Development of ceramic floor tile compositions based on quartzite and granite sludges

In the present work, industrial sludges derived from cutting and polishing natural stones (granite and quartzite) were characterised in terms of particles size distribution, chemical and mineralogical composition, and thermal behaviour and their potential to be incorporated as main components in red-clay-based stoneware tiles was evaluated. High levels (60–70 wt.%) of incorporation were attempted aiming at designing new formulations intended to be less expensive and possess better final properties (lower water absorption and higher flexural strength) in comparison to an industrial reference body used in the production of rustic tiles by extrusion, characterised 8–9% water absorption and a flexural strength of 17–18 MPa. Extruded rods of different formulations were produced and fired at 1100 °C, 1125 °C, 1150 °C and 1200 °C. The experimental results showed that all the new formulations performed better with the most significant improvements being obtained with incorporation of granite sludge. Flexural strength values more than triplicate and water absorption decreased by more than one order of magnitude in comparison to the reference paste. The new products fulfil the requirements of the ISO 13006 standard, group BIa (porcelain tiles).     

Trays for gas-liquid contacting

A type of tray for gas-liquid contacting is described, in which the free area for gas flow through the tray is variable with and controlled by the gas flowrate. The property through which control of the free area is effected is the surface tension of the liquid phase. The advantages are the same as those of ballast and valve trays; namely, reduced pressure drop at high gas rates resulting in increased column capacity, and reduced free space at lower gas rates resulting in high mass transfer efficiency at low and medium vapor loadings as well. Tooling and production costs for the trays of the present investigation, however, are considerably lower than for ballast or valve trays or any other types which require machining operations in their fabrication, and are as low or lower than for sieve trays. Initial experimental comparisons with conventional trays demonstrated that the trays of the present investigation, although designed primarily for operation at high vapor loadings, were indeed capable of yielding high mass transfer efficiencies in the low-to-medium range of vapor loading     

Lipids in soil

As much as 20% of soil humus occurs in the form of lipids. High values are characteristic of Podzol soils and highmoor peats. Lipids of the following types are known to be present: paraffin hydrocarbons, phospholipids, fats, waxes, fatty acids, and terpenoids. A long list of compounds have been reported; the identification of many of them require confirmation using modern analytical techniques. Some of the lipids known to occur in soil have phytotoxic properties; these may have a depressing effect on seed germination and on root and shoot growth. Waxes and similar materials may be responsible for the difficultly wettable condition of certain sands.     

Glass transition temperature and critical properties

In a preceding paper it was shown that for high molecular weight polymers, the volume of the repeating unit at T_g is proportional to the total free space defined as V_c?V₀ where V_c is the volume of the repeating unit at the critical temperature and V₀ is the volume of the repeating unit at absolute zero. Here it will be demonstrated that this proportionality is also true for a host of low molecular weight liquids. In addition, an empirical method of estimating T_c for a high molecular weight polymer is proposed which provides values of T_c which are consistent with those for low molecular weight liquids.     

Deposition of dense isotropic carbon from acetylene in fluidized bed

Pyrolytic carbon was deposited from acetylene in a fluidized bed at 1100°C on alumina microspheres. In case when only argon was used as the diluent gas, density and BAF of the deposit decreased and deposition yield increased with increasing acetylene concentration. Hydrogen sypply suppressed carbon formation and, consequently, caused an increase in density and Lc. BAF was relatively independent of hydrogen concentration. It was found that high density, isotropic carbon can be deposited from acetylene at 1100°C, if an appropriate proportion of hydrogen is added.     

Tensile strength of polyurethane exposed to nitrogen dioxide

Polyurethane prepared from tetramethylene glycol and diisocyanate was exposed in the form of films to small pressures of NO₂ and to NO₂ plus air. Tensile strength was measured as a function of exposure time and temperature with an apparatus especially constructed for the purpose of measuring mechanical properties in different environmental “atmospheres.”