Conventional Particle Size Research Articles

Characterization of Pyrogenic Powders with Conventional Particle Sizing Technique: I. Prediction of Measured Size Distributions

AbstractPyrogenic powders consist of fractal like aggregates with nanosized primary particles. The formation of such aggregates, their hydrodynamic behavior and their optical properties are in principle well understood. Even so, there is only little experience in interpreting results from particle sizing of such materials. Dramatic differences in size distribution obtained from different measurement techniques give frequently rise to confusion on the “true” aggregate size. However, such differences can be attributed to the different particle properties used for size measurement and to the different types of quantities, by which the frequency of the individual size fractions are weighted. For two conventional sizing techniques, Dynamic Light Scattering and Optical Centrifugation Analysis, the influence of the structural properties on the relevant optical and hydrodynamic aggregate properties is discussed on the basis of virtual aggregates as well as of empirical data for pyrogenic powders. Finally measurable size distributions are predicted in a case study.

Characterization of Pyrogenic Powders with Conventional Particle Sizing Technique: II. Experimental Data

AbstractWhen the impact of an aggregate's structure on its physical properties is adequately accounted for, it is possible to use those properties for quantifying the structure. A recent paper [1] has discussed such structure‐property‐relationships for pyrogenic powders. Based on them a calculation scheme is proposed that allow the analysis of size distributions from Dynamic Light Scattering (DLS) and Optical Centrifugation Analysis (OCA) with regard to the translational hydrodynamic diameter, the diameter of gyration and the aggregation number. The scheme includes the conversion from optically weighted to number weighted distributions. The performance of this calculation scheme is tested for different grades of fumed silica, which were analyzed by two DLS and one OCA instrument. A fairly good agreement is observed with regard to medians of the distribution functions. The paper shows that differences in size distributions obtained by different measurement techniques may not only explained qualitatively but can even quantitatively traced back to distribution functions of structural aggregate parameters.

Study on the Variation of Fractal and Mutifractal Characteristics of Coal Particles in the Ultra-Fine Pulverizing Process

In respect to conventional particle size distribution, the fractal size dimension (FSD) has become a powerful tool for characterization of particles.In this paper, we applied both the single fractal law and the bi-fractal approaches to analyze the fractal and mutifractal characteristics of the Qingshuiying coal particles in the ultra-fine pulverizing process. The relationship between FSD and the ultra-fine pulverizing time was detected and had certain guidance meaning for optimizing the operational parameters and reducing energy consumption of the ultra-fine pulverization.

Experimental Research of New Technology on the Precise Reduction of Micron-Sized Iron Oxide

This study puts forward the technology of the precise reduction of micron-sized iron oxide: at lower temperature (＜1000°C), the high purity metallic iron can be reduced, separated and extract from iron ore, slag, the iron oxide in the dust which are in micron size. Precise reduction experiments are planned for high phosphorus hematite in Enshi, magnetite in Kazuo and the steel dust of a factory, in order to do the study on their reduction characteristics. According to the L16 (215) orthogonal test on high phosphorus hematite and magnetite, the result shows that: in the atmosphere of pure H2 or 100% CO, the micron-grade mineral powder can be reduced at the condition of 650~850 °C; compared with the conventional particle size powder, the reduction temperature lowers about 300~350 °C in the same reduction degree. According to the L8 (27) orthogonal test on steel dust, the result shows that: by pure H2 or 100% CO, the average metallization rate can reach 95% at the temperature of 900~1000 °C; the product of reduction keeps power state and its interparticle sintering does not occur, which means that it is reasonable to separate iron from other impurity elements through the physical method in the non-melting state.

The use of particle size distribution by surface area method in predicting the saturated hydraulic conductivity of graded granular soils

The hydraulic conductivity (k) of a fully saturated granular material can be predicted by the well-known Kozeny–Carman formula, and its slightly different variations, based on the porosity (n) and effective diameter (deff). Most variations of the Kozeny–Carman formula compute the parameter deff based on a given conventional particle size distribution by mass (PSDm), where the validation would normally be carried out by comparing against laboratory permeability tests conducted on soils having an average coefficient of uniformity (Cu) of about 3. Knowing that the Kozeny–Carman formula was originally developed for uniformly graded materials, inevitable limitations are inherited when it is applied to increasingly graded soils. This study proposes to convert the PSDm into its equivalence in surface area (PSDsa) conforming to the fundamental geometric assumption by which the Kozeny–Carman equation was originally formulated. The estimated deff based on this proposed PSDsa method appears implicitly to incorporate the size, shape and angularity of the natural grains which were traditionally represented by the shape coefficient (α). The results presented in this paper show that the suggested method is capable of predicting k for fully saturated granular soils with Cu of up 20.

Morphological characterization of super fine pulverized coal particle. Part 2. AFM investigation of single coal particle

Super fine pulverized coal combustion is a new pulverized coal combustion technology which has better stability, higher combustion efficiency and lower NO x and SO 2 emission than that using conventional particle sizes. In this paper we applied fractal analysis based on power spectral density (PSD) and slit island method (SIM), three-dimensional (3D) surface roughness measurement and surface-topography observations from AFM to form a proper investigative tool which may give a relatively full picture of surface morphology of super fine pulverized coal particles for the first time. The final results indicate that both fractal dimensions calculated by SIM and PSD and roughness of coal particle size increase with the increase of the coal particle size. Besides, the grey relational analysis was used to study the degree of relative importance of the influential factors about the microroughness of coal particle surfaces. The results show that the influence of the coal particle size is the greatest compared with the coal qualities and fractal dimensions. This work provides some reference for a relatively full picture of surface morphology of super fine pulverized coal particles. The findings from this work will be helpful to form the basis and provide guidance for further studies on the chemical and combustion characteristics of super fine pulverized coal particles.

Morphological Characterization of Super Fine Pulverized Coal Particle. Part 4. Nitrogen adsorption and Small Angle X-ray Scattering Study

Super-fine pulverized coal combustion is a new pulverized coal combustion technology that has better combustion stability, higher combustion efficiency, lower NOx and SO2 emissions, and higher comprehensive efficiency, than using conventional particle sizes. In this paper, we combined the pore surface fractal dimensions and pore structure fractal dimensions based on different methods to analyze the fractal characteristics of super fine pulverized coal particles. And the gray relational analysis was used for further study on the influencing factors of the fractal dimensions. Besides, the discrepancy between the two fractal dimensions influencing the phases during the coal combustion process was also discussed. It is found that all the fractal dimensions of the super fine pulverized coal particles range from 2.36 to 2.91, which belong to the interval 2< D < 3. It is interesting to observe that the surface fractal dimension increases with the increase of the pulverized coal particle size while the structure ...

Morphological Characterization of Superfine Pulverized Coal Particles. 1. Fractal Characteristics and Economic Fineness

Superfine pulverized coal combustion is a new pulverized coal combustion technology which has better combustion stability, higher combustion efficiency, lower NOx and SO2 emissions, and higher comprehensive efficiency than when using conventional particle sizes. In this paper, we novelly applied both the classical single power law fractal dimension and a piecewise approach to analyze the particle-size distribution (PSD) of superfine pulverized coal particles. In addition, we introduced the fractal theory into scanning electron microscopy image analysis by adopting the slit island method. The grey relational analysis was used to study the degree of relative importance of the influencing factors about fractal dimensions. Furthermore, the piecewise characteristics of the PSD of coal particles were studied in detail. All curves on the log−log scale can be approximated by two intersecting lines, and each curve can be quantified by four variables. The grey relational analysis was also used for further study on the relationships between the four parameters. Finally, a new method for identifying the economic granule size of pulverized coal particles, that is, economic fineness based on the power consumption of coal mills, E2, was proposed by a utilizing neural network method. Final results indicate that the economic fineness of Shenhua pulverized coal particles based on E2 is about 18.94, while that of Neimenggu pulverized coal particles is about 36.13. This provides some reference for a coal-fired power plant to confirm the economic granule size, which has certain guidance meaning for economical operation and low power consumption.

Stability Study of PbSe Semiconductor Nanocrystals over Concentration, Size, Atmosphere, and Light Exposure

Infrared-emitting PbSe nanocrystals are of increasing interest in both fundamental research and technical application. However, the practical applications are greatly limited by their poor stability. In this work, absorption and photoluminescence spectra of PbSe nanocrystals were utilized to observe the stability of PbSe nanocrystals over several conventional factors, that is, particle concentration, particle size, temperature, light exposure, contacting atmosphere, and storage forms (solution or solid powder). Both absorption and luminescence spectra of PbSe nanocrystals exposed to air showed dependence on particle concentration, size, and light exposure, which caused large and quick blue-shifts in the optical spectra. This air-contacted instability arising from the destructive oxidation and subsequent collision-induced decomposition was kinetically dominated and differed from the traditional thought that smaller particles with lower concentrations shrank fast. The photoluminescence emission intensity of the PbSe nanocrystal solution under ultraviolet (UV) exposure in air increased first and then decreased slowly; without UV irradiation, the emission intensity monotonously decreased over time. However, if stored under nitrogen, no obvious changes in absorption and photoluminescence spectra of the PbSe nanocrystals were observed even under UV exposure or upon being heated up to 100 degrees C.

Comparison of fused-core and conventional particle size columns by LC–MS/MS and UV: Application to pharmacokinetic study

The chromatographic performance of fused-core (superficially porous) HPLC packing materials was compared with conventional fully porous particle materials for LC–MS/MS analysis of two pharmaceuticals in rat plasma. Two commercially available antidepressants, imipramine and desipramine, were assayed using a conventional analytical C 18 column (5 μm, 2.0 mm × 30 mm) and a fused-core C 18 column (2.7 μm, 2.1 mm × 30 mm). Retention time, column efficiency, pressure drop, resolution, and loading capacity were compared under the same operating conditions. The fused-core column demonstrated reduced assay time by 34% and 2–3-fold increased efficiency ( N). Loading capacity up to 25 μl of extract injected on column showed no peak distortion. The registered back-pressure from a flow rate of 1.0 ml/min did not exceed 3400 psi making it compatible with standard HPLC equipment (typically rated to 6000 psi). Two mobile phases were examined, and morpholine as an organic base modifier yielded a 2–5-fold increase in S/N near the limit of detection over triethylamine. The 2.7 μm fused-core column was applied to the analysis of imipramine and desipramine in extracted, protein precipitated rat plasma by LC–MS/MS. The calibration curves were linear in the concentration range of 0.5–1000 ng/ml for both imipramine and desipramine. Intra-run precisions (%CV) and accuracies (%bias) were within ±7.8% and ±7.3% at three QC levels and within 14.7% and 14.4% at the LOQ level for both analytes. Following a single method qualification run, the method was applied to the quantitation of pharmacokinetic study samples after oral administration of imipramine to male rats.

Optical Scattering Mechanisms of Functional Nano-Material Films on Transmission Display Screen

In this paper, the application of new functional nano-material films prayed on transmission display screen is studied. Optical properties, such as luminance gain and scattering angle, of the screens are measured to investigate the particle size effects on the properties. The results show that the optical properties of screen sprayed with nano-material film improve notably compared with those screens with films of conventional particle sizes. When the particle size is less than 100nm, the gain is high and the viewing angle low. With increasing particle sizes, the characteristics of screens vary with particle sizes. In order to solve the contradictory relationship between gain and viewing angle and to obtain screens with desirable optical properties, suitable nano-particle sizes ranging from 400nm to 700nm should be chosen for the spraying film. The scattering mechanisms between nano-particles and light are also discussed.

Optimal particle size of radiocolloid for sentinel node identification in breast cancer — Electron microscopic study and clinical comparison

Sentinel node (SN) biopsy using a radiotracer is easy to learn, reproducible, and performed by the majority of breast cancer surgeons. However, this technique raises the question: what is the optimal particle size of colloid? Patients were injected with conventional tin colloid (median particle diameter: 700 nm) and the predominant particle size of radiocolloid retained in the SN was measured using electron microscopy. This showed a narrow distribution of colloidal size (100-150 nm). Patients were then injected with modified tin colloid having a median particle size of 100 nm. A clinical comparison was performed between conventional particle size or reduced particle size tin colloid and the SN biopsy success rate, the number of SNs, and the colloidal uptake in SNs. A total of 118 patients were injected with the conventional tin colloid (group I) and 124 patients with the smaller particle colloid (group II). The identification rate and the number of SN in both groups were almost equal, and the patients with low-uptake SNs were not significantly less in group I(p = 0.55). However, in the subgroup of patients 60 years of age or more, group II had significantly more SNs than group I(1.4 vs 1.9; p = 0.03) and low-uptake SNs were significantly less common than in group I(p = 0.02). The improvement of colloidal uptake in SNs using the smaller particle size tin colloid was confirmed, and this impact was statistically significant in the older population.

The dielectric properties of charged nanoparticle colloids at radio and microwave frequencies

Charged particle colloids typically consist of particles with negative surface charge suspended in an aqueous electrolyte solution. A layer of ions forms around each particle, and previous research has shown that the dynamics of this charge distribution, induced by an external field, lead to effective and potentially useful dielectric properties (Lyklema J and Van Leeuwen H P 1999 Adv. Colloid and Interface Sci. 83 33, O'Konski C T 1960 J. Phys. Chem. 64 605). Charged nanoparticle colloids are potentially of great benefit because they are extremely stable and their small dimensions make them highly versatile. Possible uses include electromagnetic shielding devices and medical applications. This research focuses on the dielectric properties of charged polystyrene nanoparticle colloids, which are investigated across a range of radio and microwave frequencies. The results show two distinct regions in the permittivity behaviour. The first is the dipolar relaxation of water at microwave frequencies. The second is a high amplitude, low frequency relaxation due to the diffusive motion of ions in the bulk electrolyte beyond the double layer. Effective control of the resulting dielectric response is demonstrated with particle size ranging from 20 to 220 nm. It is shown that the small nanoparticle sizes lead to faster relaxation times than those expected from conventional micron particle sizes, such that the loss extends to microwave frequencies. The results are fitted to a model where the zeta potential, ξ, and double layer thickness, κ−1, are used as fitting parameters.

Characterization of coarse particles in alumina powders by a wet sieving method

Abstract The wet-sieving method was applied to determine the content of coarse particles in commercial alumina powders by four independent research organizations participated in the Round-Robin Testing. The results showed that those powders clearly contain 700 to several thousands ppm of coarse particles with the size >25 μm, whereas they could not be detected with the conventional particle size analyzer because of their low concentration. SEM and polarized light microscope observations revealed that the coarse particles contained several types of aggregates which survived during the production processes of alumina by the Bayer process.

Ministructured catalyst bed for gas‐liquid‐solid multiphase catalytic reaction

AbstractA ministructured reactor concept improves the performance of multiphase gas‐liquid‐solid reactions over conventional packed‐bed and trickle‐bed reactors. In the mini‐structured reactor, the catalyst bed is structured at the particle level by dividing the bed into a number of identical, parallel flow channels with the channel walls being catalyzed. The hydraulic diameter of each channel opening is from 0.2 to 2 mm, comparable to the conventional particle size. The mini‐structured reactor can be assembled using monolith catalyst modules that have been a proven material technology for gas‐phase reactions. Two types of gas‐liquid‐solid reactions, olefin hydrogenation and toluene saturation, are used to test the fundamental feasibility of the mini‐structured reactor under steady‐state reaction conditions in a cocurrent down flow mode. The new reactor shows an order of magnitude increase in the activity compared to a trickle‐bed operation for reaction conditions of practical interest. This degree of activity improvement is larger than estimates based on conventional analyses of catalyst geometric surface area and/or characteristic pore diffusion lengths. Individual catalyst particles are significantly underutilized in a trickle‐bed reactor. More ideal contacting of gas, liquid and catalyst, as well as the enhancement of overall mass‐transfer processes in the mini‐structured reactor, makes it possible to dramatically improve the gas/liquid multiphase reaction performance over solid catalysts.

Estimating Average Particle Size by Focused Beam Reflectance Measurement (FBRM)

The Lasentec focused beam reflectance measurement (FBRM) probe provides in situ particle characterisation over a wide range of suspension concentrations. This is a significant advantage over conventional instruments that require sampling and dilution. However, FBRM gives a chord distribution, rather than a conventional diameter distribution. Both theoretical and empirical methods for converting from chord to diameter data are available, but the empirical method was found to be more successful. The FBRM response has been compared to conventional particle sizing techniques (laser diffraction and electrical sensing zone) for a range of sieved aluminium or calcite suspensions. The mode average of the square-weighted chord length was found to be comparable to other sizing techniques over the range from 50 to 400 μm. The square-weighted FBRM results were essentially unaffected by changes to the instrument focal position, the suspension fluid flow velocity, or the solid fraction in the range 0.1-20% w/v.

Osteoblast and Chrondrocyte Proliferation in the Presence of Alumina And Titania Nanoparticles

Proliferation of osteoblasts (bone-forming cells) and chondrocytes (cartilage-synthesizing cells) exposed to different sizes of alumina as well as titania particles at various concentrations (from 10,000 to 100 μg/ml of culture media) was investigated in the present in vitro study. Compared to respective conventional (i.e., micron) particle size ceramics, results provided the first evidence of increased osteoblast and chondrocyte proliferation in the presence of nanoparticles. Material characterization studies revealed that the only difference between respective ceramic particles was nano- and conventional-dimensions; specifically, phase, charge, and chemical properties were similar between different size alumina and titania particles, respectively. Thus, the present study provided the first evidence of a less detrimental effect of nano- as compared to conventional-dimension wear debris on cell function; such wear debris may result from friction between articulating components of orthopedic implants composed of novel nanophase ceramic materials. In this manner, results provided additional evidence to the literature that nanophase ceramics may become the next generation of bone prosthetic materials with improved osseointegrative (i.e., ability to bond to juxtaposed bone in situ) properties.

Application of atomic force microscopy to particle sizing

AFM has been applied for studying morphology and size distribution of nanometer-sized particles adsorbed on flat surfaces. For the quantitative evaluation of the images an algorithm for automatical particle detection and volume calculation has been developed. In this way a large number of particles can be automatically evaluated in order to derive size distributions or surface coverages. The method has been successfully applied to determine size distributions of environmental aerosol particles collected with an 11-stage low pressure impactor. The first four stages with average aerodynamic equivalent diameters (aed) ranging from 21 to 170 nm were investigated. The calculated aed values were in good agreement with the predicted aed for each stage. Additionally, it could be shown that sampling conditions and storage time affect the derived size distributions. Furthermore, AFM has been applied as reference method for conventional particle sizing techniques. For this purpose technologically relevant powders as titanium oxide powder and tungsten carbide powder were investigated using AFM and the results were compared with conventional techniques such as high resolution SEM and a light scattering method. The derived cumulative size distributions were in good agreement. The results clearly show that AFM constitutes a convenient tool for size determination, not only for ultrafine particles exploiting the high resolving power, but also in the case of larger particles.

Effects of brownian coagulation and brownian diffusion on fine particle size analysis by sedimentation method.

Conventional particle size analysis by sedimentation method does not give true size distributions but only apparent ones, when Brownian coagulation and Brownian diffusion exist. The difference of true and apparent size distributions was theoretically evaluated by numerically solving the population balance equation under various conditions. Then some of the theoretical results were verified experimentally for particles having various sizes and number concentrations which were obtained under sedimentation in air, in water and in centrifugal field by means of ultramicroscopic size analysis. In addition to these analyses, two parameters consisting of given measuring conditions, which were proposed herein, were found to be useful to predict whether or not coagulation and diffusion effects exist in actually observed size distributions.

Recycling in preparative liquid chromatography

Chromatographic recycling is used to allow the scale up of an analytical separation made on a 7 mm ID microparticle GPC column to a multi-gram separation on a 25 mm ID preparative column, filled with conventional particle size GPC gel.