Printable Aligned Single-Walled Carbon Nanotube Film with Outstanding Thermal Conductivity and Electromagnetic Interference Shielding Performance

Ultrathin,lightweight,and flexible aligned single-walled carbon nanotube(SWCNT)films are fabricated by a facile,environmentally friendly,and scalable printing methodology.The aligned pattern and outstanding intrinsic properties render“metal-like”thermal conductivity of the SWCNT films,as well as excellent mechanical strength,flexibility,and hydrophobicity.Further,the aligned cellular microstructure promotes the electromagnetic interference(EMI)shielding ability of the SWCNTs,leading to excellent shielding effectiveness(SE)of~39 to 90 dB despite a density of only~0.6 g cm^(−3) at thicknesses of merely 1.5-24μm,respectively.An ultrahigh thickness-specific SE of 25693 dB mm^(−1) and an unprecedented normalized specific SE of 428222 dB cm^(2)g^(−1) are accomplished by the freestanding SWCNT films,significantly surpassing previously reported shielding materials.In addition to an EMI SE greater than 54 dB in an ultra-broadband frequency range of around 400 GHz,the films demonstrate excellent EMI shielding stability and reliability when subjected to mechanical deformation,chemical(acid/alkali/organic solvent)corrosion,and high-/low-temperature environments.The novel printed SWCNT films offer significant potential for practical applications in the aerospace,defense,precision components,and smart wearable electronics industries.

Research on the Relationship between Density of States and Conducting Properties of Single-walled Carbon Nanotubes

The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current us bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)-bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT's electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.

Influence of chirality on the thermal conductivity of single-walled carbon nanotubes

The influence of chirality on the thermal conductivity of single-walled carbon nanotubes （SWNTs） is discussed in this paper, using a non-equilibrium molecular dynamics （NEMD） method. The tube lengths of the SWNTs studied here are 20, 50, and 100 nm, respectively, and at each length the relationship between chiral angle and thermal conductivity of a SWNT is revealed. We find that if the tube length is relatively short, the influence of chirality on the thermal conductivity of a SWNT is more obvious and that a SWNT with a larger chiral angle has a greater thermal conductivity. Moreover, the thermal conductivity of a zigzag SWNT is smaller than that of an armchair one. As the tube length becomes longer, the thermal conductivity increases while the influence of chirality on the thermal conductivity decreases.

On the Thermal Conductivity of Single-Walled Carbon Nanotube Ropes

Recently measured thermal conductivity in single-walled carbon nanotube ropes in the temperature range 8 - 350 K has been explained using an anisotropic dynamical model which not only takes into account the quasi two-dimensional nature of the folded graphene sheets that forms the nanotubes, but also the intertube coupling, in addition to the phonon frequency and dimensionality dependent relaxation time of phonon-phonon scattering and interaction.

Thermal properties of single-walled carbon nanotube crystal

In this work, the thermal properties of a single-walled carbon nanotube （SWCNT） crystal are studied. The thermal conductivity of the SWCNT crystal is found to have a linear dependence on temperature in the temperature range from 1.9 K to 100.0 K. In addition, a peak （658 W/mK） is found at a temperature of about 100.0 K. The thermal conductivity decreases gradually to a value of 480 W/mK and keeps almost a constant in the temperature range from 100.0 K to 300.0 K. Meanwhile, the specific heat shows an obvious linear relationship with temperature in the temperature range from 1.9 K to 300.0 K. We discuss the possible mechanisms for these unique thermal properties of the single-walled carbon nanotube crystal.

基于“两带”探查技术的顶板水害危险性分析——以伯方煤矿为例

应用钻液漏失量观测、岩芯采取统计、钻孔电视观测和钻孔电阻率动态监测等多种“两带”探查技术方法,对伯方煤矿3煤开采的覆岩导水裂隙带发育特征进行研究,分析3煤采动影响下的顶板水害危险性。研究结果表明:3213工作面导水裂隙带发育高度为87.66 m,发育至K9砂岩含水层;垮落带发育高度为22.61 m,发育至2煤下部K8砂岩含水层。3313工作面垮落带最大高度为煤层顶板20~21 m,至2煤顶板砂岩含水层;导水裂隙带最大高度为煤层顶板83~87 m,至K9砂岩含水层。由此计算得出的垮落/采厚比为3.58~3.76,裂缝/采厚比为14.85~15.56。3煤回采产生的导水裂隙可造成二叠系下石盒子组和山西组砂岩含水层与3煤采空区的连通,含水层地下水岩导水裂隙向下渗流,增加了顶板水害的风险。建议矿井严格落实顶板水害防治的相关要求,降低采动裂隙对矿井正常生产的影响。

厚煤层开采覆岩导水裂隙带发育高度研究

针对水体下采煤时覆岩受扰动后可能导致顶板涌水问题,以掌石沟煤矿15102工作面为研究对象,采用数值模拟、分段封堵测漏与钻孔电视法得到该工作面15#煤层的导水裂隙带发育高度。对模拟和实测成果分析表明:模拟和现场观测的导水裂隙带高度分别为49、48.3 m,最终确定导水裂隙带高度为48.3 m,裂采比为11.78,上界面岩层类型为砂质泥岩,厚度为4.2 m,距煤层约48 m。

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.

老虎台矿28002工作面综放开采导水裂隙发育规律

为研究综放开采覆岩导水裂隙带发育高度,以老虎台矿区28002工作面为研究背景,分析了老虎台矿区内12组工作面导水裂隙带高度实测数据,得到了导水裂隙带高度计算的回归公式,并通过理论计算和数值模拟相结合的方法,对导水裂隙带发育高度进行预测,结合钻孔窥视,观察裂隙带上方含水层的岩性特征。结果表明:经验公式、回归公式和数值模拟结果显示28002工作面采后导水裂隙带发育高度分别为131.49、117.34和153.9 m。其发育最高点均位于计军屯组的油母页岩内,而油母页岩作为良好的隔水层为顶板防水提供了有效保障;通过钻孔窥视,计军屯组上方的页岩含水层裂隙发育程度较好,易形成导水通道,威胁工作面的安全回采。

强含水层下特厚煤层综放开采导水裂隙带发育高度

导水裂隙带高度是顶板水害防治的关键参数之一,为研究强含水层下特厚煤层综放开采条件下导水裂隙带发育高度,以彬长矿区雅店煤矿ZF1405工作面为背景,采用多元非线性回归建立了导水裂隙带高度预测模型,并采用数值模拟和钻孔实测相结合的方法,对该条件下导水裂隙带高度进行了全面探测。结果表明:考虑的影响因素越多,建立的导水裂隙带高度预测模型越合理,模型预测结果为257.4m,相较于经验公式更精确;数值模拟得到的导水裂隙带最大发育高度为244.2 m,发育规律可分为缓增阶段(工作面推进0~200 m)、突增阶段(工作面推进200~280m)和稳定阶段(工作面推进280m后),其中突增阶段最易发生顶板涌水事故,现场开采时,工作面由开切眼推进至200m后需提前做好预防措施;钻孔钻液消耗量和钻孔窥视探测的导水裂隙带高度分别为247.4,238.4m;数值模拟和钻孔实测结果共同验证了预测模型的可靠性,为安全起见,取4种研究方法的最大值257.4m作为最终结果。研究结果可为类似条件的矿井导水裂隙带高度预测提供参考。

多煤层复合采动顶底板裂隙带发育规律研究

基于友众煤矿多煤层复合采动顶底板裂隙发育情况,分别采用理论计算、数值模拟和钻孔实测等方法进行研究,计算统计出150202工作面顶板垮落带发育高度分别为40.11~63.09 m、50.2 m、54~57 m,3种方式结果变化范围基本一致。结合矿井地质条件和研究结果可知,15号下煤层采动裂隙带在无构造区域内不会导通上覆3号、6号含水层,在贯穿性断层或陷落柱赋存区域内存在联通导水的可能性。因此,煤矿制定“物探先行、钻探验证、查清构造、上防下采”的防治水原则,为相关类型矿井生产提供依据。

High-performance single-wall carbon nanotube transparent conductive films

A single-wall carbon nanotube(SWCNT)has superior optical,electrical,and mechanical properties due to its unique structure and is therefore expected to be able to form flexible high-performance transparent conductive films(TCFs).However,the optoelectronic performance of these films needs to be improved to meet the requirements of many devices.The electrical resistivity of SWCNTTCFs is mainly determined by the intrinsic resistivity of individual SWCNTs and their junction resistance in networks.We analyze these key factors and focus on the optimization of SWCNTs and their networks,which include the diameter,length,crystallinity and electrical type of the SWCNTs,and the bundle size and interconnects in networks,as well as chemical doping and microgrid design.We conclude that isolated/small-bundle,heavily doped metallic or semiconducting SWCNTs with a large diameter,long length and high crystallinity are necessary to fabricate high-performance SWCNTTCFs.A simple,controllable way to construct macroscopic SWCNT networks with Y-type connections,welded junctions or microgrid design is important in achieving a low resistivity.Finally,some insights into the key challenges in the manufacture and use of SWCNT TCFs and their prospects are presented,hoping to shed light on promoting the practical application of SWCNT TCFs in future flexible and stretchable optoelectronics.

Size effect of quantum conductance in carbon nanotube Y-Junctions

This paper studies the quantum conductance properties of three-terminated carbon nanotube Y-junctions, which are built by connecting three （5,5） single-walled carbon nanotubes. The results show that the quantum conductance at the Fermi energy oscillates periodically with the junction＇s size, and the number of oscillating periodic layers is 3 which is the same as that in the two terminated （10, 0）/m（5, 5）/（10, 0） junctions. Moreover, this Y-junction with different size exhibits an obviously different distribution of electron current in the two drain branches, called shunt valve effect of electronic current. Thus the degree of this effect can be controlled and modulated directly by constructing the three branches＇ sizes or the distribution of defect. The results show in detail that the difference between the two drain currents can be up to two times for some constructions with special sizes. In addition, the uniform distribution of defects in the Y-junction leads to lower quantum conductance than that of other defect configurations.

煤层底板导水通道钻孔超前探查与多元信息识别技术

煤层底板多发育有各类导水通道,严重威胁着矿井的安全生产。为更加科学地建立底板导水通道多元信息识别技术体系,预防底板突水,首先根据导水通道类型多样、位置不明、突水危害大等特征和地面定向钻进区域探查技术的优点,提出了轨迹合理、目标层合理和探查区域最大化的探查原则。其次总结分析了淮北矿区、淮南矿区、邢台矿区、黄河北煤田等区域导水通道探查过程,发现在揭露导水通道时,岩屑、钻时、钻井液漏失量等直观指标和压水试验透水率、注浆参数等验证性指标均与正常地层有明显差别。为此将钻探过程中多源信息判识指标分为定性和定量两大类。根据钻遇导水通道时,岩屑和钻时2项定性指标的变化幅度,给出了对应的标准曲线,进而确定了导水通道类型分类体系;接着综合分析钻井液漏失量和压水试验透水率2项定量指标在钻孔揭露导水通道时的变化,提出了钻井液漏失量30 m3/h、压水试验透水率10 Lu作为导水性分级的界限,据此建立了通道导水性能双因素综合分级体系,将导水性划分为4个等级。最后以华北型煤田某典型矿井为例,根据探查原则实施4个孔组对导水通道进行了超前探查,应用多元信息识别技术成功判识出探查区域内的4条断层、2处岩溶裂隙带和1个陷落柱,并确定了导水通道的导水性等级。研究成果对提升煤层底板导水通道识别和治理具有指导作用和重要意义。

朱庄煤矿底板钻孔出水水源-通道一体化治理技术与应用

为了有效治理朱庄煤矿Ⅲ638工作面底板验证钻孔出水,分析了出水原因,明确了出水水源为L_(3)灰岩水,导水通道是未充分治理的底板岩溶裂隙发育带和JF_(1)、JF_(2)、JF_(3)等断层;提出利用地面区域治理技术对出水水源和通道进行一体化治理的思路,将治理区域划分为突水危险区、断层影响区以及深部薄弱区,针对不同区域提出“边界锁边+区域治理”的钻孔布设方案并采用梯度增压注浆工艺对底板L_(3)灰岩含水层以及断层带进行改造加固。治理结束后通过指标评价、交叉检验和井下钻探等方法验证了治理效果,工作面顺利恢复掘进;结果表明了基于地面区域治理的水源-通道一体化治理技术对封堵底板出水的优越性。

纳米材料研究现状及其在钻井液领域应用展望

纳米材料泛指尺寸在100 nm以内的微小颗粒,因其异于常规材料的光、电、热等性能而得到众多行业的广泛关注。叙述了当前无机、有机及复合纳米材料的先进制备方法及在不同领域的应用案例,总结了当前纳米材料对钻井液流变性能、滤失性能、导热性能及固壁性能的影响规律,并结合相关处理剂作用机理和不同纳米材料自身特性,展望了纳米材料在改善钻井液上述性能方面的应用前景。随着制备成本的降低及相关应用技术难题的逐步解决,纳米材料有望成为满足未来钻井液各种性能的首选材料。

浅部矿体开采覆岩运移及导水裂隙带发育高度分析

为研究浅部矿体开采覆岩运移及导水裂隙带发育特征,以红柳矿I020308工作面为研究对象,采用理论试验、数值模拟、理论研究与现场实测方法,分析采动覆岩运移规律以及导水裂隙带发育高度。结果表明:1)覆岩裂隙呈“采场上方裂隙扩张-采空区上方裂隙闭合”趋势,岩块破断呈“下位岩体垮落-上位岩体咬合-叠层同步下沉”趋势,覆岩下沉量峰值达3.268 m。2)导水裂隙带高度发育过程为极缓慢-逐步扩展-迅速发育-增速递减发育;伴随采动影响,含水层水量间歇性释放,采空区涌水量交替增-减且整体呈下降趋势,直至工作面充分采动后稳定,实测导水裂隙带高度为58 m。3)基于矿物成分及微观结构分析,覆岩内富含亲水性黏土矿物且广泛分布粗颗粒,水-岩反应下将加剧裂隙发育,造成理论与实测导水裂隙高度形成误差。

母杜柴登煤矿导水裂隙带发育高度探测分析

煤层开采后,上覆岩层导水裂隙带高度的确定对于顶板水害防治、防水安全煤岩柱留设、水体下采煤均具有重要的技术指导意义。根据母杜柴登煤矿30202工作面开采技术条件与岩石力学参数,采用经验公式解析计算、钻探实测、井下电视、超声成像、数值模拟等多种方法对导水裂隙带高度进行了分析研究。结果表明,工作面开采后,导水裂隙带发育最大高度预计为122.57 m,裂采比为25.4。经验公式与数值模拟、实测结果相差较大,表明经验公式并不适用于该条件下的导水裂隙带高度确定。针对呼吉尔特矿区地质及开采条件,总结形成了适一套导水裂缝带探查方法和体系。

大采深复杂水文地质条件下导水断层探查治理技术研究

邢东矿隶属冀中能源股份有限公司,矿井采深大于800 m,水文地质条件复杂,开采过程中主要受煤层下伏奥灰岩溶水威胁。因井田范围内存在数条大型导水断层,落差均在50m以上,为保障安全生产,按规定留设有防水煤柱。为延长矿井生产服务年限,最大限度回收资源,如何对导水断层进行探查治理,以解放防水煤柱逐渐成为研究重点。本文基于邢东矿近些年导水断层探查治理经验,论述了不同技术手段的特点和实施效果,为相似条件下导水断层探查治理提供经验借鉴。

巨厚古近系含水层下工作面导水裂隙带高度探查

为了确定巨厚古近系含水层下工作面的开采上限、预测涌水量及制定防治水方案,需要针对工作面的导水裂隙带进行现场实测。以红四煤矿HI0503工作面为研究对象,采用经验公式初步确定导水裂隙带发育高度,设计井下探查钻孔的参数。分别用0.5、1.0和1.5 MPa的水压进行压水试验,同时采用钻孔窥视对工作面覆岩中的裂隙发育程度进行观测,最后利用数值模拟对现场实测的结果进行验证。结果表明,压水试验得到HI0503工作面导水裂隙带高度为65.6~67.4 m,采用钻孔窥视法确定导水裂隙带高度为66.5~68.1 m,导水裂隙带高度数值模拟结果为65.29 m,利用3种方法综合确定HI0503工作面导水裂隙带高度为65.29~68.1 m,大于经验公式计算值59.79 m。5-2煤与巨厚古近系含水层的平均距离为95 m,工作面开采后的导水裂隙带不会波及至古近系含水层。通过现场验证,利用井下压水试验、钻孔窥视和数值模拟,综合确定的导水裂隙带高度与实际情况较为吻合,可以作为防治水工作的依据。