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Preparation and characterisation of chrome aventurine glass

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CONTENTS • • • • • • •

Introduction Literature survey Objective of the Project Experimental Result Future work References

Introduction • Scientific definition of “glass” is: “a solid having a noncrystalline structure, which continuously converts to a liquid upon heating • According to ASTM C162, “Glass is an inorganic product of fusion which has cooled to a rigid condition without crystallizing”. • The glass has been used as an engineering material since ancient times. But because of the rapid progress made in the glass industry in recent times, the glass has come out as the most versatile engineering material of the modern times. With the help of techniques developed in the glass industry, the glass of any type and quality can be produced to suit the requirements of different industries

application • Glass beads, counters, toys, and jewelry are produced almost universally • Used in the production of lenses and prisms • Vassel,laboratory apparatus • As a decorative • Here I am preparing chrome aventurine glass which is a Cr2O3 doped soda-lime-silica glass ceramic

Litrature Review • CHEMISTRY OF GLASS- The main constituent of Glass is SiO2 . The basic building block of silica has a tetrahedral pyramid shape with silicon at its centre linked symmetrically to four oxygen atoms at its corners. it has the chemical formula SiO4 and is negatively charged. •

Constituent of glass  Glass former are usually the dominant constituent SiO2, B2O3, P2O5, etc. 

Fluxes: reduce melting temperatures Na2O, PbO, K2O, Li2O, etc



Property modifiers: added to tailor chemical durability, expansion, viscosity, etc. CaO, Al2O3, etc



Colorants: oxides with 3d, 4f electron structures; minor additives (<1 wt%)



. Fining agents: minor additives (<1 wt%) to help promote bubble removal

As-, Sb-oxides, KNO3, NaNO3, NaCl, fluorides, sulfates

Classification of Glasses

The main types of glass, according to physico-chemical composition, are: Soda-lime glass-It is composed of: _ 71-75% silicon dioxide (SiO2 derived mainly from sand) _ 12-16% sodium oxide (Na2O derived from soda ash – Na2CO3) _ 10-15% calcium oxide (lime, CaO derived from limestone – CaCO3) _ Low levels of other components

Lead crystal and crystal glass-The typical lead crystal composition is: 54-65% SiO2,25-30% PbO ,13-15% Na2O or K2O Lead oxides (PbO and Pb3O4) are used to increase the refractive index of the glass Borosilicate glass-A typical borosilicate glass composition is: 70-80% silicon dioxide SiO2, 7-15% B2O3,4-8% Na2O or K2O ,7% Al2O3 Electric glass - E glass is a special type of borosilicate glass where part of the boron trioxide has been replaced by aluminum oxide, and is also characterized by a low alkali content (<2%)

Characteristics of glass • It absorbs, reflects or transmits light. • It has no sharp melting point. • It is an excellent electrical insulator at high temperatures due to the fact that glass can be considered as an ionic liquid. • It is extremely brittle. • It is possible to obtain glasses with diversified properties as the glasses may be clear, colorless, diffused and stained.

BASIC DEFINITIONS RELATED TO GLASS CRYSTAL FORMATION • Nucleation-Nucleation is the process where droplets of liquid can condense from a vapor, or bubbles of gas can form in a boiling liquid. The nucleation step is carried out at lower temperatures .it is is generally of two type homogeneous nucleation and heterogeneous nucleation • Crystal growth- Crystal growth is a major stage of a crystallization process, and consists in the addition of new atoms, ions, or polymer strings into the characteristic arrangement . growth step is carried out at higher temperatures • Glass and crystal- A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions

RECRYSTALLIZED GLASS (GLASSCERAMICS)

• Recrystallized glass, also known as polycrystalline glass, is commonly produced by adding nucleating agents to the glass batch • Glass-ceramics are mostly produced in two steps: First, a glass is formed by a glass manufacturing process. The glass is cooled down and is then Reheated in a second step In this heat treatment the glass partly crystallizes Crystallization of Glass- Crystallization from a super cooled liquid state above the Tg progresses via two processes; i.e. nucleation and crystal growth. The rates of nucleation and crystal growth depend on the heat-treatment temperature as well as crystalline composition

Glass Color Mechanisms

• Glass can be colored by dissolved ions (predominantly transition metal and rare earth ions due to different redox species at relatively high concentrations. The most commonly used transition metals are Fe, Cr, Co and N • The precise color introduced depends on the oxidation state of the ion and this in turn can be influenced by the batch composition and melting conditions. • Colorants- The first of these include there is those materials oxides which seen to be in true solution in the glass The second group includes those few elementary substances whose coloring effect seems to be due to their presence as particles of colloidal size.

NO

COLOUR

SUBSTANCE

2

DARK BLUE OR DARK BROWN OR DARK VOILET

COBALT, MANGNESE AND IRON OXIDES

3

GREEN

FERRIC OXIDE ( Fe3O4 ), CHROMIUM OXIDE ( Cr2O3)

4

RED

CUPROUS OXIDE ( Cu2O ), METALLIC GOLD

5

VOILET

MANGANESE DIOXIDE ( MnO2)

6

WHITE OPAQUE

TIN OXIDE, CALCIUM PHOSPHORATE [Ca3( PO4 )2]

7

YELLOW OR BROWN

ANTIMONY TRISULPHATE ( Sb2S3 ), CHARCOAL, SILVER BORATE, ETC.

AVENTURINE GLASS • It is a translucent glass, sometimes called Goldstone, synthetic substance which is notable for exhibiting the effect of aventurescence • Aventurine glass has been produced in reddish-brown, blue, purple and green colors • used in jewelry, and as a decorative • it is a man-made glass which consists of minute octahedral crystals of chromium dispersed in glass to created a glittering appearance. • PROPERTIES OF AVENTURINE GLASS• Structure and Color-Aventurine glass consists of many different particles embedded in glass.

• Glittering effect-This effect is present in all surfaces that use a layer of metallic flakes or crystals to obtain their appearance. In aventurescent gems the particles are much larger and further apart, which leads to the characteristic, individual sparkles found on such stones • PREVIOUS WORK ON RELATED TO THIS PROJECT• M. D. Shcheglova, 1 T. V. Bambino, 1 S. G. Polozhai and V. M. Svistun did work on aventurine formation in copper-containing sodium-lead silicate glass • The results of our experiments allow us to infer that the process of aventurine formation consists of the following stages: • -- melting of the charge components accompanied by reduction of Cu20 to metallic copper; • -- melting and fining of the glass with the formation of an emulsion of drops of metallic copper in the silicate melt; • -- cooling of the glass and coarsening of copper micro drops due to their merging and segregation

• A. G. Monaco, V. N.Pavlova, and A. V. Litvinov did work have developed and mastered a continuous method for obtaining the new glass- crystalline material • V. I. Polyushkin studies that how it is possible to make efficient use of chrome to obtain chrome aventurine fluorine-containing glasses • However, fluorine is a toxic and volatile component and found that The best decorative properties were found in the aventurine glass 22/I (1.96% Cr203)

OBJECTIVE OF THE PROJECT • preparation of chrome aventurine glass to be used for decorative purposes. • preparation of Cr2O3 doped soda-lime-silica glass followed by their suitable heat treatment to develop crystalline phases.. • batches with varying compositions will be prepared to form glass ceramic materials. the different characterization will be carried out by following techniques:• DTA/TGA of glass samples prepared • XRD of the formed samples before and after heat treatment to identify crystalline phases. • density measurement of the glass and glass ceramic samples thus prepared. • micro structural evaluation by scanning electron microscopy.

 

EXPERIMENTAL

• Batch preparation- Glass batch calculation or glass batching is used to determine the correct mix of raw materials (batch) for a glass melt. • For the development of chrome aventurine glass we took the following glass composition as parent glass composition 70 SiO2.20Na20.10CaO. • We doped various amount of Cr2O3 to the parent glass composition to study the effect of its addition.Cr2O3 doped various batch compositions are given in tables

Compound

Glass composition weight (%) TABLE SS1

SS2

SS3

SS4

SS5

SiO2

67

66

65

64

63

Na2O

20

20

20

20

20

CaO

10

10

10

10

10

P2O5

1

1

1

1

1

Cr2O3

2

3

4

5

6

• Glass Melting- , the sample system with

• • • •

crucible was put inside the electric furnace. Each batch was heated up to 1400 °C then the molten glass was casted by pouring it onto a brass plate Annealing- Annealing is a process of slowly cooling glass to relieve internal stresses after it was formed. All the glasses samples were annealed at 500°C for 5 hour to remove the thermal strain in the glass. CharacterizationX-Ray Diffraction Study- In order to confirm the amorphous nature of the glass sample X-ray diffraction patterns were observed a using XRD machine

DENSITY MEASUREMENT-

• WALKER’S STEELYARD METHOD- This apparatus consists of a long graduated beam which is pivoted near one end and counterbalanced by a heavy weight suspended from the short arm

RESULT AND DISCUTTION

• PREAPERED GLASS BEFORE CUTTING AND HEAT TREATMENT-

SS1

SS2 SS4

SS5

SS3

DENSITY MEASUREMENT D e n s ity (g m /c c )

2.57

2.56

2.55

2.54

2.53

2.52 SS1

SS2

SS3

Sample Name

• • • • •

Sample Sample Sample Sample Sample

SS1- Cr2O3-2% SS2- Cr2O3-3% SS3- cr203-4% SS4- cr2o3-5% SS5-cr2o3-6%

SS4

SS5

Phase analysis: Characterization by XRD In te n s i ty ( A .U .)

S S1

220 200 180 160 140 120 100 80 60 40 0

10

20

30

40

50

60

70

80

90

2 theta(degree)

In t e n s i t y ( A .U .)

•

240

240

SS2

220 200 180 160 140 120 100 80 60 40 0

10

20

30

40

50

2 theta (degree)

60

70

80

90

I n te n s i ty ( A . U )

200

SS3

180 160 140 120 100 80 60 40 0

10

20

30

40

50

60

70

80

90

2-theta(degree)

I n te n s i ty ( A . U ) )

220

SS4

200 180 160 140 120 100 80 60 40 0

10

20

30

40

50

2theta(degree)

60

70

80

90

I n te n s ity ( A . U )

220

SS5

200 180 160 140 120 100 80 60 40 0

10

20

30

40

50

2theta(degree)

60

70

80

90

• Above figures show that original glass samples from SS1 –SS5 has no crystalline phase after melting. hence; the glass was completely amorphous and did not undergo any crystallization during melting

. FUTURE WORK • DTA/TGA and of glass samples to find crystalline temperature of glass • Heat treatment of glass samples after cutting at different crystalline temperature and time • XRD of glass ceramic after heat treatment of glass to find crystalline phase • SEM measurement of glass to find microstructure of glass

REFRENCES • Singh K, Bahadur D, Characterization of SiO2-Na2O-Fe2O3CaO-P2O5-B2O3 glass ceramics. J. Mater. Sci.: Mater. Med. 10,481 (1999) • E. P. Mel'nikov1.J.E.Shelby, “Introduction to glass science and technology”, 2nd Edition, RS.C • V. D. Obolkin, and A. A. Evstropov, Sov. Geol., No. 8, 36 (1981); V. D. • Obolkin, E. P. Mel'nikov, and A. A. Evstropov, Izv. Akad. Nauk SSSR , No. 6, 119 (1981). • V. I. Polyushkin “SYNTHESIS OF FLUORINE-FREE CHROME AVENTURINE GLASSES” • M. D. Shcheglova, 1 T. V. Babenko, 1 S. G. Polozhai, 1 and V. M. Svistun 1”mechanism of aventurine formation 1~coppercontaining alkali-lead silicate glassVoL 53, Nos. 1- 2, 1996 • .J.E.Shelby, “Introduction to glass science and technology”, 2nd Edition, RS.C

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