Commercial Phosphors

Particle (3) is the recrystalUzed product produced by liquid transport through the flux, from material transported from particles (1) and (2). 

The cathode-ray tube is now over 100 years old. In 1880, WiUiam Crookes had demonstrated that cathode-rays, i.e.- an electron beam, would cast sharp shadows on a fluorescent screen if a mask was present within the tube. It remained for Karl Braun to invent the device that changed the world, a working cathode-ray tube (CRT) having internal electrodes which 

In a cathode-ray tube, an electron-beam is generated within an electron-gun , and caused to sweep across a faceplate containing a phosphor screen . This screen is actually a uniform layer of phosphor particles deposited by special techniques. The beam paints a series of lines on the phosphor-screen to form a rectangle called a raster which emits visible light, as shown in 6.6.1. on the next page. 

The electron gun has a cathode which emits electrons. The electrons are controlled and bunched into a beam as it exits the electron gun. The deflection coil varies the motion of the electron beam, generated within the electron gun, to form the raster. The number of separate lines within the raster is about 525, but the separate rasters are interwoven so they overlap to form the complete picture. 

The raster on the phosphor screen is excited in real time so that we see moving pictures. The human eye has a movement perception of about 1/20 of a second so that the raster, reformed about every 1/30 of a second 

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Baker and Smith in their Research on the Eucalypts state, however, that correctly speaking no general formula can be given, as commercial phosphoric acid has not always the same concentration. They found that the mean cineol content in the perfectly dry powdery compound was 59 47 per cent. The theoretical mean for the cineol from the H3PO4 found was 59 56 per cent., thus being in very fair agreement. The results showed that 59 5 was approximately the amount of cineol in 100 parts of cineol-phosphate, and not 61 1 per cent, as was previously supposed. 

C12-0081. Commercial phosphoric acid is 85% by mass H3 PO4 and 15% water. The density of the acid... 

Nonradiative energy transfer is very often used in practical applications, such as to enhance the efficiency of phosphors and lasers. A nice example is the commercial phosphor Cas(P04)3 (FCl), which is doubly activated by Sb + and Mn + ions. When the phosphor is singly activated by Mn + ions, it turns out to be very inefficient, due to the weak absorption bands of the divalent manganese ion. However, coactivation with Sb + ions produces a very intense emission from the Mn + ions, because the Sb + ions (the donor centers) efficiently absorb the ultraviolet emission (253.6 nm) of... 

Transition metal (TM) ions are frequently used as optically active dopants in commercial phosphors and in tunable sohd state lasers. TM ions are formed from atoms in the... 

Table III.—The Composition op Some Commercial Phosphoric Acids.

The materials included in this chapter for illustration are nanocomposite polymers combined with intumescent commercial phosphorous fire retardants. In this chapter, different base polymers (e.g., PA6, PBT, PP, and EVA) are mentioned for illustrating the methodology but the focus will be on PA6. For the present purpose, the composition of a PA6 nanocomposite is described next to make the development of the present methodology more clear. 

Although 95% orthophosphoric acid is recommended for this method, commercial phosphoric acid (85%) may be used, but the reaction proceeds more slowly and the yield is lower. 

Commercial phosphor-tin may contain up to 10 per cent, of phosphorus as phosphides, the crystals of which are revealed by etching with dilute nitric acid. Phosphor-tin is much used for making phos phor-bronzes.7... 

A long list of oxides was prepared sonochemically. Almost all the above-mentioned oxides were synthesized in organic solvents. The other oxides that will be discussed from here on were all prepared in aqueous solutions. Submicron size spheres of silica and alumina prepared by well-known methods were coated sonochemically by nanoparticles of oxides of europium and terbium using the same concentration of ions [81]. We have also used sonochemistry to prepare nanoparticles of silica and alumina doped with the same rare-earth ions for comparison. The highest luminescence intensities were observed for europium and terbium doped in nanoparticles of alumina of dimension 20-30 run. The intensities are comparable or higher than in commercial phosphors. 

Although the Dapex process is no longer being widely used to extract uranium from sulfuric acid leach liquors, organic phosphoric acids are favored for extracting by-product uranium from commercial phosphoric acid. Organic amines are impractical for this application because they are too fully saturated by the strong acid. 

The standard-addition method has been applied to the determination of chloride and fluoride in samples of commercial phosphors. In this application, solid-state indicator electrtKies for chloride and fluoride were used in conjunction with a reference electrode the added standard contained known quantities of the two anions. I he relative standard deviation for the measurement of replicate standard samples was 0.7% for fluoride and 0.4% for chloride. In routine use with real samples, the standard-addition method yielded relative standard deviations of l.l k) for fluoride and 0.8% for chloride. When similar samples were ana-Ivred bv the usual electrode calibration methods, the... 

In closing we note that a very different way to realize luminescence immunoassay is the use of commercial phosphors. By using YVO4 Eu, for example, it has been possible to achieve acceptable results. The powder particles are bound to the antibody and are in this way connected to the object of study. The quantum efficiencies ate high, and shielding from water molecules is no longer a problem because the luminescent species are in the solid. However, even the finest particles are very laige relative to the molecular scale on which the cryptate operates. 

A commercial phosphoric acid doped PBI membrane, Celtec V by BASF Fuel Cells, tailored for DMFC is based in a blend of PBI and poly(vinyl phosphonic acid) (PVPA). The PVPA poly acid is immobilized in the PBI matrix by interpenetration, crosslinking and covalent bonding [201]. 

Typical Impurity Levels in Commercial Phosphoric Acid (wt%)... 

Lanthanides in silicate rocks, commercial phosphoric acid, geological materials, refractory alloys, steel alloys, minerals, ores, monazite, and luminescent phosphors have been determined by HPLC. Determination of trace lanthanide impurities in nuclear grade uranium has been studied." An HPLC technique using the dynamic ion-exchange approach was also employed for the determination of Pm in urine. A typical application of lanthanide assay in nuclear industry is described next. 

LiF Mg,Ti was the first commercial phosphor, named TLD-100, introduced by the Harshaw Co. more than 30 years ago. Its preparation was under highly controlled conditions. It served for many years as the main TLD and is still widely used. A more sensitive LiF Mg Cu P was developed by Nakajima et al. (1978) and has been developed later as a commercial TLD by Wang et al. (1986) under the label GR-200. It is claimed to give sensitivities up to 50 times those of TLD-100. 

Fig. 9.9 a PL spectra = 365 nm) of the NaBaScSi207 o.iEu phosphor under different temperatures in the range of 30-300 °C. b Variations of the relative emission intensities and emission peaks as a function of temperature of the NaBaScSi207 o.iEu phosphor and data of the commercial phosphor are also given for comparison. Reproduced from Ref [39] by permission of The Royal Society of Chemistry... 

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