Brown Films Research Articles

Influence of shielding gas on the mechanical and metallurgical properties of DP-GMA-welded 5083-H321 aluminum alloy

In the present research, 6-mm-thick 5083-H321 aluminum alloy was joined by the double-pulsed gas metal arc welding (DP-GMAW) process. The objective was to investigate the influence of the shielding gas composition on the microstructure and properties of GMA welds. A macrostructural study indicated that the addition of nitrogen and oxygen to the argon shielding gas resulted in better weld penetration. Furthermore, the tensile strength and bending strength of the welds were improved when oxygen and nitrogen (at concentrations as high as approximately 0.1vol%) were added to the shielding gas; however, these properties were adversely affected when the oxygen and nitrogen contents were increased further. This behavior was attributed to the formation of excessive brown and black oxide films on the bead surface, the formation of intermetallic compounds in the weld metal, and the formation of thicker oxide layers on the bead surface with increasing nitrogen and oxygen contents in the argon-based shielding gas. Analysis by energy-dispersive X-ray spectroscopy revealed that most of these compounds are nitrides or oxides.

Liquefied agricultural residues for film elaboration

Agricultural residues (corn stover, corncob, vine shoots and blueberry tree pruning) with low added value were converted through liquefaction into liquefied products. Their capability to form films was evaluated. Results indicated that liquefied products production under liquefaction conditions is completely feasible with yields in the case of corn residues above 90%. The IOH and viscosities were in the range of 309–441mg of KOH/g and 0.16–0.19Pa·s, respectively. These values make the liquefied agricultural residues an interesting alternative to be considered as constituent in liquefied-based materials and composites elaboration. On the other hand, homogeneous, opaque and dark brown flexible films, using weight ratio of (liquefied agricultural residue/starch)/glycerol of (90/10)/30, were produced. The films obtained with corn residues as starting material showed adequate behavior considering physical and mechanical features. DMA measurements for liquefied corncob-films showed higher values of thermal and dynamic mechanical parameters (Tg: 112°C; E′: 42MPa until 110°C) compared to control film (starch/glycerol: 70/30), which showed a material with higher thermal stability. The results demonstrated the suitability in the conversion of different renewable and abundant resources into liquid form and their physico-chemical properties for first step film production, which might have interesting perspectives in polymer processing area for bioplastics development in agricultural applications.

Synthesis of thermally stable, wholly aromatic polyketones with 2,2′-dimethoxy-1,1′-binaphthyl-6,6′-diyl units through nanosized-palladium-cluster-catalyzed Suzuki–Miyaura coupling polymerization

Wholly aromatic polyketones with 2,2′-dimethoxy-1,1′-binaphthyl-6,6′-diyl units in the main chains were synthesized through Suzuki–Miyaura coupling polymerization catalyzed by nanosized palladium clusters, which were easily prepared from Pd(OAc)2, PPh3, K2CO3, and Bu4NOAc in 1,4-dioxane. The resulting polyketones have both high thermal stability (high Tg) and solubility in common organic solvents, such as CHCl3 and N,N-dimethylformamide (DMF). Flexible and pale brown films were obtained by casting from a CHCl3 solution.

Failure analysis of copper tube used in a refrigerating plant

This paper reports the failure analysis of a leaked copper tube used in a refrigerating plant for carrying polyol ester oil for lubrication and cooling of compressor bearings. Failure had occurred at the bent region of the tube in the form of a wide diametric crack. The crack was intergranular and filled with corrosion products. The failed region on the inner diameter side of the tube had red–brown and dull-black surface films which were identified as cuprous oxide. No degradation or decomposition of the lubricant oil was detected. The microscopic examination of the cross-section of the tube showed corrosion degradation on both the outer and inner diameter surfaces with similar morphology. The corrosion morphology consisted of pit tunnels with fine longitudinal cracks bridging individual pitted regions typical of ant-nest corrosion. A few cracks, at the bent region of the tube, had originated through the pits and propagated along the wall thickness. The failure was concluded to be due to ant-nest corrosion of copper in the presence of carboxylic acid. Organic compounds used during the fabrication and joining of the copper tubes, if not properly cleaned, may decompose to carboxylic acid in presence of air and moisture.

Influence of reduction processes on the colour and photochromism of amorphous mesoporous TiO2 thin films loaded with a silver salt

Silver nanoparticles were created inside mesoporous titania thin films by different reduction processes. We investigated the influence of the reduction method on the colour and photochromism of these amorphous TiO(2) films. The results highlight brown films by optical reduction, gray films by thermal reduction, and red, purple or orange films by chemical reduction. The different size distributions and localizations of the nanoparticles, characterized by UV-visible spectroscopy and electron microscopy, give various photochromic behaviours when exposed to visible laser light. We especially report the bleaching of different film colours under laser exposure.

Fabrication of porous chitosan films impregnated with silver nanoparticles: A facile approach for superior antibacterial application

The present investigation involves the synthesis of porous chitosan–silver nanocomposite films in view of their increasing areas of application in wound dressing, antibacterial application, and water purification. The entire process consists of three-steps including silver ion-poly(ethylene glycol) matrix preparation, addition of chitosan matrix, and removal of poly(ethylene glycol) from the film matrix. Uniform porous and brown colour chitosan films impregnated with silver nanoparticles (AgNPs) were successfully fabricated by this facile approach. Both, poly(ethylene glycol) (PEG) and chitosan (CS) played vital roles in the reduction of metal ions into nanoparticles (NPs) as well as provided good stability to the formed nanoparticles. The developed porous chitosan–silver nanocomposite (PCSSNC) films were characterized by UV–vis and FTIR spectroscopy, and thermogravimetric analysis for the confirmation of nanoparticles formation. The morphology of silver nanoparticles in nanocomposite films was tested by optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The embedded AgNPs were clearly observed throughout the film in SEM and the extracted AgNPs from the porous chitosan–silver nanocomposite showed ∼12 nm in TEM. Improved mechanical properties were observed for porous chitosan–silver nanocomposite than for chitosan blend (CSB) and chitosan–silver nanocomposite (CSSNC) films. Further, the examined antibacterial activity results of these films revealed that porous chitosan–silver nanocomposite films exhibited superior inhibition.

Synthesis and thermal cure of high molecular weight polybenzoxazine precursors and the properties of the thermosets

High molecular weight polybenzoxazine precursors have been synthesized from aromatic or aliphatic diamine and bisphenol-A with paraformaldehyde. The precursors were obtained as soluble white powder. Molecular weight was estimated from the size exclusion chromatography to be several thousands. The structure of the precursors was confirmed by IR, 1H NMR and elemental analysis, indicating the presence of cyclic benzoxazine structure. The ratio of the ring-closed benzoxazine structure and the ring-opened structure in the high molecular weight precursor was estimated from 1H NMR spectrum and also from the exotherm of DSC, showing that the ratio of the ring-closed benzoxazine structure was 77–98%. The precursor solution was cast on glass plate, giving transparent and self-standing precursor films, which was thermally cured up to 240 °C to give brown transparent polybenzoxazine films. The toughness of the crosslinked polybenzoxazine films from the high molecular weight precursors was greatly enhanced compared with the cured film from the typical low molecular weight monomer. Tensile measurement of the polybenzoxazine films revealed that polybenzoxazine from aromatic diamine exhibited the highest strength and modulus. While, polybenzoxazine from longer aliphatic diamine had higher elongation at break. The viscoelastic analyses showed that the glass transition temperature of the polybenzoxazines derived from the high molecular weight precursors were as high as 238–260 °C. Additionally, these novel polybenzoxazine thermosets showed excellent thermal stability.

High performance poly(urethane-imide) prepared by introducing imide blocks into the polyurethane backbone

A series of novel linear poly(urethane-imide)s were synthesized by the reaction between isocyanate-terminated polyurethane (PU) prepolymer and amine- or anhydride-terminated oligoimide. PU prepolymer was synthesized by reacting polyethylene adipatediol of molecular weight 1000 with tolylene-2,4-diisocyanate at the molar ratio of 2:3 or 1:2. Oligoimide was synthesized from the reaction of 4,4′-(hexafluoroisopropylidene)diphthalic acid with 4,4′-oxydianiline at various molar ratios. Equimolar amounts of PU prepolymer and oligoimide were reacted in N-methyl-2-pyrrolidone, followed by casting on glass plates and heat treatment at 100 and 150 °C for 1 h each to give linear poly(urethane-imide)s as transparent yellowish brown films. Poly(urethane-imide) films with less of 30% of imide component became elastomer, and films with more than 36% imide component became plastic. The effects of end-groups of oligoimide, molecular weight of oligoimide, and molecular weight of PU prepolymer on the solvent resistance, the tensile properties, viscoelastic properties, and thermogravimetric properties of poly(urethane-imide) films were systematically examined. Solvent resistance and tensile modulus of poly(urethane-imide) films from amine-terminated oligoimides were better than those from anhydride-terminated oligoimides. On the other hand, thermal stability and elongation at break for the poly(urethane-imide) films from anhydride-terminated oligoimides were higher than those from amine-terminated oligoimides.

Synthesis and characterisation of tungsten(vi) oxo-salicylate complexes for use in the chemical vapour deposition of self-cleaning films

Tungsten(VI) oxo-salicylate complexes were prepared in moderate yield (47 to 63%) by the reactions of WOCl4 and two equivalents of either 3-methylsalicylic acid (MesaliH2) or 3,5-di-isopropylsalicylic acid (di-i-PrsaliH2). Performing the reaction in refluxing toluene afforded the two analogous ditungsten complexes 1, [{WO(Mesali)(MesaliH)}2(mu-O)], and 2, [{WO(di-i-Prsali)(di-i-PrsaliH)}2(mu-O)], however in refluxing hexane the mononuclear tungsten complex , [WO(di-i-Prsali)(di-i-PrsaliH)Cl], was isolated. The single crystal X-ray study of revealed a pseudo-octahedral geometry around the tungsten centres. Aerosol assisted chemical vapour deposition of or afforded brown tungsten trioxide thin films. These films were converted to yellow fully oxidised WO3 on annealing in air at 550 degrees C for 30 minutes. The yellow WO3 films demonstrate preferred orientation on the substrate and show interesting functional properties-photo induced hydrophilicity and photocatalytic activity.

Preparation of translucent and flexible human hair protein films and their properties.

We have developed novel procedures for preparing human hair protein films (Pre-cast and Post-cast methods). The light brown films obtained by these procedures were too fragile to apply to human skin. We found that the film was also formed when the hair proteins extracted by the Shindai method were directly exposed to the solution containing MgCl(2), CaCl(2), NaCl or KCl. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that the surface of the novel protein films was smooth. The protein films mainly consist of alpha-keratins and matrix proteins. After drying, the films became translucent and flexible during folding, indicating the possibility that these protein films are useful for practical applications. Hence, we prepared gauze-coated protein films to reinforce their physical strength and tested the influence on human skin. A patch test showed that the protein films made from individual and multiple human hairs only slightly stimulated rubor and anthema, itching, drying, smarting and pain on the contact area of arm skin.

Dual‐Source Atmospheric Pressure CVD of Amorphous Molybdenum Phosphide Films on Glass Using Molybdenum(V) Chloride and Cyclohexylphosphine.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Pulsed laser deposition, characterization and thermochemical stability of SrFe yCo 1− yO x thin films

SrFe y Co 1− y O x ( y=0.0, 0.25, 0.50, 0.75, 0.90 and 1.0) thin films on sapphire substrates were prepared by laser deposition, and characterized by elemental analysis using Rutherford backscattering spectroscopy, particle-induced X-ray emission and inductively coupled plasma-atomic emission spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. In order to determine the relative stability of the films at 500 °C, the films were subjected to both thermochemical oxidizing and reducing treatments in 100% O 2 and 2% H 2/argon gas mixtures, respectively. Thermochemical oxidizing treatments of the SrFe yCo 1− y O x films resulted in dark-colored oxygen-rich films. Thermochemical reduction resulted in transparent yellow–brown films for the more iron-rich films, but not for the Co-rich films, which remained dark-colored. Fe-rich SrFe y Co 1− y O x ( y=0.50, 0.75 and 1.0) films exhibited the greatest degree of structural variation, resulting from the cubic perovskite→brownmillerite phase change upon reduction. Films with higher Co substitution showed smaller variations in the unit cell parameters. The SrCoO x film was unstable under reducing conditions, with a Sr-enriched carbonate layer forming at the interface after exposure to ambient atmosphere. XRD measurements conducted in situ at 500 °C in both air and nitrogen gases confirmed that reversible structural changes occur in the film solely as a consequence of changing the surrounding gas composition, with the largest changes in lattice spacing occurring for the SrFe 0.75Co 0.25O x and SrFe 0.5Co 0.5O x films.

Dual‐Source Atmospheric Pressure CVD of Amorphous Molybdenum Phosphide Films on Glass Using Molybdenum(V) Chloride and Cyclohexylphosphine

Molybdenum phosphide films are deposited on glass from MoCl5 and 2P(C6H11)H2. The atmospheric pressure depositions are carried out at 550 and 600 °C producing silver brown shiny films. The composition of the film is shown to be MoP1.8 with a resistivity value of ca. 3800 μΩ cm. X‐ray analysis of the deposited films indicates that they are amorphous. XPS analysis revealed binding energy shifts of 228.4 eV for Mo 3d5/2 and 128.8 eV for P 2p. The deposits passed the scotch test and could not be scratched with steel or brass scalpels. They are also resistant to common solvents but dissolve in concentrated acids.

Preparation and characterization of plasma-polymerized benzonitrile films with ultrafast optical kerr effect

Plasma-polymerized benzonitrile (PPBN) thin films were successfully prepared by radio frequency glow discharge techniques. The results of Fourier transform infrared (FTIR), UV-Visible absorption spectra, X-ray photoelectron spectroscopy (XPS) and on-line MS revealed that extensive conjugation has been formed in the PPBN thin films and the polymerization of benzonitrile took place mainly through the opening of carbon-nitrogen triple bonds. The morphology characterized by field emission microscopy (FEM) indicated that the fine, homogenous and brown transparent films could be obtained at comparatively low discharge power. Furthermore, the subpicosecond time-resolved optical Kerr effect (OKE) was used to measure the third-order optical nonlinearity. For the first time, an ultrafast response and nonresonant optical Kerr effect of PPBN films was observed.

混合原子価モリブデンオキシ水酸化物皮膜の電析とそのキャラクタリゼーション

Dark brown oxyhydroxide films were formed on aluminum, copper, and, ITO glass by cathodic pulse electrolysis in a 0.016mol L-1(NH4)6Mo7O24-0.32molL-1MgSO4 solution of pH 5 at 50°C. The XPS and ICP-AES analyses indicated that the films were composed of mixed valence molybdenum ions of Mo (IV) to Mo (VI), Mg (II) ions, and small amounts of sulfate ions. The MgSO4 is a necessary component in the solution to obtain uniform and adhesive films. The NH4+, Na+ or Zn (II) ions substituted for Mg (II) ions, and acetate, nitrate or phosphate ions substituted for sulfate ions in the solution adversely affected the formation of uniform and adhesive films. Though the decrease of Mg (II) ions in the solution increased the amount of Mo ions in the film, it also showed adverse effects. The films were amorphous by XRD even after drying at 200°C for 12h. Diffuse reflectance spectra of films showed that transmittance is about 15% in the UV-VIS region of 200-700nm in wavelength and increases to 70-80% in the near IR region of 1.5-2μm. Spectrophtometric emissivity measurements at 100°C indicated that emissivity in the IR region of 4-10μm is around 40% and increases drastically to over 90% for wave length longer than 10μm. It indicaates that the film is a selective emitter/absorber for the far IR region. The film also showed electric conductivity.

Preparation of polyacenic semiconductive thin films by excimer laser ablation

Polyacenic semiconductive thin films (PAS-TFs) were prepared onto a quartz or a KBr substrate by excimer laser ablation at 308 nm of a bulk phenol-formaldehyde (PF) resin and the bulk of a PAS material which was obtained by heat treatment of the PF resin at 535 °C (pyrolytic PAS (535 °C)). These were homogeneous brown and/or dark brown thin films consisting of fine particles. The electric conductivities of the films thus prepared from PF resin and pyrolytic PAS(535 °C) were about 10 −8 and 10 −5 S cm −1 at room temperature, respectively. Remarkable increase of electric conductivities was achieved on increasing the substrate temperature during the deposition process. In particular, the conductivity of the film from pyrolytic PAS (535 °C) reached more than 10 −2 S cm −1, which is comparable to that of bulk PAS material prepared by pyrolytic treatment at 775 °C, when deposited on a substrate at 300 °C.

Electrochemical polymerization of aromatic hydrocarbons on an ITO electrode using a composite electrolyte of aluminum chloride and copper(I) chloride

Flexible brown films of polyparaphenylene (PPP) with fibrous morphology were obtained by electro-oxidation of benzene on an indium tin oxide (ITO) electrode at a constant potential between +1.8 and +3.0 V/SCE using CuCl + AlCl 3 in nitrobenzene. The morphology of the PPP film depended on the applied potential, the electrode, the electrolyte and the solvent. This procedure was also applicable to the electropolymerization of toluene, p-xylene, diphenyl ether and naphthalene, but no fibrous morphology was observed. The electrical conductivities of the PPP and polynaphthalene (PN) films were ca. 10 −3 S cm −1 and 10 −4 S cm −1 respectively after Li + doping. The decomposition temperatures T d of the PPP, PN and poly(oxy-3,3′-biphenylene) films were 511°C, 546°C and 486°C respectively. The fairly high T d of the PN film was due to its rather high degree of polymerization.

Laser-assisted deposition of pure gold from (hexafluoroacetylacetonate)dimethylgold(III) and gas-phase luminescence identification of photofragments

Pure gold films are deposited on germanium, silicon, silicon dioxide, and quartz by photolyzing (CH 3 ) 2 Au-(hexafluoroacetylacetonate) in the gas phase. Shiny gold films are deposited at low incident fluences (<5 MJ/CM 2 ), whereas higher fluences yield dull brown deposits. The effects of the fluence and the repetition rate of the pulsed laser on the morphology of the deposited film are studied by using SEM. The film quality is analyzed by using XPS and Auger spectroscopic methods. No detectable carbon is found in either the gold or brown films, indicating that both are pure gold with different surface morphologies. Luminescence in the gas phase is observed under the conditions used for the photodeposition

Preparation and properties of aromatic polyimides from 2,2′‐bis(p‐aminophenoxy)biphenyl or 2,2′‐bis)p‐aminophenoxy)‐1,1′‐binaphthyl and aromatic tetracarboxylic dianhydrides

AbstractNew aromatic polyimides containing a biphenyl‐2,2′‐diyl or 1,1′‐binaphthyl‐2,2′‐diyl unit were prepared by a conventional two‐step method starting from 2,2′‐bis(p‐aminophenoxy) biphenyl or 2,2′‐bis(p‐aminophenoxy)‐1,1′‐binaphthyl and aromatic tetracarboxylic dianhydrides. The polyimides having inherent viscosities of 0.69–0.99 and 0.51–0.59 dL/g, respectively, were obtained. Some of these polymers were readily soluble in a variety of organic solvents including N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), dimethyl sulfoxide, and pyridine. Transparent, flexible, and pale yellow to brown films of these polymers could be cast from the DMAc or NMP polyamic acid solutions. These aromatic polyimides containing biphenyl and binaphthyl units had glass transition temperatures in the range of 200–235 and 286–358°C, respectively. They began to lose weight around 380°C, with 10% weight loss being recorded at about 470°C in air. © 1993 John Wiley &amp; Sons, Inc.

Synthesis and properties of new polyimides derived from 1,5‐bis(4‐aminophenoxy)naphthalene and aromatic tetracarboxylic dianhydrides

AbstractNovel aromatic polyimides containing bis(phenoxy)naphthalene units were synthesized from 1,5‐bis(4‐aminophenoxy)naphthalene (APN) and various aromatic tetracarboxylic dianhydrides by the usual two‐step procedure that included ring‐opening polyaddition in a polar solvent such as N,N‐dimethylacetamide (DMAc) to give poly(amic acid)s, followed by cyclodehydration to polyimides. The poly(amic acid)s had inherent viscosities between 0.72 and 1.94 dL/g, depending on the tetracarboxylic dianhydrides used. Excepting the polyimide IVb obtained from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), all other polyimides formed brown, flexible, and tough films by casting from the poly(amic acid) solutions. The polyimide synthesized from BPDA was characterized as semicrystalline, whereas the other polyimides showed amorphous patterns as shown by the x‐ray diffraction studies. Tensile strength, initial moduli, and elongation at break of the APN‐based polyimide films ranged from 105–135 MPa, 1.92–2.50 GPa, and 6–7%, respectively. These polyimides had glass transition temperatures between 228 and 317°C. Thermal analyses indicated that these polymers were fairly stable, and the 10% weight loss temperatures by TGA were recorded in the range of 543–574°C in nitrogen and 540–566°C in air atmosphere, respectively. © 1993 John Wiley &amp; Sons, Inc.