Nanoraspberry-like palladium/spongy nickel oxide for electrooxidation of five light fuels

The spongy nickel oxide (SNO) was synthesized the solution combustion method. The SNO was selected as a promoter to boost the catalytic activity of nanoraspberry-like palladium (NRPd) toward electrooxidation of five light fuels (LFs): methanol, ethanol, formaldehyde, formic acid, and ethylene glycol. The X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, and field emission scanning electron microscope techniques were used for the materials characterization. In comparison with nonpromoted Pd, the NRPd-SNO electrocatalyst shown an excellent efficiency in parameters like the electrochemical active surface area and anti-CO poisoning behavior. The turnover data and the parameters, including reaction order, activation energy, and the coefficients of electron transfer and diffusion, were evaluated for the each process of LFs electrooxidation. The outcome for NRPd-SNO activity toward LFs electrooxidation was compared to some reported electrodes. The SNO increases the removal of intermediates created in the oxidation of LFs that can poison the surface of palladium catalyst. This is due to the presence of the lattice oxygens in SNO structure and Ni switching between its high and low valances. The compatibility of the adsorption process of LFs on the surface of the NRPd-SNO catalyst with different isotherms was determined by studying the Tafel polarization and calculating the surface coverage.     

CuxNi1-xO nanostructures and their nanocomposites with reduced graphene oxide: Synthesis,characterization, and photocatalytic applications

NiO nanostructure was synthesized using a simple co-precipitation method and was embedded on reduced graphene oxide surface via ultrasonication. Structural investigations were made through X-ray diffraction (XRD) and functional groups were confirmed by Fourier transform infrared spectroscopy (FTIR). XRD analysis revealed the grain size reduction with doping. Fourier transform infrared spectroscopy confirmed the presence of metal-oxygen bond in pristine and doped NiO nanostructure as well as the presence of carbon containing groups. Scanning electron microscopy (SEM) indicated that the particle size decreased when NiO nanostructure was doped with copper. BET surface area was found to increase almost up to 43 m²/g for Cu doped NiO nanostructure/rGO composite. Current-voltage measurements were performed using two probe method. UV–Visible spectroscopic profiles showed the blue and red shift for Cu doped NiO nanostructure and Cu doped NiO Nanostructure/rGO composite respectively. Rate constant for Cu doped NiO nanostructure/rGO composite found to increase 4.4 times than pristine NiO nanostructure.     

纳米NiO粉体的制备及其表征

采用溶胶转化－凝胶法制备了纳米级NiO粉体。Ni(OH)2粉体的TG－DSC分析表明：在升温速率为10℃/min的条件下，粉体在489K时开始显著分解，626K时分解完毕。X－射线衍射分析表明：分解产物为纯净的NiO2。NiO粉体的化学成分分析表明：其纯度高于国家标准。TEM电镜分析表明：NiO粉体呈单分散的球形或棒状颗粒。对NiO粉体的热敏性能有待进一步研究。     

Experimental study of NiO electrical conductivity changes under low oxygen pressures

The electrical conductivity of NiO was measured at 740°C in an oxygen pressure range of 10^–2 –1.3 Torr. By means of continuous recording, longtime experiments were performed. The results show that for any admittance of oxygen, the electrical conductivity initially increased and then decreased to its initial value. For pressures higher than 0.1 Torr the decrease of the signal was reduced and the time required to attain the initial value sometimes reached several days. These results suggest that the electrical conductivity changes may be considered as a transitory phenomenon connected to attaining gassolid equilibrium.     

Oxidation Mechanism of Ni—20Cr Foils and Its Relation to the Oxide-Scale Microstructure

The oxidation behavior of Ni—20Cr foils of 100- and 200-m thickness wasstudied in air between 500 and 900°C. Simultaneously, the morphology,microstructure, and composition of the oxide layers were determined byscanning and transmission electron microscopies. Depending on thetemperature, the oxide layer differed significantly. The scale formedat all temperatures was complex, with an outer NiO layer having columnargrains, and an inner layer of equiaxedNiCr₂O₄+NiO+Cr₂O₃ grains. At low temperatures (500 and 600°C),the chromium content was insufficient to form a continuousCr₂O₃ layer, while such a continuous layer formed at theinner interface at oxidation temperatures of 700 to 900°C. At 600°C,internal oxidation of chromium occurred in the substrate. The oxidationmechanism is described taking into account these morphologies and theoxidation kinetics. The observation of no significant differences betweenthe oxidation behavior of thin strips and thick materials is related to thelimited exposure times of the study.     

醇-水法制备纳米NiO粉末的正交实验研究

纳米NiO粉末具有良好的催化性能、热敏性能及在各种材料中的加工性能,因而被广泛地应用在催化剂、磁性材料、电子元件材料等方面,是一种很有前途的新型功能材料。选用Ni(NO3)2.6H2O为原料,以NH4HCO3为沉淀剂,在醇-水介质中制得了纳米NiO粉末。通过扫描电子显微镜(SEM)对NiO粉末进行了表征。实验过程中,按正交表L8(27)安排了正交实验,通过方差分析确定了醇-水制备纳米NiO粉末的最佳煅烧时间、煅烧温度和醇-水比,并确定了各因素对制备过程的影响程度。     

Al/NiO复合粒子的制备与表征

以N i(NO3)2.6H2O和CO(NH2)2为主要原料,通过均匀沉淀法,90℃恒温12 h,异相成核,在片状金属铝粉表面包覆一层N i2CO3(OH)2,制备出包覆式复合粒子A l/N i2CO3(OH)2。将复合粒子在马弗炉中400℃恒温灼烧2 h,制备出了A l/N iO复合粒子。通过SEM、XRD及粒度测试等分析方法,对复合粒子的形貌、晶体结构及粒径进行了表征。     

Thermoelectric hydrogen sensor using Li x Ni1-x O synthesized by molten salt method

Li-doped NiO was synthesized by molten salt method. LiN_O3-LiOH flux was used as a source for Li doping. NiCl₂ was added to the molten Li flux and then processed to make the Li-doped NiO material. Li:Ni ratios were maintained from 5: 1 to 30: 1 during the synthetic procedure and the chemical compositions after characterization were found from Li_0.08Ni_0.92O to Li_0.16Ni_0.84O. Li doping did not change the basic cubic structural characteristics of NiO as evidenced by XRD studies; however, the lattice parameter decreased from 0.41769 nm in pure NiO to 0.41271 nm in Li_0.16Ni_0.84O. Hydrogen gas sensors were fabricated by using these materials as thick films on alumina substrates. The half surface of each sensor was coated with the Pt catalyst. The sensor, when exposed to the hydrogen gas blended in air, heated up the catalytic surface leaving the rest half surface (without catalyst) cold. The thermoelectric voltage thus built up along the hot and cold surface of the Li-doped NiO made the basis for detecting hydrogen gas. The linearity of the voltage signal vs H₂ concentration was checked up to 4% of H₂ in air (as higher concentrations above 4.65% are explosive in air) using Li_0.10Ni_0.90O as the sensor material. The response time T₉₀ and the recovery time RT90 were less than 25 sec. H₂ concentration from 0.5% to 4% showed a good linearity against voltage. There was minimum interference of other gases and hence H₂ gas can easily be detected.     

Spherical NiO-C composite for anode material of lithium ion batteries

Spherical NiO-C composite was prepared by dispersing spherical NiO in glucose solution and subsequent carbonization under hydrothermal conditions at 180 °C. The microstructure and morphology of the NiO-C and NiO powders were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the electrodes were measured by galvanostatic charge-discharge tests, cyclic voltammetric analysis (CV), and electrochemical impedance spectroscopy (EIS). SEM images showed that the amorphous carbon not only coated on the surface but also filled the inner pores of the NiO spheres. Electrochemical tests showed that the NiO-C composite exhibited higher initial coulombic efficiency (66.6%) than NiO (56.4%), and better cycling performances. The improvement of these properties is attributed to the carbon, as it can reduce the specific surface area of porous sphere, and enhance the conductivity of porous NiO.     

Modification of catalytic performances due to the co-feeding of hydrogen or carbon dioxide in the partial oxidation of methane over a NiO/γ-Al2O3 catalyst

The influence of the addition of 1–10 vol.% of hydrogen or carbon dioxide to the feed during the partial oxidation of methane was studied over a NiO/γ-Al₂O₃ catalyst. The addition of H₂ decreases the conversion and syngas selectivity. This decrease of performance seems to be related to a higher reduction of the catalyst due to the H₂ co-feeding. The addition of CO₂ also appears unfavorable to the production of hydrogen but increases the CO yield. A combination of the dry reforming and the reverse water gas shift reactions is suggested to explain the observed modifications in the product yields.