bluuebunny/crossref_metadata_2025 huggingface dataset:
Low Temperature Atmospheric Pressure Chemical Vapor Deposition of Group 14 Oxide Films
Authors: Hoffman David M. , Atagi Lauren M. , Chu Wei-Kan , Liu Jia-Rui , Zheng Zongshuang , Rubiano Rodrigo R. , Springer Robert W , Smith David C.
Published: April 2011

Depositions of high quality SiO2 and SnO2 films from the reaction of homoleptic amido precursors M(NMe2)4 (M = Si, Sn) and oxygen were carried out in an atmospheric pressure chemical vapor deposition reactor. The films were deposited on silicon, glass and quartz substrates at temperatures of 250 to 450 °C. The silicon dioxide films are stoichiometric (O/Si = 2.0) with less than 0.2 atom % C and 0.3 atom % N and have hydrogen contents of 9 ± 5 atom °. They are deposited with growth rates from 380 to 900 Å/min. The refractive indexes of the SiO2 films are 1.46, and infrared spectra show a possible Si-OH peak at 950 cm−1. X-Ray diffraction studies reveal that the SiO2 film deposited at 350°C is amorphous. The tin oxide films are stoichiometric (O/Sn = 2.0) and contain less than 0.8 atom % carbon, and 0.3 atom % N. No hydrogen was detected by elastic recoil spectroscopy. The band gap for the SnO2 films, as estimated from transmission spectra, is 3.9 eV. The resistivities of the tin oxide films are in the range 10−2 to 10−3 Ω cm and do not vary significantly with deposition temperature. The tin oxide film deposited at 350°C is crystalline cassitterite with some (101) orientation.
Atomic Force Microscopy Study of Nickel Oxide Films Modified by Reactive Element
Authors: Czerwinski F. , Szpunar J.A.
Published: April 2011

The evolution of microstructure of thin oxide films during growth has been quantitatively analysed by atomic force microscopy (AFM). The oxide films were formed in pure oxygen atmosphere at temperatures ranging from 873 to 1173 K on polycrystalline nickel substrates. The substrates were both pure and superficially modified by nanometer-sized dispersions of CeO2. The incorporation of reactive element into the oxide inhibits the growth kinetics and affects the microscopic surface morphology. The extent of this effect depends essentially on the substrate surface microstructure prior to modification and the size of CeO2 particles. A correlation was found between the surface topography and the reduction of oxide growth rate caused by the reactive element.
The Microstructural Characterization of Nanocrystalline CeO2 Ceramics Produced by the Sol-Gel Method
Authors: Czerwinski F. , Szpunar J.A.
Published: April 2011

CeO2 ceramics were manufactured in the form of surface coatings deposited onto various substrates by sol-gel technology. The size of the CeO2 crystallites, dried at room temperature, was about 5 nm and did not change significantly after heating, up to 680 K. Further increase of the temperature resulted in a rapid growth of crystallites. The process of growth depends also on the film thickness and nature of substrate. The results obtained using thermogravimetric analysis (TGA) and infrared spectroscopy (IR) demonstrated that the thermal decomposition of gel was completed at about 750 K. There was no evident texture in both the as-deposited state and after heat-treatment. X-ray diffraction (XRD), the atomic force microscopy (AFM), and transmission electron microscopy (TEM) were used to characterize the structure of coatings. The examples of application of CeO2 ceramics as coatings for high temperature corrosion protection are presented. The role of size of CeO2 particles in modification of grain boundary transport is discussed.
Interfacial Structure and Mechanical Properties of Compositionally-Modulated Au-Ni thin Films
Authors: Baker Shefford P. , Bain James A. , Clemens Bruce M. , Nix William D.
Published: April 2011

Several characteristics of compositionally-modulated Au-Ni thin films have been observed to vary with composition wavelength for wavelengths between 0.9 and 4.0 nm. The average lattice parameter normal to the film plane displays a maximum, the elastic stiffness shows a minimum and the substrate interaction stress in the film goes through a compressive peak in this regime. These variations are all consistent with a model in which deviations from bulk behavior are confined to the interfaces in the material. In this paper, we present the results of microstructural analyses of these films. Symmetric and asymmetric θ–2θ x-ray diffraction scans were conducted with scattering vectors oriented at a variety of angles to the film normal. Rocking curve analyses were also conducted. Features arising from the composition modulation in symmetric scans are quite sharp. However, asymmetric scans and rocking curves indicate that these films have a relatively poor {111} texture. Data from all scans provide clear evidence that Au intermixes preferentially into Ni. These results are supported by computer simulations of the diffraction spectra and the results of electron-image and -diffraction analyses. These measurements provide a consistent explanation for the mechanical properties of these films.
Calculation of the [111]-Texture Dependence of the Elastic Biaxial Modulus
Authors: Small Martha K. , Nix William. D.
Published: April 2011

The elastic biaxial modulus of a polycrystalline material as a function of [111] fiber texture was determined by imposing an equibiaxial strain and calculating the resulting stress assuming a plane-stress condition. The situation of a such a texture in a film under plane-stress is commonly seen in deposited thin films of face centered cubic metals. The calculation was performed by determining the average biaxial modulus of a single crystal as a function of tilt angle off the [111] plcine normal and then using these values in a Gaussian distribution of crystal tilts off the [111] to simulate varying degrees of texture. Results are presented for several fee materials with different elastic anisotropy factors.
Intrinsic Stress and Microstructural Evolution in Sputtered Nanometer Single and Multilayered Films
Authors: Nguyen Tai D.
Published: April 2011

The relationship of intrinsic stress and microstructural evolution in nanometer thick Mo and Si films, and Mo/Si multilayers deposited by magnetron sputtering at low working pressure (2.5 mTorr) is studied. The stress depends strongly on the microstructure which evolves with the film thickness. Transition from tensile to compressive films is observed in the metal films, in which nucleation and columnar grain growth occur. Deposition of layered Mo films by time-delayed sequential sputtering of thin layers results in smaller grains that do not extend through the film thickness, and in more tensile stress state than thick films of trie same thickness. The Si films are highly compressive at all thicknesses studied. The multilayers in this study show compressive stresses, with higher compressive stress at longer periods, and decreasing stress at shorter periods. The interface stress in amorphous Mo/Si multilayers is determined to be 1.1 J/m2. Comparison with values in other systems is made.
Measurement of Thermally-Induced Strains in Polycrystalline Al Thin Films on Si Using Convergent Beam Electron Diffraction
Authors: Streiffer S. K. , Bader S. , Deininger C. , Mayer J. , Rühle M.
Published: April 2011

Strains in polycrystalline Al films grown on oxidized Si wafers were measured using convergent beam electron diffraction (CBED). CBED patterns were acquired on a Zeiss EM 912 TEM equipped with an imaging energy filter and CCD camera. HOLZ line positions in the (000) CBED disk were matched using an automated refinement procedure. A sensitivity to variations in lattice parameter of approximately 0.00007 nm was obtained. Strong deviations from a simple equibiaxial strain, perfect [111] texture model were observed.
Dopant Implantation and Activation in Polycrystalline-SiGe
Authors: Edwards W.J. , Chieh Yuen-Shung , Lin Samuel , Ast D.G. , Krusius J.P. , Kamins T. I.
Published: April 2011

The activation of dopants and the evolution of the microstructure of poly-SiGe films during the activation. anneal are of interest for applications such as removable diffusion sources for shallow junctions in CMOS circuit processing, low resistance contact layers and elements for thin film transistors in active matrix flat panel displays. To study these effects, 2300Å poly-SiGe films with Ge content between 20 and 48% were deposited on 600Å poly-Si seed layers by APCVD on thermally oxidized Si substrates. Growth temperatures were between 600 and 700°C. These films were then implanted with B and As at energies of 40 and 80 keV, respectively, at two different doses of 5 × 1013/cm2 and 5 × 1016/cm2. To activate the dopants, the samples were furnace annealed at temperatures from 600 to 1000°C in an N2 ambient. Additional samples were rapidly annealed at temperatures between 800 and 1050°C for times up to 120 seconds. The sheet resistance, measured using a four-point probe, of 5 × 1016 /cm2 arsenic implanted films increased by a factor of two as the Ge content in the film increased from 20 to 48%. The boron doped film, on the other hand, showed no increase in sheet resistance with Ge content. TEM showed that in all cases the grain size increased after anneal. However, the grain sizes of the annealed, arsenic doped samples were on average 5 times larger than those of the boron-doped samples with the same anneal. The sub-grain structure of these films also changed after implantation and annealing. In particular, the twin planes increased in size in boron doped samples and sub-grain twinning virtually disappeared in the arsenic doped samples. In 5 × 1016 /cm2 As implanted samples, precipitates were formed which may indicate that the As solubility limit in the films has been exceeded. These precipitates are believed to be As or Asrich and could be responsible for the sheet resistance increase with Ge fraction, since the maximum solubility for As in Ge is lower than in Si by about a factor of ten.
Grain Growth Kinetics in Microcrystalline Materials
Authors: Sursaeva V. G.
Published: April 2011

Certain experimental results are presented concerning grain growth in microcrystalline Ag films. Dark field TEM technique was used for the measurement of grain size, trijunction velocity and grain boundary mobility. We found that the activation energy for trijunction motion is 25.0 kJ/g.atom, and the activation energy for the grain boundary motion is 50.0 kJ/g.atom.
Amorphous Silicon Alloy Photovoltaic Technology - From R&D to Production
Authors: Guha S. , Yang J. , Banerjee A. , Glatfelter T. , Hoffman K. , Ovshinsky S. R , Izu M. , Ovshinsky H. C. , Deng X.
Published: April 2011

The key requirements for photovoltaic modules to be accepted for large-scale terrestrial applications are (i) low material cost, (ii) high efficiency with good stability, (iii) low manufacturing cost with good yield and (iv) environmental safety. Thin films of amorphous silicon alloy are inexpensive; the products are also environmentally benign. The challenge has been to improve the stable efficiency of these modules and transfer the R&D results into production. Using a multijunction, multi-bandgap approach to capture the solar spectrum more efficiently, we have developed one-square-foot modules with initial efficiency of 11.8% After 1000 h of one-sun light soaking, a stable efficiency of 10.2% was obtained. Both the efficiency values were confirmed by National Renewable Energy Laboratory. The technology has been transferred to production using an automated roll-to-roll process in which different layers of the cell structure are deposited in a continuous manner onto stainless steel rolls, 14′ wide and half a mile long. The rolls are next processed into modules of different sizes. This inexpensive manufacturing process produces high efficiency modules with subcell yields greater than 99% The key features of the technology transfer and future scope for improvement are discussed.
Crystallization Behavior of the Amorphous Si1-xGex Films Deposited on SiO2 by Molecular Beam Epitaxy(MBE)
Authors: Hwang Chang-Won , Ryu Myung-Kwan , Kim Ki-Bum , Lee Seung-Chang , Kim Chang-Soo
Published: April 2011

We have investigated solid phase crystallization behavior of the MBE grown amorphous Si1-xGex (x=0 to 0.53) layers using x-ray diffractometry and transmission electron microscopy (TEM). It is found that the thermal budget of the solid phase crystallization of the film is significantly reduced as the Ge concentration in the film is increased. In addition, we find that the amorphous Si film crystallizes with a strong (111) texture while the Si1-xGex alloy film crystallizes with a (311) texture suggesting that the solid-phase crystallization mechanism is changed by the incorporation of Ge. TEM analysis of the crystallized film shows that the grain morphology of the pure Si is an elliptical or a dendrite shape with a high density of microtwins in the grains while that of the Si0.47 Ge0.53 alloy is more or less equiaxed shape with a much low density of crystalline defects in them.
Interfacial Solid-State Oxidation Reactions In The Sn-Doped In2O3 On Si And Si0.85Ge0.15 Alloy Systems
Authors: Ow-Yang Cleva W. , Shigesato Yuzo , Mohanty Rita , Paine David C.
Published: April 2011

We have experimentally demonstrated that the interface between ITO and Si or Si0.85Ge0.15 is metastable, with silicon reducing ITO to form an amorphous oxide layer and In metal. A 400nm-thick ITO layer was deposited on two types of substrates: p-type, <100> silicon wafers and a silicon wafer with a 400nm-thick layer of Si0.85Ge0.15 grown by CVD. Annealing of the ITO/Si system resulted in the growth of a 5nm-thick planar, interfacial SiO2 layer and the formation of In metal in the ITO above the SiO2 layer. In contrast, annealing of the ITO/Si0.85Ge0.15 system produced an interfacial Si0.85Ge0.15O2 layer that was non-uniform in thickness and which had a non-planar surface morphology. As-deposited and annealed samples were characterized by HREM, EDS, and C-V measurements. Thermodynamic and kinetic arguments predicted both of the different reaction paths that were observed in the two systems.
Surface Analysis Of Lcd Materials iN Various Stages of Production by Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS)
Authors: Lee J.J. , Lindley P.M. , Odom R.W.
Published: April 2011

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a surface analysis technique which provides a sensitive characterization of the elemental and molecular composition of the near-surface region (top few monolayers) of solid materials1. This mass spectrometry technique can also localize the distribution of specific elements, molecules or molecular fragments at submicrometer (µm) lateral resolutions.2
Room Temperature Laser Deposited Indium Tin Oxide Films for Display Applications
Authors: Yip W. C. , Bhat A. Gururaj , Kwok H. S.
Published: April 2011

Indium tin oxide is the most basic transparent electrode material for all flat panel displays. Commercial ITO glass is manufactured mostly by sputtering. Here, we report the use of pulsed laser deposition to produce ITO thin films on glass at room temperature. Several interesting properties of such films were observed. (1) It was found that the resistivity of 0.5mΩ-cm compared very well with the best published values produced at high deposition temperatures. Room temperature deposition affords the possibility of using plastics and other flexible substrates for displays. (2) The microstructure of these ITO films were quite different from those of commercial ITO glasses. (3) By passing a strong current through the film, a large thermally induced Δnl could be observed. This change was due to lateral stress and could be as large as 1μ m for a 1-μm thick film. An electro-optic shutter can easily be designed with such films. Applications of this electronically controlled Δnl to display technology are discussed.
Blue And Yellow Light Emitting Phosphors For Thin Film Electroluminescent Displays
Authors: Holloway Paul H. , Yu J.-E. , Rack Phillip , Sebastian Joseph , Jones Sean , Trottier Troy , Jones K. S. , Pathangey B. , Anderson T.J. , Sun S.-S. , Tuenge R. , Dickey E. , King C.N.
Published: April 2011

Following a description of the purpose and participating members in the Phosphor Technology Center of Excellence, research on the growth and characterization of modulation doped ZnS:Mn and of Ca0.95Sr0.05Ga2S4:6%Ce are reported. ZnS:Mn has been grown using MOCVD and incorporation of Mn in 1 to 5 layers from 5 to 20 nm thick separated by layers of pure ZnS from 5 to 50 nm thick. This is shown to result in lower threshold voltages for ACTFELD displays. The luminescence spectra from sputter deposited, cerium-doped thiogallate thin films were measured and the diffusion of thin ZnS passivation layers versus temperature of heat treatment was discussed.
Electrophoretic Deposition Of Phosphors For Display Technology
Authors: Shane Michael J. , Talbot Jan B. , Sluzky Esther , Hesse K. R.
Published: April 2011

Electrophoretic deposition is a process used in producing display screens, in particular highresolution CRT screens. The deposition of phosphor particles from isopropanol suspensions is investigated. It is shown that two materials deposit during electrophoretic deposition on a cathode: the phosphor particles, and hydroxides formed by chemical and electrochemical reactions occurring at the cathode. A simple model to predict the deposition rates of these two materials, given the particle and ion concentrations and mobilities, is developed. Finally, the microstructure of the resulting deposited screen is investigated using scanning and transmission electron microscopy.
Stress In Molybdenum Films Used For Fea Display Technology
Authors: Greer James A. , Pagliuca Guy F.
Published: April 2011

Flat-panel displays based on cold-cathode field emission are actively being developed in a number of laboratories world-wide. Once fully developed, Field Emitter Displays (FEDs) will compete directly with Liquid Crystal Displays (LCDs). FEDs offer several significant advantages over LCDs including higher screen brightness, wider viewing angle, lower power consumption, and operation over a broader temperature range, making FEDs desirable for applications such as lap-top computers. Presently, several materials are being evaluated for use as coldcathode field emitters including molybdenum1, silicon2, and DLC3. At this time it is unclear which material (or materials) will ultimately be incorporated into commercial or military flatpanel display products. Each potential cathode material has its own set of advantages and disadvantages, and the ultimate choice will depend on the particular display requirements and architecture.
Influence of the Deposition Rate of the a-Si:H Channel on the Field-Effect Mobility of TFTs Deposited in a VHF Glow Discharge
Authors: Meiling H. , Westendorp J. F. M. , Hautala J. , Saleh Z. M. , Malone C. T.
Published: April 2011

Inverted-staggered hydrogenated amorphous-silicon thin-film transistors (a-Si:H TFTs) were deposited in a glow discharge with an excitation frequency of 60 MHz. At 13.56 MHz it has been reported that the field-effect mobility of this type of TFT decreases with increasing deposition rate of the a-Si:H layer, due to an increase in the defect density in the channel. A successful way of increasing the deposition rate without deteriorating the material properties has turned out to be utilizing a higher excitation frequency than the conventional 13.56 MHz.

The deposition rate of the 60-MHz-deposited transistor channel was changed from 350 to 1300 Å/min by diluting the process gas silane with hydrogen and by changing the rf power. The dependence of the a-Si:H material properties on deposition parameters is described. The deposition rate dependence of the mobility in the 60-MHz deposited thin films and devices is presented and discussed in terms of hydrogen dilution in the plasma and the hydrogen content of the a-Si:H films.
A Comprehensive Study of Plasma Enhanced Crystallization of a-Si:H Films on Glass
Authors: Yin Aiguo , Fonash Stephen J. , Reber D. M. , Li Y. M. , Bennett M.
Published: April 2011

An extensive study is reported here on plasma enhanced crystallization of a-Si:H films on glass. Both electron cyclotron resonance (ECR) helium plasma exposures and ECR oxygen plasma exposures were investigated to obtain enhanced crystallization of a-Si:H films. We have found that the ECR helium plasma exposure can render more crystallization enhancement than the ECR oxygen plasma exposure. This is because ECR helium plasma exposures can produce more dangling Si bonds, voids, and “interstitial” Si atoms in a-Si:H films than ECR oxygen plasma exposures. These dangling Si bonds, voids, and “interstitial” Si atoms are believed to be the cause of the observed reduced incubation time as well as enhanced grain growth of the plasma exposed a-Si:H films in subsequent crystallization processes. This model is supported by the effects of plasma exposure time on the enhanced crystallization process of a-Si:H films.
High Power Crossed-Field Amplifier for Material Processing
Authors: Worthington M. S. , MacPhail Guilford R.
Published: April 2011

The use of microwave energy for industrial processing applications has been ongoing since the early 1950's. A number of high power tubes were developed in the mid-1960's at 805, 915 and 2,450 MHz for industrial uses. One super power crossed-field amplifier (CFA), the QKS1262, was available in either 50 or 100 kW continuous wave (CW) format. This CFA was designed with a platinum emitter which was pulse started with 100 W average power. The CFA operates at ∼20 kV at 5 amps (50 kW - CW output) or 10 amps (100 kW - CW output/65% efficiency).

This paper will describe the operating characteristics of the QKS1262 and the options in design to attain high power with high efficiency and long life (25,000 hours).
Moisture Measurement of Composites
Authors: Werner Michael J. , King Ray J.
Published: April 2011

Open reflection microwave resonator sensors have been developed for in situ measurement of the bulk moisture absorbed by nonconducting fiber-reinforced composites. These contacting sensors operate at about 4 GHz, and have sensitivities and resolutions of about 0.1% moisture. In application, two independent parameters are measured simultaneously. From these, the two components of the effective complex dielectric constant ε* (ε′= - јε″) as seen by the sensor are determined. Both ε′ and ε″ are highly linear with absorbed moisture.

Both linearly polarized sensors (for measuring anisotropie moisture absorption) and circularly polarized sensors (for measuring the average anisotropy) have been demonstrated. Moisture uptake in the polymer matrix, moisture wicking along Kevlar fibers, and the effects of moisture damage due to blistering, microcracking, etc., all have been tracked in accelerated moisture exposure tests. Where applicable, the experimentally measured profiles have been validated using a one-dimensional Fickian diffusion model.

The sensors are suitable for many applications, e.g., to map the extent of moisture contamination in composite panels, as a portable probe for aid in composite panel repairs, as a cure monitor of moisture in powder or fluid polymers, or as a permanently installed sensor for monitoring the accumulated moisture in radomes. In the latter case, exceptionally improved sensitivities and resolutions are possible.
Temperature Distribution in Microwave Sintering of Alumina Cylinders
Authors: Thomas J. R. , Katz Joel D. , Blake Rodger D.
Published: April 2011

Small cylinders of high-purity alumina were encased in a “casket” of low-density zir-conia insulation and heated to sintering temperature in a large multi-mode microwave oven. Optical fiber sensors were used to monitor the temperature at several locations in the system. It was found that the alumina samples heat faster than the zirconia insulation at temperatures above 1000°C, and that the temperature distribution in the sample is essentially uniform during the heating process.

A two-dimensional mathematical model of the heat transfer process was developed which reproduces the essential features of the observed phenomena. Literature data for all temperature-dependent properties were incorporated into the model. The model suggests that the alumina samples absorb a significant fraction of the microwave energy.
Microwave Remediation of Hazardous Waste: A Review
Authors: Oda Steven J. , Eng P.
Published: April 2011

Quantities of untreated hazardous wastes are growing at alarming rates. Intensive searches are underway to develop more effective and energy efficient solutions that can reduce or eliminate the impact of these wastes. One potential answer involves the use of microwave heating. Incorporated into process equipment, microwave heating can provide a number of important attributes that contribute to productivity improvement. These characteristics include: selective heating associated with the potential for recovery of value-added product; volumetric heating to improve processing time; the potential for remote operation to limit personnel exposure to hazardous waste; and, in situ application to reduce the risk of airborne contamination caused during material transfer. Successful applications appear in niche areas using microwave heating to provide an economic advantage over conventional surface heating techniques particularly in areas such as infectious waste, soil decontamination, solvent recovery and microwave ‘catalysis’. The perception of high cost and ‘fear-of-the-unknown’ remain obstacles preventing more widespread adoption of these technologies as in the case of other relatively new microwave applications. An understanding of the reasons for the success of existing commercial systems helps in targeting opportunities for future applications in hazardous waste treatment. This review illustrates these factors by highlighting examples of existing applications, new research and development initiatives and future opportunities.
Survey of Modern RF and Microwave Test Instruments
Authors: Rytting Doug , Slater Carla
Published: April 2011

This survey paper introduces the basics of RF and microwave device (or component) testing. It establishes a foundation of concepts and terminology.
Firing Ceramics with a Large 17.6kW Microwave Kiln
Authors: Bratt M. J. , Hamlyn M. G. , Bowden A. L.
Published: April 2011

This paper gives details of microwave firing experiments carried out with a large 17.6kW 2450 MHz microwave kiln on a range of ceramic materials.

The design of the large kiln is discussed, together with results of large batches of ceramic products. The design of successful heating experiments in terms of thermal insulation and microwave susceptors is discussed in relationship to the dielectric properties of the material to be fired.

Results are given of the fired properties from batches of products fired in the kiln, and the uniformity of the fired properties of large batches is discussed.
Phase Transformation and Densification Behavior of Microwave Sintered γ-A12O3
Authors: Freim John , McKittrick Joanna , Katz Joel , Sickafus Kurt
Published: April 2011

The phase transformation and densification behavior of gas condensation synthesized γA12O3 sintered with microwave radiation has been studied. Nucleation and growth phase transformations, which produce α-A12O3 occurred as the material was heated through the temperature range of 800–1300°C. These phase transformations resulted in anomalous grain growth with a distinct change in particle morphology, crystallite size and surface area. A12O3 derived from a chemically synthesized boehmite precursor has been shown to exhibit the same nucleation and growth phase transformation behavior when conventionally heated. It is concluded that nanocrystalline γ or β alumina will not be a viable starting material for the production of dense bodies with grain sizes of less than 100 nm.
Microwave Sintering of Nanocrystalline ZrO2 Powders
Authors: Jinsong Zhang , Yongjin Yang , Lihua Cao , Shengqi Chen , Xiaoping Shong , Fei Xia
Published: April 2011

Nanociystalline Z1O2 powders, prepared by plasma-chemical method, were sintered by microwave heating. The experimental results indicated that the thermal runaway and hot spot are two important obstacles to successful microwave sintering of nanocrystalline ZrO2. By controlling ratio of dielectric loss between sintered ZrO2 compact and adjacent thermal insulator, the ZrO2 compact with diameter larger than 30 mm could be microwave-heated rapidly and uniformly from room temperature to 1600 °C in 80 minutes, the mean grain size of ZrCh ( 96% T.D. sintered at 1500°C for 5 minutes) is lower than 20 nm determined by means of quantitative XRD and TEM. The change of ZrO2 grain size may be related to phase transformation (t→m).
Microwave Induced Polymerization of Monomer Impregnated Hardened Cement
Authors: Hetz Joseph , Chang John , Brodwin Morris
Published: April 2011

It is well known that when pores of hardened cement are filled with a suitable polymer, desirable properties are greatly enhanced. With microwave induced polymerization, significant increases in compressive strength are observed.

Mortar samples with a sand cement ratio of 2.5 and water cement ratios, 0.3, 0.4, and 0.5, were molded and hardened. After sufficient hydration, they were evacuated, filled with MMA and pressurized. The samples were then processed in a dynamic multimode applicator. Temperature was monitored and they were processed until the temperature exceeded 85°C.

The principal result is the increase in compressive strength as compared to an untreated sample. For a W/C=0.5, and a sample hydrated for one day, the strength increased by a factor of6.0. In addition, the highly porous 1 day polymerized samples exhibited significantly greater strength than 28 day unpolymerized material.
Experimental Study of Loss Mechanisms in Polymer-Metal Composites at Microwave Frequencies
Authors: Ludman John P. , Stern Curtis H.
Published: April 2011

The microwave heatability of a low loss polymer (polypropylene) was enhanced by the addition of a conductive powder (iron). The effects of the amount (5–40% iron by volume) and size of the conductive particles on the microwave heatability were studied. The complex permittivity and complex permeability at microwave frequencies and the dc resistivity were measured. Samples were also heated in a multimode microwave cavity. Results show that microwave heating increased with increasing iron concentration. However, the penetration depth of the microwaves decreased with increasing iron content, and dramatically decreased when the polypropylene-iron composites became electrically conductive at the percolation threshold.
Processing of Thermoset Prepreg Laminates Via Exposure to Microwave Radiation
Authors: Paulauskas Felix L. , Mee Thomas T.
Published: April 2011

Studies of microwave-assisted curing of neat resins (epoxy) and unidirectional glass and carbon fiber laminates have shown that a substantial reduction in the curing time was obtained [1]. This may be explained by the penetration of microwave energy directly and throughout the laminate with enhancement of the kinetics of the chemical reaction.

Results of this work indicate that the microwave assisted curing of glass fiber laminates also shows a substantial reduction of the required curing time.

Microwave radiation of 2.45 GHz has been demonstrated to be an acceptable method to cure unidirectional carbon fiber laminates. Also, effective curing of crossply (0/90) laminates through this method was observed when proper rotation of the parts accompanied the curing process. This is in accordance with previous work [2,3].

Multidirectional carbon fiber/epoxy laminates demonstrate a lack of coupling during the curing process. A direct curing of these laminates was not possible by microwave radiation with the experimental approach used, in agreement with previous work [4[. Nevertheless, a moderate reduction in the curing time of these thin laminates was observed due to hybrid curing.
Critical Assessment of Microwave-Enhanced Diffusion
Authors: Rothman Steven J.
Published: April 2011

The use of microwave heating or microwave plasmas in the sintering of ceramics has often been observed to result in more rapid sintering than the same heating schedule in a conventional furnace; the increased sintering rate has sometimes been ascribed to the enhancement of diffusion by microwave heating/plasma. Some experiments on diffusion measurements under microwave heating have also been carried out in order to check this hypothesis. In this paper, we evaluate the experimental evidence for microwave enhanced diffusion, discuss the various models that have been proposed for the enhanced diffusion, and suggest some further experiments aimed at understanding these phenomena.
High Power Gyrotrons
Authors: Temkin R. J. , Kreischer K. E.
Published: April 2011

High power gyrotrons have been developed for application to plasma heating in the program of magnetically confined nuclear fusion research. Gyrotron power levels of up to 1 MW in long pulse operation (>ls) and up to 200 kW in true continuous operation (CW) have been demonstrated at frequencies in the 8 to 140 GHz range. The status of high power gyrotron development is reviewed. One current goal of the worldwide gyrotron effort is the development of 1 MW,CW gyrotrons at a frequency of about 170 GHz for heating the proposed international tokamak ITER to ignition. Gyrotrons are also now being used in a variety of other applications including materials processing. Improved gyrotrons with features such as wide range tuning could be developed for industrial applications.
The Klystrode® Iot a New, Compact, High Efficiency Electron Tube
Authors: Peters R. Donald , Haase Andrew , Johnson Chris , Tornoe Robert N.
Published: April 2011

The Klystrode® (IOT) is a new high power electron tube which combines the features of Klystron and the Tetrode. During the past six years it has virtually taken over the UHF-TV market and has demonstrated its capabilities in high power research applications. This paper describes the principles of Klystrode IOT operation and the power and frequency ranges where it is most useful. Field experience with over fifty (50) transmitters in UHF TV service is reported as well as test results from high power scientific devices operated at 267 MHz, 250 kW (CW) and 425 MHz, 500 kW (pulse). Finally, future improvements in the Klystrode IOT to reduce cost, improve efficiency and optimize the tube for industrial applications.
Cerium-Activated Lanthanum Beryllate as A Gamma Detector Material
Authors: Czirr J. Bart , Berrondo Manuel
Published: April 2011

Abtract

We have tested a single crystal of Ce-activated lanthanum beryllate BEL(Ce) as a potential gamma detector material. The density (6.1 g.cm−3) and decay time (50 ns) are competitive with other recently developed materials. The scintillation efficiency is 57- to -95% that of BGO. For an excitation wavelength of 340 nm, the emission spectrum is a broad peak centered at 450 nm. The H2 annealed sample is transparent for wavelengths greater than 400 nm. We are continuing a program to improve the scintillation efficiency by varying the crystal growth conditions.

The crystal was prepared by M. Long and E.W. O'Dell of AlliedSignal, Inc., using the Czochralski technique.
Structure Characteristics of Cubic and Orthorhombic Phases of High Density Scintillator Pbf2 from 4.2–300 K
Authors: Shmyt'ko Ivan , Savchenko I.B. , Klassen N.V. , Bagautdinov B.Sh. , Emel'chenko G.A. , Sinitzin V.V.
Published: April 2011

An anomaly of the temperature dependence of the unit cell parameter has been observed for β–PbF2 single crystals at 200 K that is interpreted as a phase transition to a pseudocubic lattice. Such a pseudocubic phase is observable at room temperature after uniaxial plastic deformation of the bulk single crystals. The structural aspects of the β→α transition have been established. The as-grown crystals of α–PbF2 phase are shown to undergo a phase transition at 100 K.
Photoluminescence and Scintillation Properties of Pb2+ Based Quantum Dots in CsCI Host Crystal
Authors: Nikl M. , Nitsch K. , Dafinei I. , Lecoq P. , Pazzi G.P. , Fabeni P. , Gurioli M.
Published: April 2011

The spectral and kinetic properties of photoluminescence of Pb2+ aggregated phase in CsC1 host, together with scintillation characteristics of CsCI:Pb crystals, are reported in the 10 - 300 K temperature range. Absorption, steady-state excitation and emission spectra of Pb2+ phase in CsCI host are similar to those of CsPbCl3 bulk crystal (emission peak at 419 nm at 10 K). The decay of the 421 nm luminescence of the Pb2+ phase in CsCl shows single exponential behavior with extremely short decay time of 40 ps at 421 nm and 10 K,which is considerably shorter than the decay times found in the decay of CsPbCl3 bulk emission (0.45, 2.8 and 12 ns at 418 nm and 10 K). In the scintillation decay of CsCI:Pb, two components with 0.95-1 ns and 2-3 ns decay times were found and no slower component is present at room temperature.
New Fluors for Radiation Tolerant Scintillators
Authors: Gao F. , Dharia J.R. , Mcgowan W.M. , Hilinski E.F. , Johnson K.F. , Schlenoff J.B.
Published: April 2011

The new generation of high energy accelerators - LHC, CEBAF, RHIC - have encouraged the development of more robust plastic scintillators. Monitors and detectors for these machines will require plastic scintillator with greater radiation tolerance. Although the major cause of radiation damage in plastic scintillator is the creation of color centers in the base plastic, the most successful approach to date has been to utilize fluors which circumvent, rather than solve, the radiation damage problem. Two techniques have been found to be useful. First, increase the concentration of fluors so that the optical density of the fluors for absorption of the scintillation photons remains much higher than the optical density of the radiation induced color centers. Second, use fluors which emit at longer wavelengths than traditional fluors, thus avoiding radiation induced color centers. The present work attempts to meet these requirements by modifying the structure of the 3-HF molecule.
Elastic Scintillation Materials Based on Polyorganosiloxane
Authors: Grine B.V. , Andryushchenko L.A. , Shershukov V.M. , Ulanenko K.B. , Minakova R.A. , Sevastjanova I.V.
Published: April 2011

The developed elastic scintillators based on polymethylphenylsiloxane rubber are characterized by an elevated light output and a low toxicity. The increase of their light output is achieved by raising the content of phenyl chains, varying the chemical structure of luminescent additions and using isopropylnaphthalene. This high-boiling solvent introduced into the scintillation siloxane compositions is confined within siloxane matrix after the hardening of the rubber.
Relationship Between Microstructure and Efficiency of Scintillating Glasses
Authors: Bliss M. , Craig R. A. , Reeder P. L. , Sunberg D. S. , Weber M. J.
Published: April 2011

Prior work has shown that there is a correlation between trap densities and scintillation efficiency of cerium-activated, lithium-aluminosilicate glasses. Raman spectroscopy has strongly suggested that phase separation may be playing an important role in governing the scintillation efficiency. In this study, we relate the thermoluminescence glow-curve data and microstructural analysis for a compositional series. The thermoluminescence data provide information about the traps in the neighborhood of the activator (Ce3+). The microscopy and crystallization of the glasses provide direct evidence of activator partitioning.
On the Temperature Stability of NaI(T1) Scintillators
Authors: Gektin A.V. , Brinev B.V. , Serebrayannyi V.Ya. , Vinograd E.L.
Published: April 2011

The temperature stability of NaI(T1) scintillators is studied for crystals with various Tl+ impurity content. It is shown that supersaturation of the T1+ ions and regulation of solid solution decomposition increase the light output at elevated temperatures. An explanation of this phenomenon is proposed.
Energy Localization and Decay in Highly Ionic Crystals
Authors: Williams R. T. , Thoma E. D. , Bunton P. H.
Published: April 2011

Luminescence from localized states in pure wide-gap crystals is examined from the perspective of modern fast scintillator requirements. Recent advances in the understanding of self-trapped excitons are summarized with regard to excited-state configurations, spectra, and luminescence efficiency. As an example, the fast luminescence of partially quenched type I STEs in RbI offers tuneable-lifetime subnanosecond pulses which could be useful for timing applications. The possible role of hole localization in cross luminescence is discussed. Stokes-shifted luminescence in some pure rare-earth fluoride crystals probably originates from self-trapped excitons of forms to be discussed.
Cluster Models of Doped Ionic Crystal Scintillators. Quantum Calculations+
Authors: Berrondo M. , Rivas-Silva J.F. , Czirr J.B.
Published: April 2011

We have performed quantum electronic ab initio calculations of clusters of alkali halides, both pure and doped. In order to estimate the pure crystal energy gap and the dopant excitation, we have considered a central cation and four shells of ions surrounding it. We have studied KC1, Nal, NaCl and KI, both pure and with a Tl+ ion replacing thecentral alkali cation. Encouraging results are presented for absorption and emission.
Creation of Electron-Hole Pairs in Inorganic Scintillators
Authors: Rodnyi Piotr A. , Dorenbos Pieter , Van Euk Carel W.E.
Published: April 2011

Models are discussed of the first stage of the scintillation mechanism in an inorganic scintillator: the primary interaction and the thermalization process. The model predictionsare compared with experimental results, an extension of the theory is made and conclusions are drawn concerning the best description of the first stage.
Radiation Damage Mechanisms In Scintillator Materials: Applications to BaF2 and CeF3
Authors: Halliburton L. E. , Edwards G. J.
Published: April 2011

Results from recent radiation damage studies in high quality BaF2 and CeF3 crystals are presented. Optical absorption and electron paramagnetic resonance (EPR) techniques are used to identify specific radiation damage mechanisms. Specific attention is given to the role of oxygen and hydrogen in the room temperature damage of BaF2. Also, Mn2+ ions are shown to change valence state in BaF2during room temperature irradiation. Numerous optical absorption bands are created in CeF3 during irradiations at low temperature. These bands are associated with electron traps (either F centers or Ce2+ ions) and they thermal anneal below room temperature. An EPR spectrum, assigned to F centers, is observed in low-temperature irradiated CeF3.
The Radiation Effect Mechanism of Some Rare Earth Doped BaF2 Crystal
Authors: Mu Gu , Lingyan Chen , Jie Du , Kaihua Xiang , Gang Chen , Shaoxia Ren , Fengyin Zhang
Published: April 2011

In this paper, we used the Discrete Variational Xα, (DV-Xα) method to calculate the energy level of some rare earth doped BaF2 crystals and indicated that the Eu, Dy and Yb elements will change their valence from +3 to +2 under irradiation and thus change the optical properties of the crystals.The results show that this radiation effect model presented agree well with experiments.
An Investigation of Radiation Damage Induced by Hydroxyl and Oxygen Impurities In BaF2 Crystal
Authors: Lingyan Chen , Mu Gu , Liming Wang , Kaiiiua Xiang
Published: April 2011

The radiation effect in hydrolyzed BaF2 was investigated through tile changes in their optical absorption and EPR spectra before and after γ-irradiation. The resulti demonstrated that hydroxyl and oxygen can be easily introduced into BaF2by means of a hydrolysis, the most likely modes are OH— ions substituting for fluorine and O2– ions substituting for fluorine associated with charge-compensating fluorine vacancies O2– — F+. Combining with the Hartree-Fock-Slater local-density discrete variational (HFS-Xα-DV) cluster calculation on some possible defects related to hydrogen and oxygen impurities, we propose that the radiation damage observed in hydrolyzedBaF2 can be explained in terms of OH— and O2– — F+ dissociation through a radiolysis.
Growth of Halide Scintillators with a Modified Heat Exchange Method
Authors: Berthold T.G. , Grabmaier B.C.
Published: April 2011

To test the potential of the heat exchange method for growing scintillator crystals, ingots of mono-, bi- and trivalent halides were prepared. Except for monovalent halides, the removal of oxygen compounds is indispensable. In the case of CaF2 and BaF2, the purification by reaction with NH4F and a superheating of the melt could be included in the crystal growth process. Clear, monocrystalline ingots of these substances were grown in 4f-heated glassy carbon crucibles without seed crystals. Oxygen-free starting material had to be prepared for the growth of inclusion free CeF3 crystals.
Enhanced Luminescence From Rare Earth Doped Thin Films
Authors: Olmsted B. L. , Jones M. L.
Published: April 2011

Results of a study of the luminescence of rare earth ions in crystalline thin films grown on reflective substrates will be presented. As an example, the luminescence of Sm2+:CaF2 films has been calculated as a function of the separation between the active layer and a silicon substrate. These calculations involve coupling the narrow resonance of the rare earth ions to the electromagnetic modes of the film. Results including the optimum thickness for enhanced luminescence will be presented. Experimental work on Sm2+:CaF2 films grown on Si by molecular beam epitaxy will also be discussed.
Precision Machining And Polishing Of Scintillating Crystals For Large Calorimeters And Hodoscopes
Authors: Wuest Craig R. , Fuchs Baruch A. , Holdener Fred R. , Heck Joaquim L.
Published: April 2011

New machining and polishing techniques have been developed for large scintillating crystal arrays such as the Barium Fluoride Electromagnetic Calorimeter for the GEM Detector at SSCL, the Crystal Clear Collaboration's cerium fluoride or lead tungstenate calorimeter at the proposed LHC at CERN, the PHENIX Detector at RHIC (barium fluoride), and the cesium iodide Calorimeter for the BaBar Detector at PEP-I B Factory at SLAC. The machining and polishing methods to be presented in this paper provide crystalline surfaces without sub-surface damage or deformation as verified by Rutherford Back-scattering (RBS) analysis. Surface roughness of about 10-20 angstroms and sub-micron mechanical tolerances have been demonstrated on large barium fluoride crystal samples. Mass production techniques have also been developed for machining the proper angled surfaces and polishing up to five 50 cm long crystals at one time. These techniques utilize kinematic mount technology developed at LLNL to allow precision machining and polishing of complex surfaces. We will present this technology along with detailed surface studies of barium fluoride and cerium fluoride crystals polished with this technique.
Lead Tungstate For High Energy Calorimetry
Authors: Dafinei I. , Auffray E. , Lecoq P. , Schneegans M.
Published: April 2011

The very large volumes needed to build a crystal calorimeter for High Energy Physics experiments bring cost considerations at the front of the stage. A reasonable compromise between cost and performances must be reached. One possible solution is to look at very dense materials like PbWO4, which will reduce the detector volume, even if the relatively low light yield will impose some limitations to the energy resolution. A review of the different results obtained by the Crystal Clear collaboration will be given for this crystal, including spectroscopic data and radiation damage measurements.
Fiber Coating Performance in TiAl
Authors: McCullough C. , Kieschke R. R.
Published: April 2011

The interfacial chemical behavior of two candidate coating systems for use on fine diameter (∼10 μm) Al2O3 in TiAl is presented. The performance of the Nb/Y2O3 system appears to be related to the transport rate of Ti through the Y2O3 layer. Interfacial reaction is then observed at points where the Y2O3 thickness is less than about 1 μm. The main reaction product formed appears to be an oxygen saturated TiAl phase. An alternative system, C/TiN/Y2O3 is then presented as a solution to the Ti transport problem and may offer more desirable interfacial mechanical properties.