Sample records for vacuum diffusion bonding

  1. The Effects of Intermediate Layer and Surface Nanocrystallization on the Vacuum Diffusion Bonding of Commercially Pure Titanium

    NASA Astrophysics Data System (ADS)

    Chen, Chunhuan; Liu, Xiaojing; Zhao, Xiujuan; Ren, Ruiming

    Using cooper foil as intermediate layer, commercially pure titanium (CP-Ti) was vacuum diffusion welded after surface nanocrystallization. The effects of the interlayer and SNC treatment on the bonding state were discussed thereafter. The results showed that about 10 ?m nano-structured surface layer was achieved on CP-Ti. Well bonded joint could be obtained by two original CP-Ti samples welded directly at the conditions of 950°C welding temperature and 5 MPa pressure. Excellent bonding between nanocrystalline Ti and cooper substrate was achieved at 850°C but lots of cavities were observed on the interface when welded at the same temperature as that for two Ti substrates. Surface nanocrystallite utilization could play a role in promoting interface diffusion procedure by surface atoms activation and large amount of diffusion channels. Cu substrate increased the contact area of interlayer to prevent the possible influence of induced surface roughness on diffusion bonding formation.

  2. A general model for vacuum condensates and vacuum diffusive coatings

    Microsoft Academic Search

    RI Shishkov; EM Lisichkova

    1995-01-01

    The paper suggests a general model for the classification of metal coatings obtained in vacuum. The model gives the thickness, the bond character and the bond to the coated substrate, depending on : temperature, forming time and condensation rate. The coatings have been classified in two basic groups : vacuum condensates and vacuum diffusive coatings, separated by a layer zone

  3. Diffusion bonding aeroengine components

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, G. A.; Broughton, T.

    1988-10-01

    The use of diffusion bonding processes at Rolls-Royce for the manufacture of titanium-alloy aircraft engine components and structures is described. A liquid-phase diffusion bonding process called activated diffusion bonding has been developed for the manufacture of the hollow titanium wide chord fan blade. In addition, solid-state diffusion bonding is being used in the manufacture of hollow vane/blade airfoil constructions mainly in conjunction with superplastic forming and hot forming techniques.

  4. Influence of plasma treatment and cleaning on vacuum wafer bonding

    Microsoft Academic Search

    Wei Bo Yu; Cher Ming Tan; Jun Wei; Shu Sheng Deng; Mui Ling Nai

    2003-01-01

    Direct wafer bonding was performed in vacuum. We compared two kinds of bonding, Si to Si and Si to SiO2, in three different circumstances: Bonded in vacuum only, bonded in vacuum after plasma treatment and bonded in vacuum after plasma treatment and RCA1 cleaning. From the comparison of the bonding strength, we found that in both cases, Si-Si and Si-SiO2,

  5. Electrospray emitters For diffusion vacuum pumps

    E-print Network

    Diaz Gómez Maqueo, Pablo (Pablo Ly)

    2011-01-01

    Following similar principles as regular diffusion vacuum pumps, an electrospray emitter is set to produce a jet of charged particles that will drag air molecules out of a volume. To be a feasible concept, the emitted ...

  6. Impulse pressuring diffusion bonding of titanium alloy to stainless steel

    SciTech Connect

    Yuan, X.J. [College of Materials Science and Engineering, Chongqing University, 400044 (China)], E-mail: cqu_y@sina.com.cn; Sheng, G.M. [College of Materials Science and Engineering, Chongqing University, 400044 (China)], E-mail: gmsheng@cqu.edu.cn; Qin, B.; Huang, W.Z.; Zhou, B. [College of Materials Science and Engineering, Chongqing University, 400044 (China)

    2008-07-15

    Impulse pressuring diffusion bonding between a titanium alloy TA17 and an austenitic stainless steel 0Cr18Ni9Ti has been carried out in vacuum. Relationships between the bonding parameters and the tensile strength of the joints were investigated, and the optimum bond parameters were obtained: bonding temperature T = 825 deg. C, maximum impulse pressure P{sub max} = 50 MPa, minimum impulse pressure P{sub min} = 8 MPa, number of impulses N = 30, impulse frequency f = 0.5 Hz. The maximum tensile strength of the joint was 321 MPa and the effective bonding time was only 180 s. The reaction products and the interface structure of the joints were investigated by optical microscopy, scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and X-ray diffraction (XRD). The study revealed the existence of FeTi, Fe{sub 2}Ti, {sigma} phase and {beta}-Ti in the reaction zone. Brittle Fe-Ti intermetallic phases lower the strength and ductility of the impulse pressuring diffusion bonded couples significantly. This technique provides a reliable and efficient bonding method of titanium alloy and stainless steel.

  7. Effect of interface microstructure on the bond strength of the diffusion welded joints between titanium and stainless steel

    Microsoft Academic Search

    M.. Ghosh; S.. Chatterjee

    2005-01-01

    Diffusion bonding between commercially pure titanium and 304 stainless steel was carried out at a temperature of 950 °C for 30–120 min under uniaxial load in a vacuum. The diffusion bonds were characterized by optical and scanning electron microscopy. The diffusion zone contained different reaction bands and their chemical composition was determined using energy dispersive X-ray spectroscopy. The concentration of

  8. Vacuum pull down method for an enhanced bonding process

    DOEpatents

    Davidson, James C. (Livermore, CA); Balch, Joseph W. (Livermore, CA)

    1999-01-01

    A process for effectively bonding arbitrary size or shape substrates. The process incorporates vacuum pull down techniques to ensure uniform surface contact during the bonding process. The essence of the process for bonding substrates, such as glass, plastic, or alloys, etc., which have a moderate melting point with a gradual softening point curve, involves the application of an active vacuum source to evacuate interstices between the substrates while at the same time providing a positive force to hold the parts to be bonded in contact. This enables increasing the temperature of the bonding process to ensure that the softening point has been reached and small void areas are filled and come in contact with the opposing substrate. The process is most effective where at least one of the two plates or substrates contain channels or grooves that can be used to apply vacuum between the plates or substrates during the thermal bonding cycle. Also, it is beneficial to provide a vacuum groove or channel near the perimeter of the plates or substrates to ensure bonding of the perimeter of the plates or substrates and reduce the unbonded regions inside the interior region of the plates or substrates.

  9. Vacuum Head Checks Foam/Substrate Bonds

    NASA Technical Reports Server (NTRS)

    Lloyd, James F.

    1989-01-01

    Electromechanical inspection system quickly gives measurements indicating adhesion, or lack thereof, between rigid polyurethane foam and aluminum substrate. Does not damage inspected article, easy to operate, and used to perform "go/no-go" evaluations or as supplement to conventional destructive pull-plug testing. Applies vacuum to small area of foam panel and measures distance through which foam pulled into vacuum. Probe head applied to specimen and evacuated through hose to controller/monitor unit. Digital voltmeter in unit reads deflection of LVDT probe head.

  10. Roll diffusion bonding of titanium alloy panels

    NASA Technical Reports Server (NTRS)

    Bennett, J.; De Witt, T. E.; Jones, A. G.; Koeller, F.; Muser, C.

    1968-01-01

    Roll diffusion bonding technique is used for fabricating T-stiffened panel assemblies from titanium alloy. The single unit fabrication exhibits excellent strength characteristics under tensile and compressive loads. This program is applied to structures in which weight/strength ratio and integral construction are important considerations.

  11. Strength, ultrasonic and metallurgical evaluation of diffusion bonds

    SciTech Connect

    Ojard, G.C.; Buck, O.; Rehbein, D.K.

    1993-10-01

    Diffusion bonding allows similar and dissimilar materials to be bonded together in near net shape. However, differentiation of almost perfect diffusion bonds, with little variation in their acoustic response, is of critical importance since relatively significant changes in bond strength may be a consequence. Challenge is to find ultrasonic techniques sensitive enough to detect small imperfections at interface. Diffusion bonds have been produced that show only a slight variation in a single frequency reflection measurement. The total energy, reflected from bond line, can differentiate these diffusion bonds. This evaluation is based on Parseval`s theorem which states that energy in time domain is proportional to energy in the frequency domain. This measurement takes advantage of presence of voids in the diffusion bonds as well as of the interdiffusion zone. Cu and Ni were chosen as the materials to be bonded due to the case of microstructural control. Diffusion bonds fabricated of Ti-6Al-4V are also discussed.

  12. Using Diffusion Bonding in Making Piezoelectric Actuators

    NASA Technical Reports Server (NTRS)

    Sager, Frank E.

    2003-01-01

    A technique for the fabrication of piezoelectric actuators that generate acceptably large forces and deflections at relatively low applied voltages involves the stacking and diffusion bonding of multiple thin piezoelectric layers coated with film electrodes. The present technique stands in contrast to an older technique in which the layers are bonded chemically, by use of urethane or epoxy agents. The older chemical-bonding technique entails several disadvantages, including the following: It is difficult to apply the bonding agents to the piezoelectric layers. It is difficult to position the layers accurately and without making mistakes. There is a problem of disposal of hazardous urethane and epoxy wastes. The urethane and epoxy agents are nonpiezoelectric materials. As such, they contribute to the thickness of a piezoelectric laminate without contributing to its performance; conversely, for a given total thickness, the performance of the laminate is below that of a unitary piezoelectric plate of the same thickness. The figure depicts some aspects of the fabrication of a laminated piezoelectric actuator by the present diffusion- bonding technique. First, stock sheets of the piezoelectric material are inspected and tested. Next, the hole pattern shown in the figure is punched into the sheets. Alternatively, if the piezoelectric material is not a polymer, then the holes are punched in thermoplastic films. Then both faces of each punched piezoelectric sheet or thermoplastic film are coated with a silver-ink electrode material by use of a silkscreen printer. The electrode and hole patterns are designed for minimal complexity and minimal waste of material. After a final electrical test, all the coated piezoelectric layers (or piezoelectric layers and coated thermoplastic films) are stacked in an alignment jig, which, in turn, is placed in a curved press for the diffusion-bonding process. In this process, the stack is pressed and heated at a specified curing temperature and pressure for a specified curing time. The pressure, temperature, and time depend on the piezoelectric material selected. At the end of the diffusion-bonding process, the resulting laminated piezoelectric actuator is tested to verify the adequacy of the mechanical output as a function of an applied DC voltage.

  13. Solid-State Diffusion Bonding of Commercially pure Titanium and Precipitation Hardening Stainless steel

    Microsoft Academic Search

    Debasis Poddar

    Solid-state direct diffusion bonding of commercially pure Titanium (Cp-Ti) and precipitation hardening stainless steel (PHSS) has been carried out in the temperature range of 800°C to 1000°C with an interval of 50°C for 3.6 ks under 3.5 Mpa uniaxial load in (4 to 6)×10-3 Pa vacuum. The effects of temperatures have been investigated with reference to bond strength. The examination

  14. Evaluation of diffusion bonds formed between superplastic sheet materials

    Microsoft Academic Search

    Z. C. Wang; N. Ridley; G. W. Lorimer; D. Knauss; G. A. D. Briggs

    1996-01-01

    Diffusion bonds produced in microduplex titanium and stainless steel sheet materials for various bonding conditions have been evaluated using a range of techniques. These include light and scanning electron microscopy (SEM), scanning acoustic microscopy (SAM) and compressive lap shear testing. The potential of other procedures such as ultrasonic inspection and resistivity measurement are also discussed. For imperfect bonds, the bond

  15. Low-temperature diffusion bonding of pure aluminum

    NASA Astrophysics Data System (ADS)

    Chen, Haiyan; Cao, Jian; Tian, Xiaoyu; Li, Rui; Feng, Jicai

    2013-10-01

    1 keV argon ion beam was employed to remove the oxide film of pure aluminum before diffusion bonding. A sound joint of pure aluminum was obtained by ion activation-assisted diffusion bonding at the low temperature of , while the high-quality joining of pure aluminum was infeasible by conventional diffusion bonding at the temperature lower than . The residual oxide film ratios of joints decreased with the increase of ion cleaning time. When the specimens were cleaned for 120 min, the joint with the maximum tensile strength of 62.3 MPa and the elongation of 14.1 % was obtained. The argon ion beam etching surface treatment provides a new route for the low-temperature diffusion bonding. The reliable diffusion bonded joint of pure aluminum indicates that low-temperature diffusion bonding is feasible for bulk materials, especially for materials with the outstanding plasticity.

  16. On the Direct Diffusion Bonding of Titanium Alloy to Stainless Steel

    Microsoft Academic Search

    Swarup K. Ghosh; S. Chatterjee

    2010-01-01

    In the present study, direct diffusion bonding of Ti-6Al-4 V to 304 L stainless steel has been carried out in vacuum in the temperature range of 850–950°C using 3 MPa uniaxial load for 30 to 90 min durations. Different reaction layers in the diffusion zone have been examined by optical microscopy, scanning electron microscopy (SEM) using the back scattered mode, X-ray diffraction (XRD), and

  17. Isostatic diffusion bonding of IN-718SPF sheet

    SciTech Connect

    McKimpson, M.G. [Michigan Technological Univ., Houghton, MI (United States); Campbell, J.R. [Brush Wellman Inc., Elmore, OH (United States)

    1996-12-31

    Isostatic diffusion bonding represents a potentially attractive technique for joining superplastically-formable nickel-base alloys such as Inconel alloy 718SPF sheet. Isostatic diffusion bonding trials have been carried out on Inconel alloy 718SPF/Inconel alloy 718SPF couples at temperatures ranging from 950 C (1,750 F) to 1,150 C (2,100 F) and isostatic pressures ranging up to 415 MPa (60,000 psi). Materials bonded at 1,150 C and 414 MPa exhibited room temperature shear strengths nearly comparable to those of the parent metal, but also showed substantial grain growth in the base metal away from the bond plane. Materials bonded at lower temperatures exhibited similar strengths with substantially less grain coarsening. Metallographic and mechanical testing results obtained on these diffusion bonded Inconel alloy 718SPF materials are presented and compared with existing diffusion bonding models.

  18. Better vacuum by removal of diffusion-pump-oil contaminants

    NASA Technical Reports Server (NTRS)

    Buggele, A. E.

    1975-01-01

    The complex problem of why large space simulation chambers do not realize true ultimate vacuum was investigated. Some contaminating factors affecting diffusion pump performance were identified, and some advances in vacuum distillation-fractionation technology were achieved which resulted in a two-decade-or-more lower ultimate pressure. Data are presented to show the overall or individual contaminating effects of commonly used phthalate ester plasticizers of 390 to 530 molecular weight on diffusion pump performance. Methods for removing contaminants from diffusion pump silicone oil during operation and for reclaiming contaminated oil by high-vacuum molecular distillation are described. Conceptual self-cleansing designs and operating procedures are proposed for modifying large diffusion pumps into high-efficiency distillation devices. The potential exists for application of these technological advancements to other disciplines, such as medicine, biomedical materials, metallurgy, refining, and chemical (diffusion-enrichment) processing.

  19. AN INTERNAL CONVECTIVE HEATING TECHNIQUE FOR DIFFUSION BONDING ARRAYED MICROCHANNEL ARCHITECTURES

    SciTech Connect

    Paul, Brian; Bose, Sumantra; Palo, Daniel R.

    2010-01-08

    Diffusion bonding cycle times can be a large factor in the production cost of metal microchannel devices. The challenge is to significantly minimize bonding cycle times through rapid heating and cooling within the bonding process. A novel method is described which takes advantage of the internal flow passages within microchannel devices for convective heat transfer during the bonding process. The internal convective heating (ICH) technique makes use of heated inert gas to provide the microchannel assembly with rapid and uniform heat input. Results demonstrate that the ICH technique is feasible, capable of producing microchannels with higher dimensional integrity and shorter bonding cycle times than traditional vacuum hot press methods. Results suggest that this may be due to smaller thermal gradients within microchannel devices during the ICH bonding cycle.

  20. Diffusion bonding and brazing of high purity copper for linear collider accelerator structures

    NASA Astrophysics Data System (ADS)

    Elmer, J. W.; Klingmann, J.; van Bibber, K.

    2001-05-01

    Diffusion bonding and brazing of high purity copper were investigated to develop procedures for joining precision machined copper components for the Next Linear Collider (NLC). Diffusion bonds were made over a range of temperatures from 400 °C to 1000 °C, under two different loading conditions [3.45 kPa (0.5 psi) and 3.45 MPa (500 psi)], and on two different diamond machined surface finishes. Brazes were made using pure silver, pure gold, and gold-nickel alloys, and different heating rates produced by both radiation and induction heating. Braze materials were applied by both physical vapor deposition (PVD) and conventional braze alloy shims. Results of the diffusion bonding experiments showed that bond strengths very near that of the copper base metal could be made at bonding temperatures of 700 °C or higher at 3.45 MPa bonding pressure. At lower temperatures, only partial strength diffusion bonds could be made. At low bonding pressures (3.45 kPa), full strength bonds were made at temperatures of 800 °C and higher, while no bonding (zero strength) was observed at temperatures of 700 °C and lower. Observations of the fracture surfaces of the diffusion bonded samples showed the effects of surface finish on the bonding mechanism. These observations clearly indicate that bonding began by point asperity contact, and flatter surfaces resulted in a higher percentage of bonded area under similar bonding conditions. Results of the brazing experiments indicated that pure silver worked very well for brazing under both conventional and high heating rate scenarios. Similarly, pure silver brazed well for both the PVD layers and the braze alloy shims. The gold and gold-containing brazes had problems, mainly due to the high diffusivity of gold in copper. These problems led to the necessity of overdriving the temperature to ensure melting, the presence of porosity in the joint, and very wide braze joints. Based on the overall findings of this study, a two-step joining method is proposed for fabricating the NLC structures. The structure would be assembled with pure silver braze inserts using a self-aligning step joint design, then the assembly would be vacuum diffusion bonded at 700 °C and 3.45 MPa pressure to seal the critical inner portion of the assembly. Finally, during the same furnace cycle, the temperature would be increased to 800 °C in order to react the silver with the copper to form a liquid braze alloy that would join and seal the outer portion of the cells together.

  1. Diffusion Bonding of Silicon Carbide for MEMS-LDI Applications

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, J. Douglas

    2007-01-01

    A robust joining approach is critically needed for a Micro-Electro-Mechanical Systems-Lean Direct Injector (MEMS-LDI) application which requires leak free joints with high temperature mechanical capability. Diffusion bonding is well suited for the MEMS-LDI application. Diffusion bonds were fabricated using titanium interlayers between silicon carbide substrates during hot pressing. The interlayers consisted of either alloyed titanium foil or physically vapor deposited (PVD) titanium coatings. Microscopy shows that well adhered, crack free diffusion bonds are formed under optimal conditions. Under less than optimal conditions, microcracks are present in the bond layer due to the formation of intermetallic phases. Electron microprobe analysis was used to identify the reaction formed phases in the diffusion bond. Various compatibility issues among the phases in the interlayer and substrate are discussed. Also, the effects of temperature, pressure, time, silicon carbide substrate type, and type of titanium interlayer and thickness on the microstructure and composition of joints are discussed.

  2. Diffusion Bonding of Silicon Carbide Ceramics using Titanium Interlayers

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, James D.

    2006-01-01

    Robust joining approaches for silicon carbide ceramics are critically needed to fabricate leak free joints with high temperature mechanical capability. In this study, titanium foils and physical vapor deposited (PVD) titanium coatings were used to form diffusion bonds between SiC ceramics using hot pressing. Silicon carbide substrate materials used for bonding include sintered SiC and two types of CVD SiC. Microscopy results show the formation of well adhered diffusion bonds. The bond strengths as determined from pull tests are on the order of several ksi, which is much higher than required for a proposed application. Microprobe results show the distribution of silicon, carbon, titanium, and other minor elements across the diffusion bond. Compositions of several phases formed in the joint region were identified. Potential issues of material compatibility and optimal bond formation will also be discussed.

  3. Partial transient liquid phase diffusion bonding of Zircaloy-4 to stabilized austenitic stainless steel 321

    SciTech Connect

    Atabaki, M. Mazar, E-mail: m.mazaratabaki@gmail.com [Department of Materials Engineering, Faculty of Mechanical Engineering, University Technology Malaysia, 81310 (Malaysia); Hanzaei, A. Talebi [Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran (Iran, Islamic Republic of)

    2010-10-15

    An innovative method was applied for bonding Zircaloy-4 to stabilized austenitic stainless steel 321 using an active titanium interlayer. Specimens were joined by a partial transient liquid phase diffusion bonding method in a vacuum furnace at different temperatures under 1 MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength and interlayer thickness has been studied. The diffusion of Fe, Cr, Ni and Zr has been investigated by scanning electron microscopy and energy dispersive spectroscopy elemental analyses. Results showed that control of the heating and cooling rate and 20 min soaking at 1223 K produces a perfect joint. However, solid-state diffusion of the melting point depressant elements into the joint metal causes the solid/liquid interface to advance until the joint is solidified. The tensile strength of all the bonded specimens was found around 480-670 MPa. Energy dispersive spectroscopy studies indicated that the melting occurred along the interface of the bonded specimens as a result of the transfer of atoms between the interlayer and the matrix during bonding. This technique provides a reliable method of bonding zirconium alloy to stainless steel.

  4. Joining of Silicon Carbide: Diffusion Bond Optimization and Characterization

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay

    2008-01-01

    Joining and integration methods are critically needed as enabling technologies for the full utilization of advanced ceramic components in aerospace and aeronautics applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. In the application, several SiC substrates with different hole patterns to form fuel and combustion air channels are bonded to form the injector. Diffusion bonding is a joining approach that offers uniform bonds with high temperature capability, chemical stability, and high strength. Diffusion bonding was investigated with the aid of titanium foils and coatings as the interlayer between SiC substrates to aid bonding. The influence of such variables as interlayer type, interlayer thickness, substrate finish, and processing time were investigated. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

  5. Metal honeycomb to porous wireform substrate diffusion bond evaluation

    NASA Technical Reports Server (NTRS)

    Vary, A.; Moorhead, P. E.; Hull, D. R.

    1982-01-01

    Two nondestructive techniques were used to evaluate diffusion bond quality between a metal foil honeycomb and porous wireform substrate. The two techniques, cryographics and acousto-ultrasonics, are complementary in revealing variations of bond integrity and quality in shroud segments from an experimental aircraft turbine engine.

  6. Fabrication and Characterization of Diffusion Bonds for Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Halbig, Michael; Singh, Mrityunjay; Martin, Richard E.; Cosgriff, Laura M.

    2007-01-01

    Diffusion bonds of silicon carbide (SiC) were fabricated using several different types of titanium (Ti) based interlayers between the SiC substrates. The interlayers were an alloyed Ti foil, a pure Ti foil, and a physically vapor deposited (PVD) Ti coating. Microscopy was conducted to evaluate the cross-sections of the resulting bonds. Microprobe analysis identified reaction formed phases in the diffusion bonded region. Uniform and well adhered bonds were formed between the SiC substrates. In the case where the alloyed Ti foil or a thick Ti coating (i.e. 20 micron) was used as the interlayer, microcracks and several phases were present in the diffusion bonds. When a thinner interlayer was used (i.e. 10 micron PVD Ti), no microcracks were observed and only two reaction formed phases were present. The two phases were preferred and fully reacted phases that did not introduce thermal stresses or microcracks during the cool-down stage after processing. Diffusion bonded samples were evaluated with the non-destructive evaluation (NDE) methods of pulsed thermography and immersion ultrasonic testing. Joined SiC substrates that were fully bonded and that had simulated bond flaws in the interlayer were also evaluated using immersion ultrasound. Pull testing was conducted on the bonds to determine the tensile strength. To demonstrate the joining approach for a complex multilayered component for a low NOx injector application, the diffusion bonding approach was used to join three 4" diameter SiC discs that contained complex fuel and air flow channels.

  7. A Model for DC Interruption in Diffuse Vacuum Arcs

    Microsoft Academic Search

    S. E. CHILDSAND; A. N. Greenwood

    1980-01-01

    A theoretical model for current interruption in a diffuse vacuum arc with dc commutation is described. Before current zero the interelectrode plasma is modeled as an ion-neutral fluid through which electrons are flowing. After current zero a positive ion sheath grows into the plasma from the former anode, driven by the transient recovery voltage. Using the basic laws of conservation,

  8. Diffusion bonding of the oxide dispersion strengthened steel PM2000

    NASA Astrophysics Data System (ADS)

    Sittel, Wiebke; Basuki, Widodo W.; Aktaa, Jarir

    2013-11-01

    Ferritic oxide dispersion strengthened (ODS) steels are well suited as structural materials, e.g. for claddings in fission reactors and for plasma facing components in fusion power plants due to their high mechanical and oxidation stability at high temperatures and their high irradiation resistance. PM2000 is an iron based ODS ferritic steel with homogeneously distributed nanometric yttria particles. Melting joining techniques are not suitable for such ODS materials because of the precipitation and agglomeration of the oxide particles and hence the loss of their strengthening effect. Solid state diffusion bonding is thus chosen to join PM2000 and is investigated in this work with a focus on oxide particles. The diffusion bonding process is aided by the computational modeling, including the influence of the ODS particles. For modeling the microstructure stability and the creep behavior of PM2000 at various, diffusion bonding relevant temperatures (50-80% Tm) are investigated. Particle distribution (TEM), strength (tensile test) and toughness (Charpy impact test) obtained at temperatures relevant for bonding serve as input for the prediction of optimal diffusion bonding parameters. The optimally bonded specimens show comparable strength and toughness relative to the base material.

  9. Al-Ge Diffusion Bonding for Hermetic Sealing Application

    NASA Astrophysics Data System (ADS)

    Chidambaram, Vivek; Wickramanayaka, Sunil

    2015-07-01

    The high-temperature requirement of Al-Ge eutectic bonding stands as a major obstacle to its wider acceptance for hermetic sealing application in the microelectromechanical systems packaging industry, in particular for temperature-sensitive devices. It has been demonstrated that a reduction in bonding temperature is feasible without compromising the hermeticity. The change in the mode of bonding from eutectic to solid-state diffusion did not have a dramatic impact on the bonding quality. However, this resulted in a substantial increase in bonding time. The shear strength also deteriorated as a result of the decrease in thickness of the reaction interface. However, the shear strength still complied with military standards. It has been confirmed that a hermetic seal could still be achieved without any solidification occurring at the interface. This is feasible since the interdiffusion coefficients of Al in (Ge) phase and Ge in (Al) phase are closer and are comparable to diffusion between solid-solution phases of identical metals such as in Au-Au, Cu-Cu, and Si-Si bonding, which are generally used for such hermetic sealing application. An appropriate stacking mechanism for Al-Ge diffusion bonding is identified to overcome the limitations with respect to surface topography.

  10. Diffusion bonding resistant valve development for sodium service

    SciTech Connect

    Crandall, D.L.; Low, J.O.; Chung, D.T.; Loop, R.B.

    1984-04-16

    Unanticipated functional failures occurred in valves undergoing containment integrity testing for liquid sodium service. The failures resulted from diffusion bonding of the Stellite 6B valve plug to the Type 316 stainless steel (SS) seat. As a result of these failures, a valve development program was undertaken. A modified valve incorporating a Tribaloy 800 plug showed significant improvement in resistance to diffusion bonding but still failed after long term exposure in a closed position. A second modified valve using Tribaloy 800 in both the valve plug and seat successfully resisted diffusion bonding failure. This paper reports the details of the testing and posttest valve examinations. The results of scanning electron microscopy, dispersive x-ray spectrometry, and metallography provide the characteristics of the valve failures. Limitations of the various valve designs are also discussed.

  11. Diffusion bonding of commercially pure Ni using Cu interlayer

    SciTech Connect

    Rahman, A.H.M.E., E-mail: a.rahman@my.und.edu; Cavalli, M.N.

    2012-07-15

    The concentration dependence of diffusivity in a multi-component diffusion system makes it complicated to predict the concentration profiles of diffusing species. This so called chemical diffusivity can be expressed as a function of thermodynamic and kinetic data. DICTRA software can calculate the concentration profiles using appropriate mobility and thermodynamic data. It can also optimize the diffusivity data using experimental diffusivity data. Then the optimized diffusivity data is stored as mobility data which is a linear function of temperature. In this work, diffusion bonding of commercially pure Ni using Cu interlayers is reported. The mobility parameters of Ni-Cu alloy binary systems were optimized using DICTRA/Thermocalc software from the available self-, tracer and chemical diffusion coefficients. The optimized mobility parameters were used to simulate concentration profiles of Ni-Cu diffusion joints using DICTRA/Thermocalc software. The calculated and experimental concentration profiles agreed well at 1100 Degree-Sign C. Agreement between the simulated and experimental profiles was less good at 1050 Degree-Sign C due to the grain boundary contribution to the overall diffusion. - Highlights: Black-Right-Pointing-Pointer The concentration profiles of Cu in Ni-Cu diffusion joints are modeled. Black-Right-Pointing-Pointer Interdiffusion coefficients in Ni-Cu system are optimized. Black-Right-Pointing-Pointer Optimized interdiffusion coefficients are expressed as mobility parameters. Black-Right-Pointing-Pointer Simulated profiles are comparable with experimental profiles.

  12. Post arc phenomena in rapidly commutated diffuse vacuum arcs

    Microsoft Academic Search

    Mody

    1985-01-01

    The behavior of rapidly commutated (up to 1.2 kA\\/..mu..s) diffuse vacuum arcs was studied using three different interrupters: (a) GE 10-cm-diameter Cu electrode interrupter, (b) a GE 10-cm-diameter Be electrode interrupter, and (c) a VIL (V5) interrupter. These interrupters were tested using a synthetic test circuit that allowed independent variation of arc current prior to commutation. Post arc currents and

  13. Algorithm for anisotropic diffusion in hydrogen-bonded networks

    E-print Network

    Edoardo Milotti

    2007-04-04

    In this paper I describe a specialized algorithm for anisotropic diffusion determined by a field of transition rates. The algorithm can be used to describe some interesting forms of diffusion that occur in the study of proton motion in a network of hydrogen bonds. The algorithm produces data that require a nonstandard method of spectral analysis which is also developed here. Finally, I apply the algorithm to a simple specific example.

  14. Shirzadi et al. Surface and Interface Analysis 2001; 31:609-618 Interface evolution and bond strength when diffusion bonding

    E-print Network

    Cambridge, University of

    Shirzadi et al. Surface and Interface Analysis 2001; 31:609-618 1 Interface evolution and bond strength when diffusion bonding materials with stable oxide films A.A. Shirzadi* , H. Assadi and E morphologies and strengths of aluminium diffusion bonds are reviewed. Previous approaches, proposed to overcome

  15. Characterization of metallic foil joints using diffusion bonding and diffusion soldering in micro-technology-based energy and chemical systems

    SciTech Connect

    Gabriel, Michael (Oregon State Univ.); Paul, Brian K. (Oregon State Univ.); Wilson, Rick D.; Alman, David E.

    2001-01-10

    The several 316 stainless steel mesoscopic devices were made using diffusing bonding and diffusion soldering. Tensile strength, pressure drop of the devices were measured, and metallurgical examinations were made of the joints. Continuous bonds were observed in both diffusion bonded and diffusion soldered samples. Strengths of the diffusion soldered samples were up to 80% of the strength of the Ag(sub3) Sn joint material or 125 MPa. The pressure drop in diffusion soldered samples was 0.76 psi at the highest flow rates of 2.08 L/min. Diffusion bonded joints had strengths of up to 700 MPa but the back pressures were higher at all flow rates.

  16. Diffusion Bonding Aluminium Alloys and Composites: New Approaches and Modelling

    E-print Network

    Cambridge, University of

    are preserved. A fourth method, which is based on a new approach to TLP diffusion bonding by introducing friendship and food-wise logistic; Liz, Ken, Kai and Paul for improving my knowledge to the single currency.D. research was to develop new joining methods for these materials for which conventional welding methods have

  17. Tunable infrared generation with diffusion-bonded-stacked gallium arsenide

    NASA Astrophysics Data System (ADS)

    Zheng, Dong

    Mid-infrared (MIR) radiation finds increasing applications in remote sensing, spectroscopy and military counter-measures. Nonlinear optical interactions provide one approach to tunable MIR sources generation. The development of MIR nonlinear optical crystals with excellent performance at a reasonable cost is essential for applications. Diffusion-bonded-stacked (DBS) GaAs periodic structures are a new family of quasi-phasematched (QPM) nonlinear optical crystals. The bonding process preserves the optical and mechanical properties of the bulk material, while the periodic modulation of the nonlinear coefficient permits QPM interactions. DBS GaAs bonding requirements, such as number of bonded layers and tolerable optical loss, are discussed. Nonlinear optical properties like mixing gain, wavelength, temperature and angular acceptance of the bonded structure, are predicted. DBS GaAs devices with up to 50 layers were bonded and characterized. Optical loss from interfacial voids and gaps at shorter wavelengths, from processing induced p- type free carrier absorption at longer wavelengths was characterized. 'Lithographic dicing' was invented and demonstrated as a replacement for mechanical dicing, resulting in the capability to handle thin wafers and cleaner interfaces for better bonding. Absorption due to semi-insulating-to-p-type conversion, a bulk crystal loss mechanism, was found to be induced by high bonding temperatures, and dependent on wafer sources and materials in contact with the stack. Optimized bonding parameters reduced the optical loss of 36-layer DBS GaAs to less than 0.2 cm-1 at long wavelengths. Tunable 15.6 to 17.6 ?m coherent radiation at 90-ps pulse width was generated by difference frequency mixing in a 24-layer DBS GaAs device. The wavelength tuning curve agreed with theoretical predictions demonstrating that the bonding process maintained nonlinear optical phasematching over the 6 mm interaction length. Maximum mixing gain of 0.7%, or 5% internal quantum gain, was measured at 16.6 ?m. Other DBS GaAs devices for frequency doubling of CO2 laser radiation and difference frequency mixing of various laser sources were demonstrated. Tunable MIR radiation from 4.7 ?m to 17.6 ?m was generated demonstrating feasibility of diffusion bonded structures to generate broadly tunable MIR wavelengths.

  18. Joining of Silicon Carbide Through the Diffusion Bonding Approach

    NASA Technical Reports Server (NTRS)

    Halbig, Michael .; Singh, Mrityunjay

    2009-01-01

    In order for ceramics to be fully utilized as components for high-temperature and structural applications, joining and integration methods are needed. Such methods will allow for the fabrication the complex shapes and also allow for insertion of the ceramic component into a system that may have different adjacent materials. Monolithic silicon carbide (SiC) is a ceramic material of focus due to its high temperature strength and stability. Titanium foils were used as an interlayer to form diffusion bonds between chemical vapor deposited (CVD) SiC ceramics with the aid of hot pressing. The influence of such variables as interlayer thickness and processing time were investigated to see which conditions contributed to bonds that were well adhered and crack free. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

  19. The Bonding Characteristics of Gold in Ultrahigh Vacuum

    Microsoft Academic Search

    ROBERT E. CUTHRELL; DONALD W. TIPPING

    1974-01-01

    The results are reported of a study of the factors which affect the solid-phase bonding of gold wire electrical leads. Gold surfaces were cleaned by sputtering and joined with precise control of mechanical and environmental variables. Contact resistance measurements as a function of load, coefficients of adhesion, and laser interference fringe photo-microtopographs were used as diagnostics to show the effects

  20. Effect of vacuum on high-temperature degradation of gold\\/aluminum wire bonds in PEMs

    Microsoft Academic Search

    Alexander Teverovsky

    2004-01-01

    Gold\\/aluminum wire bond degradation is one of the major failure mechanisms limiting reliability of plastic encapsulated microcircuits (PEMs) at high temperatures, It is known also that oxidative degradation is the major cause of failures in epoxy composite materials; however, the effect of oxygen and\\/or vacuum conditions on degradation of PEMs has not been studied yet. In this work, three groups

  1. Mo/Ti Diffusion Bonding for Making Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeffrey; Kisor, Adam; Caillat, Thierry; Lara, Liana; Ravi, Vilupanur; Firdosy, Samad; Fleuiral, Jean-Pierre

    2007-01-01

    An all-solid-state diffusion bonding process that exploits the eutectoid reaction between molybdenum and titanium has been developed for use in fabricating thermoelectric devices based on skutterudite compounds. In essence, the process is one of heating a flat piece of pure titanium in contact with a flat piece of pure molybdenum to a temperature of about 700 C while pushing the pieces together with a slight pressure [a few psi (of the order of 10 kPa)]. The process exploits the energy of mixing of these two metals to form a strong bond between them. These two metals were selected partly because the bonds formed between them are free of brittle intermetallic phases and are mechanically and chemically stable at high temperatures. The process is a solution of the problem of bonding hot-side metallic interconnections (denoted hot shoes in thermoelectric jargon) to titanium-terminated skutterudite n and p legs during the course of fabrication of a unicouple, which is the basic unit cell of a thermoelectric device (see figure). The hot-side operating temperature required for a skutterudite thermoelectric device is 700 C. This temperature precludes the use of brazing to attach the hot shoe; because brazing compounds melt at lower temperatures, the hot shoe would become detached during operation. Moreover, the decomposition temperature of one of the skutterudite compounds is 762 C; this places an upper limit on the temperature used in bonding the hot shoe. Molybdenum was selected as the interconnection metal because the eutectoid reaction between it and the titanium at the ends of the p and n legs has characteristics that are well suited for this application. In addition to being suitable for use in the present bonding process, molybdenum has high electrical and thermal conductivity and excellent thermal stability - characteristics that are desired for hot shoes of thermoelectric devices. The process takes advantage of the chemical potential energy of mixing between molybdenum and titanium. These metals have a strong affinity for each other. They are almost completely soluble in each other and remain in the solid state at temperatures above the eutectoid temperature of 695 C. As a result, bonds formed by interdiffusion of molybdenum and titanium are mechanically stable at and well above the original bonding temperature of about 700 C. Inasmuch as the bonds are made at approximately the operating temperature, thermomechanical stresses associated with differences in thermal expansion are minimized.

  2. Electrospray Emitters For Diffusion Vacuum Pumps Pablo Diaz Gomez Maqueo, Paulo C. Lozano

    E-print Network

    Electrospray Emitters For Diffusion Vacuum Pumps Pablo Diaz Gomez Maqueo, Paulo C. Lozano June 2011 SSL # 12-11 #12;#12;Electrospray Emitters For Diffusion Vacuum Pumps Pablo Diaz Gomez Maqueo, Paulo C of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology. 1 #12;2 #12

  3. Cracking during solidification of diffusion bonded Inconel 625 in the presence of Zircaloy4 interlayer

    Microsoft Academic Search

    M. Ahmad; J. I. Akhter; M. Shahzad; M. Akhtar

    2008-01-01

    Diffusion bonded specimens of Inconel 625 in the presence of Zircaloy-4 interlayer have been investigated using scanning electron microscope (SEM) having energy dispersive system (EDS) as an attachment. Cracking is observed in the center of the diffusion zone (DZ) in both the samples bonded at 1050 and 1100°C. The bonding of Inconel 625 in the presence of Zircaloy-4 occurs due

  4. Characteristics of Copper-to-Silicon diffusion in copper wire bonding

    Microsoft Academic Search

    Shawn X. Zhang; S. W. Ricky Lee

    2007-01-01

    The replacement of Au and Al wires with Cu wires in wire bonding has become an emerging trend in IC packaging nowadays. Although some research works have been carried out for the applications of Cu wire bonding, they are mainly focused on the processing and material issues of Cu wire bonds. However, the Cu in the wire bonds may diffuse

  5. Characterization of intermetallic compound formation and copper diffusion of copper wire bonding

    Microsoft Academic Search

    Shawn Zhang; Catherine Chen; Ricky Lee; Angie KM Lau; P. P. H. Tsang; L. Mohamed; C. Y. Chan; M. Dirkzwager

    2006-01-01

    The trend to replace Au and Al wires with Cu in wire bonding has become an emerging trend for IC packaging nowadays. Although some research works have been carried out for the applications of Cu wire bonding, they are mainly focused on the processing and material issues of Cu wire bonds. However, the Cu in the wire bonds may diffuse

  6. On the Formation of a Diffusion Bond from Cold-Spray Coatings

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Birbilis, Nick; Zhang, Ming-Xing

    2012-05-01

    To understand the development of diffusion bonding, which can increase the bonding strength, three different cold-sprayed coating/substrate systems were investigated, Ni/Cu, Cu/Cu, and Al/Mg, by annealing at increased temperatures for various times. The formation of intermetallic compounds in the Al/Mg system reduced the bonding strength dramatically. In Cu/Cu and Ni-Cu, diffusion bonds developed at lower temperatures as Ni-Cu forms an isomorphous system, which increased the bonding strength effectively. However, higher temperature annealing reduced bonding strength ultimately because of the Kirkendall pores.

  7. Silver diffusion bonding and layer transfer of lithium niobate to silicon Kenneth Diest,a

    E-print Network

    Atwater, Harry

    Silver diffusion bonding and layer transfer of lithium niobate to silicon Kenneth Diest,a Melissa J substrates. A silver film was deposited onto both the silicon and lithium niobate surfaces prior to bonding silver grains to replace the as-bonded interface by a single polycrystalline silver film. The transferred

  8. Wear resistance and fatigue strength of titanium alloy VT8 with vacuum-diffused coatings

    Microsoft Academic Search

    P. A. Mikhailov; E. P. Ponomarenko; D. M. Petergerya; V. F. Rybkin; L. I. Filina; V. P. Khokhlov; G. P. Khoroshailo

    1969-01-01

    It was established that vacuum-diffusion contactless manganizing and chromizing produces a 2.5 to 3-fold increase in the wear resistance of a titanium alloy VT-8, whose fatigue strength is reduced by 50% after these treatments due to a columnar grain structure of diffused coatings.

  9. Lateral diffusion of receptor-ligand bonds in membrane adhesion zones: Effect of thermal membrane roughness

    E-print Network

    H. Krobath; G. J. Schuetz; R. Lipowsky; T. R. Weikl

    2007-03-19

    The adhesion of cells is mediated by membrane receptors that bind to complementary ligands in apposing cell membranes. It is generally assumed that the lateral diffusion of mobile receptor-ligand bonds in membrane-membrane adhesion zones is slower than the diffusion of unbound receptors and ligands. We find that this slowing down is not only caused by the larger size of the bound receptor-ligand complexes, but also by thermal fluctuations of the membrane shape. We model two adhering membranes as elastic sheets pinned together by receptor-ligand bonds and study the diffusion of the bonds using Monte Carlo simulations. In our model, the fluctuations reduce the bond diffusion constant in planar membranes by a factor close to 2 in the biologically relevant regime of small bond concentrations.

  10. A Batch Wafer Scale LIGA Assembly and Packaging Technique vai Diffusion Bonding

    SciTech Connect

    Christenson, T.R.; Schmale, D.T.

    1999-01-27

    A technique using diffusion bonding (or solid-state welding) has been used to achieve batch fabrication of two- level nickel LIGA structures. Interlayer alignment accuracy of less than 1 micron is achieved using press-fit gauge pins. A mini-scale torsion tester was built to measure the diffusion bond strength of LIGA formed specimens that has shown successful bonding at temperatures of 450"C at 7 ksi pressure with bond strength greater than 100 Mpa. Extensions to this basic process to allow for additional layers and thereby more complex assemblies as well as commensurate packaging are discussed.

  11. Developing A Laser Shockwave Model For Characterizing Diffusion Bonded Interfaces

    SciTech Connect

    James A. Smith; Jeffrey M. Lacy; Barry H. Rabin

    2014-07-01

    12. Other advances in QNDE and related topics: Preferred Session Laser-ultrasonics Developing A Laser Shockwave Model For Characterizing Diffusion Bonded Interfaces 41st Annual Review of Progress in Quantitative Nondestructive Evaluation Conference QNDE Conference July 20-25, 2014 Boise Centre 850 West Front Street Boise, Idaho 83702 James A. Smith, Jeffrey M. Lacy, Barry H. Rabin, Idaho National Laboratory, Idaho Falls, ID ABSTRACT: The US National Nuclear Security Agency has a Global Threat Reduction Initiative (GTRI) which is assigned with reducing the worldwide use of high-enriched uranium (HEU). A salient component of that initiative is the conversion of research reactors from HEU to low enriched uranium (LEU) fuels. An innovative fuel is being developed to replace HEU. The new LEU fuel is based on a monolithic fuel made from a U-Mo alloy foil encapsulated in Al-6061 cladding. In order to complete the fuel qualification process, the laser shock technique is being developed to characterize the clad-clad and fuel-clad interface strengths in fresh and irradiated fuel plates. The Laser Shockwave Technique (LST) is being investigated to characterize interface strength in fuel plates. LST is a non-contact method that uses lasers for the generation and detection of large amplitude acoustic waves to characterize interfaces in nuclear fuel plates. However the deposition of laser energy into the containment layer on specimen’s surface is intractably complex. The shock wave energy is inferred from the velocity on the backside and the depth of the impression left on the surface from the high pressure plasma pulse created by the shock laser. To help quantify the stresses and strengths at the interface, a finite element model is being developed and validated by comparing numerical and experimental results for back face velocities and front face depressions with experimental results. This paper will report on initial efforts to develop a finite element model for laser shock.

  12. Transient phonon vacuum squeezing due to femtosecond-laser-induced bond hardening

    NASA Astrophysics Data System (ADS)

    Cheenicode Kabeer, Fairoja; Grigoryan, Naira S.; Zijlstra, Eeuwe S.; Garcia, Martin E.

    2014-09-01

    Ultrashort optical pulses can be used both to create fundamental quasiparticles in crystals and to change their properties. In noble metals, femtosecond lasers induce bond hardening, but little is known about its origin and consequences. Here we simulate ultrafast laser excitation of silver at high fluences. We compute laser-excited potential-energy surfaces by all-electron ab initio theory and analyze the resulting quantum lattice dynamics. We also consider incoherent lattice heating due to electron-phonon interactions using the generalized two-temperature model. We find phonon hardening, which we attribute to the excitation of s electrons. We demonstrate that this may result in phonon vacuum squeezed states with an optimal squeezing factor of ˜0.001 at the L-point longitudinal mode. This finding implies that ultrafast laser-induced bond hardening may be used as a tool to manipulate the quantum state of opaque materials, where, so far, the squeezing of phonons below the zero-point motion has only been realized in transparent crystals by a different mechanism. On the basis of our finding, we further propose a method for directly measuring bond hardening.

  13. In-process oxidation protection in fluxless brazing or diffusion bonding of aluminum alloys

    NASA Technical Reports Server (NTRS)

    Okelly, K. P.; Featherston, A. B.

    1974-01-01

    Aluminum is cleaned of its oxide coating and is sealed immediately with polymeric material which makes it suitable for fluxless brazing or diffusion bonding. Time involved between cleaning and brazing is no longer critical factor.

  14. Method of fluxless brazing and diffusion bonding of aluminum containing components

    NASA Technical Reports Server (NTRS)

    Featherston, A. B.; Okelly, K. P. (inventors)

    1976-01-01

    A method of diffusion bonding and fluxless brazing of aluminum containing components is reported. The aluminum surfaces are freed of any aluminum oxide coating and are coated with a polymeric sealer which can be thermally removed leaving essentially no residue. The polymeric sealer is being removed in a substantially oxygen free environment, and the aluminum components are then being brazed or diffusion bonded without the use of a flux to remove oxide coating.

  15. Pulsed Plasma-Assisted Diffusion Bonding of ODS-FeCrAl Alloys

    SciTech Connect

    Tatlock, Gordon J [ORNL; Dyadko, Dr. Eugene G. [MER Corp., Tucson, AZ; Dryepondt, Sebastien N [ORNL; Wright, Ian G [ORNL

    2007-01-01

    The successful joining of ODS alloy PM2000 rods by pulsed plasma-assisted diffusion bonding is reported. During secondary recrystallisation after joining, the alloy grains grew across the original interface, which was then marked only by a row of remnant alumina particles. These did not appear to act as pinning sites for the grain boundaries, which moved easily past them, leaving a strong diffusion bond.

  16. Pulsed Plasma-Assisted Diffusion Bonding of Oxide Dispersion-Strengthened FeCrAl Alloys

    NASA Astrophysics Data System (ADS)

    Tatlock, Gordon J.; Dyadko, Eugene G.; Dryepondt, Sebastien N.; Wright, Ian G.

    2007-07-01

    The successful joining of oxide dispersion-strengthened (ODS) alloy PM2000 rods by pulsed plasma-assisted diffusion bonding is reported. During secondary recrystallization after joining, the alloy grains grew across the original interface, which was then marked by a row of remnant alumina particles. These did not appear to act as pinning sites for the alloy grain boundaries, which moved easily past them, leaving a strong diffusion bond.

  17. Corrosion behaviour of Cu-based shape memory alloys, diffusion bonded

    Microsoft Academic Search

    J. M. Gómez de Salazar; A. Soria; M. I. Barrena

    2005-01-01

    The metallographic characterization and the corrosion resistance of diffusion bonded Cu–Al–Ag shape memory alloys was performed. An electrochemical study was performed, aimed at the evaluation of corrosion parameters both of the Cu-based alloy and the diffusion bonded alloy, using potentiodynamic techniques (ASTM standard G69-81). The polarisation curves were obtained in aerated marine water (3.5% NaCl solution). The result obtained indicates

  18. Technologies of joining between ITER reference grade beryllium and copper alloys by diffusion bonding process

    Microsoft Academic Search

    E. Visca; E. Di Pietro; G. Ceccotti; G. Mercurio

    1996-01-01

    The design of plasma-facing components for ITER relies on the use of junctions for coupling the armor materials to the heat sink and cooling tubes. A suitable diffusion bonding process for manufacturing the high heat flux components of ITER has been developed. The dependence of the load applied on the sample, the bonding temperature, the dwell time and surface preparation

  19. Differential expansion provides pressure for diffusion bonding of large diameter rings

    NASA Technical Reports Server (NTRS)

    1966-01-01

    External pressure band is used to bond aluminum alloy collars to large diameter, stainless steel rings. The band contracts while cooling and exerts pressure on the joint between the silver plated surfaces of the ring and collar which expand toward the band. This diffusion bonding by differential expansion minimizes aluminum deformation.

  20. Microstructural characterisation of stainless steel-titanium interfaces in diffusion bonded joints

    NASA Astrophysics Data System (ADS)

    Srikanth, V.; Laik, A.; Vishwanadh, B.; Shirzadi, A. A.; Dey, G. K.

    2015-06-01

    A detailed characterization of stainless steel -titanium joints, produced by Ga-assisted diffusion bonding, has been carried out. The joints bonded with Ni-interlayer showed the formation of thin layers of intermetallic compounds Fe2Ti and NiTi2 at the interface, while those bonded directly showed formation of Fe2Ti and FeTi. Additionally, the formation of a eutectoid layer of ?-Ti and Ni2Ti, on the Ti side of the interface was noticed.

  1. Modified Diffusion Bonding of Chemical Mechanical Polishing Cu at 150 °C at Ambient Pressure

    NASA Astrophysics Data System (ADS)

    Shigetou, Akitsu; Suga, Tadatomo

    2009-05-01

    This paper describes the feasibility of a low-temperature bonding process for Cu thin films in ambient air. After Cu thin film surfaces were bombarded by an Ar fast atom beam in vacuum to remove the initial thick adsorbate, dry O2 gas was introduced into the vacuum chamber to prevent moisture-induced generation of thick Cu(OH)2 including water molecules. Then the surfaces were contacted with each other at atmospheric pressure. Upon heating at 150 °C for 600 s, high bonding strength, which was as high as that of Cu film breakage, was obtained through a CuO interfacial layer of around 10 nm thickness.

  2. Diffusion layers produced on carbon steel surface by means of vacuum chromizing process

    Microsoft Academic Search

    Ewa Kasprzycka; Jan Senatorski; Aleksander Nakonieczny; Tomasz Babul

    2003-01-01

    This work investigated diffusion layers produced on carbon (C) steel surfaces in the vacuum chromizing process. Studies of\\u000a layer, thickness, morphology, and chromium (Cr), C, and iron (Fe) concentration depth profiles in the diffusion zone of chromized\\u000a layers were carried out. The effect of process parameters such as time and temperature on the kinetics of layer growth on\\u000a steel surface

  3. Visualization and characterization of high-current diffuse vacuum arcs on axial magnetic field contacts

    Microsoft Academic Search

    Michael B. Schulman; Hans Schellekens

    2000-01-01

    We have investigated the behavior of drawn vacuum arcs for several designs of axial magnetic field (AMF) contacts using high-speed digital photography and arc voltage measurements, As the peak current was increased, a gradual transition occurred in the arc appearance from a multiple cathode-spot arc to the high-current diffuse mode, and then to a high-current diffuse columnar mode. Two relatively

  4. Diffusion bonding of beryllium to CuCrZr for ITER applications.

    SciTech Connect

    Cadden, Charles H.; Puskar, Joseph David; Goods, Steven Howard

    2008-08-01

    Low temperature diffusion bonding of beryllium to CuCrZr was investigated for fusion reactor applications. Hot isostatic pressing was accomplished using various metallic interlayers. Diffusion profiles suggest that titanium is effective at preventing Be-Cu intermetallics. Shear strength measurements suggest that acceptable results were obtained at temperatures as low as 540C.

  5. Diffusion bonding of a superplastic Inconel 718SPF superalloy by electroless nickel plating

    SciTech Connect

    Yeh, M.S.; Chang, C.B.; Chuang, T.H.

    2000-02-01

    Although intimate contact can be obtained for diffusion bonding of a superplastic Inconel 718SPF superalloy under a low pressure of 7 MPa, the precipitates formed at the interface retarded achievement of a sound joint. The shear strength was only 41.5 MPa for an overlap length of 12 T (T = 1.3 mm, sheet thickness). The diffusion bondability of t his Inconel 718SPF superalloy was enhanced by electroless nickel plating. In this situation, the bonding shear strength increased to 70.4 MPa for the same overlap length of 12 T under the same bonding condition, regardless of the roughness of the surface to be bonded. Upon decreasing the overlap length from 12 to 6T, the bonding strength remained constant.

  6. Vacuum-compatible standard diffuse source, manufacture and calibration

    SciTech Connect

    Byrd, D.A.; Atkins, W.H.; Bender, S.C.; Christensen, R.W.; Michaud, F.D.

    1999-03-01

    Los Alamos National Laboratories has completed the design, manufacture and calibration of a vacuum-compatible, tungsten lamp, integrated sphere. The light source has been calibrated at the National Institute of Standards and Technology (NIST) and is intended for use as a calibration standard for remote sensing instrumentation. Calibration 2{sigma} uncertainty varied with wavelength from 1.21% at 400 nm and 0.73% at 900 nm, to 3.95% at 2,400 nm. The inner radius of the Spectralon-coated sphere is 21.2 cm with a 7.4 cm square exit aperture. A small satellite sphere is attached to the main sphere and its output coupled through a stepper motor driven aperture. The variable aperture allows a constant radiance without effecting the color temperature output from the main sphere. The sphere`s output is transmitted into a vacuum test environment through a fused silica window that is an integral part of the outer housing of the vacuum shell assembly. The atmosphere within this outer housing is composed of 240 K nitrogen gas, provided by a custom LN{sub 2} vaporizer unit. Use of the nitrogen gas maintains the internal temperature of the sphere at a nominal 300 K {+-}10{degree}. The calibrated spectral range of the source is 0.4 {micro}m through 2.4 {micro}m. Three, color temperature matched, 20 W bulbs together with a 10 W bulb are within the main integrating sphere. Two 20 W bulbs, also color temperature matched, reside in the satellite integrating sphere. A Silicon and a Germanium broadband detector are situated within the inner surface of the main sphere. Their purpose is for the measurement of the internal broadband irradiance. A fiber-optic-coupled spectrometer measures the internal color temperature that is maintained by current control on the lamps. Each lamp is independently operated allowing for radiances with common color temperatures ranging from near 0.026 W/cm{sup 2}/sr to about 0.1 W/cm{sup 2}/sr at a wavelength of 0.9 {micro}m (the location of the peak spectral radiance).

  7. The effect of hydrogen bonds on diffusion mechanism of water inside single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chen, Qu; Wang, Qi; Liu, Ying-Chun; Wu, Tao

    2014-06-01

    Nanopores can serve as a molecule channel for transport of fluid, where water diffusion differs remarkably from that of simple particles. Hydrogen bonds play an essential role in the diffusion anomaly. Detailed investigations are carried out on the systems of rigid (6, 6), (7, 7), (8, 8), (9, 9), and (10, 10) armchair carbon nanotubes, solvated with Lennard-Jones water fluids. The role of hydrogen bonds is examined by diffusivity statistics and animation snapshots. It is found that in small (6,6) CNT, hydrogen bonds tend to aggregate water into a wire and lead to rapid collective drift. Confinement can stabilize the hydrogen bond of water molecules and enhance its lifetime. In relatively smaller CNTs, the diffusion mechanism could be altered by the temperature. Moreover, in larger nanotubes hydrogen bonding network allows the water to form regional concentrated clusters. This allows water fluid in extremely low density exhibit rather slow self-diffusion motion. This fundamental study attempts to provide insights in understanding nanoscale delivery system in aqueous solution.

  8. Investigation on copper diffusion depth in copper wire bonding

    Microsoft Academic Search

    Catherine H. Chen; Shawn X. Zhang; S. W. Ricky Lee; Lebbai Mohamed

    2011-01-01

    Due to the dramatic price increase of precious metals, the replacement of Au with Cu in wire bonding has become an emerging trend for IC packaging nowadays. Similar to the Pb-free soldering transition, such a replacement is not just a simple drop-in material change. Comprehensive processing and reliability investigations are required before a mass production of electronic devices with Cu

  9. A three-mask process for fabricating vacuum-sealed capacitive micromachined ultrasonic transducers using anodic bonding.

    PubMed

    Yamaner, F Yalc?n; Zhang, Xiao; Oralkan, Ömer

    2015-05-01

    This paper introduces a simplified fabrication method for vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays using anodic bonding. Anodic bonding provides the established advantages of wafer-bondingbased CMUT fabrication processes, including process simplicity, control over plate thickness and properties, high fill factor, and ability to implement large vibrating cells. In addition to these, compared with fusion bonding, anodic bonding can be performed at lower processing temperatures, i.e., 350°C as opposed to 1100°C; surface roughness requirement for anodic bonding is more than 10 times more relaxed, i.e., 5-nm rootmean- square (RMS) roughness as opposed to 0.5 nm for fusion bonding; anodic bonding can be performed on smaller contact area and hence improves the fill factor for CMUTs. Although anodic bonding has been previously used for CMUT fabrication, a CMUT with a vacuum cavity could not have been achieved, mainly because gas is trapped inside the cavities during anodic bonding. In the approach we present in this paper, the vacuum cavity is achieved by opening a channel in the plate structure to evacuate the trapped gas and subsequently sealing this channel by conformal silicon nitride deposition in the vacuum environment. The plate structure of the fabricated CMUT consists of the single-crystal silicon device layer of a silicon-on-insulator wafer and a thin silicon nitride insulation layer. The presented fabrication approach employs only three photolithographic steps and combines the advantages of anodic bonding with the advantages of a patterned metal bottom electrode on an insulating substrate, specifically low parasitic series resistance and low parasitic shunt capacitance. In this paper, the developed fabrication scheme is described in detail, including process recipes. The fabricated transducers are characterized using electrical input impedance measurements in air and hydrophone measurements in immersion. A representative design is used to demonstrate immersion operation in conventional, collapse-snapback, and collapse modes. In collapsemode operation, an output pressure of 1.67 MPa pp is shown at 7 MHz on the surface of the transducer for 60-Vpp, 3-cycle sinusoidal excitation at 30-V dc bias. PMID:25965687

  10. Diffusion bonding titanium to stainless steel using Nb/Cu/Ni multi-interlayer

    SciTech Connect

    Li Peng [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072 (China); Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi'an 710072 (China); Li Jinglong, E-mail: lijinglg@nwpu.edu.cn [Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi'an 710072 (China); Xiong Jiangtao; Zhang Fusheng; Raza, Syed Hamid [Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi'an 710072 (China)

    2012-06-15

    By using Nb/Cu/Ni structure as multi-interlayer, diffusion bonding titanium to austenitic stainless steel has been conducted. The effects of bonding temperature and bonding time on the interfacial microstructure were analyzed by scanning electron microscope equipped with energy dispersive spectroscope, and the joint strength was evaluated by tensile test. The results showed that Ni atoms aggregated at the Cu-Nb interface, which promoted Cu solution in Nb. This phenomenon forms a Cu-Nb solution strengthening effect. However, such effect would decay by using long bonding time that dilutes Ni atom aggregation, or be suppressed by using high bonding temperature that embrittles the Cu-Nb interface due to the formation of large grown intermetallic compounds. The sound joint was obtained by promoted parameters as 850 Degree-Sign C for 30-45 min, under which a bonding strength around 300 MPa could be obtained. - Highlights: Black-Right-Pointing-Pointer Titanium was diffusion bonded to stainless steel using Nb/Cu/Ni multi-interlayer. Black-Right-Pointing-Pointer The effects of bonding parameters on microstructure and joint strength were studied. Black-Right-Pointing-Pointer Nickel aggregation promotes Cu solution in Nb which can strengthen the joint. Black-Right-Pointing-Pointer The sound joint with strength of around 300 MPa was obtained by promoted parameters.

  11. Diffusion Bonding of Silicon Carbide for a Micro-Electro-Mechanical Systems Lean Direct Injector

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, James D.

    2006-01-01

    Robust approaches for joining silicon carbide (SiC) to silicon carbide sub-elements have been developed for a micro-electro-mechanical systems lean direct injector (MEMS LDI) application. The objective is to join SiC sub-elements to form a leak-free injector that has complex internal passages for the flow and mixing of fuel and air. Previous bonding technology relied upon silicate glass interlayers that were not uniform or leak free. In a newly developed joining approach, titanium foils and physically vapor deposited titanium coatings were used to form diffusion bonds between SiC materials during hot pressing. Microscopy results show the formation of well adhered diffusion bonds. Initial tests show that the bond strength is much higher than required for the component system. Benefits of the joining technology are fabrication of leak free joints with high temperature and mechanical capability.

  12. Joint design for improved fatigue life of diffusion-bonded box-stiffened panels

    NASA Technical Reports Server (NTRS)

    Davis, R. C.; Moses, P. L.; Kanenko, R. S.

    1985-01-01

    Simple photoelastic models were used to identify a cross-section geometry that would eliminate the severe stress concentrations at the bond line between box stiffeners diffusion bonded to a panel skin. Experimental fatigue-test data from titanium test specimens quantified the allowable stress in terms of cycle life for various joint geometries. It is shown that the effect of stress concentration is reduced and an acceptable fatigue life is achieved.

  13. Reaction-diffusion analysis for one-step plasma etching and bonding of microfluidic devices

    NASA Astrophysics Data System (ADS)

    Rosso, Michel; van Steijn, Volkert; de Smet, Louis C. P. M.; Sudhölter, Ernst J. R.; Kleijn, Chris R.; Kreutzer, Michiel T.

    2011-04-01

    A self-similar reaction front develops in reactive ion etching when the ions penetrate channels of shallow height h. This relates to the patterning of microchannels using a single-step etching and bonding, as described by Rhee et al. [Lab Chip 5, 102 (2005)]. Experimentally, we report that the front location scales as xf˜ht1/2 and the width is time-invariant and scales as ?˜h. Mean-field reaction-diffusion theory and Knudsen diffusion give a semiquantitative understanding of these observations and allow optimization of etching times in relation to bonding requirements.

  14. Testing and modeling of diffusion bonded prototype optical windows under ITER conditions

    SciTech Connect

    Jacobs, M. [Flemish Inst. for Technological Research, Mol (Belgium); Van Oost, G. [Dept. of Applied Physics, Ghent Univ., Ghent (Belgium); Degrieck, J.; De Baere, I. [Dept. of Materials Science and Engineering, Ghent Univ., Ghent (Belgium); Gusarov, A. [Belgian Nuclear Research Center, Mol (Belgium); Gubbels, F. [TNO, Eindhoven (Netherlands); Massaut, V. [Belgian Nuclear Research Center, Mol (Belgium)

    2011-07-01

    Glass-metal joints are a part of ITER optical diagnostics windows. These joints must be leak tight for the safety (presence of tritium in ITER) and to preserve the vacuum. They must also withstand the ITER environment: temperatures up to 220 deg.C and fast neutron fluxes of {approx}3.10{sup 9} n/cm{sup 2}.s. At the moment, little information is available about glass-metal joints suitable for ITER. Therefore, we performed mechanical and thermal tests on some prototypes of an aluminium diffusion bonded optical window. Finite element modeling with Abaqus code was used to understand the experimental results. The prototypes were helium leaking probably due to very tiny cracks in the interaction layer between the steel and the aluminium. However, they were all able to withstand a thermal cycling test up to 200 deg. C; no damage could be seen after the tests by visual inspection. The prototypes successfully passed push-out test with a 500 N load. During the destructive push-out tests the prototypes broke at a 6-12 kN load between the aluminium layer and the steel or the glass, depending on the surface quality of the glass. The microanalysis of the joints has also been performed. The finite element modeling of the push-out tests is in a reasonable agreement with the experiments. According to the model, the highest thermal stress is created in the aluminium layer. Thus, the aluminium joint seems to be the weakest part of the prototypes. If this layer is improved, it will probably make the prototype helium leak tight and as such, a good ITER window candidate. (authors)

  15. Endurance and wear resistance of steels with vacuum-diffused coatings

    Microsoft Academic Search

    P. A. Mikhailov; E. P. Ponomarenko; D. M. Petergerya; A. A. Domio; V. F. Rybkin; V. P. Khokhlov; V. G. Kas'yanenko

    1969-01-01

    The fatigue strength and wear resistance of steels St. 3, P-1, EI-802, and EI-612 after vacuum-diffusion chromizing, siliciding and boriding was studied. It was shown that the wear resistance of carbon steels is increased more than 20-fold by boriding, being approximately doubled by chromizing, and increased 1.3 times by siliciding. Of the alloy steels, only steel EI-612 has its wear

  16. Theoretical analysis of the current and energy flow to the anode in the diffuse vacuum arc

    Microsoft Academic Search

    C. Wieckert; W. Egli

    1989-01-01

    The current energy flow to the anode in a diffuse vacuum arc is investigated using a simple multicathode-spot fluid description of the interelectrodic plasma. Decisive for the current constriction and the energy flow to the anode center is the space-charge sheath in front of the anode. This sheath not only determines the current-density distribution at the anode, but also may

  17. Thermomechanical analysis of diffusion-bonded tungsten/EUROFER97 with a vanadium interlayer

    NASA Astrophysics Data System (ADS)

    Basuki, Widodo Widjaja; Dahm, Ralf; Aktaa, Jarir

    2014-12-01

    Earlier basic investigations revealed that diffusion bonding between tungsten and RAFM-steel at a relatively low temperature using a thin low-activation vanadium interlayer having a CTE between that of the parent materials can significantly reduce the residual stresses and produce defect-free bond interfaces. The joint has a high strength as well as sufficient ductility and toughness especially at the test temperature of about 550 °C. To apply this knowledge in fusion power plants, particularly in divertors, an acceptable lifetime of such structural joints is required, since they are exposed to high thermomechanical cyclic loading. To simulate the possible operational conditions of a He-cooled divertor, diffusion-bonded specimens are loaded by thermal cycling in a temperature range between 350 °C and 500 °C and a constant tensile stress based on the calculation of the internal pressure of the divertor thimble. The aim of this experimental work is to check the resistance of the diffusion-bonded W/EUROFER97 against ratcheting during thermomechanical loading and analyze the evolution of microstructures of the joint especially along the bond interfaces.

  18. Pulsed Plasma-Assisted Diffusion Bonding of ODS-FeCrAl Alloys

    Microsoft Academic Search

    Gordon J Tatlock; Eugene G. Dyadko; Sebastien N Dryepondt; Ian G Wright

    2007-01-01

    The successful joining of ODS alloy PM2000 rods by pulsed plasma-assisted diffusion bonding is reported. During secondary recrystallisation after joining, the alloy grains grew across the original interface, which was then marked only by a row of remnant alumina particles. These did not appear to act as pinning sites for the grain boundaries, which moved easily past them, leaving a

  19. 3J-6 Diffusion-Bonded Transducers for Ultrasonic Flow Measuring and NDT Applications

    Microsoft Academic Search

    V. K. Hamidullin; V. N. Parfenov; G. R. Osokin; A. A. Gnedov; S. V. Nagaevski

    2006-01-01

    This paper presents results related to design ultrasonic transducers with metallic waveguides on the base of copper and aluminum alloys and diffusion welding and brazing them to the external surface of the pipe wall. This approach provided reliable bonding clamp-on transducers and increasing the accuracy of flow measurements and the resolution in detecting defects. The choice of the Lamb wave

  20. Bond lifetime and diffusion coefficient in colloids with short-range interactions.

    PubMed

    Ndong Mintsa, E; Germain, Ph; Amokrane, S

    2015-03-01

    We use molecular dynamics simulations to study the influence of short-range structures in the interaction potential between hard-sphere-like colloidal particles. Starting from model potentials and effective potentials in binary mixtures computed from the Ornstein-Zernike equations, we investigate the influence of the range and strength of a possible tail beyond the usual core repulsion or the presence of repulsive barriers. The diffusion coefficient and mean "bond" lifetimes are used as indicators of the effect of this structure on the dynamics. The existence of correlations between the variations of these quantities with the physical parameters is discussed to assess the interpretation of dynamics slowing down in terms of long-lived bonds. We also discuss the question of a universal behaviour determined by the second virial coefficient B ((2)) and the interplay of attraction and repulsion. While the diffusion coefficient follows the B ((2)) law for purely attractive tails, this is no longer true in the presence of repulsive barriers. Furthermore, the bond lifetime shows a dependence on the physical parameters that differs from that of the diffusion coefficient. This raises the question of the precise role of bonds on the dynamics slowing down in colloidal gels. PMID:25813606

  1. Diffusion Bonding of ?(TiAl) Alloys: Influence of Composition, Microstructure, and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Herrmann, Dirk; Appel, Fritz

    2009-08-01

    The metallurgical factors governing the solid-state diffusion bonding of TiAl alloys have been characterized using scanning electron microscopy together with energy-dispersive X-ray (EDX) spectroscopy and electron backscattered diffraction (EBSD) analysis. The investigations were performed on TiAl alloys with various compositions and microstructures, which had been thoroughly mechanically characterized. The process zone of the bonds typically consists of a fine-grained layer of ? 2(Ti3Al) phase at the former contact plane, followed by relatively large, defect-free ?(TiAl) grains and a region of deformed parent material. The evolution of the process zone involves phase transformation and recrystallization processes, which are triggered by asperity deformation at the contact plane and the unavoidable contamination of the diffusion couple with oxygen and nitrogen. The structural details depend on the alloy composition and the bonding conditions. In the final section of the article, technical aspects, including the tensile strength of diffusion bonds, will be discussed.

  2. Numerical study of diffusion on a random-mixed-bond lattice

    NASA Astrophysics Data System (ADS)

    Holder, Devora; Scher, Harvey; Berkowitz, Brian

    2008-03-01

    Diffusion on lattices with random mixed bonds in two and three dimensions is reconsidered using a random walk (RW) algorithm, which is equivalent to the master equation. In this numerical study the main focus is on the simple case of two different transition rates W1,W2 along bonds between sites. Although analysis of diffusion and transport on this type of disordered medium, especially for the case of one-bond pure percolation (i.e., W1=0 ), comprises a sizable subliterature, we exhibit additional basic results for the two-bond case: When the probability p of W2 replacing W1 in a lattice of W1 bonds is below the percolation threshold pc , the mean square displacement ?r2? is a nonlinear function of time t . A best fit to the ln?r2? vs lnt plot is a straight line with the value of the slope varying with p,?,d , where ??W2/W1 and d is the dimension, i.e., ?r2??t1+?(p,?,d) with ?>0 for ?>1 . In other terms, all the diffusion (D??r2?/2t?t?) is anomalous superdiffusion for p1 for d=2,3 . Previous work in the literature for d=2 with a different RW algorithm established an effective diffusion constant Deff , which was shown to scale as (pc-p)1/2 . However, the anomalous nature (time dependence) of D(t) becomes manifest with an expanded regime of t , increased range of ? , and the use of our algorithm. The nature of the superdiffusion is related to the percolation cluster geometry and Lévy walks.

  3. A Study on Diffusion Pump Oil by the Mass Spectrometer and the Gas Analysis of the Final Vacuum

    Microsoft Academic Search

    Kazuo Hisatake; Kazuhisa Matsuda

    1953-01-01

    Diffusion pump oil is analysed by the mass spectrometer, especially for the purpose of obtaining some knowledge about the residual gases at the final vacuum when we use oil diffusion pumps. As a sample, we take alkyl-naphtalene and its spectrum is given graphically. The results of our analyses of residual gases confirm the conclusions obtained by Hickman and Blears.

  4. Diffusion Bonding of 17-4 Precipitation Hardening Stainless Steel to Ti Alloy With and Without Ni Alloy Interlayer: Interface Microstructure and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Kundu, S.; Anand, G.; Chatterjee, S.

    2013-05-01

    In the present study, the diffusion bonding of 17-4 precipitation hardening stainless steel to Ti alloy with and without nickel alloy as intermediate material was carried out in the temperature range of 1073 K to 1223 K (800 °C to 950 °C) in steps of 298 K (25 °C) for 60 minutes in vacuum. The effects of bonding temperature on interfaces microstructures of bonded joint were analyzed by light optical and scanning electron microscopy. In the case of directly bonded stainless steel and titanium alloy, the layerwise ?-Fe + ?, ?, FeTi + ?, FeTi + ?-Ti phase, and phase mixture were observed at the bond interface. However, when nickel alloy was used as an interlayer, the interfaces indicate that Ni3Ti, NiTi, and NiTi2 are formed at the nickel alloy-titanium alloy interface and the PHSS-nickel alloy interface is free from intermetallics up to 1148 K (875 °C) and above this temperature, intermetallics were formed. The irregular-shaped particles of Fe5Cr35Ni40Ti15 have been observed within the Ni3Ti intermetallic layer. The joint tensile and shear strength were measured; a maximum tensile strength of ~477 MPa and shear strength of ~356.9 MPa along with ~4.2 pct elongation were obtained for the direct bonded joint when processed at 1173 K (900 °C). However, when nickel base alloy was used as an interlayer in the same materials at the bonding temperature of 1148 K (875 °C), the bond tensile and shear strengths increase to ~523.6 and ~389.6 MPa, respectively, along with 6.2 pct elongation.

  5. Fabrication and Design Aspects of High-Temperature Compact Diffusion Bonded Heat Exchangers

    SciTech Connect

    Mylavarapu, Sai K. [Ohio State University; Sun, Xiaodong [Ohio State University; Christensen, Richard N. [Ohio State University; Glosup, Richard E. [Ohio State University; Unocic, Raymond R [ORNL

    2012-01-01

    The very high temperature reactor (VHTR), using gas-cooled reactor technology, is one of the six reactor concepts selected by the Generation IV International Forum and is anticipated to be the reactor type for the next generation nuclear plant (NGNP). In this type of reactor with an indirect power cycle system, a high-temperature and high integrity intermediate heat exchanger (IHX) with high effectiveness is required to efficiently transfer the core thermal output to secondary fluid for electricity production, process heat, or hydrogen cogeneration. The current Technology Readiness Level status issued by NGNP to all components associated with the IHX for reactor core outlet temperatures of 750-800oC is 3 on a scale of 1 to 10 with 10 being the most ready. At present, there is no proven high-temperature IHX concept for VHTRs. Amongst the various potential IHX concepts available, diffusion bonded heat exchangers (henceforth called printed circuit heat exchangers, or PCHEs) appear promising for NGNP applications. The design and fabrication of this key component of NGNP is the primary focus of this paper. In the current study, two PCHEs were fabricated using Alloy 617 plates and will be experimentally investigated for their thermal-hydraulic performance in a high-temperature helium test facility (HTHF). The HTHF was primarily designed and constructed to test the thermal-hydraulic performance of PCHEs The test facility is primarily of Alloy 800H construction and is designed to facilitate experiments at temperatures and pressures up to 800oC and 3 MPa, respectively. The PCHE fabrication related processes, i.e., photochemical machining and diffusion bonding are briefly discussed for Alloy 617 plates. Diffusion bonding of Alloy 617 plates with and without a Ni interlayer is discussed. Furthermore, preliminary microstructural and mechanical characterization studies of representative diffusion bonded Alloy 617 specimens are presented.

  6. Pulsed Plasma-Assisted Diffusion Bonding of Oxide Dispersion-Strengthened FeCrAl Alloys

    Microsoft Academic Search

    Gordon J. Tatlock; Eugene G. Dyadko; Sebastien N. Dryepondt; Ian G. Wright

    2007-01-01

    The successful joining of oxide dispersion-strengthened (ODS) alloy PM2000 rods by pulsed plasma-assisted diffusion bonding is reported. During secondary recrystallization after joining, the alloy grains grew across the original interface, which was then marked by a row of remnant alumina particles. These did not appear to act as pinning sites for the alloy grain boundaries, which moved easily past them,

  7. Pulsed Plasma-Assisted Diffusion Bonding of Oxide Dispersion-Strengthened–FeCrAl Alloys

    Microsoft Academic Search

    Gordon J. Tatlock; Eugene G. Dyadko; Sebastien N. Dryepondt; Ian G. Wright

    2007-01-01

    The successful joining of oxide dispersion-strengthened (ODS) alloy PM2000 rods by pulsed plasma-assisted diffusion bonding\\u000a is reported. During secondary recrystallization after joining, the alloy grains grew across the original interface, which\\u000a was then marked by a row of remnant alumina particles. These did not appear to act as pinning sites for the alloy grain boundaries,\\u000a which moved easily past them,

  8. Interface microstructures in the diffusion bonding of a titanium alloy Ti 6242 to an INCONEL 625

    Microsoft Academic Search

    B. Alemán; I. Gutiérrez; J. J. Urcola

    1995-01-01

    A Ti6242 alloy has been diffusion bonded to a superalloy INCONEL 625. The microstructures of the as-processed products have\\u000a been analyzed using optical metallography, scanning electron microscope (SEM), and scanning transmission electron microscope\\u000a (STEM) techniques. The interdiffusion of the different elements through the interface has been determined using energy-dispersive\\u000a spectroscopy (EDS) microanalysis in both a SEM and a STEM. Several

  9. TEM Observation of the Ti Interlayer Between SiC Substrates During Diffusion Bonding

    NASA Technical Reports Server (NTRS)

    Tsuda, Hiroshi; Mori, Shigeo; Halbig, Michael C.; Singh, Mori

    2012-01-01

    Diffusion bonding was carried out to join SiC to SiC substrates using titanium interlayers. In this study, 10 m and 20 m thick physical vapor deposited (PVD) Ti surface coatings, and 10 and 20 m thick Ti foils were used. Diffusion bonding was performed at 1250 C for PVD Ti coatings and 1200 C for Ti foil. This study investigates the microstructures of the phases formed during diffusion bonding through TEM and selected-area diffraction analysis of a sample prepared with an FIB, which allows samples to be taken from the reacted area. In all samples, Ti3SiC2, Ti5Si3Cx and TiSi2 phases were identified. In addition, TiC and unknown phases also appeared in the samples in which Ti foils were used as interlayers. Furthermore, Ti3SiC2 phases show high concentration and Ti5Si3Cx formed less when samples were processed at a higher temperature and thinner interlayer samples were used. It appears that the formation of microcracks is caused by the presence of intermediate phase Ti5Si3Cx, which has anisotropic thermal expansion, and by the presence of an unidentified Ti-Si-C ternary phase with relatively low Si content.

  10. Deformation of diffusion-bonded bi-PST and directionally solidified crystals of TiAl

    SciTech Connect

    Kishida, K.; Johnson, D.R.; Masuda, Y.; Inui, H.; Yamaguchi, M. [Kyoto Univ., Sakyo (Japan). Dept. of Materials Science and Engineering; Shimada, Y. [Mitsubishi Electric Corp., Itami, Hyogo (Japan)

    1997-12-31

    With a data base now available on the microstructural characteristics and the deformation, fracture and macroscopic flow behavior of polysynthetically twinned (PST) crystals of {gamma}/{alpha}{sub 2} TiAl-base alloys, an approach to achieve a good combination of strength, ductility and toughness in {gamma}/{alpha}{sub 2} TiAl-base alloys was proposed using directional solidification (DS) techniques to produce a columnar grain material with the lamellar orientation aligned parallel to the growth direction. Such alignment of the lamellar microstructure was recently accomplished in {gamma}/{alpha}{sub 2} TiAl-base alloys of near equiatomic compositions using an appropriately oriented seed crystal from the Ti-Al-Si system. At the same time, bi-PST crystals, each containing a planar boundary parallel to the loading axis were prepared by directional solidification and diffusion bonding of two PST crystals. Such bi-PST crystals were deformed in tension at room temperature and their deformation behavior was examined in terms of the compatibility requirements imposed at the grain boundary and the interaction of the two component PST crystals. In this paper, (i) the current status of the DS processing efforts, (ii) some result of microscopic characterization of grain boundaries in diffusion bonded bi-PST crystals and (iii) results of deformation experiments of bi-PST crystals prepared by DS processing and diffusion bonding, will be reported.

  11. Bonding

    MedlinePLUS

    ... is a procedure that uses a tooth-colored composite resin (plastic) to repair a tooth. Bonding can ... cleaned regularly by a dental hygienist. Risks The composite resin used in bonding isn't nearly as ...

  12. Microstructural characteristics of HIP-bonded monolithic nuclear fuels with a diffusion barrier

    NASA Astrophysics Data System (ADS)

    Jue, Jan-Fong; Keiser, Dennis D.; Breckenridge, Cynthia R.; Moore, Glenn A.; Meyer, Mitchell K.

    2014-05-01

    Due to the limitation of maximum uranium load achievable by dispersion fuel type, the Global Threat Reduction Initiative is developing an advanced monolithic fuel to convert US high-performance research reactors to low-enriched uranium. Hot-isostatic-press (HIP) bonding was the single process down-selected to bond monolithic U-Mo fuel meat to aluminum alloy cladding. A diffusion barrier was applied to the U-Mo fuel meat by roll-bonding process to prevent extensive interaction between fuel meat and aluminum-alloy cladding. Microstructural characterization was performed on fresh fuel plates fabricated at Idaho National Laboratory. Interfaces between the fuel meat, the cladding, and the diffusion barrier, as well as between the U-10Mo fuel meat and the Al-6061 cladding, were characterized by scanning electron microscopy. Preliminary results indicate that the interfaces contain many different phases while decomposition, second phases, and chemical banding were also observed in the fuel meat. The important attributes of the HIP-bonded monolithic fuel are: diffusion barrier with a thickness of 25 ?m. A transverse cross section that exhibits relatively equiaxed grains with an average grain diameter of 10 ?m. Chemical banding, in some areas more than 100 ?m in length, that is very pronounced in longitudinal (i.e., rolling) direction with Mo concentration varying from 7-13 wt.%. Decomposed areas containing plate-shaped low-Mo phase. A typical Zr/cladding interaction layer with a thickness of 1-2 ?m. A visible UZr2 bearing layer with a thickness of 1-2 ?m. Mo-rich precipitates (mainly Mo2Zr, forming a layer in some areas) followed by a Mo-depleted sub-layer between the visible UZr2-bearing layer and the U-Mo matrix. No excessive interaction between cladding and the uncoated fuel edge. Cladding-to-cladding bonding that exhibits no cracks or porosity with second phases high in Mg, Si, and O decorating the bond line. Some of these attributes might be critical to the irradiation performance of monolithic U-10Mo nuclear fuel. There are several issues or concerns that warrant more detailed study, such as precipitation along the cladding-to-cladding bond line, chemical banding, uncovered fuel-zone edge, and the interaction layer between the U-Mo fuel meat and zirconium. Future post-irradiation examination results will focus, among other things, on identifying in-reactor failure mechanisms and, eventually, directing further fresh fuel characterization efforts.

  13. Microstructural Characteristics of HIP-bonded Monolithic Nuclear Fuels with a Diffusion Barrier

    SciTech Connect

    Jan-Fong Jue; Dennis D. Keiser, Jr.; Cynthia R. Breckenridge; Glenn A. Moore; Mitchell K. Meyer

    2014-05-01

    Due to the limitation of maximum uranium load achievable by dispersion fuel type, the Global Threat Reduction Initiative (GTRI) is developing an advanced monolithic fuel to convert US high performance research reactors to low-enriched uranium. Hot-isostatic-press bonding was the single process down-selected to bond monolithic U-Mo fuel meat to aluminum alloy cladding. A diffusion barrier was applied to the U–Mo fuel meat by roll-bonding process to prevent extensive interaction between fuel meat and aluminum-alloy cladding. Microstructural characterization was performed on fresh fuel plates fabricated at Idaho National Laboratory. Interfaces between fuel meat, cladding, and diffusion barrier, as well as U–10Mo fuel meat and Al–6061 cladding were characterized by scanning electron microscopy. Preliminary results indicate that the interfaces contain many different phases while decomposition, second phases, and chemical banding were also observed in the fuel meat. The important attributes of the HIP-bonded monolithic fuel are • A typical Zr diffusion barrier of thickness 25 µm • Transverse cross section that exhibits relatively equiaxed grains with an average grain diameter of 10 µm • Chemical banding, in some areas more than 100 µm in length, that is very pronounced in longitudinal (i.e., rolling) direction with Mo concentration varying from 7–13 wt% • Decomposed areas containing plate-shaped low-Mo phase • A typical Zr/cladding interaction layer of thickness 1-2 µm • A visible UZr2 bearing layer of thickness 1-2 µm • Mo-rich precipitates (mainly Mo2Zr, forming a layer in some areas) followed by a Mo-depleted sub-layer between the visible UZr2-bearing layer and the U–Mo matrix • No excessive interaction between cladding and the uncoated fuel edge • Cladding-to-cladding bonding that exhibits no cracks or porosity with second phases high in Mg, Si, and O decorating the bond line. • Some of these attributes might be critical to the irradiation performance of monolithic U-10Mo nuclear fuel. There are several issues or concerns that warrant more detailed study, such as precipitation along cladding-to-cladding bond line, chemical banding, uncovered fuel-zone edge, and interaction layer between U–Mo fuel meat and zirconium. Future post-irradiation examination results will focus, among other things, on identifying in-reactor failure mechanisms and, eventually, directing further fresh fuel characterization efforts.

  14. Verification of the effect of surface preparation on Hot Isostatic Pressing diffusion bonding joints of CLAM steel

    NASA Astrophysics Data System (ADS)

    Zhao, Yanyun; Li, Chunjing; Huang, Bo; Liu, Shaojun; Huang, Qunying

    2014-12-01

    Hot Isostatic Pressing (HIP) diffusion bonding with CLAM steel is the primary candidate fabrication technique for the first wall (FW) of DFLL-TBM. Surface state is one of the key factors for the joints quality. The effect of surface state prepared with grinder and miller on HIP diffusion bonding joints of CLAM steel was investigated. HIP diffusion bonding was performed at 140 MPa and 1373 K within 3 h. The mechanical properties of the joints were investigated with instrumented Charpy V-notch impact tests and the microstructures of the joints were analyzed with scanning electron microscopy (SEM). The results showed that the milled samples with fine surface roughness were more suitable for CLAM steel HIP diffusion bonding.

  15. Diffusion bonding of commercially pure titanium to low carbon steel using a silver interlayer

    SciTech Connect

    Atasoy, Evren [Tokat Adocim Cement Factory, 60100, Tokat (Turkey); Kahraman, Nizamettin [Karabuk University, Technical Education Faculty, 78050, Karabuk (Turkey)], E-mail: nizamettinkahraman@gmail.com

    2008-10-15

    Titanium and low carbon steel plates were joined through diffusion bonding using a silver interlayer at various temperatures for various diffusion times. In order to determine the strength of the resulting joints, tensile-shear tests and hardness tests were applied. Additionally, optical, scanning electron microscopy examinations and energy dispersive spectrometry elemental analyses were carried out to determine the interface properties of the joint. The work showed that the highest interface strength was obtained for the specimens joined at 850 deg. C for 90 min. It was seen from the hardness results that the highest hardness value was obtained for the interlayer material and the hardness values on the both sides of the interlayer decreased gradually as the distance from the joint increased. In energy dispersive spectrometry analyses, it was seen that the amount of silver in the interlayer decreased markedly depending on the temperature rise. In addition, increasing diffusion time also caused some slight decrease in the amount of silver.

  16. Si-based multilayered print circuit board for MEMS packaging fabricated by Si deep etching, bonding, and vacuum metal casting

    NASA Astrophysics Data System (ADS)

    Murakoshi, Yoichi; Hanada, Kotaro; Li, Yaomin; Uchino, Kazuyoshi; Suzuki, Takaaki; Maeda, Ryutaro

    2001-11-01

    In our previous works, metal injection technique into small diameter (10 -100micrometers ) through holes was developed and applied for fabrication of Si based print circuit board. In the present work, we present the metal filling technology by vacuum casting into 3 dimensional through holes and trenches structure fabricated in stacked layered Si wafers prepared by fusion bonding of ICP etched Si wafers. Metal electrical feed through was successfully prepared by the method. Conventional print circuit boards have been fabricated with Epoxy resin based materials. In recent years Si is regarded as a candidate for next generation materials for print circuit board substrates, as the substrate whose thermal elongation same as the mounted chips is an ideal solution to residual stress problems in the elevated temperature application. In this report, we developed the double sided mountable stacked circuit board using Si deep etching technology and fusion bonding. This technology is expected to lead to the realization of the assembling of sensors, actuators and ICs, i.e. 3 dimensional MEMS packaging. In this report, we adopted micromachining technology to this application area and the special emphasis is placed on the low cost and reliable process development. The detailed items to be developed are shown as follows; 1) Development of Si wafer through holes penetration and trench formation by ICP etching. 2) Alignment and bonding of micromachined wafers. 3) Development of insulating layer with oxidation. 4) Development of formation of electrical feed through for stacked layers.

  17. Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core

    NASA Technical Reports Server (NTRS)

    Ko, W. L.

    1980-01-01

    Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.

  18. Structural dynamics of hydrogen bonded methanol oligomers: Vibrational transient hole burning studies of spectral diffusion

    NASA Astrophysics Data System (ADS)

    Piletic, I. R.; Gaffney, K. J.; Fayer, M. D.

    2003-07-01

    Frequency resolved pump-probe experiments have been conducted on the deuterated hydroxyl stretch of methanol-d in a solution containing 0.8% methanol-d/23% methanol-h in carbon tetrachloride. Methanol-d molecules that both donate and receive hydrogen bonds have an inhomogeneously broadened hydroxyl stretch absorption line centered at 2487 cm-1. With a laser tuned to 2513 cm-1, the high-frequency side of the absorption spectrum is excited. The equilibration of the excited state peak and the ground-state hole results in the time-dependent shift in the frequency of the signal, which is used to monitor the dynamics of spectral diffusion. Model calculations were conducted to address the influence of spectral diffusion in the ground and excited states on the experimental observables when the vibrational lifetime is comparable to the spectral diffusion time. The model calculations illustrate the influence on the signal of absorbers in the ground state that have relaxed from the excited state. This aspect of the problem has not been addressed in previous descriptions of frequency resolved pump-probe spectroscopy. The calculations were used to fit the time-dependent peak maximum, resulting in a bi-exponential frequency-frequency correlation function, with a fast time constant of roughly 0.1 ps and a slower time constant of 1.6±0.3 ps. The observed dynamics have been compared with the predictions of dielectric continuum theory. The inability of a simple dielectric continuum theory to predict the observed spectral diffusion dynamics suggests that these dynamics do not result from the long-wavelength, collective orientational relaxation of the solvent. Instead the dynamics are attributed to fluctuations in the local hydrogen bond network, which is consistent with recent molecular-dynamics simulations of vibrational transient hole burning in water.

  19. Diffusion Bonding Technology of Tungsten and SiC/SiC Composites for Nuclear Applications

    NASA Astrophysics Data System (ADS)

    Kishimoto, Hirotatsu; Shibayama, Tamaki; Abe, Takahiro; Shimoda, Kazuya; Kawamura, Satoshi; Kohyama, Akira

    2011-10-01

    Silicon carbide (SiC) is a candidate for the structural material in the next generation nuclear plants. Use of SiC/SiC composites is expected to increase the operation temperature of system over 1000 °C. For the high temperature system, refractory metals are planned to be used for several components. Tungsten is a candidate of armor on the divertor component in fusion, and is planned to be used for an upper-end plug of SiC/SiC fuel pin in a Gas cooled Fast Reactor (GFR). Joining technique of the SiC/SiC composites and tungsten is an important issue for nuclear systems in future. Nano-Infiltration and Transient Eutectoid (NITE) method is able to provide dense stable and high strength SiC/SiC composites having high resistance against pressure at elevated temperature, a diffusion bonding technique is usable to join the materials. Present research produces a NITE-SiC/SiC composite and tungsten as the similar dimension as a projected cladding tube of fuel pin for GFR using diffusion bonding, and investigated microstructure and mechanical properties.

  20. Behaviour of oxide at diffusion?bonded interfaces in Al?Mg?Si series 6063 alloy: Study of diffusion?bonding mechanism of aluminium alloys by transmission electron microscopy (1st Report)

    Microsoft Academic Search

    K. Ikeuchi; F. Matsuda; K. Kotani

    1996-01-01

    The behaviour of the surface oxide film during the diffusion?bonding of Al?Mg?Si series 6063 alloy and its influence on the bond strength have been investigated mainly by TEM observations in order to explain the effect of alloying elements on the bondability of aluminium alloys. When faying surfaces were finished by electro?polishing, crystalline oxide particles smaller than a few 10 ?m

  1. A Comparison Between Cold-Welded and Diffusion-Bonded Al/Cu Bimetallic Rods Produced by ECAE Process

    NASA Astrophysics Data System (ADS)

    Eslami, P.; Karimi Taheri, A.; Zebardast, M.

    2013-10-01

    In this research, the application of equal channel angular extrusion process to produce both the cold-welded and diffusion-bonded Al/Cu bimetallic rods is assessed. The joints shear strength for both of the methods are measured and compared. The microstructure examinations were also carried out using scanning electron microscope equipped with EDX system and x-ray diffraction analysis. The results exhibit that the strength of the bond in cold-welded specimens is dependent on the amount of stretch and pressure at the materials interface. But in the diffusion-bonded specimens, it is depended on the struggle between the oxidation rate of the mating surfaces accompanied by inter-metallic compounds formation and the aluminum and copper atoms ability to diffuse in the joint interface.

  2. Interface microstructures in the diffusion bonding of a titanium alloy Ti 6242 to an Inconel 625

    SciTech Connect

    Aleman, B.; Gutierrez, I.; Urcola, J.J. (Centro de Estudios e Investigaciones Tecnicos de Guipuzcoa, San Sebastian (Spain). Dept. of Materials)

    1995-02-01

    Surveys carried out by some oil companies have shown a recent and clear trend toward drilling wells to greater depths. As the drilling for oil and gas gets deeper, the requirements of materials for tubing become more stringent, due to the rise in temperature and pressure and also because the tubes have to sustain their own weight. In this paper, Ti6242 alloy has been diffusion bonded to a superalloy INCONEL 625. The microstructures of the as-processed products have been analyzed using optical metallography, scanning electron microscope (SEM), and scanning transmission electron microscope (STEM) techniques. The interdiffusion of the different elements through the interface has been determined using energy-dispersive spectroscopy (EDS) microanalysis in both a SEM and a STEM. Several regions around the original interface have been observed. Starting from the superalloy INCONEL 625, first a sigma phase (Cr[sub 4]Ni[sub 3]Mo[sub 2]), followed by several phases like NbNi[sub 3], [eta]Ni[sub 3]Ti, Cr(20 pct Mo), [beta] Cr[sub 2]Ti, NiTi, TiO, TiNi, and Ti[sub 2]Ni intermetallics, just before the Ti6242 have been identified. Because the diffusion of Ni in Ti is faster than the diffusion of Ti in the superalloy, a Kirkendall effect was produced. The sequence of formation of the different phases were in agreement with the ternary Ti-Cr-Ni diagram.

  3. [Casting faults and structural studies on bonded alloys comparing centrifugal castings and vacuum pressure castings].

    PubMed

    Fuchs, P; Küfmann, W

    1978-07-01

    The casting processes in use today such as centrifugal casting and vacuum pressure casting were compared with one another. An effort was made to answer the question whether the occurrence of shrink cavities and the mean diameter of the grain of the alloy is dependent on the method of casting. 80 crowns were made by both processes from the baked alloys Degudent Universal, Degudent N and the trial alloy 4437 of the firm Degusa. Slice sections were examined for macro and micro-porosity and the structural appearance was evaluated by linear analysis. Statistical analysis showed that casting faults and casting structure is independent of the method used and their causes must be found in the conditions of casting and the composition of the alloy. PMID:352670

  4. Microstructure, microchemistry and strength of insulating ceramics joined to a fusion candidate austenitic steel by diffusion bonding

    NASA Astrophysics Data System (ADS)

    Muroga, T.; Aono, Y.; Yoshida, N.; Murata, Y.; Fukuzawa, Y.

    1991-03-01

    Characterization of ceramic/metal joints produced by diffusion bonding using fusion candidate ceramics (A1 2O 3, ZrO 2) and alloy (JPCA) was carried out to investigate their applicability in fusion reactors. The characterization includes bending tests, SEM observation of the fracture surfaces, TEM observation and EDS microchemical analyses of the interfaces. Mechanisms of the strength degradation by bonding and possible ways of improvement were examined.

  5. Reaction diffusion behaviors for interface between Ni-based super alloys and vacuum plasma sprayed MCrAlY coatings

    SciTech Connect

    Itoh, Y.; Tamura, M. [Toshiba Corp., Kawasaki, Kanagawa (Japan)

    1999-07-01

    The object of this study is overlay coatings of MCrAlY alloy sprayed by a vacuum plasma spray (VPS) process for the protection against high-temperature corrosion and oxidation in the field of gas turbine components. Reaction diffusion behaviors at the interface between the MCrAlY coatings and the substrate, which have an important effect on coating degradation, have not always been clarified. Three kinds of substrate, equiaxis IN738LC, directional solidified CM247LC and single-crystal CMSX-2, and the four kinds of vacuum plasma sprayed MCrAlY coating have been selected for these experiments. The experimental results showed that the reaction diffusion layers consisted of aluminum compound layer and aluminum depleted layer, expecting that the aluminum depleted layer could not be observed in the case of CoNiCrAlY and NiCoCrAlY coatings. It also indicated that the diffusion thickness could be observed to follow a parabolic time dependence. The order of reaction diffusion rate was NiCrAlY > CoCrAlY > CoNiCrAlY > NiCoCrAlY independent of the substrates. A convenient computer-aided system was developed for analyzing the reaction diffusion behaviors at the interface between coating and substrate. It was also clear that the estimated results of long time diffusion behaviors by simulation analysis was in good agreement with experiments.

  6. On the numerical simulation of the diffuse arc in a vacuum interrupter

    SciTech Connect

    Langlois, Y. [Institut Jean Lamour-UMR 7198 CNRS, Ecole des Mines de Nancy, Parc de Saurupt, CS 14234, F-54042 Nancy Cedex (France); Schneider Electric Industries SAS, Usine 38V, ZAC Champ Saint Ange, F-38050 Grenoble Cedex 9 (France); Chapelle, P.; Jardy, A. [Institut Jean Lamour-UMR 7198 CNRS, Ecole des Mines de Nancy, Parc de Saurupt, CS 14234, F-54042 Nancy Cedex (France); Gentils, F. [Schneider Electric Industries SAS, Usine 38V, ZAC Champ Saint Ange, F-38050 Grenoble Cedex 9 (France)

    2011-06-01

    A 2D two-fluid numerical model is developed for the description of the diffuse arc in a vacuum interrupter under the possible influence of an axial magnetic field (AMF). This model incorporates the energy balance equations for both ions and electrons and takes into account the three components of the self-generated magnetic field. The possibility of both supersonic (at low current density) and subsonic (at high current density) plasma flow regimes is considered. Data from the literature are used to specify the values of the plasma parameters near the cathode, and the boundary conditions on the anode boundary rely on a simplified model of the anode sheath. Simulation results are presented for both ion flow regimes, with special attention to the current and plasma flow features. It is shown that there is always a contraction of the current flow, whereas the dynamics of the ions throughout the interelectrode gap is strongly influenced by their flow regime near the cathode. Finally, the influence of various operating parameters (presence of an AMF, gap length) on the current constriction at the anode is discussed.

  7. Reactive diffusion bonding of Si3N4 to MA6000

    NASA Astrophysics Data System (ADS)

    Kaysser, W. A.; Frisch, A.; Zhang, W.; Petzow, G.

    The procedure for joining Si3N4 to the MA6000 superalloy by diffusion bonding during HIP is described. Due to the large thermal mismatch between both components, it was necessary to introduce multiphase interlayers to allow relaxation of thermal stresses. Calculations of the stress development and the results of experiments showed that stress relaxation by thin soft interlayers in Si3N4/MA6000 is very limited: during bonding of Si3N4 to metals suitable as interlayers, brittle reaction products often form at the metal/ceramic interfaces. Experiments were then performed with iron-based alloys with small thermal expansion coefficients at low temperatures, combined with V, Nb, and Hf-based layers, and the reactions at the layer interfaces and the fracture surfaces were investigated by SEM, EDX, and WDX. It was found that, in systems with low deformability of the stiff reaction layers, stress relaxation by controlled microcrack formation reduced the interfacial damage and improved the mechanical stability of the joints.

  8. Reaction diffusion behaviors for interface between Ni-based super alloys and vacuum plasma sprayed MCrAlY coatings

    Microsoft Academic Search

    Y. Itoh; M. Tamura

    1999-01-01

    The object of this study is overlay coatings of MCrAlY alloy sprayed by a vacuum plasma spray (VPS) process for the protection against high-temperature corrosion and oxidation in the field of gas turbine components. Reaction diffusion behaviors at the interface between the MCrAlY coatings and the substrate, which have an important effect on coating degradation, have not always been clarified.

  9. The influence of bond-rigidity and cluster diffusion on the self-diffusion of hard spheres with square-well interaction

    E-print Network

    Sujin Babu; Jean Christophe Gimel; Taco Nicolai; C. De Michele

    2007-11-02

    Hard spheres interacting through a square-well potential were simulated using two different methods: Brownian Cluster Dynamics (BCD) and Event Driven Brownian Dynamics (EDBD). The structure of the equilibrium states obtained by both methods were compared and found to be almost the identical. Self diffusion coefficients ($D$) were determined as a function of the interaction strength. The same values were found using BCD or EDBD. Contrary the EDBD, BCD allows one to study the effect of bond rigidity and hydrodynamic interaction within the clusters. When the bonds are flexible the effect of attraction on $D$ is relatively weak compared to systems with rigid bonds. $D$ increases first with increasing attraction strength, and then decreases for stronger interaction. Introducing intra-cluster hydrodynamic interaction weakly increases $D$ for a given interaction strength. Introducing bond rigidity causes a strong decrease of $D$ which no longer shows a maximum as function of the attraction strength.

  10. Method for producing components with internal architectures, such as micro-channel reactors, via diffusion bonding sheets

    DOEpatents

    Alman, David E. (Corvallis, OR); Wilson, Rick D. (Corvallis, OR); Davis, Daniel L. (Albany, OR)

    2011-03-08

    This invention relates to a method for producing components with internal architectures, and more particularly, this invention relates to a method for producing structures with microchannels via the use of diffusion bonding of stacked laminates. Specifically, the method involves weakly bonding a stack of laminates forming internal voids and channels with a first generally low uniaxial pressure and first temperature such that bonding at least between the asperites of opposing laminates occurs and pores are isolated in interfacial contact areas, followed by a second generally higher isostatic pressure and second temperature for final bonding. The method thereby allows fabrication of micro-channel devices such as heat exchangers, recuperators, heat-pumps, chemical separators, chemical reactors, fuel processing units, and combustors without limitation on the fin aspect ratio.

  11. Effects of interface bonding and defects on boron diffusion at Si/SiO{sub 2} interface

    SciTech Connect

    Kim, Geun-Myeong; Oh, Young Jun; Chang, K. J., E-mail: kchang@kaist.ac.kr [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

    2013-12-14

    We perform first-principles density functional calculations to find the migration pathway and barrier for B diffusion at the Si/SiO{sub 2} interface. For various interface models, in which crystalline ?-quartz or amorphous silica (a-SiO{sub 2}) is placed on Si, we examine stable and metastable configurations of B-related defects which play a role in B diffusion. While a substitutional B alone is immobile in Si, it tends to diffuse to the interface via an interstitialcy mechanism in the presence of a self-interstitial and then changes into an interstitial B in oxide via a kick-out mechanism, leaving the self-interstitial at the interface. At the defect-free interface, where bridging O atoms are inserted to remove interface dangling bonds, an interstitial B prefers to intervene between the interface Si and bridging O atoms and subsequently diffuses through the hollow space or along the network of the Si-O-Si bonds in oxide. The overall migration barriers are calculated to be 2.02–2.12?eV at the Si/?-quartz interface, while they lie in the range of 2.04?±?0.44?eV at the Si/a-SiO{sub 2} interface, similar to that in ?-quartz. The migration pathway and barrier are not significantly affected by interface defects such as suboxide bond and O protrusion, while dangling bonds in the suboxide region can increase the migration barrier by about 1.5?eV. The result that the interface generally does not hinder the B diffusion from Si to SiO{sub 2} assists in understanding the underlying mechanism for B segregation which commonly occurs at the Si/SiO{sub 2} interface.

  12. Assessment of diffusion-bonded KTP crystals for efficient, low pulse energy conversion from 1 to 2 microm.

    PubMed

    Perrett, Brian J; Mason, Paul D; Orchard, David A

    2006-06-20

    Diffusion bonded (DB) walk-off compensated KTP crystals offer an alternative nonlinear medium for efficient 1 to 2 microm conversion within optical parametric oscillators (OPOs) at low pulse energies. Spatial variations in optical absorption and transmission values measured at 2 mum are reported for two DB-KTP crystals. Finally, a comparison is made between the conversion efficiency obtained from a degenerate 1 microm pumped OPO using a single 20 mm KTP crystal and an equivalent length DB-KTP crystal consisting of two bonded 10 mm crystals. PMID:16778951

  13. Indirect Versus Direct Heating of Sheet Materials: Superplastic Forming and Diffusion Bonding Using Lasers

    NASA Astrophysics Data System (ADS)

    Jocelyn, Alan; Kar, Aravinda; Fanourakis, Alexander; Flower, Terence; Ackerman, Mike; Keevil, Allen; Way, Jerome

    2010-06-01

    Many from within manufacturing industry consider superplastic forming (SPF) to be ‘high tech’, but it is often criticized as too complicated, expensive, slow and, in general, an unstable process when compared to other methods of manipulating sheet materials. Perhaps, the fundamental cause of this negative perception of SPF, and also of diffusion bonding (DB), is the fact that the current process of SPF/DB relies on indirect sources of heating to produce the conditions necessary for the material to be formed. Thus, heat is usually derived from the electrically heated platens of hydraulic presses, to a lesser extent from within furnaces and, sometimes, from heaters imbedded in ceramic moulds. Recent evaluations of these isothermal methods suggest they are slow, thermally inefficient and inappropriate for the process. In contrast, direct heating of only the material to be formed by modern, electrically efficient, lasers could transform SPF/DB into the first choice of designers in aerospace, automotive, marine, medical, architecture and leisure industries. Furthermore, ‘variable temperature’ direct heating which, in theory, is possible with a laser beam(s) may provide a means to control material thickness distribution, a goal of enormous importance as fuel efficient, lightweight structures for transportation systems are universally sought. This paper compares, and contrasts, the two systems and suggests how a change to laser heating might be achieved.

  14. Interface reaction systematics in the Cu\\/In–48Sn\\/Cu system bonded by diffusion soldering

    Microsoft Academic Search

    S. Sommadossi; A. Fernández Guillermet

    2007-01-01

    An alternative lead-free solder alloy In–48at%Sn with a melting point of 120°C and its implementation to bond Cu substrates in a diffusion soldering joining method are presented. According to the EPMA, TEM\\/EDX and electron diffraction analyses, two different behaviors were observed in the interconnection zone depending on the temperature range: (i) a single layer consisting of ? phase below 200°C;

  15. Nonproportionality in Bayard-Alpert Ionization Gauge and the Ultimate Vacuum Determination of Diffusion Pumps

    Microsoft Academic Search

    Y. Mizushima; Z. Oda

    1959-01-01

    The nonproportionality between the ion current and the electron current in a Bayard-Alpert ionization gauge is systematically examined and theoretically treated. The effective pumping speed is so modified as to include the effect of back diffusion of oil vapor from the diffusion pump and the contribution of ionization pumping. The theory is experimentally verified in some respects to deduce a

  16. Modeling Microwave Vacuum Drying Kinetics and Moisture Diffusivity of Carrot Slices

    Microsoft Academic Search

    P. P. Sutar; S. Prasad

    2007-01-01

    Carrot slices of 3.5 mm thickness were dried in a laboratory microwave vacuum dryer at five different microwave power density levels of 2, 4.66, 7.33, 10, and 12.66 W\\/g and at three vacuum chamber pressure levels of 6.66, 19.98, and 33.3 kPa to 4–6% d.b. moisture content. Inside the dryer the sample holding plate was rotated with the speed of 4 rpm for uniform

  17. The effects of metal coating on the diffusion bonding in Al 2 O 3 \\/Inconel 600 and the modulus of rupture strength of alumina

    Microsoft Academic Search

    H. R. Hwang; R. Y. Lee

    1996-01-01

    Alumina with a sputter-deposited metal film was diffusion bonded to Inconel 600. A higher bonding strength and lower joining temperature were obtained with titanium coating compared to that for the non-coated sample. The improved joining behaviour was attributed to an enhanced interface reaction and reduction in the thermal stress. Also, the effect of various coatings of 3 µm thickness on

  18. III. Vacuum PumpsIII. Vacuum Pumps Gas transfer

    E-print Network

    Liu, Kai

    : Oil Diffusion PumpB. High Vacuum: Oil Diffusion Pump (Wet, Gas Transfer)(Wet, Gas Transfer, Screw High vacuum Oil diffusion, Turbomolecular, Cryo, Ion Auxiliary Titanium Sublimation, LN2 Liu, UCDIII. Vacuum PumpsIII. Vacuum Pumps Mechanism Gas transfer Gas capture FunctionFunction Roughing

  19. An investigation on diffusion bonding of aluminum to copper using equal channel angular extrusion process

    PubMed Central

    Eslami, P.; Taheri, A. Karimi

    2011-01-01

    A new method for production of bimetallic rods, utilizing the equal channel angular extrusion (ECAE) process has been introduced before by previous researchers, but no attempt has been made to assess the effect of different temperatures and holding times in order to achieve a diffusional bond between the mating surfaces. In present research copper sheathed aluminum rods have been ECAEed at room temperature and subsequently held at a constant ECAE pressure, at different temperatures and holding times to produce a diffusional bond between the copper sheath and the aluminum core. The bonding quality of the joints was examined by shear strength test and a sound bonding interface was achieved. Based on the results, a bonding temperature of 200 °C and holding time of 60–80 min yielded the highest shear strength value. PMID:21760654

  20. Contact temperature and erosion in high-current diffuse vacuum arcs on axial magnetic field contacts

    Microsoft Academic Search

    H. Schellekens; M. B. Schulman

    2001-01-01

    We have investigated the surface heating effects of drawn vacuum arcs for several industrial designs of axial magnetic field (AMF) contacts, using near infrared (IR) photography of the Cu-Cr arcing surfaces with an image-intensified charge-coupled device (CCD) camera and an IR pyrometer. This enables detailed contact temperature mapping immediately after a half-cycle of arc current. The very homogeneous temperature distribution

  1. Brazing process using'al-Si filler alloy reliably bonds aluminum parts

    NASA Technical Reports Server (NTRS)

    Beuyukian, C. S.; Johnson, W. R.

    1966-01-01

    Brazing process employs an aluminum-silicon filler alloy for diffusion bonding of aluminum parts in a vacuum or inert gas atmosphere. This process is carried out at temperatures substantially below those required in conventional process and produces bonds of greater strength and reliability.

  2. Transient Liquid Phase Diffusion Bonding of Magnesium Alloy (Mg-AZ31) to Titanium Alloy (Ti-6Al-4V)

    NASA Astrophysics Data System (ADS)

    Atieh, Anas Mahmoud

    The magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al-4V have physical characteristics and mechanical properties that makes it attractive for a wide range of engineering applications in the aerospace and automotive industries. However, the differences in melting temperature and coefficient of thermal expansion hinder the use of traditional fusion welding techniques. Transient liquid phase (TLP) bonding of magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al- 4V was performed and different interlayer types and configurations were used to facilitate joint formation. The joining of these alloys using Ni foils was successful at a bonding temperature of 515°C, bonding pressure 0.2 MPa, for bonding time of 5 minutes. At the Ni/Mg-AZ31 bond interface, the formation of a eutectic liquid between Mg and Ni was observed. The formation of Mg2Ni and Mg3AlNi2 were identified along the bond interface resulting in an isothermally solidified joint. At the Ni/Ti-6Al-4V interface, the solid-state diffusion process results in joint formation. The use of double Ni-Cu sandwich joint resulted in further enhancement in joint formation and this produced joints with greater shear strength values. The configuration of Mg-AZ31/Cu- Ni/Ti-6Al-4V or Mg-AZ31/Ni-Cu/Ti-6Al-4V influence the mechanism of bonding and the type of intermetallics formed within the joint. The application of thin Ni electrodeposited coatings resulted in further enhancements of joint quality due to better surface-to-surface contact and a reduction in the formation of intermetallics at the joint. The effect of Cu nano-particles in the coatings was found to decrease the eutectic zone width and this resulted in an increase the shear strength of the joints. The highest shear strength of 69 MPa was possible with bonds made using coatings containing Cu nano-particle dispersion.

  3. Estimation of Post-Arc Neutral Vapor Density in the Gap Volume Generated by Evaporating Macroparticles in a Diffuse Vacuum Arc

    Microsoft Academic Search

    Z. Zalucki

    1985-01-01

    This paper presents a mathematical model of calculations of the density of atoms evaporated from macroparticles in a diffuse vacuum arc. The influence of the initial temperature, diameter, and average velocity of the droplets, as well as the kind of the cathode metal on vapor density in the volume surrounding the electrodes was investigated. Both the initial density and the

  4. Transient liquid phase diffusion bonding and associated recrystallization phenomenon when joining ODS ferritic superalloys

    Microsoft Academic Search

    T. I. Khan; E. R. Wallach

    1996-01-01

    Oxide dispersion strengthened (ODS) ferritic superalloys attribute their excellent intermediate and high temperature creep resistant properties to the distribution of an inert oxide, Y2O3 within highly directional and elongated grains. Careful selection of joining techniques is, therefore, of utmost importance so that the parent metal microstructure is not disrupted and is continuous across the bond line. Transient liquid phase (TLP)

  5. Achieving low temperature Cu to Cu diffusion bonding with self assembly monolayer (SAM) passivation

    Microsoft Academic Search

    Dau Fatt Lim; Shiv Govind Singh; Xiao Fang Ang; Jun Wei; Chee Mang Ng; Chuan Seng Tan

    2009-01-01

    In this article, we investigate the feasibility of applying a self assembly monolayer (SAM) onto Cu surface as a passivation layer so as to lower the required temperature during Cu-Cu bonding. Proprietary SAM is applied on Cu layer deposited on Si wafers and studied carefully. The stability of SAM when it is subjected to various exposure times in ambient air

  6. New method to diffusion bond superalloys A. A. Shirzadi and E. R. Wallach

    E-print Network

    Cambridge, University of

    base and cobalt base super- alloys with `virtually invisible' bond interfaces and compositions very Materials;accepted 6 February 2003. # 2004 IoM Communications Ltd. Published by Maney for the Institute or TIG welding processes, the formation of cracks remains a major problem.1,2 Other joining methods

  7. Structural dynamics of hydrogen bonded methanol oligomers: Vibrational transient hole burning studies of spectral diffusion

    E-print Network

    Fayer, Michael D.

    Structural dynamics of hydrogen bonded methanol oligomers: Vibrational transient hole burning. The continuous fluctuation of local structures also characterizes the liquid state. The micro- scopic dynamics in the time-dependent shift in the frequency of the signal, which is used to monitor the dynamics of spectral

  8. M3B2 and M5B3 Formation in Diffusion-Affected Zone During Transient Liquid Phase Bonding Single-Crystal Superalloys

    NASA Astrophysics Data System (ADS)

    Sheng, Naicheng; Hu, Xiaobing; Liu, Jide; Jin, Tao; Sun, Xiaofeng; Hu, Zhuangqi

    2015-04-01

    Precipitates in the diffusion-affected zone (DAZ) during transient liquid phase bonding (TLP) single-crystal superalloys were observed and investigated. Small size and dendritic-shaped precipitates were identified to be M3B2 borides and intergrowth of M3B2/M5B3 borides. The orientation relationships among M3B2, M5B3, and matrix were determined using transmission electron microscope (TEM). Composition characteristics of these borides were also analyzed by TEM energy-dispersive spectrometer. Because this precipitating phenomenon deviates from the traditional parabolic transient liquid phase bonding model which assumed a precipitates free DAZ during TLP bonding, some correlations between the deviation of the isothermal solidification kinetics and these newly observed precipitating behaviors were discussed and rationalized when bonding the interlayer containing the high diffusivity melting point depressant elements and substrates of low solubility.

  9. The frictional properties of a spray-bonded MoS{sub 2}/Sb{sub 2}O{sub 3} film under the fretting in vacuum

    SciTech Connect

    Shimizu, Tomoharu; Iwabuchi, Akira; Mifune, Hidenobu [Iwate Univ., Morioda (Japan)] [and others

    1995-12-01

    The frictional properties of a spray-bonded MoS{sub 2}/Sb{sub 2}O{sub 3} film coated on a Ti alloy were examined against a steel ball under fretting conditions in air and in vacuum. In air the coefficient of friction increased with the number of cycles. The increase in friction was caused by the disintegration of the film. An SO{sub 4} compound was detected by XPS. In vacuum below 10{sup -1} Pa the coefficient of friction slightly decreased with the number of cycles and reached between 0.08 and 0.1, followed by sudden increase due to the film wearing out. The coefficient of friction increased with decreasing load, irrespective of the ambient pressure. The life of the film was affected by normal load, ambient pressure and slip amplitude. The longest life obtained was over 2.2 X 10{sup 6} cycles under 1.47 N load, 20 {mu}m peak-to-peak slip amplitude and 10{sub -5} Pa pressure. The longer life at small amplitude is related to the lower removal rate of the debris particles from the interface. 24 refs., 10 figs.

  10. Evaluation of superplastic forming and co-diffusion bonding of Ti-6Al-4V titanium alloy expanded sandwich structures

    NASA Technical Reports Server (NTRS)

    Arvin, G. H.; Israeli, L.; Stolpestad, J. H.; Stacher, G. W.

    1981-01-01

    The application of the superplastic forming/diffusion bonding (SPF/DB) process to supersonic cruise research is investigated. The capability of an SPF/DB titanium structure to meet the structural requirements of the inner wing area of the NASA arrow-wing advanced supersonic transport design is evaluated. Selection of structural concepts and their optimization for minimum weight, SPF/DB process optimization, fabrication of representative specimens, and specimen testing and evaluation are described. The structural area used includes both upper and lower wing panels, where the upper wing panel is used for static compression strength evaluation and the lower panel, in tension, is used for fracture mechanics evaluations. The individual test specimens, cut from six large panels, consist of 39 static specimens, 10 fracture mechanics specimens, and one each full size panel for compression stability and fracture mechanics testing. Tests are performed at temperatures of -54 C (-65 F), room temperature, and 260 C (500 F).

  11. Effect of electron energy distribution functions on plasma generated vacuum ultraviolet in a diffusion plasma excited by a microwave surface wave

    SciTech Connect

    Zhao, J. P.; Chen, L.; Funk, M.; Sundararajan, R. [Austin Plasma Laboratory, Tokyo Electron America, Inc., Austin, Texas 78741 (United States); Nozawa, T. [Tokyo Electron Limited, TEL Technology Center Sendai, 2-1 Osawa 3-chome, Izumi-ku, Sendai 981-3137 (Japan); Samukawa, S. [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2013-07-15

    Plasma generated vacuum ultraviolet (VUV) in diffusion plasma excited by a microwave surface wave has been studied by using dielectric-based VUV sensors. Evolution of plasma VUV in the diffusion plasma as a function of the distance from the power coupling surface is investigated. Experimental results have indicated that the energy and spatial distributions of plasma VUV are mainly controlled by the energy distribution functions of the plasma electrons, i.e., electron energy distribution functions (EEDFs). The study implies that by designing EEDF of plasma, one could be able to tailor plasma VUV in different applications such as in dielectric etching or photo resist smoothing.

  12. Fabrication and evaluation of enhanced diffusion bonded titanium honeycomb core sandwich panels with titanium aluminide face sheets

    NASA Technical Reports Server (NTRS)

    Hoffmann, E. K.; Bird, R. K.; Bales, T. T.

    1989-01-01

    A joining process was developed for fabricating lightweight, high temperature sandwich panels for aerospace applications using Ti-14Al-21Nb face sheets and Ti-3Al-2.5V honeycomb core. The process, termed Enhanced Diffusion Bonding (EDB), relies on the formation of a eutectic liquid through solid-state diffusion at elevated temperatures and isothermal solidification to produce joints in thin-gage titanium and titanium aluminide structural components. A technique employing a maskant on the honeycomb core was developed which permitted electroplating a controlled amount of EDB material only on the edges of the honeycomb core in order to minimize the structural weight and metallurgical interaction effects. Metallurgical analyses were conducted to determine the interaction effects between the EDB materials and the constituents of the sandwich structure following EDB processing. The initial mechanical evaluation was conducted with butt joint specimens tested at temperatures from 1400 - 1700 F. Further mechanical evaluation was conducted with EDB sandwich specimens using flatwise tension tests at temperatures from 70 - 1100 F and edgewise compression tests at ambient temperature.

  13. Vacuum Technology: Vacuum Technology III

    NSDL National Science Digital Library

    Rack, Philip D.

    This is a link to a PDF version of lecture slides that discuss gas sources in a vacuum. The presentation explains concepts such as vapor pressure curves, thermal desorption and first and second order desorption. Keywords: Vaporization, desorption, diffusion, permeation, backstreaming

  14. Furnace brazing under partial vacuum

    NASA Technical Reports Server (NTRS)

    Mckown, R. D.

    1979-01-01

    Brazing furnace utilizing partial-vacuum technique reduces tooling requirements and produces better bond. Benefit in that partial vacuum helps to dissociate metal oxides that inhibit metal flow and eliminates heavy tooling required to hold parts together during brazing.

  15. Physical and theoretical aspects of a new vacuum arc control technology-self arc diffusion by electrode: SADE

    Microsoft Academic Search

    M. Homma; H. Somei; Y. Niwa; K. Yokokura; I. Ohshima

    1998-01-01

    Our new vacuum arc control technology: SADE doubles the high current interruption capability of our conventional AMF technology. First, we describe the vacuum arc motion behavior recorded by a high speed CCD video camera. This arc behavior is closely related to axial magnetic field intensity. In particular, it depends on the profile of the externally generated axial magnetic field. The

  16. Physical and theoretical aspects of a new vacuum arc control technology-self arc diffusion by electrode: SADE

    Microsoft Academic Search

    Mitsutaka Homma; H. Somei; Y. Niwa; K. Yokokura; I. Ohshima

    1999-01-01

    Our new vacuum arc control technology SADE doubles the high current interruption capability of our conventional axial magnetic field technology. First, we describe the vacuum arc motion behavior recorded by a high speed charge-coupled device video camera. This arc behavior is closely related to axial magnetic field intensity. In particular, it depends on the profile of the externally generated axial

  17. Preliminary carburizing of medium-carbon steel as a factor increasing corrosion resistance of diffusion layers produced by means of vacuum chromizing process

    SciTech Connect

    Kasprzycka, E.; Tacikowski, J. [Inst. of Precision Mechanics, Warsaw (Poland); Liliental, W. [Nitrex Metal Inc., Montreal, Quebec (Canada)

    1995-12-31

    Diffusion layers produced on a steel surface by means of the vacuum chromizing process has been studied. The effect of preliminary carburizing of medium-carbon steel on a chromized layer structure and its corrosion resistance has been investigated. Studies of layer thickness, its morphology, the phase composition, and Cr and Fe depth profiles in the diffusion zone of chromized steel specimens in the aggressive media of the food industry has been determined. For corrosion resistance tests chromized layers of different structure have been used: two-phase layers (consisting of a carbide layer and a solution zone) produced on the medium-carbon steel, monophase carbide layers produced on the surface of preliminary carburized medium-carbon steel and monophase solution layers produced on Armco iron. It has been proved that the corrosion resistance of monophase hard carbide layers, as well as of monophase solution layers is higher than that for two-phase layers. The results obtained by the described method indicate that the preliminary carburizing of medium-carbon steel significantly increases corrosion resistance of diffusion layers produced by means of the vacuum chromizing process.

  18. Finite-element analysis of residual stresses in Al 2O 3–TiC\\/W18Cr4V diffusion bonded joints

    Microsoft Academic Search

    Xiaoqin Shen; Yajiang Li; U. A. Putchkov; Juan Wang; Wanqun Huang

    2009-01-01

    The residual stress distribution in Al2O3–TiC\\/W18Cr4V diffusion bonded joints was calculated using finite element method (FEM). The effects of pressure and interlayer on the axial stress and shear stress were also studied. The results show that the gradients of the axial stress and shear stress are great near the joint edge and are flat near the center of the joint.

  19. Characterization of Transient Liquid-Phase Bonded Joints in a Copper-Beryllium Alloy with Silver-base Interlayer

    NASA Astrophysics Data System (ADS)

    Mazar Atabaki, M.

    2012-06-01

    Transient liquid-phase diffusion bonding was employed to join copper-beryllium alloy using three silver-base interlayers. The bonding process was carried out at different temperatures under argon and vacuum atmospheres for various hold times. Interfacial microstructures were examined by scanning electron microscopy. Microhardness, tensile, and fatigue tests were used for evaluating the mechanical properties. Maximum tensile strength of 156.45 MPa was obtained for bonds processed at 780 °C. Fatigue strength of bonds fabricated in vacuum was higher than those of bonds prepared in argon atmosphere. The diffusion of the main elements from the interlayers into the base metal was the main controlling factor pertaining to the microstructural evolution of the joint interface.

  20. Water in Hydration Shell of an Iodide Ion: Structure and Dynamics of Solute-Water Hydrogen Bonds and Vibrational Spectral Diffusion from First-Principles Simulations.

    PubMed

    Karmakar, Anwesa; Chandra, Amalendu

    2015-07-01

    The dynamics of hydrogen bonds and vibrational spectral diffusion of water in the hydration shell of an iodide ion and in bulk have been investigated for aqueous iodide solutions of two different concentrations by using ab initio molecular dynamics simulations. The effects of dispersion interactions on the dynamics have also been investigated by using a dispersion corrected density functional. For the dilute solution containing a single iodide ion, three time scales are found for the spectral diffusion of solvation shell water: A short time scale of ?150 fs, a slower time scale of ?2-3 ps and a yet longer time scale of ?14-16 ps. The long time scale of ?14-16 ps is not noticed when calculations are done for all OD modes for both the dilute and concentrated solutions. It is found that a clear separation between the solvation shell and bulk water does not exist in terms of OD stretching frequencies for the concentrated solution. The dynamics of vibrational spectral diffusion is explained in terms of hydrogen bond dynamics, other dynamical modes such as orientational relaxation and molecular diffusion, and also structural aspects of water molecules in the solvation shells. The current results are compared with those of available experimental and other theoretical studies. PMID:26125325

  1. Bonding characteristics and diffusion barrier effect of the TiC phase formed at the bonding interface in an explosively welded titanium\\/high- carbon steel clad

    Microsoft Academic Search

    A. Chiba; M. Nishida; Y. Morizono; K. Imamura

    1995-01-01

    Microstructural aspects and bonding characteristics of the explosively welded titanium\\/high-carbon steel clad of the as-welded\\u000a and postannealed states were investigated. Amorphous and ?Ti phases were observed at the interface in the as-welded clad.\\u000a These were considered to be the trace of melting and subsequently rapid solidification of thin layers along the contact surface\\u000a of both the parent materials. The melting

  2. Effects of Barrier Layer on Copper-to-Silicon Diffusion and Intermetallic Compound Formation in Copper Wire Bonding

    Microsoft Academic Search

    S. Zhang; C. Chen; R. Lee; A. K. M. Lau; P. P. H. Tsang; L. Mohamed; C. Y. Chan; M. Dirkzwager

    2006-01-01

    Summary form only given. The conventional wire bonding has employed gold and aluminum wires as interconnection material for decades. With the requirements for high speed, high power and fine pitch applications, copper is emerging as the alternative bonding wires to replace gold and aluminum. In principle, copper has relatively good electrical mechanical and thermal properties. However, copper is known as

  3. Chemical behavior in diffusion bonding of Si{sub 3}N{sub 4}-Ni and Si{sub 3}N{sub 4}-superalloy IN-738

    SciTech Connect

    Chen, Y.C.; Iwamoto, C.; Ishida, Y. [Univ. of Tokyo (Japan). Dept. of Material Science] [Univ. of Tokyo (Japan). Dept. of Material Science

    1996-09-15

    The bulk chemical reactions between Si{sub 3}N{sub 4} and Ni have been investigated from a thermodynamics perspective by Klomp et al. and Heikinheimo et al., and from experiments by Suganuma et al., Schuster et al., Brito et al., Ishikawa et al., and Heikinheimo et al. The chemical interaction between Si{sub 3}N{sub 4} and Ni-based alloy was investigated by Benett et al., Mehan et al., and Peteves et al. In this work, instead of the Ni-Cr, or model Ni-based superalloy (Ni-Cr-Al alloy), the industrial superalloy, IN-738, was used. For comparing the different chemical behaviors between the pure Ni and Ni-based superalloy with Si{sub 3}N{sub 4}, solid state diffusion bonding of Ni/Si{sub 3}N{sub 4} and IN-738/Si{sub 3}N{sub 4} were bonded in the same bonding conditions, except Ni/Si{sub 3}N{sub 4} specimens whose bonding time were longer than that of IN-738/Si{sub 3}N{sub 4} specimen.

  4. Thermocompression bonding of alumina ceramics to metal

    Microsoft Academic Search

    S. Das; A. N. Tiwari; A. R. Kulkarni

    2004-01-01

    Alumina ceramics and Kovar with aluminum interlayer are pressed together under vacuum at temperatures around 600°C for joining. This process produces mechanically strong ceramic to metal bonds in one step in an economic manner. In order to arrive at the optimum conditions for solid-state bonding, effects of bonding temperature, pressure and time on the bond strength have been studied. Bonding

  5. Optical Properties of Some Silicone Diffusion-Pump Oils in the Vacuum Ultraviolet—Using an Open-Dish Technique

    Microsoft Academic Search

    G. D. Kerr; M. W. Williams; R. D. Birkhoff; L. R. Painter

    1971-01-01

    The optical properties of Dow Corning-704 and -705 diffusion-pump oils have been measured from 4?24.8 eV using an open-dish technique. These are the first liquids for which optical constants have been obtained above 11.8 eV. In the region above 10.6 eV, the real part of the dielectric constant is structureless. A collective oscillation involving ? and ? electrons is seen

  6. Optical Properties of Some Silicone Diffusion-Pump Oils in the Vacuum Ultraviolet—Using a Closed-Cell Technique

    Microsoft Academic Search

    B. L. Sowers; M. W. Williams; R. N. Hamm; E. T. Arakawa

    1971-01-01

    The optical properties of Dow Corning-704 and -705 diffusion-pump oils have been measured from 2?10.6 eV using a closed-cell technique. The data are interpreted in terms of molecular excitations of ?, ?, and nonbonding electrons in the complex pump oil molecules and in terms of collective oscillations of electrons in the liquids. The optical constants of Dow Corning-200, another silicone

  7. Diffuse Reflectance Fourier Transform Infrared Spectroscopic Study of Chemical Bonding and Hydrothermal Stability of an Aminosilane on Metal Oxide Surfaces

    Microsoft Academic Search

    Somsak Naviroj; Jack L Koenig; Hatsuo Ishida

    1985-01-01

    Fourier transform infrared spectroscopy was used to study the metal oxide\\/silane interface. Structures of ?-aminopropyldimethylethoxysilane (?-APDMES) coupling agent on the surface of metal oxide powders are proposed. The structures depend on the surface characteristics of the substrate. The amine group of the silane molecule forms a hydrogen bond with the silica surface. The enhanced intensity of the amine band around

  8. Diffusion

    NSDL National Science Digital Library

    Christopher Thomas (None; )

    2006-11-09

    Diffusion is the movement of particles from an area of high concentration to an area of low concentration. The molecules move until equilibrium is reached. If a perfume is sprayed on one side of the room, the perfume molecules will eventually spread out all over the room until there are equal concentrations of the molecules throughout the space.

  9. Diffusion

    NSDL National Science Digital Library

    Since the advent of the internet, a number of artists and related organizations have become interested in utilizing the web to promulgate new forms of artistic creation and their subsequent dissemination. Supported by the Arts Council of England, these Diffusion eBooks are essentially pdf files that readers can download, print out and make into booklets. As the site suggests, "the Diffusion format challenges conventions of interactivity-blending the physical and the virtual and breaking the dominance of mouse and screen as the primary forms of human computer interaction...the format's aim is to take the reader away from the screen and computer and engage them in the process of production." There are a number of creative booklets available here for visitors, complete with instruction on how to assemble them for the desired effect. For anyone with even a remote interest in the possibilities afforded by this rather curious new form of expression, this website is worth a look.

  10. Vacuum Energy in Quantum Graphs

    E-print Network

    Wilson, Justin

    2007-07-14

    energy density. Both methods are done heuristically for star graphs then rigorously for general graphs. We also discuss some properties of the vacuum energy in quantum graphs including: repulsive Casimir forces, convergence and continuity in bond lengths....

  11. Strong bonding between sputtered bioglass-ceramic films and Ti-substrate implants induced by atomic inter-diffusion post-deposition heat-treatments

    NASA Astrophysics Data System (ADS)

    Stan, G. E.; Popa, A. C.; Galca, A. C.; Aldica, G.; Ferreira, J. M. F.

    2013-09-01

    Bioglasses (BG) are the inorganic materials exhibiting the highest indices of bioactivity. Their appliance as films for bio-functionalization of metallic implant surfaces has been regarded as an optimal solution for surpassing their limited bulk mechanical properties. This study reports on magnetron sputtering of alkali-free BG thin films by varying the target-to-substrate working distance, which proved to play an important role in determining the films’ properties. Post deposition heat-treatments at temperatures slightly above the glass transformation temperature were then applied to induce inter-diffusion processes at the BG/titanium substrate interface and strengthening the bonding as determined by pull-out adherence measurements. The morphological and structural features assessed by SEM-EDS, XRD, and FTIR revealed a good correlation between the formations of inter-metallic titanium silicide phases and the films’ bonding strength. The highest mean value of pull-out adherence (60.3 ± 4.6 MPa), which is adequate even for load-bearing biomedical applications, was recorded for films deposited at a working distance of 35 mm followed by a heat-treatment at 750 °C for 2 h in air. The experimental findings are explained on the basis of structural, compositional and thermodynamic considerations.

  12. Bonding thermoplastic polymers

    DOEpatents

    Wallow, Thomas I. (Fremont, CA); Hunter, Marion C. (Livermore, CA); Krafcik, Karen Lee (Livermore, CA); Morales, Alfredo M. (Livermore, CA); Simmons, Blake A. (San Francisco, CA); Domeier, Linda A. (Danville, CA)

    2008-06-24

    We demonstrate a new method for joining patterned thermoplastic parts into layered structures. The method takes advantage of case-II permeant diffusion to generate dimensionally controlled, activated bonding layers at the surfaces being joined. It is capable of producing bonds characterized by cohesive failure while preserving the fidelity of patterned features in the bonding surfaces. This approach is uniquely suited to production of microfluidic multilayer structures, as it allows the bond-forming interface between plastic parts to be precisely manipulated at micrometer length scales. The bond enhancing procedure is easily integrated in standard process flows and requires no specialized equipment.

  13. The characteristics of atmospheric ice nuclei measured at the top of Huangshan (the Yellow Mountains) in Southeast China using a newly built static vacuum water vapor diffusion chamber

    NASA Astrophysics Data System (ADS)

    Jiang, Hui; Yin, Yan; Su, Hang; Shan, Yunpeng; Gao, Renjie

    2015-02-01

    A newly built static vacuum water vapor diffusion chamber was built to measure the concentration of ice nuclei (INs) at the top of Huangshan (the Yellow Mountains) in Southeast China. The experiments were conducted under temperatures between - 15 °C and - 23 °C and supersaturations with respect to ice between 4% and 25%. The results show that the average IN concentration was in the range of 0.27 to 7.02 L- 1, when the temperature was varied from - 15 °C to - 23 °C. The changes in IN concentrations with time were correlated with the change of number concentration of the aerosol particles of 0.5-20 ?m in diameter. The square correlation coefficients (R2) between IN and coarse aerosol particles (0.5-20 ?m in diameter) were all higher than 0.60, much higher than that (0.10) between IN and smaller particles (0.01-0.5 ?m). The concentration of ice nuclei at 14:00 LST was significantly higher than that at 08:00 LST, which is correlated with the diurnal variation of the concentration of aerosol particles. A parametric equation was developed based on measurements to represent the variations of IN concentration with temperature and supersaturation.

  14. K-130 Cyclotron vacuum system

    NASA Astrophysics Data System (ADS)

    Yadav, R. C.; Bhattacharya, S.; Bhole, R. B.; Roy, Anindya; Pal, Sarbajit; Mallik, C.; Bhandari, R. K.

    2012-11-01

    The vacuum system for K-130 cyclotron has been operational since 1977. It consists of two sub-systems, main vacuum system and beam line vacuum system. The main vacuum system is designed to achieve and maintain vacuum of about 1 × 10-6 mbar inside the 23 m3 volume of acceleration chamber comprising the Resonator tank and the Dee tank. The beam line vacuum system is required for transporting the extracted beam with minimum loss. These vacuum systems consist of diffusion pumps backed by mechanical pumps like roots and rotary pumps. The large vacuum pumps and valves of the cyclotron vacuum system were operational for more than twenty five years. In recent times, problems of frequent failures and maintenance were occurring due to aging and lack of appropriate spares. Hence, modernisation of the vacuum systems was taken up in order to ensure a stable high voltage for radio frequency system and the extraction system. This is required for efficient acceleration and transportation of high intensity ion beam. The vacuum systems have been upgraded by replacing several pumps, valves, gauges and freon units. The relay based control system for main vacuum system has also been replaced by PLC based state of the art control system. The upgraded control system enables inclusion of additional operational logics and safety interlocks into the system. The paper presents the details of the vacuum system and describes the modifications carried out for improving the performance and reliability of the vacuum system.

  15. Plates for vacuum thermal fusion

    DOEpatents

    Davidson, James C. (Livermore, CA); Balch, Joseph W. (Livermore, CA)

    2002-01-01

    A process for effectively bonding arbitrary size or shape substrates. The process incorporates vacuum pull down techniques to ensure uniform surface contact during the bonding process. The essence of the process for bonding substrates, such as glass, plastic, or alloys, etc., which have a moderate melting point with a gradual softening point curve, involves the application of an active vacuum source to evacuate interstices between the substrates while at the same time providing a positive force to hold the parts to be bonded in contact. This enables increasing the temperature of the bonding process to ensure that the softening point has been reached and small void areas are filled and come in contact with the opposing substrate. The process is most effective where at least one of the two plates or substrates contain channels or grooves that can be used to apply vacuum between the plates or substrates during the thermal bonding cycle. Also, it is beneficial to provide a vacuum groove or channel near the perimeter of the plates or substrates to ensure bonding of the perimeter of the plates or substrates and reduce the unbonded regions inside the interior region of the plates or substrates.

  16. Anode modes in vacuum arcs

    Microsoft Academic Search

    H. Craig Miller

    1997-01-01

    This paper reviews the five different anode discharge modes which can occur in a vacuum arc. These modes are diffuse arc (low current, with or without anode sputtering), footpoint (intermediate current), and anode spot or intense arc (high current). Descriptions of the various modes are presented, based primarily on experimental results. The hot anode vacuum arc mode, which occurs only

  17. Vacuum die attach for integrated circuits

    DOEpatents

    Schmitt, E.H.; Tuckerman, D.B.

    1991-09-10

    A thin film eutectic bond for attaching an integrated circuit die to a circuit substrate is formed by coating at least one bonding surface on the die and substrate with an alloying metal, assembling the die and substrate under compression loading, and heating the assembly to an alloying temperature in a vacuum. A very thin bond, 10 microns or less, which is substantially void free, is produced. These bonds have high reliability, good heat and electrical conduction, and high temperature tolerance. The bonds are formed in a vacuum chamber, using a positioning and loading fixture to compression load the die, and an IR lamp or other heat source. For bonding a silicon die to a silicon substrate, a gold silicon alloy bond is used. Multiple dies can be bonded simultaneously. No scrubbing is required. 1 figure.

  18. In Situ Monitoring of Vacuum Carburizing

    Microsoft Academic Search

    M. Bruncko; A. C. Kneissl; I. Anzel

    2009-01-01

    The present article describes development and testing of a new measurement method that enables nondestructive and in situ monitoring of a vacuum carburizing process. The principle of the method is based on monitoring the carbon diffusion during vacuum carburizing by the in-situ measurement of electrical resistance changes in the carburizing sample. Using this method the electrical resistance changes during vacuum

  19. Inorganic bonding of semiconductor strain gages

    NASA Technical Reports Server (NTRS)

    Woodruff, N. L.

    1970-01-01

    Inorganic bonding materials minimize outgassing and improve electrical and mechanical properties of semiconductor strain-gage transducers in high-vacuum and high-temperature operations. The two basic methods described are ceramic-glass-bonding and metallic bond formation between the strain gage and the substrate.

  20. Vacuum Plasma Spraying Replaces Electrodeposition

    NASA Technical Reports Server (NTRS)

    Holmes, Richard R.; Power, Chris; Burns, David H.; Daniel, Ron; Mckechnie, Timothy N.

    1992-01-01

    Vacuum plasma spraying used to fabricate large parts with complicated contours and inner structures, without uninspectable welds. Reduces time, and expense of fabrication. Wall of combustion chamber built up inside of outer nickel-alloy jacket by plasma spraying. Particles of metal sprayed partially melted in plasma gun and thrown at supersonic speed toward deposition surface. Vacuum plasma-spray produces stronger bond between the grooves and covering layer completing channels and wall of combustion chamber. In tests, bond withstood pressure of 20 kpsi, three times allowable limit by old method.

  1. Vacuum Technology

    SciTech Connect

    Biltoft, P J

    2004-10-15

    The environmental condition called vacuum is created any time the pressure of a gas is reduced compared to atmospheric pressure. On earth we typically create a vacuum by connecting a pump capable of moving gas to a relatively leak free vessel. Through operation of the gas pump the number of gas molecules per unit volume is decreased within the vessel. As soon as one creates a vacuum natural forces (in this case entropy) work to restore equilibrium pressure; the practical effect of this is that gas molecules attempt to enter the evacuated space by any means possible. It is useful to think of vacuum in terms of a gas at a pressure below atmospheric pressure. In even the best vacuum vessels ever created there are approximately 3,500,000 molecules of gas per cubic meter of volume remaining inside the vessel. The lowest pressure environment known is in interstellar space where there are approximately four molecules of gas per cubic meter. Researchers are currently developing vacuum technology components (pumps, gauges, valves, etc.) using micro electro mechanical systems (MEMS) technology. Miniature vacuum components and systems will open the possibility for significant savings in energy cost and will open the doors to advances in electronics, manufacturing and semiconductor fabrication. In conclusion, an understanding of the basic principles of vacuum technology as presented in this summary is essential for the successful execution of all projects that involve vacuum technology. Using the principles described above, a practitioner of vacuum technology can design a vacuum system that will achieve the project requirements.

  2. Vacuum mechatronics

    NASA Technical Reports Server (NTRS)

    Hackwood, Susan; Belinski, Steven E.; Beni, Gerardo

    1989-01-01

    The discipline of vacuum mechatronics is defined as the design and development of vacuum-compatible computer-controlled mechanisms for manipulating, sensing and testing in a vacuum environment. The importance of vacuum mechatronics is growing with an increased application of vacuum in space studies and in manufacturing for material processing, medicine, microelectronics, emission studies, lyophylisation, freeze drying and packaging. The quickly developing field of vacuum mechatronics will also be the driving force for the realization of an advanced era of totally enclosed clean manufacturing cells. High technology manufacturing has increasingly demanding requirements for precision manipulation, in situ process monitoring and contamination-free environments. To remove the contamination problems associated with human workers, the tendency in many manufacturing processes is to move towards total automation. This will become a requirement in the near future for e.g., microelectronics manufacturing. Automation in ultra-clean manufacturing environments is evolving into the concept of self-contained and fully enclosed manufacturing. A Self Contained Automated Robotic Factory (SCARF) is being developed as a flexible research facility for totally enclosed manufacturing. The construction and successful operation of a SCARF will provide a novel, flexible, self-contained, clean, vacuum manufacturing environment. SCARF also requires very high reliability and intelligent control. The trends in vacuum mechatronics and some of the key research issues are reviewed.

  3. Reliability of MEMS packaging: vacuum maintenance and packaging induced stress

    Microsoft Academic Search

    Sung-Hoon Choa

    2005-01-01

    In this study, the dominant reliability issues of MEMS packaging that include vacuum maintenance and packaging induced stress, are discussed, and design considerations to improve the reliability are presented. The MEMS vibratory gyroscope sensor is fabricated with anodically bonded wafer level vacuum packaging followed by die-bonding and wire-bonding processes. The epoxy-molding compound (EMC) is applied to encapsulate the gyroscope sensor.

  4. Chemical Bonds

    NSDL National Science Digital Library

    The Concord Consortium

    2011-12-11

    Electrons are key to forming the two broad categories of chemical bonds: covalent and ionic. Atoms, which have a nucleus surrounded by electrons, are represented in several different ways. In the Chemical Bonds activity, students explore the different kinds of chemical bonds that can form, ranging from non-polar covalent to ionic. In the model depicted above students adjust the electronegativity of two atoms and see the effect it has on electron distribution and bond type.

  5. Vacuum arc ion currents and electrode phenomena

    Microsoft Academic Search

    C. W. Kimblin

    1971-01-01

    Properties of dc vacuum arcs between copper electrodes are studied in both a vacuum interrupter and a metal walled arc chamber. Maximum ion currents of ?8 to 20 percent of the arc current (100 to 3000 A) are drawn from the diffuse arc plasma when the bounding metal wall or shield is biased negative. This maximum ion current is a

  6. Application of self assembly monolayer (SAM) in lowering the process temperature during Cu-Cu diffusion bonding of 3D IC

    Microsoft Academic Search

    Dau Fatt Lim; Shiv Govind Singh; Xiao Fang Ang; Jun Wei; Chee Mang Ng; Chuan Seng Tan

    2009-01-01

    In this research work, we investigate the feasibility of lowering the bonding temperature by refining the copper surface with the application of a self assembly monolayer (SAM). First, the stability of SAM when it is subjected to different exposure environments is measured quantitatively by the change in the contact angle. The different environments includes: 1) exposure in clean room ambient;

  7. Degassing procedure for ultrahigh vacuum

    NASA Technical Reports Server (NTRS)

    Moore, B. C.

    1979-01-01

    Calculations based on diffusion coefficients and degassing rates for stainless-steel vacuum chambers indicate that baking at lower temperatures for longer periods give lower ultimate pressures than rapid baking at high temperatures. Process could reduce pressures in chambers for particle accelerators, fusion reactors, material research, and other applications.

  8. Diffuse reflectance Fourier transform infrared spectroscopic study of chemical bonding and hydrothermal stability of an amino silane on metal oxide surfaces. Technical report

    Microsoft Academic Search

    S. Naviroj; J. L. Koenig; H. Ishida

    1982-01-01

    Fourier transform infrared spectroscopy is used to study the metal oxide\\/silane interface. Structures of gamma-aminopropyldimethylethoxysilane (gamma-APDMES) coupling agent on the surface of metal oxide powders are proposed. The structure depends on the surface characteristics of the substrate. The amine group of the silane molecule forms a hydrogen bond with the silica surface. The enhanced intensity of the amine band around

  9. Fabricating capacitive micromachined ultrasonic transducers with wafer-bonding technology

    Microsoft Academic Search

    Yongli Huang; A. Sanli Ergun; E. Haeggstrom; Mohammed H. Badi; B. T. Khuri-Yakub

    2003-01-01

    Introduces a new method for fabricating capacitive micromachined ultrasonic transducers (CMUTs) that uses a wafer bonding technique. The transducer membrane and cavity are defined on an SOI (silicon-on-insulator) wafer and on a prime wafer, respectively. Then, using silicon direct bonding in a vacuum environment, the two wafers are bonded together to form a transducer. This new technique, capable of fabricating

  10. Surface activated bonding for copper plate by excimer laser irradiation

    Microsoft Academic Search

    Takashi Suzuki; Takao Araki; Minoru Nishida

    2003-01-01

    When a pair of clean solid surface are brought close to the atoms distance in the vacuum, the solids were bonded by the gravitation and binding force. Such a way of bonding is called a surface activated bonding. In this work, a laser irradiated to a couple of copper plates surface under various conditions of laser irradiation. The surface oxidation

  11. High-temperature adhesives for bonding polyimide film. [bonding Kapton film for solar sails

    NASA Technical Reports Server (NTRS)

    St.clair, A. K.; Slemp, W. S.; St.clair, T. L.

    1980-01-01

    Experimental polyimide resins were developed and evaluated as potential high temperature adhesives for bonding Kapton polyimide film. Lap shear strengths of Kapton/Kapton bonds were obtained as a function of test temperature, adherend thickness, and long term aging at 575 K (575 F) in vacuum. Glass transition temperatures of the polyimide/"Kapton" bondlines were monitored by thermomechanical analysis.

  12. D-Zero Vacuum System

    SciTech Connect

    Wintercorn, S.J.; /Fermilab

    1986-04-07

    The system pumping speed was calculated by taking the reciprocal of the sum of the reciprocal pump speed and the reciprocal line conductances. The conductances of the pipe were calculated from the following formulas taken from the Varian vacuum manual. This report updates the original to reflect the pumping curves and basic vacuum system characteristics for the purchased components and installed piping of the D-Zero vacuum system. The system consists of two Edward's E2M275 two stage mechanical pumps, a Leybold-Heraeus WSU2000 Blower and three Varian 4' diffusion pumps (one for each cryostat). Individual pump and system pumping speed curves and a diagram of the system is included.

  13. Vacuum plasma spray coating

    NASA Technical Reports Server (NTRS)

    Holmes, Richard R.; Mckechnie, Timothy N.

    1989-01-01

    Currently, protective plasma spray coatings are applied to space shuttle main engine turbine blades of high-performance nickel alloys by an air plasma spray process. Originally, a ceramic coating of yttria-stabilized zirconia (ZrO2.12Y2O3) was applied for thermal protection, but was removed because of severe spalling. In vacuum plasma spray coating, plasma coatings of nickel-chromium-aluminum-yttrium (NiCrAlY) are applied in a reduced atmosphere of argon/helium. These enhanced coatings showed no spalling after 40 MSFC burner rig thermal shock cycles between 927 C (1700 F) and -253 C (-423 F), while current coatings spalled during 5 to 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2.8Y2O3 to the turbine blades of first-stage high-pressure fuel turbopumps utilizing the enhanced NiCrAlY bond-coating process. NiCrAlY bond coating is applied first, with ZrO2.8Y2O3 added sequentially in increasing amounts until a thermal barrier coating is obtained. The enchanced thermal barrier coating has successfully passed 40 burner rig thermal shock cycles.

  14. Rapid bonding of Pyrex glass microchips.

    PubMed

    Akiyama, Yoshitake; Morishima, Keisuke; Kogi, Atsuna; Kikutani, Yoshikuni; Tokeshi, Manabu; Kitamori, Takehiko

    2007-03-01

    A newly developed vacuum hot press system has been specially designed for the thermal bonding of glass substrates in the fabrication process of Pyrex glass microchemical chips. This system includes a vacuum chamber equipped with a high-pressure piston cylinder and carbon plate heaters. A temperature of up to 900 degrees C and a force of as much as 9800 N could be applied to the substrates in a vacuum atmosphere. The Pyrex substrates bonded with this system under different temperatures, pressures, and heating times were evaluated by tensile strength tests, by measurements of thickness, and by observations of the cross-sectional shapes of the microchannels. The optimal bonding conditions of the Pyrex glass substrates were 570 degrees C for 10 min under 4.7 N/mm(2) of applied pressure. Whereas more than 16 h is required for thermal bonding with a conventional furnace, the new system could complete the whole bonding processes within just 79 min, including heating and cooling periods. Such improvements should considerably enhance the production rate of Pyrex glass microchemical chips. Whereas flat and dust-free surfaces are required for conventional thermal bonding, especially without long and repeated heating periods, our hot press system could press a fine dust into glass substrates so that even the areas around the dust were bonded. Using this capability, we were able to successfully integrate Pt/Ti thin film electrodes into a Pyrex glass microchip. PMID:17370301

  15. Novel hydrophilic SiO2 wafer bonding using combined surface-activated bonding technique

    NASA Astrophysics Data System (ADS)

    He, Ran; Fujino, Masahisa; Yamauchi, Akira; Suga, Tadatomo

    2015-03-01

    Low-temperature hydrophilic SiO2–SiO2 wafer bonding has been performed in vacuum by a new combined surface-activated bonding (SAB) technique. In this technique, wafers are irradiated by ion beam bombardment and simultaneously deposited with silicon by in situ silicon sputter deposition, and then terminated with Si–OH groups by water vapor exposure prior to bonding in vacuum. A surface energy of more than 1 J/m2 was achieved by 200 °C postbonding annealing. A void-free oxide intermediate layer with a thickness of about 15 nm was observed at the bonding interface by transmission electron microscopy (TEM). The increased bonding energy can be attributed to the greater number of Si–OH formed through hydroxylation of the silicon deposited on the SiO2 surfaces.

  16. Performance tests of large thin vacuum windows

    SciTech Connect

    Hall Crannell

    2011-02-01

    Tests of thin composition vacuum windows of the type used for the Tagger in Hall B at the Thomas Jefferson National Accelerator Facility are described. Three different tests have been performed. These include: (1) measurement of the deformation and durability of a window under long term (>8 years) almost continuous vacuum load, (2) measurement of the deformation as a function of flexing of the window as it is cycled between vacuum and atmosphere, and (3) measurement of the relative diffusion rate of gas through a variety of thin window membranes.

  17. Diffusion of nitrogen gas in ice Ih

    Microsoft Academic Search

    Tomoko Ikeda-Fukazawa; Katsuyuki Kawamura; Takeo Hondoh

    2004-01-01

    Diffusion of N2 in ice crystal has been found from Raman scattering of the natural ice from the Antarctic ice sheet. In order to investigate the diffusion mechanism, we perform molecular dynamics simulations of diffusion of N2 in ice. The results show that the N2 molecule hops in the crystal by breaking hydrogen bonds in the ice lattice. The diffusion

  18. Inhomogeneous vacuum energy

    NASA Astrophysics Data System (ADS)

    Wands, David; De-Santiago, Josue; Wang, Yuting

    2012-07-01

    Vacuum energy remains the simplest model of dark energy which could drive the accelerated expansion of the Universe without necessarily introducing any new degrees of freedom. Inhomogeneous vacuum energy is necessarily interacting in general relativity. Although the 4-velocity of vacuum energy is undefined, an interacting vacuum has an energy transfer and the vacuum energy defines a particular foliation of spacetime. In particular we will discuss cosmological solutions where the background vacuum energy is spatially homogeneous. It is possible to give a consistent description of vacuum dynamics and in particular the relativistic equations of motion for spatially inhomogeneous perturbations given a covariant prescription for the vacuum energy, or equivalently the energy transfer 4-vector, and we construct gauge-invariant vacuum perturbations. We show that any dark energy cosmology can be decomposed into an interacting vacuum+matter cosmology whose inhomogeneous perturbations obey simple first-order equations.

  19. Germanium detector vacuum encapsulation

    NASA Technical Reports Server (NTRS)

    Madden, N. W.; Malone, D. F.; Pehl, R. H.; Cork, C. P.; Luke, P. N.; Landis, D. A.; Pollard, M. J.

    1991-01-01

    This paper describes an encapsulation technology that should significantly improve the viability of germanium gamma-ray detectors for a number of important applications. A specialized vacuum chamber has been constructed in which the detector and the encapsulating module are processed in high vacuum. Very high vacuum conductance is achieved within the valveless encapsulating module. The detector module is then sealed without breaking the chamber vacuum. The details of the vacuum chamber, valveless module, processing, and sealing method are presented.

  20. Germanium detector vacuum encapsulation

    NASA Astrophysics Data System (ADS)

    Madden, N. W.; Malone, D. F.; Pehl, R. H.; Cork, C. P.; Luke, P. N.; Landis, D. A.; Pollard, M. J.

    1991-08-01

    This paper describes an encapsulation technology that should significantly improve the viability of germanium gamma-ray detectors for a number of important applications. A specialized vacuum chamber has been constructed in which the detector and the encapsulating module are processed in high vacuum. Very high vacuum conductance is achieved within the valveless encapsulating module. The detector module is then sealed without breaking the chamber vacuum. The details of the vacuum chamber, valveless module, processing, and sealing method are presented.

  1. Diffusion Geometry Diffusion Geometry

    E-print Network

    Hirn, Matthew

    Diffusion Geometry Diffusion Geometry for High Dimensional Data Matthew J. Hirn July 3, 2013 #12;Diffusion Geometry Introduction Embedding of closed curve Figure: Left: A closed, non-self-intersecting curve in 3 dimensions. Right: Its embedding as a circle. #12;Diffusion Geometry Introduction Cartoon

  2. Pi Bond Orders and Bond Lengths

    ERIC Educational Resources Information Center

    Herndon, William C.; Parkanyi, Cyril

    1976-01-01

    Discusses three methods of correlating bond orders and bond lengths in unsaturated hydrocarbons: the Pauling theory, the Huckel molecular orbital technique, and self-consistent-field techniques. (MLH)

  3. Heater decomposes oil backstreaming from high-vacuum pumps

    NASA Technical Reports Server (NTRS)

    Shapiro, H.

    1965-01-01

    Heater placed between an oil diffusion pump and a vacuum chamber prevents backstreaming of oil molecules into the work area of the chamber. It breaks the oil molecules into basic constituents that can be pumped away.

  4. Baffles for Oil Diffusion Pumps

    Microsoft Academic Search

    Richard S. Morse

    1940-01-01

    Although in the use of oil diffusion pumps for the production of high vacuum, extremely cold traps in the usual sense are not required, some means must be provided to prevent both direct backstreaming and diffusion of the oil vapor. The relative advantages of (1) charcoal traps, (2) cold traps, (3) hot baffles, (4) electrical baffles, (5) mechanical baffles are

  5. Some interruption criteria for short high-frequency vacuum arcs

    Microsoft Academic Search

    M. Glinkowski; A. Greenwood

    1989-01-01

    If the contacts of a vacuum interrupter open shortly before a current zero, the transient recovery voltage (TRV) can cause a reignition and reestablish the arc. When the current in a diffuse vacuum arc passes through zero, there is a distinct pause before the TRV builds up (approximately 40 ns for copper). During this pause the gap carries conduction current

  6. Finite element analysis of AMF vacuum contacts

    Microsoft Academic Search

    Paul N. Stoving; E. Fred Bestel

    1998-01-01

    It has been known for some time that the presence of an axial magnetic field (AMF) can increase the upper limit on the interrupting ability of vacuum contacts by keeping the arc plasma in the diffuse mode. Many designs have been proposed for contact structures to induce this magnetic field, most of which involve forcing the current to travel in

  7. A fluxless bonding technology using indium-silver multilayer composites

    Microsoft Academic Search

    Yi-Chia Chen; William W. So; Chin C. Lee

    1997-01-01

    A fluxless bonding process has been developed using indium-silver multilayer composites deposited on silicon and GaAs wafers in one high vacuum cycle to inhibit the oxidation of the bonding media. The in situ formation of AgIn2 intermetallic outer layer protects the inner media from oxidation when exposed to atmosphere. The bonding process is performed at 180°C temperature in inert environment

  8. Spectral radiance source for vacuum ultraviolet calibrations

    NASA Astrophysics Data System (ADS)

    Sherrell, Fred G.

    1993-01-01

    A working standard extended source of spectral radiance has been assembled and calibrated for use in the 150- to 260-nm region. The assembly consists of a 10-kw, argon arc lamp mounted to irradiate a 4-in. diameter diffuser. The reflected energy from the diffuser is utilized as a calibration source. The procedure for calibrating the spectral radiance of the diffuser is reviewed. Traceability is accomplished by the use of a standard vacuum photodiode. The total uncertainty in the calibration of the source is estimated to be +/- 15 percent.

  9. Bonded Lubricants

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Another spinoff to the food processing industry involves a dry lubricant developed by General Magnaplate Corp. of Linden, N.J. Used in such spacecraft as Apollo, Skylab and Viking, the lubricant is a coating bonded to metal surfaces providing permanent lubrication and corrosion resistance. The coating lengthens equipment life and permits machinery to be operated at greater speed, thus increasing productivity and reducing costs. Bonded lubricants are used in scores of commercia1 applications. They have proved particularly valuable to food processing firms because, while increasing production efficiency, they also help meet the stringent USDA sanitation codes for food-handling equipment. For example, a cookie manufacturer plagued production interruptions because sticky batter was clogging the cookie molds had the brass molds coated to solve the problem. Similarly, a pasta producer faced USDA action on a sanitation violation because dough was clinging to an automatic ravioli-forming machine; use of the anti-stick coating on the steel forming plates solved the dual problem of sanitation deficiency and production line downtime.

  10. Educational Vacuum Trainers

    NSDL National Science Digital Library

    Hansen, Steve

    Have you inherited a bell jar vacuum system and are scratching your head over how to set it up or are unsure of its operations or capabilities? Or do you want to do more with your bell jar vacuum? The forum on Bell Jar Vacuums - with the topic Vacuum Trainers can help you. The intent of this forum is for this to be a place where technical issues, classroom exercises, activities, etc. can be discussed. There's no endorsement by manufacturers and commercial issues are off limits. Steve Hansen (bell jar expert) gives some brief descriptions of the vacuum trainers that are or have been available over the past decade or so - Varian, MKS, Science Source, American Vacuum Society. Links are provided to various data sheets, articles and online exercises. Steve, the forum moderator has experience in all of these.Keywords: vacuum, "vacuum trainer","bell jar" and/or belljar, MKSVarian, VPAL, VTS, sputtering, plasma

  11. Radiation hard vacuum switch

    DOEpatents

    Boettcher, Gordon E. (Albuquerque, NM)

    1990-01-01

    A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction.

  12. Relationship between bond energy and total work of fracture for asphalt binder-aggregate systems

    Microsoft Academic Search

    Jonathan Howson; Eyad Masad; Dallas Little; Emad Kassem

    2012-01-01

    Surface free energy is a thermodynamic material property representing the work required to create new surfaces of unit area in a vacuum. Surface free energy has been used to quantify and screen both the cohesive bond energy of asphalt binders and the adhesive bond energy of asphalt binder–aggregate interfaces in wet and dry conditions. The bond energy is computed based

  13. Heating steels in vacuum

    SciTech Connect

    Marmer, E.N.

    1983-03-01

    It is recommended that high-strength and corrosion-resistant steels be heated in an electric vacuum furnace. Absence of oxidation and decarburization, decrease in the deformation of the part, increase in service life, plus safety, and nontoxicity in the shop, are cited as advantages. Annealing, carburizing, hardening, brazing, and sintering--all detailed-can be more efficiently accomplished in vacuum heating. As vacuum heating requires certain surface conditions, the compositions of residual mediums is studied. The microrelief and surface finish obtained after vacuum heating is determined. Annealing in a vacuum is compared to annealing in air, a depletion in manganese indicating a greater savings by use of vacuum. Ductility is also tested. The gas of special purity nitrogen is recommended for best results. In general, then, use of electric vacuum furnaces is recommended.

  14. Chemical Bonds II

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    The continuation of a paper discussing chemical bonding from a bond energy viewpoint, with a number of examples of single and multiple bonds. (Part I appeared in volume 1 number 3, pages 16-23, February 1972.) (AL)

  15. Bonding with Grandparents

    MedlinePLUS

    ... Sports: Keeping Kids Safe Concussions: What to Know Bonding With Grandparents KidsHealth > Parents > School & Family Life > Family ... encouraging a close relationship can benefit everyone involved. Bonding Benefits Establishing a bond with grandparents can benefit ...

  16. Bonding with Your Baby

    MedlinePLUS

    ... the child's social and cognitive development. Why Is Bonding Important? Bonding is essential for a baby. Studies ... as biological parents and their children. Back Continue Bonding With Daddy Men these days spend more time ...

  17. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

  18. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

  19. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

  20. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

  1. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

  2. Bonding Diamond To Metal In Electronic Circuits

    NASA Technical Reports Server (NTRS)

    Jacquez, Andrew E.

    1993-01-01

    Improved technique for bonding diamond to metal evolved from older technique of soldering or brazing and more suitable for fabrication of delicate electronic circuits. Involves diffusion bonding, developed to take advantage of electrically insulating, heat-conducting properties of diamond, using small diamond bars as supports for slow-wave transmission-line structures in traveling-wave-tube microwave amplifiers. No fillets or side coats formed because metal bonding strips not melted. Technique also used to mount such devices as transistors and diodes electrically insulated from, but thermally connected to, heat sinks.

  3. Surface activated bonding for copper plate by excimer laser irradiation

    NASA Astrophysics Data System (ADS)

    Suzuki, Takashi; Araki, Takao; Nishida, Minoru

    2003-02-01

    When a pair of clean solid surface are brought close to the atoms distance in the vacuum, the solids were bonded by the gravitation and binding force. Such a way of bonding is called a surface activated bonding. In this work, a laser irradiated to a couple of copper plates surface under various conditions of laser irradiation. The surface oxidation layer and organic layer were removed by laser ablation. After the irradiation, a couple of copper plates surface get close to each other. The possibility of the bonding was examined by AFM.

  4. Adhesives For Use In Vacuum, Radiation, And Cold

    NASA Technical Reports Server (NTRS)

    Bouquet, Frank L.

    1988-01-01

    Report presents results of literature searches and tests of eight adhesives for use in high-radiation, low-temperature, vacuum environment of Galileo spacecraft mission to Jupiter. Used as bonding agents for thermal blankets, instruments, structural members, and coatings. Adhesives tested for contamination, reflectance, bond integrity, color, transmittance, outgassing, dielectric constant, coefficient of thermal expansion, optical interference, peel strength, and shear strength. Some of tests conducted at temperature of liquid nitrogen (-150 degree C).

  5. Heating steels in vacuum

    Microsoft Academic Search

    Marmer

    1983-01-01

    It is recommended that high-strength and corrosion-resistant steels be heated in an electric vacuum furnace. Absence of oxidation and decarburization, decrease in the deformation of the part, increase in service life, plus safety, and nontoxicity in the shop, are cited as advantages. Annealing, carburizing, hardening, brazing, and sintering--all detailed-can be more efficiently accomplished in vacuum heating. As vacuum heating requires

  6. Li diffusion in zircon

    Microsoft Academic Search

    D. J. CherniakE; E. B. Watson

    2010-01-01

    Diffusion of Li under anhydrous conditions at 1 atm and under fluid-present elevated pressure (1.0–1.2 GPa) conditions has\\u000a been measured in natural zircon. The source of diffusant for 1-atm experiments was ground natural spodumene, which was sealed\\u000a under vacuum in silica glass capsules with polished slabs of zircon. An experiment using a Dy-bearing source was also conducted\\u000a to evaluate possible rate-limiting effects

  7. Vacuum probe surface sampler

    NASA Technical Reports Server (NTRS)

    Zahlava, B. A. (inventor)

    1973-01-01

    A vacuum probe surface sampler is described for rapidly sampling relatively large surface areas which possess relatively light loading densities of micro-organism, drug particles or the like. A vacuum head with a hollow handle connected to a suitable vacuum source is frictionally attached to a cone assembly terminating in a flared tip adapted to be passed over the surface to be sampled. A fine mesh screen carried by the vacuum head provides support for a membrane filter which collects the microorganisms or other particles. The head assembly is easily removed from the cone assembly without contacting the cone assembly with human hands.

  8. In-service helium leak testing of vacuum furnace

    NASA Astrophysics Data System (ADS)

    Ahmad, Anis; Tripathi, S. K.; Sawant, P. S.; Mukharjee, D.; Shah, B. K.

    2012-11-01

    Helium leak detection of vacuum furnaces and equipments used for processing of nuclear material is generally carried out by utilizing vacuum spray technique. In this technique helium leak detector is connected to the furnace, back ground reading is noted and helium gas is sprayed on all the suspected joints. Any increase in back ground is noted as leak signal. Processing of Zirconium alloy cladded fuel pins is carried out in vacuum furnace of about 3 meter length and 500 mm inside diameter. Furnace is connected with two numbers of rotary vacuum pump and one number of diffusion pump for creating vacuum (1 × 10-6 torr) inside the furnace. It is desirable that furnace should have good vacuum and best possible leak tightness during dynamic and static vacuum. During dynamic vacuum at higher temperature although required vacuum is achieved the furnace may have fine leakage through which air may enter and cause oxidation of clad tube leading to change in its coloration. This change in coloration will cause rejection of fuel element. Such fine leakages may not be reflected in the dynamic vacuum of the system at high temperature. During trial run change in coloration of outside surface of clad tube was observed although dynamic vacuum of the furnace was in the range of 1×10-6 torr range. To eliminate such possibilities of oxidation due to fine leakages in the system, it was decided to carry out in-service leak testing of the furnace. Helium leak testing of the furnace was carried out by using vacuum spray method and leaks observed were repaired and furnace was retested to ensure the leak tightness. The in-service helium leak testing of the furnace helped in maintaining its leak tightness during service under dynamic vacuum and prevent oxidation of fuel element. This paper describes the techniques of in- service helium leak testing, it's importance for detection of fine leak under dynamic vacuum and discusses details of the testing method and result obtained.

  9. Effect of Ti, Nb, and Ti + Nb Coatings on the Bond Strength-Structure Relationship in Al/Al2O3 Joints

    NASA Astrophysics Data System (ADS)

    Ksiazek, Marzanna; Richert, Maria; Tchorz, Aam; Boron, Lukasz

    2012-05-01

    There is a growing interest in metal-ceramic bonding for wide range of applications in electronic devices and high technology industry for fabrication of metal matrix composites and bonding of ceramic components to metals. The object of the work was to study the effect of Ti, Nb, and Ti + Nb thin films deposited by PVD method on alumina substrates on structure and bond strength properties of Al/Al2O3 joints. The joints were fabricated using the results of a wetting experiment and the sessile drop method at a temperature of 1223 K in a vacuum of 0.2 MPa for 30 min of contact. The structure of the metal/ceramic interface was investigated using scanning electron microscopy. The elemental distribution at the metal-ceramic interface was analyzed using energy dispersive x-ray spectroscopy. Transmission electron microscopy was also used to investigate some aspects of the metal/ceramic interface. The bond strength properties of joints were measured using shear test. The shear strength results demonstrated significant improvement of shear strength of Al/Al2O3 joints due to the application of Ti + Nb thin film on alumina substrate. Microstructural investigations of the interface indicated that Al/coating/Al2O3 couples have diffusion transition interface which influences the strengthening of these joints. A conclusion could be drawn that the presence of thin film layers changes the character of interaction and leads to the formation of new reaction products in the bonding layer.

  10. A Road Map to Extreme High Vacuum

    SciTech Connect

    Ganapati Rao Myneni

    2007-06-20

    Ultimate pressure of a well-designed vacuum system very much depends on pretreatments, processing and the procedures [1,2]. Until now much attention has been paid in minimizing hydrogen outgassing from the chamber material. However, procedures and processing deserves further scrutiny than hitherto given so far. For reducing the gas load, high sensitivity helium leak detection techniques with sensitivities better than 1× 10-12 Torr l/sec need to be used. Effects that are induced by vacuum instrumentation need to be reduced in order to obtain accurate pressure measurements. This presentation will discuss: clean assembly procedures, metal sponges for cryosorption pumping of hydrogen to extreme high vacuum, low cost surface diffusion barriers for reducing the hydrogen gas load, cascade pumping, sensitive helium leak detection techniques and the use of modified extractor and residual gas analyzers. Further, alternative back up pumping systems based on active NEG’s [3] for turbo molecular pumps will be presented.

  11. Hydrogen bond dynamics in bulk alcohols

    NASA Astrophysics Data System (ADS)

    Shinokita, Keisuke; Cunha, Ana V.; Jansen, Thomas L. C.; Pshenichnikov, Maxim S.

    2015-06-01

    Hydrogen-bonded liquids play a significant role in numerous chemical and biological phenomena. In the past decade, impressive developments in multidimensional vibrational spectroscopy and combined molecular dynamics-quantum mechanical simulation have established many intriguing features of hydrogen bond dynamics in one of the fundamental solvents in nature, water. The next class of a hydrogen-bonded liquid—alcohols—has attracted much less attention. This is surprising given such important differences between water and alcohols as the imbalance between the number of hydrogen bonds, each molecule can accept (two) and donate (one) and the very presence of the hydrophobic group in alcohols. Here, we use polarization-resolved pump-probe and 2D infrared spectroscopy supported by extensive theoretical modeling to investigate hydrogen bond dynamics in methanol, ethanol, and isopropanol employing the OH stretching mode as a reporter. The sub-ps dynamics in alcohols are similar to those in water as they are determined by similar librational and hydrogen-bond stretch motions. However, lower density of hydrogen bond acceptors and donors in alcohols leads to the appearance of slow diffusion-controlled hydrogen bond exchange dynamics, which are essentially absent in water. We anticipate that the findings herein would have a potential impact on fundamental chemistry and biology as many processes in nature involve the interplay of hydrophobic and hydrophilic groups.

  12. Hydrogen bond dynamics in bulk alcohols.

    PubMed

    Shinokita, Keisuke; Cunha, Ana V; Jansen, Thomas L C; Pshenichnikov, Maxim S

    2015-06-01

    Hydrogen-bonded liquids play a significant role in numerous chemical and biological phenomena. In the past decade, impressive developments in multidimensional vibrational spectroscopy and combined molecular dynamics-quantum mechanical simulation have established many intriguing features of hydrogen bond dynamics in one of the fundamental solvents in nature, water. The next class of a hydrogen-bonded liquid-alcohols-has attracted much less attention. This is surprising given such important differences between water and alcohols as the imbalance between the number of hydrogen bonds, each molecule can accept (two) and donate (one) and the very presence of the hydrophobic group in alcohols. Here, we use polarization-resolved pump-probe and 2D infrared spectroscopy supported by extensive theoretical modeling to investigate hydrogen bond dynamics in methanol, ethanol, and isopropanol employing the OH stretching mode as a reporter. The sub-ps dynamics in alcohols are similar to those in water as they are determined by similar librational and hydrogen-bond stretch motions. However, lower density of hydrogen bond acceptors and donors in alcohols leads to the appearance of slow diffusion-controlled hydrogen bond exchange dynamics, which are essentially absent in water. We anticipate that the findings herein would have a potential impact on fundamental chemistry and biology as many processes in nature involve the interplay of hydrophobic and hydrophilic groups. PMID:26049470

  13. The Diffusion Process

    NSDL National Science Digital Library

    This website includes an animation which illustrates the diffusion process. The two models that have been developed to explain the mechanism for the diffusion of dopants into silicon are the Vacancy model and the Interstitial model. It is the different bonding characteristics of the dopants with silicon that determine the diffusion mechanism. Although each model is based on these differences, they are not mutually exclusive. Objective: Explain the difference between the Vacancy and Interstitial diffusion models. You can find this animation under the heading "Process & Equipment III." This simulation is from Module 019 of the Process & Equipment III Cluster of the MATEC Module Library (MML). To view other clusters or for more information about the MML visit http://matec.org/ps/library3/process_I.shtmlKey

  14. Investing in Bonds.com

    NSDL National Science Digital Library

    Investing in Bonds was created by the Bond Market Association to educate investors about the benefits of bonds investing. The Investor's Guide to Bond Basics educates investors about the types of bonds available, criteria for evaluating a bond, a guide to buying bonds, bond investment strategies and a glossary of bond market terms. The Bond Market section provides an overview of the U.S. bond market while the Investor's Checklist section takes the investor step-by-step through the bond investment decision process. Investors will also find sections with information on municipal bonds, corporate bonds, mortgage securities and U.S. Inflation-Indexed Securities.

  15. Wire-bond void formation during high temperature aging

    Microsoft Academic Search

    Hen-So Chang; Ker-Chang Hsieh; Theo Martens; Albert Yang

    2004-01-01

    Voids formed in Au-Al intermetallic phases degrade the long-term reliability of gold wire bonds to aluminum pads. In this study, a series of microstructural studies were performed to evaluate void formation in wire bonds. Voids are classified as initial, annular or minute. Probe marks and Al pad contamination are the main causes of initial voids that block alloy diffusion and

  16. Chapter 13. The Vacuum System

    E-print Network

    Brookhaven National Laboratory - Experiment 821

    to the exact radius for a 28 degree arc. A short aluminum bellows adapter is placed between each vacuum chamberChapter 13. The Vacuum System Revised February 1994 13.1. The Vacuum Chambers A plan view of the assembled vacuum chamber ring is shown in Fig. 13.1.1. The vacuum chamber ring includes twelve 28 degree

  17. Photon acceleration in vacuum

    E-print Network

    J. T. Mendonca; M. Marklund; P. K. Shukla; G. Brodin

    2006-08-16

    A new process associated with the nonlinear optical properties of the electromagnetic vacuum, as predicted by quantum electrodynamics, is described. This can be called photon acceleration in vacuum, and corresponds to the frequency shift that takes place when a given test photon interacts with an intense beam of background radiation.

  18. Vacuum Arc Anode Phenomena

    Microsoft Academic Search

    H. Craig Miller

    1983-01-01

    This paper briefly reviews anode phenomena in vacuum arcs, specially experimental work. It discusses, in succession, arc modes at the anode, anode temperature measurements, anode ions, transitions of the arc into various modes (principally the anode spot mode), and theoretical explanations of anode phenomena. The two most common anode modes in a vacuum arc are a low current mode where

  19. Bonded ultrasonic transducer and method for making

    DOEpatents

    Dixon, Raymond D. (Los Alamos, NM); Roe, Lawrence H. (Los Alamos, NM); Migliori, Albert (Santa Fe, NM)

    1995-01-01

    An ultrasonic transducer is formed as a diffusion bonded assembly of piezoelectric crystal, backing material, and, optionally, a ceramic wear surface. The mating surfaces of each component are silver films that are diffusion bonded together under the application of pressure and heat. Each mating surface may also be coated with a reactive metal, such as hafnium, to increase the adhesion of the silver films to the component surfaces. Only thin silver films are deposited, e.g., a thickness of about 0.00635 mm, to form a substantially non-compliant bond between surfaces. The resulting transducer assembly is substantially free of self-resonances over normal operating ranges for taking resonant ultrasound measurements.

  20. Tungsten diffusion in olivine

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Van Orman, J. A.

    2014-03-01

    Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.

  1. Design and construction of a compact vacuum furnace for scientific research

    Microsoft Academic Search

    Chin C. Lee; David T. Wang; Won S. Choi

    2006-01-01

    The design, construction, and measurement of a compact vacuum furnace are reported. This type of furnace has many scientific applications in material processing and growth research. One example is the fluxless bonding process, where elevated temperature is needed to melt the solder and vacuum environment is required to inhibit solder oxidation. The primary objective of the furnace design is to

  2. LET'S BOND! A Chemical Bonding Webquest

    NSDL National Science Digital Library

    Mrs. Hicken

    2009-04-08

    Today we are going to use the internet to explore chemical bonding! Even though there are just a few questions for each website, you need to read the entire content. Don't worry about understanding all of it, but make sure that you are familiar with it! Stay on task and have fun! Let's start with some basics. Click on the link below and answer the questions on your worksheet under "Bonding Basics". Bonding Basics Good job! Lets move on and talk about ions. Ions are a big part of bonding, so make sure you get this section down pat! Click on the ...

  3. Anode-Spot Formation and Motion of Vacuum Arcs

    Microsoft Academic Search

    A. Kaltenecker; M. Schussek

    1985-01-01

    This paper reports about experimental investigations on high-current vacuum-arc phenomena, especially anode-spot formation, arc states, and motion. The presented work was stimulated by lack of information about the transition process from the diffuse low-current mode to the high-current mode characterized by anode spot(s). Optoelectronic measurements, streak photographs, high-speed movies, and correlated arc voltage\\/current records yielded remarkable results on power-frequency vacuum

  4. The Interaction of Vacuum Arcs with Magnetic Fields and Applications

    Microsoft Academic Search

    J. G. Gorman; C. W. Kimblin; R. E. Voshall; R. E. Wien; P. G. Slade

    1983-01-01

    Vacuum arc\\/magnetic field interactions are reviewed and extended. An axial magnetic field (parallel to current flow) produces a stable and diffuse vacuum arc. These properties have been used to build a reliable dc switch for the Tokamak Fusion Test Reactor at Princeton. The switching duty for this Ohmic Heating Interrupter involves repetitive interruption of 24kA dc against a 27kV recovery

  5. Thermal behaviors of petn base polymer bonded explosives

    Microsoft Academic Search

    K.-S. Jaw; J.-S. Lee

    2008-01-01

    The thermal behaviors of three pentaerythritol tetranitrate (PETN) base polymer bonded explosives (PBX), Detasheet A (EL506A,\\u000a red) and Datasheet C (EL506C, yellow-green) that supply by DuPont Co., PBXN-301 were investigated using thermal techniques\\u000a in this work. The thermal properties of PETN base polymer bonded explosives, such as vacuum thermal stability (VTS), time\\u000a to ignition, auto-ignition and shelf life of PBX

  6. Channel Bonding Notes 03/25/2004 Channel Bonding Notes

    E-print Network

    Jain, Amit

    Channel Bonding Notes 03/25/2004 Channel Bonding Notes Luke Hindman Department of Computer Science by attempting to use the Linux kernel bonding driver (bonding.o) to implement channel bonding on the master node. However, each time I would bring up the bonded interface (bond0) I would loose communication

  7. Reliable aluminum contact formation by electrostatic bonding

    NASA Astrophysics Data System (ADS)

    Kárpáti, T.; Pap, A. E.; Radnóczi, Gy; Beke, B.; Bársony, I.; Fürjes, P.

    2015-07-01

    The paper presents a detailed study of a reliable method developed for aluminum fusion wafer bonding assisted by the electrostatic force evolving during the anodic bonding process. The IC-compatible procedure described allows the parallel formation of electrical and mechanical contacts, facilitating a reliable packaging of electromechanical systems with backside electrical contacts. This fusion bonding method supports the fabrication of complex microelectromechanical systems (MEMS) and micro-opto-electromechanical systems (MOEMS) structures with enhanced temperature stability, which is crucial in mechanical sensor applications such as pressure or force sensors. Due to the applied electrical potential of???1000?V the Al metal layers are compressed by electrostatic force, and at the bonding temperature of 450?°C intermetallic diffusion causes aluminum ions to migrate between metal layers.

  8. The quantum vacuum

    E-print Network

    G. S. Paraoanu

    2014-12-12

    The vacuum is the lowest energy state of a field in a certain region of space. This definition implies that no particles can be present in the vacuum state. In classical physics, the only features of vacuum are those of its geometry. For example, in the general theory of relativity the geometry is a dynamical structure that guides the motion of matter, and, in turn, it is bent and curved by the presence of matter. Other than this, the classical vacuum is a structure void of any physical properties, since classically properties are strictly associated with physical objects such as particles and finite-amplitude fields. The situation is very different in quantum physics. As I will show in this paper, the difference stems from the fact that in quantum physics the properties are not strictly tied to objects. We know for example that physical properties come into existence - as values of observables - only when the object is measured. Thus, quantum physics allows us to detach properties from objects. This has consequences: one does not need pre-existing real objects to create actual properties, and indeed under certain perturbations the quantum vacuum produces observable effects such as energy shifts and creation of particles. An open question is if by necessity the vacuum comes with an embedded geometry, and if it is possible to construct viable physical theories in which geometry is detached from the vacuum.

  9. Compact waves in microscopic nonlinear diffusion.

    PubMed

    Hurtado, P I; Krapivsky, P L

    2012-06-01

    We analyze the spread of a localized peak of energy into vacuum for nonlinear diffusive processes. In contrast with standard diffusion, the nonlinearity results in a compact wave with a sharp front separating the perturbed region from vacuum. In d spatial dimensions, the front advances as t^{1/(2+da)} according to hydrodynamics, with a the nonlinearity exponent. We show that fluctuations in the front position grow as ?t^{?}?, where ?<1/2+da is an exponent that we measure and ? is a random variable whose distribution we characterize. Fluctuating corrections to hydrodynamic profiles give rise to an excess penetration into vacuum, revealing scaling behaviors and robust features. We also examine the discharge of a nonlinear rarefaction wave into vacuum. Our results suggest the existence of universal scaling behaviors at the fluctuating level in nonlinear diffusion. PMID:23005044

  10. Thermophoretic vacuum wand

    DOEpatents

    Klebanoff, Leonard Elliott (San Ramon, CA); Rader, Daniel John (Lafayette, CA)

    2000-01-01

    A thermophoretic vacuum wand that is particularly suited for transporting articles in a cleanroom environment so that potential particle contaminants in the air do not become adhered to the surface of the article is described. The wand includes a housing having a platen with a front surface with suction port(s) through the platen; a vacuum source for applying a negative pressure to the suction port(s); and heating device for the object. Heating the article when it is held by the vacuum wand affords thermophoretic protection that effectively prevents particles in the air from depositing onto the article.

  11. Thermophoretic vacuum wand

    DOEpatents

    Klebanoff, Leonard Elliott (San Ramon, CA); Rader, Daniel John (Lafayette, CA)

    2001-01-01

    A thermophoretic vacuum wand that is particularly suited for transporting articles in a cleanroom environment so that potential particle contaminants in the air do not become adhered to the surface of the article is described. The wand includes a housing having a platen with a front surface with suction port(s) through the platen; a vacuum source for applying a negative pressure to the suction port(s); and heating device for the object. Heating the article when it is held by the vacuum wand affords thermophoretic protection that effectively prevents particles in the air from depositing onto the article.

  12. Evading death by vacuum

    E-print Network

    A. Barroso; P. M. Ferreira; I. P. Ivanov; Rui Santos; João P. Silva

    2013-03-15

    In the Standard Model, the Higgs potential allows only one minimum at tree-level. But the open possibility that there might be two scalar doublets enriches the vacuum structure, allowing for the risk that we might now be in a metastable state, which we dub the panic vacuum. Current experiments at the LHC are probing the Higgs particle predicted as a result of the spontaneous symmetry breaking. Remarkably, in the two Higgs model with a softly broken U(1) symmetry, the LHC experiments already preclude panic vacuum solutions.

  13. Vacuum chamber-free centrifuge with magnetic bearings

    NASA Astrophysics Data System (ADS)

    Park, Cheol Hoon; Kim, Soohyun; Kim, Kyung-Soo

    2013-09-01

    Centrifuges are devices that separate particles of different densities and sizes through the application of a centrifugal force. If a centrifuge could be operated under atmospheric conditions, all vacuum-related components such as the vacuum chamber, vacuum pump, diffusion pump, and sealing could be removed from a conventional centrifuge system. The design and manufacturing procedure for centrifuges could then be greatly simplified to facilitate the production of lightweight centrifuge systems of smaller volume. Furthermore, the maintenance costs incurred owing to wear and tear due to conventional ball bearings would be eliminated. In this study, we describe a novel vacuum chamber-free centrifuge supported by magnetic bearings. We demonstrate the feasibility of the vacuum chamber-free centrifuge by presenting experimental results that verify its high-speed support capability and motoring power capacity.

  14. Realization of MEMS-IC Vertical Integration Utilizing Smart Bumpless Bonding

    NASA Astrophysics Data System (ADS)

    Shiozaki, Masayoshi; Moriguchi, Makoto; Sasaki, Sho; Oba, Masatoshi

    This paper reports fundamental technologies, properties, and new experimental results of SBB (Smart Bumpless Bonding) to realize MEMS-IC vertical integration. Although conventional bonding technologies have had difficulties integrating MEMS and its processing circuit because of their rough bonding surfaces, fragile structures, and thermal restriction, SBB technology realized the vertical integration without thermal treatment, any adhesive materials including bumps, and chemical mechanical polishing. The SBB technology bonds sealing parts for vacuum sealing and electrodes for electrical connection simultaneously as published in previous experimental study. The plasma CVD SiO2 is utilized to realize vacuum sealing as sealing material. And Au projection studs are formed on each electrode and connected electrically between two wafers by compressive plastic deformation and surface activation. In this paper, new experimental results including vacuum sealing properties, electrical improvement, IC bonding results on the described fundamental concept and properties are reported.

  15. Vacuum mechatronics first international workshop

    SciTech Connect

    Belinski, S.E.; Shirazi, M.; Hackwood, S.; Beni, G. (eds.) (California Univ., Santa Barbara, CA (USA))

    1989-01-01

    This report contains papers on the following topics: proposed epitaxial thin film growth in the ultra-vacuum of space; particle monitoring and control in vacuum processing equipment; electrostatic dust collector for use in vacuum systems; materials evaluation of an electrically noisy vacuum slip ring assembly; an overview of lubrication and associated materials for vacuum service; the usage of lubricants in a vacuum environment; guidelines and practical applications for lubrication in vacuum; recent development in leak detector and calibrator designs; the durability of ballscrews for ultrahigh vacuum; vacuum-compatible robot for self-contained manufacturing systems; the design, fabrication, and assembly of an advanced vacuum robotics system for space payload calibration; design criteria for mechanisms used in space; and concepts and requirements for semiconductor multiprocess integration in vacuum. These papers are indexed separately elsewhere.

  16. Essays on corporate bonds

    E-print Network

    Bao, Jack (Jack C.)

    2009-01-01

    This thesis consists of three empirical essays on corporate bonds, examining the role of both credit risk and liquidity. In the first chapter, I test the ability of structural models of default to price corporate bonds in ...

  17. Multiple station thermal diffusivity instrument

    SciTech Connect

    Wang, H.; Dinwiddie, R.B. [Oak Ridge National Lab., TN (United States); Gaal, P.S. [Anter Corp., Pittsburgh (United States)

    1995-12-31

    A multiple furnace laser flash thermal diffusivity system has been developed. The system is equipped with a movable Nd:Glass laser unit, two IR detectors and furnaces for precise measurements of thermal diffusivity over the temperature range from {minus}150{degree}C to 2500{degree}C. All furnaces can operate in vacuum and inert gas; the environmental effects furnace also supports oxidizing and reducing environments. To increase testing speed the graphite and aluminum furnaces are both equipped with six-sample carousels. Thermal diffusivity measurements of three standard reference materials show excellent results over the entire temperature range.

  18. Supermite vacuum interface design

    NASA Astrophysics Data System (ADS)

    Moore, W. B.; Stinnett, R. W.; McDaniel, D. H.

    A new water plastic vacuum interface has been designed for Sandia Laboratory's Supermite (2.8 MV, 2.2 ohm) accelerator. This design was based on the PBFA I vacuum interface. Electrostatic field plots show that in positive polarity the water feed to the PBFA I interface will fail at 2 MV on Supermite. This is confirmed by positive polarity experiments and field plots using the PBFA I style vacuum interface at the Naval Research Labs. Modifications to the water section geometry to increase the water breakdown strength in positive polarity result in equivalent electric field grading at the plastic vacuum interface but allow positive polarity operation at voltages up to 3.1 MV. This is accomplished by incorporating a dielectric field shaper which significantly improves the electric field grading across the insulator.

  19. Vacuum Camera Cooler

    NASA Technical Reports Server (NTRS)

    Laugen, Geoffrey A.

    2011-01-01

    Acquiring cheap, moving video was impossible in a vacuum environment, due to camera overheating. This overheating is brought on by the lack of cooling media in vacuum. A water-jacketed camera cooler enclosure machined and assembled from copper plate and tube has been developed. The camera cooler (see figure) is cup-shaped and cooled by circulating water or nitrogen gas through copper tubing. The camera, a store-bought "spy type," is not designed to work in a vacuum. With some modifications the unit can be thermally connected when mounted in the cup portion of the camera cooler. The thermal conductivity is provided by copper tape between parts of the camera and the cooled enclosure. During initial testing of the demonstration unit, the camera cooler kept the CPU (central processing unit) of this video camera at operating temperature. This development allowed video recording of an in-progress test, within a vacuum environment.

  20. Bonding silicones with epoxies

    SciTech Connect

    Tira, J.S.

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.

  1. Allosteric Disulfide Bonds

    Microsoft Academic Search

    Jason W. H. Wong; Philip J. Hogg

    \\u000a Protein disulfide bonds link cysteine residues in the polypeptide chain. The bonds contribute, sometimes crucially, to protein\\u000a stability and function and are strongly conserved through the evolution of species. By analyzing the conservation of all structurally\\u000a validated disulfide bonds across 29 completely sequenced eukaryotic genomes, we found that disulfide-bonded cysteines are\\u000a even more conserved than tryptophan – the most conserved

  2. Making and Breaking Bonds

    NSDL National Science Digital Library

    The Concord Consortium

    2011-12-11

    Atoms collide and, under certain circumstances, react to form bonds with one another. The process of association is the bonding of atoms into a molecule while dissociation is the process by which a molecule breaks apart into simpler groups of atoms, individual atoms, or ions. Students interact with a molecular dynamics model to explore the making and breaking of bonds.

  3. Rapid adhesive bonding concepts

    NASA Technical Reports Server (NTRS)

    Stein, B. A.; Tyeryar, J. R.; Hodges, W. T.

    1984-01-01

    Adhesive bonding in the aerospace industry typically utilizes autoclaves or presses which have considerable thermal mass. As a consequence, the rates of heatup and cooldown of the bonded parts are limited and the total time and cost of the bonding process is often relatively high. Many of the adhesives themselves do not inherently require long processing times. Bonding could be performed rapidly if the heat was concentrated in the bond lines or at least in the adherends. Rapid adhesive bonding concepts were developed to utilize induction heating techniques to provide heat directly to the bond line and/or adherends without heating the entire structure, supports, and fixtures of a bonding assembly. Bonding times for specimens are cut by a factor of 10 to 100 compared to standard press bonding. The development of rapid adhesive bonding for lap shear specimens (per ASTM D1003 and D3163), for aerospace panel bonding, and for field repair needs of metallic and advanced fiber reinforced polymeric matrix composite structures are reviewed.

  4. Dielectric Recovery of Vacuum Arcs after Strong Anode Spot Activity

    Microsoft Academic Search

    E. Dullni; E. Schade; B. Gellert

    1987-01-01

    Recovery of dielectric strength and post-arc currents after diffuse and constricted vacuum arcs were measured for filat OFHC-Cu contacts (D = 25 mm, d = 7.5 mm) enclosed in a bakable UHV chamber. The arc current pulse had a trapezoidal shape of 5.5-ms duration with peak values up to 11 kA. In comparison with the fast recovery of diffuse arcs,

  5. Prospective bonding applications

    NASA Astrophysics Data System (ADS)

    Ancenay, H.; Benazet, D.

    1981-07-01

    Adhesive bonding in industry and in the laboratory is surveyed and prospects for its wider utilization are assessed. The economic impact of bonding technology on industry is discussed. Research is reviewed, centering on the development of nondestructive testing and inspection techniques. Traditional (wood) as well as new materials susceptible to bonding are considered. Applications in construction and civil engineering, in aeronautics, and in the automobile industry are covered. The use of glues in mechanical constructions, in assembling cylindrical parts, and in metal-metal bonding are examined. Hybrid assembling and bonding of composite materials are included.

  6. Bonding of reinforced Teflon to metals

    NASA Technical Reports Server (NTRS)

    Laiacona, F. P. (inventor)

    1971-01-01

    Reinforced FEP Teflon composite material is bonded to a metal substrate by applying a thin layer of copper on the metal surface and disposing irregularly shaped copper particles on the coated surface. The reinforced Teflon is then assembled in contact with the particles, and the assembly is heated under pressure at an elevated temperature below the melting point of the Teflon. A diffusion bond stronger than the reinforced Teflon component is produced, thus enabling the fabrication of self-lubricating bodies with relatively high strength.

  7. Wafer-level hermetic packaging of 3D microsystems with low-temperature Cu-to-Cu thermo-compression bonding and its reliability

    NASA Astrophysics Data System (ADS)

    Fan, J.; Peng, L.; Li, K. H.; Tan, C. S.

    2012-10-01

    Low-temperature wafer-level Cu-to-Cu thermo-compression bonding and its reliability for hermetic sealing application have been investigated in this work. The volume of the encapsulated cavities is about 1.4×10-3 cm3 in accordance with the MIL-STD-883E standard prescribed for microelectronics packaging hermeticity measurement. The samples under test are bonded at 300 °C under a bonding force of 5500 N for 1 h in vacuum (˜2.5 × 10-4 mbar) with a 300 nm thick Cu diffusion layer and 50 nm thick Ti barrier layer which are deposited in an e-beam evaporator. The reliability test is accomplished through a temperature cycling test (TCT) from -40 to 125 °C up to 1000 cycles and a humidity test based on IPC/JEDEC J-STD-020 standard. In addition, an immersion in acid/base solution is applied to verify the corrosion resistance of the Cu frame for hermetic application. Excellent helium leak rate which is smaller than the reject limit defined by the MIL-STD-883E standard (method 1014.10) is detected for all the samples. These excellent helium leak rates show an outstanding bonding quality against harsh environment for hermetic encapsulation in 3D integration applications.

  8. Hydroxide catalysis bonding for astronomical instruments

    NASA Astrophysics Data System (ADS)

    van Veggel, Anna-Maria A.; Killow, Christian J.

    2014-06-01

    Hydroxide catalysis bonding (HCB) as a jointing technique has been under development for astronomical applications since ˜1998 (patented by D.-H. Gwo). It uses an aqueous hydroxide solution to form a chemical bond between oxide or oxidisable materials (e.g., SiO2, sapphire, silicon and SiC). It forms strong, extremely thin bonds, and is suitable for room temperature bonding, precision alignment, operation in ultra-low vacuum and down to temperatures of 2.5 K. It has been applied in the NASA satellite mission Gravity Probe B and in the ground-based gravitational wave (GW) detector GEO600. It will soon fly again on the ESA LISA Pathfinder mission and is currently being implemented in the Advanced LIGO and Virgo ground-based GW detectors. This technique is also of considerable interest for use in other astronomical fields and indeed more broadly, due to its desirable, and adjustable, combination of properties. This paper gives an overview of how HCB has been and can be applied in astronomical instruments, including an overview of the current literature on the properties of hydroxide catalysis bonds.

  9. Vacuum Energy: Myths and Reality

    Microsoft Academic Search

    2006-01-01

    We discuss the main myths related to the vacuum energy and cosmological\\u000aconstant, such as: ``unbearable lightness of space-time''; the dominating\\u000acontribution of zero point energy of quantum fields to the vacuum energy;\\u000anon-zero vacuum energy of the false vacuum; dependence of the vacuum energy on\\u000athe overall shift of energy; the absolute value of energy only has significance\\u000afor

  10. Vacuum Packaging of MEMS With Multiple Internal Seal Rings

    NASA Technical Reports Server (NTRS)

    Hayworth, Ken; Yee, Karl; Shcheglov, Kirill; Bae, Youngsam; Wiberg, Dean; Peay, Chris; Challoner, Anthony

    2008-01-01

    A proposed method of design and fabrication of vacuum-packaged microelectromechanical systems (MEMS) and of individual microelectromechanical devices involves the use of multiple internal seal rings (MISRs) in conjunction with vias (through holes plated with metal for electrical contacts). The proposed method is compatible with mass production in a wafer-level fabrication process, in which the dozens of MEMS or individual microelectromechanical devices on a typical wafer are simultaneously vacuum packaged by bonding a capping wafer before the devices are singulated (cut apart by use of a dicing saw). In addition to being compatible with mass production, the proposed method would eliminate the need for some complex and expensive production steps and would yield more reliable vacuum seals. Conventionally, each MEMS or individual microelectromechanical device is fabricated as one of many identical units on a device wafer. Vacuum packaging is accomplished by bonding the device wafer to a capping wafer with metal seal rings (one ring surrounding each unit) that have been formed on the capping wafer. The electrical leads of each unit are laid out on what would otherwise be a flat surface of the device wafer, against which the seal ring is to be pressed for sealing. The resulting pattern of metal lines and their insulating oxide coverings presents a very rough and uneven surface, upon which it is difficult to pattern the sealing metal. Consequently, the seal is prone to leakage unless additional costly and complex planarization steps are performed before patterning the seal ring and bonding the wafers.

  11. Stellarator helical vacuum vessel

    SciTech Connect

    Yavornik, E.J.

    1983-01-01

    A design study of a stainless steel, heavy wall, helically shaped vacuum torus has been made for use in a proposed Stellarator configuration. The study concerns itself with the shape of the vacuum vessel and the division of the vessel into components that can be machined and welded together into a helical configuration. A complication in the design requires that a circular magnet coil be located at the minor toroidal axis and that this coil be embedded within the periphery of the vacuum vessel. The vacuum vessel has a minor toroidal axis diameter of 4 meters, a 68.6-cm shell diameter, and a 1.9-cm wall thickness. It twists about the minor toroidal axis twice in 360/sup 0/C. (An n value of 2). It is proposed that the unit be made of cylindrical segments with the ends of the cylinders cut at appropriate lengths and angles to form the helix. A mathematical derivation of the dimensions necessary to produce the required shapes of the segments has been made. Also, drawings of the vacuum vessel components have been produced on LANL's CTR CAD/CAM system. The procedure developed can be used for any value of n as dictated by physics requirements.

  12. Vacuum Techniques Lecture Notes

    NSDL National Science Digital Library

    Most modern day experimental research in physical chemistry is performed with the use of some sort of vacuum system. Organic and inorganic chemists are also finding it is essential to conduct synthetic and kinetic work under controlled or reduced pressures. The term "vacuum system" is applied rather broadly, from instrumentation that operates at very low pressures (i.e., below 10-8 torr) to systems that are only pumped down once to remove air and then used to handle gases at moderate pressures (up to and sometimes over one atmosphere). Vacuum systems vary widely in their size and complexity (and expense) depending on the requirements of pumping speed and attainable vacuum. This experiment is designed to illustrate the purpose and use of the basic components found on typical vacuum apparati. The volumes of the isolatable sections of the system will be measured. Also, some of the variables, such as pumping speed, which should be considered in designing such a system, will be investigated.

  13. Diffusion /Osmosis

    NSDL National Science Digital Library

    Jensen

    2007-11-26

    This project is use to review the concepts of diffusion and osmosis 1. Watch the tutorials on diffusion and osmosis. Take the online quiz at the end of each one. Diffusion Animation Osmosis Animation 2. Do the interactive lab on diffusion. Stop when you get to the calculating water potential section. Diffusion/Osmosis Interactive Demo 3. Play the Quia review games. Quia Games- matching/concetration Quia Jeopardy 4. Check out the Elodea leaf cells. Be able to ...

  14. Improving Vacuum Cleaners

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Under a Space Act Agreement between the Kirby company and Lewis Research Center, NASA technology was applied to a commercial vacuum cleaner product line. Kirby engineers were interested in advanced operational concepts, such as particle flow behavior and vibration, critical factors to improve vacuum cleaner performance. An evaluation of the company 1994 home care system, the Kirby G4, led to the refinement of the new G5 and future models. Under the cooperative agreement, Kirby had access to Lewis' holography equipment, which added insight into how long a vacuum cleaner fan would perform, as well as advanced computer software that can simulate the flow of air through fans. The collaboration resulted in several successes including fan blade redesign and continuing dialogue on how to improve air-flow traits in various nozzle designs.

  15. Separation of spiral contacts and the motion of vacuum arcs at high AC currents

    Microsoft Academic Search

    M. Bruce Schulman

    1993-01-01

    A framing camera is used to photograph the vacuum arc between separating spiral-petal vacuum interrupter contacts. The rupture of the molten bridge between the contacts first leads to a high-pressure, transient arc column. This arc motion can become constricted for several milliseconds before it goes diffuse as the current decreases to zero. The current through the spiral contacts produces a

  16. Numerical simulation of high-current vacuum arcs with an external axial magnetic field

    Microsoft Academic Search

    Ekkehard Schade; Dmitry Leonidovich Shmelev

    2003-01-01

    Numerical simulations are presented for physical behavior and heat flux to the anode of high-current diffuse of arcs as found in vacuum interrupters. The magnetohydrodynamic approach is applied. Of importance is the consideration of energy balance. Heat flux densities to the anode are predicted in the right order of magnitude and essential physical details of the high-current vacuum arc are

  17. Eutectic bonding of austenitic stainless steel 316L to magnesium alloy AZ31 using copper interlayer

    Microsoft Academic Search

    Waled M. Elthalabawy; Tahir I. Khan

    2011-01-01

    The eutectic bonding of magnesium alloy (AZ31) to austenitic stainless steel alloy (316L) was performed using pure Cu interlayers.\\u000a The effect of hold time on the microstructural developments across the joint region and the related effect on bond shear strength\\u000a were studied at a bonding temperature of 530°C. The bonding process took place through a sequential occurrence of solid-state\\u000a diffusion

  18. Diffusion of water submonolayers on hydrophilic surfaces.

    PubMed

    Park, Jae Hyun; Aluru, N R

    2008-12-22

    In this letter, we investigate using molecular dynamics simulations the diffusion of water submonolayers on hydrophilic surfaces. In contrast to a strong hydrophilic Ag surface, on a weak hydrophilic Pb surface, the diffusion coefficient is remarkably enhanced at a critical surface coverage and a Lambda-shape anomaly with surface coverage is observed, i.e., the diffusion coefficient increases with the increase in surface coverage until a critical surface coverage, beyond which the diffusion coefficient decreases. We explain the anomalous diffusion of water on hydrophilic surfaces by a detailed understanding of molecular cavities and monolayer tail contributing to three-dimensional hydrogen bonding. PMID:19529784

  19. Cleaning of a thermal vacuum chamber with shrouds in place

    Microsoft Academic Search

    William R. Bond

    1992-01-01

    In February, 1991, a failure of a rotary booster pump caused the diffusion pumps to backstream into a 10 ft x 15 ft thermal vacuum chamber. Concerns existed about the difficulty of removing and reinstalling the shrouds without causing leaks. The time required for the shroud removal was also of concern. These concerns prompted us to attempt to clean the

  20. Semipermanent sealing of leaks in high vacuum systems

    NASA Technical Reports Server (NTRS)

    Christian, J. D.; Gilbreath, W. P.

    1974-01-01

    Silicone-rubber adhesive is applied externally to seal hair-line cracks in sections of high vacuum system while system is partially evacuated. No pretreatment of surface is required since adhesive will be drawn into crack while diffusion or ion pump is off.

  1. Bayesian field theoretic reconstruction of bond potential and bond mobility in single molecule force spectroscopy

    E-print Network

    Chang, Joshua C; Chou, Tom

    2015-01-01

    Quantifying the forces between and within macromolecules is a necessary first step in understanding the mechanics of molecular structure, protein folding, and enzyme function and performance. In such macromolecular settings, dynamic single-molecule force spectroscopy (DFS) has been used to distort bonds. The resulting responses, in the form of rupture forces, work applied, and trajectories of displacements, have been used to reconstruct bond potentials. Such approaches often rely on simple parameterizations of one-dimensional bond potentials, assumptions on equilibrium starting states, and/or large amounts of trajectory data. Parametric approaches typically fail at inferring complex-shaped bond potentials with multiple minima, while piecewise estimation may not guarantee smooth results with the appropriate behavior at large distances. Existing techniques, particularly those based on work theorems, also do not address spatial variations in the diffusivity that may arise from spatially inhomogeneous coupling to...

  2. Vacuum Arc Ion Sources

    E-print Network

    Brown, I

    2013-01-01

    The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources.

  3. Spacecraft thermal vacuum testing

    NASA Technical Reports Server (NTRS)

    Elam, B. F.; Lancaster, L. D.

    1972-01-01

    An approach for developing a general thermal vacuum test program philosophy is discussed. Guidelines are established that will assist the project engineer in relating the risk associated with flying any spacecraft to its test program. Computerized techniques can be used to help ascertain these guidelines, which relate the risk to the level of test (component, subsystem, etc), as well as to the type of test (development, qualification, etc). The interrelationship between the test program and the analytical effort is also discussed. The Skylab Apollo telescope mount general thermal vacuum test program, including test schedules, instrumentation, and test results is also discussed.

  4. The vacuum interpretation of quantum mechanics and the vacuum universe

    E-print Network

    Ding-Yu Chung

    2001-10-27

    Quantum mechanics is interpreted by the adjacent vacuum that behaves as a virtual particle to be absorbed and emitted by its matter. As described in the vacuum universe model, the adjacent vacuum is derived from the pre-inflationary universe in which the pre-adjacent vacuum is absorbed by the pre-matter. This absorbed pre-adjacent vacuum is emitted to become the added space for the inflation in the inflationary universe whose space-time is separated from the pre-inflationary universe. This added space is the adjacent vacuum. The absorption of the adjacent vacuum as the added space results in the adjacent zero space (no space), Quantum mechanics is the interaction between matter and the three different types of vacuum: the adjacent vacuum, the adjacent zero space, and the empty space. The absorption of the adjacent vacuum results in the empty space superimposed with the adjacent zero space, confining the matter in the form of particle. When the absorbed vacuum is emitted, the adjacent vacuum can be anywhere instantly in the empty space superimposed with the adjacent zero space where any point can be the starting point (zero point) of space-time. Consequently, the matter that expands into the adjacent vacuum has the probability to be anywhere instantly in the form of wavefunction. In the vacuum universe model, the universe not only gains its existence from the vacuum but also fattens itself with the vacuum. During the inflation, the adjacent vacuum also generates the periodic table of elementary particles to account for all elementary particles and their masses in a good agreement with the observed values.

  5. Bonded semiconductor substrate

    DOEpatents

    Atwater, Jr.; Harry A. (South Pasadena, CA), Zahler; James M. (Pasadena, CA)

    2010-07-13

    Ge/Si and other nonsilicon film heterostructures are formed by hydrogen-induced exfoliation of the Ge film which is wafer bonded to a cheaper substrate, such as Si. A thin, single-crystal layer of Ge is transferred to Si substrate. The bond at the interface of the Ge/Si heterostructures is covalent to ensure good thermal contact, mechanical strength, and to enable the formation of an ohmic contact between the Si substrate and Ge layers. To accomplish this type of bond, hydrophobic wafer bonding is used, because as the invention demonstrates the hydrogen-surface-terminating species that facilitate van der Waals bonding evolves at temperatures above 600.degree. C. into covalent bonding in hydrophobically bound Ge/Si layer transferred systems.

  6. Cu-Cu direct bonding achieved by surface method at room temperature

    NASA Astrophysics Data System (ADS)

    Utsumi, Jun; Ichiyanagi, Yuko

    2014-02-01

    The metal bonding is a key technology in the processes for the microelectromechanical systems (MEMS) devices and the semiconductor devices to improve functionality and higher density integration. Strong adhesion between surfaces at the atomic level is crucial; however, it is difficult to achieve close bonding in such a system. Cu films were deposited on Si substrates by vacuum deposition, and then, two Cu films were bonded directly by means of surface activated bonding (SAB) at room temperature. The two Cu films, with the surface roughness Ra about 1.3nm, were bonded by using SAB at room temperature, however, the bonding strength was very weak in this method. In order to improve the bonding strength between the Cu films, samples were annealed at low temperatures, between 323 and 473 K, in air. As the result, the Cu-Cu bonding strength was 10 times higher than that of the original samples without annealing.

  7. Cu-Cu direct bonding achieved by surface method at room temperature

    SciTech Connect

    Utsumi, Jun [Advanced Technology Research Center, Mitsubishi Heavy Industries, Ltd., 1-8-1 Sachiura, Kanazawa-ku, Yokohama 236-8515 (Japan); Ichiyanagi, Yuko, E-mail: yuko@ynu.ac.jp [Department of Physics, Graduate School of Engineering, Yokohama National University, Tokiwadai, Hodogaya, Yokohama 240-8501 (Japan)

    2014-02-20

    The metal bonding is a key technology in the processes for the microelectromechanical systems (MEMS) devices and the semiconductor devices to improve functionality and higher density integration. Strong adhesion between surfaces at the atomic level is crucial; however, it is difficult to achieve close bonding in such a system. Cu films were deposited on Si substrates by vacuum deposition, and then, two Cu films were bonded directly by means of surface activated bonding (SAB) at room temperature. The two Cu films, with the surface roughness Ra about 1.3nm, were bonded by using SAB at room temperature, however, the bonding strength was very weak in this method. In order to improve the bonding strength between the Cu films, samples were annealed at low temperatures, between 323 and 473 K, in air. As the result, the Cu-Cu bonding strength was 10 times higher than that of the original samples without annealing.

  8. Semiconductor Wafer Bonding

    Microsoft Academic Search

    U. Gosele; Q.-Y. Tong

    1998-01-01

    When mirror-polished, flat, and clean wafers of almost any material are brought into contact at room temperature, they are locally attracted to each other by van der Waals forces and adhere or bond. This phenomenon is referred to as wafer bonding. The most prominent applications of wafer bonding are silicon-on-insulator (SOI) devices, silicon-based sensors and actuators, as well as optical

  9. Energy pulse bonding

    NASA Technical Reports Server (NTRS)

    Smith, G. C.

    1972-01-01

    To eliminate many of the present termination problems a technique called energy pulse bonding (EPB) was developed. The process demonstrated the capability of: (1) joining conductors without prior removal of insulations, (2) joining conductors without danger of brittle intermetallics, (3) increased joint temperature capability, (4) simultaneous formation of several bonds, (5) capability of higher joint density, and (6) a production oriented process. The following metals were successfully bonded in the solid state: copper, beryllium copper, phosphor bronze, aluminum, brass, and Kovar.

  10. Chemical bonding technology

    NASA Technical Reports Server (NTRS)

    Plueddemann, E.

    1986-01-01

    Primers employed in bonding together the various material interfaces in a photovoltaic module are being developed. The approach develops interfacial adhesion by generating actual chemical bonds between the various materials bonded together. The current status of the program is described along with the progress toward developing two general purpose primers for ethylene vinyl acetate (EVA), one for glass and metals, and another for plastic films.

  11. Femtosecond dynamics in hydrogen-bonded solvents

    SciTech Connect

    Castner, E.W. Jr.; Chang, Y.J.

    1993-09-01

    We present results on the ultrafast dynamics of pure hydrogen-bonding solvents, obtained using femtosecond Fourier-transform optical-heterodyne-detected, Raman-induced Kerr effect spectroscopy. Solvent systems we have studied include the formamides, water, ethylene glycol, and acetic acid. Inertial and diffusive motions are clearly resolved. We comment on the effect that such ultrafast solvent motions have on chemical reactions in solution.

  12. One Bond Strategy

    NSDL National Science Digital Library

    2001-01-01

    Provided by SmartMoney.com (see the May 20, 1999 Scout Report for Business & Economics), this quick and easy yet thorough guide takes readers through the process of developing a bond portfolio. At the site, users will find help on deciding how much to invest in bonds, how to divide their portfolio, and tips on investing for both income and profit. First, however, visitors might want to wet their feet in the bond primer section, which covers all the basics, explains the yield curve, offers a calculator and glossary, and throws in "ten things your broker won't tell you about bonds" for good measure.

  13. Hydrogen bonding and anaesthesia

    NASA Astrophysics Data System (ADS)

    Sándorfy, C.

    2004-12-01

    General anaesthetics act by perturbing intermolecular associations without breaking or forming covalent bonds. These associations might be due to a variety of van der Waals interactions or hydrogen bonding. Neurotransmitters all contain OH or NH groups, which are prone to form hydrogen bonds with those of the neurotransmitter receptors. These could be perturbed by anaesthetics. Aromatic rings in amino acids can act as weak hydrogen bond acceptors. On the other hand the acidic hydrogen in halothane type anaesthetics are weak proton donors. These two facts together lead to a probable mechanism of action for all general anaesthetics.

  14. The vacuum conservation theorem

    E-print Network

    E. Minguzzi

    2015-02-28

    A version of the vacuum conservation theorem is proved which does not assume the existence of a time function nor demands stronger properties than the dominant energy condition. However, it is shown that a stronger stable version plays a role in the study of compact Cauchy horizons.

  15. Langmuir vacuum and superconductivity

    SciTech Connect

    Veklenko, B. A. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

    2012-06-15

    It is shown that, in the 'jelly' model of cold electron-ion plasma, the interaction between electrons and the quantum electromagnetic vacuum of Langmuir waves involves plasma superconductivity with an energy gap proportional to the energy of the Langmuir quantum.

  16. Vacuum insulator coating development

    Microsoft Academic Search

    I. S. Roth; P. S. Sincerny; L. Mandelcorn; M. Mendelsohn; D. Smith; T. G. Engel; L. Schlitt; C. M. Cooke

    1997-01-01

    The authors discuss the electrical and mechanical requirements for vacuum insulators in high peak power generators. To increase the lifetime of these insulators, they have developed a coating called Dendresist. This coating has extended the insulator lifetime on the PITHON, DM2, CASINO, and Double-EAGLE pulsed power generators. They describe its development, and compare its electrical and mechanical strength to that

  17. Vacuum Kundt waves

    NASA Astrophysics Data System (ADS)

    McNutt, David; Milson, Robert; Coley, Alan

    2013-03-01

    We discuss the invariant classification of vacuum Kundt waves using the Cartan-Karlhede algorithm and determine the upper bound on the number of iterations of the Karlhede algorithm to classify the vacuum Kundt waves (Collins (1991 Class. Quantum Grav. 8 1859-69), Machado Ramos (1996 Class. Quantum Grav. 13 1589)). By choosing a particular coordinate system we partially construct the canonical coframe used in the classification to study the functional dependence of the invariants arising at each iteration of the algorithm. We provide a new upper bound, q ? 4, and show that this bound is sharp by analyzing the subclass of Kundt waves with invariant count beginning with (0, 1,…) to show that the class with invariant count (0, 1, 3, 4, 4) exists. This class of vacuum Kundt waves is shown to be unique as the only set of metrics requiring the fourth covariant derivatives of the curvature. We conclude with an invariant classification of the vacuum Kundt waves using a suite of invariants.

  18. Safety of Minkowski Vacuum

    E-print Network

    Gia Dvali

    2011-07-05

    We give a simple argument suggesting that in a consistent quantum field theory tunneling from Minkowski to a lower energy vacuum must be impossible. Theories that allow for such a tunneling also allow for localized states of negative mass, and therefore, should be inconsistent.

  19. What is vacuum?

    Microsoft Academic Search

    Peter Rowlands

    2008-01-01

    Vacuum can be defined with exact mathematical precision as the state which remains when a fermion, with all its special characteristics, is created out of absolutely nothing. The definition leads to a special form of relativistic quantum mechanics, which only requires the construction of a creation operator. This form of quantum mechanics is especially powerful for analytic calculation, at the

  20. Vacuum Arc Anode Phenomena

    Microsoft Academic Search

    H. Craig Miller

    1977-01-01

    This paper presents a brief review of anode phenomena in vacuum arcs. It discusses in succession the transition of the arc into the anode spot mode; the temperature of the anode before, during, and after formation of an anode spot; and anode ions. Characteristically the anode spot has a temperature of the order of the atmospheric boiling point of the

  1. Vacuum arc recovery phenomena

    Microsoft Academic Search

    J. A. Rich; G. A. Farrall

    1964-01-01

    The present experimental and theoretical study has been designed to uncover the mechanism underlying the rapid recovery of electrical strength of a short vacuum gap after arcing. In the experiment the contacts were of gas-free silver and the contact area and gap length were varied. Recovery strength was measured following the forced extinction of a 250 amp arc in 0.5

  2. Vacuum arcs and switching

    Microsoft Academic Search

    G. A. Farrall

    1973-01-01

    This paper is a review of vacuum-arc phenomena which are related to switching devices. Despite the device overtones, the approach adopted for this paper is fundamental. Topics discussed include the drawn arc, the triggered arc, the power input to the cathode spot, cathode-spot division, arc stability, substructure of the cathode spot, dielectric recovery processes, and breakdown between electrodes subjected to

  3. Vacuum arc deposition devices

    SciTech Connect

    Boxman, R.L.; Zhitomirsky, V.N. [Electrical Discharge and Plasma Laboratory, Faculty of Engineering, Tel Aviv University, P.O. Box 39040, Tel Aviv 69978 (Israel)

    2006-02-15

    The vacuum arc is a high-current, low-voltage electrical discharge which produces a plasma consisting of vaporized and ionized electrode material. In the most common cathodic arc deposition systems, the arc concentrates at minute cathode spots on the cathode surface and the plasma is emitted as a hypersonic jet, with some degree of contamination by molten droplets [known as macroparticles (MPs)] of the cathode material. In vacuum arc deposition systems, the location and motion of the cathode spots are confined to desired surfaces by an applied magnetic field and shields around undesired surfaces. Substrates are mounted on a holder so that they intercept some portion of the plasma jet. The substrate often provides for negative bias to control the energy of depositing ions and heating or cooling to control the substrate temperature. In some systems, a magnetic field is used to guide the plasma around an obstacle which blocks the MPs. These elements are integrated with a deposition chamber, cooling, vacuum gauges and pumps, and power supplies to produce a vacuum arc deposition system.

  4. Nonlinear Oscillators Vacuum Squeezing

    E-print Network

    Haviland, David

    dz mtF dt dz mzzk =++ =+ --- Classical Physics: The Driven Damped Harmonic Oscillator - a modelNonlinear Oscillators and Vacuum Squeezing David Haviland Nanosturcture Physics, Dept. Applied #12;Splitting of Cavity Resonance Now consider damping: excitation is ½ photon, ½ atom decay rate: 2

  5. Decoherence and Vacuum Fluctuations

    Microsoft Academic Search

    L. H. Ford

    1995-01-01

    The interference pattern of coherent electrons is effected by coupling to the quantized electromagnetic field. The amplitudes of the interference maxima are changed by a factor which depends upon a double line integral of the photon two-point function around the closed path of the electrons. The interference pattern is sensitive to shifts in the vacuum fluctuations in regions from which

  6. Light-front vacuum

    NASA Astrophysics Data System (ADS)

    Herrmann, Marc; Polyzou, W. N.

    2015-04-01

    The purpose of this work is to understand the relation between the trivial vacuum in light-front field theory and the nontrivial vacuum in canonical representations of quantum field theory and the role of zero-modes in this relation. The role of the underlying field algebra in the definition of the vacuum is exploited to understand these relations. The trivial vacuum defined by an annihilation operator defines a linear functional on the algebra of fields restricted to a light front. This is extended to a linear functional on the algebra of local fields. The extension defines a unitary mapping between the physical representation of the local algebra and a sub-algebra of the light-front Fock algebra. The dynamics appears in the mapping and the structure of the sub-algebra. This correspondence provides a formulation of locality and Poincaré invariance on the light-front Fock space. Zero modes do not appear in the final mapping, but may be needed in the construction of the mapping using a local Lagrangian.

  7. The vacuum conservation theorem

    NASA Astrophysics Data System (ADS)

    Minguzzi, E.

    2015-03-01

    A version of the vacuum conservation theorem is proved which does not assume the existence of a time function nor demands stronger properties than the dominant energy condition. However, it is shown that a stronger stable version plays a role in the study of compact Cauchy horizons.

  8. The quantum vacuum

    E-print Network

    Paraoanu, G S

    2014-01-01

    The vacuum is the lowest energy state of a field in a certain region of space. This definition implies that no particles can be present in the vacuum state. In classical physics, the only features of vacuum are those of its geometry. For example, in the general theory of relativity the geometry is a dynamical structure that guides the motion of matter, and, in turn, it is bent and curved by the presence of matter. Other than this, the classical vacuum is a structure void of any physical properties, since classically properties are strictly associated with physical objects such as particles and finite-amplitude fields. The situation is very different in quantum physics. As I will show in this paper, the difference stems form the fact that in quantum physics the properties are not strictly tied to objects. We know for example that physical properties come into existence - as values of observables - only when the object is measured. Thus, quantum physics allows us to detach properties from objects. This has cons...

  9. Vacuum configurations for superstrings

    Microsoft Academic Search

    P. Candelas; Gary T. Horowitz; Andrew Strominger; Edward Witten

    1985-01-01

    We study candidate vacuum configurations in ten-dimensional O(32) and E8 × E8 supergravity and superstring theory that have unbroken N = 1 supersymmetry in four dimensions. This condition permits only a few possibilities, all of which have vanishing cosmological constant. In the E8 × E8 case, one of these possibilities leads to a model that in four dimensions has an

  10. Demonstrations with a Vacuum: Old Demonstrations for New Vacuum Pumps.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1989-01-01

    Explains mechanisms of 19th-century vacuum pumps. Describes demonstrations using the pump including guinea and feather tube, aurora tube, electric egg, Gassiots cascade, air mill, bell in vacuum, density and buoyancy of air, fountain in vacuum, mercury shower, palm and bladder glasses, Bacchus demonstration, pneumatic man-lifter, and Magdeburg…

  11. Chemical Bonding, again ionic bonding (in salts): transfer of e-

    E-print Network

    Zakarian, Armen

    Chemical Bonding, again · ionic bonding (in salts): transfer of e- · covalent bonding (organic molecules, non-metals): sharing e- · metallic bonding: electron pooling (delocalization) Lewis electron 3A 4A 5A 6A 7A 8A 2 3 (exceptions) #12;Ionic Bonding Model See sample problem 9.1 4Na + O2 ! 2Na2O

  12. Bonding and Sealing Evaluations for Cryogenic Tanks

    NASA Technical Reports Server (NTRS)

    Glass, David E.

    1997-01-01

    Several different cryogenic tank concepts are being considered for reusable launch vehicles (RLV'S) . Though different tank concepts are being considered, many will require that the cryogenic insulation be evacuated and be bonded to a structure. In this work, an attempt was made to evaluate the effectiveness of maintaining a vacuum on a specimen where foam or honeycomb core was encased within Gr/Ep. In addition to these tests, flatwise adhesion pull off tests were performed at room temperature with PR 1664, EA 9394, FM-300, Crest 3170, and HT 435 adhesives. The materials bonded included Gr/Ep, Gr/BMI, Al, and stainless steel facesheets, and Ti honeycomb, Hexcel honeycomb, and Rohacell foam core materials.

  13. Transient liquid phase bonding of ferritic oxide dispersion strengthened alloys

    NASA Astrophysics Data System (ADS)

    Krishnardula, Venu Gopal

    2006-04-01

    Oxide dispersion strengthened (ODS) alloys possess excellent properties including resistance to oxidation, corrosion, creep and thermal fatigue. In addition, ferritic ODS alloys exhibit resistance to void swelling and are of particular interest to the nuclear industry. The present study involves the joining of fuel cans to end caps that will be utilized in the nuclear industry. Mechanically alloyed (MA) ODS alloys possess coarse columnar grain structure strengthened with nanosize yttria dispersoids. In that past, fusion welding techniques resulted in microstructural disruption leading to poor joints. This work investigated joining of two ferritic MA ODS alloys, MA956 and PM2000, using; (a) Transient liquid phase (TLP) bonding and (b) Solid-state diffusion bonding. TLP bonds were prepared with MA956 and PM2000 in the unrecrystallized and recrystallized conditions using electron beam physical vapor deposited (EBPVD) boron thin films as interlayers. The use of thin interlayers reduced the amount of substrate dissolution and minimized the bondline microstructural disruption. Different bond orientations were also investigated. Successful bonds with better microstructural continuity were obtained when substrates were joined in the unrecrystallized condition followed by post bond recrystallization heat treatment with the substrate faying surface aligned along the working (extrusion or rolling) direction than when substrates were aligned perpendicular to the working direction. This was attributed to the number of yttria stringers cut by the bondline, which is less when the substrate faying surface is lying parallel to the working direction than when the substrate faying surface is lying perpendicular to the working direction. Solid-state diffusion bonding was conducted using MA956 and PM2000 in the unrecrystallized and recrystallized conditions. Bonding occurred only when an unrecrystallized substrate was involved. Bonding occurred at unusually low stresses. This may be attributed to the grain boundary diffusion, owing to submicron grain size of the unrecrystallized substrates. Post bond heat treatment was conducted in order to induce recrystallization in the bonds. Room temperature mechanical testing was conducted on the bonds and the bulk. Bond shear strengths and tensile strengths of up to 80% and 110% of bulk, respectively, were obtained. Defects in the bulk material such as porosity and unwanted fine grain formation were observed. Pore formation at the bondline during post bond heat treatment seems to decrease the bond strength. These defects were attributed to prior thermomechanical history of the materials.

  14. Tritium handling in vacuum systems

    SciTech Connect

    Gill, J.T. [Monsanto Research Corp., Miamisburg, OH (United States). Mound Facility; Coffin, D.O. [Los Alamos National Lab., NM (United States)

    1986-10-01

    This report provides a course in Tritium handling in vacuum systems. Topics presented are: Properties of Tritium; Tritium compatibility of materials; Tritium-compatible vacuum equipment; and Tritium waste treatment.

  15. Flash vacuum pyrolysis of lignin model compounds

    SciTech Connect

    Cooney, M.J.; Britt, P.F.; Buchanan, A.C. III

    1997-03-01

    Despite the extensive research into the pyrolysis of lignin, the underlying chemical reactions that lead to product formation are poorly understood. Detailed mechanistic studies on the pyrolysis of biomass and lignin under conditions relevant to current process conditions could provide insight into utilizing this renewable resource for the production of chemicals and fuel. Currently, flash or fast pyrolysis is the most promising process to maximize the yields of liquid products (up to 80 wt %) from biomass by rapidly heating the substrate to moderate temperatures, typically 500{degrees}C, for short residence times, typically less than two seconds. To provide mechanistic insight into the primary reaction pathways under process relevant conditions, we are investigating the flash vacuum pyrolysis (FVP) of lignin model compounds that contain a {beta}-ether. linkage and {alpha}- or {gamma}-alcohol, which are key structural elements in lignin. The dominant products from the FVP of PhCH{sub 2}CH{sub 2}OPh (PPE), PhC(OH)HCH{sub 2}OPh, and PhCH{sub 2}CH(CH{sub 2}OH)OPh at 500{degrees}C can be attributed to homolysis of the weakest bond in the molecule (C-O bond) or 1,2-elimination. Surprisingly, the hydroxy-substituent dramatically increases the decomposition of PPE. It is proposed that internal hydrogen bonding is accelerating the reaction.

  16. Difficult to process? Vacuum it!

    SciTech Connect

    Eckles, A.J. [Atlanta Technology Group, GA (United States)

    1997-09-01

    Recent improvements in vacuum processing have broadened the technology`s use in the chemical process industries, running the gamut from vacuum distillation and evaporation, degassing, freeze drying, vapor deposition and etching, to vacuum filtrations. The paper discusses process improvements, attaining liquid distribution, medium-vacuum processing, falling-film evaporators, wiped-film evaporators, short-path evaporators, evaporation and crystallization, filtration, drying, refrigeration, freeze drying, degassing, semiconductor processing, pumps and their selection, and leak testing.

  17. A radiation hard vacuum switch

    DOEpatents

    Boettcher, G.E.

    1988-07-19

    A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction. 3 figs.

  18. Chemical Bonds I

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    Chemical bonding is discussed from a bond energy, rather than a wave mechanics, viewpoint. This approach is considered to be more suitable for the average student. (The second part of the article will appear in a later issue of the journal.) (AL)

  19. The Sibling Bond.

    ERIC Educational Resources Information Center

    Bank, Stephen P.; Kahn, Michael D.

    The relationships among brothers and sisters are infinitely varied, but whatever their characteristics, these bonds last throughout life. This book examines the sibling relationship as a distinctive emotional, passionate, painful, and solacing power. Chapter 1, "Unraveling the Sibling Bond," addresses research on siblings and development of the…

  20. Convertible Bonds as \\

    Microsoft Academic Search

    Jeremy C. Stein

    1992-01-01

    This paper argues that corporations may use convertible bonds as an indirect (albeit possibly risky) method for getting equity into their capital structures in situations where adverse selection problems make a conventional stock issue unattractive. Unlike other theories of convertible bond issuance, the model of this paper highlights: 1) the importance of call provisions on convertibles; and 2) the significance

  1. PBGA wire bonding development

    Microsoft Academic Search

    W. K. Shu

    1996-01-01

    In a PBGA package, the existence of a glass transition temperature of 170~215°C for PCB substrate puts an upper ceiling to the usable wire bond temperature. The low thermal conductivity of PCB substrate and the need for a thicker material make fine pad pitch wire bonding even more difficult to do. To compensate for the limitation in thermal energy, high

  2. A vacuum-driven peristaltic micropump with valved actuation chambers

    NASA Astrophysics Data System (ADS)

    Cui, Jianguo; Pan, Tingrui

    2011-06-01

    This paper presents a simple peristaltic micropump design incorporated with valved actuation chambers and propelled by a pulsed vacuum source. The vacuum-driven peristaltic micropump offers high pumping rates, low backflow, appreciable tolerance to air bubbles, and minimal destruction to fluid contents. The pumping device, fabricated by laser micromachining and plasma bonding of three polydimethylsiloxane (PDMS) layers, includes a pneumatic network, actuation membranes, and microfluidic channels. As the key to peristaltic motion, the sequential deflection of the elastic membranes is achieved by periodic pressure waveforms (negative) traveling through the pneumatic network, provided by a vacuum source regulated by an electromagnetic valve. This configuration eliminates the complicated control logic typically required in peristaltic motion. Importantly, the valved actuation chambers substantially reduce backflow and improve the pumping rates. In addition, the pneumatic network with negative pressure provides a means to effectively remove air bubbles present in the microflow through the gas-permeable PDMS membrane, which can be highly desired in handling complex fluidic samples. Experimental characterization of the micropump performance has been conducted by controlling the resistance of the pneumatic network, the number of normally closed valves, the vacuum pressure, and the frequency of pressure pulses. A maximal flow rate of 600 µL min-1 has been optimized at the pulsed vacuum frequency of 30 Hz with a vacuum pressure of 50 kPa, which is comparable to that of compressed air-actuated peristaltic micropumps.

  3. Ultrasonically bonded value assembly

    NASA Technical Reports Server (NTRS)

    Salvinski, R. J. (inventor)

    1975-01-01

    A valve apparatus capable of maintaining a fluid-tight seal over a relatively long period of time by releasably bonding a valve member to its seat is described. The valve member is bonded or welded to the seat and then released by the application of the same energy to the bond joint. The valve member is held in place during the bonding by a clamping device. An appropriate force device can activate the opening and closing of the valve member. Various combinations of material for the valve member and valve seat can be utilized to provide an adequate sealing bond. Aluminum oxide, stainless steel, inconel, tungsten carbide as hard materials and copper, aluminum, titanium, silver, and gold as soft materials are suggested.

  4. Vacuum Energy: Myths and Reality

    E-print Network

    G. E. Volovik

    2006-07-10

    We discuss the main myths related to the vacuum energy and cosmological constant, such as: ``unbearable lightness of space-time''; the dominating contribution of zero point energy of quantum fields to the vacuum energy; non-zero vacuum energy of the false vacuum; dependence of the vacuum energy on the overall shift of energy; the absolute value of energy only has significance for gravity; the vacuum energy depends on the vacuum content; cosmological constant changes after the phase transition; zero-point energy of the vacuum between the plates in Casimir effect must gravitate, that is why the zero-point energy in the vacuum outside the plates must also gravitate; etc. All these and some other conjectures appear to be wrong when one considers the thermodynamics of the ground state of the quantum many-body system, which mimics macroscopic thermodynamics of quantum vacuum. In particular, in spite of the ultraviolet divergence of the zero-point energy, the natural value of the vacuum energy is comparable with the observed dark energy. That is why the vacuum energy is the plausible candidate for the dark energy.

  5. Compact vacuum insulation embodiments

    DOEpatents

    Benson, D.K.; Potter, T.F.

    1992-04-28

    An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially point' or line' contacts with the metal wall sheets. In the case of monolithic spacers that form line' contacts, two such spacers with the line contacts running perpendicular to each other form effectively point' contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included. 26 figs.

  6. Vacuum tool manipulator

    DOEpatents

    Zollinger, W.T.

    1993-11-23

    Apparatus for manipulating a vacuum hose in a reactor vessel comprises a housing with two opposing openings, an arm carried by the housing and deployable from a stowed position essentially completely within the housing to an extended position where the arm extends through the two openings in a generally horizontal position. The arm preferably has a two-fingered gripping device for gripping the vacuum hose but may carry a different end effector such as a grinding wheel. The fingers are opened and closed by one air cylinder. A second air cylinder extends the device. A third air cylinder within the housing pivotally pulls the opposing end of the arm into the housing via a pivoting member pivotally connected between the third air cylinder shaft and the arm. 6 figures.

  7. Vacuum tool manipulator

    DOEpatents

    Zollinger, William T. (3927 Almon Dr., Martinez, GA 30907)

    1993-01-01

    Apparatus for manipulating a vacuum hose in a reactor vessel comprises a housing with two opposing openings, an arm carried by the housing and deployable from a stowed position essentially completely within the housing to an extended position where the arm extends through the two openings in a generally horizontal position. The arm preferably has a two-fingered gripping device for gripping the vacuum hose but may carry a different end effector such as a grinding wheel. The fingers are opened and closed by one air cylinder. A second air cylinder extends the device. A third air cylinder within the housing pivotally pulls the opposing end of the arm into the housing via a pivoting member pivotally connected between the third air cylinder shaft and the arm.

  8. Compact vacuum insulation

    DOEpatents

    Benson, D.K.; Potter, T.F.

    1993-01-05

    An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially point'' or line'' contacts with the metal wall sheets. In the case of monolithic spacers that form line'' contacts, two such spacers with the line contacts running perpendicular to each other form effectively point'' contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

  9. Development and evaluation of vacuum pressure gauge components from carbon and graphite

    NASA Technical Reports Server (NTRS)

    Benson, D. K.; Beitel, G. A.

    1972-01-01

    A prototype all carbon triode ultrahigh vacuum gage was fabricated and tested. The gage exhibited a sensitivity of 3.7 per torr for nitrogen and an X-ray background approximately 0.1 as large as would be expected of a metal gage of the same design. The gage made from these materials, showed good sensitivity and durability. A practical technique was developed for bonding carbon components together without metal fasteners. The bond is made with a cross-linked phenolic resin which is converted to vitreous carbon by a careful pyrolysis procedure. The resulting bonds are strong, electrically conductive, and can withstand repeated excursions to 2500 K in vacuum. Measurements of adsorption and outgassing characteristics of four refractory carbons have confirmed that such materials are suitable for use in ultrahigh vacuum and that some are superior refractory metals in man respects.

  10. Decoherence and Vacuum Fluctuations

    Microsoft Academic Search

    L. H. Ford

    1994-01-01

    The interference pattern of coherent electrons is effected by coupling to the\\u000aquantized electromagnetic field. The amplitudes of the interference maxima are\\u000achanged by a factor which depends upon a double line integral of the photon\\u000atwo-point function around the closed path of the electrons. The interference\\u000apattern is sensitive to shifts in the vacuum fluctuations in regions from which

  11. Decoherence and Vacuum Fluctuations

    E-print Network

    L. H. Ford

    1994-08-30

    The interference pattern of coherent electrons is effected by coupling to the quantized electromagnetic field. The amplitudes of the interference maxima are changed by a factor which depends upon a double line integral of the photon two-point function around the closed path of the electrons. The interference pattern is sensitive to shifts in the vacuum fluctuations in regions from which the electrons are excluded. Thus this effect combines aspects of both the Casimir and the Aharonov-Bohm effects. The coupling to the quantized electromagnetic field tends to decrease the amplitude of the interference oscillations, and hence is a form of decoherence. The contributions due to photon emission and to vacuum fluctuations may be separately identified. It is to be expected that photon emission leads to decoherence, as it can reveal which path an electron takes. It is less obvious that vacuum fluctuations also can cause decoherence. What is directly observable is a shift in the fluctuations due, for example, to the presence of a conducting plate. In the case of electrons moving parallel to conducting boundaries, the dominant decohering influence is that of the vacuum fluctuations. The shift in the interference amplitudes can be of the order of a few percent, so experimental verification of this effect may be possible. The possibility of using this effect to probe the interior of matter, e.g., to determine the electrical conductivity of a rod by means of electrons encircling it is discussed. (Presented at the Conference on Fundamental Problems in Quantum Theory, University of Maryland, Baltimore County, June 18-22, 1994.)

  12. Vacuum Ultraviolet Detector

    NASA Astrophysics Data System (ADS)

    Shao, Chun-Lin; Tomita, Kazuhiro; Jimbo, Takashi; Umeno, Masayoshi; Hattori, Shuzo

    1985-02-01

    A new vacuum ultraviolet detector has been fabricated. A sample was made using a crystalline quartz plate on the surface of which a metal electrode was deposited. It has been experimentally established that the sample is sensitive to VUV radiation, and the external quantum efficiency is estimated to be higher than several percent. The new photodetector also has very good stability and should be a practicable new VUV photodetector.

  13. Decoherence and vacuum fluctuations

    E-print Network

    Ford, L H

    1994-01-01

    The interference pattern of coherent electrons is effected by coupling to the quantized electromagnetic field. The amplitudes of the interference maxima are changed by a factor which depends upon a double line integral of the photon two-point function around the closed path of the electrons. The interference pattern is sensitive to shifts in the vacuum fluctuations in regions from which the electrons are excluded. Thus this effect combines aspects of both the Casimir and the Aharonov-Bohm effects. The coupling to the quantized electromagnetic field tends to decrease the amplitude of the interference oscillations, and hence is a form of decoherence. The contributions due to photon emission and to vacuum fluctuations may be separately identified. It is to be expected that photon emission leads to decoherence, as it can reveal which path an electron takes. It is less obvious that vacuum fluctuations also can cause decoherence. What is directly observable is a shift in the fluctuations due, for example, to the pr...

  14. Vacuum melting and mechanical testing of simulated lunar glasses

    NASA Technical Reports Server (NTRS)

    Carsley, J. E.; Blacic, J. D.; Pletka, B. J.

    1992-01-01

    Lunar silicate glasses may possess superior mechanical properties compared to terrestrial glasses because the anhydrous lunar environment should prevent hydrolytic weakening of the strong Si-O bonds. This hypothesis was tested by melting, solidifying, and determining the fracture toughness of simulated mare and highlands composition glasses in a high vacuum chamber. The fracture toughness, K(IC), of the resulting glasses was obtained via microindentation techniques. K(IC) increased as the testing environment was changed from air to a vacuum of 10 exp -7 torr. However, this increase in toughness may not result solely from a reduction in the hydrolytic weakening effect; the vacuum-melting process produced both the formation of spinel crystallites on the surfaces of the glass samples and significant changes in the compositions which may have contributed to the improved K(IC).

  15. Kissing bonds A kissing bond is adhesively bonded but holds little of the strength usually

    E-print Network

    Sóbester, András

    Kissing bonds · A kissing bond is adhesively bonded but holds little of the strength usually weight saving and excellent stress transfer. · The ability to reliably assess defects in adhesive bonds · To develop a non destructive method to assess the integrity of adhesive bonds using pulsed phase thermography

  16. Wafer-Level Thermocompression Bonds

    E-print Network

    Tsau, Christine H.

    Thermocompression bonding of gold is a promising technique for achieving low temperature, wafer-level bonding without the application of an electric field or complicated pre-bond cleaning procedure. The presence of a ductile ...

  17. Wafer-level vacuum packaging technology based on selective electroplating

    NASA Astrophysics Data System (ADS)

    Topart, Patrice A.; Leclair, Sebastien; Alain, Christine; Jerominek, Hubert

    2004-01-01

    A novel concept for low-cost, wafer-level packaging of MEMS is proposed and applied to vacuum packaging of INO"s 160x120 pixel uncooled bolometric focal plane arrays, FPAs, based on vanadium oxide thermistor material. A wafer-scale metallic tray composed of several tens of micropackages is electroplated by using the thick resist SU-8 as a micromold. FPA dies and infrared windows are then soldered to the main tray by flip-chip bonding. Contrary to the conventional wafer to wafer bonding approach, assembly and vacuum sealing steps are dissociated. For this purpose, each micropackage is equipped with a pump-out hole for outgassing under vacuum and at elevated temperature prior to vacuum sealing. The process flow for fabrication of micropackages is described. The influence of DC and pulse plating conditions on the stress and properties of deposited nickel packages was investigated. Results on the selective electroplating of indium solder on antireflection-coated IR window wafers and the formation of a solderable layer around the chip are presented.

  18. Ceramic-to-metal bonding for pressure transducers

    NASA Technical Reports Server (NTRS)

    Mackenzie, J. D.

    1984-01-01

    A solid-state diffusion technique involving the placement of a gold foil between INCONEL X-750 and a machinable glass-ceramic "MACOR" was shown to be successful in bonding these two materials. This technique was selected after an exhaustive literature search on ceramic-metal bonding methods. Small expansion mismatch between the Inconel and the MACOR resulted in fracture of the MACOR when the bonded body was subjected to tensile stress of 535 psi. The bonded parts were submitted to a cyclic loading test in an air atmosphere at 1 Hz from 0 to 60 KPa. Failure was observed after 700,000 cycles at 650 C. Ceramic-Inconel bonding was not achieved with this method for boron nitride and silica glass.

  19. Self diffusion of reversibly aggregating spheres

    E-print Network

    Sujin Babu; Jean Christophe Gimel; Taco Nicolai

    2007-05-10

    Reversible diffusion limited cluster aggregation of hard spheres with rigid bonds was simulated and the self diffusion coefficient was determined for equilibrated systems. The effect of increasing attraction strength was determined for systems at different volume fractions and different interaction ranges. It was found that the slowing down of the diffusion coefficient due to crowding is decoupled from that due to cluster formation. The diffusion coefficient could be calculated from the cluster size distribution and became zero only at infinite attraction strength when permanent gels are formed. It is concluded that so-called attractive glasses are not formed at finite interaction strength.

  20. Diffusion and phase transformation on interface between substrate and NiCrAlY in Y-PSZ thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Chen, H.; Jin, Z.; Liu, C.; Zhou, K.

    2004-12-01

    NiCrAlY/Y2O3-Y-PSZ (yttria-partially stabilized zirconia) thermal barrier coatings were developed on a superalloy (Ni-10Co-9Cr-7W-5Al, wt.%) surface. The superalloys were first coated with a bond coat of Ni-19Cr-8Al-0.5Y (wt.%) alloy that was deposited by low-pressure plasma spraying and then covered with a top coat of ZrO2-8wt.%Y2O3 by air plasma spraying. The microstructure near the interface was analyzed using an optical microscope, a scanning electron microscope, microhardness measurements, and x-ray diffraction, and the phases of composition were measured using an electron probe microanalyzer after exposure at 1100°C for different times in air or a vacuum. The reaction processes also were simulated using diffusion-controlled transformation (DICTRA) software in which diffusion was considered as being only the ? phase, and the ?? phase was treated as spheroidal particles in ?. From the authors’ results, it can be concluded that a ??-phase layer is observed at the interface between substrate and bond coat, and its thickness increases with increasing exposure times in air at 1100 °C. This layer showed good cohesion with the substrate and bond coat. It can also be concluded that the formation of the ??-phase layer can be predicted from DICTRA simulation. The simulation also shows the same trend of the composition profiles as experimental data.

  1. Ti Diffusion in Pyroxene

    NASA Astrophysics Data System (ADS)

    Cherniak, D.; Liang, Y.

    2008-12-01

    Diffusion of titanium has been characterized in natural enstatite and diopside under buffered conditions and in air. The sources of diffusant for the enstatite experiments were mixtures of Mg, Si and Ti oxide powders, which were combined and heated at 1300°C overnight, and then thoroughly mixed with synthesized enstatite powder and heated for an additional day at 1300°C. Sources for diopside experiments were prepared similarly, using Ca, Mg, Si, and Ti oxide powders combined with synthesized diopside powder, with heating of source materials at 1200°C. Buffered experiments were prepared by enclosing source material and pyroxene (polished and pre-annealed under conditions comparable to those to be experienced in the experiment) in AgPd or platinum capsules, placing the metal capsule in a silica glass capsule with a solid buffer (to buffer at NNO or IW) and sealing the assembly under vacuum. Some experiments on enstatite were run in air; sample and source were placed in Pt capsules and crimped shut. Prepared capsules were then annealed in 1 atm furnaces for times ranging from 8 hours to a few months, at temperatures from 950 to 1200°C. The Ti distributions in the pyroxene were profiled with Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for Ti diffusion in a natural enstatite, for diffusion normal to the (210) cleavage face (950 - 1150°C, experiments run in air): DTi = 1.9×10-10 exp(-300 ± 44 kJ mol-1/RT) m2 sec-1. Diffusion under NNO and IW-buffered conditions is similar to that for experiments run in air, suggesting little dependence of Ti diffusion on oxygen fugacity. There is also little evidence of anisotropy, as diffusion normal to (001) does not differ significantly from diffusion for the other orientation. Preliminary findings for Ti diffusion in diopside suggest diffusivities similar to those for enstatite. Ti diffusivities in enstatite are similar to those of the trivalent REEs (Cherniak and Liang, 2007), but more than two orders of magnitude slower than those of Fe-Mg (ter Heege et al., 2006) and Cr (Ganguly et al., 2007). These respective variations may reflect the interplay of cation size and charge, or may point to the substitution of Ti on the tetrahedral site. Measurements of diffusion under a broader range of conditions and for other high field strength elements are underway to better interpret these findings. Major and trace element zoning in pyroxenes have been observed in residual peridotites and mafic cumulates. The large differences in cation mobility among Ti, Cr, and Fe-Mg in pyroxene may allow us to distinguish the dominant process that gives rise to the chemical disequilibria. In contrast to those produced by subsolidus reequilibration during cooling, the apparent diffusive boundary layer thicknesses as measured by major and trace elements in a pyroxene grain are not sensitive to the respective cation diffusion rates if zoning is produced by magmatic processes that involves dissolution- precipitation. Examples of zoning in pyroxenes produced by magmatic and subsolidus processes will be discussed. Ganguly et al. (2007) GCA 71, 3915-3925; ter Heege et al. (2006) Eos Trans. AGU 87, Fall Mtg. Suppl. MR21A-0004; Cherniak and Liang (2007) GCA 71, 1324-1340

  2. Gold Thermocompression Wafer Bonding

    E-print Network

    Spearing, S. Mark

    Thermocompression bonding of gold is a promising technique for the fabrication and packaging microelectronic and MEMS devices. The use of a gold interlayer and moderate temperatures and pressures results in a hermetic, ...

  3. Characterization of anodic bonding

    E-print Network

    Tudryn, Carissa Debra, 1978-

    2004-01-01

    Anodic bonding is a common process used in MicroElectroMechanical Systems (MEMS) device fabrication and packaging. Polycrystalline chemical vapor deposited (CVD) silicon carbide (SiC) is emerging as a new MEMS device and ...

  4. Hydrogen bonds animation

    NSDL National Science Digital Library

    Northland Community and Technical College Biology Department

    2007-12-12

    This color animation of water molecules interacting and forming hydrogen bonds is a hybrid between a PowerPoint slide show an an animation. Students can replay portions or click next if they do not need to replay a segment.

  5. Junk-Bond Colleges.

    ERIC Educational Resources Information Center

    Van Der Werf, Martin

    2003-01-01

    Describes how a long-predicted decline in the fortunes of small private colleges is beginning to show up in the bond market, as the number of colleges now rated in the junk category has nearly doubled. (EV)

  6. Bonding aerogels with polyurethanes

    SciTech Connect

    Matthews, F.M.; Hoffman, D.M.

    1989-11-01

    Aerogels, porous silica glasses with ultra-fine cell size (30nm), are made by a solution gelation (sol-gel) process. The resulting gel is critical point dried to densities from 0.15--0.60 g/cc. This material is machinable, homogeneous, transparent, coatable and bondable. To bond aerogel an adhesive should have long cure time, no attack on the aerogel structure, and high strength. Several epoxies and urethanes were examined to determine if they satisfied these conditions. Bond strengths above 13 psi were found with double bubble and DP-110 epoxies and XI-208/ODA-1000 and Castall U-2630 urethanes. Hardman Kalex Tough Stuff'' A-85 hardness urethane gave 18 psi bond strength. Hardman A-85, Tuff-Stuff'' was selected for further evaluation because it produced bond strengths comparable to the adherend cohesive strength. 5 refs., 2 figs.

  7. Roof bolt bond tester

    SciTech Connect

    Not Available

    1982-01-01

    An intrinsically safe, electronic instrument has been developed that determines the holding quality of a fully grouted roof bolt by testing the integrity of the resin bond to both the bolt and to the surrounding rock.

  8. All about Chemical Bonding

    NSDL National Science Digital Library

    Lower, Stephen

    Stephen Lower, a retired professor at Simon Fraser University, created this expansive and instructive website as a supplement to formal chemistry education for undergraduate students. Visitors will find in-depth descriptions along with several diagrams dealing with chemical bonding issues including their properties, shared-electron covalent bonds, hybrid orbitals, coordination complexes, and metals and semiconductors. General chemistry students looking for assistance should visit this well-developed educational site.

  9. Water's Hydrogen Bond Strength

    E-print Network

    Martin Chaplin

    2007-06-10

    Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperatures. The overall conclusion of this investigation is that water's hydrogen bond strength is poised centrally within a narrow window of its suitability for life.

  10. 30 CFR 581.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...Resources 2 2013-07-01 2013-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 581.33 Bonds and bonding requirements. (a) When the leasing notice...

  11. Fair Scheduling on Parallel Bonded Channels with Intersecting Bonding Groups

    E-print Network

    Martin, Jim

    Fair Scheduling on Parallel Bonded Channels with Intersecting Bonding Groups Gongbing Hong, James for providing weighted sharing of aggregate capacity in networks having parallel bonded channels in which a single channel may simultaneously be a member of multiple bonding groups. Our work is motivated

  12. 30 CFR 281.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...Resources 2 2011-07-01 2011-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 281.33 Bonds and bonding requirements. (a) When the leasing notice...

  13. 30 CFR 581.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...Resources 2 2014-07-01 2014-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 581.33 Bonds and bonding requirements. (a) When the leasing notice...

  14. 30 CFR 581.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...Resources 2 2012-07-01 2012-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 581.33 Bonds and bonding requirements. (a) When the leasing notice...

  15. What is vacuum?

    E-print Network

    Rowlands, Peter

    2008-01-01

    Vacuum can be defined with exact mathematical precision as the state which remains when a fermion, with all its special characteristics, is created out of absolutely nothing. The definition leads to a special form of relativistic quantum mechanics, which only requires the construction of a creation operator. This form of quantum mechanics is especially powerful for analytic calculation, at the same time as explaining, from first principles, many aspects of the Standard Model of particle physics. In particular, the characteristics of the weak, strong and electric interactions can be derived from the structure of the creation operator itself.

  16. What is vacuum?

    E-print Network

    Peter Rowlands

    2008-10-01

    Vacuum can be defined with exact mathematical precision as the state which remains when a fermion, with all its special characteristics, is created out of absolutely nothing. The definition leads to a special form of relativistic quantum mechanics, which only requires the construction of a creation operator. This form of quantum mechanics is especially powerful for analytic calculation, at the same time as explaining, from first principles, many aspects of the Standard Model of particle physics. In particular, the characteristics of the weak, strong and electric interactions can be derived from the structure of the creation operator itself.

  17. Avoiding Death by Vacuum

    E-print Network

    A. Barroso; P. M. Ferreira; I. Ivanov; R. Santos; Joao P. Silva

    2013-05-08

    The two-Higgs doublet model (2HDM) can have two electroweak breaking, CP-conserving, minima. The possibility arises that the minimum which corresponds to the known elementary particle spectrum is metastable, a possibility we call the "panic vacuum". We present analytical bounds on the parameters of the softly broken Peccei-Quinn 2HDM which are necessary and sufficient conditions to avoid this possibility. We also show that, for this particular model, the current LHC data already tell us that we are necessarily in the global minimum of the theory, regardless of any cosmological considerations about the lifetime of the false vacua.

  18. Polymers in a Vacuum

    SciTech Connect

    Deutsch, J. M. [Department of Physics, University of California, Santa Cruz, California 95064 (United States)

    2007-12-07

    In a variety of situations, isolated polymer molecules are found in a vacuum, and here we examine their properties. Angular momentum conservation is shown to significantly alter the average size of a chain and its conservation is only broken slowly by thermal radiation. For an ideal chain, the time autocorrelation for monomer position oscillates with a period proportional to chain length. The oscillations and damping are analyzed in detail. Short-range repulsive interactions suppress oscillations and speed up relaxation, but stretched chains still show damped oscillatory correlations.

  19. R&D ERL: Vacuum

    SciTech Connect

    Mapes, M.; Smart, L.; Weiss, D.; Steszyn, A.; Todd, R.

    2010-01-01

    The ERL Vacuum systems are depicted in a figure. ERL has eight vacuum volumes with various sets of requirements. A summary of vacuum related requirements is provided in a table. Five of the eight volumes comprise the electron beamline. They are the 5-cell Superconducting RF Cavity, Superconducting e-gun, injection, loop and beam dump. Two vacuum regions are the individual cryostats insulating the 5-cell Superconducting RF Cavity and the Superconducting e-gun structures. The last ERL vacuum volume not shown in the schematic is the laser transport line. The beamline vacuum regions are separated by electropneumatic gate valves. The beam dump is common with loop beamline but is considered a separate volume due to geometry and requirements. Vacuum in the 5-cell SRF cavity is maintained in the {approx}10{sup -9} torr range at room temperature by two 20 l/s ion pumps and in the e-gun SRF cavity by one 60 l/s ion pump. Vacuum in the SRF cavities operated at 2{sup o}K is reduced to low 10{sup -11} torr via cryopumping of the cavity walls. The cathode of the e-gun must be protected from poisoning, which can occur if vacuum adjacent to the e-gun in the injection line exceeds 10-11 torr range in the injection warm beamline near the e-gun exit. The vacuum requirements for beam operation in the loop and beam dump are 10-9 torr range. The beamlines are evacuated from atmospheric pressure to high vacuum level with a particulate free, oil free turbomolecular pumping cart. 25 l/s shielded ion pumps distributed throughout the beamlines maintain the vacuum requirement. Due to the more demanding vacuum requirement of the injection beamline proximate to the e-gun, a vacuum bakeout of the injection beamline is required. In addition, two 200 l/s diode ion pumps and supplemental pumping provided by titanium sublimation pumps are installed in the injection line just beyond the exit of the e-gun. Due to expected gas load a similar pumping arrangement is planned for the beam dump. The cryostat vacuum thermally insulating the SRF cavities need only reduce the convective heat load such that heat loss is primarily radiation through several layers of multi-layer insulation and conductive end-losses which are contained by 5{sup o}K thermal transitions. Prior to cool down rough vacuum {approx}10{sup -5} torr range is established and maintained by a dedicated turbomolecular pump station. Cryopumping by the cold mass and heat shields reduces the insulating vacuum to 10{sup -7} torr range after cool down.

  20. An Investigation of Bonding Mechanism in Metal Cladding by Warm Rolling 

    E-print Network

    Yang, Wei

    2012-02-14

    coefficients of aluminum and iron are estimated through experimental method. A thermo-mechanical model was developed to describe the rolling plastic deformation of component metal sheets and the diffusion evolution during a roll bonding process of dissimilar...

  1. Silver-silicon bonding on silica surfaces

    SciTech Connect

    Pitts, J.R.

    1985-04-01

    The properties of Ag films deposited on silica or silica-based glass substrates have been investigated using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), ion scattering spectrometry (ISS), and secondary ion mass spectrometry (SIMS). Interfacial studies are reported for films prepared by decomposing organometallic Ag on glass, depositing Ag by the wet chemical electroless method onto glass and SiO/sub 2/, and vacuum evaporating Ag onto SiO/sub 2/. For organometallic Ag films on glass, depth profiles indicate that the interfacial regions are enriched in Si or depleted in O. For electroless films, Sn-Si bonds are formed after sensitization with tin chloride and Ag-Si bonds are formed after silvering without reducers. Silver is strongly bonded to Si via a set of Sn insertion reactions, but impurities were found at the interfaces and these probably contribute to the rapid degradation of mirrors in terrestrial environments. Particle bombardment of silica with He, Ne, Ar or electrons in the range of 0.25 to 8 keV results in reduction of the surface to form SiO/sub x/ (x 2). Although complete reduction was not observed, enrichment of the surface in Si prior to vacuum deposition of Ag improves the adhesion of the film. Angle resolved XPS and ISS on one monolayer of evaporated Ag and SiO/sub 2/ indicate that Si is preferentially masked by the Ag, suggesting that Ag is in an atop position over the Si atoms in silica.

  2. Fokker-Planck . . . Diffusion . . .

    E-print Network

    Fokker-Planck . . . Diffusion . . . Diffusion- . . . Application: . . . Summary and . . . First #12;Fokker-Planck . . . Diffusion . . . Diffusion- . . . Application: . . . Summary and . . . Topics: 1. Fokker-Planck transport equation 2. Diffusion approximation 3. Diffusion-convection transport

  3. Introduction Diffusion Tensor Imaging

    E-print Network

    Zhang, Shuzhong

    Introduction Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further ·Full Screen ·Close ·Quit Diffusion Tensor and Diffusion Kurtosis Tensor in Biomedical Engineering Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further Discussion Home Page

  4. Silicon Wafer Bonding by Modified Surface Activated Bonding Methods

    Microsoft Academic Search

    Chenxi Wang; E. Higurashi; T. Suga

    2007-01-01

    8-inch Si-Si wafer bonding at room temperature is performed by means of two modified surface activated bonding (SAB) methods respectively, namely the SAB with nano-adhesion layer and sequential plasma activated bonding (SPAB). And post-annealing processes in atmospheric air utilized do not aim to improve the bonding strength, but to investigate void formation if the bonded wafers heated in subsequent heated

  5. Vacuum vapor deposition

    NASA Technical Reports Server (NTRS)

    Poorman, Richard M. (inventor); Weeks, Jack L. (inventor)

    1995-01-01

    A method and apparatus is described for vapor deposition of a thin metallic film utilizing an ionized gas arc directed onto a source material spaced from a substrate to be coated in a substantial vacuum while providing a pressure differential between the source and the substrate so that, as a portion of the source is vaporized, the vapors are carried to the substrate. The apparatus includes a modified tungsten arc welding torch having a hollow electrode through which a gas, preferably inert, flows and an arc is struck between the electrode and the source. The torch, source, and substrate are confined within a chamber within which a vacuum is drawn. When the arc is struck, a portion of the source is vaporized and the vapors flow rapidly toward the substrate. A reflecting shield is positioned about the torch above the electrode and the source to ensure that the arc is struck between the electrode and the source at startup. The electrode and the source may be confined within a vapor guide housing having a duct opening toward the substrate for directing the vapors onto the substrate.

  6. Changing MFTF vacuum environment

    SciTech Connect

    Margolies, D.; Valby, L.

    1982-12-01

    The Mirror Fusion Test Facility (MFTF) vacuum vessel will be about 60m long and 10m in diameter at the widest point. The allowable operating densities range from 2 x 10/sup 9/ to 5 x 10/sup 10/ particles per cc. The maximum leak rate of 10/sup -6/ tl/sec is dominated during operation by the deliberately injected cold gas of 250 tl/sec. This gas is pumped by over 1000 square meters of cryopanels, external sorption pumps and getters. The design and requirements have changed radically over the past several years, and they are still not in final form. The vacuum system design has also changed, but more slowly and less radically. This paper discusses the engineering effort necessary to meet these stringent and changing requirements. Much of the analysis of the internal systems has been carried out using a 3-D Monte Carlo computer code, which can estimate time dependent operational pressures. This code and its use will also be described.

  7. Motor actuated vacuum door

    NASA Astrophysics Data System (ADS)

    Hanagud, A. V.

    1986-10-01

    Doors that allow scientific instruments to record and retrieve the observed data are often required to be designed and installed as a part of sounding rocket hardware. The motor-actuated vacuum door was designed to maintain a medium vacuum of the order of 0.0001 torr or better while closed, and to provide an opening 15 inches long x 8.5 inches wide while open for cameras to image Halley's comet. When the electric motor receives the instruction to open the door through the payload battery, timer, and relay circuit, the first operation is to unlock the door. After unlatching, the torque transmitted by the motor to the main shaft through the links opens the door. A microswitch actuator, which rides on the linear motion conversion mechanism, is adjusted to trip the limit switch at the end of the travel. The process is repeated in the reverse order to close the door. 'O' rings are designed to maintain the seal. Door mechanisms similar to the one described have flown on Aerobee 17.018 and Black Brant 27.047 payloads.

  8. Relativistic diffusion

    E-print Network

    Haba, Z

    2008-01-01

    We define a relativistic diffusion equation on the phase space. We consider stochastic Ito (Langevin) differential equation on the phase space as a perturbation by noise of relativistic dynamics. The motion in an electromagnetic field is treated as an example. Transport equations and equilibrium probability distributions are investigated. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  9. Hillslope diffusion

    NSDL National Science Digital Library

    Jeni McDermott

    This lab is designed to help students apply hillslope diffusion equations (derived in class prior to the lab) to understand real-world hillslopes. The major goal is a deeper understanding of hillslope processes and the equations used to describe hillslope diffusion by observing the same factors described in the equations on real-world hillslopes.

  10. Improvement in Joint Reliability of SiC Power Devices by a Diffusion Barrier Between Au-Ge Solder and Cu/Ni(P)-Metalized Ceramic Substrates

    NASA Astrophysics Data System (ADS)

    Lang, Fengqun; Yamaguchi, Hiroshi; Ohashi, Hiromichi; Sato, Hiroshi

    2011-07-01

    The long-term joint reliability of SiC power devices bonded on a ceramic substrate metalized with copper (Cu) and electroless nickel-phosphorus [Ni(P)] using a gold-germanium (Au-Ge) eutectic solder was investigated at 330°C in air. Rapid growth of Ni-Ge intermetallic compounds (IMCs) at the solder/Ni(P) interface and subsequent oxidation of the conductive Cu layer at the IMCs/Cu interface led to a dramatic decrease in bond strength and an increase in the electrical resistance of the joint. To improve the joint reliability, a 250-nm-thick tungsten (W) diffusion barrier (DB) was prepared on the surface of the substrate using a sputtering process. SiC Schottky barrier diode (SBD) power devices were then die-bonded to the W-DB-modified substrate with the Au-Ge eutectic solder using a vacuum reflow system. The bonded samples were aged at 330°C in air. After 1600 h, the joint strength was two times higher than that on the W-DB-free substrate, and no change was observed in the electrical resistance.

  11. Advanced copper wire bonding technology

    Microsoft Academic Search

    Hong Meng Ho

    2010-01-01

    Wire bonding is the most dominant form of first-level chip interconnects in microelectronics with gold wire bonding taking the lead for the past few decades. Today, it is evident that the shift from gold to copper wire bonding is genuinely picking up, due to both a surge in gold prices and recent developments in copper wire bonding technology. The course

  12. Wire bonds over active circuits

    Microsoft Academic Search

    Gail Heinen; Roger J. Stierman; Darvin Edwards; L. Nye

    1994-01-01

    A reliable process-for wire bonding over active integrated circuits, which are subsequently assembled in plastic packages, has been developed. This technology accommodates reducing the silicon die area required for bond pads and for on-chip bussing. Further, it supports area array wire bonding by allowing larger bond pads with relaxed pitch without sacrificing silicon area. This is accomplished by processing an

  13. Modeling of Diffusion in Closed Cell Polymeric Foams

    Microsoft Academic Search

    Sacide Alsoy

    1999-01-01

    Closed-cell foams made of polymers have the lowest thermal conductivity of any currently available insulation material other than vacuum insulation systems. The increase of foam conductivity with age occurs as air diffuses into the foam while the blowing agent diffuses out, thus modifying the cell gas composition. Also, the change in cell gas composition influences the dimensional stability of the

  14. On the Rate of Decomposition of Diffusion Pump Oil

    Microsoft Academic Search

    Chikara Hayashi

    1954-01-01

    The rate of decomposition of diffusion pump oil under the working condition seems to be an important quantity in reference to the vacuum. The following experiment was carried out to give an answer to the problems, ``Whether various metals really catalyse the decomposition of diffusion pump oil ? and ``Will the gaseous components of the decomposition products limit the ultimate

  15. Effect of temperature and layer thickness on these strengths of carbon bonding for carbon\\/carbon composites

    Microsoft Academic Search

    Masashi Koyama; Hiroshi Hatta; Hiroshi Fukuda

    2005-01-01

    In order to apply carbon\\/carbon composites (C\\/Cs) to various hot structures, secondary bonding techniques effective at elevated temperatures are frequently required. In the present study, carbon bonding between lamination type C\\/Cs was formed by the carbonation of polymer adhesive, and the strength of the bonding was evaluated at temperatures up to 2273K in a vacuum using the double-notched shear method.

  16. Use of Silicones as Diffusion Pump Oils

    Microsoft Academic Search

    Gordon P. Brown

    1945-01-01

    Comparative performances of Litton C, Octoil, Narcoil, and two typical silicones in a non-fractionating diffusion pump are presented with a discussion of vapor pressure, stability to heat and oxidation, and the ability to operate against high forepressures. Extrapolated vapor pressure, temperature data, and test results show the high boiling silicone to produce the highest vacuum as indicated by an untrapped

  17. A Two-Stage Oil Diffusion Pump

    Microsoft Academic Search

    Joseph E. Henderson

    1935-01-01

    A two-stage oil diffusion pump built of glass is described which makes possible the utilization of the advantages of oil without requiring the use of an unusually good coarse vacuum. The novelty of the pump resides in the first stage which is so designed that it cannot clog even with the small clearances needed to work against high pressures.

  18. Low partial discharge vacuum feedthrough

    NASA Technical Reports Server (NTRS)

    Benham, J. W.; Peck, S. R.

    1979-01-01

    Relatively discharge free vacuum feedthrough uses silver-plated copper conductor jacketed by carbon filled silicon semiconductor to reduce concentrated electric fields and minimize occurrence of partial discharge.

  19. From bonding to biting: Conversational joking and identity display

    Microsoft Academic Search

    Diana Boxer; Florencia Cortés-Conde

    1997-01-01

    Teasing and joking are instruments by which social control is exerted and through which social identity is displayed. Situational humor, or conversational joking — especially teasing — has been seen as a double-edged sword that both diffuses and controls conflict. Little attention has been given, though, to the bonding role of joking. Through an ethnography of speaking approach, we examine

  20. Vacuum ultraviolet photoionization of carbohydrates and nucleotides

    SciTech Connect

    Shin, Joong-Won, E-mail: jshin@govst.edu [Division of Science, Governors State University, University Park, Illinois 60484-0975 (United States) [Division of Science, Governors State University, University Park, Illinois 60484-0975 (United States); Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872 (United States); Bernstein, Elliot R., E-mail: erb@lamar.colostate.edu [Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872 (United States)

    2014-01-28

    Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5{sup ?}-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate, rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C–C and C–O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results.

  1. Fundamentals of thermo-sonic copper wire bonding in microelectronics packaging

    Microsoft Academic Search

    S. Murali; N. Srikanth; Y. M. Wong; Charles J. Vath

    2007-01-01

    Fine copper wire bonding is capable of making reliable electrical interconnections in microelectronic packages. Copper wires\\u000a of 0.8–6 mil diameter have been successfully bonded to different bond pad metallized and plated substrate materials such as\\u000a Al, Cu, Ag, Au and Pd. The three metallurgical related factors; solid-solubility and diffusion of dissimilar contact metals,\\u000a oxide film breakage and plastic deformation of asperities

  2. Control Dewar Secondary Vacuum Container

    SciTech Connect

    Rucinski, R.; /Fermilab

    1993-10-04

    This engineering note provides background information regarding the control dewar secondary vacuum container. The secondary vacuum container has it's origin with the CDP control dewar design. The name secondary vacuum container replaced the CDP term 'Watt can' which was named after Bob Watt (SLAC), a PAC/DOE review committee member who participated in a review of CDP and recommended a secondary vacuum enclosure. One of the most fragile parts of the control dewar design is the ceramic electrical feed throughs located in the secondary vacuum container. The secondary vacuum container is provided to guard against potential leaks in these ceramic insulating feed throughs. The secondary vacuum container has a pumping line separate from the main solenoid/control dewar insulating vacuum. This pumping line is connected to the inlet of the turbo pump for initial pumpdown. Under normal operation the container is isolated. Should a feedthrough develop a small leak, alternate pumping arrangements for the secondary vacuum container could be arranged. The pressure in the secondary vacuum container should be kept in a range that the breakdown voltage is kept at a maximum. The breakdown voltage is known to be a function of pressure and is described by a Paschen curve. I cannot find a copy of the curve at this time, but from what I remember, the breakdown voltage is a minimum somewhere around 10-3 torr. Ideally the pressure in the secondary vacuum can should be kept very low, around 10 E-6 or 10 E-7 torr for maximum breakdown voltage. If however a leak developed and this was not possible, then one could operate at a pressure higher than the minima point.

  3. Bonding and Integration Technologies for Silicon Carbide Based Injector Components

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay

    2008-01-01

    Advanced ceramic bonding and integration technologies play a critical role in the fabrication and application of silicon carbide based components for a number of aerospace and ground based applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. Ceramic to ceramic diffusion bonding and ceramic to metal brazing technologies are being developed for this injector application. For the diffusion bonding, titanium interlayers (PVD and foils) were used to aid in the joining of silicon carbide (SiC) substrates. The influence of such variables as surface finish, interlayer thickness (10, 20, and 50 microns), processing time and temperature, and cooling rates were investigated. Microprobe analysis was used to identify the phases in the bonded region. For bonds that were not fully reacted an intermediate phase, Ti5Si3Cx, formed that is thermally incompatible in its thermal expansion and caused thermal stresses and cracking during the processing cool-down. Thinner titanium interlayers and/or longer processing times resulted in stable and compatible phases that did not contribute to microcracking and resulted in an optimized microstructure. Tensile tests on the joined materials resulted in strengths of 13-28 MPa depending on the SiC substrate material. Non-destructive evaluation using ultrasonic immersion showed well formed bonds. For the joining technology of brazing Kovar fuel tubes to silicon carbide, preliminary development of the joining approach has begun. Various technical issues and requirements for the injector application are addressed.

  4. Insulation bonding test system

    NASA Technical Reports Server (NTRS)

    Beggs, J. M.; Johnston, G. D.; Coleman, A. D.; Portwood, J. N.; Saunders, J. M.; Redmon, J. W.; Porter, A. C. (inventors)

    1984-01-01

    A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact.

  5. Theory of the expanding plasma of vacuum arcs

    Microsoft Academic Search

    E. Hantzsche

    1991-01-01

    Investigations of the diffuse plasma expanding from cathode arc spots into a vacuum have revealed some unexpected properties calling for physical explanation. A theoretical model of such plasmas which is based on one-dimensional time-independent hydrodynamic two-fluid equations can be solved analytically in the form of asymptotic power series approximately describing the plasma parameters as functions of the variable s=(I\\/r)2\\/5(current I,

  6. Numerical Simulation of Vacuum Drying by Luikov's Equations

    Microsoft Academic Search

    F. Nadi; G. H. Rahimi; R. Younsi; T. Tavakoli; Z. Hamidi-Esfahani

    2012-01-01

    A two-dimensional mathematical model was developed to simulate coupled heat and mass transfer in apple under vacuum drying. Luikov's equations are the governing equations in analyzing heat and mass diffusion problems for capillary-porous bodies. The model considers temperature- and moisture-dependent material properties. The aim of this study is to analyze the influence of some of the most important operating variables,

  7. Entrapment Type Vacuum Pumps

    NSDL National Science Digital Library

    This is a description for a learning module from Maricopa Advanced Technology Education Center. This PDF describes the module; access may be purchased by visiting the MATEC website. Entrapment type pumps operate primarily in the high to ultra-high vacuum ranges. The discussion in this MATEC module includes applications, theory of operation, operating range and preventative maintenance. The focus is on three major types of pumps: cryosorption, cryogenic and sputter-ion. The overall performance of these types of pumps depends on a variety of parameters. For example, it is important that learners understand the balance between pumping speed and capacity. Competency is demonstrated as the learners specify systems for defined process applications.

  8. Modeling Vacuum Arcs

    E-print Network

    Insepov, Z; Proslier, T; Huang, D; Mahalingam, S; Veitzer, S

    2010-01-01

    We are developing a model of vacuum arcs. This model assumes that arcs develop as a result of mechanical failure of the surface due to Coulomb explosions, followed by ionization of fragments by field emission and the development of a small, dense plasma that interacts with the surface primarily through self sputtering and terminates as a unipolar arc capable of producing breakdown sites with high enhancement factors. We have attempted to produce a self consistent picture of triggering, arc evolution and surface damage. We are modeling these mechanisms using Molecular Dynamics (mechanical failure, Coulomb explosions, self sputtering), Particle-In-Cell (PIC) codes (plasma evolution), mesoscale surface thermodynamics (surface evolution), and finite element electrostatic modeling (field enhancements). We can present a variety of numerical results. We identify where our model differs from other descriptions of this phenomenon.

  9. Adhesive bond degradation sensor

    NASA Astrophysics Data System (ADS)

    Wilson, Alan R.; Olsson-Jacques, Christina; Muscat, Richard F.

    2002-11-01

    Early detection of adhesive bond degradation using sensing elements embedded within the 100um bond-line of aluminium epoxy adhesive joints has been demonstrated. Sensing elements of varying heights were fabricated at the ends of narrow conductors on a flexi-circuit carrier. This construction simulates the active sensing region on a patented silicon adhesive bond degradation sensor and has been used to characterize the sensing elements without the expense and time associated with fabricating the complete integrated silicon sensor. The highest elements on the flexi-circuit serve both as electrical pickup studs, providing a circuit from the flexi-circuit to the top aluminium plate, and as spacers to ensure that the shorter sensing elements do not contact the aluminium plate. The non-contacting sensing elements are thus arranged to be close to the metal/adhesive interface and are sensitive to any change in conductivity in this region due to release of ions as the interface is degraded by the environment. Accelerated aging tests were performed on flexi-circuit sensors embedded in the bond-line of double cantilever beam specimens. The specimens were immersed in 50° C water and pre-loaded to just initiate a crack. Load on the specimen was then maintained by applying a constant load point displacement with a very low velocity to ensure that the environment would degrade the bond-line in advance of the crack front. The change of load and the conductivity measured by the sensing elements were then logged with time. The onset of bond degradation was detected approximately 10-20 mm ahead of the crack tip.

  10. Steel bonded dense silicon nitride compositions and method for their fabrication

    DOEpatents

    Landingham, Richard L. (Livermore, CA); Shell, Thomas E. (Tracy, CA)

    1987-01-01

    A two-stage bonding technique for bonding high density silicon nitride and other ceramic materials to stainless steel and other hard metals, and multilayered ceramic-metal composites prepared by the technique are disclosed. The technique involves initially slurry coating a surface of the ceramic material at about 1500.degree. C. in a vacuum with a refractory material and the stainless steel is then pressure bonded to the metallic coated surface by brazing it with nickel-copper-silver or nickel-copper-manganese alloys at a temperature in the range of about 850.degree. to 950.degree. C. in a vacuum. The two-stage bonding technique minimizes the temperature-expansion mismatch between the dissimilar materials.

  11. Steel bonded dense silicon nitride compositions and method for their fabrication

    DOEpatents

    Landingham, R.L.; Shell, T.E.

    1985-05-20

    A two-stage bonding technique for bonding high density silicon nitride and other ceramic materials to stainless steel and other hard metals, and multilayered ceramic-metal composites prepared by the technique are disclosed. The technique involves initially slurry coating a surface of the ceramic material at about 1500/sup 0/C in a vacuum with a refractory material and the stainless steel is then pressure bonded to the metallic coated surface by brazing it with nickel-copper-silver or nickel-copper-manganese alloys at a temperature in the range of about 850/sup 0/ to 950/sup 0/C in a vacuum. The two-stage bonding technique minimizes the temperature-expansion mismatch between the dissimilar materials.

  12. Cartridge getter for vacuum jacketing

    NASA Technical Reports Server (NTRS)

    Luebbers, C. J.

    1977-01-01

    Inexpensively-manufactured getter cartridge save users time in vacuum system maintenance and allows almost anyone to carry out replacement procedure that formerly required skilled welder. Cartridge screws into port in outer wall of vacuum jacket. Getter is replaced by simply unscrewing cartridge rather than cutting and rewelding.

  13. Technical specification for vacuum systems

    Microsoft Academic Search

    Khaw

    1987-01-01

    The vacuum systems at the Stanford Linear Accelerator Center (SLAC) are primarily of all-metal construction and operate at pressures from 10 to 10¹¹ Torr. The primary gas loads during operation result from thermal desorption and beam-induced desorption from the vacuum chamber walls. These desorption rates can be extremely high in the case of hydrocarbons and other contaminants. These specifications place

  14. Vacuum energy as dark matter

    NASA Astrophysics Data System (ADS)

    Albareti, F. D.; Cembranos, J. A. R.; Maroto, A. L.

    2014-12-01

    We consider the vacuum energy of massive quantum fields in an expanding universe. We define a conserved renormalized energy-momentum tensor by means of a comoving cutoff regularization. Using exact solutions for de Sitter space-time, we show that in a certain range of mass and renormalization scales there is a contribution to the vacuum energy density that scales as nonrelativistic matter and that such a contribution becomes dominant at late times. By means of the WKB approximation, we find that these results can be extended to arbitrary Robertson-Walker geometries. We study the range of parameters in which the vacuum energy density would be compatible with current limits on dark matter abundance. Finally, by calculating the vacuum energy in a perturbed Robertson-Walker background, we obtain the speed of sound of density perturbations and show that the vacuum energy density contrast can grow on sub-Hubble scales as in standard cold dark matter scenarios.

  15. Spacetime structure and vacuum entanglement

    E-print Network

    Eduardo Martin-Martinez; Alexander R. H. Smith; Daniel R. Terno

    2015-07-09

    We study the role that both vacuum fluctuations and vacuum entanglement of a scalar field play in identifying the spacetime topology, which is not prescribed from first principles---neither in general relativity or quantum gravity. We analyze how the entanglement and observable correlations acquired between two particle detectors are sensitive to the spatial topology of spacetime. We examine the detector's time evolution to all orders in perturbation theory and then study the phenomenon of vacuum entanglement harvesting in Minkowski spacetime and two flat topologically distinct spacetimes constructed from identifications of the Minkowski space. We show that, for instance, if the spatial topology induces a preferred direction, this direction may be inferred from the dependence of correlations between the two detectors on their orientation. We therefore show that vacuum fluctuations and vacuum entanglement harvesting makes it, in principle, possible to distinguish spacetimes with identical local geometry that differ only in their topology.

  16. Diffuse radiation

    NASA Technical Reports Server (NTRS)

    1981-01-01

    A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

  17. Device-level hermetic packaging of microresonators by RTP aluminum-to-nitride bonding

    Microsoft Academic Search

    Mu Chiao; Liwei Lin

    2006-01-01

    This paper presents a device-level microelectromechanical systems (MEMS) packaging process with accelerated tests and reliability analysis. Surface-micromachined microresonators are sealed inside microcavities by a rapid thermal processing (RTP) aluminum-to-silicon nitride bonding and packaging technique. Chip-to-chip bonding is used to form packages both under atmospheric pressure and in vacuum. The hermeticity of the package seals are evaluated by IPA (isopropyl alcohol)

  18. How many hydrogen-bonded ?-turns are possible?

    PubMed

    Schreiber, Anette; Schramm, Peter; Hofmann, Hans-Jörg

    2011-06-01

    The formation of ?-turns is a possibility to reverse the direction of peptide sequences via five amino acids. In this paper, a systematic conformational analysis was performed to find the possible isolated ?-turns with a hydrogen bond between the first and fifth amino acid employing the methods of ab initio MO theory in vacuum (HF/6-31G*, B3LYP/6-311?+?G*) and in solution (CPCM/HF/6-31G*). Only few ?-turn structures with glycine and alanine backbones fulfill the geometry criteria for the i?(i?+?4) hydrogen bond satisfactorily. The most stable representatives agree with structures found in the Protein Data Bank. There is a general tendency to form additional hydrogen bonds for smaller pseudocycles corresponding to ?- and ?-turns with better hydrogen bond geometries. Sometimes, this competition weakens or even destroys the i?(i?+?4) hydrogen bond leading to very stable double ?-turn structures. This is also the reason why an "ideal" ?-turn with three central amino acids having the perfect backbone angle values of an ?-helix could not be localized. There are numerous hints for stable ?-turns with a distance between the C(?)-atoms of the first and fifth amino acid smaller than 6-7 Å, but without an i?(i?+?4) hydrogen bond. PMID:20842396

  19. Microwave Induced Direct Bonding of Single Crystal Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Budraa, N. K.; Jackson, H. W.; Barmatz, M.

    1999-01-01

    We have heated polished doped single-crystal silicon wafers in a single mode microwave cavity to temperatures where surface to surface bonding occurred. The absorption of microwaves and heating of the wafers is attributed to the inclusion of n-type or p-type impurities into these substrates. A cylindrical cavity TM (sub 010) standing wave mode was used to irradiate samples of various geometry's at positions of high magnetic field. This process was conducted in vacuum to exclude plasma effects. This initial study suggests that the inclusion of impurities in single crystal silicon significantly improved its microwave absorption (loss factor) to a point where heating silicon wafers directly can be accomplished in minimal time. Bonding of these substrates, however, occurs only at points of intimate surface to surface contact. The inclusion of a thin metallic layer on the surfaces enhances the bonding process.

  20. Effect of preoxidation on the bond strength of titanium and porcelain.

    PubMed

    Mahale, K M; Nagda, S J

    2014-06-01

    The purpose of this study was to investigate the effect of preoxidation on porcelain titanium- bond strength and the effect of paste bonder (adhesive) on the titanium porcelain bond strength. 11 specimens of commercially pure titanium (26 x 7 x 3 mm) were prepared by different heat treatments in programmable dental furnace. Identification of the oxides formed on the metal surface was conducted with an X-Ray diffractometer with CuKalpha radiation. Vickers hardness numbers were determine. Additional 50 specimens of commercially pure titanium were used to bond with low fusing porcelain. The bond strength was measured in a universal testing machine. X-ray diffraction analysis of the surface of pure titanium revealed that the relative peak intensity of alpha -Ti decreased and that of TiO2 increased with increasing firing temperature. The Vickers hardness number decreased initially as the temperature increased but it increased remarkably above 900 degrees C & was harder in air than vacuum. The tensile shear bond strength was highest in the green stage i.e. without preoxidation of metal, and decreased above 900 degrees C, and was the lowest in the group without paste bonder application. The difference in bond strengths was statistically highly significant for all groups. Preoxidation under vacuum before porcelain firing can effectively improve bonding. The adhesive provided with the low fusing porcelain helps in the bond between titanium & porcelain. PMID:25134366

  1. Bond University Queensland, Australia

    E-print Network

    Duchowski, Andrew T.

    Private fiber optic Internet network upon subscription o Within walking distance to campus o Large lagoon pool with water features overlooking Lake Orr o An RA from Bond University lives on site The Retreat o Adjacent to The Retreat o 2 and 3 bedrooms o Gourmet kitchen - stone kitchen tops & glass splash backs

  2. Investing in Bonds 

    E-print Network

    Johnson, Jason; Polk, Wade

    2002-08-12

    maturi- ty tend to have higher interest E-163 8-02 INVESTING IN BONDS Jason Johnson and Wade Polk* *Assistant Professor and Extension Economist?Management, and Extension Program Specialist?Risk Management, The Texas A&M University System rates (coupons...

  3. Thread bonds in molecules

    E-print Network

    Ivlev, B

    2015-01-01

    Unusual chemical bonds are proposed. Each bond is almost covalent but is characterized by the thread of a small radius $\\sim 0.6\\times 10^{-11}$cm, between two nuclei in a molecule. The main electron density is concentrated outside the thread as in a covalent bond. The thread is formed by the electron wave function which has a tendency to be singular on it. The singularity along the thread is cut off by electron "vibrations" due to the interaction with zero point electromagnetic oscillations. The electron energy has its typical value of (1-10)eV. Due to the small tread radius the uncertainty of the electron momentum inside the thread is large resulting in a large electron kinetic energy $\\sim 1 MeV$. This energy is compensated by formation of a potential well due to the reduction of the energy of electromagnetic zero point oscillations. This is similar to formation of a negative van der Waals potential. Thread bonds are stable and cannot be created or destructed in chemical or optical processes.

  4. Bonding silicones with epoxies

    Microsoft Academic Search

    Tira

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone

  5. Bonding with the Past.

    ERIC Educational Resources Information Center

    Common Ground: Archeology and Ethnography in the Public Interest, 1998

    1998-01-01

    An interview with Linda Mayro, archaeologist and cultural resources manager for Pima County, Arizona, discusses efforts of local groups to preserve local Native-American and Mexican cultural-heritage sites in oppositon to commercial land developers. A public information campaign led to passage of a $6.4 million historic preservation bond. (SAS)

  6. Durability of bonded assemblies

    Microsoft Academic Search

    Karim Benzarti; Pierre Argoul; Francesco Freddi; Michel Frémond; Thi Hoa Tam Nguyen

    2009-01-01

    An advanced model coupling bulk and interfacial damages is proposed in order to predict the durability of adhesively bonded joints. The underlying theory, based on the principle of virtual power, is briefly presented in the first part of the paper. The second part is devoted to the validation the cited theory. The model is first implemented to describe the damage

  7. Photochemical tissue bonding

    DOEpatents

    Redmond, Robert W. (Brookline, MA); Kochevar, Irene E. (Charlestown, MA)

    2012-01-10

    Photochemical tissue bonding methods include the application of a photosensitizer to a tissue and/or tissue graft, followed by irradiation with electromagnetic energy to produce a tissue seal. The methods are useful for tissue adhesion, such as in wound closure, tissue grafting, skin grafting, musculoskeletal tissue repair, ligament or tendon repair and corneal repair.

  8. A Review of Arcing Phenomena in Vacuum and in the Transition to Atmospheric Pressure Arcs

    Microsoft Academic Search

    C. W. Kimblin

    1982-01-01

    This paper reviews vacuum-arc phenomena, and the effect of low-pressure gaseous ambients on electrode phenomena in the transition to atmospheric pressure arcs. The 5 main areas addressed are cathode-spot phenomena, anode-spot phenomena, the properties of the interelectrode plasma for both diffuse arcs and columnar arcs, the interaction of vacuum arcs with axial and transverse magnetic fields, and finally, the transition

  9. Micromachined pressure gauge for the vacuum range based on damping of a resonator

    NASA Astrophysics Data System (ADS)

    Kurth, Steffen; Hiller, Karla; Zichner, Norbert; Mehner, Jan; Iwert, Thomas; Biehl, Steffen; Doetzel, Wolfram; Gessner, Thomas

    2001-10-01

    Vacuum pressure measuring has been a field low permeated by micromachined devices until now. We designed a micromachined resonating system for friction vacuum gauge and tested it with the related electronics. The Silicon resonator is electrostically driven and capacitively sensed. Working at the fundamental resonant frequency (14 kHz), the damping of the oscillation is a measure for the pressure. We use bulk micromaching for the fabrication of the sensor cells. They consist of two fusion bonded silicon layers forming the resonator and two anodically bonded glass layers for caring sensing electrodes. A modified tuning fork design has been used for the resonator. It has a mechanical Q-factor of 33.000 at the low measurement range. The electronic circuit consists of a phase locked loop for driving at resonance and a PI controller to keep a constant vibration magnitude. The sensor has a nearly logarithmic transfer in a vacuum pressure range of 10-3 mbar ... 100 mbar.

  10. Nickel-palladium bond pads for copper wire bonding

    Microsoft Academic Search

    Horst Clauberg; Petra Backus; Bob Chylak

    2011-01-01

    The semiconductor packaging industry is undergoing a step-change transition from gold to copper wire bonding brought on by a quadrupling of gold cost over the last 8years. The transition has been exceptionally rapid over the last 3years and virtually all companies in the industry now have significant copper wire bonding production. Among the challenges to copper wire bonding is the

  11. Vacuum energy and cosmological evolution

    NASA Astrophysics Data System (ADS)

    Solà, Joan

    2014-07-01

    An expanding universe is not expected to have a static vacuum energy density. The so-called cosmological constant ? should be an approximation, certainly a good one for a fraction of a Hubble time, but it is most likely a temporary description of a true dynamical vacuum energy variable that is evolving from the inflationary epoch to the present day. We can compare the evolving vacuum energy with a Casimir device where the parallel plates slowly move apart ("expand"). The total vacuum energy density cannot be measured, only the effect associated to the presence of the plates, and then also their increasing separation with time. In the universe there is a nonvanishing spacetime curvature R as compared to Minkowskian spacetime that is changing with the expansion. The vacuum energy density must change accordingly, and we naturally expect ??˜R˜H2. A class of dynamical vacuum models that trace such rate of change can be constructed. They are compatible with the current cosmological data, and conveniently extended can account for the complete cosmic evolution from the inflationary epoch till the present days. These models are very close to the ?CDM model for the late universe, but very different from it at the early times. Traces of the inherent vacuum dynamics could be detectable in our recent past.

  12. Vacuum Brazing of Accelerator Components

    NASA Astrophysics Data System (ADS)

    Singh, Rajvir; Pant, K. K.; Lal, Shankar; Yadav, D. P.; Garg, S. R.; Raghuvanshi, V. K.; Mundra, G.

    2012-11-01

    Commonly used materials for accelerator components are those which are vacuum compatible and thermally conductive. Stainless steel, aluminum and copper are common among them. Stainless steel is a poor heat conductor and not very common in use where good thermal conductivity is required. Aluminum and copper and their alloys meet the above requirements and are frequently used for the above purpose. The accelerator components made of aluminum and its alloys using welding process have become a common practice now a days. It is mandatory to use copper and its other grades in RF devices required for accelerators. Beam line and Front End components of the accelerators are fabricated from stainless steel and OFHC copper. Fabrication of components made of copper using welding process is very difficult and in most of the cases it is impossible. Fabrication and joining in such cases is possible using brazing process especially under vacuum and inert gas atmosphere. Several accelerator components have been vacuum brazed for Indus projects at Raja Ramanna Centre for Advanced Technology (RRCAT), Indore using vacuum brazing facility available at RRCAT, Indore. This paper presents details regarding development of the above mentioned high value and strategic components/assemblies. It will include basics required for vacuum brazing, details of vacuum brazing facility, joint design, fixturing of the jobs, selection of filler alloys, optimization of brazing parameters so as to obtain high quality brazed joints, brief description of vacuum brazed accelerator components etc.

  13. Space simulation ultimate pressure lowered two decades by removal of diffusion pump oil contaminants during operation

    NASA Technical Reports Server (NTRS)

    Buggele, A. E.

    1973-01-01

    The complex problem why large space simulation chambers do not realize the true ultimate vacuum was investigated. Some contaminating factors affecting diffusion pump performance have been identified and some advances in vacuum/distillation/fractionation technology have been achieved which resulted in a two decade or more lower ultimate pressure. Data are presented to show the overall or individual contaminating effect of commonly used phthalate ester plasticizers of 390 to 530 molecular weight on diffusion pump performance. Methods for removing contaminants from diffusion pump silicone oil during operation and reclaiming contaminated oil by high vacuum molecular distillation are described.

  14. Changing MFTF vacuum environment

    SciTech Connect

    Margolies, D.; Valby, L.

    1982-08-19

    The Mirror Fusion Test Facility (MFTF) vaccum vessel will be about 60m long and 10m in diameter at the widest point. The allowable operating densities range from 2 x 10/sup 9/ to 5 x 10/sup 10/ particles per cc. The maximum leak rate of 10/sup -6/ tl/sec is dominated during operation by the deliberately injected cold gas of 250 tl/sec. This gas is pumped by over 1000 square meters of cryopanels, external sorbtion pumps and getters. The design and requirements have changed radically over the past several years, and they are still not in final form. The vacuum system design has also changed, but more slowly and less radically. This paper discusses the engineering effort necessary to meet these stringent and changing requirements. Much of the analysis of the internal systems has been carried out using a 3-D Monte Carlo computer code, which can estimate time dependent operational pressures. This code and its use will also be described.

  15. Novel methods of bonding solar cells

    NASA Astrophysics Data System (ADS)

    Thomaier, Rob

    2011-09-01

    Messy liquid adhesives, short work times, long cure times, difficult clean-up of stray adhesive - all of these are associated with liquid adhesives for bonding solar cells. Current adhesion methods have been in place since the '70s: mix a two-part liquid silicone adhesive, coat a portion of adhesive onto a section of substrate, place the cells in a vacuum bag and wait for the adhesive to cure. Alternatively, one can use a fairly complicated robotic procedure to apply adhesive then fix a cell down and, again, wait for the adhesive to cure. Some difficulties that need to be overcome include balancing the amount adhesive to spread out with the available worktime in order to get all the cells onto the substrate with good adhesion; controlling the bondline; ensuring that the adhesive cures correctly after application; and, finally, if there is any re-work, removing the part from the adhesive without damaging everything around it.

  16. Effects of surface treatment on the bonding quality of wafer-level Cu-to-Cu thermo-compression bonding for 3D integration

    NASA Astrophysics Data System (ADS)

    Fan, J.; Lim, D. F.; Tan, C. S.

    2013-04-01

    Various surface treatments are applied for surface oxide removal prior to wafer-level Cu-to-Cu thermo-compression bonding and the bonding quality is systematically analyzed in this work. Three methods are investigated: self-assembled monolayer (SAM) passivation, forming gas annealing and acetic acid wet cleaning. The surface conditions are carefully examined including roughness, contact angle and x-ray photoelectron spectroscopy (XPS) scan. The wafer pairs are bonded at 250 °C under a bonding force of 5500 N for a duration of 1 h in a vacuum environment. The bonding medium consists of a Cu (300 nm) bonding layer and a Ti (50 nm) barrier layer. The bonding quality investigation consists of two parts: hermeticity based on helium leak test and mechanical strength using four-point bending method. Although all samples under test with different surface treatment methods present an excellent hermetic seal and a robust mechanical support, the measurement results show that samples bonded after SAM passivation exhibit the best hermeticity and bonding strength for 3D integration application.

  17. ChemTeacher: Metallic Bonds

    NSDL National Science Digital Library

    2012-07-20

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Metallic Bonds page includes resources for teaching students about metallic bonding.

  18. ChemTeacher: Ionic Bonds

    NSDL National Science Digital Library

    2012-07-20

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Ionic Bonds page includes resources for teaching students about ionic bonding.

  19. ChemTeacher: Covalent Bonds

    NSDL National Science Digital Library

    2012-07-20

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Covalent Bonds page includes resources for teaching students about covalent bonding.

  20. The Illiquidity of Corporate Bonds

    E-print Network

    Bao, Jack

    This paper examines the illiquidity of corporate bonds and its asset-pricing implications. Using transactions data from 2003 to 2009, we show that the illiquidity in corporate bonds is substantial, significantly greater ...

  1. Vacuum Function Operation and Systems

    NSDL National Science Digital Library

    The understanding of vacuum function and systems is essential for students and employees working within the micro- and nanofabrication industry. This presentation/webinar highlights the use, construction, and examples of current vacuum technology systems today. Prepared by WHO, of the Nanotechnology Applications and Career Knowledge (NACK), a National ATE Center, this presentation provides material presented from the instructor/engineer viewpoint. Discussions include vacuum pump function, gauge use and ranges, applicable design considerations, as well as insight on cost and equipment training methodologies that have been utilized by the NACK Center. This site requires a free log-in to access.

  2. Wafer-level vacuum/hermetic packaging technologies for MEMS

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hyun; Mitchell, Jay; Welch, Warren; Lee, Sangwoo; Najafi, Khalil

    2010-02-01

    An overview of wafer-level packaging technologies developed at the University of Michigan is presented. Two sets of packaging technologies are discussed: (i) a low temperature wafer-level packaging processes for vacuum/hermeticity sealing, and (ii) an environmentally resistant packaging (ERP) technology for thermal and mechanical control as well as vacuum packaging. The low temperature wafer-level encapsulation processes are implemented using solder bond rings which are first patterned on a cap wafer and then mated with a device wafer in order to encircle and encapsulate the device at temperatures ranging from 200 to 390 °C. Vacuum levels below 10 mTorr were achieved with yields in an optimized process of better than 90%. Pressures were monitored for more than 4 years yielding important information on reliability and process control. The ERP adopts an environment isolation platform in the packaging substrate. The isolation platform is designed to provide low power oven-control, vibration isolation and shock protection. It involves batch flip-chip assembly of a MEMS device onto the isolation platform wafer. The MEMS device and isolation structure are encapsulated at the wafer-level by another substrate with vertical feedthroughs for vacuum/hermetic sealing and electrical signal connections. This technology was developed for high performance gyroscopes, but can be applied to any type of MEMS device.

  3. Study of the formation, evolution, and dissolution of interfacial defects in silicon wafer bonding

    NASA Astrophysics Data System (ADS)

    Vincent, S.; Penot, J.-D.; Radu, I.; Letertre, F.; Rieutord, F.

    2010-05-01

    Interface defects formed during the wafer bonding process upon annealing have been studied. Based on the hydrogen diffusion in SiO2 and the stability of the bubbles at the bonding interface, models of the growth and further dissolution of the defects are presented. Considering the hydrogen diffusion through the interfacial oxide, diffusion coefficients and activation energy (Ea=0.25 eV) are obtained. It has been shown that the defect dissolution is driven by the exodiffusion of the hydrogen toward the silicon substrates.

  4. Continuing Conversation about Continuing Bonds

    ERIC Educational Resources Information Center

    Klass, Dennis

    2006-01-01

    The article is a response to the contributions the special issue of Death Studies on continuing bonds. The contributions indicate that the conversation among scholars has clarified our thinking on how bonds function in individual grief. The author discussed two issues to help keep the conversation moving: (a) the relationship of continuing bonds

  5. Cyclic Bonds in Branched Polymers

    E-print Network

    Kazumi Suematsu

    2015-02-19

    In the gelation theory it has been implicitly assumed that (I) a cyclic bond is a finite bond that returns to itself; (II) cyclic bonds distribute at random in network structures. In this paper these two assumptions are reexamined from a new point of view. The physical soundness of the assumptions are assessed through comparison with experimental observations.

  6. Coulombic Models in Chemical Bonding.

    ERIC Educational Resources Information Center

    Sacks, Lawrence J.

    1986-01-01

    Compares the coulumbic point charge model for hydrogen chloride with the valence bond model. It is not possible to assign either a nonpolar or ionic canonical form of the valence bond model, while the covalent-ionic bond distribution does conform to the point charge model. (JM)

  7. Low temperature gold wire bonding

    Microsoft Academic Search

    Y. M. Cheung; S. W; S. Ching

    1999-01-01

    We demonstrated that the bonding of gold wires for COB application was feasible at temperatures ~100°C or below by using a wedge bonder with a high frequency ultrasonic transducer (~138 kHz). An automatic rotary bondhead wedge bonder equipped with the transducer was employed to perform wire bonding. Bonding of gold wires was conducted on the aluminum pads of a test

  8. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

  9. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

  10. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

  11. BONDING PROCEDURES MUNICIPAL STREETS SEMINAR

    E-print Network

    BONDING PROCEDURES MUNICIPAL STREETS SEMINAR Ahlers & Cooney, P.C. Mark Cory & Minniette Bucklin Association, Polk County and Iowa Bar Associations and the National Association of Bond Lawyers. Mr. Cory has of governmental bonds, but she also advises clients with respect to issues involving economic development

  12. Infrared spectroscopic investigation of photoionization-induced acidic C-h bonds in cyclic ethers.

    PubMed

    Xie, Min; Matsuda, Yoshiyuki; Fujii, Asuka

    2015-06-01

    Infrared (IR) predissociation spectroscopy based on vacuum-ultraviolet photoionization detection is performed for the neutral and cationic tetrahydrofuran (THF) and tetrahydropyran (THP). The CH bonds in neutral THF and THP are regarded as aprotic, even though the CH bonds are weakened by the negative hyperconjugation. After 118 nm photoionization, however, the negative hyperconjugation changes to the positive hyperconjugation and their CH bond acidities remarkably increase. In the IR spectrum of the THF cation, an intense band is observed at ca. 2700 cm(-1). This band is assigned to the antisymmetric stretch vibration of the two C?H bonds next to the oxygen atom. The high intensity and low frequency of this band are due to the delocalization of the ? electrons of the two C?H bonds to the singly occupied molecular orbital (SOMO) through the hyperconjugation. In the IR spectrum of the THP cation, on the other hand, the stretch bands of the C?H bonds do not show obvious low-frequency shift and intensity enhancement, while the stretch band of the equatorial C?H bond, at the para-position to the oxygen atom, appears at 2855 cm(-1) with high intensity. This acidity enhancement of the equatorial C?H bond is attributed to the mutiple hyperconjugation among the C?H bond, two C?C? bonds, and SOMO of the oxygen atom. These results suggest that the difference of the hyperconjugation mechanism between the THF and THP cations arises from their preferable conformations. PMID:25978525

  13. Low temperature reactive bonding

    DOEpatents

    Makowiecki, Daniel M. (Livermore, CA); Bionta, Richard M. (Livermore, CA)

    1995-01-01

    The joining technique requires no external heat source and generates very little heat during joining. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process.

  14. Pollution prevention in vacuum processes

    SciTech Connect

    Mulholland, K.L.; Dyer, J.A. [E.I. du Pont de Nemours and Co., Wilmington, DE (United States)] [E.I. du Pont de Nemours and Co., Wilmington, DE (United States)

    1999-05-01

    The gaseous emissions from vacuum systems often contain volatile organic compounds (VOCs)--one or more of which may be regulated as Hazardous Air Pollutants (HAPs) under the 1990 Clean Air Act Amendments. Typically, regulated emission sources will require greater than 98% control of using an end-of-pipe abatement or recovery technology. VOCs from vacuum generation are expensive to control and increase the investment and operating cost of the vacuum system. When noncondensibles or inerts are present, the amount of VOCs emitted to the environment will increase dramatically. This article discusses approaches which process and project engineers can apply to reduce or eliminate vacuum system emissions. Actual case histories are included which reflect the range of solutions that are being applied.

  15. Alumina barrier for vacuum brazing

    NASA Technical Reports Server (NTRS)

    Beuyukian, C. S.

    1980-01-01

    Heating platens of vacuum-brazing press will not stick to workpiece if aluminum oxide "paper" is interposed. Paper does not disintegrate in press, will not contaminate braze alloy, and helps form smoothly contoured, regular fillet at brazed edges.

  16. Disulfide bonds of acetylcholinesterase

    SciTech Connect

    MacPhee-Quigley, K.; Vedvick, T.; Taylor, P.; Taylor, S.

    1986-05-01

    The positions of the inter- and intrasubunit disulfide bridges were established for the 11S form of acetylcholinesterase (AChE) isolated from Torpedo californica. A major form of AChE localized within the basal lamina of the synapse is a dimensionally asymmetric molecule which contains either two (13S) or three (17S) sets of catalytic subunits linked to collagenous and non-collagenous structural subunits. Limited proteolysis yields a tetramer of catalytic subunits which sediments at 11S. Each catalytic subunit contains 8 cysteine residues. Initially, these Cys residues were identified following trypsin digestion of the reduced protein alkylated with (/sup 14/C)-iodoacetate. Peptides were resolved by gel filtration followed by reverse phase HPLC. To determine the disulfide bonding profile, native non-reduced 11S AChE was treated with a fluorescent, sulfhydryl-specific reagent, monobromobimane, prior to proteolytic digestion. One fluorescent Cys peptide was identified indicating that a single sulfhydryl residue was present in its reduced form. Three pairs of disulfide bonded peptides were identified, sequenced, and localized in the polypeptide chain. The Cys residue that is located in the C-terminal tryptic peptide was disulfide bonded to an identical peptide and thus forms the intersubunit crosslink. Finally, the cysteine positions have been compared with the sequence of the homologous protein, thyroglobulin. Both likely share a common pattern of folding.

  17. Neutron radiation hardness of vacuum compatible two-component adhesives

    NASA Astrophysics Data System (ADS)

    Bertsch, J.; Goeltl, L.; Kirch, K.; Lauss, B.; Zubler, R.

    2009-04-01

    This paper reports the investigation of the irradiation dependent bonding strength of two-component glues which have low outgassing compatible with vacuum applications. The strength of the glue joints is compared before and after exposure to a thermal neutron fluence of 2.35×10 neutrons per cm. The goal of this work is to establish a glue which is applicable to join glass and metal parts of the ultra-cold neutron (UCN) guide system at the Paul Scherrer Institute's UCN source.

  18. Evaluation of wire bonding performance, process conditions, and metallurgical integrity of chip on board wire bonds

    Microsoft Academic Search

    Daniel T. Rooney; Deepak Nager; David Geiger; Dongkai Shanguan

    2005-01-01

    Chip on board wire bonding presents challenges to modern wire bonding technology which include smaller, closely spaced wire bond pads; bonding to soft substrates without special processing and pad construction; and diverse first bond and second bond metallurgies. These challenges are addressed by extensive bonding accuracy tests, a design of experiments approach for optimizing wire bond process parameters, reliability testing,

  19. Diffusion bonded boron/aluminum spar-shell fan blade

    NASA Technical Reports Server (NTRS)

    Carlson, C. E. K.; Cutler, J. L.; Fisher, W. J.; Memmott, J. V. W.

    1980-01-01

    Design and process development tasks intended to demonstrate composite blade application in large high by-pass ratio turbofan engines are described. Studies on a 3.0 aspect radio space and shell construction fan blade indicate a potential weight savings for a first stage fan rotor of 39% when a hollow titanium spar is employed. An alternate design which featured substantial blade internal volume filled with titanium honeycomb inserts achieved a 14% potential weight savings over the B/M rotor system. This second configuration requires a smaller development effort and entails less risk to translate a design into a successful product. The feasibility of metal joining large subsonic spar and shell fan blades was demonstrated. Initial aluminum alloy screening indicates a distinct preference for AA6061 aluminum alloy for use as a joint material. The simulated airfoil pressings established the necessity of rigid air surfaces when joining materials of different compressive rigidities. The two aluminum alloy matrix choices both were successfully formed into blade shells.

  20. Fabrication of a first wall panel by diffusion bonding

    Microsoft Academic Search

    L. F Moreschi; A Pizzuto; I Alessandrini

    2002-01-01

    Separated First Wall Panels mechanically attached to a shield block is now the reference concept for the Primary Wall Modules of RTO\\/RC ITER. The objective of the present work is to demonstrate the practical feasibility of a First Wall Panel utilizing a duplex round (steel) in square (copper) heat sink wound around a steel core and covered by Beryllium armour

  1. Developing a laser shockwave model for characterizing diffusion bonded interfaces

    NASA Astrophysics Data System (ADS)

    Lacy, Jeffrey M.; Smith, James A.; Rabin, Barry H.

    2015-03-01

    The US National Nuclear Security Agency has a Global Threat Reduction Initiative (GTRI) with the goal of reducing the worldwide use of high-enriched uranium (HEU). A salient component of that initiative is the conversion of research reactors from HEU to low enriched uranium (LEU) fuels. An innovative fuel is being developed to replace HEU in high-power research reactors. The new LEU fuel is a monolithic fuel made from a U-Mo alloy foil encapsulated in Al-6061 cladding. In order to support the fuel qualification process, the Laser Shockwave Technique (LST) is being developed to characterize the clad-clad and fuel-clad interface strengths in fresh and irradiated fuel plates. LST is a non-contact method that uses lasers for the generation and detection of large amplitude acoustic waves to characterize interfaces in nuclear fuel plates. However, because the deposition of laser energy into the containment layer on a specimen's surface is intractably complex, the shock wave energy is inferred from the surface velocity measured on the backside of the fuel plate and the depth of the impression left on the surface by the high pressure plasma pulse created by the shock laser. To help quantify the stresses generated at the interfaces, a finite element method (FEM) model is being utilized. This paper will report on initial efforts to develop and validate the model by comparing numerical and experimental results for back surface velocities and front surface depressions in a single aluminum plate representative of the fuel cladding.

  2. Microstructural and mechanical characterization of diffusion bonded hybrid joints

    Microsoft Academic Search

    G. Çam; U. Özdemir; V. Ventzke; M. Koçak

    2008-01-01

    Ti-alloys, particularly TiAl, are becoming attractive for the use in the production of high-temperature components such as\\u000a turbine blades and exhaust valves, owing to their low density. However, these components may not be cost-effectively cast\\u000a totally from TiAl alloys and casting defects may occur in investment casting of these complex parts. Other manufacturing technologies,\\u000a such as machining, cannot be economically

  3. Cold cathode vacuum gauging system

    DOEpatents

    Denny, Edward C. (Knoxville, TN)

    2004-03-09

    A vacuum gauging system of the cold cathode type is provided for measuring the pressure of a plurality of separate vacuum systems, such as in a gas centrifuge cascade. Each casing is fitted with a gauge tube assembly which communicates with the vacuum system in the centrifuge casing. Each gauge tube contains an anode which may be in the form of a slender rod or wire hoop and a cathode which may be formed by the wall of the gauge tube. The tube is provided with an insulated high voltage connector to the anode which has a terminal for external connection outside the vacuum casing. The tube extends from the casing so that a portable magnet assembly may be inserted about the tube to provide a magnetic field in the area between the anode and cathode necessary for pressure measurements in a cold cathode-type vacuum gauge arrangement. The portable magnetic assembly is provided with a connector which engages the external high voltage terminal for providing power to the anode within in the gauge tube. Measurement is made in the same manner as the prior cold cathode gauges in that the current through the anode to the cathode is measured as an indication of the pressure. By providing the portable magnetic assembly, a considerable savings in cost, installation, and maintenance of vacuum gauges for pressure measurement in a gas centrifuge cascade is realizable.

  4. Relativistic diffusion.

    PubMed

    Haba, Z

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed. PMID:19391727

  5. Relativistic diffusion

    E-print Network

    Z. Haba

    2009-02-26

    We discuss a relativistic diffusion in the proper time in an approach of Schay and Dudley. We derive (Langevin) stochastic differential equations in various coordinates.We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form.We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution.We discuss drag terms leading to an equilibrium distribution.The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Juettner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  6. Relativistic diffusion

    Microsoft Academic Search

    Z. Haba

    2009-01-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic

  7. Diffusion Models

    NSDL National Science Digital Library

    Alexei Sharov

    Web-based intructional material describing the use of diffusion models in population ecology. This page is part of a set of on-line lectures on Quantitative Population Ecology produced by Alexei Sharov in the Department of Entomology at Virginia Tech.

  8. Relativistic diffusion

    NASA Astrophysics Data System (ADS)

    Haba, Z.

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  9. 77 FR 32128 - Cancellation of Bond Subject to Enhanced Bonding Requirements Upon CBP's Acceptance of Qualified...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-31

    ...Cancellation of Bond Subject to Enhanced Bonding Requirements Upon CBP's Acceptance of...amount was calculated pursuant to enhanced bonding requirements (EBR bond) upon the agency's...INFORMATION: Background I. Enhanced Bonding Requirements In 2004, U.S....

  10. Bond Inspection by Impact Test

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Xiang, D.; Qin, Y.; Li, F.; Coulter, R. V.

    2010-02-01

    Kissing bond detection has been a challenging issue for NDE of bonded structures in aeronautical industry. A novel impact test technique for bond inspection has been developed, which shows great potential for kissing bond detection. The impact test employs a solenoid to produce impact forces in a bonded structure, and the induced elastic wave in the structure was picked up by an EMAT sensor, which located side by side with the solenoid. Both solenoid and EMAT sensor are integrated into a tap header that is mounted onto an automatic 2-D scanner to realize an automatic 2-D scanning. Multiple samples with artificial defects including kissing bonds and disbonds were used to test the impact test technique. The results show that those bond defects in the samples can be detected by the developed impact test technique. For comparison purpose, those samples were also tested with traditional ultrasonic C-scan.

  11. Teaching vacuum technology using spreadsheet calculations

    Microsoft Academic Search

    R. E. Pearson; G. M. Atkinson

    2003-01-01

    Vacuum technology is an important part of nano-fabrication. Automated control systems for vacuum equipment have made operation easy and safe but have also isolated the user from the need to understand the physics of vacuum systems. In spite of this, many equipment and process decisions revolve around choices made concerning the vacuum components of a processing tool. Students can use

  12. Leak rate measurements for large vacuum chambers

    Microsoft Academic Search

    HE Nuss; I Streuff

    1995-01-01

    For large vacuum chambers of volume between 50 and 500 m3, which are required for space simulation and thermal vacuum testing of spacecraft systems and subsystems, a specific method for the determination of the vacuum chamber leak rate is described. The main characteristics of the facility including irradiation, thermal shroud, motion and vacuum subsystem are presented. The outgassing and desorption

  13. Kinetics of scrap tyre pyrolysis under vacuum conditions.

    PubMed

    Lopez, Gartzen; Aguado, Roberto; Olazar, Martín; Arabiourrutia, Miriam; Bilbao, Javier

    2009-10-01

    Scrap tyre pyrolysis under vacuum is attractive because it allows easier product condensation and control of composition (gas, liquid and solid). With the aim of determining the effect of vacuum on the pyrolysis kinetics, a study has been carried out in thermobalance. Two data analysis methods have been used in the kinetic study: (i) the treatment of experimental data of weight loss and (ii) the deconvolution of DTG (differential thermogravimetry) curve. The former allows for distinguishing the pyrolysis of the three main components (volatile components, natural rubber and styrene-butadiene rubber) according to three successive steps. The latter method identifies the kinetics for the pyrolysis of individual components by means of DTG curve deconvolution. The effect of vacuum in the process is significant. The values of activation energy for the pyrolysis of individual components of easier devolatilization (volatiles and NR) are lower for pyrolysis under vacuum with a reduction of 12K in the reaction starting temperature. The kinetic constant at 503K for devolatilization of volatile additives at 0.25atm is 1.7 times higher than that at 1atm, and that corresponding to styrene-butadiene rubber at 723K is 2.8 times higher. Vacuum enhances the volatilization and internal diffusion of products in the pyrolysis process, which contributes to attenuating the secondary reactions of the repolymerization and carbonization of these products on the surface of the char (carbon black). The higher quality of carbon black is interesting for process viability. The large-scale implementation of this process in continuous mode requires a comparison to be made between the economic advantages of using a vacuum and the energy costs, which will be lower when the technologies used for pyrolysis require a lower ratio between reactor volume and scrap tyre flow rate. PMID:19589669

  14. Stable, high quantum efficiency silicon photodiodes for vacuum-UV applications

    NASA Astrophysics Data System (ADS)

    Korde, Raj; Canfield, L. Randall; Wallis, Brad

    1988-01-01

    Silicon photodiodes have been developed by defect-free phosphorus diffusion having practically no carrier recombination at the SiSiO2 interface or in the front diffused region. The quantum efficiency of these photodiodes was found to be around 120 percent at 100 nm. Unlike the previously tested silicon photodiodes, the developed photodiodes exhibit extremely stable quantum efficiency over extended periods of time. The possibility of using these photodiodes as vacuum ultraviolet detector standards is being currently investigated.

  15. The Dissociation Energies of He2, HeH, and ArH; A Bond Function Study

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Arnold, James (Technical Monitor)

    1998-01-01

    The bond energies and bond lengths are determined for He2, HeH, and ArH at the CCSD(T) level using both atom-centered basis sets and those that include bond functions. The addition of bond functions dramatically improves the rate of convergence of the results with respect to the size of the atom-centered basis set; with bond functions, triple zeta atom-centered basis set, outperform quintuple zeta basis sets without bond functions. The addition of bond functions also reduces the number of diffuse functions that must be added to the atom-centered sets. Employing bond functions appear to offer a very cost effective method of computing the interaction between weakly bound systems, especially for He.

  16. Theoretical Aspects of the Biological Catch Bond

    Microsoft Academic Search

    Oleg V. Prezhdo; Yuriy V. Pereverzev

    2009-01-01

    he biological catch bond is fascinating and counterintuitive. When an external force is applied to a catch bond, either in vivo or in vitro, the bond resists breaking and becomes stronger instead. In contrast, ordinary slip bonds, which represent the vast majority of biological and chemical bonds, dissociate faster when subjected to a force. Catch-bond behavior was first predicted theoretically

  17. Sulfur passivation techniques for III-V wafer bonding

    NASA Astrophysics Data System (ADS)

    Jackson, Michael James

    The use of direct wafer bonding in a multijunction III-V solar cell structure requires the formation of a low resistance bonded interface with minimal thermal treatment. A wafer bonded interface behaves as two independent surfaces in close proximity, hence a major source of resistance is Fermi level pinning common in III-V surfaces. This study demonstrates the use of sulfur passivation in III-V wafer bonding to reduce the energy barrier at the interface. Two different sulfur passivation processes are addressed. A dry sulfur passivation method that utilizes elemental sulfur vapor activated by ultraviolet light in vacuum is compared with aqueous sulfide and native oxide etch treatments. Through the addition of a sulfur desorption step in vacuum, the UV-S treatment achieves bondable surfaces free of particles contamination or surface roughening. X-ray photoelectron spectroscopy measurements of the sulfur treated GaAs surfaces find lower levels of oxide and the appearance of sulfide species. After 4 hrs of air exposure, the UV-S treated GaAs actually showed an increase in the amount of sulfide bonded to the semiconductor, resulting in less oxidation compared to the aqueous sulfide treatment. Large area bonding is achieved for sulfur treated GaAs / GaAs and InP / InP with bulk fracture strength achieved after annealing at 400 °C and 300 °C respectively, without large compressive forces. The electrical conductivity across a sulfur treated 400 °C bonded n-GaAs/n-GaAs interface significantly increased with a short anneal (1-2 minutes) at elevated temperatures (50--600 °C). Interfaces treated with the NH4OH oxide etch, on the other hand, exhibited only mild improvement in accordance with previously published studies in this area. TEM and STEM images revealed similar interfacial microstructure changes with annealing for both sulfur treated and NH4OH interfaces, whereby some areas have direct semiconductor-semiconductor contact without any interfacial layer. Fitting the observed temperature dependence of zero bias conductance using a model for tunneling through a grain boundary reveals that the addition of sulfur at the interface lowered the interfacial energy barrier by 0.2 eV. The interface resistance for these sulfur-treated structures is less than 0.03 O·cm 2 at room temperature. These results emphasize that sulfur passivation techniques reduce interface states that otherwise limit the implementation of wafer bonding for high efficiency solar cells and other devices.

  18. Low temperature reactive bonding

    DOEpatents

    Makowiecki, D.M.; Bionta, R.M.

    1995-01-17

    The joining technique is disclosed that requires no external heat source and generates very little heat during joining. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process. 5 figures.

  19. Probability distribution of the vacuum energy density

    E-print Network

    G. Duplancic; D. Glavan; H. Stefancic

    2010-11-26

    As the vacuum state of a quantum field is not an eigenstate of the Hamiltonian density, the vacuum energy density can be represented as a random variable. We present an analytical calculation of the probability distribution of the vacuum energy density for real and complex massless scalar fields in Minkowski space. The obtained probability distributions are broad and the vacuum expectation value of the Hamiltonian density is not fully representative of the vacuum energy density.

  20. Probability distribution of the vacuum energy density

    SciTech Connect

    Duplancic, Goran; Stefancic, Hrvoje [Theoretical Physics Division, Rudjer Boskovic Institute, P.O. Box 180, HR-10002 Zagreb (Croatia); Glavan, Drazen [Department of Physics, Faculty of Science, University of Zagreb, P.O. Box 331, HR-10002 Zagreb (Croatia)

    2010-12-15

    As the vacuum state of a quantum field is not an eigenstate of the Hamiltonian density, the vacuum energy density can be represented as a random variable. We present an analytical calculation of the probability distribution of the vacuum energy density for real and complex massless scalar fields in Minkowski space. The obtained probability distributions are broad and the vacuum expectation value of the Hamiltonian density is not fully representative of the vacuum energy density.

  1. Plasma cleaning on bond pad surfaces for gold wire bonding

    Microsoft Academic Search

    Wu-Hu Li; Klaus Reingruber; Norbert Mais; Albert Acuesta; Christian Alde Yape

    2009-01-01

    Ar plasma was employed to remove\\/reduce the oxidation of two typical types of bond pad surfaces, namely aluminum (Al) surface and gold (Au)-coated palladium (Pd) surface, prior to Au wire-bonding process. Field emission scanning electron microscopy (FESEM) and Auger electron spectroscopy (AES) were employed to characterize the bond pad surfaces without and with the plasma cleaning. Processability and reliability results

  2. Measurement of partial pressures in vacuum technology and vacuum physics

    NASA Technical Reports Server (NTRS)

    Huber, W. K.

    1986-01-01

    It is pointed out that the measurement of gaseous pressures of less than 0.0001 torr is based on the ionization of gas atoms and molecules due to collisions with electrons. The particle density is determined in place of the pressure. The ionization cross sections for molecules of various gases are discussed. It is found that the true pressure in a vacuum system cannot be determined with certainty if it is unknown which gas is present. Effects of partial pressure determination on the condition of the vacuum system are discussed together with ion sources, systems of separation, and ion detection.

  3. The coefficient of bond thermal expansion measured by extended x-ray absorption fine structure

    NASA Astrophysics Data System (ADS)

    Fornasini, P.; Grisenti, R.

    2014-10-01

    The bond thermal expansion is in principle different from the lattice expansion and can be measured by correlation sensitive probes such as extended x-ray absorption fine structure (EXAFS) and diffuse scattering. The temperature dependence of the coefficient ?bond(T) of bond thermal expansion has been obtained from EXAFS for CdTe and for Cu. A coefficient ?tens(T) of negative expansion due to tension effects has been calculated from the comparison of bond and lattice expansions. Negative lattice expansion is present in temperature intervals where ?bond prevails over ?tens; this real-space approach is complementary but not equivalent to the Grüneisen theory. The relevance of taking into account the asymmetry of the nearest-neighbours distribution of distances in order to get reliable bond expansion values and the physical meaning of the third cumulant are thoroughly discussed.

  4. Solder extrusion pressure bonding process and bonded products produced thereby

    DOEpatents

    Beavis, Leonard C. (Albuquerque, NM); Karnowsky, Maurice M. (Albuquerque, NM); Yost, Frederick G. (Ceder Crest, NM)

    1992-01-01

    Production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about -40.degree. C. and 110.degree. C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

  5. Solder extrusion pressure bonding process and bonded products produced thereby

    DOEpatents

    Beavis, L.C.; Karnowsky, M.M.; Yost, F.G.

    1992-06-16

    Disclosed is a process for production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about [minus]40 C and 110 C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

  6. From diffusion pumps to cryopumps: The conversion of GSFC's space environment simulator

    Microsoft Academic Search

    Ron Cary

    1992-01-01

    The SES (Space Environmental Simulator), largest of the Thermal Vacuum Facilities at The Goddard Space Flight Center, recently was converted from an oil diffusion pumped chamber to a Cryopumped chamber. This modification was driven by requirements of flight projects. The basic requirement was to retain or enhance the operational parameters of the chamber such as pumping speed, ultimate vacuum, pump

  7. Eutectic bonding of boron-aluminum structural components. II

    NASA Technical Reports Server (NTRS)

    Niemann, J. T.; Garrett, R. A.

    1974-01-01

    Eutectic bonding is a diffusion brazing process developed for fabricating boron-aluminum components from composite monolayer. This process relies on the diffusion of a thin surface film of copper into the aluminum matrix to form a liquid phase when heated above the copper-aluminum eutectic temperature of 1018 F. This type of fabrication offers design flexibility in that skin thickness may be varied, the stiffness geometry and orientation can be varied, and local reinforcement can be added. In addition, this type of boron-aluminum structure offers high efficiency. Also, this method of construction can be cost-comparative with complex titanium shapes; simple tooling permits easy layup, bonding is a one-step operation, and little finish machining is required.

  8. Tracer gas diffusion sampling test plan

    SciTech Connect

    Rohay, V.J.

    1993-10-01

    Efforts are under way to employ active and passive vapor extraction to remove carbon tetrachloride from the soil in the 200 West Area an the Hanford Site as part of the 200 West Area Carbon Tetrachloride Expedited Response Action. In the active approach, a vacuum is applied to a well, which causes soil gas surrounding the well to be drawn up to the surface. The contaminated air is cleaned by passage through a granular activated carbon bed. There are questions concerning the radius of influence associated with application of the vacuum system and related uncertainties about the soil-gas diffusion rates with and without the vacuum system present. To address these questions, a series of tracer gas diffusion sampling tests is proposed in which an inert, nontoxic tracer gas, sulfur hexafluoride (SF{sub 6}), will be injected into a well, and the rates of SF{sub 6} diffusion through the surrounding soil horizon will be measured by sampling in nearby wells. Tracer gas tests will be conducted at sites very near the active vacuum extraction system and also at sites beyond the radius of influence of the active vacuum system. In the passive vapor extraction approach, barometric pressure fluctuations cause soil gas to be drawn to the surface through the well. At the passive sites, the effects of barometric ``pumping`` due to changes in atmospheric pressure will be investigated. Application of tracer gas testing to both the active and passive vapor extraction methods is described in the wellfield enhancement work plan (Rohay and Cameron 1993).

  9. The source of chemical bonding.

    PubMed

    Needham, Paul

    2014-03-01

    Developments in the application of quantum mechanics to the understanding of the chemical bond are traced with a view to examining the evolving conception of the covalent bond. Beginning with the first quantum mechanical resolution of the apparent paradox in Lewis's conception of a shared electron pair bond by Heitler and London, the ensuing account takes up the challenge molecular orbital theory seemed to pose to the classical conception of the bond. We will see that the threat of delocalisation can be overstated, although it is questionable whether this should be seen as reinstating the issue of the existence of the chemical bond. More salient are some recent developments in a longstanding discussion of how to understand the causal aspects of the bonding interaction--the nature of the force involved in the covalent link--which are taken up in the latter part of the paper. PMID:24984444

  10. Design and construction of a compact vacuum furnace for scientific research

    NASA Astrophysics Data System (ADS)

    Lee, Chin C.; Wang, David T.; Choi, Won S.

    2006-12-01

    The design, construction, and measurement of a compact vacuum furnace are reported. This type of furnace has many scientific applications in material processing and growth research. One example is the fluxless bonding process, where elevated temperature is needed to melt the solder and vacuum environment is required to inhibit solder oxidation. The primary objective of the furnace design is to keep the vacuum enclosure cool using only natural convection while allowing the heating platform to reach high temperature. This characteristic is necessary to enable us to seal the vacuum chamber using O-rings. To achieve this, the platform was designed to be thermally isolated from the chamber enclosure. Heat losses from the platform by conduction, convection, and radiation were analyzed. The dominating loss was found to be caused by the blackbody radiation, which can thus be used to estimate the relationship between platform temperature and the drive power needed. With a graphite platform of 75×75×25mm3, only 270W of power is needed to drive the platform to 400°C. At this temperature, the temperature of the furnace enclosure is below 55°C, allowing O-rings to be used to seal the vacuum chamber. Using a mechanical pump, the furnace can be pumped down to 40mTorr, which is low enough for our fluxless bonding processes. With a temperature controller, the platform temperature can be controlled within 1%. The heat-up time to 400°C is only 7min.

  11. Materials Science and Engineering A 394 (2005) 4352 NiAl bond coats made by a directed vapor deposition approach

    E-print Network

    Wadley, Haydn

    2005-01-01

    in revised form 28 October 2004 Abstract Intermetallic, nickel aluminide alloys are widely used as bond coat- nificantly affected by the bond coats composition. Near equiatomic ( -phase) nickel aluminide alloys have a B­diffusion heat treatments was later explored as a method for synthesizing thin film nickel aluminides [13

  12. Mathematical theory of physical vacuum

    NASA Astrophysics Data System (ADS)

    Magnitskii, N. A.

    2011-06-01

    This article sets out mathematical basics of unifying fundamental physical theory, with a single postulate of nonvoid physical vacuum. It will be shown that all basic equations of classical electrodynamics, quantum mechanics and gravitation theory could be derived from two nonlinear equations, which define dynamics of physical vacuum in three-dimensional Euclidean space and, in turn, are derived from equations of Newtonian mechanics. Through the characteristics of physical vacuum, namely its density and propagation velocity of various density's perturbations, such principal physical conceptions as matter and antimatter, electric, magnetic and gravitational fields, velocity of light, electron, photon and other elementary particles, internal energy, mass, charge, spin, quantum properties, Planck constant and fine structure constant will have clear and sane definitions.

  13. Impedances of Laminated Vacuum Chambers

    SciTech Connect

    Burov, A.; Lebedev, V.; /Fermilab

    2011-06-22

    First publications on impedance of laminated vacuum chambers are related to early 70s: those are of S. C. Snowdon [1] and of A. G. Ruggiero [2]; fifteen years later, a revision paper of R. Gluckstern appeared [3]. All the publications were presented as Fermilab preprints, and there is no surprise in that: the Fermilab Booster has its laminated magnets open to the beam. Being in a reasonable mutual agreement, these publications were all devoted to the longitudinal impedance of round vacuum chambers. The transverse impedance and the flat geometry case were addressed in more recent paper of K. Y. Ng [4]. The latest calculations of A. Macridin et al. [5] revealed some disagreement with Ref. [4]; this fact stimulated us to get our own results on that matter. Longitudinal and transverse impendances are derived for round and flat laminated vacuum chambers. Results of this paper agree with Ref. [5].

  14. Visualizing the mixed bonding properties of liquid boron with high-resolution x-ray compton scattering.

    PubMed

    Okada, J T; Sit, P H-L; Watanabe, Y; Barbiellini, B; Ishikawa, T; Wang, Y J; Itou, M; Sakurai, Y; Bansil, A; Ishikawa, R; Hamaishi, M; Paradis, P-F; Kimura, K; Ishikawa, T; Nanao, S

    2015-05-01

    Bonding characteristics of liquid boron at 2500 K are studied by using high-resolution Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parrinello molecular dynamics simulations. Covalent bond pairs are clearly shown to dominate in liquid boron along with the coexistence of diffuse pairs. Our study reveals the complex bonding pattern of liquid boron and gives insight into the unusual properties of this high-temperature liquid. PMID:25978262

  15. VersaBond bone cement

    Microsoft Academic Search

    Tore Dalén; Kjell G. Nilsson

    2005-01-01

    VersaBond is a newly developed bone cement. To investigate its clinical performance, VersaBond was compared to Palacos R in a prospective randomized study in total knee replacement. Fifty-nine patients (61 knees) undergoing total knee replacement were randomized to either VersaBond or Palacos R bone cement and followed for 24 months using radiostereometric analysis (RSA).Up to 2 years there were no

  16. Beryllium and Strong Hydrogen Bonds

    Microsoft Academic Search

    T. Mark McCleskey; Brian L. Scott

    2009-01-01

    We compare beryllium to H and show that beryllium can displace H in many “strong hydrogen bonds” where Be as a “tetrahedral proton” (O-Be-O angle is tetrahedral as opposed to the nearly linear O-H—O angle) is thermodynamically preferred. The strong hydrogen bond provides two advantages. First, the O–X distance in a strong hydrogen bond is in the range 2.4–2.8 Å,

  17. 27 CFR 70.282 - Single bond in lieu of multiple bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Single bond in lieu of multiple bonds. 70...Occupational) Tax Bonds § 70.282 Single bond in lieu of multiple bonds. In the case of bonds required under this part, a single bond will not be accepted in lieu of...

  18. 27 CFR 70.282 - Single bond in lieu of multiple bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Single bond in lieu of multiple bonds. 70...Occupational) Tax Bonds § 70.282 Single bond in lieu of multiple bonds. In the case of bonds required under this part, a single bond will not be accepted in lieu of...

  19. 27 CFR 70.282 - Single bond in lieu of multiple bonds.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2011-04-01 true Single bond in lieu of multiple bonds. 70...Occupational) Tax Bonds § 70.282 Single bond in lieu of multiple bonds. In the case of bonds required under this part, a single bond will not be accepted in lieu of...

  20. 27 CFR 70.282 - Single bond in lieu of multiple bonds.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Single bond in lieu of multiple bonds. 70...Occupational) Tax Bonds § 70.282 Single bond in lieu of multiple bonds. In the case of bonds required under this part, a single bond will not be accepted in lieu of...

  1. Modeling the effects of an axial magnetic field on the vacuum arc

    Microsoft Academic Search

    Michael Keidar; Michael Bruce Schulman

    2001-01-01

    A quantitative two-dimensional model of a vacuum arc in an applied magnetic field is presented. For the particular case, a uniform axial magnetic field BZ, it provides a unified condition for the two regimes of arc voltage versus BZ, i.e. ? the steeply falling voltage branch (low BZ), and the slowly rising voltage branch (high BZ, which characterizes the diffuse

  2. Interaction between Vacuum Arcs and Transverse Magnetic Fields with Application to Current Limitation

    Microsoft Academic Search

    P. R. Emtage; C. W. Kimblin; J. G. Gorman; F. A. Holmes; J. V. R. Heberlein; R. E. Voshall; P. G. Slade

    1980-01-01

    The interaction between diffuse vacuum arcs and magnetic fields applied transverse to the electrode axis has been investigated both theoretically and experimentally. For arc currents < 6 kA, Hall electric fields, generated by the interaction, bow the plasma out of contact with the anode and raise the arc voltage. In the presence of a parallel capacitor, the arc current falls

  3. Events Associated with Zero Current Passage during the Rapid Commutation of a Vacuum Arc

    Microsoft Academic Search

    Susan E. Childs; Allan N. Greenwood; J. S. Sullivan

    1983-01-01

    Events associated with the rapid commutation of the current in a diffuse vacuum arc are explored experimentally and analytically in the short interval during which the current is brought to zero and the recovery voltage is established across the residual plasma. A brief pause of the order of 100 ns is observed between the passage of current through zero and

  4. In the vacuum: Physicists produce a Bose-Einstein condensate in a

    E-print Network

    Falge, Eva

    the brain's circuit diagrams. Diffusion tensor imaging, for instance, shows the complex patterns of nerveIn the vacuum: Physicists produce a Bose-Einstein condensate in a glass cell.50 The Flexible Brain ­ and that for research purposes, no less. But researchers at the Max Planck Institute for Human Cognitive and Brain

  5. QED vacuum loops and Inflation

    E-print Network

    H. M. Fried; Y. Gabellini

    2014-11-19

    A QED-based model of a new version of Vacuum Energy has recently been suggested, which leads to a simple, finite, one parameter representation of Dark Energy. An elementary, obvious, but perhaps radical generalization is then able to describe both Dark Energy and Inflation in the same framework of Vacuum Energy. One further, obvious generalization then leads to a relation between Inflation and the Big Bang, to the automatic inclusion of Dark Matter, and to a possible understanding of the birth (and death) of a Universe.

  6. The development of a portable ultrahigh vacuum chamber via silicon block

    NASA Astrophysics Data System (ADS)

    Chuang, Ho-Chiao; Huang, Chia-Shiuan

    2014-05-01

    This paper describes a nonmetallic, light weight portable chamber for ultra-high vacuum (UHV) applications. The chamber consists of a processed silicon block anodically bonding five polished Pyrex glass windows and a Pyrex glass adapter, without using any screws, bolts or vacuum adhesives. The design features provide an alternative chamber for UHV applications which require nonmetallic components. We have cyclically baked the chamber up to 180 °C for 160 h and have achieved an ultimate pressure of 1.4 × 10-9 Torr (limited by our pumping station), with no leak detected. Both Pyrex glass windows and Pyrex glass adapter have been used successfully.

  7. Effect of oxidation heat treatment on the bond strength between a ceramic and cast and milled cobalt-chromium alloys.

    PubMed

    Li, Jieyin; Ye, Xiuhua; Li, Bohua; Liao, Juankun; Zhuang, Peilin; Ye, Jiantao

    2015-08-01

    There is a dearth of dental scientific literature on the effect of different oxidation heat treatments (OHTs) (as surface pretreatments) on the bonding performance of cast and milled cobalt-chromium (CoCr) alloys. The objective of this study was to evaluate the effect of different OHTs on the bond strength between a ceramic and cast and milled CoCr alloys. Cobalt-chromium metallic specimens were prepared using either a cast or a milled method. Specimens were subjected to four different OHT methods: without OHT; OHT under normal atmospheric pressure; OHT under vacuum; and OHT under vacuum followed by sandblasting. The metal-ceramic bond strength was evaluated using a three-point bending test according to ISO9693. Scanning electron microscopy and energy-dispersive spectroscopy were used to study the specimens' microstructure and elemental composition. The bond strength was not affected by the CoCr manufacturing method. Oxidation heat treatment performed under normal atmospheric pressure resulted in the highest bond strength. The concentration of oxygen on the alloy surfaces varied with the different pretreatment methods in the following order: OHT under normal atmospheric pressure > OHT under vacuum > without OHT ? OHT under vacuum followed by sandblasting. PMID:26104804

  8. Bonding and Structure of Intermetallics: A New Bond Order Potential

    Microsoft Academic Search

    D. G. Pettifor; M. Aoki; J. N. Murrell; A. Cottrell; A. M. Stoneham

    1991-01-01

    Intermetallics such as the transition metal aluminides present theorists with a challenge since bonding is not well described by currently available pair or embedded atom potentials. We show that a new angularly dependent, many-body potential for the bond order has all the necessary ingredients for an adequate description. In particular, by linearizing the moment-recursion coefficient relations, a cluster expansion is

  9. Bond pad surface quality for reliable wire bonding

    Microsoft Academic Search

    D. Martin Knotter; Ingrid A. Rink; Wim A. P. Claassen; Jos H. M. Philipsen

    The impact of fluoride and AlOx contaminants on the quality of wire bonding (Au to Al welding) has been measured. No or minor impact of these contaminants has been found with a standard ball shear test. Despite an accelerated lifetime test, the shear strength remains above the required specification limits. Intermetallic coverage, the percentage of the interface between the bond

  10. Bonding topologies in diamondlike amorphous-carbon films

    SciTech Connect

    SIEGAL,MICHAEL P.; PROVENCIO,PAULA P.; TALLANT,DAVID R.; SIMPSON,REGINA L.; KLEINSORGE,B.; MILNE,W.I.

    2000-01-27

    The carbon ion energy used during filtered cathodic vacuum arc deposition determines the bonding topologies of amorphous-carbon (a-C) films. Regions of relatively low density occur near the substrate/film and film/surface interfaces and their thicknesses increase with increasing deposition energy. The ion subplantation growth results in mass density gradients in the bulk portion of a-C in the growth direction; density decreases with distance from the substrate for films grown using ion energies < 60 eV and increases for films grown using ion energies > 160 eV. Films grown between these energies are the most diamondlike with relatively uniform bulk density and the highest optical transparencies. Bonding topologies evolve with increasing growth energy consistent with the propagation of subplanted carbon ions inducing a partial transformation of 4-fold to 3-fold coordinated carbon atoms.

  11. Fast anomalous diffusion of small hydrophobic species in water.

    PubMed

    Kirchner, Barbara; Stubbs, John; Marx, Dominik

    2002-11-18

    Using Car-Parrinello molecular dynamics a structural diffusion mechanism for the simplest hydrophobic species in water, an H atom, is proposed. The hydrophobic solvation cavity is a highly dynamical aggregate that actually drives, by its own hydrogen-bond fluctuations, the diffusion of the enclosed solute. This makes possible an anomalously fast diffusion that falls only short of that of "Grotthuss structural diffusion" of H+ in water. Here, the picture of a static, i.e., "iceberglike," clathrate cage is a misleading concept. The uncovered scenario is similar to the "dynamical hole mechanism" found in a very different context, that is, large molecules moving in hot polymeric melts. PMID:12443432

  12. Deformation and bonding processes in aluminum ultrasonic wire wedge bonding

    NASA Astrophysics Data System (ADS)

    Krzanowski, James E.; Murdeshwar, Nikhil

    1990-09-01

    The ultrasonic wire bonding (UWB) process has been examined using transmission electron microscopy (TEM) and standard wire pull testing techniques. Al-0.5 wt.% Mg wires 75 ?m in diameter were bonded to pure and alloyed Al substrates. The bonding parameters, surface roughness, and surface contamination levels were variables in the experiments. Cross-section TEM specimens were made from these samples. TEM analysis was conducted on the wire, wire/substrate interface and substrate. Pull tests showed that for the Al substrates the surface roughness or the presence of contamination did not effect the bond strength, whereas for contaminated stainless steel substrates, a three ?m surface finish resulted in the highest bond pull strength. The TEM observations revealed features such as low-angle grain boundaries, dislocation loops and the absence of a high dislocation density, indicating that the wire and substrate were dynamically annealed during bonding. Based on the width of a zone near a grain boundary in the wire which was depleted of dislocation loops, it was estimated that local heating equivalent to a temperature of 250° C for 90 msec was achieved in the wire during bonding. No evidence was found for melting along the bond interface, indicating that UWB is a solid-state process. Based on the TEM observations of the bond interface and the pull tests, it is concluded that the ultrasonic vibrations clean the surfaces to be joined to the extent that a good bond can be obtained by intimate metal-metal contact in the clean areas.

  13. Vacuum-injection-molding processing

    SciTech Connect

    Kramer, D.P.; Massey, R.T.

    1982-01-01

    An improved processing technique for the manufacture of glass or glass-ceramic headers has been developed. Vacuum-injection molding is a relatively easy processing technique that has been used successfully in the fabrication of several different advantages in certain applications over the present fabrication process which uses glass preforms.

  14. Recent advances in Vacuum Electronics

    Microsoft Academic Search

    Baruch Levush

    2008-01-01

    Vacuum Electronics (VE) technology has been and will continue to be the enabling technology for entire classes of high-power high-frequency amplifiers with the most demanding specifications for use in both military and commercial systems. Here in this paper, TWT design and its application has been described. Among the wide variety of applications requiring high power, communication, radar, EW, and broadcasting

  15. Fluctuation Noise in Vacuum Tubes

    Microsoft Academic Search

    G. L. Pearson

    1934-01-01

    The fluctuation noises originating in vacuum tubes are treated theoretically under the following headings: (1) thermal agitation in the internal plate resistance of the tube, (2) shot effect and flicker effect from space current in the presence of space charge, (3) shot effect from electrons produced by collision ionization and secondary emission, and (4) space charge fluctuations due to positive

  16. Vacuum coating of plastic optics

    Microsoft Academic Search

    Ulrike Schulz; Norbert Kaiser

    2006-01-01

    Vacuum technologies for the deposition of optical interference coatings on polymer substrates, based on long-term experience in glass coating, have been under development for about 20 years. A growing market for precision optical elements and consumer optics moulded from thermoplastic polymers requires antireflective properties and hard coatings. Owing to the manifold chemical and physical properties of optical polymers, special efforts

  17. Peoperties of vacuum brass coatings

    Microsoft Academic Search

    I. L. Roikh; L. K. Glukhova; E. V. Efimovich; S. R. Pustotina; N. A. Litovchenko; V. P. Kirichenko

    1975-01-01

    This communication deals with the structure, phase composition, and mechanical properties of coatings of the system Cu-Zn, deposited by simultaneous condensation of Cu and Zn in a vacuum of 1 ?9 10 -4 torr from various evaporants at deposition rates of 3 ~\\/min and 5 p\\/min, respectively. The thickness of the coatings investigated was less than 20 tt. Depending on

  18. DCI wiggler magnet vacuum system

    SciTech Connect

    Souchet, R.; Marx, J.P.

    1988-09-30

    With the end of the high energy experiments in DCI, developments could take place at LURE and a five pole wiggler magnet program was launched in 1983 to exclusively dedicate DCI as a synchrotron radiation source. Design and performance measurements of the wiggler magnet vacuum system at DCI is presented. (AIP)

  19. HIGH PRODUCTIVITY VACUUM BLASTING SYSTEM

    SciTech Connect

    Dr. M.A. Ebadian

    2000-01-13

    The purpose of the project is to increase the productivity and economics of existing vacuum blasting technology. This technology is used to remove radioactive contamination, PCB's and lead-base paint and provides worker and environmental protection by continuously recycling the blast media and the full containment of the dust generated in the process.

  20. A vacuum ultraviolet spectrophotometric system

    NASA Technical Reports Server (NTRS)

    Spann, James F.; Keffer, Charles E.; Zukic, Muamer

    1993-01-01

    The development of a vacuum ultraviolet spectrophotometric system for measuring transmittance and reflectance at variable angles is presented. Using various detectors and sources, the spectrophotometric system has been used for wavelengths from 80 nm to 300 nm with optical components up to 80 mm in diameter. The capability exists to make measurements through the visible range.

  1. Vacuum barrier for excimer lasers

    DOEpatents

    Shurter, R.P.

    1992-09-15

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput. 3 figs.

  2. Vacuum Flushing of Sewer Solids

    EPA Science Inventory

    The vacuum sewer and tank cleaning (flushing) technology removes sewer solids from urban drainage systems, such as storage tanks and pipes. This technology is both effective and inexpensive. In addition, it can be considered a true green technology. It operates under atmospheri...

  3. Vacuum barrier for excimer lasers

    DOEpatents

    Shurter, Roger P. (Jemez Springs, NM)

    1992-01-01

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

  4. VACUUM SYSTEMS PHYSICS 359E

    E-print Network

    Landstreet, John D.

    experiments in high vacuum is to permit atoms or ions to move with- out colliding with air molecules. The mean at room temperature corresponds to a particle density of 3.5 × 1016 particles cm-3. Pressures in the range, metal gaskets, and a selection of ion pumps, cryopumps, molecular turbopumps, and titanium sublimation

  5. HIGH PRODUCTIVITY VACUUM BLASTING SYSTEM

    SciTech Connect

    William S. McPhee

    1999-05-31

    The objective of this project is to improve the productivity and lower the expense of existing vacuum blasting technology. This technology is used to remove radioactive contamination, PCBs, and lead-based paint and provides worker protection by continuously recycling the material and dust for the decontamination tasks. The proposed work would increase the cleaning rate and provide safe and cost-effective decontamination of the DOE sites. This work focuses on redesigning and improving existing vacuum blasting technology including blast head nozzles, ergonomic handling of the blast head by reducing its weight; brush-ring design, vacuum level regulator, efficiency of the dust separator, and operational control sensors. The redesign is expected to enhance the productivity and economy of the vacuum blasting system by at least 50% over current vacuum blasting systems. There are three phases in the project. Phase I consists of developing and testing mathematical models. Phase II consists of pre-prototype design and fabrication and pre-prototype unit testing. Phase III consists of prototype design and field verification testing. In phase I, mathematical models are developed and analyzed for the nozzle, blast head, wind curtain, and dust separator, first as individual devices and then combined as an integrated model. This allows study of respective airflow and design parameters. The Contractor shall, based on the results of the mathematical modeling studies, design experimental models of the components and test these models. In addition, the Contractor shall develop sensors to detect the relationship of the blast head to the blast surfaces and controls to minimize the dependency on an operator's skill and judgment to obtain optimum positioning, as well as real-time characterization sensors to determine as the blast head is moving the depth to which coatings must be removed, thereby improving production and minimizing waste. In phase II, the Contractor shall design and construct a pre-prototype of the nozzle, blast head with wind curtain, sensors, and dust separator and test this system to assess the performance of the new design under controlled conditions at the contractor's facility. In phase III, the Contractor shall design and construct a prototype of the High Productivity Vacuum Blasting System, based on the results of the pre-prototype design and testing performed. This unit will be a full-scale prototype and will be tested at a designated Department of Energy (DOE) facility. Based on the results, the system performance, the productivity, and the economy of the improved vacuum blasting system will be evaluated.

  6. Regulating vacuum pump speed with feedback control

    SciTech Connect

    Ludington, D.C.; Aneshansley, D.J.; Pellerin, R.; Guo, F.

    1992-01-01

    Considerable energy is wasted by the vacuum pump/motor on dairy farms. The output capacity (m{sup 3}/min or cfm) of the vacuum pump always exceeds the capacity needed to milk cows and wash pipelines. Vacuum pumps run at full speed and load regardless of actual need for air. Excess air is admitted through a controller. Energy can be saved from electrical demand reduced by regulating vacuum pump speed according to air based on air usage. An adjustable speed drive (ASD) on the motor and controlled based upon air usage, can reduce the energy used by the vacuum pump. However, the ASD unit tested could not maintain vacuum levels within generally accepted guidelines when air usage changed. Adding a high vacuum reserve and a dual vacuum controller between the vacuum pump and the milking pipeline brought vacuum stability within guidelines. The ASD/dual vacuum system can reduce energy consumption and demand by at least 50 percent during milking and provide better vacuum stability than conventional systems. Tests were not run during washing cycles. Using 1990 costs and only the energy saved during milking, the simple payback on investment in new equipment for a 5 hp motor, speed controller and vacuum regulator would be about 5 years.

  7. A wire bond reliability model

    Microsoft Academic Search

    T. L. Heleine; R. M. Murcko; S.-C. Wang

    1991-01-01

    A defect modeling approach is developed which allows the determination of the true failure rate with a minimal sample size. A model was developed using the proposed approach to estimate the failure rate of an aluminium\\/1% silicon wire ultrasonically bonded to aluminum and to gold pads. For this reliability model the variable was wire-bond width. Dependent upon the width of

  8. Failure Analysis of Wire Bonds

    Microsoft Academic Search

    Harry A. Schafft

    1973-01-01

    Failure analysis of wire bonds has an important part to play in determining the causes of microelectronic device failure and ways for making and using devices to achieve greater reliability. Several tests and procedures used in the failure analysis of wire bonds are reviewed. Some of the inferences. about possible causes of permanent or intermittent failure that can be drawn

  9. Vacuum polarization and Hawking radiation

    NASA Astrophysics Data System (ADS)

    Rahmati, Shohreh

    Quantum gravity is one of the interesting fields in contemporary physics which is still in progress. The purpose of quantum gravity is to present a quantum description for spacetime at 10-33cm or find the 'quanta' of gravitational interaction.. At present, the most viable theory to describe gravitational interaction is general relativity which is a classical theory. Semi-classical quantum gravity or quantum field theory in curved spacetime is an approximation to a full quantum theory of gravity. This approximation considers gravity as a classical field and matter fields are quantized. One interesting phenomena in semi-classical quantum gravity is Hawking radiation. Hawking radiation was derived by Stephen Hawking as a thermal emission of particles from the black hole horizon. In this thesis we obtain the spectrum of Hawking radiation using a new method. Vacuum is defined as the possible lowest energy state which is filled with pairs of virtual particle-antiparticle. Vacuum polarization is a consequence of pair creation in the presence of an external field such as an electromagnetic or gravitational field. Vacuum polarization in the vicinity of a black hole horizon can be interpreted as the cause of the emission from black holes known as Hawking radiation. In this thesis we try to obtain the Hawking spectrum using this approach. We re-examine vacuum polarization of a scalar field in a quasi-local volume that includes the horizon. We study the interaction of a scalar field with the background gravitational field of the black hole in the desired quasi-local region. The quasi-local volume is a hollow cylinder enclosed by two membranes, one inside the horizon and one outside the horizon. The net rate of particle emission can be obtained as the difference of the vacuum polarization from the outer boundary and inner boundary of the cylinder. Thus we found a new method to derive Hawking emission which is unitary and well defined in quantum field theory.

  10. Nitrogen self-diffusion in magnetron sputtered Si-C-N films

    SciTech Connect

    Hueger, E.; Schmidt, H. [Institute of Metallurgy, Materials Physics Group, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Geue, T.; Stahn, J. [Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Tietze, U.; Lott, D. [Helmholtz-Zentrum Geesthacht, Max Planck Str. 1, D-21502 Geesthacht (Germany); Markwitz, A. [National Isotope Centre, GNS Science, 30 Gracefield Road, PO Box 31-312 Lower Hutt (New Zealand); Geckle, U.; Bruns, M. [Institute for Materials Research III, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)

    2011-05-01

    Self-diffusion was studied in magnetron sputtered nitrogen-rich amorphous compounds of the system Si-C-N by using nitrogen as a model tracer. As shown by infra-red spectroscopy a transient metastable region exists, where the structure of the material can be visualized as silicon nitride tetrahedra which are connected by carbo-diimide (-N=C=N-) bonds to a three dimensional amorphous network. In this region diffusion studies are carried out by neutron reflectometry and isotope multilayers as a function of annealing time, temperature and chemical composition. Low diffusivities between 10{sup -20} and 10{sup -24} m{sup 2}/s were found. In the metastable region, diffusion is faster than diffusion in amorphous silicon nitride by 1 to 2 orders of magnitude, while the activation enthalpies of diffusion between 3.1 and 3.4 eV are the same within error limits. This can be explained by the fact that the diffusion mechanism along SiN{sub 4} tetrahedra is identical to that in amorphous silicon nitride, however, the carbo-diimide bonds seem to widen the structure, allowing faster diffusion. A correlation between diffusivities and the number of carbo-diimid bonds present in the material is found, where the highest diffusivities are observed for materials with the highest number of carbo-diimid bonds, close to the composition Si{sub 2}CN{sub 4}.

  11. Social bonding: regulation by neuropeptides

    PubMed Central

    Lieberwirth, Claudia; Wang, Zuoxin

    2014-01-01

    Affiliative social relationships (e.g., among spouses, family members, and friends) play an essential role in human society. These relationships affect psychological, physiological, and behavioral functions. As positive and enduring bonds are critical for the overall well-being of humans, it is not surprising that considerable effort has been made to study the neurobiological mechanisms that underlie social bonding behaviors. The present review details the involvement of the nonapeptides, oxytocin (OT), and arginine vasopressin (AVP), in the regulation of social bonding in mammals including humans. In particular, we will discuss the role of OT and AVP in the formation of social bonds between partners of a mating pair as well as between parents and their offspring. Furthermore, the role of OT and AVP in the formation of interpersonal bonding involving trust is also discussed. PMID:25009457

  12. Metal vapor plasma behavior during vacuum arc remelting of alloy 718

    SciTech Connect

    Zanner, F.J.; Maguire, M.C.; Williamson, R.L. (Sandia National Labs., Albuquerque, NM (United States)); Adasczik, C.B. (Teledyne Allvac Corp., Monroe, NC (United States)); Roberts, R.R. (Concarsc Corp., Rancocas, NJ (United States)); Strohecker, R. (Strohecker Corp., East Palestine, OH (United States))

    1992-01-01

    A production vacuum arc remelt (VAR) furnace was modified to enable direct viewing of the metal vapor arc and molten electrode tip during melting of 432 mm dia. alloy 718 electrodes into 508 mm dia. ingots. Diffuse and constricted arcing conditions were characterized using high speed cinematography, standard video format, and monochromatic imaging. Constricted arcing was observed while melting electrodes contaminated with oxide slag of the type used for refractory linings in vacuum induction furnaces. Monochromatic imaging was used in visualize the ion distribution in the arc plasma; these images clearly showed whether the arc operated in a diffuse or constricted model. Diffuse arc melting conditions were very similar to those previously reported in the literature for smaller laboratory sized melts.

  13. Equilibrium Pricing of Special Bearer Bonds

    Microsoft Academic Search

    Jayanth Rama Varma

    In 1981, the Government issued Special Bearer Bonds under a scheme which allowed people to invest their black money in these bonds and enjoy freedom from investigations and prosecutions for tax evasion in respect of their holdings of these bonds. Through these bonds are no longer available in tap, there is an active secondary market for these bonds; the complete

  14. hp calculators HP 50g Bond Price

    E-print Network

    Vetter, Frederick J.

    hp calculators HP 50g Bond Price The FINANCE menu Bond Price Practice solving for the price of a bond #12;hp calculators HP 50g Bond Price hp calculators - 2 - HP 50g Bond Price The FINANCE menu. To exit from this data entry screen, press the $ key. Figure 2 The HP 50g Financial solver follows

  15. hp calculators HP 50g Bond Yield

    E-print Network

    Vetter, Frederick J.

    hp calculators HP 50g Bond Yield The FINANCE menu Bond Yield Practice solving for the yield of a bond #12;hp calculators HP 50g Bond Yield hp calculators - 2 - HP 50g Bond Yield The FINANCE menu as Beg if chosen. To exit from this data entry screen, press the $ key. Figure 2 The HP 50g Financial

  16. Microstructural evolution of platinum modified nickel aluminide bond coat during thermal cycling

    Microsoft Academic Search

    M. W. Chen; R. T. Ott; T. C. Hufnagel; P. K. Wright; K. J. Hemker

    2003-01-01

    Microstructural evolution induced by thermal cycling in a platinum modified diffusion aluminide bond coat was investigated with transmission electron microscopy and elevated temperature X-ray diffraction (XRD). Before thermal cycling, the structure of the as-received bond coat was confirmed to be an ordered B2 phase, but significant lattice strains were found which were associated with the formation of a modulated structure.

  17. Purfication kinetics of beryllium during vacuum induction melting

    NASA Technical Reports Server (NTRS)

    Mukherjee, J. L.; Gupta, K. P.; Li, C. H.

    1972-01-01

    The kinetics of evaporation in binary alloys were quantitatively treated. The formalism so developed works well for several systems studied. The kinetics of purification of beryllium was studied through evaporation data actually acquired during vacuum induction melting. Normal evaporation equations are shown to be generally valid and useful for understanding the kinetics of beryllium purification. The normal evaporation analysis has been extended to cover cases of limited liquid diffusion. It was shown that under steady-state evaporation, the solute concentration near the surface may be up to six orders of magnitude different from the bulk concentration. Corrections for limited liquid diffusion are definitely needed for the highly evaporative solute elements, such as Zn, Mg, and Na, for which the computed evaporation times are improved by five orders of magnitude. The commonly observed logarithmic relation between evaporation time and final concentration further supports the validity of the normal evaporation equations.

  18. A Class of Stationary Electromagnetic Vacuum Fields

    E-print Network

    Israel, Werner; Wilson, Gordon A.

    1972-01-10

    It is shown how a new class of stationary electromagnetic vacuum fields can be generated from solutions of Laplace's equation. These fields are a stationary generalization of the static electromagnetic vacuum fields of Weyl, Majumdar, and Papapetrou...

  19. Halogen bonding (X-bonding): A biological perspective

    PubMed Central

    Scholfield, Matthew R; Zanden, Crystal M Vander; Carter, Megan; Ho, P Shing

    2013-01-01

    The concept of the halogen bond (or X-bond) has become recognized as contributing significantly to the specificity in recognition of a large class of halogenated compounds. The interaction is most easily understood as primarily an electrostatically driven molecular interaction, where an electropositive crown, or ?-hole, serves as a Lewis acid to attract a variety of electron-rich Lewis bases, in analogous fashion to a classic hydrogen bonding (H-bond) interaction. We present here a broad overview of X-bonds from the perspective of a biologist who may not be familiar with this recently rediscovered class of interactions and, consequently, may be interested in how they can be applied as a highly directional and specific component of the molecular toolbox. This overview includes a discussion for where X-bonds are found in biomolecular structures, and how their structure–energy relationships are studied experimentally and modeled computationally. In total, our understanding of these basic concepts will allow X-bonds to be incorporated into strategies for the rational design of new halogenated inhibitors against biomolecular targets or toward molecular engineering of new biological-based materials. PMID:23225628

  20. 27 CFR 19.152 - Types of bonds.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...DEPARTMENT OF THE TREASURY ALCOHOL DISTILLED SPIRITS PLANTS Bonds and Consents of Surety Bonding Requirements for A Dsp § 19.152 Types of bonds. (a) Basic Bonds. There are two basic types of bonds: the operations bond, and the...