Ion Sandu

Carbon nanopowders from the continuous-wave CO2 laser-induced pyrolysis of ethylene

Abstract Carbon nanopowders were obtained by the laser pyrolysis of ethylene. The high-temperature gradients and very rapid reaction times characteristic of the process lead to the formation of very fine powders. Carbon powders obtained in runs with different laser power values (400–900 W), pressures (250–950 mbar), and gas flows (100–300 sccm) were characterised by transmission electron microscopy (TEM), including high-resolution mode (HREM), electron energy loss spectroscopy (EELS), X-ray diffraction (XRD) and Raman spectroscopy. The carbon particles were found to be approximately spherical in shape, with diameters around 45 nm, which may coalesce into larger agglomerates. The particles were found to be made up of layers forming a turbostratic structure. The experimental parameters influence the soot morphology and particle microstructure. Increasing the laser power and gas pressure leads to less coalescence and increased order. Structural parameters are presented for particles produced under different conditions.

Thermogravimetric study on the ageing of lime wood supports of old paintings

Abstract This paper presents thermogravimetric data of some samples of soft lime tree ( Tillia cordata Mill ) wood from the structure of the supports of old paintings (mobile icons and iconostasis) 100–200 years old. In order to determine the ageing processes, the physical, structural and chemical changes that have occurred in time under the influence of environment have been correlated with thermogravimetric data. It has been established that the thermal characteristics for the elimination of physically adsorbed water depend on the samples age and on the conservation treatments. The variation of the thermal characteristics with the wood age is important for the main decomposition step. The temperatures for the onset and the maximum rate of degradation as well as the global activation energy increase with the woods age while the weight loss decreases. These characteristics could be used to assess the age and conservation status of the paintings. The variation of the characteristics could be due both to the loss in time of the volatile compounds that lead to lower thermal characteristics and to the structural changes occurring in the wood that, for the highly deteriorated and/or degraded wood leads to a totally different thermal behaviour.

Nanoscale powders of different iron oxide phases prepared by continuous laser irradiation of iron pentacarbonyl-containing gas precursors

Abstract Different iron oxide-based nanosized powders were obtained by the IR laser synthesis from gas phase reactants by using iron pentacarbonyl vapor as iron donor. In the flowing gas mixture, oxidizers (like nitrous oxide and air) and sensitizers (like sulfur hexafluoride and ethylene) have been used. A major amount of γ-Fe2O3 was obtained after a series of experiments in which α-Fe2O3 and iron fluorides were the dominant phases. The mean size of the obtained γ-iron oxide particles was in the range 3–7 nm. The structural characterization of the new elaborated materials points out to the crucial influence that the experimental parameters (particularly the combined choice of the oxidizer/sensitizer agents) have on the specific oxide phase formation as well as on its purity.

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, water absorption, and wetting capability studies on evaluation of the influence of nano-zinc oxide as additive to paraloid B72 solutions used for wooden artifacts consolidation

Consolidation of frail, degraded wood is a key issue of wooden cultural heritage conservation. Paraloid B72 is one of the most often used consolidant in conservation practice. The present research aimed at formulating stable consolidation solutions of Paraloid B72 with ZnO nano‐additives and at determining the influence of these additives on the penetration pathways, retention of the consolidation material into wood and on the water behavior of the treated wood. The experiments were performed on sound samples of aspen (Populus tremula). The addition of nano‐ZnO slightly increased the uptake and retention of the consolidant within the wooden structure and led to hydrophobic surfaces. However, the influence of nano‐ZnO additives to the water absorption was not conclusive. Scanning Electron Microscope coupled with an EDX Detector investigation proved vessels, fibers, and interconnecting pits as main pathways of consolidant penetration into the wooden structure as well as the presence and distribution of nano‐ZnO. Microsc. Res. Tech., 2013.

Integrated Methodology for the Evaluation of Cleaning Effectiveness in Two Russian Icons (16th-17th Centuries)

This article covers a methodology for evaluating the effectiveness of cleaning two Russian icons. The icons belong to a group of five from the same iconographic school, dating from the 16th to 17th centuries. An integrated and complementary approach to varnish and overpaint removal involved microscopic techniques (optical and scanning electron microscopy) and colorimetry (CIE L*a*b* system). The materials and techniques used in these icons have been characterized previously. Cleaning revealed extensive overpainting that had not only dramatically changed the original appearance, but also the meaning and attribution of one of the two icons. The analyses carried out were useful in determining the extent of the overpainting and led to a better assessment of the results and effectiveness of the restoration. Microsc. Res. Tech. 73:752–760, 2010.

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.

Comparison of various sensitive and selective spectrophotometric assays of environmental cyanide

A review is presented to show the advantages involved in the use of some new spectrophotometric cyanide (CN) assays, which are highly sensitive and selective, quick and affordable. Among these, the ninhydrin-based assay, the method based on CN reaction with resorcinol, as well as the Berthelot reaction were found to be highly selective. The old Aldridge 1 method, based on the formation of cyanogen bromide and its subsequent reaction with pyridine and benzidine to form a highly-colored polymethine chromophore is still in use, although recent assays using isonicotinic acid–sodium barbiturate are safe, selective, and sensitive (with a detection limit of 0.005–0.01 mg L−1 CN). Ninhydrin-based procedures are suitable to detect low trace amounts of CN with a molar absorptivity below 2.2 × 105 L M− 1 cm−1 and detection limit of less than 1 ng cm−1 CN. The sensitivity, specificity, and reliability of the investigated methods were compared and the most appropriate protocol for a given analytical problem described.

Assessment of cleaning effectiveness for new ecological systems on ancient tempera icon by complementary microscopy techniques

The study presents an old icon painted in egg tempera on lime wood, with a poor conservation condition and clogged dirt deposits. The icon is attributed to an anonymous painter of XIXth century and to the neo‐classical style of painting. The painting layer was done with only a hand full of pigments, earth colors that were often used in painting the icons from XVIIth to XIXth century in Eastern Europe, that have Byzantine influences. Taking into consideration the nature and the structure of the materials from the upper layers of the painting, affected by deposits of dirt over time, a series of cleaning recipes were studied, using the so called cleaning tests with compatible mixtures of different juices and infusion from indigenes plants, that were freshly done and odorless. A low alkaline 95% ethyl alcohol solution, combined with a few drops of ammoniac 25%, was used as a reference system, due to its compatibility with the greasy deposits found on the polychrome layer and on the wood. The cleaning capacity of the new systems used, in comparison with the standard solution, was analyzed through modern analytical methods of evaluating the degree of cleaning, more exactly by means of visible and UV reflectography, CIE L*a*b* colorimetry by reflection assisted by SEM‐EDX and IR spectroscopy. Microsc. Res. Tech. 77:1060–1070, 2014.

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.