High-temperature Harsh Environment Research Articles

Fiber-optic flow sensors for high-temperature environment operation up to 800°C.

This Letter presents an all-optical high-temperature flow sensor based on hot-wire anemometry. High-attenuation fibers (HAFs) were used as the heating elements. High-temperature-stable regenerated fiber Bragg gratings were inscribed in HAFs and in standard telecom fibers as temperature sensors. Using in-fiber light as both the heating power source and the interrogation light source, regenerative fiber Bragg grating sensors were used to gauge the heat transfer from an optically powered heating element induced by the gas flow. Reliable gas flow measurements were demonstrated between 0.066 m/s and 0.66 m/s from the room temperature to 800°C. This Letter presents a compact, low-cost, and multiflexible approach to measure gas flow for high-temperature harsh environments.

High-Temperature Single Photon Detection Performance of 4H-SiC Avalanche Photodiodes

In this letter, the high-temperature performance of 4H-SiC avalanche photodiodes (APDs) working in Geiger mode is studied for the first time. At unity gain bias, the maximum quantum efficiency of the APD increases from 53.4% at 290 nm to 63.3% at 295 nm as temperature rises from room temperature to 150 °C. Meanwhile, the dark current of the APD before breakdown increases by more than two to three orders of magnitude. At a fixed gain of 1.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> , the single photon counting efficiency at 280 nm only slightly drops from 6.17% to 6% in the same temperature range, whereas the dark count rate increases from 22 to 80 KHz. This letter indicates that SiC APDs have the potential to work in a high-temperature harsh environment with single photon counting capability.

A Miniature Fabry–Pérot Interferometer for High Temperature Measurement Using a Double-Core Photonic Crystal Fiber

A miniature Fabry-Pérot interferometer is proposed and experimentally demonstrated for high temperature measurement. The device is fabricated by alignment splicing a short section of double-core photonic crystal fiber (DC-PCF) to the lead-in single mode fiber. Due to the optical path difference of reflective light from splicing region and end-face of DC-PCF, a well-defined interference spectrum is obtained based on ~ 72.3 μm-long cavity. Experimental results indicate that the proposed sensor has a considerable temperature sensitivity of 13.9 pm/°C in the measurement range of 30 °C-900 °C. The proposed sensor has advantages of small size and high stability, and so on, making it a good candidate in harsh high temperature environment with limited-space.

Ionic Liquids at Electrified Interfaces

Until recently, “room-temperature” (<100–150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)–(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of “first-generation” room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the “later generation” RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in “cocktails” of one’s choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost “universal” solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) “sister-systems”.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules.

Pt-CeO2 nanofibers based high-frequency impedancemetric gas sensor for selective CO and C3H8 detection in high-temperature harsh environment

High-temperature gas sensors are highly demanded to improve the combustion efficiency and reduce the emission of pollutant. In this study, Pt-CeO2 nanofibers (Pt-CeO2 NFs) were prepared using a facile two-step synthetic route (electrospinning followed by calcination). The impedance spectroscopy of the Pt-CeO2 NFs based sensor was investigated in pure N2 and different gas mixtures (O2, CO, CO2, NO, SO2, and C3H8 balanced by N2) with various concentrations at 800°C. For the first time, the sensor without solid electrolyte was operated at high frequency (100kHz), so that the sensor response towards O2, CO2, NO and SO2 (balanced with N2) was completely eliminated and strong reducing gases (e.g., CO and C3H8) can be selectively detected with good sensitivity, suggesting that high-frequency impedancemetric technique is a promising approach to improve the selectivity of high-temperature harsh environment gas sensors when operated at an appropriate frequency.

State Analysis on Reactor Furnace Pipe Used over a Design Cycle

. Reformer furnace is the typical high-temperature equipment in petrochemical installations, but furnace pipe is the heart. The creep, thermal fatigue, thermal oxidation, carburization, corrosion and other phenomena may occur in harsh high temperature environments during service of furnace pipe. These factors make the properties degrade and life time short during all times of service. It will have significant economic losses if the rupture facture accident occurs suddenly. Comprehensive state analysis and life evaluation of reformer pipe run over service period to understand microstructure and property of furnace pipe by a range of material analysis methods, so that this will have important reference value for designer, manufacturer and user.

A new Mach-Zehnder interferometer in a thinned-cladding fiber fabricated by electric arc for high sensitivity refractive index sensing

This study proposes an inline electric-arc induced Mach-Zehnder interferometer (MZI) in a thinned cladding fiber. The proposed MZI is used for refractive index (RI) sensing. At the diameter of 56μm and the length of 18mm, in the RI of 1.3348–1.3558, the sensitivity is ∼580nm/RIU, that is about 20 times greater than those of taper-based MZI sensors. Temperature characteristics of the MZI are investigated in 50–800°C. It is demonstrated that the proposed MZI is a good choice for high-temperature harsh environment sensing.

Packaging Technology for Electronic Applications in Harsh High-Temperature Environments

Silicon-on-insulator (SOI) integrated circuits have been demonstrated for use at temperatures up to 300 °C. However, to build functional electronics, multiple devices must be interconnected to provide the desired functionality. A system-in-package approach has been developed using thick-film technology on Si3N4 ceramic substrates. Si3N4 has a near coefficient-of-thermal-expansion match to Si and a higher flexural modulus than Al2O3, which is commonly used for thick-film applications. The conductor metallization is Au. For 300 °C operation, eutectic Au-Ge die attach was used with a Ti/Ti:W/Au backside die metallization. After 3000 h at 325 °C, the mean die shear strength decreased from 3.96 to 3.33 kg/mm2, a decrease of only 16%. Formation of Au-Si-Ge ternary eutectic (melting point 326 °C) was observed and limits the use of Au-Ge die attach to 300 °C. SOI dies typically have Al wire bond pads that are not compatible with Au thermosonic wire bonding for high-temperature applications. Two plating processes have been examined: electroless Ni/immersion Au/electroless Au and electroless Ni/electroless Pd/immersion Au. The plating processes provide a barrier layer (Ni) and a wire-bondable finish (Au or Pd-Au) over the Al wire bond pads. After 10 000 h at 300 °C, the wire pull force for the Ni/Au samples decreased by ~30% due to annealing of the Au wire, while the ball shear force increased by ~35%. The daisy-chain electrical resistance remained relatively constant. For the Ni-Pd-Au samples, after 2000 h at 320 °C, the ball shear force remained constant or increased slightly, the wire pull force decreased by ~25% due to annealing of the Au wire, and the daisy-chain resistance remained relatively constant. After 3000 h, however, cratering of the Si wire bond pad was observed corresponding to some first bond pad lifts and increased daisy-chain resistance. Optimization of the wire-bonding parameters for bonding to the harder Ni/Pd/Au bond pad is required to eliminate cratering.

Void-free strong bonding of surface activated silicon wafers from room temperature to annealing at 600 °C

In order to investigate the high temperature application of surface activated silicon/silicon wafer bonding, the wafers were bonded at room temperature and annealed up to 600 °C followed by optical, electrical, mechanical and nanostructure characterization of the interface. Void-free interface with high bonding strength was observed that was independent of the annealing temperature. The bonding strength was as high as 20 MPa. The normalized interfacial current density was increased with the increase in the annealing temperature. A thin interfacial amorphous layer with a thickness of 8.3 nm was found before annealing, which was diminished at 600 °C. A correlation between the current density and nanostructure of the interface was observed as a function of the annealing temperature. The high quality silicon/silicon bonding indicates its potential use not only in low temperature microelectronic applications, but also in high temperature harsh environments.

Visualization of thermal cutting fluid flows

Outside of the fields where flow visualization is traditionally applied, there exist many processes where fluid phenomena are critical. Here, we survey flow visualization work with a focus on two thermal metal cutting processes. These two processes – plasma-arc cutting and gas assisted laser cutting – account for a large fraction of the means by which steel is cut in our world. Plasma-arc cutting utilizes an electric arc transferred between a cathode and the steel being cut to produce a high temperature gas jet that melts and removes metal. In gas assisted laser cutting, the assist jet is often high-pressure supersonic nitrogen for stainless steel, or near-atmospheric pressure, low-speed oxygen for carbon steel. Visualization of these millimeter-range diameter jets helps to understand the different roles that the assist gas has in these cutting processes, particularly with how the jets interact with the metal being cut. We describe experimental techniques for visualization of the arc jet and gas assist jet, as well as the liquid metal flows being removed from the cut and the gas flow in the torch itself. These visualizations overcome the small physical scales of the process, the bright illumination from the arc itself, and harsh high-temperature environment. The results lend perspective and understanding of the physical phenomena important to process control.

6H-SiC Solid State Detector Development for a Neutron Measurement

A new solid state detector based on 6H-SiC is one of the promising devices in the nuclear industry for high-level radiation applications in a harsh high-temperature environment. SiC is a semi-conductor with a 3.03-eV band gap energy, and known as a radiation-resistance material. SiC detectors were fabricated by using a 6H-SiC wafer. The properties of the 6H-SiC wafer were over a 106 ohm-cm resistivity, a 380 μm thickness, and a (0001)-oriented type. The 6H-SiC detector was prepared by the processes of a dicing, etching, removal of an oxidation layer and a mounting on an alumina substrate. SiC detector was 10×10 mm2 with a 19.6mm2 active area. The circular metal contacts consisted of a Si-face/Ni/Au and a C-face/Ni/Au structure. Thin LiF and B film was coated onto the SiC detector surface for a neutron converter. The electrical current-voltage performances of the detectors were measured by using the Keithley 4200-SCS parameter analyzer with self voltage sources. Neutron responses were measured by using a 252Cf source.

Miniaturized fiber inline Fabry-Perot interferometer fabricated with a femtosecond laser

We report a miniaturized inline Fabry-Perot interferometer directly fabricated on a single-mode optical fiber with a femtosecond laser. The device had a loss of 16 dB and an interference visibility exceeding 14 dB. The device was tested and survived in high temperatures up to 1100 degrees C. With an accessible cavity and all-glass structure, the new device is attractive for sensing applications in high-temperature harsh environments.

MICROMAT - International conference on micro materials

s of all invited or accepted papers for oral or poster presentation at the MicroMat conference were published in an Abstract Volume which was distributed upon registration at the conference. After the conference, a 1273 pages Conference Proceedings containing the 326 paper presentations of Plenary Session and Poster was made available for participants of the conference. Some of these papers are published in this Microsystem Technologies issue. The International Program Committee of the Micro Materials Conference decided to hold the third MicroMat in April 2000, in Berlin. The aim of this third congress is to identify and highlight the progresses achieved in different fields of micro materials applications since the first 1 conferences and bring together specialists from all over the world to discuss the recent trends. For the preparation, the chairmen Bernd Michel (Berlin), Matthias Werner (Teltow) and Hansjorg Fecht (Ulm) would like to enlist again a recognized international program committee. Some of the topics will be: f Thermomechanical reliability of microsystems f Advanced testing methods for microcomponents and microsystems f Micro materials for high temperature applications and harsh environment f Nanomaterials and nanoanalytics f Fracture Electronics f Micro materials in advanced electronic packaging f Simulation tools and applications f New micro materials f Macro materials applications in various fields MicroMat 2000 conference site will be directly in the center of Berlin city. The congress will be structured into plenary sessions, parallel sessions (including invited or key-note lectures), an extended poster session, an exhibition, and finally post-conference workshops on 20 April. More information will be available on the Web: http://www.micromaterials.com