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1
Content available XRD and STA Characterization of Phosphate Layers Deposited on the Carbon Steel Surface
Burduhos-Nergis Diana Petronela, Bejinariu Costica, Cazac Alin Marian, Sandu Andrei Victor, Vizureanu Petrica
Archives of Metallurgy and Materials
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2023
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Vol. 68, iss. 3
955--960
EN
Carbon steel is one of the most widely used alloys in many industries, however, its use is limited by its low corrosion resistance. Depositing a layer of phosphate on its surface improves the corrosion resistance as well as other properties, such as wear resistance, adhesion etc. Accordingly, preliminary studies demonstrated that carbon steel coated with phosphate layers can be used in the manufacture of carabiners for various fields: civil engineering, oil industry etc. Whereas, to demonstrate their capacity to operate in severe conditions related to fire rescue and extinguishing operations, it is necessary to evaluate the thermal behaviour of these materials. Thus, the main goal of this paper is to study the behaviour at high temperatures of three different types of phosphate layers deposited on carbon steel surface, by STA analysis. Also, the paper aims to study the formation of different phosphate layers by determining the types of compounds formed after the completion of the phosphating process, by XRD analysis.
2
Content available The Influence of Sintering Temperature on the Microstructure of Coal-Ash Based Geopolymers
Burduhos-Nergis Dumitru Doru, Vizureanu Petrica, Achitei Dragos C., Sandu Andrei Victor, Burduhos-Nergis Diana Petronela, Abdullah Mohd Mustafa Al Bakri
Archives of Metallurgy and Materials
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2023
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Vol. 68, iss. 2
631--637
EN
Currently, one of the main challenges of civil engineering and science materials engineers is to develop a sustainable substitute for Ordinary Portland Cement. While the most promising solution is provided by the geopolymerisation technology, most of the studied geopolymers are based on natural raw materials (kaolin). The metakaolin is mainly preferred because of its rapid rate of dissolution in the activator solution, easy control of the Si/Al ratio, and white color. However, its high cost prevents it from being widely used in geopolymer composites or other materials that can become an industrial alternative for Ordinary Portland Cement. Several studies have shown that geopolymers with good performance can also be obtained from secondary raw materials (industrial wastes such as coal ash or slag). This explains why countries with rapidly developing economies are so interested in this technology. These countries have significant amounts of industrial waste and lack a well-developed recycling infrastructure. Therefore, the use of these by-products for geopolymers manufacturing could solve a waste problem while simultaneously lowering virgin raw material consumption. This study evaluates the effect of replacing different amounts of coal ash with sand on the microstructure of sintered geopolymers. Accordingly, scanning electron microscopy and energy dispersive X-ray analysis were involved to highlight the morphological particularities of room-cured and sintered geopolymers.
3
Content available 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.
4
Content available Phosphate Conversion Coating - A Short Review
Burduhos-Nergis Diana Petronela, Sandu Andrei Victor, Burduhos-Nergis Dumitru Doru, Vizureanu Petrica, Bejinariu Costica
Archives of Metallurgy and Materials
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2023
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Vol. 68, iss. 3
1029--1034
EN
Phosphating is the process of depositing, by conversion, a layer of insoluble phosphate compounds, on the metal’s surface. Although phosphate coatings have been studied since the early nineteenth century, they are not only still being studied, but are an area of interest due to their many applications. The advantages of these types of coatings are well known, such as the low cost of the deposition process, the improvement of corrosion resistance properties, and the improvement of wear resistance and adhesion of further deposited layers such as paint. All this, leads to studies on the constant improvement of the properties of the phosphate coating, by modifying the parameters of the phosphating process, as well as by modifying/replacing the substances used in the phosphating solutions with “environmentally friendly” solutions. Also due to these advantages, several researchers are studying the possibility of using phosphate coatings in fields such as civil engineering or medicine (biomaterials coatings). This paper aims to present some essential aspects of phosphating and to bring to the fore the latest research on “eco-friendly” phosphating solutions and the possibility of using the phosphating process in other fields, such as the medical field. Also, the paper aims to discuss the possibility of eliminating/reducing the harmful effect that the use of phosphating has on the environment.
5
Content available 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.
6
Content available 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.
7
Content available 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.
8
Content available Impact Behavior of the Ballistic Targets Package Composed of Dyneema Polymer and High Entropy Alloy Structures
Voiculescu Ionelia, Geanta Victor, Chereches Tudor, Vizureanu Petrica, Stefanoiu Radu, Rotariu Adrian-Nicolae, Mitrica Dumitru
Archives of Metallurgy and Materials
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2022
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Vol. 67, iss. 2
569--576
EN
Ballistic targets are multi-material assemblies that can be made of various materials, such as metal alloys, ceramics, and polymers. Their role is to provide collective or individual ballistic protection against high-speed dynamic penetrators or kinetic fragments. The paper presents the impact behavior with incendiary perforating bullets having 7.62 mm of ballistic packages made of combinations between Dyneema ultra-high-molecular-weight polyethylene and high entropy alloy from alloying system AlCoCrFeNi, by analyzing the dynamic phenomena (deformation, perforation) that take place at high speeds. The geometry evolution of the physical model subjected to numerical simulation allows a very good control over the discretization network and also allows the export for modeling to nonlinear transient phenomena. The results obtained by numerical simulation showed that the analyzed ballistic package does not allow sufficient protection for values of impact velocities over 500 m/sec.
9
Content available Effect of Solid-To-Liquids and Na2SiO3-To-NaOH Ratio on Metakaolin Membrane Geopolymers
Ibrahim Masdiyana, Wan Ibrahim Wan Mastura, Al Bakri Abdullah Mohd Mustafa, Sauffi Ahmad Syauqi, Vizureanu Petrica
Archives of Metallurgy and Materials
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2022
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Vol. 67, iss. 2
695--702
EN
Geopolymer is synthesized by polycondensation of SiO4 and AlO4 aluminosilicate complexes, tetrahedral frames linked with shared sialate oxygen. This paper studies the effect of the solids-to-fluids (S/L) and Na2SiO3/NaOH proportions on the preparing of metakaolin inorganic membrane geopolymer. By consolidating a mixture of metakaolin with sodium hydroxide, sodium silicate and foaming agent, the geopolymer membrane was made in required shape about 1 cm and cured at 80°C for 24 hours. After the curing process, the properties of the samples were tested on days 7. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution were utilized as an alkaline activator with a NaOH fixation fixed at 10 M. The geopolymer inorganic membrane tests were set up with various S/L proportions (0.8, 1.0, 1.2 and 1.4) and Na2SiO3/NaOH proportions (0.5, 1.0, 1.5, 2.0 and 2.5). Aluminium (Al) powder as a foaming agent was used to create bubbles in porous structure and provide details on the development of membrane geopolymers. This metakaolin membrane, based on the geopolymer, was synthesized by a suspension that depends on the fast cementing mechanism of high-temperature slurries. Porous geopolymeric circles provided a homogeneous composition and quantitative distribution of pores. The water absorption, density, impact toughness testing and microstructure analyses were studied. However, considering the promising results, an adjustment in the mix design of the metakaolin inorganic membrane geopolymer mixtures could increase their mechanical properties without negatively affecting the mechanical properties and porosity, making these sustainable materials a suitable alternative to traditional porous cement concrete.
10
Content available Effect of NaOH Molar Concentration on Microstructure and Compressive Strength of Dolomite/Fly Ash-Based Geopolymers
Azimi Emy Aizat, Mohd Salleh M. A. A., Al Bakri Abdullah Mohd Mustafa, Aziz Ikmal Hakem A., Hussin Kamarudin, Chaiprapa Jitrin, Vizureanu Petrica, Yoriya Sorachon, Nabiałek Marcin, Wyslocki Jerzy J.
Archives of Metallurgy and Materials
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2022
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Vol. 67, iss. 3
993--998
EN
Dolomite can be used as a source of aluminosilicate to produce geopolymers; however, this approach is limited by its low reactivity. This study analyzes the viability of producing geopolymers using dolomite/fly-ash with sodium silicate and NaOH solutions (at multiple concentrations) by determining the resultant geopolymers’ compressive strengths. The dolomite/fly-ash-based geopolymers at a NaOH concentration of ~22 M resulted in an optimum compressive strength of 46.38 MPa after being cured for 28 days, and the SEM and FTIR analyses confirmed the denser surface of the geopolymer matrix. The synchrotron micro-XRF analyses confirmed that the Ca concentration exceeded that of Si and Mg, leading to the formation of calcium silicate hydrate, which strengthens the resulting geopolymers.
11
Content available Correlation between Microstructure and Electrochemical Properties of Al-Si Alloys
Minciuna Mirabela G., Vizureanu Petrica, Jeż Bartłomiej, Sandu Andrei Victor, Nabiałek Marcin, Achitei Dragos C.
Archives of Metallurgy and Materials
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2022
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Vol. 67, iss. 3
1067--1070
EN
The composition and structural modification of aluminium alloys influence their strength, tribological properties and structural stability. The phase composition of the structure as well as the characteristics of the elementary cell of each identified phase was established by X-ray diffraction, and the main objective was to determine the compositional phases, microstructure and microcomposition of the alloy. Based on the cyclic voltammograms it can be said that on the OCP interval (+1.5 V… -1.1 V), after the breakthrough potential is an intensification of the anodic process by the pronounced increase of the current density, in these conditions the Al-Si alloy has low values which means that it has a better corrosion resistance.
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