scholarly journals Synthesis of Nano-Composites Mg2TiO4 Powders via Mechanical Alloying Method and Characterization

2020 ◽  
Author(s):  
Ranjan Kumar Bhuyan ◽  
Bhagban Kisan ◽  
Santosh Kumar Parida ◽  
Soumya Patra ◽  
Sunil Kumar
Keyword(s):  
Optical Properties ◽  
Composite System ◽  
Milled Powder ◽  
Standard Pattern ◽  
Tem Analysis ◽  
Peak Broadening ◽  
High Resolution Tem ◽  
Crystallite Sizes ◽  
Decomposition Behavior ◽  
Nanocrystalline Composite

In this chapter a systematic investigation of impact of mechanical activation on structural, microstructural, thermal and optical properties of MgO – TiO2 nanocrystalline composite system, synthesized via high energy ball milling techniques. Williamson-Hall (W-H) plot method was employed to understand the signature of the broadening in the XRD peaks and for the estimation of crystallite size of MgO – TiO2 nanocrystalline composite system. It revealed that the peak broadening is not only due to reduced coherently diffracting domain size but also due to a significant strain distribution. The calculated strain was 9.01× 10−3 and the average crystallite sizes were 40–60 nm for 35 hours (hrs) milled powder and this result is very much consistent with transmission electron microscopy (TEM) analysis. The SAED ring pattern indicates that the phase of Mg2TiO4 - nanoparticles was polycrystalline in structure and the distance between crystalline planes was consistent with the standard pattern for a spinel Mg2TiO4 crystal structure. To analyze the lattice fringes for the 35 hrs milled samples high resolution-TEM (HR-TEM) study was carried out and the result revealed that the each particle has single crystalline structure. Morphological studies were carried out by using SEM analysis. The thermal decomposition behavior of the milled powders was examined by a thermo-gravimetric analyzer (TGA) in argon atmosphere. Also, MTO nanoparticles showed a strong absorption at ~356 nm and the band gap values ranged between 3.26-3.78 eV with an increase of milling time from 0 to 35 hr. The mechanically derived MTO nanoparticles showed promising optical properties which are suitable for commercial optoelectronic applications.

ROLE OF CALCINATION TEMPERATURES ON THE STRUCTURAL AND OPTICAL PROPERTIES OF NiO NANOPARTICLES

2019 ◽  
Vol 26 (08) ◽  
pp. 1950043
Author(s):  
H. MOHAMED MOHAIDEEN ◽  
S. SHEIK FAREED ◽  
B. NATARAJAN
Keyword(s):  
Optical Properties ◽  
Sol Gel ◽  
Near Band Edge ◽  
Band Edge Emission ◽  
Nickel Oxide Nanoparticles ◽  
Tem Analysis ◽  
Calcination Temperatures ◽  
Peak Broadening ◽  
Strain Components ◽  
Nio Nps

Nickel oxide nanoparticles (NiO NPs) were synthesized through template free sol–gel method. Synthesized particles were calcined at 300∘C, 500∘C and 700∘C for 2[Formula: see text]h and further the particles were characterized for its thermal, functional, structural, morphological and optical properties. The peak broadening analysis was undertaken in order to calculate the variation in size and strain components of the particles with the calcinations temperature. The Debye–Scherer, Williamson–Hall and Size-strain plot methods were employed in peak broadening analysis and were compared with TEM results. All the NiO NPs crystallite size and lattice strain value were found to be in good agreement with all the models. The TEM analysis revealed that the calcinations at 700∘C NiO NPs have sphere like structure of less than 20[Formula: see text]nm particles size value. The strong peak observed at 360.5[Formula: see text]nm bandgap emission relates to the bandgap of 3.44[Formula: see text]eV which is because of the near band edge emission.

TEM Analysis of Long-Period Polytypes in SiC—S

1976 ◽  
Vol 34 ◽  
pp. 630-631
Author(s):  
S. Shinozaki ◽  
J. W. Sprys
Keyword(s):  
Electron Diffraction ◽  
Isothermal Annealing ◽  
Tem Analysis ◽  
Long Period ◽  
Transmission Electron ◽  
Average Grain Size ◽  
High Resolution Tem ◽  
Structural Lattice ◽  
The Stability ◽  
Continuous Curves

In reaction sintered SiC (∽ 5um average grain size), about 15% of the grains were found to have long-period structures, which were identifiable by transmission electron microscopy (TEM). In order to investigate the stability of the long-period polytypes at high temperature, crystal structures as well as microstructural changes in the long-period polytypes were analyzed as a function of time in isothermal annealing.Each polytype was analyzed by two methods: (1) Electron diffraction, and (2) Electron micrograph analysis. Fig. 1 shows microdensitometer traces of ED patterns (continuous curves) and calculated intensities (vertical lines) along 10.l row for 6H and 84R (Ramsdell notation). Intensity distributions were calculated based on the Zhdanov notation of (33) for 6H and [ (33)3 (32)2 ]3 for 84R. Because of the dynamical effect in electron diffraction, the observed intensities do not exactly coincide with those intensities obtained by structure factor calculations. Fig. 2 shows the high resolution TEM micrographs, where the striped patterns correspond to direct resolution of the structural lattice periodicities of 6H and 84R structures and the spacings shown in the figures are as expected for those structures.

Formation of Large, Orientation-Controlled, Nearly Single Crystalline Si Thin Films on SiO2 Using Contact Printing of Rolled and Annealed Nickel Tapes

2003 ◽  
Vol 762 ◽  
Author(s):  
Hwang Huh ◽  
Jung H. Shin
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
High Resolution ◽  
Amorphous Silicon ◽  
Tem Analysis ◽  
Contact Printing ◽  
Single Crystalline ◽  
High Resolution Tem ◽  
Lateral Crystallization ◽  
Si Films

AbstractAmorphous silicon (a-Si) films prepared on oxidized silicon wafer were crystallized to a highly textured form using contact printing of rolled and annealed nickel tapes. Crystallization was achieved by first annealing the a-Si film in contact with patterned Ni tape at 600°C for 20 min in a flowing forming gas (90 % N2, 10 % H2) environment, then removing the Ni tape and further annealing the a-Si film in vacuum for2hrsat600°C. An array of crystalline regions with diameters of up to 20 μm could be formed. Electron microscopy indicates that the regions are essentially single-crystalline except for the presence of twins and/or type A-B formations, and that all regions have the same orientation in all 3 directions even when separated by more than hundreds of microns. High resolution TEM analysis shows that formation of such orientation-controlled, nearly single crystalline regions is due to formation of nearly single crystalline NiSi2 under the point of contact, which then acts as the template for silicide-induced lateral crystallization. Furthermore, the orientation relationship between Si grains and Ni tape is observed to be Si (110) || Ni (001)

scholarly journals Enhancement on the Tribological Properties of the Multilayer RGO/Al Matrix Composites by Cu-Coating Method

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3163
Author(s):  
Fengguo Liu ◽  
Ning Su ◽  
Renguo Guan
Keyword(s):  
Electron Microscope ◽  
Tribological Properties ◽  
Milled Powder ◽  
Wear Loss ◽  
Matrix Composites ◽  
Tem Analysis ◽  
Lubricating Film ◽  
Coating Method ◽  
Al Matrix Composites ◽  
Al Matrix

Multilayer reduced graphene oxide (mrGO) was chemically modified by electroless plating of copper on surface to form mrGO-Cu. The scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis revealed that nano-Cu particles were uniformly dispersed on the surface of mrGO. The mrGO-Cu powders were further utilized as reinforcements for aluminum (Al) matrix and the mrGO-Cu/Al composite was successfully fabricated through clad rolling of milled powder. The tribological properties of the mrGO-Cu/Al composites were explored. The tribological results show that the mrGO-Cu could reduce the friction coefficient and wear loss of mrGO-Cu/Al composites, since the mrGO-Cu participated in lubricating processes due to the formation of a transfer layer on the contact surface. Furthermore, it is found that the composition of mrGO-Cu could significantly influence the tribological properties of the mrGO-Cu/Al composites. The composites with 4% of mrGO-Cu for composites exhibited the best tribological behavior, which transformed from adhesive wear to abrasive wear, due to the formation of a graphite lubricating film.

The Interfacial Diffusion Zone in Magnetron Sputtered Ni-Ti Thin Films Deposited on Different Si Substrates Studied by HR-TEM

2008 ◽  
Vol 587-588 ◽  
pp. 820-823 ◽  
Author(s):  
Rui M.S. Martins ◽  
Manfred Beckers ◽  
A. Mücklich ◽  
Norbert Schell ◽  
Rui Jorge C. Silva ◽  
...  
Keyword(s):  
Thin Films ◽  
Growth Front ◽  
Interfacial Structure ◽  
Interfacial Diffusion ◽  
Tem Analysis ◽  
Si Substrates ◽  
Microelectromechanical Devices ◽  
Preferential Diffusion ◽  
High Resolution Tem ◽  
Columnar Grains

Ni-Ti Shape Memory Alloy thin films are suitable materials for microelectromechanical devices. During the deposition of Ni-Ti thin films on Si substrates, there exist interfacial diffusion and chemical interactions at the interface due to the high temperature processing necessary to crystallize the film. For the present study, Ni-Ti thin films were prepared by magnetron cosputtering from Ni-Ti and Ti targets in a specially designed chamber mounted on the 6-circle goniometer of the ROssendorf BeamLine (ROBL-CRG) at ESRF, Grenoble (France). The objective of this study has been to investigate the interfacial structure resulting from depositions (at a temperature of ≈ 470°C) on different substrates: naturally oxidized Si(100), Si(111) and poly-Si substrates. A detailed High-Resolution TEM analysis of the interfacial structure has been performed. When Ni-Ti is deposited on Si(100) substrate, a considerable diffusion of Ni into the substrate takes place, resulting in the growth of semi-octaeder A-NiSi2 silicide. In the case of Ni-Ti deposited on Si(111), there appears an uniform thickness plate, due to the alignment between substrate orientation and the [111]-growth front. For Ni-Ti deposited on poly-Si, the diffusion is inhomogeneous. Preferential diffusion is found along the columnar grains of poly-Si, which are favourably aligned for Ni diffusion. These results show that for the Ni-Ti/Si system, the morphology of the diffusion interface is strongly dependent on the type of substrates.

OPTICAL PROPERTIES OF CdTe AND CdS QUANTUM DOTS IN GLASS

1992 ◽  
Vol 01 (01) ◽  
pp. 25-50 ◽  
Author(s):  
V. ESCH ◽  
K. KANG ◽  
B. FLUEGEL ◽  
Y.Z. HU ◽  
G. KHITROVA ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Optical Nonlinearities ◽  
Cds Quantum Dots ◽  
Temperature Dependent ◽  
Linear Absorption ◽  
Crystallite Sizes ◽  
Band Mixing ◽  
Quantum Confined ◽  
Coulomb Effects

We summarize the linear and nonlinear optical properties of a variety of CdTe and CdS quantum dots in glass. The measured linear absorption of the CdTe sample is compared with calculations involving valence-band mixing due to the quantum confinement. The temperature dependence of the lowest quantum-confined transition and its linewidth for samples with various crystallite sizes are measured and compared with a simple model. It is found that the shift of the energetically lowest quantum-confined transition as a function of temperature is the same as the temperature-dependent band-gap reduction in bulk materials. Excitation of the sample with pulses ranging from femtoseconds to microseconds allows distinguishing between various mechanisms responsible for the observed optical nonlinearities. At very early times, phase-space filling and Coulomb interaction between the excited charged carriers are responsible for the absorption changes. At later times, Coulomb effects due to “trapped” carriers remain and last for nanoseconds or microseconds.

scholarly journals High-Resolution TEM Analysis of Supported Metal Nanoparticles Combining with Image Simulation

2013 ◽  
Vol 19 (S2) ◽  
pp. 1556-1557 ◽  
Author(s):  
B. Zhang ◽  
W. Zhang ◽  
L. Shao ◽  
D.S. Su
Keyword(s):  
High Resolution ◽  
Metal Nanoparticles ◽  
Image Simulation ◽  
Tem Analysis ◽  
High Resolution Tem ◽  
Supported Metal Nanoparticles ◽  
Supported Metal

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Study of Nanocrystalline ZnAl2O4 and ZnFe2O4 with SiO2 on Structural and Optical Properties Synthesized by Sol-Gel Method

2015 ◽  
Vol 1119 ◽  
pp. 96-100
Author(s):  
Mohd Syafiq Zulfakar ◽  
Huda Abdullah ◽  
Wan Nasarudin Wan Jalal ◽  
Zalita Zainuddin ◽  
Sahbudin Shaari
Keyword(s):  
Optical Properties ◽  
Spinel Structure ◽  
Dielectric Material ◽  
Sol Gel ◽  
Zinc Aluminate ◽  
Gel Method ◽  
Sol Gel Method ◽  
Tauc Plot ◽  
Crystallite Sizes ◽  
Spinel Structures

Zinc aluminate (ZnAl2O4) and zinc ferrite (ZnFe2O4) nanocrystalline structures dispersed into SiO2 matrix were prepared by sol-gel method. Phase formation of ZnAl2O4 and ZnFe2O4 was confirmed by X-ray diffraction (XRD) analysis. The crystallite sizes was determine using Scherer’s equation from the broadening of dominant peak at (311) plane. It was found the crystallite size of both compound decreased due to the decrement compositions of Zn2+ ion and Al3+ / Fe3+ ions. The crystallite sizes for ZnAl2O4 and ZnFe2O4 was calculated to be around ~ 14.16 – 11.27 nm and ~ 11.27 – 4.72 nm, respectively. FTIR analysis was done to determine the formation of spinel structures. FTIR results analysis confirmed that the formation of spinel structure where it has been observed that the bands around 800 cm-1 was associated to the vibrations of aluminum-oxygen and metal-oxygen-aluminum bonds. This characteristic was identified to the formation of zinc aluminate spinel structure. The optical properties have been done to determine the energy bandgap of ZnAl2O4 and ZnFe2O4 samples. The Uv-Visible absorption spectra have been done within wavelength 300 – 800 nm and the graph was plotted into the Tauc plot. This new dielectric material was purposed to improve the value of dielectric permittivity with addition of SiO2 where it can be applied as microwave dielectric material without changing the original spinel structures.

Stresses experienced by AlN films grown on sapphire

2005 ◽  
Vol 892 ◽  
Author(s):  
Jie Bai ◽  
J. Bai ◽  
V.L. Tassev ◽  
M. Lal Nakarmi ◽  
W. Sun ◽  
...  
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Lattice Mismatch ◽  
Tem Analysis ◽  
Mocvd Growth ◽  
Compressive Stresses ◽  
Show Evidence ◽  
High Resolution Tem ◽  
Final Stress ◽  
Lower Temperature

AbstractThe evolution of stress during the MOCVD growth of AlN thin films on sapphire substrates under both low and high temperature conditions has been evaluated. The final stress state of the films is assumed to consist of the summation of stresses from three different sources: (1) the stress which arises from residual lattice mismatch between film and substrate i.e. that which persists after partial relaxation by misfit dislocation formation. The extent of relaxation is determined from High Resolution TEM analysis of the substrate/film interface; (2) the stress arising from the coalescence of the 3D islands nucleated in this high mismatch epitaxy process. This requires knowledge of the island sizes just prior to coalescence and this was provided by AFM studies of samples grown under the conditions of interest; and (3) the stress generated during post-growth cooling which arises from the differences in thermal expansion coefficient between AlN and sapphire. The final resultant stress, comprising the summation of stresses arising from these three sources, is found to be tensile in the sample grown at lower temperature and compressive in the sample grown at higher temperature. These results are in general qualitative agreement with results of TEM and High resolution X-ray diffraction (HRXRD) studies, which show evidence for tensile and compressive stresses in the low temperature and high temperature cases, respectively.

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