Doping with urea

It has long been known that it is difficult to wash chromia gel free of ammonium nitrate when it is prepared by methods similar to ours (2, S). A sample of our gel was analyzed in duplicate by the Micro-Tech Laboratories, Skokie, Illinois and reported to contain carbon, 1.26, 1.45% nitrogen, 2.60, 2.68% hydrogen, 3.12, 3.23%. Distillation from a solution of sodium hydroxide liberated ammonia equivalent to 1.60% nitrogen. Distillation from 3% sulfuric acid liberated carbon dioxide equivalent to 0.28% carbon. The nature of the remaining carbon is unknown. Infrared absorption of the pellets described in Section XI,A exhibited a sharp line at 1384 cm i characteristic of both NO3 and COg. Analysis of catalysts deliberately doped with urea established that urea, if any, corresponded to less than 0.15% carbon and 0.35% nitrogen. 

Urea linkages have been monitored during the extrusion production of a polyurethane-urea, through doping with a fluorescent aromatic diamine chain extender, whereas soluble poly(arylene etherjs, thioethers and sulfones have been synthesized which emit strongly in blue and red regions. Brownian dynamics have been used to determine the distribution of fluorescent resonance... 

Figure 7 showed that neither NaCl nor CaCl2 affected the swellability of poly (PVA-MA) at pH 5 and below. However, NaCl suppressed the expansion significantly between pH 5 and 7. It has been reported that urea enhanced the pH-induced swelling of poly-HEMA hydrogel doped with methacrylic acid. However, we have found fhat urea suppressed the expansion of poly(PVA-MA). 

Deposition-precipitation with urea has been also used to prepare Eu doped-YjOj/silica materials (39), which find application not in catalysis, but in the field of phosphor emitting in fluorescent lamps and cathode ray tubes. The method has been applied for depositing yttria (9.7 wt %) doped with Eu (0.30 wt %) from a mixture of nitrates heated at 80°C in the presence of urea and silica for 90 min. After thermal treatment at 900°C, YjOj particles are 12 nm large, coated by a silicate, and after thermal treatment at 1000°C, the a-YjSijO, phase forms. It exhibits interesting luminescent properties, and the authors conclude that this method of preparation is more promising than the sol-gel method. 

Yttrium aluminum garnet (YAG) doped with trivalent cerium was synthesized by Lu et al. (2002) from nitrate salts of yttrium, cerium and aluminum, as also polyvinyl alcohol and urea. A sol was obtained by homogenization at 100°C for 2 h heating at 250°C for 2 h yielded a yellow gel. Calcination of the gel at 800-1100°C for 4 h produced phase-pure nano- or micrometer-size powders ofYAG Ce +. Under specific conditions of preparation, the particles could be as small as 20 nm. 

To illustrate the spectroscopic analysis usually adopted to study LT/urea interactions in di-ureasil systems, we will refer in this section to the analysis carried out with the d-U(2000)-based xerogels doped with LiCFsSOs. ... 

For the divalent system studied by Nunes et aL, consisting of Zn(CF3S03)2-doped di-ureas ormolytes with °o > n > 1, materials obtained with n > 5 were completely amorphous. Only in the n = 1 compound was a crystalline PEO-Zn(CF3S03)2 complex formed. The stoichiometry of this phase is not known. ... 

What kind of business This depends largely on what kind of dope you plan to manufacture. Amine-type precursors go hand in hand with perfumery or dyes. Nitrating-type compounds (nitromethane, nitroethane) are also used as solvents, and rocket fuels. Indole has been used in perfumery. Tyrosine and tryptophan are nutrients added to feeds. Urea is a plant fertilizer and a feed additive. 

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