模板法合成MoS2纳米管及其摩擦学性能的研究

为了研究MoS2纳米管的摩擦学性能,用模板法在低温(450℃)条件下热分解(NH4)2MoS4合成出MoS2纳米管,利用SEM,EDS,TEM和AFM对样品的形貌和结构进行分析.结果表明:用模板法制备的MoS2纳米管的形状和尺寸高度均匀一致,直径约为100nm,长度大于5μm,与模板孔洞的参数一致.在CETR UMT-2试验机进行摩擦实验,结果显示MoS2纳米管具有优良的润滑性能.     

纳米SiO2对聚丙烯酸酯复合涂层在水润滑下摩擦学性能的影响

考察了纳米SiO₂对聚丙烯酸酯复合涂层在水润滑下摩擦磨损性能的影响。利用FTIR分析纳米SiO₂与聚丙烯酸酯的界面结合;利用SEM观察复合涂层磨损表面,并结合FTIR和摩擦磨损实验分析其磨损机理。结果表明:水润滑时,聚丙烯酸酯在摩擦过程中会发生摩擦化学反应,引起涂层摩擦腐蚀磨损;而纳米SiO₂能与聚丙烯酸酯以化学键的形式结合,它的加入有助于摩擦界面在水介质中形成具有较好减摩作用的表面膜和水分子膜,提高聚丙烯酸酯复合涂层的耐磨性。在水润滑下,当纳米SiO₂的含量较低时,涂层表面的磨损形式为摩擦腐蚀磨损和磨粒磨损;当纳米SiO₂的含量达到5wt% 时,涂层表面形成完整的表面膜和水分子膜,此时涂层具有良好的摩擦学性能。      

纳米铜胶的原位合成及其摩擦学性能研究

以醋酸铜为母体,维生素C（Vc）为还原剂,吐温-80为修饰剂,用原位合成一步法在基础油液体石蜡中成功制备了粒径分布为2．3—9．5nm、平均粒径为4．3nm的纳米铜胶。以制备的纳米铜胶的液体石蜡为润滑油添加剂,将其分散于关孚1号5w-30全合成机油中,制得分散稳定性、兼容性优良的纳米润滑油,在UMT-II摩擦磨损实验机、四球摩擦磨损实验机上分别考察添加纳米铜胶的润滑油的摩擦学性能,利用扫描电镜（SEM）和能谱散射光谱（EDS）分析磨损表面形貌,结果表明,添加的纳米铜胶在摩擦表面的划痕和犁沟处沉积并铺展成膜,相比关孚1号5w-30全合成机油,较大程度地降低了摩擦副的摩擦因数,显著改善了润滑油的润滑性能,表现出优异的抗磨减磨性能、极压性能和极限工作能力等摩擦学性能。     

层状Cr2AlC纳米晶的合成及其摩擦学行为

通过液相磁力搅拌混合原料粉末2Cr/1.2Al/1C,在1400℃无压烧结合成了Cr2AlC。X射线衍射结果表明,Cr2AlC具有良好的结晶性,扫描电镜照片显示合成的Cr2AlC为层状结构,厚度大约在50~100 nm。将其以不同质量分数分散到基础油100SN中,利用摩擦磨损试验机初步研究了滑行速度,载荷等对其摩擦学性能的影响,结果表明,Cr2AlC添加量较低时,分散性较好,能显著降低基础油的摩擦系数和摩擦磨损,高载荷会加剧磨损,实验条件下,Cr2AlC添加量为0.6%和1%的润滑油在10N载荷时,摩擦过程中在表面形成具有减摩抗磨作用的润滑膜,表现出较好的摩擦学性能。     

硬脂酸修饰纳米TiO2颗粒的摩擦学性能研究

采用溶胶一凝胶法制备了硬脂酸表面修饰纳米TiO2颗粒，使用冷冻蚀刻电镜（FEEM）对其进行了形貌表征，用MM-WlA型四球试验机评价了其摩擦学性能，并考察了与硫化烯烃的复配规律。结果表明，所制备的纳米TiO2颗粒大小均匀，没有明显的团聚现象，在基础油中能起到极压抗磨作用，具有良好的极压性能，有利于提高油品的承载能力。另外，所制备的纳米TiO2添加剂与硫化烯烃有很好的复配效应，可以大幅度提高基础油的抗烧结负荷，这对于提高齿轮油的承载能力，具有非常重要的应用价值。     

MgFe2O4纳米颗粒制备及其电磁性能研究

将Mg(OH)2/Fe(OH)3混合体超声活化4h,固相合成制备了尖晶石型MgFe2O4粉末。通过TG-DTA、XRD和TEM测试,分析固相反应的机理、材料的化学成分和微观结构。用振动样品磁强计(VSM)、矢量网络分析仪研究材料的电磁性能。结果表明,700℃下制备的MgFe2O4颗粒为纳米级单晶结构,纯度高,结晶性好,粒径分布为20～45nm;Mg-Fe2O4的比饱和磁化强度Ms=21.015A.m2/kg,剩磁Mr=2.5798A.m2/kg,矫顽力Hc=9.017×10-3T,MgFe2O4对7～18GHz范围内的电磁波表现为介电损耗。     

SiO2／SnO2复合纳米粒子的制备及其在菜籽油中的摩擦学性能

采用化学方法制备了SiO2／SnO2复合纳米添加剂,在四球摩擦磨损试验机上考察了其在菜籽基础油中的抗磨减摩性能。用扫描电子显微镜观察分析钢球磨斑表面的形貌,同时通过对钢球磨痕表面进行X-射线光电子能谱分析,探讨了SiO2／SnO2复合纳米添加剂的抗磨减摩机理。结果表明：SiO2／SnO2复合纳米添加剂具有优良的减摩抗磨性能,其润滑作用机理是因为SiO2／SnO2复合纳米添加剂在摩擦表面沉积并在接触区的高温高压作用下熔融铺展,形成低剪切强度的表面膜,由于这层膜的剪切强度比较低,可以减少摩擦界面的粘着磨损,故表现出良好的减摩抗磨性能。     

改性纳米SiO2/环氧树脂涂料的制备及其性能

为提高纳米SiO2在环氧树脂中的分散程度,充分发挥纳米SiO2的力学性能和耐热性,采用乙烯基三乙氧基硅烷与丙烯酸对纳米SiO2表面进行接枝改性,利用红外光谱对改性纳米SiO2的结构进行了表征;将改性纳米SiO2添加到环氧树脂中混合固化,得到改性纳米SiO2/环氧树脂复合涂料(SAE),并通过附着力、吸水率、电化学试验等方法对SAE涂层的耐蚀性能进行了评价。结果表明:改性后的纳米SiO2出现新的吸收峰;SAE具有附着力高、抗渗透性强、极化电流小等优良的耐腐蚀性能。     

纳米SiO2对聚醚砜酮复合材料摩擦学性能的影响

在MM-2000型摩擦磨损试验机上考察了不同载荷和速度下纳米SiO2含量对聚醚砜酮（PPESK）复合材料摩擦磨损性能的影响，并利用扫描电子显微镜（SEM）观察分析PPESK及纳米SiO2/PPESK复合材料磨损表面形貌及磨损机理，结果表明：纳米SiO2不但可以提高PPESK的耐磨性，而且还有较好的减摩作用，在本研究的试验条件下，当纳米SiO2的质量分数为25%时，填充PPESK复合材料具有最佳摩擦学性能。随着载荷的增大，填充PPESK的摩擦系数降低，填料含量在20%质量分数以下时随载荷增大其耐磨性提高较明显，而填料含量超过20%质量分数时载荷对复合材料耐磨性的影响不大。     

纳米α-MnO_2的固相制备及电化学性能

用KMnO4和醋酸锰为原料,在室温下固相反应经过热处理和酸处理制备纳米-αMnO2,采用X射线衍射技术和扫描电子显微镜(SEM)分析了MnO2的结晶结构及表面形态;通过循环伏安法、恒流充放电和交流阻抗测试研究了样品的电化学行为。合成的α-MnO2在1.0mol/L Na2SO4电解液中,-0.1~0.8V(vs.SCE)范围内,电流密度为300mA/g,3mV/s的扫描速度下的比电容可达222.7F/g,经1000次循环后,容量保持85%以上,有着较好的循环性能和电容稳定性。     

FeCrBSi/FeS层真空辐照环境下的组织结构与摩擦学性能研究

采用超音速等离子喷涂+低温离子渗硫技术在45#钢基体上制备了FeCrBSi/FeS复合涂层,考察了该复合涂层在大气、真空、原子氧辐照、紫外线辐照后的表面形貌、磨痕形貌及元素组成。利用真空摩擦磨损试验机分别完成了干摩擦条件下四种环境中的摩擦磨损性能测试。结果表明:复合FeCrBSi/FeS层经过原子氧及紫外线辐照后,有部分元素被氧化及化合物分解的现象,但并没有发生明显的材料性能改变以及润滑涂层的破坏。与45#钢相比,四种环境下该复合涂层均具有良好的润滑减摩效果。此研究表明,复合FeCrBSi/FeS层具有一定的抗原子氧和紫外线辐照的能力。     

Ultrafast Growth of High‐Quality Monolayer WSe2 on Au

The ultrafast growth of high‐quality uniform monolayer WSe₂ is reported with a growth rate of ≈26 µm s^?1 by chemical vapor deposition on reusable Au substrate, which is ≈2–3 orders of magnitude faster than those of most 2D transition metal dichalcogenides grown on nonmetal substrates. Such ultrafast growth allows for the fabrication of millimeter‐size single‐crystal WSe₂ domains in ≈30 s and large‐area continuous films in ≈60 s. Importantly, the ultrafast grown WSe₂ shows excellent crystal quality and extraordinary electrical performance comparable to those of the mechanically exfoliated samples, with a high mobility up to ≈143 cm² V^?1 s^?1 and ON/OFF ratio up to 9 × 10⁶ at room temperature. Density functional theory calculations reveal that the ultrafast growth of WSe₂ is due to the small energy barriers and exothermic characteristic for the diffusion and attachment of W and Se on the edges of WSe₂ on Au substrate.     

Various and Tunable Transport Properties of WSe2 Transistor Formed by Metal Contacts

The abundant electronic and optical properties of 2D materials that are just one‐atom thick pave the way for many novel electronic applications. One important application is to explore the band‐to‐band tunneling in the heterojunction built by different 2D materials. Here, a gate‐controlled WSe₂ transistor is constructed by using different work function metals to form the drain (Pt) and source (Cr) electrodes. The device can be gate‐modulated to exhibit three modes of operation, i.e., the tunneling mode with remarkable negative differential resistance, the transition mode with a second electron tunneling phenomenon for backward bias, and finally the conventional diode mode with rectifying characteristics. In contrast to the heterojunctions built by different 2D materials, these devices show significantly enhanced tunneling current by two orders of magnitude, which may largely benefit from the clean interfaces. These results pave the way toward design of novel electronic devices using the modulation of metal work functions.     

Tunneling Diode Based on WSe2/SnS2 Heterostructure Incorporating High Detectivity and Responsivity

van der Waals (vdW) heterostructures based on atomically thin 2D materials have led to a new era in next‐generation optoelectronics due to their tailored energy band alignments and ultrathin morphological features, especially in photodetectors. However, these photodetectors often show an inevitable compromise between photodetectivity and photoresponsivity with one high and the other low. Herein, a highly sensitive WSe₂/SnS₂ photodiode is constructed on BN thin film by exfoliating each material and manually stacking them. The WSe₂/SnS₂ vdW heterostructure shows ultralow dark currents resulting from the depletion region at the junction and high direct tunneling current when illuminated, which is confirmed by the energy band structures and electrical characteristics fitted with direct tunneling. Thus, the distinctive WSe₂/SnS₂ vdW heterostructure exhibits both ultrahigh photodetectivity of 1.29 × 10¹³ Jones (I_ph/I_dark ratio of ≈10⁶) and photoresponsivity of 244 A W^?1 at a reverse bias under the illumination of 550 nm light (3.77 mW cm^?2).     

一种新的自润滑铜-石墨-NbSe2复合材料的合成及摩擦性能研究

研究了NbSe2的添加对铜-石墨固体自润滑材料的影响,采用粉末冶金法将制备的不同质量百分比含量的纤维状或片层状的纳米NbSe2材料与铜粉、石墨粉混合均匀,冷压制成小圆盘.采用光学显微镜,SEM(JSM-7001F扫描电子显微镜)等手段表征表面形貌.并在超低温摩擦磨损机和UMT-2摩擦试验仪上测试其摩擦性能.实验结果表明...     

Mechanical Exfoliation and Characterization of Single‐ and Few‐Layer Nanosheets of WSe2, TaS2, and TaSe2

Single‐ and few‐layer transition‐metal dichalcogenide nanosheets, such as WSe₂, TaS₂, and TaSe₂, are prepared by mechanical exfoliation. A Raman microscope is employed to characterize the single‐layer (1L) to quinary‐layer (5L) WSe₂ nanosheets and WSe₂ single crystals with a laser excitation power ranging from 20 μW to 5.1 mW. Typical first‐order together with some second‐order and combinational Raman modes are observed. A new peak at around 308 cm^?1 is observed in WSe₂ except for the 1L WSe₂, which might arise from interlayer interactions. Red shifting of the A_1g mode and the Raman peak around 308 cm^?1 is observed from 1L to 5L WSe₂. Interestingly, hexagonal‐ and monoclinic‐structured WO₃ thin films are obtained during the local oxidation of thinner (1L–3L) and thicker (4L and 5L) WSe₂ nanosheets, while laser‐burned holes are found during the local oxidation of the WSe₂ single crystal. In addition, the characterization of TaS₂ and TaSe₂ thin layers is also conducted.     

Tribological behavior of radio-frequency sputtering WS2 thin films with vacuum annealing

Thin films of tungsten disulfide (WS₂) were deposited on 3Cr13 martensitic stain less steel substrate by radio-frequency (RF) sputtering. The as-deposited films were annealed at 473, 673 and 873 K respectively for 2 h in 5 × 10^− 4 Pa vacuum. Composition of the films was inspected by energy dispersive spectroscopy. Surface morphology and structure properties were studied by scanning electron microscopy and X-ray diffraction techniques. Tribological behavior was also examined using tribometer. At 473 K, the films exhibited low crystallization structure and no significant improvement in the tribological performance. At 673 K, the tribological performance was improved and a transition from non-crystalline to hexagonal structure took in place. When the annealing temperature rose up to 873 K, the films cracked and fell off from the substrate. The results suggested that with suitable technical parameters vacuum annealing could promote crystallization and improve tribological performance of RF sputtering WS₂ films.     

Ultrafast Self‐Limited Growth of Strictly Monolayer WSe2 Crystals

The controllable synthesis of uniform tungsten diselenide (WSe₂) is crucial for its emerging applications due to the high sensitivity of its extraordinary physicochemical properties to its layer numbers. However, undesirable multilayer regions inevitably form during the fabrication of WSe₂ via the traditional chemical vapor deposition process resulted from the lack of significantly energetically favorable competition between layer accumulation and size expansion. This work innovatively introduces Cu to occupy the hexagonal site positioned at the center of the six membered ring of the WSe₂ surface, thus filtrates the undesired reaction path through precisely thermodynamical control and achieves self‐limited growth WSe₂ crystals. The as‐obtained WSe₂ crystals are characterized as strictly single‐layer over the entire wafer. Furthermore, the strictly self‐limited growth behavior can achieve the “win–win” cooperation with the synthesis efficiency. The fastest growth (≈15 times of the growth rate in the previous work) of strictly monolayer WSe₂ crystals thus far is realized due to the high‐efficiency simultaneous selenization process. The as‐proposed ultrafast Cu‐assisted self‐limited growth method opens a new avenue to fabricate strictly monolayer transition metal dichalcogenides crystals and further promotes their practical applications in the future industrial applications.     

Cr和Mo掺杂对单层WSe_2能带结构影响的第一性原理研究

采用基于密度泛函理论的第一性原理平面波赝势方法,研究了Cr和Mo掺杂对单层WSe2能带结构的影响。计算结果表明,Mo对单层WSe2的能带结构没有影响,而Cr则影响很大。随着掺杂浓度的增加,带隙宽度逐渐减小,能带由原来的直接带隙变为了间接带隙。Cr掺杂后所产生的应力是导致能带结构发生变化的直接原因。     

尺寸效应对MoS2/WSe2范德华异质结构层间与俄歇复合的界面调控

为探索界面工程对二维材料范德华异质结构中载流子复合率的影响, 本工作基于界面键弛豫理论和费米黄金定则, 建立了范德华异质结俄歇和层间复合率与各结构组元尺寸之间的理论模型。结果表明, MoS₂/WSe₂异质结的俄歇复合寿命随着组元尺寸的增大而增加, 且异质结的俄歇复合率远小于相应的单组元体系。在MoS₂/WSe₂双层异质结中引入薄h-BN插层后, 体系的层间复合率和俄歇复合率随h-BN厚度的增加而分别呈现减小和增大的趋势; 在组元处于单层MoS₂和WSe₂情况下, 当界面插层h-BN厚度达到9.1 nm时, 俄歇复合率将趋于5.3 ns ^-1。该研究结果为二维过渡金属硫族化合物基异质结光电器件的优化设计提供了一种理论依据。