Diamond knives
Encyclopedia
A diamond knife is a very sharp knife whose blade is made from diamond
. The cost is very high; diamond knives are used for scientific applications where an extremely sharp and long-lasting edge is essential.
evolved, it was also determined that metal knives made of standard histology or razor blades were too dull to cut ultrathin sections. The metal knives were soft and fragile and would lose their cutting edges when thin sections were required for transmission electron microscopy
. In 1959, Latta and Hartman discovered that the edge of broken glass could be used to cut thin sections of specimen. Glass knives
are very popular in ultramicrotomy
for trimming specimen blocks and cutting thin sections. However, some hard specimens, such as bone, plants, and thick-walled spores, are difficult to cut, even with a good glass knife, because the edge dulls too quickly. Humberto Fernández-Morán discovered that a gem-quality diamond could be used to fabricate a more durable knife for use in the microtomy process; diamond was a logical material to use since it is the hardest known material.
Diamond knives are both delicate and expensive, usually costing several thousand dollars. Natural gemstones used to produce diamond knives are usually pale yellow, of regular crystal structure and of the greatest possible purity. Diamond dust is used on a turning table to cleave large stones into smaller segments. The grinding process usually reduces the stones to 50% of their original weight. The diamond blade is then mounted into a soft metal shaft (Wood's metal
) and finally polished to a very sharp edge. The knife's edge is extremely sharp and free of imperfections, which helps to get accurate views of specimens at high magnifications with the transmission electron microscope (TEM). The shaft containing the final edge is then mounted in a metal trough, or "boat", and cemented, usually with an epoxy plastic.
Diamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
. The cost is very high; diamond knives are used for scientific applications where an extremely sharp and long-lasting edge is essential.
Diamond knives for ultramicrotomy
When the development of ultramicrotomyUltramicrotomy
Ultramicrotomy is a method for cutting specimen into extremely thin slices or sections, that can be viewed in a transmission electron microscope . Sections must be very thin because the 50 to 125kV electrons of the standard electron microscope cannot pass through biological material much thicker...
evolved, it was also determined that metal knives made of standard histology or razor blades were too dull to cut ultrathin sections. The metal knives were soft and fragile and would lose their cutting edges when thin sections were required for transmission electron microscopy
Transmission electron microscopy
Transmission electron microscopy is a microscopy technique whereby a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it passes through...
. In 1959, Latta and Hartman discovered that the edge of broken glass could be used to cut thin sections of specimen. Glass knives
Glass knife
A glass knife is a knife with a blade composed of glass. The cutting edge of a glass knife is formed from a fracture line, and is extremely sharp....
are very popular in ultramicrotomy
Ultramicrotomy
Ultramicrotomy is a method for cutting specimen into extremely thin slices or sections, that can be viewed in a transmission electron microscope . Sections must be very thin because the 50 to 125kV electrons of the standard electron microscope cannot pass through biological material much thicker...
for trimming specimen blocks and cutting thin sections. However, some hard specimens, such as bone, plants, and thick-walled spores, are difficult to cut, even with a good glass knife, because the edge dulls too quickly. Humberto Fernández-Morán discovered that a gem-quality diamond could be used to fabricate a more durable knife for use in the microtomy process; diamond was a logical material to use since it is the hardest known material.
Diamond knives are both delicate and expensive, usually costing several thousand dollars. Natural gemstones used to produce diamond knives are usually pale yellow, of regular crystal structure and of the greatest possible purity. Diamond dust is used on a turning table to cleave large stones into smaller segments. The grinding process usually reduces the stones to 50% of their original weight. The diamond blade is then mounted into a soft metal shaft (Wood's metal
Wood's metal
Wood's metal, also known as Lipowitz's alloy or by the commercial names cerrobend, bendalloy, pewtalloy or MCP 158, is a eutectic, fusible alloy with a melting point of approximately . It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. It...
) and finally polished to a very sharp edge. The knife's edge is extremely sharp and free of imperfections, which helps to get accurate views of specimens at high magnifications with the transmission electron microscope (TEM). The shaft containing the final edge is then mounted in a metal trough, or "boat", and cemented, usually with an epoxy plastic.