Hydrothermal Hot-pressing Method Research Articles

Hydrothermal Hot Pressing of CaCO3‐Chitosan Composites with High CaCO3 Content

In this study, a hydrothermal hot pressing (HHP) method was used for the preparation of molded composites with high CaCO3 content. Specifically, composites consisting of chemically synthesized CaCO3 and chitosan and scallop shells milled with a ball mill were molded by the HHP method; the structures, mechanical properties, and vibration absorption characteristics of the resulting disc‐shaped molded composites were investigated. All the composites had high CaCO3 contents (93%); flexural strengths (several megapascals) comparable to those of limestone and cement; and vibration absorption characteristics (logarithmic attenuation factors of 0.07–0.18) superior to those of aluminum alloys, stainless steel, and ceramics (which have logarithmic attenuation factors of <0.01). The composites prepared from the CaCO3‐chitosan composites can be expected to find application as light‐control materials, as materials for controlling the propagation of light, sound, and vibration waves including vibration‐isolating materials and as CO2‐fixation materials.

Synthesis of HA compounding TCP bone substitute by hydrothermal hot-pressing method

Synthesis of HA compounding TCP bone substitute by hydrothermal hot-pressing method

Properties of binderless coal slime briquette via hydrothermal hot pressing dewatering

ABSTRACTDewatering and binderless briquetting of Liulin coal slime by hydrothermal hot pressing (HHP) method were studied under a wide range of process conditions. Fourier transform infrared spectroscopy and XRD were used for characterization. Results indicated that the optimal conditions were a pressure at 4.2 Mpa, a temperature of 150℃, and additive NaOH at 3.0%. The increase of temperature caused the loss of absorbed water in clay minerals and also some organic species having functional groups, such as -CH3 and -CH2. The alkalinity caused the loss of oxygen functional groups and the formation of hydroxysodalite, which reduced the water storage capacity and promoted coal particles agglomeration.

Synthesis of porous β-TCP by hydrothermal hot-pressing method

Synthesis of porous β-TCP by hydrothermal hot-pressing method

Synthesis and Characterization of Dense Mesoporous Alumina

Dense mesoporous alumina bulks were successfully synthesized by a hydrothermal hot-pressing (HHP) method for mesoporous alumina powders prepared as starting material with a high BET surface area and narrow pore size distribution. As a result, mesoporous alumina HHP bulks had high density with uniformity pore size distribution and a high specific surface area. Their microstructural features for dense mesoporous alumina bulks were observed by SEM. The characterization of mesopores was examined.

Highly Densified Mesoporous Bulk Silica Prepared with Colloidal Mesoporous Silica Nanoparticles toward a New Low-k Material

Abstract We report the fabrication of highly densified mesoporous bulk silica consisting of colloidal mesoporous silica nanoparticles (MSNs) by using a hydrothermal hot-pressing method. No cracks or voids are found in the synthesized bulk. The mesoporous structure of the bulk is maintained as well as that of the original MSNs. The MSN-based bulk with large pore volume shows potential as a low-k material.

Novel low temperature processing techniques for apatite ceramics and chitosan polymer composite bulk materials and its mechanical properties

A co-precipitation method was used for processing chitosan (CHI)/calcium hydrogen phosphate dehydrate (DCPD) hybrid material. CHI solution was mixed into 1.0-M calcium nitrate solution. CHI/DCPD hybrid material was prepared by the above explained addition of CHI and Ca ion source to 1.0-M diammonium hydrogen phosphate solution. It was observed by transmission electron microscopy that CHI and DCPD were mixed within submicron meter scale. CHI/HA bulk materials derived from the CHI/DCPD hybrid materials were obtained by using a hydrothermal hot-pressing (HHP) method. A pressure of 40MPa was initially applied to the sample. An HHP autoclave was heated up to 150°C for 2h. Modified 3-point bending tests were conducted to obtain an easy estimate of the fracture toughness for the CHI/HA bulk materials made with the HHP method. The critical stress intensity factor Kc of the fabricated CHI/HA bulk materials was enhanced from 0.30 to 0.40MPam1/2 by the hybridization of CHI into DCPD.

New technique for bonding hydroxyapatite ceramics and magnesium alloy by hydrothermal hot-pressing method

The solidification of hydroxyapatite (HA:Ca10(PO4)6(OH)2) and its bonding with Magnesium (Mg) alloys (AZ31; Mg–3Al–1Zn) were achieved simultaneously by using a hydrothermal hot-pressing method at a low temperature as low as 150°C with no special surface treatment of Mg alloy. A mixture of calcium hydrogen phosphate dihydrate and calcium hydroxide was used as a starting powder material for solidifying HA. 3-point bending tests were conducted to obtain an estimate of the fracture toughness for the HA/Mg interface as well as for the HA ceramics only. The fracture toughness tests showed that the induced crack from the pre-crack tip deviated from the HA/Mg interface and propagated into the HA. The fracture toughness determined on the bonded HA/Mg specimen was close to that of the HA ceramics only (0.30MPam1/2).

Preparation of γ-Al2O3 porous nanosolid/fluorescein fluorescent nanocomposites by a simple method

Abstract γ-Al2O3 porous nanosolid has been successfully prepared by a hydrothermal hot-press method, using γ-Al2O3 nanoparticles as the raw material. Furthermore, an orange-red compound, C20H12O5, that exhibits intense fluorescence in alkaline solution, fluorescein was assembled into the pores of γ-Al2O3 porous nanosolids by a simple method, thus a γ-Al2O3/fluorescein nanocomposite was obtained. Because of the interaction between fluorescein molecules and the surface atoms of pores of γ-Al2O3 porous nanosolid, a photoluminescent enhancement was observed in γ-Al2O3/fluorescein nanocomposite by comparing with that of fluorescein. In addition, the effect of the fluorescein concentrations on the photoluminescence of the nanocomposites was also investigated.

Microstructural Control of Mesoporous Bulk Composed of TiO2-Derived Titanate Nanotubes

The mesoporous bulks composed of TiO(2)-derived titanate nanotubes fabricated from a hydrothermal treatment of commercial TiO(2) particles in a concentrated NaOH aqueous solution were obtained by a hydrothermal hot-pressing (HHP) method and subsequent steam-curing process with HCl solutions. The mesopore size and sodium concentration for the bulky TiO(2)-derived titanate nanotubes were dependent on the treatment conditions on the steam curing process with HCl solutions. The effect of the sodium concentration (Na/Ti) on microstructures were examined on the steam curing process for the application of the bulky TiO(2)-derived titanate nanotubes to several new fields.

Hydroxyapatite ceramics coating on magnesium alloy via a double layered capsule hydrothermal hot-pressing

Hydroxyapatite (HA: Ca10(PO4)6(OH)2) ceramic coating on magnesium (Mg) alloy (AZ31; Mg–3Al–1Zn) was achieved simultaneously by using a double layered capsule hydrothermal hot-pressing (DC-HHP) method at the low temperature as low as 150°C with no special surface treatment on the surface of the Mg alloy. A mixture of calcium hydrogen phosphate dehydrate (DCPD) and calcium hydroxide (Ca(OH)2) was used as a starting powder material for solidifying HA. Pull-out tests were conducted in order to obtain an estimate of adhesive properties for the HA coating to the Mg alloy. Average value of maximum shear stress was determined to 6.1 ± 1.0 MPa. After the pull-out fracture tests, it was revealed that HA ceramics remained on the surface of the Mg alloy. The Mg alloy could be bonded to HA ceramics with good adhesive properties.

Low temperature sintering and color of a new compound Sn 1.24Ti 1.94O 3.66(OH) 1.50F 1.42

Nanopowder of a new tin(II) titanium(IV) oxide hydroxide fluoride, Sn 1.24Ti 1.94O 3.66(OH) 1.50F 1.42 with the pyrochlore-type structure (cubic a = 10.3777(7) Å, space group Fd-3 m) was prepared by using a microwave-assisted solvothermal reaction. The grain size of the nanopowder was 20–30 nm in diameter. Sn 1.24Ti 1.94O 3.66(OH) 1.50F 1.42 decomposed above 300 °C, but could be sintered to relative density greater than 99% by a hydrothermal hot-pressing (HHP) method at 270 °C and 80 MPa for 4 h. The synthesized powder and solidified body obtained using HHP showed significantly different color, probably due to the difference in water content.

New concept bioceramics composed of octacalcium phosphate (OCP) and dicarboxylic acid-intercalated OCP via hydrothermal hot-pressing

Octacalcium phosphate (OCP) and adipic acid-intercalated complexed OCP ( Adi-OCP) were synthesized. Moreover, we made ceramic bodies out of them through a hydrothermal hot-pressing (HHP) method. Characteristic features of both the powder and ceramics were investigated by the X-ray diffraction method (XRD). Surface morphology of the ceramics was observed by scanning electron microscopy (SEM). Density, compressive strength and pore size distribution of the ceramics were measured. Crystalline structure of the newly developed OCP ceramics had no phase transformation from the starting materials. Moreover, the newly developed OCP ceramics had good mechanical properties only through the HHP treatment with a temperature as low as 110 °C. In order to evaluate bioactivity, the ceramics were immersed in simulating body fluid (SBF). It was predicted that OCP and Adi-OCP had better bioactivity than that of conventional HAp ceramics.

水熱ホットプレス法による高炉スラグを原料とした微細孔を有する固化体の作製および熱伝導率測定

水熱ホットプレス法による高炉スラグを原料とした微細孔を有する固化体の作製および熱伝導率測定

Evaluation of microstructures and properties of bulk mesoporous silica

Synthesis of mesoporous MCM-type bulks prepared by hydrothermal hot-pressing (HHP) method using MCM-type mesoporous powder was attempted. Scanning electron microscopy (SEM), bulk density measurement, N2 adsorption-desorption isotherms and formaldehyde adsorption test have been employed to characterize the bulky products. As a result, we succeeded in preparing a dense and strong mesoporous bulks with high BET over 1000 m2/g through the hydrothermal hot-pressing method under appropriate conditions.

Preparation and characterization of ZrO2 porous nanosolid and its composite fluorescent materials

ZrO2 porous nanosolid has been successfully prepared by a novel hydrothermal hot-press (HHP) method, using ZrO2 nanoparticles as the starting material. Furthermore, a kind of O, O-donating chelating regent, morin was assembled into the pores of ZrO2 porous nanosolids, and a morin/ZrO2 porous nanocomposite was obtained. Because of the interaction between morin molecules and the surface of ZrO2 porous nanosolid, a blue-shift of the photoluminescence (PL) peak was observed in ZrO2/morin nanocomposite by comparing with that of morin.

Synthesis and characterization of bulky mesoporous silica Pd-MCM-41

Bulky palladium catalyst supported on mesoporous silica MCM-41 (Pd-MCM-41) was successfully synthesized by hydrothermal hot-pressing method. In this study, the structure of the palladium species in Pd-MCM-41 bulk before and after heat-treatment process was revealed by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) and transmission electron microscopy (TEM). Also, the microstructure and mesoporous property of Pd-MCM-41 bulk was discussed. As a result, it was revealed that these dense Pd-MCM-41 bulks possessed a high surface area of over 1000 m2/g and the structure of palladium of Pd-MCM-41 bulk is almost equal to palladium (0) metal.

Synthesis of bulky mesoporous silica (FSM) by hydrothermal hot-pressing method

In this study, we successfully synthesized the bulk of dense mesoporous silica (FSM) bodies by a short-term hydrothermal hot-pressing (HHP) method. It was thought that these dense bodies were achieved by solution/precipitation mechanism during HHP. Bulk pieces with the dimension in the range of centimeters in diameter possessed a high surface area of over 1000 m 2/g and sharp distribution of mesopores with an average diameter of approximately 2.4 nm. This successful synthesis of bulky mesoporous silica will expand the capabilities of application to various fields, for example, gas separation (CO 2 and H 2 etc.) and catalysis.

Preparation of ZrO 2 porous nanosolid and its composite fluorescent materials

ZrO 2 porous nanosolid has been successfully prepared by a novel hydrothermal hot-press (HHP) method, using ZrO 2 nanoparticles and deionized water as the starting materials. Furthermore, an organic dye, rhodamine B (RhB) was assembled into the pores of ZrO 2 porous nanosolids, and RhB/ZrO 2 porous nanocomposite was obtained. Because of the interaction between RhB molecules and the surface atoms of ZrO 2 porous nanosolid, a photoluminescence (PL) enhancement and a blue-shift of the PL peak were observed in ZrO 2/RhB composites compared with that of RhB.

Synthesis and Evaluation of Bulky Y‐Zeolites by Hydrothermal Hot‐Pressing Method

In this study, the syntheses of bulks of Y‐zeolite were attempted by a hydrothermal hot‐pressing (HHP) method with various conditions such as the amounts and concentrations of NaOH solution, reaction temperatures, and reaction times. Dense bulks of Y‐zeolite were successfully obtained by this HHP method. Under an optimum synthetic condition of HHP, solidified bulks of Y‐zeolite possessed translucency with high values of specific surface area. Transmission electron microscopy observation of these translucent bulks of Y‐zeolite showed that their microstructures were densified like polycrystalline ceramics sintered by heat treatments and no amorphous phase was observed at the boundaries of Y‐zeolite grains. As a result, in these unique bulks of Y‐zeolite synthesized by the HHP method, the microporous network was thoroughly connected at the grain boundaries of Y‐zeolite.