scholarly journals Исследование механизмов изменения степени униполярности при термической обработке сильно легированных кристаллов LiNbO-=SUB=-3-=/SUB=-:ZnO

2020 ◽  
Vol 90 (8) ◽  
pp. 1296
Author(s):  
М.Н. Палатников ◽  
В.А. Сандлер ◽  
Н.В. Сидоров ◽  
О.В. Макарова
Keyword(s):  
Thermal Decomposition ◽  
Thermal Treatment ◽  
Thermal Behavior ◽  
Domain Structure ◽  
Domain Walls ◽  
Short Circuit ◽  
Charge Carriers ◽  
Order Of Magnitude ◽  
Polar Clusters ◽  
Additional Charge

Phenomenological mechanisms of an increase in unipolarity degree at thermal treatment under short circuit conditions of strongly doped crystals are researched by comparison with thermal behavior of nominally pure LiNbO3 crystals of congruent composition. It has been shown that an increase in unipolarity degree, and correspondingly vanishing of domain structure in strongly doped LiNbO3:ZnО crystals starts by thermal decomposition of charged polar clusters. These clusters stabilize domain walls. The decomposition is accompanied by sharp jump-like injection of additional charge carriers (Li+ cations). Due to this, conductivity of LiNbO3:ZnО crystals is one order of magnitude higher at temperature above 800K than in nominally pure LiNbO3 crystals of congruent composition. The injection leads to decomposition of domain structure in LiNbO3:ZnО crystals in spite of LiNbO3 crystals of congruent composition.

Synthesis, Characterization and Thermal studies of Novel Organomercury Driven from Sulfa Drugs Part 1

2011 ◽  
Vol 7 (2) ◽  
pp. 1338-1347
Author(s):  
Tarek Ali Fahad ◽  
Shaker.A.N. AL-Jadaan
Keyword(s):  
Thermal Decomposition ◽  
Thermal Behavior ◽  
1H Nmr ◽  
Elemental Analysis ◽  
Thermal Studies ◽  
Spectroscopic Techniques ◽  
Sulfa Drugs ◽  
Acid Base ◽  
Ph Values ◽  
Multi Stage

Two new heterocyclic Organmercury compounds   were prepared from the reaction of Sulfamethaxazole and Sulfadiazine with 4-acetaminophenol as a coupler and separated as solids with characteristic colors. these compounds were characterized by F.T.IR-spectroscopy 1H-NMR , Micro-elemental Analysis and UV-Vis spectroscopic techniques . The work involves a study of acid – base properties compounds at different pH values, the ionization and protonation constants were calculated. The thermal behavior of these two compounds   were investigated on the basis of thermogravimetric (TGA) and differential thermogravimetric (DTG) analyses, Thermal decomposition of these compounds is multi-stage processes.

scholarly journals Thermal behavior and decomposition kinetics of rifampicin polymorphs under isothermal and non-isothermal conditions

2010 ◽  
Vol 46 (2) ◽  
pp. 343-351 ◽  
Author(s):  
Ricardo Alves ◽  
Thaís Vitória da Silva Reis ◽  
Luis Carlos Cides da Silva ◽  
Silvia Storpírtis ◽  
Lucildes Pita Mercuri ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Thermal Behavior ◽  
Melting Process ◽  
Decomposition Process ◽  
Stable Form ◽  
Thermal Decomposition Process ◽  
Mean Values ◽  
Conversion Level ◽  
Polymorphic Forms ◽  
Crystalline Forms

The thermal behavior of two polymorphic forms of rifampicin was studied by DSC and TG/DTG. The thermoanalytical results clearly showed the differences between the two crystalline forms. Polymorph I was the most thermally stable form, the DSC curve showed no fusion for this species and the thermal decomposition process occurred around 245 ºC. The DSC curve of polymorph II showed two consecutive events, an endothermic event (Tpeak = 193.9 ºC) and one exothermic event (Tpeak = 209.4 ºC), due to a melting process followed by recrystallization, which was attributed to the conversion of form II to form I. Isothermal and non-isothermal thermogravimetric methods were used to determine the kinetic parameters of the thermal decomposition process. For non-isothermal experiments, the activation energy (Ea) was derived from the plot of Log β vs 1/T, yielding values for polymorph form I and II of 154 and 123 kJ mol-1, respectively. In the isothermal experiments, the Ea was obtained from the plot of lnt vs 1/T at a constant conversion level. The mean values found for form I and form II were 137 and 144 kJ mol-1, respectively.

Improvement of Radiation Resistance of Multijunction GaInP/Ga(In)As/Ge Solar Cells with Application of Bragg Reflectors

2010 ◽  
Vol 74 ◽  
pp. 225-230 ◽  
Author(s):  
Vladimir M. Lantratov ◽  
Viktor M. Emelyanov ◽  
Nikolay A. Kalyuzhnyy ◽  
Sergey A. Mintairov ◽  
Maxim Z. Shvarts
Keyword(s):  
Solar Cells ◽  
Radiation Resistance ◽  
Radiation Treatment ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Charge Carriers ◽  
Bragg Reflectors ◽  
Multijunction Solar Cells ◽  
Operation Period ◽  
Long Operation

Feasibility to increase the radiation resistance of multijunction solar cells in using Bragg reflectors has been shown. Two designs of Bragg reflectors for multijunction solar cells, which allow ensuring in the Ga(In)As subcell base an effective collection of minority charge carriers at the decrease of their diffusion length caused by radiation treatment, have been investigated. Influence of subcells’ thicknesses of n-p GaInP/Ga(In)As/Ge solar cell under 1 MeV electron irradiation with fluences up to 3•1015 cm–2 on short circuit current was considered. Optimal thicknesses of GaInP and GaInAs subcells with Bragg reflectors, depending on the rated operation period on the geostationary orbit, were estimated. It has been shown that such an optimization allows to achieve efficiency at long operation of solar cells on the orbit noticeably higher than that of non-optimized cells.

The effect of Dzyaloshinskii–Moriya interaction on direct and backward transition between magnetic states of Pt/Co/Ir/Co/Pr synthetic ferrimagnet

2021 ◽  
Vol 6 (3) ◽  
pp. 167-178
Author(s):  
Artem D. Talantsev ◽  
Ekaterina I. Kunitsyna ◽  
Roman B. Morgunov
Keyword(s):  
Thin Layer ◽  
Domain Structure ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Ferromagnetic Layers ◽  
Magneto Optical Kerr Effect ◽  
Magnetic States ◽  
Fluctuation Fields ◽  
Moriya Interaction ◽  
Effect Technique

In this paper, we present the study of domain structure accompanying interstate transitions in Pt/Co/Ir/Co/Pr synthetic ferrimagnet (SF) of 1.1 nm thick and 0.6 – 1.0 nm thin ferromagnetic Co layers. Variation in the thickness of the thin layer causes noticeable changes in the domain structure and mechanism of magnetization reversal revealed by MOKE (Magneto-Optical Kerr Effect) technique. Magnetization reversal includes coherent rotation of magnetization of the ferromagnetic layers, generation of magnetic nuclei, spreading of domain walls (DW), and development of areas similar with strip domains, dependently on thickness of the thin layer. Inequivalence of the direct and backward transitions between magnetic states of SF with parallel and antiparallel magnetizations was observed in sample with thin layer thicknesses 0.8 nm and 1.0 nm. Asymmetry of the transition between these states is expressed in difference fluctuation fields and shapes of reversal magnetization nucleus contributing to the correspondent forward and backward transitions. We proposed simple model based on asymmetry of Dzyaloshinskii–Moriya interaction. This model explains competition between nucleation and domain wall propagation due to increase/decrease of the DW energy dependently on direction of the spin rotation into the DW in respect to external field.

scholarly journals Direct AFM-based nanoscale mapping and tomography of open-circuit voltages for photovoltaics

2018 ◽  
Vol 9 ◽  
pp. 1802-1808 ◽  
Author(s):  
Katherine Atamanuk ◽  
Justin Luria ◽  
Bryan D Huey
Keyword(s):  
Solar Cells ◽  
Open Circuit Voltage ◽  
Short Circuit ◽  
Photovoltaic Performance ◽  
Three Dimensional ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Photovoltaic Properties ◽  
Order Of Magnitude ◽  
Individual Grains

The nanoscale optoelectronic properties of materials can be especially important for polycrystalline photovoltaics including many sensor and solar cell designs. For thin film solar cells such as CdTe, the open-circuit voltage and short-circuit current are especially critical performance indicators, often varying between and even within individual grains. A new method for directly mapping the open-circuit voltage leverages photo-conducting AFM, along with an additional proportional-integral-derivative feedback loop configured to maintain open-circuit conditions while scanning. Alternating with short-circuit current mapping efficiently provides complementary insight into the highly microstructurally sensitive local and ensemble photovoltaic performance. Furthermore, direct open-circuit voltage mapping is compatible with tomographic AFM, which additionally leverages gradual nanoscale milling by the AFM probe essentially for serial sectioning. The two-dimensional and three-dimensional results for CdTe solar cells during in situ illumination reveal local to mesoscale contributions to PV performance based on the order of magnitude variations in photovoltaic properties with distinct grains, at grain boundaries, and for sub-granular planar defects.

scholarly journals Study of thermal behavior of phytic acid

2013 ◽  
Vol 49 (2) ◽  
pp. 275-283 ◽  
Author(s):  
André Luis Máximo Daneluti ◽  
Jivaldo do Rosário Matos
Keyword(s):  
Thermal Decomposition ◽  
Thermal Behavior ◽  
Mass Loss ◽  
Kinetic Study ◽  
Phytic Acid ◽  
Absorption Spectroscopy ◽  
Elemental Analysis ◽  
Reaction Order ◽  
Dehydration Process ◽  
Thermogravimetric Method

Phytic acid is a natural compound widely used as depigmenting agent in galenic cosmetic emulsions. However, we have observed experimentally that phytic acid, when heated to 150 ºC for around one hour, shows evidence of thermal decomposition. Few studies investigating this substance alone with regard to its stability are available in the literature. This fact prompted the present study to characterize this species and its thermal behavior using thermal analysis (TG/DTG and DSC) and to associate the results of these techniques with those obtained by elemental analysis (EA) and absorption spectroscopy in the infrared region. The TG/DTG and DSC curves allowed evaluation of the thermal behavior of the sample of phytic acid and enabled use of the non-isothermal thermogravimetric method to study the kinetics of the three main mass-loss events: dehydration I, dehydration II and thermal decomposition. The combination of infrared absorption spectroscopy and elemental analysis techniques allowed evaluation of the intermediate products of the thermal decomposition of phytic acid. The infrared spectra of samples taken during the heating process revealed a reduction in the intensity of the absorption band related to O-H stretching as a result of the dehydration process. Furthermore, elemental analysis results showed an increase in the carbon content and a decrease in the hydrogen content at temperatures of 95, 150, 263 and 380 °C. Visually, darkening of the material was observed at 150 °C, indicating that the thermal decomposition of the material started at this temperature. At a temperature of 380 °C, thermal decomposition progressed, leading to a decrease in carbon and hydrogen. The results of thermogravimetry coupled with those of elemental analysis allow us to conclude that there was agreement between the percentages of phytic acid found in aqueous solution. The kinetic study by the non-isothermal thermogravimetric method showed that the dehydration process occurred in two stages. Dehydration step I promoted a process of vaporization of water (reaction order of zero), whereas dehydration step II showed an order of reaction equal to five. This change in reaction order was attributed to loss of chemically bonded water molecules of phytic acid or to the presence of volatile substances. Finally, the thermal decomposition step revealed an order of reaction equal to one. It was not possible to perform the kinetic study for other stages of mass loss.

Thermal behavior and thermal decomposition study of porphyrin polymers containing different spacer groups

2004 ◽  
Vol 413 (1-2) ◽  
pp. 31-38 ◽  
Author(s):  
Chunxiu Guan ◽  
liqing Li ◽  
Donghua Chen ◽  
Zongyong Gao ◽  
Wenbo Sun
Keyword(s):  
Thermal Decomposition ◽  
Thermal Behavior ◽  
Porphyrin Polymers

scholarly journals Preparation, characterization of spherical 1,1-diamino-2,2-dinitroethene (FOX-7), and study of its thermal decomposition characteristics

RSC Advances ◽  
2021 ◽  
Vol 11 (53) ◽  
pp. 33522-33530
Author(s):  
Xinhua Zhao ◽  
Dan He ◽  
Xiaoping Ma ◽  
Xueying Liu ◽  
Zishuai Xu ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Thermal Behavior ◽  
Crystal Morphology ◽  
Size Structure ◽  
Crystallization Method ◽  
Cooling Crystallization ◽  
Grinding Technique

Spherical FOX-7 was produced via a combination of cooling crystallization method and repeated grinding technique, and the crystal morphology, size, structure, and thermal behavior were systematically investigated in detail.

scholarly journals The influence of the nature and textural properties of different supports on the thermal behavior of Keggin type heteropolyacids

2006 ◽  
Vol 71 (3) ◽  
pp. 235-249 ◽  
Author(s):  
Alexandru Popa ◽  
Viorel Sasca ◽  
Mircea Stefanescu ◽  
Erne Kis ◽  
Radmila Marinkovic-Neducin
Keyword(s):  
Thermal Stability ◽  
Thermal Decomposition ◽  
Thermal Behavior ◽  
Solid Phase ◽  
Textural Properties ◽  
Nitrogen Adsorption ◽  
Active Phase ◽  
Support Surface ◽  
Sem Images ◽  
The Stability

In order to obtain highly dispersed heteropolyacids (HPAs) species, H3PMo12O40 and H4PVMo11O40 were supported on various supports: silica (Aerosil - Degussa and Romsil types) and TiO2. The structure and thermal decomposition of supported and unsupported HPAs were followed by different techniques (TGA-DTA, FTIR, XRD, low temperature nitrogen adsorption, scanning electron microscopy). All the supported HPAs were prepared by impregnation using the incipient wetness technique with a 1:1 mixture of water-ethanol. Samples were prepared with different concentrations to examine the effect of loading on the thermal behavior of the supported acid catalysts. The thermal stability was evaluated with reference to the bulk solid acids and mechanical mixtures. After deposition on silica types supports, an important decrease in thermal stability was observed on the Romsil types and a small decrease on the Aerosil type. The stability of the heteropolyacids supported on titania increased due to an anion-support interaction, as the thermal decomposition proceeded in two steps. The structure of the HPAs was not totally destroyed at 450 ?C as some IR bands were still preserved. A relatively uniform distribution of HPAs on the support surface was observed for all compositions of the active phase. No separate crystallites of solid phase HPAs were found in the SEM images.

scholarly journals Improvement in Carbonization Efficiency of Cellulosic Fibres Using Silylated Acetylene and Alkoxysilanes

Fibers ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 84
Author(s):  
Maria Mironova ◽  
Igor Makarov ◽  
Lyudmila Golova ◽  
Markel Vinogradov ◽  
Georgy Shandryuk ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Thermal Behavior ◽  
Comparative Studies ◽  
Decomposition Reaction ◽  
Activation Energies ◽  
Composite Fibers ◽  
Carbon Yield ◽  
Pyrolysis Reaction ◽  
Cellulosic Fibres

Comparative studies of the structure and thermal behavior of cellulose and composite precursors with additives of silyl-substituted acetylene and alkoxysilanes were carried out. It is shown that the introduction of silicon-containing additives into the cellulose matrix influenced the thermal behavior of the composite fibers and the carbon yield after carbonization. Comparison of the activation energies of the thermal decomposition reaction renders it possible to determine the type of additive and its concentration, which reduces the energy necessary for pyrolysis. It is shown that the C/O ratio in the additive and the presence of the Si–C bond affected the activation energy and the temperature of the beginning and the end of the pyrolysis reaction.

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