bluuebunny/crossref_metadata_2025 huggingface dataset:
The impact performance of thermoplastic sheet composites
Authors: Bigg D. M. , Bradbury E. J.
Published: December 2004

Sheet composites of polypropylene and poly(ethylene terephthalate) were produced by melt consolidation of alternating layers of polymer films and random glass fiber mats. The composites had a nominal glass content of 50 wt% (∼30 vol%). The sheets were stamped into a complex part from which test specimens were machined, and mechanical properties determined. Flexural strengths as high as 159 MPa were recorded for polypropylene composites and 313 MPa for poly(ethylene terephthalate) composites. The flexural modulus of the polypropylene composites reached 9.1 MPa, whereas the modulus of the stiffest poly(ethylene terephthalate) composite was 15 GPa. The impact properties of the composites were equally high. Polypropylene composites absorbed up to 257 J/cm during an instrumented falling dart impact test. Poly(ethylene terephthalate) composites absorbed as much as 116 J/cm in the same test.
Processing of thermotropic liquid crystalline polymers and their blends—analysis of an in‐situ LCP composite system
Authors: Lee Wan‐Chung , Dibenedetto Anthony T.
Published: December 2004

Thermotropic LCP/LCP fiber blends were prepared by a combination of meltblending and hot‐drawing, using a wholly aromatic copolyester KU‐9211 (also called K161 from Bayer A.G.) and an aliphatic containing LCP (liquid crystalline polymer) PET/PHB60 (from Kodak Tennessee Eastman). Morphological evidence, including scanning electron (SEM) and transmission electron microscopy (TEM), showed that the dispersed phase consisted primarily of highly oriented, 0.5 to 2 μm diameter rigid‐rods of aromatic fibers imbedded in a matrix of predominantly aliphatic LCP fibrils with diameters in the range of 20 to 50 nm. An interphase of approximately 50 nm strongly bonded the two phases together. The fiber blends were characterized using dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), gas chromotography/mass spectroscopy (GC/MS), and rheological measurements. It appears that the processing conditions employed for melt blending had caused PET/PHB60 to undergo chain scission, thereby creating chemical interactions between the two LCP components during the melt blending process. Differential scanning calorimetry (DSC) thermograms as well as nuclear magnetic resonance (NMR) spectra of the extracted fraction from the mixture of 30 wt% K161/70 wt% PET(PHB60) confirmed the chemical interaction between the two thermotropic liquid crystalline polymers.
Electrical conductivity of short carbon fiber‐reinforced polychloroprene rubber and mechanism of conduction
Authors: Jana Purnendu B. , Chaudhuri S. , Pal A. K. , De S. K.
Published: December 2004

The effects of concentration and aspect ratio of carbon fiber and temperature on volume resistivity of polychloroprene‐carbon fiber composites have been studied. The critical concentration of fiber wherein a sharp transition of electrical performance occurs from insulative range to conductive range is in the range of 5 to 10 phr for fibers of higher aspect ratio (∼ 100) and in the range of 20 to 25 phr for fibers with lower aspect ratio (∼ 25). Experimental values of electrical conductivity agreed reasonably well with the calculated values from a theory based on probability of formation of conductive network. Heating and cooling curves in the variation of volume resistivity with temperature do not follow the same path and results in a “hysteresis loop,” up to carbon fiber loadings of 30 phr. Such loops disappear at 40 phr loading. The activation energy of conduction for carbon fiber‐filled polychloroprene varies from 1.10 × 10−20 to 0.96 × 10−20 J. Linearity in current‐voltage relation was observed at room temperature. Increasing interfiber distance at higher temperatures disrupts the linear relation. The type of carrier in carbon fiber‐filled polychloroprene thermovulcanizate was found to be n‐type. The carrier concentration and drift mobility determined by studying the Hall effect were found in the range of 2.5 × 1022 to 2.90 × 1025 m−3 and 1.66 × 10−4 to 14.25 × 10−4 m2 V−1 s−1, respectively.
Non‐Isothermal crystallization of isotactic polypropylene in dotriacontane. II: Effects of dilution, cooling rate, and nucleating agent addition on growth rate
Authors: Lim Gordon B. A. , McGuire Kenneth S. , Lloyd Douglas R.
Published: December 2004

Non‐isothermal crystallization growth rates of nucleated and non‐nucleated isotactic polypropylene (iPP) in dotriacontane were determined experimentally by thermal optical microscopy. Adipic acid was used as the nucleating agent. The non‐isothermal growth rates of the nucleated and non‐nucleated systems were compared with experimentally determined isothermal growth rates. The Lauritzen and Hoffman growth rate equation, originally developed for isothermal crystallization, was modified to describe the non‐isothermal growth. The modified Lauritzen‐Hoffman equation was used to predict isothermal growth rates from non‐isothermal crystallization for the nucleated and non‐nucleated polymer‐diluent mixtures. This study is the first to deal with polymer‐diluent‐nucleating agent systems vital to membrane production.
Dielectric studies of the polymerization of diethylene glycol bis(allyl carbonate)
Authors: de Meuse M.
Published: December 2004

Results of dielectric studies are presented for the polymerization of diethylene glycol bis (allyl carbonate). Two transitions are observed in the dielectric spectra, one that can be related to motion of the carbonate unit and another that has been identified as the glass transition. A relation between the glass transition temperature and the level of conversion of double bonds has been established for this system in the 70 to 100% conversion range. While there appears to be a one‐to‐one relationship between these two parameters, such is not the case for the position of the low‐temperature, secondary transition and the level of conversion. This latter result is interpreted in terms of the local free volume available in the crosslinked system.
Modeling of the dynamics of R‐11 blown polyurethane foam formation
Authors: Baser S. A. , Khakhar D. V.
Published: December 2004

The dynamics of R‐11 blown polyurethane foam formation depend on the rates of viscosity increase of the reacting mixture and R‐11 evaporation, and both are controlled by the polymerization process. Detailed experiments were carried out to study the dynamics of foaming and the measurements made included the cream and rise times, the density change of the expanding foam with time, and the temperature rise during reaction. Dynamic temperature measurements at different points in the foaming mixture were also made to study the spatial variation of the temperature in the foam. The experimental results showed the rate of foaming, the final density, and the maximum temperature decreased with increasing R‐11 concentration. The heat losses from the foam were also found to be significant towards the later stages of foaming when density was low. Theoretical models were developed to predict the temperature and density change with time and spatial variation of temperature in the foam due to heat losses, by considering the foaming dynamics to be either heat generation controlled or heat and mass transfer controlled. In the former, the foam was assumed to be a pseudohomogeneous phase and the approach was similar to that of Rojas,et al.(5). New features accounted for in the model were dilution of the reactant concentration due to the presence of liquid blowing agent and heat loss from the foam due to radiation. While excellent agreement between theoretical predictions and experimental results was obtained for temperature variation with time at different locations in the foam, the model gave a much sharper reduction in density with time as compared to the experimental data. In the second model, the rate of foaming was assumed to be controlled by the rate of heat and mass transfer to a single bubble in the foam. Assuming a film model for heat and mass transfer, the theoretical predictions for both temperature and density were found to be in very good agreement with experimental data.
Influence of processing history on the properties of a thermotropic copolyester/polycarbonate blend
Authors: Turek Douglas E. , Simon George P. , Tiu Carlos
Published: December 2004

Relationships between the rheological, morphological, and tensile properties of an immiscible blend of 25 wt% of a thermotropic liquid crystalline polymer (LCP) with polycarbonate are presented. The shear viscosity of the blend is intermediate between the two constituent materials, and indicates immiscibility in the melt. Extrudate swell behavior is examined and found to be closely related to that of polycarbonate. The morphology of the dispersed LCP phase varies between droplets and oriented fibrils, and is highly correlated with changes in tensile properties. Fibrils are associated with increased tensile modulus, and their development is favored in the elongation flow fields present in the spinline and in the die convergence section. In all cases, blend stiffness is less than that predicted for a continuous fiber‐reinforced composite. Enhanced tensile modulus is associated with both extrusion from shorter length dies and increases in spinline draw ratio, with the latter proving the most important in fibril formation.
The effect of a partly hydrolyzed styrene‐tert‐butyl acrylate diblock copolymer on the properties of poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) and polyamide‐6 (PA) blends
Authors: Kim Ho Cheol , Jo Won Ho
Published: December 2004

The compatibilizing effect of a polystyrene‐hydrolyzed poly(t‐butyl acrylate) diblock copolymer (SBAH) on the phase structure, rheological properties, and mechanical properties of immiscible poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) and polyamide‐6 (PA) blends was investigated. The SBAH was prepared by sequential anionic polymerization of styrene and t‐butyl acrylate, followed by acid‐catalyzed hydrolysis of t‐butyl acrylate block. Scanning electron micrographs show that the blends exhibit a more regular and finer dispersion when the SBAH of 47% hydrolyzed t‐butyl acrylate block is added. By addition of small amount of the block copolymer, the blends show non‐Newtonian power‐law behavior, and the contribution of storage modulus (G′) to the total response increases. Solubility tests support the formation of graft copolymer by chemical reaction between amine groups of the PA and carboxyl groups of the SBAH. Both modulus and strength are improved about 20% with addition of the 3 wt% SBAH, while the elongation at break decreases notably; thus, the blends fail in a brittle manner.
Time dependent response of polycarbonate and microcellular polycarbonate
Authors: Wing Gregory , Pasricha Arun , Tuttle Mark , Kumar Vipin
Published: December 2004

Microcellular polycarbonate is a novel cellular material with cells on the order of 10 μm in diameter and a cell density on the order of 109 cells per cm3. In this study the room temperature creep response of microcellular polycarbonate is experimentally determined and compared with the creep behavior of polycarbonate. The viscoelastic response of polycarbonate and microcellular polycarbonate is characterized using Schapery's theory of nonlinear viscoelasticity. Polycarbonate exhibited a nonlinear creep response at stress levels above 24.13 MPa, while the nonlinear behavior in microcellular polycarbonate was initiated at lower stress levels. Creep strains of microcellular polycarbonate contain a significantly higher viscoplastic component compared with the unfoamed material.
Morphology and barrier properties of oriented blends of poly(ethylene terephthalate) and poly(ethylene 2,6‐naphthalate) with poly(ethylene‐co‐vinyl alcohol)
Authors: Kit Kevin M. , Schultz Jerold M. , Gohil Ramesh M.
Published: December 2004

Morphology and oxygen permeability studies were carried out for blends of poly(ethylene terephthalate), PET, and poly(ethylene 2,6‐naphthalate), PEN, with poly(ethylene‐co‐vinyl alcohol), EVOH. PET/EVOH blends are seen as a possible substitute for poly(vinylidene chloride)‐coated PET packaging films. The effects of several processing parameters such as draw temperature and draw ratio on blend morphology and barrier properties suggest that the morphology of the EVOH phase dictates to a large extent the oxygen permeabilities of these blends. The relationships between morphology and oxygen permeability and explained are explained by consideration of two‐phase conduction models. The model of Fricke is found to be a good predictor of the barrier properties of the PET/EVOH system. The oxygen permeability of PET was reduced by a factor of 4.2 with the addition of 20 wt% EVOH and that of PEN by a factor of 2.7 with the addition of 15 wt% EVOH. Water vapor permeabilities and mechanical properties of PET and PEN were only slightly affected by the addition of 15 wt% EVOH.
Property Function for Product Development
Authors: Polke Reinhard
Published: December 2004

A knowledge of the effects of the physical parameters of solids on the product quality – the property function – is necessary for selective optimisation, to determine the cause of discrepancies and to permit corrections to be made as early as possible in a process. Property functions apply not only to the end products but to every stage of the process. The particle properties of the end product affect the quality, for example the colour strength, while those of the intermediates influence processing properties, for example the filtration resistance and subsequent process stages such as washing and granulation.

In order that the property functions can be determined, the properties, performance characteristics as well as physical characteristics, must be quantifiable. Particle measuring technology was initially restricted to the measurement of physical characteristics but is increasingly becoming concerned also with performance characteristics such as the flow behavior of bulk solids and their abrasion resistance. The remaining performance characteristics can either be estimated, quantified or merely treated qualitatively.
Detection of Water Droplet Size and Anion Species by Nonlinear Optical Scattering
Authors: Eickmans Johannes H. , Qian Shi‐Xiong , Chang Richard K.
Published: December 2004

The liquid‐air interface causes the droplet to act as an optical cavity which provides large internal fields and feedback. The stimulated Raman scattering (SRS) spectra of micrometer‐size water droplets containing different anions (e.g., NO, SO, and PO) can be generated by a single laser pulse and detected by an optical multichannel analyzer. When the spontaneous Raman intensity of the ν1 mode of the anions is larger than that of the O‐H stretching mode of water, the SRS spectra consist of the peak at ν1 and multiple peaks of nearly equal wavelength separation within the O‐H stretching mode of water. These multiple peaks are associated with the morphology‐dependent resonances of a sphere and the refractive index of water. Thus, the wavelength spacing of these SRS peaks provides information on the droplet radius. At higher anion concentrations, sequentially pumped SRS involving the ν1 anion mode can also be detected at Raman shifts equal to 2ν1 and equal to the O‐H stretching mode plus ν1. The Raman shift of the ν1 mode in wavenumbers provides molecular specific information.
Sampling Probes as Precollectors for Cascade Impactor Measurements on Aerosols in Gas Flows
Authors: Bürkholz Armin
Published: December 2004

In the measurement of dust particles or droplets with cascade impactors, coarser particles are lost both in the impactor and in the sampling train. In order to reduce these losses and to recover this coarse fraction, the use of a precollector is recommended. As a rule, measurements in industry must generally be made with sampling probes. It is, therefore, reasonable to combine the probe and precollector.

We measured the particle losses which occur in probes as a consequence of sedimentation and inertial forces. Wall losses through turbulent deposition seem to play only a minor role. By adjusting the gas inlet to a nozzle‐impaction plate sampling system, the coarse fraction can be collected and assessed quantitatively. Particle losses in the subsequent probe and impactor can, thus, be kept very low.

By using nozzles of different apertures and by varying the gas flow rate, isokinetic sampling conditions can be achieved. The collecting properties of the nozzle‐impaction plate system inlet correspond very closely to those predicted by impaction theory. A special adaptation of the nozzle can give a cut point of the precollector close to 10 microns. Cut points at greater particle sizes are not recommended because of uncontrollable particle losses in the probe.
Laser Beam Scattering by Individual Spherical Particles: Numerical results and application to optical sizing
Authors: Maheu Bruno , Gréhan Gérard , Gouesbet Gérard
Published: December 2004

Starting from the expressions of the Generalized Lorenz Mie Theory (GLMT), this paper first presents numerical results for the specific gn coefficients involved in Gaussian beam scattering theory. These results are computed in the special case where on‐axis scatterers are considered. The localized interpretation of the gn coefficients is then developped and discussed, leading to significant simplifications of the numerical computations. Finally, this localized interpretation is used for comparisons of the Generalized Lorenz Mie Theory with other experimental and theoretical data.
Visible Infra‐red Double Extinction Measurements in Densely Laden Media, New Progress
Authors: Gouesbet Gérard , Gougeon Patrick , Le Toulouzan Jean‐Noël , Thioye Massamba , Guidt Jean‐Bernard
Published: December 2004

This paper describes new progress obtained with an optical technique called V.I.D.E. (Visible Infra‐red Double Extinction) which simultaneously measures mean particle size in the range of 10–120 μm and mean number density in densely laden media (up to 0.1% volume fraction). The underlying theory, taking account of multiple light scattering, is recalled. Simultaneous size and concentration measurements are obtained by simultaneously recording transmittances of the medium at two well chosen wavelengths. Experimental results for suspensions of glass particles in air, are described and discussed. The size of particles given by the technique agrees with that given by optical microscopy and Malvern diffractometry. The V.I.D.E. technique is shown to be very suitable to investigate dense media whose optical thickness is up to nine and for which other techniques fail.
The Phase‐Doppler‐Difference‐Method, a New‐Laser‐Doppler Technique for Simultaneous Size and Velocity Measurements. Part 2: Optical particle characteristics as a base for the new diagnostic technique
Authors: Bauckhage Klaus , Floegel Hans‐H. , Fritsching Udo , Hiller Rüdiger
Published: December 2004

Simultaneous size and velocity measurements can be obtained by using photodetector positions of different off‐axis‐angles. But not for all of these positions one receives unambiguous results for the correlation between the phase difference and the particle diameter. This can be clearly demonstrated by the plots of the numerical calculations of the complete Mie's scattering equations. These plots show that for transparent particles which exceed the continuous phase in density at special off‐axis‐angles the situation of light refraction changes into a situation of additional light reflection or vice versa. On the other hand for transparent particles which are less dense compared with the continuous phase and for totally absorbing materials these plots confirm the simplified equations for reckoning the particle diameter by the laws of geometrical optics. The good agreement between these results can also be verified for the backscatter mode for measurements of metallic spheres with an imaginary refractive index.
Optimal Filtering Applied to the Inversion of the Laplace Transform
Authors: Ross Douglas A.
Published: December 2004

Inversion of the Laplace transform, used in the laser scattering measurement of colloidal particle size distributions, presents severe numerical difficulties. In the presence of noise the variance of the inversion integral is infinite, indicating maximum uncertainty in the inversion. This paper applies the method of minimum variance, or “optimal”, filtering to the eigenfunction spectrum of the Laplace transform, giving an inversion which has finite variance.

Spectral decomposition using the eigenfunctions of the Laplace transform gives a representation of the noise and desired signals analogous to the Fourier spectrum used in linear system theory. It is possible to obtain a filtered estimate of the unknown linewidth distribution. The requirement that the variance of this filtered estimate is minimum leads to a Wiener‐Hopf integral equation defining the optimal filter.

The results of this paper provide a basis of comparison of all methods of inversion of the Laplace transform, including the extensive literature of colloidal particle sizing by laser scattering or photon correlation.
Investigation of Bubbly Flow by Ultrasonic Tomography
Authors: Wolf Jörg
Published: December 2004

Computerized tomography (CT) means reconstruction of pictures from projections taken at different angles. This method is well known in fields such as medical diagnostics and nondestructive testing. The application of CT to gas/liquid flow measurement results in a non‐intrusive method for measuring the spatial distribution of the gas phase in a cross‐section of the flow. In our application the projection data are obtained from measurement of the extinction along a set of ultrasonic rays in this cross‐section, using piezo‐ceramic ultrasonic transducers. The transducers are arranged in a circular sensor array which is directly integrated in the pipe wall of the flow; instead of mechanical rotation, the sensors are sequentially switched.
Prediction of the Drop Size and Velocity Distribution in a Spray, Based on the maximum entropy formalism
Authors: Sellens Richard W.
Published: December 2004

A new basis for the prediction of the drop size and velocity distribution in a spray is developed, using the maximum entropy formalism. The prediction considers the imposition of integral conservation constraints for mass, momentum and mechanical energy on the breakup of an undulating liquid sheet. The resulting drop size distribution is similar to the widely used empirical distributions, while the velocity distribution is Gaussian, with a variance that decreases with increasing drop size. Measurements were made in a simple water spray using the Phase/Doppler technique to obtain the joint size/velocity PDF. Photographic measurements were used to obtain an estimate of the geometry of the breakup region, necessary as input to the model. Good agreement was found between the measurements and the predictions, except in the region where drag forces had strongly influenced the distribution. This discrepancy was expected, as drag effects were not included in the model.
Particle Motion in a Turbulent Two‐Phase Dilute Suspension Flow
Authors: Lee S. L.
Published: December 2004

Presented here is new unified theory on particle motion in a turbulent dilute two‐phase suspension flow. Results of numerical calculations based on this theory have been found to agree closely with results of recent in‐situ local measurements of a two‐phase flow in a vertical pipe by the use of the non‐intrusive laser‐Doppler anemometry. In particular, a more plausible explanation is now provided for the measured peculiar migratory behaviors of particles in the region close to the pipe wall.
Lower Detection Limit of an Optical Particle Counter in the measurement of particle size distributions
Authors: Sachweh Bernd , Büttner Helmut , Ebert Fritz
Published: December 2004

An Optical Particle Counter with optically defined measuring volume was investigated with regard to an application in the range of fine particles (f.i. water droplets less then 1.5 μm in diameter). Because of a problematic detection behaviour in the examined size range caused by the analogue signal processor, it was necessary to explore signals generated by the measurement system. In view of the results obtained an alternative signal evaluation method was developed on basis of a digital system. The high flexibility of software systems in signal processing rendered possible on the one hand a clear definition of the lower detection limit of the instrument. On the other hand it was possible to lower the detection limit and herewith the size of particles to be resolved. A practical application for the new evaluation technique is given by the measurement of fractional efficiency curves of technical separators and classifiers, which clearly shows the advantages of the system presented. Most recent investigations are concerned with the maximum number concentration detectable with the Optical Particle Counter, which could be increased up to five times.
Comparative Study of some Probability Distributions Applied to Liquid Sprays
Authors: Bhatia Jagdish C. , Durst Franz
Published: December 2004

A comparative study of a few probability distributions generally used in describing various spray properties based on droplet size and velocity is described. Four different size distributions and three different coupled distributions, representing jointly size and velocity, are considered. A comparison of the results calculated for eight sets of data, taken from three different sources for the size distribution, and one data set for the joint size and velocity distribution, shows that the log‐hyperbolic function presents the best choice among both one‐ and two‐dimensional distributions.

Considerations on one‐ and two‐dimensional probability distributions are followed by a description of the conservation laws and their use in the prediction of the loss of momentum and energy of doplets. Finally, a proposal is made for how the sprays should be studied experimentally and analysed theoretically in order to obtain the maximum possible information. A few suggestions are then provided for further research in this direction.
Determination of Effective Surface Area for the Chemical Reaction of Fine Particulate Materials
Authors: Senna Mamoru
Published: December 2004

A concept of effective surface area was defined as a geometrical controlling factor for a chemical reaction involving powdery materials. It is not uniquely determined for the specific material but depends on the sort of chemical reaction as well as the state of agglomeration. Case studies were given for dissolution or decomposition reaction for MgO, Mg(OH)2 and Pb(CO)3 with and without preliminary mechanical activation and granulation. The effective surface area for dissolution is mostly the external surface of the agglomerates, although the internal surface plays a role to some extent, depending on the compactness of the agglomerates.
Fractal Mathematics Applied to Flow in Porous Systems
Authors: Bayles Gary A. , Klinzing George E. , Chiang Shiao‐Hung
Published: December 2004

The Leitz TAS‐Plus image analysis system was programmed to automatically measure both the ‘shape’ fractal and ‘fragmentation’ fractal for various types of fine particle filter cakes. The automated nature of the analysis facilitated the collection of statistically significant volumes of ‘fractal’ data. This data was then revised, where possible, to conventional theories of flow behavior. Several new insights evolved from the study as explained in the following analysis.
Axial‐View Measurements of Particle Motion in a Turbulent Pipe Flow
Authors: Govan Alastair H. , Hewitt Geoffrey F. , Terry John W.
Published: December 2004

This paper describes experimental measurements and numerical predictions of the motion of particles of size 500–800 m̈m diameter in a 20 m long (i. e. 620 pipe diameters) vertical tube. The numerical simulations suggest that the particles attain a fluctuating r.m.s. velocity in a direction normal to the axis of the tube which is at least one order of magnitude less than that of the gas phase turbulence fluctuations. However, the measured values are of the same order as the gas phase turbulence fluctuations (i. e. 0.5 to 1 m/s). This discrepancy is likely to occur because of particle/wall interactions and these were investigated in separate experiments. Although the cause of the measured coefficients of restitution in the normal direction being greater than unity was not finally demonstrated, the results indicated strongly that the effects were due to non‐ideal bouncing of the particles in the presence of particle spin.
Droplet Deposition from a Mist Flow on a Parallel Vertical Wall
Authors: Issapour I. , Lee S. L.
Published: December 2004

A primarily experimental investigation of the deposition of droplets from a turbulent two‐phase suspension flow on a parallel vertical wall has been found to be closely related to the ratio of fluctuation velocity of the droplets to that of the flow and the size of the droplets. Data are obtained for an air‐water mist flow parallel to a vertical flat plat at Re = 1.54 × 105 to 4.2 × 105 by the use of a particle‐sizing two‐dimensional reference‐mode laser‐Doppler anemometry technique. Although no rigorous theory can be formulated at present due to the complexities involved, however, an analytical attempt is made in the hope of providing an explanation to the physics of the phenomenon. It is based on an apparent turbulent viscosity of the fluid as felt by the moving particles in a turbulent two‐phase suspension flow and the most energetic eddy frequency of the flow.
Agglomeration and Solution of Particles During Sedimenation Analysis
Authors: Staudinger Gernot , Hangl Manfred
Published: December 2004

A basic requirement of particle size analysis through sedimentation is the perfect dispersion of the particles in suspension. The dispersion must be perfect and stable. To ensure this, for a number of solids DIN 66111 specifies sedimentation liquids and suitable dispersing agents and defines an upper limit for the concentration of the solids in suspension. Some instruments require higher solids concentrations than are recommended in DIN 66111. However, there is no simple test to prove the stability of a dispersion with sedimenting particles.

An effective method for testing the stability of a dispersion is to make a number of simultaneous sedimentation analyses, measuring the concentration of the particles at different distances from the surface of the liquid. If the dispersion remains perfect, identical particle concentrations have to be measured, when the measuring time is normalized to one distance from the surface (e.g. t1′ = t(h3/h1), t2′ = t(h3/h2) …). From the particle concentration, distance from the surface and time, the particle size distribution can be calculated.

If the results of the lower (and hence later) measurement show a shift to the larger diameters, agglomeration has occurred. If the sensing technique is light extinction, then the effect is particularly pronounced.

A photosedimentometer with three light beams at distances from the surface of 1.5, 15 and 150 mm was used to demonstrate the effect of agglomeration on particle size distribution and to optimize sedimentation liquids and dispersing agents. An attempt was made to determine the kinetics of agglomeration from the increase in transmission of a light beam through a suspension.
Mean Particle Diameters. Part I: Evaluation of definition systems
Authors: Alderliesten Maarten
Published: December 2004

Mean particle diameters are important for the science of particulate systems because they provide information on particlesize distributions in such a way that they can be related to physical or physiological processes or product properties. There are different notation systems for such mean diameters which may cause much confusion. This equally applies to their nomenclature. The present paper is concerned with comments on the “Moment‐Ratio” and German (DIN) notations. The Moment‐Ratio notation is recommended for standardization. A more extensive contribution of statistics to the science of particulate systems is recommended.
Error Estimates in the Sampling From Particle Size Distributions
Authors: Paine Anthony J.
Published: December 2004

It is often necessary to estimate the properties of particle size distributions from limited samples taken from large populations. When the distributions are broad, and higher order moments required, as in the case of volume based particle size distributions, the inferred parameters d3,50 (volume median diameter) and GSD (geometric standard deviation) can have high intrinsic errors not immediately obvious to the measuring scientist. We show that there is a critical number of particles, Ncrit, which must be counted or else the error may blow up catastrophically. Ncrit is very sensitive to the width of the distribution, and is approximately proportional to GSD11 We develop formulae to estimate the random sampling error inherent in measured values of the d3,50 and GSD for the log‐normal distribution; compare the predictions to a typical experimental particle size measurement; and then generalize to the median of any arbitrary moment, dr, 50.
Scattered Light Photometer for On‐Line monitoring of size distribution parameters and particle number concentration
Authors: Jerkovic Angelo , Fissan Heinz J.
Published: December 2004

A scattered light photometer which monitors the particle number concentration of aerosols is described. The photometer measures the scattered light from illuminated submicron particle clouds with known material properties at certain scattering angles. Intensity ratios in combination with the degree of polarization are used to determine the mean particle diameter and the geometric standard deviation of an assumed log‐normal particle size distribution. The determination of the particle size distribution is based on an algorithm which compares the measured and calculated (Mie theory) relative intensity quantities described. Furthermore, the particle number concentration is monitored from a single absolute intensity measurement at one scattering angle. In order to obtain quantitative results a spherical particle shape is required.
Description of Two‐dimensional Distributions of Particle Size and Particle Velocity of a flowing discontinuous phase by means of special mathematical functions
Authors: Raasch Jürgen
Published: December 2004

As potential approximation functions for measured two‐dimensional distributions, the two‐dimensional normal distribution and the two‐dimensional log‐normal distribution are presented, in addition to mixed forms in which one of the two variables is linearly and the other logarithmically normally distributed. For all four distribution functions, regression curves are calculated, with x being understood as independent and y as dependent variable. The general concept is applied to the specific case of a two‐dimensional distribution of particle size x and particle velocity y. In this context, a number of particularities result from the fact that a distinction has to be made between concentration‐dependent and flux‐dependent measurement.
Image Analysis for Off‐Line Characterisation of mineral particles and prediction of processing properties
Authors: Sutherland David N.
Published: December 2004

The paper discusses the application of image analysis to multiphase mineral particles. The emphasis is on the development of automatic and routine methods which provide reliable data for the process engineer. Optical systems are discussed briefly, but electron beam instruments are shown to offer many advantages for the identification and discrimination of mineral species. Image capture and analysis procedures are described together with the application of the measured data to aid our understanding of the processing properties of particles of complex structure. Examples are given from studies of beach sands, silver minerals, flyashes, ore characterisation, flotation of base metals, grinding and liberation.
Calibration of the electrical aerosol analyzer at subambient pressures
Authors: Romay Francisco J. , Pui David Y. H. , Liu Benjamin Y. H. , Goles Ronald W.
Published: December 2004

A commercial Electrical Aerosol Analyzer (EAA, TSI Inc. model 3030) was calibrated experimentally at three subambient pressures (i. e., 0.901, 0.878, and 0.853 atm). Each calibration resulted in a 19 × 11 response matrix and a size dependent sensitivity curve \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{pA}}{{{\# \mathord{\left/ {\vphantom {\# {cm^3}}} \right. \kern-\nulldelimiterspace} {cm^3}}}}} \right) $\end{document}. The results of the calibration were incorporated into a data reduction computer program for size distribution inversion. The accuracy of the calibration was tested by measuring the size distribution of a NaCl polydisperse aerosol at the three subambient pressures. All the tests gave good agreement in the inverted mean geometric diameter and geometric standard deviation of the aerosol number size distribution.
Determination of Size, Evaporation Rate and Freezing of Water Droplets using light scattering and radiation pressure
Authors: Roth Norbert , Anders Klaus , Frohn Arnold
Published: December 2004

Two independent optical diagnostic techniques for studying the evaporation and freezing of optically levitated droplets are described. In the first technique the size of the droplet is determined by evaluation of the fringe spacing of the light scattered in the forward hemisphere at a scattering angle of 45°. The other technique evaluates the oscillations of optically leviated droplets caused by fluctuations in the radiation pressure. The frequency of these fluctuations is a direct measure for the change of radius with time. In both methods the signals change drastically when freezing of the droplet occurs. Hence the moment of freezing can easily be detected.
Johnson's SB distribution function as applied in the mathematical representation of particle size distributions. Part 1: Theoretical background and numerical simulation
Authors: Yu Ai‐Bing
Published: December 2004

An investigation was carried out of the transformation between the number, length, surface and volume size distributions expressed by Johnson's SB distribution function – the bounded log‐normal distribution function. As is well known, if any of the number, length, surface and volume distributions is log‐normal, all the others will also be log‐normal. Theoretical analysis suggests that the SB function may have a similar property. This was confirmed by a computer‐aided numerical simulation, in which emphasis was given to the transformation between successive order size distributions, i.e. ƒi(x) → ƒi + 1(x) or ƒi(x) → ƒi − 1(x). The numerical results can be applied to the particle size distribution transformation because this transformation can generally be made step by step, for example, ƒi → ƒi−1 (x) → ƒi − 2(x) → … → ƒj(x) for ƒi(x) → ƒj(x) ( i > j).
Interaction Between Shaped Beams and an Infinite Cylinder, including a discussion of Gaussian beams
Authors: Gouesbet Gérard , Gréhan Gérard
Published: December 2004

The theory of interaction between a shaped beam and an infinite cylinder arbitrarily located in it is presented. The same approach as for the generalized Lorenz‐Mie theory is first used. In particular, variable separability is assumed in solving the wave equation. The special case of Gaussian beams, however, implies that, unexpectedly, a special class of non‐separable scalar potentials is required for some kinds of beams.
A Theoretical and Experimental Study of the Total Light Scattering Technique for particle size analysis
Authors: Wang Nai‐ning , Zheng Gang , Cai Xiao‐shu
Published: December 2004

The total light scattering method for particle size measurement has a series of outstanding features, e.g. very simple instrumental arrangement, no serious requirements for its optical, photodetecting and electronic systems and its ease of use. Nevertheless, some problems still remain unsolved which should be dealt with to improve its further applications. An improvement has been made in this work. Comprehensive theoretical studies showed that this method is applicable to particle size analysis in the range 0.1–10 μm, i.e. for those particles whose diameter lies between the lower limit of the diffraction method and the upper limit of photon correlation spectroscopic (PCS) technique. Experimental studies with different monodisperse polystyrene latex spheres as standard reference material give good agreement with their nominal values.
Small Angle X‐Ray Scattering of Hematite Aggregates
Authors: Amal Rose , Gazeau Didier , Waite T. David
Published: December 2004

Small angle X‐ray scattering has been utilised to study the structure of hematite aggregates. The small angle X‐ray scattering (SAXS) spectra obtained provided insight into structure of the hematite aggregates and the size of the primary particles. The structural analysis results obtained by SAXS are consistent with previous results obtained from static light scattering studies. Both techniques indicate that the mass fractal dimensions of hematite aggregates are markedly higher than those obtained for other particle systems.
Effect of Laser Beam Dimensions on Electrophoretic Mobility Measurements
Authors: Finsy Robert , Xu Renliang , Deriemaeker Luc
Published: December 2004

The effect of the finite dimension of the measuring probe, i. e. the laser beam width, on the electrophoretic mobility distribution as determined by electrophoretic light scattering in closed capillary cells is presented on a quantitative basis. The experimental mobility broadening as a function of the probe position in the capillary is in agreement with the broadening expected from the laser beam waist. A strategy for the accurate determination of average mobility and mobility distributions is proposed.
Influence of Porosity on the Electrical Sensing Zone and Laser Diffraction Sizing of Silicas. A collaborative study
Authors: Michoel Armand , De Jaeger Nicolas , Sneyers Rik , De Wispelaere Walter , Geladeé Erik , Kern Jo , Gorter Wim , van Amsterdam Peter , Tandt Youry Den , Houtmeyers Eddy , van Cotthem Luc
Published: December 2004

The objective of a continuing study by the Belgian Particle Technology Group involves difficulties in practical size determinations. This part describes the behaviour of silicas with different porosities during sizing by electrical sensing zone and laser diffraction methods. Anisotropy and porosity were identified to be important particle characteristics in understanding the differences between the two methods. Especially large pore diameters and pore volumes were found to be responsible for shifts in size distribution of 50 to 100%. The use of optical values and optical models was shown to influence these shifts considerably. In the case of spherical silica particles with moderate porosity, no significant differences could be found between the two sizing methods.
Investigation of the Behaviour of Powders under and after Consolidation
Authors: Maltby Lars P. , Enstad Gisle G. , de Selva Sunil R.
Published: December 2004

A biaxial tester was utilized in order to characterize mechanical powder behaviour. Tests were aimed at characterizing the virgin consolidation behaviour of CRM 116 limestone powder, standardized by the Community Bureau of Reference (BCR). The tests indicated that the virgin consolidation behaviour of the powder can be represented by means of topographic maps and surface plots in the principal stress space irrespective of the consolidation stress paths. Resulting strains and bulk densities can also be represented in the same manner. Reloading tests were also carried out on samples consolidated by following different stress paths (consolidation procedures). By applying stresses to the previously consolidated samples and determination of points of initial plastic deformations, the yield surface for each specific type of consolidation was drawn. These tests revealed anisotropic behaviour of the powder, depending on the type of consolidation.
Lattice models, packing density, and Boltzmann‐like distribution of cavities in proteins
Authors: Rashin Alexander A. , Rashin Abraham H. L.
Published: December 2004

A model reproducing the experimental Boltzmann‐like distribution of empty cavity sizes in proteins is introduced. Proteins are represented by lattices of different dimensionalities, corresponding to different numbers of nearest neighbor contacts. Small cavities emerge and join into larger ones in a random process that can be related to random mutations. Simulations of cavity creation are performed under the constraint of a limiting total packing density. Cavities sufficiently large (20 Å3 or more), that they might accommodate at least one additional methyl group produced by a mutation, are counted and compared to the distribution of cavities according to their sizes from protein statistics. The distributions calculated with this very simple model within a realistic range of packing densities are in good agreement with the empirical cavity distribution. The results suggest that the Boltzmann‐like distribution of cavities in proteins might be affected by a mechanism controlled by limiting packing density and maximum allowed protein destabilization. This supports an earlier suggestion that the agreement between the free energies of cavity formation from the mutational experiments and from the statistics of the empty cavity distribution in X‐ray protein structures is nonfortuitous. A possible relation of the suggested model to the Boltzmann hypothesis is discussed. Proteins 2005. © 2004 Wiley‐Liss, Inc.
Soldering external connections to thin film systems
Authors: Keller H. N. , Morabito J. M.
Published: December 2004

External connections to thin film hybrid integrated circuits (HICs) by solder bonding have several advantages over those bonded by solid phase or thermocompression bonding. This paper reviews these advantages and discusses the parameters necessary for high strength, reliable solder joints to thin films. Dissolution of the soluble thin film(s) into solder limits the solder reflow times. Recent work has shown that dissolution rates of thin films in solder depend primarily on the degree of thin film heat treatment prior to soldering, substrate surface texture, and the method of thin film deposition. Auger in‐depth profiling data show that alloy formation and internal oxidation reduces film dissolution during solder reflow. Metallographic sectioning and chemical analysis are used to identify weak solder bond interfaces which result from intermetallic formation. Tin from the solder diffuses rapidly and reacts with soluble metals such as gold, palladium and copper to form brittle intermetallics such as AuSn4, PdSn4 and Cu6Sn5. Intermetallic formation between the solder and the thin film systems of interest can affect joint strength and reliability.
Studies of oxide supported metal clusters
Authors: Watters Kenneth L.
Published: December 2004

The metal cluster carbonyl compounds, Rh6(CO)16 and [Pt3(CO)6] (n = 5,6) have been deposited from solution onto alumina and silica supports. Exposure to air results in decarbonylation of the surface supported compounds in each case. Gas adsoprtion and IR measurements for the alumina supported rhodium material indicate a unique and interesting chemistry in which CO and oxygen react with a surface species to form CO2 and the surface rhodium material is reversibly converted from a fully carbonylated form [apparently Rh6(CO)16] to a fully oxygenated (decarbonylated) form which may retain the Rh6 cluster integrity.

The supported platinum complexes displayed a more conventional chemistry. After deposition on alumina or silica they could be decarbonylated in air. Exposure to CO failed to regenerate the starting material, but behaviour consistent with that reported for conventional reduced Pt on alumina or silica was observed.
Modification of the Beer–Lambert equation for application to concentration gradients
Authors: Paynter R. W.
Published: December 2004

An algorithm for modelling the angular behaviour of the XPS signal corresponding to a postulated depth profile containing concentration gradients is presented.