Synthesis of colloidal LaF3： 0.04Yb^3＋, 0.01Er^3＋ nanocrystals with green upconversion luminescence

A synthesis of LaF3：0.04Yb^3＋,0.01Er^3＋ nanocrystals with oleic acid as a capping ligand was presemed. The X-Ray Diffraction （XRD） pattern indicated that the power was a single hexagonal phase. Transmission Electron Microscopy （TEM） demonstrated that the average size of the nanocrystals was less than 10 nm, with a narrow size distribution. The nanocrystals were dispersible in nonpolar solvents and form a fully transparent colloidal solution, and the solution was stable for several months without any aggregates. The Yb^3＋-Er^3＋ codoped nanocrystal colloidal solution exhibited a bright green upconversion fluorescence under 980 nm excitation from a diode laser. The nanocrystals were potentially applicable in biolabeling and bioimaging.     

Catalytic combustion of diesel soot over K2NiF4-type oxides La2-xKxCuO4

Nanostructure K2NiF4 type oxides La2-xKxCuO4 complex oxides were prepared using the Sol-Gel method, characterized by X-Ray Diffraction （XRD）, Fourier Transform Infrared （FT-IR）, and Scanning Electron Microscopy （SEM）. The catalytic activity for soot combustion was evaluated by the Temperature-Programmed Reaction （TPO） technique. The results demonstrated that the substitution quality of K^＋ for La^3＋ at the A-site would increase the catalytic activities of La2-xKxCuO4 for soot combustion greatly; the substitution quality affected the structure and catalytic activity obviously. The La1.8K0.2CuO4 complex oxides with tetrahedral structures had the best catalytic activity for soot combustion, and the ignition temperature of soot combustion was lowered from 490 to 320 ℃.     

Explore the Strengthening Mechanisms of the Ultra-Low Carbon and Low Alloy Steel

Room temperature tensile tests were carried on the hot-rolled state ultra-low carbon and low alloy cabainite and martensite steels which were get by different finishing temperatures and different cooling methods.We used the Scanning Electron Microscopy (SEM),Electron Backscattered Diffraction (EBSD) and X-Ray Diffractometer (XRD) to identify the metallographic structure and analyse the precipitated phase.The inherent mechanism of high strength of ultra-low carbon and low alloy bainite and martensite steels was discussed,and the analysis indicated that the reinforcement of ultra-low carbon and low alloy bainite and martensite steels was mainly produced by the superposition of the dislocation strengthening,solution strengthening and grain refinement strengthening.     

Some fundamental aspects of annealing and pickling stainless steels

The effects of annealing conditions on the scaling behavior of Types 304 and 430 strip and bar products were investigated as were surfaces resulting from three conventional descaling practices. Scanning Electron Microscopy (SEM), Scanning Auger Microprobe (SAM), Electron Spectroscopy for Chemical Analysis (ESCA), and X-Ray Diffraction (XRD) studies were aimed at correlating scale characteristics with ease of scale removal. Scale morphology as well as scale composition affects ease of scale removal; the magnitude of the effect depends on the descaling process used. For Type 304, the presence of a Mn sublayer seems to enhance descalability. The easy-to-descale samples of Type 430 all had a prominent Cr sublayer.     

Effect of annealing temperature on microstructure and electrochemical performance of La0.75Mg0.25Ni3.5Co0.2 hydrogen storage electrode alloy

To improve the cyclic stability of La-Mg-Ni system alloy, as-cast La0.75Mg0.25Ni3.5Co0.2 alloy was annealed at 1123, 1223, and 1323 K for 10 h in 0.3 MPa argon. The microstructure and electrochemical performance of different annealed alloys were investigated systematically by X-Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM）, X-Ray Photoelectron Spectroscopy （XPS）, and electrochemical experiments. The results obtained by XRD and SEM showed that the as-cast and annealed （1123 K） alloys had multiphase structure containing LaNis, （La, Mg）2（Ni, Co）7 and few LaNi2 phases. When annealing temperatures approached 1223 and 1323 K, LaNi2 phase disappeared. The annealed alloys at 1223 and 1323 K were composed of LaNi5, （La, Mg）2（Ni, Co）7 and （La, Mg）（Ni, Co）3 phases. With increasing annealing temperature, the maximum discharge capacity of the alloy decreased monotonously, but the cyclic stability was improved owing to structure homogeneity and grain growth after annealing, as well as the enhancement of anti-oxidation/corrosion ability and the suppression of pulverization during cycling in KOH electrolyte.     

Alkoxide route for preparing hydroxyapatite and its coatings

The preparation of hydroxyapatite using n-butanol or ethanol solutions of P2O5 and Ca glycoxide as precursors of P and Ca was investigated by nuclear magnetic resonance (NMR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Stable mixed solutions of the precursors could be obtained in the presence of acetic acid (HOAC). For the mixed solution of Ca glycoxide with the ethanol solution of P2O5, a lower HOAC/Ca ratio was needed since the ethanol solution of P2O5 contained a lower concentration of H3PO4, a species that easily forms precipitates in the presence of the Ca containing species. An amorphous powder was obtained by heating the stable solution of Ca glycoxide and PO(OH)x(OEt)3-x with an HOAC/Ca ratio of 4 in a hot plate at approximately 150 degrees C. Hydroxyapatite (HAP) was directly formed after calcining the amorphous powder at 500 degrees C. The stable mixed solutions of Ca glycoxide and the alcoholic solutions of P2O5 were used to prepare HAP coatings on alumina substrates using a dip-coating method. The resulting ceramic coatings have a rough surface and an adhesion strength of about 10 MPa. The morphology of the coatings is dependent on the preparation chemistry.     

Sol-gel processed Ce^3＋, Tb^3＋ codoped white emitting phosphors in Sr2Al2SiO7

Sr2Al2SiO7：Ce^3＋, Tb^3＋ white emitting phosphors were fabricated using the sol-gel method. X-Ray Powder Diffraction （XRD） analysis confirmed the formation of Sr2Al2SiO7：Ce^3＋, Tb^3＋. Scanning Electron Microscopy （SEM） observation indicated that the microstructure of the phosphor consisted of regular fine grains with an average size of about 0.5-1 μm. Luminescence properties were analyzed by measuring the photoluminescence spectra. The Ce^3＋, Tb^3＋-codoped Sr2Al2SiO7 phosphors showed four main emission peaks： one at 414 nm for Ce^3＋ and three at 482, 543, and 588 nm for Tb^3＋. The emission spectra of the samples with different doping concentrations showed that the Tb^3＋ emission was dominant because of the persistent energy transfer from Ce^3＋. The decay characteristic was better than that prepared by the solid-state process in the comparable condition. The codoped phosphor displayed long persistent white phosphorescence.     

Preparation and CO conversion activity of ceria nanotubes by carbon nanotubes templating method

Ceria nanotubes with high CO conversion activity by means of carbon nanotubes as removable templates in the simple liquid phase process were fabricated under moderate conditions. The pristine CNTs were first pretreated by refluxing in a 30% nitric acid solution at 140 ℃ for 24 h, then dispersed in an ethanolic Ce（NO3）3.6H2O solution with ultrasonic radiation at room temperature for 1 h. Under vigorous stirring, NaOH solution was added drop by drop into the above ethanolic solution until the pH value was 10. The product was collected and repeatedly washed with ethanol and on drying at 60 ℃, the CeO2/CNT composites were obtained. Then, the as-prepared composites were heated at 450 ℃ in an air atmosphere for 30 min to remove CNTs. The ceria nanotubes were characterized by X-Ray Diffraction （XRD）, Transmission Electron Microscopy （TEM）, and X-Ray Photoelectron Spectrum （XPS）. The results showed that the ceria nanotubes were polycrystalline face-centered cubic phase and were composed of lots of dense cefia nanoparficles. The diameter of cefia nanotubes was about 40-50 nm. Catalytic activity of the product for CO oxidation was carded out at the region of 30-300 ℃ in a U-shaped quartz reactor with feeding about 0.15 g of the catalyst, which was loaded on Al2O3 carder. The inlet gas composition was 1.0% CO and 28% O2 with N2 as balance, and the rate of flow was kept at 40 ml/min. The catalytic products were analyzed by gas chromatography. The as-repared CeO2 nanotubes showed higher CO oxidation activity, which indicated that the morphology of ceria products affected the catalytic performance. The ceria nanotubes supported on Al2O3 demonstrated that conversion temperature for CO oxidation to CO2 was lower than that for bulk catalysts.     

Ti-Deoxidized Products and Formation Mechanism of Intragranular Ferrite in High Grade Pipeline Steels

 High grade pipeline steels were prepared using vacuum carbon deoxidization process combined with a final Ti-deoxidation process. The microstructure of the as-cast steels was investigated by using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). SEM observation shows the formation of Intragranular ferrite (IGF) structure was induced by fine inclusions. TEM selected area diffraction patterns (SAD) and elemental distribution analysis indicated that these inclusions are mainly Ti2O3 and MnS. It was also found that Ti2O3 may act as nucleus in the formation of MnS during solidification process. Raman spectroscopic analysis demonstrated the presence of another phase, MnTiO3, which could be formed through entrapment of Mn element by Ti2O3. It is believed that the formation of Mn-depleted region in the inclusions and thus the formation of MnTiO3 phase will lead to increased Mn pickup from matrix and promoted the formation of IGF during solidification of molten steel.     

镍铬铸铁的冲蚀磨损行为

利用MCF-30型冲蚀磨损试验机对镍铬铸铁进行冲蚀磨损试验,采用扫描电镜(SEM)、透射电镜(TEM)、XRD技术对其组织和冲蚀磨损后的形貌进行表征,分析了冲蚀角、冲蚀介质酸碱度对其冲蚀磨损性能的影响,总结了其冲蚀磨损规律。结果表明,镍铬铸铁在960℃风淬+250℃回火处理后,Cr与Fe、C形成(Fe,Cr)3C型合金碳化物,呈断续网状分布,起到了抗磨骨架的作用,Ni固溶于铁素体中强化基体;不同冲蚀角下,其冲蚀磨损曲线呈现"M"形,最大冲蚀率出现在60°冲蚀角;强酸对其冲蚀磨损影响较大,当pH≥3的时候,弱酸对其冲蚀磨损量几乎无影响。对其冲蚀磨损机理进行了分析。     

Effect of Ho-doping on photocatalytic activity of nanosized TiO2 catalyst

Ho-doped TiO2 nanoparticles with higher photocatalytic activity were prepared by an acid-catalyzed sol-gel method. The photocatalytic decomposition of methyl orange in aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The effects of Ho doping on the crystallite sizes, crystal pattern, surface composition, and optical property of the catalysts were investigated by means of techniques such as X-Ray Diffraction （XRD）, Transmission Electron Microscopy （TEM）, Diffuse Reflectance UV-Vis Spectroscopy （UV-Vis DRS）, Fourier Transform Infrared （FT-IR）, and Photo-Luminiscence （PL） spectra. Moreover, the modification mechanism of Ho doping was also discussed. The results showed that Ho doping could inhibit phase transformation from anatase to rntile, suppress the growth of TiO2 grains, cause blue shift of the absorption spectrum edge, accelerate surface hydroxylation, and enhance the separation efficiency of photoinduced electron-hole pairs, which resulted in a significant improvement in the photoreactivity of Ho-doped TiO2. Among them, the Ho-doped TiO2 calcined at 500℃ achieved the highest photocatalytic activity.     

机械化学对Na-MMT结构性质的影响

以钠基蒙脱土(Na-MMT)为研究对象,分别对其在分散介质空气、无水乙醇、N,N-二甲基甲酰胺(DMF)中进行球磨,再利用粒度分析(LPS)、X-射线衍射(XRD)、热重分析(TGA)、扫描电镜分析(SEM)等方法研究了不同分散介质中球磨对钠基蒙脱土结构性质的影响。     

落球冲击下高铬铸铁磨球中残余奥氏体的形变与相变

用透射电镜和微区Ｘ射线衍射分析了落球冲击后高铬铸铁磨球皮下不同深度残余奥氏体形变和相变情况。发现不同深度发生形变和相变的程度是不同的，在磨球表面最大，随着深度增加形变和相变的程度减小。产生可观塑性变形的深度在５ｍｍ以内，而发生相变的深度可达１０ｍｍ。不同深度相变的机理不同。共晶碳化物在落球冲击下也能发生一定的塑性变形。最后分别讨论了显微组织变形和相变对磨球抗剥落破碎性能的影响。     

溶胶-凝胶法制备金银合金纳米线阵列

金银纳米材料因其纳米尺度而在光电等方面有许多优良的性质和用途, 若将两者混合可大大改善其性能. 为此, 利用阳极氧化法制备出氧化铝模板, 并用自制的模板结合溶胶凝胶法成功地制备了金银合金纳米线. 扫描电镜照片显示氧化铝模板具有比较直的孔道和高的孔洞率, 金银合金纳米线由于模板的限制作用而呈现出高度的有序性. 透射电镜照片显示单根纳米线长而光滑, 选区电子衍射显示纳米线具有多晶结构, 能谱分析表明纳米线是由金和银两种元素组成. 文中对合金纳米线的形成原因和影响因素都做了简单的分析.     

Effect of Plastic Deformation on Magnetic Properties of Fe-40%Ni-2%Mn Austenitic Alloy

The effects of plastic deformation on the magnetic properties of austenite structure in an Fe-40% Ni-2 % Mn alloy is investigated by using Mossbauer spectroscopy and Differential Scanning Calorimetry （DSC） techniques The morphology of the alloy has been obtained by using Scanning Electron Microscopy （SEM）. The magnetic behaviour of austenite state is ferromagnetic. After plastic deformation, a mixed magnetic structure including both paramagnet- ic and ferromagnetic states has been obtained at the room temperature. The volume fraction changes, the effective hyperfine fields of the ferromagnetic austenite phase and isomery shift values have also been determined by Mossbauer spectroscopy. The Curie point （Tc） and the Neel temperature （TN） have been investigated by means of DSC system for non-deformed and deformed Fe-Ni-Mn alloy. The plastic deformation of the alloy reduces the TN and enhances the paramagnetic character of austenitic Fe-Ni-Mn alloy.     

Preparation and characterization of BaLiF3：Er^3＋ nanoparticles by the hydrothermal microemulsion synthesized method

Nanoparticles of BaLiF3：Er^3＋ were prepared from the quaternary microemulsions of Cetyltrim-Enthyl Ammonium Bromide （CTAB）, n-butanol, n-octane, and water, using the hydrothermal-microemulsion technique. The complex fluorides were characterized by means of X-ray power diffraction, Environmental Scanning Electron Microscopy （ESEM）, and fluorescence spectra. The positions and intensifies of the peaks in the XRD pattern of the final products indicate the formation of BaLiF3·Er^3＋. No other peaks or impurities were detected. The average size of the nanoparticles, calculated with the Debye-Scherrer equation was 98.45 nm, which was in agreement with the result of ESEM. The infrared fluorescence spectra consisted of four peaks with a predominant peak located at 1540 nm.     

大塑性变形对纯铜力学性能的影响

室温下采用锻压对纯铜进行了大变形加工，对变形后的纯铜样品进行了拉伸和硬度测试，并采用扫描电镜对拉伸试样的断口进行了分析。研究结果表明：经过大变形后，由于纯铜的晶粒得以细化，抗拉强度、屈服强度、硬度和断裂延伸率都显著增加。     

Infrared to ultraviolet upconversion luminescence in Nd3+ doped nano-glass-ceramic

Nd3+ doped transparent oxyfluoride glass ceramic containing β-YF3 nanocrystals was prepared and the upconversion luminescence behaviors of Nd3+ in the precursor glass and glass ceramic were investigated. Under 796 nm laser excitation, ultraviolet upconversion emissions of Nd3+ ions at 354 nm (4D3/2→4I9/2) and 382 nm (4D3/2→4I11/2) were observed at room temperature. Power dependence analysis demonstrated that three-photon upconversion processes populated the 4D3/2 excited state. In comparison with those of the precursor glass, the ultraviolet emissions were enhanced by a factor of 500 in the glass ceramic, which was attributed to the change in the ligand field of Nd3+ ions and the decrease in phonon energy because of the partition of Nd3+ ions into the β-YF3 nanocrystals after crystallization.     

ESEM observation of thermal shock cracking

We report a simple method for a quick and efficient localization of thermal shock cracks as narrow as 1 micron or less, using Environmental Scanning Electron Microscopy (ESEM). The non-destructive character of the technique is exploited in order to observe relevant fractographic features of the crack pattern.