Селенид ниобия (NbSe2)

Description

Niobium diselenide NbSe2 is a layered transition metal chalcogenide. The Se–Nb–Se layers are interconnected by van der Waals forces, so the crystal easily splits into nanosheets, up to a monolayer. Electrical conductivity is higher than that of graphite. The material combines two low-temperature phenomena: superconductivity with a critical temperature of 7.2 K and a charge density wave with a transition temperature of 33 K. The second practical quality is a solid lubricant that works in vacuum and when heated.

Basic Attributes

• CAS No.: 12034-77-4
• Chemical formula: NbSe2
• Molecular weight: 250.83
• Exact weight: 254.75500
• EU number: 234-811-8
• NSC Number: 378353
• PSA Features: 0
• XLogP3: −0.53660

Physico-chemical characteristics

• Appearance: Powder
• Density: 1.016 g/ml at 25 °C (lit.)
• Boiling point: 243–244 °C (lit.)
• Flash point: >230°F (>110°C)
• Refractive index: n20/D 1.535 (lit.)
• Solubility in water: insoluble

The values ​​of density, boiling point and refractive index are given according to the supplier’s passport; for layered refractory chalcogenide they look atypical, and before technological calculation they should be confirmed with a certificate for a specific batch.

Scope of application

• solid lubricant for vacuum, high temperatures and sliding electrical contacts: ecfoliated micro- and nanoparticles have a friction coefficient of about 0.3 with moderate wear and a service life of about 120 minutes; for the NbSe2 lubricating film, the friction coefficient decreases from 0.25 to 0.02, the service life increases by at least 7 times and reaches 100,000 cycles or more
• superconducting devices and low temperature physics: coexistence of superconductivity (Tc 7.2 K) and charge density wave (TCDW 33 K) in atomically thin nanosheets
• solar cell electrodes, photocatalysis, photovoltaics
• catalysts for chemical reactions and hydrogen evolution reactions (HER)
• lithium-ion batteries, field-effect transistors, spintronics, gas sensors
• shielding of electromagnetic interference - coatings made of exfoliated NbSe2

Toxicity and safety information

• Packing level: III
• Hazard category: 6.1
• Transport codes: UN3283
• Hazard class code: 23/25-33-50/53
• Safety instructions: 20/21-28-45-60-61
• RTECS number: QU0420000
• Tags: T, N
• Hazard statements: H301 + H331, H373, H410
• Precautions: P260, P304 + P340 + P312, P403 + P233
• GHS classification: signal word "Hazard", H301 + H331 (90.48%) - toxic if swallowed or inhaled; P260, P261, P264, P270, P271, P273, P301 + P310, P304 + P340, P311, P314, P321, P330, P391, P403 + P233, P405, P501

GHS information is aggregated from 42 companies across 2 notifications to the ECHA C&L register; one notice may apply to several companies.

Storage and transportation conditions

Selenide is a toxic substance of Class 6.1, transported under UN number 3283, packing group III. Storage in sealed containers, in a dry, ventilated area, away from food products and acids. Handle the powder only under a fume hood: inhalation of dust and ingestion are hazardous, the substance causes damage to organs with prolonged exposure (H373) and is very toxic to the aquatic environment with long lasting effects (H410) - do not discharge into drains or waterways. Protective equipment: gloves, goggles, respirator.