Effect of heat on characteristics of chitosan film coated on theophylline tablets

The effect of heat on the characteristics of chitosan film coated on theophylline tablets was studied. Chitosan of high viscosity grade with molecular weight in the range of 800,000-1,000,000, 80-85% degree of deacetylation was used as a film former by dissolving in 1% v/v acetic acid solution. The coated tablets had been cured at 40, 60, and 100°C for 6, 12, and 24 hr. The morphology of the film at the edge and surface of coated tablets was investigated using scanning electron microscopy. Film cracking was increased and clearly observed in the coated tablets cured at 100°C for 24 hr. As a result, more water could be absorbed into the tablets, followed by faster disintegration and faster drug release. The evidence of partial conversion of chitosonium acetate to chitin in the ¹³C nuclear magnetic resonance (NMR) spectra of chitosan films cured at 40, 60, and 100°C was observed, but it had no effect on drug release behavior. Theophylline tablets coated with chitosan films gave sustained release behavior in various media, i.e., distilled water, 0.1 N hydrochloric acid, pH 4.5 acetate buffer, and pH 6.8 phosphate buffer. In addition, the film coating temperature at 55-60°C and curing process at 40 and 60°C had no effect on the drug release from theophylline tablets coated with chitosan polymer. Finally, it might be concluded that both the physical and chemical properties of chitosan films were affected by heat.     

Effects of rapid thermal annealing on the morphology and electrical properties of ZnO/In films

Zinc oxide (ZnO) films were prepared by ultrasonic spray pyrolysis on indium (In) films deposited by evaporation and subsequently subjected to rapid thermal annealing (RTA) in air or vacuum. The crystallographic properties and surface morphology of the films were characterized before and after RTA by X-ray diffraction and scanning electron microscopy, respectively. The variation in resistivity of the films with RTA temperature and time was measured by the four-point probe method. Auger electron spectroscopy (AES) was carried out to determine the distribution of indium atoms in the ZnO films. The resistivity of the ZnO on In (ZnO/In) films decreased to 2×10⁻³ Ω cm by diffusion of the In. Indium diffusion into the ZnO films roughened the film surface. The results of depth profiling by AES showed a hump of In atoms around ZnO/In interface after RTA at 800 °C, which disappeared on RTA at 1000 °C. The effects of temperature, time and atmosphere during RTA on the structural and electrical properties of the ZnO/In films are discussed.     

Thickness-dependent properties of sprayed iridium oxide thin films

Iridium oxide thin films with variable thickness were deposited by spray pyrolysis technique (SPT), onto the amorphous glass substrates kept at 350 °C. The volume of iridium chloride solution was varied to obtain iridium oxide thin films with thickness ranging from 700 to 2250 Å. The effect of film thickness on structural and electrical properties was studied. The X-ray diffraction (XRD) studies revealed that the as-deposited samples were amorphous and those annealed at 600 °C for 3 h in milieu of air were polycrystalline IrO₂. The crystallinity of Ir-oxide films ameliorate with film thickness thereby preferred orientation along (1 1 0) remains unchanged. The infrared spectroscopic results show Ir–O and Ir–O₂ bands. The room temperature electrical resistivity (ρ_RT) of these films decreases with increase in film thickness. The p-type semiconductor to metallic transition was observed at 600 °C.     

Preparation of alumina–silica–nickel nanocomposite by in situ reduction through sol–gel route

Ceramic based composites with dispersion of nano sized metal/metal carbide particles have generated wide technological interest for their improved mechanical properties — hardness, fracture strength as well as fracture toughness, superior electrical properties and magnetic properties. In the present investigation alumina–silica gels have been prepared along with nickel chloride and dextrose distributed in the nanometric pores of the gel. The gels are prepared with different molar proportions of alumina and silica containing 5 wt% of nickel chloride and 50 wt% excess dextrose. During heat treatment at a temperature of 9008C for half an hour in nitrogen atmosphere, nickel chloride is reduced to metallic nickel by in situ generated hydrogen in the silica–alumina matrix. X-ray analyses indicate that no nickel chloride reduction is possible upto 50 mol% silica in alumina–silica matrix. Beyond this range, higher the silica content, higher is the reduction of nickel chloride. The presence of metallic nickel has been substantiated further by SAD analysis. Particle size analysis based on X-ray diffraction as well as transmission electron micrograph shows the presence of nickel particles of size ,20 nm distributed in the alumina–silica nanocomposite.     

Preparation of alumina–silica–nickel nanocomposite by in situ reduction through sol–gel route

Ceramic based composites with dispersion of nano sized metal/metal carbide particles have generated wide technological interest for their improved mechanical properties — hardness, fracture strength as well as fracture toughness, superior electrical properties and magnetic properties. In the present investigation alumina–silica gels have been prepared along with nickel chloride and dextrose distributed in the nanometric pores of the gel. The gels are prepared with different molar proportions of alumina and silica containing 5 wt% of nickel chloride and 50 wt% excess dextrose. During heat treatment at a temperature of 900°C for half an hour in nitrogen atmosphere, nickel chloride is reduced to metallic nickel by in situ generated hydrogen in the silica–alumina matrix. X-ray analyses indicate that no nickel chloride reduction is possible upto 50 mol% silica in alumina–silica matrix. Beyond this range, higher the silica content, higher is the reduction of nickel chloride. The presence of metallic nickel has been substantiated further by SAD analysis. Particle size analysis based on X-ray diffraction as well as transmission electron micrograph shows the presence of nickel particles of size ∼20 nm distributed in the alumina–silica nanocomposite.     

A study of thin films of V2O5 containing molybdenum from an evaporation boat

An attempt was made to produce thin films of vanadium oxide by evaporating V₂O₅ in vacuum using molybdenum boats. Following analysis of the films by X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry, it was found that the films contained a large amount of molybdenum (atomic ratio of Mo:V>1). Films were chemically inhomogeneous along the direction of growth such that the value of the atomic ratio decreased from the substrate side of the film to its interface with the air. However, a study of the optical properties of the films revealed that they were optically homogeneous. The films went through a semiconductor-to-metal phase transition at a temperature of approximately 200 °C. When annealed in vacuum at a temperature of 275 °C, it was found that, (a) the films remained amorphous, (b) there was a loss of oxygen leading to an increase in their electrical conductivity, (c) their thickness decreased leading to a larger refractive index of the films, and (d) their band gap energy shifted to a higher photon energy by approximately 0.1 eV.     

Formation of a highly oriented FeO thin film by phase transition of Fe3O4 and Fe nanocrystallines

A highly oriented FeO thin film was formed from a Fe₃O₄ thin film containing Fe nanocrystallines by post-annealing at 600°C. Fe₃O₄ thin films were grown on Si(100) substrates by ion beam sputter deposition under oxygen ambient. The stoichiometry of the iron oxide thin film could be precisely controlled by in situ X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) pattern of the Fe₃O₄ thin film grown at substrate temperature of 300°C showed a mixed phase of Fe₃O₄ and Fe nanocrystallines with a preferred orientation (110). However, the mixed phase was converted to a highly oriented FeO(200) phase by post-annealing at 600°C. This could be inverted as a result of Ostwald ripening of the Fe₃O₄ and Fe nanocrystallines.     

Incorporation of cobalt and nickel metal nano-particles in nano-grain zirconia film matrix by solution route

Precursor solutions of cobalt/nickel incorporated nano-grain zirconia films were prepared from aquo-organic solutions of zirconium oxychloride octahydrate and corresponding transition metal nitrate. The films were deposited onto silica glass substrate by the dipping technique. Annealing was made at different temperatures from 450°C to 1200°C ± 5°C in air atmosphere. The range of thickness of the films baked at 450°C was 1800–1870 å. For cobalt system Co₃O₄ was formed initially at 450°C which gradually transformed to alpha cobalt and next to cubic cobalt along with a non-stoichiometric compound (Zr_0.71Co_0.23O_0.06) with increasing annealing temperature. On the other hand, for nickel system nickel metal of nano-size was observed in the nano-grain zirconia film matrix at 450°C. By increasing annealing temperature to 1200°C, a compound, ZrNi₄O, was formed which was found to be stable for ～ 30 days.     

Low-temperature, direct synthesis of β-SiC by metal vapor vacuum arc ion source implantation

Crystalline β-SiC surface layers with strong (111) preferred orientation were synthesized by direct ion implantation into Si(111) substrates at a low temperature of 400°C using a metal vapor vacuum arc ion source. Both X-ray diffraction and Fourier transform infrared spectroscopy reveal an augment in the amount of β-SiC with increasing implantation doses at 400°C. Scanning electron microscopy shows the formation of an almost continuous SiC surface layer after implantation at 400°C with a dose of 7×10¹⁷/cm². The full width at half maximum of the X-ray rocking curve of β-SiC(111) was measured to be 1.4° for the sample implanted at a dose of 2×10¹⁷/cm² at 700°C, revealing a good alignment of β-SiC with the Si matrix.     

A simple route to electrophoretic deposition of transition metal-coated nickel oxide films for electrochemical capacitors

Nickel hydroxide films coated with transition metals such as nickel and cobalt were fabricated directly by a one-step electrophoretic deposition (EPD) in the presence of charging additives (transition metal salts). A nickel hydroxide particle with a weakly charged surface in an isopropanol solution was found to be detrimental to EPD and dispersion. When a small amount of charging additive was added to the suspension, the adsorption of dissolved metal ions on the nickel hydroxide resulted in a more positively charged particle surface, facilitating EPD and dispersion. When nickel hydroxide particles migrated to the negative electrode during the EPD process, the metal ions adsorbed on the particle were reduced electrochemically to form a metal layer. The as-deposited nickel hydroxide film converted to nickel oxide following heat treatment at 300 °C. Our results revealed that nickel oxide films coated with nickel and cobalt showed better capacitive behavior than the bare film. The improved capacitive behavior was attributed to the co-deposition of transition metals, which provided additional active sites on the nickel oxide surface for the electrochemical reaction to occur.     

催化剂对乙醇催化燃烧法制备碳纳米纤维的影响

分别以硝酸铁、硝酸钴、硝酸镍以及氯化铁、氯化钴、氯化镍作为催化剂先体，利用乙醇催化燃烧法制备了碳纳米纤维。利用扫描电子显微术、透射电子显微术和X射线能量分散谱术对样品进行了表征。讨论了不同种类的催化剂先体对产物形貌和生长机制的影响。     

Structural, morphological, and electrical characteristics of the electrodeposited cobalt oxide electrode for supercapacitor applications

Cobalt oxide (Co₃O₄) thin films were prepared through electrodeposition on copper substrates using an ammonia-complexed cobalt chloride solution. The structural and morphological properties of the film were studied using an X-ray diffractometer and scanning electron microscopy, and the results showed that the electrodeposited cobalt oxide film had a nanocrystalline and porous structure. The electrochemical behavior of the electrodeposited cobalt oxide electrode was evaluated in a KOH solution using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. The electrodeposited cobalt oxide electrode exhibited a specific capacitance of 235 F/g at a scan rate of 20 mV/s. The specific energy and the specific power of the electrode were 4.0 Wh/kg and 1.33 kW/kg, respectively.     

Preparation of Pt-PtOx thin films as electrode for memory capacitors

Pt-PtO_x thin films were prepared on Si(100) substrates at temperatures from 30 to 700°C by reactive r.f. magnetron sputtering with platinum target. Deposition atmosphere was varied with O₂/Ar flow ratio. The deposited films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. Resistively of the deposited films was measured by d.c. four probe method. The films mainly consisted of amorphous PtO and Pt₃O₄ (or Pt₂O₃) below 400°C, and amorphous Pt was increased in the film as a deposition temperature increased to 600°C. When deposition temperature was thoroughly increased, (111) oriented pure Pt films were formed at 700°C. Compounds included in the films strongly depended on substrate temperature rather than O₂/Ar flow ratio. Electrical resistivity of Pt-PtO_x films was measured to be from the order of 10⁻¹ Ω cm to 10⁻⁵ Ω cm, which was related to the amount of Pt phase included in the deposited films.     

Formation and characterization of cobalt oxide layers on polyimide films via surface modification and ion-exchange technique

Polyimide (PI) films with thin cobalt oxide (Co₃O₄) layers on both film sides have been prepared via a surface modification and ion-exchange technique. The method works by hydrolyzing the PI film surfaces in aqueous potassium hydroxide solution and incorporating Co²⁺ into the hydrolyzed layers of PI film via subsequent ion exchange, and followed by thermal treatment in ambient atmosphere. The PI composite films were characterized by Attenuated total reflection-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractions, scanning electron microscopy, transmission electron microscopy and thermogravimetric analyses, as well as surface resistance and mechanical measurements. By varying the absorbed cobalt ion content, a series of PI/Co₃O₄ composite films with insulative to semiconductive surfaces were obtained. The room temperature surface resistances of the semiconductive composite films reached to about 10⁷ Ω. The Co₃O₄ particle formed on PI film surfaces was in the range of 10-40 nm. The final composite films maintained the essential mechanical properties and thermal stability of the pristine PI films. The adhesion between surface Co₃O₄ layers and PI matrix was acceptable.     

Effect of the titanium ion concentration on electrodeposition of nanostructured TiNi films

Electrodeposition of nanostructured titanium–nickel films was performed and the effect of the concentration of the titanium source on the film characteristics was investigated. Scanning electron microscopy indicated circular crystallites on the surface of the electrodeposited titanium–nickel film with a fairly uniform size distribution. XRD studies showed that the electrodeposited TiNi films contained TiNi with a preferred crystallographic orientation of [002]. Surface analysis using X-ray photoelectron spectroscopy (XPS) revealed that the electrodeposited titanium–nickel film contained elemental titanium and nickel, hydroxide of nickel, and oxides of titanium and nickel. As the titanium ion concentration was increased, the titanium content in the film was increased while the deposition rate and crystallite size of the film were decreased. A blue-shift in the UV/Vis peak was also observed with increasing titanium ion concentration.     

Effect of catalyst for nickel films for NiSi formation with improved interface roughness

Iodine is an effective catalyst to obtain homogeneous and smooth metal films with good interface properties. We adopted an iodine catalyst during the nickel film deposition by using atomic layer deposition (ALD) with bis(1-dimethylamino-2-methyl-2-butoxide)nickel [Ni(dmamb)₂] precursor and hydrogen reactant gas. The effect of iodine catalyst to nickel nucleation process was studied. The deposited films were silicided by rapid thermal process (RTP) which was performed by varying temperature from 400 °C to 900 °C in nitrogen ambient. The crystalline properties of nickel and nickel silicide films were examined by X-ray diffractometer (XRD) with various deposition temperatures. The interface properties and the surface morphology of nickel silicide films were studied by using Auger electron spectroscopy (AES) depth profile analyses and scanning electron microscopy (SEM). The experimental results showed that the iodine-catalyzed silicide film, which have a clean and smooth interface, exhibit lower resistivity, and lower leakage current density compared to that of non iodine-catalyzed films in implemented n⁺/p junction diode.     

Polishing of polycrystalline diamond by hot nickel surface

A microwave plasma technique has been employed to deposit polycrystalline diamond film over a molybdenum substrate button using a gas mixture of hydrogen and methane at a substrate temperature of 851°C. A CVD diamond coated molybdenum substrate button was mounted with a load against hot nickel plate and rotated for 3.45 h in a hydrogen ambient. Hot tungsten filament was used as a heat source to maintain the temperature of the nickel block and CVD diamond coated molybdenum button at 848°C. This experiment has reproducibly shown the successful polishing of polycrystalline CVD diamond by hot nickel. A Tencor profilometer and scanning electron microscope have been used to evaluate the surface smoothness and morphology before and after polishing the polycrystalline diamond thin films.     

Preparation and properties of electrochromic iridium oxide thin film by sol-gel process

We established a method for preparation of iridium oxide thin film by the sol-gel dip-coating process where iridium chloride was used as a starting material. The coating solution was prepared by reacting iridium chloride, ethanol and acetic acid. Iridium oxide coating was formed at 2.0 cm/min withdrawing rate. The coating films heat treated at 300°C did not contain impurities. Iridium oxide crystallized at temperatures above 450°C. Both crystalline and amorphous iridium oxide thin films showed electrochromism. The change in transmittance of the crystalline Ir₂O₃ film is larger than that of the amorphous Ir₂O₃ under the same experimental conditions. The transmittance of the crystalline thin film (film thickness 200 nm, measured at 400 nm) decreased 13.0% on application of 3 V for 1 s.     

X-ray photoelectron spectroscopic studies on pyrolysis of thin films of plasma-polymerized acrylonitrile

X-ray photoelectron spectroscopy is used to elucidate the chemical environments of the atoms in as-deposited plasma-polymerized acrylonitrile (PPAN) thin film and PPAN films pyrolysed at the temperatures 573 and 773 K. The photoelectron spectra are collected at the electron take-off angles of 20° and 70°. The C 1s, N 1s, and O 1s spectra of all the samples demonstrate clearly that the structural modifications take place owing to pyrolysis in the PPAN structure. Apart from the structural modifications, a decrease of nitrogen and an uptake of oxygen are evidenced. A few chemical species other than the usual ones are also detected.     

Characterization of intermetallic phases and oxides formed in annealed Ni/Al multilayer structures

Two different multilayer structures composed of ten alternating Ni and Al thin films were sputter deposited on Si (111) substrates. These multilayers with individual Ni and Al thin film thicknesses of about 25 nm and 38 nm and of 25 nm and 13 nm, respectively, have the average compositions of Ni_0.50Al_0.50 and Ni_0.75Al_0.25. The samples were heat treated in a differential scanning calorimeter instrument with a constant heating rate of 40 °C min ⁻¹ in Ar from room temperature to 550 °C. The compositions of as-deposited and heat-treated samples were studied with high-resolution Auger electron spectroscopy (AES) rotational depth profiling. X-ray photoelectron spectroscopy (XPS) analyses show an excess of Ni in both annealed samples. X-ray diffraction measurements of annealed multilayers show the formation of Ni₂Al₃ and NiAl₃ phases in the Ni_0.50Al_0.50 sample and the presence of Ni₃Al and Ni A1₃ phases with some excess of Ni in the Ni_0.75Al_0.75 sample. AES and XPS investigations of the reacted layers after 15 min annealing in air at 500 °C disclose considerably different surface oxide thin films: on the Ni_0.50Al_0.50 layer the oxide thin film consists of Al₂O₃ with a small amount of NiO, whereas that on the top of the Ni_0.75Al_0.25 layer is thicker and consists of NiO on top and some Al₂O₃ below.