Hydrogen storage of multiwalled carbon nanotubes coated with Pd-Ni nanoparticles under moderate conditions

A type of novel material with a high hy-drogen storage capacity was prepared by supporting PdNi18 alloy nanoparticles,which were synthesized by using a new colloid method,on the surface of pretreated multiwalled carbon nanotubes (MWCNTs). The average PdNi18 alloy particle sizes calculated from XRD patterns were ca. 3 nm,and the high dis-persion of these particles on MWCNTs was con-firmed by TEM image. Hydrogen storage perform-ance of the composite was investigated under mod-erate pressure (0.1―1.5 MPa) at room temperature,and a maximum storage capacity of ca. 2.3 wt% was achieved under 1.5 MPa at room temperature,which was much higher than that reported previously under the same conditions.     

A new route of ferric ions rejection in a synthetic nickel leach solution

A new route of impurity rejection to remove ferric iron from a synthetic nickel leach solution was introduced, which simulated the chemical composition of a typical acid leach solution of nickel laterites under atmospheric pressure. The synthetic solution underwent a stepwise neutralization process, with each step adopting different pH value-temperature combinations. In a conventional nickel atmospheric leach (AL) process, the nickel loss could be as high as 10wt%, which was a longstanding issue and prevented this process from commercialization. The new impurity rejection route is the first step towards resolving this issue. The results show that, the best neutralization performance is achieved at the nickel loss of 3.4wt% in the neutralization scheme that employs ethylenediaminetetraacetic acid as a nickel stabilizer (pH: 1.3–3.5; temperature: 95–70℃)     

Effect of residual structural strain caused by the addition of Co_3O_4 nanoparticles on the structural,hardness and magnetic properties of an Al/Co_3O_4 nanocomposite produced by powder metallurgy

Al composites are of interest due to their appropriate ratio of strength to weight. In our research, an Al/Co_3O_4 nanocomposite was generated using a sintering technique. The powders of Al with various Co_3O_4 nanoparticle contents(0 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, and2.5 wt%) were first blended using planetary milling for 30 min, and compressed in a cylindrical steel mold with a diameter of 1 cm and a height of5 cm at a pressure of 80 MPa. The samples were evaluated with X-ray diffractometry(XRD), scanning electron microscopy(SEM), Vickers hardness, and a vibrating sample magnetometer(VSM). Although the crystallite size of the Al particles remained constant at 7–10 nm, the accumulation of nanoparticles in the Al particle interspace increased the structural tensile strain from 0.0045 to 0.0063, the hardness from HV 28 to HV 52 and the magnetic saturation from 0.044 to 0.404 emu/g with an increase in Co_3O_4 nanoparticle content from 0 wt% to 2.5 wt%.     

添加Co3O4纳米颗粒引起的残余结构应变对粉末冶金制备的Al/Co3O4纳米复合材料的结构、硬度和磁性能的影响

Al composites are of interest due to their appropriate ratio of strength to weight. In our research, an Al/Co₃O₄ nanocomposite was generated using a sintering technique. The powders of Al with various Co₃O₄ nanoparticle contents (0wt%, 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, and 2.5wt%) were first blended using planetary milling for 30 min, and compressed in a cylindrical steel mold with a diameter of 1 cm and a height of 5 cm at a pressure of 80 MPa. The samples were evaluated with X-ray diffractometry (XRD), scanning electron microscopy (SEM), Vickers hardness, and a vibrating sample magnetometer (VSM). Although the crystallite size of the Al particles remained constant at 7–10 nm, the accumulation of nanoparticles in the Al particle interspace increased the structural tensile strain from 0.0045 to 0.0063, the hardness from HV 28 to HV 52 and the magnetic saturation from 0.044 to 0.404 emu/g with an increase in Co₃O₄ nanoparticle content from 0wt% to 2.5wt%.     

Effect of Mo content on the thermal stability of Ti–Mo-bearing ferritic steel

The effects of tempering holding time at 700°C on the morphology, mechanical properties, and behavior of nanoparticles in Ti–Mo ferritic steel with different Mo contents were analyzed using scanning electron microscopy and transmission electron microscopy. The equilibrium solid solution amounts of Mo, Ti, and C in ferritic steel at various temperatures were calculated, and changes in the sizes of nanoparticles over time at different Mo contents were analyzed. The experimental results and theoretical calculations were in good agreement with each other and showed that the size of nanoparticles in middle Mo content nano-ferrite(MNF) steel changed the least during aging. High Mo contents inhibited the maturation and growth of nanoparticles, but no obvious inhibitory effect was observed when the Mo content exceeded 0.37 wt%.The tensile strength and yield strength continuously decreased with the tempering time. Analysis of the strengthening and toughening mechanisms showed that the different mechanical properties among the three different Mo content experiment steels were mainly determined by grain refinement strengthening(the difference range was 30–40 MPa) and precipitation strengthening(the difference range was 78–127 MPa). MNF steel displayed an ideal chemical ratio and the highest thermodynamic stability, whereas low Mo content nano-ferrite(LNF) steel and high Mo content nano-ferrite(HNF) steel displayed relatively similar thermodynamic stabilities.     

Effect of high pressure sintering and annealing on microstructure and thermoelectric properties of nanocrystalline Bi2Te2.7Se0.3 doped with Gd

Bi2Te2.7Se0.3of high performance doped with Gd bulk materials was prepared by a high pressure(6.0 GPa) sintering(HPS) method at 593 K,633 K, 673 K and 693 K. The sample was then annealed for 36 h in a vacuum at 633 K. The phase composition, crystal structure and morphology of the sample were analyzed by X-ray diffraction and scanning electron microscopy. The electric conductivity, Seebeck coefficient, and thermal conductivity aspects of the sample were measured from 298 K to 473 K. The results show that high pressure sintering and the doping with Gd has a great effect on the crystal structure and the thermoelectric properties of the samples. The samples are consisted of nanoparticles before and after annealing, and these nanostructures have good stability at high temperature. HPS together with annealing can improve the TE properties of the sample by decreasing the thermal conductivity of the sample with nanostructures. The maximum ZT value of 0.74 was obtained at 423 K for the sample, which was sintered at 673 K and then annealed at 633 K for 36 h. Compared with the zone melting sample, it was increased by 85% at423 K. Hence the temperature of the maximum of figure of merit was increased. The results can be applied to the field of thermoelectric power generation materials.     

Reverse-transformation austenite structure control with micro/nanometer size

To control the reverse-transformation austenite structure through manipulation of the micro/nanometer grain structure, the influences of cold deformation and annealing parameters on the microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. The samples were first cold-rolled, and then samples deformed to different extents were annealed at different temperatures. The microstructure evolutions were analyzed by optical microscopy, scanning electron microscopy (SEM), magnetic measurements, and X-ray diffraction (XRD); the mechanical properties are also determined by tensile tests. The results showed that the fraction of stain-induced martensite was approximately 72% in the 90% cold-rolled steel. The micro/nanometric microstructure was obtained after reversion annealing at 820-870℃ for 60 s. Nearly 100% reversed austenite was obtained in samples annealed at 850℃, where grains with a diameter ≤ 500 nm accounted for 30% and those with a diameter >0.5 μm accounted for 70%. The micro/nanometer-grain steel exhibited not only a high strength level (approximately 959 MPa) but also a desirable elongation of approximately 45%.     

Mo含量对Ti–Mo系铁素体钢热稳定性影响

The effects of tempering holding time at 700°C on the morphology, mechanical properties, and behavior of nanoparticles in Ti–Mo ferritic steel with different Mo contents were analyzed using scanning electron microscopy and transmission electron microscopy. The equilibrium solid solution amounts of Mo, Ti, and C in ferritic steel at various temperatures were calculated, and changes in the sizes of nanoparticles over time at different Mo contents were analyzed. The experimental results and theoretical calculations were in good agreement with each other and showed that the size of nanoparticles in middle Mo content nano-ferrite (MNF) steel changed the least during aging. High Mo contents inhibited the maturation and growth of nanoparticles, but no obvious inhibitory effect was observed when the Mo content exceeded 0.37wt%. The tensile strength and yield strength continuously decreased with the tempering time. Analysis of the strengthening and toughening mechanisms showed that the different mechanical properties among the three different Mo content experiment steels were mainly determined by grain refinement strengthening (the difference range was 30–40 MPa) and precipitation strengthening (the difference range was 78–127 MPa). MNF steel displayed an ideal chemical ratio and the highest thermodynamic stability, whereas low Mo content nano-ferrite (LNF) steel and high Mo content nano-ferrite (HNF) steel displayed relatively similar thermodynamic stabilities.     

Effect of Mo content on the thermal stability of Ti-Mo-bearing ferritic steel

The effects of tempering holding time at 700℃on the morphology,mechanical properties,and behavior of nanoparticles in Ti-Mo ferritic steel with different Mo contents were analyzed using scanning electron microscopy and transmission electron microscopy.The equilibrium solid solution amounts of Mo,Ti,and C in ferritic steel at various temperatures were calculated,and changes in the sizes of nanoparticles over time at different Mo contents were analyzed.The experimental results and theoretical calculations were in good agreement with each other and showed that the size of nanoparticles in middle Mo content nano-ferrite(MNF)steel changed the least during aging.High Mo contents inhibited the maturation and growth of nanoparticles,but no obvious inhibitory effect was observed when the Mo content exceeded 0.37wt%.The tensile strength and yield strength continuously decreased with the tempering time.Analysis of the strengthening and toughening mechanisms showed that the different mechanical properties among the three different Mo content experiment steels were mainly determined by grain refinement strengthening(the difference range was 30-40 MPa)and precipitation strengthening(the difference range was 78-127 MPa).MNF steel displayed an ideal chemical ratio and the highest thermodynamic stability,whereas low Mo content nano-ferrite(LNF)steel and high Mo content nano-ferrite(HNF)steel displayed relatively similar thermodynamic stabilities.     

Thermal conductivity measurements on xonotlite-type calcium silicate by the transient hot-strip method

The experimental results of the thermal conductivities of xonotlite-type calcium silicate insulation materials were presented at different temperatures and pressures. Two appropriative surroundings, i.e. an elevated temperature surrounding from ambient temperature to 1450 K and a vacuum surrounding from atmosphere pressure to 10-3 Pa, were designed for the transient hot-strip (THS) method. The thermal conductivities of xonotlite-type calcium silicate with four densities from ambient temperature to 1000 K and 0.045 Pa to atmospheric pressure were measured. The results show that the thermal conductivity of xonotlite-type calcium silicate decreases apparently with the fall of density, and decreases apparently with the drop of pressure, and reaches the least value at about 100 Pa. The thermal conductivity of xonotlite-type calcium silicate increases almost linearly with T3, and increases more abundantly with low density than with high density. The thermal conductivity measurement uncertainty is estimated to be approximately 3% at ambient temperature, and 6% at 800 K.     

Comparative characterization of iridium loading on catalyst assessment under different conditions

To discuss the potential role of iridium(Ir) nanoparticles loaded under atmospheric and high pressures, we prepared a series of catalysts with the same active phase but different contents of 10 wt%, 20 wt%, and 30 wt% on gamma-alumina for decomposition of hydrazine. Under atmospheric pressure, the performance of the catalyst was better when 30 wt% of the Ir nanoparticles was used with chelating agent that had greater selectivity of approximately 27%. The increase in the reaction rate from 175 to 220 h~(-1) at higher Ir loading(30 wt%) was due to a good dispersion of high-number active phases rather than an agglomeration surface. As a satisfactory result of this investigation at high pressure, Ir catalysts with different weight percentages showed the same stability against crushing and activity with a characteristic velocity of approximately 1300 m/s.     

构建TiO2柱状多层石墨烯纳米复合材料作为降解环丙沙星的高效光催化剂

We successfully constructed TiO₂-pillared multilayer graphene nanocomposites (T-MLGs) via a facile method as follows: dodecanediamine pre-pillaring, ion exchange (Ti4+ pillaring), and interlayer in-situ formation of TiO₂ by hydrothermal method. TiO₂ nanoparticles were distributed uniformly on the graphene interlayer. The special structure combined the advantages of graphene and TiO₂ nanoparticles. As a result, T-MLGs with 64.3wt% TiO₂ showed the optimum photodegradation rate and adsorption capabilities toward ciprofloxacin. The photodegradation rate of T-MLGs with 64.3wt% TiO₂ was 78% under light-emitting diode light irradiation for 150 min. Meanwhile, the pseudo-first-order rate constant of T-MLGs with 64.3wt% TiO₂ was 3.89 times than that of pristine TiO₂. The composites also exhibited high stability and reusability after five consecutive photocatalytic tests. This work provides a facile method to synthesize semiconductor-pillared graphene nanocomposites by replacing TiO₂ nanoparticles with other nanoparticles and a feasible means for sustainable utilization of photocatalysts in wastewater control.     

Tuning Li3PO4 modification on the electrochemical performance of nickel-rich LiNi0.6Co0.2Mn0.2O2

Surface deterioration occurs more easily in nickel-rich cathode materials with the increase of nickel content. To simultaneously pre-vent deterioration of active cathode materials and improve the electrochemical performance of the nickel-rich cathode material, the surface of nickel-rich LiNi0.6Co0.2Mn0.2O2 cathode material is decorated with the stable structure and conductive Li3PO4 by a facile method. The LiNi0.6Co0.2Mn0.2O2–1wt％, 2wt％, 3wt％Li 3PO4 samples deliver a high-capacity retention of more than 85％ after 100 cycles at 1 C under a high voltage of 4.5 V. The effect of different coating amounts (0–5wt％) for the LiNi0.6Co0.2Mn0.2O2 cathode is analyzed in detail. Results show that 2wt％ coating of Li3PO4 gives better performance compared to other coating concentrations. Detailed analysis of the structure of the samples during the charge?discharge process is performed by in-situ X-ray diffraction. It is indicated that the modification for LiNi0.6Co0.2Mn0.2O2 cathode could protect the well-layered structure under high voltages. In consequence, the electrochemical performance of modified samples is greatly improved.     

低压环境对高压细水雾雾滴粒径影响的实验分析

为揭示环境压力降低对高压细水雾性能的影响,本文通过搭建高压细水雾实验平台测量了常压、低压环境下高压细水雾的喷雾流量及雾滴粒径,研究了环境压力的变化对高压细水雾喷雾流量和雾滴粒径的影响问题。实验结果表明：环境压力降低对高压细水雾性能影响较大。在喷嘴流量系数K=3.4、额定工作压力分别为4、6、8、10和12 Mpa下,且环境大气压力为60 kPa时,高压细水雾的喷雾流量从常压(101 kPa)下的0.500、0.652、0.770、0.880、0.958 m3·h-1增加至0.515、0.685、0.812、0.975、1.073 m3·h-1,增长率分别为3%、5.1%、5.5%、10.8%、12%;相同情况下,高压细水雾的雾滴粒径从常压(101 kPa)下的292.6、280.8、255.9、253.9、252.9 um增加至336.9、291.6、277.2、266.9、254.4 um,增长率分别为15%、3.8%、8.3%、5.1%、0.6%。得出低压环境下高压细水雾的喷雾流量和雾滴粒径都将增大。可见在低压环境下高压细水雾仍然具有良好的灭火性能。     

Preparation and characterization of aligned carbon nanotubes coated with titania nanoparticles

Titania (TiO2) is an environmental-friendly photo- catalyst material with high stability and efficiency, so its preparation methods received extensive atten- tion[1―4], and the products were advanced from dis- persed nano-powder and fastness nano-film[5,…     

Effect of reinforcement content on the adhesive wear behavior of Cu10Sn5Ni/Si3N4 composites produced by stir casting

The main objective of this paper was to fabricate Cu10Sn5Ni alloy and its composites reinforced with various contents of Si3N4 particles (5wt％,10wt％,and 15wt％) and to investigate their dry sliding wear behavior using a pin-on-disk tribometer.Microstructural examinations of the specimens revealed a uniform dispersion of Si3N4 particles in the copper matrix.Wear experiments were performed for all combinations of parameters,such as load (10,20,and 30 N),sliding distance (500,1000,and 1500 m),and sliding velocity (1,2,and 3 m/s),for the alloy and the composites.The results revealed that wear rate increased with increasing load and increasing sliding distance,whereas the wear rate decreased and then increased with increasing sliding velocity.The primary wear mechanism encountered at low loads was mild adhesive wear,whereas that at high loads was severe delamination wear.An oxide layer was formed at low velocities,whereas a combination of shear and plastic deformation occurred at high velocities.The mechanism at short sliding distances was ploughing action of Si3N4 particles,which act as protrusions;by contrast,at long sliding distances,direct metal-metal contact occurred.Among the investigated samples,the Cu/10wt％ Si3N4 composite exhibited the best wear resistance at a load of 10 N,a velocity of 2 m/s,and a sliding distance of 500 m.     

Two-stage reduction for the preparation of ferronickel alloy from nickel laterite ore with low Co and high MgO contents

The preparation of ferronickel alloy from the nickel laterite ore with low Co and high MgO contents was studied by using a pre-reduction-smelting method. The effects of reduction time, calcination temperature, quantity of reductant and calcium oxide (CaO), and pellet diameter on the reduction ratio of Fe and on the pellet strength were investigated. The results show that, for a roasting temperature >800℃, a roasting time >30 min, 1.5wt% added anthracite coal, 5wt% added CaO, and a pellet size of~10 mm, the reduction ratio of Fe exceeds 70% and the compressive strength of the pellets exceeds 10 kg per pellet. Reduction smelting experiments were performed by varying the smelting time, temperature, quantity of reductant and CaO, and reduction ratio of Fe in the pellets. Optimal conditions for the reduction smelting process are as follows:smelting time, 30-45 min; smelting temperature, 1550℃; quantity of reductant, 4wt%-5wt%; and quantity of CaO, 5wt%; leading to an Fe reduction ratio of 75% in the pellets. In addition, the mineral composition of the raw ore and that during the reduction process were investigated by process mineralogy.     

机械合金化法制备的Cu/SiC纳米复合材料的组织、热性能和力学性能评估

Nano-sized silicon carbide (SiC: 0wt%, 1wt%, 2wt%, 4wt%, and 8wt%) reinforced copper (Cu) matrix nanocomposites were manufactured, pressed, and sintered at 775 and 875°C in an argon atmosphere. X-ray diffraction (XRD) and scanning electron microscopy were performed to characterize the microstructural evolution. The density, thermal expansion, mechanical, and electrical properties were studied. XRD analyses showed that with increasing SiC content, the microstrain and dislocation density increased, while the crystal size decreased. The coefficient of thermal expansion (CTE) of the nanocomposites was less than that of the Cu matrix. The improvement in the CTE with increasing sintering temperature may be because of densification of the microstructure. Moreover, the mechanical properties of these nanocomposites showed noticeable enhancements with the addition of SiC and sintering temperatures, where the microhardness and apparent strengthening efficiency of nanocomposites containing 8wt% SiC and sintered at 875°C were 958.7 MPa and 1.07 vol%?1, respectively. The electrical conductivity of the sample slightly decreased with additional SiC and increased with sintering temperature. The prepared Cu/SiC nanocomposites possessed good electrical conductivity, high thermal stability, and excellent mechanical properties.     

粉末冶金制备的AISI 8620钢渗碳后的磨损和力学性能

The effect of carburization on the tensile strength and wear resistance of AISI 8620 steel produced via powder metallurgy was investigated. Alloys 1 and 2 (with 0.2wt% C and 0.25wt% C, respectively) were first pressed at 700 MPa and then sintered at 1300, 1400, or 1500°C for 1 h. The ideal sintering temperature of 1400°C was determined. Afterward, Alloys 1 and 2 sintered at 1400°C were carburized at 925°C for 4 h. The microstructure characterization of alloys was performed via optical microscopy and scanning electron microscopy. The mechanical and wear behavior of carburized and noncarburized alloys were investigated via hardness, tensile, and wear tests. After carburization, the ultimate tensile strength of Alloys 1 and 2 increased to 134.4% and 138.1%, respectively. However, the elongation rate of Alloys 1 and 2 decreased to 62.6% and 64.7%, respectively. The wear depth values of Alloy 2 under noncarburized and carburized conditions and a load of 30 N were 231.2 and 100.1 μm, respectively. Oxidative wear changed to abrasive wear when the load transitioned from 15 to 30 N.