Andrei Rotaru

THERMAL DECOMPOSITION KINETICS OF SOME AROMATIC AZOMONOEHTERS Part II. Non-isothermal study of three liquid crystals in dynamic air atmosphere

Thermal analysis of three azomonoether dyes, exhibiting liquid-crystalline properties, was performed in dynamic air atmosphere. Thermal stability studies and the evaluation of the kinetic parameters of each physical or chemical transformations are essential for a full characterization, before attempting accurate thin films’ depositions of such materials used in non-linear optical applications. New synthesized dyes with general formula: where R is a nematogenic group: CN, CF3 or a highly polarizable group: NO2 were investigated using TG, DTG, DTA and DSC techniques, under non-isothermal regime. The evolved gases were analyzed by FTIR spectroscopy. The activation energies of the first decomposition step were evaluated for each compound, the obtained results revealing complex mechanisms.

Thermal analysis and kinetic study of Petroşani bituminous coal from Romania in comparison with a sample of Ural bituminous coal

Solid fuels represent one of the most used sources of energy in many countries. In terms of ranking for the coal deposits, Romania occupies the 26th place in the world, and the 11th place in Europe, with reserves of 22 million tones of bituminous coal (BC) and 472 million tones of lignite. The National Bituminous Coal Company extracts the most significant amount of BC from the Jiu Valley area, a Subcharpatian basin in the Parâng Mountains. In the present article, the BC extracted from the Livezeni depth mine next to Petroşani city is investigated from the microstructural, thermal, and kinetic point of view, in comparison with a sample from Ural Mountains in Russia. Scanning electron microscopy, FTIR spectroscopy, and thermal analysis (TG/DSC/DTA in air and inert atmosphere) measurements were performed. The KAS isoconversional kinetic method was applied for the in-depth understanding of thermal decompositions and burning processes that occur. Even if the thermal behavior of the two samples is generally similar, the non-isothermal kinetic study revealed important differences in the pathways of the oxidative decomposition of volatiles and formation of coke. Also, the kinetics of coke burning depends only on the amount of fix carbon, regardless of the provenience of BC.

Thermal behaviour and antimicrobial assay of some new zinc(II) 2-aminobenzoate complex compounds with bioactive ligands

New zinc(II) 2-aminobenzoate complexes with general formula Zn(2-NH2benz)2(L)2 (where 2-NH2benz is 2-aminobenzoate, and L is phenazone, N-methylnicotinamide, nicotinamide and isonicotinamide) were prepared and characterized by elemental analysis and by FTIR spectroscopy. The stability and thermal behaviour of the compounds were studied by thermal analysis techniques (TG/DTG, DTA), and the decomposition reactions were proposed. The decomposition of the studied compounds is always a multistep process, when after the release of the bioactive ligand, 2-aminobenzenecarbaldehyde, 2-aminobenzene and carbon dioxide were evolved. The solid intermediate compounds were confirmed by FTIR spectroscopy, and the volatile products were identified by mass spectrometry. The final solid product of thermal decompositions was zinc oxide, which was confirmed by XRD and FTIR analysis. The non-isothermal kinetic investigation of Zn(2-NH2benz)2(mnad)2 decomposition in air was performed by means of isoconversional methods, for a better understanding of the undergoing processes. The antimicrobial assay was carried out comparatively for the investigated compounds; they have higher biological activity towards Staphylococcus aureus, Escherichia coli and Candida albicans in comparison with zinc(II) 4-bromobenzoates.

Discriminating within the kinetic models for heterogeneous processes of materials by employing a combined procedure under TKS-SP 2.0 software

Kinetics of heterogeneous processes of materials is an important topic of thermal analysis field; it directly describes the dynamics of condensed matter systems, revealing “hot insights” of materials towards a better understanding of their structural, functional and transition-related properties. The advanced thermal and kinetic software by standard procedure TKS-SP 2.0 was successfully employed to perform kinetic computations, by making use of an extended spectrum of procedures, methods and discrimination criteria, it produces in real-time, high-volume and accurate sets of kinetic data from thermally induced processes. The discrimination between the kinetic models and the selection of the appropriate one is explained here in an in-depth study, employing the Perez-Maqueda et al. criterion under both integral and differential procedures in combination with the Gotor et al. master plots method. Perez-Maqueda et al. criterion describes the independence of the kinetic parameters from the heating rate, while the master plots method of Gotor et al. give the fastest way to check the kinetic models just by fitting in a continuous and visual manner the normalised transformation rate of a chemical or physical process with the relation ([f(α)·g(α)]/[f(αmax)·g(αmax)])—where the adjustment of the step of the kinetic model and of the values for the conversion degree at the maximal conversion rate inside the relation is performed. A working procedure is proposed to be applied for the step-by-step evaluations, discrimination and selection of the unique kinetic triplet {E, A, f(α)} corresponding to a certain investigated process.

Hydroxyapatite–alendronate composite systems for biocompatible materials

In this study, hydroxyapatite–alendronate composites were synthesized from calcium nitrate, diammonium hydrogen phosphate and alendronate by chemical precipitation method. The obtained materials were analysed by physical–chemical methods, while the compositional and structural characteristics of hydroxyapatite–alendronate phases were determined by a combination of crystallographic, spectroscopic and thermal analysis investigations; moreover, the alendronate content, its maximal incorporation efficiency to hydroxyapatite and stability were determined. A two-level full factorial design was chosen to determine the optimum set of process parameters (synthesis temperature, reactant addition rate and ripening time) and their effects on various hydroxyapatite–alendronate characteristics: alendronate incorporation efficiency, hydroxyapatite crystallite size (XRD), hydroxyapatite particle size distribution (DLS). These effects were quantified using design of experiments. The in vitro release profile of alendronate from hydroxyapatite–alendronate tablets was assessed.

Thermal behaviour of CODA azoic dye liquid crystal and nanostructuring by drop cast and spin coating techniques

Abstract This study comes to complete the initial investigation of the liquid crystalline properties of 4-[(4-chlorobenzyl)oxy]-3,4′-dichloroazobenzene (CODA). Here, the thermal analysis of CODA dye was performed in air flow and nitrogen flow atmospheres by means of simultaneous thermogravimetry TG, derivative thermogravimetry DTG, differential thermal analysis DTA and differential scanning calorimetry DSC; differences between the two steps of the thermal degradation of CODA related to the two experimental atmospheres were observed. Drops cast and spin coating techniques were used for nanostructuring CODA on platinum (Pt) substrates; the deposited materials were characterised by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Exotic crystalline nanowires of CODA were obtained as function of used deposition technique, while the deposition time decisively influenced their features. The present results advocate for employing these materials as template matrices for producing high-aspect-ratio inorganic nanomaterials (i.e. Au) in the form of nanotubes, nanowires, nanorods or nanoparticles with enhanced functional properties.

Thermal and kinetic study of hexagonal boric acid versus triclinic boric acid in air flow

Boric acid is a very important inorganic material with diverse uses in optoelectronics, petroleum industry, medicine, agriculture, etc. Recently, it was reported on the modification of the crystallization system of the triclinic boric acid (TBA) to hexagonal boric acid (HBA), when a special obtaining procedure is applied. In this paper, the thermokinetic stability of HBA novel material was comparatively studied with respect to the well-known TBA, in air flow atmosphere. Both HBA and TBA undergo a three-step overall thermal decomposition reaction (dehydration), following similar pathways; from the thermodynamic point of view HBA is more stable—decomposition temperatures and ΔH are higher in this case compared to those of TBA. The kinetic analysis was performed by means of the isoconversional methods, for each step of dehydration observing different thermokinetic regions. Higher thermal stability for HBA enables it to be employed at higher temperatures instead of TBA, explaining why the triclinic symmetry enhances the formation actually of the pseudo-hexagonal crystals as crystal habit at the macroscopic scale. Lower thermodynamic and kinetic stability of HBA makes it easier to be activated and thus more instable at the microstructural scale: this is an indirect proof of the TBA presence in the usual surrounding conditions and in the same time raises the probability for HBA molecules to slide onto their crystalline layers due to the lability of hydrogen bonds keeping them and thus increased potential to intercalate with other molecules. The present results open the possibility for promising applications of HBA as a better lubricant for various industries, while in the medical sector superior cleanser, antifungal and antibacterial properties may be foreseen.

Twenty-five years of Thermal Analysis and Calorimetry at the Romanian Academy

This compilation is based on the peer-reviewed and selected papers presented at the 25th Symposium on Thermal Analysis and Calorimetry—Eugen Segal (CATCAR25) Dr. Petru Budrugeac Dr. Andrei Rotaru ICPE-CA National Institute for University of Craiova and Research and Development in INFLPR National Institute for Laser, Electrical Engineering Plasma and Radiation Physics petru.budrugeac@icpe-ca.ro andrei.rotaru@inflpr.ro

New Trends in Thermal Analysis and Calorimetry in Central and Eastern Europe

Dr. Andrei RotaruINFLPR—National Institute for LaserPlasma and Radiation Physics, Laser DepartmentMagurele (Ilfov), Bucharest, Romaniaandrei.rotaru@inflpr.roThis compilation is based on the peer-reviewed and selected papers presented at CEEC-TAC2Prof. Daumantas MatulisDepartment of Biothermodynamics and DrugDesign, Institute of BiotechnologyVilnius University, Vilnius, Lithuaniamatulis@ibt.lt

New Regional Editor

Andrei Rotaru was born on the 9th of August 1983 in Craiova, Romania. Since November 2006, he is working at the National Institute for Laser, Plasma and Radiation Physics (INFLPR) Bucharest, Romania, where he currently holds the position of Researcher III (equiv. to Lecturer). Andrei has received his BSc in Chemistry and Physics from the Faculty of Chemistry of the University of Bucharest in 2006, specializing in Physical chemistry. Since 2004, he has carried out research in the field of thermal analysis and kinetics of heterogeneous processes (decomposition of various systems, including liquid crystals and dyes, complex inorganic materials and precursors, biomass and coal). He has also developed a software for performing kinetic computations (TKS-SP) and later on used this knowledge in studying, modelling and processing of thin films by laser-assisted techniques (mainly MAPLE). In 2007, Andrei has received an EPSRC grant, followed by a prestigious fellowship of the Roberto Rocca ‘‘Educational Program’’ for his doctoral studies in solid-state chemistry of ceramic materials at the University of St Andrews, United Kingdom. These more recent interests are related to the fabrication, thermal processing and characterization of novel electroceramic materials with tetragonal tungsten bronze structure. In general, a special interest was directed on modelling relaxation processes in polar dielectric ceramics and investigating the structure–properties relations to induce and control ferroelectricity and ferromagnetism. In 2011, he was the co-chairman of the 1st Central and East European Conference on Thermal Analysis and Calorimetry (CEEC-TAC1), and in 2008 a member of the scientific committee of the 14th International Congress on Thermal Analysis and Calorimetry (ICTAC14) in Brazil; he is a member of the International Confederation for Thermal Analysis and Calorimetry (ICTAC), Commission for Thermal Analysis and Calorimetry of the Romanian Academy (CATCAR), Kinetics committee at ICTAC, International Society for Optics and Photonics (SPIE), and president of the Central and Eastern European Committee for Thermal Analysis and Calorimetry (CEEC-TAC). Currently, he acts as an editor for thermal analysis at the Global Journal of Analytical Chemistry and as a reviewer for several journals: The Journal of Physical Chemistry, Journal of Thermal Analysis and Calorimetry, Thermochimica Acta, Journal of Applied Polymer Science, Dyes & Pigments, Chemical Industry & Chemical Engineering Quarterly, etc. Andrei has been an invited lecturer at several universities and institutes from Lithuania, Estonia, Slovakia, Czech Republic, Poland, and is directly involved and interested in A. Rotaru (&) INFLPR – National Institute for Laser, Plasma and Radiation Physics, Bvd. Atomistilor, nr 409, Măgurele (Ilfov), Bucharest, Romania e-mail: andrei.rotaru@inflpr.ro Name: A. Rotaru