Pore formation during the pyrolysis of C-Nb2O5 and C-Ta2O5 xerogels

Binary organic-inorganic gels have been prepared by mixing a carbonaceous hydrosol and a Nb₂O₅ or Ta₂O₅ sol derived by hydrolysis of the alkoxides. The gels are pyrolyzed under an inert atmosphere into precursors in which carbon and the metal oxides are mixed very intimately. High temperature treatment converts the precursors into the cubic face centered carbides. The precursors as well as the carbides have been shown to be micro- and mesoporous materials. Measurements of nitrogen adsorption reveal a characteristic change of the shapes of the isotherms (Type I Type IV) and of the hysteresis loops (H4H2H1) during the thermal processes. Pore widening has been observed with rising temperature. The phenomena of crystallization, carbothermal reduction and sintering were found to control the pore shape and size. The results of the adsorption measurement correlate well with those of the thermoanalytical and X-ray diffraction studies.Dedicated to Professor Dr. rer.nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Studies on ABX6 Compounds. II. The BaThBr6 structure type

The compounds AThBr₆ (A: Ca, Sr, Ba) crystallize in an ordered substitution variant of the PuBr₃ type. Their syntheses and special features of the crystal structures are described.     

UCr4C4 with filled MoNi4 type structure

The title compound was prepared by arc melting coldpressed pellets of the elemental components with subsequent annealing at both 800°C or 1100°C. UCr₄C₄ crystallizes tetragonal, space group I4/m,a=0.79363 (4) nm,c=0.30754 (3) nm,V=0.19370 nm³ withZ=2 formula units per cell. The structure was determined from single-crystal X-ray data and refined to a residual ofR=0.027 for 16 variable parameters and 279 structure factors. The positions of the metal atoms correspond to those of the MoNi₄ type structure. The carbon atoms occupy octahedral voids formed by four chromium and two adjacent uranium atoms. Chemical bonding in UCr₄C₄ and in other interstitial compounds is briefly discussed. The average valence electron number of the metal atoms is usually greater for the unfilled (host) structure than for the corresponding filled structure.Dedicated to Prof. Dr.Kurt Komarek and to Prof. Dr.Adolf Neckel on the occasion of their 60th birthdays.     

Excess volumes of ternary mixtures of N,N-dimethylformamide-diethyl ketone-1-alkanols at 303.15K

Volume changes on mixing of ternary liquid mixtures of N,N-dimethylformamide and diethyl ketone with 1-alkanols have been measured as a function of composition at 303.15 K. The alkanols include 1-propanol, 1-butanol, 1-pentanol and 1-hexanol. The measured V^E values are negative in the mixtures of N,N-dimethylformamide, diethyl ketone and 1-propanol, or 1-butanol. The V^E data exhibits an inversion in sign in the mixture containing 1-pentanol and positive excess volumes are observed in the mixture containing 1-hexanol. The measured data are compared with predicted values based upon empirical relations. The excess volume for the binary mixture of N,N-dimethylformamide with diethyl ketone has been measured over the entire range of composition at 303.15 K. The V^E values are negative for the binary mixture.     

Preparation of safe water–lipid mixed electrolytes for application in ion capacitor

Aqueous electrolytes are safe, economic, and environmentally friendly. However, they have a narrow potential window. On the other hand, organic electrolytes exhibit good thermodynamic stability but are inflammable and moisture sensitive. In this study, we prepared water–PEG–lipid ternary electrolytes(TEs). To combine the advantages of water, polyethylene glycol(PEG) and propylene carbonate(PC). The nonflammable mixed electrolytes exhibited a wide potential window of about 2.8 V due to the beneficial effects of PEG and PC. Using these TEs, a lithium manganate–active carbon ion capacitor could be operated at 2.4 V with an energy density of 32 Wh/kg, based on the total active electrode material(current density of 3.3 m A/cm~2). This value was significantly higher than that achieved using an aqueous electrolyte, thereby rationalizing the higher energy density.     

Novel hybrids of Cu2+ ternary complexes of salicylidene-amino acid Schiff base with phenanthroline（or bipyridine） intercalated in Mg/Al-NO3-layered double hydroxide

Four Cu²⁺ complexes of salicylidene-amino acid Schiff base with 1,10-phenanthroline（Phen） or 2,2’- bipyridine（Bipy） were successfully intercalated in interlayer galleries of Mg/Al-NO₃-layered double hydroxide（LDH） by the swelling-restored method.The hybrids were characterized by elemental analysis,X-ray diffraction,FT-IR spectra,UV-vis DRS,TG-DTA and SEM observation.Good protection of the complexes by LDH in neutral and weak acidic solutions was revealed by UV spectra,cyclic voltammograms and luminescence spectra.     

Synthesis of Chemical Modified β-cyclodextrin and its Inclusion Behavior in Alcohol/Water Mixed Solvents

Abstract

The chemical modified β-cyclodextrin(CD), which bears a fluorophore group — N,N-dimethylamino-chalcone (DMAC), was synthesized. The self-inclusion behavior of this compound in aqueous solution and in alcohol/water mixed solvents was investigated in detail, and compared with the inclusion system of non-modified CD with free DMAC molecule. The results showed that a deep self-inclusion complex was formed for this compound in aqueous solution and had the ability to recognize different organic molecules by two fully different modes: “in-out” and “co-inclusion” mechanisms. The inclusion behavior of these systems in various ratio of alcohol/water mixture as solvents was investigated. The results indicated that the self-inclusion complex has a higher stability in alcohol/water mixed solvents than that in the case of non-modified CD. The chalcone group appended at β-CD enabled the host as a sensitive probe to study the inclusion behavior of CD.     

Enhanced Sensitive Electrochemical Sensor for Simultaneous Catechol and Hydroquinone Detection by Using Ultrasmall Ternary Pt-based Nanomaterial

The simple and effective method for the novel synthesis of Pt-based nanoparticle was presented with high efficiency. The sensitive catalyst for the simultaneous detection of catechol and hydroquinone was prepared by depositing ternary metal complex on fluorine-doped tin-oxide (FTO). The composition and morphology of nanomaterials were characterized by TEM, HRTEM, XRD, XPS, and EDS (energy dispersive spectroscopy). The size of the Pt-based nanomaterial was about 5±1 nm. The electrochemical performance of the modified catalyst was studied by CV, DPV, and EIS. The modified PtNiCu@FTO catalyst possessed good electro-oxidation activity for hydroquinone and catechol and used for simultaneous detection of catechol and hydroquinone at scan rate of 20 mV s⁻¹ (vs. Ag/AgCl). Detection responses were found in the ranges of 5–2900 μM for hydroquinone and 5–3000 μM for catechol. The detection limits (LOD) for HQ and CC were observed as 0.35 and 0.29 μM, respectively. The sensitivity of HQ and CC were 1515.55 and 1485 μA mM⁻¹ cm⁻², respectively. The prepared nanomaterial were effectively applied for the determination of CC and HQ in real samples.     

Thermal evolution of the first stage Cs(THF)1.75C24 graphitide,an example of segregation and decorrelation at low temperature

The thermal variation of the first stage ternary compound Cs(THF)_1.75C₂₄ has been investigated by powder neutron diffraction. Two phase transitions have been observed. The first one occurs at 248 K and can be interpreted as a three-dimensional segregation within the graphitic host. The second one starts at about 180 K and is continuous down to 50 K. This corresponds to a decorrelation of the graphen planes at low temperature. The origin of this transition could be the elastic constraint due to the kinks of the planes.     

Surface Tension of Ternary Liquid Mixtures

Abstract

Surface tension has been measured by the differential capillary rise method for three ternary mixtures containing alkanes (hexane + cyclohexane+benzene, pentane + hexane + benzene and cyclohexane + heptane + toluene at 298.15\pm 0.1°K). The sign and magnitude of the excess surface tension and excess volume depend ultimately upon the chain length of the component of the mixtures. The results of the surface tension were compared with theoretical values obtained from Flory theory, Sanchez method, Brock-Bird relation and volume fraction statistics. There is reasonable agreement between theory and experiment.