KOSEN 한인과학기술자네트워크

>안녕하세요. > >biofilm에 대해 실험을 진행중인데요, >관련 논문을 보면, borosilicate glass tube를 이용하여 >biofilm 형성을 측정하는 경우가 있는데요(사진촬영) >borosilicate glass tube가 쓰이는 이유에 대해 >알고 싶습니다.(재질의 특성같은 이유도 알려주셨으면 합니다) > >감사합니다(--)(__) 아래는 wikipedia의 설명인데요. biofilm과 연관된 내용은 없는 것 같군요. borosilicate glass는 투명하고 열에 강하며 화학적으로 산과 염기에도 내구성이 좋은 물질로서 pyrex 등 대부분의 반응용기로 이제품을 사용하는 것 같군요. Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are most well known for having very low coefficient of thermal expansion (~ 5 ×10-6 / °C at 20°C), making them resistant to thermal shock, more so than any other common glass. Borosilicate glass was first developed by German glassmaker Otto Schott in the late 19th century[1] and sold under the brand name "Duran" in 1893. After Corning Glass Works introduced Pyrex (more properly, "Pyrex®") in 1915, it became a synonym for borosilicate glass in the English-speaking world. Kimble-Kontessee[2] sells its own line of Kimax® brand borosilicate glass products. In 1998 American manufacturer World Kitchen, formerly the Corning consumer products division, changed its Pyrex kitchen brand glass products from borosilicate glass to tempered soda-lime glass[3], while European manufacturer Arc International continues the use of borosilicate glass in its Pyrex glass kitchen products. (See, e.g., http://www.arc-international-cookware.com/en/aboutus/pyrex-history.php). Thus Pyrex can refer to either soda-lime glass or borosilicate glass when discussing kitchen glassware, while Pyrex, Duran, and Kimax all refer to borosilicate glass when discussing laboratory glassware. Most borosilicate glass is clear. Colored borosilicate, for the art glass trade, was first widely brought onto the market in 1986 when Paul Trautman founded Northstar Glassworks[citation needed]. There are now a number of small companies in the U.S. and abroad that manufacture and sell colored borosilicate glass for the art glass market. In addition to the quartz, sodium carbonate, and calcium carbonate traditionally used in glassmaking, boron is used in the manufacture of borosilicate glass. Typically, the resulting glass composition is about 70% silica, 10% boron oxide, 8% sodium oxide, 8% potassium oxide, and 1% calcium oxide (lime). Though somewhat more difficult to make than traditional glass (Corning conducted a major revamp of their operations to make it), it is economical to produce because its superior durability, chemical and heat resistance finds excellent use in chemical laboratory equipment, cookware, lighting, and in certain cases, windows. Borosilicate glass has a very low thermal expansion coefficient, about one-third that of ordinary glass. This reduces material stresses caused by temperature gradients, thus making it more resistant to breaking. This makes it a popular material for objects like telescope mirrors, where it is essential to have very little deviation in shape. It is also used in the processing of high-level nuclear waste, where the waste is immobilised in the glass through a process known as vitrification (contrast with Synroc). Borosilicate glass begins to soften around 821 °C (1510°F); at this temperature, the viscosity of type 7740 Pyrex is 107.6 poise. [4] Borosilicate glass is less dense than ordinary glass. While more resistant to thermal shock than other types of glass, borosilicate glass can still crack or shatter when subject to rapid or uneven temperature variations. When broken, borosilicate glass tends to crack into large pieces rather than shattering (it will snap rather than splinter). Optically, borosilicate glasses are crown glasses with low dispersion (Abbe numbers around 65) and relatively low refractive indices (1.51?1.54 across the visible range). Physical properties A feature of DURAN® borosilicate glass, which makes it especially suitable for laboratory use, is its thermal resistance. The following individual properties are of particular importance. Temperature and thermal shock resistance when heated The maximum permissible operating temperature for DURAN® is 500°C. Above a temperature of 525°C the glass begins to “soften”, i.e. it begins to change from the solid state to the viscous state. DURAN® is not only highly resistant to chemical attack, but it also has a very low coefficient of thermal expansion and, as a result, a high resistance to thermal shock. This thermal shock resistance exceeds that of ordinary glass by a factor of three. That means that any change from hot to cold can be handled very well (up to Dt = 100K). The linear coefficient of expansion of DURAN® (20/300°C) is 3.3 · 10-6/K. That means that for an increase in temperature of 1K the glass only expands by 3.3 · 10-6 relative units of length. That is so minimal that hardly any stress is set up in the glass and the glass does not break when, for example, boiling water is poured into it. Temperature resistance at freezing temperatures DURAN® can be cooled down to the maximum possible negative temperature. That means that DURAN® is also suitable for use in liquid air (approx. -192°C). In general DURAN® products are recommended for use down to -70°C. When cooling down and thawing, care must be taken to avoid a temperature difference of more than 100K. When freezing substances in such items as DURAN® bottles or DURAN® test tubes, the container should only be filled to a maximum of ¾ of its capacity and it must be frozen on a 45°-angle. Use in the microwave DURAN® is suitable for use in microwaves Optical properties DURAN® borosilicate glass exhibits no significant absorption in the visible range of the spectrum. This means that the appearance of DURAN® is clear and colorless. In approximately the 310-2200nm range of the spectrum, the absorption of DURAN® is negligibly low. For work with light-sensitive substances the surface of the glass can be tinted brown with a diffusion color. This results in strong absorption in the short-wave region. For work with light-sensitive substances the surface of the glass can be tinted brown with a diffusion color. This results in strong absorption in the short-wave region. The absorption margin for tinted glass is at about 500nm. In photochemical processes the light transmission of DURAN® in the ultraviolet range is of particular importance. The degree of transmission in the UV range shows that photochemical reactions, for example chlorinations and sulfochlorinations, can be carried out. The chlorine molecule absorbs in the 280―400nm range and thus serves as a carrier of the radiation energy. Chemical properties The chemical resistance of DURAN® exceeds that of most metals and other materials even where long exposure times and temperatures in excess of 100°C are involved. Exposure to water and acids only results in the leaching out of very small amounts of mainly univalent ions from the glass. The resultant very thin layer of silica, with few pores in it, that is formed on the surface inhibits further attack. DURAN® is highly resistant to attack by water, neutral and acid salt solutions, strong acids and mixtures thereof, and also chlorine, bromine, iodine and organic substances. Only hydrofluoric acid, solutions containing fluorides such as ammonium fluoride, very hot phosphoric acid and strongly alkaline solutions attack the surface of the glass to an increasing extent at higher concentrations and temperatures.