Hiroaki Onoda

Bio: Hiroaki Onoda is an academic researcher from Kyoto Prefectural University. The author has contributed to research in topics: Phosphoric acid & Phosphate. The author has an hindex of 18, co-authored 100 publications receiving 963 citations. Previous affiliations of Hiroaki Onoda include Kobe University & Ritsumeikan University.

Formation and catalytic characterization of various rare earth phosphates

Abstract: 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.

Decomposition of trifluoromethane over nickel pyrophosphate catalysts containing metal cation

Abstract: Nickel pyrophosphates containing metal cations were prepared from aqueous solutions. The obtained phosphates were characterized with inductively coupled plasma (ICP), differential thermal analyses (DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), specific surface area, acid strength, amount of acidic sites, and adsorbed carbon measurements. The phosphates were used as a catalyst for decomposition of trifluoromethane. The kinds and ratios of metal cation added were discussed. The nickel pyrophosphate catalysts containing magnesium had higher selectivity to CO 2 and longer lifetimes than aluminum orthophosphate for decomposition of trifluoromethane.

Improvement of acid and base resistance of nickel phosphate pigment by the addition of lanthanum cation

Abstract: Transition metal phosphates are used as inorganic pigments, however these materials had a weak point for acid and base resistance. Because lanthanum phosphate is insoluble in acidic and basic solution, the addition of lanthanum cation was tried for the improvement of the acid and base resistance of nickel phosphate pigment. The lanthanum-doped nickel phosphates were prepared from phosphoric acid, nickel nitrate, and lanthanum nitrate solution. The additional effects of lanthanum cation were studied on the chemical composition, particle shape and size distribution, specific surface area, color, acid and base resistance of the precipitations and their thermal products.

Addition of rare earth cation on formation and properties of various cobalt phosphates

Abstract: Various cobalt phosphate pigments were prepared with the addition of rare earth cation by heating the mixtures of ammonium dihydrogenphosphate, cobalt carbonate, and rare earth (Y, La, and Nd) oxide. The thermal behavior of these mixtures was characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), and FT–IR analyses. The thermal products were estimated from scanning electron micrographs (SEM), particle size distribution, specific surface area, UV–vis reflectance spectra, and fluorescence spectra. Furthermore, the acid and base resistance of these materials was evaluated. The thermal reactions were clarified in these systems. Formation of cobalt–neodymium phosphate composite particles were considered from specific surface area. Cobalt pyrophosphate and cyclo -tetraphosphate had more vivid color hue than cobalt orthophosphate. These condensed phosphates had better acid and base resistance. By the addition of rare earth elements, the acidic and basic resistance of cobalt phosphates was remarkably improved.

Systematic synthesis and characterization of single-crystal lanthanide orthophosphate nanowires.

Abstract: A simple hydrothermal method has been developed for the systematic synthesis of lanthanide orthophosphate crystals with different crystalline phases and morphologies. It has been shown that pure LnPO4 compounds change structure with decreasing Ln ionic radius: i.e., the orthophosphates from Ho to Lu as well as Y exist only in the tetragonal zircon (xenotime) structure, while the orthophosphates from La to Dy exist in the hexagonal structure under hydrothermal treatment. The obtained hexagonal structured lanthanide orthophosphate LnPO4 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) products have a wirelike morphology. In contrast, tetragonal LnPO4 (Ln = Ho, Er, Tm, Yb, Lu, Y) samples prepared under the same experimental conditions consist of nanoparticles. The obtained hexagonal LnPO4 (Ln = La → Tb) can convert to the monoclinic monazite structured products, and their morphologies remained the same after calcination at 900 °C in air (Hexagonal DyPO4 is an exceptional case, it transformed to tetragonal DyPO...

Physics-Informed Neural Networks for Heat Transfer Problems

Abstract: Physics-informed neural networks (PINNs) have gained popularity across different engineering fields due to their effectiveness in solving realistic problems with noisy data and often partially missing physics. In PINNs, automatic differentiation is leveraged to evaluate differential operators without discretization errors, and a multitask learning problem is defined in order to simultaneously fit observed data while respecting the underlying governing laws of physics. Here, we present applications of PINNs to various prototype heat transfer problems, targeting in particular realistic conditions not readily tackled with traditional computational methods. To this end, we first consider forced and mixed convection with unknown thermal boundary conditions on the heated surfaces and aim to obtain the temperature and velocity fields everywhere in the domain, including the boundaries, given some sparse temperature measurements. We also consider the prototype Stefan problem for two-phase flow, aiming to infer the moving interface, the velocity and temperature fields everywhere as well as the different conductivities of a solid and a liquid phase, given a few temperature measurements inside the domain. Finally, we present some realistic industrial applications related to power electronics to highlight the practicality of PINNs as well as the effective use of neural networks in solving general heat transfer problems of industrial complexity. Taken together, the results presented herein demonstrate that PINNs not only can solve ill-posed problems, which are beyond the reach of traditional computational methods, but they can also bridge the gap between computational and experimental heat transfer.

Transmission and emission x-ray microscopy: operation modes, contrast mechanisms and applications.

Abstract: Advances in microscopy techniques based on x-rays have opened unprecedented opportunities in terms of spatial resolution, combined with chemical and morphology sensitivity, to analyze solid, soft and liquid matter. The advent of ultrabright third and fourth generation photon sources and the continuous development of x-ray optics and detectors has pushed the limits of imaging and spectroscopic analysis to structures as small as a few tens of nanometers. Specific interactions of x-rays with matter provide elemental and chemical sensitivity that have made x-ray spectromicroscopy techniques a very attractive tool, complementary to other microscopies, for characterization in all actual research fields. The x-ray penetration power meets the demand to examine samples too thick for electron microscopes implementing 3D imaging and recently also 4D imaging which adds time resolution as well. Implementation of a variety of phase contrast techniques enhances the structural sensitivity, especially for the hard x-ray regime. Implementation of lensless or diffraction imaging helps to enhance the lateral resolution of x-ray imaging to the wavelength dependent diffraction limit.