Nanocomposite electrode materials for low temperature solid oxide fuel cells using the ceria-carbonate composite electrolytes

Low temperature solid oxide fuel cell (LTSOFC, 300–600 °C) is one of the hot areas in recent fuel cell developments. In order to develop high performance LTSOFCs, compatible electrodes are highly demanded. We used NANOCOFC (nanocomposites for advanced fuel cell technology) approach to develop nanocomposite electrodes based on metal oxides Ni–Cu–Zn-oxide and samarium doped ceria (SDC). It was found that the materials consist of individual metal oxide and SDC phase, indicating the material as a composite with a homogenous distribution for all constituent components. Highly homogenous distribution of the particles enhanced the catalyst function for electrode applications in LTSOFC devices. We constructed the devices using the SDC-carbonate nanocomposite (NSDC) as the electrolyte and above as prepared composite as electrodes in a symmetrical configuration. We found that the prepared composite electrodes had good catalytic function for both H₂ and O₂, to prove its anode and cathode functions. Based on the material properties, the LTSOFC devices have reached a power output more than 730 mW cm⁻² at 550 °C.     

Dual template synthesis and photoelectrochemical performance of 3-D hierarchical porous zinc oxide

In this work, a novel hierarchical porous ZnO is successfully synthesized through a sol–gel method, in which a kind of biological material is used as hard template, block copolymer Pluronic F127 as soft template. The phase and morphology of the products are characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The results show that the as-prepared ZnO with a hierarchical porous architecture is assembled by multiple-layered porous nanosheets, of which the pore structure is highly ordered. The photocatalytic activity of the as-prepared ZnO is evaluated by photodegradation reaction of methylene blue. The photoelectrochemical (PEC) property of the hierarchical porous ZnO film is also investigated in this work.     

Enhanced Damping Capacity in Graphene-Al Nanolaminated Composite Pillars Under Compression Cyclic Loading

Cyclic compression tests were conducted on 2.5-μm-diameter nanolaminated graphene-aluminum (Al) composite pillars. The composite possessed three times higher damping coefficient than its pure Al counterpart, which was rationalized by the enhanced dislocation hindrance at the graphene/Al interfaces in the composites. Moreover, the cyclic compression of micro-pillars produced similar damping coefficients as the corresponding bulk sample, providing a novel and convenient approach to assess the cyclic deformation behavior and damping properties of structural materials.

     

聚合物热解法制备碳纳米管/铝复合粉末及其反应动力学研究

采用聚合物热解化学气相沉积(PP-CVD)法, 通过聚乙二醇(PEG)的原位热解提供碳源、柠檬酸(CA)和硝酸钴反应产生催化剂纳米粒子, 在微纳米级的片状铝粉基底上原位生长碳纳米管(CNTs)。通过实验和反应动力学建模研究了PP-CVD反应机理, 揭示了PEG热解气相成分和催化剂纳米粒子表面气-固反应对CNTs生长速率的影响规律。CO初始分压和反应温度提高, CNTs生长速率提高; H₂初始分压和催化剂密度提高, CNTs生长速率降低。模型预测的CNTs平均长度随反应温度和反应时间的变化趋势符合实验结果。因此, 本研究为进一步优化CNTs/铝复合粉末制备工艺提供了新的理论依据。     

Synthesis of hierarchically porous LiNiCuZn-oxide and its electrochemical performance for low-temperature fuel cells

In this work, hierarchically porous composite metal oxide LiNiCuZn-oxide (LNCZO) was successfully synthesized through a sol–gel method with a bio-Artemia cyst shell (AS) as a hard template. The phase and morphology of the products were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM). The as-synthesized material was used as symmetrical electrodes, anode and cathode, for the SDC-LiNaCO₃ (LNSDC) electrolyte based low temperature solid oxide fuel cell (LTSOFCs), achieving a maximum power density of 132 mW cm⁻² at 550 °C. Besides, a single-component fuel cell device was also demonstrated using a mixture of as-prepared LNCZO and ionic conductor LNSDC, and a corresponding peak power output of 155 mW cm⁻² was obtained, suggesting that the hierarchically porous product has high prospective in the single-component fuel cell.     

Size and Crystallographic Orientation Effects on the Mechanical Behavior of 4H-SiC Micro-/nano-pillars

Single crystalline 4H-SiC micro-/nano-pillars of various sizes and different crystallographic orientations were fabricated and tested by uniaxial compression. The pillars with zero shear stress resolved on the basal slip system were found to fracture in a brittle manner without showing significant size dependence, while the pillars with non-zero resolved shear stress showed a “smaller is stronger” behavior and a jerky plastic flow. These observations were interpreted by homogeneous dislocation nucleation and dislocation glide on the basal plane.     

Orientation-Dependent Tensile Behavior of Nanolaminated Graphene-Al Composites: An <Emphasis Type="Italic">In Situ</Emphasis> Study

We conducted in situ microtension experiments in a scanning electron microscope (SEM) to study the orientation-dependent mechanical behavior of nanolaminated graphene-Al composite. We found a transition from a weak-and-brittle behavior in the isostress composite configuration to a strong-yet-ductile tensile response in the composite under isostrain condition. This is explained by the excellent load-bearing capacity of the graphene nanosheets and a crack deflection mechanism rendered by the laminate structure. These in situ measurements enabled direct observation of the deformation procedure and the exact failure mode, which highlight the importance of microstructural control in tailoring the mechanical properties of advanced metal matrix composites (MMCs).     

Titanium carbide derived nanoporous carbon for supercapacitor applications

Carbide derived carbons (CDCs) are porous carbons produced by extraction metals from metal carbides. In this paper, nanoporous carbon with large surface area of above 1000 m²/g has been prepared by thermo-chemical etching of titanium carbide (TiC) in chlorine atmosphere. An improved design of accurate control on the reaction time with high yield percentage above 98% is reported. Transmission electron microscope (TEM) and X-ray diffraction (XRD) analysis showed the existence of ordered graphite phase in this mostly amorphous titanium carbide derived carbon (TiC-CDC), and the degree of ordering increased with chlorination temperature. Raman spectra study demonstrated that the TiC-CDC consisted of both D-band and G band of graphitic carbon, and the ratio of the integrated intensities I_D/I_G decreased with chlorination temperature. T-plot nitrogen sorption measurements proved the co-existence of micropores (<2 nm) and mesopores (2–50 nm), while the highest specific surface area was achieved from sample synthesized at 400 °C. Cyclic voltammetry measurements on the TiC-CDC did not show any major Faradic reactions within the experimental voltage range. A specific capacitance of 138.3 F/g was achieved from sample synthesized at 400 °C. The specific capacitance increased with increasing the amount of microporous area.