scholarly journals A side-by-side comparison of the solidification dynamics of quasicrystalline and approximant phases in the Al–Co–Ni system

2019 ◽  
Vol 75 (2) ◽  
pp. 281-296 ◽  
Author(s):  
Insung Han ◽  
Xianghui Xiao ◽  
Haiping Sun ◽  
Ashwin J. Shahani
Keyword(s):  
Driving Forces ◽  
Nucleation And Growth ◽  
Experimental Investigations ◽  
X Rays ◽  
Decagonal Quasicrystal ◽  
First Order ◽  
First Order Kinetics ◽  
Complex Crystal ◽  
Widespread Interest

Quasicrystals and their approximants have triggered widespread interest due to the challenge of solving their complex crystal structures as well as their possibly exceptional properties. The structural motifs of approximants are similar to those of the corresponding quasicrystals, but to what extent are their crystallization pathways the same? Unfortunately, there have been very few in situ experimental investigations to answer this question. Here, by leveraging the high penetrating power of hard X-rays, synchrotron-based X-ray tomography was conducted in order to capture the nucleation and growth of a decagonal quasicrystal and its related approximant. The combination of data-driven computational analysis with new thermodynamic databases allowed the characterization, with high precision, of the constitutional and kinetic driving forces for crystallization. The experimental results prove that the growth of both crystals from a liquid is dominated by first-order kinetics. Nevertheless, and somewhat surprisingly, significant differences were observed in their rates of nucleation and growth. The reasons for such divergent behaviours are discussed in light of contemporary theories of intermetallic crystallization.

Modified ferron assay for speciation characterization of hydrolyzed Al(III): a precise k value based judgment

2009 ◽  
Vol 59 (4) ◽  
pp. 823-832 ◽  
Author(s):  
Ye Changqing ◽  
Wang Dongsheng ◽  
Wu Xiaohong ◽  
Qu Jiuhui ◽  
John Gregory
Keyword(s):  
Kinetic Constant ◽  
Nonlinear Least Squares ◽  
Precise Determination ◽  
K Value ◽  
First Order ◽  
First Order Kinetics ◽  
Parallel Reactions

The speciation of Al-OH complexes in terms of Ala, Alb and Alc could be achieved by traditional ferron assay and Alb is generally considered as Al13, however, the inherent correlation between them remains an enigma. This paper presents a modified ferron assay to get precise determination of Al13 using nonlinear least squares analysis, and to clarify the correlation between Alb and Al13. Two parallel reactions conforming to pseudo-first-order kinetics can simulate the complicate reactions between polynuclear complexes and ferron successfully. Four types of experimental kinetic constant (k value) of Al-OH complexes can be observed by this method when investigating three typical aluminium solutions. Comparing with the results of 27Al NMR, the species with moderate kinetics around 0.001 s−1 can be confirmed to resemble to Al13 polycation. The other types of kinetics are also well-regulated in partially neutralized aluminium solutions with various OH/Al ratios (b values) in the range 0 ∼ 2.5. It would provide potential means to trace the in-situ formation of Al13 in dilute solutions such as coagulation with Al-based coagulants

scholarly journals An Electrochemical Process Comparison of As(III) in Simulated Groundwater at Low Voltage in Mixed and Divided Electrolytic Cells

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1126 ◽  
Author(s):  
Yanyan Qin ◽  
Yanping Cui ◽  
Lidan Lei ◽  
Ya Gao ◽  
Zhengwei Zhou ◽  
...  
Keyword(s):  
Low Voltage ◽  
Electrochemical Process ◽  
First Order ◽  
Electrolytic Cells ◽  
Process Comparison ◽  
First Order Kinetics ◽  
Simulated Groundwater ◽  
High Arsenic ◽  
High Arsenic Groundwater

A relatively low voltage can be favor of e- transfer and peroxide generation from dominant 2e--reduction of O2 on carbon materials as cathode, with low energy loss. In this study the conversion of As(III) in simulated high arsenic groundwater at low voltage was compared in a mixed and a anode–cathode separated electrolytic system. With applied voltages (the potential difference between cathode and anode) from 0.1 V to 0.8 V, As(III) was found to be efficiently converted to As(V) in the mixed electrolytic cells and in separated anodic cells. The complete oxidation of As(III) to As(V) at 0.1–0.8 V was also achieved on graphite in divided cathodic cells which could be long-running. The As(III) conversion process in mixed electrolytic cells, anodic cells and cathodic cells all conformed to the pseudo first-order kinetics equation. The energy consumed by As(III) conversion was decreased as the applied voltage declined. Low voltage electrolysis is of great significance for saving energy consumption and improving the current efficiency and can be applied to in-situ electrochemical pre-oxidation for As(III) in high arsenic groundwater.

Recrystallization of AA1050 Studied by 3DXRD

2006 ◽  
Vol 519-521 ◽  
pp. 1569-1578
Author(s):  
Dorte Juul Jensen
Keyword(s):  
Single Crystals ◽  
High Energy ◽  
Nucleation And Growth ◽  
X Rays ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
X Ray ◽  
3 Dimensional ◽  
Kinetics Of

By 3 dimensional X-ray diffraction (3DXRD) using high energy X-rays from synchrotron sources it is possible to study in-situ the nucleation and growth during recrystallization. In this paper it is described and discussed how 3DXRD can supplement EBSP measurements of nucleation and growth. Three types of studies are considered: i) orientation relationships between nuclei and parent deformed matrix, ii) recrystallization kinetics of individual bulk grains and iii) filming of growing grains in deformed single crystals.

Relationship Between Radiation Stability and Molecular Structure of Nitramine Explosives

1992 ◽  
Vol 296 ◽  
Author(s):  
James J. Pinto
Keyword(s):  
Molecular Structure ◽  
Binding Energy ◽  
Mass Spectra ◽  
Bond Distance ◽  
Radiation Stability ◽  
Photoelectron Spectra ◽  
X Rays ◽  
First Order ◽  
First Order Kinetics ◽  
Cyclotrimethylene Trinitramine

AbstractThe radiation stabilities of the nitramine explosives 1,4-dinitroglycolurile (DINGU), 1,4-dimethyl-2,5-dinitroglycolurile (DMD) and hexanitrohexaazaisowurtzitane (HNIW) have been determined using XPS. Samples were exposed to x-rays for times up to eight hours while photoelectron spectra were recorded in the carbon, oxygen, and nitrogen Is energy regions and mass spectra were recorded of gases evolved during the decomposition process. These data are compared to the previously determined stabilities for cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HlMX). The N1s spectra of the irradiated materials show the NO2 peak decreases relative to the total nitrogen signal while low binding energy peaks grow. The rate of loss of the NO2 peak was fit to first order kinetics and the rate constants obtained show some correlation with the N-N bond strength as measured by the average N-N bond distance and the average NO2 asymetric stretch frequency. Despite the differences in structure of these molecules (DINGU and DMD are bicyclic rings, RDX and HMX are rings and HNIW is a cage) the radiation stability appears to be controlled by the strength of the N-N bond.

scholarly journals Effect of Frying Treatments on Texture and Colour Parameters of Deep Fat Fried Yellow Fleshed Cassava Chips

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
A. B. Oyedeji ◽  
O. P. Sobukola ◽  
Folake Henshaw ◽  
M. O. Adegunwa ◽  
O. A. Ijabadeniyi ◽  
...  
Keyword(s):  
Driving Forces ◽  
Colour Change ◽  
Quality Attributes ◽  
Deep Fat Frying ◽  
Sharp Reduction ◽  
First Order ◽  
First Order Kinetics ◽  
Cassava Root ◽  
Vacuum Frying ◽  
Colour Parameters

Effects of frying treatments on texture (hardness) and colour parameters (L,a,b,ΔE) during deep fat frying of yellow fleshed cassava root slices (TMS 01/1371) were investigated. Slices (dimension of 40 mm × 25 mm × 3 mm) were divided into three portions and subjected to vacuum frying (fresh slices) and atmospheric frying (fresh and predried slices) and equivalent thermal driving forces (ETDF) of 60°C, 70°C, and 80°C were maintained during frying. The quality attributes investigated were best preserved in vacuum fried chips. The overall colour change in chips fried under vacuum conditions at 118°C and 8 min was the least (21.20) compared to fresh and atmospherically predried ones (16.69 and 14.81, resp.). A sharp reduction in the breaking force was obtained for all frying treatments after 8 min and this effect was the least in vacuum fried chips. First-order kinetics modeled the changes in quality attributes for all the temperatures investigated. Rate constants k (min−1) obtained for vacuum frying were almost equal to that of atmospheric frying while activation energies for hardness and colour change were 53.30 and 467.11 KJ/mol, respectively. Quality attributes studied were best preserved during vacuum frying.

Ag7 AND Ag8 QUANTUM CLUSTERS SUPPORTED ON ALUMINA: NEW CATALYSTS FOR ORGANIC REACTIONS

2011 ◽  
Vol 10 (04n05) ◽  
pp. 839-843 ◽  
Author(s):  
ANNAMALAI LEELAVATHI ◽  
THUMU UDAYA BHASKARA RAO ◽  
THALAPPIL PRADEEP
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Solid Phase ◽  
Kinetic Studies ◽  
X Rays ◽  
First Order ◽  
First Order Kinetics ◽  
Mercaptosuccinic Acid ◽  
Transmission Electron ◽  
Quantum Clusters

Silver quantum clusters (QCs) stabilized by mercaptosuccinic acid (MSA) have been synthesized at room temperature from Ag nanoparticles through an interfacial etching process. The as-synthesized red emitting QCs were coated on alumina and the supported clusters have been characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX) and fluorescence spectroscopy. Catalytic activity of Ag QCs supported on alumina have been exploited for the reduction of 4-nitrophenol in presence of sodium borohydride. The reaction followed pseudo-first order kinetics. The catalyst separated from the product remains active and can be recycled several times. Other nitroaromatic compounds have also been tested. Synthesis of the solid phase catalyst, applications and detailed kinetic studies of the reduction of 4-nitrophenol are reported.

scholarly journals In situ chemichromic studies of interactions between a lutetium bis-octaalkyl-substituted phthalocyanine and selected biological cofactors

2011 ◽  
Vol 9 (66) ◽  
pp. 183-189 ◽  
Author(s):  
C. Pal ◽  
A. N. Cammidge ◽  
M. J. Cook ◽  
J. L. Sosa-Sanchez ◽  
A. K. Sharma ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Nicotinamide Adenine Dinucleotide ◽  
Reduction Rate ◽  
Lithium Perchlorate ◽  
Linear Increase ◽  
First Order ◽  
Glass Substrates ◽  
First Order Kinetics ◽  
Neutralization Process

Spin-coated films, approximately 100 nm thick, of a newly synthesized bis[octakis(octyl)phthalocyaninato] lutetium(III) complex on ultrasonically cleaned glass substrates exhibit pronounced chemichromic behaviour with potential application in healthcare. In situ kinetic optical absorption spectroscopic measurements show that the phthalocyanine Q-band is red shifted by 60 nm upon oxidation arising from exposure to bromine vapour. Recovery to the original state is achieved by the treatment of the oxidized films with nicotinamide adenine dinucleotide and l -ascorbic acid (vitamin C) in an aqueous solution containing 1.5 M lithium perchlorate. The neutralization process is found to be governed by first-order kinetics. The linear increase of the reduction rate with increasing concentration of cofactors provides a basis for calibration of analyte concentrations ranging from 3.5 mM down to 0.03 mM.

Kinetics of Desulfuration Product Sulphoaluminate Calcium

2010 ◽  
Vol 113-116 ◽  
pp. 1814-1817 ◽  
Author(s):  
Hui Ling Guo ◽  
Jun Lin Xie
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Formation Rate ◽  
Experimental Investigations ◽  
Exponential Factor ◽  
First Order ◽  
First Order Kinetics ◽  
Formation Kinetics ◽  
Competitive Reactions ◽  
Kinetics Of

The formation kinetics of sulphoaluminate calcium was studied by variations of sulfur release with time from SC-132 based on competitive reactions, the generation of sulphoaluminate calcium and the decomposition of CaSO4. Experimental investigations and theoretical derivations show that the formation rate of sulphoaluminate calcium can be described as first-order kinetics at high temperature, and it belongs to the mechanism of random nucleus growth. The apparent activation energy is 456.37 KJ•mol-1 and pre-exponential factor is 1.545×1012.

In-situ electrochemical ESR: First-order kinetics and transient signals

1984 ◽  
Vol 163 (1-2) ◽  
pp. 65-75 ◽  
Author(s):  
Richard G. Compton ◽  
David J. Page ◽  
George R. Sealy
Keyword(s):  
Transient Signals ◽  
First Order ◽  
First Order Kinetics

Role of boundaries in the crystallization of amorphous films

1988 ◽  
Vol 46 ◽  
pp. 626-627
Author(s):  
D. A. Smith
Keyword(s):  
Low Temperature ◽  
Amorphous State ◽  
Nucleation And Growth ◽  
Amorphous Films ◽  
Island Nucleation ◽  
Surface Steps ◽  
Transmission Electron ◽  
Component Systems ◽  
Temperature Deposition

The nucleation and growth processes which lead to the formation of a thin film are particularly amenable to investigation by transmission electron microscopy either in situ or subsequent to deposition. In situ studies have enabled the observation of island nucleation and growth, together with addition of atoms to surface steps. This paper is concerned with post-deposition crystallization of amorphous alloys. It will be argued that the processes occurring during low temperature deposition of one component systems are related but the evidence is mainly indirect. Amorphous films result when the deposition conditions such as low temperature or the presence of impurities (intentional or unintentional) preclude the atomic mobility necessary for crystallization. Representative examples of this behavior are CVD silicon grown below about 670°C, metalloids, such as antimony deposited at room temperature, binary alloys or compounds such as Cu-Ag or Cr O2, respectively. Elemental metals are not stable in the amorphous state.

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