scholarly journals High Temperature Microelectromechanical Systems Using Piezoelectric Aluminum Nitride

2014 ◽  
Vol 2014 (HITEC) ◽  
pp. 000040-000046
Author(s):  
Benjamin A. Griffin ◽  
Scott D. Habermehl ◽  
Peggy J. Clews
Keyword(s):  
Thin Films ◽  
High Temperature ◽  
Aluminum Nitride ◽  
Mechanical Strength ◽  
Gas Turbines ◽  
Power Plants ◽  
Microelectromechanical Systems ◽  
Elevated Temperatures ◽  
Coefficient Of Thermal Expansion ◽  
Temperature Limit

We report on the efforts at Sandia National Laboratories to develop high temperature capable microelectromechanical systems (MEMS). MEMS transducers are pervasive in today's culture, with examples found in cell phones, automobiles, gaming consoles, and televisions. There is currently a need for MEMS transducers that can operate in more harsh environments, such as automobile engines, gas turbines, nuclear and coal power plants, and petroleum and geothermal well drilling. Our development focuses on the coupling of silicon carbide (SiC) and aluminum nitride (AlN) thin films on SiC wafers to form a MEMS material set capable of temperatures beyond 1000°C. SiC is recognized as a promising material for high temperature capable MEMS transducers and electronics because it has the highest mechanical strength of semiconductors with the exception of diamond and its upper temperature limit exceeds 2500°C, where it sublimates rather than melts. Most transduction schemes in SiC are focused on measuring changes in capacitance or resistance, which require biasing or modulation schemes that can withstand elevated temperatures. Instead, we are coupling temperature hardened, micro-scale SiC mechanical components with piezoelectric AlN thin films. AlN is a non-ferroelectric piezoelectric material, enabling piezoelectric transduction at temperatures exceeding 1000°C. AlN is a favorable MEMS material due to its high thermal, electrical, and mechanical strength. It is also closely matched to SiC for coefficient of thermal expansion.

A Brief Overview on High Temperature Friction and Wear

2010 ◽  
Author(s):  
Mustafa Bulut Coskun ◽  
Mahmut Faruk Aksit
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Friction And Wear ◽  
Oxidation Behavior ◽  
Elevated Temperatures ◽  
Wear Performance ◽  
Large Pressure ◽  
Higher Power ◽  
Vibratory Motion ◽  
Increasing Temperature

With the race for higher power and efficiency new gas turbines operate at ever increasing pressures and temperatures. Increased compression ratios and firing temperatures require many engine parts to survive extended service hours under large pressure loads and thermal distortions while sustaining relative vibratory motion. On the other hand, wear at elevated temperatures limits part life. Combined with rapid oxidation for most materials wear resistance reduces rapidly with increasing temperature. In order to achieve improved wear performance at elevated temperatures better understanding of combined wear and oxidation behavior of high temperature super alloys and coatings needed. In an attempt to aid designers for high temperature applications, this work provides a quick reference for the high temperature friction and wear research available in open literature. High temperature friction and wear data have been collected, grouped and summarized in tables.

Assessment of the Potential of Combined Micro Gas Turbine and High Temperature Fuel Cell Systems

2002 ◽  
Author(s):  
Dieter Bohn ◽  
Nathalie Po¨ppe ◽  
Joachim Lepers
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Advanced Materials ◽  
Cell Systems ◽  
Micro Gas Turbine ◽  
Technological Assessment

The present paper reports a detailed technological assessment of two concepts of integrated micro gas turbine and high temperature (SOFC) fuel cell systems. The first concept is the coupling of micro gas turbines and fuel cells with heat exchangers, maximising availability of each component by the option for easy stand-alone operation. The second concept considers a direct coupling of both components and a pressurised operation of the fuel cell, yielding additional efficiency augmentation. Based on state-of-the-art technology of micro gas turbines and solid oxide fuel cells, the paper analyses effects of advanced cycle parameters based on future material improvements on the performance of 300–400 kW combined micro gas turbine and fuel cell power plants. Results show a major potential for future increase of net efficiencies of such power plants utilising advanced materials yet to be developed. For small sized plants under consideration, potential net efficiencies around 70% were determined. This implies possible power-to-heat-ratios around 9.1 being a basis for efficient utilisation of this technology in decentralised CHP applications.

Piezoelectric Coefficients of Aluminum Nitride and Gallium Nitride

1999 ◽  
Vol 572 ◽  
Author(s):  
C. M. Lueng ◽  
H. L. W. Chan ◽  
W. K. Fong ◽  
C. Surya ◽  
C. L. Choy
Keyword(s):  
Thin Films ◽  
Gallium Nitride ◽  
High Temperature ◽  
Molecular Beam Epitaxy ◽  
Aluminum Nitride ◽  
Composite Film ◽  
High Frequency ◽  
Molecular Beam ◽  
Silicon Substrates ◽  
Heterodyne Interferometer

ABSTRACTAluminum nitride (AlN) and gallium nitride (GaN) thin films have potential uses in high temperature, high frequency (e.g. microwave) acoustic devices. In this work, the piezoelectric coefficients of wurtzite AlN and GaN/AlN composite film grown on silicon substrates by molecular beam epitaxy were measured by a Mach-Zehnder type heterodyne interferometer. The effects of the substrate on the measured coefficients are discussed.

The Effect of Alternative Turbine Cooling Schemes on the Performance of Utility Gas Turbine Powerplants

1982 ◽  
Author(s):  
Arthur Cohn ◽  
Mark Waters
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Power Plants ◽  
Heat Rate ◽  
Combined Cycle ◽  
Specific Power ◽  
Cooling Effectiveness ◽  
Turbine Cooling ◽  
The Impact ◽  
Systems Studies

It is important that the requirements and cycle penalties related to the cooling of high temperature turbines be thoroughly understood and accurately factored into cycle analyses and power plant systems studies. Various methods used for the cooling of high temperature gas turbines are considered and cooling effectiveness curves established for each. These methods include convection, film and transpiration cooling using compressor bleed and/or discharge air. In addition, the effects of chilling the compressor discharge cooling gas are considered. Performance is developed to demonstrate the impact of the turbine cooling schemes on the heat rate and specific power of Combined–Cycle power plants.

Impact of Sputter Deposition Parameters on the Leakage Current Behavior of Aluminum Nitride Thin Films

2012 ◽  
Vol 77 ◽  
pp. 29-34 ◽  
Author(s):  
Michael Schneider ◽  
Tobias Strunz ◽  
Achim Bittner ◽  
Ulrich Schmid
Keyword(s):  
Thin Films ◽  
Electric Field ◽  
Aluminum Nitride ◽  
Leakage Current ◽  
Microelectromechanical Systems ◽  
Constant Electric Field ◽  
Strong Negative Correlation ◽  
Axis Orientation ◽  
Sputter Deposited ◽  
Current Behavior

In microelectromechanical systems, piezoelectric aluminum nitride (AlN) thin films are commonly used as functional material for sensing and actuating purposes. This is due to excellent dielectric properties as well as a high chemical and thermal stability of AlN. In this work, we investigate the leakage current behavior (i.e. IV characteristic and charging behavior) of AlN thin films sputter deposited at varying plasma powers (300 W – 800 W) and deposition pressures (4 µbar – 8 µbar) up to an electric field of 0.5 MV/cm. First results show a Poole-Frenkel behavior for all samples with an increase in leakage current by orders of magnitude as the degree of c-axis orientation decreases. In addition, the discharging curves (i.e. meaning the current discharge after an applied constant electric field) agree well with the empirical Curie - von Schweidler Law (I(t) = I0 + I1t-n) and an increase of the parameter I1 with temperature is observed. I1 shows qualitatively the same behavior as the overall stored charge. Furthermore, the results show a strong negative correlation between the parameters n and the time constant τ1/2 (i.e. defined as the time after which half the stored charge has decayed), proofing that n is a good indicator for the decay time of the stored charge.

The Effect of High Temperature on the Degradation of Heat-Resistant and High-Temperature Alloys

2009 ◽  
Vol 147-149 ◽  
pp. 744-751 ◽  
Author(s):  
Józef Błachnio
Keyword(s):  
High Temperature ◽  
Mechanical Strength ◽  
Gas Turbines ◽  
Base Alloy ◽  
Heat Resistant ◽  
High Temperature Materials ◽  
High Temperature Alloys ◽  
Aerospace Technology ◽  
Aero Engines ◽  
Nickel Base

Heat-resistant and high-temperature materials are used to manufacture components, devices, and systems operated at high temperatures, i.e. under severe heat loads. Gas turbines used in the power industry, the traction, marine, and aircraft engines, the aerospace technology, etc. are good examples of such systems. Generally, as the temperature increases, the mechanical strength of materials decreases. While making such materials, there is a tendency to keep possibly low thermal weakening. In the course of operating gas turbines, various kinds of failures/defects/ damages may occur to components thereof, in particular, to blades. Predominating failures/damages are those attributable to the material overheating and thermal fatigue, all of them resulting in the loss of mechanical strength. The paper has been intended to present findings on changes in the microstructure of blades made of nickel-base alloy due to high temperature. The material gets overheated, which results in the deterioration of the microstructure’s condition. The material being in such condition presents low high-temperature creep resistance. Any component, within which such an effect occurs, is exposed to a failure/damage usually resulting in the malfunctioning of the turbine, and sometimes (as with aero-engines) in a fatal accident. Failures/damages of this kind always need major repairs, which are very expensive.

Creep Assessment of Large Size High Temperature Components Using Small Creep Test Specimens

2016 ◽  
Author(s):  
Balhassn S. M. Ali
Keyword(s):  
High Temperature ◽  
Creep Test ◽  
Nuclear Power ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Life Time ◽  
Safe Operation ◽  
Large Size ◽  
Testing Techniques ◽  
High Temperature Components

Most of the large components in the thermal, traditional and nuclear power plants such as pressurized vessels and pipes are operating at elevated temperatures. These temperatures and stress are high enough for creep to occur. For variety of reasons many of these power plants are now operating beyond their design life time. It is -known fact that as the high temperature components aged the failure rate normally increases as a result of their time dependent material damage. Further running of these components may become un-safe and dangerous in some cases. Therefore, creep assessment of the high temperature components of these plants is essential for their safe operation. Mainly for economic reasons these components have to be creep assessed as they are in service. However, assessing the creep strength for these high temperature components as they are in service, it can be challenging task, especially when these components are operating under extremely high temperature and/or stress. This paper introduces newly invented, small creep test specimens techniques. These new small types of specimens can be used to assess the remaining life times for the high temperature components, using only small material samples. These small material samples can be removed from the operating components surface, without affecting their safe operation. Two of the high temperature materials are used to validate the new testing techniques.

Model Combustor to Assess the Oxidation Behavior of Ceramic Materials Under Real Engine Conditions

1999 ◽  
Author(s):  
D. Filsinger ◽  
A. Schulz ◽  
S. Wittig ◽  
C. Taut ◽  
H. Klemm ◽  
...  
Keyword(s):  
High Temperature ◽  
International Development ◽  
Gas Turbines ◽  
Gas Flow ◽  
Oxidation Behavior ◽  
Elevated Temperatures ◽  
Ceramic Materials ◽  
Test Rig ◽  
Combustion Gas ◽  
Wide Range

A further increase of thermal efficiency and a reduction of the exhaust emissions of ground based gas turbines can be achieved by introducing new high temperature resistant materials. Therfore, ceramics are under international development. They offer excellent strengths at room and elevated temperatures. For gas turbine combustor applications, however, these materials have to maintain their advantageous properties under hostile environment. For the assessment and comparison of the oxidation behavior of different nonoxide ceramic materials a test rig was developed at the Institute for Thermal Turbomachinery (ITS), University of Karlsruhe, Germany. The test rig was integrated into the high temperature/ high pressure laboratory. A ceramic model combustion chamber was designed which allowed the exposure of standard four-point flexure specimens to the hot combustion gas flow. Gas temperatures and pressures could be varied in a wide range. Additionally, the partial steam pressure could be adjusted to real combustor conditions. The present paper gives a detailed description of the test rig and presents results of 100 hours endurance tests of ceramic materials at 1400°C. The initial strengths and the strengths after oxidation tests are compared. In addition to this, photographs illustrating the changes of the material’s microstructure are presented.

CRUTEMP 25

Alloy Digest ◽  
1975 ◽  
Vol 24 (4) ◽  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Control Systems ◽  
Gas Turbines ◽  
Elevated Temperatures ◽  
High Strength ◽  
Heat Treating ◽  
Temperature Performance ◽  
Automotive Emission

Abstract CRUTEMP 25 is a fully austenitic stainless steel with outstanding resistance to scaling at elevated temperatures. It also has high strength at elevated temperatures and its weldability is excellent. It is used in such applications as automotive emission control systems and gas turbines. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-309. Producer or source: Crucible Stainless Steel Division, Colt Industries.

An Advanced Extreme-Environment Wireless Telemetry System for Turbine Blade Instrumentation

2017 ◽  
Vol 14 (4) ◽  
pp. 158-165 ◽  
Author(s):  
John R. Fraley ◽  
Brett Sparkman ◽  
Stephen Minden ◽  
Anand Kulkarni ◽  
Joshua McConkey
Keyword(s):  
High Temperature ◽  
Natural Gas ◽  
System Integration ◽  
Gas Turbines ◽  
Power Plants ◽  
Mechanical Design ◽  
Extreme Environment ◽  
Department Of Energy ◽  
Future Direction ◽  
High Level

As advanced natural gas power generation systems evolve, the thrust for increased efficiencies and reduced emissions results in increasingly harsh conditions inside the turbine environment. These high temperatures, pressures, and corrosive atmospheres result in accelerated rates of degradation, leading to failure of turbine materials and components. Wolfspeed, A Cree Company, Siemens Energy, and Siemens Corporate Technology, in collaboration with the Department of Energy (DOE)'s National Energy Technology Laboratory, are developing a reliable and long-term monitoring capability in the turbine hot gas path in the form of novel ceramic-based thermocouples and wide bandgap instrumentation electronics that will contribute to the overall reliability of gas turbines. When equipped with better monitoring and controls, power plants can operate with increased fuel-burning efficiency, improved process dynamics and gas concentrations, and increased overall longevity of the power plant components. This will result in increased turbine availability and a reduction in outages and maintenance costs. The technology being developed in this program is based on advanced techniques and innovations in nearly every aspect of high-temperature electronics, including materials, semiconductor devices, subcomponents, electronic packaging, and system integration. The environment in which this wireless system must operate has continuous centrifugal loads with a gravitation force on the order of 16,000 times the force of gravity (16,000 g) and temperatures exceeding 400°C. This article will specifically discuss the background and motivation for the high-temperature instrumentation system and will explain the high-level electrical system, the construction of the instrumentation package, the techniques used for integration onto rotating components, as well as the wireless power and data transmission systems. In addition to the electrical and mechanical design, this article will also discuss results from laboratory bench testing as well as heated spin rig testing. Finally, this article will highlight the future direction of the instrumentation system evolution, with a final objective of insertion into Siemens natural gas turbine power plants.

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