Structural and transport properties of cubic spinel ZnCo2O4 thin films grown by reactive magnetron sputtering

We report on the growth of cubic spinel ZnCo₂O₄ thin films by reactive magnetron sputtering and bipolarity of their conduction type by tuning of oxygen partial pressure ratio in the sputtering gas mixture. Crystal structure of zinc cobalt oxide films sputtered in an oxygen partial pressure ratio of 90% was found to change from wurtzite Zn_1−xCo_xO to spinel ZnCo₂O₄ with an increase of the sputtering power ratio between the Co and Zn metal targets, D_Co/D_Zn, from 0.1 to 2.2. For a fixed D_Co/D_Zn of 2.0 yielding single-phase spinel ZnCo₂O₄ films, the conduction type was found to be dependent on the oxygen partial pressure ratio: n-type and p-type for the oxygen partial pressure ratio below ∼70% and above ∼85%, respectively. The electron and hole concentrations for the ZnCo₂O₄ films at 300 K were as high as 1.37×10²⁰ and 2.81×10²⁰ cm⁻³, respectively, with a mobility of more than 0.2 cm²/V s and a conductivity of more than 1.8 S cm⁻¹.     

Simultaneous recording of fringe patterns with one camera

A novel method to separate and simultaneously record the Moiré interferometry fringe patterns of three deformation fields with only one CCD camera is developed; details of its operation principle, key points and error analysis are presented. With this technique, the deformation inU, V andW fields can be measured simultaneously, so dynamic test with comprehensive information can be performed. The advantage of this technique over other similar techniques lies in its simplicity, easy implementation and low cost. An application of this technique is given to show its feasibility. Technical problems that may be caused with this technique are also analyzed.     

Radio frequency characteristics of Fe-filled carbon nanotube film

The conduction noise suppression in radio frequency region using film type of the Fe-filled carbon nanotubes and its epoxy composite was evaluated on a coplanar waveguide. Fe in carbon nanotubes have shown α-Fe crystalline structure and had a coercivity of 650 Oe. The magnitudes of the signal attenuation of Fe-filled carbon nanotubes on coplanar waveguide were shown in the range of about 10–18 dB/cm at 20 GHz (the stop-band frequency region). The power losses of these films exhibited 65–85% at 20 GHz in the stop-band frequency.     

Surface and Through Curing Studies by ATR

The degrees of surface and through cure of UV curable acrylate-based pigmented systems were studied by using ATR(Attenuated Total Reflection) spectroscopy. This paper describes curing investigations of ink coating layer on optical fibers.     

A note on differential operators of infinite order

A sufficient condition for entire functions f and g to be such that the series ∑_m=0^∞f^(m)(0)g^(m)/m! represents an entire function is established; and in that case, the growth of the resulting function is described.     

The thermodynamics of synergistic solvent extraction of Zn(II) with 1-phenyl-3- methyl-4-benzoyl-pyrazole-5-one

The synergistic extraction of Zn(II) has been studied in the PMBP—TBP system (where PMBP = 1-phenyl-3-methyl-4-benzoyl-pyrazole-5-one and TBP = tri-n- butyl phosphate) at various temperatures using a radiochemical technique. The thermodynamic parameters for the reactions involved support the mechanism for the synergistic extraction in which the 5-coordinate monohydrated Zn(PMBP) ₂ chelate exchanges a water molecule for TBP.     

Effect of photoreactivity of polyimide on the molecular orientation of liquid crystals on photoreactive polymer/polyimide blends

We prepared blend alignment layers from polymethacrylate with coumarin side chains (PMA-g-coumarin) and polyimides for the orientation of liquid crystals (LCs) using linearly polarized ultraviolet (UV) irradiation. We used two different polyimides, namely 4,4'-(hexafluoro-isopropylidene) diphthalic anhydride-3,5-diamino-benzoic acid (6FDA-DBA) and pyromellitic dianhydride-4,4'-oxydianiline (PMDA-ODA). It was found that the molecular orientation of the LC depended on the type of polyimide in the blend alignment layer. The thermal stability of the LC orientation was enhanced regardless of the type of polyimide, while the direction of LC orientation was different for each type of polyimide. The photoreactivity of the polyimide was a very important factor in determining the molecular orientation of the LC on the blend alignment layer. This may be attributed to the different mechanisms of LC orientation on PMA-g-coumarin and polyimide induced by the polarized UV irradiation. The direction of the LC orientation could be changed by controlling the photoreaction of the polyimides using the appropriate UV filter for the polarized UV irradiation.     

Microencapsulation of cholesteryl alkanoate by polymerization‐induced phase separation and its association with drugs

A new microencapsulation technique is presented in which cholesteryl nonanoate (CN)/poly(methyl methacrylate) (PMMA) microcapsules are produced by the induction of phase separation between CN and PMMA within the droplets during the polymerization. The concentration of CN is the most important factor determining the final morphology of the microcapsules. For example, a polynuclear type is obtained at a low concentration (<20 wt %), a mononuclear type is obtained at a medium concentration (20–30 wt %), and an irregular phase is obtained at a high concentration (>40 wt %). To evaluate the effectiveness of the technique for stabilizing an unstable drug, we selected retinol (vitamin A) as a model drug and loaded it into the CN/PMMA microcapsules. We used a process called solute codiffusion, in which a fine solvent emulsion containing the retinol was diffused uniformly into the CN/PMMA microcapsules. The loading efficiency of retinol was predicted successfully with the aid of a thermodynamic equation. In the thermal stability test of retinol, we found that an effective association with the CN phase was the most important factor determining the limit of its molecular stability. The technique reported in this article has great potential for the microencapsulation of soft materials via a simple process and for the stabilization of unstable drugs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2202–2213, 2004     

The fabrication and characterization of ZnO UV detector

ZnO films were deposited on GaAs substrates by radio frequency (rf) magnetron sputtering followed by an ambient-controlled heat treatment process for arsenic doping. In Hall measurements, the As-doped ZnO films showed the characteristics of p-type semiconductor. The ZnO thin film p–n homojuctions were then fabricated to investigate the electrical properties of the films. The p–n homojunctions exhibited the distinct rectifying current–voltage (I–V) characteristics. The turn-on voltage was measured to be 3.0 V under the forward bias. When ultraviolet (UV) light (λ = 325 nm) was irradiated on the p–n homojunction, photocurrent of 2 mA was detected. Based on these results, it is proposed that the p–n homojunction herein is a potential candidate for UV photodetector and optical devices.     

Simultaneous two-line operation of a CW CO laser with arbitrary choice of laser transitions

An experimental scheme is discussed, by which we can operate a CO laser at two individually selectable lines from the same gain tube. There are virtually no restrictions on the wavelength separation of the two lines within the manifold of the available lasing transitions. Experimental verifications of this scheme are described and the mutual influence of the simultaneous laser operation is discussed.Dedicated to Professor Siegfried Penselin on the occasion of his 60th birthday