匀度指数对碳纸原纸强度与孔隙特性的影响研究

本研究以碳纤维为原料,通过改变分散剂种类制备具有不同匀度性能的碳纸原纸,考察了碳纤维浆料的分散稳定性及其均匀性变化规律,探讨了匀度指数与透气度、抗张强度、孔隙率等指标之间的关系。结果表明,与单一APAM、TOCNs和PU分散剂相比,质量分数0.1%APAM和1.0%PU复合的分散剂体系制备的碳纤维浆料分散稳定性和均匀性得到改善,该复合分散剂制备碳纸原纸匀度指数最好,为10.32。随着匀度指数的减小,碳纸原纸厚度偏差从21.76 mm降至0.96 mm,抗张强度从0.15 kN/m增加到1.68 kN/m,孔隙率从93.5%下降到90.5%,透气度从1 658.9 L/(m^(2)·s)下降到1 171.5 L/(m^(2)·s)。

基于GA-BPNN算法的碳纸原纸性能指标建模预测研究

本研究通过改变碳纤维长度、碳纤维占比、分散剂用量等工艺参数,制备不同碳纸原纸,探究不同工艺参数对其抗张强度、孔隙率、透气性、电阻率的影响,采用遗传算法改进反向传播神经网络算法(GA-BPNN算法),构建了碳纸原纸性能预测模型。结果表明,碳纤维长度与碳纸原纸抗张强度、孔隙率、透气性呈正相关,与电阻率呈负相关;碳纤维占比与碳纸原纸抗张强度呈负相关,与孔隙率、透气性、电阻率呈正相关;分散剂用量与碳纸原纸抗张强度、电阻率呈正相关,与孔隙率、透气性呈负相关;碳纸原纸抗张强度、孔隙率、透气性、电阻率预测模型平均相对误差(MRE)分别为5.49%、5.75%、5.21%、5.54%,预测模型MRE均小于10%,与实验得到的工艺参数对碳纸原纸性能的关系趋势一致。

生物炭配施氮磷钾与微肥对圆齿野鸦椿色原酮碳苷的影响

为探讨施肥对圆齿野鸦椿果皮高抗炎物质色原酮碳苷(5,7-二羟基-2-甲基-色原酮-8-c-β-d-葡萄糖苷和5,7-二羟基-2-甲基-色原酮-6-c-β-d-葡萄糖苷)含量的影响,采用L18(35)正交试验设计,选取4年生圆齿野鸦椿幼树,设置生物炭、氮、磷、钾元素肥与微肥施肥配比,并设空白对照组,共19个处理。经方差、相关性、线性回归和隶属函数等分析,结果表明:在本研究条件下,元素肥单施效果不明显,钾肥与微肥使isobiflorin(B1)和biflorin(B2)含量较大;配施时,B1、B2含量在T16处理时最大,分别为24.39、24.93 mg·g^(-1),与隶属函数分析结果一致;B1和B2含量相关性为0.999,显著度<0.001,一元线性回归方程为B2=-0.082+1.026×B1。综上,T16处理是色原酮高含量药用林培育的施肥方案,圆齿野鸦椿存在体内互相转换的可能。本研究为其科学培育与利用提供理论与技术支持。

黑碳添加对土壤活性有机碳和原有机碳的影响

通过室内培养实验,向土壤(甘蔗土)中分别添加不同用量的黑碳(BC,350℃热解水稻秸秆),添加量分别为0(BC0)、1%(BC1)、2%(BC2)、3%(BC3)、4%(BC4)和5%(BC5),研究黑碳添加量对土壤活性有机碳和原有机碳的影响。结果表明,在25℃培养条件下,土壤易矿化碳(Cm)随黑碳添加量的增加而增加;土壤微生物生物量碳含量亦随添加量的增加呈增加趋势(BC3处理除外)。土壤可溶性有机碳含量在BC1、BC2和BC3处理之间的差异不显著,并显著低于对照土壤(BC0);应用δ13C自然丰度方法研究发现,BC1处理抑制了土壤原有机碳分解,而BC2、BC3、BC4和BC5处理促进了土壤原有机碳的分解,但统计上未达显著水平。

HPLC法同时测定闽产圆齿野鸦椿中两种色原酮碳苷的含量

建立了HPLC同时测定圆齿野鸦椿中两个成分5,7-二羟基-2-甲基-色原酮-8-C-β-D-葡萄糖苷(A)和5,7-二羟基-2-甲基-色原酮-6-C-β-D-葡萄糖苷(B)的方法,并测定了这两个成分在闽产圆齿野鸦椿枝条、叶片、果皮和种子中的含量。结果表明:HPLC测试条件为色谱柱DikmaDiamonsil C18柱(250 mm×4.6 mm,5μm),流动相甲醇/水(25∶75,体积比),等度洗脱,流速为1.0 mL/min;检测波长256 nm,柱温30℃,检测时间15 min时,化合物A和B分别在2.000 2～20.002 0μg和2.001 6～20.016 0μg范围内线性关系良好(r=0.999 9),平均加样回收率分别为98.42%和99.77%,RSD均小于1.00%(n=6)。HPLC法快速简便、重复性和稳定性好、结果准确可靠,可为今后圆齿野鸦椿在药用植物资源开发应用方面提供依据。

碱预处理对碳纤维分散及碳纸原纸性能的研究

本研究以碳纤维为原料,研究碱预处理对碳纤维分散稳定性及湿法抄造制备碳纸原纸性能的影响。具体考察了碳纤维在碱预处理后表面形貌和表面基团的变化,探讨了碳纤维浆料悬浮液的稳定性变化规律,并表征了碳纸原纸的匀度、透气性、抗张强度和电阻率的变化情况。结果表明,与使用去离子水处理的碳纤维相比,经0.75 mol/L的碱液预处理60 min后,碳纤维可以更好地在水中分散,制备出的碳纸原纸匀度性能更好,碳纸原纸的透气度从1432 mm/s降至1080 mm/s,抗张强度从1.44kN/m提升至2.49 kN/m,电阻率从143.58 mΩ/cm降至68.10 mΩ/cm。

Cu single-atom electrocatalyst on nitrogen-containing graphdiyne for CO_(2)electroreduction to CH4

Developing Cu single-atom catalysts(SACs)with well-defined active sites is highly desirable for producing CH4 in the electrochemical CO_(2)reduction reaction and understanding the structure-property relationship.Herein,a new graphdiyne analogue with uniformly distributed N2-bidentate(note that N2-bidentate site=N^N-bidentate site;N2¹dinitrogen gas in this work)sites are synthesized.Due to the strong interaction between Cu and the N2-bidentate site,a Cu SAC with isolated undercoordinated Cu-N2 sites(Cu1.0/N2-GDY)is obtained,with the Cu loading of 1.0 wt%.Cu1.0/N2-GDY exhibits the highest Faradaic efficiency(FE)of 80.6%for CH4 in electrocatalytic reduction of CO_(2)at-0.96 V vs.RHE,and the partial current density of CH4 is 160 mA cm^(-2).The selectivity for CH4 is maintained above 70%when the total current density is 100 to 300 mA cm^(-2).More remarkably,the Cu1.0/N2-GDY achieves a mass activity of 53.2 A/mgCu toward CH4 under-1.18 V vs.RHE.In situ electrochemical spectroscopic studies reveal that undercoordinated Cu-N2 sites are more favorable in generating key*COOH and*CHO intermediate than Cu nanoparticle counterparts.This work provides an effective pathway to produce SACs with undercoordinated Metal-N2 sites toward efficient electrocatalysis.

Chalcogen heteroatoms doped nickel-nitrogen-carbon single-atom catalysts with asymmetric coordination for efficient electrochemical CO_(2)reduction

The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2)reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N4-C)configuration to obtain Ni-X-N3-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N3-C(X:S,Se,and Te)SACs,Ni-Se-N3-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98%at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2)battery integrated with Ni-Se-N3-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm-2 and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N4-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N3-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of*COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.

Boosting CO_(2)photoreduction by synergistic optimization of multiple processes through metal vacancy engineering

The photoreduction of greenhouse gas CO_(2)using photocatalytic technologies not only benefits en-vironmental remediation but also facilitates the production of raw materials for chemicals.Howev-er,the efficiency of CO_(2)photoreduction remains generally low due to the challenging activation of CO_(2)and the limited light absorption and separation of charge.Defect engineering of catalysts rep-resents a pivotal strategy to enhance the photocatalytic activity for CO_(2),with most research on met-al oxide catalysts focusing on the creation of anionic vacancies.The exploration of metal vacancies and their effects,however,is still underexplored.In this study,we prepared an In2O3 catalyst with indium vacancies(VIn)through defect engineering for CO_(2)photoreduction.Experimental and theo-retical calculations results demonstrate that VIn not only facilitate light absorption and charge sepa-ration in the catalyst but also enhance CO_(2)adsorption and reduce the energy barrier for the for-mation of the key intermediate*COOH during CO_(2)reduction.Through metal vacancy engineering,the activity of the catalyst was 7.4 times,reaching an outstanding rate of 841.32μmol g(-1)h^(-1).This work unveils the mechanism of metal vacancies in CO_(2)photoreduction and provides theoretical guidance for the development of novel CO_(2)photoreduction catalysts.

Catalytically altering the redox pathway of sulfur in propylene carbonate electrolyte using dual-nitrogen/oxygen-containing carbon

Carbonate electrolytes are one of the most desirable electrolytes for high-energy lithium-sulfur batteries(LSBs)because of their successful implementation in commercial Li-ion batteries.The low-polysulfide-solubility feature of some carbonate solvents also makes them very promising for overcoming the shuttle effects of LSBs.However,regular sulfur electrodes experience undesired electrochemical mechanisms in carbonate electrolytes due to side reactions.In this study,we report a catalytic redox mechanism of sulfur in propylene carbonate(PC)electrolyte based on a compari-son study.The catalytic mechanism is characterized by the interactions between polysulfides and dual N/O functional groups on the host carbon,which largely prevents side reactions between pol-ysulfides and the carbonate electrolyte.Such a mechanism coupled with the low-polysulfide-solubility feature leads to stable cycling of LSBs in PC electrolyte.Favorable dual N/O functional groups are identified via a density functional theory study.This work provides an alternative route for enabling LSBs in carbonate electrolytes.

Mesoporous Carbon Nanofibers Loaded with Ordered PtFe Alloy Nanoparticles for Electrocatalytic Nitrate Reduction to Ammonia

Highly dispersed bimetallic alloy nanoparticle electrocatalysts have been demonstrated to exhibit exceptional performance in driving the nitrate reduction reaction(NO_(3)RR)to generate ammonia(NH_(3)).In this study,we prepared mesoporous carbon nanofibers(mCNFs)functionalized with ordered PtFe alloys(O-PtFe-mCNFs)by a composite micelle interface-induced co-assembly method using poly(ethylene oxide)-block-polystyrene(PEO-b-PS)as a template.When employed as electrocatalysts,O-PtFe-mCNFs exhibited superior electrocatalytic performance for the NO_(3RR)compared to the mCNFs functionalized with disordered PtFe alloys(D-PtFe-mCNFs).Notably,the NH_(3)production performance was particularly outstanding,with a maximum NH_(3)yield of up to 959.6μmol/(h·cm~2).Furthermore,the Faraday efficiency(FE)was even 88.0%at-0.4 V vs.reversible hydrogen electrode(RHE).This finding provides compelling evidence of the potential of ordered PtFe alloy catalysts for the electrocatalytic NO_(3)RR.

Poly(ethylenimine)-assisted synthesis of hollow carbon spheres comprising multi-sized Ni species for CO_(2)electroreduction

Electrochemical CO_(2)reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2)electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2)and a Faradaic efficiency of 93.0%at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2)reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.

Preparation and electromagnetic shielding properties of PET/rGO/SWCNT composite fabric

Graphene oxide(GO)with excellent dispersion ability can assist the dispersion of single-walled carbon nanotube(SWCNT)and promote the formation of uniform and stable GO/SWCNT coating liquid.The highly conductive polyethylene terephthalate/reduced graphene oxide/SWCNT(PET/rGO/SWCNT)electromagnetic shielding composite fabric was successfully prepared by anchoring rGO/SWCNT on PET fabric via dip-coating piror to low-temperature thermal reduction.The results showed that the carboxyl groups and hydroxyl groups formed of hydrophilic-treated PET were conducive to the formation of hydrogen bonds with that of GO,which enhanced the interaction between PET fabric and GO/SWCNT coating;the loading of GO/SWCNT increased with the number of dip-coating,the unit area loading of rGO/SWCNT in the final composite fabric was 2.7 mg/cm^(2) after 10 dip-coating cycles and thermal reduction;the PET/rGO/SWCNT composite fabric had a continuous and dense conductive network,with a conductivity of up to 41.6 S/m and the average electromagnetic interference shielding effectiveness in X-band was 22 dB;the flexible PET/rGO/SWCNT composite fabric was not only easy to process,but also exhibited excellent conductivity and shielding efficiency,showing great potential in the application of electromagnetic shielding fabrics.

低碳视角下我国水泥工业发展路径探索

本文首先分析巴黎气候大会所达成的长期目标,以及中国政府的行动目标,其次陈述中国水泥工业碳减排所面临的严峻形势以及我国水泥工业低碳发展的必要性,进而结合国际视角提出中国水泥工业碳减排的路径。

二氮杂萘酮衍生物的核磁共振结构鉴定

用1 H ,1 3CNMR及多种二维核磁共振谱确定了一系列新合成的二氮杂萘酮衍生物的结构 ,完成了1 H和1 3CNMR谱的归属 ,给出了该系列衍生物的氢。

判定环状化合物C^＊R／S构型的简单方法

以R/S构型标记法直接应用于Fischer投影式 ,按特点规则判断其构型为依据 。

Preparation of TiC powders by carbothermal reduction method in vacuum

The preparation of fine TiC powders by carbothermal reduction of TiO2 in vacuum was investigated by XRD,SEM,XRF and laser particle sizer.Thermodynamic analysis indicates that it is easy to prepare TiC in vacuum and the formation sequence of products are Ti4O7（Magneli phase）,Ti3O5,Ti2O3,TiCxO1-x and TiC with the increase of reaction temperature.Experimental results demonstrate that TiC powders with single phase are obtained with molar ratio of TiO2 to C ranging from 1：3.2 to 1：6 at 1 550 ℃ for 4 h when the system pressure is 50 Pa,and TiC1.0 is gained when the molar ratio of TiO2 to C is 1：4 and 1：5.In addition,fine TiC1.0 powders（D50 equals 3.04 μm） with single phase and low impurities are obtained when the molar ratio of TiO2 to C is 1：4.SEM observation shows that uniform shape,low agglomeration,and loose structure are observed on the surface of block product.

Fabrication of β-Sialon/ZrN/ZrON composites using fly ash and zircon

β-Sialon/ZrN/ZrON composites were successfully fabricated by an in-situ carbothermal reduction？nitridation process with fly ash, zircon and active carbon as raw materials. The effects of raw materials composition and holding time on synthesis process were investigated, and the formation process of the composites was also discussed. The phase composition and microstructure of the composites were characterized by means of XRD and SEM. It was found that increasing carbon content in a sample and holding time could promote the formation of β-Sialon, ZrN and ZrON. The proper processing parameters to synthesize β-Sialon/ZrN/ZrON composites were mass ratio of zircon to fly ash to active carbon of 49：100：100, synthesis temperature of 1550 °C and holding time of 15 h. The average grain size ofβ-Sialon and ZrN（ZrON） synthesized at 1550 °C for 15 h reached about 2 and 1μm, respectively. The fabrication process ofβ-Sialon/ZrN/ZrON composites included the formation ofβ-Sialon and ZrO2 as well as the conversion of ZrO2 to ZrN and ZrON.

Enhanced photochemical oxidation ability of carbon nitride by π-πstacking interactions with graphene

A one-pot method for the preparation of g-C3N4/reduced graphene oxide（rGO） composite photocatalysts with controllable band structures is presented.The photocatalysts are characterized by Fouirer transform infrared spectroscopy,X-ray diffraction,scanning electron microscope,transmission electron microscope,and Mott-Schottky analysis.The valance band（VB） of g-C3N4 exhibits a noticeable positive shift upon hybridizing with rGO,and thus results in a strong photo-oxidation ability.The g-C3N4/rGO composites show a higher photodegradation activity for 2,4-dichlorophenol（2,4-DCP） and rhodamine B（RhB） under visible light irradiation（λ≥420 ran）.The g-C3N4/rGO-1sample exhibits the highest photocatalytic activity,which is 1.49 and 1.52 times higher than that of bulk g-C3N4 for 2,4-DCP and 1.52 times degradation,respectively.The enhanced photocatalytic activity for g-C3N4 originates from the improved visible light usage,enhanced electronic conductivity and photo-oxidation ability by the formed strong π-π stacking interactions with rGO.

NO reduction by CO over TiO_2-γ-Al_2O_3 supported In/Ag catalyst under lean burn conditions

TiO2/γ-Al2O3 supported In/Ag catalysts were prepared by impregnation method,and investigated for NO reduction with CO as the reducing agent under lean burn conditions.The microscopic structure and surface properties of the catalysts were studied by N2 adsorption-desorption,X-ray diffraction,transmission electron microscopy,X-ray photoelectron spectroscopy,ultraviolet-visible spectroscopy,H2 temperature-programmed reduction and Fourier transform infrared spectroscopy.TiO2/γ-Al2O3 supported In/Ag is a good catalyst for the reduction of NO to N2.It displayed high dispersion,large amounts of surface active components and high NO adsorption capacity,which gave good catalytic performance and stability for the reduction of NO with CO under lean burn conditions.The silver species stabilized and improved the dispersion of the indium species.The introduction of TiO2 into the γ-Al2O3 support promoted NO adsorption and improved the dispersion of the indium species and silver species.