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Mechanism of hardening for the surface phosphates under external high pressure

Pawlak, Zenon, Yarlagadda, Prasad K., Hargreaves, Douglas J., Kosse, Vladis, Frost, Ray L., Rauckyte, Teresa, & Zak, Slawomir (2007) Mechanism of hardening for the surface phosphates under external high pressure. [Working Paper] (Unpublished)

Abstract

Mechanism by which Zn/Fe methaphosphate material is transformed to glassy meta-phosphate is partially understood. The two decades of intensive study demonstrates that Zn and Fe ions participate to cross-link network under friction, hardening the phosphate.

In the present work we consider our (in progress) spectroscopy study of zinc and iron phosphates under the influence external high pressure to determine Zn ion change coordination from tetrahedral to octahedral (or hexahedral) structure. The standard equipment is the optical high pressure cell with diamond (DAC). The DAC is assembled and then vibrational or electronic spectra are collected by mounting the cell in an infrared, Raman, EXAFS or UV-visible spectrometer.

Transition metal atoms with d orbital have flexible coordination numbers, for example zinc acts as a cross-linking agent increasing hardness, by changing coordination from tetrahedral to octahedral. Perhaps the external pressure effect on the [Zn–(O-P-)4 ] complex causes a transformation to an [Zn –(O-P-)6] grouping High pressure spectroscopy has been extensively applied for the investigation of 3d transition metal ions in solids. When studying pressure effects on coordination compounds structure, we can expect changes in ground electronic state (spin-crossovers), electronic spectra due to structural distortions (piezochromism), and changes in the ligand field causing shifts in the electronic transitions.

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ID Code: 6175
Item Type: Working Paper
Additional URLs:
Keywords: antiwear additive, hardness, external pressure, transition metals, flexible coordination number, spectroscopy
Subjects: Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > MATERIALS ENGINEERING (091200)
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Past > QUT Faculties & Divisions > Faculty of Science and Technology
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2007 The Author(s)
Deposited On: 15 Feb 2007
Last Modified: 22 Oct 2013 11:15

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