Raman Spectroscopy Characterization of Ion-beam-modified Polyimide Films

Raman spectroscopy was employed in studying the effects of irradiation conditions on the structural modifications of irradlated polyimide films. A decomposing approach of data analysis for the experimental Raman spectra demonstrates that the implantation conditions play important but different roles in the formation of the final structures. A calculation was also performed to find out the contribution from the phonon state density of amorphous graphite to the Raman spectrum profiles.     

Synthesis and Characterization of Nanocrystalline Ni-Ti and Ni-Cr Powders by Mechanical Alloying

Nanocrystalline powders in the Ni-Ti and Ni-Cr systems were prepared by mechanical alloying (MA) of elemental crystalline powders in an inert atmosphere. The microstructure of the mechanically alloyed powders were characterized by XRD and TEM. The ball-milling process results in a drastic decrease of the crystallite size to the nanometer scale. X-ray diffraction analysis reveals that in the Ni-Cr system, no diffraction peaks from NiCr compound were observed even after 20 h of ball milling; while the lattice parameter of Ni increased with the milling time. In the Ni-Ti system, amorphous alloy was formed. Crystalline intermetallic compounds were obtained by post heat treatment of the amorphous alloy.The crystallization temperature of the amorphous NiTi alloy was obtained be DSC measurement.     

Characterization of highly absorbing black appliqués in the infrared

Angular and polarimetric directional hemispherical reflectance (DHR) measurements of three highly absorbing appliqués in the 2.5-14.3-mum IR spectral region are presented. In addition, scanning electron microscopy (SEM) images are presented to probe the surface morphology of these appliqués. DHR measurements of Energy Science Laboratory, Incorporated (ESLI), Rippey, and Rodel appliqués were obtained at incidence angles of 8 degrees , 30 degrees , and 50 degrees and as a function of S, P, and unpolarized incident light. The ESLI appliqué exhibited the lowest DHR for all angles and incident polarization states. SEM images revealed a fibrous structure for the ESLI appliqué with fiber diameters of the order of 7-8 mum, whereas the Rippey and the Rodel appliqués showed spongelike surfaces with pore diameters of 40-50 and 30-40 mum, respectively. All the appliqués use cavities or fibers in conjunction with carbon compounds to absorb IR radiation. The optical system designed to perform these measurements, a method for correcting off-normal DHR measurements in center-mount integrating spheres, and sources of measurement error are also discussed.     

In situ measurements of ion-exchange processes in single polymer particles: laser trapping microspectroscopy and confocal fluorescence microspectroscopy

Ion-exchange processes of a cationic dye (Rhodamine B; RhB) were studied for individual polymer particles (diameter of 16-20 μm) by laser trapping microspectroscopy and confocal fluorescence laser microspectroscopy. The absorbance of RhB at 565 nm adsorbed on a cation-exchange particle increased linearly with the concentration of RhB in the aqueous phase, while it was independent of the particle diameter. Fluorescence intensity profile measurements of RhB along the particle diameter by confocal fluorescence microspectroscopy directly proved that ion exchange took place in the surface layer (～2-μm thickness) of the particle in the initial stage (1 h). Diffusion of RhB in the particle was very slow, and ion exchange proceeded gradually to the inner volume in the order of days. The ion-exchange processes were analyzed on the basis of simulation of the time course of the concentration profile of RhB in the particle, and the diffusion coefficient of RhB was determined to be (2-4) × 10(-11) cm(2)·s(-1).     

Manufacture of copper weapons and tools from the chalcolithic settlement of São Pedro (Portugal)

ABSTRACT

A collection of 30 copper-based artefacts recovered during archeological excavations at the São Pedro settlement (Redondo, Portugal) was characterized by optical microscopy and Vickers microhardness testing. The radiocarbon dating of bone samples and the existence of Bell Beaker ceramics establish a chronology of c. 2700–2000 BC for tools and weapons made of copper with varying arsenic contents. The manufacture included one or more cycles of forging and annealing, while final work hardening was uncommon. The collection shows a wide range of hardness (52–142 HV0.2) without any correlation with typology or arsenic content, suggesting unawareness of the hardening potential of this alloying element. Technological features of São Pedro artefacts were compared with those of coeval metallurgies from neighboring regions (Portuguese Estremadura and Southern Andalusia) revealing common and distinctive characteristics that help to understand the use of arsenical copper alloys among communities of the third millennium BC.     

Synthesis and Characterization of Electrochromic Polyimides

Following the initial work by Haushalter and Krause,1 the redox properties of some common phthalimides and naphthalimides as well as phthalimide polymers have been described.2,3 Owing to its electron affinity, an imide can undergo the electrochemical reduction.     

Characterization and Magnetic Properties of Cobalt Nano-Particles Prepared by Metal Vapor Synthesis Technique

The metal vapor synthesis technique was employed to prepare Co nanoparticles. The characteristics and properties of the particles were studied by transmission electron microscopy, X-ray diffraction, temperature-programmed desorption,chemisorption and magnetic measurements. The experimental results showed that the particle size of Co powders depended on the initial Co concentration in the toluene matrix, reaching average crystallite diameter of 1.5 nm for the highest concentration (6.4 at. pct) investigated. The particles with size of 10 nm exist, due to the agglomerates of microcrystallites. The Co particles were surrounded by a thin carbonaceous layer formed due to toluene decomposition on cocondate melt-down and subsequent warming to room temperature. The carbonaceous layer was composed primarily of C1 fragments. The Co powders demonstrated ferromagnetic behavior.     

On a 1947 Rediscovery: Archive,memory and self-inscription in the work of Julião Sarmento

This paper deals with the experience of archive and memory as key aspects in the photographic work of the Portuguese artist Julião Sarmento. Taking the installation entitled 1947 — based on the appropriation of an ensemble of found photographs — as the central object of study, this paper seeks to discuss the relationship between archive, memory and the photographic, or the filmic. It is argued that in Julião Sarmento’s artistic work the problematic of the archive acquires an autographical dimension, allowing us to think over the role of both archive and memory as creative processes involving distinct supports and temporalities of the image. It is through the articulation of the psychoanalytical theory regarding recurrence and the unconscious and crucial references whose authors directly or indirectly approach the theme of the archive (J. Derrida, G. Didi-Huberman, H. Foster, A. Buchanan and J. Schwartz, among others) that we will be able to understand the way the archive structure acquires, in Julião Sarmento’s oeuvre, the meaning of a device of (counter-)narration able to materialize the movements of memory itself. The article seeks, therefore, to highlight a temporal and affective dimension that reveals itself to be central in archival practices that comprise the personal archive and found photography.     

Characterization of Nanocrystalline Intermetallic Compound NiAl Synthesized by Condensation

Nanocrystalline intermetallic compound NiAl was Synthesized by evaporating NiAl master alloy in inert-gas followed by in situ compaction, and its structure was studied by means of X-ray diffractometry and transmission electron microscope. Experimental results reveal that the assynthesized nanocrystalline sample has a mean grain size of less than 10 nm and it is dominantly composed of the cubic structure phase NiAl. However, nanocrystalline Ni3Al as a trace phase mixed in NiAl phase, was also detected by transmission electron microscope observation.     

Characterization of Cu–Ni alloy electrodeposition and synthesis of nanoparticles by pulsed sonoelectrochemistry

Binary alloy Cu–Ni nanoparticles were synthesized by sonoelectrochemical technique from aqueous bath in presence of Na-citrate as complexing agent, to allow co-deposition of Cu and Ni. Alloy Pulsed Electro-Deposition (PED) was carried out to study nucleation kinetic and the effects of pH and surfactant on the final product physical and chemical properties, with the aim to determine optimized parameters for subsequent sonoelectrosyntheses of nanoparticles. Role of pH and Na-citrate in the synthesis process was investigated and it was found that i) pH is the main parameter affecting the stability of synthesis solutions, ii) Na-citrate content influences the sonoelectrochemical process efficiency but at the same time iii) the complexing agent is necessary to obtain Cu and Ni co-deposition; iv) produced nanoparticles are made of CuNi alloy with a fcc crystalline structure and v) pH is weakly responsible of increase in mean grain size of produced nanoparticles.     

Raman spectroscopy and in situ Raman spectroelectrochemistry of bilayer ¹²C/¹³C graphene

Bilayer graphene was prepared by the subsequent deposition of a (13)C single-layer graphene and a (12)C single-layer graphene on top of a SiO(2)/Si substrate. The bilayer graphene thus prepared was studied using Raman spectroscopy and in situ Raman spectroelectrochemistry. The Raman frequencies of the (13)C graphene bands are significantly shifted with respect to those of (12)C graphene, which allows us to investigate the single layer components of bilayer graphene individually. It is shown that the bottom layer of the bilayer graphene is significantly doped from the substrate, while the top layer does not exhibit a signature of the doping from the environment. The electrochemical doping has the same effect on the charge carrier concentration at the top and the bottom layer despite the top layer being the only layer in contact with the electrolyte. This is here demonstrated by essentially the same frequency shifts of the G and G' bands as a function of the electrode potential for both the top and bottom layers. Nevertheless, analysis of the intensity of the Raman modes showed an anomalous bleaching of the Raman intensity of the G mode with increasing electrode potential, which was not observed previously in one-layer graphene.     

Synthesis and Characterization of Mesoporous Titania Particles and Thin Films

Well-organized mesoporous titania particles and thin films were successfully synthesized by using tetrabutyl titanate as the inorganic precursor and triblock copolymer （Pluronic P123） as the template via evaporationinduced self-assembly process. The resulting materials were characterized by high resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）. Fourier-transform infrared spectroscopy （FT-IR）,Brunauer-Emmett-Teller （BET） and atomic force microscopy （AFM）. Macro shape of mesoporous titania would greatly influence the mesostructure of materials, and the probable reasons were also discussed.     

Preparation and Characterization of Albendazole β-Cyclodextrin Complexes

Albendazole (ABZ), mebendazole (MBZ), and ricobendazole (RBZ) are low-soluble anthelmintic benzimidazole carbamate drugs. To increase their aqueous solubility, three different types of β-cyclodextrins (CyDs): β-cyclodextrin (CD), hydroxypropyl-β-cyclodextrin (HPCD), and methyl-β-cyclodextrin (MCD) were used. Solubility depended on the type of CyDs. Increased solubility was obtained when the more substituted CyDs (HPCD or MCD) were used instead of nonsubstituted CD. Stability constants were calculated assuming a 1:1 stoichiometry. Calculated stability constant values depended on initial solubility of drug and pH of the medium. Solid ABZ complexes were prepared by coprecipitation and freeze-drying methods. These products were compared with physical mixtures of ABZ and CyDs. The characterization of these products was made by differential scanning calorimetry (DSC) and drug release studies. True inclusion complexes were obtained only by the freeze-drying method. Drug release studies showed that the freeze-dried inclusion complexes increased the solubility rate of ABZ, although a supersaturation effect was observed when drug release studies were performed in nonsink conditions. A bioavailability study on mice was done with a formulation of ABZ : HPCD complex and was compared to a conventional ABZ suspension. A significantly (p <. 05) shorter T_max of absorption was obtained by using the complex formulation. Greater and significant (p <. 05) differences for AUC and C_max were observed.     

Characterization of C-N Thin Films Prepared by Ion Beam Sputtering

C-N thin films have been prepared by ion beam sputtering using pure N2 as discharge gas. The ratio N/C of the films measured by Auger spectrum is 20% on an average. The results of X-ray diffraction and transmission electron microscopy show that β-C3N4 phase exists in the films. Xray photoelectron spectroscopy shows that nitrogen is mostly combined with carbon with triple (C=N) and double (C=N) bonds. The IR absorption shows an absorption bond near 2185 cm-1assigned to the C=N, no trace of C-C bond was observed     

Arc-Discharge Synthesis and Microstructure Characterization of AIN Nanowires

AIN nanowires with a hexagonal structure were synthesized using an improved arc-discharge method and their microstructures were characterized using a high-resolution transmission electron microscope. The synthesized AIN nanowires were of various shapes. Their diameters ranged from 20 to 110 nm and the lengths were up to 20 μm. Most of the AIN nanowires were coated by an amorphous layer of aluminum oxide. Fabrication yield was about several grams. The growth mechanism was considered to be a vapor-liquid-solid process and an AI droplet formed on the top of as-grown AIN nanowire played a role of catalyst.     

Characterization of silicon phases in spray-formed and extruded hypereutectic Al–Si alloys by image analysis

The silicon phases in the spray-formed and extruded hypereutectic Al–Si alloys (AlSi18, AlSi25 and AlSi35) have been quantitatively evaluated by means of image analysis technique. The influence of silicon content in the alloys, thermal conditions during spray forming of the alloys and hot extrusion of the spray-formed alloys on the size, shape, dispersion and orientation of the silicon phases have been studied and discussed. In general, the silicon phases are greatly refined and uniformly distributed in the spray-formed Al–Si alloys. This improvement in the silicon phases is further facilitated by low thermal input as well as fast cooling conditions during spray forming. The silicon particles in the as-extruded Al–Si alloys appear more homogeneous and regular than those in the as-deposited Al–Si alloys but exhibit a certain amount of anisotropy and a tendency to preferred orientation. The silicon particles, depending on the particle size and shape, may fracture or coarsen during extrusion.     

Preparation and Characterization of Fe3O4 Magnetic Nano-particles by 60Co γ-ray Irradiation

By using a new method, ^60Co γ-ray irradiation, Fe3O4 magnetic nano-particles were successfully synthesized at room temperature under ambient pressure. The structure, morphology and magnetic properties of these nanoparticles were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM） and vibrating sample magnetometer （VSM）, respectively. The radiation formation mechanism was also discussed. The results show that the absorbed dose can greatly influence the structure, morphology and magnetic properties of the products. XRD and TEM studies show that the product prepared by γ-ray irradiation （10 kGy） is pure FesO4 phase and the mean diameter of these nano-particles is about 21 nm. The Fe3O4 nano-particles synthesized by γ-ray irradiation （10 kGy） are mainly in small cubic shape and the size uniformity of these particles is good.     

Characterization of hydroxyapatite– and bioglass–316L fibre composites prepared by spark plasma sintering

To improve the mechanical properties of pure hydroxyapatite (HA) ceramics and pure 45S5 bioglasses, HA–316L fibre composites and bioglass 45S5–316L fibre composites were produced by spark plasma sintering (SPS) at 950 and 850 °C, respectively. While the HA phase in the HA–316L fibre composites did not decompose after the SPS process, microcracks were found around the 316L fibres in the composites. Consequently, the HA–316L fibre composites could not effectively improve the mechanical properties of the pure HA ceramics. In contrast, the bioglass 45S5–316L fibre composites showed no microcracks around the 316L fibres and thus exhibited bending strengths of up to 115 MPa.     

Cooperation and technological areas in the state universities of São Paulo: An analysis from the perspective of the triple helix model

This article analyzes the technological cooperation networks, and their respective areas, of the public universities of the State of São Paulo that resulted in patent. The cooperation networks were built from the assignee data and for the technology areas networks the International Patent Classification. It adopted the metrics of Social Network Analysis to characterize these partnerships and analyze it from the perspective of the Triple Helix. A total of 458 technology partnerships were identified that resulted in patents, 210 at USP, 173 at UNICAMP and 75 at UNESP. The main partners were companies and other universities, follow by research institutes, government support institutions and support foundations had low participation, except for FAPESP and EMBRAPA. Regarding technological areas, technologies with applications in the health sector and chemical were the most representative. It was found that the cooperation is still developed in an incipient way, especially regarding the continuity of technological development. In general, there is the multidisciplinary portfolio of patents from universities, but with strong guidance for the areas of health, indicating the search for expertise in this area of expertise.