Amorphous products

Sodium borate solutions near the Na20 B202 ratio of maximum solubihty can be spray-dried to form an amorphous product with the approximate composition Na20 4B202 4H20 commonly referred to as sodium octaborate (64). This material dissolves rapidly in water without any decrease in temperature to form supersaturated solutions. Such solutions have found apphcation in treating ceUulosic materials to impart fire-retardant and decay-resistant properties (see Cellulose). 

Epichlorohydrin Elastomers without AGE. ECH homopolymer, polyepichlorohydrin [24969-06-0] (1), and ECH—EO copolymer, poly(epichlorohydrin- (9-ethylene oxide) [24969-10-6] (2), are linear and amorphous. Because it is unsymmetrical, ECH monomer can polymerize in the head-to-head, tail-to-tail, or head-to-tail fashion. The commercial polymer is 97—99% head-to-tail, and has been shown to be stereorandom and atactic (15—17). Only low degrees of crystallinity are present in commercial ECH homopolymers the amorphous product is preferred. 

Septentrionaline, C33H45O9N2, is amorphous, m.p. 131°, [a]J, ° + 32-7° (EtOH). Weidemann states that it contains four methoxyl groups, and on hydrolysis by alkalis yields (1) a crystalline acid, CgHgO N, m.p. 125-6°, which on further treatment with alkali yields anthranilic acid, C,H,02N, and must be a near relative of the latter and (2) a basic amorphous product, C25H390,N, m.p. 89°, [a]p °-f- 29-55° (EtOH), which yields a crystalline hydrochloride. 

Cypresaeoe yields, nn ovidaiion with nitric acid, an amoi plioos yellow product aud au aoid possessing the odour of isovaleric acid the amorphous product dissolve.- in aitalies with a red coloration. 

The aqueous phase was discarded and the combined ethereal phases were washed with water, dried over sodium sulfate, filtered and distilled to dryness, to obtain 20.240 grams of 3-me-thoxy-17o-methyl-19-nor-A - " hpregnadiene-20-ol, which product was utilized as such for the next step. The compound occurred in the form of an amorphous product which was soluble in alcohol, ether, benzene and acetone and insoluble in water. 

Little information exists on low-T precipitation of borides from solution. Chromium, cobalt and platinum borides are the only ones claimed to have been obtained from aqueous solution ". Ni2B and C02B are precipitated from a solution of nickel or cobalt acetates by adding a solution of sodium tetrahydroborate ". The formation of these borides at RT gives amorphous products. Hence, heat treatment at 300-700°C leads to crystalline NijB as the main constituent, although the average composition of the precipitate corresponds to NijB . 

The cyclotrisilazane (R = Me) produced in reaction (14) is recycled at 650°C [by reaction with MeNHo) the reverse of reaction (14)] to increase the yield of processible polymer. Physicochemical characterization of this material shows it to have a softening point at 190°C and a C Si ratio of 1 1.18. Filaments 5-18 pm in diameter can be spun at 315°C. The precursor fiber is then rendered infusible by exposure to air and transformed into a ceramic fiber by heating to 1200°C under N2- The ceramic yield is on the order of 54% although, the composition of the resulting amorphous product is not reported. The approach used by Verbeek is quite similar to that employed by Yajima et al. (13) in the pyrolytic preparation of polycarbosilane and its transformation into SiC fibers. 

Depending on the processing variables, including the additives, the end product of a lyophilization process may be amorphous or crystalline or of intermediate crystallinity. As explained below the amorphous product has a higher free energy and therefore dissolves faster and tends to be less stable and more hygroscopic than the crystalline product. The choice between the crystalline and amorphous material may depend on whether an improved solubility or improved stability is required. 

PVP decreases the temperatures of crystallization less than GL, the temperatures of devitrification being higher with PVP than with GL. With GL crystallization can be avoided until = -70 °C, but PVP pushes devitrification in an amorphous product to higher temperatures. 

During the secondary drying, the water will be removed which interacts with the solids such that the water cannot crystallize. The water can be bound to the surface of crystals in a crystallized product, or can be included in amorphous product. Pikal et al. [1.59] have listed four statements concerning secondary drying ... 

Slade, L. and Levine, H. 2002. Progress in food processing and storage, based on amorphous product technology. In Amorphous Food and Pharmaceutical Systems (H. Levine, ed.), pp. 139-144. Royal Society of Chemistry, Cambridge, UK. 

In an attempt to synthesize 2-desoxy-L-ribose, Mukherjee and Todd68 treated methyl 2,3-anhydro-jS-L-ribopyranoside (LXXII) with sodium thiomethoxide and then reduced the amorphous product. The sulfur-free sirup thus obtained was inert to the action of periodate and is therefore methyl 3-desoxy-/3-L-riboside (ayn., methyl 3-desoxy-/3-L-xyloside) (LXXIV) rather than the desired 2-desoxy derivative. The methylthio intermediate (LXXIII) was consequently a 3-methylthio-L-xylose derivative rather than a 2-methylthio-L-arabinose compound. The presence of a trace of the latter, however, is not wholly excluded since the sirupy desoxypentoside (LXXIV) gave a feeble green coloration in the Keller-Kiliani test, a reaction generally accepted as being specific for 2-desoxy-sugars. 

The final mother liquors, on evaporation to dryness, yield 2-3 g. of a light brown, amorphous product which is readily soluble in water but insoluble in 95 per cent alcohol. In concentrated hydrobromic acid this by-product forms a dark solution, the color of which is discharged on dilution with water. 

Preparation of amorphous products The preparation of metals (Fe, Co, Ni, Pd, Au), alloys (Au-Pd, Fe-Co, etc.), oxides, chalcogenides, etc. has been reported. The synthesis of sulphides, for instance, has been obtained in solutions (in water, ethanol, etc.) of the metal chloride or acetate using thioacetamide or thiourea as sulphur precursor. 

The major drawbacks to standard sol-gel synthesis include slow growth rate and the typically amorphous product, rather than defined crystals, which requires crystallization and post annealing steps. Growth rate and crystallization of the fabricated hybrid can be improved via solvothermal, reflux [224], sonication, and microwave [225] treatment. However, the air oxidation of CNTs (600 °C) and graphene (450 °C) may still be lower than MO crystallization temperature. Moreover, it has been shown that the MO coatings on CNTs can drastically affect their thermal oxidation, particularly with easily reducible metal oxides (e.g. TiOz = 520 °C, Bi203 = 330 °C) [180]. It appears that metal oxides can catalyze the oxidation of CNTs via a Mars van Krevelen mechanism, limiting the maximum temperature of their synthesis as well as applications (i.e. catalysis, fuel cells). 

The yellow phosphides M3P7 differ from all other phosphides by a remarkable property they sublime congruently dissociative (cf. NHi Cl). In the gas phase only M,g and Pi,g appear, whereas under similar conditions the phosphides M3P11 dissociate into M3P7 and Pi ( ). These compounds can also be obtained as amorphous products by sublimation under suitable conditions. It has been shown that these amorphous products are extraordinarily reactive, therefore they are the most suitable starting materials for the transformations discussed above. 

Nickel sulfide is mined directly from natural deposits. Also, it can be prepared in the laboratory by precipitation from an aqueous solution of a nickel salt with ammonium sulfide, (NH4)2S, or by precipitation from an acetic acid solution with hydrogen sulfide. While the aqueous solution method yields an amorphous product (alpha-NiS) which rapidly changes on exposure to air and contact with the solution to a brown crystalline sulfide (beta-NiS), the acid solution method forms only crystalline beta-NiS. 

Silica is an amorphous product with several types of silanol groups on its surface [4,5]. In Figure 2.1, the different types are shown. From the IR data, the presence of isolated silanol groups with a sharp absorption band at 3746 cm is evident. These isolated silanol groups are the more acidic ones (pK 5) and can act as the cation exchanger. Their acidity depends on the surface impurities... 

ZnO displays similar redox and alloying chemistry to the tin oxides on Li insertion [353]. Therefore, it may be an interesting network modifier for tin oxides. Also, ZnSnOs was proposed as a new anode material for lithium-ion batteries [354]. It was prepared as the amorphous product by pyrolysis of ZnSn(OH)6. The reversible capacity of the ZnSn03 electrode was found to be more than 0.8 Ah/g. Zhao and Cao [356] studied antimony-zinc alloy as a potential material for such batteries. Also, zinc-graphite composite was investigated [357] as a candidate for an electrode in lithium-ion batteries. Zinc parhcles were deposited mainly onto graphite surfaces. Also, zinc-polyaniline batteries were developed [358]. The authors examined the parameters that affect the life cycle of such batteries. They found that Zn passivahon is the main factor of the life cycle of zinc-polyaniline batteries. In recent times [359], zinc-poly(anihne-co-o-aminophenol) rechargeable battery was also studied. Other types of batteries based on zinc were of some interest [360]. 

In 1909, Dr. E. Weintraub of the General Electric Company ran high-potential alternating current arcs between cooled copper electrodes in a mixture of boron chloride with a large excess of hydrogen (51), obtaining pure fused boron which differed greatly in properties from the impure amorphous product of earlier workers. 

The separation of the layers may be difficult due to formation of amorphous products. 

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