Substrate-independent and large-area synthesis of carbon nanotube thin films using ZnO nanorods as template and dopamine as carbon precursor

In this study, we introduce a method for large-area and substrate-independent synthesis of the big-inner-diameter carbon nanotube (BIDI-CNT) thin films by utilizing polydopamine (PDA) as carbon source and ZnO nanorods (NRs) as sacrificing template for the first time. ZnO NRs with hexagonal morphology were coated with PDA films via the ammonium persulfate-induced polymerization of dopamine at neutral pH for avoiding the degradation of amphoteric ZnO at alkaline pH needed by the conventional oxygen-induced polymerization of dopamine. After carbonization in N₂ atmosphere at 500 °C followed by ZnO removal, the hollow BIDI-CNTs with tuned wall thickness and hexagonal morphology were obtained. In addition, the obtained BIDI-CNTs were found to be N-doped. Furthermore, on the base of the outstanding substrate-independent growth properties of both ZnO NRs and PDA, the large area thin films of the N-doped BIDI-CNTs could be synthesized on various solid substrates, for instance, Al₂O₃, gold, fluorine-doped tin oxide-coated glass, platinum, silicon, mica, and quartz.     

High magneto-optical performance of GdFeO3 thin film with high orientation and heavy Ce3+ doping

In this paper, GdFeO₃ thin films with high orientation and heavily Ce³⁺ doping were deposited by radio frequency magnetron sputtering with a matching substrate. The effects of substrates and Ce³⁺ doping on the structure, magnetic and magneto-optical properties of thin films were investigated. As a result, Ce³⁺ doping can not only increase the saturation magnetization but also greatly enhance the magnetic circular dichroism signals of Ce:GdFeO₃ thin films. Based on the density functional theory calculation, it can be found that the probability of electron transition between Ce³⁺ 4f and Fe³⁺ 3d and the difference in the absorption of right and left circularly polarized light increase, which results in the strong magneto-optical effect of Ce:GdFeO₃/STO thin films.     

Mechanochemical fabrication of geopolymer composites based on the reinforcement effect of microfibrillated cellulose

In this study, microfibrillated cellulose-reinforced geopolymer organic/inorganic hybrid materials, were prepared via a simple green mechanochemical method. The interaction between microfibrillated nanocellulose and geopolymer was further investigated by molecular dynamics simulation. The study established that mechanical ball milling could effectively promote the microfibrillation of bamboo pulp fibers to form reinforced geopolymer composites with a uniformly distributed cellulose skeleton network. The compressive strength of geopolymer blended with 2% microfibrillated cellulose was shown to be 85.1% higher than that of the pristine geopolymer after 30 days. In addition, the hybrid system was found to maintain excellent thermal stability due to the effective protection of the biomass components by the inorganic matrix. This one-step mechanochemical process provided an efficient approach for preparing geopolymer composites, which offers significant application potential for use in road repairs, high-temperature-resistant materials, and additive manufacturing via 3D printing.     

(Ce,Gd):YAG-Al2O3 composite ceramics for high-brightness yellow light-emitting diode applications

(Ce,Gd):YAG-Al₂O₃ composite ceramics were prepared for high-brightness yellow LED (565?590 nm) applications. Phase fraction, microstructure, thermal quenching effect, and luminescent properties of composite ceramics with varying compositions were studied in detail. Collaborating composite ceramics with InGaN blue chips, the relationship between thermal conductivity, temperature rise during LED-driven phosphor conversion, and steady-state luminous efficiency were elucidated. As the proportion of Al₂O₃ increases from 0 to 40 wt%, the steady-state luminous efficiency of yellow LED is enhanced from 100.88–109.49 lm W^?1, benefiting from the increased thermal stability and reduced operating temperature of ceramics (from 141.1–132.2 °C). Additionally, scattering behavior and extraction efficiency of composite ceramics with different thicknesses were investigated.     

Ag掺杂TiO2纳米管制备与性能研究

常压下,采用强碱熔融-水热法,制备了Ag修饰复合TiO2纳米管,并就材料的组织与形貌进行了表征。XRD表征显示复合TiO2纳米管由锐钛矿和金红石相组成。TiO2纳米管形貌清晰,较均匀整齐,管径约为3～5nm,由3～5层单壁组成,管壁壁厚约为0.5nm,其中,Ti和Ag纳米颗粒清晰地附着在纳米管之间以及最外层纳米管壁上。在350nm波长以内,均出现带-带跃迁。表面光电压谱(surface photovoltagespectroscopy,SPS)和场致诱导表面光电压谱(electricfield-induced surface photovoltage spectroscopy,FISPS)光伏响应强度随着外电场极性的改变作不对称变化,出现束缚激子亚带隙跃迁的特征。Ag修饰对TiO2纳米管光伏响应影响大。     

PtS2/g-C3N4 van der Waals heterostructure: A direct Z-scheme photocatalyst with high optical absorption,solar-to-hydrogen efficiency and catalytic activity

Using two-dimensional semiconductors to build heterojunction as photocatalyst for water splitting is an important green and clean energy technology and has wide development prospects. Here, the monolayered PtS₂ and g-C₃N₄ are used to build the direct Z-scheme van der Waals (vdW) heterostructure, and the structure, electrical, Bader charge, optical properties and solar-to-hydrogen efficiency are calculated in detail through first-principle calculations. The direct Z-scheme PtS₂/g-C₃N₄ vdW heterostructure has an inherent type-II band alignment that enables it to reduce the photogenerated carriers aggregation, and it also possesses a decent band edge position to fully induce the redox reactions of decomposed water. The charge density shows that PtS₂ monolayer is negatively charged while g-C₃N₄ monolayer is positively charged, and the interface potential drop of PtS₂/g-C₃N₄ vdW heterostructure forms a built-in electric field with the direction from g-C₃N₄ to PtS₂. The PtS₂/g-C₃N₄ vdW heterostructure has suitable optical property, outstanding solar-to-hydrogen efficiency, high catalytic activity and thus a promising application prospect for photocatalytic water splitting.     

Electrocatalytic performance of copper selenide as structural phase dependent for hydrogen evolution reaction

A cost-effective, efficient and stable electrocatalyst is a remarkable and significant prospect for hydrogen evolution reaction. By adjusting the copper contents, the Hexagonal and Tetragonal phases of the copper selenide have been synthesized using the solvo-hydrothermal process. Hexagonal phased-based copper selenide has exhibited a greater current density than the Tetragonal phase. However, the augmented structure, lower Gibbs Free energy, greater electrical conductivity and electrochemical surface promoted the electrocatalytic behavior of Hexa-CuSe-1.04 nanosheets. Hexa-CuSe-1.04 nanosheets exhibit a good overpotential of 61 mV at the state of art current density of 10 mAcm⁻² along with Tafel slope of 59 mV dec⁻¹ in 1 M KOH, which is better than the other Hexagonal phase structure, Hexa-CuSe-1.67 nanosheets and Tetra-Cu₂Se-1.30 phase of the copper selenides. The electrocatalyst Hexa-CuSe-1.04 maintains the current density for a long duration and exhibits a similar linear sweep voltammetry curve in 1 M KOH during the chronoamperometry test. Moreover, Hexa-CuSe-1.04 nanosheets show a good Tafel slope of 26 mV dec⁻¹ with a good turnover frequency of 72.40 m s⁻¹ in 0.5 M H₂SO₄ and follow the Tafel phenomenon. Optimized density functional theory reveals that Hexa-CuSe-1.04 exhibits the lower Gibbs of 1.04 eV, free energy, which promotes the desorption and recombination process of the active hydrogen atoms at the active sites and enhanced the hydrogen evolution process. All results indicate the leading potential application of the Hexagonal phase of Hexa-CuSe-1.04 for hydrogen evolution reaction.     

Transient performance during start-up of a two-phase anaerobic digestion process demonstration unit treating carbohydrate-rich waste with biochar addition

The paper reports an experimental investigation into the transient performance during the start-up of a pilot-scale two-phase anaerobic digestion (TPAD) process demonstration unit (PDU) treating food waste with biochar addition. Hydrogen (H₂) was produced in the first phase (R1) and methane (CH₄) was produced in the second phase (R2). A fed-batch operation strategy was applied to the start-up of both phases, followed by semi-continuous operation. Production rates and yields of H₂ and CH₄ and volatile fatty acids (VFA) were measured while the pH and temperature were monitored throughout the process. Fed-batch operation allowed microbe enrichment and gradual VFA production in both phases, which was observed to be efficient in starting up the TPAD PDU. Under semi-continuous operation, R1 produced biogas with composition up to 49% of H₂ and at a yield of 46 L H₂.kg ⁻¹ VS. CH₄ composition and yield reached up to 59% and 301 L CH₄.kg⁻¹ VS in the R2.     

Characterization of naphtha and carbon black obtained by vacuum pyrolysis of polyisoprene rubber

Pure polyisoprene and a commercial rubber sample containing 52% polyisoprene and 31% carbon black were pyrolysed at 500°C and at a total pressure varying between 0.8 and 28.0 kPa. The yields of gas, oil and pyrolytic carbon black (CB_P) changed little with the pyrolysis pressure. However, the oil composition and the CB_P characteristics depended considerably on the pyrolysis pressure. For example, the amount of dl-limonene, a valuable compound in the naphtha fraction, decreased with increasing pyrolysis pressure. The CB_P and the commercial carbon black initially present in the rubber sample were analysed by ESCA, SIMS and SEM. With decreasing pyrolysis pressure the surface chemistry of the CB_P became similar to that of the commercial carbon black initially present in the rubber. Therefore, rubber pyrolysis should be performed at low pressures in order to obtain products with a higher commercial value.     

Uncertainty comparison of three visual odometry systems in different operative conditions

An experimental comparison among visual odometry systems using lenses with three different focal lengths (an ultra wide angle, a medium wide angle and a telephoto lens) is presented. For each focal length, several translational and rotational tests are performed, taking into account and analyzing different positions of the system inside the laboratory. The influence of several operative parameters is analyzed, highlighting their effect on the visual odometry systems equipped with different lenses. Experimental errors and uncertainties obtained by the three systems are compared.