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1

Method for vacuum fusion bonding  

DOEpatents

An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

Ackler, Harold D. (Sunnyvale, CA); Swierkowski, Stefan P. (Livermore, CA); Tarte, Lisa A. (Livermore, CA); Hicks, Randall K. (Stockton, CA)

2001-01-01

2

Diffusion bonding of Al 2O 3TiC composite ceramic and W18Cr4V high speed steel in vacuum  

Microsoft Academic Search

Al2O3-TiC composite ceramic and W18Cr4V high speed steel were joined by diffusion bonding with a Ti-Cu-Ti multi-interlayer in a vacuum of 10?4–10?5Pa. The interfacial microstructures of the Al2O3-TiC\\/W18Cr4V joint were investigated with optical microscope and scanning electron microscopy. The elemental concentration near the diffusion interface was evaluated by electron probe microanalysis. The results indicate that an obvious transition zone was formed

Xiaoqin Shen; Li Yajiang; Wang Juan; Huang Wanqun; Yu Fusheng

2009-01-01

3

Vacuum fusion bonding of glass plates  

DOEpatents

An improved apparatus and method for vacuum fusion bonding of large, patterned glass plates. One or both glass plates are patterned with etched features such as microstructure capillaries and a vacuum pumpout moat, with one plate having at least one hole therethrough for communication with a vacuum pumpout fixture. High accuracy alignment of the plates is accomplished by a temporary clamping fixture until the start of the fusion bonding heat cycle. A complete, void-free fusion bond of seamless, full-strength quality is obtained through the plates; because the glass is heated well into its softening point and because of a large, distributed force that is developed that presses the two plates together from the difference in pressure between the furnace ambient (high pressure) and the channeling and microstructures in the plates (low pressure) due to the vacuum drawn. The apparatus and method may be used to fabricate microcapillary arrays for chemical electrophoresis; for example, any apparatus using a network of microfluidic channels embedded between plates of glass or similar moderate melting point substrates with a gradual softening point curve, or for assembly of glass-based substrates onto larger substrates, such as in flat panel display systems.

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

2001-01-01

4

Vacuum fusion bonding of glass plates  

DOEpatents

An improved apparatus and method for vacuum fusion bonding of large, patterned glass plates. One or both glass plates are patterned with etched features such as microstructure capillaries and a vacuum pumpout moat, with one plate having at least one hole therethrough for communication with a vacuum pumpout fixture. High accuracy alignment of the plates is accomplished by a temporary clamping fixture until the start of the fusion bonding heat cycle. A complete, void-free fusion bond of seamless, full-strength quality is obtained through the plates; because the glass is heated well into its softening point and because of a large, distributed force that is developed that presses the two plates together from the difference in pressure between the furnace ambient (high pressure) and the channeling and microstructures in the plates (low pressure) due to the vacuum drawn. The apparatus and method may be used to fabricate microcapillary arrays for chemical electrophoresis; for example, any apparatus using a network of microfluidic channels embedded between plates of glass or similar moderate melting point substrates with a gradual softening point curve, or for assembly of glass-based substrates onto larger substrates, such as in flat panel display systems.

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

2000-01-01

5

Diffusion bonding of aluminium alloy, 8090  

Microsoft Academic Search

Ability to diffusion bond aluminum (Al) alloys, in particular superplastic aluminum alloys, will complete the technology-base that is strongly needed to enhance the use of superplastic forming (SPF) technology. Diffusion bonding (DB) is an attractive manufacturing option for applications where the preservation of the base metal microstructure and, in turn, mechanical properties is important in the bond area. As the

Sunwoo

1994-01-01

6

Diffusion Bonding of Gold to Gold.  

National Technical Information Service (NTIS)

Low temperature diffusion bonds of gold to gold are made in which the bond tensile strength exceeds the yield point of gold. This is done by wetting the bonding surfaces with mercury and clamping the wetted surfaces together with moderate pressure, at a t...

E. Catalano D. L. Ornellas

1975-01-01

7

Preparation of Mo Mo step by vacuum bond  

NASA Astrophysics Data System (ADS)

The diffusion bond method was applied to prepare Mo-Mo steps used in equation of state (EOS) measurement experiments. A di-middle layer diffusion bond technique was developed to decrease the bond temperature. Al and Au atoms were deposited on Mo foils surface by magnetron sputter technique. As a result, tight bonds were formed by the mutual diffusion of Al and Au atoms. The structures of the bond interface were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).

Du, Kai; Xie, Jun; Luo, Qing; Zheng, Feng-cheng

2008-11-01

8

Partial transient liquid phase diffusion bonding of Zircaloy4 to stabilized austenitic stainless steel 321  

Microsoft Academic Search

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 1MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength and interlayer thickness

M. Mazar Atabaki; A. Talebi Hanzaei

2010-01-01

9

Diffusion bonding of stainless steel to Zircaloy4 in the presence of a Ta intermediate layer  

Microsoft Academic Search

Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been investigated using diffusion couples heat treated at 1150 °C under vacuum for 3 h. Different types of regions have been observed in stainless steel, Zircaloy-4 and Ta foil. A Cr rich layer formed in stainless steel is found to act as a diffusion barrier.

M. Ahmad; J. I. Akhter; Q. Zaman; M. A Shaikh; M. Akhtar; M. Iqbal; E. Ahmed

2003-01-01

10

Vacuum Head Checks Foam/Substrate Bonds  

NASA Technical Reports Server (NTRS)

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.

Lloyd, James F.

1989-01-01

11

Vacuum pull down method for an enhanced bonding process  

DOEpatents

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.

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

1999-01-01

12

Transition joints between Zircaloy-2 and stainless steel by diffusion bonding  

NASA Astrophysics Data System (ADS)

The diffusion bonding between Zircaloy-2 and stainless steel (AISI 304L) using niobium, nickel and copper as intermediate layers has been investigated in the temperature range of 750 to 900°C. Bonding was carried out in a vacuum hot press, under compressive loading. Electron probe microanalysis and metallographic analysis showed a good metallurgical compatibility and also indicated the absence of discontunities, micropores and intermetallic compounds at various interfaces. The bond strength of the diffusion bonded assembly was found to be about 400 MPa for the couples bonded at 870°C for 2 h. The dimple structure on the fractured surface is indicative of the ductile mode of failure of the bonded assembly.

Bhanumurthy, K.; Krishnan, J.; Kale, G. B.; Banerjee, S.

1994-11-01

13

Better Vacuum by Removal of Diffusion-Pump-Oil Contaminants.  

National Technical Information Service (NTIS)

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 techno...

A. E. Buggele

1975-01-01

14

Diffusion bonding of Ti coated Zircaloy4 and 316-L stainless steel  

Microsoft Academic Search

Diffusion bonding of Zircaloy-4 and Type 316-L stainless steel was carried out by coating the joining surfaces with Ti to minimize the interlayer effect. Bonding heat treatments were carried out in vacuum at 1000 °C for 4 h and 1050 °C for 1 h. The microstructure of the diffusion zone was investigated by scanning electron microscopy and the phases in the diffusion zone were

J. I. Akhter; M. Ahmad; G. Ali

2009-01-01

15

Diffusion bonding of Ti coated Zircaloy-4 and 316-L stainless steel  

SciTech Connect

Diffusion bonding of Zircaloy-4 and Type 316-L stainless steel was carried out by coating the joining surfaces with Ti to minimize the interlayer effect. Bonding heat treatments were carried out in vacuum at 1000 deg. C for 4 h and 1050 deg. C for 1 h. The microstructure of the diffusion zone was investigated by scanning electron microscopy and the phases in the diffusion zone were analyzed by energy dispersive spectroscopy. It is observed that Ti coating at the interface produced a dendritic structure in the diffusion zone formed in the Zircaloy-4. The concentration of the dendrites increases with an increase in bonding temperature.

Akhter, J.I. [Physics Division, Pakistan Institute of Nuclear Science and Technology, P. O. Nilore, Islamabad (Pakistan)], E-mail: jiakhter@yahoo.com; Ahmad, M.; Ali, G. [Physics Division, Pakistan Institute of Nuclear Science and Technology, P. O. Nilore, Islamabad (Pakistan)

2009-03-15

16

Vacuum fusion bonded glass plates having microstructures thereon  

DOEpatents

An improved apparatus and method for vacuum fusion bonding of large, patterned glass plates. One or both glass plates are patterned with etched features such as microstructure capillaries and a vacuum pumpout moat, with one plate having at least one hole therethrough for communication with a vacuum pumpout fixture. High accuracy alignment of the plates is accomplished by a temporary clamping fixture until the start of the fusion bonding heat cycle. A complete, void-free fusion bond of seamless, full-strength quality is obtained through the plates; because the glass is heated well into its softening point and because of a large, distributed force that is developed that presses the two plates together from the difference in pressure between the furnace ambient (high pressure) and the channeling and microstructures in the plates (low pressure) due to the vacuum drawn. The apparatus and method may be used to fabricate microcapillary arrays for chemical electrophoresis; for example, any apparatus using a network of microfluidic channels embedded between plates of glass or similar moderate melting point substrates with a gradual softening point curve, or for assembly of glass-based substrates onto larger substrates, such as in flat panel display systems.

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

2001-01-01

17

A new model for vacuum quality and lifetime prediction in hermetic vacuum bonded MEMS  

NASA Astrophysics Data System (ADS)

In many MEMS applications the level of vacuum is a key issue as it directly affects the quality of the device, in terms of response reliability. Due to the unavoidable desorption phenomena of gaseous species from the internal surfaces, the vacuum inside a MEMS, after bonding encapsulation, tends to be degraded, unless a proper getter solution is applied. The in situ getter film (PaGeWafer®) is recognised to be the most reliable way to get rid of degassed species, assuring uniform, high quality performances of the device throughout the lifetime. Moreover, post process vacuum quality control and reliability for hermetic bonding is extremely important for overall device reliability and process yield. In this paper we will discuss the main factors that are critical in the attainment of vacuum and will present a novel calculation model that enables the prediction of vacuum level after bonding, making also possible the estimate of the lifetime. Furthermore, a new analytical method based on the residual gas analyses (RGA) will be presented that gives the main characteristics of the materials. Modeling and simulation work support the process optimization and system design.

Bonucci, A.; Guadagnuolo, S.; Caterino, A.; Conte, A.; Moraja, M.

2008-03-01

18

Development of the diffusion bonding process  

SciTech Connect

The diffusion bonding process was adapted for a unique low-temperature application involving the attachment of thin copper materials used in the flexible printed circuit industry. The work completed to date has demonstrated the feasibility of welding 0.0002-in. thick copper foil to 0.0014-in. thick oxygen-free, high-conductivity (OFHC) copper sheeting. The 0.0002-in. foil is an electrodeposited material on a Kapton substrate. The 0.0014-in. copper sheet is part of a cable assembly consisting of Kapton, epoxy, Pyralux adhesive, and additional copper layers. Heat must be applied through all these materials to effect welding at the interface. Diffusion bonding parameters of 5000 psi, a 3-min time period, and a weld interface temperature of 288/sup 0/C (550/sup 0/F) were found to form effective welds without causing appreciable degradation of the assembly, as shown by high voltage breakdown testing.

Kwiatkowski, J.J.; Jones, W.H.

1987-02-25

19

Strength, ultrasonic and metallurgical evaluation of diffusion bonds  

SciTech Connect

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.

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

1993-10-01

20

Vacuum bag bonding with a high temperature adhesive  

NASA Technical Reports Server (NTRS)

A novel controlled molecular weight form of LARC-TPI polymide that exhibits an exceptionally high degree of melt flow in the 340-360 C temperature range has been developed. This material has been evaluated as a high-temperature adhesive, and because of its flow, cost-effective vacuum bag/oven processing can be used. Comparison of adhesive performance with higher molecular weight forms bonded at higher pressures shows this novel material to be equal in mechanical strength.

Progar, Donald J.; St. Clair, Terry L.

1991-01-01

21

Development of the diffusion bonding process  

Microsoft Academic Search

The diffusion bonding process was adapted for a unique low-temperature application involving the attachment of thin copper materials used in the flexible printed circuit industry. The work completed to date has demonstrated the feasibility of welding 0.0002-in. thick copper foil to 0.0014-in. thick oxygen-free, high-conductivity (OFHC) copper sheeting. The 0.0002-in. foil is an electrodeposited material on a Kapton substrate. The

J. J. Kwiatkowski; W. H. Jones

1987-01-01

22

Diffusion bonding of silicon nitride to titanium  

Microsoft Academic Search

The use of ceramic has gradually increased over the past few years. Si3N4 is one of the most important ceramics used as structural material for high temperature applications. The practical use of advanced ceramics depends on the reliability of ceramic\\/metal joining techniques and the properties of the resulting interfaces. This work focuses on various aspects of diffusion bonding of Si3N4

Jose Lemus-Ruiz

2001-01-01

23

Better vacuum by removal of diffusion-pump-oil contaminants  

NASA Technical Reports Server (NTRS)

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.

Buggele, A. E.

1975-01-01

24

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

Microsoft Academic Search

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

Debasis Poddar

25

On the Direct Diffusion Bonding of Titanium Alloy to Stainless Steel  

Microsoft Academic Search

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

Swarup K. Ghosh; S. Chatterjee

2010-01-01

26

Diffusion bonding of commercially pure titanium and 17-4 precipitation hardening stainless steel  

Microsoft Academic Search

Commercially pure titanium and 17-4 precipitation hardening stainless steel were diffusion bonded in the temperature range of 850–950°C for 7.2ks under 3.5MPa uniaxial load in vacuum. The transition joints were examined in optical and scanning electron microscope. The chemical compositions of reaction layers in the diffusion zone were determined by energy dispersive spectroscopy and the formation of intermetallics like ?

S. Kundu; M. Ghosh; S. Chatterjee

2006-01-01

27

Low-temperature diffusion bonding of pure aluminum  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

28

Diffusion bonding between ODS ferritic steel and F82H steel for fusion applications  

NASA Astrophysics Data System (ADS)

Diffusion bonding techniques were employed to join high Cr oxide dispersion strengthened (ODS) ferritic steel (Fe-15Cr-2W-0.2Ti-0.35Y2O3) and F82H steel under uni-axial hydrostatic pressure using a high vacuum hot press, and the microstructure and mechanical properties of the joints were investigated. The dissimilar joints were bonded by solid-state diffusion bonding (SSDB) and liquid phase diffusion bonding (LPDB). After bonding process, heat treatments were conducted to utilize the phase transformation of F82H steel for recovering the martensitic structure. Tensile tests with miniaturized specimens were carried out to investigate and compare the bonding strengths of each joint. Microstructure was observed for the bonding interface, and fracture mode was investigated after the tensile tests. LPDB joint of interfacial F82H steel fully recovered to martensite phase by post-joining heat treatments, while SSDB joint had ferrite phases at the interface even after heat treatment, which is considered to be due to decarburization of F82H steel during the bonding process. Therefore it is considered that the insert material plays a role as diffusion barrier of carbon during LPDB process. Microstructure observations and tensile tests of the joints revealed that the LPDB joints possess suitable tensile properties which are comparable to that of F82H steel. This indicates that LPDB is more promising method to bond ODS-FS and F82H steel than SSDB.

Noh, Sanghoon; Kim, Byungjun; Kasada, Ryuta; Kimura, Akihiko

2012-07-01

29

Fabrication of titanium parts by massive diffusion bonding  

Microsoft Academic Search

Massive diffusion bonding (MDB) is an innovative manufacturing method to produce heavy titanium parts with solid-state bonding of multi-sheets by applying low pressure of inert gas. Massive solid-state bonding is different from conventional diffusion bonding, which is utilized for sandwich panels during superplastic forming of two or three thin-sheets. The advantages of MDB are its ability to produce heavy titanium

Ho-Sung Lee; Jong-Hoon Yoon; Yeong-Moo Yi

2008-01-01

30

Evaluation of Amorphous Diffusion Bonding by Nonlinear Ultrasonic Method  

Microsoft Academic Search

The characteristic of bond interface in amorphous diffusion bonding, of which evaluation is impossible by conventional method, was quantitatively evaluated by the second harmonic amplitude. Steel bars were bonded with Ni-based amorphous film. Conventional ultrasonic method, e.g. the echo height reflected from bond interface, could not identify samples manufactured at different bonding temperatures 1050, 1150 and 1250°C. Therefore, nonlinear ultrasonic

Y. Ohara; K. Kawashima; R. Yamada; H. Horio

2004-01-01

31

DIFFUSION BONDING: A NEW WAY TO JOIN CRITICAL PARTS  

Microsoft Academic Search

A method is described for joining critical parts by the diffusion of a ; metal with the base metals. The method can produce a joint with controlled ; microstructure closely resembling that of the base metal. The advantages of ; diffusion bonding over brazing are asserted. The results of tests conducted on ; Zircaloy-2 tubes bonded to spacers of the

McQuillan

1960-01-01

32

Ultrasonic NDT of titanium diffusion bonding with guided waves  

SciTech Connect

An ultrasonic guided wave technique is developed for the NDT of diffusion bonded titanium-to-titanium structures. A three-layer model based on the normal beam experimental results has been proposed. Dispersion curves and wave structure are analyzed to direct the experimental study. Two features related to Lamb waves propagating in diffusion bonded titanium plates, the spectral peak to peak ratios and the wave mode frequency shift, are extracted from the guided wave experimental results for both 2 mm (0.08 in.) and 4 mm (0.16 in.) diffusion bond panels. It is found for some specific modes and frequencies that these two features are sensitive to the diffusion bonding states and, therefore, could be used to distinguish good bond panels from poor bond ones.

Rose, J.L.; Zhu, W. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Engineering Science and Mechanics; Zaidi, M. [Boeing Co., Long Beach, CA (United States)

1998-04-01

33

Diffusion Bonding of Silicon Carbide for MEMS-LDI Applications  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

34

Diffusion Bonding of Silicon Carbide Ceramics using Titanium Interlayers  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

35

Ultrasonic NDE of titanium diffusion bonds using signal phase  

NASA Astrophysics Data System (ADS)

Diffusion bonding is a highly advantageous solid-state welding method. However, its full exploitation in titanium components is currently limited by a lack of robust NDE techniques capable of detecting anything but gross bond-line defects. A novel ultrasonic technique has been developed to address this lack of capability. This technique, based on the ultrasonic signal phase, has been demonstrated in a `single-sided' scenario where only one side of the diffusion bond was accessible. Samples with differing degrees of bond quality were evaluated, and excellent agreement was found between the single-sided and double-sided experiments.

Escobar-Ruiz, E.; Cawley, P.; Nagy, P. B.; Collison, I.; Wright, D.

2013-01-01

36

Ultrasonic evaluation of beryllium-copper diffusion bonds  

SciTech Connect

A study was performed to compare the effectiveness of several advanced ultrasonic techniques when used to determine the strength of diffusion bonded beryllium-copper, which heretofore have each been applied to only a few material systems. The use of integrated backscatter calculations, frequency domain reflection coefficients, and time-of-flight variance was compared in their ability to characterize the bond strength in a series of beryllium-copper diffusion bond samples having a wide variation in bond quality. Correlation of integrated backscatter calculations and time-of-flight variance with bond strength was good. Some correlation of the slope of the frequency based reflection coefficient was shown for medium and high strength bonds, while its Y-intercept showed moderate correlation for all bond strengths.

Jamieson, E.E.

2000-06-08

37

Application of diffusion bonding to electronic interconnection of flatpack leads  

NASA Technical Reports Server (NTRS)

Diffusion-bonded joints between gold-plated Kovar leads and indium-plated copper circuit pads offer some advantages for electronic circuit packaging. Test results show that consistent high strength bonds stronger than the copper circuit foil are achieved by parallel-gap bonding at relatively low power settings. The bonds are basically formed by the alloying of the gold, indium and copper at the bond interface. Other low melting metals such as tin can also be used; however, tin does not offer the ease of bonding that results in consistent separation of the copper foil during pull testing. The investigation was conducted in three parts consisting of: (1) an evaluation of the physical strength of resulting bonds at ambient and elevated temperature, (2) a metallurgical analysis of bonds using scanning electron microscopy and nondispersive X-ray analysis, and (3) evaluation and development of various schemes for multiple lead flatpack bonding.

Korb, R. W.; Lardenoit, V. F.

1973-01-01

38

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

SciTech Connect

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.

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

39

Effect of hydrogen bond on coal extraction by in-situ vacuum FTIR  

SciTech Connect

Coal chemical formation environment might result in different properties of hydrogen bonds in coal structure. The thermo stability, amount and types of hydrogen bond in six typical Chinese coal macerals were investigated by in situ vacuum Fourier transform infrared spectroscopy (FTIR). It was found that three types of hydrogen bond were involved in coal structure, which were OH-N, OH self associated, and OH tetrapolymer hydrogen bond. There was no correlation between the amount of three types of hydrogen bonds and extraction yield. The thermo stability of hydrogen bond in inertinite was stronger than that of vitrinite, especially the thermo stability of hydrogen bond in Pingshuo inertinite.

Li, J.; Feng, J.; Li, W.Y.; Chang, H.Z.; Xie, K.C. [Taiyuan University of Technol, Taiyuan (China)

2009-07-01

40

Joining of Silicon Carbide: Diffusion Bond Optimization and Characterization  

NASA Technical Reports Server (NTRS)

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.

Halbig, Michael C.; Singh, Mrityunjay

2008-01-01

41

Metal honeycomb to porous wireform substrate diffusion bond evaluation  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

42

Mechanical properties of diffusion bonded beryllium ingot sheet  

Microsoft Academic Search

A technique for producing thick beryllium plate from ingot source material by diffusion-bonding together thin sheets is described. The bonds produced are at least as strong as the matrix, and are produced under conditions where no significant grain growth occurs. The laminated plate has better mechanical properties than the sheet from which it was made, and properties substantially superior to

Clinton R. Heiple

1972-01-01

43

Transient liquid-phase diffusion bonding of two-dimensional carbon–carbon composites to niobium alloy  

Microsoft Academic Search

Two-dimensional carbon–carbon composites (C\\/C) were successfully bonded to Nb alloy with a Ti\\/Cu interlayer by transient liquid-phase diffusion bonding (TLP-DB) in vacuum condition. The joining process consisted of two stages: solid diffusion bonding at 780°C under joining pressure of 4MPa for 30min, and TLP-DB at 1050°C for 30min under 0 or 0.03MPa. The results show that the eutectic Ti–Cu liquid,

J.-L. Li; J.-T. Xiong; F.-S. Zhang

2008-01-01

44

Interfacial microstructure and properties of Ti(C, N)\\/Ni bonded by transient liquid-phase diffusion  

Microsoft Academic Search

Effects of the main process parameters(temperature and time) on microstructure and properties of Ti(C, N)\\/Ni interface bonded\\u000a by (Cu+Nb) interlayer in a vacuum diffusion bonding device were investigated. The interfacial microstructures consisted initially\\u000a of Ni3Nb metallic compound and eutectic of Ni3Nb+CuNiSS, and finally transformed to (Ti, Nb) (C, N)+Ni3Nb near Ti (C, N) and NiCuSS+Ni3Nb near Ni when diffusion bonding

Shiquan Zhou; Xiaogang Li; Weihao Xiong; Yunhong Zhou

2009-01-01

45

Fabrication and Characterization of Diffusion Bonds for Silicon Carbide  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

46

Fast Through-Bond Diffusion of Nitrogen in Silicon  

SciTech Connect

The authors report first principles total energy calculations of interaction of nitrogen in silicon with silicon self-interstitials. Substitutional nitrogen captures a silicon interstitial with 3.5 eV binding energy forming a {l_angle}001{r_angle} split interstitial ground state geometry, with the nitrogen forming three bonds. The low energy migration path is through a bond bridge state having two bonds. Fast diffusion of nitrogen occurs through a pure interstitialcy mechanism; the nitrogen never has less than two bonds. Near-zero formation energy of the nitrogen interstitialcy with respect to the substitutional rationalizes the low solubility of substitutional nitrogen in silicon.

SCHULTZ,PETER A.; NELSON,JEFFREY S.

2000-07-12

47

Diffusion bonding of the oxide dispersion strengthened steel PM2000  

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

48

Micro thermal shear stress sensor based on vacuum anodic bonding and bulk-micromachining  

NASA Astrophysics Data System (ADS)

This paper describes a micro thermal shear stress sensor with a cavity underneath, based on vacuum anodic bonding and bulk micromachined technology. A Ti/Pt alloy strip, 2?m × 100?m, is deposited on the top of a thin silicon nitride diaphragm and functioned as the thermal sensor element. By using vacuum anodic bonding and bulk-si anisotropic wet etching process instead of the sacrificial-layer technique, a cavity, functioned as the adiabatic vacuum chamber, 200?m × 200?m × 400?m, is placed between the silicon nitride diaphragm and glass (Corning 7740). This method totally avoid adhesion problem which is a major issue of the sacrificial-layer technique.

Yi, Liang; Ou, Yi; Shi, Sha-Li; Ma, Jin; Chen, Da-Peng; Ye, Tian-Chun

2008-06-01

49

Superplastically formed diffusion bonded metallic structure  

NASA Technical Reports Server (NTRS)

A metallic sandwich structure particularly suited for use in aerospace industries comprising a base plate, a cover plate, and an orthogonally corrugated core is described. A pair of core plates formed of a superplastic alloy are interposed between the base plate and the cover plate and bonded. Each of the core plates is characterized by a plurality of protrusions comprising square-based, truncated pyramids uniformly aligned along orthogonally related axes perpendicularly bisecting the legs of the bases of the pyramids and alternately inverted along orthogonally related planes diagonally bisecting the pyramids, whereby an orthogonally corrugated core is provided.

Ko, W. L. (inventor)

1981-01-01

50

Diffusion bonding stainless steel to alumina using aluminium interlayers  

Microsoft Academic Search

A study has been conducted to identify the effects of fabrication temperatures pressures, times and other variables on the strengths of diffusion-bonded joints between alumina and BS321 stainless steel produced using aluminium foil interlayers. The strengths of the alumina-aluminium and steel-aluminium interfaces were found to be influenced differently by some fabrication parameters, thus increasing the fabrication temperature promoted alumina-aluminium bonding

M. G. Nicholas; R. M. Crispin

1982-01-01

51

Mechanical properties of diffusion bonded beryllium ingot sheet  

Microsoft Academic Search

A technique for producing thick beryllium plate from ingot source material by diffusion-bonding together thin sheets is described.\\u000a The bonds produced are at least as strong as the matrix, and are produced under conditions where no significant grain growth\\u000a occurs. The laminated plate has better mechanical properties than the sheet from which it was made, and properties substantially\\u000a superior to

Clinton R. Heiple

1972-01-01

52

A local view of bonding and diffusion at metal surfaces  

SciTech Connect

First-principles density functional calculations and corresponding experimental results underline the importance of basic chemical concepts, such as coordination, valence saturation and promotion-hybridization energetics, in understanding bonding and diffusion of atoms at and on metal surfaces. Several examples are reviewed, including outer-layer relaxations of clean hcp(0001) surfaces, liquid-metal-embrittlement energetics, separation energies of metal-adatom dimers, concerted substitutional self-diffusion on fcc(001) surfaces, and adsorption and diffusion barrier sites for adatoms near steps.

Feibelman, P.J.

1996-09-01

53

Silver plating ensures reliable diffusion bonding of dissimilar metals  

NASA Technical Reports Server (NTRS)

Dissimilar metals are reliably joined by diffusion bonding when the surfaces are electroplated with silver. The process involves cleaning and etching, anodization, silver striking, and silver plating with a conventional plating bath. It minimizes the formation of detrimental intermetallic phases and provides greater tolerance of processing parameters.

1967-01-01

54

Diffusion bonding of stainless steel to Zircaloy-4 in the presence of a Ta intermediate layer  

NASA Astrophysics Data System (ADS)

Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been investigated using diffusion couples heat treated at 1150 °C under vacuum for 3 h. Different types of regions have been observed in stainless steel, Zircaloy-4 and Ta foil. A Cr rich layer formed in stainless steel is found to act as a diffusion barrier. A region observed with the Ta foil in Zircaloy-4 is rich in Cr, Ta, Fe and Zr while two zones are formed in Zircaoly-4 containing Zr, Ta, Cr, Fe and Ni. The zone rich in Zr gives black contrast and the other zone gives grey contrast and these are identified as eutectic phases of the type TaCr 2-Liq.-?-Zr and Ta(Cr,Fe) 2-Liq.-?-Zr.

Ahmad, M.; Akhter, J. I.; Zaman, Q.; Shaikh, M. A.; Akhtar, M.; Iqbal, M.; Ahmed, E.

2003-05-01

55

Explosive bonding of plates with diffusion barrier interfaces  

NASA Astrophysics Data System (ADS)

Composite plates, with and without, ``waves'' were made using improved explosive welding techniques. Oriented heat treatment of one surface of a steel-titanium composite introduces brittle intermetallic material at the specific interface. Currently, we are investigating methods to minimize this layer. While ``waveless'' interfaces revealed minimum intermetallic material; failure of the bond during ballistic impact necessitated production of a semi-compatible diffusion barrier using a fine layer of pure metal. Methods of producing composite plates with different interlayer materials and the effect of variables in optimizing the bond quality is presented. .

Joshi, V. S.; Banks, M. L.; Krebsbach, J.

2000-04-01

56

Explosive Bonding of Plates with Diffusion Barrier Interfaces  

NASA Astrophysics Data System (ADS)

Composite plates, with and without, “waves” were made using improved explosive welding techniques. Oriented heat treatment of one surface of a steel-titanium composite introduces brittle intermetallic material at the specific interface. Currently, we are investigating methods to minimize this layer. While “waveless” interfaces revealed minimum intermetallic material; failure of the bond during ballistic impact necessitated production of a semi-compatible diffusion barrier using a fine layer of pure metal. Methods of producing composite plates with different interlayer materials and the effect of variables in optimizing the bond quality will be presented.

Joshi, Vasant; Banks, Marvin; Krebsbach, John

1999-06-01

57

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

Microsoft Academic Search

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

Alexander Teverovsky

2004-01-01

58

Metallurgical integrity of the frit vent assembly diffusion bond  

NASA Astrophysics Data System (ADS)

The metallurgical integrity of frit vent assemblies produced by Martin Marietta Energy Systems, Inc. (Energy Systems) were compared to those produced G-Mound Applied Technologies, Inc. (EG&G-MAT). Frit vent assemblies were metallographically prepared and examined at magnifications from 50X to 1000X. Scanning electron microscope (SEM) examinations were made of the diffusion bonded powder in finished frit vent assemblies produced by Energy Systems and EG&G-MAT. The metallographic and SEM examinations of the particle-to-particle and particel-to-foil component diffusion bonds indicated that the Energy Systems-produced and EG&G-MAT-produced frit vent assemblies have comparable metallurgical integrity. The Energy Systems production data show that the frit vent manufacturing yield is 91%.

Ulrich, George B.

1995-01-01

59

Metallurgical integrity of the frit vent assembly diffusion bond  

SciTech Connect

The metallurgical integrity of frit vent assemblies produced by Martin Marietta Energy Systems, Inc. (Energy Systems) were compared to those produced previously by EG&G-Mound Applied Technologies, Inc. (EG&G-MAT). Frit vent assemblies were metallographically prepared and examined at magnifications from 50X to 1000X. Scanning electron microscope (SEM) examinations were made of the diffusion bonded powder in finished frit vent assemblies produced by Energy Systems and EG&G-MAT. The metallographic and SEM examinations of the particle-to-particle and particel-to-foil component diffusion bonds indicated that the Energy Systems-produced and EG&G-MAT-produced frit vent assemblies have comparable metallurgical integrity. The Energy Systems production data show that the frit vent manufacturing yield is 91%. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}

Ulrich, G.B. [Oak Ridge Y-12 Plant, Martin Marietta Energy Systems, Inc., P.O. Box 2009, Oak Ridge, Tennessee 37831-8096 (United States)

1995-01-20

60

Joining of Silicon Carbide Through the Diffusion Bonding Approach  

NASA Technical Reports Server (NTRS)

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.

Halbig, Michael .; Singh, Mrityunjay

2009-01-01

61

Mo/Ti Diffusion Bonding for Making Thermoelectric Devices  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

62

Elastic constants for superplastically formed/diffusion-bonded sandwich structures  

NASA Technical Reports Server (NTRS)

Formulae and the associated graphs are presented for contrasting the effective elastic constants for a superplastically formed/diffusion-bonded (SPF/DB) corrugated sandwich core and a honeycomb sandwich core. The results used in the comparison of the structural properties of the two types of sandwich cores are under conditions of equal sandwich density. It was found that the stiffness in the thickness direction of the optimum SPF/DB corrugated core (i.e., triangular truss core) was lower than that of the honeycomb core, and that the former had higher transverse shear stiffness than the latter.

Ko, W. L.

1979-01-01

63

Analyzing the Effect of Diffusion Bonding Process Parameters on Bond Characteristics of Mg-Al Dissimilar Joints  

NASA Astrophysics Data System (ADS)

The principle difficulty when joining magnesium (Mg)-aluminium (Al) lies in the existence of formation of oxide films and brittle intermetallic in the bond region. However, diffusion bonding can be used to join these alloys without much difficulty. Temperature, pressure, and holding time are the three main variables which govern the integrity of a diffusion bond. This paper focuses on the effect of these parameters on diffusion layer thickness, hardness and strength of AZ31B magnesium-AA2024 aluminium dissimilar joints. The experiments were conducted based on three factors, five-level, and central composite rotatable design with full replications technique. Empirical relationships were developed to predict diffusion layer thickness, hardness and strength using response surface methodology. From this investigation, it is found that bonding temperature has predominant effect on bond characteristics.

Mahendran, G.; Babu, S.; Balasubramanian, V.

2010-07-01

64

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

Microsoft Academic Search

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

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

2008-01-01

65

Diffusion bonding of grey cast iron to ARMCO iron and a carbon steel  

Microsoft Academic Search

The microstructure transformations produced during the diffusion bonding of grey cast iron to pure iron (ARMCO iron) and to a hypoeutectic steel (0.55% C) have been studied. The indirect determination of the carbon concentration profiles has produced a diffusion equation that relates the microstructure of the bond interface to the bonding temperature and time. A new tensile test specimen is

F. A. Calvo; A. Ureña; J. M. Gomez de Salazar; F. Molleda

1989-01-01

66

Vacuum-Bonded Covering Withstands Low Temperature: A composite material for wrapping pipes withstands liquid oxygen and liquid air.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. Aluminum foil, tetrafluoroethylene (TRE), and glass fabric can be vacuum-bonded together to make a composite covering material that is flexible and easy to handle. I...

1981-01-01

67

The diffusion bonding of silicon carbide and boron carbide using refractory metals  

SciTech Connect

Joining is an enabling technology for the application of structural ceramics at high temperatures. Metal foil diffusion bonding is a simple process for joining silicon carbide or boron carbide by solid-state, diffusive conversion of the metal foil into carbide and silicide compounds that produce bonding. Metal diffusion bonding trials were performed using thin foils (5 {micro}m to 100 {micro}m) of refractory metals (niobium, titanium, tungsten, and molybdenum) with plates of silicon carbide (both {alpha}-SiC and {beta}-SiC) or boron carbide that were lapped flat prior to bonding. The influence of bonding temperature, bonding pressure, and foil thickness on bond quality was determined from metallographic inspection of the bonds. The microstructure and phases in the joint region of the diffusion bonds were evaluated using SEM, microprobe, and AES analysis. The use of molybdenum foil appeared to result in the highest quality bond of the metal foils evaluated for the diffusion bonding of silicon carbide and boron carbide. Bonding pressure appeared to have little influence on bond quality. The use of a thinner metal foil improved the bond quality. The microstructure of the bond region produced with either the {alpha}-SiC and {beta}-SiC polytypes were similar.

Cockeram, B.V.

1999-10-01

68

Theoretical and experimental analyses of atom diffusion characteristics on wire bonding interfaces  

NASA Astrophysics Data System (ADS)

The features of ultrasonic bonding interface were inspected by using a high resolution transmission electron microscope. Stress of ultrasonic bonding interface was analysed by the finite elements simulation. Results show that the high stress of bonding interface was caused by ultrasonic vibration, which increased the dislocation density inside the metal crystalline lattice which provides the fast diffusion channels, and provided driving force for atom inter-diffusion. 'Short-circuit diffusion' during ultrasonic bonding is more prominent than crystal diffusion. For the given ultrasonic bonding parameters, depth of atom diffusion at Au/Al interface of ultrasonic bonding was about 100-300 nm in several ten milliseconds, which forms the bonding strength of 0.65 N, and it is an inter-metallic compound of AuAl2. These will be helpful for further analysis.

Li, Junhui; Fuliang, Wang; Han, Lei; Zhong, Jue

2008-07-01

69

Capacitive Absolute Pressure Sensor with Vacuum Cavity Formed by Bonding Silicon to Soiwafer for Upper Air Observations  

Microsoft Academic Search

We present a capacitive absolute pressure sensor with a large deflected diaphragm that was fabricated with a sealed vacuum cavity formed by removing handling silicon wafer and oxide layers from a SOI wafer after eutectic bonding of a silicon wafer to the SOI wafer. The deflected displacements of the diaphragm formed by the vacuum cavity in the fabricated sensor were

K. R. Lee; K. Kim; Y. K. Kim; H. D. Park; S. W. Choi; W. B. Choi; B. K. Ju

2006-01-01

70

The metallurgical integrity of the frit vent assembly diffusion bond  

SciTech Connect

Iridium alloy clad vent sets (CVSs) are now being made by Energy Systems at the Oak Ridge Y-12 Plant. These CVSs are being made for the US Department of Energy`s (NE-53) General Purpose Heat Source- Radioisotope Thermoelectric Generator (GPHS-RTG) program, which is to supply electrical power for the National Aeronautics and Space Administration`s Cassini mission to Saturn. A GPHS-RTG has 72 CVSs. Each CVS encapsulates one {sup 238}PuO{sub 2} fuel pellet. The helium gas produced from the alpha decay of the {sup 238}Pu is vented through a nominal 0.45-mm-diam hole in the vent cup of each CVS. A frit vent assembly that is electron beam welded over the vent hole allows helium gas to escape but prevents plutonia fines from exiting. The metallurgical integrity of frit vent assemblies produced by Martin Marietta Energy Systems, Inc. (Energy Systems) were compared with those produced earlier by EG&G-Mound Applied Technology, Inc. (EG&G-MAT). Scanning electron microscope (SEM) photographs were taken (at magnifications of from 126X to 1,000X) of the starting frit vent powder and the diffusion-bonded powder in finished frit vent assemblies produced by Energy Systems and EG&G-MAT. Frit vent assemblies also were metallographically prepared and visually examined/photographed at magnifications of from 50X to 1,000X. The SEM and metallographic examinations of the particle-to-particle and particle-to-foil component diffusion bonds indicated that the Energy Systems-produced and EG&G-MAT-produced frit vent assemblies have comparable metallurgical integrity. Statistical analysis of the Energy Systems production data shows that the frit vent manufacturing yield is 91%.

Ulrich, G.B. [Oak Ridge Y-12 Plant, TN (United States). Process Metallurgy Dept.

1994-06-01

71

Microstructures of diffusion bonded SiC ceramics using Ti and Mo interlayers  

NASA Astrophysics Data System (ADS)

SiC plates were diffusion bonded using metallic interlayers of Ti and Mo foils. For the joining, a uniaxial pressure of ˜7 MPa was applied at 1400 °C for 1 h in a vacuum. The interfacial microstructures along with their atomic compositions of the SiC/SiC joints were analyzed. For the Ti interlayer, Ti was converted into a Ti3SiC2 phase owing to the diffusion of silicon and carbon from the SiC part. A crystallographic orientation relationship was found between the SiC and Ti3SiC2 grains. At the middle of the Ti interlayer, a TiSi2 phase also existed, forming a dual-phase region. For the Mo interlayer, the diffusion of silicon into Mo induced the formation of the Mo5Si3C phase at the SiC/Mo interface. An unreacted metallic phase was still observed in the middle of the Mo insert. The shear strengths of the joints were 67 MPa and 76 MPa for the Ti and Mo interlayers, respectively.

Jung, Yang-Il; Kim, Sun-Han; Kim, Hyun-Gil; Park, Jeong-Yong; Kim, Weon-Ju

2013-10-01

72

AN EVALUATION OF THE DIFFUSION-BONDING CHARACTERISTICS OF ZIRCALOY2  

Microsoft Academic Search

Ten promising diffuser elements were used in experiments aimed at ; joining Zircaloy-2 components by a diffusion-bonding technique. Copper, nickel, ; nickel-phosphorus, manganese, and silicon appear most favorable for this purpose. ; (auth);

Feduska

1959-01-01

73

Vacuum-compatible standard diffuse source, manufacture, and calibration  

Microsoft Academic Search

Los Alamos National Laboratories has completed the design, manufacture and calibration of a vacuum-compatible, tungsten lamp, integrating sphere. The light source has been calibrated at the National Institute of Standards and Technology 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

Donald A. Byrd; W. H. Atkins; Steven C. Bender; R. W. Christensen; Francis D. Michaud

1998-01-01

74

Vacuum-compatible standard diffuse source, manufacture and calibration  

Microsoft Academic Search

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 2Ï uncertainty varied with wavelength from 1.21% at 400 nm and 0.73% at

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

1999-01-01

75

Supplement A to production test IP-546-A irradiation of diffusion-bonded fuel elements.  

National Technical Information Service (NTIS)

The original test authorized the irradiation of about 20 fuel columns containing hot-die-sized, diffusion-bonded fuel elements. Objectives of this supplement are to permit irradiation of an additional ten columns of hot-die-sized, diffusion-bonded fuel el...

K. L. Hladek

1964-01-01

76

Special features of the formation of the diffusion bonded joints between copper and aluminium  

Microsoft Academic Search

A metallographic study of diffusion bonds between aluminium and copper has been made in order to further understanding of the mechanism of bond formation for joints between dissimilar metals that form intermediate phases or intermetallic compounds. A three-stage mechanistic model based upon sintering principles has been proposed to explain this kind of diffusion joint.

F. A. Calvo; A. Ureng; J. M. Gomez De Salazar; F. Molleda

1988-01-01

77

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

NASA Astrophysics Data System (ADS)

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

Kasprzycka, Ewa; Senatorski, Jan; Nakonieczny, Aleksander; Babul, Tomasz

2003-12-01

78

Leakage rates and thermal requirements for the diffusion bonding of microchannel arrays via internal convective heating  

SciTech Connect

Diffusion bonding cycle times can be a large cost factor in the production of metal microchannel devices. The challenge is to significantly minimize this cost by reducing the bonding cycle time through rapid and uniform heating and cooling within the bonding process. Heating rates in diffusion bonding processes are typically limited by the need to minimize thermal gradients during bonding. 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. This paper will demonstrate the ability to effectively diffusion bond microchannel laminae using the ICH method by investigating the leakage rates.

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

2007-07-24

79

Research on Transient Liquid Phase Diffusion Bonding of Steel Sandwich Panels Under Small Plastic Deformation  

Microsoft Academic Search

Plastic deformation was newly introduced in transient liquid phase (TLP) diffusion bonding of steel sandwich panels. The effect\\u000a of plastic deformation on bonding strength was investigated through lab experiments. It was assumed that three factors, including\\u000a newly generated metal surface area, deformation heat, and lattice distortion, contribute to the acceleration of interface\\u000a atoms diffusion and increase of diffusion coefficients. A

H. Li; Z. X. Li

2008-01-01

80

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

NASA Astrophysics Data System (ADS)

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.

Krobath, H.; Schütz, G. J.; Lipowsky, R.; Weikl, T. R.

2007-05-01

81

Bonding Mechanisms in Resistance Microwelding of 316 Low-Carbon Vacuum Melted Stainless Steel Wires  

NASA Astrophysics Data System (ADS)

Resistance microwelding (RMW) is an important joining process used in the fabrication of miniature instruments, such as electrical and medical devices. The excellent corrosion resistance of 316 low-carbon vacuum melted (LVM) stainless steel (SS) wire makes it ideal for biomedical applications. The current study examines the microstructure and mechanical properties of crossed resistance microwelded 316LVM wire. Microtensile and microhardness testing was used to analyze the mechanical performance of welds, and fracture surfaces were examined using scanning electron microscopy. Finally, a bonding mechanism is proposed based on optimum joint breaking force (JBF) using metallurgical observations of weld cross sections. Moreover, comparisons with RMWs of Ni, Au-plated Ni, and SUS304 SS wire are discussed.

Khan, M. I.; Kim, J. M.; Kuntz, M. L.; Zhou, Y.

2009-04-01

82

Light-induced hydrogen evolution from hydrogenated amorphous silicon: Hydrogen diffusion by formation of bond centered hydrogen  

NASA Astrophysics Data System (ADS)

The light-induced hydrogen evolution (LIHE) from amorphous (a-) Si:H by the order of at. % is observed during white light soaking (WLS) of 100-400 mW/cm2 at 350-500 K or ultra violet light soaking (UVLS) of 30-120 mW/cm2 at 305-320 K in a vacuum. The thermal desorption spectroscopy indicates that LIHE originated from bonded hydrogen takes place through the diffusion of light-induced mobile hydrogen (LIMH) with the activation energy of 0.5 eV. LIMH is assigned to bond centered hydrogen and the hydrogen diffusion process becomes prominent when LIMH can leave from a-Si:H such under light soaking in a vacuum above room temperature. For H2 in microvoids, the hydrogen evolution rate is governed by the surface barrier and its activation energy of 1.0 eV in dark decreases to 0.4 eV under WLS or UVLS.

Tanimoto, H.; Arai, H.; Mizubayashi, H.; Yamanaka, M.; Sakata, I.

2014-02-01

83

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

Microsoft Academic Search

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

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

2001-01-01

84

Diffusion bonding and its application to manufacturing. [for joining of metal parts  

NASA Technical Reports Server (NTRS)

In its simplest form diffusion bonding is accomplished by placing clean metal surfaces together under a sufficient load and heating. The natural interatomic attractive force between atoms transforms the interface into a natural grain boundary. Therefore, in principle, the properties of the bond area are identical to those of the parent metal. Other advantages of diffusion bonding over conventional methods of bonding include freedom from residual stresses, excessive deformation, foreign metals, or changed crystal structures. Stainless steels, nickel-base superalloys, and aluminum alloys have all been successfully joined. Complex hardware, including integrated flueric devices, jet engine servovalves, and porous woven structures have been fabricated. The processing involved is discussed, along with such theoretical considerations as the role of metal surfaces, the formation of metal contact junctions, and the mechanisms of material transport in diffusion bonding.

Spurgeon, W. M.

1972-01-01

85

Surface Preparation of IPNS (Intense Pulsed Neutron Source) Booster Target Components Prior to Diffusion Bonding.  

National Technical Information Service (NTIS)

In support of Argonne National Laboratory's Intense Pulsed Neutron Source (IPNS) program, the Oak Ridge Y-12 Plant has fabricated 15 Zircaloy-2 clad, enriched uranium booster targets using hot isostatic pressing (HIP) to effect diffusion bonding between t...

R. F. Simandl H. L. Richards L. M. Thompson

1988-01-01

86

Reactive diffusion in the roll bonded iron–aluminum system  

Microsoft Academic Search

The diffusion-controlled growth of iron aluminide (Fe2Al5) was studied on bulk Fe–Al solid state diffusion couples annealed for 10–90 min at 773–873 K. The layer growth kinetics was parabolic. The parabolic growth constants of the second kind for the exclusive growth of Fe2Al5 from the adjacent phases were calculated from the measurement on the Fe–Al diffusion couples. The rate constants

Vikas Jindal; V. C. Srivastava; Arpan Das; R. N. Ghosh

2006-01-01

87

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

Microsoft Academic Search

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

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

2001-01-01

88

Method of fluxless brazing and diffusion bonding of aluminum containing components  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

89

Supplement A to production test IP546-A irradiation of diffusion-bonded fuel elements  

Microsoft Academic Search

The original test authorized the irradiation of about 20 fuel columns containing hot-die-sized, diffusion-bonded fuel elements. Objectives of this supplement are to permit irradiation of an additional ten columns of hot-die-sized, diffusion-bonded fuel elements, and to obtain data on the relation of the coolant temperature distribution and fuel element behavior. These fuel columns will be irradiated in smooth-bore Zircaloy-2 process

Hladek

1964-01-01

90

Probing the diffusion of vacuum ultraviolet ( ? = 172 nm) induced oxidants by nanoparticles immobilization  

NASA Astrophysics Data System (ADS)

Vacuum ultraviolet (VUV, ? = 172 nm) patterning of alkyl monolayer on silicon surface has been demonstrated with emphasis on the diffusion of VUV induced oxygen-derived active species, which are accountable for the pattern broadening. The VUV photons photo-dissociates the atmospheric oxygen and water molecules into the oxygen-derived active species (oxidants). These oxidants photo-oxidize the hexadecyl (HD) monolayer in VUV irradiated regions (Khatri et al., Langmuir. 24 (2008) 12077), as well as the little concentration of oxidants diffuses towards the masked areas. In this study, we performed VUV patterning at a vacuum pressure of 10 Pa to track the diffusion pathways for the oxidants with help of gold nanoparticles (AuNPs; ? = 10 nm) immobilization. At VUV irradiated sites AuNPs are found as uniformly distributed, but adjacent to the pattern boundary we observed quasi-linear arrays of AuNPs, which are determined by diffusion pathways of the oxidants. The diffusion of oxidants plays vital role in pattern broadening. The site selective anchoring of AuNPs demonstrates the utility of VUV photons for the construction of functional materials with microstructural architecture.

Khatri, Om P.; Hatanaka, Takeshi; Murase, Kuniaki; Sugimura, Hiroyuki

2009-09-01

91

Probing the diffusion of vacuum ultraviolet ( ? = 172 nm) induced oxidants by nanoparticles immobilization  

Microsoft Academic Search

Vacuum ultraviolet (VUV, ?=172nm) patterning of alkyl monolayer on silicon surface has been demonstrated with emphasis on the diffusion of VUV induced oxygen-derived active species, which are accountable for the pattern broadening. The VUV photons photo-dissociates the atmospheric oxygen and water molecules into the oxygen-derived active species (oxidants). These oxidants photo-oxidize the hexadecyl (HD) monolayer in VUV irradiated regions (Khatri

Om P. Khatri; Takeshi Hatanaka; Kuniaki Murase; Hiroyuki Sugimura

2009-01-01

92

Diffusion welding. [heat treatment of nickel alloys following single step vacuum welding process  

NASA Technical Reports Server (NTRS)

Dispersion-strengthened nickel alloys are sanded on one side and chemically polished. This is followed by a single-step welding process wherein the polished surfaces are forced into intimate contact at 1,400 F for one hour in a vacuum. Diffusion, recrystallization, and grain growth across the original weld interface are obtained during postheating at 2,150 F for two hours in hydrogen.

Holko, K. H. (inventors)

1974-01-01

93

SOLID-STATE DIFFUSION BONDING OF INCONEL ALLOY 718 TO 17-4 PH STAINLESS STEEL  

Microsoft Academic Search

Solid-state diffusion bonding of Inconel® alloy 718 to 17-4 PH® stainless steel was studied. Mechanical tests and metallographic examinations were used to evaluate the joint quality. The effect of bonding pressure on the joint integrity was assessed. In all joints, failure occurred nearly without plastic deformation. The thermal residual stress generated from cooling to room temperature was calculated by finite

Zhang Guoge; R. S. Chandel; H. P. Seow

2001-01-01

94

Fracture and Fatigue of Diffusion, Adhesive, and Roll Bonded Aluminum, Titanium, and Ultrahigh Carbon Steel Laminates.  

National Technical Information Service (NTIS)

The fracture characteristics of twelve different diffusion bonded Al/Al, Ti/Ti and Ultrahigh Carbon Steel/Iron and adhesively bonded Al/Epoxy laminates were evaluated. The effects of periodic overloads on the fatigue crack retardation behavior in a roll b...

R. M. Johnson

1978-01-01

95

Bonding strength in carbon steel sandwich panels under condition of diffusion-rolling with small reduction  

Microsoft Academic Search

One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant\\u000a coat. A bonding assistant coat used below 850 C was developed. It contained copper as basic element and zinc as main alloy\\u000a element. Other small elements and rare metals were added to decrease the melting point and to obtain a better

Jing Liu; Jing-tao Han; Ding-mei Fu

2005-01-01

96

The fabrication of all-silicon micro gas chromatography columns using gold diffusion eutectic bonding  

NASA Astrophysics Data System (ADS)

Temperature programming of gas chromatography (GC) separation columns accelerates the elution rate of chemical species through the column, increasing the speed of analysis, and hence making it a favorable technique to speedup separations in microfabricated GCs (micro-GC). Temperature-programmed separations would be preferred in an all-silicon micro-column compared to a silicon-Pyrex® micro-column given that the thermal conductivity and diffusivity of silicon is 2 orders of magnitude higher than Pyrex®. This paper demonstrates how to fabricate all-silicon micro-columns that can withstand the temperature cycling required for temperature-programmed separations. The columns were sealed using a novel bonding process where they were first bonded using a gold eutectic bond, then annealed at 1100 °C to allow gold diffusion into silicon and form what we call a gold diffusion eutectic bond. The gold diffusion eutectic-bonded micro-columns when examined using scanning electron microscopy (SEM), scanning acoustic microscopy (SAM) and blade insertion techniques showed bonding strength comparable to the previously reported anodic-bonded columns. Gas chromatography-based methane injections were also used as a novel way to investigate proper sealing between channels. A unique methane elution peak at various carrier gas inlet pressures demonstrated the suitability of gold diffusion eutectic-bonded channels as micro-GC columns. The application of gold diffusion eutectic-bonded all-silicon micro-columns to temperature-programmed separations (120 °C min-1) was demonstrated with the near-baseline separation of n-C6 to n-C12 alkanes in 35 s.

Radadia, A. D.; Salehi-Khojin, A.; Masel, R. I.; Shannon, M. A.

2010-01-01

97

Diffusion Bonding of Silicon Carbide and Boron Carbide Using Refractory Metals.  

National Technical Information Service (NTIS)

Joining is an enabling technology for the application of structural ceramics at high temperatures. Metal foil diffusion bonding is a simple process for joining silicon carbide or boron carbide by solid-state, diffusive conversion of the metal foil into ca...

B. V. Cockeram

1999-01-01

98

Diffusion bonding of beryllium to CuCrZr for ITER applications.  

SciTech Connect

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.

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

2008-08-01

99

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

PubMed

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. PMID:24908026

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

2014-06-01

100

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

101

A Numerical Study on Heat Flow and Load Distribution During Chip to Wafer or Wafer to Wafer Bonding in Vacuum  

Microsoft Academic Search

In this paper Authors report the implementation of a Finite Element Method (FEM) in modelling the heat flow and the deformation of the main part of the bonding machine, the work undertaken in order to develop and optimize the technology for innovative waferlevel vacuum packaging process, addressed to high volume System-in-Package (SiP) production. The investigated new approach is based on

K. Malecki; L. Pikur; T. Falat; G. Bock; G. Hillmann; A. Sigl; N. Marenco; K. Friedel

2008-01-01

102

Diffusion behavior and mechanism of co-sputtering metals as bonding materials for 3D IC interconnects during annealing treatment  

Microsoft Academic Search

A diffusion behavior was observed for co-sputtered metals during thermal treatment, while these metals were fabricated as bonding mediums in 3D IC applications. This paper reports and discusses the mechanical behavior of co-sputtering metals before and after annealing. In addition, co-sputtering metal bonding seems to be an option for bonding technology based on their excellent bonding results.

S. Y. Hsu; J. Y. Shih; K. N. Chen

2011-01-01

103

H/sub 2/ fluorescence and the diffuse galactic light in the vacuum ultraviolet  

SciTech Connect

Fluorescence by molecular H/sub 2/ within the Lyman and Werner bands, as well as to continuum levels of the X/sup 1/S/sub g/ /sup +/ state, occurs at wavelengths l< or =0.18 mm. This emission is shown to be of intensity comparable to that scattered by dust over the same wavelength range in diffuse clouds. The implied increase in dust albedo in the vacuum ultraviolet (VUV) is likely due to this effect. Thus the small particles responsible for VUV extinction are of conventional chemical composition, i.e., absorbing oxides, silicates, or carbons.

Duley, W.W.; Williams, D.A.

1980-12-15

104

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

SciTech Connect

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.

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

105

Effect of Surface Preparation on CLAM/CLAM Hot Isostatic Pressing diffusion bonding joints  

NASA Astrophysics Data System (ADS)

Surface preparation is essential for the Hot Isostatic Pressing (HIP) diffusion bonding of RAFM steels. Hot Isostatic Pressing (HIP) diffusion bonding experiments on China Low Activation Martensitic (CLAM) steel was performed to study the effect of surface preparation. A few approaches such as hand lapping, dry-milling and grinding etc., were used to prepare the faying surfaces of the HIP joints. Different sealing techniques were used as well. The HIP parameters were 150 MPa/3 h/1150 °C. After post HIP heat treatment (PHHT), the tensile and Charpy impact tests were carried out. The results showed that hand lapping was not suitable to prepare the faying surfaces of HIP diffusion bonding specimens although the surface roughness by hand lapping was very low.

Li, C.; Huang, Q.; Zhang, P.

2009-04-01

106

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

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

107

Study of the Interface Characteristic of Be/HR-1 Stainless Steel Following Diffusion Bonding  

NASA Astrophysics Data System (ADS)

The interface structure of Be/HR-1 stainless steel (SS) joint following diffusion bonding was investigated. Metallurgical observation, electron scanning microscopy, X-ray diffraction and scanning Auger microspectroscopy were performed for basic evaluation of bonded joints. There are intermetallic compounds such as Be11Fe and Be12Cr in the interface region of Be/SS joints, which drastically reduce the mechanical strength of the joints. Cu, Ag and Al barriers can block effective inter-diffusion of Be and HR-1 stainless steel, then forming brittle phases.

Zhang, Peng-Cheng; Bai, Bin; Yang, Jiang-Rong; Zou, Jue-Sheng; Zhou, Shou-Qi

108

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

NASA Astrophysics Data System (ADS)

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.

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

2011-04-01

109

A probabilistic, semi-empirical approach to modeling diffusion bond strength.  

SciTech Connect

Manufacture of critical diffusion bonded components could benefit from predictive models of diffusion bond joint strength. Existing models focus on porosity closure, which is a necessary but not sufficient condition for acceptable joint strength. The present work identifies modeled dynamics intrinsic to manufacturing but not captured in existing models. Controls regulating these dynamics are proposed, and the topography of real engineering surfaces is described by distribution functions. Pore closure kinetics then can successfully link initial surface topography and final porosity distribution, which in turn correlates to joint strength given experimental data linking porosity to joint strength.

Dave, V. R. (Vivek R.); Hartman, D. A. (Daniel A.); Barieri, J. M. (Joann M.)

2001-01-01

110

Transient liquid phase diffusion bonding of Udimet 720 for Stirling power converter applications  

NASA Astrophysics Data System (ADS)

Udimet 720 has been selected for use on Stirling power converters for space applications. Because Udimet 720 is generally considered susceptible to strain age cracking if traditional fusion welding is used, other joining methods are being considered. A process for transient liquid phase diffusion bonding of Udimet 720 has been theoretically developed in an effort to eliminate the strain age crack concern. This development has taken into account such variables as final grain size, joint homogenization, joint efficiency related to bonding aid material, bonding aid material application method, and thermal cycle.

Mittendorf, Donald L.; Baggenstoss, William G.

111

Transient liquid phase diffusion bonding of Udimet 720 for Stirling power converter applications  

NASA Technical Reports Server (NTRS)

Udimet 720 has been selected for use on Stirling power converters for space applications. Because Udimet 720 is generally considered susceptible to strain age cracking if traditional fusion welding is used, other joining methods are being considered. A process for transient liquid phase diffusion bonding of Udimet 720 has been theoretically developed in an effort to eliminate the strain age crack concern. This development has taken into account such variables as final grain size, joint homogenization, joint efficiency related to bonding aid material, bonding aid material application method, and thermal cycle.

Mittendorf, Donald L.; Baggenstoss, William G.

1992-01-01

112

The Breathing Orbital Valence Bond Method in Diffusion Monte Carlo: C-H Bond Dissociation ofAcetylene  

SciTech Connect

This study explores the use of breathing orbital valence bond (BOVB) trial wave functions for diffusion Monte Carlo (DMC). The approach is applied to the computation of the carbon-hydrogen (C-H) bond dissociation energy (BDE) of acetylene. DMC with BOVB trial wave functions yields a C-H BDE of 132.4 {+-} 0.9 kcal/mol, which is in excellent accord with the recommended experimental value of 132.8 {+-} 0.7 kcal/mol. These values are to be compared with DMC results obtained with single determinant trial wave functions, using Hartree-Fock orbitals (137.5 {+-} 0.5 kcal/mol) and local spin density (LDA) Kohn-Sham orbitals (135.6 {+-} 0.5 kcal/mol).

Domin, D.; Braida, Benoit; Lester Jr., William A.

2008-05-30

113

Materials evaluation of diffusion bonded steel bar and its impact characteristics  

Microsoft Academic Search

When we apply non-destructive test for evaluating the soundness of weld joints it is necessary to know the mechanical properties of the joints by destructive test. In this paper we tried to obtain the correlation between the data by ultrasonic C-scope method and the absorbed energy by Charpy impact test for diffusion bonded steel bars. The surface roughness of specimens

Mitsuaki Katoh; Kazumasa Nishio; Tomiko Yamaguchi

2002-01-01

114

The applicability of plate wave techniques for the inspection of adhesive and diffusion bonded joints  

Microsoft Academic Search

The role of plate waves in the inspection of adhesive and diffusion bonded joints is examined. This involves a review of the modal techniques which have been proposed for the measurement of the adhesion and cohesion properties of adhesive joints and the presentation of some of our own studies on the detection and characterization of an unwanted layer of brittle

M. J. S. Lowe; P. Cawley

1994-01-01

115

Diffusion bonding of aluminium oxide to stainless steel using stress relief interlayers  

Microsoft Academic Search

Aluminium oxide was diffusion bonded to AISI 304 steel using Ti, Cu or Mo as interlayer materials. It was observed that Ti joins easily to both ceramic and steel parts, giving an average shear strength equal to 20 MPa. However, within the experimental conditions applied, the adhesion between Al2O3 and Cu or Mo was unsuccessful. A finite element modelling (FEM)

Dilermando Travessa; Maurizio Ferrante; Gert den Ouden

2002-01-01

116

Transient liquid phase diffusion bonding of Udimet 720 for Stirling power converter applications  

Microsoft Academic Search

Udimet 720 has been selected for use on Stirling power converters for space applications. Because Udimet 720 is generally considered susceptible to strain age cracking if traditional fusion welding is used, other joining methods are being considered. A process for transient liquid phase diffusion bonding of Udimet 720 has been theoretically developed in an effort to eliminate the strain age

Donald L. Mittendorf; William G. Baggenstoss

1992-01-01

117

Design and fabrication of high performance wafer-level vacuum packaging based on glass-silicon-glass bonding techniques  

NASA Astrophysics Data System (ADS)

In this paper, a high performance wafer-level vacuum packaging technology based on GSG triple-layer sealing structure for encapsulating large mass inertial MEMS devices fabricated by silicon-on-glass bulk micromachining technology is presented. Roughness controlling strategy of bonding surfaces was proposed and described in detail. Silicon substrate was thinned and polished by CMP after the first bonding with the glass substrate and was then bonded with the glass micro-cap. Zr thin film was embedded into the concave of the micro-cap by a shadow-mask technique. The glass substrate was thinned to about 100 µm, wet etched through and metalized for realizing vertical feedthrough. During the fabrication, all patterning processes were operated carefully so as to reduce extrusive fragments to as little as possible. In addition, a high-performance micro-Pirani vacuum gauge was integrated into the package for monitoring the pressure and the leak rate further. The result shows that the pressure in the package is about 120 Pa and has no obvious change for more than one year indicating 10-13 stdcc s-1 leak rate.

Zhang, Jinwen; Jiang, Wei; Wang, Xin; Zhou, Jilong; Yang, Huabing

2012-12-01

118

Microstructural characterization of the Al\\/Cu\\/steel diffusion bonded joint  

Microsoft Academic Search

A vacuum hot-pressed diffusion method was used to prepare an Al\\/Cu\\/steel composite with a gradient structure. The Al\\/Cu interface\\u000a was investigated layer by layer by means of scanning electron microscopy, energy dispersive X-ray spectrometry, electron probe\\u000a microanalysis, and Vickers microhardness. The results show that two kinds of intermetallic compounds, Cu9Al4 adjacent to the Cu side and CuAl2 adjacent to the

Xiaole Cheng; Bingzhe Bai; Yimin Gao; Chun Feng

2009-01-01

119

Role of Hydrogen-Bonding in Nonelectrolyte Diffusion through Dense Artificial Membranes  

PubMed Central

The diffusion of two series of alcohols and amides through complex cellulose acetate membranes was studied. The thin dense part of these membranes behaves as a nonporous layer of low water content. In this layer, called the skin, the solute diffusion coefficients, ?, depend upon size, steric configuration, and the partition coefficient, K8, between membrane and bathing solution. From the experimental values of ? and K8, the over-all friction, f, experienced by the solutes in the membrane was computed. It was found that f depends upon the chemical nature of the solute and is related to hydrogen-bonding ability. In the coarse, porous layer of the cellulose acetate membrane, diffusion occurs mainly through aqueous channels. In this instance also the hydrogen-bonding ability of the solute seems to exercise a smaller but significant influence.

Gary-Bobo, C. M.; DiPolo, R.; Solomon, A. K.

1969-01-01

120

Water Dimer Diffusion on Pd{111} Assisted by an H-Bond Donor-Acceptor Tunneling Exchange  

Microsoft Academic Search

Based on the results of density functional theory calculations, a novel mechanism for the diffusion of water dimers on metal surfaces is proposed, which relies on the ability of H bonds to rearrange through quantum tunneling. The mechanism involves quasifree rotation of the dimer and exchange of H-bond donor and acceptor molecules. At appropriate temperatures, water dimers diffuse more rapidly

V. A. Ranea; A. Michaelides; R. Ramírez; P. L. de Andres; J. A. Vergés; D. A. King

2004-01-01

121

Effect of Bonding Time on Interfacial Reaction and Mechanical Properties of Diffusion-Bonded Joint Between Ti-6Al-4V and 304 Stainless Steel Using Nickel as an Intermediate Material  

NASA Astrophysics Data System (ADS)

In the current study, solid-state diffusion bonding between Ti-6Al-4V (TiA) and 304 stainless steel (SS) using pure nickel (Ni) of 200- ?m thickness as an intermediate material was carried out in vacuum. Uniaxial compressive pressure and temperature were kept at 4 MPa and 1023 K (750 °C), respectively, and the bonding time was varied from 30 to 120 minutes in steps of 15 minutes. Scanning electron microscopy images, in backscattered electron mode, revealed the layerwise Ti-Ni-based intermetallics like either Ni3Ti or both Ni3Ti and NiTi at titanium alloy-nickel (TiA/Ni) interface, whereas nickel-stainless steel (Ni/SS) interface was free from intermetallic phases for all the joints. Chemical composition of the reaction layers was determined by energy dispersive spectroscopy (SEM-EDS) and confirmed by X-ray diffraction study. Maximum tensile strength of ~382 MPa along with ~3.7 pct ductility was observed for the joints processed for 60 minutes. It was found that the extent of diffusion zone at Ni/SS interface was greater than that of TiA/Ni interface. From the microhardness profile, fractured surfaces, and fracture path, it was demonstrated that the failure of the joints was initiated and propagated apparently at TiA/Ni interface near Ni3Ti intermetallic for bonding time less than 90 minutes, and through Ni for bonding time 90 minutes and greater.

Thirunavukarasu, Gopinath; Kundu, Sukumar; Mishra, Brajendra; Chatterjee, Subrata

2014-04-01

122

Visible to vacuum-UV range optical absorption of oxygen dangling bonds in amorphous SiO2  

NASA Astrophysics Data System (ADS)

Synthetic silica glass with an optical absorption spectrum dominated by oxygen dangling bonds (nonbridging oxygen hole centers, or NBOHCs) and having negligible (<1%) contribution from the usually copresent Si dangling bonds (E'-centers), was prepared by room temperature ultraviolet photobleaching of high SiOH content (“wet”) silica, irradiated by F2 laser (7.9 eV) at T = 80 K. This allowed us to obtain the up-to-now controversial optical absorption spectrum of NBOHC in the ultraviolet and vacuum-ultraviolet (UV-VUV) region of the spectrum and to show that it is semicontinuous from 4 to 7.8 eV and cannot be represented by a pair of distinct Gaussian bands. Since NBOHC is one of the main UV-VUV range optical absorbers in silica, its spectral shape provides a tool to disentangle contributions of different color centers to optical losses in this spectral region.

Skuja, Linards; Kajihara, Koichi; Hirano, Masahiro; Hosono, Hideo

2011-11-01

123

Microstructure and mechanical properties of diffusion bonded SiC\\/steel joint using W\\/Ni interlayer  

Microsoft Academic Search

This paper describes the design and examination of W\\/Ni double interlayer to produce a joint between SiC and ferritic stainless steel. Diffusion bonding was performed by a two steps solid state diffusion bonding process. Microstructural examination and mechanical properties evaluation of the joints show that bonding of SiC to steel was successful. EDS and XRD analysis revealed that W5Si3 and

Zhihong Zhong; Tatsuya Hinoki; Hun-Chea Jung; Yi-Hyun Park; Akira Kohyama

2010-01-01

124

Microstructure of Diffusion-Bonded Mg-Ag-Al Multilayer Composite Materials  

NASA Astrophysics Data System (ADS)

Mg-Al bonded composite materials expand Mg and Al alloys' applications by combining their unique performances together. However, the formation of Mg-Al intermetallic compounds in interface zone of Mg/Al directly-bonded joint seriously obstructs its further development. To solve this problem, Mg-Ag-Al multilayer composite materials have been successfully prepared by diffusion bonding technology. The effect of key process parameter (bonding temperature) on microstructure of this material has been mainly investigated. The results show that Mg and Al were well bonded by using silver interlayer when the bonding temperature exceeded 370°C. But Mg17Al12 and Mg2Al3 compounds were formed in the interface zone at temperatures higher than 420°C. By means of controlling the bonding temperature (380 °C-420 °C), silver interlayer effectively restrained the generation of Mg-Al intermetallic compounds, and Mg-Ag intermetallic compounds (Mg3Ag, MgAg) were formed in the interface zone instead.

Wang, Yiyu; Luo, Guoqiang; Zhang, Jian; Shen, Qiang; Zhang, Lianmeng

2013-03-01

125

Effect of Bonding Temperature on Interfacial Reaction and Mechanical Properties of Diffusion-Bonded Joint Between Ti-6Al-4V and 304 Stainless Steel Using Nickel as an Intermediate Material  

NASA Astrophysics Data System (ADS)

An investigation was carried out on the solid-state diffusion bonding between Ti-6Al-4V (TiA) and 304 stainless steel (SS) using pure nickel (Ni) of 200- ?m thickness as an intermediate material prepared in vacuum in the temperature range from 973 K to 1073 K (700 °C to 800 °C) in steps of 298 K (25 °C) using uniaxial compressive pressure of 3 MPa and 60 minutes as bonding time. Scanning electron microscopy images, in backscattered electron mode, had revealed existence of layerwise Ti-Ni-based intermetallics such as either Ni3Ti or both Ni3Ti and NiTi at titanium alloy-nickel (TiA/Ni) interface, whereas nickel-stainless steel (Ni/SS) diffusion zone was free from intermetallic phases for all joints processed. Chemical composition of the reaction layers was determined in atomic percentage by energy dispersive spectroscopy and confirmed by X-ray diffraction study. Room-temperature properties of the bonded joints were characterized using microhardness evaluation and tensile testing. The maximum hardness value of ~800 HV was observed at TiA/Ni interface for the bond processed at 1073 K (800 °C). The hardness value at Ni/SS interface for all the bonds was found to be ~330 HV. Maximum tensile strength of ~206 MPa along with ~2.9 pct ductility was obtained for the joint processed at 1023 K (750 °C). It was observed from the activation study that the diffusion rate at TiA/Ni interface is lesser than that at the Ni/SS interface. From microhardness profile, fractured surfaces and fracture path, it was demonstrated that failure of the joints was initiated and propagated apparently at the TiA/Ni interface near Ni3Ti intermetallic phase.

Thirunavukarasu, Gopinath; Kundu, Sukumar; Mishra, Brajendra; Chatterjee, Subrata

2014-04-01

126

Surface preparation of IPNS (Intense Pulsed Neutron Source) booster target components prior to diffusion bonding  

SciTech Connect

In support of Argonne National Laboratory's Intense Pulsed Neutron Source (IPNS) program, the Oak Ridge Y-12 Plant has fabricated 15 Zircaloy-2 clad, enriched uranium booster targets using hot isostatic pressing (HIP) to effect diffusion bonding between the enriched uranium core and the Zircaloy-2 cladding. Guided by x-ray photoelectron spectroscopy for chemical analysis (XPS/ESCA) data, surface preparation procedures for both the Zircaloy-2 and uranium were refined to ensure 100% bonding between the dissimilar metals and survival of the rigors of beta quenching. 7 refs., 11 figs., 4 tabs.

Simandl, R.F.; Richards, H.L.; Thompson, L.M.

1988-10-06

127

Infrared thermographic inspection of superplastically formed\\/diffusion-bonded titanium structures  

Microsoft Academic Search

The increasing complexity of aerospace structures necessitates the development of advanced Nondestructive Inspection techniques\\/methods while current economic pressures require these inspections to be performed at lower costs. To this end, an automated infrared (IR) thermographic inspection system has been developed for the inspection of Superplastically Formed\\/Diffusion Bonded (SPF\\/DB) titanium structures. The IR thermographic system has demonstrated high reliability, while reducing

Duane A. Theilen; Richard J. Christofersen; B. G. Dods; David C. Emahiser; B. H. Robles

1993-01-01

128

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

Microsoft Academic Search

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

B. Alemán; I. Gutiérrez; J. J. Urcola

1995-01-01

129

Surface preparation of IPNS (Intense Pulsed Neutron Source) booster target components prior to diffusion bonding  

Microsoft Academic Search

In support of Argonne National Laboratory's Intense Pulsed Neutron Source (IPNS) program, the Oak Ridge Y-12 Plant has fabricated 15 Zircaloy-2 clad, enriched uranium booster targets using hot isostatic pressing (HIP) to effect diffusion bonding between the enriched uranium core and the Zircaloy-2 cladding. Guided by x-ray photoelectron spectroscopy for chemical analysis (XPS\\/ESCA) data, surface preparation procedures for both the

R. F. Simandl; H. L. Richards; L. M. Thompson

1988-01-01

130

Al 2O 3\\/Ti interlayer\\/AISI 304 diffusion bonded joint  

Microsoft Academic Search

Sintered alumina and AISI 304 stainless-steel discs were joined at 900°C by solid state diffusion bonding, making use of a Ti foil acting as thermal stress relief interlayer. The microstructure of the two interfaces thus formed, that is, Al2O3\\/Ti and Ti\\/AISI 304 was investigated by a variety of characterization techniques such as scanning and transmission electron microscopy (TEM), energy-dispersive X-ray

A. M Kliauga; D Travessa; M Ferrante

2001-01-01

131

Influence of silicon dangling bonds on germanium thermal diffusion within SiO2 glass  

NASA Astrophysics Data System (ADS)

We study the influence of silicon dangling bonds on germanium thermal diffusion within silicon oxide and fused silica substrates heated to high temperatures. By using scanning electron microscopy and Rutherford backscattering spectroscopy, we determine that the lower mobility of Ge found within SiO2/Si films can be associated with the presence of unsaturated SiOx chemical bonds. Comparative measurements obtained by x-ray photoelectron spectroscopy show that 10% of silicon dangling bonds can reduce Ge desorption by 80%. Thus, the decrease of the silicon oxidation state yields a greater thermal stability of Ge inside SiO2 glass, which could enable to considerably extend the performance of Ge-based devices above 1300 K.

Barba, D.; Cai, R. S.; Demarche, J.; Wang, Y. Q.; Terwagne, G.; Rosei, F.; Martin, F.; Ross, G. G.

2014-03-01

132

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

133

Vacuum-assisted thermal bonding of plastic capillary electrophoresis microchip imprinted with stainless steel template  

Microsoft Academic Search

An improved fabrication of poly(methyl methacrylate) (PMMA)-based capillary electrophoresis microchips has been demonstrated. The microchannel structures on PMMA substrates were generated by one-step hot embossing procedure using a stainless steel template. Hundreds of patterned PMMA substrates have been successfully obtained using the single metal template. Sequent microchannel enclosure with high yield up to 90% was accomplished by a vacuum-assisted thermal

Zhifeng Chen; Yunhua Gao; Jinming Lin; Rongguo Su; Yu Xie

2004-01-01

134

Formation of Nitrogen-Pearlite in the Diffusion Bonding of Sialon to 316L Stainless Steel  

NASA Astrophysics Data System (ADS)

The objective of this study is to investigate the interface reaction and diffusion bonding between 316L stainless steel and sialon. Bonding was carried out in a hot press at 1250° C under the pressure of 15 MN/m2 for 1 hour and was cooled slowly in the furnace to prevent the mismatch between the sialon and the steel. Scanning Electron microscopy (SEM) revealed the interdiffusion and intereaction between the steel and the sialon. The elements diffusing into sialon were illustrated by the Energy Dispersive Spectrometer (EDS) analysis where the presence of Fe, Cr, Ni and Mn are significant. The formation of nitrogen pearlite can be described as a result of the reaction between the stainless steel and the silicon nitride component of sialon which release nitrogen. Mechanical behavior of the nitrogen diffused layer was also investigated using microhardness tester and at the reaction layer an increase in hardness was observed. Conclusion can be deduced that the formation of nitrogen pearlite in the stainless steel is quite significant especially on joining sialon to as-received nitrogen-free austenite stainless steel. The formation of nitrogen pearlite could be understood by the diffusion of nitrogen into the stainless steel. Thus, the continuous precipitates form lamellar nitrogen pearlite.

Hussain, P.; Mamat, O.; Mohammad, M.; Jaafar, W. M. N. W.

2010-03-01

135

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

SciTech Connect

The Very High Temperature Reactor (VHTR) using gas-cooled reactor technology is anticipated to be the reactor type for the Next Generation Nuclear Plant (NGNP). In this reactor concept 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 a secondary fluid for electricity generation, hydrogen production, and/or industrial process heat applications. At present, there is no proven IHX concept for VHTRs. The current Technology Readiness Level (TRL) status issued by NGNP to all components associated with the IHX for reduced nominal reactor outlet temperatures of 750–800 degrees C is 3 on a 1–10 scale, with 10 indicating omplete technological maturity. Among 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 with Alloy 617, a candidate high-temperature structural material for NGNP applications, are the primary focus of this paper. In the current study, diffusion bonding of Alloy 617 has been demonstrated, although the optimum diffusion bonding process parameters to engineer a quasi interface-free joint are yet to be determined. The PCHE fabrication related processes, i.e., photochemical etching and diffusion bonding are discussed for Alloy 617 plates. In addition, the authors’ experiences with these non-conventional machining and joining techniques are discussed. Two PCHEs are fabricated using Alloy 617 plates and are being experimentally investigated for their thermal-hydraulic performance in a High-Temperature Helium Facility (HTHF). The HTHF is primarily of Alloy 800H construction and is designed to facilitate experiments at temperatures and pressures up to 800 degrees C and 3 MPa, respectively. Furthermore, some preliminary microstructural and mechanical property characterization studies of representative diffusion bonded Alloy 617 specimens are presented. The characterization studies are restricted and less severe from an NGNP perspective but provide sufficient confidence to ensure safe operation of the heat exchangers in the HTHF. The test results are used to determine the design operating conditions for the PCHEs fabricated.

Sai K. Mylavarapu; Richard N. Christensen; Raymond R. Unocic; Richard E. Glosup; Mike W. Patterson

2012-08-01

136

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

NASA Astrophysics Data System (ADS)

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: A typical Zr 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.

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

2014-05-01

137

Studies of the pressure induced transition from diffuse to constricted arcing in large vacuum arc furnaces  

SciTech Connect

Vacuum arc remelting (VAR) is a secondary melting process used to produce superalloys. A dc arc is utilized to melt the alloy at normal pressures of {approximately}1 Pa. However, in some instances the pressure in the region of the arc can reach abnormally high values due to CO evolution from the molten ingot, giving rise to a furnace condition known as glow.'' This phenomenon was investigated by studying metal vapor arcs burning on 152 mm diameter Alloy 718 electrodes at 2.3 kA in a modified VAR furnace in CO ambients of 1.3, 13.3, and 66.7 Pa. Electrical signatures and high speed photographic data were recorded at all pressures. At the lowest pressure, the arc was diffuse with cathode spots distributed randomly across the molten electrode surface. Under these conditions, the inter-electrode space appeared to be uniformly filled with plasma. Monochromatic images taken at this pressure show mobile ion channels connecting regions of cathode spot activity with the molten ingot pool. Because spot motion is fast compared to the thermal diffusion speed in the ingot, this arc constitutes a quasi-uniform heat source necessary for successful application of the process. At a CO pressure of 66.7 Pa, the arc was localized and normal cathode spot action had ceased, although normal appearing constricted plasma attachments were observed to spontaneously appear at the bottom of molten metal protuberances as they dripped from the electrode and drew within a few millimeters of the ingot surface. At this pressure, the arc was observed to operate in either of the two modes, one characterized by high'' voltage ({minus}24 V), and the other by low voltage ({minus}19 V). At 13.3 Pa CO the arc was not stable, although heating of the electrode remained quasi-uniform. 14 refs., 12 figs.

Williamson, R.; Zanner, F.; Hareland, W.

1990-01-01

138

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

SciTech Connect

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.

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

1999-07-01

139

Effects of hydrogen on diffusion bonding of TiAl-based intermetallics using hydrogenated Ti 6Al 4V interlayer  

Microsoft Academic Search

The diffusion bonding of TiAl-based intermetallics using the hydrogenated Ti6Al4V interlayer was carried out. The results were investigated by SEM, EPMA, XRD and TG\\/DSC. According to the experimental observations, the reaction layer of diffusion bonding using the hydrogenated Ti6Al4V interlayer containing 0.5 wt% hydrogen formed at 850 °C for 15 min under a pressure of 15 MPa, and the shear strength of the joint

P. He; L. Fan; H. Liu; J. C. Feng

2010-01-01

140

Bonding  

NSDL National Science Digital Library

Bonding Purpose: To review the 3 Types of Bonds and the 4 Intermolecular Forces. Assignment: Answer the following questions on a separate piece of paper: 1) List the 3 types of bonding, give descriptions and one example of each 2) List the 4 intermolecular forces and draw examples of each. Be ...

Cutting, Mrs.

2008-03-08

141

Effect of iron particle size on the diffusion bonding of Fe–5%Cu powder compact to wrought carbon steels  

Microsoft Academic Search

In the present work, diffusion bonding of Fe–5%Cu powder compact to wrought carbon steels was studied. Effects of iron particle size and carbon content of the solid component on the bond strength, which is the maximum shear stress required to obtain separation at the interface, were investigated. Atomized iron powders with the mean particle size of 36, 56, 90, 106,

M. G. Fillabi; A. Simchi; A. H. Kokabi

2008-01-01

142

The influence of interface impurities on fracture energy of UHV diffusion bonded metal-ceramic bicrystals  

SciTech Connect

In both the practical and theoretical aspects of joining metals to ceramics the influence of impurities on the interfacial bond strength is not fully understood. In the present paper the authors describe part of a study in which the interface of niobium-sapphire bicrystals was contaminated under defined conditions and the interfacial fracture energy of these UHV diffusion bonded bicrystals was determined as a measure of their bond strength. The model combination niobium-sapphire shows at high temperatures a simple reaction in which alumina dissolves in niobium without forming an interlayer. Furthermore, niobium and sapphire are characterized by nearly the same expansion behavior which minimizes the development of thermal stresses during cooling down from the bonding temperature. The authors report on experiments in which silver or titanium atoms have been chosen as interfacial impurity elements. Silver is practically insoluble in niobium and sapphire whereas titanium possesses a highly negative free enthalpy of oxide formation. It is assumed that both these properties are associated with interfacially active elements in the system niobium-sapphire.

Elssner, G.; Korn, D.; Ruehle, M. (Max-Planck-Inst. fuer Metallforschung, Stuttgart (Germany). Inst. fuer Werkstoffwissenschaft)

1994-10-15

143

Optimizing Diffusion Bonding Parameters in AA6061-T6 Aluminum and AZ80 Magnesium Alloy Dissimilar Joints  

NASA Astrophysics Data System (ADS)

The main difficulty when joining magnesium (Mg) and aluminum (Al) alloys by fusion welding lies in the formation of oxide films and brittle intermetallic in the bond region which affects the integrity of the joints. However, diffusion bonding is a suitable process to join these two materials as no such characteristic defects are produced at the joints. The diffusion bonding process parameters such as bonding temperature, bonding pressure, holding time, and surface roughness of the specimen play a major role in determining the joint strength. In this investigation, an attempt was made to develop empirical relationships to predict the strengths of diffusion bonded AZ80 magnesium and AA6061 aluminum alloys dissimilar joints from the process parameters based on central composite factorial design. Response surface methodology was applied to optimize the process parameters to attain the maximum shear strength and bonding strength of the joint. From this investigation, it was found that the bonds produced with the temperature of 405.87 °C, pressure of 7.87 MPa, holding time of 29.02 min and surface roughness of 0.10 ?m exhibited maximum shear strength and bonding strength of 57.70 and 76.90 MPa, respectively. The intermetallic formation at the interface was identified.

Joseph Fernandus, M.; Senthilkumar, T.; Balasubramanian, V.; Rajakumar, S.

2012-11-01

144

Presumable Mechanism of the Formation of a Diffusion Joint of Bonded Metals of a High Affinity to Oxygen.  

National Technical Information Service (NTIS)

The tests conducted on the diffusion bonding of 1H18N9T and 2H13 steels, alloys E1437B and Armco iron in an oxidized state, as well as the thermodynamic analysis of the interoxide reactions taking place showed that a diffusion joint forms either as the re...

W. Karlinski

1977-01-01

145

Water dimer diffusion on Pd[111] assisted by an H-bond donor-acceptor tunneling exchange.  

PubMed

Based on the results of density functional theory calculations, a novel mechanism for the diffusion of water dimers on metal surfaces is proposed, which relies on the ability of H bonds to rearrange through quantum tunneling. The mechanism involves quasifree rotation of the dimer and exchange of H-bond donor and acceptor molecules. At appropriate temperatures, water dimers diffuse more rapidly than water monomers, thus providing a physical explanation for the experimentally measured high diffusivity of water dimers on Pd[111] [Science 297, 1850 (2002)

Ranea, V A; Michaelides, A; Ramírez, R; de Andres, P L; Vergés, J A; King, D A

2004-04-01

146

Diffusion Bonding of Ti-6Al-4V Sheet with Ti-6Al-4V Foam for Biomedical Implant Applications  

NASA Astrophysics Data System (ADS)

Advanced metallic bone implants are designed to have a porous surface to improve osseointegration and reduce risks of loosening. An alternative approach to existing surface treatments to create a porous surface is to bond separately produced metallic foams onto the implant. To assess the feasibility of this approach, a Ti-6Al-4V foam was diffusion bonded onto bulk Ti-6Al-4V in an argon atmosphere at temperatures between 1173 K and 1223 K (900 °C and 950 °C) for times between 45 and 75 minutes. These specimens were tested in tension to determine bond quality: failures occurred in the foam, indicating a strong diffusion-bonded interface. The quality of the bond was confirmed by metallographic studies, indicating that this approach, which can also be applied to creating of sandwich with porous cores, is successful.

Hamilton, Brittany; Oppenheimer, Scott; Dunand, David C.; Lewis, Daniel

2013-12-01

147

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

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

148

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

SciTech Connect

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.

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

1995-02-01

149

Measurement and Modeling of Water-Vapor Diffusion in Elastomers with Impact in Humidity and Vacuum Measurements  

NASA Astrophysics Data System (ADS)

The dynamics of water-vapor dissolution in Viton O-rings is measured with a gravimetric method using a precise mass comparator. A sample gasket was degassed in high vacuum for a sufficiently long period to remove more than 99 % of the dissolved water vapor. After that, it was exposed to the ambient atmosphere with a controlled temperature, and relative humidity and water-vapor uptake curves were measured gravimetrically with a precise balance. The dynamics of a water-vapor release into vacuum from another sample that was previously saturated with water vapor at room temperature was determined. The sample was placed in a vacuum outgassing rate measurement apparatus. The time dependence of the evolved water vapor was calculated by integrating the measured outgassing rate. The physical process of water absorption can be described by the diffusion equation. The geometry of the samples required solving the diffusion equation in cylindrical coordinates. This was done numerically using a finite-difference method. As a result of the modeling, room temperature values of the diffusion constant D, the solubility s, and the permeability K = D× s of water vapor in the sample material (Viton A-401C) were obtained. For sample 1, we obtained D = 8.0 × 10 ^{-8} cm2 {\\cdot } s^{-1} and s = 6.5 × 10^{-7} g {\\cdot } cm^-3 Pa^{-1}, while for sample 2, D = 3.0 × 10^{-7} cm2 s^{-1} and s = 3.5 × 10^{-7} g {\\cdot } cm^{-3} {\\cdot } Pa^{-1}.

Šetina, Janez; Sefa, Makfir; Erjavec, Bojan; Hudoklin, Domen

2013-03-01

150

Strength and fracture behaviour of diffusion bonded joints in Al-Li (8090) alloy. III - Peel strength  

NASA Astrophysics Data System (ADS)

Peel strengths at room temperature and under superplastic forming conditions at 530 C were measured for diffusion-bonded joints in Al-Li 8090 alloy sheet. The bonds were made in the solid state, or via a transient liquid phase using interlayers. The effect of strain rate, sheet thickness and heat treatment were investigated. The significance of these results for the testing of DB joints and for their use in DB/SPF structures is discussed.

Dunford, D. V.; Partridge, P. G.

1992-11-01

151

Application of superplastically formed and diffusion bonded aluminum to a laminar flow control leading edge  

NASA Technical Reports Server (NTRS)

NASA sponsored the Aircraft Energy Efficiency (ACEE) program in 1976 to develop technologies to improve fuel efficiency. Laminar flow control was one such technology. Two approaches for achieving laminar flow were designed and manufactured under NASA sponsored programs: the perforated skin concept used at McDonnell Douglas and the slotted design used at Lockheed-Georgia. Both achieved laminar flow, with the slotted design to a lesser degree (JetStar flight test program). The latter design had several fabrication problems concerning springback and adhesive flow clogging the air flow passages. The Lockheed-Georgia Company accomplishments is documented in designing and fabricating a small section of a leading edge article addressing a simpler fabrication method to overcome the previous program's manufacturing problems, i.e., design and fabrication using advanced technologies such as diffusion bonding of aluminum, which has not been used on aerospace structures to date, and the superplastic forming of aluminum.

Goodyear, M. D.

1987-01-01

152

Microstructural characterization in diffusion bonded TiCAl 2 O 3 \\/Cr18Ni8 joint with Ti interlayer  

Microsoft Academic Search

Ceramic matrix composite, TiC-Al2O2, and stainless steel, Cr18-Ni8, were joined at 1400 K by solid state diffusion bonding, making use of a Ti foil acting as\\u000a thermal stress relief interlayer. The microstructure of the joint was thus formed. The diffusion bonded TiC-Al2O3\\/Cr18-Ni8 joint was investigated by a variety of characterization techniques such as scanning electron microscope (SEM) with\\u000a energy dispersion

Wang Juan; Li Yajiang; Yin Yansheng

2006-01-01

153

A hydrodynamic model of plasma initiation off irradiated metallic aerosols in vacuum - The diffusive regime  

Microsoft Academic Search

The analogy between chemical reactions and cascade ionization is exploited to study the spatial and temporal dynamics of plasma formation in the vapor that is formed on a metallic aerosol that is being irradiated by a high-energy laser beam, in vacuum. The present hydrodynamic model is valid for relatively low laser fluences and pulses of the order of nanoseconds or

Shirish M. Chitanvis

1989-01-01

154

Low cycle fatigue strength of diffusion bonded joints of alumina dispersion-strengthened copper to stainless steel  

NASA Astrophysics Data System (ADS)

It is proposed that the first wall and divertor components of ITER employ alumina dispersion-strengthened copper (DS Cu) joined to austenitic stainless steel. In this work, low cycle fatigue tests were performed on a direct diffusion bonded joint, a diffusion bonded joint with a Au interlayer, stainless steel and DS Cu in order to investigate their fatigue strength and fracture behavior. For the direct diffusion bonded joint, the fatigue strength in the small strain range was considerably lower than that of the DS Cu, while in the large strain range the fatigue strength was similar to that of the DS Cu. The low cycle fatigue strength of the Au interlayer joint increased compared with the direct diffusion bonded joint, and was the same as that of the DS Cu. The strain distribution in joint specimens was not uniform, because the deformation stress was different between the 316 stainless steel and the DS Cu. The fracture locations for the joint specimens varied depending on their strain distribution.

Nishi, H.; Araki, T.

2000-12-01

155

Thermal fatigue testing of a diffusion-bonded beryllium divertor mock-up under ITER relevant conditions  

Microsoft Academic Search

Thermal response and thermal fatigue tests of four 5 mm thick beryllium tiles on a Russian divertor mock-up were completed on the Electron Beam Test System at Sandia National Laboratories. The beryllium tiles were diffusion bonded onto an OFHC copper saddleblock and a DSCu (MAGT) tube containing a porous coating. Thermal response tests were performed on the tiles to an

D. L. Youchison; R. Guiniiatouline; R. D. Watson

1994-01-01

156

Thermal fatigue testing of a diffusion-bonded beryllium divertor mock-up under ITER relevant conditions.  

National Technical Information Service (NTIS)

Thermal response and thermal fatigue tests of four 5 mm thick beryllium tiles on a Russian divertor mock-up were completed on the Electron Beam Test System at Sandia National Laboratories. The beryllium tiles were diffusion bonded onto an OFHC copper sadd...

D. L. Youchison R. Guiniiatouline R. D. Watson

1994-01-01

157

Effect of hydrogen on diffusion bonding of commercially pure titanium and hydrogenated Ti6Al4V alloys  

Microsoft Academic Search

The diffusion bonding of commercially pure titanium and hydrogenated Ti6Al4V alloys was carried out, and the effect of hydrogen was investigated by SEM, XRD, TEM and TG\\/DSC. The ?H phase increased with the hydrogen content increasing in hydrogenated alloys, and the ? titanium hydride and ?? martensite were found in high hydrogen content. The TG curves of hydrogenated alloys descended

H. Liu; J. Cao; P. He; J. C. Feng

2009-01-01

158

Diffusion bonding of CMSX-4 to UDIMET 720 using PVD-coated interfaces and HIP  

SciTech Connect

There is an increasing interest in development of manufacturing methods for Dual Property BLISKs (BLaded dISKs), consisting of creep resistant airfoils and fatigue resistant disks bonded together by a durable joint. Optimum heat treatments are, however, very different for creep resistant single crystal CMSX-4 and fatigue resistant polycrystalline Udimet 720 selected in this study, but fortunately the first aging treatment for CMSX-4 (1140 C, 2-6h, AC) is similar to the partial solution treatment of U 720 HS2 (1115 C, 4h, OQ). Based on this, diffusion bonding was performed by HIP at 1120 C and 200 MPa argon pressure for 4 h, followed by cooling to 400 C. Subsequently, a shortened Udimet 720 HS2 two-step aging treatment was adopted by heating to 650 C for 6 h followed by cooling to 400 C, heating to 760 C for 2 h, and finally cooling to R.T. under remaining HIP pressure. Plasma etching followed by thin (80 nm) PVD coating with either nickel or titanium were used to clean and protect the polished surfaces before joining. The selection of coatings was governed by the possibility to reduce oxidized nickel by flushing with hydrogen at 330 C during evacuation of the HIP capsules, and by the large solubility of oxygen in titanium. Hot tensile testing was performed at 750 C on both joined and reference materials subjected to the modified heat treatment. Initially solution treated Udimet 720 and CMSX-4 comprised the reference materials. The testing showed that joints with Ni-PV coatings were almost as strong as Udimet 720 (although with very limited elongation), while the joints with Ti-PVD coatings were weaker.

Larker, R. [Lulea Univ. of Technology (Sweden). Div. of Engineering Materials; Ockborn, J.; Selling, B. [Volvo Aero Corp., Trollhattan (Sweden)

1999-07-01

159

A hydrodynamic model of plasma initiation off irradiated metallic aerosols in vacuum: The diffusive regime  

Microsoft Academic Search

We exploit the analogy between chemical reactions and cascade ionization to study the spatial and temporal dynamics of plasma formation in the vapor that is formed off a metallic aerosol that is being irradiated by a high-energy laser beam, in vacuum. Our hydrodynamic model is valid for relatively low laser fluences (103 J\\/cm2 for aluminum aerosols) and pulses of the

Shirish M. Chitanvis

1989-01-01

160

Solid-state transformations during diffusion bonding of copper to iron  

Microsoft Academic Search

Solid-state bonding between dissimilar metals, produced at elevated temperatures with the application of a bonding pressure, causes structural changes in the microstructure of the zones nearest to the bond interface. These metallurgical transformations, produced by interdiffusion in the vicinity of the bond, decide the final properties of the joint. In the present paper, such diffusional transformations have been investigated for

F. A. Calvo; A. Ureña; J. Ma. Gomez de Salazar; F. Molleda; A. J. Criado

1988-01-01

161

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

DOEpatents

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.

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

2011-03-08

162

Nanostructure Particle-Reinforced Transient Liquid Phase Diffusion Bonding: a Comparative Study  

NASA Astrophysics Data System (ADS)

Particle-reinforced aluminum-metal matrix composites (Al-MMCs) are used in many engineering applications, because they provide significant advantages when compared to monolithic aluminum alloys. However, there still exists the need to identify a suitable joining process for these materials, which minimizes particulate disruption and retains the strength of the MMC within the joint region. This study presents a comparison between joint qualities achieved when a monolithic interlayer is used vs when a nanoparticle-reinforced composite interlayer is used during transient liquid phase diffusion bonding of Al-6061 alloy containing 15 vol pct of Al2O3 particles. Examination of the joint region using scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS), and X-ray diffraction (XRD) showed the formation of eutectic phases such as Al3Ni, Al9FeNi, and Ni3Si within the joint zone. The results indicate that the addition of nanoparticle reinforcements into the interlayer can be used to improve joint strength and minimize particle segregation.

Cooke, Kavian O.; Khan, Tahir I.; Oliver, Gossett D.

2011-08-01

163

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

NASA Astrophysics Data System (ADS)

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.

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

2010-06-01

164

Effects of hydrogen on diffusion bonding of hydrogenated Ti6Al4V alloy containing 0.3 wt% hydrogen at fast heating rate  

Microsoft Academic Search

The diffusion bonding of hydrogenated Ti6Al4V alloy containing 0.3wt% hydrogen was carried out. The effects of hydrogen on diffusion bonding at fast heating rate were investigated by SEM, EPMA, XRD, TEM and TG\\/DSC. According to the experimental observations, the featheriness ?? martensite and ?H phase disappeared after bonding, and the fine needle ?? martensite and lamellar (?+?) structure were formed.

J. C. Feng; H. Liu; P. He; J. Cao

2007-01-01

165

Evaluation of Cu as an interlayer in Be/F82H diffusion bonds for ITER TBM  

NASA Astrophysics Data System (ADS)

Copper has been investigated as a potential interlayer material for diffusion bonds between beryllium and Reduced Activation Ferritic/Martensitic (RAFM) steel. Utilizing Hot Isostatic Pressing (HIP), copper was directly bonded to a RAFM steel, F82H, at 650 °C, 700 °C, 750 °C, 800 °C and 850 °C, under 103 MPa for 2 h. Interdiffusion across the bonded interface was limited to 1 ?m or less, even at the highest HIP'ing temperature. Through mechanical testing it was found that samples HIP'ed at 750 °C and above remain bonded up to 211 MPa under tensile loading, at which point ductile failure occurred in the bulk copper. As titanium will be used as a barrier layer to prevent the formation of brittle Be/Cu intermetallics, additional annealing studies were performed on copper samples coated with a titanium thin film to study Ti/Cu interdiffusion characteristics. Samples were heated to temperatures between 650 °C and 850 °C for 2 h in order to mimic the range of likely HIP temperatures. A correlation was drawn between HIP temperature and diffusion depth for use in determining the minimum Ti film thickness necessary to block diffusion in the Be/F82H joint.

Hunt, R. M.; Goods, S. H.; Ying, A.; Dorn, C. K.; Abdou, M.

2011-10-01

166

The Structure and Properties of Diffusion Assisted Bonded Joints in 17-4 PH, Type 347, 15-5 PH and Nitronic 40 Stainless Steels  

NASA Technical Reports Server (NTRS)

Diffusion assisted bonds are formed in 17-4 PH, 15-5 PH, type 347 and Nitronic 40 stainless steels using electrodeposited copper as the bonding agent. The bonds are analyzed by conventional metallographic, electron microprobe analysis, and scanning electron microscopic techniques as well as Charpy V-notch impact tests at temperatures of 77 and 300 K. Results are discussed in terms of a postulated model for the bonding process.

Wigley, D. A.

1981-01-01

167

Diffusion Bonding Behavior and Characterization of Joints Made Between 316L Stainless Steel Alloy and AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The 316L austenitic stainless steel and AZ31 magnesium alloy have physical and mechanical properties which makes these alloys suitable in a number of high technology based industries such as the aerospace and automotive sectors. However, for these alloys to be used in engineering applications, components must be fabricated and joined successfully. The differences in the physical and metallurgical properties between these two alloys prevents the use of conventional fusion welding processes commonly employed in aerospace and transport industry. Therefore, alternative techniques need to be developed and diffusion bonding technology is a process that has considerable potential to join these two dissimilar alloys. In this research work both solid-state and transient liquid phase (TLP) bonding processes were applied. The solid-state bonding of 316L steel to AZ31 magnesium alloy was possible at a bonding temperature of 550°C for 120 minutes using a pressure of 1.3 MPa. The interface characterization of the joint showed a thin intermetallic zone rich in Fe-Al was responsible for providing a metallurgical bond. However, low joint shear strengths were recorded and this was attributed to the poor surface to surface contact. The macro-deformation of the AZ31 alloy prevented the use of higher bonding pressures and longer bonding times. In order to overcome these problems, the TLP bonding process was implemented using pure Cu and Ni foils as interlayers which produced a eutectic phase at the bonding temperature. This research identified the bonding mechanism through microstructural and differential scanning calorimetry investigations. The microstructural characterization of the TLP joints identified intermetallics which became concentrated along the 316L steel/AZ31 bond interface due to the "pushing effect" of the solid/liquid interface during isothermal solidification stage of bonding. The size and concentration of the intermetallics had a noticeable effect on the final joint strength properties. TLP bonding using electrodeposited coatings of Cu and Ni were used as a way of controlling the volume of eutectic liquid formed at the joint. Theoretical and experimental work showed that the use of thin coatings was successful in reducing the size and amount of intermetallics formed at the joint and this had the effect on increasing joint shear strength values.

Elthalabawy, Waled Mohamed

168

The evolution of residual stress in the thermally grown oxide on Pt diffusion bond coats in TBCs  

Microsoft Academic Search

The evolution of residual stress in the thermally grown oxide (TGO), formed on bond coats (BC) produced by diffusion of Pt into a Ni-based superalloy, has been studied as a function of thermal cycling using photo-luminescence piezo-spectroscopy through the yttria-stabilised zirconia (YSZ) thermal barrier coating. The luminescence spectra were analysed in terms of a high stress and a low stress

A. Selçuk; A. Atkinson

2003-01-01

169

Development of a Low-Cost Process for Manufacturing of Ti-Metal Matrix Composite by Roll-Diffusion Bonding  

NASA Astrophysics Data System (ADS)

Composite materials with titanium-alloy matrix are currently the class of material with the highest specific resistance at temperatures up to 800 °C. The main hurdle to their application is their final cost. Even if it is clear that the costs of constituent materials are decreasing due to volume production effects, the production processing costs remain high due to the batch production approach. Centro Sviluppo Materiali’s (CSM) efforts have focused on the manufacturing process in order to obtain an innovative solution to reduce the manufacturing costs with respect to the hot isostatic pressing (HIP) process that represents the standard production process for this class of materials. The new approach can allow a cost reduction of about 40%; this result was obtained by developing an experimental “diffusion bonding” plant for co-rolling at high temperature in a superplastic rolling regime, sheets of titanium alloy and monofilament silicon carbide fabrics. The experimental pilot plant was proposed for patent with RM2006A000261 in May 2006. This paper describes the manufacturing phases and process results. Moreover, has been shown that the diffusion in the solid state was obtained in a process window that was at least 100 times faster than that of HIP. High-temperature tensile tests were carried out on specimens machined from metallic matrix composite materials produced with the roll-diffusion bonding (RDB) process. The samples produced were also submitted to electrochemical dissolution tests of the metallic matrix in order to verify the geometric integrity of the fibers inside the matrix after the bonding phase. The results achieved as well as the process knowledge acquired with the CSM pilot plant are the base for further development of industrial application of the titanium roll-diffusion bonding.

Testani, C.; Ferraro, F.

2010-06-01

170

Theoretical study on the diffusive transport of 2,4,6-trinitrotoluene in polymer-bonded explosive.  

PubMed

Molecular dynamics (MD) simulations were performed to study the migration of 2,4,6-trinitrotoluene (TNT) in the fluorine rubber binder of polymer-bonded explosives (PBX) over a wide range of temperatures. The diffusion coefficient (D) of TNT is determined via microcanonical (NVE) MD simulation using the COMPASS force field. The calculated diffusion coefficient (D) was then used to compute the migration time of TNT based on Fick's second law and the results agree well with the experimental data. The relation between D of TNT and temperature was confirmed and the results confirm the temperature-dependence of diffusion coefficients of TNT in the binder, but a break is seen about the melt point (the temperature at which the elastomeric state of the binder changes to a viscosity state) in the Arrhenius plot of ln(D) versus 1/T. PMID:21360179

Zhou, Yang; Long, Xinping; Wei, Xingwen

2011-11-01

171

Effect of High Temperature Storage in Vacuum, Air, and Humid Conditions on Degradation of Gold/Aluminum Wire Bonds in PEMs  

NASA Technical Reports Server (NTRS)

Microcircuits encapsulated in three plastic package styles were stored in different environments at temperatures varying from 130 C to 225 C for up to 4,000 hours in some cases. To assess the effect of oxygen, the parts were aged at high temperatures in air and in vacuum chambers. The effect of humidity was evaluated during long-term highly accelerated temperature and humidity stress testing (HAST) at temperatures of 130 C and 150 C. High temperature storage testing of decapsulated microcircuits in air, vacuum, and HAST chambers was carried out to evaluate the role of molding compounds in the environmentally-induced degradation and failure of wire bonds (WB). This paper reports on accelerating factors of environment and molding compound on WB failures. It has been shown that all environments, including oxygen, moisture, and the presence of molding compounds reduce time-to-failures compared to unencapsulated devices in vacuum conditions. The mechanism of the environmental effect on KB degradation is discussed.

Teverovsky, Alexander

2006-01-01

172

MEASUREMENT OF ADHESION STRENGTH OF SOLID-STATE DIFFUSION BONDING BETWEEN NICKEL AND COPPER BY MEANS OF LASER SHOCK SPALLATION METHOD  

SciTech Connect

Coating and bonding techniques between different materials are essential to the field of technology. Bond mechanism is of interest from scientific point of view. A well-established method to make bonding between unalloyed nickel and copper was utilized, that was solid-state diffusion bonding at elevated temperatures. Irradiation by Nd:YAG laser with 7ns-pulse width created shock wave that caused tensile stress after reflection at free surface. The adhesion strength was determined by the critical laser power that caused exfoliation of the bonding interface.

Satou, M.; Akamatsu, H.; Hasegawa, A. [Dept. Quantum Science and Energy Engineering, Tohoku University, Sendai 980-8579 (Japan)

2009-12-28

173

Formation of dendritic structure in the diffusion zone of the bonded Zircaloy4 and stainless steel 316L in the presence of Ti interlayer  

Microsoft Academic Search

Microstructure of the diffusion bonded samples of stainless steel 316L and Zircaloy-4 in the presence of Ti interlayer at 1000°C and 1050°C is investigated by scanning electron microscopy (SEM) and the phases in the diffusion zone (DZ) have been analyzed by energy dispersive system (EDS) attached with SEM. Five distinct regions have been observed in the sample bonded at 1000°C

J. I. Akhter; M. Ahmad; M. Iqbal; M. Akhtar; M. A. Shaikh

2005-01-01

174

Study of diffusion bond development in 6061 aluminum and its relationship to future high density fuels fabrication.  

SciTech Connect

Powder metallurgy dispersions of uranium alloys and silicides in an aluminum matrix have been developed by the RERTR program as a new generation of proliferation-resistant fuels. Testing is done with miniplate-type fuel plates to simulate standard fuel with cladding and matrix in plate-type configurations. In order to seal the dispersion fuel plates, a diffusion bond must exist between the aluminum coverplates surrounding the fuel meat. Four different variations in the standard method for roll-bonding 6061 aluminum were studied. They included mechanical cleaning, addition of a getter material, modifications to the standard chemical etching, and welding methods. Aluminum test pieces were subjected to a bend test after each rolling pass. Results, based on 400 samples, indicate that at least a 70% reduction in thickness is required to produce a diffusion bond using the standard rollbonding method versus a 60% reduction using the Type II method in which the assembly was welded 100% and contained open 9mm holes at frame corners.

Prokofiev, I.; Wiencek, T.; McGann, D.

1997-10-07

175

Microstructural evolution in the partial transient liquid phase diffusion bonding of Zircaloy4 to stainless steel 321 using active titanium filler metal  

Microsoft Academic Search

Microstructural evolution of the partial transient liquid phase diffusion bonded Zircaloy-4 and stainless steel 321 using an active Ti-base interlayer were studied at different temperatures. Additionally, simple analytical models were developed to predict the evolution of the interlayer and intermetallics during the bonding operation. Bonds were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Precision measurement of the

M. Mazar Atabaki

2010-01-01

176

Comparison of structural behavior of superplastically formed/diffusion-bonded sandwich structures and honeycomb core sandwich structures  

NASA Technical Reports Server (NTRS)

A superplasticity formed/diffusion-bonded (SPF/DB) orthogonally corrugated core sandwich structure is discussed and its structural behavior is compared to that of a conventional honeycomb core sandwich structure. The stiffness and buckling characteristics of the two types of sandwich structures are compared under conditions of equal structural density. It is shown that under certain conditions, the SPF/DB orthogonally corrugated core sandwich structure is slightly more efficient than the optimum honeycomb core (square-cell core) sandwich structure. However, under different conditions, this effect can be reversed.

Ko, W. L.

1980-01-01

177

Interfacial Microstructure and Mechanical Strength of 93W/Ta Diffusion-Bonded Joints with Ni Interlayer  

NASA Astrophysics Data System (ADS)

93W alloy and Ta metal were successfully diffusion bonded using a Ni interlayer. Ni4W was found at the W-Ni interface, and Ni3Ta and Ni2Ta were formed at the Ni-Ta interface. The shear strength of the joints increases with increasing holding time, reaching a value of 202 MPa for a joint prepared using a 90-minute holding time at 1103 K (830 °C) and 20 MPa. The fracture of this joint occurred within the Ni/Ta interface.

Luo, Guoqiang; Zhang, Jian; Li, Meijuan; Wei, Qinqin; Shen, Qiang; Zhang, Lianmeng

2013-02-01

178

RBS in situ studies of the kinetics of optically-induced diffusion of Ag in vacuum evaporated films with composition of As 33S 67  

NASA Astrophysics Data System (ADS)

Optically-induced dissolution and diffusion (OIDD) of Ag into thin films of amorphous vacuum evaporated films with composition As 33S 67 has been studied. Rutherford backscattering spectrometry (RBS), as a non-destructive method for depth profiles measurements, was used for in situ measurements of the OIDD process. A bilayer of Ag/As 33S 67 deposited on quartz substrate was placed into RBS measuring chamber and step-by-step illuminated by the second harmonic green light from solid state Nd-doped laser with beam diameter of 5 mm, a wavelength of 532 nm and a power output of 21 mW. Silver diffusion depth profile development has been resolved using GISA 3 code. The silver diffusion profiles can be described by an error function. Their behaviour is typical for diffusion process from limited source influenced by chemical reaction of silver on the boundary between doped and undoped film.

Pe?ina, Vratislav; Wágner, Tomáš; Krbal, Miloš; Frumar, Miloslav

2006-08-01

179

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

Microsoft Academic Search

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 °C and fast neutron fluxes of ?3·109 n\\/cm2·s. At the moment, little information is available about glass-metal joints suitable for

Marijke Jacobs; Guido Van Oost; Joris Degrieck; Ives De Baere; Andrei Gusarov; Frits Gubbels; Vincent Massaut

2011-01-01

180

Vacuum Technology: Vacuum Technology III  

NSDL National Science Digital Library

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

Rack, Philip D.

2012-12-12

181

The effect of hydrogen bonding on the diffusion of water in n-alkanes and n-alcohols measured with a novel single microdroplet method  

PubMed Central

While the Stokes–Einstein (SE) equation predicts that the diffusion coefficient of a solute will be inversely proportional to the viscosity of the solvent, this relation is commonly known to fail for solutes, which are the same size or smaller than the solvent. Multiple researchers have reported that for small solutes, the diffusion coefficient is inversely proportional to the viscosity to a fractional power, and that solutes actually diffuse faster than SE predicts. For other solvent systems, attractive solute-solvent interactions, such as hydrogen bonding, are known to retard the diffusion of a solute. Some researchers have interpreted the slower diffusion due to hydrogen bonding as resulting from the effective diffusion of a larger complex of a solute and solvent molecules. We have developed and used a novel micropipette technique, which can form and hold a single microdroplet of water while it dissolves in a diffusion controlled environment into the solvent. This method has been used to examine the diffusion of water in both n-alkanes and n-alcohols. It was found that the polar solute water, diffusing in a solvent with which it cannot hydrogen bond, closely resembles small nonpolar solutes such as xenon and krypton diffusing in n-alkanes, with diffusion coefficients ranging from 12.5×10?5 cm2?s for water in n-pentane to 1.15×10?5 cm2?s for water in hexadecane. Diffusion coefficients were found to be inversely proportional to viscosity to a fractional power, and diffusion coefficients were faster than SE predicts. For water diffusing in a solvent (n-alcohols) with which it can hydrogen bond, diffusion coefficient values ranged from 1.75×10?5 cm2?s in n-methanol to 0.364×10?5 cm2?s in n-octanol, and diffusion was slower than an alkane of corresponding viscosity. We find no evidence for solute-solvent complex diffusion. Rather, it is possible that the small solute water may be retarded by relatively longer residence times (compared to non-H-bonding solvents) as it moves through the liquid.

Su, Jonathan T.; Duncan, P. Brent; Momaya, Amit; Jutila, Arimatti; Needham, David

2010-01-01

182

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

SciTech Connect

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.

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

1995-12-01

183

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

Microsoft Academic Search

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)

T. I. Khan; E. R. Wallach

1996-01-01

184

Diffusion bonding of CMSX-4 to UDIMET 720 using PVD-coated interfaces and HIP  

Microsoft Academic Search

There is an increasing interest in development of manufacturing methods for Dual Property BLISKs (BLaded dISKs), consisting of creep resistant airfoils and fatigue resistant disks bonded together by a durable joint. Optimum heat treatments are, however, very different for creep resistant single crystal CMSX-4 and fatigue resistant polycrystalline Udimet 720 selected in this study, but fortunately the first aging treatment

R. Larker; J. Ockborn; B. Selling

1999-01-01

185

Furnace brazing under partial vacuum  

NASA Technical Reports Server (NTRS)

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.

Mckown, R. D.

1979-01-01

186

The fabrication of all-silicon micro gas chromatography columns using gold diffusion eutectic bonding  

Microsoft Academic Search

Temperature programming of gas chromatography (GC) separation columns accelerates the elution rate of chemical species through the column, increasing the speed of analysis, and hence making it a favorable technique to speedup separations in microfabricated GCs (micro-GC). Temperature-programmed separations would be preferred in an all-silicon micro-column compared to a silicon-Pyrex® micro-column given that the thermal conductivity and diffusivity of silicon

A. D. Radadia; A. Salehi-Khojin; R. I. Masel; M. A. Shannon

2010-01-01

187

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

NASA Technical Reports Server (NTRS)

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).

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

1981-01-01

188

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

189

Solvent-dependent spectral diffusion in a hydrogen bonded "vibrational aggregate".  

PubMed

Two-dimensional infrared spectroscopy (2DIR) is used to measure the viscosity-dependent spectral diffusion of a model vibrational probe, Mn(2)(CO)(10) (dimanganese decacarbonyl, DMDC), in a series of alcohols with time scales ranging from 2.67 ps in methanol to 5.33 ps in 1-hexanol. Alcohol-alkane solvent mixtures were found to produce indistinguishable linear IR spectra, while still demonstrating viscosity-dependent spectral diffusion. Using a vibrational exciton model to characterize the inhomogeneous energy landscape, several analogies emerge with multichromophoric electronic systems, such as J-aggregates and light-harvesting protein complexes. An excitonic, local vibrational mode Hamiltonian parametrized to reproduce the vibrational structure of DMDC serves as a starting point from which site energies (i.e., local carbonyl frequencies) are given Gaussian distributed disorder. The model gives excellent agreement with both the linear IR spectrum and the inhomogeneous widths extracted from 2DIR, indicating the system can be considered to be a "vibrational aggregate." This model naturally leads to exchange narrowing due to disorder-induced exciton localization, producing line widths consistent with our 1D and 2D measurements. Further, the diagonal disorder alone effectively reduces the molecular symmetry, leading to the appearance of Raman bands in the IR spectrum in accord with the measurements. Here, we show that the static inhomogeneity of the excitonic model with disorder successfully captures the essential details of the 1D spectrum while predicting the degree of IR activity of forbidden modes as well as the inhomogeneous widths and relative magnitudes of the transition moments. PMID:20831231

King, John T; Baiz, Carlos R; Kubarych, Kevin J

2010-10-01

190

Diffusion  

NSDL National Science Digital Library

Diffusion is the net movement of particles from areas of high concentration (number of particles per unit area) to low concentration. In this activity, students use a molecular dynamics model to view the behavior of diffusion in gases and liquids.

Consortium, The C.

2011-12-11

191

Breather cloth for vacuum curing  

NASA Technical Reports Server (NTRS)

Finely-woven nylon cloth that has been treated with Teflon improves vacuum adhesive bonding of coatings to substrates. Cloth is placed over coating; entire assembly, including substrate, coating, and cloth, is placed in plastic vacuum bag for curing. Cloth allows coating to "breathe" when bag is evacuated. Applications include bonding film coatings to solar concentrators and collectors.

Reed, M. W.

1979-01-01

192

Microstructural evolution in the partial transient liquid phase diffusion bonding of Zircaloy-4 to stainless steel 321 using active titanium filler metal  

NASA Astrophysics Data System (ADS)

Microstructural evolution of the partial transient liquid phase diffusion bonded Zircaloy-4 and stainless steel 321 using an active Ti-base interlayer were studied at different temperatures. Additionally, simple analytical models were developed to predict the evolution of the interlayer and intermetallics during the bonding operation. Bonds were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Precision measurement of the interlayer width was made as a function of the bonding temperature. The liquid film migration occurred as a result of chemical solubility differences between the stable and metastable phases. The formation and growth model of the intermetallic compounds at the interfaces of Zircaloy-4/Ti-base interlayer and stainless steel 321/Ti-base interlayer for controlling the bonding process was studied considering the diffusion kinetics and the thermodynamics. The evolution of the interlayer thickness indicated a good agreement between the calculation and experimental measurement. It was also demonstrated that the low isothermal solidification kinetic was not only due to the enrichment of the liquid phase with the base alloying elements such as Ti and Zr, but also the reduction of solid solubility limit of Cu in the base alloys contributed to the reduction of isothermal solidification kinetic.

Atabaki, M. Mazar

193

Vacuum Mechatronics.  

National Technical Information Service (NTIS)

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 incr...

S. Hackwood S. E. Belinski G. Beni

1989-01-01

194

A first principles theoretical study of vibrational spectral diffusion and hydrogen bond dynamics in aqueous ionic solutions: D2O in hydration shells of Cl- ions  

NASA Astrophysics Data System (ADS)

A theoretical study of vibrational spectral diffusion and hydrogen bond dynamics in aqueous ionic solutions is presented from first principles without employing any empirical potential models. The present calculations are based on ab initio molecular dynamics for trajectory generation and wavelet analysis of the simulated trajectories for time dependent frequency calculations. Results are obtained for two different deuterated aqueous solutions: the first one is a relatively dilute solution of a single Cl- ion and the second one is a concentrated solution of NaCl (~3M) dissolved in liquid D2O. It is found that the frequencies of OD bonds in the anion hydration shell, i.e., those which are hydrogen bonded to the chloride ion, have a higher stretch frequency than those in the bulk water. Also, on average, the frequencies of hydration shell OD modes are found to increase with increase in the anion-water hydrogen bond distance. On the dynamical side, when the vibrational spectral diffusion is calculated exclusively for the hydration shell water molecules in the first solution, the dynamics reveals three time scales: a short-time relaxation (~200 fs) corresponding to the dynamics of intact ion-water hydrogen bonds, a slower relaxation (~3 ps) corresponding to the lifetimes of chloride ion-water hydrogen bonds, and another longer-time constant (~20 ps) corresponding to the escape dynamics of water from the anion hydration shell. Existence of such three time scales for hydration shell water molecules was also reported earlier for water containing a single iodide ion using classical molecular dynamics [B. Nigro et al., J. Phys. Chem. A 110, 11237 (2006)]. Hence, the present study confirms the basic results of this earlier work using a different methodology. However, when the vibrational spectral diffusion is calculated over all the OD modes, only two time scales of ~150 fs and ~2.7 ps are found without the slowest component of ~20 ps. This is likely because of the very small weight that the hydration shell water molecules carry to the overall spectral diffusion in the solution containing a single ion. For the concentrated solution also, the slowest component of ~20 ps is not found in the spectral diffusion of all water molecules because a distinct separation between the hydration shell and bulk water in terms of their stretch frequencies does not hold at this high concentration regime. The present first principles results are compared with those of the available experiments and classical simulations.

Mallik, Bhabani S.; Semparithi, A.; Chandra, Amalendu

2008-11-01

195

In-situ reactive synthesis of the Ni3Al intermetallic compound and subsequent diffusion bonding with different steels for surface coating  

Microsoft Academic Search

The Ni3Al intermetallic compound has been in situ reaction synthesized from elemental powders to form a surface coating material and then diffusion bonded with three representative steels, i.e. a carbon steel, a stainless steel and a tool steel, in order to improve the high-temperature corrosion and wear resistance of these conventional materials. The as-reaction-formed intermetallic has been found to have

J. Duszczyk; J. Zhou; L. Marvina; L. Z. Zhuang

1999-01-01

196

Hydrogen bonding effects in adsorption of water-alcohol mixtures in zeolites and the consequences for the characteristics of the Maxwell-Stefan diffusivities.  

PubMed

This work highlights a variety of peculiar characteristics of adsorption and diffusion of polar molecules such as water, methanol and ethanol in zeolites. These peculiarities are investigated with the aid of configurational-bias Monte Carlo (CBMC) simulations of adsorption isotherms, and molecular dynamics (MD) simulations of diffusivities in FAU, MFI, DDR, and LTA zeolites. Because of strong hydrogen bonding, significant clustering of the guest molecules occurs in all investigated structures. Because of molecular clustering, the inverse thermodynamic factor 1/Gamma(i) identical with (d[ln c(i)])/(d[ln f(i)]) exceeds unity for a range molar concentrations c(i) within the micropores. The degree of clustering is lowered as the temperature is increased. For the concentration ranges for which 1/Gamma(i) > 1, the Fick diffusivity, D(i), for unary diffusion is often lower than both the Maxwell-Stefan, D(i), and the self-diffusivity, D(i,self). For water-alcohol mixtures, the hydrogen bonding between water and alcohol molecules is much more predominant than for water-water, and alcohol-alcohol molecule pairs. Consequently, the adsorption of water-alcohol mixtures shows significant deviations from the predictions of the ideal adsorbed solution theory (IAST). The water-alcohol bonding also leaves its imprint on the mixture diffusion characteristics. The Maxwell-Stefan diffusivity, D(i), of either component in water-alcohol mixtures is lower than the corresponding values of the pure components; this behavior is distinctly different from that for mixtures of nonpolar guest molecules. The binary exchange coefficient D(12) for water-alcohol mixtures is also significantly lower than either self-exchange coefficients D(11) and D(22) of the constituent species. This implies that correlation effects are significantly stronger in water-alcohol mixtures than for the constituent species. Correlation effects are found to be significant for water-alcohol mixture diffusion in DDR and LTA zeolites, even though such effects are negligible for the pure constituents. The major conclusion to emerge from this investigation is that, unlike mixtures of nonpolar molecules, it is not possible to estimate water-alcohol mixture adsorption and diffusion characteristics on the basis of pure component data. PMID:20411951

Krishna, Rajamani; van Baten, Jasper M

2010-07-01

197

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

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

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

1995-01-01

198

Effect of thermally grown oxide (TGO) microstructure on the durability of TBCs with PtNiAl diffusion bond coats  

Microsoft Academic Search

The role of pre-oxidation surface treatments on the oxide microstructure and the failure mechanism of multi-layer thermal barrier systems based on Pt-modified NiAl bond coats and electron beam deposited thermal barrier coatings (TBCs) have been studied. The primary pre-oxidation experimental variable was the partial pressure of oxygen in the pre-oxidizing atmosphere at constant temperature and bond coat composition. The durability

Irene Spitsberg; Karren More

2006-01-01

199

In Situ Characterization of NiTi/Ti6Al4V Joints During Reaction-Assisted Diffusion Bonding Using Ni/Ti Multilayers  

NASA Astrophysics Data System (ADS)

Reaction-assisted diffusion bonding process of NiTi and Ti6Al4V was studied in situ. For this purpose, experiments were carried out at the High Energy Materials Science beamline (P-07) at PETRA-III (DESY). Ni/Ti multilayer thin films 2.5 ?m thick with 12 and 25 nm modulation periods were directly deposited by magnetron sputtering onto the materials being joined. The NiTi and Ti6Al4V coated parts were placed with the films facing each other in a dilatometer equipped with Kapton windows for the x-ray beams. Microjoining was promoted by applying a 10 MPa pressure and inductively heating the materials, while simultaneously acquiring x-ray diffraction scans across the bond interface. Sound joints were produced at 750 °C. The formation of the NiTi2 phase could not be avoided.

Cavaleiro, A. J.; Ramos, A. S.; Braz Fernandes, F. M.; Schell, N.; Vieira, M. T.

2014-05-01

200

Nickel nanoparticles-assisted diffusion brazing of stainless steel 316 for microfluidic applications  

NASA Astrophysics Data System (ADS)

Transient liquid-phase diffusion brazing is used in precision, hermetic joining applications as a replacement for diffusion bonding to reduce cycle times, reduce bonding pressure and improve yields. Studies showed that the interlayer used in diffusion brazing can be detrimental due to the use of melting point depressants (MPDs). The goal of this study was to investigate the role of nanoparticles and their size distribution in reducing bonding temperature of stainless steel surfaces for Microfluidic applications, as nanoparticles have inherently lower melting point and higher diffusivity than that of their bulk counterpart. The conventional interlayer has been replaced by a nickel nanoparticle (NiNP) film without any MPDs for diffusion brazing of stainless steel 316L laminae. Brazing was carried out in a uni-axial vacuum hot press at temperatures 750°C, 800°C, 900°C and 1000°C; at a bonding pressure of 10 MPa; at a heating rate of 10°C/min and dwell times of 1 and 2 hrs at each temperature. Comparison among the conventionally diffusion bonded, diffusion brazed and NiNP diffusion brazed samples is made with regard to microstructural evolution, diffusional profile and bond strength. Taken together, the results show that NiNP-assisted diffusion brazed samples have continuous bond line with low void fraction and high shear strength compared to conventionally diffusion bonded and brazed samples. Also, comparing within the NiNP diffusion brazed group, the samples brazed at 900°C have the best results. Effect of particle size on diffusion brazing of stainless steel 316 was also studied with the help of two different sets of nanoparticles (N1: average particle size of 46.7+/-6.2 nm and N2: average particle size 8.8+/-0.9 nm.) Results showed that the sample brazed with 8.8 nm particles indicated better results with a more homogeneous bondline structure. The findings of this work have positive implications for the economics of NP-assisted diffusion brazing.

Tiwari, Santosh K.

201

Diffusion of a self-interstitial atom in an ultrathin fcc film bonded to a rigid substrate  

NASA Astrophysics Data System (ADS)

The determination of the interstitial sites and saddle points corresponding to the diffusion of an interstitial atom in ultrathin face-centered cubic (fcc) film is of particular interest. The outcome is strongly influenced not only by the orientation of the free surface but also by the location of the defect with respect to the free surface and film-rigid substrate interface. In this article, an atomic-scale simulation is conducted to analyze the effects of depth on the out-of-plane interstitial mechanism of diffusion. To ensure reasonable accuracy and numerical convergence, the atomic interaction up to the second-nearest neighbor is considered. The ab initio examination of the above-mentioned problem associated with thin films requires a large supercell and is computationally time consuming. However, for the sake of demonstration, the values of the barrier height energy pertinent to a diffusing self-interstitial atom in the bulk material are computed using both the first principles density functional theory (DFT) and the developed technique, indicating reasonable correspondence.

Shodja, Hossein M.; Tabatabaei, Maryam; Pahlevani, Ladan; Ostadhossein, Alireza

2013-04-01

202

Role of the Si-Si bond stability in the first stages of Ti diffusion on a Si(1 1 1) 2 × 1 surface. A periodic DFT study  

NASA Astrophysics Data System (ADS)

A periodic Density Functional Theory (DFT) study, using Generalized Gradient Approximation (GGA), of the Ti deposition on a clean 2 × 1 reconstructed Si (1 1 1) surface was carried out. Results indicate that as in the case of the Si(0 0 1) surface, a TiSi monolayer is formed at 6.8 × 1014 Ti atom cm-2 which shows its high reactivity in presence of Ti even at RT. However, the TiSi interface on the Si(1 1 1) presents Ti-Ti and Si-Si interactions forming atom rows in a zigzag arrangement. Ti deposition on the TiSi interface suggests that remaining Si-Si bonds on the surface could play a very important role in the Ti diffusion on the Si surface.

Añez, Rafael; Sierraalta, Anibal; San-Miguel, Miguel A.; Sanz, Javier Fdez.

2013-05-01

203

Plates for vacuum thermal fusion  

DOEpatents

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.

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

2002-01-01

204

Method for vacuum pressing electrochemical cell components  

NASA Technical Reports Server (NTRS)

Assembling electrochemical cell components using a bonding agent comprising aligning components of the electrochemical cell, applying a bonding agent between the components to bond the components together, placing the components within a container that is essentially a pliable bag, and drawing a vacuum within the bag, wherein the bag conforms to the shape of the components from the pressure outside the bag, thereby holding the components securely in place. The vacuum is passively maintained until the adhesive has cured and the components are securely bonded. The bonding agent used to bond the components of the electrochemical cell may be distributed to the bonding surface from distribution channels in the components. To prevent contamination with bonding agent, some areas may be treated to produce regions of preferred adhesive distribution and protected regions. Treatments may include polishing, etching, coating and providing protective grooves between the bonding surfaces and the protected regions.

Andrews, Craig C. (Inventor); Murphy, Oliver J. (Inventor)

2004-01-01

205

Vacuum Technology  

SciTech Connect

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.

Biltoft, P J

2004-10-15

206

Patterning and bonding of TiNi shape memory thin film for fabrication of micropump  

NASA Astrophysics Data System (ADS)

In order to develop a micropump driven by shape memory actuation, we require a TiNi diaphragm structure with a cap to act as a chamber for applying bias pressure to the diaphragm. With the purpose of realizing such a structure, we studied the photoetching of TiNi thin film on a Si substrate and two bonding processes-diffusion bonding and anodic bonding- for patterning and assembling. TiNi thin film deposited on Si substrates by flash evaporation was etched in HF/HNO3/H2O solutions using negative photoresist masks. HF:HNO3:H2O equals 1:1:4 solution proved capable of etching it at a rate of about 30 nm/s without etching of the Si substrate. Patterned TiNi thin film of 6 micrometers in thickness on a Si substrate was diffusion bonded to another Si substrate coated with the same TiNi thin film at a thickness of 300 nm. Bonding was conducted in a vacuum at a bonding pressure of 210 MPa. TiNi-TiNi diffusion bonding was obtained at temperatures of more than 300 degrees C. A 4-point bending test revealed that the bond strength of specimens bonded at 400 degrees C was 15-20 MPa. Anodic bonding was conducted between TiNi thin film on a Si substrate and a Pyrex 7740 glass substrate at an applied voltage of 600 V. Two substrates were bonded in nitrogen ambient at temperatures of more than 350 degrees C, giving a bond strength of about 15 MPa at 400 degrees C bonding.

Makino, Eiji; Mitsuya, Takashi; Nakatsuji, Tae; Shibata, Takayuki

1999-03-01

207

Vacuum mechatronics  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

208

Vacuum Virtues  

ERIC Educational Resources Information Center

Upright vacuums, like cars, vary in quality, features and performance. Like automobiles, some uprights are reliable, others may be problematic, and some become a problem as a result of neglect or improper use. So, how do education institutions make an informed choice and, having done so, ensure that an upright vacuum goes the distance? In this…

Rathey, Allen

2007-01-01

209

Vacuum regulator  

Microsoft Academic Search

This patent describes a vacuum regulator for automotive vehicles of the type having an engine exhaust system and a computer controlled exhaust gas recirculation system. The vacuum regulator consists of: a housing having separate interconnected upper and lower portions; a solenoid in the housing including a bobbin having a valve seat; a mechanism for defining an inlet for atmospheric air

M. Slavin; R. P. Fontecchio

1986-01-01

210

Bonding thermoplastic polymers  

DOEpatents

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.

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

211

Vacuum Plasma Spraying Replaces Electrodeposition  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

212

Vacuum die attach for integrated circuits  

DOEpatents

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.

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

1991-09-10

213

Vacuum die attach for integrated circuits  

DOEpatents

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.

Schmitt, Edward H. (Livermore, CA); Tuckerman, David B. (Livermore, CA)

1991-01-01

214

Vacuum applications of metal foams  

NASA Technical Reports Server (NTRS)

Several vacuum applications of copper foams in the density range 2-5% and pore sizes of 0.5-0.7 mm are discussed, such as a foreline hydrocarbon trap in a mechanical vacuum pump, a molecular-flow resistor, a diffuser, and a water injector. Other suggested applications include the use of foam copper in the form of an externally heated plug to remove traces of oxygen from inert gases bled into a vacuum system through a stainless steel line and the use of the porous surface for minimizing release of secondary electrons from electrodes in the path of charged particle beams.

Kendall, B. R. F.

1980-01-01

215

Vacuum applications of metal foams  

NASA Astrophysics Data System (ADS)

Several vacuum applications of copper foams in the density range 2-5% and pore sizes of 0.5-0.7 mm are discussed, such as a foreline hydrocarbon trap in a mechanical vacuum pump, a molecular-flow resistor, a diffuser, and a water injector. Other suggested applications include the use of foam copper in the form of an externally heated plug to remove traces of oxygen from inert gases bled into a vacuum system through a stainless steel line and the use of the porous surface for minimizing release of secondary electrons from electrodes in the path of charged particle beams.

Kendall, B. R. F.

1980-12-01

216

Vacuum considerations in the design of a space simulator  

NASA Technical Reports Server (NTRS)

Vacuum considerations in the techniques for design, fabrication, and testing of space simulators are discussed. Particular emphasis is given to a diffusion pump-rotary pump combination for the vacuum system.

Ramachandran, S.

1975-01-01

217

Diffusionless bonding of aluminum to Zircaloy2  

Microsoft Academic Search

Aluminum can be bonded to zirconium without difficulty even when a thin layer of oxide is present on the surface of the zirconium. No detectable diffusion takes place during the bonding process. The bond layer can be stretched as much as 8% without affecting the bond. The bond can be heated for 1000 hours at 260 deg C (500 deg

1965-01-01

218

Vacuum Ultraviolet Photochemistry of Tetrahydrothiophene and Sulfolane.  

National Technical Information Service (NTIS)

The vacuum uv photolysis of tetrahydrothiophene (THT) involves the breaking of the S to alpha -C bond. Besides ethylene, C sub 3 H sub 6 and 1,3-butadiene are also formed. Photolyses of THT, tetrahydrofuran, and pyrrolidine are similar. The vacuum uv phot...

A. A. Scala I. Colon

1979-01-01

219

Fusion bonding and alignment fixture  

DOEpatents

An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all the components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

Ackler, Harold D. (Sunnyvale, CA); Swierkowski, Stefan P. (Livermore, CA); Tarte, Lisa A. (Livermore, CA); Hicks, Randall K. (Stockton, CA)

2000-01-01

220

Vacuum Gauges  

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. Semiconductor manufacturing equipment requires the use of many different types of vacuum gauges. Selection is based on range of process operations and production requirements. This MATEC module explores the theory and functionality of vacuum gauges and provides many examples of different types of gauges. The focus is on understanding the operating ranges and application constraints of each type of gauge. Mathematical equations are used to explain calibration, sensitivity, and overall operations of each type of gauge.

2012-11-28

221

An investigation of the thermal diffusivity and thermal conductivity of insulating powders at atmospheric pressure and in vacuum by various methods  

Microsoft Academic Search

This paper gives the results of measurements of the thermal diffusivity and thermal conductivity of an aerogel, perlite powder, and white soot by the steady-state method, the continuous heating method, and the method of the regular regime of the first kind. The experimental data agree well with theory.

M. G. Kaganer; R. S. Semenova

1967-01-01

222

Microstructural evolution during transient liquid phase bonding of Inconel 738LC using AMS 4777 filler alloy  

SciTech Connect

IN-738LC nickel-based superalloy was joined by transient liquid phase diffusion bonding using AMS 4777 filler alloy. The bonding process was carried out at 1050 Degree-Sign C under vacuum atmosphere for various hold times. Microstructures of the joints were studied by optical and scanning electron microscopy. Continuous centerline eutectic phases, characterized as nickel-rich boride, chromium-rich boride and nickel-rich silicide were observed at the bonds with incomplete isothermal solidification. In addition to the centerline eutectic products, precipitation of boron-rich particles was observed in the diffusion affected zone. The results showed that, as the bonding time was increased to 75 min, the width of the eutectic zone was completely removed and the joint was isothermally solidified. Homogenization of isothermally solidified joints at 1120 Degree-Sign C for 300 min resulted in the elimination of intermetallic phases formed at the diffusion affected zone and the formation of significant {gamma} Prime precipitates in the joint region. - Highlights: Black-Right-Pointing-Pointer TLP bonding of IN-738LC superalloy was performed using AMS 4777 filler alloy. Black-Right-Pointing-Pointer Insufficient diffusion time resulted in the formation of eutectic product. Black-Right-Pointing-Pointer Precipitation of B-rich particles was observed within the DAZ. Black-Right-Pointing-Pointer The extent of isothermal solidification increased with increasing holding time. Black-Right-Pointing-Pointer Homogenizing of joints resulted in the dissolution of DAZ intermetallics.

Jalilvand, V., E-mail: jalilvand@aut.ac.ir [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of); Omidvar, H. [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of)] [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of); Shakeri, H.R. [Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada)] [Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada); Rahimipour, M.R. [Department of Ceramic, Materials and Energy Research Center, Karaj 31787-316 (Iran, Islamic Republic of)] [Department of Ceramic, Materials and Energy Research Center, Karaj 31787-316 (Iran, Islamic Republic of)

2013-01-15

223

Bent Bonds and Multiple Bonds.  

ERIC Educational Resources Information Center

Considers carbon-carbon multiple bonds in terms of Pauling's bent bond model, which allows direct calculation of double and triple bonds from the length of a CC single bond. Lengths of these multiple bonds are estimated from direct measurements on "bent-bond" models constructed of plastic tubing and standard kits. (CS)

Robinson, Edward A.; Gillespie, Ronald J.

1980-01-01

224

Structure and properties of diffusion layers formed in vacuum cyanidation of steel 20Kh13 in an atmosphere of pyrolysis of liquid hydrocarbons  

Microsoft Academic Search

The use of carburized high-chromium steels with 13–18% Cr for the production of wear-resistant shaping tools and attachments\\u000a is advantageous for many branches of industry. At the same time, the deposition of carbide diffusion layers on corrosion-resistant\\u000a high-chromium steels has some special features and technological difficulties, specifically, in quenching, tempering, and\\u000a polishing of parts and tools. The results described in

A. N. Tarasov

1998-01-01

225

Degassing procedure for ultrahigh vacuum  

NASA Technical Reports Server (NTRS)

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.

Moore, B. C.

1979-01-01

226

Gauge calibration by diffusion  

NASA Technical Reports Server (NTRS)

Vacuum gage calibration by diffusing a known quantity of gas through a heated barrier into a gauge is examined. The gas flow raises the pressure in the gauge to known level and is then compared with the gauge's pressure reading.

Brock, F. J.; Feakes, F. (inventors)

1968-01-01

227

Method of bonding silver to glass and mirrors produced according to this method  

DOEpatents

A method for adhering silver to a glass substrate for producing mirrors includes attaining a silicon enriched substrate surface by reducing the oxygen therein in a vacuum and then vacuum depositing a silver layer onto the silicon enriched surface. The silicon enrichment can be attained by electron beam bombardment, ion beam bombardment, or neutral beam bombardment. It can also be attained by depositing a metal, such as aluminum, on the substrate surface, allowing the metal to oxidize by pulling oxygen from the substrate surface, thereby leaving a silicon enriched surface, and then etching or eroding the metal oxide layer away to expose the silicon enriched surface. Ultraviolet rays can be used to maintain dangling silicon bonds on the enriched surface until covalent bonding with the silver can occur. This disclosure also includes encapsulated mirrors with diffusion layers built therein. One of these mirrors is assembled on a polymer substrate.

Pitts, John R. (Golden, CO); Thomas, Terence M. (Arvada, CO); Czanderna, Alvin W. (Lakewood, CO)

1985-01-01

228

Edge conduction in vacuum glazing  

SciTech Connect

Vacuum glazing is a form of low-conductance double glazing using in internal vacuum between the two glass sheets to eliminate heat transport by gas conduction and convection. An array of small support pillars separates the sheets; fused solder glass forms the edge seal. Heat transfer through the glazing occurs by radiation across the vacuum gap, conduction through the support pillars, and conduction through the bonded edge seal. Edge conduction is problematic because it affects stresses in the edge region, leading to possible failure of the glazing; in addition, excessive heat transfer because of thermal bridging in the edge region can lower overall window thermal performance and decrease resistance to condensation. Infrared thermography was used to analyze the thermal performance of prototype vacuum glazings, and, for comparison, atmospheric pressure superwindows. Research focused on mitigating the edge effects of vacuum glazings through the use of insulating trim, recessed edges, and framing materials. Experimentally validated finite-element and finite-difference modeling tools were used for thermal analysis of prototype vacuum glazing units and complete windows. Experimental measurements of edge conduction using infrared imaging were found to be in good agreement with finite-element modeling results for a given set of conditions. Finite-element modeling validates an analytic model developed for edge conduction.

Simko, T.M.; Collins, R.E. [Sydney Univ., NSW (Australia). Dept. of Applied Physics; Beck, F.A.; Arasteh, D. [Lawrence Berkeley Lab., CA (United States)

1995-03-01

229

Theoretical model of the grasp with vacuum gripper  

Microsoft Academic Search

Vacuum grippers are often notably diffused for grasping and moving very large and heavy objects.The absence of theoretical models able to foresee the behavior of the suction cup notably limits the applications and development of vacuum grippers.In this work, a study of grasping with a vacuum gripper has been carried out. A mathematical model is proposed for determining the forces

Giacomo Mantriota

2007-01-01

230

Determining the mode of high voltage breakdowns in vacuum devices  

Microsoft Academic Search

Vacuum diodes equipped with windows allowing observation of high voltage breakdowns were constructed. The waveform of the applied voltage was photographed, and the X-ray output was monitored to investigate electrical breakdown in these vacuum diodes. Breakdowns may be divided into types: (1) vacuum (interelectrode) breakdown - characterized by a diffuse moderately bright discharge, a relative slow and smooth voltage collapse,

H. C. Miller; E. J. Furno; J. P. Sturtz

1980-01-01

231

Heat-shrinkable film improves adhesive bonds  

NASA Technical Reports Server (NTRS)

Pressure is applied during adhesive bonding by wrapping parts in heat-shrinkable plastic film. Film eliminates need to vacuum bag or heat parts in expensive autoclave. With procedure, operators are trained quickly, and no special skills are required.

Johns, J. M.; Reed, M. W.

1980-01-01

232

NMR relaxation and self-diffusion studies of H-bond exchange and molecular motion in pivalic acid and binary solutions of pivalic acid and carbon tetrachloride  

NASA Astrophysics Data System (ADS)

1H NMR relaxation times ( T1) and, in particular, self-diffusion coefficients in the liquid and plastic phases of neat pivalic acid (PA) and binary mixtures of PA and carbon tetrachloride are reported. The slight increase in T1 of the methyl protons on dilution is ascribed to reduced viscosity. The T1 measurements of PA monitor reorientations of complete dimers rather than monomers in the liquid. The large increase in T1 of the carboxy proton on dilution, followed by a corresponding reduction in the activation energy, is the result of a decreasing contribution from intermolecular interactions and enhanced mobility. The diffusion coefficients (approximately 10 -9 m 2s -1), obtained from the methyl and carboxy resonances, are mutually identical in both PA and the most dilute sample (6.4 mol%). This indicates that the carboxy hydrogen is diffusing at the same rate as the rest of the molecule. The average life time of the cyclic dimer thus appears to be longer than the mean time between diffusional jumps in the liquid state. In the disordered solid the diffusion coefficient of the carboxy hydrogen (8 × 10 -12 m 2s -1 at 286 K) is about three orders of magnitude larger than the whole-molecule diffusion coefficient (approximately 10 -14 m 2s -1), whereas the corresponding activation energies are 18 and 59 kJ mol -1. These observations show that the carboxy hydrogen is moving through the lattice approximately a thousand times faster than the rest of the molecule.

Aksnes, D. W.; Kimtys, L.

1994-06-01

233

QED vacuum loops and vacuum energy  

NASA Astrophysics Data System (ADS)

A QED-based "bootstrap" mechanism is suggested as a possible source of vacuum energy. In place of the conventional assumption that the vacuum expectation value of the current operator j ? vanishes in the absence of a classical, external field, one notes the possibility that, on very small scales, the vacuum fluctuations can generate an equation for an effective, C-number giving rise to a finite and computable vacuum energy.

Fried, H. M.; Gabellini, Y.

2013-12-01

234

Vacuum plasma spray coating  

NASA Technical Reports Server (NTRS)

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.

Holmes, Richard R.; Mckechnie, Timothy N.

1989-01-01

235

Chemical Bonds  

NSDL National Science Digital Library

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.

Consortium, The C.

2011-12-11

236

Sticker Bonding.  

ERIC Educational Resources Information Center

Introduces a science activity on the bonding of chemical compounds. Assigns students the role of either a cation or anion and asks them to write the ions they may bond with. Assesses students' understanding of charge, bonding, and other concepts. (YDS)

Frazier, Laura Corbin

2000-01-01

237

High Temperature Adhesives for Bonding Kapton  

NASA Technical Reports Server (NTRS)

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 575K (575 F) in vacuum. Glass transition temperatures of the polyimide/Kapton bondlines were monitored by thermomechanical analysis.

Stclair, A. K.; Slemp, W. S.; Stclair, T. L.

1978-01-01

238

High temperature adhesives for bonding Kapton  

NASA Technical Reports Server (NTRS)

Experimental polyimide resins have been 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 575K (575 F) in vacuum. Glass transition temperatures of the polyimide/'Kapton' bondlines were monitored by thermomechanical analysis.

Saint Clair, A. K.; Slemp, W. S.; Saint Clair, T. L.

1978-01-01

239

Resistance Projection Welding of Vacuum Tube Getter Assembly.  

National Technical Information Service (NTIS)

Tungsten inert gas welding the leads to a vacuum tube getter assembly can result in fusion of gettering powder, lowering gas absorption capability. Using resistance projection welding with ball-ended leads, getter bodies were successfully bonded to the le...

F. Kuncz

1980-01-01

240

Performance tests of large thin vacuum windows  

NASA Astrophysics Data System (ADS)

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.

Crannell, Hall

2011-02-01

241

The Vacuum Bubble Nucleation  

SciTech Connect

We study the nucleation of a vacuum bubble via the vacuum-to-vacuum tunneling transition in curved spacetime. We consider Coleman-de Luccia's semiclassical approximation at zero temperature in pure Einstein theory of gravity and the theory with nonminimal coupling. We discuss the dynamics of a nucleated vacuum bubble.

Lee, Bum-Hoon [Department of Physics and Center for Quantum Spacetime, Sogang University Seoul 121-742 (Korea, Republic of); Lee, Wonwoo [Center for Quantum Spacetime, Sogang University, Seoul 121-742 (Korea, Republic of)

2009-07-10

242

Natural vacuum electronics  

NASA Technical Reports Server (NTRS)

The ambient natural vacuum of space is proposed as a basis for electron valves. Each valve is an electron controlling structure similiar to a vacuum tube that is operated without a vacuum sustaining envelope. The natural vacuum electron valves discussed offer a viable substitute for solid state devices. The natural vacuum valve is highly resistant to ionizing radiation, system generated electromagnetic pulse, current transients, and direct exposure to space conditions.

Leggett, Nickolaus

1990-01-01

243

Germanium detector vacuum encapsulation  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

244

Fabricating capacitive micromachined ultrasonic transducers with wafer-bonding technology  

Microsoft Academic Search

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

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

2003-01-01

245

Vacuum carburizing of chromium-nickel steel  

Microsoft Academic Search

The main features of formation of diffusion layers due to vacuum carburizing of chromium-nickel steel 20Kh2N4A in an acetylene\\u000a medium are considered. Analysis of the structure of the saturated surface and of the results of carburizing is used to show\\u000a that the diffusion layer is formed under a thin layer of condensed carbon in a kinetic regime the intensity of

N. M. Ryzhov; A. E. Smirnov; R. S. Fakhurtdinov; A. I. Mordovin

2008-01-01

246

Origin of the diffuse vibrational signature of a cyclic intramolecular proton bond: Anharmonic analysis of protonated 1,8-disubstituted naphthalene ions  

NASA Astrophysics Data System (ADS)

We analyze the structures and spectral signatures of the cyclic intramolecular proton bond, N-H+-A, A = O and F, formed when an excess proton is added to derivatives of the 1,8-disubstituted naphthalene scaffold. These compounds provide a quasi-rigid framework with which to study the spectral complexity often associated with the N-H+-A entity. Vibrational spectra were obtained by monitoring photodissociation of weakly bound H2 adducts of the mass-selected ions cooled close to 10 K. Several bands across the 900-3500 cm-1 spectral range were traced to involvement of the bridging proton by their telltale shifts upon selective H/D isotopic substitution at that position. We account for the complex patterns that occur near the expected locations of the NH stretching fundamentals in the context of background levels mixing with a ``bright'' zero-order state through cubic terms in the potential energy expansion. Thus, this system provides a detailed picture of one of the mechanisms behind the line broadening often displayed by embedded excess protons. It does so in a sufficiently sparse density of states regime that many discrete transitions are observed in the vicinity of the harmonic stretching transition involving displacement of the trapped proton.

DeBlase, Andrew F.; Bloom, Steven; Lectka, Thomas; Jordan, Kenneth D.; McCoy, Anne B.; Johnson, Mark A.

2013-07-01

247

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

248

Inverse response of polypropylene to gamma radiation under vacuum  

Microsoft Academic Search

The effect of gamma radiation under vacuum on polypropylene is analysed on the basis of a simple kinetic model. The influence of the irradiation parameters, total absorbed dose and dose rate, on the rates of the main reactions occurring during irradiation, i.e. ?-scission, addition to double bonds and termination, is studied. Using kinetic equations, and free radical and double bond

L. Sarcinelli; A. Valenza; G. Spadaro

1997-01-01

249

Educational Vacuum Trainers  

NSDL National Science Digital Library

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

Hansen, Steve

2012-07-31

250

Optimizing process vacuum condensers  

SciTech Connect

Vacuum condensers play a critical role in supporting vacuum processing operations. Although they may appear similar to atmospheric units, vacuum condensers have their own special designs, considerations and installation needs. By adding vacuum condensers, precondensers and intercondensers, system cost efficiency can be optimized. Vacuum-condensing systems permit reclamation of high-value product by use of a precondenser, or reduce operating costs with intercondensers. A precondenser placed between the vacuum vessel and ejector system will recover valuable process vapors and reduce vapor load to an ejector system--minimizing the system`s capital and operating costs. Similarly, an intercondenser positioned between ejector stages can condense motive steam and process vapors and reduce vapor load to downstream ejectors as well as lower capital and operating costs. The paper describes vacuum condenser systems, types of vacuum condensers, shellside condensing, tubeside condensing, noncondensable gases, precondenser pressure drop, system interdependency, equipment installation, and equipment layout.

Lines, J.R.; Tice, D.W. [Graham Mfg. Co., Batavia, NY (United States)

1997-09-01

251

Vacuum Probe Surface Sampler.  

National Technical Information Service (NTIS)

A vacuum probe surface sampler for rapidly sampling relatively large surface areas which possess relatively light loading densities of microorganisms, drug particles or the like is described. A vacuum head having a hollow handle connected to a suitable va...

B. A. Zahlava

1971-01-01

252

The Classical Vacuum.  

ERIC Educational Resources Information Center

The classical vacuum of physics is not empty, but contains a distinctive pattern of electromagnetic fields. Discovery of the vacuum, thermal spectrum, classical electron theory, zero-point spectrum, and effects of acceleration are discussed. Connection between thermal radiation and the classical vacuum reveals unexpected unity in the laws of…

Boyer, Timothy H.

1985-01-01

253

Forming Bonds.  

ERIC Educational Resources Information Center

Explains how one North Carolina school district was able to pass high-dollar bond issues for school construction. Discusses the planning and bidding processes, and the district's philosophy towards incorporating innovative changes in design and equipment. (GR)

Spoor, Dana L.

1998-01-01

254

Heating steels in vacuum  

SciTech Connect

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.

Marmer, E.N.

1983-03-01

255

Influence of Joining Conditions on Bonding Strength of Joints: Efficacy of Low-Temperature Bonding Using Cu Nanoparticle Paste  

NASA Astrophysics Data System (ADS)

We investigated a new low-temperature bonding process utilizing Cu nanoparticle paste without addition of sintering promoter. Joint bonding strengths above 30 MPa were achieved even at a low bonding temperature of 250ºC. We attribute the higher bonding strengths of joints fabricated using the vacuum preheating process to the rapid progression of Cu nanoparticle sintering due to the activated nanoparticle surface at lower temperatures. The increase in bonding strength depended on the applied pressure, in addition to the bonding temperature. The formation of a dimple-like morphology was confirmed in the ductile fracture area. This indicated that the joint bonded strongly with the bonding layer, in agreement with the results of bonding tests carried out on strongly bonded joints. The bonding ability of the joints obtained using Cu nanoparticle paste could be improved by controlling the joint fabrication conditions.

Yamakawa, Tomohiro; Takemoto, Tadashi; Shimoda, Masayoshi; Nishikawa, Hiroshi; Shiokawa, Kunio; Terada, Nobuto

2013-06-01

256

Vacuum probe surface sampler  

NASA Technical Reports Server (NTRS)

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.

Zahlava, B. A. (inventor)

1973-01-01

257

Li diffusion in zircon  

NASA Astrophysics Data System (ADS)

Diffusion of Li under anhydrous conditions at 1 atm and under fluid-present elevated pressure (1.0-1.2 GPa) conditions has been measured in natural zircon. The source of diffusant for 1-atm experiments was ground natural spodumene, which was sealed under vacuum in silica glass capsules with polished slabs of zircon. An experiment using a Dy-bearing source was also conducted to evaluate possible rate-limiting effects on Li diffusion of slow-diffusing REE+3 that might provide charge balance. Diffusion experiments performed in the presence of H2O-CO2 fluid were run in a piston-cylinder apparatus, using a source consisting of a powdered mixture of spodumene, quartz and zircon with oxalic acid added to produce H2O-CO2 fluid. Nuclear reaction analysis (NRA) with the resonant nuclear reaction 7Li(p,?)8Be was used to measure diffusion profiles for the experiments. The following Arrhenius parameters were obtained for Li diffusion normal to the c-axis over the temperature range 703-1.151°C at 1 atm for experiments run with the spodumene source: D_{text{Li}} = 7.17 × 10^{ - 7} { exp }( - 275 ± 11 {text{kJmol}}^{ - 1} /{text{RT}}){text{m}}2 {text{s}}^{ - 1}. Diffusivities are similar for transport parallel to the c-axis, indicating little anisotropy for Li diffusion in zircon. Similar Li diffusivities were also found for experiments run under fluid-present conditions and for the experiment run with the Dy-bearing source. Li diffusion is considerably faster than diffusion of other cations in zircon, with a smaller activation energy for diffusion. Although Li diffusion in zircon is comparatively rapid, zircons will be moderately retentive of Li signatures at mid-crustal metamorphic temperatures, but they are unlikely to retain this information for geologically significant times under high-grade metamorphism.

Cherniak, D. J.; Watson, E. B.

2010-09-01

258

Superplastically Formed Diffusion Bonded Metallic Structure.  

National Technical Information Service (NTIS)

A pair of core plates formed of a superplastic alloy are interposed between the base plate and the cover plate in a sandwich relationship. Each of the core plates are characterized by a plurality of protrusions of square-based, truncated pyramids. These p...

W. L. Ko

1979-01-01

259

In-service helium leak testing of vacuum furnace  

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

260

Compact vacuum insulation embodiments  

Microsoft Academic Search

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

D. K. Benson; T. F. Potter

1992-01-01

261

Compact vacuum insulation  

Microsoft Academic Search

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

David K. Benson; Thomas F. Potter

1993-01-01

262

Working in a Vacuum  

ERIC Educational Resources Information Center

In this article, the author discusses several myths about vacuum cleaners and offers tips on evaluating and purchasing this essential maintenance tool. These myths are: (1) Amps mean performance; (2) Everyone needs high-efficiency particulate air (HEPA): (3) Picking up a "bowling ball" shows cleaning power; (4) All vacuum bags are the same; (5)…

Rathey, Allen

2005-01-01

263

Study of Vacuum Welding.  

National Technical Information Service (NTIS)

Vacuum cold welding and shear friction of several engineering materials was studied at extremely high vacuum levels above 10 to the -12th power torr in the temperature range 90 to 260 C with interface contact stresses up to 1000 psi. The effect of surface...

M. J. Hordon J. R. Roehrig

1967-01-01

264

Vacuuming radioactive sludge  

SciTech Connect

Vacuuming an estimated 55 cubic yards of radioactive sludge from the floor of Hanford's K East Basin was a complicated process. Workers stood on grates suspended above the 20-foot deep basin and manipulated vacuuming equipment at the end of long poles--using underwater cameras to guide their work.

2006-10-16

265

Vacuum Probe Surface Sampler.  

National Technical Information Service (NTIS)

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 vacu...

B. A. Zahlava

1973-01-01

266

Vacuum driven accelerated expansion  

Microsoft Academic Search

It has been shown that an improved estimation of quantum vacuum energy can yield not only acceptable but also experimentally sensible results. The very idea consists in a straightforward extraction of gravitationally interacting part of the full quantum vacuum energy by means of gauge transformations. The implementation of the idea has been performed in the formalism of effective action, in

B. Broda; P. Bronowski; Marcin Ostrowski; Micha? Szanecki

2008-01-01

267

Stellarator Helical Vacuum Vessel.  

National Technical Information Service (NTIS)

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...

E. J. Yavornik

1983-01-01

268

A fluxless oxidation-free bonding technology  

Microsoft Academic Search

A fluxless oxidation-free bonding technology is reported. The technology uses the direct deposition of multilayer composite in high vacuum to prevent oxidation. The outer layer of the composite is either gold or copper which protects the inner layers from oxidation when the composite is later exposed to atmosphere. As a result of oxidation prevention neither flux nor scrubbing action is

Chin C. Lee; Yi-Chia Chen; Goran Matijasevic; Richard Metzler

1994-01-01

269

Bonding and Sealing Evaluations for Cryogenic Tanks  

Microsoft Academic Search

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

David E. Glass

270

Chemical Recognition Tunneling via Hydrogen Bond  

Microsoft Academic Search

Hydrogen bonds enhance electron tunneling rates over vacuum tunneling as well as making chemically selective attachments to target molecules when patterns of donors and acceptors match. This raises the possibility of a completely new approach to transducing chemical information into electrical signals, based on forming an electrical circuit via a target molecule that bridges a gap between two electrodes by

Jin He; Shuai Chang; Lisha Lin; Shuo Huang; Ashley Kibel; Myeong Lee; Peiming Zhang; Otto Sankey; Stuart Lindsay

2009-01-01

271

Characteristic features of carburizing of steel during vacuum carburizing  

Microsoft Academic Search

1.The quantitative relationship obtained between the carbon concentration in the case and the basic parameters of the vacuum carburizing process makes it possible to determine the effective case depth for any ratio of saturation and diffusion times.2.The duration of the diffusion stage dependents on the final surface concentration of carbon required.3.The variation obtained for a given duration of the diffusion

S. N. Tsepov

1979-01-01

272

Cryogenic vacuum tight adhesive  

NASA Astrophysics Data System (ADS)

A synthetic adhesive for vacuum tight joints at cryogenic temperatures has been developed. It consists of three components, the main component being epoxy silicone organic resin. The joints made with the adhesive remain vacuum tight at liquid helium temperature, including superfluid helium. It was found possible to connect different materials with the adhesive (copper and stainless steel with each other, aluminum, aluminum alloys, fiberglass, etc.). The joints withstood thermal shock tests of ten repeated sharps cooling to liquid nitrogen temperature and heating in hot water. Using the adhesive a lot of different vacuum tight low temperature joints have been made. More than fifteen years of wide application of this adhesive in vacuum tight cryogenic joints proved its high reliability. Some designs of vacuum tight cryogenic joints are presented and the technique of their manufacturing is described.

Anashkin, O. P.; Keilin, V. E.; Patrikeev, V. M.

1999-12-01

273

Chalcogen bond: a sister noncovalent bond to halogen bond.  

PubMed

A sister noncovalent bond to halogen bond, termed chalcogen bond, is defined in this article. By selecting the complexes H(2)CS...Cl(-), F(2)CS...Cl(-), OCS...Cl(-), and SCS...Cl(-) as models, the bond-length change, interaction energy, topological property of the electron charge density and its Laplacian, and the charge transfer of the chalcogen bond have been investigated in detail theoretically. It was found that the similar misshaped electron clouds of the chalcogen atom and the halogen atom result in the similar properties of the chalcogen bond and the halogen bond. Experimental results are in good agreement with the theoretical predictions. PMID:19537765

Wang, Weizhou; Ji, Baoming; Zhang, Yu

2009-07-16

274

Pi Bond Orders and Bond Lengths  

ERIC Educational Resources Information Center

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)

Herndon, William C.; Parkanyi, Cyril

1976-01-01

275

Thermophoretic vacuum wand  

SciTech Connect

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.

Klebanoff, L.E.; Rader, D.J.

2000-06-06

276

Thermophoretic vacuum wand  

SciTech Connect

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.

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

2000-01-01

277

Thermophoretic vacuum wand  

DOEpatents

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.

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

2001-01-01

278

Evading death by vacuum  

NASA Astrophysics Data System (ADS)

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 allow to exclude many panic vacuum solutions.

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

2013-09-01

279

Vacuum deposition system  

SciTech Connect

The Physics Section vacuum deposition system is available for several types of thin film techniques. This vacuum evaporation system operates in the high vacuum range. The evaporation source is a resistive heating element, either a boat or a filament design. Coating is then line of sight from the source. Substrates to be coated can have a maximum diameter of 17 inches. At this time the variations in the thickness of the coatings can be controlled, by monitor, to within about 100 angstroms. The system diagrams follow the Operation Procedures and the Sample Coating Procedures provided in this document. 3 figs.

Austin, S.; Bark, D.

1990-05-31

280

A road map to extreme high vacuum  

NASA Astrophysics Data System (ADS)

Ultimate pressure of a well-designed vacuum system very much depends on pretreatments, processing and procedures [1, 2]. Until now much attention has been paid to minimizing hydrogen outgassing from the vacuum chamber wall materials, however, procedures and processing deserve further scrutiny. For reducing the gas load, high sensitivity helium leak detection techniques with sensitivities better than 1×10-12 Torr l/sec should be used. Effects that are induced by vacuum instrumentation need to be reduced in order to obtain accurate pressure measurements. This paper presents the current status of the CEBAF DC photogun. This state of the art technology is driving the need for Extreme High Vacuum (XHV). We also present sensitive helium leak detection techniques with RGA's, vacuum gauge and RGA calibration procedures, metal sponges for cryosorption pumping of hydrogen to XHV, low cost surface diffusion barriers for reducing the hydrogen gas load and clean assembly procedures. Further, alternative backing pump systems based on active NEGs [3] for turbo molecular pumps are also discussed.

Adderley, P.; Myneni, G.

2008-05-01

281

Adhesives For Use In Vacuum, Radiation, And Cold  

NASA Technical Reports Server (NTRS)

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).

Bouquet, Frank L.

1988-01-01

282

Supermite vacuum interface design  

SciTech Connect

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.

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

1985-01-01

283

Multistage Turbomolecular Vacuum Pump.  

National Technical Information Service (NTIS)

The patent describes a multistage vacuum turbomolecular pump which consists of a housing containing rotor and stator disks having working elements (blades, radial slots) along their periphery. To increase the compression stage and reducing the reverse flo...

B. V. Ivanov I. D. Anokhin L. B. Leonov V. I. Kuznetsov

1973-01-01

284

Vacuum Pump Explosion Study.  

National Technical Information Service (NTIS)

An investigation was made into explosions and backfires occurring in vacuum pumps used on Navy oxygen component test stands. Research and testing uncovered several fire and toxicity hazards on these pumps which carry gaseous oxygen flows. Corrective recom...

H. H. Yuen T. D. Weikel

1972-01-01

285

On Gowdy vacuum spacetimes  

NASA Astrophysics Data System (ADS)

Using Fuchsian techniques, a large family of Gowdy vacuum spacetimes have been constructed for which one has detailed control over asymptotic behaviour. In this paper we formulate a condition on initial data yielding the same form of asymptotics.

Ringström, Hans

2004-03-01

286

Vacuum Camera Cooler  

NASA Technical Reports Server (NTRS)

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.

Laugen, Geoffrey A.

2011-01-01

287

Nonlinear Squeezed Vacuum States:  

NASA Astrophysics Data System (ADS)

Some of the properties of nonlinear squeezed vacuum states associated with trapped ions are considered, especially the photon number distribution, the phase properties, the Husimi-Kano Q function and the Wigner-Moyal W function of these nonlinear squeezed vacuum states. The structure of these functions is shown to depend on the nonlinearity parameter, its functional dependence and the squeezing parameter. It is shown that increasing the nonlinearity parameter results in the photon number distribution being squeezed independent.

Darwish, M.

288

Precision of Vacuum Mechanisms  

Microsoft Academic Search

The required precision of vacuum installations in most technologies (thin film coating, electron beam welding, diffusionwelding)\\u000a is the same as in traditional engineering industry, but operating conditions of the mechanisms work are much worse, because\\u000a of vacuum and periodical outgassing baking (see Tables 1.1, 1.2, 1.4). At the same time, the equipment of surface research,\\u000a electron beam-, ion beam lithography,

E. A. Deulin; V. P. Mikhailov; Yu. V. Panfilov; R. A. Nevshupa

289

Vacuum Erection Devices  

Microsoft Academic Search

Vacuum erection devices (VEDs) are safe, effective treatments for erectile dysfunction with few side effects. Vacuum negative\\u000a pressure more than 100 mmHg causes a combination of arterial and venous blood to fill the corpora cavernosum. The use of an\\u000a elastic band to trap the blood within the penis allows sufficient rigidity for penetration. Devices approved by the Food and\\u000a Drug

Hunter Wessells

290

Annealing effects on the bonding structures, optical and mechanical properties for radio frequency reactive sputtered germanium carbide films  

NASA Astrophysics Data System (ADS)

The effects of thermal annealing in vacuum on the bonding structures, optical and mechanical properties for germanium carbide (Ge 1- xC x) thin films, deposited by radio frequency (RF) reactive sputtering of pure Ge(1 1 1) target in a CH 4/Ar mixture discharge, are investigated. We find that there are no significant changes in the bonding structure of the films annealed below 300 °C. The fraction of Ge-H bonds for the film annealed at temperatures ( Ta) above 300 °C decreases, whereas that of C-H bonds show a decrease only when Ta exceeds 400 °C. The out-diffusion of hydrogen promotes the formation of Ge-C bonds at Ta above 400 °C and thus leads to a substantial increase in the compressive stress and hardness for the film. The refractive indices and optical gaps for Ge 1- xC x films are almost constant against Ta, which can be ascribed to the unchanged ratios of Ge/C and sp 2-C/sp 3-C concentrations. Furthermore, we also find that the excellent optical transmission for an antireflection Ge 1- xC x double-layer film on ZnS substrate is still maintained after annealing at 700 °C.

Hu, C. Q.; Zhu, J. Q.; Zheng, W. T.; Han, J. C.

2009-01-01

291

Vacuum self-magnetization?  

SciTech Connect

We study vacuum properties in a strong magnetic field as the zero temperature and zero density limit of quantum statistics. For charged vector bosons (W bosons) the vacuum energy density diverges for B > B{sub c} = m{sub w}{sup 2}/e, leading to vacuum instability. A logarithmic divergence of vacuum magnetization is found for B = Bc, which suggests that if the magnetic field is large enough, it is self-consistently maintained, and this mechanism actually prevents B from reaching the critical value Bc. For virtual neutral vector bosons bearing an anomalous magnetic moment, the instability of the ground state for B > B{sub c}{sup '} = m{sub n}{sup 2}/q also leads to the vacuum energy density divergence for fields B > B{sub c}{sup '} and to the magnetization divergence for B B{sub c}{sup '}. The possibility of virtual electron-positron pairs bosonization in strong magnetic field and the applicability of the neutral bosons model to describe the virtual positronium behavior in a magnetic field are discussed. We conjecture that this could lead to vacuum self-magnetization in QED.

Perez Rojas, H.; Rodriguez Querts, E. [Instituto de Cibernetica, Matematica y Fisica, Calle E No. 309, esq. a 15 Vedado, C. Havana (Cuba)

2006-06-19

292

Vacuum chamber-free centrifuge with magnetic bearings  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

293

Vacuum chamber-free centrifuge with magnetic bearings.  

PubMed

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. PMID:24089865

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

2013-09-01

294

Unconventional applications of wire bonding create opportunities for microsystem integration  

NASA Astrophysics Data System (ADS)

Automatic wire bonding is a highly mature, cost-efficient and broadly available back-end process, intended to create electrical interconnections in semiconductor chip packaging. Modern production wire-bonding tools can bond wires with speeds of up to 30 bonds per second with placement accuracies of better than {2\\;\\unicode{xb5}{m}}, and the ability to form each wire individually into a desired shape. These features render wire bonding a versatile tool also for integrating wires in applications other than electrical interconnections. Wire bonding has been adapted and used to implement a variety of innovative microstructures. This paper reviews unconventional uses and applications of wire bonding that have been reported in the literature. The used wire-bonding techniques and materials are discussed, and the implemented applications are presented. They include the realization and integration of coils, transformers, inductors, antennas, electrodes, through silicon vias, plugs, liquid and vacuum seals, plastic fibers, shape memory alloy actuators, energy harvesters and sensors.

Fischer, A. C.; Korvink, J. G.; Roxhed, N.; Stemme, G.; Wallrabe, U.; Niklaus, F.

2013-08-01

295

Vacuum plasma spray applications on liquid fuel rocket engines  

Microsoft Academic Search

The vacuum plasma spray process (VPS) has been developed by NASA and Rocketdyne for a variety of applications on liquid fuel rocket engines, including the Space Shuttle Main Engine. These applications encompass thermal barrier coatings which are thermal shock resistant for turbopump blades and nozzles; bond coatings for cryogenic titanium components; wear resistant coatings and materials; high conductivity copper, NaRloy-Z,

T. N. McKechnie; F. R. Zimmerman; M. A. Bryant

1992-01-01

296

p-n Junctions in vacuum deposited polycrystalline silicon thin films  

Microsoft Academic Search

Diffused p-n junctions formed in vacuum deposited polycrystalline silicon films on sapphire substrates were examined as functions of both diffusion and deposition conditions. Thick films (5-33 µm) with large crystallites suitable for solar cell and large area device applications are described. Comparisons are made between amorphous silicon films converted to polycrystalline during diffusion processing and films deposited in polycrystalline form

C. Feldman; F. G. Satkiewicz

1976-01-01

297

Vacuum Technology in the study of Graphene  

NASA Astrophysics Data System (ADS)

Graphene, an allotrope of carbon is a two-dimensional sheet of covalently bonded carbon atoms that has been attracting great attention in the field of electronics. In a recent review graphene is defined as a flat monolayer of carbon atoms tightly packed into a 2-D honeycomb lattice. A survey has been made of the production processes and instrumentation for characterization of graphene. In the production of graphene, the methods mainly used are Epitaxial growth, oxide reduction, growth from metal-carbon melts, growth from sugar. In the characterization of graphene, the instruments that are mainly used to study the atomic properties, electronic properties, optical properties, spin properties are Scanning Electron Microscopy, Transmission Electron Microscopy, Raman Spectroscopy. In all these instruments high or ultra-high vacuum is required. This paper attempts to correlate vacuum technology in the production and characterization of graphene.

Ghoshal, A. K.; Banerjee, S. N.; Chakraborty, D.

2012-11-01

298

Stellarator helical vacuum vessel  

SciTech Connect

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.

Yavornik, E.J.

1983-01-01

299

REE Diffusion in Olivine  

NASA Astrophysics Data System (ADS)

Diffusion of rare earth elements has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of REE aluminate garnet powder and synthetic forsterite powder in 3:1 proportions. Experiments were prepared by enclosing source material and polished forsterite in platinum capsules, which were crimped shut. For experiments on natural olivine, samples were placed with the source in AgPd capsules, which were sealed under vacuum in silica glass ampoules with a solid buffer to buffer at NNO. Prepared capsules were then annealed in 1 atm furnaces for times ranging from an hour to several weeks, at temperatures from 850 to 1300°C. REE distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for Dy diffusion in forsterite: D = 2.3x10-10 exp(-273 kJ mol-1/RT) m2sec-1. Diffusivities of Yb and La in forsterite appear similar, and preliminary results for Dy diffusion in natural olivine also suggest similar diffusivities. REE diffusivities in forsterite are about an order of magnitude faster than those of REE+3 in enstatite (Cherniak and Liang, 2007). However, if the Arrhenius relation above is extrapolated up to 1450C, it yields diffusivities about three orders of magnitude smaller than those determined for REE diffusion in olivine by Spandler et al. (2007). Work is currently underway in further characterizing diffusion in Fe-bearing olivine. If an Arrhenius relation similar to that for forsterite is found to apply, timescales for preservation of REE signatures in olivine-hosted melt inclusions may be relatively long. Cherniak and Liang (2007) GCA 71, 1324-1340; Spandler et al. (2007) Nature 447, 303-306.

Cherniak, D. J.

2007-12-01

300

Improving Vacuum Cleaners  

NASA Technical Reports Server (NTRS)

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.

1997-01-01

301

Electrostatic Levitator Vacuum Chamber  

NASA Technical Reports Server (NTRS)

Optical ports ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (beam passes through the window at left), positioning lasers (one port is at center), and lamps to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

1998-01-01

302

Vacuum tool manipulator.  

National Technical Information Service (NTIS)

This invention is comprised of an apparatus for manipulating a vacuum hose in a reactor vessel comprising a housing with two opposing openings, an arm carried by the housing and deployable from a stowed position essentially completely within the housing t...

W. T. Zollinger

1992-01-01

303

Vacuum insulating panel  

Microsoft Academic Search

Theoretical aspects and practical possibilities for realization of a new type of thermal insulation, vacuum panel insulation (VPI), are given. From a functional point of view, it is a flat all metal Dewar flask with an array of supporting beads. They span metal foils at desired distances and limit conduction by internal, near-point contacts. Model studies and first reports show

V Nemani?

1995-01-01

304

Vacuum thermal insulation panel  

Microsoft Academic Search

A vacuum thermal insulation panel comprises a pair of laminated plastic and aluminum sheets together with a plastic edge strip sealed to the edges of the sheets so as to define an evacuable volume in which a glass fiber mat is disposed. The insulation panel of the present invention takes advantage of the light-weight, low cost and low thermal conductivity

J. R. Young; R. M. Schreck

1984-01-01

305

Compact vacuum insulation  

Microsoft Academic Search

Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases there between are evacuated to form a vacuum. These spherical glass

D. K. Benson; T. F. Potter

1992-01-01

306

Compact vacuum insulation  

Microsoft Academic Search

Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases therebetween are evacuated to form a vacuum. These spherical glass beads

David K. Benson; Thomas F. Potter

1992-01-01

307

Topics in vacuum decay  

NASA Astrophysics Data System (ADS)

If a theory has more than one classically stable vacuum, quantum tunneling and thermal jumps make the transition between the vacua possible. The transition happens through a first order phase transition started by nucleation of a bubble of the new vacuum. The outward pressure of the truer vacuum makes the bubble expand and consequently eat away more of the old phase. In the presence of gravity this phenomenon gets more complicated and meanwhile more interesting. It can potentially have important cosmological consequences. Some aspects of this decay are studied in this thesis. Solutions with different symmetry than the generically used O(4) symmetry are studied and their actions calculated. Vacuum decay in a spatial vector field is studied and novel features like kinky domain walls are presented. The question of stability of vacua in a landscape of potentials is studied and the possible instability in large dimension of fields is shown. Finally a compactification of the Einstein-Maxwell theory is studied which can be a good lab to understand the decay rates in compactification models of arbitrary dimensions.

Masoumi, Ali

308

High Vacuum Valve.  

National Technical Information Service (NTIS)

The metal-to-metal seal vacuum valve is provided with a bellows which aids in preventing leakage through the housing cover and about the stem. The inner surface of the valve housing is provided with a metal valve seat having a relatively sharp edge around...

J. M. Frame

1965-01-01

309

Inexpensive high vacuum feedthroughs.  

NASA Technical Reports Server (NTRS)

Description of the use of rigid coaxial cable in the construction of high vacuum coaxial and coaxial push-pull rotary motion feedthroughs. This type of feedthroughs is shown to be extremely cheap and simple to make and modify. It can be used for moderately high voltages and provides a continuous, well shielded, low-noise feedthrough cable in any desired configuration.

Gerber, S.; Post, D.

1973-01-01

310

Operating a vacuum system  

Microsoft Academic Search

This discussion of vacuum gas gathering systems refers to the operation of a gathering system below atmospheric pressure. Advantages include recovery of gas that would otherwise remain in the reservoir, increased GPM content of the gathered gas, harmlessness of leaks, possibility of installing lower-priced pipe, and ability to make temporary repair of leaks. Disadvantages include difficulty of detecting leaks, severe

Felts

1981-01-01

311

Vacuum System at IUAC  

NASA Astrophysics Data System (ADS)

Vacuum technology is an integral part of any accelerator system. At IUAC we have a 15UD PELLETRON, superconduting LINAC, Low Energy Ion beam Facility and a 1.7MV pelletron. Vacuum requirement in these accelerators is ~10-8 torr. Various types of Vacuum pump are used in different zones of the accelerators depending on load. Since the whole accelerator is quite long, distributed pumps are placed in different sections as per load. In ion sources displacement type pump viz turbo-pumps are usually used as the gas load is quite high. In other parts of the accelerator combination of getter and ion pumps are used. It is very much necessary to isolate different sections for maintenance purpose. Proper valves are used to isolate the sections and to avoid vacuum accidents proper interlock system is introduced. If air goes in some sections accidentally, valves will close automatically to protect other sections. The talk will cover different types of pumps and interlock used in accelerators at IUAC.

Mandal, A.

2012-11-01

312

VACUUM FLOW STEEL DEGASSING  

Microsoft Academic Search

A steel degassing technique developed and used by the Henrichschutte ; steel plant in Germany's Ehr is described. The process, reportedly capable of ; reduci Hâ, Nâ, and Oâ contents of all types of steels to those ; levels obtalned by vacuum casting techniques, require from 12 to 15 min in a 6O ; to 80-ton ladle. The metal i

Starratt

1958-01-01

313

HYDC Vacuum Circuit Breakers  

Microsoft Academic Search

The effectiveness of the commutation principle, using vacuum interrupters as a means for interrupting high direct current at high voltage, has been demonstrated convincingly by a large number of tests. Currents in excess of 15 kA at 20 kV have been interrupted by a single device in an inductive circuit. Tests are reported in which higher current were cleared by

A. N. Greenwood; P. Barkan; W. C. Kracht

1972-01-01

314

Vacuum ultraviolet holography  

NASA Technical Reports Server (NTRS)

The authors report the first demonstration of holographic techniques in the vacuum ultraviolet spectral region. Holograms were produced with coherent 1182 A radiation. The holograms were recorded in polymethyl methacrylate and read out with an electron microscope. A holographic grating with a fringe spacing of 836 A was produced and far-field Fraunhofer holograms of sub-micron particles were recorded.

Bjorklund, G. C.; Harris, S. E.; Young, J. F.

1974-01-01

315

Various unique vacuum holders  

SciTech Connect

Glassblowers use vacuum holding devices to support a flat plate in the glassflowing lathe to seal onto the end of, or inside of, a glass cylinder. Glassblowing blowhose swivels tend to leak; a rotating union from the hydraulics industry is better. Various graphite holder designs are described.

Gregar, J.S.

1992-12-01

316

Multiple Internal Seal Right Micro-electro-mechanical System Vacuum Package.  

National Technical Information Service (NTIS)

A Multiple Internal Seal Ring (MISR) Micro-Electro-Mechanical System (MEMS) vacuum package that hermetically seals MEMS devices using MISR. The method bonds a capping plate having metal seal rings to a base plate having metal seal rings by wafer bonding t...

A. D. Challoner C. S. Peay D. V. Wiberg K. J. Hayworth K. V. Shcheglov K. Y. Yee Y. Bae

2007-01-01

317

Predictive model for the carbon concentration profile of vacuum carburized steels with acetylene  

Microsoft Academic Search

A predictive model for the carbon concentration profile in vacuum carburized steels with acetylene was proposed. The model\\u000a involves the process and boundary conditions based on the characteristic of vacuum carburizing with acetylene and carbon diffusivity\\u000a with an alloying element effect. In order to verify the predictive model, the carbon concentration profile of a cylindrical\\u000a SCM415 steel specimen vacuum carburized

Minsu Jung; Sehoon Oh; Young-Kook Lee

2009-01-01

318

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

ERIC Educational Resources Information Center

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…

Greenslade, Thomas B., Jr.

1989-01-01

319

Recent progress in copper-based wafer bonding for 3-D ICs application  

Microsoft Academic Search

This article discusses thermo-compression bonding (also known as diffusion bonding) of metallic copper and its application in 3-D stacking of ICs. Bonding process is described and characterization results are presented. A survey on recent progress of copper-based wafer bonding, particularly low temperature process, and its application for on wafer 3-D ICs are presented.

Chuan Seng Tan

2008-01-01

320

Bonding Diamond To Metal In Electronic Circuits  

NASA Technical Reports Server (NTRS)

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.

Jacquez, Andrew E.

1993-01-01

321

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

Code of Federal Regulations, 2010 CFR

...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 §...

2009-07-01

322

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

Code of Federal Regulations, 2010 CFR

...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 §...

2010-07-01

323

Gas bearing operates in vacuum  

NASA Technical Reports Server (NTRS)

Bearing has restrictions to reduce air leaks and is connected to external pumpout facility which removes exhausted air. Token amount of air which is lost to vacuum is easily removed by conventional vacuum pump.

Perkins, G. S.

1975-01-01

324

Semipermanent sealing of leaks in high vacuum systems  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

325

A radiation hard vacuum switch  

DOEpatents

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.

Boettcher, G.E.

1988-07-19

326

Understand vacuum-system fundamentals  

Microsoft Academic Search

Crude vacuum unit heavy vacuum gas-oil (HVGO) yield is significantly impacted by ejector-system performance, especially at conditions below 20 mmHg absolute pressure. A deepcut vacuum unit, to reliably meet the yields, calls for proper design of all the major pieces of equipment. Ejector-system performance at deepcut vacuum column pressures may be independently or concurrently affected by: atmospheric column overflash, stripper

G. R. Martin; J. R. Lines; S. W. Golden

1994-01-01

327

Vacuum Packaging of MEMS With Multiple Internal Seal Rings  

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

328

Surge-damping vacuum valve  

DOEpatents

A valve having a mechanism for damping out flow surges in a vacuum system which utilizes a slotted spring-loaded disk positioned adjacent the valve's vacuum port. Under flow surge conditions, the differential pressure forces the disk into sealing engagement with the vacuum port, thereby restricting the flow path to the slots in the disk damping out the flow surge.

Bullock, Jack C. (Pleasanton, CA) [Pleasanton, CA; Kelly, Benjamin E. (Tracy, CA) [Tracy, CA

1980-01-01

329

Perfluoropolyethers as Vacuum Pump Fluids  

ERIC Educational Resources Information Center

Discusses the state of the art in the field of utilizing perfluoropolyethers in the creation of "clean" vacuums, when the term "clean" vacuum defines one that does not contain contaminates which interfere with the process to be carried out in the vacuum. (SL)

Laurenson, L.

1977-01-01

330

Portable vacuum object handling device  

DOEpatents

The disclosure relates to a portable device adapted to handle objects which are not to be touched by hand. A piston and bore wall form a vacuum chamber communicating with an adaptor sealably engageable with an object to be lifted. The piston is manually moved and set to establish vacuum. A valve is manually actuable to apply the vacuum to lift the object.

Anderson, G.H.

1981-07-30

331

Insertion device vacuum system designs  

SciTech Connect

Synchrotron light source insertion device vacuum systems now in operation and systems proposed for the future are reviewed. An overview of insertion devices is given and four generic vacuum chamber designs, transition section design and pumping considerations are discussed. Examples of vacuum chamber systems are presented.

Hoyer, E.

1988-05-01

332

RFQ Vacuum brazing at CERN  

Microsoft Academic Search

The aim of this paper is to describe the vacuum brazing procedure used at CERN for the brazing of Radio Frequency Quadrupole (RFQ). The RFQ is made of high precision machined OFE copper pieces assembled together. Vacuum brazing is one of the most promising techniques used to join the individual components leading to vacuum tightness and high precision alignment. The

S Mathot

2008-01-01

333

Bond strengths of two dental bonding systems.  

PubMed

A new bonding system named Kevloc has been introduced. It is based on acrylization of the metal surface with the goal of preventing the occurrence of a marginal gap between the metal and the resin. The purpose of this investigation was to determine the values of the shear bond strength achieved using the Kevloc technique on Ag-Pd (Auropal SE) and Co-Cr (Basil S) alloys and to compare them with those obtained with the OVS technique. The shear bond strengths were measured with the Smitz-Schulmayer shear test in a universal testing machine for polymer materials. A microscope image analyzer was used to measure the thickness of bonding layers and to reveal the possible occurrence of the marginal gap with both techniques. No marginal gap was detected with either technique. Kevloc provided better results than OVS only in a group of specimens tested after polymerization. Immersion in water and thermocycling reduced the initially high bond strength values of Kevloc specimens, whereas the bond strength values of OVS specimens remained unchanged regardless of which aging treatment was used. Microscopic examination did not reveal the existence of the marginal gap for either bonding system. According to the results obtained, it can be concluded that the Kevloc bonding system does not provide better shearing bond strength than the OVS bonding system. PMID:10920659

Vojvodic, D; Jerolimov, V; Zabarovic, D; Loncar, A

2000-07-01

334

Edison's vacuum technology patents  

NASA Astrophysics Data System (ADS)

During 1879 Thomas Edison's Menlo Park, New Jersey laboratory developed the means to evacuate glass lamp globes to less than a mTorr in 20 min and in mid-1880 began production of carbon-filament incandescent lamps. Among Edison's nearly 1100 U.S. patents are five for vacuum pump improvements, and at least eight others that are vacuum-related; all applied for between 1880 and 1886. Inspired by an 1878 article by De La Rue and Müller [Philos. Trans. R. Soc. London, Ser. A 169, 155 (1878)] on studies of glow discharges, Edison devised a combination pump using the Geissler pump as a rough pump and the Sprengel pump for continuous exhaustion. Edison's patents described means to control the mercury flow and automate the delivery of the mercury to banks of up to a hundred pumps. Other patents described various means to remove residual gases during lamp processing.

Waits, Robert K.

2003-07-01

335

Electrostatic Levitator Vacuum Chambers  

NASA Technical Reports Server (NTRS)

Optical prots ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (the beam passes through the window at left), poisitioning lasers (one port is at center), and lamps (such as the deuterium arc lamp at right), and to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

1998-01-01

336

Electrostatic Levitator Vacuum Chamber  

NASA Technical Reports Server (NTRS)

Optical prots ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (the beam passes through the window at left), poisitioning lasers (one port is at center), and lamps (arc lamp at right), and to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

1998-01-01

337

Integrated structure vacuum tube  

NASA Technical Reports Server (NTRS)

High efficiency, multi-dimensional thin film vacuum tubes suitable for use in high temperature, high radiation environments are described. The tubes are fabricated by placing thin film electrode members in selected arrays on facing interior wall surfaces of an alumina substrate envelope. Cathode members are formed using thin films of triple carbonate. The photoresist used in photolithography aids in activation of the cathodes by carbonizing and reacting with the reduced carbonates when heated in vacuum during forming. The finely powdered triple carbonate is mixed with the photoresist used to delineate the cathode locations in the conventional solid state photolithographic manner. Anode and grid members are formed using thin films of refractory metal. Electron flow in the tubes is between grid elements from cathode to anode as in a conventional three-dimensional tube.

Dimeff, J.; Kerwin, W. J. (inventors)

1976-01-01

338

Vacuum tool manipulator  

DOEpatents

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.

Zollinger, W.T.

1993-11-23

339

Vacuum tool manipulator  

DOEpatents

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.

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

1993-01-01

340

Compact vacuum insulation  

DOEpatents

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.

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

1993-01-05

341

Compact vacuum insulation embodiments  

DOEpatents

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.

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

1992-04-28

342

The MEA vacuum system  

NASA Astrophysics Data System (ADS)

The leak security system and multiple pump unit with turbomolecular pump of the MEA vacuum system, consisting of a klystron system with diode pump and a bunch-conducting system with triode pump, is described. The triode pump has better pump capacities for rare gases but as it only works from 0.0001 Torr the pump unit has to be used. To replace the klystrons the two systems are coupled by two windows with nitrogen in between for high frequencies. To safeguard the system, slow isolation valves with Pirami gages, fast valves with ionization gages, and residual gas analyzers are installed. Hand valves and residual gas analyzer heads are used for the pump unit. The vacuum level is better than 0.0000001 Torr.

Stroo, R.; Schwebeke, H.; Heine, E.

1984-12-01

343

Aspects of vacuum alignment  

NASA Astrophysics Data System (ADS)

In the presence of both spontaneous symmetry breaking and explicit symmetry breaking, the ground state of a system is determined by vacuum alignment. In this thesis I examine the consequences of vacuum alignment in models with many competing explicit symmetry breaking interactions. In particular, I investigate the appearance of unexpectedly massless pseudo-Goldstone bosons and their connection to second order phase transitions in the symmetry of the ground state. The foundation for this investigation is a model based on the spontaneous symmetry breaking pattern SU(3)L ? SU(3)R ? SU(3). One feature of this model, repeated phase transitions, motivates a new approach toward generating light states. In this approach, states are light because there are many nearby phase transitions rather than as a consequence of a symmetry. I test this new approach by applying repeated phase transitions to composite higgs models of electroweak symmetry breaking. This investigation not only elucidates the advantages and disadvantages of repeated phase transitions but it also provides a new path to a light composite higgs. A more familiar approach to a light composite higgs is the Little Higgs mechanism. This achieves a light higgs by protecting it with additional global symmetries. As a consequence of these additional symmetries, new TeV scale particles must be introduced which tend to cause conflicts with precise low energy experiments. Imposing a discrete symmetry known as T parity on these models not only removes many problematic processes but also creates a dark matter candidate. I construct a T parity invariant version of the Simplest Little Higgs model and find a cosmologically viable dark matter candidate. To demonstrate an application of vacuum alignment outside of electroweak symmetry breaking, I also examine the constraints from B meson mixings and decays on models of spontaneous CP violation in topcolor-assisted technicolor. In these models, CP is violated as a consequence of vacuum alignment in the technicolor sector, then communicated to the standard model fields through quark mass terms.

Martin, Adam O.

344

Vacuum Beat Wave Acceleration  

Microsoft Academic Search

The Vacuum Beat Wave Accelerator (VBWA) utilizes two laser beams with differing wavelengths to accelerate particles in vacuo.(Sprangle et al., Opt. Comm. 124), 69 (1996); Esarey et al., Phys. Rev. E 52, 5443 (1995). The mechanism relies on the v×B force, circumventing the so-called Lawson-Woodward theorem. A proof-of-principle experiment will be performed at the Naval Research Laboratory, based on design

C. I. Moore; B. Hafizi; E. Esarey; P. Sprangle; A. Ganguly; J. L. Hirshfield

1997-01-01

345

The covered bond market  

Microsoft Academic Search

The covered bond market offers investors an alternative to developed country government securities. The valuation of covered bonds is complex. While there is some evidence of differences in the pricing of these bonds by nationality of issuer, these appear to be only weakly related to differences in the respective legislative frameworks. Recent cases show the pricing of covered bonds to

Frank Packer; Ryan Stever; Christian Upper

2007-01-01

346

Wire Bond Temperature Sensor  

Microsoft Academic Search

This work reports the first demonstration of a bond pad test structure with embedded thermopile sensors for the measurement of the transient temperature response during the wire bonding operation. This paper will present the design and operation of the bond pad test structure and show and discuss temperature measurements during the wire bonding operation. The test structure can be used

Shivesh Suman; Michael Gaitan; Yogendra Joshi; George Harman

347

Vacuum application of thermal barrier plasma coatings  

NASA Technical Reports Server (NTRS)

Coatings are presently applied to Space Shuttle Main Engine (SSME) turbine blades for protection against the harsh environment realized in the engine during lift off-to-orbit. High performance nickel, chromium, aluminum, and yttrium (NiCrAlY) alloy coatings, which are applied by atmospheric plasma spraying, crack and spall off because of the severe thermal shock experienced during start-up and shut-down of the engine. Ceramic coatings of yttria stabilized zirconia (ZrO2-Y2O3) were applied initially as a thermal barrier over coating to the NiCrAlY but were removed because of even greater spalling. Utilizing a vacuum plasma spraying process, bond coatings of NiCrAlY were applied in a low pressure atmosphere of argon/helium, producing significantly improved coating-to-blade bonding. The improved coatings showed no spalling after 40 MSFC burner rig thermal shock cycles, cycling between 1700 and -423 F. The current atmospheric plasma NiCrAlY coatings spalled during 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2-Y2O3 to the turbine blades of first stage high-pressure fuel turbopumps utilizing the vacuum plasma process. The improved thermal barrier coating has successfully passed 40 burner rig thermal shock cycles without spalling. Hot firing in an SSME turbine engine is scheduled for the blades. Tooling was installed in preparation for vacuum plasma spray coating other SSME hardware, e.g., the titanium main fuel valve housing (MFVH) and the fuel turbopump nozzle/stator.

Holmes, R. R.; Mckechnie, T. N.

1988-01-01

348

The ITER vacuum systems  

NASA Astrophysics Data System (ADS)

ITER is a large vacuum facility which comprises many service, diagnostic and monitoring vacuum sub-systems as well as three large cryogenic pumping systems for evacuation and maintenance of the required pressure levels. Control of the gas throughput is one of the key issues affecting the performance and achievable burn time of a fusion reactor. The main pumping systems are the torus exhaust pumping, the cryopumps for the neutral beam injection systems for plasma heating, and the cryopumps for the ITER cryostat. All customized cryosorption pumps are force-cooled with supercritical helium and share a similar modular design of cryosorption pumping panels. For regeneration of the cryopumps as well as for roughing down the system volumes prior to operation, four identical sets of forepump trains are used. This paper will focus on the areas of the ITER vacuum systems which require customized developments and cannot rely on commercial solutions. The complex pumps have been tailored for the very specific applications and requirements at ITER, especially characterised by the need to be tritium compatible. An outline of the development path which was needed to come up with a sound design for the ITER cryopumps is given. The way of development is culminating in the manufacturing of 1:1 scale prototypes, which will be extensively tested in dedicated test facilities to ensure compatibility with all design requirements.

Day, C.; Murdoch, D.

2008-05-01

349

Vacuum: From Art to Exact Science.  

ERIC Educational Resources Information Center

Reviews the history of vacuum technology. Includes vacuum pump developments (mechanical, ion, and cyrogenic pumps), measurement techniques, the development of the American Vacuum Society, and electronics in vacuum technology. (JN)

Lafferty, James M.

1981-01-01

350

Savings Bonds Value Calculator  

NSDL National Science Digital Library

From the Federal Reserve Bank of New York, this site computes the redemption value of users's US savings bonds. Easy-to-use pull-down menus allow visitors to enter information such as the date of issue and face value of their Series E bonds, Series EE bonds, and Series S bonds. After entering the information, the Calculator will then show a chart of issue dates and denominations and actual worth of the bonds, if cashed within a set period of time.

351

Direct bonding and beyond  

Microsoft Academic Search

We present a number of recent evaluations of direct bonding, a glueless bonding technology, performed under ambient conditions. If combined with bond-strengthening, this geometry-conserving technology is well suited for an application in far ultraviolet immersion lithography. Our term beyond direct bonding refers to taking at least one additional technological step beyond direct bonding, involving chemical interface engineering, advanced silicon-on-insulator (SOI)

Jan Haisma; Nico Hattu; Esther Steding; Jan C. G. Vervest

2007-01-01

352

LET'S BOND! A Chemical Bonding Webquest  

NSDL National Science Digital Library

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 ...

Hicken, Mrs.

2009-04-08

353

Fluxless indium and silver-indium bonding processes for photonics and high-temperature electronics  

NASA Astrophysics Data System (ADS)

A fluxless oxidation-free bonding technology using multilayer composite solders based on indium, or low melting temperature indium. alloys such as Ag-In, In-Sn and Au-In has been developed and studied. This technology eliminates the need of flux and scrubbing motion that are used in conventional soldering processes, and still produces good quality joints. By depositing multilayer composite materials in high vacuum, we eliminate the formation of an oxide layer thus removing the origin of the problem---solder oxidation. To understand the oxidation kinetics in the bonding process, I have modeled the oxidation rate of tin, which follows a parabolic growth law. For completeness of the oxidation model, I incorporated the temperature dependency of Henry's coefficient in the oxidation model. To prevent the solder material from oxidation when exposing to atmosphere, I have developed a technique, which utilizes the in-situ formation of stable intermetallic compound on the outer surface, or a gold layer to protect the bonding materials. The bonding is achieved by means of solid-liquid interdiffusion (SLID) and in-situ compound formation. The first alloy system that I studied is indium-silver. GaAs and silicon dice have been successfully bonded on silicon or glass substrates. The bonding quality is examined by a Scanning Acoustic Microscope (SAM). The results confirm that void-free joints are achieved. Cross-sections of the joint are examined using a Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray (EDX) spectroscopy. The results reveal that the joint is composed of AuIn2, AgIn2-intermetallic compound and pure indium. From the Ag-In phase diagram, as indium composition is reduced to 25 wt. %, the solidus temperature jumps from 144 to above 695°C. By modifying the design of the multilayer composite, we developed a 210°C process to produce 700°C joints. All the well-bonded devices, before or after annealing, exceed the shear test force requirement of 2.5 kg. Indium has been a choice for bonding photonic devices such as laser diodes. A major concern is the change of solder composition during device operation caused by diffusion of copper atoms from the copper substrate. Copper atoms can easily diffuse into and react with the indium joint to form intermetallic compounds Cu2In, CuIn, Cu9In4, Cu11 In9. This reaction continues even after the bonding process is completed and the device is put in operation at some temperature. Consequently, the composition, the microstructure and physical properties of the joint change during the device life.To prevent the intermetallic formation, the solder joint must remain indium rich. A barrier metallization on the copper substrate is necessary to stop copper atoms from getting into the solder joint. Device packages usually need more than one soldering operation to complete. The indium-rich alloys have a 156°C melting temperature. During subsequent bonding operations, another process with a bonding temperature lower than 156°C is valuable. Desirable bonding temperature should be lower than 156°C but higher than the maximum temperature of the joint during device operation. In-Sn eutectic alloy with a melting temperature of 118°C is chosen. (Abstract shortened by UMI.)

So, William Wilson

354

Thermal behaviors of petn base polymer bonded explosives  

Microsoft Academic Search

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

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

2008-01-01

355

The solid state bonding of nickel to alumina  

Microsoft Academic Search

The paper describes the effect of sintering atmosphere (argon, hydrogen and vacuum), sintering temperatures (700 to 1300° C), sintering pressure (1\\/2 to 6 tsi [7.7 to 92.4 MN. m-2]) and sintering time (1\\/2 to 24 h) on the room temperature shear bond strength developed between nickel powder compacts and alumina single crystals: bond strengths of 3 to 11×103 psi (20.7

C. A. Calow; I. T. Porter

1971-01-01

356

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.

357

Vacuum MOCVD fabrication of high efficience cells  

NASA Technical Reports Server (NTRS)

Vacuum metal-organic-chemical-vapor-deposition (MOCVD) is a new fabrication process with improved safety and easier scalability due to its metal rather than glass construction and its uniform multiport gas injection system. It uses source materials more efficiently than other methods because the vacuum molecular flow conditions allow the high sticking coefficient reactants to reach the substrates as undeflected molecular beams and the hot chamber walls cause the low sticking coefficient reactants to bounce off the walls and interact with the substrates many times. This high source utilization reduces the materials costs power device and substantially decreases the amounts of toxic materials that must be handled as process effluents. The molecular beams allow precise growth control. With improved source purifications, vacuum MOCVD has provided p GaAs layers with 10-micron minority carrier diffusion lengths and GaAs and GaAsSb solar cells with 20% AMO efficiencies at 59X and 99X sunlight concentration ratios. Mechanical stacking has been identified as the quickest, most direct and logical path to stacked multiple-junction solar cells that perform better than the best single-junction devices. The mechanical stack is configured for immediate use in solar arrays and allows interconnections that improve the system end-of-life performance in space.

Partain, L. D.; Fraas, L. M.; Mcleod, P. S.; Cape, J. A.

1985-01-01

358

Bonded ultrasonic transducer and method for making  

DOEpatents

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.

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

1995-01-01

359

Hydroxide-catalyzed bonding  

NASA Technical Reports Server (NTRS)

A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.

Gwo, Dz-Hung (Inventor)

2003-01-01

360

Modelling the transient liquid phase bonding behaviour of a duplex stainless steel using copper interlayers  

Microsoft Academic Search

Analytical models for isothermal solidification and homogenisation stages were applied to the TLP bonding of a duplex stainless steel using copper interlayers to estimate the time for completion of these stages and compare them with experimental results. Diffusivities of copper in iron representing different diffusion mechanisms (lattice diffusion, grain boundary diffusion, and contribution of both) were considered. Good agreement between

T. Padron; T. I. Khan; M. J. Kabir

2004-01-01

361

Sealing of adhesive bonded devices on wafer level  

Microsoft Academic Search

In this paper, we present a low temperature wafer-level encapsulation technique to hermetically seal adhesive bonded microsystem structures by cladding the adhesive with an additional diffusion barrier. Two wafers containing cavities for MEMS devices were bonded together using benzocyclobutene (BCB). The devices were sealed by a combined dicing and self-aligning etching technique and by finally coating the structures with evaporated

Joachim Oberhammer; Frank Niklaus; Göran Stemme

2004-01-01

362

Supramolecular hydrogen-bonding assembly of silanediols with bifunctional heterocycles.  

PubMed

X-ray crystallography showcases the distinct self-association and hydrogen-bonding patterns of organic silanediols, R2Si(OH)2, with bifunctional heterocycles for supramolecular assembly. Diffusion-ordered spectroscopy (DOSY) studies identify the dominant hydrogen-bonding patterns and structures in solution, which correlate with solid-state patterns at high concentrations. PMID:24577634

Tran, Ngon T; Wilson, Sean O; Franz, Annaliese K

2014-04-11

363

Bonding soft rubber or plasticized elastomers to metal  

NASA Technical Reports Server (NTRS)

Approach using bond-cover coat of unplasticized rubber between soft rubber and adhesive eliminates diffusion problem. Approach is useful in making improved seals in automobile engines, industrial and public plumbing, and in other areas using soft-rubber-to-metal bonds. Seals and gaskets made this way would not have to be replaced very often, reducing cost of maintenance.

Clemons, J. M.; Ledbetter, F. E., III; White, W. T.

1980-01-01

364

Avoiding Death by Vacuum  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

365

Flash vacuum pyrolysis of lignin model compounds  

SciTech Connect

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.

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

1997-03-01

366

The Bond Market Association  

NSDL National Science Digital Library

The Bond Market Association "represents securities firms and banks that underwrite, trade and sell debt securities." Their web site is divided into several sections. The Research Desk presents the results of research conducted by the association, including forecasts of economic growth and analysis of bond market trends. The Legislative Issues and Regulatory sections provide a summary of legislative and regulatory developments of interest to the bond market community. Market Practices contains guidelines and procedures to be followed in the bond market. The site also provides information to investors on how to invest in corporate bonds, tax-exempt municipal bonds, and mortgage securities.

1998-01-01

367

R&D ERL: Vacuum  

SciTech Connect

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.

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

2010-01-01

368

Effect of surface oxide layers on deuterium permeation through stainless steels with reference to outgassing reduction in ultra- to extremely high vacuum  

Microsoft Academic Search

Hydrogen is a dominant outgassing species from stainless steel vacuum chambers in ultra- to extremely high vacuum. Oxidation of stainless steel surfaces has been known to reduce the outgassing. The oxide layer formed on the stainless steel surface is expected to serve as a diffusion barrier for hydrogen diffusing from the bulk. In the present study the effects of oxidation

Yuichi Ishikawa; Toshihiko Yoshimura; Masatsugu Arai

1996-01-01

369

Vacuum-plasma-sprayed silicon coatings for biomedical application  

Microsoft Academic Search

Silicon coating was deposited on titanium alloy substrates by vacuum plasma spraying technology. The morphologies and phase composition of the coatings were analyzed by field-emission scanning electron microscopy and X-ray diffraction. The thermal expansion coefficient of silicon coating was measured to be about 3.70×10?6 K?1. The bond strength of coating was approximately 20.6 MPa. The density, open porosity, roughness and Young's

Yaran Niu; Xuanyong Liu; Chuanxian Ding

2008-01-01

370

Vacuum plasma spray applications on liquid fuel rocket engines  

NASA Technical Reports Server (NTRS)

The vacuum plasma spray process (VPS) has been developed by NASA and Rocketdyne for a variety of applications on liquid fuel rocket engines, including the Space Shuttle Main Engine. These applications encompass thermal barrier coatings which are thermal shock resistant for turbopump blades and nozzles; bond coatings for cryogenic titanium components; wear resistant coatings and materials; high conductivity copper, NaRloy-Z, combustion chamber liners, and structural nickel base material, Inconel 718, for nozzle and combustion chamber support jackets.

Mckechnie, T. N.; Zimmerman, F. R.; Bryant, M. A.

1992-01-01

371

Vacuum plasma spray applications on liquid fuel rocket engines  

NASA Astrophysics Data System (ADS)

The vacuum plasma spray process (VPS) has been developed by NASA and Rocketdyne for a variety of applications on liquid fuel rocket engines, including the Space Shuttle Main Engine. These applications encompass thermal barrier coatings which are thermal shock resistant for turbopump blades and nozzles; bond coatings for cryogenic titanium components; wear resistant coatings and materials; high conductivity copper, NaRloy-Z, combustion chamber liners, and structural nickel base material, Inconel 718, for nozzle and combustion chamber support jackets.

McKechnie, T. N.; Zimmerman, F. R.; Bryant, M. A.

1992-07-01

372

[Indirect bonding technics].  

PubMed

The indirect bonding technique is pivotal for success in lingual orthodontics. There are different laboratory techniques available for indirect positioning and bonding of lingual brackets. Different approaches are presented and described to perform a clinical application. PMID:19552882

Sorel, Olivier; Mehdi, Sarah; Mano, Marie-Charlotte

2009-06-01

373

Direct bonding and beyond  

NASA Astrophysics Data System (ADS)

We present a number of recent evaluations of direct bonding, a glueless bonding technology, performed under ambient conditions. If combined with bond-strengthening, this geometry-conserving technology is well suited for an application in far ultraviolet immersion lithography. Our term beyond direct bonding refers to taking at least one additional technological step beyond direct bonding, involving chemical interface engineering, advanced silicon-on-insulator (SOI) technology, whereby the unwanted influence of dilatation mismatch is obviated. The combination of successive direct bonding, nanopillar lattice structures and silicon-technological engineering makes it possible for us to arrange quantum dots, wires, and planes in a transversal cascade. We also address the interrelationship between direct bonding and elasticity, as well as plasticity; the latter is in relation to direct bonded glass wafers that are thermally treated to create the geometric shape, e.g., required for specific lab-on-a-chip components with a three-dimensional overall configuration.

Haisma, Jan; Hattu, Nico; (Dook) Pulles, J. T. C. M.; Steding, Esther; Vervest, Jan C. G.

2007-09-01

374

Solid-State Bonding of Molybdenum and TZM.  

National Technical Information Service (NTIS)

Solid-state bonding of reactive metals requires a suitable welding plant with oil-free high-vacuum, graphite-free pressure rams and reproducible conditions of heat and pressure application. For the joining of molybdenum and TZM without the use of interlay...

G. Haufler H. G. Mayer

1978-01-01

375

Braze alloy holds bonding strength over wide temperature range  

NASA Technical Reports Server (NTRS)

Copper-based quaternary alloys of the solid solution type is used for vacuum furnace brazing of large stainless steel components at a maximum temperature of 1975 deg F. The alloy has high bonding strength and good ductility over a temperature range extending from the cryogenic region to approximately 800 deg F.

1966-01-01

376

Diffusion of highly charged cations in olivine  

NASA Astrophysics Data System (ADS)

Diffusion of tungsten, titanium and phosphorus have been measured in natural iron-bearing olivine (~Fo90) and synthetic forsterite. Experiments were run under buffered conditions (with iron-wustite or Ni-NiO buffers) in 1-atm furnaces. The sources of diffusant for experiments were MgWO4 for tungsten diffusion, Mg2TiO4 for Ti diffusion, and AlPO4 for P diffusion; in all cases these compounds were pre-reacted at high temperature with Mg2SiO4 or Fe-bearing olivine prior to diffusion anneals. Samples were placed with the source materials in noble metal or silica capsules, which were sealed under vacuum in silica glass ampoules with solid buffers. Rutherford backscattering spectrometry (RBS) was used to measure depth profiles for all sets of experiments; measurements of P were also made with Nuclear Reaction Analysis using the 31P(?,p)34S reaction. These new data suggest marked differences among diffusivities of these cations, with titanium diffusion faster than diffusion of tungsten, but slower than diffusion of phosphorus over the conditions investigated. Diffusivities of all of these elements appear significantly slower than those of divalent cations in olivine. These results will be discussed in context with extant diffusion data for major, trace and minor elements in olivine. The effects of oxygen fugacity and olivine composition on diffusion, and potential implications for diffusion mechanisms will also be considered.

Cherniak, D. J.; Watson, E. B.; Liang, Y.

2012-12-01

377

Cosmology with a decaying vacuum  

NASA Astrophysics Data System (ADS)

Properties of unstable false vacuum states are analyzed from the point of view of the quantum theory of unstable states. Some of false vacuum states survive up to times when their survival probability has a non-exponential form. At times much latter than the transition time, when contributions to the survival probability of its exponential and non-exponential parts are comparable, the survival probability as a function of time t has an inverse power-like form. We show that at this time region the instantaneous energy of the false vacuum states tends to the energy of the true vacuum state as 1/t2 for t --> ?.

Urbanowski, K.; Szyd?owski, M.

2013-02-01

378

Low partial discharge vacuum feedthrough  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

379

Vacuum leak detector and method  

DOEpatents

Apparatus and method for detecting leakage in a vacuum system involves a moisture trap chamber connected to the vacuum system and to a pressure gauge. Moisture in the trap chamber is captured by freezing or by a moisture adsorbent to reduce the residual water vapor pressure therein to a negligible amount. The pressure gauge is then read to determine whether the vacuum system is leaky. By directing a stream of carbon dioxide or helium at potentially leaky parts of the vacuum system, the apparatus can be used with supplemental means to locate leaks.

Edwards, Jr., David (7 Brown's La., Bellport, NY 11713)

1983-01-01

380

Covalent and Ionic Bonds  

NSDL National Science Digital Library

Atoms can attain a more stable arrangement of electrons in their outermost shell by interacting with one another. An ionic bond is formed when electrons are transferred from one atom to the other. A covalent bond is formed when electrons are shared between atoms. The two cases shown represent extremes; often, covalent bonds form with a partial transfer (unequal sharing of electrons), resulting in a polar covalent bond

BEGIN:VCARD VERSION:2.1 FN:Bruce Alberts N:Alberts;Bruce REV:2005-04-16 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Dennis Bray N:Bray;Dennis REV:2005-04-16 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Alexander Johnson N:Johnson;Alexander REV:2005-04-16 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Julian Lewis N:Lewis;Julian REV:2005-04-16 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Martin Raff N:Raff;Martin REV:2005-04-16 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Keith Roberts N:Roberts;Keith REV:2005-04-16 END:VCARD

1998-07-01

381

Allosteric Disulfide Bonds  

Microsoft Academic Search

\\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

Jason W. H. Wong; Philip J. Hogg

382

Solid state bonding of Zircaloy-2 with stainless steel  

NASA Astrophysics Data System (ADS)

Zircaloy-2 and stainless steel have been diffusion bonded together with titanium and iron as barriers. Electron microprobe and optical microscopy studies reveal that no intermetallic compound/intermediate phase forms at the interfaces involved. Layer growth kinetics of diffusion zones have also been studied and the absence of these intermediate phases have been discussed with respect to their nucleation and growth parameters.

Kale, G. B.; Bhanumurthy, K.; Ratnakala, K. C.; Khera, S. K.

1986-03-01

383

Rapid adhesive bonding concepts  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

384

Acrylic mechanical bond tests  

SciTech Connect

The tensile strength of bonded acrylic is tested as a function of bond joint thickness. 0.125 in. thick bond joints were found to posses the maximum strength while the acceptable range of joints varied from 0.063 in. to almost 0.25 in. Such joints are used in the Sudbury Neutrino Observatory.

Wouters, J.M.; Doe, P.J.

1991-02-01

385

A large high vacuum, high pumping speed space simulation chamber for electric propulsion  

NASA Technical Reports Server (NTRS)

Testing high power electric propulsion devices poses unique requirements on space simulation facilities. Very high pumping speeds are required to maintain high vacuum levels while handling large volumes of exhaust products. These pumping speeds are significantly higher than those available in most existing vacuum facilities. There is also a requirement for relatively large vacuum chamber dimensions to minimize facility wall/thruster plume interactions and to accommodate far field plume diagnostic measurements. A 4.57 m (15 ft) diameter by 19.2 m (63 ft) long vacuum chamber at NASA Lewis Research Center is described. The chamber utilizes oil diffusion pumps in combination with cryopanels to achieve high vacuum pumping speeds at high vacuum levels. The facility is computer controlled for all phases of operation from start-up, through testing, to shutdown. The computer control system increases the utilization of the facility and reduces the manpower requirements needed for facility operations.

Grisnik, Stanley P.; Parkes, James E.

1994-01-01

386

Control Dewar Secondary Vacuum Container  

SciTech Connect

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.

Rucinski, R.; /Fermilab

1993-10-04

387

Vacuum thermal insulation panel  

SciTech Connect

A vacuum thermal insulation panel comprises a pair of laminated plastic and aluminum sheets together with a plastic edge strip sealed to the edges of the sheets so as to define an evacuable volume in which a glass fiber mat is disposed. The insulation panel of the present invention takes advantage of the light-weight, low cost and low thermal conductivity of plastic materials to form an evacuable volume into which a glass fiber insulating mat is disposed for support of the panel which is evacuated to provide improved thermal insulation. Additionally, a gas permeation barrier is employed on the edge strip of the panel to minimize gas permeation at its edges. A metal foil layer provides gas permeation protection through the large surface areas of the sheets themselves.

Young, J.R.; Schreck, R.M.

1984-04-24

388

Pseudoredundant vacuum energy  

SciTech Connect

We discuss models that can account for today's dark energy. The underlying cosmological constant may be Planck scale but starts as a redundant coupling which can be eliminated by a field redefinition. The observed vacuum energy arises when the redundancy is explicitly broken, say by a nonminimal coupling to curvature. We give a recipe for constructing models, including R+1/R-type models, that realize this mechanism and satisfy all solar system constraints on gravity. A similar model, based on Gauss-Bonnet gravity, provides a technically natural explanation for dark energy and exhibits an interesting seesaw behavior: a large underlying cosmological constant gives rise to both low- and high-curvature solutions. Such models could be statistically favored in the string landscape.

Batra, Puneet; Hinterbichler, Kurt; Hui, Lam; Kabat, Daniel [Institute for Strings, Cosmology and Astroparticle Physics and Department of Physics, Columbia University, New York, New York 10027 (United States)

2008-08-15

389

Vacuum Powder Injector  

NASA Technical Reports Server (NTRS)

Method developed to provide uniform impregnation of bundles of carbon-fiber tow with low-solubility, high-melt-flow polymer powder materials to produce composite prepregs. Vacuum powder injector expands bundle of fiber tow, applies polymer to it, then compresses bundle to hold powder. System provides for control of amount of polymer on bundle. Crystallinity of polymer maintained by controlled melt on takeup system. All powder entrapped, and most collected for reuse. Process provides inexpensive and efficient method for making composite materials. Allows for coating of any bundle of fine fibers with powders. Shows high potential for making prepregs of improved materials and for preparation of high-temperature, high-modulus, reinforced thermoplastics.

Working, Dennis C.

1991-01-01

390

LIGO vacuum system study  

NASA Technical Reports Server (NTRS)

A laser interferometer gravitational wave observatory (LIGO) is being developed with sensitivities which will have a high probability of detecting gravitational waves from astrophysical sources. A major component of LIGO is a total of 16 km of 1.2 m (48 inch) diameter tube at a pressure of less than 10 to the minus 8th power torr. It will be of 304L stainless steel procured directly from the steel mills with the initial hydrogen content specially reduced. Projections of the outgassing rates of hydrogen and of water vapor as a function of time are given and the uncertainties discussed. Based on these, a preliminary analysis of the vacuum system is presented.

Livas, Jeffrey C.; Moore, Boude C.

1988-01-01

391

Particle bonding, annealing response, and mechanical properties of dynamically consolidated type 304 stainless steel powders  

Microsoft Academic Search

The nature of interparticle bonding in explosively consolidated, centrifugally atomized (CA), and vacuum gas-atomized (VGA) Type 304 stainless steel powders has been examined. Stress waves with sufficient amplitude to produce full density do not necessarily produce metallurgical bonds between particles; the local strain and strain rate are found to determine the degree of local heating and, in turn, the degree

R. N. Wright; G. E. Korth; J. E. Flinn

1989-01-01

392

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

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

393

Explosive bonding and its application in the Advanced Photon Source front-end and beamline components design  

NASA Astrophysics Data System (ADS)

Explosive bonding is a bonding method in which the controlled energy of a detonating explosive is used to create a metallurgical bonding between two or more similar or dissimilar materials. Since 1991, a number of explosive-bonding joints have been designed for high-thermal-load ultrahigh-vacuum (UHV) compatible components in the Advanced Photon Source. A series of standardized explosive bonded joint units has also been designed and tested, such as: oxygen-free copper (OFHC) to stainless-steel vacuum joints for slits and shutters, GlidCop to stainless-steel vacuum joints for fixed masks, and GlidCop to OFHC thermal and mechanical joints for shutter face-plates, etc. The design and test results for the explosive bonding units to be used in the Advanced Photon Source front ends and beamlines will be discussed in this paper.

Shu, D.; Li, Y.; Ryding, D.; Kuzay, T. M.; Brasher, D.

1994-07-01

394

Explosive bonding and its application in the Advanced Photon Source front-end and beamline components design  

SciTech Connect

Explosive bonding is a bonding method in which the controlled energy of a detonating explosive is used to create a metallurgical bonding between two or more similar or dissimilar materials. Since 1991, a number of explosive-bonding joints have been designed for high-thermal-load ultrahigh-vacuum (UHV) compatible components in the Advanced Photon Source. A series of standardized explosive bonded joint units has also been designed and tested, such as: oxygen-free copper (OFHC) to stainless-steel vacuum joints for slits and shutters, GlidCop to stainless-steel vacuum joints for fixed masks, and GlidCop to OFHC thermal and mechanical joints for shutter face-plates, etc. The design and test results for the explosive bonding units to be used in the Advanced Photon Source front ends and beamlines will be discussed in this paper.

Shu, D.; Li, Y.; Ryding, D.; Kuzay, T.M. [Argonne National Lab., IL (United States). Experimental Facilities Div.; Brasher, D. [Northwest Technical Industries, Inc., Sequim, WA (United States)

1994-12-01

395

Hydroxide catalysis bonding for astronomical instruments  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

396

Chemical Bonding, Interfaces and Defects in Hafnium Oxide/Germanium Oxynitride Gate Stacks on Ge (100)  

SciTech Connect

Correlations among interface properties and chemical bonding characteristics in HfO{sub 2}/GeO{sub x}N{sub y}/Ge MIS stacks were investigated using in-situ remote nitridation of the Ge (100) surface prior to HfO{sub 2} atomic layer deposition (ALD). Ultra thin ({approx}1.1 nm), thermally stable and aqueous etch-resistant GeO{sub x}N{sub y} interfaces layers that exhibited Ge core level photoelectron spectra (PES) similar to stoichiometric Ge{sub 3}N{sub 4} were synthesized. To evaluate GeO{sub x}N{sub y}/Ge interface defects, the density of interface states (D{sub it}) was extracted by the conductance method across the band gap. Forming gas annealed (FGA) samples exhibited substantially lower D{sub it} ({approx} 1 x 10{sup 12} cm{sup -2} eV{sup -1}) than did high vacuum annealed (HVA) and inert gas anneal (IGA) samples ({approx} 1x 10{sup 13} cm{sup -2} eV{sup -1}). Germanium core level photoelectron spectra from similar FGA-treated samples detected out-diffusion of germanium oxide to the HfO{sub 2} film surface and apparent modification of chemical bonding at the GeO{sub x}N{sub y}/Ge interface, which is related to the reduced D{sub it}.

Oshima, Yasuhiro; /Stanford U., Materials Sci. Dept.; Sun, Yun; /SLAC, SSRL; Kuzum, Duygu; /Stanford U.; Sugawara, Takuya; Saraswat, Krishna C.; Pianetta, Piero; /SLAC, SSRL; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.

2008-10-31

397

Chemical Reactions and Mechanical Properties of the Directly Bonded Ge-Si Interface  

NASA Astrophysics Data System (ADS)

In this study, chemical reactions and mechanical properties of directly bonded Ge-Si interfaces are investigated. The Ge-Si bonded interface has been systematically characterized as a function of the thermal budget (200 °C and 300 °C), which demonstrated that the formation of a thin GeO2 cap layer by radical pre-treatment can reduce the generation rate of voids at the bonded interface significantly. Patterning of one of the wafers prior to bonding can help to achieve high bonding quality thanks to enhanced out-diffusion of reaction by-products and stress reduction at the bonded interface. Both numerical modeling and structural analysis show that the presence of diffusion path (channels) at the bonded interfaces result in a maximum bond strength and minimum stress at the bonded interface.

Byun, Ki Yeol; Ferain, Isabelle; Yu, Ran; Colinge, Cindy

2011-12-01

398

Vacuum Plasma Sprayed titanium- manganese electrode layers for MnO 2 deposition  

Microsoft Academic Search

Vacuum-plasma-sprayed titanium-manganese alloy electrode layers are intended to improve the economy and efficiency of the\\u000a synthesis of electrolytic manganese dioxide, which is commercially used as cathodic material in primary batteries. Titanium\\u000a anodes with a high content of manganese offer high electrochemical activity and corrosion resistance, but poor mechanical\\u000a stability. Therefore, dense and well-bonded coatings of this brittle alloy were vacuum

H. D. Steffens; M. Brune

1995-01-01

399

Vacuum Enhanced Cutaneous Biopsy Instrument  

SciTech Connect

A syringe-like disposable cutaneous biopsy instrument equipped with a tubular blade at its lower end, and designed so that a vacuum is created during use, said vacuum serving to retain undeformed a plug of tissue cut from a patient's skin.

Collins, Joseph

1999-06-25

400

Vacuum barrier for excimer lasers  

Microsoft Academic Search

This patent describes a vacuum barrier for separating a region of vacuum from a pressurized gaseous region in an excimer laser. It comprises a first thin layer of metal having a thickness in the range of 2000-4000 Angstroms; a first thin layer of polyimide having a thickness of approximately 1 mil overlying the first thin layer of metal; a second

Shuter

1992-01-01

401

Vacuum pyrolysis of sugarcane bagasse  

Microsoft Academic Search

The objective of this study was to provide background data on sugarcane bagasse vacuum pyrolysis. Product yields and properties were investigated. Vacuum pyrolysis tests were performed at bench and pilot plant scales. The bagasse finest particles with a diameter smaller than 450 ?m were removed in order to overcome difficulties caused by their low density and high ash content. In

Abdelkader Chaala; Christian Roy

2002-01-01

402

Purifying Aluminum by Vacuum Distillation  

NASA Technical Reports Server (NTRS)

Proposed method for purifying aluminum employs one-step vacuum distillation. Raw material for process impure aluminum produced in electrolysis of aluminum ore. Impure metal melted in vacuum. Since aluminum has much higher vapor pressure than other constituents, boils off and condenses on nearby cold surfaces in proportions much greater than those of other constituents.

Du Fresne, E. R.

1985-01-01

403

Vacuum outgassing of various materials  

Microsoft Academic Search

A gas analytical system for measuring the evolved gases from materials during vacuum degassing is discussed. The outgassing data are based upon the throughput measurement and a computer-controlled quadrupole mass spectrometer allows the determination of residual gas species. A variety of materials have been tested in the ''as-received'' condition at room temperature vacuum exposure. Test results are presented for materials

E. D. Erikson; T. G. Beat; D. D. Berger; B. A. Frazier

1984-01-01

404

Vacuum outgassing of various materials  

Microsoft Academic Search

A gas analytical system for measuring the evolved gases from materials during vacuum degassing is discussed. The outgassing data are based upon the throughput measurement and a computer-controlled quadrupole mass spectrometer allows the determination of residual gas species. A variety of materials have been tested in the as received condition at room-temperature vacuum exposure. Test results are presented for some

E. D. Erikson; T. G. Beat; D. D. Berger; B. A. Frazier

1983-01-01

405

Vacuum outgassing of various materials  

Microsoft Academic Search

A gas analytical system for measuring the evolved gases from materials during vacuum degassing is discussed. The outgassing data are based upon the throughput measurement and a computer-controlled quadrupole mass spectrometer allows the determination of residual gas species. A variety of materials have been tested in the as received condition at room temperature vacuum exposure. Test results are presented for

E. D. Erikson; T. G. Beat; D. D. Berger; B. A. Frazier

1983-01-01

406

Vacuum enhanced cutaneous biopsy instrument  

DOEpatents

A syringe-like disposable cutaneous biopsy instrument equipped with a tubular blade at its lower end, and designed so that a vacuum is created during use, said vacuum serving to retain undeformed a plug of tissue cut from a patient's skin.

Collins, Joseph (St. Petersburg, FL)

2000-01-01

407

Vacuum Gas Tungsten Arc Welding  

NASA Technical Reports Server (NTRS)

A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

Weeks, J. L.; Todd, D. T.; Wooten, J. R.

1997-01-01

408

Vacuum carburizing—process optimization  

Microsoft Academic Search

An increased interest in vacuum carburizing concept is being observed in the last years all around the world as a result of the progress in designing of modern furnaces for thermo-chemical treatment under low pressure and of better knowledge of physico-chemistry of these processes. This in turn allows a precise control with aid of computer simulations. The vacuum carburizing simulation

P. Kula; R. Pietrasik; K. Dybowski

2005-01-01

409

Vacuum flash evaporated polymer composites  

DOEpatents

A method for fabrication of polymer composite layers in a vacuum is disclosed. More specifically, the method of dissolving salts in a monomer solution, vacuum flash evaporating the solution, condensing the flash evaporated solution as a liquid film, and forming the condensed liquid film into a polymer composite layer on a substrate is disclosed.

Affinito, J.D.; Gross, M.E.

1997-10-28

410

The AGS Booster vacuum systems  

SciTech Connect

The AGS Booster is a synchrotron for the acceleration of both protons and heavy ions. The design pressure of low 10{sup {minus}11} mbar is required to minimize beam loss of the partially stripped heavy ions. To remove contaminants and to reduce outgassing, the vacuum chambers and the components located in them will be chemically cleaned, vacuum fired, baked then treated with nitric oxide. The vacuum sector will be insitu baked to a minimum of 200{degree}C and pumped by the combination of sputter ion pumps and titanium sublimation pumps. This paper describes the design and the processing of this ultra high vacuum system, and the performance of some half-cell vacuum chambers. 9 refs., 7 figs.

Hseuh, H.C.

1989-01-01

411

Bonded multilayer Laue Lens for focusing hard x-rays.  

SciTech Connect

We have fabricated partial Multilayer Laue Lens (MLL) linear zone plate structures with thousands of alternating WSi{sub 2} and Si layers and various outermost zone widths according to the Fresnel zone plate formula. Using partial MLL structures, we were able to focus hard X-rays to line foci with a width of 30 nm and below. Here, we describe challenges and approaches used to bond these multilayers to achieve line and point focusing. Bonding was done by coating two multilayers with AuSn and heating in a vacuum oven at 280-300 C. X-ray reflectivity measurements confirmed that there was no change in the multilayers after heating to 350 C. A bonded MLL was polished to a 5-25 {micro}m wedge without cracking. SEM image analyses found well-positioned multilayers after bonding. These results demonstrate the feasibility of a bonded full MLL for focusing hard X-rays.

Liu, C.; Conley, R.; Qian, J.; Kewish, C.M.; Macrander, A.T.; Maser, J.; Kang, H.C.; Yan, H.; Stephenson, G.B.; Advanced Photonics Research Institute; Gwangju Institute of Science and Technology

2007-11-11

412

Nickel nanoparticles-assisted diffusion brazing of stainless steel 316 for microfluidic applications  

Microsoft Academic Search

Transient liquid-phase diffusion brazing is used in precision, hermetic joining applications as a replacement for diffusion bonding to reduce cycle times, reduce bonding pressure and improve yields. Studies showed that the interlayer used in diffusion brazing can be detrimental due to the use of melting point depressants (MPDs). The goal of this study was to investigate the role of nanoparticles

Santosh K. Tiwari

2010-01-01

413

Multi-cavity vacuum electron beam device for operating at terahertz frequencies  

US Patent & Trademark Office Database

The present invention relates to the formation of a vacuum electronics circuit by the fusion bonding of multiple substrate wafers, e.g., silicon, copper, or other suitable conductive material, each etched using DRIE, cut using EDM, or machined by other suitable means. Other aspects of the invention relate to the alignment of a cathode with tube by fusion bonding the cathode wafer to a tube built using the fabrication methods described herein. Yet other aspects involve the alignment of dies or wafers during the fabrication of a vacuum electronics device using the "lego" technique outlined herein. In yet other aspects, fabrication methods are described.

2013-05-14

414

Weak bond screening system  

NASA Astrophysics Data System (ADS)

Consideration is given to the development of a weak bond screening system which is based on the utilization of a high power ultrasonic (HPU) technique. The instrumentation of the prototype bond strength screening system is described, and the adhesively bonded specimens used in the system developmental effort are detailed. Test results obtained from these specimens are presented in terms of bond strength and level of high power ultrasound irradiation. The following observations were made: (1) for Al/Al specimens, 2.6 sec of HPU irradiation will screen weak bond conditions due to improper preparation of bonding surfaces; (2) for composite/composite specimens, 2.0 sec of HPU irradiation will disrupt weak bonds due to under-cured conditions; (3) for Al honeycomb core with composite skin structure, 3.5 sec of HPU irradiation will disrupt weak bonds due to bad adhesive or oils contamination of bonding surfaces; and (4) for Nomex honeycomb with Al skin structure, 1.3 sec of HPU irradiation will disrupt weak bonds due to bad adhesive.

Chuang, S. Y.; Chang, F. H.; Bell, J. R.

415

Ti Diffusion in Pyroxene  

NASA Astrophysics Data System (ADS)

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

Cherniak, D.; Liang, Y.

2008-12-01

416

Partial Transient Liquid-Phase Bonding, Part I: A Novel Selection Procedure for Determining Ideal Interlayer Combinations, Validated Against Al2O3 PTLP Bonding Experience  

NASA Astrophysics Data System (ADS)

Partial transient liquid-phase (PTLP) bonding is a bonding process that can bond hard-to-join materials, such as ceramics. The process uses a multi-layer interlayer composed of a thick refractory core and thin diffusant layers on each side. Upon heating, the diffusant material melts, and diffusion occurs until the liquid isothermally solidifies. Selecting interlayer materials is a key problem in producing strong, reliable PTLP bonds; materials are usually selected empirically or system by system. This article presents a novel selection procedure that provides a generalized, comprehensive, first-principles-based approach. Components of the selection procedure are linked directly to key characteristics of PTLP bonding. A filtering routine that provides structure for the selection procedure is summarized in this article and detailed in a companion article. Specific capabilities of the routine, such as non-symmetric bonds, add to its effectiveness in identifying additional PTLP bond candidates. By way of example, output from the selection procedure, in conjunction with sessile drop data, is used to analyze all Al2O3 PTLP bonds in the current literature. All analyzed bonds are included in various outputs from the selection procedure, validating its comprehensiveness. Also, Al2O3 PTLP bonds are analyzed as a whole, leading to the identification of important trends that result in increased bond strength. Finally, additional interlayer combinations for PTLP bonding of Al2O3 are presented based on output from the selection procedure and existing sessile drop data.

Cook, Grant O.; Sorensen, Carl D.

2013-12-01

417

Vacuum Packaging for Microelectromechanical Systems (MEMS).  

National Technical Information Service (NTIS)

The Vacuum Packaging for MEMS Program focused on the development of an integrated set of packaging technologies which in totality provide a low cost, high volume product-neutral vacuum packaging capability which addresses all MEMS vacuum packaging require...

T. Schimert R. Howe M. Schmidt S. Montague

2002-01-01

418

Cleaning of a thermal vacuum chamber with shrouds in place  

NASA Astrophysics Data System (ADS)

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 chamber without removing the shrouds.

Bond, William R.

1992-11-01

419

Precooler Ring Vacuum System  

SciTech Connect

The precooler vacuum system, as proposed by FNAL, is based on a suitable modification of the existing Electron Cooling Ring System. Because of the magnetic cycle of the bending magnets, distributed ion pumping, as exists in the Electron Cooling Ring, is not applicable. Instead, the proposed pumping will be done with commercial appendage ion pumps mounted approximately every two meters around the circumference of the ring. The loss of effective pumping speed and non-uniformity of system pressure with appendage pumps may not be major considerations but the large number required does effect experimental and analytical equipment placement considerations. There is a distributed pumping technique available which: (1) is not affected by the magnetic cycle of the bending magnets; (2) will provide a minimum of four times the hydrogen pumping speed of the proposed appendage ion pumps; (3) will require no power during pumping after the strip is activated; (4) will provide the heat source for bakeout; (5) is easily replaceable; and (6) can be purchased, installed, and operated at a generous economic advantage over the presently proposed ion pumped system. The pumping technique referred to is non-evaporable gettering with ST101 Zr/Al pumping strip. A technical description of this pumping strip is given on Data Sheet 1 and 2 attached to this report.

Moenich, J.

1980-10-02

420

Compact vacuum insulation  

DOEpatents

Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases there between are evacuated to form a vacuum. These spherical glass beads provide the maximum support while minimizing thermal conductance. In its preferred embodiment; these two metal sheets are textured with ribs or concave protrusions in conjunction with the glass beads to maximize the structural integrity of the panels while increasing the spacing between beads, thereby reducing the number of beads and the number of thermal conduction paths. Glass or porcelain-enameled liners in combination with the glass spacers and metal sidewalls effectively decrease thermal conductivity, and various laminates, including wood, porcelain-enameled metal, and others effectively increase the strength and insulation capabilities of the panels. Also, a metal web is provided to hold the spacers in place, and strategic grooves are shown to accommodate expansion and contraction or shaping of the panels. 35 figs.

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

1992-10-27

421

Compact vacuum insulation  

DOEpatents

Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases therebetween are evacuated to form a vacuum. These spherical glass beads provide the maximum support while minimizing thermal conductance. In its preferred embodiment; these two metal sheets are textured with ribs or concave protrusions in conjunction with the glass beads to maximize the structural integrity of the panels while increasing the spacing between beads, thereby reducing the number of beads and the number of thermal conduction paths. Glass or porcelain-enameled liners in combination with the glass spacers and metal sidewalls effectively decrease thermal conductivity, and variious laminates, including wood, porcelain-enameled metal, and others effectively increase the strength and insulation capabilities of the panels. Also, a metal web is provided to hold the spacers in place, and strategic grooves are shown to accommodate expansion and contraction or shaping of the panels.

Benson, David K. (Golden, CO); Potter, Thomas F. (Denver, CO)

1992-01-01

422

NCSX Vacuum Vessel Fabrication  

SciTech Connect

The National Compact Stellarator Experiment (NCSX) is being constructed at the Princeton Plasma Physics Laboratory (PPPL) in conjunction with the Oak Ridge National Laboratory (ORNL). The goal of this experiment is to develop a device which has the steady state properties of a traditional stellarator along with the high performance characteristics of a tokamak. A key element of this device is its highly shaped Inconel 625 vacuum vessel. This paper describes the manufacturing of the vessel. The vessel is being fabricated by Major Tool and Machine, Inc. (MTM) in three identical 120º vessel segments, corresponding to the three NCSX field periods, in order to accommodate assembly of the device. The port extensions are welded on, leak checked, cut off within 1" of the vessel surface at MTM and then reattached at PPPL, to accommodate assembly of the close-fitting modular coils that surround the vessel. The 120º vessel segments are formed by welding two 60º segments together. Each 60º segment is fabricated by welding ten press-formed panels together over a collapsible welding fixture which is needed to precisely position the panels. The vessel is joined at assembly by welding via custom machined 8" (20.3 cm) wide spacer "spool pieces." The vessel must have a total leak rate less than 5 X 10-6 t-l/s, magnetic permeability less than 1.02?, and its contours must be within 0.188" (4.76 mm). It is scheduled for completion in January 2006.

Viola, M. E.; Brown, T.; Heitzenroeder, P.; Malinowski, F.; Reiersen, W.; Sutton, L.; Goranson, P.; Nelson, B.; Cole, M.; Manuel, M.; McCorkle, D.

2005-10-07

423

Bonded semiconductor substrate  

DOEpatents

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.

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

2010-07-13

424

Energy pulse bonding  

NASA Technical Reports Server (NTRS)

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.

Smith, G. C.

1972-01-01

425

Chemical bonding technology  

NASA Technical Reports Server (NTRS)

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.

Plueddemann, E.

1986-01-01

426

Indirect bonding technique.  

PubMed

Accurate bracket placement is the key for the successful treatment of an orthodontic case. With indirect bonding, not only is the bracket placement more accurate but this technique also significantly reduces chairtime. In this article, the author explains use of thermal glue in an indirect bonding technique. In cases of constricted arches, a modified rapid maxillary expander can be used along with indirect bonding to reduce overall treatment time. PMID:17190232

Kothari, Ashok

2006-01-01

427

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.

2009-10-06

428

Bonding and Sealing Evaluations for Cryogenic Tanks  

NASA Technical Reports Server (NTRS)

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.

Glass, David E.

1997-01-01

429

A Review of Maintenance of Vacuum inside Vacuum Insulation Panels  

Microsoft Academic Search

The growing concerns over global energy crisis and the phasing out of polyurethane foams blown with CFC-11, which has high Ozone Depletion Potential(ODP), have pushed thermal insulation technology to improve its efficiency. Vacuum Insulation Panel(VIP) has been regarded as a super thermal insulation material with a thermal resistance of about 5-10 times higher than conventional thermal insulation. Appropriate vacuum in

Chun Guang Yang; Lie Xu

2010-01-01

430

Teachers' Domain: Covalent Bonding  

NSDL National Science Digital Library

This Flash interactive tutorial explores covalent bonding, a type of chemical bond that involves sharing of electrons. Learners investigate the attractive and repulsive forces that act on atomic particles and how the sharing of electrons can keep atoms together. See how two hydrogen atoms interact with each other to create a covalent bond. Learn about patterns in the periodic table and how electrostatic potential energy determines the bond length. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-08-16

431

Hillslope diffusion  

NSDL National Science Digital Library

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.

Mcdermott, Jeni

432

Amorphous Ternary Diffusion Barriers for Silicon Metallizations  

NASA Astrophysics Data System (ADS)

Reactively sputtered from transition-metal silicide or boride targets in Ar/N_2 discharges, thin amorphous films of TM-Si-N (TM = Mo, Ta, Ti, or W) and W-B-N are investigated. Resistivity, density, stress, and structure are given as functions of composition, and in some cases, temperature. Transmission electron microscopy shows that most of the films are marginally amorphous with the scale of local order ranging from 0.5 to 1.5 nm. Small -angle scattering measurements reveal chemically dissimilary regions in the films. When fully nitrided, Si appears to be preferentially bonded to nitrogen in the form of Si_3N_4 in the TM-Si-N films, according to extended energy loss fine structure (EXELFS) measurements. By tests on shallow-junction diodes, 100-nm thick TM-Si-N barriers are able to prevent aluminum overlayers from spiking the Si substrate at temperatures above aluminum's melting point, 660^circC. The exceptional stability is partly attributable to a 3 nm, self-sealing AlN layer which grows at the TM-Si-N/Al interface. The performance of the TM-Si-N and W-B-N barriers with copper overlayers is equally impressive. At the proper compositions, 100-nm barriers prevent copper from diffusing into the junction at 800^circC or higher for a 30-min vacuum annealing. Diode failure typically corresponds to the crystallization temperature of the barrier, which can be reduced by the presence of copper. Preliminary diffusion measurements of Cu in Ta _{36}Si_ {14}N_{50} films by SIMS yield an approximate diffusivity constant of D_{CU} = (0.014 cm ^2/s) times exp(-2.7 eV/kT). A 10-nm-thick TM-Si-N barrier with a Cu overlayer on MOS capacitors reveals no penetration of Cu into SiO_2 during an 80 h bias-thermal-stress at 300^circ C and 1 MV/cm applied field. Through a microscopic four-point probe lithographically defined on a Cu/barrier/Cu trilayer stack, the specific contact resistances of barrier/Cu interfaces are determined for TM-Si-N, TiN, and W barriers. In all instances, the contact resistivty is approximately 10^ {-9} Omega cm^2 for as-deposited samples.

Reid, Jason Sven

1995-01-01

433

Study of zirconium/stainless steel interface in tubular junctions made by eutectic diffusion.  

National Technical Information Service (NTIS)

Reprocessing plants and pressurized water loops for fuels irradiation have zirconium (or zircaloy) and austenitic stainless steel tubes connected by mean of diffusion bondings. These bondings are achieved by producing an eutectic film at the interface bet...

J. Y. Blanc R. Le Goff P. Regnier

1990-01-01

434

Femtosecond dynamics in hydrogen-bonded solvents  

SciTech Connect

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.

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

1993-09-01

435

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

NASA Astrophysics Data System (ADS)

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.

Utsumi, Jun; Ichiyanagi, Yuko

2014-02-01

436

Fluxless eutectic bonding of GaAs-on-Si by using Ag/Sn solder  

NASA Astrophysics Data System (ADS)

Fluxless GaAs-on-Si wafer bonding using Ag/Sn solder was investigated to realize uniform and void-free heterogeneous material integration. The effects of the diffusion barrier, Ag/Sn thickness, and Ar plasma treatment were studied to achieve the optimal fluxless bonding process. Pt on a GaAs wafer and Mo on a Si wafer act as diffusion barriers by preventing the flow of Ag/Sn solder into both the wafers. The bonding strength is closely related to the Ag/Sn thickness and Ar plasma treatment. A shear strength test was carried out to investigate the bonding strength. Under identical bonding conditions, the Ag/Sn thickness was optimized to achieve higher bonding strength and to avoid the formation of voids due to thermal stress. An Ar plasma pretreatment process improved the bonding strength because the Ar plasma removed carbon contaminants and metal-oxide bonds from the metal surface.

Eo, Sung-Hwa; Kim, Dae-Seon; Jeong, Ho-Jung; Jang, Jae-Hyung

2013-11-01

437

Pollution prevention in vacuum processes  

SciTech Connect

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.

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

438

APS storage ring vacuum system  

SciTech Connect

The Advanced Photon Source synchrotron radiation facility, under construction at the Argonne National Laboratory, incorporates a large ring for the storage of 7 GeV positrons for the generation of photon beams for the facility's experimental program. The Storage Ring's 1104 m circumference is divided into 40 functional sectors. The sectors include vacuum, beam transport, control, acceleration and insertion device components. The vacuum system, which is designed to operate at a pressure of 1 n Torr, consists of 240 connected sections, the majority of which are fabricated from an aluminum alloy extrusion. The sections are equipped with distributed NeG pumping, photon absorbers with lumped pumping, beam position monitors, vacuum diagnostics and valving. The details of the vacuum system design, selected results of the development program and general construction plans are presented. 11 refs., 6 figs., 3 tabs.

Niemann, R.C.; Benaroya, R.; Choi, M.; Dortwegt, R.J.; Goeppner, G.A.; Gonczy, J.; Krieger, C.; Howell, J.; Nielsen, R.W.; Roop, B.; Wehrle, R.B.

1990-01-01

439

Vacuum system pump down analysis  

SciTech Connect

My assignment on the SP-100 Vacuum Vessel Vacuum System Team was to perform a transient pump down analysis for the vacuum vessel that will house the SP-100 reactor during testing. Pump down time was calculated for air and helium. For all cases the proposed vacuum system will be able to pump down the vessel within the required time. The use of a larger rotary piston pump (DUO250) improves the pump down time by 35 minutes and therefore should be considered. The 6-inch duct for the roughing line is optimal, however, because all cases are well below the 24 hour time frame, the 4-inch duct is sufficient. The use of the single turbomolecular pump during pump down is sufficient. A pump down with helium in the vessel and a helium inleakage delays the time to achieve the base pressure marginally and is acceptable.

Rohrdanz, D.R.

1990-08-01

440

Simple vacuum pump exhaust filter  

Microsoft Academic Search

A simple vacuum pump exhaust filter based upon an automotive air cleaner has been constructed and tested. The major virtues of the filter system are ease of coupling to an external exhaust and the availability of filter elements.

Richard A. Forman; Harvey D. Kratz

1984-01-01

441

Alumina barrier for vacuum brazing  

NASA Technical Reports Server (NTRS)

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.

Beuyukian, C. S.

1980-01-01

442

Vacuum Outgassing of Various Materials.  

National Technical Information Service (NTIS)

A gas analytical system for measuring the evolved gases from materials during vacuum degassing is discussed. The outgassing data are based upon the throughput measurement and a computer-controlled quadrupole mass spectrometer allows the determination of r...

E. D. Erikson T. G. Beat D. D. Berger B. A. Frazier

1983-01-01

443

Control of KEKB vacuum system  

Microsoft Academic Search

In a vacuum system of the KEKB accelerator that is a two ring electron-positron collider, there are nearly 10,000 control points. A large number of vacuum related components should be controlled and\\/or monitored at the rings and the beam transport line from the linac. Those component hardwares are connected to their sub-interfaces such as ADC interfaced by devices of CAMAC,

S. Kato; K. Kanazawa; Y. Suetsugu; H. Hisamatsu; M. Shimamoto; M. Sato; M. Shirai; M. Takagi

2001-01-01

444

[Comparison vacuum extractor versus forceps].  

PubMed

The aim of the study was to search for objective criteria witch might help us to make a choice between obstetrical forceps and vacuum extractor in front of such a clinical situation. In that purpose, we realised a medline research to compare those two obstetrical instruments in term of advantages, disadvantages and specific complications. Vacuum extractor is the most used in the industrialized countries, learning seems to be quickest, time from decision to extraction a little bit longer than with forceps (Level II-2). Vacuum extractor is recommended in case of low presentation with transversal or posterior variety (Level III) or when no analgesia is available (Level III). Forceps are more successful than vacuum (Level II-1), are recommended in case of prematurity and complete anesthesia (Level III). Immediate maternal complications (cervical tear, vaginal and perineal laceration, use of episiotomy) are less frequent with vacuum extractor (Level II-1). Long term effects on the pelvic floor and the bladder continence are comparable with natural delivery for both forceps and vacuum (Level II-1) but anal incontinence is increased, especially with forceps (Level II-1). Benign immediate neonatal morbidity is comparable for both instruments, but there are some specific complications (Level II-1). Thus, cephalhaematomas and potentially dramatic extensive subgaleal haematomas (even rare), retinal haemorrhage are more frequent with the use of vacuum extractor (Level II-1). Facial nerve paralysis, skull fracture (even rare) are more frequent with forceps (Level II-2). Neonatal convulsions frequency is comparable with both instruments (Level II-2), such are middle and long term complications (Level II-3). Finally, failure of forceps extraction needs a caesarean section but there is no clear evidence in the literature for the sequential use of forceps after failure of vacuum (Level III). PMID:19268200

Schaal, J-P; Equy, V; Hoffman, P

2008-12-01

445

Vacuum Variable Medium Temperature Blackbody  

Microsoft Academic Search

This article describes the vacuum variable medium-temperature blackbody (VMTBB) constructed to serve as a highly stable reference\\u000a source with an aperture diameter of 20 mm in the temperature range from 150 °C to 430 °C under medium-vacuum conditions (10?3 Pa) and in a reduced background environment (liquid-nitrogen-cooled shroud). The VMTBB was realized for the calibration facility\\u000a at the PTB in the field of

S. P. Morozova; N. A. Parfentiev; B. E. Lisiansky; U. A. Melenevsky; B. Gutschwager; C. Monte; J. Hollandt

2010-01-01

446

Extracting energies from the vacuum  

Microsoft Academic Search

We present and study a possible mechanism of extracting energies from the\\u000avacuum by external classical fields. Taking a constant magnetic field as an\\u000aexample, we discuss why and how the vacuum energy can be released in the\\u000acontext of quantum field theories. In addition, we give a theoretical\\u000acomputation showing how much vacuum energies can be released. The possibilities

She-Sheng Xue

2000-01-01

447

Hydrogen bonding probes of phenol -OH groups.  

PubMed

Correlations between hydrogen bonds and solvent effects on phenol -OH proton shieldings, temperature coefficients (??/?T) and effects on OH diffusion coefficients for numerous phenolic acids, flavonols, flavones, and oleuropein derivatives of biological interest were investigated in several organic solvents and were shown to serve as reliable indicators of hydrogen bonding and solvation state of -OH groups. The temperature coefficients span a range of -0.5 to -12.3 ppb K(-1). Shielding differences of 2.0 to 2.9 ppm at 298 K were observed for solvent exposed OH groups between DMSO-d(6) and CD(3)CN which should be compared with a shielding range of ~7 ppm. This demonstrates that the solvation state of hydroxyl protons is a key factor in determining the value of the chemical shift. For -OH protons showing temperature gradients more positive than -2.5 ppb K(-1), shielding changes between DMSO-d(6) and CD(3)CN below 0.6 ppm, and diffusion coefficients significantly different from those of traces of H(2)O, there is an intramolecular hydrogen bond predictivity value of 100%. The C-3 OH protons of flavonols show very significant negative temperature coefficients and shielding changes between DMSO-d(6) and CD(3)CN of ~2.3 ppm, which indicate the absence of persistent intramolecular hydrogen bonds, contrary to numerous X-ray structures. PMID:23292312

Kontogianni, Vassiliki G; Charisiadis, Pantelis; Primikyri, Alexandra; Pappas, Charalambos G; Exarchou, Vassiliki; Tzakos, Andreas G; Gerothanassis, Ioannis P

2013-02-14

448

Vaneless diffusers  

NASA Astrophysics Data System (ADS)

The influence of vaneless diffusers on flow in centrifugal compressors, particularly on surge, is discussed. A vaneless diffuser can demonstrate stable operation in a wide flow range only if it is installed with a backward leaning blade impeller. The circumferential distortion of flow in the impeller disappears quickly in the vaneless diffuser. The axial distortion of flow at the diffuser inlet does not decay easily. In large specific speed compressors, flow out of the impeller is distorted axially. Pressure recovery of diffusers at distorted inlet flow is considerably improved by half guide vanes. The best height of the vanes is a little 1/2 diffuser width. In small specific speed compressors, flow out of the impeller is not much distorted and pressure recovery can be predicted with one-dimensional flow analysis. Wall friction loss is significant in narrow diffusers. The large pressure drop at a small flow rate can cause the positive gradient of the pressure-flow rate characteristic curve, which may cause surging.

Senoo, Y.

449

Visionlearning: Chemical Bonding  

NSDL National Science Digital Library

This digital learning module provides an easily-understood overview of chemical bonding for users with little formal background in chemistry or physics. It explores ionic bonding through the example of sodium (an alkali metal) reacting with chlorine gas to produce common table salt. A concept simulation further illustrates the process.

Carpi, Anthony

2011-07-12

450

Interactive Pi Bonding Effects  

NSDL National Science Digital Library

This application demonstrates the effect of pi bonding on the one-electron ligand field splitting in an octahedral. By clicking on the appropriate buttons students can see how D changes when you move from ligands with no pi bonding capability to pi donor and pi acceptor ligands.

451

The dissociative bond.  

PubMed

Dissociation leaves a psychic void and a lingering sense of psychic absence. How do 2 people bond while they are both suffering from dissociation? The author explores the notion of a dissociative bond that occurs in the aftermath of trauma--a bond that holds at its core an understanding and shared detachment from the self. Such a bond is confined to unspoken terms that are established in the relational unconscious. The author proposes understanding the dissociative bond as a transitional space that may not lead to full integration of dissociated knowledge yet offers some healing. This is exemplified by R. Prince's (2009) clinical case study. A relational perspective is adopted, focusing on the intersubjective aspects of a dyadic relationship. In the dissociative bond, recognition of the need to experience mutual dissociation can accommodate a psychic state that yearns for relationship when the psyche cannot fully confront past wounds. Such a bond speaks to the need to reestablish a sense of human relatedness and connection when both parties in the relationship suffer from disconnection. This bond is bound to a silence that becomes both a means of protection against the horror of traumatic memory and a way to convey unspoken gestures toward the other. PMID:23282044

Gordon, Nirit

2013-01-01

452

Chemical Bonds I  

ERIC Educational Resources Information Center

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)

Sanderson, R. T.

1972-01-01

453

Mother-Child Bonding.  

ERIC Educational Resources Information Center

Examines the nature of mother-child bonding from the prenatal stage through early infancy, discussing how the mother's actions, even before birth, stimulate her child's senses. Explains the crucial role that physical contact, breastfeeding, and visual stimuli have on mother-child bonding in human and animal newborns. (MDM)

Pearce, Joseph Chilton

1994-01-01

454

The Sibling Bond.  

ERIC Educational Resources Information Center

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…

Bank, Stephen P.; Kahn, Michael D.

455

Cold cathode vacuum gauging system  

DOEpatents

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.

Denny, Edward C. (Knoxville, TN)

2004-03-09

456

Shape Bonding method  

NASA Technical Reports Server (NTRS)

The present invention is directed to a method of bonding at least two surfaces together. The methods step of the present invention include applying a strip of adhesive to a first surface along a predefined outer boundary of a bond area and thereby defining a remaining open area there within. A second surface, or gusset plate, is affixed onto the adhesive before the adhesive cures. The strip of adhesive is allowed to cure and then a second amount of adhesive is applied to cover the remaining open area and substantially fill a void between said first and second surfaces about said bond area. A stencil may be used to precisely apply the strip of adhesive. When the strip cures, it acts as a dam to prevent overflow of the subsequent application of adhesive to undesired areas. The method results in a precise bond area free of undesired shapes and of a preferred profile which eliminate the drawbacks of the prior art bonds.

Pontius, James T. (Inventor)

2010-01-01

457

Technology of bonding elastomers  

NASA Astrophysics Data System (ADS)

The paper reviews current bonding theories and examines the application of these concepts to the production of reliable commercial bonding elastomers. Fundamental aspects of elastomer bonding (such as the elastomer surface thermodynamics, the mechanics of the adhesive failure, and the elastomer self-adhesion) are discussed along with the types of elastomers and the technology used in producing these compounds, with particular consideration given to the factors affecting the strength and durability of elastomer bonds. Tables are presented listing elastomers' designations according to ASTM D1418; the elastomers' surface properties; the elastomer surface energy dispersive and polar components; the commonly used elastomer types selected to meet specific ASTM test requirements; the ASTM adhesion test methods; and selected metal primers, cover coats, and bonding agents.

Symes, Ted; Oldfield, David

458

Wood Bond Testing  

NASA Technical Reports Server (NTRS)

A joint development program between Hartford Steam Boiler Inspection Technologies and The Weyerhaeuser Company resulted in an internal bond analyzer (IBA), a device which combines ultrasonics with acoustic emission testing techniques. It is actually a spinoff from a spinoff, stemming from a NASA Lewis invented acousto-ultrasonic technique that became a system for testing bond strength of composite materials. Hartford's parent company, Acoustic Emission Technology Corporation (AET) refined and commercialized the technology. The IBA builds on the original system and incorporates on-line process control systems. The IBA determines bond strength by measuring changes in pulsar ultrasonic waves injected into a board. Analysis of the wave determines the average internal bond strength for the panel. Results are displayed immediately. Using the system, a mill operator can adjust resin/wood proportion, reduce setup time and waste, produce internal bonds of a consistent quality and automatically mark deficient products.

1989-01-01

459

Ultrasonically bonded value assembly  

NASA Technical Reports Server (NTRS)

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.

Salvinski, R. J. (inventor)

1975-01-01

460

Four-year Water Degradation of Total-etch Adhesives Bonded to Dentin  

Microsoft Academic Search

Resin-dentin bonds degrade over time. The objective of this study was to evaluate the influence of variables like hybridization effectiveness and diffusion\\/elution of interface components on degradation. Hypotheses tested were: (1) There is no difference in degradation over time between two-and three-step total-etch adhesives; and (2) a composite-enamel bond protects the adjacent composite-dentin bond against degradation. The micro-tensile bond strength

J. De Munck; B. Van Meerbeek; Y. Yoshida; S. Inoue; M. Vargas; K. Suzuki; P. Lambrechts; G. Vanherle

2003-01-01

461

Pneumatically Actuated Miniature Peristaltic Vacuum Pumps  

NASA Technical Reports Server (NTRS)

Pneumatically actuated miniature peristaltic vacuum pumps have been proposed for incorporation into advanced miniature versions of scientific instruments that depend on vacuum for proper operation. These pumps are expected to be capable of reaching vacuum-side pressures in the torr to millitorr range (from .133 down to .0.13 Pa). Vacuum pumps that operate in this range are often denoted roughing pumps. In comparison with previously available roughing pumps, these pumps are expected to be an order of magnitude less massive and less power-hungry. In addition, they would be extremely robust, and would operate with little or no maintenance and without need for oil or other lubricants. Portable mass spectrometers are typical examples of instruments that could incorporate the proposed pumps. In addition, the proposed pumps could be used as roughing pumps in general laboratory applications in which low pumping rates could be tolerated. The proposed pumps could be designed and fabricated in conventionally machined and micromachined versions. A typical micromachined version (see figure) would include a rigid glass, metal, or plastic substrate and two layers of silicone rubber. The bottom silicone layer would contain shallow pump channels covered by silicone arches that could be pushed down pneumatically to block the channels. The bottom silicone layer would be covered with a thin layer of material with very low gas permeability, and would be bonded to the substrate everywhere except in the channel areas. The top silicone layer would be attached to the bottom silicone layer and would contain pneumatic- actuation channels that would lie crosswise to the pump channels. This version is said to be micromachined because the two silicone layers containing the channels would be fabricated by casting silicone rubber on micromachined silicon molds. The pneumatic-actuation channels would be alternately connected to a compressed gas and (depending on pump design) either to atmospheric pressure or to a partial vacuum source. The design would be such that the higher pneumatic pressure would be sufficient to push the silicone arches down onto the substrates, blocking the channels. Thus, by connecting pneumatic- actuation channels to the two pneumatic sources in spatial and temporal alternation, waves of opening and closing, equivalent to peristalsis, could be made to move along the pump channels. A pump according to this concept could be manufactured inexpensively. Pneumatic sources (compressors and partial vacuum sources) similar those needed for actuation are commercially available; they typically have masses of .100 g and power demands of the order of several W. In a design-optimization effort, it should be possible to reduce masses and power demands below even these low levels and to integrate pneumatic sources along with the proposed pumps into miniature units with overall dimensions of no more than a few centimeters per side.

Feldman, Sabrina; Feldman, Jason; Svehla, Danielle

2003-01-01

462

Dynamic Simulation of the Thermal Decomposition of Pyrite Under Vacuum  

NASA Astrophysics Data System (ADS)

The ultrasoft pseudopotential plane wave method is applied to dynamic simulation of the thermal decomposition mechanism of FeS2 under vacuum. The FeS2 (100), (111), and (210) surface relaxation and the geometric and electronic structure of the reactants and products are calculated. The results indicate that FeS2 (100) is the most preferred surface to dissociate and also the most common cleavage surface. The thermal decomposition mechanism of FeS2 is explained by dynamic simulation on a micro stratum: in general, the S-Fe bond gradually elongated until it fractured, the S-S bond strengthened gradually, the S-Fe bond was cleaved to form S, the force is relatively weaker between different layers, and thermal decomposition occurred easily between the layers. Simultaneously, the intermediate products, such as Fe x S y , were formed. Evidence of Fe pyrolysis into Fe metal was not found, and the intermediate products decomposed further. The contributions of the p and d orbitals of Fe increased, whereas that of the s orbital decreased. The contributions of the s and p orbitals of S decreased. The results obtained from FeS2 thermal decomposition experiments under vacuum and differential thermal analysis—thermogravimetry are consistent with the results of calculation and simulation.

Deng, Jiushuai; Wen, Shuming; Chen, Xiumin; Xian, Yongjun; Wu, Dandn

2014-05-01

463

Wafer-level vacuum/hermetic packaging technologies for MEMS  

NASA Astrophysics Data System (ADS)

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.

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

2010-02-01

464

Effects of post-diffusion annealing on Zn-diffused GaAs:Si  

Microsoft Academic Search

After Zn diffusion into Si-doped GaAs (n≊1.5×1018 cm?3), the Zn-diffused samples are annealed under different conditions: (i) in vacuum, (ii) in arsenic vapor, and (iii) with a Si3N4 mask capping the sample surface. The Zn concentration profiles obtained by secondary-ion-mass spectroscopy and the photoluminescence (PL) spectra taken at different depths below the sample surface are studied in detail. After annealing

Nguyen Hong Ky; F. K. Reinhart; B. Blanchard; J. C. Pfister

1993-01-01

465

Transient liquid phase bonding of ferritic oxide dispersion strengthened alloys  

NASA Astrophysics Data System (ADS)

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.

Krishnardula, Venu Gopal

466

Development of High Temperature Type Vacuum Insulation Panel using Soluble Polyimide and Characteristic Evaluation  

Microsoft Academic Search

The utilization is expected from the high-insulated characteristic as a tool for energy saving also in the high temperature insulation fields as in vacuum insulation panels (VIP) in the future. For high temperature, the material composition and process of VIP were reviewed, the SUS foil was adopted as packaging material, and soluble polyimide was developed as the thermo compression bonding

Kuninari Araki; Daigorou Kamoto; Shin-Ichi Matsuoka

2009-01-01

467

Axial Compression Testing of Vacuum Tube Glass-Ceramic/Molybdenum Frames.  

National Technical Information Service (NTIS)

The strength of a vacuum tube subassembly is affected by many factors, including the subassembly design, the process used to bond the parts, and the type of equipment used to measure the strength. In this study, these variables were examined for a subasse...

R. K. Spears

1980-01-01

468

PREPARATIVE COMPOUND CLASS SEPARATION OF HEAVY OIL VACUUM RESIDUA BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY  

Microsoft Academic Search

An HPLC system is used to separate deasphalted vacuum resids of heavy oils, into saturates, aromatics and two types of resins at preparative scale. The separation is achieved using two silica and one cyano bonded silica columns, and cyclopentane, a mixture of chloroform-methanol and dichleramethane as solvents. Automated repetitive injection is required. Recoveries of the sample are around 100%.

Lante Carbognani; Alejandro Izquierdo

1990-01-01

469

Comparison of release torques of tightened bolts in vacuum and air  

NASA Technical Reports Server (NTRS)

Various combinations of stainless steel, mild steel, and aluminum bolt-nut couples are tightened to 60 lb-ft in partial vacuum and in air. Results are given for tests with and without two lubricants /a fluorosilicone and a sodium silicate bonded dry-film/.

Demorest, K. E.

1970-01-01

470

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

NASA Astrophysics Data System (ADS)

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.

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

2004-12-01

471

Theoretical modeling of crossed-field electron vacuum devices  

NASA Astrophysics Data System (ADS)

The modeling of crossed-field electron vacuum devices, such as magnetrons and crossed-field amplifiers with a dc background mode and an rf pump mode is discussed. The dominant interaction in these devices is the wave-particle interaction (diocotron). This interaction drives the classical Brillouin flow nonlinearly unstable through a Rayleigh-type instability in a shear flow. This linear instability triggers the nonlinear instability, which is a second-order nonlinear diffusion process. This diffusion process is driven by the density gradient at the edge of the sheath, which causes the electron density to evolve into a new density profile, one which will be in equilibrium with the nonlinear diffusion process. The general physics of the various processes contained in this model is discussed, including a possible explanation for the ultra-low noise phenomena.

Kaup, D. J.

2001-05-01

472

Reduce costs with vacuum excavation  

SciTech Connect

Although vacuum excavation equipment and methods are in their infancy, this developing technology offers tremendous promise for the future. The author explains Brooklyn Union Gas Co.'s experience with five vacuum trucks and the procedures that are used. In recent years, the higher cost of natural gas has increased the need for gas utilities to reduce their operating expenses. One way, which has been successful at Brooklyn Union Gas, is the use of vacuum excavation. Although vacuum excavation equipment and techniques are in their infancy, this developing technology offers substantial savings today and tremendous promise for the future. Brooklyn Union started its vacuum digging program by locating keyhole cutoffs--small surface openings ranging from 1 ft by 1 ft to 1 1/2 ft by 1 1/2 ft (0.3 m to 0.45 m square). It is no easy task to accurately locate a service that was installed 60 years ago. Reading the street indications, locating an existing curb valve or repair opening, gaining access to the building, making a physical lineup, and using an M-scope, plus any other tools available, have produced a high success rate.

Vitale, S.A.

1983-09-01

473