Pd增强缺陷态TiO2纳米管阵列的光催化产氢性能

通过光还原沉积法, 利用氧空位诱导作用, 在Ni掺杂的缺陷态TiO₂纳米管阵列(TNT-Ni)上得到金属 Pd含量不同的Pd-TNT-Ni催化剂. 采用场发射扫描电子显微镜(SEM)、 X射线光电子能谱(XPS)、 紫外-可见 漫反射(UV-Vis DRS)、 表面光电压(SPV)、 光致发光光谱(PL)和电化学测试等表征手段, 探究了Pd与Ni掺杂的缺陷态TiO₂纳米管阵列之间的强相互作用对其光吸收特性和载流子分离及传输效率的影响, 阐明了强相互 作用对材料光催化活性的调控机理, 提出了Pd增强Pd-TNT-Ni光催化性能的作用机理. 结果表明, 通过光还 原法制备的Pd纳米颗粒尺寸为10~20 nm的Pd₁₂₀-TNT-Ni样品的光响应值为4.22 mA/cm², 是未负载Pd样品光 响应值(1.14 mA/cm²)的3.7倍, 其具有最佳的平均产氢速率(5.16 mmol·g^?1·h^?1), 是TNT样品平均产氢速率 (0.45 mmol·g^?1·h^?1)的12倍, 表明Pd与缺陷态TiO₂纳米管阵列之间的强相互作用驱动了载流子的分离及传输, 且Pd作为电子捕获势阱及反应活性位点, 显著提高了材料的光催化性能.     

P-Al/NaX结构和酸碱性位调控对甲苯甲醇侧链烷基化性能影响

采用水热法原位合成了P-Al/NaX催化剂,然后通过浸渍NaOH对其进行酸碱性调控,并探究了它在甲苯甲醇侧链烷基化反应中的催化性能。结合X射线衍射（XRD）、X射线光电子能谱（XPS）、N₂吸附-脱附等表征及催化活性数据发现,原位负载P、Al后,合成的磷铝硅酸盐（Na₁₃Al₂₄Si₁₃P₁₁O₉₆·H₂O）结构展现出较好的甲苯甲醇侧链烷基催化活性;随着NaOH负载量的增加,乙苯和苯乙烯的选择性呈先上升后下降的趋势,当负载质量分数为9%的NaOH时,苯乙烯选择性为45.84%,乙苯和苯乙烯的收率之和达到63.08%。这可能是由于NaOH的负载有利于催化剂表面碱性的提高和酸性的降低,而高的强碱性位和弱酸性位数量有利于甲苯甲醇侧链烷基化反应的进行。     

A theory of finite tensile deformation of double-network hydrogels

A continuum damage model was developed to describe the finite tensile deformation of tough double-network (DN) hydrogels synthesized by polymerization of a water-soluble monomer inside a highly crosslinked rigid polyelectrolyte network. Damage evolution in DN hydrogels was characterized by performing loading-unloading tensile tests and oscillatory shear rheometry on DN hydrogels synthesized from 3-sulfopropyl acrylate potassium salt (SAPS) and acrylamide (AAm). The model can explain all the mechanical features of finite tensile deformation of DN hydrogels, including idealized Mullins effect and permanent set observed after unloading, qualitatively and quantitatively. The constitutive equation can describe the finite elasto-plastic tensile behavior of DN hydrogels without resorting to a yield function. It was showed that tensile mechanics of DN hydrogels in the model is controlled by two material parameters which are related to the elastic moduli of first and second networks. In effect, the ratio of these two parameters is a dimensionless number that controls the behavior of material. The model can capture the stable branch of material response during neck propagation where engineering stress becomes constant. Consistent with experimental data, by increasing the elastic modulus of the second network the finite tensile behavior of the DN hydrogel changes from necking to strain hardening.     

基于氮掺杂活性炭催化氧化合成氮甲基氧化吗啉的研究

以三聚氰胺为氮源,商用活性炭为研究对象,通过“浸渍吸附+高温热处理”的方式制得系列氮掺杂活性炭,并用于催化氧化合成氮甲基氧化吗啉（NMMO）。采用N₂吸附/脱附、Raman、XPS等对氮掺杂活性炭的孔结构和表面性质进行了表征。结果表明：随着三聚氰胺负载量的增大,氮掺杂活性炭的表面碱性含氮官能团含量增大,进而体现出更好的催化氧化合成NMMO活性。最佳催化剂（ACO850-20N）在催化剂加量为0.02 wt%,反应温度70 ℃和反应时间4 h的工艺条件下,氮甲基吗啉的转化率和NMMO收率可达99.76%和94.31%。      

Robust nickel silicate catalysts with high Ni loading for CO2 methanation

CO₂ is the main component of greenhouse gases and also an important carbon source. The hydrogenation of CO₂ to methane using Ni-based catalysts can not only alleviate CO₂ emissions but also obtain useful fuels. However, Ni-based catalysts face one major problem of the sintering of Ni nanoparticles in the process of CO₂ methanation. Thus, this work has synthesized a series of efficient and robust nickel silicate catalysts (NiPS−X) with different nickel content derived from nickel phyllosilicate by the hydrothermal method. It was found that the Ni loading plays a critical role in the structure and catalytic performance of the NiPS−X catalysts. The catalytic performance gradually increases with the increase of Ni loading. In particular, the highly dispersed NiPS-1.6 catalyst with a high Ni loading of 34.3 wt% could obtain the CO₂ conversion greater than 80%, and the methane selectivity was close to 100% for 48 h at 330 °C and the GHSV of 40,000 mL g⁻¹ h⁻¹. The excellent catalytic property can be assigned to the high dispersion of Ni nanoparticles and the strong interaction between the active component and the carrier, which is derived from a unique layered silicate structure with lots of nickel phyllosilicate and a large number of Lewis acid sites.     

Rate sensitivity and deformation mechanism of semi-crystalline polymers during instrumented indentation

Instrumented indentation tests using both constant loading rate (CLR) and continuous stiffness measurement (CSM) operation modes were performed to investigate the deformation mechanism and their sensitivity to the deformation rate in semi-crystalline polymers through the quantitative analysis of load-depth loading and unloading curves. The strain rate was constant during the CSM tests, while the strain rate decreased with the increasing of loading time in CLR tests. The mechanical response mechanism of the semi-crystalline polymers to these tests was very complicated because of the combined effects of strain-hardening in the crystal phase and strain-softening in the amorphous phase. Results show that the loading index m reflects the strain-hardening or strain-softening response during indentation. When m > 2, the mechanical response was due to the strain-hardening, and when m < 2, the response was due to strain-softening. A method based on the measured contact hardness was proposed to obtain the unloading stiffness, and the other mechanical parameters could then be determined according to the unloading stiffness.     

Enhanced Physical and Mechanical Properties of Nitrile-Butadiene Rubber Composites with N-Cetylpyridinium Bromide-Carbon Black

The physical and mechanical properties of nitrile–butadiene rubber (NBR) composites with N-cetylpyridinium bromide-carbon black (CPB-CB) were investigated. Addition of 5 parts per hundred rubber (phr) of CPB-CB into NBR improved the tensile strength by 124%, vulcanization rate by 41%, shore hardness by 15%, and decreased the volumetric wear by 7% compared to those of the base rubber-CB composite.     

Influence of Musa acuminate bio-filler on the thermal,mechanical and visco-elastic behavior of poly (propylene) carbonate biocomposites

Biocomposites were fabricated using poly(propylene) carbonate as matrix and cellulosic polysaccharide banana (Musa acuminate) peel powder as filler in varying concentrations (5–25?wt.%) and were characterized for their functional properties. Microscopic analysis indicated the uniform distribution and existence of microfibrils in the filler. The thermal stability of the composites was lower than the matrix till 320?°C, beyond which it increased. The visco-elastic and mechanical behavior of the biocomposites was found to be enhanced with the addition of fillers. Thus, with better thermal, visco-elastic, and mechanical properties, the biocomposite films can be a replacement for the non-biodegradable polymers for packaging applications.     

Modification of the resistance of two epoxy resins to accelerated weathering using calcium sulfate as a photostabilizer

Epoxy-timber composites have received increasing attention during the last decades because there are many advantages related to their uses as construction materials in applications such as timber bridges. However, the durability of epoxy-timber composites under outdoor conditions has become a concern for many epoxy resins. This study evaluated the chemical, thermal, and mechanical properties of two cured epoxies, the product of the diglycidyl ether of bisphenol A with 2,4-trimethyl-1,6-hexanediamine (DGEBA-TMDA) and the analogous resin prepared with the hydrogenated diglycidyl ether of bisphenol A (HDGEBA-TMDA), each mixed with 2?wt. % calcium sulfate (CS). We hypothesized that the use of CS, as an inorganic UV absorber, could decrease undesirable effects arising from exposure to UV light, moisture, and extreme temperatures.

An accelerated aging chamber simulated natural weathering for 1, 2, 3, 4, and 6?months. Chemical changes in cured epoxy systems over time in the presence and absence of CS fillers were determined using Fourier transform infrared spectroscopy (FT-IR). Thermal degradation profiles before and after exposure to accelerated weathering were followed by thermogravimetric analysis (TGA). The glass transition temperatures (T_g) before and after accelerated weathering were measured, and the effect of accelerated weathering on the surface morphology of the epoxy systems was investigated by scanning electron microscopy (SEM). In the presence of CS, after 6?months accelerated weathering the tensile strength of DGEBA-TMDA reduced by 23.8?±?2.4%, compared to 46.5?±?5.5% in its absence, while the corresponding values for HDGEBA-TMDA were 21.4?±?2.1% and 28.7?±?1.8%.     

Photocatalytic Organic Syntheses: Selective Cyclization of Amino Acids in Aqueous Suspensions

Photocatalytic reactions occurring at semiconductor particles/solution interfaces can be applied to organic syntheses. In this review article, examples of photocatalytic syntheses of cyclic amino acids by suspended semiconductor particles, e.g., titanium(IV) oxide or cadmium(II) sulfide are introduced and interpreted. Different from the photocatalytic decomposition of pollutants under aerobic conditions, selective conversion of organic compounds can be driven by the photocatalytic reactions under deaerated conditions.