150 Questions
What is the purpose of annealing glass within a long cooling tunnel?
To gradually cool the glass and prevent residual stresses
Which method is used to produce very thin glass sheets?
Fusion forming
At what temperature is the glass melt cooled to give the correct viscosity for a float bath?
~1100°C
What is the main advantage of the 'overflow and down-draw method' over the float bath method?
Produces flatter and more uniform thickness glass sheets
What is the displacement vector needed to close a circuit around the dislocation line called?
Burgers vector
Which type of dislocation has its Burgers vector perpendicular to the dislocation line?
Edge dislocation
What phenomenon is responsible for the plastic deformation of crystalline material?
Dislocation glide
What determines the yield strength of a material by indicating the minimum stress required for dislocation glide?
Critical resolved shear stress (CRSS)
In an FCC crystal, what type of planes host unique close-packed slip directions?
{111}-type planes
How many unique close-packed {111}-type planes are found in an FCC crystal?
4
Which type of directions link lattice sites in an FCC crystal?
{111}-type directions
Why are FCC crystals considered comparatively plastic?
Due to high number of slip systems
What type of strengthening does Zinc provide in Aluminum alloys?
Solution strengthening
In Al alloys, what type of mechanical properties are controlled by work hardening?
Strength and hardness
What do white blobs indicate in the context of Al alloy deformation?
Nucleation sites of recrystallized grains
How does cryogenic deformation affect the strength of aluminum alloys?
Increases strength at the expense of ductility
What does cold rolling do to the strength of an aluminum alloy?
Substantially increases it
Which element can be exploited to improve strain hardening in aluminum alloys based on the information provided?
Magnesium (Mg)
What is the primary mechanism that slows down dynamic recovery in aluminum alloys?
Cellular structure formation
Which process can substantially increase both UTS and yield stress in an aluminum alloy?
Cold rolling
Which coating process is faster but results in a rougher and more porous coating?
Plasma spraying
What property makes technical ceramics suitable for high-temperature applications?
High stiffness
In terms of hardness and wear resistance, how do most technical ceramics compare to metal alloys and polymers?
Considerably harder with excellent wear resistance
What property does CFRP (ceramic-reinforced polymer) possess in terms of density compared to technical ceramics?
Lower density
Which material is primarily an electrical insulator with moderate thermal conductivity?
Ceramics
What property allows technical ceramics to have the highest specific stiffness and specific strength?
Low density
What can be said about precipitate-free zones (PFZ)?
They act as stress concentrators.
How can the width of precipitate-free zones be controlled?
By heat treatment and alloying.
Why are grain boundaries considered good sites for precipitate formation?
Since they provide faster solute diffusion and nucleation sites.
What effect does cold work have when used in conjunction with the heat treatment for ageing in Al alloys?
Allows a coarser but more uniform precipitate distribution.
How does the protective oxide film on aluminium contribute to its corrosion resistance?
By forming a barrier against further corrosion.
What happens when aluminium is in contact with an electrolyte and a less reactive metal?
It acts as a sacrificial anode and corrodes rapidly.
What property is not covered in this course?
Conductivity
What is the relationship between force and extension in Hooke's law?
Force is directly proportional to extension
In tension, the strain in a material is:
Always positive
What type of testing machine is commonly used for stress-strain testing?
Hydraulically actuated
What is the main difference between tensile and compressive stresses?
Tensile stresses are positive; compressive stresses are negative
What property does Hooke's law aim to derive that is independent of spring shape?
Force constant k
Positive strain occurs in which situation?
Tension
What is the main purpose of a binder additive in technical ceramics?
Ensures cohesion of the ceramic powder in the green parts
What is a characteristic property of lead glass?
Absorption of radiation
Which process is used to adjust the properties of ceramic powder by decreasing viscosity and increasing particle concentration?
Dispersing
Which application is NOT associated with the use of Bioglass?
Solar heat collectors
What stage involves the removal of the binder from ceramic parts before sintering?
Binder removal
What sets glass ceramics apart from traditional glasses?
Controlled crystallization
What is the primary function of lead oxide in lead glass?
Lower the melt viscosity
What is the primary function of a dispersant additive in technical ceramics processing?
Reduces viscosity of the mixture
Why are bioglasses formulated to be chemically similar to hydroxyapatite?
To enhance mineral growth in bones
In technical ceramics production, what does green machining refer to?
Machining ceramics in their unfired state
What is the primary function of granulating in technical ceramics processing?
Creating cohesive green parts for moulding/forming
What role does the negative thermal expansion coefficient of crystalline phases play in glass ceramics?
Contributes to net zero thermal expansion
Which stage of technical ceramics processing involves adjusting ceramic properties by milling or turning?
Finishing
What makes the crystalline phase in glass ceramics unique in terms of thermal expansion?
Negative thermal expansion coefficient
How does bioglass promote the growth of new bone tissue?
"Stimulates formation of hydroxyapatite"
What is the purpose of plasticising in technical ceramics processing?
Enhancing the plasticity of ceramic mixtures
In the context of ceramics, which stage involves the shaping of the material into the desired form?
Forming/shaping
What is a typical application of ceramics involving the creation of high-temperature structural components?
Creating refractories and crucibles
When was the first man-made glass most likely produced?
3000 BCE
What was the status of glass as a material during the Roman Empire?
Luxury material
Which natural material containing glass-like properties has been used by people since prehistoric times to make tools and artefacts?
Obsidian
During which historical period did glass usage expand to include building materials like stained glass windows?
Middle Ages
'Knapping' as a technique has been applied to which glass-like natural material by people since prehistoric times?
Obsidian
What is the primary difference between the 2xxx and 6xxx series aluminum alloys mentioned in the text?
The primary intermetallic phases present
Which Al alloy series is known for being used in aircraft rivets even today?
2017
What property led to the development of alloys like 2618 for supersonic aircraft?
Creep resistance
Which alloy series is primarily recognized for having the most complex precipitation processes?
6xxx
What is the distinguishing feature of Al-Mg-Si alloys in terms of strength?
Correlated with magnesium and silicon content
Which property do 2xxx series aluminum alloys possess in addition to high strength?
Excellent corrosion resistance
Why are Al-Cu-Mg alloys like Duralumin no longer widely used today?
Replaced by newer derivative systems with higher strength
Which element plays a significant role in providing medium strength in Al-Cu, Al-Cu-Mg, and Al-Zn-Mg-Cu alloys?
3.5
Which type of glass is used to immobilize highly radioactive nuclear waste?
Borosilicate glass
What is the process of turning molten glass into flat glass sheets called?
Vitrification process
What is the role of tin in the Pilkington float glass process?
Increases thermal conductivity
Which glass type was produced by glass-blowers before the nuclear age and fluoresces under UV light?
Lead glass
What is an essential characteristic of uranium glass made before the nuclear age?
High thermal conductivity
Which type of ceramic system is used in applications like cooktops and fireplaces?
Borosilicate ceramic
What is the purpose of vitrification in dealing with highly radioactive waste?
To create a water-soluble formulation
What is a distinctive feature of glass ceramics compared to traditional glasses?
High thermal expansion coefficient
What is the purpose of HIP-ing in additive manufacturing?
To reduce the porosity of products
In slip casting, what happens when the plaster absorbs moisture from the adjacent slip?
The slip becomes more viscous
What is the primary function of a doctor blade in tape casting?
To adjust the height of the ceramic tape
Which method allows mass production of ceramics with very complex relief?
Slip casting
What is the key advantage of gel-casting for technical ceramic forming?
Enables a high degree of precision and complex geometries
What is formed in freeze casting using a suspension of ceramic particles in water?
Gel-like material
What is the primary difference between ceramics and glass in terms of their natural occurrence?
Ceramics occur in minerals like obsidian, while glass occurs in fused sand.
What was the significance of glass during the middle ages?
It was commonly used as a building material for stained glass windows.
What was one of the first uses of man-made glass?
Incidental production during metal-working processes.
In what way did the Roman Empire contribute to the adoption of glass as a more common material?
By using glass extensively in architecture and interior design.
What technological advancement enabled the widespread use of full glass windows?
Advancement of modern plate glass technologies.
What natural event can lead to the formation of glass from sand?
Lightning strike
What technique was used by people since prehistoric times to shape materials like obsidian?
Knapping
Why was glass considered a luxury material until its adoption in the Roman Empire?
Because of the high production costs involved.
What is the main focus in developing superplastic behavior in high-strength 7xxx series alloys?
Reducing forming strain rates
What is a common feature of cast Al alloys in applications such as anodizing and engine blocks?
Impurities from recycled stock
Why is the ratio of cast aluminum to wrought constantly increasing?
Increased use of castings in automotive industry
Which type of aluminum castings are divided into 'primary' and 'secondary' categories based on their material source?
Alloys prepared from recycled metals
In 2004, what was the Cast:Wrought ratio in USA automotive use?
1:2
What is a distinguishing factor between 'primary' and 'secondary' cast aluminum alloys?
Impurity levels
Which application is a common end-use for Al-Si, Al-Si-Mg, and Al-Si-Cu systems?
Transmissions casings
What is the purpose of the primary ageing treatment in the heat treatment process of turbine blades?
To grow the desired distribution of g’ precipitates
What is a common issue that may lead to a blade being scrapped during directional solidification?
Secondary Grains
What is the main purpose of depositing TBC on turbine blades?
Effusion cooling
Why are the heat-treated blades subjected to further finishing and quality control procedures post-casting?
For heat treatment to optimize microstructure
Which possible casting defect can result from low-angle grain boundaries?
Freckles
What is the main purpose of Neutron Radiograph in the context of turbine blades?
Machine blade to shape and perform NDT
What is the purpose of HIP-ing in additive manufacturing?
Reducing porosity of products
What distinguishes tape casting from slip casting in ceramic production?
Tape casting produces thin ceramic tapes or sheets
Which method is known for allowing a high degree of precision in forming highly advanced technical ceramics?
Sol-gel processing
What happens during freeze casting in terms of the suspension used?
Ceramic particles are suspended in water
What is the main function of the doctor blade in the tape casting process?
Adjusting the thickness of the ceramic tape
Which stage in gel-casting involves filling complex molds with a specific substance?
Polymerization reaction
How does slip casting enable mass production of ceramics with intricate designs?
By allowing drying to a 'leather dry' state
In which method does a gel form to bind ceramic particles before drying and sintering?
Gel-casting
What is a distinguishing feature of bioglass mentioned in the text?
Water solubility
What sets lead glass apart from regular glassware in terms of composition?
Additional lead oxide
What is a primary application of glass ceramics mentioned in the text?
Production of materials with net zero thermal expansion
What property of glass ceramics allows for the growth of new bone tissue as mentioned in the text?
Negative thermal expansion coefficient
What is a common use of lead glass not mentioned in relation to its toxicity?
Optics
Which type of glass has evidence of toxicity and poor thermal shock resistance?
Lead glass
What makes traditional glasses different from glass ceramics in terms of thermal expansion?
Glass ceramics have negative thermal expansion coefficient
Which element in bioglass becomes part of the growth of new bone tissue within the body?
$CaO$
What process increases the strength of a material by creating fine particles with a stronger crystal structure within the parent crystal?
Precipitation hardening
In polycrystalline materials, why are grain boundaries important for strength?
They hinder atomic diffusion
Which mechanism involves dislocations either cutting through particles or bypassing them to increase material strength?
Orowan bowing
What is the parameter used to quantify the obstacle to dislocation motion in a material?
APB energy
What type of crystallographic defects are formed when polycrystalline materials consist of mis-oriented grains?
Grain boundaries
In the context of materials science, what is the significance of the Burgers vector?
It represents dislocation magnitude and direction
How do fine particles formed through precipitation hardening affect dislocation glide?
They act as obstacles
Which phenomenon arises when dislocations must cut through particles or bypass them via Orowan bowing?
Precipitate pinning
Which lecture in the course is likely to cover the topic of defects in the atomic structure of materials?
Lecture 4 Properties and processing of ceramics
Which book could be most helpful for understanding the engineering aspects of materials?
Engineering materials - Ashby and Jones
Which type of materials are likely to be discussed in Lecture 5 of the course?
Glass materials
Which alloy type is typically known for its application in high-temperature environments?
Superalloys
What is a common characteristic shared by ceramics, glasses, and light alloys?
High temperature resistance
What distinguishes light alloys from high-temperature alloys?
Heat resistance
Which process is crucial for enhancing specific stiffness and specific strength in technical ceramics?
Sintering
Which boron nitride form has the second-highest hardness after diamond?
Cubic boron nitride (c-BN)
What is a key application of Silicon Nitride (Si3N4) mentioned in the text?
High-temperature structural parts
What distinguishes Boron Nitride Nanotubes (BNNTs) from Carbon Nanotubes (CNTs)?
Flammability in air
What is the primary use of hexagonal boron nitride (h-BN) as mentioned in the text?
High-temperature lubricants
Which material offers moderate properties at a moderate cost in various applications?
Silicon Nitride (Si3N4)
What makes cubic Boron Nitride (c-BN) suitable for grinding wheels and abrasives?
Second-highest hardness after diamond
Why might Silicon Nitride (Si3N4) be chosen over other ceramics and metals for certain applications?
Moderate properties at a moderate cost
What is a method mentioned in the text to refine the grain size of an aluminum casting?
Creating more grain nuclei by breaking up dendrites during solidification
Which term describes the property of semi-solid slurries where their viscosity decreases with stirring?
Thixotropic
What is the difference between rheocasting and thixoforming?
Rheocasting requires expensive specialized billets, while thixoforming allows the use of existing alloys.
What is a characteristic of aluminium casting globular structure?
It contributes to a semi-solid state
Why is recycling important for aluminum alloys according to the text?
To reduce energy consumption during extraction
Which statement accurately describes the processing methods of rheocasting and thixoforming?
Rheocasting uses existing alloys, while thixoforming requires specialized billets.
Why are aluminium alloys considered relatively easy to process?
Having a comparatively low melting point
Study Notes
- Raw materials for glass production are melted at 1600°C.
- Molten glass is homogenized and bubbles are removed.
- The glass melt is then cooled to 1100°C to achieve the correct viscosity for the float bath process.
- In the float bath process, glass flows over a smooth molten tin bath at around 500°C in a protective atmosphere of nitrogen and hydrogen.
- The glass is annealed in a cooling tunnel to avoid residual stresses before being electronically inspected, cut into sheets, and packed for shipment.
- Fusion forming, also known as the overflow and down-draw method, is used to produce flat glass sheets with high precision and uniform thickness.
- Blow molding is utilized to manufacture glass containers like bottles and jars using compressed gas inside forming molds.
- Dislocation glide is the mechanism responsible for the plastic deformation of crystalline materials, where shear stress allows dislocations to move through the crystal lattice.
- Work hardening and annealing are processes used to control the mechanical properties of aluminum alloys, impacting their strength and yield stress.
- Thermal and electrical conductivity of ceramics vary, with most ceramics being electrical insulators and having high to moderate thermal conductivity.
- Technical ceramics offer high melting points, stiffness, low thermal expansion, hardness, wear resistance, and reasonable strength and fracture toughness.
- Structural properties of materials, including stiffness, strength, hardness, ductility, fracture toughness, wear resistance, environmental resistance, thermal expansion, and thermal shock resistance, play crucial roles in material performance.
- Stress-strain testing is conducted to measure material properties such as Young's modulus, which determines the material's stiffness and elastic behavior.
- Lead glass, also known as lead crystal, contains lead oxide which enhances refractive index and light dispersal but has poor thermal shock resistance.
- Bioglass is designed for medical applications to repair damaged bone tissue by promoting new bone growth through its water-soluble and bioactive composition.
- Glass ceramics combine crystalline and amorphous phases for materials with net zero thermal expansion, achieved through controlled crystallization processes.
Learn about the three possible types of dislocations: edge, screw, and mixed dislocations, which are described by their Burgers vector. Explore how dislocations can move through a crystal via dislocation glide, involving the breaking and re-forming of inter-atomic bonds.
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