One-step floating conversion of biomass into highly graphitized and continuous carbon nanotube yarns

The rapid growth of the demand for carbon nanotubes(CNTs) has greatly promoted their large-scale synthesis and development. However,the continuous production of CNT fibers by floating catalyst chemical vapor deposition(FCCVD) requires a large amount of non-renewable carbon sources. Here, the continuous production of highly graphitized CNT yarns from biomass tannic acid(TA) is reported. The chelation of TA and catalyst promotes the rapid cracking of biomass into carbon source gas, and the pyrolysis cracking produces the reducing gas, which solves the problems of the continuous production of CNT yarns using biomass. Through simple twisting, the mechanical strength of CNT yarn can reach 886 ± 46 MPa, and the electrical conductivity and graphitization(IG/ID) can reach 2 × 10^(5)S m^(-1)and 6.3, respectively. This work presents a promising solution for the continuous preparation of CNT yarns based on green raw material.

Emitter Quality Optimization Using Lightly Doped Phosphorus Diffusion and Thermal Oxide Anneal for Cell Efficiency Improvement in Multi-Crystalline Black Silicon Solar Cells

Improving solar cell performance by increasing solar cell efficiency by various process optimization had always been a simple straight-forward methodology followed in a R&D or in a solar cell manufacturing company. This is also the most cost-effective practice to improve a product performance using the same technology without the need to procure alternative or expensive raw materials or by adopting advanced solar cell processing techniques. Aluminium Back Surface Field (Al-BSF) technology using multi-crystalline wafers (mc-Si) had been a well-established and a dominant product in the solar industry for more than two decades. However, as the industry progresses, the demand for high efficiency solar cells and modules started going up and full area Aluminium BSF based cells suffers from a lot of inherent limitations on cell efficiency. This is primarily due to the intrinsic high density of crystal lattice defects or otherwise called as grain boundary defects present dominantly only in mc-Si wafers. These grain boundaries tends to accumulate several defects and become trap centres which cause high recombination for minority carriers thereby exhibiting lower conversion efficiency and higher dispersion in electrical parameters in batches of tested cells. Years of research using this material have helped to derive the maximum benefits using this mc-Si wafer in producing industrial full area BSF cells and we can say with certainty that the efficiency potential has reached the saturation point with this technology. An interesting development that happened in the area of improving the final product performance using mc-Si wafers at both cell and module level, is by replacing the conventional acid texturing process with an introduction of a nano-texturing process called Metal Catalysed Chemical Etching (MCCE) using specialized chemicals which improves the light trapping capabilities by creation of inverted pyramid texture on the silicon wafer surface and thereby enabling the wafers to absorb sunlight over a broader range of wavelength and incident angle. With this development done in mc-Si wafers in recent past, it is still a daunting task to surpass cell efficiencies beyond 19.0% using this wafer source. Hence for cell manufacturing lines which use mc-Si wafers, there is always a constant need to improve the cell manufacturing processes to reduce the impact of poor intrinsic quality of mc-Si wafers and improve the final product performance without adding any significant cost factor.

Catalytic Decomposition of Nitric Oxide by LaCoO3 Nano-particles Prepared by Rotary CVD

Catalytic direct decomposition of NO by perovskite-type catalysts has attracted much attention for the various possible components and the unique structure. LaCoO_3 nanoparticles were precipitated on a-Al_2O_3 micro powders by rotary chemical vapor deposition（rotary CVD） and its catalytic performance for the decomposition of NO was investigated. LaCoO_3 nano-particles with 100 nm in average diameter and 1.5% in mass were uniformly dispersed on a-Al_2O_3 powder. The conversion of NO increased with increasing temperature from 400 to 950 ℃, and reached 28.7% at 950 ℃. The gas velocity of transformed NO on LaCoO_3 nano-particles catalyst per mass unit was 7.7 mL/（g min）, showing a good catalytic activity over the calculated results of pure catalysts. After five times of aging performance experiments, the NO conversion kept the same value, showing a good aging performance and thermal stability.

Catalysts and thermodynamic coupling of chemical reactions

The condition of occurrence of the thermodynamic coupling of chemical reactions is analysed from kinetics. It is found that the thermodynamic coupling is impossible for those reactions which obey kinetically the mass action law. The thermodynamic coupling of chemical reactions is further analysed in the case with catalyst. It is found that the thermodynamic coupling which is impossible without catalyst may become possible by introducing proper catalyst into the system. This implies that the catalysts can change not only the rates of chemical reactions, but also the behaviors of thermodynamic coupling of chemical reactions, including the direction of some reactions. Such role of catalysts comes into play not by changing the total free energy of the system, but by changing the reaction mechanism.

Effects of bimetallic catalysts on synthesis of nitrogen-doped carbon nanotubes as nanoscale energetic materials

Well aligned nitrogen-doped carbon nanotubes （CNx-NTs）, as energetic materials, are synthesized on a silicon substrate by aerosol-assisted chemical vapor deposition, Tungsten （W） and molybdenum （Mo） metals are respectively introduced to combine with iron （Fe） to act as a bimetallic co-catalyst layer. Cor- relations between the composition and shape of the co-catalyst and morphology, size, growth rate and nitrogen doping amount of the synthesized CNx-NTs are investigated by secondary and backscattered electron imaging in a field emission scanning electron microscope （FESEM） and X-ray photoelectron spectrometer （XPS）. Compared to pure iron catalyst, W-Fe co-catalyst can result in lower growth rate, larger diameter and wider size distribution of the CNx-NTs; while incorporation of molybdenum into the iron catalyst layer can reduce the diameter and size distribution of the nanotubes. Compared to the sole iron catalyst, Fe-W catalyst impedes nitrogen doping while Fe-Mo catalyst promotes the incorporation of nitrogen into the nanotubes. The present work indicates that CNx-NTs with modulated size, growth rate and nitrogen doping concentration are expected to be synthesized by tuning the size and composition of co-catalysts, which may find great potential in producing CNx-NTs with controlled structure and properties,

Catalyst Enhanced Chemical Vapor Deposition of Nano-Particle Nickel Films on Teflon Surface

Films formed with nanosized nickel particles on teflon surface were prepared by means of catalyst enhanced chemical vapor deposition （CECVD） with Ni（dmg）2, Ni（acac）2, Ni（hfac）2, Ni（TMHD）2, and Ni（cp）2 as precursors, and complexes Pd（hfac）2, PdC12 and Pd（η^3-2-methylallyl）acac as catalyst under cartier gas （H2）. The film growth rate depends on the precursors and substrate temperature. The chemical value, purity and surface morphology of the Ni particle films were characterized by X-ray photoelectron spectroscopy （XPS） and scanning electron microscopy （SEM）. The films obtained were shiny with silvery color, and consisted of grains with a particle size of 50-140 nm. The Ni was metallic of which the purity was about 90%-95% from XPS analysis. SEM micrograph showed that the film had good morphology.

Catalysis in biodiesel production-a review

Catalysts play a significant role in transesterification of vegetable oils.Currently,chemical and biological catalysts are being investigated,and both have their inherent merits and demerits.In large-scale applications,these catalysts are expected to be cost effective and environmentally friendly.If the catalyst is homogeneous in its physical form it is more effective than is the heterogeneous catalyst,but its separation from the mixture is a major issue.Some of the heterogeneous catalysts suffer leaching in harsh reaction conditions.Of late,nanocatalysts that demonstrate high efficiency are being studed.Nanoparticles are used in biological catalysts as solid carriers for lipase immobilization.Lipase immobilized on magnetic nanoparticles has proved to be a versatile biocatalyst for biodiesel production.This article reviews the role of various catalytic systems commonly used in the transesterification reaction of oils in biodiesel generation.

Suspended superconducting weak links from aerosol-synthesized single-walled carbon nanotubes

We report a new scheme for fabrication of clean,suspended superconducting weak links from pristine single-walled carbon nanotubes(SWCNT).The SWCNTs were grown using the floating-catalyst chemical vapour deposition(FC-CVD)and directly deposited on top of prefabricated superconducting molybdenum-rhenium(MoRe)electrodes by thermophoresis at nearly ambient conditions.Transparent contacts to SWCNTs were obtained by vacuum-annealing the devices at 900℃,which enabled proximity-induced supercurrents up to 53 nA.SWCNT weak links fabricated on MoRe/palladium bilayer sustained supercurrents up to 0.4 nA after annealing at relatively low temperature of 220℃.The fabrication process does neither expose SWCNTs to lithographic chemicals,nor the contact electrodes to the harsh conditions of in situ CVD growth.Our scheme facilitates new experimental possibilities for hybrid superconducting devices.

High-performance transparent conducting films of long single-walled carbon nanotubes synthesized from toluene alone

Single-walled carbon nanotube(SWCNT)transparent conducting films(TCFs)are attracting increasing attention due to their exceptional optoelectronic properties.Toluene is a proposed carbon source for SWCNT synthesis,but the growth parameters of SWCNTs and their TCF optoelectronic performance(i.e.,sheet resistance versus transmittance)have been insufficiently evaluated.Here,we have for the first time reported a systematic study of the fabrication of high-performance SWCNT TCFs using toluene alone as the carbon source.The mechanisms behind each observed phenomenon were elucidated using optical and microscopy techniques.By optimizing the growth parameters,high yields of SWCNT TCFs exhibiting a considerably low sheet resistance of 57Ω/sq at 90%transmittance were obtained.This competitive optoelectronic performance is mainly attributable to long SWCNT bundles(mean length is 41.4μm)in the film.Additionally,a chirality map determined by electron diffraction displays a bimodal distribution of chiral angles divided at 15°,which is close to both armchair and zigzag edges.Our study paved the way towards scaled-up production of SWCNTs for the fabrication of high-performance TCFs for industrial applications.