Synthesis of Submicron, Narrow Size Distribution Spherical Zincite

1986 ◽  
Vol 73 ◽  
Author(s):  
Robert H. Heistand ◽  
Yee-Ho Chia
Keyword(s):  
Size Distribution ◽  
Surface Area ◽  
Systematic Study ◽  
Spherical Particles ◽  
Narrow Size Distribution ◽  
Crystallite Sizes ◽  
Hydrolysis Of ◽  
Controlled Hydrolysis

ABSTRACTZincite has been produced by the controlled hydrolysis of an alkylzinc alkoxide (ethylzinc-t-butoxide) resulting in ∼0.2 μm spherical particles with a narrow size distribution consisting of 150 Å crystallites. The surface area is 30 m2/g. Variation of the concentration of the water drastically affects the particle and crystallite sizes. The results of a systematic study of the hydrolysis parameters are reported here.

A systematic study of halide-template effects in the assembly of lanthanide hydroxide cluster complexes with histidine

2021 ◽  
Vol 8 (1) ◽  
pp. 26-34
Author(s):  
Weiming Huang ◽  
Zhonghao Zhang ◽  
Yinglan Wu ◽  
Wanmin Chen ◽  
David A. Rotsch ◽  
...  
Keyword(s):  
Systematic Study ◽  
Lanthanide Ions ◽  
Cluster Complexes ◽  
Hydrolysis Of ◽  
Lanthanide Hydroxide ◽  
Controlled Hydrolysis

Controlled hydrolysis of lanthanide ions in the presence of histidine and halide templates of different sizes produced dodeca- and pentadecanuclear lanthanide hydroxide clusters.

Preparation of Uniform Hypercrosslinked Microspheres with Large Specific Surface Area

2011 ◽  
Vol 239-242 ◽  
pp. 1842-1845 ◽  
Author(s):  
Qing Zhou ◽  
Song Lin Tang ◽  
Man Cheng Zhang ◽  
Ai Min Li
Keyword(s):  
Particle Size ◽  
Specific Surface ◽  
Size Distribution ◽  
Surface Area ◽  
Specific Surface Area ◽  
Suspension Polymerization ◽  
Large Specific Surface Area ◽  
Narrow Size Distribution ◽  
Membrane Emulsification

The membrane emulsification-suspension polymerization (MESP) method was used to synthesize hypercrosslinked microspheres with a narrow size distribution. The resulting polymers possessed large specific surface area (over 1300 m2/g) and their particle size was controllable. The particles were more hydrophilic when using nitrobenzene as solvent instead of 1, 2-dichloroethane in the postcrosslinking process.

Evolution of Surface area During the Controlled Growth of Silica Spheres

1990 ◽  
Vol 180 ◽  
Author(s):  
Gregory H. Bogush ◽  
C. J. Brinker ◽  
P. D. Majors ◽  
D. M. Smith
Keyword(s):  
Surface Area ◽  
Growth Process ◽  
Growth Models ◽  
Silica Spheres ◽  
Conventional Model ◽  
Silicon Alkoxides ◽  
Aggregative Growth ◽  
Hydrolysis Of ◽  
Controlled Hydrolysis

ABSTRACTSeveral mechanisms have been proposed for the growth of silica spheres by the controlled hydrolysis of silicon alkoxides, the limiting cases of which are the conventional and aggregative growth models. The evolution of surface area predicted from the two models is substantially different at early times into the reaction. In order to probe the change in surface area during growth, 1H NMR measurements of the solvent were made during the growth process. It has been demonstrated that the spin-spin relaxation time.(T2) for an absorbed phase is less than that of the bulk solvent. Using this principal, the change in surface area can be followed in situ during the reaction. The experimental results were compared to the predictions of the conventional model and found not to be in agreement.

scholarly journals Structure investigations of nanocrystalline glass ceramics by ASAXS

2014 ◽  
Vol 70 (a1) ◽  
pp. C744-C744
Author(s):  
Armin Hoell ◽  
Vikram Raghuwanshi ◽  
Christian Rüssel
Keyword(s):  
Heat Treatment ◽  
Size Distribution ◽  
Glass Ceramics ◽  
Growth Effect ◽  
Spherical Particles ◽  
Diffraction Measurement ◽  
Narrow Size Distribution ◽  
Laser Materials ◽  
X Ray ◽  
Fluoride Crystals

Glass ceramics containing fluoride crystals such as BaF2 or CaF2 with crystallite sizes in the range from 5 to 100 nm are potential candidates for numerous photonic applications. Glass ceramics containing rare-earth-doped fluoride crystals are candidates for laser materials. The size distribution plays an important role and often a narrow size distribution is required for photonic applications. In the last years a hindered growth effect leading to a more narrow size distribution was observed during the crystallization of BaF2 as well as CaF2 nanocrystals in oxy-fluoride glasses. The aim of this study is a detailed quantitative structural and nano-chemical analysis of the formation of BaF2 or CaF2 in two glass ceramics by Anomalous Small-Angle X-ray Scattering (ASAXS) to reveal and understand the mechanism of hindered growth. Nanocrystals of BaF2 precipitate during heat treatment of a silicate glass of composition 69.6SiO2-7.52Al2O3-15.04K2O-1.88Na2O-4BaF2-2BaO. X-ray diffraction measurement proved the formation of BaF2 crystals in the glass matrix. High resolution TEM showed the formation of spherical particles of sizes in range from 10-40 nm surrounded by a layer enriched with SiO2. SAXS reveal the growth of nanocrystals with increasing annealing time and temperatures. ASAXS experiments are done at four energies close to the Ba-L3 X-ray absorption edge (5247eV). The ASAXS curves for the sample annealed at 5400C for 20h revealed a spherical core-shell model. It turned out that the layer surrounding the BaF2 crystals is enriched with SiO2. Sizes and compositions of these layers are analyzed quantitatively. Furthermore, the ASAXS analysis reveals the presence of very small nucleates of size of about 3 nm in the as melted glass sample already [1]. A precipitation of CaF2 nanoparticles takes place during heat treatment of glasses of composition 7.65Na2O–7.69K2O–10.58CaO–12.5CaF2–5.77Al2O3–55.8SiO2 up to 40 hours. SAXS experiments and especially ASAXS near the Ca-K edge proves the formation of CaF2 nanoparticle surrounded with SiO2 enriched layers, quantitatively. The ASAXS effect is very pronounced at this untypical low energy for ASAXS studies at the Ca-K edge. The ASAXS result reveals crystal sizes between 10-20 nm surrounded by a shell of lower electron density. Additional very small heterogeneities are found after long annealing with diameters of about 1.6 nm [2].

Macrostructure and microphysics of Saturn's E-ring

1984 ◽  
Vol 75 ◽  
pp. 607-613 ◽  
Author(s):  
Kevin D. Pang ◽  
Charles C. Voge ◽  
Jack W. Rhoads
Keyword(s):  
Size Distribution ◽  
Spherical Shape ◽  
Mie Scattering ◽  
Narrow Size Distribution ◽  
Electrostatic Levitation ◽  
Volcanic Origin ◽  
Micron Diameter

Abstract.All observed optical and infrared properties of Saturn's E-ring can be explained in terms of Mie scattering by a narrow size distribution of ice spheres of 2 - 2.5 micron diameter. The spherical shape of the ring particles and their narrow size distribution imply a molten (possibly volcanic) origin on Enceladus. The E-ring consists of many layers, possibly stratified by electrostatic levitation.

pyGAPS: A Python-Based Framework for Adsorption Isotherm Processing and Material Characterisation

2019 ◽  
Author(s):  
Paul Iacomi ◽  
Philip L. Llewellyn
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Surface Area ◽  
Isosteric Heat ◽  
Material Characterisation ◽  
Mixture Adsorption ◽  
Surface Energetics ◽  
Adsorption Processing ◽  
User Friendly

Material characterisation through adsorption is a widely-used laboratory technique. The isotherms obtained through volumetric or gravimetric experiments impart insight through their features but can also be analysed to determine material characteristics such as specific surface area, pore size distribution, surface energetics, or used for predicting mixture adsorption. The pyGAPS (python General Adsorption Processing Suite) framework was developed to address the need for high-throughput processing of such adsorption data, independent of the origin, while also being capable of presenting individual results in a user-friendly manner. It contains many common characterisation methods such as: BET and Langmuir surface area, t and α plots, pore size distribution calculations (BJH, Dollimore-Heal, Horvath-Kawazoe, DFT/NLDFT kernel fitting), isosteric heat calculations, IAST calculations, isotherm modelling and more, as well as the ability to import and store data from Excel, CSV, JSON and sqlite databases. In this work, a description of the capabilities of pyGAPS is presented. The code is then be used in two case studies: a routine characterisation of a UiO-66(Zr) sample and in the processing of an adsorption dataset of a commercial carbon (Takeda 5A) for applications in gas separation.

Preparation of Organized Mesoporous Silica from Sodium Metasilicate Solutions in Alkaline Medium Using Nonionic Surfactants

2003 ◽  
Vol 68 (10) ◽  
pp. 2019-2031 ◽  
Author(s):  
Markéta Zukalová ◽  
Jiří Rathouský ◽  
Arnošt Zukal
Keyword(s):  
Mesoporous Silica ◽  
Ethylene Oxide ◽  
Sodium Metasilicate ◽  
Spherical Particles ◽  
Structure Directing Agent ◽  
Inorganic Species ◽  
Poly Ethylene Oxide ◽  
Acidic Conditions ◽  
Poly Ethylene ◽  
Hydrolysis Of

A new procedure has been developed, which is based on homogeneous precipitation of organized mesoporous silica from an aqueous solution of sodium metasilicate and a nonionic poly(ethylene oxide) surfactant serving as a structure-directing agent. The decrease in pH, which induces the polycondensation of silica, is achieved by hydrolysis of ethyl acetate. Owing to the complexation of Na+ cations by poly(ethylene oxide) segments, assembling of the mesostructure appears to occur under electrostatic control by the S0Na+I- pathway, where S0 and I- are surfactant and inorganic species, respectively. As the complexation of Na+ cations causes extended conformation of poly(ethylene oxide) segments, the pore size and pore volume of organized mesoporous silica increase in comparison with materials prepared under neutral or acidic conditions. The assembling of particles can be fully separated from their solidification, which results in the formation of highly regular spherical particles of mesoporous silica.

scholarly journals Air filtration improvement of konjac glucomannan-based aerogel air filters through physical structure design

2021 ◽  
Author(s):  
Hong Qian ◽  
Ying Fang ◽  
Kao Wu ◽  
Hao Wang ◽  
Bin Li ◽  
...  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Surface Area ◽  
Physical Structure ◽  
Structure Design ◽  
Air Filtration ◽  
Air Filters ◽  
Air Filter ◽  
Purification Time

Abstract This study presents two methods to improve the air filtration performance of konjac glucomannan (KGM)-based aerogel air filters through physical structure design by changing the pore-size distribution and the surface area, using an air purifier. Results indicated that KGM-based aerogels had a comparable filtration effect with the commercial air filter with a longer purification time. This purification time could be shortened by over 50%, by changing the pore-size distribution from large size to small size or increase the surface area with the fold structure. This should boost the development of polysaccharide-based aerogel used as the air filter.

Sign in / Sign up

Export Citation Format

Share Document