Characteristics of Eddy Current Attenuation and Thickness Measurement of Metallic Plate

Abstract(#br)In eddy current testing, the law of attenuation of eddy current (EC) is of great concern. In conductive half space under the excitation of uniform magnetic field, the EC density decreases exponentially in the depth direction. However, in conductor with finite thickness tested by coil, the distribution of EC in the depth direction is more complicated. This paper studies the characteristics of EC attenuation in metallic plate of finite thickness. Simulation results show that there is an EC reflection at the bottom of plate, which changes the law of EC attenuation. A new concept, namely the equivalent attenuation coefficient, is proposed to quantify the speed of EC attenuation. The characteristics of EC attenuation are utilized to explain the nonmonotonic relation between coil..

Advances in test and measurement of the interface adhesion and bond strengths in coating-substrate systems, emphasising blister and bulk techniques

In this paper, recent advances in the minimum-destructive testing of the adhesion of coating-substrate systems are reviewed, focusing on key techniques such as micro- and nano-scale levels of indentation, scratching, laser-induced wave shock, as well as the blister and buckle approach. Along with adhesion failure tests, the latest and most extensive applications of the adhesion test methods in nano-, micro- and bulk-coating technology and the associated techniques to determine the minimum damage defects left on the coatings are discussed and their use reviewed

Production and Characterization of Novel Nanostructure Materials

The research presented here was conducted in the Department of Chemistry at the University of Pittsburgh, in the Surface Science Center, under the supervision of Prof. John T. Yates, Jr. The work described can be divided into two main parts. As the size of materials decreases, they experience confinement. The electronic properties of materials are strongly correlated to the confinement experienced by the material or device being studied. New tools and experimental techniques need to be developed in order to probe the properties of such objects at sub-micrometer scales in a non-interfering way. The development of such an instrument and its usefulness in measuring electronic properties of confined objects is the topic of the first part of this dissertation, covering sections 1, 5 and 6. The Nanoworkbench is a unique multiple-probe instrument operating under ultrahigh vacuum conditions. It combines a molecular-beam epitaxy chamber for nucleation of quantum dots or the growth of thin films, a preparation and analysis chamber equipped with standard surface science tools such as Auger electron spectroscopy, X-ray photoelectron spectroscopy and mass spectrometry. The core of the system is the multiple-probe STM chamber combined with a scanning electron microscope, allowing precise controlled motion of the probes and the realization of sub-micrometer scale four-point probe measurements. This instrument was fully conceived, designed and assembled in the Department of Chemistry, at the University of Pittsburgh. The application of the Nanoworkbench to sub-micrometer four-point probe conductivity measurements and the formation of a roaming field-effect transistor on a silicon-on-insulator surface is demonstrated in section 5. Additionally the Nanoworkbench was used to electrically sense the normal motion of the interface between a metal (Al(111)) and its oxide coating, and a semiconductor (Si(100)) during its oxidation, finding that Al(111) oxidizes in conformance with the Mott-Cabrera model. Here Al3+ ions move away from the Al/Al2O3 interface to the outer Al2O3 surface when oxide film growth occurs. In contrast, oxygen penetration into covalent Si(100) occurs during oxide film formation. The second part of this dissertation - sections 7 to 10 - deals with the formation of dense arrays of sub-10nm Ge islands on Si(100). Upon deposition of Ge on Si(100), Ge islands are randomly nucleated on the surface by self-assembly after the formation of a wetting layer, whose thickness depends on the experimental conditions. These islands have rather large diameters and a broad size distribution and are therefore not suitable for application in quantum computing architecture for instance. The object of this study is the formation of arrays of Ge islands with control over both the island diameter (10nm, ± 2nm) and the islands spacing (as small as 35nm, ± 1nm). We will show that the pre-adsorption of small islands of carbon on Si(100) leads to the formation of Ge islands that are smaller than Ge islands nucleated on a clean Si(100) substrate. We can use this carbon effect" by creating a carbon template on the Si(100) surface by electron-beam-induced deposition. These carbon deposits transform into SiC after annealing under UHV conditions. Upon subsequent Ge deposition, ultra-small Ge islands will nucleate by directed self-assembly on the surface in perfect registry with the carbon template.Conceptual ideas will be provided as a background for the research described in sections 5 to 10. These conceptual ideas include a description of the four-point probe measurement technique, the framework of the Mott-Cabrera theory for oxide film growth on metal surfaces, a description of heteroepitaxy, and finally the description of the formation of Ge islands in Si/Ge and Si/C/Ge system along with the attempts at ordering these islands

Electric and Magnetic Manipulation of Liquid Metals

Over the past decade, gallium-based liquid metals have attracted enormous attention, emerging as a new cutting-edge multi-functional material for reconfigurable electronics, soft robotics, microfluidics, and biomedical applications, based on utilizing the intrinsic advantages of liquid metal. These unique advantages that combine high electrical conductivity, thermal conductivity, biocompatibility, low mechanical compliance, and viscosity all-in-one make the liquid metal applicable for a tremendous number of applications. Moreover, the self-passivating oxide skin of the liquid metal in an ambient environment forms a unique core (oxide skin)-shell (liquid metal) structure and provides a new strategy for two-dimensional thin films with a thickness of a few nanometers. The reports on the liquid metal can be mainly divided into three categories: 1) liquid-metal-based composite structures; 2) the core-shell strategy for thin films; and 3) electrochemical manipulation of the liquid metal in electrolyte. The liquid metal (LM) composites represent material systems in which LM alloys are either suspended as small droplets within a soft polymer matrix or mixed with metallic nanoparticles to form a biphasic composition, through which the electrical, dielectric, and thermal properties of composites can be controlled, thus enabling their applications in soft-matter sensing, actuation, and energy harvesting. Moreover, the fluidity and conductivity of the liquid metal make it suitable to be directly patterned (i.e., liquid metal ink) on various soft substrates (e.g., polydimethylsiloxane (PDMS) for ultra-stretchable electronics. Compared to the traditional electronics, which are typically composed of intrinsically rigid materials that have limited deformability, the liquid metal based soft electronics are highly flexible, stretchable, and conformable. Most importantly, they are capable of electrical self-healing, enabling their electrical functionality, even under severe damage. These properties and applications of liquid metal composites show great potential for practical usage

NASA SBIR abstracts of 1990 phase 1 projects

The research objectives of the 280 projects placed under contract in the National Aeronautics and Space Administration (NASA) 1990 Small Business Innovation Research (SBIR) Phase 1 program are described. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses in response to NASA's 1990 SBIR Phase 1 Program Solicitation. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 280, in order of its appearance in the body of the report. The document also includes Appendixes to provide additional information about the SBIR program and permit cross-reference in the 1990 Phase 1 projects by company name, location by state, principal investigator, NASA field center responsible for management of each project, and NASA contract number

Electromagnetic Interference Shielding Effectiveness of Interlayered Systems Containing Metal-Oxide, Conducting Polymer and Carbon Nanotube Reinforced Polymeric Composites

The Electromagnetic Interference (EMI) Shielding Effectiveness (SE) has become one of the important requirements for the devices associated with telecommunication systems consisting of large frequency bands. The degradation of the quality of transmitting signal influenced by frequencies emitting from external sources can be reduced by covering the circuits of the devices by EMI Shielding materials like polymer composites, metal-based nanofiber mats, the metal of oxide films, etc. The investigation strives for the attenuation of EMI by introducing two composite mats from conducting polymer-based, multiwalled carbon nanotubes (MWCNTs) coated Nylon 6 nanofiber composites. Two other composite mats are also developed by the Forcespinning® method using sol solution of functionalized multiwalled carbon nanotubes (f-MWCNTs) and magnetite (Fe3O4) into as-prepared polyacrylonitrile (PAN) which is then carbonized at elevated temperature to convert it into carbon nanofiber (CNF). A total of four layers of mats are stacked and compression molded together to develop one multilayered composite (MLC 1). The Fe3O4 has higher magnetic properties which may provide a good magnetic loss effect. The focus is to investigate the synergistic effects between higher magnetic Fe3O4, conductive MWCNTs nanofillers with the dielectric CNF, conducting polymer, and functionalized MWCNTs coated nanofiber composite which can provide information about the dominating mechanism. (Absorption, reflection, or multiple reflections) for EMI SE. The multilayered composite (MLC 2) consisting 8 layers (repeating the stacking sequence again) has given the highest obtained value more than 40 dB EMI SE in the frequency range from 300–500 MHz. The results will bring some findings of optimized materials yielding good EMI SE in lightweight applications