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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

A low-cost solar-cell front contact using trapped silver mesh and electrostatic bonding

A new system to provide a contact with a silver mesh trapped between the cell and an encapsulating glass cover is described. Borosilicate glass is joined to the cell by electrostatic bonding during which the glass is deformed around the silver mesh to form a permanent optically coupled integral bond to the cell. The hermetic seal prevents the silver from oxidizing and destroying the electrical contact formed during the bonding process. It is demonstrated that electrostatic glass/silicon bonds have excellent stability under a variety of accelerated environmental tests. Electrostatic bonds to thin films of AL2O3, Ta2O5, and ZrO2 on glass can be used to make antireflective coatings for solar cells manufactured by this process. Test solar cells were manufactured by electrostatic bonding with good curve fill factors and efficiencies of 10 percent.

Landis, Geoffrey A.↗
NASA NTRS1965

Thermoelectric elements diffusion-bonded to tungsten electrodes

Solid-state diffusion process bonds lead telluride and lead telluride-tin telluride thermoelectric elements to tungsten electrodes. The resulting bond is nonmagnetic and has high strength and low electrical and thermal resistance. This method is also used with tantalum electrodes.

Source record↗
NASA NTRS1976

Macroscopic aspects of interfacial reactions

The extent of interdiffusion and formation of new phases is determined by the constitution diagram of the alloy system, the interdiffusion coefficients of the phases present, and the thermal conditions (temperature and time) associated with the bonding process and/or subsequent use of the bonded structure. In many instance, the kinetics of interdiffusion and phase formation can be predicted from known parameters using numerical methods and computer techniques. Predictions are compared with experimentally determined parameters for a variety of metallurgical alloy systems.

Heckel, R. W.↗
NASA NTRS2018

Optimization of Picosecond Laser Parameters for Surface Treatment of Composites Using a Design of Experiments (DOE) Approach

Based on guidelines from the Federal Aviation Administration, research supported by the NASA Advanced Composites Project is investigating methods to improve process control for surface preparation and pre-bond surface characterization on aerospace composite structures. The overall goal is to identify high fidelity, rapid, and reproducible surface treatments and surface characterization methods to reduce the uncertainty associated with the bonding process. The desired outcome is a more reliable bonded airframe structure, and to reduce time to achieve certification. In this work, a design of experiments (DoE) approach was conducted to determine optimum laser ablation conditions using a pulsed laser source with a nominal pulse width of 10 picoseconds. The laser power, frequency, scan speed, and number of passes (1 or 2) were varied within the laser system operating boundaries. Aerospace structural carbon fiber reinforced composites (Torayca® 3900-2/T800H) were laser treated, then characterized for contamination, and finally bonded for mechanical testing. Pre-bond characterization included water contact angle (WCA) using a handheld device, ablation depth measurement using scanning electron microscopy (SEM), and silicone contamination measurement using laser induced breakdown spectroscopy (LIBS). In order to accommodate the large number of specimens in the DoE, a rapid-screening, double cantilever beam (DCB) test specimen configuration was devised based on modifications to ASTM D5528. Specimens were tested to assess the failure modes observed under the various laser surface treatment parameters. The models obtained from this DoE indicated that results were most sensitive to variation in the average laser power. Excellent bond performance was observed with nearly 100% cohesive failure for a wide range of laser parameters. Below about 200 mW, adhesive failure was observed because contamination was left on the surface. For laser powers greater than about 600 mW, large amounts of fiber were exposed, and the failure mode was predominately fiber tear.

Palmieri, Frank L.↗
NASA NTRS1997

Development of Statistical Process Control Methodology for an Environmentally Compliant Surface Cleaning Process in a Bonding Laboratory

Bonding labs at both MSFC and the northern Utah production plant prepare bond test specimens which simulate or witness the production of NASA's Reusable Solid Rocket Motor (RSRM). The current process for preparing the bonding surfaces employs 1,1,1-trichloroethane vapor degreasing, which simulates the current RSRM process. Government regulations (e.g., the 1990 Amendments to the Clean Air Act) have mandated a production phase-out of a number of ozone depleting compounds (ODC) including 1,1,1-trichloroethane. In order to comply with these regulations, the RSRM Program is qualifying a spray-in-air (SIA) precision cleaning process using Brulin 1990, an aqueous blend of surfactants. Accordingly, surface preparation prior to bonding process simulation test specimens must reflect the new production cleaning process. The Bonding Lab Statistical Process Control (SPC) program monitors the progress of the lab and its capabilities, as well as certifies the bonding technicians, by periodically preparing D6AC steel tensile adhesion panels with EA-91 3NA epoxy adhesive using a standardized process. SPC methods are then used to ensure the process is statistically in control, thus producing reliable data for bonding studies, and identify any problems which might develop. Since the specimen cleaning process is being changed, new SPC limits must be established. This report summarizes side-by-side testing of D6AC steel tensile adhesion witness panels and tapered double cantilevered beams (TDCBs) using both the current baseline vapor degreasing process and a lab-scale spray-in-air process. A Proceco 26 inches Typhoon dishwasher cleaned both tensile adhesion witness panels and TDCBs in a process which simulates the new production process. The tests were performed six times during 1995, subsequent statistical analysis of the data established new upper control limits (UCL) and lower control limits (LCL). The data also demonstrated that the new process was equivalent to the vapor degreasing process.

Hutchens, Dale E.↗
NASA NTRS1969

Explosive bonding of metal-matrix composites

Explosive bonding process produces sheet composites of aluminum alloy reinforced by high-strength stainless steel wires. The bonds are excellent metallurgically, no external heat is required, various metals can be bonded, and the process is inexpensive.

Reece, O. Y.↗
NASA NTRS1976

Polyimide adhesives for weld-bonding titanium

Two weld bonding processes were developed for joining titanium alloy; one process utilizes a weld-through technique and the other a capillary-flow technique. The adhesive used for the weld-through process is similar to the P4/A5F system and a new adhesive system, CP/CFA, was used in the capillary-flow process. Static property information was generated for weld-bonded joints over the temperature range of 219K (-65 F) to 561K (550 F) and fatigue strength information was generated at room temperature. Significant improvement in fatigue strength was demonstrated for weld-bonded joints over spot-welded joints. A demonstration was made of the applicability of weld-bonding for fabricating stringer stiffened skin panels.

Vaughan, R. W.↗
NASA NTRS2019

Alignment and Bonding of Silicon Mirrors for High-Resolution X-Ray Optics

How to align and bond sub-arc second silicon mirrors? (1) Description of the alignment and bonding process. (2) Technical challenges and advances in aligning and bonding precise silicon mirrors. (a) Precise mirror placement (b) Measurement of focusing (c) Method of spacer adjustment (d) Bonding distortion and displacement (e) Co-alignment and bonding of subsequent mirrors.

Chan, Kai-Wing↗
NASA NTRS1983

Polymer Bonding of Optical Fibers

Optical waveguies coupled through their sides. In fiber etching process bonded length for coupling determined by observing optical output powers in two fibers. Surface tension of etchant remaining between two fibes holds then in contact when raised from solution for power measurement. When fibers reimmersed, they separate allowing free access by etchant.

Goss, W.↗
NASA NTRS1978

Fabrication of stainless steel clad tubing

The feasibility of producing stainless steel clad carbon steel tubing by a gas pressure bonding process was evaluated. Such a tube product could provide substantial chromium savings over monolithic stainless tubing in the event of a serious chromium shortage. The process consists of the initial assembly of three component tubesets from conventionally produced tubing, the formation of a strong metallurgical bond between the three components by gas pressure bonding, and conventional cold draw and anneal processing to final size. The quality of the tubes produced was excellent from the standpoint of bond strength, mechanical, and forming properties. The only significant quality problem encountered was carburization of the stainless clad by the carbon steel core which can be overcome by further refinement through at least three different approaches. The estimated cost of clad tubing produced by this process is greater than that for monolithic stainless tubing, but not so high as to make the process impractical as a chromium conservation method.

Kovach, C. W.↗
NASA NTRS1972

Diffusion bonded columbium panels for the shuttle heat shield.

Work at North American Rockwell in the development of a satisfactory panel diffusion bonding method for Nb shuttle orbiter heat shield panel designs is reviewed. The topics include the diffusion bonding process, panel fabrication and quality control. A practicable Nb alloy diffusion bonding method, using a Ti foil interleaf, is described and is characterized as one providing a production basis at competitive cost.

Korb, L. J.↗
NASA NTRS1977

Fabrication and evaluation of advanced titanium structural panels for supersonic cruise aircraft

Flightworthy primary structural panels were designed, fabricated, and tested to investigate two advanced fabrication methods for titanium alloys. Skin-stringer panels fabricated using the weldbraze process, and honeycomb-core sandwich panels fabricated using a diffusion bonding process, were designed to replace an existing integrally stiffened shear panel on the upper wing surface of the NASA YF-12 research aircraft. The investigation included ground testing and Mach 3 flight testing of full-scale panels, and laboratory testing of representative structural element specimens. Test results obtained on full-scale panels and structural element specimens indicate that both of the fabrication methods investigated are suitable for primary structural applications on future civil and military supersonic cruise aircraft.

Payne, L.↗
NASA NTRS1987

Evaluation of high temperature structural adhesives for extended service, phase 5

The evaluation of 3 experimental polymers from NASA-Langley and a commercially produced polymer from Mitsui Toatsu Chemicals as high temperature structural adhesives is presented. A polyphenylquinoxaline (PPQ), polyimide (STPI/LaRC-2), and a polyarylene ether (PAE-SO2) were evaluated as metal-to-metal adhesives. Lap shear, crack extension, and climbing drum peel specimens were fabricated from all three polymers and tested after thermal, combined thermal/humidity, and stressed hydraulic fluid (Skydrol) exposure. The fourth polymer, LARC-TPI was evaluated as an adhesive for titanium honeycomb sandwich structure. All three experimental polymers performed well as metal-to-metal adhesives from 219 K (-65 F) to 505 K (450 F), including humidity exposure. Structural adhesive strength was also maintained at 505 K for a minimum of 3000 hours. LaRC-TPI was evaluated as a high temperature (505 K) adhesive for titanium honeycomb sandwich structure. The LaRC-TPI bonding process development concentrated on improving the honeycomb core-to-skin bond. The most promising approach of those evaluated combined a LaRC-TPI polymer solution with a semi-crystalline LaRC-TPI powder for adhesive film fabrication and fillet formation.

Hendricks, C. L.↗
NASA NTRS1997

An OSEE Based Portable Surface Contamination Monitor

Many industrial and aerospace processes involving the joining of materials, require sufficient surface cleanliness to insure proper bonding. Processes as diverse as painting, welding, or the soldering of electronic circuits will be compromised if prior inspection and removal of surface contaminants is inadequate. As process requirements become more stringent and the number of different materials and identified contaminants increases, various instruments and techniques have been developed for improved inspection. One such technique based on the principle of Optically Stimulated Electron Emission (OSEE) has been explored for a number of years as a tool for surface contamination monitoring. Some of the benefits of OSEE are: it's non-contacting; requires little operator training; and has very high contamination sensitivity. This paper describes the development of a portable OSEE based surface contamination monitor. The instrument is suitable for both hand-held and robotic inspections with either manual or automated control of instrument operation. In addition, instrument output data is visually displayed to the operator and may be output to an external computer for archiving or analysis.

Perey, Daniel F.↗
NASA NTRS1996

A Portable Surface Contamination Monitor Based on the Principle of Optically Stimulated Electron Emission (OSEE)

Many industrial and aerospace processes involving the joining of materials, require sufficient surface cleanliness to insure proper bonding. Processes as diverse as painting, welding, or the soldering of electronic circuits will be compromised if prior inspection and removal of surface contaminants is inadequate. As process requirements become more stringent and the number of different materials and identified contaminants increases, various instruments and techniques have been developed for improved inspection. One such technique, based on the principle of Optically Stimulated Electron Emission (OSEE), has been explored for a number of years as a tool for surface contamination monitoring. Some of the benefits of OSEE are: it is non-contacting; requires little operator training; and has very high contamination sensitivity. This paper describes the development of a portable OSEE based surface contamination monitor. The instrument is suitable for both hand-held and robotic inspections with either manual or automated control of instrument operation. In addition, instrument output data is visually displayed to the operator and may be sent to an external computer for archiving or analysis.

Perey, D. F.↗
NASA NTRS1994

Study on contaminants on flight and other critical surfaces

The control of surface contamination in the manufacture of space hardware can become a critical step in the production process. Bonded surfaces have been shown to be affected markedly by contamination. It is important to insure surface cleanliness by preventing contamination prior to bonding. In this vein techniques are needed in which the contamination which may affect bonding are easily found and removed. Likewise, if materials which are detrimental to bonding are not easily removed, then they should not be used in the manufacturing process. This study will address the development of techniques to locate and quantify contamination levels of particular contaminants. With other data becoming available from MSFC and its contractors, this study will also quantify how certain contaminants affect bondlines and how easily they are removed in manufacturing.

Workman, Gary L.↗
NASA NTRS1995

High temperature barrier coatings for refractory metals

Improvements in high temperature oxidation resistant metal coating technology will allow NASA and commercial entities to develop competitive civil space transport and communication systems. The success of investigations completed in this program will have a positive impact on broadening the technology base for high temperature materials. The work reported herein describes processes and procedures for successfully depositing coherent oxidation barrier coatings on refractory metals to prevent degradation under very severe operating environments. Application of the new technology developed is now being utilized in numerous Phase 3 applications through several prominent aerospace firms. Major achievements have included: (1) development of means to deposit thick platinum and rhodium coatings with lower stress and fewer microcracks than could be previously achieved; (2) development of processes to deposit thick adherent coatings of platinum group metals on refractory substrates that remain bonded through high temperature excursions and without need for intermediate coatings (bonding processes unique to specific refractory metals and alloys have been defined; (3) demonstration that useful alloys of refractory and platinum coatings can be made through thermal diffusion means; (4) demonstration that selected barrier coatings on refractory substrates can withstand severe oxidizing environments in the range of 1260 deg and 1760 deg C for long time periods essential to the life requirements of the hardware; and (5) successful application of the processes and procedures to prototype hardware. The results of these studies have been instrumental in improved thermal oxidation barrier coatings for the NASP propulsion system. Other Phase 3 applications currently being exploited include small uncooled thrusters for spacecraft and microsatellite maneuvering systems.

Malone, G. A.↗