scholarly journals Nonradiative and Radiative Recombination in CdS Polycrystalline Structures

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
E. Gaubas ◽  
V. Borschak ◽  
I. Brytavskyi ◽  
T. Čeponis ◽  
D. Dobrovolskas ◽  
...  
Keyword(s):  
Grain Size ◽  
Laser Excitation ◽  
Polycrystalline Material ◽  
Photoluminescence Intensity ◽  
Sampling Area ◽  
Excitation Beam ◽  
Simultaneous Record ◽  
Grain Distribution ◽  
Spectrally Resolved ◽  
Polycrystalline Structures

Properties of polycrystalline CdS layers, employed in formation of the CdS-Cu2S heterostructures, have been studied by combining contactless techniques of the time and spectrally resolved photoluminescence (TR-PL) spectroscopy and microwave-probed photoconductivity (MW-PC) transients. The confocal microscopy has been employed to correlate the homogeneity of photoluminescence and grain size in CdS layers. Three types of samples with crystallite grain size of <1 μm (the I-type) and of 2–10 μm of homogeneous (II-type) and inhomogeneous (III-type) grain distribution have been separated. The simultaneous record of MW-PC and TR-PL responses ensures the same sampling area on the layer under investigation, as both (MW-PC and TR-PL) signals are generated by the same UV laser excitation beam. Two PL bands peaked at 500 and 700 nm were revealed. It has been demonstrated that photoluminescence intensity strongly depends on the properties of the polycrystalline 15–26 μm thick CdS layers with equilibrium carrier density of about1.5×1013 cm−3, which serve as the substrates to form CdS-Cu2S junctions. The different carrier decay components were ascribed to different microareas with characteristic MW-PC and PL decay lifetimes of 2–10 ns, ascribed to microcrystallites with PL instantaneous decay lifetimes of 40–200 ns, and MW-PC decay lifetimes in the range of 100–1000 μs attributed to the inter-crystallite areas of CdS polycrystalline material.

scholarly journals Characterization of sand boils with grading entropy

2012 ◽  
pp. 73-88
Author(s):  
Laslo Nadj
Keyword(s):  
Grain Size ◽  
Distribution Curve ◽  
Practical Consideration ◽  
Implicit Information ◽  
Sand Boil ◽  
Sand Boils ◽  
Grain Distribution ◽  
Soil Behaviour ◽  
The Relationship

Grain size and grain distribution by size are dominant factors determining soil behaviour. The shape and position of a grain distribution curve contain implicit information about the propensity of sand boiling or piping at flood conditions. The author used 1040-grain distribution curves taken from 12 sand boil locations to study the relationship between sand boils, hydraulic soil failures and entropy. The results have justified the hypotheses and indicated some fairly important details for practical consideration. Calculating grain distribution entropy is not ?magic? with mathematics: it simply helps put the expected behaviour of soils into a different perspective and promotes orientation for classifying soils according to a new parameter related to grain movement.

Study on the Simulation of Grinding Based on Virtual Reality Technology

2007 ◽  
Vol 561-565 ◽  
pp. 1887-1890
Author(s):  
Tian Biao Yu ◽  
Jian Yu Yang ◽  
Ya Dong Gong ◽  
F. Xu ◽  
F. Liang ◽  
...  
Keyword(s):  
Grain Size ◽  
Virtual Reality ◽  
Wheel Speed ◽  
Grinding Wheel ◽  
Feed Speed ◽  
Processing Quality ◽  
Virtual Reality Technology ◽  
Forming Mechanism ◽  
Wheel Model ◽  
Grain Distribution

For properly choosing grinding parameters, predicting probable faults and processing quality, simulation of grinding based on virtual reality technology was study. Physiognomy forming mechanism of grinding wheel was analyzed and a 3D virtual grinding wheel models was built. Effects to grinding wheel physiognomy by grain size and organization number were analyzed and grain distribution was visually represented. Effect to processing quality by grinding wheel granularity, dressing parameters, grinding wheel speed, feed speed and grinding depth was simulated. And experiments were carried out for comparative analyzing. Experiments result proved the reliability and practicality of the virtual grinding wheel model.

scholarly journals Investigation of Strain Gradients and Magnitudes During Microbending

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Lijie Wang ◽  
Yannis Korkolis ◽  
Brad L. Kinsey
Keyword(s):  
Grain Size ◽  
Metal Forming ◽  
Polycrystalline Material ◽  
Current Trend ◽  
Electronics Industry ◽  
Image Correlation ◽  
Feature Size ◽  
Strain Gradients ◽  
Data Scatter ◽  
Individual Grains

Sheet metal forming of parts with microscale dimensions is gaining importance due to the current trend toward miniaturization, especially in the electronics industry. In microforming, although the process dimensions are scaled down, the polycrystalline material stays the same (e.g., the grain size remains constant). When the specimen feature size approaches the grain size, the properties of individual grains begin to affect the overall deformation behavior. This results in inhomogeneous deformation and increased data scatter of the process parameters. In this research, the influence of the specimen size and the grain size on the distribution of plastic deformation through the thickness during a three-point microbending process is investigated via digital image correlation (DIC). Results showed that with miniaturization, a decrease in the strain gradient existed which matched previous research with respect to microhardness measurement.

Grain Characteristics of Nanocrystalline ZrO2 Powders

2007 ◽  
Vol 336-338 ◽  
pp. 2558-2561 ◽  
Author(s):  
Hui Yan Yin ◽  
Min Fang Han
Keyword(s):  
Grain Size ◽  
Nanocrystalline Powders ◽  
Crystalline Domain ◽  
Grain Sizes ◽  
Grain Distribution ◽  
Agglomeration Coefficient

The grain characteristics of four kinds of ZrO2 nanocrystalline powders were manifested and discussed in this paper. The grain size of sample 1 tested by XRD, TEM and BET is consistent. The agglomeration coefficient of Sample 1 is higher, about 62.5, and the span of grain distribution is 14.58. The grain sizes of Sample 2 and 3 tested by XRD, TEM and BET are different. These differences identify the crystalline domain including 2~3 unite, which make the departure spheres in TEM. There are more soft agglomerates in Sample 2 with the agglomeration coefficient of 25.71 and the span of grain distribution being 18.94 than that in Sample 3 with the agglomeration coefficient of 6.89 and the span of grain distribution being 8.91. The grain sizes of Sample 4 tested by XRD, TEM and BET are obviously different. That identifies the large hard agglomerates.

Influence of SiO2 Content on Fractal of Grain Distribution in Low Silicon Sinter

2011 ◽  
Vol 391-392 ◽  
pp. 269-273
Author(s):  
Qing Jun Zhang ◽  
Li Mei Jiang ◽  
Wen Ling Mo ◽  
Yu Zhu Zhang
Keyword(s):  
Grain Size ◽  
Fractal Dimension ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Fractal Theory ◽  
Fractal Characteristic ◽  
Important Index ◽  
Grain Distribution

Grain size distribution in the sinter is an important index sign to measure the quality of sinter. In this paper, according to the fractal theory and the contrast experiment of sinter, the fractal characteristic of grain size distribution of sinter with low SiO2is discussed. The relation between the fractal dimension and content of SiO2is proposed. Combine with the SEM graphs of the sinter with low SiO2, the relation between the fractal dimension and microstructure of sinter with low SiO2is also analyzed. Pass to the quantificational description of the grain size distribution of sinter with low SiO2, to predict and optimize the grain size constitution of sinter, and offer a new idea, a new way for the further thorough research of sinter ore.

Numerical Simulation and Experimental Analysis on the Crystal Growth of Excimer-Laser Crystallization of a-Si Film

2008 ◽  
Author(s):  
Long-Sun Chao ◽  
Yu-Ru Chen ◽  
Hsiun-Chang Peng
Keyword(s):  
Electron Microscopy ◽  
Numerical Simulation ◽  
Scanning Electron Microscopy ◽  
Grain Size ◽  
Grain Growth ◽  
Excimer Laser ◽  
Crystallographic Direction ◽  
Grain Distribution ◽  
Induced Crystallization ◽  
Scanning Electron

In this work, the excimer-laser-induced crystallization of amorphous silicon (a-Si) films was investigated numerically and experimentally. The basic structure is an a-Si film on a glass substrate. This study had investigated the effects of irradiating energy density on the grain size and structure by scanning electron microscopy (SEM). In the surface microstructure analysis of the laser-irradiated area, the critical fluences (full-melt threshold, FMT) between the partial melting and complete melting regimes can be found by applying scanning electron microscopy. An efficient two-dimensional numerical model is carried out to predict the critical fluences (FMT) and the transient temperature distribution during the laser processing. Numerical analysis of the temperature profile showed that a temperature drop occurred at the center of melted zone immediately after laser irradiation. From the analysis of temperature responses, the FMT obtained from the simulation results of the proposed model agree fairly well with those from the experimental data reported in the literature and acquired in this research. Furthermore, the grain growth of the poly-Si was studied by the grain observation of the cross section and its corresponding numerical simulation. The cross-sectional grain structure of the resulting poly-Si film was observed with different laser intensities. The grain sizes decreased with increasing irradiating energy intensity in the partial melting regime. From the surface observation, the grain distribution was uniform and most of the grain has a single crystallographic direction. The average grain size had the biggest value at FMT. But some super large grains occurred and combined with more than one crystallographic direction when the film obtained sufficiently high energy intensities that was closed or over the FMT. The grain distribution was not uniform. The super large gain was around the small grain size. The modified cellular automation method (MCA) was used to simulate the grain growth two-dimensionally and explain the grain development during the solidification process. The grain morphology of the numerical simulation was satisfied with the experimental observation. From the analysis of the grain growth, this model was able to simulate the undercooling effect and grain growth phenomenon and fitted for the experimental grain observation in the excimer-laser-induced crystallization.

Influence of Asymmetric Hot Rolling on Microstructures of Vessel Steel

2014 ◽  
Vol 1049-1050 ◽  
pp. 35-38
Author(s):  
Xiao Lei Bai ◽  
Zhen Guang Liu ◽  
Xiu Hua Gao ◽  
Yong Lu ◽  
Jian Ping Li
Keyword(s):  
Grain Size ◽  
Hot Rolling ◽  
Vessel Steel ◽  
Gradient Distribution ◽  
Transmission Electron ◽  
Rolled Specimen ◽  
Grain Distribution ◽  
The One ◽  
Asymmetric Hot Rolling ◽  
Electron Back Scattered Diffraction

The symmetric/asymmetric hot rolling experiments were carried out to investigate the effect of shear deformation on microstructure of vessel steel by using electron back-scattered diffraction (EBSD) and field emission transmission electron microscope. The study shows that gradient distribution grain size through the thickness is formed in asymmetric rolled specimen. The grain size in surface is smaller than the one in center. The grain distribution is homogeneous in symmetric rolled specimen. The grain in asymmetric rolled specimen is smaller than the one in symmetric rolled specimen in the same thickness position. The precipitate particles morphology are random precipitate and interphase precipitate in symmetric and asymmetric rolled specimen. The precipitate particles tend to nucleate and grow in the grain in symmetric rolled specimen. The precipitate particles located in grain boundary are observed in asymmetric rolled specimen.

Effect of grain size on the resistivity of polycrystalline material

Solar Cells ◽  
1983 ◽  
Vol 9 (4) ◽  
pp. 261-267 ◽  
Author(s):  
D.P. Joshi ◽  
K. Sen
Keyword(s):  
Grain Size ◽  
Polycrystalline Material

scholarly journals PLUME-MoM 1.0: A new integral model of volcanic plumes based on the method of moments

2015 ◽  
Vol 8 (8) ◽  
pp. 2447-2463 ◽  
Author(s):  
M. de' Michieli Vitturi ◽  
A. Neri ◽  
S. Barsotti
Keyword(s):  
Grain Size ◽  
Standard Deviation ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Method Of Moments ◽  
Integral Model ◽  
Plume Height ◽  
New Model ◽  
Volcanic Plumes ◽  
Grain Distribution

Abstract. In this paper a new integral mathematical model for volcanic plumes, named PLUME-MoM, is presented. The model describes the steady-state dynamics of a plume in a 3-D coordinate system, accounting for continuous variability in particle size distribution of the pyroclastic mixture ejected at the vent. Volcanic plumes are composed of pyroclastic particles of many different sizes ranging from a few microns up to several centimeters and more. A proper description of such a multi-particle nature is crucial when quantifying changes in grain-size distribution along the plume and, therefore, for better characterization of source conditions of ash dispersal models. The new model is based on the method of moments, which allows for a description of the pyroclastic mixture dynamics not only in the spatial domain but also in the space of parameters of the continuous size distribution of the particles. This is achieved by formulation of fundamental transport equations for the multi-particle mixture with respect to the different moments of the grain-size distribution. Different formulations, in terms of the distribution of the particle number, as well as of the mass distribution expressed in terms of the Krumbein log scale, are also derived. Comparison between the new moments-based formulation and the classical approach, based on the discretization of the mixture in N discrete phases, shows that the new model allows for the same results to be obtained with a significantly lower computational cost (particularly when a large number of discrete phases is adopted). Application of the new model, coupled with uncertainty quantification and global sensitivity analyses, enables the investigation of the response of four key output variables (mean and standard deviation of the grain-size distribution at the top of the plume, plume height and amount of mass lost by the plume during the ascent) to changes in the main input parameters (mean and standard deviation) characterizing the pyroclastic mixture at the base of the plume. Results show that, for the range of parameters investigated and without considering interparticle processes such as aggregation or comminution, the grain-size distribution at the top of the plume is remarkably similar to that at the base and that the plume height is only weakly affected by the parameters of the grain distribution. The adopted approach can be potentially extended to the consideration of key particle–particle effects occurring in the plume including particle aggregation and fragmentation.

Effect of ZrB2 Nanoparticle Addition: Nano-LPSO-Grain Structured Ultra-High Strength Mg-RE Alloy

2014 ◽  
Vol 783-786 ◽  
pp. 425-430
Author(s):  
Muralidharan Paramsothy ◽  
Manoj Gupta
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Yield Strength ◽  
Polycrystalline Material ◽  
High Strength ◽  
Tensile Yield Strength ◽  
Intermetallic Formation ◽  
Long Period ◽  
Ordered Phases ◽  
The Common

Currently, long period stacking/ordered phases (LPSO phases) are known to reinforceMg97Y2Zn1 type Mg-RE alloys. The LPSO phases are composed of a solid solution of Y and Znatoms placed orderly in long periods along the Mg basal plane. Also, an efficient way to strengthena polycrystalline material is to reduce its grain size. This increases the density of grain boundarieswhich impede the flow of dislocations. In many of the LPSO forming solidification processed Mg-RE alloys, the common practice is to solutionize the ingot, quench in warm water, hot extrude andthermally age. While this practice is suitable for obtaining high strength Mg-RE alloys, itconveniently employs the common idea in conventional metallurgy of fine intermetallicstrengthening while refining the grain size to within the micron regime. In this work, an alternativemethod involving boride nanoparticle addition to obtain a selected solidification processed ultrahighstrength (tensile yield strength > 400 MPa) Mg-RE alloy is discussed. Here, LPSO phaserather than fine intermetallic formation while retaining grain size under the micron regime ishighlighted.

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