Sintering of Pd Automotive Catalysts

2001 ◽  
Vol 7 (S2) ◽  
pp. 1080-1081
Author(s):  
Q. Xu ◽  
K.C.C. Kharas ◽  
A.K. Datye
Keyword(s):  
High Temperature ◽  
Surface Area ◽  
Metal Surface ◽  
Alumina Support ◽  
Automotive Catalysts ◽  
Active Metal ◽  
Gas Atmosphere ◽  
Fundamental Understanding ◽  
High Temperature Operation

The focus of this work is on processes that lead to loss of active metal surface area during high temperature operation of automotive catalysts. As under-floor catalytic converters are moved closer to the engine to achieve faster light off, the catalyst is subjected to higher operating temperatures during the normal driving cycle. Sintering of the active metal phase leading to loss of surface area represents one of the most important factors limiting the long-term durability of automotive catalysts. Despite its obvious technological importance, fundamental understanding of sintering is still lacking.In this research, we have prepared a series of Pd metal catalysts on a θ alumina support. The metal loading was varied from 1.1 wt% to 7 wt%. The catalysts were subjected to sintering at 900 °C for up to 192 hours. To ensure relevance to automotive catalysts, the sintering was performed in a gas atmosphere that contained 10 mol % H2O in flowing N2 or in air.

Test Evolution and Oil-Free Engine Experience of a High Temperature Foil Air Bearing Coating

2006 ◽  
Author(s):  
Daniel Lubell ◽  
Christopher DellaCorte ◽  
Malcolm Stanford
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Solid Lubricants ◽  
Deposition Process ◽  
Air Bearing ◽  
Free Gas ◽  
Foil Bearings ◽  
Start Up ◽  
High Temperature Operation

During the start-up and shut-down of a turbomachine supported on compliant foil bearings, before the bearings have full development of the hydrodynamic gas film, sliding occurs between the rotor and the bearing foils. Traditional solid lubricants (e.g., graphite, Teflon®) readily solve this problem at low temperature. High temperature operation, however, has been a key obstacle. Without a suitable high temperature coating, foil air bearing use is limited to about 300°C (570°F). In oil-free gas turbines, a hot section bearing presents a very aggressive environment for these coatings. A NASA developed coating, PS304, represents one tribological approach to this challenge. In this paper, the use of PS304 as a rotor coating operating against a hot foil gas bearing is reviewed and discussed. During the course of several long term, high cycle, engine tests, which included two coating related failures, the PS304 technology evolved and improved. For instance, a post deposition thermal treatment to improve dimensional stability, and improvements to the deposition process to enhance strength resulted from the engine evaluations. Largely because of this work, the bearing/coating combination has been successfully demonstrated at over 500°C (930°F) in an oil-free gas turbine for over 2500 hours and 2900 start-stop cycles without damage or loss of performance when properly applied. Ongoing testing at Glenn Research Center as part of a long term program is over 3500 hours and 150 cycles.

scholarly journals Evaluation of printed-circuit boards materials for high temperature operation

2017 ◽  
Vol 2017 (HiTEN) ◽  
pp. 000057-000062
Author(s):  
Oriol Aviño-Salvado ◽  
Wissam Sabbah ◽  
Cyril Buttay ◽  
Hervé Morel ◽  
Pascal Bevilacqua
Keyword(s):  
High Temperature ◽  
Printed Circuit Boards ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Physical Measurements ◽  
Epoxy Material ◽  
High Temperature Operation

ABSTRACT This article presents the long term (1000 h) behaviour of two printed-circuit board materials (Panasonic R1755V, a high-TG glass-epoxy composite and Arlon 85N, a polyimide-based laminate) stored at high temperature (190 °C). Tests are performed in air and in nitrogen atmospheres. Electrical and physical measurements are performed regularly (once per week). Almost no degradation is observed for both materials, when stored in nitrogen. On the contrary, the board stored in air show the consequences of ageing. This is especially true for the glass-epoxy material, which becomes unusable after 2 weeks, because of large swelling.

Long-term reliability of Al-free InGaAsP/GaAs (λ=808 nm) lasers at high-power high-temperature operation

1997 ◽  
Vol 71 (21) ◽  
pp. 3042-3044 ◽  
Author(s):  
J. Diaz ◽  
H. J. Yi ◽  
M. Razeghi ◽  
G. T. Burnham
Keyword(s):  
High Temperature ◽  
High Power ◽  
High Temperature Operation

An Ultra-Low Noise Instrumentation Amplifer Designed for High Temperature Applications

2012 ◽  
Vol 2012 (HITEC) ◽  
pp. 000082-000086
Author(s):  
Jeff Watson ◽  
Gustavo Castro
Keyword(s):  
High Temperature ◽  
High Performance ◽  
Low Noise ◽  
Silicon On Insulator ◽  
Instrumentation Amplifier ◽  
Leakage Currents ◽  
Comprehensive Reliability ◽  
High Temperature Operation ◽  
Temperature Applications

This paper discusses a very low noise instrumentation amplifier designed specifically for high temperature applications. The device uses a proprietary silicon-on-insulator process that minimizes parasitic leakage currents at elevated temperature. Variance in device parameters are managed to maintain high performance over a wide temperature range. Layout and packaging considerations that would affect long term reliability are addressed. The amplifier is well characterized above 200°C and attains much higher performance than amplifiers not optimized for high temperature operation. Comprehensive reliability testing over temperature has been completed.

scholarly journals Evaluation of Printed-Circuit Board Materials for High-Temperature Operation

2017 ◽  
Vol 14 (4) ◽  
pp. 166-171
Author(s):  
Oriol Aviño-Salvado ◽  
Wissam Sabbah ◽  
Cyril Buttay ◽  
Hervé Morel ◽  
Pascal Bevilacqua
Keyword(s):  
High Temperature ◽  
Printed Circuit Board ◽  
Epoxy Composite ◽  
Circuit Board ◽  
Printed Circuit ◽  
Physical Measurements ◽  
Epoxy Material ◽  
High Temperature Operation

This article presents the long-term (1,000 h) behavior of two printed-circuit board materials (Panasonic R1755V, a high-TG glass-epoxy composite and Arlon 85N, a polyimide-based laminate) stored at high temperature (190°C). Tests are performed in air and in nitrogen atmospheres. Electrical and physical measurements are performed regularly (once per week). Almost no degradation is observed for both materials when stored in nitrogen. On the contrary, the board stored in air shows the consequences of ageing. This is especially true for the glass-epoxy material, which becomes unusable after 2 w, because of large swelling.

Long-term high-temperature operation of the HTTR

2012 ◽  
Vol 251 ◽  
pp. 181-190 ◽  
Author(s):  
Minoru Goto ◽  
Masanori Shinohara ◽  
Daisuke Tochio ◽  
Yosuke Shimazaki ◽  
Shinpei Hamamoto ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperature Operation

Silicon Carbide Junction Transistors and Schottky Rectifiers optimized for 250°C operation

2014 ◽  
Vol 1693 ◽  
Author(s):  
Siddarth Sundaresan ◽  
Brian Grummel ◽  
Ranbir Singh
Keyword(s):  
High Temperature ◽  
Fine Tuning ◽  
Electrical Performance ◽  
Current Gain ◽  
Leakage Currents ◽  
Schottky Rectifiers ◽  
Blocking Voltage ◽  
High Temperature Operation ◽  
Single Current Pulse

ABSTRACTElectrical performance and reliability of SiC Junction Transistors (SJTs) and Schottky rectifiers are presented. The 650 V/50 A-rated SiC SJTs feature current gains (β) up to 110 at room-temperature, 70 at 250°C, and stable breakdown characteristics. Single current pulse measurements indicate an almost invariant β up to 800 A/cm2 at 175°C – a measure of the SOA boundary for pulsed current SJT operation. Lower than 5 mA/cm2 leakage currents are measured on the SJTs at the rated blocking voltage and at 250°C. 1200 V Schottky rectifiers designed for high-temperature operation display < 3 mA/cm2 leakage currents up to 250°C. A 10x reduction in leakage current and 23% reduction in junction capacitance are observed when compared to the nearest competitor. The high-temperature Schottky rectifiers and SJTs display stable breakdown voltages and on-state characteristics after long-term HTRB stressing. A significant improvement in current gain stability is achieved by fine-tuning the fabrication process.

Evaluation of Ceramic Substrates for High Power and High Temperature Applications

2011 ◽  
Vol 2011 (CICMT) ◽  
pp. 000199-000206
Author(s):  
Srikanth Kulkarni ◽  
Shams Arifeen ◽  
Brian Patterson ◽  
Gabriel Potirniche ◽  
Aicha Elshabini ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Shock ◽  
High Power ◽  
Metal Layer ◽  
Process Conditions ◽  
Ceramic Substrates ◽  
Active Metal ◽  
Film Conductor ◽  
Delamination Cracks ◽  
High Temperature Operation

Ceramic substrates with thin film and thick film conductor traces are widely used in microelectronic packages for high temperature operation. In high power applications where the maximum current in the package may be hundreds of amperes, much thicker conductive traces are normally required. For such applications, Direct Bonded Copper (DBC), Direct Bonded Aluminum (DBA) or Active Metal Bonded (AMB) substrates are good candidates. These substrates provide low electrical resistance and high ampacity, thereby enable the design of high power circuits for high temperature operation. The most commonly observed failure mode in these substrates is the delamination of metal layer from the ceramic. The lifetime of a ceramic substrate can be significantly reduced by the processing conditions such as maximum process temperature, and the process gases that the substrates are exposed to. It has also been shown that the propagation of cracks in the ceramic can be abated by dimpling the metal layers along edges and corners. In order to evaluate the effectiveness of these types of substrates for power applications, substrates with various combinations of metal thicknesses and ceramic composition (Al2O3 and AlN) were evaluated for delamination as a function of thermal shock cycles. These samples included both dimpled and non-dimpled metallization. The samples were thermally cycled between −40 °C and 200 °C. A few of these substrates were exposed to forming gas at 340 °C prior to thermal cycling to imitate process conditions. Sample randomization was performed to provide statistically significant data. After a certain number of thermal cycles, delamination cracks were observed to nucleate and propagate in the substrates. Data regarding the reliability of these substrates as a function of thermal shock cycles is presented in this paper, along with failure mechanisms that are commonly observed. Computer simulations were performed to understand the conditions that lead to delamination cracks, and to estimate the crack growth rates in these substrates.

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