Effect of Sm on hydrogen storage performance of La–Sm–Mg–Ni alloys

In this study, Sm was adopted in order to completely replace the expensive Pr/Nd elements in the A2B7 type alloy. The results indicate that Sm is a favourable element for forming Ce2Ni7 type and Ce5Co19 type phases. With the increasing amount of Sm, the discharge capacity of the alloy retains a value of 283·3 mAh g^?1 at the current density of 1200 mA g^?1. The maximum discharge capacity of the alloys increases with the increasing Sm content when Mg content is relatively low. By optimising the composition and processing technology, the cycle life the alloy enhances from 74 cycles to more than 540 cycles, and the maximum discharge capacity also increases from 300 to 355 mAh g^?1.     

Development of novel refractory ceramic continuous fibers of fly ash and comparison of mechanical properties with those of E-glass fibers using the Weibull distribution

This study aimed to develop manufacturing technology for high-strength refractory ceramic fibers (RCFs) using fly ash, which is a highly promising material for the exterior and thermal insulation industry. The technology also contributes to reducing the environmental pollution caused by landfilling fly ash after coal is burned. Fly ash discharged from a thermal power plant, which had aluminosilicate chemical compositions, was used as the main material. As auxiliary materials, basalt, anorthite, feldspar, dolomite, and calcite were used to adjust the melt flowability, and frit, silica sand, and burr stone were used to lower the melting temperature. Moreover, the development of aluminosilicate fly ash fiber has the advantages of lower cost for raw materials and processing. Fly ash and natural rocks are inexpensive, and most of all, unlike the case for glass fiber production, the high cost of B₂O₃ is not a necessary expense. Fly ash is retrieved in powder form, which is advantageous compared to the starting materials for glass; the grinding process of raw materials can be skipped. From the fibrilization index calculation, we showed that the spinnability was influenced by the chemical composition of the salt-forming oxides in the fly ash compounds. We also found a correlation between the winding speed and the fiber diameter. The mechanical properties of a series of fly ash fibers were assessed by the Weibull distribution and then compared with those of the E-glass fibers that were melt-spun under an analogous condition.     

Zirconia-alumina multiphase ceramic fibers with exceptional thermal stability by melt-spinning from solid ceramic precursor

Zirconia-alumina multiphase ceramic fibers with 80 wt% (Z80A20 fiber) and 10 wt% (Z10A90 fiber) proportions of zirconia were prepared via melt-spinning and calcination from solid ceramic precursors synthesized by controllable hydrolysis of metallorganics. The zirconia-alumina multiphase fibers had a diameter of about 10 µm and were evenly distributed with alumina and zirconia grains. The Z80A20 and Z10A90 ceramic fibers had the highest filament tensile strength of 1.78 GPa and 1.87 GPa, respectively, with a peak value of 2.62 GPa and 2.71 GPa. The Z80A20 ceramic fiber has superior thermal stability compared to the Z10A90 ceramic fiber and a higher rate of filament strength retention due to the stability in grain size. After heat treatment at 1100 °C, 1200 °C, and 1300 °C for 1 h respectively, the filament tensile strength retention rate of Z80A20 ceramic fibers was 87 %, 80 %, and 40 %. While Z10A90 ceramic fiber was fragile after being heated at 1300 °C. The results showed that the high zirconia content facilitated the fiber's thermal stability.     

Effect of Bismuth on hydrogen storage properties of melt-spun LaNi4.7-x Al0.3Bix (x = 0.0, 0.1, 0.2, 0.3) ribbons

The LaNi₅ intermetallic compound is an AB5 type hydrogen storage alloy which exhibits low operating temperature, easy activation, low pressure and tolerance to impurities. In this study, LaNi_4.7-x Al_0.3Bi_x (x = 0.0, 0.1, 0.2, 0.3) alloys were produced by melt-spinning technique and the effects of Al and Bi additions on the microstructure, thermal and hydrogen storage properties of LaNi₅ were investigated. The results showed that substitution of Ni with Al led to a desired decrease in absorption/desorption plateau pressure and hysteresis without a decrease in hydrogen storage capacity. In contrast, Bi substitution with Ni increased the absorption/desorption plateau pressure, reduced the hydrogen capacity and increased pulverization resistance of the alloy due to the formation of BiLa and AlNi₃ intermetallic phases at the grain boundaries.     

快速凝固法制备Mg-Al-Ca合金薄带

通过单辊快淬法制备了Mg-8.2Al-4.7Ca合金薄带,采用XRF、XRD、金相显微分析、显微硬度测量等分析方法研究了其凝固组织及相结构,以及转速对镁合金条带厚度和显微硬度的影响。研究结果表明,急冷快速凝固条件下,合金形成非晶相 细小hcp-Mg(Al,Ca)相;镁合金薄带显微组织沿厚度方向分为近辊面细晶区、内部柱状晶和自由面粗晶区;随着辊速的提高,晶粒不断细化,薄带的硬度不断提高。晶粒细化是显微硬度提高的主要原因。     

Characterization and microstructural evolution of SiC(OAl) fibers to SiC(Al) fibers derived from aluminum-containing polycarbosilane

The SiC(OAl) fibers and the SiC(Al) fibers were fabricated by the use of aluminum-containing polycarbosilane (Al–PCS) precursor. The two types of fibers have been characterized. Chemical element analysis, AES, SEM, XRD, RMS and NMR have been employed. The chemical formula of SiC(OAl) fibers is SiC_1.31O_0.25Al_0.018 with C and O rich on the surface. The microstructure of SiC(OAl) fibers is a mixture of β-SiC nanocrystals, free carbon, and an amorphous silicon oxycarbide (Si–C–O phase), which have been confirmed by an amount of SiC₂O₂, SiCO₃, SiO₄ and SiC₃O units in the ²⁹Si MAS NMR spectrum. A small quantity of aluminum is embedded uniformly in the Si–C–O amorphous continuous phase. For SiC(Al) fibers, nearly stoichiometric composition was confirmed as chemical composition of SiC_1.03O_0.013Al_0.024. The fiber is composed of a large number of β-SiC crystallites, a small amount of -SiC crystalline and SiC amorphous phase. The aluminum in the SiC(Al) fibers mainly exists in two manners: Al–C bonds connected with the surfaces of the β-SiC grains and Al–O bonds, or Al₂O₃, to the amorphous phase.     

High performance PA6/CNTs nanohybrid fibers prepared in the melt

Commercial and home-made carbon nanotubes (CNTs) were plasma treated under oxygen atmosphere and then added to polyamide 6 (PA6) in order to prepare fibres by melt spinning. For comparison, pristine nanofillers were used too. The effect of functionalization and of filler characteristics on the morphological, rheological, mechanical and electrical properties of the fibres was studied by TEM and SEM, rheological measurements, tensile and electrical conductivity tests. The results demonstrated that the functionalization led to a better mechanical performance and the morphological analysis confirmed that the adhesion, the dispersion and the alignment of the nanotubes within the polymer matrix were improved when using functionalized CNTs. Electrical tests marked that functionalization slightly reduced the conductivity of the materials.     

快淬速度及热处理对Nd26Pr3FebalCo4Ga0.42B0.92快淬薄带微观结构和磁性的影响

研究了快淬速度（v=15、20、25、30和35 m/s）和热处理对熔体快淬法制备的成分为Nd26Pr3FebalCo4Ga0.42B0.92的快淬薄带的微观结构和磁性能的影响。v<25m/s 时,薄带自由面具有明显的取向,c轴垂直于薄带表面;随着快淬速度的提升,取向度明显降低。提高快淬速度可以细化晶粒,提升至v>25 m/s以上时非晶含量明显提升,当v<25 m/s时初始磁化曲线表现为一步磁化过程,退磁曲线的方形度较好;当v>25 m/s时向两步磁化转变,退磁曲线出现明显塌腰;在v=25 m/s时取得最佳磁性能,分别为Br=0.91T,μ0Hcj=1.70 T,（BH）max=108.22 kJ/m3。对快淬薄带进行适当的晶化退火处理后,快淬带中的非晶含量显著减少,v≤25 m/s的快淬薄带的磁性能有所改善;v>25 m/s时退磁曲线塌腰消失,矫顽力大幅提升,方形度明显改善;在v=35 m/s制备的快淬薄带取得最高矫顽力,μ0Hcj = 2.10 T;v=30 m/s时取得最佳磁性能,分别为Br=0.91T,μ0Hcj=1.82 T,（BH）max=141.61 kJ/m3。快淬薄带形貌沿厚度方向变化,热处理前其贴辊面一侧以非晶及细晶为主,自由面晶粒较大;热处理后贴辊面一侧的非晶含量显著减少。     

快淬Nd—Fe—B粘结磁体在步进电机上的应用研究

本文主要报道快淬Nd-Fe-B粘结磁体在36BY_(02)型永磁式步进电机中作为24极转子磁钢的应用研究,分析磁体性能与工作点设计及电机性能参数关系。     

Production of metallic glassy bipolar plates for PEM fuel cells by hot pressing in the supercooled liquid state

A screening test was conducted to optimize the alloy composition in the Ni₆₀Nb_xCr_yMo_zP₁₆B₄ (x + y + z = 20 at%) alloy system in order to achieve a large supercooled liquid region, ΔT_x, and a low crystallization temperature, T_x. From this study, the Ni₆₀Nb₂Cr₁₆Mo₂P₁₆B₄ glassy alloy was found to be the optimal alloy. The static and potentiodynamic corrosion behaviors of this glassy alloy were measured. Polarization measurements showed that the current density of the non-polished glassy alloy sample was smaller than that of a SUS316L sample. By contrast, the current density of the surface-polished glassy sample was slightly larger than that of the SUS316L sample in the voltage range of 0.2–0.7 V. The interfacial contact resistance of the Ni₆₀Nb₂Cr₁₆Mo₂P₁₆B₄ glassy alloy was smaller than that of the SUS316L alloy and it decreased with increasing compaction force. A bipolar plate was successfully produced by hot pressing the glassy alloy sheet in a supercooled liquid state. The I–V characteristics of a single cell with the glassy bipolar plates were measured.