Effect of the addition of silanated silica on the mechanical properties of microwave heat-cured acrylic resin

Effect of the addition of silanated silica on the mechanical properties of microwave heat-cured acrylic resinObjectives: The purpose of this study was to evaluate the flexural strength and Vickers hardness of a microwave energy heat-cured acrylic resin by adding different concentrations of silane surface-treated nanoparticle silica.Methods: Acrylic resin specimens with dimensions of 65 x 10 x 2.5 mm were formed and divided into five experimental groups (n = 10) according to the silica concentration added to the acrylic resin mass (weight %) prior to polymerisation : G1, without silica; G2, 0.1% silica; G3, 0.5% silica; G4, 1.0% silica; and G5, 5.0% silica. The specimens were submitted to a three-point flexural strength test and to the Vickers hardness test (HVN). The data obtained were statistically analysed by ANOVA and the Tukey test (alpha = 0.05).Results: Regarding flexural strength, G5 differed from the other experimental groups (G1, G2, G3 and G4) presenting the lowest mean, while G4 presented a significantly higher mean, with the exception of group G3. Regarding Vickers hardness, a decrease in values was observed, in which G1 presented the highest hardness compared with the other experimental groups.Conclusion: Incorporating surface-treated silica resulted in direct benefits in the flexural strength of the acrylic resin activated by microwave energy; however, similar results were not achieved for hardness.

Influence of iron addition on the microstructure and the electrochemical corrosion of Al-Zn-Mg alloys

The effect of Fe addition on the microstructural properties and the corrosion resistance of Al-Zn-Mg alloys submitted to different heat treatments (cast, annealed and aged), has been studied in chloride solutions using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), cyclic polarization (CP) and open circuit potential (o.c.p.) measurements. The presence of 0.3% Fe in the alloy limited the growth of the MgZn2 precipitates, both in the annealed and in the quenched specimens. No effect of Cr on the grain size in the presence of Fe was found because of the accumulation of Cr in the Fe-rich particles. Fe in the Al-Zn-Mg alloys also made them more susceptible to pitting. Pitting occurred mainly near the Fe-rich particles both, under o.c.p. conditions in O-2-saturated solutions and during the CP.

Zero valent iron mediated degradation of the pharmaceutical diazepam

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

Effect of iron on bovine enamel and on the composition of the dental biofilm formed in situ

Objectives: This study investigated in situ the effect of iron (Fe) on the reduction of demineralization of bovine enamel, as well as on the composition of dental biofilm.Design and methods: Twelve volunteers were included in this blind crossover study, which was conducted in two stages of 14 days each. For each stage, the volunteers received palatal appliances containing four blocks of bovine enamel (4 mm x 4 mm x 2.5 mm). Six volunteers dripped a solution of 15 mmol L-1 ferrous sulphate onto the fragments and the remaining six dripped deionized water (eight times per day). After five minutes, a fresh 20% (w/v) sucrose solution was dripped onto all enamel blocks. During the experimental period the volunteers brushed their teeth with non-fluoridated dentifrice. After each stage, the percentage of surface microhardness change (%SMHC) and area of mineral toss (Delta Z) were determined on enamel and the dental biofilm formed on the blocks was collected and analysed for F, P, Ca, Fe and alkali-soluble carbohydrates. The concentrations of F, Ca and Fe in enamel were also analysed after acid biopsies.Results: There was a statistically significant increase in the P and Fe concentrations in the biofilms treated with ferrous sulphate (p < 0.05), which was not observed for F, Ca and alkali-soluble carbohydrates. The group treated with ferrous sulphate had significantly lower %SMHC and Delta Z when compared to control (p < 0.05).Conclusions: These results showed that ferrous sulphate reduced the demineralization of enamel blocks and altered the ionic composition of the dental biofilm formed in situ. (c) 2005 Elsevier Ltd. All rights reserved.

Heterogeneous Fenton reactants: a study of the behavior of iron oxide nanoparticles obtained by the polymeric precursor method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Study of cutting forces on machinability properties of gray cast iron using new ceramics cutting tools

During gray cast iron cutting, the great rate of mechanical energy from cutting forces is converted into heat. Considerable heat is generated, principally in three areas: the shear zone, rake face and at the clearance side of the cutting edge. Excessive heat will cause undesirable high temperature in the tool which leads to softening of the tool and its accelerated wear and breakage. Nowadays the advanced ceramics are widely used in cutting tools. In this paper a composition special of Si3N4 was sintering, characterized, cut and ground to make SNGN120408 and applyed in machining gray cast iron with hardness equal 205 HB in dry cutting conditions by using digital controlled computer lathe. The tool performance was analysed in function of cutting forces, flank wear, temperature and roughness. Therefore metal removing process is carried out for three different cutting speeds (300 m/min, 600 m/min, and 800 m/min), while a cutting depth of 1 mm and a feed rate of 0.33 mm/rev are kept constant. As a result of the experiments, the lowest main cutting force, which depends on cutting speed, is obtained as 264 N at 600 m/min while the highest main cutting force is recorded as 294 N at 300 m/min.

Plasma nitriding and nitrocarburising of a supermartensitic stainless steel

Supermartensitic stainless steels (SMSSs) are a new generation of the classic 13%Cr martensitic steels, lower in carbon and with additional alloying of nickel and molybdenum offering better weldabilty and low temperature toughness. Several works have shown that plasma nitriding and nitrocarburising of stainless steels at low temperatures produces a hard surface layer which results in increased wear resistance. In this work, SMSS samples were plasma nitrided and nitrocarburised at 400, 450 and 500 °C. The plasma treated SMSS samples were characterised by means of optical microscopy, microhardness, X-ray diffraction and dry wear tests. The thickness of the layers produced increases as temperature is raised, for both plasma nitriding and nitrocarburising. X-ray diffraction demonstrates that the chromium nitride content grows with temperature for nitriding and nitrocarburising, which also showed increasing content of iron and chromium carbides with temperature. After plasma treating, it was found that the wear volume decreases for all temperatures and the wear resistance increased as the treatment temperature was raised. The main wear mechanism observed for both treated and untreated samples was grooving abrasion. © 2012 IHTSE Partnership Published by Maney on behalf of the Partnership.

Heat shock protein production and immunity and altered fetal development in diabetic pregnant rats

We evaluated associations between the concentrations of heat shock proteins (hsp60 and hsp70) and their respective antibodies, alterations in maternal reproductive performance, and fetal malformations in pregnant rats with hyperglycemia. Mild diabetes (MD) or severe diabetes (SD) was induced in Sprague-Dawley rats prior to mating; non-treated non-diabetic rats (ND) served as controls. On day 21 of pregnancy, maternal blood was analyzed for hsp60 and hsp70 and their antibodies; and fetuses were weighed and analyzed for congenital malformations. Hsp and anti-hsp levels were correlated with blood glucose levels during gestation. There was a positive correlation between hsp60 and hsp70 levels and the total number of malformations (R∈=∈0.5908, P∈=∈0.0024; R∈=∈0.4877, P∈=∈0.0134, respectively) and the number of malformations per fetus (R∈=∈0.6103, P∈=∈0.0015; R∈=∈0.4875, P∈=∈0.0134, respectively). The anti-hsp60 IgG concentration was correlated with the number of malformations per fetus (R∈=∈0.3887, P∈=∈0.0451) and the anti-hsp70 IgG level correlated with the total number of malformations (R∈=∈0.3999, P∈=∈0.0387). Moreover, both hsp and anti-hsp antibodies showed negative correlations with fetal weight. The results suggest that there is a relationship between hsp60 and hsp70 levels and their respective antibodies and alterations in maternal reproductive performance and impaired fetal development and growth in pregnancies associated with diabetes. © 2012 Cell Stress Society International.

Testing extractants for Cu, Fe, Mn, and Zn in tropical soils treated with sewage sludge for 13 consecutive years

In this paper, we report on a field experiment being carried out in a Typic Eutrorthox. The experiment was initiated in the 1997-98 agricultural season as a randomized block design with four treatments (0, 5, 10, and 20 t ha -1) of sewage sludge and five replicates. Compound soil samples were obtained from 20 subsamples collected at depths of 0-0.1 and 0.1-0.2 m. Cu, Fe, Mn, and Zn concentrations were extracted with DTPA pH 7.3; 0.1 mol L -1 HCl, Mehlich-I, Mehlich-III, and 0.01 mol L-1 CaCl 2. Metal concentrations were determined via atomic absorption spectrometry. Diagnostic leaves and the whole above-ground portion of plants were collected to determine Cu, Fe, Mn, and Zn concentrations extracted by nitric-perchloric digestion and later determined via atomic absorption spectrometry. Sewage sludge application caused increases in the concentrations of soil Cu, Fe, and Mn in samples taken from the 0-0.1 m depth evaluated by the extractants Mehlich-I, Mehlich-III, 0.01 mol L-1 HCl and DTPA pH 7.3. None of the extractants provided efficient estimates of changes in Mn concentrations. The acid extractants extracted more Cu, Fe, Mn, and Zn than the saline and chelating solutions. The highest concentrations of Cu, Fe, and Zn were obtained with Mehlich-III, while the highest concentrations of Mn were obtained with HCl. We did not observe a correlation between the extractants and the concentrations of elements in the diagnostic leaves nor in the tissues of the whole maize plant (Zea mays L.). © 2013 Springer Science+Business Media Dordrecht.

Behavior of Peruvian carrot (Arracacia xanthorrhiza) and cassava (Manihot esculenta) starches subjected to heat-moisture treatment

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

Spin-dependent beating patterns in thermoelectric properties: Filtering the carriers of the heat flux in a Kondo adatom system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Heat Treatment and Yb-Fiber Laser Welding of a Maraging Steel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Behavior of Peruvian carrot (Arracacia xanthorrhiza) and cassava (Manihot esculenta) starches subjected to the heat-moisture treatment

Peruvian carrot and cassava starches were isolated, adjusted to 30 and 35% moisture, and heatedat 90°C for 8 h. Structural and physicochemical characteristics of the treated starches wereevaluated and compared. High performance anion exchange chromatography with pulsedamperometric detector (HPAEC-PAD), gel permeation chromatography (GPC), and amylosecontent, revealed that the HMT did not change the chemical structures of the starches. A largeagglomeration of granules was observed from SEM, particularly in the Peruvian carrot starch.Crystalline patterns in Peruvian carrot and cassava starches changed from B to C and CAto A,respectively. Relative crystallinity decreased from 30 to 25% in Peruvian Carrot starch, andincreased from 35 to 37% in cassava starch adjusted to 30% moisture. SF and peak viscositydecreased, breakdown was almost completely eliminated (particularly in the Peruvian carrotstarch), and final viscosity increased. WAI and WSI increased as moisture levels of bothstarches increased. Gelatinization temperatures increased and enthalpy decreased. Degrees ofgelatinization increased as the moisture level increased, reaching 33 and 72% in the cassavaand Peruvian carrot starches, respectively. HMT strengthened the intra- and intermolecularinteractions of starches and increased their stability during heating and shearing, but also causeda partial gelatinization in the starches, particularly in Peruvian carrot starch.

Parameters optimization of heat treatment for obtaining luminescent PZT powders

Low crystalline PZT powder samples were successfully synthesized using polymeric precursor method and slow decomposition steps. The polymeric resin precursor was thermal treated in a muffle type oven varying the temperature from 250 °C to 700 °C and the time from 3 to 24 hours in order to investigate the order/disorder mechanism toward the amorphous powders. Powder samples with low crystalline phases were obtained at lower temperatures and long time of thermal treatment, demonstrating a kinetic dependence for organic removal and a thermodynamic barrier for crystallization processes. Through XRD and FTIR spectroscopy characterizations the long time thermal treated samples showed to be composed of the solid solution of metal oxides in absent of organic matter, originating broad XRD peaks profiles and no carbonaceous bands in FTIR spectra. A Photoluminescence characterization showed that the peak emission is higher for disordered and homogeneous phases, which only can be reached through the long time of thermal treatment.

Effect of the iron doping on the thermal decomposition of the polymeric precursor for the titanium dioxide powder synthesis

The Polymeric Precursor Method has proved suitable for synthesizing reactive powders using low temperatures of calcination, especially when compared with conventional methods. However, during the thermal decomposition of the polymeric precursor the combustion event can be releases an additional heat that raises the temperature of the sample in several tens of degrees Celsius above the set temperature of the oven. This event may be detrimental to some material types, such as the titanium dioxide semiconductor. This ceramic material has a phase transition at around 600 ° C, which involves the irreversible structural rearrangement, characterized by the phase transition from anatase to rutile TiO2 phase. The control of the calcination step then becomes very important because the efficiency of the photocatalyst is dependent on the amount of anatase phase in the material. Furthermore, use of dopant in the material aims to improve various properties, such as increasing the absorption of radiation and in the time of the excited state, shifting of the absorption edge to the visible region, and increasing of the thermal stability of anatase. In this work, samples of titanium dioxide were synthesized by the Polymeric Precursor Method in order to investigate the effect of Fe (III) doping on the calcination stages. Thermal analysis has demonstrated that the Fe (III) insertion at 1 mol% anticipates the organic decomposition, reducing the combustion event in the final calcination. Furthermore, FTIR-PAS, XRD and SEM results showed that organic matter amount was reduced in the Fe (III)-doped TiO2 sample, which reduced the rutile phase amount and increased the reactivity and crystallinity of the powder samples.