Chemical properties of Chemical properties of glass, ceramics, and glass, ceramics, and

refractoriesrefractories

Ing. Milena Pavlíková, Ph.D.K123, D1045

224 354 688, milena.pavlikova@fsv.cvut.cz

tpm.fsv.cvut.cz

OverviewOverview

TerminologyTerminologySilicatesSilicates

andand

aluminatesaluminates

GlassGlassCeramicsCeramicsRefractoriesRefractories

TechnicalsTechnicals

PolymorfismPolymorfism

ModificationModification

GlassGlass

SinteringSintering

RheologyRheology

CeramicsCeramics

RefractoriesRefractories

Aluminates

and

silicates

Silica dioxide SiO2

Aluminium oxide Al2O3

Silica

dioxideThe chemical compound silicon dioxide, also known as silica or silox (from the Latin "silex"), is an oxide of silicon, chemical formula SiO2.Silica is the most commonly found in nature as sand or quartz, as well as in the cell walls of diatoms. Sources: crystalline as a quartz, tridymit a crystobalit

Crystalline:Mountain crystal, rock crystal – pure silica glass

Optics, chemical dishesquartz sands

Ceramics, cement, sand filtersquartzite

Milling stones and support if milling apparatusquartzy sandstones

glass production

Silica

dioxideAmorphous (vitreous silica):

Diatomaceous earth (soil)Thermal and sound insulator, filtering materila

opalSynthetic gels

Grouting, injection, facade coatingSemiprecious stonesrocks – quarzite, sandstone, granite, gneissGravel (ballast) and sand soils

a)

isolated

tetrahedrons

b)

holms

–

b,c, d, ec)

linear–

f, gd)

3D –

h, i

In the vast majority of silicates, including silicate minerals, the Si atom shows tetrahedral coordination by 4 oxygens. In different minerals the tetrahedra show different degrees of polymerization: they occur singly, joined together in pairs, in larger finite clusters including rings, in chains, double chains, sheets, and three-dimensional frameworks. The minerals are classified into groups based on these anion structures.

Nesosilicates

(lone

tetrahedron) -

[SiO4]4−, eg olivine. Sorosilicates

(double tetrahedra) -

[Si2O7]6−, eg epidote.

Cyclosilicates

(rings) -

[SinO3n]2n−, eg tourmaline

group.

Inosilicates

(single chain) -

[SinO3n]2n−, eg pyroxene

group.

Inosilicates(double chain) -

[Si4nO11n]6n−, eg amphibole

group. Phyllosilicates

(sheets) -

[Si2nO5n]2n−, eg micas

and

clays.

Tectosilicates

(3D framework) -

[AlxSiyO2(x+y)]x−, eg quartz, feldspars, zeolites.

Phase

modifications

melt-

guartz

-

guartz

Volume change (%)

transformation

- quartz

Volume changes during polymorhic transformations of SiO2

- quartz

- quartz

- quartz

Volume changes during polymorhic transformations of SiO2

Volu

me

chan

ge

good abrasion resistance

electrical insulation

high thermal stability

insoluble in all acids with the exception of hydrogen fluoride (HF).

slowly soluble in hot alkaline solutions

UV permeable

Properties

of

silica

dioxide

Compounds

of

siliconSilicic acid, [SiOx(OH)4-2x]n , H4SiO4),

formed by acidification of silicate salts (such as sodium silicate) in aqueous solution

when heated they lose water to form silica gel (M=6000 g/mol) - an active form of silicon dioxide

Silicones [R2SiO]n

largely inert compounds with a wide variety of forms and uses

typically heat-resistant, nonstick and rubberlike

frequently used in cookware, medical applications, sealants, lubricants and insulation

hypothetical

silicone

group, such species do not exist

Compounds

of

siliconSilicate - an anion in which one or more central silicon atoms are surrounded by electronegative ligands

hexafluorosilicate ("fluorosilicate"), [SiF6]2−

silicon with oxygen as the ligandSilicide - silicon with more electropositive elements

Examples:sodium silicide, Na2Si magnesium silicide, Mg2Si

Silicon carbide, SiCused as an abrasive (trademark carborundum) semiconductor and diamond simulant of gem quality

Silicon nitride, Si3N4

ceramics, which have relatively good shock resistance insulator layer to electrically isolate different structures or as an etch mask in bulk micromachiningused as a dielectric between polysilicon layers in capacitors in analog chips

Silane, SiH4

used as:coupling agents to adhere glass fibers to a polymer matrix, stabilizing the composite materialwater repellents, masonry protection

Aluminiumthe most abundant metal in the Earth's crust, and the third mostabundant element therein, after oxygen and silicon. It makes up about 8% by weight of the Earth’s solid surface.

too reactive chemically to occur in nature as the free metal

is found combined in over 270 different minerals

chief source of aluminium - bauxite ore

silvery white and ductile

nontoxic, nonmagnetic, and nonsparking

good thermal and electrical conductor

Aluminium oxide, Al2

O3

also alumina or aloxiteelectrical insulator but has a relatively high thermal conductivityresistance to weatheringproduced by the Bayer process from bauxiteSources:

crystalline form - corundum or α-aluminium oxide (α-Al2O3) - rubiesand sapphires are gem-quality forms main component of bauxite

Used:in the production of aluminium metalas an abrasive due to its hardness as a refractory material due to its high melting pointindustrial diamond

Aluminium ammonium sulfate ([Al(NH4)](SO4)2) - is used as a mordant, in water purification and sewage treatment, in paper production, as a food additive, and in leather tanningAluminium borate (Al2O3 B2O3) - used in the production of glass and ceramic. Aluminium chloride (AlCl3) - used in paint manufacturing, in antiperspirants, in petroleum refining and in the production of synthetic rubber. Aluminium fluorosilicate (Al2(SiF6)3) - used in the production of synthetic gemstones, glass and ceramic. Aluminium hydroxide (Al(OH)3) – used as an antacid, as a mordant, in water purification, in the manufacture of glass and ceramic and in the waterproofing of fabrics. Aluminium phosphate (AlPO4) - used in the manufacture: of glass and ceramic, pulp and paper products, cosmetics, paints and varnishes and in making dental cement. Aluminium sulfate (Al2(SO4)3) - used in the manufacture of paper, as a mordant, in a fire extinguisher, in water purification and sewage treatment, as a food additive, in fireproofing, and in leather tanning.

Coumpounds

of

aluminium

GlassGlass

an inorganic product of fusion which has been cooled to yield an amorphism of rigid condition without crystallizing

In the scientific sense the term glass is often extended to all amorphous solids.

The optical and physical properties of glass make it suitable for applications such as flat glass, container glass, optics and optoelectronics material, laboratory equipment, thermal insulator (glass wool), reinforcement fiber (glass-reinforced plastic, glass fiber reinforced concrete), and art.

Properties: hard, brittle, transparent solid

prevalent due to its transparency to visible light

brittle at normal temperature, at 500-1000°C plastic and workability, over 1400°C liquid

resistance to weathering

electric and heat insulator

GlassGlass

structurestructure

[Gedeon, Macháček]

ChemicalChemical

resistanceresistance

ofof

glassglass

insoluble in water and all acids with the exception of hydrogen fluoride (HF).slowly soluble in hot alkaline solutionspossibility of glass leaching (alkalies, Pb)

ProductionProductionGlass ingredients:

fused quartzsodium carbonate (Na2CO3), which lowers the melting point to about 1500 °C (2700 °F) in soda-lime glass;

"soda" refers to the original source of sodium carbonate in the soda ash obtained from certain plantslime (calcium oxide (CaO), generally obtained from limestone), some magnesium oxide (MgO) and aluminium oxide are added to provide for a better chemical durability

recycled glass ("cullet") Contemporary glass production in glass batch preparation:

mixing the raw materials → batchtransportation to the furnace (gas fired units, electric melters, pot furnaces orday tanks)melting at 1000-1200°Chomogenization and refining (removal of bubbles) at 1400°Cannealing for the removal of stresses at 900-1200°Csurface treatment

Commercial techniques

Float glass process · Blowing

and

pressing

(containers)

· Extrusion

/ Drawing

(fibers, glasswool)

· Drawing

(optical

fibers)

· Overflow

downdraw

method

· Pressing

· Casting

· Cutting

· Flame

polishing

· Diamond

turning

· Rolling

Artistic and historic techniques

Beadmaking

· Blowing

· Blown

plate

· Broad

sheet

· Caneworking

· Crown

glass

· Cylinder

blown

sheet

·

Etching

· Fourcault

process

· Fusing

· Lampworking

· Machine

drawn

cylinder

sheet

· Millefiori

· Polished

plate

·

Slumping

· Stained

glass

fusing

· Stained

glass

productionIn addition, glass

can

be

formed

by other

techniques

that

are common

for

ceramics

or

metals, including

polishing, sintering, sawing, grinding, drilling, cutting, and

bending. For

application

to glass

these techniques

may

need

to

be

adjusted.

Glass forming techniques

Float glass process

Drawing and rolling Blowing and pressing

MainMain

industrialindustrial

glassesglasses

Silica glass: SiO2

Water glass: 70 SiO2 – 30 Na2O (wt.%)

Flat glass, bottles: 72 SiO2 – 12 CaO – 14 Na2O

Crystal glass: 60 SiO2 – 26 PbO – 14 K2O (PbO between 24-36)

3.3 glass (Pyrex, Simax): 80 SiO2 – 15 B2O3 – 5 Na2O

Glass fibres: 53 SiO2 – 15 Al2O3 – 16 CaO – 4 MgO – 10 B2O3

GlassGlass

typestypes

accordingaccording

to to thethe

chemicalchemical

compositioncompositionSoda-lime glass:

the most prevalent type of glassprepared by melting the raw materials, such as soda, lime, silica, alumina, and small quantities of fining agents (e.g., sodium sulfate, sodium chloride) in a glass furnace at temperatures locally up to 1675°CGreen and brown bottles are obtained from raw materials containing iron oxide. For lowering the price of the raw materials, purechemicals are not used, but relatively inexpensive minerals such as trona, sand, and feldsparused for windowpanes, and glass containers (bottles and jars) for beverages, food, and some commodity items

Borosilicate glass(Pyrex):having very low coefficient of thermal expansion (~ 3 x 10-6 / C at 20°C), making them resistant to thermal shock

superior durability, chemical and heat resistance use in chemical laboratory equipment, cookware, lighting, and in certain cases, windows.

Fused quartz and fused silica:manufactured by melting naturally occurring quartz crystals of high purity at approximately 2000°Cused to make optical fiber for telecommunicationsused as the envelope of halogen lampsused to make various refractory shapes such as crucibles, trays, shrouds, and rollers for many high temperature thermal processes including steel making, foundries, and glass manufacture

Lead crystal glassmuch higher index of refraction than normal glass, and consequently much greater "sparkle"much more difficult to form crystal during manufacturingLead crystal typically contains 24–35 percent lead oxide

Chalcogenide glass (sulfur, selenium or tellurium)ideal for incorporation into laser and other active devicesoptical discssandwiched between dielectric layers

Fluorosilicate glass (FSG)dielectric used in between copper metal layers during silicon integrated circuit fabrication process

Photochromic glass:embedding of microcrystalline silver halides (usually silver chloride), or molecules in a glass substratedarken substantially in response to UV light in less than one minute, and then continue to darken very slightly over the next fifteen minutesUsed as eyeglass lens

To control the amount of heat and light that passes through the glass. Three types of glass designed for this purpose are:

Reflective Glass - clear or tinted glass that has a very thin layer of metal or metallic oxide on the surface. The reflective coating reduces heat gain and glare from the outside while allowing visible light to enterLow Emissivity Glass- with very thin metallic coatings that reduce visible light transmission by about 10 percent compared to uncoated glass, reduces heat loss through windowsInsulating Glass - made from two or more lites of glass separated by a sealed air space. The metal tube around the perimeter of the insulated unit which seperates the two lites of glass is called the spacer

Specialty Glass:Mirrors - made from high quality annealed float glass, depositing a layer of silver on one surface of the glassSpandrel Glass - must be either heat strengthened or fully tempered because the frit causes the glass to absorb heatLaminated Glass - used as the inboard lite in skylights, varying the thickness and color, can be used to reduce the transmission of solar energy, control glare, and screen out ultraviolet radiation Art Glass - opalescent, cathedral or stained glass, usually produced in small batch operations

Fiberglass (fibreglass or glass fibre):material made from extremely fine fibers of glassused as a reinforcing agent for many polymer products; the resulting composite material, properly known as fiber-reinforced polymer (FRP) or glass-reinforced plastic (GRP), is called "fiberglass" in popular usageuses for regular fiber glass - mats, insulation, reinforcement, sound absorption, heat resistant fabrics, corrosion resistant fabrics and high strength fabricsthe main source of material used by the modern automobile industry

Sinteringmethod for making objects from powder, by heating the material (below its melting point -

solid state sintering) until its particles adhere

to each othertraditionally used for manufacturing ceramic objects, and has also found uses in such fields as powder metallurgysome

ceramic raw materials have a lower affinity for water and a lower

plasticity index than clay, requiring organic additives in the stages before sinteringsinterisation

is associated to a remarkable shrinkage of the material due

to the fact that glass phases flow, once their transition temperature is reached, and start consolidating the powdery structure and considerably reducing the porosity of the materialThere are two types of sintering: with pressure (also known as hot pressing), and without pressure.

Rheology

study of the deformation and flow of matter under the influence of an applied stress, which might be, for example, a shear stress or extensional stressrheometry

-

the experimental characterisation

of a material's rheological

behaviourTheoretical aspects of rheology

are:

the relation of the flow/deformation behaviour

of material and its internal structure (e.g. the orientation and elongation of polymer molecules)the flow/deformation behaviour

of materials that cannot be described by

classical fluid mechanics or elasticityThis is also often called Non-Newtonian fluid mechanics in the case of fluids.

Ceramics

Porcelain, chinawarePotteryBricks, roof tiles, tiles, sanitary ceramicsAdvanced (engineering) ceramics - Al2O3, ZrO2, UO2

RefractoriesNon-oxide ceramics (nitrides, carbides)

Ceramics

Polycrystalline materialUsually prepared by high-temperature processestypical HT reaction kaolinite – mullite

Al2

O3

.2SiO2

.2H2

O→3 Al2

O3

.2SiO2

+ SiO2 + H2

O

sintering processderived from the Greek word κεραμικός (keramos)The term covers inorganic non-metallic materials which are formed by the action of heat.

Raw materialsplastic – clays, soils, tillsnonplastic – grog (inert filler) – sand, corund, mullitaddition – alkaline feldspar

Many ceramic materials are hard, porous, and brittle

Kaolinite

Al2Si2O5(OH)4, Aluminum SilicateHydroxide

White or colored with impurities

above 1200°C mullite formation –Al6Si2O13

The most important phase in ceramicmicrostructure – high strength, refractoriness, durability

Needlelike shape

important to the production of ceramics and porcelain.

used as a filler for paint, rubber and plastics since it is relatively inert and is long lasting

Types of ceramic materialsStructural

including bricks, pipes, floor and roof tiles

Whitewaresincluding tableware, wall tiles, decorative art objects and sanitary ware

Technical (Engineering, Advanced, Special, and in Japan, Fine Ceramics)

includes tiles used in the Space Shuttle program, gas burner nozzles, ballistic protection, nuclear fuel uranium oxide pellets, bio-medical implants, jet engine turbine blades, and missile nose cones

Refractoriesas kiln linings, gas fire radiants, steel and glass making crucibles

Frequently the raw materials do not include clays.

Structural ceramics

Construction bricks. Floor and roof tiles. Sewage pipes

Whiteware ceramicsBone china:

type of porcelain body first developed in Britain,calcined ox bone (bone ash) - major constituentcharacterised by high whiteness, translucency and strengthProduction usually involves a two stage firing where the first, bisque, is without a glaze at 1280 °C (2336 °F), which gives a translucent product and then glaze, or glost, fired at a lower temperature below 1080 °C (1976 °F).

Earthenware:common ceramic material, which is used extensively for pottery tableware and decorative objectsgeneric composition is 25% ball clay, 28% kaolin, 32% quartz, and 15% feldsparcommonly bisque, or biscuit, fired to temperatures in the range of 1000 and 1150 degrees Celsius (1800 and 2100 degrees Fahrenheit, and glost fired from 950 to 1050°C (1750 to 1925°F)After firing the body is porous and opaque with colours ranging from white to red depending on the raw materials usedless strong, less tough, and more porous than stoneware - but its low cost and easier working compensate for these deficiencies. Due to its higher porosity, earthenware must usually be glazed in order to be watertight

Ceramic glazelayer or coating of a vitreous substance fired to fuse to a ceramic object to color, decorate, strengthen or waterproof itimportant for earthenware vesselsmay be applied by dry dusting a dry mixture over the surface of the clay bodyLiquid glazes - suspensions of various powdered minerals, and metal oxides - can be applied by dipping pieces directly into the glaze, pouring the glaze over the piece, spraying it onto the piece with an airbrush or similar tool, with a brush, or with any tool that will achieve the desired effect

Porcelain:ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between 1,200 °C (2,192 °F) and 1,400 °C (2,552 °F)toughness, strength, and translucence of porcelain arise mainly from the formation of glass and the mineral mullite within the fired body at these high temperatures used to make table, kitchen, sanitary, and decorative wares; objects of fine art; and tiles. Its high resistance to the passage of electricity makes porcelain an excellent insulator. It is also used in dentistry to make false teeth, caps and crowns.

Stoneware:category of claydistinguished primarily by its firing and maturation temperature (from about 1200°C to 1315 °C)man-made stonedense, impermeable and hard enough to resist scratching by a steel pointcoloured grey or brownish because of impurities in the clay used for its manufacture, and is normally glazed

Technical ceramicsOxides

aluminazirconia - zirconium dioxide (ZrO2),

white crystalline oxide of zirconiumused as a refractory material, in insulation, abrasives, enamels and ceramic glazeshigh ionic conductivity (and a low electronic conductivity) makes it one of the most useful electroceramics

Compositesparticulate reinforcedcombinations of oxides and non-oxides

Non-oxidesCarbides - compound of carbon with a more electronegative element

SiCBorides

generally high melting and are not ionic in natureexhibit very useful physical properties (high melting and inert, super conductivity)

Nitridesrefractory materialslubricant BN cutting materials e.g. silicon nitride, Si3N4 insulators e.g. boron nitride, BN, silicon nitride, Si3N4 semiconductors e.g. gallium nitride, GaNmetal coatings e.g. titanium nitride, TiNhydrogen storage e.g Lithium nitride, Li3N

Silicidesinert to aqueous solutions of everything with exception of hydrofluoric acidreact with more aggressive agents, eg. melted potassium hydroxide, or fluorine and chlorine

Examples of technical ceramicsBarium titanate (often mixed with strontium titanate) displays ferroelectricity, meaning that its mechanical, electrical, and thermal responses are coupled to one another and also history-dependent. It is widely used in electromechanical transducers, ceramic capacitors, and data storage elements. Grain boundary conditions can create PTC effects in heating elements. Bismuth strontium calcium copper oxide, a high-temperature superconductor Boron nitride is structurally isoelectronic to carbon and takes on similar physical forms: a graphite-like one used as a lubricant, and a diamond-like one used as an abrasive. Ferrite (Fe3O4), which is ferrimagnetic and is used in the magnetic cores of electrical transformers and magnetic core memory. Lead zirconate titanate is another ferroelectric material. Magnesium diboride (MgB2), which is an unconventional superconductor. Sialons / Silicon Aluminium Oxynitrides, high strength, high thermal shock / chemical / wear resistance, low density ceramics used in non-ferrous molten metal handling, weld pins and the chemical industry. Silicon carbide (SiC), which is used as a susceptor in microwave furnaces, a commonly used abrasive, and as a refractory material. Silicon nitride (Si3N4), which is used as an abrasive powder. Steatite (magnesium silicates) is used as an electrical insulator. Uranium oxide (UO2), used as fuel in nuclear reactors. Yttrium barium copper oxide (YBa2Cu3O7-x), another high temperature superconductor. Zinc oxide (ZnO), which is a semiconductor, and used in the construction of varistors. Zirconium dioxide (zirconia), which in pure form undergoes many phase changes between room temperature and practical sintering temperatures, can be chemically "stabilized" in several different forms. Its high oxygen ion conductivity recommends it for use in fuel cells. In another variant, metastable structures can impart transformation toughening for mechanical applications; most ceramic knife blades are made of this material.

Each one of these classes can developunique material properties

Manufacturing: Properties are influenced due to

Composition and granularity of raw materials

Temperature, time and medium of firing

20-200°C drying

200-450°C water evaporation

450-600 °C metakaolinite formation

Above 1000°C mullit formation andsintering

Mixing water, binder, deflocculant, and unfired ceramic powder to form a slurry Spray-drying the slurry Putting the spray dried powder into a mold and pressing it to form a green body (an unsinteredceramic item) Heating the green body at low temperature to burn off the binder Sintering at a high temperature to fuse the ceramic particles together

The general procedure of creating ceramic objects

Furnace, kiln, heater

Chamber

furnace

(storey)

Circular

kiln

Tunnel

kiln

Refractoriesmaterial to withstand temperatures above 1100 °C without softeningmust be strong at high temperaturesresistant to thermal shockchemically inerthave low thermal conductivities and coefficients of expansionBricks are pre-sintered forms which can hold their shape. Monolithics are loose material which can be formed into complex shapes, or sprayed into place, and have to be sintered before use.

silica r.fireclay r. (grog, chamotte)corundum r.magnesite r.chrome-magnesite r.fusion-cast

refractoriness – technical property

refractoriness testtip touching

support (3-5°C.min-1)

Main types of refractories

Refractories – composition, properties

silica r. (dinas) (refractoriness 1710-1750°C)>93% silica quartz, tridymite, cristobalite, glass

Fireclay r. (grog, chamotte) (1600-1750°C)15-46% Al2O3 - SiO2, mullite 3Al2O3.2SiO2

corundum (1850-2000°C)a-Al2O3

magnesite r. (>2000°C)MgO periclase

chrome-magnesite r. (1920-2000°C)MgO.Cr2O3

fusion-cast corundum/badelleyite r. (no open pores!)a-Al2O3, ZrO2, SiO2 glass phase

acid

neutral

basic

LiteraturaLiteratura

http://en.wikipedia.org/wiki/Glass

http://www.azom.com/details.asp?ArticleID=1114

http://en.wikipedia.org/wiki/Brick

http://en.wikipedia.org/wiki/Tile

http://en.wikipedia.org/wiki/Pipe_%28material%29

http://en.wikipedia.org/wiki/Silicon_carbide