Page 18 - Chalcogenide Glasses for Infrared Optics
P. 18

Intr oduction   xvii

              described. Glasses have a major advantage over crystalline materials
              in that they can be easily cast, molded, extruded, and drawn into
              fiber. Such processes generally cannot be applied to crystalline
              materials but were applied to chalcogenide glasses.  Also, the
              composition of a glass can be changed within limits to enhance
              properties important to an application. Very little such latitude exists
              with crystals. The ratios among constituent atoms of most crystalline
              materials are fixed. Examples of how the composition of some glasses
              was changed at AMI to enhance a property will be discussed.
                 Comments to the readers who are students: The author considers
              himself a physical chemist. Chemistry is an applied science and mostly
              empirical. Tools used while conducting a research project have
              changed immensely since 1948 when this author started out, from
              slide rules and burets to computers, infrared FTIR spectrophotometers,
              Raman instruments, electron microscopes, and differential thermal
              analysis (DTA) for glasses. Lasers were not even invented until 1959.
              There was no material sciences school, only chemistry and physics.
              Chemical structural theories have changed greatly based on results
              from the new instruments and techniques. The language of science is
              constantly changing, reflecting people’s increased understanding,
              which improves their descriptions. Not nature! Nature never changes.
              Avoid having a preconceived solution to a problem before you start.
              Let nature guide you through the results of your experiments. Always
              remember, it is the investigation that is important, not the investigator.
              It is not important to be right at the start—only at the finish.
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