Preparation of Na_(3)V_(2)(PO_(4))_(3) Cathode Materials by Hydrothermal Assisted Sol-Gel Method for Sodium -Ion Batteries

Na_(3)V_(2)(PO_(4))_(3)(NVP)cathode material of the sodium ion battery(1 C=117 mAh g-1)has a NASICON-type structure,which not only facilitates the rapid migration of sodium ions,but also has a small volume deformation during sodium ion de-intercalation and the main frame mechanism remains unchanged,and thus is seen as an energy storage material for a wide range of applications,but has a limited electronic conductivity due to its structure.In this paper,NVP cathode materials with finer primary particles are successfully prepared using a simple hydrothermal treatment-assisted sol-gel method.The increased pore size of the NVP materials prepared under the hydrothermal process allows for more active sites and more effective resistance to the volume deformation of sodium ions during insertion/extraction processes,effectively facilitating the diffusion of ions and electrons.The Na_(3)V_(2)(PO_(4))_(3) material obtained by the optimized process exhibited good crystallinity in XRD characterization,as well as superior electrochemical properties in a series of electrochemical tests.A specific capacitance of 106.3 mAh g^(-1) at 0.2 C is demonstrated,compared to 96.5 mAh g^(-1) for Na_(3)V_(2)(PO_(4))_(3) without hydrothermal treatment,and cycling performance is also improved with 93%capacity retention.The calculated sodium ion diffusion coefficient(DNa=5.68×10^(-14))obtained after EIS curve fitting of the improved sample illustrates that the pore structure is beneficial to the performance of the Na_(3)V_(2)(PO_(4))_(3)cathode material.

Rapid Microwave-assisted Hydrothermal Synthesis of Bi0.76Sb1.24S3 and Its Application in the Photocatalytic Degradation of Pollutants by Visible Light Irradiation

Bi（0.76）Sb（1.24）S3 nanocrystals were synthesized by a rapid microwave-assisted hydrothermal method using bismuth nitrate, antimony pentoxide and thioacetamide as starting materials and characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and UV-vis diffuse reflectance spectroscopy（DRS）. The effects of the synthetic condition on the product composition were investigated. The photocatalytic activities of Bi（0.76）Sb（1.24）S3 nanocrystals for the degradation of methyl orange and p-hydroxyazobenzene under visible light irradiation were evaluated. Bi（0.76）Sb（1.24）S3 exhibited good and stable visible light photocatalytic activity.

Photoluminescence and Structural Properties of ZnO Nanorods Growth by Assisted-Hydrothermal Method

Semiconducting zinc oxide (ZnO) nanorods were obtained in bulk quantity by an hexamethylenetetramine (HMTA)-assisted hydrothermal method at low temperature (90°C) with methenamine ((CH3)6N4 as surfactant and catalyst and zinc nitrate Zn(NO3)2·6H2O as Zn source. The structure and phase of ZnO nanorods were studied using x-ray diffraction (XRD) and high resolution transmission electron microscopy techniques (HRTEM). The morphology of the nanostructures was studied by scanning electron microscope (SEM) method. The photoluminescence (PL) properties were investigated founding two emission bands under UV excitation.

ZnO Planar-Tetrapod Synthesized by Cethyltrimethylamonium Hydroxide-Assisted Hydrothermal Method at Low Temperature

Planar tetrapods ZnO (PTP-ZnO) or cross shaped tetrapod nanostructures were synthesized by a cethyltrimethylamonium hydroxide (CTAOH)-assisted hydrothermal method at low temperature (120°C). The XRD diffractogram showed that the PTP-ZnO nanostructures showed a hexagonal wurtzite phase. The studies with high resolution transmission electron microscopy (HRTEM) and select area specific diffraction (SAED) revealed that the ZnO pods were single crystals and preferentially grew up along [002] direction. The growth mechanism of the CTAOH assisted-hydrothermal synthesized PTP-ZnO nanostructures is explained using the final shape guiding of materials nanostructured and surfactant-action theories.

Hydrothermal Treatment of Sol-Gel TiO_2 Film

The preparation of TiO_2 film has been an important research area.In our work,we obtained the TiO_2 film by hydrothermal treating the amorphous film prepared by sol-gel method or the hydrolysis of titanium alkoxide.The influence of temperature and duration time on the film properties was investigated.The photo degradation of methyl orange in aqueous solution of the film was studied.The films were characterized by XRD and Uv-Vis spectroscope.

Comparison of Hydrothermal and Sol-Gel Synthesis of Nano-Particulate Hydroxyapatite by Characterisation at the Bulk and Particle Level

Hydrothermal and sol-gel synthesis methods have been used to prepare nano-particulate hydroxyapatite (HA) powders for detailed characterisation. Bulk elemental analysis data are compared from X-ray diffraction, X-ray fluorescence and Fourier transform infrared spectroscopy. These show the presence of secondary phases in the sol-gel powders which can be attributed to evaporative loss of precursor phosphite phases during specimen preparation and breakdown of the primary HA phase during calcination. Only the primary HA phase is detected in the hydrothermally prepared powder. In addition, Ca/P ratios of each powder are determined at the particle level using transmission electron microscopy with energy dispersive X-ray spectroscopy (TEM-EDX), having first established a threshold electron fluence below which significant electron-beam-induced alteration of the composition of HA does not occur. The TEM-EDX results show a greater compositional variability of particles from the sol-gel preparation route compared to the hydrothermal route. Overall it is the combination of the analysis techniques that shows the hydrothermal synthesis route produces near- stoichiometric, single phase, hydroxyapatite.

Characteristics of Eu²⁺, Dy³⁺-Doped SrAl₂O₄Synthesized by Hydrothermal Reaction and Its Photocatalytic Properties

Eu2+, Dy3+-doped SrAl2O4 was prepared by a hydrothermal reaction through the process of calcination at lower temperature. The physicochemical properties of the SrAl2O4: Eu2+, Dy3+ phosphor were characterized and compared to those of the SrAl2O4: Eu2+, Dy3+ prepared by sol-gel method. The photocatalytic properties of the SrAl2O4: Eu2+, Dy3+ were evaluated in photocatalytic water decomposition for hydrogen production. The SrAl2O4: Eu2+, Dy3+ prepared by hydrothermal reaction exhibited excellent phosphor properties which were similar with that prepared by sol-gel method. Its photocatalytic activity for hydrogen evolution was higher than that of TiO2 photocatalyst.

Mild-temperature Synthesis of Covellite Copper Sulfide Hexagonal Nanoplatelets via the Hydrothermal Route

Covellite CuS hexagonal nanoplatelets were prepared by a simple hydrothermal process at mild temperature, using sodium dodecyl benzene sulfonate （SDBS） as an assisting reagent. The products were characterized by X-ray powder diffraction （XRD）, transmission electron microscopy （TEM） and UV-vis absorption spectroscopy. An energy-dispersive X-ray spectrometer （EDS） was used to analyze the elementary compositions of the intermediate products. A possible formation mechanism of hexagonal nanoplatelets is discussed, using TEM observations.

Bright blue photoluminescence from a mixed tin and manganese oxide xerogel prepared via sol-hydrothermal-gel process

A new blue photoluminescent material, a mixed tin and manganese oxide xerogel, is prepared via sol-hydrothermalgel process assisted by citric acid. The composition xerogel exhibits strong blue emission at room temperature, with an emission maximum at 434 nm under short （234 nm） or long-wavelength （343 nm） ultraviolet excitation. The photoluminescent excitation spectrum of the mixed tin and manganese oxide xerogel, monitored at an intensity maximum wavelength of 434 nm of the emission, consists of two excitation peaks at 234 nm and 343 am. With heat treatment temperature increasing from 110 ℃ to 200 ℃, the blue emission intensity increases remarkably, whereas it is almost completely quenched after being treated at 300 ℃. The carbon impurities in the mixed tin and manganese oxide xerogel, confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, should be responsible for the bright blue photoluminescence.

Microwave-assisted hydrothermal synthesis of Pt/SnO2 gas sensor for CO detection

In this paper,the Pt/SnO2 nanostructures were prepared via a facile one-step microwave assisted hydrothermal route.The structure of the introduced Pt/SnO2 and its gas-sensing properties toward CO were investigated.The results from the TEM test reveal that Pt grows on the SnO2 nanostructure,which was not found for bulk in this situ method,constructing Pt/SnO2.The results indicated that the sensor using 3.0 wt%Pt/SnO2 to 100 ppm carbon monoxide performed a superior sensing properties compared to 1.5 wt%and 4.5 wt%Pt/SnO2 at 225℃.The response time of 3.0 wt%sensor is 16 s to 100 ppm CO at225℃.Such enhanced gas sensing performances could be attributed to the chemical and electrical factors.In view of chemical factors,the presence of Pt facilitates the surface reaction,which will improve the gas sensing properties.With respect to the electrical factors,the Pt/SnO2 plays roles in increasing the sensor’s response due to its characteristic configuration.In addition,the one-step in situ microwave assisted process provides a promising and versatile choice for the preparation of gas sensing materials.

Microwave assisted hydrothermal synthesis of tin niobates nanosheets with high cycle stability as lithium-ion battery anodes

In this study, SnNb_2O_6 and Sn_2Nb_2O_7 nanosheets are synthetized via microwave assisted hydrothermal method, and innovatively employed as anode materials for lithium-ion battery. The SnNb_2O_6 electrode exhibits high reversible capacity and excellent cycling stability(498 mAh/g at 0.1 A/g after 100 cycles),which is superior to that of Sn_2Nb_2O_7 electrode(173 mAh/g at 0.1 A/g after 100 cycles). Even increasing the current density to 2.0 A/g, the SnNb_2O_6 electrode still delivers a reversible capacity up to 306 mAh/g.The rate performance of the SnNb_2O_6 electrode is also better than that of Sn_2 Nb_2O_7 electrode at different current densities from 0.1 A/g to 2.0 A/g. The enhanced electrochemical performance of SnNb_2O_6 nanosheets can be attributed to the unique layered structure, which is conducive to the diffusion of the lithium ions and the migration of electrons during discharge/charge.

Crystalline boron nitride nanosheets by sonication-assisted hydrothermal exfoliation

A simple method to prepare two-dimensional hexagonal boron nitride(h-BN) scalably is essential for practical applications. Despite intense research in this area, high-yield production of two-dimensional h-BN with large size and high crystallinity is still a key challenge. In the present work, we propose a simple exfoliation process for boron nitride nanosheets(BNNSs) with high crystallinity by sonication-assisted hydrothermal method, via the synergistic effect of the high pressure, and cavitation of the sonication. Compared with the method only by sonication, the sonication-assisted hydrothermal method can get the fewer-layer BNNSs with high crystallinity.Meanwhile, it can reach higher yield of nearly 1.68%, as the hydrothermal method with the yield of only 0.12%. The simple sonication-assisted hydrothermal method has potential applications in exfoliating other layered materials, thus opening new ways to produce other layered materials in high yield and high crystallinity.

Microwave-assisted hydrothermal synthesis and gas sensitivity of nanostructured SnO_2

Precursors for nanostructured SnO2 were synthesized via a microwave-assisted hydrothermal method under different conditions, using SnCI2.2H2 O, urea and citric acid as reactants. After calcination of the pre-cursors at 700 ℃ for 2 h, nanostructured SnO2 with different morphologies were obtained, and were then characterized using X-ray powder diffraction （XRD）, and field-emission scanning electron microscopy （FESEM）. The results show that synthesis temperature and time play an important role in the formation of the 3D hierarchical morphology of the nanostructured SnO2. Gas sensing experiments demonstrate that the synthesized SnO2 materials, especially those with a 3D network structure, exhibit superb sensitivity to alcohol vaoors at 240 ℃.

Rapid Microwave-assisted Hydrothermal Synthesis of SrWO4：Eu^3＋ Nanowires and Their Luminescence Properties

SrWO4：Eu^3＋ nanowires were synthesized at 160 ℃ within 10 min via a microwave-assisted hydrothermal method. In examining the influences of synthesis temperature and reaction time on the morphology of nanowires, it was found that any temperatures and reaction time except 160 ℃ and 10 min gave rise to poorer morphologies under otherwise equal conditions. The synthesized nanowires were characterized by means of X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, high-resolution transmission electron microscopy（HRTEM）, energy dispersive X-ray（EDX） and Raman spectrometry, respectively. The results suggest that the samples are homogenous and dispersive single phase nanowires. The photoluminescence properties of the nanowires were determined with a spectrofluorometer. Two obviously sharp peaks at 395 and 464 nm and a broad peak centered at 290 nm were found in their excitation spectrum. Under excitation at 395 and 464 nm, the ^5D0→^7F2 transition is the dominant process which means Eu^3＋ ion is located at a low symmetry site, while the ^5D0→^7F2 transition dominates under the excitation at 290 nm, showing a highly symmetric field around the Eu^3＋ ion, which indicates the presence of the two local Eu^3＋ environments.

Ultralong and Mesoporous ZnO and γ-Al_2O_3 Oriented Nanowires Obtained by Template-assisted Hydrothermal Approach

Highly mesoporous Zn O and g-Al2O3nanowires（NWs） are both synthesized by a hydrothermal method using commercially available porous anodic aluminium oxide（AAO） as template. AAO membrane acts as template for Zn O NWs and both as template and precursor for g-Al2O3 NWs. The formation of intermediate phases of porous Zn6Al2（OH）16CO3and boehmite（g-Al OOH） were observed, both occurring during the hydrothermal synthesis of porous Zn O and g-Al2O3 NWs, respectively, and disappearing after annealing at 600 C. This novel template-assisted hydrothermal process leads to the formation of porous Zn O and g-Al2O3NWs（specific surface area of 192 m2 g 1and 263 m2 g 1, respectively）, showing pore sizes around 4 nm in diameter. The influence of the reaction parameters on the nanostructure morphology was also investigated. A Zn O seed layer, deposited on the AAO channels prior to the hydrothermal synthesis, leads to more compact Zn O nanowires（99 m2 g-1） protecting the AAO host from the chemical attack of the precursor solution.

Preparation and electrochemical performance of Li_2Mn_(0.5)Fe_(0.5)SiO_4 cathode material with sol-gel method for lithium ion batteries

Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5SiO4 was studied. The final sample was identified as Li2Fe0.5Mn0.5SiO4 with a Pmn21 monoclinic structure by X-ray diffraction analysis. The crystal phases components and crystal phase structure of the Li2Fe0.5Mn0.4SiO4 material were improved as the increase of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+). Field-emission scanning electron microscopy verified that the Li2Fe0.5Mn0.5SiO4 particles are agglomerates of Li2Fe0.5Mn0.5SiO4 primary particles with a geometric mean diameter of 220 nm. The Li2Fe0.5Mn0.5SiO4 sample was used as an electrode material for rechargeable lithium ion batteries, and the electrochemical measurements were carried out at room temperature. The Li2Fe0.5Mn0.5SiO4 electrode delivered a first discharge capacity of 230.1 mAh/g at the current density of 10 mA/g in first cycle and about 162 mAh/g after 20 cycles at the current density of 20 mA/g.

H_(2)O_(2)辅助污泥水热过程水DOM的光化学行为研究

采用水热炭化和添加4%H_(2)O_(2)辅助水热炭化两种工艺处理脱水污泥,在测定两种过程水DOM基本理化性质的基础上,重点比较了两种DOM的光漂白行为和光生活性物种的产生情况.结果表明,与水热炭化工艺相比,H_(2)O_(2)辅助水热炭化工艺中伴生的过程水DOM的pH值较低,电导率、TOC、腐殖质类物质含量、芳香性官能团、分子量及腐殖化程度均较高,并表现出更强的光敏感性.在模拟自然光照射条件下,其芳香性和腐殖化程度随光照时间延长而降低,荧光组分含量显著下降,其中腐殖质类组分降低最为明显.光照过程中产生更多的单线态氧(1O2)和三重激发态(^(3)DOM^(*)),可显著促进四环素的光降解(93.22%),且^(3)DOM^(*)起主导作用.本研究明确了H_(2)O_(2)辅助水热炭化过程水DOM的光化学行为,可为水热炭化处理污泥产生的过程水的进一步处理及利用提供理论依据.

Sm^(3+)掺杂LaOF荧光粉的制备及光学性能

以LaOF晶体为基质,利用水热辅助固相法制备出一系列Sm^(3+)掺杂LaOF荧光粉。采用XRD、TEM、荧光光谱仪等测试手段对所制得的样品的相结构、微观形貌及光学性能进行表征。结果表明,LaOF在不同煅烧温度下会产生四方相和斜方六面体两种不同晶相。此外,由于受跃迁概率和局域对称性的影响,Sm^(3+)掺杂四方相LaOF发光强度更大,其各浓度样品在405 nm光激发下,于567 nm、605 nm、651 nm和710 nm等处均出现了Sm^(3+)的特征发射峰,并且随着Sm^(3+)掺杂量的增加,其发光强度呈现先增大后减小的趋势,且当Sm^(3+)掺杂量为3.0%(摩尔分数,下同)时,La_(1-x)Sm_(x)OF样品发光强度达最大值。此外,所得样品的色纯度极高,其多个激发峰均位于商用近紫外和蓝光LED芯片的发射波长附近,可实现多种波长激发下的可见橙光发射。

Comparison of the morphology and structure of W03 nanomaterials synthesized by a sol-gel method followed by calcination^or hydrothermal treatment

Tungsten （VI） oxide （WO3） nanomaterials were synthesized by a sol-gel method using WC16 and C2HsOH as precursors followed by calcination or hydrothermal treatment. X-Ray diffraction （XRD）, scanning electron microscopy （SEM） and high resolution transmission electron microscopy （HRTEM） equipped with energy dispersive X-ray spectroscopy （EDX） were used to characterize the structure and morphology of the materials. There were significant differences between the WO3 materials that were calcinated and those that were subjected to a hydrothermal process. The XRD results revealed that calcination temperatures of 300℃and 400℃ gave hexagonal structures and temperatures of 500℃ and 600℃ gave monoclinic structures. The SEM images showed that an increase in calcination temperature led to a decrease in the WO3 powder particle size. The TEM analysis showed that several nanoparticles agglomerated to form bigger clusters. The hydrothermal process produced hexagonal structures for holding times of 12, 16, and 20 h and monoclinic structures for a holding time of 24 h. The SEM results showed transparent rectangular panicles which according to the TEM results originated from the aggregation of several nanotubes.

Tb^(3+)、Eu^(3+)离子共掺杂的MgAl_(2)O_(4)发光性能研究

采用水热辅助固相法,以Al(NO_(3))_(3)·9H_(2)O和Mg(NO_(3))_(2)·6H_(2)O为原料,尿素为沉淀剂,制备了Tb^(3+)、Eu^(3+)共掺杂镁铝尖晶石荧光粉。用X射线衍射、扫描电子显微镜对所得产物的相结构和形貌予以表征,结合荧光激发、发射光谱和CIE色度图分析了荧光粉的光致发光性能。结果表明:在一定浓度范围内,掺杂Tb3+和Eu^(3+)离子后基质MgAl_(2)O_(4)的晶体结构并未发生改变,而当引入沉淀剂后,获得了具有良好分散性的棒状颗粒,且Tb^(3+)与Eu^(3+)间的浓度变化对样品形貌的影响甚微。在此基础上,以377 nm近紫外光作为激发光源实现了可见光区由粉至红的多色可调谐发射。