scholarly journals CHARACTERIZATION OF RECENTLY DEVELOPED HIGH-TEMPERATURE POLYMERS: RADIATION RESISTANCE OF POLYIMIDE AT ELEVATED TEMPERATURES.

1968 ◽  
Author(s):  
N.R. Gordon ◽  
N.R. Langley
Keyword(s):  
High Temperature ◽  
Radiation Resistance ◽  
Elevated Temperatures

Performance and Reliability of MEMS Gyroscopes and Packaging at High Temperatures

2010 ◽  
Vol 2010 (HITEC) ◽  
pp. 000359-000366 ◽  
Author(s):  
Patrick McCluskey ◽  
Chandradip Patel ◽  
David Lemus
Keyword(s):  
High Temperature ◽  
Indoor Environment ◽  
Elevated Temperatures ◽  
High Sensitivity ◽  
Effect Of Temperature ◽  
Gps Tracking ◽  
Mems Gyroscope ◽  
Mems Gyroscopes ◽  
Gyroscope Sensor

Elevated temperatures can significantly affect the performance and reliability of MEMS gyroscope sensors. A MEMS vibrating resonant gyroscope measures angular velocity via a displacement measurement which can be on the order on nanometers. High sensitivity to small changes in displacement causes the MEMS Gyroscope sensor to be strongly affected by changes in temperature which can affect the displacement of the sensor due to thermal expansion and thermomechanical stresses. Analyzing the effect of temperature on MEMS gyroscope sensor measurements is essential in mission critical high temperature applications, such as inertial tracking of the movement of a fire fighter in a smoke filled indoor environment where GPS tracking is not possible. In this paper, we will discuss the development of the high temperature package for the tracking application, including the characterization of the temperature effects on the performance of a MEMS gyroscope. Both stationary and rotary tests were performed at room and at elevated temperatures on 10 individual single axis MEMS gyroscope sensors.

Characterization of Pyromark 2500 Paint for High-Temperature Solar Receivers

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Clifford K. Ho ◽  
A. Roderick Mahoney ◽  
Andrea Ambrosini ◽  
Marlene Bencomo ◽  
Aaron Hall ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Normal Incidence ◽  
Radiative Properties ◽  
Solar Absorptance ◽  
Thermal Emittance ◽  
Percentage Points ◽  
Original Coating

Pyromark 2500 is a silicone-based high-temperature paint that has been used on central receivers to increase solar absorptance. The radiative properties, aging, and selective absorber efficiency of Pyromark 2500 are presented in this paper for use as a baseline for comparison to high-temperature solar selective absorber coatings currently being developed. The solar absorptance ranged from ∼0.97 at near-normal incidence angles to ∼0.8 at glancing (80°) incidence angles, and the thermal emittance ranged from ∼0.8 at 100 °C to ∼0.9 at 1000 °C. After thermal aging at temperatures of ∼750 °C or higher, the solar absorptance decreased by several percentage points within a few days. It was postulated that the substrate may have contributed to a change in the crystal structure of the original coating at elevated temperatures.

Characterization of grain boundary phases in Si3N4 sintered using Y-Si-Al-O-N additives

1990 ◽  
Vol 48 (4) ◽  
pp. 1070-1071
Author(s):  
C. Koehler ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Secondary Phases ◽  
Amorphous Phases ◽  
High Temperature Mechanical Properties

The usefulness of silicon nitride as a high temperature ceramic can be limited by the presence of amorphous phases at the grain boundaries. Dense silicon nitride ceramics are produced using pressureless sintering of Si3N4 with Y-Si-Al-O-N additives. When these additives are left as a glassy phase at the grain boundaries and triple grain junctions, the mechanical properties at elevated temperatures are weakened due to these low viscous glasses. Post-sintering heat treatments and close compositional control can be effective in transforming the glass into crystalline phases at the grain boundaries thereby increasing the refractoriness.To optimize high temperature mechanical properties, processing must be controlled not only to fully crystallize the grain boundaries but also to avoid certain unstable secondary phases whose oxidation leads to large molar volume changes which causes possible cracking. Transmisssion electron microscopy and x-ray microanalysis (EDS) are significant methods to characterize the amorphous grain boundary pockets and to identify the crystalline grain boundary phases.

High Temperature Electrical Characterization of 4H-SiC MESFET Basic Logic Gates

2014 ◽  
Vol 778-780 ◽  
pp. 1130-1134 ◽  
Author(s):  
Mihaela Alexandru ◽  
Viorel Banu ◽  
Matthieu Florentin ◽  
Xavier Jordá ◽  
Miguel Vellvehi ◽  
...  
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Schottky Contact ◽  
Electrical Characterization ◽  
Logic Gates ◽  
Basic Logic ◽  
Process Maturity ◽  
Integration Density ◽  
Device Integration

Due to our demonstrated stable Tungsten-Schottky barrier at elevated temperatures, and also thanks to our technological process maturity regarding SiC-Schottky contact fabrication, we have implemented the digital logic gates library adopting a normally-on MESFET topology. In this paper we present new experimental results showing the thermal behavior up to 300oC of 4H-SiC logic gates library, monolithically integrating normally-on MESFETs and epitaxial resistors. The implemented SiC devices are based on important CMOS features and are specially designed for large ICs device integration density.

Structure and Microstructure of Advanced Materials Characterized by Neutron Diffraction

2021 ◽  
Vol 1016 ◽  
pp. 1404-1410
Author(s):  
Pavel Strunz ◽  
Radim Kocich ◽  
Přemysl Beran ◽  
Lenka Kunčická ◽  
Debashis Mukherji ◽  
...  
Keyword(s):  
High Temperature ◽  
Neutron Diffraction ◽  
Elevated Temperatures ◽  
Advanced Materials ◽  
High Temperature Alloys ◽  
The Matrix ◽  
Structure And Microstructure ◽  
Zr Alloy

Characterization of advanced materials by neutron powder diffraction provides information not accessible by other techniques. Thanks to the low absorption of neutrons, the bulk of the material and large-grain samples can be investigated, moreover in situ at elevated temperatures. The neutron diffraction use is demonstrated on two types of technologically important materials: Ti-Zr alloy and Co-Re high temperature alloy. In Ti-Zr alloy, the residual stress relief and microstrain evolution after ECAP was established. Boron influence on TaC strengthening precipitates in Co-Re high temperature alloys was shown not to be significant at the foreseen alloy operation temperatures, although boron content has a strong influence on the matrix phase.

Evaluation of TFR-Characteristics in aWide Temperature Range

2013 ◽  
Vol 2013 (CICMT) ◽  
pp. 000247-000251
Author(s):  
Uwe Partsch ◽  
Christian Lenz ◽  
Marco Wenzel ◽  
Markus Eberstein
Keyword(s):  
Thermal Expansion ◽  
Glass Transition ◽  
High Temperature ◽  
Transition Temperature ◽  
Elevated Temperatures ◽  
Electronic Packages ◽  
Electrical Characteristics ◽  
Sensor Applications ◽  
Thermal Range

Thick-Film Resistors (TFR) are applied for many years for the manufacturing of ceramic electronic packages as well as for mechanical or thermal sensors. The resistors characteristics (e.g. Rsqr, HTCR, CTCR) are guaranteed by paste suppliers for a thermal range of operation between −55 and 125°C. However, specific sensor applications require higher operation temperatures of up to 500°C. In the paper the results of the characterization of commercial TFR at elevated temperatures on alumina substrates are presented. Electrical characteristics (e.g. Rsqr, HTCR, CTCR, GF) are correlated with materials characteristics (TFR thermal expansion, glass transition temperature, microstructure). Different requirements are discussed regarding an improved high temperature applicability of TFR. Advantages and limits of the commercial TFR will be presented.

High-temperature characterization of oxygen-deficient K2NiF4-type Nd2−xSrxNiO4−δ (x = 1.0–1.6) for potential SOFC/SOEC applications

2015 ◽  
Vol 3 (47) ◽  
pp. 23852-23863 ◽  
Author(s):  
Ekaterina Kravchenko ◽  
Dmitry Khalyavin ◽  
Kiryl Zakharchuk ◽  
Jekabs Grins ◽  
Gunnar Svensson ◽  
...  
Keyword(s):  
High Temperature ◽  
Crystal Lattice ◽  
Electronic Transport ◽  
Elevated Temperatures ◽  
Oxygen Deficiency ◽  
Electronic Conductivity

Substitution by strontium induces significant oxygen deficiency in the crystal lattice of K2NiF4-type Nd2−xSrxNiO4−δ at elevated temperatures which, in combination with significant electronic conductivity, implies enhanced mixed ionic–electronic transport.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

Sign in / Sign up

Export Citation Format

Share Document