Hiroaki Onoda

Formation and catalytic characterization of various rare earth phosphates

Various rare earth phosphates [rare earth elements: R = La, Ce, Pr, Nd, Sm, Yb, and Y; phosphates: Monazite-type, Xenotime-type, Rhabdophane-type, and Weinshenkite-type orthophosphates RPO4, polyphosphate R(PO3)3, and ultraphosphate RP5O14] were synthesized by heating the mixtures of each rare earth oxide and diammonium hydrogenphosphate or phosphoric acid. The compositions of rare earth phosphates were determined by XRD, FT-IR, and TG–DTA. Catalytic properties were studied as one of properties of various rare earth phosphates. Specific surface areas of samples were measured by the BET method. Acid strengths and amounts of acidic sites were measured using several indicators by n-butylamine titration. Acidic properties were also confirmed by adsorption of ammonia. Various rare earth phosphates were characterized by catalytic activities on dehydration reaction of 2-propanol, cracking/dehydrogenation reaction of cumene, and isomerization reaction of butene. The characterization of catalysts was discussed with regard to type of rare earth elements, type of phosphates, and type of phosphorus resources.

Syntheses of various rare earth phosphates from some rare earth compounds

Abstract Each rare earth compound (rare earth element; R=La, Ce, and Nd, anion; oxide, carbonate, chloride, nitrate, sulfate, oxalate, and fluoride) was mixed with (NH4)2HPO4 or H3PO4 in P/R=1, 3, and 5, and heated in air. The resulting salts were analyzed by TG-DTA, XRD and FT-IR. CePO4·nH2O was not formed in the system of CeO2–H3PO4. However, this phosphate was synthesized in the systems of Ce(NO3)3·6H2O–(NH4)2HPO4, Ce2(CO3)3·8H2O–, CeCl3·7H2O–, and Ce(NO3)3·6H2O–H3PO4. The crystallinity of CePO4·nH2O was high in the systems of CeCl3·7H2O–, and Ce(NO3)3·6H2O–H3PO4. In P/Ce=1, formation of CeO2 was observed in the systems of Ce2(CO3)3·8H2O–, CeCl3·7H2O–, and Ce2(C2O4)3·9H2O–(NH4)2HPO4.

Acid-free synthesis of poly-organo-siloxane spherical particles using a W/O emulsion

Poly-organo-siloxane spherical particles were synthesized by a sol–gel method from methyltrimethoxysilane (MTMS) using a W/O emulsion comprising of sorbitantrioleate (SPAN85), n-octane, and H2O. MTMS was hydrolyzed and condensed without acid and/or basic catalysts in this W/O emulsion at room temperature. The size of the spherical silica particle depends on both the composition of the emulsion and the reaction time, ranging from 1 to 80 µm in diameter. A W/O emulsion comprising 10 wt% SPAN85, 60 wt% n-octane, and 30 wt% H2O was appropriate for the uniformity and reproducibility of spherical particles. The particle size increased with increasing reaction time. It is considered that the formation mechanism of poly-organo-siloxane spherical particles consists of three steps. The first step is that MTMS is hydrolyzed at the interface between oil and water phases. The second step is that spherical pre-polymers are synthesized by condensation of silanol. The third step is particle growth by condensation of spherical pre-polymers and silanol.

Spectroscopic properties of Er3+ in sol–gel derived ZrO2 films

Abstract Films of ( x /2)Er 2 O 3 –100ZrO 2 ( x =0, 0.1, 1 and 5) were prepared by the sol–gel and dip-coating methods, and the influences of the type of ZrO 2 phase on Er 3+ spectroscopic properties were investigated. X-ray diffraction patterns show the existence of metastable tetragonal phase at low temperatures, which are probably caused by both the excess surface energy due to the small crystallite-size effect (J. Phys. Chem. 4 (1965) 1238) and the stabilization of ZrO 2 with the addition of Er 2 O 3 (J. Phys. Chem. B 106 (2002) 1909; J. Ceram. Soc. Jpn. 107 (1999) 1111). Under excitation at 488 nm, the green (525+545 nm) downconversion fluorescence due to the ( 2 H 11/2 + 4 S 3/2 )→ 4 I 15/2 transition and the red (670 nm) downconversion fluorescence due to the 4 F 9/2 → 4 I 15/2 transition were observed, and their intensities increased with increasing the heat-treatment temperature regardless of the type of the ZrO 2 phase. On the other hand, the intensity of red upconversion fluorescence also increased monotonically with the heat-treatment temperature under excitation at 780 nm, while the green upconversion fluorescence was hardly observed in the tetragonal phase (for the film with x =1, below 800 °C; x =5, below 700 °C), but was observed in the cubic ( x =1, at 800 °C or above; x =5, at 700 °C or above) and monoclinic ( x =0.1, at 600 °C or above) phases under excitations at 647 and 780 nm. The reason is probably that the f–f transition probability concerning the 4 I 13/2 , from which the excited state absorption occurs, varied sensitively with the local structure of Er 3+ ions in the different phase of ZrO 2 .

Synthesis and pigmental properties of titanium phosphates with the addition of urea

As a white pigment, titanium oxide is used for cosmetic application. This oxide is well known to have the photo catalytic activity. Therefore, a certain degree of sebum is decomposed by the ultraviolet radiation in the sunlight. In this work, titanium phosphates were prepared as a novel white pigment. Their chemical composition, powder properties, photo catalytic activity, moisture retention and smooth were studied with the addition of urea. These white pigments had little photo catalytic activity. The addition of urea improved the moisture retention of titanium phosphates. The slipping resistance of samples became small by heating, on the other hand, the roughness of samples became small by the addition of urea.

Addition of Urea or Biuret on Synthesis of Rhabdophane-Type Neodymium and Cerium Phosphates

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.

Influence of ultrasonic treatment on preparation and powder properties of titanium phosphates

In this work, titanium phosphates were prepared by hydrothermal processes. Then they were treated with ultrasound as a novel white pigment for cosmetics. Their chemical composition, powder properties, photocatalytic activity, colour phase, and smoothness were studied. The obtained materials had a higher Ti/P ratio than that used in preparation conditions because of the formation of titanium oxide and hydroxide. Samples showed homogenized spherical particles by ultrasonic treatment. These titanium phosphates had less photocatalytic activity to protect the sebum on the skin. The obtained materials in hydrothermal process and their thermal products at 100 °C showed high reflectance at the range of visible light.

Mechanochemical Effects on the Synthesis of Copper Orthophosphate and cyclo-Tetraphosphate Bulks by the Hydrothermal Hot Pressing Method

Copper orthophosphate, Cu3(PO4)2, and cyclo-tetraphosphates, Cu2P4O12, were synthesized using phosphoric acid and basic copper carbonate, and then treated with a planetary mill for up to 360 minutes. The un-milled and milled samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. SEM images, particle size distribution, specific surface area, UV-Vis reflectance spectra were also used to evaluate the materials. The un-milled and milled materials were used to fabricate copper phosphate bulks by a hydrothermal hot pressing method. The influence of powder condition on the sintering behavior of the copper phosphates was studied.

Preparation of titanium phosphate white pigments with titanium sulfate and their powder properties

Titanium oxide that has photocatalytic activity is used as white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by the ultraviolet radiation in sunlight. In this work, as novel white pigment, titanium phosphates were synthesized with titanium sulfate and phosphoric acid for cosmetics. Their chemical composition, powder properties, photocatalytic activity, color phase, moisture retention, and smoothness were studied. These titanium phosphates had less photocatalytic activity to protect the sebum on the skin. Samples without heating and those heated at 100 °C showed high reflectance in the range of visible light. Sample prepared in Ti/P = 3/2 had higher moisture retention than samples prepared in other Ti/P ratios.

Homogenous hydrothermal synthesis of calcium phosphate with calcium carbonate and corbicula shells

Abstract In this work, we prepared calcium phosphate by a general homogenous hydrothermal process, either from commercial calcium carbonate and phosphoric acid, or from corbicula shells and phosphoric acid. The chemical composition and properties of the resulting products were also investigated. Commercial calcium carbonate and corbicula shells reacted with phosphoric acid to produce calcium hydrogen phosphate and hydroxyapatite via a homogeneous hydrothermal process. The chemical composition of the products was influenced by both processing temperature as well as time. The compositions themselves influenced the substitution of calcium with iron and the absorption of trimethylamine gas.