Heat release during the hydration of calcinated α-C<Subscript>2</Subscript>SH and its mixture with killalaite

In this work, the influence of the mineral composition of the synthesized calcium silicate hydrates on their hydraulic activity after thermal treatment was determined. Primary mixture, consisting of quartz sand and burnt limestone (CaO/SiO₂ = 2), was treated hydrothermally with NaOH additive at 200 °C. It was determined that α-C₂SH prevailed in the product after 4 h of the synthesis. The results of DSC and XRD analysis revealed that α-C₂SH was partially decomposed after 12 h of the synthesis and newly formed compounds were identified—killalaite, portlandite and C–S–H. The products of 4 and 12 h synthesis were treated thermally at temperatures between 450 and 1000 °C. It was determined that dellaite and x-C₂S formed already at 450 °C, β-C₂S at 600 °C and α′_L-C₂S at 800 °C when the 4 h synthesis product, in which α-C₂SH prevailed, was treated thermally. On the other hand, killalaite remained stable up to 600 °C, and the temperature values, at which mentioned calcium silicates formed, increased in case of a 12 h synthesis product. Heat flow values of the main hydration reaction and total heat release exceeded 3.1 mW g^?1 and 140 J g^?1 accordingly in case of the samples in which α-C₂SH prevailed. However, increase in the thermal treatment temperature resulted in a decrease in the mixtures hydraulic activity. It was proved that killalaite formation in the product of the 12 h hydrothermal synthesis vividly decreases its hydraulic activity after the thermal treatment in the temperature range of 450–1000 °C. No increment in the heat flow values that could be attributed to the main hydration reaction (acceleration period) was witnessed in all the curves of the heat flow analysis in this case.     

Extraction of pertechnetates from HNO<Subscript>3</Subscript> solutions into ionic liquids

The effect of the oxidation temperature of sintered UO₂ pellets on the powder properties of U₃O₈ was studied in the temperature range 250–900 °C in air. The U₃O₈ was obtained at 450 °C after 180 min and its particle size and surface area are respectively, 35 µm and 0.7 m²/g. The reduction of the U₃O₈ powder resulted in UO₂ after 30 min with a surface area of 0.8 m²/g. This value was improved more than 3.5 times by applying five alternating oxidation–reduction cycles.     

Preparation and characterization of CaCu3Ti4O12 powders by non-hydrolytic sol–gel method

CaCu₃Ti₄O₁₂ (CCTO) powders were prepared via a non-hydrolytic sol–gel (NHSG) method by using acetylacetone as chelating agent and ethylene glycol as solvent. The samples were characterized by TG–DSC, Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscope. The dielectric properties of ceramics were also measured. The pure perovskite-like CCTO powders were obtained by heat treatment at 800 °C for 2 h. The average particle sizes of CCTO powders calcined at 800 °C were approximately 350–450 nm. The samples sintered at 1,000 °C showed the mean grain size of 2.5–4 μm. Specially, the ceramics exhibited high dielectric constant (1.19 × 10⁵–1.40 × 10⁵) and low dielectric loss (0.051–0.1) in the temperature range of 30–110 °C. Moreover, with the NHSG method the period of synthesis process was greatly shortened.     

Pyrolysis of Eucalyptus wood in a fluidized-bed reactor

Eucalyptus wood can be utilized as a biomass feedstock for conversion to bio-oil using a pyrolysis process. Eucalyptus wood samples were initially pyrolyzed on a laboratory-scale pyrolysis system at different values in the ranges of 300–800 °C and 0.050–0.300 L min^?1 to determine the effects of operation temperature and N₂ flow rate, respectively, on the yields of products. Then, the bio-oil in the highest yield (wB = 44.37 %), which was obtained at pyrolysis final temperature (450 °C), heating rate (35 °C min^?1), particle size (850 μm), and sweeping flow rate (0.200 L min^?1), was characterized by Fourier transform infra-red spectroscopy, gas chromatography/mass spectrometry and column chromatography. Subsequently, it was shown that the operating temperature and N₂ gas flow rate parameters affected the product yields. Also, some important physico-chemical properties of the pyrolytic oil obtained in high yield were determined as a calorific value of 37.85 MJ kg^?1, an empirical formula of CH_1.651O_0.105N_0.042S_0.001, a rich chemical content containing many different chemical groups, a density of 981.48 kg m^?3, and a viscosity of 61.24 mm² s^?1. Based on the determined properties of the pyrolytic oil, it was concluded that the use of pyrolytic oil derived from Eucalyptus wood may be useful for the production of alternative liquid fuels and fine chemicals after the necessary improvements.     

Determination of Glimepiride in Human Plasma by LC–MS–MS

Liquid chromatography combined with electrospray ionization tandem mass spectrometry positive ion mode is used for the determination of glimepiride in human plasma. Gliclazide was used as the internal standard. The chromatographic separation was performed on a ACE 5 C18, 50 × 4 mm, 5 μm column at 30 °C with mobil phase consisting of 200 mL water, 450 mL acetonitrile, 350 mL methanol, 0.6 mL glacial acetic acid with a 0.5 mL min⁻¹ flow rate. The work-up procedure involved a liquid–liquid extraction of the compounds. Mass spectrometric data were acquired in single ion monitoring of the ions 324.11 > 127.25 and 491.16 > 352.08 for glimepiride and gliclazide, respectively. The method was validated in the concentration range of 5–1,000 ng mL⁻¹. Retention times of glimepiride and gliclazide were 1.65 and 1.36 min, respectively. The run time was 2.5 min. The method was found suitable to analyse human plasma samples for application in pharmacokinetic, pharmacodynamic, bioavailability/bioequivalance studies.

     

Bovine Serum Albumin Nanospheres Synchronously Encapsulating “Gold Selenium/Gold” Nanoparticles and Photosensitizer for High-Efficiency Cancer Phototherapy

Gold nanostructures have generated significant attention in biomedical areas because of their major role in cancer photothermal therapeutics. In order to conveniently combine gold nanostructures and drugs into one nanocomposite, Au₂Se/Au core–shell nanostructures with strong near-infrared-absorbing properties were synthesized using a simple method and embedded inside bovine serum albumin (BSA) nanospheres by using a spray dryer equipped with an ultrasonic atomizer followed by thermal denaturation. The nanospheres with narrow size distribution mainly ranging from 450 to 600 nm were obtained. The Au₂Se/Au-loaded BSA nanospheres (1 mg) adsorbed at least 0.01 mg of water-insoluble zinc phthalocyanine (ZnPc) photosensitizer. After irradiation with a 655-nm laser (20 min), the temperature of the Au₂Se/Au-loaded BSA nanospheres [200 μL, 2 mg/mL, BSA/Au₂Se/Au 10:1 (w/w)] increased by over 20 °C from the initial temperature of 24.82?±?0.15 °C, and the release of ZnPc was improved compared with a corresponding sample without irradiation. After being incubated with cancer cells (human esophageal carcinoma Eca-109), the nanospheres exhibited photothermal and photodynamic therapy with a synergistic effect upon laser irradiation. This work provides novel Au₂Se/Au-loaded polymer nanospheres prepared by a high-efficiency strategy for incorporating drugs for improving the efficiency in killing cancer cells.     

Preparation of 99Mo/99mTc generator based on alumina 99Mo-molybdate (VI) gel

In this work alumina ⁹⁹Mo-molybdate (VI) gel is evaluated as a column matrix for use in the preparation of small chromatographic column type ^99mTc generator. Alumina molybdate (VI) gel is prepared by dissolving inactive MoO₃ with aluminum foil in 5 M NaOH solution containing ⁹⁹Mo radiotracer. After complete dissolution, 0.5 H₂O₂ was added to the reaction mixture solution and acidified to pH 5.5 with concentrated HNO₃. The formed AlMo precipitate was washed with NaNO₃ solution, dried at 50 °C for 24 h and then packed in the form of a chromatographic column for elution of the generated ^99mTc radionuclide with physiological saline solution (0.9 % NaCl). Greater than 86 % of the generated ^99mTc activity is immediately and reproducibly eluted with passing 10 mL of the saline solution through 2.0 g of alumina ⁹⁹Mo-molybdate column bed at a flow rate of about 1.0 mL/min. The high radiochemical ≥98.6 % TcO₄ ^?, radionuclidic ≥99.90 % ^99mTc and chemical purities of the eluates satisfy the specifications for use in nuclear medicine.     

Solid electrolytes with cesium cation conductivity in the Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript>-Cs<Subscript>2</Subscript>O system

Solid solutions based on cesium monogallate CsGaO₂ are synthesized in the Ga₂O₃-TiO₂-Cs₂O system. Their crystalline structure and also temperature and concentration conductivity dependences are studied. The cesium cation character of conductivity is confirmed. The most conducting samples contain an excess of cesium oxide and have the structure of high-temperature γ-modification of KAlO₂. Their specific conductivity is (5.0–6.7) × 10^?3 S cm^?1 at 400 °C, (2.5–5.0) × 10^?2 S cm^?1 at 700°C at the activation energy of 33–35 kJ/mol^?1.     

Optical, mechanical, and dielectric properties of Bi1/2Na1/2TiO3 thin film synthesized by sol–gel method

The Bi_1/2Na_1/2TiO₃ (BNT) thin film has been researched as an excellent candidate of lead-free ferroelectric materials. We synthesized BNT thin film on Si wafers or quartz glass by sol–gel spin coating method. The homogeneous and crack-free BNT thin film was synthesized by cost effective solution sol gel coating method. The main crystal phase of the film was identified as Bi_1/2Na_1/2TiO₃. The BNT thin film which was coated 3 times and heat-treated at 700 °C had about 70% of transmittance in the ultra-violet visible (UV–VIS) light wavelength region. The calculated band gap energies from the UV transmittance spectra were 3.0 and 3.5 eV for indirect and direct transition, respectively and the refractive index of BNT thin film was 2.16 at 898 nm of wavelength. The hardness and elastic modulus of the film were about 9 and 136 GPa at 10 mN load, where the penetration depth was about 220 nm. BNT thin film showed the diffuse type of dielectric properties due to its Na⁺ and Bi³⁺ ions in A′_1/2A″_1/2BO₃-type perovskite structure and the dielectric constant was about 10 until 300 °C and showed maximum value at 550 °C, 450 at 1 kHz.     

Thermoelectric properties of n-type Bi2Te3 alloys produced by a combined process of magnetic pulsed compaction (MPC) and spark plasma sintering (SPS)

In this study, n-type 95 %Bi₂Te₃-5 %Bi₂Se₃ thermoelectric materials have been produced by a combined process of gas atomization with subsequent magnetic pulsed compaction and spark plasma sintering, and then we investigated the behavior of transport properties with sintering temperature. The microstructural observation was performed by optical microscopy and scanning electron microscopy. The crystal structures were analyzed by X-ray diffractometer. The mechanical properties were calculated by measuring the density and micro-Vickers hardness of the samples. It was found that with increasing sintering temperature the gaps between powder particles decreases and the grain sizes were coarsened. The mechanical properties shows higher values along the parallel direction compared to the perpendicular direction to the pressing. The transport properties of the thermoelectric material were investigated with variation of the sintering temperatures. The maximum power factor 1.7 × 10^?3 Wm^?1 K^?2 was measured at the sintering temperature of 450 °C.     

Characterization and Wear Behavior of Plasma Nitrided Nickel Based Dental Alloy

In the present work, the plasma nitriding behavior of a nickel based dental alloy was investigated. Plasma nitriding experiments carried out under constant gas mixture (15% H₂?C85% N₂) for different process parameters including time (4, 6, 10, and 20 h) and temperature (400, 450, 500, and 550 °C). Depending on nitriding parameters, it was found that triple or double layers formed on the surface of the samples. Increasing of treatment time and temperature has resulted in a double layer. ??_N1 layer was in formed all nitrided samples. However, ??_N2 layer is formed only at low temperatures and in short times. Layer growth of nickel based alloys increases until a critical time or a critical temperature reached. Above these critical values, it is observed that the layer thickness decreases. It was also found that plasma nitriding not only increases the surface hardness but also improves the wear resistance of nickel based dental alloy. The maximum wear resistance was observed at 400 °C for 10 h due to the high hardness and thickness of the nitride layers.     

Slow molecular mobility in the amorphous thermoplastic polysulfone

The thermally stimulated depolarization current (TSDC) technique has been used to study the slow molecular mobility of polysulfone in the glassy state and in the glass transformation region, i.e., in the temperature ranging from ?155 to 183 °C. Since the polysulfone is a rigid polymer without polar side-groups, a broad and low-intensity secondary relaxation was detected in the temperature region from ?120 °C up to the glass transition; the activation energy of the motional modes of this secondary relaxation is in the range between 35 and 100 kJ mol^?1. The glass transition temperature of polysulfone provided by the TSDC technique is T _M = T _g = 176 °C (at 4 °C min^?1). The relaxation time at this temperature is τ(T _g) = 33 s and the fragility index was found to be m = 91. Our results are compared with literature values obtained by dynamic mechanical analysis and by dielectric relaxation spectroscopy. The amorphous polysulfone was also characterized by DSC; a glass transition signal with an onset at T _on = 185.5 ± 0.3 °C (heating rate 10 °C min^?1) was detected, with ΔC _p = 0.21 ± 0.01 J g^?1 °C^?1.     

Fabrication of self-organized TiO2 nanotube arrays for photocatalytic reduction of CO2

The photocatalytic conversion of CO₂ and H₂O to alcohols was achieved using self-organized TiO₂ nanotube arrays (TNAs), which were prepared by electrochemical anodization of Ti foils in 1 M (NH₄)₂SO₄ electrolyte containing 0.5 wt% NH₄F. Experimental results revealed that the morphology and structure of self-organized TNAs could be strongly influenced by the applied voltage and anodization temperature, and the optimized TNAs were prepared by electrochemical anodization of Ti foils under optimal conditions (i.e., at 20 V for 2 h at 30 °C). The as-prepared TNAs were amorphous and could be transformed to anatase phase during the thermal treatment at 450 °C in air for 3 h. By using the annealed TNAs as a photocatalyst, the photocatalytic reduction of CO₂ to alcohol, predominately methanol and ethanol, was demonstrated under Xenon lamp illumination. Based on the photocatalytic measurements, the production rates of methanol and ethanol were calculated to be ～10 and ～9 nmol cm^?2 h^?1, respectively. In addition, the formation mechanism of methanol and ethanol was also tentatively proposed.     

57Fe-Mössbauer study of electrically conductive alkaline iron vanadate glasses

A relationship between local structure, thermal stability and electrical conductivity (σ) of xR₂O·10Fe₂O₃·(90 ? x)V₂O₅ glasses (abbreviated as xRFV glasses, where R = Li, Na, K; x = 20 and 40 in mol %) was investigated by ⁵⁷Fe-Mössbauer spectroscopy, X-ray diffractometry, differential thermal analysis (DTA) and DC two- and four-probe method. From DTA study, thermal stability of 20RFV glasses is lower than that of 40RFV glasses by evaluating Hruby parameter (K _gl). Constant activation energy for crystallization (E _a) of 2.5 eV obtained from both 20RFV and 40RFV glasses indicate that the crystallization proceeds with the cleavage of Fe–O bond having the energy of 2.6 eV. Isochronally annealed 20RFV glass at 400–450 °C resulted in the increase in electrical conductivity (σ) from the order of 10^?3 to 10^?1 S cm^?1, whereas slight decrease in σ was observed for 20RFV glass annealed above 460 °C. A paramagnetic doublet with an identical isomer shift (δ) of 0.39 mm s^?1 was observed in the ⁵⁷Fe-Mössbauer spectra of 20RFV glass after isothermal annealing conducted at 400–450 °C for 100 min, which caused a decrease of quadruple splitting (Δ) from 0.67 to 0.52 mm s^?1 for 20LiFV glass and from 0.66 to 0.53 mm s^?1 for 20NaFV glass. On the other hand, three paramagnetic doublets with δ and Δ of 0.40 and 0.25, 0.38 and 0.60, and 0.31 and 1.11 mm s^?1 respectively were observed for 20RFV glass annealed at 460–550 °C, reflecting precipitation of semiconducting FeVO₄ phase having σ of 6.0 × 10^?7 S cm^?1. It can be concluded that isochronal annealing of 20RFV glass below 450 °C resulted in increase in σ due to the structural relaxation, while annealing above 500 °C resulted in the decrease of σ due to the precipitation of FeVO₄ phase.     

Rapid separation of nickel for 59Ni and 63Ni activity measurement in radioactive waste samples

A separation procedure of Ni has been described for the quantification of ⁵⁹Ni and ⁶³Ni in radioactive wastes discharged from nuclear power plants and various research activities related to the nuclear fuel cycle. For a rapid separation of the Ni-nuclides in sixteen sample solutions in 0.2 M NH₄-oxalate, a separation system composed of a peristaltic pump with sixteen channels and the same number of Ni–Resin columns was constructed. After sorption of the Ni-nuclides by sequentially passing 100 mL of the sample solution in 0.2 M NH₄-oxalate, 130 mL of 0.1 M NH₄-oxalate solution and 10 mL of deionized water as a wash into the columns, these were purely recovered by passing 10 mL of 9 M HCl into the Ni–Resin columns stacked in series on the anion exchange resin columns. The separation of the Ni-nuclides in sixteen sample solutions can be achieved within 7 h. The chemical yield of the proposed procedure is 92.3 ± 0.8 % (n = 5) and the gravimetric recovery in the preparation stage of the Ni-nuclide sources is also acceptable, 88.5 ± 1.3 % (n = 5).     

Influence of annealing temperature on the electrochemical and surface properties of the 5-V spinel cathode material LiCr0.2Ni0.4Mn1.4O4 synthesized by a sol–gel technique

LiCr_0.2Ni_0.4Mn_1.4O₄ was synthesized by a sol–gel technique in which tartaric acid was used as oxide precursor. The synthesized powder was annealed at five different temperatures from 600 to 1,000 °C and tested as a 5-V cathode material in Li-ion batteries. The study shows that annealing at higher temperatures resulted in improved electrochemical performance, increased particle size, and a differentiated surface composition. Spinel powders synthesized at 900 °C had initial discharge capacities close to 130 mAh g^?1 at C and C/2 discharge rates. Powders synthesized at 1,000 °C showed capacity retention values higher than 85 % at C/2, C, and 2C rates at 25 °C after 50 cycles. Annealing at 600–800 °C resulted in formation of spinel particles smaller than 200 nm, while almost micron-sized particles were obtained at 900–1,000 °C. Chromium deficiency was detected at the surface of the active materials annealed at low temperatures. The XPS results indicate presence of Cr⁶⁺ impurity when the annealing temperature was not high enough. The study revealed that increased annealing temperature is beneficial for both improved electrochemical performance of LiCr_0.2Ni_0.4Mn_1.4O₄ and for avoiding formation of Cr⁶⁺ impurity on its surface.     

Thermal stability of nanocrystalline ε-Fe2O3

Thermal behavior of highly crystalline ε-Fe₂O₃ nanoparticles of different apparent crystallite sizes was characterized using thermogravimetry, differential thermal analysis, and analysis of evolved gas by mass spectrometry. Phase composition of the samples was monitored ex situ by X-ray powder diffraction. The results show that the thermal stability of this metastable iron oxide polymorph decreases with increasing particle size. For the particle diameter of 19(2) nm, the transformation temperature was equal to 794(5) °C, while for 28(2) nm only 755(10) °C. Surface of the nanoparticles contained adsorbed water and carbon dioxide. Elimination of these species proceeds in two steps. Water is removed at temperatures below 200 °C and CO₂ in the temperature range between 200 and 450 °C.     

Purification and biochemical properties of SDS-stable low molecular weight alkaline serine protease from Citrullus colocynthis

A low molecular weight serine protease from seeds of Citrullus colocynthis was purified to electrophoretic homogeneity with high level of catalytic efficiency (22,945 M^?1 S^?1). The enzyme was a monomer with molecular mass of 25 kDa estimated by SDS–PAGE. The enzyme was highly active over a pH range of 6.5–9.0 and temperature range of 20–80 °C, with maximum activity at pH 7.5 and at 50 °C. The K_m and K_cat were 73 μg/mL and 67/s, respectively. The enzyme was strongly inhibited by PMSF, moderately by soybean trypsin inhibitor, indicating that the enzyme was a serine protease. The enzyme retained 86 and 73% of its activity in the presence of urea and DTT, respectively, and its activity was slightly enhanced in the presence of anionic detergent (SDS). Thus, the enzyme is a novel SDS-stable protease with high catalytic efficiency over wide ranges of pH and temperature which is commercially promising for various industrial applications.     

Low temperature synthesis of Li5La3Nb2O12 with cubic garnet-type structure by sol–gel process

A cubic Li₅La₃Nb₂O₁₂ phase with a garnet framework was synthesized by the sol–gel process, in which lithium hydroxide, niobium oxide and acetic lanthanum were used as starting materials, while water was used as solvent. Pure garnet-like Li₅La₃Nb₂O₁₂ powders were obtained after heating the gel precursor at 700 °C for 6 h with 10 % excess lithium salt. The calcination temperature is nearly 250 °C lower than that by the solid state reaction. The phase transforms from cubic to tetragonal symmetry with loss of lithium at 717 °C, but the garnet framework remains stable to above 900 °C. A pellet annealed at 900 °C for 6 h had a room-temperature Li⁺-ion conductivity σ_Li (22 °C) = 1.0 × 10^?5 S cm^?1, a little higher than that attained by solid-state synthesis. The Li₅La₃Nb₂O₁₂ compound was chemically stable against two commonly used cathode materials, LiMn₂O₄ and LiCoO₂, up to 900 °C and against metallic lithium.     

Effects of humidity and temperature on the electrochemical activities of H2/O2 PEMFCs using hybrid membrane electrolytes

Electrochemical characteristics of single cell performances at various humidity conditions and constant temperatures of 40?100 °C using membrane electrode assemblies (MEAs) were studied. The MEAs consist of alternative proton-conducting hybrid membrane electrolyte and noble Pt/C catalyst for the H₂/O₂ proton exchange membrane fuel cells (PEMFCs). The function of humidity on the cell performances was investigated at larger current density values of 501 mA cm^?2 and constant cell temperatures of 80 and 90 °C and the relative humidity of 100 %. The power density value of 400 mW cm^?2 was obtained when the same MEA at similar operating conditions was used. The effects of temperature on the single cell performances were investigated at various temperature ranges of 40–100 °C and constant relative humidity of 50, 70, and 100 %. The maximum current density and power density values of about 600 mA cm^?2 and 160 mW cm^?2, respectively, were obtained at 90 °C with 100 % RH. The results were compared with the reported results of Nafion membrane and similar hybrid membranes operating at low temperatures for H₂/O₂ fuel cells. Finally, the results provided an alternative proton-conducting electrolyte as promising candidate for low/intermediate temperature operating H₂/O₂ fuel cells.