About Transparent Aluminum (An Emerging Material)

1. TRANSPARENT ALUMINIUM
Aluminium Oxynitride (An Advanced Polycrystalline Transparent Ceramic)
Commercially available as ALON®
MD ASIF AKBARI, B.Tech(Civil)
Ex-Engineer, RITES LTD ( A GOI Undertaking, Ministry of Railways)
An Aligarh Muslim University Alumnus
+91-9521930692
https://www.linkedin.com/in/akbariasif12

2. Advantages
Transparent : High optical transmission (>85%) near-UV to mid-IR
wavelengths (0.25to4.0μm).
Crystal Clear : Excellent clarity and no inherent birefringence. Very high
refractive index homogeneity over large areas.
Durable : Outstanding hardness, scratch resistance, chemical resistance and
high strength.
Commercially Available : Large 18x35-in windows as well as shapes including
hyper-hemispherical, ogive and hemispherical domes are available.
Robust Process : Enables manufacturer to reliably manufacture and supply
components of consistently high quality.
MD ASIF AKBARI
SPA/BEM/711

3. What is this?
• It is crystal-clear and ultra-hard advanced transparent ceramic material
that is manufactured via powder processing. It has been fielded in many
defense systems and is available commercially in large sizes and
quantities.
• is the best transparent ceramic armor there is and the material of choice
for ultra high resolution reconnaissance windows.
• Transparent aluminum, also known as aluminum oxynitride, is a
transparent polycrystalline ceramic with a cubic spinel crystal structure
made of nitrogen, oxygen and aluminum.
• Domes, tubes, transparent windows, rods and plates can be produced
from this material using conventional ceramic powder processing
methods. Methods for manufacturing transparent aluminum remain
refined. The cost of this material is similar to that of synthetic sapphire.
MD ASIF AKBARI
SPA/BEM/711

4. Material
Composition
• It is basically made up of MgAl2O4
• Linear Formula: (AlN)x • (Al2O3)1-x
• Aluminium oxynitride (AlON) is a transparent ceramic composed of
aluminium, oxygen and nitrogen. (such as varying the aluminium
content from about 30% to 36%, which hasbeen reported to affect
the bulk and shear moduli by only 1–2%.)
• Synonyms - aluminum oxynitride, ALON, Al23O27N5, aluminum
oxynitride, transparent alumina, aluminum oxynitride powder,
ALON powder, spinel, CAS# 12633-97-5
• Typical chemistries available (99.0%, 99.9%, 99.99% and 99.999%)
Chemical Specification
99% Aluminum Oxynitride
99.9% Aluminum Oxynitride
99.99% Aluminum Oxynitride
99.999% Aluminum Oxynitride
MD ASIF AKBARI
SPA/BEM/711

5. Manufacturing
Process
MD ASIF AKBARI
SPA/BEM/711

6. Manufacturing
Process
Transparent aluminum starts out as a pile of white aluminum oxynitride
powder. That powder gets packed into a rubber mold in the rough shape of the
desired part, and subjected to a procedure called isostatic pressing, in which
the mold is compressed in a tank of hydraulic fluid to 15,000 psi, which
mashes the AlON into a grainy “green body.” The grainy structure is then
fused together by heating at 2000 °C for several days. The surface of the
resulting part is cloudy, and has to be mechanically polished to make it
optically clear.MD ASIF AKBARI
SPA/BEM/711

7. Physical Properties
• It is optically transparent in the near ultraviolet, visible and infrared
regions. It is four times harder than fused silica glass, 85% harder than
sapphire and 15% harder than magnesium aluminate spinel. The material
remains solid up to 1200°C (2190°F). It has good corrosion resistance
and resistance to damage from radiation and oxidation. It is about three
times harder than steel of the same thickness.
PROPERTIES VALUES
Compressive strength 2.68 GPa
Flexural strength 0.380.7 Gpa
Fracture toughness 2 MPa.m
Knoop hardness 1800 kg/mm
Poisson ratio 0.24
Shear modulus 135 GPa
Young modulus 334 GPa
MD ASIF AKBARI
SPA/BEM/711

8. Chemical
Properties
• Typical chemistries available (99.0%, 99.9%, 99.99% and
99.999%)
Chemical Formulae Al23-1/3XO27+XN5-X (0.429 < X < 2)
Crystal Structure Cubic, Spinel
Form Polycrystalline
Chemical Resistant(Yes/No)
HFAcid Yes
Fluorine Plasma Yes
Extreme Weather Yes
Sea/SaltWater Yes
Cryogenic Temperatures YesMD ASIF AKBARI
SPA/BEM/711

9. Optical
Properties
Transmission range (>80%) ~0.22 – 4.5 micron
Refractive index
Index of Refraction
l(m m) n
0.48 1.803
0.50 1.801
0.64 1.790
0.68 1.788
0.70 1.787
1.00 1.779
2.00 1.761
3.00 1.737
4.00 1.702
5.00 1.653
Typical Haze <3%
Typical Clarity >95%
Typical RI inhomogeneity 5ppm over 11-inch dia apertureMD ASIF AKBARI
SPA/BEM/711

10. Optical
Properties
(Continued)
MD ASIF AKBARI
SPA/BEM/711

11. Electrical
Properties
Volume resistivity$ (ohm-cm) >1014
Dielectric Constant
f (GHz) k
35-45 9.19
55-60 9.18
90-110 9.17
Loss Tangent ( tan d , x10-5)
f (GHz) tan d
35-45 31
55-60 67
90-110 96
Dielectric Strength (kV/mm) ~23
MD ASIF AKBARI
SPA/BEM/711

12. Thermal
Properties
Melting Point (0C) 2,150
Thermal Conductivity (W/mK) ~13
Coefficient of Thermal Expansion (x10-
6)
7.50
(30-900oC)
Specific Heat (cal/g-oC) 0.22
Max. Usable Temperature (inert atm.) 1,900oC
MD ASIF AKBARI
SPA/BEM/711

13. Thermal Properties
(Continued)
PROPERTY Γ-ALON UNIT
Refractive index (at wavelength 0.5 μm)6 1.8
dn/dT (in 3–5 μm wavelength range)6 3
10–6 K–
1
Absorption coefficient (at 3.39 μm
wavelength)6
0.1 cm–1
Total integrated optical scatter (at 0.64 μm;
~5 mm thick sample)6
2.1 %
Transmission wavelength range* 0.22–6 μm
Optical homogeneity achieved in 15 in. 3
25 in. part with
~5 ppm
3.4 in. aperture
Typical transmittance without AR coatings
(in the visible range)*
>84 %
Typical haze (in the visible range)* <2 %
Typical clarity (in the visible range)* >98 %MD ASIF AKBARI
SPA/BEM/711

14. Ballistic resistant
&
Biological
Properties
STANAG 4569 Level,
3-shots
1 2 3
50calAP 1
shot
Areal density, kg/sq.m. 57 69 130 83
Thickness, mm 31 37 59 41
• Non-toxic and Biocompatible - (Based on in vitro cell biology test results
and in vivo test results in a rat distal femur model)
• Better Wear Resistance than Alumina in DMEMcell media (Wear rate: 1.845
±0.428 (x10-6mm3 N-1 m−1) –1000m with 10N load)
STANAG LEVEL-3 as per NATO
MD ASIF AKBARI
SPA/BEM/711

15. Durability
• Glass-based systems tend to degrade due to non-ballistic phenomena
such as strikes, sand erosion and prolonged UV exposure. These
conditions can quickly impair the clarity and function of glass-based
transparent system.
• ALON® transparent aluminium, however, has proven to be
exceptionally resistant to such conditions.
1. Rock-Proof: Kicked up rocks and large debris can cause significant
damage to glass-based transparent armor windows; however, at the
same size and thickness, Surmet's ALON® ceramic can withstand
granite rock strikes at over 4x the impact force required to shatter glass.
2. Scratch-Proof: The optical transmission of glass-based transparent
armor tends to degrade over time, due to thousands of tiny scratched
made by wind-swept sand and dust. In controlled sand erosion testing,
the optical transmission of glass-based armor reduced by 23% while the
optical transmission of ALON® transparent armor remained the same.
MD ASIF AKBARI
SPA/BEM/711

16. Durability
(continued)
3. Delamination Resistant: ALON® transparent armor has low
interlaminar residual stresses due to the compatible coefficient of
thermal expansion (CTE) with both glass and polycarbonate. Under
thermal cycling, ALON® transparent armor has a much lower
propensity for delamination than glass-based armor.
4. Tolerant of Extreme Conditions: ALON® transparent armor is an
exceptionally high-performing material in extreme environmental
conditions. ALON® transparent armor has proven to withstand both
mechanical stresses (vibration, mechanical shock, g-loading and sudden
pressure release) and environmental stresses (solar radiation, humidity,
temperature ranges from +185°F to -67°F and thermal cycling).
MD ASIF AKBARI
SPA/BEM/711

17. Performance
Requirement
Direct Fire and Blast Protection
• ALON is three times harder than glass, and therefore breaks up and erodes
the projectile much more efficiently. The projectile debris is captured by
the polycarbonate backing.
1. Superior Ballistic Performance: Ballistic testing conducted at the Army
Research Labs in Aberdeen, MD compared current glass based transparent
armor to armor based on three transparent ceramic materials: ALON,
Spinel and Sapphire. Surmet's ALON® ceramic performed 10% better
than Spinel armor and 20% better than Sapphire armor — and 250% better
than conventional glass based armor.
2. Increased Window Size: To provide protection over extra large apertures,
Surmet has developed tiled ALON® transparent armor. The tiled armor
employs specially engineered seams that are virtually invisible to the
viewer.
3. Excellent Multi-Hit Performance: Tiled ALON® armor has successfully
defended against a variety of multi-hit threats including 30calAPM2
rounds and 50calAPM2 rounds. In each test, ALON® transparent armor
easily defeated the given threat.
MD ASIF AKBARI
SPA/BEM/711

18. Inspection and
testing procedures
Weibull modulus and characteristic strength
Weibull modulus and characteristic strength were determined by fitting the
measured data to a standard two parameter Weibull distribution given by
Equation 1, ASTM C 1239-94a.
Test fixture used for the biaxial flexure strength
Grafoil™ discs having a thickness of
0.005” thick were placed between the
sample disc and the load and support
rings to reduce the contact stresses
that are thought to cause some
samples to fail under the loading ring
or support ring.
The loading rate used was 0.02”/min
for all measurements; Humidity 50%;
Temperature 21° C and 500 °C
MD ASIF AKBARI
SPA/BEM/711

19. Inspection and
testing procedures
Sample Size and Test Fixture Dimensions
Test Period
Sample
Diameter
Sample
Thickness
Load Ring
Diameter
Support
Diameter
(Historical )
Raytheon 2002
0.998” 0.051” 0.4500” 0.9000”
(Surmet) May
2004
0.994” 0.055” 0.4166” 0.8330”
(Surmet) October
2004
1.244” 0.055” 0.4166” 0.8330”
MD ASIF AKBARI
SPA/BEM/711

20. Inspection and
testing procedures
Elastic Properties Measurements
• The elastic properties of Transparent Aluminium were measured
according to ASTM C1259-01 using the same disc specimens (1.25”
diameter x 0.055” thick) used for biaxial flexure testing.
• Test specimens in all three set of measurements were 100% dense
transparent Aluminium Oxynitride.
• The difference may be in the due to the greater accuracy of the flexural
resonance method used in the current measurements.
Value UDRI (2004)
Historical*(ref 4,5,6 )
SORI (1988)
Historical*(ref 7)
Raytheon (1984)
Young’s Modulus , E (GPa) 321.05 321.3 323.8
Shear Modulus, G (GPa) 127.35 124.55 130.24
Poisson’s Ration ,υ 0.26 0.24 0.24
* Historical (1988 and 1984) Data Measured in four point flexure using strain gages.
Room Temperature Elastic Properties (E, G and υ) of ALONMD ASIF AKBARI
SPA/BEM/711

21. Inspection and
testing procedures
Biaxial Flexure Strength Measurements
• The testing program initially set out to compare three different grades of
ALON and two test temperatures (RT and 500°C).
• Since the material is transparent it is relatively easy to inspect for the
presence of strength limiting flaws. Having not found anything of
significance the next step was to examine other possible reasons for the
wide variation in strengths. There were some concerns that there was
damage introduced into the samples by the fixed abrasive grinding
process.
MD ASIF AKBARI
SPA/BEM/711

22. Inspection and
testing procedures
Sample Set Descriptions
Sample Set
TEMP
(°C)
RH
Number of
Samples
UDRI TEST
ID
Grain
Size
(µm)
Fixed No Etch RT 21 54% 14 SMG-04-2-46 233±29
Loose No Etch RT 21 48% 15 SMG-04-2-47 252±34
Combined No Etch 21 N/A 29 N/A
Fixed/Loose No Etch 500 500 AIR 8 SMG-04-2-59 233±29
Fixed Etched RT 21 50% 16 SMG-04-2-48 233±29
Loose Etched RT 21 50% 14 SMG-04-2-49 252±34
CG ALON RT 21 75% 30 SMG-04-1-84
HP ALON RT 21 49% 29 SMG-04-1-58 309±60
LS ALON RT 21 64% 30 SMG-04-1-72 254±43
HP ALON 500C 500 AIR 30 SMG-04-1-43 309±60
2002-RT 21 28 N/A 250
2002-500C 500 AIR 31 N/A 250MD ASIF AKBARI
SPA/BEM/711

23. Inspection and
testing procedures
Test Matrix for ALON Biaxial Flexure Strength Measurements
Number of Samples Tested at Each Condition
Material
Classification
Loose Abrasive
Grind
Fixed Abrasive
Grind
Mild Etch Deep Etch
Test
Temperatures
21°C 500°C 21°C 500°C 21°C 500°C 21°C 500°C
Surmet CG Grade
(May 2004)
0 0 30 0 0 0 0 0
Surmet HP Grade
(May 2004)
0 0 30 30 0 0 0 0
Surmet LS Grade
(May (2004)
0 0 30 0 0 0 0 0
LS Grade
(September 2004)
15 3 14 5 15 0 15 0
Raytheon
Historical
(2002)
28 31 0 0 0 0 0 0
MD ASIF AKBARI
SPA/BEM/711

24. Inspection and
testing procedures
Strength and Weibull Analysis for ALON Sample Sets
Sample Set
AVG
σ (MPa)
STDEV
(MPa)
Weibull
Characteristic
Strength
σθ (MPa)
Weibull
Modulus
Biased m
Weibull *
Modulus
Unbiased
mu
R2
Surmet September (2004)
Fixed No Etch RT 700 169 750 8.5 7.7 0.982
Loose No Etch RT 753 179 811.9 5.6 5.1 0.968
Combined No Etch 727 173 777.7 7.0 6.6 0.979
Fixed/Loose No Etch 500°C 622 93 635.5 8.4 6.9 0.91
Fixed Etched RT (light etch) 422 59 451 10.1 9.2 0.951
Loose Etched RT (deep
etch)
281 18 287.8 26.3 23.7 0.977
Surmet May (2004)
CG ALON RT 308 126 325.1 2.9 2.8 0.952
HP ALON RT 344 146 361.6 3.0 2.8 0.953
LS ALON RT 389 135 425.2 3.2 3.1 0.988
HP ALON 500° C 364 123 410.4 3.0 2.8 0.990
Raytheon (2002)
2002-RT 374.7 85.8 409.2 4.6 4.4 0.995
2002-500C 367.9 47.7 384.4 7.8 7.4 0.964
* The Unbiased Weibull Modulus is determined using Table 1 in ASTM C1239-94a. An unbiasing factor is used to
best estimate the Weibull Modulus for small data sets. The factor approaches 1 as the # samples > 40.
MD ASIF AKBARI
SPA/BEM/711

25. Inspection and
testing procedures
Weibull Failure Probability Distribution for HP-ALON (May 2004) Tested at Room Temperature
MD ASIF AKBARI
SPA/BEM/711

26. Inspection and
testing procedures
Sample Test Specimen
Photo of fracture test disc #119 (LS-Grade, May 2004 group) and an optical
micrograph of the etched sample near the fracture origin. Strength: σf = 197
MPa and Average Grain Size = 277 μm. Scratches on the sample near the
fracture origin are revealed by etching.
MD ASIF AKBARI
SPA/BEM/711

27. Inspection and
testing procedures
Surface roughness
• Surface roughness measurement is done using a ZYGO NewView 100
optical profilometer.
• These were measured for samples from the two etch groups and an un-
etched sample from the high strength group.
• The most deeply etch surface sample has a roughness PV roughness of 5.0
μm and an Ra of 0.657 μm compared to a PV roughness of 2.44 μm and
an Ra of 0.215 μm for the lightly etched sample.
• The Ra of the “super” polished samples is 10 Å and the PV roughness is
30 nm.
• The lower surface roughness “super” polished sample group has the
highest strength and the increased roughness caused by etching lowers the
strength accordingly.
• The greater etch depth smoothes out the distribution of larger subsurface
flaws introduced by machining and creates a new controlled distribution
of larger flaws that lowers the average strength but increases the Weibull
modulus.MD ASIF AKBARI
SPA/BEM/711

28. Inspection and
testing procedures
Surface roughness of polished and etched ALON biaxial flexure test samples.
MD ASIF AKBARI
SPA/BEM/711

29. Inspection and
testing procedures
Surface roughness of polished and etched ALON biaxial flexure test samples.
Sample Set
Measured
Average
Strength
(MPa)
Weibull
Modulus
Calculated
Flaw Size
( µm)
Measured PV
Surface
Roughness
(µm)
Measured
Grain Size
(µm)
Polished Fixed
Abrasive 9/2004
700 ±169 7.7 12 0.030 233±29
Mild Etch Fixed
Abrasive 9/2004
422 ±59 9.2 32 2.44 233±29
Deep Etch Loose
Abrasive 9/2004
281 ±18 23.7 73 5.04 233±29
Sample #119 from LS-
Group
197( individual) 148 scratched 277±48
LS-Group May 2004
testing
389 ±135 3.1 254±43
Predicted Flaw Size for ALON Fracture Test Samples Compared to the Surface Roughness
MD ASIF AKBARI
SPA/BEM/711

30. Construction
specifications and
working details
• It comes in 1 ft x 1.5 ft panels.
Large ALON® window with invisible
engineered seams.MD ASIF AKBARI
SPA/BEM/711

31. Codes and
standards
Codes Governing to different properties of Transparent Aluminium
Properties Codes
elastic properties ASTM C1259-01
Young’s Modulus ASTM C1499-03
Poisson’s Ratio ASTM C1259-01
Weibull distribution ASTM C 1239-94a
Weibull Modulus ASTM C1239-94a
Laser Flash Diffusivity ASTM E1461
MD ASIF AKBARI
SPA/BEM/711

32. Material and
execution cost
• Glass costs about $3.25 per square inch, while ALON runs between $10
and $15 per square inch, he said.
• But in the long run, the new transparent armor could save money.
• Because it is lighter than glass, it would significantly reduce the dead
weight and hence the overall construction cost of frame if produced on a
large scale in future.
MD ASIF AKBARI
SPA/BEM/711

33. Material Cost
(Continued)
MD ASIF AKBARI
SPA/BEM/711

34. Conclusion
• (Transparent Aluminium) use in large windows will require significant
investments in manufacturing technology and test and evaluation to
demonstrate the required protection factors, especially against a multi-
hit threat. Note that “large size” is a relative term.
• If in future it can be produced commercially on a large scale with
cheaper cost, then this will define building construction specially for tall
buildings, at present the cost of ALON is 5 times that of Glass-ceramic
per square unit area.
• The cost and dead weight reduction will create new possibilities for tall
structures at the same time the structural strength will increase
significantly.
• As the density of ALON is 3.7 g/cc as compared to glass 2.7g/cc but
strength wise glass is no where comparable to ALON, so the façade can
itself work as load resisting and stiffening membrane. This will be the
future scope of work for researchers.
MD ASIF AKBARI
SPA/BEM/711

35. THANK YOU
MD ASIFAKBARI SPA/BEM/711