Calcium carbide is used in carbide lamps. Water dripping on carbide produces acetylene gas, which burns and produces light. While these lamps gave steadier and brighter light than candles, they were dangerous in coal mines, where flammable methane gas made them a serious hazard. The presence of flammable gases in coal mines led to miner safety lamps such as the Davy lamp, in which a wire gauze reduces the risk of methane ignition. Carbide lamps were still used extensively in slate, copper, and tin mines where methane is not a serious hazard. Most miners' lamps have now been replaced by electric lamps.
Carbide lamps were also used extensively as headlights in early automobiles, motorcycles and bicycles, but have been replaced entirely by electric lamps.
Carbide lamps are still used for mining in some less wealthy countries, for example in the silver mines near Potosí, Bolivia. Carbide lamps are also still used by some cavers exploring caves and other underground areas, although they are increasingly being replaced in this use by LED lights.
In 2008, AME developed a carbide hot saw which cuts off the ends on hot-forged axles for the railroad industry.
In 2004, the New South Wales Minister for Planning granted consent for additional remediation of the former Union Carbide site to proceed, including parts of Homebush Bay. Approximately 900,000 tons of soil were excavated from the site, 190,000 tons of soil from the adjacent Allied Feeds site, and approximately 50,000 tons of sediment from the bay. Remediation of the Allied Feeds Site was completed in August 2009, Homebush Bay sediments in August 2010, and the Union Carbide site in March 2011. The cost of the remediation work was $35M for the Allied Feeds site, and $100 million for Union Carbide site and Homebush Bay sediments.
Union Carbide ceased operations in Australia in 1985. In 1987, the New South Wales Pollution Control Commission ordered Union Carbide to remediate the site. This work, which cost Union Carbide $30 million, was conducted between 1988 and 1993. The work involved excavation and encapsulation of the contaminated soil.
Union Carbide reclaimed land on neighboring properties by depositing spent lime and ash into the adjacent marshes in Homebush Bay. This practice, which had been approved by the Maritime Services Board, ceased in 1970.
Union Carbide's operations in Australia commenced in 1957, when it purchased the plant of the Australian-owned company Timbrol Ltd. The Timbrol factory was on the shore of Homebush Bay in the Sydney suburb of Rhodes. Homebush Bay is on the Parramatta River which flows into Sydney Harbour. Tibrol produced phenol, the insecticides chlorobenzene/chlorophenol/DDT, and the herbicides 2,4-D and 2,4,5-T. Union Carbide continued the production of the 2,4-D and 2,4,5-T until 1976 and chlorobenzene/chlorophenol/DDT until 1983. Union Carbide also commenced the production of bisphenol A in 1960 and phenol formaldehyde resins in 1964.
Methanides are a subset of carbides distinguished by their tendency to decompose in water producing methane. Three examples are aluminium carbide, magnesium carbide and beryllium carbide.
Several carbides are assumed to be salts of the acetylide anion C 2 2– (also called percarbide), which has a triple bond between the two carbon atoms. Alkali metals, alkaline earth metals, and lanthanoid metals form acetylides, e.g., sodium carbide Na 2 C 2, calcium carbide CaC 2 , and LaC 2. Lanthanides also form carbides (sesquicarbides, see below) with formula M 2 C 3. Metals from group 11 also tend to form acetylides, such as copper(I) acetylide and silver acetylide. Carbides of the actinide elements, which have stoichiometry MC 2 and M 2 C 3, are also described as salt-like derivatives of.
The carbides of the group 4, 5 and 6 transition metals (with the exception of chromium) are often described as interstitial compounds. These carbides have metallic properties and are refractory. Some exhibit a range of stoichiometries, e.g. titanium carbide, TiC. Titanium carbide and tungsten carbide are important industrially and are used to coat metals in cutting tools.
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.
Transition metal carbides are not saline carbides but their reaction with water is very slow and is usually neglected. For example, depending on surface porosity, 5–30 atomic layers of titanium carbide are hydrolyzed, forming methane within 5 minutes at ambient conditions, following by saturation of the reaction.
Carbides can be generally classified by the chemical bonds type as follows: (i) salt-like, (ii) covalent compounds, (iii) interstitial compounds, and (iv) "intermediate" transition metal carbides. Examples include calcium carbide (CaC 2 ), silicon carbide (SiC), tungsten carbide (WC; often called, simply, carbide when referring to machine tooling), and cementite (Fe 3 C), each used in key industrial applications. The naming of ionic carbides is not systematic.
The carbides of silicon and boron are described as "covalent carbides", although virtually all compounds of carbon exhibit some covalent character. Silicon carbide has two similar crystalline forms, which are both related to the diamond structure. Boron carbide, B 4 C, on the other hand, has an unusual structure which includes icosahedral boron units linked by carbon atoms. In this respect boron carbide is similar to the boron rich borides. Both silicon carbide (also known as carborundum) and boron carbide are very hard materials and refractory. Both materials are important industrially. Boron also forms other covalent carbides, e.g. B 25 C.
Much of what is known about uranium carbide is in the form of pin-type fuel elements for liquid metal fast reactors during their intense study during the 1960s and 1970s. However, recently there has been a revived interest in uranium carbide in the form of plate fuel and most notably, micro fuel particles (such as TRISO particles).
The IMCB publicly condemned Union Carbide and reiterated the company's full liability not only for responsibility in causing the deadly gas leak, but also for the confounding role of its behaviour with respect to pre-accident preventive and exposure mitigating efforts, and the timely and effective application of the appropriate medical measures at the time of the accident. This included the lack of transparency about the composition of the gases released, resulting in the absence of rational methods of care and planning resulting in loss of sight and in some cases life, and creation of suspicion and conflict among professionals and the population. There was also a lack of emergency preparation which would have made the public and professionals aware of the potential toxins inside the plant and how to respond to an accident.
Because of the B 12 structural unit, the chemical formula of "ideal" boron carbide is often written not as B 4 C, but as B 12 C 3, and the carbon deficiency of boron carbide described in terms of a combination of the B 12 C 3 and B 12 C 2 units. Some studies indicate the possibility of incorporation of one or more carbon atoms into the boron icosahedra, giving rise to formulas such as (B 11 C)CBC = B 4 C at the carbon-heavy end of the stoichiometry, but formulas such as B 12 (CBB) = B 14 C at the boron-rich end. "Boron carbide" is thus not a single compound, but a family of compounds of different compositions. A common intermediate, which approximates a commonly found ratio of elements, is B 12 (CBC) = B 6.5 C. Quantum mechanical calculations have demonstrated that configurational disorder between boron and carbon atoms on the different positions in the crystal determines several of the materials properties - in particular, the crystal symmetry of the B 4 C composition and the non-metallic electrical character of the B 13 C 2 composition.
Aluminum carbide can be used as an abrasive in high-speed cutting tools. It has approximately the same hardness as topaz.
As nuclear fuel, uranium carbide can be used either on its own, or mixed with plutonium carbide (PuC and Pu 2 C 3 ). The mixture is also labeled as uranium-plutonium carbide ( (U,Pu)C ).