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Analysis of Ear Formation in Deep-Drawn Cups

Description: From Introduction: "The purpose of this paper is to show that the number and location of ears can be computed on the basis of single-crystal behavior and a knowledge of the orientation of the polycrystalline aggregate. Although the proposed method is a general one, only face-centered cubic metals are considered in this paper."
Date: May 1955
Creator: McEvily, Arthur J., Jr.
Partner: UNT Libraries Government Documents Department

A Study of Slip Formation in Polycrystalline Aluminum

Description: Note presenting experimental results that shed light on the assumptions that have been made in several attempts to bridge the gap between physical and mathematical theories of plasticity. The experimental results are compatible with, but do not verify, the conception that plastic deformation in strain-hardening materials is primarily due to slip. Results regarding the mechanism of plastic deformation, development of slip in a polycrystal, number of slip systems in operation, and equality of stresses or strains in all grains are provided.
Date: December 1951
Creator: Johnson, Aldie E., Jr. & Batdorf, S. B.
Partner: UNT Libraries Government Documents Department

Study of the Micro-Nonuniformity of the Plastic Deformation of Steel

Description: "The plastic flow during deformation of real polycrystalline metals has specific characteristics which distinguish the plastic deformation of metals from the deformation of ordinary isotropic bodies. One of these characteristics is the marked micro-nonuniformity of the plastic deformation of metals. P.O. Pashkov demonstrated the presence of a considerable micro-nonuniformity of the plastic deformation of coarse-grained steel wit medium or low carbon content" (p. 1).
Date: August 1957
Creator: Chechulin, B. B.
Partner: UNT Libraries Government Documents Department

Creep of Aluminum-Copper Alloys During Age Hardening

Description: Note presenting a study of the interrelation of aging during creep and of creep during aging in polycrystalline aluminum alloys containing 1 to 4 percent copper. Experimental procedures included interrupted creep tests, tensile tests of crept specimens, quantitative metallographic determination of the percent precipitation during creep, hardness measurements on unstressed and stressed aged alloys, X-ray studies of deformation in the crystalline lattice, and microscopic examination of the surface-deformation markings.
Date: February 1958
Creator: Underwood, E. E.; Marsh, L. L. & Manning, G. K.
Partner: UNT Libraries Government Documents Department

Predicting fracture in micron-scale polycrystalline silicon MEMS structures.

Description: Designing reliable MEMS structures presents numerous challenges. Polycrystalline silicon fractures in a brittle manner with considerable variability in measured strength. Furthermore, it is not clear how to use a measured tensile strength distribution to predict the strength of a complex MEMS structure. To address such issues, two recently developed high throughput MEMS tensile test techniques have been used to measure strength distribution tails. The measured tensile strength distributions enable the definition of a threshold strength as well as an inferred maximum flaw size. The nature of strength-controlling flaws has been identified and sources of the observed variation in strength investigated. A double edge-notched specimen geometry was also tested to study the effect of a severe, micron-scale stress concentration on the measured strength distribution. Strength-based, Weibull-based, and fracture mechanics-based failure analyses were performed and compared with the experimental results.
Date: September 1, 2010
Creator: Hazra, Siddharth S. (Carnegie Mellon University, Pittsburgh, PA); de Boer, Maarten Pieter (Carnegie Mellon University, Pittsburgh, PA); Boyce, Brad Lee; Ohlhausen, James Anthony; Foulk, James W., III & Reedy, Earl David, Jr.
Partner: UNT Libraries Government Documents Department

Thermal conductivity measurements of Summit polycrystalline silicon.

Description: A capability for measuring the thermal conductivity of microelectromechanical systems (MEMS) materials using a steady state resistance technique was developed and used to measure the thermal conductivities of SUMMiT{trademark} V layers. Thermal conductivities were measured over two temperature ranges: 100K to 350K and 293K to 575K in order to generate two data sets. The steady state resistance technique uses surface micromachined bridge structures fabricated using the standard SUMMiT fabrication process. Electrical resistance and resistivity data are reported for poly1-poly2 laminate, poly2, poly3, and poly4 polysilicon structural layers in the SUMMiT process from 83K to 575K. Thermal conductivity measurements for these polysilicon layers demonstrate for the first time that the thermal conductivity is a function of the particular SUMMiT layer. Also, the poly2 layer has a different variation in thermal conductivity as the temperature is decreased than the poly1-poly2 laminate, poly3, and poly4 layers. As the temperature increases above room temperature, the difference in thermal conductivity between the layers decreases.
Date: November 1, 2006
Creator: Clemens, Rebecca; Kuppers, Jaron D. & Phinney, Leslie Mary
Partner: UNT Libraries Government Documents Department

Fatigue of polycrystalline silicon for MEMS applications: Crack growth and stability under resonant loading conditions

Description: Although bulk silicon is not known to exhibit susceptibility to cyclic fatigue, micron-scale structures made from silicon films are known to be vulnerable to degradation by fatigue in ambient air environments, a phenomenon that has been recently modeled in terms of a mechanism of sequential oxidation and stress-corrosion cracking of the native oxide layer.
Date: December 5, 2001
Creator: Muhlstein, C.L.; Howe, R.T. & Ritchie, R.O.
Partner: UNT Libraries Government Documents Department

Technical evaluation of Solar Cells, Inc., CdTe modules and array at NREL

Description: The Engineering and Technology Validation Team at the National Renewable Energy Laboratory (NREL) conducts in-situ technical evaluations of polycrystalline thin-film photovoltaic (PV) modules and arrays. This paper focuses on the technical evaluation of Solar Cells, Inc., (SCI) cadmium telluride (CdTe) module and array performance by attempting to correlate individual module and array performance. This is done by examining the performance and stability of the modules and array over a period of more than one year. Temperature coefficients for module and array parameters (P{sub max}V{sub oc}, V{sub max}, I{sub sc}, I{sub max}) are also calculated.
Date: May 1, 1996
Creator: Kroposki, B.; Strand, T. & Hansen, R.
Partner: UNT Libraries Government Documents Department

Integrating Deposition, Processing, and Characterization Equipment within the National Center for Photovoltaics

Description: The purpose of the process integration project of the National Center for Photovoltaics (NCPV) is to develop an infrastructure that will allow researchers to gain new knowledge that is difficult--if not impossible--to obtain with existing equipment. This difficulty is due, in part, to the state of our existing tool set, which lacks sufficient in-situ or real-time measurement capabilities, or lacks access to analytical tools where the sample remains in a controlled environment between deposition and processing or measurement. This new infrastructure will provide flexible and robust integration of deposition, processing (etching, annealing, etc.), and characterization tools via a standardized transfer interface such that samples move between tools in a controlled ambient. This concept will also require the cooperation of experts from various material technologies and characterization disciplines to work directly with each other to obtain answers to key scientific and technological questions. Ultimately, this synergistic effort between NREL staff, universities, and the photovoltaic (PV) industry--around an integrated tool base--will add to the PV knowledge base and help move many PV technologies forward.
Date: January 1, 2005
Creator: Nelson, B.; Robbins, S. & Sheldon, P.
Partner: UNT Libraries Government Documents Department

Polycrystalline Thin Film Device Degradation Studies

Description: Oxygen during vapor CdCl2 (VCC) treatments significantly reduced resistive shunts observed in CdS/CdTe polycrystalline devices using thinner CdS layers during 100 deg C, open-circuit, 1-sun accelerated stress testing. Cu oxidation resulting from the reduction of various trace oxides present in as-grown and VCC treated films is the proposed mechanism by which Cu diffusion, and subsequent shunts are controlled. Graphite paste layers between metallization and CdTe behave like diffusion barriers and similarly benefit device stability. Ni-based contacts form a protective Ni2Te3 intermetallic layer that reduces metal diffusion but degrades performance through increased series resistance.
Date: November 1, 2005
Creator: Albin, D. S.; McMahon, T. J.; Pankow, J. W.; Noufi, R.; Demtsu, S. H. & Davies, A.
Partner: UNT Libraries Government Documents Department

Development and testing of a Mudjet-augmented PDC bit.

Description: This report describes a project to develop technology to integrate passively pulsating, cavitating nozzles within Polycrystalline Diamond Compact (PDC) bits for use with conventional rig pressures to improve the rock-cutting process in geothermal formations. The hydraulic horsepower on a conventional drill rig is significantly greater than that delivered to the rock through bit rotation. This project seeks to leverage this hydraulic resource to extend PDC bits to geothermal drilling.
Date: January 1, 2006
Creator: Black, Alan (TerraTek, Inc.); Chahine, Georges (DynaFlow, Inc.); Raymond, David Wayne; Matthews, Oliver (Security DBS); Grossman, James W.; Bertagnolli, Ken (US Synthetic) et al.
Partner: UNT Libraries Government Documents Department

Device physics of thin-film polycrystalline cells and modules. Annual subcontract report, December 6, 1994--December 5, 1995

Description: This report describes the work on a number of projects carried out at both the cell and the module level during the past year. We investigated the effects of CdS thickness in collaboration with six CdTe cell-fabrication laboratories; there appears to be a critical thickness, between 500 and 1000 {Angstrom} depending on fabrication process, below which junction quality is degraded. Our experimental and modeling project showed that conduction-band offsets less than about 0.3 eV have little effect on the performance of a CuInSe{sub 2} (CIS) or CdTe cell under the traditional assumption that the absorber material accounts for most of the depletion region. The work in several other cell projects included the role of Ga distribution in Cu{sub 1-x}Ga{sub x}Se{sub 2} (CIGS) cells, changes that occur in some cells over time, optical characterization of commonly used CdTe substrates and front contacts, and comparative characterization of CIGS cells where identical absorbers were combined with variations in window fabrication. Our work on the primary module-characterization project developed the successful use of chopping-frequency variation in a scanning beam to separate photocurrent and shunting problems affecting individual cells of an encapsulated module. Other module projects included modifications in analysis required by the typical module-cell geometry, the practical effect of nonuniformities in light intensity or cell temperature, and the advantages and pitfalls of forward bias across a module during a light scan.
Date: August 1, 1996
Creator: Sites, J.R.
Partner: UNT Libraries Government Documents Department

Energy Production and Performance of Polycrystalline Silicon Technology Photovoltaic Modules in the Field: Preprint

Description: Presented at the 2001 NCPV Program Review Meeting: Energy production and performance of polycrystalline silicon technology photovoltaic modules in the field. Six polycrystalline silicon photovoltaic modules--two apiece from three manufacturers--were simultaneously deployed outdoors on the performance and energy ratings testbed at NREL's Outdoor Test Facility (OTF) in June 2000. In situ electrical performance and energy production from these modules obtained under ambient conditions in the field between June 2000 and August 2001 are compared. The average effective efficiency--derived from module energy out divided by solar energy in calculations averaged on a weekly basis--is analyzed and compared with module current-voltage measurements performed at standard reporting conditions (SRC). The effective efficiencies exhibit seasonal variations correlated with average module temperatures--becoming larger at colder temperatures. The performance ratios (PRs) defined as the effective efficiency divided by the efficiency at SRC, range from 78% to 96%, depending on the module and time of the year. The PRs exhibit seasonal variations that range from 11% to 15%.
Date: October 1, 2001
Creator: del Cueto, J. A.
Partner: UNT Libraries Government Documents Department

Polycrystalline Thin-Film Multijunction Solar Cells

Description: We present a digest of our research on the thin-film material components that comprise the top and bottom cells of three different material systems and the tandem devices constructed from them.
Date: November 1, 2005
Creator: Noufi, R.; Wu, X.; Abu-Shama, J.; Ramanathan, K; Dhere, R.; Zhou, J. et al.
Partner: UNT Libraries Government Documents Department