A microsystem for the fracture characterization of polysilicon at the micro-scale

To characterize the effective fracture energy G_IC of polysilicon wafers at room temperature, an on-chip MEMS test structure has been designed and fabricated. The device can provide fatigue pre-cracking at the notch apex and subsequently impose a monotonical load up to failure. The proposed procedure combines the experimental data with outcomes of numerical simulations. A continuously monitored decrease in stiffness of the system is linked to the crack length and the effective fracture energy for the non-standard geometry of the testing device. An average value of G_IC = 12.0 ± 1.8 N m^?1 is found. These values are then used in numerical micro-scale fracture analyses taking into account the material heterogeneity due to the grain structure and reproducing the crack propagation process with a cohesive approach.     

Use of a glass residue in the removal of heavy metals from wastewater

The extraction of silica from powdered glass cullet with an aqueous solution of sodium hydroxide has been proposed as an alternative to glass recycling aimed to the low temperature production of sodium silicates. The unextracted residue obtained after a counter current two-step extractive process at approximately 100 degrees C and room pressure is mainly made of calcium and sodium silicate and shows high porosity and a large surface area. We thought that it could be active as an agent for the removal of heavy metals from wastewater. In this paper the capacity of the unextracted residue of removing six metal ions (i.e., Cu2+, Ni2+, Zn2+, Cd2+, Pb2+ e Cr3+) was studied in a stirred batch reactor. The data obtained demonstrate that the removal of metal ions from wastewater is achieved with high capacity in a short time and their concentration is lowered under the legal limits without any appreciable influence from changes of physical and chemical conditions. Sodium and calcium ions take the place of heavy metals in water while pH keeps almost neutral. The exchange mechanism was identified.     

Solid damping in micro electro mechanical systems

This paper focuses on the problem of the numerical evaluation of dissipation induced by thermoelastic coupling in microelectromechanical systems. An ad hoc conceived, FE based, numerical procedure for the evaluation of the thermoelastic dissipation is proposed and the numerical results are compared with analytical solutions. In order to introduce in the numerical response a dependence on the size of the resonating devices, which is experimentally observed at very small dimensions, a new enhanced non-local coupled thermoelastic model is proposed and the first results are discussed. An erratum to this article can be found at     

Finite element modelling of a rotating piezoelectric ultrasonic motor

The evaluation of the performance of ultrasonic motors as a function of input parameters such as the driving frequency, voltage input and pre-load on the rotor is of key importance to their development and is here addressed by means of a finite element three-dimensional model. First the stator is simulated as a fully deformable elastic body and the travelling wave dynamics is accurately reproduced; secondly the interaction through contact between the stator and the rotor is accounted for by assuming that the rotor behaves as a rigid surface. Numerical results for the whole motor are finally compared to available experimental data.     

3-phenyl-5-isoxazolon-4-carboxylic acid ethyl ester as a selective reagent for the spectrophotometric determination of iron(III)

The red complex developed on interaction of iron(III) with 3-phenyl-5-isoxazolon-4-carboxylic acid ethyl ester in the pH range 2-5 can be extracted into methyl isobutyl carbinol. Based on this, a selective and rapid method for the spectrophotometric determination of traces of iron has been developed. The complex has an absorption maximum at 490 nm. Beer's law is followed up to 15.0 ppm of iron. The molar absorptivity is 4.2 x 10(3) l.mole(-1). cm(-1). None of the common ions interferes in the determination of iron, even though present in large excess.