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Selenium (pronounced /sɨˈlɛniəm/
si-LEN-ee-əm
or /sɨˈliːniəm/
si-LEE-nee-əm)
is a chemical
element with the atomic number 34,
represented by the chemical symbol Se,
an atomic mass
of 78.96. It is a nonmetal,
chemically related to sulfur
and tellurium, and
rarely occurs in its elemental state in nature.
Isolated
selenium occurs in several different forms, the most stable of which is a
dense purplish-gray semi-metal (semiconductor)
form that is structurally a trigonal polymer chain. It conducts electricity better
in the light than in the dark, and is used in photocells (see
section Allotropes
below). Selenium also exists in many non-conductive forms: a black glass-like allotrope, as
well as several red crystalline forms built of eight-membered ring molecules,
like its lighter cousin sulfur.
Selenium is found in economic
quantities in sulfide
ores such as pyrite,
partially replacing the sulfur in the ore matrix. Minerals that are
selenide or selenate compounds are also known, but are rare. The chief
commercial uses for selenium today are in glassmaking and in chemicals
and pigments. Uses in
electronics,
once important, have been supplanted by silicon semiconductor
devices.
Selenium salts are toxic in large amounts, but trace
amounts of the element are necessary for cellular function in most, if
not all, animals, forming the active center of the enzymes glutathione
peroxidase and thioredoxin
reductase (which indirectly reduce certain oxidized molecules in
animals and some plants) and three known deiodinase enzymes
(which convert one thyroid hormone
to another). Selenium requirements in plants differ by species, with
some plants, it seems, requiring none.
Selenium (Greek σελήνη selene meaning
"Moon") was discovered in 1817 by Jöns Jakob
Berzelius,who found the element associated with tellurium (named for
the Earth). It was discovered as a byproduct of sulfuric acid
production.
It came to medical notice later because of its
toxicity to humans working in industry. It was also recognized as an
important veterinary toxin. In 1954, the first hints of specific
biological functions of selenium were discovered in microorganisms.
Its essentiality for mammalian life was discovered in 1957. In the
1970s, it was shown to be present in two independent sets of enzymes. This was
followed by the discovery of selenocysteine in
proteins. During the 1980s, it was shown that selenocysteine is encoded
by the codon TGA.
The recoding mechanism was worked out first in bacteria and then in mammals (see SECIS element).
Growth
in selenium consumption was historically driven by steady development
of new uses, including applications in rubber compounding, steel alloying, and selenium
rectifiers. Selenium is also an essential material in the drums of
laser printers and copiers. By 1970, selenium in rectifiers had largely
been replaced by silicon,
but its use as a photoconductor in plain-paper copiers had become its
leading application. During the 1980s, the photoconductor application
declined (although it was still a large end-use) as more and more
copiers using organic photoconductors were produced. At the current
time, the largest use of selenium worldwide is in glass manufacturing,
followed by uses in chemicals and pigments. Electronics use, despite a
number of continued applications, continues to decline.
In the
late 1990s, the use of selenium (usually with bismuth) as an additive
to plumbing brasses to meet no-lead
environmental standards became important. At present, total world
selenium production continues to increase modestly.
Selenium
occurs naturally in a number of inorganic forms, including selenide, selenate, and selenite. In
soils, selenium most often occurs in soluble forms such as selenate
(analogous to sulfate), which are leached into rivers very easily by
runoff.
Selenium has a biological role, and it is found in
organic compounds such as dimethyl selenide, selenomethionine,
selenocysteine,
and methylselenocysteine.
In these compounds selenium plays a role analogous to that of sulfur.
Selenium
is most commonly produced from selenide in many sulfide ores, such as those of copper, silver, or lead. It is obtained as a
byproduct of the processing of these ores, from the anode mud of copper
refineries and the mud from the lead chambers
of sulfuric acid
plants. These muds can be processed by a number of means to obtain free
selenium.
Natural sources of selenium include certain
selenium-rich soils, and selenium that has been bioconcentrated
by certain plants. Anthropogenic sources of selenium include coal
burning and the mining and smelting of sulfide
Structure of trigonal selenium
Native
selenium is a rare mineral, which does not usually form good crystals,
but, when it does, they are steep rhombohedrons or tiny acicular
(hair-like) crystals.Isolation of selenium is often complicated by the
presence of other compounds and elements.
Most elemental selenium
comes as a byproduct of refining
copper or producing sulfuric acid.
Industrial
production of selenium often involves the extraction of selenium dioxide
from residues obtained during the purification of copper. Commonly,
production begins by oxidation with sodium carbonate
to produce selenium dioxide. The selenium dioxide is then mixed with
water and the solution is acidified
to form selenous
acid (oxidation
step). Selenous acid is bubbled with sulfur dioxide (reduction step) to give
elemental selenium.
Elemental selenium produced in chemical
reactions invariably appears as the amorphous red form: an insoluble,
brick-red powder. When this form is rapidly melted, it forms the black,
vitreous form, which is usually sold industrially as beads. The most
thermodynamically stable and densest form of selenium is the
electrically conductive gray (trigonal) form, which is composed of long
helical chains of selenium atoms (see figure). The conductivity of this
form is notably light-sensitive. Selenium also exists in three different
deep-red crystalline monoclinic forms, which are composed of Se8
molecules, similar to many allotropes of sulfur. However, selenium does
not exhibit the unusual changes in viscosity that sulfur undergoes when
gradually heated.
Selenium has six naturally occurring isotopes, five of which
are stable: 74Se, 76Se, 77Se, 78Se,
and 80Se. The last three also occur as fission products,
along with 79Se,
which has a half-life
of 295,000 years. The final naturally occurring isotope, 82Se,
has a very long half-life (~1020 yr, decaying via double
beta decay to 82Kr),
which, for practical purposes, can be considered to be stable.
Twenty-three other unstable isotopes have been characterized.
See
also Selenium-79
for more information on recent changes in the measured half-life of
this long-lived fission product, important for the dose calculations
performed in the frame of the geological disposal of long-lived radioactive waste.
Although it is toxic in large doses, selenium is an essential micronutrient for
animals. In plants, it occurs as a bystander mineral, sometimes in
toxic proportions in forage
(some plants may accumulate selenium as a defense against being eaten
by animals, but other plants such as locoweed require
selenium, and their growth indicates the presence of selenium in soil).
It is a component of the unusual amino acids selenocysteine
and selenomethionine.
In humans, selenium is a trace element
nutrient that functions as cofactor
for reduction of antioxidant enzymes
such as glutathione
peroxidases and certain forms of thioredoxin
reductase found in animals and some plants (this enzyme occurs in
all living organisms, but not all forms of it in plants require
selenium).
The glutathione
peroxidase family of enzymes (GSH-Px) catalyze certain reactions
that remove reactive oxygen species such as hydrogen peroxide
and organic hydroperoxides:
- 2 GSH + H2O2----GSH-Px → GSSG + 2 H2O
Selenium also plays a role in the functioning of the thyroid gland and in
every cell that utilizes thyroid hormone, by participating as a cofactor
for the three known thyroid hormone deiodinases, which
activate and then deactivate various thyroid hormones and their
metabolites. It may inhibit Hashimotos's
disease, in which the body's own thyroid cells are attacked as
alien. A reduction of 21% on TPO antibodies was reported with the
dietary intake of 0.2 mg of selenium.
Dietary selenium comes from
nuts, cereals, meat, fish, and eggs. Brazil nuts are the
richest ordinary dietary source (though this is soil-dependent, since
the Brazil nut does not require high levels of the element for its own
needs). In descending order of concentration, high levels are also found
in kidney, tuna, crab, and lobster.
The
human body's burden of selenium is believed to be in the 13-20 milligram
range.
Although selenium is an essential trace element,
it is toxic if taken in excess. Exceeding the Tolerable
Upper Intake Level of 400 micrograms per day can lead to selenosis
This 400 microgram Tolerable Upper Intake Level is based primarily on a
1986 study of five Chinese patients who exhibited overt signs of
selenosis and a follow up study on the same five people in 1992. The
1992 study actually found the maximum safe dietary Se intake to be
approximately 800 micrograms per day (15 micrograms per kilogram body
weight), but suggested 400 micrograms per day to not only avoid toxicity, but also to
avoid creating an imbalance of nutrients in the diet and to account for
data from other countries. The Chinese people who suffered from selenium
toxicity ingested selenium by eating corn grown in extremely
selenium-rich stony coal (carbonaceous shale). This coal was
shown to have selenium content as high as 9.1%, the highest
concentration in coal ever recorded in literature. A dose of selenium as
small as 5 mg per day can be lethal for many humans.
Reference
ranges for blood tests, showing selenium in purple in center
Symptoms
of selenosis include a garlic odor on the breath, gastrointestinal
disorders, hair loss, sloughing of nails, fatigue, irritability, and
neurological damage. Extreme cases of selenosis can result in cirrhosis of the
liver, pulmonary
edema, and death. Elemental selenium and most metallic selenides have
relatively low toxicities because of their low bioavailability.
By contrast, selenates
and selenites
are very toxic, having an oxidant mode of action similar to that of
arsenic trioxide. The chronic toxic dose of selenite for human beings is
about 2400 to 3000 micrograms of selenium per day for a long time. Hydrogen selenide
is an extremely toxic, corrosive gas. Selenium also occurs in organic
compounds such as dimethyl selenide, selenomethionine,
selenocysteine
and methylselenocysteine,
all of which have high bioavailability
and are toxic in large doses. Nano-size
selenium has equal efficacy, but much lower toxicity.
On April
19, 2009, twenty-one polo
ponies began to die shortly before a match in the United States Polo
Open. Three days later, a pharmacy released a statement explaining that
the horses had received an incorrect dose of one of the ingredients used
in a vitamin compound, with which the horses had been injected. Such
vitamin injections are common to promote recovery after a match. The
pharmacy did not initially release the name of the specific ingredient
due to ongoing law-enforcement and other investigations. Analysis of inorganic
compounds of the vitamin supplement indicated that selenium
concentrations were ten to fifteen times higher than normal in the
horses' blood
samples and 15 to 20 times higher than normal in their liver
samples. It was later confirmed that selenium was the ingredient in
question.
Selenium
poisoning of water systems may result whenever new agricultural
runoff courses through normally dry undeveloped lands. This process
leaches natural soluble selenium compounds (such as selenates) into the
water, which may then be concentrated in new "wetlands" as the water
evaporates. High selenium levels produced in this fashion have been
found to have caused certain congenital disorders in wetland birds.
Selenium
deficiency is relatively rare in healthy, well-nourished individuals.
It can occur in patients with severely compromised intestinal function,
those undergoing total
parenteral nutrition, and also on advanced-aged people (over 90).
Also, people dependent on food grown from selenium-deficient soil are
also at risk. However, although New Zealand has low
levels of selenium in its soil, adverse health effects have not been
detected.
Selenium deficiency may only occur when a low selenium
status is linked with an additional stress such as chemical exposure or
increased oxidant stress due to vitamin E deficiency.
There are
interactions between selenium and other nutrient such as iodine and vitamin E. The
interaction is observed in the etiology of many
deficiency diseases in animals and pure selenium deficiency is in fact
rare. The effect of selenium deficiency on health remains uncertain, in
particular, in relation to Kashin-Beck
disease.
- Cancer
Several studies have
suggested a possible link between cancer and selenium deficiency. One
study, known as the NPC, was conducted to test the effect of selenium
supplementation on the recurrence of skin cancers on selenium-deficient
men. It did not demonstrate a reduced rate of recurrence of skin
cancers, but did show a reduced occurrence of total cancers, although
without a statistically significant change in overall mortality.The
preventative effect observed in the NPC was greatest in those with the
lowest baseline selenium levels.In 2009 the 5.5 year SELECT study
reported that selenium and vitamin E supplementation, both alone and
together, did not significantly reduce the incidence of prostate cancer
in 35,000 men who "generally were replete in selenium at baseline". The
SELECT trial found that vitamin E did not reduce prostate cancer as it
had in the Alpha-Tocopherol, Beta Carotene (ATBC) study, but the ATBC
had a large percentage of smokers while the SELECT trial did not.. There
was a slight trend toward more prostate cancer in the SELECT trial, but
in the vitamin E only arm of the trial, where no selenium was given.
Dietary
selenium prevents chemically induced carcinogenesis in many rodent
studies. It has been proposed that selenium may help prevent cancer by
acting as an antioxidant
or by enhancing immune activity. Not all studies agree on the
cancer-fighting effects of selenium. One study of naturally occurring
levels of selenium in over 60,000 participants did not show a
significant correlation between those levels and cancer. The SU.VI.MAX
study concluded that low-dose supplementation (with 120 mg of ascorbic
acid, 30 mg of vitamin E, 6 mg of beta carotene, 100 µg of selenium, and
20 mg of zinc) resulted in a 30% reduction in the incidence of cancer
and a 37% reduction in all-cause mortality in males, but did not get a
significant result for females.However, there is evidence that selenium
can help chemotherapy treatment by enhancing the efficacy of the
treatment, reducing the toxicity of chemotherapeutic drugs, and
preventing the body's resistance to the drugs. Studies of cancer cells
in vitro showed that chemotherapeutic drugs, such as Taxol and
Adriamycin, were more toxic to strains of cancer cells grown in culture
when selenium was added.
In March 2009, Vitamin E (400 IU) and
selenium (200 micrograms) supplements were reported to affect gene
expression and can act as a tumor suppressor. Eric Klein, MD from the
Glickman Urological and Kidney Institute in Ohio said the new study
“lend credence to the previous evidence that selenium and vitamin E
might be active as cancer preventatives”.In an attempt to rationalize
the differences between epidemiological and in vitro studies and
randomized trials like SELECT, Klein said that randomized controlled
trials “do not always validate what we believe biology indicates and
that our model systems are imperfect measures of clinical outcomes in
the real world”.
- HIV/AIDS
Some research has
indicated a geographical link between regions of selenium-deficient
soils and peak incidences of HIV/AIDS infection. For
example, much of sub-Saharan
Africa is low in selenium. However, Senegal is not, and also
has a significantly lower level of AIDS infection than the rest of the
continent. AIDS appears to involve a slow and progressive decline in
levels of selenium in the body. Whether this decline in selenium levels
is a direct result of the replication of HIV or related more generally
to the overall malabsorption of nutrients by AIDS patients remains
debated.
Low selenium levels in AIDS patients have been directly
correlated with decreased immune cell count and increased disease
progression and risk of death. Selenium normally acts as an antioxidant, so low
levels of it may increase oxidative stress on the immune system leading
to more rapid decline of the immune system. Others have argued that
T-cell associated genes encode selenoproteins similar to human glutathione
peroxidase. Depleted selenium levels in turn lead to a decline in
CD4 helper T-cells,
further weakening the immune system.
Regardless of the cause of
depleted selenium levels in AIDS patients, studies have shown that
selenium deficiency does strongly correlate with the progression of the
disease and the risk of death.
- Tuberculosis
Some
research has suggested that selenium supplementation, along with other
nutrients, can help prevent the recurrence of tuberculosis.
- Diabetes
A well-controlled study showed that selenium intake is
positively correlated with the risk of developing type 2
diabetes. Because high serum selenium levels are positively
associated with the prevalence of diabetes, and because selenium
deficiency is rare, supplementation is not recommended in well-nourished
populations such as the U.S.
- Mercury
Experimental
findings have demonstrated a protective effect of selenium on methylmercury
toxicity, but epidemiological studies have been inconclusive in linking
selenium to protection against the adverse effects of methylmercury.
- Chemistry
Selenium is a catalyst in many chemical
reactions and is widely used in various industrial and laboratory
syntheses, especially organoselenium
chemistry. It is also widely used in structure determination of
proteins and nucleic acids by X-ray crystallography (incorporation of
one or more Se atoms helps with MAD
and SAD
phasing.)
- Manufacturing and materials use
The
largest use of selenium worldwide is in glass and ceramic manufacturing,
where it is used to give a red color to glasses, enamels and glazes as well as
to remove color from glass by counteracting the green tint imparted by
ferrous impurities.
Selenium is used with bismuth in brasses to replace more
toxic lead. It is also
used to improve abrasion resistance in vulcanized rubbers.
- Electronics
Because of its photovoltaic and photoconductive
properties, selenium is used in photocopying, photocells, light meters and solar cells. It was
once widely used in rectifiers.
These uses have mostly been replaced by silicon-based devices, or are
in the process of being replaced. The most notable exception is in power
DC surge
protection, where the superior energy capabilities of selenium
suppressors make them more desirable than metal oxide
varistors.
Sheets of amorphous selenium convert x-ray images to patterns
of charge in xeroradiography
and in solid-state, flat-panel x-ray cameras.
- Photography
Selenium is used in the toning of
photographic prints, and it is sold as a toner by numerous
photographic manufacturers including Kodak and Fotospeed.
Its use intensifies and extends the tonal range of black and white
photographic images as well as improving the permanence of prints.
Early
photographic light
meters used selenium
but this application is now obsolete.
The substance loosely
called selenium
sulfide (approximate formula SeS2) is the active
ingredient in some anti-dandruff shampoos.The selenium compound kills
the scalp fungus Malassezia,
which causes shedding of dry skin fragments. The ingredient is also
used in body lotions to treat Tinea versicolor
due to infection by a different species of Malassezia fungus.
- Nutrition
Selenium is used widely in vitamin preparations and
other dietary
supplements, in small doses (typically 50 to 200 micrograms per day
for adult humans). Some livestock feeds are fortified with
selenium as well.
Selenium may be measured in blood, plasma,
serum or urine to monitor excessive environmental or occupational
exposure, confirm a diagnosis of poisoning in hospitalized victims or to
assist in a forensic investigation in a case of fatal overdosage. Some
analytical techniques are capable of distinguishing organic from
inorganic forms of the element. Both organic and inorganic forms of
selenium are largely converted to monosaccharide conjugates
(selenosugars) in the body prior to being eliminated in the urine.
Cancer patients receiving daily oral doses of selenothionine may achieve
very high plasma and urine selenium concentrations.
Main
article: Evolution
of dietary antioxidants
Over three billion years ago,
blue-green algae were the most primitive oxygenic photosynthetic
organisms and are ancestors of multicellular eukaryotic algae. Algae
that contain the highest amount of antioxidant selenium, iodide, and
peroxidase enzymes were the first living cells to produce poisonous
oxygen in the atmosphere. It has been suggested that algal cells
required a protective antioxidant action, in which selenium and iodides,
through peroxidase enzymes, have had this specific role.Selenium, which
acts synergistically with iodine, is a primitive mineral antioxidant,
greatly present in the sea and prokaryotic cells, where it is an
essential component of the family of glutathione
peroxidase (GSH-Px) antioxidant enzymes; seaweeds accumulate high
quantity of selenium and iodine. In 2008, a study showed that iodide
also scavenges reactive oxygen species (ROS) in algae, and that its
biological role is that of an inorganic antioxidant, the first to be
described in a living system, active also in an in vitro assay with the
blood cells of today’s humans."
From about three billion years
ago, prokaryotic selenoprotein families drive selenocysteine evolution.
Selenium is incorporated into several prokaryotic selenoprotein families
in bacteria, archaea and eukaryotes as selenocysteine, where
selenoprotein peroxiredoxins protect bacterial and eukaryotic cells
against oxidative damage. Selenoprotein families of GSH-Px and the
deiodinases of eukaryotic cells seem to have a bacterial phylogenetic
origin. The selenocysteine-containing form occurs in species as diverse
as green algae, diatoms, sea urchin, fish and chicken. Selenium enzymes
are involved in utilization of the small reducing molecules glutathione and thioredoxin. One
family of selenium-containing molecules (the glutathione
peroxidases) destroy peroxide and repair damaged peroxidized cell
membranes, using glutathione. Another selenium-containing enzyme in some
plants and in animals (thioredoxin
reductase) generates reduced thioredoxin, a dithiol that serves as
an electron source for peroxidases and also the important reducing
enzyme ribonucleotide
reductase that makes DNA presursors from RNA precursors.
At
about 500 Mya, plants and animals began to transfer from the sea to
rivers and land, the environmental deficiency of marine mineral
antioxidants (as selenium, iodine, etc.) was a challenge to the
evolution of terrestrial life. Trace elements involved in GSH-Px and
superoxide dismutase enzymes activities, i.e. selenium, vanadium, magnesium, copper, and zinc, may have been lacking
in some terrestrial mineral-deficient areas.Marine organisms retained
and sometimes expanded their seleno-proteomes, whereas the
seleno-proteomes of some terrestrial organisms were reduced or
completely lost. These findings suggest that, with the exception of vertebrates, aquatic
life supports selenium utilization, whereas terrestrial habitats lead to
reduced use of this trace element Marine fishes and vertebrate thyroid
glands have the highest concentration of selenium and iodine. From about
500 Mya, freshwater and terrestrial plants slowly optimized the
production of “new” endogenous antioxidants such as ascorbic acid
(Vitamin C), polyphenols
(including flavonoids), tocopherols, etc. A
few of these appeared more recently, in the last 50–200 million years,
in fruits and flowers of angiosperm plants. In fact, the angiosperms
(the dominant type of plant today) and most of their antioxidant
pigments evolved during the late Jurassic period.
The
deiodinase isoenzymes
constitute another family of eukaryotic selenoproteins with identified
enzyme function. Deiodinases are able to extract electrons from iodides,
and iodides from iodothyronines. They are, thus, involved in
thyroid-hormone regulation, participating in the protection of thyrocytes
from damage by H2O2 produced for thyroid-hormone
biosynthesis.About 200 Mya, new selenoproteins were developed as
mammalian GSH-Px enzymes.
Chalcogen
compounds
Selenium forms two oxides: selenium dioxide
(SeO2) and selenium trioxide
(SeO3). Selenium dioxide is formed by the reaction of
elemental selenium with oxygen:
- Se8 + 8 O2
→ 8 SeO2
It is a polymeric solid that
forms monomeric SeO2 molecules in the gas phase. It dissolves
in water to form selenous
acid, H2SeO3. Selenous acid can also be made
directly by oxidising elemental selenium with nitric acid:
- 3 Se + 4 HNO3 → 3 H2SeO3 + 4 NO
Salts
of selenous acid are called selenites. These include silver selenite
(Ag2SeO3) and sodium selenite
(Na2SeO3).
Hydrogen sulfide
reacts with aqueous selenous acid to produce selenium
disulfide:
- H2SeO3 + 2 H2S
→ SeS2 + 3 H2O
Selenium disulfide
consists of 8-membered rings of sulfur atoms with selenium replacing
some of the sulfur atoms. It has an approximate composition of SeS2,
with individual rings varying in composition, such as Se4S4
and Se2S6. It has various applications, including
use in shampoo as an anti-dandruff agent, an
inhibitor in polymer chemistry, a glass dye, and a reducing agent in fireworks.
Unlike
sulfur, which forms a stable trioxide,
selenium trioxide is unstable and decomposes to the dioxide above 185
°C:
- 2 SeO3 → 2 SeO2 + O2
(ΔH = −54 kJ/mol)
Selenium trioxide may be synthesized by
dehydrating selenic
acid, H2SeO4, which is itself produced by the
oxidation of selenium dioxide with hydrogen peroxide:
- SeO2 + H2O2 → H2SeO4
Hot, concentrated selenic acid is capable of dissolving gold,
forming gold(III) selenate.
Selenium reacts with fluorine to form selenium
hexafluoride:
- Se8 + 24 F2 → 8 SeF6
Unlike its sulfur counterpart, sulfur
hexafluoride, however, SeF6 is more reactive and is a
toxic pulmonary irritant. It can cause frostbite and severe
irritation on contact with skin.
Other selenium halides include SeF4,
Se2Cl2, SeCl4, and Se2Br2.
Selenium dichloride (SeCl2), an important reagent in the
study of selenium chemistry, may be prepared in pure form by reacting
elemental selenium with SO2Cl2
in THF
solution. Some of the selenium oxyhalides, such as SeOF2, are
useful as nonaqueous solvents.
Like oxygen and sulfur, selenium
forms selenides with
metals. For example, reaction with aluminum forms aluminum selenide:
- 3 Se8 + 16 Al → 8 Al2Se3
Other selenides include mercury selenide
(HgSe), lead
selenide (PbSe), and zinc selenide
(ZnSe). An important selenide is copper
indium gallium selenide (Cu(Ga,In)Se2), a semiconductor.
Selenium
does not react directly with hydrogen; so hydrogen selenide,
the analogue of hydrogen sulfide and water, is prepared by first
reacting selenium with a metal to produce a selenide, and then protonating the
selenide anion with an acid to produce H2Se.
Tetraselenium
tetranitride, Se4N4, is an explosive orange
compound analogous to S4N4
It can be synthesized by the reaction of SeCl4 with [((CH3)3Si)2N]2Se
in dichloromethane
solution at −78 °C.
Selenium reacts with cyanides to yield selenocyanates.For
example:
- 8 KCN + Se8 → 8 KSeCN
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wide range of industries, like mold & die, aerospace, electronic,
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like to solve every problem from you. Please feel free to contact us,
its our pleasure to serve for you. BW product including: cutting tool、aerospace tool .HSS DIN Cutting tool、Carbide end mills、Carbide cutting tool、NAS Cutting tool、NAS986 NAS965 NAS897 NAS937orNAS907 Cutting Tools,Carbide end mill、disc milling cutter,Aerospace
cutting tool、hss
drill’Фрезеры’Carbide drill、High speed steel、Compound Sharpener’Milling cutter、INDUCTORS FOR PCD’CVDD(Chemical Vapor Deposition
Diamond )’PCBN
(Polycrystalline Cubic Boron Nitride) ’Core drill、Tapered end
mills、CVD Diamond
Tools Inserts’PCD
Edge-Beveling Cutter(Golden Finger’PCD V-Cutter’PCD Wood tools’PCD Cutting tools’PCD Circular Saw Blade’PVDD End Mills’diamond tool. INDUCTORS FOR PCD .
POWDER FORMING MACHINE
‘Single Crystal
Diamond ‘Metric
end mills、Miniature
end mills、Специальные
режущие инструменты ‘Пустотелое сверло
‘Pilot reamer、Fraises’Fresas con mango’
PCD (Polycrystalline
diamond) ‘Frese’POWDER
FORMING MACHINE’Electronics cutter、Step drill、Metal cutting saw、Double margin drill、Gun barrel、Angle milling cutter、Carbide burrs、Carbide tipped cutter、Chamfering tool、IC card engraving cutter、Side cutter、Staple Cutter’PCD diamond cutter specialized in
grooving floors’V-Cut
PCD Circular Diamond Tipped Saw Blade with Indexable Insert’
PCD Diamond Tool’
Saw Blade with Indexable Insert’NAS tool、DIN or JIS tool、Special tool、Metal slitting saws、Shell end mills、Side and face milling cutters、Side chip clearance saws、Long end mills’end mill grinder’drill grinder’sharpener、Stub roughing end mills、Dovetail milling cutters、Carbide slot drills、Carbide torus cutters、Angel carbide end mills、Carbide torus cutters、Carbide ball-nosed slot drills、Mould
cutter、Tool manufacturer.
Bewise Inc. www.tool-tool.com
よ
うこそBewise Inc.の
世界へお越し下さいませ、先ず御目出度たいのは新たな
情報を受け取って頂き、もっと各産業に競争力プラス展開。
弊社は専門なエンド・ミルの製造メーカーで、客先に色んな分野のニーズ、
豊富なパリエーションを満足させ、特にハイテク品質要求にサポート致します。
弊社は各領域に供給
できる内容は:
(1)精密
HSSエンド・ミルのR&D
(2)Carbide Cutting tools設計
(3)鎢鋼エンド・ミ
ル設計
(4)航空エ
ンド・ミル設計
(5)超高硬度エンド・ミル
(6)ダイヤモンド・エンド・ミ
ル
(7)医療用品エ
ンド・ミル設計
(8)自動車部品&材料加工向けエンド・ミル設計
弊社の製品の供給調達機能は:
(1)生活産業~ハイテク工業までのエンド・ミル設計
(2)ミクロ・エ
ンド・ミル~大型エンド・ミル供給
(3)小Lot生産~大量発注対応供給
(4)オートメーション整備調達
(5)スポット対応~流れ生産対応
弊社
の全般供給体制及び技術自慢の総合専門製造メーカーに貴方のご体験を御待ちしております。
Bewise
Inc. talaşlı imalat sanayinde en fazla kullanılan ve üç eksende (x,y,z)
talaş kaldırabilen freze takımlarından olan Parmak Freze imalatçısıdır.
Çok geniş ürün yelpazesine sahip olan firmanın başlıca ürünlerini
Karbür Parmak Frezeler, Kalıpçı Frezeleri, Kaba Talaş Frezeleri, Konik
Alın Frezeler, Köşe Radyüs Frezeler, İki Ağızlı Kısa ve Uzun Küresel
Frezeler, İç Bükey Frezeler vb. şeklinde sıralayabiliriz.
BW специализируется в
научных исследованиях и разработках, и снабжаем самым
высокотехнологичным карбидовым материалом для поставки режущих /
фрезеровочных инструментов для почвы, воздушного пространства и
электронной индустрии. В нашу основную продукцию входит твердый карбид /
быстрорежущая сталь, а также двигатели, микроэлектрические дрели, IC
картонорезальные машины, фрезы для гравирования, режущие пилы,
фрезеры-расширители, фрезеры-расширители с резцом, дрели, резаки форм
для шлицевого вала / звездочки роликовой цепи, и специальные нано
инструменты. Пожалуйста, посетите сайт www.tool-tool.com для
получения большей информации.
BW is specialized in
R&D and sourcing the most advanced carbide material with high-tech
coating to supply cutting / milling tool for mould & die, aero space
and electronic industry. Our main products include solid carbide / HSS
end mills, micro electronic drill, IC card cutter, engraving cutter,
shell end mills, cutting saw, reamer, thread reamer, leading drill,
involute gear cutter for spur wheel, rack and worm milling cutter,
thread milling cutter, form cutters for spline shaft/roller chain
sprocket, and special tool, with nano grade. Please visit our web www.tool-tool.com
for more info.