scholarly journals Effect of Different Selenium Precursors on Structural Characteristics and Chemical Composition of Cu2ZnSnSe4 Nanocrystals

2021 ◽  
Author(s):  
Stanislav Igorovich Kakherskiy ◽  
Roman Pshenychnyi ◽  
Oleksandr Dobrozhan ◽  
Jaroslav Vaziev ◽  
Anatoliy Opanasyuk ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Structural Characteristics ◽  
Synthesis Temperature ◽  
Amorphous Selenium ◽  
Molar Ratio ◽  
Optimal Conditions ◽  
Synthesis Time ◽  
X Ray ◽  
Electron Microscopies ◽  
Precursor Composition

Abstract In the presented work Cu2ZnSnSe4 nanocrystals have been synthesized by the polyol method. The chemical composition, morphological, structural, and microstructural properties of Cu2ZnSnSe4 nanocrystals depending on synthesis temperature and time as well as precursor composition have been thoroughly investigated using scanning and transmission electron microscopies, energy dispersive X-ray analysis, X-Ray diffraction, FTIR spectroscopy. We compared the properties of nanocrystals synthesized from different precursors containing selenourea or amorphous selenium as a source of selenium and then determined the optimal conditions for nanocrystals synthesis. It was found that the optimal synthesis time for nanocrystals obtained using the first approach was t = (30-45) min, and for the second approach t = 120 min. It was also found that the optimal composition for the synthesis of single-phase Cu2ZnSnSe4 nanocrystals by the second approach is the molar ratio of precursors 2:1.5:1:4 and synthesis temperature T = 280 оС. Cu2ZnSnSe4 nanocrystals synthesized under optimal conditions were used to develop nanoinks for printing solar cell absorbers by 2D and 3D printers.

Composition-dependent magnitude of atomic shuffles in Ti–Nb martensites

2014 ◽  
Vol 47 (4) ◽  
pp. 1374-1379 ◽  
Author(s):  
Matthias Bönisch ◽  
Mariana Calin ◽  
Lars Giebeler ◽  
Arne Helth ◽  
Annett Gebert ◽  
...  
Keyword(s):  
Experimental Data ◽  
Chemical Composition ◽  
Diffraction Data ◽  
Structural Changes ◽  
Structural Characteristics ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Orthorhombic Unit Cell ◽  
Homogenization Treatment ◽  
X Ray

In this work the structural characteristics of martensitic phases in the Ti–Nb system are studied in detail. While the distortion of the orthorhombic unit cell of α′′-martensite by the addition of β-stabilizing atoms is well documented in the literature, comprehensive experimental data on the detailed atomic positions and how they vary with chemical composition are missing. For this study, a series of binary Ti–Nb alloys were prepared by casting techniques, followed by homogenization treatment and water quenching. Rietveld-based analyses of X-ray diffraction data were used to study the gradual structural changes of α′- and α′′-martensites effected by the addition of Nb, and their compositional boundaries were determined. In the case of orthorhombic α′′, it was established that, besides the lattice parameters, the positions of the atoms on the (002)α′′planes respond very sensitively to the amount of Nb present.

Synthesis and sintering of SiC under high pressure and high temperature

1999 ◽  
Vol 14 (3) ◽  
pp. 906-911 ◽  
Author(s):  
S. K. Bhaumik ◽  
C. Divakar ◽  
S. Usha Devi ◽  
A. K. Singh
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
High Pressure ◽  
Silicon Powder ◽  
Synthesis Temperature ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microscopic Studies ◽  
Simultaneous Synthesis

Starting from elemental powders, simultaneous synthesis and compaction of SiC were conducted at 3 GPa pressure and temperatures in the range 2100–2900 K. The sintered compacts were characterized by x-ray diffraction, microhardness measurements, and microscopic studies. The efficiency of formation of SiC was dependent on the particle size of the silicon powder, crystallinity of the reactant carbon, molar ratio of silicon and carbon, and synthesis temperature and time. Carbon in excess of the stoichiometric amount was required to obtain compacts free from residual silicon. The SiC samples, with a Si: C molar ratio 1: 1.05, prepared at 2100 K for 300 s had a density and hardness of 3.21 g/cm3 (98.8% of theoretical density) and 22 GPa, respectively. The crystal structure of the SiC depended on the synthesis temperature. Pure β–SiC in the temperature range 2100–2500 K, and a mixture of α– and β–SiC above 2500 K were obtained. The β–SiC was highly crystalline and nearly defect-free.

scholarly journals Hydrogen-Assisted Thermocatalysis over Titanium Nanotube for Oxidative Desulfurization

Catalysts ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 29
Author(s):  
Weiwei Tang ◽  
Yue Yao ◽  
Xiaoqiao Huang
Keyword(s):  
Diffuse Reflectance ◽  
Oxidative Desulfurization ◽  
Molar Ratio ◽  
Optimal Conditions ◽  
X Ray Diffraction ◽  
Step Method ◽  
X Ray ◽  
Diffuse Reflectance Spectra ◽  
Ft Ir ◽  
Catalyst Dosage

Titanium nanotubes were hydrothermally synthesized via a two-step method for ODS (oxidative desulfurization). The catalysts’ structures were characterized by XRD (X-ray diffraction), FT-IR, UV-Vis (UV-Vis diffuse reflectance spectra), NH3-TPD, etc. The effects of O/S molar ratio and catalyst dosage, etc., were systematically investigated. The catalyst exhibited remarkable performance, so that the removal of DBT (dibenzothiophene) was nearly 100% under the optimal conditions in 10 min. Also, the catalysts could be easily reused for six consecutive cycles. The hydrogen-assisted thermocatalytic mechanism over titanium nanotubes for ODS was also studied and an effective reactant concentration (ERC) number of 70.8 was calculated.

Photocatalytic Degradation of Indigo Carmine by ZnO-Cu2O/Graphene Oxide Composites Synthesized via Hydrothermal Method

2013 ◽  
Vol 668 ◽  
pp. 105-109 ◽  
Author(s):  
Huai Di Wu ◽  
Lu Sheng Chen ◽  
Jin Chao Hu
Keyword(s):  
Photocatalytic Activity ◽  
Graphene Oxide ◽  
Hydrothermal Method ◽  
Photoelectron Spectroscopy ◽  
Indigo Carmine ◽  
Synthesis Temperature ◽  
X Ray Diffraction ◽  
Synthesis Time ◽  
X Ray ◽  
Oxide Composites

In this work, ZnO–Cu2O/graphene oxide (GO) composites have been synthesized by using simple hydrothermal method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the crystal structure and composite elements. The photocatalytic activity of the composites has been conducted by measuring the degradation of indigo carmine under UV irradiation. When the atom ratio of Zn/Cu is 5/2, 120 °C of hydrothermal synthesis temperature and 20 h of synthesis time, the ZnO/Cu2O/GO composite exhibits good photocatalytic activity with 96.5% degradation rate of indigo carmine aqueous solution under 500 W high pressure Hg lamp irradiation for 240 min.

Synthesis of ZnO at Different Atomic Proportion Produced by Chemical Precipitation

2012 ◽  
Vol 1481 ◽  
pp. 127-133
Author(s):  
A. Medina ◽  
L. Béjar ◽  
G. Herrera-Pérez
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chemical Composition ◽  
Chemical Precipitation ◽  
Growth Direction ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wurtzite Crystal Structure ◽  
Transmission Electron

ABSTRACTZinc oxide (ZnO) nanoparticles were produced using chemical precipitation synthesis with a molar ratio of 1:1, 1:2 and 1:3. The structure, chemical composition and morphology were investigated by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). XRD and EDS demonstrated that the all particles formed at different atomic proportion were of wurtzite crystal structure with the same chemical composition. SEM and TEM showed the formation of hexagonal particles with a molar ratio of 1:1 while the samples synthesized with a molar ratio 1:2 and 1:3 showed a circular shape. HRTEM and Fast Fourier Transform (FFT) demonstrated that the all particles were formed with a preferable [0001] growth direction.

scholarly journals Study of synthesis parameters of MIL-53(Al) using experimental design methodology for CO2/CH4 separation

2017 ◽  
Vol 36 (1-2) ◽  
pp. 247-269 ◽  
Author(s):  
Armin Taheri ◽  
Ensieh Ganji Babakhani ◽  
Jafar Towfighi
Keyword(s):  
Experimental Design ◽  
Specific Surface ◽  
Surface Area ◽  
Calcination Temperature ◽  
Specific Surface Area ◽  
Synthesis Temperature ◽  
Molar Ratio ◽  
Calcination Time ◽  
Relative Crystallinity ◽  
Synthesis Time

In this study hydrothermal method was used to synthesize MIL-53(Al) (MIL stands for Materials Institute of Lavoisier). Plackett–Burman (P–B) as an experimental design method was applied to investigate the effect of synthesis and activation conditions on specific surface area, relative crystallinity, and production yield of MIL-53(Al) synthesis. Some parameters such as ligand-to-metal molar ratio, synthesis time, synthesis temperature, calcination temperature, and calcination time were selected as the variables. The Brunauer–Emmett–Teller (BET) technique was used in order to estimate the specific surface area of samples while the relative crystallinity of the samples was estimated by comparing their X-Ray Diffraction (XRD) pattern. The morphology of the samples was investigated by field emission scanning electron microscopy. The yield of final products was determined based on organic ligands. The results revealed the significant effect of synthesis temperature on BET surface area, particle size, yield, and crystallinity. The calcination temperature has significant positive effect on BET and crystallinity. Also, the negative significant effect of molar ratio on yield was concluded from the results. However, negligible effect of synthesis and calcination time on the properties of prepared materials were observed. Furthermore, separation capability of a selected sample for carbon dioxide (CO2) and methane (CH4) was measured. Pure gas adsorption data were successfully fitted to Langmuir, Sips, and Toth models. The selected sample provided high adsorption capacity for both gases. The binary adsorption of gases was also investigated based on extended Langmuir equations and the ideal adsorbed solution theory (IAST) models. Comparing the experimental and models data indicated good agreement between the IAST model and experiments. Finally, high CO2/CH4 selectivity of 7.6 was obtained experimentally for the CO2/CH4 molar ratio of 0.2/0.8.

scholarly journals Chemical Composition and Microstructural Morphology of Spines and Tests of Three Common Sea Urchins Species of the Sublittoral Zone of the Mediterranean Sea

Animals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1351
Author(s):  
Anastasios Varkoulis ◽  
Konstantinos Voulgaris ◽  
Stefanos Zaoutsos ◽  
Antonios Stratakis ◽  
Dimitrios Vafidis
Keyword(s):  
Chemical Composition ◽  
Mediterranean Sea ◽  
Sea Urchins ◽  
Abiotic Factors ◽  
Molar Ratio ◽  
X Ray ◽  
Temporal Differences ◽  
Sublittoral Zone ◽  
Microstructural Morphology ◽  
The Mediterranean

In the Mediterranean Sea, the species Arbacia lixula, Paracentrotus lividus and Sphaerechinus granularis often coexist, occupying different subareas of the same habitat. The mechanical and chemical properties of their calcitic skeletons are affected both by their microstructural morphology and chemical composition. The present study describes the main morphologic features and the possible temporal differences in elemental composition of the test and spines of the three species, while also determining the molar ratio of each element of their crystalline phase. Scanning electron microscopy showed major differences in the ultrastructure of the spines, while minor differences in the test were also noticed. More specifically, the spines of all three sea urchins possess wedges, however A. lixula exhibits bridges connecting each wedge, while barbs are observed in the wedges of S. granularis. The spines of P. lividus are devoid of both microstructures. Secondary tubercles are absent in the test of A. lixula, while the tests and spines of all three species are characterized by different superficial stereom. Energy dispersive x-ray spectroscopy detected that Ca, Mg, S, Na and Cl were present in all specimen. Mg and Mg/Ca showed significant differences between species both in test and spines with S. granularis having the highest concentration. The spines of P. lividus exhibited lowest values between all species. Differences between spines and test were observed in all elements for P. lividus except S. A. lixula exhibited different concentrations between test and spines for Ca, Mg and Mg/Ca, whereas S. granularis for Mg, Cl and Mg/Ca. Finally, temporal differences for Ca were observed in the test of P. lividus and the spines of S. granularis, for Mg in test of S. granularis, for S in the spines of A. lixula and the test and spine of S. granularis, for Na in the test of P. lividus and A. lixula and for Cl and Mg/Ca in the test P. lividus. Powder X-ray diffractometry determined that, out of all three species, the spines of P. lividus contained the least Mg, while the test of the same species exhibited higher Mg concentration compared to A. lixula and S. granularis. The current study, although not labeling the specimens attempts to estimate potential time-related elemental differences among other results. These may occur due to changes in abiotic factors, probably water temperature, salinity and/or pH. Divergence in food preference and food availability may also play a key role in possible temporal differences the skeletons of these species

Neptunium Incorporation into Uranium(Vi) Compounds formed During Aqueous Corrosion of Neptunium-Bearing Uranium Oxides

2002 ◽  
Vol 713 ◽  
Author(s):  
Robert J. Finch ◽  
Jeffery A. Fortner ◽  
Edgar C. Buck ◽  
Stephen F. Wol
Keyword(s):  
Experimental Studies ◽  
Maximum Amount ◽  
Molar Ratio ◽  
Uranium Oxides ◽  
Aqueous Corrosion ◽  
Experimental Conditions ◽  
X Ray ◽  
Electron Microscopies ◽  
Transmission Electron ◽  
Electron Energy Loss

ABSTRACTWe report results of experimental studies on the behavior of Np during aqueous corrosion of unirradiated Np-bearing U oxides. Np-doped U oxides were reacted in humid air at 90°C and 150°C for several weeks within sealed stainless-steel vessels. Reacted solids were examined by scanning and transmission electron microscopies (SEM and TEM), electron energy-loss spectroscopy (EELS), and X-ray powder diffraction (XRD). Dehydrated schoepite, (UO2)O0.25-z(OH)1.5+2z (0 ≤z ≤0.15), is the predominant U(VI) compound formed in these experiments. Preliminary EELS analysis on crushed grains verify that dehydrated schoepite formed at 150°C contains up to approximately 2 wt.% Np, corresponding to a maximum Np:U molar ratio of approximately 1:40. These are maximum values because the degree to which surface-sorbed Np is present on the grains analyzed is not yet known. Crystalline NpO2 also precipitated during these experiments, and the concentration of Np in dehydrated schoepite may represent the maximum amount of Np that can be incorporated into dehydrated schoepite under the experimental conditions.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

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