Kobaltový kov: Vlastnosti, Použití, a průmyslový význam

1. Zavedení

Cobalt traces its roots to the early 18th century, named from the German kobold or “goblin,” a nod to miners’ frustrations when ores refused to yield copper but released toxic vapors.

Dnes, cobalt is indispensable in modern technology: it stabilizes lithium‑ion batteries, endows superalloys with extreme‑temperature resilience, drives key chemical catalysts, and imparts the iconic deep blue of ceramics and pigments.

2. What Is Cobalt?

Cobalt is a chemical element with the symbol Co and atomic number 27.

Located in Group 9 of the periodic table, it’s a hard, silvery-gray, ferromagnetic transition metal.

As a transition metal, cobalt exhibits a variety of oxidation states and forms numerous compounds, which contribute to its wide range of applications.

In nature, cobalt is not found in its pure form but is mainly associated with nickel and copper ores.

This association means that most of the cobalt production is a by-product of nickel and copper mining operations.

The Democratic Republic of Congo (DRC) is the world’s largest producer of cobalt, accounting for approximately 70% of global production in recent years.

Other major cobalt-producing countries include Russia, which has significant cobalt reserves associated with its nickel-copper-platinum group metal deposits, and Australia, known for its high-quality cobalt-bearing ores.

3. Fyzikální & Chemical Properties of Cobalt

Cobalt is a hard, lesklý, silver‑gray transition metal with a suite of physical and chemical characteristics that underpin its diverse industrial uses:

4. Cobalt Production and Refining

Cobalt is primarily extracted as a by-product from copper-cobalt and nickel-cobalt ores.

The two main mining techniques used for cobalt-bearing ores are underground mining a open-pit mining.

Underground mining is typically employed for deeper ore bodies, offering better ore concentration but higher operational costs.

Naopak, open-pit mining is more suitable for near-surface deposits and is generally more cost-effective for large-scale production.

Once the ore is extracted, it undergoes a series of metallurgical processes to separate and purify the cobalt content:

Pyrometallurgy

This high-temperature technique involves:

• Tavení: The ore is heated with a reducing agent to separate metal from the surrounding material. This process is commonly used for sulfide ores.
• Roasting: Converts metal sulfides into oxides by heating in the presence of oxygen, enabling easier recovery in subsequent steps.

Hydrometallurgy

A more selective and widely adopted method for cobalt extraction, especially from laterite and oxidized ores. Key steps include:

• Sulfate Leaching: The ore is treated with sulfuric acid to dissolve cobalt, along with other valuable metals like nickel and copper.
• Precipitation: Chemical reagents are used to selectively separate cobalt from the leach solution, often producing cobalt hydroxide or sulfate as intermediates.

Rafinace

Refining is essential to obtain high-purity cobalt suitable for industrial and technological applications:

• Solvent Extraction: Organic solvents are used to selectively extract cobalt ions from the aqueous phase, effectively removing impurities such as iron, mangan, a měď.
• Electrowinning: The final purification step, where a direct electric current is passed through a cobalt-containing solution to deposit pure cobalt metal (99.8%–99.99%) onto cathodes.

5. Cobalt Grades and Forms

Cobalt is available in a range of commercial grades and forms, each tailored for specific industrial uses depending on required purity, physical structure, and chemical composition.

These variants support applications in battery manufacturing, high-temperature alloys, elektronika, catalysts, and magnetic materials.

Below is a breakdown of the most common grades and forms of cobalt:

6. Key Cobalt Alloys

Cobalt’s unique properties—such as high-temperature strength, odolnost proti korozi, magnetic performance, and wear resistance—make it an essential element in numerous advanced alloys.

Cobalt-Based Superalloys

• Popis: These alloys are designed to withstand extreme temperatures and oxidative environments, making them ideal for turbine engines and aerospace components.
• Typical Compositions: Co–Cr–W, Co–Ni–Cr, and Co–Mo–Ni alloys.
• Vlastnosti:

• • Síla vysoké teploty (> 1000° C.)
  • Excellent oxidation and corrosion resistance
  • Good thermal fatigue performance

• Aplikace:

• • Jet engine turbine blades and vanes
  • Industrial gas turbines
  • Combustion liners and heat shields

• Example Alloys: Haynes 188, Stellite 21, MAR-M509

Cobalt-Containing High-Speed Steels (HSS)

• Popis: Cobalt is added to HSS to improve red hardness—allowing tools to maintain hardness at elevated temperatures during cutting.
• Typical Grade: M42 (8% CO)
• Vlastnosti:

• • Enhanced hot hardness and wear resistance
  • Improved cutting edge retention under high loads

• Aplikace:

• • Řezací nástroje, cvičení, stopkové frézy, broaches
  • Forming tools for metal and plastic

• Poznámka: M42 HSS has become a standard in precision machining due to its cobalt content.

Cobalt-Based Permanent Magnets

• Typy:

• • Alnico (Aluminum–Nickel–Cobalt): High magnetic strength and temperature resistance
  • Samarium Cobalt (SmCo): Rare-earth cobalt magnet with excellent stability and corrosion resistance

• Vlastnosti:

• • High coercivity and energy product
  • Excellent thermal stability (up to 350–550°C for SmCo)

• Aplikace:

• • Motors and generators
  • Aerospace sensors
  • Medical imaging (MRI)

• Výkon: SmCo magnets typically have an energy product of 20–32 MGOe (Mega Gauss Oersteds)

Cobalt-Chromium Alloys (Co-Cr)

• Popis: Biocompatible alloys with high wear and corrosion resistance; often used in medical and dental applications.
• Vlastnosti:

• • Nemagnetický, vysoká síla
  • Excellent biocompatibility

• Aplikace:

• • Ortopedické implantáty (hips, knees)
  • Dental prosthetics
  • Heart valve components

• Example Alloys: ASTM F75 (cast Co-Cr-Mo), ASTM F799 (wrought Co-Cr-Mo)

Hardfacing Alloys (NAPŘ., Stellite)

• Popis: Wear-resistant cobalt alloys used as surface coatings to extend tool or part life.
• Vlastnosti:

• • Exceptional resistance to abrasion, eroze, and galling
  • Retains hardness up to 900°C

• Aplikace:

• • Ventil sedadla, cutting blades, mining tools
  • Engine components in high-wear environments

Tabulka: common cobalt alloy grades

7. Industrial Applications of Cobalt

Cobalt plays a vital role across a wide range of industrial sectors due to its unique physical, chemikálie, and magnetic properties.

Its ability to withstand high temperatures, resist corrosion, and enhance the performance of other materials makes cobalt indispensable in both high-tech and traditional industries.

Energy Storage and Batteries

• Primary Use: Lithium-ion batteries
• Funkce: Cobalt is used in the cathodes of lithium-ion batteries—especially in Nickel Manganese Cobalt (NMC) a Nickel Cobalt Aluminum (NCA) chemistries.
• Výhody:

• • Improves energy density and battery life
  • Enhances thermal and structural stability

• Market Insight:

• • Nad 60% of cobalt demand is driven by the battery sector.
  • Cobalt usage per electric vehicle (EV) battery ranges from 4 na 14 kg, depending on chemistry.

Aerospace and Turbine Engines

• Primary Use: Cobalt-based superalloys
• Funkce: Superalloys containing cobalt are used in jet engine components, plynové turbíny, and rocket motors.
• Výhody:

• • Maintains strength and corrosion resistance at high temperatures (above 1000°C)
  • Withstands oxidative and thermal fatigue

• Klíčové komponenty:

• • Turbínové čepele, vanes, spalovací komory

Cutting Tools and Wear-Resistant Materials

• Primary Use: Cemented carbides and high-speed steels
• Funkce: Cobalt serves as a binder in cemented carbides and enhances hardness in high-speed steel.
• Výhody:

• • Improves tool toughness and resistance to deformation under heat
  • Extends tool life under high-speed or high-pressure cutting conditions

• Příklady:

• • Drill bits, stopkové frézy, stamping dies, mining tools

Catalysts in Chemical and Petroleum Industries

• Primary Use: Catalysts for synthesis and refining
• Types of Catalytic Applications:

• • Fischer-Tropsch synthesis: Produces liquid hydrocarbons from syngas (CO + H2)
  • Hydrodesulfurization (HDS): Removes sulfur from crude oil to produce clean fuels

• Výhody:

• • High catalytic efficiency and durability under harsh chemical environments

Medical and Biomedical Devices

• Primary Use: Cobalt-chromium alloys
• Funkce: Used for implants, Protetika, and surgical instruments due to their excellent biocompatibility.
• Příklady:

• • Artificial hips and knees
  • Stents, zubní implantáty

• Special Case:

• • Cobalt-60 (Co-60): A radioactive isotope used in cancer radiotherapy and medical equipment sterilization

Permanent Magnets and Electronics

• Typy:

• • Alnico magnets: Used in electric motors, senzory, and electric guitars
  • Samarium Cobalt (SmCo): Rare earth magnets with high coercivity and stability

• Výhody:

• • Stable magnetic performance at high temperatures
  • Corrosion resistance in harsh environments

• Aplikace:

• • Aerospace instruments, MRI machines, Robotika, audio equipment

Pigments, Sklo, and Ceramics

• Cobalt Compounds Used:

• • Cobalt oxide (Co₃O₄) a cobalt aluminate (CoAl₂O₄)

• Funkce:

• • Used to produce cobalt blue, a stable, vibrant pigment

• Aplikace:

• • Artistic ceramics, automotive glass, architectural tiles
  • High-tech glass applications due to UV-absorbing properties

8. Bezpečnost, Zacházení, and Toxicology of Cobalt

While cobalt is indispensable in many modern technologies, it poses several health, bezpečnost, and environmental risks if not properly managed.

Understanding its toxicological profile, exposure limits, and safe handling practices is essential for industries using cobalt in mining, výrobní, a zpracování.

Occupational Exposure Limits

Regulatory bodies such as OSHA, NIOSH, and ACGIH have established exposure limits to ensure safe working conditions:

Health Effects of Cobalt Exposure

Cobalt can enter the body via inhalation, ingestion, or skin contact.

The severity of health effects depends on the form of cobalt (kovový, soluble salts, or radioactive isotopes) and duration of exposure.

Short-Term (Acute) Effects:

• Respiratory irritation: coughing, wheezing
• Skin rashes or dermatitis from contact
• Eye irritation

Long-Term (Chronic) Effects:

• Cobalt lung: interstitial lung disease from inhaling cobalt dust/fumes
• Cardiomyopathy (heart muscle damage) with high systemic exposure
• Allergic responses and asthma
• Possible neurotoxic effects with prolonged high-dose exposure

Carcinogenicity:

• The International Agency for Research on Cancer (IARC) classifies cobalt and cobalt compounds as Group 2B: “possibly carcinogenic to humans” based on limited human evidence and sufficient animal studies.

Radioactive Cobalt (Cobalt-60)

Cobalt-60 (⁶⁰Co) is a synthetic radioactive isotope used in:

• Radiation therapy (cancer treatment)
• Sterilization of medical equipment
• Industrial radiography

Hazards:

• Emits high-energy gamma rays
• Can cause radiation burns, DNA damage, and increased cancer risk if mishandled
• Must be stored and transported under strict regulatory guidelines (NAPŘ., lead shielding, secure containers)

Best Practices for Cobalt Safety

9. Comparison with Related Elements

Cobalt shares several characteristics with neighboring elements in the periodic table, particularly iron (Fe), nikl (V), a mangan (Mn).

Comparing cobalt with these elements helps to highlight its unique properties and advantages in various industrial applications.

10. Závěr

Cobalt is a crucial metal known for its high melting point, odolnost proti korozi, and magnetic properties.

It plays a key role in superalloys, permanent magnets, and lithium-ion batteries, making it vital for aerospace, clean energy, and electronics industries.