TiO_2纳米管/g-C_3N_4/石墨烯三元复合材料的制备及其催化果糖降解制备5-羟甲基糠醛的研究

以氧化石墨(GO)、石墨相氮化碳(g-C_3N_4)和P25TiO_2为原料,采用碱性水热法制备了不同g-C_3N_4掺杂量的TiO_2纳米管/石墨烯(TiO_2NT/g-C_3 N_4/RGO)三元复合材料。利用XRD、FT-IR、TEM、XPS等表征手段对其物相结构、微观形貌进行分析,并通过微波辅助加热的方式将其应用于催化果糖脱水制备5-羟甲基糠醛(5-HMF)。结果表明,当g-C_3N_4掺杂量为2%时,利用TiO_2纳米管、g-C_3N_4和石墨烯的协同作用,复合材料催化果糖降解性能最好此时,5-HMF的产率达67.2%。     

还原氧化石墨烯/辐照改性氮化碳降解罗丹明B

染料废水中的典型代表污染物-罗丹明B(RhB)具有色度大、累积性强以及处理难度复杂等问题。本研究采用辐照改性氮化碳(g-C_3N_4)/还原氧化石墨烯复合光催化剂(g-C_3N_4/rGO)降解RhB。通过考察催化剂用量、电子束辐照剂量及rGO负载量对光催化降解RhB的影响。在反应温度为30℃时,复合材料的吸附平衡时间为30 min,且在催化剂浓度为0.04 mg/mL时,180 min完全能将污染物降解。当rGO的比例在4%和辐照剂量在30 kGy时,复合材料表现出最好的吸附能力与光催化降解能力。     

石墨烯/玻璃块体复合材料的制备及性能

本文报道了还原氧化石墨烯/钠钙硅(rGO/SLS)玻璃块体复合材料的热压制备和力学性能。首先以3-氨基丙基三乙氧基硅烷为表面活性剂修饰玻璃粉微粒;然后在水溶液中带负电的氧化石墨烯(GO)纳米片通过静电自组装与被氨基修饰过带正电的玻璃颗粒相结合生成复合颗粒。通过高温真空热压烧结,GO被还原成rGO,从而原位生成rGO/SLS玻璃块状复合材料。结果表明,rGO均匀分布在玻璃基质中,并明显增强了复合材料的机械性能。rGO/SLS玻璃块体复合材料中rGO的含量为0.5%(质量分数)时,复合材料的弯曲强度比纯的SLS玻璃提高了约一倍。     

g-C_3N_4/C/Ag复合材料的制备及其光催化性能的影响

为了提高石墨型氮化碳(g-C_3N_4)的光催化性能,通过水热还原法制备了g-C_3N_4/C/Ag纳米复合材料,并用扫描电子显微镜(SEM),X射线衍射仪(XRD)和高分辨率傅立叶变换红外(FTIR)光谱表征了产品的微观形貌和化学组成。产品的紫外可见光吸收光谱分析表明,加入的纳米银可以提高复合材料的光吸收范围和可见光的吸收强度。用制备得到的四种样品进行了亚甲基蓝的降解实验,发现当反应条件为180℃,反应时间为6 h时,得到的g-C_3N_4/C/Ag纳米复合材料的光催化降解性能最好。表明成功制备出了g-C_3N_4/C/Ag纳米复合材料,其光催化性能比g-C_3N_4更强。     

石墨烯插层介孔氮化碳光催化剂制备及其催化性能研究

以单氰胺,胶态二氧化硅和氧化石墨烯(GO)为原料,采用热聚合的方法制备出了石墨烯插层的介孔氮化碳(mpg-C_3N_4/r GO)光催化剂。对其形态结构及物理化学特性进行了表征和分析,研究了催化剂在氙灯照射下对甲基橙的光催化活性及降解机理,考察了石墨烯掺杂比例对光催化剂催化性能的影响。结果表明,经热聚合反应,GO和mpg-C_3N_4成功复合;相较于g-C_3N_4,mpg-C_3N_4/r GO的比表面积增大11倍。mpg-C_3N_4/r GO的降解效率明显优于g-C_3N_4和mpg-C_3N_4,且优化的GO掺杂质量分数为0.5%,90 min对甲基橙去除率接近100%。在甲基橙光催化降解中(h~+)和(O_2~(·-))是主要活性物质。     

ZnO/g-C_3N_4的制备及其光催化性能研究

以六水硝酸锌、2-甲基咪唑为原料制备氧化锌,分别与尿素、硫脲复合,高温聚合制备ZnO/g-C_3N_4复合材料。利用扫描电子显微镜(SEM)、红外光谱仪(IR)、X射线衍射仪(XRD)对试样进行表征,并对所得试样进行光催化性能测试。光催化测试结果表明,ZnO/g-C_3N_4复合材料比ZnO的光催化性能好,两种不同原料制备的ZnO/g-C_3N_4复合材料催化性能相比,以尿素为原料制备的ZnO/g-C_3N_4复合材料的光催化性能最佳。     

聚偏氟乙烯/石墨烯复合材料的制备及性能研究

用溶液共混法制备出聚偏氟乙烯/氧化石墨烯复合材料(PVDF/GO)，经高温热压将GO还原得到聚偏氟乙烯/还原氧化石墨烯复合材料(PVDF/rGO)。研究了填料种类及含量对复合材料电学性能、热稳定性和力学性能的影响。结果表明：随GO和rGO的添加，两种复合材料的介电常数(ε _r)均变大、介电损耗(tanδ)变化不大；低含量下GO和rGO均能提高PVDF的热稳定性，但rGO对PVDF性能的改善效果更好；随填料含量从0增加到8%(质量)，100 Hz下PVDF/rGO复合材料的ε _r从3.60增加到38.30，PVDF/rGO[4%(质量)]复合材料失重率为5%的分解温度较纯PVDF提高了6.44℃。rGO增强了PVDF的刚性，PVDF/rGO复合材料的拉伸强度先增大后减小，杨氏模量逐渐增大，当rGO含量为4%(质量)时拉伸强度最大，拉伸强度和弹性模量分别较纯PVDF提高了35.30%、22.58%。但GO和rGO都降低了复合材料的击穿场强。     

氧化石墨烯/密胺树脂导电复合材料的制备与性能研究

采用的改进的Hummers法和组合剥离技术制备了氧化石墨烯(GO),并以氧化石墨烯、甲醛溶液、三聚氰胺为原料,采用原位合成技术制备石墨烯/密胺树脂导电复合材料(GO/MF)及含有水合肼的氧化石墨烯/密胺树脂复合材料(GO/MF+N_2H_4),并对其结构、热稳定性和导电性等进行研究分析。试验结果表明:GO/MF+N_2H_4试样的热稳定性最佳,氧化石墨烯的加入,提高了密胺树脂材料的导电性,且添加质量分数0.9%GO的GO/MF+N_2H_4试样出现导电临界值,体积电阻率达到1.5×10~4Ω·m,为制备具有抗静电性能和导电性能的密胺树脂新型复合材料提供一定的基础理论参考。     

聚吡咯/石墨相氮化碳光催化材料的制备及其铀降解性能研究

为了提高g-C_3N_4的光催化性能,通过原位聚合法制备了PPy/g-C_3N_4复合材料。通过SEM、XRD、BET和FTIR等表征手段研究PPy/g-C_3N_4的微观形貌、化学组成以及光催化降解铀的性能。结果表明,PPy抑制了g-C_3N_4晶粒的生长,提高了g-C_3N_4的比表面积。在降解时间60 min,pH=5,U(VI)初始浓度5 mg/L,光催化剂投加量200 mg/L的条件下,g-C_3N_4和PPy/g-C_3N_4复合材料对U(VI)的降解率分别为83.11%和96.20%。重复使用3次后,PPy/g-C_3N_4对U(VI)的降解率仍达92.4%。     

聚吡咯/石墨相氮化碳光催化材料的制备及其铀降解性能研究

为了提高g-C_3N_4的光催化性能,通过原位聚合法制备了PPy/g-C_3N_4复合材料。通过SEM、XRD、BET和FTIR等表征手段研究PPy/g-C_3N_4的微观形貌、化学组成以及光催化降解铀的性能。结果表明,PPy抑制了g-C_3N_4晶粒的生长,提高了g-C_3N_4的比表面积。在降解时间60 min,pH=5,U(VI)初始浓度5 mg/L,光催化剂投加量200 mg/L的条件下,g-C_3N_4和PPy/g-C_3N_4复合材料对U(VI)的降解率分别为83.11%和96.20%。重复使用3次后,PPy/g-C_3N_4对U(VI)的降解率仍达92.4%。     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

The System Si3N4-SiO2-Y2O3

Subsolidus phase relations were established in the system Si₃N₄-SiO₂-Y₂O₃. Four ternary compounds were confirmed, with compositions of Y₄Si₂O₇N₂, Y₂Si₃O₃N₄, YSiO₂N, and Y₁₀(SiO₄)₆N₂. The eutectic in the triangle Si₃N₄-Y₂Si₂O₇-Y₁₀(SiO₄)₆N₂ melts at 1500°C and that in the triangle Si₂N₂O-SiO₂-Y₂Si₂O₇ at 1550°C. The eutectic temperature of the Si₃N₄-Y₂Si₂O₇ join was ∼ 1520°C.     

Compact Swelling in Bi1.4Pb0.6Sr2Ca2Cu3.6Oy During the Formation of High-Tc Superconducting Phase

Compact swelling in Pb-doped Bi-Sr-Ca-Cu-O superconductor has been studied by observing the effects of the size of calcined powders, volatilization of materials, and sintering of high- T _c (2223) powders. The bulk density increases at the early stage of sintering, for about 20 h, and then decreases. Densification occurs when the low- T _c (2212) phase and a liquid phase exist, whereas dedensification occurs with the formation of the 2223 phase regardless of the presence of the liquid. Gas evolution from specimens does not appear to be responsible for compact swelling. Compact swelling is explained by anisotropic growth of thin, platelike 2223 grains in random orientation. When 2223 grains grow in a preferred direction, compact swelling is suppressed.