Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase

2014 ◽  
Vol 43 (16) ◽  
pp. 6139-6147 ◽  
Author(s):  
Wei Yu ◽  
Wen Xu ◽  
Hongwei Song ◽  
Shuang Zhang
Keyword(s):  
Particle Size ◽  
Oleic Acid ◽  
Crystalline Phase ◽  
Upconversion Luminescence ◽  
Temperature Dependent ◽  
Crystalline Phases ◽  
Upconversion Nanocrystals

Oleic acid-capped NaYF4:Yb3+/Er3+ upconversion nanocrystals with different sizes and crystalline phases were prepared, and their temperature-dependent upconversion luminescence and dynamics were studied.

scholarly journals Influence of microstructure and crystalline phases on impedance spectra of sodium conducting glass ceramics produced from glass powder

2021 ◽  
Author(s):  
Mihails Kusnezoff ◽  
Dörte Wagner ◽  
Jochen Schilm ◽  
Christian Heubner ◽  
Björn Matthey ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Crystalline Phase ◽  
Glass Phase ◽  
Boundary Resistance ◽  
Phase Content ◽  
Impedance Spectra ◽  
Temperature Dependent ◽  
Crystalline Phases ◽  
Parent Glass ◽  
Ion Conducting

AbstractCrystallization of highly ionic conductive N5 (Na5YSi4O12) phase from melted Na3+3x-1Y1-xPySi3-yO9 parent glass provides an attractive pathway for cost-effective manufacturing of Na-ion conducting thin electrolyte substrates. The temperature-dependent crystallization of parent glass results in several crystalline phases in the microstructure (N3 (Na3YSi2O7), N5 and N8 (Na8.1Y Si6O18) phases) as well as in rest glass phase with temperature dependent viscosity. The electrical properties of dense parent glass and of compositions densified and crystallized at 700 °C, 800 °C, 900 °C, 1000 °C, and 1100 °C are investigated by impedance spectroscopy and linked to their microstructure and crystalline phase content determined by Rietveld refinement. The parent glass has high isolation resistance and predominantly electrons as charge carriers. For sintering at ≥ 900 °C, sufficient N5 phase content is formed to exceed the percolation limit and form ion-conducting pathways. At the same time, the highest content of crystalline phase and the lowest grain boundary resistance are observed. Further increase of the sintering temperature leads to a decrease of the grain resistance and an increase of grain boundary resistance. The grain boundary resistance increases remarkably for samples sintered at 1100 °C due to softening of the residual glass phase and wetting of the grain boundaries. The conductivity of fully crystallized N5 phase (grain conductivity) is calculated from thorough impedance spectra analysis using its volume content estimated from Rietveld analysis, density measurements and assuming reasonable tortuosity to 2.8 10−3 S cm−1 at room temperature. The excellent conductivity and easy processing demonstrate the great potential for the use of this phase in the preparation of solid-state sodium electrolytes.

Temperature-dependent Upconversion Luminescence of NaYF4:Yb3+,Er3+ Nanoparticles

2013 ◽  
Vol 42 (3) ◽  
pp. 310-312 ◽  
Author(s):  
Junwei Zhao ◽  
Haitao Li ◽  
Qinghui Zeng ◽  
Kai Song ◽  
Xiaofeng Wang ◽  
...  
Keyword(s):  
Upconversion Luminescence ◽  
Temperature Dependent

Effect of Annealing Temperature on Phase Transition of Nanoalumina Synthesized by Auto-Combustion Route

2016 ◽  
Vol 41 ◽  
pp. 74-86 ◽  
Author(s):  
Muhammad Adil ◽  
Hasnah Mohd Zaid ◽  
Kean Chuan Lee ◽  
Noor Rasyada Ahmad Latiff
Keyword(s):  
Phase Transition ◽  
Particle Size ◽  
Sol Gel ◽  
Thermo Gravimetric Analysis ◽  
Amorphous State ◽  
Specific Area ◽  
Combustion Method ◽  
Gravimetric Analysis ◽  
Crystalline Phases ◽  
Auto Combustion

Nanocrystalline Al2O3 powder has been successfully synthesized by a simple and fast sol-gel auto-combustion method. The transformation of crystalline phases of as-synthesized nano powders was investigated through X-ray diffraction in terms of their crystallinity and crystallite size. Subsequently, a detailed transmission electron microscopy (TEM) investigation, including specific area electron diffraction (SAED) analysis revealed the crystallographic alterations and morphological information even at lattice scale which co-include the XRD analysis. The results obtained allow to explain the evolution of an amorphous state into different crystalline phases with increased calcining temperature; and their relation to particle size. The particle size is found to be closely related to phase transition of Al2O3 from γ → δ → θ → κ →α. The existence of distinctive bonds and band energy were studied by employing Fourier-transform infrared spectroscopy (FTIR) and UV-visible spectroscopy, respectively. On the other hand, thermo gravimetric analysis (TGA) had also been performed to confirm the phase purity of nano powder.

Microwave Synthesis of Silicon Carbide Nano Powders with Silicon and Carbon

2014 ◽  
Vol 602-603 ◽  
pp. 118-121
Author(s):  
You Jun Lu ◽  
Hong Fang Shen ◽  
Sheng Wei Guo
Keyword(s):  
Silicon Carbide ◽  
Particle Size ◽  
Microwave Heating ◽  
Chemical Reaction ◽  
Crystalline Phase ◽  
Microwave Synthesis ◽  
Time Effects ◽  
Xrd Patterns

Nanosized silicon carbide powders were synthesized from a mixture of silicon and carbon by microwave heating methods. The Result Indicates SiC can be formed at lower temperatures by using the Si-C reaction at 1200°C for 30min. XRD patterns shows that SiC peaks appeared as the only crystalline phase. SEM photo shows the particle size was 100～200 nanometer. At the same time, Effects of chemical reaction of silicon and carbon was researched by mechanical activated microwave synthesis.

scholarly journals LOW-TEMPERATURE SYNTHESIS OF SUPERPARAMAGNETIC Zn0.8Ni0.2Fe2O4 FERRITE NANOPARTICLES

2018 ◽  
Vol 56 (1) ◽  
pp. 31
Author(s):  
Luong Thi Quynh Anh ◽  
Nguyen Van Dan ◽  
Do Minh Nghiep
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Oleic Acid ◽  
Low Temperature ◽  
Coercive Force ◽  
Saturation Magnetization ◽  
Ferrite Nanoparticles ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Co Precipitation

The crystalline nanoparticles of Ni0.2Zn0.8Fe2O4 ferrite were synthesized by chemical co-precipitation with precursor concentration of 0.1M, then modified by 0.25M solution of oleic acid in pentanol, finally heated at temperatures 120, 140, 160 and 180oC for 6h in autoclave. The XRD, EDS and TEM confirmed that all of samples are crystalline and their particle size are 6, 6.5, 7 and 8 nm. The magnetic properties showed that the coercive force, the remanence of samples are about zero, the saturation magnetization Ms has values from 14.20 to 27.12 emu/g.

scholarly journals Ex-vivo Ex-Vivo Absorption Study of a Novel Dabigatran Etexilate Loaded Nanostructured Lipid Carrier Using Non-Everted Intestinal Sac Model

2019 ◽  
Vol 28 (2) ◽  
pp. 37-45
Author(s):  
Haithem N Abed ◽  
Ahmed A. Hussein
Keyword(s):  
Particle Size ◽  
Oleic Acid ◽  
Zeta Potential ◽  
Oral Absorption ◽  
Ex Vivo ◽  
Dabigatran Etexilate ◽  
Entrapment Efficiency ◽  
Nanostructured Lipid Carrier ◽  
Loading Capacity ◽  
Intestinal Permeation

Abstract The purpose of our study was to develop Dabigatran Etexilate loaded nanostructured lipid carriers (DE-NLCs) using Glyceryl monostearate and Oleic acid as lipid matrix, and to estimate the potential of the developed delivery system to improve oral absorption of low bioavailability drug, different Oleic acid ratios effect on particle size, zeta potential, entrapment efficiency and loading capacity were studied, the optimized DE-NLCs shows a particle size within the nanorange, the zeta potential (ZP) was 33.81±0.73mV with drug entrapment efficiency (EE%) of  92.42±2.31% and a loading capacity (DL%) of 7.69±0.17%. about 92% of drug was released in 24hr in a controlled manner, the ex-vivo intestinal permeation study using the non-everted sac model shows four folds increment in the permeation of DE-NLCs compared to dabigatran etexilate suspension (DE-S).

Microemulsion-assisted synthesis of ultrafine Li4Ti5O12/C nanocomposite with oleic acid as carbon precursor and particle size controller

2014 ◽  
Vol 246 ◽  
pp. 213-218 ◽  
Author(s):  
Yuan Wang ◽  
Haibo Rong ◽  
Benzhen Li ◽  
Lidan Xing ◽  
Xiaoping Li ◽  
...  
Keyword(s):  
Particle Size ◽  
Oleic Acid ◽  
Carbon Precursor

Investigation of Isothermal Treatment on the Structural, Microstructure and Physical Properties of Li2O-Al2O3-SiO2 Glass-Ceramic

2020 ◽  
Author(s):  
Husniyah Aliyah Lutpi ◽  
Hasmaliza Mohamad ◽  
Tuti Katrina Abdullah
Keyword(s):  
Grain Size ◽  
Elevated Temperature ◽  
Physical Properties ◽  
Thermal Shock ◽  
Glass Ceramic ◽  
Crystalline Phase ◽  
Sintering Temperature ◽  
Isothermal Treatment ◽  
Crystalline Phases ◽  
Average Grain Size

Abstract The present work aims to investigate the effects of isothermal treatment on the structural, microstructure and physical properties of Li2O-Al2O3-SiO2 glass-ceramic. Sintering temperature plays a major role in producing the desired lithium aluminosilicate (LAS) glass-ceramic crystalline phases. This work also aims to achieve a low thermal expansion coefficient β-spodumene (LiAlSi2O6) crystalline phase with improved density and lower porosity, which can be useful for the applications with thermal shock properties. The LAS glass-ceramic was fabricated by the melt-quenching technique at 1550 °C for 5 h before being isothermally sintered at an elevated temperature of 900 to 1200 °C for 30 min. The evolution of LAS glass-ceramic crystalline phases was identified using differential thermal analysis and the β-spodumene exothermic peak appeared at 999 °C. Based on the X-ray diffraction results, the complete transformation of β-spodumene from high-quartz solid solution (β-quartz) occurred at 1000 °C. However, the sintering temperature did not change the crystalline phase when sintered above 1000 °C, but the lattice parameter of the crystal structure was slightly altered. Moreover, it was observed that the LAS glass-ceramic grain size increased with temperature, whereby the smallest average grain size recorded (0.61 µm) for LAS glass-ceramic sintered at 1100 °C. Meanwhile, the fully densified LAS glass-ceramic at 1100 ° C was measured at 2.47 g/cm3 with 0.52% porosity. The isothermal treatment at elevated temperature indicated that sintering at 1100 °C provided a denser, less porous, and small average grain size which is preferred for thermal shock resistance applications.

FORMATION OF IRON SULFIDES BY SULPHATE-REDUCING BACTERIA FROM GEOTHERMAL ECOSYSTEMS

2020 ◽  
pp. 367-368
Author(s):  
D. Antsiferov ◽  
A. Lukina ◽  
O. Ikkert
Keyword(s):  
Cell Surface ◽  
Crystalline Phase ◽  
Periplasmic Space ◽  
Iron Sulfides ◽  
Crystalline Phases ◽  
Sulphate Reducing Bacteria ◽  
Physicochemical Conditions ◽  
Reducing Bacteria

Crystalline phases in biogenic sediments formed by Desulfotomaculum sp. DPr and Desulfovibrio sp. KZ1 from geothermal sources were studied. Marcasite (FeS2), melnikovite (FeSххH2O) and greigite (Fe3S4) were detected. Composition of the crystalline phase depends on the physicochemical conditions of the environment. The association of crystals with the cell surface, membranes and periplasmic space was revealed. Intracellular crystallization presumably involves systems responsible for the transport or cation chelation.

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