Characterization of Amorphous Tantalum Oxide for Insulating Acoustic Mirrors

This work describes the assessment of the acoustic properties of sputtered tantalum oxide films intended as high impedance films for the acoustic isolation of bulk acoustic wave devices operating in the GHz frequency range. The films are grown by sputtering a metallic tantalum target under different oxygen and argon gas mixtures, total pressures, pulsed DC powers and substrate bias. The structural properties of the films are assessed through infrared absorption spectroscopy and X-ray diffraction measurements. Their acoustic impedance is obtained after estimating the mass density by X-ray reflectometry measurements and the longitudinal acoustic velocity by analyzing the longitudinal λ/2 resonance induced in a tantalum oxide film inserted between an acoustic reflector and an AlN-based resonator. A second measurement of the sound velocity is achieved through picosecond acoustic spectroscopy.

High-Acoustic-Impedance Tantalum Oxide Layers for Insulating Acoustic Reflectors

This work describes the assessment of the acoustic properties of sputtered tantalum oxide films intended for use as high-impedance films of acoustic reflectors for solidly mounted resonators operating in the gigahertz frequency range. The films are grown by sputtering a metallic tantalum target under different oxygen and argon gas mixtures, total pressures, pulsed dc powers, and substrate biases. The structural properties of the films are assessed through infrared absorption spectroscopy and X-ray diffraction measurements. Their acoustic impedance is assessed by deriving the mass density from X-ray reflectometry measurements and the acoustic velocity from picosecond acoustic spectroscopy and the analysis of the frequency response of the test resonators.

The effects of tantalum addition on the microtexture and mechanical behaviour of tungsten for ITER applications

Tungsten (W) and its alloys are very promising materials for producing plasma-facing components (PFCs) in the fusion power reactors of the near future, even as a structural part in them. However, whereas the properties of pure tungsten are suitable for a PFC, its structural applications are still limited due to its low toughness, ductile to brittle transition temperature and recrystallization behaviour. Therefore, many efforts have been made to improve its performance by alloying tungsten with other elements. Hence, in this investigation, the thermo-mechanical performance of two new tungsten-tantalum materials has been evaluated. Materials with We5wt.%Ta and We15wt.%Ta were processed by mechanical alloying (MA) and later consolidation by hot isostatic pressing (HIP), with distinct settings for each composition. Thus, it was possible to determine the relationship between the microstructure and the addition of Ta with the macroscopic mechanical properties. These were measured by means of hardness, flexural strength and fracture toughness, in the temperature range of 300e1473 K. The microstructure and the fracture surfaces features of the tested materials were analysed by Field Emission Scanning Electron Microscopy (FESEM).

Growth of AlN oriented films on insulating substrates.

This work describes the structural and piezoelectric assessment of aluminum nitride (AlN) thin films deposited by pulsed-DC reactive sputtering on insulating substrates. We investigate the effect of different insulating seed layers on AlN properties (crystallinity, residual stress and piezoelectric activity). The seed layers investigated, silicon nitride (Si3N4), silicon dioxide (SiO2), amorphous tantalum oxide (Ta2O5), and amorphous or nano-crystalline titanium oxide (TiO2) are deposited on glass plates to a thickness lower than 100 nm. Before AlN films deposition, their surface is pre-treated with a soft ionic cleaning, either with argon or nitrogen ions. Only AlN films grown of TiO2 seed layers exhibit a significant piezoelectric activity to be used in acoustic device applications. Pure c-axis oriented films, with FWHM of rocking curve of 6º, stress below 500 MPa, and electromechanical coupling factors measured in SAW devices of 1.25% are obtained. The best AlN films are achieved on amorphous TiO2 seed layers deposited at high target power and low sputtering pressure. On the other hand, AlN films deposited on Si3N4, SiO2 and TaOx exhibit a mixed orientation, high stress and very low piezoelectric activity, which invalidate their use in acoustic devices.

Proyecto de viabilidad de una planta de tratamiento para mineral de estaño y tántalo

El proyecto tiene como objeto definir la viabilidad de explotación de un importante yacimiento de Estaño y Tántalo que se encuentra en una formación geológica de base pegmatítica situada en el norte de España. En base a las reservas calculadas, se define la capacidad de tratamiento de la planta de procesamiento del mineral para un periodo de explotación de 10 años. Como primer paso se estudian los ensayos de caracterización y concentración realizados en laboratorio a partir de muestras de mano representativas del mineral así como otros en planta piloto llevados a cabo anteriormente. Una vez definida la recuperación del Estaño y Tántalo se procede al diseño conceptual del proceso. Posteriormente se desarrolla un diseño e ingeniería preliminar más aproximados, a partir de los cuales se evalúan los costes de equipos y operacionales que, en base a los retornos por la venta de los concentrados, permitirán calcular la rentabilidad del proyecto y riesgos de la inversión. ABSTRACT The purpose of this project is to define the feasibility of mining a major deposit of tin and tantalum found in a pegmatite formation in northern Spain. Based on the estimated reserves, the operating capacity for mining and mineral processing plant was defined for a period of 10 years. As a first step for the development, a research program for characterization and concentration of the ore, were performed in the laboratory based on representative samples from the deposit. In addition, previous pilot plant results were also taken into account. Once determined the recovery of tin and tantalum, the conceptual design process was defined. As a second step, it was developed a preliminary design and engineering, from which the capital and operating costs were estimated .By means of the calculated returns from the sale of concentrates, the profitability of the project and investment risks were finally assessed