#materials properties

Automated high-throughput system developed to generate structural materials databases

A NIMS research team has developed an automated high-throughput system capable of generating datasets from a single sample of a superalloy used in aircraft engines. The system successfully produced an experimental dataset containing several thousand records—each consisting of interconnected processing conditions, microstructural features and resulting yield strengths (referred to as "Process–Structure–Property datasets" below)—in just 13 days. Datasets are generated over 200 times faster than when using conventional methods. The system's ability to rapidly produce large-scale, comprehensive datasets has the potential to significantly accelerate data-driven materials design. This research is published in Materials & Design.

Mirror-like graphite films break records in strength and conductivity

Graphite has attracted global interest due to its unique anisotropic properties, including excellent electrical and thermal conductivity. Widely used as a battery anode material and in applications such as electromagnetic shielding, catalysis, and nuclear technology, graphite remains a critical material in both industrial and research fields. For decades, researchers have sought to produce high-quality artificial graphite with large grains and smooth, layered structures. Conventional methods typically involve high-temperature treatment of polymer films under mechanical stress. However, the resulting materials often suffer from limited grain size, lower density, and surface irregularities, with their bulk mechanical properties seldom evaluated. Another well-known synthetic form, highly oriented pyrolytic graphite (HOPG), offers improved crystallinity, but still exhibits relatively small domain sizes.

You guys are really trying to target the hard hitting questions, huh?

Alright, here's my answer: List of materials properties. 😁

In all seriousness, I can't give a single answer, but I suppose I can narrow it down from every property ever conceived of! My answer would probably vary from day to day, but if I had to pick a single property...

... drum roll please ...

Density!

I don't know, something about picking up two hunks of metal that are the exact same size and having one (aluminum, for example) be really light while the other (lets go with tungsten) is really heavy is just neat. Have you seen Galileo thermometers, where you can measure temperature based on the effect it has on the density of liquids? And it's fun to measure density the way Archimedes did it, by the displacement of water.

Honorable mentions that might replace density on any given day (though I'm not familiar with the methods of measuring all these properties, hence why some of them didn't win out!):

I'm a mechanical properties person through and through. Microhardness tests are super neat. I love seeing the little diamonds they form in a metal (Vickers is more common, but Knoop is cool too). Yield strength is a classic, measured, of course, through tensile tests. (Did you know you can measure elastic modulus through ultrasonic testing?)

The coefficient of thermal expansion. The idea that things shrink or grow based on temperature, also very neat. Supposedly the two halves of the Gateway Arch in St. Louis in the US didn't line up properly because of thermal expansion in the heat, so they had to cool it down with hoses to get the last piece in!

Conductivity. Thermal or electrical. I think about thermal conductivity every time I sit down on a park bench in the sun (is it a metal bench? wood?), and electrical conductivity... well, we all know electricity is just magic sufficiently explained, isn't it?

Speaking of magic... I'm not going to go into specifics here but, just... magnetism. Magnetic properties are wild.

Refraction. The angle of light changing as it passes through a transparent/semi-transparent material? Wild. And birefringence? Have you seen that?

Color. Yes, color can be considered an optical property (for the most part; perception matters too). And as someone with a favorite color, I enjoy it very much.

Okay, I had to cut myself off there before the list got too long! Thanks for the ask!

Density

One commonly known thermodynamic property of materials is density, or a substance's mass per unit volume. A material's density gives an indication of how tightly packed the atoms or molecules of that substance are. Mathematically, density is typically represented by the Greek letter rho. Density cannot often be calculated simply from knowing a material's composition: changes in pressure, temperature, material's processing, crystal structure, etc. all influence density. In addition, for solid, non-pure substances (i.e., a copper-nickel alloy, instead of just pure nickel) the bond lengths will be different in the mixture than in the pure substances. Given this, known densities are typically from experimental measurements.

Intensive and Extensive Properties

Materials properties are often classified as intensive or extensive properties. Intensive properties are intrinsic based on the material's composition - they do not depend on how much of a substance there is. The boiling point of a liquid is an intensive property, as is chemical potential, energy density, pressure, etc. Extensive properties are dependent on the amount of a substance, though they can be related to a material's composition. The volume of a substance is an extensive property, as is the enthalpy, entropy, and mass.

Beyond intensive and extensive, there are also specific and molar properties. Specific properties as those divided by mass only; molar properties are thus similar but they are divided by moles, not mass. Entropy is an extensive property. Entropy over mass is the specific entropy and entropy over moles is the molar entropy, both intensive properties.

How do ceramic particles strengthen metallic copper?

Publishing in the International Journal of Extreme Manufacturing, scientists from Jilin University and Edith Cowan University comprehensively reviewed the latest preparation techniques of copper matrix composites and the effect of ceramic particles on the mechanical properties, thermal conductivity and thermal expansion behavior of the composites. Four main aspects of particle characterization were included: particle content, particle size, particle morphology and interfacial bonding of particles to copper matrix. Team leader, Feng Qiu, said, "By reviewing the preparation techniques and effect mechanisms of particle reinforced copper matrix composites, it is hoped that this will serve as a basis for more precise design and manipulation of composite microstructure to meet the growing demand for copper matrix composites in a wide range of application fields." So far, endeavors have been focusing on how to choose suitable ceramic components and fully exert the strengthening effect of ceramic particles in the copper matrix. Currently, the preparation of copper matrix composites by powder metallurgy is the most mature technique, but it still faces many unresolved process drawbacks.

Ultrathin vanadium oxychloride demonstrates strong optical anisotropic properties

The optical, electrical and mechanical properties of some materials change depending on the direction or orientation of the material. Depending on how wood is cut, for example, the orientation of the wood grain can result in a stronger or weaker material with different appearances. This same principal applies to ultrathin, two-dimensional (2D) materials with unique properties such as magnetism.

Depending on the direction of a mechanical strain placed on one of these materials, the magnetic properties of the material change. This may facilitate the design of unique magnetic strain sensors that can convert force into a measurable electrical change. And while the anisotropy of the magnetic, mechanical, optical and other properties of these materials can, in theory, be predicted, the predictions must be supported or rejected based on empirical measurements to determine the true suitability of a material for a particular application.

A recent study led by scientists at Beihang University was designed specifically to experimentally assess the physical properties of ultrathin vanadium oxychloride (VOCl) because of its potential suitability for various nanotechnologies based on theoretical calculations. The research team systematically characterized the directionality of the optical properties of the 2D material in response to the arrangement of its atoms, using polarized light. The findings are reported in the January 5, 2023, issue of Nano Research.

New approach extracts more data on steel alloys for materials databases

A new approach uses data from one type of test on small metal alloy samples to extract enough information for building databases that can be used to predict the properties and potentials of new materials. The details were published in the journal Science and Technology of Advanced Materials: Methods.

The test is called instrumented indentation. It involves driving an indenter tip into a material to probe some of its properties, such as hardness and elastic stiffness. Scientists have been using the data extracted from instrumented indentation to estimate the stress-strain curve of materials using computational simulations.

This curve, and the data it provides, is important for understanding a material's properties. That data is also used for building massive materials databases, which can be used, in conjunction with artificial intelligence, for predicting new materials.

A problem scientists face is that this approach for estimating material properties is limited when it comes to materials called "high work-hardening alloys": metal alloys, like steel, that are strengthened through physical processes like rolling and forging. Only so much information can be estimated from the curve of these materials. To get the necessary additional information needed to determine their properties, more experiments would need to be done, which costs time, effort and money.