Structure of Tungsten Carbide

WC structure, carbon atoms are gray

There are two forms of WC, a hexagonal form, α-WC, and a cubic high temperature form, β-WC, which has the rock salt structure. The hexagonal form can be visualized as made up of hexagonally close packed layers of metal atoms with layers lying directly over one another, with carbon atoms filling half the interstices giving both tungsten and carbon a regular trigonal prismatic, 6 coordination. From the unit cell dimensions the following bond lengths can be determined; the distance between the tungsten atoms in a hexagonally packed layer is 291 pm, the shortest distance between tungsten atoms in adjoining layers is 284 pm, and the tungsten carbon bond length is 220 pm. The tungsten-carbon bond length is therefore comparable to the single bond in W(CH₃)₆ (218 pm) in which there is strongly distorted trigonal prismatic coordination of tungsten.

Molecular WC has been investigated and this gas phase species has a bond length of 171 pm for ¹⁸⁴W¹²C.

Physical properties of Tungsten Carbide

Tungsten carbide is high melting, 2,870 °C (5,200 °F), extremely hard 8.5–9.0 Mohs scale at 22 GPa Vickers hardness (Vickers Hardness number = 2242) with low electrical resistivity (1.7–2.2×10⁻⁷ Ohm·m), comparable with metals (e.g. vanadium1.99×10⁻⁷ Ohm·m).

WC is readily wetted by both molten nickel and cobalt nikel and cobalt. Investigation of the phase diagram of the W-C-Co system shows that WC and Co form a pseudo binary eutectic. The phase diagram also shows that there are so-called η-carbides with composition (W,Co)₆C that can be formed and the fact that these phases are brittle is the reason why control of the carbon content in WC-Co hard metals is important.

Chemical Properties of Tungsten Carbide

There are two well characterized compounds of tungsten and carbon, WC and tungsten semicarbide, W₂C. Both compounds may be present in coatings and the proportions can depend on the coating method.

WC can be prepared by reaction of tungsten metal and carbon at 1400–2000 °C. Other methods include a patented fluid bed process that reacts either tungsten metal or blue WO3 with CO/CO₂ mixture and H₂ between 900 and 1200 °C. Chemical vapor deposition methods that have been investigated include:

• Tungsten hexachloride with hydrogen, as reducing agent and methane as the source of carbon at 670 °C (1,238 °F)

WCl₆ + H₂ + CH₄ → WC + 6 HCl

Tungsten hexachloride

• reacting tungsten hexafluoride with hydrogen as reducing agent and methanol as source of carbon at 350 °C (662 °F)

WF₆ + H₂ + CH₃OH → WC + 6 HF + H₂O

• At high temperatures WC decomposes to tungsten and carbon and this can occur during high temperature thermal spray, e.g. high velocity oxygen fuel (HVOF) and high energy plasma (HEP) methods.

• Oxidation of WC starts at 500–600 °C. It is resistant to acids and is only attacked by hydrofluoric acid/nitric acid (HF/HNO₃) mixtures above room temperature. It reacts with fluorine gas at room temperature and chlorine above 400 °C (752 °F) and is unreactive to dry H₂ up to its melting point.

WC has been investigated for its potential use as a catalyst and it has been found to resemble platinum in its catalysis of the production of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the Isomerisation of 2,2-dimethylpropane to 2-methylbutane. It has been proposed as a replacement for the iridium catalyst in hydrazine powered satellite thrusters.

Tungsten carbide

Tungsten carbide (WC), also known as tungsten steel, is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery, tools, abrasives, as well as jewelry. Tungsten carbide is approximately three times stiffer than steel, with a Young's modulus of approximately 550 GPa, and is much denser than steel or titanium. It is comparable with corundum in hardness and can only be polished and finished with abrasives of superior hardness such as silicon carbide, cubic boron nitride and diamond amongst others , in the form of powder, wheels and compounds.

Carbon steel

Carbon steel, also called plain carbon steel, is steel where the main alloying constituent is carbon.

Clear (diamond), black (graphite)

The american iron and Steel Institute (AISI) defines carbon steel as: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, colombium, molybdenum, nickel, Titanium, Tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 percent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60."

The term "carbon steel" may also be used in reference to steel which is not stainless steel; in this use carbon steel may include alloy steels.

Steel with a low carbon content has properties similar to iron. As the carbon content rises, the metal becomes harder and stronger but less ductile and more difficult to weld. In general, higher carbon content lowers the melting point and its temperature resistance. Carbon content influences the yield strength of steel because carbon atoms fit into the interstitial crystalline lattice sites of the body-centerd cubic (BCC) arrangement of the iron atoms. The interstitial carbon reduces the mobility of dislocations, which in turn has a hardening effect on the iron. To get dislocations to move, a high enough stress level must be applied in order for the dislocations to "break away". This is because the interstitial carbon atoms cause some of the iron BCC lattice cells to distort.

85% of all steel used in the U.S. is carbon steel.

The use of rubber

The use of rubber is widespread, ranging from household to industrial products, entering the production stream at the intermediate stage or as final products. Tires and tubes are the largest consumers of rubber. The remaining 44% are taken up by the general rubber goods (GRG) sector, which includes all products except tires and tubes. Pre-historical uses The first use of rubber was natural latex from the Hevea Tree in 1600 BC by the Ancient. They boiled the harvested latex to make a ball for sport. Manufacturing Other significant uses of rubber are door and window profiles, hoses, belts, matting, flooring and dampeners (anti-vibration mounts) for the automotive industry in what is known as the "under the bonnet" products.

Leather gloves

Gloves (medical, household and industrial) and toy ballons are also large consumers of rubber, although the type of rubber used is that of the concentrated latex. Significant tonnage of rubber is used as adhesives in many manufacturing industries and products, although the two most noticeable are the paper and the carpet industry.

Rubber bands

common erasers

Rubber is also commonly used to make rubber bands and pencil erasers.

Natural rubber

Natural rubber is an elastomer (an elastic hydrocarbon polymer) that was originally derived from a milky colloidal suspension or latex, found in the sap of some plants.

The extraction of latex from a tree; latex is used in rubber production

The purified form of natural rubber is the chemical polyisoprene, which can also be produced synthetically. Natural rubber is used extensively in many applications and products, as is synthetic rubber.

Types of Recycled Material

Recycling materials is one way to help protect the environment. If you are interested in becoming more proactive in earth-friendly tasks, recycling is a simple way to start. There are many different types of materials that are recyclable. Each is turned into one of a variety of products, from paper bags to glassware.

Paper

Paper is widely recycled across the country. Paper products are turned back into paper products by mashing and re-pulping the material. Some of the most common types of paper recyclables include paper shopping bags, printer paper, newspapers, paper cups and cardboard packaging materials. This is often deposited into a town recycling bin, or one of the many recyclable bins located in cities and in businesses.

Metals

Metal recycling is another common form of recycling. In fact, it has been around for a while. The most common types of recycling metal products include soda cans and food cans. However, a variety of materials in this class are recycled on a large scale every day. Cars, steel frames, old junked appliances and many other metal products are turned into scrap metal, which is recycled and reused.

Glass

Glass is another category of recycled products. This includes soda bottles, water bottles and milk bottles. In addition, glassware in the kitchen may be recycled. This includes glasses and dishes. Another large portion of glass recycling includes the reusing of automotive windshield glass from crushed cars. Other glass parts, including the windshield, are salvaged and reused, a form of recycling.

UV and light curing adhesives

Ultraviolet (UV) light curing adhesives, also known as light curing materials (LCM), have become popular within the manufacturing sector due to their rapid curing time and strong bond strength. Light curing adhesives can cure in as little as a second and many formulations can bond dissimilar substrates (materials) and withstand harsh temperatures.
These qualities make UV curing adhesives essential to the manufacturing of items in many industrial markets such as electronics, telecommunications, medical, aerospace, glass, and optical. Unlike traditional adhesives, UV light curing adhesives not only bond materials together but they can also be used to seal and coat products.

Emulsion adhesives

Milky-white dispersions often based on polyvinyl acetate(PVA). Used extensively in the woodworking and packaging industries. Also used with fabrics and fabric-based components, and in engineered products such as loudspeaker cones.

Hot adhesives

Hot adhesives, also known as hot melt adhesives, are simply thermoplastics applied in molten form (in the 65-180 C range) which solidify on cooling to form strong bonds between a wide range of materials. These adhesives are popular for crafts because of their ease of use and the wide range of common materials they can join. A glue gun (shown at right) is one method of applying hot adhesives. The glue gun melts the solid adhesive, then allows the liquid to pass through its barrel onto the material, where it solidifies.

Stress strain graph of thermoplastic material

Paul E. Cope is reputed to have invented thermoplastic glue around 1940 while working for Procter & Gamble as a chemical and packaging engineer. His invention solved a problem with water-based adhesives that were commonly used in packaging at that time. Water-based adhesives often failed in humid climates, causing packages to open and become damaged.

Contact adhesives

Contact adhesives must be applied to both surfaces and allowed some time to dry before the two surfaces are pushed together. Some contact adhesives require as long as 24 hours to dry before the surfaces are to be held together.Once the surfaces are pushed together, the bond forms very quickly.It is usually not necessary to apply pressure for a long time, so there is no need to use clamps.

Natural rubber and polychloroprene (Neoprene) are commonly used contact adhesives. Both of these elastomers undergo strain crystallization. Contact adhesives are used in strong bonds with high sheer-resistance like laminates, such as bonding Formica to a wooden counter, and in footwear, such as attaching an outsole to an upper.

Synthetic adhesives

Elastomers, thermoplastics, Emulsion, and thermosetting adhesives based on polyvinyl acetate, epoxy, polyyurethane, cynoacrylate polymers are examples of synthetic adhesives.

Natural Adhesives

Animal glue in granules

Natural adhesives are made from inorganic mineral sources, or biological sources such as vegetable matter, strach (dextrin), natural resins or from animals e.g.animal glue. They are often referred to as bioadhesives. One example is a simple paste made by cooking flour in water. Animal glues are traditionally used in bookbinding, wood joining, and many other areas but now are largely replaced by synthetic glues. Casein are mainly used in glass bottle labelling. Starch based adhesives are used in corrugated board production and paper sack production, paper tube winding, wall paper adhesives. Another form of natural adhesive is blood albumen (made from protein component of blood), which is used in the plywood industry. Animal glue remains the preferred glue of the luthier.

History of Adhesive

The English word glue was loaned from French in the late medieval period, ultimately from Late Latin glus, glutem "glue", replicing Old English lím.

The oldest known adhesive, dated to approximately 200,000 BC, is from spear stone flakes glued to a wood with birch-bark-tar, which was found in central Italy. The use of compound glues to haft stone spears into wood dates back to round 70,000 BC. Evidence for this has been found in Sibudu Cave, South Africa and the compound glues used were made from plant gum and red ochre The Tyrolean Iceman had weapons fixed together with the aid of glue.

6000-year-old ceramics show evidence of adhesives based upon animal glues made by rendering animal products such as horse teeth. During the times of Babylonia, tar-like glue was used for gluing statues. The Egyptians made much use of animal glues to adhere furniture, ivory, and papyrus. The Mongols also used adhesives to make their short bows, and the Natives Americans of the eastern United States used a mixture of spruce gum and fat as adhesives to fashion waterproof seams in their birchbark canoes.

In medieval Europe, egg whites were used as glue to decorate parchments with gold leaf. The first actual glue factory was founded in Holland in the early 1700s. In the 1750s, the English introduced fish glue. As the modern world evolved, several other patented materials, such as bones, starch, fish, and casein, were introduced as alternative materials for glue manufacture. Modern glues have improved flexibility, toughness, curing rate, and chemical resistance.

Adhesive

An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together.

Nitrocellulose adhesive outside a tube

Adhesives may come from either natural or synthetic sources. Some modern adhesives are extremely strong, and are becoming increasingly important in modern construction and industry. The types of materials that can be bonded using adhesives are virtually limitless, but they are especially useful for bonding thin materials. Adhesives usually require a controlled temperature to cure or set. They can be electrically and thermally conductive or non-conductive. The earliest date for a simple glue is 200,000 BC and for a compound glue 70,000 BC.

Biopolymer DNA

Biopolymers are polymers produced by living organisms. Cellulose, strarch and chitin, proteins and peptides, and DNA and RNA are all examples of biopolymers, in which the monomeric units, respectively, are sugars, animo acids, and nucleoties.

DNA is a biopolymer

is Cellulose is a biopolymer

Cellulose is both the most common biopolymer and the most common organic compound on Earth. About 33 percent of all plant matter is cellulose (the cellulose content of cotton is 90 percent and that of wood is 50 percent).

Types of Wood

The materials for most projects will fall into three categories: softwood, hardwood and manufactured panels such as plywood.

What you use for any given project depends on various factors: strength, hardness, grain characteristics, cost, stability, weight, color, durability and availability. Usually beginning woodworkers start out with a softwood such as pine. It's soft and easy to work so you don't need expensive tools to get good results. It is readily available at local lumberyards and home centers. It has it's limitations in furniture making, it is a soft wood and will damage easily.

Softwood Lumber

Softwood is from an evergreen or coniferous (cone-bearing) tree. Common varieties are pine, fir, spruce, hemlock, cedar and redwood. These woods are mostly used in the home construction industry. Cedar and redwood are excellent choices for outdoor projects, while pine is often used for "Early American Country Style" furniture.

Pine and most other softwoods will absorb and lose moisture more than hardwoods so are not as stable. Purchase the lumber at least two weeks before starting your project and keep it indoors. Place stickers (small pieces of scrap wood) between the boards to permit good air circulation around each piece of stock. This will allow the wood to reach an equilibrium with the indoor environment which reduces the likelihood of dramatic wood movement after a project is complete.

You will generally find only two grades at most suppliers: select and No. 2 common. The common grade allows tight, solid knots in the face of the board. For furniture applications the select grade is the better choice as it is free from most knots, though tight pin knots and small resin pockets are allowed.

You can achieve a more uniform stained surface by applying a wood conditioner to pine first, it's a good idea to run a test first on an inconspicuous part of your project to make sure you're happy with the results.

You will find that softwoods are sold in standard thickness and widths, for example a 1 X 4 will be 3/4" thick and 3 1/2" wide similar to construction materials. The material will usually be priced per lineal foot and the price will increase accordingly for the wider boards.

Panels made from strips glued together and sold as shelving are also available, these range from 12 to 24 inches wide and 2 to 8 feet in length.

Hardwood Lumber

Hardwood lumber comes from deciduous trees, the ones that shed their leaves annually. Popular domestic species are oak, maple, cherry, birch, walnut, ash and poplar. Of these common native hardwoods, only red oak and poplar are usually stocked in home centers and lumberyards, the others have to be obtained from speciality stores. The material stocked at home centers and lumberyards is usually sold in similar dimensions to softwood and by the lineal foot as well.

At speciality stores the thickness of hardwood lumber is specified in quarters of an inch, measured when the wood is in a rough state. The thinnest stock is 4/4, representing 1 in., and the thickest usually available is 16/4, representing 4 in. Rather than being milled to specified dimensions, like pine, hardwoods are sold in random widths and lengths.

Hardwoods are sold by the board foot, which is defined as a square foot of rough lumber that is 1 in. thick. If a board is thicker than 1 in., the dealer multiplies the square footage by the thickness to arrive at the sale price. An 8/4 board will therefore cost twice as much as a 4/4 board of the same size.

Working with hardwoods is quite different from working with pine, you cannot drive a screw through hardwood lumber without first boring a pilot hole. Cutting and planing hardwoods requires extremely sharp tools.

Plywood and Manufactured Sheets

You will likely be working with either plywood, consisting of an uneven number of alternating layers of wood, or a type of manufactured sheet.

Plywood and manufactured sheets often come in thicknesses that actually measure thinner than standard dimensions, for example a 1/4" router bit will be too wide you will need a 15/64" bit to cut a dado to fit it.

The two most common manufactured sheets goods used in furniture making are MDF (Medium Density Fiberboard) and Particle Board. Both are made from wood particles, combined with glue and bonded under pressure. MDF has finer particles than Particle Board so produces a smoother and stronger finished product.

MDF machines very well and is often used for moulded components on painted furniture. Its main draw back is that it is a very heavy product compared to real wood.

Hardwoods are also commonly used as outer veneers on manufactured sheets. These veneers are extremely thin sheets of wood that are glued to a panel core of plywood or particleboard. Such panels are usually 4'x 8' sheets, but they are available in other sizes, for example Baltic Birch is sold in 5' widths. Their thicknesses range from 1/8 inch to over 1 inch.

Because of their laminated construction, they are extremely stable in all dimensions. Since the veneers on any given panel are usually cut sequentially from the same log, the panel should display a uniform color and grain. Matching the grain pattern of solid wood to the generally uniform grain pattern on the panels can be difficult. But careful planning can yield good matches in the most visible areas of your project.

Manufactured sheets do have limitations, whenever they are used, regardless of the core, the edge must be hidden and the veneers on the surface are extremely thin, often less than 1/32 in. Because of this, the surface is fragile and has a tendency to split out, especially on the back side of a saw cut. Also, since the veneer is so thin aggressive sanding can quickly work through the veneer and expose the unattractive core underneath.

Types of Glass

	Typical container glass	Typical float glass	Approximate limits
SiO2	74.42	71.86	63-81
Al2O3	0.75	0.08	0-2
MgO	0.30	5.64	0-6
CaO	11.27	9.23	7-14
Li2O	0.00	0.00	0-2
Na2O	12.9	13.13	9-15
K2O	0.19	0.02	0-1.5
Fe2O3	0.01	0.04	0-0.6
Cr2O3	0.00	0.00	0-0.2
MnO2	0.00	0.00	0-0.2
Co3O4	0.00	0.00	0-0.1
TiO2	0.01	0.01	0-0.8
SO3	0.16	0.00	0-0.2
Se	0.00	0.00	0-0.1

Soda-lime glass composition (containers, float glass e.g. for windows), mol%

Approximate E glass composition in mol%:

	Typical E glass	Approximate limits
SiO2	56.99	43-74
B2O3	6.12	0-8.5
Al2O3	8.78	6-10
MgO	6.50	0.5-9
CaO	19.64	15-28
Na2O	0.61	0-2.5
K2O	0.00	0-0.5
Fe2O3	0.13	0-0.3
TiO2	0.44	0-1
F	0.70	0-2

TV panel glass composition, in mol %

	Typical TV panel glass	Approximate limits
SiO2	71.93	62-85
Al2O3	1.42	0.5-2.5
MgO	0.00	0-2.7
CaO	0.06	0-4.5
SrO	6.23	0.5-7.5
BaO	4.23	0.5-6.5
Li2O	0.02	0-1.5
Na2O	8.66	6-11
K2O	5.63	4-7
Fe2O3	0.02	0-0.02
TiO2	0.38	0-0.5
CeO2	0.11	0-0.3
ZrO2	0.79	0-2
PbO	0.00	0-1
ZnO	0.44	0-1.5
As2O3	0.00	0-0.1
Sb2O3	0.07	0-0.2
F	0.00	0-3

Futher borosilicate glass compositions

Low expansion borosilicate glass, e.g. Pyrex ^TM, Kimax ^TM, Duran ^TM, or Jenaer Glas ^TM, approximate glass composition in mol%:

	Typical low expansion borosilicate glass	Approximate limits
SiO2	83.34	65-85
B2O3	11.19	8-15
Al2O3	1.33	1-5
CaO	0.03	0-2.5
Na2O	4.08	3-9
K2O	0.04	0-2
BaO	0.00	0-1

Fiber wool borosilicate glass, approximate composition in mol%:

	Typical fiber wool borosilicate glass	Approximate limits
SiO2	63.51	50-78
B2O3	2.89	2.5-9
Al2O3	2.92	0-4
MgO	5.22	1.5-8
CaO	8.97	5-15
Na2O	15.70	12-18
K2O	0.54	0-1.5
Fe2O3	0.12	0-0.3
F	0.00	0-2.5
SO3	0.13	0-0.2