scholarly journals Structure and formation mechanisms of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 particles under hydrothermal conditions

2020 ◽  
Vol 14 (4) ◽  
pp. 346-354
Author(s):  
Xingrui Li ◽  
Xinwei Shi
Keyword(s):  
Crystal Growth ◽  
Lattice Structure ◽  
Early Stage ◽  
Average Particle Size ◽  
Phase Evolution ◽  
Alkali Concentration ◽  
Formation Mechanisms ◽  
Average Particle ◽  
Hydrothermal Conditions ◽  
Layered Growth

(K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders were synthesized via hydrothermal method. The effects of different reaction conditions on crystal structure, micro-morphology and phase formation were analysed by XRD and SEM in detail. The results reveal that (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders with orthorhombic lattice structure are synthesized at 200?C for 18 h with the total initial alkali concentration of 8mol/l. The average particle size of synthesized powders is about 500-700 nm, which has regular cubic morphology with uniform distribution. Moreover, doping with La3+ and Sb5+ inhibits the crystal growth. The phase evolution of the powders revealed that the hydrothermal synthesis of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 underwent two steps, where an intermediate product of K4Na4Nb6O19? 9H2O was found in the early stage at 140?C. Based on the results, the formation mechanism of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders was proposed. It can be inferred that the crystal growth model of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 is dissolution-crystal growth-recrystallization with the characteristics of layered growth.

scholarly journals Characterization of dispersion strengthened copper with 3wt%Al2O3 by mechanical alloying

2004 ◽  
Vol 36 (3) ◽  
pp. 205-211 ◽  
Author(s):  
Viseslava Rajkovic ◽  
Olivera Eric ◽  
Dusan Bozic ◽  
M. Mitkov ◽  
Endre Romhanji
Keyword(s):  
Mechanical Alloying ◽  
Structural Changes ◽  
Early Stage ◽  
Structure Refinement ◽  
Average Particle Size ◽  
Copper Matrix ◽  
Alumina Powder ◽  
Average Particle ◽  
Micro Hardness ◽  
Electrolytic Copper Powder

The copper matrix has been dispersion strengthened with 3wt.%Al2O3 by mechanical alloying. Commercial alumina powder with an average particle size of 0.75mm was used for alloying. The mechanical alloying process was performed in a planetary ball mill up to 20h in air. After milling all powders were treated in H2 at 4000C for 1h, and finally hot pressing was used for compaction (800oC, 3h, Ar). Structure observations revealed a lamellar structure (Al2O3 particles largely restricted to interlamellar planes between adjacent copper lamellae) accompanied also by structure refinement. These structural changes were mostly completed in the early stage of milling, and retained after compaction. Micro hardness was found to progressively increase with milling time. So, after 5h of milling the micro hardness of the Cu+3twt%Al2O3 compact was 1540MPa, i.e. 2.5 times greater than for the as-received electrolytic copper powder (638MPa) compacted under identical conditions, while after 20h of milling it was 2370 MPa. However after exposing the tested compact at 800oC up to 5h, the achieved hardening effect vanished.

Low Temperature Hydrothermal Synthesis of Nanophase BaTiO3 and BaFe12O19 Powders

1996 ◽  
Vol 457 ◽  
Author(s):  
Fatih Dogan ◽  
Shawn O'rourke ◽  
Mao-Xu Qian ◽  
Mehmet Sarikaya
Keyword(s):  
Particle Size ◽  
Hydrothermal Reaction ◽  
Average Particle Size ◽  
Reaction Times ◽  
Nanocrystalline Powders ◽  
Molar Ratio ◽  
Average Particle ◽  
Hydrothermal Conditions ◽  
Processing Variables ◽  
Xrd And Tem

ABSTRACTNanocrystalline powders with an average particle size of 50 nm has been synthesized in two materials systems under hydrothermal conditions below 100°C. Processing variables, such as temperature, concentration and molar ratio of reactants and reaction time were optimized to obtain particles of reduced size and stoichiometric compositions. Hydrothermal reaction takes place between Ba(OH)2 solution and titanium/iron precursors in sealed polyethylene bottles in the BaTiO3 and BaFe12O19 systems, respectively. While crystalline BaTiO3 forms relatively fast within a few hours, formation of fully crystalline and stoichiometric BaFei20i9 require considerably longer reaction times up to several weeks and strongly dependent on the Ba:Fe ratio of the precursors. The structural and compositional evaluation of the nanophase powders were studied by XRD and TEM techniques.

Phase evolution and crystal growth of VO2 nanostructures under hydrothermal reactions

RSC Advances ◽  
2016 ◽  
Vol 6 (9) ◽  
pp. 7113-7120 ◽  
Author(s):  
Weilai Yu ◽  
Shuai Li ◽  
Chi Huang
Keyword(s):  
Crystal Growth ◽  
Phase Evolution ◽  
Hydrothermal Conditions ◽  
Hydrothermal Reactions ◽  
First Time

The phase evolution and crystal growth of VO2 nanostructures under hydrothermal conditions was comprehensively investigated and the feasibility of the Ostwald's step rules towards VO2 polymorph evolution was for the first time demonstrated.

scholarly journals Adsorption-Semiconductor Sensor Based on Nanosized SnO2 for Early Warning of Indoor Fires

2021 ◽  
Author(s):  
Nelli Maksymovych ◽  
Ludmila Oleksenko ◽  
George Fedorenko
Keyword(s):  
Tin Dioxide ◽  
Early Stage ◽  
Dynamic Properties ◽  
Sol Gel ◽  
Average Particle Size ◽  
High Sensitivity ◽  
Average Particle ◽  
Semiconductor Sensor ◽  
Wide Range

The paper is devoted for a solution of indoors fires prevention at early stage by determination of H2 (fire precursor gas) in air using a semiconductor sensor. A material based on Pt-containing nanosized tin dioxide with an average particle size of 10–11 nm obtained via a sol–gel method was created for a gas sensitive layer of the sensor. The developed sensor has high sensitivity to H2 micro concentration, a wide range of its detectable content in air, selectivity of H2 measuring in the presence of СО and СН4, good dynamic properties. The combination of these properties is very important for prevention of inflammations on their early stages before the open fires appearance. Economic benefit of the proposed sensor is due to a lower cost and higher reliability of the fire situation detection.

Temperature Sensitivity of Magnetic Nanoparticle Hyperthermia Using IR Thermography

2020 ◽  
pp. 2150002
Author(s):  
Femy Francis ◽  
J. Shebha Anandhi ◽  
G. Antilen Jacob ◽  
D. Sastikumar ◽  
R. Justin Joseyphus
Keyword(s):  
Infrared Thermography ◽  
Temperature Sensitivity ◽  
Magnetite Nanoparticles ◽  
Magnetic Nanoparticle ◽  
Early Stage ◽  
Average Particle Size ◽  
Average Particle ◽  
Thermal Profile ◽  
Stage Of Development ◽  
Magnetic Nanoparticle Hyperthermia

Magnetite nanoparticles are extensively studied for their applications in magnetic nanoparticle hyperthermia. However, existing methods involve invasive methods for monitoring the thermal profile while the heat generated by the magnetite nanoparticles is utilized for cancer therapy. Tumor diagnosis utilizing thermography for monitoring the thermal profile is in the early stage of development since the temperature sensitivity is influenced by various experimental factors. Magnetite nanoparticles embedded in agar matrix which mimics the human tissues and their heating characteristics were investigated using infrared thermography. The magnetite nanoparticles with an average particle size of 10[Formula: see text]nm were subjected to heating in an applied frequency of 500[Formula: see text]kHz. The influence of concentration, area and depth on the heating characteristics of the tumor phantoms were deduced from the thermography images. The parameters that influence the therapeutical sensitivity while using infrared thermography for magnetic nanoparticle hyperthermia, have been studied for potential applications in theranostics.

Octyl-β-D-glucopyranoside mediated synthesis of nanocrystalline BaTiO3 using a single-source precursor

2008 ◽  
Vol 23 (3) ◽  
pp. 842-848 ◽  
Author(s):  
Yatendra S. Chaudhary ◽  
Umananda M. Bhatta ◽  
Deepa Khushalani
Keyword(s):  
Lattice Structure ◽  
Perovskite Phase ◽  
Average Particle Size ◽  
Longitudinal Optical ◽  
Average Particle ◽  
Single Source ◽  
Single Source Precursor ◽  
Optical Modes ◽  
Diffraction Patterns ◽  
Barium Titanium

A new amphiphile: octyl-β-D-glucopyranoside along with a single-source precursor, barium titanium methoxyethoxide, were used to develop a facile route for synthesis of BaTiO3, via either a hydrolytic or a nonhydrolytic method. The average particle size for the samples was on the order of 20 to 30 nm, while that for the control samples (without the amphiphile) ranged from 100 nm to several microns. The high-resolution transmission electron microscopy (HRTEM) images and selected-area electron- diffraction patterns revealed that these nanoparticles were single crystalline; the Raman active longitudinal optical modes observed in calcined (650 °C) samples at 718 and 304 cm−1 directly indicated the presence of tetragonal domains in an overall cubic lattice structure. Moreover, the one-step nonhydrolytic approach developed for the synthesis of BaTiO3 is fast, and it eliminates tedious steps such as prolonged refluxing and aging. Thermogravimetric and Fourier transform infrared (FTIR) analysis were performed to investigate the role of octyl-β-D-glucopyranoside in the evolution of the perovskite phase, grain size, and morphology. These techniques suggested that van der Waals type of interactions were present between the amphiphile and barium titanium methoxyethoxide oligomers, and in turn they led to the controlled growth of nanoparticles.

Effect of chromium substitution on crystal and lattice structure of soft manganese zinc ferrites

2017 ◽  
Vol 31 (14) ◽  
pp. 1750153 ◽  
Author(s):  
Anand Yadav ◽  
Dinesh Varshney
Keyword(s):  
Zinc Ferrite ◽  
Lattice Structure ◽  
Average Particle Size ◽  
Wave Number ◽  
Average Particle ◽  
Phonon Modes ◽  
Ionic Radii ◽  
Small Shift ◽  
Manganese Zinc ◽  
Manganese Zinc Ferrite

Chromium-doped manganese–zinc ferrite samples were prepared by solid-state reaction route to probe the effect of chromium ion on the crystal and lattice structure of mixed manganese–zinc ferrite. X-ray diffraction patterns reveal that Mn[Formula: see text]Zn[Formula: see text]Cr[Formula: see text]Fe[Formula: see text]O[Formula: see text] ([Formula: see text] = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) ferrite has polycrystalline cubic spinel structure with some secondary phase of [Formula: see text]–Fe[Formula: see text]O[Formula: see text]. The Raman spectra reveal four Raman active phonon modes in the measurement range of 200–750 cm[Formula: see text] with small shift in Raman modes towards higher wave number. The average particle size for Mn[Formula: see text]Zn[Formula: see text]Fe[Formula: see text]O[Formula: see text] is found to be 37.28 nm which reduces to 33.64 nm for Mn[Formula: see text]Cr[Formula: see text]Fe[Formula: see text]O[Formula: see text]. As the ion doping of chromium increases, the modes of vibration are found to shift towards higher wavelength and blueshift is attributed to the higher ionic radii of Cr[Formula: see text] as compared to Zn[Formula: see text].

scholarly journals Synthesis of TiN-Si3N4 composites from rutile and quartz by carbothermal reduction nitridation

2012 ◽  
Vol 44 (1) ◽  
pp. 57-64 ◽  
Author(s):  
Kai Chen ◽  
Zhaohui Huang ◽  
Minghao Fang ◽  
Yan-Gai Liu
Keyword(s):  
Carbothermal Reduction ◽  
Raw Materials ◽  
Average Particle Size ◽  
Equilibrium Phase ◽  
Phase Evolution ◽  
Equilibrium Phase Diagram ◽  
Nitrogen Pressure ◽  
Average Particle ◽  
Carbon Addition ◽  
Composite Powders

TiN-Si3N4 composite powders were prepared by carbothermal reduction nitridation using rutile and quartz as raw materials. The influence of temperature and carbon addition on the phase evolution and microstructure of the products were investigated. The equilibrium phase diagram of Si-C-N-O and Ti-C-N-O system at different temperatures under 0.2 MPa nitrogen pressure was drew. The results show that the optimum parameters for synthesizing TiN-Si3N4 by carbothermal reduction nitridation process are carbon addition of stoichiometric content, temperature of 1873 K for 4 h and nitrogen pressure of 0.2 MPa. The produced TiN-Si3N4 in this experiment exist in granular and hexagonal columnar shape, and the average particle size of the synthesized powders is 2 ~ 10 ?m.

scholarly journals Crystal Growth and Kinetic Behaviour of Pseudoalteromonas espejiana Assisted Biosynthesized Gold Nanoparticles

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Rashmi Gupta ◽  
Gourav Kumar ◽  
Sabya Sachi Das ◽  
Saad Alkahtani ◽  
Abdullah Alkahtane ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Crystal Growth ◽  
Average Particle Size ◽  
Time Interval ◽  
Average Particle ◽  
Ph Profile ◽  
Maximum Production ◽  
Enzyme Substrate ◽  
Gold Precursor ◽  
Substrate Ratio

Pseudoalteromonas espejiana (P. espejiana) is a marine bacterium known for its high resistance to alkalinity. The ability of P. espejiana to reduce Au (III) and biosynthesize gold nanoparticles (AuNPs) is found positive and was confirmed using UV-VIS, EDS, SEM, and TEM studies. Previously, many studies have been reported regarding the crystalline nature of AuNPs; therefore, this research aims at studying the crystal growth behaviour of AuNPs through DLS and TEM studies. Spherically shaped and monodispersed, AuNPs ranging between 5 to 160 nm were obtained with an average particle size of 62 nm. Also, to achieve maximum production of AuNPs, the reaction kinetic study was performed using an ICP-OES method and the effect of various parameters including pH, temperature, rpm, and concentration of substrate was analyzed. During the biosynthesis process, an appropriate phase of nucleation, crystal growth, and saturation was observed and this helped to determine the rate constants and order of reaction. The parameters such as pH profile (pH 9), temperature (30°C), agitation speed (150 rpm), and enzyme substrate ratio (2 : 3) were found to be the best fits for maximum production of low size AuNPs. This demonstrates that in initial few hours, a quick conversion of the ionic gold precursor takes place into metallic gold nuclei, trailed by crystal growth via coalescence of small nuclei. Subsequently, it can be concluded that coalescence processes drive the crystal growth process of AuNPs over a time interval and finally leads to saturation and no newer particle formation in the solution.

Modified Polyol-Mediated Synthesis of Doped TiO2 Nanoparticles as the Photoanode in Dye Solar Cells (DSCs)

2014 ◽  
Vol 925 ◽  
pp. 575-579
Author(s):  
Sattar Bashardoust ◽  
Muti Mohamed Norani ◽  
Boon Hoong Ong ◽  
Siti Nur Azella Zaine
Keyword(s):  
Crystal Structure ◽  
Solar Cells ◽  
Lattice Structure ◽  
Average Particle Size ◽  
Spherical Particles ◽  
Hydroxyl Group ◽  
Molar Ratio ◽  
Average Particle ◽  
X Ray ◽  
Dye Solar Cells

Synthesis of nanoscale TiO2exhibiting specific properties of electron or ion conductivity is critical to improve the performance of dye solar cells (DSC). This paper presents the modified polyol-mediated synthesis of doped TiO2nanoparticles. TiO2samples were doped with cobalt (Co) and nickel (Ni) and the effects of calcination temperature (550 °C and 650 °C) on the crystallinity of pure samples were investigated. X-ray diffraction (XRD) analysis was used to determine the effect of dopant in lattice structure. The morphology and Crystal structure of TiO2samples and their chemical analysis was conducted using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrometer respectively. Results show agglomeration of spherical particles in all doped samples. Crystal structure in the doped samples reveals modified phases and major crystal phase identical to anatase. It is observed that the molar ratio of water to metal can control the nucleation and growth and prevents significant agglomeration of nanoparticles. More effective doping was recorded for samples with 0.5 % concentration. Effective hydroxyl group is detected in both 0.5% Ni and Co promising good photocatalytic material. SEM images of 0.2% Ni-doped sample shows smallest average particle size.

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