bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microwave Radiation Effects on Ionic Current in Ionic Crystalline Solids
Authors: Freeman S. , Booske J. , Cooper R. , Meng B. 
Published: April 2011

ABSTRACTWe describe experiments to test for microwave enhancement of bulk vacancy diffusion in NaCl, bulk interstitial diffusion in AgCl, and grain boundary diffusion in NaCl. Experimental results for bulk vacancy diffusion in NaCl indicate that intrinsic vacancy mobility is not enhanced by microwave field intensities typical of microwave sintering experiments. Nevertheless, a microwave effect is observed with features consistent with a recent theory for microwave-enhanced driving forces.
Experimental Observations of Thermal Spikes in Microwave Processing of Ceramic Oxide Fibers
Authors: Vogt Gerald J. , Unruh Wesley P. , Thomas J. R. 
Published: April 2011

ABSTRACTMicrowave heating of alumina/silica fiber tows in a single-mode microwave cavity at 2.45 GHz has produced a surprising thermal spike behavior on the fiber bundles. During a thermal spike, a “hot spot” on the tow brightens rapidly, persists for a few seconds, and then rapidly extinguishes. A hot spot can encompass the entire tow in the cavity or just a localized portion of the tow. Some local hot spots propagate along the fiber. Thermal spikes are triggered by relatively small (<15%) increases in power, thus having obvious implications for the development of practical microwave fiber processing systems. A tow can be heated through several successive thermal spikes, after which the tow is left substantially cooler than it was originally, although the applied microwave electric field is much larger. X-ray diffraction studies show that after each temperature spike there is a partial phase transformation of the tow material into mullite. After several excursions the tow has been largely transformed to the new, less lossy phase and is more difficult to heat. Heating experiments with Nextel 550 tows are examined for a plausible explanation of this microwave heating behavior.
Microwave Vulcanization: A Lesson in Business and Technology
Authors: Krieger Bernard 
Published: April 2011

ABSTRACTSuccessful applications of microwave heating technology result from much more than successful engineering and pilot demonstration. Of utmost importance is translating this information into meaningful customer satisfaction through business concepts intrinsic to the industry being served. Microwave heating companies and laboratories are poorly positioned to commercialize new applications. They do not have the depth of experience in each of the industries which they serve. Success comes only from in-depth knowledge of real customer needs.Microwave vulcanization of rubber is one of the very successful applications. This paper uses the Rubber Industry as an example of the type of thinking necessary to develop a “customer” focus as opposed to a “microwave” focus.
Microwave Pyrolysis of Emulsified Ceramic Precursor Ocompounds
Authors: Willert-Porada M. , Dennhöfer S. , Hachmeister D. 
Published: April 2011

ABSTRACTApplication of paraffin as a MW-transparent matrix for microwave pyrolysis of metalorganic compounds enables synthesis of large quantities of nanosized powders with excellent storability and packing behavior. Fully crystalline, nanosized t-ZrO2 powders with specific surface area > 200 m 2 g -1 are obtained from Zr-alcoholate, and alumina powders with > 500 m2g-1 from Al-alcoholates. Some differences exist between microwave pyrolysis and conventional pyrolysis of such mixtures. Powders from microwave pyrolysis transform at lower calcination temperature to α-A12O3 and exhibit after calcination a more homogeneous morphology as compared to powders from conventional pyrolysis. Furthermore, a different composition of the volatile pyrolysis products is found. t-ZrO2 powder from the microwave processing route exhibits an increased stability towards transformation to monoclinic ZrO2 as well as smaller initial grain sizes than a conventionally synthesized powder.
Plasma Assisted Microwave Sintering and Joining of Ceramics
Authors: Samandi M. , Doroudian M. 
Published: April 2011

ABSTRACTDirect microwave sintering and joining of low temperature ceramics such as mullite have been extensively studied. However, it is recognised that microwave sintering and joining of high temperature oxide and non-oxide ceramics poses serious problems, primarily because of the difficulty of coupling microwave energy into these non-absorbing materials which make up the bulk of advanced ceramics. Attempts to overcome this problem by using indirect auxiliary heating or utilisation of intermediary or impure materials have been, by and large, unsatisfactory. Indeed, this fundamental physical barrier has seriously impaired the penetration of microwave heating in ceramic processing.In order to overcome this seemingly insurmountable fundamental barrier, a radical approach is required. This has been recently achieved by using a Microwave Induced Plasma (MIP) whereby microwave energy is utilised in a hybrid fashion. In this method, a microwave plasma is used to rapidly heat the ceramic to temperatures at which it becomes absorbing. At this point, microwave radiation is directly coupled to the ceramic and the plasma is extinguished since energy is no longer available to ionise the gas and sustain a plasma. This hybrid approach circumvents the limitations of conventional microwave heating for sintering and joining of advanced materials. In this review paper the fundamentals of microwave/materials interaction and conventional approach to microwave heating of ceramics will be thoroughly discussed. In addition, the new hybrid heating developed by the authors will be described and the possibility of MIP-assisted sintering/joining of industrially important materials will be demonstrated.
Microwave Processing of Polymer Composites
Authors: Hawley Martin C. , Wei Jianghua , Adegbite Valerie 
Published: April 2011

ABSTRACTMicrowave processing has been investigated as an alternative to conventional thermal method in processing polymer matrix composite materials. The main advantages of microwave processing over thermal processing are that: 1) microwave heating is volumetric, direct, selective, instantaneous, and controllable which offers advantages such as fast heating and minimization of temperature excursion; 2) microwave radiation can provide many desirable features in polymer and composite processing, such as enhanced polymerization rates and glass transition temperatures of thermosets, improved mechanical properties of composite materials, and increased adhesion between graphite fibers and matrix.Microwave heating has been used in food processing, drying, material processing, waste treatment, and organic synthesis. This paper summarizes the current status of microwave technology for the processing of polymer matrix composite materials. The discussion will be focused on the use and development of batch and continuous techniques using tunable single mode resonant microwave cavities for processing polymer composites.
Microwave Processing of Polyimide Thin Films
Authors: Lewis David A. , Lamaire Susan J. , Nunes Thomas 
Published: April 2011

ABSTRACTMicrowave processing has been used to reduce the long process cycles normally associated with the curing cycles for highly ordered polyimides, such as BPDA-PDA. These materials have found applications in the electronics industry due to the excellent thermal stability and low coefficient of thermal expansion of this class of polymers. Thin polymer films - an application not normally considered for microwave curing - were processed and the dependence of the mechanical properties compared with conventional thermal processing.
Dielectric Analysis Of Semi-Crystalline Poly(Ethylene Terephthalate)
Authors: Wei Jianghua , Delgado Richard , Hawley Martin C. , T.Demeuse Mark 
Published: April 2011

ABSTRACTDielectric properties of poly(ethylene terephthalate) (PET) were measured over a frequency range of 10 KHz to 2.45 GHz and a temperature range of 20 to 110°C. Relaxation peaks were identified at 1) fixed frequency with variable temperatures, and 2) fixed temperature with variable frequencies. The crystallinity of poly (ethylene terephthalate) was measured using differential scanning calorimetry (DSC). Relationships between crystallinity, dielectric properties, and location of the dielectric relaxation peak on the frequency and temperature scales were studied for poly(ethylene terephthalate). Also, the dielectric loss factor decreases with increased crystallinity at 2.45 GHz and 4 GHz within the temperature range studied.
Use of High-Power Traveling Wave Tubes as a Microwave Heating Source
Authors: Everleigh C. A. , Johnson A. C. , Espinosa R. J. , Garard R. S. 
Published: April 2011

ABSTRACTThis paper reports on the use of high-power traveling wave tubes (TWTs) as a source of microwave energy for materials processing applications. Recent work by Oak Ridge National Laboratories and Microwave Laboratories personnel has demonstrated the usefulness of sweeping the microwave processing frequency over substantial (>20%) bandwidths in order to achieve uniformity of heating over volumes unattainable using conventional microwave sources ∼ e.g., magnetrons. Properly constructed high-power TWTs are a logical choice of microwave source in such systems. After briefly reviewing the basic operating principles of the TWT, the required characteristics of a TWT for materials processing applications and how those requirements affect the TWT's design are discussed. Comments on the present product lines and areas of development for all of the major TWT manufacturers are also presented. Finally, the issue of the ultimate potential cost of TWTs designed for microwave processing applications is addressed.
Crystal Growth and Scintillation Properties of CeF3
Authors: Allain J.L. , Couchaud M. , Ferrand B. , Grange Y. , Utts B. , Wyon Ch. 
Published: April 2011

ABSTRACTLarge single crystals of CeF3, 40 mm in diameter up to 140 mm in length, have been grown using the vertical Bridgman technique. Their optical and scintillation properties and their radiation hardness have been measured.
Cerium-Doped Yttrium Aluminum Perovskite (Yap): Properties of Commercial Crystals
Authors: Trower W. Peter 
Published: April 2011

ABSTRACTThe journey of YAP from interesting laboratory curiosity to a material with commercial possibilities has taken two full decades. The reported YAP properties which motivated this effort are its rapid (~ 27 ns) dominant (~ 97%) decay which results in negligible afterglow; high density (~ 5.55 g/cm3); brightness (~ 50% of NaI:Tl); energy resolution (~ 6% at 455 keV); physical ruggedness; and chemical nonreactivity. Lone among its draw backs as a practical scintillator is its emission which is centered in the UV (~ 350 nm). Three firms now offer YAP crystals of sufficient size and quality that industrial applications are becoming possible.To date, the physical properties of YAP have only been published on small laboratory samples. Here we report a comprehensive and comparative evaluation of physical properties of material from all known commercial sources. Further, we speculate on the physical origin of variations among samples. Finally, we attempt to predict what can ultimately be expected from YAP as further refinements in its processing techniques are perfected.
Scintillating Glass Fiber-Optic Neutron Sensors
Authors: Abel K.H. , Arthur R.J. , Bliss M. , Brite D.W. , Brodzinski R.L. , Craig R.A. , Geelhood B.D. , Goldman D.S. , Griffin J.W. , Perkins R.W. , Reeder P.L. , Richey W.C. , Stahl K A. , Sunberg D.S. , Warner R.A. , Weber M. J. , Wogman N.A. 
Published: April 2011

ABSTRACTPacific Northwest Laboratory (PNL) has fabricated cerium-activated lithium silicate scintillating fibers via a hot-downdraw process. These fibers, which, as produced, typically have a transmission length (e−1 length) of greater than 2 meters, are found to undergo aging when subjected to room air. The aging, which is complete in a few weeks, reduces the transmission length to the order of 0.5 meter. Because of the high alkali content of the glass (on the order of 20-30 mole % lithia), we have attributed this aging to aqueous corrosion at the polymer cladding/glass interface. Changes in transmission with chemical treatment of the surface support the corrosion model. Fiber transmission performance has been preserved by modifying the hot-downdraw to a double crucible to produce glass-on-glass waveguides.
Activation of Lead Fluoride Room Temperature Luminescence by Structural Modifications
Authors: Alov D.L. , Bazhenov A.V. , Egorov V.K. , Emelchenko G.A. , Klassen N.V. , Kolchin A.A. , Kondakov S.F. , Kulakov A.B. , Mahonin S.I. , Prokopenko V.M. , Rybchenko S.I. , Savchenko I.B. , Sinitzin V.V. , Soloviev A.V. , Shmyt'ko I.M. , Shmurak S.Z. 
Published: April 2011

ABSTRACTThe connection of lead fluoride luminescence properties with its structural characteristics has been studied. Single crystals of the cubic and orthorombic phases, cubic and orthorombic powders, pressure compacted orthorombic ceramics, plastically deformed crystals were used. The photo- and X-ray excited luminescence spectra have been investigated. The experimental results have shown that the room temperature luminescence of lead fluoride can be accounted for local light emitting centers which are produced by the intrinsic structural defects in the orthorombic lead fluoride.
Crystal Detectors in Particle Physics
Authors: Newman Harvey B. , Gratta Giorgio , Zhu Ren-yuan 
Published: April 2011

ABSTRACTWe review the principal characteristics driving the design of precision calorimeters composed of inorganic crystal scintillators now in operation (L3, CLEO II) or developed for the next generation of particle physics experiments. The unique discovery potential of these detectors (1.5 to 50 m3of crystals; 104to > 105elements) is the result of their high electron and photon energy resolution over a wide energy range, uniform hermetic acceptance and fine granularity.Experiments at CERN's multi-TeV Large Hadron Collider (LHC) will search for the Higgs particles thought to be responsible for mass, and for many other new physics processes. In order to exploit the intrinsically high resolution of crystal detectors, exceptionally high speed (1 to 30 ns decay time) and radiation resistance are required. BaF2and CeF3are currently the preferred choices, and higher density alternatives such as PbWO4are under investigation.Lower energy, high luminosity experiments that will measure rare particle decays, and explore the violation of the fundamental “CP” symmetry that may be related to the predominance of matter over antimatter in our universe, have chosen Cesium Iodide for its combination of high light output, speed, and radiation resistance.Recent developments by Caltech include the use of photons generated by anH−beam from an RFQ accelerator to calibrate and provide sub-percent resolution in the L3 BGO calorimeter, and anin situoptical bleaching technique that renders large BaF2crystals now mass produced in China radiation hard up to dose levels ≳l 10 MegaRads.
Optical Properties and Radiation Damages of Cerium Fluoride Crystals Doped with Alkali-Earth and Rare-Earth Elements.
Authors: Gusev Yu.I. , Melchakov E.N. , Mironov I.A. , Panteleev L.A. , Reiterov V.M. , Rodnyi P.A. , Seliverstov D.M. , Shchetkowsky A.I. , Yazikov D.M. , Zakharov N.G. 
Published: April 2011

ABSTRACTStudy of optical properties and radiation damages of Cerium Fluoride crystals doped with Ca, Ba, Sr, La, Nd, Zr and Hf in the wide range of concentrations has been performed withthe goal to obtain high optical transparency of crystals at different cumulative doses under γ-irradiation. Time decay curves and relative light yields of scintillators asa function of doping level were measured using X-ray excitation of samples and single photon counting method.
Study of neutron damage resistance of some scintillating crystals and associated photodetectors with the nuclear reactor ULYSSE
Authors: Chipaux R. , Faure J.-L. , Pansart J.-P. , Poinsignon J. , Rebourgeard P. , Tartas J. , Dauphin France G. , Safieh J. 
Published: April 2011

ABSTRACTRadiation resistance is a mandatory requirement for a major part of the active or passivecomponents of the particle detectors planned for the future high energy accelerator LHC.Ulysse is a training reactor of the Institut National des Sciences et Techniques Nucl éaires (INSTN), in Saclay, and a very suitable tool for testing materials and devicesfor these future large detectors. Its radiation spectrum characteristics are very similarto those expected in these detectors, in terms of spectra of fast neutrons, thermal neutrons and gamma photons, and ratios between those types of radiation.Results are presented on the neutron resistance of two scintillating crystals, candidatesfor electromagnetic calorimetry, cerium fluoride (CeF3) and lead tungstate (PbWO4), and on the behaviour under neutron irradiation of some avalanche photodiodes, currently under development for light detection of these crystals.
PROGRESS ON SCINTILLATOR RESEARCH BY THE CRYSTAL CLEAR COLLABORATION
Authors: Lecoq Paul 
Published: April 2011

ABSTRACTA large effort has been undertaken since nearly 2 years by 14 research institutes (the “Crystal Clear” collaboration, CERN RD project 18), in order to develop and investigate new dense, radiation hard and fast inorganic scintillators suitable for very good resolution electromagnetic calorimeters to be built at the new high luminosity accelerators. Other fields of interest like nuclear physics, gamma ray astronomy, medical imaging (PET), safety systems and non destructive industrial applications are also rapidly growing. Progress on cerium fluoride will be reviewed with some comments about mass scale production and cost considerations. The pro's and con's of potentially cheaper solutions based on fluoride glasses or lead compounds will be discussed. Finally some attractive candidates will be mentioned for low energy gamma ray applications.
The Chemistry Of Two-Component Fluoride Crystalline Optical Media For Heavy, Fast, Radiation Hard Scintillators
Authors: Sobolev B.P. , Krivandina E.A. , Fedorov P.P. , Vasilchenko V.G. 
Published: April 2011

ABSTRACTProspects for preparation of two-component dense optical materials for scintillators are shown, using data on phase diagrams of about 300 MFm - RFn (m, n ≤ 4) type systems, formed by metal fluorides. Primary characteristics (decay time and light output of luminescence, radiation hardness, etc.) of some multicomponent crystals are reported.
Photoluminescence Of Zincselenide Single Crystals Annealed In Zinc Or Selenium Atmosphere
Authors: Yoshino Kenji , Matsushima Yasushi , Kinoshita Hiroyoshi , Hiramatsu Makoto 
Published: April 2011

ABSTRACTZincselenide single crystals grown by the sublimation method are annealed in Zn or Se atmosphere. The annealing effects are examined by means of photoluminescence (PL) and reflection spectroscopy at 4.2 K. In the PL spectrum for the as-grown crystal, bound exciton lines (I2, I1) are observed. For the Zn-annealed crystal, the free exciton line is clearly observed. For the Se-annealed crystal, peak positions of all lines shift to the higher energies and all lines become sharp, compared with the spectra for the as-grown crystal. It is concluded that Sc-vacancies affect the bandgap energy more than Zn-vacancies do.
Deformation Welding Of Scintillating Materials
Authors: Bazhenov A.V. , Egorov V.K. , Gasparov L.V. , Klassen N.V. , Mahonin S.I. , Shmurak S.Z. , Shmyt'Ko I.M. 
Published: April 2011

ABSTRACTExperiments on connecting scintillating crystals to form homogeneous pieces by means of plastical deformation are described. Optical transmission, radiation hardness, and scintillation spectra have been used for the evaluation of the quality of the bond. The results of experiments on fluorides of cerium, barium, and lead; and cesium iodide confirm that deformation welding can be used successfully for economic manufacturing of large homogeneous scintillators from several smaller parts.
Thermal Misfit and Thermal Fatigue Induced Damage in Brittle Composites
Authors: Sridhar N. , Rickman J. M. , Srolovitz D. J. 
Published: April 2011

AbstractWe examine the conditions under which differences in thermal expansion between a particle and the matrix leads to crack growth within the matrix. Using linear elastic fracture mechanics, we obtain closed-form, analytical results for the case of a penny shaped crack present in the matrix interacting with a spherical inclusion which is misfitting with respect to the matrix. A simple and direct relationship is established between the strain energy release rate, the crack size, the crack orientation with respect to the inclusion, the crack/inclusion separation, the degree of thermal expansion mismatch and the elastic properties of the medium. We also analyze the size to which these cracks can grow and find that for a given misfit strain and material properties, crack growth is inhibited beyond a certain critical crack size. Finally, the preferred orientation of these cracks as a function of misfit strain is predicted. The implication of these results for thermal cycling are analyzed.
Issues in Potential IMC Application for Aerospace Structures
Authors: Ward Charles H. , Culbertson Andrew S. 
Published: April 2011

AbstractIntermetallic-matrix composites (IMCs) are intended for applications involving higher temperatures and stresses than conventional metallic matrix composites. Consequently, environmental effects, thermo-mechanical fatigue, interfacial thermodynamic stability, creep resistance, processing and cost are only a few of the obstacles to introduction in real products. The primary goal of current IMC development efforts is to provide ‘revolutionary’ materials for components that are enabling technologies in advanced demonstrator gas turbine engines. As compared to production applications, the hurdles for entry into demonstrator engine programs are not as high due to the limited operating time and the small number of parts to be produced. This paper examines the barriers to the introduction of IMCs in the context of application to production aerospace structures.
Numerical Simulations of Creep in Ductile-Phase Toughened Intermetallic Matrix Composites
Authors: Henshall Gregory A. , Strum Michael J. 
Published: April 2011

AbstractAnalytical and finite element method (FEM) simulations of creep in idealized ductilephase toughened intermetallic composites are described. For these strong-matrix materials, the two types of analyses predict similar time-independent composite creep rates if each phase individually exhibits only steady-state creep. The composite creep rate increases above that of the monolithic intermetallic with increases in the stress exponent of the intermetallic, the volume fraction of the ductile phase, and the creep rate of the ductile phase. FEM analysis shows that the shape of the ductile phase does not affect the creep rate but may affect the internal stress and strain distributions, and thus damage accumulation rates. If primary creep occurs in one or both of the individual phases, the composite also exhibits primary creep. In this case, there can be significant deviations in the creep curves computed by the analytical and FEM models. The model predictions are compared with data for the Nb5Si3/Nb system.