Current Assisted Densification Process (CADPro)
Current assisted densification is a method of rapidly densifying nanocrystalline powders to full density by applying very large DC currents (upto 5,000 amps) while also applying pressure to the powder in a die. The rapid densification and short process times limits grain growth, preserving nanocrystalline grain size. In this manner transparent ceramics can be produced as illustrated with transparent zirconium dioxide (below). It also enables nanocrystalline ceramics to be produced so that the effect of grain size on physical properties can be established. Our CADPro system is under LabVIEW control.
Confocal Raman and Luminescence Spectroscopy
In addition to a variety of luminescence and Raman spectroscopy systems, our laboratory on the fifth floor of the LISE building is equipped with a high-performance Horiba LabRAM ARAMIS system. This optical microprobe system has capabilities for confocal Raman and luminescence imaging and mapping, as well as measurements up to 1500oC. Excitation can be switched between three different, pre-aligned lasers, a HeCd laser operating at 325 nm, a solid-state laser at 514 nm and a solid-state laser at 785 nm. In-situ strain measurements can be performed with a specially designed strain fixture that fits under the optical microprobe.
Laser Ablation—Inductively Coupled Plasma—Mass Spectroscopy (LA-ICP-MS)
LA-ICP-MS is a technique for the analysis of solutions and solids vaporized by pulsed laser ablation. For solids, the surface is ablated with a pulsed laser and the vapor is carried by a helium jet into an ICP-MS system. This complements other micro-analysis methods since it is sensitive to extremely low concentrations of elements. We are currently extensively using it to investigate which elements are being harvested by different microbial strains and also the effects of minor elements on oxidation of bond-coat alloys. The system consists of a CETAC laser ablation system (LSX213G2) connected to an Agilent 7700 ICP-MS system. The instrument is also equipped with AutoSampler for automatic solution-based analysis.
The instrument was purchased as a result of a successful proposal to the Office of Naval Research DURIP program in 2011.
Optical-Electrical-Strain Characterization of Elastomers and Compliant Electrodes
We have designed and constructed a loading system for measuring the optical transmission/reflection properties of elastomers and polymers, as well as their electrical resistivity, as a function of strain. The testing can be under either uniaxial or biaxial loading conditions. The loading is applied through two perpendicular displacement drives under LabVIEW control and the loads measured by in-line load cells. The maximum possible displacements are 320 mm. The spectral optical properties are usually measured using a fiber-optic connected to an Ocean Optics spectrometer. Higher spectral resolutions are attainable using more specialized spectrometers. We also have high resolution camera dan microscope that can be used with biaxial setup.
Thermoelectric Measurement System
We use a commercial, state-of-the-art ULVAC ZEM-3 M10 system for measuring the Seebeck coefficient and electrical conductivity of thermoelectric samples up to a maximum of 1000oC. These measurements are combined with separate measurements of the thermal conductivity to calculate the thermoelectric figure of merit.
Thermal Flash Diffusivity System
We use a commercial laser-flash diffusivity system (LFA 457) from Netzsch Systems for determining the thermal diffusivity of thin, disc shaped samples. Measurements can usually be made from room temperature up to 1000oC in an inert atmosphere, such as argon. Many of the materials we are interested in are, in essence, wide-band gap, transparent solids, so they must first be coated with a thin layer of gold or platinum on both sides before then coating with graphite to prevent direct transmission of the laser pulse through the sample to the infra-red detector.
High Temperature Luminescence and Luminescence Lifetime Measurements
We have designed and constructed a fiber-optic based system for measuring the luminescence, and luminescence lifetime, of oxide materials up to temperatures approaching 1500oC. The original motivation for constructing the system was to calibrate the luminescence lifetime as a function of temperature for a variety of rare-earth ion doped zirconia ceramics in order to facilitate the in-situ temperature measurement of TBC coated turbine components. (see Chambers and Clarke pdf).
Photons from either a frequency doubled or tripled Nd:YAG or an excimer laser are directed through free-space to ceramic samples in a high-temperature furnace. The photo-stimulated luminescence from the sample is collected using either a silica or sapphire fiber-optic close to the sample and connected through a suitable set of filters to a grating spectrometer, a high speed photomultiplier detector and a high-speed oscilloscope for analysis of lifetime and spectral intensity.
Fluorescent Microscope with High Resolution and Large Working Distance Objectives
We have a Leica DM4000 upright microscope system customizable color filters and polarizers. The system is configured for reflected light illumination.
High-Temperature Laboratory Furnaces
Various box furnaces and tube furnaces that can be used up to 1100 to 1400oC. The atmosphere in the tube furnace can be controlled as a neutral or reducing condition.