Variable Temperature Study of Au and Au-Pt Nanoparticles on Selected Oxide Supports

2010 ◽  
Vol 1279 ◽  
Author(s):  
D. Barrett ◽  
P. Franklyn ◽  
M. Scurrell
Keyword(s):  
Particle Size ◽  
Variable Temperature ◽  
Anatase Phase ◽  
Pt Nanoparticles ◽  
Ammonium Hydroxide ◽  
Nano Particles ◽  
Oxide Supports ◽  
Temperature Range ◽  
Size Relationship ◽  
Relationship Of

AbstractWe report on the size relationship of Au and Au-Pt nanoparticles that were synthesised on silica and anatase phase titania supports. Deposition-precipitation (DP) of metal chlorides with the addition of urea and ammonium hydroxide was used to produce the nanoparticles. The relative particle size relationship of the Au and Au-Pt nano particles (NP's) was investigated, relating the Pt concentration and the support polymorph over a temperature range. It was found, with the use of in-situ variable temperature powder X-ray diffraction (VT-PXRD) and transmission electron microscopy (TEM), that the addition of Pt to the Au system corresponded to a reduction in particle size over a broad temperature range.

scholarly journals Reduction Mechanism of Fine Hematite Ore Particles in Suspension

2021 ◽  
Author(s):  
Zhiyuan Chen ◽  
Christiaan Zeilstra ◽  
Jan van der Stel ◽  
Jilt Sietsma ◽  
Yongxiang Yang
Keyword(s):  
Particle Size ◽  
Temperature Drop ◽  
Reduction Rate ◽  
Reduction Process ◽  
Reciprocal Relationship ◽  
Drop Tube ◽  
Surface Nucleation ◽  
Order Of Magnitude ◽  
Relationship Of ◽  
Kinetics Of

AbstractIn order to understand the pre-reduction behaviour of fine hematite particles in the HIsarna process, change of morphology, phase and crystallography during the reduction were investigated in the high temperature drop tube furnace. Polycrystalline magnetite shell formed within 200 ms during the reduction. The grain size of the magnetite is in the order of magnitude of 10 µm. Lath magnetite was observed in the partly reduced samples. The grain boundary of magnetite was reduced to molten FeO firstly, and then the particle turned to be a droplet. The Johnson-Mehl-Avrami-Kolmogorov model is proposed to describe the kinetics of the reduction process. Both bulk and surface nucleation occurred during the reduction, which leads to the effect of size on the reduction rate in the nucleation and growth process. As a result, the reduction rate constant of hematite particles increases with the increasing particle size until 85 µm. It then decreases with a reciprocal relationship of the particle size above 85 µm.

scholarly journals Electron donation of non-oxide supports boosts O2 activation on nano-platinum catalysts

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tao Gan ◽  
Jingxiu Yang ◽  
David Morris ◽  
Xuefeng Chu ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Catalytic Oxidation ◽  
Pt Nanoparticles ◽  
Catalytic Performance ◽  
Nitrogen Vacancy ◽  
Innovative Strategy ◽  
Oxide Supports ◽  
Heterogeneous Catalytic ◽  
Highly Active ◽  
Electron Sink ◽  
Nitrogen Vacancies

AbstractActivation of O2 is a critical step in heterogeneous catalytic oxidation. Here, the concept of increased electron donors induced by nitrogen vacancy is adopted to propose an efficient strategy to develop highly active and stable catalysts for molecular O2 activation. Carbon nitride with nitrogen vacancies is prepared to serve as a support as well as electron sink to construct a synergistic catalyst with Pt nanoparticles. Extensive characterizations combined with the first-principles calculations reveal that nitrogen vacancies with excess electrons could effectively stabilize metallic Pt nanoparticles by strong p-d coupling. The Pt atoms and the dangling carbon atoms surround the vacancy can synergistically donate electrons to the antibonding orbital of the adsorbed O2. This synergistic catalyst shows great enhancement of catalytic performance and durability in toluene oxidation. The introduction of electron-rich non-oxide substrate is an innovative strategy to develop active Pt-based oxidation catalysts, which could be conceivably extended to a variety of metal-based catalysts for catalytic oxidation.

scholarly journals Immobilization of Pt nanoparticles on hydrolyzed polyacrylonitrile-based nanofiber paper

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Soon Yeol Kwon ◽  
EunJu Ra ◽  
Dong Geon Jung ◽  
Seong Ho Kong
Keyword(s):  
Particle Size ◽  
Uniform Distribution ◽  
Pt Nanoparticles ◽  
Electrochemical Activity ◽  
Aggregate Formation ◽  
Free Standing ◽  
Pt Electrode ◽  
Catalytic Current ◽  
Nucleation Sites ◽  
Hydrolysis Of

AbstractThe electrochemical activity of catalysts strongly depends on the uniform distribution of monodisperse Pt nanoparticles without aggregates. Here, we propose a new hydrolysis-assisted smearing method for Pt loading on a free-standing paper-type electrode. Polyacrylonitrile (PAN)-based nanofiber paper was used as the electrode, and it acted as a Pt support. Hydrolysis of the electrode tripled the number of active nucleation sites for Pt adsorption on the PAN nanofibers, thereby significantly enhancing the wettability of the nanofibers. This facilitated the uniform distribution of Pt nanoparticles without aggregate formation up to 40 wt% (about 0.8 mg/cm2) with a particle size of about 3 nm. The catalytic current of the hydrolyzed Pt electrode in CH3OH/H2SO4 solution exceeded 213 mA/cm2 Pt mg, which was considerably greater than the current was 148 mA/cm2 Pt mg for an unhydrolyzed electrode.

The Relationship of Particle Size to Olfactory Nerve Uptake of a Non-Soluble Form of Manganese Into Brain

2002 ◽  
Vol 23 (2) ◽  
pp. 177-183 ◽  
Author(s):  
Laurence D. Fechter ◽  
David L. Johnson ◽  
Robert A. Lynch
Keyword(s):  
Particle Size ◽  
Olfactory Nerve ◽  
Soluble Form ◽  
Relationship Of ◽  
The Relationship

Substituent effects on the thermodynamic functions of ionization of metasubstituted anilinium ions

1968 ◽  
Vol 21 (4) ◽  
pp. 939 ◽  
Author(s):  
PD Bolton ◽  
FM Hall
Keyword(s):  
Linear Function ◽  
Thermodynamic Functions ◽  
Substituent Effects ◽  
Negative Slope ◽  
Hammett Equation ◽  
Reaction Parameter ◽  
Reaction Series ◽  
Acidity Constants ◽  
Temperature Range ◽  
Relationship Of

Thermodynamic acidity constants of the meta-methoxyanilinium, meta- chloroanilinium, meta-bromoanilinium, and meta-iodoanilinium ions have been measured spectrophotometrically over the temperature range 5-50� and those of the meta-nitroanilinium ion over the temperature range 5-60�. The thermodynamic functions of ionization, ΔG25, ΔH25, ΔS25, and ΔCp,25, have also been calculated for each ion. For a series of seven meta-substituted anilinium ions the acidity constants show close obedience to the Hammett equation over the temperature range 10-50� with the reaction parameter p being a precise linear function of 1/T. The same reaction series also shows a well-defined isoequilibrium relationship of negative slope.

SCREENING OF BIODEGRADABLE POLYMER AND MOST EFFECTIVE VARIABLES IN PREPARATION OF ESSENTIAL OIL LOADED NANO PARTICLES FOR PULMONARY DELIVERY USING TAGUCHI DESIGN

INDIAN DRUGS ◽  
2021 ◽  
Vol 58 (02) ◽  
pp. 68-75
Author(s):  
Avani Khristi ◽  
Lalit L. Jha ◽  
Abhay Dharamsi ◽  
Keyword(s):  
Particle Size ◽  
Essential Oil ◽  
Biodegradable Polymers ◽  
Drug Loading ◽  
Pulmonary Inflammation ◽  
Pulmonary Delivery ◽  
Entrapment Efficiency ◽  
Nano Particles ◽  
Favorable Conditions ◽  
Insoluble Polymers

The biodegradability of inhalable nanoparticles (NPs) is an important criterion in prevention of lung toxicity due to NPs which have been taken to cure the condition. Pulmonary inflammation may result due to non-biodegradation or insoluble polymers used to produce NPs. Biodegradable polymers are widely used for manufacturing safe drug-entrapped inhalable NPs for pulmonary delivery. Here in this study, for preparing ajwain essential oil loaded NPs for pulmonary delivery, biodegradable polymers chitosan, gelatin and alginic acid have been evaluated for suitability. Based on the results of trial batches prepared from each polymer, the responses particle size and entrapment efficiency were measured and compared. Out of the three polymers, chitosan was having very good entrapment efficiency, poly dispersive index, drug loading and zeta potential-favorable conditions for pulmonary delivery of essential oils. Further screening of most effective variables in manufacturing nano particles using chitosan, eight batches of nano particles have been prepared as per taguchi orthogonal 2 level array L8 experimental design (Design expert software, version 7.0) where two responses, particle size and entrapment efficiency, have been observed. Based on the results of eight batches, standard effects have been calculated and significant variables identified, for both particle size and entrapment efficiency, for further optimization under design of experiment.

Relationship of Electrical Properties and Partical Size of Piezoelectric Ceramics Fabricated by Digital Light Processing 3D Printing

2021 ◽  
Author(s):  
Kai Liu ◽  
Jiaming Hu ◽  
Yusheng Shi ◽  
Chenyang Zhou ◽  
Yunfei Sun ◽  
...  
Keyword(s):  
Particle Size ◽  
Electrical Properties ◽  
3D Printing ◽  
Piezoelectric Sensor ◽  
Piezoelectric Ceramics ◽  
Particle Sizes ◽  
Digital Light Processing ◽  
Relationship Of ◽  
Partical Size ◽  
Functional Ceramics

Abstract To improve electrical properties of BaTiO3 piezoelectric ceramics fabricated by 3D printing, effects of particle sizes was investigated on rheological and curing properties of ceramic slurries, electrical properties of BaTiO3 fabricated by Digital Light Processing 3D printing method. It was found that the curing ability of ceramic slurries decreased first and then increased with the increase of particle size from 136 nm to 1486 nm, while the viscosity of the slurries kept decreasing. When the particle size in a range of submicron, the grain size of sintered ceramics decreased from 13.27 μm to 6.84 μm as particle size increasing. Immediately, the relative density, piezoelectric constant, relative permittivity and remanent polarization of sintered ceramics were measured and it turns out to reach 95.32%, 161.4 pC/N, 1512 and 7.59 uC/cm2 respectively while using the BaTiO3 powder with particle sizes of 993 nm. Finally, a cellular structural BaTiO3 ceramics was fabricated by using optimized powder and process parameters and packaged as a piezoelectric sensor, showing a good function of force-electricity conversion. These results demonstrated the feasibility of fabricating high-quality functional ceramics with designed geometry by Digital Light Processing.

scholarly journals Ammoniacal System Mechanisms for Leaching Copper from Converter Slag

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 712
Author(s):  
Alvaro Aracena ◽  
Andrés Valencia ◽  
Oscar Jerez
Keyword(s):  
Particle Size ◽  
Converter Slag ◽  
Research Work ◽  
Ammonium Hydroxide ◽  
Copper Extraction ◽  
Solution Ph ◽  
Intraparticle Diffusion Model ◽  
Electron Microscopy Analysis ◽  
Leaching Solution ◽  
Conversion Stage

In pyrometallurgical processes refining copper, the main source of loss in the conversion stage is from slag. This paper reports on research work treating converter slag containing high percentages of copper (36 wt%) using ammonium hydroxide at room temperature. Variables analyzed are solution pH, agitation, temperature, NH4OH concentration and particle size. Results showed that the hydronium ion resulting from ammonium hydroxide dissociation was the main oxidant of copper compounds in slag, such as CuO, Cu2O and Cu, with the exception of CuFeO2. The particles contain a large amount of microcracks (porosity) in their refractory structure (analyzed by compositional image capture (BSE)). Thus, the diffusion of the leaching solution through the microcracks making contact with the copper oxides would be allowed. Leaching mechanisms were corroborated by X-ray diffraction and scanning electron microscopy analysis. Increasing temperature and NH4OH concentration while decreasing particle size obtained higher copper recoveries, reaching values of 84.8%. Under the same conditions, the main impurity (iron) was minimal (<2%). Solution pH also affected slag leaching. Agitation of the solution positively affected the rate of copper extraction. Leaching kinetics of the leaching solution through the porosity formed in the slag was analyzed under the intraparticle diffusion model. The reaction order was 1.2 with respect to the concentration of ammonium hydroxide and the model was inversely proportional to the square of the particle radius. The activation energy obtained was 42.3 kJ/mol for temperature range 283 to 333 K.

Relationship of Particle Size to Coccidiostatic Efficacy of Buquinolate

1969 ◽  
Vol 13 (2) ◽  
pp. 297 ◽  
Author(s):  
Michael K. Eckman ◽  
Robert E. Kohls ◽  
Richard P. Humphrey
Keyword(s):  
Particle Size ◽  
Relationship Of
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