Ch1 Flashcards
What does structure relate to?
Structure relates to the arrangement of something’s internal components
What is the difference between material science and material engineering
Material science-investigates the relationship that exist between the structures and properties of materials and develops or synthesizes new materials
Material engineering-creates new products or systems using existing materials to develop new techniques for processing materials
What is subatomic structure
Structure that involves electrons with in the individual atoms and interactions with in the nuclei
Microscopic vs. macroscopic
Microscopic must be seen with a microscope, while macroscopic may be seen with the naked eye
What is a property?
A property is a material trait in terms of the kind and magnitude of the response to a specific imposed stimulus (properties are independent of material shape and size).
How many properties are there, and what does each relate to?
There are 6 properties:
Mechanical-relate deformation to an applied load or force(stiffness,strength, and toughness)
Electrical-electrical conductivity, dialectic const.,the stimulus is an electric field
Thermal- in terms of heat capacity and thermal conductivity
Magnetic-response of a material to the application of a magnetic field
Optical- stimulus is electromagnetic or light radiation; index or refraction, reflectivity
Deteriorative- the chemical reductivity of materials
How are processing, structure, properties, and performance of a material related?
The structure of the material depends on how it was processed, and it’s properties are based on its structures. Finally the materials performance is based on the properties of the material.
How are materials selected?
1) in service conditions must be characterized, these dictate the properties required of the material. Keep in mind no material is perfect, so there will be trade offs
2) consider any deterioration of material properties that will occur during the operation
3) take the economics into account
What are the 3 basic categories of materials?
Metals, ceramics, and polymers
This is based primarily on chemical make up and atomic structure
And exception are composites which are a combination of multiple materials, and advanced materials used in high technology
What are ceramics, and what are some common properties, and examples?
A ceramic is a compound of metallic and non-metallic elements. They mostly include oxides, nitrides, and carbides. They can be characterized by the type of bond or by properties.
Ceramic properties include: High: Stiffness Compressive strength Hardness Brittleness
Low: Thermal conductivity Electrical conductivity Ductility Tensile strength
Ceramics are typically insulation to the passage of heat and electricity and are more resistant to harsh environments than metals and polymers
May be transparent, translucent, or even opaque
Some ceramics have have magnetic properties
Examples of ceramics include:
-al2o3-used in sandpaper and cd polish( has a high hardness)
SiO2-used in microelectronics to block current(low conductivity)
Si3N4-used to make car engine parts(low thermal conductivity)
Traditional ceramics are clay, cement, porcelain, and glass
What are metals and their properties, and examples
Metals are composed of one or more metallic elements and sometimes small amounts of non-metallic elements.
Atoms in metals are arranged in a very orderly manner and relatively dense in comparison to ceramics and polymers.
They have a large number of non localized(delocalized) electrons, which are electrons that are not bound to particular atoms
Many properties of metals are directly attributable to these electrons
Properties of metals: High: Density Stiffness Strength Ductility Thermal conductivity Electrical conductivity
Low:
Transparency
Metals are typically stiff, strong, ductile(capable of large amounts of deformation, without fracture), and are resistant to fracture.
Examples of metals are:
Copper wire-electrical wiring(night electrical conductivity, high ductility)
Gold-jewelry(high ductility)
Aluminum- cans(high ductility and strength)
What is a metal alloy?
A metal alloy is a metallic substance made of 2 or more elements
Ex: brass is made from copper and zinc
Sterling silver is made from silver and copper
What are polymers and their properties, and examples?
Polymers are compound of high molecular weight which has a structure of chains made of repeating molecular units( these chains usually have a carbon back bone and many are organic compounds that are based on carbon, hydrogen, and other non-metallic elements)
Properties of polymers: High: Ductility Plasticity Flexibility
Low: Strength Density Stiffness Electrical conductivity Thermal conductivity
However, there are a lot of exceptions to this because of a wider variety of polymers
Polymers typically :
- have large molecular structures
- have a stiffness to strength ratio on a per mass basis that is comparable to those of metals and ceramics
- are easily pliable and formed into complex shapes
- relatively inert chemically and unreactive in many environments
- -a major drawback is their tendency to soften and or decompose at higher temperatures, which greatly limits their use
- are NOT magnetic
Common polymers:
Low density polyethylene(ldpe)- used in grocery bags(flexible and ductile)
Nylon(s)- makes clothing( flexible, ductile)
Polyvinyl-chloride(pvc) used for making pipes(ductile)
What are composites and some of their properties, examples
A composite is a material composed of 2 or more materials from polymers, metals, and ceramics
There are no properties directly associated with this groups: each composite is designed to have a custom combination of properties.
Examples:
Fiberglass is composed of ceramic, glass fibers in a polymer. This allows it to be stiff and strong because glass fibers and flexible because of the polymer
Carbon fiber reinforced polymer(carp)- carbon fibers that are embattled in a polymer. They are stronger and stiffer than glass fiber reinforced materials, but more expensive. Used in aerospace and expensive sporting equipment. The 787 Dreamliner has this.
What are advanced materials?
Materials that are used in high technology applications like electronics, computers, fiber-optic systems, spacecraft, aircraft, and military rocketry.
These advanced materials are typically traditional materials with enhanced properties or newly developed high performance materials.
Includes materials of all types(ceramics, polymers, and metals) and are normally very expensive
Sometimes referred to as materials of the future
Sub-groups include: semi-conductors, biomaterials, smart materials, and nano materials
What are semi conductors and their characteristics
Materials with electrical properties between those of electrical conductors and insulators
They are extremely sensitive to the presence of minute concentration of impurity atoms for which the concentration may be controlled over very small spatial regions.
This technology has revolutionized the electronics and computer industry over the past 30 years.
What are bio materials and their characteristics?
Used in components implanted into the human body to replace diseased or damaged body parts.
These materials must not produce toxic substances and must be compatible with body tissue so that they are not rejected by the body
Metals, ceramics, polymers, composites, and semiconductors have all been used as biomaterials
What are smart materials, and what are some of the common types of smart materials? What are the components of a smart materials? What are the common types of materials/systems used in the components of smart materials?
Smart materials are materials that are able to sense changes in their environment and then respond to these changes in a predetermined manner kind of like a living organism
These materials have 2 components:
1) some type of sensor that detects an I put signal or stimulus
2) an actuator that performs a responsive and adaptive function. These may change shape, position, natural frequency, or mechanical characteristics in response to change in temperature, electric field, or magnetic field
There are 4 types of actuators being used:
1)Shape-memory alloys- metals that after having been deformed, revert to their original shape when the temperature is changed
2) piezoelectric ceramics- expand and contrast in response to an applied electric field or voltage. Conversely, they also generate an electric field when their dimensions are altered.
3) magneto restrictive materials- act exactly like piezoelectric materials except they are responsive to magnetic fields
4) electroheological and magnetohealogical fluids-are liquids that experience dramatic changes in viscosity upon the application of electric or magnetic fields.
Typically the sensors use optical fibers, piezoelectric materials(including some polymers) and microelectromechanical systems (mems)
Examples of smart material applications:
Systems used in helicopters to reduce aerodynamic cockpit noise created by the rotor blades. Piezoelectric sensors inserted into the blades monitor blade stress and deformation: feedback signals from these sensors are fed into a computer-controlled adaptive device that generates noise canceling anti-noise
Explain nano materials and some of the science behind them
Nano materials are new materials that can be metals, ceramics, polymers, or composites. Nano means 10^-9 so about 500 atoms wide. These new materials show fascinating properties and promise.
Nanotechnology is basically the science of carefully rearranging the atoms of a materials to get certain benefits or properties. This is known as a bottom-up scientific approach.
Many properties depend on the nanoscale domain, and can change drastically as you approach the atomic dimensions. Ex: materials that are opaque in macroscopic domain, may become transparent on the nanoscale. Solids may become liquids, chemically stable may become unstable, and electric insulators may become conductors and ect.
Some of these effects may be quantum mechanical, or related to surface phenomenon- which is where the proportion of atoms located on the surface sites of a particle increase dramatically as its size decreases.
Examples:
Catalytic converter, nanocarbons, magnetic particles that store data
Compare top down and bottom up science.
Top down science-studies large and complex structures and then investigates the fundamental building blocks of these structures that are smaller and simpler
Bottom up science-is building new structures from their atomic level constituents, one atom or molecule at a time.
What are some common problems solved by material engineers/scientist, as well as some modern needs of materials?
Modern needs:
-sophisticated materials that are environmentally considerate
Ex: nuclear waste and disposing of it. And hydrogen fuel cell technology
Common problems of materials:
We need new materials to replace those that have depleted (oil)
We need materials that will make processes more efficient
We need materials that are way more environmentally efficient.
Compare metals, ceramics, polymers and composites in:
1) density
2) stiffness( Young’s modulus)
3) strength
4) resistivity to fracture
5) electrical conductivity
These rankings are from high to low. Also keep in mind that this is only general rankings…ex: some composites can be stronger than some metals ect…:
1) density Metals(most dense) Ceramics Polymers Composites(least dense)
2) stiffness
Ceramics(most stiff)
Composites and metals tie
Polymers(least stiff)
3) strength Metals(strongest) Composites Ceramics Polymers(weakest)
4) resistivity to fracture: Metals(most resistive) Composites Ceramics Polymers(least resistive)
5) electrical conductivity
metals(most conductive)
Semiconductors
Ceramics and polymers (tie for least conductive)
