Scott Walck - Profile on Academia.edu (original) (raw)
Papers by Scott Walck
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
MoVN-Cu Coatings for In Situ Tribocatalytic Formation of Carbon-Rich Tribofilms in Low-Viscosity Fuels
ACS Applied Materials & Interfaces
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
A Field-Effect Fim Specimen Holder For Jeol 200CX
Proceedings, annual meeting, Electron Microscopy Society of America, 1985
Very large field-induced stresses are imposed on specimens in the Field-Ion Microscope (FIM) and ... more Very large field-induced stresses are imposed on specimens in the Field-Ion Microscope (FIM) and the magnitude of these stresses approach the theoretical strengths for many metals. The interaction of the field- induced stresses with defects such as grain boundaries or precipitates is usually the cause of fracture failure of samples in the FIM. It has long been known that the stresses in the emitters cause most dislocations to be swept out of the sample in the field-affected region. Frequently, results obtained by FIM techniques are questioned because of the presence of these stresses. Eaton and Bayuzick used a FIM image-brightness, mapping technique to find the actual geometry of a tungsten specimen and then obtained the stress state within it by using finite element analysis. Their analysis shows the distribution of shear stresses to be quite complicated.
Analysis of Selected Area Diffraction Patterns With Winjade
Microscopy and Microanalysis, 1998
The analysis of Selected Area Diffraction (SAD) patterns that are collected from a single phase m... more The analysis of Selected Area Diffraction (SAD) patterns that are collected from a single phase material having sufficient crystallites to provide continuous rings is relatively straightforward. However, when this condition is not met and there may be several phases present having rings of a spotty nature, the pattern is complex and can be quite difficult to analyze manually because of the vast number of discrete spots. WinJade from MDI is an X-ray diffraction (XRD) analysis program with an Electron Diffraction Program Module (EDPM) that can be used to aid in the analysis of SAD patterns. The EDPM produces Integrated Circular Density Plots (ICDP), which are one-dimensional intensity profiles plotted as a function of equivalent XRD 20 values or crystal d-spacings. These ICDP's can be overlayed with XRD patterns or with reference lines from the NIST and JCPDS crystalline databases for direct comparisons.
TEM examination of wear debris from a self-lubricating metal-matrix composite prepared by ultramicrotomy
Proceedings, annual meeting, Electron Microscopy Society of America, 1995
Self-lubricating materials are usually multi-phase composites comprising of a solid lubricant dis... more Self-lubricating materials are usually multi-phase composites comprising of a solid lubricant dispersed in a matrix of a metal or a polymer. During sliding contact, chemical reactions among the constituent phases of the composite, the counterface and the gases in the surrounding environment are inevitable. The wear debris is a product of such chemical (or tribochemical) reactions. Determination of the chemistry and the crystal structure of the wear debris is therefore crucial to the understanding of the wear mechanisms. In self-lubricating composites, the quantity of the debris generated is often too small to perform x-ray diffraction.It has been previously demonstrated that self-lubricating aluminum metal-matrix composites can be synthesized by dispersing silicon carbide and tungsten disulfide particles in commercial aluminum alloy matrices. A typical microstructure of an Al-0.10SiC-0.05WS2 MMC is shown in Fig. 1. The friction and wear test was performed, in a ball-on-disk configur...
Electron microscopy of pulsed-laser-deposited thin films for tribological applications
Proceedings, annual meeting, Electron Microscopy Society of America, 1993
Pulsed laser deposition (PLD) is a novel thin film deposition technique which has recently been a... more Pulsed laser deposition (PLD) is a novel thin film deposition technique which has recently been applied to tribological materials with great success. PLD has several inherent advantages over conventional deposition techniques, including excellent film adhesion, replication of target chemistry, and low film deposition temperature. Because load-bearing materials are typically hardened, heat treated alloys, these properties of PLD are ideally suited for tribological applications. In addition to being a relatively simple deposition technique, considerable processing flexibility is inherent with PLD. Dense, nonporous, stoichiometric films of solid lubricants, such as MoS2, have been grown having long wear lives with low coefficients of friction. Hard coating materials, such as TiC, have been grown at room temperature that were polycrystalline and had excellent wear properties.A significant feature of pulsed laser deposited (PLD) thin films is the incorporation of spherical particles with...
Combustion and Flame, 2019
Aluminum nanoparticles (nAl) have great potential for energetic applications. However, the native... more Aluminum nanoparticles (nAl) have great potential for energetic applications. However, the native oxide shell (amorphous alumina, Al 2 O 3 ) inhibits efficient energy release and acts as a barrier for aluminum (Al) oxidation. An energetic oxidizer, aluminum iodate hexahydrate (AIH), has recently been demonstrated as an effective coating for nAl. However, the current chemical synthesis method has led to widely varying AIH concentrations on nAl particles. Plasma surface treatment of nAl is a novel "energy coupled to material" technique which alters the nAl surface properties without changing the bulk active Al core. This work explores a new approach to engineering the nAl surface using atmospheric argon (Ar) plasma to accomplish two objectives: (1) reduce the nAl oxide shell thickness, and (2) synthesize AIH on the treated particle surface. Transmission electron microscopy (TEM) reveals more than 40% reduction in the oxide thickness after 10 min Ar plasma treatment. Laser-induced air shock from energetic materials (LASEM) experiments show significant energy release enhancements for the plasma-treated nAl with AIH coating (PT-nAl-AIH) compared to commercial nAl as well as untreated nAl with AIH coating (UT-nAl-AIH). The results demonstrate the potential of applying atmospheric plasma techniques to modify nAl for enhanced reactivity.
Plasmonic gold nanostars as optical nano-additives for injection molded polymer composites
Nanotechnology, 2017
Nanoscale engineering of noble metal particles has provided numerous material configurations to s... more Nanoscale engineering of noble metal particles has provided numerous material configurations to selectively confine and manipulate light across the electromagnetic spectrum. Transitioning these materials to a composite form while maintaining the desired resonance properties has proven challenging. In this work, the successful integration of plasmon-focusing gold nanostars (GNSs) into polymer nanocomposites (PNCs) is demonstrated. Tailored GNSs are produced with over a 90% yield and methods to control the branching structures are shown. A protective silica capping shell is employed on the nanomaterials to facilitate survivability in the high temperate/high shear processing parameters to create optically-tuned injection molded PNCs. The developed GNS PNCs possess dichroic scattering and absorption behavior, opening up potential applications in the fields of holographic imaging, optical filtering and photovoltaics.
Characterization and visualization of the state and entanglement of two spins
European Journal of Physics, Jul 1, 2001
We characterize and classify the quantum states of a pair of spin-½ particles in terms of the ent... more We characterize and classify the quantum states of a pair of spin-½ particles in terms of the entanglement of the pair. We describe a general strategy for classifying the quantum states of entangled systems, and apply it to the simplest entangled system available - a pair of spin-½ particles. The method is based on local unitary transformations. We give a set of six parameters that describe an arbitrary pure state of a pair of spins, one of which is the entanglement of the pair. We discuss visual representations of the state of this system, and propose a visualization using a Bloch sphere for each subsystem and a disc to record the `shared' information.
Substrates coated with a polycrystalline functional coating
Architecture of multilayer nanocomposite coatings with super-hard diamond-like carbon layers for wear protection at high contact loads
Wear, 1997
ABSTRACT Super-hard and low-friction diamond-like carbon (DLC) coatings deposited at low temperat... more ABSTRACT Super-hard and low-friction diamond-like carbon (DLC) coatings deposited at low temperatures are currently of great interest for wear protection and friction reduction. However, their high hardness (50–80 GPa), intrinsic stresses, and poor adhesion limit their use to applications where contact pressures are below I GPa and the coating thickness is below 0.5 μm to prevent cracking and delamination. These negative effects are especially pronounced when the coatings are applied to relatively soft substrates, such as steels. The limitations were removed by a multilayer design, where metal and ceramic layers were used to increase the load support capability, improve the adhesion strength, and increase the thickness of DLC layers. Existing approaches to the design of tough multilayer coatings were considered critically and a coating architecture was suggested using the following concepts: (i) formation of a load support and adhesion promoting underlayer with mechanical characteristics varied gradually from the substrate to the DLC layer; (ii) separation of hard DLC layers with interlayers of softer material to reduce stresses and brake cracks; (iii) use of crystalline interlayers with thickness permitting operation of dislocation sources for stress relaxation and deflection of cross-sectional cracks. The development of these concepts is discussed sequentially from bilayer ceramic/DLC coatings to functionally gradient metal/carbide/DLC coatings, and finally to nanocomposite coatings consisting of stacks of Ti/DLC, TiC/DLC, and CN/DLC layers with individual thickness within 10–60 nm deposited onto a gradient TiTiC-DLC underlayer. The coatings were deposited onto stainless steel substrates by a hybrid of magnetron sputtering and pulsed laser deposition. They had a 1–2 μm total thickness of super-hard (60–70 GPa) DLC layers and resisted delamination to 50–80 N loads in scratch adhesion tests. In ball-on-disk sliding tests, these coatings supported Hertzian contact pressures above 2 GPa and had friction coefficients around 0.1. Their wear lives exceed 106 cycles under initial contact pressures of 1.4 GPa. The conceptual architecture of multilayer nanocomposite coatings presented extends the range of wear resistant applications for super-hard DLC materials.
Applications of Reactive Gas Plasma Cleaning Technology in Minimizing Contamination Of Specimens During Transmission and Analytical Electron Microscopy
The generation and usage of a reactive gas plasma for a wide range of applications has been cited... more The generation and usage of a reactive gas plasma for a wide range of applications has been cited since the early 1970's. More recently, the use of a plasma generating system has been applied to analytical transmission electron microscopy to minimize and, in some cases, eliminate the problems associated with various contamination sources, including the specimen holder and the specimen itself. Although the technology is well known, no definitive characterization of process parameters has been developed for specimen and specimen holder cleaning applications. An investigation of the effects that power levels and gas mixtures have upon contamination rates and removal were done using a Philips CM30T. Measurements of contamination rates both prior to and following plasma cleaning were done to characterize the effects of various parameter changes. Results of different process parameters and contamination rates will be reported.
MRS Proceedings, 1991
Thin films of titanium carbide (TiC) and boron carbide (B4C) were grown by excimer pulsed laser d... more Thin films of titanium carbide (TiC) and boron carbide (B4C) were grown by excimer pulsed laser deposition (PLD) at room temperature (RT) and 300°C. Films were deposited using the output of an excimer laser operating with KrF gas (λ = 248 nm, 15 ns pulse duration) to ablate hot-pressed targets. Film chemistry, morphology, and crystallinity were investigated. Stoichiometric, crystalline TiC films were grown on 440C stainless steel and NaCl substrates at room temperature and at 300°C. The films grown on NaCI were nanocrystallinc, cubic TiC, with a grain size ranging between 2 and 10 nm in diameter. Boron carbide films were grown on silicon {100} substrates at room temperature and at 300°C. Film chemistry and stoichiometry duplicated that of the B4C target, which contained B4C and a mixed C-B-O-N binder phase. SEM analysis indicated that the morphology of the films was uniform, nonporous, and fine-grained. The films exhibited good adhesion and wear resistance, based on friction and wea...
Le Journal de Physique Colloques, 1986
Surface Science Aspects of Contamination in Tem Sample Preparation
MRS Proceedings, 1997
With the advent of the modem analytical electron microscope with its ultrahigh vacuum conditions,... more With the advent of the modem analytical electron microscope with its ultrahigh vacuum conditions, extremely high current density in a very small probe, and its light element analysis capability, it is imperative that contamination of the TEM sample, particularly by hydrocarbons, is eliminated. The degree of cleanliness required for analysis using surface sensitive techniques is also much greater than for other forms of analysis. Contamination of samples can occur (a) prior to analysis, due to the way samples are prepared or handled, or (b) during analysis. Examples of surface contamination prior to analysis and during analysis will be given, in order to illustrate their effect on an analysis.Polished Si, Ni, and Ti bulk samples and pre-thinned TEM Ni and Ti samples were intentionally contaminated by two methods. One set of samples was put on a liquid nitrogen cooled stage for one hour in a diffusion pumped Gatan Duomill in which the liquid nitrogen cold trap above the diffusion pump...
The Effects of Dopants on the Chemistry and Tribology of Sputter-Deposited MoS2Films
Tribology Transactions, 1995
Page 1. The Effects of Dopants on the Chemistry and Tribology ... 7 %com!lriliott belrteetrloj,cr... more Page 1. The Effects of Dopants on the Chemistry and Tribology ... 7 %com!lriliott belrteetrloj,crnts, Jilm properties, and tribology is 1li.sni.sse11 i,tr rle(rril. ...
Thin Solid Films, 1997
The structural and tribologicat properties of niobium nitride (NbN) films are investigated becaus... more The structural and tribologicat properties of niobium nitride (NbN) films are investigated because of their potential to improve the wear-life and corrosion resistance of bearing components operating in extreme environments such as turbine engines and spacecraft. The films are deposited onto 440C stainless steel substrates by magnetron sputtering. Nitrogen partial pressure (PN 2) is varied to change the crystal structure of the films. At 4 X 10 -4 tort, the films are cubic; as the partial pressure of the gas is increased, an increasing fraction of hexagonal 8'-NbN phase appears. The substrate bias potential is adjusted to affect the film microstmcture. Wear properties and friction coefficients are studied using a ball-on-flat tribometer with Si3N 4 and stainless steel balls as the counterface materials. Film hardness and adhesion properties are measured using a nano indentation tester and a scratch tester. Chemistry and microstructure are characterized using X-ray photoelectron spectroscopy, XRD, SEM and TEM. The films have friction coefficients of approximately 0.6 and 0.7 when slid against Ni3N 4 and stainless steel balls, respectively. They have hardnesses of about 30 GPa and an adhesion of 2-3 kgf, as measured by scratch testing. SEM micrographs indicate the films are smooth and dense. The films are somewhat N deficient; on the basis of XPS, the film chemistry and stoichiometry do not change significantly with bias or PN 2. © i997 Elsevier Science S.A.
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
MoVN-Cu Coatings for In Situ Tribocatalytic Formation of Carbon-Rich Tribofilms in Low-Viscosity Fuels
ACS Applied Materials & Interfaces
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
A Field-Effect Fim Specimen Holder For Jeol 200CX
Proceedings, annual meeting, Electron Microscopy Society of America, 1985
Very large field-induced stresses are imposed on specimens in the Field-Ion Microscope (FIM) and ... more Very large field-induced stresses are imposed on specimens in the Field-Ion Microscope (FIM) and the magnitude of these stresses approach the theoretical strengths for many metals. The interaction of the field- induced stresses with defects such as grain boundaries or precipitates is usually the cause of fracture failure of samples in the FIM. It has long been known that the stresses in the emitters cause most dislocations to be swept out of the sample in the field-affected region. Frequently, results obtained by FIM techniques are questioned because of the presence of these stresses. Eaton and Bayuzick used a FIM image-brightness, mapping technique to find the actual geometry of a tungsten specimen and then obtained the stress state within it by using finite element analysis. Their analysis shows the distribution of shear stresses to be quite complicated.
Analysis of Selected Area Diffraction Patterns With Winjade
Microscopy and Microanalysis, 1998
The analysis of Selected Area Diffraction (SAD) patterns that are collected from a single phase m... more The analysis of Selected Area Diffraction (SAD) patterns that are collected from a single phase material having sufficient crystallites to provide continuous rings is relatively straightforward. However, when this condition is not met and there may be several phases present having rings of a spotty nature, the pattern is complex and can be quite difficult to analyze manually because of the vast number of discrete spots. WinJade from MDI is an X-ray diffraction (XRD) analysis program with an Electron Diffraction Program Module (EDPM) that can be used to aid in the analysis of SAD patterns. The EDPM produces Integrated Circular Density Plots (ICDP), which are one-dimensional intensity profiles plotted as a function of equivalent XRD 20 values or crystal d-spacings. These ICDP's can be overlayed with XRD patterns or with reference lines from the NIST and JCPDS crystalline databases for direct comparisons.
TEM examination of wear debris from a self-lubricating metal-matrix composite prepared by ultramicrotomy
Proceedings, annual meeting, Electron Microscopy Society of America, 1995
Self-lubricating materials are usually multi-phase composites comprising of a solid lubricant dis... more Self-lubricating materials are usually multi-phase composites comprising of a solid lubricant dispersed in a matrix of a metal or a polymer. During sliding contact, chemical reactions among the constituent phases of the composite, the counterface and the gases in the surrounding environment are inevitable. The wear debris is a product of such chemical (or tribochemical) reactions. Determination of the chemistry and the crystal structure of the wear debris is therefore crucial to the understanding of the wear mechanisms. In self-lubricating composites, the quantity of the debris generated is often too small to perform x-ray diffraction.It has been previously demonstrated that self-lubricating aluminum metal-matrix composites can be synthesized by dispersing silicon carbide and tungsten disulfide particles in commercial aluminum alloy matrices. A typical microstructure of an Al-0.10SiC-0.05WS2 MMC is shown in Fig. 1. The friction and wear test was performed, in a ball-on-disk configur...
Electron microscopy of pulsed-laser-deposited thin films for tribological applications
Proceedings, annual meeting, Electron Microscopy Society of America, 1993
Pulsed laser deposition (PLD) is a novel thin film deposition technique which has recently been a... more Pulsed laser deposition (PLD) is a novel thin film deposition technique which has recently been applied to tribological materials with great success. PLD has several inherent advantages over conventional deposition techniques, including excellent film adhesion, replication of target chemistry, and low film deposition temperature. Because load-bearing materials are typically hardened, heat treated alloys, these properties of PLD are ideally suited for tribological applications. In addition to being a relatively simple deposition technique, considerable processing flexibility is inherent with PLD. Dense, nonporous, stoichiometric films of solid lubricants, such as MoS2, have been grown having long wear lives with low coefficients of friction. Hard coating materials, such as TiC, have been grown at room temperature that were polycrystalline and had excellent wear properties.A significant feature of pulsed laser deposited (PLD) thin films is the incorporation of spherical particles with...
Combustion and Flame, 2019
Aluminum nanoparticles (nAl) have great potential for energetic applications. However, the native... more Aluminum nanoparticles (nAl) have great potential for energetic applications. However, the native oxide shell (amorphous alumina, Al 2 O 3 ) inhibits efficient energy release and acts as a barrier for aluminum (Al) oxidation. An energetic oxidizer, aluminum iodate hexahydrate (AIH), has recently been demonstrated as an effective coating for nAl. However, the current chemical synthesis method has led to widely varying AIH concentrations on nAl particles. Plasma surface treatment of nAl is a novel "energy coupled to material" technique which alters the nAl surface properties without changing the bulk active Al core. This work explores a new approach to engineering the nAl surface using atmospheric argon (Ar) plasma to accomplish two objectives: (1) reduce the nAl oxide shell thickness, and (2) synthesize AIH on the treated particle surface. Transmission electron microscopy (TEM) reveals more than 40% reduction in the oxide thickness after 10 min Ar plasma treatment. Laser-induced air shock from energetic materials (LASEM) experiments show significant energy release enhancements for the plasma-treated nAl with AIH coating (PT-nAl-AIH) compared to commercial nAl as well as untreated nAl with AIH coating (UT-nAl-AIH). The results demonstrate the potential of applying atmospheric plasma techniques to modify nAl for enhanced reactivity.
Plasmonic gold nanostars as optical nano-additives for injection molded polymer composites
Nanotechnology, 2017
Nanoscale engineering of noble metal particles has provided numerous material configurations to s... more Nanoscale engineering of noble metal particles has provided numerous material configurations to selectively confine and manipulate light across the electromagnetic spectrum. Transitioning these materials to a composite form while maintaining the desired resonance properties has proven challenging. In this work, the successful integration of plasmon-focusing gold nanostars (GNSs) into polymer nanocomposites (PNCs) is demonstrated. Tailored GNSs are produced with over a 90% yield and methods to control the branching structures are shown. A protective silica capping shell is employed on the nanomaterials to facilitate survivability in the high temperate/high shear processing parameters to create optically-tuned injection molded PNCs. The developed GNS PNCs possess dichroic scattering and absorption behavior, opening up potential applications in the fields of holographic imaging, optical filtering and photovoltaics.
Characterization and visualization of the state and entanglement of two spins
European Journal of Physics, Jul 1, 2001
We characterize and classify the quantum states of a pair of spin-½ particles in terms of the ent... more We characterize and classify the quantum states of a pair of spin-½ particles in terms of the entanglement of the pair. We describe a general strategy for classifying the quantum states of entangled systems, and apply it to the simplest entangled system available - a pair of spin-½ particles. The method is based on local unitary transformations. We give a set of six parameters that describe an arbitrary pure state of a pair of spins, one of which is the entanglement of the pair. We discuss visual representations of the state of this system, and propose a visualization using a Bloch sphere for each subsystem and a disc to record the `shared' information.
Substrates coated with a polycrystalline functional coating
Architecture of multilayer nanocomposite coatings with super-hard diamond-like carbon layers for wear protection at high contact loads
Wear, 1997
ABSTRACT Super-hard and low-friction diamond-like carbon (DLC) coatings deposited at low temperat... more ABSTRACT Super-hard and low-friction diamond-like carbon (DLC) coatings deposited at low temperatures are currently of great interest for wear protection and friction reduction. However, their high hardness (50–80 GPa), intrinsic stresses, and poor adhesion limit their use to applications where contact pressures are below I GPa and the coating thickness is below 0.5 μm to prevent cracking and delamination. These negative effects are especially pronounced when the coatings are applied to relatively soft substrates, such as steels. The limitations were removed by a multilayer design, where metal and ceramic layers were used to increase the load support capability, improve the adhesion strength, and increase the thickness of DLC layers. Existing approaches to the design of tough multilayer coatings were considered critically and a coating architecture was suggested using the following concepts: (i) formation of a load support and adhesion promoting underlayer with mechanical characteristics varied gradually from the substrate to the DLC layer; (ii) separation of hard DLC layers with interlayers of softer material to reduce stresses and brake cracks; (iii) use of crystalline interlayers with thickness permitting operation of dislocation sources for stress relaxation and deflection of cross-sectional cracks. The development of these concepts is discussed sequentially from bilayer ceramic/DLC coatings to functionally gradient metal/carbide/DLC coatings, and finally to nanocomposite coatings consisting of stacks of Ti/DLC, TiC/DLC, and CN/DLC layers with individual thickness within 10–60 nm deposited onto a gradient TiTiC-DLC underlayer. The coatings were deposited onto stainless steel substrates by a hybrid of magnetron sputtering and pulsed laser deposition. They had a 1–2 μm total thickness of super-hard (60–70 GPa) DLC layers and resisted delamination to 50–80 N loads in scratch adhesion tests. In ball-on-disk sliding tests, these coatings supported Hertzian contact pressures above 2 GPa and had friction coefficients around 0.1. Their wear lives exceed 106 cycles under initial contact pressures of 1.4 GPa. The conceptual architecture of multilayer nanocomposite coatings presented extends the range of wear resistant applications for super-hard DLC materials.
Applications of Reactive Gas Plasma Cleaning Technology in Minimizing Contamination Of Specimens During Transmission and Analytical Electron Microscopy
The generation and usage of a reactive gas plasma for a wide range of applications has been cited... more The generation and usage of a reactive gas plasma for a wide range of applications has been cited since the early 1970's. More recently, the use of a plasma generating system has been applied to analytical transmission electron microscopy to minimize and, in some cases, eliminate the problems associated with various contamination sources, including the specimen holder and the specimen itself. Although the technology is well known, no definitive characterization of process parameters has been developed for specimen and specimen holder cleaning applications. An investigation of the effects that power levels and gas mixtures have upon contamination rates and removal were done using a Philips CM30T. Measurements of contamination rates both prior to and following plasma cleaning were done to characterize the effects of various parameter changes. Results of different process parameters and contamination rates will be reported.
MRS Proceedings, 1991
Thin films of titanium carbide (TiC) and boron carbide (B4C) were grown by excimer pulsed laser d... more Thin films of titanium carbide (TiC) and boron carbide (B4C) were grown by excimer pulsed laser deposition (PLD) at room temperature (RT) and 300°C. Films were deposited using the output of an excimer laser operating with KrF gas (λ = 248 nm, 15 ns pulse duration) to ablate hot-pressed targets. Film chemistry, morphology, and crystallinity were investigated. Stoichiometric, crystalline TiC films were grown on 440C stainless steel and NaCl substrates at room temperature and at 300°C. The films grown on NaCI were nanocrystallinc, cubic TiC, with a grain size ranging between 2 and 10 nm in diameter. Boron carbide films were grown on silicon {100} substrates at room temperature and at 300°C. Film chemistry and stoichiometry duplicated that of the B4C target, which contained B4C and a mixed C-B-O-N binder phase. SEM analysis indicated that the morphology of the films was uniform, nonporous, and fine-grained. The films exhibited good adhesion and wear resistance, based on friction and wea...
Le Journal de Physique Colloques, 1986
Surface Science Aspects of Contamination in Tem Sample Preparation
MRS Proceedings, 1997
With the advent of the modem analytical electron microscope with its ultrahigh vacuum conditions,... more With the advent of the modem analytical electron microscope with its ultrahigh vacuum conditions, extremely high current density in a very small probe, and its light element analysis capability, it is imperative that contamination of the TEM sample, particularly by hydrocarbons, is eliminated. The degree of cleanliness required for analysis using surface sensitive techniques is also much greater than for other forms of analysis. Contamination of samples can occur (a) prior to analysis, due to the way samples are prepared or handled, or (b) during analysis. Examples of surface contamination prior to analysis and during analysis will be given, in order to illustrate their effect on an analysis.Polished Si, Ni, and Ti bulk samples and pre-thinned TEM Ni and Ti samples were intentionally contaminated by two methods. One set of samples was put on a liquid nitrogen cooled stage for one hour in a diffusion pumped Gatan Duomill in which the liquid nitrogen cold trap above the diffusion pump...
The Effects of Dopants on the Chemistry and Tribology of Sputter-Deposited MoS2Films
Tribology Transactions, 1995
Page 1. The Effects of Dopants on the Chemistry and Tribology ... 7 %com!lriliott belrteetrloj,cr... more Page 1. The Effects of Dopants on the Chemistry and Tribology ... 7 %com!lriliott belrteetrloj,crnts, Jilm properties, and tribology is 1li.sni.sse11 i,tr rle(rril. ...
Thin Solid Films, 1997
The structural and tribologicat properties of niobium nitride (NbN) films are investigated becaus... more The structural and tribologicat properties of niobium nitride (NbN) films are investigated because of their potential to improve the wear-life and corrosion resistance of bearing components operating in extreme environments such as turbine engines and spacecraft. The films are deposited onto 440C stainless steel substrates by magnetron sputtering. Nitrogen partial pressure (PN 2) is varied to change the crystal structure of the films. At 4 X 10 -4 tort, the films are cubic; as the partial pressure of the gas is increased, an increasing fraction of hexagonal 8'-NbN phase appears. The substrate bias potential is adjusted to affect the film microstmcture. Wear properties and friction coefficients are studied using a ball-on-flat tribometer with Si3N 4 and stainless steel balls as the counterface materials. Film hardness and adhesion properties are measured using a nano indentation tester and a scratch tester. Chemistry and microstructure are characterized using X-ray photoelectron spectroscopy, XRD, SEM and TEM. The films have friction coefficients of approximately 0.6 and 0.7 when slid against Ni3N 4 and stainless steel balls, respectively. They have hardnesses of about 30 GPa and an adhesion of 2-3 kgf, as measured by scratch testing. SEM micrographs indicate the films are smooth and dense. The films are somewhat N deficient; on the basis of XPS, the film chemistry and stoichiometry do not change significantly with bias or PN 2. © i997 Elsevier Science S.A.