光电化学刻蚀方法去除SiC衬底外延石墨烯缓冲层及其表征

高温条件下裂解碳化硅(SiC)单晶,在直径5cm的4H-SiC(0001)面制备出单层石墨烯。利用光电化学刻蚀方法,使KOH刻蚀液与SiC发生反应,降低石墨烯与衬底之间的相互作用力,去掉原位生长过程中SiC衬底与石墨烯之间存在的缓冲层,获得准自由的双层石墨烯。首先通过对比不同的电流密度和光照强度,总结出电流密度为6mA·cm-2、紫外灯与样品间距为3cm时,石墨烯缓冲层的去除效率以及石墨烯质量皆为最佳。采用此优化后工艺处理的样品,拉曼光谱表明原位生长的缓冲层与衬底脱离,表现出准自由石墨烯的特性。X射线光电子能谱(XPS)C1s谱图中代表上层石墨烯与衬底Si悬键结合的S1、S2特征峰消失,即石墨烯缓冲层消失。通过分析刻蚀过程中的电化学曲线,提出了刻蚀过程的化学反应过程中的动态特性。     

绝缘衬底上化学气相沉积法生长石墨烯材料

利用化学气相沉积法,在Si衬底、蓝宝石衬底和SiC衬底上生长石墨烯材料,研究石墨烯的表面形貌、缺陷、晶体质量和电学特性。原子力显微镜、光学显微镜和拉曼光谱测试表明,Si_3N_4覆盖层可以有效抑制3CSiC缓冲层的形成;低温生长有利于保持材料表面的平整度,高温生长有利于提高材料的晶体质量。5.08cm蓝宝石衬底上石墨烯材料,室温下非接触Hall测试迁移超过1000cm2·V~(-1)·s~(-1),方块电阻不均匀性为2.6%。相对于Si衬底和蓝宝石衬底,SiC衬底上生长石墨烯材料的表面形态学更好,缺陷更低,晶体质量和电学特性更好,迁移率最高为4900cm2·V~(-1)·s~(-1)。     

绝缘衬底上化学气相沉积法生长石墨烯材料

利用化学气相沉积法,在Si衬底、蓝宝石衬底和SiC衬底上生长石墨烯材料,研究石墨烯的表面形貌、缺陷、晶体质量和电学特性。原子力显微镜、光学显微镜和拉曼光谱测试表明,Si₃N₄覆盖层可以有效抑制3C-SiC缓冲层的形成;低温生长有利于保持材料表面的平整度,高温生长有利于提高材料的晶体质量。5.08 cm蓝宝石衬底上石墨烯材料,室温下非接触Hall测试迁移超过1000 cm²·V^-1·s^-1,方块电阻不均匀性为2.6%。相对于Si衬底和蓝宝石衬底,SiC衬底上生长石墨烯材料的表面形态学更好,缺陷更低,晶体质量和电学特性更好,迁移率最高为4900 cm²·V^-1·s^-1。     

不同降温方式对单晶石墨烯氢气刻蚀的改善

以化学气相沉积（CVD）的方法在铜衬底上制备了大尺寸的单晶石墨烯。研究了在3种不同降温方式下，石墨烯受氢气刻蚀程度的变化，以及在降温过程中通入甲烷后，对刻蚀的影响与改善，并对刻蚀机理进行了探讨。结果表明：经开盖降温的石墨烯受刻蚀最轻，随炉降温的样品受刻蚀次之，缓慢降温的样品受刻蚀最为严重。在降温过程中通入甲烷之后，3种样品的刻蚀都得到了进一步的改善，且开盖降温样品的结晶质量有大幅提升；随炉降温样品的结晶质量有小幅提升；缓慢降温样品的结晶质量有所下降。     

不同降温方式对单晶石墨烯氢气刻蚀的改善

以化学气相沉积(CVD)的方法在铜衬底上制备了大尺寸的单晶石墨烯。研究了在3种不同降温方式下,石墨烯受氢气刻蚀程度的变化,以及在降温过程中通入甲烷后,对刻蚀的影响与改善,并对刻蚀机理进行了探讨。结果表明:经开盖降温的石墨烯受刻蚀最轻,随炉降温的样品受刻蚀次之,缓慢降温的样品受刻蚀最为严重。在降温过程中通入甲烷之后,3种样品的刻蚀都得到了进一步的改善,且开盖降温样品的结晶质量有大幅提升;随炉降温样品的结晶质量有小幅提升;缓慢降温样品的结晶质量有所下降。     

利用氧化锌缓冲层生长单晶氧化锌薄膜的方法

本发明是一种利用氧化锌缓冲层生长单晶氧化锌薄膜的方法，其特征包括如下步骤：1）取一衬底；2）在该衬底上的硅（001）晶面上采用磁控溅射的方法低温生长氧化锌缓冲层；3）在氧化锌缓冲层上，采用MOCVD方法低温生长氧化锌外延薄膜。     

电流密度对碳化硅电镀镍的影响

以SiC片为基体,分别在直流(DC)电源和脉冲(PC)电源下电镀Ni。研究了电流密度对Ni镀层表面形貌、粗糙度、显微硬度以及SiC和Ni镀层刻蚀选择性的影响。结果表明,随直流电流密度增大,Ni镀层的表面形貌先变好后变差,表面粗糙度先减小后增大,显微硬度和SiC/Ni刻蚀选择比逐渐减小。随脉冲电流密度增大,Ni镀层的表面形貌和粗糙度的变化趋势与直流电镀时相近,但显微硬度和SiC/Ni刻蚀选择比均逐渐增大。当电流密度较大时,在相同电流密度下脉冲电镀Ni层的各项性能均优于直流电镀Ni层。在1.4 A/dm²的平均电流密度下脉冲电镀可获得综合性能较优的Ni镀层。     

硫掺杂石墨烯电催化降解偶氮染料RBK5

采用改进的Hummers方法制备氧化石墨烯（GO）,以二苯二硫醚（BDS）为掺杂剂,在一氧化碳（CO）氛围下,采用一步退火法合成硫掺杂石墨烯（SG）。通过透射电子显微镜（TEM）、傅氏转换红外线光谱分析（FTIR）、拉曼光谱（Raman）、X射线光电子能谱（XPS）等对样品的微观结构和形貌进行表征,利用电化学阻抗技术测试杂化后石墨烯电导性能,以RBK5为目标污染物进行硫掺杂石墨烯电催化性能研究。研究结果显示,经S掺杂后的石墨烯具有高于纯石墨烯的导电能力与催化活性,当退火温度为400℃且S∶C（质量比）=1.31时,得到的硫掺杂石墨烯（400℃-SG-1.31）在初始pH为3.0时对偶氮染料RBK5的降解效果最好。在初始浓度5mg/L,电流密度为20mA,初始pH为3.0条件下,反应20min即可达到99%的RBK5降解效率。     

水热组装合成石墨烯/聚苯胺/石墨烯复合电极材料的研究

通过在氧化石墨烯表面原位聚合苯胺制备聚苯胺阵列/石墨烯复合物,再将一定量的石墨烯加入到复合物分散液中,经水热反应制备了石墨烯/聚苯胺/石墨烯复合材料。利用SEM和FT-IR对其形貌和结构进行了表征,讨论了投料比、水热温度及水热时间对材料电化学性能的影响。结果表明,质量比PGO∶GO(后加的)=15∶1,180℃下水热反应4h,所得样品用作超级电容器电极时,表现出优异的电化学性能,当电流密度为1A/g时,其比电容为553F/g;且在电流密度为20A/g,1000次恒电流充放电后,其比电容保持率高达94.2%。     

单层石墨烯制备及其耐腐蚀特性实验研究

采用低压气相化学沉积方法在铜基底表面制备了单层石墨烯,微观表征了其单层特性;然后通过电化学分析方法研究了单层石墨烯/铜的耐腐蚀特性,量化分析了其抗腐蚀能力。研究结果表明,单层石墨烯能够有效地抑制铜在电解液中的氧化还原反应而自身不会损坏,但如果石墨烯生长不完整或存在缺陷则相应部位的铜会被腐蚀。石墨烯/铜比裸铜的腐蚀电位提高了20 m V,电流密度降低了近1个数量级,其腐蚀阻抗模值较裸铜提高了1个数量级。研究表明,单层石墨烯能很好地将铜基底与电解液隔离,有效增强了铜的抗腐蚀能力。     

纯Fe在酸性AlCl3-EMIC离子液体中的阳极行为

重点研究了纯铁（Fe）在2∶1酸性AlCl₃-氯化1-甲基-3-乙基咪唑（AlCl₃-EMIC）中的阳极行为。通过三电极体系测定了Fe在AlCl₃-EMIC中的阳极极化和不同电位下的电流-时间曲线,利用恒电位溶解计算了Fe溶解的价态,最后通过扫描电子显微镜（SEM）观察了不同电流密度下Fe的溶解形貌。结果表明：Fe表面的氧化膜会阻碍Fe的溶解,在去除氧化膜后,当电位达到-0.35 V时,Fe开始发生活性溶解,产物为Fe（Ⅱ）。Fe的阳极电流密度随电位的增加而增加,达到峰值后显著下降。小电流密度下（如2 mA·cm^-2）,Fe的溶解形貌随时间的延长,呈现先点状腐蚀再均匀腐蚀的特点;而大电流密度下（如15 mA·cm^-2）,Fe电极表面会生成一层固态物质,同时可见清晰的划痕,即不发生明显的腐蚀。     

Co2P4O12/NF纳米线阵列的制备与电解水性能研究

以CoCl₂·6H₂O为原料,通过溶剂热法和磷化工艺在泡沫镍表面构建Co₂P₄O₁₂阵列,Co₂P₄O₁₂纳米线直径约200 nm。采用SEM、TEM和XRD进行形貌和晶体学特性表征,并利用三电极体系在碱性环境下测量电化学性能。在析氢过程中,只需要122 mV过电位就能达到10 mA·cm^-2电流密度。析氧过程中,仅需要334 mV的过电位就能达到15 mA·cm^-2电流密度。组装的电解池在15 mA·cm^-2的电流密度下工作40 h后电解槽电压没有发生明显变化,展现出很好的稳定性。Co₂P₄O₁₂/NF是一种有潜力的双功能催化剂。     

Buffer layer free graphene on SiC(0 0 0 1) via interface oxidation in water vapor

Intercalation of various elements has become a popular technique to decouple the buffer layer of epitaxial graphene on SiC(0 0 0 1) from the substrate. Among many other elements, oxygen can be used to passivate the SiC interface, causing the buffer layer to transform into graphene. Here, we study a gentle oxidation of the interface by annealing buffer layer and monolayer graphene samples in water vapor. X-ray photoelectron spectroscopy demonstrates the decoupling of the buffer layer from the SiC substrate. Raman spectroscopy is utilized to investigate a possible introduction of defects. Angle-resolved photoemission spectroscopy shows that the electronic structure of the water vapor treated samples. Low-energy electron microscopy (LEEM) measurements demonstrate that the decoupling takes place without changes in the surface morphology. The LEEM reflectivity spectra are discussed in terms of two different interpretations.     

无皂乳液聚合法合成聚苯乙烯微球应用于准固态电解质染料敏化太阳能电池

制备了一种提高染料敏化太阳能电池短路电流和电池光电转化效率的准固态凝胶电解质,该电解质含有5%高聚物PVDF-HFP和2% TiO₂纳米颗粒。另外,通过乙醇相无皂乳液聚合法合成了大小均一的聚苯乙烯微球,并用于制备染料敏化太阳能电池的多孔光阳极。研究了准固态电解质和液态电解质应用于不同光阳极染料敏化太阳能电池的规律。结果表明,与液态电解质相反,准固态电解更适用于孔洞较多的光阳极,在相同测试条件下,电池的短路电流由12.80 mA·cm^-2提高到13.53 mA·cm^-2,效率比液态提高11.43%,达到6.63%。     

含油废水吸附饱和活性炭纤维的电化学再生

为了对有机物吸附饱和的活性炭纤维(ACF)进行电化学再生研究,以含油废水为模拟有机物,通过测量再生前后ACF对含油废水的吸附效果,考察了电流密度、再生时间、pH值、电解质的电化学再生的影响因素,并研究了电化学再生过程对ACF结构的影响以及ACF电化学再生的机理。结果表明,在电流密度为30 mA·cm^-2,pH值为4,15 g·L^-1 NaCl的溶液中再生120 min,再生率可达到90%,5次电化学再生循环后,ACF保持较高的吸附容量。再生后ACF的表面没有明显损伤,比表面积也没有明显减小,微孔孔径分布于0.5～1.0 nm。由紫外光谱分析可知,ACF的电化学再生机理主要包括电脱附及电化学氧化过程。     

A low frequency Raman study of SrBi2Ta2O9-Bi3TiNbO9

Raman spectra of SrBi₂Ta₂O₉ (SBT), Bi₃TiNbO₉(BTN), and x(SBT) + (1-x)(BTN) samples were studied for the first time in the low frequency region. The BTN spectra show two features around 33 and 41 cm^-1, while only one feature, around 30 cm^-1, is found in SBT. The stoichiometric evolution of the Raman spectra shows that the frequency positions of these bands decrease as x changes from 0 to 1. Strong correlation is found between the frequency positions of these modes and both the Curie temperature and the a-parameter. The results are interpreted in terms of the ferroelectric displacive modes, which are responsible for the strong spontaneous polarization along a-axis. The band around 65 cm^-1is assigned to oxygen motion in the B₂O₂ layer.     

制备高纯超细氧化铝粉体新方法

以99.99% 高纯铝板为阳极原料,采用电化学方法制备氧化铝前体氢氧化铝,讨论分析了氢氧化铝的焙烧温度、保温时间对制备高纯超细氧化铝的影响,考察了不同电流密度放电对氧化铝形貌和粒度的影响。结果表明：在70 mA·cm^-2的较高电流密度下铝/空气电池放电过程可得到平均粒度为268 nm的氢氧化铝;制备的氢氧化铝经洗涤,在1400℃焙烧,保温3 h,可得到平均粒度为200 nm,形貌为近似球状的99.99% 的超细氧化铝粉体;而低电流密度所得氧化铝颗粒团聚严重。主要原因是高电流密度使放电过程中产生的氢氧化铝晶体的介稳区宽度变窄所致。     

Determination of the Molecular Structure of Interphases Between Epoxy/4,4'-Diaminodiphenylsulfone Adhesives and Silver Substrates Using SERS and XPS

The molecular structure of interphases formed by curing an epoxy/4,4'-diaminodiphenylsulfone (DADPS) adhesive against rough silver substrates was determined using surface-enhanced Raman scattering (SERS) and x-ray photoelectron spectroscopy (XPS). SERS spectra obtained from the adhesive deposited onto silver island films were very similar to SERS spectra obtained from the DADPS curing agent spun onto silver island films, indicating that DADPS in the adhesive system segregated to the interphase and was preferentially adsorbed onto the silver substrate. Differences in the relative intensity of several bands in the normal Raman and SERS spectra of DADPS were observed. For example, the band near 1603 cm^-1 was stronger in SERS spectra of DADPS than in normal Raman spectra. The band near 1150 cm^-1 was weaker in SERS spectra of DADPS than in normal Raman spectra. These results implied that DADPS was adsorbed through one of the NH groups with an end-on conformation. Consistent results were also obtained from XPS spectra. C(ls) spectra of the adhesive and silver fracture surfaces of specimens prepared by curing the adhesive against silver substrates were more similar to the C(ls) spectra of DADPS than to those of the bulk adhesive. These results confirmed the preferential adsorption of DADPS onto the silver substrate from the adhesive system. The similarity of the C(ls) spectra obtained from adhesive and silver fracture surfaces indicated that a thin DADPS-rich interphase was formed between the bulk adhesive and the silver substrate and that the locus of failure was partially within this layer. However, less nitrogen and sulfur were detected on the silver fracture surface than on the adhesive fracture surface. A large amount of silver was observed on the substrate fracture surface and a trace was found on the adhesive fracture surface. These results indicated that failure of the adhesive joints was within the interphase but near the silver substrate. No evidence of chemisorption of DADPS onto the substrate was observed.     

Raman study of SrBi2Ta2O9 thin films

Thin films of SrBi₂Ta₂O₉ (SBT) were deposited on Si using Sol-Gel technique. The thicknesses of the films 200 nm (SBT2) and 400 nm (SBT4), respectively. SEM were studies showed most of the grains in the film are smaller than 0.1 μ. FTIR reflectivity measurements of the samples showed bands around 1260, 936(for SBT2), 955(for SBT4), 770, 600 cm^-1. Micro Raman spectra shows bands corresponding to the SBT materials, but some frequency shifts and broadening were observed. Particularly, the band around 818 cm^-1, which corresponds to a stretching of the TaO₆ octahedron, was found to change from 785 to 827 cm^-1. This change seems to be related to the Ta-O bond length.