Materials & Chemicals : Nanocomposites

Materials & Chemicals Portfolios


Superabsorbent, Sustainable Aerogels

UW–Madison researchers have developed organic aerogels with excellent absorbent properties. They are made by combining a water soluble polymer and cellulose nanocrystals/nanofibers (CNFs) derived from biomass. The polymer, such as PVA (polyvinyl alcohol), is cross-linked to form a gel and then water is removed by freeze-drying. The surface of the aerogel is coated with an organosilane, making it highly water repellent and superoleophilic (‘oil loving’).

Sustainable Organic Aerogels for Insulation

UW–Madison researchers have developed hybrid organic aerogels with desirable insulation properties. They are made by combining a water soluble polymer and a carbon nanofiller such as graphene oxide nanosheet with cellulose nanofibrilliated fibers (CNFs) derived from biomass. The organic polymer, such as polyvinyl alcohol (PVA), is cross-linked to form a gel and water is removed by freeze-drying. The surface of the aerogel can by further modified.

Superior Nanocomposite Welding Wire

UW–Madison researchers have developed methods to fabricate welding wires exhibiting significantly reduced hot cracking defects.

The wires can be made from a range of metal alloys, including aluminum, steel and titanium-based alloys. Nanoparticles composed of high-temperature inorganic materials, such as intermetallic compounds or ceramics, are dispersed into the alloy. The composite material is extruded in a single stage to form wire.

Improved Immiscible Alloy Formation with Stabilizing Nanoparticles

UW–Madison researchers have developed a method for controlling the size of minority phase droplets during alloy formation. The approach utilizes nanoparticles to rapidly restrict the growth of the droplets after they nucleate and to inhibit coagulation when they collide, allowing for a more uniform mixture.

The nanoparticles are made of a thermally stable ceramic or other material, and are added to the hot liquid alloy solution. Only then is the melt allowed to cool, with the nanoparticles spontaneously assembling between the growing droplets and the rest of the material. In this way, the nanoparticles act as a thin coating around the droplets to prevent them from growing, coalescing and sinking.

Improved Method for Incorporating and Uniformly Dispersing Nanoparticles into Metal-Based Materials

UW–Madison researchers have developed a method to incorporate and uniformly disperse nanoparticles into a metal matrix through a combination of liquid state processing and solid state stirring. The method comprises introducing nanomaterials into a metal-based material in a liquid state, cooling the materials to a viscous state and stirring the materials to disperse the nanomaterials therein. The metal-based material may be used to maintain dispersion as the metal cools. Ultrasonic or mechanical stirring is used to initially disperse the nanomaterials within the molten metal, with subsequent stirring in the partially solidified state to break up clusters or other agglomerations of the nanomaterials.

Improved System for Large-Scale Production of Metal Matrix Nanocomposites

UW–Madison researchers have developed an apparatus for producing metal matrix nanocomposites on an industrial scale. The apparatus has three main integrated systems: a nanoparticle feeding system, a mechanical mixing system and a cavitation system. The apparatus also comprises a production chamber defining a cavity and a pumping conduit. In addition, the researchers have developed a method for producing MMNCs that involves introducing nanoparticle agglomerates into a volume of molten metal, wherein a flow is created that continuously carries the nanoparticle agglomerates.

Production of Nanoparticle Reinforced Metal-Matrix Nanocomposites from Master Nanocomposites

UW–Madison researchers have developed a method of producing a metal-matrix nanocomposite using a master material containing a higher percentage of wetted nanoparticles than the molten metal to which the master material is introduced. The master metal-matrix nanocomposite is introduced into a molten metal at a temperature above the melting temperature of the master metal-matrix nanocomposite. The master metal-matrix nanocomposite contains a first matrix metal and selected nanoparticles dispersed in the matrix metal. The first matrix metal may be an alloy containing a primary metal element and a wettability enhancing metal element. A portion of the master metal-matrix nancomposite is introduced by immersion as a solid or semisolid, or by addition as a liquid, and the master material melts into the molten metal. Then, the mixed molten metal solidifies to provide a second metal-matrix nancomposite containing a second matrix metal and at least a portion of the nanoparticles dispersed in the second matrix metal.

The use of a master nanocomposite allows the initial volume of metal processed with the nanoparticles to be reduced to a process in which the nanoparticles are added at their intended final concentration to a melt that will be added into the final nanocomposite. This enables the sale of solid master nanocomposites to foundries where they can be used easily to cast nanocomposites with desired nanoparticle concentrations without specialized training or expertise in nanoparticle handling and processing.

Nanoreactors as Time-Temperature Indicators for Monitoring Product Quality and Safety

UW-Madison researchers have developed a method to create a time-temperature indicator, referred to as a “nanoreactor,” that consists of a metal nanoparticle such as gold and a biopolymer carrier such as gelatin. When gelatin comes into contact with a gold-containing precursor compound such as chloroauric acid, the gelatin chemically reduces the compound to form gold nanoparticles, and then stabilizes the nanoparticles by surrounding them in a matrix of gelatin proteins.

The structures of these nanoparticles and the containing matrix change in response to time, light and temperature. This particle-level structure determines what wavelengths of light the composition absorbs, and correspondingly determines what the human eye perceives to be the color of the composition. The changes in structure, absorption and color after exposure to time and temperature change are shown in the figures below.

The results of the different conditions that induce changes to the nanoparticles are distinct and reproducible. For example, the form the nanoparticles take after being exposed to intense heat and then chilled will be different than the form after brief bursts of intense heat. As a result, these nanoreactor compositions are useful as indicators to identify when materials are no longer safe for use based on the exposure history of the material. Changes to the indicator could be monitored qualitatively through visual inspection of color change, or quantitatively by using a spectrophotometer to measure changes in light absorption. The nanoreactor also is completely safe to use as an indicator added directly to the material of interest, since both gold and gelatin are routinely put into human bodies without causing harm.

Method of Orientating Fillers in Polymer Composite Materials

UW–Madison researchers have developed a method for fabricating polymer composites incorporating fillers with multi-directional orientations that allow for the fillers to be orientated in a direction or concentration suitable for a particular composite requirement. After depositing fillers in a matrix material, fillers are aligned by exposing specific portions of the matrix material to an electric field. This alignment creates a pseudo-fiber representative of chains of the filler particles, which is oriented parallel to the electric field direction. The filler particles then are locked into position by hardening of the polymer matrix through UV curing or other means. The process is repeated with pseudo-fiber alignment in desired directions for multiple layers, which are bonded together naturally through the hardening process. This process may be used to create laminated composites with multi-directional filler orientations with natural or synthetic fillers in a variety of shapes. This process also can be easily incorporated with existing rapid prototyping machines and processes to produce parts with significantly improved performance due to the added capability of manipulating the filler orientation and distribution within the matrix material.

Methods and Novel Spectophotometer for Achieving Uniform Dispersion of Carbon Nanotubes, Graphene and Nanocellulose

Researchers at UW-Platteville have developed enabling technologies that address the purification and dispersion problems inherent when processing graphene, carbon nanotubes and other nanomaterials. A sensitive photon counting static light scattering (SLS) spectrophotometer was built to collect data for calculating various thermodynamic parameters of dilute samples. The data is used to identify the existence of a solvent resonance whose local extreme identifies the intrinsic property of an ideal solvent (for a given solute). The intrinsic property identified by the solvent resonance can be employed to inform a search for a solvent having the best match to this intrinsic property.

Low-Temperature, Corrosion-Resistant Integrated Metal Coatings to Improve Efficiency of Coal Plants

UW-Madison researchers have developed an improved method for the low-temperature synthesis of integrated, corrosion-resistant coatings for metal substrates. The low-temperature process avoids the degradation of substrate mechanical properties that occurs in traditional pack cementation processes. The new method also improves upon previous technologies by widening the scope of its application. For example, synthesis of aluminide coatings on steel alloys via low-temperature pack cementation can enhance oxidation resistance in conditions of extreme temperature and moisture, as in high-temperature operation of steam power generation plants. 

In general, the integrated coating consists of the substrate metal, a diffusion-barrier that hinders diffusion of the coating components into the substrate, a corrosion-resistant layer and an oxidation barrier. Deposition of the integrated structure can be achieved via pack cementation at a temperature lower than 700°C, or by thermal spray, vapor deposition or electrodeposition methods.

The substrate, diffusion layer and corrosion-resistant layer can consist of metals, intermetallic compounds or metalloid alloys, depending on the specific application of the integrated structure. For example, a chromium/molybdenum/steel alloy substrate could be coated with an aluminum/iron/intermetallic diffusion-barrier and an aluminum/iron corrosion-resistant layer for use in coal-fired power plants, in which the integrated coating is in contact with supercritical steam. With these techniques, coal-fired power plants can operate at higher temperatures to exploit supercritical steam properties, improving efficiency and reducing overall emissions.

Semi-Solid Forming of Metal-Matrix Nanocomposites

UW-Madison researchers have developed a method of incorporating nanoparticles into a semi-solid casting process, so the resulting metal-matrix nanocomposite has the appropriate globular microstructure and improved mechanical properties. The metal-matrix nanocomposite is formed by heating a metal until it reaches a liquid state and then adding nanoparticles to the liquid metal. To uniformly distribute the nanoparticles throughout the metal, the metal/nanoparticle mixture is agitated by inserting a probe that vibrates at ultrasonic frequencies into the mixture. The mixture can then be cooled, and the vibrating probe removed. When the mixture reaches a semi-solid state, it can be injected into a mold cavity for SSC.

Carbon Nanotube Schottky Barrier Photovoltaic Device

UW-Madison researchers have developed a cost- and energy-efficient photovoltaic cell that uses carbon nanotubes as the photoconducting material. Unlike semiconductor materials, carbon nanotubes absorb different spectra of light depending on the diameter and chirality of each tube. A variety of nanotube sizes and chiralities can be used within a photovoltaic array to significantly increase the efficiency over current technologies.

The invention also includes a novel method of manufacturing the nanotube array. Normally, nanotubes are grown with a catalyst and preserved in a fluid, which the end user must go through several steps to remove. The nanotubes described here can be grown and then directly attached to the array surface.

Because large numbers of nanotubes are needed to generate current efficiently, they are attached in a dense, but random arrangement. After the nanotubes are deposited on the surface, the metallic contacts from which the current is gathered are applied in a uniform grid over the nanotubes.

Small-Scale Powder Deposition for Three-Dimensional MEMS

UW–Madison researchers have developed a new process for manufacturing three-dimensional heterogeneous MEMS. In this way, devices can be made from a variety of materials with desirable properties such as improved robustness, ductility and fatigue life.

The new process uses a feed mechanism capable of dispensing small-scale fabrication materials (e.g., dry micro- or nano-powders and biological cells). The material is loaded into a glass capillary and deposited on a substrate with the help of ultrasonic vibrations, which cause the material to discharge in a controlled fashion. A micromachining laser turns the powder into a solid and patterns it.

Oxidation Resistant Coatings for Ultra-High Temperature Transition Metals and Metal Alloys

UW-Madison researchers have developed a multilayered coating for the surface of Mo-Si-B alloys, which includes a diffusion barrier layer, an oxidation resistant layer and an oxidation barrier layer. The coatings form a stable gradient of integrated layers that prevents cracking, peeling and delamination of Mo-Si-B alloys under extreme operating conditions.

Method and Apparatus for Carbon Nanotube Production

A UW-Madison researcher has developed a method for driving the cathode ultrasonically, resulting in a high tip acceleration that dislodges large carbon chunks, leaving the lighter nanotubes to form. The method also describes the use of a cooling method on the cathode to diminish the formation of unwanted carbon material. Nanotubes created using this technique are greatly increased in length (greater than one mm) and quantity.