Dynamic Air Atmosphere Research Articles

Pyrolysis kinetics of waste ryegrass under nitrogen and air atmosphere

To investigate the pyrolysis reaction of ryegrass, we conducted a simultaneous thermal analysis using thermogravimetric(TG) analyzers. This involved obtaining data through Thermogravimetry (TG), Derivative Thermogravimetry (DTG), and Differential thermal analysis (DTA) techniques. The experiments were conducted under dynamic nitrogen and air atmospheres at different heating rates. The kinetic parameters of ryegrass pyrolysis were determined using the Kissinger method, the Flynn-Wall-Ozawa (FWO) peak conversion rate approximate equivalence method, the Flynn-Wall-Ozawa (FWO) equal conversion rate method, and the Škvára-Šesták (S–S) method. It provides a theoretical basis for the reuse of ryegrass resources. The findings indicated that the pyrolysis temperature of ryegrass increased with the accelerated rate of temperature increase in both atmospheres. The average weight loss rate of pyrolysis of ryegrass in the air atmosphere (92.27 %) is higher than that compared to that in a nitrogen atmosphere (86.11 %). Additionally, the temperature required for complete decomposition is lower in the former case. The FWO peak conversion rate approximation equivalence approach and the FWO equal conversion rate method do not apply to the solution of the pyrolysis activation energy of ryegrass. The pyrolysis activation energy for the two decomposition stages, as calculated by the Kissinger method, is 165.73 and 185.86 kJ/mol−1 in the air atmosphere, and 219.99 and 277.02 kJ/mol−1 in a nitrogen atmosphere, respectively. The activation energy and mechanism function of ryegrass pyrolysis calculated by using the S–S method are as follows: [−ln(1−α)]2, 119.79, 104.31, 95.75, and 91.93 kJ/mol−1 in air atmosphere, (1−α)−1, 176.64, 67.89, 61.15, and 54.25 kJ/mol−1 in nitrogen atmosphere, respectively. The activation energy of ryegrass pyrolysis, as determined by both the Kissinger method and S–S method, was found to be higher under an air atmosphere compared to a nitrogen atmosphere.

Spectroscopic Characterization, Thermogravimetry and Biological Studies of Ru(III), Pt(IV), Au(III) Complexes with Sulfamethoxazole Drug Ligand

Complexes of Ru(III), Pt(IV), and Au(III) with sulfamethoxazole (SMX) were experimentally produced. The resulted formations of novel metal complexes were discussed using several techniques, such as effective magnetic moment molar conductivity, IR, UV, and 1H NMR spectra, elemental analyses, thermal analysis, microscopic and XRD analyses. The X-ray diffraction patterns of the solid powders of the synthesized sulfamethoxazole complexes indicated their identical formulation. The surface uniformity of the complexes’ samples was confirmed by SEM images. These complexes appear as spots, dark in appearance, with particle sizes of 100–200 nanometers in transmission electron microscopy (TEM) pictures. The sulfamethoxazole ligand was shown to be bidentate coordinated to the metallic ions with sulfonyle oxygen and amido nitrogen groups, according to IR spectral data. Both Ru(III) and Au(III) complexes have an electrolytic nature, but the Pt(IV) complex has non-electrolytic properties. TG and DTG experiments proved the assigned composition and provided information regarding the thermal stability of complexes in a dynamic air atmosphere, according to the thermal analysis. The effect of the novel prepared complexes was examined for antibacterial and antifungal activity in vitro against a variety of pathogens, and they exceeded the sulfamethoxazole ligand in antibacterial activity. It was observed that the Pt(IV) complex has the ultimate activity versus all the assessed organisms relative to all compounds.

Formation mechanism of strontium cobaltite containing equimolar amounts of Sr and Co from SrCO3 and Co3O4

Strontium cobaltite containing equimolar amounts of Sr and Co was produced by heating the mixture of SrCO3 and Co3O4 starting materials with a mole ratio of 1:0.333 under dynamic air atmosphere. The chemical reactions occurred during heating were determined and the intermediate and final products obtained at each critical temperature were characterized using TG/DTA-MS, ICP-OES, XRD and FT-IR analytical techniques. The volumetric analysis method (iodometric titration) and carbonation process were carried out to determine the oxygen stoichiometry of strontium cobaltite.It was determined by thermal analysis results that pure SrCO3 and Co3O4 were decomposed to SrO and CoO final products, respectively. Sr6Co5O15-β was formed by solid-state reaction between SrO and Co3O4 and by gaining O2 from air. Sr2Co2O5-δ was produced at elevated temperatures by solid-state reaction between Sr6Co5O15-β and Co3O4 by releasing O2. At temperature where the decomposition of SrCO3 is not completed and the decomposition temperature of Co3O4 is reached, firstly the formation of Sr6Co5O15-β and then Sr2Co2O5-δ takes place with CoO instead of Co3O4.Strontium cobaltite releases oxygen from its structure during heating as the temperature increases in the air atmosphere and it gains oxygen during cooling as the temperature decreases. Sr2Co2O5-δ is converted firstly to Sr6Co5O15 and CoO and then CoO reacts with O2 to form Co3O4 when cooled to the room temperature from the temperature it was obtained.

Production of Chitosan from Crab Shells Using an Aqueous Extract of Wood Ash for the Deacetylation of Chitin: An Innovative, Eco-friendly, and Low-cost Method

The importance of chitosan has grown significantly over the last years due to its medicinal, agricultural, and industrial applications, as well as the biodegradability properties. The present study aimed to describe for the first time, the preparation of chitosan from chitin using wood ash aqueous extract as an alkaline medium. Chitin was obtained from crab shells in a microbial fermentation process using fish viscera for protease. Pilled and milled sweet potatoes and cassava water extracts were used separately in the deproteinization and demineralization steps as sources of carbon. The obtained chitin samples were then converted into the respective chitosan samples (B-C2 and M-B2) by an innovative, low-cost, and eco-friendly method using an aqueous extract (pH=12.4) prepared from wood ash, instead of the chemical process using sodium hydroxide solution in the deacetylation of chitin. The yield of the obtained chitosan was found to be 11.5% for B-C2 and 9.4% for M-C2. The presence of chitosan was determined by the analysis of the FTIR spectrum of both samples. The degree of acetylation was found to be 77.3% and 83.2% for B-C2 and M-B2, respectively, based on the IR analysis of absorption bands at 3456 and 1636 cm-1, and 75.4% and 84.1% based on the potentiometric titration. The average molecular weight (192.1 kDa for B-C2 and 194.3 kDa for M-B2) was determined using the viscometer method. The solubility of B-C2 and M-B2 in 1% acetic acid was found to be 77.8% and 63.9%, respectively. The analysis of SEM photographs of B-C2 showed an amorphous morphology while M-B2 showed a crystalline morphology. The TGA and DSC curves obtained in a dynamic air atmosphere showed three degradation stages. In the main event (the second stage), an exothermic peak was observed at 355°C for B-C2 coupled with the weigh-loss of 7%, while for M-C2 was observed at 365°C coupled with weight-loss of 10%. Due to their high degree of deacetylation, low molecular weight, and viscosity, both chitosan samples could be utilized unambiguously in the agri-food field as a biofertilizer or as a bio-adsorbent in the wastewater treatment.

Impact of Tb3+ ion concentration on the morphology, structure and photoluminescence of Gd2 O2 SO4 :Tb3+ phosphor obtained using thermal decomposition of sulfate hydrate.

Gadolinium oxysulfate doped with terbium (Gd2 O2 SO4 :Tb3+ ; 0.1, 1.0, and 10.0 mol%) materials were obtained using thermal decomposition from sulfate hydrate under a dynamic air atmosphere and between 1320-1400 K. The materials were characterized using Fourier transform infrared spectroscopy, thermogravimetric/derivative thermogravimetric investigations and X-ray powder diffraction patterns. The Tb2 O2 SO4 compound was obtained at 1300 K and was used to compare thermal stability and photoluminescence behaviour with that of Gd2 O2 SO4 :Tb3+ (0.1, 1.0, and 10.0 mol%). Magnetic susceptibility measurements indicated the presence of 15% Tb4+ phases within Tb2 O2 SO4 . The materials were excited at 377 nm and displayed green narrow lines with the strongest emission peak at 545.5 nm due to the 5 D4 →7 F5 transition of Tb3+ ions. Brightness of terbium-activated gadolinium oxysulfate phosphors was enhanced with increase in the concentration of Tb3+ . Detailed analysis of spectroscopic properties of materials under investigations revealed efficient Gd2 O2 SO4 to Tb3+ and Tb3+ to Tb3+ energy transfers. Increase in dopant concentration led to the enhancement of 5 D4 →7 FJ emission intensity and reduction of 5 D3 →7 FJ emission intensity via cross-relaxation mechanisms. Distribution of particle size was increased by controlling dopant concentration in the host lattice. Obtained results confirmed that these materials could be applied potentially in field emission display devices and light-emitting diodes.

Advances in new multicomponent crystal system: structure, thermal kinetic analysis, photoluminescent, and biological activity investigations

Multicomponent organic crystals based on natural metabolites or pharmaceutical active ingredients play an important role in solid state chemistry, agriculture, and pharmaceutical industry. This study reveals the synthesis of a new luminescent alkanolammonium salt of 4-nitrobenzoic acid (MMEA4NB, methylethanolammonium 4-nitrobenzoate), together with the detailed investigation of its structural motifs, thermal stability, decomposition kinetics, and validation of its plant growth regulatory activity. The new compound was obtained at room temperature in excellent yield and shorter reaction time. Thermal stability and decomposition were studied in a dynamic air atmosphere by thermogravimetry—differential thermal analysis—derivative thermogravimetric techniques. The kinetics and mechanism of the thermal decomposition reaction were evaluated under non-isothermal conditions using three different isoconversional methods Flynn–Wall and Ozawa, Friedman, and modified nonparametric kinetics method in order to obtain the activation energy. Proton transfer and hydrogen bonding in the organic salt were elucidated and confirmed by infrared spectroscopy and single-crystal X-ray diffraction. The crystal structure revealed cation–anion heterosynthons and cation–cation homosynthon. The relation between the protonation state of the components, intermolecular interactions, and thermal stability of MMEA4NB is discussed. This study demonstrates the importance of MMEA4NB in the development of new specific luminescent plant growth regulators, possible viewers of localization and distribution in plants.

Microwave synthesis of nanocrystalline LaCoO3 samples and their catalytic activity towards decomposition of isopropanol

Nanocrystalline LaCoO3 powders were fabricated via the sol–gel microwave-induced combustion approach using metal nitrates as oxidant and citric acid as fuel. Calcination of the precursor was performed in the temperature range 400–800 °C. The precursor of the LaCoO3 powder as well as the calcination products were investigated using thermal analysis (TGA and DTA), FTIR, XRD and N2 adsorption techniques. In a dynamic air atmosphere, calcination was implemented in the temperature range 400–800 °C. XRD patterns show the fabrication of the perovskite rhombohedral phase of LaCoO3. The average nanoparticle size calculated from the XRD patterns was in the range 8–21 nm. Surface area measurements calculated from the N2 adsorption isotherms show low surface area values. The porosity of these materials was identified to be microporous in nature. SEM and TEM tests endorsed the findings. Analysis of TGA and DTA showed a sharp exothermic peak of about 358 °C and a steady weight loss of up to about 600 °C. The vapor-phase dehydration/dehydrogenation of isopropanol, in the temperature range 350–425 °C, was adopted to assess the catalytic performance. The activity of the LaMnO3 catalysts is mainly directed towards the dehydrogenation reaction forming acetone as a main product. The maximum yield was found for the sample calcined at 600 °C. A strong correlation was identified between the selectivity of dehydrogenation and the redox couple species evaluated. A potential reaction mechanism was suggested that would be compatible with the data obtained.

Study of thermally induced interactions between theobromine and various sweeteners

In the past few decades, theobromine has been discovered to play an important role in dental caries prevention being used in different toothpastes for children. Theobromine is recognized in the literature for the vasodilatation effect, for stimulation of heart, etc. Sweeteners are known to be present in two different forms, such as natural and synthetic sweeteners, both with applications in different types of foods. The aim of this study was to obtain a perspective on the compatibility of different sweeteners with theobromine. The compatibility of the selected sweeteners (Ar. gum; trehalose; lactose; sorbitol; fructose; glucose; and galactose) with Th has been studied to verify whether these sweeteners can be used in the preparation of chewing gum or candy with properties in the prevention of caries in children. In order to evaluate the compatibility between the sweeteners and the active substance, the binary systems were designed in a 1:1 ratio. The investigation techniques used during the study were attenuated by total reflection of Fourier transform infrared spectroscopy (ATR-FTIR) and thermoanalytical techniques: thermogravimetry (TG)/derivative thermogravimetry (DTG)/heat flow (HF). The ATR-FTIR clearly suggested absence of the interaction at room temperature between sweetener and active substance for all designed systems. Thermal analysis (TG/DTG/HF) performed on open crucibles in a dynamic air atmosphere suggested that the systems designed for trehalose/Th are not possible to be used in both types of formulations (medicated chewing gum and candy). System designed for lactose/Th can be used in chewing gum preparation but for candy formulation is not feasible to be used because the degradation process is starting close to the lower temperature used in candy preparation process.

Albendazole-cyclodextrins binary systems

The aim of this study was to characterize the interaction between the binary systems of albendazole (ABZ)—cyclodextrins (CDs) with pharmaceutical excipients. Hydroxyl-propyl-beta-cyclodextrin (HPBCD) and random methyl-beta-cyclodextrin (RAMEB) were used as cyclodextrins and magnesium stearate, mannitol, polyvinylpyrrolidone K30 (PVP K30), colloidal silica, starch, and talc were used as excipients. The utilized investigation techniques were attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), powder X-ray diffractometry (PXRD) and thermoanalytical techniques: thermogravimetry (TG)/derivative thermogravimetry (DTG)/heat flow (HF) and differential scanning calorimetry (DSC). The ATR-FTIR analysis clearly suggested interactions under ambient conditions between ABZ-HPBCD with PVP K30 and SiO2 and between ABZ-RAMEB with SiO2 and talc. The PXRD patterns indicated the formation of less crystalline mixtures but with no clear indication of interactions, since no peaks appeared nor disappeared. The modifications on the DSC curves suggested an interaction between ABZ-HPBCD and PVP K30 and SiO2 respectively, and in case of ABZ-RAMEB was observed an interaction with talc. Thermal analysis (TG/DTG/HF) carried out in open crucibles in dynamic air atmosphere suggested that at temperatures over 40 °C dehydration of samples occurred, later followed by thermolysis and appearance of interactions in all studied cases. Our study concludes by recommending precautionary measures in elaborating new solid formulations containing ABZ, HPBCD and PVP K30/SiO2 and for the ones containing ABZ, RAMEB and Talc/SiO2, due to the present interactions under ambient conditions.

Synthesis, photoluminescence properties and thermal investigation by TG-MS of RE(DAS)3·xH2O (RE = Eu3+, Tb3+)

Rare earth (III) diphenyl-4-amine sulfonates (RE(DAS)3·xH2O, RE = Eu3+, Tb3+) phosphors were synthesized by precursor method from barium diphenyl-4-amine sulfonate and rare earth sulfates. FTIR, TG/DSC coupled to mass spectrometry (TG/DSC/MS), X-ray powder diffraction (XPD), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy were utilized to structurally and morphologically characterize the samples. Thermal decomposition of Eu(DAS)3·7H2O and Tb(DAS)3·2H2O at 973 K under dynamic air atmosphere results in crystalline Eu2O2SO4 and Tb2O2SO4 materials, respectively. Accordingly, MS spectra reveal the liberation of thermal decomposition products of precursors, largely as CO2, NO2 and SO2 gases. The diphenyl-4-amine sulfonate (DAS) ligand demonstrats a good stabilizing property for Eu3+ and Tb3+ ions. The Eu(DAS)3·7H2O and Tb(DAS)3·2H2O compounds display efficient red and green emissions, under UV excitation, arising from the 5D0 → 7FJ (J = 0–4) and 5D4 → 7FJ (J = 0–6) transitions of the Eu3+ and Tb3+ ions, respectively.

Reaction mechanism of strontium cobaltite synthesis from equimolar mixture of Sr(NO3)2 and Co(NO3)2∙6H2O under air atmosphere

Strontium cobaltite was produced by heating the mixture containing equimolar amounts of Sr(NO3)2 and Co(NO3)2∙6H2O under dynamic air atmosphere. The reactions occurred during heating were determined and the intermediate and final products obtained at each reaction step were characterized using TG/DTA-MS, ICP-OES, XRD and FT-IR techniques. The oxygen stoichiometry of strontium cobaltite was determined using iodometric titration method and carbonation process.It was determined by thermal analysis results that Co(NO3)2∙6H2O was decomposed to CoO by forming the intermediate products Co(NO3)2∙4H2O, Co(NO3)2∙2H2O, Co(NO3)2∙H2O, Co(NO3)2, CoOOH, Co2O3 and Co3O4. Sr(NO3)2 was decomposed to SrO. Sr6Co5O15 was formed by solid state reaction of SrO, Co3O4 and O2. Sr2Co2O5 was produced at elevated temperatures from Sr6Co5O15 and Co3O4.Analyses carried out for the characterization of compounds obtained at different isothermal conditions showed that final product Sr2Co2O5 was obtained via Sr14Co11O33 and Sr6Co5O15. Sr2Co2O5 was decomposed to a mixture of Sr6Co5O15 and Co3O4 with a mole ratio of 1 : 0.333 during slow cooling to the room temperature.

Thermal analysis (TG–DSC, DSC–microscopy and EGA) and characterization of heavy trivalent lanthanides and yttrium isonicotinates

The trivalent lanthanide isonicotinates were synthesized to obtain stoichiometry Lu(IN)3 and Ln(IN)3·2H2O (Ln = Tb to Lu, and Y; IN = isonicotinate). A deep study of the thermal behavior in oxidant (air) and inert (N2) atmospheres was carried out using the following thermoanalytical techniques: simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC), differential scanning calorimetry (DSC) and evolved gas analysis (EGA by TG–DSC–FTIR). From these results, it was possible to determine that dehydration occurs in a single step and the thermal decomposition of the anhydrous compounds occurs in one or two (air), and two or three steps (N2). The final residues of thermal decomposition were Tb4O7 and Ln2O3 (Ln = Dy to Lu, and Y) in air atmosphere, while in N2 atmosphere the mass loss is still being observed up to 1000 °C. The identified gaseous products evolved during the thermal decomposition in dynamic dry air and nitrogen atmospheres were water, CO2, pyridine and CO. From these thermoanalytical data, it was possible to propose a general equation of thermal decomposition of these compounds in the N2 atmosphere. DSC curves of Tb and Ho compounds presented endothermic peaks corresponding to a reversible phase transition, confirmed by powder X-ray diffractometry (XRD), not previously reported. In addition, infrared vibrational spectroscopy (IR) suggests the coordination through carboxylate as bridging bidentate ligand toward the heavy trivalent lanthanides metals. This paper is complementary to our previous study involving the series of light trivalent lanthanides isonicotinates.

Effect of Ni substitute in off-stoichiometric Bi(Pb)-Sr-Ca-Cu(Ni)-O superconductor. Excess conductivity, XRD analysis and thermal behaviour

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.

Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) transition metals isonicotinate complexes: Thermal behavior in N2 and air atmospheres and spectroscopic characterization

Solid-state M(IN)2·nH2O complexes, where M stands for bivalent transition metals (Mn, Fe, Co, Ni, Cu and Zn), IN is isonicotinate and n = 0.5 to 4.0 H2O, were synthesized. Characterization and thermal behavior of the compounds were performed employing elemental analysis (EA), complexometric titration with EDTA, powder X-ray diffraction (PXRD), infrared spectroscopy (FTIR), simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC) in dynamic dry air and nitrogen atmospheres, differential scanning calorimetry (DSC) and TG–DSC coupled to FTIR. The thermal behavior of isonicotinic acid and its sodium salt was also investigated in both atmospheres. The dehydration of these compounds occurs in a single step in both atmospheres. In air atmosphere, the thermal decomposition of the anhydrous compounds also occurs in a single step, except for the copper compound where two steps are observed. In N2 the thermal decomposition of the anhydrous compounds occurs in two consecutive steps, except for iron compound, where three steps are observed. The main gaseous products of thermal decomposition/pyrolysis of the compounds were identified as CO, CO2 and Pyridine. Mn, Co, Cu and Zn compounds show a physical transformation process in DSC curves. The ligand coordinates through the pyridine nitrogen atom to the metal and for the Zn compound, the carboxylate group also participates in the coordination. The IR absorption profile of hydrated and dehydrated compounds suggest that there is a probable change in the coordination mode of the ligand upon dehydration. This change needs to be further investigated, once it is not possible to ensure only with infrared spectroscopy data.

Synthesis, structural characterization and luminescence properties of 1-carboxymethyl-3-ethylimidazolium chloride.

A microcrystalline carboxyl-functionalized imidazolium chloride, namely 1-carboxymethyl-3-ethylimidazolium chloride, C7H11N2O2+·Cl-, has been synthesized and characterized by elemental analysis, attenuated total reflectance Fourier transform IR spectroscopy (ATR-FT-IR), single-crystal X-ray diffraction, thermal analysis (TGA/DSC), and photoluminescence spectroscopy. In the crystal structure, cations and anions are linked by C-H...Cl and C-H...O hydrogen bonds to create a helix along the [010] direction. Adjacent helical chains are further interconnected through O-H...Cl and C-H...O hydrogen bonds to form a (10-1) layer. Finally, neighboring layers are joined together via C-H...Cl contacts to generate a three-dimensional supramolecular architecture. Thermal analyses reveal that the compound melts at 449.7 K and is stable up to 560.0 K under a dynamic air atmosphere. Photoluminescence measurements show that the compound exhibits a blue fluorescence and a green phosphorescence associated with spin-allowed (1π←1π*) and spin-forbidden (1π←3π*) transitions, respectively. The average luminescence lifetime was determined to be 1.40 ns for the short-lived (1π←1π*) transition and 105 ms for the long-lived (1π←3π*) transition.

Thermal behavior of entacapone, a catechol-O-methyltransferase inhibitor used in Parkinson’s disease

Entacapone, a selective and reversible inhibitor of catechol-O-methyltransferase, is used in the treatment of Parkinson’s disease in combination with levodopa/carbidopa to treat the symptoms of end-of-dose “wearing-off” effect. Considering that new formulations are researched constantly, proper knowledge of the active pharmaceutical ingredients is crucial in the preformulation stages. Kinetic analysis was performed using three methods: one integral—Flynn–Wall–Ozawa method, one differential—Friedman method, and modified nonparametric kinetics method (NPK). The thermoanalytical curves were registered at five different heating rates: β = 5, 7, 10, 12, and 15 °C min−1. Analysis was conducted in the dynamic air atmosphere to highlight potential thermooxidative processes. This paper deals with the investigation of solid-state stability and compatibility of binary mixture of entacapone with various pharmaceutical excipients by two instrumental techniques, such as universal attenuated total reflection Fourier transform infrared and thermal analysis (TG/DTG/HF). The excipients used in the mixture were: mannitol, silicon dioxide, talc, sorbitol, magnesium stearate, and povidone.

New metal(II) complexes with ceftazidime Schiff base

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.

Non-Isothermal Kinetic Analysis of the Dehydroxylation of Kaolinite in Dynamic Air Atmosphere

Abstract A non-isothermal kinetic analysis of kaolinite dehydroxylation was carried out using thermogravimetric analysis on powder samples with heating rates from 1 to 30 °C・min-1 in a dynamic air atmosphere. The mechanism of the reaction, values of overall activation energy and pre-exponential factor were determined from a series of thermogravimetric experiments by the Coats- Redfern method. The results show that the dehydroxylation of kaolinite is controlled by the rate of the third-order reaction (F3) with the mean values of overall activation energy (EA) 255 kJ・mol-1 and pre-exponential factor (A) 25.56 × 1014 s-1.

Simple synthesis of free surface nanostructured spinel NiFe2O4 with a tunable particle size

Nanostructured nickel ferrite stoichiometric spinel NiFe2O4 is intensively studied as a material suitable for catalysts or medical applications. Thus, it is very important to find a simple and cost-effective method for the synthesis of nanoparticles with homogenous and tunable particle size. In this work, we successfully synthetized nickel ferrite nanoparticles by thermal decomposition of nickel-iron glycerolate in a dynamic air atmosphere at different temperatures. We studied the thermal decomposition process by STA. The nickel-iron glycerolate precursor was analyzed by XRD, XPS, AAS, Raman spectroscopy, EDS and SEM to obtain exact composition and information about the morphology. The particle size of the obtained nanoparticles was determined from XRD diffraction patterns using Scherrer equation and also by TEM. Magnetic properties were studied using VSM in PPMS.

Study of Outgassing and Removal of Tritium from Metallic Construction Materials of ITER Vacuum Vessel Components

The subject of this study is the evaluation of tritium outgassing and removal from metals such as tungsten, beryllium, stainless steel, and copper alloy. In addition, a composite sample assembled from tungsten, copper alloy, and stainless steel was also studied. Samples of individual materials and composite samples were of thicknesses and compositions representing the internal components of the ITER vacuum vessel. The samples of materials were loaded with tritium by exposure to a gaseous tritium-deuterium mixture (about 1:1) at a temperature of 473 K and a pressure of about 0.05 MPa. The rate of outgassing was measured at temperatures of about 295, 308, and 323 K under static or dynamic atmospheres either of ambient air or dry air or argon. The study allows recommendation of conditions for storage of in-vessel components and reduction of the rate of tritium outgassing. The metals’ samples were also subject to study of tritium removal by thermal desorption under purge with argon containing 5 vol % of hydrogen. The study has demonstrated that this detritiation procedure allows for removal of large portions of the tritium inventory and substantial reduction in tritium outgassing rates.