Graphite in pencils

These different structures lead to vastly different properties (and costs ) of the materials. You can see in Figure 7.23 that graphite forms layers. These layers flake off easily, which is why we use graphite in pencils. Diamond, on the other hand, has a much more stable structure, a structure so stable that... 

Fun fact We commonly refer to the graphite in pencils as pencil lead, but there s no lead (Pb) in there. The Romans did use lead for writing, but the practice didn t meike it much farther in history than that. The paint on the outside of pencils did, however,... 

Graphite is a modification of carbon. It takes its name from the Greek word grapho, to write, which alludes to the utilization of graphite in pencils. Graphite is soft and unctuous. It conducts electricity well and is immune to most acids. 

Pure substances can themselves be divided into two types elements and compounds. Copper is an example of an element, a substance that cannot be broken down into simpler substances. The graphite in pencils is also an element—carbon. No chemical transformation can decompose graphite into simpler substances it is pure carbon. All known elements are listed in the periodic table in the inside front cover of this book and in alphabetical order on the inside back cover of this book. 

FIGURE 1 -5 The graphite in pencils is composed of carbon, an element. 

Majac jet-piilverizer performance on natural graphite is given in Table 20-27. Graphite for pencils has 47, 83, 91, and 94 percent by weight smaher than 4, 9, 18, and 31 [Lm respectively. 

The USA used 37 ktonnes of natural graphite in 1989, nearly all imported in addition, over 300 ktonnes of graphite was manufactured. Natural graphite is used in refractories (27%), lubricants (17%), foundries (14%), brake linings (12%), pencils (5.3%), crucibles, retorts, stoppers, sleeves and nozzles (4.0%) etc. 

PEN blow-molded bottles, 20 50-51 Pencil leads, kaolin application, 6 688t, 696 Pencils, graphite in, 12 795 PEN copolymer bottles, 20 52 Pendant cationic azo dye, 9 423 Pendant chain polymers, fullerene,... 

CV of graphite (from pencil) electrode modified by surface adsorption of pfiosphomoiyWic acid in 0.5 M sulfuric add... 

Diamond and graphite are allotropes of carbon. The density of diamond is 3.5 g/cm3 and that of graphite is 2.2 g/cm3. Diamond is used to cut other hard materials such as glass because of its hardness. On the other hand, softer graphite is used in pencils. 

Diamonds, when cut, are sparkly and beautiful. They are also the hardest substance known. Graphite, which is used in pencils, is dull and gray and so soft you can write with it. About as different as you can get, right ... 

Graphite is used for the lead in pencils, as a dry lubricant, and as electrodes in arc lamps. Of course, carbon is a popular jewelry item (e.g., diamonds). 

Carbon is something we encounter every day. Graphite, which is pure carbon, is the lead in pencils. Diamonds are carbon and so is charcoal. Some hard coals are up to 98% carbon. Carbon is also present in all living things. Forests, for example, are made almost entirely of carbon-containing compounds. Carbon and carbon compounds are widely used as raw materials in industrial products. Many plastics, detergents, foods, and medicines are made from carbon-containing compounds. 

Some elements have several different forms. In the case of carbon, charcoal was the only recognized form until early in the nineteenth century. The name carbon actually comes from the Eatin word carbo, meaning charcoal. In 1812, Sir Humphry Davy used sunlight to set a diamond on fire. This demonstration, combined with his scientific explanation, proved that diamonds were made of pure carbon. Around the same time, Davy also showed that coal was another form of carbon. Graphite, which is the lead in pencils, is... 

The German mineralogist. A.G. Wemer. devised the name graphite from the Greek meaning to write, with reference to its use in pencils. 

Van der Waals bonds are very weak bonds formed by residual charges from the other types of chemical bonds. Graphite is probably the best example of the nature of Van der Waals bonds. The atoms in graphite s carbon layers are covalently bonded, but a weak residual charge attracts the layers to one another. Van der Waals bonds make graphite a very soft mineral, excellent for use in pencil lead. 

Carbon exists in a number of allotropic forms. Allotropes are forms of an element with different physical and chemical properties. Two allotropes of carbon have crystalline structures diamond and graphite. In a crystalline material, atoms are arranged in a neat orderly pattern. Graphite is found in pencil lead and ball-bearing lubricants. Among the noncrystalline allotropes of carbon are coal, lampblack, charcoal, carbon black, and coke. Carbon black is similar to soot. Coke is nearly pure carbon formed when coal is heated in the absence of air. Carbon allotropes that lack crystalline structure are amorphous, or without crystalline shape. 

Figure 5.15. Spectrum of graphite in No. 2 pencil lead obtained with Dilor microscope and 50 x objective. Five spectral segments with total acquisition time of 20 min 5 mW at sample, 100 pm slit, resolution of 4 cm .

An important exception to these generalizations about properties is graphite, an allotropic form of carbon. It has the layer structure shown in Figure 13-32c. The overlap of an extended Tr-electron network in each plane makes graphite an excellent conductor. The very weak attraction between layers allows these layers to slide over one another easily. Graphite is used as a lubricant, as an additive for motor oil, and in pencil lead (combined with clay and other fillers to control hardness). 

In Group 14, only carbon and tin exist as allotropes under normal conditions. For most of recorded history, the only known allotropes of carbon were diamond and graphite. Both are polymeric solids. Diamond forms hard, clear, colorless crystals, and was the first element to have its structure determined by x-ray diffraction. It has the highest melting point and is the hardest of the naturally occurring solids. Graphite, the most thermodynamically stable form of carbon, is a dark gray, waxy solid, used extensively as a lubricant. It also comprises the lead in pencils. 

Diamond is the hardest of all substances. Graphite, in contrast, is a slippery, soft solid most familiar to us as the lead in pencils. Both materials, in spite of their very different physical properties, contain only carbon atoms. The two substances differ solely in the nature of the carbon-carbon bonds holding them together. Diamond consists of a rigid three-dimensional network of atoms, with each carbon bonded to four other car-... 

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