Ileana Nicoleta Popescu

• PhD
• Professor (Associate) at Valahia University of Targoviste

Polyacrylonitryle (PAN) fibers are used on a large scale in textile industry but, some sorts of PAN fibers are valuable precursors for specific carbon fiber (CF) due to their best fitness to the purpose e.g. for high strength CF or for active CF. The application of PAN as precursors of CF is based on its specific structure and texture. Thus, the pr...

Over the last few decades, researchers has been focused on the study of processing using different methods of new biocompatible and/or biodegradable materials such as permanent or temporary medical implants in reconstructive surgery. The advantages of obtaining biomedical implants by Powder Metallurgy (P/M) techniques are (i) obtaining the near-net...

Powder mixtures compaction behavior can be quantitatively expressed by densification equations that describe the relationship between densities - applied pressure during the compaction stages, using correction factors. The modelling of one phase (metal/ceramic) powders or two-phase metal-ceramic powder composites was studied by many researchers, us...

In line with the ongoing advancement of high-performance materials that are multifunctional and environmentally friendly, this paper provides an overview of recent developments in lightweight and ultra-lightweight multifunctional materials. We primarily examine the various types of low-density multifunctional materials, their production techniques,...

In this work, a number of significant factors are highlighted that affect the optical emission spectrochemical tests with spark or electric arc excitation on stainless steels with multiple synergistic purposes such as: acquiring new knowledge, increasing the amount of information obtained about the material, increasing the efficiency and quality of...

bstract: In this brief review, porous and non-porous biomaterials used as scaffolds in regenerative medicine and tissue engineering and new innovative techniques to obtain biomaterials were discussed. Various methods have been presented to obtain advanced materials used as scaffolds, such as (i) 3D printed biomineral composites obtained with bact...

In this paper was synthesized a bioceramic material based on calcium and phosphorus. Also, the effect of synthesis parameters on the structure and properties of the obtained powders has been studied. In this sense, the stirring speed and the aging time of the precipitates, in the case of some hydroxyapatite powders, are studied. The results show pr...

Considering that worldwide the amount of sludge from sewage treatment plants has increased, which through storage pollutes the environment, solutions must be found for its management. In this paper, through an analysis of studies from the literature, we present an ecological method of recovery of sewage sludge (SS) in agriculture through vermicompo...

An overview of the recent research works and trends in the design and fabrication of microfluidic devices and microfluidics-integrated biosensors for pollution analysis and monitoring of environmental contaminants is presented in this paper. In alignment with the tendency in miniaturization and integration into “lab on a chip” devices to reduce the...

The paper presents an overview of (i) the different polluting materials, classified according to their (bio)degradability, (ii) the sources of pollution (iii) the general effects of pollution on natural resources and on the economy and people’s health. The paper also summarizes directions/solutions to eliminate these effects, including “eco” techno...

The aim of this paper is to present a handmade laboratory device with data acquisition for estimating the thermomechanical characteristics (caused by dimensional changes in height) of polymeric materials. This experimental device is able to perform penetration tests, monitoring the expansion of the samples and based on experimental tests, the therm...

Diffraction techniques and methods with X-rays and less diffraction of electrons, neutrons, etc. are frequently used to investigate the fine structure. X-ray techniques have the advantage that they are cheaper and provide statistical information at the level of fine ordered structure and are not significantly disturbed by the magnetic state of the...

Interest in the synthesis and fabrication of gallium oxide (Ga2O3) nanostructures as wide bandgap semiconductor-based ultraviolet (UV) photodetectors has recently increased due to their importance in cases of deep-UV photodetectors operating in high power/temperature conditions. Due to their unique properties, i.e., higher surface-to-volume ratio a...

The importance of Ga2O3-based material for harsh environmental applications has attracted the interest of researchers in exploring various fabrication and growth techniques of Ga2O3-based nanomaterials using effective and low-cost processes. Herein, a demonstration to improve the wettability of liquid gallium on a rough silicon surface is presented...

The society is currently facing two major aspects: on the one hand an alarming increases in the requirements of high-performance new materials and products and, on the other hand, the need to achieve and operate them according to the environmental requirements of non-pollution of the environment. As a result, the researchers' efforts are directed t...

The coronavirus disease 2019 (COVID-19) pandemic is considered a public health emergency of international concern. The 2019 novel coronavirus (2019-nCoV) or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that caused this pandemic has spread rapidly to over 200 countries, and has drastically affected public health and the economies of...

Corrosion of the tank made of aluminum alloy AlMg2,7Mn (5454) has been studied by electrochemical methods in methanolic solution containing different concentrations of acid, chloride, sulphate and water as impurities. In all these cases, the alloy exhibited a sponge passivity. Adding a 1mM solution in fuel leads to a considerable increase in corros...

In order for automatic microinjection to serve biomedical and genetic research, we have designed and manufactured a PDMS-based sensor with a circular section channel using the microwire molding technique. For the very precise control of microfluidic transport, we developed a microfluidic pulse width modulation system (MPWM) for automatic microinjec...

The appearance of quick wear of rolling paths and rolling elements (balls) through contact fatigue phenomena and through surface defects lead to a decrease in the life of ball bearings in service. One of the causes is the interruption of the lubricating film between surfaces with relative motion under load conditions and high speeds, which leads to...

The paper is focused on the elaboration of some sintered steels with Cr concentration between (1-2 %) wt., carbon as graphite with a concentration of 0,4% wt. and Fe for the balance. The samples were die pressed at 600 MPa and sintered at 1150 °C in argon atmosphere. The samples were studied from the point of view of wear behavior against three typ...

In this paper, obtaining by PM of aluminum based materials, characterization of them and Finite Element Analysis (FEA) of compaction were investigated. Sintered aluminum alloys (Al-Cu and Al-Mg-Si) were tested from physical and mechanical point of view and the obtained experimental results were compared with those of sintered bronze powder material...

This paper presents the most used processes for the synthesis of hydroxyapatite from aqueous solutions: chemical precipitation, the hydrothermal process and the sol-gel method. The experimental part includes the synthesis of hydroxyapatite by chemical precipitation. The obtained results confirm the obtaining of a ceramic with a high purity and a hi...

A microfluidic device designated for measurement of fluidic flows with different viscosity, necessary within trapping/realising of cells/particles system has been developed. We use a new concept as Microfluidic Pulse Width Modulation (MPWM) for controlling transport of a single cell/particle. The image processing helped the nano-hydraulic volumes/f...

The application of plastic materials in various areas of contemporary technology can lead to improvements in the function, quality and performance of engineering components. When determining the field of use of these materials, it is necessary, in addition to knowing the physical and mechanical properties, information about their behavior in servic...

The working conditions of the composite materials used to produce machine parts lead to different forms of wear. The fact that, for example, for a kinematic coupling with sliding motion is often used a material with higher hardness (cast iron, steel) in combination with a material with a lower hardness (a composite material) there is the possibilit...

The aim of the paper was to develop a device (“pin-on-disc” type) for the measurement of friction in plane friction couplings with sliding movement. On tribometric device (made in our laboratory) we can measure the friction force, friction coefficient and wear, for different loading conditions, speeds, time and material coupling. For the measuremen...

In this presentation are evidenced instrumental characterization by Electronic Scanning Microscopy (SEM) equipped with EDS / WDS of aluminum alloys such 2024 alloy with multiple synergistic purposes as: acquisition of new knowledge, increase the amount of information obtainable about the material, increasing the efficiency and the quality of the te...

In this paper is studied the hot plastic deformability (plasticity and resistance to deformation) for the lowalloyed steel of heat treatment for mechanical engineering in two ways: Compression and tension. Groups of low alloy steels is very important in terms of quality and quantity, the products of these steels have developed internal and external...

The basic purpose of compaction is to obtain a green compact with sufficient strength to withstand further handling operations. The strength of green compact is influenced by the characteristics of the powders (apparent density, particle size and shape, internal pores etc.), the processing parameters (applied force, pressing type, and temperature)...

This paper presents experimental results revealed on the samples type 2024 aluminum alloy used in aeronautics. Adequate characterization of 2024 aluminum alloys with special destination (aviation) was achieved by combined investigations:(i) wet chemical analysis, (ii) spectrochemical analysis, (iii) X-ray diffraction and (iv) electron microscopy. T...

The strength of green compact is influenced by the characteristics of the powders (apparent or tap density, particle size and shape, internal pores etc.), the processing parameters (applied force, pressing type, temperature) and testing conditions (strain rate etc.). For elucidation the phenomena that arise in the compaction of metallic and ceramic...

In order to determine the optimum geometry of the ingot mold format (the format of ingot mold with a diameter per height ratio H / D <3 and the conicity of minimum 7%) was analyzed by mathematical modeling of solidification and segregation of the carbon and sulfur in it. It was considered 205Cr115 steel type (according with , STAS 3611 - Romanian s...

The theoretical and experimental researches on developing of friction coupling materials that are part of the disc-pad braking systems of vehicle and analysis the tribological behavior of them, has been in the spotlight of the specialists in this field in the past decades. Explaining the phenomena that occur at the level of friction surfaces in rel...

This paper presents solutions and the equipment for preheating combustion air from scrap aluminum melting furnaces through flue gas heat recovery. For sizing convection pre-heaters, there has been developed a mathematical model which has been transcribed into a computer program in C + +. A constructive version of the pre-heater was drawn up and a r...

Heat treatable aluminum alloys and other alloys with similar properties are the most widely used light alloys in aeronautical construction [1-3]. These alloys have (i) high resistance to crack initiation and propagation, (ii) resistance to developing a strong lift force of the wings, (iii) high temperature, (iv)creep and fatigue vibration resistanc...

Desirable performance requirements for vehicle brake friction materials that work in normal and especially in heavy-duty conditions should have highly physical, mechanical properties and service characteristics such as: (a) stable and high friction coefficient in various conditions, including high temperatures (b) very good wear resistant material...

This paper presents experimental results revealed on the samples type 2024 aluminum alloy used in aeronautics. The results of microstructural and compositional investigations presented in this paper were performed on samples taken from 2024 Al alloy samples produced by ALRO Slatina. The main objective of the investigation is the conformity assessme...

Rapid developments in telecommunications and digital processing of information are facing the problem of electromagnetic wave pollution and interference. The aim of this article is the characterization at microwave frequencies of composite materials based on silicone rubber. These materials contain 80% siloxane rubber and only 20% powdery feeling l...

For ensuring fuel consumption and pollution reduction, the researches made in the past decades considerable efforts to replacing steel with aluminum alloys in manufacturing auto bodies, or in naval transportation, because the promising weight saving. The researches consisted in general corrosion (the gravimetric index and the corrosion rate, Vcorr)...

Worldwide is manifested a great interest in producing lightweight parts with different technologies. Among the lightweight materials used in the transport (road, rail or aviation) industry by well-known companies in the field, are also the aluminum composite materials. In the first part of the paper are (i) generally defined composite materials, (i...

In the last years, the trend worldwide has been to obtain materials increasingly lighter, non-pluted materials, with a cost as low as possible. Lightweight materials (light aluminum/ magnesium / titanium alloys or light metal or plastic matrix composites) are environmentally friendly and economically efficient simply because it takes less effort (m...

This paper presents experimental results revealed on the samples type 2024 aluminum alloy used in aeronautics. The results of microstructural and compositional investigations presented in this paper were performed on samples taken from 2024 Al alloy samples produced by ALRO Slatina. The main objective of the investigation is the conformity assessme...

This paper examine a number of factors involved in the phenomena occurring into the interaction of X-rays and crystals. The mathematical modelling are the scientific way of proposal and implementation of analysis techniques based on previously models tested in laboratory. Normally, in diffraction experiments, a beam of incident X ray radiation is s...

The Lorentz factor is a sensitive issue of X –ray diffraction because it is taking into account some factors witch influence the intensity of diffracted X-radiation, such as: (i) the geometry of the experiment and also (ii) the single crystal or poly-crystals size in the irradiation case of a set of crystallites (crystalline powder) . The difficult...

The objective of this research is to observe the influence of the sintering temperature on the wear testing for some steel samples elaborated by powder metallurgy technology. For obtaining the steels there were used iron powders and graphite powders. The powders were homogenized in a high energy ball mill Pulverisette 6, cold compacted and then sin...

The purpose of these researches was to determine the effect of silicon carbide particles (SiCp) proportion and the effect of some process parameters (temperatures and times of aging) on characteristics of Al-Cu/SiCp composites obtained by P/M route. The age-hardened composites and un-reinforced alloys solution treated at 515 ± 5°C, maintaining time...

This paper proposes a novel algorithm for the condition detection in which the slip state transitions in a stick-slip motion, or the solution breaks down and also to study the state transition of nodes belonging to the contact area: stick, slip or open contact state. We designed a Matlab Simulink program to simulate the occurrence conditions for th...

We define and present some theoretical characterizations of associated constitutive equations for a visco-plastic deformation of a composite. Introducing of an adequate topological framework for some visco-plastic state parameters, when considered a nonlinear stress–strain relations of Prandtl–Reuss type, we obtain the existence and uniqueness resu...

The aim of the present paper were to determine compressibility behaviour of post-compacts depending on compaction pressure and the silicon carbide content in the Al–Cu matrix powder mixtures. Determination of Al-4 wt.% Cu with 5–20 wt.% SiC powder mixtures’ compressibility was performed in a double action hardened steel die at pressures between 50...

The sintered iron–copper based composites for automotive brake pads have a complex composite composition and should have good physical, mechanical and tribological characteristics. In this paper, we obtained frictional composites by Powder Metallurgy (P/M) technique and we have characterized them by microstructural and tribological point of view. T...

The aim of this paper was to obtain and characterize (surface morphology and fine structure) two types of materials: Ca10(PO4)6(OH)2 hydroxyapatite powder (HAp) as biocompatible ceramic materials and AISI 316L austenitic stainless steels as metallic biomaterials, which are the components of the metal–ceramic composites used for medical implants in...

The experimental work aimed to obtaining the aluminum alloy contact lines for trams or light rail. For this purpose was elaborated AlMgSi0.5 Aluminum alloy was elaborated and semi-continuous casted into rods of φ 175 x 6000 mm, and then homogenized (520° C / for 16 hours) for the continuous extrusion process. A chamber extrusion die was designed an...

The aim of this paper was to experimental study of obtaining composites with Al-Mg-Si alloy as matrix reinforced with steel in two versions: steel strip of 0.3 mm thick and steel wire (F 0.8 mm). The composites was prepared in an induction furnace at 700-740oC. The casting semi-products composites were than hot-rolled (plastic deformation temperatu...

This paper reports the outcome of morphological and microcompozitional (SEM, EDS, X-Ray Maps, Compo and Morpho images) and tribological (friction and wear) investigations of iron-copper based composite for automotive brake pads. The sintered friction materials were obtained by conventional P/M route, and compared with a commercial brake pad used as...

Al-Cu matrix composite materials with 5-20 wt. proportions of SiC hard particles and un-reinforced Al-Cu alloys obtained by powder metallurgy (P/M), in the same homogenization (20 r.p.m., about 7 hours)– pressing (450 MPa for composites) - presintering (300-420oC/30 min/H2) conditions but at different sintering temperatures (520-620oC/60min/H2, fur...

The paper proposes the establishment of liquid-solid interface position and depth of solidification cone by using tungsten pellets at the continuous casting of lead-based alloys in a laboratory facility, and also obtain some experimental results that will be used later to validate a mathematical model and realize a graphical interface. To highlight...

In this paper we examined the effect of contact pressure (applied load) and relative speed in braking points on the coefficient of friction and wear of aluminum composites, sintered at 620°C for one hour in hydrogen atmosphere and after that solution treated at 515±5o C for 6 hours, quenched in water and artificial aging at 170° C for respectively...

The practice of technologically advanced countries and economic default and the current rules of the European Union (EU), all measurements have undergone a significant process of standards to ensure quality undisputed of the test results. In the spectrometric field there are standards of competence of laboratories, as well as of analytical method....

Quality of metal powders depends on manufacturing process and heat treating parameters. Among the physical, mechanical and structural characteristics of powders, the average particle size, size distribution, particle shape and microstructure of powders are defining characteristics to obtain powders with superior performance. The objective of the pr...

In this second part of researches the compacted composites was presintering at 400 o C/30 minutes and sintering at different temperatures between 520 and 620 o C/ 1 hour maintaining, both thermal treatment made in protective atmosphere for achieved advanced matrix homogeneity and maximum densification. Sintered samples were investigated by parallel...

A powerful, simple and fast technique for non-destructive multi-element analysis of materials is energy dispersive X-ray fluorescence (EDXRF) technique. This method is based on radioisotope excited energy dispersive X-ray fluorescence (EDXRF) spectrometry and does not require any type-standards. For these reasons, the EDXRF method was chosen in thi...

The continuous development of technology in automotive manufacturing process has required new solutions adapted to the growing requirements of lightweight, non-pollution for the environment materials with a low cost production. According with these required characteristics of materials, the aims of this paper were to manufacturing Al-Cu/SiCp c...

The material for experiments was an aluminum alloys series 2xxx obtained by thermo-mechanical processing using different parameters of artificial aging. The slab of Al alloys was rolled at 450-400oC for 7-8 hours , solution treated at 500 ± 5o C, maintaining time 40 minutes, quenched in water and artificial aging at 100-220o C during respectively...

The material for experiments was an aluminum alloys series 7xxx obtained by thermo-mechanical processing. We studied the influence of different artificial aging parameters on mechanical characteristic and corrosion of Al-Zn-Mg-Cu-alloy. The Al alloys was solution treated at 475±5o C for 60 minutes, quenched in water 40-60oC and artificial aging at...

The paper presents the experimental results concerning fabrication through powder metallurgy (P/M) of new ecological aluminum matrix composites (AMC) at a low cost for automotive industry applications. The difficult compaction and sintering of aluminum powder products and especially of powders from aluminum composite mixtures reinforced with hard c...

This paper presents the results of structural and compositional investigations on the aluminum alloys "2024" samples products for the aviation industry ALRO Slatina. Key words: aluminum alloys " 2024 " , structural and compositional investigation

The production of composites in the liquid state is based on the activation of surface phenomena directly on the reinforcement surface. The fabrication of cast aluminum alloy-graphite particle composites and hybrid aluminum composites, by stirring graphite particles and graphite + Al2O3 or graphite + TiC particles in molten aluminum alloys (above t...

The dry sliding wear behavior of cast Al-based composites reinforced with ceramic particles (Graphite, Al2O3 and Graphite + Al2O3) in different proportion was studied. The prepared composite aluminium matrix contains (1-3) vol. % Graphite particles (1-5) vol.%Al2O3 and hybrid composites with 5 vol.% Al2O3 + 1 vol. % Graphite. The composite alloy wa...

Because the polymeric materials have a wide applicability in biomaterials we propose in this paper to improve their properties, especially to obtain a better biocompatibility of them. For that reason we tested the three types of polymer blends using following methods of physical-mechanical analysis Differential Scanning Calorimetry (DSC) investiga...

The pieces made from cooper alloys such as Cu-Al-Ni-Fe-Mn present advanced wear, can be reconditioned by electric arc welding by means of special electrodes, compatible with the basic material. In this work are presented experiments to obtain some special coated electrodes from sintered powder materials