Rice lab discovers titanium-gold alloy that is four times harder than most steels
Titanium is the leading material for artificial knee and hip joints because it’s strong, wear-resistant and nontoxic, but an unexpected discovery by Rice University physicists shows that the gold standard for artificial joints can be improved with the addition of some actual gold.
“It is about 3-4 times harder than most steels,” said Emilia Morosan, the lead scientist on a new study in Science Advances that describes the properties of a 3-to-1 mixture of titanium and gold with a specific atomic structure that imparts hardness. “It’s four times harder than pure titanium, which is what’s currently being used in most dental implants and replacement joints.”
Morosan, a physicist who specializes in the design and synthesis of compounds with exotic electronic and magnetic properties, said the new study is “a first for me in a number of ways. This compound is not difficult to make, and it’s not a new material.”
In fact, the atomic structure of the material — its atoms are tightly packed in a “cubic” crystalline structure that’s often associated with hardness — was previously known. It’s not even clear that Morosan and former graduate student Eteri Svanidze, the study’s lead co-author, were the first to make a pure sample of the ultrahard “beta” form of the compound. But due to a couple of lucky breaks, they and their co-authors are the first to document the material’s remarkable properties.
“This began from my core research,” said Morosan, professor of physics and astronomy, of chemistry and of materials science and nanoengineering at Rice. “We published a study not long ago on titanium-gold, a 1-to-1 ratio compound that was a magnetic material made from nonmagnetic elements. One of the things that we do when we make a new compound is try to grind it into powder for X-ray purposes. This helps with identifying the composition, the purity, the crystal structure and other structural properties.
“When we tried to grind up titanium-gold, we couldn’t,” she recalled. “I even bought a diamond (coated) mortar and pestle, and we still couldn’t grind it up.”
Morosan and Svanidze decided to do follow-up tests to determine exactly how hard the compound was, and while they were at it, they also decided to measure the hardness of the other compositions of titanium and gold that they had used as comparisons in the original study.
One of the extra compounds was a mixture of three parts titanium and one part gold that had been prepared at high temperature.
What the team didn’t know at the time was that making titanium-3-gold at relatively high temperature produces an almost pure crystalline form of the beta version of the alloy — the crystal structure that’s four times harder than titanium. At lower temperatures, the atoms tend to arrange in another cubic structure — the alpha form of titanium-3-gold. The alpha structure is about as hard as regular titanium. It appears that labs that had previously measured the hardness of titanium-3-gold had measured samples that largely consisted of the alpha arrangement of atoms.
The team measured the hardness of the beta form of the crystal in conjunction with colleagues at Texas A&M University’s Turbomachinery Laboratory and at the National High Magnetic Field Laboratory at Florida State University, Morosan and Svanidze also performed other comparisons with titanium. For biomedical implants, for example, two key measures are biocompatibility and wear resistance. Because titanium and gold by themselves are among the most biocompatible metals and are often used in medical implants, the team believed titanium-3-gold would be comparable. In fact, tests by colleagues at the University of Texas MD Anderson Cancer Center in Houston determined that the new alloy was even more biocompatible than pure titanium. The story proved much the same for wear resistance: Titanium-3-gold also outperformed pure titanium.
Morosan said she has no plans to become a materials scientist or dramatically alter her lab’s focus, but she said her group is planning to conduct follow-up tests to further investigate the crystal structure of beta titanium-3-gold and to see if chemical dopants might improve its hardness even further.
Researchers look for better ways to reduce memory loss in people with age-related disorders
Although brains—even adult brains—are far more malleable than we used to think, they are eventually subject to age-related illnesses, like dementia, and loss of cognitive function.
Someday, though, we may actually be able to replace brain cells and restore memory. Recent work by Ashok K. Shetty, Ph.D., a professor in the Department of Molecular and Cellular Medicine, associate director of the Institute for Regenerative Medicine, and research career scientist at the Central Texas Veterans Health Care System, and his team at the Texas A&M Health Science Center College of Medicine hints at this possibility with a new technique of preparing donor neural stem cells and grafting them into an aged brain.
Shetty and his team took neural stem cells and implanted them into the hippocampus—which plays an important role in making new memories and connecting them to emotions—of an animal model, essentially enabling them to regenerate tissue. Findings were published in the journal Stem Cells Translational Medicine.
“We chose the hippocampus because it’s so important in learning, memory and mood function,” Shetty said. “We’re interested in understanding aging in the brain, especially in the hippocampus, which seems particularly vulnerable to age-related changes.” The volume of this part of the brain seems to decrease during the aging process, and this decrease may be related to age-related decline in neurogenesis (production of new neurons) and the memory deficits some people experience as they grow older.
Texas A&M University (A&M or TAMU) is a coeducational public research university located in College Station, Texas, United States.
It is the flagship institution of the Texas A&M University System, the fourth-largest university in the United States and the largest university in Texas. Texas A&M’s designation as a land, sea, and space grant institution reflects a broad range of research with ongoing projects funded by agencies such as the National Aeronautics and Space Administration (NASA), the National Institutes of Health, the National Science Foundation, and the Office of Naval Research. The school ranks in the top 20 American research institutes in terms of funding and has made notable contributions to such fields as animal cloning and petroleum engineering.
The first public institution of higher education in Texas, though not the first general university in the state, the school opened on October 4, 1876 as the Agricultural and Mechanical College of Texas under the provisions of the Morrill Land-Grant Acts. Originally, the college taught no classes in agriculture, instead concentrating on classical studies, languages, literature, and applied mathematics. After four years, students could attain degrees in scientific agriculture, civil and mining engineering, and language and literature. Under the leadership of President James Earl Rudder, in the 1960s A&M desegregated, became coeducational, and dropped the requirement for participation in the Corps of Cadets. To reflect the institution’s expanded roles and academic offerings, the Texas Legislature renamed the school to Texas A&M University in 1963. The letters “A&M”, originally short for “Agricultural and Mechanical”, are retained only as a link to the university’s past. The school’s students, alumni, and sports teams are known as “Aggies”.
The main campus is one of the largest in America, spanning 5,500 acres (22 km2), and includes the George Bush Presidential Library. Approximately one-fifth of the student body lives on campus. Texas A&M has approximately 800 officially recognized student organizations. Many students also observe the traditions of Texas A&M University, which govern daily life as well as special occasions, including sports events. On July 1, 2012, the school joined the Southeastern Conference. A&M operates two branches: Texas A&M at Qatar and Texas A&M University at Galveston. Working with agencies such as the Texas AgriLife Research and Texas AgriLife Extension Service, Texas A&M has a direct presence in each of the 254 counties in Texas. The university offers degrees in over 150 courses of study through ten colleges and houses 18 research institutes. Texas A&M has awarded over 320,000 degrees, including 70,000 graduate and professional degrees.
As a Senior Military College, Texas A&M is one of three public universities with a full-time, volunteer Corps of Cadets.
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Texas A&M University research articles from Innovation Toronto
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Scientists at Rice University have discovered that the strong force field emitted by a Tesla coil causes carbon nanotubes to self-assemble into long wires, a phenomenon they call “Teslaphoresis.”
Cherukuri sees this research as setting a clear path toward scalable assembly of nanotubes from the bottom up. The system works by remotely oscillating positive and negative charges in each nanotube, causing them to chain together into long wires. Cherukuri’s specially designed Tesla coil even generates a tractor beam-like effect as nanotube wires are pulled toward the coil over long distances.
“Electric fields have been used to move small objects, but only over ultrashort distances,” Cherukuri said. “With Teslaphoresis, we have the ability to massively scale up force fields to move matter remotely.”