Possibilities of Physical-Chemical Sensors' Use for Optimizing the Processing of Metallurgical Melting Based on Computer Systems.

This article presents aspects regarding the possibilities of optimizing the quality of the elaboration of metallurgical melts by determining their physical-chemical properties. Thus, the article analyzes and presents methods for determining the viscosity and electrical conductivity related to metallurgical melts. Among the viscosity determination methods, two methods are presented, namely: the rotary viscometer method and the electro-vibratory viscometer method. Determining the electrical conductivity of a metallurgical melt is also of particular importance for ensuring the quality of the elaboration and refining of the melt. The article also presents the possibilities of using and implementing computer systems that ensure the accuracy of determining the physical-chemical properties of metallurgical melts, as well as examples of the use of physical-chemical sensors and specific computer systems for determining the analyzed parameters. The specific electrical conductivity measurements of oxide melts are performed by direct methods (by contact), with Ohm's law as a starting point. Thus, the article presents the voltmeter-ammeter method and the point method (or the zero method). The novelty of this article is the description and the use of specific methods and sensors for certain determinations (viscosity and electrical conductivity) for metallurgical melts. The motivation here is the presentation of the authors' research in the addressed field. The article presents an original contribution of the adaptation and use of some methods for determining some physico-chemical parameters, including specific sensors, in the field of the elaboration of metal alloys, with the aim of optimizing their quality.

Glass Foam from Flat Glass Waste Produced by the Microwave Irradiation Technique.

A glass foam with good thermal insulation characteristics (apparent density of 0.38 g/cm3, porosity of 81.9% and thermal conductivity of 0.089 W/m·K), high compressive strength (3.9 MPa) and a satisfactory microstructural homogeneity with pore size between 0.6-1.0 mm was obtained by sintering at 927 °C of flat glass waste, a glass waste usually not used in the manufacture of glass foam. The manufacturing recipe has been improved by the simultaneous use of two microwave susceptible foaming agents (SiC and Si3N4) and the addition of coal fly ash and an oxygen-supplying agent (MnO2). The originality of the work was the simultaneous use of the two foaming agents and also the application of the technique of predominantly direct microwave heating, compared to the conventional heating methods commonly used in the manufacture of glass foam. The remarkable energy efficiency of the microwave heating technique led to high average heating rates without affecting the structural homogeneity and very low specific energy consumption.

High-Strength and Heat-Insulating Cellular Building Concrete Based on Calcined Gypsum.

A cellular concrete with a fine porous structure was experimentally made using the corrosion technique for aluminum powder as an expanding agent in an aqueous solution of Ca(OH)2. The originality of this paper was the use of our own production method for the fine aluminum powder through atomizing the recycled molten waste of this metal using concentrated jets of nitrogen. Additionally, the waste melting technique involved our own microwave heating method. A high weight proportion of calcined gypsum (maximum 82.3%) represented the main concrete binder. Using moderate contents of coal fly ash (3.6-11.1%) together with perlite (4.6-6.4%) to reduce the pore size and silica fume (0.3-1.2%) with pozzolanic properties, the aim was to obtain a macrostructure characterized by a very low pore size and to increase the compressive strength (by up to 4.1 MPa), despite the relatively low density (below 641 kg/m3). An industrial method of increasing the mechanical strength by steam curing fresh concrete was applied.