Properties and mechanism of solar absorber CdTe thin film synthesis by unipolar galvanic pulsed electrodeposition

Electrochemical deposition of CdTe semiconductor thin films over transparent conducting glass substrates by sequential unipolar current pulses is described. The magnitude of pulsed current and pulse periodicity affects the crystalline structure, morphology, optical absorbance and composition of CdTe films. CdTe films formed under high magnitude pulsed current density ~5–15 mA cm⁻² are crystalline with dominant cubic structure having (111) plane oriented parallel to the substrate. Stoichiometric CdTe film growth occurs with current pulses of short 25–300 ms periodicity and 3–50 ms duration. A mechanism of the CdTe growth involving in situ cathodic tellurization process step involving H₂Te formation and reaction with electrochemically deposited Cd monolayer is described. CdTe film growth in the pulsed electrodeposition occurs under mass transport conditions under strong influence of high magnitude pulsed current. This results in much higher growth rates ~5–8 μm h⁻¹ for CdTe films which is attractive for CdTe solar cells in a production environment.     

Promoting Effect of Triglyme on Lean NO<Subscript>x</Subscript> Reduction Over Ag/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Abstract  

The highly oxygenated hydrocarbon triethylene glycol dimethyl ether or triglyme (CH₃O–(C₂H₄O–)₃CH₃) was found to efficiently reduce NO_x under lean conditions over Ag/Al₂O₃, but gave a low NO_x conversion over Cu-ZSM-5. Furthermore, triglyme showed an extraordinary promoting effect when added together with propene as reducing agent for NO_x over Ag/Al₂O₃ at low temperature. This is most likely due to that triglyme promotes the activation of propene.     

Synthesis and characterization of novel comb-type amphiphilic graft copolymers containing polypropylene and polyethylene glycol

Amphiphilic comb-type graft copolymers containing polypropylene (PP) and polyethylene glycol (PEG) have been prepared. Polypropylene-g-polyethylene glycol comb-type thermoplastic amphiphilic copolymers were synthesized by the reaction between chlorinated polypropylene and polyethylene glycol in the presence of a base via a “grafting to” technique. A series of graft copolymers containing PEGs with molecular weights of 600 and 2,000 Da in the range of 4–34 mol% PEG were obtained. The amphiphilic graft copolymers with PEG segments in range between 20 and 30 mol% PEG displayed good film properties with elongation at break 275–440%. The hydrophilicity of the amphiphilic copolymers increases with the increasing PEG content in the copolymer while the mechanical properties decrease. Therefore, PP-g-PEG2000 with PEG contents in the range of 20–30 mol% PEG should be useful for medical and industrial applications where good film properties are needed.     

Synthesis of polymer having β,β-triketone unit in the main chain and its copper (II) complex

Summary A novel polymer having β,β-triketone unit in the main chain was prepared by polycondensation of triethylene glycol bis(p-butoxycarbonylphenyl) ether (1) with triethylene glycol bis(p-acetylacetophenyl) ether (4). The obtained polymer was soluble in CHCl₃, DMF, and DMSO. The structure of the polymer was confirmed by ¹H-NMR. Insoluble brownish yellow copper (II) chelate was obtained by adding a methanol solution of copper (II) acetate to a chloroform solution of the polymer. The IR analysis and the measurement of copper content by iodometric titration showed the quantitative formation of binuclear copper (II) complex. Received: 20 March 1998/Accepted: 17 April 1998     

A new core–shell type fluorinated acrylic and siliconated polyurethane hybrid emulsion

A novel core–shell type fluorinated acrylic and siliconated polyurethane (FSiPUA) hybrid emulsion was prepared by seeded emulsion polymerization using siliconated polyurethane (SiPU) as a seed and forming the structure with SiPU as a shell and the copolymer of butyl acrylate (BA) with 2,2,2-trifluoroethylmethacrylate (TFEMA) as a core. SiPU was synthesized using isophorone diisocyanate (IPDI), polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), dihydroxybutyl-terminated polydimethylsiloxane (PDMS), dimethylol propionic acid (DMPA), 1,6-hexanediol (HDO) and triethylamine (TEA). The contents of siloxane and fluorine were determined according to the feed ratio. Fourier transform infrared spectroscopy (FTIR) was used to identify the chain structure of SiPU and FSiPUA. Investigation of transmission electron microscopy (TEM) confirmed the core–shell structure of FSiPUA emulsion and gave the particle size at about 50 nm. The measurement results of water contact angles and the solvent absorptions in water and n-octane for cured films showed that the water and the oil repellency for FSiPUA had been improved significantly with a suitable content of fluorine and siloxane.     

Corrosion performance of chemically synthesized poly(aniline-co-o-toluidine) copolymer coating on mild steel

A soluble copolymer from aniline and o-toluidine [poly(aniline-co-o-toluidine)] was synthesized by chemical oxidative copolymerization using ammonium persulphate as an oxidant in hydrochloride aqueous medium. The resultant copolymer was characterized by Fourier Transform Infrared (FTIR) spectroscopy and chemically deposited on mild steel specimens using N-methyl-2-pyrrolidone (NMP) as solvent via solution evaporation method. The anticorrosive properties of copolymer coating was investigated in major corrosive environments, such as 0.1 M HCl, 5% NaCl solution, artificial seawater, distilled water and open atmosphere by conducting various corrosion tests which include: immersion test, open circuit potential (OCP) measurements, potentiodynamic polarization measurements and atmospheric exposure test. The corrosion performance of copolymer coating was also compared separately with polyaniline (PANi) and poly(o-toluidine) (POT) homopolymer coatings. The surface morphologies of polymer coatings were evaluated using scanning electron microscopy (SEM). The synthesized copolymer exhibited excellent protection against mild steel corrosion; the protection efficiency being in the range of 78–94% after 30 days of immersion. The corrosion performance of copolymer in 5% NaCl and artificial seawater was comparable, which was only marginally better than in 0.1 M HCl. In general, the performance of copolymer coating was found to be better than that of homopolymer coatings.     

Electrochemical synthesis and characterization of poly(pyrrole-co-o-toluidine)

The electrochemical polymerization of o-toluidine has been investigated in oxalic acid solution. It was shown that the oxidation of monomer could be achieved but this process does not yield a stable, homogenous polymer film on either platinum or mild steel electrodes. Therefore the copolymerization between pyrrole and o-toluidine has been studied as an alternative method for obtaining good quality coating (low permeability and water mobility, high stability), which could also be easily synthesized on steel. For this aim, various monomer feed ratio solutions of pyrrole:o-toluidine 9:1, 8:2 and 7:3 have been examined, in aqueous oxalic acid solution. By using cyclic voltammetry technique, copolymer films were realized on platinum and steel, successfully. The temperature of synthesis solution was found to have a vital role on polymerization and film growth, as much as the monomer feed ratio. The synthesis of homogenous copolymer film could only be achieved under ≤25 °C conditions with using the 9:1 ratio, while the 8:2 ratios could only produce stable films below 5 °C. As the amount of o-toludine increased the required temperature value decreased further, 7:3 ratio could only give a stable copolymer film below 2 °C. The characterization of deposited copolymer coating has been realized by using SEM micrographs, UV–vis and FT-IR spectroscopy techniques and cyclic voltammetry. The protective behaviour of these coatings was also investigated against mild steel corrosion in 3.5% NaCl solution, by means of electrochemical impedance spectroscopy (EIS) and anodic polarization curves. It was found that the monomer feed 8:2 ratio gave the most effective coating against the corrosion of mild steel.     

Synthesis, characterization, and antibacterial activity of metal nanoparticles embedded into amphiphilic comb-type graft copolymers

The synthesis, spectroscopic characterization, and antimicrobial efficiency of gold and silver nanoparticles embedded in novel amphiphilic comb-type graft copolymers having good film-forming properties have been described. Amphiphilic comb-type graft copolymers were synthesized by the reaction of chlorinated polypropylene (PP) (M _w = 140,000 Da) with polyethylene glycol (PEG) (M _n  = 2,000 Da) at different molar ratios. Metal nanoparticles embedded graft copolymers were prepared by reducing solutions of the salts of silver or gold and the copolymer in tetrahydrofuran. The optical properties of the metal nanoparticle embedded copolymers were determined by using UV–visible spectroscopy. Surface plasmon resonance (SPR) of the gold and silver nanoparticle embedded copolymers in toluene was observed at a maximum wavelength (λ_max) of 428 and 551 nm in the UV–VIS absorption spectra, respectively. The average particle diameters of the gold and silver nanoparticles were found to be 50 nm from the high resolution scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Amphiphilic polymer films containing silver and gold nanoparticles were found to be highly antimicrobial by virtue of their antiseptic properties to Escherichia coli and Staphylococcus aureus.     

High Brightness Green Light-Emitting Diode Based on Silole-Containing Polyfluorenes

A novel silole-containing polyfuorene (PSFN) was successfully synthesized by palladium(0)-catalyzed Suziki coupling reactions. Optoelectronic properties of the copolymer were characterized by NMR, UV absorption, photoluminescence, and electroluminescence (EL). The film of the copolymer showed silole-dominant green emission. An EL device of the copolymer with a sandwich configuration of ITO/Polymer/Al displayed exclusive silole emission, which peaked at ~532 nm with the CIE coordinate of (0.33, 0.54). The polymer layer contained a conjugated silole-containing polyfluorene that emits green light, trimethylolpropane trimethacrylate, a low vapor pressure highly crosslinkable liquid, and lithium trifluoromethane sulfonate at a weight ratio of 20:5:1. A dynamic p–i–n junction was formed in thin films of light-emitting polymers admixed with an ionically conductive medium. The PLEC device was turned on at 8 V and the brightness reached up to 2000 cd/m² at 12 V.     

Use of photodegradable inhibitors in UV-curable compositions to form polymeric 2D-structures by visible light

The process of two-wave photopolymerization of a UV-curable composition with an optically degrading inhibitor is considered. By numerical simulation, it is shown that in the composition layer uniformly exposed to UV-radiation, such systems allow getting segments with different conversion under the action of inhomogeneous visible light. Based on the data on the photopolymerization kinetics of the compositions from triethylene glycol dimethacrylate (TEGDMA) and bisphenol-A glycidyl dimethacrylate (bis-GMA) with the UV-initiator 2,2-dimethoxy-2-phenylacetophenone (DMPA), it was shown that 3,5-di-tert-butyl-o-benzoquinone (35Q) with N,N-dimethylaniline (DMA, “Aldrich”, 99%) can serve as an inhibitor that degrades under action of visible radiation. Combining inhomogeneous visible light generated with a conventional DLP-projector and uniform UV-radiation of LED (365 nm) the two-wave lithographic process was implemented to create polymeric 2D-structures in 20 μm layer of the compositions from TEGDMA (70)/bis-GMA (30)/DMPA (0.05 wt%)/35Q (0.5 wt%)/DMA (1 wt%).     

Preparation and electrochemical properties of an electropolymerized polyacrylamide-based cross-linking copolymer film on 6063 Al alloy

An acrylamide-based cross-linking copolymer film was electrodeposited on 6063 Al alloy using ethylene glycol maleic rosinate acrylate (EGMRA) as the cross-linking agent. The corrosion resistance of polyacrylamide (PAA)-based films in the absence and presence of EGMRA was evaluated in 3.5 wt.% NaCl solution through polarization curves and electrochemical impedance spectroscopy. Compared with the uncoated Al alloy and electrodeposited film, the cross-linked film provided more effective protection for the Al alloy. The chemical structures and morphologies of the copolymer films were, respectively, analyzed using Fourier-transform infrared spectroscopy and scanning electron microscopy. Results confirmed that PAA-based cross-linking copolymer films were deposited on 6063 Al alloy.     

Reactions of unsaturated fatty alcohols. X. Preparation of some copolymers of nonconjugated linseed vinyl ether

Summary Vinyl ethers were prepared from benzyl, 2-phenylethyl, 3-phenylpropyl, 2-benzyloxyethyl, 2-(para-tertiary-butylphenoxy)-ethyl, tetrahydrofurfuryl, and 2-cyanoethyl alcohols. The vinyl ethers, as well as 1-methoxy-1,3-butadiene and cyclohexyl vinyl ether, when copolymerized with nonconjugated linseed vinyl ether produced viscous liquids that baked to films of moderate hardness and with fair resistance to alkali and acid. These copolymer films offered little improvement in hardness over similarly prepared films from nonconjugated linseed vinyl ether homopolymer. Baked films of nonconjugated linseed-2- (para-tertiary-butylphenoxy) ethyl vinyl ether copolymers had improved alkali resistance over the homopolymer baked films and were considered to be the best of the copolymer films studied. Presented at fall meeting, American Oil Chemists' Society, Los Angeles, Calif., September 28–30, 1959. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Optical and structural study of thin film of polyazomethine with triphenylamine unit prepared via spin-coating method

A conjugated aromatic polyazomethine (PAZ) with triphenylamine (TPA) unit in the main chain was obtained by high temperature solution polycondensation of diformyltriphenylamine with o-dianisidine (Fast blue B). A major feature of the PAZ containing TPA unit in the main chain is their complete solubility in comparison with PAZ obtained from terephthaldicarboxaldehyde and o-dianisidine (abbreviated hereinafter as PAZ1). Both polymers were analyzed by thermogravimetric analysis and FTIR spectroscopy. UV–vis absorption, X-ray diffraction (X-ray) and Atomic Force Microscopy (AFM) techniques were used to probe the optical properties and morphology of the thin films of the PAZ prepared by spin-coating technique on the glass and quartz substrate. Thickness of the PAZ thin layer on the glass and quartz substrate were determined by ellipsometer at the range 150–220 nm. The optical band gap value (E _g) of the thin films PAZ was detected at 2.45 eV. The current–voltage (I–V) characteristic was measured to confirm semiconductor nature of the PAZ.     

Characteristics of a tungsten film electrodeposited in a KF–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–WO<Subscript>3</Subscript> melt and preparation of W–Cu–W three-layered films for heat sink application

A tungsten film of 13 μm in thickness was obtained on a copper substrate by galvanostatic electrolysis at 30 mA cm⁻² for 40 min in a KF–B₂O₃–WO₃ (67:26:7 mol%) melt at 850 °C. By cross-sectional scanning electron microscopy observation and energy dispersive X-ray analysis, the tungsten layer was found to be compact and free from cracks, voids and melt inclusion. The X-ray diffractometry analysis revealed that the phase was α-tungsten, and that (222) plane was significantly oriented parallel to the substrate. By nanoindentation, its hardness was found to be 8.4 GPa, which was larger than that of single crystal tungsten. Its Young’s modulus was measured to be 410 GPa, which was similar with the reported value of single crystal tungsten. Its coefficient of linear thermal expansion and thermal conductivity were 4.5 × 10⁻⁶ K⁻¹ and 178 W m⁻¹ K⁻¹, respectively, which were similar values for the tungsten produced by a conventional powder metallurgy method. Finally, W–Cu–W three-layered films were prepared for a heat sink application. It was confirmed that a three-layered film having a desired coefficient of linear thermal expansion can be prepared easily by this new molten salt method.     

Influence of the glycol component in dibenzoate plasticizers on the properties of plasticized PVC films

A series of glycol dibenzoates was synthesized by transesterification of glycols with methyl benzoate. PVC films were prepared from suspension grade PVC and the dibenzoates at a constant content of the dibenzoates. The mechanical properties of the films were measured. In addition, the extractability and the absorption of various liquids was determined. The effect of the structure of the glycol component in the dibenzoates on the mechanical properties of the films and the plasticizing efficiency was investigated. Neopentyl glycol dibenzoate exhibits the highest plasticizing effect, followed by triethylene and ethylene glycol dibenzoates and the 2‐(n‐butyl)‐2‐ethyl‐1,3‐propanediol derivative. It was found that the ether linkages in the dibenzoates mainly contribute to the plasticization of PVC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 822–824, 2005     

Synthesis, Crystal Structure and Magnetic Properties of a Nickel(II) Coordination Polymer Based the V-Shaped Ligands

Abstract  

A new nickel(II) coordination polymer, Ni₂(DBA)₂(BIDPE)₂(H₂O) (1) (H₂DBA = 4,4′-methylenedibenzoic acid and BIDPE = 4,4′-bis(imidazole-l-yl)diphenyl ether), has been prepared by hydrothermal synthesis and structurally characterized by IR, elemental analysis, TGA and single crystal X-ray diffraction. Complex 1 features a one-dimensional chain structure based on triply bridged binuclear units, which is further interlinked into a higher-dimensional supramolecular framework by intermolecular weak interactions. Variable-temperature magnetic data shows weak antiferromagnetic behavior in 1.     

Characterization of polydimethylsiloxane–polyurethanes synthesized by graft or block copolymerizations

We synthesized polydimethylsiloxane–polyurethane dispersions modified with graft copolymerization (PDMS-G-PUDs) and polydimethylsiloxane–polyurethane dispersions modified with block copolymerization (PDMS-B-PUDs). We systematically investigated the effects of PDMS’s structure, content, and molecular weight on properties of copolymer including viscosity, particle size, and stability of dispersions as well as the properties of the film formed by dispersions including gloss, contact angle, water resistance, oil resistance, and mechanical properties. The results demonstrated that the viscosity, particle size, water resistance increased but gloss decreased with the increase of PDMS content and molecular weight. In addition, we compared the properties of PDMS-B-PUD films and PDMS-G-PUD films with the same amount of PDMS and similar molecular weight. PDMS-G-PUD films showed higher water and oil resistance, but lower gloss and poorer mechanical properties. Scanning electron microscopy–energy dispersive spectroscopy analysis (SEM–EDS) indicated that the films of PDMS-G-PUD had better microphase separation and PDMS surface enrichment.     

Electro-oxidation of ethanol on PtSn/CeO2–C electrocatalyst

PtSn/CeO₂–C electrocatalyst was prepared in a single step by an alcohol-reduction process using ethylene glycol as solvent and reducing agent and CeO₂ (15 wt%) and Vulcan XC72 (85 wt%) as supports. The performance for ethanol oxidation was investigated by cyclic voltammetry and in situ FTIR spectroscopy. The electrocatalytic activity of the PtSn/CeO₂–C electrocatalyst was higher than that of the PtSn/C electrocatalyst. FTIR studies for ethanol oxidation on PtSn/C electrocatalyst showed that acetaldehyde and acetic acid were the principal products formed, while on PtSn/CeO₂–C electrocatalyst the principal products formed were CO₂ and acetic acid.     

The effect of catalyst film thickness on the magnitude of the electrochemical promotion of catalytic reactions

The effect of catalyst film thickness on the magnitude of the effect of electrochemical promotion was investigated for the model catalytic reaction of C₂H₄ oxidation on porous Pt paste catalyst-electrodes deposited on YSZ. It was found that the catalytic rate enhancement ρ is up to 400 for thinner (0.2 μm) Pt films (40,000% rate enhancement) and gradually decreases to 50 for thicker (1 μm) films. The Faradaic efficiency Λ was found to increase moderately with increasing film thickness and to be described semiquantitatively by the ratio 2Fr _o/I ₀, where r _o is the unpromoted rate and I ₀ is the exchange current of the catalyst–electrolyte interface. The results are in good qualitative agreement with model predictions describing the diffusion and reaction of the backspillover O^2- species, which causes electrochemical promotion.     

Two Novel Bimetallic Cyano-Bridged Coordination Polymers Containing the 2,2′-(Ethylenedioxy)bis (Ethylamine): Syntheses,Structural, Thermal and Magnetic Properties

Two new cyano bridged bimetallic polymeric complexes, [Ni(edbea)Ni(CN)₄]·1/2H₂O (1) and [Cu(μ-edbea)(μ-CN)₂ Ni(CN)₂]·H₂O (2) [edbea = 2,2′-(ethylenedioxy)bis(ethylamine)] have been synthesized by adding metal chloride (M = Ni^II and Cu^II), and edbea into [Ni(CN)₄]²⁻ in water–ethanol solution and then characterized by elemental analysis, infrared (IR) and electron paramagnetic resonance (EPR) (for only complex 2) spectra, variable temperature magnetic measurement, and thermal gravimetric analysis. The X-ray diffraction crystal structure of complex 2 shows a 2D polymeric chain –edbea(N5,O1)–Cu1–N1C1–Ni(CN)2–C4N6–Cu1–(N6,O2) edbea– in which the Cu^II centers are linked by two cyano and one edbea. The powder EPR spectrum of the complex 2 has shown that Cu^II ions are located in rhombically distorted octahedral sites. The magnetic properties of the coordination polymers have been studied in temperature range of 15–300 K. The magnetic behaviors investigation of complexes 1 and 2 indicated the presence of a very weak antiferromagnetic interaction.