Supercritical hydrothermal synthesis of UO2+x: stoichiometry, crystal shape and size, and homogeneity observed using 23Na-NMR spectroscopy of (U, Na)O2+x

CrystEngComm ◽  
2021 ◽  
Author(s):  
Chihiro Tabata ◽  
Kenji Shirasaki ◽  
Ayaki Sunaga ◽  
Hironori Sakai ◽  
Dexin Li ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Nmr Spectroscopy ◽  
Supercritical Water ◽  
Uranium Dioxide ◽  
Nitrate Solution ◽  
Starting Material ◽  
Crystal Shape ◽  
Supercritical Hydrothermal Synthesis ◽  
23Na Nmr ◽  
Shape And Size

The hydrothermal synthesis of pure uranium dioxide under supercritical water (SCW) conditions was investigated using a starting material composed of a uranyl(vi) nitrate solution at 450 °C.

Supercritical Hydrothermal Synthesis of Ultra-Fine Copper Particles Using Different Precursors

2017 ◽  
Vol 744 ◽  
pp. 493-497 ◽  
Author(s):  
Pan Pan Sun ◽  
Shu Zhong Wang ◽  
Yan Hui Li ◽  
Tuo Zhang
Keyword(s):  
Hydrothermal Synthesis ◽  
Supercritical Water ◽  
Fine Particles ◽  
Copper Ions ◽  
Synthesis Method ◽  
Reaction Times ◽  
Copper Particles ◽  
Supercritical Hydrothermal Synthesis ◽  
Ultra Fine Particles ◽  
Fine Copper

Supercritical hydrothermal synthesis is a green synthesis method for metal and metal oxide ultra-fine particles. Ultra-fine copper particles are of great interests for the researchers because of the excellent performance in recent years. In this paper, supercritical hydrothermal synthesis of copper ultra-fine particles with three different precursors (CuSO4, Cu(NO3)2, Cu(HCOO)2) are reported. This thesis reports that different products are produced with different precursors. Also, three kinds of reaction mechanisms with different precursors in supercritical water were explained. The conversion of copper ions in the reaction of Cu(HCOO)2 in supercritical water is the highest, the value reaches 100.0%. In the process of synthesizing ultra-fine copper particles, different additional HCOOH concentrations (0, 0.1 mol/L, 0.2 mol/L) and different reaction times (5 mins, 10 mins) were applied. Zero-valent ultra-fine copper particles without impurity were synthesized. The synthesized copper ultra-fine particles were cubic aggregations with micro-meter size

scholarly journals One-pot synthesis of nano titanium dioxide in supercritical water

2020 ◽  
Vol 9 (1) ◽  
pp. 410-417
Author(s):  
Panpan Sun ◽  
Shuzhong Wang ◽  
Yanhui Li ◽  
Tuo Zhang ◽  
Dong Wang ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Supercritical Water ◽  
Particle Surface ◽  
Organic Ligand ◽  
Growth Direction ◽  
Degree Of Crystallinity ◽  
Subcritical State ◽  
One Pot ◽  
Supercritical Hydrothermal Synthesis ◽  
Nano Titanium Dioxide

AbstractSupercritical hydrothermal synthesis of nanosized metal oxides is of great interest for scholars due to its one-pot and readily realizing commercial production process. Hydrothermal synthesis of nanosized TiO2 in subcritical and supercritical water was investigated with different reaction temperatures (250–450°C), time (3–10 min), precursor species (Ti(SO4)2, TiCl4), and the addition of a surfactant (CH3(CH2)5NH2). TiO2 synthesized under supercritical state has a higher degree of crystallinity when compared with TiO2 obtained from subcritical state, which is attributed to a higher reaction rate. Extending reaction time from 3 to 10 min leads to the growth of crystal and broader size distribution (36.66 ± 8.5 nm). More uniform products can be obtained when Ti(SO4)2 acting as the precursor compared with TiCl4 being the precursor. The application of surfactant CH3(CH2)5NH2 in the synthesis makes chemical bonding between the particle surface and organic ligand. It affects the growth direction of TiO2 crystal; as a result, rod-like TiO2 crystal is obtained.

Super Hybrid Materials

2011 ◽  
Vol 700 ◽  
pp. 145-149 ◽  
Author(s):  
Tadafumi Adschiri ◽  
S. Takami ◽  
K. Minami ◽  
T. Yamagata ◽  
K. Miyata ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Refractive Index ◽  
Supercritical Water ◽  
Metal Salt ◽  
High Surface ◽  
Functional Materials ◽  
High Refractive Index ◽  
High Thermal Conductivity ◽  
Base Catalysts ◽  
Supercritical Hydrothermal Synthesis

Various composite materials have been developed, but in many cases problems arise due to the combined materials such as fabrication becoming difficult because of the significant increase in viscosity, and transparency of the polymer is sacrificed. These issues can be overcome by controlling the nanointerface; however, this is considered as a difficult task since nanoparticles (NPs) easily aggregate in polymer matrices because of their high surface energy. Organic functionalization of inorganic NPs is required to increase affinity between NPs and polymers. For fabricating multi-functional materials, we proposed a new method to synthesize organic modified NPs by using supercritical water. Because organic molecules and metal salt aqueous solutions are miscible in supercritical water and water molecules serve as acid/base catalysts for the reactions, hybrid organic/inorganic NPs can be synthesized under the supercritical condition. The hybrid NPs show high affinity for the organic solvent and the polymer matrix, which leads to the fabrication of these super hybrid NPs. How to release the heat from the devices is the bottle neck of developing the future power devices, and thus nanohybrid materials of polymer and ceramics are required to achieve both high thermal conductivity and easy thin film flexible fabrication, namely trade-off functions. Surface modification of the BN particles via supercritical hydrothermal synthesis improves the affinity between BN and the polymers. This increases the BN loading ratio in the polymers, thus resulting in high thermal conductivity. Transparent dispersion of high refractive index NPs, such as TiO2 and ZrO2, in the polymers is required to fabricate optical materials. By adjusting the affinity between NPs and the polymers, we could fabricate super hybrid nanomaterials, which have flexiblility and high refractive index and transparency.

Solid-state 23Na NMR spectroscopy studies of ordered and disordered cellulose nanocrystal films

2019 ◽  
Vol 97 ◽  
pp. 31-39 ◽  
Author(s):  
Ryutaro Ohashi ◽  
Carl A. Michal ◽  
Wadood Y. Hamad ◽  
Thanh-Dinh Nguyen ◽  
Motohiro Mizuno ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Cellulose Nanocrystal ◽  
Nanocrystal Films ◽  
Spectroscopy Studies ◽  
23Na Nmr

Supercritical hydrothermal synthesis of zeolites from coal fly ash for mercury removal from coal derived gas

2015 ◽  
Vol 136 ◽  
pp. 96-105 ◽  
Author(s):  
Jiancheng Wang ◽  
Dekui Li ◽  
Fenglong Ju ◽  
Lina Han ◽  
Liping Chang ◽  
...  
Keyword(s):  
Fly Ash ◽  
Hydrothermal Synthesis ◽  
Coal Fly Ash ◽  
Mercury Removal ◽  
Supercritical Hydrothermal Synthesis
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