Thermal Treatment Impact on the Mechanical Properties of Mg3Si2O5(OH)4 Nanoscrolls

Our plain-English summary of Thermal Treatment Impact on the Mechanical Properties of Mg3Si2O5(OH)4 Nanoscrolls, by A. Krasilin, M. Khalisov, E. Khrapova, et al (Materials, 2022).

The study

• Authors: A. Krasilin, M. Khalisov, E. Khrapova, V. Ugolkov, A. Enyashin, A. Ankudinov
• Journal: Materials
• Published: 2022;15(24)
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A group of phyllosilicate nanoscrolls conjoins several hydrosilicate layered compounds with a size mismatch between octahedral and tetrahedral sheets. Among them, synthetic Mg3Si2O5(OH)4 chrysotile nanoscrolls (obtained via the hydrothermal method) possess high thermal stability and mechanical properties, making them prospective composite materials fillers. However, accurate determination of these nano-objects with Young's modulus remains challenging. Here, we report on a study of the mechanical properties evolution of individual synthetic phyllosilicate nanoscrolls after a series of heat treatments, observed with an atomic force microscopy and calculated using the density functional theory. It appears that the Young's modulus, as well as shear deformation's contribution to the nanoscrolls mechanical behavior, can be controlled by heat treatment. The main reason for this is the heat-induced formation of covalent bonding between the adjacent layers, which complicate the shear deformation.

In plain English

This was a laboratory materials-science study, not a health study. It did not examine people, animals or disease. The authors made synthetic Mg3Si2O5(OH)4 nanoscrolls with a chrysotile structure by a hydrothermal process and laid them across grooves on a silicon grid. Using atomic force microscopy, they bent the same individual scrolls before heating, after 8 hours at 400 degrees C, and after 8 hours at 600 degrees C. They also ran computer calculations (density functional theory) of the stiffness of chrysotile and sepiolite crystal structures. Heating removed water and hydroxyl groups and partly converted the scrolls to a sepiolite-like phase. The mean Young's modulus, a measure of stiffness, increased almost two times, mainly after 600 degrees C. The earlier dependence of stiffness on scroll diameter almost disappeared. The data indicated a significant increase in the scrolls' shear modulus. The calculated stiffness for sepiolite was lower than the measured values, which the authors attributed partly to their simplified sepiolite model. The authors concluded that the mechanical behavior of these nanoscrolls can be controlled by heat treatment.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: laboratory materials-science experiment: atomic force microscopy bending tests of individual nanoscrolls, compared with density functional theory (computer) modeling
• Who was studied: synthetic Mg3Si2O5(OH)4 phyllosilicate nanoscrolls (chrysotile structure) made by hydrothermal synthesis. About 100 scrolls spanning grooves on a silicon grid were located by electron microscopy, and some of these were tested. The exact number tested is not stated.
• Exposure: heat treatment of the nanoscrolls for 8 hours at 400 degrees C and then at 600 degrees C (in argon flow for the AFM samples), with the same individual scrolls tested after each step
• Main results:
  • In thermal analysis of the synthesis product, a weight loss of about 4% around 100 degrees C was due to removal of adsorbed water
  • Removal of hydroxyl groups on heating led to partial joining of adjacent layers and formation of a sepiolite-like phase
  • In the tested nanoscrolls, bending stiffness increased relatively weakly with treatment temperature
  • With higher treatment temperature, most nanoscrolls behaved more like a supported beam (a change in how they were held at their ends)
  • Heat treatment produced an almost two times increase in the mean Young's modulus of the nanoscrolls
  • The main increase in Young's modulus occurred after treatment at 600 degrees C
  • The dependence of Young's modulus on outer diameter, seen in this study, almost vanished after heat treatment
  • The estimated stiffness of the elastic foundation decreased by more than an order of magnitude with higher heat treatment temperature
  • After 600 degrees C, the data indicated a significant increase in the shear modulus of individual nanoscrolls
  • The computer modeling showed sepiolite had a larger average shear modulus than chrysotile
  • The calculated Young's modulus for sepiolite was lower than the values measured after 600 degrees C, so the calculated values could not fit those data
• The authors' conclusion: The authors concluded that heat treatment joined adjacent layers with Si-O-Si bonds instead of hydrogen bonds, which prevented shear strain, and that the mechanical behavior of these nanoscrolls can be controlled by heat treatment
• Limitations the authors state:
  • The computer model used a sepiolite cell in its native form, while the real heated nanoscroll structure is complicated by dehydroxylation and amorphous material. The authors suggest this may explain the gap between calculated and measured values.
  • Some water molecules in the sepiolite structure were left out of the model
  • The model underestimated one sepiolite lattice parameter (the a-parameter)

Topics

Medical terms in this study, explained in our Lexicon: Phyllosilicates, Chrysotile, Thermal Stability.

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