Featured Research

from universities, journals, and other organizations

Ultra-High-Temperature Ceramics To Withstand 2000 Degrees Celsius

Date:
October 21, 2003
Source:
Sandia National Laboratories
Summary:
Researchers at the Department of Energy's Sandia National Laboratories have developed a new lightweight material to withstand ultra-high temperatures on hypersonic vehicles, such as the space shuttle.

Researchers at the Department of Energy's Sandia National Laboratories have developed a new lightweight material to withstand ultra-high temperatures on hypersonic vehicles, such as the space shuttle.

Related Articles


The ultra-high-temperature ceramics (UHTCs), created in Sandia's Advanced Materials Laboratory, can withstand up to 2000 degrees C (about 3,800 degrees F).

Ron Loehman, a senior scientist in Sandia's Ceramic Materials, said results from the first seven months of the project have exceeded his expectations.

"We plan to have demonstrated successful performance at the lab scale in another year with scale-up the next year," Loehman said.

Thermal insulation materials for sharp leading edges on hypersonic vehicles must be stable at very high temperatures (near 2000 degrees C). The materials must resist evaporation, erosion, and oxidation, and should exhibit low thermal diffusivity to limit heat transfer to support structures.

Composite materials

UHTCs are composed of zirconium diboride (ZrB2) and hafnium diboride (HfB2), and composites of those ceramics with silicon carbide (SiC). These ceramics are extremely hard and have high melting temperatures (3245 degrees C for ZrB2 and 3380 degrees C for HfB2). When combined, the material forms protective, oxidation-resistant coatings, and has low vapor pressures at potential use temperatures.

"However, in their present state of development, UHTCs have exhibited poor strength and thermal shock behavior, a deficiency that has been attributed to inability to make them as fully dense ceramics with good microstructures," Loehman said.

Loehman said the initial evaluation of UHTC specimens provided by the NASA Thermal Protection Branch about a year ago suggests that the poor properties were due to agglomerates, inhomogeneities, and grain boundary impurities, all of which could be traced to errors in ceramic processing.

During the first seven months, the researchers made UHTCs in both the ZrB2 and HfB2 systems that are 100 percent dense or nearly so. They have favorable microstructures, as indicated by preliminary electron microscopic examination. In addition, the researchers have hot pressed UHTCs with a much wider range of SiC contents than ever before. Availability of a range of compositions and microstructures will give system engineers added flexibility in optimizing their designs.

Collaborations

The project is part of the Sandia Thermal Protection Materials Program and represents the work of several Sandia researchers. The primary research team consists of Jill Glass, Paul Kotula, David Kuntz, and University of New Mexico doctoral student Hans-Peter Dumm.

Kuntz said his primary responsibility is to compute aeroheating, design thermal protection systems (heat shields), compute material thermal response on high-speed flight vehicles, and to develop tools to improve these capabilities.

"If a vehicle flies fast enough to get hot, we analyze it," Kuntz said. "Our tools consist of a set of computer codes that compute the flowfield around a high-speed flight vehicle, the resultant heating on the surface of the vehicle, and the subsequent temperatures and ablation of the materials which form the surface of the vehicle."

Glass works with high-temperature mechanical properties and fracture analysis, and Kotula performs microstructural and microchemical analysis on the ceramic materials.

Kotula applies the Automated eXpert Spectral Image Analysis (AXSIA) software (developed by Kotula and Michael Keenan, and recently patented and winner of a 2002 R&D 100 award) to the characterization of hafnium and zirconium diboride/silicon carbide UHTCs. Kotula looks at these materials at the micron to subnanometer length scale for grain size and phase distribution as well as impurities or contaminants that can adversely affect their mechanical properties.

Boron and carbon are difficult to analyze because they give off low-energy or soft X-rays when excited with an electron beam as in a scanning or transmission electron microscope typically used for such analyses. Instead of using X-ray analysis techniques, the research team has developed other analytical capabilities based on electron energy-loss spectrometry to determine amounts and nanometer-scale lateral distributions of the light elements in the UHTCs.

Oxygen, in particular, is an important impurity since, in combination with the silicon present in the UHTCs and other impurities, it can form glasses or other phases that typically can't take the required high-operation temperatures and would melt or crack in service, causing the material to fail.

"If enough of the wrong contaminants find their way into the process, the material will have no high-temperature strength or stability," Kotula said.


Story Source:

The above story is based on materials provided by Sandia National Laboratories. Note: Materials may be edited for content and length.


Cite This Page:

Sandia National Laboratories. "Ultra-High-Temperature Ceramics To Withstand 2000 Degrees Celsius." ScienceDaily. ScienceDaily, 21 October 2003. <www.sciencedaily.com/releases/2003/10/031020055530.htm>.
Sandia National Laboratories. (2003, October 21). Ultra-High-Temperature Ceramics To Withstand 2000 Degrees Celsius. ScienceDaily. Retrieved November 26, 2014 from www.sciencedaily.com/releases/2003/10/031020055530.htm
Sandia National Laboratories. "Ultra-High-Temperature Ceramics To Withstand 2000 Degrees Celsius." ScienceDaily. www.sciencedaily.com/releases/2003/10/031020055530.htm (accessed November 26, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Wednesday, November 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Who Will Failed Nuclear Talks Hurt Most?

Who Will Failed Nuclear Talks Hurt Most?

Reuters - Business Video Online (Nov. 25, 2014) With no immediate prospect of sanctions relief for Iran, and no solid progress in negotiations with the West over the country's nuclear programme, Ciara Lee asks why talks have still not produced results and what a resolution would mean for both parties. Video provided by Reuters
Powered by NewsLook.com
Flying Enthusiast Converts Real-Life Aircraft Cockpit Into Simulator

Flying Enthusiast Converts Real-Life Aircraft Cockpit Into Simulator

Reuters - Innovations Video Online (Nov. 25, 2014) A virtual flying enthusiast converts parts of a written-off Airbus aircraft into a working flight simulator in his northern Slovenian home. Jim Drury reports. Video provided by Reuters
Powered by NewsLook.com
Car Park Solution for Flexible Green Energy

Car Park Solution for Flexible Green Energy

Reuters - Innovations Video Online (Nov. 24, 2014) A British solar power start-up says that by covering millions of existing car park spaces around the UK with flexible solar panels, the country's power problems could be solved. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com
Microsoft Adds Robot Guards, Ushers In Sci-Fi Apocalypse

Microsoft Adds Robot Guards, Ushers In Sci-Fi Apocalypse

Newsy (Nov. 23, 2014) Microsoft has robotic security guards working at its Silicon Valley Campus. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins