Preparation and characterization of N–I co-doped nanocrystal anatase TiO2 with enhanced photocatalytic activity under visible-light irradiation

N–I co-doped TiO₂ nanoparticles were prepared by hydrolysis method, using ammonia and iodic acid as the doping sources and Ti(OBu)₄ as the titanium source. The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible diffuse reflection spectroscopy (UV–vis DRS). XRD spectra show that N–I–TiO₂ samples calcined at 673 K for 3 h are of anatase structure. XPS analysis of N–I–TiO₂samples indicates that some N atoms replace O atoms in TiO₂ lattice, and I exist in I⁷⁺, I⁻ and I⁵⁺ chemical states in the samples. UV–vis DRS results reveal that N–I–TiO₂ had significant optical absorption in the region of 400–600 nm. The photocatalytic activity of catalysts was evaluated by monitoring the photocatalytic degradation of methyl orange (MO). Compared with P25 and mono-doped TiO₂, N–I–TiO₂ powder shows higher photocatalytic activity under both visible-light (λ > 420 nm) and UV–vis light irradiation. Furthermore, N–I–TiO₂ also displays higher COD removal rate under UV–vis light irradiation.     

ZrO2–TiO2Materials

The magnetic, electrical, catalytic, and photocatalytic properties of ZrO₂–TiO₂materials were studied. The ZrO₂–TiO₂system was shown to contain ZrO₂-, TiO₂, and ZrTiO₄-based solid solutions. Procedures for the preparation of high-activity ZrO₂–TiO₂photocatalysts and photostable pigments were developed.     

Alginate polyelectrolyte ionotropic gels

The kinetics and mechanism of exchange of Ni²⁺ by H⁺ ions in ionotropic nickel alginate polymembrane gels of capillary structure have been studied by pH-metric and conductimetric techniques. The rate of exchange conforms to; rate=k ₁ [nickel alginate] [H⁺]- k _–1 [alginic acid] [Ni²⁺] with k ₁=6.34×10^–2dm³mol^–1s^–1 and k _–1=8.83×10^–4 s^–1 at 20°C, respectively. The activation parameters have been evaluated and a mechanism consistent with the kinetic data is discussed.     

Fabrication and properties of an anisotropic PZT/polymer 0–3 composite

Anisotropic 0–3 PZT platelet/polymer composites were prepared by a route involving the tape casting and sintering of PZT sheets and the subsequent alignment of platelets in a polymer matrix by either calendering or tape casting; both techniques induced a strong alignment of the platelets. At 60 vol 1/2 loading, measured d ₃₃- and d _h-values of ~ 30 pC N^–1 and ~ 100 pC N^–1, respectively, were obtained; the calculated g _h-value was 83 mV mN^–1. A strong relaxation effect observed is considered most likely to be dependent on the characteristics of the polymer phase.     

New polyurethane-anatase titania porous hybrid composite for the degradation of azo-compounds wastes

New TiO₂-based organic–inorganic porous hybrid materials were developed for color degradation and tested in azo-compounds aqueous solution. Porous composite materials, with pore size between 100 and 200 μm and pore volume fraction between 62% and 76%, were synthesized using micro-particles of TiO₂ in anatase phase agglutinated with solvent-free, mono-component polyurethane; the pores were generated by the CO₂ produced during the chemical reaction. The high porosity of the samples improves the contact with the colored solution increasing the photocatalytic effect. The degradation process was well fitted using a first order chemical reaction and the constant rate k determined. The best samples showed k values of 0.091 h⁻¹ and 0.076 h⁻¹ using visible light with a power of 100 mW/cm² and k values of 1.465 h⁻¹ and 1.652 h⁻¹ using UV light with a power of 80 mW/cm²; these values are comparable or better to other reported in literature obtained under similar conditions. Additionally, the use of polyurethane increases the abrasion resistance improving the lifetime of the photocatalytic material. The materials were characterized using X-rays diffraction, SEM and UV–Vis spectroscopy.     

Optical and electrical properties of electrodeposited silver based thin films

The electrodeposited superionic conductor Ag₆I₄WO₄ was doped with various concentrations of [CrO₄]^2– to form the quarternary compound Ag₆I₄WO_4(1–xCrO_4(x). The doping level,x, was varied from 0 to 0.6 and the optimum compound was used for further analysis. X-ray diffraction (XRD) analysis indicated major peaks occurring atd values of 3.75,2.29,1.96 and 3.96 in the order of decreasing intensity. The energy dispersive analysis of X-rays (EDAX) technique verified quantitatively the ratio of the components in the solid electrolyte. From the fringes seen in the interference pattern of the transmission spectrum, the refractive index and thickness of the film was calculated. The absorption spectrum indicated the characteristic chromate peak at 310 nm when the dopant was present. An open circuit voltage (OCV) of 670 mV was observed for the fabricated cells with optimum performance at a doping level ofx=0.1, where the best discharge characteristics were observed. The subsequent conductivity was calculated to be of the order 10^–3–1 cm^–1 from the Cole-Cole plot.     

Aerobic composting of tobacco industry solid waste—simulation of the process

Solid waste accumulated during the processing of tobacco for cigarette manufacture mostly contains tobacco particles and flavoring agents. Its main characteristics are a high content of nicotine (2,000 mg per kg of total solids), which is a toxic compound, and high value of total organic carbon of the aqueous extract (12,620.0 mg l^–1). Because of this fact tobacco waste cannot be disposed of with urban waste.The aim of this work was to stabilize tobacco solid waste by aerobic composting. The experiments were carried out in closed thermally insulated column reactors (1.0 l and 25 l) under adiabatic conditions and at an airflow rate of 0.9 l min^–1 kg^–1 of volatile solids for 16 days. During the process, temperature changes in the reactor, CO₂ production and the numbers of mesophilic and thermophilic organisms in the mixed microbial culture were closely monitored. Nicotine concentration in the samples was analyzed at the start and at the end of process. It was estimated that at the end of composting the volume and mass of total solids in the tobacco waste were reduced by about 50% and those of nicotine by 80%. A simple empirical model was used to simulate the biodegradation rate of the organic fraction of the solid waste. It was found that the selected model describes aerobic composting fairly well, although only two kinetic parameters (k₀ and n) were estimated.List of symbols c_pS specific heat capacity of the substrate, kJ kg^–1 K^–1 - c_pz specific heat capacity of air, kJ kg^–1 K^–1 - F_Ku and F_Ki molar airflow at the reactor inlet and outlet, mol h^–1 - H_r reaction enthalpy, kJ kg^–1 of dry substrate - k specific rate, Eqs. (5) and (9), h^–1 - k_o constant in Eq. (9), day^–1 - m_o initial mass of the substrate, kg - m_S mass of dry substrate, kg - n order of the reaction in Eq. (5) - n_K molar amount of oxygen, mol - Q_v airflow volume, m³ h^–1 - r_K oxygen depletion rate, mol kg^–1 h^–1 - r_S degradation rate, kg kg^–1 h^–1 - _z air density, kg m^–3 - SD mean square deviation - t time, h - T temperature in reactor, °C - T_o temperature of substrate at the beginning of reaction, °C - T_K temperature of compost at the end of reaction, °C - T_u temperature of air at the reactor inlet - space time, day - w_S mass fraction of compost, m_sm_o^–1, kg kg^–1     

Analytical technique for the determination of solidification rates during the inward freezing of cylinders

An analytical/experimental approach which permits the determination of solidification rates during the inward solidification of cylinders is proposed. The technique is based on a previous analytical solution that treats the generalized problem of solidification of slabs. This solution is modified by a geometric correlation to compensate for the cylindrical geometry. A number of experiments have been carried out with a special experimental set-up, designed to simulate the inward solidification of cylinders in a water-cooled mould. A series of comparisons of experimental results, numerical predictions and calculations furnished by the proposed technique were made, showing good agreement for any case examined.Nomenclature a _s Thermal diffusivity of solid metal = k _s/c _s d _s (m² sec^–1) - A _i Internal surface area of the mould (m²) - b _s Heat diffusivity of solid metal = (k _s c _s d _s ^1/2(J m^–2 sec^–1/2 K^–1) - c _s Specific heat of solid metal (J kg^–1 K^–1) - d _s Density of solid metal (kg m^–3) - h Newtonian heat transfer coefficien (W m^–2 K^–1) - H Latent heat of fusion (J kg^–1) - k _s Thermal conductivity of solid metal (W m^–1 K^–1) - q Heat flux (W m^–2) - r Radial position (m) - r _o Radius of cylinder (m) - r _f Radius of solid/liquid interface (m) - S Thickness of solidified metal (m) - S _o Thickness of metal side adjunct (m) - t Solidification time (sec) - T Temperature (K) - T _i Surface temperature (K) - T _f Freezing temperature of metal (K) - T _o Temperature of the coolant (K) - T _s Temperature at any point in the solidified metal (K) - V ₁ Volume of remaining liquid metal during the solidification (m³) - V _s Volume of solidified metal (m³) - V _T Total volume of metal in the mould (m³) - x Distance from metal/mould interface (m) - Dimensionless solidification constant.     

Sorption of 131I? and 131IO3? from Aqueous Solutions on Porous Inorganic Sorbents Modified with d-Element Ammoniates at 25°C

Sorption of ¹³¹I⁻ and ¹³¹IO ₃ ⁻ from aqueous solutions on porous inorganic sorbents modified with d elements is studied at 25°C. The sorbents modified with Ag, Zn, Ni, Cu, and Co ammoniates are characterized by low distribution coefficients of ¹³¹I⁻ and ¹³¹IO ₃ ⁻ (K _d <150 ml g⁻¹ at V/m = 1000). Calcination of the sorbents modified with Ag, Cu, and Zn ammoniates at a temperature above 250°C affects the chemical state of the metals in the sorbent matrix, which is accompanied by slight increase in K _d of ¹³¹I⁻ and ¹³¹IO ₃ ⁻ as compared to as-prepared samples. With the γ-Al₂O₃-based sorbents modified with Ni or Cu, K _d of ¹³¹I⁻ and ¹³¹IO ₃ ⁻ is well comparable with that for the Ag-modified sorbents based on MSKG silica gel.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 265–268.Original Russian Text Copyright © 2005 by Kulyukhin, Mizina, Krasavina, Rumer, Konovalova, Tanashchuk, Bogachev.     

Yttrium-substituted bismuth titanate (Bi4−x Y x Ti3O12) thin film for use in non-volatile memories

Fatigue-free Bi_3.2Y_0.8Ti₃O₁₂ (BYT) thin films were grown on Pt/TiO₂/SiO₂/Si substrates using direct liquid injection–metal organic chemical vapor deposition. The BYT film capacitor with top Au electrode showed higher remanent polarization (2P _r) and lower leakage current density compared with Bi_3.2La_0.8Ti₃O₁₂ (BLT) film capacitors. BYT films showed strong (1 1 7) orientation with smaller grain size, while BLT films showed strong c-axis orientation. The 2P _r value of the BYT capacitor was 15 C cm^–2 and remained essentially constant up to 1×10¹⁰ read/write switching cycles at a frequency of 1 MHz. The leakage current of the BYT film was 3.5×10^–7 A cm^–2 at an applied voltage of 2 V, which is about three orders lower than that of the BLT film.     

Sulphur,nitrogen-doped TiO2/graphene oxide composites as a high performance photocatalyst

Sulphur (S), nitrogen (N)-doped TiO₂/graphene oxide (GO) composites were environmentally friendly synthesised using thiourea (CS(NH₂)₂) as a binary-element doping reagent by a simple colloidal blending method. The S, N-doped TiO₂/GO composites show higher photocatalytic degradation rates on methyl orange (MO) compared to TiO₂. The average value of k (the apparent rate constant) for the S, N-doped TiO₂/5%GO (k?=?0.035?min^?1) was found to be eight times higher than that of TiO₂ grown in solution (k?=?0.0038?min^?1) and four times higher than that of P25 (k?=?0.008?min^?1). The investigation showed that the contribution of GO to the high photocatalytic activities of the composites come from its high specific surface area, oxygen-containing functional groups and large aromatic domains that were inclined to be bound by conjugated MO molecules via π–π stacking. The doping of S and N can increase the numbers of photo-generated electrons and holes, which produce more charge carriers to form reactive species, and thus promote the degradation of MO. This work could offer a route to improve the photocatalytic activities of TiO₂ and facilitate their application in reality.     

Prediction of thermal diffusion in binary mixtures of nonelectrolyte liquids by the use of nonequilibrium thermodynamics

A derivation based on nonequilibrium thermodynamic leads to this expression for the thermal diffusion factor, _T=M ₂(h ₂ ^xs -h ₁ ^xs )/RT ₂, where M ₂ is the molecular weight of the lighter of the two components, h ₁ ^xs is the partial excess enthalpy of component i, J/g, R is 8.314 J · K ^–1 · mol ^–1, T is temperature in K, and ₂ is the thermodynamic correction factor (1 + d ln ₂/d ln X ₂), where ₂ is an activity coefficient and X ₂ is the mole fraction. The correctness of this theoretical prediction is verified for the liquid system ethanol-water at 298 K.Paper submitted to the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Preparation and characterization of the Sb-doped TiO2 photocatalysts

Doped TiO₂ photocatalysts have been prepared by a coprecipitation method. Uniformly doped nanocrystalline TiO₂ of 10–20 nm sizes was synthesized by calcinating the coprecipitated gels at 400–650°C. Photocatalytic characterization along with the microstructural investigation for each catalyst provides better understanding of the photocatalytic behavior. It was found that the photodegradation of methylene blue (MB) was a complex function of the doping type and its concentration and the microstructural characteristics of the catalysts. Antimony doing significantly improved photocatalytic performance as compared to the undoped TiO₂. Post-treatment of the as-precipitated wet doped Ti gels in an organic solvent also increased the surface area, forming approximately 8 nm size doped TiO₂ with surface area 149 m²/g. Superior catalytic activity was observed in the Sb-doped TiO₂ samples at a doping concentration ranging from 1 to 5 at%. Using the 5 at% Sb-doped TiO₂ catalyst treated in butanol, 100 ppm of MB could be decomposed completely within 1 h, which was better than the commercial Degussa P-25.     

Diffusion coefficients of tetrazolium blue in homogeneous and micellar solutions

Diffusion coefficients of the electron acceptor dye tetrazolium blue were measured by the Taylor dispersion method, with an accuracy better than 4%, in two solvents: (i) a homogeneous one-aqueous phosphate buffer, 0.1 M, pH=7.0 (medium I); and (ii) a heterogeneous one-nonionic micelles of Triton X-100, 2.0 mM (where M stands for mol·dm^–3), in the same aqueous phosphate buffer (medium II). The values obtained were D ₁₂ ^I =3.64×10^–10m²·s^–1 and D ₁₂ ^II =3.01×10^–10m²·s^–1·D ₁₂ ^II has the meaning of a macroscopird or average diffusion coefficient, in which the partition coefficient of tetrazolium blue between micelles and water, as well as the diffusion coefficients of this dye and of the micelles in the aqueous phase, are involved.     

An assessment of expressions for the apparent thermal conductivity of cellular materials

Diverse expressions for the thermal conductivity of cellular materials are reviewed. Most expressions address only the conductive contribution to heat transfer; some expressions also consider the radiative contribution. Convection is considered to be negligible for cell diameters less than 4 mm. The predicted results are compared with measured conductivities for materials ranging from fine-pore foams to coarse packaging materials. The dependencies of the predicted conductivities on the material parameters which are most open to intervention are presented graphically for the various models.Nomenclature a Absorption coefficient - C _v (Jmol^–1 K^–1) Specific heat - E Emissivity - E _L Emissivity of hypothetical thin parallel layer - E ₀ Boundary surfaces emissivity - f Fraction of solid normal to heat flow - fics Fraction of total solid in struts of cell - K(m^–1) Mean extinction coefficient - k(W m^–1 K^–1) Effective thermal conductivity of foam - k _cd(W m^–1 K^–1) Conductive contribution - k _cr(W m^–1 K^–1) Convective contribution - k _g(W m^–1 K^–1) Thermal conductivity of cell gas - k _r(W m^–1 K^–1) Radiative contribution - k _s(W m^–1 K^–1) Thermal conductivity of solid - L(m) Thickness of sample - L _g(m) Diameter of cell - L _s(m) Cell-wall thickness - n Number of cell layers - r Reflection coefficient - t Transmission coefficient - T(K) Absolute temperature - T _m(K) Mean temperature - T _N Fraction of energy passing through cell wall - T ₁(K) Temperature of hot plate - T ₂(K) Temperature of cold plate - V _g Volume fraction of gas - V _w Volume fraction of total solid in the windows - w Refractive index - (m) Effective molecular diameter - (Pa s) Gas viscosity - Structural angle with respect to rise direction - (W m^–2 K^–4) Stefan constant     

Convective heat transfer in the entrance region of a rectangular duct with two indented sides

This study presents a numerical solution to convective heat transfer in laminar flow in the thermal entrance region of a rectangular duct with two indented sides. The flow is considered to be hydrodynamically fully developed and thermally developing laminar flow of incompressible, Newtonian fluids with constant thermal properties. The ducts are subjected to a constant wall temperature. An algebraic technique is used to discretize the solution domain and a boundary-fitted coordinate system is numerically developed. The governing equations in the boundary-fitted coordinates are solved by the control volume-based finite difference method. Distribution of the bulk temperature and the Nusselt number along the direction of flow is calculated and presented graphically. Also calculated is the thermal entrance length of the rectangular ducts with two indented sides. The parameters, such as the friction factor times the Reynolds number, and the Nusselt number for the fully developed flow and thermally developing flow are obtained.List of symbols a half-width of duct [m] - A cross-sectional area [m²] - b half-height of duct [m] - C _p specific heat [kJ kg^-1 K^-1] - D _h hydraulic diameter [m] - f skin friction factor = - h _z local heat transfer coefficient [Wm^–2 K^–1] - h _T asymptotic heat transfer coefficient [Wm^–2 K^–1] - J Jacobian matrix of transformation, Eq. (20) - k thermal conductivity [Wm^–1 K^–1] - L thermal entrance length [m] - L ^* dimensionless thermal entrance length =L/D _h RePr - L1 maximum number of grids in direction - M1 maximum number of grids in direction - Nu _T asymptotic Nusselt number =h _T D _h /k - p pressure [n m^–2] - P circumferential length [m] - Pr Prandtl number = /_T - Re Reynolds number =w _m D _h / - T temperature [K] - T _b bulk temperature [K] - T _i inlet temperature - T _w circumferential duct wall temperature [K] - w velocity [ms^–1] - w _m mean velocity [ms^–1] - W dimensionless velocity = – - W _m dimensionless mean velocity - x, y transveral coordinates [m] - X,Y dimensionless transversal coordinates =      

Measurements of the Thermal Diffusivity Tensor of Polymer–Carbon Fiber Composites by Photothermal Methods

The thermal diffusivity tensor of a polymer–carbon fiber composite with unidirectionally distributed fibers has been measured using a modulated photothermal mirage device. The thermal diffusivity along the fibers is k =6.0±0.5 mm²·s^–1, that perpendicular to the fibers is k =0.35±0.05 mm²·s^–1, and that perpendicular to the sample surface is k _z=0.40±0.15 mm²·s^–1. These results have been confirmed by independent measurements on the sample by other laboratories using three other different photothermal techniques. A previous claim on anomalous results found on this sample (k <k and high thermal diffusivities) can be explained by the inappropriate use of the frequency range. We have also found that there is not perfect thermal contact between the fibers and the matrix, which can be characterized by the thermal contact resistance of R _th=(9±2)×10^–6m²·K·W^–1.     

Dielectric properties of (Ba,Sr)O-(Sm,La)2O3-TiO2 ceramics at microwave frequencies

The dielectric properties of (Ba, Sr)O-(Sm, La)₂O₃-TiO₂ material at microwave frequencies were investigated. By varying the amount of strontium from 0–25 mol% in the 0.15(Ba_1–x Sr _x )O-0.15Sm₂O₃-0.7TiO₂ composition, it was possible to adjust the frequency temperature coefficient, _f, from –13 p.p.m. °C^–1 to + 30 p.p.m. °C^–1. When 7 mol% Sr was substituted for barium, _f=0 p.p.m. °C^–1 was obtained. TiO₂ with rutile phase (_f400 p.p.m. °C^–1) acted as a dominant element in _f variation of the 0.15(Ba_1–x Sr _x )O-0.15(Sm_1–y La _y )₂O₃-0.7TiO₂ (0x0.25, 0y0.6) system. Additionally, increasing the quantity of lanthanum substitution for samarium had a greater positive effect on _f than strontium substitution for barium. When 60 mol% La was substituted for samarium with 7mol% Sr substitution barium, _f of the system reached 95 p.p.m. °C^–1. The effect on microwave dielectric characteristics of the 0.15(Ba_0.93Sr_0.07)O-0.15Sm₂O₃-0.7TiO₂ (BSST) ceramics by varying the calcination and/or sintering conditions or doping additives, were studied. The added SnO₂ acted as a firing agent to lower the sintering temperature, and the dielectricQ(Q _d) value was improved by properly adding CdO. With 1 wt% CdO addition, the highestQ _d value of the BSST resonator, after calcination at 1100 °C/2 h and sintering at 1370 °C/4 h, reached 4180 at 4 GHz with a small _f of –4 p.p.m. °C^–1 and an _r of 80.7 was obtained.     

Preparation of High-Purity Indium and Gallium via Electrotransfer in a Magnetic Field

High-purity (7N) indium and gallium are obtained via electrotransfer in melts placed in a static transverse magnetic field. The resistance ratios of the indium and gallium thus purified (25000 and 85000, respectively) are larger than in commercial grades of these metals. The magnetoresistance of liquid gallium is measured as a function of magnetic field. A multiband model for the Fermi surface of liquid gallium is proposed, which includes an electronic sphere of radius k _F ^e = 1.654 × 10⁸ cm^–1 and a spherical hole shell of thickness k = 0.5 × 10⁸ cm^–1 and radius k _F ^h = 1.114 × 10⁸ cm^–1. The model accounts for the observed magnetoresistive response of liquid gallium in a transverse magnetic field.