ABSTRACT The objective of this paper is to present the differences which appear in terms of therm... more ABSTRACT The objective of this paper is to present the differences which appear in terms of thermodynamics and structure in the elaboration process of two composite materials produced through an aluminothermic reduction of molten salts. There were conducted two sets of experiments of reduction of liquid Potassium Fluoroborate (KBF 4) and the mix of salts (KBF 4 + K 2 TiF 6) with aluminium. In order to indentify the formed compounds there were carried out XRD analysis, electronic microscopy analysis (SEM+EDS) and optical microscopy analysis. Keywords: potassium tetrafluoroborate, aluminium diboride, titanium diboride, potassium fluorotitanate In recent years, aluminum matrix composites reinforced with ceramic particles represent a significant area in the research of structural composites. For the study of MMCs (metal matrix composites) there has been developed a large variety in the fabrication procedures. Thus, the composite materials have been obtained by different techniques like powder metallurgy, sputter deposition and casting methods.[5] The in-situ composites occured in the mid '80s, offers a termodynamic stability to fine and dispersed particles into the metal matrix due to the growth and germination of the reinforcement particles which takes place into the matrix alloy, assuring a strong link at the particle – matrix interface [6-8]. The purpose of this paper is to make a paralel between the thermodynamics and mechanism of the forming reactions of borides (TiB 2 and AlB 2) by an aluminothermic reduction of fluorides. A1-B System It is agreed that an eutectic exists at low boron contents, and that boron has a low solubility (< 100 ppm) in the solid. However, there is disagreement on the boron solubility in the liquid. The older data, when extrapolated to 660 °C give an eutectic composition of 0.09 wt [1]. More recent studies show the eutectic to be at 0.022 wt and 659.7°C and give higher boron solubilities at temperatures higher than 900 °C. The boron composition of the hypoeutectic liquid is given by the relation
ABSTRACT The aim of this paper is to present the mechanism of TiB 2 formation during the manufact... more ABSTRACT The aim of this paper is to present the mechanism of TiB 2 formation during the manufacturing of Al/TiB 2 in-situ composites using the reaction of liquid melts in the Al-K 2 TiF 6-KBF 4 system. The evolution of TiB 2 particles formation at maintained temperatures between 750-950 0 C was observed through optical and electron microscopy (SEM+EDAX) and also through X-ray diffraction. It was noticed that with increasing the maintained temperature the TiAl 3 particles were breaking up, increasing their merging rate, as well as the TiB 2 particles formation rate.
The present work reports on the synthesis and properties of inorganic polymers (&quot... more The present work reports on the synthesis and properties of inorganic polymers ("geopolymers") made of 100% fly ash from lignite's combustion, 100% primary lead slag and mixtures of the two. In the inorganic polymers with both fly ash and lead slag the main crystalline phases detected are wüstite, magnetite, sodium zinc silicate, quartz, anorthite, and gehlenite; litharge partially dissolves. FTIR analysis in these samples revealed that the main peaks and bands of end members also exist, along with a new amorphous reaction product. In terms of microstructure, both fly ash and lead slag dissolve and contribute in the binding phase whereas the larger particles act as aggregates. For an increasing lead slag in the composition, the binding phase is changing in chemistry and reaches PbO values higher than 50 wt.% for the 100% lead slag inorganic polymer. Regarding the properties of fly ash and lead slag inorganic polymers, compressive strength is higher than 35 MPa in all cases and water absorption diminishes as the lead slag content increases. A comparison of leaching results before and after polymerisation reveals that pH is an important factor as Pb is immobilised in the binding phase, unlike Zn and As.
IOP Conference Series: Materials Science and Engineering, 2015
In this paper we present the results of industrial experiments consisted in determination, by spe... more In this paper we present the results of industrial experiments consisted in determination, by specialized measurements, of the dust percentage in the evacuated gases from the EAF and of chemical composition of polluting burnt gases. The electric arc furnaces (EAFs), as powerful energy consumers, are also polluting emissions generators with an important environmental impact. The steel refining in the EAF is based on a complex mechanism of oxidizing chemical processes, due to the introduced oxygen and air. A first step is the diffusion and adsorption on the slag surface of molecular oxygen. The most significant polluting emissions of the EAF are metallic and oxides powders driven by emergent gases.
Prin aceastæ lucrare Moshe Idel propune analiza unui motiv pe care-l consideræ componenta magicæ ... more Prin aceastæ lucrare Moshe Idel propune analiza unui motiv pe care-l consideræ componenta magicæ a literaturii mistice evreieïti. Demersul lui Idel tinde spre o apropiere a diferitelor sinteze dintre tradiii magice evreieïti ïi neevreieïti; astfel cæ acordæ o mai mare importanæ ...
These specific and contradictory attitudes make the author assert that some of the first kabbalis... more These specific and contradictory attitudes make the author assert that some of the first kabbalists had tried to re-emphasize the importance of an older mystical tradition in response to Maimonides' two important statements by which he considered that authentic Jewish ...
ABSTRACT This paper presents theoretical considerations on the mechanism and kinetics of liquid m... more ABSTRACT This paper presents theoretical considerations on the mechanism and kinetics of liquid metal filtration as it is used in the refining of aluminium and ferrous alloys. The mechanisms are: adherence and sintering of inclusions to the filter surface; chemical reaction between the inclusion and the filter surface; and precipitation of secondary inclusions due to the drop in temperature when the liquid alloy flows through the filter. Of these the first mechanism is considered to be the most important as a source of inclusions in the material being refined. The second mechanism is useful to the refining process in that it reduces the amount of inclusions, and the third mechanism can be avoided by preheating the filter.
ABSTRACT The objective of this paper is to present the differences which appear in terms of therm... more ABSTRACT The objective of this paper is to present the differences which appear in terms of thermodynamics and structure in the elaboration process of two composite materials produced through an aluminothermic reduction of molten salts. There were conducted two sets of experiments of reduction of liquid Potassium Fluoroborate (KBF 4) and the mix of salts (KBF 4 + K 2 TiF 6) with aluminium. In order to indentify the formed compounds there were carried out XRD analysis, electronic microscopy analysis (SEM+EDS) and optical microscopy analysis. Keywords: potassium tetrafluoroborate, aluminium diboride, titanium diboride, potassium fluorotitanate In recent years, aluminum matrix composites reinforced with ceramic particles represent a significant area in the research of structural composites. For the study of MMCs (metal matrix composites) there has been developed a large variety in the fabrication procedures. Thus, the composite materials have been obtained by different techniques like powder metallurgy, sputter deposition and casting methods.[5] The in-situ composites occured in the mid '80s, offers a termodynamic stability to fine and dispersed particles into the metal matrix due to the growth and germination of the reinforcement particles which takes place into the matrix alloy, assuring a strong link at the particle – matrix interface [6-8]. The purpose of this paper is to make a paralel between the thermodynamics and mechanism of the forming reactions of borides (TiB 2 and AlB 2) by an aluminothermic reduction of fluorides. A1-B System It is agreed that an eutectic exists at low boron contents, and that boron has a low solubility (< 100 ppm) in the solid. However, there is disagreement on the boron solubility in the liquid. The older data, when extrapolated to 660 °C give an eutectic composition of 0.09 wt [1]. More recent studies show the eutectic to be at 0.022 wt and 659.7°C and give higher boron solubilities at temperatures higher than 900 °C. The boron composition of the hypoeutectic liquid is given by the relation
ABSTRACT The aim of this paper is to present the mechanism of TiB 2 formation during the manufact... more ABSTRACT The aim of this paper is to present the mechanism of TiB 2 formation during the manufacturing of Al/TiB 2 in-situ composites using the reaction of liquid melts in the Al-K 2 TiF 6-KBF 4 system. The evolution of TiB 2 particles formation at maintained temperatures between 750-950 0 C was observed through optical and electron microscopy (SEM+EDAX) and also through X-ray diffraction. It was noticed that with increasing the maintained temperature the TiAl 3 particles were breaking up, increasing their merging rate, as well as the TiB 2 particles formation rate.
The present work reports on the synthesis and properties of inorganic polymers (&quot... more The present work reports on the synthesis and properties of inorganic polymers ("geopolymers") made of 100% fly ash from lignite's combustion, 100% primary lead slag and mixtures of the two. In the inorganic polymers with both fly ash and lead slag the main crystalline phases detected are wüstite, magnetite, sodium zinc silicate, quartz, anorthite, and gehlenite; litharge partially dissolves. FTIR analysis in these samples revealed that the main peaks and bands of end members also exist, along with a new amorphous reaction product. In terms of microstructure, both fly ash and lead slag dissolve and contribute in the binding phase whereas the larger particles act as aggregates. For an increasing lead slag in the composition, the binding phase is changing in chemistry and reaches PbO values higher than 50 wt.% for the 100% lead slag inorganic polymer. Regarding the properties of fly ash and lead slag inorganic polymers, compressive strength is higher than 35 MPa in all cases and water absorption diminishes as the lead slag content increases. A comparison of leaching results before and after polymerisation reveals that pH is an important factor as Pb is immobilised in the binding phase, unlike Zn and As.
IOP Conference Series: Materials Science and Engineering, 2015
In this paper we present the results of industrial experiments consisted in determination, by spe... more In this paper we present the results of industrial experiments consisted in determination, by specialized measurements, of the dust percentage in the evacuated gases from the EAF and of chemical composition of polluting burnt gases. The electric arc furnaces (EAFs), as powerful energy consumers, are also polluting emissions generators with an important environmental impact. The steel refining in the EAF is based on a complex mechanism of oxidizing chemical processes, due to the introduced oxygen and air. A first step is the diffusion and adsorption on the slag surface of molecular oxygen. The most significant polluting emissions of the EAF are metallic and oxides powders driven by emergent gases.
Prin aceastæ lucrare Moshe Idel propune analiza unui motiv pe care-l consideræ componenta magicæ ... more Prin aceastæ lucrare Moshe Idel propune analiza unui motiv pe care-l consideræ componenta magicæ a literaturii mistice evreieïti. Demersul lui Idel tinde spre o apropiere a diferitelor sinteze dintre tradiii magice evreieïti ïi neevreieïti; astfel cæ acordæ o mai mare importanæ ...
These specific and contradictory attitudes make the author assert that some of the first kabbalis... more These specific and contradictory attitudes make the author assert that some of the first kabbalists had tried to re-emphasize the importance of an older mystical tradition in response to Maimonides' two important statements by which he considered that authentic Jewish ...
ABSTRACT This paper presents theoretical considerations on the mechanism and kinetics of liquid m... more ABSTRACT This paper presents theoretical considerations on the mechanism and kinetics of liquid metal filtration as it is used in the refining of aluminium and ferrous alloys. The mechanisms are: adherence and sintering of inclusions to the filter surface; chemical reaction between the inclusion and the filter surface; and precipitation of secondary inclusions due to the drop in temperature when the liquid alloy flows through the filter. Of these the first mechanism is considered to be the most important as a source of inclusions in the material being refined. The second mechanism is useful to the refining process in that it reduces the amount of inclusions, and the third mechanism can be avoided by preheating the filter.
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