Materials Science Overview
Purpose: the front door to the MaterialsScience library. Surveys what materials are, the framework by which they’re studied (the structure-property-processing-performance tetrahedron), the length scales involved, and the major classes of behaviour. Points at every other note in the library for deeper coverage.
Adjacent libraries: Engineering (application context), Chemistry (synthesis routes), Biology (biomaterials interface), Math (DFT / MD numerical foundations).
1. What is materials science?
Materials science is the discipline that explains why a given solid does what it does, how to make one with a desired set of properties, and what variants exist. It sits between physics (which provides the fundamental electromagnetism, quantum mechanics, and thermodynamics) and engineering (which selects and integrates materials into systems). The unit of study is the material — a solid (occasionally a liquid or gas) intended for use because of its properties.
Modern materials science is unified by one organizing principle: the structure-property-processing-performance (SPPP) tetrahedron. Choose any vertex; the other three are coupled to it.
Structure
/ \
/ \
/ \
Processing -------- Properties
\ /
\ /
\ /
Performance
The same atoms arranged into different crystal structures (graphite vs diamond, austenite vs martensite, amorphous vs crystalline silica) yield wildly different properties. The same composition processed differently (cold-rolled steel vs annealed, sand-cast aluminum vs wrought, melt-spun amorphous metal vs slow-cooled crystalline) yields different microstructure and so different properties. The performance the engineer wants (creep resistance at 1000 °C; brittle-to-ductile transition below 0 °C; transparency at 1550 nm) selects which property combinations matter, which selects which structure, which selects which processing route.
This note tours the four vertices in turn, then surveys the major classes of materials, then maps the library so a reader can dive deeper on any topic.
2. Why it matters
Materials enable or constrain every engineered system. Concrete examples:
- The Wright brothers built their 1903 engine with a custom aluminum-copper crankcase because nothing lighter-yet-strong existed; aerospace aluminum alloys (2024, 7075, lithium-bearing 2050) define what aircraft are buildable.
- The 1970s integrated-circuit revolution required materials-grade silicon at 10 ppb impurities (silicon refining via Siemens trichlorosilane route, then float-zone or Czochralski crystal growth), high-quality SiO₂ gate dielectric, and aluminium then copper interconnect — each a materials problem.
- Lithium-ion batteries require cobalt-nickel-manganese cathode chemistries, graphite anodes, lithium-salt electrolytes, polyolefin separators, and aluminium-copper foil current collectors. The 2020s electric-vehicle transition is fundamentally a materials chain.
- 5+ T MRI magnets need Nb-Ti or Nb₃Sn superconducting wire kept below 4.2 K with liquid helium. Each layer is a materials achievement.
- High-entropy alloys (HEAs), discovered around 2004 (Yeh, Cantor), opened a million-composition design space; lead-halide perovskites for solar cells went from research curiosity in 2009 (Miyasaka) to >26 % cell efficiency in 2024. The discipline still generates new families.
Globally: materials-related industries (metals, ceramics, polymers, semiconductors, composites) represent ~25 % of world GDP. Material science underlies the rate-of-progress for energy, computing, transportation, healthcare, and infrastructure.
3. The four vertices
3.1 Structure
Structure is what’s where, at every length scale. It is multi-scale by necessity.
| Length scale | Phenomenon | Probe |
|---|---|---|
| Electronic (~Å) | Bonding, band structure, magnetism | DFT, ARPES, XPS, EELS |
| Atomic (Å–nm) | Crystal structure, defects, short-range order | XRD, neutron diffraction, HRTEM, atom probe |
| Microstructural (nm–mm) | Grains, phases, dislocation network, precipitates, voids | SEM, TEM, EBSD, FIB tomography, micro-CT |
| Macroscopic (mm–m) | Texture, residual stress, anisotropy, parts geometry | X-ray, neutron diffraction, ultrasonic, mechanical test |
A common student error is to identify “structure” with just the crystal lattice. The full structure picture spans roughly 9 orders of magnitude in length, and any given property may be controlled at a different scale (yield stress by dislocations + grain size; fracture toughness by porosity + inclusions; permeability by pore network at the μm–mm scale; dielectric strength by impurities at the ppm level).
The library coverage of structure:
- crystallography-phase-diagrams — Bravais lattices, Miller indices, point/space groups, equilibrium phase diagrams (binary + ternary), invariant reactions, lever rule.
- electronic-structure-and-computational-materials — DFT, tight-binding, band-structure calculation, MD, ab-initio thermodynamics.
- characterization-methods — Tier 1 reference of probes.
- characterization-techniques-deep — Tier 2 deep companion with every instrument family enumerated.
3.2 Properties
Properties are the measured response of a material to an external stimulus. Categorized by stimulus:
| Stimulus | Properties | Library reference |
|---|---|---|
| Mechanical force | Yield stress, ultimate tensile stress, ductility, hardness, fracture toughness, fatigue limit, creep rate | mechanical-behavior-of-materials |
| Heat | Thermal conductivity, specific heat, expansion coefficient, melting temperature, glass transition | heat-transfer, characterization-methods (DSC/TGA) |
| Electric field | Resistivity, dielectric constant, breakdown strength, piezo/ferroelectric coefficients | semiconductor-devices, semiconductor-materials-and-process-deep |
| Magnetic field | Susceptibility, coercivity, remanence, saturation magnetization, Curie temperature | magnetic-and-optical-materials |
| Light / EM | Refractive index, absorption coefficient, band-gap, photoluminescence | magnetic-and-optical-materials |
| Chemical | Corrosion rate, oxidation resistance, catalytic activity, solubility | photocatalysts-deep, surface-treatments |
| Biological | Cytotoxicity, biocompatibility, osseointegration, hemocompatibility | biomaterials, biomaterials-advanced |
| Nuclear | Neutron cross-section, activation, swelling under irradiation | nuclear-engineering |
A property may be intrinsic (does not depend on geometry — density, melting temperature, modulus, resistivity) or extrinsic / property-of-the-part (depends on geometry or processing history — yield stress, hardness, ductility, fracture toughness for a given crack geometry).
3.3 Processing
Processing is everything done to a feedstock to make it into a usable form. Common routes by material class:
| Class | Primary processing routes | Library reference |
|---|---|---|
| Metals | Casting, forging, rolling, extrusion, drawing, sheet forming, machining, powder metallurgy, additive (PBF, DED, binder-jet) | casting-forging-forming, machining, additive-manufacturing |
| Polymers | Extrusion, injection molding, blow molding, thermoforming, calendering, casting, RIM, compression molding | materials-polymers |
| Ceramics | Powder pressing + sintering, slip casting, tape casting, slurry casting, sol-gel, hot pressing, HIP | materials-ceramics |
| Composites | Layup (hand, automated tape, fiber placement), RTM, autoclave cure, filament winding, pultrusion | materials-composites |
| Semiconductors | Czochralski / float zone growth, epitaxy (MBE/MOCVD/CVD), oxidation, ion implantation, photolithography, etch, CMP | semiconductor-processing, semiconductor-materials-and-process-deep |
| Biomaterials | Sterilization, surface functionalization, scaffolding (electrospinning, 3D printing) | biomaterials, biomaterials-advanced |
The library’s cross-cutting comparison _compare_processing-routes aligns these.
3.4 Performance
Performance is fitness for the application — the integration of properties under operating conditions. A creep-resistant superalloy needs not just high yield stress at 1000 °C but also resistance to oxidation, low fatigue crack growth, and weldability for repair. A bone-screw biomaterial needs cytocompatibility, the right elastic modulus (to avoid stress shielding), MR compatibility, and machinability. Materials selection for a given performance target is itself a discipline; covered in materials-selection with Ashby diagrams and Pugh matrix techniques.
4. Length scales — a tour
A property control diagram traces which length-scale feature controls which property:
| Property | Controlling scale | Mechanism |
|---|---|---|
| Yield stress | Dislocation density + grain size | Hall-Petch σ_y = σ_0 + k·d^(-1/2) |
| Tensile elongation | Inclusions + grain shape | Void nucleation / coalescence |
| Fracture toughness | Grain size, second-phase + ductile-particle | Crack-tip plasticity zone |
| Fatigue life | Surface roughness + inclusion population | Stage-I crack initiation at surface or sub-surface inclusion |
| Creep rate | Grain boundary chemistry + secondary precipitates | Coble vs Nabarro-Herring; dislocation climb |
| Hardness | Hardness phases (carbides, nitrides) volume fraction | Indentation plastic-zone interaction |
| Thermal conductivity (metals) | Electronic contribution dominated by impurity scattering | Wiedemann-Franz law k = L·σ·T |
| Thermal conductivity (ceramics) | Phonon scattering by point defects + grain boundaries | Phonon mean-free-path |
| Electrical conductivity | Carrier density (doping) + mobility (scattering) | Drude model |
| Dielectric breakdown | Defect chains + impurity ions | Avalanche or thermal mechanism |
| Coercivity | Magnetic domain wall pinning sites | Pinning at grain boundaries / precipitates |
| Catalytic activity | Active-site surface density | Sabatier principle |
This is why characterization is so multi-modal: every property depends on a different feature at a different scale.
5. Bonding
The five categories of interatomic bonding and what materials they make:
5.1 Metallic
Delocalized electron sea; positive ion cores in periodic potential. Properties: high electrical and thermal conductivity (free electron scattering), opacity (free electrons absorb visible photons), ductility (planes can slide without breaking the bond network), high density. Examples: Fe, Cu, Al, Ti, Au, all alloys.
5.2 Ionic
Electron transfer from electropositive to electronegative; non-directional Coulomb attraction between cations and anions. Properties: high melting temperature, hardness, brittleness, electrical insulation in solid (no free carriers; ionic conduction at high T), often transparent, soluble in polar solvents. Examples: NaCl, MgO, Al₂O₃, Cu₂O, BaTiO₃.
5.3 Covalent
Shared electrons; highly directional. Properties: high modulus, often transparent to band-gap-energy photons, semiconducting or insulating, often brittle. Examples: Si, Ge, diamond, GaAs, SiC, BN, organic polymers (within chains).
5.4 Van der Waals (dispersion / London)
Weak fluctuating-dipole attraction; ~kJ/mol vs ~hundreds for covalent/metallic. Properties: low melting temperature, easy cleavage along weakly-bonded planes (graphite basal slip, mica), van-der-Waals heterostructure assembly (2D materials). Examples: graphite layer-to-layer, polymer chain-to-chain, noble-gas crystals, MoS₂ layers.
5.5 Hydrogen
Special case of dipole interaction involving H bonded to electronegative atom (N, O, F) and another lone pair. Properties: explains water’s anomalies (high boiling point, density max at 4 °C, surface tension), DNA base pairing, polymer chain interactions. Examples: water, ice, biological polymers (proteins, nucleic acids), nylon.
Real materials almost always involve mixed bonding (Si-O is partly ionic + partly covalent; metallic compounds with strong covalent contributions; ionic ceramics with secondary covalent character). Materials’ properties are interpretable as superpositions of these archetypes.
6. Crystal structures and defects
6.1 The seven crystal systems and 14 Bravais lattices
Crystal periodicity is constrained to seven crystal systems (cubic, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal, trigonal/rhombohedral) and 14 distinct Bravais lattices once centerings are accounted for. Of these, three dominate engineering metals:
- Body-centred cubic (BCC): α-Fe (ferrite), W, Mo, V, Cr, Nb, Ta, β-Ti. Coordination 8, atomic packing factor 0.68. Has ductile-to-brittle transition; slip on {110}, {112}, {123}.
- Face-centred cubic (FCC): γ-Fe (austenite), Cu, Al, Ni, Au, Ag, Pt, Pb. Coordination 12, packing 0.74. No DBT; slip on {111}<110>.
- Hexagonal close-packed (HCP): α-Ti, Mg, Zn, Co, Zr, Be. Coordination 12, packing 0.74. Limited slip systems → anisotropy + twinning.
Other industrially relevant lattices: diamond cubic (Si, Ge, C diamond — coordination 4), zinc-blende (GaAs, GaN cubic, ZnS), wurtzite (GaN hexagonal, ZnO), rocksalt (NaCl, MgO), fluorite (CaF₂, UO₂, CeO₂, YSZ), spinel (MgAl₂O₄, magnetite), perovskite (BaTiO₃, SrTiO₃, lead-halide solar cells), corundum (α-Al₂O₃, sapphire).
Detailed coverage: crystallography-phase-diagrams.
6.2 Defects by dimensionality
| Type | Dimension | Examples | What they do |
|---|---|---|---|
| Point defect | 0D | Vacancy, interstitial (self / foreign), substitutional, Frenkel, Schottky pair | Diffusion, doping, electrical / optical properties |
| Line defect | 1D | Edge dislocation, screw dislocation, mixed | Plastic deformation, work hardening |
| Planar defect | 2D | Grain boundary, twin boundary, stacking fault, antiphase boundary, surface | Hall-Petch strengthening, fracture path, surface energy |
| Volumetric defect | 3D | Pore, inclusion, precipitate, void | Fatigue initiation, fracture toughness, hardness phases |
Real materials have all four; engineering materials are defect-engineered. Heat treatment of steel manipulates dislocation density (cold work → high dislocation density; anneal → recover, recrystallize → low density). Age-hardening (Al-Cu, Ni-base) manipulates 3D defect (precipitate) distribution. Casting microstructure manipulates 2D defect (grain boundary) network. Doping a semiconductor manipulates 0D defect (substitutional or interstitial dopant) concentration.
7. Materials classes
7.1 Metals
Most-engineered class; ~80 % of structural mass in transportation and infrastructure. Properties: high modulus, ductile, electrically and thermally conductive, recyclable. Subclasses:
- Ferrous — steels (carbon, low-alloy, stainless), cast irons. Workhorse of construction, automotive, oil and gas.
- Light alloys — aluminum, magnesium, titanium, beryllium. Aerospace, EV, biomedical.
- Heavy alloys — copper, nickel, lead, tin, zinc. Electrical (Cu), corrosion (Ni), batteries (Pb, Zn), soldering (Sn).
- Refractory — Mo, W, Nb, Ta, Re. High-temperature furnace and rocket-nozzle.
- Precious — Au, Ag, Pt, Pd, Rh. Electrical contacts, catalysis, jewelry.
- Superalloys — Ni-base (Inconel, Waspaloy, René), Co-base (Stellite), Fe-Ni (Incoloy). Turbine blades and combustors.
- High-entropy alloys — multi-principal-element (CoCrFeMnNi “Cantor”, FeCoNiCrMn, refractory HEAs). high-entropy-alloys-deep.
- Amorphous metallic alloys — metallic glasses; bulk glass-forming compositions (Vit1 Zr-Ti-Cu-Ni-Be).
- Quasi-crystals — long-range order, no translational periodicity (Al-Mn icosahedral, discovered Shechtman 1982; Nobel 2011).
Engineering coverage: materials-steel, materials-aluminum, stainless-steels, aluminum-alloys, titanium-alloys, steel-grades, copper-alloys. Tier 3 catalog: alloy-and-superalloy-catalog.
7.2 Ceramics
Inorganic, non-metallic, typically crystalline, with ionic-covalent bonding. Properties: high hardness, high melting point, low ductility, low fracture toughness, electrical insulation (mostly), corrosion-resistant. Subclasses:
- Oxide — Al₂O₃, ZrO₂, MgO, SiO₂, BeO, Y₂O₃-stabilized ZrO₂ (YSZ).
- Non-oxide — SiC, Si₃N₄, BN (hexagonal soft + cubic hard), AlN, B₄C.
- Glass — amorphous; silicate, borosilicate, aluminosilicate, fused silica, glass-ceramic (Zerodur, Robax), chalcogenide glass.
- Refractory — high-T furnace lining; firebrick, MgO, fused silica.
- Cement and concrete — Portland cement, geopolymer alternatives. geopolymer-and-concrete-chemistry-deep.
- Bioceramics — hydroxyapatite, bioglass, β-TCP.
Coverage: materials-ceramics, ceramics-taxonomy.
7.3 Polymers
Long-chain organic molecules. Properties: low density, low modulus (vs metals and ceramics), wide range of toughness, viscoelastic, formable at low temperature, electrically insulating (mostly). Subclasses by behavior:
- Thermoplastic — linear or branched, soften reversibly with heat. PE, PP, PS, PMMA, PVC, PC, PA (nylon), PET, PEEK, PEKK.
- Thermoset — cross-linked network, cannot remelt. Epoxy, phenolic, polyurethane (cross-linked), polyester, vinyl ester.
- Elastomer — cross-linked but above T_g; rubbery. Natural rubber, SBR, EPDM, silicone, fluoroelastomer (FKM).
- High-performance — PEEK, PEKK, PEI, PSU, PPS, PI (Kapton), PBO (Zylon), PBI.
- Biodegradable — PLA, PGA, PCL, PHB.
- Conducting polymers — polyaniline, PEDOT:PSS, polypyrrole, polyacetylene (Nobel 2000).
- Liquid crystal polymer — Vectra, Xydar; oriented chains for high modulus.
- Hydrogels — water-swollen networks for biomedical.
Coverage: materials-polymers, polymers-taxonomy, polymer-properties-and-applications, soft-matter-and-self-assembly.
7.4 Composites
Engineered combinations of two or more materials that retain their identity. Properties: tailored, often anisotropic, lightweight, expensive. Subclasses by matrix:
- Polymer matrix (PMC) — CFRP (carbon fiber), GFRP (glass fiber), AFRP (aramid). Aerospace, automotive, sporting goods.
- Metal matrix (MMC) — Al-SiC, Mg-SiC, Ti-SiC, brake-rotor and drive-shaft applications.
- Ceramic matrix (CMC) — SiC-SiC, C-C, oxide-oxide. Turbine vanes, brake discs (carbon-ceramic).
- Carbon-carbon (C/C) — pyrolyzed phenolic + carbon-fiber; rocket nozzles, F1 brakes, leading edges.
- Sandwich — face sheets + honeycomb or foam core. Aerospace panels.
- Particulate — random short fiber or particles; bulk molding compound, SMC.
- Functionally graded — gradient in composition or volume fraction.
Coverage: materials-composites, composites-taxonomy, composite-materials-advanced.
7.5 Semiconductors
Covalent-bonded materials with intermediate band-gap (0.1–6 eV). Properties: conductivity controllable by doping over 10+ orders of magnitude; the substrate for electronics, photonics, photovoltaics.
- Elemental — Si (the workhorse), Ge (high-mobility, SiGe alloys), C (diamond, ultra-wide-band-gap).
- III-V compound — GaAs, GaN, InP, InGaAs, InGaP, AlGaAs, AlN; LEDs, lasers, HEMT power devices, photovoltaic.
- II-VI compound — CdTe (thin-film PV), CdS, ZnSe, ZnO; PV and optoelectronics.
- IV-IV compound — SiC (4H polytype dominant; high-power, EV inverter), SiGe.
- Wide-band-gap — GaN, SiC, AlN, β-Ga₂O₃; power electronics, RF.
- Ultra-wide-band-gap — diamond, AlN; emerging power electronics.
- Halide perovskite — methylammonium lead iodide and its family; PV.
- Organic — pentacene, PCBM, P3HT; OLED, OPV.
Coverage: semiconductor-devices, semiconductor-processing, semiconductor-materials, semiconductor-materials-and-process-deep.
7.6 Biomaterials
Materials designed to interface with biology. Properties: biocompatibility, sometimes bioresorbability, mechanical match to host tissue. Categories:
- Inert — Ti-6Al-4V, Co-Cr-Mo, 316L stainless, PEEK, alumina, zirconia.
- Bioactive — bioglass 45S5, hydroxyapatite-coated implants.
- Resorbable — PLA, PGA, PCL, β-TCP, magnesium alloys.
- Hydrogels and soft — PEG, PHEMA, alginate, collagen, silk fibroin.
- Bio-inspired — nacre-like ceramic-polymer composites, gecko-foot adhesives, lotus-effect superhydrophobic surfaces.
Coverage: biomaterials, biomaterials-advanced.
7.7 Quantum and topological materials
Materials in which quantum effects (electron correlation, topological band structure, spin-orbit coupling) drive emergent macroscopic behaviour. Subclasses: superconductors (BCS, cuprates, iron-pnictides, twisted bilayer graphene), topological insulators (Bi₂Se₃, Bi₂Te₃), Weyl/Dirac semimetals (TaAs, Cd₃As₂), magnetic skyrmion hosts (MnSi, FeGe), strongly correlated oxides (manganites, ruthenates). Coverage: quantum-materials-and-topological-phases.
7.8 Soft matter
Materials whose response is dominated by thermal fluctuations and entropy at room temperature: polymers, colloids, liquid crystals, surfactant assemblies, biological membranes. Distinguished from “hard” matter by typical bond energy ~kT. Coverage: soft-matter-and-self-assembly.
7.9 Two-dimensional materials
Single- or few-atom-thick layers exfoliated from layered bulk: graphene, hBN, MoS₂, WSe₂ (TMD family), black phosphorus, MXenes (Ti₃C₂Tₓ). Van-der-Waals stacking (“heterostructures”) creates new electronic phases.
7.10 Metamaterials
Designed periodic or aperiodic structures with effective properties not seen in nature: negative refractive index (split-ring resonators), acoustic cloaks, mechanical pentamodes, photonic crystals. The “material” is the architecture, not the constituent.
8. Length-scale modeling
Modern computational materials science spans:
| Scale | Method | Output |
|---|---|---|
| Electron (~10⁻¹⁰ m) | DFT (VASP, Quantum ESPRESSO, CASTEP, GPAW) | Band structure, formation energy, magnetic moments |
| Atomic (~10⁻⁹ m) | Molecular dynamics (LAMMPS, GROMACS, NAMD, OpenMM) | Diffusion, melt, phase transition, fracture nucleation |
| Mesoscale (~10⁻⁷ m) | Phase-field (MOOSE, PRISMS-PF, MICRESS), kinetic Monte Carlo, dislocation dynamics | Microstructure evolution, grain growth, recrystallization |
| Microscale (~10⁻⁴ m) | Crystal plasticity FEM (DAMASK, Z-set) | Texture, polycrystal mechanical response |
| Macroscale (~10⁻¹ m) | Continuum FEM (Abaqus, Ansys, Nastran) | Part-scale stress, deflection, lifetime |
Bridging scales is the active research front; the ICME (Integrated Computational Materials Engineering) vision is closed-loop multiscale design.
Coverage: electronic-structure-and-computational-materials.
9. Materials selection
The engineering question — given a function and a constraint, which material is best? — is its own discipline.
Ashby methodology (Cambridge / Granta-Ansys):
- Identify the function (transmit load; conduct heat; store energy).
- Translate function to a performance index — a combination of material properties whose maximum (or minimum) optimizes the function for a given geometry constraint. Example: a stiff-light tie of fixed cross-section has index E/ρ (specific stiffness); of fixed length and minimum mass for given stiffness has index E^(1/2)/ρ (bending) or E^(1/3)/ρ (panel).
- Plot on an Ashby chart (property pair: E vs ρ, σ_y vs ρ, K_IC vs σ_y, etc.) and find the material that maximizes the index.
- Apply screening constraints (cost ceiling, temperature limit, corrosion environment).
- Decision-matrix the survivors (Pugh matrix, FMEA, life-cycle analysis).
Coverage: materials-selection, _compare_materials-selection-criteria.
10. Library map
This section is a flat index for navigation. Read it before searching elsewhere.
Tier 1 — foundational deep notes
| Topic | File |
|---|---|
| Crystallography & phase diagrams | crystallography-phase-diagrams |
| Characterization methods | characterization-methods |
| Electronic structure & computational materials | electronic-structure-and-computational-materials |
| Mechanical behavior of materials | mechanical-behavior-of-materials |
| Biomaterials | biomaterials |
Tier 2 — specialty deep notes
| Topic | File |
|---|---|
| Soft matter & self-assembly | soft-matter-and-self-assembly |
| Biomaterials advanced | biomaterials-advanced |
| Quantum materials & topological phases | quantum-materials-and-topological-phases |
| Composite materials advanced | composite-materials-advanced |
| Geopolymer & concrete chemistry deep | geopolymer-and-concrete-chemistry-deep |
| Semiconductor materials & process deep | semiconductor-materials-and-process-deep |
| High-entropy alloys deep | high-entropy-alloys-deep |
| Photocatalysts deep | photocatalysts-deep |
| Characterization techniques deep | characterization-techniques-deep |
Tier 3 — family indexes / catalogs
| Topic | File |
|---|---|
| Tier 3 index | _index |
| Alloy & superalloy catalog | alloy-and-superalloy-catalog |
| Polymer properties & applications | polymer-properties-and-applications |
| High-entropy alloys & nanomaterials | high-entropy-alloys-and-nanomaterials |
| MOF / COF / perovskite catalog | mof-cof-perovskite-catalog |
| Magnetic & optical materials | magnetic-and-optical-materials |
| Refractory & thin-film deposition | refractory-and-thin-film-deposition |
Cross-cutting
| Topic | File |
|---|---|
| Processing-route comparison | _compare_processing-routes |
11p. Edge cases / gotchas — for the materials-curious
- “Material” vs “alloy” vs “compound” — alloy and compound have specific meanings; a “carbon-fiber material” is a composite, not a material in the narrow sense.
- Engineering vs true stress — the engineering stress σ_e = F/A_0 uses the original area; true stress σ_t = F/A_i uses instantaneous area. They diverge after necking. Material database values are usually engineering.
- Modulus is not strength — Young’s modulus and yield/tensile strength are independent. Tool steel and mild steel have similar moduli (~200 GPa) but very different yield (≈2 GPa vs ≈300 MPa).
- Hardness conversions are approximate — Vickers, Rockwell, Brinell scales correlate but are not equivalent; conversion tables (ASTM E140) are calibrated and only work in the calibrated regime.
- Anisotropy — wrought metals, composites, single crystals, and rolled sheets are not isotropic. Yield in the rolling direction can be 10–30 % higher than transverse; rolled aluminum sheet can have a 15 % difference between L, LT, and ST.
- Strain-rate dependence — steel yield doubles between 10⁻³ s⁻¹ (quasi-static) and 10³ s⁻¹ (impact). HCP metals show stronger rate effects than FCC. Quasi-static handbook numbers are not crash-load numbers.
- Temperature dependence — every property is a function of T. Modulus drops 30–50 % from RT to T_m/2 for metals; polymers undergo glass transition and lose 3 orders of modulus across T_g.
- Property scatter — ceramics, composites, and high-cycle fatigue data are not normally distributed; Weibull statistics apply. Use the design allowable, not the mean.
- Impurity sensitivity — semiconductor properties shift orders of magnitude at ppb impurity; superconductor T_c shifts with at% substitution; aluminum alloy ductility crashes with μg/g Fe; corrosion resistance plummets with ppm Cl⁻.
- The “miracle material” problem — every decade introduces a hype cycle (carbon nanotubes 2000s; graphene 2010s; perovskite PV 2010s+; MXenes 2020s; HEAs 2010s–2020s). The discipline tolerates them; the production economics rarely catch up to the lab demonstration in <20 years.
- Sustainability and recyclability are property-level — circular-economy designs require closed-loop reusability, not just curbside-bin recyclability. PMMA, PP, PET have credible recycling streams; CFRP, thermosets, blended fiber + matrix composites largely do not.
- Patent and supply-chain reality — neodymium, dysprosium, cobalt, lithium, gallium, germanium, magnesium, REE oxides are concentrated in 1–3 countries (China dominant for most). Materials choices have geopolitical exposure.
12p. Tools & software
DFT / ab-initio — VASP, Quantum ESPRESSO, GPAW, ABINIT, CASTEP, FHI-aims, FLEUR, Wien2k, FPLO.
Molecular dynamics — LAMMPS (the workhorse), GROMACS (biomolecular), NAMD, OpenMM, AMBER, CHARMM.
Phase-field — MOOSE / PRISMS-PF (Idaho), MICRESS (commercial), OpenPhase, FENICS-based codes.
Crystal plasticity / micromech — DAMASK (Düsseldorf), Z-set (Mines ParisTech), Abaqus crystal-plasticity user subroutines.
Continuum FEM — Abaqus (Dassault), Ansys Mechanical, Nastran (Hexagon), MSC Marc, LS-DYNA (Ansys), COMSOL Multiphysics.
Materials databases — Granta MI / Ansys Granta (commercial, Ashby originals), Total Materia, MatWeb (free), AZoM, ASM Handbook digital, NIST Materials Data Repository, Materials Project (LBNL, free DFT data), AFLOW, OQMD.
Characterization data reduction — TOPAS, GSAS-II, FullProf (Rietveld); HKL Channel 5, AZtecCrystal (EBSD); Digital Micrograph, Velox (TEM); Gatan, ImageJ.
Materials informatics — pymatgen, ASE (Atomic Simulation Environment), AIIDA, Materials Studio, jarvis-tools, scikit-learn / PyTorch for ML.
13. Cross-references
- Engineering Library — application context; nearly every Engineering note depends on a materials choice.
- materials-selection — Ashby methodology in engineering-application form.
- _compare_materials-selection-criteria — cross-cutting comparison.
- Chemistry Library — synthesis chemistry, polymerization, sol-gel.
- Biology Library — biomaterials interface, ECM, biomineralization.
- Math Library — numerical methods underlying DFT, MD, FEM.
- standards-bodies — ASM, ASTM, ISO/TC 119 (PM), ISO/TC 164 (mechanical testing), ISO/TC 206 (advanced ceramics), ISO/TC 61 (plastics).