Cyclic-oxidation behavior of Ti3SiC2-base material at 1100��c

The cyclic-oxidation behavior of Ti3SiC2-base material was studied at 1100��C in air. Scale spallation and weight loss were not observed in the present tests and the weight gain would just continue if the experiments were not interrupted. The present results demonstrated that the scale growth on Ti3SiC2-base material obeyed a parabolic rate law up to 20 cycles. It then changed to a linear rate with further increasing cycles. The scales formed on the Ti3SiC2base material were composed of an inward-growing, fine-grain mixture of Ti022 + SiO2 and an outward-growing, coarse-grain TiO2. Theoretical calculations show that the mismatch in thermal expansion coefficients between the inner scale and Ti3SiC2-base matrix is small. The outer TiO2 layer was under very low compressive stress, while the inner TiO2 + SiO2 layer was under tensile stress during cooling. Scale spaliation is, therefore, not expected and the scale formed on Ti3SiC2-base material is adherent and resistant to cyclic oxidation.

Base material characterisation of spoil piles at BMA coal mines

This project was an initiation to investigate slaking induced properties detrition of spoil pile materials with overburden pressure and time. The changes in the material properties over time are important parameters that control the behaviour and performance of the piles. The time dependent mechanical and hydraulic properties reported together with mineralogical changes. One chamber designed to apply slaking in the laboratory and geotechnical investigation conducted to fulfil the objective of this project.

Effect of monomer treatment and polymerisation methods on the bond strength of resin teeth to denture base material

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Bonding strength between a hard chairside reline resin and a denture base material as influenced by surface treatment

Direct relining of dentures made with hard chairside reline resins is faster than laboratory-processed reline systems and the patient is not without the prosthesis for the time necessary to perform the laboratory procedures. However, a weak bond between the autopolymerizing acrylic reline resins and the denture base material has been observed. This study evaluated the effect of six different surface treatments on the bond strength between a hard chairside reline acrylic resin and ia heat-cured acrylic resin. Specimens of the heat-cured acrylic resin were divided into seven groups. one of these groups remained intact. In the other groups, a 10-mm square section was removed from the centre of each specimen. The bonding surfaces were then treated with (i) methyl methacrylate monomer, (ii) isobutyl methacrylate monomer, (iii) chloroform, (iv) acetone, (v) experimental adhesive and (vi) no surface treatment-control group. Kooliner acrylic resin was packed,into the square sections and polymerized. The bonding strength was evaluated by a three-point loading test. The results were submitted to one-way analysis of variance (ANOVA) followed by a Tukey multiple range test at a 5% level of significance. No significant difference was found between the surface treatment with Lucitone 550 monomer or chloroform, but both were stronger than the majority of the other groups. The bond strength provided by all the surface treatments was lower than that of the intact heat-cured resin.

Color stability of resins and nylon as denture base material in beverages

Purpose: Staining of prosthodontic materials may result in patient dissatisfaction and additional expense for replacement. This study aimed to determine the color stability of two heat-cured denture base acrylic (Lucitone 550, Vipi Cril) and one nylon denture base resin (Transflex) after immersion in beverages. Materials and Methods: Forty disks of each resin (20.0-mm diameter, 3.0-mm thick) were prepared and stored in distilled water for 24 hours at 37��C. During that time (T 0), the color of all specimens was spectrophotometrically measured. Each specimen was immersed in coffee, cola, red wine, and distilled water as a means of control. After 15-day (T 1) and 30-day (T 2) periods of immersion, the color of the specimens was measured again. The CIE (Commission Internationale de L' Eclairage) L*a*b* system was used to determine mean ��E (color changes) values for each material and compared statistically with two-way ANOVA and Bonferroni intervals at 0.95. Results: In ��ET 0T 1 and ��ET 0T 2 the most severe staining was apparent with red wine (p < 0.001), followed by coffee (p < 0.01), when compared to the specimens stored in distilled water. Transflex also showed significant color change after immersion in cola (p < 0.01). In ��ET 1T 2 only red wine promoted significant staining of all resins (p < 0.0001). Conclusion: Chromatic changes were exhibited by specimens immersed in red wine, followed by coffee. For Transflex, cola also promoted color changes. The values of color changes converted to National Bureau of Standard units showed them to be perceivable to the human eye. �� 2011 by the American College of Prosthodontists.

O Estado no sistema sociometab��lico do capital: uma rela����o de complementaridade na base material

P��s-gradua����o em Ci��ncias Sociais - FFC

Method development using ICP-MS and LA-ICP-MS and their application in environmental and material science

Within this PhD thesis several methods were developed and validated which can find applicationare suitable for environmental sample and material science and should be applicable for monitoring of particular radionuclides and the analysis of the chemical composition of construction materials in the frame of ESS project. The study demonstrated that ICP-MS is a powerful analytical technique for ultrasensitive determination of 129I, 90Sr and lanthanides in both artificial and environmental samples such as water and soil. In particular ICP-MS with collision cell allows measuring extremely low isotope ratios of iodine. It was demonstrated that isotope ratios of 129I/127I as low as 10-7 can be measured with an accuracy and precision suitable for distinguishing sample origins. ICP-MS with collision cell, in particular in combination with cool plasma conditions, reduces the influence of isobaric interferences on m/z = 90 and is therefore well-suited for 90Sr analysis in water samples. However, the applied ICP-CC-QMS in this work is limited for the measurement of 90Sr due to the tailing of 88Sr+ and in particular Daly detector noise. Hyphenation of capillary electrophoresis with ICP-MS was shown to resolve atomic ions of all lanthanides and polyatomic interferences. The elimination of polyatomic and isobaric ICP-MS interferences was accomplished without compromising the sensitivity by the use of a high resolution mode as available on ICP-SFMS. Combination of laser ablation with ICP-MS allowed direct micro and local uranium isotope ratio measurements at the ultratrace concentrations on the surface of biological samples. In particular, the application of a cooled laser ablation chamber improves the precision and accuracy of uranium isotopic ratios measurements in comparison to the non-cooled laser ablation chamber by up to one order of magnitude. In order to reduce the quantification problem, a mono gas on-line solution-based calibration was built based on the insertion of a microflow nebulizer DS-5 directly into the laser ablation chamber. A micro local method to determine the lateral element distribution on NiCrAlY-based alloy and coating after oxidation in air was tested and validated. Calibration procedures involving external calibration, quantification by relative sensitivity coefficients (RSCs) and solution-based calibration were investigated. The analytical method was validated by comparison of the LA-ICP-MS results with data acquired by EDX.

Estudo da remedia����o de um aqu��fero contaminado com sulfato e metais atrav��s de barreira reativa perme��vel org��nica.

Este trabalho teve como objetivo geral estudar a viabilidade t��cnica de utilizar baga��o de cana como meio reativo de barreiras reativas perme��veis (BRP) para remo����o de sulfato e metais de ��guas subterr��neas contaminadas. O estudo baseou-se em investiga����o experimental, por meio de ensaios laboratoriais de coluna, e em modelagem matem��tica, para a qual utilizaram-se tamb��m alguns dados obtidos em um estudo de caso de uma unidade industrial contaminada com sulfato e metais. Neste local contaminado, as caracter��sticas hidrogeol��gicas e topogr��ficas propiciam a utiliza����o de uma barreira reativa perme��vel como t��cnica de remedia����o. Barreiras reativas perme��veis s��o uma alternativa para remedia����o de ��guas subterr��neas que vem progredindo rapidamente na ��ltima d��cada, a partir de ensaios de bancada e coluna em laborat��rio para implementa����o em escala real em campo. Tr��s colunas bi��ticas foram montadas utilizando baga��o de cana como meio reativo e um material de base poroso constitu��do de areia e cascalho para fornecer adequada condutividade hidr��ulica, com a propor����o de 1:28 em massa seca. Tamb��m foi adicionado ao meio reativo um in��culo bacteriano composto por esterco bovino dissolvido. Uma quarta coluna, sem in��culo e contendo um agente biocida, comp��s o experimento branco (abi��tico). Uma solu����o sint��tica foi introduzida nas colunas simulando condi����es da ��gua subterr��nea do estudo de caso, com velocidade de Darcy em torno de 2,0x10-7 m/s composta por sulfato e metais (zinco e n��quel) com concentra����es de 6.000 mg/L e 15 mg/L, respectivamente. Os resultados das an��lises da fase l��quida das colunas bi��ticas apresentaram: (i) m��dia da taxa de remo����o de sulfato durante todo o tempo do experimento de 49 mg/L/dia; (ii) as concentra����es de Zn e Ni diminu��ram de 15 mg/L para valores n��o detect��veis pela t��cnica anal��tica utilizada (< 0,01 mg/L); (iii) aumento do pH de 5.5-5.8 para valores entre 6,8-8,0; (iv) redu����o do valor do potencial de ��xido redu����o (Eh) para valores de at�� -200mV. N��o foram observadas redu����es das concentra����es de metais e sulfato na fase l��quida da coluna abi��tica e os valores de pH e Eh permaneceram dentro das faixas iniciais. An��lises nas fases s��lidas das colunas bi��ticas por MEV e EDS ap��s o t��rmino do experimento identificaram a presen��a de Ni, Zn, S e Mn, indicando a precipita����o desses metais em forma de sulfetos. Estes elementos n��o foram detectados na fase s��lida da coluna abi��tica. Assim, p��de-se inferir que toda a remo����o de sulfato verificada nas colunas bi��ticas pode ser atribu��da a redu����o bacteriana de sulfato. A partir das condi����es experimentais dos ensaios, foi realizada a modelagem e o dimensionamento da BRP. Para a estimativa da cin��tica de redu����o de sulfato, aplicou-se a solu����o anal��tica de Van Genuchten para transporte de contaminantes com degrada����o, obtendo-se uma taxa de decaimento de primeira ordem de 0,01 dia-1. A determina����o da espessura e tempo de resid��ncia da barreira foi realizada considerando que a concentra����o de sulfato na sa��da da barreira fosse menor ou igual a 250 mg/L. O resultado do dimensionamento de uma BRP preenchida com baga��o de cana e areia nas propor����es de 1:28 em massa seca resultaria em uma BRP de 7,1 m de espessura, com tempo de resid��ncia de 950 dias, no local de estudo de caso. Caso fosse utilizado o dobro da propor����o de baga��o de cana e areia em massa seca (1:14), a implanta����o da BRP apresentar-se-ia vi��vel, com espessura aproximada de 4 m. Atrav��s destes resultados, p��de ser comprovada a hip��tese de que baga��o de cana como substrato e esterco bovino como in��culo comp��em um meio reativo vi��vel para a redu����o de sulfato e precipita����o de metais em uma BRP.

Concurrent multi-scale modeling of civil infrastructures for analyses on structural deterioration���Part I : Modeling methodology and strategy

This paper aims to develop the methodology and strategy for concurrent finite element modeling of civil infrastructures at the different scale levels for the purposes of analyses of structural deteriorating. The modeling strategy and method were investigated to develop the concurrent multi-scale model of structural behavior (CMSM-of-SB) in which the global structural behavior and nonlinear damage features of local details in a large complicated structure could be concurrently analyzed in order to meet the needs of structural-state evaluation as well as structural deteriorating. In the proposed method, the ���large-scale��� modeling is adopted for the global structure with linear responses between stress and strain and the ���small-scale��� modeling is available for nonlinear damage analyses of the local welded details. A longitudinal truss in steel bridge decks was selected as a case to study how a CMSM-of-SB was developed. The reduced-scale specimen of the longitudinal truss was studied in the laboratory to measure its dynamic and static behavior in global truss and local welded details, while the multi-scale models using constraint equations and substructuring were developed for numerical simulation. The comparison of dynamic and static response between the calculated results by different models indicated that the proposed multi-scale model was found to be the most efficient and accurate. The verification of the model with results from the tested truss under the specific loading showed that, responses at the material scale in the vicinity of local details as well as structural global behaviors could be obtained and fit well with the measured results. The proposed concurrent multi-scale modeling strategy and implementation procedures were applied to Runyang cable-stayed bridge (RYCB) and the CMSM-of-SB of the bridge deck system was accordingly constructed as a practical application.

Taming of large diameter triaxial setup

Triaxial tests are essential to estimate the shear strength properties of the soil or rock. Normally triaxial tests are carried out on samples of 38 mm diameter and 76 mm height. Granular materials, predominantly used in base/sub-base construction of pavements or in railways have size range of 60-75 mm. Determination of shear strength parameters of those materials can be made possible only through triaxial tests on large diameter samples. This paper describes a large diameter cyclic triaxial testing facility set up in the Geotechnical Engineering lab of Indian Institute of Science. This setup consists of 100 kN capacity dynamic loading frame, which facilitates testing of samples of up to 300 mm diameter and 600 mm height. The loading ram can be actuated up to a maximum frequency of 10 Hz, with maximum amplitude of 100 mm. The setup is capable of carrying out static as well as dynamic triaxial tests under isotropic, anisotropic conditions with a maximum confining pressure of 1 MPa. Working with this setup is a difficult task because of the size of the sample. In this paper, a detailed discussion on the various problems encountered during the initial testing using the equipment, the ideas and solutions adopted to solve them are presented. Pilot experiments on granular sub-base material of 53 mm down size are also presented.

Laser Guiding in the Randomicity of Discrete Surface Strengthening by Arc Discharge

Several discharge areas by laser-guided discharge (LGD) were compared with those by common arc discharge. The randomicity of discharge areas by common arc discharge was controlled by laser guiding on two scales: large scale (the spacing of the discharge areas) and small scale (the inside of the discharge area). The position of the discharge area overlapped completely with a laser focus; therefore, the distribution and surface shape of the discharge areas were controlled. The stochastic movement of anode spot in the discharge area was controlled by laser guiding. As such, the repetitive melting and solidifying of microstructures in the discharge area was constrained. The tempered microstruc- tures in the discharge area were voided, the utilization ef���ciency of input energy was improved, and the strengthened depth of the discharge areas was increased. The regularity of cross-sectional shape of the discharge area was also improved. The hardness of microstructures in both discharge areas is greater than that of the base material. The highest level of hardness of microstructures in both discharge areas measures above 1000 HV. In summary, the hardness ofmicrostructures in the discharge area by LGD is larger and more discrete than that by common arc discharge.

Thermal barrier coating of lanthanum-zirconium-cerium composite oxide made by electron beam-physical vapor deposition

Lanthanum-zirconium-cerium composite oxide (La-2(Zr0.7Ce0.3)(2)O-7, LZ7C3) as a candidate material for thermal barrier coatings (TBCs) was prepared by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, thermophysical properties, surface and cross-sectional morphologies and cyclic oxidation behavior of the LZ7C3 coating were studied. The results indicated that LZ7C3 has a high phase stability between 298 K and 1573 K, and its linear thermal expansion coefficient (TEC) is similar to that of zirconia containing 8 wt% yttria (8YSZ). The thermal conductivity of LZ7C3 is 0.87 W m(-1) K-1 at 1273 K, which is almost 60% lower than that of 8YSZ. The deviation of coating composition from the ingot can be overcome by the addition of excess CeO2 and ZrO2 during ingot preparation or by adjusting the process parameters.

Development of germanium/silicon integration for near infrared detection

Silicon (Si) is the base material for electronic technologies and is emerging as a very attractive platform for photonic integrated circuits (PICs). PICs allow optical systems to be made more compact with higher performance than discrete optical components. Applications for PICs are in the area of fibre-optic communication, biomedical devices, photovoltaics and imaging. Germanium (Ge), due to its suitable bandgap for telecommunications and its compatibility with Si technology is preferred over III-V compounds as an integrated on-chip detector at near infrared wavelengths. There are two main approaches for Ge/Si integration: through epitaxial growth and through direct wafer bonding. The lattice mismatch of ~4.2% between Ge and Si is the main problem of the former technique which leads to a high density of dislocations while the bond strength and conductivity of the interface are the main challenges of the latter. Both result in trap states which are expected to play a critical role. Understanding the physics of the interface is a key contribution of this thesis. This thesis investigates Ge/Si diodes using these two methods. The effects of interface traps on the static and dynamic performance of Ge/Si avalanche photodetectors have been modelled for the first time. The thesis outlines the original process development and characterization of mesa diodes which were fabricated by transferring a ~700 nm thick layer of p-type Ge onto n-type Si using direct wafer bonding and layer exfoliation. The effects of low temperature annealing on the device performance and on the conductivity of the interface have been investigated. It is shown that the diode ideality factor and the series resistance of the device are reduced after annealing. The carrier transport mechanism is shown to be dominated by generation–recombination before annealing and by direct tunnelling in forward bias and band-to-band tunnelling in reverse bias after annealing. The thesis presents a novel technique to realise photodetectors where one of the substrates is thinned by chemical mechanical polishing (CMP) after bonding the Si-Ge wafers. Based on this technique, Ge/Si detectors with remarkably high responsivities, in excess of 3.5 A/W at 1.55 ��m at ���2 V, under surface normal illumination have been measured. By performing electrical and optical measurements at various temperatures, the carrier transport through the hetero-interface is analysed by monitoring the Ge band bending from which a detailed band structure of the Ge/Si interface is proposed for the first time. The above unity responsivity of the detectors was explained by light induced potential barrier lowering at the interface. To our knowledge this is the first report of light-gated responsivity for vertically illuminated Ge/Si photodiodes. The wafer bonding approach followed by layer exfoliation or by CMP is a low temperature wafer scale process. In principle, the technique could be extended to other materials such as Ge on GaAs, or Ge on SOI. The unique results reported here are compatible with surface normal illumination and are capable of being integrated with CMOS electronics and readout units in the form of 2D arrays of detectors. One potential future application is a low-cost Si process-compatible near infrared camera.

Programa de valoracions ��cid-base. 'Programa de valoraciones ��cido-base'.

Programa en MS-DOS para Secundaria en Ciencias Experimentales, orientado a las asignaturas de Qu��mica. El objetivo fundamental de este programa de simulaci��n es reforzar y clarificar los trabajos hechos por el alumnado en el laboratorio en torno a procesos ��cido-base. Para ello dota de ayudas claras para el manejo del programa y de un ejemplo completo a visualizar antes de empezar a introducir datos. Tras la introducci��n de los datos que considere el alumno el sistema genera un resumen de ��stos y pasa a una simulaci��n visual del desarrollo en laboratorio. Posteriormente reproducir�� el proceso secuencial en gr��ficas y finalmente ofrece una valoraci��n.