scholarly journals Selective Suppression of {112} Anatase Facet by Fluorination for Enhanced TiO2 Particle Size and Phase Stability at Elevated Temperatures

2021 ◽  
Author(s):  
Emerson Cristofer Kohlrausch ◽  
Roberto dos Reis ◽  
Rhys Lodge ◽  
Isabel Vicente ◽  
Alexandre Brolo ◽  
...  
Keyword(s):  
Particle Size ◽  
Phase Stability ◽  
Elevated Temperatures ◽  
Rutile Phase ◽  
Tio2 Particle ◽  
Recombination Rates ◽  
Selective Suppression ◽  
Photocatalytic Applications

Generally, anatase is the most desirable TiO2 polymorphic phase for photovoltaic and photocatalytic applications due to its higher photoconductivity and lower recombination rates compared to rutile phase. However, in applications...

scholarly journals Population Balance Application in TiO2 Particle Deagglomeration Process Modeling

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3523
Author(s):  
Radosław Krzosa ◽  
Łukasz Makowski ◽  
Wojciech Orciuch ◽  
Radosław Adamek
Keyword(s):  
Particle Size ◽  
Titanium Dioxide ◽  
Mechanistic Model ◽  
Population Balance ◽  
Tio2 Particle ◽  
Application Process ◽  
Titanium Dioxide Powder ◽  
Dioxide Powder ◽  
Computational Fluid Dynamics Cfd ◽  
Hydrodynamic Stresses

The deagglomeration of titanium-dioxide powder in water suspension performed in a stirring tank was investigated. Owing to the widespread applications of the deagglomeration process and titanium dioxide powder, new, more efficient devices and methods of predicting the process result are highly needed. A brief literature review of the application process, the device used, and process mechanism is presented herein. In the experiments, deagglomeration of the titanium dioxide suspension was performed. The change in particle size distribution in time was investigated for different impeller geometries and rotational speeds. The modification of impeller geometry allowed the improvement of the process of solid particle breakage. In the modelling part, numerical simulations of the chosen impeller geometries were performed using computational-fluid-dynamics (CFD) methods whereby the flow field, hydrodynamic stresses, and other useful parameters were calculated. Finally, based on the simulation results, the population-balance with a mechanistic model of suspension flow was developed. Model predictions of the change in particle size showed good agreement with the experimental data. Using the presented method in the process design allowed the prediction of the product size and the comparison of the efficiency of different impeller geometries.

Effect of particle size and strain on phase stability of (Li0.06 Na0.94) NbO3

2014 ◽  
Vol 115 (17) ◽  
pp. 174104 ◽  
Author(s):  
S. K. Mishra ◽  
A. B. Shinde ◽  
P. S. R. Krishna
Keyword(s):  
Particle Size ◽  
Phase Stability ◽  
Effect Of Particle Size

Rapid Synthesis and Characterization of Maghemite Nanoparticles

2008 ◽  
Vol 8 (2) ◽  
pp. 861-866 ◽  
Author(s):  
Bilsen Tural ◽  
Macit Özenbaş ◽  
Selçuk Atalay ◽  
Mürvet Volkan
Keyword(s):  
Particle Size ◽  
Elevated Temperatures ◽  
Sol Gel ◽  
Volume Ratio ◽  
Silica Matrix ◽  
Superparamagnetic Nanoparticles ◽  
Maghemite Nanoparticles ◽  
Gelation Temperature ◽  
Iron Oxide Particles ◽  
Evaporation Surface

Fe2O3–SiO2 nanocomposites were prepared by a sol–gel method using various evaporation surface to volume (S/V) ratios ranging from 0.03 to 0.2. The Fe2O3–SiO2 sols were gelated at various temperatures ranging from 50 °C to 70 °C, and subsequently they were calcined in air at 400 °C for 4 hours. The structure and the magnetic properties of the prepared Fe2O3–SiO2 nanocomposites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) measurements. The gelation temperature of the Fe2O3–SiO2 sols influenced strongly the particle size and crystallinity of the maghemite nanoparticles. It was observed that the particle size of maghemite nanoparticles increased with the increasing of the gelation temperature of the sols, which may be due to the agglomeration of the maghemite particles at elevated temperatures inside the microporosity of the silica matrix during the gelation process, and the subsequent calcination of these gels at 400 °C resulted in the formation of large size iron oxide particles. Magnetization studies at temperatures of 10, 195, and 300 K showed superparamagnetic behavior for all the nanocomposites prepared using the evaporation surface to volume ratio (S/V) of 0.1, 0.2, 0.09, and 0.08. The saturation magnetization, Ms, values measured at 10K were 5.5, 8.5, and 9.5 emu/g, for the samples gelated at 50, 60, and 70 °C, respectively. At the gelation temperature of 70 °C, γ-Fe2O3 crystalline superparamagnetic nanoparticles with the particle size of 9±2 nm were formed in 12 hours for the samples prepared at the S/V ratio of 0.2.

scholarly journals Blend of natural waxes as a matrix for aroma encapsulation

2017 ◽  
Vol 15 (2) ◽  
pp. 103-111
Author(s):  
Jelena Milanovic ◽  
Gordana Ilic-Sevic ◽  
Marijana Gavrilovic ◽  
Milutin Milosavljevic ◽  
Branko Bugarski
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Elevated Temperatures ◽  
Thermal Characteristics ◽  
Feed Additives ◽  
Morphological Properties ◽  
Particle Size Range ◽  
Carnauba Wax ◽  
Potential Applications

In this study, the possibility of using a blend of natural waxes (bees and carnauba) for encapsulation of some aroma compounds was investigated. Melt dispersion/melt solidification technique was applied for microbeads production. Since one of the most important characteristics of the particles are the size and shape, particle size distribution as well as morphological properties are tested. Thermal characteristics are also examined as significant properties for thermal behavior at elevated temperatures, important for application of encapsulated particles in food production processes. Different contents of the carnauba wax in the mixture with beeswax are investigated, from 10% to 50% (w/w). Since one of the potential applications of the encapsulated aroma is in feed additives production, the targeted particle size range was under 300 ?m to be suitable for handling and mixing with other powder substances. According to the obtained results, a higher carnauba wax content in the wax blend had an impact on particle size distribution. Also, it had an impact on the surface morphology and thermal properties. The obtained results may contribute to the development of methods of encapsulation of hydrophobic aromas in the natural wax matrix.

scholarly journals Influence of nitrogen and air atmosphere during thermal treatment on micro and nano sized powders and sintered TiO2 specimens

2014 ◽  
Vol 46 (3) ◽  
pp. 365-375
Author(s):  
N. Labus ◽  
S. Mentus ◽  
Z.Z. Djuric ◽  
M.V. Nikolic
Keyword(s):  
Phase Transition ◽  
Particle Size ◽  
Powder Particle ◽  
Rutile Phase ◽  
Nitrogen Atmosphere ◽  
Powder Particle Size ◽  
Nano Tio2 ◽  
Thermo Gravimetric ◽  
Air Atmosphere ◽  
Thermal Techniques

The influence of air and nitrogen atmosphere during heating on TiO2 nano and micro sized powders as well as sintered polycrystalline specimens was analyzed. Sintering of TiO2 nano and micro powders in air atmosphere was monitored in a dilatometer. Non compacted nano and micro powders were analyzed separately in air and nitrogen atmospheres during heating using thermo gravimetric (TG) and differential thermal analysis (DTA). The anatase to rutile phase transition temperature interval is influenced by the powder particle size and atmosphere change. At lower temperatures for nano TiO2 powder a second order phase transition was detected by both thermal techniques. Polycrystalline specimens obtained by sintering from nano powders were reheated in the dilatometer in nitrogen and air atmosphere, and their shrinkage is found to be different. Powder particle size influence, as well as the air and nitrogen atmosphere influence was discussed.

Phase Stability and High Temperature Tensile Properties of W doped gamma-TiAl

2000 ◽  
Vol 646 ◽  
Author(s):  
Keizo Hashimoto ◽  
Hirohiko Hirata ◽  
Youji Mizuhara
Keyword(s):  
High Temperature ◽  
Phase Stability ◽  
Ternary Phase ◽  
Elevated Temperatures ◽  
Ternary Phase Diagram ◽  
Arc Melting ◽  
Structural Applications ◽  
High Temperature Tensile ◽  
Promising Alloys ◽  
High Temperature Tensile Properties

ABSTRACTTungsten (W) doped γ-TiAl is one of promising alloys among many other proposed TiAl base alloys, for the purpose of structural applications at elevated temperatures. Ingots of W doped γ-TiAl were produced by plasma arc melting, followed by homogenizing heat treatment and isothermal forging to control their microstructures. The phase stability of W doped γ-TiAl has been studied quantitatively, using the specimens quenched from 1273 K. Equilibrium compositions of consisting phases were analyzed by means of EDS analysis in a TEM. An isothermal cross section of the Ti-Al-W ternary phase diagram at 1273K has been proposed based on the experimental observations. Small amounts of W addition (< 1at%) to Ti-48at%Al cause a phase shift from α2+γ to α2+β+γ, which suggests that W is the strongest β stabilizer among transition metals, such as Cr and Mo. Mechanical property measurements of W doped γ-TiAl show that the high temperature tensile strength has been improved by the W addition. Relationships between the microstructures and the mechanical properties of W doped γ-TiAl have been discussed.

Effect of Warm Rolling on Microstructure and High Temperature Mechanical Behavior of a Nano-Structured Al-8Fe-2Mo-2V-1Zr Alloy

2005 ◽  
Vol 486-487 ◽  
pp. 411-414 ◽  
Author(s):  
Won Yong Kim ◽  
Jae Sung Park ◽  
Mok Soon Kim
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Elevated Temperatures ◽  
Hot Extrusion ◽  
Warm Rolling ◽  
Spray Forming ◽  
Grain Structure ◽  
Average Grain Size ◽  
Two Samples ◽  
Additional Process

Mechanical properties of a nano-structured Al-8Fe-2Mo-2V-1Zr alloy produced by spray forming and subsequent hot-extrusion at 420°C were investigated in terms of tensile test as a function of temperature. Warm rolling was adapted as an additional process to expect further refinement in microstructure. Well-defined equiaxed grain structure and finely distributed dispersoids with nano-scale in particle size were observed in the spray formed and hot extruded sample (as-received sample). The average grain size and particle size were measured to 500 nm and 50 nm, respectively. While it was found that warm rolling gives rise to precipitate fine dispersoids less than 10 nm without influencing the grain size of matrix phase, in the temperature range of RT∼150°C, distinguishable changes in ultimate tensile strength were not found between the as-received and warm-rolled samples. At elevated temperatures ranging from 350 to 550°C, warm-rolled sample showed a higher value of elongation than as-received one although similar values of elongation were observed between two samples at temperatures lower than 350°C.

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