Thermal analysis of heat-treated silver fir wood and larval frass

Glasses having composition 5Li₂O–5ZnO– xBi₂O₃ –(90 ? x) P₂O₅ (x = 5, 10, 15, 20 and 25 mol%) were prepared by the normal melt quenching technique. Nanocomposite glass containing bismuth phosphate BiPO₄ nanocrystals was obtained, which can be attributed to homogeneous nucleation process. The formation of BiPO₄ nanocrystals was confirmed and characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), differential scanning calorimetry, optical absorption (UV–Vis) and micro-hardness studies. The morphological analysis by XRD and TEM microscopy showed the formation of hexagonal BiPO₄ nanocrystals, and its estimated nanocrystalline sizes were found to be varying from 5.35 to 11.53 nm depending on the Bi₂O₃ concentrations. The density (ρ) and molar volume (V _m) were also determined and found to be in compositional dependence. Glass transition temperature (T _g) and glass crystallization temperature (T _c) were obtained and found to be increased (from 240.0 to 337.2 °C) with increasing Bi₂O₃ up to 20 mol% and then decreased (from 337.2 to 331.8 °C) due to the structural changes in the glass network. Effect of BiPO₄ content on the optical properties had been investigated. From the UV–Vis spectra, it was observed that the fundamental absorption edge shifts toward lower wavelengths, i.e., blueshifts with increasing Bi₂O₃ mol% up to 20 mol%, and then shifts toward higher wavelengths, i.e., redshifts beyond 20 mol%. It was also observed that the obtained E _opt (for indirect and direct transitions) increases with gradual increase in Bi₂O₃ content up to 20 mol% and then decreases beyond 20 mol%. This may be due to the introduction of Bi cations into the glass network as a network former up to 20 mol% causing a decrease in ΔE values, beyond 20 mol%, the introduction of Bi ions into the glass network interstitially leads to increase the values of ΔE. The optical properties of the present nanocrystallized glasses showed a quantum size dependence, in which the optical band gap energy (E _opt) was changed as a function of BiPO₄ nanocrystalline sizes.     

Resistance of composite materials based on BaCeO3 against the corrosive effects of carbon dioxide and water vapour at intermediate fuel cell operating temperatures

The objective of this work is to analyse the chemical stability of BaCe_0.85Y_0.15O_3?δ –Ce_0.85Y_0.15O_2?δ (BCY15–YDC15) composite materials at 600 °C and to compare the aforementioned chemical stability with that of pure BCY15. The composite powders were obtained by mixing together powders of BCY15 and YDC15 in the following volume fractions: 90 % BCY15 + 10 % YDC15, 70 % BCY15 + 30 % YDC15, 30 % BCY15 + 70 % YDC15, 20 % BCY15 + 80 % YDC15 and 10 % BCY15 + 90 % YDC15. After that both powders and sintered samples of the BCY15 and the BCY15–YDC15 composites were saturated in two different atmospheres at 600 °C: CO₂/H₂O (3.1 mol% H₂O) and N₂/H₂O (46.8 mol% H₂O). The effects of the previously mentioned atmospheres on the physicochemical properties of the samples were investigated via differential thermal analysis (DTA) combined with thermogravimetric analysis (TG). Furthermore, mass spectrometry was used to analyse the chemical composition of the gases released from the samples during the DTA–TG heating process. The surface and cross-section morphology of the samples were examined by scanning electron microscopy. Moreover, the phase composition of each sample was studied via X-ray Diffraction. From the combined analysis, it can be concluded that the addition of YDC15 in the composite samples leads to an increase in resistance against the corrosive effects of CO₂. Furthermore, it was determined that all samples maintain stability in the presence of H₂O at 600 °C.     

Proton-conducting membranes: poly (N-vinyl pyrrolidone) complexes with various ammonium salts

The present study focuses on the proton-conducting polymer electrolytes; poly (N-vinyl pyrrolidone)–ammonium thiocyanate and poly (N-vinyl pyrrolidone)–ammonium acetate prepared by solution casting technique. The XRD analysis indicates the amorphous nature of the polymer electrolytes. The Raman spectra of the C=O vibration of pure polymer PVP at 1,663 cm^?1 has been appeared as doublet in the polymer electrolytes. The introduction of this new peak in the salt-doped polymer electrolytes may be due to interaction of the cation with the polymer. The room temperature ionic conductivity σ _303κ has been found to be high, 1.7?×?10^?4 S cm^?1 for 80 mol% PVP–20 mol% NH₄SCN and 1.5?×?10^?6 S cm^?1 for 75 mol% PVP–25 mol% CH₃COONH₄. The polymer electrolytes have been tested for their application in Zn–air battery.     

Thermal analysis on C<Subscript>6</Subscript>H<Subscript>10</Subscript>Ge<Subscript>2</Subscript>O<Subscript>7</Subscript>-doped MgB<Subscript>2</Subscript>

Additives to MgB₂ can improve the superconducting functional characteristics, such as critical current density (J _c) and irreversibility field (H _irr). Recently, we have shown that repagermanium (C₆H₁₀Ge₂O₇) is an effective additive, enhancing both J _c and H _irr. To look into details of the processes taking place during the reactive sintering, a thermal analysis study (0.167 K s^?1, in Ar) is reported. We used differential scanning calorimetry between 298 and 863 K and simultaneous thermogravimetric—differential thermal analysis between 298 and 1233 K. Samples were mixtures of powders with composition 97 mol% MgB₂ and 3 mol% C₆H₁₀Ge₂O₇. Up to 863 K, repagermanium decomposes by multiple steps and forms amorphous phases. A reaction with MgB₂ is not observed. Above this temperature, partial decomposition of MgB₂ occurs. Crystalline Ge and MgO are detected before formation of Mg₂Ge and MgB₄, when temperature approaches the melting point of Ge (1211 K). Carbon substitution for boron in the crystal lattice of MgB₂ is observed for samples heated above 863 K. The amount of substitutional C does not significantly change with temperature.     

Application of heating microscopy to the study of thermal behaviour of ZnO–P2O5–WO3 glasses

The effect of WO₃ on thermal behaviour and thermal stability of ZnO–P₂O₅–WO₃ glasses prepared in compositional series (100 ? x)[0.5ZnO–0.5P₂O₅] ? xWO₃ (x = 0–60) was investigated by heating microscopy and the results were correlated with the results determined by conventional thermodilatometry and differential thermal analysis. Thermoanalytical studies showed that the glass transformation temperature and dilatation softening temperature increase with increasing WO₃ content while thermal expansion coefficient decreases. The highest stability towards crystallization possess glasses containing 20–30 mol% WO₃. Major compounds formed by the crystallization of the glasses were Zn(PO₃)₂, WO₃ and W₁₈P₂O₅₉. The values of sphere temperature, hemisphere temperature and flow temperature obtained using heating microscopy were strongly influenced by the degree of crystallization process at the sintering.     

Characterization of electrically conductive vanadate glass containing tungsten oxide

New conductive glass with a composition of 20BaO·10Fe₂O₃·xWO₃·(70 ? x)V₂O₅ (x = 10–50) was investigated by means of Mössbauer spectroscopy. A marked decrease in quadrupole splitting (Δ) was observed after the isothermal annealing at 500 °C for 1,000 min, due to the structural relaxation of 3D-network composed of FeO₄, VO₄, and VO₅ units. After the isothermal annealing, a marked increase in the electrical conductivity (σ) was observed from 1.7 × 10^?5 to 1.0 × 10^?1 S cm^?1 when “x” was 10, whereas comparable σ values of 1.1 × 10^?4 and 2.0 × 10^?4 S cm^?1 were observed when “x” was 40. These results evidently show that structural relaxation of 3D-network structure involved with a marked increase in σ is intrinsic of “vanadate glass”. XRD pattern indicated several weak peaks due to needle-like BaFe₂O₄ and α-Fe₂O₃ when the glass sample with “x” of 20 was annealed at 500 °C for 1,000 min. SEM study proved the formation of needle-like BaFe₂O₄ just on the surface of the sample, whereas hexagonal BaFe₁₂O₁₉ were observed in the annealed sample with “x” of 40. Chemical durability of WO₃-containing vanadate glass was investigated by immersing each glass sample into 20 %-HCl solution for 72 h.     

Thermal properties and structure of (As2S3)100−x(Sb4S4)x glassy system

Thermal properties and structure of bulk glasses of (As₂S₃)_1?x(Sb₄S₄)_x system (x varies from 0 to 60 mol%) were studied by differential scanning calorimetry and Raman spectroscopy. It was found that with increasing Sb content the glasses can be sorted out to the three groups. The structure of glasses with x ≤ 10 is build-up mainly from AsS_3/2 pyramidal units and the well-known crystallization resistance of As₂S₃ can explain the reluctance of these undercooled liquids against crystallization. In glasses with a higher content of antimony, i.e., 10 < x ≤ 30 mol%, the vibration characteristics of As₄S₄ clusters appear. Undercooled melts of these glasses crystallize forming both β-As₄S₄ and high-temperature phases of Sb₂S₃. Structure of glasses with the highest antimony content (x > 30 mol%) is based on SbS_3/2 structural units significantly lowering stability of their undercooled melts from which only Sb₂S₃ crystallizes.     

Synthesis,characterization, and thermochemical property of a novel mixed alkali metal borate: NaCs[B10O14(OH)4]

A novel mixed alkali metal hydrated borate NaCs[B₁₀O₁₄(OH)₄] was synthesized under hydrothermal conditions. Its structure was determined by single-crystal X-ray diffraction and further characterized by FT-IR spectroscopy, TG-DTA, powder X-ray diffraction, and chemical analysis. NaCs[B₁₀O₁₄(OH)₄] crystallizes in monoclinic space group P2/c with a = 7.6588(3) Å, b = 9.0074(3) Å, c = 11.8708(6) Å, and β = 115.682(3)°. The crystal structure of NaCs[B₁₀O₁₄(OH)₄] consists of Na–O, Cs–O polyhedral, and [B₁₀O₁₄(OH)₄]^2? polyborate anions. [B₁₀O₁₄(OH)₄]^2? units are connected together through common oxygen atoms forming a 1D helical chain-like structure, which are further connected by O–H···O hydrogen bonds forming a 3D supramolecular structure. Through a designed thermochemical cycle, the standard molar enthalpy of formation of this borate was determined to be ?7888.6 ± 8.1 kJ mol^?1 by using a heat conduction microcalorimeter.     

Thermal and spectroscopic characterization of nanostructured zirconia–scandia–dysprosia

Zirconia containing 10 mol% scandia and x mol% dysprosia (0 ≤ x ≤ 1.5) gels was synthesized by simultaneous precipitation at room temperature. The aim of this work is to verify the effect of dysprosium on the cubic phase stabilization of the zirconia–scandia solid electrolyte. The gel was characterized by thermogravimetry, differential scanning calorimetry, and differential thermal analyses. The thermally treated powders were analyzed by Fourier transform infrared spectroscopy, thermal analyses, and X-ray diffraction techniques. For comparison purpose, a commercial zirconia–10 mol% scandia powder was subjected to some characterization techniques. The infrared spectrum shows characteristic absorption bands due to residual material from the synthesis on the surface of the powder particles. Nanostructured powders were obtained after thermal treatments at 500 °C for 2 h. Infrared spectroscopy and X-ray diffraction results evidence the stabilization of the cubic phase in zirconia–scandia containing dysprosium. The thermal stability of the cubic phase during thermal cycling was ascertained by thermal analysis.     

A Convenient Method for Protection and Deprotection of Alcohols and Phenols as Alkylsilyl Ethers Catalyzed by Iodine Under Microwave Irradiation

Abstract

Irradiation of alcohols or phenols with tert-butyldimethylsilyl chloride (TBDMSCl) or trimethylsilyl chloride (TMSCl) in presence of catalytic amount (20 mol%) of iodine in a microwave oven for 2 min gives the corresponding silyl ethers in excellent yield. Iodine in methanol deprotects the silyl ether into its parent alcohol or phenol under similar reaction conditions.     

Synthesis and properties of BaCe1−xYxO3−δ–BaWO4 composite protonic conductors

Barium cerate doped by trivalent rare earth metal ions is a potentially huge component of materials for electrochemical industry due to its high protonic conductivity. However, the poor chemical stability especially in the presence of CO₂, SO₂ or H₂O, resulting in decreasing the mechanical durability of obtained materials, limits their possible applications. The new approach towards stable ceramic protonic conductors with high electrical conductivity is presented. Thermal stability of yttrium doped (10 mol%) of BaCeO₃ was enhanced by forming the composite material BaCe_0.9Y_0.1O₃–BaWO₄ (10 mol% of BaWO₄). The synthesis was performed by solid-state reaction method. The detailed study of thermal decomposition of starting powders mixture was performed using thermogravimetry and differential thermal analysis (TG/DTA) techniques combined with Evolved Gas Analysis (EGA—mass spectrometry). Structure, phase composition and microstructure together with thermal stability of sintered materials were determined. The exposition tests were performed to characterise the stability of composites in carbon dioxide and water vapour-rich atmospheres. The samples were exposed to atmosphere containing CO₂/H₂O (7 % of CO₂ in air, 100 % RH) at temperature of 25 °C for 300 h. Thermal analysis supplied with mass spectrometry was applied to analyse the materials after the test. The results of this experiment showed better chemical resistance of composite material—BaCe_0.9Y_0.1O₃ with 10 mol% of BaWO₄ compared to single phase material.     

Synthesis and study of mixed oxide inorganic pigment from Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZnO–CeO<Subscript>2</Subscript> system

Novel environment-friendly yellow mixed oxide inorganic pigment from Bi₂O₃–ZnO–CeO₂ system with the composition 23 mol% Bi₂O₃, 15 mol% ZnO and 62 mol% CeO₂ was successfully synthesized by a conventional solid-state reaction method. Comprehensive analyses were carried out to characterize the develop pigment powder including simultaneous TG–DTA thermal analysis, colour properties and particle size distribution. The results demonstrated that the optimum calcination for pigment synthesis was located at a range 800–950 °C. The colour of the studied mixed oxide pigment is connected with the calcination condition. The substitution of Zn²⁺ changes the colour from orange to yellow. The colour of the obtained samples was dependent on the calcination condition and the particle size distribution. The most saturated yellow hue was obtained at the calcination temperature of 950 °C for 2 h in a furnace of pure air and after its application into organic binder in mass tone. The value C of this sample was approx. 65. The mixed oxide pigments were also evaluated from the standpoint of their particle size distribution. Bi₂Ce₂O₇ is considered to be a non-toxic compound, and the other component (Zn²⁺ ions) is also the safe element. Therefore, the present mixed oxide could be an attractive candidate as a novel environment-friendly inorganic yellow pigment.     

Synthesis, structural and photocatalytic studies of Mn-doped CdS nanoparticles

Mn-doped CdS nanoparticles (Cd_1?x Mn _x S; where x = 0.00–0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope, transmission electron microscope (TEM), and UV–Vis spectrometer. The XRD and TEM measurements show that the size of crystallites is in the range of 10–40 nm. Optical measurements indicated a red shift in the absorption band edge upon Mn doping. The direct allowed band gaps of undoped and Mn-doped CdS nanoparticles measured by UV–Vis spectrometer were 2.3 and 2.4 eV at 400 °C, respectively. Photocatalytic activities of CdS and Mn-doped CdS were evaluated by irradiating the solution to ultraviolet light and taking methyl orange (MO) as organic dye. It was found that 5 mol% Mn-doped CdS bleaches MO much faster than undoped CdS upon its exposure to the ultraviolet light. The experiment demonstrated that the photo-degradation efficiency of 5 mol% Mn-doped CdS was significantly higher than that of undoped CdS.     

Electrodeposition of Al,Zn, and Pt on silver-coated textile fibres from ionic liquids

In the present paper, we report on the electrodeposition of aluminium, zinc and platinum on silver-coated textile fibres from ionic liquids. For electrodeposition of Al, the 60:40 mol% mixture of AlCl₃/1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) and 1.7 M AlCl₃ in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py_1,4]TFSA) were employed. It was observed that microcrystalline aluminium was electrodeposited on the textile fibres in 60:40 mol% AlCl₃/[EMIm]Cl. The deposited Al layers either on single fibres or on textile assemblies are well adherent and uniform. An adherent, homogeneous and nanocrystalline Al layer was obtained on the silver-coated textile samples from 1.7 M AlCl₃/[Py_1,4]TFSA at 75 °C. The obtained Al layers from 60:40 mol% AlCl₃/[EMIm]Cl on the textile fibres exhibit a good corrosion resistance in an aqueous iodide/iodine electrolyte. Furthermore, we obtain Al microtubes from the investigated ionic liquids after dissolving the textile fibres. In addition, zinc electrodeposition was carried out on the textile samples from 60:40 mol% ZnCl₂/[EMIm]Cl at 80 °C. The electrodeposition of platinum on the textiles was done from 50 mM PtCl₂ in 1-butyl-1-methylpyrrolidinium dicyanamide ([Py_1,4]DCA).     

Synthesis of Co3O4/WO3 Nanoheterojunction Photocatalyst for the Decomposition of Organic Pollutants Under Visible Light Irradiation

A highly efficient and visible light (λ ≥ 420 nm) responsive nanocomposite photocatalyst Co₃O₄/WO₃ was developed by dispersing p-type semiconductor Co₃O₄ on the surface of n-type semiconductor WO₃. The heterojunction Co₃O₄/WO₃ demonstrated higher photocatalytic activity than WO₃, Co₃O₄ and TiO₂ nanoparticles for the complete decomposition of 2-propanol in gas phase and phenol in aqueous phase and evolution of CO₂ under visible light irradiation. The highest photocatalytic efficiency of the composite Co₃O₄/WO₃ was observed when calcined at 300 °C for 2 h with 4.91 mol% Co₃O₄/WO₃. The enhanced photocatalytic efficiency of the heterojunction was discussed based on the unique relative energy band positions and profound absorption of visible light by the semiconductors.     

Characterizations of white-light ZnWO4 phosphor prepared by blending complementary phosphor

In the preparation of ZnWO₄ phosphor, crystalline ZnWO₄ was created, even though the concentration of WO₃ was only 10 mol%. ZnWO₄ was the dominant crystallization phase when the concentration of WO₃ exceeded 40 mol%. The optimal crystallization of ZnWO₄ phosphor was obtained when the composition molar ratio of ZnO to WO₃ was 1:1, and sintering was carried out at 1,100°C for 3 h. In this condition, a bluish-green emission with a peak at 460 nm was observed. For Y₂O₃:Eu³⁺,Li⁺, the complementary phosphor of ZnWO₄, the Li flux improved phosphor crystallization. The red emission peak of the Y₂O₃:Eu³⁺,Li⁺ phosphor was measured at about 612 nm. The optimal photoluminescence intensity of the Y₂O₃:Eu³⁺,Li⁺ phosphor was obtained when it was sintered at 1,200°C for 5 h and was mixed with 11 mol% Eu₂O₃ and 70 mol% Li₂CO₃. When the weight ratio of Y₂O₃:Eu³⁺,Li⁺ to ZnWO₄ was 1:4, the Y₂O₃:Eu³⁺,Li⁺-blended ZnWO₄ phosphor showed white-light emission with Commission Internationale de l’Eclairage coordinates at (0.34, 0.30). The luminance of the white-light phosphor excited by a 6-W UV lamp was around 160 cd/m².     

The Catalytic Cycle of Oxidation of Iodide Ion in the Oxygen/Nitrous Acid/Nitric Oxide System and Its Potential for Analytical Applications

Abstract

The oxidation of iodide to iodine by nitrous acid in aqueous acidic medium takes place catalytically in the presence of dissolved oxygen and can be followed spectrophotometrically at 288 and 352 nm. An indirect molar absorptivity for nitrite on the basis of I₃ ^? formation can be as high as 8.5×10⁵ L mol^?1 cm^?1 at 288 nm. Analytical curves were established. The iodine released in the catalytic cycle can also be titrated with thiosulfate. The reaction is pseudo–second‐order in oxygen consumed, with t_1/2=15.7 min at 25°C. A rate determining step could be the NO · O₂ as the activated species. Measurements of the iodine formed at catalytic conditions was used to determine nitrite in meat extracts and NOx in car exhausts.     

Thermal analysis of 5′-deoxy-5′-iodo-2′,3′-O-isopropylidene-5-fluorouridine

The melting temperature, melting enthalpy, and specific heat capacities (C _p) of 5′-deoxy-5′-iodo-2′,3′-O-isopropylidene-5-fluorouridine (DIOIPF) were measured using DSC-60 Differential Scanning Calorimetry. The melting temperature and melting enthalpy were obtained to be 453.80 K and 33.22 J g^?1, respectively. The relationship between the specific heat capacity and temperature was obtained to be C _p/J g^?1 K^?1 = 2.0261 – 0.0096T + 2 × 10^?5 T ² at the temperature range from 320.15 to 430.15 K. The thermal decomposition process was studied by the TG–DTA analyzer. The results showed that the thermal decomposition temperature of DIOIPF was above 487.84 K, and the decomposition process can be divided into three stages: the first stage is the decomposition of impurities, the mass loss in the second stage may be the sublimation of iodine and thermal decomposition process of the side-group C₄H₂O₂N₂F, and the third stage may be the thermal decomposition process of both the groups –CH₃ and –CH₂OCH₂–. The obtained thermodynamic basic data are helpful for exploiting new synthetic method, engineering design, and commercial process of DIOIPF.     

Synthesis, characterization and thermal behaviour of new copper and rare-earth metal tungstates

Three series of new copper and rare-earth metal tungstates with the formulas: CuRE ₂W₂O₁₀ (RE = Nd, Sm, Eu) and Cu₃ RE ₂W₄O₁₈ (RE = Sm, Eu or RE = Dy, Ho, Er) were synthesized by the solid-state reaction method. The CuRE ₂W₂O₁₀ and Cu₃ RE ₂W₄O₁₈ (RE = Dy, Ho, Er) compounds crystallize in the monoclinic system. The Cu₃ RE ₂W₄O₁₈ phases with the large rare-earth ions crystallize in the triclinic system. All obtained compounds melt incongruently below 1273 K. The anion lattice of the Cu₃ RE ₂W₄O₁₈ phases is built from isolated groups of octahedra (W₄O₁₆)^8?, while CuRE ₂W₂O₁₀ from WO₆ octahedra forming structural elements [(W₂O₉)^6?]^∞. The EPR spectra of analyzed compounds consisted of an intense line originating generally from the rare-earth ions and a weak, narrow line from Cu²⁺ separate centers appearing only on the surface of the grains. The absence of bulk copper in the EPR spectrum is probably due to a very short relaxation time of the Cu²⁺ subsystem.     

Efficient Synthesis of Homoallylic Alcohols/Amines from Allyltributylstannane and Carbonyl Compounds/Imines Using Iodine as Catalyst Under Acetic Acid–Water Medium

This paper describes a general method for the synthesis of homoallylic alcohols and amines by nucleophilic addition reaction of allyltributylstannane to carbonyl compounds and aldimines where iodine acts as a catalyst in H₂O/acetic acid (1:1) medium. Only 10 mol% of I₂ is required for various organic transformations. By using this process, various homoallylic alcohols and amines are produced in good to excellent yields.