高温吸碳材料的合成

用硅酸锂溶液与氢氧化锂水热反应,利用高温固相反应在不同温度下合成了硅酸锂材料,用X射线粉末衍射技术表征了合成材料,用差热-热重技术分析了硅酸锂材料吸收CO2的性能。结果表明,在350、450、550℃温度下煅烧,材料中生成物相的是Li2SiO3和Li2CO3。合成出的材料在常温空气和CO2环境下具备一定的吸碳能力。在650、750℃煅烧分别生成了Li4SiO4和Li2SiO3。合成温度较高时,Li4SiO4生成量较高,对CO2的吸收值也相应提高。

热解碳泡沫材料吸波机理研究

为避开高分子材料作为基体,进一步拓展碳系吸波材料在空间环境或仿空间环境中的应用,本工作提出了预制体法结合热解工艺制备热解碳泡沫吸波材料的新思路,采取从400℃到1 500℃的不同目标热解温度制备了一系列热解碳泡沫材料,通过对不同温度热解碳泡沫材料的傅里叶红外光谱、热重-差热、X射线衍射和电化学分析,明确了热解碳泡沫为半导体材料,其热解残余基团无序区造成的阈值效应、共轭效应和位阻效应抑制π电子离域移动,控制载流子浓度,进而影响热解碳泡沫材料的电磁性能。对不同温度热解碳泡沫材料电磁参数的测试表明,600~700℃热解的碳泡沫材料的介电常数实部和虚部大小适合,适合作吸波材料。

吸波材料研究现状及碳团簇型吸波材料设计

简要介绍了铁氧体吸波材料 ,手性材料 ,金属微粉吸波材料 ,导电高聚物材料 ,多晶铁纤维材料 ,纳米材料和智能隐身材料的研究和应用现状。并根据吸波材料工作原理 ,进行碳团簇型吸波材料实验研究 ,结果显示 ,所制样品有很好的吸波性能 ,在总厚度为 2 .11mm的情况下 ,在 8.2～ 12 .4GHz频带内 ,最大反射衰减可达 - 2 9dB ,有效频宽占总带宽的 10 0 % ,基本达到实用水平。

磁性纳米洋葱碳基复合材料的制备及其吸波性能

采用化学气相沉积法制备了磁性纳米洋葱碳(MCNOs)和多壁纳米碳管(MWCNTs),超声喷雾造粒后制备得到MCNO/MWCNT复合吸波材料。通过XRD、SEM、TEM、Raman及VSM等手段表征所制材料的结构和磁性能,并采用微波矢量网络分析仪对材料的电磁参数进行测试。分别研究了MCNOs、MWCNTs及MCNO/MWCN三者的吸波性能,并探讨了其吸波机理。结果表明,相较于MCNOs和MWCNTs,同等条件下二者复合后在2～18 GHz频率范围内的吸波性能显著提高。微波吸收峰随材料涂层厚度的增加向低频方向移动,当涂层厚度为3.5 mm时,最大峰值可以达到-25.6 dB,在-10 dB以上有效带宽达到2.2 GHz;基于微波介电损耗机制,分析了不同材料在2～18 GHz频率范围内的电磁性能。

MOFs衍生碳基复合吸波材料的研究进展

电磁吸波材料对于防护电磁辐射危害是极为有效的一种手段,吸波材料所具有的吸波性能对军用和民用都有重大意义。Metal-organic frameworks(MOFs)衍生碳基复合材料是一种新型吸波材料,具有合成工艺简单、热稳定性好、比表面积大、孔隙率高等优点。本文简要介绍电磁吸波机理,综述碳基复合吸波材料研究现状,分析MOFs衍生碳基复合材料在电磁吸波领域研究进展,展望MOFs衍生碳基复合吸波材料未来发展前景。

碳系吸波材料研究现状及在建材中的应用展望

随着科学技术的发展,生活空间中电子产品的增多让人类处于不同程度的电磁辐射环境中,对人体组织、器官和系统等会造成一定破坏,其对环境的污染和人体的危害越来越受到人们的重视。目前已有很多关于吸波材料电磁波吸收性能的研究,但很多是针对军事方面的雷达吸波,而关于其在民用方面的应用研究较少,特别是在室内吸波材料及墙体整体结构式防护方面几乎没有,因此,开展吸波材料在建筑材料方面应用显得尤为迫切。碳系吸波材料在建材中的推广应用无论是在技术成熟度还是成本方面,相对于其它吸波材料都均有一定优势,简述了石墨、炭黑、碳纤维等碳系吸波材料的研究现状及其在建材中的应用情况,并对吸波材料在建材中的深入应用进行了展望,提出开发室内建筑吸波材料及墙体结构式防护措施。

MOFs衍生的碳复合吸波材料的研究进展

金属有机框架(MOFs)衍生的碳复合材料由于轻质、多孔、组分多样、损耗机制多样以及电磁参数可设计性强的优势,在复合吸波材料应用领域极具潜力。总结了近几年来MOFs衍生的不同种类的碳复合材料在吸波领域的最新研究进展。重点分析了根据合成方法分类的碳复合材料微观结构、微波吸收性能的差异,并讨论了不同方法的特点,最后概述了提高MOFs衍生碳复合材料吸波性能的方法,并对其未来发展方向进行了展望。

吸波材料的研究进展

综述了目前国内外吸波材料的研究动态,介绍了传统吸波材料以及新型吸波材料,如铁氧体吸波材料、碳纤维结构吸波材料、纳米吸波材料、手性吸波材料,多晶铁纤维吸波材料,导电高聚物吸波材料,雷达红外兼容吸波材料的研究状况。

低频2.0GHz5.0GHz微波低透射率材料的原子分子设计

理论研究了碳环对称转子的碳环面积与反磁化率的关系 ;讨论了对称转子振动谱带的转子结构 ,表明转子能级恰好处于微波范围 .同时基于量子力学中二维势阱理论和量子化学的离域效应 ,揭示出碳环面积越大 ,则系统能量越低 ,转动常数B和能级间隔会不断减少 ,从而有利于吸收低频微波 .量子力学方法B3P86 /6 311G计算完全证实了理论分析 .根据理论指导 ,研究了新型碳团簇材料AⅡ在低频段 2 .0GHz5 .0GHz范围内的微波透射性能 ,讨论了碳化温度、厚度、分子材料Ⅱ对其微波透射性能的影响 .

Effect of specific pressure on fabrication of 2D-C_f/Al composite by vacuum and pressure infiltration

Carbon fiber reinforced aluminum matrix （Cf/Al） composite has many excellent properties, and it has received more and more attention. Two-dimensional （2D） Cf/Al composites were fabricated by vacuum and pressure infiltration, which was an integrated technique and could provide high vacuum and high infiltration pressure. The effect of specific pressure on the infiltration quality of the obtained composites was comparatively evaluated through microstructure observation. The experimental results show that satisfied Cf/Al composites could be fabricated at the specific pressure of 75 MPa. In this case, the preform was infiltrated much more completely by aluminum alloy liquid, and the residual porosity was seldom found. It is found that the ultimate tensile strength of the obtained Cf/Al composite reached maximum at the specific pressure of 75 MPa, which was improved by 138.9% compared with that of matrix alloy.

An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption

Amorphous carbon materials play a vital role in adsorbed natural gas(ANG) storage. One of the key issues in the more prevalent use of ANG is the limited adsorption capacity, which is primarily determined by the porosity and surface characteristics of porous materials. To identify suitable adsorbents, we need a reliable computational tool for pore characterization and, subsequently, quantitative prediction of the adsorption behavior. Within the framework of adsorption integral equation(AIE), the pore-size distribution(PSD) is sensitive to the adopted theoretical models and numerical algorithms through isotherm fitting. In recent years, the classical density functional theory(DFT) has emerged as a common choice to describe adsorption isotherms for AIE kernel construction. However,rarely considered is the accuracy of the mean-field approximation(MFA) commonly used in commercial software. In this work, we calibrate four versions of DFT methods with grand canonical Monte Carlo(GCMC) molecular simulation for the adsorption of CH_4 and CO_2 gas in slit pores at 298 K with the pore width varying from 0.65 to 5.00 nm and pressure from 0.2 to 2.0 MPa. It is found that a weighted-density approximation proposed by Yu(WDA-Yu) is more accurate than MFA and other non-local DFT methods. In combination with the trapezoid discretization of AIE, the WDA-Yu method provides a faithful representation of experimental data, with the accuracy and stability improved by 90.0% and 91.2%, respectively, in comparison with the corresponding results from MFA for fitting CO_2 isotherms. In particular, those distributions in the feature pore width range(FPWR)are proved more representative for the pore-size analysis. The new theoretical procedure for pore characterization has also been tested with the methane adsorption capacity in seven activated carbon samples.

Fibrous TiO_2 prepared by chemical vapor deposition using activated carbon fibers as template via adsorption,hydrolysis and calcinations

TiO2 fibers were prepared via alternatively introducing water vapor and Ti precursor carried by N2 to an APCVD （chemical vapor deposition under atmospheric pressure） reactor at ≤200 ℃. Activated carbon fibers （ACFs） were used as templates for deposition and later removed by calcinations. The obtained catalysts were characterized by scanning electron micros- copy （SEM）, transmission electron microscopy （TEM）, Brunauer, Emmett and Teller （BET） and X-ray diffraction （XRD） analysis The pores within TiO2 fibers included micro-range and meso-range, e.g., 7 nm, and the specific surface areas for TiO2 fibers were 141 m^2/g and 148 m^2/g for samples deposited at 100 ℃ and 200℃ （using ACFI700 as template）, respectively. The deposition temperature significantly influenced TiO2 morphology. The special advantages of this technique for preparing porous nano-material include no consumption of organic solvent in the process and easy control of deposition conditions and speeds.

Review on porous nanomaterials for adsorption and photocatalytic conversion of CO_2

Photocatalytic conversion of“greenhouse gas”CO2is considered to be one of the most effective ways to alleviate current energy and environmental problems without additional energy consumption and pollutant emission.The performance of many traditional semiconductor photocatalysts is not efficient enough to satisfy the requirements of practical applications because of their limited specific surface area and low CO2adsorption capacity.Therefore,the exploration of photocatalysts with high CO2uptake is significant in the field of CO2conversion.Recently the porous materials appeared to be a kind of superior candidate for enriching the CO2molecules on the surface of photocatalysts for catalytic conversion.This paper first summarizes the advances in the development of nanoporous adsorbents for CO2capture.Three main classes of porous materials are considered:inorganic porous materials,metal organic frameworks,and microporous organic polymers.Based on systematic research on CO2uptake,we then highlight the recent progress in these porous‐material‐based photocatalysts for CO2conversion.Benefiting from the improved CO2uptake capacity,the porous‐material‐based photocatalysts exhibited remarkably enhanced efficiency in the reduction of CO2to chemical fuels,such as CO,CH4,and CH3OH.Based on reported recent achievements,we predict a trend of development in multifunctional materials with both high adsorption capability and photocatalytic performance for CO2utilization.

Production of carbonaceous material from avocado peel for its application as alternative adsorbent for dyes removal

Adsorption processes have received special attention for contaminants removal thanks to their capability to gen- erate effluents with high quality as well as their simple design. In the current work, the agro-waste residue avo- cado peel is proposed to be used as alternative to conventional activated carbons whose use is sometimes restricted to high costs, upgraded by their exhausting after long term operations. The carbonization procedure was optimized and analyzed through factorial design and response surface methodology by evaluating temper- ature （400-900 ℃） and time （30-90 min） effects： optimal conditions were found at 900℃ and 65 min, gener- ating an adsorbent with 87.52 m2.g 1 of BET surface area, a mesopore volume of 74% and a zero point charge at 8.6. The feasibility of the carbonaceous material was proved for the removal of a variety of dyes by investigating substrate （10-50 mg.L 1） and solid （0.5-20 g.L-1） concentration effects and statistical significance： complete removal of Naphthol Blue Black and Reactive Black 5 was reached under optimal conditions （10 mg.L 1 and 20g.L 1 of dye and solid, respectively）, while Basic Blue 41 was eliminated by using 13.4 g. L- 1 of the adsorbent. Overall, dyes removal by adsorption on carbonized avocado peel is presented as a promising technology due to the low cost and easy availability of the precursor, as well as the straightforward generation, the satisfactory char- acteristics and the proved adsorption capacity of the adsorbent.

A micro-sphere catalyst complex with nano CaCO_3 precursor for hydrogen production used in ReSER process

This paper describes the preparation and evaluation of a micro-sphere catalytic complex for the hydrogen production in a Reactive Sorption Enhanced Reforming （ReSER） process. The catalytic complex made by a spray technique has a dual function containing Ni as a catalytic material and CaO as an adsorption material used in the ReSER process. The attrition characteristics of the catalytic complex are acceptable for the commercial used. The nano GaCO3 material used as a precursor of CaO showed a desirable durability with a CO2 sorption capacity of 0.6 mol CO2/kg after 10 repeating cycles under the carbonation temperature of 600 ℃, a CO2 partial pressure of 0.02 MPa, and a calcination temperature of 750 ℃ in N2 measured by a thermal gravimetric analyzer. The testing of the catalytic complex for ReSER showed a hydrogen yield of over 95 % （v/v） in the laboratory fixed fluidized bed reactor. The catalytic system has an attractive prospect in the ReSER process for hydrogen production, especially in the fluidized mode where reactor and regenerator combined in a cycling process.

Characterization and adsorption behaviors of a novel synthesized mesoporous silica coated carbon composite

A novel mesoporous silica coated carbon composite(denoted SEG) with hierarchical pore structure has been successfully prepared in an aqueous solution that contains triblock copolymer template, aluminum chloride, siliceous source and expanded graphite. Textural property and morphology of the SEG composite were characterized by the combination of X-ray diffraction, N_2 adsorption–desorption, scanning electron microscopy,transmission electron microscopy and Fourier transform infrared measurements. Results show that mesoporous silica is steadily and uniformly grown on the surface of the graphite slices and the thickness of the silica layer can be finely tuned according to the silica/C molar ratio in the initial reaction solution. This newly synthesized SEG composite shows greatly increased adsorption capacity to methylene blue than the pristine expanded graphite in the batch tests. Both Langmuir and Frendlich models were further used to evaluate the adsorption isotherms of methylene blue over expanded graphite and SEG samples with different silica contents. Finally, pseudosecond-order model was used to describe the kinetics of methylene blue over expanded graphite and the silica-carbon composites.

Collapse behavior evaluation of hybrid thin-walled member by stacking condition

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.

CO2 Capture by Adsorption on MCM-68 Solid Sorbent Materials

Solid sorbents adsorption is considered as one of the potential options for CO2 capture process. CO2 adsorption on MCM-68 （Si/AI ratio 22） sorbent material was investigated. MCM-68 was synthesized using N,N,N＇,N＇-tetraethylbicyclo [2.2.2] oct-7-ene-2,3：5,6-dipyrrolidinium diiodide （TEBOP^2＋（I^＋）2） as a structure-directing agent （SDA）. CO2 adsorption capacity on MCM-68 sorbent was measured at a broad temperature window i.e. 60 ℃, 300 ℃ and at 400 ℃. The presence of ordered mesoporous structure, high surface area （456 me/g） and high thermal stability （TGA analysis up to 900℃） in MCM-68 are thought to be to be advantageous for the CO2 adsorption in broad temperature window.

文摘

阳极焙烧炉内煤气流动和燃烧的数值模拟,阳极焙烧炉的热工测试及分析,碳团簇型吸波材料的结构与性能研究,大型电解铝厂选址新理念,飞机机轮炭／炭刹车盘金属件铆接工艺分析,大型铝电解槽侧部破损原因分析及对策,焙烧炉烟气污染防治对策的探讨.

Polymer-coated nanoporous carbons for trace seawater uranium adsorption

Polymer-coated mesoporous carbon nanocomposites were prepared from the immobilization of acrylonitrile and acrylic acid copolymers with divinylbenzene as a crosslinker onto a mesoporous carbon framework.High surface areas were maintained after polymerization with accessible porosity.This functional nanocomposite was tested as an adsorbent for uranium from high salinity solutions.Uranium adsorption results have shown that the adsorption capacities are strongly influenced by the density of the amidoxime groups and the specific surface area.