Andrei Victor Sandu

SEM and EDX studies of bioactive hydroxyapatite coatings on titanium implants

This work presents a study on an alternative coating method based on biomimetic techniques which are designed to form a crystalline hydroxyapatite layer very similar to the process corresponding to the formation of natural bone. The HA formation on the surface of titanium alloy pretreated with NaOH solution is investigated. Two types of solutions such as supersaturated calcification solution (SCS) and modified SCS (M-SCS) were used to investigate bone-like apatite formation on alkali-treated titanium. The hydroxyapatite deposits are investigated by means of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The data suggest that the method utilized in this work can be successfully applied to obtain deposition of uniform coatings of crystalline hydroxyapatite on titanium substrates.

SEM‐EDX and microftir studies on evaluation of protection capacity of some thin phosphate layers

This article presents the SEM‐EDX and microFTIR study and the corrosion behavior of new five types of phosphated coatings obtained by coprecipitation in acid aqueous medium of some metal cations, pursuing the influence of the addition of other cations and a moderator of precipitation, on the uniformity and compactness of the layers and on the morphology of dendritic structure of Zn(II) and Fe(II) phosphates. Microsc. Res. Tech. 2012.

The Effect of Various Waste Materials’ Contents on the Attenuation Level of Anti-Radiation Shielding Concrete

Samples of concrete contain various waste materials, such as iron particulates, steel balls of used ball bearings and slags from steel industry were assessed for their anti-radiation attenuation coefficient properties. The attenuation measurements were performed using gamma spectrometer of NaI (Tl) detector. The utilized radiation sources comprised 137Cs and 60Co radioactive elements with photon energies of 0.662 MeV for 137Cs and two energy levels of 1.17 and 1.33 MeV for the 60Co. Likewise the mean free paths for the tested samples were obtained. The aim of this work is to investigate the effect of the waste loading rates and the particulate dispersive manner within the concrete matrix on the attenuation coefficients. The maximum linear attenuation coefficient (μ) was attained for concrete incorporates iron filling wastes of 30 wt %. They were of 1.12 ± 1.31×10−3 for 137Cs and 0.92 ± 1.57 × 10−3 for 60Co. Substantial improvement in attenuation performance by 20%–25% was achieved for concrete samples incorporate iron fillings as opposed to that of steel ball samples at different (5%–30%) loading rates. The steel balls and the steel slags gave much inferior values. The microstructure, concrete-metal composite density, the homogeneity and particulate dispersion were examined and evaluated using different metallographic, microscopic and measurement facilities.

Electrochemical Mechanism of Nickel and Zinc-Nickel Alloy Electrodeposition

The mechanism of electrochemical deposition of nickel and zinc-nickel alloy was described as in actually science literature. To prove practically the proposed mechanism, it was used as interesting effect which consists in an increase of the deposited mass more than Faraday law predicts. Nickel was deposited and zinc-nickel alloy was codeposited using a potentiostat-galvanostat Parstat 2273 coupled with an Electrochemical Quartz Crystal Microbalance (EQCM). The mass distribution of deposited metal and alloy was monitored during the process, together with electrochemical parameters (potential, current density, and temperature). The electrodeposited layers were characterized with SEM-EDX techniques. A mathematical relation referring to the process was proposed in order to describe the evolution of mass electrode versus time in the first step of the electrodeposition.

Colorimetric and microscopic study of the thermal behavior of new ceramic pigments

The article studies thermal resistance variation by analyzing the colorimetric parameters correlated with the optical microscopy data of two groups of ceramic pigments obtained by co‐precipitation in aqueous medium of phosphate anion and of a mixture of chromium phosphate with various chromophore cations. This research enabled us to reveal the thermal thresholds/domains within which significant color changes occur, thus allowing the choice of pigments compatible with the thermal varnishing‐glazing processes involved in the manufacture of tesserae for mosaic and stained glass and of colored materials for floor tiles, wall tiles and painted porcelain. Microsc. Res. Tech. 76:564–571, 2013.

Study of the atypical formations in the corrosion bulks of an ancient bronze shield, by optical and electron microscopy

This article presents the atypical formations in the structure of the corrosion crust and in the partially mineralized metallic core, which resulted during the underground stay of a bronze shield, dated between the 1st century B.C. and the 1st century A.D. For our study, we choose a representative fragment from the rim of the shield, which was analyzed by optical microscopy and by electron microscopy coupled with energy‐dispersive X‐ray spectroscopy, to study its morphology, its composition, and the location of chemical compounds on the surface and inside the bulk formed during the underground stay, by processes of chemical and physical alteration, assisted by contamination with structural elements from the site. Those processes, by monolithization and mineralization formed a series of structures consisting of congruent elements and phases with a complex composition. Those formations, defined as surface effects generated by exogenous factors and endogenous factors inside the bulk, are frequently found in ancient bronze objects (such as the exterior flat mole formations and the Liesegang effect in the stratigraphic structure of the bulk). Some of those structures have atypical characteristics as regards their structure, composition, and formation mechanism, which may be used in archeometry. Moreover, that includes the object in the category of special cases, in terms of artifact evolution during underground stay and of the atypical formations resulted from the action of pedological and environmental factors. Microsc. Res. Tech. 2012.

Characterization of Cuprous Oxide Thin Films Prepared by Sol-Gel Spin Coating Technique with Different Additives

Cuprous oxide (Cu2O) thin films were formed onto indium tin oxide (ITO) coated glass substrate by sol-gel spin coating technique using different additives namely polyethylene glycol and ethylene glycol. It was found that the organic additives added had an important influenced on the formation mechanism of Cu2O films and lead to different microstructures and optical properties. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and ultraviolet-visible spectroscopy (UV-Vis). Based on the FESEM micrographs the grain size of film prepared by polyethylene glycol has smallest grain of about 83 nm with irregular shape. The highest optical absorbance film was obtained by the addition of polyethylene glycol.

Effect of Solid/Liquid Ratio on Mechanical Properties of Kaolin Coated Teak Wood via Geopolymer Technology

Kaolin, an aluminosilicate source materials was mixed with alkaline activator solution to create a geopolmer paste which was coated on teak wood subsrates. In this work, the effect of solid/liquid ratio (0.4, 0.6, 0.8 and 1.0) was analysed while other parameters were maintained constant. Coating teak wood substrates via geopolymer technology was focused to see the enhancement made to the mechanical properties of teak wood. Various test such as adhesive strength test, water absorption and morphology study was conducted after seventh day of sample preparation. Kaolin coated sample with 1.0 solid/liquid ratio showed the highest adhesive strength of 10.5 MPa and the lowest water absorption of 6.3%. Morphology studies also supported the trend of promising compatibility between kaolin coating and teak wood substrate at 1.0 solid/liquid ratio which further evident the accuracy of collected data.

Establishing the archaeo‐metallurgic ornamentation process of an axe from the bronze age by OM, SEM‐EDX, and Micro‐FTIR

Our article presents the results of the analyses we performed by corroborating the Optical Microscopy, Scanning Electron Microscopy, Energy Dispersive Xray Analysis and micro Fourier Transformed InfraRed Analysis techniques to identify the archaeo‐metallurgic casting and ornamentation procedure of a decorated disk‐butted axe, which was discovered recently east of the Carpathian mountains, in the Moldavian Plateau. There are few known axes of that type found (A1, according to the usual typologies), as they are specific to the Middle Bronze Age period west of the Carpathians—the Wietenberg, Suciu de Sus, and Otomani‐Füzesabony cultures. The experimental data on the item under study revealed the fact that after casting it in molds made from porous silicone‐based stone, the object was coated with a thin layer, by immersing it in a lightly fusible tin alloy, whose main alloy component was copper and arsenic and iron as secondary components. After refining the shiny white layer, they applied a beautiful decoration pattern made by incision and engraving. This battle axe was an indication of higher status, such items usually being owned by community leaders. This important fact proves that the ancient metallurgic craftsmen were able to elaborate and manufacture various alloys from which they made beautiful objects and it also offers a new insight into the social and symbolic function of certain antique bronze items. Microsc. Res. Tech. 77:918–927, 2014.

Improvement of Properties of Aluminum Bronze CuAl7Mn3 by Heat Treatments

Top domains of technology, such as aerospace, nuclear technology, electrical engineering, electronics, energy, require materials and alloys with special properties: superconductivity, superplasticity, high resistance to corrosion, shape memory, exceptional mechanical strength, magnetism, and resistivity. Aluminum bronzes are bronze with very good mechanical and chemical properties, which are factory profiles, strips, bearings, gears, valves, parts and fittings for chemical and food industry, gears, water pump housings, mainly parts corrosion resistant in aggressive environments.