Formation, Defect Structure, and Electrical Properties of La3+ -Doped M-Type Calcium Ferrite Prepared by Coprecipitation

The reaction process and the optimum preparation conditions of the M-type calcium ferrite by the chemically coprecipitated method were studied using differential thermal, thermogravimetric, and X-ray analyses. It is found that the formation mechanism using the coprecipitated method is the same as that of the solid-state reaction, and the precursor CaO·2Fe₂O₃ cannot be avoided, but it could be formed at lower temperature. The defect structure based on the replacement of Ca²⁺ by La³⁺, the charge compensation by Fe²⁺, and release of oxygen is supported by the DTA/TGA and conductivity data. The conductivity is suggested to occur through a hopping mechanism. The estimated values of the activation energy based on the small-polaron conduction are 0.34 to 0.44 eV in the high-temperature region and 0.029 to 0.049 eV in the low-temperature region. The preexponential factor depends exponentially on the fraction of the M phase in the specimen.     

Study of poly(vinyl alcohol)/titanium oxide composite polymer membranes and their application on alkaline direct alcohol fuel cell

The novel poly(vinyl alcohol)/titanium oxide (PVA/TiO₂) composite polymer membrane was prepared using a solution casting method. The characteristic properties of the PVA/TiO₂ composite polymer membrane were investigated by thermal gravimetric analysis (TGA), a scanning electron microscopy (SEM), a micro-Raman spectroscopy, a methanol permeability measurement and the AC impedance method. An alkaline direct alcohol (methanol, ethanol and isopropanol) fuel cell (DAFC), consisting of an air cathode based on MnO₂/C inks, an anode based on PtRu (1:1) black and a PVA/TiO₂ composite polymer membrane, was assembled and examined for the first time. The results indicate that the alkaline DAFC comprised of a cheap, non-perfluorinated PVA/TiO₂ composite polymer membrane shows an improved electrochemical performances. The maximum power densities of alkaline DAFCs with 4 M KOH + 2 M CH₃OH, 2 M C₂H₅OH and 2 M isopropanol (IPA) solutions at room temperature and ambient air are 9.25, 8.00, and 5.45 mW cm⁻², respectively. As a result, methanol shows the highest maximum power density among three alcohols. The PVA/TiO₂ composite polymer membrane with the permeability values in the order of 10⁻⁷ to 10⁻⁸ cm² s⁻¹ is a potential candidate for use on alkaline DAFCs.     

A direct borohydride fuel cell based on poly(vinyl alcohol)/hydroxyapatite composite polymer electrolyte membrane

A new poly(vinyl alcohol)/hydroxyapatite (PVA/HAP) composite polymer membrane was synthesized using a solution casting method. Alkaline direct borohydride fuel cells (DBFCs), consisting of an air cathode based on MnO₂/C inks on Ni-foam, anodes based on PtRu black and Au catalysts on Ni-foam, and the PVA/HAP composite polymer membrane, were assembled and investigated for the first time. It was demonstrated that the alkaline direct borohydride fuel cell comprised of this low-cost PVA/HAP composite polymer membrane showed good electrochemical performance. As a result, the maximum power density of the alkaline DBFC based on the PtRu anode (45 mW cm⁻²) proved higher than that of the DBFC based on the Au anode (33 mW cm⁻²) in a 4 M KOH + 1 M KBH₄ solution at ambient conditions. This novel PVA/HAP composite polymer electrolyte membrane with high ionic conductivity at the order of 10⁻² S cm⁻¹ has great potential for alkaline DBFC applications.     

The temperature-composition phase diagram and the miscibility gap of Hg1-xCdxTe solid solutions by dynamic mass-loss measurements

The dynamic mass-loss technique has been employed to measure Hg partial pressures over Te-saturated Hg_1-xCd_xTe solid solutions with x = 0.40, 0.54, and 0.70 in the 10^-1 to 10^-4 atm range. The relative chemical potentials of HgTe in Hg_1-xCd_xTe solid solutions have been calculated using the measured Hg partial pressures at temperatures below 413°C, and fitted into an analytical expression. A Gibbs-Duhem integration yielded the relative chemical potentials of CdTe. By combining the relative chemical potentials of the binary components HgTe and CdTe, an expression for the Gibbs free energy of mixing was derived. The binodal (miscibility gap) and spinodal curves of the Hg_1-xCd_xTe solid solutions have been established with the critical temperature and composition of 221°C and Hg_0.40Cd_0.60Te.     

Iterative learning controller synthesis using FIR models for batch processes

Adaptive iterative learning control based on the measured input-output data is proposed to solve the traditional iterative learning control problem in the batch process. It produces a control law with self-tuning capability by combining a batch-to-batch model estimation procedure with the control design technique. To build the unknown batch operation system, the finite impulse response (FIR) model with the lifted system is constructed for easy construction of a recursive least squares algorithm. It can identify the pattern of the current operation batch. The proposed model reference control method is applied to feedback control of the lifted system. It finds an appropriate control input so that the desired performance of the batch output can track the prescribed finite-time trajectory by iterative trials. Furthermore, on-line tracking control is developed to explore the possible adjustments of the future input trajectories within a batch. This can remove the disturbances in the current batch rather than the next batch trial and keep the product specifications consistent at the end of each batch. To validate the theoretical findings of the proposed strategies, two simulation problems are investigated.     

Observation of phase separation in Hg1−xCdxTe solid solutions by low incident angle x-ray diffraction

The low incident angle (surface analysis) and the conventional wide angle (bulk analysis) x-ray diffraction techniques were employed to investigate the existence of a miscibility gap in the Hg_1−xCd_xTe system. Samples of initial composition Hg_0.46Cd_0.54Te were annealed at 140 and 400°C, respectively, for four weeks. The diffraction planes (531) and (642) have been selected for the x-ray diffraction analysis. The results of this work provide the first, direct experimental evidence for the existence of a miscibility gap at lower temperature in the Hg_1−xCd_xTe system. The phase separation occurs primarily in a thin surface layer at 140°C and is reversible after annealing at 530°C. The compositions of the two compounds at the tie-line at 140°C are Hg_0.22Cd_0.78Te and Hg_0.63Cd_0.37Te.     

Formation Mechanisms of La3+-Doped CaO·6Fe2O3 with the Magnetoplumbite Structue

Several experiments were conducted to investigate the formation mechanisms of the magnetoplumbite phase in La³⁺-doped CaO 6Fe₂O₃. It is shown that the CaO·2Fe₂O₃ phase plays a crucial role in forming the magnetoplumbite phase. The formation mechanisms are proposed and verified.     

Supercritical fluid-assisted dispersion of C.I. pigment violet 23 in an organic medium

This study investigates the dispersions of 1 wt.% C.I. pigment violet 23 particles in propylene glycol monomethyl ether acetate (PGMEA) using a supercritical fluid-assisted dispersion process (SFAD). The favorable formulation of dispersants is a blend of 40% AJISPER PB821 and 10% FC-4430 in a PGMEA medium. The SFAD processes holding at the supercritical state are good for improving dispersion. Under favorable conditions, 328.2 K and 20 MPa, the mean size of pigment dispersoid with blended dispersants in PGMEA is as small as 175 nm that meets the required range of 100-200 nm in industrial applications. The TGA analyses indicate the adsorbed amount of blended dispersants (40% PB821 and 10% 4430) on the surface of pigment particles in the PGMEA medium is about 1.77 mg/m². Thus, the transmittances, color analyses, and TEM images of pigment dispersoids prove that the SFAD process can disperse pigment particles in PGMEA.     

Optical properties of CdS<Subscript>0.2</Subscript>Se<Subscript>0.8</Subscript>:V

We report here a comparison between two methods for calculating the index of refraction of the CdS_xSe_1−x alloy system and a calculation of the phase-matching angles for second harmonic generation for this system. Analytical expressions for the index and the birefringence of all x values are presented. The low-temperature photoluminescence spectrum has been measured and reveals a native defect at 1.45 eV and a peak at 1.8 eV caused by the vanadium dopant, as well as an exciton peak at 2.24 eV. The transmission spectrum displays three peaks due to the vanadium dopant at 0.979 eV, 1.087 eV, and 1.181 eV. The birefringence has been measured for x = 0.2 from 1 μm to 14 μm and varies from 0.0185 to 0.0125.     

Preparation of a PVA/HAP composite polymer membrane for a direct ethanol fuel cell (DEFC)

A novel PVA/Hydroxyapatite (HAP) composite polymer membrane was prepared by the direct blend process and solution casting method. The characteristic properties of the PVA/HAP composite polymer membranes were investigated using thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), micro-Raman spectroscopy and the AC impedance method. An alkaline direct ethanol fuel cell, consisting of an air cathode with MnO₂ carbon inks based on Ni-foam, an anode with PtRu black on Ni-foam, and the PVA/HAP composite polymer membrane, was assembled and investigated. It was found that the alkaline direct ethanol fuel cell comprising of a novel cheap PVA/HAP composite polymer membrane showed an improved electrochemical performance in ambient temperature and air. As a result, the maximum power density of the alkaline DEFC, using a PtRu anode based on Ni-foam (10.74 mW cm⁻²), is higher than that of DEFC using an E-TEK PtRu anode based on carbon (7.56 mW cm⁻²) in an 8M KOH + 2M C₂H₅OH solution at ambient temperature and air. These PVA/HAP composite polymer membranes are a potential candidate for alkaline DEFC applications.