Archives—February 2009

Environmental Brake Engineering: Materials Countermeasures

Friday, February 27, 2009 3:00 – 4:00 pm
Room 610, M&M Building

Paul Sanders
Chassis Materials Technical Leader
Ford Research and Advanced Engineering
Ford Motor Company


Failure mode avoidance is a product development strategy at Ford Motor Company todeliver improved vehicle performance. The root cause of customer perceived failuremodes such as brake wear, dust, and vibration are analyzed and individual materialscountermeasures are discussed. The high-level environmental impact of theseindependent countermeasures is noted.After this “component-level” approach, a system-level solution will be presented thataddresses the same failure modes. This system approach will require rotor substrateand wear-layer materials development. Through a detailed understanding of the systemperformance, the materials requirements can be clearly defined. In the case of the rotorsubstrate, the material must have > 10 MPa yield strength and < 10-5/s creep rate at ≈500°C. The low stress and time at temperature (< 1 hr lifetime) may enable the design ofa high-temperature aluminum alloy for the rotor structure. The friction wear layer musthave similar tribological behavior to the baseline cast iron in addition to matching thermalexpansion and galvanic potential of the aluminum substrate. General corrosionresistance will significantly reduce rotor and lining wear. This materials-system solutionwill facilitate a lightweight, “lifetime” brake rotor that reduces use-phase environmentalimpact.

Surfaces and Interfaces in Nanoscale Electronic Materials: From Understanding to Engineering

Monday, February 23, 2009 4:00 – 5:00 pm
Room 610, M&M Building

Pengpeng Zhang
Department of Chemistry and Physics
The Pennsylvania State University


Surfaces and interfaces play a critical role in determining properties andfunctions of nanomaterials, in many cases simply dominating bulk properties,owing to the large surface- and interface-to-volume ratio. One can further engineerand improve the performance of nanoscale devices through the control of surfaceand interface chemistry.  Using Si nanomembranes as a model system, we haveinvestigated how surfaces and interfaces influence electrical transport propertiesat the nanoscale by means of scanning tunneling microscopy (STM) and fourprobe measurements. We show that electronic conduction in Si nanomembranesis not determined by bulk dopants but by the interplay of surface and interfaceelectronic structures with the “bulk” band structure of the thin Si membrane, whichcan be thought of as “surface transfer doping.” Additionally, we characterize selfassembled alkanethiolate monolayers (SAMs) on Au{111} with embedded staticdipole groups in the adsorbate molecules using Kelvin probe force microscopy(KPFM), X-ray photoelectron spectroscopy (XPS) and quantitative infraredvibrational spectroscopy (IR) techniques. We have modulated the metal workfunction by adjusting the orientation of the embedded dipole and the geometricstructures of the SAMs, which will facilitate applications in charge injection inorganic electronic devices. Recently, we have also studied divergent dipoles andintermolecular interactions in geometrically identical adsorbates, finding thatdiffering orientations of molecular dipole moments influence SAM properties,including the stability of the monolayers in competitive binding and exchangeenvironments. These studies demonstrate that a thorough physical understandingof emerging phenomena at the nano- or molecular scale can advancetechnologies in nanoelectronics and molecular electronics.