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An environmentally friendly NaCl–H2O(v) system was developed to prepare β-CaSiO3 nanostructures from commercially available raw materials, CaCO3 and amorphous SiO2 (α-SiO2), by a one-step solid-state reaction at 575°C for 2 h. The formation of β-CaSiO3 was accelerated by NaCl–H2O(v) system. The results demonstrated that both NaCl and H2O(v) played vital roles in the formation of β-CaSiO3 nanostructures at a lower temperature. NaCl is considered to enhance the diffusivity of starting materials and the rate of solid-state reactions, and promote the crystallization at lower temperature. Water vapor can accelerate the decomposition of CaCO3, and absorbed water on the surface of solid materials can dissolve NaCl to form an aqueous ionic liquid composed of Na and Cl ions, which is similar to a hydrothermal process, and will further increase the diffusivity of components and reduce the reaction temperature.

BACKGROUND: Sea algae cellulose has been little utilized because the cellulose content in sea algae is low. For the effective utilization of sea algae cellulose, cellulose must be converted without drying into valuable material with a high rate and yield. From this viewpoint, effects of hydrothermal pretreatments of sea algae to enhance the glucose production by enzymatic hydrolysis of sea algae cellulose were investigated. RESULTS: Using hydrothermal pretreatment performed at 423 K for Monostroma nitidum Wittrock (green alga) and at 473 K for Solieria pacifica (red alga) for 30 min, yields of extracted water-soluble components containing monosaccharides were 0.51 g g−1 for the green alga and 0.62 g g−1 for the red alga. The apparent rate of glucose production from hydrothermally pretreated green alga by enzymatic hydrolysis was > 10 times faster than that of the non-pretreated sample. Yields of glucose from cellulose by enzymatic hydrolysis were 79.9% for the green alga and 87.8% for the red alga. CONCLUSION: Cellulose of sea algae was successfully fractionated by hydrothermal pretreatments, which resulted in high susceptibility of sea algae cellulose to enzyme attack. This process leads to the effective utilization of sea algae cellulose. Copyright © 2008 Society of Chemical Industry

Barium titanate (BaTiO 3 ) particles with book-like and spherical morphology were prepared by using a hydrothermal soft chemical process in the presence of a cationic surfactant. A layered titanate of H 1.07 Ti 1.73 O 4 with a lepidocrocite-like structure and plate-like particle morphology was used as the precursor. The layered titanate was hydrothermally treated in a Ba(OH) 2 -(HTMA-OH) (n-hexadecyltrimethylammonium hydroxide) solution or a Ba(OH) 2 -(HTMA-Br) (n-hexadecyltrimethylammonium bromide) solution in a temperature range of 80°-250°C to prepare BaTiO 3 . The intercalation reaction of HTMA + with the layered titanate promotes the structural transformation reaction from the layered titanates to BaTiO 3 , while it inhibits the structural transformation reaction to anatase under the hydrothermal conditions. The particle morphology of BaTiO 3 prepared by this method dramatically changes with changing reaction conditions. HTMA + plays an important role in changing particle morphology in the hydrothermal soft chemical process.

Thermodynamic calculations were used to estimate the free energy for reactions of anatase and TiO2·nH2O with K2CO3 to generate potassium dititanate at 25–1200°C, and the results showed that amorphous TiO2·nH2O with reaction activity higher than that of anatase can decrease the lowest generation temperature of potassium dititanate. The precise temperatures of 300°C for TiO2·nH2O and 500°C for anatase were determined by experiments. The crystal growth of potassium dititanate was studied experimentally. It was found that potassium dititanate hydrate is first formed from TiO2·nH2O at 300°C, and converts into K2Ti2O5·0.35H2O at 640°C. The dehydration of K2Ti2O5·0.35H2O occurs at 660–820°C, ending with the generation of K2Ti2O5 single crystals at 820°C. Potassium dititanates with a diversity of morphologies, sizes, water contents, and crystallinities, showing various abilities for optical absorption/reflex, were fabricated from TiO2·nH2O under control, whereas only K2Ti2O5 was prepared from anatase at 500–850°C, which indicate that reaction processes and properties of products are determined according to the type of reactants and the reaction temperature. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1568–1577, 2004

Carbon nanotubes (CNTs) with excellent electron conductivity are widely used to improve the electrochemical performance of the SnO2 anode. However, the chemical bonding between SnO2 and CNTs is not clearly elucidated despite it may affect the lithiation/delithiation behavior greatly. In this work, an SnO2 @CNT composite with SnC and SnOC bonds as a linkage bridge is reported and the influence of the SnC and SnOC bonds on the lithium storage properties is revealed. It is found that the SnC bond can act as an ultrafast electron transfer path, facilitating the reversible conversion reaction between Sn and Li2 O to form SnO2 . Therefore, the SnO2 @CNT composite with more SnC bond shows high reversible capacity and nearly half capacity contributes from conversion reaction. It is opposite for the SnO2 @CNT composite with more SnOC bond that the electrons cannot be transferred directly to CNTs, resulting in depressed conversion reaction kinetics. Consequently, this work can provide new insight for exploration and design of metal oxide/carbon composite anode materials in lithium-ion battery.

Birnessite-type manganese oxide can be transformed to tunnel structures by hydrothermal treatment.

Anatase porous ceramics were produced at low temperatures below 350°C by hydrothermal hot-pressing of amorphous titania consisting of spherical particles prepared by hydrolysis of titanium tetraethoxide. After fine anatase crystals were formed in the original amorphous spheres by hydrothermal hot-pressing, the spherical particles were deformed and the fine anatase crystals flowed into the interstices among the original spheres by compression from outside the autoclave to form a compact with homogeneous distribution of fine pores. The fine anatase crystals in the compacts were bonded together by dissolution and deposition to form a compact with high mechanical strength. The porous anatase ceramics with open pores were prepared by drying in air after removing water which had occupied the pores in the compacts during hydrothermal hot-pressing.

A novel one-dimensional zirconium phosphate inorganic polymer, [NH4]3[Zr(OH)2(PO4)(HPO4)] has been synthesized in (HOCH2CH2)2O medium with F- ions in presence, and structurally characterized. The compound consists of macroanionic chains of [ZrP2O10H3]3- separated by NH4+ cations.

Y{sub 2}O{sub 3} sheets, rods, needles and tubes were synthesized from three precursors through hydrothermal reactions followed by calcination. The phase distribution and decomposition behaviors of the three precursors, Y{sub 2}(OH){sub 5.14}(NO{sub 3}){sub 0.86}.H{sub 2}O, Y{sub 4}O(OH){sub 9}(NO{sub 3}) and hexagonal Y(OH){sub 3}, were investigated. The reaction temperature and initial pH value during the hydrothermal reaction showed great influence on the shape and particle size of the products. The precursors were converted to Y{sub 2}O{sub 3} particles with the retained original morphology of the precursors. - Graphical abstract: Y{sub 2}O{sub 3} particles in the shape of sheet, rod, needle and tube with controlled size were synthesized from three precursors, Y{sub 2}(OH){sub 5.14}(NO{sub 3}){sub 0.86}.H{sub 2}O, Y{sub 4}O(OH){sub 9}(NO{sub 3}) and hexagonal Y(OH){sub 3}, obtained by hydrothermal reactions with controlled pH value and reaction temperature. Display Omitted.

Borosilicate glass powder with simulated high-level radioactive waste (HLW) was solidified by a hydrothermal hot-pressing method. A leach test of the solid bodies was performed. Twenty-one elements composing the simulated HLW in the leachant were analyzed quantitatively by neutron activation analysis. The addition of Al(OH){sub 3}, up to 7.5% of the starting powder, reduced the leachability. The first densification of the starting powder during hydrothermal hot-pressing takes place by the rearrangement of particles, followed by solution-precipitation. The densification fits two types of rate equations. Activation energies obtained from two rate equations agree and are smaller than those of the glass without simulated HLW. The results indicate that simulated HLW in the starting powder acts to reduce the activation energy for densification during hydrothermal hot-pressing.

A novel aromatic ring-alkylation was achieved by condensation between aniline·HCl salts and cyclic or acyclic ketones under hydrothermal conditions.