A schematic of a double perovskite heterostructure magnetic tunnel junction. (Credit: OSU.)

Last month I shared a story on the work Ohio State University researchers’ development of a computer-controlled “blowtorch” to simulate the high-temperature environment in gas turbine engines (to provide rapid thermal cycling of coatings to predict lifetimes as well as understand the effects of impurities ingested in the engines).

There is more work going on at OSU in the development of materials that can withstand the high temperatures of turbine engines. Referred to as double perovskites, these structures of ceramic oxide crystals may be able to withstand extreme temperatures of up to 1,000ºC without burning because, according to OSU researchers, they’re already oxidized and can retain their properties.

In an article written in OSU’s News in Engineering, the university’s College of Engineering publication, Joan Slattery Wall describes the double-perovskite structure:

The structure of perovskites consists of eight-sided building blocks, or octahedra — atoms that form four-sided pyramids arranged bottom to bottom. Four of these blocks group together like a cube with a different atom nestled in the center. The cubes stack together to form the perovskite crystal. In the double perovskite crystal, the center atom alternates between two different atoms, for example, iron and molybdenum in Sr₂FeMoO₆, to manipulate the magnetic qualities.

The team is led by Leonard Brillson, a professor in electrical and computer engineering in the school’s Center for Emergent Materials. He explains that the atomic latticework of double perovskites give the structure electromagnetic properties that can sense temperature, pressure, magnetic field and voltage.

“A perovskite is a building block that has special properties and properties you can design just by choosing the right atom to put in it and these can make sensors and computing elements,” Brillson says in the article.

Potential applications for double perovskites include aircraft turbine sensors, computer circuits as well as phased array  antennas. The layered structure prevents loss of electrical signal, since that typically occurs between stacked layers. The article states:

“Using oxide molecular beam epitaxy, or MBE, a technique to grow crystals on a substrate, Brillson can ’spray paint’ atomic layers one at a time as a thin film on a wafer, carefully forming the perovskite crystals to minimize imperfections and allow electrons to pass through the layers with a particular spin. Spin is a property of electrons that a magnetic field can sense and that doubles the amount of information carried through an electrical circuit.”

As a sidenote, Brillson presented a tutorial at ACerS’ 2010 Materials Challenges in Alternative & Renewable Energy. His presentation (coauthored by Sandra DeVincent Wolf and Duane B. Dimos), “Advanced Materials for Our Energy Future,” can be downloaded in PowerPoint format here.

Share

Map of southwestern grid transmission project, Southwest Intertie Project. Credit: DOI.

The DOE announced it is using Recovery Act monies to provide a loan guarantee for $343 million to assist a consortium building a 500 kV transmission line poised to transmit 600 MW of power throughout the Southwest.

The significance of this grid loan guarantee is that it’s the first of its kind, and most likely the first of many, as the nation’s push to integrate renewables into a national grid will call for a heavy network of transmission lines to transport the energy from its source.

The One Nevada Transmission Line project, or ON Line, is phase one of a two-phase transmission project, the Southwest Intertie Project. SWIP will link Nevada, Wyoming and Idaho to the entire southwest region and California. At the end of both phases, SWIP will consist of a 510-mile transmission system spanning Idaho to southern Nevada. The entire project is estimated to cost $1.6 billion, according to the Department of the Interior.

“As our country increases its use of alternative energy sources, new transmissions lines like the ON Line project will play a vital role in moving clean energy from one region to another,” says Steven Chu in a DOE press release.

“Traveling through several areas under consideration for wind, solar and geothermal power generation projects, this line will provide the critical transmission infrastructure to bring that potential to western communities,” said DOI Secretary Ken Salazar at the On Line groundbreaking ceremony last October.

The ON Line portion of the SWIP project is estimated to cost $510 million to build. The additional $167 million will be gathered from equity and debt from NV Energy, according to a report by the Las Vegas Review-Journal.

ON Line should be fully operational by early 2013. The full SWIP project has an operational date of 2014. Fund guarantees for the second phase of the project, known as SWIP-North, will most likely be granted in mid-2011 as Great Basin Transmission (contributing as a joint-venture energy company alongside NV Energy) anticipates having all permit requirements complete at that time.

Share

Typically, photovoltaic units composed of thin-film silicon materials do not involve amorphous or single-crystalline silicon, and making thin-films with poly-silicon is still a frontier field (see previous post). But researchers at the Japan Advanced Institute of Science and Technology may have developed the world’s first thin-film amorphous silicon photovoltaic cell made by using liquid silicon “inks.”

The group says its units have an energy conversion efficiency of 1.79 percent, according to Tatsuya Shimoda, professor at the JAIST School of Materials Science who is leading the team.

The energy conversion level is not a revelation, but the printing process may be a significant innovation.

(WARNING: Some of the details of what Shimoda’s group is doing are a little sketchy because the translations of their work from Japanese to English range from pretty bad to really, really bad. So, be forewarned that some of the following details may be faulty.)

The cells that are created by the group are pin-type (sometimes noted as p-i-n-type), where the p-, i- and n- layers are added to a glass substrate using an innovative “printing” technique.

It looks like the group uses a method that starts with cyclopentasilane. The CPS is polymerize to make polysilanes. The materials were developed a few years ago when the researchers were learning how to make the polysilane from the CPS (the polymer molecules are made by bonding SiH₂ like a chain). At that point, JAIST  researchers were able to form amorphous silicon-thin film transistors using a chemical vapor deposition procedure.

In time, the group was able to make pin-type cells, however the group found it difficult to create a uniform polysilane film with all layers being formed through the CVP method. Thus, they shifted their focus to a printing-based process.

The researchers say that by printing the layers, they are able to increase the conversion efficiency from the previous (all CVP) method of 0.51% to 1.79%. They feel confident they can improve conversion efficiency, but they have a long way to go before they catch up the leading thin-film silicon cells, such as United Solar’s 12% efficiency level recently confirmed by NREL.

Perhaps it will be more import that they have been able to come up with a process to mass produce amorphous silicon PV cells using roll-to-roll manufacturing.

Share

Micromeritics, a manufacturer of particle and nanotechnology instruments and equipment, is offering a free materials characterization workshop and plant tour on March 15, 2011, at its headquarters located in Norcross, Ga. The company says the workshop will benefit scientists, laboratory supervisors and technicians in industry and academia where knowledge of the physical characteristics of powders and solids is essential.

Three presentations are being given by Micromeritics staff scientists. The presentations will conclude with a question and answer session. The sessions will be followed by a tour of the company’s manufacturing facility.

• Determination of Particle Size Distribution of Powders by Various Analytical Methods, Including Characterization of Particle Shape – led by Anthony Thornton, director of Product Integrity and Performance
  Six methods, including one for characterizing shape of particles, will be discussed. A description of each method, including the principle of operation, data reduction and reporting and advantages and applications, will be provided. Methods to be discussed are X-ray monitored gravity sedimentation, static laser light scattering, dynamic laser light scattering, electrical sensing zone, air permeability and dynamic image analysis.

• An Examination of Chemisorption - A Powerful Tool Widely Used in the Study and Characterization of Catalysts – led by Simon Yunes, senior application scientist
  Chemical adsorption analyses can provide much of the information needed to evaluate catalyst materials in the design and production phases, as well as after a period of use. The chemical adsorption isotherm reveals information about the active surface of a material and researchers have used if for many years as a standard analytical tool for the evaluation of catalysts. In addition, thermo-programmed techniques have emerged as an indispensible companion to chemisorption isotherm analyses.

• Physical Adsorption - A Powerful Technique for Determining the Surface and Pore Structure of Solids – led by Jeff Kenvin, group leader of the Scientific Services Group and Jacek Jagiello, senior scientist
  This seminar will compare traditional techniques for surface area and pore structure to modern techniques including the use of non-local density functional theory and statistical mechanics. Additional topics will also include the use high pressure adsorption and the determination of the heat of adsorption for adsorbents.

For detailed information, presentation descriptions and to register for the workshop and plant tour, visit Micromeritics.

Share

We’ve reported in the past on the incredible magnification powers of scanning electron microscopes. An SEM is a type of electron microscope that images the sample surface by scanning it with a high-energy beam of electrons. The electrons interact with the atoms that make up the sample producing signals that contain information about the sample’s surface topography, composition and other properties such as electrical conductivity.

Scientists at the Electron Microscopy Unit of the USDA’s Beltsville Agricultural Research Center in Maryland have posted images of snowflakes taken with an SEM. It’s clear what they say is true: No two snowflakes are alike.

Share