[PSUBS-MAILIST] FYI: Transparent Aluminium update

[Peter McKellar <submckellar@earthlink.net>]

Hi all,

 

just found this info - seems things have come a long way since the translucent aluminium ceramic posted here about 1 yr ago.

 

Raytheon have developed Aluminum oxynitride spinel (Al23O27N5) and there is another material (public domain?) called Magnesium aluminate spinel (MgAl2O4).  Both are ceramics and I picked this up in an article on transparent armour (was searching for aluminium, not armour btw)

The problem seems to be making big pieces, the AION has been produced in 11in curved plates (viewport anyone?), the pinel had a sample of 4in diameter and 0.44in thick with plans to make 10in pieces.  The properties of both are below:

                                               AlON Spinel

Density                         g/cm3  3.67                   3.58                 

Elastic Modulus              GPa    315                   277

Mean Flexure Strength    MPa    228                  241

Weibull Modulus                         8.7                  19.5

Fracture Toughness MPaÖm     2.40 ± 0.11       1.72 ± 0.06

Knoop Hardness (HK2) GPa    13.8 ± 0.3         12.1 ± 0.2

- http://amptiac.alionscience.com/pdf/AMPQ4_3.pdf

this raises a question also.  could someone please explain what all these different moduli are and how they relate (if at all).  I have seen Youngs modulus, and now Weibull's, are there any others im likely to encounter (and need)?.  Elasticity im ok with.

 

cheers

peter

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