Monodisperse Sols of Barium Sulfate. III. Electron-Microscopic Study of Internal Structure of Particles

The internal structure of monodisperse barium. sulfate particles precipitated from homogeneous solution was studied. The elliptically shaped particles were examined by a sufficiently penetrating electron beam (acceleration voltage 80 kV) and by the ultramicrotomic technique. The particles did not appear compact but had a sponge-like structure with an average pore size of 30 A. The present results are supporting the assumption of barium sulfate particles being possibly formed by an aggregation mechanism predominantly over the direct diffusion growth of primary particles

Monodisperse Sols of Barium Sulfate. III. Electron-Microscopic Study of Internal Structure of Particles

The internal structure of monodisperse barium. sulfate particles precipitated from homogeneous solution was studied. The elliptically shaped particles were examined by a sufficiently penetrating electron beam (acceleration voltage 80 kV) and by the ultramicrotomic technique. The particles did not appear compact but had a sponge-like structure with an average pore size of 30 A. The present results are supporting the assumption of barium sulfate particles being possibly formed by an aggregation mechanism predominantly over the direct diffusion growth of primary particles

Micelle Formation by Tritons in Aqueous Solutions

The critical micellar concentrations and the mass-average micellar molecular masses of non-ionic surfactants, i. e. the members of the homologous series of t-octyl-phenoxy-polyethoxy-ethanols : Triton X-114, Triton X-100, Triton X-305, Triton X-405, and Triton X-705 have been determined by means of light scattering and other methods at 298 K. Variations in aggregation number from 6 to 220 (or micellar molecular mass from 19,000 to 120,000) have been found, depending on the length of monomeric molecule. These quantities, as well as c.m.c./mol dm-3, decrease with the increasing length of the hydrophilic part of the molecule, as has already been reported for other non-ionic surfactants

Monodisperse Sols of Barium Sulfate. I. Preparation of Stable Sols

Monodisperse sols of barium sulfate were prepared by a modified method of homogeneous precipitation and characterized by electron microscopy. The particles were spindle-shaped and of a rather uniform distribution when prepared with concentrations of barium and sulfate ions of 4 X 10·3 M. The degree of monodispersity obtained depends on the cleanliness of solutions and glassware, and good results were obtained by filtration of solutions and careful cleaning of glassware. Morphological changes in the particles during the reaction are studied. Monodisperse particles dispersed in the mother liquor are not stable, since they aggregate and recrystallize by aging. However, addition of nonionic detergents stabilizes the particles for longer periods, as detected by electron microscopy and ultramicroscopy. Stable sols of barium sulfate of particle size from 195 to 480 mμ for the longer axis, and from 95 to 188 m~t for the shorter axis, respectively, were prepared

Monodisperse Sols of Barium Sulfate. II. Morphological Characteristics, Aging and Dissolution of Particles

A morphological study is made of barium sulfate particles precipitated from a homogeneous solution at 25° and 50° C in the presence of various foreign substances and without them. As foreign substances several types of compounds were chosen: a nonionic detergent (Triton X-100), an anionic detergent (Aerosol MA), and complexing agents (citrate and EDTA). The particles were studied by electron microscopy. In all cases anisotropic particles were formed with more or less defined structures, and most of the systems were monodisperse. The appearance of twins, grown together in different profile planes, was observed. The aging of particles in mother liquor was studied, as well as the dissolution of particles in water. On the basis of particle slize data, the morphological characteristics of particles, and their aging and dissolution, the mechanisms of particle foTmation were discussed. The -i!nfluence of foreign substances is discussed in terms of their chemical properties. lt lis sugges,ted that particles of barium sulfate are predominantly formed by aggregation of primary particles, whilst pure diffusion growth is encountered only under restricted conditions

Viscosimetric Determination of Latex Coagulation

The viscosity of latices was investigated in dependence upon the pH value of suspensions, their aging and the concentration of added electrolyte. The systems used were well-defined monodisperse polystyrene latices within the concentration range from 0.1 to 10/o, and with a high negative charge oh the latex particle surface. It was found that viscosity measurement in a dispersion at a certain concentration of the dispersed phase could be used for latex coagulation determination. On the basis of this finding an attempt was made to determine the critical coagulation concentration. The values obtained were concordant with those determined by t4rbidity measurements. In order to determine the exact pH region in which a decrease in the pH value leads to a sudden change of stability, viscosity measurements were performed in relation to the pH value of latex suspensions. The limiting pH value was independent of the time of measuring, latex concentration, and the ionic strength of the added electrolyte. In our opinion this value is characteristic of a given system and it points to the dependence of the destabilization of a dispersion on the pH value. Therefore, it can be called »critical pH value« by analogy to the term »critical coagulation concen tra ti on«

Optimal Management of Marine Inspection with Autonomous Underwater Vehicles

t New technologies and system communications are being applied in the industry, improving the efficiency and effectiveness. This paper is focused on novel technologies, software and materials that allow to explore deep ocean floor. Autonomous underwater vehicles require planning navigation models and algorithms. Sensors equipped in underwater vehicles allow to inspect and analyse inaccessible areas. Monitor and control measurement process is required to ensure suitable underwater operations. This paper presents a model using the main inspection process variables. The model calculates the field of view of the autonomous underwater vehicle to be determined according to the type of sensor, the orientation and the distance from the floor. This study aims at stabilising the fundaments to develop an autonomous route for the autonomous underwater vehicles and optimize its operation performance