Showing papers in "Powder Technology in 1981"

TL;DR: Mercury porosimetry is used extensively for the characterization of various aspects of porous media and powders as mentioned in this paper, such as vapour sorption and sorption hysteresis, micrography and E.T. isotherm.

TL;DR: In this article, the form and hysteresis of mercury injection, withdrawal and reinjection capillary pressure curves are investigated by the geometry of pores and their connections in samples of sedimentary rocks and also in artificial and theoretical pore-network models.

TL;DR: In this article, the authors investigated the kinetics of dry grinding of several cement clinkers and two coals in a laboratory tumbling ball mill, and demonstrated that the slowing of the breakage rates applies to all sizes in the mill, indicating that the cushioning action of fines affects the whole breakage process, even though mill power remains constant.

TL;DR: In this paper, a computer program generated 3000 interpenetrating spheres in a cubic container and used a relaxation technique to reduce overlaps, which resulted in an isotropic and homogeneous packing with a density of 0.6366.

TL;DR: In this paper, a theoretical investigation of sample thickness effects through application of the concepts of percolation theory of chaotic media is made through applying integral equations which account for all prominent features of drainage and imhibition, including threshold pressure, hystereses, residual saturations and dependence of residual saturation on initial saturation.

TL;DR: The wall heat transfer coefficient of the gas-liquid-solid fluidized beds in the range of stable fluidization state runs correlated as a function of modified Nusselt number, modified Reynolds number and gas phase Froude number as discussed by the authors.

TL;DR: In this paper, the authors investigated the role of the slope of the walls in the conical parts of the pore in the cause of volume hysteresis of the wetting angel of mercury.

TL;DR: In this paper, the pore size distribution was determined by a mercury porosimeter from a practical point of view, more with the practical applicability and the reproducibility of the method in view than the absolute correctness of the methods.

TL;DR: In this article, the first-order specific rates of breakage and the cumulative primary daughter fragment distributions were determined in a small laboratory ball mill under standard conditions, including crystalline quartz, silicon carbide, three coals of different rank and a cement clinker.

TL;DR: In this paper, a model for pore surfaces, in which the pores are represented as cylinders with surfaces that are very rough and that contain void spaces corresponding to the entrances of branch pores, is developed.

TL;DR: In this article, the porosity of Czechoslovak coal was measured in the pore radii range 0.1 - 7500 nm and then divided into the following groups: micropores (smaller than 1.8 nm), mesopores (1.8 - 30 nm), and macropores over 30 nm.

TL;DR: In this article, the basic principles of mill action were investigated in the batch Hardgrove ball-race machine, modified by the addition of a torque device, and it was found that the torque to drive the mill after correction for bearing friction was almost proportional to load M on the balls and independent of rotational speed ω.

TL;DR: In this paper, the contact force distribution in an idealized granular material is related to the macroscopic state of the stress, and the relationship connecting them is provided by a variational method called the principle o f virtual work.

TL;DR: In this article, a tentative form of equation is proposed for segregation by size; the equations of Rowe are useful predictors for segregation of coarse particle systems at all velocities when a very wide size range is present.

TL;DR: In this paper, the importance of interparticulate friction and the effects of environmental factors are emphasized, the necessity to correlate porosity characteristics with powder characteristics is discussed, and the problems of powder characterization are discussed.

TL;DR: In this article, the pore size distributions of lactose tablets are presented and calculated values for the porosity, pore diameter and specific surface area are compared with results from air permeability and nitrogen adsorption measurements.

TL;DR: In this article, it was shown that the size of the entry pores is very small in comparison with the volume of the much larger (up to four times) pores which are penetrated through the entry pore, and the accessibility of a wide diameter range is controlled by pore necks of diameters which are distributed over a narrower range.

TL;DR: A review of the mechanical quantities of interest in die compaction, in relation to a number of experiments on the bulk and wall stresses, displacements, deformation and density changes that occur during the compaction of powders, illustrated by results on iron oxide and ferrite samples, is given in this article.

TL;DR: In this paper, a simple and accurate mercury porosimeter has been built and used to determine the primary drainage, imbibition, and secondary drainage curves of sandstone samples in the pressure range of 0 to 1000 cm Hg column.

TL;DR: In this paper, the effects of raw particle size and the amount of bridging liquid on the average size of resultant agglomerate were investigated, and a linear correlation on a log-log plot was observed between the aggregates size and a small amount of saturated aqueous lactose solution to wet the particles preferentially.

TL;DR: In this paper, the vertical segregation pattern of an ordered mixture was investigated under various conditions: mixture concentrations, energy input and bed heights, and a critical assessment of the application of classical segregation mechanisms and an elaboration of the concepts of ordered unit segregation and constituent segregation were made.

TL;DR: In this article, a mathematical procedure is outlined for obtaining the complete selectivity curve based on extra-polation of the smaller sizes of the feed size distribution on a Schuhmann plot, and fitting the selectivity curves to a three-parameter function (bypass, d 50 and steepness parameters).

TL;DR: In this paper, the authors measured the viscosities of gas-fluidized beds at pressures up to 20 bar by a falling-sphere technique and found that an increase in gas pressure leads to a substantial decrease in viscosity of the fine powder when fluidised but the viscoability of fluidised beds of powders larger than about 100 μm is almost independent of pressure.

TL;DR: Pore growth during the early stages of sintering several materials was first identified by PSD as mentioned in this paper, which has proved valuable for evaluating the firing of basic refractories, brick and sanitary ware.

TL;DR: In this paper, simultaneous estimation of rate and breakage distribution parameters has been carried out for a complex pyritic ore from the batch ball mill size distribution data using back-calculation approach.

TL;DR: In this paper, the shape of particles produced by comminution is reviewed and some agreement among workers as to the shapes of particles which are produced by the comminutions machinery is found.

TL;DR: Pore size distributions, measured by mercury intrusion, have been used to better explain, and even predict, the behavior of a variety of construction materials, viz. hydrated portland cement, portland concrete aggregates, compacted fine-grained soils, and shales as discussed by the authors.

TL;DR: In this paper, the choice of the gas distributor to bed pressure drop ratio for the stable operation of gas fluidised beds is determined by the type of gas distributor and by the characteristics of the bed material.

TL;DR: In this paper, the change in the specific surface area of several metallic powders has been investigated during the various stages of sintering, and a simple mathematical model has been constructed to describe the results.