Material Science - Chemistry Notes

Role of Chemists in Material Science

  • Chemists play a central role in creating and improving materials.
  • Their crucial roles include:
    • Understanding and manipulating matter.
    • Designing and synthesizing new materials.
    • Optimizing existing material production.
    • Modifying and functionalizing materials.
    • Ensuring sustainability and safety.
    • Collaboration and interdisciplinary work.

Understanding and Manipulating Matter

  • Chemists understand and manipulate matter at the molecular level.
  • This involves:
    • Understanding the composition, structure, properties, and reactions of matter.
    • Understanding how atoms and molecules interact.
    • Tailoring material characteristics by understanding bonds, intermolecular forces, and reactivity.

Design and Synthesis of New Materials

  • Chemists are involved in discovering and synthesizing new materials.
  • This involves:
    • Exploring combinations of elements and molecular architectures.
    • Employing computational methods and theoretical understanding to predict material properties before synthesis.
    • Approaching more efficient and targeted material development.

Optimizing Existing Material Production

  • Chemists develop efficient and cost-effective processes for producing existing materials.
  • This includes:
    • Optimizing reaction conditions.
    • Improving yields.
    • Reducing waste.
    • Enhancing the purity of the final product.
  • They apply analytical skills to identify the root cause of issues and develop solutions.

Modifying and Functionalizing Materials

  • Chemists develop and apply surface treatments to alter the properties of existing materials.
  • This can enhance corrosion resistance.
  • They combine different materials with enhanced properties.
  • They understand chemical interactions of materials and how to optimize their performance.

Ensuring Sustainability and Safety

  • Chemists develop sustainable and environmentally friendly methods for material production.
  • This includes:
    • Using less hazardous chemicals.
    • Reducing energy consumption.
    • Minimizing waste.
    • Exploring renewable resources.
  • They develop safety protocols, ensure compliance with environmental regulations, and work to create safer materials for consumers.

Collaboration and Interdisciplinary Work

  • Material science involves collaboration of chemists, engineers, physicists, biologists, lawyers, governmental powers, etc.
  • Chemists provide chemical insights that complement the expertise of other disciplines.

Studying Materials

  • Learning about properties, applications, and structure of materials like:
    • Ceramics
    • Semiconductors
    • Polymers
    • Composites (Assigned reading page 210)

Concrete

  • Concrete is made of cement, stone or sand, and water.
  • When these components mix, they form a solid and very hard material.

The Roman Colosseum

  • The Colosseum is a great feat of architecture.
  • It has survived multiple fires, earthquakes, and other disasters.

Ceramics

  • Concrete is a ceramic material.
  • Ceramics are very stable materials and have been used for thousands of years.
  • Ceramics are usually made up of bonded metals and nonmetal atoms and are typically inorganic (not made of carbon).
  • Earth materials are mixed, usually in the form of powders.
  • Water is added to begin a reaction that forms the chemical bonds between the powdered materials.
  • Other ceramics are activated when the mixture is heated.

Ceramics - Chemical Bonds

  • Ceramics materials have both, ionic and covalent bonds.
  • Ionic bonds form between metal and nonmetal atoms.
  • Covalent bonds form between nonmetal atoms.
  • The structure formed follows a regular 3D rigid network in which electrons are transferred and shared between the atoms involved.

Ceramics - Chemical Properties

  • Inertness: Ceramics exhibit high resistance to chemical reactions.
    • Strong ionic and covalent bonds make them stable and less likely to react with acids, bases, solvents, and oxidizing agents.
  • Oxidation resistance: Ceramic materials are already in their highest oxidation state.
    • This makes them highly resistance to further oxidation.
    • Useful for aerospace and high temperature processes.
  • Thermal stability: strong bonds lead to high melting points and decomposition
    • Maintain structural integrity and properties at very high temperatures

Ceramics - Applications

  • Construction and housing: bricks, roof tiles, walls, sanitary ware
  • Tableware and decorative items: pottery, porcelain, stoneware
  • Abrasives: Griding, cutting, polishing, and sanding other materials
  • Refractories: inner lining of high-temperature equipment
  • Electrical and electronic applications: insulators
  • Automotive industry: for engine parts
  • Aerospace industry: engines and thermal barrier coatings
  • Biomedical applications: bone and artificial joints
  • Cutting tools: cutting tools for machines
  • Mention the property of ceramics that is useful for each mentioned application

Semiconductors

  • Semiconductors are materials that have properties between an insulator and a conductor
  • Conductor - material with high electrical conductivity
  • Insulator - material with very low electrical conductivity
  • The ability of a semiconductor to conduct electricity can be controlled and varied by factors such as temperature

Semiconductors - Elements

  • The metalloid elements in pure form are semiconductors
  • Electrons in metalloids do not flow as freely as they do in metals
  • The most common semiconductors are silicon(Si) and germanium (Ge)

Conducting Electricity

  • In order for materials to conduct electricity, valence electrons must be able to move from a band called “valence band” to a band called a “conduction band”

Semiconductors - Chemical Properties

  • Band Gap: Semiconductors have an energy gap between the valence gap and the conduction gap smaller than that of insulators, allowing some electrons to cross and conduct electricity
  • Semiconductors can conduct electricity depending on electrons of free movement

Semiconductors - Band Gap

  • What can cause an electron to cross the band gap into the conduction band?
    • External force - voltage
    • Thermal energy - temperature

Semiconductors - Covalent Bonding

  • Covalent bonding - valence electrons of semiconductors form strong covalent bonds with their neighboring atoms in a crystal lattice structure
  • At low temperature, these electrons are all involved in bonds, leaving very few free electrons to conduct electricity
  • This causes the element to behave as an insulator

Semiconductors - Doping

  • Doping - Process of intentionally adding small amounts of impurities with a different number of valence electrons to pure semiconductor crystals
  • Added electrons are not involved in bonds and have free movement
  • They can carry electricity and allow the material to act as a conductor

Semiconductors - Temperature Dependence

  • Temperature Dependance - conductivity of semiconductors increase with temperature
  • As temperature rises, more thermal energy is available to excite electrons
  • Excited electrons can cross the band gap into the conduction band
  • This allows the semiconductor to act as a strong conductor

Semiconductors - Applications

  • Electronic Industry - semiconductors allow the control con energy flow
  • Transistors - switch or amplify signals
  • Diodes - allow current flow in one direction (LEDs and lasers)
  • Memory devices - store and retrieve digital info
  • Energy Generation - many devices use semiconductors to convert sunlight into electricity
  • Communication Devices - semiconductors signal processing, amplification and transmission
  • Medical Devices - monitoring systems like CT and MRI scanners

Semiconductors - Silicon

  • Silicon is the most widely-used semiconductor
    • Behavior: its conductivity can be highly controlled
    • Abundance: silicon is the second most abundant element in Earth‘s crust
    • Processing: it can be easily extracted and purified
    • Thermal stability: has a high melting point and good thermal conductivity
    • Well-established manufacturing techniques: many sophisticated techniques have been developed for silicon processing

Polymers

  • Polymers are large molecules made up of repeating small units called monomers
  • Polymers are bonded, forming long chains
  • These chains can be branched or interconnected

Polymers - macromolecules

  • Polymers have diverse applications thanks to the different monomers that can form them
  • Polymer science focuses on macromolecules, their synthesis, characterization, and applications
    • Polymerization - process by which small molecules join together
    • Macromolecules - large molecules composed of smaller units = polymer

Polymers - Chemical Properties

  • Bonding and Reactivity - these materials have strong covalent bonds within the polymer chain and weaker intermolecular forces
    • Chains contain functional groups - specific atoms or groups that impart characteristics chemical and physical properties to the material

Polymers - Chemical Resistance

  • Chemical Resistance - these materials exhibit good resistance to chemicals due to their stable covalent structures and low reactivity
    • This makes polymers suitable to withstand harsh environments

Polymers - Biodegradability

  • Biodegradability - their structure allow them to be broken down by microorganisms
    • Important for industries that are trying to reduce environmental impact

Polymers - Adhesion

  • Adhesion - chemical interactions between a polymer and a surface influence the ability to adhere
    • Vital for paints, adhesive, and composites
  • Melting Points vary according to the type of polymer and the chain formed

Polymers - Applications

  • Packaging - films, bottles and container are made of common polymers like polyethylene
  • Textiles - fibers like nylon and acrylics are used in clothing, carpets due to their durability and elasticity
  • Sports - used in athletic wear and equipment like helmets and racquets
  • Agriculture - used in mulching films, greenhouse covers, and for superabsorbent materials for water retention
  • Electronics - some polymers have conductive properties
  • Medicine - syringes, catheters, implants are some made of polymer for their chemical resistance and biocompatibility

Polymers - Diversity

  • Polymers are incredibly diverse
  • They can be produced synthetically, such as plastic, but also biologically like DNA and proteins
  • Polymers are amazingly “tunable” Capable of being adjusted, modified, or adapted to achieve a desire outcome or setting
  • Polymers can even act like crystals or glass this behavior relates with a property in amorphous and semi-crystalline polymers
  • Polymers are Everywhere!