Two-step pyrolytic engineering to form porous nitrogen-rich carbons with a 3D network structure for Zn-air battery oxygen reduction electrocatalysis

It is of great urgency to design inexpensive and high-performance oxygen reduction reaction (ORR) electrocatalysts derived from biowastes as substitutes for Pt-based materials in electrochemical energy-conversion devices. Here we propose a strategy to synthesize three-dimensional (3D) porous nitrogen-doped network carbons to catalyze the ORR from two-step pyrolysis engineering of biowaste scale combined with the use of a ZnCl₂ activator and a FeCl₂ promotor. Electrochemical tests show that the synthesized network carbons have exhibited comparable ORR catalytic activity with a half-wave potential (~0.85 V vs. RHE) and outstanding cyclical stability in comparison to the Pt/C catalyst. Beyond that, a high electron transfer number (~3.8) and a low peroxide yield (<7.6%) can be obtained, indicating a four-electron reaction pathway. The maximum power density is ~68 mW cm^?2, but continuous discharge curves (at a constant potential of ~1.30 V) for 12 h are not obviously declined in Zn-air battery tests using synthesized network carbons as the cathodic catalyst. The formation of 3D porous structures with high BET surface area can effectively expose the surface catalytic sites and promote mass transportation to boost the ORR activity. This work may open a new idea to prepare porous carbon-based catalysts for some important reactions in new energy devices.     

Composition-tunable PtCu porous nanowires as highly active and durable catalyst for oxygen reduction reaction

To accelerate the commercialization of fuel cells, many efforts have been made to develope highly active and durable Pt-based catalyst for oxygen reduction reaction (ORR). Herein, PtCu porous nanowires (PNWs) with controllable composition are synthesized through an ultrasound-assisted galvanic replacement reaction. The porous structure, surface strain, and electronic property of PtCu PNWs are optimized by tuning composition, which can improve activity for ORR. Electrochemical tests reveal that the mass activity of Pt_0.5Cu_0.5 PNWs (Pt/Cu atomic ratio of 1:1) reaches 0.80 A mg_Pt^?1, which is about 5 times higher than that of the commercial Pt/C catalyst. Notably, the improved activity of the porous nanowire catalyst is also confirmed in the single-cell test. In addition, the large contact area with the carrier and internal interconnection structure of Pt_0.5Cu_0.5 PNWs enables them to exhibit much better durability than the commercial Pt/C catalyst and Pt_0.5Cu_0.5 nanotubes in accelerated durability test.     

What are the potential strategies to achieve potentially more healthful meat products?

In recent years, much attention has been paid to the consumption of meat and processed meat, and their relationship with a healthy diet. This review provides an overview of the potential strategies, which can be used to provide the implications for producing healthy, wholesome and consistently high-quality meat products. Genetic selection, nutrition and feeding management, and gene manipulation techniques have been used as the main strategies to induce beneficial changes in meat and meat composition. Besides, the incorporation of ingredients that play a technological role and are potentially health-enhancing, such as fibre, fat substitutes, natural antioxidants and the reduction of sodium and nitrites, has a high potential in the development of healthier meat products. In this review, we have observed that many strategies have been successfully used to obtain products with low fat, reduced sodium and nitrite content, low cholesterol and absence of synthetic antioxidants. Another point to be highlighted is that some of these strategies also allow obtaining products with positive health effects that can be potential alternatives to improve consumer acceptance.     

Dual needle corona discharge to generate stable bipolar ion for neutralizing electrosprayed nanoparticles

The performances of dual needle corona discharge (NCD) as bipolar ion source to neutralize the electrospray (ES) particles were characterized and optimized. The NCD was constructed from a tungsten needle and grounded mesh electrode in the needle-to-plane configuration. The dual NCD created a bipolar ion environment by mixing the balanced concentration of positive and negative ions produced by each NCD. The dual NCD was placed in an electrospray aerosol generator (EAG) apparatus to reduce the charge state of the ES particles. Polystyrene latex (PSL) suspensions having the particle size range of 96–256 nm were used as the precursor solution for the electrospray process. Some characterizations to the NCD were carried out to obtain optimum operating voltage and air flow rate. The size distribution and charge fraction of the electrospray PSL (ES-PSL) particles exiting the EAG were also investigated. The result showed the dual NCD could generate stable bipolar ions by mixing positive and negative ions with balanced concentration. The bipolar ions from the dual NCD were capable of neutralizing and reducing the charge state of highly charged ES-PSL particles larger than 100 nm. The EAG, equipped with the dual NCD, could generate ES-PSL particles with stable concentration and consistent size distribution. The charge fraction calculation of the ES-PSL particles showed that more than 80% of the particles exiting the EAG were positively charged.     

碱度对包钢高炉渣物理性能的影响

摘要：为探明二元碱度对包钢高炉渣物理性能的影响机理，基于包钢7号高炉渣化学组成，添加纯试剂CaO、SiO2调整炉渣的二元碱度。通过实验研究二元碱度对包钢7号高炉渣熔化温度、黏度和熔化性温度的影响规律；同时采用Factsage70热力学软件，计算了不同碱度下炉渣的液相线温度和热焓值。结果表明：随着碱度升高，炉渣熔化温度不断升高，黏度和熔化性温度先降低后升高，碱度在1.1～1.3之间，碱度每提高0.1，炉渣半球温度提高4.67℃，软熔区间为3.33～4.60℃；碱度在1.1～1.4之间，1450℃以上炉渣黏度均低于0.5Pa·s，流动性良好；Factsage7.0计算结果表明：随着碱度的升高，炉渣的液相线温度不断升高，热焓值不断降低。综合考虑碱度对包钢炉渣熔化温度、熔化性温度、热焓和黏度的影响规律，建议包钢高炉渣的碱度应控制在1.1～1.3之间。     

铁尾矿对矿渣纤维制备中熔体流动性的影响

 为了探究以铁尾矿为调质剂制备高炉渣基矿渣纤维的可行性及最佳工艺参数，测定了不同铁尾矿添加量时调质高炉熔渣的变温黏度，研究了铁尾矿添加量对调质高炉熔渣黏度、流动度、质点移动活化能及渣系结构的影响。结果表明,随着铁尾矿添加量的增加，调质高炉熔渣的黏度逐渐增大，流动度逐渐减小；渣系质点移动活化能随着铁尾矿添加量的增加呈先增大后减小再增大的趋势；综合考虑矿渣纤维的质量和成纤条件的可行性，调质剂铁尾矿的最佳添加量为20%。     

Microbial Production of Natural and Unnatural Monolignols with Escherichia coli

Phenylpropanoids and phenylpropanoid-derived plant polyphenols find numerous applications in the food and pharmaceutical industries. In recent years, several microbial platform organisms have been engineered towards producing such compounds. However, for the most part, microbial (poly)phenol production is inspired by nature, so naturally occurring compounds have predominantly been produced to date. Here we have taken advantage of the promiscuity of the enzymes involved in phenylpropanoid synthesis and exploited the versatility of an engineered Escherichia coli strain harboring a synthetic monolignol pathway to convert supplemented natural and unnatural phenylpropenoic acids into their corresponding monolignols. The performed biotransformations showed that this strain is able to catalyze the stepwise reduction of chemically interesting unnatural phenylpropenoic acids such as 3,4,5-trimethoxycinnamic acid, 5-bromoferulic acid, 2-nitroferulic acid, and a “bicyclic” p-coumaric acid derivative, in addition to six naturally occurring phenylpropenoic acids.     

基于多特定决策类的不完备决策系统正域约简

现有的属性约简方法大部分关注决策系统中的所有决策类，而在实际决策过程中决策者往往仅关注决策系统中的一种或几种决策类。针对上述问题，提出基于多特定决策类的不完备决策系统正域约简的理论框架。首先，给出不完备决策系统单特定决策类正域约简的概念；第二，将单特定决策类正域约简推广到多特定决策类，构造了相应的差别矩阵及区分函数；第三，分析并证明了相关定理，提出基于差别矩阵的不完备决策系统多特定决策类正域约简算法（PRMDM）；最后，选取4组UCI数据集进行实验。在数据集Teaching-assistant-evaluation、House、Connectionist-bench和Cardiotocography上，基于差别矩阵的不完备决策系正域约简算法（PRDM）的平均约简长度分别为4.00、13.00、9.00和20.00，PRMDM算法（多特定决策类中决策类数目为2）的平均约简长度分别为3.00、8.00、8.00和18.00。实验结果验证了PRMDM算法的有效性。     

乙二醇高温还原制备燃料电池核壳结构Cu@Pt-Pd电极的研究

通过对以碳为核心的燃料电池电催化剂Cu@Pt-Pd的制备方法的研究,以还原法成功将Cu、Pt、Pd还原到了靶核C上制备出了核壳结构电催化剂Cu@Pt-Pd。该催化剂以Cu为核来提升催化剂的表面积比,同时掺杂金属Pd,降低贵金属铂的使用量,在提高催化效率的同时可以降低成本。经过对所制备的催化剂的XRD和CV的测试与分析,探究出制备的成品具有一定的提升氧化还原反应的催化效率的能力,同时该制备方法简单易于操作,利于大量制备。     

Synthesis of rod-like ZrB2 crystals by boro/carbothermal reduction

Rod-like ZrB₂ crystals were synthesized at 1600 °C in Ar atmosphere by boro/carbothermal reduction using ZrOCl₂⋅8H₂O, B₄C and carbon powders as raw materials. The optimum molar ratio of raw materials required to form pure ZrB₂ grains was found to be 2: 1.2: 3. With increase in temperature and subsequent heat preservation stage, ZrB₂ powders grew into a rod-like morphology along the c axis. The rod-like ZrB₂ grains obtained at 1600 °C have diameters of 0.5–3 μm and high aspect ratios of >8. Effects of molar ratio of raw materials, heating temperature and holding time on the phase composition and final morphology were investigated. Growth mechanism of rod-like ZrB₂ grains was also analyzed.