A team of researchers from the University of Texas at Dallas, in collaboration with scientists from Brazil, has made a groundbreaking discovery regarding carbon nanotube films. Their findings reveal that these films exhibit unusual mechanical behaviors when stretched or compressed uniformly. These unexpected yet highly beneficial properties open up new possibilities for applications such as advanced composites, artificial muscles, gaskets, and sensors. The study was recently published in the April 25 issue of *Science*.
Most materials tend to become thinner in one direction when stretched—similar to how a rubber band stretches and thins out. However, this unique material, known as "buckypaper," behaves differently. When stretched, it actually expands in width, and under uniform compression, it increases both in length and width. This kind of behavior is rare and offers exciting potential for engineering applications.
The phenomenon of lateral shrinking when stretched is described by Poisson's ratio. This ratio measures how much a material expands or contracts laterally when subjected to tension or compression. For centuries, people have used this principle, most notably in cork stoppers. Corks with a near-zero but positive Poisson’s ratio are harder to insert but easier to remove, while those with a negative ratio behave oppositely.
To create their buckypaper, the researchers used an ancient papermaking technique—drying fiber slurries. The slurry they used contained both single-walled and multi-walled carbon nanotubes. By adjusting the ratio of these nanotubes, they were able to significantly alter the Poisson’s ratio, shifting it from approximately 0.06 to as low as -0.20.
The team explained the change by drawing an analogy to collapsible wine racks. When the structure is allowed to collapse, the material exhibits a positive Poisson’s ratio, meaning it narrows when stretched. But if the structure is locked in place, making the pillars more extensible, the material shows a negative Poisson’s ratio, expanding in width when stretched.
In addition to the Poisson’s ratio adjustment, the mixed nanotube films showed remarkable improvements in mechanical performance. Compared to pure single- or multi-walled nanotube films, the hybrid version exhibited 1.6 times higher strength-to-weight ratio, 1.4 times greater stiffness, and 2.4 times better elastic modulus.
This discovery suggests that combining different types of carbon nanotubes could lead to even more advanced materials, such as nanotube membranes and other nanostructured arrays. It also opens the door to designing new functional devices like membrane composites, artificial muscles, pressure sensors, and even chemical sensors. With further research, this innovative material could revolutionize multiple fields of science and engineering.
Heat Treated Steel Bar And Tube
HEAT TREATED STEEL BAR AND TUBE
Heat treated steel bar is produced by heating and cooling in different temperature based on the steel grades to improve the steel bar mechanical properties or machinability for various industrial applications. Heat treated steel bar includes annealed steel bars, Normalized Steel Bar, quenched and temper qt steel bar.
Annealed steel bar has better ductility and lower hardness, which can be easier to be machined. The annealing processing is usually widely used for steel grade with higher carbon content above 0.5%. However, some low carbon steel also requires to do annealing for special usage such as 20CrMnTi gear steel. For some special material such as 20CrMnTi gear steel and GCr15 such bearing steel, spheroidizing annealing is often required.
Normalized steel bar sometime is also one kind of annealing processing. It mainly changes the grain to remove the impurities in steel and improves the strength and hardness. For some hot rolled steel bars, to keep the basic mechanical properties, normalizing is often used.
Quenching and Tempering, abbreviated as Q&T is a king of processing that strengthen or harden steel bars by heating the materials and then cooling in water, oil or other liquid medium, that rapidly the change from austenite to perlite to get the proper properties for various usage. The quenched & tempered steel bar materials are usually with carbon from 0.30% - 0.60%, it is widely used as merchant bars in components of various machines.
Our advantages on producing heat treated steel bars:
1) Big stocks of hot rolled round bars or wire rods as raw materials
2) Wide range of Cold Drawn Steel Bar sizes: from 10mm to 150mm
3) Different cold drawing medias powder or oil to get different surface
4) Straightening machines to get better straightness up to 0.5mm/m
5) Grinding and polishing machines to get better roughness upto 0.4um
6) Heat treating furnaces to adjust the mechanical properties
7) Full sets of testing equipment to test the sizes, mechanical properties and microstructure.
8) Multiple packages to avoid broken packages and anti-rusty
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