A study of titanium thin films in transmission laser micro-joining of titanium-coated glass to polyimide

Electron beam evaporation (EB-PVD) and cathodic arc physical vapor deposition (CA-PVD) techniques were used for the preparation of titanium (Ti) thin films onto Pyrex borosilicate 7740 glass wafers and the deposited films were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The microstructure and surface morphology of the films were studied as a function of the film deposition techniques. Film properties such as, adherence, microstructure and roughness were interconnected to the laser joint strength between Ti coated glass wafers and polyimide films. Ti thin films on glass had a natural oxide layer on the surface as found from XPS. AFM study showed the formation of a uniform Ti coating consisted of packed crystallites with average size of 35 nm by EB-PVD. The root-mean-square surface roughness of the films was 1-2 nm. Whereas, films prepared by CA-PVD had crystallites with an average size of 120 nm and defects in the form of macro-particles which is a common attribute of this deposition system. The surface roughness of the film was 125 nm. The laser joint strength was found to be influenced by the Ti film quality on the glass substrate.     

Physicochemical and functional properties of ten cultivars of seem (Lablab purpureus L.), an underexploited bean in Bangladesh

BACKGROUND: Increasing global protein consumption has led to the demand for new sources of food protein, particularly plant sources. Many inexpensive but protein‐rich bean cultivars have not been well evaluated and are thus underutilised. In this study the physicochemical and functional properties of seeds of ten seem cultivars were assessed. RESULTS: In agreement with their sizes, seeds of Airet had the highest 1000‐seed weight and volume, while those of Bari had the lowest. In terms of proximate composition (g kg^?1), protein content ranged from 240.08 (Ashina) to 292.63 (Puti), fat content from 31.47 (Goalgadda) to 38.40 (Puti), ash content from 32.80 (Puli) to 45.53 (Goalgadda) and fibre content from 21.90 (Tatulia) to 28.90 (Noldog). Hydration (g kg^?1) and swelling (mL L^?1) capacities ranged from 1688.60 and 1850.43 (Goalgadda) to 1999.40 and 2208.66 (Rupbhan) respectively. Similarly, cooking time (min) varied from 114 (Rupbhan) to 179 (Goalgadda). Lowest gelation concentration was in the range 80–100 g kg^?1. Water and fat absorption capacities (g kg^?1) ranged from 941.00 and 644.44 (Ashina) to 1043.33 and 749.26 (Puti) respectively. Foaming capacity and stability (mL L^?1) ranged from 443 (Puli) to 635 (Puti) and from 314 (Ashina) to 643 (Rupbhan) respectively. CONCLUSION: Seeds of seem cultivars appear to be a promising food in terms of their protein content and functionality. Copyright © 2009 Society of Chemical Industry     

Oxide layer development under thermal cycling and its role on damage evolution and spallation in TBC system

The nature and cause of failure of thermal barrier coatings (TBCs) consisting of physical vapor deposited (PVD) yttria stabilized zirconia (YSZ, 8 wt.% Y₂O₃) and a diffusion aluminide bond coat (Pt-Al) were investigated after oxidative thermal cycling and isothermal heat treatment at 1177 °C in air. Experiments were conducted for 45 and 10-minute hold times and for isothermal condition for disk specimens with and without TBC. It is found that microcracks starts in the oxide scales at the bond coat grain boundary protrusions. Total number of thermal cycles affect the density of microcracks within the TGO layer. Evidence is presented that higher density of microcracks in the 10-min hold-time experiments tend to separate the TBC from the TGO layer via extensive coating micro-decohesion and promotes 'complete' TBC separation as opposed to traditional 'partial' spallation of TBC from the substrate as in the 45-min hold-time and isothermal experiments.     

Laser fabrication and characterization of sub-millimeter joints between polyimide and Ti-coated borosilicate glass

Laser-fabricated joints of sub-millimeter widths between biocompatible, dissimilar materials have the potential for application as encapsulation of miniature implantable biomedical devices. In this work, we briefly describe the laser joining method of a very promising system, polyimide/titanium-coated borosilicate glass, and present results from characterization of such laser joints by means of mechanical failure (tensile) tests, optical and scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Our results suggest that the formation of the joints is a result of the creation of strong chemical bonds between Ti-containing species and certain polymeric functional groups. Mechanical tensile strength failure testing showed that such joints experience some degradation as a result of soaking in physiological solutions. This degradation is limited and, even after relatively long-term exposure the joints retain considerable strength.     

A comprehensive approach and methods for glacial lake outburst flood risk assessment,with examples from Nepal and the transboundary area

Like other mountainous areas, Nepal is highly vulnerable to glacial lake outburst floods (GLOFs), and this vulnerability has increased due to climate change. Risk reduction strategies must be based on a comprehensive risk assessment. A comprehensive methodological approach for GLOF risk assessment is described and illustrated in case studies of the potential GLOF risk posed in Nepal by four glacial lakes, one located in China. People, property and public infrastructure (including hydropower plants, roads and bridges) are vulnerable, and there is a need to integrate GLOF risk reduction strategies into national policies and programmes.     

Extension of fuzzy TOPSIS method based on interval-valued fuzzy sets

Decision making is one of the most complex administrative processes in management. In circumstances where the members of the decision making team are uncertain in determining and defining the decision making criteria, fuzzy theory provides a proper tool to encounter with such uncertainties. However, if decision makers cannot reach an agreement on the method of defining linguistic variables based on the fuzzy sets, the interval-valued fuzzy set theory can provide a more accurate modeling. In this paper the interval-valued fuzzy TOPSIS method is presented aiming at solving MCDM problems in which the weights of criteria are unequal, using interval-valued fuzzy sets concepts.     

Improved Analytical Models for Mixed-Mode Bending Tests of Adhesively Bonded Joints

In this paper, improved analytical models have been developed for more accurate determination of mode I and mode II compliances and strain energy release rates of adhesively bonded Double Cantilever Beam (DCB) type specimens. In these models, the effects of adhesive layer, elastic foundation and shearing deformation ahead of the crack tip due to the Saint-Venant end effect were considered. The improved analytical models were verified using finite element analysis (FEA), and excellent agreements were found for a variety of crack lengths. The comparisons of the measured and predicted testing machine loading point compliances with crack length at three different mixed-mode loading conditions for the adhesive layer thickness of 0.254 mm were also performed for further validation. In addition, contributions to the total mode I strain energy release rate from each effect are summarized.     

Influence of weldlines on tensile properties of hybrid acrylonitrile butadiene styrene (ABS) composites filled with short glass fibres (GF) and glass beads (GB)

The present study investigated the effect of weldlines on tensile strength and modulus of injection moulded ABS polymer reinforced with both short fibres (GF) and spherical glass beads (GB). It was observed that tensile strength and modulus of ABS/GF/GB hybrids increased with increasing the concentration total of glass in the hybrid as well as the concentration of glass fibres in the hybrid (χ _GF ). Results indicated that tensile strength and modulus of ABS/GF/GB hybrids obey the rule-of-mixtures. The presence of weldlines had a negative effect on tensile properties of ABS/GF/GB hybrids. Although tensile strength and modulus of ABS/GF/GB hybrids were reduced in the presence of weldlines, nonetheless both increased with increasing the total concentration of the glass particles and χ _GF . The observed linearity of weldline strength and modulus with χ _GF indicated that these properties like their unweld counterparts can be expressed by simple rule-of-mixtures. It was noted also that weldline integrity factor for tensile modulus and strength decreased with increasing χ _GF and the total concentration of the glass particles in the hybrids. Weldline integrity values indicated that hybrid tensile strength was more affected by the weldlines than hybrid modulus.     

A neural cell culture study on thin film electrode materials

Functional neural stimulation requires good interface between the neural cells and the electrode surfaces. In order to study the effect of electrode materials and surface structure on cell adhesion and biocompatibility, we cultured cortical neurons on thin films of platinum and iridium oxide. We used both flat, as-deposited and laser micro-structured films. The laser micro-structuring consisted of creating regular arrays of micro-bumps or holes with diameters of 4–5 μm and height of about 1.5 μm. The micro-bumps were fabricated onto platinum and iridium film surfaces deposited on borosilicate glass substrates, using mask-projection irradiation with single nano-second pulses from a KrF excimer laser (λ = 248 nm). Amorphous and crystalline (deposited at 250 °C) IrO₂ films were deposited onto the laser micro-structured iridium films by pulsed-DC reactive sputtering to obtain micro-structured IrO₂ films. Cortical neurons isolated from rat embryo brain were cultured onto these film surfaces. Our results indicate that flat and micro-structured film surfaces are biocompatible and non-toxic for neural cell growth. The use of poly-d-lysine as a mediator for cell adhesion onto the thin film surfaces is also discussed.