Estudo da síntese e sinterização de pós compósitos do sistema Ta-Cu

Ta-Cu bulk composites combine high mechanical resistance of the Ta with high electrical and thermal conductivity of the Cu. These are important characteristics to electrical contacts, microwave absorber and heat skinks. However, the low wettability of Ta under Cu liquid and insolubility mutual these elements come hard sintering this composite. High-energy milling (HEM) produces composite powders with high homogeneity and refines the grain size. This work focus to study Ta-20wt%Cu composite powders prepared by mechanical mixture and HEM with two different conditions of milling in a planetary ball mill and then their sintering using hydrogen plasma furnace and a resistive vacuum furnace. After milling, the powders were pressed in a steel dye at a pressure of 200 MPa. The cylindrical samples pressed were sintered by resistive vacuum furnace at 10-4torr with a sintering temperature at 1100ºC / 60 minutes and with heat rate at 10ºC/min and were sintered by plasma furnace with sintering temperatures at 550, 660 and 800ºC without isotherm under hydrogen atmosphere with heat rate at 80ºC/min. The characterizations of the powders produced were analyzed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and laser granulometry. After the sintering the samples were analyzed by SEM, XRD and density and mass loss tests. The results had shown that to high intense milling condition produced composite particles with shorter milling time and amorphization of both phases after 50 hours of milling. The composite particles can produce denser structure than mixed powders, if heated above the Cu melting point. After the Cu to arrive in the melting point, liquid copper leaves the composite particles and fills the pores

Piezoelectric effect in composite polyurethane - Ferroelectric ceramics

Flexible and free-standing films of piezoelectric composites made up of lead zirconate titanate (PZT) ceramic powder dispersed in a castor oil-based polyurethane (PU) matrix were obtained by spin coating and characterised as materials for sensor applications. The piezoelectric coefficients d(31) and d(33) were measured with the usual technique. The piezoelectric charge constant d(33) yields values up to less than or equal to 24 pC/N, even at lower PZT content (33 vol%). Some desirable properties like piezoelectricity, flexibility and good mechanical resistance show this new material to be a good alternative for use as sensors and actuators.

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.

Dielectric and pyroelectric properties of a composite of ferroelectric ceramic and polyurethane

Flexible piezo- and pyroelectric composite was made in the thin film form by spin coating. Lead Zirconate Titanate (PZT) ceramic powder was dispersed in a castor oil-based polyurethane (PU) matrix, providing a composite with 0-3 connectivity. The dielectric data, measured over a wide range of frequency (10(-5) Hz to 105 Hz), shows a loss peak around 100 Hz related with impurities in the polymer matrix. There is also an evidence of a peak in the range 10(-4) Hz, possibly originating from the glass transition temperature T of the polymer. The pyroelectric coefficient at 34 K is 7.0x10(-5) C(.)m(-2.)K(-1) which is higher than that of P-PVDF (1X10(-5) C(.)m(-2.)K(-1)).

Pyroelectric composite film for X-ray intensity detection

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

Comparison of the univariate and multivariate methods in the optimization of experimental conditions for determining Cu, Pb, Ni and Cd in biodiesel by GFAAS

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

Piezo and Dielectric Properties of PHB-PZT Composite

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

Assessing the surface roughness of a posterior resin composite: effect of surface sealing

This study assessed the in vitro influence of surface sealing on the surface roughness of a posterior resin composite before and after tooth-brushing. Thirty. specimens (13 nun diameter x 1 mm high) were fabricated from Filtek-P60 resin composite and randomly assigned to three groups (n=10): a non-sealed control and two groups sealed with one of the tested materials-a surface-penetrating sealant (Protect-it!-PI) and a one bottle adhesive system (Single Bond-SB). The samples were subjected to a surface roughness reading to determine the initial roughness, then submitted to simulated toothbrushing with 35,600 cycles for 100 minutes. Specimens were then cleaned and a post-abrasion surface roughness reading accomplished. Means (pm), recorded before (B) and after (A) toothbrushing, and standard deviations were: Control-(B): 0.032 (+/-0.005), (A): 0.054 (+/-0.005); PI-(B): 0.034 (+/-0.005), (A): 0.060 (+/-0.034); SB (B): 0.031 (+/-0.004), (A): 0.047 (+/-0.007). Data were tabulated and submitted to two-way ANOVA. No statistically significant difference was observed when the control and experimental groups were compared. However, a significant difference (p<0.05) was found between the measurements performed before and after toothbrushing. Based on these results, it may be concluded that using either a surface penetrating sealant or a one bottle adhesive system did not provide the optimization of superficial integrity. The use of a dentifrice and toothbrush resulted in significant alterations to the surface smoothness of the resin composite.

Measurement of shrinkage of composite resin by laser speckle contrast analysis

The aim of this study was to evaluate the shrinkage of a microhybrid dental composite resin photo-activated by one LED with different power densities by means of speckle technique. The dental composite resin Filtek (TM) Z-250 (3M/ESPE) at color A(2) was used for the samples preparation. Uncured composite was packed in a metallic mold and irradiated during 20 s from 100 to 1000 mW cm(-2). For the photo-activation of the samples, it was used a LED prototype (Light Emission Diode) with wavelength centered at 470 nm and adjustable power density until 1 W cm(-2). The speckle patterns obtained from the bottom composite surfaces were monitored using a CCD camera without lens. The speckle field is recorded in a digital picture and stored by CCD camera as the carrier of information on the displacement of the tested surface. The calculated values were obtained for each pair of adjacent patterns and the changes in speckle contrast as a function of time were obtained from six repeated measurements. The speckle contrasts obtained from the bottom surface with 100 mW cm(-1) were smaller than those than the other power densities. The higher power densities provided the higher shrinkage.

Evaluation of Cu, Mn, and Se in Vegetables Using Ultrasonic Extraction and GFAAS Quantification

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

Measurement of W+W- production and search for the Higgs boson in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of W gamma and Z gamma production in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for a heavy gauge boson W ' in the final state with an electron and large missing transverse energy in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for a W ' boson decaying to a muon and a neutrino in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Charge injection in an LED with a hybrid composite as the emissive layer

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