Method to measure tree-ring width,density,elemental composition,and stable carbon and oxygen isotopes using one sample

Tree-ring width(RW),density,elemental com-position,and stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)are widely used as proxies to assess climate change,ecology,and environmental pollution;however,a specific pretreat-ment has been needed for each proxy.Here,we developed a method by which each proxy can be measured in the same sample.First,the sample is polished for ring width meas-urement.After obtaining the ring width data,the sample is cut to form a 1-mm-thick wood plate.The sample is then mounted in a vertical sample holder,and gradually scanned by an X-ray beam.Simultaneously,the count rates of the fluorescent photons of elements(for chemical characteriza-tion)and a radiographic grayscale image(for wood density)are obtained,i.e.the density and the element content are obtained.Then,cellulose is isolated from the 1-mm wood plate by removal of lignin,and hemicellulose.After producing this cellulose plate,cellulose subsamples are separated by knife under the microscope for inter-annual and intra-annual stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)analysis.Based on this method,RW,density,elemental composition,δ^(13)C,and δ^(18)O can be measured from the same sample,which reduces sample amount and treatment time,and is helpful for multi-proxy comparison and combination research.

High microwave absorption performances for single-walled carbon nanotube–epoxy composites with ultra-low loadings

Microwave-absorbing polymeric composites based on single-walled carbon nanotubes （SWNTs） are fabricated via a simple yet versatile method, and these SWNT-epoxy composites exhibit very impressive microwave absorption perfor- mances in a range of 2 GHz-18 GHz. For instance, a maximum absorbing value as high as 28 dB can be achieved for each of these SWNT-epoxy composites （1.3-mm thickness） with only 1 wt% loading of SWNTs, and about 4.8 GHz bandwidth, corresponding to a microwave absorption performance higher than 10 dB, is obtained. Furthermore, such low and appro- priate loadings of SWNTs also enhance the mechanical strength of the composite. It is suggested that these remarkable results are mainly attributable to the excellent intrinsic properties of SWNTs and their homogeneous dispersion state in the polymer matrix.

Fabrication method and microstructural characteristics of coal-tar-pitchbased 2D carbon/carbon composites

The lignin-cellulosic texture of wood was used to produce two-dimensional （2D） carbon/carbon （C/C） composites using coal tar pitch. Ash content tests were conducted to select two samples among the different kinds of woods present in lran, including walnut, white poplar, cherry, willow, buttonwood, apricots, berry, and blue wood. Walnut and white poplar with ash contents of 1.994wt% and 0.35 lwt%, respectively, were selected. The behavior of these woods during pyrolysis was investigated by differential thermal analysis （DTA） and thermo gravimetric （TG） analysis. The bulk density and open porosity were measured after carbonization and densification. The mierostruc- tural characteristics of samples were investigated by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and Fourier-transform infrared （FT-IR） spectroscopy. The results indicate that the density of both the walnut and white poplar is increased, and the open porosity is decreased with the increasing number of carbonization cycles. The XRD patterns of the wood charcoal change gradually with increasing py- rolysis temperature, possibly as a result of the ultra-structural changes in the charcoal or the presence of carbonized coal tar pitch in the composite＇s body.

Pyrolyzed Iron Phthalocyanine-Modified Multi-Walled Carbon Nanotubes as Composite Anode in Marine Sediment Microbial Fuel Cells and Its Electrochemical Performance

Improving the performance of anode is a crucial step for increasing output power of marine sediment microbial fuel cells(MSMFCs)to drive marine monitor to work for a long term on the ocean floor.A pyrolyzed iron phthalocyanine modified multi-walled carbon nanotubes composite(FePc/MWCNTs)has been utilized as a novel nodified anode in the MSMFC.Its structure of the composite modified anode and electrochemical performance have been investigated respectively in the paper.There is a substantial improvement in electron-transfer efficiency from the bacteria biofilm to the modified anode via the pyrolyzed FePc/MWCNTs composite based on their cyclic voltammetry(CV)and Tafel curves.The electron transfer kinetic activity of the FePc/MWCNTs-modified anode is 1.86 times higher than of the unmodified anode.The maximum power density of the modified MSMFC was 572.3±14 m W m^-2,which is 2.6 times larger than the unmodified one(218.3±11 m W m^-2).The anodic structure and cell scale would be greatly minimized to obtain the same output power by the modified MSMFC,so that it will make the MSMFC to be easily deployed on the remote ocean floor.Therefore,it would have a great significance for us to design a novel and renewable long term power source.Finally,a novel molecular synergetic mechanism is proposed to elucidate its excellent electrochemical performance.

Adsorption and Kinetic Study of Activated Carbon Produced from Post-Consumer Low-Density Polyethylene (LDPE) Wastes

Post-consumer polymeric wastes in form of low-density polyethylene (LDPE) can now be considered suitable as a precursor for the synthesis of low-cost activated carbon (AC). This study produced AC from LDPE using sulphuric acid (H2SO4) and potassium hydroxide (KOH) as the activating agent. The reaction conditions for pyrolysis were varied in the range of 0.50 - 2.00 M, 400°C - 500°C, and 45 - 60 minutes. Physico-chemical investigations reveal that AC yield is significantly dependent on both carbonization temperatures and time. The obtained optimum values of 446.50°C and 51.09 mins gave a yield of 24% for the base-activated carbon. The high iodine numbers obtained strongly indicate the presence of large surface area and pore volumes is further confirmed using the Scanning Electron Microscopy (SEM) analysis which reveals the presence of pores on the external surface of the carbons. Fourier Transform Infrared Technique (FTIR) analysis further shows that the synthesized compounds are purely carbon with rich oxy-gen-surface complexes on the surface which is as a result of the introduction of the chemical oxidizing agents. The produced carbons were found to have high adsorption affinity for selected inorganic ions which are: Mn7+, Co2+, and Cr6+. Adsorption isotherm results show the adsorption process to be favourable with the Langmuir isotherm parameter RL having values of <1, while the Freudlich adsorption model was found to perfectly fit the data at selected adsorbent dosages and adsorbate concentrations. The pseu-do-second-order model provides the best correlation for the kinetic analysis. The acid-activated carbon was found to have better adsorption capacities than the base-activated carbon.

Carbon Equivalent Fundamentals in Evaluating the Weldability of Microalloy and Low Alloy Steels

Understanding the weldability of steel in relation to the use of carbon equivalent is very necessary for the welding industry. The study was poised to unearth the fundamentals of carbon equivalent as applied in evaluating the weldability of steel. The study used a two-stage design approach to address the problem of carbon equivalence weldability of steel, thus, survey and experimental. Two different steels were tested to ascertain their chemical composition which could inform carbon equivalent calculation, and the results revealed microalloy and low alloy steels respectively. In subjecting the microalloy steel to carbon equivalent analyses of the AWS and IIW coefficients;revealed a value (CEV) = 0.11 each, suggesting that this microalloy steel has excellent weldability;no preheating is required. A successful welding operation on this steel does not depend on preheating. Also, the average results of the low alloy steel revealed a value (CEV) = 0.37 and 0.32 respectively, suggesting that this type of steel has very good weldability and may require to preheat. It is recommended that welders have a general idea about the weldability of steel with regard to carbon equivalent calculation. In addition, they should understand the chemical compositions of steels they are dealing with.

Synthesis of SAPO-34/graphite composites for low temperature heat adsorption pumps

Low temperature heat adsorption pumps represent the innovative cooling systems, where cold is generated through adsorption/desorption cycle of water by a suitable adsorbent with good adsorption and high thermal conductive properties. In this work, the hydrothermal synthesis of zeolite SAPO-34 on thermal conductive grapbitic supports, aiming at the development of highly pertbrming adsorbent materials, is reported. The synthesis was carried out using as-received and oxidized commercial carbon papers, and graphite plate. Composites were characterized by XRD, SEM and also by a thermogravimetric method, using a Cahn microbalance. The water adsorbing capacity showed typical S-shape trend and the maximum water loading was around 25 wt%, a value close to water adsorption capability of pure SAPO-34. These results are very promising for their application in heat adsorption pumps.

Supercritical CO2 Assisted Preparation of Open-cell Foams of Linear Low-density Polyethylene and Linear Low-density Polyethylene/Carbon Nanotube Composites

The open-cell structure foams of linear low-density polyethylene（LLDPE） and linear low-density polyethylene（LLDPE）/multi-wall carbon nanotubes（MWCNTs） composites are prepared by using supercritical carbon dioxide（sc-CO2）as a foaming agent. The effects of processing parameters（foaming temperature, saturation pressure, and depressurization rate） and the addition of MWCNTs on the evolution of cell opening are studied systematically. For LLDPE foaming, the foaming temperature and saturation pressure are two key factors for preparing open-cell foams. An increase in temperature and pressure promotes both the cell wall thinning and cell rupture, because a high temperature results in a decrease in the viscosity of the polymer, and a high pressure leads to a larger amount of cell nucleation. Moreover, for the given temperature and pressure, the high pressurization rate results in a high pressure gradient, favoring cell rupture. For LLDPE/MWCNTs foaming, the addition of MWCNTs not only promotes the cell heterogeneous nucleation, but also prevents the cell collapse during cell opening, which is critical to achieve the open-cell structures with small cell size and high cell density.

Mechanisms of carbon isotopic fractionation in the process of natural gas generation: Geochemical evidence from thermal simulation experiment

Low maturity coal samples were taken from the Ordos Basin to conduct gold tube thermal simulation experiment in a closed system,and the characteristics of the products were analyzed to find out the fractionation mechanism of carbon isotopes and the causes of abnormal carbon isotopic compositions of natural gas.At the heating rates of 2℃/h(slow)and 20℃/h(rapid),the low maturity coal samples of the Ordos Basin had the maximum yields of alkane gas of 302.74 mL/g and 230.16 mL/g,theδ13C1 ranges of-34.8‰to-23.6‰and-35.5‰to-24.0‰;δ13C2 ranges of-28.0‰to-9.0‰and-28.9‰to-8.3‰;andδ13C3 ranges of-25.8‰to-14.7‰and-26.4‰to-13.2‰,respectively.Alkane gas in the thermal simulation products of rapid temperature rise process showed obvious partial reversal of carbon isotope series at 550℃,and at other temperatures showed positive carbon isotope series.In the two heating processes,theδ13C1 turned lighter first and then heavier,and the non-monotonic variation of theδ13C1 values is because the early CH4 is from different parent materials resulted from heterogeneity of organic matter or the carbon isotope fractionation formed by activation energy difference of early enriched 12CH4 and late enriched 13CH4.The reversal of carbon isotope values of heavy hydrocarbon gas can occur not only in high to over mature shale gas(oil-type gas),but also in coal-derived gas.Through thermal simulation experiment of toluene,it is confirmed that the carbon isotope value of heavy hydrocarbon gas can be reversed and inversed at high to over mature stage.The isotope fractionation effect caused by demethylation and methyl linkage of aromatic hydrocarbons may be an important reason for carbon isotope inversion and reversal of alkane gas at the high to over mature stage.

CIPs@Mn_(0.8)Zn_(0.2)Fe_(2)O_(4)-CNTs复合材料低频吸波性能研究

随着5G无线通信与低频雷达侦察技术的飞速发展,低频电磁波辐射已成为当代的严重问题。目前,中高频段吸波材料的研究已趋于成熟,而设计低频段吸波材料仍面临巨大的挑战,亟待研究者们解决。基于四分之一波长相消机制,本研究设计了0.5~3 GHz低频段复合吸波材料。采用简单的一步水热法,诱导铁氧体在羰基铁粉与碳纳米管表面生长,制备出CIPs@Mn_(0.8)Zn_(0.2)Fe_(2)O_(4)-CNTs三元复合材料,对比研究了碳纳米管含量对材料吸收峰频率的影响。实验结果表明,引入碳纳米管,一方面为材料带来了界面极化、偶极极化等额外的损耗机制,增加了材料的衰减系数;另一方面基于四分之一波长相消机制,高介电与高磁导率的耦合,使材料在低频段获得良好的阻抗匹配。最终,在4 mm厚度下,样品分别在2.11与1.75 GHz处,获得了–40.8与–32.1 dB的反射损耗,–10 dB带宽分别为1.70~2.70 GHz和1.40~2.20 GHz。该复合材料制备工艺简单,低频吸收性能良好,具有很大的应用潜力,为开发更有效的低频吸波材料提供了新的思路和方法。

LLDPE/碳纤维网复合膜的制备及性能

为了提高线型低密度聚乙烯(LLDPE)的拉伸强度和模量,将碳纤维(CF)梳理成均匀的碳纤维网,将其作为增强材料与LLDPE复合制备LLDPE/CF复合膜,综合利用热失重分析(TG)、扫描示差量热分析(DSC)、扫描电子显微镜(SEM)及拉伸测试等手段分析碳纤维网含量对复合膜结构及性能的影响。结果表明:与LLDPE膜相比,LLDPE/CF复合膜的拉伸强度和杨氏模量显著提高并随碳纤维网含量增加而增大,当碳纤维网质量分数仅为1%时,拉伸强度从10.6MPa提高到28.7MPa,提高了171%,杨氏模量由75MPa增大到1119MPa,约提高到原来的15倍;碳纤维网的引入有利于LLDPE/CF复合膜热稳定性能的提高,当碳纤维网含量仅为1%时,LLDPE/CF的初始热分解温度和最大热分解速率温度与LLDPE相比分别提高了21℃和11℃;碳纤维网的引入促进了LLDPE分子链的结晶,使LLDPE/CF复合膜的结晶度增大,有利于拉伸强度和模量提高;SEM结果显示碳纤维网与LLDPE基体间的界面结合较强,有利于力学性能的提高。研究成果可为高性能聚合物/碳纤维复合材料的制备提供实验依据和理论指导价值。

高低温对碳纤维/环氧树脂复合材料高压气瓶的性能影响

为了获得T1000碳纤维/环氧树脂复合材料高压气瓶环境适应能力,有效地掌握气瓶高低温适应性固有规律,以容积50 L、工作压力30 MPa的复合材料气瓶(钛为内衬、碳纤维/环氧树脂为复合层)为研究对象,首先介绍了高低温循环下带压气瓶(在-40~80℃范围内成功通过热真空、热循环验证,具备高压承载能力)的热真空、热循环试验数据,然后采用与气瓶相同复合材料的拉伸试样(缠绕角分别为0°和90°),通过高低温极限摸底试验获得了复合材料经历不同梯度高低温后的拉伸性能数据,通过数据比对分析获得了高低温影响拉伸强度衰减的规律。同时,提出了一种高低温极限摸底试验的可靠性评估方法。结果表明,在-50~100℃范围内,试样拉伸强度及断裂伸长率变化较小;当温度高于100℃时,纤维和树脂的性能发生衰减,导致拉伸强度明显降低;当温度低于-50℃时,树脂的性能发生衰减,纤维受到的影响较小。试样高低温极限摸底试验的可靠度大于0.999,表明采用拉伸试样高低温拉伸强度数据的替代方式具有较高的等效性。

基于比较研究的华中三省产业结构与低碳经济的关系分析

为了促进中部地区的崛起,实现经济低碳化发展与产业优化转型,研究产业结构与低碳经济之间的相互关系具有重要意义。论文以河南、湖北和湖南三省为研究对象,运用熵值-Topsis法对2007—2022年三省的产业结构与低碳经济指标进行综合测评,并基于脱钩理论与协同学理论,运用Tapio脱钩模型和复合系统协同度模型对2008—2022年三省各自的脱钩状态与协同效应演化进行科学分析。结果表明:(1)研究期内,华中三省的产业结构综合指数和低碳经济综合指数不断提高,整体发展趋势良好。(2)大多数年份三省都处于相对脱钩状态,产业结构综合指数增长速度低于低碳经济综合指数增长速度;湖北率先达到理想的扩张负脱钩状态,湖南次之。(3)2008—2022年三省的协同效应一直较弱,且都具有一定的波动性特征;整体来看,湖北的协同水平略高于河南和湖南。

低碳复合胶凝材料对水泥和混凝土性能的影响

将粉煤灰和矿粉按不同质量比(m_(粉煤灰)∶m_(矿粉)=7∶3、6∶4、5∶5)制备成了低碳复合辅助性胶凝材料,研究了其等质量替代15%、30%的水泥对胶凝材料需水量比、流动度比和活性指数的影响,优选出了最佳m_(粉煤灰)∶m_(矿粉)。在此基础上,研究了低碳复合辅助性胶凝材料等质量替代0、10%、15%、20%、30%的水泥对胶凝材料标准稠度用水量和凝结时间的影响,以及等质量替代0、10%、20%、30%、40%的水泥对C50混凝土工作性和力学性能的影响。结果表明:在水泥中掺入适量低碳复合辅助性胶凝材料有效改善了胶凝材料体系的工作性,延缓了早期(3 d)水化速度,提高了胶砂7 d、28 d抗压强度,最佳m_(粉煤灰)∶m_(矿粉)为5∶5;随着低碳复合辅助性胶凝材料掺量的增加,胶凝材料的标准稠度用水量变化很小,凝结时间延长;C50混凝土的坍落度随着低碳复合辅助性胶凝材料掺量的增加而增大,7 d和28 d抗压强度先增大后减小,最佳掺量为30%。

Effects of Nanometer Carbon Black on Performance of Low-Carbon MgO-C Composites

The low-carbon magnesia-carbon （MgO-C） composites containing 3% （mass fraction, the same below） carbon were prepared by adding various types of carbon black （CB）. The mechanical properties, oxidation resistance at 1 100 ℃ in oxidizing atmosphere, and thermal shock resistance after 5 times dipping in 1 600 ℃molten steel of the low-carbon composite samples were investigated, compared with a commercial high-carbon MgO-C composite contai- ning carbon of 16 %. The results show that the mechanical properties, oxidation resistance and thermal shock resist- ance of the low-carbon samples are improved with the decrease of CB particle size. Thermal shock resistance of the low-carbon sample containing nanometer CB N220 is obviously better than that of other low-carbon samples, and rea- ches the level of the high-carbon samples.

连铸机末端重压下对高建Z向钢铸坯质量的影响

针对铸坯内部中心偏析、板材探伤合格率(80%以下)低的问题,河钢集团唐山中厚板材有限公司在280 mm×1800 mm断面板坯连铸机10#、11#扇形段位置实施了重压下技术,总压下量达到24 mm,在生产高建Z向钢时,铸坯致密度提高,中心偏析明显改善,铸坯晶粒尺寸随着压下量的提高显著细化。利用低倍、金相组织分析,以及铸坯碳偏析指数、致密度和真密度等实验,分析了重压下对连铸坯内部质量的影响。结果表明:随着压下量的增加,铸坯中心偏析与疏松逐步改善,低倍C级品率由原来的85%提高至98%;连铸坯断面组织也发生晶粒的细化,有明显的细化晶粒效果;当铸坯中心偏析为C级1.0时,中心碳偏析指数均可有效控制在1.10以内;铸坯的真密度整体提升,重压下工艺下铸坯中心位置真密度提升0.17%;C级≤0.5级比例≥98%;铸坯中心偏析C级率(≤0.5级比例)综合比例达92.9%。重压下技术应用后,高建Z向钢铸坯晶粒尺寸随着压下量的提高显著细化,中心偏析得到明显改善。

乙烯基非交联电缆屏蔽料性能与分散剂含量关系研究

非交联绝缘材料具有优异的电气机械性能,同时生产能耗少、可回收利用,成为目前电缆绝缘料的研究热点,但与之匹配的非交联半导电屏蔽料的研究还鲜有报道。导电炭黑的分散性对屏蔽料的性能影响重大。文中选用线性低密度聚乙烯(LLDPE)为基体树脂,白油为分散剂,采用熔融共混法制备了非交联电缆屏蔽料。研究了白油含量对屏蔽料中炭黑分散、结晶性能、体积电阻率和机械性能的影响。结果表明添加白油会促进炭黑的分散,但白油含量过大会降低屏蔽料的结晶度,增加其体积电阻率并降低拉伸强度和断裂伸长率。当白油含量为2 wt%时,屏蔽料体积电阻率最小,力学性能最佳。该研究为非交联半导电屏蔽料在乙烯基非交联电缆的应用研究提供了参考。

ZSM-5基复合分子筛催化裂解制低碳烯烃研究进展

系统介绍了ZSM-5基复合分子筛的合成方法;针对典型的核-壳结构和微-介孔结构,阐述了复合结构对其孔隙结构、酸性质和水热稳定性等的调控方法和规律。在此基础上,详细综述了复合分子筛在甲醇、轻烃、生物质及其混合原料催化裂解制低碳烯烃领域的应用,提出复合分子筛催化材料未来发展前景。

低频交流电压下低密度聚乙烯的空间电荷特性

分频输电技术已逐步成为实现碳中和及海上风电远距离传输的主流方案之一。然而,对高压分频输电背景下的电气设备研究较为欠缺,在频率改变对电缆绝缘材料特性影响方面尚需深入研究。为此,采用具备快速检测能力的脉冲电声测试系统,研究了低密度聚乙烯材料在分频电压下不同电场强度、温度时的空间电荷特性以及频率改变对电荷积聚行为的影响。结果表明:当场强及温度条件较为苛刻时,电荷积聚明显;而随着频率的降低电荷积聚量增加,频率下降至20 Hz后,电荷增长速度显著提高。在此基础上,建立了应用于交变电场下的双极型载流子模型,通过仿真计算对实验观察进行了合理化解释,揭示了电场、温度及频率对空间电荷行为的影响机理。研究方法和结果可为海上风电分频输电系统中的频率选择及线缆绝缘优化设计提供理论支撑。