The Nature and Properties of Materials
The Nature of Materials
Structure:
Arrangement of the internal components of a material.
Atomic number Z:
Atomic property equal to the number of protons in the nucleus.
Atomic radius R:
Atomic property equal to the distance from the center of an atom to its boundaries.
Electric charge Q:
Atomic property by which matter in an electric field experiences a force.
Ion:
An atom which required a net electric charge by gaining or losing electrons.
Electronegativity:
Tendency of an atom to attract electrons towards itself.
Atomic mass:
Sum of the masses of the protons and neutrons within the nucleus.
Isotope:
Variant of an element in number of neutrons having the same number of protons.
Atomic weight A:
Weighted average of the atomic masses of an atom.
Surface tension:
Tension force in liquids which makes them get the least surface as possible.
Chemical composition:
Identity and proportion of the chemical elements that make up a compound.
TYPES OF STRUCTURES
Nanoscopic scale:
Subatomic particle within the atom and organization of atoms or molecules relative to one another. ex. atoms and subatomic particles
Microscopic scale:
Large group of atoms agglomerated together ex. large groups of atoms
Macroscopic scale:
Structural components that can be viewed with the naked eye ex. building construction materials
Megascopic scale:
ex. buildings and building elements
QUANTUM MECHANICS
Wave particle duality (De Broglie):
Is a theory that proposes that every elementary particle exhibits the properties of not only particles, but also waves
Uncertainty principle (Heisenberg):
States that the position and velocity of a subparticle atom cannot both be measured exactly at the same time
Wave mechanics (Schroedinger):
Is a partial differential equation that describes how the quantum state of a physical system changes with time by using quantum numbers.
Ionic bonds:
Transfer of electrons, Ionic bonds are non-directional meaning that atoms so bonded do not prefer a specific orientation relative to one another. Provide: hardness-ability to be scratch resistant or abrasion resistant, brittleness-inability to be deformed permanently, porosity-quality of being porous or having a fraction of void space, electrical insulation(at low temp), electrical conduction(when they are melted), solubility in water, high fire resistance, good thermal inertia. Oxides between a metal and oxygen CaSo4 sulphur+4 oxygens= sulphates.
Covalent bonds:
Sharing electrons, are directional meaning that atoms so
bonded preferspecific orientations relative to one another, this in turn gives molecules definitive shapes. provide: hardness-ability to be scratch resistant or abrasion resistant, undeformability-inability to be deformed, tetrahedral structures- strucutres having the form of a tetrahedron, distance between atom, electrical insulation- inability to conduct electricity, very high fire resistance, high melting point. oxides between a non-metal and oxygen, bonds between same atoms H2, Cl2, O2
Metallic bonds: non-directional sharing of electrons, are described by the electron sea model, the valence of electons of the metals atoms are spread out throught the lattice of the metal. provide: electrical conduictivity, thermal conductivity, ductility-.ability to deform under a tensile stress, malleability-ability to deform under a compressive stress, lustre- ability to have a shiny appearance, high melting point (solid to liquid), high boiling point (liquid to gas), low fire resistance.
Chemical composition: identitiy and proportion of the chemical elemtns that make up a compound
nanostructure: very small structure of a material
microstructure: small structure of a material
Megastrusture: large strucutre of a material above 1 m
Crystalline microstructure: long range order microstructure consiting either of whiskers or grains
Non-crystalline microstructures: short range order microstructure or not ordered at all
Crystal: highly order microstructure formed by a lattice which is extended in all directions
unit cell: the smallest unit composed of atoms that stacked in three dimensional space from a crystal
coordination number: number of the nearest neigbour atom with respect to one of them
atomic packing factor: volume fraction in a crystal that is occupied by atoms
thermal inertia: slowness with which the temperature of a body, approaches that of its surroundings
exfoliation: natural removal of layers from a material
hardness: scratch resitant or abrasion resistant
STATES OF MATTER
Solids: they dont change either their volume or shape, they can bear shear forces, the arragement of the particle doesnt change, crystalline solids- sodium chloride, sugar, steel, Non crystalline solids- glass, polymers, gels
Liquids: they dont change their volume but their shape, their atoms or molecules are not continusly bonded, they cant bear shear forces
Gases: they change their volume and their shape
TYPES OF MICROSTRUCTURE
Single crystalls (whiskers) : large range arrangement size (long range order up to 1mm), crystals can be seen without using a microscope, ex. diamond, quartz, salt, gypsum
Polycrystals: short range arrangement size up to 0.1mm ex. metals, ceramics, many natural stones
Vitreous materials: really short range arrangement size (several atoms) ex. glass
Amorphous materials: Not order at all ex. gels, bituminous materials, many polymers
TYPES OF CRYSTALS
metallic crystals: provide- a metallic shine, high thermal and electrical conductivity, ductility and malleability, close packed arranged structures, high melting and boiling points, low fire resistance. slip is a permanent displacement of one part of the crystal relative to the other part, it involves sliding of one plane of an atom form one part to another. Twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner.
Ionic crystal: get the most close packed structres as possible thanks to the non directional ionic bonding. provides- hardness and brittleness, porous structures, slight tendecy to be anisotropic, electrical insulation at low temperatures, electrical conduction when they are melted, solubility in water, good thermal inertia
Covalent crystal: cant get the close packed structres due to the directional covbalent bonding. they form tetrahedral microstructures, provide- hardness, undeformability, tetrahedral strucutres due to directional bonding, non close packed arrangements, a rigis 3 dimensional lattice, high melting points, very high resistance to fire, electrical insulation.
CAUSES OF DEFECTS IN CRYSTALS
Chemical compostion: substitutions, solutes, impurities, and vacancies
Structural integrity: Dislocations ex. linear displacmetns in the crystaline lattice
Extension: defects caused by the space limits between grains in polycrystalline materials
Internal dynamics: lattice vibrations due to thermal mechanical cause
Point defects: those affecting isolated sites in the crystalline microstructures
Linear defects: Those affecting lines along which the crystal pattern is broken
Planar defects: Those affecting boundaries between crystalline regions
3d defects: those affecting the lattice due to its vibrations
POLYMERS
Polymers: complex structres from carbon compiunds ( a molecule made by the repetition of a basic unit-monomer)
Monomers: basic unit (is a molecule that may bind chemically to other molecules to form a polymer)
Polymerization process: is a process of reacting monomer molecules together in a chemical reaxtion to form polymer chains or three dimensional networks by breaking the dobkle or triple bonds between carbon toms
condensation polymers: any kind of polymers formed through a condensation reaction, molecules join together loosing small molecules as by products such as water or methanol ex. polyester, polyamide, nylon, kevlar, polycarbonates
Types of Polymers:
-thermoplastic: they flow when heated and harden when cooled, their molecular structure shows almost no crossing patterns in the chains
-thermosetting: they chemically break dwon when heated instead of flowing, they have a cross linking microstructure which avoids the molecules to relatively shift
-elastomers: rubbers
Bitominous material: Asphalt, also known as bitumen is a sticky, black, highly viscous liquidor semi-solid form of petroleum.Although asphalt is a porous material, it originates otherimpervious materials and elements. It can be combined withaggregates and a filler to be used as a road paving or roofingmaterial.
Bituminous or asphalt felts: are the base element used to make roof shingles andit is a waterproof coverings in residential and commercial roofs.
Bituminous paints: are the cheapest and easiest of all the paint on waterproofingpaints.
Bituminous sealants bond and adhere to most things including, built up feltroofs, asphalt, concrete, asbestos or cement sheeting and metal sheetingincluding lead, zinc, galvanised steel and iron.
Gel: A dispersion of a solid and a liquid (sometimes, a solid and a gas).Mixed in a really fine way (they have a uniquebehaviour).Non-crystalline structure (no order or arrangement atall).It’s a hygroscopic material (tends to retain water).
Types of gels according to their behaviour:
-Elastic: They can absorb water, form a liquid solution, change theirviscosity/thickness and harden afterwards, e.g., hand soap, shampoo, etc.
-Rigid: They allow a certain amount of water, harden, and it’s not a reversibleprocess, e.g., silica gel
Types of gels according to their microstructure:
-Colloidal gels, such as toothpaste, jam, gelatin, jelly, milk, or whipped cream.Every colloidal gel consists of two parts: colloidal particles and a dispersingmedium.
-Hydrogels:, such as silica gel. Hydrogels are made of polymer chains which arehydrophilic in which water is the dispersion medium. Silica gel is used toabsorb moisture and keep things dry. It is a hydrogel because of its highmoisture content (typically 60-65%). They are synthetic amorphous gels.Hydrogels are extraordinarily tough.
-Organogels:, such as polymer chains dispersed in a mineral or vegetable oil.-Xerogels and Aerogels:, with a high porosity (up to 50%). The water has beenreplaced by a gas.-Nanocomposite gels:, when other particles are incorporated to the hydrogel
PHYSICAL PROPERTIES
Waterproof: material or treatment which resists the passage of water under pressure.
Damproof: material that resists the passage of water due to capillary action.
Weatherproof: material not able to be changed or damaged by the effects of sun, wind, and/or rain.
Capillary action: ability of a liquid to flow in narrow spaces in opposition to gravity.
Surface tension: tendency of liquid surfaces at rest to shrink into the minimum surfacearea possible.
Efflorescence: (to “flower out” in French) migration of a salt to the surface of a porousmaterial.
Scaling: Detachment of stone fish scales or parallel to the stone surface.
Blistering: Bursting process of a porous material to reveal a powdery decayed interior.
DAMAGES IN BUILDINGS
Physical agent: freeze thaw resistance, loss of thermal insulation, erosion, movements of foundations
water damages: limestone alveolization, alveolization of porous ceramics, blistering, flanking
chemical agent: solutions, decolorations, effloresnces, desintegration by pollution
electrochemical agent: rusting, corrosion
biological agent: woodworm, termites
MECHANICAL PROPERTIES
Stiffness: Extent to which an object resists deformation in response to a force.
Flexibility: Complementary concept to stiffness. The more flexible an object is, the less stiff it is.
Elasticity: Ability of a solid to resist a force and return to its original size and shape when it’s removed.
Plasticity: Ability of a solid to undergo permanent deformations (i.e., a non-reversible change of shape).
Ductilily: A material’s amenability to drawing into wires.
Brittleness: Property of a material which fractures without significant plastic deformation.
Modulus of elasticity: Measure of the stiffness of a material under the action of a force.
Poisson’s ratio: Measure of the deformation of a material perpendicularly to loading.
Yield strength: Maximum stress withstood by a material before plastic deformation if applicable.
Failure strength: Maximum stress withstood by a material before breaking.
UTS: Ultimate tensile strength.
UCS: Ultimate compressive strength.
ductile fracture: involves a large amount of plasticdeformation and can be detected beforehand. High energy is absorbed by microvoid coalescence (high energy fracturemode): less catastrophic. Ductile fracture is a much less serious problem than brittle fracture sincethere is an observable plastic deformation prior to failure (necking).
brittle fracture: Brittle failure is more catastrophic and cannot be detected beforehand. Low energy is absorbed during transgranular cleavage fracture (low energyfracture mode): more catastrophic
STRESS STRAIN ANALYSIS
Natural stones, ceramic materials, mortars, and concrete: they have high strength in compression, low strength in tension.Their tensile strength depends upon its porosity.They have a brittle behaviour at failure.
Glass: it has a good strength in tension and compression due to the absence of pores.It has a brittle behaviour at failure.
Metals: they have a similar strength in tension and compression.They are ductile, with a significant plastic area.They may undergo creep and fatigue.
Timber and cork: they have a similar behaviour to metals, but less strength and stiffnessThey also suffer from creep and fatigue, with significant influence of temperature or moisture on woodDURABLITY AND PERFORMANCE
Sustainability: Capacity to minimize the negative environmental impact of architecture
Durability: Ability of building construction materials to be permanent because of being resistant.
Toxicity: Degree to which a substance can harm human or animal health.
Reactivity: Rate at which a material tends to undergo a chemical reaction.
Compatibility: State in which two materials are able to occur together without problems or conflict.
Performance: the action or process of carrying out a particular functional requirement.
Differential Movements1. Due to mechanical loads2. Due to variations in their moisture content3. Due to variations in their temperature
Damages of materials1. Chemical causes2. Physical causes3. Biological causes
Differential Movements
1. Due to mechanical loads
Timber: Ductile behaviourSimilar compressive and tensile strengthLarge plastic deformation before failureLess ultimate strength and toughness than metalsCreeping due to variations in moistured) Polymers: Ductile behaviourLow strength. Really large plastic behaviourPostponed deformations. Large deformations due to heat
2. Due to variations in their moisture content
Variations of volume due to loss or gain of moisture content: expansion and shrinkage:Timber: reversible process. It can cause failure by fatigue. Large change in sizeCeramics: the expansion is partially reversibleMetals: it’s almost irrelevantPolymers: it only affects those with a cellulose baseb) Variations of volume due to the setting process in binders Cements, limes, and concretes: they shrink while settingGypsum/Plaster of Paris: they expand while setting
3. Due to variations in their temperature
Natural stones and ceramics: Low expansion coefficient at common temperaturesThey are not affected by temperature changesThey undergo internal structure changes at high temperatures
Metallic materials: High expansion coefficientCorrosion and rust when used outdoorsFree expansion of each element must be allowedCreeping processes at high temperaturesThey become brittle at low temperatures
Timber: low expansion coefficient, non-isotropic behaviour.
Polymers: very high expansion coefficient, highly visible creeping processes.
COMPATIBILITY OF METALS WITH BINDERS, MORTARS AND CONCRETE
Steel: Good performance with cement and limeBad performance with gypsum
Stainless steel: Good performance with any binder
Copper: Good performance with any binderDangerous with other metals
Aluminum: Compatible with gypsumIncompatible with cement and lime
Lead: Compatible with gypsumIncompatible with cement and limeStages in the life cycle of a building
a) Design b) Constructionc) Maintenanced) Repair/Demolition
Materials properties: Specifications, standards and regulations
a) Identification of the materials to be usedb) Specification of their propertiesc) Measurement of their propertiesd) Standardisation of the types of materials used
Performance criteria
-Stability (structural safety)-Fire (resistance to fire and release of toxic fumes)-Durability (for the planned lifetime)-Toxicity (no risk to health due to chemical/physical effectsof the materials)-Sustainability (“go green”: embodied energy, recyclingpotential, (4 “R’s”), environmental management)
Durability
FIRE-RESISTANT (FIREPROOF), WATER-RESISTANT (WATERPROOF, DAMP PROOF, WEATHERPROOF), ABRASION RESISTANT (DUST-RESISTANT, SCRATCH-RESISTANT), CORROSION RESISTANT (RUST-PROOF), FREEZE-THAW RESISTAN), THERMAL-RESISTANTELECTRICAL-RESISTANT, UV-RESISTANT,HIGH ENERGY RADIATION-RESISTANT
GYPSUM
Heated in a furnace up to 120-130º, it loses water:CaSO4· ½ H2O + 3/2 H2O ↑
This process is reversible:CaSO4· ½ H2O + 3/2 H2O → CaSO4· 2H2O + Q↑
If we keep heating the hemihydrate (plaster of Paris) up to 150º:CaSO4· ½ H2O + Q → CaSO4 + ½ H2O↑
If we heat the sulphate (anhydrite) up to 800-900º:CaSO4 + Q → Ca^2+ + SO4^2─.
If we keep heating, we can obtain anions S^2─ and O^2─