Structural and chemical changes in binary versus ternary tetrahedral semiconductors

1985 ◽  
Vol 32 (4) ◽  
pp. 2689-2692 ◽  
Author(s):  
José Luís Martins ◽  
Alex Zunger
Keyword(s):  
Chemical Changes ◽  
Tetrahedral Semiconductors ◽  
Binary Versus

Friedel'S law breakdown and interpretation of stacking fault images in tetrahedral semiconductors

1987 ◽  
Vol 45 ◽  
pp. 318-319
Author(s):  
Rob. W. Glaisher ◽  
A.E.C. Spargo
Keyword(s):  
Relative Phase ◽  
Point Group ◽  
Binary Compound ◽  
Stacking Fault ◽  
Fold Axis ◽  
Atom Pair ◽  
Tetrahedral Semiconductors ◽  
Group Symmetries ◽  
Thin Crystal ◽  
Phase Differences

Images of <11> oriented crystals with diamond structure (i.e. C,Si,Ge) are dominated by white spot contrast which, depending on thickness and defocus, can correspond to either atom-pair columns or tunnel sites. Olsen and Spence have demonstrated a method for identifying the correspondence which involves the assumed structure of a stacking fault and the preservation of point-group symmetries by correctly aligned and stigmated images. For an intrinsic stacking fault, a two-fold axis lies on a row of atoms (not tunnels) and the contrast (black/white) of the atoms is that of the {111} fringe containing the two-fold axis. The breakdown of Friedel's law renders this technique unsuitable for the related, but non-centrosymmetric binary compound sphalerite materials (e.g. GaAs, InP, CdTe). Under dynamical scattering conditions, Bijvoet related reflections (e.g. (111)/(111)) rapidly acquire relative phase differences deviating markedly from thin-crystal (kinematic) values, which alter the apparent location of the symmetry elements needed to identify the defect.

TWO YEAR PROGRESSION OF SOIL CHEMICAL CHANGES AS A RESULT OF THE 16 MILE FIRE, DELAWARE STATE FOREST, PA

2019 ◽  
Author(s):  
Jeremy Scott ◽  
◽  
Jennifer R. Callanan ◽  
Jonathan Harris ◽  
Ryan Wizner ◽  
...  
Keyword(s):  
Chemical Changes

Biostimulant action of Lithothamnium sp. promoting growth, yield, and biochemical and chemical changes on onion

2021 ◽  
Author(s):  
Atila Francisco Mógor ◽  
Juliana Oliveira Amatussi ◽  
Gilda Mógor ◽  
Luiz Gabriel Gemin
Keyword(s):  
Growth Yield ◽  
Chemical Changes

scholarly journals Effect of Water Leaching on Photodegraded Scots Pine and Spruce Timbers Monitored by FTIR Spectroscopy

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 833
Author(s):  
Edina Preklet ◽  
László Tolvaj ◽  
Eszter Visi-Rajczi ◽  
Tamás Hofmann
Keyword(s):  
Ftir Spectroscopy ◽  
Scots Pine ◽  
Uv Irradiation ◽  
Chemical Elements ◽  
Uv Light ◽  
Carbonyl Groups ◽  
Water Leaching ◽  
Absorption Bands ◽  
Chemical Changes ◽  
Absorption Increase

The goal of this research was the systematic study and comparison of the divided individual effects of UV light irradiation and water leaching during artificial weathering. Spruce (Picea abies Karst.) and Scots pine (Pinus sylvestris L.) samples were irradiated by ultraviolet (UV) light. Another sequence of samples was treated with the combination of UV irradiation and water leaching. The total extent of UV treatment was 20 days for both series of samples. Time relation of UV irradiation and water leaching was 2:1. The chemical changes were observed by FTIR spectroscopy. The difference spectrum was used for determination of the chemical changes. Degradation of lignin was greater for the leached samples than for the pure UV treated samples. Scots pine suffered greater lignin degradation than spruce, and produced higher absorption increase on the absorption region of unconjugated carbonyls. The unconjugated carbonyl groups were the most responsive chemical elements to leaching. Spruce was more susceptible to leaching of unconjugated carbonyl groups than Scots pine. Two absorption bands of unconjugated carbonyl groups at 1706 and 1764 cm−1 wavenumbers were produced by photodegradation. The absorption band at 1764 cm−1 was more sensitive to water leaching than the band at 1706 cm−1.

scholarly journals Physico-Chemical Investigation of Endodontic Sealers Exposed to Simulated Intracanal Heat Application: Hydraulic Calcium Silicate-Based Sealers

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 728
Author(s):  
David Donnermeyer ◽  
Magdalena Ibing ◽  
Sebastian Bürklein ◽  
Iris Weber ◽  
Maximilian P. Reitze ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Treatment ◽  
Film Thickness ◽  
Physical Properties ◽  
Calcium Silicate ◽  
Setting Time ◽  
Chemical Properties ◽  
Chemical Changes ◽  
Time Flow ◽  
Heat Application

The aim of this study was to gain information about the effect of thermal treatment of calcium silicate-based sealers. BioRoot RCS (BR), Total Fill BC Sealer (TFBC), and Total Fill BC Sealer HiFlow (TFHF) were exposed to thermal treatment at 37 °C, 47 °C, 57 °C, 67 °C, 77 °C, 87 °C and 97 °C for 30 s. Heat treatment at 97 °C was performed for 60 and 180 s to simulate inappropriate application of warm obturation techniques. Thereafter, specimens were cooled to 37 °C and physical properties (setting time/flow/film thickness according to ISO 6876) were evaluated. Chemical properties (Fourier-transform infrared spectroscopy) were assessed after incubation of the specimens in an incubator at 37 °C and 100% humidity for 8 weeks. Statistical analysis of physical properties was performed using the Kruskal-Wallis-Test (P = 0.05). The setting time, flow, and film thickness of TFBC and TFHF were not relevantly influenced by thermal treatment. Setting time of BR decreased slightly when temperature of heat application increased from 37 °C to 77 °C (P < 0.05). Further heat treatment of BR above 77 °C led to an immediate setting. FT-IR spectroscopy did not reveal any chemical changes for either sealers. Thermal treatment did not lead to any substantial chemical changes at all temperature levels, while physical properties of BR were compromised by heating. TFBC and TFHF can be considered suitable for warm obturation techniques.

Modeling soil chemical changes induced by grassland afforestation in a sedimentary plain with shallow groundwater

Geoderma ◽  
2021 ◽  
Vol 400 ◽  
pp. 115158
Author(s):  
Claudio R. Mujica ◽  
Sergio A. Bea ◽  
Esteban G. Jobbágy
Keyword(s):  
Shallow Groundwater ◽  
Chemical Changes

scholarly journals SiO2 Promoted CaO Diffusion to C Phase at 1500 and 1700 °C

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 587
Author(s):  
Lijuan Ni ◽  
Renxing Wang ◽  
Qingya Liu ◽  
Junfei Wu ◽  
Yue Pan ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Close Contact ◽  
Chemical Changes ◽  
Physical And Chemical ◽  
Diffusion Behaviors

To better understand the mass transfer behaviors in CaC2 production from CaO and coke, this paper studies the diffusion behaviors of CaO and graphite, with or without ash, at 1500 and 1700 °C. CaO and graphite are pressed into tablets and heated alone or in close contact. Physical and chemical changes in these tablets are analyzed by XRD and SEM+EDX. In some experiments, thin Mo wires are placed between the closely contacted CaO and graphite tablets to identify the diffusion direction. It is found that the diffusion between CaO and low-ash graphite is very limited. SiO2 in a high-ash graphite diffuses into CaO tablet and reacts with CaO to form Ca2SiO4, which then diffuses into the graphite tablet easily and leads to CaC2 formation at 1700 °C.

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