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Mixtures of ammonium dihydrogen phosphate and basic nickel carbonate with P/Ni molar ratios of 2/3, 1/1, and 2/1 were ground in a planetary mill. The thermal behavior of the milled samples was investigated by differential thermal analysis, x-ray diffraction, and Fourier transform infrared spectroscopy. In addition, the samples were characterized by ultraviolet-visible reflectance spectroscopy, particle size distribution, scanning electron microscopy, and nitrogen adsorption measurements. As a result of mechanochemical effects, the targeted nickel phosphates were formed at lower temperatures, had a more vivid color, and consisted of more regularly shaped particles.

Urea or biuret was added to the thermal synthetic system of Rhabdophane-type neodymium and cerium phosphates. The mixture of a rare earth compound, a phosphorus compound, and an additive [CO(NH2)2 or NH(CONH2)2] was heated at 150°C or 300°C for 20 hr, and the thermal products were analyzed by the XRD, FT-IR, and BET methods. H3PO4 and (NH4)2HPO4 were used for phosphorus compounds, and for rare earth compounds, Nd2O3, Nd(NO3)3 · 6H2O, NdCl3 · 6H2O, Nd2(CO3)3 · 8H2O, CeO2, Ce(NO3)3 · 6H2O, CeCl3 · 7H2O, and Ce2(CO3)3 · 8H2O were used. Urea and biuret worked not only as a dispersing agent but also as a reactant. By the addition of biuret, the thermal products changed from cerium oxide to Rhabdophane-type cerium phosphate in the system using CeCl3 · 7H2O and (NH4)2HPO4. Addition of urea or biuret influenced the specific surface area of Rhabdophane-type neodymium and cerium phosphates. Furthermore, to increase the reactivity of the raw solid materials, mechanical treatment was performed. The mixture of diammonium hydrogenphosphate and a rare earth compound was ground with water and then heated. The influence of the addition of urea or biuret was also studied in these systems.

Hexa-ammonium tetraphosphate dihydrate, (NH4)6P4O13·2H2O (HATP), was prepared by the hydrolysis of sodium cyclo-tetraphosphate with sodium hydroxide solution, followed by ion-exchange with ammonium. Thermal decomposition in static air was first carried out dynamically, at a heating rate of 5 K min-1 as used in thermal analysis (thermogravimetric-differential thermal analysis), and also isothermally. To examine the effect of humidity on the thermal decomposition, HATP was heated isothermally in streams of dry and humid air. The products were characterized by X-ray diffraction analysis and high-performance liquid chromatography–flow injection analysis. At 100°C, HATP was decomposed to mono- and triphosphates and to 2 mol diphosphate, and this was accelerated by humidity. Further degradation of the triphosphate to mono- and diphosphates took place slowly. The 2 mol diphosphate also decomposed slowly to 4 mol monophosphate. At temperatures above 150°C, the form I of ammonium polyphosphate (I-APP) was produced. I-APP was further hydrolysed by humidity to shorter-chain phosphates, such as mono-, di- and triphosphates.

The intercalation reaction of n-alkylamines from methyl- to hexadecylamine into α-tin(IV) bis(hydrogenphosphate) has been investigated. The reaction was conducted by mixing the phosphate and solutions of the amines dissolved in water or benzene. The amine/ phosphate molar ratios in the reaction mixtures were 0.43, 0.85, 1.71 and 3.41. The nitrogen/phosphorus atomic ratio in the intercalation compound was not changed by the amine/phosphate molar ratio. The interlayer distances of the intercalates obtained in the reaction mixtures with molar ratios of 3.41 and 1.71 increased with an increase in the number of carbon atoms in the alkyl chain of the amine. The slope of the straight line obtained in plot of interlayer distance versus number of carbon atoms in the alkyl chain of the amine indicates that the amine molecules form a double layer in the interlayer space of the phosphate and are inclined at an approximate angle of 67.7° to the phosphate layer. The interlayer distances of the intercalates of butyl- to nonylamines obtained at the molar ratio of 0.85 are smaller than those of the corresponding compounds from the molar ratios of 3.41 and 1.71, while those of decyl- to hexadecylamine intercalates lie on the previously discussed line. This behaviour is interpreted by assuming kink formation in the short alkyl chains between the phosphate layers.