Glass made of silica and boron trioxide
Borosilicate glass
is a type of
glass
with
silica
and
boron trioxide
as the main glass-forming constituents. Borosilicate glasses are known for having very low
coefficients of thermal expansion
(?3 × 10
?6
K
?1
at 20 °C), making them more resistant to
thermal shock
than any other common glass. Such glass is subjected to less
thermal stress
and can withstand temperature differentials without
fracturing
of about 165 °C (300 °F).
[1]
It is commonly used for the construction of
reagent bottles
and
flasks
, as well as lighting, electronics, and cookware.
Borosilicate glass is sold under various trade names, including
Borosil
,
Duran
,
Pyrex
, Glassco, Supertek, Suprax, Simax, Bellco, Marinex (Brazil), BSA 60, BSC 51 (by NIPRO), Heatex, Endural,
Schott
,
Refmex
, Kimax, Gemstone Well, United Scientific, and MG (India).
Single-ended self-starting lamps are insulated with a
mica
disc and contained in a borosilicate glass gas discharge tube (arc tube) and a metal cap.
[2]
[3]
They include the
sodium-vapor lamp
that is commonly used in street lighting.
[4]
[5]
[2]
[3]
Borosilicate glass usually melts at about 1,650 °C (3,000 °F; 1,920 K).
History
[
edit
]
Borosilicate glass was first developed by German glassmaker
Otto Schott
in the late 19th century in
Jena
. This early borosilicate glass thus came to be known as
Jena glass
. After
Corning Glass Works
introduced
Pyrex
in 1915, the name became synonymous with borosilicate glass in the English-speaking world (since the 1940s, a sizable portion of glass produced under the Pyrex brand has also been made of
soda?lime glass
). Borosilicate glass is the name of a glass family with various members tailored to completely different purposes. Most common today is borosilicate 3.3 or 5.0x glass such as Duran, Corning33, Corning51-V (clear), Corning51-L (amber), International Cookware's NIPRO BSA 60, and BSC 51.
Manufacturing process
[
edit
]
Borosilicate glass is created by combining and melting
boric oxide
, silica sand,
soda ash
,
[6]
and alumina. Since borosilicate glass melts at a higher temperature than ordinary
silicate glass
, some new techniques were required for industrial production.
In addition to
quartz
,
sodium carbonate
, and
aluminium oxide
traditionally used in
glassmaking
,
boron
is used in the manufacture of borosilicate glass. The composition of low-expansion borosilicate glass, such as those laboratory glasses mentioned above, is approximately 80%
silica
, 13%
boric oxide
, 4%
sodium oxide
or
potassium oxide
and 2?3%
aluminium oxide
. Though more difficult to make than traditional glass due to its high melting temperature, it is economical to produce. Its superior durability, chemical and heat resistance finds use in
chemical
laboratory
equipment, cookware, lighting, and in certain kinds of windows.
The manufacturing process depends on the product geometry and can be differentiated between different methods like
floating
,
tube drawing
, or
molding
.
Physical characteristics
[
edit
]
The common type of borosilicate glass used for laboratory glassware has a very low
thermal expansion
coefficient (3.3 × 10
?6
K
?1
),
[7]
about one-third that of ordinary soda?lime glass. This reduces material stresses caused by temperature gradients, which makes borosilicate a more suitable type of glass for certain applications (see below).
Fused quartzware
is even better in this respect (having one-fifteenth the thermal expansion of soda?lime glass); however, the difficulty of working with fused quartz makes quartzware much more expensive, and borosilicate glass is a low-cost compromise. While more resistant to
thermal shock
than other types of glass, borosilicate glass can still crack or shatter when subjected to rapid or uneven temperature variations.
Among the characteristic properties of this glass family are:
- Different borosilicate glasses cover a wide range of different thermal expansions, enabling direct seals with various metals and alloys like
molybdenum
glass with a CTE (
coefficient of thermal expansion
) of 4.6,
tungsten
with a CTE around 4.0 and
Kovar
with a CTE around 5.0 because of the matched CTE with the sealing partner
- Allowing high maximum temperatures of typically about 500 °C (930 °F)
- Showing an extremely high chemical resistance in corrosive environments. Norm tests for example for
acid resistance
create extreme conditions and reveal very low impacts on glass
The
softening point
(temperature at which
viscosity
is approximately 10
7.6
poise
) of type 7740 Pyrex is 820 °C (1,510 °F).
[8]
Borosilicate glass is less
dense
(about 2.23 g/cm
3
) than typical soda?lime glass due to the low atomic mass of boron. Its mean specific heat capacity at constant pressure (20?100 °C) is 0.83 J/(g?K), roughly one fifth of water's.
[9]
The temperature differential that borosilicate glass can withstand before fracturing is about 330 °F (180 °C), whereas soda?lime glass can withstand only about a 100 °F (55 °C) change in temperature. This is why typical kitchenware made from traditional soda?lime glass will shatter if a vessel containing boiling water is placed on ice, but Pyrex or other borosilicate laboratory glass will not.
[1]
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).
Families
[
edit
]
For the purposes of classification, borosilicate glass can be roughly arranged in the following groups, according to their oxide composition (in
mass fractions
). Characteristic of borosilicate glasses is the presence of substantial amounts of silica (SiO
2
) and boric oxide (B
2
O
3
, >8%) as glass network formers. The amount of boric oxide affects the glass properties in a particular way. Apart from the highly resistant varieties (B
2
O
3
up to a maximum of 13%), there are others that ? due to the different way in which the boric oxide is incorporated into the structural network ? have only low chemical resistance (B
2
O
3
content over 15%).
[10]
Hence we differentiate between the following subtypes.
Non-alkaline-earth
[
edit
]
The B
2
O
3
content for borosilicate glass is typically 12?13% and the SiO
2
content over 80%. High chemical durability and low thermal expansion (3.3 × 10
?6
K
?1
) ? the lowest of all commercial glasses for large-scale technical applications ? make this a versatile glass material. High-grade borosilicate flat glasses are used in a wide variety of industries, mainly for technical applications that require either good thermal resistance, excellent chemical durability, or high light transmission in combination with a pristine surface quality. Other typical applications for different forms of borosilicate glass include glass tubing, glass
piping
, glass containers, etc. especially for the chemical industry.
Alkaline-earth
[
edit
]
In addition to about 75% SiO
2
and 8?12% B
2
O
3
, these glasses contain up to 5% oxides of
alkaline earth metal
and alumina (Al
2
O
3
). This is a subtype of slightly softer glasses, which have thermal expansions in the range (4.0?5.0) × 10
?6
K
?1
.
[11]
This is not to be confused with simple borosilicate glass-alumina composites.
[12]
High-borate
[
edit
]
Glasses containing 15?25% B
2
O
3
, 65?70% SiO
2
, and smaller amounts of alkalis and Al
2
O
3
as additional components have low softening points and low thermal expansion. Sealability to metals in the expansion range of tungsten and molybdenum and high electrical insulation are their most important features. The increased B
2
O
3
content reduces the chemical resistance; in this respect, high-borate borosilicate glasses differ widely from non-alkaline-earth and alkaline-earth borosilicate glasses. Among these are also borosilicate glasses that transmit UV light down to 180 nm, which combine the best of the borosilicate glass and the quartz world.
[10]
Uses
[
edit
]
Borosilicate glass has a wide variety of uses ranging from cookware to lab equipment, as well as a component of high-quality products such as implantable
medical devices
and devices used in
space exploration
.
Health and science
[
edit
]
Virtually all modern laboratory glassware is made of borosilicate glass. It is widely used in this application due to its chemical and thermal resistance and good optical clarity, but the glass can react with
sodium hydride
upon heating to produce
sodium borohydride
, a common laboratory reducing agent.
Fused quartz
is also found in some laboratory equipment when its higher melting point and transmission of UV are required (e.g. for tube furnace liners and UV
cuvettes
), but the cost and manufacturing difficulties associated with fused quartz make it an impractical investment for the majority of laboratory equipment.
Additionally, borosilicate tubing is used as the feedstock for the production of
parenteral
drug packaging, such as vials and pre-filled
syringes
, as well as
ampoules
and
dental cartridges
. The chemical resistance of borosilicate glass minimizes the migration of sodium ions from the glass matrix, thus making it well suited for
injectable-drug
applications. This type of glass is typically referred to as USP / EP JP Type I.
Borosilicate is widely used in implantable
medical devices
such as prosthetic eyes, artificial hip joints, bone cements, dental composite materials (white fillings)
[13]
and even in
breast implants
.
Many implantable devices benefit from the unique advantages of borosilicate glass encapsulation. Applications include
veterinary tracking devices
, neurostimulators for the treatment of epilepsy, implantable drug pumps,
cochlear implants
, and physiological sensors.
[14]
Electronics
[
edit
]
During the mid-20th century, borosilicate glass tubing was used to pipe coolants (often
distilled water
) through high-power
vacuum-tube
?based electronic equipment, such as commercial broadcast transmitters. It was also used for the envelope material for glass transmitting tubes which operated at high temperatures.
Borosilicate glasses also have an application in the
semiconductor industry
in the development of
microelectromechanical systems
(MEMS), as part of stacks of
etched
silicon
wafers
bonded to the etched borosilicate glass.
Cookware
[
edit
]
Cookware is another common usage for borosilicate glass, including bakeware. It is used for some measuring cups, featuring screen printed markings providing graduated measurements. Borosilicate glass is sometimes used for high-quality beverage glassware, particularly in pieces designed for hot drinks. Items made of borosilicate glass can be thin yet durable, or thicker for extra strength, and are
microwave
- and dishwasher-safe.
[15]
Lighting
[
edit
]
Many high-quality flashlights use borosilicate glass for the lens. This increases
light transmittance
through the lens compared to plastics and lower-quality glass.
Several types of
high-intensity discharge
(HID) lamps, such as
mercury-vapor
and
metal-halide lamps
, use borosilicate glass as the outer envelope material.
New
lampworking
techniques led to artistic applications such as contemporary glass
marbles
. The modern
studio glass
movement has responded to color. Borosilicate is commonly used in the
glassblowing
form of
lampworking
and the artists create a range of products such as
jewelry
,
kitchenware
,
sculpture
, as well as for artistic glass smoking pipes.
Lighting manufacturers use borosilicate glass in some of their lenses.
[
citation needed
]
Organic light-emitting diodes
(OLED) (for display and lighting purposes) also use borosilicate glass (BK7). The thicknesses of the BK7 glass substrates are usually less than 1 millimeter for OLED fabrication. Due to its optical and mechanical characteristics in relation with cost, BK7 is a common substrate in OLEDs. However, depending on the application,
soda?lime glass
substrates of similar thicknesses are also used in OLED fabrication.
Optics
[
edit
]
Many astronomical
reflecting telescopes
use glass mirror components made of borosilicate glass because of its low coefficient of thermal expansion. This makes very precise optical surfaces possible that change very little with temperature, and matched glass mirror components that "track" across temperature changes and retain the optical system's characteristics.
The Hale Telescope's
200 inch mirror
is made of borosilicate glass.
[16]
The optical glass most often used for making instrument
lenses
is
Schott
BK-7 (or the equivalent from other makers, such as the Chinese crown glass
K9
), a very finely made borosilicate
crown glass
.
[17]
It is also designated as 517642 glass after its 1.517 refractive index and 64.2
Abbe number
. Other less costly borosilicate glasses, such as Schott B270 or the equivalent, are used to make "
crown-glass
" eyeglass lenses. Ordinary lower-cost borosilicate glass, like that used to make kitchenware and even reflecting telescope mirrors, cannot be used for high-quality lenses because of the striations and
inclusions
common to lower grades of this type of glass. The maximal working temperature is 268 °C (514 °F). While it transitions to a liquid starting at 288 °C (550 °F) (just before it turns red-hot), it is not workable until it reaches over 538 °C (1,000 °F). That means that in order to industrially produce this glass, oxygen/fuel torches must be used. Glassblowers borrowed technology and techniques from welders.
Rapid prototyping
[
edit
]
Borosilicate glass has become the material of choice for
fused deposition modeling
(FDM), or fused filament fabrication (FFF), build plates.
[18]
Its low coefficient of expansion makes borosilicate glass, when used in combination with resistance-heating plates and pads, an ideal material for the heated build platform onto which plastic materials are extruded one layer at a time. The initial layer of build must be placed onto a substantially flat, heated surface to minimize shrinkage of some build materials (
ABS
,
polycarbonate
,
polyamide
, etc.) due to cooling after deposition. Depending on the material used, the build plate will cycle from room temperature to between 50 °C and 130 °C for each prototype that is built. The temperature, along with various coatings (
Kapton tape
, painter's tape, hair spray, glue stick, ABS+acetone slurry, etc.), ensure that the first layer may be adhered to and remain adhered to the plate, without warping, as the first and subsequent layers cool following extrusion. Subsequently, following the build, the heating elements and plate are allowed to cool. The resulting residual stress formed when the plastic contracts as it cools, while the glass remains relatively dimensionally unchanged due to the low coefficient of
thermal expansion
, provides a convenient aid in removing the otherwise mechanically bonded plastic from the build plate. In some cases the parts self-separate as the developed stresses overcome the adhesive bond of the build material to the coating material and underlying plate.
Other
[
edit
]
Aquarium heaters are sometimes made of borosilicate glass. Due to its high heat resistance, it can tolerate the significant temperature difference between the water and the
nichrome
heating element
.
[
citation needed
]
Specialty glass
smoking pipes
for
cannabis
and
tobacco
can be made from borosilicate glass. The high heat resistance makes the pipes more durable. Some
harm reduction
organizations also give out borosilicate pipes intended for smoking
crack cocaine
, as the heat resistance prevents the glass from cracking, causing cuts and burns that can spread
hepatitis C
.
[19]
Most premanufactured glass
guitar slides
are made of borosilicate glass.
[
citation needed
]
Borosilicate is also a material of choice for
evacuated-tube solar thermal technology
because of its high strength and heat resistance.
[
citation needed
]
The
thermal insulation tiles
on the
Space Shuttle
were coated with a borosilicate glass.
[20]
Borosilicate glasses are used for immobilisation and disposal of
radioactive wastes
. In most countries
high-level radioactive waste
has been incorporated into alkali borosilicate or phosphate vitreous waste forms for many years;
vitrification
is an established technology.
[21]
Vitrification is a particularly attractive immobilization route because of the high chemical durability of the vitrified glass product. The chemical resistance of glass can allow it to remain in a corrosive environment for many thousands or even millions of years.
Borosilicate glass tubing is used in specialty
TIG welding
torch nozzles in place of standard
alumina
nozzles. This allows a clear view of the arc in situations where visibility is limited.
[
citation needed
]
Trade names
[
edit
]
Borosilicate glass is offered in slightly different compositions under different trade names:
- Borofloat of
Schott AG
, a borosilicate glass, which is produced to flat glass in a
float process
.
- Borosil
, manufactured by the company of the same name, used in laboratory glassware and microwaveable kitchenware in India
- BK7 of Schott, a borosilicate glass with a high level of purity. Main use in lens and mirrors for laser, cameras and telescopes.
- Duran
of
DURAN Group
, similar to Pyrex, Simax or Jenaer Glas.
- Pyrex
borosilicate glass of
Corning
- Fiolax
of Schott, mainly used for containers for pharmaceutical applications.
- Ilmabor
of
TGI
[
de
]
(2014 insolvency), mainly used for containers and equipment in laboratories and medicine.
- Jenaer Glas
of
Zwiesel Kristallglas
, formerly Schott AG. Mainly used for kitchenware.
- Kimax is the trademark for borosilicate glassware from
Kimble
- United Scientific, manufacturers and distributors of laboratory glassware
- Rasotherm
of VEB Jenaer Glaswerk Schott & Genossen, for technical glass
- Simax of Kavalierglass a.s., Czechia, produced for both laboratory and consumer markets.
- Supertek, manufacturer of scientific lab equipment and glassware.
- Willow Glass
is an alkali free, thin and flexible borosilicate glass of
Corning
- Boroux
is a brand of borosilicate glass drinking bottles.
- Endural is a brand name of
Holophane
Borosilicate nanoparticles
[
edit
]
It was initially thought that borosilicate glass could not be formed into
nanoparticles
, since an unstable
boron oxide
precursor would prevent successful forming of these shapes. However, in 2008 a team of researchers from the Swiss
Federal Institute of Technology
at
Lausanne
were successful in forming borosilicate nanoparticles of 100 to 500
nanometers
in diameter. The researchers formed a
gel
of tetraethylorthosilicate and trimethoxyboroxine. When this gel is exposed to water under proper conditions, a dynamic reaction ensues, which results in the nanoparticles.
[22]
In lampworking
[
edit
]
Borosilicate (or "boro", as it is often called) is used extensively in the
glassblowing
process
lampworking
; the glassworker uses a burner torch to melt and form glass, using a variety of metal and
graphite
tools to shape it. Borosilicate is referred to as "hard glass" and has a higher melting point (approximately 3,000 °F / 1648 °C) than "soft glass", which is preferred for glassblowing by beadmakers. Raw glass used in lampworking comes in glass rods for solid work and
glass tubes
for hollow work tubes and vessels/containers. Lampworking is used to make complex and custom scientific apparatus; most major universities have a lampworking shop to manufacture and repair their glassware. For this kind of "scientific glassblowing", the specifications must be exact and the glassblower must be highly skilled and able to work with precision. Lampworking is also done as art, and common items made include goblets, paper weights, pipes, pendants, compositions and figurines.
In 1968, English metallurgist John Burton brought his hobby of hand-mixing metallic oxides into borosilicate glass to Los Angeles. Burton began a glass workshop at Pepperdine College, with instructor Margaret Youd. A few of the students in the classes, including Suellen Fowler, discovered that a specific combination of oxides made a glass that would shift from
amber
to purples and blues, depending on the heat and flame atmosphere. Fowler shared this combination with Paul Trautman, who formulated the first small-batch colored borosilicate recipes. He then founded Northstar Glassworks in the mid-1980s, the first factory devoted solely to producing colored borosilicate glass rods and tubes for use by artists in the flame. Trautman also developed the techniques and technology to make the small-batch colored boro that is used by a number of similar companies.
[23]
Beadmaking
[
edit
]
In recent years, with the resurgence of lampworking as a technique to make handmade glass beads, borosilicate has become a popular material in many glass artists' studios. Borosilicate for beadmaking comes in thin, pencil-like rods. Glass Alchemy, Trautman Art Glass, and Northstar are popular manufacturers, although there are other brands available. The metals used to color borosilicate glass, particularly silver, often create strikingly beautiful and unpredictable results when melted in an oxygen-gas torch flame. Because it is more shock-resistant and stronger than soft glass, borosilicate is particularly suited for pipe making, as well as sculpting figures and creating large beads. The tools used for making glass beads from borosilicate glass are the same as those used for making glass beads from soft glass.
References
[
edit
]
- ^
a
b
Brandt, R. C.; Martens, R. I. (September 2012),
"Shattering Glass Cookware"
,
American Ceramics Society Bulletin
, American Ceramics Society,
archived
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- ^
a
b
"The Low Pressure Sodium Lamp"
.
- ^
a
b
"The Low Pressure Sodium Lamp"
.
- ^
"Lighting Comparison: LED vs High Pressure Sodium/Low Pressure Sodium"
.
www.stouchlighting.com
.
- ^
"The Sodium Lamp ? How it works and history"
.
edisontechcenter.org
.
- ^
Spinosa, E. D.; Hooie, D. T.; Bennett, R. B. (1979).
Summary Report on Emissions from the Glass Manufacturing Industry
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- ^
"Borosilicato"
.
refmexgl.com
.
Archived
from the original on 2012-06-30
. Retrieved
2012-11-02
.
- ^
Weissler, G. L. (1979).
Vacuum Physics and Technology
(2 ed.). Academic Press. p. 315.
ISBN
978-0-12-475914-5
.
- ^
"Borosilikatglas BOROFLOAT® ? Thermische Produkteigenschaften"
.
www.schott.com
. Schott AG
. Retrieved
31 August
2018
.
- ^
a
b
"Technical glasses"
(PDF)
.
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. Retrieved
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.
- ^
Pires, Ricardo A.; Abrahams, Isaac; Nunes, Teresa G.; Hawkes, Geoffrey E. (2009). "The role of alumina in aluminoborosilicate glasses for use in glass?ionomer cements".
Journal of Materials Chemistry
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.
- ^
Lima, M.M.R.A.; Monteiro, R.C.C.; Graca, M.P.F.; Ferreira da Silva, M.G. (October 2012). "Structural, electrical and thermal properties of borosilicate glass?alumina composites".
Journal of Alloys and Compounds
.
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: 66?72.
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:
10.1016/j.jallcom.2012.05.024
.
- ^
R Wananuruksawong et al 2011 IOP Conf. Ser.: Mater. Sci. Eng. 18 192010 doi:10.1088/1757-899X/18/19/192010 Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material
- ^
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.
- ^
Estes, Adam Clark (March 16, 2019).
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.
Gizmodo
. Retrieved
2019-03-22
.
- ^
Angel, J. R. P. (1988).
"8 m Borosilicate Honeycomb Mirrors"
.
Very Large Telescopes and Their Instrumentation, Vol. 2
.
30
: 281.
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1988ESOC...30..281A
. Retrieved
14 February
2021
.
- ^
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.
Archived
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Reynolds, Sheila (2018-02-15).
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.
Swift Glass
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2022-08-05
.
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.
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"SPACE SHUTTLE ORBITER SYSTEMS THERMAL PROTECTION SYSTEM"
.
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2009-07-15
.
- ^
M. I. Ojovan and W.E. Lee. An Introduction to Nuclear Waste Immobilisation, Elsevier, Amsterdam, 315 p. (2005)
- ^
Chemical & Engineering News
Vol. 86 No. 37, 15 September 2008, "Making Borosilicate nanoparticles is now possible", p. 35
- ^
Robert Mickelsen, "Art Glass Lampworking History" Online Glass Museum,
http://www.theglassmuseum.com/lampwork.html
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