纳米羟基磷灰石的制备及表征

采用化学沉淀法制备了羟基磷灰石纳米粒子,并且通过扫描电子显微镜(SEM)、X射线衍射(XRD)、红外光谱(IR)等测试手段,对其进行了表征。实验结果表明:以Ca(OH)2和H3PO4为原料所制备出的纳米羟基磷灰石纳米粒子多呈针状或短棒状,平均粒径20~25 nm,长75~80 nm,且大小均匀,分散性好。尺寸和形状更接近人体骨磷灰石结构,并能与骨形成牢固的化学结合,是一种很有应用前景的人工骨和人工口腔材料。     

Carboxylic acids and polyethylene glycol assisted synthesis of nanocrystalline nickel ferrites

Different synthesis methods for the preparation of nanocrystalline nickel ferrites are reported: the thermal decomposition of precursors, made of: (i) metal-nitrate salts with carboxylic acids (citric, malonic and tartaric), and (ii) metal-nitrate salts and polyethylene glycol (PEG), in the presence of potassium chloride as a capping agent. The as-prepared gel precursors were characterized by TGA/DTA, while the samples obtained after annealing at 450 °C were investigated by FTIR, FESEM, XRD and Mössbauer spectroscopy. Regardless of the type of carboxylic acid used, nanocrystallites prepared by (i) method are similar in size (11–16 nm), while the method (ii) gives crystallites ∼33 nm in size with negligible microstrain. The differences in the lattice parameter, ranging from 8.3369(2) to 8.3574(2) Å, result from cation distribution, nonstoichiometry and structural imperfections in the nickel ferrite nanoparticles. The Mössbauer spectra analysis indicates existence of large distortions of tetrahedral and octahedral sites in these spinel compounds.     

A review of nanoparticle-enhanced membrane distillation membranes: membrane synthesis and applications in water treatment

Membrane distillation (MD) is a thermally driven process that uses low-grade energy to operate and has been extensively explored as an alternative cost-effective and efficient water treatment process compared to conventional membrane processes. MD membranes are synthesized from hydrophobic polymers, e.g. polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or polypropylene (PP), using various methods including phase inversion and electrospinning techniques. Recent literature on MD membranes clearly shows their important role in surface water/wastewater treatment and seawater desalination. Modification of MD membranes with nanoscale materials significantly improves their performance, preventing wetting and fouling. This review presents a critical assessment of the progress on the use of nanomaterials for the modification of MD membranes. The techniques commonly used to synthesize MD membranes, the modifications that have been adopted for the incorporation of nanomaterials onto membranes, and the unique properties these nanomaterials impart on the membranes are discussed. The use of modified membranes in different MD configurations and their application in groundwater, surface water, wastewater, brackish water and seawater treatment is reviewed. Finally, cost implications, commercial viability, environmental sustainability, and future prospects of MD are also discussed to elucidate promising approaches for a future and successful implementation of MD at an industrial scale. © 2019 Society of Chemical Industry     

Thermodynamic analysis of ZnO nanoparticle formation by wire explosion process and characterization

Zinc Oxide (ZnO) nanoparticles were synthesized by wire explosion process through deposition of different levels of energy to the exploding conductor in oxygen ambience at different pressures. The produced nanoparticles were analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX) and by Brunauer-Emmett-Teller (BET) studies. Energy dependent formation reaction mechanisms were formulated based on Born-Haber cycle. The size dependent gas phase reaction energetics was analyzed by using Hess's diagram. Butler's multicomponent molten oxide model was adopted to predict the surface tension of ZnO. Thermodynamic modelling studies revealed that the amount of energy deposited has an impact on saturation ratio, activation free energy, and nucleation rate of nanoparticles. It is observed based on experimental and modelling studies that the amount of energy deposited to the current carrying conductor, ambient pressure of oxygen and the saturation ratio influence the size of nanoparticle formed.     

Synthesis,properties, and multifarious applications of SiC nanoparticles: A review

The development of particulate materials is accelerating at a tremendous speed and nanoparticles have gradually gained worldwide attention. Among them, silicon carbide (SiC) nanoparticles have attracted much attention due to their excellent performance and great application potential. This article mainly presents a comprehensive overview on the synthesis, properties and potential applications of SiC nanoparticles. Firstly, various synthesis techniques for SiC nanoparticles were discussed, with the classification of solid phase, liquid phase and vapor phase processes. Subsequently, the unique properties of SiC nanoparticles such as surface properties, thermal properties, electrical properties and biocompatibility properties were highlighted. Thereafter, diversified applications of SiC nanoparticles including composites, catalysts, fluorescent biological labels, bioadhesives and flexible field emitters have been discussed. Finally, contents of the article were summarized and outlooks of future research were stated.     

Continuous supercritical hydrothermal synthesis of dispersible zero-valent copper nanoparticles for ink applications in printed electronics

Surface-modified zero-valent copper nanoparticles (CuNPs) are of interest as conductive inks for applications in printed electronics. In this work, we report on the synthesis, stability and characterization of CuNPs formed with a continuous supercritical hydrothermal synthesis method. The precursor, copper formate, was fed as an aqueous solution with polyvinylpyrrolidone (PVP) surface modifier and mixed with an aqueous water and formic acid stream to have reaction conditions of 400 °C, 30 MPa and 1.1 s mean residence time. The reaction pathway seemed to proceed step-wise as the hydrolysis of copper formate, followed by dehydration to oxide products and subsequent reduction by hydrogen derived from precursor and formic acid decomposition. The formed surface-modified zero-valent CuNPs had particle sizes of ca. 18 nm, were spherical in shape and contained no oxide contaminants. The formed CuNPs were found to exhibit long-term (>1 year) stability in ethanol as evaluated by shifts in the surface plasmon resonance band of product solutions. Conductive films (0.33 μm thickness) prepared with the CuNPs had a resistivity of 16 μΩ cm. The methods reported in this work show promise for producing conductive inks for use in practical printed electronics.     

Recent advances in systemic and local delivery of ginsenosides using nanoparticles and nanofibers

Ginsenosides are the main pharmacologically active constituents of ginseng which have been used in East Asian countries for centuries to modulate blood pressure, metabolism and immune function. Following the technological advances in isolation, purification and mass production, their mechanisms of action are gradually elucidated, providing solid basis for clinical applications. Ginseng extracts (total ginsenosides) and ginsenoside Rg3, CK, Rd have been marketed or entered clinical trials as drugs or dietary supplements. Despite the proven safety and efficacy of some ginsenosides, their applications are hindered by inferior pharmacokinetics such as low solubility, poor membrane permeability and metabolic instability. Nanoparticle formulation of drugs and implantable drug depots are effective strategies to improve the pharmacokinetics of therapeutic agents by enhancing solubility, providing protection, facilitating intracellular transport, and enabling sustained and controlled release. This mini-review summarizes the recent advances in systemic delivery of ginsenosides using liposomes, micelles, albumin-based nanoparticles, and inorganic nanoparticles, as well as local delivery of ginsenosides by electronspun fibrous membranes and hydrogels.     

A review: Recent advances in sol-gel-derived hydroxyapatite nanocoatings for clinical applications

The prospect of modifying the surface properties of the substrate (or base) material to enhance its corrosion and wear resistance as well as its reliability, performance, and more importantly its bioactivity is made possible using nanocoatings. An effective technique of synthesizing high purity nanocoatings in addition to nanopowders and fibers is to utilize the sol-gel approach. It is an attractive and versatile method that can be carried out with relative ease. Ceramic coatings, such as hydroxyapatite (HAp), can be fabricated through chemical means from solutions and consequently complex shapes can be coated economically. Given the fact that mixing takes place on the atomic scale, one of the key advantages of the sol-gel technique is its capacity to produce homogeneous materials, and it has been shown that the mechanical properties of sol-gel coatings are enhanced due to the presence of nanocrystalline grain structures. This review covers a brief insight into the recent application of HAp nanocoatings derived from sol-gel technique.     

A novel thermal decomposition method for the synthesis of ZnO nanoparticles from low concentration ZnSO4 solutions

In this research work, ZnO nanoparticles were prepared by direct thermal decomposition method with Zn₄(SO₄)(OH)₆·0.5 H₂O as a precursor. The precursor was calcinated in air for 1 h at 825 °C. Samples were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), infrared spectrum (IR), and scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD, EDS, and IR results indicated that the ZnO nanoparticles were pure. The average crystallite and particle size of the ZnO nanoparticles were estimated to be 87 nm and 92 nm by XRD and TEM, respectively. The SEM and TEM images showed that the ZnO nanoparticles were of spherical shape. The simplicity of the present method suggests its potential application at industrial scale as a cheap and convenient way to produce pure ZnO nanoparticles from low concentration ZnSO₄ solutions.     

Recent progress in synthesis,growth mechanisms,properties, and applications of silicon nitride nanowires

With advances in nanotechnology, nanowires have gained worldwide attention because of their novel properties and promising applications. Among them, silicon nitride (Si₃N₄) nanowires have attracted increasing attention due to their excellent performance and huge application potential. In this review, various synthesis methods of Si₃N₄ nanowires are introduced in detail, and then the growth mechanisms are also stated. Subsequently, the novel properties of Si₃N₄ nanowires including mechanical, optical, electrical, thermal, and wetting performance are highlighted. Applications corresponding to performance are also summarized later, such as composites, field emitters, field-effect transistors (FETs), photodetectors, photocatalysts, and microwave absorbers. Finally, the contents of this article are concluded and outlooks of future research directions are stated. This article reviews the recent advances and provides the prospects and challenges of Si₃N₄ nanowires.     

Biopolymer-assisted green synthesis and characterization of calcium hydroxide nanoparticles

The use of biopolymers in the synthesis of different nanostructures can be a cost effective and eco-friendly approach. In the present study, a facile and “green” sol–gel method was employed for preparing calcium hydroxide nanoparticles (Ca(OH)₂-NPs) in gelatin matrix as a bio-template. Prepared nanoparticles were characterized by different instruments such as powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR). The PXRD analysis revealed hexagonal Ca(OH)₂-NPs with preferential orientation in (101) reflection plane. They are hexagonal in shape with a mean particle size of approximately 42 nm in thickness. The synthesized Ca(OH)₂-NPs using gelatin were found to be comparable to those obtained from conventional methods using hazardous capping/stabilizing polymeric agents or surfactants and this route can be an excellent alternative for the synthesis of Ca(OH)₂-NPs using biomaterials.     

The synthesis and characterization of Al-Beta and all-silica Beta formed in fluoride and caustic media

The influence of various parameters upon the synthesis of the BEA structure in fluoride and caustic media is investigated and results are compared and related to some previous studies in the literature. High crystalline, low faulted BEA structure has been made in an excess of fluoride (F⁻/SiO₂ ratio of 1.5) across the entire gel Si/Al ratio range of 20 to ∞ using a fumed silica source and in the absence of seed crystals or stirring. Although, for gel Si/Al ratios >20, no aluminium was found in the products. The scope for further investigation of the effects of H₂O content and stirring vs. non-stirring upon crystallinity and aluminium uptake, especially in conditions of lower fluoride concentration, is shown. Results from the caustic media syntheses agree with those from previous studies and it is found that the uptake of aluminium into the zeolite during synthesis is required for the formation of the BEA structure. Product characterization of Al-Beta confirms the framework incorporation of aluminium through increased d-spacings, the presence of tetrahedral coordinate aluminium and lowering of the FT-IR external asymmetric stretch and double bend vibration relative to an all-silica sample.     

Microwave synthesis of magnetically separable ZnFe2O4-reduced graphene oxide for wastewater treatment

A magnetically separable ZnFe₂O₄-reduced graphene oxide (rGO) nano-composite was synthesised via a microwave method. Field emission scanning electron microscopy images of the nano-composite showed a uniform dispersion of nanoparticles on the rGO sheets. The performance of the nano-composite in wastewater treatment was assessed by observing the decomposition of methylene blue. The nano-composite showed excellent bifunctionality, i.e. adsorption and photocatalytic degradation of methylene blue, for up to five cycles of water treatment when illuminated with light from a halogen bulb. In contrast, water treatment with the nano-composite without illumination and the illuminated rGO, with no decoration of nanoparticles, diminished significantly after the first treatment. The reclamation of the ZnFe₂O₄-rGO nano-composite from treated water could be easily achieved by applying an external magnetic field.     

Recent advances in synthesis, physical properties and applications of conducting polymer nanotubes and nanofibers

This article summarizes and reviews the various preparation methods, physical properties, and potential applications of one-dimensional nanostructures of conjugated polyaniline (PANI), polypyrrole (PPY) and poly(3,4-ethylenedioxythiophene) (PEDOT). The synthesis approaches include hard physical template method, soft chemical template method, electrospinning, and lithography techniques. Particularly, the electronic transport (e.g., electrical conductivity, current-voltage (I-V) characteristics, magnetoresistance, and nanocontact resistance) and mechanical properties of individual nanowires/tubes, and specific heat capacity, magnetic susceptibility, and optical properties of the polymer nanostructures are presented with emphasis on size-dependent behaviors. Several potential applications and corresponding challenges of these nanofibers and nanotubes in chemical, optical and bio-sensors, nano-diodes, field effect transistors, field emission and electrochromic displays, super-capacitors and energy storage, actuators, drug delivery, neural interfaces, and protein purification are also discussed.     

Recent advances in gold-metal oxide core-shell nanoparticles: Synthesis,characterization, and their application for heterogeneous catalysis

Heterogeneous catalysis with core-shell structures has been a large area of focus for many years. This paper reviews the most recent work and research in coreshell catalysts utilizing noble metals, specifically gold, as the core within a metal oxide shell. The advantage of the core-shell structure lies in its capacity to retain catalytic activity under thermal and mechanical stress, which is a pivotal consideration when synthesizing any catalyst. This framework is particularly useful for gold nanoparticles in protecting them from sintering so that they retain their size, structure, and most importantly their catalytic efficiency. The different methods of synthesizing such a structure have been compiled into three categories: seed-mediated growth, post selective oxidation treatment, and one-pot chemical synthesis. The selective oxidation of carbon monoxide and reduction of nitrogen containing compounds, such as nitrophenol and nitrostyrene, have been studied over the past few years to evaluate the functionality and stability of the core-shell catalysts. Different factors that could influence the catalyst’s performance are the size, structure, choice of metal oxide shell and noble metal core and thereby the interfacial synergy and lattice mismatch between the core and shell. In addition, the morphology of the shell also plays a critical role, including its porosity, density, and thickness. This review covers the synthesis and characterization of gold-metal oxide core-shell structures, as well as how they are utilized as catalysts for carbon monoxide (CO) oxidation and selective reduction of nitrogen-containing compounds.

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Preparation and characterization of CaO nanoparticles from Ca(OH)2 by direct thermal decomposition method

CaO is an important material because of its application as catalyst and effective chemisorbents for toxic gases. In this research CaO nanoparticles were prepared via direct thermal decomposition method using Ca(OH)₂ as a wet chemically synthesized precursor. Nanocrystalline particles of Ca(OH)₂ have been obtained by adding 1 and 2 M NaOH aqueous solutions to 0.5 M CaCl₂·2H₂O aqueous solutions at 80 °C. The precursor [Ca(OH)₂] was calcined in N₂ atmosphere at 650 °C for 1 h. Samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectrum (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunaure–Emett–Teller (BET). SEM images showed that CaO nano-particles were nearly spherical in morphology. TEM images illustrated that produced CaO nano-particles had the mean particle size of 91 and 94 nm for 1 and 2 M NaOH concentration, respectively. As a result, this method could be used for production of CaO nano-particles on large-scale as a cheap and convenient way, without using any surfactant, organic medium or complicated equipment.     

Growth,characterization and thermo-mechanical analysis of Al/Al2O3 core/shell nanoparticles obtained under H2 atmosphere

In this work, growth, characterization and thermo-mechanical behavior of Al/Al₂O₃ core/shell nanoparticles (NP) is performed. The growth was carried out by gas condensation methods using H₂ as carrier gas at a pressure of 100 Pa and with a temperature of the evaporation source of 1315 °C. The prepared NP were characterized by Energy Dispersive X-ray Spectroscopy for chemical information, transmission electron microscopy for morphological study, and electron diffraction patterns for structural information. The prepared Al NP exhibit a thin Al₂O₃ passivating oxide shell due to the air exposure when removed from the preparation vacuum chamber. Afterwards, the growth of the Al₂O₃ oxide shell of the Al NP and the thermo-mechanical interaction between this growing oxide shell and its Al core was studied by performing in-situ thermal X-ray diffraction from RT up to 505 °C. Coefficients of thermal expansion of both Al core and Al₂O₃ oxide shell were obtained by means of X-ray strain analysis. It was found that the thickness of the Al₂O₃ shell increases with temperature and the thermal stress induced in the system increases linearly with temperature. Our results highlight that these NP overcome higher values of fracture toughness compared with Al₂O₃ NP used in micro-nano composites, thus improving their mechanical properties for nanofluid applications.     

面向应用的石墨烯制备研究进展

二维石墨烯具有卓越的光、电、热和力学等性能,在众多传统产业和战略性新兴产业中有巨大的应用前景,被誉为下一代关键基础材料。然而,石墨烯产业化及应用的瓶颈性问题是如何高效率、规模化、低成本和环境友好地制备高质量石墨烯产品。本综述系统地比较了现有石墨烯制备方法的优缺点,结合不同应用领域的特殊要求,阐明了材料化学工程的放大理论和方法是解决石墨烯大规模制备和应用瓶颈性问题的重要保障。     

A mixed integer optimisation approach for integrated water resources management

In areas lacking substantial freshwater resources, the utilisation of alternative water sources, such as desalinated seawater and reclaimed water, is a sustainable alternative option. This paper presents an optimisation approach for the integrated management of water resources, including desalinated seawater, wastewater and reclaimed water, for insular water deficient areas. The proposed mixed integer linear programming (MILP) model takes into account the subdivided regions on the island, the subsequent localised needs for water use (including water quality) and wastewater production, as well as geographical aspects. In addition, the integration of potable and non-potable water systems is considered. The optimal water management decisions, including the location of desalination, wastewater treatment, and reclamation plants, as well as the conveyance infrastructure for desalinated water, wastewater and reclaimed water, are obtained by minimising the annualised total capital and operating costs. Finally, the proposed approach is applied to two Greek islands: Syros and Paros-Antiparos, for case study and scenario analysis.