二维Ti3C2Tx MXene材料的制备与工艺优化

二维（2D）过渡金属碳/氮化物（MXene）材料是当前最受关注的二维材料之一,其中二维碳化钛（Ti₃C₂T_x MXene）材料的研究最为广泛。该材料目前主要通过刻蚀三元碳化物或氮化物（MAX相）后进一步插层得到,因此MAX相材料的纯度和制备工艺条件直接决定了Ti₃C₂T_x MXene材料的物化性质。主要完成了不同Ti₃AlC₂ MAX相材料的筛选,选择氢氟酸（HF）刻蚀,并优化了不同的插层方法,制备了一系列Ti₃C₂T_x MXene材料。通过X射线衍射（XRD）、场发射扫描电镜（FESEM）、透射电子显微镜（TEM）、原子力显微镜（AFM）和X射线光电子能谱（XPS）等表征,确定使用原位锂离子（Li⁺）插层法可有效获得单层Ti₃C₂T_x MXene材料。制备的单层Ti₃C₂T_x MXene材料的表面平整,片径约为150 nm,厚度约为2 nm。同时,创新性地采用涡旋震荡辅助材料分层,极大地缩短了超声时间,提高了单层Ti₃C₂T_x MXene材料的产率（可达70%）,并且可以避免材料氧化,为Ti₃C₂T_x MXene材料未来应用提供了新方法。     

Integrated Bi2O3 nanostructure modified with Au nanoparticles for enhanced photocatalytic activity under visible light irradiation

An integrated Bi_2O_3(i-Bi_2O_3) nanostructure with a particle size 10 nm inducing agglomerated structure were synthesized by dissolving bismuth nitrate pentahydrate in diethylene glycol at 180 ℃ with post heat treatment.The prepared i-Bi_2O_3 nanostructures were employed for the construction of Au/i-Bi_2O_3 composite system and characterized by X-ray diffraction pattern,UV-visible diffuse reflectance spectroscopy(DRS),and transmission electron microscopy,X-ray photoemission spectroscopy(XPS) and Energy dispersive X-ray spectroscopy(EDS).The i-Bi_2O_3 nanostructure and Au/i-Bi_2O_3 composite system were found to exhibit high photocatalytic activity than commercial Bi_2O_3 in decomposing salicylic acid under visible light irradiation.The high catalytic activity of i-Bi_2O_3 nanostructure was deduced to be caused by charge separation facilitated by electron hopping between the particles within the integrated structure and space-charge separation between i-Bi_2O_3 and Au.The charge separation behavior in i-Bi_2O_3 nanostructure was further bolstered by comparing the measured.OH radical produced in the solution with i-Bi_2O_3 nanostructure,commercial Bi_2O_3 and Au/i-Bi_2O_3 composite which readily react with 1,4-terephthalic acid(TA) inducing 2-hydroxy terephthalic acid(TAOH) that shows unique fluorescence peak at 426 nm.The space-charge separation between i-Bi_2O_3 and An was confirmed by measuring the electron spin resonance(ESR) spectra.     

络合试剂对溶胶凝胶燃烧法合成LaCoO3的物化性能及对VOCs催化净化效果的影响

分别以甘氨酸、柠檬酸和丙烯酰胺辅助柠檬酸为络合试剂,采用溶胶凝胶燃烧法合成LaCoO_3复合氧化物,并对它们进行XRD、BET、SEM及O_2-TPD分析.实验结果表明,三种络合剂制备得到的产物均为纯钙钛矿LaCoO_3相;丙烯酰胺辅助柠檬酸溶胶凝胶燃烧法制得的LaCoO_3颗粒均匀且较小,比表面积最大,其O_2-TPD曲线中的峰面积最大,对苯完全催化氧化效果最好.     

Influence of interactions between chromium and cerium on catalytic performances of CrO_x–CeO_2/Ti-PILC catalysts for deep oxidation of n-butylamine

A series of CrOx-CeO2/Ti-PILC （PILC is pillared interlayered clay） catalysts for n-butylamine oxidation were prepared using an impregnation method, and the structures, surface acidity distributions, and redox properties of the catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, H2 temperature-programmed reduction, and NH3 temperature-programmed desorption. The results show that addition of an appropriate amount of CeO2 enhances the interactions between Cr and Ce, and this increases the acid strength and mobility of active oxygen species on the cata- lyst. 8CrCe（6：1）/Ti-PILC（12,20） exhibits the best catalytic performance and control of NOx in n-butylamine oxidation.     

Biotemplated fabrication of hierarchical mesoporous CeO2 derived from diatom and its application for catalytic oxidation of CO

Hierarchically hollow nanostructures have been the focus of numerous studies due to their prominent physicochemical properties that differ significantly from bulk materials and their potential for extensive applications. We present a novel diatom-based scaffold for the synthesis of hierarchically biomorphic CeO2 with special porous structure via incorporating Ce ions into the frustule. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen adsorption-desorption measure- ments were adopted to characterize the products. Owing to its unique hierarchical structure and periodic meso-macro scale features, the obtained CeO2 exhibits high catalytic activity in CO oxidation. This facile strategy may design a new way towards replicating desired biological structures for metal oxide catalyst in other potential applications.     

Reduced graphene oxide wrapped 3D-ultrathin CoS2 nanoflakes as an absorbing material with enhanced microwave absorption

Novel 3D-ultrathin CoS₂ nanoflakes wrapped by reduced graphene oxide (CoS₂/RGO) were successfully prepared via a facile method. The morphology and structure of the materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The microwave absorption properties of the CoS₂/RGO composites were also investigated. The composites exhibited optimal microwave absorption properties at a CoS₂/RGO loading of 20 ?wt.% in paraffin matrix, with a reflection loss (R_L) value of ?36.5 ?dB at 12.1 ?GHz and a thickness of 2.0 ?mm. Furthermore, CoS₂/RGO composites have an excellent absorption bandwidth (reflection loss below ?10 dB) of 6.5 ?GHz. The results indicate that the RGO-wrapped 3D-ultrathin CoS₂ nanoflakes have a broad microwave absorption bandwidth, strong absorption, and are the candidates for the application as the advanced microwave absorbers.     

Synthesis of nano onion-like fullerenes by using Fe/Al2O3 as catalyst by chemical vapor deposition

Nano-carbon materials were synthesized by the catalytic decomposition of acetylene at 400℃ by using Fe/Al₂O₃ as catalyst. The product was refluxed in 36% concentrated HCl at 60℃ for 48 h in order to remove the catalyst support. The samples were examined by scanning and high resolution transmission electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The results show that nano onion-like fullerenes encapsulating a Fe₃C core were obtained. These had a structure of stacked graphitic fragments, with diameters ranging from 15―50 nm. When the product was further heat- treated at 1100℃ for 2 h, nano onion-like fullerenes with a clear concentric graphitic layer structure were obtained. The growth mechanism of nano onion-like fullerenes encapsulating metal cores is suggested to follow a vapor-solid growth model.     

Improved ethanol, acetone and H2 sensing performances of micro-sensors based on loose ZnO nanofibers

Both one-dimensional nanostructures and porous nanostructures are benefit to the sensing enhancement of semiconducting functional materials.The present paper shows an effective route to combining the advantages of these two nanostructures for a novel type of ZnO nanomaterials.Basically,a pore-forming material is employed in an electrospinning method,and the products are characterized by X-ray powder diffraction(XRD),energy dispersive X-ray spectroscopy(EDX),and transmission electron microscopy(TEM).The obtained materials are loose ZnO nanofibers,which own both porous and one-dimensional nanostructures.Micro-sensors are fabricated by sputtering and etching techniques,and the as-prepared nanofibers are used as the functional materials in them.The sensors show improved sensing properties both in sensitivity and response-speeds.The sensitivity is enhanced from 4 to 8 and the response time is shortened from 14 to 10 s when the sensors are exposed to 100 μL/L ethanol at 260℃.Similar results are also observed in acetone and H2 sensing tests.These enhancements are based on the one-dimensional and porous nanostructures of the nanofibers.     

Pr掺杂对Ce0.87Sm0.13O2-δ结构及电性能的影响

采用溶胶 凝胶法合成Ce_0.87Sm_0.13-xPr_xO_2-δ(x=0.00, 0.01, 0.02)氧化物, 通过X射线衍射、 拉曼光谱、 场发射扫描电镜对氧化物进行结构表征, 利用交流阻抗谱测试电性能, 并讨论 了掺杂Pr对Ce_0.87Sm_0.13O_2-δ微观结构和电性能的影响. 结果表 明, 掺入少量Pr³⁺可减少或消除晶粒表面和晶界处的坑痕或孔隙, 增加材料的致密 性, 从而降低材料的晶界电阻和电极界面电阻以及晶界电阻在总电阻中所占的比例, 提高了材料的电导率.     

Short-term exposure of low-alloyed steels in Qinghai Salt Lake atmosphere

The rusts formed on carbon steel and weathering steel exposed in Qinghai Salt Lake atmosphere for 6 months were characterized by X-ray diffraction （XRD）, infrared transmission spectroscopy （iRS）, scanning electron microscopy （SEM）, electron probe micro analyzer （EPMA） and electrochemical po- larization techniques. The two kinds of steels showed the similar corrosion rate, corrosion product composition and electrochemical polarization behavior. Their rusts were mainly composed of β-FeOOH, Fe8（O,OH）16Cl1.3 and a little γ-FeOOH. Cl^- played an important role during the corrosion process of low-alloyed steels. The alloyed elements Cr, Ni and Cu in weathering steel were detected in the rusts; however, they showed no remarkable protective ability.     

Tree decomposition

A tree decomposition of graph G=(V, E) is referred to as a partition of edge set E into edge-disjoint trees. Given (not necessarily distinct) vertices u-1, u-2...u-k∈V with k≥2, a sufficient and necessary condition is given for a connected graph G=(V,E) to have a tree decomposition {T-1, T-2...T-k} such that V(T-i)=V{u-i}, i=1,2,... k.     

用于邻苯基苯酚合成的Pt-K/Al2O3脱氢催化剂(Ⅱ):催化剂失活机制

采用热重-差热分析(TG-DTA)、元素分析、氢氧滴定(HOT)、扫描电镜能谱分析(SEM-EDS)、透射电镜(TEM)等对Pt-K催化剂可能的失活机制进行研究。结果表明:积碳并非Pt-K催化剂失活的主要原因;脱氢催化剂上铂颗粒的尺寸在运转过程中没有明显的增大,即铂中心烧结也不是催化剂失活的主要原因;Pt-K催化剂在运转过程中铂分散度明显下降而且无法通过再生恢复;Pt-K/Al2O3催化剂的失活极有可能源自催化剂运转过程中钾物种对铂中心的过度覆盖作用。     

Immobilization of 12-phosphotungstic heteropolyacid on amine-functionalized SiO<Subscript>2</Subscript> for tetrahydrofuran polymerization

The 12-phosphotungstic heteropolyacid (HPW) was immobilized on the surface of a silica carrier modified by the amine groups of organosilane γ-aminopropyl triethoxysilane (APTES), and its catalytic performance was investigated for tetrahydrofuran (THF) ring-opening polymerization. This amine-functionalized catalyst exhibited better activity, and the polytetramethylene ether glycol (PTMG) yield was 63.7%. The 12-phosphotungstic heteropolyacid supported on aminopropyl-functionalized SiO₂ support (HPW/SiO₂-APTES) was reused four times and showed a good maintenance of activity which was better than that of the conven-tional catalyst HPW supported on SiO₂ (HPW/SiO₂). These results were obtained using infrared spectroscopy, nuclear magnetic resonance spectroscopy, nitrogen adsorption and X-ray diffraction. HPW on the HPW/SiO₂-APTES catalyst exhibited higher dispersed state and maintained a more stable structure than that of the HPW/SiO₂ sample.     

Enhanced photocatalytic activity of electrochemically synthesized aluminum oxide nanoparticles

In this study, aluminum oxide (Al₂O₃) nanoparticles (NPs) were synthesized via an electrochemical method. The effects of reaction parameters such as supporting electrolytes, solvent, current and electrolysis time on the shape and size of the resulting NPs were investigated. The Al₂O₃ NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis/differential thermal analysis, energy-dispersive X-ray analysis, and ultraviolet–visible spectroscopy. Moreover, the Al₂O₃ NPs were explored for photocatalytic degradation of malachite green (MG) dye under sunlight irradiation via two processes: adsorption followed by photocatalysis; coupled adsorption and photocatalysis. The coupled process exhibited a higher photodegradation efficiency (45%) compared to adsorption followed by photocatalysis (32%). The obtained kinetic data was well fitted using a pseudo-first-order model for MG degradation.     

Self-assemb led array of rect angular single- crystal microtube s of perchlorina ted copper phthalocy anines

The rectangular microtubes array of perchlorinated copper phthalocyanines(G₁₆CuPc),were synthesized by physical vapor deposition technique without using any template or catalyst.The synthesis process of the tubular structure is very simple,easy to control,and a little raw material is used.The morphology and crystal structure of the obtained samples were analyzed by means of scanning and transmission electron microscopy（SEM and TEM）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR） and X-ray photoelectron spectroscopy（XPS）.The microtubes have an entire hollow interior,open ends with rectangular cross-section,a large interior of 1.4-1.8 urn width,and the thin walls of 80-100 nm.The obtained products exhibit excellent crystalline nature,high chemical and thermodynamic stability,excellent biocompatibility,as well as innocuity.It is believed that these well-defined microtubular structures of an organic material will be used as active materials for solar cells,nanodevices for field emission apparatus,microchannels for biochip and microvessel for drug delivery.     

A Novel Polymethyl Methacrylate （PMMA）TiO2 Nanocomposite and Its Thermal and Photic Stability

A new kind of polymethyl methacrylate （PMMA）-TiO2 nanocomposite was synthesized through polymerization. The thermal and photic stability of this PMMA TiO2 nanocomposites were investigated. The as prepared samples were characterized by scanning electron microscopy （SEM）, UV-Vis spectroscopy, differential thermal analysis （DTA） and the photo-induced weight loss, The results show that the photostability of the PMMA-TiO2 nanocomposite is higher than that of the pure PMMA under UV-light irradiation, The weight loss of the pure PMMA reaches 30 % after 300 h UVirradiation, while the composite only 0.3% under the identical experimental condition. The glass transition temperature （TR） of pure PMMA is only 80℃, while the Tg of the composite reaches 258℃. Compared with pure PMMA, the thermal stability of the composite is greatly enhanced.     

Microstructural characterization of as-cast and homogenized 2D70 aluminum alloy

The microstructure of the as-cast 2D70 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The results indicate that the microstructure of the as-cast 2D70 aluminum alloy mainly consists of the dendritic network of aluminum solid solution and intermetallic compounds (Al₂CuMg, Al₂Cu, Al₉FeNi, Cu₂FeAl₇, and Al₇Cu₄Ni). After conventional homogenization, Al/Al₂CuMg eutectic phases are dissolved into the matrix, and a small amount of high melting-point eutectic Al/Al₂Cu phases exist in the matrix, resulting in an increase in the starting melting temperature. Under double homogenization, the high melting point Al/Al₂Cu phases are dissolved, and no obvious change is observed for the size and morphology of Al₉FeNi, Cu₂FeAl₇, and Al₇CuaNi compounds.     

Synthesis, structure, and optical properties of manganese phthalocyanine thin films and nanostructures

Manganese phthalocyanine(MnPc) nanostructures with different morphologies were prepared on porous anodic alumina oxide(AAO) at different substrate temperature(T_S=50 ℃,80 ℃,120 ℃,180 ℃,240 ℃) in an organic molecular beam deposition(OMBD) system.The nanostructures morphologies were studied using scanning electron microscopy(SEM) and the results showed that the nanostructures morphologies could be modulated by the control of T_S,as a result,the continuous film was obtained at 50 ℃,whereas the nanorods(NRs),nanoribbons(NBs),nanowires(NWs),nanosheets(NSs) and nanoparticles(NPs) were facilely generated as T_S increased.At the same time,the density and the uniformity of the nanostructures decreased.The results of X-ray diffraction(XRD) indicated that only the(3-phase polymorph formed throughout the growth process irrelevant to the T_S.Additionally,the ultraviolet visible(UV-Vis) absorption spectra demonstrated that the main absorption bands of MnPc nanostructures showed a remarkable band broadening as the T_S was increased.     

One-pot synthesis of Sb-Fe-carbon-fiber composites with in situ catalytic growth of carbon fibers

A Sb-Fe-carbon-fiber (CF) composite was prepared by a chemical vapor deposition (CVD) method with in situ growth of CFs using Sb₂O₃/Fe₂O₃ as the precursor and acetylene (C₂H₂) as the carbon source. The Sb-Fe-CF composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), and its electrochemical performance was investigated by galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy. The Sb-Fe-CF composite shows a better cycling stability than the Sb-amorphous-carbon composite prepared by the same CVD method but using Sb₂O₃ as the precursor. Improvements in cycling stability of the Sb-Fe-CF composite can be attributed to the formation of three-dimensional network structure by CFs, which can connect Sb particles firmly. In addition, the CF layer can buffer the volume change effectively.     

Polypyrrole-coated styrene-butyl acrylate copolymer composite particles with tunable conductivity

A series of near or monodisperse styrene-butyl acrylate (SBA) copolymer latex particles with different butyl acrylate contents were coated with polypyrrole. The structure of the SBA/PPy composites was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) andstandard fourprobe method. The core-shell morphology of the SBA/PPy composite particles was confirmed. The result of DSC showed that TR of the composite is mainly determined by the core component. The effects of the concentration of polypyrrole, the butyl acrylate content in SBA copolymer and the nature of the counter-anion on the electrical conductivity of compression-moulded samples were studied. It was first found that the electrical conductivity of the samples can be tuned by varying the butyl acrylate content in SBA copolymer and the highest conductivity of the core-shell composite was 0.17 S. cm^-1