ALTERNATIVE SULPHUR FERTILISERS IN NEW ZEALAND

1986 ◽  
pp. 233-242
Author(s):  
Cc Boswell ◽  
B. Swanney
Keyword(s):  
New Zealand ◽  
Bentonite Clay ◽  
Commercial Production ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Sodium Bentonite ◽  
Suitable Material ◽  
Oxidation Rates ◽  
S Oxidation

Interest in high analysis sulphur (S) fertilisers is centred on elemental S which is generally mixed with other materials for safety reasons and to improve effectiveness. Central to the effectiveness of S fertilisers is the rate of oxidation to sulphate-S (SO4S)) for plant uptake. Oxidation rates increase as particle fineness increases. The distribution of S particle sizes in mixtures therefore affects the effectiveness of the fertiliser in any environment. Rates of oxidation vary between environments and thus different S particle size distributions suit different environments. Currently the choice of alternative commercial available S fertilisers is restricted to screened 'agricultural's" and mixtures of S" with superphosphate. Of these, molten mixed S superphosphate is the most suitable material for most environments but especially where S oxidation is slow. Commercial production of alternative S" fertiliser mixtures in New Zealand is imminent. Mixtures of S and sodium bentonite offer the possibility of preparing fertilisers to suit different environments. Granulated ground S" mixed with bentonite clay can be expected to release SO4-S more slowly but this has advantages where leaching of sulphate is likely. Production of SO4-S from two improved Canadian S/bentonite materials is expected to be similar to or slower than that from granulated ground S. Two other imported products, S impregnated urea (20% S, 36%N) and 'Thiovit' (85%S) contain finely divided and ultra finely divided S" respectively. They are raptdly and very rapidly oxidised to sulphate and may have specialised uses in cropping and horticultural enterprises. Keywords: Sulphur fertilisers, elemental sulphur, sulphur/sodium bentonite, plant sulphate, oxidation rates

Distributions of Micro- and Nano-Sized Particles Under Decaying Turbulence in a Chamber

2003 ◽  
Author(s):  
Z. Charlie Zheng ◽  
N. Zhang
Keyword(s):  
Particle Number ◽  
Particle Number Density ◽  
Particle Sizes ◽  
Size Distributions ◽  
Number Density ◽  
Particle Size Distributions ◽  
Integral Scales ◽  
Decaying Turbulence ◽  
Collision Kernels ◽  
Rectangular Chamber

Distributions of particles from micro- to nano-sizes in a rectangular chamber are investigated under the influence of an impulsively-started, decaying turbulence generated by a jet. The unsteady, compressible flowfield is simulated using a k-ε model and the related turbulence scales are analyzed. Stokes numbers, based on the turbulence microscales and integral scales, are used as the selection criteria for turbulence collision kernels. Population balance models are then used to calculate the particle size distributions. Histories of particle number density at several locations in the chamber have been compared with different initial particle sizes under different jet speeds. Lower coagulation rates have been shown to relate with lower jet speeds.

Automated particle analysis in Electron Microscopy

1993 ◽  
Vol 51 ◽  
pp. 738-739
Author(s):  
Tim B. Vander Wood
Keyword(s):  
Electron Microscopy ◽  
Analytical Approach ◽  
Complete Characterization ◽  
Particle Analysis ◽  
Particle Sizes ◽  
Particle Sizing ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
X Ray ◽  
Many Sources

The ability to quickly and economically characterize particle samples is increasingly important. A knowledge of particle size distributions can be critical in a wide variety of processes, from powder metallurgy to ethical drug delivery. Powdered materials may be contaminated at levels of only one particle in one thousand and still be unsuitable for use. Particulate samples may represent a variety of materials from many sources, requiring complex analyses for complete characterization. The traditional analytical approach to these problems, dictated by the need for economy, has been the application of batch techniques (e.g. light scattering) to the problem of particle sizing and trace component and bulk techniques (e.g. atomic absorption, x-ray fluorescence) to the problems of particle analysis. Scanning electron microscopy (SEM), combined with energy-dispersive x-ray spectrometry (EDS), is capable of directly measuring the required individual particle sizes, morphologies and compositions but has not been widely applied due to the high cost of analysis of several hundred to thousands of particles which may be required to adequately represent an entire population.

Determination of Latex Particle Size Distributions by Fractional Creaming with Sodium Alginate

1961 ◽  
Vol 34 (2) ◽  
pp. 433-445 ◽  
Author(s):  
E. Schmidt ◽  
P. H. Biddison
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Sodium Alginate ◽  
Mass Distribution ◽  
Average Particle Size ◽  
Average Particle ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions

Abstract Knowledge of mass distribution of particle sizes in latex is very important to the latex technologist. Therefore, it is desirable to have available a simple method for the determination of mass distribution of particle sizes. This paper presents a method, based on fractional creaming of latex with sodium alginate, which can be used in any laboratory without special equipment. The method is particularly advantageous for analyzing latexes of very wide particle size distributions. When analyzed with an electron microscope, these latexes require counting a very large number of particles. McGavack found that partial creaming of normal hevea latex with ammonium alginate gives concentrates of larger average particle size than the original latex. He found that the average particle size in the cream approaches that of the original latex as the amount of creaming agent is increased. In a previous paper from this laboratory, Schmidt and Kelsey demonstrated that the phenomenon of fractionation according to particle size with increasing amounts of creaming agent is applicable in a wide variety of anionic latex systems and in colloidal silica. Their results indicated also the existence of a quantitative relationship, independent of the nature of the dispersed particles, between the concentration of creaming agent and size of creamed particles. Maron confirmed fractionation with respect to particle size as a consequence of partial creaming with alginate. He showed that the mass average particle sizes of fractions, determined optically, cumulate to that of the original latex. Although the previous paper by Schmidt and Kelsey implied the basic concept of a method of determining particle size distribution by fractional creaming, it was not exploited at that time. In order to adapt the fractional creaming phenomenon to a quantitative method for particle size determination, we required a more precise knowledge of the relation between creaming agent concentration and size of particles creamed. It was proposed to establish this relationship with the aid of the electron microscope. Various factors influencing the creaming of latex, such as polymer concentration, electrolyte, soap content, and variability of the creaming agent, had to be considered in standardizing the creaming procedure.

Particle Size Characterisation of Tin Oxide (SnO2) Precipitated by Various Techniques: Consistency of Data

2007 ◽  
Vol 561-565 ◽  
pp. 2155-2158
Author(s):  
H. Taib ◽  
Charles C. Sorrell
Keyword(s):  
Particle Size ◽  
Light Scattering ◽  
Tin Oxide ◽  
Spherical Shape ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Oxide Powders ◽  
Spherical Agglomerates ◽  
The Individual

The particle size distributions of tin oxide powders produced from the calcining of precipitated tin oxalate were determined by four methods, these being two static and two dynamic light scattering techniques. Although the individual particle sizes were ~ 75 nm, all of the powders were heavily agglomerated as plates. The non-spherical shape resulted in the following interpretational problems: • None of the measurements was in agreement with any others. • There were very significant disagreements between the two light scattering methods. • The particle size distributions were multimodal. • The main peaks in the distribution curves, which were used to calculate the averages and standard deviations, were not Gaussian. The main uncertainty with these data is associated with the non-spherical agglomerates, which result in the multimodal size distributions. These probably were caused by variable-sized but large platy agglomerates.

scholarly journals Liquefaction

1993 ◽  
Vol 26 (4) ◽  
pp. 411-414 ◽  
Author(s):  
J. B. Berrill ◽  
R. Beetham ◽  
H. Tanaka
Keyword(s):  
New Zealand ◽  
Lateral Spreading ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Case Histories ◽  
Reclaimed Land ◽  
Port Area ◽  
Port Facilities ◽  
Three Samples ◽  
Surrounding Soil

In studies of liquefaction case histories, particle size distributions of ejected sand have been useful in identifying layers which have liquefied. The aim of this note is to describe samples of ejecta that were retrieved by the New Zealand reconnaissance team to the M7.8 Hokkaido-Nansei-Oki, Japan earthquake in the hope that these might be useful in subsequent investigations. Three samples of ejected sand were brought back to New Zealand for analysis: two from Hakodate, where many port facilities were damaged by liquefaction, and one from the Nakanosawa Primary School at Oshamanbe, where piles failed in shear due to liquefaction and lateral spreading of the surrounding soil. The Hakodate samples were both retrieved from the Hokodate Port area, sample HAKDl from near the 2500 tonne Nittetsu Cement Company silo which had tilted by about 3° and whose base had displaced about 200 mm horizontally, and sample HAKD2 from the clearly reclaimed land of the wharf area some 300 m to the south. Hakodate is 172 km from the epicentre and Oshamanbe 107 km. The two sites are shown on a magnitude-distance plot in Figure 1, and it is seen that the Hakodate sites lie just inside the criterion of Kuribayashi and Tatsuoka (1974) for distance to furthest site of liquefaction.

Novel Precipitation Route to Silica Grain

1992 ◽  
Vol 271 ◽  
Author(s):  
Barbara Simms ◽  
Tom Gallo
Keyword(s):  
Particle Size ◽  
Acetic Acid ◽  
Aqueous Ammonia ◽  
Sol Gel ◽  
Average Particle ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Small Particles ◽  
High Degree

ABSTRACTWe describe a novel precipitation route to silica grain that lies in the interface between sol-gel and Stöber-type silica. The use of acetic acid as a catalyst for TEOS hydrolysis provides access to a precipitation window in which partially hydrolyzed TEOS and TEOS monomer, when reacted with aqueous ammonia, combine to form pumice-like silica particles in up to 90% yield as SlO2. Precipitated particles exhibit narrow particle size distributions that may be controlled for average particle sizes from 50µ to 400 µ. SEM micrographs show that the particles are agglomerates of small particles, which is consistent with the high degree of observed macroporosity.

scholarly journals Tuning Aerosol Particle Size Distribution of Metered Dose Inhalers Using Cosolvents and Surfactants

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Imran Y. Saleem ◽  
Hugh D. C. Smyth
Keyword(s):  
Particle Size ◽  
Fine Particle ◽  
Laser Diffraction ◽  
Particle Sizes ◽  
Size Distributions ◽  
Metered Dose Inhalers ◽  
Particle Size Distributions ◽  
Metered Dose ◽  
Aerosol Particle Size ◽  
Median Particle

Objectives.The purpose of these studies was to understand the influence of cosolvent and surfactant contributions to particle size distributions emitted from solution metered dose inhalers (pMDIs) based on the propellant HFA 227.Methods.Two sets of formulations were prepared: (a) pMDIs-HFA 227 containing cosolvent (5–15% w/w ethanol) with constant surfactant (pluronic) concentration and (b) pMDIs-HFA 227 containing surfactant (0–5.45% w/w pluronic) with constant cosolvent concentration. Particle size distributions emitted from these pMDIs were analyzed using aerodynamic characterization (inertial impaction) and laser diffraction methods.Results. Both cosolvent and surfactant concentrations were positively correlated with median particle sizes; that is, drug particle size increased with increasing ethanol and pluronic concentrations. However, evaluation of particle size distributions showed that cosolvent caused reduction in the fine particle mode magnitude while the surfactant caused a shift in the mode position. These findings highlight the different mechanisms by which these components influence droplet formation and demonstrate the ability to utilize the different effects in formulations of pMDI-HFA 227 for independently modulating particle sizes in the respirable region.Conclusion. Potentially, the formulation design window generated using these excipients in combination could be used to match the particle size output of reformulated products to preexisting pMDI products.

Processing of Optimized Cements and Concretes Via Particle Packing

MRS Bulletin ◽  
1993 ◽  
Vol 18 (3) ◽  
pp. 45-49 ◽  
Author(s):  
D.M. Roy ◽  
B.E. Scheetz ◽  
M.R. Silsbee
Keyword(s):  
Particle Size ◽  
Discrete Systems ◽  
Particle Packing ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Small Particles ◽  
Fresh Material ◽  
Simple Cubic ◽  
Packing Efficiency

It has been well-recognized for many years that the particle-size distributions of the cement and the grading of the aggregates play an important role in determining the properties and characteristics of cement and concrete products. DSP (densified with small particles) type cements and concretes, to a certain extent, MDF (macro-defect-free) cements, and optimized concretes are recently recognized outstanding examples of the application of this principle. The preset characteristics of the cementitious slurry are also strongly influenced by these factors. Both the workability of the fresh material, and the microstructure development are controlled to a considerable extent by these geometric parameters.Two seminal works in the areas of continuous particle size distributions and particle packing are those of Andreason and Furnas, respectively. Furnas deals mainly with discrete systems and Andreason with continuous distributions. As early as 1907, the concept of idealized particle packing was being used to optimize cements and concretes. Figure 1a shows an idealized cross section of a simple cubic packing of monodispersed spheres. This system has a maximum packing density of 0.65%. In an ideally packed system of discrete size ranges, the size of the next smallest particles would be such that they just fit in the gaps between the largest size particles, and so on for subsequent particle sizes; this system is represented schematically in Figure 1b. Not only the sizes but also the relative numbers of particles are important; Figures 1c and 1d show systems where some fraction of the smaller and larger particle sizes, respectively, are missing. Figure 1e shows a system where the size of the second largest particles is too large to fit into the gaps between the largest particles, resulting in a lower packing efficiency. Thus, both the particle size and fractions are important when considering packing efficiency.

scholarly journals Improvement of Ti Processing through Colloidal Techniques

2012 ◽  
Vol 520 ◽  
pp. 335-340 ◽  
Author(s):  
R.G. Neves ◽  
J.A. Escribano ◽  
Begoña Ferrari ◽  
Elena Gordo ◽  
Antonio Javier Sanchez-Herencia
Keyword(s):  
Particle Size ◽  
Sintering Behavior ◽  
Particle Sizes ◽  
Size Distributions ◽  
Colloid Chemistry ◽  
Particle Size Distributions ◽  
Broad Distribution ◽  
Dry Process ◽  
Chemical Physic ◽  
Titanium Powders

The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to prepare Ti powders with small particle size for a better pressing behavior through the spray dry process. The chemical-physic behavior of titanium powders with two different particle size distributions dispersed in water has been studied by measuring the zeta potential as a function of pH, and dispersant concentration. The employment of poly-acrylic dispersants allowed the fabrication of stable slurries with solid contents up to 50 vol% that have been sprayed under different conditions to form agglomerates ranging between 50 and 200 µm. Conditions were selected to achieve spherical agglomerates formed by a broad distribution of particle sizes that shown excellent flowability. Agglomerates were pressed in a uniaxial die to measure the compressibility, showing an improvement in pressing behavior with respect to powders with bigger particle size. The sintering behavior is also improved, as values of 96 % of the theoretical density were obtained for compacts sintered in vacuum at 1100 °C for 30 minutes.

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