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Sample records for materials microwave properties

  1. Mechanisms Responsible for Microwave Properties in High Performance Dielectric Materials

    NASA Astrophysics Data System (ADS)

    Zhang, Shengke

    Microwave properties of low-loss commercial dielectric materials are optimized by adding transition-metal dopants or alloying agents (i.e. Ni, Co, Mn) to tune the temperature coefficient of resonant frequency (tau f) to zero. This occurs as a result of the temperature dependence of dielectric constant offsetting the thermal expansion. At cryogenic temperatures, the microwave loss in these dielectric materials is dominated by electron paramagnetic resonance (EPR) loss, which results from the spin-excitations of d-shell electron spins in exchange-coupled clusters. We show that the origin of the observed magnetically-induced shifts in the dielectric resonator frequency originates from the same mechanism, as described by the Kramers-Kronig relations. The temperature coefficient of resonator frequency, tauf, is related to three material parameters according to the equation, tau f = - (½ tauepsilon + ½ taumu + alphaL), where tauepsilon, taumu , and alphaL are the temperature coefficient of dielectric constant, magnetic permeability, and lattice constant, respectively. Each of these parameters for dielectric materials of interest are measured experimentally. These results, in combination with density functional simulations, developed a much improved understanding of the fundamental mechanisms responsible for tau f. The same experimental methods have been used to characterize in-situ the physical nature and concentration of performance-degrading point defects in the dielectrics of superconducting planar microwave resonators.

  2. Dielectric properties of pharmaceutical materials relevant to microwave processing: effects of field frequency, material density, and moisture content.

    PubMed

    Heng, Paul W S; Loh, Z H; Liew, Celine V; Lee, C C

    2010-02-01

    The rising popularity of microwaves for drying, material processing and quality sensing has fuelled the need for knowledge concerning dielectric properties of common pharmaceutical materials. This article represents one of the few reports on the density and moisture content dependence of the dielectric properties of primary pharmaceutical materials and their relevance to microwave-assisted processing. Dielectric constants (epsilon') and losses (epsilon'') of 13 pharmaceutical materials were measured over a frequency range of 1 MHz-1 GHz at 23 +/- 1 degrees C using a parallel-electrode measurement system. Effects of field frequency, material density and moisture content on dielectric properties were studied. Material dielectric properties varied considerably with frequency. At microwave frequencies, linear relationships were established between cube-root functions of the dielectric parameters [symbols: see text] and density which enabled dielectric properties of materials at various densities to be estimated by regression. Moisture content was the main factor that contributed to the disparities in dielectric properties and heating capabilities of the materials in a laboratory microwave oven. The effectiveness of a single frequency density-independent dielectric function for moisture sensing applications was explored and found to be suitable within low ranges of moisture contents for a model material. PMID:19708060

  3. Dielectric properties of materials at cryogenic temperatures and microwave frequencies

    SciTech Connect

    Geyer, R.G.; Krupka, J.

    1994-12-31

    The permittivity and dielectric loss tangent of single- crystal quartz, cross-linked polystyrene (Rexolite), and polytetrafluoroethylene (Teflon) were measured at microwave frequencies and at temperatures of 77 K and 300 K using a dielectric resonator technique. Application of high-temperature superconducting (HTS) films as the endplates of the dielectric resonator made it possible to determine dielectric loss tangents of about 7 x 10{sup -6} at 77 K. Two permittivity tensor components for uniaxially anisotropic crystalline quartz were measured. Although the permittivities at 77 K changed very little from their room temperature values at 300 K, large changes in dielectric losses were observed. The decreased loss characteristics of these microelectronic substrates can markedly improve the performance of many microwave devices at cryogenic temperatures.

  4. Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.

    PubMed

    Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

    2012-12-21

    In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications. PMID:23171130

  5. Microwave properties of geological materials: Studies of penetration depth and moisture effects

    NASA Technical Reports Server (NTRS)

    Blinn, J. C., III; Quade, J. G.

    1972-01-01

    Summarized are the results of two of a series of controlled experiments performed during the summer of 1970. The first series of experiments to determine penetration depth showed the value of having a modeled response and data reduced in real time for examination in the field. The results suggest a radiometric method for measuring the microwave properties of materials in bulk and are applicable to studies of sea ice and other naturally layered media. The sensitivity of the microwave emission to changes in moisture content has inspired a number of airborne and ground based investigations. Although the effect is dominent under certain conditions, the complicating factors of soil type, roughness, vegetation, etc. seem to govern the conclusions regarding its application at this time.

  6. Spin canting effect and microwave absorption properties of Sm-Mn substituted nanosized material

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Naeem Ashiq, Muhammad; Asif Iqbal, M.; Ali, Irshad; Khan, M. A.; Niaz, Shanawar; Rana, M. U.

    2015-12-01

    In order to understand the substitutional effect of rare earth element Sm3+ and divalent Mn2+ on structural, magnetic and microwave absorption properties of hexagonal ferrites, a series of Sr2-x Smx Ni2 Fe28-yMnyO46 X-type hexagonal ferrites with concentration (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and y=0, 0.1, 0.2, 0.3, 0.4, 0.5) was synthesized by the sol-gel method. The XRD analysis shows that the material crystallized into single X-type hexagonal phase. The absorption bands at low wave number in FTIR curves are the characteristics of the X-type hexagonal ferrites. Decreasing trend in the magnetic properties with the substitution of Sm-Mn contents was also observed, which may be attributed to the oxidation of Mn2+ ions into Mn3+ ions and spin canting effect of rare earth element Sm3+. The reflection loss peak shifted towards the low frequency and microwave absorption properties of the material enhanced with the substitution of Sm-Mn contents which reflects its applications in super high frequency (SHF) devices. The attenuation constant curves are in good agreement with the reflection loss peak.

  7. Study on preparation and microwave absorption property of the core-nanoshell composite materials doped with La.

    PubMed

    Wei, Liqiu; Che, Ruxin; Jiang, Yijun; Yu, Bing

    2013-12-01

    Microwave absorbing material plays a great role in electromagnetic pollution controlling, electromagnetic interference shielding and stealth technology, etc. The core-nanoshell composite materials doped with La were prepared by a solid-state reaction method, which is applied to the electromagnetic wave absorption. The core is magnetic fly-ash hollow cenosphere, and the shell is the nanosized ferrite doped with La. The thermal decomposition process of the sample was investigated by thermogravimetry and differential thermal analysis. The morphology and components of the composite materials were investigated by the X-ray diffraction analysis, the microstructure was observed by scanning electron microscope and transmission electron microscope. The results of vibrating sample magnetometer analysis indicated that the exchange-coupling interaction happens between ferrite of magnetic fly-ash hollow cenosphere and nanosized ferrite coating, which caused outstanding magnetic properties. The microwave absorbing property of the sample was measured by reflectivity far field radar cross section of radar microwave absorbing material with vector network analyzer. The results indicated that the exchange-coupling interaction enhanced magnetic loss of composite materials. Therefore, in the frequency of 5 GHz, the reflection coefficient can achieve -24 dB. It is better than single material and is consistent with requirements of the microwave absorbing material at the low-frequency absorption. PMID:25078834

  8. A dielectric resonator method of measuring dielectric properties of low loss materials in the microwave region

    NASA Astrophysics Data System (ADS)

    Sheen, Jyh

    2008-05-01

    A technique for the measurement of dielectric properties of low loss and homogeneously isotropic media in the microwave region is studied. The measuring structure is a resonator made up of a cylindrical dielectric rod and conducting plates. The dielectric constants and loss tangents are computed from the resonant frequencies, structure dimensions and unloaded Qs of the TE01δ mode. A simple field model is introduced to analyze this resonator structure. Unlike other simple models, this model does not have the defect of low measurement accuracy of dielectric properties. Important factors affecting the dielectric properties measurements are introduced. Error sources for measurements are also discussed. The measurement accuracy is justified by comparing the results with those of other techniques. In addition, various methods for calculating the power factor and conducting loss and for measuring the conductivity of the conducting plates are discussed. The accuracies of certain of these methods have not previously been studied, but are given in this paper. The swept frequency capability was also studied. It was found that dielectric properties in microwave frequencies could be measured within a frequency range of 3 GHz.

  9. Two-dimensional nanosheets of MoS2: a promising material with high dielectric properties and microwave absorption performance

    NASA Astrophysics Data System (ADS)

    Ning, Ming-Qiang; Lu, Ming-Ming; Li, Jing-Bo; Chen, Zhuo; Dou, Yan-Kun; Wang, Cheng-Zhi; Rehman, Fida; Cao, Mao-Sheng; Jin, Hai-Bo

    2015-09-01

    In this study, few-layered MoS2 nanosheets (MoS2-NS) were obtained via the top-down exfoliation method from bulk MoS2 (MoS2-Bulk), and the dielectric properties and microwave absorption performance of MoS2-NS were first reported. The dimension-dependent dielectric properties and microwave absorption performance of MoS2 were investigated by presenting a comparative study between MoS2-NS and MoS2-Bulk. Our results show that the imaginary permittivity (ε'') of MoS2-NS/wax is twice as large as that of MoS2-Bulk/wax. The minimum reflection loss (RL) value of MoS2-NS/wax with 60 wt% loading is -38.42 dB at a thickness of 2.4 mm, which is almost 4 times higher than that of MoS2-Bulk/wax, and the corresponding bandwidth with effective attenuation (<-10 dB) of MoS2-NS/wax is up to 4.1 GHz (9.6-13.76 GHz). The microwave absorption performance of MoS2-NS is comparable to those reported in carbon-related nanomaterials. The enhanced microwave absorption performance of MoS2-NS is attributed to the defect dipole polarization arising from Mo and S vacancies and its higher specific surface area. These results suggest that MoS2-NS is a promising candidate material not only in fundamental studies but also in practical microwave applications.In this study, few-layered MoS2 nanosheets (MoS2-NS) were obtained via the top-down exfoliation method from bulk MoS2 (MoS2-Bulk), and the dielectric properties and microwave absorption performance of MoS2-NS were first reported. The dimension-dependent dielectric properties and microwave absorption performance of MoS2 were investigated by presenting a comparative study between MoS2-NS and MoS2-Bulk. Our results show that the imaginary permittivity (ε'') of MoS2-NS/wax is twice as large as that of MoS2-Bulk/wax. The minimum reflection loss (RL) value of MoS2-NS/wax with 60 wt% loading is -38.42 dB at a thickness of 2.4 mm, which is almost 4 times higher than that of MoS2-Bulk/wax, and the corresponding bandwidth with effective attenuation (<-10

  10. Using microwave and macroscopic samples of dielectric solids to study the photonic properties of disordered photonic bandgap materials.

    PubMed

    Hashemizad, Seyed Reza; Tsitrin, Sam; Yadak, Polin; He, Yingquan; Cuneo, Daniel; Williamson, Eric Paul; Liner, Devin; Man, Weining

    2014-01-01

    Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). In this article we will describe the methods for constructing and characterizing macroscopic disordered photonic structures using microwaves. The microwave regime offers the most convenient experimental sample size to build and test PBG media. Easily manipulated dielectric lattice components extend flexibility in building various 2D structures on top of pre-printed plastic templates. Once built, the structures could be quickly modified with point and line defects to make freeform waveguides and filters. Testing is done using a widely available Vector Network Analyzer and pairs of microwave horn antennas. Due to the scale invariance property of electromagnetic fields, the results we obtained in the microwave region can be directly applied to infrared and optical regions. Our approach is simple but delivers exciting new insight into the nature of light and disordered matter interaction. Our representative results include the first experimental demonstration of the existence of a complete and isotropic PBG in a two-dimensional (2D) hyperuniform disordered dielectric structure. Additionally we demonstrate experimentally the ability of this novel photonic structure to guide electromagnetic waves (EM) through freeform waveguides of arbitrary shape. PMID:25285416

  11. Investigation of mechanical and thermal properties of microwave-sintered lunar simulant materials using 2.45 GHz radiation

    NASA Technical Reports Server (NTRS)

    Meek, T. T.

    1990-01-01

    The mechanical and thermal properties of lunar simulant material were investigated. An alternative method of examining thermal shock in microwave-sintered lunar samples was researched. A computer code was developed that models how the fracture toughness of a thermally shocked lunar simulant sample is related to the sample hardness as measured by a micro-hardness indentor apparatus. This technique enables much data to be gathered from a few samples. Several samples were sintered at different temperatures and for different times at the temperatures. The melting and recrystallization characteristics of a well-studied binary system were also investigated to see if the thermodynamic barrier for the nucleation of a crystalline phase may be affected by the presence of a microwave field. The system chosen was the albite (sodium alumino silicate) anorthite system (calcium alumino silicate). The results of these investigations are presented.

  12. The physicochemical properties of microwave-assisted encapsulated anthocyanins from Ipomoea batatas as affected by different wall materials

    PubMed Central

    Mohd Nawi, Norazlina; Muhamad, Ida Idayu; Mohd Marsin, Aishah

    2015-01-01

    This study focuses on the impact of different wall materials on the physicochemical properties of microwave-assisted encapsulated anthocyanins from Ipomoea batatas. Using the powder characterization technique, purple sweet potato anthocyanin (PSPAs) powders were analysed for moisture content, water activity, dissolution time, hygroscopicity, color and morphology. PSPAs were produced using different wall materials: maltodextrin (MD), gum arabic (GA) and a combination of gum arabic and maltodextrin (GA + MD) at a 1:1 ratio. Each of the wall materials was homogenized to the core material at a core/wall material ratio of 5 and were microencapsulated by microwave-assisted drying at 1100 W. Results indicated that encapsulated powder with the GA and MD combination presented better quality of powder with the lowest value of moisture content and water activity. With respect to morphology, the microcapsule encapsulated with GA + MD showed several dents in coating surrounding its core material, whereas other encapsulated powders showed small or slight dents entrapped onto the bioactive compound. Colorimetric analysis showed changes in values of L, a*, b*, hue and chroma in the reconstituted powder compared to the initial powder. PMID:25838887

  13. Microwave resonant technique in studies of photodielectric properties of bulk, thin film and nanoparticle materials

    NASA Astrophysics Data System (ADS)

    Pavlov, V. V.; Rakhmatullin, R. M.; Cefalas, A. C.; Semashko, V. V.

    2016-06-01

    An enhanced contactless microwave technique allows us to study the photoconductivity of materials. The transient response of the complex permittivity of matter (ε ={ε1}-j{ε2} ) under optical irradiation is measured with nanosecond time resolution. The main advantage of the novel methodology is the elimination of the polarization effect in evaluating photoconductivity. The potential of the methodology was demonstrated by photoconductivity measurements in Si [1 0 0] crystal, CeO2 nanocrystalline powder and Ce-doped LiYF4 single crystal. The variations of complex permittivity (δ {ε1} and δ {ε2} ) of Si [1 0 0] crystal, CeO2 nanocrystalline powder and Ce-doped LiYF4 single crystal under optical irradiation was measured and accurate values for crystalline band gaps were extracted. Finally, quantum confinement effects were observed in nano-size crystalline powders.

  14. Preparation and low-frequency microwave-absorbing properties of MWCNTs/Co-Ni/Fe3O4 hybrid material

    NASA Astrophysics Data System (ADS)

    Lu, Shao-Wei; Yuan, Chao-Jun; Jia, Cai-Xia; Ma, Ke-Ming; Wang, Xiao-Qiang

    2016-04-01

    MWCNTs/Co-Ni/Fe3O4 hybrid material has been successfully prepared by electroless plating and coprecipitation method, which is applied to the low-frequency microwave absorption. Their surface morphology, structure, magnetism and electromagnetic properties in the low-frequency range of 1-4GHz were characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and vector network analyzer. Results indicated that magnetic Co-Ni/Fe3O4 particles were attached on the surface of multi-walled carbon nanotubes successfully. The saturation magnetization of MWCNTs/Co-Ni/Fe3O4 hybrid materials was 68.6emu/g and the coercivity is 17.9 Oe. The electromagnetic and microwave absorbing properties analysis in the low-frequency range of 1-4GHz indicated that the hybrid material exhibited excellent magnetic loss and the maximum reflection loss could reach ‑13.57dB at 1.51GHz with 1.05GHz bandwidth below ‑5dB.

  15. The effect of grain size on the biocompatibility, cell-materials interface, and mechanical properties of microwave-sintered bioceramics.

    PubMed

    Veljović, Djordje; Colić, Miodrag; Kojić, Vesna; Bogdanović, Gordana; Kojić, Zvezdana; Banjac, Andrijana; Palcevskis, Eriks; Petrović, Rada; Janaćković, Djordje

    2012-11-01

    The effect of decreasing the grain size on the biocompatibility, cell-material interface, and mechanical properties of microwave-sintered monophase hydroxyapatite bioceramics was investigated in this study. A nanosized stoichiometric hydroxyapatite powder was isostatically pressed at high pressure and sintered in a microwave furnace in order to obtain fine grained dense bioceramics. The samples sintered at 1200°C, with a density near the theoretical one, were composed of micron-sized grains, while the grain size decreased to 130 nm on decreasing the sintering temperature to 900°C. This decrease in the grain size certainly led to increases in the fracture toughness by much as 54%. An in vitro investigation of biocompatibility with L929 and human MRC-5 fibroblast cells showed noncytotoxic effects for both types of bioceramics, while the relative cell proliferation rate, cell attachment and metabolic activity of the fibroblasts were improved with decreasing of grain size. An initial in vivo investigation of biocompatibility by the primary cutaneous irritation test showed that both materials exhibited no irritation properties. PMID:22733649

  16. Magnetic field effects on microwave absorbing materials

    NASA Technical Reports Server (NTRS)

    Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

    1991-01-01

    The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

  17. Microwavable thermal energy storage material

    DOEpatents

    Salyer, Ival O.

    1998-09-08

    A microwavable thermal energy storage material is provided which includes a mixture of a phase change material and silica, and a carbon black additive in the form of a conformable dry powder of phase change material/silica/carbon black, or solid pellets, films, fibers, moldings or strands of phase change material/high density polyethylene/ethylene-vinyl acetate/silica/carbon black which allows the phase change material to be rapidly heated in a microwave oven. The carbon black additive, which is preferably an electrically conductive carbon black, may be added in low concentrations of from 0.5 to 15% by weight, and may be used to tailor the heating times of the phase change material as desired. The microwavable thermal energy storage material can be used in food serving applications such as tableware items or pizza warmers, and in medical wraps and garments.

  18. Microwavable thermal energy storage material

    DOEpatents

    Salyer, I.O.

    1998-09-08

    A microwavable thermal energy storage material is provided which includes a mixture of a phase change material and silica, and a carbon black additive in the form of a conformable dry powder of phase change material/silica/carbon black, or solid pellets, films, fibers, moldings or strands of phase change material/high density polyethylene/ethylene vinyl acetate/silica/carbon black which allows the phase change material to be rapidly heated in a microwave oven. The carbon black additive, which is preferably an electrically conductive carbon black, may be added in low concentrations of from 0.5 to 15% by weight, and may be used to tailor the heating times of the phase change material as desired. The microwavable thermal energy storage material can be used in food serving applications such as tableware items or pizza warmers, and in medical wraps and garments. 3 figs.

  19. Microwave Dielectric Properties of Cereal Grains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of five cereal grains (wheat, corn, barley, oats, and grain sorghum) were 19 measured at 23 oC over broad microwave frequency range (5 GHz to 15 GHz) with a free-space-transmission 20 technique. Results of dielectric properties measurement are tabulated for each material for mo...

  20. Plasma-assisted microwave processing of materials

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin (Inventor); Ylin, Tzu-yuan (Inventor); Jackson, Henry (Inventor)

    1998-01-01

    A microwave plasma assisted method and system for heating and joining materials. The invention uses a microwave induced plasma to controllably preheat workpiece materials that are poorly microwave absorbing. The plasma preheats the workpiece to a temperature that improves the materials' ability to absorb microwave energy. The plasma is extinguished and microwave energy is able to volumetrically heat the workpiece. Localized heating of good microwave absorbing materials is done by shielding certain parts of the workpiece and igniting the plasma in the areas not shielded. Microwave induced plasma is also used to induce self-propagating high temperature synthesis (SHS) process for the joining of materials. Preferably, a microwave induced plasma preheats the material and then microwave energy ignites the center of the material, thereby causing a high temperature spherical wave front from the center outward.

  1. Correlation Between Material Properties of Ferroelectric Thin Films and Design Parameters for Microwave Device Applications: Modeling Examples and Experimental Verification

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; VanKeuls, Fred W.; Subramanyam, Guru; Mueller, Carl H.; Romanofsky, Robert R.; Rosado, Gerardo

    2000-01-01

    The application of thin ferroelectric films for frequency and phase agile components is the topic of interest of many research groups worldwide. Consequently, proof-of-concepts (POC) of different tunable microwave components using either (HTS, metal)/ferroelectric thin film/dielectric heterostructures or (thick, thin) film "flip-chip" technology have been reported. Either as ferroelectric thin film characterization tools or from the point of view of circuit implementation approach, both configurations have their respective advantages and limitations. However, we believe that because of the progress made so far using the heterostructure (i.e., multilayer) approach, and due to its intrinsic features such as planar configuration and monolithic integration, a study on the correlation of circuit geometry aspects and ferroelectric material properties could accelerate the insertion of this technology into working systems. In this paper, we will discuss our study performed on circuits based on microstrip lines at frequencies above 10 GHz, where the multilayer configuration offers greater ease of insertion due to circuit's size reduction. Modeled results of relevant circuit parameters such as the characteristic impedance, effective dielectric constant, and attenuation as a function of ferroelectric film's dielectric constant, tans, and thickness, will be presented for SrTiO3 and Ba(x)Sr(1-x)TiO3 ferroelectric films. A comparison between the modeled and experimental data for some of these parameters will be presented.

  2. Microwave techniques for physical property measurements

    NASA Technical Reports Server (NTRS)

    Barmatz, M.

    1993-01-01

    Industrial processing of metals and ceramics is now being streamlined by the development of theoretical models. High temperature thermophysical properties of these materials are required to successfully apply these theories. Unfortunately, there is insufficient experimental data available for many of these properties, particularly in the molten state. Microwave fields can be used to measure specific heat, thermal diffusivity, thermal conductivity and dielectric constants at high temperatures. We propose to (1) develop a microwave flash method (analogous to the laser flash technique) that can simultaneously measure the thermal diffusivity and specific heat of insulators and semiconductors at high temperatures, (2) an appropriate theory and experimental apparatus to demonstrate the measurement of the specific heat of a metal using a new microwave ac specific heat technique, and (3) experimental methods for noncontact measurement of the real and imaginary dielectric constants.

  3. Microwave processing of radioactive materials-I

    SciTech Connect

    White, T.L.; Berry, J.B.

    1989-01-01

    This paper is the first of two papers that reviews the major past and present applications of microwave energy for processing radioactive materials, with particular emphasis on processing radioactive wastes. Microwave heating occurs through the internal friction produced inside a dielectric material when its molecules vibrate in response to an oscillating microwave field. For this presentation, we shall focus on the two FCC-approved microwave frequencies for industrial, scientific, and medical use, 915 and 2450 MHz. Also, because of space limitations, we shall postpone addressing plasma processing of hazardous wastes using microwave energy until a later date. 13 refs., 4 figs.

  4. Cryogenic microwave anisotropic artificial materials

    NASA Astrophysics Data System (ADS)

    Trang, Frank

    This thesis addresses analysis and design of a cryogenic microwave anisotropic wave guiding structure that isolates an antenna from external incident fields from specific directions. The focus of this research is to design and optimize the radome's constituent material parameters for maximizing the isolation between an interior receiver antenna and an exterior transmitter without significantly disturbing the transmitter antenna far field characteristics. The design, characterization, and optimization of high-temperature superconducting metamaterials constitutive parameters are developed in this work at X-band frequencies. A calibrated characterization method for testing arrays of split-ring resonators at cryogenic temperature inside a TE10 waveguide was developed and used to back-out anisotropic equivalent material parameters. The artificial material elements (YBCO split-ring resonators on MgO substrate) are optimized to improve the narrowband performance of the metamaterial radome with respect to maximizing isolation and minimizing shadowing, defined as a reduction of the transmitted power external to the radome. The optimized radome is fabricated and characterized in a parallel plate waveguide in a cryogenic environment to demonstrate the degree of isolation and shadowing resulting from its presence. At 11.12 GHz, measurements show that the HTS metamaterial radome achieved an isolation of 10.5 dB and the external power at 100 mm behind the radome is reduced by 1.9 dB. This work demonstrates the feasibility of fabricating a structure that provides good isolation between two antennas and low disturbance of the transmitter's fields.

  5. Investigation of dielectric properties of different cake formulations during microwave and infrared-microwave combination baking.

    PubMed

    Sakiyan, Ozge; Sumnu, Gulum; Sahin, Serpil; Meda, Venkatesh

    2007-05-01

    Dielectric properties can be used to understand the behavior of food materials during microwave processing. Dielectric properties influence the level of interaction between food and high frequency electromagnetic energy. Dielectric properties are, therefore, important in the design of foods intended for microwave preparation. In this study, it was aimed to determine the variation of dielectric properties of different cake formulations during baking in microwave and infrared-microwave combination oven. In addition, the effects of formulation and temperature on dielectric properties of cake batter were examined. Dielectric constant and loss factor of cake samples were shown to be dependent on formulation, baking time, and temperature. The increase in baking time and temperature decreased dielectric constant and loss factor of all formulations. Fat content was shown to increase dielectric constant and loss factor of cakes. PMID:17995773

  6. Method of sintering materials with microwave radiation

    DOEpatents

    Kimrey, Jr., Harold D.; Holcombe, Jr., Cressie E.; Dykes, Norman L.

    1994-01-01

    A method of sintering ceramic materials following: A compacted article comprising inorganic particles coated with carbon is provided, the carbon providing improved microwave coupling. The compacted article is then heated by microwave radiation to a temperature and for a period of time sufficient to sinter the compacted article.

  7. Excellent microwave absorption property of Graphene-coated Fe nanocomposites

    PubMed Central

    Zhao, Xingchen; Zhang, Zhengming; Wang, Liaoyu; Xi, Kai; Cao, Qingqi; Wang, Dunhui; Yang, Yi; Du, Youwei

    2013-01-01

    Graphene has evoked extensive interests for its abundant physical properties and potential applications. It is reported that the interfacial electronic interaction between metal and graphene would give rise to charge transfer and change the electronic properties of graphene, leading to some novel electrical and magnetic properties in metal-graphene heterostructure. In addition, large specific surface area, low density and high chemical stability make graphene act as an ideal coating material. Taking full advantage of the aforementioned features of graphene, we synthesized graphene-coated Fe nanocomposites for the first time and investigated their microwave absorption properties. Due to the charge transfer at Fe-graphene interface in Fe/G, the nanocomposites show distinct dielectric properties, which result in excellent microwave absorption performance in a wide frequency range. This work provides a novel approach for exploring high-performance microwave absorption material as well as expands the application field of graphene-based materials. PMID:24305606

  8. A microwave interferometer to measure transient properties

    SciTech Connect

    Warthen, B.J.; Luther, G.G.

    1982-12-31

    A simple K-band microwave interferometer has been developed at the Los Alamos National Laboratory to measure various transient properties in both energetic (high explosive) and passive (grout and Teflon) materials. The interferometer measures the position as a function of time of either a dielectric discontinuity, i.e., a shock front, or the position as a function of time of a conducting surface such as the detonation wave in a high explosive. By embedding a reflector in a dielectric material, both the particle velocity and the shock velocity may be measured at the same time and in the same place. The interferometer is constructed (with slight modifications) of commercially available microwave components. The total material cost for a complete working instrument is a few hundred dollars. Details of the construction will be given. As an example of the range of uses of the interferometer, it has been used to measure the detonation-to-deflagration transition in HMX and the shock properties of the grout in a nuclear test in Nevada. Data on these and other experiments are presented.

  9. Microwave processing of lunar materials: potential applications

    SciTech Connect

    Meek, T.T.; Cocks, F.H.; Vaniman, D.T.; Wright, R.A.

    1984-01-01

    The microwave processing of lunar materials holds promise for the production of either water, oxygen, primary metals, or ceramic materials. Extra high frequency microwave (EHF) at between 100 and 500 gigahertz have the potential for selective coupling to specific atomic species and a concomitant low energy requirement for the extraction of specific materials, such as oxygen, from lunar ores. The coupling of ultra high frequency (UHF) (e.g., 2.45 gigahertz) microwave frequencies to hydrogen-oxygen bonds might enable the preferential and low energy cost removal (as H/sub 2/O) of implanted protons from the sun or of adosrbed water which might be found in lunar dust in permanently shadowed polar areas. Microwave melting and selective phase melting of lunar materials could also be used either in the preparation of simplified ceramic geometries (e.g., bricks) with custom-tailored microstructures, or for the direct preparation of hermetic walls in underground structures. Speculatively, the preparation of photovoltaic devices based on lunar materials, especially ilmenite, may be a potential use of microwave processing on the moon. Preliminary experiments on UHF melting of terrestrial basalt, basalt/ilmenite and mixtures show that microwave processing is feasible.

  10. The Workshop on Microwave-Absorbing Materials for Accelerators

    SciTech Connect

    Isidoro Campisi

    1993-05-01

    A workshop on the physics and applications of microwave-absorbing materials in accelerators and related systems was held at CEBAF February 22-24, 1993. The gathering brought together about 150 scientists and representatives of industries from all over the world. The main topics of discussion were the properties of ''absorbing'' materials and how the stringent conditions in an accelerator environment restrict the choice of usable material.

  11. Microwave processing of materials. Final report

    SciTech Connect

    McMillan, A.D.; Lauf, R.J.; Garard, R.S.

    1997-11-01

    A Cooperative Research and Development Agreement (CRADA) between Lockheed Martin Energy Systems, Inc. (LMES) and Lambda Technologies, Inc. (Lambda) of Raleigh, N.C., was initiated in May 1995. [Lockheed Martin Energy Research, Corp. (LMER) has replaced LMES]. The completion data for the Agreement was December 31, 1996. The purpose of this work is to explore the feasibility of several advanced microwave processing concepts to develop new energy-efficient materials and processes. The project includes two tasks: (1) commercialization of the variable-frequency microwave furnace (VFMF); and (2) microwave curing of polymer composites. The VFMF, whose initial conception and design was funded by the Advanced Industrial Concepts (AIC) Materials Program, will allow us, for the first time, to conduct microwave processing studies over a wide frequency range. This novel design uses a high-power traveling wave tube (TWT) originally developed for electronic warfare. By using this microwave source, one can not only select individual microwave frequencies for particular experiments, but also achieve uniform power densities over a large area by the superposition of many different frequencies.

  12. Microwave heating of lunar materials. Appendix A

    NASA Technical Reports Server (NTRS)

    Meek, Thomas T.

    1992-01-01

    Microwave heating of nonmetallic inorganic material has been of interest for many years. Von Hippel in the late 1940's and early 1950's investigated how microwave radiation up to 10 GHz couples to various insulator materials. Perhaps the most work has been done by Wayne Tinga at the University of Edmonton. Most of the work to date has been done at the two frequency bands allowed in industrial use (0.915 GHz and 2.45 GHz). However some work has recently been carried out at 28 GHz and 60 GHz. Work done in this area at Los Alamos National Laboratory is discussed.

  13. Slow microwaves in left-handed materials

    NASA Astrophysics Data System (ADS)

    di Gennaro, E.; Parimi, P. V.; Lu, W. T.; Sridhar, S.; Derov, J. S.; Turchinetz, B.

    2005-07-01

    Remarkably slow propagation of microwaves in two different classes of left-handed materials (LHM’s) is reported from microwave-pulse and continuous-wave transmission measurements. Microwave dispersion in a composite LHM made of split-ring resonators and wire strips reveals group velocity vg˜c/50 , where c is the free-space light velocity. Photonic crystals (PhC’s) made of dielectric Al2O3 rods reveal vg˜c/10 . Group delay dispersion of both the composite LHM and PhC’s determined from the experiment is in complete agreement with that obtained from theory. The slow group velocities are quantitatively described by the strong dispersion observed in these materials.

  14. Materials and techniques for controllable microwave surfaces

    NASA Astrophysics Data System (ADS)

    Barnes, Alan; Ford, Kenneth L.; Wright, Peter V.; Chambers, Barry; Smith, Christopher D.; Thompson, Denise A.; Pavri, Francis

    2000-08-01

    Discs and waveguide samples of polymeric mixed conductor nanocomposite materials comprising a conducting polymer and redox active switching agent in a polymer electrolyte have been prepared and studied. These novel materials have been shown to exhibit large, rapid and reversible changes in their microwave impedance when small d.c. electric fields are applied across them from the edges. The results of simultaneous cyclic voltammetry or potential square waves and microwave transmission measurements have shown that the changes are apparantly instantaneous with the application or removal of the applied field. Analysis of the microwave results has shown that the impedance of the materials changes by a factor of up to almost 50 with the imposition or removal of the fields. Nanocomposite materials having either poly(pyrrole) or poly(aniline) as the conducting polymer component and either silver/silver tetrafluoroborate or copper/copper(II) tetrafluoroborate as the redox active components have been investigated. The results of the nanocomposite materials are compared with those of microparticulate composities of similar composition. A new configuration of single layer tunable microwave absorber using only resistive control has been investigated and shown to exhibit wideband, low reflectivity performance combined with reduced thickness. A major advantage of the new topology is the requirement for only a 3:1 change in controllable resistance.

  15. Materials processing using a variable frequency microwave furnace

    SciTech Connect

    Lauf, R.J.; Bible, D.W.; Maddox, S.R.; Everleigh, C.A.; Espinosa, R.J.; Johnson, A.C.

    1993-12-31

    We describe a materials processing system that uses a high power traveling wave tube (TWT) as the microwave source. The TWT provides approximately one octave bandwidth and variable power levels up to 2 kW into a multimode cavity. By controlling the frequency, efficient coupling to the load can be maintained even as the load`s dielectric properties change. Alternatively, can be used as a means of mode stirring at rates far beyond those attainable through mechanical stirring. The system has been tested for sintering alumina ceramics, annealing a tungsten penetrator alloy, curing epoxy resin, and depositing diamond films from a microwave plasma.

  16. Electrically tunable materials for microwave applications

    NASA Astrophysics Data System (ADS)

    Ahmed, Aftab; Goldthorpe, Irene A.; Khandani, Amir K.

    2015-03-01

    Microwave devices based on tunable materials are of vigorous current interest. Typical applications include phase shifters, antenna beam steering, filters, voltage controlled oscillators, matching networks, and tunable power splitters. The objective of this review is to assist in the material selection process for various applications in the microwave regime considering response time, required level of tunability, operating temperature, and loss tangent. The performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals. Particular attention is given to ferroelectric materials as they are the most promising candidates when response time, dielectric loss, and tunability are important. However, polymers and liquid crystals are emerging as potential candidates for a number of new applications, offering mechanical flexibility, lower weight, and lower tuning voltages.

  17. Electrically tunable materials for microwave applications

    SciTech Connect

    Ahmed, Aftab Goldthorpe, Irene A.; Khandani, Amir K.

    2015-03-15

    Microwave devices based on tunable materials are of vigorous current interest. Typical applications include phase shifters, antenna beam steering, filters, voltage controlled oscillators, matching networks, and tunable power splitters. The objective of this review is to assist in the material selection process for various applications in the microwave regime considering response time, required level of tunability, operating temperature, and loss tangent. The performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals. Particular attention is given to ferroelectric materials as they are the most promising candidates when response time, dielectric loss, and tunability are important. However, polymers and liquid crystals are emerging as potential candidates for a number of new applications, offering mechanical flexibility, lower weight, and lower tuning voltages.

  18. MICROWAVE MEASUREMENT OF REFRACTORY MATERIALS AT HIGH-TEMPERATURE

    SciTech Connect

    Kharkovsky, S.; Zoughi, R.; Smith, J.; Davis, B.; Limmer, R.

    2009-03-03

    Knowledge of the electrical behavior of refractory materials may enable the development and optimization of microwave nondestructive techniques to detect and evaluate changes in their physical properties while the materials are in service. This paper presents the results of a limited and preliminary investigation in which two refractory materials (dense chrome and dense zircon) were subjected to increasing temperature in a furnace and in which a frequency-modulated continuous-wave radar operating in the frequency range of 8-18 GHz radar was used to evaluate their attenuation properties.

  19. Ceramic transactions: Microwaves - theory and application in materials processing III. Volume 49

    SciTech Connect

    1995-12-31

    This symposium continued the series on microwave processing of materials initiated in 1988. Papers are presented on the following topics: steps to commercialization, manufacturing with microwaves, waste remediation, processing equipment, microwave/materials interactions, dielectric properties, process modeling, joining, processing and thermal effects, chemical and reaction synthesis, and current issues and future activities. Individual papers have been processed separately for the United States Department of Energy databases.

  20. Microwave techniques for measuring complex permittivity and permeability of materials

    SciTech Connect

    Guillon, P.

    1995-08-01

    Different materials are of fundamental importance to the aerospace, microwave, electronics and communications industries, and include for example microwave absorbing materials, antennas lenses and radomes, substrates for MMIC and microwave components and antennaes. Basic measurements for the complex permittivity and permeability of those homogeneous solid materials in the microwave spectral region are described including hardware, instrumentation and analysis. Elevated temperature measurements as well as measurements intercomparisons, with a discussion of the strengths and weaknesses of each techniques are also presented.

  1. Microwave properties of Ni-based ferromagnetic inverse opals

    NASA Astrophysics Data System (ADS)

    Kostylev, M.; Stashkevich, A. A.; Roussigné, Y.; Grigoryeva, N. A.; Mistonov, A. A.; Menzel, D.; Sapoletova, N. A.; Napolskii, K. S.; Eliseev, A. A.; Lukashin, A. V.; Grigoriev, S. V.; Samarin, S. N.

    2012-11-01

    Investigations of microwave properties of Ni-based inverse ferromagnetic opal-like film with the [111] axis of the fcc structure along the normal direction to the film have been carried out in the 2-18 GHz frequency band. We observed multiple spin wave resonances for the magnetic field applied perpendicular to the film, i.e., along the [111] axis of this artificial crystal. For the field applied in the film plane, a broad band of microwave absorption is observed, which does not contain a fine structure. The field ranges of the responses observed are quite different for these two magnetization directions. This suggests a collective magnetic ground state or shape anisotropy and collective microwave dynamics for this foam-like material. This result is in agreement with SQUID measurements of hysteresis loops for the material. Two different models for this collective behavior are suggested that satisfactorily explain the major experimental results.

  2. Microwave impregnation of porous materials with thermal energy storage materials

    SciTech Connect

    Benson, D.K.; Burrows, R.W.

    1992-12-31

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  3. Microwave impregnation of porous materials with thermal energy storage materials

    DOEpatents

    Benson, D.K.; Burrows, R.W.

    1993-04-13

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  4. Microwave impregnation of porous materials with thermal energy storage materials

    DOEpatents

    Benson, David K.; Burrows, Richard W.

    1993-01-01

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  5. A container for heat treating materials in microwave ovens

    DOEpatents

    Holcombe, C.E.; Dykes, N.L.; Kimrey, H.D. Jr.; Mills, J.E.

    1988-01-26

    The efficiency of a microwave oven of a conventional two-source configuration and energy level is increased by providing the oven with a container for housing a refractory material to be treated. The container is formed to top and bottom walls transparent to microwaves while the sidewalls, in a circular configuration, are formed of a nonmetallic material opaque to microwave radiation for reflecting the radiation penetrating the top and bottom walls radially inwardly into the center of the container wherein a casket of heat-insulating material is provided for housing the material to be heat treated. The reflection of the microwave radiation from the sidewalls increases the concentration of the microwaves upon the material being heat treated while the concentration of the microwaves upon the material being heat treated while the casket retains the heat to permit the heating of the material to a substantially higher temperature than achievable in the oven without the container.

  6. Passive microwave retrieval of land surface properties

    NASA Astrophysics Data System (ADS)

    Owe, Manfred; de Jeu, Richard A. M.; Holmes, Thomas R. H.

    2006-05-01

    A methodology for retrieving land surface properties from passive microwave observations is presented. Dual polarization microwave brightness temperature data, together with a simple radiative transfer model are used to derive surface soil moisture and vegetation optical depth simultaneously, in a non linear optimization procedure using a forward modeling approach. Soil temperature is derived off-line with a common heat flow model, driven by high frequency vertical polarization microwave data and remotely sensed observations of net radiation. The methodology does not require any field observations of soil moisture or canopy biophysical properties for calibration purposes and is independent of wavelength. Remote sensing provides an excellent opportunity to monitor and gather environmental data in regions that have little or no instrumentation. Moreover, microwave technology provides a more all-weather capability than is typically afforded with visible and near infrared wavelengths. The model was developed for regional- to global-scale monitoring and related environmental applications such as surface energy balance modelling, numerical weather prediction, flood and drought forecasting, and climate change studies. However, at higher spatial resolutions, which would be possible with aircraft, especially unmanned vehicles, tactical applications may be realized as well. Retrieval results compare well with field observations of soil moisture and satellite-derived vegetation index data from optical sensors.

  7. Knowledge based control for microwave curing of polymer composite materials

    SciTech Connect

    Hawkins, R.; Sticklen, J.; Hawley, M.C.

    1996-12-31

    Traditionally, the majority of thermoset composite materials have been autoclave cured. Some alternatives to curing in an autoclave include E-Beam and microwave curing. In the Microwave Research Group at MSU, microwave curing technology is being pursued for the purpose of achieving higher throughput, lower cost and higher energy efficiency, relative to autoclave curing.

  8. Topological properties of microwave magnetoelectric fields.

    PubMed

    Berezin, M; Kamenetskii, E O; Shavit, R

    2014-02-01

    Collective excitations of electron spins in a ferromagnetic sample dominated by the magnetic dipole-dipole interaction strongly influence the field structure of microwave radiation. A small quasi-two-dimensional ferrite disk with magnetic-dipolar-mode (MDM) oscillation spectra can behave as a source of specific fields in vacuum, termed magnetoelectric (ME) fields. A coupling between the time-varying electric and magnetic fields in the ME-field structures is different from such a coupling in regular electromagnetic fields. The ME fields are characterized by strong energy confinement at a subwavelength region of microwave radiation, topologically distinctive power-flow vortices, and helicity parameters [E. O. Kamenetskii, R. Joffe, and R. Shavit, Phys. Rev. E 87, 023201 (2013)]. We study topological properties of microwave ME fields by loading a MDM ferrite particle with different dielectric samples. We establish a close connection between the permittivity parameters of dielectric environment and the topology of ME fields. We show that the topology of ME fields is strongly correlated with the Fano-resonance spectra observed at terminals of a microwave structure. We reveal specific thresholds in the Fano-resonance spectra appearing at certain permittivity parameters of dielectric samples. We show that ME fields originated from MDM ferrite disks can be distinguished by topological portraits of the helicity parameters and can have a torsion degree of freedom. Importantly, the ME-field phenomena can be viewed as implementations of space-time coordinate transformations on waves. PMID:25353595

  9. Calorimetry study of microwave absorption of some solid materials.

    PubMed

    He, Chun Lin; Ma, Shao Jian; Su, Xiu Juan; Chen, Yan Qing; Liang, Yu Shi

    2013-01-01

    In practice, the dielectric constant of a material varies the applied frequency the material composition, particle size, purity, temperature, physical state (solid or liquid), and moisture content. All of these parameters might change during processing, therefore, it is difficult to predict how well a material will absorb microwave energy in a given process. When the temperature is measured by a digital thermometer, it could not accurately reflect the true temperature of the bulk materials, especially for mixed materials. Thus, in this paper we measured the microwave absorption characteristics of different materials by calorimetry. The microwave power levels, irradiation times, and masses of the materials were varied. It was difficult to predict the microwave energy absorption characteristics of reagent-grade inorganic compounds based on their color, metallic cation, or water stoichiometry. CuO, MnO2, Fe3O4, and MnSO4 x H2O (Taishan) strongly absorbed microwave energy. Most of the remaining inorganic compounds were poor absorbers, with silica hardly absorbing any microwave energy. Carbon-based materials had significantly different microwave absorption characteristics. Activated carbon and coke were especially sensitive to microwaves, but different types of coal were poor absorbers. The jamesonite concentrate absorbed microwave energy strongly, while the zinc concentrate was a poor absorber. PMID:24779227

  10. Hydrogen recovery from extraterrestrial materials using microwave energy

    NASA Astrophysics Data System (ADS)

    Tucker, D. S.; Vaniman, D. T.; Anderson, J. L.; Clinard, F. W., Jr.; Feber, R. C., Jr.; Frost, H. M.; Meek, T. T.; Wallace, T. C.

    The feasibility of recovering hydrogen from extraterrestrial materials (lunar and Martian soils, asteroids) using microwave energy is presented. Reasons for harvesting and origins and locations of hydrogen are reviewed. Problems of hydrogen recovery are discussed in terms of hydrogen release characteristics and microwave coupling to insulating materials. From results of studies of hydrogen diffusivities (oxides, glasses) and tritium release (oxides) as well as studies of microwave coupling to ilmenite, alkali basalt and ceramic oxides it is concluded that using microwave heating in hydrogen recovery from extraterrestrial materials could be the basis for a workable process.

  11. Trends of microwave dielectric materials for antenna application

    NASA Astrophysics Data System (ADS)

    Sulong, T. A. T.; Osman, R. A. M.; Idris, M. S.

    2016-07-01

    Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (ɛr), high quality factor (Q f ≥ 5000GH z) and good temperature coefficient of resonant frequency (τf). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

  12. Microwave Assisted 2D Materials Exfoliation

    NASA Astrophysics Data System (ADS)

    Wang, Yanbin

    Two-dimensional materials have emerged as extremely important materials with applications ranging from energy and environmental science to electronics and biology. Here we report our discovery of a universal, ultrafast, green, solvo-thermal technology for producing excellent-quality, few-layered nanosheets in liquid phase from well-known 2D materials such as such hexagonal boron nitride (h-BN), graphite, and MoS2. We start by mixing the uniform bulk-layered material with a common organic solvent that matches its surface energy to reduce the van der Waals attractive interactions between the layers; next, the solutions are heated in a commercial microwave oven to overcome the energy barrier between bulk and few-layers states. We discovered the minutes-long rapid exfoliation process is highly temperature dependent, which requires precise thermal management to obtain high-quality inks. We hypothesize a possible mechanism of this proposed solvo-thermal process; our theory confirms the basis of this novel technique for exfoliation of high-quality, layered 2D materials by using an as yet unknown role of the solvent.

  13. Microwave absorption properties of pyrolytic carbon nanofilm

    PubMed Central

    2013-01-01

    We analyzed the electromagnetic (EM) shielding effectiveness in the Ka band (26 to 37 GHz) of highly amorphous nanometrically thin pyrolytic carbon (PyC) films with lateral dimensions of 7.2 × 3.4 mm2, which consists of randomly oriented and intertwined graphene flakes with a typical size of a few nanometers. We discovered that the manufactured PyC films, whose thickness is thousand times less than the skin depth of conventional metals, provide a reasonably high EM attenuation. The latter is caused by absorption losses that can be as high as 38% to 20% in the microwave frequency range. Being semi-transparent in visible and infrared spectral ranges and highly conductive at room temperature, PyC films emerge as a promising material for manufacturing ultrathin microwave (e.g., Ka band) filters and shields. PMID:23388194

  14. Container for heat treating materials in microwave ovens

    DOEpatents

    Holcombe, Cressie E.; Dykes, Norman L.; Kimrey, Jr., Harold D.; Mills, James E.

    1989-01-01

    The efficiency of a microwave oven of a conventional two-source configuration and energy level is increased by providing the oven with a container for housing a refractory material to be treated. The container is formed of top and bottom walls transparent to microwaves while the sidewalls, in a circular configuration, are formed of a nonmetallic material opaque to microwave radiation reflecting the radiation penetrating the top and bottom walls radially inwardly into the center of the container wherein a casket of heat-insulating material is provided for housing the material to be heat treated. The reflection of the microwave radiation from the sidewalls increases the concentration of the microwaves upon the material being heat treated while the casket retains the heat to permit the heating of the material to a substantially higher temperature than achieveable in the oven without the container.

  15. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B.; Jackson, Henry W.

    2010-01-01

    A paper discusses the need to perform accurate dielectric property measurements on larger sized samples, particularly liquids at microwave frequencies. These types of measurements cannot be obtained using conventional cavity perturbation methods, particularly for liquids or powdered or granulated solids that require a surrounding container. To solve this problem, a model has been developed for the resonant frequency and quality factor of a cylindrical microwave cavity containing concentric cylindrical samples. This model can then be inverted to obtain the real and imaginary dielectric constants of the material of interest. This approach is based on using exact solutions to Maxwell s equations for the resonant properties of a cylindrical microwave cavity and also using the effective electrical conductivity of the cavity walls that is estimated from the measured empty cavity quality factor. This new approach calculates the complex resonant frequency and associated electromagnetic fields for a cylindrical microwave cavity with lossy walls that is loaded with concentric, axially aligned, lossy dielectric cylindrical samples. In this approach, the calculated complex resonant frequency, consisting of real and imaginary parts, is related to the experimentally measured quantities. Because this approach uses Maxwell's equations to determine the perturbed electromagnetic fields in the cavity with the material(s) inserted, one can calculate the expected wall losses using the fields for the loaded cavity rather than just depending on the value of the fields obtained from the empty cavity quality factor. These additional calculations provide a more accurate determination of the complex dielectric constant of the material being studied. The improved approach will be particularly important when working with larger samples or samples with larger dielectric constants that will further perturb the cavity electromagnetic fields. Also, this approach enables the ability to have a

  16. Inexpensive Microwave Moisture Sensor for Granular Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A prototype microwave moisture sensor is described that was assembled from relatively inexpensive microwave components and tested for sensing moisture content in corn and wheat. Components include off-the-shelf voltage-controlled oscillator, isolator, power splitter, two 19-dBi microstrip patch ant...

  17. Apparatus and method for microwave processing of materials

    DOEpatents

    Johnson, A.C.; Lauf, R.J.; Bible, D.W.; Markunas, R.J.

    1996-05-28

    Disclosed is a variable frequency microwave heating apparatus designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity for testing or other selected applications. The variable frequency heating apparatus is used in the method of the present invention to monitor the resonant processing frequency within the furnace cavity depending upon the material, including the state thereof, from which the workpiece is fabricated. The variable frequency microwave heating apparatus includes a microwave signal generator and a high-power microwave amplifier or a microwave voltage-controlled oscillator. A power supply is provided for operation of the high-power microwave oscillator or microwave amplifier. A directional coupler is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load. 10 figs.

  18. Apparatus and method for microwave processing of materials

    DOEpatents

    Johnson, Arvid C.; Lauf, Robert J.; Bible, Don W.; Markunas, Robert J.

    1996-01-01

    A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity (34) for testing or other selected applications. The variable frequency heating apparatus (10) is used in the method of the present invention to monitor the resonant processing frequency within the furnace cavity (34) depending upon the material, including the state thereof, from which the workpiece (36) is fabricated. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a microwave voltage-controlled oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

  19. Microwave Moisture Meter for Granular and Particulate Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A low-cost microwave moisture meter operating at a single frequency for instantaneous and nondestructive determination of moisture content of granular and particulate materials was developed, calibrated and tested with different kinds of grain and seed. The meter operates at a single microwave freq...

  20. Thermal imaging of subsurface microwave absorbers in dielectric materials

    NASA Astrophysics Data System (ADS)

    Osiander, Robert; Maclachlan Spicer, Jane W.; Murphy, John C.

    1994-03-01

    The use of microwaves as a heating source in time-resolved IR radiometry provides the ability to heat surface and subsurface microwave-absorbing regions of a specimen directly. This can improve the contrast and spatial resolution of such regions and enhance their detectibility when compared with conventional laser or flashlamp sources. The experiments reported here use microwave heating with IR detection. Results on plexiglass-water-Teflon test specimens with absorbers at different depths in the sample are described by a 1D analytical model. Measurements using microwave and optical heating on epoxy-coated steel pipes are compared and demonstrate the ability of microwave heating to detect subsurface water voids very efficiently. Other applications of the method to microwave imaging, field mapping and imaging of defects in composite materials are discussed.

  1. Microwave properties of high transition temperature superconducting thin films

    NASA Technical Reports Server (NTRS)

    Gordon, W. L.

    1991-01-01

    Extensive studies of the interaction of microwaves with YBa2Cu3O(7-delta), Bi-based, and Tl-based superconducting thin films deposited in several microwave substrates were performed. The data were obtained by measuring the microwave power transmitted through the film in the normal and the superconducting state and by resonant cavity techniques. The main motives were to qualify and understand the physical parameters such as the magnetic penetration depth, the complex conductivity, and the surface impedance, of high temperature superconducting (HTS) materials at microwave frequencies. Based on these parameters, the suitability of these HTS thin films is discussed for microwave applications.

  2. Microwave dielectric behavior of vegetation material

    NASA Technical Reports Server (NTRS)

    Elrayes, Mohamed A.; Ulaby, Fawwaz T.

    1987-01-01

    The microwave dielectric behavior of vegetation was examined through the development of theoretical models involving dielectric dispersion by both bound and free water and supported by extensive dielectric measurements conducted over a wide range of conditions. The experimental data were acquired using an open-ended coaxial probe that was developed for sensing the dielectric constant of thin layers of materials, such as leaves, from measurements of the complex reflection coefficient using a network analyzer. The probe system was successfully used to record the spectral variation of the dielectric constant over a wide frequency range extending from 0.5 to 20.4 GHz at numerous temperatures between -40 to +40 C. The vegetation samples were measured over a wide range of moisture conditions. To model the dielectric spectrum of the bound water component of the water included in vegetation, dielectric measurements were made for several sucrose-water solutions as analogs for the situation in vegetation. The results were used in conjunction with the experimental data for leaves to determine some of the constant coefficients in the theoretical models. Two models, both of which provide good fit to the data, are proposed.

  3. Effects of Microwave Radiation on Selected Mechanical Properties of Silk

    NASA Astrophysics Data System (ADS)

    Reed, Emily Jane

    Impressive mechanical properties have served to peak interest in silk as an engineering material. In addition, the ease with which silk can be altered through processing has led to its use in various biomaterial applications. As the uses of silk branch into new territory, it is imperative (and inevitable) to discover the boundary conditions beyond which silk no longer performs as expected. These boundary conditions include factors as familiar as temperature and humidity, but may also include other less familiar contributions, such as exposure to different types of radiation. The inherent variations in mechanical properties of silk, as well as its sensitivity to moisture, suggest that in an engineering context silk is best suited for use in composite materials; that way, silk can be shielded from ambient moisture fluctuations, and the surrounding matrix allows efficient load transfer from weaker fibers to stronger ones. One such application is to use silk as a reinforcing fiber in epoxy composites. When used in this way, there are several instances in which exposure to microwave radiation is likely (for example, as a means of speeding epoxy cure rates), the effects of which remain mostly unstudied. It will be the purpose of this dissertation to determine whether selected mechanical properties of B. mori cocoon silk are affected by exposure to microwave radiation, under specified temperature and humidity conditions. Results of our analyses are directly applicable wherever exposure of silk to microwave radiation is possible, including in fiber reinforced epoxy composites (the entire composite may be microwaved to speed epoxy cure time), or when silk is used as a component in the material used to construct the radome of an aircraft (RADAR units use frequencies in the microwave range of the electromagnetic spectrum), or when microwave energy is used to sterilize biomaterials (such as cell scaffolds) made of silk. In general, we find that microwave exposure does not

  4. Conducting polymer composite materials for smart microwave windows

    NASA Astrophysics Data System (ADS)

    Barnes, Alan; Lees, K.; Wright, Peter V.; Chambers, Barry

    1999-07-01

    Samples of poly(aniline)-silver-polymer electrolyte particulate composites have been characterized at microwave frequencies when small d.c. electric fields are applied across them in both coaxial line and waveguide measurement test sets. The experimental data shows that the initial conductivity of the materials is dependent on the concentration of sliver metal and suggest that changes in resistance due to chemical switching take place, at least in part, in the manufacture of the composites. When silver is used as the electrodes, the experimental data show that changes in the slope of the cyclic voltammograms coincide with large changes in microwave reflectivity or transmission consistent with increasing conductivity of the composites when fields are applied. The reverse change occurs when the fields are removed. Measurements have shown that the composites are able to switch between the two impedance stats in times of less than one second for well over a million cycles with no apparent depreciation in material properties. Large area films have also been prepared and studied using the 'free space' technique.

  5. Influence of Water content of RF and Microwave Dielectric Properties of Foods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    ABSTRACT The importance of dielectric properties of food materials is discussed with respect to their influence on the heating of materials by radio-frequency and microwave energy and their use for rapid, nondestructive sensing of quality characteristics of such materials. Data are presented graph...

  6. A PORTABLE MICROWAVE INTERFERENCE SCANNING SYSTEM FOR NONDESTRUCTIVE TESTING OF MULTI-LAYERED DIELECTRIC MATERIALS

    SciTech Connect

    Schmidt, K. F.; Little, J. R.; Ellingson, W. A.; Green, W.

    2009-03-03

    A portable, microwave interference scanning system, that can be used in situ, with one-sided, non-contact access, has been developed. It has demonstrated capability of damage detection on composite ceramic armor. Specimens used for validation included specially fabricated surrogates, and non-ballistic impact-damaged specimens. Microwave data results were corroborated with high resolution direct-digital x-ray imaging. Microwave interference scanning detects cracks, laminar features and material properties variations. This paper will present details of the system and discuss results obtained.

  7. MICROWAVE SYSTEM FOR LOCATING FAULTS IN HAZARDOUS MATERIAL DIKES

    EPA Science Inventory

    Continuous-wave microwave and pulsed radio-frequency (ground-penetrating radar) methods were developed and assessed for nondestructive monitoring of sub-surface environmental problems concerning hazardous material impoundments. The primary objective of the project was to conduct ...

  8. Mechanical properties of microwave hydrothermally synthesized titanate nanowires

    NASA Astrophysics Data System (ADS)

    Chang, M.; Chung, C. C.; Deka, J. R.; Lin, C. H.; Chung, T. W.

    2008-01-01

    In this investigation titanate nanowires were synthesized by a microwave hydrothermal process and their nanomechanical characterization was carried out by a compression experiment via buckling instability using a nanomanipulator inside a scanning electron microscope. Nanowires of diameters 120-150 nm and length tens of microns can be synthesized by keeping a commercial nanoparticle inside a microwave oven at 350 W and 210 °C for 5 h. The nanowire was clamped between two cantilevered AFM tips attached to two opposing stages of the manipulator for nanomechanical characterization. The elasticity coefficients of the titanate nanowires were measured by applying a continuously increasing load and observing the buckling instability of the nanowires. The buckling behavior of a nanowire was analyzed from the series of SEM images of displacement of the cantilever attached to the nanowire due to application of load. The critical loads for different sized titanate nanowires were determined and their corresponding Young's modulus was computed with the Euler pinned-fixed end model. The Young's modulus of these microwave hydrothermal process synthesized titanate nanowires were determined to be approximately in the range 14-17 GPa. This investigation confirms the capability of the nanomanipulator via the buckling technique as a constructive device for measuring the mechanical properties of nanoscale materials.

  9. The microwave effects on the properties of alumina at high frequencies of microwave sintering

    NASA Astrophysics Data System (ADS)

    Sudiana, I. Nyoman; Mitsudo, Seitaro; Sako, Katsuhide; Inagaki, Shunsuke; Ngkoimani, La Ode; Usman, Ida; Aripin, H.

    2016-03-01

    Microwave sintering of materials has attracted much research interest because of its significant advantages (e.g. reduced sintering temperatures and soaking times) over the conventional heating. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a `non-thermal effect` which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. Moreover, recent progress on microwave sources such as gyrotrons has opened the possibility for processing materials by using a higher microwave frequency. Therefore, the technology is expected to exhibit a stronger non-thermal effect. This paper presents results from a series of experiments to study the non-thermal effect on microwave sintered alumina. Sintering by using a wide rage of microwave frequencies up to 300 GHz as well as a conventional furnace was carried out. The linear shrinkages of samples for each sintering method were measured. Pores and grains taken from scanning electron microstructure (SEM) images of cut surfaces were also examined. The results of a comparative study of the shrinkages and microstructure evolutions of the sintered samples under annealing in microwave heating systems and in an electric furnace were analyzed. A notably different behavior of the shrinkages and microstructures of alumina after being annealed was found. The results suggested that microwave radiations provided an additional force for mass transports. The results also indicated that the sintering process depended on microwave frequencies.

  10. Novel aspects of microwave processing of ceramic materials

    SciTech Connect

    Willert-Porada, M.

    1995-09-01

    A brief description of microwave sintering with respect to the chemical selectivity of heating by microwaves is given. For low dielectric loss materials, like alumina, selective heating is used to preheat the ceramic in order to increase the dielectric loss. As compared to conventional sintering an increased grain growth and neck growth as well as grain facetting of the Al{sub 2}O{sub 3}-ceramic is found in the early stage of sintering. The microstructure-modeling potential of microwave heating based on the selectivity of microwave-material interaction is further demonstrated for Al{sub 2}O{sub 3}-TiO{sub 2} ceramics and for metal-ceramic gradient materials.

  11. Uniform bulk Material Processing using Multimode Microwave Radiation

    SciTech Connect

    Varma, Ravi; Vaughan, Worth E.

    1999-06-18

    An apparatus for generating uniform heating in material contained in a cylindrical vessel is described. TE{sub 10}-mode microwave radiation is coupled into a cylindrical microwave transition such that microwave radiation having TE{sub 11}-, TE{sub 01}- and TM{sub 01}-cylindrical modes is excited therein. By adjusting the intensities of these modes, substantially uniform heating of materials contained in a cylindrical drum which is coupled to the microwave transition through a rotatable choke can be achieved. The use of a poor microwave absorbing insulating cylindrical insert, such as aluminum oxide, for separating the material in the container from the container walls and for providing a volume through which air is circulated is expected to maintain the container walls at room temperature. The use of layer of highly microwave absorbing material, such as SiC, inside of the insulating insert and facing the material to be heated is calculated to improve the heating pattern of the present apparatus.

  12. Uniform bulk material processing using multimode microwave radiation

    DOEpatents

    Varma, Ravi; Vaughn, Worth E.

    2000-01-01

    An apparatus for generating uniform heating in material contained in a cylindrical vessel is described. TE.sub.10 -mode microwave radiation is coupled into a cylindrical microwave transition such that microwave radiation having TE.sub.11 -, TE.sub.01 - and TM.sub.01 -cylindrical modes is excited therein. By adjusting the intensities of these modes, substantially uniform heating of materials contained in a cylindrical drum which is coupled to the microwave transition through a rotatable choke can be achieved. The use of a poor microwave absorbing insulating cylindrical insert, such as aluminum oxide, for separating the material in the container from the container walls and for providing a volume through which air is circulated is expected to maintain the container walls at room temperature. The use of layer of highly microwave absorbing material, such as SiC, inside of the insulating insert and facing the material to be heated is calculated to improve the heating pattern of the present apparatus.

  13. OPTIMIZING A PORTABLE MICROWAVE INTERFERENCE SCANNING SYSTEM FOR NONDESTRUCTIVE TESTING OF MULTI-LAYERED DIELECTRIC MATERIALS

    SciTech Connect

    Schmidt, K. F. Jr.; Little, J. R. Jr.; Ellingson, W. A.; Green, W.

    2010-02-22

    The projected microwave energy pattern, wave guide geometry, positioning methods and process variables have been optimized for use of a portable, non-contact, lap-top computer-controlled microwave interference scanning system on multi-layered dielectric materials. The system can be used in situ with one-sided access and has demonstrated capability of damage detection on composite ceramic armor. Specimens used for validation included specially fabricated surrogates, and ballistic impact-damaged specimens. Microwave data results were corroborated with high resolution direct-digital x-ray imaging. Microwave interference scanning detects cracks, laminar features and material properties variations. This paper presents the details of the system, the optimization steps and discusses results obtained.

  14. Materials characterization and diagnosis using variable frequency microwaves

    SciTech Connect

    Wei, J.B.; Fathi, Z.; Tucker, D.A.; Hampton, M.L.; Garard, R.S.; Lauf, R.J.

    1996-12-31

    Product quality control is a crucial part of manufacturing and usually involves materials characterization and diagnosis. Though various microwave assisted nondestructive evaluation (MA-NDE) systems have been fabricated for materials inspection, none of the systems can be applied to materials within a mold or reactor. A broadband variable frequency microwave based, resonant mode MA-NDE was studied as an alternative for characterization of materials within a cavity. The main advantage of the resonant mode MA-NDE are non-intrusive and volumetric diagnosis of the material inside a mold. The principles and possible applications of the resonant mode MA-NDE are discussed. Resonant mode MA-NDE was fully demonstrated by using Vari-Wave to trace material status during microwave curing of Diglycidyl Ether of Bisphenol A (DGEBA)/Diaminodiphenylsulphone (DDS) epoxy samples.

  15. Ultrasonic material property determinations

    NASA Technical Reports Server (NTRS)

    Serabian, S.

    1986-01-01

    The use and potential offered by ultrasonic velocity and attenuation measurements to determine and/or monitor material properties is explored. The basis for such unique measurements along with examples of materials from a variety of industries are presented.

  16. TOPICAL REVIEW: High-temperature microwave processing of materials

    NASA Astrophysics Data System (ADS)

    Bykov, Yu V.; Rybakov, K. I.; Semenov, V. E.

    2001-07-01

    This article reviews the physical aspects of a cross-disciplinary science and technology field: the microwave processing of materials. High-temperature microwave processing has a clear industrial perspective in such areas as the production of advanced ceramics, the deposition of thermal barrier coatings, the remediation of hazardous wastes etc. This review starts with the relevant fundamental notions regarding the absorption of electromagnetic waves, heat transfer and the electrodynamics of single- and multimode microwave cavities. Useful formulae, estimates, and interrelations between process variables are presented. This is followed by a review of process examples illustrating the specific features of microwave processing: reduction in energy consumption and process duration, rapid and controllable heating, peculiar temperature distribution, and selectivity of energy deposition. Much attention is given to the advantages of higher-frequency millimetre-wave processing, which include the enhanced absorption in many materials of industrial interest, improved uniformity of electromagnetic energy and temperature, and the possibility of surface treatment. The phenomenon of microwave process rate enhancement is addressed in connection with the problem of the non-thermal microwave effect on mass transport in solids. Both experimental and theoretical approaches to the identification of the mechanism responsible for this effect are illustrated. Finally, the physical and technical factors influencing microwave technology scaleup and transfer to industry are discussed.

  17. Microwave sintering of nanopowder ZnNb2O6: Densification, microstructure and microwave dielectric properties

    NASA Astrophysics Data System (ADS)

    Bafrooei, H. Barzegar; Nassaj, E. Taheri; Hu, C. F.; Huang, Q.; Ebadzadeh, T.

    2014-12-01

    High density ZnNb2O6 ceramics were successfully fabricated by microwave sintering of ZnO-Nb2O5 and ZnNb2O6 nanopowders. Phase formation, microstructure and microwave electrical properties of the microwave sintered (MS) and microwave reaction sintered (MRS) specimens were examined using X-ray diffraction, field emission scanning electron microscopy and microwave dielectric properties measurement. Specimens were sintered in a temperature range from 950 to 1075 °C for 30 min at an interval of 25 °C using a microwave furnace operated at 2.45 GHz frequency, 3 kW power. XRD pattern revealed the formation of pure columbite phase of ZnNb2O6. The SEM micrographs show grain growth and reduction in porosity of specimens with the increase in sintering temperature. Good combination of microwave dielectric properties (εr~23.6, Qf~64,300 GHz and τf~-66 ppm/°C and εr~24, Qf~75,800 GHz and τf~-64 ppm/°C) was obtained for MS- and MRS-prepared samples at 1000 °C and 1050 °C for 30 min, respectively.

  18. Rapid microwave synthesis of indium filled skutterudites: An energy efficient route to high performance thermoelectric materials

    SciTech Connect

    Biswas, Krishnendu; Muir, Sean; Subramanian, M.A.

    2011-12-15

    Graphical abstract: Filled skutterudites are promising thermoelectric materials. We report the microwave assisted synthesis of CoSb{sub 3} and In{sub 0.2}Co{sub 4}Sb{sub 12}. This method reduces the calcination time for skutterudite phase formation from 2 days to 2 min, thereby significantly reducing the time and energy needed to produce materials suitable for property and device testing. Highlights: Black-Right-Pointing-Pointer The microwave assisted solid state synthesis of CoSb{sub 3} and In{sub 0.2}Co{sub 4}Sb{sub 12} is reported. Black-Right-Pointing-Pointer This method allows the calcination time to be reduced from 2 days to 2 min. Black-Right-Pointing-Pointer Physical properties of microwave samples match those prepared conventionally. -- Abstract: Filled skutterudites are promising thermoelectric materials due to reduced thermal conductivity upon inserting a guest atom or 'rattler' into the CoSb{sub 3} structure. By using an indium rattler dimensionless Figure of Merit (ZT) values >1 at 650 K have been reported. The conventional synthesis of these compounds typically takes several days ({approx}3 days) to obtain the final well-sintered material for property measurements. We report here a microwave-assisted synthesis method that reduces the initial calcination time from 2 days to 2 min. This route significantly reduces the time needed to produce materials suitable for property and device testing.

  19. Novel microwave near-field sensors for material characterization, biology, and nanotechnology

    NASA Astrophysics Data System (ADS)

    Joffe, R.; Kamenetskii, E. O.; Shavit, R.

    2013-02-01

    The wide range of interesting electromagnetic behavior of contemporary materials requires that experimentalists working in this field master many diverse measurement techniques and have a broad understanding of condensed matter physics and biophysics. Measurement of the electromagnetic response of materials at microwave frequencies is important for both fundamental and practical reasons. In this paper, we propose a novel near-field microwave sensor with application to material characterization, biology, and nanotechnology. The sensor is based on a subwavelength ferrite-disk resonator with magnetic-dipolar-mode (MDM) oscillations. Strong energy concentration and unique topological structures of the near fields originated from the MDM resonators allow effective measuring material parameters in microwaves, both for ordinary structures and objects with chiral properties.

  20. High Temperature Microwave Dielectric Properties of JSC-1AC Lunar Simulant

    NASA Technical Reports Server (NTRS)

    Allan, Shawn M.; Merritt, Brandon J.; Griffin, Brittany F.; Hintze, Paul E.; Shulman, Holly S.

    2011-01-01

    Microwave heating has many potential lunar applications including sintering regolith for lunar surface stabilization and heating regolith for various oxygen production reactors. The microwave properties of lunar simulants must be understood so this technology can be applied to lunar operations. Dielectric properties at microwave frequencies for a common lunar simulant, JSC-1AC, were measured up to 1100 C, which is approximately the melting point. The experimentally determined dielectric properties included real and imaginary permittivity (epsilon', epsilon"), loss tangent (tan delta), and half-power depth, the di stance at which a material absorbs 50% of incident microwave energy. Measurements at 2.45 GHz revealed tan delta of JSC-1A increases from 0.02 at 25 C to 0.31 at 110 C. The corresponding half-power depth decreases from a peak of 286 mm at 110 C, to 13 mm at 1100 C. These data indicate that JSC-1AC becomes more absorbing, and thus a better microwave heater as temperature increases. A half-power depth maximum at 100-200 C presents a barrier to direct microwave heating at low temperatures. Microwave heating experiments confirm the sluggish heating effect of weak absorption below 200 C, and increasingly strong absorption above 200 C, leading to rapid heating and melting of JSC-1AC.

  1. An optical model for the microwave properties of sea ice

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Larabee, J. K.

    1981-01-01

    The complex refractive index of sea ice is modeled and used to predict the microwave signatures of various sea ice types. Results are shown to correspond well with the observed values of the complex index inferred from dielectic constant and dielectric loss measurements performed in the field, and with observed microwave signatures of sea ice. The success of this modeling procedure vis a vis modeling of the dielectric properties of sea ice constituents used earlier by several others is explained. Multiple layer radiative transfer calculations are used to predict the microwave properties of first-year sea ice with and without snow, and multiyear sea ice.

  2. Effect of Ca on microwave properties of strontium manganite synthesized by microwave processing

    NASA Astrophysics Data System (ADS)

    Pawar, Rani P.; Jadhav, Rupali N.; Puri, Vijaya

    2012-06-01

    Nanostructured Sr1- x Ca x MnO3 was prepared by oxalic precursor method and sintered using microwave process. The pervoskite structure was confirmed by x-ray diffraction. The complex permittivity and permeability with calcium concentration were measured by VSWR in the frequency range 8-12 GHz. We present the frequency dependence of microwave absorbing properties of Sr1- x Ca x MnO3 (0 ≤ x ≤ 0.4) powders at room temperature which is correlated to the value of its complex permittivity and permeability. The composition dependent microwave absorption was observed and it increased with Ca concentration from 47% to 68% at 9.7 GHz. The excellent microwave absorption properties were attributed to a better electromagnetic impedance match and a higher electric resistivity.

  3. Factors Influencing the Dielectric Properties of Agricultural and Food Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of materials are defined, and the major factors that influence these properties of agricultural and food materials, namely, frequency of the applied radio-frequency or microwave electric fields, and water content, temperature, and density of the materials, are discussed on the ...

  4. Microwave remote sensing of snowpack properties

    NASA Technical Reports Server (NTRS)

    Rango, A. (Editor)

    1980-01-01

    Topic concerning remote sensing capabilities for providing reliable snow cover data and measurement of snow water equivalents are discussed. Specific remote sensing technqiues discussed include those in the microwave region of the electromagnetic spectrum.

  5. Microwave interferometry to elucidate shock properties

    SciTech Connect

    Luther, G.G.; Warthen, B.J.

    1993-09-01

    A series of measurements have been performed using a simple, light weight, inexpensive, compact K-Band (SLICK) interferometer to measure the shock properties of passive (Teflon, grout) and energetic (HE) materials. Shock and particle velocity measurements are made simultaneously along the same path. This path is determined by either a thin walled (1/2 mil aluminum foil) waveguide embedded in the material or the caustic of a Teflon axicon. Typically the velocities are determined to about a percent. The measurements will be described and data presented.

  6. Spatial observation and quantification of microwave heating in materials

    NASA Astrophysics Data System (ADS)

    Crane, C. A.; Pantoya, M. L.; Weeks, B. L.

    2013-08-01

    An electromagnetic exposure chamber was designed to safely deliver electromagnetic power in the range of microwaves between 0.8 and 4.2 GHz to a thin cylindrical materials. This instrumentation is unique because the diagnostics not only measure sample heating with a response time of 1.3 ms, but also energy transmitted and reflected. Energy absorption at different frequencies was quantified via electromagnetic heating using an infrared camera. This in situ IR imaging of the spatial distribution of temperature during microwave exposure coupled with sensors for determining transmitted and reflected energy enables novel new microwave energy experiments. Samples were exposed to a portion of both the electric and magnetic fields inside a waveguide and based on sample dimensions, the field strengths were assumed uniform across the sample. Three materials were examined: two were borosilicate, first coated with graphite paint and a second without the coating; and, the third was a compressed sample of flake graphite pressed to 69% of its bulk density. Results are in agreement with the theories of microwave heating and verify the functionality of this experimental design. This diagnostic will be important in future tests where a variety of different materials can be exposed to weak electromagnetic waves and their efficiency in coupling to the microwaves can be examined.

  7. Building Materials Property Table

    SciTech Connect

    2010-04-16

    This information sheet describes a table of some of the key technical properties of many of the most common building materials taken from ASHRAE Fundamentals - 2001, Moisture Control in Buildings, CMHC, NRC/IRC, IEA Annex 24, and manufacturer data.

  8. Artificial metamaterials for reprogrammable magnetic and microwave properties

    NASA Astrophysics Data System (ADS)

    Haldar, Arabinda; Adeyeye, Adekunle Olusola

    2016-01-01

    We demonstrate a reliable method for realizing various antiferromagnetic states in lithographically defined, dipolar coupled rhomboid nanomagnets. We directly probe the remanent state using magnetic force microscopy and measured the microwave absorptions using broadband ferromagnetic resonance spectroscopy technique. Reprogrammable microwave absorption properties are shown by switching between ferromagnetic and antiferromagnetic remanent states using a simple field initialization. There is a direct correlation between the magnetic remanent states and the microwave responses. Experimental results were supported by micromagnetic simulations which show a good agreement. The results may find applications in low power magnonic devices based on reprogrammable magnetic metamaterials.

  9. Mechanisms of Microwave Loss Tangent in High Performance Dielectric Materials

    NASA Astrophysics Data System (ADS)

    Liu, Lingtao

    The mechanism of loss in high performance microwave dielectrics with complex perovskite structure, including Ba(Zn1/3Ta2/3)O 3, Ba(Cd1/3Ta2/3)O3, ZrTiO4-ZnNb 2O6, Ba(Zn1/3Nb2/3)O3, and BaTi4O9-BaZn2Ti4O11, has been investigated. We studied materials synthesized in our own lab and from commercial vendors. Then the measured loss tangent was correlated to the optical, structural, and electrical properties of the material. To accurately and quantitatively determine the microwave loss and Electron Paramagnetic Resonance (EPR) spectra as a function of temperature and magnetic field, we developed parallel plate resonator (PPR) and dielectric resonator (DR) techniques. Our studies found a marked increase in the loss at low temperatures is found in materials containing transition metal with unpaired d-electrons as a result of resonant spin excitations in isolated atoms (light doping) or exchange coupled clusters (moderate to high doping); a mechanism that differs from the usual suspects. The loss tangent can be drastically reduced by applying static magnetic fields. Our measurements also show that this mechanism significantly contributes to room temperature loss, but does not dominate. In order to study the electronic structure of these materials, we grew single crystal thin film dielectrics for spectroscopic studies, including angular resolved photoemission spectroscopy (ARPES) experiment. We have synthesized stoichiometric Ba(Cd1/3Ta2/3)O3 [BCT] (100) dielectric thin films on MgO (100) substrates using Pulsed Laser Deposition. Over 99% of the BCT film was found to be epitaxial when grown with an elevated substrate temperature of 635 °C, an enhanced oxygen pressures of 53 Pa and a Cd-enriched BCT target with a 1 mol BCT: 1.5 mol CdO composition. Analysis of ultra violet optical absorption results indicate that BCT has a bandgap of 4.9 eV.

  10. System design development for microwave and millimeter-wave materials processing

    NASA Astrophysics Data System (ADS)

    Feher, Lambert; Thumm, Manfred

    2002-06-01

    The most notable effect in processing dielectrics with micro- and millimeter-waves is volumetric heating of these materials, offering the opportunity of very high heating rates for the samples. In comparison to conventional heating where the heat transfer is diffusive and depends on the thermal conductivity of the material, the microwave field penetrates the sample and acts as an instantaneous heat source at each point of the sample. By this unique property, microwave heating at 2.45 GHz and 915 MHz ISM (Industrial, Medical, Scientific) frequencies is established as an important industrial technology since more than 50 years ago. Successful application of microwaves in industries has been reported e.g. by food processing systems, domestic ovens, rubber industry, vacuum drying etc. The present paper shows some outlines of microwave system development at Forschungszentrum Karlsruhe, IHM by transferring properties from the higher frequency regime (millimeter-waves) to lower frequency applications. Anyway, the need for using higher frequencies like 24 GHz (ISM frequency) for industrial applications has to be carefully verified with respect to special physical/engineering advantages or to limits the standard microwave technology meets for the specific problem.

  11. Dielectric Characterization of PCL-Based Thermoplastic Materials for Microwave Diagnostic and Therapeutic Applications

    PubMed Central

    Aguilar, Suzette M.; Shea, Jacob D.; Al-Joumayly, Mudar A.; Van Veen, Barry D.; Behdad, Nader; Hagness, Susan C.

    2011-01-01

    We propose the use of a polycaprolactone (PCL)-based thermoplastic mesh as a tissue-immobilization interface for microwave imaging and microwave hyperthermia treatment. An investigation of the dielectric properties of two PCL-based thermoplastic materials in the frequency range of 0.5 – 3.5 GHz is presented. The frequency-dependent dielectric constant and effective conductivity of the PCL-based thermoplastics are characterized using measurements of microstrip transmission lines fabricated on substrates comprised of the thermoplastic meshes. We also examine the impact of the presence of a PCL-based thermoplastic mesh on microwave breast imaging. We use a numerical test bed comprised of a previously reported three-dimensional anatomically realistic breast phantom and a multi-frequency microwave inverse scattering algorithm. We demonstrate that the PCL-based thermoplastic material and the assumed biocompatible medium of vegetable oil are sufficiently well matched such that the PCL layer may be neglected by the imaging solution without sacrificing imaging quality. Our results suggest that PCL-based thermoplastics are promising materials as tissue immobilization structures for microwave diagnostic and therapeutic applications. PMID:21622068

  12. Dielectric properties of agricultural materials and their application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This book is prepared as a comprehensive source of information on dielectric properties of agricultural materials for scientific researchers and engineers involved in practical application of radio-frequency and microwave energy for potential problem solutions. Dielectric properties of materials det...

  13. Microwave Nondestructive Evaluation of Dielectric Materials with a Metamaterial Lens

    NASA Technical Reports Server (NTRS)

    Shreiber, Daniel; Gupta, Mool; Cravey, Robin L.

    2008-01-01

    A novel microwave Nondestructive Evaluation (NDE) sensor was developed in an attempt to increase the sensitivity of the microwave NDE method for detection of defects small relative to a wavelength. The sensor was designed on the basis of a negative index material (NIM) lens. Characterization of the lens was performed to determine its resonant frequency, index of refraction, focus spot size, and optimal focusing length (for proper sample location). A sub-wavelength spot size (3 dB) of 0.48 lambda was obtained. The proof of concept for the sensor was achieved when a fiberglass sample with a 3 mm diameter through hole (perpendicular to the propagation direction of the wave) was tested. The hole was successfully detected with an 8.2 cm wavelength electromagnetic wave. This method is able to detect a defect that is 0.037 lambda. This method has certain advantages over other far field and near field microwave NDE methods currently in use.

  14. A Study on a Microwave-Driven Smart Material Actuator

    NASA Technical Reports Server (NTRS)

    Choi, Sang H.; Chu, Sang-Hyon; Kwak, M.; Cutler, A. D.

    2001-01-01

    NASA s Next Generation Space Telescope (NGST) has a large deployable, fragmented optical surface (greater than or = 2 8 m in diameter) that requires autonomous correction of deployment misalignments and thermal effects. Its high and stringent resolution requirement imposes a great deal of challenge for optical correction. The threshold value for optical correction is dictated by lambda/20 (30 nm for NGST optics). Control of an adaptive optics array consisting of a large number of optical elements and smart material actuators is so complex that power distribution for activation and control of actuators must be done by other than hard-wired circuitry. The concept of microwave-driven smart actuators is envisioned as the best option to alleviate the complexity associated with hard-wiring. A microwave-driven actuator was studied to realize such a concept for future applications. Piezoelectric material was used as an actuator that shows dimensional change with high electric field. The actuators were coupled with microwave rectenna and tested to correlate the coupling effect of electromagnetic wave. In experiments, a 3x3 rectenna patch array generated more than 50 volts which is a threshold voltage for 30-nm displacement of a single piezoelectric material. Overall, the test results indicate that the microwave-driven actuator concept can be adopted for NGST applications.

  15. Microwave-assisted synthesis of graphene-Ni composites with enhanced microwave absorption properties in Ku-band

    NASA Astrophysics Data System (ADS)

    Zhu, Zetao; Sun, Xin; Li, Guoxian; Xue, Hairong; Guo, Hu; Fan, Xiaoli; Pan, Xuchen; He, Jianping

    2015-03-01

    Recently, graphene has been applied as a new microwave absorber because of its high dielectric loss and low density. Nevertheless, the high dielectric constant of pristine graphene has caused unbalanced electromagnetic parameters and results in a bad impedance matching characteristic. In this study, we report a facile microwave-assisted heating approach to produce reduced graphene oxide-nickel (RGO-Ni) composites. The phase and morphology of as-synthesized RGO-Ni composites are characterized by XRD, Raman, FESEM and TEM. The results show that Ni nanoparticles with a diameter around 20 nm are grown densely and uniformly on the RGO sheets. In addition, enhanced microwave absorption properties in Ku-band of RGO-Ni composites is mainly due to the synergistic effect of dielectric loss and magnetic loss and the dramatically electron polarizations caused by the formation of large conductive network. The minimum reflection loss of RGO-Ni-2 composite with the thickness of 2 mm can reaches -42 dB at 17.6 GHz. The RGO-Ni composite is an attractive candidate for the new type of high performance microwave absorbing material.

  16. Microwave measurement and modeling of the dielectric properties of vegetation

    NASA Astrophysics Data System (ADS)

    Shrestha, Bijay Lal

    Some of the important applications of microwaves in the industrial, scientific and medical sectors include processing and treatment of various materials, and determining their physical properties. The dielectric properties of the materials of interest are paramount irrespective of the applications, hence, a wide range of materials covering food products, building materials, ores and fuels, and biological materials have been investigated for their dielectric properties. However, very few studies have been conducted towards the measurement of dielectric properties of green vegetations, including commercially important plant crops such as alfalfa. Because of its high nutritional value, there is a huge demand for this plant and its processed products in national and international markets, and an investigation into the possibility of applying microwaves to improve both the net yield and quality of the crop can be beneficial. Therefore, a dielectric measurement system based upon the probe reflection technique has been set up to measure dielectric properties of green plants over a frequency range from 300 MHz to 18 GHz, moisture contents from 12%, wet basis to 79%, wet basis, and temperatures from -15°C to 30°C. Dielectric properties of chopped alfalfa were measured with this system over frequency range of 300 MHz to 18 GHz, moisture content from 11.5%, wet basis, to 73%, wet basis, and density over the range from 139 kg m-3 to 716 kg m-3 at 23°C. The system accuracy was found to be +/-6% and +/-10% in measuring the dielectric constant and loss factor respectively. Empirical, semi empirical and theoretical models that require only moisture content and operating frequency were determined to represent the dielectric properties of both leaves and stems of alfalfa at 22°C. The empirical models fitted the measured dielectric data extremely well. The root mean square error (RMSE) and the coefficient of determination (r2) for dielectric constant and loss factor of leaves

  17. Microwave properties of a quiet sea

    NASA Technical Reports Server (NTRS)

    Stacey, J.

    1985-01-01

    The microwave flux responses of a quiet sea are observed at five microwave frequencies and with both horizontal and vertical polarizations at each frequency--a simultaneous 10 channel receiving system. The measurements are taken from Earth orbit with an articulating antenna. The 10 channel responses are taken simultaneously since they share a common articulating collector with a multifrequency feed. The plotted flux responses show: (1) the effects of the relative, on-axis-gain of the collecting aperture for each frequency; (2) the effects of polarization rotation in the output responses of the receive when the collecting aperture mechanically rotates about a feed that is fixed; (3) the difference between the flux magnitudes for the horizontal and vertical channels, at each of the five frequencies, and for each pointing position, over a 44 degree scan angle; and (4) the RMS value of the clutter--as reckoned over the interval of a full swath for each of the 10 channels. The clutter is derived from the standard error of estimate of the plotted swath response for each channel. The expected value of the background temperature is computed for each of the three quiet seas. The background temperature includes contributions from the cosmic background, the downwelling path, the sea surface, and the upwelling path.

  18. Structure-Property Correlations in Microwave Joining of Inconel 718

    NASA Astrophysics Data System (ADS)

    Bansal, Amit; Sharma, Apurbba Kumar; Kumar, Pradeep; Das, Shantanu

    2015-09-01

    The butt joining of Inconel 718 plates at 981°C solution treated and aged (981STA) condition was carried out using the microwave hybrid heating technique with Inconel 718 powder as a filler material. The developed joints were free from any microfissures (cracks) and were metallurgically bonded through complete melting of the powder particles. The as-welded joints were subjected to postweld heat treatments, including direct-aged, 981STA and 1080STA. The microstructural features of the welded joints were investigated using a field emission-scanning electron microscope equipped with x-ray elemental analysis. Microhardness and room-temperature tensile properties of the welded joints were evaluated. The postweld heat-treated specimens exhibited higher microhardness and tensile strength than the as-welded specimens due to the formation of strengthening precipitates in the microstructure after postweld heat treatments. The microhardness of the fusion zone of the joint in 1080STA condition was higher than all welded conditions due to the complete dissolution of Laves phase after 1080STA treatment. However, the tensile strength of the welded specimen in 981STA condition was higher than all welded conditions. The tensile strength in 1080STA condition was lower than that in 981STA condition because of the grain coarsening that took place after 1080STA condition. The fractography of the fractured surfaces was carried out to determine the structure-property-fracture correlation.

  19. Novel microwave magnetic and magnetoelectric composite materials and devices

    NASA Astrophysics Data System (ADS)

    Pettiford, Carl I.

    Bulk microwave magnetic materials and devices have been widely used in different RF/microwave devices such as inductors, filters, circulars, isolators, and phase shifters. With the even increasing level of integration of RFIC and MMIC, there is an urgent need for new microwave magnetic thin film materials and new integrated RF/microwave magnetic devices. In this thesis, we have addressed these needs in three different areas: (1) exchange biased ferromagnetic/anti-ferromagnetic multilayer thin films with enhanced anisotropy fields, (2) magneto-electric heterostructures and devices, and (3) metamaterial multilayers for FMR enhancement, tunability, and plane wave absorption. Metallic soft magnetic thin films have been demonstrated to have high saturation magnetization, large permeability and relatively high self-biased ferromagnetic resonance (FMR) frequencies, showing great promise for applications in integrated RF and microwave magnetic devices. One problem for these metallic magnetic films is however their relatively low anisotropy fields that are typically in the range of 10˜30 Oe, which severely limit their application frequency range. In this work, we investigated the exchange coupled ferromagnetic/anti-ferromagnetic/ferromagnetic CoFe/PtMn/CoFe multilayer films. These CoFe/PtMn/CoFe multilayer films showed a significantly enhanced anisotropy field of 160 Oe, which was 5˜10 times of that of the FeCo films. In addition, a narrow FMR linewidth of 45 Oe at X-band was achieved in the CoFe/PtMn/CoFe trilayer. The exchange coupling in the ferromagnetic/anti-ferromagnetic/ferromagnetic trilayers leads to a significantly enhanced anisotropy field that is crucial for the application of metallic magnetic films in integrated magnetic RF/microwave devices. The magnetoelectric coupling of novel YIG/PZT, FeCoB/PZT and FeGaB/PZT multiferroic heterostructures were investigated at DC and at microwave frequencies. An electrostatically tunable band-reject filter device was

  20. Microwave Dielectric Properties Models for Grain and Seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Based on microwave dielectric properties of wheat, corn, barley, oats, grain sorghum, soybeans, canola, shelled peanuts and pod peanuts measured over ranges of frequency and moisture content, models are developed for predicting the dielectric constant and loss factor of these commodities. Nearly lin...

  1. Models for the Microwave Dielectric Properties of Grain and Seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Based on microwave dielectric properties of wheat, corn, barley, oats, grain sorghum, soybeans, canola, shelled peanuts and pod peanuts measured over ranges of frequency and moisture content, models are developed for predicting the dielectric constant and loss factor of these commodities. Nearly li...

  2. Microwave sintering of ceramics

    SciTech Connect

    Snyder, W.B.

    1989-01-01

    Successful adaptation of microwave heating to the densification of ceramic materials require a marriage of microwave and materials technologies. Using an interdisciplinary team of microwave and materials engineers, we have successfully demonstrated the ability to density ceramic materials over a wide range of temperatures. Microstructural evolution during microwave sintering has been found to be significantly different from that observed in conventional sintering. Our results and those of others indicate that microwave sintering has the potential to fabricate components to near net shape with mechanical properties equivalent to hot pressed or hot isostatically pressed material. 6 refs., 11 figs.

  3. Rhenium material properties

    NASA Technical Reports Server (NTRS)

    Biaglow, James A.

    1995-01-01

    Tensile data were obtained from four different types of rhenium at ambient and elevated temperatures. The four types of rhenium included chemical vapor deposition (CVD) and three powder metallurgy (PM) types, i.e., rolled sheet and pressed and sintered bars, with and without hot isostatic pressure (HIP) treatment. Results revealed a wide range of values with ultimate strengths at ambient temperatures varying from 663 MPa for CVD rhenium to 943 MPa for rolled sheet. A similar spread was also obtained for material tested at 1088 K and 1644 K. The wide variance observed with the different materials indicated that the rhenium manufacturing process, material composition and prior handling strongly dictated its properties. In addition to tensile properties, CVD, pressed and sintered material and HIP rhenium successfully completed 100 cycles of low cycle fatigue. Creep data were also obtained showing that CVD and pressed and sintered rhenium could sustain five hours of testing under a tension of 27.5 MPa at 1922 K.

  4. Rhenium material properties

    SciTech Connect

    Biaglow, J.A.

    1995-09-01

    Tensile data were obtained from four different types of rhenium at ambient and elevated temperatures. The four types of rhenium included chemical vapor deposition (CVD) and three powder metallurgy (PM) types, i.e., rolled sheet and pressed and sintered bars, with and without hot isostatic pressure (HIP) treatment. Results revealed a wide range of values with ultimate strengths at ambient temperatures varying from 663 MPa for CVD rhenium to 943 MPa for rolled sheet. A similar spread was also obtained for material tested at 1088 K and 1644 K. The wide variance observed with the different materials indicated that the rhenium manufacturing process, material composition and prior handling strongly dictated its properties. In addition to tensile properties, CVD, pressed and sintered material and HIP rhenium successfully completed 100 cycles of low cycle fatigue. Creep data were also obtained showing that CVD and pressed and sintered rhenium could sustain five hours of testing under a tension of 27.5 MPa at 1922 K.

  5. Materials property measurements

    SciTech Connect

    Boyd, D.M.; Green, E.R.; Doctor, S.R.; Good, M.S.

    1990-04-19

    An in-depth review of the measurement techniques that could be used in materials characterization is presented. The measurement techniques to non-destructively determine the in-service or time-related aging of materials considered include ultrasonic velocity and attenuation, eddy current conductivity, neutron scattering and absorption, conventional and tomographic imaging for ultrasonic and radiation imaging, x-ray scattering, thermal impedance, and magnetic hysteresis. The three sections of the report include a review of failure mechanisms in steel and a discussion of nondestructive evaluation techniques and fracture mechanics, a description of a chart on Measurement Techniques versus Material Properties, and recommendations on the techniques and tests to be performed for the experimental investigations and analysis task of the project. 49 refs., 7 figs.

  6. Results of the Workshop on Microwave-Absorbing Materials for Accelerators (MAMA): A Personal View

    SciTech Connect

    Campisi, I E

    1993-04-01

    The first workshop on the properties and uses of special materials for absorption of microwaves in particle accelerators was held at the Continuous Electron Beam Accelerator Facility (CEBAF) in Newport News, February 22-24, 1993. The meeting's purpose was to review the advances of ceramic and materials science and to describe the accelerator projects the success of which strongly depends on the existence and availability of microwave-absorbing materials with special characteristics. Scientists from various branches of physics, materials science, microwave engineering, accelerator physics and from national and international laboratories, from universities and industries participated in this gathering. This interdisciplinary meeting brought new people and new ideas together which in the future will bloom into better understanding of general materials and of physical processes and eventually to collaborative efforts to design and produce custom made materials. This paper describes the major topics covered in the workshop and is a personal elaboration of the author on the future possibilities opened by this interaction.

  7. Microwave absorbance properties of zirconium–manganese substituted cobalt nanoferrite as electromagnetic (EM) wave absorbers

    SciTech Connect

    Khan, Kishwar Rehman, Sarish

    2014-02-01

    Highlights: • Good candidates for EM materials with low reflectivity. • Good candidates for broad bandwidth at microwave frequency. • Microwave absorbing bandwidth was modulated simply by manipulating the Zr–Mn. • Higher the Zr–Mn content, the higher absorption rates for the electromagnetic radiation. • The predicted reflection loss shows that this can be used for thin ferrite absorber. - Abstract: Nanocrystalline Zr–Mn (x) substituted Co ferrite having chemical formula CoFe{sub 2−2x}Zr{sub x}Mn{sub x}O{sub 4} (x = 0.1–0.4) was prepared by co-precipitation technique. Combining properties such as structural, electrical, magnetic and reflection loss characteristics. Crystal structure and surface morphology of the calcined samples were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). By using two point probe homemade resistivity apparatus to find resistivity of the sample. Electromagnetic (EM) properties are measured through RF impedance/materials analyzer over 1 MHz–3 GHz. The room-temperature dielectric measurements show dispersion behavior with increasing frequency from 100 Hz to 3 MHz. Magnetic properties confirmed relatively strong dependence of saturation magnetization on Zr–Mn composition. Curie temperature is also found to decrease linearly with addition of Zr–Mn. Furthermore, comprehensive analysis of microwave reflection loss (RL) is carried out as a function of substitution, frequency, and thickness. Composition accompanying maximum microwave absorption is suggested.

  8. PETI-298 Prepared by Microwave Synthesis: Neat Resin and Composite Properties

    NASA Technical Reports Server (NTRS)

    Smith, Joseph G.; Connell, John W.; Li, Chao-Jun; Wu, Wei; Criss, Jim M., Jr.

    2004-01-01

    PETI-298 is a high temperature/high performance matrix resin that is processable into composites by resin transfer molding (RTM), resin infusion and vacuum assisted RTM techniques. It is typically synthesized in a polar aprotic solvent from the reaction of an aromatic anhydride and a combination of diamines and endcapped with phenylethynylphthalic anhydride. Microwave synthesis of PETI-298 was investigated as a means to eliminate solvent and decrease reaction time. The monomers were manually mixed and placed in a microwave oven for various times to determine optimum reaction conditions. The synthetic process was subsequently scaled-up to 330g. Three batches were synthesized and combined to give 1 kg of material that was characterized for thermal and rheological properties and compared to PETI-298 prepared by the classic solution based synthetic method. The microwave synthesized PETI-298 was subsequently used to fabricate flat laminates on T650 carbon fabric by RTM. The composite panels were analyzed and mechanical properties determined and compared with those fabricated from PETI-298 prepared by the classic solution method. The microwave synthesis process and characterization of neat resin and carbon fiber reinforced composites fabricated by RTM will be presented. KEY WORDS: Resin Transfer Molding, High Temperature Polymers, Phenylethynyl Terminated Imides, Microwave Synthesis

  9. Dielectric properties of semi-insulating silicon at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Krupka, Jerzy; Kamiński, Paweł; Kozłowski, Roman; Surma, Barbara; Dierlamm, Alexander; Kwestarz, Michał

    2015-08-01

    The permittivity and dielectric loss tangent of high-purity silicon with semi-insulating properties achieved by the irradiation with 23-MeV protons have been measured at frequencies from 1 GHz to 15 GHz. The dielectric losses were separated from the conductor losses on the basis of the total loss tangent measurements versus frequency. The resistivity measurements of the material performed at radio frequencies (RF) by means of the capacitance spectroscopy method have shown the non-uniform resistivity distribution in the direction perpendicular to the surface of the semi-insulating wafer. The excellent agreement between the resistivity measurements results at RF and those obtained by using microwave methods have been achieved. It has been confirmed that high-purity, semi-insulating silicon is practically non-dispersive and possesses extremely low dielectric losses that are constant to within experimental errors in the frequency range from 1 GHz to 350 GHz. In this frequency range, the dielectric loss tangent of semi-insulating silicon is equal to 1.2 ×10-5 .

  10. Microwave synthesis and thermal properties of polyacrylate derivatives containing itaconic anhydride moieties

    PubMed Central

    2012-01-01

    Background Microwave irradiation as an alternative heat source is now a well-known method in synthetic chemistry. Microwave heating has emerged as a powerful technique to promote a variety of chemical reactions, offering reduced pollution, low cost and offer high yields together with simplicity in processing and handling. On the other hand, copolymers containing both hydrophilic and hydrophobic segments are drawing considerable attention because of their possible use in biological systems. Various copolymer compositions can produce a very large number of different arrangements, producing materials of varying chemical and physical properties. Thus, the hydrophilicity of copolymers can be modified by changing the amount of incorporated itaconic anhydride. Results A series of methyl methacrylate (MMA) and acrylamide (AA) copolymers containing itaconic anhydride (ITA) were synthesized by microwave irradiation employing a multimode reactor (Synthos 3000 Aton Paar, GmbH, 1400 W maximum magnetron) as well as conventional method. The thermal properties of the copolymers were evaluated by different techniques. Structure-thermal property correlation based on changing the itaconic anhydride ratio was demonstrated. Results revealed that the incorporation of itaconic anhydride into the polymeric backbone of all series affect the thermal stability of copolymers. In addition, the use of the microwave method offers high molecular weight copolymers which lead eventually to an increase in thermal stability. Conclusions Microwave irradiation method showed advantages for the produced copolymers compared to that prepared by conventional method, where it can offer a copolymer in short time, high yield, more pure compounds and more thermally stable copolymers, rather than conventional method. Also, microwave irradiation method gives higher molecular weight due to prevention of the chain transfer. Moreover, as the itaconic anhydride content increases the thermal stability and Tg increase

  11. Apparatus with moderating material for microwave heat treatment of manufactured components

    DOEpatents

    Ripley, Edward B.

    2011-05-10

    An apparatus for heat treating manufactured components using microwave energy and microwave susceptor material. Heat treating medium such as eutectic salts may be employed. A fluidized bed introduces process gases which may include carburizing or nitriding gases The process may be operated in a batch mode or continuous process mode. A microwave heating probe may be used to restart a frozen eutectic salt bath.

  12. Microwave-absorbing properties of Co-filled carbon nanotubes

    SciTech Connect

    Lin Haiyan; Zhu Hong Guo Hongfan; Yu Liufang

    2008-10-02

    Co-filled carbon nanotubes composites were synthesized via using a simple and efficient wet chemistry solution method. The samples were characterized by transmission electron microscopy. Microwave-absorbing properties were investigated by measuring complex permittivity and complex permeability of the absorber in a frequency range of 2-18 GHz. The reflection loss (R.L.), matching frequency (f{sub m}) and matching thickness (d{sub m}) were calculated using the theory of the absorbing wall. The electromagnetic properties and microwave-absorbing characteristics effects of the modified carbon nanotubes by the encapsulation of metal Co were investigated. A matching thickness is found corresponding to a matching frequency. The maximum reflection loss is about -39.32 dB and the bandwidth corresponding to the reflection loss below -10 dB is 3.47 GHz. With increasing thickness, the maximum reflection loss shifts to lower frequency.

  13. Microwave absorption properties of Ni/(C, silicides) nanocapsules

    PubMed Central

    2012-01-01

    The microwave absorption properties of Ni/(C, silicides) nanocapsules prepared by an arc discharge method have been studied. The composition and the microstructure of the Ni/(C, silicides) nanocapsules were determined by means of X-ray diffraction, X-ray photoelectric spectroscopy, and transmission electron microscope observations. Silicides, in the forms of SiOx and SiC, mainly exist in the shells of the nanocapsules and result in a large amount of defects at the ‘core/shell’ interfaces as well as in the shells. The complex permittivity and microwave absorption properties of the Ni/(C, silicides) nanocapsules are improved by the doped silicides. Compared with those of Ni/C nanocapsules, the positions of maximum absorption peaks of the Ni/(C, silicides) nanocapsules exhibit large red shifts. An electric dipole model is proposed to explain this red shift phenomenon. PMID:22548846

  14. Microwave conductance properties of aligned multiwall carbon nanotube textile sheets

    NASA Astrophysics Data System (ADS)

    Brown, Brian L.; Martinez, Patricia; Zakhidov, Anvar A.; Shaner, Eric A.; Lee, Mark

    2015-07-01

    Understanding the conductance properties of multi-walled carbon nanotube (MWNT) textile sheets in the microwave regime is essential for their potential use in high-speed and high-frequency applications. To expand current knowledge, complex high-frequency conductance measurements from 0.01 to 50 GHz and across temperatures from 4.2 K to 300 K and magnetic fields up to 2 T were made on textile sheets of highly aligned MWNTs with strand alignment oriented both parallel and perpendicular to the microwave electric field polarization. Sheets were drawn from 329 and 520 μm high MWNT forests that resulted in different DC resistance anisotropy. For all samples, the microwave conductance can be modeled approximately by a shunt capacitance in parallel with a frequency-independent conductance, but with no inductive contribution. This is consistent with diffusive Drude conduction as the primary transport mechanism up to 50 GHz. Further, it is found that the microwave conductance is essentially independent of both temperature and magnetic field.

  15. Microwave absorption properties of double-layer composites using CoZn/NiZn/MnZn-ferrite and titanium dioxide

    NASA Astrophysics Data System (ADS)

    Das, Sukanta; Nayak, G. C.; Sahu, S. K.; Routray, P. C.; Roy, A. K.; Baskey, H.

    2015-03-01

    Zinc substituted ferrite powders Me0.5Zn0.5Fe2O4 (Me=Co, Mn and Ni) were prepared by the sol-gel auto-combustion method. The present study highlights development of Single layer and double layer composite microwave absorbing materials using Ferrites, Titanium dioxide and Epoxy matrix. Moreover microwave absorption property, i.e. reflection loss evaluated at X-band frequency. XRD analysis of the filler particles were carried out to evaluate crystal structure, average crystallite diameter. Morphology of the filler particles were studied with FESEM. Hysteresis behavior of the ferrites samples were studied with Vibrating Sample Magnetometer. The most important parameter governing the absorption properties of microwave absorbers i.e. permittivity and permeability studied in a vector network analyzer. Measured reflection loss value of single-layer NiZn-ferrite based microwave absorber reaches -11.2 dB at 12.05 GHz. Whereas, reflection loss value of double-layer CoZn-ferrite/ TiO2 based microwave absorber reaches -24.3 dB at 12.02 GHz. The result shows that microwave absorption property and bandwidth of absorption of double-layer microwave absorber was found to improve comparison to single layer.

  16. Impact of hydrogen forming gas annealing on microwave properties of Ba(Zn1/3Ta2/3)O3 dielectric ceramics

    NASA Astrophysics Data System (ADS)

    Sezer, N.; Saka, E.

    2016-03-01

    The effect of H2 forming gas annealing on the microwave properties of Ba(Zn1/3Ta2/3)O3 (BZT) dielectric ceramics has been studied. The structural, microwave, DC electrical and optical properties were analyzed by experiment results. With elevated temperature annealing, the microwave loss of BZT was increased. This trend correlated with high DC conductivity of annealed samples, as well as dampened phonons found in Raman spectra. These evidences, together, prove that the enhancement of oxygen vacancy defects induced by oxygen deficient sintering environment is one of the main extrinsic root causes for the high microwave loss in practical ceramic materials.

  17. Microwave axial dielectric properties of carbon fiber

    PubMed Central

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-01-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4 GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity. PMID:26477579

  18. Microwave axial dielectric properties of carbon fiber.

    PubMed

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-01-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4 GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity. PMID:26477579

  19. Microwave axial dielectric properties of carbon fiber

    NASA Astrophysics Data System (ADS)

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-10-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4 GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity.

  20. The microwave adsorption behavior and microwave-assisted heteroatoms doping of graphene-based nano-carbon materials

    PubMed Central

    Tang, Pei; Hu, Gang; Gao, Yongjun; Li, Wenjing; Yao, Siyu; Liu, Zongyuan; Ma, Ding

    2014-01-01

    Microwave-assisted heating method is used to treat graphite oxide (GO), pyrolytic graphene oxide (PGO) and hydrogen-reduced pyrolytic graphene oxide (HPGO). Pure or doped graphene are prepared in the time of minutes and a thermal deoxygenization reduction mechanism is proposed to understand their microwave adsorption behaviors. These carbon materials are excellent catalysts in the reduction of nitrobenzene. The defects are believed to play an important role in the catalytic performance. PMID:25109492

  1. The microwave adsorption behavior and microwave-assisted heteroatoms doping of graphene-based nano-carbon materials

    NASA Astrophysics Data System (ADS)

    Tang, Pei; Hu, Gang; Gao, Yongjun; Li, Wenjing; Yao, Siyu; Liu, Zongyuan; Ma, Ding

    2014-08-01

    Microwave-assisted heating method is used to treat graphite oxide (GO), pyrolytic graphene oxide (PGO) and hydrogen-reduced pyrolytic graphene oxide (HPGO). Pure or doped graphene are prepared in the time of minutes and a thermal deoxygenization reduction mechanism is proposed to understand their microwave adsorption behaviors. These carbon materials are excellent catalysts in the reduction of nitrobenzene. The defects are believed to play an important role in the catalytic performance.

  2. Electromagnetic properties and microwave absorption of W-type hexagonal ferrites doped with La 3+

    NASA Astrophysics Data System (ADS)

    Deng, Lianwen; Ding, Li; Zhou, Kesheng; Huang, Shengxiang; Hu, Zhaowen; Yang, Bingchu

    2011-07-01

    W-type barium hexaferrites with compositions of Ba 1Co 0.9Zn 1.1Fe 16O 27 and Ba 0.8La 0.2Co 0.9Zn 1.1Fe 16O 27 were synthesized by the sol-gel method. The electromagnetic properties and microwave absorption behavior of these two ferrites were studied in the 2-18 GHz frequency range. The microstructure and morphology of the ferrites were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The complex permittivity spectra, the complex permeability spectra and microwave reflection loss were measured by a microwave vector network analyzer. The XRD patterns show that the main phase of the Co 2W ferrite forms without other intermediate phases when calcined at 1200 °C. The SEM images indicate that flake-like hexagonal crystals distribute uniformly in the materials. Both the magnetic and dielectric losses are significantly enhanced by partial substitution of La 3+ for Ba 2+ in the W-type barium hexaferrites. The microwave absorption property of the La 3+ doping W-type hexaferrite sample is enhanced with the bandwidth below -10 dB around 8 GHz and the peak value of reflection loss about -39.6 dB at the layer thickness of 2 mm.

  3. The effect of dielectric properties of sintering additives on microwave sintered silicon nitride ceramics.

    PubMed

    Chockalingam, Sreekumar; George, Jacob; Earl, David; Amarakoon, Vasantha R W

    2008-01-01

    Silicon nitride requires the use of susceptive additives for microwave liquid phase sintering due to the material's low dielectric loss. In this article, we report the effect of complex dielectric properties of two compositions of sintering aids on 2.45 GHz microwave sintered Si3N4 with respect to power absorption, temperature distribution and densification behavior. The temperature dependent dielectric properties were measured from 25 degrees C to 1400 degrees C using a conventional cavity perturbation technique. Finite Difference Time Domain (FDTD) electromagnetic simulations coupled with a thermal solver was used to predict the microwave power absorption and the corresponding temperature evolution inside the samples. The additive with higher dielectric loss (4 wt% MgO, 6 wt% Y2O3 and 2.5 wt% ZrO2) produces a greater sintered density than the lower loss additive (4 wt% MgO and 6 wt% Y2O3) or pure Si3N4. Although microwave loss at temperatures below 600 degrees C is insignificant with or without the additives, the loss begins to increase at higher temperatures when the additives are present and has a strong upward trend above 1000 degrees C. Above 1200 degrees C the sample containing ZrO2 exhibited the greatest loss. Numerical simulations at the peak sintering temperature show greater microwave power absorption and higher temperature in the sample with the highest loss additive. The simulation results correlate to the difference in densification behavior observed. The simulation was also useful because the material temperature was not accurately provided by optical pyrometer measurements of the crucible sample holder. PMID:19227072

  4. Spark plasma sintering and microwave electromagnetic properties of MnFe2O4 ceramics

    NASA Astrophysics Data System (ADS)

    Penchal Reddy, M.; Mohamed, A. M. A.; Venkata Ramana, M.; Zhou, X. B.; Huang, Q.

    2015-12-01

    MnFe2O4 ferrite powder was synthesized by a facile one-pot hydrothermal route and then consolidated into dense nanostructured compacts by the spark plasma sintering (SPS) technique. The effect of sintering temperature, on densification, morphology, magnetic and microwave absorption properties was examined. Spark plasma sintering resulted in uniform microstructure, as well as maximum relative density of 98%. The magnetic analysis indicated that the MnFe2O4 ferrite nanoparticles showed ferrimagnetic behavior. Moreover, the dielectric loss and magnetic loss properties of MnFe2O4 ferrite nanoparticles were both enhanced due to its better dipole polarization, interfacial polarization and shape anisotropy. It is believed that such spark plasma sintered ceramic material will be applied widely in microwave absorbing area.

  5. Surface modification of plasmonic nanostructured materials with thiolated oligonucleotides in 10 seconds using selective microwave heating.

    PubMed

    Abel, Biebele; Aslan, Kadir

    2012-11-01

    This study demonstrates the proof-of-principle of rapid surface modification of plasmonic nanostructured materials with oligonucleotides using low power microwave heating. Due to their interesting optical and electronic properties, silver nanoparticle films (SNFs, 2 nm thick) deposited onto glass slides were used as the model plasmonic nanostructured materials. Rapid surface modification of SNFs with oligonucleotides was carried out using two strategies (1) Strategy 1: for ss-oligonucleotides, surface hybridization and (2) Strategy 2: for ds-oligonucleotides, solution hybridization), where the samples were exposed to 10, 15, 30 and 60 seconds microwave heating. To assess the efficacy of our new rapid surface modification technique, identical experiments carried out without the microwave heating (i.e., conventional method), which requires 24 hours for the completion of the identical steps. It was found that SNFs can be modified with ss- and ds-oligonucleotides in 10 seconds, which typically requires several hours of incubation time for the chemisorption of thiol groups on to the planar metal surface using conventional techniques. PMID:23645933

  6. Materials properties data base computerization

    NASA Technical Reports Server (NTRS)

    Baur, R. G.; Donthnier, M. L.; Moran, M. C.; Mortman, I.; Pinter, R. S.

    1984-01-01

    Material property data plays a key role in the design of jet engine components. Consistency, accuracy and efficient use of material property data is of prime importance to the engineering community. The system conception, development, implementation, and future plans for computer software that captures the Material Properties Handbook into a scientific data base are described. The engineering community is given access to raw data and property curves, display of multiple curves for material evaluation and selection, direct access by design analysis computer programs, display of the material specification, and a historical repository for the material evolution. The impact of this activity includes significant productivity gains and cost reductions; all users have access to the same information nd provides consistent, rapid response to the needs of the engineering community. Future plans include incorporating the materials properties data base into a network environment to access information from other data bases and download information to engineering work stations.

  7. Properties of linear microwave plasma sustained by coaxial TEM waveguide

    NASA Astrophysics Data System (ADS)

    Han, Moon-Ki; Seo, Kwon-Sang; Kim, Dong Hyun; Lee, Hae June; Lee, Ho-Jun

    2013-09-01

    A linear 2.45GHz microwave plasma sustained by coaxial circular TEM waveguide has been developed for the low temperature large area plasma enhanced chemical vapor deposition application. TE-TEM microwave power coupling was achieved by copper rod located at λg/4 from short-end of TE10 waveguide. TEM waveguide consists of quartz tube surrounded by plasma and copper rod electrode. TEM waveguide is 60 cm in length and 3 cm in diameter, which is terminated with shorted metal cap. For the operation condition of 300 W input power and Ar pressure of 200 mTorr, a clear standing wave pattern with wavelength of 10 cm was observed. Measured plasma density and temperature at 5 cm from quartz wall was 1.2 × 1017/cm3 and 1.7 eV respectively. Density non-uniformity was less than 6% along quartz tube in spite of standing wave set-up. In addition, properties of the microwave source are also investigated through electromagnetic field simulation coupled with drift-diffusion approximation of plasma. Calculated and measured standing wave pattern was almost identical. Electron density and temperature distribution show similar behavior with experimental results. S11 value of input port of TE10 waveguide was calculated as 17dB.

  8. Microwave evaluation of anisotropy in glass and reflection properties of glass fibers under static load

    SciTech Connect

    Frank, M.; Handjojo, L.; Qaddoumi, N.; Bois, K.; Zoughi, R.

    1999-12-02

    Detection and evaluation of glass properties, such as the degree of anisotropy, is an important issue in glass making industry. In addition, a nondestructive means by which glass tensile strength may be correlated to some measurable parameter is also desirable. Microwave nondestructive material characterization techniques have shown great potential for evaluating glass properties. In this study these techniques have been utilized at S- and X-band to determine the potential of evaluating anisotropy and obtain some useful correlation to tensile strength in glass fibers.

  9. Microwave Sensing of Density and Moisture in Granular Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The importance of moisture measurement in grain and seed is discussed, and a brief history of the development of moisture sensing instruments, based on sensing of dielectric properties of these materials, is presented. Data are presented graphically on the permittivities or dielectric properties of...

  10. Facile Synthesis of Fe3O4/GCs Composites and Their Enhanced Microwave Absorption Properties.

    PubMed

    Jian, Xian; Wu, Biao; Wei, Yufeng; Dou, Shi Xue; Wang, Xiaolin; He, Weidong; Mahmood, Nasir

    2016-03-01

    Graphene has good stability and adjustable dielectric properties along with tunable morphologies, and hence can be used to design novel and high-performance functional materials. Here, we have reported a facile synthesis method of nanoscale Fe3O4/graphene capsules (GCs) composites using the combination of catalytic chemical vapor deposition (CCVD) and hydrothermal process. The resulting composite has the advantage of unique morphology that offers better synergism among the Fe3O4 particles as well as particles and GCs. The microwave-absorbing characteristics of developed composites were investigated through experimentally measured electromagnetic properties and simulation studies based on the transmission line theory, explained on the basis of eddy current, natural and exchange resonance, as well as dielectric relaxation processes. The composites bear minimum RL value of -32 dB at 8.76 GHz along with the absorption bandwidth range from 5.4 to 17 GHz for RL lower than -10 dB. The better performance of the composite based on the reasonable impedance characteristic, existence of interfaces around the composites, and the polarization of free carriers in 3D GCs that make the as-prepared composites capable of absorbing microwave more effectively. These results offer an effective way to design high-performance functional materials to facilitate the research in electromagnetic shielding and microwave absorption. PMID:26890224

  11. Fabrication and microwave properties of Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O thin films

    NASA Astrophysics Data System (ADS)

    Sobolewski, Roman; Konopka, Janusz; Kula, Witold; Gierlowski, Piotr; Konopka, Anna

    1989-03-01

    Studies are reported of the interaction of Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O thin films with microwaves. The films were prepared on cubic zirconia and magnesium oxide substrates using a modified spray deposition technique. The tested films were about 1-3 microns thick and exhibited good superconducting properties. Several test structures have been designed by spraying a mixture of nitrate precursors on heated substrates through very thin stencil marks. The supercurrent dependence on millimeter wavelength microwave illumination was measured, and microwave detection and mixing experiments were performed. The films of both materials exhibited properties characteristic of granular superconductors, with Josephson-type coupling at the intergrain connections. The results also indicate that these materials can be successfully used as very sensitive millimeter radiation detectors operational at liquid-nitrogen temperatures.

  12. Controlled Synthesis and Microwave Absorption Property of Chain-Like Co Flower

    PubMed Central

    Wang, Chao; Hu, Surong; Han, Xijiang; Huang, Wen; Tian, Lunfu

    2013-01-01

    Chain-like Co flower is synthesized by simply modulating the reaction conditions via a facile liquid-phase reduction method. The morphology evolution process and transformation mechanism from particle to flower and finally to chain-like flower have been systematically investigated. [001] is the preferred growth orientation due to the existence of easy magnetic axis. The microwave loss mechanism can be attributed to the synergistic effect of magnetic loss and dielectric loss, while magnetic loss is the main loss mechanism. In addition, the special microstructure of chain-like Co flower may further enhance microwave attenuation. The architectural design of functional material morphology is critical for improving its property toward future application. PMID:23437073

  13. Factors Influencing the Dielectric Properties of Agricultural Products and Food Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of materials are defined, and the major factors that influence these properties of agricultural and food materials, namely, frequency of the applied radio-frequency and microwave electric fields, water content, temperature, and density of the materials are discussed on the bas...

  14. Digestion of titanium bearing geologic materials involving microwaves.

    PubMed

    Tripathi, Anju; Chattopadhyay, Partha

    2007-10-01

    An environmentally friendly and rapid digestion procedure involving 10 mL of acid mixture (HNO3 : HCl : HF = 2:2:1) for 0.1 g of sample in closed vessel microwave digester following heating program : 250W for 10 min., hold time 2 min., 600 W for 17 min, and Ventilation time 10 min was developed. The operating parameters were varied and optimized by factorial design approach using "Steepest Ascent" method. The validity of the recommended digestion procedure were examined by analyzing several well characterized standard reference materials such as diabase (W2), basalt (BIR-1, JB-3, BHVO-1), granite (G2), gabbro (JGb-1), Mn-nodule (Nod-A-1, Nod-P-1), sediment (STSD-4, LKSD-2), limestone (KH-2), soil (SAu-1), ilmenite (IGS-31), rutile (IGS-32), Zircon (IGS-35) and titanium dioxide (SRM-154b) employing both inductively coupled plasma-atomic emission spectrometry (ICP-AES) and well known spectrophotometric method. An excellent agreement between the methods and the certified values of standard reference materials suggest that the digestion procedure can be used for quality control and allied purposes. PMID:18153999

  15. Tunable microwave absorbing nano-material for X-band applications

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Ashiq, Muhammad Naeem; Khan, M. A.; Niaz, Shanawer; Rana, M. U.

    2016-03-01

    The effect of rare earth elements substitution in Sr1.96RE0.04Co2Fe27.80Mn0.2O46 (RE=Ce, Gd, Nd, La and Sm) X-type hexagonal ferrites prepared by using sol gel autocombustion method was studied. The XRD and FTIR analysis show the single phase of the prepared material. The lattice constants a (Å) and c (Å) varies with the additives. The particle size measured by Scherer formula for all the samples varies in the range of 54-100 nm and confirmed by the TEM analysis. The average grain size measured by SEM analysis lies in the range of 0.672-1.01 μm for all the samples. The Gd-substituted ferrite has higher value of coercivity (526.06 G) among all the samples which could be a good material for longitudinal recording media. The results also indicate that the Gd-substituted sample has maximum reflection loss of -25.2 dB at 11.878 GHz, can exhibit the best microwave absorption properties among all the substituted samples. Furthermore, the minimum value of reflection loss shifts towards the lower and higher frequencies with the substitution of rare earth elements which confirms that the microwave absorption properties can be tuned with the substitution of rare earth elements in pure ferrites. The peak value of attenuation constant at higher frequency agrees well the reflection loss data.

  16. Synthesis and Microwave Absorption Properties of BaTiO3-polypyrrole Composite

    NASA Astrophysics Data System (ADS)

    Li, Qiao-ling; Zhang, Cun-rui; Li, Jian-qiang

    2010-10-01

    BaTiO3 powders are prepared by sol-gel method by cotton template. Polypyrrole is prepared by chemical oxidation route in the emulsion polymerization system. Then BaTiO3-polypyrrole composites with different mixture ratios are prepared by as-prepared material. The structure, morphology, and properties of the composites are characterized with Infrared spectrum, X-ray diffraction, scanning electron microscope, and net-wok analyzer. The complex permittivity and reflection loss of the composites are measured at different microwave frequencies in S-band and C-band (0.03-6 GHz) employing vector network analyzer model PNA 3629D vector. The effect of the mass ratio of BaTiO3 to polypyrrole on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of BaTiO3-polypyrrole composite is proposed. The BaTiO3-polypyrrole composite can find applications in suppression of electromagnetic interference and reduction of radar signature.

  17. Facile synthesis of BaTiO3 nanotubes and their microwave absorption properties.

    PubMed

    Zhu, Yao-Feng; Zhang, Li; Natsuki, Toshiaki; Fu, Ya-Qin; Ni, Qing-Qing

    2012-04-01

    Uniform BaTiO(3) nanotubes were synthesized via a simple wet chemical route at low temperature (50 °C). The as-synthesized BaTiO(3) nanotubes were characterized using powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The results show that the BaTiO(3) nanotubes formed a cubic phase with an average diameter of ~10 nm and wall thickness of 3 nm at room temperature. The composition of the mixed solvent (ethanol and deionized water) was a key factor in the formation of these nanotubes; we discuss possible synthetic mechanisms. The microwave absorption properties of the BaTiO(3) nanotubes were studied at microwave frequencies between 0.5 and 15 GHz. The minimum reflection loss of the BaTiO(3) nanotubes/paraffin wax composite (BaTiO(3) nanotubes weight fraction = 70%) reached 21.8 dB (~99.99% absorption) at 15 GHz, and the frequency bandwidth less than -10 dB is from 13.3 to 15 GHz. The excellent absorption property of BaTiO(3) nanotubes at high frequency indicates that these nanotubes could be promising microwave-absorbing materials. PMID:22409350

  18. Preparation and microwave absorbing properties of carbon/cobalt ferromagnetic composites.

    PubMed

    Li, Wangchang; Qiao, Xiaojing; Zhao, Hui; Wang, Shuman; Ren, Qingguo

    2013-02-01

    Carbon/cobalt ferromagnetic light composites with high performance of microwave absorbing properties were prepared by hydrothermal method using starch and hollow cobalt ferrites. It was concluded that after carbonization the spinel structure ferrites changed to Co3Fe7 alloys and the temperature of graphitization was significantly decreased for the catalytic of CoFe2O4/Co3Fe7. The increase of carbon content, and exist of CoFe2O4/Co3Fe7 heightened the microwave absorbing properties. Electromagnetic parameters were tested with 40% of the titled materials and 60% of paraffin wax composites by using HP8722ES vector network analyzer. The reflection was also simulated through transmission line theory. The microwave absorbers exhibited a maximum reflection loss -43 dB and the electromagnetic wave absorption less than -10 dB was found to exceed 3.0 GHz between 11.6 GHz and 15 GHz for an absorber thickness of 2 mm. PMID:23646517

  19. Microwave Dielectric and Propagation Properties of Vegetation Canopies

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T. (Principal Investigator)

    1985-01-01

    A vegetation canopy is a highly inhomogeneous medium at microwave frequencies, and because the scattering elements (leaves, stalks, fruits, and branches) have a nonuniform distribution in orientation, the canopy is likely to exhibit nonisotropic attenuation properties. In some canopies, the stalk may contain the overwhelming majority of the plant's biomass, which suggests that an incident radar wave would be differentially attenuated by the canopy depending on the direction of the incident electric field relative to the stalks' orientation. The propagation properties of a vegetation canopy play a central role in modeling both the backscattering behavior observed by an imaging radar and the emission observed by a radiometer. These propagation properties are in turn governed by the dielectric properties and the size, shape, and slope distributions of the scatteres. In spite of the critical need for canopy propagation models and experimental data, very few investigations had been conducted (prior to this study) to determine the extinction properties of vegetation canopies, either by constituent type (leaves, stalks, etc.) or as a whole.

  20. Microwave properties of composites with glass coated amorphous magnetic microwires

    NASA Astrophysics Data System (ADS)

    Starostenko, S. N.; Rozanov, K. N.; Osipov, A. V.

    2006-03-01

    The complex permittivity and permeability of composites filled with Fe-based microwires are measured in a coaxial line at frequencies from 0.01 to 10 GHz.The samples under study consist of closely packed wire sections with various orientations relative to wave vector. The composites, where the wires are collinear to the coaxial axis, are found to be low permeable. Their permittivity has frequency dispersion governed by the length of the wire and its linear impedance. The middle section of the wire has higher impedance than that of the end sections where the regular domain structure is distorted. Magnetic bias parallel to the wire axis affects the linear impedance and parameters of dielectric absorption of a composite, the effect is proportional to bias strength. The samples of a coil-type structure, where the wires are wound around the coaxial axis, display the intensive magnetic absorption attributed to the domain wall motion. The absorption takes place in the megahertz band, at microwaves the permeability is close to unity. The microwave properties of diluted composites filled with randomly oriented permeable wires are discussed.

  1. Microwave Dielectric Properties of Soil and Vegetation and Their Estimation From Spaceborne Radar

    NASA Technical Reports Server (NTRS)

    Dobson, M. Craig; McDonald, Kyle C.

    1996-01-01

    This paper is largely tutorial in nature and provides an overview of the microwave dielectric properties of certain natural terrestrial media (soils and vegetation) and recent results in estimating these properties remotely from airborne and orbital synthetic aperture radar (SAR).

  2. Microwave pulse propagation measurements in left-handed materials

    NASA Astrophysics Data System (ADS)

    di Gennaro, Emiliano; Parimi, Patanjali V.; Vodo, Plarenta; Lu, Wentao; Sridhar, Srinivas

    2004-03-01

    Left handed electromagnetism is well established in media with negative permeability and permittivity and in photonic crystals [1]. In such media the negative refractive index is accompanied by large dispersion dn/dω, and consequently a very low group velocity is predicted for left-handed metamaterial (LHM). It is well known that an artificial material consisting of interleaved arrays of wires and split ring resonators in a certain microwave frequency range shows left handed behavior. We have carried out pulse measurements on LHM using a transition analyzer in order to measure the group velocity. Time delay measurements are performed in an X-band and parallel plate waveguide. Sending a 100ns width pulse with a carrier frequency ranging between 9 and 11 GHz, we analyze the signal delay due to the sample. The results suggest that the group velocity in the LHM is very low. Pulse delay measurements in photonic crystals are also discussed. Work supported by NSF & AFRL [1]. P. V. Parimi et al., submitted (2003).

  3. Magnetic, DC Transport, and Microwave Properties of High Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Nguyen, Paul Phong

    This thesis involves three major projects: (1) Effects of bromination on YBa_2Cu _3O_{7-x} (YBCO) single crystals, (2) Power dependence of the microwave surface impedance of YBCO thin films, and (3) Microwave properties of YBCO Josephson junctions. In the first project, de-oxygenated non-superconducting YBa_2Cu_3O _{6.2} single crystals are doped with Br. The resulting crystals (YBCOBr) become superconducting with T_{c} {~}.92 K, Delta T_{c} {~} 1.0 K. The normal resistivity in the best sample is linear in temperature. The large ratio in resistivity of the brominated to the pristine YBCO single crystals suggests that bromination greatly increases the scattering rate. The upper critical fields are measured resistively and the corresponding coherence lengths xi_ {ab}(0) and xi_{c }(0) are estimated. A comparison with the fully oxygenated YBCO single crystals shows that xi_{ab}(0) remains approximately the same, whereas xi_{c} (0) decreases by a factor of {~ }3, suggesting that Br never enters the CuO _2 planes. The pinning energy for vortex motion in the ab plane decreases after bromination and this decrease can be attributed to the increased anisotropy. Compared with the fully oxygenated YBCO single crystals, the critical current density is suppressed by bromination and is strongly dependent on the applied magnetic field. The reduced lower critical field H_{c1} in YBCOBr indicates a reduction in the carrier density. The second project involves measurements of the surface impedance Z_{s} for the first time as a function of frequency (1-20 GHz), temperature (4.2-91 K), and peak rf magnetic field (0 < H_{rf} < 500 Oe) for high-quality epitaxial YBa_2Cu _3O_{7-x} thin films, using a stripline-resonator technique. The results for Z_{s} in the low- and intermediate-rf-field regime (H_ {rm rf} < 50 Oe at 77 K) are explained quantitatively by a power-dependent coupled-grain model, which treats the film as a network of superconducting grains connected by grain boundaries

  4. Microwave processed nanocrystalline hydroxyapatite: Simultaneous enhancement of mechanical and biological properties

    PubMed Central

    Bose, Susmita; Dasgupta, Sudip; Tarafder, Solaiman; Bandyopadhyay, Amit

    2010-01-01

    Despite excellent bioactivity of hydroxyapatite (HA) ceramics, poor mechanical strength has limited its applications primarily to coatings and other non-load bearing areas as bone grafts. Using synthesized HA nanopowder, dense compacts with grain sizes in nanometers to micrometers were processed via microwave sintering between 1000 and 1150 °C for 20 minutes. Here we demonstrate that mechanical properties, such as compressive strength, hardness and indentation fracture toughness of HA compacts increased with a decrease in grain size. HA with 168± 86 nm grain size showed the highest compressive strength of 395±42 MPa, hardness of 8.4±0.4 GPa and indentation fracture toughness of 1.9 ±0.2 MPam1/2. To study the in vitro biological properties, HA compacts with grain size between 168 nm and 1.16 µm were assessed for in vitro bone cell-materials interactions with human osteoblast cell line. Vinculin protein expression for cell attachment and bone cell proliferation using MTT assay showed surfaces with finer grains provided better bone cell-materials interactions than coarse grained samples. Our results indicate simultaneous improvements in mechanical and biological properties in microwave sintered HA compacts with nanoscale grain size. PMID:20230922

  5. Estimation of soil hydraulic properties with microwave techniques

    NASA Technical Reports Server (NTRS)

    Oneill, P. E.; Gurney, R. J.; Camillo, P. J.

    1985-01-01

    Useful quantitative information about soil properties may be obtained by calibrating energy and moisture balance models with remotely sensed data. A soil physics model solves heat and moisture flux equations in the soil profile and is driven by the surface energy balance. Model generated surface temperature and soil moisture and temperature profiles are then used in a microwave emission model to predict the soil brightness temperature. The model hydraulic parameters are varied until the predicted temperatures agree with the remotely sensed values. This method is used to estimate values for saturated hydraulic conductivity, saturated matrix potential, and a soil texture parameter. The conductivity agreed well with a value measured with an infiltration ring and the other parameters agreed with values in the literature.

  6. Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Qi, Xiaosi; Xu, Jianle; Hu, Qi; Deng, Yu; Xie, Ren; Jiang, Yang; Zhong, Wei; Du, Youwei

    2016-06-01

    In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism.

  7. Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties

    PubMed Central

    Qi, Xiaosi; Xu, Jianle; Hu, Qi; Deng, Yu; Xie, Ren; Jiang, Yang; Zhong, Wei; Du, Youwei

    2016-01-01

    In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism. PMID:27324290

  8. Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties.

    PubMed

    Qi, Xiaosi; Xu, Jianle; Hu, Qi; Deng, Yu; Xie, Ren; Jiang, Yang; Zhong, Wei; Du, Youwei

    2016-01-01

    In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism. PMID:27324290

  9. Synthesis, Characterization, and Microwave Absorption Properties of Reduced Graphene Oxide/Strontium Ferrite/Polyaniline Nanocomposites.

    PubMed

    Luo, Juhua; Shen, Pan; Yao, Wei; Jiang, Cuifeng; Xu, Jianguang

    2016-12-01

    Strontium ferrite nanoparticles were prepared by a coprecipitation method, and reduced graphene oxide/strontium ferrite/polyaniline (R-GO/SF/PANI) ternary nanocomposites were prepared by in situ polymerization method. The morphology, structure, and magnetic properties of the ternary nanocomposites were investigated by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), TEM, Raman, and VSM. The microwave-absorbing properties of the composites were measured by a vector network analyzer. The XRD patterns show the single phase of strontium hexaferrite without other intermediate phases. TEM photographs reveal that strontium ferrite nanoparticles are uniformly dispersed on the surfaces of R-GO sheets. The R-GO/SF/PANI nanocomposite exhibited the best absorption property with the optimum matching thickness of 1.5 mm in the frequency of 2-18 GHz. The value of the maximum RL was -45.00 dB at 16.08 GHz with the 5.48-GHz bandwidth. The excellent absorption properties of R-GO/SF/PANI nanocomposites indicated their great potential as microwave-absorbing materials. PMID:26969594

  10. Synthesis, Characterization, and Microwave Absorption Properties of Reduced Graphene Oxide/Strontium Ferrite/Polyaniline Nanocomposites

    NASA Astrophysics Data System (ADS)

    Luo, Juhua; Shen, Pan; Yao, Wei; Jiang, Cuifeng; Xu, Jianguang

    2016-03-01

    Strontium ferrite nanoparticles were prepared by a coprecipitation method, and reduced graphene oxide/strontium ferrite/polyaniline (R-GO/SF/PANI) ternary nanocomposites were prepared by in situ polymerization method. The morphology, structure, and magnetic properties of the ternary nanocomposites were investigated by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), TEM, Raman, and VSM. The microwave-absorbing properties of the composites were measured by a vector network analyzer. The XRD patterns show the single phase of strontium hexaferrite without other intermediate phases. TEM photographs reveal that strontium ferrite nanoparticles are uniformly dispersed on the surfaces of R-GO sheets. The R-GO/SF/PANI nanocomposite exhibited the best absorption property with the optimum matching thickness of 1.5 mm in the frequency of 2-18 GHz. The value of the maximum RL was -45.00 dB at 16.08 GHz with the 5.48-GHz bandwidth. The excellent absorption properties of R-GO/SF/PANI nanocomposites indicated their great potential as microwave-absorbing materials.

  11. Design and simulation of a microwave powered microplasma system for local area materials processing

    NASA Astrophysics Data System (ADS)

    Narendra, Jeffri Julliarsa

    A microwave powered microplasma source is developed and tested for materials processing on spatially localized areas. A small diameter stream of plasma (less than 2 mm in diameter) is created by focusing microwave energy inside a discharge tube. The discharge then flows out the end of the tube onto the surface being processed delivering ions and reactive radicals. The diameter of the plasma stream from the tube to the material being processed can be controlled by an aperture mounted at the end of the tube. The spot size of the localized plasma stream ranges from 2 mm down to 10's micrometers depending on the aperture size. The discharge is created by using 2.45 GHz microwave energy that is coupled into the discharge using a small foreshortened cylindrical cavity that has a hollow inner conductor and a small capacitive gap at the end of the cavity. A processing gas mixture is fed through a 2 mm inner diameter quartz tube which is located inside the hollow inner conductor of the cavity. This tube is exposed to a high electric field at the small gap end of the cavity thus generating a surface wave plasma. The length of the surface wave discharge in the tube can be extended by increasing the microwave power to the discharge so that the plasma reaches the aperture. The operating pressures range from 0.5 Torr to 100 Torr and the microwave power utilized ranges from a few Watts to 10's Watts. Several properties of the discharge including plasma power density, electron density and electron temperature are measured. The power densities of argon and Ar/O2 plasma discharges vary from 10's to over 450 W/cm 3. The plasma density and electron temperature of argon discharges are measured using a double Langmuir probe placed in the materials processing area. The plasma densities are in the range of 1011 -- 1013 cm-3. Computational modeling of the plasma discharge and the microwave excitation of the discharge is performed using a finite element analysis. The goal of the modeling

  12. Mechanical properties of nanophase materials

    SciTech Connect

    Siegel, R.W.; Fougere, G.E.

    1993-11-01

    It has become possible in recent years to synthesize new materials under controlled conditions with constituent structures on a nanometer size scale (below 100 nm). These novel nanophase materials have grain-size dependent mechanical properties significantly different than those of their coarser-grained counterparts. For example, nanophase metals are much stronger and apparently less ductile than conventional metals, while nanophase ceramics are more ductile and more easily formed than conventional ceramics. The observed mechanical property changes are related to grain size limitations and/or the large percentage of atoms in grain boundary environments; they can also be affected by such features as flaw populations, strains and impurity levels that can result from differing synthesis and processing methods. An overview of what is presently known about the mechanical properties of nanophase materials, including both metals and ceramics, is presented. Some possible atomic mechanisms responsible for the observed behavior in these materials are considered in light of their unique structures.

  13. Effects of "Natural" Water and "Added" Water on Microwave Dielectric Properties of Shelled Corn at Microwave Frequencies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of samples of shelled corn of “natural” water content and those prepared by adding water were measured in free space at microwave frequencies and 23 oC. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 6 GHz show no difference betw...

  14. Microstructure and antibacterial properties of microwave plasma nitrided layers on biomedical stainless steels

    NASA Astrophysics Data System (ADS)

    Lin, Li-Hsiang; Chen, Shih-Chung; Wu, Ching-Zong; Hung, Jing-Ming; Ou, Keng-Liang

    2011-06-01

    Nitriding of AISI 303 austenitic stainless steel using microwave plasma system at various temperatures was conducted in the present study. The nitrided layers were characterized via scanning electron microscopy, glancing angle X-ray diffraction, transmission electron microscopy and Vickers microhardness tester. The antibacterial properties of this nitrided layer were evaluated. During nitriding treatment between 350 °C and 550 °C, the phase transformation sequence on the nitrided layers of the alloys was found to be γ → (γ + γ N) → (γ + α + CrN). The analytical results revealed that the surface hardness of AISI 303 stainless steel could be enhanced with the formation of γ N phase in nitriding process. Antibacterial test also demonstrated the nitrided layer processed the excellent antibacterial properties. The enhanced surface hardness and antibacterial properties make the nitrided AISI 303 austenitic stainless steel to be one of the essential materials in the biomedical applications.

  15. Magnetic and microwave properties of amorphous FeCoNbBCu thin films

    NASA Astrophysics Data System (ADS)

    Bi, Mei; Wang, Xin; Lu, Haipeng; Deng, Longjiang; Sunday, Katie Jo; Taheri, Mitra L.; Harris, Vincent G.

    2016-01-01

    The soft magnetic and microwave properties of amorphous FeCoNbBCu thin films with thicknesses varying from 70 nm to 450 nm have been systematically investigated. Due to the amorphous structure, the coercivity is 1.5 Oe in thicker films. The thickness-dependent microwave characteristics of the films were measured over the range 0.5-6 GHz and analyzed using the Landau-Lifshitz-Gilbert equation. Without applying magnetic field during deposition and measurement, an in-plane uniaxial anisotropy in amorphous thin films was obtained, ranging from 21 to 45 Oe. The interface interaction between substrate and film is confirmed to be the origin of the induced anisotropy, whereas the volume anisotropy contribution is more pronounced with increasing film thickness. For films possessing an in-plane uniaxial anisotropy, the shift of resonance frequency with thickness is observed and verified by the Kittel equation. The demonstration of a controllable and tunable anisotropy suggests that the FeCoNbBCu thin films have potential application as magnetic materials for Spintronics-based microwave devices.

  16. Structure-property correlations in nanostructured WC-12Co microwave clad

    NASA Astrophysics Data System (ADS)

    Zafar, Sunny; Sharma, Apurbba Kumar

    2016-05-01

    Nanostructured materials are known for enhanced properties as compared to their conventional counterparts. In the present work, microwave cladding technique was explored for depositing nanostructured WC-12Co clads on stainless steel substrates. Phase analysis of the WC-12Co microwave clads revealed the presence of Co6W6C, Co7W6, Co3W9C4, W2C and WC phases. The microstructure of the WC-12Co clads confirmed uniform distribution of nano-carbides in the form of clusters enclosed in the carbide network. Mechanical characterisation of the nanostructured clads was carried in terms of microhardness assessment and flexural strength measurement. The microwave induced clads exhibited excellent metallurgical bonding with the substrate and were free from interfacial cracks. The average microhardness of the developed clads was found in the order of 1760 ± 128HV. The flexural strength of the developed clads was observed to be 671 ± 28 MPa. The nanostructured clads exhibited good adhesion with the substrate without getting peeled-off under a load of 3.75 kN and a displacement of 3.72 mm.

  17. Microwave absorption properties of BaGdxFe12-xO19 nanoparticles synthesized by wet milling process

    NASA Astrophysics Data System (ADS)

    Kaynar, Mehmet; Ozcan, Sadan; Shah, S.

    2013-03-01

    It is a big demand to have a wide band, easy to synthesize microwave absorption materials with a high absorption ratio according to their weight. As a solution, nanoparticles are used for the couple of years because of their tunable frequencies by just changing their particle size. Most interesting nano structures for this objective are ferrites. In this work as a microwave absorber, BaFe12O19 and BaGd2Fe10O19 nanoparticles with different particles size are synthesized by the wet milling process. Their crystal structure analyzed by XRD, mean particle sizes were calculated from XRD patterns using rietveld analysis and from TEM images. Magnetic properties are analyzed by using Quantum design VSM. Microwave absorption properties are measured by using coaxial transmission method with an Agilent E5071 VNA. With the change of the last milling time from 0 to 20-hour crystalline sizes are changed from 48 nm to 13 nm. Decrease of particle size give rise to a decrease at coercivity and saturation magnetization of the samples. Change at the hysteresis loops gives a clue to the change of the microwave absorption frequency which is directly observed from the microwave measurements. Supported by TUBITAK-BIDEB 2214-Abroad Research Scholarship program.

  18. Tunable dielectric properties and excellent microwave absorbing properties of elliptical Fe3O4 nanorings

    NASA Astrophysics Data System (ADS)

    Tong, Guoxiu; Liu, Yun; Cui, Tingting; Li, Yana; Zhao, Yanting; Guan, Jianguo

    2016-02-01

    Elliptical Fe3O4 nanorings (NRs) with continuously tunable axes that range from 40 nm to 145 nm in length were prepared through a precursor-directed synthetic route to determine the electromagnetic responses generated at 2-18 GHz. The tunability of the dielectric properties of Fe3O4 NRs depends on the long axis rather than on the specific surface area, internal stress, and grain size. Elliptical Fe3O4 NRs exhibit the excellent microwave absorbing properties due to the unique ring-like configuration, which significantly enhances permittivity, multiple scattering, oscillation resonance absorption, microantenna radiation, and interference. These findings indicate that ring-like nanostructures are promising for devising effective microwave absorbers.

  19. Property Status of Lunar Material

    NASA Astrophysics Data System (ADS)

    Pop, V.

    Most of the lunar material in private hands is of meteoric origin, and its property sta- tus does not present many challenges. The intention of Applied Space Resources, Inc, to fly a commercial lunar sample return mission and to subsequently offer lunar ma- terial for sale, raises the issue of the legality of exploitation and private ownership of retrieved lunar material. Lunar samples have been returned in the past by means of the Apollo (US) and Luna (USSR) missions and, while most of the material re- mains government property and is used for scientific means, a small fraction has been transferred abroad and some has entered the private market. Apollo-collected moon- rocks have been offered, symbolically, to heads of States, and some foreign nations have subsequently transferred ownership to private individuals. The same, lunar ma- terial of Soviet provenience has entered the private market, this forming a valuable legal precedent for the lawfulness of sale of lunar material. Recently, plans were made public to award the Apollo astronauts with lunar rocks. While in the US there is a popular misconception that it is illegal to own lunar material, the truth lies elsewhere. As the Apollo samples are the property of the US government and a small fraction was stolen, lost, or misplaced, the US government intends to recover this material, unlawfully owned. In the same time, a significant number of individuals have been prosecuted for offering for sale fake lunar rocks. The present paper will analyse the different categories of lunar material according to its ownership status, and will as- sert that private property of lunar material is lawful, and lunar material that will be returned in the future will be able to enter the market without hindrances.

  20. Microwave Dielectric Properties of Ceramic/Semicrystalline Polymer Composites

    NASA Astrophysics Data System (ADS)

    Im, Dong Hyeok; Ju, Han Sae; Kim, Eung Soo

    2012-09-01

    The effects of various ceramics and semicrystalline polymers on the dielectric properties of MgMoO4/polypropylene (PP), MgWO4/PP, NiNb2O6/poly(tetrafluoroethylene) (PTFE), and MgNb2O6/PTFE composites were investigated at microwave frequencies. In the frequency range from 1 to 9.4 GHz, the dielectric constant (K) of the composites showed good frequency stability, while their dielectric loss (\\tan δ) increased with increasing frequency, due to the dipolar relaxation process associated with the matrices. With increasing ceramic content, the K and \\tan δ values of the composites increased, due to the K values of the individual components and interfacial polarization between the ceramics and polymers. For the composites with the same amounts of ceramics, the K value and temperature coefficient of the resonant frequency (TCF) of the composites were dependent on the type of ceramics. Also, the measured K values of the composites were compared with the effective dielectric properties calculated by different theoretical models.

  1. Microwave Dielectric Properties of Ceramic/Semicrystalline Polymer Composites

    NASA Astrophysics Data System (ADS)

    Hyeok Im, Dong; Ju, Han Sae; Kim, Eung Soo

    2012-09-01

    The effects of various ceramics and semicrystalline polymers on the dielectric properties of MgMoO4/polypropylene (PP), MgWO4/PP, NiNb2O6/poly(tetrafluoroethylene) (PTFE), and MgNb2O6/PTFE composites were investigated at microwave frequencies. In the frequency range from 1 to 9.4 GHz, the dielectric constant (K) of the composites showed good frequency stability, while their dielectric loss (tan δ) increased with increasing frequency, due to the dipolar relaxation process associated with the matrices. With increasing ceramic content, the K and tan δ values of the composites increased, due to the K values of the individual components and interfacial polarization between the ceramics and polymers. For the composites with the same amounts of ceramics, the K value and temperature coefficient of the resonant frequency (TCF) of the composites were dependent on the type of ceramics. Also, the measured K values of the composites were compared with the effective dielectric properties calculated by different theoretical models.

  2. Microwave absorption properties of FeCo-coated carbon fibers with varying morphologies

    NASA Astrophysics Data System (ADS)

    Wan, Yizao; Xiao, Jian; Li, Chunzhi; Xiong, Guangyao; Guo, Ruisong; Li, Lili; Han, Ming; Luo, Honglin

    2016-02-01

    Hybridizing carbon materials with magnetic metals and oxides has attracted much attention for enhanced microwave absorption. In this study, a magnetic Fe-Co alloy was coated on the surface of carbon fibers (FeCo@CFs) by electrodeposition. For the first time, different Fe-Co coating morphologies (thin plate, irregular particle, and pyramid) were obtained by adjusting the plating temperature. The morphology, structure, magnetic properties, and complex permittivity and permeability of the FeCo@CFs were determined as a function of plating temperature. Results show that the FeCo@CFs with different coating morphologies exhibit different magnetic properties and complex permittivity. The FeCo@CFs with plate-like morphology demonstrate the best absorption performance. It has been shown that the absorption of FeCo@CFs can be controlled by adjusting the morphology of Fe-Co coating, which provides a new and effective way to endow Fe-Co-coated carbon fibers with good microwave absorption properties.

  3. Properties of aircraft tire materials

    NASA Technical Reports Server (NTRS)

    Dodge, Richard N.; Clark, Samuel K.

    1988-01-01

    A summary is presented of measured elastomeric composite response suitable for linear structural and thermoelastic analysis in aircraft tires. Both real and loss properties are presented for a variety of operating conditions including the effects of temperature and frequency. Suitable micro-mechanics models are used for predictions of these properties for other material combinations and the applicability of laminate theory is discussed relative to measured values.

  4. Functional Properties of Nanostructured Materials

    NASA Astrophysics Data System (ADS)

    Kassing, Rainer; Petkov, Plamen; Kulisch, Wilhelm; Popov, Cyril

    This book, based on the lectures and contributions of the NATO ASI on "Functional Properties of Nanostructured Materials", gives a broad overview on this topic, as it combines basic theoretical articles, papers dealing with experimental techniques, and contributions on advanced and up-to-date applications in fields such as microelectronics, optoelectronics, electrochemistry, sensorics, and biotechnology. In addition, it presents an interdisciplinary approach since the authors came from such different fields as physics, chemistry, engineering, materials science and biology.

  5. On the microwave optical properties of randomly oriented ice hydrometeors

    NASA Astrophysics Data System (ADS)

    Eriksson, P.; Jamali, M.; Mendrok, J.; Buehler, S. A.

    2015-05-01

    Microwave remote sensing is important for observing the mass of ice hydrometeors. One of the main error sources of microwave ice mass retrievals is that approximations around the shape of the particles are unavoidable. One common approach to represent particles of irregular shape is the soft particle approximation (SPA). We show that it is possible to define a SPA that mimics mean optical particles of available reference data over narrow frequency ranges, considering a single observation technique at the time, but that SPA does not work in a broader context. Most critically, the required air fraction varies with frequency and application, as well as with particle size. In addition, the air fraction matching established density parameterisations results in far too soft particles, at least for frequencies above 90 GHz. That is, alternatives to SPA must be found. One alternative was recently presented by Geer and Baordo (2014). They used a subset of the same reference data and simply selected as "shape model" the particle type giving the best overall agreement with observations. We present a way to perform the same selection of a representative particle shape but without involving assumptions on particle size distribution and actual ice mass contents. Only an assumption on the occurrence frequency of different particle shapes is still required. Our analysis leads to the same selection of representative shape as found by Geer and Baordo (2014). In addition, we show that the selected particle shape has the desired properties at higher frequencies as well as for radar applications. Finally, we demonstrate that in this context the assumption on particle shape is likely less critical when using mass equivalent diameter to characterise particle size compared to using maximum dimension, but a better understanding of the variability of size distributions is required to fully characterise the advantage. Further advancements on these subjects are presently difficult to achieve

  6. On the microwave optical properties of randomly oriented ice hydrometeors

    NASA Astrophysics Data System (ADS)

    Eriksson, P.; Jamali, M.; Mendrok, J.; Buehler, S. A.

    2014-12-01

    Microwave remote sensing is important for observing the mass of ice hydrometeors. One of the main error sources of microwave ice mass retrievals is that approximations around the shape of the particles are unavoidable. One common approach to represent particles of irregular shape is the soft particle approximation (SPA). We show that it is possible to define a SPA that mimics mean optical particles of available reference data over narrow frequency ranges, considering a single observation technique at the time, but SPA does not work in a broader context. Most critically, the required air fraction varies with frequency and application, as well as with particle size. In addition, the air fraction matching established density parameterisations results in far too soft particles, at least for frequencies above 90 GHz. That is, alternatives to SPA must be found. One alternative was recently presented by Geer and Baordo (2014). They used a sub-set of the same reference data and simply selected as "shape model" the particle type giving the best overall agreement with observations. We present a way to perform the same selection of a representative particle shape, but without involving assumptions on particle size distribution and actual ice mass contents. Only an assumption on the occurrence frequency of different particle shapes is still required. Our analysis leads to the same selection of representative shape as found by Geer and Baordo (2014). In addition, we show that the selected particle shape has the desired properties also at higher frequencies as well as for radar applications. Finally, we demonstrate that in this context the assumption on particle shape is likely less critical when using mass equivalent diameter to characterise particle size, compared to using maximum dimension, but a better understanding of the variability of size distributions is required to fully characterise the advantage. Further advancements on these subjects are presently difficult to

  7. Near-field microwave inspection and characterization of cement based materials

    NASA Astrophysics Data System (ADS)

    Bois, Karl Joseph

    The objective of this research project has been to investigate the potential of correlating the near-field microwave reflection coefficient properties of hardened cement paste (water and cement powder), mortar (water, cement powder and sand) and concrete (water, cement powder, sand and coarse aggregate) specimens to their various constituent make-up and compressive strengths. The measurements were conducted using open-ended rectangular waveguide probes operating at various microwave frequencies and in-contact with cubic specimens. For each material, various properties of the measured microwave reflection coefficient, such as the mean of the measured magnitude of reflection coefficient, and the standard deviation of the measured magnitude of reflection coefficient at various frequencies were monitored. Subsequently, the measurements were correlated to important parameters such as w/c ratio, s/c ratio, ca/c ratio, cure-state, constituent volume content and compressive strength. Other issues such as the detection of aggregate segregation in concrete as well as the detection chloride in cement paste and mortar were also addressed. Other related issues such as the detection of grout in masonry blocks were also investigated. In achieving these objectives, several theoretical modeling efforts were required, constituting significant contributions to the available literature. A complete analytical full wave expression (i.e. inclusion of higher-order modes) for the fields at the aperture of an open-ended waveguide probe radiating into a dielectric infinite half-space was derived. Also a novel two-port transmission line dielectric property measurement technique for granular and liquid materials was developed. A decision making process, based on the maximum likelihood scheme, was also implemented to determine w/c, s/c and ca/c ratios from the measured mean and standard deviation of reflection coefficient at two frequency bands. Finally, the issue of non-contact measurement was

  8. Design of an ellipsoidal mirror for freewave characterization of materials at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Rojo, M.; Muñoz, J.; Molina-Cuberos, G. J.; García-Collado, Á. J.; Margineda, J.

    2016-03-01

    Free-wave characterization of the electromagnetic properties of materials at microwave frequencies requires that scattering at the edges of the samples and/or holder be minimized. Here, an ellipsoidal mirror is designed and characterized in order to decrease the size of the beam, thereby avoiding the scattering problems, even when relatively small samples are used. In the experimental configuration, both the emitting antenna and sample are located at the mirror focuses. Since both the emitted and reflected (focused) beams are Gaussian in nature, we make use of Gaussian beam theory to carry out the design. The mirror parameters are optimized by numerical simulations (COMSOL Multiphysics®) and then experimentally tested. An experimental setup is presented for dielectric, magnetic and chiral measurement in the 4.5-18 GHz band.

  9. Manufacture of electrical and magnetic graded and anisotropic materials for novel manipulations of microwaves

    PubMed Central

    Grant, P. S.; Castles, F.; Lei, Q.; Wang, Y.; Janurudin, J. M.; Isakov, D.; Speller, S.; Dancer, C.; Grovenor, C. R. M.

    2015-01-01

    Spatial transformations (ST) provide a design framework to generate a required spatial distribution of electrical and magnetic properties of materials to effect manipulations of electromagnetic waves. To obtain the electromagnetic properties required by these designs, the most common materials approach has involved periodic arrays of metal-containing subwavelength elements. While aspects of ST theory have been confirmed using these structures, they are often disadvantaged by narrowband operation, high losses and difficulties in implementation. An all-dielectric approach involves weaker interactions with applied fields, but may offer more flexibility for practical implementation. This paper investigates manufacturing approaches to produce composite materials that may be conveniently arranged spatially, according to ST-based designs. A key aim is to highlight the limitations and possibilities of various manufacturing approaches, to constrain designs to those that may be achievable. The article focuses on polymer-based nano- and microcomposites in which interactions with microwaves are achieved by loading the polymers with high-permittivity and high-permeability particles, and manufacturing approaches based on spray deposition, extrusion, casting and additive manufacture. PMID:26217051

  10. Manufacture of electrical and magnetic graded and anisotropic materials for novel manipulations of microwaves.

    PubMed

    Grant, P S; Castles, F; Lei, Q; Wang, Y; Janurudin, J M; Isakov, D; Speller, S; Dancer, C; Grovenor, C R M

    2015-08-28

    Spatial transformations (ST) provide a design framework to generate a required spatial distribution of electrical and magnetic properties of materials to effect manipulations of electromagnetic waves. To obtain the electromagnetic properties required by these designs, the most common materials approach has involved periodic arrays of metal-containing subwavelength elements. While aspects of ST theory have been confirmed using these structures, they are often disadvantaged by narrowband operation, high losses and difficulties in implementation. An all-dielectric approach involves weaker interactions with applied fields, but may offer more flexibility for practical implementation. This paper investigates manufacturing approaches to produce composite materials that may be conveniently arranged spatially, according to ST-based designs. A key aim is to highlight the limitations and possibilities of various manufacturing approaches, to constrain designs to those that may be achievable. The article focuses on polymer-based nano- and microcomposites in which interactions with microwaves are achieved by loading the polymers with high-permittivity and high-permeability particles, and manufacturing approaches based on spray deposition, extrusion, casting and additive manufacture. PMID:26217051

  11. Graphite immobilisation in iron phosphate glass composite materials produced by microwave and conventional sintering routes

    NASA Astrophysics Data System (ADS)

    Mayzan, M. Z. H.; Stennett, M. C.; Hyatt, N. C.; Hand, R. J.

    2014-11-01

    An investigation of microwave and conventional processing of iron phosphate based graphite glass composite materials as potential wasteforms for the immobilisation of irradiated graphite is reported. For the base iron phosphate glass, full reaction of the raw materials and formation of a glass melt occurs with consequent removal of porosity at 8 min microwave processing. When graphite is present, iron phosphate crystalline phases are formed with higher levels of residual porosity than in the sample prepared using conventional sintering under argon. It is found that graphite reacts with the microwave field when in powder form but this reaction is minimised when the graphite is incorporated into a pellet, and that the graphite also impedes sintering of the glass. Mössbauer spectroscopy indicates that reduction of iron also occurs with concomitant graphite oxidation. Conventionally sintered samples had lower porosities than the equivalent microwaved ones.

  12. Mechanical, Dielectric, and Microwave-Absorption Properties of Alumina Ceramic Containing Dispersed Ti3SiC2

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Luo, Fa; Su, Jinbu; Zhou, Wancheng; Zhu, Dongmei

    2015-03-01

    Dense Al2O3 ceramics containing dispersed Ti3SiC2 were fabricated by hot-pressed sintering. Effects of Ti3SiC2 content on the mechanical, dielectric, and microwave-absorption properties of the ceramics were investigated. The bulk density, flexural strength, and dielectric constant were enhanced by increasing the Ti3SiC2 content. The complex permittivity increased dramatically when the Ti3SiC2 content was above the percolation threshold. The dielectric performance of the ceramics at high temperatures was also studied. The results revealed increases in both the real and imaginary parts with increasing temperature. Ceramic 2.2 mm thick containing 10% ( w/ w) Ti3SiC2 had the optimum microwave-absorption properties. The absorption bandwidth below -5 dB was in the range 8.2-12.4 GHz with a minimum value of -20 dB at 9.56 GHz. Although the reflection loss increased with the increasing temperature, the ceramic still had favorable microwave-absorption properties throughout the X-band. This study contributes to the development of the microwave absorption materials for high-temperature application.

  13. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1987-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and Earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorping properties of potential constituents is available. The use of theoretically derived microwave absorption properties for such atmospheric constituents, or laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurement of the microwave properties of atmospheric gases under simulated conditions for the outer planets were conducted. Results of these measurements are discussed.

  14. Investigation of interlayer materials for the microwave joining of SiC

    SciTech Connect

    Silberglitt, R.; Palaith, D. ); Black, W.M.; Sa'adaldin, H.S. ); Katz, J.D.; Blake, R.D. )

    1991-01-01

    Microwave joining of ceramics has the potential for increased speed and convenience. Joints have been made in alumina, mullite and silicon nitride with flexure strength approaching, and in some cases exceeding, that of the as received material in a fraction of the time that is customarily required with conventional techniques. This paper describes the initial results of investigations aimed at applying microwave joining to SiC and other carbide ceramics. 8 refs., 5 figs.

  15. Properties of microwave plasma torch operating at a low pressure

    SciTech Connect

    Cho, Soon C.; Uhm, Han S.; Hong, Yong C.; Kim, Jae H.

    2008-10-15

    A microwave plasma torch system is attached to a low-pressure chamber in this study. The electric field induced in a quartz discharge tube by microwave radiation breaks down the gas at a sufficiently low pressure, igniting the plasma, which is continuously sustained by the microwave radiation. The plasma profile at a very low pressure is shown to be asymmetric with higher density on the incoming side of the microwaves. The gas temperature at the bright spot of the torch plasma measured via the optical emission from hydroxide radicals is shown to increase drastically upon high-pressure operation as the microwave power increases. The electron density at the torch flame is measured by recording the Stark broadening of the hydrogen Balmer beta line. The plasma density increases as the microwave power increases. The typical argon plasma density of a plasma torch powered at 500 W under a pressure of 150 Torr is on the order of 10{sup 14}/cm{sup 3}. The electron temperature in the argon torch plasma was estimated to be 1.5 eV, thereby effectively exciting the molecules in the torch gas. Disintegration of nitrogen fluoride (NF{sub 3}) indicates that a microwave plasma torch operating at a low pressure can efficiently generate an abundant amount of chemical radicals.

  16. Laboratory evaluation of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, P. G.

    1984-01-01

    The microwave absorbing properties of gaseous sulfuric acid (H2SO4) under Venus atmospheric conditions are investigated. The results are applied to measurements from Mariner 5, Mariner 10, and Pioneer/Venus Radio Occultation experiments, to determine abundancies of gaseous sulfuric acid in the Venus atmosphere. The microwave properties of the vapors accompanying liquid H2SO4 are studied to estimate the vapor pressure in an atmospheric model.

  17. Satellite material contaminant optical properties

    NASA Technical Reports Server (NTRS)

    Wood, B. E.; Bertrand, W. T.; Seiber, B. L.; Kiech, E. L.; Falco, P. M.; Holt, J. D.

    1990-01-01

    The Air Force Wright Research and Development Center and the Arnold Engineering Development Center are continuing a program for measuring optical effects of satellite material outgassing products on cryo-optic surfaces. Presented here are infrared (4000 to 700 cm(-1)) transmittance data for contaminant films condensed on a 77 K geranium window. From the transmittance data, the contaminant film refractive and absorptive indices (n, k) were derived using an analytical thin-film interference model with a nonlinear least-squares algorithm. To date 19 materials have been studied with the optical contents determined for 13 of those. The materials include adhesives, paints, composites, films, and lubricants. This program is continuing and properties for other materials will be available in the future.

  18. Dynamic properties of ceramic materials

    SciTech Connect

    Grady, D.E.; Wise, J.L.

    1993-09-01

    Controlled impact methods have been employed to obtain dynamic response properties of armor materials. Experimental data have been obtained for high-strength ceramics. Continued analysis of time-resolved velocity interferometer measurements has produced systematic material-property data for Hugoniot and release response, initial and post-yield strength, pressure-induced phase transformation, and dynamic fracture strength. A new technique has been developed to measure hydrodynamic properties of ceramic through shock-wave experiments on metal-ceramic composites and data obtained for silicon carbide. Additional data on several titanium diboride ceramics and high-quality aluminum oxide ceramic have been acquired, and issues regarding the influence of microstructure on dynamic properties have emerged. Comparison of dynamic (Hugoniot elastic limit) strength and indentation hardness data has been performed and important correlations revealed. Innovative impact experiments on confined and unconfined alumina rods using axial and transverse VISAR diagnostics have been demonstrated which permit acquisition of multiaxial dynamic response data. Dynamic failure properties of a high-density aluminosilicate glass, similar in composition to the intergranular glassy phase of some aluminas, have been investigated with regard to yield, spall, and failure-wave propagation.

  19. Excellent microwave-absorbing properties of elliptical Fe₃O₄ nanorings made by a rapid microwave-assisted hydrothermal approach.

    PubMed

    Liu, Yun; Cui, Tingting; Wu, Tong; Li, Yana; Tong, Guoxiu

    2016-04-22

    High-quality elliptical polycrystalline Fe3O4 nanorings (NRs) with continuously tunable size have been synthesized in large amounts via a rapid microwave-assisted hydrothermal approach. The surface-protected glucose reducing/etching/Ostwald ripening mechanism is responsible for the formation of NRs. Ring size can be modulated by selecting iron glycolate nanosheets with various sizes as precursors. The size-dependent magnetic behavior of the NRs was observed. Our research gives insights into the understanding of the microwave absorption mechanism of elliptical Fe3O4 NRs. Owing to their large specific surface area, shape anisotropy, and closed ring-like configuration, elliptical polycrystalline Fe3O4 NRs exhibited significantly enhanced microwave absorption performance compared with Fe3O4 circular NRs, nanosheets, microspheres, nanospindles, and nanotubes. An optimal reflection loss value of -41.59 dB is achieved at 5.84 GHz and R(L) values (≤-20 dB) are observed at 3.2-10.4 GHz. Some new mechanisms including multiple scattering, oscillation resonance absorption, microantenna radiation, and interference are also crucial to the enhanced absorption properties of NRs. These findings indicate that ring-like nanostructures are a promising structure for devising new and effective microwave absorbers. PMID:26962718

  20. The research of ceramic materials for applications in the glass industry including microwave heating techniques

    NASA Astrophysics Data System (ADS)

    Kogut, K.; Kasprzyk, K.; Zboromirska-Wnukiewicz, B.; Ruziewicz, T.

    2016-02-01

    The melting of a glass is a very energy-intensive process. Selection of energy sources, the heating technique and the method of heating recovery are a fundamental issue from the furnace design point of view of and economic effectiveness of the process. In these processes the problem constitutes the lack of the appropriate ceramic materials that would meet the requirements. In this work the standard ceramic materials were examined and verified. The possibilities of application of microwave techniques were evaluated. In addition the requirements regarding the parameters of new ceramic materials applied for microwave technologies were determined.

  1. Size limitations for microwave cavity to simulate heating of blanket material in fusion reactor

    SciTech Connect

    Wolf, D.

    1987-01-01

    The power profile in the blanket material of a nuclear fusion reactor can be simulated by using microwaves at 200 MHz. Using these microwaves, ceramic breeder materials can be thermally tested to determine their acceptability as blanket materials without entering a nuclear fusion environment. A resonating cavity design is employed which can achieve uniform cross sectional heating in the plane transverse to the neutron flux. As the sample size increases in height and width, higher order modes, above the dominant mode, are propagated and destroy the approximation to the heating produced in a fusion reactor. The limits at which these modes develop are determined in the paper.

  2. Noise properties of microwave signals synthesized with femtosecond lasers.

    PubMed

    Ivanov, Eugene N; McFerran, John J; Diddams, Scott A; Hollberg, Leo

    2007-04-01

    We discuss various aspects of high resolution measurements of phase fluctuations at microwave frequencies. This includes methods to achieve thermal noise limited sensitivity, along with the improved immunity to oscillator amplitude noise. A few prototype measurement systems were developed to measure phase fluctuations of microwave signals extracted from the optical pulse trains generated by femtosecond lasers. This enabled first reliable measurements of the excess phase noise associated with optical-to-microwave frequency division. The spectral density of the excess phase noise was found to be -140 dBc/Hz at 100 Hz offset from the 10 GHz carrier which was almost 40 dB better than that of a high quality microwave synthesizer. PMID:17441583

  3. Novel materials, fabrication techniques and algorithms for microwave and THz components, systems and applications

    NASA Astrophysics Data System (ADS)

    Liang, Min

    This dissertation presents the investigation of several additive manufactured components in RF and THz frequency, as well as the applications of gradient index lens based direction of arrival (DOA) estimation system and broadband electronically beam scanning system. Also, a polymer matrix composite method to achieve artificially controlled effective dielectric properties for 3D printing material is studied. Moreover, the characterization of carbon based nano-materials at microwave and THz frequency, photoconductive antenna array based Terahertz time-domain spectroscopy (THz-TDS) near field imaging system, and a compressive sensing based microwave imaging system is discussed in this dissertation. First, the design, fabrication and characterization of several 3D printed components in microwave and THz frequency are presented. These components include 3D printed broadband Luneburg lens, 3D printed patch antenna, 3D printed multilayer microstrip line structure with vertical transition, THz all-dielectric EMXT waveguide to planar microstrip transition structure and 3D printed dielectric reflectarrays. Second, the additive manufactured 3D Luneburg Lens is employed for DOA estimation application. Using the special property of a Luneburg lens that every point on the surface of the Lens is the focal point of a plane wave incident from the opposite side, 36 detectors are mounted around the surface of the lens to estimate the direction of arrival (DOA) of a microwave signal. The direction finding results using a correlation algorithm show that the averaged error is smaller than 1º for all 360 degree incident angles. Third, a novel broadband electronic scanning system based on Luneburg lens phased array structure is reported. The radiation elements of the phased array are mounted around the surface of a Luneburg lens. By controlling the phase and amplitude of only a few adjacent elements, electronic beam scanning with various radiation patterns can be easily achieved

  4. Controlled growth of Cu-Ni nanowires and nanospheres for enhanced microwave absorption properties.

    PubMed

    Wang, Xiaoxia; Dong, Lifeng; Zhang, Baoqin; Yu, Mingxun; Liu, Jingquan

    2016-03-29

    Copper is a good dielectric loss material but has low stability, whereas nickel is a good magnetic loss material and is corrosion resistant but with low conductivity, therefore Cu-Ni hybrid nanostructures have synergistic advantages as microwave absorption (MA) materials. Different Cu/Ni molar ratios of bimetallic nanowires (Cu13@Ni7, Cu5@Ni5 and Cu7@Ni13) and nanospheres (Cu13@Ni7, Cu5@Ni5 and Cu1@Ni3) have been successfully synthesized via facile reduction of hydrazine under similar reaction conditions, and the morphology can be easily tuned by varying the feed ratio or the complexing agent. Apart from the concentrations of Cu(2+) and Ni(2+), the reduction parameters are similar for all samples to confirm the effects of the Cu/Ni molar ratio and morphology on MA properties. Ni is incorporated into the Cu-Ni nanomaterials as a shell over the Cu core at low temperature, as proved by XRD, SEM, TEM and XPS. Through the complex relative permittivity and permeability, reflection loss was evaluated, which revealed that the MA capacity greatly depended on the Cu/Ni molar ratio and morphology. For Cu@Ni nanowires, as the molar ratio of Ni shell increased the MA properties decreased accordingly. However, for Cu@Ni nanospheres, the opposite trend was found, that is, as the molar ratio of the Ni shell increased the MA properties increased. PMID:26890585

  5. Controlled growth of Cu-Ni nanowires and nanospheres for enhanced microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxia; Dong, Lifeng; Zhang, Baoqin; Yu, Mingxun; Liu, Jingquan

    2016-03-01

    Copper is a good dielectric loss material but has low stability, whereas nickel is a good magnetic loss material and is corrosion resistant but with low conductivity, therefore Cu-Ni hybrid nanostructures have synergistic advantages as microwave absorption (MA) materials. Different Cu/Ni molar ratios of bimetallic nanowires (Cu13@Ni7, Cu5@Ni5 and Cu7@Ni13) and nanospheres (Cu13@Ni7, Cu5@Ni5 and Cu1@Ni3) have been successfully synthesized via facile reduction of hydrazine under similar reaction conditions, and the morphology can be easily tuned by varying the feed ratio or the complexing agent. Apart from the concentrations of Cu2+ and Ni2+, the reduction parameters are similar for all samples to confirm the effects of the Cu/Ni molar ratio and morphology on MA properties. Ni is incorporated into the Cu-Ni nanomaterials as a shell over the Cu core at low temperature, as proved by XRD, SEM, TEM and XPS. Through the complex relative permittivity and permeability, reflection loss was evaluated, which revealed that the MA capacity greatly depended on the Cu/Ni molar ratio and morphology. For Cu@Ni nanowires, as the molar ratio of Ni shell increased the MA properties decreased accordingly. However, for Cu@Ni nanospheres, the opposite trend was found, that is, as the molar ratio of the Ni shell increased the MA properties increased.

  6. Method of producing carbon monoxide and hydrogen by gasification of solid carbonaceous material involving microwave irradiation

    SciTech Connect

    Helm, J.L. Jr.

    1984-03-06

    A process is claimed for the gasification of carbon of solid carbonaceous material to form carbon monoxide and hydrogen by contacting the material with superheated steam and irradiating the product of said contacting with an amount of microwave energy sufficient to gasify said carbon, and apparatus therefor.

  7. Electrical conductivity of microwave heated polyaniline nanotubes and possible mechanism of microwave absorption by materials.

    PubMed

    Murai, Takahiro; Fukasawa, Ryo; Muraoka, Tohru; Takauchi, Hiroyuki; Gotoh, Yasuo; Takizawa, Tokihiro; Matsuse, Takehiro

    2009-01-01

    In the course of experiments to perform deprotonation and carbonization of doped polyaniline (PANI) nanotubes (NTs) by irradiating directly 2.45 GHz microwave (MW) in our microwave heating system (MWHS), we have discovered that the PANI-NTs self heat by absorbing the MW but the temperature of the PANI-NTs stops rising around 300 degrees C in spite of the heightened MW power Furthermore, we have found that the MW irradiated PANI-NTs have transferred from electrical conductor to insulator depending on the temperature of the PANI-NTs. By measuring electron spin resonance (ESR) spectra of the MW heated PANI-NTs, the existence of the unpaired electrons is shown to have a strong correlation between the degree of MW absorption and the transition in the electrical conductivities. In order to deprotonate and carbonize further the PANI-NTs, we have performed heat treatment for the PANI-NTs up to a temperature (T(HT)) of about 1200 degrees C in the same MWHS using carbon fiber which self heats by absorbing MW. The chemical transformations in the PANI-NTs induced by the heat treatments are discussed by measuring the X-ray photoelectron spectroscopy (XPS) spectra. Finally, the temperature dependence of electrical conductivities of the PANI-NTs are measured in order to investigate the mechanism of electrical conduction of the heat treated PANI-NTs. PMID:21384721

  8. Microcrystalline-cellulose and polypropylene based composite: A simple, selective and effective material for microwavable packaging.

    PubMed

    Ummartyotin, S; Pechyen, C

    2016-05-20

    Cellulose based composite was successfully designed as active packaging with additional feature of microwavable properties. Small amount of cellulose with 10 μm in diameter was integrated into polypropylene matrix. The use of maleic anhydride was employed as coupling agent. Thermal and mechanical properties of cellulose based composite were superior depending on polypropylene matrix. Crystallization temperature and compressive strength were estimated to be 130 °C and 5.5 MPa. The crystal formation and its percentage were therefore estimated to be 50% and it can be predicted on the feasibility of microwavable packaging. Morphological properties of cellulose based composite presented the good distribution and excellent uniformity. It was remarkable to note that cellulose derived from cotton can be prepared as composite with polypropylene matrix. It can be used as packaging for microwave application. PMID:26917383

  9. Preparation and characterization of novel glass-ceramic tile with microwave absorption properties from iron ore tailings

    NASA Astrophysics Data System (ADS)

    Yao, Rui; Liao, SongYi; Dai, ChangLu; Liu, YuChen; Chen, XiaoYu; Zheng, Feng

    2015-03-01

    A novel glass-ceramic tile consisting of one glass-ceramic layer (GC) attaining microwave absorption properties atop ceramic substrate was prepared through quench-heat treatment route derived from iron ore tailings (IOTs) and commercial raw materials (purity range 73-99%). X-ray diffraction (XRD), SEM, Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Physical property measurement system (PPMS) and Vector network analyzer (VNA) measurements were carried out to investigate phase, microstructure, magnetic and microwave absorption aspects of the glass-ceramic layer. Roughly 80.6±1.7 wt% borosilicate glass and 19.4±1.7 wt% spinel ferrite with chemical formula of (Zn2+0.17Fe3+0.83)[Fe3+1.17Fe2+0.06Ni2+0.77]O4 were found among the tested samples. Absorption of Electromagnetic wave by 3 mm thick glass-ceramic layer at frequency of 2-18 GHz reached peak reflection loss (RL) of -17.61 dB (98.27% microwave absorption) at 10.31 GHz. Altering the thickness of the glass-ceramic layer can meet the requirements of different level of microwave absorption.

  10. High temperature acoustic and hybrid microwave/acoustic levitators for materials processing

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin

    1990-01-01

    The physical acoustics group at the Jet Propulsion Laboratory developed a single mode acoustic levitator technique for advanced containerless materials processing. The technique was successfully demonstrated in ground based studies to temperatures of about 1000 C in a uniform temperature furnace environment and to temperatures of about 1500 C using laser beams to locally heat the sample. Researchers are evaluating microwaves as a more efficient means than lasers for locally heating a positioned sample. Recent tests of a prototype single mode hybrid microwave/acoustic levitator successfully demonstrated the feasibility of using microwave power as a heating source. The potential advantages of combining acoustic positioning forces and microwave heating for containerless processing investigations are presented in outline form.

  11. Material properties of oxide superconductors

    SciTech Connect

    Phillips, J.C.

    1996-12-31

    The differences between the old (inter-) metallic superconductors and the new oxide superconductors are not limited to the much higher values of {Tc} attainable in the latter. There are many pervasive differences caused directly by oxide chemistry, quasi-perovskite local coordination configurations, and layered metal-semiconductor-metal{prime}-semiconductor-structures. When these differences are ignored, for instance in theoretical models which make effective medium approximations, many experiments appear to present anomalous results. These anomalies largely disappear when account is taken of the real materials properties of the cuprates and other new oxide superconductors, for instance in theoretical models which treat transport as a partially percolative process. This percolative process directly reflects the fact that the highest values of {Tc}, as well as the most anomalous normal-state transport properties, occur in materials vicinal to a metal-insulator transition. As the metallic and insulating regions alternate even in single-crystal samples, effective medium models, and most effective-medium parameters, lose their significance. Examples of attempts to measure microscopic properties illustrate the importance of filamentary effects on both normal-state and superconductive properties.

  12. Synthesis and microwave absorption properties of magnetite nanoparticles.

    PubMed

    Shao, XiaoPing; Dai, Bo; Zhang, XiaoWei; Ma, YongJun

    2012-02-01

    Nanoparticles of Fe3O4 with various sizes were synthesized from FeCl3 x 6H2O, FeCl2 x 4H2O and NaOH by coprecipitation process. The crystal structure, morphology, particle size and magnetic property of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). It was found that the molar ratio of ferrous to ferric played an important role in the formation of Fe3O4 nanoparticles. The particle mean diameter swelled from approximately 10 to approximately 20 nm with the molar ratio range from 1:2 to 6:1. The saturation magnetization and the coercivity increased correspondingly. The complex permittivity epsilon(r) and permeability mu(r) of the Fe3O4 mixture with paraffin were measured using vector network analysis. Values of epsilon(r), and mu(r) were used to determine the reflection loss at various sample thicknesses, based on a model of microwave absorbing layer backed by a metal plate. The minimal reflection loss or the dip shifts to a lower frequency region with increasing thickness. When the thickness is 5 mm, the minimal reflection loss of Fe3O4 synthesized with the molar ratio of 6:1 and paraffin wax composites reaches -35.1 dB at 5.2 GHz and -30.2 dB at 17.6 GHz, respectively. The minimal reflection loss is attributed to the thickness of the absorber approximates an odd number multiple of a quarter of the propagation wavelength. PMID:22629906

  13. Microwave cavity studies for thermal testing of ceramic breeder materials

    SciTech Connect

    Kuston, R.L.

    1987-01-01

    Dielectric heating of proposed ceramic tritium breeder material to study the thermomechanical and thermal-hydraulic properties of the material has been previously suggested. Recent computer studies using codes capable of modeling three-dimensional EM cavities with enclosed dielectric material have been used to determine the size limitations of cavity designs at 200 MHz. The sample can be as large as 0.44 /times/ 0.72m in the plane that is transverse to the direction of neutron flux. The uniformity of volumetric heating over the transverse plane is constant to within a few percent. The sample can be as long as 10cm in the direction of the heat flux and match the expected exponential decay of heat generation, exp( /minus/z/lambda), to within +/minus/8%. The design of the chamber is decribed, including the sample region, additional dielectric loading blocks on two sides of the sample region that are required to generate the field uniformity in the transverse plane, and a description of the matching-section portion of the cavity which provides the correct geometry to cause the cavity to resonate at 200 MHz with the right z dependence to stimulate the exponentially-decaying heat profile in the sample region. The matching section consists of two dielectric slabs, one on each wall of the chamber, and an air or free space region in the center of the matching section. The coupling loop is located near the wall end of the matching section in the free space region. 7 refs., 2 figs.

  14. Determination of Electromagnetic Properties of Mesh Material Using Advanced Radiometer Techniques

    NASA Technical Reports Server (NTRS)

    Arrington, R. F.; Blume, H. J. C.

    1985-01-01

    The need for a large diameter deployable antenna to map soil moisture with a 10 kilometer or better resolution using a microwave radiometer is discussed. A 6 meter deployable antenna is also needed to map sea surface temperature on the Navy Remote Ocean Sensor System (NROSS). Both of these deployable antennas require a mesh membrane material as the reflecting surface. The determination of the electromagnetic properties of mesh materials is a difficult problem. The Antenna and Microwave Research Branch (AMRB) of Langley Research Center was asked to measure the material to be used on MROSS by NRL. A cooperative program was initiated to measure this mesh material using two advanced radiometer techniques.

  15. Microwave absorption property of plasma spray W-type hexagonal ferrite coating

    NASA Astrophysics Data System (ADS)

    Wei, Shicheng; Liu, Yi; Tian, Haoliang; Tong, Hui; Liu, Yuxin; Xu, Binshi

    2015-03-01

    In order to enhance the adhesion strength of microwave absorbing materials, W-type hexagonal ferrite coating is fabricated by plasma spray. The feedstock of ferrite powders is synthesized by solid-state reaction and spray dried process. Microstructures of the coating are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectra (EDS). Hexagonal ferrite coating is successfully deposited on the substrate with adhesion strength of 28 MPa. The magnetic property of ferrite samples is measured using vibrating sample magnetometer (VSM). Saturation magnetization of the ferrite coating is lower than ferrite powder. Reflection loss of the hexagonal ferrite coating is measured in frequency of 2-18 GHz. The result shows that the coating is suitable for electromagnetic wave absorbers in Ku-band.

  16. Preparation and Microwave Absorption Properties of Novel Carbon Nanofiber/Fe3O4 Composites.

    PubMed

    Ren, Yong; Dai, Bo; Wang, Gai-Hua; Zhang, Xiao-Wei; Zhu, Pei; Li, Shi-Rong

    2015-04-01

    Novel, carbonized bacterial cellulose (CBC)/Fe3O4 nanocomposites were synthesized using vacuum filtration and annealing (VFA) methods. The as-synthesized products were characterized by scanning electron microscopy, vibrating sample magnetometry, and transmission electron microscopy. The complex permittivity and permeability of Fe3O4-CBC (5 wt.% CBC)/paraffin wax composites were measured by vector network analysis. To study the microwave absorption (MA) performances, we compared the VFA products with the vacuum filtration (VF) products. The VFA products exhibited better absorption performances because of their larger dielectric loss. When the matching thickness was 2.4 mm, the calculated reflection loss reached a minimum value of -27 dB when VFA was used and a value of -11 dB when VF was used. The wide-range MA properties of these materials lead to potential applications in MA fields. PMID:26353503

  17. Microwave processing of cement and concrete materials – towards an industrial reality?

    SciTech Connect

    Buttress, Adam Jones, Aled; Kingman, Sam

    2015-02-15

    Each year a substantial body of literature is published on the use of microwave to process cement and concrete materials. Yet to date, very few if any have lead the realisation of a commercial scale industrial system and is the context under which this review has been undertaken. The state-of the–art is evaluated for opportunities, and the key barriers to the development of new microwave-based processing techniques to enhance production, processing and recycling of cement and concrete materials. Applications reviewed include pyro-processing of cement clinker; accelerated curing, non-destructive testing and evaluation (NDT&E), and end-of-life processing including radionuclide decontamination.

  18. Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

    DOEpatents

    Meek, T.T.; Blake, R.D.

    1985-04-03

    A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate.

  19. Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

    DOEpatents

    Meek, T.T.; Blake, R.D.

    1987-09-22

    A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate. 2 figs.

  20. Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

    DOEpatents

    Meek, Thomas T.; Blake, Rodger D.

    1987-01-01

    A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate.

  1. Microwave properties of polymer composites containing combinations of micro- and nano-sized magnetic fillers.

    PubMed

    Kolev, Svetoslav; Koutzarova, Tatyana; Yanev, Andrey; Ghelev, Chavdar; Nedkov, Ivan

    2008-02-01

    We investigated the microwave absorbing properties of composite bulk samples with nanostructured and micron-sized fillers. As magnetic fillers we used magnetite powder (Fe3O4 with low magnetocrystalline anisotropy) and strontium hexaferrite (SrFe12O9 with high magnetocrystalline anisotropy). The dielectric matrix consisted of silicone rubber. The average particle size was 30 nm for the magnetite powder and 6 micro/m for the strontium hexaferrite powder. The micron-sized SrFe12O19 powder was prepared using a solid-state reaction. We investigated the influence of the filler concentration and the filler ratio (Fe3O4/SrFe12O19) in the polymer matrix on the microwave absorption in a large frequency range (1 / 18 GHz). The results obtained showed that the highly anisotropic particles become centers of clusterification and the small magnetite particles form magnetic balls with different diameter depending on the concentration. The effect of adding micron-sized SrFe12O19 to the nanosized Fe3O4 filler in composites absorbing structures has to do with the ferromagnetic resonance (FMR) shifting to the higher frequencies due to the changes in the ferrite filler's properties induced by the presence of a magnetic material with high magnetocrystalline anisotropy. The two-component filler possesses new values of the saturation magnetization and of the anisotropy constant, differing from those of both SrFe12O1919 and Fe3O4, which leads to a rise in the effective anisotropy field. The results demonstrate the possibility to vary the composite's absorption characteristics in a controlled manner by way of introducing a second magnetic material. PMID:18464386

  2. Measurements of microwave transmission characteristics through various configurations of fluidized bed materials

    SciTech Connect

    Not Available

    1980-05-01

    The feasibility of developing a microwave diagnostic system for measurement of bubbles in a fluidized bed combustion system has been experimentally investigated. Experiments were performed in a simple waveguide geometry, using microwave frequencies from 2.4 to 3.9 GHz. Styrofoam spacers were used to simulate bubbles in bed materials, such as Greer limestone. The results show that it is feasible to develop a diagnostic system based on microwave transmission through a system consisting of gaps in a limestone media, such as a fluidized bed. The gap has been shown to perturb the transmitted power, and to be very sensitive to bubble and bed material dimensions. Resonance effects are shown to occur when dimensions are integer multiples of a quarter wavelength.

  3. Effect of Microwave Irradiation on the Physicochemical and Digestive Properties of Lotus Seed Starch.

    PubMed

    Zeng, Shaoxiao; Chen, Bingyan; Zeng, Hongliang; Guo, Zebin; Lu, Xu; Zhang, Yi; Zheng, Baodong

    2016-03-30

    The objective of this study is to investigate the effect of microwave irradiation on the physicochemical and digestive properties of lotus seed starch. The physicochemical properties of lotus seed starch were characterized by light microscopy, (1)H NMR, FT-IR spectroscopy, and HPSEC-MALLS-RI. The starch-water interaction and crystalline region increased due to the changed water distribution of starch granules and the increase of the double-helix structure. The swelling power, amylose leaching, molecular properties, and radius of gyration reduced with the increasing microwave power, which further affected the sensitivity of lotus seed starch to enzymatic degradation. Furthermore, the resistant starch and slowly digestible starch increased with the increasing microwave irradiation, which further resulted in their decreasing hydrolysis index and glycemic index. The digestive properties of lotus seed starch were mainly influenced by the reduced branching degree of amylopectin and the strong amylose-amylose interaction. PMID:26912092

  4. Processing, electrical and microwave properties of sputtered Tl-Ca-Ba-Cu-O superconducting thin films

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; Kapoor, V. J.; Chorey, C. M.; Bhasin, K. B.

    1993-01-01

    A reproducible fabrication process has been established for TlCaBaCuO thin films on LaAlO3 substrates by RF magnetron sputtering and post-deposition processing methods. Electrical transport properties of the thin films were measured on patterned four-probe test devices. Microwave properties of the films were obtained from unloaded Q measurements of all-superconducting ring resonators. This paper describes the processing, electrical and microwave properties of Tl2Ca1Ba2Cu2O(x) 2122-plane phase thin films.

  5. Microwave properties of RF- sputtered ZnFe{sub 2}O{sub 4} thin films

    SciTech Connect

    Garg, T. Kulkarni, A. R.; Venkataramani, N.; Sahu, B. N.; Prasad, Shiva

    2014-04-24

    In this work, RF- magnetron sputtering technique has been employed to deposit nanocrystalline ZnFe{sub 2}O{sub 4} thin films at room temperature. The as grown films were ex-situ annealed in air for 2 h at temperatures from 150°C to 650°C. X-ray diffraction, vibrating sample magnetometer and ferromagnetic resonance were used to analyze the phase formation, magnetic properties and microwave properties respectively. From the hysteresis loops and ferromagnetic resonance spectra taken at room temperature, a systematic study on the effect of O{sub 2} plasma on microwave properties with respect to processing temperature has been carried out.

  6. Studies of Microwave Absorption Properties of Carbon Nanotubes/Epoxy Composites

    NASA Astrophysics Data System (ADS)

    Zhao, Guang-Lin

    2010-10-01

    Less weight, excellent mechanical properties, and high efficiency in absorbing electromagnetic (EM) wave make carbon nanotubes (CNTs) composites attractive for microwave technology applications. Multi-walled carbon nanotubes (MWNTs) have much higher performance-to-price ratio (PPR) than SWNTs do in the composite applications. In this work, we aim to study the effect of the outside diameter (OD) distributions of MWNTs on their microwave absorption properties. We have fabricated six groups of carbon nanotube/epoxy composite samples with various OD distributions. The weight percentages of MWNTs in the composites were controlled in the range from 1 to 10%. We utilized a microwave resonant cavity technique to measure the microwave absorption properties of all the sixty samples around the central frequency of 9.968 GHz. Our results have shown that the maxima of EM wave absorptions for the six groups of samples were all around 7% MWNTs weight percentage. We further studied the effective attenuations of the electric and magnetic fields in six groups of MWNT composite samples with the same (7 %) MWNT blend in epoxy. The results show that, in general, the MWNTs with smaller diameters have higher microwave absorption at 9.968 GHz. However, sample group M5 (OD<8nm) shows unusual results, a lower microwave absorption than the other samples. We then used a scanning electron microscope (SEM) to study the morphologies of the MWNT samples. Based on the SEM analysis and microwave absorption measurements, we found that the efficiency of the microwave absorption of MWNT/Epoxy composites is strongly affected by the morphologies/structures of MWNTs in individual bundles.

  7. Enhanced microwave absorption properties of CTAB assisted Pr-Cu substituted nanomaterial

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Riaz, Saira; Khan, Hasan M.; Ashiq, Muhammad Naeem; Hussain, S. Sajjad; Rana, Mazhar

    2016-09-01

    In this study, the rare earth Pr3+and divalent Cu2+ elements substituted Sr1-xPrxMn2Fe16-yCuyO27 (x=0, 0.02, 0.06, 0.1 and y=0, 0.1, 0.3, 0.5) W-type hexagonal ferrites were prepared by Sol-Gel method. TGA and DSC analysis of as prepared material was carried out to confirm the temperature at which required phase can be obtained. The XRD patterns exhibit the single phase for all the samples and the lattice parameters were changed with the additives. The absorption bands at wave number 636 and 554 cm-1 in FTIR spectrum indicate the stretching vibration of metal-oxygen ions which also ratifies the single phase for the prepared material. Microstructural analysis confirms the agglomeration of nanograins which leads to formation of platelet like structure which cause in the enhancement of the microwave absorption properties of material. The minimum reflection loss of -59.8 dB at 9.34 GHz frequency was observed makes the prepared material good candidate to be used in super high frequency application. The attenuation constant and reflectivity results are also in good agreement with minimum reflection losses results.

  8. Study on microwave absorbing properties of carbonyl-iron composite coating based on PVC and Al sheet

    NASA Astrophysics Data System (ADS)

    Yuping, Duan; Guangli, Wu; Shuchao, Gu; Shuqing, Li; Guojia, Ma

    2012-05-01

    To suppress the increasingly terrible electromagnetic pollution, microwave absorption coatings based on polyvinyl chloride (PVC) sheet have been fabricated, employing polyurethane varnish (PU) as matrix and carbonyl-iron particle (CIP) as absorbent. The morphology, static magnetic and microwave absorption properties of CIP were characterized by scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA), respectively. Bruggeman's equation was introduced to calculate the electromagnetic parameters of materials in the frequency range of 2-18 GHz and the loss mechanisms were discussed. Furthermore, the microwave absorption properties of composite coatings with different component content and thickness were investigated. The results show that the electromagnetic properties of the composite heavily depended on the particle loadings. The minimum reflection peaks of the coatings shift towards the lower frequency region with the increase of CIP content or coating thickness. PVC-based coatings with a component content of 1:7 (PU:CIP mass ratio) in CIP/PU layer, exhibit a minimum reflection loss value of -29 dB at 4 GHz and a permissible reflection loss (RL ≤ -10 dB) frequency band of 2-6 GHz, which is much better than the performance of the common metal-based coatings in the lower frequency.

  9. Microwave-assisted catalytic pyrolysis of switchgrass for improving bio-oil and biochar properties.

    PubMed

    Mohamed, Badr A; Kim, Chang Soo; Ellis, Naoko; Bi, Xiaotao

    2016-02-01

    Solid additives were used as a microwave absorber to improve the low microwave absorption rate of switchgrass going through pyrolysis, and as a catalyst to improve the bio-oil and biochar characteristics. The synergistic effects were manifested in the presence of a mixture of K3PO4 and clinoptilolite or bentonite compared with single catalyst, resulting in increased microwave absorption rate, and improved bio-oil and biochar quality. The sample of microwave heating switchgrass with 10wt.% K3PO4+10wt.% bentonite reached 400°C after 2.8min, compared with 28.8min through conventional heating, producing biochar with increase in BET surface area from 0.33m(2)/g to 76.3m(2)/g compared with conventional heating. Furthermore, water content of the bio-oil reduced from 22.7 to 15.0wt.% compared with biomass mixed with 20wt.% SiC, a chemically-inert microwave absorbing material used to increase microwave heating. Introducing catalysts showed a great potential for accelerating microwave heating and improving bio-oil and biochar qualities. PMID:26642217

  10. Microwave-Assisted Synthesis of Nano-materials in Aqueous

    EPA Science Inventory

    Whether it is termed a revolution or simply a continuous evolution, clearly development of new materials and their understanding on smaller and smaller length scale is at the root of progress in many areas of materials science.1 This is true in developing existing bulk materials...

  11. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, III, Jerome J.; Halpern, Bret L.

    1993-01-01

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures.

  12. Practical Microwave Meter for Sensing Moisture and Density in Granular Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A low-cost microwave sensor for rapid and nondestructive sensing of bulk density and moisture content in granular and particulate materials has been built and tested. The sensor was made with inexpensive, off-the-shelf components and operates at 5.8 GHz. Three permittivity-based algorithms were us...

  13. Dynamic measurement of bulk modulus of dielectric materials using a microwave phase shift technique

    NASA Technical Reports Server (NTRS)

    Barker, B. J.; Strand, L. D.

    1972-01-01

    A microwave Doppler shift technique was developed for measuring the dynamic bulk modulus of dielectric materials such as solid propellants. The system has a demonstrated time resolution on the order of milliseconds and a theoretical spatial resolution of a few microns. Accuracy of the technique is dependent on an accurate knowledge of the wavelength of the microwave in the sample being tested. Such measurement techniques are discussed. Preliminary tests with two solid propellants, one non-aluminized and one containing 16% aluminum, yielded reasonable, reproducible results. It was concluded that with refinements the technique holds promise as a practical means for obtaining accurate dynamic bulk modulus data over a variety of transient conditions.

  14. Plasma Properties of Microwave Produced Plasma in a Toroidal Device

    NASA Astrophysics Data System (ADS)

    Singh, Ajay; Edwards, W. F.; Held, Eric

    2011-10-01

    We have modified a small tokamak, STOR-1M, on loan from University of Saskatchewan, to operate as a low-temperature (~5 eV) toroidal plasma machine with externally induced toroidal magnetic fields ranging from zero to ~50 G. The plasma is produced using microwave discharges at relatively high pressures. Microwaves are produced by a kitchen microwave-oven magnetron operating at 2.45 GHz in continuous operating mode, resulting in pulses ~0.5 s in duration. Initial measurements of plasma formation in this device with and without applied magnetic fields are presented. Plasma density and temperature profiles have been measured using Langmuir probes and the magnetic field profile inside the plasma has been obtained using Hall probes. When the discharge is created with no applied toroidal magnetic field, the plasma does not fill the entire torus due to high background pressure. However, when a toroidal magnetic field is applied, the plasma flows along the applied field, filling the torus. Increasing the applied magnetic field seems to aid plasma formation - the peak density increases and the density gradient becomes steeper. Above a threshold magnetic field, the plasma develops low-frequency density oscillations due to probable excitation of flute modes in the plasma.

  15. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1987-01-01

    Laboratory measurements were conducted to evaluate properties of atmospheric gases under simulated conditions for the outer planets. A significant addition to this effort was the capability to make such measurements at millimeter wavelengths. Measurements should soon be completed on the millimeter wave absorption from ammonia under Jovian conditions. Also studied will be the feasibility of measuring the microwave and millimeter wave properties of phosphine (PH3) under simulated Jovian conditions. Further analysis and application of the laboratory results to microwave and millimeter wave absorption data for the outer planet, such as Voyager Radio Occultation experiments, will be pursued.

  16. Effect of annealing temperature of nano-sized BaFe12O19 in Novolac phenolic resin on microwave properties for use as EMI shielding material in X-band

    NASA Astrophysics Data System (ADS)

    Ozah, S.; Bhattacharyya, N. S.

    2013-01-01

    Nanosized barium ferrite (BaFe12O19) powders are synthesized using co-precipitation technique at three different annealing temperatures. The X-Ray Diffraction pattern indicates the presence of hexagonal structure for all the three samples. Transmission electron microscopy (TEM) shows the particles are hexagonal in shape. The synthesized BaFe12O19 powder samples are mechanically mixed with Novolac phenolic resin (NPR) with filler to polymer weight ratio of 30:60 to prepare pellets of BaFe12O19/NPR composites of dimensions, 10.38 mm x 22.94 mm x 4 mm. The complex permittivity, ɛr and complex permeability, μr of the developed samples are measured at X-band by Nicolson-Ross method using Agilent E8362C vector network analyzer. The effect of the annealing temperature on the complex permittivity and permeability in the X-band is studied. The maximum dielectric constant and permeability is obtained of the BaFe12O19/NPR composite with BaFe12O19 annealed at 9000C as 6 and 2 respectively. The composite is a good candidate for microwave absorption study.

  17. Detoxification mechanism of asbestos materials by microwave treatment.

    PubMed

    Yoshikawa, N; Kashimura, K; Hashiguchi, M; Sato, M; Horikoshi, S; Mitani, T; Shinohara, N

    2015-03-01

    The detoxification mechanism of asbestos materials was investigated through simulations and experiments. The permittivities of pure CaO and Mg3Si4O12, as quasi-asbestos materials, were measured using the cavity perturbation method. The real and imaginary parts of the relative permittivity (ɛr' and ɛr″) of CaO are functions of temperature, and numerical simulations revealed the thermal distributions in an electromagnetic field with respect to both asbestos shape and material configuration based on permittivity. Optical microscopic observation revealed that the thickness of chrysotile fibers decreased as a result of CaO heating. The heating mechanism of asbestos materials has been determined using CaO phase, and the detoxification mechanism of asbestos materials was discussed based on the heating mechanism. PMID:25463234

  18. Novel materials, fabrication techniques and algorithms for microwave and THz components, systems and applications

    NASA Astrophysics Data System (ADS)

    Liang, Min

    This dissertation presents the investigation of several additive manufactured components in RF and THz frequency, as well as the applications of gradient index lens based direction of arrival (DOA) estimation system and broadband electronically beam scanning system. Also, a polymer matrix composite method to achieve artificially controlled effective dielectric properties for 3D printing material is studied. Moreover, the characterization of carbon based nano-materials at microwave and THz frequency, photoconductive antenna array based Terahertz time-domain spectroscopy (THz-TDS) near field imaging system, and a compressive sensing based microwave imaging system is discussed in this dissertation. First, the design, fabrication and characterization of several 3D printed components in microwave and THz frequency are presented. These components include 3D printed broadband Luneburg lens, 3D printed patch antenna, 3D printed multilayer microstrip line structure with vertical transition, THz all-dielectric EMXT waveguide to planar microstrip transition structure and 3D printed dielectric reflectarrays. Second, the additive manufactured 3D Luneburg Lens is employed for DOA estimation application. Using the special property of a Luneburg lens that every point on the surface of the Lens is the focal point of a plane wave incident from the opposite side, 36 detectors are mounted around the surface of the lens to estimate the direction of arrival (DOA) of a microwave signal. The direction finding results using a correlation algorithm show that the averaged error is smaller than 1º for all 360 degree incident angles. Third, a novel broadband electronic scanning system based on Luneburg lens phased array structure is reported. The radiation elements of the phased array are mounted around the surface of a Luneburg lens. By controlling the phase and amplitude of only a few adjacent elements, electronic beam scanning with various radiation patterns can be easily achieved

  19. Reflection/Transmission study of two fabrics with microwave properties.

    PubMed

    Odman, Torbjörn; Lindén, Maria; Larsson, Christer

    2014-01-01

    In this study, the transmission and reflection of two conductive fabrics are investigated in the frequency range from 2 to 18 GHz. One of the fabrics is a non-woven polypyrrole, and the other consists of a polyethylene warp with steel threads in the weft. Reflection and transmission measurements are performed in order to characterize the electromagnetic properties of the materials. Reflection measurements are performed for two polarizations at normal, 0°, and 60° incident angles. Transmission measurements are also done for two polarization directions at normal incidence. The results show that the fabric with the steel filler reflects most of the incident radiation, and has very low transmission with some polarization dependence. The polypyrrole non-woven fabric, on the other hand, has reflection and transmission properties that show that it is absorbing the incident radiation. Wearable on-body sensors that in addition are comfortable to wear can be integrated in the textile of clothes. These sensors can e.g., be used to monitor health or analyze gait. The fabrics have the potential to be used in health applications when designing on-body sensors, e.g. for movement analysis. PMID:24851970

  20. Properties of plasma flames sustained by microwaves and burning hydrocarbon fuels

    SciTech Connect

    Hong, Yong Cheol; Uhm, Han Sup

    2006-11-15

    Plasma flames made of atmospheric microwave plasma and a fuel-burning flame were presented and their properties were investigated experimentally. The plasma flame generator consists of a fuel injector and a plasma flame exit connected in series to a microwave plasma torch. The plasma flames are sustained by injecting hydrocarbon fuels into a microwave plasma torch in air discharge. The microwave plasma torch in the plasma flame system can burn a hydrocarbon fuel by high-temperature plasma and high atomic oxygen density, decomposing the hydrogen and carbon containing fuel. We present the visual observations of the sustained plasma flames and measure the gas temperature using a thermocouple device in terms of the gas-fuel mixture and flow rate. The plasma flame volume of the hydrocarbon fuel burners was more than approximately 30-50 times that of the torch plasma. While the temperature of the torch plasma flame was only 868 K at a measurement point, that of the diesel microwave plasma flame with the addition of 0.019 lpm diesel and 30 lpm oxygen increased drastically to about 2280 K. Preliminary experiments for methane plasma flame were also carried out, measuring the temperature profiles of flames along the radial and axial directions. Finally, we investigated the influence of the microwave plasma on combustion flame by observing and comparing OH molecular spectra for the methane plasma flame and methane flame only.

  1. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1988-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The key activity for this grant year has continued to be laboratory measurements of the microwave and millimeter-wave properties of the simulated atmospheres of the outer planets and their satellites. A Fabry-Perot spectrometer system capable of operation from 32 to 41 GHz was developed. Initially this spectrometer was used to complete laboratory measurements of the 7.5 to 9.3 mm absorption spectrum of ammonia. Laboratory measurements were begun at wavelengths near 3.2 mm, where a large number of observations of the emission from the outer planets were made. A description of this system is presented.

  2. The Effect of Microwave Radiation on the Supramolecular Structure of Polypropylene Fiber Materials

    NASA Astrophysics Data System (ADS)

    Potekaev, A. I.; Lysak, I. A.; Malinovskaya, T. D.; Lysak, G. V.; Egorova, L. A.

    2016-04-01

    The results of investigations of structural-phase transitions in the polypropylene melt-blown fiber materials before and after their short-term exposure to microwave radiation are presented. Using the methods of X-ray diffraction analysis and differential scanning calorimetry (DSC), it is shown that the smectic mesomorphic phase transforms into a stable monoclinic α-crystalline structure due to dielectric heating of the water molecules adsorbed on the surface of the material, without any changes in its crystallinity degree. Based on the calorimetric data, it is found that a microwave treatment of the material results in the formation of a crystalline phase with a homogeneous structure and increases its melting temperature.

  3. Microwave absorbability of unidirectional SiC fiber composites as a function of the constituents’ properties

    NASA Astrophysics Data System (ADS)

    Wan, Guangchao; Jiang, Jianjun; He, Yun; Bie, Shaowei

    2016-06-01

    The electromagnetic properties of unidirectional SiC fibre composites can be efficiently tailored by adjusting the properties of the composite’s constituents making these composites potential microwave absorbers. In this study, the microwave absorbing properties of unidirectional SiC fibre composites were investigated based on the electromagnetic properties of the constituents at frequencies ranging from 8 to 18 GHz. The composite was composed of two types of SiC fibres that individually exhibit relatively high and low electrical conductivity. The matrix together with the low-conductivity SiC fibres were characterized by effective permittivity and conductivity which provided a theoretical calculation of the microwave reflectivity. The theoretical calculation was based on formulas about anisotropic unidirectional composites and was compared to the results obtained from numerical simulations. There was good agreement in the results obtained from both methods. It was found that the intensity of microwave absorption of the composite was dependent primarily on the properties of the high-conductivity SiC fibres. The absorption band appeared to be dependent on the effective permittivity of the matrix and the low-conductivity SiC fibres and the conductivity of the high-conductivity SiC fibres.

  4. Microwave absorption properties of conducting polymer composite with barium ferrite nanoparticles in 12.4-18 GHz

    NASA Astrophysics Data System (ADS)

    Ohlan, Anil; Singh, Kuldeep; Chandra, Amita; Dhawan, S. K.

    2008-08-01

    Conducting polymer nanocomposites of polyphenyl amine with barium ferrite nanoparticles (50-70nm) have been synthesized via emulsion polymerization. The complex permittivity, permeability, and microwave absorption properties of the composite were studied in the 12.4-18GHz (Ku band) frequency range. The composite has shown high shielding effectiveness due to absorption (SEA) of 28.9dB (˜99.9%), which strongly depends on dielectric loss, magnetic permeability, and volume fraction of barium ferrite nanoparticles. The high value of SEA suggests that these composites can be used as a promising radar absorbing materials.

  5. Electronic properties of superconductors studied using photo induced activation of microwave absorption (PIAMA)

    SciTech Connect

    Feenstra, B.J.; Schooveld, W.A.; Bos, C.

    1995-12-31

    Electronic properties of superconductors are contemporarily being studied using many different experimental techniques, among which infrared spectrometry, photoelectron spectroscopy and microwave cavity techniques play an important role. The data analysis, however, is complicated by the fact that in these materials the phonon-frequency range overlaps with the one in which the energy gap is expected. This problem can be circumvented by making use of two different sources, one to induce the excitations (the Free Electron Laser in Nieuwegein, The Netherlands, FELIX), and one to study the behavior of these excitations (i.e. quasiparticles). In our case the latter source is monochromatic microwave radiation, transmitted through a thin superconducting film. We measured both a conventional superconductor (NbN, T{sub c} = 17 K) and a high T{sub c} superconductor (SmBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, T{sub c} = 92 K). For NbN we observed a positive change in transmission, followed by a relaxation to a transmission smaller than the original value, after which the starting situation was restored within {approximately} 100 {mu}s. In case of SmBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, the changes persisted above T{sub c}. At very low temperatures we observed slow oscillations ({approximately} 4kHz) in the induced signal, which were absent in NbN. The long time scales can possibly be explained by the so-called bottleneck, i.e. quasiparticles excited with a lot of excess energy lose part of their energy by exciting other quasiparticles. In this case the quasiparticle lifetime is enhanced considerably. The oscillations point towards an intrinsic difference of the low energy excitations, i.e. the symmetry of the pairing.

  6. COSMIC MICROWAVE BACKGROUND CONSTRAINTS OF DECAYING DARK MATTER PARTICLE PROPERTIES

    SciTech Connect

    Yeung, S.; Chan, M. H.; Chu, M.-C.

    2012-08-20

    If a component of cosmological dark matter is made up of massive particles-such as sterile neutrinos-that decay with cosmological lifetime to emit photons, the reionization history of the universe would be affected, and cosmic microwave background anisotropies can be used to constrain such a decaying particle model of dark matter. The optical depth depends rather sensitively on the decaying dark matter particle mass m{sub dm}, lifetime {tau}{sub dm}, and the mass fraction of cold dark matter f that they account for in this model. Assuming that there are no other sources of reionization and using the Wilkinson Microwave Anisotropy Probe 7-year data, we find that 250 eV {approx}< m{sub dm} {approx}< 1 MeV, whereas 2.23 Multiplication-Sign 10{sup 3} yr {approx}< {tau}{sub dm}/f {approx}< 1.23 Multiplication-Sign 10{sup 18} yr. The best-fit values for m{sub dm} and {tau}{sub dm}/f are 17.3 keV and 2.03 Multiplication-Sign 10{sup 16} yr, respectively.

  7. Magnetic properties of lithium zinc ferrites synthesized by microwave sintered method

    NASA Astrophysics Data System (ADS)

    Yang, Qinghui; Zhang, Huaiwu; Wen, Qiye; Liu, Yingli; Yang, Xuwen

    2016-05-01

    In this paper, a series of polycrystalline ferrite samples were prepared with the composition of Zn0.1Li0.525-xTi0.15MgxFe2.225-0.5xO4 (LiZn) (x=0, 0.05, 0.10, 0.15 and 0.20) using both microwave sintering (MS) and conventional sintering (CS) technologies, respectively. The sintering time and temperature were 22 hours and 1000°C for the CS process, and 2 hours and 880°C for the MS process. Experiments showed that the MS treated LiZn ferrites exhibited more excellent magnetic properties and denser, more uniform micro-structures comparing with the ones treated by CS method. For the LiZn ferrite (x=0.1) sintered at 880°C using MS, the saturation magnetic induction (Bs) is 242.3 mT, the coercive force (Hc) is 135 A/m, the square ratio (Br/Bs) is 0.87 and the ferromagnetic resonance line-width (Δ H) is 143.2 Oe. These results represented very good properties for an X-band phase shifter material and indicated that the MS method is a potentially important technique for fabricating low temperature co-fired ceramics (LTCC).

  8. Effect of "Natural" Water and "Added" Water on Dielectric Properties of Shelled Corn at Microwave Frequencies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of samples of shelled corn of “natural” water content and those prepared by adding water were measured in free space at microwave frequencies and room temperature of 23 oC. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 6 GHz show...

  9. Dielectric properties of almond shells in the development of radio frequency and microwave pasteurization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To develop pasteurization treatments based on radio frequency (RF) or microwave energy, dielectric properties of almond shells were determined using an open-ended coaxial-probe with an impedance analyzer over a frequency range of 10 to 1800 MHz. Both the dielectric constant and loss factor of almond...

  10. Electromagnetic and microwave-absorbing properties of magnetic nickel ferrite nanocrystals.

    PubMed

    Zhu, Weimo; Wang, Lei; Zhao, Rui; Ren, Jiawen; Lu, Guanzhong; Wang, Yanqin

    2011-07-01

    The electromagnetic and microwave absorbing properties of nickel ferrite nanocrystals were investigated for the first time. There were two frequencies corresponding to the maximum reflection loss in a wide thickness range from 3.0 to 5.0 mm, which may be bought by the nanosize effect and the good crystallization of the nanocrystals. PMID:21633731

  11. NIST Materials Properties Databases for Advanced Ceramics

    PubMed Central

    Munro, R. G.

    2001-01-01

    The NIST Ceramics Division maintains two databases on the physical, mechanical, thermal, and other properties of high temperature superconductors and structural ceramics. Crystallographic data are featured prominently among the physical property data and serve several important functions in the classification and evaluation of the property values. The scope of materials, properties, and data evaluation protocols are discussed for the two databases.

  12. Property Data Summaries for Advanced Materials

    National Institute of Standards and Technology Data Gateway

    SRD 150 NIST Property Data Summaries for Advanced Materials (Web, free access)   Property Data Summaries are topical collections of property values derived from surveys of published data. Thermal, mechanical, structural, and chemical properties are included in the collections.

  13. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, J.J. III; Halpern, B.L.

    1993-10-26

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures. 5 figures.

  14. The microwave properties of simulated melting precipitation particles: sensitivity to initial melting

    NASA Astrophysics Data System (ADS)

    Johnson, B. T.; Olson, W. S.; Skofronick-Jackson, G.

    2015-06-01

    A simplified approach is presented for assessing the microwave response to the initial melting of realistically-shaped ice particles. This paper is divided into two parts: (1) a description of the Single Particle Melting Model (SPMM): a heuristic melting simulation for ice-phase precipitation particles of any shape or size. SPMM is applied to two simulated aggregate snow particles, simulating melting up to 0.15 melt fraction by mass; and (2) the computation of the single-particle microwave scattering and extinction properties these hydrometeors, using the discrete dipole approximation (via DDSCAT), at the following selected frequencies: 13.4, 35.6, 94.0 GHz for radar applications; and 89, 165.0 and 183.31 GHz for radiometer applications. These selected frequencies are consistent with current microwave remote sensing platforms, such as CloudSat and the Global Precipitation Measurement (GPM) mission. Comparisons with calculations using variable-density spheres indicate significant deviations in scattering and extinction properties throughout the initial range of melting (liquid volume fractions less than 0.15). Integration of the single-particle properties over an exponential particle-size distribution provides additional insight into idealized radar reflectivity and passive microwave brightness temperature sensitivity to variations in size/mass, shape, melt fraction, and particle orientation.

  15. The microwave properties of simulated melting precipitation particles: sensitivity to initial melting

    NASA Astrophysics Data System (ADS)

    Johnson, B. T.; Olson, W. S.; Skofronick-Jackson, G.

    2016-01-01

    A simplified approach is presented for assessing the microwave response to the initial melting of realistically shaped ice particles. This paper is divided into two parts: (1) a description of the Single Particle Melting Model (SPMM), a heuristic melting simulation for ice-phase precipitation particles of any shape or size (SPMM is applied to two simulated aggregate snow particles, simulating melting up to 0.15 melt fraction by mass), and (2) the computation of the single-particle microwave scattering and extinction properties of these hydrometeors, using the discrete dipole approximation (via DDSCAT), at the following selected frequencies: 13.4, 35.6, and 94.0 GHz for radar applications and 89, 165.0, and 183.31 GHz for radiometer applications. These selected frequencies are consistent with current microwave remote-sensing platforms, such as CloudSat and the Global Precipitation Measurement (GPM) mission. Comparisons with calculations using variable-density spheres indicate significant deviations in scattering and extinction properties throughout the initial range of melting (liquid volume fractions less than 0.15). Integration of the single-particle properties over an exponential particle size distribution provides additional insight into idealized radar reflectivity and passive microwave brightness temperature sensitivity to variations in size/mass, shape, melt fraction, and particle orientation.

  16. Microwave-assisted hydrothermal synthesis of porous SnO{sub 2} nanotubes and their lithium ion storage properties

    SciTech Connect

    Wang, H.E.; Xi, L.J.; Ma, R.G.; Lu, Z.G.; Chung, C.Y.; Bello, I.; Zapien, J.A.

    2012-06-15

    Porous SnO{sub 2} nanotubes have been synthesized by a rapid microwave-assisted hydrothermal process followed by annealing in air. The detailed morphological and structural studies indicate that the SnO{sub 2} tubes typically have diameters from 200 to 400 nm, lengths from 0.5 to 1.5 {mu}m and wall thicknesses from 50 to 100 nm. The SnO{sub 2} nanotubes are self-assembled by interconnected nanocrystals with sizes {approx}8 nm resulting in a specific surface area of {approx}54 m{sup 2} g{sup -1}. The pristine SnO{sub 2} nanotubes are used to fabricate lithium half cells to evaluate their lithium ion storage properties. The porous SnO{sub 2} nanotubes are characteristic with high lithium ion storage capacity, that is found to be 1258, 951, 757, 603, 458, and 288 mAh g{sup -1}, at 0.1, 0.2, 0.5, 1, 2, and 4C, respectively. The enhanced electrochemical properties of the SnO{sub 2} nanotubes can be ascribed to their unique geometry and porous structures. - Graphical abstract: Porous SnO{sub 2} nanotubes are synthesized by a fast microwave-assisted hydrothermal process and exhibit high lithium ion storage properties due to their unique geometry and porous characteristics. Highlights: Black-Right-Pointing-Pointer A microwave-assisted hydrothermal method was used to prepare porous SnO{sub 2} nanotubes. Black-Right-Pointing-Pointer The porous SnO{sub 2} nanotubes have abundant mesopores on their tube walls. Black-Right-Pointing-Pointer The porous SnO{sub 2} nanotubes possess high lithium ion storage properties. Black-Right-Pointing-Pointer Our results may promote the development of high-performance anode materials.

  17. ELECTROMAGNETIC MICROWAVE PROPERTIES OF Fe82B17Cu1 BALL MILLED ALLOY

    NASA Astrophysics Data System (ADS)

    Tian, N.; Fan, X. D.; Wang, J. W.; You, C. Y.; Lu, Z. X.; Ge, L. L.

    2013-07-01

    High saturation magnetization and magnetic anisotropy are helpful for getting a high frequency electromagnetic microwave absorption performance. The α-Fe possesses a high saturation magnetization. Fe-B phases exhibit a relatively higher magnetic anisotropy and higher resistivity than α-Fe simultaneously. In this work, we made nanocrystalline powders of Fe82B17Cu1, mainly consisting of α-Fe and Fe2B phases, by ball milling and post-annealing. Electromagnetic microwave characterization shows that Fe82B17Cu1 powders possess a relative high permeability and considerable permittivity. Due to a good electromagnetic impedance matching, a good electromagnetic microwave absorption property (RL < -35 dB) has been achieved at 3.6 GHz. The experimental frequency and the matching thickness are coincident with the quarter wavelength matching condition.

  18. Enhanced Dielectric Properties and High-Temperature Microwave Absorption Performance of Zn-Doped Al2O3 Ceramic

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Luo, Fa; Wei, Ping; Zhou, Wancheng; Zhu, Dongmei

    2015-07-01

    To improve the dielectric and microwave absorption properties of Al2O3 ceramic, Zn-doped Al2O3 ceramic was prepared by conventional ceramic processing. X-ray diffraction analysis confirmed that Zn atoms successfully entered the Al2O3 ceramic lattice and occupied Al sites. The complex permittivity increased with increasing Zn concentration, which is mainly attributed to the increase in charged vacancy defects and densification of the Al2O3 ceramic. In addition, the temperature-dependent complex permittivity of 3% Zn-doped Al2O3 ceramic was determined in the temperature range from 298 K to 873 K. Both the real and imaginary parts of the complex permittivity increased monotonically with increasing temperature, which can be ascribed to the shortened relaxation time and increasing electrical conductivity. The increased complex permittivity leads to a great improvement in microwave absorption. In particular, when the temperature is up to 873 K, the 3% Zn-doped Al2O3 ceramic exhibited the best absorption performance with a maximum peak (-12.1 dB) and broad effective absorption bandwidth (reflection loss less than -10 dB from 9.3 GHz to 12.3 GHz). These results reveal that Zn-doped Al2O3 ceramic is a promising candidate for use as a kind of high-temperature microwave absorption material.

  19. High frequency dielectric properties of A5B4O15 microwave ceramics

    NASA Astrophysics Data System (ADS)

    Kamba, S.; Petzelt, J.; Buixaderas, E.; Haubrich, D.; Vaněk, P.; Kužel, P.; Jawahar, I. N.; Sebastian, M. T.; Mohanan, P.

    2001-04-01

    High-frequency dielectric properties of A5B4O15 (A=Ba, Sr, Mg, Zn, Ca; B=Nb, Ta) dielectric ceramics are studied by means of the microwave cavity technique, a combination of far-infrared reflection and transmission spectroscopy and time-resolved terahertz transmission spectroscopy. Microwave permittivity ɛ' and Q×f factor vary, depending on the chemical composition, between 11 and 51, and 2.4 and 88 THz, respectively. The temperature coefficient τf varies between -73 and 232 ppm/°C, and in two samples |τf| is less than 15 ppm/°C. It is shown that the microwave permittivity ɛ' of the ceramics studied is determined by the polar phonon contributions and that linear extrapolation of the submillimeter dielectric loss ɛ″ down to the microwave region is in agreement with the microwave data of single phase samples. The relationship among phonon spectra, the crystal structure, and the unit cell volume is discussed.

  20. Adsorption of dyes onto carbonaceous materials produced from coffee grounds by microwave treatment.

    PubMed

    Hirata, Mizuho; Kawasaki, Naohito; Nakamura, Takeo; Matsumoto, Kazuoki; Kabayama, Mineaki; Tamura, Takamichi; Tanada, Seiki

    2002-10-01

    Organic wastes have been burned for reclamation. However, they have to be recycled and reused for industrial sustainable development. Carbonaceous materials were produced from coffee grounds by microwave treatment. There are many phenolic hydroxyl and carboxyl groups on the surface of carbonaceous materials. The base consumption of the carbonaceous materials was larger than that of the commercially activated carbon. The carbonaceous materials produced from coffee grounds were applied to the adsorbates for the removal of basic dyes (methylene blue and gentian violet) in wastewater. This result indicated that the adsorption of dyes depended upon the surface polar groups on the carbonaceous materials. Moreover, the Freundlich constants of isotherms for the adsorption of methylene blue and gentian violet onto the carbonaceous materials produced from coffee grounds were greater than those for adsorption onto activated carbon or ceramic activated carbon. The interaction was greatest between the surface or porosity of the carbonaceous materials and methylene blue and gentian violet. The microwave treatment would be useful for the carbonization of organic wastes to save energy. PMID:12702420

  1. A planar transmission-line sensor for measuring the microwave permittivity of liquid and semisolid biological materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A planar transmission-line configuration for rapid, nondestructive, wideband permittivity measurements of liquid and semisolid materials at microwave frequencies is described. The transmission-line propagation constant of the proposed configuration is determined with the multiline technique from sca...

  2. Characterization and Modeling of Microwave Plasmas Used for Materials Processing

    NASA Astrophysics Data System (ADS)

    Wei, Peter

    1995-11-01

    Detailed models of the behavior of both charged and neutral species in nitrogen afterglows and hydrogen/argon discharges were developed in this study. Mass continuity equations were solved to investigate the dominant transport and rate processes in a low-pressure, non-isothermal nitrogen afterglow. Electron density and N-atom flux were measured as a function of position in the afterglow and compared with model results. It was found that the model, with no adjustable parameters, yielded very good agreement with experimental measurements. The radial gradient of N-atom concentration was shown to be insignificant, which reduced the model to a one-dimensional mass continuity equation. However, the model of charged species behavior must be carried out in two dimensions. Wall recombination play a very important role for both neutral and charges species while the homogeneous recombination can be ignored. A volume-averaged model coupling species and power balance equations was developed to predict the electron temperature and species concentration as a function of operating parameters in a pure hydrogen discharge. It was found that the pressure, power, flow rate, reactor radius, and gas temperature all affect the generation of H-atoms. Electron temperature is mainly determined by the gas pressure. Finally, the effect of argon addition on a hydrogen discharge was studied. The model results showed that the argon addition increases the electron density through direct ionization of ground state Ar, which in turn, enhances the degree of hydrogen dissociation. It was also found that the plasma retains the basic properties of a hydrogen plasma even for mixtures containing 90% Ar. Electron temperature and H-atom concentration are only slightly changed with argon addition, and the dominant ionic species is still H_3^+..

  3. Apparatus and method for microwave processing of materials using field-perturbing tool

    DOEpatents

    Tucker, Denise A.; Fathi, Zakaryae; Lauf, Robert J.

    2001-01-01

    A variable frequency microwave heating apparatus designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity for heating or other selected applications. A field-perturbing tool is disposed within the cavity to perturb the microwave power distribution in order to apply a desired level of microwave power to the workpiece.

  4. Properties of microplasmas excited by microwaves for VUV photon sources

    NASA Astrophysics Data System (ADS)

    Cooley, James E.; Urdahl, Randall; Xue, Jun; Denning, Mark; Tian, Peng; Kushner, Mark J.

    2015-12-01

    Microplasma sources typically take advantage of pd (pressure  ×  size) scaling by increasing pressure to operate at dimensions as small as tens of microns. In many applications, low pressure operation is desirable, which makes miniaturization difficult. In this paper, the characteristics of low pressure microplasma sources excited by microwave power are discussed based on results from experimental and computational studies. The intended application is production of VUV radiation for chemical analysis, and so emphasis in this study is on the production of resonant excited states of rare gases and radiation transport. The systems of interest operate at a few to 10 Torr in Ar and He/Ar mixtures with cavity dimensions of hundreds of microns to 1 mm. Power deposition is a few watts which produces fractional ionization of about 0.1%. We found that production of VUV radiation from argon microplasmas at 104.8 nm and 106.7 nm saturates as a function of power deposition due to a quasi-equilibrium that is established between the electron temperature (that is not terribly sensitive to power deposition) and the population of the Ar(4s) manifold.

  5. Effect of microwave treatment on the luminescence properties of CdS and CdTe:Cl Single Crystals

    SciTech Connect

    Red’ko, R. A. Budzulyak, S. I.; Korbutyak, D. V.; Lotsko, A. P.; Vakhnyak, N. D.; Demchyna, L. A.; Kalytchuk, S. M.; Konakova, R. V.; Milenin, V. V.; Bykov, Yu. V. Egorov, S. V.; Eremeev, A. G.

    2015-07-15

    The effect of microwave radiation on the luminescence properties of CdS and CdTe:Cl single crystals is studied. It is established that the exposure of these semiconductors to short-term (≤30 s) microwave radiation substantially modifies their impurity and defect structure. The mechanisms of transformation of the defect subsystem of II–VI single crystals upon microwave treatment are discussed. It is shown that the experimentally observed changes are defined by the nonthermal effects of microwave radiation at a power density of 7.5 W cm{sup –2}; at 90 W cm{sup –2}, nonthermal effects are prevailing.

  6. Radio to microwave dielectric characterisation of constitutive electromagnetic soil properties using vector network analyses

    NASA Astrophysics Data System (ADS)

    Schwing, M.; Wagner, N.; Karlovsek, J.; Chen, Z.; Williams, D. J.; Scheuermann, A.

    2016-04-01

    The knowledge of constitutive broadband electromagnetic (EM) properties of porous media such as soils and rocks is essential in the theoretical and numerical modeling of EM wave propagation in the subsurface. This paper presents an experimental and numerical study on the performance EM measuring instruments for broadband EM wave in the radio-microwave frequency range. 3-D numerical calculations of a specific sensor were carried out using the Ansys HFSS (high frequency structural simulator) to further evaluate the probe performance. In addition, six different sensors of varying design, application purpose, and operational frequency range, were tested on different calibration liquids and a sample of fine-grained soil over a frequency range of 1 MHz-40 GHz using four vector network analysers. The resulting dielectric spectrum of the soil was analysed and interpreted using a 3-term Cole-Cole model under consideration of a direct current conductivity contribution. Comparison of sensor performances on calibration materials and fine-grained soils showed consistency in the measured dielectric spectra at a frequency range from 100 MHz-2 GHz. By combining open-ended coaxial line and coaxial transmission line measurements, the observable frequency window could be extended to a truly broad frequency range of 1 MHz-40 GHz.

  7. Controlled Microwave Processing of IGZO Thin Films for Improved Optical and Electrical Properties

    NASA Astrophysics Data System (ADS)

    Dhar, Aritra; Alford, T. L.

    2015-07-01

    Amorphous indium gallium zinc oxides (IGZO) of 100 nm thickness were deposited onto glass substrates by sputtering at room temperature. The films were subsequently annealed in air, vacuum, forming gas and O2 environments by both conventional and microwave methods. The optical and electrical properties of the as-deposited and annealed samples were measured and compared. It was seen that microwave annealing had a dual advantage of reduced time and lower temperature compared to conventional annealing. The optical and electrical properties of the IGZO thin films were measured by UV-Visible spectrophotometry, Hall measurement and four-point probe analyses, respectively. On microwave anneals of 4 min at 200°C, the resistivity of IGZO thin films was lowered to 4.45 and 4.24 × 10-3 Ω-cm in vacuum and forming gas, respectively. However in conventional annealing at 400°C, it took 24 h to reach 4.5 and 4.2 × 10-3 Ω-cm in vacuum and forming gas, respectively. The average transmittance of IGZO improved from 80% to almost 86% for microwave annealing.

  8. Microwave absorption properties of Al- and Cr-substituted M-type barium hexaferrite

    NASA Astrophysics Data System (ADS)

    Qiu, Jianxun; Gu, Mingyuan; Shen, Haigen

    2005-09-01

    Aluminum- and chromium-substituted barium ferrite particles with single magnetic domain were prepared using self-propagating combustion method. The crystalline structure, size, coercivity and microwave absorption property of the particles were investigated by means of X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry and vector network analyzer. The results show that the crystalline structure of BaFe 12-xAl xO 19 is still hexagonal. But when the chromium substitution amount y exceeds 0.6, the extra chromium ions cannot enter the lattice of BaFe 12-yCr yO 19. After Fe 3+ is partly substituted with Al 3+ and Cr 3+, the microwave absorption properties of barium ferrite are improved. The maximum absorption reaches 34.76 dB. The ferromagnetic resonance is an important channel of barium ferrite to absorb microwaves with high frequency. Aluminum and chromium substitutions change the ferromagnetic resonant frequency of barium ferrite. The multipeak phenomenon of the ferromagnetic resonance increases the microwave absorption capability of barium ferrite.

  9. Safety assessment of microwave susceptors and other high temperature packaging materials.

    PubMed

    Risch, S

    1993-01-01

    A number of packaging materials are being used not only to contain food during distribution but also to serve as the cooking container. The higher temperatures that these materials reach led the US Food and Drug Administration (FDA) to issue an intent to publish new regulations in 1989. The food and packaging industries responded by conducting extensive research and submitting the results to FDA. The methods used and results obtained are discussed. Most of the data were focused on microwave susceptors and the volatile compounds generated. One project showed that for a specific product, popcorn, there was no transfer into the food. Work is continuing to validate methods to test for non-volatile compounds. In addition to susceptors, various paper and plastic materials are used in dual ovenable (microwave and conventional ovens) applications. Most of the research on these materials has investigated the food contact temperatures on testing for migrants. An update on the current regulatory status of packaging materials intended for high temperature use in the US is discussed. PMID:8288009

  10. Millimeter wave and terahertz dielectric properties of biological materials

    NASA Astrophysics Data System (ADS)

    Khan, Usman Ansar

    Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to