The study focuses on high-performance combined electro-spark alloying of titanium and titanium alloy (VT1-0, VT16) surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of biocompatible layered metal-oxide system Ti-Ta-(Ti,Ta)xOy. It was found that during electro-spark alloying the concentration of tantalum on the titanium surface ranges from 0.1 to 3.2 at.%. Morphology of the deposited splats is represented by uniformly grown crystals of titanium and tantalum oxides, which increase from nano- to submicron size.
Phononic crystals (PnC) with a specifically designed defect have been recently introduced as novel sensor platform. Those sensors feature a band gap covering the typical input span of the measurand as well as a narrow transmission peak within the band gap where the frequency of maximum transmission is governed by the measurand. This innovative approach has been applied for determination of compounds in liquids . Improvement of sensitivity requires higher probing frequencies around 100 MHz and above. In this range surface acoustic wave devices (SAW) provide a promising basis for PnC based microsensors . The respective feature size of the PnC SAW sensor has dimensions in the range of 100 μm and below. Whereas those dimensions are state of the art for common MEMS materials, etching of holes and cavities in piezoelectric materials having an aspect ratio diameter/depth is challenging. In this contribution we describe an improved technological process to manufacture considerably deep and uniform phononic crystal structures inside of SAW substrates.
Acoustic band gap materials, so-called phononic crystals, provide a new sensor platform. Phononic crystals are periodic
composite materials with spatial modulation of elasticity, mass density as well as longitudinal and transverse velocities
of elastic waves. When utilized as sensor, the input parameter to be measured changes characteristic properties of the
phononic crystal in a distinct manner. These changes can be detected by measuring the transmission behavior of
ultrasonic waves through the phononic crystal. The most optimal feature for detection is a sharp isolated transmission
peak which corresponds to the input parameter. When applying as liquid property sensor one component building the
phononic crystal is the liquid to be analyzed. Here we present recent results gathered from different sensor realizations.
In the second part we report on experimental investigations based on laser vibrometry which provide deeper insides to
the so-called extraordinary transmission. These analyses reveal that structural resonance effects are responsible for the
smart properties of the device.