Materials#

In the Electrochemistry Domain Ontology, materials represent physical matter that has a defined composition, structure, and form. This includes solids, liquids, and gases — but in this section we focus primarily on solid materials for convenience.

Materials can be raw substances (like copper or graphite), processed forms (like foils, powders, or coatings), or engineered composites (like polymer electrolytes or catalyst inks).

A material can exist as part of a larger object (for example, as the active material in an electrode) or as an independent entity (for example, a powder in a storage container).

Conceptual overview#

In EMMO, the class Material sits between the purely chemical (ChemicalSubstance) and the physical (PhysicalObject) perspectives:

ChemicalSubstance – describes what the material is made of, chemically.
Material – describes the physical realization of that substance, including phase, morphology, and form.
PhysicalObject – describes a specific instance of a material existing in space and time.

You can think of Material as the bridge between chemistry and physics: it connects chemical identity to physical form.

Material vs. Substance vs. Component

Material → A physical manifestation of matter with properties (e.g., a zinc foil, a powder, a polymer film).
ChemicalSubstance → The abstract chemical identity (e.g., Zinc, LiFePO₄, H₂O).
Component → A role that a material plays as part of something larger (e.g., “the binder component” in a coating).

In practice, you describe what it is (substance), how it exists (material), and what it does (component or role).

Guidelines for Use#

To represent a material using the ontology, follow three key steps:

Identify the Material Choose the appropriate subclass of Material or use multiple inheritance to refine meaning. For example, something that is both Zinc (chemical substance) and Foil (material form) can be declared as both.
Assign Properties Attach quantitative or qualitative properties using hasProperty. These may include conventional, measured, or modelled properties such as density, porosity, or conductivity.
Link the Material to its Role or Context Use domain-specific object properties like hasActiveMaterial, hasBinder, or hasAdditive to connect the material to another entity (for example, an ElectrodeCoating).

Representation Patterns#

1. Pure Substance in a Defined Form

A simple zinc foil material with basic properties.

{
    "@context": "https://w3id.org/emmo/domain/electrochemistry/context",
    "@type": ["Zinc", "Foil"],
    "hasProperty": {
       "@type": ["Density", "ConventionalProperty"],
       "hasNumericalPart": {
         "@type": "RealData",
         "hasNumberValue": 7.14
       },
       "hasMeasurementUnit": "emmo:GramPerCubicCentimetre"
    }
}

Here we combine multiple inheritance (Zinc and Foil) to indicate what it is and in what form. The density is expressed as a conventional property — taken from a datasheet rather than directly measured.

2. Material in Context — Used as an Active Material

This shows the same zinc foil linked as an active material in an electrode.

{
    "@context": "https://w3id.org/emmo/domain/electrochemistry/context",
    "@type": "Electrode",
    "hasActiveMaterial": {
       "@type": ["Zinc", "Foil"],
       "hasProperty": {
         "@type": "Density",
         "hasNumericalPart": {
           "@type": "RealData",
           "hasNumberValue": 7.14
         },
         "hasMeasurementUnit": "emmo:GramPerCubicCentimetre"
       }
    }
}

Here, the same material description is reused in a different context through the role relation hasActiveMaterial.

3. Composite Material or Mixture

An electrolyte composed of multiple constituents.

{
    "@context": "https://w3id.org/emmo/domain/electrochemistry/context",
    "@type": "Electrolyte",
    "rdfs:label": "LP50",
    "rdfs:comment": ["This example demonstates custom electrolyte composition descriptions using properties 'hasSolvent' and 'hasSolute'.", "Quantities like 'MassFraction' that are defined with respect to some total value refer back to the nearest holistic whole that they are part of. For example, the mass fraction of ethylene carbonate is defined with respect to the total mass of the solvent, while the mass fraction of the lithium salt is defined with respect to the whole electrolyte.", "The notation LP50 is derived from a manufacturer-specific product line and doesn not have general applicability. It has been adopted as a shorthand in the domain, but it is not a regulated descriptive code."],
    "hasSolvent": {
        "@type": "Solvent",
        "hasConstituent": [
            {
                "@type": "EthyleneCarbonate",
                "hasProperty": {
                    "@type": "MassFraction",
                    "hasNumericalPart": {
                        "@type": "RealData",
                        "hasNumberValue": 0.5
                    },
                    "hasMeasurementUnit": "emmo:UnitOne"
                }
            },
            {
                "@type": "EthylMethylCarbonate",
                "hasProperty": {
                    "@type": "MassFraction",
                    "hasNumericalPart": {
                        "@type": "RealData",
                        "hasNumberValue": 0.5
                    },
                    "hasMeasurementUnit": "emmo:UnitOne"
                }
            }
        ]
    },
    "hasSolute": {
        "@type": "LithiumHexafluorophosphate",
        "hasProperty": {
            "@type": "MassFraction",
            "hasNumericalPart": {
                "@type": "RealData",
                "hasNumberValue": 0.122
            },
            "hasMeasurementUnit": "emmo:UnitOne"
        }
    }
}

The solvent is a mixture of two chemical substances with a lithium salt solute.

Reasoning and Reuse#

Because the ontology defines ActiveMaterial, Binder, and Additive as subclasses of Material, any description that uses those roles can be automatically inferred to involve materials.

For example, a reasoner will infer:

::: If A hasActiveMaterial B → A hasPart B and B is a Material.

This consistency allows generic SPARQL queries for hasPart or Material to still return domain-specific relations.

Best Practices#

Use multiple inheritance to express both chemical identity and physical form.
Attach properties (e.g., Density, ElectricalConductivity) using hasProperty.
Use domain-specific part relations (hasActiveMaterial, hasBinder, etc.) whenever possible.
When referencing datasheet or literature values, classify the property as a ConventionalProperty.
Reuse material nodes rather than duplicating them — this improves linking and consistency across datasets.