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Study of the Effect of Intensity of Vibrations and Temperature on the Cooling Characteristics of Quenching Media

Perju Manuela-Cristina, Nejneru Carmen, Burduhos-Nergis Dumitru Doru, Vizureanu Petrica, Minciuna Mirabela G., Sandu Andrei Victor

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 3

997--1002

EN

Quenching technology requires the use of media with different cooling intensities and various shapes of cooling curves that show different particularities compared to that of conventional media such as water, oil, or emulsions. The use of synthetic quenching media is relatively new and also has multiple advantages such as non-flammability, safety in use and low cost. In this study, the cooling media tested was obtained by mixing 2 wt% carboxymethyl cellulose with 2 wt% NaOH in one litter of water. Moreover, three different temperatures (20°C, 40°C and 60°C) of the quenching media were evaluated. By dissolution in water, a synthetic solution with low viscosity, surfactant and lubricant was obtained. Because carboxymethyl cellulose is a biodegradable organic material, that is obtained as a by-product in the manufacture of paper, a basic substance with a preservative effect was added. According to this study, both the variation diagram of the heat transfer coefficient and the diagram of the cooling rates, during the cooling stages give important indications regarding the use of a liquid cooling medium for quenching.

2

Structural and Physical Characterization of New Ti-Based Alloys

Baltatu Iustinian, Sandu Andrei Victor, Baltatu Madalina Simona, Benchea Marcelin, Achitei Dragos, Ciolacu Florin, Perju Manuela-Cristina, Vizureanu Petrica, Benea Lidia

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

255--259

EN

Production of Ti-based alloys with non-toxic elements give the possibility to control the market of medical applications, using alloys with appropriate properties for human body, contributing to improving the health of the population. Determination of parameters of atomic and magnetic structure of functional biomaterials demonstrating interesting physical phenomena and being promising for medical applications in a wide range of thermodynamic parameters; exploration of the role of cluster aggregation in the formation of physical properties. Paper is about the obtaining of the new titanium system alloys, the determining their characteristics and structure, and obtaining information concerning phase transitions and some mechanical properties. Ti15Mo7ZrxTa (5 wt.%, 10 wt.% and 15 wt.%) alloys developed shows a predominant β phase highlighted by optical microstructure and XRD patterns. A very low young modulus of alloys was obtained (43-51 GPa) which recommends them as very good alloys for orthopedic applications.

3

Some Aspects Concerning Titanium Coverage with Hydroxyapatite

Perju Manuela-Cristina, Nejneru Carmen, Vizureanu Petrica, Aelenei Andra-Adorata, Sandu Andrei Victor, Sachelarie Liliana, Nabiałek Marcin

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

521--527

EN

Generally, the metallic implants do not exhibit any bio-integration properties in contact with bone tissues. To improve the interfacial properties of metallic implants in contact with bone, the coatings with thin biocompatible films are used. Two methods to coating titanium implants with hydroxyapatite are described. The first is a two phase method, where by cathodic polarization is deposed a monetite film followed by an alkaline treatment when the monetite is converted to hydroxyapatite. The second method is a biomimetic deposition on an alkaline activate titanium surface, using a five time more concentrated simulated body fluid (5xSBF). After deposition this samples was drying at 120℃ and was sintered at 700℃ for three hours. Optical microscopy, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray (EDX) were used to characterize structure, morphology and compositions of the deposed films. In this study, electrochemical deposition and biomimetic deposition of hydroxyapatite are compared.

4

Microstructural Analysis of Ambient Cured Phosphate Based-Geopolymers with Coal-Ash as Precursor

Burduhos Nergis Dumitru Doru, Vizureanu Petrica, Lupescu Stefan, Burduhos Nergis Diana Petronela, Perju Manuela-Cristina, Sandu Andrei Victor

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

595--600

EN

An alternative for Ordinary Portland cement (OPC) consumption is the production and integration of green cement. In other words, the clinker consumption has to be replaced with new low-carbon binders. A possible solution was introduced by the geopolymerisation technology. However, the alkaline activation of geopolymers offers the possibility of obtaining greener materials with high properties, superior to OPC, but due to the high price of sodium silicate, their industrial use is limited. In the past few years, a new activator has been discovered, namely phosphoric acid. This study approaches the obtaining of coal ash-based geopolymers activated with acid solution cured at room temperature. Accordingly, phosphoric acid, 85% by mass, was diluted in distilled water to obtain a corresponding activation solution for H3PO4/Al2O3 ratio of 1.0 and two types of geopolymers were ambient cured (22°C ±2°C). Moreover, to evaluate the geopolymerisation potential of this system (coal ash - phosphoric acid), SEM and EDS analysis was performed to investigate their morphologic characteristics.