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Azorubine (E122), an azoic dye with the chemical formula C20H12N2Na2O7S2, has a wide range of applications in the food and cosmetic industries. Physical properties of azorubine were investigated by correlating the optical properties (refractive index, electric susceptibility and optical anisotropy) with the acidity study and biological activity. The optical study of azorubine shows that its refractive indexes are decreasing when the temperature of the solution is increased. The optical anisotropy of azorubine was observed/studied under polarized light at room temperature (RT). Azorubine exhibits the phenomenon of birefringence in results crystallites by drying and crystallization at RT of aqueous solution with concentration of 5%. THz spectroscopy identified the THz spectral “signature” of azorubine at a few wavelengths. The azorubine solution has, at a temperature of 24 °C, a weak alkaline character, corresponding to a pH = 7.14, and as the temperature increases, the acidity of the sample increases, the pH reaching value of 6.70 at the temperature of 55 °C. Five spectroscopic techniques were used to identify spectral properties of azorubine in powder and solution form: Fourier-transform infrared (FTIR), UV–Vis, Raman, laser fluorescence and THz spectroscopy. The morphology and chemical composition of azorubine were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDXS). Thermal analysis effectuated in air indicates the evaporation of absorbed and physically bonded water up to 200 °C, after which the material possesses thermal stability up to 300 °C. Oxidative decomposition takes place in three exothermic steps between 300 and 687 °C; also, a high-temperature oxidation of the Na-based residues increases the mass above 815 °C. Azorubine has moderate biophysical activity when interacting with proteins (bovine serum albumin and collagen); the antioxidant activity of azorubine is increasing with increasing its concentration, while the phytotoxicity study indicates an overall inhibition of the wheat growth with increasing the concentration of azorubine and feeding time.

Ti-based composite materials with remarkable mechanical properties and good thermal stability were obtained and studied with the purpose of employment for producing resistant and versatile components in the automotive industry. The raw materials having the overall Ti80Mn8Al6Sn3Zr2C1 composition were prepared by mechanosynthesis from powders of comprising elements; after thermal processing and by following four different sintering pathways, both in the argon flow, the four samples (S1–S4) reached a specific composition of metallic and ceramic phases. Thermal analysis and calorimetry showed that the composite materials adsorb considerable amounts of argon, these being related to the obtained composition and microstructure. The results of the thermal study were used when choosing the thermal treatment conditions for sintering; in order to select the optimal processing conditions within the four different regimes of sintering for the raw materials and the final sample with the best functional properties, a comprehensive study for determining the composition, structure and morphological features was carried out by means of X-ray diffraction, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Two samples (S1 & S4) of the obtained composite materials have increased porosity due to the presence of titanium aluminium carbides (Ti3AlC & Ti3AlC2) that are known as highly porous ceramics, therefore absorbing more argon during the preparation process. The roughness and wear tests showed that the best results (smallest roughness: Ra = 1.11 μm and smallest wear: w = 2.472·10−4 mm3 N−1 m−1) belong to the S2 sample sintered in argon for 15 min at 1100 °C and further calcinated at 1050 °C for 75 min.

This paper presents an experimental investigation of a commercial shape memory alloy strip consisting of nickel and titanium (NiTi SMA), which correlates the thermal properties (phase transitions) with the electrical and mechanical properties of the material, allowing to be used for control applications in engineering. The bending performances of the SMA strip at different values of the activation electric current, during heating process, are also investigated. By using the differential scanning calorimetry (DSC) experiments, the thermal characteristics of the SMA strip were identified. The results of this thermal analysis were the basis for determining the equilibrium temperature, entropy and force developed by the SMA strip during the phase transformation. For the study of the SMA strip, the authors have developed an experimental platform, which uses a portable reconfigurable I/O (RIO) device and LabVIEW graphical programming environment for the measurement, testing and rapid control of parameters, and a piezo-film sensor for controlling of SMA strip movement. The real-time measurements and acquired waveforms are displayed on a PC screen, and the data associated with these waveforms are stored for later use, i.e. for applications in safety engineering like the fire extinguishing control, where very short response/activation times are required.

In this work, some physical properties of a commercial Ni–Ti (nitinol) shape-memory alloy with cylindrical geometry (wire) were investigated; the focus was on the thermomechanical, calorimetric and magnetic characterization. By dynamical mechanical analysis, the range of elasticity, the elasticity–viscoelasticity coexistence domain and the domain in which a maximum force is applied were determined for the SMA wire. By using the temperature-modulated differential scanning calorimetry method, a multi-step temperature variation program was applied to the wire with cylindrical geometry, in two stages (heating–cooling) and through the interpretation of heat fluxes (reversible, nonreversible and total), and the phase transitions in the formation of martensite, austenite and rhombohedral phase (R-phase) were identified and correlated with those observed during the thermomechanical study; also, the formation of austenite and martensite was evidenced by the regular differential scanning calorimetry method; by magnetic measurements, it was established that the SMA wire had magnetic properties at room temperature, and the nitinol sample is paramagnetic and linear in the intensity of the magnetizing magnetic field; these results were compared with those previously obtained for the investigation of the nitinol SMA stripe.

The synthetic red azo dye Ponceau 4R is an additive with widely utilization in food processing technology. Thermal behavior of the trisodium (8Z)-7-oxo-8-[(4-sulfonatonaphthalen-1-yl)hydrazinylidene] naphthalene-1,3-disulfonate, appointed Ponceau 4R or E124, was studied. Thermal analysis measurements of Ponceau 4R revealed thermal stability until 300 °C. Ponceau 4R is an anisotropic crystalline dye that has the property of birefringence. The THz spectroscopy allowed the determination of the characteristic absorption frequencies of this colorant and its identification in any food. In the THz spectrum of Ponceau 4R, it can be seen that the strongest absorption is produced for the radiation with frequency of 1.41, 1.74 and 3.81 THz. THz spectroscopy of Ponceau 4R identified spectral “signatures” of azo food dye studied, which were obtained by the processing of the numerical data of THz spectroscopy.

Some physical properties like the thermal, thermomechanical, calorimetric, magnetic, and adhesive properties of a commercial shape memory alloy (SMA) with rectangular geometry were studied. Depending on the applied forces, there were identified range of elasticity, the elasticity–viscoelasticity coexistence domain, and the domain in which a maximum force of 18 N is applied, for the SMA strip. The controlled force module, in the tension mode, was used for the determination of the SMA strip elongation at application of the stretching forces from 0 to 13 N, at 30 °C, maintaining each static force value for 3 min. By employing the multi-frequency strain–stress modulus in the tension mode, DMA cyclic heating–cooling measurements were carried out. The measured dynamic mechanical properties for SMA strip were Storage Modulus, Loss Modulus, tanδ, and Stiffness, both at heating and cooling. Thus, the characteristic temperatures of the phase transitions (As, Af, Ms, Mf), of SMA strip were identified. Also, the values of the elasticity modulus (Young’s Modulus) of the SMA strip were calculated at 30 °C. With the DSC Q2000 device, using temperature-modulated differential scanning calorimetry method, a multi-step temperature variation program was applied to the rectangular strip in two stages (heating–cooling). Through the interpretation of heat fluxes (reversible, nonreversible, and total), the phase transitions in the formation of martensite, austenite, and also of the rhombohedral phase (R phase) and moreover enabled for the R phase identification, thermomechanical analysis confirmed the results obtained by classical DSC method. The adherence of some commercial azoic dyes on the rectangular SMA strip, as well as the modification of the surface roughness of the strip after the deposition of the dye, was also studied. By magnetic measurements, it was established that the SMA strip had magnetic properties at room temperature, in which magnetization is the sum of a superparamagnetic contribution and a paramagnetic term, linear in the intensity of the magnetizing magnetic field.

The thermal behavior of the eutectic powder particles mixture Ag-28% Cu (mass) represents the aim of this research. This comportment is studied from the point of view of the structural changes induced to the powder mixture processing by the wet mechanical alloying (WMA) technique. After 80 h of WMA in ethylene glycol aqueous solution and argon atmosphere, the initial powder mixture becomes nanostructured composite particles with bimetallic AgCu matrix reinforced by in situ processed Cu2O. The particle size distribution, depicted by laser diffraction technique, reveals the nanometric range of the composite particles between 60 and 80 nm. The phase identification, quantitative analysis as well as crystallite size measurements by XRD confirm the nanostructured feature of the bimetallic matrix, acknowledged by SEM with EDX and FIB, as well as the reinforcing components synthesis during the WMA process. Two successive melting processes have been developed to point out the increased melting point in the range of 928.00–946.10 °C. The thermal analysis, developed in argon atmosphere, highlights the thermal effects of AgCu/Cu2O nanoparticles generated by argon adsorption/desorption from the powders surface.

Four coordination compounds, that include the discrete binuclear complex [Zn(H2O)4(bda4Py)]2(SO4)2 (1), two isomorphous one-dimensional coordination polymers, {[Zn(NO3)2(bda4Py)2]·2H2O}n (2) and {[Cd(NO3)2(bda4Py)2]·2H2O}n (3), and one two-dimensional coordination polymer {[Cd(bda4Py)2(dpa)2]·2H2O}n (4) [where bda4Py = N-((pyridin-4-yl)methylene)benzene-1,4-diamine, H2dpa = diphenic acid, as a potential anionic competitor ligand having two carboxylic groups] were obtained as the products of partial hydrolysis of the ligand N1,N4-bis(pyridin-4-ylmethylene)-benzene-1,4-diamine (bda4bPy) in the reaction conditions. Single crystal X-ray data reveal that N-((pyridin-4-yl)methylene)benzene-1,4-diamine acts as a bidentate linker between two metal centers through nitrogen atoms of pyridino- and amino-groups. The additional stabilization of the crystalline solids 1–4 is provided via hydrogen bonds. N-((pyridin-4-yl)methylene)benzene-1,4-diamine (bda4Py) was also obtained by direct synthesis, and two ligands (bda4bPy and bda4Py) were characterized in the solid state and in solution by spectroscopic (FTIR, UV–vis, NMR) methods. Luminescence studies for the reported compounds are also documented.

Two phases (2223 and 2212) are identified in Bi1.8Pb0.3Sr2Ca2(Cu1-xNix)3.3Oy superconductor system, sintered at 847 °C for 322 h, in partial nitrogen atmosphere. The volume fraction of 2223-phase is strongly dependent on Ni doping: 78.37% for x = 0.002, 70.29% for x = 0.005% and 51.13% for x = 0.015. The unit cells of 2223 and 2212 phases were indexed as tetragonal structures, having different lattice constants. Plots of resistance versus temperature (four points method) on cooling to 77 K, evidenced that the critical temperature for the transition to the superconductor phase, Tc, is linearly decreasing from 106.21 to 93.47 K when the Ni content is varying from x = 0.002 to x = 0.03. From log-log plots of the excess-conductivity we calculated the cross-over temperatures between 3D and 2D dimensionality as well as from 2D to SWF (short wavelength fluctuation) behaviour, the coupling factor and the coherence length for all the samples. Thermal analysis of the resulting samples (after the last sintering) was performed by heating each sample from room temperature (RT) to 1000 °C at a rate of 10 K min−1 in dynamic air atmosphere (150 cm3 min−1). A clear dependence on Ni content is seen by TG and DSC, but a relative thermal equilibrium between the two phases, 2223 and 2212, in RT-869 °C range, is observed. Strong endothermic effects (melting accompanied by small decomposition processes) begin at around 869 °C for all Ni doped samples. The results for the specific heat capacities, calculated from DSC plots, are also presented. Contribution of the crystal lattice to the estimated specific heat capacity was in conformity with the Einstein model, the Einstein temperature values being dependent on Ni content.

Two YBa 2 Cu 3 O 7-x materials (YBCO-I sintered at 1000 °C, and YBCO-II sintered at 960 °C and following special cooling programs) belonging to the orthorhombic system were obtained. YBCO-I has a complete volume texture, while for YBCO-II it is only on sample surface. On heating in air (with 10 K min −1 in the temperature range 20–1000 °C), two endothermic processes are recorded on DSC curves (of YBCO-II) and they are due to oxygen diffusion from O1 to O5 sites, and then to the release into the environment; second endothermic effect is attributed to the decomposition reaction. Different behaviour is encountered on heating in argon: an endothermic process in two steps; continuous mass decrease (oxygen loss) during argon cooling is recorded on the thermogravimetric curve. In argon atmosphere, the obtained material shall correspond to the chemical composition: YBa 2 Cu 3 O 6.77 , while in air atmosphere, the maximal composition than may be obtained is: YBa 2 Cu 3 O 6.88 . The barrier energies from Arrhenius plots of resistivity vs. temperature (91–93 K) show 2D (YBCO-I) and 3D (YBCO-II) behaviour for the thermally activated flow of melted vortex lattice, below the critical temperature.

The food-colouring dye tartrazine is a significant additive and in the same time a biologically active material. Thermal behaviour of trisodium (4E)-5-oxo-1-(4-sulphonatophenyl)-4-[(4-sulphonatophenyl)hydrazono]-3-pyrazole carboxylate, tartrazine or E102 as it is also known, was studied in relation with the physical, chemical, thermal and biophysical (interaction with proteins, antioxidant and phytotoxicity) properties. Tartrazine structure and microstructure have been determined by X-ray diffraction and scanning electron microscopy investigations. Tartrazine has a monoclinic crystalline structure (space group C2/c). Electronic transitions and atomic bonds behaviour in molecules and fluorescent excitation of the compound have been identified by spectroscopic methods: Fourier-transformed infrared, UV–Vis, atomic fluorescence and Raman spectroscopies. Tartrazine absorbs in the visible region at 436.36 nm and shows laser fluorescence of all its elements. Chemical (acidity) and optical properties (refractive index and electric susceptibility) were determined for different concentrations on a sensitive range of temperatures. Thermal analysis measurements of tartrazine revealed thermal stability until 200 °C in air, while in the inert environment (argon) the stability is increased to 300 °C. Biological and biophysical activities and properties of tartrazine have been evidenced through its interaction with animal proteins, comparison with the standard gallic acid and phytotoxicity towards wheat strains/roots, when several concentrations of tartrazine solutions were used. Tartrazine has moderate biological activity when interacting with proteins, obtained antioxidant activity above a threshold concentration of 0.25% and presents plant growth phytotoxicity.

Thermal, thermomechanical, and caloric properties of commercial orthodontic wires (produced by Natural Orthodontics Corp., USA) with cylindrical and rectangular geometry were studied. Depending on the applied forces, there were identified the range of elasticity, the elasticity–viscoelasticity coexistence domain and the domain in which a maximum force of 18 N is applied, for the orthodontic wires. When increasing the thickness of orthodontic wires, deformation decreases. The Controlled Force Module, in the tension mode, was used for the determination of the orthodontic wires elongation at application of the stretching forces from 0 to 13 N, at 35 °C, maintaining each static force value for 3 min. The increase in the cross-sectional area of the orthodontic wires disfavors the process of elongation of the sample, at the same applied static force. Using the Multi-Frequency–Strain–Stress modulus, in the tension mode, DMA cyclic heating–cooling measurements were performed. The measured physical quantities for orthodontic wires were Storage Modulus, Loss Modulus, Tanδ and Stiffness, at heating and cooling. Thus, the characteristic temperatures of the phase transitions (As, Af, Ms, Mf), of all the studied orthodontic wires were identified. Also, the values of the elasticity modulus (Young’s Modulus) of the orthodontic wires were calculated at 35 °C. With the DSC Q200 device, using temperature-modulated differential scanning calorimetry method, a multi-step temperature variation program, was applied to a rectangular wire, in three stages (cooling–heating–cooling). Through the interpretation of heat fluxes (reversible, irreversible and total), the phase transitions in the formation of martensite, austenite, but also of the rombohedral phase (R-phase), were identified. Formations of austenite and martensite were also evidenced by the classical DSC method, but the classical DSC method also enabled the R-phase identification. The adherence of some food dyes on the orthodontic wires, as well as the modification of the surface roughness of the orthodontic wire after the deposition of the food dye, was also studied. By magnetic measurements, it was established that the orthodontic wires had paramagnetic properties at room temperature, and nitinol was a mixture of 49.2% austenite and 50.8% martensite.

The current research represents one section of our studies concerning the improvement of the biocompatibility related to the biocomposite materials for bone grafts application. The submicronic/nanometric hydroxyapatite stands for the progress in biocompatibility. This study highlights the wet mechanical milling process and its effects on the morphological and thermophysical properties of the hydroxyapatite powder particles (30-50µm as raw material) obtained by this method (500 nm average). The scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) facility point out the morphological and chemical compositional features of the processed powders during 10 hours in dry argon atmosphere. The thermal analysis (TA) in argon atmosphere, too, reveals the influence of the milling parameters on the thermal effects generated by the processed hydroxyapatite powders. The experimental results of our research validate some milling mechanisms reported by the literature for wet/dry mechanochemical process conditions.

New mixed-ligand Co(II) and Ni(II) complexes with enrofloxacin and 1,10-phenanthroline/8-hydroxyquinoline have been synthesized. The metal complexes have been characterized by elemental analyses, molar conductance, FT-IR, solid reflectance, magnetic moment, thermal analyses, X-ray powder diffraction (XRD) and SEM analysis. Conductance measurements indicate that all the complexes are non-electrolytes. Spectral IR data showed that the deprotonated enrofloxacin is bidentately bound to the metal ion through the pyridone oxygen and the carboxylated oxygen; 1,10-phenanthroline acts as neutral bidentate ligand coordinated through two nitrogen donor atoms, and the deprotonated 8-hydroxyquinoline is coordinated through nitrogen and oxygen donor atoms. The geometry of the complexes was elucidated with solid reflectance UV and magnetic moments. Thermal analysis recorded that TG/DTG/DSC experiments revealed the thermal stability of metal complexes and confirmed their compositions suggested by the analytical data. In addition to experimental data, a molecular modelling study has been performed to establish the optimized geometries of metal complexes. The XRD analysis of powders evidences the nanocrystalline nature of all complexes. The results are in agreement with molecular modelling data. SEM images revealed highly agglomerated particles with irregular shape with sizes in the micrometre range. The ligand and their metal complexes were screened for their antimicrobial activity against Escherichia coli 25922, Staphylococcus aureus 25923, Pseudomonas aeruginosa 27853 and Candida albicans 10231. The metal complexes were also investigated for their cytotoxicity using an in vitro assay.

Complexes of Co(II), Ni(II) and Cu(II) with the Schiff base (LH) derived from ceftazidime and salicylaldehyde were synthesized. The proposed structures of the new metal complexes based on the results of elemental analyses, molar conductivity, IR, DRUV and 1H NMR spectra, effective magnetic moment and thermal analysis were discussed. The surface morphology of Schiff base and metal complexes was studied by SEM. The composition of the metal complexes was ML2, where L is the deprotonated Schiff base ligand and M = Co(II), Ni(II) and Cu(II). IR spectral data indicated the Schiff base ligand being bidentately coordinated to the metallic ions with N and O atoms from azomethine and phenolic groups. All the complexes have square-planar geometry and are nonelectrolytes. The thermal analysis recorded that TG, DTG, DTA and DSC experiments confirmed the assigned composition and gave information about the thermal stability of complexes in dynamic air atmosphere. Theoretical investigation of the molecular structure of Schiff base ligand and its complexes was studied using programs dedicated to chemical modeling and quantomolecular calculation of chemical properties. The newly synthesized complexes were tested for in vitro antibacterial activity against selected Gram-negative and Gram-positive bacterial strains, and they exhibited an antibacterial activity superior to that of the Schiff base ligand.

A study is made on optical emission spectrum modification during X-ray exposure, in the case of a high-pressure mercury discharge lamp operated at several powers. A strong dependence on the lamp operating power for all the spectral lines intensities is observed. Erosion of the emissive mixture based on barium, calcium and yttrium compounds is evidenced by higher values recorded for spectral line intensities in all cases of X-ray exposure compared with those corresponding to non-irradiated lamps. Boltzmann type functions fitted the experimental data of measured optical emission intensities versus time for Ba+, Ca+ and Y+ lines. However, X-ray influence on plasma electron temperature is not significant. The spectroscopic data are correlated with the results of electrical measurements and of thermal analysis performed for the electrode having the emissive mixture based on barium, calcium and yttrium compounds. A qualitative explanation of the results is also given.

In shape memory alloys (SMAs), the thermoelastic martensitic transformation between austenite and martensite phases leads to the appearance of the shape memory effect and super-elasticity. In addition, these alloys present high mechanical strength, great ductility, vibration damping property and hysteresis behavior. All of the above-mentioned properties make these alloys very promising for industrial applications and their usage leads to the increase of productivity and efficiency of the devices they pertain to. The purpose of this article is, on the one hand, to increase the awareness of R & D engineers about the existence and use of SMAs by describing and promoting the unusual properties and effects of these materials and, on the other hand, to outline some of their most promising industrial applications.

The influence of the mechanical alloying processing parameters on the elaboration of AgCu-based bimetallic matrix composites reinforced by in-situ synthesized Cu 2 O has been studied. The milling time (20, 45 and 80 h) of the initial 72% mass Ag + 28% mass Cu micrometric powders mixture influences the particle size distribution of the obtained composite particles. After 80 h of mechanical alloying, AgCu/Cu 2 O nanoparticles of 60–80 nm are obtained and their chemical composition at bulk/surface level has been determined by X-ray diffraction and photoelectron spectroscopy. The effect of milling time on the thermal behavior of the powders samples has been studied by thermogravimetry and differential scanning calorimetry measurements in argon atmosphere. The argon chemosorbtive reaction from the particles surface has been identified and the binding energy (0.9–1.99 eV) has been calculated. The isothermal drop calorimetry and the linear thermal expansion measurements were used to evaluate the correlation between thermal stability and thermal expansion properties of the in-situ synthesized AgCu/Cu 2 O nanocomposite.

Seven new complexes of 2-pyridyl ketone Schiff bases N,N′-bis-(pyridin-2-yl-benziliden)-propan-1,3-diamine (bpbpd) and N,N′-bis-[1-(pyridin-2-yl)-etiliden]-propan-1,3-diamine (bpepd) with Co(II), Ni(II), Zn(II) and Cd(II) nitrates and perchlorates were synthesized and investigated using elemental analysis, spectroscopic techniques (IR and UV–Vis–NIR) as well as magnetic and conductometric measurements. The structure of a cadmium(II) complex was accomplished by single-crystal X-ray diffraction. The Schiff base ligands act as NNNN tetradentate ligands coordinating through pyridine nitrogens and azomethine nitrogens to transition metal ions. The metal ions are six-coordinate for Co(II) and Ni(II), four-coordinate in the case of Zn(II) and eight-coordinate for Cd(II) ions. The coordination sphere of cobalt and nickel complexes is completed by two water molecules, resulting a distorted octahedron. In the case of zinc(II) complexes has been proposed a distorted tetrahedral geometry. The Cd(II) ions are surrounded by a tetradentate Schiff base ligand and two bidentate nitrate anions, leading to a dodecahedral coordination environment. Thermal decomposition of these compounds is a multistage process. Generally, water elimination occurs in the first step and the decomposition of nitrate groups and organic ligands in the next stages. The last step of decomposition for all complexes is strong exothermic and corresponds to oxidative combustion of the Schiff base ligand.

The nanostructured biocomposites with hydroxyapatite (HAP) matrix reinforced by titanium (Ti), processed by two steps sintering (TSS) route in argon atmosphere, provide excellent wear behaviour when they are elaborated in specific sintering parameters. The wear tests, developed in steel ball-on-disc dry conditions, show low wear rates about 2x10-4 [mm3/Nm] when the biocomposites are processed at 750...8000oC for 450...600 min. in comparison with high wear rates 7x10-4 [mm3/Nm] in 700...7500oC for 300 min. as TSS parameters. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis outline the structural features that explain this wear behaviour.

Any transformer oil undergoes continuous degradation because of all electric, thermal, mechanical, and climatic stresses it suffers while operating in the transformer. Therefore, the oil has to be checked on regular basis in order to decide whether it is necessary to regenerate or replace it, avoiding thus a sudden failure of the transformer. This article presents results of in-the-laboratory-performed experiments on transformer mineral oil samples. Those samples came from a power transformer that works in the Romanian power network. There were three monitoring stages conducted over four-and-a-half years. We used two measuring techniques: (i) measurement of the state parameters of transformer oil (breakdown voltage, loss factor, water contents, acidity index, interfacial tension, number of particles larger than 5 microns, and gas contents) in order to describe the oil condition during the monitoring period and to anticipate any severe fault. This enables the user to take preventive action before a severe fault might eventually occur; (ii) thermal analysis (TA) and Fourier transform infrared spectroscopy (FTIR), in order to determine the stability of oil samples. By using TA and FTIR, and by evaluating each and every significant parameter, it has been proven that the tested oil is still adequate for further employment in the power transformer.

A new azoester, 4-(4-chloro-phenyldiazenyl)-2,6-dimethyl-phenyl 2-furoate (CPPF), has been synthesized by condensing 4-(4-chloro-phenylazo)-2,6-dimethyl-phenol with 2-furoyl chloride in pyridine. This compound has been characterized by elemental analysis (C, H, N), FTIR, UV–Vis, NMR (1H and 13C), and thermal analysis studies. Spectral analysis results confirmed the structure of the compound synthesized. Thermal analysis established that CPPF is stable up to 260 °C; melts at about 178 °C; and between 260 and 450 °C, it decomposes in two steps.

When a special preparation procedure has been applied, the crystallization system of boric acid has been changed from triclinic to hexagonal: at temperatures between 60 and 70 °C, under controlled pH conditions, the boric acid belonging to triclinic system was mixed with d-glucose, calcium carbonate, and calcium hydroxide. Thermal analysis evidenced a final compound with quite similar thermal behavior as that of initial triclinic boric acid but having some differences in decomposition kinetics. X-ray diffraction analysis showed a new compound, named HBA, belonging to the hexagonal crystallization system with the following lattice parameters: a = b = 20.4869 A and c = 12.1506 A. This strong anisotropic structure was also confirmed by the hexagonal form of the crystallites, grown from HBA and water solutions, which have been observed with a light polarized optical microscope. Exotic polycrystalline conglomerates grown from water solution of HBA have nice colours that are changing when they are set different angles between polarizer and analyser. FTIR measurements revealed the IR absorbance bands belonging to O–H, O–B, and H–O–B bonds of the trigonal planar boric acid, for both crystallographic systems, but some small differences between wave-numbers and peak intensities were encountered. Finally, the dielectric properties of the water solutions of HBA are analyzed by performing electric susceptibility measurements at different temperatures, from 25 to 50 °C.

The paper presents a complete model for a modular mechatronic structure actuated by a one-way memory effect shape memory alloy actuator. In order to claim the complete attribute of the model, the austenite transformation temperature evolution of actuator was evaluated in relation with the precision and repeatability related capabilities of the mechatronic structure. The evolution of austenite transformation temperature was obtained through determinations based on DSC method. Those determinations were performed on the shape memory alloy wire used as actuator in the modular mechatronic structure. The wire is subject of intense and repetitive operating mode. All determinations are performed on the SMA wire used as actuator system after 5,000, and 1,003,600 cycles, respectively. The results indicate a shift in both A s and A f temperatures, a trend that is heavily dependent on the operating history of the system. Using experimental results, authors built a graph (surface) that is based on heating time schedule, heating current, and austenite finish temperature. Also, the results lead to the conclusion that for any desired heating time, it can be identified (in a restricted but relatively wide range), at least a pair of both austenite finish temperature and heating current. If the control algorithm modifies the electrical current in accordance with the number of working cycles and austenite transformation temperature evolution, the time response and, by default, the structure repeatability are assured even after over 1 million working cycles.

Mono-phase high critical temperature (Bi,Pb)-2223 superconductor from the off-stoichiometric Bi1.8Pb0.3Sr2Ca2Cu3.3Ox belonging to the tetragonal system, has been obtained. We studied the crystalline structure, the stress of second order, and the texture of the surface pellet, in the framework of XRD diffractometry. Results of the thermal measurements made in the nitrogen, with a heating rate of 10 K min−1, from room temperature (RT) to 1273.15 K, show a slow mass decrease of 1.25 % from RT to 1003.15 K probably due to the elimination of water, oxygen, and of the other gases accumulated on the crystallite surface through chemical adsorption. Two endothermic processes were evidenced on DSC, and DTG curves: the first in the range of 1135.15–1193.15 K (melting and slow decomposition), and another after 1217.45 K (decomposition). The contribution of crystal lattice to the estimated specific heat capacity was in conformity with the Einstein model, giving for the Einstein temperature a value of 1297.5 K. In conformity with the Muller critical state model, we found linear dependences for intragrain critical transition temperature, T g, and intergrain coupling temperature, T p, versus the amplitude of the external AC magnetic fields. There was evidenced that intergrain critical currents are five orders smaller than the intragrain critical currents.

Aminophylline (AMF) was studied as corrosion inhibitor for carbon steel in 1.0 mol L−1 HCl solution using electrochemical measurements associated with UV–Vis spectrophotometry and optical microscopy. Simultaneous thermogravimetry/derivative thermogravimetry and differential scanning calorimetry analysis was performed in order to determine the temperature range in which AMF is an effective inhibitor, without the decomposition risk that could change the inhibition mechanism. Thermal behaviour restricts AMF application as corrosion inhibitor for carbon steel in 1.0 mol L−1 HCl solution at temperatures ≤45 °C where there are no significant modifications of the adsorption mechanism. According to the results of electrochemical measurements, in association with UV–Vis spectrophotometry and optical microscopy techniques, AMF is a mixed-type inhibitor for carbon steel corrosion in 1.0 mol L−1 HCl solution, simultaneously suppressing the anodic and cathodic processes and acting via spontaneous physisorption on the metal surfaces.

The thermal stability and the adsorption properties have been investigated for three benzothiazole compounds: 2-mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole sulfenamide (NCBSA), and 2,2′-dibenzothiazole disulphide (BTD), reported in our early studies as corrosion inhibitors for carbon steel in different media. The electrochemical results were used to calculate the degree of surface coverage (θ). The adsorption mechanism of the three inhibitors was discussed according to the free energy of adsorption ( $$ \Delta G_{{\text{ads}}}^{\circ } $$ ) value obtained from Temkin adsorption isotherm, this being the best way to quantitatively express the adsorption process of their molecules on carbon steel surface. Thus, a mixed type mechanism involving the synergism between physisorption and chemisorption was proposed. The thermal analysis curves showed that, for the occurred events up to 470 °C, mass losses take place with endothermic effects followed by the total oxidation of the residue with an exothermic effect around 520 °C. Consequently, their effectiveness follows the order: BTD > NCBSA ≥ MBT, while the thermal stability ranges as follows: NCBSA

NdFeB thin films, showing a notable out-of-plane c-axis texture, were prepared by radiofrequency plasma-assisted pulsed laser deposition technique. Their optical, morphological and magnetic properties were investigated. Thermal analysis was performed in order to evaluate the thermal behaviour and stability, in air, and in nitrogen dynamic atmospheres. The effects of deposition time, nitrogen and argon plasma use, and substrate temperature, are discussed.

The evolution of the polymerization of a light-cured methacrylate-based composite material (Pekalite) used in dentistry was studied. Fourier transform infrared spectroscopy and thermal analysis (TA) showed that with increasing the photo-polymerization time from 5 to 60 s, the degree of conversion increases from 32.5 to 59.6 % and thermal stability of the composite material increases from 144.6 to 270 °C. Growth of photo-polymerization time from 5 to 60 s produces an improvement in the mechanical strength of the composite material from 153 to 248 MPa. Spectral analysis and TA are two complementary and rapid methods for determining the degree of polymerization of composite materials used in dentistry.

International audience; Ag/polyvinylphenol (PVP) multilayered pixels are printed by laser-induced forward transfer (LIFT) technique for thin film microcapacitor applications. The third harmonic (3 omega/355 nm, tau = 50 ps) of a solid state neodymium-doped yttrium aluminium garnet (Nd:YAG) laser source is employed throughout our LIFT experiments. By selecting adequate printing parameters (e.g. donor thickness, laser fluence, background pressure), we show how functional microcapacitors are fabricated. At similar to 350 mu m in lateral size and 300 nm thickness of the dielectric film, the pixels have capacities in the picofarad range. We discuss the laser influence during the pixel transfer process and highlight the polymer's thermal behaviour.

Titanium is a low density element with excellent mechanical properties, and is an attractive material for structural and biomedical applications. In recent years, a new process technology is emerging by which titanium and titanium alloys can be obtained by using titanium hydride (TiH2) as a precursor for Ti and its mixture with alloying elements. The feasibility of this manufacturing approach has been fully demonstrated from powder to sintering and from microstructure to mechanical properties. In this paper, a study concerning powder metallurgy processing of Ti by spark plasma sintering (SPS) route is presented. The influence of the technological parameters on the hardness and microstructures change during SPS has been studied. The experimental results are related to microscopic, thermal, and mechanical analysis.

This article studied two sorts of biomass (corn and beech sawdust) and two varieties of coal (bituminous coal and lignite), which can produce energy using two different technologies: co-firing and anaerobic fermentation in pilot installations, in order to determine the future perspectives of those materials for large scale applications. By thermal analysis, the thermochemical characteristics of biomass (corn and beech sawdust) and of coal (bituminous coal from Jiu Valley and lignite from Oltenia basin) were determined. The co-firing tests have been achieved at a ratio of 15 % biomass, the rest being coal. At biomass–coal co-firing, the SO2, NOx, CO, CO2 and fly ash concentrations in the flue gases is lower than the burning of fossil fuels. In the anaerobic fermentation of biomass, the maximum concentration of methane inside the produced biogas was 50–55 % by volume in the beech sawdust batch and 67–68 % by volume in the corn batch.

Thermal analysis of YxEu1−xVO4 powder (used as “phosphor” coating for a high pressure mercury lamp) was done under a non-isothermal linear regime, both in a dynamic air regime and in a nitrogen atmosphere. The heating in air atmosphere gave on TG curve small rate of mass increase due to oxygenation and two endothermic effects are observed on DTA and DSC curves. By contrary, in nitrogen atmosphere a continuous stepped mass loss of powder (around 0.65 %), is recorded in the range of temperatures from room temperatures to 1,200 °C, and only one endothermic effect, to eliminate the gases accumulated on the crystallite surface. The powder was heated for 3 h in a Nabertherm furnace at 350, 800, and 1,100 °C using quite similar rate for heating program followed by a furnace cooling to room temperature. XRD and FTIR analyses showed the sample purification by thermal treatment and a very small increase of nanocrystallite sizes. The time evolution of the optical emission spectra in the range from 186.2 to 877.47 nm were recorded for different lamp powers in two different situations: with the outer bulb coated with YxEu1−xVO4 type “phosphor”, and without it. We observed that UV-Hg lines are absorbed by YxEu1−xVO4 type “phosphor” with different percents (100 % for 253.73 nm, 95 % for 312.65 nm, and 33 % for 365.12 nm) but the heating of the powder do not influence the UV-absorption properties of the powder.

The azo-ester, namely 4-(phenyldiazenyl)phenyl 2-furoate (PPF) by a coupling reaction between 4-(phenyldiazenyl)phenol and 2-furoyl chloride in the presence of pyridine was obtained. For characterization of this compound UV–Vis, FTIR, and thermal analysis were used. PPF was investigated as corrosion inhibitor for carbon steel in saline waters using potentiodynamic polarization. Morphology of the surface before and after corrosion was examined by optical microscopy. Potentiodynamic polarization shows that the corrosion current densities decrease and values of polarization resistance and inhibition efficiency increase with PPF concentration reaching a maximum of 89.6 %, at 0.1 mmol L−1.

The study concerns an experimental model using a SMA spring actuator for improving the whole performance of a barrier structure. The study is, specifically, focused on the thermal analysis of the SMA spring material and on determination of the SMA spring working time periods at different values of the activating electric current inducing different phase changing speeds.

Many hybrid metal–organic complex materials which exhibit crystalline nature, nonlinear optical properties and chemoselective behavior generate interest as choice materials in various applications. In this paper we report results on Cu(II) 2,2′-dihydroxyazobenzene thin films deposited on silicon and quartz substrates by matrix assisted pulsed laser evaporation using a Nd:YAG laser, at 266 and 355 nm laser wavelengths. Thermal analysis, atomic force microscopy, scanning electron microscopy and spectroscopic ellipsometry were performed in order to investigate thin film properties. Micrometric pixels of the compound have been transferred on glass plates by laser-induced forward transfer for chemoselective sensor development purposes.

A newly synthesized copper-complex exhibiting nonlinear optical properties, crystalline nature, and generating interest as a material for non-linear optical applications was investigated. As thermal stability studies are indispensable before attempting any laser-assisted processing experiments, the thermal behavior of 2,2′-dihydroxy azobenzene with Cu2+ cations that are found to organize themselves as non-central symmetric crystallites, was investigated. The thin films were deposited on silicon substrates by matrix-assisted pulsed laser evaporation using a Nd:YAG laser working at 266 and 355 nm. Thermal analysis of the bulk compound indicates a higher thermal stability in argon flow when compared to the air atmosphere; as well, since, the adhesion of the compound onto the substrate enhances the bonding, the thermal stability of the Cu complex increases. Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, spectroscopic ellipsometry, and ultraviolet–visible spectroscopy investigations were also performed.

Using the Williamson method, a new dye 4-[(4-chlorobenzyl)oxy]-3,4′-dichloroazobenzene (CODA) with liquid crystalline properties was synthesized. The structure and the thermal behavior of CODA were investigated by means of nuclear magnetic resonance, X-ray diffraction, differential scanning calorimetry, and light polarized optical microscopy techniques. The thermophysical processes were monitored by heating–cooling cycles, but the formation of liquid crystal phases were exhibited only for small values of the cooling rates. For the first heating–cooling cycle, the melting and the solidification processes, thus the characteristic temperatures, are shifted to higher values when compared to the following cycles.

The biomaterials most widely used for hard tissue implants (in orthopaedics, dental implants, and skull bones) are Ti-based biomaterials and Ti coated with hydroxiapatite (HAP). Because metallic biomaterials have some disadvantages as reported previously (mainly due to the difference between the mechanical characteristics of the human bone and the metallic implant), biocomposites have become an interesting solution to improve the hard tissue implants for the human body. This article presents the experimental results concerning the processing of HAP/Ti biocomposites by powder metallurgy technology. The initial powder mixture consists of HAP powder particles (7.6 g/cm3). The tribological behaviour of the processed biocomposites is appreciated on the basis of the coefficient of friction and wear rate, corroborated with the wear track depth. The final remarks of this article underline the potential use of SPS technology to obtain HAP/Ti biocomposites with comparable wear properties as similar materials processed by more complex technologies. Also, TSS allows processing HAP/Ti materials comparable with the SPS-ed ones from the point of view of the wear behaviour, except for the dwell time of the second step, which is critical for the wear behaviour.

Zinc(II) coordination compounds may provide a better source for ZnO thin films obtaining, since ZnO was found as the final product of their thermal decomposition. Thin films of zinc benzoate have been obtained on silicon substrates by matrix assisted pulsed laser evaporation (MAPLE) technique, using a Nd:YAG laser working at 266 nm. A comparative study of 1% zinc benzoate frozen solution in methanol at different fulences was carried out for 20,000 laser pulses; for the best deposition fluence a double deposition time was employed. Comparative thermal analysis and non-isothermal kinetic investigation of Zn(C6H5COO)2·2H2O dehydration and decomposition was performed. Thin films of ZnO have been obtained by thermal treatment of the MAPLE obtained thin films, according to the thermal analysis and decomposition kinetics of zinc benzoate. The obtained morphologies, before and after thermal treatment, have been investigated by atomic force microscopy (AFM).

Pyridine derivative complexes are widely employed as biological active materials especially as antibacterial agents. Five transition metal(II) mpk com- plexes (mpk = methyl 2-pyridyl ketone) were synthesized and investigated using elemental analysis, spectroscopic techniques (IR and UV-Vis-NIR) and conductometric measurements. The general formulae established from experimental data were found to be (M(mpk)2(NO3)2)� xH2 O( x = 0 for M = Cd(II), Zn(II), x = 2 for M = Cu(II)) and (M(mpk)2(H2O)2)(NO3)2 (M = Co(II), Ni(II)). These compositions were further confirmed by thermal analysis and their thermal stability in dynamic air atmo- sphere investigated.

For two typical actuators of intelligent systems (Ni–Ti SMA cantilever and SMA helical spring), the evaluation of their thermal characteristics is presented. In order to determine the transformation temperatures and other thermal parameters of the two studied elements, the attention was concentrated on thermal analysis experiments. For each actuator configuration, comprehensive graphical interfaces have been developed, to run in Visual Basic, with respect to the results of performed thermal analyses.