scholarly journals Nickel(III) containing layered double hydroxides with hydrotalcite structure

2019 ◽  
Vol 57 (2) ◽  
pp. 116-122
Author(s):  
Irina G. Ryltsova ◽  
◽  
Olga V. Nestroinaia ◽  
Olga E. Lebedeva ◽  
◽  
...  
Keyword(s):  
Heat Treatment ◽  
Layered Double Hydroxides ◽  
Reaction System ◽  
Second Stage ◽  
Transmission Electron ◽  
Crystalline Water ◽  
Two Stages ◽  
Double Hydroxides ◽  
Synthesized Materials ◽  
Thermal Stability Of

Synthesis of layered double hydroxides (LDH) was carried out by the method of coprecipitating of components from the solution at room temperature and variable pH, followed by aging at 98 °C for 2 days. During the synthesis the following compositions were specified: M2+6M3+1.5Ni3+0.5, where M2+ is Mg, Cu or Ca, M3+ is Al, Fe, or Co. In order to convert nickel cations to oxidation state +3, an oxidizing agent – sodium hypochlorite – was introduced into the reaction system. It is shown that the use of this method of synthesis allows to obtain layered double hydroxides containing aluminum and nickel or iron and nickel in the positions of triply charged cations in the structure of brucite-like layers. The formation of hydrotalcite-like structure was confirmed by XRD. The synthesized materials had morphology typical for layered double hydroxides. According to transmission electron microscopy, the samples consisted of aggregates of plate-like particles. The behavior during heat treatment was studied by thermogravimetric analysis. It was shown that the replacement of aluminum with iron cations in the structure of nickel-containing LDH led to a slight decrease in thermal stability of LDH. The thermal destruction of the obtained samples occured in two stages. The first stage, observed in the temperature range from 20 to 220 °C, included the loss of physically sorbed and crystalline water. In the second stage, when heated above 220 °C, simultaneous dehydroxylation of brucite-like layers and removal of carbonate anions from the interlayer space were observed, which resulted in the destruction of the layered structure. Heat treatment at 500 °C led to the transformation of layered double hydroxides into a mixture of corresponding oxides.

Thermodynamic Stability of Ptal Thin Films on GaAs

1990 ◽  
Vol 181 ◽  
Author(s):  
Dae-Hong Ko ◽  
Robert Sinclair
Keyword(s):  
Thin Films ◽  
Solid Phase ◽  
Second Stage ◽  
Sequential Deposition ◽  
Low Temperature Annealing ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
C 30 ◽  
Two Stages ◽  
Thermal Stability Of

ABSTRACTThe thermal stability of PtAl thin films on GaAs substrates has been studied using transmission electron microscopy and Auger electron spectroscopy. The PtAl thin films were formed by sequential deposition of discrete Pt and Al layers on GaAs by e-beam evaporation followed by subsequent annealing processes. Interfacial reactions in the Al/Pt/GaAs system proceed in two stages. Upon low temperature annealing Pt and GaAs react to form PtGa and PtAs2. Further high temperature annealing causes PtGa, PtAs2 and Al to react together producing the desired PtAl on GaAs. We observed solid-phase epitaxial regrowth of GaAs during the second stage of reaction. The PtAl/GaAs interface is determined to be thermally stable during an 800°C/30 min. anneal, while remaining morphologically uniform on GaAs.

In-Situ Study of Ti/TiN Stability under Nitrogen Anneal

1999 ◽  
Vol 564 ◽  
Author(s):  
P. W. DeHaven ◽  
K. P. Rodbell ◽  
L. Gignac
Keyword(s):  
Annealing Temperature ◽  
Time Range ◽  
Second Phase ◽  
Transformation Rate ◽  
Transformation Mechanism ◽  
Second Stage ◽  
Transmission Electron ◽  
Reaction Proceeds ◽  
Two Stages

AbstractThe effectiveness of a TiN capping layer to prevent the conversion of α-titantium to titanium nitride when annealed in a nitrogen ambient has been studied over the temperature range 300–700°C using in-situ high temperature diffraction and transmission electron microscopy. Over the time range of interest (four hours), no evidence of Ti reaction was observed at 300°C. At 450°C. nitrogen was found to diffuse into the Ti to form a Ti(N) solid solution. Above 500°C the titanium is transformed to a second phase: however this reaction follows two different kinetic paths, depending on the annealing temperature. Below 600°C. the reaction proceeds in two stages, with the first stage consisting of Ti(N) formation, and the second stage consisting of the conversion of the Ti(N) with a transformation mechanism characteristic of short range diffusion (grain edge nucleation). Above 600°C, a simple linear transformation rate is observed.

scholarly journals Designing Magnetic Layered Double Hydroxides and Two-Dimensional Magnetic Nano-Nets of Cobalt Ferrite through a Novel Approach

2018 ◽  
Vol 8 (11) ◽  
pp. 2099 ◽  
Author(s):  
Osama Saber ◽  
Abdullah Aljaafari ◽  
Sarah Asiri ◽  
Khalid Batoo
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Layered Double Hydroxides ◽  
Cobalt Ferrite ◽  
High Coercivity ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Double Hydroxides

The present study has a dual aim of supporting magnetic nanoparticles over the nanolayers of LDHs and designing two-dimensional magnetic nano-nets of cobalt ferrite. In this trend, nanoparticles of CoFe2O4 were prepared and supported by Co-Fe LDH through urea hydrolysis. The nanolayered structures of Co-Fe LDH were confirmed by X-ray diffraction, energy-dispersive X-ray spectrometry, FT-IR spectra, thermal analyses, and transmission electron microscopy. In addition, they indicated that 13.2% CoFe2O4 were supported over Co-Fe LDH. Transformation of the nanolayered structures of Co-Fe LDH to nano-nets was achieved by the catalytic effect of the supported CoFe2O4 nanoparticles through solvent thermal technique. X-ray diffraction patterns and transmission electron microscopy images confirmed the transformation of the supported Co-Fe LDH to nano-nets of cobalt ferrite. In order to indicate the effect of the LDH for designing the nano-nets, nanoparticles of cobalt ferrite were prepared by the same technique without LDH. The magnetic behavior of the nano-nets and the supported Co-Fe LDH were measured and compared with the nanoparticles through vibrating sample magnetometer technique. The magnetic parameters indicated that the prepared nano-nets have ferromagnetic behavior and high coercivity. However, the prepared nanoparticles revealed a superparamagnetic state and low coercivity. The experimental results concluded that the incorporation of nanoparticles with nanowires into nano-net structures has been found to be an efficient way to improve their magnetic properties and prevent their agglomerations. Finally, layered double hydroxides are an important source for constructing magnetic nanolayered structures and nano-nets.

Structure and Optical Properties of ZnO and ZnO2 Nanoparticles

2019 ◽  
Vol 56 ◽  
pp. 49-62 ◽  
Author(s):  
Javier Eliel Morales-Mendoza ◽  
Francisco Paraguay-Delgado ◽  
J.A. Duarte Moller ◽  
Guillermo Herrera-Pérez ◽  
Nicolaza Pariona
Keyword(s):  
Heat Treatment ◽  
Band Edge Emission ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Colloidal Method ◽  
Zinc Peroxide ◽  
Average Size ◽  
Thermal Stability Of ◽  
Raman And Ir Spectroscopy

Zinc oxide (ZnO) and Zinc peroxide (ZnO2) nanoparticles were synthesized by colloidal method at low temperature. The thermal stability of ZnO2was studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-Ray diffraction (XRD). The crystalline structure and phase change from ZnO2to ZnO by heat treatment was studied in detail. Morphology and particle size was examined using Transmission Electron Microscopy (TEM), for as synthesized ZnO and ZnO2the shape of particles were cuasi-spherical for both materials with average size of 10±2.2 nm and 2.5±0.4 nm, respectively; The crystal size for ZnO obtained by heat treatment was 8±2.2 nm. Electron density contours show the chemical bond type ionic and covalent for ZnO and ZnO2. The vibrational properties were analyzed by Raman and IR spectroscopy. Band gap values were obtained from ultraviolet-visible (UV-Vis) absorbance spectrum. Photoluminescence (PL) spectrum for ZnO shows two emission edges located at 445 and 492 nm and in the case of ZnO2presents one edge at 364 nm originated from the band edge emission. The optical spectra present a hypsochromic shift, compared with some reported in the literature.

scholarly journals Microstructure and Thermal Stability of Transition Metal Nitrides and Borides on GaN

2000 ◽  
Vol 622 ◽  
Author(s):  
Jacek Jasiński ◽  
Eliana Kamińska ◽  
Anna Piotrowska ◽  
Adam Barcz ◽  
Marcin Zieliński
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Thermal Stability ◽  
Contact Structure ◽  
Secondary Ion Mass Spectrometry ◽  
Metal Nitrides ◽  
Transition Metal Nitrides ◽  
Transmission Electron ◽  
Secondary Ion ◽  
Thermal Stability Of

ABSTRACTMicrostructure and thermal stability of ZrN/ZrB2 bilayer deposited on GaN have been studied using transmission electron microscopy methods (TEM) and secondary ion mass spectrometry (SIMS). It has been demonstrated that annealing of the contact structure at 1100°C in N2 atmosphere does not lead to any observable metal/semiconductor interaction. In contrast, a failure of the integrity of ZrN/ZrB2 metallization at 800°C, when the heat treatment is performed in O2 ambient has been observed.

scholarly journals Modification of nano-sized layered double hydroxides by long-chain organic aliphatic surfactants

2008 ◽  
Vol 73 (3) ◽  
pp. 321-331 ◽  
Author(s):  
Ramasamy Anbarasan ◽  
Wanduc Lee ◽  
Seung Soon
Keyword(s):  
Thermal Stability ◽  
Layered Double Hydroxides ◽  
Exchange Process ◽  
Xrd Analysis ◽  
Basal Spacing ◽  
Ion Exchange Process ◽  
Dodecanedioic Acid ◽  
Double Hydroxides ◽  
Thermal Stability Of ◽  
Long Chain

The inter-layer anion of layered double hydroxides (LDH) with a hydrotalcite (HT)-like structure was ion-exchanged with various organic surfactants, particularly with long chain aliphatic surfactants. After the ion-exchange process, the basal spacing of the LDH was increased and the increase of the basal spacing depended on various factors, such as the intercalation capacity functionality and orientation capability of the surfactant. Of the employed surfactants, stearic acid intercalated LDH showed the highest increase of the basal spacing, which was confirmed by XRD analysis. FTIR results supported the interaction of the surfactants with the LDH. In addition, an increase in the thermal stability of the dodecanedioic acid intercalated HT was evidenced by the TGA method.

The Red-Shift of Surface Plasmon Absorption of 2D Nanogold Arrangement from Disordered to Ordered

2008 ◽  
Vol 8 (1) ◽  
pp. 348-352 ◽  
Author(s):  
Junke Tang ◽  
Jinru Li ◽  
Huiling Rong ◽  
Bingsuo Zou ◽  
Long Jiang
Keyword(s):  
Long Range ◽  
Surface Plasmon ◽  
Red Shift ◽  
Strong Increase ◽  
Two Dimension ◽  
Second Stage ◽  
Transmission Electron ◽  
Dipolar Moment ◽  
Random Patterns ◽  
Two Stages

In this article, the changing of surface plasmon resonance (SPR) absorption of 2D arrangement of Au (3 nm) nanoparticles coated with 1-dodecanethiol (C12H25SH), obtained at different desolvation extents, had been investigated. It has been found that an obvious red-shifted happened when these arrays changed from loose, disordered to close-packed and ordered. Both transmission electron microscopy pictures and variation of SPR absorption of these arrays showed that the formation of long range two-dimension (2D) arrangement of nanoparticles coated with C12H25SH might be involved in two stages: At the first stage the particles can move freely and random patterns from loose to close package was driven by the Brownian Movement of solvated particles and as a result the voids were eliminated. The red shift of SPR absorption with the coverage (dλ/d) is relative low. At the second stage, where the particles cannot move freely because of lack of solvent and a long-range two-dimension crystal was formed, the SPR shift to a longer wavelength with a larger dλ/d. It is mainly attributed to the strong increase of the orientation and dipolar moment of the absorbed C12H25SH molecule on nanoparticles.

scholarly journals Preparation of polypropylene/Mg–Al layered double hydroxides nanocomposites through wet pan-milling: formation of a second-staging structure in LDHs intercalates

RSC Advances ◽  
2017 ◽  
Vol 7 (3) ◽  
pp. 1520-1530 ◽  
Author(s):  
Yilei Zheng ◽  
Yinghong Chen
Keyword(s):  
Layered Double Hydroxides ◽  
Intermediate Formation ◽  
Sulfate Anion ◽  
Macromolecular Chain ◽  
Second Stage ◽  
Dodecyl Sulfate ◽  
Double Hydroxides

Pan-milling mechanochemistry induces second stage intermediate formation via co-intercalation of the dodecyl sulfate anion and PP macromolecular chain into the LDH gallery.

scholarly journals Synthesis of FePcS–PMA–LDH Cointercalation Composite with Enhanced Visible Light Photo-Fenton Catalytic Activity for BPA Degradation at Circumneutral pH

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1951 ◽  
Author(s):  
Fenglian Huang ◽  
Shiqiang Tian ◽  
Yan Qi ◽  
Erping Li ◽  
Liangliang Zhou ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Bisphenol A ◽  
Visible Light ◽  
Layered Double Hydroxides ◽  
Electrochemical Impedance ◽  
Reaction System ◽  
High Catalytic Activity ◽  
Exchange Method ◽  
Double Hydroxides ◽  
Circumneutral Ph

(1) Background: Iron tetrasulfophthalocyanine with a large nonlinear optical coefficient, good stability, and high catalytic activity has aroused the attention of researchers in the field of photo-Fenton reaction. Further improvement of the visible light photo-Fenton catalytic activity under circumneutral pH conditions for their practical application is still of great importance. (2) Methods: In this paper, iron tetrasulfophthalocyanine (FePcS) and phosphomolybdic acid (PMA) cointercalated layered double hydroxides (LDH) were synthesized by the ion-exchange method. All samples were fully characterized by various techniques and the results showed that FePcS and PMA were successfully intercalated in layered double hydroxides and the resulted compound exhibited strong absorption in the visible light region. The cointercalation compound was tested as a heterogeneous catalyst for the visible light photo-Fenton degradation of bisphenol A (BPA) at circumneutral pH. (3) Results: The results showed that the degradation and total organic carbon removal efficiencies of bisphenol A were 100% and 69.2%, respectively. (4) Conclusions: The cyclic voltammetry and electrochemical impedance spectroscopy measurements demonstrated that the main contribution of PMA to the enhanced photo-Fenton activity of FePcS–PMA–LDH comes from the acceleration of electron transfer in the reaction system. Additionally, the possible reaction mechanism in the photo-Fenton system catalyzed by FePcS–PMA–LDH was also proposed.

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