Features of the Use of Equilibrium State Diagrams for Description of Crystal Growth from Metastable Melts

2020 ◽  
Vol 299 ◽  
pp. 622-627
Author(s):  
Maxim V. Dudorov ◽  
Alexander D. Drozin ◽  
B.G. Plastinin
Keyword(s):  
Growth Rate ◽  
Crystal Surface ◽  
Crystallization Front ◽  
Local Equilibrium ◽  
Product Formation ◽  
Metal Alloys ◽  
High Rate ◽  
Crystal Nucleus ◽  
State Diagrams ◽  
Equilibrium Effect

The crystallization of metastable metal alloys is characterized by a high rate of the crystallization front, which leads to the effect of "impurity capture" and deviation from the local equilibrium near the surface of the growing crystal. To calculate the growth rate of the crystalline nuclei, a method was developed for prediction of deviation of the components’ concentration near the crystal surface from the equilibrium values. A crystal nucleus was considered to be growing from the initial multicomponent phase, due to interphase transition of the components through its surface. It became possible to distinguish the equilibrium and non-equilibrium effect of the nucleus growth rate by decomposing the molar rate of the product formation near equilibrium, as a function of the molar concentration of the components in the Taylor series and limiting with the linear members. The practical calculations were carried out for the crystallization of the amorphous alloy Fe73,5Cu1Nb3Si13,5B9 of the FINEMET type. The local deviations were investigated for the silicon concentration from the equilibrium values at the surface of the growing crystal.

scholarly journals Simulation of crystal growth in multicomponent metastable alloys

2020 ◽  
Vol 62 (12) ◽  
pp. 943-949
Author(s):  
M. V. Dudorov ◽  
V. E. Roshchin
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Diffusion Processes ◽  
Mutual Influence ◽  
Crystallization Front ◽  
Metastable Phase ◽  
Phase Interface ◽  
Primary Crystallization ◽  
High Rate ◽  
Silicon Concentration

A method for predicting the regularities of crystal growth from metastable melts has been developed. The process of crystal growth from a multicomponent melt is described by the methods of nonequilibrium thermodynamics, taking into account the mutual influence of thermal and diffusion processes. The application of a new variational approach to the constructed system of equations made it possible to obtain expressions of the crystal growth rate from a multicomponent melt convenient for practical calculations. The obtained technique allowed us to analyze the features of crystal growth at high rate of crystallization front, which leads to “impurity capture” effect – deviation from equilibrium conditions at the phase interface. The developed mathematical model makes it possible to calculate the growth rate of new phase particles and to estimate the effect of metastable effects on deviation of the components’ concentration at surface of the growing crystal from equilibrium values. Thus, using the obtained method, a “metastable” phase diagram of the system under study can be constructed. The developed approach is applied to the calculation of growth of α-Fe(Si) nanocrystals during annealing of amorphous alloy Fe73,5 Cu1 Nb3 Si13,5B9. The calculation results were compared with the results of the experiment on the alloy primary crystallization. It is shown that the concentration of Fe at the surface of the growing crystal does not significantly deviate from the equilibrium values. On the other hand, silicon atoms are captured by the crystallization front, silicon concentration at the surface of the growing nanocrystal deviates significantly from equilibrium values. The calculation has shown that after the initial crystallization of the amorphous phase, occurring at a temperature of 400 – 450 °C, the deviation of silicon concentration from equilibrium value is about 2 %, while this equilibrium value is about 13.3 %.

Ligninases remove phenolic inhibitors and facilitate yeast growth in lignocellulosic hydrolysate

Holzforschung ◽  
2019 ◽  
Vol 73 (7) ◽  
pp. 681-687 ◽  
Author(s):  
Honglei Chen ◽  
Xin Zhao ◽  
Yu Liu ◽  
Fangong Kong ◽  
Xingxiang Ji
Keyword(s):  
Growth Rate ◽  
Enzyme System ◽  
Removal Rate ◽  
New Product ◽  
Product Formation ◽  
Enzyme Treatment ◽  
Yeast Growth ◽  
Fermentation Inhibitors ◽  
Alcohol Production ◽  
Kinetics Of

Abstract Sugar-containing hydrolysates as byproducts of dissolving pulp production could be a source of alcohol production, but the presence of fermentation inhibitors hampers this utilization route. In the present study, nine types of phenolic inhibitors were found and their removal by ligninases gave satisfactory results. Laccase removed 73.1% of phenolic inhibitors and produced three new aromatic compounds, whereas the combination of laccase and lignin peroxidase (as a dual-enzyme treatment) resulted in a removal rate of 91.7% without new product formation. Xylose as the main sugar in the hydrolysate was retained with a 90% yield, regardless of the enzymatic treatment, which modified, however, the kinetics of yeast growth. Laccase improved cells’ maximum specific growth rate (vmax) from 0.115 to 0.154 and reduced the saturation constant (Ks) from 53.4 to 42.5, whereas the dual-enzyme system improved vmax to 0.206 and reduced Ks to 42.44. The greater vmax and the smaller Ks imply a better growth rate, and accordingly, the dual-enzyme system is better suited for removing phenolic inhibitors.

High rate growth of device grade silicon thin films for solar cells

2001 ◽  
Vol 664 ◽  
Author(s):  
M. Kondo ◽  
S. Suzuki ◽  
Y. Nasuno ◽  
A. Matsuda
Keyword(s):  
Growth Rate ◽  
Solar Cells ◽  
Defect Density ◽  
Chemical Vapor ◽  
High Growth ◽  
Ion Bombardment ◽  
High Rate ◽  
Limiting Factors ◽  
Material Quality ◽  
Deuterium Dilution

ABSTRACTWe have developed a plasma enhanced chemical vapor deposition (PECVD) technique for high-rate growth of µc-Si:H at low temperatures using hydrogen diluted monosilane source gas under high-pressure depletion conditions. It was found that material qualities deteriorate, e.g. crystallinity decreases and defect density increases with increasing growth rate mainly due to ion damage from the plasma. We have found that deuterium dilution improves not only the crystallinity but also defect density as compared to hydrogen dilution and that deuterium to hydrogen ratio incorporated in the film has a good correlation with crystallinity. The advantages of the deuterium dilution are ascribed to lower ion bombardment due to slower ambipolar diffusion of deuterium ion from the plasma. Further improvement of material quality has been achieved using a triode technique where a mesh electrode inserted between cathode and anode electrodes prevents from ion bombardment. In combination with a shower head cathode, the triode technique remarkably improves the crystallinity as well as defect density at a high growth rate. As a consequence, we have succeeded to obtain much better crystallinity and uniformity at 5.8 nm/s with a defect density of 2.6×1016cm−3. We also discuss the limiting factors of growth rate and material quality for µc-Si solar cells.

Effect of Phosphate and Silica on the Rate of Crystallization of Sucrose

2005 ◽  
Vol 1 (5) ◽  
Author(s):  
Ms. Aamarpali Ratna Puri ◽  
S. Kaur
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Mother Liquor ◽  
Crystal Surface ◽  
Mass Transfer Process ◽  
Sugar Solution ◽  
Local Conditions ◽  
Concentration Difference ◽  
Different Temperatures ◽  
Sucrose Crystals

Sucrose Crystallization is a mass transfer process. Sucrose molecule's migration from solution to crystal is driven by concentration difference between the mother liquor and the crystal surface; the coefficient of super saturation is the most important parameter for the process. Supersaturation of sugar solution depends on the purity and brix of the mother liquor. It has large influence on product's quantity and quality (crystal yield, crystal size and size distribution) and on the cost of production i.e output/hour and energy consumption. However there is still no generally applicable theory, which permits an accurate prediction of the effects of all the factors that govern the industrial processes of crystallization from solution. The crystal growth depends on the viscosity, which further depends on the nature and amount of impurities. If the local conditions are favourable, localized layers of molecules of impurity can statistically remain on the surface for a period of time. On the other hand, if the interaction between the impurity and the layer is weak, then there will be competition between impurity and sucrose molecules thus affecting the sucrose crystal growth rate. In the present study, the growth rate of sugar crystals was studied, using two-litre automatic laboratory vacuum pan, under controlled conditions in the presence of impurities. The effect of phosphate and silica (adding one at time) on the growth rate of sugar crystals was studied at two different temperatures 328 and 338K and with two different seed sizes of sucrose (850 and 600µm). The growth rate was studied at two degrees of supersaturation (1.10 and 1.15). The growth rate of sucrose crystals (with or without added impurities) showed significant increase with the 10°C rise in temperature. The growth rate of sucrose crystals increased with the increase in the level of phosphate but decreased with the increase in the level of silica in sugar solution.

Control of Materials and Interfaces in μc-Si:H-based Solar Cells Grown at High Rate

2011 ◽  
Vol 1321 ◽  
Author(s):  
Yasushi Sobajima ◽  
Chitose Sada ◽  
Akihisa Matsuda ◽  
Hiroaki Okamoto
Keyword(s):  
Growth Rate ◽  
Solar Cells ◽  
Film Growth ◽  
Defect Density ◽  
Density Measurement ◽  
High Growth ◽  
High Growth Rate ◽  
High Rate ◽  
Bulk Region ◽  
Dangling Bond

ABSTRACTGrowth process of microcrystalline silicon (μc-Si:H) using plasma-enhanced chemicalvapor- deposition method under high-rate-growth condition has been studied for the control of optoelectronic properties in the resulting materials. We have found two important things for the spatial-defect distribution in the resulting μc-Si:H through a precise dangling-bond-density measurement, e. g., (1) dangling-bond defects are uniformly distributed in the bulk region of μc- Si:H films independent of their crystallite size and (2) large number of dangling bonds are located at the surface of μc-Si:H especially when the film is deposited at high growth rate. Starting procedure of film growth has been investigated as an important process to control the dangling-bond-defect density in the bulk region of resulting μc-Si:H through the change in the electron temperature by the presence of particulates produced at the starting period of the plasma. Deposition of Si-compress thin layer on μc-Si:H grown at high rate followed by thermal annealing has been proposed as an effective method to reduce the defect density at the surface of resulting μc-Si:H. Utilizing the starting-procedure-controlling method and the compress-layerdeposition method together with several interface-controlling methods, we have demonstrated the fabrication of high conversion-efficiency (9.27%) substrate-type (n-i-p) μc-Si:H solar cells whose intrinsic μc-Si:H layer is deposited at high growth rate of 2.3 nm/sec.

India's Agricultural Exports

2000 ◽  
Vol 35 (1) ◽  
pp. 32-46 ◽  
Author(s):  
S.K. Goyal ◽  
R.N. Pandey ◽  
J.P. Singh
Keyword(s):  
Growth Rate ◽  
High Rate ◽  
Agricultural Exports ◽  
Rate Of Growth ◽  
Oil Cakes ◽  
The World ◽  
High Volatility ◽  
Marine Products ◽  
Coffee Oil ◽  
Manufactured Exports

The composition of Indian exports indicated the rising share of manufactured exports and the decline of agricultural exports. Of the various agricultural & allied items, tea & mate, cashew kernels, spices and coffee were the dominant exportable items during 1970s but their share later on had declined. Further it was found that during the nineties, marine products, oil cakes, rice, fruits, etc. have potential for export earnings. The total agricultural exports increased at the annual compound growth rate of about 25 per cent during 1991-98. The compound growth rate of all the agricultural and allied items except tea & mate and sugar & honey were higher during nineties (1991-98) than in seventies and eighties. During this period (1991-98), coffee, oil cakes, tobacco, raw cotton, rice, spices and fish & products exhibited high volatility in exports. The share of our agricultural exports in world exports although is very low but is increasing over the years. For competing with other countries and, therefore, to raise its share in the world exports, sustained high rate of growth of Indian exports is of paramount importance. The prospects for increasing agricultural exports have improved after the liberalisation.

Development of a High Rate 4H-SiC Epitaxial Growth Technique Achieving Large-Area Uniformity

2008 ◽  
Vol 600-603 ◽  
pp. 111-114 ◽  
Author(s):  
Masahiko Ito ◽  
L. Storasta ◽  
Hidekazu Tsuchida
Keyword(s):  
Growth Rate ◽  
Epitaxial Growth ◽  
Free Exciton ◽  
High Growth ◽  
Maximum Growth ◽  
High Growth Rate ◽  
Maximum Growth Rate ◽  
High Rate ◽  
Intrinsic Defect ◽  
Large Area

A vertical hot-wall type epi-reactor that makes it possible to simultaneously achieve both a high rate of epitaxial growth and large-area uniformity at the same time has been developed. A maximum growth rate of 250 µm/h is achieved at 1650 °C. Thickness uniformity of 1.1 % and doping uniformity of 6.7 % for a 65 mm radius area are achieved while maintaining a high growth rate of 79 µm/h. We also succeeded in growing a 280 µm-thick epilayer with excellent surface morphology and long carrier lifetime of ~1 µs on average. The LTPL spectrum shows free exciton peaks as dominant, and few impurity-related or intrinsic defect related peaks are observed. The DLTS measurement for an epilayer grown at 80 µm/h shows low trap concentrations of 1.2×1012 cm-3 for Z1/2 center and 6.3×1011 cm-3 for EH6/7 center, respectively.

scholarly journals Analysis of Crime Data in the Limpopo Province

2017 ◽  
Vol 9 (3(J)) ◽  
pp. 19-27
Author(s):  
Kwabena A Kyei
Keyword(s):  
South Africa ◽  
Growth Rate ◽  
Secondary Data ◽  
Youth Unemployment ◽  
Positive Influence ◽  
Limpopo Province ◽  
High Rate ◽  
Multivariate Statistical ◽  
Crime Types ◽  
Continuous Use

South Africa has a very high rate of murders, assaults, rapes and other crimes compared to most countries. Most South Africans who immigrate to other countries cite crime as the major reason. Crime has become a concern for all, the police, private security industry, real estate developer, car manufacturers, businessmen, etc. There is a high demand for crime prevention; and this calls for a continuous use of new, advanced and reliable methods to prevent crime. How bad is the level of crime in Limpopo and what are the major crime types? This study uses secondary data from the 2011 Census conducted by Statistics South Africa; and tries to look at the composition of crime in the province and the variables that influence crime, in order to propose measures to tackle and minimize crime in the province. Multivariate statistical analysis has been employed, and the study shows that the following variables; the population size, number of households, youth unemployment, growth rate, and dependency ratio; have a positive influence in the occurrence of crime. The study recommends the slowing down of population growth rate, decrease in household size and the reduction of youth unemployment to curb crime in the province.

Sign in / Sign up

Export Citation Format

Share Document