Preparation and properties of nano-sized SnO2 powder

1　INTRODUCTIONSnO2isoneofthemainmaterialsusedingassensor.Becauseofthehumidityandgassensingfunction,itattractsmoreandmoreattentions.Butthepresentproblemishowtoimprovethestabilityandsensibilityofgassensor.Researchershavetakenmanymeasurestoresolvethisproble…     

Preparation and electrocatalytic properties of Ti/IrO2-Ta2O5 anodes for oxygen evolution

1 Introduction Oxygen and chlorine evolution reaction are the common and most important electrochemical reactions in electrolysis industry. As the Ti/RuO2-TiO2 anode has been successfully developed and widely employed in the electrochemical industry, the …     

8～14μm波段低发射率涂层材料的制备及性能研究

目的为满足市场对低发射率涂层的需要,制备了低发射率涂层材料,并讨论填料和基体树脂对其红外发射率的影响。方法以325、500、800、1000、1200、1500目铝粉为填料,丙烯酸树脂(AR)、环氧树脂(ER)和聚氨酯树脂(PR)为基体树脂,制备了低发射率涂层,分别从基体树脂种类、黏度、铝粉粒径及含量四个方面对涂层红外发射率进行了研究。结果 PR涂层在8~14μm波段的红外发射率最低,PR为低发射率涂层用基体树脂的最佳选择。涂层红外发射率随着基体树脂黏度的增大逐渐降低,并且变化趋势接近于线性。在研究范围内,铝粉的最佳粒径为325目,且涂层红外发射率随铝粉含量的增加而降低。结论制备的低发射率涂层的红外发射率低,而且环保。     

Preparation and photocatalytic activity of nano-TiO2 codoped with fluorine and ferric

Nano-F /Fe^3＋/TiO2 particles were prepared by hydrolysis of tetrabutyl titanate in a mixed CF3COOH-Fe（NO3）3-H2O solution. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe to evaluate their photocatalytic activities. The powders were characterized by X-ray diffraction （XRD）, energy dispersion X-ray spectrum （EDS） and Brunauer-Emmett-Teller （BET） surface area analysis. The results show that F- and Fe^3＋ are doped into TiO2. The F^- and Fe^3＋ doping can help to enhance the nano-TiO2 photocatalytic activity greatly. The appropriate codoping conditions for F-Fe are n（F）/n（TiO2）=2%, n（Fe）/n（TiO2）=0.05%, and the degradation rate of methylene blue at l h is improved from 73.2% to 87.5%. The codoped nano-F /Fe^3＋/TiO2 particles have higher BET specific surface area, smaller crystallite size and higher photocatalytic activity than those of undoped TiO2 particles.     

Preparation and Performance of Sm1-xCaxCrO3-δ as New Interconnect Materials for IT-SOFC

为了探索适用于中温固体氧化物燃料电池的连接材料,采用柠檬酸法制备了Sm1-xCaxCrO3-δ(x=0,0.1,0.2,0.3,0.4)粉体,研究了Ca2+掺杂对材料烧结性能、电性能和热膨胀性能等的影响。实验结果表明,Sm0.7Ca0.3CrO3-δ材料在空气中700℃时电导率为29.8 S·cm-1,氢气气氛中600°C时为1.68 S·cm-1。在30~1000℃温度范围内随着Ca2+掺杂量从0.1增加到0.4,平均热膨胀系数(TECs)值从7.34×10–6增大到8.05×10-6 K-1,与其它常用固体氧化物燃料电池材料热匹配性良好。     

Preparation and Performance of Spherical Ni Powder for SLM ProcessingEI北大核心CSCD

3D printing has attracted increasing interests in the field of metallic materials as it can effectively shorten the production cycle and create parts with complex shapes, which can hardly be produced by traditional methods. However, the gas atomization, as the mainstream method of preparing metal and alloy powders to meet the requirements of the processing of selective laser melting (SLM) at present, still has some limitations, such as hollow and/or satellite balls in the powder. This influences directly the density and performance of the printing parts. Moreover, the laser absorption in the smooth surface of powder particle is generally less than 10% in the laser processing, which hinders rapid heating of the powder. It has been found that the material can obtain multiple absorption of laser energy by increasing the surface roughness of powder particles, which can effectively improve the laser absorption rate and is beneficial to get the dense printing parts. Based on this, a novel method combining low temperature spray-drying with heat treatment was developed to prepare Ni powder with high purity, good sphericity, high flowability and narrow particle size distribution. The microstructure and laser absorptivity of the prepared Ni powder were compared with those of the commercial Ni powder prepared by gas atomization, and their influences on the microstructure and properties of the 3D printed bulk materials were investigated. It is found that the laser absorptivity of the Ni powder prepared by spray-drying is more than 2 times as high as that of the commercial Ni powder. This leads to a wider melting channel, smaller surface ten-sion and liquid-bridging force between particles in the printing process. As a result, the spheroidization phenomenon occurred on the surface of the printed bulk material can be avoided by the use of the spraydried powder, and the relative density is achieved as 99.2% at the as-printed state. In the microstructure of the printed bulk material, in addition to the cellular crystals, there are a number of fine columnar crystals, grown across the interlaminar boundaries, which is favorable for a high bonding strength between the interlayers.     

Preparation and electrochemical properties of LiNi1/3Co1/3Mn1/3O2–PPy composites cathode materials for lithium-ion battery

Layered LiNi_1/3Co_1/3Mn_1/3O₂ was synthesized by co-precipitation method, and a series of polypyrrole–LiNi_1/3Co_1/3Mn_1/3O₂ composites were then prepared by polymerizing pyrrole monomers on the surface of LiNi_1/3Co_1/3Mn_1/3O₂. The bare sample and composites were subjected to analysis and characterization by the techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical properties of the composites were investigated with galvanostatic charge–discharge test and AC impedance measurements, which show that the formed coats of polypyrrole (PPy) significantly decrease the charge-transfer resistance of LiNi_1/3Co_1/3Mn_1/3O₂. And the composite containing 2.0 wt% PPy exhibits a good electrochemical performance, its specific discharge capacity is 182 mAh g^?1 at 0.1C rate and voltage limits of 2.8–4.6 V, while the capacity of the bare sample is only 134 mAh g^?1.     

Preparation and characterization of Cd1−x Zn x S buffer layers for thin film solar cells

Cd1-xZnxS(x = 0, 0.1, 0.2, 0.3, 1.0) thin films have been grown successfully on soda-lime glass substrates by chemical bath deposition technique as a very promising buffer layer material for optoelectronic device applications. The composition, structural properties, surface morphology, and optical properties of Cd1-xZnxS thin films were characterized by energy dispersive analysis of X-ray technique (EDAX), X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis spectrophotometer techniques, respectively. The annealed films were observed to possess the deficient sulfur composition. The results of XRD show that the Cd1-xZnxS (x = 0.1) thin film annealed at 450 ℃ forms hexagonal (wurtzite) structure with lattice parameters a = 0.408814 nm, c = 0.666059 nm, and its average grain size is 24.9902 nm. The diffraction peaks become strong with the increasing annealing temperatures. The surface of Cd1-xZnxS (x = 0.1) thin film annealed at 450℃ is uninterrupted and homogenous as compared to other temperatures. From optical properties, it is observed that the presence of small amount of Zn results in marked changes in the optical band gap of CdS. The band gaps of the Cd1-xZnxS thin films vary from 2.42 to 3.51 eV as composition varies from x = 0.0 to 1.0.     

Preparation of Ultrafine Li_(4 x) Al_xSi_(1-x)O_4 by Sol-Gel Method and Its Ionic Conductivity

1 ＩｎｔｒｏｄｕｃｔｉｏｎＬｉｔｈｉｕｍｉｏｎｃｏｎｄｕｃｔｏｒｓａｒｅｐｒｏｍｉｓｉｎｇｍａｔｅｒｉａｌｓｆｏｒｄｅｖｅｌｏｐｉｎｇｈｉｇｈ ｅｎｅｒｇｙｄｅｎｓｉｔｙｂａｔｔｅｒｉｅｓ[1 ].Ｔｈｅｐｒｏｐｅｒｔｉｅｓｏｆｈｉｇｈｉｏｎｉｃｃｏｎｄｕｃｔｉｖｉｔｙ ,ｈｉｇｈｄｅｃｏｍｐｏｓｉｔｉｏｎｐｏｔｅｎｔｉａｌａｎｄｌｅｓｓｒｅａｃｔｉｖｉｔｙｗｉｔｈｗａｔｅｒａｎｄｃａｒｂｏｎｄｉｏｘｉｄｅｗｉｌｌｂｅｒｅｑｕｉｒｅｄｗｈｅｎｔｈｅｙａｒｅａｐ ｐｌｉｅｄｔｏｓｏｌｉｄｅｌｅｃｔｒｏｌｙ…     

Preparation and electrochemical performance of 2LiFe1–xCoxPO4–Li3V2(PO4)3/C cathode material for lithium-ion batteries

2LiFe_1–xCo_xPO₄–Li₃V₂(PO₄)₃/C was synthesized using Fe_1–2xCo_2xVO₄ as precursor which was prepared by a simple co-precipitation method. 2LiFe_1–xCo_xPO₄–Li₃V₂(PO₄)₃/C samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. All 2LiFe_1–xCo_xPO₄–Li₃V₂(PO₄)₃/C composites are of the similar crystal structure. The XRD analysis and SEM images show that 2LiFe_0.96Co_0.04PO₄–Li₃V₂(PO₄)₃/C sample has the best-ordered structure and the smallest particle size. The charge–discharge tests demonstrate that these powders have the best electrochemical properties with an initial discharge capacity of 144.1 mA·h/g and capacity retention of 95.6% after 100 cycles when cycled at a current density of 0.1C between 2.5 and 4.5 V.     

Preparation and mechanical properties of Al2O3–15wt.%ZrO2 composites

Low-temperature-sinterable high purity α-alumina powder was mixed with Zr(OH)₄ gel synthesized by a precipitation method. The resulting gel mixture was calcined at 600 °C for 2 h. The Al₂O₃–15wt.%ZrO₂ composites were sintered for 2 h in air in the temperature range between 1350 and 1500 °C. Nearly full densification and the maximum bending strength of 932 MPa were achieved for the Al₂O₃–15wt.%ZrO₂ composites sintered at 1425 °C, whereas the highest fracture toughness of 8.5 MPa m^1/2 was obtained after sintering at 1475 °C.     

Preparation and characterization of La0.8Cu0. 2MnO（3＋δ） perovskite-type catalyst for methane combustion

La0.8Cu0. 2MnO（3 δ) perovskite-type catalyst for methane combustion prepared through sol-gel process was characterized by X-ray Diffractometry(XRD), X-ray Photoelectron Spectroscopy(XPS) and Scanning Electron Microscopy(SEM). XPS analyses reveal that the surface characteristics of the catalyst are changed. The lattice defects and oxygen vacancies on the catalyst surface are enhanced due to a part of La^3 being substituted by Cuz .Temperature-programmed-desorption(TPD) and temperature-programmed-reduction(TPR) analyses were carried out to study the catalytic behavior. It is found that there are two O2-desorption peaks at 350℃ and 650℃ in the TPD pattern, and two CH4-consumption peaks at 420℃ and 750℃ in the TPR patterns respectively, which indicates that the two kinds of oxygen species, so-called a and t3 oxygen, can react with the methane during catalytic combustion process. The catalytic activity tests were performed in a fixed-bed reactor, and the results show that the T1/2 at which the conversion of methane attains 50 % of La0.8Cu0. 2MnO（3 δ) is lower by 55℃ than that of LaMnO3.This indicates that the catalytic activity of La0.8Cu0. 2MnO（3 δ) is increased with partial substitution of Cuz for Las .     

Preparation of the Thermal-assisted Self-healing Bionic Super Slippery Surface on Aluminum Alloy Substrate and the Effect of Lubricant on Its PerformanceEI北大核心CSCD

仿猪笼草超滑表面具有疏液性和防污性等优异性能。然而仿生超滑表面的润滑油膜受损后,其超滑性能会被破坏, 因此制备具有自修复性能的仿生超滑表面对于解决其耐久性差的问题至关重要。首先采用阳极氧化法在铝合金基体表面制备锥形微结构,然后经过全氟硅烷进行低能修饰,最后往微结构间隙中注入全氟聚醚、低黏度硅油和高黏度硅油三种不同的润滑油,得到三种仿生超滑表面。水滴在三种仿生超滑表面的接触角分别为~116°、~105°、~103°,滑动角分别为~10°、~10°、~9°。试验结果表明,全氟聚醚和低黏度硅油的仿生超滑表面比高黏度硅油的仿生超滑表面具有更优的自清洁性和防污性,可以有效地预防污染物堆积造成的疏液性失效。此外,全氟聚醚与低黏度硅油的仿生超滑表面呈现较好的热辅助自修复性,修复后的疏水性与新制备样品基本一致;高黏度硅油仿生超滑表面只表现出一定的自修复能力,修复后与新制备样品的疏水性存在差异。所制备出的具有热辅助自修复功能的铝合金基底仿生超滑涂层,在海洋生物污损防护方面具有潜在的应用前景,并为克服传统仿生超滑表面使用耐久性差的问题提供了解决思路。     

Influence of the HVOF Gas Composition on the Thermal Spraying of WC-Co Submicron Powders (−8 + 1 μm) to Produce Superfine Structured Cermet Coatings

Thermal spraying technology represents a novel and promising approach to protect forming tools with complex surfaces and highest shape accuracy against abrasive wear and galling. However, due to high or nonuniform layer thicknesses or inappropriate surface roughness conventional coarse-structured coatings are not suitable to achieve this aim. The application of novel submicron or nanoscaled feedstock materials in the thermal spray process can provide the deposition of cermet coatings with significantly improved characteristics and is recently of great interest in science and industry. In this collaborative study, the feeding and HVOF spraying of WC-Co submicron powders (?8 + 1 μm) have been investigated to manufacture superfine structured, wear resistant, near-net-shape coatings with improved macroscopic properties and smooth surfaces. The influences of varying HVOF gas compositions on the spray process and the coating properties have been analyzed.     

Synthesis and electrochemical properties of Li[NixCoyMn1-x-y]O2 （x, y= 2/8, 3/8） cathode materials for lithium ion batteries

The uniform layered Li(Ni_2/8Co_3/8Mn_3/8)O₂, Li(Ni_3/8Co_2/8Mn_3/8)O₂, and Li(Ni_3/8Co_3/8Mn_2/8)O₂ cathode materials for lithium ion batteries were prepared using the hydroxide co-precipitation method. The effects of calcination temperature and transition metal contents on the structure and electrochemical properties of the Li-Ni-Co-Mn-O were systemically studied. The results of XRD and electrochemical performance measurement show that the ideal preparation conditions were to prepare the Li(Ni_3/8Co_3/8Mn_2/8)O₂ cathode material calcined at 900°C for 10 h. The well-ordered Li(Ni_3/8Co_3/8Mn_2/8)O₂ synthesized under the optimal conditions has the I ₀₀₃/I ₁₀₄ ratio of 1.25 and the R value of 0.48 and delivers the initial discharge capacity of 172.9 mA·h·g⁻¹, the discharge capacity of 166.2 mA·h·g⁻¹ after 20 cycles at 0.2C rate, and the impedance of 558 Ω after the first cycle. The decrease of Ni content results in the decrease of discharge capacity and the bad cycling performance of the Li-Ni-Co-Mn-O cathode materials, but the decreases of Mn content and Co content to a certain extent can improve the electrochemical properties of the Li-Ni-Co-Mn-O cathode materials.     

Preparation and mechanical properties of Fe_3Al/Al_2O_3 nano-/micro-composite

1　INTRODUCTIONAlumina(Al2 O3)ceramicsareoftenconsideredforstructuralapplications,duetotheirpropertiesofhighhardness ,chemicalandwearresistanceandgoodmechanicalpropertiesatroomandhightemperature .Thewellknownlimitationfortheseceramics ,how ever ,istheverylowtoughness .Recentstudieshaveshownsignificantimprovementsinmechanicalprop erties ,includingtoughness ,byaddingductilesecondphaseparticles ,suchasNi,Al,MoandCu[14 ] .Anincreaseof 80 % 333%inthefracturetoughnesshasbeenreportedforAl2 O3…     

Comparison of 10 μm and 20 nm Al-Al2O3 Metal Matrix Composite Coatings Fabricated by Low-Pressure Cold Gas Dynamic Spraying

Cold-gas dynamic spraying (“cold spraying”) was used to deposit aluminum-alumina (Al-Al₂O₃) metal-matrix composite (MMC) coatings onto 6061 Al alloy. The powders consisted of ?45 μm commercially pure Al that was admixed with either 10 μm or agglomerated 20 nm Al₂O₃ in weight fractions of 25, 50, 75, 90, and 95 wt.%. Scanning electron microscopy (SEM), Vickers microhardness testing, and image analysis were conducted to determine the microstructure, properties, and the volume fractions of reinforcing particles in the coatings, which was then converted to weight fractions. As the weight fraction of the Al₂O₃ in the coatings increased, the hardness values of the MMC coatings increased. A maximum hardness of 96 ± 10 HV_0.2 was observed for the MMC coating that contained the agglomerated 20 nm Al₂O₃ particles, while a maximum hardness of 85 ± 24 HV_0.2 was observed for the coatings with the 10 μm Al₂O₃ particles. The slight increase in hardness of the coating containing the agglomerated 20 nm Al₂O₃ particles occurred in a coating of Al₂O₃ content that was lower than that in the coating that contained the 10 μm reinforcing Al₂O₃ particles. The increased hardness of the MMC coatings that contained the agglomerated 20 nm Al₂O₃ particles and at lower reinforcing particle content was attributed to the increased spreading of the nanoagglomerated particles in the coating, which increased load-sharing and reinforcement capability of the particles. These results suggest that the use of nanoagglomerated, reinforcing hard-phase particles in cold-sprayed MMC coatings may be a more efficient alternative to the use of conventional micronsized reinforcing particles.     

Preparation and Characterization of Cu_2ZnSn（S_xSe_（1-x））_4Thin Films by Synchronous Sulfo-Selenization of Single-Source Evaporated Metallic Precursors

Cu2ZnSn(S,Se)4(CZTSSe) thin film was prepared using a simple two-step approach based on the single-source evaporation and synchronous sulfo-selenization.Composition,microstructure,morphology,and properties of the asprepared CZTSSe thin films were investigated.XRD and Raman patterns confirmed the formation of single-phase CZTSSe solid solutions.SEM results showed that the CZTSSe thin film had a uniform morphology and large grains.EDS results revealed the composition of CZTSSe film was Cu:Zn:Sn:S:Se = 23.7:12.6:12.2:37.7:13.8(in at%),which was in accordance with the stoichiometric Cu2ZnSn(S,Se)4.The optical band gap of CZTSSe thin film evaluated from its UV–Vis spectrum was 1.33 eV.The resistivity,carrier concentration,and mobility were 0.53 X cm,7.9 9 1018cm3,and 7.5 cm2/(Vs),respectively.