Room-temperature synthesis of submicron platinum and palladium powders in glycols

1999 ◽  
Vol 14 (9) ◽  
pp. 3707-3712 ◽  
Author(s):  
K. Tekaia-Elhsissen ◽  
F. Bonet ◽  
S. Grugeon ◽  
S. Lambert ◽  
R. Herrera-Urbina
Keyword(s):  
Size Distribution ◽  
Room Temperature ◽  
Spherical Particles ◽  
Average Particle ◽  
Particle Sizes ◽  
Temperature Synthesis ◽  
Bimodal Size Distribution ◽  
Hydrazine Reduction ◽  
Average Size ◽  
Palladium Particles

Platinum and palladium powders with average particle sizes in the submicron range have been synthesized at room temperature by hydrazine reduction of and , respectively, in glycols. Platinum powders contain spherical particles with a bimodal size distribution. Palladium powders also contain spherical particles, but the size distribution is narrow. The effect of both ammonia and hydrazine concentration on the size distribution and average size of palladium particles was investigated.

Preparation and Characterization of Gold Nanoparticles in the Presence of Citrate and Soybean Seed Extract in an Acidic Conditions

Drug Research ◽  
2017 ◽  
Vol 67 (05) ◽  
pp. 266-270 ◽  
Author(s):  
Ebrahim Izadi ◽  
Ali Rasooli ◽  
Abolfazl Akbarzadeh ◽  
Soodabeh Davaran
Keyword(s):  
Particle Size ◽  
Gold Nanoparticles ◽  
Size Distribution ◽  
Average Particle Size ◽  
Soybean Seed ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Soybean Extract ◽  
Average Size

AbstractThrough the present study, an eco-friendly method was used to synthesize the gold nanoparticles (GNPs) by using the sodium citrate and extract of the soybean seed as reducing the agents at PH 3. X-Ray diffraction (XRD) method was used to evaluate the crystal structure of as-synthesized NPs and it’s revealed that this method leads to well crystallized GNPs. In order to determine the particle size and their distribution, field emission scanning microscopy (FE-SEM) and dynamic light scattering (DLS) were used. The results showed that, the average particle size distribution of synthesized GNPs in solutions containing of the soybean extract and 1% citrate at PH 3 is about 109.6 and 140.9 nm, respectively. Also, we find that the average size of GNPs is 40 and 33 nm from solutions of citrate and soybean extract, respectively. It was concluded that using the extract of soybean seeds as reducing agent can lead to GNPs with small size and narrow size distribution.

scholarly journals Transformation of Combustion Nanocatalysts inside Solid Rocket Motor under Various Pressures

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 381 ◽  
Author(s):  
Jun-Qiang Li ◽  
Linlin Liu ◽  
Xiaolong Fu ◽  
Deyun Tang ◽  
Yin Wang ◽  
...  
Keyword(s):  
Metallic Copper ◽  
Rocket Motor ◽  
Lead Salt ◽  
Spherical Particles ◽  
Chamber Pressure ◽  
Average Particle ◽  
Particle Sizes ◽  
Solid Rocket Motor ◽  
Condensed Combustion Products ◽  
Double Base

In this paper, the dependences of the morphology, particle sizes, and compositions of the condensed combustion products (CCP) of modified double-base propellants (1,3,5-trimethylenetrinitramine (RDX) as oxidizer) on the chamber pressure (<35 MPa) and nickel inclusion have been evaluated under a practical rocket motor operation. It has been shown that higher pressure results in smaller average particle sizes of the CCPs. The CCPs of Ni-containing propellants have more diverse morphologies, including spherical particles, large layered structures, and small flakes coated on large particles depending on the pressure. The specific surface area (SSA) of CCPs is in the range of 2.49 to 3.24 m2 g−1 for propellants without nickel are less dependent on the pressure, whereas it is 1.22 to 3.81 Ni-based propellants. The C, N, O, Al, Cu, Pb, and Si are the major elements presented on the surfaces of the CCP particles of both propellants. The compositions of CCPs from Ni-propellant are much more diverse than another one, but only three or four major phases have been found for both propellants under any pressure. The metallic copper is presented in CCPs for both propellants when the chamber pressure is low. The lead salt as the catalyst has been transformed in to Pb(OH)Cl as the most common products of lead-based catalysts with pressure lower than 15 MPa. When pressure is higher than 5 MPa, the nickel-based CCPs has been found to contain one of the following crystalline phases: Pb2Ni(NO2)6, (NH4)2Ni(SO4)2·6H2O, C2H2NiO4·2H2O, and NiO, depending on the pressure.

scholarly journals Mean grain diameters from thin sections: matching the average to the problem

2017 ◽  
Vol 81 (3) ◽  
pp. 515-530 ◽  
Author(s):  
Robert S. Farr ◽  
Victoria C. Honour ◽  
Marian B. Holness
Keyword(s):  
Size Distribution ◽  
Thin Section ◽  
Continuous Process ◽  
Average Particle Size ◽  
Particle Diameter ◽  
Spherical Particles ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Thin Sections ◽  
Wide Range

AbstractIt is common practice to estimate a mean diameter for spherical or sub-spherical particles or vesicles in a rock by multiplying the average diameter of the approximately circular cross-sections visible in thin section by a factor of 1.273. This number-weighted average may be dominatedby the hard-to-measure fine tail of the size distribution, and is unlikely to be representative of the average particle diameter of greatest interest for a wide range of geological problems or processes. Average particle size can be quantified in a variety of ways, based on the mass or surfacearea of the particles, and here we provide exact relations of these different average measures to straightforward measurements possible in thin section, including an analysis of how many particles to measure to achieve a desired level of uncertainty. The use of average particle diameter isillustrated firstly with a consideration of the accumulation of olivine phenocrysts on the floor of the 135 m thick picrodolerite/crinanite unit of the Shiant Isles Main Sill. We show that the 45 m thick crystal pile on the sill floor could have formed by crystal settling within about a year.The second geological example is provided by an analysis of the sizes of exsolved Fe-rich droplets during unmixing of a basaltic melt in a suite of experimental charges. We show that the size distribution cannot be explained by sudden nucleation, followed by either Ostwald ripening or Browniancoalescence. We deduce that a continuous process of droplet nucleation during cooling is likely to have occurred.

scholarly journals CO2 Absorption of Powdered Ba2Fe2O5 with Different Particle Size

2018 ◽  
Vol 37 (9-10) ◽  
pp. 1001-1006
Author(s):  
Jun-Hao Liu ◽  
Guo-Hua Zhang ◽  
Zhi Wang
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Product Layer ◽  
Average Particle ◽  
Co2 Absorption ◽  
Particle Sizes ◽  
Distribution Measurement ◽  
Particle Size Distribution Measurement ◽  
Adsorption Desorption

AbstractParticle size dependence of CO2 absorption rate of powdered Ba2Fe2O5 with three kinds of particle size was studied by XRD, SEM, particle size distribution measurement and thermogravimetry. From the particle size distribution measurement, average particle sizes of the powdered Ba2Fe2O5 samples were estimated about 52.5 μm, 77.5 μm and 100.0 μm, respectively. Results show that the reaction of CO2 with Ba2Fe2O5 was controlled by the diffusion step in the product layer, and the kinetics process could be described by the RPP model (Real Physical Picture). Moreover, Ba2Fe2O5 exhibits a good recycling performance though the adsorption capacity is reduced slightly during the cycle processes, and the pathway of the CO2 adsorption–desorption on Ba2Fe2O5 has also been obtained, which suggested that Ba2Fe2O5 is a promising CO2 absorbent material.

The influence of crystallinity on magnetic ordering in natural ferrihydrites

Clay Minerals ◽  
1988 ◽  
Vol 23 (2) ◽  
pp. 161-173 ◽  
Author(s):  
E. Murad ◽  
L. H. Bowen ◽  
G. J. Long ◽  
T. G. Quin
Keyword(s):  
Room Temperature ◽  
Magnetic Ordering ◽  
Average Particle ◽  
Particle Sizes ◽  
Hyperfine Fields ◽  
Quadrupole Split ◽  
Mossbauer Spectra ◽  
Spectral Components ◽  
Temperature Spectra ◽  
Magnetically Ordered

AbstractMössbauer spectra of three natural ferrihydrites of different crystallinities were collected between 295 and 4·2 K. Optimal fits of the room-temperature spectra were obtained using distributions of quadrupole-split doublets; half-widths of the distributions (0·71–0·86 mm/s) increased, and maxima (at 0·62–0·78 mm/s) shifted to higher quadrupole splittings with decreasing crystallinity. Rather poorly-defined magnetically-ordered spectral components appeared and gradually replaced the superparamagnetic doublets as temperatures were reduced. Blocking temperatures between 115 and 28 K, derived from the relative areas under the doublets and magnetic sextets, indicated average particle sizes between ∼ 5 and 3 nm. The sextets were relatively broad and could be fitted with distributions of hyperfine fields. These distributions narrowed and their maxima shifted to higher fields as temperatures decreased; the influence of superparamagnetism was no longer apparent at 4·2 K.

scholarly journals Monitoring of Superparamagnetic Particle Sizes in the Langevin Law Regime

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Daniel Henrard ◽  
Quoc Lam Vuong ◽  
Sébastien Delangre ◽  
Xavier Valentini ◽  
Denis Nonclercq ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Size Distribution ◽  
Room Temperature ◽  
Freezing Point ◽  
Particle Sizes ◽  
Size Distributions ◽  
Resonance Imaging ◽  
Superparamagnetic Particle ◽  
Brownian Rotation ◽  
Magnetic Resonance Imaging Mri

In this work, aqueous solutions of magnetite nanoparticles (NPs) are studied. Magnetite NPs are very useful in biomedicine for magnetic resonance imaging (MRI), for drug delivery therapy, and also for hyperthermia. In order to predict the NP efficiency in these applications, it is crucial to accurately characterize their size distribution and their magnetization. Magnetometry, through the dependence of NP magnetization on the magnetic induction (MB curve), can provide interesting information on these physical properties. In this work, the extraction of the NP size distribution and magnetization from experimental MB curves of aqueous solutions of magnetite NPs is discussed. The results are compared to TEM and XRD characterizations. It is shown that an expression taking into account the size distribution better fits the results than the commonly used simple Langevin function. The size distributions obtained by magnetometry seem comparable to those obtained by TEM measurements. However, a closer look at the results shows some nonnegligible discrepancies: the size distributions obtained by magnetometry vary with the temperature and are closer to the TEM ones at room temperature. Our study suggests that it could be explained by the nonnegligible anisotropy energy of the NPs at low temperature and the lack of NP Brownian rotation below the freezing point of water. This demonstrates that care must be taken when interpreting the results obtained by magnetometry of magnetite NPs: only the size and size distribution obtained at room temperature should be used.

Effects of Al2O3 Species and Particle Sizes on Properties of Al2O3-Cr2O3 Refractories

2013 ◽  
Vol 745-746 ◽  
pp. 610-615
Author(s):  
Hong Gang Sun ◽  
Peng Tao Li ◽  
Shuang Zhi Yan ◽  
Gang Wang ◽  
Jian Qiang Li ◽  
...  
Keyword(s):  
Pore Size ◽  
Bulk Density ◽  
Size Distribution ◽  
Modulus Of Rupture ◽  
Alumina Powder ◽  
Particle Sizes ◽  
Activated Alumina ◽  
Bimodal Size Distribution ◽  
Lower Porosity ◽  
Shock Resistance

The microstructure of Al2O3-Cr2O3 refractories is an important factor to affect its high temperature performance. The Al2O3-Cr2O3 green bodies were prepared by hot pressing using aluminum oxide and Cr2O3 powder mixture by adding a binder. And then the specimens were sintered at 1650 for 4h in the electric muffle furnace. Properties of specimens with different species of Al2O3 powders were studied, including α-Al2O3 powder, ρ-Al2O3 powder, and fused corundum powder. Moreover, three sizes of α-Al2O3 powder (D50=0.8 μm, 1.4 μm, 4.0 μm) were used as additive. Properties of specimens, including apparent porosity, bulk density, cold modulus of rupture, pore size distribution were tested. The morphology of sintered specimens was analyzed by the Scanning Electron Microscope. The results showed that the specimens adding α-Al2O3 powder had the better properties since α-Al2O3 powder has higher sintering activity, and it was more efficient for Al2O3-Cr2O3 solid solution. The specimens with α-Al2O3 had lower porosity, higher bulk density and cold modulus of rupture, and more uniform pore distribution. There were great differences in sintering activity for specimens with different particle size of α-Al2O3 powder. And the microstructure of Al2O3-Cr2O3 was significantly dissimilar. The specimen with the addition of the activated alumina powder of D50 with the size of 1.4 μm and bimodal size distribution showed the perfect performance, including high density and high flexural strength. The experimental results showed that the microstructure of this specimen was uniform and its pore size was homogeneous. This special microstructure is beneficial for improving the slag resistance and thermal shock resistance of Al2O3-Cr2O3 refractories.

scholarly journals Thermal Annealing of Solid Kr Precipitates in Ni

1989 ◽  
Vol 157 ◽  
Author(s):  
R. C. Birtcher ◽  
J. Rest ◽  
D. S. Bergstrom
Keyword(s):  
Size Distribution ◽  
Thermal Annealing ◽  
Room Temperature ◽  
Precipitate Size ◽  
Rate Theory ◽  
Bimodal Size Distribution ◽  
Transmission Electron ◽  
Precipitate Size Distribution ◽  
Subsequent Thermal Annealing ◽  
Annealing Experiments

ABSTRACTAfter implantation into Ni at room temperature, Kr condenses under high pressure as an fee solid aligned with the Ni lattice. Evolution of these precipitates during subsequent thermal annealing to a temperature of 650 C has been followed with transmission electron microscopy and modeled with rate theory.Room temperature implantation results in a monomodal size distribution of small solid Kr precipitates. When Kr is implanted into Ni at 500 C, some precipitates grow to larger sizes, and the precipitate size distribution becomes bimodal. Annealing to temperatures below 600 C after room temperature implantation produces a bimodal size distribution consisting of small solid Kr precipitates and large Kr bubbles. Annealing above 600 C leads to more complete precipitate motion and coalescence that eliminates all small precipitates and results in a monomodal size distribution of large faceted bubbles.Rate-theory modelling of Kr implantation into Ni at 500 C suggests that small solid Kr precipitates are immobile and that Kr melting is required for precipitate mobility. Similar calculations for thermal annealing experiments show that the bubble size distribution becomes bimodal when only a small fraction of the small precipitates melt and become mobile during annealing, while the size distribution remains monomodal when all precipitates become mobile after Kr melting at higher temperatures.

Microstructure and Interconnections Characteristics of Titanium Foam

2016 ◽  
Vol 687 ◽  
pp. 25-32 ◽  
Author(s):  
Krzysztof Pałka ◽  
Grzegorz Adamek ◽  
Jarosław Jakubowicz
Keyword(s):  
Particle Size ◽  
Chemical Reactions ◽  
Open Porosity ◽  
Spherical Particles ◽  
Particle Sizes ◽  
High Permeability ◽  
Titanium Particle ◽  
Average Size ◽  
Titanium Foam ◽  
To Receive

Titanium foams are widely used as biomaterials and potentially as a twin skinned, sandwich, structures for aerospace structures, filter or a catalyst or catalysts carrier for chemical reactions. The porosity is particularly important for tissues ingrowth and vascularity. Open porosity is essential in the case of flow-on machines. The distribution and size of pores is significant to achieve a uniform material effort and ensure to receive an appropriate hydraulic properties.The aim of this study was to determine the effect of titanium particle size and the amount of porogen on the microstructure and the size of pore interconnections in titanium foams made using saccharose as the space holder material.The paper characterizes titanium foam, made from the Grade 1 Ti powders (Alfa Aesar) with a particle sizes of 0.150 mm and 0.044 mm (separately) and spherical particles of saccharose (Pfeifer & Langen) having an average size of 0.7 ÷ 0.9 mm, as a porogen. There was prepared a mixture of powders of the proposed porosity of 50, 60 and 70%. Summarizing 6 mixtures were prepared. After sintering there were received specimens having a diameter of 8 mm and a height of 5 mm. Microstructure analysis was performed using the microtomography Skyscan 1172 (Bruker microCT) and the CTAn software (Bruker microCT).The results indicate the uniform pore distribution and size of the interconnections allowing high permeability.

scholarly journals STRUCTURAL CHANGES IN PULSED LASER ABLATED CuInSe2 COMPOUND STRUKTURĀLĀS IZMAIŅAS IMPULSA LĀZERA ABLĒTAJĀ CuInSe2 SAVIENOJUMĀ

2013 ◽  
Vol 50 (6) ◽  
pp. 54-60
Author(s):  
A. Ogurcovs ◽  
V. Gerbreders ◽  
E. Tamanis ◽  
E. Sledevskis ◽  
A. Gerbreders
Keyword(s):  
Particle Size ◽  
Structural Changes ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Xrd Analysis ◽  
Spherical Particles ◽  
Nonlinear Relationship ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Average Size

Abstract CuInSe2 (CISe) compound was produced by high-temperature synthesis. After mechanical milling, the average CISe particle size decreased to 10μm. The authors study structural changes of the compound after ablation in liquid by a 1064 nm pulsed laser. The SEM examination indicated the presence of spherical particles with the average size of ~ 450 nm. A nonlinear relationship was established between the laser radiation dose and the quantity of spherical particles. The XRD analysis has shown an improvement in the CISe crystalline structure and the absence of significant changes in its stoichiometry. The 3 μm thick experimental CISe samples were screen-printed on planar Ni electrodes, and improvement also was revealed in their photosensitivity. The conclusion is that the pulsed-laser ablation can be applied to chalcopyrite structures like CISe without destruction of their initial properties.

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