Oxygen reduction activity of Pt and Pt-Mn-Co electrocatalysts sputtered on nano-structured thin film support

We report on extensive measurements of oxygen reduction activity of Pt and Pt-Co-Mn electrocatalysts using the rotating ring-disk electrode (RRDE) method. The electrocatalysts were prepared by sputtering from Pt or Pt, Co and Mn targets onto 3M's nano-structured thin film support (NSTF) structures. The area specific activity of Pt/NSTF, measured in 0.1 M HClO₄ and at room temperature, is similar to that of bulk Pt. The area specific measurements show a 20 mV reduction in the Pt-Co-Mn/NSTF overpotential compared to Pt/NSTF. The corresponding kinetic gain in the area specific activity of the ternary alloy is about a factor of two. This ORR enhancement factor observed in the ternary Pt-Co-Mn/NSTF by RRDE measurements is similar to the results obtained in 50 cm² H₂/air fuel cells.     

HAN-TEAN-H_2O 三元体系的相变及其相图

用ＤＳＣ研究了ＨＡＮ－ＴＥＡＮ－Ｈ２Ｏ三元体系的低温热行为，建立了该体系低温下相变与组分关系的相图。考察了玻璃化转化温度随ＨＡＮ／ＴＥＡＮ比例的变化规律。发现了三元体系的溶液性质在ＨＡＮ－ＴＥＡＮ比率较大时，与ＨＡＮ－Ｈ２Ｏ二元体系相似，而在ＨＡＮ／ＴＥＡＮ比率较小时，则与ＴＥＡＮ－Ｈ２Ｏ二元体系相似。     

Oxidation behavior of ZrB2-SiC-ZrC at 1700 °C

The oxidation behaviors of four compositions of ZrB₂-SiC-ZrC and one composition of ZrB₂-SiC were studied at 1700 °C in air and under low oxygen partial pressure. Volatility diagrams for ZrB₂-SiC-ZrC and ZrB₂-SiC were used to thermodynamically elucidate the oxidation mechanisms. SiO₂ and ZrO₂ layers formed on the surfaces of ZrB₂-SiC-ZrC and ZrB₂-SiC oxidized at 1700 °C. A SiC-depleted layer only formed on the surface of the ZrB₂-SiC oxidized under low oxygen partial pressure. The oxide layer thickened with increasing ZrC volume content during oxidation in air and under low oxygen partial pressure. The ZrB₂-SiC-ZrC oxide surface exploded in air when the ZrC volume content was more than 50%. Under low oxygen partial pressure, the oxide surfaces of all the ZrB₂-SiC-ZrC specimens bubbled.     

Pressureless sintering and properties of boron carbide composite materials

Boron carbide and Tantalum boride composites were prepared by pressureless sintering of B₄C with addition of TaC powder. The effect of TaC addition on the sinterability of boron carbide was studied. High densified ceramic with a relative density of 98.7% was obtained at sintering temperature of 2250°C. The composition and the microstructure of the dense composites are characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX). The studies show that the composites contain boron carbide, TaB₂, and carbon phases with a homogeneous structure. In addition, the correlation between the composition and the electrical conductivity was investigated. The electrical conductivity of the composite increased with increasing addition of TaC, and a change in conduction behavior from semiconducting to metallic was observed. High hardness value of 28.49 ± 1.33 GPa was obtained by the sample with 30 wt% TaC addition.     

Ternary Blends of Renewable Fast Pyrolysis Bio-Oil,Advanced Bioethanol,and Marine Gasoil as Potential Marine Biofuel

An alternative for reducing emissions from marine fuel is to blend bio-oil from lignocellulose non-edible feedstocks to diesel fossil fuels. Phase diagrams of the ternary systems were built to represent the transition from heterogeneous regions to homogeneous regions. Four homogeneous blends of bio-oil of eucalyptus-bioethanol-marine gasoil were experimentally characterized with respect to the most important fuel parameters for marine engines: water content, flash point, low heating value, viscosity, and acidity. Blends with closer properties to marine gasoil replacement, lower costs, and environmental impacts should be tested for large engines.     

Boro/carbothermal reduction co-synthesis of dual-phase high-entropy boride-carbide ceramics

Dense, dual-phase (Cr,Hf,Nb,Ta,Ti,Zr)B₂-(Cr,Hf,Nb,Ta,Ti,Zr)C ceramics were synthesized by boro/carbothermal reduction of oxides and densified by spark plasma sintering. The high-entropy carbide content was about 14.5 wt%. Grain growth was suppressed by the pinning effect of the two-phase ceramic, which resulted in average grain sizes of 2.7 ± 1.3 µm for the high-entropy boride phase and 1.6 ± 0.7 µm for the high-entropy carbide phase. Vickers hardness values increased from 25.2 ± 1.1 GPa for an indentation load of 9.81 N to 38.9 ± 2.5 GPa for an indentation load of 0.49 N due to the indentation size effect. Boro/carbothermal reduction is a facile process for the synthesis and densification of dual-phase high entropy boride-carbide ceramics with both different combinations of transition metals and different proportions of boride and carbide phases.     

DSC and DMTA characterization of ternary blends

The phase behavior of ternary blends made of poly(epichlorohydrin) (PECH), poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). DMTA measurements have been shown to be more sensitive than DSC for the detection of a second phase, for the determination of the composition of each phase, and the distribution of PECH in each of them. About 70% PECH was required to obtain a single narrow T_g in the ternary system, which suggests a single homogeneous phase in the limit of sensitivity of DMTA. This study also emphasizes the importance of the composition of the immiscible polymer pair (i.e. the PVAc/PMMA pair in the PECH/PVAc/PMMA system), in addition to the thermodynamic interaction parameters, for controling the phase behavior of ternary systems.     

丙烯酸酯三元共聚物酸掺杂改性聚苯胺的研究

选择丙烯酸 (AA)、丙烯酸丁酯 (BA)和甲基丙烯酸甲酯 (MMA)三元共聚物对聚苯胺 (PAn)进行改性 ,研究了BA的用量和引发剂浓度对PAn导电率的影响 ,对样品进行DSC、FTIR和SEM测试。结果表明 ,丙烯酸酯三元共聚物酸对PAn有良好的掺杂改性作用 ,当共聚单体 (AA -BA -MMA)组成为 10∶45∶45 (质量比 ) ,引发剂浓度为0 0 5 48mol·L-1时 ,可制得电导率达 1 42 1S·cm-1的导电PAn。     

Criteria dilemma of phase behavior in ternary blends comprising polystyrene, poly(alpha-methyl styrene), and poly(4-methyl styrene)

A ternary blend system of polystyrene (aPS), poly(α-methyl styrene) (PαMS), and poly(4-methyl styrene) (P4MS) (blends of three styrenic homopolymers of similar molecular structures) was investigated by using differential scanning calorimetry (DSC), polarized-light optical microscopy (POM), scanning electron microscopy (SEM), and solid-state ¹³C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR). This ternary system of aPS/PαMS/P4MS exhibits a small miscibility loop only at relatively high percentages of PαMS (≥80%), while most of the aPS/PαMS/P4MS compositions exhibit two coexisting aPS/PαMS and aPS/P4MS phases in the immiscibility loop. In the immiscible loop, SEM measurements revealed evidence in contrasting with DSC for criteria of miscibility. DSC characterization revealed a single T_g for most ternary blend compositions; however, SEM graphs apparently indicated sub-micron phase domains, except for several PαMS-rich compositions (>80%). The and techniques using NMR were found to resolve the dilemma between the conventional thermal analysis and microscopy results, and indeed supported that the ternary blends at above 80% PαMS are completely homogeneous on the molecular level. Attempts have been made to resolve the seemingly contradictory interpretations on the complex ternary phase structures and domains from the DSC, and microscopy results.     

Static and dynamic studies of phase composition in a polydisperse system

We have conducted a study of the phase compositions of a ternary solution containing dextran/polyethylene glycol (PEG)/water using UV-visible spectrometry to study the equilibrium behaviour and confocal microscopy to study the dynamic behaviour observed when the system undergoes phase separation driven by the loss of water. Such a study of phase compositions using confocal microscopy is a new development of the technique. In the static experiments, we find a cloud curve, which lies above the coexistence curve on the PEG rich side of the phase diagram, this is found to be in qualitative agreement with calculations of the phase behaviour for a model polydisperse system. In the dynamic experiments, we are able to measure the phase composition using confocal microscopy in the late stages of separation. Here, the compositions lie well inside the coexistence curve at lower drying rates but converge with it at higher drying rates. This is linked to a change in phase morphology: at low rates, a droplet morphology is observed throughout the process whilst at high drying rates a gross phase separation into two layers is observed to occur even at the earliest times probed by the experiment.