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Category: materials – Page 4

Hypersonic impact rapidly transforms diamond into graphite, revealing energy-absorbing mechanism

Rice University researchers have developed a way to stabilize diamond during high-temperature and low-pressure processing, creating a strong bulk composite and discovering that high-speed collisions can rapidly transform diamond into graphite. Their study is published in Materials Today.

Diamond is one of the hardest known materials, with high thermal conductivity, properties that make it valuable for technologies that operate under extreme conditions. The findings could help researchers design tougher materials for aerospace, defense and other demanding environments by showing how diamond changes and absorbs energy under extreme force.

“This was quite an exciting outcome as it is nearly impossible to sinter diamond at lower pressures, and this new process we have developed could lead to the large-scale manufacturing of diamond-based composites,” said Pulickel Ajayan, the lead author of the study and the Benjamin M. and Mary Greenwood Anderson Professor of Engineering.

Soft vibrations reveal warning signs before granular crystals yield

Sand, powders, and other collections of visible-sized grains are found throughout daily life, from food and pharmaceuticals to soils and industrial materials. When grains of similar size are arranged regularly, they can form a strong crystal-like solid. Yet what happens inside such an ordered structure immediately before it begins to break has remained unclear.

Researchers at the University of Osaka, Shimane University, and Kyoto Sangyo University have now theoretically identified an unusual pattern of vibrations that emerges just before a crystal made of regularly arranged grains yields. Many vibrational modes soften simultaneously along particular directions, while long-wavelength waves travel more slowly than shorter ones. The findings, published in Physical Review E, reveal a possible physical precursor to failure in highly ordered particulate materials.

Long-range magnetic interactions govern how a ferrimagnet approaches its phase transition

Close to a phase transition, very different materials can follow the same mathematical rules. The concept of universality, which groups seemingly distinct systems based on their common properties, was developed to describe this phenomenon.

In magnetic systems, ferromagnets, ferrimagnets and antiferromagnets fall into the same universality class when short-range interactions dominate and their spatial and spin dimensionalities coincide. However, this universality has not been established when long-range interactions dominate.

In insulating magnets, long-range coupling may originate from dipole-dipole interactions. However, dipolar-driven mean-field criticality has only been firmly established in ferromagnets, leaving the ferrimagnetic and antiferromagnetic cases unexplored.

Unusual superconductivity could emerge in valley-imbalanced rhombohedral graphene

Superconductors are materials in which electrical current flows with a resistance of zero, typically below specific temperatures. In conventional superconductors, this state of matter emerges when two electrons bind together at low temperatures, forming so-called Cooper pairs.

Yet some materials, referred to as unconventional superconductors, exhibit superconductivity under unusual conditions and cannot be explained by conventional theories. Understanding these unusual cases could lead to the development of superconductors that can operate at high enough temperatures to be used in real-world devices with less refrigeration.

Researchers at Harvard University and the University of Stuttgart theoretically demonstrated that an unusual form of graphene, known as valley-imbalanced rhombohedral tetralayer graphene, could host unconventional superconducting states.

Chinese scientists employ new technology to scan cultural heritage sites for first time

Chinese scientists have successfully employed 3D hyperspectral imaging technology for the first time to create comprehensive digital archives of two ancient Buddhist grottoes at the Yungang Grottoes in Shanxi Province. This was reported by Science and Technology Daily, a partner of TV BRICS.

According to Li Lihong, a researcher at the Yungang Grottoes Research Institute, the technology can simultaneously record the geometric shapes, materials and distribution of defects in the heritage sites, creating a “spectral fingerprint” for every point on the surface.

Caves No. 7 and No. 8, carved between 471 and 494 AD, constitute the first pair of twin caves at Yungang. They blend Greek-style columns, Indian Gandhara Buddhist statues and traditional architectural elements from the Central Plains, bearing witness to the exchange between Eastern and Western civilisations and holding great significance in the history of the Yungang Grottoes. However, due to their complex curved surfaces and vast surface area, it had long been impossible to create a complete digital replica using standard equipment.

Anomalous quantum oscillations reveal new physics in a topological insulator

A study has been published in Nature Communications that identifies an unusual regime of quantum oscillations in a three-dimensional topological insulator. The results show that, when subjected to temperatures near absolute zero and extreme magnetic fields, electrons in the material zirconium pentatelluride (ZrTe₅) exhibit behavior that deviates from the pattern predicted by conventional theory.

The study, led by researchers from the University of São Paulo (USP) in Brazil, Los Alamos National Laboratory and the University of Washington, among other U.S. institutions, combines electrical transport experiments conducted in magnetic fields of up to 60 tesla and at temperatures around 0.7 kelvin (−272.45 °C) with detailed theoretical modeling.

“This work expands our understanding of electron transport in exotic phases of matter and suggests that topological insulators support the transport of not only electric charge, but also another fundamental degree of freedom: electron spin,” says Julio Larrea Jiménez, a professor at USP’s Physics Institute (IF) and co-founder and director of the Laboratory for Quantum Matter under Extreme Conditions (LQMEC).

Controlling the rotation direction of light without complex new materials

A new pathway has opened for controlling the rotation direction of light simply by changing how molecules are arranged, without having to synthesize complex new materials. Circularly polarized light is a special form of light that travels while rotating like a pinwheel to the left or right. Because different rotation directions can carry different information, it is drawing attention as a key light source for next-generation displays, optical communications and security technologies.

KAIST researchers have developed a platform technology that arranges symmetric molecules into “microscopic pinwheels,” enabling circularly polarized light with a desired rotation direction. The research results were published in the Nature Communications.

Uniaxial strain reveals new way to tune electron flow in altermagnet material

Altermagnetism is a new, third type of magnetism of great interest for spin-transport applications like computer memory. If properly harnessed, it could combine the benefits of the two existing types of magnetism, ferromagnetism and antiferromagnetism, ultimately reducing or eliminating heat during information transfer and increasing the ability to miniaturize next-generation technologies. Rice University’s Pengcheng Dai recently published a paper in Physical Review X describing the first successful efforts to put a proposed altermagnetic material into a single magnetic-domain state, allowing the research team to characterize the material’s intrinsic magnetic structure.

“Altermagnets like hexagonal manganese telluride typically form multidomain structures where the magnetic forces divide into separate equivalent domains that spin in different directions to satisfy the underlying threefold rotational symmetry of the hexagonal lattice,” said Dai, the Sam and Helen Worden Professor of Physics and Astronomy.

“The signals from these coexisting domains could overlap, making it hard to know what the underlying magnetic structure actually is. Here, we were able to apply a uniaxial strain, which resulted in a single magnetic domain we could clearly resolve into the underlying magnetic structure.”

Prostate cancer: evading immunity, inspiring therapy

Mereu et al. present ESPACE, a single-cell multi-omic atlas of the human pancreas spanning fetal development, adulthood, and type 2 diabetes. Combining transcriptomics, chromatin accessibility, and spatial imaging, they uncover a rare population of plastic centroacinar cells and hidden diversity among hormone-producing islet cells, informing pancreas regeneration and disease.

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