Entity

Time filter

Source Type


Berkun I.,Michigan State University | Demlow S.N.,Michigan State University | Suwanmonkha N.,Michigan State University | Hogan T.P.,Michigan State University | And 2 more authors.
Materials Research Society Symposium Proceedings | Year: 2013

A temperature dependent Hall Effect measurement system with software based data acquisition and control was built and tested. Transport measurements are shown for boron-doped single crystal diamond (SCD) films deposited in a microwave plasma-assisted chemical vapor deposition (MPCVD) reactor. The influence of Ohmic contacts and temperature control accuracy are studied. For a temperature range of 300K-700K IV curves, Hall mobilities and carrier concentrations are presented. © 2013 Materials Research Society. Source


Grant
Agency: National Science Foundation | Branch: | Program: STTR | Phase: Phase I | Award Amount: 149.99K | Year: 2009

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This Small Business Technology Transfer Phase I project will demonstrate the effectiveness of a new window insulation technology with thermal performance properties comparable to a well insulated wall. In the United States, buildings account for more than 40% of total energy consumption. Because windows are between 20-40% of the vertical surface area of an average building, they consume 30-60% of heating and cooling energy, representing an annual impact of more than 4.1 quadrillion BTU of primary energy, costing building owners over $40 billion/year. Our innovation is to use nanometer sized spherically shaped silica particles attached to glass fibers to create an insulation material with extremely small points of contact that can be used to make thin vacuum insulation panels. This Phase I project will determine the feasibility of incorporating these nanoparticle-modified fibers into innovative Multilayer Vacuum Insulation Panels to achieve target thermal insulation properties in a commercially viable, dynamic window covering. This technology will exceed the US DOE's target window insulation properties in a commercially viable product that will serve as a cost effective solution for net-zero energy new construction as well as a retrofit product to improve the energy efficiency of existing buildings. By facilitating the development and commercialization of a product that will substantially reduce unwanted heat transfer through fenestration, the research in this Phase I STTR project will contribute a partial solution to global energy and environmental challenges. The development of new core materials for vacuum insulation panels offers enormous opportunities for the improvement of the energy efficiency of buildings while also contributing a substantial financial savings over time. The educational impact of this research will be significant on two levels: 1) a substantial amount of the work will be performed by students under the direct supervision of recognized experts and 2) the research will significantly advance the state of the art in thermal insulation technology.


Haubold L.,Fraunhofer Center for Laser Applications | Schuelke T.,Fraunhofer Center for Laser Applications | Becker M.,Fraunhofer Center for Laser Applications | Woodrough G.,Symmetry Medical
Diamond and Related Materials | Year: 2010

Hydrogen-free and predominantly tetrahedrally bonded amorphous carbon thin films (ta-C) are excellent coatings to protect surfaces from wear due to their low coefficient of friction and high hardness. Since these coatings may be several times harder than common engineering materials counterpart wear can be significant. Therefore the surface texture of the ta-C coating is critical to wear applications. While the surface roughness is an important factor, the paper shows that other surface texture parameters have to be considered as well to predict the wear performance of the coating. Wear data are compared of as deposited, polished and brushed ta-C coatings. The results show that typically referenced average values for the surface roughness such as Ra and Rz may prove insufficient to reliably predict the wear behavior of the coating. Additional parameters describing the surface texture such as the "Skewness" (Rsk) and "Kurtosis" (Rku) can provide relevant information. For example, a brushed ta-C surface with an average roughness of Ra = 31 nm showed a tenfold improved wear performance over a polished ta-C surface with an average roughness of Ra = 10 nm. This phenomenon is explained by analyzing the Rsk and Rku data, which prove to more closely capture the post-treatment specific changes to the surface texture of the coatings. © 2009 Elsevier B.V. All rights reserved. Source


Schuelke T.,Fraunhofer Center for Laser Applications | Grotjohn T.A.,Michigan State University
Diamond and Related Materials | Year: 2013

The empirical know-how of single crystalline diamond polishing has been developed over centuries in the diamond gem cutting industry. Since the 1950s new and varied uses and potential applications for synthetically produced diamond have been consistently proposed and developed. This innovation process continues with the availability of ever better, more specialized and less costly single crystalline and polycrystalline diamond materials. Yet, the potential exploitation of this hardest of materials is still in its infancy. Polishing is a critical and limiting step for advancing diamond applications in terms of cost effective processing and the achievable material surface finish. The current state-of-the-art of polishing single crystalline and polycrystalline diamond materials is reviewed based on the published literature. The material removal process during traditional mechanical polishing using diamond grit and polishing wheels is strongly anisotropic and depends upon crystal planes and polishing directions. Wear debris analyses and molecular dynamic simulations led to the understanding that this anisotropy is primarily caused by a mechanically induced transition from diamond to an amorphous carbon phase rather than by microchipping as previously thought. Mechanical polishing also leads to subsurface damage and limits the achievable surface finish for single crystalline diamond. Advanced techniques are discussed to improve the polished crystal's surface quality. Mechanical polishing of polycrystalline diamond films and freestanding plates is particularly slow due to the intrinsic structure variations in such materials. To overcome these limitations faster polishing techniques have been developed and are reviewed and compared. These techniques introduce additional chemical and physical means of material removal extending the capabilities of mechanical polishing. There is no single method that can address all requirements, but the available variety affords the careful selection of an optimal process for a given task. Finally, while diamond polishing is a subject of interest since centuries, it still remains a very important research area required to unfold the promise of diamond as a technical material. © 2012 Elsevier B.V. Source


Lu J.,Michigan State University | Gu Y.,Michigan State University | Grotjohn T.A.,Michigan State University | Grotjohn T.A.,Fraunhofer Center for Laser Applications | And 3 more authors.
Diamond and Related Materials | Year: 2013

The detailed experimental behavior of a microwave plasma assisted chemical vapor deposition (MPACVD) reactor operating within the high, 180-300 torr, pressure regime is presented. An experimental methodology is described that first defines the reactor operating field map and then enables, while operating at these high pressures, the determination of the efficient, safe and discharge stable diamond synthesis process window. Within this operating window discharge absorbed power densities of 300-1000 W/cm3 are achieved and high quality, single crystal diamond (SCD) synthesis rates of 20-75 μm/h are demonstrated. The influence of several input experimental variables including pressure, N2 concentration, CH4 percentage and substrate temperature on SCD deposition is explored. At a constant pressure of 240 torr, a high quality, high growth rate SCD synthesis window versus substrate temperature is experimentally identified between 1030 and 1250 C. When the input nitrogen impurity level is reduced below 10 ppm in the gas phase the quality of the synthesized diamond is of type IIa or better. © 2013 Elsevier B.V. Source

Discover hidden collaborations