燃烧法制备纳米CdFe2O4及表征

以Fe（NO3）3.9H2O和Cd（NO3）2.4H2O为原料,以柠檬酸为还原剂,采用燃烧法制备了CdFe2O4纳米粉体,用X射线粉末衍射仪（XRD）、透射电子显微镜（TEM）、红外光谱（IR）和振动样品磁强计（VSM）等手段对样品进行了表征,结果表明,样品为尖晶石型铁酸镉纳米粉体,其粒径大约为20—50nm,且具有超顺磁性。     

尖晶石型纳米铁酸镍的制备与磁性研究

以Fe（NO3）3·9H2O和Ni（NO3）2·6H2O为原料,用柠檬酸为还原剂,采用燃烧法制备了NiFe2O4纳米粉体,用X射线粉末衍射仪（XRD）、透射电子显微镜（TEM）、红外光谱（IR）和振动样品磁强计（VSM）等手段对样品进行了表征,结果表明,样品为立方晶系尖晶石铁酸镍纳米粉体,其粒径在20—40nm之间,具有超顺磁性,并探讨了焙烧温度、焙烧时间对样品磁性的影响。     

在N2中［VnCr3－n(μ3-O)（μ-O2CCH3）6（THF）3］X［n＝0－3，X＝Cl－，ClO－4，（VO5）－0.5］及［VnFe3－n（μ3-O）（μ-O2CCH3）6（THF）3］X（n＝0－3，X＝Cl－）反应行为的原位红外光谱研究

利用原位红外光谱研究标题化合物在N2中的反应行为。发现它们在不同温度下能使乙酸分别转化为丙酮和甲烷。它们对乙酸的丙酮化反应活性顺序：［V3OAT］＞［VFe2OAT］，［V2CrOAT］＞［Fe3OAT］，［VCr2OAT］＞［Cr3OAT］［OAT＝（μ3-O）（μ-O2CCH3）6（THF）3］。它们对乙酸的甲烷化反应活性顺序：［Cr3OAT］＞［VCr2OAT］，［V2CrOAT］＞［V3OAT］＞［VFe2OAT］，［FeO3OAT］。对乙酸的丙酮化反应活性［Fe3OAT］明显低于［Fe3OAH］［OAH＝（μ3-O）（μ-O2CCH3）6（H2O）3］。对乙酸的甲烷化反应活性［Cr3OAT］也明显低于［CrOAH］。并对上述［Fe3OAT］，［Cr3OAT］与［Fe3OAH］，［Cr3OAH］之间差异进行了讨论     

水热法掺杂的Yb^3＋对NiYbxFe2-xO4铁氧体磁性和形貌的影响

本文以研究稀土元素镱掺杂对镍铁氧体磁性能的影响用为目的,采用水热法,去离子水作为溶剂,用硝酸镍（Ni（NO3）2·6H2O）,硝酸铁（Fe（NO）3·9H2O）,硝酸镱Yb（NO3）3·5H2O,氢氧化钠（NaOH）为原料,制备出镍铁氧体NiYbxFe2-xO4纳米粉体.利用X射线衍射（XRD）,X射线能谱仪（EDS）,扫描电镜（SEM）,透射电子显微镜（TEM）,振动样品磁强计（VSM）在成分,定性定量和形貌等方面进行了表征.结果表明,稀土元素镱掺杂将会降低镍铁氧体纳米粉体的晶粒尺寸.稀土离子磁矩的磁稀释作用导致镍铁氧体纳米磁性材料的饱和磁化强度降低,并且随着掺杂量的逐渐增加,样品的饱和磁化强度和矫顽力逐渐降低.     

聚合物对非离子十二烷基聚氧乙烯聚氧丙烯醚浊点的影响

测定了水溶性高分子聚乙二醇（PEG1000、PEG2000、PEG6000）和聚乙烯吡咯烷酮（PVP－K30、PVP－K90）对三种非离子表面活性剂十二烷基聚氧乙烯聚氧丙烯醚C12H25O（EO ）m(PO)nH(LS36,m=3,n=6,LS45,m=4,n=5;LS54,m=5,n=4)浊点的影响。结果表明,聚乙二醇（PEG） 可使三种表面活性剂水溶液浊点降低;而聚乙烯吡咯烷酮（PVP）随其浓度增加,表面活性剂溶液浊点先升高然后又下降;浊点下降程度与聚合物浓度和分子量有关。     

水热法制备均一形貌的ZnO微米棒

以Zn（Ac）2· 2H2O、KI和N2H4· H2O反应物,在未使用任何表面活性剂的简单水热反应体系中制得了ZnO微米棒.采用X射线粉末衍射仪（XRD）、扫描电子显微镜（SEM）对产物的晶体结构、形貌进行了表征和分析.测试结果表明,所得产物为六方纤锌矿结构ZnO微米棒,平均直径为1μm,长度4μm.     

SnO2纳米晶的水热合成及其气敏特性

以SnCl2·2H2O和H2O2为主要原料,在无水乙醇和水的混合溶剂中,不同温度下,水热法制备了不同粒径的SnO2纳米晶.利用X射线粉末衍射、透射电子显微镜和比表面积测定等手段对产物进行了表征,并对产物的气敏性进行了测定和分析.结果表明,120、150和180℃时制备的产物均为单相SnO2,其对应的比表面积分别为210.3、125.6和69.2m2/g.产物SnO2对还原性气体CO和C2H5OH均有一定的气敏性,其中对C2H5OH气体的气敏性远大于CO气体.产物气敏性的大小与其比表面积的大小有关,比表面积越大,气敏性越高.     

稀土N，N＇-双（2-吡啶甲酰胺）-1，2-乙烷配合物合成及与DNA的作用

合成了四种N，N＇-双（2-吡啶甲酰胺）-1，2-乙烷（H2L）稀土配合物。经过对元素分析，红外光谱，紫外光谱，热重分析和摩尔电导值的分析，确定配合物的组成为：[Ln（H2L）（NO3）2]（NO3）·3H2O（Ln=Sm，Eu，Gd，Tb）。光谱测试结果表明：配体H2L中酰胺羰基氧和吡啶氮分别与稀土离子配位，硝酸根为双齿配体，Ln（Ⅲ）与H2L形成了1：1的螯合物。另外，通过紫外光谱、荧光光谱和表面增强拉曼光谱方法对Sm配合物与DNA之间的作用进行了初步的研究。实验结果显示随着DNA的加入[Sm（H2L）（NO3）2]（NO3）·3H2O配合物在265m处的紫外吸收峰逐渐减小，并产生红移现象，得到配合物与DNA的结合常数为1．24×10^5.Sm配合物使EB-DNA体系发生荧光猝灭，由于配合物和EB争夺与DNA的结合位点，从而使体系中游离的EB增多。表面增强拉曼光谱峰的变化亦显示随着DNA的加入配合物的谱峰强度减弱，同时1282cm^-1处的谱峰消失，说明配体的吡啶环在一定程度上插入了DNA的双螺旋平面，导致吡啶环的电子云密度发生改变。以上结果表明配合物和DNA发生了显著的作用。     

NdKYW新型全固体激光器研究

报道了采用半导体二极管抽运的掺钕钨酸钇钾［Nd3+KY(WO4)2］(简称NdKYW)蓝绿光激光器。腔内倍频采用了Ⅰ类临界相位匹配LBO(LiB3O5)晶体作为倍频器,阈值抽运功率为400 mW,在抽运功率为2 W时获得了200 mW的530 nm连续激光输出,其倍频光的光-光转换效率为10%。     

希夫碱配合物M3L3(NO3)6(H3O)2的合成与光谱性质

以4-氨基-1,2,4-三氮唑与对二甲氨基苯甲醛为原料, 在冰醋酸催化下合成了配体4-氨基-1,2,4-三氮唑缩对二甲氨基苯甲醛（L）。 然后利用L与过渡金属硝酸盐［M(NO3)2·xH2O(M=Cu,　Co,　Zn,　Cd; x=3～6)］在无水乙醇中反应, 制得固态配合物M3L6(NO3)6(H2O)2。 通过元素分析、 红外光谱、 紫外光谱、 荧光光谱等手段对合成的配体及配合物进行了表征。 实验结果表明, 该物质是一种多晶粉末状的发光材料,　在紫外光的激发下,　在乙醇溶液体系中的荧光发射峰在416 nm处,　为蓝色荧光, 色纯度高,　荧光量子效率高, 而配合物M3L6(NO3)6(H2O)2的荧光发射峰则红移至445 nm左右, 同时荧光强度显著增强。　M3L6(NO3)6(H2O)2中与M(Ⅱ)发生配位作用的基团是配体中三氮唑环上的氮原子。     

Particle Size of Pneumatically Conveyed Powders Measured Using Impact Duration

CSIRO Minerals has developed a technique for measuring particle size in pneumatically conveyed powders [1] by measurement of the acoustic waves produced by particle impacts upon a specially designed transducer. Previous work has focused on using the peak acoustic wave amplitude to determine particle size. This produces a spectrum that is hard to determine the particle size from, as the peak amplitude is a non‐linear function of particle diameter, and is strongly affected by angle of incidence and velocity of the impacting particle. In this paper impact duration measurements are used to overcome these difficulties while retaining the advantages of being able to measure in high solids loadings of up to at least 0.5 kg/m³ of powder. In laboratory tests the impact size monitor's (ISM) results have been correlated with optical diffraction measurements of the mean (by number) powder size with a correlation coefficient of 0.985 and a relative error of 5.5 %. The ISM operated successfully in the laboratory at a loading of 0.5 kg/m³ of powder and measured particles down to 50 microns in size.     

Synthesis and characterization of nanocrystalline titanium nitride powder from rutile and anatase as precursors

In this research nanosized titanium nitride powder was synthesized through reaction of titanium oxide with ammonia gas. The reaction was carried out at a very slow heating rate. Two different TiO₂ starting powders contained rutile and anatase phase and differed in initial particle size and surface area. The crystallite size of TiN powders synthesized at 1000 °C was obtained about 40 nm for anatase sample. Surface area and particle size were found to be 19 m²/g, 70 nm for rutile sample and 31 m²/g, 39 nm for anatase sample, respectively. The rutile sample showed an increasing trend in surface area during conversion to the nitride, whilst the anatase sample followed an adverse trend. TiN powder synthesized from anatase had the highest surface area and smallest particle size due to the specification of initial precursor.     

Core-loss reduction of Fe–Si–Cr crystalline alloy according to particle size in the high frequency band

We used different sizes of gas atomized Fe–Si–Cr alloy powder to produce soft magnetic composites (SMCs), this alloy has higher resistivity than existing materials used in SMCs. These powders were prepared by sieving raw materials which had an average size from less than 25 μm to over 63 μm. Our experiments show that as particle size decreases, the magnetic saturation tends to increase, the sample made from the powder with particles 25–38 μm in size recorded the highest magnetic saturation of 169.38 emu/g. Additionally, as particle size decreased, permeability increased. The sample made from powder with particles under 25 μm had a permeability of 20.7 H/m at 1 MHz. Also, the relationship between particle size and quality factor was found to be inversely proportional. Finally, the minimum core-loss was 187.26 kW/m³ at 1 MHz for the sample made from powder whose constituent particles are under 25 μm.     

Synthesis and characterization of nanoparticulate films for intermediate temperature solid oxide fuel cells

Nanocrystalline strontium-doped lanthanum manganite (LSM) with a high specific surface area of 70 m²/g was synthesized via spray pyrolysis. The as prepared powder was characterized by ex-situ X-ray diffraction (XRD), in-situ high temperature X-ray diffraction (HTXRD), ex-situ nitrogen adsorption and high resolution scanning electron microscopy (HRSEM). LSM nanopowders with a mean particle size of 40 nm were dispersed in water-based media using ultrasonication. Nanocomposite LSM-GDC (gadolinium doped ceria) thin films were prepared by single step spin coating of co-stabilized LSM and GDC dispersions. The thickness of these thin films (≤ 1 μm) is more than 10 times lower than conventional cathode layers prepared by screen printing. The interfacial polarization resistances were 68, 118 and 220 mΩ cm² at 850, 800 and 750 °C, respectively. The high performance is attributed to small grain size, high porosity and large specific surface area. This method offers a very cost effective approach for the preparation of electrochemically highly active porous thin films, particularly applicable for micro solid oxide fuel cells.     

Influence of particle size and compaction pressure on the magnetic properties of iron-phenolic soft magnetic composites

This paper investigates the effect of particle size and compaction pressure on the magnetic properties of iron-phenolic soft magnetic composites (50 Hz-1000 kHz). The results showed that the optimum amount of phenolic resin to attain maximum permeability and minimum loss factor at 10 kHz is 0.7 wt% for samples containing iron powder with average particle size ∼150 μm compacted at 800 MPa. In accordance with this resin content, at high frequencies (>300 kHz), the sample with lower particle size ∼10 μm exhibits higher magnetic permeability, higher operating frequencies and lower imaginary part of permeability. With increase in the compaction pressure, specific resistivity decreases and imaginary and real parts of permeability increase at low frequencies.     

Effect of starting powder on screen-printed YSZ films used as electrolyte in SOFCs

Screen-printing technology was developed to fabricate dense YSZ electrolyte films onto NiO–YSZ porous anode substrates. A single fuel cell of Ni-YSZ/YSZ (31 μm)/LSM-YSZ was successfully prepared by screen-printing technology. Using humidified hydrogen as fuel and ambient air as oxidant, the fuel cell provided the maximum power densities of 0.18, 0.33, 0.58, 0.97 and 1.3 W/cm² at 650, 700, 750, 800 and 850 °C, respectively. The properties of the starting YSZ powder exerted a significant effect on the characteristics of the screen-printed YSZ electrolyte films. The aggregates of the powder could be partially broken by ball milling. The YSZ powder with a small particle size and a narrow particle size distribution helped to obtain dense YSZ films. The films prepared from the YSZ powder with high aggregates were very porous, which resulted in a low open circuit voltage, a high ohmic resistance, a high polarization resistance and thus a poor cell performance.     

Increase of the blue upconversion emission in YAG:Tm3+ nanopowders by codoping with Yb3+ ions

The YAG nanopowders were prepared by a co-precipitation method using nitrate and ammonium hydrogen carbonate as raw materials. To obtain homogenous precipitate, reverse-strike (adding salt solutions to the precipitant solution) technique was adopted. Therefore, single (Tm³⁺) and codoped (Tm³⁺–Yb³⁺) YAG nanopowders with a size between 40–90 nm have been obtained.Blue upconversion emission at around 480 nm has been found in YAG: Tm³⁺ nanopowders under excitation to the ³H₄ level of Tm³⁺ at around 800 nm. However, this upconversion emission in nanopowders codoped with Tm³⁺–Yb³⁺ ions is increased by a factor of about 10. The analysis of the temporal evolution of the involved levels and the dependence of the upconversion intensity on the pump power at 800 nm allowed to distinguish the upconversion mechanism. In YAG: Tm³⁺ nanopowders the upconversion mechanism is due to excited state absorption processes. However, in the codoped samples, Yb³⁺ ions acts as the sensitizers; in consequence, the blue upconversion is strongly increased.     

Influence of pH on characteristics of BaFe12O19 powder prepared by sol–gel auto-combustion

BaFe₁₂O₁₉ powders with nanocrystalline sizes were produced by sol–gel auto-combustion. Fe³⁺ and Ba²⁺, in a molar ratio of 11.5, were chelated by citric acid ions at different pH. After dehydration, auto-combustion and calcinations, BaFe₁₂O₁₉ powders were formed. TG/DSC indicated the action to form BaFe₁₂O₁₉ first occurred at about 800. XRD patterns of the annealed powders showed that the well-crystalline powder was produced when pH=10. In addition, the data from XRD showed the lattice parameters a and c, and the unit-cell volume V had a little decrease and the density went up with the increasing pH. The data from PPMS exhibited that pH in the starting solution had an important influence on magnetic properties. In this case, BaFe₁₂O₁₉ powder, of maximum magnetization M(3 T)≈60 A m²/kg, the remanent magnetization M_r≈33 A m²/kg and the intrinsic coercive H_c≈432 kA/m, was produced under the molar ratio of citric acid to the metal nitrate of 1.5 when pH=10.     

Exfoliation process of graphite via intercalation compounds with sulfuric acid

Exfoliation process of graphite via its residue compound from intercalation compound with sulfuric acid was discussed by measuring exfoliation volume and pore sizes among and inside their worm-like particles. Exfoliation process was found to divide into three steps, below 650, 650–800 °C and above 800 °C. Below 650 °C, exfoliation of graphite flakes to form worm-like particles occurred rapidly and so exfoliation volume increased. Above 650 °C, increase in exfoliation volume, i.e. decrease in bulk density, became more rapid, but the growth of pores inside the particles was not so much pronounced. Above 800 °C, the increasing rate in exfoliation volume seemed to become slow, change in bulk density looking small, but pores inside the particles grew more. Exfoliated graphite prepared at 1000 °C had the exfoliation volume of about 0.15 m³/kg (bulk density of about 7 kg/m³), which is composed of large spaces with the cross-sectional area of more than 8000 μm² and worm-like particles containing ellipsoidal pores with averaged cross-sectional area of about 320 μm² and sizes of about 31×11 μm².     

Synthesis of dendritic silver nanostructures by means of ultrasonic irradiation

In this paper, a simple and effective route for the synthesis of silver dendritic nanostructures by means of ultrasonic irradiation has been developed. Well-defined silver dendritic nanostructures were obtained by sonicating the aqueous solution of 0.04 mol/L silver nitrate with 4.0 mol/L isopropanol as reducing agent and 0.01 mol/L PEG400 as disperser for 2 h. The effects of the irradiation time, the concentration of Ag⁺ and the molar ratio of PEG to AgNO₃ on the morphology of silver nanostructures were discussed. The structures of the obtained samples were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray powder diffraction (XRD), and the chemical composition of the dendrites was examined by energy-dispersive X-ray spectrum (EDS).