Obtaining of Ni–P–TiO2 Composite Coatings with TiO2 Sol and Surfactants and Their Properties

The influence of surfactants and TiO₂ sol on mechanical, catalytic, and corrosive properties of electroless Ni–P coatings was investigated. Additives of the surfactants caused the decrease of internal stresses in the Ni–P coatings and smoothing of their surfaces. Incorporation of the TiO₂ particles facilitated the rise of microhardness of the Ni–P coatings from 545 ± 11 Hv up to 614 ± 17 Hv. Additives of the surfactants accelerated hydrogen evolution reaction on the composite Ni–P–TiO₂ coatings in acid and alkaline media, and increased photocatalytic activity in methylene blue decomposition. Incorporation of the TiO₂ particles and application of the surfactants resulted in an improvement in the corrosion resistance of original Ni–P coatings in 0.5 M H₂SO₄.     

A methyl parathion electrochemical sensor based on Nano-TiO2, graphene composite film modified electrode

A methyl parathion electrochemical sensor based on nano-TiO₂ and graphene composite film modified glassy carbon electrode has been developed. The electrochemical behavior of MP at the sensor was investigated by cyclic voltammetry and linear sweep voltammetry. Scanning electron microscopy was used to characterize the surface morphology of nano-TiO₂ and graphene composite film. Compared with a bare glassy carbon electrode or a mono-film modified electrode, the redox peak currents of methyl parathion on the composite film modified electrode improved greatly, indicating that the sensor showed good catalytic effects. The optimal experimental condition was obtained. The results indicated that the linear sweep voltammetry responses of methyl parathion, in pH 5.2 acetate buffer solution with open-circuit accumulation for 2 min, were linear with concentrations of methyl parathion in two ranges of 0.002～5 μM and 5～100 μM. The linear equations were i_Pc(μA) = 0.0136 + 4.965c_MP(μM) (R₁² = 0.9911) and i_Pc(μA) = 21.87 + 0.8206c_MP(μM) (R₂² = 0.9914), respectively. The detection limit was 1.0 nM (S/N = 3). The sensor exhibited high sensitivity and good reproducibility as well as certain anti-interference ability. It was applied to the determination of residual MP in fresh apple sample with the recovery of 92%～102%. The result was satisfactory.     

Kinetic Properties of Orientational Phase Transition in Polymerized States of Fullerites C60

Abstract

In the present work, we have shown that at early stages of dimerization, which occur during synthesis of C₆₀ fullerite T _syn = 10–40°C and P _syn = 1.5–8 GPa, kinetics of the sc→fcc phase transition, may be well described by Avrami law with Avrami's exponent n _Avr = 3 (i.e., in this case we are dealing with martensite‐like transformation). Fullerite's samples produced at higher temperatures (40°C < T _syn < 120°C) exhibit different kinetics with lower Avrami‐exponent. This behavior we attribute to the transformation switching to diffusion‐controlled kinetics.     

Optical properties of carbon-containing titanium oxide nanocomposites obtained by the pulsed plasma chemical method

This paper presents the results of an experimental investigation on the optical properties of the TiO₂ and Ti_xC_yO_z nanopowders, produced by the pulsed plasma chemical method. Pulsed plasma chemical synthesis is realized on the laboratory stand, including a plasma chemical reactor (6 l) and TEA-500 electron accelerator. The parameters of the electron beam are as follows: 400–450 keV electron energy, 60 ns half-amplitude pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. In TiO₂ sample, obtained using the pulsed plasma chemical method, the particles can be divided into two groups: 100–500 nm large spherical particles and tiny complex particles (sized less than 100 nm). For TixCyOz sample, the morphology of the particles is mainly presented with irregular fragment shape. The average size of the particles is ranged from 200 to 300 nm. The band gap for all synthesized samples is within 2.94–3.35 eV.     

Thermal nonlinear optical response of meso-tetraphenylporphyrin under aggregation conditions versus that in the absence of aggregation

In this work, measurement of thermally induced nonlinear refractive index of meso-tetraphenylporphyrin (H₂TPP) at different concentrations in 1,2-dicoloroethane using a double-grating interferometer set-up in a pump–probe configuration is reported. The formation of aggregates of H₂TPP at concentrations greater than ca. 5 × 10^?5 M was evident by deviation from Beer’s law. An almost focused pump beam passes through the solution. A part of the pump beam energy is absorbed by the sample and therefore a thermal lens is generated in the sample. An expanded probe beam propagates through the sample and indicates the sample refractive index changes. Just after the sample a band-pass filter cuts off the pump beam from the path but the distorted probe beam passes through a double-grating interferometer consisting of two similar diffraction gratings with a few centimetres distance. A CCD camera is installed after the interferometer in which on its sensitive area two diffraction orders of the gratings are overlying and producing interference pattern. The refractive index changes of the sample are obtained from the phase distribution of the successive interference patterns recorded at different times after turning on of the pump beam using Fourier transform method. In this study, for different concentrations of H₂TPP in 1,2-dichloroethane solution the thermal nonlinear refractive index is determined. Also, we present the measurement of the temperature changes induced by the pump beam in the solution. We found that value of nonlinear refractive index increased by increasing the concentration up to a concentration of 5 × 10^?4 M and then decreased at higher concentrations. In addition, we have investigated the stability of the observed thermal nonlinearity after a period of two weeks from the sample preparation.     

Statistical Mechanical Study of Thermodynamic Properties of a Family of Fullerites from C36 to C96 in the Equilibrium with Their Vapors

Abstract

The temperature dependence of saturated vapor pressure of fullerites C₃₆–C₉₆ and their thermodynamic properties along with the sublimation curves up to the spinodal are calculated. The saturated vapor pressures along all the range of temperatures are approximated by logP _sat = A ? (B/T) ? CT. The coefficient A practically does not depend on the number of atoms in the molecule (varying only by 2.2%), B increases noticeably while C decreases from the C₃₆ to the C₉₆, both of them by approximately two. The isothermal bulk modulus B _T and the shear modulus C₄₄ vanish at the spinodal points.     

Quaternary co-electrodeposition of the Cu2ZnSnS4 films as potential solar cell absorbers

Cu₂ZnSnS₄ (CZTS) films are successfully prepared on Mo substrate by electrochemical epitaxial method. An electrolyte contains 0.124 M CuSO₄·5H₂O, 0.14 M ZnSO₄, 0.13 M SnCl₂·2H₂O, 0.16 M Na₂S₂O₃·5H₂O, 2.25 M NaOH, 1.36 M C₆H₅Na₃O₇, 1.00 M C₄H₆O₆. The equilibrium potential for quaternary co-electrodeposited solution is set at ?1.1 ～ ?1.20 V. The results show that elements are deposited in the following sequence: Cu/S/Zn/S/Cu/S/Sn/S…. The ternary and quaternary compounds are formed with the increasing temperature during annealing. Finally the CZTS film can be well formed at 550 °C. The resistivity of CZTS is about 5.6 × 10⁴ Ω cm.     

Study on microstructure and properties of centrifugal casting 35Cr45NiNb+MA furnace tubes during service

In the present study, the microstructure evolution of 35Cr45NiNb+MA ethylene cracking furnace tubes during service and its effect on the properties were investigated. According to the results, in the early stage of service, the skeletal M₇C₃ and vermicular NbC were transformed into blocky M₂₃C₆ and G phase (Ni₁₆Nb₆Si₇), respectively, accompanied with many dispersed M₂₃C₆ secondary carbides. With the extension of service time, M₂₃C₆ carbides on the grain boundaries were transformed into M₇C₃ with high stacking fault structure and coarsened, and the blocky G phase was transformed into granular NbC. The yield strength and ultimate tensile strength of the aging furnace tubes decreased by 9%-18%, yet the elongation after fracture decreased significantly from 10.0%-14.0% to 3.0%-5.0%. The hardness of the carburized zone of the carburized tubes increased by 10%-17%, and the rupture time decreased by 45%-75% under the test condition of 1100℃ and 16MPa. Finally, the evolution map was summarized.     

Effect of Additives on Calcium Sulfate Hemihydrate Whiskers Morphology from Calcium Sulfate Dehydrate and Phosphogypsum

The influence of P₂O₅ on the whiskers morphology of CaSO₄ · 0.5H₂O was discussed by using CaSO₄ · 2H₂O as raw materials and the hydrothermal process at 140°C for 2 h. The result indicated whiskers were obtained by adding 0.2% P₂O₅, with a smooth surface, uniform diameter (～1–3 µm), and an aspect ratio of about 45. The aspect ratio of whiskers decreased as the addition amount of P₂O₅ increased. Raw phosphogypsum (PG) was ground by using a planetary ball mill and then washed using distilled water in order to reduce the P₂O₅ content. Washed PG constituted ～50% of the sample, with an agglomerate size of 32.6 µm, and contained 0.43 wt% P₂O_5. The influence of glycerol on the morphology of CaSO₄ · 0.5H₂O whiskers was investigated by also using the hydrothermal method. The aspect ratio of whiskers first increased and then decreased while the amount of glycerol increased. The whiskers were also prepared by using added 1.3 wt% calcium oxide (CaO) PG at 140°C for 2 h and the effect of phosphorus on whiskers growth can be decreased.     

Synthesis of High-Phase Purity SrTi1–xZrxO3 Ceramics by Sol-Spray Pyrolysis Method

SrTi₁–_xZr_xO₃ (0 ≤ x ≤ 1.0) ceramics were synthesized from powders generated by sol-spray pyrolysis. Crystal symmetry, morphology, and the band gap of the prepared ceramics were investigated as a function of Ti/Zr ratio. Substitution of Zr⁴⁺ for Ti⁴⁺ in the solid solution markedly effects crystal symmetry and grain growth and results in an increased band gap. Single-phase products with good crystallinity and dense microstructure were obtained after sintering at 1250°C.     

Polyethyleneimine functionalised nanocarbons for the efficient adsorption ofcarbon dioxide with a low temperature of regeneration

Polyethyleneimine (PEI) conjugates with a range of nanocarbons (NCs) have been prepared, and their performances with regard to carbon dioxide absorption and liberation are compared. PEI-functionalised multi-walled carbon nanotubes (PEI-MWNTs) prepared by the reaction of branched PEI (25,000 Da) with F-MWNTs in the presence of pyridine, showed a lower CO₂ capacity at 25 °C (5 wt%, 1.1 mmol CO₂/g adsorbent) as compared to PEI-SWNTs (9.2 wt%, 2.1 mmol CO₂/g adsorbent), consistent with the interior layers of the MWNTs adding weight to the base NC without adding functionality. PEI-functionalised graphite/graphene was prepared by three routes: fluorinated graphite intercalation compounds, prepared from natural graphite powder, were reacted with PEI in EtOH with pyridine; exfoliated natural graphite powder was reacted with Boc–Phe(4-N₃)–OH, and subsequently PEI to give PEI-Phe(4-N-G); graphite oxide (GO) was reacted with PEI in the presence of NEt₃ to give PEI-GO. The CO₂ capacity of PEI-GO at 25 °C (8 wt%, 1.8 mmol CO₂/g adsorbent) was comparable to that of PEI-SWNTs making GO a valid and cheaper alternative to the SWNT scaffold. The temperature of CO₂ desorption of the PEI-NCs was 75 °C, providing a lower energy load for regeneration compared to current amine-based scrubbing units. The rate of CO₂ uptake is seen to depend on the curvature of the NC substrate.     

Synthesis of nanometric LaCr0.5Mn0.5O3 perovskite at low temperature by the polyvinyl alcohol gel combustion method

Nanosized LaCr_0.5Mn_0.5O₃ perovskite was synthesised with relatively high surface area (15.5 m²/g) at low temperature (650 °C) by the combustion method using polyvinyl alcohol (PVA) and corresponding metal nitrates. The perovskite was characterised by X-ray diffraction, thermogravimetric and differential thermal analysis, field emission scanning electron microscopy and Brunauer–Emmett–Teller technique. The optimal preparative conditions were PVA/metals 3:1 by mole, pH = 3–4 and 80 °C for gel formation. Perovskite exhibits a good catalytic activity in total oxidation of m-xylene at the low temperature of reaction (250 °C).     

Preparation and Properties of Al2O3-doping LiNi1/3Co1/3Mn1/3O2 Cathode Materials

LiNi_1/3Co_1/3-xMn_1/3O₂ doped with Al₂O₃ (x = 0%, 2.5%, 5%, 10%) was synthesized by co-precipitation of Ni, Co, and Mn acetates. The influence of Al₂O₃ doping on structure and electrochemical performances of LiNi_1/3Co_1/3Mn_1/3O₂ was studied using X-ray diffraction (XRD) analysis, scanning electron microscopy, charge/discharge tester, and electrochemical workstation. It was found that the materials achieved the best electrochemical properties when x was 5%. The first discharge capacity was 156.3 mAh · g^?1(0.1 C, 2.0–4.8 V), which was close to the un-doped sample (156.8 mAh · g^?1). After 20 cycles, the capacity retention ratios at the C-ratios of 0.1C, 0.2C, and 0.5 C were 96.1%, 94.9%, and 89.4%, respectively, while the capacity retention ratios of the un-doped samples were only 92.6% (0.1 C), 91.8% (0.2 C), and 88.7% (0.5C). The alternating current impedance shows that the charge transfer in the electrode interface was the easiest when x was 5%.     

Synthesis,Spectral Investigations,and Thermal Stability of [60]Fullerene Complexes with TMTSF: 2(C60) · 2(TMTSF) · (C6H6), C60 · TMTSF · 2(CS2), and 2(C60) · 2(TMTSF) · (C6H5Cl)

Abstract

Molecular complexes of [60]fullerene with tetramethyltetraselenafulvalene (TMTSF): C₆₀ · (TMTSF) · 2(CS₂) (1), 2(C₆₀) · (2(TMTSF) · (C₆H₆) (2), and 2(C₆₀) · (2(TMTSF) · (C₆H₅Cl) (3) have been synthesized and their thermal stability and IR spectra vs. light polarization and temperature have been performed.     

Single-Step Synthesis of Sr4V2O6Fe2As2: The Blocking Layer Based Potential Future Superconductor

We report synthesis, structural details and transport measurements on Sr₄V₂O₆Fe₂As₂. Namely, the stoichiometric amounts of V₂O₅+1/2×SrO₂+7/2×Sr+2×FeAs are weighed mixed, ground thoroughly and palletized in rectangular form in a glove box in high purity Ar atmosphere. The pellet is further sealed in an evacuated (10^?5 torr) quartz tube and put for heat treatments at 750 and 1150°C in a single step for 12 and 36 hours respectively. Finally the quartz ampoule is allowed to cool naturally to room temperature. The as-synthesized sample is black in color. The compound crystallized in P4/nmm space group with lattice parameters a=b=3.925 Å and c=15.870 Å. Also seen are some small impurity lines. The compound did not exhibit superconductivity but instead a spin density wave (SDW) like metallic step at around 175 K is seen in R(T) measurements. Principally in [FeAs]^?1{Sr₄V₂O₆}^C[FeAs]^?1 the net value of blocking layer charge C must be either less or more than 2, to let it be electron or hole type superconductor respectively. Efforts are under way to achieve superconductivity in the studied system.     

Production and characterization of AA6082-(Si3N4 + Gr) stir cast hybrid composites

The present research work emphasizes the development of hybrid aluminum (AA6082) matrix composites (HAMCs) reinforced with different weight percentages (wt.%) of ball-milled (silicon nitride (Si₃N₄) + graphite (Gr)) ceramic particulates by conventional stir casting process. Si₃N₄ and Gr are ball milled to obtain a definite density of combined powder. The weight percentage of ball-milled ceramic powder is varied from 0 to 12 wt.% in a stage of 3%. The microstructures as well as mechanical properties of the fabricated hybrid composites are analyzed. The scanning electron micrograph reveals the uniform distribution of ball-milled (Si₃N₄ + Gr) ceramic particulates in the aluminum matrix. The distribution of ball-milled (Si₃N₄ + Gr) ceramic particulates has also been analyzed with x-ray diffraction (XRD) technique. Both the hardness and ultimate tensile strength have enhanced with a reduction in percentage elongation with increase in weight percentage of ball-milled (Si₃N₄ + Gr) ceramic particulates in the aluminum matrix.     

Singlet‐Triplet Transition in the C60 2− Dianion

Abstract

The C₆₀ complexes with decamethylcobaltocene: (Cp*₂Co)₂C₆₀(C₆H₄Cl₂, C₆H₅CN)₂ (1) and [K · (18‐crown‐6)]₂ · C₆₀ · (DMF)₄ (2) have been obtained as single crystals by the diffusion method. The IR‐ and UV‐VIS‐NIR‐spectra justify the formation of the C₆₀ ^2? dianions in these salts. EPR measurements show that the low temperature signals of 1 in the 4–140 K range and 2 in the 4–60 K range have intensity corresponding only to 0.4% and 3.5% from total C₆₀. Because of this, most of the complexes are EPR silent, and, consequently, C₆₀ ^2? has a diamagnetic singlet (S = 0) state in these temperature ranges. The appearance of a broad EPR signal in the spectum of 1 above 140 K and 2 above ～60 K is assigned to a thermal population of a close lying excited triplet (S = 1) state. The singlet–triplet energy gap for C₆₀ ^2? in solid 1 and 2 was estimated to be 730 ± 10 and 300 ± 10 cm^?1.     

Selection of scattering enhancement particles for improving color homogeneity and luminous flux of phosphor-converted LEDs

Abstract

At the present time, color homogeneity and luminous flux are the two essentials utilized to appraise high-quality phosphor-converted LEDs (pcLEDs). In this paper, we present the search for the optimal selection among scattering enhancement particles (SEPs) to apply to improve these essentials for pcLEDs having correlated color temperature of 8500 K. The interested contenders include CaCO₃, CaF₂, SiO₂, and TiO₂. Each of them is added to yellow phosphor compounding (Y₃Al₅O₁₂:Ce³⁺). Firstly, the LightTools program is employed to do the optical simulations. Secondly, the obtained results are verified and analyzed based on Mie scattering theory. The scattering computation of SEPs includes the scattering coefficients, the anisotropic scattering, the reduced scattering and the scattering amplitudes at 455 and 595 nm. It is observed that TiO₂ particles provide the highest color homogeneity among the SEPs but the luminous flux reduces significantly as its concentration increases. By using CaCO₃ particles, the highest luminous flux of 792 lm is obtained. CaCO₃ particles can also reduce the deviation of color correlated temperature to 620 K at 30% concentration. Therefore, CaCO₃ particles should be selected to enhance both color homogeneity and luminous flux.     

Hydrothermal synthesis and photoluminescence properties of cerium-doped cadmium tungstate nanophosphor

The present paper reports synthesis and photoluminescence studies of cadmium tungstate (CdWO₄) and cerium-doped cadmium tungstate. The samples were synthesised by low cost and low temperature hydrothermal method and characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence analysis. XRD pattern reveals that the CdWO₄ has monoclinic wolframite structure. The FTIR spectrum of cerium-doped CdWO₄ exhibits broadband below 700 cm^?1 which is due to the δ (Ce–O–C) mode. The TEM images show that size of particle is approximately 60–120 nm in both samples. A broad intense peak was observed at 474 nm when the samples were excited with 263 nm. A broad intense peak was observed at 475 nm when the samples were excited with 600 nm. The intensity of the 474 nm peak decreases with increase in cerium doping concentration. The observation of 475 nm peak when excited with 600 nm is upconversion luminescence. This upconversion emission is due to energy transfer upconversion process involving Cd²⁺ ions and [WO₆]^6? ions. Ce³⁺ ion is responsible for the peak shift of 6 nm.     

Electroforming of TiB2-Reinforced Copper Matrix Electrode for EDM

TiB₂ particle-reinforced copper matrix composite is electroformed in copper sulfate on stainless steel plate. The impact of the particle content in electroforming solution on the surface morphology, hardness, and electrical conductivity of the electroformed composite are studied, and the influence of electroforming current density on the effective content of particles in the composite is also analyzed. The results show that when the content of particles in electroforming solution is 25 g/L, the current density is 4 A/dm², particles in the electroformed composite are well-distributed, and the average grain diameter can be reduced to 20 µm. The microhardness of Cu/TiB₂ composite reinforced by particles with diameter of 3 µm is 25% higher than that of electroformed copper, and its conductivity remains 86% of the copper.