Novel Azaferrocenyliminonickel Catalysts for Olefin Polymerization

Summary: The azaferrocenyliminonickel dibromide complexes 1 bearing a pentaphenylcyclopentadienyl group and a wide range of N‐aryl groups were synthesized and examined as catalysts for ethylene polymerization. Both the ortho‐ (R¹) and para‐substituents (R²) of the N‐aryl groups in 1 were found to strongly influence both the polymerization activity and the properties of the obtained polyethylenes. The effect of changing the polymerization conditions, such as temperature, ethylene pressure, and cocatalyst, was also examined.

Azaferrocenyliminonickel(II ) complexes.     

Fabrication of Metal‐Block‐Copolymer Composite Films by a Palladium‐Catalyzed Electroless Nickel‐Plating Process

Summary: Homogeneous films of PI‐b‐PDMAEMA are prepared on top of silicon (100) substrates. The free film surface shows microdomains of PDMAEMA within a PI matrix. These microdomains act as templates for the highly site‐selective synthesis of metal nanoparticles via palladium‐catalyzed electroless nickel plating. The particle formation is studied by atomic force microscopy in tapping mode and implications for a redox reaction and a nanoparticle growth mechanism on the surface of nanopatterned films are discussed.

Chemical structure of the PI‐b‐PDMAEMA copolymer and AFM phase image of a PI‐b‐PDMAEMA film on Si (100) substrate.     

Experimental Evaluation of Procedures for Heat Capacity Measurement by Differential Scanning Calorimetry

Experimental evaluation of the procedures adopted for heat capacity measurements employing differential scanning calorimetry (DSC) has been carried out by taking nickel and sapphire as test samples. Among the various methodologies reported in literature, the absolute dual step method was chosen for this purpose due to its simplicity and minimum number of measurements required. By proper temperature and heat flux calibration employing indium as reference, it was possible to obtain the calibration factor independent of temperature. This was ascertained by analysing other pure metals namely Sn, Zn, Cd, and Pb and determining their melting temperatures and heats of melting. Various operator- and sample-dependent parameters such as heating rate, sample mass, the structure of the sample, reproducibility and repeatability in the measurements were investigated. Heat capacities of both nickel and sapphire have been determined using the above method. Further, the heat capacity of nickel has also been determined using the widely employed three-step method taking sapphire as the heat flux calibration standard. Both methods yielded the comparable heat capacity values for nickel. Based on the parameters investigated and their influence, it could be concluded that reasonably precise and accurate heat capacity measurements are possible with DSC. One advantage of this method is the elimination of a separate calibration run using a reference material of known heat capacity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Oxidation Kinetics of Ni100–xPx Powders

The oxidation of Ni_100–xP_x(7.3 at%<x<25.0 at%) powders in air in the temperature range 350–450°C was determined by kinetics and X-ray diffraction. The isothermal kinetics was modeled using theGinstling–Brounstein equations. The oxidation process was found to be thermally activated with activation energy 127.8 kJ mol^–1 for x=7.3 at% to 157.7 kJ mol^–1 for x=25.0 at%. It was found that the rate constants for x=7.3 at% were approximately 100 times lower than those for x=25.0 at%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Physicochemical and electrochemical hydriding–dehydriding characteristics of amorphous MgNi x (x=1.0, 1.5, 2.0) alloys prepared by mechanical alloying

 Physicochemical and electrochemical hydriding-dehydriding characteristics of amorphous MgNi _x (x=1.0, 1.5, 2.0) alloys prepared by mechanical alloying have been investigated. It was found that the increase of Ni content in the alloys resulted in greatly enhanced kinetics for both absorption and desorption of hydrogen, while the saturation capacity showed the reverse tendency. Charge–discharge tests showed that the increase in Ni content lead to a significant enhancement in cycle performance of MgNi _x alloy electrodes. X-ray photoelectron spectroscopic and X-ray excited Auger electron spectroscopic investigations indicated the existence of a significantly thicker Ni-enriched layer for the MgNi_1.5 and MgNi_2.0 alloys than for the MgNi alloy. These results reveal that excess of Ni in MgNi _x alloys may improve the cycle performance of alloy electrodes by suppressing the segregation of Mg during electrochemical cycling, and the Ni in the topmost surface layer is mainly responsible for the improvement in the kinetics of hydrogen absorption. Received: 28 August 1999 / Accepted: 23 November 1999     

Evaluation of the corrosion resistance of electroless Ni-P and Ni-P composite coatings by electrochemical impedance spectroscopy

Electroless Ni-P composite coatings have gained a good deal of popularity and acceptance in recent years as they provide considerable improvement of desirable qualities such as hardness, wear, abrasion resistance, etc. The disagreement among researchers on the corrosion behaviour of these coatings warrants a thorough investigation. Among the various techniques available for the determination of corrosion resistance, electrochemical impedance spectroscopy (EIS) is considered to be superior as it provides not only an assessment of the corrosion resistance of different deposits but also enables the mechanistic pathway by which the deposits become corroded to be determined. The present investigation focuses on the evaluation of the corrosion resistance of electroless Ni-P and Ni-P-Si₃N₄, Ni-P-CeO₂ and Ni-P-TiO₂ composite coatings produced using an acidic hypophosphite-reduced electroless nickel bath, using EIS. The study makes evident that the same fundamental reaction is occurring on all the coatings of the present study but over a different effective area in each case. The charge transfer resistance of electroless Ni-P and Ni-P composite deposits are in the range 32,253–90,700 Ω cm², whereas the capacitances of these coatings are in the range 11–17 μF/cm². The improved corrosion resistance obtained for electroless Ni-P and Ni-P composite coatings is due to the enrichment of phosphorus on the electrode surface, which enables the preferential hydrolysis of phosphorus over that of nickel. The better corrosion resistance obtained for electroless Ni-P composite coatings can be ascribed to the decrease in the effective metallic area prone to corrosion. Among the three electroless Ni-P composite coatings, the corrosion resistance is in the following order: Ni-P-CeO₂=Ni-P-Si₃N₄>Ni-P-TiO₂. Electronic Publication     

主晶相为莫来石复合纳米晶的制备、结构表征及性能测试

以高岭土为原料,采用水热晶化法,制得了主晶相为莫来石的复合纳米晶。利用XRD、TEM、BET及TG－TDA以在不同条件下制得的纳米晶物相、粒度及热稳定性进行了表征。对复合纳米晶进行了CO、SO2程序升温脱附性能测试。对负载Ni、Mo、Co进行程序升温还原测试。结果表明：在脱附物中检测出CO2与固体硫,证明吸附质在纳米晶表面发生了反应。微米晶与纳米晶负载Ni、Co、Mn后,随着粒度的不同,负载上的氧化物与载体的相互作用力不同,而表现出不同的峰温与峰面积,表面负载上Ni、Co、Mn的氧化物与载体有结构效应,且随晶体表面结构的不同,而表现出不同的H2消耗量。     

两次双波长分光光度法同时测定原油中的镍和钒

采用系数补偿和双峰双波长的两次双波长分光光度法,以5-B r-PADAP为显色剂、Triton X-100为增溶增敏剂,同时测定原油中N i(Ⅱ)和V(Ⅴ)。N i(Ⅱ)和V(Ⅴ)的线性范围分别为:0~15μg/(25 mL)和0~10μg/(25mL),回收率分别为95.0%~103.0%、96.0%~101.5%,测定结果的相对标准偏差分别为0.39%、3.33%。     

Production of COx-Free Hydrogen and Few-Layer Graphene Nanoplatelets by Catalytic Decomposition of Methane over Ni-Lignin-Derived Nanoparticles

Nickel (Ni)-lignin nanocomposites were synthesized from nickel nitrate and kraft lignin then catalytically graphitized to few-layer graphene-encapsulated nickel nanoparticles (Ni@G). Ni@G nanoparticles were used for catalytic decomposition of methane (CDM) to produce COx-free hydrogen and graphene nanoplatelets. Ni@G showed high catalytic activity for methane decomposition at temperatures of 800 to 900 °C and exhibited long-term stability of 600 min time-on-stream (TOS) without apparent deactivation. The catalytic stability may be attributed to the nickel dispersion in the Ni@G sample. During the CDM reaction process, graphene shells over Ni@G nanoparticles were cracked and peeled off the nickel cores at high temperature. Both the exposed nickel nanoparticles and the cracked graphene shells may participate the CDM reaction, making Ni@G samples highly active for CDM reaction. The vacancy defects and edges in the cracked graphene shells serve as the active sites for methane decomposition. The edges are continuously regenerated by methane molecules through CDM reaction.     

基于碳纳米管和铁氰酸镍纳米颗粒协同作用的葡萄糖生物传感器

将制备的铁氰酸镍纳米颗粒(NiNP)与多壁碳纳米管(CNT)混合, 分散于壳聚糖溶液中, 形成一种新的纳米复合成分(NiNP-CNT-CHIT), 将其修饰在玻碳电极表面. 新复合膜体现了NiNP和CNT之间的协同作用, 由于CNT的良好的传递电子性能, 促使NiNP催化氧化还原能力有了较大的提高. 此NiNP-CNT-CHIT复合膜修饰的玻碳电极在较低电位下对过氧化氢具有良好的电催化性能, 与NiNP-CHIT膜比较, 测定H₂O₂的灵敏度增大了50倍. 通过戊二醛在电极表面固定葡萄糖氧化酶制备了一种新的葡萄糖传感器. 该传感器在－0.2 V下对葡萄糖的线性范围为0.05～10 mmol/L, 检测下限为10 μmol/L.