绿色化学法合成单分散Zn_(0.3)Fe_(2.7)O_4纳米微粒

磁性纳米材料Zn_(0.3)Fe_(2.7)O_4具有极好的生物相容性,但是在传统常规有机溶剂液相法制备过程中,有机溶剂难以除去,纳米颗粒容易聚集并且尺寸难以控制。本研究将绿色化学乙醇/水合成法引入到液相合成过程中不仅可以降低合成过程中有机溶剂对环境的污染而且能大大改善其粒径分散性。本文通过乙醇/水共沉淀法制备了Zn_(0.3)Fe_(2.7)O_4纳米微粒,研究了反应时间、温度、反应物浓度等条件对Zn_(0.3)Fe_(2.7)O_4纳米微粒的形成及相关粒径的影响。通过研究,得到制备Zn_(0.3)Fe_(2.7)O_4最佳的实验条件是:温度60℃,反应物初始浓度1.0 mol·L~(-1),反应时间40 min。     

Fe_3O_4@MOF纳米复合材料高效催化降解废水中罗丹明B

通过共沉淀法分步合成Fe_3O_4/Cu_3(BTC)_2金属有机骨架(MOF)纳米复合材料,并对材料进行了傅里叶红外光谱、X射线衍射、透射电镜和磁化强度表征。结果表明,复合纳米材料具有较好的晶形和磁性,易于分离。在初始溶液pH为5.6、反应温度为40℃、H_2O_2浓度为0.1 mol/L时,0.2 g/L Fe_3O_4/Cu_3(BTC)_2复合纳米材料对质量浓度10mg/L的RhB的脱色率大于98.8%。通过猝灭实验,提出·OH自由基是参与催化降解反应的主要活性中间体。基于经济、高效的催化降解能力和易于分离,Fe_3O_4/Cu_3(BTC)_2MOF材料可用于染料废水中RhB的催化降解去除。     

氧化铝溶胶浸渍法制备氧化铝纤维的工艺研究

为了制备高性能Al_2O_3纤维隔膜,以粘胶纤维为模板,以铝粉、氯化铝、酸性硅溶胶和去离子水制备的Al_2O_3质量分数为10%、15%和20%的氧化铝溶胶为浸渍液,采用浸渍法制备了氧化铝纤维,研究了浸渍液中Al_2O_3的质量分数和煅烧温度(500、900和1 300℃)对氧化铝纤维的影响。结果表明,粘胶纤维在w(Al_2O_3)=15%的Al_2O_3溶胶中浸渍,经1 300℃煅烧后的Al_2O_3纤维表面光滑,直径均匀,纤维的形态较好;随着煅烧温度的升高,Al_2O_3纤维由无定形态向晶态转变。     

介质阻挡放电协同Ag改性钙钛矿型催化剂脱硝研究

采用双极性高压介质阻挡放电协同钙钛矿型催化剂对NO_x进行处理,研究了介质阻挡放电协同不同焙烧温度下La_(0.7)Sr_(0.3)Ni_(0.2)Mn_(0.5)Fe_(0.3)O_3催化剂及A位不同Ag掺杂量的La_(0.7-x)Ag_xSr_(0.3)Ni_(0.2)Mn_(0.5)Fe_(0.3)O_3催化剂在不同反应条件下对去除NO_x的影响,并利用XRD、SEM分析各种催化剂性能。结果表明,焙烧温度为650℃的La_(0.7)Sr_(0.3)Ni_(0.5)Mn_(0.2)Fe_(0.3)O_3催化剂的效果最佳; A位掺杂Ag对催化剂进行改性,NO转化率和NO_x去除率随着Ag质量分数的增大而降低,两者均在添加量为0.1时达到最大,分别为96.62%和85%。     

碳纳米管包覆LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2纳米纤维制备及其电化学性能研究

采用静电纺丝技术结合低温固相煅烧合成了中空多孔的LiNi_(0.8)Mn_(0.1)Co_(0.1)O_2纳米纤维,并通过球磨方式实现了碳纳米管表面修饰LiNi_(0.8)Mn_(0.1)Co_(0.1)O_2纳米纤维。采用TG-DTA、XRD、SEM等分析手段,对合成样品的煅烧温度、物相结构和微观形貌进行表征,然后对其综合电化学性能进行研究。结果表明:CNT表面修饰LiNi_(0.8)Mn_(0.1)Co_(0.1)O_2纳米纤维可显著改善材料的综合电化学性能。其首次放电比容量达到242.8m Ah/g,1C循环50次后容量保持率达到91.61%,2C倍率放电比容量达到165.8m Ah/g。CNT独特的管状结构,促进了LiNi_(0.8)Mn_(0.1)Co_(0.1)O_2纳米纤维比容量的发挥,同时为循环过程中电极体积变化提高缓冲层,改善了材料的电子电导率,结合LiNi_(0.8)Mn_(0.1)Co_(0.1)O_2纳米纤维中空多孔结构为锂离子快速扩散提供了通道,从而实现了LiNi_(0.8)Mn_(0.1)Co_(0.1)O_2纳米纤维比容量、倍率和循环性能的显著提高。     

添加磁性纳米粒子制备气体分离功能炭膜

以聚酰胺酸为炭膜前驱体,分别以Fe_3O_4、γ-Fe_2O_3、Zn_(0.5)Ni_(0.5)Fe_2O_4以及二茂铁为掺杂物,经高温热解制备了4种Fe系物质掺杂的气体分离功能炭膜,对所制备的功能炭膜微结构及磁性能进行了表征.结果表明,各掺杂物在热解炭化过程中发生了物相结构的变化,其中Fe_3O_4和Zn_(0.5)Ni_(0.5)Fe_2O_4纳米粒子对前驱体起到了催化石墨化的作用.气体渗透测试结果表明,各掺杂物所制备的功能炭膜以分子筛分机理为主导进行气体分离,且气体渗透性能都有了显著的提高,特别是小分子气体H2渗透性最大提高了近48倍,Fe3O4掺杂所制备的功能炭膜,其H_2、CO_2、O_2、N_2和CH_4等单组分气体的渗透系数分别达到了12 194、3 433、1 175、136和74 Barters[1Barter=1×10~(-10)cm~3(STP)·cm/cm~2·s·cmHg].经FeO_4、γ-Fe_2O_3和Zn_(0.5)Ni_(0.5)Fe_2O_4掺杂制备的功能炭膜更是提高了H_2/CO_2的分离选择性.     

EDTA-柠檬酸复合络合法制备阴极材料La_(0.4)Sr_(0.6)Co_(0.4)Fe_(0.6)O_3粉体

本文采用EDTA-柠檬酸复合络合法制备了SOFC阴极La_(0.4)Sr_(0.6)Co_(0.4)Fe_(0.6)O_3纳米粉体。并分别通过SEM、TEM、XRD及电化学极化阻抗仪对La_(0.4)Sr_(0.6)Co_(0.4)Fe_(0.6)O_3粉体形貌、尺寸、晶相及电化学性能进行了表征。实验结果表明:采用EDTA-柠檬酸复合络合法获得的干凝胶,经800℃煅烧后可获得粒径为20~30 nm、结晶度高的钙钛矿结构的La_(0.4)Sr_(0.6)Co_(0.4)Fe_(0.6)O_3纳米粉体。以La_(0.4)Sr_(0.6)Co_(0.4)Fe_(0.6)O_3粉体及添加20wt%的GDC粉体制备成的复合阴极在700℃下的极化阻抗为0.15Ω·cm~2、电导率为715 S·cm~(-1)。     

静电纺丝法制备中温固体氧化物燃料电池阴极用纳米La_(0.6)Sr_(0.4)Co_(0.4)Fe_(0.6)O_3纤维

采用静电纺丝技术和溶胶–凝胶法制备了聚乙烯吡咯烷酮(polyvinylpyrrolidone,PVP)/La0.6Sr0.4Co0.4Fe0.6O3(LSCF)复合纳米纤维,经过不同温度煅烧处理,获得了具有单晶结构的LSCF纳米纤维,并对纤维样品的煅烧过程、形貌、物相、结构以及电性能进行了表征。结果表明:PVP/LSCF复合纳米纤维中的水分和有机物在达到560℃前已经完全挥发和分解。经煅烧处理,可获得具有斜方六面体结构LSCF。经800℃煅烧后的LSCF纳米纤维的直径主要分布在130～240nm;以LSCF纳米纤维为阴极制备的单电池在750℃工作温度下,其最大功率密度为1.18W/cm2。与用传统溶胶–凝胶法在相同条件下制得的LSCF粉体相比,其单电池的电流–电压–功率性能有显著提高。     

Zn_(1-x)Co_xO纳米纤维的电纺制备及其吸波性能

采用溶胶-凝胶技术和静电纺丝法制备了聚乙烯吡咯烷酮(PVP)/Zn_(1-x)Co_xO(0～0.08)复合纳米纤维,经过600℃煅烧处理,获得了Zn_(1-x)Co_xO(0～0.08)纳米纤维,通过X射线衍射、Fourier红外光谱、扫描电子显微镜、能谱仪和矢量网络分析仪等技术对样品的物相、形貌、结构和电磁参数进行表征。结果表明:600℃煅烧2 h得到的Zn_(1-x)Co_xO纳米纤维为六方纤锌矿型结构,纤维直径在100 nm左右。相对于纯Zn O纳米纤维,Zn_(1-x)Co_xO纳米纤维的微波吸收性能得到显著提高,其主要吸波机制为介电损耗。当匹配层厚度为2 mm,x=0.04时,样品吸收效果最佳,在频率为8.2 GHz时,最低反射率达-30.6 d B,低于-10 d B的吸收频带为6.7～9.7 GHz,带宽达到3 GHz,与传统溶胶-凝胶法在相同条件下制得的Zn_(0.96)Co_(0.04)O粉体样品相比,吸波性能显著提高。     

基于LaNi_(0.6)Fe_(0.4)O_(3–δ)致密扩散障型极限电流氧传感器的制备及性能

采用溶胶–凝胶法制备LaNi_(0.6)Fe_(0.4)O_(3–δ)(LNF)和Ce_(0.9)Gd_(0.1)O_(1.95)(GDC)粉体,用X射线衍射仪对LNF粉体进行表征,利用扫描电子显微镜对LNF和GDC陶瓷片的断面形貌进行分析。以LNF为致密扩散障、GDC为固体电解质,用Pt浆黏合法制备致密扩散障型极限电流氧传感器,研究了氧含量和温度对氧传感器氧敏性能的影响。结果表明:LNF形成钙钛矿结构,LNF和GDC陶瓷片都烧结致密,无明显气孔;氧传感器在740~820℃温度范围内低氧含量(0.3%~1.1%)中显示出良好的极限电流平台;氧传感器响应时间和恢复时间较短,分别约为18和23 s,并且极限电流值与氧浓度φ(O_2)和温度(T~(–0.5))之间存在较好的线性关系。     

Victrex® poly(ethersulfone) (PES) and Victrex® poly(etheretherketone) (PEEK)

Properties of two high performance engineering thermoplastics, amorphous polyethersulfone (PES) and semicrystalline polyetheretherketone (PEEK), are discussed. Both resins can be processed by conventional techniques, compounded with high performance fibers, and have high service temperature (up to 300°C). Due to the amorphous character PES can be dissolved and spray coated into metals.     

Photopyroelectric Spectroscopic Studies of ZnO-MnO(2)-Co(3)O(4)-V(2)O(5) Ceramics

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO(2) + 0.4Co(3)O(4) + xV(2)O(5)), x = 0-1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300-800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (E(g)) was 2.11 eV for 0.3 mol% V(2)O(5) at a sintering temperature of 1025 °C as determined from the plot (ρhυ)(2)versushυ. With a further increase in V(2)O(5), the value of E(g) was found to be 2.59 eV. Steepness factor 'σ(A)' and 'σ(B)', which characterize the slope of exponential optical absorption, is discussed with reference to the variation of E(g). XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively.     

Calcium silicate hydrate (II) (“C-S-H(II)”)

This semicrystalline phase, originally named ‘calcium silicate hydrate(II)’ by Taylor (1950), has been studied with X-rays, electron optics, chemical investigation of silicate anion type, infrared spectra, and thermal methods. It is structurally related to jennite (C₉S₆H₁₁) and probably also to the fibrous CSH of cement pastes, the three phases forming a sequence of decreasing crystallinity. The specimen studied had approximate composition C₂SH_3.2 after standing over saturated CaCλ₂ at about 15°C. CSH(II) contains metasilicate chains and pyrosilicate groups and has a disordered layer structure. Much of the water can be lost reversibly without significant change in lattice parameters.     

(Ba1-αSrα)4.8(Sm0.7La0.3)8.8Ti18O54陶瓷的微波介电性能

采用固相合成法制备了(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54(α=0.1～0.5)系陶瓷,表征了该陶瓷的相组成和显微结构,测试了微波介电性能.结果表明:α=0.3时,(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54系陶瓷为单相的新钨青铜结构固溶体.α>0.3时,相继出现了第二相BaLa2Ti4O12和La0.66TiO2.993.随α的增加,(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54系陶瓷的相对介电常数(εr)先增大后有所波动,品质因数(Qf)先增大后减小,谐振频率温度系数(τf)单调减小.α=0.3时,在1 350℃烧结的陶瓷的微波介电性能最佳:εr=98.77,Qf=5184GHz,τf=10.9×10-6/℃,优于不掺杂的BaO-Sm2O3-TiO2陶瓷的.     

Poly(butadiene-acrylic acid(g)acrylonitrile(g)acrylic acid)

Summary In the present work we describe, the synthesis and characterization of a new gel obtained by crosslinking a cooligomer of butadiene-acrylic acid (BuAA), by reaction with acrylonitrile and acrylic acid. The purified product was characterized by FTIR, elemental analyses and scanning electronic microscopy. The thermal properties were studied and swelling indexes were determined in different solvents and at different pH values. The capacity of poly(butadiene-acrylic acid(g)acrylonitrile(g)acrylic acid) [gel A] to separate different organic substances, such as amino acids and colorants, was determined.     

Thermal studies of blends of poly(phenylene sulfide) (PPS) with poly(phenylene sulfide sulfone) (PPSS) and with poly(phenylene sulfide ether) (PPSE)

The miscibilities of poly(phenylene) sulfide/poly(phenylene sulfide sulfone) (PPS/PPSS) and poly(phenylene) sulfide/poly(phenylene sulfide ether) (PPS/PPSE) blends were invesigated in terms of shifts of glass transition temperatures T_g of pure PPS, PPSS, a dn PPSE. The crystallization kinetics of PPS/PPSS blends was also studied as a function of molar composition. The PPS/PPSS and PPS/PPSE blends are respectively partially and fully miscible. PPSE shows a plasticizing effect on PPS as does PPS on PPSS, which necessarily improves te processibility in the respective systems. We can control T_g and melting temperature T_m of PPS by varying amounts of PPSE in blends. The melt crystallization temperature T_mc of PPS/PPSE blends was higher than that of the PPSE homopolymer. Therefore, these blends require shorter cycle times in processing than pure PPSE. The overall rate of crystallization for PPS/PPSS blends follows the Avrami equation with an exponent ?2. The maximal rate of crystallization for PPS/PPSS blends occurs at a temperatre higher by 10°C than that for PPS, while the crystallization half time t_1/2 is 4 times shorter. In the cold crystallization range, crystal growth rates increase and Avrami exponents decrease significantly as the temperature increases.     

Photooxidative stability of substituted poly(phenylene vinylene) (PPV) and poly(phenylene acetylene) (PPA)

The addition of side groups to improve the photooxidative stability of polymers used in polymer-based light-emitting diodes (LEDs) is explored. Infrared spectroscopy and computational chemistry techniques are used to study the effects of chemical substitution of the reactive vinylene moiety in poly(phenylene vinylene) (PPV). The bond order of the vinylene group in small oligomers is calculated using semiempirical techniques to assess the improvement in stability toward oxidants such as singlet oxygen. We find that PPV dimers allow relative comparisons across a range of possible substitutions. Experimental results correlate well with these calculations. The addition of electron-withdrawing substituents, such as nitrile groups, to the vinylene moiety is found to be particularly effective in reducing the reactivity of alkoxy-substituted PPV toward singlet oxygen. The photooxidative stability of a poly(phenylene acetylene) (PPA) derivative is also studied. It appears that this family of polymers is more stable toward photooxidation than are its PPV analogs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2451–2458, 1998     

Chemical cross-linking of conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) using poly(ethylene oxide) (PEO)

Hybrid films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) were prepared with different molecular weights of poly(ethylene oxide) (PEO). The cross-linking reaction between PEO and PEDOT:PSS was performed at high temperature and confirmed by using differential scanning calorimeter (DSC), contact angle measurement, and solid-state ¹H NMR. The effect of chemical reaction on the conductivity and morphology of these hybrid films was studied by using 4-point probe and atomic force microscope (AFM), respectively. As-spun PEO/PEDOT:PSS films have lower electric conductivity due to the addition of nonconductive PEO, and exhibits no molecular weight dependence on conductivity. After chemical cross-linking reaction at high temperature, only PEDOT:PSS films with lowest molecular weight PEO additives show enhanced conductivity with increasing reaction time. AFM result indicates that the heat-treated PEO/PEDOT:PSS hybrid films show grain-like morphology compared to ethylene glycol treated PEDOT:PSS films which shows continuous PEDOT domain. In the present work we demonstrate that the cross-linking reaction can be used to improve the wet stability of PEDOT:PSS nanofiber, showing good water resistance and excellent dimensional stability.