{
  "node": {
    "id": "term:hot-disk-method",
    "type": "Term",
    "label": "Hot-disk method",
    "properties": {
      "id": "hot-disk-method",
      "name": "Hot-disk method",
      "aka": [
        "transient plane source",
        "TPS",
        "hot disk"
      ],
      "section": "topic-testing",
      "definition": "Sandwiching a thin nickel spiral sensor between two pieces of a sample, heating it briefly and using its own resistance as the thermometer, then fitting the temperature rise to get thermal conductivity and diffusivity. It suits large flat samples such as cell stacks and pads and, for anisotropic materials, separates in-plane from through-plane conductivity.",
      "related": [
        "thermal-characterisation",
        "laser-flash-analysis",
        "thermal-model",
        "thermal-interface-material"
      ],
      "url": "https://lemonergy.com/learn/glossary/hot-disk-method/",
      "mentions": [
        "diffusion-coefficient",
        "thermal-conductivity"
      ]
    }
  },
  "edges": [
    {
      "id": "edge:5510",
      "source": "term:hot-disk-method",
      "target": "topic:topic-testing",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:5511",
      "source": "term:hot-disk-method",
      "target": "term:thermal-characterisation",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5512",
      "source": "term:hot-disk-method",
      "target": "term:laser-flash-analysis",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5513",
      "source": "term:hot-disk-method",
      "target": "term:thermal-model",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5514",
      "source": "term:hot-disk-method",
      "target": "term:thermal-interface-material",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/hot-disk-method/diffusion-coefficient",
      "source": "term:hot-disk-method",
      "target": "term:diffusion-coefficient",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/hot-disk-method/thermal-conductivity",
      "source": "term:hot-disk-method",
      "target": "term:thermal-conductivity",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    }
  ],
  "neighbors": [
    {
      "id": "topic:topic-testing",
      "type": "Topic",
      "label": "Testing methods",
      "properties": {
        "id": "topic-testing",
        "name": "Testing methods",
        "lede": "The measurements and test procedures that characterise a cell or pack, from capacity and pulse tests to abuse and environmental tests.",
        "context": "Record specimen, state, instrument, temperature and timing.",
        "example": "Resistance immediately after a current step can differ from a ten-second value because slower polarization contributes.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/",
        "lesson_label": "Open capacity measurements"
      }
    },
    {
      "id": "term:thermal-characterisation",
      "type": "Term",
      "label": "Thermal characterisation",
      "properties": {
        "id": "thermal-characterisation",
        "name": "Thermal characterisation",
        "aka": [
          "heat capacity test",
          "entropy test"
        ],
        "section": "topic-testing",
        "definition": "Measuring the thermal properties a model needs: specific heat capacity in a calorimeter, thermal conductivity through and along the layers, the entropy coefficient from OCV against temperature, and heat generation under load. Without them a thermal model is a guess.",
        "related": [
          "heat-generation",
          "entropy-coefficient",
          "thermal-model",
          "accelerating-rate-calorimetry"
        ],
        "url": "https://lemonergy.com/learn/glossary/thermal-characterisation/",
        "mentions": [
          "open-circuit-voltage",
          "thermal-conductivity",
          "specific-heat-capacity"
        ]
      }
    },
    {
      "id": "term:laser-flash-analysis",
      "type": "Term",
      "label": "Laser flash analysis",
      "properties": {
        "id": "laser-flash-analysis",
        "name": "Laser flash analysis",
        "abbr": "LFA",
        "aka": [
          "laser flash method",
          "flash method"
        ],
        "section": "topic-testing",
        "definition": "Firing a brief laser pulse at one face of a thin disc and timing the temperature rise on the far face with an infrared detector, which gives thermal diffusivity. Multiplying by density and specific heat yields thermal conductivity — the through-plane value for electrodes, separators and layered cell samples.",
        "formula": "α = 0.1388·L² / t½; k = α·ρ·c_p",
        "related": [
          "thermal-characterisation",
          "hot-disk-method",
          "thermal-model",
          "heat-generation"
        ],
        "example": {
          "title": "Convert a half-rise time into diffusivity",
          "text": "For an ideal 1 mm slab with a rear-surface half-rise time of 0.10 s, α = 0.1388L²/t½ gives 1.388×10⁻⁶ m²/s. Heat loss, finite pulse duration and material anisotropy can require corrections."
        },
        "url": "https://lemonergy.com/learn/glossary/laser-flash-analysis/",
        "mentions": [
          "diffusion-coefficient",
          "thermal-conductivity",
          "specific-heat-capacity",
          "thermal-diffusivity"
        ]
      }
    },
    {
      "id": "term:thermal-model",
      "type": "Term",
      "label": "Thermal model",
      "properties": {
        "id": "thermal-model",
        "name": "Thermal model",
        "aka": [
          "lumped thermal model"
        ],
        "section": "topic-thermal",
        "definition": "A model of cell temperature: at its simplest one thermal mass with heat generation inside and convection outside, at its most detailed a 3D simulation of the pack. Temperature feeds back into every rate, so electrical and thermal models are usually solved together.",
        "related": [
          "heat-generation",
          "thermal-management",
          "arrhenius",
          "newman-model",
          "thermal-characterisation"
        ],
        "url": "https://lemonergy.com/learn/glossary/thermal-model/",
        "mentions": [
          "thermal-mass",
          "heat-transfer-modes"
        ]
      }
    },
    {
      "id": "term:thermal-interface-material",
      "type": "Term",
      "label": "Thermal interface material",
      "properties": {
        "id": "thermal-interface-material",
        "name": "Thermal interface material",
        "abbr": "TIM",
        "aka": [
          "gap filler"
        ],
        "section": "topic-thermal",
        "definition": "A soft, thermally conductive paste or pad that fills the gap between cells and the cooling plate so heat does not have to cross air. It is dispensed by the kilogram in a pack and is a surprising share of its cost.",
        "related": [
          "cooling-plate",
          "thermal-management"
        ],
        "url": "https://lemonergy.com/learn/glossary/thermal-interface-material/",
        "mentions": []
      }
    },
    {
      "id": "term:diffusion-coefficient",
      "type": "Term",
      "label": "Diffusion coefficient",
      "properties": {
        "id": "diffusion-coefficient",
        "name": "Diffusion coefficient",
        "abbr": "D",
        "aka": [
          "diffusivity"
        ],
        "section": "topic-transport",
        "definition": "The proportionality constant D in Fick’s first law, in m²/s. It sets how fast a species spreads for a given concentration gradient.",
        "unit": "m²/s",
        "related": [
          "ficks-first-law",
          "solid-state-diffusion",
          "gitt",
          "diffusion"
        ],
        "lesson": "transport/ficks-first-law/#law",
        "url": "https://lemonergy.com/learn/glossary/diffusion-coefficient/",
        "mentions": [
          "concentration-gradient"
        ]
      }
    },
    {
      "id": "term:thermal-conductivity",
      "type": "Term",
      "label": "Thermal conductivity",
      "properties": {
        "id": "thermal-conductivity",
        "name": "Thermal conductivity",
        "abbr": "k",
        "aka": [
          "λ",
          "through-plane conductivity",
          "in-plane conductivity"
        ],
        "section": "topic-thermal",
        "definition": "How readily a material conducts heat: the heat flux per unit temperature gradient. Cells are strongly anisotropic — around 25–45 W/(m·K) in-plane, along the metal foils, but below 1 W/(m·K) through-plane, across separators and coatings — so the side a cell is cooled from decides how hot its core runs.",
        "formula": "q″ = −k·dT/dx",
        "unit": "W/(m·K)",
        "related": [
          "thermal-resistance",
          "thermal-diffusivity",
          "thermal-characterisation",
          "thermal-interface-material",
          "biot-number",
          "thermal-model"
        ],
        "example": {
          "title": "Calculate a slab heat flow",
          "text": "An illustrative 2 mm layer with k = 1 W/(m·K), area 0.01 m² and a 10 K temperature difference transfers 50 W in steady one-dimensional conduction. Contact resistances and edge losses are omitted."
        },
        "url": "https://lemonergy.com/learn/glossary/thermal-conductivity/",
        "mentions": [
          "heat-flux",
          "thermal-gradient"
        ]
      }
    }
  ]
}