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CERAMICS AND GLASSES
Transcript of CERAMICS AND GLASSES
STATIC FATIGUE & CREEP
WEAK in TENSION but relatively STRONG in COMPRESSION.
Monday, July 20, 2015
Ceramics, Glasses & Glass-Ceramics
FRACTURE caused by HIGH TEMPERATURE
CERAMICS AND GLASSES
Lyn F. Santos
: Jenny, Ate Jen, Ganda
: gumawa ng loombands w/ kevin <3 (sa kwarto)
: You would not know it until you see it. :">
: EE din kasi si kevirn eh :">
: maging magandang housewife
Brai, nard, Jan, Brainard, Bj, Jay
Preaching, gumawa ng kabutihan sa kapwa, maging mabait, gumawa ng tama, maging good samaritan, mag kawang-gawa ng walang hinihiling na kapalit na pera.
magbilang ng pera na hindi tatagal ng bente segundo, magpa xerox, mag-GM, magtanong kung may pasok/klase, mag ayos ng schedule, mangolekta ng bayad, magpa-XEROX
VISCOUS DEFORMATION OF GLASSES
OPTICAL PROPERTIES OF CERAMICS AND GLASSES
-one of the most fundamental optical properties, where n, defined as
Where: Vvac=speed of light in vacuum
V = speed of light in transparent material
θi = angle of incidence
θr= angle of refraction
*Typical Values of n for ceramics and glasses run from 1.5 to 2.5.
TRANSPARENCY,TRANSLUCENCY, AND OPACITY
CERAMICS AND GLASSES
THESE REPRESENTS SOME OF THE EARLIEST AND MOST ENVIRONMENTALLY DURABLE MATERIALS FOR ENGINEERING
THEY ALSO REPRESENTS SOME OF THE MOST ADVANCED MATERIALS BEING DEVELOPED FOR THE AEROSPACE AND ELECTRONIC INDUSTRIES
THREE MAIN CATEGORIES
I. Crystalline Ceramics
I. CRYSTALLINE CERAMICS
These include the traditional silicate and the many oxide and non oxide compounds widely used in both traditional and advanced technologies
Silicate-Silicon dioxide, the main ingredient in most ceramic products
Pottery - this is a part of the category of ceramics known as white wares
It is the basis of structural clay product
REFRACTORY AND CEMENT
-High temperature-resistant structural materials that play crucial roles in industry
-about 40% of the refractories industry output consists of the clay-based silicates
-Include some traditional materials such as magnesia (MgO), a refractory widely used in the steel industry
A. Silicon Carbide
B. Silicon Nitrite
II. GLASSES-NONCRYSTALLINE MATERIALS
The traditional examples of this type of material are the silicate glasses
The term "glasses" is often used to refer only to the specific material.
in fact, the manufacturing of various glass products accounts for a much larger tonnage that involved in producing crystalline ceramics.
A. Network Formers
THE MAJOR COMMERCIAL SILICATE GLASSES
Various reference points of viscosity are defined that are useful in the processing and manufacture of glass products:
• Melting point – The temperature where the material is fluid enough to be considered a liquid. This corresponds to a viscosity of about 100 P.
• Working point – The temperature corresponding to 104 P. At this temperature glass fabrication operations can be carried out.
• Softening point – 107.6 poises. At this temperature the glass will flow at an appreciable rate under its own weight.
• Annealing point – 1013.4 poises. Internal stresses can be relieved in about 15 minutes at this temperature. This is roughly Tg.
1. Virteous Silica
2. Borosilicate Glasses
Zirconium Tetra fluoride
Combine the nature of Crystalline ceramics w/ glass. The result Is a product especially with attractive qualities.
a significant advantage is their ability to be formed into a product shape as economically and precisely as glasses.
The final crystalline grain sizes are generally between 0.1m and 1millimeter.
Its final product is characterized by mechanical and thermal shock resistance for superior to conventional ceramics.
Two unique Mechanical Responses in measuring Thermal Expansion of glass:
1. Glass transition Temperature (Tg)
2. Softening Temperature (Ts)
Above Tg, viscosity follows an Arrhenius form: where Q is the molar activation energy for viscous flow, R is the universal Gas constant, T is the Absolute Temp.
Viscous Behavior of glasses can be described by the viscosity:
TWO THERMAL PROPERTIES :
Water (H20) as universal solvent
Glass is extremely susceptible to stress corrosion by water in the environment.
This phenomenon is known in the glass as static fatigue or delayed time failure
How does a glass loses its strength?
1.Decrease in under normal ambient temperature.
2.Due to chemical reaction in water containing environments.
3.Rapid increase in stress load (dynamic fatigue)
Crack growth by chemical breaking of oxide network
The role of H20 in static fatigue depends on its reaction with silicate network. One H20 molecule and Si-O-Si segment generate two Si-OH units. This is equivalent to a break in the network.
Deformation at elevated temperature.
Moderate creep relieves tensile stresses that might otherwise lead to cracking.
Glass is noted for Its chemical inertness and General resistance to corrosion.