Manufacturing & Prototyping

Integrated PEMFC Flow Field Design for Gravity-Independent Passive Water Removal

The design solves safety as well as reliability issues. A gravity-independent PEM (proton exchange membrane) fuel cell stack has been developed that will operate at high-pressure H2 and O2 conditions with the requirement for relatively modest H2 and O2 gas circulation. Until now, in order to get higher efficiency, excess reactant gas flow was required to prevent water slug formation in gas channels, thus reducing fuel cell performance. In addition, this excess gas flow is typically supported by mechanical pumps and/or a high-pressure ejector system. All of these in a closed space environment contributed to potential safety as well as reliability issues due to the potential failure of mechanical pumps and ejectors.

Posted in: Manufacturing & Prototyping, Briefs

Read More >>

Metal-Assisted Fabrication of Biodegradable Porous Silicon Nanostructures

Silicon nanostructures are fabricated from single-crystal silicon by an electroless chemical etch process. Porous silicon nanowires are fabricated by two-step, metal-assisted electroless chemical etching of p-type or n-type silicon wafers. This method, in combination with nanolithography or nanopatterning, can be applied to fabricate porous silicon nanostructures of different shapes and sizes, such as nanorods, nanobelts, nanostrips, and nanochains. The specific resistivity of the silicon substrate, and composition of the etching solution, determine the porosity and pore size or lack thereof of the resulting nanostructures. Silicon doping, type of metal catalyst, concentrations of H2O2, and solvent all affect the formation of porous nanostructures at various resistivity ranges of silicon. A phase diagram summarizing the relation of porosification and doping, metal, concentrations of H2O2, and solvent can be generated. In this innovation, high-aspect-ratio porous silicon nanostructures, such as those previously mentioned, were fabricated from single-crystal silicon by an electroless chemical etch process. A metal film, metal nanofeatures, or metal nanoparticles were coated on the silicon substrate first, and a solution of HF and hydrogen peroxide was then used to anisotropically etch the silicon to form the porous silicon nanostructures. Up to hundreds of micron-long high-aspect-ratio porous silicon nanostructures can be fabricated, and the patterns of the cross-section of porous silicon structures can be controlled by photolithography, nanolithography, or nanoparticle-assisted patterning. The porosity is related to the resistivity range of the silicon substrate, the metal catalysts, the chemical concentration, and the additive solvent. The fabricated porous silicon nanostructure is biodegradable, and the degradation time can be controlled by surface treatments. Porous silicon nanowires can be fabricated with a two-step process. A nanostructured metal layer can be deposited on a silicon substrate by an electroless chemical deposition or electrochemical deposition. This step determines the shape of the final nanowires. Alternatively, metal nanoparticles can be spun on the silicon surface to form a metal layer, or a metal layer can be physically or chemically deposited on the silicon through a nanopatterned mask. The metal-coated silicon can be etched in a solution of HF, water, and H2O2 to produce porous silicon nanowires. Solvent can be added to the solution to modulate the features of the porous silicon nanowires. This work was done by Mauro Ferrari, Xuewu Liu, and Ciro Chappini of the University of Texas Health Science Center at Houston for Johnson Space Center. For further information, contact the JSC Innovation Partnerships Office at (281) 483-3809. In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:   The University of Texas  Health and Science Center at Houston  Office of Technology Management  7000 Fannin Street, Suite 720  Houston, TX 77030 MSC-24690-1

Posted in: Manufacturing & Prototyping, Semiconductors & ICs, Briefs

Read More >>

Post-Growth, In Situ Adhesion of Carbon Nanotubes to a Substrate for Robust CNT Cathodes

This technology can be used down-hole in oil wells, and in high-temperature, high-pressure, corrosive environments in the automotive industry. The field emission electron sources using carbon nanotubes (CNTs) are being targeted for low-power vacuum microelectronic applications for harshenvironment operation (high temperature, pressure, and corrosive atmosphere). While CNTs have demonstrated excellent properties in terms of low threshold field, low-power operation, and high current densities, one problem with vacuum electronic applications is poor adhesion of CNTs to the substrate on which they are synthesized. The chemical vapor deposition (CVD) process used to grow CNTs on silicon or other metallic substrates using an iron catalyst with a thin oxide diffusion barrier layer has consistently provided reproducible growth. The CNTs are only surface- adhering in these cases, and are easily removed from the surface with the application of minor forces — typically pressures of 20 to 60 kPa. This causes catastrophic failures of CNT field emitters since the applied field could exceed the adhesion strength of CNTs to the substrate.

Posted in: Manufacturing & Prototyping, Briefs

Read More >>

Thermal Mechanical Preparation of Glass Spheres

The forming process allows a very wide variety of material to be processed into spheres. Samples of lunar regolith have included small glass spheres. Most literature has suggested the small spheres were formed by meteorite impacts. The resulting transformation of kinetic energy to thermal energy caused the lunar surface to melt. The process yielded glass spheres. Recreating a meteorite impact that yields glass spheres is very challenging. Furthermore, the melting temperature of certain minerals on the Moon precludes the use of standard thermal techniques.

Posted in: Manufacturing & Prototyping, Briefs

Read More >>

The Significance of Critical Cleaning for Solar Module Fabrication

With increased governmental commitments to support renewable energy initiatives, winners and losers in solar module fabrication will be determined more quickly and by a variety of factors. One factor will be the elimination of defects to increase yields in the manufacturing process. Critical cleaning of substrates and superstrates is an essential component in achieving an optimal solar module fabrication process which reduces the cost per watt. Depending on the material being cleaned and the cleaning process employed, various Alconox products, including ALCONOX, DETOJET, LIQUINOX, CITRANOX and CITRAJET, have already been selected by major manufacturers as the critical cleaners of choice to reduce or eliminate manufacturing defects in solar module fabrication and are being employed in additional emerging processes.

Posted in: Manufacturing & Prototyping, White Papers

Read More >>

Key Procedures and Aqueous Cleaning Agents for Metal and Electronic Component Cleaning

Effective use of aqueous cleaners for electronics and metals hinges on the orchestration of basic variables of cleaning agents and procedures. The terms precision or critical cleaning apply whenever residue can cause a failure in the performance or function of the surface being cleaned. In general industry this includes electronic component cleaning, and surface preparation of metals prior to coating or bonding. Current practice for critical cleaning includes the use of volatile solvents, corrosive chemicals, and aqueous detergents. In today’ hazard-sensitive workplace, however, many companies are re-examining their use of volatile-solvent and corrosive-chemical cleaners. By using the right aqueous cleaning technologies now, it’ possible to minimize hazards without sacrificing critical cleaning performance. Many aqueous cleaners now offer cleaning performance comparable to - or better than solvent cleaning systems.

Posted in: Manufacturing & Prototyping, White Papers

Read More >>

Additive Manufacturing of Ti-6Al-4V Alloy Components for Spacecraft Applications

Additive manufacturing is a viable and affordable process to manufacture complex parts for aerospace, medical, and automotive applications. In the past two decades, there have been significant advancements in the field of additive manufacturing (AM) of titanium alloy (Ti-6Al-4V) and other metallic components for aerospace applications.

Posted in: Manufacturing & Prototyping, Briefs

Read More >>

White Papers

Magnetics Design: Specification, Performance & Economics
Sponsored by Datatronics
10 Ways to Make Your Wiring and Harness Design Faster and Better
Sponsored by Mentor Graphics
Selecting Miniature Motors for your Medical Devices
Sponsored by Portescap
Solving the System-Level Thermal Management Challenges of LEDs
Sponsored by Mentor Graphics
“Surfin’ on the Highway”
Sponsored by TDK
Changing Face of Robotics
Sponsored by Maplesoft

White Papers Sponsored By: