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Abstract  

Phosphogypsum (PG) is a residue of the phosphate fertilizer industry that has relatively high concentrations of harmful radioactive materials. The reduction in concentration of the radionuclides from PG was investigated. The removal process is based on leaching of radionuclides using suitable organic extractants. The studied radionuclides were 226Ra, 210Pb, 238U and 40K. The factors affect the leaching process such as type of leaching materials, contact time, concentration of the desired solvent, liquid to solid ratio, and temperature were studied. Based on the experimental results, about 71.1, 76.4, 62.4, and 75.7% of 226Ra, 210Pb, 238U and 40K respectively were successfully removed from the PG. The reduction in the concentration of radionuclides was accompanied by reduction in the concentration of rare earth elements (∑REE) equals to 69.8%. Using the desired organic extractant under optimum conditions for treatment of the PG waste leads to obtain a decontaminated product that can be safely used in many industrial applications.

Open access

Abstract

The results of calorimetric investigations of electrolyte solutions in the mixtures of water, methanol, N,N-dimethylformamide, and acetonitrile with numerous organic cosolvents are discussed with regard to the intermolecular interactions that occur in the solution. Particular attention is given to answer the questions how and to what extent the properties of the systems examined are modified by the cosolvent added and how much the properties of the cosolvent are revealed in the mixtures with the solvents mentioned above. To this goal, the analysis of the electrolyte dissolution enthalpies, single ionic transfer enthalpies, and enthalpic pair interaction coefficients as well as the preferential solvation (PS) model are applied. The analysis performed shows that in the case of the dissolution enthalpies of simple inorganic electrolytes in water–organic solvent mixtures, the shape of the dependence of the standard dissolution enthalpy on the mixed solvent composition reflects to a large extent the hydrophobic properties of the organic cosolvent. In the mixtures of methanol with organic cosolvents, the ions are preferentially solvated either by methanol molecules or by molecules of the cosolvent, depending on the properties of the mixed solvent components. The behavior of inorganic salts in the mixtures containing N,N-dimethylformamide is mostly influenced by the DMF which is a relatively strongly ion solvating solvent, whereas in acetonitrile mixtures, the thermochemical behavior of electrolyte solutions is influenced to a large extent by the properties of the cosolvent particularly due to the PS of cation by the cosolvent molecules.

Open access

Abstract

The effect of mechanical activation on the structure and thermal reactions of glasses has been studied on the example of Na–Al–Fe phosphate glasses. These glasses are used in nuclear technology for immobilization of radioactive waste. The glasses were activated by grinding in a planetary mill. Mechanical activation causes a decrease of the T g temperature as well as of the glass crystallization temperature. The type of crystalline phases formed and the quantitative proportions between them are changing. Analysis of inter-atomic interactions in the structure of glass was applied to explain the observed regularities governing the crystallization of the activated glasses.

Open access

Abstract

Ceramic composites are widely used in various technologies such as tool production, aerospace technology, and nuclear power engineering. Their key features are considerable hardness and resistance to wear and corrosion at high temperature. Because many ceramic nanocomposites are designed to work at high temperature, it is important to determine their high temperature corrosion resistance. The subject of the investigation in this study were nanocomposite MMC (metal matrix composite) materials. As matrix the 316L stainless steel was used and the filler (nanoparticles) was nc-TiC. Using carbonized and purified nc-TiC particles the technology of the production of the nanocomposite structures based on the selective laser melting (SLM) technology was worked out. The MCP HEK Realizer II device was applied. The particles have been depicted by TEM method, whereas characterization of structure and particles size was performed by XRD method. The results of investigations on oxidation process of the steel/ncTiC nanocomposites in dry air have been presented. TG-DSC measurements were carried out under non-isothermal conditions at linear change of samples temperature in time and under isothermal conditions. MS method was used to determine evolved gaseous products.

Open access

Abstract

In this study, new series of lanthanide 4,4′-oxybis(benzoates) of the general formula Ln2oba3·nH2O, where Ln = lanthanides from La(III) to Lu(III), oba = C12H8O(COO)2 2− and n = 3–6, has been prepared under hydrothermal conditions. The compounds were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction patterns measurements and different methods of thermal analysis (TG, DSC, and TG-FTIR). In addition, photoluminescence properties of the selected complexes have been investigated. Crystalline compounds are isostructural in the whole series. Both carboxylate groups are deprotonated and engaged in the coordination of Ln(III) ions. Heating of the complexes leads to the dehydration and next decomposition processes. Although of the same structure, the removal of water molecules proceeds in different ways. In the nitrogen atmosphere, they decompose releasing water, carbon oxides and phenol molecules. The complexes of Eu(III), Tb(III) and Dy(III) exhibit photoluminescence in the visible range, whereas the compounds of Nd(III) and Yb(III) in the near-infrared region upon excitation by UV light.

Open access

SBA-15 silicas containing sucrose

Chemical, structural, and thermal studies

Journal of Thermal Analysis and Calorimetry
Authors: M. Barczak, M. Oszust-Cieniuch, P. Borowski, Z. Fekner and E. Zięba

Abstract

Mesoporous silicas were synthesized by condensation of tetraethoxysilane (TEOS) in the presence of Pluronic P123 as a structure-forming agent, and sucrose as an auxiliary agent, to investigate the effect of sucrose and aging temperature on the final properties, particularly structure-adsorption characteristics. Obtained materials have been characterized by XRD, nitrogen sorption measurements SEM-EDX, TEM, thermogravimetry, and FT-IR. The obtained materials have well-developed porous structure—values of the specific surface area (S BET) are in the range of 300–950 m2/g and the sizes of primary mesopores are in the range of 9–11 nm. It was established that S BET and ordering significantly decreases with an increasing content of sucrose in the initial mixture.

Open access

Abstract  

In situ gamma-ray measurements were taken at six locations in the Modane Underground Laboratory. Count rates for gamma radiation within the energy range of 7–2734 keV varied from 15 to 108 γs−1. The arithmetic mean was 79 γs−1 for measurements taken without a collimator. The metamorphic rocks surrounding the Lab are characterized by low activity concentrations of uranium and thorium equal to 12 and 10 Bq kg−1, respectively.

Open access

Abstract

Vitrification is currently considered to be an effective method for immobilization of radioactive waste. It is based on the enclosing of harmful elements in the structure of the glass. This work presents the results of studies on the thermal properties of glasses from P2O5–Al2O3–Na2O and P2O5–Al2O3–Fe2O3–Na2O systems for rendering nuclear waste in the form of salts such as sulfates, halides, and phosphates with high sodium content. These substances are not accepted by borosilicate glass, commonly used up to now for nuclear waste immobilization. Formation of sinters of glass-waste mixtures was selected as the method for immobilization, and the thermal chemistry of this process was studied. CaCl2 was used as the model chloride waste substance. The process of immobilization consists of its sintering with Na, Al, Fe-phosphate glasses containing more than 50 wt% P2O5 as the amorphous matrix. Thermal analysis showed that all glasses exhibit an ability for crystallization, with that the intensiveness of this process is determined by the chemical composition of these glasses. The addition of Fe2O3 to the glass intensified crystallization process. Leaching of components of sinters tests established that glass containing Fe2O3 in its composition most effectively binds waste in comparison to Al2O3 containing phosphate glass. The test results allow for the statement that the waste substance in the form of chloride salts such as CaCl2 is stable bound in the glass–crystalline sinters, which ensures its effective immobilization.

Open access
Journal of Thermal Analysis and Calorimetry
Authors: Dariusz Szychowski, Barbara Pacewska, Grzegorz Makomaski, Janusz Zieliński, Wiesława Ciesińska and Tatiana Brzozowska

Abstract

The purpose of this study was to determine the possibility of producing hydrophobic mesoporous mineral–carbon sorbents from aluminum hydroxide and compositions of coal tar pitch–polymers on carbonization at 600 °C in a nitrogen atmosphere. Blends of the products of co-precipitation of aluminum hydroxide in the carbonaceous substances medium were subjected to carbonization process. The extent of porous structure development was evaluated using low temperature nitrogen adsorption, adsorption of benzene vapors, and adsorption of iodine from aqueous solution. The highest value of BET surface area of about 370 m2/g was achieved for the carbonization product obtained from co-precipitated raw components with 10 wt% compositions coal tar pitch–polymer. These materials demonstrated high capacity to reduce organic pollutions from sewage. Pitch–polymer composition containing poly(ethylene terephthalate) or phenol–formaldehyde resin was studied by the means of DSC method in order to determine the high-temperature transformations taking place under the conditions of carbonization. DSC method enables to determine i.a. the decomposition temperatures of carbonizates produced from pitch–polymer compositions and the evaluation of their sorption abilities. The additive of poly(ethylene terephthalate) and phenol–formaldehyde resin caused the increase of thermal resistance of the pitch expressed by higher decomposition temperatures.

Open access
Journal of Thermal Analysis and Calorimetry
Authors: V. Sydorchuk, W. Janusz, S. Khalameida, E. Skwarek, J. Skubiszewska-Zięba, R. Leboda and V. Zazhigalov

Abstract

Deposited zirconium phosphate samples on the base of silica and titania have been prepared using the sol–gel and mechanochemical methods. Porous structure, phase composition, and electrokinetic parameters have been studied by means of nitrogen adsorption–desorption, XRD, DTA-TG, FTIR, electrophoresis, and potentiometric titration. The compositions possess varied parameters of porous structure, structure of deposited phase, and electrokinetic properties depending on support nature and synthesis conditions.

Open access
Journal of Thermal Analysis and Calorimetry
Authors: G. Janowska, A. Kucharska-Jastrzabek, W. M. Rzymski and A. Pajak

Abstract

The article describes the measurements results of the thermal properties of cross-linked blends of butadiene–acrylonitrile rubber (XNBR, Krynac X.7.50) and chlorosulfonated polyethylene containing different quantity of combined chlorine (CSM24—Hypalon 48, CSM29—Hypalon 20, CSM35—Hypalon 40, and CSM43—Hypalon 30) under inert gas (DSC) and in air (derivatography). The blends were non-conventionally cross linked at a temperature of 150 °C by means of MgO in the presence of stearic acid. The thermal curves obtained were interpreted from the point of view of phase transitions and chemical reactions of the macromolecular components used. It has been found that the elastomers investigated show a good compatibility brought about by the formation of both interpolymeric covalent bonds and interpolymeric and intrapolymeric ionic bridges, which play the role of a chemical compatibilizer. The results of the examinations performed show that the non-conventional cross-linked XNBR/CSM blends prove very good mechanical properties and are self-extinguished in air. Their flammability defined with the value of OI and combustion time in air clearly depends on the type of CSM.

Open access

Abstract

A study of the interaction between some simple molecules (dihydrogen, acetylene, and ethylene) and Pd–Pb catalysts has been performed using the B3LYP hybrid density functional. The reaction paths for the H2 molecule reacting with the PdPb dimer are reported for the singlet and triplet spin states. The C2H2 and C2H4 molecules were adsorbed in a few characteristic sites on the Pd(100) surface doped with Pb. This surface was modeled using Pd13Pb clusters. The results of the calculations indicate that the Pd–Pb catalysts interact with the H2, C2H2, and C2H4 molecules more weakly than the corresponding monometallic Pd catalysts do, and thus the bimetallic catalysts exhibit the reduced activity toward these simple molecules.

Open access
Journal of Thermal Analysis and Calorimetry
Authors: Wiesława Ferenc, Beata Cristóvão, Jan Sarzyński and Paweł Sadowski

Abstract

In this study, 4-methoxycinnamates of Mn(II), Co(II), Ni(II), Cu(II), Cd(II), Nd(III) and Gd(III) were synthesised. From the infrared (IR) spectra analysis of complexes, sodium salt and according to the spectroscopic criteria the carboxylate groups seem to be bidentate chelating. The complexes of 4-methoxycinnamates lose the water molecules in one or two steps. The final products of their decomposition are oxides of the respective metals. The enthalpy values of dehydration process were determined. The FTIR spectra of the gas phase products indicate that the decomposition of the complexes is connected mainly with the release of molecules of water (H2O), carbon dioxide (CO2), carbon monoxide (CO), methane (CH4) and other hydrocarbons. The analysed compounds follow the Curie–Weiss law. The magnetic moment values experimentally determined change as follows: from 5.90 μ B to 6.27 μ B for Mn(II) complex, from 4.57 μ B to 4.99 μ B for Co(II) complex, from 3.68 μ B to 3.30 μ B for Ni(II) complex, from 1.87 μ B to 1.96 μ B for Cu(II) complex, from 3.06 μ B to 3.51 μ B for Nd(III) complex, and from 6.91 μ B to 6.90 μ B for Gd(III) complex.

Open access

Abstract

Mesoporous titanium-containing silicas with different Titania contents were investigated. The structural parameters of the materials were characterized by low-temperature adsorption/desorption of nitrogen and X-ray diffraction analysis. The thermodesorption of water using the quasi-isothermal thermogravimetry as well as the differential scanning calorimetry were used to characterize thermal and surface properties of these materials. The adsorbed water layers and the concentration of weakly and strongly bound water as well as the surface free energy on the adsorbent/water interfaces were calculated. It was stated that the increase of Titania content causes a gradual decrease of specific surface area and formation of biporous structure inside the tested materials. The water thermodesorption from the surface proceeds in two or three stages, which is connected mainly with pore distribution and TiO2 content. One can observe the increase of the total surface free energy (ΔG Σ) with the increasing TiO2 content, but the largest ΔG Σ value at the adsorbent/strongly bound water interface is exhibited by the adsorbent of intermediate content (30%) of TiO2. Freezing temperature of water contained in the pores of the studied materials is connected largely with their porous structure. Due to the well developed porous structure, the water freezing process is a multi-stage one.

Open access

Abstract

For dehydration of CaC2O4·H2O and thermal dissociation of CaCO3 carried out in Mettler Toledo TGA/SDTA-851e/STARe thermobalance similar experimental conditions was applied: 9–10 heating rates, q = 0.2, 0.5, 1, 2, 3, 6, 12, 24, 30, and 36 K min−1, for sample mass 10 mg, in nitrogen atmosphere (100 ml min−1) and in Al2O3 crucibles (70 μl). There were analyzed changes of typical TGA quantities, i.e., T, TG and DTG in the form of the relative rate of reaction/process intended to be analyzed on-line by formula (). For comparative purposes, the relationship between experimental and equilibrium conversion degrees was used (for ). It was found that the solid phase decomposition proceeds in quasi-equilibrium state and enthalpy of reaction is easily “obscured” by activation energy. For small stoichiometric coefficients on gas phase side (here: ν = 1) discussed decomposition processes have typical features of phenomena analyzable by known thermokinetic methods.

Open access

Instrumentation and calibration of the Calvet calorimeter

Enthalpy of solution of PrBr3 at standard conditions

Journal of Thermal Analysis and Calorimetry
Authors: Beata Salamon, Jan Kapała and Marcelle Gaune-Escard

Abstract

The original Calvet calorimeter, made from aluminum block, were instrumented. The cells for the solution calorimetry measurement have been projected and constructed. The calibration of calorimeter was performed by measurement of the dependence of reference material on temperature and the influence of mechanical events on thermograms. The enthalpies of solution in water and 0.01 M HCl were investigated for chlorides and bromides of alkali metals (Na···Cs), PrBr3 and Rb3PrBr6. The enthalpies of solution of alkali halides have been compared to the reference data obtained for infinite solution. The decomposition of Rb3PrBr6 at temperatures lower than 399 K has been stated. The enthalpy of solution PrBr3 at 298.15 K has been determined.

Open access

Abstract

The study evaluated the applicability of differential scanning calorimetry (DSC) for the detection of water content in butter. High correlation coefficients were found between the water content and the enthalpies of the ice melting/water crystallization. The correlation equations were adopted to calculate the water content for seven tested kinds of butter, and the results were compared with the values, obtained by using the reference method. The difference between the water content determined by the reference method and by DSC ranged between 0.2 and 2.6% for the measured enthalpy of ice melting, and between 1 and 5.6% for the enthalpy of water crystallization. In relation to the data obtained, it can be concluded that the parameter of ice melting enthalpy can be used in the identification of adulterations or confirmation of butter authenticity.

Open access

Abstract

Mixtures of poly(ethylene terephthalate) (PET) with magnesium compounds including carbonate, hydroxide, and oxide, with different weight ratios of the components, were subjected to thermogravimetric measurements up to 850 °C in argon atmosphere. For reference, pure components of the examined mixtures were analyzed at the same conditions. During the heating, PET underwent carbonization and magnesium carbonate and hydroxide decomposed to MgO with evolution of gaseous products (CO2 and/or H2O). As found, carbon yields calculated from the residual masses depended on the qualitative and quantitative composition of the starting mixture. Yields of carbon obtained from PET mixed with MgO did not depend on MgO/PET ratio. However, yields of carbon formed through pyrolysis of PET contained in the mixture with either magnesium carbonate or magnesium hydroxide were in general higher and depended on the weight ratio of components in the starting material. Reasons of these inconsistent results are discussed and explained. An influence of gasification of char on the carbon yield is explained.

Open access
Journal of Thermal Analysis and Calorimetry
Authors: Lin-Quan Liao, Hong-Jian Wei, Ji-Zhen Li, Xue-Zhong Fan, Ya Zheng, Yue-Ping Ji, Xiao-Long Fu, Ya-Jun Zhang and Fang-Li Liu

Abstract

The compatibility of poly(3-nitromethyl-3-methyloxetane) (PNIMMO) with some energetic materials are studied by using pressure DSC method in detail. Cyclotetramethylenetetranitroamine (HMX), cyclotrimethylenetrinitramine (RDX), nitrocellulose (NC), nitroglycerine (NG), N-nitrodihydroxyethylaminedinitrate (DINA), and aluminum powder (Al) are used as common energetic materials, and 3,4-dinitrofurzanfuroxan (DNTF), 1,3,3-trinitroazetidine (TNAZ), hexanitrohexazaisowurtzitane (CL-20), 4,6-dinitro-5,7-diaminobenzenfuroxan (CL-14), 1,1-diamino-2,2-dinitroethylene (DADNE), and 4-amino-5-nitro-1,2,3-triazole (ANTZ) are used as new energetic materials. The results show that the binary systems of PNIMMO with HMX, RDX, NC, NG, DINA, Al, CL-14 and DADNE are compatible, with TNAZ, CL-20 and ANTZ are slightly sensitive, and with DNTF is sensitive.

Open access

Abstract  

The activity concentrations of 40K, 232Th, and 238U in the characteristic rocks of the Modane-Aussois region (Western Alps, France) were determined using an HPGe gamma-ray spectrometry system. The activity concentrations of 40K varied from 18 Bqkg−1 (limestone dolomite) to 392 Bqkg−1 (calcschist), while those of 232Th varied from 0.7 Bqkg−1 (limestone dolomite) to 18 Bqkg−1 (calcschist). The activities associated with 238U ranged from 9 (quartzite) to 29 Bqkg−1 (dolomite). In the investigated rock samples, concentrations of 238U (ppm) and 40K (%) had a strong negative correlation.

Open access

Abstract

The thermogravimetry (TG) was used for characterization of the fly ash (FA)-based MCM-41 mesoporous materials. MCM-41 mesoporous materials were synthesized using silica extracts from different FA. The synthesis of MCM-41 from FA was carried out by the hydrothermal method using the supernatants of coal FA (in the form of sodium silicate) and cationic cetyltrimethylammonium bromide (CTAB) surfactants as the structure-directing agents. On the basis of the data obtained from the TG analysis, thermal behaviour of FA-based MCM-41 mesoporous materials was assessed. This study has established the range of temperatures corresponding to the desorption of water, decomposition of the surfactant and condensation of silanol, thereby making the overall quality assessment of FA-based MCM-41 mesoporous materials.

Open access

Abstract  

In situ leaching of uranium ores with sulfuric acid during active uranium mining activity on the Gessenheap has caused longstanding environmental problems of acid mine drainage and elevated concentrations of uranium. To study there remediation measures the test site Gessenwiese, a recultivated former uranium mining heap near Ronnenburg/East Thuringia/Germany, was installed as a part of a research program of the Friedrich-Schiller University Jena to study, among other techniques, the phytoremediation capacity of native and selected plants towards uranium. In the first step the uranium speciation in surface seepage and soil pore waters from Gessenwiese, ranging in pH from 3.2 to 4.0, were studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Both types of water samples showed mono-exponential luminescence decay, indicating the presence of only one major species. The detected emission bands were found at 477.5, 491.8, 513.0, 537.2, 562.3, and 590.7 nm in case of the surface water samples, and were found at 477.2, 493.2, 513.8, 537.0, 562.4, and 590.0 nm in case of the soil water samples. These characteristic peak maxima together with the observed mono-exponential decay indicated that the uranium speciation in the seepage and soil pore waters is dominated by the uranium (VI) sulfate species UO2SO4(aq). Due to the presence of luminescence quenchers in the natural water samples the measured luminescence lifetimes of the UO2SO4(aq) species of 1.0–2.6 μs were reduced in comparison to pure uranium sulfate solutions, which show a luminescence lifetime of 4.7 μs. These results convincingly show that in the pH range of 3.2–4.0 TRLFS is a suitable and very useful technique to study the uranium speciation in naturally occurring water samples.

Open access
Journal of Thermal Analysis and Calorimetry
Authors: Barbara Marciniec, Katarzyna Dettlaff, Marek Naskrent, Zuzanna Pietralik and Maciej Kozak

Abstract

The effect of ionising radiation on the physico-chemical properties of disulfiram (Antabuse, Esperal, bisdiethylthiocarbamoil disulphide) has been studied by DSC, FTIR, EPR, MS, TLC and HPLC. Sterilisation was carried out in the solid state, at room temperature and normal air humidity using the electron beam of 9.96 Mev from accelerator. All the measurements were made simultaneously for the irradiated and nonirradiated substance. It has been found that the drug studied in solid phase when subjected to an electron beam corresponding to the irradiation in the doses 10–100 kGy shows the presence of free radicals (EPR), and a change in colour from white to pale green-grey that disappears after solution in water or methanol. After the irradiation with the dose of 100 kGy, its melting point and enthalpy slightly decreased. Also the content of the active substance decreases (HPLC −1.5%, UV −3.6%, iodometric titration method −2.7%) and trace amounts of the radiolysis products appear (HPLC). The substance irradiated with the doses 10–50 kGy does not show changes in the melting point, in the content and presence of the radiolysis products. The EPR results have shown that free radicals disappear after about a year and the discolouring disappears with them. The results of this study have shown that disulfiram can be subjected to sterilisation by irradiation with no deterioration of its physico-chemical properties, but a long time of storage needed to remove free radicals and discolouration questions the economic justification for this type of sterilisation.

Open access

Abstract

The aim of this study is to encapsulate two drugs: 5-fluorouracil (5-FU) with the hydrophobic properties and 1-β-D-arabinofuranosylcytosine (Ara-C) with the amphiphilic properties into liposomes prepared by the modified reverse-phase evaporation method (mREV) from L-α-phosphatidylcholine dipalmitoyl (DPPC). We studied the thermotropic phase behavior of liposome entrapped 5-FU and Ara-C. It is known that the stability of liposomes depends not only on the method of chemical gradient loading, the use of membrane stabilizer such as sterols, but also on the phase transition temperature (T c) of phospholipids, which undergoes an alteration after encapsulation of drugs to liposomes. The competition of these two drugs entrapped in liposomes was analyzed by the use of two spectroscopies: 1H NMR and UV on the basis of the analysis of the signals of each drug in the liposome—drug system. The percent of encapsulation in DPPC/Ara-C/5-FU liposome obtained by the use of UV spectroscopy amounted 93.84 and 96.05% for 5-FU and Ara-C, respectively. Phase transition temperature T c of liposomes containing Ara-C did not significantly change while for the liposomes containing 5-FU it increased in comparison with T c of the reference liposomes formed from DPPC.

Open access

Abstract

This article presents a procedure of the activation of halloysite and a method of the synthesis of nucleus-sheath type filler. The effects of the nanoadditives obtained on the thermal properties, flammabilities and fire hazards of peroxide and sulfur vulcanizates of NBR and SBR rubbers, are discussed. Based on the test results obtained by derivatography, oxygen index, FAA micro-calorimeter and cone calorimeter, the thermal stability, flammability, and fire hazard of the nanocomposites investigated were determined. The results obtained were interpreted from the point of view of the chemical structure of the diene elastomers investigated, their spatial network structure, and the method of halloysite modification.

Open access

Abstract  

A Prompt Gamma Ray Neutron Activation Analysis (PGNAA) system, incorporating an isotopic neutron source has been simulated using the MCNPX Monte Carlo code. In order to improve the signal to noise ratio different collimators and a filter were placed between the neutron source and the object. The effect of the positioning of the neutron beam and the detector relative to the object has been studied. In this work the optimisation procedure is demonstrated for boron. Monte Carlo calculations were carried out to compare the performance of the proposed PGNAA system using four different neutron sources (241Am/Be, 252Cf, 241Am/B, and DT neutron generator). Among the different systems the 252Cf neutron based PGNAA system has the best performance.

Open access

Abstract

The new derivatives of 3,4-pyridinedicarboximide were synthesised. Experimental measurements were carried out using 1H NMR spectra, IR spectra, elemental analyses and differential scanning calorimetry. The purpose of this study was to study the thermal stability of these four new compounds and to establish a solid-state polymorphism. Measurements were carried out for samples obtained from ethanol and n-hexane and after a long-time storage.

Open access

Abstract  

The development on neutron activation analysis (NAA) into a technique of practical interest effectively started about 60 years ago, when nuclear reactors became available and widely accessible as intense sources of neutrons. During 50 out these 60 years, the series of Modern Trends in Activation Analysis (MTAA) Conferences acted as a true companion and facilitator of this growth. As trendwatcher they signalized the many initiatives that contributed to the development of activation analysis and its applications. A period has come to an end of impressive development resulting from sometimes revolutionary changes in radiation detection and data processing, and much improved irradiation facilities, NAA has reached a full stage of development, with emphasis on routine application and with remaining developments of in marginal impact. NAA is being challenged increasingly in the last 30 years by alternative techniques for multi trace element analysis. The MTAA Conference and with it the ICAA, the International Committee on Activation Analysis, can play an important and active role in this process of identifying and selecting key areas, and even promoting concerted action in those areas. Such an evolution of focus from retrospective to prospective, from trendwatcher to trendsetter, may well allow the MTAA Conference to continue and even expand its role in future development of NAA and its applications. The ideas about the future of the MTAA Conferences and its organization are elaborated upon and some possible subjects for focused development activities are indicated.

Open access

Abstract

Using special thermogravimetry Q-TG method, physicochemical properties of lunar sample surfaces were investigated. The numerical and analytical procedures for the evaluation of energetic heterogeneous properties on the basis of liquid thermodesorption from the sample surfaces under the quasi-equilibrium conditions are presented. The calculations of the adsorption capacity and energy distribution functions of liquids on lunar surfaces on the basis of the thermogravimetry data are presented.

Open access

Abstract

Hydroxypropyl methylcellulose (HPMC) and polyvinyl alcohol (PVA) are important polymers in pharmaceutical, food and other industries being largely used as encapsulation agents. The characterization of two reference grades of HPMC (Pharmacoat® 603 and Pharmacoat® 615) and one reference grade of PVA (Mowiol® 4–98), through X-ray diffraction (XRD) and thermogravimetry (TG) is described. Specific analyses were performed by means of dynamic vapour sorption analysis of water adsorption/desorption from vapours at 10, 25, 40, 55 and 70 °C. Guggenheim–Anderson–de Boer (GAB), Brunauer–Emmett–Teller (BET), Park and n-layer BET models were successfully used to fit the experimental data. The glass transition temperature as function of water content was measured by means of differential scanning calorimetry (DSC). The experimental data were analysed according to Linear, Gordon–Taylor, Fox and Roos equations. XRD studies revealed amorphous structure for the Pharmacoat® 603 and Pharmacoat® 615 and crystalline for Mowiol® 4–98. Single and multi-step temperature degradation point was found for Pharmacoat® 603 and Pharmacoat® 615 and Mowiol® 4–98, respectively. The water uptake is higher for Pharmacoat® 603 and Pharmacoat® 615 than Mowiol® 4–98. The influence of temperature on water uptake is opposite for the two types of polymers. GAB and n-layer BET were found to better model Pharmacoat® 603 and Pharmacoat® 615 and Mowiol® 4–98 data, respectively. The water makes the glass transition to decrease quite drastically. Gordon–Taylor is better fitting the experimental data both for Pharmacoat® 603 and Pharmacoat® 615 and Mowiol® 4–98.

Open access

Abstract

Kinetic investigations on the syntheses of higher aliphatic alcohol (C7, C9, C11) phthalates have been conducted in an isothermal, semibatch reactor. The first stage of the process, the formation of monoester, is very fast and irreversible. The second stage, the esterification of monoester towards diester, is slow and catalyst should be used. These reactions appear to be first order with respect to monoester and do not depend on the concentration of alcohol.

Open access
Journal of Thermal Analysis and Calorimetry
Authors: Przemysław Rybiński, Grażyna Janowska, Agnieszka Kucharska-Jastrząbek, Agnieszka Pająk, Iwona Wójcik, Dorota Wesołek and Krzysztof Bujnowicz

Abstract

This article discusses the effect of the cross-linking of diene elastomers (BR, SBR, NBR), with the use of an organic peroxide or sulfur, on their flammability and fire hazard. Flammability tests were carried out by the method of oxygen index, combustion time (in air) and ignition temperature measurements. Fire hazard was determined on the basis of test results obtained by means of a cone calorimeter. Toxicometric coefficients ( and WLC50SM) and the emission of polycyclic aromatic hydrocarbons (PAH) were determined. Test results were interpreted from the point of view of the chemical constitution of elastomer macromolecules as well as the structure of its network structure.

Open access

Abstract  

The assumption that the shape of the epithermal neutron spectrum can be described, in any research reactor, by the 1/E 1+α function is a fundamental starting point of the k 0 standardization. This assumption may be questioned from a reactor physics viewpoint. The type of moderator, the existence of neutron reflectors, the additional production of (γ, n) neutrons and resonance capture by construction materials may be different for each reactor, with consequences for the shape of the neutron spectrum. This dependency may explain that various practitioners reported contradicting experiences with the use of Zr–Au flux monitors for the determination of the α-parameter. An objective view on the influence of the design of the reactor and irradiation facility on the shape of the neutron spectrum can be obtained by modeling. This has been applied in the Reactor Institute Delft for reactor configurations in which the irradiation facilities face the fuel elements with the presence of beryllium reflector elements. The Monte Carlo calculations indicate a distortion of the 1/E 1+α relationship at the higher energy edge of the epithermal neutron spectrum. This distortion is attributed to the formation and thermalisation of both photoneutrons and (n, 2n) produced fast neutrons in the beryllium, and has a direct impact on the resonance activation of 95Zr, other than represented by the 1/E 1+α function. The obtained relationship between neutron flux and neutron energy was also used for estimating the f-value and compared with the value obtained by the Delft Cr–Mo–Au flux monitor.

Open access

Abstract

The cyanate ester (CE) and epoxy (EP) resins were cured together at various mass compositions. The curing behavior of CE and CE/EP systems was studied by means of differential scanning calorimetry (DSC) in non-isothermal conditions. The DSC measurements indicated that the curing reactions were dependent on the stoichiometric ratio of the mixtures and showed the dilution effect of the EP resin in the cyclotrimerization of the catalyzed CE resin. The CE and CE/EP (70/30) systems were modified using reactive liquid butadiene-acrylonitrile copolymer (ETBN) and polysiloxane core–shell (PS) elastomer. The influence of ETBN and PS on the curing process and glass transition temperature (T g) of CE/EP systems was determined. The impact resistance characteristics of the completely cured systems indicated the influence of the modifiers and the EP content in the mixtures on its impact resistance.

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Abstract

The magnesium sulphate complex compounds of general formulae [Mg(H2O)6]2+·2(C6H12N4)·SO4 2−·5(H2O) (1) and Mg(C12H8N2)(H2O)3SO4 (2) have been synthesized, characterised by elemental and thermal analysis, IR, UV–VIS and fluorescence spectroscopy, and X-ray crystallography. The obtained compounds are air stable at room temperature and well soluble in water. In the structures of the investigated complex compounds the O–H…O, O–H…N, and C–H…O hydrogen bonds exist, and they create N2C2 2(8), R2 2(8) (compound 1) and N1C1 1(6), N1R2 2(12) (compound 2) patterns. Their thermal decomposition processes in the investigated atmospheres (air and helium) are different. After the slightly similar dehydratation, the observed transitions and the obtained final products are different (in helium atmosphere the sulphate ion of studied compounds undergoes decomposing what does not take place in air atmosphere). The UV–VIS spectrum of 2 shows maxima that are typical for π π* and nπ* transitions, and fluorescence spectrum of the same compound displays its great fluoresce properties. The 1 does not exhibit absorption in the investigated region of electromagnetic spectrum due to the absence of respect chromophore groups. The IR spectrum of 2 shows typical vibrations for chelating amine molecule. An interesting fact is that in 1 the SO stretching vibrations (existing at 1119 and 1182 cm−1) are doubled in comparison to the magnesium sulphate whilst in 2 these vibrations are absent.

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Abstract  

Neutron activation laboratories worldwide are at a turning point at which new staff has to be found for the retiring pioneers from the 1960s–1970s. A scientific career in a well-understood technique, often characterized as ‘mature’ may only be attractive to young scientists if still challenges for further improvement and inspiring new applications can be offered. The strengths and weaknesses of neutron activation analysis (NAA) are revisited to identify opportunities for innovation. Position-sensitive detection of elements in large samples, Monte Carlo calculations replacing the use of standards, use of scintillator detectors and new deconvolution techniques for increasing the sensitivity are examples of challenging new roads in NAA. Material science provides challenges for the application of NAA in both bulk samples, ultrathin layers and ultrapure materials.

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Abstract  

The laboratory for instrumental neutron activation analysis at the Reactor Institute Delft, Delft University of Technology uses a network of 3 gamma-ray spectrometers with well-type detectors and 2 gamma-ray spectrometers with coaxial detectors, all equipped with modern sample changers, as well as 2 spectrometers with coaxial detectors at the two fast rabbit systems. A wide variety of samples is processed through the system, all at specific optimized (and thus different) analytical protocols, and using different combination of the spectrometer systems. The gamma-ray spectra are analyzed by several qualified operators. The laboratory therefore needs to anticipate on the occurrence of random and systematic inconsistencies in the results (such as bias, non-linearity or wrong assignments due to spectral interferences) resulting from differences in operator performance, selection of analytical protocol and experimental conditions. This has been accomplished by taking advantage of the systematic processing of internal quality control samples such as certified reference materials and blanks in each test run. The data from these internal quality control analyses have been stored in a databank since 1991, and are now used to assess the various method performance indicators as indicators for the method’s robustness.

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Abstract

Four copper(II) new mix ligand complexes of the coumarin derivative (A1 = 7-hydroxy-10,11-dihydroindeno[5,4-c]chromen-6(9H)-one, A2 = 2-bromo-7-hydroxy-10,11- dihydroindeno[5,4-c]chromen-6(9H)-one, A3 = 7-hydroxy-4-methoxy-10,11-dihydroindeno[5,4-c]chromen-6(9H)-one, and A4 = 5-hydroxy-8,9-dihydrobenzo[f]indeno[5,4-c]chromen-4(7H)-one) and 1,10-Phenanthroline have been synthesized. The structural interpretations were confirmed from elemental analyses, magnetic susceptibility and FAB mass spectral, as well as from IR spectral studies. From the analytical, spectroscopic, and thermal data, the stoichiometry of the mentioned complexes was found to be 1:1:1 (coumarin ligand:copper metal:1,10-Phenanthroline). The thermal stabilities of these complexes were studied by thermogravimetric (TG/DTG) and the decomposition steps of these four complexes are investigated. Kinetic parameters such as order of reaction (n) and the energy of activation (E a) were calculated using Freeman–Carroll method. The pre-exponential factor (A), the activation entropy (S∗), the activation enthalpy (H∗), and the free energy of activation (G∗) were calculated using Horowitz–Matzger equations. Based on the E a values, the thermal stabilities of complexes in the decreasing order are Cu(II)-2 > Cu(II)-3 > Cu(II)-4 > Cu(II)-1.

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Abstract

A thermopile has been constructed for detecting heat of reaction during the individual steps taking place in the growth cycles of atomic layer deposition (ALD). The thermopile sensor consists of 64 junctions of thermocouple type K. It has successfully been applied to characterize ALD growth of Al2O3 from Al(CH3)3 (TMA) and H2O, and has furthermore been applied to explore energetics of ALD growth for the following combinations of precursors: TMA + O3, TMA + O2, TMA + hydroquinone, TiCl4 + H2O, and Zn(CH3CH2)2 + H2O. The thermopile clearly identifies exo/endothermal reaction steps, the effect of surface temperature on exposure to precursors from cold sources as well as variation in the flow of gases, and allows setting up of experiments where variations in precursors and pulsing parameters may provide mechanistic insight into the ALD growth. The sensor represents a new and complementary tool for in situ characterization of thin film growth by ALD.

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Abstract

The influence of support porosity on the selectivity of home-made 5%Pd–2%In/support (support = SiO2, Al2O3, TiO2) catalysts in nitrate reduction was studied. The main final products of the reaction were N2 and NH4 +. Together with the decrease in pore diameter, an increase in ammonia concentration in the reaction mixture was observed. It is probably caused by slow diffusion of OH ions from narrow pores to the solution.

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Abstract

The dissolution enthalpies of NaI in the mixtures of methanol with 1,2-alkanediols (1,2-propanediol, 1,2-butanediol, 1,2-pentanediol) and with α,ω-alkanediols (1,3-propanediol, 1,4-butanediol, 1,5-pentanediol), as well NaI in the mixtures of water with 1,3-propanediol and 1,2-pentanediol, were determined at 298.15 K. The energetic effect of interactions between the investigated alkanediols and NaI in methanol and in water was calculated using the enthalpic pair interaction coefficients (h xy) model. These results along with the other data concerning the NaI–non-electrolyte pairs taken from our earlier reports and from the literature were analyzed with respect to the effect of the non-electrolyte properties on the variations of the h xy values. The group contributions illustrating the interactions of NaI with selected functional groups in non-electrolyte (alkanediol and alkanol) molecules, namely: CH2 and OH groups were calculated and discussed.

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Abstract

The influence of three mineral additives, i.e. fly ashes from pulverized combustion and from fluidized combustion of hard coal as well as Portland cement, on early hydration (up to 28th day) of calcium aluminate cement was investigated. Cement pastes containing 0, 5 and 25 wt% of additives were studied by the use of calorimetry, thermal analysis and infrared spectroscopy methods. It was confirmed that hydration of calcium aluminate cement is closely dependent on the type of addition and its amount. The influence of additives of different properties on cement hydration was discussed basing on received results and other literature reports.

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Abstract

The influence of tertiary aromatic amines on the course of BPO initiated cure reaction of unsaturated epoxy polyesters with different styrene content has been studied by non-isothermal differential scanning calorimetry. Unsaturated epoxy polyesters prepared from cyclohex-4-ene-1,2-dicarboxylic anhydride, maleic anhydride and suitable aliphatic glycol: ethylene glycol or 1,4-butanediol or 1,6-hexanediol were dissolved in vinyl monomer (styrene) resulting in a styrene content of 20–80% by weight. The styrene solutions of polyesters were subjected to the cure reaction with suitable curing agent: benzoyl peroxide (BPO) used in various concentration (0.5–3.0 wt%) or the mixture of BPO/stoichiometric ratio of chosen tertiary aromatic amines: (N,N-dimethylbenzylamine (BDMA) or 2,4,6-tri(dimethylaminomethyl) phenol (DMP-30). The curing characteristic such as: temperature of the cure initiation (T onset), peak maximum temperature (T max), final cure temperature (T end), heat generated during the cure reaction (ΔH) were evaluated. It has been found that the course of the cure reaction depended on the styrene content in prepared compositions and the initiating system used. The performed investigations confirmed that one of the applied tertiary aromatic amine: BDMA was an effective promoter for BPO decomposition process, causing a decrease in characteristic curing temperatures of unsaturated epoxy polyesters with styrene. The organic peroxide-amine interactions caused the promotion of BPO decomposition to benzoyloxy radicals at lower temperatures and thus accelerated the copolymerization process. However, DMP-30 was a very sluggish promoter for BPO decomposition, probably due to the presence of both hydroxyl group, their ortho-position to two of three amine groups and their branched structure. The redox reaction between BPO and DMP-30 probably resulted in non-radical products or radical formation which was incapable of initiating the polymerization reaction.

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Abstract

The influence of working pressure on the mechanisms of the CO2/H2 reaction on a co-precipitated CuO/ZnO/Al2O3 catalyst have been studied at 230 °C and in the pressure range of 1–75 bar. In the CO2 hydrogenation using CuO/ZnO/Al2O3, the products were found to be CO, methanol and water almost exclusively. Only a trace of methane formation was observed. Methanol and carbon monoxide are competitively formed. The former is produced directly from CO2 whatever the pressure whereas carbon monoxide stems either from CO2 directly at high pressure or both methanol decomposition and CO2 directly at low pressure.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Bojanowska-Czajka, H. Nichipor, P. Drzewicz, B. Szostek, A. Gałęzowska, S. Męczyńska, M. Kruszewski, Z. Zimek, G. Nałęcz-Jawecki and M. Trojanowicz

Abstract  

The radiolytic degradation of widely used fungicide, carbendazim, in synthetic aqueous solutions and industrial wastewater was investigated employing γ-irradiation. The effect of the absorbed dose, initial concentration and pH of irradiated solution on the effectiveness of carbendazim decomposition were investigated. Decomposition of carbendazim in 100 μM concentration in synthetic aqueous solutions required irradiation with 600 Gy dose. The aqueous solutions of carbendazim have been irradiated in different conditions, where particular active radical species from water radiolysis predominate. The obtained data have been compared with the kinetic modeling. The reversed-phase high-performance liquid chromatography was used for the determination of carbendazim and its radiolytic decomposition products in irradiated solutions. The changes of toxicity of irradiated solutions were examined with different test organisms and human leukemia cells.

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Abstract

Thermogravimetric analysis of azo-peroxyesters revealed two decomposition stages on TG curves. Molecular nitrogen is released in the first stage and carbon dioxide in the second. Fitting the thermogravimetric data by means of the three-parameter model and a classic one based on an Arrhenius-type kinetic equation showed that the former approach satisfactorily describes the process within the wide range of the extent of decomposition. It was found that two coefficients of the three-parameter equation are related to the temperature of maximum reaction rate. One of the coefficients of the three-parameter equation is also related to the activation energy. The compounds investigated can be grouped with respect to their kinetic characteristics, structure and stage of decomposition.

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Abstract

The results of the epoxidation of allyl alcohol with 30% hydrogen peroxide over the Ti-MWW catalyst have been presented. The studies were carried out under atmospheric pressure and in the presence of methanol as a solvent. The influence of the following technological parameters on the course of epoxidation was examined: temperature (20–60 °C), the molar ratio of AA/H2O2 (1:1–5:1), methanol concentration (5–90 wt%), catalyst content (0–5.0 wt%), reaction time (5–300 min) and intensity of stirring (0–500 rpm).

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Abstract

A novel mixed-ligand complexes with empirical formulae: Ln(4-bpy)1.5(CCl3COO)3·nH2O (where Ln(III) = Pr, Sm, Eu, Gd, Tb; n = 1 for Pr, Sm, Eu and n = 3 for Gd, Tb; 4-bpy = 4,4′-bipyridine) were prepared and characterized by chemical, elemental analysis and IR spectroscopy. Conductivity studies (in methanol, dimethylformamide and dimethylsulfoxide) were also described. All complexes are crystalline. The way of metal–ligand coordination was discussed. The thermal properties of complexes in the solid state were studied under non-isothermal conditions in air atmosphere. During heating the complexes decompose via intermediate products to the oxides: Pr6O11, Ln2O3 (for Sm, Eu, Gd) and Tb4O7. TG-MS system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis of Pr(III) and Sm(III) compounds in air.

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Journal of Thermal Analysis and Calorimetry
Authors: Juliusz Leszczynski, Krzysztof T. Wojciechowski and Andrzej Leslaw Malecki

Abstract

Thermal durability of CoSb3 in vacuum, helium and air was investigated over the temperature range of 20–850 °C. A scanning electron microscope (SEM) and X-ray powder diffraction technique were used to investigate the microstructure and to carry out the phase analysis of the degradation products. The analysis of a non-isothermal and isothermal decomposition and oxidation of the CoSb3 powders and polycrystalline samples were performed using simultaneous TG/DTA technique. More detailed studies were carried out on the oxidation in the temperature range 400–600 °C. It was established that the decomposition products are CoSb2 and a volatile antimony. In case of oxidation a complex three-layered scale is formed, consisting of CoSb2O4, CoSb2O6 and Sb2O4 layers. Both the decomposition and the oxidation kinetics are determined by a diffusion through the growing layers of products. The electrical resistivity and Seebeck coefficient measurements have been also performed on pure and oxidized samples, which showed a large influence of the oxidation on the electrical properties.

Open access
Journal of Thermal Analysis and Calorimetry
Authors: A. Sykuła-Zając, E. Łodyga-Chruścińska, B. Pałecz, R. E. Dinnebier, U. J. Griesser and V. Niederwanger

Abstract

An amide-type local anesthetic drug, bupivacaine hydrochloride (BupiHCl), in the form of racemate is listed in the European and American pharmacopoeias and continues to be used in medicine. Thermal and X-ray analysis of commercial BupiHCl monohydrate was performed by differential scanning calorimetry with thermogravimetry, hot stage microscopy, and X-ray diffraction. Endothermic dehydration occurs at the temperature range of 73–130 °C for DSC–TG 111 (Setaram) and at 83–150 °C for DSC 404 (Netzsch). Both curves at 2 and 10 °C min−1 clearly reflect phase transformation of anhydrous Form I into II before reaching the melting point. A well-defined exothermic phase transition of BupiHCl was detected at a lower heating rate. Temperature-resolved X-ray diffraction in conjunction with DSC led to determining a similarity between the obtained thermal events. Microscopic investigation also confirmed the above-mentioned transformations.

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Abstract

The influence of spent catalyst from catalytic cracking in fluidized bed (FCC) on the hydration of two kinds of calcium aluminate cements (of about 40 and 70% content of alumina) was studied. Cement pastes were prepared with constant ratio of water/binder = 0.5 and with content of 0, 5 and 25% mass of addition as replacement of cement. The samples were stored at room temperature. Thermal analysis (TG, DTG), infrared absorption (FTIR) and X-ray diffraction methods were applied to investigate changes in various periods of hydration (up to 150 days). The compressive strength of cement mortars was also examined. On the basis of presented results it was affirmed that in studied conditions spent FCC catalyst is a reactive addition in calcium aluminate cement (CAC) pastes, which probably can create a new phase type C–A–S–H. It may be an interesting alternative for limitation of the negative phenomenon of conversion of aluminate hydrates, although the degree of the influence of the mineral additive depends on the composition of CAC and of the quantity of the used waste.

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Abstract

A thermophysical study of the sulfur containing amino acids l-cysteine and l-cystine has been carried out by differential scanning calorimetry (DSC). Heat capacities of both compounds were measured in the temperature interval from T = 268 K to near their respective melting temperatures. DSC and variable temperature powder X-ray diffraction analysis (PXRD) gave evidence for a solid–solid phase transition close to the melting point only in the l-cysteine sample. DSC experiments show that this solid–solid transition is not reversible in the temperature interval T = 235–485 K and presents a behavior depending on heating temperature, time, and rate. This behavior is also supported by variable-temperature PXRD. The patterns for the commercial samples, at room temperature, are consistent with those simulated for the orthorhombic and hexagonal polymorphic forms from the single-crystal X-ray analysis.

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Journal of Thermal Analysis and Calorimetry
Authors: Lucjan Chmielarz, Małgorzata Rutkowska, Piotr Kuśtrowski, Marek Drozdek, Zofia Piwowarska, Barbara Dudek, Roman Dziembaj and Marek Michalik

Abstract

Hydrotalcite-like materials containing apart from magnesium and aluminum also copper, cobalt, nickel, and iron were prepared by a co-precipitation method. Thermal transformations of hydrotalcite-like materials were studied by thermal analysis methods as well as XRD, UV–vis–DRS, and XPS measurements of the samples calcined at various temperatures (600, 700, and 800 °C). Calcined hydrotalcites, especially those containing cobalt and copper, were found to be active and selective catalysts of N2O decomposition. It was shown that an increase in the calcination temperature significantly activated the Co-containing catalysts. Promotion of the samples with potassium resulted in activation of the hydrotalcite-based catalysts.

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Abstract

This article presents the effect of the method of NBR cross linking on the thermal properties, flammability and fire hazard of its nanocomposites containing modified montmorillonite (NanoBent or Nanofil), using test results obtained by means of a derivatograph, oxygen index and cone calorimetry. It has been found that the thermal stability and flammability of the nanocomposites investigated depend on both the rubber network structure and the type of montmorillonite. The nanoadditives used reduce the flammability of cross-linked nitrile rubber and considerably limit its fire hazard.

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Abstract  

PET with 68Ga from the TiO2- or SnO2- based 68Ge/68Ga generators is of increasing interest for PET imaging in nuclear medicine. In general, radionuclidic purity (68Ge vs. 68Ga activity) of the eluate of these generators varies between 0.01 and 0.001%. Liquid waste containing low amounts of 68Ge activity is produced by eluting the 68Ge/68Ga generators and residues from PET chemistry. Since clearance level of 68Ge activity in waste may not exceed 10 Bq/g, as stated by European Directive 96/29/EURATOM, our purpose was to reduce 68Ge activity in solution from >10 kBq/g to <10 Bq/g; which implies the solution can be discarded as regular waste. Most efficient method to reduce the 68Ge activity is by sorption of TiO2 or Fe2O3 and subsequent centrifugation. The required 10 Bq per mL level of 68Ge activity in waste was reached by Fe2O3 logarithmically, whereas with TiO2 asymptotically. The procedure with Fe2O3 eliminates ≥90% of the 68Ge activity per treatment. Eventually, to simplify the processing a recirculation system was used to investigate 68Ge activity sorption on TiO2, Fe2O3 or Zeolite. Zeolite was introduced for its high sorption at low pH, therefore 68Ge activity containing waste could directly be used without further interventions. 68Ge activity containing liquid waste at different HCl concentrations (0.05–1.0 M HCl), was recirculated at 1 mL/min. With Zeolite in the recirculation system, 68Ge activity showed highest sorption.

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Abstract

Enhancement of the dissolution rate of poorly soluble compounds through the formation of drug–drug eutectics was investigated using fenofibrate and acetylsalicylic acid. Solid–liquid equilibria in the system under study were investigated by differential scanning calorimetry (DSC). The phase diagram for the whole range of compositions was constructed. In addition, existence of a metastable polymorph of fenofibrate has been confirmed. The investigation has revealed that acetylsalicylic acid and fenofibrate form a simple eutectic mixture containing 0.958 mol fraction of fenofibrate at the eutectic point. Dissolution rate improvement of fenofibrate correlated with the phase diagram. The amount of fenofibrate released from the solid dispersions that contained fenofibrate as the eutectic mixture with acetylsalicylic acid was at least threefold higher compared to untreated fenofibrate.

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Abstract

The adsorption and dissociation of the H2 molecule on the PdAg, PdAu, PtAg, and PtAu heteronuclear dimers, both isolated and deposited on carbon, were investigated by means of density functional theory. It was found that the Pd and Pt ends of the isolated dimers adsorb H2 more exoenergetically than the Ag and Au ends. The dimers were also deposited on a carbon support and it turned out that they prefer to adsorb on the support by their Pd and Pt ends rather than by the Ag and Au ends. The adsorption of H2 on the carbon-supported dimers is somewhat less exoenergetic than that on the isolated dimers but, after the dissociation of H2, the binding of the H atoms to the dimers remains stronger in the presence of the support.

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Abstract

The catalytic effect of buffers (phosphate, acetate, borate, carbonate) on the degradation of doripenem in aqueous solutions was studied at 313 K in the pH range 0.82–11.56 (μ = 0.50 mol L−1) by an HPLC-UV method developed for kinetic studies of doripenem. It was observed that general acid–base catalysis occurred in all buffers and so catalytic rate constants were calculated. Specific acid–base catalysis of doripenem involved degradation of protonated molecules and zwitter ions of doripenem catalyzed by hydrogen ions, spontaneous degradation of zwitter ions under the influence of water and degradation of zwitter ions and monoanions catalyzed by hydroxide ions.

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Abstract  

Pyrroloquinoline quinone (PQQ), an essential nutrient, antioxidant, redox modulator and nerve growth factor found in a class of enzymes called quinoproteins, was labeled with 99mTc by using stannous fluoride (SnF2) method. Radiolabeling qualification, quality control and characterization of 99mTc-PQQ and its biodistribution studies in mice were performed and discussed. Effects of pH values, temperature, time and reducing agents concentration on the radiolabeling yield were investigated. The quality control procedure of 99mTc-PQQ was determined by thin layer chromatography (TLC), radio high-performance liquid chromatography (RHPLC) and paper electrophoresis methods. The average radiolabeling yield was 94 ± 1% under optimum conditions of 0.99 mg of PQQ, 30 μg of SnF2, 0.5 mg of ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) and 18.5 MBq of Na99mTcO4 at pH 6 and 25 °C with a response volume of 1 ± 0.1 mL. 99mTc-PQQ was stable and anionic. Lipid–water partition coefficient of 99mTc-PQQ was −1.49 ± 0.16. The pharmacokinetics parameters of 99mTc-PQQ were t 1/2α = 18.16 min, t 1/2β = 100.45 min, K 12 = 0.013 min−1, K 21 = 0.017 min−1, K e = 0.016 min−1, AUC (area under the curve) = 1040.78 ID% g−1 min and CL (plasma clearance) = 0.096 mL min−1. The dual-exponential equation was Y = 10.88e−0.038t + 5.21e−0.0069t. The biodistribution of 99mTc-PQQ was studied in ICR (Institute for Cancer Research 7701 Burhelme Are., Fox Chase, Philadelphia, PA 1911 USA) mice. In vitro autoradiographic studies clearly showed that the 99mTc-PQQ radioactivity accumulated predominantly in the hippocampus and cortex, which had a high density of N-methyl-d-aspartate Receptor (NMDAR). The enrichment can be blocked by NMDAR redox modulatory site antagonists-ebselen (EB) and 99mTc-PQQ is therefore a promising candidate for the molecular imaging of NMDAR. To date, however, there have been no studies characterizing 99mTc-PQQ.

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Abstract

The severe heating of soil during wildfires and prescribed burns may result in adverse effects on soil fertility due to organic matter loss. No rapid and reliable procedure exists to evaluate soil organic matter (SOM) losses due to heating. Enthalpy of SOM combustion correlates with organic matter content. Quartz is a ubiquitous mineral in soils and has a remarkably constant composition and reversible α–β phase transition at 575 °C. We suggest that SOM content in heated and unheated soils can be compared using the ratio of SOM combustion enthalpy on heating to the β–α quartz transition enthalpy measured on cooling of the same sample. This eliminates the need to dry and weigh the samples, making possible field applications of the proposed method. The feasibility of using the (ΔH comb SOM)/(ΔH β–α Qz) ratio was established with experiments on soil samples heated in the laboratory and the method was then used for evaluation of SOM loss on two pile burn sites at UC Berkeley's Blodgett Forest Research Station in Georgetown, California.

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Abstract

The influence of solution pH on the structure of polyvinyl alcohol adsorption layer on the alumina surface was investigated. The spectrophotometry, viscosimetry, thermogravimetry, potentiometric titration and microelectrophoresis were applied in experiments. These methods enable determination of the following parameters: adsorbed amount of PVA, stability of suspension without and with polymer, thickness of its adsorption layers, changes in thermal characteristics of Al2O3 surface with the adsorbed polymer, surface charge density and zeta potential of solid particles in the presence and absence of PVA, respectively. All measurements were carried out in the pH range 3–9. The obtained results indicate that pH has a great influence on the conformation of PVA chains adsorbed on the alumina surface. It is due to incomplete hydrolysis of acetate groups of polyvinyl alcohol macromolecules (degree of hydrolysis 97.5%), which dissociate with the increasing pH. Moreover, the polymer adsorption on the alumina surface causes changes in the course of thermogravimetric curves. The effect of weight loss for Al2O3–PVA systems is smaller than that of Al2O3 without polymer. It is due to elimination of water molecules from the solid surface by adsorbed polymer.

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