表面修饰In纳米微粒的声化学法制备及结构表征

Surface modified indium nanoparticles were prepared by a simple and rapid process from bulk indium via ultrasound dispersion. The morphology and structure of synthesized nanoparticles were characterized by TEM, XRD, XPS and FTIR. The results show that the morphology of indium nanoparticles is spherical and the structure of indium nanoparticles is the tetragonal phase. The surface of indium nanoparticles was coated by 2 ethyl hexanoic acid, which could almost hold back oxidation of the indium nanoparticles. In addition, the tribological property of indium nanoparticles as additives in oil was evaluated on a four-ball tester and the results show that indium nanoparticles exhibit good performance in wear.     

铝锌合金的微观结构及抗腐蚀行为研究

Electro-chemical experiment was carded out to test the corrosion rates of aluminium-zinc hot-dip coating. It is shown that 5.3% aluminium-zinc alloy （weight ratio） has superior anti-corrosion property. The determined microstructure has displayed amorphous structure composed of nanometer sized particle of the system. The analysis indicated large negative change of Gibbs energy of 5.3% aluminium-zinc system. Molecular dynamics simulation showed that 5.3% aluminium-zinc system has very different behavior from other systems. A phase transition of this particular system was observed from simulation. The transition temperature was determined around 400 K. The simulation indicated that 5.3% aluminium-zinc system is amorphous over temperature range from 300 to 900 K, supporting the inference from experiments that amorphous solid of aluminium-zinc alloy has special anti-corrosion character.     

纳米粒子相变的分子动力学研究：Cu453的性质、结构与结晶成核

Molecular dynamics （MD） computer simulations have been carried out to study the structures, properties and crystal nucleation of nanoparticles with 453 Cu atoms. Structure information was analyzed from the MD simulations, while properties of nanoparticles of Cu453, such as melting point, freezing temperature, heat capacity and mo- lar volumes, have been estimated. The face center cubic （FCC） phase and icosahedron （Ih） phase were observed during the quenching process, and nucleation rates of crystallization to FCC crystal of Cu453 at temperatures of 650, 700, 750, and 800 K were analyzed. Both classical nucleation theory （CNT） and diffuse interface theory （DIT） were used to interpret our observed nucleation rates. The free energy and diffuse interface thickness between the liquid and the FCC crystal phases were estimated by the CNT and DIT respectively, and the results show that the DIT does not work properly to the system.     

Precipitation of hematite nanoparticles via reverse microemulsion process

Hematite nanoparticles have been successfully synthesized via two processing routes:(i) conventional precipitation route and (ii) reverse microemulsion route.The particle precipitation was carried out in a semibatch reactor.A microemulsion system consisting of water,chloroform,1-butanol and surfactant was loaded with iron nitrates to form iron nanoparticles precipitation.The precipitation was performed in the single-phase microemulsion operating region.Three technical surfactants,with different structure and HLB value are employed.The influence of surfactant characterization on the size of produced iron oxide particle has been studied to gain a deeper understanding of the important controlling mechanisms in the formation of nanoparticles in a microemulsion.Transmission electron microscopy (TEM),surface area,pore volume,average pore diameter,pore size distribution and XRD were used to analyze the size,size distribution,shape and structure of precipitated iron nanoparticles.     

Facet-dependent electrochemiluminescence spectrum of nanostructured ZnO

A facet-dependent electrochemiluminescence (ECL) behavior was found for nanostructured ZnO with different dominant exposing planes.The ECL spectrum of nanostructured ZnO was recorded by the emission scan mode with a fluorescence spectrometer and applied to investigate the difference of surface state for different crystal planes.Electronic structure calculations based on density functional theory were used to study the effect of crystal plane on the band structure and density of states.It revealed that the ECL emission was originated primarily from the recombination of electrons from Zn 4s and the hole from O 2p,which could be utilized to study the physical and chemical properties of surface structures of as-prepared nanostructured ZnO.A physical model was suggested to elucidate the differences of ECL spectra.A concept was proposed that the energy released as photons during ECL process of nanocrystalline semiconductor materials will be correlated with the energy level of active sites located at different crystal planes.     

Flame Retardant and Smoke Suppressant of Fe‐Organophilic Montmorillonite in Polyvinyl Chloride Nanocomposites

Two kinds of polyvinyl chloride (PVC)/organophilic montmorillonite (OMT) nanocomposites are prepared by a melt intercalation method. This study has been designed to determine if the presence of iron and zinc ions in the structure of montmorillonite (MMT) lattice can affect thermal, flame retardant and smoke suppressant properties. The information about the morphological structure of PVC/OMT nanocomposites was obtained using X-ray diffraction and transmission electron microscopy. The thermal and flame retardant properties of the nanocomposites were characterized by thermogravimetric analysis, limiting oxygen index and smoke density. The nanocomposites based on Fe-OMT exhibit better thermal, flame retardant properties and lower degradation degree than those of pure PVC. The degradation mechanism was studied by pyrolysis, gas chromatography and mass spectrometry (Py-GC-MS).     

Synthesis–structure correlations of manganese–cobalt mixed metal oxide nanoparticles

Mixed metal oxides in the nanoscale are of great interest for many aspects of energy related research topics as water splitting, fuel cells and battery technology. The development of scalable, cost-efficient and robust synthetic routes toward well-defined solid state structures is a major objective in this field.While monometallic oxides have been studied in much detail, reliable synthetic recipes targeting specific crystal structures of mixed metal oxide nanoparticles are largely missing. Yet, in order to meet the requirements for a broad range of technical implementation it is necessary to tailor the properties of mixed metal oxides to the particular purpose. Here, we present a study on the impact of the nature of the gas environment on the resulting crystal structure during a post-synthesis thermal heat treatment of manganese–cobalt oxide nanoparticles. We monitor the evolution of the crystal phase structure as the gas atmosphere is altered from pure nitrogen to synthetic air and pure oxygen. The particle size and homogeneity of the resulting nanoparticles increase with oxygen content, while the crystal structure gradually changes from rocksalt-like to pure spinel. We find the composition of the particles to be independent of the gas atmosphere. The manganese–cobalt oxide nanoparticles exhibited promising electrocatalytic activity regarding oxygen evolution in alkaline electrolyte. These findings offer new synthesis pathways for the direct preparation of versatile utilizable mixed metal oxides.     

Effects of Na2SiF6 on Preparing Mullite Material with Sludge from the Aluminum Profile Factory and Pyrophyllite

In this research,the mullite material with sludge from aluminum profile factory and pyrophyllite as primary raw materials was prepared. Based on the optimal formula,optimal calcining temperature and holding time determined in the research,effects of Na2SiF6 mineralizer on crystal structure,microstructure and properties of mullite were discussed to determine the optimal addition of Na2SiF6 mineralizer. With XRD and SEM methods,crystal structure and microstructure of the test samples were characterized; with Rietveld Quantification method,contents of various crystal phases in the test samples were determined; properties of the test samples were tested. In combination with the structural and property analysis results,the optimal Na2SiF6 addition was determined to be 2%. Correspondingly,the content of solid solution of mullite-Al4.59Si1.41O9.7 was 96.9wt%,the bulk density was 2.10 g/cm3,the degree of porosity was 27.0%,the water absorption rate was 12.8%,the rupture strength was 24.30 MPa and primary thermal-shock rupture strength retention rate was 87.4%.     

Synthesis and Soft Magnetic Properties of Mg-doped Ni Nanoparticles

Mg-doped Ni nanoparticles with good soft magnetic properties were prepared with the sol-gel method and were sintered at 400, 500, 600, and 900℃ in argon atmosphere, respectively. The structure and magnetic properties of the samples were studied by means of X-ray diffraction, TEM, and VSM magnetometers. X-Ray powder diffraction results show that Ni-Mg solid solution was formed with the single phase of face-centered cubic（fcc） structure. The particle size became larger with the increase of temperature. When the sintering temperature was 400 °C, the particle size was 6.3 nm, whereas it was 46.2 nm at 900 °C. Both the saturation magnetization（Ms） and the coercivity were enhanced with the increase of the particle size. The Ms values of the samples ranged from 18.965 to 46.766 emu/g and the coercivity ranged from 1051.3568 to 9145.0848 A/m.     

Molecular dynamics studies of the kinetics of phase changes in clusters III: structures, properties, and crystal nucleation of iron nanoparticle Fe331

Molecular dynamics (MD) computer simulations have been carried out to study the structures, properties, and crystal nucleation of iron nanoparticles with 331 Fe atoms or with diameter around 2 nm. Structure information for the nanoparticles was analyzed from the MD simulations. Three crystalline phases and one amorphous phase were obtained by cooling the nanoparticles from their molten droplets at different cooling rates or with different lengths of cooling time periods. Molten droplets froze into three different solid phases and a solid-solid transition from a disordered body-centered cubic (BCC) phase to an ordered BCC phase were observed during the slow cooling and the quenching processes. Properties of nanoparticle Fe₃₃₁, such as melting point, freezing temperature, heat capacity, heat of fusion, heat of crystallization, molar volume, thermal expansion coefficient, and diffusion coefficient, have been estimated. Nucleation rates of crystallization to two solid phases for Fe₃₃₁ at temperatures of 750, 800, and 850 K are presented. Both classical nucleation theory and diffuse interface theory are used to interpret our observed nucleation results. The interfacial free energy and the diffuse interface thickness between the liquid phase and two different solid phases are estimated from these nucleation theories.     

Molten-salt Synthesis and Properties of ZnS with Hexagonal Prism Morphology

ZnS with hexagonal prism morphology has been synthesized successfully by molten-salt method with ZnS nanoparticles as precursors, and the ZnS nanoparticles were prepared by one-step solid-state reaction of Zn（CH3COO）2·2H2O with Na2S·9H2O at ambient temperature. Crystal structure and morphology of the product were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and HRTEM. Ultraviolet-visible optical absorption spectrum of the ZnS hexagonal prism shows a distinct red shift from that of bulk ZnS crystals and photoluminescence spectrum exhibits strong emissions at 380 and 500 nm, respectively. Further experiments were designed and the formation mechanism of the ZnS hexagonal prism has been also discussed in brief.     

Nanocomposites based on opal matrices and iron subgroup metal nanoparticles

Three-dimensional nanocomposites based on ordered opal matrices (OMs) and metal nanoparticles were prepared by the reduction of salts and oxides of iron subgroup metals (M = Ni, Co, and Fe) and their binary and ternary mixtures with isopropanol in a supercritical state. The effect of the composition of the initial salts (nitrates or chlorides) on the phase composition of OM/M composites was determined. For a binary system of Ni and Co nitrates (1 : 1), the particles of a NiCo solid solution in a cubic modification were formed in an opal matrix after treatment in supercritical isopropanol. For the Ni-Fe and Co-Fe systems, the nanoparticles of solid solutions based on nickel or ??-, ??-cobalt metal and also oxides or an MFe₂O₄ phase with the spinel structure were formed in opal matrices with the use of iron trichloride. The nanoparticles of iron metal and Ni₃Fe, NiFe, and CoFe intermetallic compounds with regular distributions of metal atoms were detected for the first time in addition to spinel phases upon the reduction of composites with Fe, Ni-Fe, and Co-Fe nitrates with supercritical isopropanol. The reduction of composites obtained by the thermal treatment of a ternary mixture of nickel and cobalt nitrates and iron chloride in supercritical isopropanol led to the formation of solid solution nanoparticles based on Ni, Co, and Fe with an fcc structure and an oxide phase with the spinel structure in the voids of opal matrices. In the composite based on an opal matrix and a ternary system of Ni-Co-Fe nitrates (1 : 1 : 1), the complete reduction of spinel phases to the intermetallic phases of Ni₃Fe, NiFe, and CoFe was noted.     

Fe_(6-x)Al_x团簇的结构和磁性能

在密度泛函理论的BPW91水平上,对Fe6-xAlx团簇进行了结构优化,并将获得的最低能结构进行稳定性分析以及电子结构和磁性能的计算.计算结果表明,铁原子倾向团聚在一起并占据最高配位,Al原子则倾向分布在铁簇的周围尽最大可能地与Fe配位成键.Fe6-xAlx团簇的磁性随Al原子数目增加呈现下降趋势,自然轨道分析揭示Fe4s和Al3s与Fe3d之间的杂化是导致团簇磁矩下降的主要原因.     

3C-SiC的结构和热力学性质

利用第一性原理平面波模守恒赝势密度泛函理论研究了3C-SiC的结构, 其零温(0 K)零压下的晶格常数、体弹模量及其对压强的一阶导数、弹性常数的计算结果与实验值和其它理论计算结果相符合. 通过准谐德拜模型, 得到了不同温度不同压强下的热容和德拜温度, 发现热容随着压强增加而减小, 德拜温度随压强增加而增加, 并成功地获得了相对晶格常数、相对体积、体弹模量、热膨胀系数与温度和压强的关系.     

掺铁碳化硅陶瓷的制备及其吸波性能

将羰基铁和液态聚碳硅烷(LPCS)反应生成的铁(Fe)溶胶与固态聚碳硅烷(PCS)混合,合成出不同Fe质量分数的PCS先驱体,然后经氧化交联和高温热解制备了不同Fe质量分数的磁性碳化硅陶瓷(Fe/SiC),系统地研究了Fe元素的引入对SiC陶瓷的组成、结构、磁性能和介电性能的影响规律。 研究发现,当Fe质量分数小于8.94%时,在热解过程中,Fe元素可以显著促进SiC_xO_y的分解,生成β-SiC,且随着Fe质量分数的增加,β-SiC的结晶峰越来越强;但随着Fe质量分数继续增加,达11.78%时,则主要生成Fe₃Si;Fe/SiC陶瓷均呈铁磁性,其饱和磁化强度随着Fe质量分数的增加而呈指数形式增加;当Fe质量分数为4.19%时Fe/SiC陶瓷在12.4 GHz具有最小的反射损耗,为-9.4 dB,同时低于-5 dB的带宽为2.4 GHz,Fe质量分数为8.94%时,低于-5 dB的带宽则为3.7 GHz,可用作良好的微波吸收材料。     

On the Use of Amine–Borane Complexes To Synthesize Iron Nanoparticles

The effectiveness of amine–borane as reducing agent for the synthesis of iron nanoparticles has been investigated. Large (2–4 nm) Fe nanoparticles were obtained from [Fe{N(SiMe₃)₂}₂]. Inclusion of boron in the nanoparticles is clearly evidenced by extended X‐ray absorption fine structure spectroscopy and Mössbauer spectrometry. Furthermore, the reactivity of amine–borane and amino–borane complexes in the presence of pure Fe nanoparticles has been investigated. Dihydrogen evolution was observed in both cases, which suggests the potential of Fe nanoparticles to promote the release of dihydrogen from amine–borane and amino–borane moieties.     

The structural,electronic, elastic,vibration and thermodynamic properties of GdMg

We have investigated the structural, elastic, electronic, vibration and thermodynamic properties of GdMg alloy using the methods of density functional theory within the generalized gradient approximation (GGA) for the exchange-correlation functional. We have presented the results on the basic physical parameters, such as the lattice constant, bulk modulus, pressure derivative of bulk modulus with and without spin-polarization (SP), second-order elastic constants, Zener anisotropy factor, Poisson's ratio, Young's modulus, and isotropic shear modulus. The thermodynamic properties of the considered compound are obtained through the quasi-harmonic Debye model. In order to obtain further information, we have also studied the pressure and temperature-dependent behavior of the volume, bulk modulus, thermal expansion coefficient, heat capacity, and Debye temperature in a wide temperature range of 0–1200 K. We have also calculated phonon frequencies and one-phonon density of states for B2 structure of GdMg compound. The temperature-dependent behavior of heat capacity and entropy obtained from phonon density of states for GdMg compound in B2 phase is also presented.     

超声波分散法制备SnS纳米微粒及其光学性能

在有机介质液体石蜡中,以金属锡和硫粉为原料,通过超声波分散的方法快速地制备了SnS纳米微粒,并提出了可能的形成机理.采用透射电子显微镜、X射线粉末衍射仪和X射线光电子能谱仪对产品进行了形貌、组成和结构表征,并在室温下研究了其光致发光性能.     

Molecular dynamics simulation of amorphous SiO2 nanoparticles

Molecular dynamics simulation of amorphous SiO2 spherical nanoparticles has been carried out in a model with different sizes, 2, 4, and 6 nm, under non-periodic boundary conditions. We use the pair interatomic potentials which have weak Coulomb interaction and Morse type short-range interaction. Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation. Structural properties of amorphous nanoparticles obtained at 350 K have been studied via partial radial distribution functions (PRDFs), mean interatomic distances, coordination numbers, and bond-angle distributions, which are compared with those observed in the bulk. Calculations of the radial density profile in nanoparticles show the tendency of oxygen to concentrate at the surface as observed previously in other amorphous clusters or thin films. Size effects on structure of nanosized models are significant. The calculations show that if the size is larger than 4 nm, amorphous SiO2 nanoparticles have a distorted tetrahedral network structure with the mean coordination number ZSi-O approximately 4.0 and ZO-Si approximately 2.0 like those observed in the bulk. Surface structure, surface energy, and glass transition temperature of SiO2 nanoparticles have been obtained and presented.