Amorphous selenium is red in powder form and is black in vitreous form. Gray crystalline 'metallic' selenium conducts electricity better in the light than in the dark (photoconductive) and it can convert light directly into electricity (photovoltaic). read more. 08 Dec, 2019. Selenium. Selenium with a lattice-type crystalline structure is a deep red glassy solid. Selenium also occurs inОнлайн-запрос
Red amorphous selenium is obtained by precipitating selenium from a solution of selenious acid in methanol or ethanol with hydrazine or a soluble salt thereof at a temperature between about -20° C. and the freezing point of the solution. Furthermore, the stable red amorphous selenium may contain a
Red amorphous selenium is colloidal and is formed in reduction reactions (Hoffmann and King 1997). Important selenium oxidation states are -2, 0, +4, and +6. The chemical properties of selenium are similar to sulfur. Selenium combines with metals and many nonmetals directly or in aqueous solution. The selenides resemble sulfides in appearance, composition, and properties (Hoffmann and King
22/02/1977· Red amorphous selenium is obtained by precipitating selenium from a solution of selenious acid in methanol or ethanol with hydrazine or a soluble salt thereof at a temperature between about -20° C. and the freezing point of the solution. Furthermore, the stable red amorphous selenium may contain a halogen.Онлайн-запрос
as-prepared amorphous, red selenium: Abbreviation Variation Long Form Variation Pair(Abbreviation/Long Form) Variation No. Year Title Co-occurring Abbreviation ; 1 : 2014: Colloidally stable [email protected] selenide [email protected] nanoparticles as selenium source for manufacturing of copper-indium-selenide solar cells.Онлайн-запрос
08/06/2001· The red, amorphous selenium has a deformed chain structure, high resistivity (ρ=10 13 –10 16 Ω cm) and upon heat treatment transforms to stable hexagonal modification. In recent years, the great interest in various allotropes of selenium and their interconversion is due to its use in electronics and solid-state technology [9] , [10] , [13] , [16] .
We use a new approach to generate amorphous selenium structures by an ab initio molecular dynamics method. We start with crystalline cubic supercells in a diamond-like structure with 64, 150 and 216 atoms, and with the experimental microscopic densities of ρ = 0.0324 (4.25 g cm −3) and ρ = 0.0340 atoms Å −3 (4.45 g cm −3).The samples are amorphized using DMol 3 from the suite in
Amorphous Selenium (a-Se) Many of the detector systems being developed in our lab use a photoconductor called amorphous Selenium (a-Se) as the X-ray detector material, i.e. the material which 'catches the X-rays', and converts them to either charge or lower energy photons. On this page we describe photoconductors and compare them with phosphor screens, and discuss why we choose toОнлайн-запрос
Selenium forms several allotropes that interconvert with temperature changes, depending somewhat on the rate of temperature change. When prepared in chemical reactions, selenium is usually an amorphous, brick-red powder.When rapidly melted, it forms the black, vitreous form, usually sold commercially as beads. The structure of black selenium is irregular and complex and consists of
Red amorphous selenium is obtained by precipitating selenium from a solution of selenious acid in methanol or ethanol with hydrazine or a soluble salt thereof at a temperature between about -20° C. and the freezing point of the solution. Further, the stable red amorphous may contain thallium which may then contain a halogen.Онлайн-запрос
Selenium, 4, 6, 50 amorphous Selenium exists in several allotropic forms.Three are generally recognized, but as many as that have been claimed.Selenium can be prepared with either an amorphous or crystalline structure.The color of amorphous selenium is either red, in powder form, or black, in vitreous form.Онлайн-запрос
Selenium can be prepd with either amorphous or crystalline structure. Amorphous is either red, in powder form or black, in vitreous form. Crystalline monoclinic selenium is deep red; crystalline hexagonal form, the most stable variety, is a metallic gray. CRC Handbook of Chemistry and Physics 88TH Edition 2007-2008 . Find more information on this substance at: PubChem, PubMed. PDFОнлайн-запрос
08/02/1977· Red amorphous selenium is obtained by precipitating selenium from a solution of selenious acid in methanol or ethanol with hydrazine or a soluble salt thereof at a temperature between about -20° C. and the freezing point of the solution. Further, the stable red amorphous may contain thallium which may then contain a halogen. Inventors: Buckley, David A. (Rochester, NY) ApplicationОнлайн-запрос
01/02/2008· In terms of sensitivity and SN ratio, amorphous selenium (a-Se) is known to be one of the best candidates among other photoconductive target. Combined with a-Se, a diamond cold cathode would be one of the best options in order to steadily emit electrons under low vacuum. The a-Se film is modified with Arsenic (As) and Tellurium (Te) to prevent crystallization and narrow the optical gap for redОнлайн-запрос
18/09/2019· Have you ever wondered why selenium is found in the form of biconcave disc? Well, in this video I will tell you this secret.
01/02/2010· We use a new approach to generate amorphous selenium structures by an ab initio molecular dynamics method. We start with crystalline cubic supercellsОнлайн-запрос
Amorphous selenium (a-Se) is a promising material for a high-sensitivity photodetector that has low thermal noise and a wide detectable wavelength range that covers visible to the UV [11], as well as X-rays [2–4]. The high sensitivity of a-Se based photodetector is explained by signal enhancement due to an internal carrier multiplication: this effect leads to quantum efficiency of greaterОнлайн-запрос
Grey crysstalline selenium Grey selenium in glass sphere. Crystals of gray Selenium. Granules of amorphous selenium (4N) Ingot of amorphous selenium (99.5+%) Ingot of glassy selenium. Red selenium. Selenium rectifiers. Directionally solidified grey Selenium. Monoclinic Selenium crystals. Has dark red color in transmitting light.Онлайн-запрос
19/07/2016· Selenium toxicity is generally not a widespread threat to humans. The Agency for Toxic Substances and Disease Registry assigned selenium a “minimal” risk level. In fact, selenium deficiency is far more common than selenium toxicity. Selenium is usually excreted from the body naturally within 24 hours, although rare exceptions do occur.Онлайн-запрос
Red amorphous selenium is obtained by precipitating selenium from a solution of selenious acid in methanol or ethanol with hydrazine or a soluble salt thereof at a temperature between about -20° C. and the freezing point of the solution. Further, the stable red amorphous may contain thallium which may then contain a halogen.Онлайн-запрос
Abstract A novel solution growth methodology for fabrication of amorphous, red selenium thin films and their conversion to the hexagonal, gray modification is presented. The method is based on deposition process from aqueous solution of selenosulfate by citric or ascorbic acid as oxidizing agents. The X-ray diffraction method is used for identification of the deposited materials.Онлайн-запрос
Selenium can be prepd with either amorphous or crystalline structure. Amorphous is either red, in powder form or black, in vitreous form. Crystalline monoclinic selenium is deep red; crystalline hexagonal form, the most stable variety, is a metallic gray. CRC Handbook of Chemistry and Physics 88TH Edition 2007-2008 . Find more information on this substance at: PubChem, PubMed. PDFОнлайн-запрос
Selenium is a non metallic chemical element exists in several allotropic forms, although three are generally recognized. In chemical activity and physical properties it resembles sulfur and tellurium. It can be prepared with either an amorphous or a crystalline structure. The color of amorphous selenium is either red (in powder form) or black (in vitreous form).Онлайн-запрос
25/09/2020· Amorphous or red: Has a brick-red color, as is the most common form of selenium obtained from chemical reactions. Black: Also known as vitreous selenium, this form is a dull grey solid, obtained by rapidly melting its amorphous form. The structure of black selenium is irregular and complex, consisting of polymeric rings.Онлайн-запрос
18/09/2019· Have you ever wondered why selenium is found in the form of biconcave disc? Well, in this video I will tell you this secret.
Grey crysstalline selenium Grey selenium in glass sphere. Crystals of gray Selenium. Granules of amorphous selenium (4N) Ingot of amorphous selenium (99.5+%) Ingot of glassy selenium. Red selenium. Selenium rectifiers. Directionally solidified grey Selenium. Monoclinic Selenium crystals. Has dark red color in transmitting light.Онлайн-запрос
01/03/1999· The orange-red amorphous allotrope produced by the bacterial cells was stable for months in aged cultures, as was the chemically reduced selenium in a cell-free spent medium obtained from a stationary-phase selenite-containing culture. In contrast, selenite reduced by thioglycolate in fresh medium was converted to a black form within a few days (data not shown).
In case of amorphous selenium, the position of T e appears to be driven more by viscous flow (in combination with surface tension) at low temperatures. Thus, the activation energy determined from the TMA measurements at low q + gets closer to E η. There are of course many consequences associated with the temperature variation of crystallization activation energies. In the last part of theОнлайн-запрос