scholarly journals Mossbauer Investigations in Hematite Nanoparticles

2021 ◽  
Vol 12 (4) ◽  
pp. 4626-4636
Keyword(s):  
Sol Gel ◽  
Weighted Average ◽  
Ferromagnetic Behavior ◽  
Morin Transition ◽  
Hematite Nanoparticles ◽  
Hematite Phase ◽  
Potential Applications ◽  
Average Size ◽  
20 Nm ◽  
Structural Characterizations

Hematite nanoparticles of average size 20 nm were synthesized using the sol-gel method, and the structural characterizations were conducted using XRD and TEM. The XRD profile revealed a small fraction of the maghemite phase and the main hematite phase. Mössbauer spectroscopy was used to study the magnetic structure of the particles and revealed a third but very slight non-magnetic phase. Mössbauer spectrum shows 35% of the nanoparticles exhibiting superparamagnetism. The weighted average Morin transition temperature for the particles determined by Mössbauer is 262 K, which is remarkably similar to the bulk value and higher than the Morin transition determined by VSM (about 250 K). The reported findings on the hematite nanoparticles will help understand the enhanced ferromagnetic behavior of the hematite nanoparticles at room temperature, which is crucial for potential applications.

scholarly journals Synthesis of SiO2-TiO2:Yb3+ glass-ceramics and characterization of structure and optical properties

2017 ◽  
Vol 1 (T1) ◽  
pp. 114-121
Author(s):  
Thanh Tat Huynh ◽  
Van Thi Thanh Tran
Keyword(s):  
Sol Gel ◽  
Glass Ceramics ◽  
Xrd Analysis ◽  
Silica Matrix ◽  
Photoluminescence Intensity ◽  
Raman Spectroscopic ◽  
Characteristic Emission ◽  
Ft Ir ◽  
Average Size ◽  
20 Nm

In this work, the monoliths of 85 % SiO2-15 % TiO2 doped Yb3+ ions at different contents have been prepared by sol-gel method. The measurement of FT-IR, Raman spectroscopic and XRD analysis show the formation of anatase TiO2 nanocrystals with average size about 15–20 nm in silica matrix. Moreover, the pyrochlore crystals of Yb2Ti2O7 begin to form in the samples when content of Yb3+ reaches to 1 mol %. TiO2 Yb3+ 2F7/2 2F5/2 truyền năng lƣợng kích thích UV EV EC mức khuyết tật 974 nm The energy transferred from TiO2 crystals to Yb3+ ions is proven by the characteristic emission spectrum of Yb3+ at the wavelength of 980 nm when the samples are excited by the wavelength of 300 nm. The photoluminescence intensity is highest at 0.1% mol of Yb3+ and gradually decreases with doping content

Synthesis of Monodisperse Fe3O4 and MnFe2O4 Nanospheres by Using a Solvothermal Reduction Method

2011 ◽  
Vol 181-182 ◽  
pp. 393-396 ◽  
Author(s):  
Gui Hua Ren ◽  
Zhi Song Yu
Keyword(s):  
Reduction Method ◽  
Hydrothermal Reaction ◽  
Spinel Ferrite ◽  
Sol Gel ◽  
Decomposition Methods ◽  
Spinel Ferrites ◽  
Storage Devices ◽  
Auto Combustion ◽  
Potential Applications ◽  
Average Size

The spinel ferrites, MFe2O4(where M=Fe, Mn, Co, Ni, Zn, Mg, etc.) have attracted considerable interest during the last few decades due to their potential applications in high frequency transformers, filters, high density storage devices, and microwave applications. In the latest several years, many synthesis technologies such as sol-gel, auto-combustion, thermal decomposition methods and hydrothermal reaction have been developed to prepare spinel ferrite nanoparticles. In this paper, the spinel ferrites Fe3O4and MnFe2O4nanoparticles were synthesized by using a solvothermal reduction method. X-ray diffraction (XRD) and Raman analysis shows that all the peaks are close to the data for Fe3O4and MnFe2O4, indicating the prepared particles are single phase. The scan electronic microscopy (SEM) shows that the prepared Fe3O4and MnFe2O4are monodisperse nanospheres and with the average size of around 300nm.

Synthesis of Hollow ß-Phase GeO2 in Microemulsion

2013 ◽  
Vol 669 ◽  
pp. 360-365
Author(s):  
Xu Zou ◽  
Bing Bing Liu ◽  
Wei Wu ◽  
Dong Mei Li ◽  
Quan Jun Li ◽  
...  
Keyword(s):  
Optical Properties ◽  
Ostwald Ripening ◽  
Hollow Structure ◽  
Simple Method ◽  
Light Emitting ◽  
Hollow Interior ◽  
Potential Applications ◽  
One Step ◽  
Average Size ◽  
20 Nm

We fabricated mono-dispersed hollow waxberry shaped ß-quartz GeO2by a facile one-step synthesis in emulsion at room temperature. TEM images indicated that hollow waxberry shaped GeO2were consisted of nano-sphere whose average size were estimated to be 20 nm. The growth mechanism and optical properties of the products were also investigated. The possible formation mechanism of the hollow interior is proposed as the Ostwald ripening. The optical properties of the ß-GeO2nanoparticles with hollow shapes were also studied with photoluminescence spectrum, which reveals a broad emission, suggesting potential applications in electronic and optoelectronic nanodevices. These attractive results provide us a new simple method further used to fabricate other specific hollow structure and indicate hollow waxberry shaped GeO2may have potential applications in light-emitting nanodevices.

Effect of fuel content on formation of zinc aluminate nano and micro-particles synthesised by high rate sol–gel autoignition of glycine-nitrates

2016 ◽  
Vol 70 (3) ◽  
Author(s):  
Shiva Salem
Keyword(s):  
Thermal Analyses ◽  
Sol Gel ◽  
High Rate ◽  
Zinc Aluminate ◽  
X Ray Diffraction ◽  
Micro Particles ◽  
Transmission Electron ◽  
Xrd Patterns ◽  
Average Size ◽  
20 Nm

AbstractThe autoignition technique using glycine as fuel and related nitrate salts as an oxidiser is able to produce zinc aluminate spinel. The precursors were synthesised with lean and rich fuel at pH of 7.0 and the materials so obtained were calcined at various temperatures ranging from 600-1200°C. The autoignition process of precursors was studied by the simultaneous thermo-gravimetric and differential thermal analyses to determine the ignition mechanism. The calcined powders were characterised by X-ray diffraction, Brunauer-Emmett-Teller technique and transmission electron microscopy. The product contains nano-sized particles with an average size of approximately 20 nm. The XRD patterns showed the formation of ZnO in the powder obtained by the fuel-rich precursor and calcined at 600°C which disappears at 800°C due to solid-state reaction and proper crystallisation after heat treatment. The results presented here can be useful in manufacturing nano and micro-sized ZnAl

scholarly journals The Structural and Magnetic Properties of the Double Rearth Elements La1−xNdxFeO3 Nanoparticles

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Nguyen Thi Thuy ◽  
Bach Thanh Cong ◽  
Dang Le Minh
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Magnetic Property ◽  
Room Temperature ◽  
Sol Gel ◽  
Ferromagnetic Behavior ◽  
Orthorhombic Structure ◽  
Nanosized Powders ◽  
Structural And Magnetic Properties ◽  
20 Nm

The double rearth elements La1−xNdxFeO3 (0≤x≤0.5) nanosized powders with orthorhombic structure were prepared by sol-gel method. The particle size of the La1−xNdxFeO3 powder is about 20 nm. The doping of the second rearth element in the A position of the compound ABO3 influenced the crystalline structure and magnetic property of the samples. The M(H) dependence shows that the nanosized La1−xNdxFeO3 samples exhibit ferromagnetic behavior in the room temperature and the M(H) curves are well fitted by Langevin functions.

Field-dependent Morin Transition and Temperature-Dependent Spin-flop in Synthetic Hematite Nanoparticles

2019 ◽  
Vol 16 ◽  
Author(s):  
Ihab M. Obaidat ◽  
Sulaiman Alaabed ◽  
Imad A. Al-Omari ◽  
Venkatesha Narayanaswamy ◽  
Bashar Issa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Transition Temperature ◽  
Temperature Dependent ◽  
Morin Transition ◽  
Hematite Nanoparticles ◽  
Xrd Patterns ◽  
20 Nm ◽  
Applied Fields ◽  
Nano Size

Background: In nano-size α-Fe2O3 particles, Morin transition temperature was reported to be suppressed. This suppression of the TM in nano-size α-Fe2O3 was suggested to be due to high internal strain and to the enhanced role of surface spins because of the enhanced surface to volume ratio. It was reported that for nanoparticles of diameters less than 20 nm, no Morin transition was observed and the antiferromagnetic phase disappears. In addition, annealing of samples was reported to result in both an increase of TM and a sharper transition which were attributed to reduction in de¬fects, crystal growth, or both. Objective: In this work we investigated the role of applied magnetic field on TM, the extent of the Morin transition, thermal hysteresis, and the spin-flop field in synthetic α-Fe2O3 nanoparticles of diameter around 20 nm. Methods: Hematite nanoparticles were synthesized using sol-gel method. Morphology and structural studies of the particles were done using TEM, and XRD, respectively. The XRD patterns confirm that the particles are hematite with a very small maghemite phase. The average size of the nanoparticles is estimated from both TEM images and XRD patterns to be around 20 nm. The magnetization versus temperature measurements were conducted upon heating from 5 K to 400 K and cooling down back to 5 K at several applied fields between 50 Oe and 500 Oe. Magnetization versus magnetic field measurements between -5 T and +5 T were conducted at several temperatures in the temperature range of 2-300 K. Results: We report three significant findings in these hematite nanoparticles. First, we report the occurrence of Morin transition in hematite nanoparticles of such size. Second, we report the slight field dependence of Morin transition temperature. Third, we report the strong temperature dependence of the spin-flop. Zero-field-cooled magnetization versus temperature measurements were conducted at several applied magnetic fields. Conclusion: From the magnetization versus temperature curves, Morin transition was observed to occur at all applied fields at Morin transition temperature, TM which is around 250 K with slight field dependence. From the magnetization versus magnetic field curves, spin-flop in the antiferromagnetic state was observed and found to be strongly temperature dependent. The results are discussed in terms of three components of magnetic phase in our sample. These are, the paramagnetic, soft ferromagnetic, and hard ferromagnetic components.

Ultradispersed Powdery Y2O3-Bi2O3-ZnO Composition with High Chemical Homogeneity for Fine-Grained Ceramics

2014 ◽  
Vol 87 ◽  
pp. 36-41
Author(s):  
Elena A. Trusova ◽  
Kirill V. Vokhmintcev ◽  
Aleksey N. Kirichenko
Keyword(s):  
Sol Gel ◽  
Particle Sizes ◽  
High Chemical ◽  
Chemical Homogeneity ◽  
Fine Grained ◽  
Gel Technique ◽  
Average Size ◽  
20 Nm ◽  
New Generation ◽  
Xrd And Tem

The technologically acceptable modified sol-gel technique was developed for obtaining the ultradispersed powdery composition Y2O3-Bi2O3-ZnO, which is promising new generation material for photocatalysts and solar cells. The solution for preparing a sintering composition with a high chemical homogeneity was proposed to provide using ultradispersed powders consisting of ZnO nanoparticles (40-70 nm), decorating with Bi2O3 and Y2O3 particles with average size of 4-20 nm. All synthesized powders were characterized by XRD and TEM methods. It was found that ZnO surface differently affects the dispersity of Bi2O3 and Y2O3 in the composites. TEM microphotographs show that the Bi2O3 particles uniformly distributed over ZnO surface. The Bi2O3 particle size on ZnO surface was 5-11 nm, which is significantly less than in the single powder of Bi2O3 (110-130 nm). However, in the case of Y2O3 similar effect was not observed, and average size of its crystallites was 5-12 nm, which agrees well with particle sizes in single powder.

scholarly journals Upconversion Luminescence of Silica–Calcia Nanoparticles Co-doped with Tm3+ and Yb3+ Ions

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 937
Author(s):  
Katarzyna Halubek-Gluchowska ◽  
Damian Szymański ◽  
Thi Ngoc Lam Tran ◽  
Maurizio Ferrari ◽  
Anna Lukowiak
Keyword(s):  
Energy Transfer ◽  
Near Infrared ◽  
Upconversion Luminescence ◽  
Sol Gel ◽  
Emission Spectra ◽  
Transmission Electron ◽  
Characteristic Emission ◽  
Diffraction Patterns ◽  
Size Of Particles ◽  
Average Size

Looking for upconverting biocompatible nanoparticles, we have prepared by the sol–gel method, silica–calcia glass nanopowders doped with different concentration of Tm3+ and Yb3+ ions (Tm3+ from 0.15 mol% up to 0.5 mol% and Yb3+ from 1 mol% up to 4 mol%) and characterized their structure, morphology, and optical properties. X-ray diffraction patterns indicated an amorphous phase of the silica-based glass with partial crystallization of samples with a higher content of lanthanides ions. Transmission electron microscopy images showed that the average size of particles decreased with increasing lanthanides content. The upconversion (UC) emission spectra and fluorescence lifetimes were registered under near infrared excitation (980 nm) at room temperature to study the energy transfer between Yb3+ and Tm3+ at various active ions concentrations. Characteristic emission bands of Tm3+ ions in the range of 350 nm to 850 nm were observed. To understand the mechanism of Yb3+–Tm3+ UC energy transfer in the SiO2–CaO powders, the kinetics of luminescence decays were studied.

Direct Synthesis of 3,5-Dinitropyrazole Catalyzed by Newly Sulfated Nanosolid Superacid TiO2/ SO

2011 ◽  
Vol 391-392 ◽  
pp. 1296-1301
Author(s):  
Li Min Xi ◽  
Xin Xin Zhang
Keyword(s):  
Direct Synthesis ◽  
Sol Gel ◽  
Acid Base ◽  
Direct Transformation ◽  
Acid Base Titration ◽  
Optimal Reaction Condition ◽  
Superacid Catalyst ◽  
Average Size ◽  
Optimal Reaction ◽  
Xrd And Tem

The newly sulfated nanosolid superacid TiO2/SO4 prepared by sol-gel method was broadly characterized by acid base titration, XRD and TEM, which identified that the superfine solid TiO2/SO4 showing good dispersibility with average size of 27 nm belongs to kind of crystalline nanoparticles. With the help of the catalyst TiO2/SO4, the optimal reaction condition for direct transformation of pyrazole and nitrosonitric acid into 3, 5-Dinitropyrazole was n (pyrazol)=0.10 mol, m (TiO2/SO4 )＝1.5g, V(n-octannol)＝90mL, and V(nitrosonitric acid)＝50mL. Moreover, the optimal yield of the catalytic reaction reached up to 59.4% when the reaction time is 7 hours. The nanosolid superacid catalyst is still of high activity after regenerating eight times by calcination at 600。C.

Formation of Core-Shell Nanoparticles by Laser Ablation of Copper and Brass in Liquids

2005 ◽  
Vol 106 ◽  
pp. 23-26 ◽  
Author(s):  
P.V. Kazakevich ◽  
A.V. Simakin ◽  
V.V. Voronov ◽  
G.A. Shafeev ◽  
D. Starikov ◽  
...  
Keyword(s):  
Core Shell ◽  
Copper Vapour Laser ◽  
Shell Nanoparticles ◽  
Liquid Environment ◽  
Pulsed Nd:Yag Laser ◽  
Plasmon Peak ◽  
Average Size ◽  
Core Shell Nanoparticles ◽  
20 Nm ◽  
Surrounding Liquid

Experimental results are presented on the ablation of copper and brass targets in a liquid environment: ethanol, acetone, or water by irradiation with either a pulsed copper vapour laser (0.51 μm) or a pulsed Nd:YAG laser (1.06 μm). The ablated material was ejected into the surrounding liquid as nanoparticles of average size 20 nm. The nanoparticle composition depends on the nature of the liquid. Ablation of 60%Cu, 40%Zn brass in ethanol results in formation of core-shell nanoparticles. Brass nanoparticles were characterized by a well-defined plasmon peak at 510-520 nm.

Sign in / Sign up

Export Citation Format

Share Document