enable them to be machined in the manufacture of optical elements. A comprehensive study of the inhomogeneities and crack resistance of KCNSH crystal as a function of the growth conditions was carried out. The influence of the radial and mosaic inhomogeneity, as well as other structural defects, on the crack resistance of the crystals was analyzed. To assess the crack resistance of crystals, the parameters ca (crack length), c/a (the ratio of crack length to the size of the indentation), and KC (fracture toughness) were used. The correctness of the obtained results was analyzed. The conditions for growing KCNSH crystals with the best crack resistance were determined on the basis of the results of the study. It is shown that growing the mixed crystals using the temperature difference technique with a peripheral solution supply into the shaper provides the best crystal quality.

Characterization of Structural Defects in Germanium Epitaxially Grown on Nano-Structured Silicon

2011 ◽  
Vol 178-179 ◽  
pp. 43-49 ◽  
Author(s):  
Peter Zaumseil ◽  
Yuji Yamamoto ◽  
Joachim Bauer ◽  
Markus Andreas Schubert ◽  
Jana Matejova ◽  
...  
Keyword(s):  
Oxide Thickness ◽  
Growth Conditions ◽  
Structural Defects ◽  
Misfit Dislocations ◽  
Strain Partitioning ◽  
X Ray Diffraction ◽  
Reduced Pressure ◽  
Periodic Arrays ◽  
Transmission Electron

Selective epitaxial growth of germanium (Ge) on nano-structured Si(001) wafers is studied to evaluate the applicability of the nano-heteroepitaxy (NHE) approach on Ge-Si system. Based on a gate spacer technology established in advanced silicon microelectronics periodic arrays of nano-scaled Si islands are prepared, where Ge is deposited on top by reduced pressure CVD. The spacing of these structures is 360 nm. The structural perfection of the deposited Ge is investigated by transmission electron microscopy and X-ray diffraction. It is found that SiO2used as masking material is responsible for the suppression of the desired strain partitioning effect according to NHE. Even for 10 nm oxide thickness, the lattice of Ge layers deposited on Si nano-islands relaxes completely by generation of misfit dislocations at the interface. The occurrence of additional structural defects like stacking faults and micro twins can be controlled by suited growth conditions.

Development of Homoepitaxially Grown GaN Thin Film Layers on Freestanding Bulk m-plane Substrates by Metalorganic Chemical Vapor Deposition (MOCVD)

2007 ◽  
Vol 1040 ◽  
Author(s):  
Vibhu Jindal ◽  
James Grandusky ◽  
Neeraj Tripathi ◽  
Mihir Tungare ◽  
Fatemeh Shahedipour-Sandvik ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Growth Rates ◽  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Structural Defects ◽  
Lateral Growth ◽  
High Quality ◽  
Metalorganic Chemical

AbstractHigh quality homoepitaxial growth of m-plane GaN films on freestanding m-plane HVPE GaN substrates has been performed using metalorganic chemical vapor deposition. For this a large growth space was studied. Large areas of no-nucleation along with presence of high density of defects were observed when layers were grown under growth conditions for c-plane GaN. It is believed that these structural defects were in large part due to the low lateral growth rates as well as unequal lateral growth rates in a- and c- crystallographic directions. To achieve high quality, fully coalesced epitaxial layers, growth conditions were optimized with respect to growth temperature, V/III ratios and reactor pressure. Higher growth temperatures led to smoother surfaces due to increased surface diffusion of adatoms. Overall, growth at higher temperature and lower V/III ratio decreased the surface roughness and resulted in better optical properties as observed by photoluminescence. Although optimization resulted in highly smooth layers, some macroscopic defects were still observed on the epi-surface as a result of contamination and subsurface damage remaining on bulk substrates possibly due to polishing. Addition of a step involving annealing of the bulk substrate under H2: N2 environment, prior to growth, drastically reduced such macroscopic defects.

Ultraviolet Photodetection Properties of ZnO Microtubes

2006 ◽  
Vol 957 ◽  
Author(s):  
Jiping Cheng ◽  
Ming Fu ◽  
Yunjin Zhang ◽  
Ruyan Guo
Keyword(s):  
Low Cost ◽  
Optical Filters ◽  
Wide Bandgap ◽  
Low Power Consumption ◽  
Uv Detectors ◽  
Solar Blind ◽  
High Efficient ◽  
Potential Applications ◽  
Growth Method ◽  
Bandgap Semiconductors

ABSTRACTPhotodetectors based on wide-bandgap semiconductors have demonstrated several advantages over traditional ultraviolet (UV) detectors (photomultiplier tubes and Si-based UV detectors) such as low power consumption, high stability, and no need of other optical filters. ZnO stands a good chance of being a candidate material for solar-blind UV detection because of its direct bandgap of 3.37eV and high photoresponse. In this work, single crystal ZnO microtubes synthesized using a microwave-heating growth method and their UV photodetection properties were studied. The ZnO microtubes exhibited relatively fast UV photoresponse with a cut-off wavelength ∼370 nm, indicating their potential applications as high efficient and low cost UV detectors.

The Relationship of Growth Conditions to Structural Defects of LPE-ALXGa1-XSb

1991 ◽  
Vol 38-41 ◽  
pp. 917-922 ◽  
Author(s):  
Naritaka Kitamura ◽  
K. Higuchi ◽  
Masaya Ichimura ◽  
A. Usami ◽  
T. Wada
Keyword(s):  
Growth Conditions ◽  
Structural Defects ◽  
Relationship Of ◽  
The Relationship

scholarly journals PREVENTION OF CRACK FORMATION IN DETAILS IN PROVISION OF RELIABLE COMPOUNDS WITH A TENSION

2018 ◽  
Vol 12 (3) ◽  
pp. 76-81
Author(s):  
Сергей Попов ◽  
Sergey Popov ◽  
Анатолий Русанов ◽  
Anatoliy Rusanov
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Resistance ◽  
Structural Defects ◽  
Outer Diameter ◽  
The Press ◽  
External Part ◽  
The Impact

When repairing agricultural machinery, the pressing of repair bushings for the restoration of worn parts is widely used. In the process of assembling a joint in the external part, cracks are often formed, which can be caused either by defects in its surface or by structural defects. Therefore, increasing the crack growth resistance of the press connection during assembly is an urgent task. The work analyzes the impact of the geometry of the external part on the resistance to fracture. Since it is possible to obtain complete information on defects by nondestructive testing methods only in individual cases, a technique for modeling the defects of the surface crack of a semielliptical shape was used. To evaluate the crack resistance, the force criterion of fracture mechanics is used - the stress intensity factor. As a result, it was found that the relationship between the thickness of the wall of the external part and its outer diameter makes a significant impact on the fracture toughness of the compression joint, which makes it possible to reduce the probability of nucleation and development of cracks by changing these parameters. Such a technique can be used in cases where the mechanical assembly is used for assembling the connection - by means of a press and a thermal one - with heating of the external part, methods of assembly. The greatest strength of the connection is achieved by cooling the internal part during assembly, but in this case the probability of formation and growth of cracks increases. This is due to a decrease in the critical stress intensity factor (fracture toughness), which is a mechanical characteristic of crack resistance when the temperature of the external part is lowered. The effect of this factor can be reduced by using a combined method of assembling the joint by cooling the internal and heating the external part. To evaluate the fracture resistance at low temperatures, it is optimal to carry out full-scale tests, where the cooling and heating temperatures of the press connection parts act as experimental factors.

Superconductivities and structure modulations in Tl-Ba-Ca-Cu-O oxides

1989 ◽  
Vol 47 ◽  
pp. 170-171
Author(s):  
Sumio Iijima
Keyword(s):  
Charge Carrier ◽  
Crystal Structures ◽  
Growth Conditions ◽  
Structural Defects ◽  
High Tc ◽  
Wide Range ◽  
Axis Length ◽  
Oxide Crystals ◽  
Sintering Method

Charge carrier sources for the superconductivities of high Tc oxides have been sought by various techniques. The role of lattice defects in the superconductivity, and structural defects which are common in these oxides, were investigated by electron microscopists. In this paper, microstructures on TBCCO oxide crystals, in particular, superlattice modulations in the 2201 phase, and Y-doped 2212 phases which are prepared under various growth conditions, are presented. All specimens were prepared in the standard sintering method.In contrast with the 2212 and 2223 compounds, the 2201 compounds showed a wide range of Tc values. Their variations were found to be strongly affected by oxygen content.This was concluded from the fact that the nonsuperconductive specimen became conductive by quenching after heating in O2 atmosphere at 400°C. This was further confirmed when the superconductivity vanished by annealing. It was also demonstrated that crystal symmetries of the compounds, orthorhombic and tetragona1 are not directly related to the superconductivity as was proposed by Hewat et al. The orthorhombic structures are obtained at preparation temperatures above 840°C. It was also found that the Tc value increases linearly with an increase in the c-axis length which is independent of crystal structures.

scholarly journals Comprehensive Study Of Duckweed Cultivation And Growth Conditions Under Controlled Eutrophication

2015 ◽  
Vol 23 (36) ◽  
pp. 103-107
Author(s):  
Alica Bartošová ◽  
Maroš Sirotiak ◽  
Jozef Fiala
Keyword(s):  
Water Clarity ◽  
Growth Conditions ◽  
Ammonium Nitrogen ◽  
Solar Irradiation ◽  
Natural Conditions ◽  
Spectrophotometric Methods ◽  
Grown Sample ◽  
Nitrite Nitrate ◽  
Biomass Increase ◽  
Comprehensive Study

Abstract The paper discussed the issue of eutrophication. The most conspicuous effect of eutrophication is the creation of dense blooms of noxious, foul-smelling phytoplankton that reduce water clarity and harm water quality. Nutrient concentration, temperature and pH of the water largely influence the growth rate and composition of duckweed in general, but it can be said that the temperature and solar irradiation are the most important factors. In order to compare the rate of biomass increase of duckweed biomass in natural conditions and in a laboratory grown sample was analysed by spectrophotometric methods in UV/VIS region (Spectrophotometer GENESYSTM) for the selected nutrients such as ammonium, ammonium nitrogen, nitrite, nitrate, and phosphate.

The Optimization of Termination in Combined Technique of Magnetorheological Finishing and HF Etching for Laser-Induced Damage Threshold High-Efficiency Improving of Fused Silica

2014 ◽  
Vol 1027 ◽  
pp. 199-202
Author(s):  
Ye Tian ◽  
Xiao Qiang Peng ◽  
Yi Fan Dai ◽  
Feng Shi ◽  
Wen Wan
Keyword(s):  
High Efficiency ◽  
Experimental Parameter ◽  
Damage Threshold ◽  
Fused Silica ◽  
Fdtd Simulation ◽  
Structural Defects ◽  
Process Time ◽  
Optical Elements ◽  
Laser Systems ◽  
Laser Induced Damage

The developing high-power laser systems are requiring higher laser-induced damage threshold (LIDT) and fabrication efficiency of fused silica optical elements. To solve these problems, MRF polishing and HF etching have been combined utilized wiping and passivating structural defects as well as removing impurities. Furthermore, the LIDT improvement is dependent greatly on the corporation of processes. But the LIDT improving mechanism is partly ambiguous yet, that may lead to random or experimental parameter choice and ultimately generate unsatisfied results. Consequently, this paper focuses on the termination mechanism of the process. Atom Force Microscope (AFM) measurement, finite difference time-domain (FDTD) simulation and LIDT test will be utilized to analysis and validate the optimization theoretically and practically. Finally, in one side, the LIDT value of optimized-terminated sample is 16.7J/cm2, which is about the same level (even 3.7% higher) as that of the over-etched one. In another side, the etching process time could be shorted by 32% using the optimized method.

scholarly journals Mechanical and Morphological Characterization of Selected Natural Fibres

2006 ◽  
Vol 15 (2) ◽  
pp. 096369350601500 ◽  
Author(s):  
Ralf Schledjewski ◽  
Luisa Medina ◽  
Alois K. Schlarb
Keyword(s):  
Mechanical Properties ◽  
Weibull Distribution ◽  
High Standard ◽  
Growth Conditions ◽  
Single Fibre ◽  
Morphological Characterization ◽  
Natural Fibres ◽  
Strength Data ◽  
Comprehensive Study

The present work aims to characterize the morphological and mechanical properties of hemp and kenaf fibres. The mechanical properties of natural fibres highly depend on many factors like soil, growth conditions, harvest time or fibre treatment. Since the mechanical properties of the composite are highly conditioned by the characteristics of the fibres, a comprehensive study of the mechanical properties of the fibres is required in order to optimize the composite's properties. The fibres were characterized by single fibre tensile testing. Due to the high standard deviation of the measurements, the tensile strength data were statistically assessed. To describe strength data the Weibull distribution function was used. It has been assumed that the fracture stresses of natural fibres are distributed according to the two-parametric Weibull distribution.

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