BOEHMITE

Boehmite is a crystalline aluminium oxyhydroxide used as a functional mineral, ceramic precursor, catalyst-support raw material and high-temperature inorganic filler.
Its hydroxylated surface, controllable particle morphology and conversion to transition alumina connect powder characteristics directly with dispersion, binding, coating and calcination performance.
Commercial selection is strongly grade-specific because crystalline, pseudo-boehmite, battery, catalyst, ceramic and polymer grades are engineered for different surface-area, purity and particle-size requirements.

CHEMICAL IDENTITY AND COMMON NAMES

Boehmite is the orthorhombic gamma polymorph of aluminium oxyhydroxide and is represented by AlO(OH) or AlOOH.
Its structure contains aluminium in oxygen-centred octahedral coordination, with hydroxyl-bearing layers joined through hydrogen bonding.
Diaspore has the same AlO(OH) composition but a different alpha crystal structure, while aluminium trihydroxide has the distinct formula Al(OH)3.

Synonyms and Common Names: Böhmite, Bohmite, Aluminium oxide hydroxide, Aluminum oxide hydroxide, Aluminium oxyhydroxide, Aluminum oxyhydroxide, Aluminium hydroxide oxide, Aluminum hydroxide oxide, Aluminium oxide monohydrate, Aluminum oxide monohydrate, Alumina monohydrate, Monohydrated alumina, Alpha-alumina monohydrate, Gamma-aluminium oxyhydroxide, Gamma-aluminum oxyhydroxide, γ-Aluminium oxyhydroxide, γ-Aluminum oxyhydroxide, γ-AlOOH, AlOOH, OAlOH, Aluminium monohydroxide monoxide, Aluminum monohydroxide monoxide, Hydroxy(oxo)alumane, Nanoboehmite, Boehmite nanopowder

TECHNICAL IDENTIFICATION

CAS Number: 1318-23-6
EC / EINECS Number: 215-284-3
Chemical Formula: AlO(OH), commonly written AlOOH
Molar Mass: 59.99 g/mol per AlOOH formula unit
Al2O3 Equivalent: 84.98% by mass for stoichiometric Boehmite
Theoretical Structural Water: 15.02% by mass
Mineral Class: Aluminium oxyhydroxide
Crystal System: Orthorhombic
Space Group: Cmcm
Crystal-Phase Designation: γ-AlOOH

PHYSICAL AND CHEMICAL PROPERTIES

Appearance: White to off-white crystalline powder in synthetic grades
Natural Appearance: White, grey, yellowish, reddish or brownish mineral depending on associated impurities
Odour: Odourless
True Density: Approximately 3.01–3.07 g/cm³
Mohs Hardness: Approximately 3.0–3.5
Water Solubility: Insoluble
Acid and Alkali Behaviour: Dissolves in sufficiently strong acidic or alkaline media, especially when heated
Vapour Pressure: Negligible
Flammability: Non-combustible
Electrical Behaviour: Electrically insulating
Point of Zero Charge: Approximately pH 9
BET Specific Surface Area: Grade-defining, from single-digit values in dense crystalline grades to above 300 m²/g in highly porous pseudo-boehmite
Particle Form: Nanoscale primary crystallites, platelets, rods, fibrils or controlled micron-scale agglomerates determined by synthesis route
Melting Behaviour: Dehydroxylation and phase transformation occur before conventional melting
Dehydroxylation Range: Begins at approximately 250–350 °C and proceeds mainly through approximately 400–500 °C
Primary Calcination Product: Transition alumina, principally γ-Al2O3 under controlled intermediate-temperature calcination

The theoretical conversion of two formula units of Boehmite produces one formula unit of alumina and one molecule of water.
Adsorbed moisture, excess structural water and surface hydroxyl content can raise measured loss on ignition above the stoichiometric 15.02% value.

STRUCTURE AND FUNCTIONAL CHARACTERISTICS

Boehmite consists of double sheets of edge-sharing AlO6 octahedra separated by hydrogen-bonded interfaces.
This anisotropic structure supports platelet, rod-like and fibrillar morphologies whose aspect ratio affects packing, rheology, reinforcement and coating smoothness.

Surface hydroxyl groups give Boehmite amphoteric behaviour and provide sites for hydrogen bonding, acid peptisation, adsorption and reaction with coupling agents.
The surface is positively charged below its point of zero charge and becomes increasingly negative above that region, making pH and ionic strength central to aqueous dispersion design.

The inorganic lattice combines electrical insulation with thermal stability beyond the processing window of many polymers.
During stronger heating, endothermic dehydroxylation absorbs energy, releases water vapour and leaves an alumina-rich mineral barrier.

PRODUCTION AND COMMERCIAL FORMS

Natural Boehmite occurs in bauxite, lateritic deposits and hydrothermally altered aluminium-bearing rocks, but controlled industrial grades are generally produced synthetically.
Synthetic manufacture enables direct control of purity, crystallinity, primary-particle size, agglomeration, morphology, surface area and dispersibility.

One commercial route precipitates an aluminium hydroxide or oxyhydroxide gel from sodium aluminate or soluble aluminium salts and then converts the precursor through controlled aging or hydrothermal treatment.
Thorough washing is important in this route because residual sodium, chloride, sulfate and other soluble ions can impair catalysis, electrical insulation, sintering and dispersion stability.

Hydrolysis of aluminium alkoxides provides a high-purity route with particularly low alkali-metal and transition-metal contamination.
Hydrothermal conversion of aluminium hydroxide, activated alumina or other purified aluminium precursors is also used to develop well-crystallised Boehmite with selected platelet or rod morphology.

Precipitation pH, temperature, aging time, seed concentration and mineralising agents control nucleation and crystal growth.
After solid-liquid separation, the material is washed, dried and milled, followed when required by classification, surface treatment, spray drying or preparation as an aqueous dispersion.

Commercial forms include dry crystalline powder, nanoboehmite, high-surface-area pseudo-boehmite, peptisable powder, stable aqueous sol, concentrated dispersion and surface-modified powder.
The selected form determines how Boehmite can be incorporated into catalyst pastes, coating slurries, polymer compounds or ceramic bodies.

BOEHMITE AND PSEUDO-BOEHMITE DISTINCTION

Well-crystallised Boehmite has sharp phase-characteristic diffraction peaks, comparatively ordered layers and lower excess water content.
These characteristics suit high-purity coatings, thermally stable fillers and applications where controlled particle geometry is more important than maximum surface area.

Pseudo-boehmite retains the basic Boehmite-type local structure but contains very small, poorly ordered crystallites, additional adsorbed or interlayer water and a much larger accessible surface.
Its high surface area, pore volume and acid peptisability make pseudo-boehmite particularly useful as a catalyst binder, catalyst-support precursor and sol-forming raw material.

Commercial terminology can group both materials under the Boehmite name, but they are not functionally interchangeable.
X-ray diffraction, BET surface area, pore volume, loss on ignition, crystallite size and peptisation response establish the grade distinction for procurement.

THERMAL CONVERSION TO ALUMINA

Thermal Conversion Reaction: 2AlO(OH) → Al2O3 + H2O

Calcination first removes physically adsorbed water and then dehydroxylates Boehmite to porous γ-alumina.
The transformation is largely topotactic, so precursor crystallite size, morphology and aggregation influence the surface area and pore architecture of the calcined material.

Further heating converts γ-alumina through progressively ordered transition-alumina phases and ultimately to stable α-alumina.
Calcination temperature, heating rate, residence time, atmosphere, seed content and impurities govern phase development, sintering shrinkage, pore collapse and final mechanical properties.

APPLICATIONS AND INDUSTRIES

Catalyst carriers and catalyst binders

High-surface-area Boehmite and pseudo-boehmite are peptised to form cohesive alumina-rich pastes, sols and binders for shaped heterogeneous catalysts.
Acid peptisation separates fine crystallites and develops the rheology needed for extrusion, spray drying, washcoating and formation of mechanically durable catalyst bodies.

Calcination converts the precursor into porous γ-alumina while retaining useful mesoporosity and surface area for dispersion of catalytically active species.
These materials support petroleum-refining, hydrogenation, oxidation, reforming and emissions-control catalyst systems where pore structure, impurity content and hydrothermal stability are critical.

Lithium-ion battery separator coatings

Fine high-purity Boehmite is used as a ceramic coating material on polyethylene and polypropylene battery separators.
The coating improves dimensional stability at elevated temperature, supports electrolyte wetting and reinforces the porous membrane without providing electronic conductivity.

Submicron particle size, narrow distribution and low agglomerate content allow thin, uniform coatings with controlled porosity and limited impact on ion transport.
Very low iron, copper, nickel, chromium and other conductive or magnetic contaminants are essential because metallic particles can create local defects and electrical-failure risks.

Flame-retardant polymer compounds

Boehmite functions as a halogen-free mineral flame-retardant component and synergist in engineering thermoplastics, thermosets, cable compounds, electrical components and copper-clad laminate systems.
Its dehydroxylation occurs at a substantially higher temperature than that of aluminium trihydroxide, allowing processing in polymers whose melt temperatures would prematurely dehydrate lower-temperature mineral hydrates.

During severe heating, Boehmite absorbs heat, releases water and leaves an alumina residue that contributes to a protective condensed-phase barrier.
Particle size, surface treatment, loading, polymer chemistry and interaction with phosphorus- or nitrogen-containing flame-retardant components determine the final fire, mechanical and electrical performance.

Ceramics and refractory systems

Boehmite serves as a reactive alumina precursor, sol-gel feedstock and inorganic binder in advanced ceramics, refractory bodies and ceramic coatings.
Fine crystallites promote uniform green-body binding and can be transformed into transition aluminas or α-alumina through a controlled firing schedule.

Ceramic processing uses phase purity, sintering activity and morphology to manage green strength, shrinkage, pore development, grain growth and final density.
Alpha-alumina seeding can accelerate transformation and help refine the microstructure of Boehmite-derived ceramic bodies.

Activated alumina, adsorbents and membrane materials

High-surface-area Boehmite is an important precursor for activated and mesoporous alumina used in adsorption, separation and catalyst-support applications.
Peptised sols can be cast or deposited as thin porous layers for ceramic membranes, filtration media and controlled-pore coatings.

The precursor morphology and calcination programme determine the resulting alumina pore diameter, pore volume, surface acidity and resistance to sintering.
Direct adsorption applications use the hydroxylated Boehmite surface for interaction with water, ions and polar species.

Coatings and polymer nanocomposites

Nanoboehmite is incorporated into epoxy, polyamide, polyolefin and other polymer matrices to modify stiffness, dimensional stability, thermal response and barrier performance.
Surface hydroxyl groups can be functionalised with silanes or other coupling chemistries to improve compatibility and interfacial stress transfer.

In protective coatings, well-dispersed Boehmite can increase inorganic content, reinforce the film and provide a route to alumina-rich heat-resistant layers after thermal treatment.
Agglomerate control is essential because coarse clusters reduce surface quality and can act as mechanical defects.

Polishing and abrasive-material production

Controlled Boehmite powders and sols are used as precursors for fine alumina particles employed in polishing, lapping and engineered abrasive materials.
Particle morphology, phase-conversion temperature and impurity content influence the hardness, cut rate, surface finish and contamination profile of the resulting calcined alumina.

GRADE SELECTION AND PRODUCT SUITABILITY

Battery-Separator Grade: High-purity crystalline Boehmite with narrow submicron or fine-micron particle distribution, low agglomeration and extremely low metallic contamination
Catalyst and Binder Grade: High-surface-area, porous and readily peptisable Boehmite or pseudo-boehmite with controlled sodium, silica, iron, chloride and sulfate
Polymer and Flame-Retardant Grade: Thermally stable powder with controlled dehydration profile, moisture, whiteness, particle size and optional surface treatment
Ceramic Grade: Phase-pure, sinter-active Boehmite with controlled morphology, loss on ignition, agglomerate size and calcination behaviour
Dispersible and Sol Grade: Fine peptisable material with defined acid demand, solids content, pH, viscosity and colloidal stability
High-Purity Alumina Precursor Grade: Low-alkali and low-transition-metal Boehmite for controlled production of transition or α-alumina

Purity expressed only as total AlOOH or Al2O3 equivalent does not fully describe application performance.
Sodium, iron, silicon, calcium, magnesium, chloride, sulfate and trace transition metals can change surface chemistry, electrical behaviour, colour, catalyst response and ceramic densification.

Particle-size data should include D10, D50, D90 and oversize or agglomerate information rather than a single average value.
BET surface area, pore volume, crystallinity and morphology complete the physical profile needed to compare grades with similar chemical assay.

FORMULATION AND PROCESS CONSIDERATIONS

Aqueous dispersion behaviour is controlled by surface charge, electrolyte concentration, solids loading and the distance between formulation pH and the point of zero charge.
Near the point of zero charge, reduced electrostatic repulsion promotes aggregation and rapid viscosity change.

Pseudo-boehmite can be peptised with a controlled quantity of suitable acid to form a stable colloidal sol or plastic binder phase.
Insufficient peptisation leaves agglomerates, while excessive acid or high ionic strength can compress the electrical double layer, change pore development and destabilise the system.

High-surface-area grades adsorb more dispersant, binder and liquid than dense crystalline grades.
Formulators therefore evaluate wetting sequence, shear history, solids loading, viscosity development, sedimentation, foam and storage stability for the selected grade.

Battery-separator slurries require smooth coating flow, limited hard settling, rapid redispersion and compatibility with the polymeric binder and electrolyte-wetting design.
Coating evaluation includes thickness uniformity, pinholes, adhesion, air permeability, pore retention, thermal shrinkage and ionic resistance.

Polymer compounding requires effective drying and deagglomeration because retained moisture can cause voids or hydrolytic damage in moisture-sensitive resins.
Surface-treated grades improve wetting by non-polar or weakly polar matrices and can reduce the viscosity increase associated with untreated hydroxyl-rich particles.

Ceramic and catalyst processing must account for the approximately 15% theoretical mass loss and the accompanying volume change during dehydroxylation.
Heating profiles and green-body permeability should allow water vapour to escape without cracking, blistering or disrupting pore structure.

QUALITY, SPECIFICATIONS AND DOCUMENTATION

Phase Identification: X-ray diffraction for Boehmite content, competing hydroxide phases, transition alumina and crystallite characteristics
Chemical Composition: X-ray fluorescence or elemental analysis for Al2O3 equivalent and major inorganic impurities
Trace Metals: Sensitive elemental analysis for sodium, iron, silicon, calcium, magnesium, copper, nickel, chromium and other application-critical elements
Thermal Profile: Thermogravimetric and differential thermal analysis for adsorbed water, loss on ignition and dehydroxylation behaviour
Surface and Porosity: BET specific surface area, pore volume and pore-size distribution
Particle Profile: Laser-diffraction D10, D50 and D90 values supported by oversize, morphology and agglomeration assessment
Dispersion Properties: pH, conductivity, zeta potential, acid demand, peptisation index, viscosity and sedimentation where relevant
Physical Quality: Moisture, bulk density, tapped density, whiteness, flow and packaging integrity

A Certificate of Analysis links the production batch to its chemical and physical specification.
A Technical Data Sheet describes grade design, test methods, processing characteristics and intended application class.
A Safety Data Sheet provides handling, exposure-control, first-aid, transport and disposal information.

Battery and electronic applications can require particle-distribution curves, magnetic-particle control, trace-metal data and slurry-performance records.
Catalyst and ceramic projects can additionally require calcined surface area, pore volume, crush-strength development, phase-transformation data and representative calcination conditions.

SAFETY AND ENVIRONMENTAL CONSIDERATIONS

Pure Boehmite is generally not classified as hazardous under the Globally Harmonized System.
Fine airborne dust can nevertheless cause mechanical irritation of the eyes, skin and respiratory tract.

Engineering controls should prevent routine dust generation during bag opening, charging, milling, blending and packaging.
Nanopowder and ultrafine grades require enclosed transfer or effective local exhaust because their small particles remain airborne more readily than coarse powders.

Boehmite is non-combustible and does not support fire.
Thermal processing releases water vapour, so sealed or poorly vented equipment can develop pressure during dehydroxylation.

Spilled dry material can create a slipping and dust hazard.
Use a filtered industrial vacuum or dust-minimising collection method and prevent powder or slurry from entering drains and surface water.

FIRST AID

Inhalation: Move the affected person to fresh air and obtain medical attention if coughing, breathing discomfort or irritation persists.
Skin Contact: Wash exposed skin with soap and water and remove contaminated clothing.
Eye Contact: Rinse cautiously with clean water for at least 15 minutes and obtain medical attention if irritation continues.
Ingestion: Rinse the mouth, give water to an alert person and obtain medical advice if discomfort develops.
Note to Physicians: Provide symptomatic and supportive treatment for mechanical dust exposure.

HANDLING AND STORAGE

Handling: Avoid generating airborne dust and use closed charging, local exhaust and grounded powder-handling equipment where practical.
Personal Protection: Wear safety glasses, suitable gloves and protective clothing, with particulate respiratory protection when engineering controls do not adequately control dust.
Storage: Keep Boehmite tightly sealed in a cool, dry and well-ventilated area protected from moisture and contamination.
Incompatibilities: Segregate Boehmite from strong acids and strong alkalis that can dissolve or alter the aluminium oxyhydroxide surface.
Process Protection: Keep opened containers closed between uses because moisture uptake changes flow, loss on drying, dispersion and compounding behaviour.

PACKAGING AND PROCUREMENT CONSIDERATIONS

Dry Boehmite is commonly packed in moisture-resistant multiwall bags, fibre drums, lined bulk bags or other sealed containers suitable for fine inorganic powder.
Aqueous sols and dispersions require compatible lined drums or intermediate bulk containers that preserve solids content and prevent ionic or metallic contamination.

Packaging selection should reflect particle fineness, dust-control needs, moisture sensitivity, batch size and the cleanliness requirements of the destination process.
Battery and electronic grades benefit from controlled filling, sealed inner liners, clean pallets and protection from ferrous contamination during transport and warehousing.

Procurement specifications should define crystalline or pseudo-boehmite form, phase purity, Al2O3 equivalent, trace impurities, particle-size distribution, BET area, pore volume, loss on ignition, moisture, surface treatment and packaging.
Application-focused documentation should also define the relevant dispersion, peptisation, calcination, coating, electrical or compounding tests.

ATAMAN KIMYA SUPPLY AND CONTACT

Ataman Kimya supports Boehmite procurement with attention to crystalline form, surface area, particle size, impurity limits, dispersibility, application grade, documentation and packaging.
For Boehmite specifications, formulation requirements and supply planning, contact Ataman Kimya by telephone at +90 216 577 10 10 or by email at info@atamankimya.com.