Ion Surface Engineering 

The ion surface engineering program at Southwest Research Institute (SwRI) is dedicated to the practical treatment of materials and components using energetic ions. SwRI scientists utilize ion beams and plasmas to treat material surfaces to increase their resistance to corrosion, wear, fatigue failure, fretting, and oxidation or to add functionality such as sensing, actuation, and hydrophobicity. Institute staff members, with more than 35 years of experience in surface modification of advanced materials, have pioneered research in many aspects of these technologies.

The Institute's ion surface engineering activities have supported aerospace, biomedical, energy, transportation, and tool and die industries. SwRI has also served government agencies such as the Department of Energy, Department of Defense, and the Defense Advanced Research Projects Agency. SwRI's ion surface engineering activities include:

• Thin-film materials research
• New process development
• Proof-of-concept demonstrations
• Pilot- to medium-scale production
• Specialized vacuum processes design and development in client facilities

All programs remain confidential. As part of a long-held tradition, patent rights arising from sponsored research at the Institute are often assigned to the client. SwRI generally retains the rights to Institute-funded advancements.

Ion Beam Facilities

The Institute operates and maintains seven vacuum chambers that are among the world's largest and most unique facilities for modifying material surfaces. These systems allow surface modification of large tools and components or numerous smaller items. Projects range from small-batch, single-day processing jobs to long-term research and development studies. Specific facilities include:

• 2.0-cubic meter system for broad-beam ion implantation and ion beam-assisted deposition (IBAD)
• 2.0-cubic meter chamber used for novel alloy and transparent conductive oxide films
• 2.7-cubic meter system for non-line-of-sight treatment using plasma-based methods
• 1.0-cubic meter chamber for IBAD of specialized multilayer films for optical thin films
• 1.5-cubic meter roll coater for treating flexible metal and polymer sheet materials
• 1.0-cubic meter chamber for multilayer and nanocomposite film development
• 0.5-cubic meter chamber for use with novel plasma nitriding techniques

SwRI has state-of-the-art equipment in place and technical personnel dedicated to facilitating access to research, development, and demonstration of PIII and PIIP technologies.

Ion Beam Processing

The semiconductor industry has fabricated integrated circuits using ion beam processing for decades. SwRI has expanded and adapted the use of ion beams for a broad range of materials and applications. Unlike conventional surface treatments such as plating or vapor deposition, many ion beam processes alter surface properties of a component without changing its dimension or surface finish. Specific processes include:

• Ion implantation
• Ion beam texturing and sputtering
• High-intensity ion nitriding

Many of these processes can be carried out at temperatures lower than 150°C, eliminating thermal distortion or tempering. Ion beam processing has been used to modify:

• Surface hardness
• Friction and wear resistance
• Fatigue life
• Corrosion and oxidation resistance
• Surface texture and wettability

Institute facilities include a variety of ion sources to supply:

• Gaseous species from H to Kr
• High-energy ions at 30 to 100 keV, 65 mA
• Medium-energy ions at 1 to 10 keV, 100 mA
• Low-energy ions at 0.1 to 1.5 keV, 300 mA
• Beams up to 50 centimeters in diameter

SwRI scientists have investigated a variety of materials, including:

• Metals (tool steels, hard chrome, and Ti, Al, and Ni alloys)
• Ceramics (SiC, carbides, and TiN)
• Polymers (nylons, polyethylene, and polytetrafluoroethylene [PTFE])

Ion beam processing can aid in applications such as:

• Injection molds
• Forming dies and punches
• Extremely sharp cutting tools
• Microelectronics and electro-optics
• Food-processing equipment

A high-energy plasma bucket ion source provides a high-current, large-diameter beam that permits nitrogen ion implantation of areas up to four square feet.

Vacuum Coating

SwRI uses a broad range of physical vapor deposition processes, including electron beam evaporation, magnetron sputtering, and ion beam-assisted deposition. Different chambers can be configured with multiple electron beam hearths, magnetron sputter guns, and ion sources. Scientists have performed research and development in areas such as:

• Functionally graded coatings
• Nanocomposite coatings
• Corrosion- and oxidation-resistant coatings
• Tribological coatings for challenging environments
• Multilayer and superlattice optical and electronic coatings

SwRI has demonstrated experience with a variety of materials, including:

• Ceramics, such as Ta₂O₅, Al₂O₃, TiO₂, and SiO₂
• Metals, such as Pt, Au, Ag, Ni, Cr, Ti, and Ta
• Others, such as ITO, a-SiN, and a-C:H

The Institute has explored a variety of application areas, including:

• Environmentally acceptable alternatives to electroplated chromium and cadmium
• Scratch-resistant and transparent conductive coatings for plastics
• Magnetic multilayer coatings for sensors
• Transparent conductive oxides for flat-panel displays
• Hydrophobic/hydrophilic and barrier coatings

In IBAD, an ion source is used to deposit dense, low-stress coatings with improved adhesion.

Large-Area Plasma Processing

Building on established capabilities in ion beam surface modification, SwRI has implemented plasma immersion ion implantation (PIII) and plasma immersion ion deposition (PIID). Both techniques allow non-line-of-sight ion implantation and coating of materials with higher throughput and at a potentially lower cost.

PIII and PIID use a high-voltage power supply to generate large-area pulsed radio frequency or glow discharge plasmas that totally surround the treated components. Advantages of these methods include:

• Single-batch treatment of several square meters surface area
• Low processing temperatures of less than 150°C
• Part manipulation not required
• Batch processing times of 2 to 8 hours
• Internal surface treatment possible
• Plasmas generated from a variety of gases and organic precursors
• Ability to generate metal plasmas (in development)

The large-area, non-line-of-sight PIIP process promises several advantages over conventional vacuum-coating processes including higher throughput (at lower cost), reduced component heating, and the ability to treat external surfaces simultaneously without manipulation.

Precision-tempered steel bearings generally cannot be coated because even very thin layers of coating may result in unacceptable dimension and surface finish changes. SwRI has evaluated the use of carbon ion implantation using PIII in bearing steels to improve wear and corrosion resistance.

Diamond-Like Carbon Coating

SwRI scientists have used ion beam- and plasma-based processes to deposit coatings of diamond-like carbon (DLC). These DLC films possess many diamond-like properties including low friction, high hardness, and chemical inertness. Specific DLC properties include:

• Microhardness: 8 to 25 GPa
• Friction coefficient: Less than 0.1 under dry sliding conditions (humidity up to
  80 percent)
• Compressive stress: 50 to 2,000 MPa
• Adhesion to metals: Excellent with interlayer or other pretreatments
• Deposition temperature: Less than 150°C
• Hydrogen content: 15 to 35 atomic percent
• Electrical resistivity: Controllable from 1.0 to 10¹² ohm·cm

SwRI scientists have evaluated DLC in areas such as:

• Friction and wear coatings for pump components
• Release coatings for compression and injection molds
• Protective coatings for resistance to chemical attack

Using the PIID process, SwRI staff have deposited DLC coatings on the inner surfaces of tubes up to 70-centimeters long and as narrow as 2 centimeters in diameter.

Web Processing of Materials

SwRI maintains a versatile system for pilot-scale vacuum coating and surface treatment of flexible polymeric and metallic materials in roll form. Key attributes of the system include:

• Dual electron beam and magnetron sputtering for simultaneous or sequential deposition
• Integrated linear ion source for web cleaning, surface activation, or texturing
• Fully automated closed-loop control of all pump-down, web-handling, and treatment processes
• Fast pumping times for rapid material turnaround
• Processing of rolls up to 12 inches wide and 15 inches in diameter (approximately 1,000 feet long) at speeds up to 30 feet per minute

This resource can be used to address client needs in areas such as:

• Thermal, chemical, and vapor barrier coatings
• Flexible electronic circuits
• Integrated device structures such as photovoltaics, batteries, and ultracapacitors
• Nanostructured surfaces including
  • High surface areas
  • Catalysis
• Electrostatic discharge coating
• Transparent conductive oxides

SwRI has established a pilot-scale vacuum web-coating system for treating a variety of flexible materials in roll form.

Biomedical Applications

A significant focus of the Institute's surface engineering work is related to medical device applications. Working with SwRI's bioengineering group, Institute scientists can conduct biomedical projects in accordance with a quality system for medical device development that is compliant with the U.S. Food and Drug Administration's Quality System Regulation.

Areas of interest for ion implantation and plasma nitriding include:

• High-intensity plasma ion nitriding of metal alloys for wear-resistant orthopedics
• Improved cutting performance of ultra-sharp surgical tools
• Implantation of bioactive ceramics
• Implantation of radioactive tracers for precision measurement of polyethylene wear

SwRI scientists have also used vacuum coatings for a number of applications including:

• Radioactive coatings for brachytherapy
• Radiopaque coatings for stents
• Corrosion-resistant coatings for implantable devices
• Titanium coatings for enhanced osseointegration

Diamond-like carbon, a highly biocompatible and blood-compatible material, might be as nonclotting as pyrolytic carbon. DLC biomedical applications include:

• Cardiovascular pumps
• Catheters
• Surgical seals
• Stents

SwRI has also developed a novel silver-doped DLC with significant potential to reduce device-related infection. Key aspects of this coating include:

• Reduced potential for tissue irritation in comparison to solid silver coating
• Improved adhesion to a wide variety of polymers
• Additional resistance to bacterial adhesion with DLC
• Ability to tailor color and reflectivity

SwRI has applied radioactive coatings to implantable medical devices to accelerate the formation of scar tissue.

Transportation Applications

Noted for its work in the automotive and transportation fields, the Institute develops surface treatments on components to reduce friction and wear. Areas of development for automotive applications include:

• Fuel pump and injector components
• Valve train components
• Piston pins and skirts
• Water pump seals

Work for the aerospace industry includes:

• Wear and corrosion treatments for bearing and gears
• Coatings for hydraulic actuators and seals
• Wear and diffusion barriers for turbine blades and disks

DLC-coated gear may improve service life in challenging lubrication conditions.

Institute scientists coat titanium-alloy connecting rods and other components to reduce wear and galling, particularly in high-performance vehicles.

Energy Applications

Using novel vacuum coating and surface treatment processes, SwRI scientists are involved in various aspects of energy production and storage. Areas of interest include:

• Fuel cells
  • Corrosion- and oxidation-resistant materials for solid oxide fuel cells
  • Catalytic coatings for polymer electrolyte fuel cells
• Hydrogen production
  • Photochemical generation of hydrogen
  • Ultra-thin metal membranes for hydrogen purification
• Thin-film devices
  • Coated fibers and planar structures for energy production and storage
  • Remote wireless sensors for demanding environments, such as gas turbine engines and coal-fired reactors

SwRI has developed a free-standing palladium alloy membrane for hydrogen separation using vacuum-deposition methods. Shown here is a membrane sandwiched between metal screens.

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