Optimum Particle Size Range Research Articles

The optimum particle size of anaerobic ammonia oxidation granular sludge under different substrate concentrations

The nitrogen removal performance of anaerobic ammonia oxidation granular sludge (AnGS) varies widely among particle sizes. In this paper, the nitrogen removal performance, extracellular polymeric substances (EPS) secretion level and microbial community of AnGS with different particle sizes were investigated to select the optimal particle size for different substrate concentrations. The results showed that the optimal particle size migrated from 0.6-1.6 mm to 1.6–2.5 mm and then to 2.5–3.2 mm as the substrate concentration increased. When the influent concentration of NH4+-N was 110 mg/L, granular sludge with particle size of 1.6–2.5 mm showed excellent nitrogen removal performance with the highest EPS secretion, while the highest EPS secretion gradually migrated to smaller particles as the substrate concentration decreased. The nitrogen removal performance of AnGS with different particle sizes depends on different proportions of anaerobic ammonium-oxidizing (anammox) bacteria (Candidates_Jettenia, Candidates_Kuenenia, Candidatus_Brocadia), heterotrophic nitrification aerobic denitrifying bacteria (Acinetobacter) and denitrifying bacteria (Denitratisoma). The optimum particle size range for AnGS has been clarified for different influent nitrogen concentrations, which can provide some new understanding for the application of anammox reactors.

Predicting the recovery and grade of a rougher flotation circuit from liberation data

A flotation model has been validated against the survey data obtained from a copper rougher flotation circuit with a circulating load. The model was developed using the hydrophobic force as a kinetic parameter, which made it possible to use the contact angles of the free and composite particles as input parameters so that the model can predict both recoveries and grades. The model also recognizes the role of bubble coarsening in determining the froth phase recoveries and grades. The model predictions are in good agreement with the survey data. The size-by-size recovery curve as predicted from the model shows an optimum particle size range that is consistent with most of the operating data reported in the literature. The model suggests that the upper particle size limit may be determined by the instability of the froth phase rather than the turbulence in the pulp phase of a flotation cell.

Mitigating Metal Dissolution and Redeposition of Pt-Co Catalysts in PEM Fuel Cells: Impacts of Structural Ordering and Particle Size

Metal dissolution and redeposition are considered to be the most important degradation mechanism for Pt-based fuel cell electrocatalysts. Understanding key factors mitigating the dissolution and migration under realistic proton-exchange-membrane (PEM) fuel cells is crucial for improving their performance and durability. Using ordered and disordered PtCo electrocatalysts, we address how structural ordering and particle size can affect the dissolution of Co/Pt and their redeposition into the membrane upon catalyst accelerated durability test in PEM fuel cells by statistical scanning transmission electron microscopy (STEM) and spectroscopic analysis. Consistent with the improved performance and durability, we observe that both Co and Pt dissolution were mitigated in the ordered PtCo catalyst compared to the disordered one. The suppressed Pt dissolution was evidenced from the relieved particle coarsening and significantly suppressed Pt redeposition/migration in the membrane after the durability test. Moreover, we reveal an optimum particle size range between 2–5 nm for ordered PtCo catalysts, which favors the highest structural ordering degree and hence the highest retention of Co. These results provide a rationale for implementing ordered Pt intermetallic electrocatalysts in PEM fuel cells and further particle size optimization for improved durability.

Experimental evaluation of crushed Moringa oleifera Lam. seeds and powder waste during coagulation-flocculation processes

Moringa oleifera (MO) Lam. seeds and MO powder waste (an available residue from oil-extracted MO cotyledon), available in the Ecuadorian coast region were investigated as natural coagulant-flocculant agents for drinking and wastewater treatment applications. The optimum particle size range of crushed moringa seeds without husk at a fixed dosage of 50 mg/L was evaluated during jar tests. Three water sources from the Metropolitan District of Quito (MDQ), Ecuador: Monjas and San Pedro Rivers (main rivers that crosses the district) and the effluent from a Pilot Water Resource Recovery Facility (PWRRF), were selected. When coagulation-flocculation process was applied as a sole process after the recollection of crude water, the statistical results from a Randomized Complete Block Design (RCBD) over the sources concluded that water quality was improved by 41.90–51.94%, 55.32–71.10%, and 74.42–87.73%, for chemical oxygen demand (COD), turbidity and E. Coli, respectively. In addition, the use of moringa powder waste and complete moringa seeds also proved suitable for COD, iron, and turbidity removal, where moringa powder was significantly apt for turbidity removal, and moringa treatments with husk, were significantly apt for iron reduction. The statistical differences from particle size range and dosage studies, as well as the results from the use of different moringa seed parts are thoroughly discussed in this work.

The effect of particle size distribution on froth stability in flotation

Abstract Separation of particles of different surface properties using froth flotation is a widely-used industrial process, particularly in the minerals industry where it is used to concentrate minerals from ore. One of the key challenges in developing models to predict flotation performance is the interdependent nature of the process variables and operating parameters, which limits the application of optimising process control strategies at industrial scale. Froth stability, which can be quantified using air recovery (the fraction of air entering a flotation cell that overflows in the concentrate as unburst bubbles), has been shown to be linked to flotation separation performance, with stable froths yielding improved mineral recoveries. While it is widely acknowledged that there is an optimum particle size range for collection of particles in the pulp phase, the role of particle size on the measured air recovery and the resulting link to changes in flotation performance is less well understood. This is related to the difficulty in separating particle size and liberation effects. In this work, the effects of particle size distribution on air recovery are studied in a single species (silica) system using a continuous steady-state laboratory flotation cell. This allows an investigation into the effects of particle size distribution only on froth stability, using solids content and solids recovery as indicators of flotation performance. It is shown that, as the cell air rate is increased, the air recovery of the silica system passes through a peak, exhibiting the same froth behaviour as measured industrially. The air recovery profiles of systems with three different particle size distributions (d80 of 89.6, 103.5 and 157.1 μm) are compared. The results show that, at lower air rates, the intermediate particle size distribution (103.5 μm) yields the most stable froth, while at higher air rates, the finest particles (89.6 μm) result in higher air recoveries. This is subsequently linked to changes in flotation performance. The results presented here highlight, for the first time, the link between particle size distribution in flotation feeds, air recovery and flotation performance. The results demonstrate that there is an optimal air rate for each particle size distribution, therefore changes in particle size distribution in the feed to flotation cells require a change in air rate in order to maximise mineral recovery.

Effect of Al4C3 Particle Size Distribution in a Al–2.5C Master Alloy on the Refining Efficiency of the AZ31 Alloy

The Al–2.5C master alloy is prepared to investigate the effect of the Al4C3 particle size distribution on the refining efficiency of the AZ31 alloy. The results indicate that the Al4C3 particles are potent nucleation substrates for primary α-Mg grains. With 1.0 wt% master alloy addition, the grain size is reduced from 204 to 70 μm. The grain refining efficiency of the Al4C3 particles on the AZ31 alloy is calculated to be 0.04%–0.75%. Such low refining efficiency is mainly attributed to the size distribution of the Al4C3 particles. The particle sizes are in the range from 0.18 to 7.08 μm, and their distribution is well fitted by a log-normal function. The optimum particle size range for significant grain refinement is proposed to be around 5.0–7.08 μm in the present conditions.

Physical and Mechanical Properties of Briquettes Produced from Energy Plants

The study deals with the use of energy crops for the production of thermal energy in the form of briquettes and devising appropriate parameters for their production. Briquettes were produced from seven kinds of energy crops, Salix viminalis, Miscanthus sinensis, Rosa multiflora, Polygonum sachalinensis, Helianthus tuberosus, Sida hermaphrodita and Spartina pectinata, specifically. In the production of briquettes, moisture is the most important properties of material to be pressed, which ranges from 8 to 15 % as it was observed. At a higher humidity it has not been possible to produce briquettes farther in the study conditions. Another important condition for the successful production of briquettes was the particle size of chopped mass. The optimum particle size range from 8 to 20 %. The briquettes were pressed at a pressure of 21 MPa and with diameter of 50 %. Subsequently, physical and mechanical properties (density, moisture, mechanical resistance) and chemical properties (chlorine, iron, nitrogen, calcium, ash, lignin content) were measured. The briquettes density reached from 800 to 900 kg.m−3 with calorific value from 14 to 19 MJ.kg−1 which refers to fact that energy crops are competitive to fossil fuels by their calorific value.

Influence of particle size on gas-adsorption experiments of shales: An example from a Longmaxi Shale sample from the Sichuan Basin, China

To explore the optimum particle size range for low-pressure gas adsorption experiments of shales, a sample of the Longmaxi shale from the Sichuan Basin, China, was crushed into various particle sizes between 4 and 0.058mm. Low-pressure CO2 and N2 adsorption experiments were then performed on these crushed samples, and the pore volume, surface area, and pore size distribution (PSD) were determined from isotherms of gas adsorption. Variations in the volume of sorbed gas, pore volume, surface area, and PSD were recorded across the two series of experiments. In the CO2 adsorption experiments, in which particle size ranged from 4 to 0.83mm, sorbed gas volume, pore volume, and surface area increased with decreasing particle size. No obvious changes were found in sorbed volume, pore volume, surface area, or PSD for the samples with particle sizes from 0.83 to 0.058mm. In the N2 adsorption experiments, the sorbed gas volume and surface area increased with decreasing particle size in samples from 4 to 0.113mm, whereas no obvious variations were observed in the 0.113–0.058mm samples. Similarly, pore volume and PSD showed clear changes with decreasing particle size for the 4–0.113mm samples. The results show that 0.113mm (130 mesh) is the optimum particle size for low-pressure CO2 and N2 adsorption experiments that seek to analyze the characteristics of shale reservoirs.

Optimizing magnetic anisotropy of La1−xSrxMnO3 nanoparticles for hyperthermia applications

Maximizing the magnetothermal response of magnetic nanoparticles (MNP's) for hyperthermia applications is a complex problem, because it depends sensitively upon interrelated magnetic and structural parameters. The task is somewhat simpler for systems with fixed composition, e.g. Fe3O4 or CoFe2O4, in which the particle size is the only means of modifying the magnetic anisotropy, and hence the magnetothermal response. In the La1−xSrxMnO3 system however, the magnetic interactions as well as the particle size both change with the Sr concentration x, which makes it a much more complex system for which to optimize the hyperthermia response. We have investigated the effect of magnetic anisotropy on the magnetothermal response of La1−xSrxMnO3 nanoparticles as a function of the particle size as well as the Sr concentration x where 0.20≤x≤0.45. The optimum particle size range is 25–30nm for all concentrations, where the specific absorption rate (SAR) has a maximum. The linear response theory (LRT) has been applied to this system and good agreement has been found between the experimental and theoretically determined values of the SAR for samples lying in the single domain regime and having large enough anisotropy energies. The agreement is much better for the intermediate concentrations of 0.27 and 0.33, because of their large anisotropy as compared to other concentrations. It is concluded that the LRT can be successfully used to predict the SAR of these nanoparticles, provided they possess large enough effective anisotropies. Values of the ILP have been obtained for these samples and found to be comparable to those of magnetite and some commercial ferrofluids.

Effect of oyster shell as an aggregate replacement on the characteristics of concrete

The aim of this study is to provide basic experimental data to help prevent environmental pollution and to pursue resource recycling by examining the use of waste oyster shells (OS) as concrete aggregate. The possibilities of manufacturing the waste into lightweight concrete and hollow concrete blocks are also examined. The physicochemical characteristics of OS are analysed and the materials and mechanical characteristics according to age are evaluated for fresh and hardened concretes. New chemical reactions and abnormal substances from the mixing of OS are found to be absent. Although problems in strength and workability with increased OS replacement rate of natural aggregates are generated, these can be resolved by using admixtures and stone powder. With respect to strength and workability, 10–13 mm is found be the optimum particle size range of OS as coarse aggregate. In addition, when the replacement rate of the coarse aggregate is 50%, the unit volume weight stands at 1993 kg/m3, which represents roughly 10% lightening. Results from assessing the quality of the hollow concrete produced indicate that, even if 50% of the fine aggregate is substituted with OS, the absorption rate almost satisfies the standards. Utilisation of OS is therefore expected to be adequate.

Linear theory on temporal instability of megahertz faraday waves for monodisperse microdroplet ejection.

A linear theory on temporal instability of megahertz Faraday waves for monodisperse microdroplet ejection based on mass conservation and linearized Navier-Stokes equations is presented using the most recently observed micrometer- sized droplet ejection from a millimeter-sized spherical water ball as a specific example. The theory is verified in the experiments utilizing silicon-based multiple-Fourier horn ultrasonic nozzles at megahertz frequency to facilitate temporal instability of the Faraday waves. Specifically, the linear theory not only correctly predicted the Faraday wave frequency and onset threshold of Faraday instability, the effect of viscosity, the dynamics of droplet ejection, but also established the first theoretical formula for the size of the ejected droplets, namely, the droplet diameter equals four-tenths of the Faraday wavelength involved. The high rate of increase in Faraday wave amplitude at megahertz drive frequency subsequent to onset threshold, together with enhanced excitation displacement on the nozzle end face, facilitated by the megahertz multiple Fourier horns in resonance, led to high-rate ejection of micrometer- sized monodisperse droplets (>10(7) droplets/s) at low electrical drive power (<;1 W) with short initiation time (<;0.05 s). This is in stark contrast to the Rayleigh-Plateau instability of a liquid jet, which ejects one droplet at a time. The measured diameters of the droplets ranging from 2.2 to 4.6 μm at 2 to 1 MHz drive frequency fall within the optimum particle size range for pulmonary drug delivery.

Nanoparticle and Microparticle Flow in Porous and Fractured Media— An Experimental Study

Summary The goal of this research was to develop methods for acquiring reservoir pressure and temperature data near the wellbore and farther out into the formation and to correlate such information to fracture connectivity and geometry. Existing reservoir-characterization tools allow pressure and temperature to be measured only at the wellbore. The development of temperature- and pressuresensitive nanosensors will enable in-situ measurements within the reservoir. This paper provides the details of the experimental work performed in the process of developing temperature nanosensors. The study investigated the parameters involved in the mobility of nanoparticles through porous and fractured media. These parameters include particle size or size distribution, shape, and surface charge or affinity to rock materials. The principal findings of this study were that spherically shaped nanoparticles of a certain size and surface charge compatible with that expected in formation rock are most likely to be transported successfully, without being trapped because of physical straining, chemical, or electrostatic effects. We found that tin-bismuth (Sn-Bi) nanoparticles of 200 nm and smaller were transported through Berea sandstone. Larger particles were trapped at the inlet of the core, indicating that there was an optimum particle size range. We also found that the entrapment of silver (Ag) nanowires was primarily because of their shape. This conclusion was supported by the recovery of the spherical Ag nanoparticles with the same surface characteristics through the same porous media used during the Ag nanowires injection. The entrapment of hematite nanorice was attributed to its affinity to the porous matrix caused by surface charge. The hematite coated with surfactant (which modified its surface charge to one compatible with flow media) flowed through the glass beads, emphasizing the importance of particle surface charge. Preliminary investigation of the flow mechanism of nanoparticles through a naturally fractured greywacke core was conducted by injecting fluorescent silica microspheres. We found that silica microspheres of different sizes (smaller than the fracture opening) could be transported through the fracture. We demonstrated the possibility of using microspheres to estimate fracture aperture by injecting a polydisperse microsphere sample. It was observed that only spheres of 20 μm and smaller were transported. This result agreed reasonably well with the measurement of hydraulic fracture aperture (27 μm), as determined by the cubic law.

NO x control through reburning using biomass in a laboratory furnace: Effect of particle size

This article describes an experimental study to evaluate the effect of the particle size distribution of the reburn fuel on the effectiveness of the reburning process to reduce NO x emissions in a large-scale laboratory furnace. Rice husk, with three distinct particle size distributions, was used as reburn fuel. Initially, flue-gas data (gaseous pollutants and particle burnout) was obtained for a wide range of experimental conditions with the “three” rice husks. Subsequently, in order to improve the understanding of the relationship between reburning effectiveness and reburn fuel particle size, detailed measurements of local mean O 2, CO, CO 2, HC and NO x concentrations, and gas temperatures have been gathered from the reburn zone for three furnace operating conditions that used the “three” rice husks. The results suggest that, for the present combustor and operating conditions, there is an optimum particle size range for enhanced NO x reduction through reburning. Below or above the optimum particle size range of the rice husk the reburn mechanism is less effective probably because the biomass devolatilization process either finishes before or extends well beyond the end of the reburn zone, respectively, impeding the exposure of NO to CH i and HCCO and facilitating the CH i and HCCO interaction with oxygen. In addition, the results show that the particle burnout decreases slightly as the NO x reduction increases, regardless of the rice husk particle size range. Given that the present combustor has only the roof section and the upper four segments lined with a layer of refractory, it can be anticipated that reburning using rice husk as reburn fuel in full-scale equipment would have even a lower impact in particle burnout than that observed in this study.

Insulin-Loaded Nanoparticles are Prepared by Alginate Ionotropic Pre-Gelation Followed by Chitosan Polyelectrolyte Complexation

Alginate nanoparticles were prepared from dilute alginate sol by inducing a pre-gel with calcium counter ions, followed by polyelectrolyte complex coating with chitosan. Particles in the nanometer size range were obtained with 0.05% alginate and 0.9 mM Ca2+. The mean particle size was influenced by time and stirring speed of nanoparticle preparation, by alginate guluronic acid content and chitosan molecular weight and by the initial alginate:chitosan mass ratio. The association efficiency of insulin into alginate nanoparticles, as well as loading capacity were mainly influenced by the alginate:chitosan mass ratio. Under optimized size conditions, the association efficiency and loading capacities were as high as 92% and 14.3%, respectively. Approximately 50% of the protein was partially retained by the nanoparticles in gastric pH environment up to 24 hours while a more extensive release close to 75% was observed under intestinal pH conditions. Mild formulation conditions, optimum particle size range obtained, high insulin entrapment efficiency, and resistance to gastrointestinal release seem to be synergic and promising factors toward development of an oral insulin delivery form.

Nanoparticle Size Effects on Methanol Electrochemical Oxidation on Carbon Supported Platinum Catalysts

The particle size effect observed on the performance of Pt/C electrocatalysts toward the methanol oxidation reaction (MOR) has been investigated with differential electrochemical mass spectrometry (DEMS). The investigation has been conducted under both potentiodynamic and potentiostatic conditions as research on methanol electrochemical oxidation is closely related to interest in direct methanol fuel cells. The particle size effect observed on the MOR is commonly regarded as a reflection of different Pt-CO and Pt-OH bond strengths for different particle sizes. This work focuses mainly on the mechanism of methanol dehydrogenation on platinum which is central to the problem of the optimization of the efficiency of methanol electro-oxidation by favoring the CO(2) formation pathway. It was found that the partitioning of the methanol precursor among the end products on supported platinum nanoparticles is strongly dependent on particle size distribution. Also, it is postulated that the coupling among particles of different sizes via soluble products must be considered in order to understand the particle size effects on the observed trends of product formation. An optimum particle size range for efficiently electro-oxidizing methanol to CO(2) was found between 3 and 10 nm, and loss in efficiency is mostly related to the partial oxidation of methanol to formaldehyde on either too small or too large particles. The possible reasons for these observations are also discussed.

Mass spectrometry of individual particles between 50 and 750 nm in diameter at the Baltimore Supersite.

The performance of the real-time single-particle mass spectrometer RSMS III is evaluated for ambient fine and ultrafine particle number concentration measurements. The RSMS III couples aerodynamic size selection with laser ablation time-of-flight mass spectrometry for single-particle analysis. It was deployed at the Baltimore particulate matter Supersite for semi-continuous operation over an 8-month period. The sampling protocol adopted for this study permitted the analysis of on average 2000 particles per day. The number of particles analyzed is a tradeoff between generating a statistically significant data set and maintaining instrument operation over a long period of time. The optimum particle size range of analysis was found to be ca. 50-770 nm in diameter, although particles as small as 45 nm and as large as 1250 nm were also analyzed. While nitrate, sulfate, and carbon (elemental and organic) were found to dominate the ambient aerosol, over 10% of the detected particles contained transition and/or heavy metals. The (size-dependent) detection efficiency, defined as the fraction of particles entering the inlet that are analyzed, was determined by comparison with scanning mobility particle sizing data. Using the experimentally determined detection efficiencies, particle number concentrations of specific chemical components were estimated. While the sampling protocol allowed the particle concentrations of major chemical components to be followed as a function of both time and particle size, minor components required averaging over time and/or size to achieve adequate precision.

00/02300 Coal transporters gain ground

This article describes an experimental study to evaluate the effect of the particle size distribution of the reburn fuel on the effectiveness of the reburning process to reduce NOx emissions in a large-scale laboratory furnace. Rice husk, with three distinct particle size distributions, was used as reburn fuel. Initially, flue-gas data (gaseous pollutants and particle burnout) was obtained for a wide range of experimental conditions with the “three” rice husks. Subsequently, in order to improve the understanding of the relationship between reburning effectiveness and reburn fuel particle size, detailed measurements of local mean O2, CO, CO2, HC and NOx concentrations, and gas temperatures have been gathered from the reburn zone for three furnace operating conditions that used the “three” rice husks. The results suggest that, for the present combustor and operating conditions, there is an optimum particle size range for enhanced NOx reduction through reburning. Below or above the optimum particle size range of the rice husk the reburn mechanism is less effective probably because the biomass devolatilization process either finishes before or extends well beyond the end of the reburn zone, respectively, impeding the exposure of NO to CHi and HCCO and facilitating the CHi and HCCO interaction with oxygen. In addition, the results show that the particle burnout decreases slightly as the NOx reduction increases, regardless of the rice husk particle size range. Given that the present combustor has only the roof section and the upper four segments lined with a layer of refractory, it can be anticipated that reburning using rice husk as reburn fuel in full-scale equipment would have even a lower impact in particle burnout than that observed in this study.

Effect of Particle Size on Deformation and Compaction Characteristics of Ascorbic acid and Potassium Chloride: Neat and Granulated Drug

Deformation and compaction characteristics of two soluble drugs, ascorbic acid and potassium chloride, were investigated. Five different particle size fractions of ascorbic acid with mean particle size (d50) ranging from 30–300μm and four different particle size fractions of potassium chloride with d50 ranging from 20–400 μm were selected in the study. The compaction behavior of the drug substances as neat drugs or as granulated drugs were evaluated on both a Carver press and an instrumented single-punch tablet press. The results clearly show that mean particle size of the drug substances plays an important role in their compactibility. Intrinsic compactibility of both drug substances was slightly improved with increased particle size. Granulations of the drugs with polyvinyl pyrrolidone significantly improved their compactibility. However, this effect was more pronounced in the drug substance with finer particle size. The Heckel plots indicate that deformation characteristics of both granulated drugs were related to their original mean particle sizes. The granulations prepared from the coarser particle size (d50 250 μm to 400 μm) underwent two stages of deformation, so-called “brittle fracture” and “plastic deformation”. While the granulations prepared from the finer particle size predoninantly underwent “plastic deformation”. The results indicated that the plastic deformation of both granulated drugs was progressively enhanced whilst fragmentation of particles was correspondingly reduced as the particle size of the drugs was decreased. Scanning electron photomicrographs indicated that the granulation process changed the surface morphology of the drug particles imparting more “microirregularities” or “defects”, thereby providing greater “interparticulate bonding” as compared with the neat drugs. Optimum particle size range of ascorbic acid and potassium chloride for satisfactory compactibility was found to be 30–40 μm and 20–40 μm, respectively. The present study demonstrates the importance of selecting the appropriate particle size of drug for the development of tablet dosage forms.

INFLUENCE OF ZrO 2 PARTICLE SIZE ON TRANSFORMATION TOUGHENING IN Y-TZP

The influence of particle size on the fraction of tetragonal ZrO2 transformable as induced by stress as well as on the mechanical properties has been studied. The fraction of tetragonal ZrO2 particles does not increase monotonously as the particle size decreases in Y-TZP with a constant Y2O3 content. The experimental results show that there is an optimum particle size range, at which the fraction of tetragonal ZrO2 in the material and the volume fraction of tetragonal ZrO2 transformable as induced by stress are both the highest while at the same time both the flexual strength and the fracture toughness of the material reach the optimum values. For Y-TZP samples containing constant Y2O3 contents, there is a linear relationship between the fracture toughness and the volume fraction of transformable tetragonal grO2 under tensile stress. All these above-mentioned results are discussed by the rationalized thermodynamical formulae and a revised expression for the critical stress intensity factor.

The vibratory consolidation of particle size fractions of powders.

The use of controlled sinusoidal vibration as a means of consolidating packings of lactose within small containers has been examined. Vertical vibration was found significantly more effective and reproducible than horizontal vibration in terms of the degree of consolidation achieved. An optimum frequency range was identified within which the densification was greatest, and this range was largely independent of particle size for particle size fractions of mean volume diameters ranging from 15.6 to 155 micrometers. The consolidation increased with increasing vibration acceleration up to a level beyond which no further decrease in porosity resulted. Typical effective vibration conditions were characterized by amplitudes of an order of magnitude similar to the particle sizes studied. For particle size fractions of mean diameters 17.8, 37.5 and 80.8 micrometers, there is evidence that an optimum particle size range exists, within which energy requirements for consolidation are at a minimum.