Petru Moldovan

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Papers by Petru Moldovan

Influence of mechanical activation on the kinetics of non ferrous metal sulphides oxidation

University Politehnica of Bucharest Scientific Bulletin-series A-applied Mathematics and Physics, 2010

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Complex processing of molten secondary aluminium

Journal de physique, Nov 1, 1993

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CHARACTERISATION OF A NEW Cu-Fe3O4 NANOCOMPOSITE

Cu-Fe 3 O 4 nanocomposites obtained by compacting and sintering nanometric copper and magnetite p... more Cu-Fe 3 O 4 nanocomposites obtained by compacting and sintering nanometric copper and magnetite powders, were characterised from the point of view of their structure and main physical and magnetic properties. The structure and morphology of nanocomposites was determined by X-ray diffraction (XRD), bright field transmission electron microscopy (TEMBF) and scanning electron microscopy (SEM). Thermal and electrical conductivities of nanocomposites were also determined as well as certain magnetic properties.

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Thermodynamics and Mechanism of Metalothermic Reduction of Molten Salts

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 &amp;#39;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 (&amp;lt; 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

In-situ Al/TiB 2 composite obtained through reaction in liquid phase

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.

In situ development of AlBx/AA6060 and AA5083 alloys cast composites

Composites Part B-engineering, Jul 1, 2016

Al e AlB x (x ¼ 2,12) , AA6060 e AlB x (x ¼ 2,12) and AA5083 e AlB x (x ¼ 2,12) composites with 3... more Al e AlB x (x ¼ 2,12) , AA6060 e AlB x (x ¼ 2,12) and AA5083 e AlB x (x ¼ 2,12) composites with 3 wt % AlB x particles were developed by in-situ reaction of molten aluminium and alloys (AA5083 and AA6060) with inorganic salt KBF 4 at a temperature of 900 C. The chemical reaction produces boron, which dissolves into the molten alloy and subsequently forms aluminium borides (AlB 2 and AlB 12). The thermodynamic properties of the reactions are calculated by HSC Chemistry 6.0 software. In the case of aluminium matrix the melt solidified in the crucible, between 980 C and 200 C, in order to develop the peritectic reaction AlB 12 þ 5Al (l) ¼ 6AlB 2. It was found that both in the case of aluminium and aluminium alloys the peritectic reaction occurs partially. The composites were characterised by SEM and XRD analysis. The stress-strain measurement showed 8% improvement towards the matrix alloys. The fracture features of composites were examined using SEM analysis. Ductile and brittle locally fractography is revealed. Composites exhibited a higher resistance to crack initiation than the matrix alloys. The results obtained in the experiments and analysis helps to clarify the mechanism of interaction between liquid aluminium and KBF 4 at high temperatures.

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Thermodynamics of in situ formation of TiB2 particulates in complex aluminium alloys for aeronautics

Journal of Engineering Sciences and Innovation, Sep 3, 2019

Aluminum complex alloy AlCuMgZn, reinforced by in-situ TiB2 particles are fabricated via liquid m... more Aluminum complex alloy AlCuMgZn, reinforced by in-situ TiB2 particles are fabricated via liquid metallurgy route based on the exothermic reactions between matrix alloy and inorganic salt mixture (K2TiF6 and KBF4), at 750 o C, at various time (60, 90 and 120 minutes). The XRD patterns revealed the formation of TiB2. At working temperature by thermodynamic point of view (negative G), some secondary reaction also was possible, and AlB12, MgB2 and MgB12 can to form. The main alloying elements of AlCuMgZn alloy do not influence final reaction products. Increasing the reaction time from 60 to 120 minutes leads to agglomeration of TiB2 particles. Form and dimensions of TiB2 particles obtained after separation from aluminium matrix were determined by Transmission Electron Microscopy (TEM) and through Dynamic Light Scattering (Zetasizer Nano ZS Malvern).

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New in-situ composite materials with aluminium alloy matrix (6063) and vanadium boride particles

Journal of Engineering Sciences and Innovation, Sep 14, 2022

The exothermic reactions between AA 6063 alloy, AlV master alloy, and inorganic salt mixture (KBF... more The exothermic reactions between AA 6063 alloy, AlV master alloy, and inorganic salt mixture (KBF4) result in the fabrication of matrix alloy 6063 reinforced by in-situ obtained VB2 particles via liquid metallurgy. The presence of VB2 was revealed using optical microscopy and by the XRD patterns. The reinforcing particles act as a grain refiner at 1% concentration of VB2. A set of compressive tests were taken to showcase the compressive stress-strain curves of the different samples at different concentrations of VB2.

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Synthesis of inorganic polymers using fly ash and primary lead slag

Journal of Hazardous Materials, 2012

The present work reports on the synthesis and properties of inorganic polymers (&amp;amp;quot... more The present work reports on the synthesis and properties of inorganic polymers (&amp;amp;quot;geopolymers&amp;amp;quot;) made of 100% fly ash from lignite&amp;amp;#39;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.

(SUMMARY OF Ph.D. THESIS) PHYTOSANITARY RISK ANALYSIS IN THE CONTROL OF POWDERY MILDEW IN FOREST ECOSYSTEMS IN THE CONTEXT OF CLIMATE CHANGE

The Gospel of Judas, edited by Johanna Brankaer

Gnosis: Journal of Gnostic Studies, 2021

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Christian Origins and the Establishment of the Early Jesus Movement, edited by Stanley E. Porter and Andrew W. Pitts

Gnosis: Journal of Gnostic Studies, 2021

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The Forgotten Creed: Christianity’s Original Struggle Against Bigotry, Slavery, and Sexism, written by Stephen Patterson

Gnosis: Journal of Gnostic Studies, 2021

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A Theory of the Aphorism: From Confucius to Twitter, written by Andrew Hui

Gnosis: Journal of Gnostic Studies, 2021

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The Gospel of Thomas and Plato. A Study of the Impact of Platonism on the ‘Fifth Gospel’, written by Ivan Miroshnikov

Vigiliae Christianae, 2020

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Religion, Theory, Critique: Classic and Contemporary Approaches and Methodologies. Edited by RichardKing. New York: Columbia University Press, 2017. Pp. xi + 689. Hardback, $180; Paper, $60; eBook, $59.99

Religious Studies Review, 2018

The Copernican Turn in the Study of Religion richard king The academic future of religion as a co... more The Copernican Turn in the Study of Religion richard king The academic future of religion as a concept will need to focus on deconstructing the category and analyzing its function within popular discourse, rather than assuming that the category has content and seeking to specify what that content is.

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Authority and Identity in Emerging Christianities in Asia Minor and Greece

Authority and Identity in Emerging Christianities in Asia Minor and Greece, 2018

Fees are subject to change. This book is printed on acid-free paper and produced in a sustainable... more

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About EAF and environment

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.

Constructive and functional modernization of EAF

IOP Conference Series: Materials Science and Engineering, 2015

This article presents the main constructive and functional modernization of Electric Arc Furnace ... more This article presents the main constructive and functional modernization of Electric Arc Furnace (EAF). Schwabe is the creator of UHP (Ultra High Power) EAF. We present in this article the optimal use of EAF power and time aspects. These two main factors determine the increase in the productivity of the Electric Arc Furnace. Electric arc furnace operation can be based on either the short arc (with high intensity and low voltage) or long arc version (with low intensity and high voltage). Introduction of vault walls and water cooled has resulted in major reductions in the consumption of refractory bricks from electric arc furnace. Another important technological evolution inserted in the process of elaboration of steel in electric arc furnace is lowering the temperature of the exhaust. Using a system of intensive oxygen insufflation during melting can get many technological advantages. Another constructive and functional modernization is EAF inflatable sealing device for retention of slug.

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