| Micro Gas Turbine Generators |
DEC 2000 |
23 pages |
| Authors:
A. H. Epstein; K. S. Breuer; J. H. Lang; M. A. Schmidt; S. D. Senturia; MASSACHUSETTS INST OF TECH CAMBRIDGE GAS TURBINE LAB
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 | MIT has developed the technology for micro-gas turbine generators. These are millimeter- to centimeter-size heat engines fabricated with semiconductor industry micromachining techniques (MEMS), ultimately capable of producing 10-100 W of power in less than a cubic centimeter. Applications include compact power sources offering energy and power densities an order of magnitude better than current battery technology; propulsion for small air vehicles; and a variety of microblowers, compressors, and heat pumps. ... |
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| Dielectric Analysis of the Cure of Thermosetting Epoxy/Amine Systems, |
MAY 1987 |
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| Authors:
S. A. Bidstrup; N. F. Sheppard; S. D. Senturia
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 | The dielectric properties of a low-molecular-weight thermosetting epoxy resin (cured isothermally with an aromatic amine hardener) were measured as a function of frequency, reaction time, and cure temperature. The changes in dielectric properties were directly correlated with the build-up of network structure during polymerization. (Author, modified). |
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| Monitoring the Cure of a Composite Matrix Resin with Microdielectrometry, |
MAY 1987 |
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| Authors:
W. W. Bidstrup; S. D. Senturia
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| The dielectrical permittivity and loss factor of a curing matrix resin in composite structures were monitored using the microdielectrometry system. Neat resin and epoxy/glass and epoxy/graphite composites were cured in a hydraulic press. The derivative of the loss factor with respect to time was related to the glass-transition temperature through a constitutive relation. Physical properties of the composites also were monitored during cure and related to the glass transition. (Author, ... |
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| Dielectric Analysis of Thermoset Cure |
07 OCT 85 |
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| Authors:
S. D. Senturia; N. F. Sheppard Jr; MASSACHUSETTS INST OF TECH CAMBRIDGE CENTER FOR MATERIALS SCIENCE AND ENGINEERING
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| Measurements of dielectric properties have been used to monitor chemical reactions in organic materials for more than fifty years. This review addresses the application of dielectric measurements to thermosetting polymers including basic dielectric properties, the methods used to measure these properties, key experimental artifacts that must be understood by the investigator, the physical origin of those artifacts, and a survey of the current published literature with emphasis on the correlations ... |
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| WLF (Williams-Landel-Ferry) Dependence of the Dielectric Properties of DGEBA (Diglycidyl Ether of Bisphenol-A) Epoxy Resins |
23 AUG 85 |
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| Authors:
N. F. Sheppard Jr.; S. D. Senturia; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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| The frequency and temperature dependence of the complex dielectric constant (Epsilon) of seven diglycidyl ether of bisphenol-A (DGEBA) epoxy resins having epoxide equivalent weights (EEW) in the range 175 to 1880 have been measured from T subscript -30 C to T subscript + 70 C at frequencies between 0.1 and 10,000 Hz. In the vicinity of T subscript g, Epsilon is dominated by dipole relaxation, while at higher temperatures ionic ... |
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| Monitoring of Laminate Cure with Microdielectrometry |
30 NOV 84 |
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| Authors:
W. W. Bidstrup; N. F. Sheppard Jr.; S. D. Senturia; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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| We report the use of microdielectrometry for monitoring the cure of the matrix resins in epoxy-glass and epoxy-graphite composites. The multi-ply laminates are cured in a press using ramped temperatures. The microdielectrometer sensor is embedded in a cavity made by cutting a hole in each of the inner plies. For a brominated-epoxy glass-reinforced prepreg ramped to final cure temperatures as high as 200 C and at pressure up to 60 ... |
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| Chemical Interpretation of the Relaxed Permittivity during Epoxy Resin Cure |
30 NOV 84 |
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| Authors:
N. F. Sheppard Jr.; S. D. Senturia; MASSACHUSETTS INST OF TECH CAMBRIDGE
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| The change in dielectric constant during cure of a diglycidyl ether of bisphenol-A resin (EPON 825) with diamino diphenyl sulfone was studied using microdielectrometry and differential scanning calorimetry. The dipole moments attributable to the epoxide and amine groups were obtained by dielectric measurements on the starting materials, and on related model compounds whose functionality precludes crosslinking. The decrease of the relaxed dielectric constant, Epsilon sub r, during cure can be ... |
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| The Role of Boundary Layer Capacitance at Blocking Electrodes in the Interpretation of Dielectric Cure Data in Adhesives |
31 MAY 1984 |
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| Authors:
D. R. Day; T. J. Lewis; H. L. Lee; S. D. Senturia; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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| The use of dielectric measurement techniques for monitoring the cure of adhesives and matrix resins used in composite materials is well known. Either parallel-plate electrodes or recently introduced dielectric microsensors can be used. During a typical cure, the quantitative results obtained from dielectric measurements early in cure, where the resin is a viscous liquid, have been shown to depend on the presence or absence of blocking layers at one or ... |
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| Electrical Monitoring of Polymerization Reactions with the Charge-Flow Transistor |
31 MAY 1984 |
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| Authors:
S. D. Senturia; MASSACHUSETTS INST OF TECH CAMBRIDGE CENTER FOR MATERIALS SCIENCE AND ENGINEERING
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| The primary goal of this program was to develop a promising new technique for the electrical monitoring of polymerizations based on a device called the charge-flow transistor, and its related device, the floating-gate charge-flow transistor. The program was directed toward the development of the instrumentation capabilities of the device and toward the research use of the method for the study of selected polymer systems. |
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| A Dielectric Study of the Time-Temperature-Transformation (TTT) Diagram of DGEBA Epoxy Resins Cured With DDS, |
03 APR 1984 |
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| Authors:
N. F. Sheppard Jr.; M. C. Coln; S. D. Senturia
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| Microdielectrometry and differential scanning calorimetry were used to study the isothermal cure of EPON 825 with diaminodiphenylsulfone (DDS). The results are compared with published torsional braid analysis (TBA) studies of the same system using a time-temperature-transformation diagram. (Author, modified). |
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| A Dielectric Study of the Time-Temperature-Transformation (TTT) Diagram of DGEBA Epoxy Resins Cured with DDS (Diaminodiphenylsulfone) |
14 DEC 1983 |
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| Authors:
N. F. Sheppard Jr.; M. C. W. Coln; S. D. Senturia; MASSACHUSETTS INST OF TECH CAMBRIDGE
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| Microdielectrometry and differential scanning calorimetry have been used to study the isothermal cure of EPON 825 with diaminodiphenylsulfone (DDS). The results are compared with published torsional braid analysis (TBA) studies of the same system using a time-temperature-transformation diagram. The dielectric measurements were made at temperatures between 100 and 220 C using measurement frequencies between 0.1 Hz and 10,000 Hz. The DSC was operated in an isothermal mode to determine extent ... |
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| Cure Monitoring and Control With Combined Dielectric/Temperature Probes, |
12 APR 1983 |
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| Authors:
S. D. Senturia; N. E. Sheppard Jr.; H. L. Lee; S. B. Marshall
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| The dielectric and conductive properties of resins used as adhesives and as matrices in composites undergo large changes during cure. The use of these changing electrical properties to monitor cure is a well established technique. A new development in microdielectrometry technology (via the addition of a temperature sensor to the probe.) is reported. The combined dielectric/temperature probe provides highly localized measurements of both temperature and changing dielectric properties. Data are ... |
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| In-Situ Measurement of the Properties of Curing Systems with Microdielectrometry |
04 MAY 1982 |
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| Authors:
S. D. Senturia; N. F. Sheppard Jr.; H. L. Lee; David R. Day; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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| This paper reports the measurement of low frequency dielectric properties of several epoxy-amine systems undergoing cure. Results from isothermal cures of DGEBA-MPDA are shown to provide a measurement of a low- frequency relaxation time that can be correlated with bulk viscosity prior to gelation. Also studied was the effect of PGE diluent in the DGEBA-DDS system. It is shown that as little as 5 phr diluent produces observable changes in ... |
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| Charge-Flow Structures as Polymeric Early-Warning Fire-Alarm Devices. |
MAY 1977 |
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| Authors:
C. M. Sechen ; S. D. Senturia; MASSACHUSETTS INST OF TECH CAMBRIDGE
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| The objective of this thesis was to investigate a new device called a charge-flow transistor and its applications for fire detection and gas sensing. A simpler device, the lock-and-key, was first used to determine the utility of various thin-film polymers as possible sensing materials. Two polymers, 1)a polyimidazole and 20a poly Schiff base were found to be particularly suitable for fire detection. One polymer, polyaminophenylacetylene, PAPA, was found to be ... |
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