Investigation of fabrication of gas diffusion substrate for proton exchange membrane fuel cells

The gas diffusion substrate (GDS) is essential in the proton exchange membrane fuel cells. Its fabrication techniques affect the performance significantly and are worthy of investigation. In this study, a manufacturing process of the GDS is proposed to understand the formation process of GDS and promote its structure and performance more pertinently. Different states during the preparation process, raw carbon paper, pre-curing, curing, carbonation, and graphitization, are characterized and measured. Experimental and numerical methods are employed to determine the relationships between microstructure, transport, and mechanical performance variation with the fabricating processes. The results show that its porosity, average pore size, and effective diffusivity decrease first and increase after curing. These parameters after graphitization are lower than that of the carbon paper (CP). The electrical resistivity increases dramatically while pre-curing and decreases gradually after curing, carbonation, and graphitization, and it is much reduced after graphitization. Moreover, mechanical measurement results show that both the picks of tensile strength and flexural modulus occur after curing. Its tensile strength shows little change after graphitization compared to the initial paper's. In contrast, the flexural modulus is improved significantly.     

One-step to prepare high-performance gas diffusion layer (GDL) with three different functional layers for proton exchange membrane fuel cells (PEMFCs)

Gas diffusion layer (GDL) is one of the most important components of fuel cells. In order to improve the fuel cell performance, GDL has developed from single layer to dual layers, and then to multiple layers. However, dual or multi layers in GDL are usually prepared by layer-by-layer methods, which cost too much time, energy, and resources. In this work, we successfully developed a facile one-step method to prepare a GDL with three functional layers by utilizing the different sedimentation rates and filtration rates of short carbon fiber (CF) and carbon nanotube (CNT). The treatment temperature for this GDL is much lower than that of traditional method. The thickness of the GDL can be effectively controlled from as thin as 50 μm to more than 200 μm by simply adjusting the content of CF. The GDL with high flexibility is suitable to develop high performance flexible electronics. The fuel cell with the GDL has the maximum power density 1021 mW cm^?2, which shows 19% improvement comparing to the conventional one. Therefore, this work breaks the traditional concept that GDL for fuel cells only can be prepared by very complex and high-cost procedure.     

Quantum effect of cooling down the environment temperature of mesoscopic LC circuit

We examine the quantum effect of cooling down the environment temperature of mesoscopic LC circuit, and find that the ground state of the circuit is no longer in the thermo vacuum state, but in a negative binomial state. We calculate energy of the circuit in this new state, which increases with the cooling of the environment.     

Paper mill sludge as a renewable substrate for the production of acetone-butanol-ethanol using Clostridium sporogenes NCIM 2337

In the present study, pre-treated paper mill sludge (PMS) was evaluated extensively as a substrate for production of acetone-butanol-ethanol using Clostridium sporogenes NCIM 2337. The PMS was subjected to three types of pre-treatment methods namely alkali, mechanical, and thermal treatment and was analyzed by SEM. The pre-treatment of PMS by alkali was observed to be more effective over the other pre-treatment methods. The alkali pre-treated sludge was then made to undergo fermentation, which showed the conventional process of acidogenesis followed by solventogenesis. The acetone, butanol, and ethanol concentration for 15% alkali pre-treated PMS was estimated to be maximum.     

Vacuum impregnation of chitosan‐based edible coating in minimally processed pumpkin

The goal of this research was to evaluate the use of vacuum impregnation (VI) and soaking techniques (ST) in the application of edible coatings of chitosan and chitosan + lauric acid to minimally processed pumpkins (MPP). The vacuum impregnation method led to greater component incorporation (5.9% and 1.75%, respectively) in the pumpkins when compared to soaking and consequently the formation of more uniform, thicker coatings (25.6 and 22.3 μm, respectively). However, VI caused greater changes in pH, acidity, colour and firmness. Relating to water content and carotenoid content, noncoated pumpkins presented greater losses during the storage period, regardless of impregnation method. The pumpkins with edible coatings, regardless of method, presented lower numbers of psychrotrophic micro‐organisms and coliforms during the storage period. Therefore, soaking was considered the best method for the application of chitosan‐based edible coatings to minimally processed pumpkins, as it led to smaller changes in the properties of the product.     

软土地基的真空预压+水载法处理施工技术

结合横琴国际商务中心(二期)项目中的软土地基处理实践,介绍了真空预压+水载法施工技术。从真空预压加速固结、设置水泥土搅拌桩形成密封墙等方面出发,对关键工艺进行了阐述。真空预压+水载法施工技术实施后,项目取得了良好的社会效益和经济效益,可供相关工程参考。     

Preceramic paper-derived Ti3Al(Si)C2-based composites obtained by spark plasma sintering

The paper describes the structure and properties of preceramic paper-derived Ti₃Al(Si)C₂-based composites fabricated by spark plasma sintering. The effect of sintering temperature and pressure on microstructure and mechanical properties of the composites was studied. The microstructure and phase composition were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. It was found that at 1150 °C the sintering of materials with the MAX-phase content above 84 vol% leads to nearly dense composites. The partial decomposition of the Ti₃Al(Si)C₂ phase becomes stronger with the temperature increase from 1150 to 1350 °C. In this case, composite materials with more than 20 vol% of TiC were obtained. The paper-derived Ti₃Al(Si)C₂-based composites with the flexural strength > 900 MPa and fracture toughness of >5 MPa m^1/2 were sintered at 1150 °C. The high values of flexural strength were attributed to fine microstructure and strengthening effect by secondary TiC and Al₂O₃ phases. The flexural strength and fracture toughness decrease with increase of the sintering temperature that is caused by phase composition and porosity of the composites. The hardness of composites increases from ~9.7 GPa (at 1150 °C) to ~11.2 GPa (at 1350 °C) due to higher content of TiC and Al₂O₃ phases.     

Moulded pulp products manufacturing with thermoforming

For an effective optimization of pulp thermoforming and of the moulded pulp products manufactured by this process, a full understanding of the process physics combined with full knowledge of the pressing equipment is necessary. For this reason, in this Addendum, we clarify how the process parameters “Holding time,” “Vacuum time,” “Cycle time,” and “Temperature” were interpreted and subsequently defined for the analysis of the process and product‐related outputs of the thermoforming experiments.     

Controllable electrodeposition synthesis of Pd/TMxOy-rGO/CFP composite electrode for highly efficient methanol electro-oxidation

A novel and high-efficiency Pd/TM_xO_y-rGO/CFP (TM_xO_y = Co₃O₄, Mn₃O₄, Ni(OH)₂) electrocatalyst for directly integrated membrane electrode was synthesized by controllable cyclic voltammetry electrodeposition combined with hydrothermal process. The results showed excellent performance towards methanol oxidation reduction. The Pd/Co₃O₄-rGO/CFP as-prepared catalyst has the best electrocatalytic activity, and mass activity is 5181 mA·mg⁻¹_Pd, which is about 40 times and 4.3 times that of the commercial Pd/C and Pt/C catalyst (JM). It can be attributed that the small size of Pd nanoparticle, uniformity of distribution, and the synergistic interaction between transition metal oxide on the support surface and Pd nanoparticles. The prepared Pd/TM_xO_y-rGO/CFP composite electrode is a promising catalyst for integrated membrane electrode assembly of proton exchange membrane fuel cells in the future.