Hybrid 2D/3D Graphitic Carbon Nitride-Based High-Temperature Position-Sensitive Detector

Ultraviolet position-sensitive detectors(PSDs)are expected to undergo harsh environments,such as high temperatures,for a wide variety of applications in military,civilian,and aerospace.However,no report on relevant PSDs operating at high temperatures can be found up to now.Herein,we design a new 2D/3D graphitic carbon nitride(g-C_(3)N_(4))/gallium nitride(GaN)hybrid heterojunction to construct the ultraviolet high-temperature-resistant PSD.The g-C_(3)N_(4)/GaN PSD exhibits a high position sensitivity of 355 mV mm^(-1),a rise/fall response time of 1.7/2.3 ms,and a nonlinearity of 0.5%at room temperature.The ultralow formation energy of-0.917 eV atom^(-1)has been obtained via the thermodynamic phase stability calculations,which endows g-C_(3)N_(4)with robust stability against heat.By merits of the strong built-in electric field of the 2D/3D hybrid heterojunction and robust thermo-stability of g-C_(3)N_(4),the g-C_(3)N_(4)/GaN PSD delivers an excellent position sensitivity and angle detection nonlinearity of 315 mV mm^(-1)and 1.4%,respectively,with high repeatability at a high temperature up to 700 K,outperforming most of the other counterparts and even commercial silicon-based devices.This work unveils the high-temperature PSD,and pioneers a new path to constructing g-C_(3)N_(4)-based harsh-environment-tolerant optoelectronic devices.

The influence of composition of asphaltenes of different genesis on the properties of carbon materials manufactured from them by plasma processing

The results of experimental studies of carbon materials, which are formed in the plasma of a direct current (DC) arc discharge initiated in open air from the asphaltenes of different origins, extracted from the natural asphaltite and from the oil of the Sredne-Ugutskoye Oilfield, are presented. The influence of the initial asphaltene composition on the composition and properties of the resulting carbon materials is analyzed. The initial asphaltenes and the samples of the carbon materials are characterized by the methods of X-ray diffraction, differential thermal analysis, X-ray fluorescence analysis, IR-Fourier spectroscopy, laser diffraction, transmission and scanning electron microscopy. The changes in the composition and structure of the asphaltenes are determined before and after their plasma treatment and the hypotheses are put forward concerning the chemical processes causing the changes in the molecular structure of the samples. As a result of plasma treatment of asphaltenes (100 A, 30 s), it was shown that graphitization occurs, as well as oxidation, and a decrease in sulfur content. Moreover, nanotubes and nano-onions have been detected using electron microscopy. Petroleum asphaltenes after plasma treatment give a less thermostable carbon material, but with a lower content of heteroatoms, and with a large amount of sulfur in the composition of sulfoxide structural fragments. This method is shown to be a promising technology for processing the petroleum feedstock enriched with heavy asphaltene components for the manufacture of carbon nanomaterials: nanotubes, nano-onions and polyhedral graphite.

Multidimensional(0D-3D)functional nanocarbon:Promising material to strengthen the photocatalytic activity of graphitic carbon nitride

As a prospective visible-light-responsive photochemical material,graphitic carbon nitride(g-C_(3)N_(4))has become a burgeoning research hot topics and aroused a wide interest as a metal-free semiconductor in the area of energy utilization and conversion,environmental protection due to its unique properties,such as facile synthesis,high physicochemical stability,excellent electronic band structure,and sustainability.However,the shortcomings of high recombination rate of charge carriers,relatively low electrical conductivity and visible light absorption impede its practical application.Various strategies,such as surface photosensitization,heteroatom deposition,semiconductor hybridization,etc.,have been applied to overcome the barriers.Among all the strategies,functional nanocarbon materials with various dimensions(0D~3D)attract much attention as modifiers of g-C_(3)N_(4)due to their unique electronic properties,optical properties,and easy functionalization.More importantly,the properties of these functional nanocarbon materials can be tuned by various dimensions and thus there will be a way to overcome the defects of g-C_(3)N_(4)by choosing different dimensional carbon materials.Distinguishing from some present reviews,this review starts with the fundamental physicochemical characteristics of g-C_(3)N_(4)materials,followed by analyzing the advantages of functional nanocarbon materials modifying gC_(3)N_(4).Then,we present a systematic introduction to various dimensional carbon materials.The design philosophy of carbon/g-C_(3)N_(4)composites and the advanced studies are exemplified in detail.Finally,a nichetargeting summary and outlook on the major challenges,opportunities for future research in high-powered carbon/g-C_(3)N_(4)composites was proposed.

Piezoresistivity of Carbon Fiber Graphite Cement-based Composites with CCCW

The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites（CFGCC） with carbon fiber content（1% by the weight of cement）,graphite powder contents （0%-50% by the weight of cement） and CCCW（cementitious capillary crystalline waterproofing materials,4% by the weight of cement） were studied.The experimental results showed that the relationship between the resistivity of CFGCC and the concentration of graphite powders had typical features of percolation phenomena.The percolation threshold was about 20%.A clear piezoresistive effect was observed in CFGCC with 1wt% of carbon fibers,20wt% or 30wt% of graphite powders under uniaxial compressive tests,indicating that this type of smart composites was a promising candidate for strain sensing.The measured gage factor （defined as the fractional change in resistance per unit strain） of CFGCC with graphite content of 20wt% and 30wt% were 37 and 22,respectively.With the addition of CCCW,the mechanical properties of CFGCC were improved,which benefited CFGCC piezoresistivity of stability.

Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

Adsorption of phenol from aqueous solution by a hierarchical micro-nano porous carbon material

A hierarchical micro-nano porous carbon material (MNC) was prepared using expanded graphite (EG), sucrose, and phosphoric acid as raw materials, followed by sucrose-phosphoric acid solution impregnation, solidification, carbonization and activation. Nitrogen adsorption and mercury porosimetry show that mixed nanopores and micropores coexist in MNC with a high specific surface area of 1978 m2·g-1 and a total pore volume of 0.99 cm3·g-1. In addition, the MNC is found to consist of EG and activated carbon with the latter deposited on the interior and the exterior surfaces of the EG pores. The thickness of the activated carbon layer is calculated to be about one hundred nanometers and is further confirmed by scanning electron microscope (SEM) and transmission election microscope (TEM). A maximum static phenol adsorption of 241.2 mg·g-1 was obtained by using MNC, slightly higher than that of 220.4 mg·g-1 by using commercial activated carbon (CAC). The phenol adsorption kinetics were investigated and the data fitted well to a pseudo-second-order model. Also, an intra-particle diffusion mechanism was proposed. Furthermore, it is found that the dynamic adsorption capacity of MNC is nearly three times that of CAC. The results suggest that the MNC is a more efficient adsorbent than CAC for the removal of phenol from aqueous solution.

Insights into Enhanced Capacitive Behavior of Carbon Cathode for Lithium Ion Capacitors: The Coupling of Pore Size and Graphitization Engineering

The lack of methods to modulate intrinsic textures of carbon cathode has seriously hindered the revelation of in-depth relationship between inherent natures and capacitive behaviors,limiting the advancement of lithium ion capacitors(LICs).Here,an orientateddesigned pore size distribution(range from 0.5 to 200 nm)and graphitization engineering strategy of carbon materials through regulating molar ratios of Zn/Co ions has been proposed,which provides an effective platform to deeply evaluate the capacitive behaviors of carbon cathode.Significantly,after the systematical analysis cooperating with experimental result and density functional theory calculation,it is uncovered that the size of solvated PF6-ion is about 1.5 nm.Moreover,the capacitive behaviors of carbon cathode could be enhanced attributed to the controlled pore size of 1.5-3 nm.Triggered with synergistic effect of graphitization and appropriate pore size distribution,optimized carbon cathode(Zn90Co10-APC)displays excellent capacitive performances with a reversible specific capacity of^50 mAh g-1at a current density of 5 A g-1.Furthermore,the assembly pre-lithiated graphite(PLG)//Zn90Co10-APC LIC could deliver a large energy density of 108 Wh kg-1 and a high power density of 150,000 W kg-1 as well as excellent long-term ability with 10,000 cycles.This elaborate work might shed light on the intensive understanding of the improved capacitive behavior in LiPF<sub>6 electrolyte and provide a feasible principle for elaborate fabrication of carbon cathodes for LIC systems.

Lost circulation material for abnormally high temperature and pressure fractured-vuggy carbonate reservoirs in Tazhong block, Tarim Basin, NW China

To effectively solve the problem of lost circulation and well kick frequently occurring during the drilling of abnormally high temperature and pressure fractured-vuggy reservoirs in the Tazhong block, a rigid particle material, GZD, with high temperature tolerance, high rigidity(> 8 MPa) and low abrasiveness has been selected based on geological characteristics of the theft zones in the reservoirs. Through static pressure sealing experiments, its dosage when used alone and when used in combination with lignin fiber, elastic material SQD-98 and calcium carbonate were optimized, and the formula of a new type(SXM-I) of compound lost circulation material with high temperature tolerance and high strength was formed. Its performance was evaluated by compatibility test, static sealing experiment and sand bed plugging experiment. The test results show that it has good compatibility with drilling fluid used commonly and is able to plug fractures and vugs, the sealed fractures are able to withstand the static pressure of more than 9 MPa and the cumulative leakage is 13.4 mL. The mud filtrate invasion depth is only 2.5 cm in 30 min when the sand bed is made of particles with sizes between 10 mesh and 20 mesh. Overall, with good sealing property and high temperature and high pressure tolerance, the lost circulation material provides strong technical support for the safety drilling in the block.

煤的结构基因与煤基碳材料构建研究进展

“双碳”目标的实现必将带来煤炭作为燃料用量的迅速减少,寻找煤炭的高附加值利用途径是煤炭行业可持续发展的迫切需求。简要介绍了基于单原子组装的无烟煤催化石墨化研究和焦炭催化石墨化研究,以及碳化硅炉炉芯石墨产品和特征,其晶体片径可达100um及以上,且受煤及煤基中间体结构的影响较少。重点介绍了无烟煤、烟煤、褐煤的结构特征与碳材料构建,研究发现煤的结构基因对煤基碳材料的构建有着决定性影响。无烟煤高固定碳含量的稳固碳结构有利于形成高强度的多孔炭和增碳补强剂等碳材料,无烟煤基高温石墨片径在几微米左右,片层平行度较差、交叉较多,适用于制备大规格炭电极的多晶石墨电极、电解槽、化学惰性通道。以烟煤为原料的煤沥青和焦炭中的炭青质是构成褶皱石墨的良好前驱体,煤沥青经针状焦石墨化因包含晶体液相生长过程,晶体片径尺寸可达数十微米以上,所形成的褶皱石墨经球团和浸渍包覆可以作为锂离子电池良好的负极储锂材料;焦炭中非晶态的固定碳也是制备硬碳材料的良好原料。褐煤稀疏的大分子架构和多孔颗粒形态有利于浸渍类碳材料的构建,是制备催化剂载体的优质原料。

光催化材料石墨相氮化碳的合成、改性及应用

石墨相氮化碳(g-C_(3)N_(4))作为一种对环境温和的半导体材料,在光催化领域具有良好的应用前景。但是,纯g-C_(3)N_(4)因比表面积小、光生载流子分离难等缺点影响了其光催化性能,限制了其大规模应用,因此对g-C_(3)N_(4)进行改性使其光催化性能得到提升具有重要意义。从合成方法和改性策略出发,综述了近年来g-C_(3)N_(4)光催化剂的研究进展,并总结了g-C_(3)N_(4)光催化剂在废水处理降解污染物、产H_(2)及产H_(2)O_(2)等领域的应用发展。结果表明,改性后的g-C_(3)N_(4)光催化剂性能得到了巨大的提升。最后,对g-C_(3)N_(4)的发展方向进行了展望。

壳聚糖衍生碳包覆纳米硅复合材料锂离子电池性能研究

硅负极材料因具有较高的理论容量(Li22Si5合金相对应4200 mAh/g)、较低的工作电压(0.2~0.3 V vs Li/Li+)和地球上丰富的原材料储备,成为代替石墨负极的理想材料之一。但是,低电导率及在循环过程中发生剧烈体积膨胀导致电极失效问题限制了硅负极材料的进一步发展。因此,本工作通过物理法利用壳聚糖和石墨对纳米硅实现碳包覆和复合,制备壳聚糖/石墨@纳米硅复合材料(C/G@Si复合材料),对C/G@Si复合材料的结构、形貌和电化学性能进行研究。结果表明:随着石墨添加量的提高,C/G@Si复合材料的可逆比容量略微下降,循环性能和导电性能显著提高。当添加50%(质量分数)石墨时,在100 mA/g的电流密度下,C/G@Si复合材料的首次放电比容量为1136.1 mAh/g,循环充放电100次后剩余容量保持在658.5 mAh/g,展示出优异的电化学性能,对进一步推广硅碳负极材料具有一定的参考价值。

石墨相氮化碳基光催化剂研究进展

石墨相氮化碳是一种新型的非金属碳氮聚合物,具有优异的光催化性能。本文总结了近年来氮化碳光催化剂的设计与合成,对如何提高其光催化性能的相关工作进行了归纳总结,包括掺杂非金属元素和贵价金属、构建异质结、染料敏化、形貌调控等,并对石墨相氮化碳基光催化剂的后续应用和未来发展进行了展望。

基于响应面法的地热钻采碳纳米管复合水泥基材料的研究

针对现有导热固井水泥存在的性能不足问题,本文研制了一种新型地热钻采碳纳米管复合水泥基材料(CNTs-CC)。首先,选用石墨、氮化硅作为主要导热填料,硅微粉作为热稳定材料,碳纳米管作为协同增强填料,初步研制出纳米复合水泥材料基础液;其次,基于响应曲面法Box-Behnken试验设计,开展17组配比优化试验,构建了以2 d抗压强度和导热系数为响应指标的二次多项式预测模型,结合方差分析和响应曲面考察了各因素对响应指标的影响,并得到胶凝材料最优配比;最后,对复合水泥基材料的工程性能进行评估,并结合XRD与SEM研究了材料的水化机理。结果表明:复合水泥基材料的导热性能与抗压强度受多因素交互作用影响,其中早强剂与减水剂交互影响显著;CNTs-CC水泥石28 d抗压强度达8.15 MPa,导热系数为2.236 W/(m·K);导热填料不参与水化过程,碳纳米管粉可发挥“填充”及“桥连”效应,外加剂调控水化进程。

离子推力器碳基材料栅极研制与应用现状及启示

离子推力器是广泛应用于空间航天任务的电推力器之一,栅极在离子推力器中承担着引出离子并加速进而实现推力的作用,直接影响推力器性能及寿命。相比于传统钼栅,碳基栅极具有热膨胀系数低、耐离子溅射高等优势,是未来高比冲、大推力、长寿命离子推力器栅极的理想候选材料,已被国外部分先进离子推力器成功在轨应用。分析对比了不同栅极材料特性,调研总结了国内外碳基栅极研制过程及技术特点,并报道了作者近期在小口径不同构型C/C栅极与一体化C/C栅极研制方面的相关进展,最后针对我国离子电推进发展趋势,提出了后续碳基栅极研究的经验启示与建议。

浸锑石墨与无压烧结SiC和3D打印SiC密封材料配对副的摩擦磨损特性研究

为研究干气密封用密封材料的摩擦学特性,采用销盘旋转试验台研究3种浸锑石墨在干摩擦条件下分别与无压烧结SiC和3D打印SiC配对时的摩擦磨损特性,探讨了速度、载荷对密封材料摩擦磨损特性的影响,揭示了配对副材料表面的磨损机理。结果表明:随着载荷p与速度v的乘积(pv值)的增大,摩擦因数和磨损率均呈现逐渐减小趋势;在pv值较小时磨损机理为严重的磨粒磨损和轻微的黏着磨损,在pv值较高时磨损主要发生在碳化硅摩擦表面黏附的石墨转移层间,磨损机理主要表现为黏着磨损;在研究pv值变化对浸锑石墨与SiC密封材料配对副摩擦磨损特性的影响时,首选定载荷变速度试验方法。

碳基材料应用的研究进展

碳基材料因结构多样、表面化学性质丰富、可调控性强、比表面积大、孔结构丰富、热稳定性好、机械强度高及吸附容量高等优点被广泛应用于催化及储能领域。分析了石墨烯、碳纳米管、碳纳米线及碳化硅等碳基材料的制备方法、改性方法及应用领域,综述了碳基材料的研究进展,对其未来发展方向进行了展望。

表面包覆碳层孔隙对石墨负极材料倍率性能的影响

为了研究表面包覆碳层孔隙对石墨负极材料倍率性能的影响,引入少量硼酸,在包覆沥青软化阶段形成硼酸气化逸出效应,再通过碳化工艺在天然石墨尾料表面形成具有一定孔隙的包覆碳层,得到具有不同比例孔隙的石墨负极材料。结果表明,硼酸在材料颗粒表面形成了含有孔隙的碳层,其孔隙类型为介孔和大孔;表面碳层中的介孔比例越高,碳层L_(C)中形成Li^(+)的扩散通道数量越多,Li^(+)的扩散阻抗越低,材料倍率性能及循环性能得以改善。

浸银石墨触头材料熔焊性能研究

采用热等静压浸银工艺制备了AgC(30)、AgC(40)、AgC(50)、AgC(60)四种不同微观结构和性能的银石墨触头材料。利用熔焊力测试装置研究了不同碳含量的银石墨触头材料的抗熔焊性能。研究表明,随着触点电流的增大,熔焊力增大;随着碳含量增多,熔焊力增大,抗熔焊性能减弱。AgC(30)材料具有最优的抗熔焊性能。

高性能氯丁橡胶基动态密封材料的生胶和补强体系优化

为了提高氯丁橡胶(CR)基动态密封材料的综合性能,通过改变生胶和补强体系,考察了并用顺丁橡胶(BR)和白炭黑对材料耐疲劳性、耐老化性、耐磨性和弹性等主要性能指标的影响。结果表明,并用BR后,胶料硫化速率、拉断伸长率、回弹性、耐磨性以及动态疲劳性能均有改善,但撕裂强度、耐热空气老化性能变差,CR与BR的最佳并用质量比为70/30;并用白炭黑后,胶料的拉伸强度、撕裂强度、硬度、定伸应力、耐磨性提高,但回弹性、耐疲劳性能降低,炭黑与白炭黑并用质量比为20/20时,胶料的综合性能最佳。

One dimensional pea-shaped NiSe_(2) nanoparticles encapsulated in N-doped graphitic carbon fibers to boost redox reversibility in sodium-ion batteries

In recent years,sodium-ion batteries(SIBs)have emerged as a promising technology for energy storage systems(ESSs)because of the abundance and affordability of sodium.Recently,metal selenides have been studied as promising high-performance conversion-type anode materials in SIBs.Among them,nickel se-lenide(NiSe_(2))has received considerable attention due to its high theoretical capacity of 495 mAh g^(-1)and conductivity.However,it still suffers from poor cycling stability because of the low electrochemical reactivity,large volume expansion,and structural instability during cycles.To address these challenges,NiSe_(2)nanoparticles encapsulated in N-doped graphitic carbon fibers(NiSe_(2)@NGCF)were synthesized by using ZIF-8 as a template.NiSe_(2)@NGCF showed a high discharge capacity of 558.3 mAh g^(-1)with a fading rate of 0.14%per cycle after 200 cycles at 0.5 A g^(-1)in 0.01-3.0 V.At a very high current density of 5 A g^(-1),the capacity still displayed excellent long-term cycle life with a discharge capacity of 406.1 mAh g^(-1)with a fading rate of 0.016%per cycle after 3000 cycles.The mechanism of the excellent electrochem-ical performance of NiSe_(2)@NGCF was thoroughly investigated by ex-situ XRD,TEM,and SEM analyses.Furthermore,NiSe_(2)@NGCF//Na_(3)V_(2)(PO_(4))_(3)full-cell also delivered an excellent reversible capacity of 378.7 mAh g^(−1)at 0.1 A g^(−1)after 50 cycles,demonstrating its potential for practical application in SIBs.