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The state-of-the-art Carbon Dioxide Reduction Assembly (CRA) was delivered to the International Space Station (ISS) in April 2010. The system is designed to accept carbon dioxide from the Carbon Dioxide Removal Assembly and hydrogen from the Oxygen Generation Assembly. The two gases are reacted in the CRA in a Sabatier reactor to produce water and methane. Venting of methane results in an oxygen resupply requirement of about 378 lbs per crew member per year. If the oxygen is supplied as water, the total weight for resupply is about 476 lb per crew member per year. For long-term missions beyond low Earth orbit, during which resupply capabilities will be further limited, recovery of hydrogen from methane is highly desirable. For this purpose, NASA is pursuing development of a Plasma Pyrolysis Assembly (PPA) capable of recovering hydrogen from methane. Under certain conditions, water vapor and carbon dioxide (nominally intended to be separated from the CRA outlet stream) may be present in the PPA feed stream. Thus, testing was conducted in 2010 to determine the effect of these "oxygenated" compounds on PPA performance, particularly the effect of inlet carbon dioxide and water variations on the PPA product stream. This paper discusses the test set-up, analysis, and results of this testing

The state-of-the-art Carbon Dioxide Reduction Assembly (CRA) was delivered to the International Space Station (ISS) in April 2010. The system is designed to accept carbon dioxide from the Carbon Dioxide Removal Assembly and hydrogen from the Oxygen Generation Assembly. The two gases are reacted in the CRA in a Sabatier reactor to produce water and methane. Venting of methane results in an oxygen resupply requirement of about 378 lbs per crew member per year. If the oxygen is supplied as water, the total weight for resupply is about 476 lb per crew member per year. For long-term missions beyond low Earth orbit, during which resupply capabilities will be further limited, recovery of hydrogen from methane is highly desirable. For this purpose, NASA is pursuing development of a Plasma Pyrolysis Assembly (PPA) capable of recovering hydrogen from methane. Under certain conditions, water vapor and carbon dioxide (nominally intended to be separated from the CRA outlet stream) may be present in the PPA feed stream. Thus, testing was conducted in 2010 to determine the effect of these "oxygenated" compounds on PPA performance, particularly the effect of inlet carbon dioxide and water variations on the PPA product stream. This paper discusses the test set-up, analysis, and results of this testing

Plasma chemistry and technology represents a significant advance and improvement for green manufacturing, pollution control, and various processing applications. The US Army as well as the DoD have a very large number of operational and military needs that can be addressed by state-of-the-art plasma technologies. These include clean-up/restoration of a wide range of contaminated sites (soils and groundwater), control of release of toxic vapors during peacetime operations at military bases and depots, as well as combat applications such as decontamination of personnel clothing and materiel contaminated by CBW agents. The Pacific Basin Chemical Societies jointly organize a major Congress every five years. The Pacifichem 2000 was held from December 14-19, 2000 in Honolulu, HI. This Congress consists of over 120 symposia. amongst them the Symposium on Plasma Chemistry and Technology for Green Manufacturing, Pollution Control, and Processing Applications. This symposium was aimed at highlighting many of the new and exciting developments in the plasma chemistry many field beyond the more traditional and mature fields of semiconductor and materials processing. This symposium was focus on three areas: Pollution Control with Standard and Hybrid Non-Thermal Plasmas; Green Chemical Synthesis, Conversion, and Materials Modification; and Plasmas in Food and Agricultural applications.

Plasma chemistry and technology represents a significant advance and improvement for green manufacturing, pollution control, and various processing applications. The US Army as well as the DoD have a very large number of operational and military needs that can be addressed by state-of-the-art plasma technologies. These include clean-up/restoration of a wide range of contaminated sites (soils and groundwater), control of release of toxic vapors during peacetime operations at military bases and depots, as well as combat applications such as decontamination of personnel clothing and materiel contaminated by CBW agents. The Pacific Basin Chemical Societies jointly organize a major Congress every five years. The Pacifichem 2000 was held from December 14-19, 2000 in Honolulu, HI. This Congress consists of over 120 symposia. amongst them the Symposium on Plasma Chemistry and Technology for Green Manufacturing, Pollution Control, and Processing Applications. This symposium was aimed at highlighting many of the new and exciting developments in the plasma chemistry many field beyond the more traditional and mature fields of semiconductor and materials processing. This symposium was focus on three areas: Pollution Control with Standard and Hybrid Non-Thermal Plasmas; Green Chemical Synthesis, Conversion, and Materials Modification; and Plasmas in Food and Agricultural applications.

Boron carbide, most often used in personnel armor systems, is rather difficult to form and is almost always densified from ceramic powders under heat and pressure. Recent developments by PPG and Georgia Tech are allowing for the full densification of nano-sized powders through a pressureless sintering route. PPG is manufacturing these powders in a plasma processing technique, and they are less expensive than traditionally produced powders. The powders are fonned directly in the plasma, and they can be doped with densification aids. Pressureless sintering teclmiques developed by Georgia Tech offers a low-cost processing route for B4C that was previously unavailable. Together both efforts will lead to boron carbide with shapes and sizes unavailable today and using a fine-grained domestically produced starting powder.

A more liberal and less constrained handling of plasma norepinephrine (NE) and epinephrine (EPI) samples simplifies analysis and improves laboratory efficiency. We tested their stability in heparin or EDTA plasmas alone or combined with the antioxidant glutathione at 24 C or following long-term storage at -70 C. NE and EPI measured by high-pressure liquid chromatography (HPLC) with electrochemical detection are stable in heparinized plasma for 24 hours at 24 C (6% degradation/d). In EDTA plasma, NE and EPI levels decrease less than 10% after 6 hours at 24 C but decay by 50% between 6 and 24 hours. At -70 C, NE and EPI in heparin or EDTA plasma are stable for 8 months, and the addition of antioxidant has no effect. Whole blood anticoagulated with heparin or EDTA does not alter plasma NE over the initial 6 hours at 24 C. We conclude that simple heparinization of human venous blood provides optimal conditions for quantitation of the in vivo concentration of plasma NE and EPI. Reprints.

Space weathering on the moon and asteroids results largely from the alteration of the outer surfaces of regolith grains by the combined effects of solar ion irradiation and other processes that include deposition of impact or sputter-derived vapors. Although no longer considered the sole driver of space weathering, solar ion irradiation remains a key part of the space weathering puzzle, and quantitative data on its effects on regolith minerals are still in short supply. For the lunar regolith, previous transmission electron microscope (TEM) studies performed by ourselves and others have uncovered altered rims on ilmenite (FeTiO3) grains that point to this phase as a unique "witness plate" for unraveling nanoscale space weathering processes. Most notably, the radiation processed portions of these ilmenite rims consistently have a crystalline structure, in contrast to radiation damaged rims on regolith silicates that are characteristically amorphous. While this has tended to support informal designation of ilmenite as a "radiation resistant" regolith mineral, there are to date no experimental data that directly and quantitatively compare ilmenite s response to ion radiation relative to lunar silicates. Such data are needed because the radiation processed rims on ilmenite grains, although crystalline, are microstructurally and chemically complex, and exhibit changes linked to the formation of nanophase Fe metal, a key space weathering process. We report here the first ion radiation processing study of ilmenite performed by in-situ means using the Intermediate Voltage Electron Microscope- Tandem Irradiation facility (IVEM-Tandem) at Argonne National Laboratory. The capability of this facility for performing real time TEM observations of samples concurrent with ion irradiation makes it uniquely suited for studying the dose-dependence of amorphization and other changes in irradiated samples.

Space weathering on the moon and asteroids results largely from the alteration of the outer surfaces of regolith grains by the combined effects of solar ion irradiation and other processes that include deposition of impact or sputter-derived vapors. Although no longer considered the sole driver of space weathering, solar ion irradiation remains a key part of the space weathering puzzle, and quantitative data on its effects on regolith minerals are still in short supply. For the lunar regolith, previous transmission electron microscope (TEM) studies performed by ourselves and others have uncovered altered rims on ilmenite (FeTiO3) grains that point to this phase as a unique "witness plate" for unraveling nanoscale space weathering processes. Most notably, the radiation processed portions of these ilmenite rims consistently have a crystalline structure, in contrast to radiation damaged rims on regolith silicates that are characteristically amorphous. While this has tended to support informal designation of ilmenite as a "radiation resistant" regolith mineral, there are to date no experimental data that directly and quantitatively compare ilmenite s response to ion radiation relative to lunar silicates. Such data are needed because the radiation processed rims on ilmenite grains, although crystalline, are microstructurally and chemically complex, and exhibit changes linked to the formation of nanophase Fe metal, a key space weathering process. We report here the first ion radiation processing study of ilmenite performed by in-situ means using the Intermediate Voltage Electron Microscope- Tandem Irradiation facility (IVEM-Tandem) at Argonne National Laboratory. The capability of this facility for performing real time TEM observations of samples concurrent with ion irradiation makes it uniquely suited for studying the dose-dependence of amorphization and other changes in irradiated samples.

This report contains an assessment of recent developments in processing materials through the use of plasma technology. Advances in this field in foreign countries are discussed and the potentials for this type of processing relative to selected materials from the standpoints of cost- effectiveness and technical viability made. It addresses thermal plasma melting and remelting technology, extracting and refining technology, plasma deposition, thermal plasma synthesis and consolidation and processing using low-pressure nonequilibrium plasmas. Conclusions and recommendations are made for potential research and development projects in each of the technologies studied. Originator-supplied keywords include: Plasma Deposition, Materials Processing, Melting & Remelting Technology, Thermal Plasma Synthesis & Consolidation, Plasma Sintering, Low Pressure, Nonequilibrium Plasmas, Plasma Extractive Metallurgy, Melting & Refining of Superalloys, Plasma Coatings.

The MURI Center on Modeling and Control of Plasma Processing at the University of Michigan started in September, 1995, and concluded technical work at the end of August 2001. As the name indicates, the major research goals of the center are in the areas of modeling and control of plasma deposition and etching processing. These plasma processes are used extensively in the manufacture of integrated circuits as well as active matrix liquid crystal displays. These applications areas motivate our selection of research problems in modeling and control. Significant accomplishments were made in all of these areas (as will be discussed in the body of the report) Particular program highlights include: (1) An optical technique was developed to monitor in situ and in real time the critical dimensions and wall-shapes of evolving features in reactive ion etchers. An advanced signal processing scheme was devised to use this technique to perform the first fully-automated etch-to-target-dimension etches. One-nanometer-level (or better) accuracy was demonstrated enabling possibilities for extremely high accuracy semiconductor fabrication control. (2) The state-of-the-art of 1st principles plasma equipment modeling was advanced so that the entire system of the sensors, plasma process equipment, and control systems could be modeled numerically. (3) Novel RF Sensing to non-invasively measure the electrical state of plasma systems was developed and applications to detecting common faults were demonstrated. (4) Improved statistical methods for detecting and identifying the causes of spatially clustered defects in semiconductor manufacturing. (5) Development of a novel ion-beam modification process for the deposition of Al films which are more resistant to grain-growth.

The MURI Center on Modeling and Control of Plasma Processing at the University of Michigan started in September, 1995, and concluded technical work at the end of August 2001. As the name indicates, the major research goals of the center are in the areas of modeling and control of plasma deposition and etching processing. These plasma processes are used extensively in the manufacture of integrated circuits as well as active matrix liquid crystal displays. These applications areas motivate our selection of research problems in modeling and control. Significant accomplishments were made in all of these areas (as will be discussed in the body of the report) Particular program highlights include: (1) An optical technique was developed to monitor in situ and in real time the critical dimensions and wall-shapes of evolving features in reactive ion etchers. An advanced signal processing scheme was devised to use this technique to perform the first fully-automated etch-to-target-dimension etches. One-nanometer-level (or better) accuracy was demonstrated enabling possibilities for extremely high accuracy semiconductor fabrication control. (2) The state-of-the-art of 1st principles plasma equipment modeling was advanced so that the entire system of the sensors, plasma process equipment, and control systems could be modeled numerically. (3) Novel RF Sensing to non-invasively measure the electrical state of plasma systems was developed and applications to detecting common faults were demonstrated. (4) Improved statistical methods for detecting and identifying the causes of spatially clustered defects in semiconductor manufacturing. (5) Development of a novel ion-beam modification process for the deposition of Al films which are more resistant to grain-growth.

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The utilization of a cold plasma in chlorination processing is described. Essential equipment and instruments were received, the experimental apparatus assembled and tested, and preliminary experiments conducted. The results of the latter lend support to the original hypothesis: a cold plasma can both significantly enhance and bias chemical reactions. In two separate experiments, a cold plasma was used to reduce TiCl4 vapor and chlorinate ilmenite. The latter, reacted in an argon-chlorine plasma, yielded oxygen. The former experiment reveals that chlorine can be recovered as HCl vapor from metal chlorides in a hydrogen plasma. Furthermore, the success of the hydrogen experiments has lead to an analysis of the feasibility of direct hydrogen reduction of metal oxides in a cold plasma. That process would produce water vapor and numerous metal by-products.

The utilization of a cold plasma in chlorination processing is described. Essential equipment and instruments were received, the experimental apparatus assembled and tested, and preliminary experiments conducted. The results of the latter lend support to the original hypothesis: a cold plasma can both significantly enhance and bias chemical reactions. In two separate experiments, a cold plasma was used to reduce TiCl4 vapor and chlorinate ilmenite. The latter, reacted in an argon-chlorine plasma, yielded oxygen. The former experiment reveals that chlorine can be recovered as HCl vapor from metal chlorides in a hydrogen plasma. Furthermore, the success of the hydrogen experiments has lead to an analysis of the feasibility of direct hydrogen reduction of metal oxides in a cold plasma. That process would produce water vapor and numerous metal by-products.

The thermal plasma experiment is one of five experiments to be flown on the HILAT satellite in a polar orbit. The experiment consists of an ion drift-meter, an ion retarding potential analyzers and a spherical electron Langmuir probe. The details of the instruments are described. The calibrations and conversion factor to change from telemetry units to scientific units are given. Algorithms for converting the raw data into the parameters of interest are given. These algorithms are intended for obtaining quick-look information. Refinements to the algorithm will be required before the final results are released. (Author)

The thermal plasma experiment is one of five experiments to be flown on the HILAT satellite in a polar orbit. The experiment consists of an ion drift-meter, an ion retarding potential analyzers and a spherical electron Langmuir probe. The details of the instruments are described. The calibrations and conversion factor to change from telemetry units to scientific units are given. Algorithms for converting the raw data into the parameters of interest are given. These algorithms are intended for obtaining quick-look information. Refinements to the algorithm will be required before the final results are released. (Author)

This article is from Nutrients , volume 4 . Abstract The associations between dietary cholesterol and heart disease are highly controversial. While epidemiological studies and clinical interventions have shown the lack of correlation between cholesterol intake and cardiovascular disease (CVD) risk, there is still concern among health practitioners and the general population regarding dietary cholesterol. In this review, several clinical studies utilizing cholesterol challenges are analyzed in terms of changes that occur in lipoprotein metabolism resulting from excess consumption of cholesterol. Dietary cholesterol has been shown to increase both LDL and HDL in those individuals who respond to a cholesterol challenge without altering the LDL cholesterol/HDL cholesterol ratio, a key marker of CVD risk. Further, dietary cholesterol has been shown to increase only HDL with no changes in LDL with average cholesterol consumption and during weight loss interventions. Ingestion of cholesterol has also been shown to increase the size of both LDL and HDL particles with the associated implications of a less atherogenic LDL particle as well as more functional HDL in reverse cholesterol transport. Other changes observed in lipoprotein metabolism are a greater number of large LDL and decreases in small LDL subfractions. All this information put together points to specific roles of dietary cholesterol in substantially altering intravascular processing of lipoproteins as well as reverse cholesterol transport.

This article is from Nutrients , volume 4 . Abstract The associations between dietary cholesterol and heart disease are highly controversial. While epidemiological studies and clinical interventions have shown the lack of correlation between cholesterol intake and cardiovascular disease (CVD) risk, there is still concern among health practitioners and the general population regarding dietary cholesterol. In this review, several clinical studies utilizing cholesterol challenges are analyzed in terms of changes that occur in lipoprotein metabolism resulting from excess consumption of cholesterol. Dietary cholesterol has been shown to increase both LDL and HDL in those individuals who respond to a cholesterol challenge without altering the LDL cholesterol/HDL cholesterol ratio, a key marker of CVD risk. Further, dietary cholesterol has been shown to increase only HDL with no changes in LDL with average cholesterol consumption and during weight loss interventions. Ingestion of cholesterol has also been shown to increase the size of both LDL and HDL particles with the associated implications of a less atherogenic LDL particle as well as more functional HDL in reverse cholesterol transport. Other changes observed in lipoprotein metabolism are a greater number of large LDL and decreases in small LDL subfractions. All this information put together points to specific roles of dietary cholesterol in substantially altering intravascular processing of lipoproteins as well as reverse cholesterol transport.

This article is from Nutrients , volume 4 . Abstract The associations between dietary cholesterol and heart disease are highly controversial. While epidemiological studies and clinical interventions have shown the lack of correlation between cholesterol intake and cardiovascular disease (CVD) risk, there is still concern among health practitioners and the general population regarding dietary cholesterol. In this review, several clinical studies utilizing cholesterol challenges are analyzed in terms of changes that occur in lipoprotein metabolism resulting from excess consumption of cholesterol. Dietary cholesterol has been shown to increase both LDL and HDL in those individuals who respond to a cholesterol challenge without altering the LDL cholesterol/HDL cholesterol ratio, a key marker of CVD risk. Further, dietary cholesterol has been shown to increase only HDL with no changes in LDL with average cholesterol consumption and during weight loss interventions. Ingestion of cholesterol has also been shown to increase the size of both LDL and HDL particles with the associated implications of a less atherogenic LDL particle as well as more functional HDL in reverse cholesterol transport. Other changes observed in lipoprotein metabolism are a greater number of large LDL and decreases in small LDL subfractions. All this information put together points to specific roles of dietary cholesterol in substantially altering intravascular processing of lipoproteins as well as reverse cholesterol transport.

Plasma etching is finding new applications beyond the microelectronics industry. There are new challenges in the devising and controlling of plasma-surface interactions.

Plasma etching is finding new applications beyond the microelectronics industry. There are new challenges in the devising and controlling of plasma-surface interactions.

The two-photon laser induced fluorescence (TALIF) diagnostic has been developed and/or applied to plasma processing systems involving H, 0, and N atoms. Based upon TALIF data, models have been developed for the spatial and temporal variation of the absolute atomic concentrations in H2, 02, and N2 plasmas. The portability of the TALIF diagnostic has been demonstrated. Limitations of the technique due to stimulated emission and fluorescence quenching have been investigated and procedures developed to minimize their effects.

This research program was conducted to provide a small bench-scale Plasma Waste Processing System to the Air Force Research Laboratory (AFRL/MLQ). The program was successful in this effort to develop, and set up a batch-type 15 kW Plasma Waste Processing Demonstration System at the Air Force Research Laboratory at Tyndall Air Force Base, Florida. The system allows the AFRL to demonstrate laboratory processing of small quantities of waste materials (up to 8 ounces) using an alternating current (AC) plasma torch system in a custom-fabricated reactor unit. Larger scale systems for the processing of wastes can be developed and demonstrated in future research programs by evaluating the performance and characteristics of using this bench-type system.

The state-of-the-art Carbon Dioxide Reduction Assembly (CRA) was delivered to the International Space Station (ISS) in April 2010. The system is designed to accept carbon dioxide from the Carbon Dioxide Removal Assembly and hydrogen from the Oxygen Generation Assembly. The two gases are reacted in the CRA in a Sabatier reactor to produce water and methane. Venting of methane results in an oxygen resupply requirement of about 378 lbs per crew member per year. If the oxygen is supplied as water, the total weight for resupply is about 476 lb per crew member per year. For long-term missions beyond low Earth orbit, during which resupply capabilities will be further limited, recovery of hydrogen from methane is highly desirable. For this purpose, NASA is pursuing development of a Plasma Pyrolysis Assembly (PPA) capable of recovering hydrogen from methane. Under certain conditions, water vapor and carbon dioxide (nominally intended to be separated from the CRA outlet stream) may be present in the PPA feed stream. Thus, testing was conducted in 2010 to determine the effect of these oxygenated compounds on PPA performance, particularly the effect of inlet carbon dioxide and water variations on the PPA product stream. This paper discusses the test set-up, analysis, and results of this testing.

The state-of-the-art Carbon Dioxide Reduction Assembly (CRA) was delivered to the International Space Station (ISS) in April 2010. The system is designed to accept carbon dioxide from the Carbon Dioxide Removal Assembly and hydrogen from the Oxygen Generation Assembly. The two gases are reacted in the CRA in a Sabatier reactor to produce water and methane. Venting of methane results in an oxygen resupply requirement of about 378 lbs per crew member per year. If the oxygen is supplied as water, the total weight for resupply is about 476 lb per crew member per year. For long-term missions beyond low Earth orbit, during which resupply capabilities will be further limited, recovery of hydrogen from methane is highly desirable. For this purpose, NASA is pursuing development of a Plasma Pyrolysis Assembly (PPA) capable of recovering hydrogen from methane. Under certain conditions, water vapor and carbon dioxide (nominally intended to be separated from the CRA outlet stream) may be present in the PPA feed stream. Thus, testing was conducted in 2010 to determine the effect of these oxygenated compounds on PPA performance, particularly the effect of inlet carbon dioxide and water variations on the PPA product stream. This paper discusses the test set-up, analysis, and results of this testing.

The goal of the project is to develop a process for the patterning of SiNx films over GaAs which maintains sub-micron line shape while minimizing damage to the GaAs crystal substrate. The development activities are being pursued using an ECR source to provide a high density plasma and an RF powered substrate holder to provide the ion energy and directionality. The chemistry chosen is CF4/02 buffered with Argon.The goals of the program are to develop an understanding of the key physical processes which determine etch line shape, damage to the GaAs crystal substrate and etch radial uniformity through an integrated experimental and modelling program. Based on this understanding a new process and reactor hardware set and diagnostics will be developed; the development and construction of this new process hardware diagnostic set would be undertaken in Phase II.

This workshop focuses on plasma simulations on graphic processing units (GPU). A plasma is a gas in which an important fraction of the atoms is ionized, so that the electrons and ions are separately free. We need to keep track of Plasma's evolution, both in spatial and velocity space. Modeling methodologies include fluid methods and kinetic methods.

Radiofrequency (rf) discharges of tungsten hexafluoxide/hydrogen or molybdenum/hexafluoride/hydrogen have been used to deposit films of tungsten or molybdenum. The tungsten depositions resulted in high purity films with as-deposited resistivities ranging from 40 to 170 micron omega cm, depending upon the deposition conditions. Short (20 min) heat treatments in hydrogen/nitrogen atmospheres at temperatures above 700 deg C resulted in a decrease in the resistivity of the films to approximately 8 micron omega-cm, essentially independent of the initial film resistivity. Unlike tungsten, molybdenum films displayed high (10,000 micron omega cm) resistivities. These results were due to approximately 15 atomic percent fluorine incorporated into the film structure during deposition. (Author)

In the LAPPS processing scheme, RF bias can be used for either of two purposes: to provide energetic ion bombardment of a substrate, or to controllably raise the electron temperature (which is intrinsically very cool) to the desired value. The physics of RF bias in LAPPS differs from the situation in conventional processing reactors, for several reasons: (1) The plasma density adjacent to the substrate can be so high that the ion plasma frequency exceeds the microwave frequency. (2) Plasma transport to the substrate is across a magnetic field. (3) Ionization occurs only in a thin, well-defined planar sheet, and thus the volume occupied by plasma is very broad in two dimensions but thin in the third dimension. (4) The surface area of the substrate is comparable to that of the containment vessel. We discuss the modifications to the theory of RF bias that are needed to account for these factors. We examine the partition of RF power into various plasma channels and show that, for a given RF current, the presence of the magnetic field does not substantially change the ion bombardment energy or power, but does significantly increase the electron heating power. We address the issue of return current path for the RF current, and show that the presence of the magnetic field does not influence the return current flow. In conventional reactors, the vessel area is large compared to the substrate, and return current can be transported through the plasma and dissipated over the vessel walls. But in LAPPS, it may be preferable to provide a return current collector immediately adjacent to the plasma sheet.

Partial contents: Introduction to Plasma Etching; Plasma Chemistry, Basic Processes and PECVD; The Role of ions in Reactive Ion Etching with Low Density Plasmas; SiO2 Etching in High-Density Plasmas: Differences with Low-Density Plasmas; Introduction to Plasma Enhanced Chemical Vapor Deposition; Topography Evolution During Semiconductor Processing; Deposition of Amorphous Silicon; High Density Sources for Plasma Etching; Resonant Plasma Excitation by Electron Cyclotron Waves-Fundamentals and Applications; The Transition from Capacitive to Inductive to Wave Sustained Discharges.

The research performed under this grant was focused on two aspects of GaN-dielectric interfaces: (1) the development of remote plasma processing to yield device quality interfaces suitable for applications including metal oxide semiconductor (MOS) devices, as well surface passivation for high electron mobility transistor (HEMT) devices, and (2) determination of band offset energies between GaN and dielectrics including silicon dioxide ?SiO2), silicon nitride (Si3N4) and a representative high-k alternative dielectric, hafnium oxide (HfO2). Considerable progress was made in each of these areas, and the research has been documented in numerous publications. In particular, a low temperature (300 deg C) remote plasma processing sequence was developed which minimized interfacial traps (d(sub it)), and identified the importance of self-organized gallium suboxide, (GaO(x), x1.5) interfacial layers. Conduction band offset energies between GaN and the representative dielectrics studied were adequate for MOS and surface passivation applications. The critical nature of the self-organized GaO(x) layer was verified by showing that interfaces with thicker layers, approx. 1.5 nm as contrasted with appro. 0.8 nm, yielded increased densities of interfacial defects, attributed to the inability balance bond and macroscopic strain.

The research performed under this grant was focused on two aspects of GaN-dielectric interfaces: (1) the development of remote plasma processing to yield device quality interfaces suitable for applications including metal oxide semiconductor (MOS) devices, as well surface passivation for high electron mobility transistor (HEMT) devices, and (2) determination of band offset energies between GaN and dielectrics including silicon dioxide ?SiO2), silicon nitride (Si3N4) and a representative high-k alternative dielectric, hafnium oxide (HfO2). Considerable progress was made in each of these areas, and the research has been documented in numerous publications. In particular, a low temperature (300 deg C) remote plasma processing sequence was developed which minimized interfacial traps (d(sub it)), and identified the importance of self-organized gallium suboxide, (GaO(x), x1.5) interfacial layers. Conduction band offset energies between GaN and the representative dielectrics studied were adequate for MOS and surface passivation applications. The critical nature of the self-organized GaO(x) layer was verified by showing that interfaces with thicker layers, approx. 1.5 nm as contrasted with appro. 0.8 nm, yielded increased densities of interfacial defects, attributed to the inability balance bond and macroscopic strain.

The technique of Electro-Plasma Processing (EPP) was developed and evaluated for DoD use. The EPP process is a high voltage aqueous process (150-200V) that takes place in an electrolyte jet or foam. It can be used to clean metal surfaces or to deposit alloy coatings, the easiest and most common of which are Zn-based. The process operates in the continuous discharge region of the electrolytic current-voltage curve, where the cathodic workpiece is covered with a plasma envelope from a layer of hydrogen electrolyzed at its surface. Material from the solution is deposited by a combination of electrolytic deposition and evaporation across the hydrogen layer. When used as a cleaning method, the technique produces a very clean, roughened, practically amorphous surface comprising a thin heat-treated outmost layer (0.5-2m or 0.00002-0.0001 thick). Nevertheless, there was no measurable fatigue debit for EPP-cleaned surfaces. Nor was there any hydrogen embrittlement, even though copious quantities of hydrogen are evolved in the process. When used as a coating method, the technique produced nodular coatings with very high porosity. A number of different coating chemistries were evaluated, culminating in corrosion, embrittlement and fatigue testing of ZnNi with chromate (Dipsol IZ-258S) and trivalent chrome (Metalast TCPHF) sealers, and ZnMg with a phosphate/silicate sealer. Again there was no hydrogen embrittlement, but there was a fatigue debit of perhaps a factor of two, with a larger debit for ZnNi at high stress (above 130ksi). This debit is similar to that caused by standard electroplated alkaline ZnNi.

This study presents a comparative technical and economic analysis of the current, powder metallurgy, and an alternate, plasmarc processing, method of producing improved armor penetrator materials. This technology assessment effort was conducted in order to highlight industrial applications of plasma arc melting technology for the manufacture of refractory metals and their eutectic alloys. Primary focus of this survey is on potential military uses of plasma technology which could provide both strategic and economic advantages.

A design of experiments (DOE) was conducted to determine the effects of processing parameters on the physical, thermal, and combustion properties of nanometer scale aluminum powders prepared via an inductively-coupled plasma (ICP) inert gas condensation method. A four-factor, two-level half-fractional factorial array was developed to minimize the number of experiments. Factors chosen for the DOE were plasma power, system pressure, feed rate, and quench rate. Particle size was chosen as the measured response due to its predominant effect on material properties. The results of the DOE showed that feed rate and quench rate have the largest effect on particle size. All synthesized powders were characterized by thermogravimetric analysis/differential scanning calorimetry; field emission scanning electron microscope, Brunauer, Emmet, and Teller; and bomb calorimetry.

A large area plasma processing system (LAPPS) is under development at NRL. In LAPPS, the plasma is generated by a sheet electron beam with voltages and current densities of the order of kilovolts and tens of milliamps per sq cm. The plasma dimensions are a meter square by a few centimeters thick. The beam is guided by a magnetic field of 50-300 Gauss. Since an electron beam of this type efficiently ionizes any gas, high electron densities, n approx. 10(exp 12) - 10(exp 13)/cu cm are easily are easily generated at 30-100 mTorr back ground pressure. In addition to large area and high electron density, LAPPS has advantages for plasma processing. These include independent control of ion and free radical fluxes to the surface, very high uniformity, very low electron temperature (Te 1eV, but can be controllably increased to a desired value) and a geometry that is well suited for many applications. This paper sketches an initial theoretical overview of issues in LAPPS and compares aspects of the theory to a preliminary experiment.

Plasma and ultraviolet (UV) ozone treatments were compared as methods to functionalize ultrahigh molecular weight polyethylene films in order to make them more compatible with materials or reactive for subsequent surface chemistry. Oxidation states and atomic compositions were determined using x-ray photoelectron spectroscopy, while surface energy and bond stability were probed with contact angle goniometry. Both modification techniques increased the surface energy of the polymer, and the bonds formed were found to be stable over a period of 30 days. Plasma treatment times were much shorter than UV ozone; thus, plasma was determined to be a more efficient surface modification technique.

Plasma

A microwave plasma assisted method and system for heating and joining materials. The invention uses a microwave induced plasma to controllably preheat workpiece materials that are poorly microwave absorbing. The plasma preheats the workpiece to a temperature that improves the materials' ability to absorb microwave energy. The plasma is extinguished and microwave energy is able to volumetrically heat the workpiece. Localized heating of good microwave absorbing materials is done by shielding certain parts of the workpiece and igniting the plasma in the areas not shielded. Microwave induced plasma is also used to induce self-propagating high temperature synthesis (SHS) process for the joining of materials. Preferably, a microwave induced plasma preheats the material and then microwave energy ignites the center of the material, thereby causing a high temperature spherical wave front from the center outward.

Two photon laser induced fluorescence (TALIF) has been developed as a convenient and reliable diagnostic of H atoms in plasma processing environments. It has high spatial and temporal resolution, good sensitivity, and the capability of absolute concentration measurements. Detailed diagnostics have been carried out in plasma reactors with and without semiconducting wafers. These measurements have led to a model that incorporates H atom production, diffusion, and surface recombination. This model has accurately predicted both the spatial and temporal behavior of the H-atom concentration in a plasma processing environment. Atomic H, Glow discharge, Plasma processing, Laser diagnostics III-V semiconductors

Chemically and microstructurally complex altered rims around grains in the finest size fraction (

Plasma processing has grown into a tremendously important industrial capability over the last 20 years, and has done so with virtually no input from traditional plasma physicists. Plasma processing is important in such areas as nanocircuit fabrication, diamond thin film deposition, superconducting film deposition, and nanocube production and deposition. Undoubtedly there are other users in the laboratory also. There are plasma modeling efforts going on in the major industrial users, and university plasma physicists are beginning to set up programs. This memo attempts to set out in fairly simple form as much of the basic theory of processing discharges as is possible given constraints of reasonable length and simplicity. One thing about plasma processing is that it is very much an interdisciplinary area involving (at least) plasma physics, surface physics, atomic and molecular physics, and chemistry. This memo involves mainly the plasma physics; it touches on the atomic physics and chemistry for fairly simple plasmas, and it regards surfaces as passive objects that absorb whatever is incident and (mostly) do not emit anything. Better plasma processing models must ultimately treat the surface as an active substance which itself affects the plasma.

1-Basic Physics of Plasmas/Discharges. 2-Low Temperature Plasma Chemistry. 3-Optical Diagnostic Techniques for Low Pressure Plasmas and Plasma Processing. 4-Modern Plasma Probe Diagnostics. 5-Transport Phenomena in Plasma Processing.

Radiofrequency (rf) discharges have been used to deposit films of tungsten, molybdenum and titanium silicide. As-deposited tungsten films, from tungsten hexafluoride and hydrogen source gases, were metastable (beta W), with significant (1 atomic percent) fluorine incorporation. Film resistivities were 40-55 micro ohm - cm due to the beta W, but dropped to about 8 micro ohm cm after a short heat treatment at 700 C which resulted in a phase transition to alpha W (bcc form). The high resistivity (10,000 micro ohm) associated with molybdenum films deposited from molybdenum hexafluoride and hydrogen appeared to be a result of the formation of molybdenum trifluoride in the deposited material. Titanium silicide films formed from a discharge of titanium tetrachloride, silane, and hydrogen, displayed resistivities of about 150 micro ohm cm, due to small amounts of oxygen and chlorine incorporated during deposition. Plasma etching studies of tungsten films with fluorine containing gases suggest that the etchant species for tungsten in these discharges are fluorine atoms. Keywords: Plasma enhance etching; Plasma enhanced deposition; Transition metal films; Transition metal silicide films.

Введение.  Электролитно-плазменные технологии, применяемые для размерной и финишной обработки металлических поверхностей, привлекают внимание своей высокой эффективностью и точностью. Ключевым фактором, определяющим качество обработки, является температура электролитно-плазменного разряда (ЭПР), влияющая на ионизацию электролита и свойства поверхности. Отсутствие комплексных исследований температурных характеристик струйной ЭПР ограничивает оптимизацию технологических процессов. Целью исследования является определение распределения температур и тепловых потоков в системе «струйный электролитический катод — металлический анод» при различных условиях обработки. Материалы и методы.   Исследования проводили с использованием струи электролита диаметром 3 мм с массовым расходом 0,25–3,75 г/с при напряжении 20–500 В. В качестве анодов использовали стали марок ХВГ и 08Х18Н9Т, электролитами служили водные растворы NaCl, (NH4 ) 2SO4, C6H8O7 с концентрацией 4–50 г / л . Температуру измеряли хромель-алюмелевой термопарой, инфракрасным пирометром и тепловизором. Результаты.   Разработано уравнение теплового баланса, описывающее распределение тепла между металлическим анодом (МА), струйным катодом, электролитом, паром и излучением. Анализ вольт-амперных характеристик (ВАХ) показал рост тока при малых расходах электролита (0,75–1,2 г/с) с последующим спадом при 300–500 В и параболическую зависимость с максимумом 2,6 А при расходе 2,37 г/с. Максимальная температура МА достигала 100 °С (NaCl, 4–35 г/л), снижаясь до 82 °С при 150 г/л, а полого катода – 158 °С при начальной температуре электролита 90 °С. Температуры паров варьировались от 67,3 °С (большие расходы) до 87,5 °С (малые расходы). Потери электролита на испарение достигли 5,8 г при 300–340°С. Температура на периферии анода была на 15–20% выше, чем в центре. Обсуждение и заключение.   Основным источником тепла являлся закон Джоуля-Ленца с вкладом экзотермических реакций окисления углерода до 260 В. Максимальное тепловыделение наблюдалось в зоне ЭПД, образующей эллипсоид. Полученные данные и уравнение теплового баланса создают основу для оптимизации струйной электролитно-плазменной полировки в машиностроении, медицине и микроэлектронике.

The utilization of a cold or nonequilibrium plasma in chlorination processing is discussed. Titanium dioxide (TiO2) was successfully chlorinated at temperatures between 700 and 900 C without the aid of carbon. In addition to these initial experiments, a technique was developed for determining the temperature of a specimen in a plasma. Development of that technique has required evaluating the emissivity of TiO2, ZrO2, and FeOTiO2 and analyzing the specimen temperature in a plasma as a function of both power absorbed by the plasma and the pressure of the plasma. The mass spectrometer was also calibrated with TiCl4 and CCl4 vapor.

Hydrogen reduction of ilmenite has been studied by a number of investigators as a potential means for recovery of oxygen from lunar soil. Interest in this process has always rested with the simplicity of the flow diagram and the utilization of established technology. Effective utilization of hydrogen in the reduction process at temperatures of 1200 C and below has always been disappointing and, as such, has led other investigators to focus attention on other systems. Effective utilization of hydrogen in the reduction of ilmenite can be significantly enhanced in the presence of a non-equilibrium hydrogen plasma. Ilmenite at solid specimen temperatures of 600 C to 970 C were reacted in a hydrogen plasma. Those experiments revealed that hydrogen utilization can be significantly enhanced. At a specimen temperature of 850 C the fraction of H2 reacted was 24 percent compared to the 7 percent theoretical limit calculated with thermodynamic theory for the same temperature. An added advantage for a hydrogen plasma involves further reduction of TiO2. Reduction of the iron oxide in ilmenite yields TiO2 and metallic iron as by products. Titanium forms a number of oxides including TiO, Ti2O3, Ti3O5 and the Magneli oxides (Ti4O7 to Ti50O99). In conventional processing of ilmenite with hydrogen it is possible to reduce TiO2 to Ti7O13 within approximately an hour, but with poor utilization of hydrogen on the order of one mole of H2 per thousand. In the cold or non-equilibrium plasma TiO2 can be rapidly reduced to Ti2O3 with hydrogen utilization exceeding 10 percent. Based on design considerations of the plasma reactor greater utilization of the hydrogen in the reduction of TiO2 is possible.

A method for plasma heating of levitated samples to be used in containerless microgravity processing is disclosed. A sample is levitated by electrostatic, electromagnetic, aerodynamic, or acoustic systems, as is appropriate for the physical properties of the particular sample. The sample is heated by a plasma torch at atmospheric pressure. A ground plate is provided to help direct the plasma towards the sample. In addition, Helmholtz coils are provided to produce a magnetic field that can be used to spiral the plasma around the sample. The plasma heating system is oriented such that it does not interfere with the levitation system.

Low temperature plasmas represent an expansive region in the density- temperature parameter space of experimentally generated plasmas. With densities ranging from 10(exp 6) to 10(exp 17) cu cm, and temperatures ranging from 10(exp -2) to 10 eV, these plasmas exhibit a variety of collective behaviors, supporting many physical states and interactions among the particle species within the plasma. It is precisely this variety in physical conditions that lends the plasma environment so well to the myriad of applications that have developed in plasma processing. These applications are examples by; processing of solid state materials by ion implantation, thin film deposition, plasma enhanced chemical vapor deposition, plasma etching and also applications involving hardening and improving wear and corrosion resistance of refractory metals and composites. These applications have enjoyed great advancement in technological development. Much of this advancement is very system dependent and does not enjoy the fundamental scientific underpinning evident in other disciplines. The absence of this strong theoretical foundation is not only of interest for the aesthetics of academics inquiry of poorly understood systems, but also of interest due to the practical benefit of industrial technology expansion. Both, system process optimization and cross disciplinary transfer of technology would be aided by a strengthening in the understanding of the foundation that supports technological advances. This increased understanding can form the basis of expanding beyond existing system specific parameters and providing for process optimization and design.