solid glass defects identification using sem-edx …solid glass defects identification using sem-edx...
TRANSCRIPT
Solid Glass Defects Identification
Using
SEM-EDX Microanalysis
Martina Jezikova
GLASS SERVICE, a.s.
June 22, 2017
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Solid glass defects analyses
Field of interest
cords clear knots
metallic inclusions surface defects knots with crystals
secondary stones
cords with crystals
stones
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Field of interest
- foreign solid inclusions in glass products with different optical, chemical, mechanical, thermo-physical, color and structural properties
Goal
- identification of the defect source in order to avoid production loss
- understanding why the defect appeared
Approach
- correct sampling (representative set of marked samples, statistical evaluation)
- piece of the suspected material to compare with the defects
- considering all the information about the production process, furnace design, its corrosion state and repair history
- chemical and phase composition of the defects provided by the laboratory
Motivation
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Observation by naked eye, using magnifying glass or polariscope
- location in the product (on the surface, in the mass), shape (sharp or
rounded edges), dimensions, color, transparency/opacity, stress,
presence of accompanying bubbles, crystals or cords, other phenomena
Identification methods
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Observation under the polarizing microscope
- transmitted polarized light without analyzer – microstructure and
morphological properties; optical properties
- transmitted polarized light with analyzer (nicols crossed) – microstructure
and morphological properties; optical properties
- incident light – surface structure of the opaque samples
- thin sections of the stones (approx. 30 microns thick) – stone
microstructure
Identification methods
polarizing
microscope
polarized light polarized light,
crossed nicols
crossed nicols
lambda plate
incident light
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Sample preparation for the SEM-EDX microanalysis
- cutting the defect out of the glass product
- grinding the defect to expose the core (EDX is surface sensitive method)
- preparing a cross-section of the sample containing cords
- polishing the section of the sample
- coating of electrically conducting material – carbon coater
- preparing thin section of the stone for the final microscopic observation
Identification methods
stone
before cutting
stone
in a section
knot
in a cross-section
stone in
thin section
knot
before cutting
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Scanning electron microscope (SEM) coupled with an
Energy-Dispersive X-ray Detector (EDX)
Identification methods
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Identification methods
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Point analysis
- points or other differently shaped areas of the sample surface can be
defined as areas for the analysis
- cumulated intensities of X-ray spectra are then quantified and
recalculated to mass percent composition
SEM-EDX microanalysis
Zone A
Knot
Zone 1
Knot
Glass
/Float
Ox% Ox% Ox%
Na2O 14.56 14.75 13.90
MgO 0.93 0.60 4.00
Al2O3 14.81 16.02 0.42
SiO2 66.78 65.67 72.93
CaO 2.92 2.35 8.75
ZrO2 – 0.61 –
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Line scan analysis
- primary electron beam is scanning the sample along a selected straight
line of individual measuring points
- the resulting concentration profiles for selected elements are plotted in a
diagram
SEM-EDX microanalysis
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X-Ray mapping
- creating element X-ray compositional maps over a broader area by
means of rastering the beam
- two-dimensional concentration distribution of elements in the sample
- higher brightness of the single color displays higher concentration of the
corresponding element
SEM-EDX microanalysis
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Defect: Partially translucent white stones
- surface is composed of granular particles with almost spherical shapes
and reflects light well; low stress
Case sudy No. 1
in float glass in green container glass
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Source: Imperfectly melted sand
- stones with lower degree of transformation
- remnants of the silica sand grains – dense aggregates of lath-shaped
Tridymite (SiO2)
- obvious recrystalization in the grain boundaries
Case study No. 1
Zone A
SiO2 grain
Zone 1
Tridymite
Zone 2
Vitreous
Glass
/Container
Ox% Ox% Ox% Ox%
Na2O 0.30 – 13.67 14.15
MgO – – – 0.34
Al2O3 0.53 – 1.61 1.76
SiO2 98.89 100.00 77.56 73.72
CaO 0.29 – 7.16 9.82
FeO 0.25 – – 0.21
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Stones from the silica crown
- free cluster of Tridymite crystals (SiO2)
- increased content of Al2O3 in the glassy phase
- liquid corrosive products of the silica crown run
down over a zone where some Al2O3
containing material is used
Case study No. 2
Zone 1
Tridymite
Zone 2
Vitreous
Glass
/Float
Ox% Ox% Ox%
Na2O – 13.24 14.55
MgO – 2.38 4.45
Al2O3 – 2.05 0.78
SiO2 100 74.7 71.5
CaO – 7.62 8.72
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Defect: Large clear knots in float glass
- considerable stress – cracks appeared during the grinding of the knots
- no crystalline phase
Case study No. 3
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Analysis results:
- ZrO2 and high content of Al2O3 → AZS?
- content of TiO2, ZnO, As2O3 as well
- absence or very low content of CaO
Case study No. 3
Zone A
Knot
Glass
/Float
Ox% Ox%
Na2O 10.89 13.58
MgO 0.24 4.13
Al2O3 19.64 1.12
SiO2 63.96 72.26
K2O 0.45 0.14
CaO – 8.76
TiO2 1.94 –
ZnO 0.39 –
As2O3 1.37 –
ZrO2 1.12 –
BaO – –
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Source: Contamination of the batch by glass ceramics
- piece of a suspicious material to compare with
- most glass ceramic materials contain 20–25 mass% of Al2O3
- note: Lithium (Li) cannot be detected using SEM-EDX microanalysis
Case study No. 3
Zone A
Knot
Zone B
Knot
Glass
/Float
Glass
Ceramics
Ox% Ox% Ox% Ox%
Na2O 10.89 12.01 13.58 0.44
MgO 0.24 0.28 4.13 1.55
Al2O3 19.64 19.33 1.12 24.32
SiO2 63.96 62.95 72.26 68.08
K2O 0.45 0.44 0.14 0.26
CaO – 0.24 8.76 –
TiO2 1.94 2.16 – 2.20
ZnO 0.39 0.46 – –
As2O3 1.37 1.10 – 24.32
ZrO2 1.12 1.03 – 2.68
BaO – – – 0.47
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Defect: Milky white opaque glassy inclusions in container glass
- the defect appears non-crystalline
- contain clusters of rounded particles composed of glassy phase
Case study No. 4
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Analysis results:
- alumino-silicate-zirconia core of the glassy particle
- colloidal Zirconia particles (ZrO2) in the border part of each glassy particle
Case study No. 4
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Source: Ceramic fibre insulation
- alumino-silicate-zirconia insulation
- boards, blankets and papers commonly used
as glass tank exterior wall insulation, glass tank
linings and back up insulation
Case study No. 4
Zone A
Defect
Zone B
Defect
Zone C
Defect
Glass
/Container
Fibrous
insulation
Ox% Ox% Ox% Ox% Ox%
Na2O – 10.16 10.85 12.80 –
MgO – – 1.04 3.18 1.04
Al2O3 33.66 29.82 16.02 2.66 32.14
SiO2 54.30 48.05 55.43 70.38 55.22
K2O – 1.55 1.23 0.96 –
CaO – – 2.17 10.02 –
FeO – – – – 0.47
ZrO2 12.04 10.42 13.27 – 11.14
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Defect: White opaque stone with granular surface in container glass
- translucent rounded grains similar in shape to quartz grains, but with high
relief and birefringence – usually 2–6 μm
Case study No. 5
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Analysis results:
- Zircon grains in the core (ZrO2.SiO2)
- rims of fine grained Zirconia crystals (ZrO2)
Case study No. 5
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Source: Zirconia-silicate (Zircon) refractories or cements
- in alkali glasses in the low temperature region Zircon only dissolves –
only melted-off grains are released from the refractory
- at higher temperatures above 1 250 °C Zircon decomposes to Zirconia
(ZrO2) and glass melt
- Zirconia clusters resembling the original particles of Zircon particles
Case study No. 5
Zone A
Zircon
Zone 1
Zirconia
Glass
/Container
Ox% Ox% Ox%
Na2O – – 14.36
MgO – – 1.44
Al2O3 – – 1.94
SiO2 39.16 – 72.99
K2O – – 0.90
CaO – – 8.37
ZrO2 60.84 97.99 –
HfO2 – 2.01 –
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Defect: Recrystallized Zirconia grains (ZrO2)
- stone composed of unusually shaped small white grains
Case study No. 6
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Defect: Magnesia Spinel (MgO.Al2O3)
- grain with no birefringence
- crystals of the Magnesia Spinel were accompanied by Zirconia (ZrO2)
grains
Case study No. 6
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Analysis results:
- Spinel is generated by the reaction of the
following solid phases: MgO originating from
the raw materials and Al2O3 coming from the
refractory
Case study No. 6
Zone A
Spinel
Zone B
Zirconia
Zone B
Zirconia
Glass
/Float
Ox% Ox% Ox% Ox%
Na2O – – – 13.49
MgO 26.66 – – 4.10
Al2O3 73.34 – – 0.24
SiO2 – – – 73.35
CaO – – – 8.83
ZrO2 – 99.02 99.05 –
HfO2 – 0.98 0.95 –
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Source: Fused-cast AZS from the zone of the burner ports
- changes in the AZS microstructure in the highly corrosive environment of
the port mouths (high temperature, alkali vapors, batch carryover,
combustion gases flow)
Case study No. 6
piece of AZS applied at the
burner port area
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Defect: Rounded dark stones with laths on the surface – float glass
- greenish light-reflecting Escolaite (Cr2O3) laths
- no solution sac
Case study No. 7
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Source: Chromite – accessory mineral present in the silica sand
- Chromite core [(Fe2+, Mg2+) (Cr3+, Fe3+, Al3+)2O4]
- high density – these stones usually sink at the bottom of the furnace
Case study No. 7
Zone A
Chromite
Zone 1
Escolaite
Glass
/Float
Ox% Ox% Ox%
Na2O – – 14.28
MgO 22.03 – 3.26
Al2O3 17.45 – 0.81
SiO2 – – 75.08
K2O – – 0.20
CaO – – 6.37
TiO2 0.39 – –
Cr2O3 50.61 99.09 –
FeO 9.51 0.91 –
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Thank you for your attention
GLASS SERVICE, Inc.
Rokytnice 60 755 01 Vsetin Czech Republic
+420 571 498 511 [email protected] www.gsl.cz