Physical Vapor Deposited Thin Films of Lignins Extracted from Sugar Cane Bagasse: Morphology, Electrical Properties, and Sensing Applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nanostructured hybrid films containing nanophosphor: Fabrication and electronic spectral properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Tailoring the Structural Properties of PVDF and P(VDF-TrFE) by Using Natural Polymers as Additives

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Improvement of electrical properties of Sr-modified (Pb,Ca)TiO3 thin films grown by soft chemistry route

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Corrosion behavior of Ti-6Al-4V alloy treated by plasma immersion ion implantation process

Ti-6Al-4V alloy is one of the most frequently used Ti alloys with diverse applications in aerospace and biomedical areas due to its favorable mechanical properties, corrosion resistance and biocompatibility. Meanwhile, its surface can stiffer intense corrosion caused by wear processes due to its poor tribological properties. Thus in the present study, PIII processing of Ti-6Al-4V alloy was carried out to evaluate its corrosion resistance in 3.5% NaCl solution. Two different sets of Ti-6Al-4V samples were PIII treated, varying the plasma gases and the treatment time. The corrosion behavior is correlated with the surface morphology, and the nitrogen content. SEM micrographs of the untreated sample reveal a typical two-phase structure. PIII processing promotes surface sputtering and the surface morphology is completely different for samples treated with N-2/H-2 mixture and N-2 only. The highest penetration of nitrogen (similar to 88 nm), corresponding to 33% of N-2 was obtained for the sample treated with N-2/H-2 mixture for 1:30 h. The corrosion behavior of the samples was investigated by a potentiodynamic polarization method. A large passive region of the polarization curves (similar to 1.5 V), associated with the formation of a protective film, was observed for all samples. The passive current density (similar to 3 x 10(-6) A cm(-2)) of the PIII-treated Ti-6Al-4V samples is about 10 times higher than for the untreated sample. This current value is still rather low and maintains good corrosion resistance. The anodic branches of the polarization curves for all treated Ti-6Al-4V samples demonstrate also that the oxide films break down at approximately 1.6 V, forming an active region. Although the sample treated by N-2/H-2 mixture for 1.30 It has thicker nitrogen enriched layer, better corrosion resistance is obtained for the PIII process performed with N, gas only. (c) 2007 Elsevier B.V. All rights reserved.

Optical and structural properties of PEO-like plasma polymers

This paper deals with the study of optical, structural and biocompatible properties of PEO-like plasma polymerized films resulting from RF excited diethylene glycol dimethyl ether (CH3O(CH2CH2O)(2)CH3 diglyme) glow discharges. The study was carried out using visible-ultraviolet and FTIR spectroscopies and contact angle measurements. FTIR spectra of plasma polymerized diglyme showed a stronger presence of ethylene glycol groups in film structure for lower RF power levels. The contact angle measurements for water revealed an increasing from 30degrees to 62,5degrees when the RF power was varied from 2 to 45 W, indicating the decreasing of the hydrophilic character of diglyme films with the increasing of RF power. This trend is in agreement with FTIR results. The data from visible-ultraviolet reflectance and transmittance spectra revealed alterations on optical properties of plasma polymerized diglyme films. The film's optical gap varied from 3.8 to 3 eV for RF power running from 5 to 45 W.

Argon ion implantation inducing modifications in the properties of benzene plasma polymers

Benzene plasma polymer films were bombarded with Ar ions by plasma immersion ion implantation. The treatments were performed using argon pressure of 3 Pa and 70 W of applied power. The substrate holder was polarized with high voltage negative pulses (25 kV, 3 Hz). Exposure time to the immersion plasma, t, was varied from 0 to 9000 s. Optical gap and chemical composition of the samples were determined by ultraviolet-visible and Rutherford backscattering spectroscopies, respectively. Film wettability was investigated by the contact angle between a water drop and the film surface. Nanoindentation technique was employed in the hardness measurements. It was observed growth in carbon and oxygen concentrations while there was decrease in the concentration of H atoms with increasing t. Furthermore, film hardness and wettability increased and the optical gap decreased with t. Interpretation of these results is proposed in terms of the chain crosslinking and unsaturation. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Properties of hydrogenated amorphous carbon films deposited by PECVD and modified by SF6 plasma

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ferroelectric and piezoelectric properties of bismuth layered thin films grown on (100) Pt electrodes

The effect of film orientation on piezoelectric and ferroelectric properties of bismuth layered compounds deposited on platinum coated silicon substrates was investigated. Piezo-force microscopy was used to probe the local piezoelectric properties of Bi(4)Ti(3)O(12), CaBi(4)Ti(4)O(15) and SrBi(4)Ti(4)O(15) films. Our measurements on individual grains clearly reveal that the local piezoelectric properties are determined by the polarization state of the grain. A piezoelectric coefficient of 65 pm/V was attained after poling in a grain with a polar axis very close to the normal direction. The piezoelectric coefficient and the remanent polarization were larger for a-b axes oriented than for c-axis-oriented films. (c) 2007 Elsevier B.V All rights reserved.

Effect of the microwave oven on structural, morphological and electrical properties of SrBi4Ti4O15 thin films grown on Pt/Ti/SiO2/Si substrates by a soft chemical method

Thin films of SrBi4Ti4O15 (SBTi), a prototype of the Bi-layered-ferroelectric oxide family, were obtained by a soft chemical method and crystallized in a domestic microwave oven. For comparison, films were also crystallized in a conventional method at 700 degrees C for 2 h. Structural and morphological characterization of the SBTi thin films were investigated by Xray diffraction (XRD) and atomic force microscopy (AFM), respectively. Using platinum coated silicon substrates, the ferroelectric properties of the films were determined. Remanent polarization P-r and a coercive field E-c values of 5.1 mu C/cm(2) and 135 kV/cm for the film thermally treated in the microwave oven and 5.4 mu C/cm(2) and 85 kv/cm for the film thermally treated in conventional furnace were found. The films thermally treated in the conventional furnace exhibited excellent fatigue-free characteristics up to 10(10) switching cycles indicating that SBTi thin films are a promising material for use in non-volatile memories. (C) 2007 Elsevier B.V. All rights reserved.

Effect of oxidizing atmosphere on the electrical properties of SrBi4Ti4O15 thin films obtained by the polymeric precursor method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Enhanced ferroelectric properties of La-substituted BiFeO3 thin films on LaSrCoO3/Pt/TiO2/SiO2/Si (100) substrates prepared by the soft chemical method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electromechanical properties of 0-3 vegetable based polyurethane and lead zirconate titanate composite.

Composite made of Lead Zirconate Titranate (PZT) ceramic powder and castor oil based polyurethane (PU) were prepared in the thin film form with 0-3 connectivity by spin coating. The composite films were obtained in the thickness range of 100 mum to 300 mum using 33-vol.% of ceramic. The samples mechanical resistance. The material was characterised by dielectric spectroscopy, thermally stimulated discharge current (TSDC), hysteresis measurements and laser-intensity-modulation method (LIMM). The pyroelectric coefficient at 343 K was 7x10(-5) C.m(-2) K-1 for the sample poled with 10 MV/m at 373 K for Ih. The results show that this new composite can be used as suitable piezo and pyroelectric sensors.

Effects of crystallization conditions on dielectric and ferroelectric properties of PZT thin films

This paper reports studies on dielectric and ferroelectric properties of lead zirconate titanate (PZT) thin films crystallized by conventional thermal annealing (CTA) and rapid thermal annealing (RTA) in air, oxygen and nitrogen atmospheres to better understand, control and optimize these properties. The dielectric constant (epsilon) and dissipation factor (tan delta) values, at a frequency of 100 kHz; for film crystallized in air by CTA process, were 358 and 0.039, respectively. Considering the same frequency for film crystallized in air by RTA, these values were 611 and 0.026, respectively. The different dielectric values were justified by a space-charge or interfacial polarization in films, often characterized as Maxwell-Wagner type. This effect was also responsible to dispersion at frequencies above 1 MHz in film crystallized in air by CTA process and film crystallized by RTA in oxygen atmosphere. The film crystallized by RTA under nitrogen atmosphere presented an evident dispersion at frequencies around 100 Hz, characterized by an increase in both epsilon and tan delta. This dispersion was attributed to conductivity effects. The remanent polarization (P-r) and coercive field (E-c) were also obtained for all films. Films obtained from RTA in air presented higher P-r (17.8 muC cm(-2)) than film crystallized from CTA (7.8 muC cm(-2)). As a function of the crystallization atmospheres, films crystallized by RTA in air and nitrogen presented essentially the same P-r values (around 18 muC cm(-2)) but the P-r (3.9 muC cm(-2)) obtained from film crystallized under oxygen atmosphere was profoundly influenced.

Properties of DLC films deposited by an oxyacetylene flame

Diamond-like carbon (DLC) films were obtained by spinning a tungsten carbide substrate at a high speed using an oxyacetylene flame. The films deposited at a typical experimental condition of substrate temperature of 810 degrees C, rotation of 600 rpm and 3 h deposition time, exhibited an uniform, very smooth, hard and glassy surface covering the entire exposed face of the substrate. These films were identified as DLC by their characteristic broad Raman spectra centered at 1554 cm(-1) and micro-Vicker's hardness > 3400 kg mm(-2). For substrate temperatures < 800 degrees C the film started losing the uniform glassy surface and the hardness deteriorated. For temperatures > 950 degrees C the film was still hard and shiny, but black in color. DLC films were also obtained in a wide range of speeds of rotation (300-750 rpm), as long as the temperature remained close to 850 degrees C. (C) 1999 Elsevier B.V. S.A. All rights reserved.