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Micro and Nano Technology
Nur für XING Mitglieder sichtbar Customized Diode Laser System
The Diode Laser System (with Homogenizer and Projection lens) should present the following specifications / parameters:
- Line width: 82mm ± 2mm at homogenized area (to ensure minimum of 80mm homogenized line)
- Line height: 200µm ± 50µm at FWHM
- Working distance: TDB
- 10kW/cm² power density focal plane
- ≥ 95% homogenity
- Wavelength: 980nm +/- 10nm
- 2kW at mask plane (behind homogenizer)
Additional details can be provided upon request. Thank you!
Christian Walz Reaktive Nanofolien als Wärmequelle zum "kalten", verzugsfreien Löten
Reaktive Nanofolien geben bei Ihrer Reaktion nur sehr kurzfristig eine Temperatur im Bereich von 1.200°C ab. Die hohe Reaktionsgeschwindigkeit von 10-30m/s führt zu einem sehr begrenzten Wärmeeintrag in das Bauteil.
Durch die mechanische Trennung der beiden Fügepartner kann jedes Teil mit dem optimalen Lotwerkstoff versehen werden.
Das Verfahren eignet sich zum Fügen von artgleichen und artungleichen Werkstoffen. Vor allem temperaturempfindliche Bauteile können so mit besten Fügestellenqualitäten verbunden werden. Da die Bauteile nicht gemeinsam aufgeheizt werden, wie beim konventionellen Ofenlöten, kommt es zu keinen Spannungen in den Bauteilen aufgrund von unterschiedlichen Wärmeausdehnungskoeffizienten.
Ein weiterer Kommentar
Letzter Kommentar:
Christian Walz
Hallo Herr Barth,
die reaktiven Nanofolien erzeugen derzeit eine Temperatur von 1.200°C. Neue Entwicklungen werden in Kürze 2.000°C bringen. Daher sind Lote mit Schmelztemperaturen von 1.800°C mit den Nanofolien derzeit nicht zu verafrbeiten.
Mit freundlichen Grüßen
Christian Walz
Stephan Kallee Subpicosecond pulses for Nd:YAG laser ablation can cause production of X-rays
Generally, Nd:YAG lasers do not produce X-rays as used in welding applications.
According to Gary Zeman of the Health Physics Society in the USA, there are some new research applications in nanotechnology wherein Nd:YAG lasers are used to ablate materials by concentrating the laser energy into subpicosecond (shorter than a millionth of a millionth of a second) pulses. The physical interactions due to the extremely high rate of energy deposition at the surface of materials exposed to such pulses can cause production of X-rays. He recommends that if your research involves using subpicosecond pulses for laser ablation then you should be involving your X-ray safety officer as well as your laser safety officer in the review of your procedures:
We are looking forward to your comments or observations regarding this potential health hazard.
Stephan Kallee Nanotech in Space - Alumina in Teflon and Conductive Polymer Nanocomposites Exposed to the Rigors of Space
Nanotech in Space: Rensselaer Experiment to Weather the Trials of Orbit
The project, funded by the U.S. Air Force Multi University Research Initiative (MURI), seeks to test the performance of the new nanocomposites in orbit. Space Shuttle Atlantis will carry the samples to the International Space Station (ISS). The materials will then be mounted to the station’s outer hull in a Passive Experiment Carrier (PEC), and exposed to the rigors of space.
Rensselaer professors Linda Schadler, of the Department of Materials Science and Engineering, and Thierry Blanchet, of the Department of Mechanical, Aerospace, and Nuclear Engineering, worked with a team of researchers from the University of Florida to develop two different types of experimental nanomaterials. The MURI project and the University of Florida research team are led by Rensselaer alumnus W. Greg Sawyer ’99, who earned his bachelor’s, master’s, and doctoral degrees from Rensselaer and is now the N. C. Ebaugh Professor of Mechanical and Aerospace Engineering at the University of Florida. Blanchet was Sawyer’s doctoral adviser.
The first new material is a wear-resistant, low-friction nanocomposite, created by mixing nanoscale alumina particles with polytetrafluoroethylene (PTFE), which is known commercially as Teflon. Schadler and her research group introduced different fluorine-coated nanoparticles into conventional PTFE. The small amount of additive caused the wear rate of the PTFE to drop by four orders of magnitude, without affecting the PTFE’s coefficient of friction. The end result is a stronger, more durable PTFE that is almost as nonstick and slippery as untreated PTFE.
The gained benefit, Schadler said, is the difference between PTFE that can survive sliding along a surface for a few kilometers before wearing away, and a nanocomposite that could slide across a surface for more than 100,000 kilometers before wearing away. PTFE is often used to coat the surface of moving parts in different devices. The less friction on the surface of these moving parts, the less energy is required to move the parts, Schadler said.
“We’re very excited to have this experiment installed in the ISS, and to see how the new material performs in space,” Schadler said. “In a laboratory setting, the wear rate of the material is four orders of magnitude lower than pure PTFE, which means it is considerably more resistant to wear and tear. Just as important, these advances don’t increase the material’s coefficient of friction, which means the increase in durability won’t come at the expense of creating extra friction.”
Affixed to the station, which travels at about 27,700 kph, the nanocomposite sample will be exposed to ultraviolet radiation, and temperatures ranging from -40 degrees to 60 degrees Celsius. The nanocomposite will be mounted on a tribometer, developed by Sawyer, which will measure the friction of the material’s surface. A control sample of the material, protected in a vacuum chamber in the PEC, will also be tested. The apparatus will send data in real-time to the ISS laboratory, which in turn will be forwarded to the research team.
The second set of nanomaterials to be launched into space are conductive polymer nanocomposites. During the loading of the tribometers into the PEC for space travel, an opportunity arose to also test the conductivity of carbon nanotube-filled polyamideimide and liquid crystalline polymers as a function of space exposure. The conductive composites, developed by Schadler and former Rensselaer postdoctoral researcher Justin Bult – who is now a researcher at the U.S. Department of Energy National Renewable Energy Laboratory — had to be developed in less than a week.
“It was an exciting week and we weren’t sure if the composites would hold up to the rigorous testing imposed on them to determine if they could even be launched into space,” Schadler said. “It was a thrill when some of them did, and to see the pictures of them mounted in the PEC.”
Blanchet said he’s very pleased, but not surprised, at the success of his former student, Sawyer, in leading this space-bound research study.
“Greg is at the top of his game, and it’s wonderful to see the research areas he was introduced to as a student here at Rensselaer evolve into such an important, high-profile experiment in the International Space Station,” Blanchet said. “The fact that he’s collaborating with Rensselaer researchers makes it even better.”
Schadler and Blanchet’s nanocomposites experiments are the second Rensselaer project to launch into space this year. In August, an experimental heat transfer system designed by Rensselaer professors Joel Plawsky and Peter Wayner was carried to the ISS aboard Space Shuttle Discovery.
The project, called the Constrained Vapor Bubble (CVB), will remain installed in the ISS for up to three years. The experiment could yield important fundamental insights into the nature of heat and mass transfer operations that involve a phase change, such as evaporation, condensation, and boiling, as well as engineering data that could lead to the development of new cooling systems for spacecraft and electronics devices.