Diameter and Density Control of Single‐Walled Carbon Nanotube Forests by Modulating Ostwald Ripening through Decoupling the Catalyst Formation and Growth Processes

A continuous and wide range control of the diameter (1.9?3.2 nm) and density (0.03?0.11 g cm^?3) of single‐walled carbon nanotube (SWNT) forests is demonstrated by decoupling the catalyst formation and SWNT growth processes. Specifically, by managing the catalyst formation temperature and H₂ exposure, the redistribution of the Fe catalyst thin film into nanoparticles is controlled while a fixed growth condition preserved the growth yield. The diameter and density are inversely correlated, where low/high density forests would consist of large/small diameter SWNTs, which is proposed as a general rule for the structural control of SWNT forests. The catalyst formation process is modeled by considering the competing processes, Ostwald ripening, and subsurface diffusion, where the dominant mechanism is found to be Ostwald ripening. Specifically, H₂ exposure increases catalyst surface energy and decreases diameter, while increased temperature leads to increased diffusion on the surface and an increase in diameter.     

Evaluation of Undrained Shear Strength Using Full-Flow Penetrometers

Full-flow penetrometers (the T-bar and ball) are increasingly used on sites with thick deposits of soft clays, particularly prevalent offshore. Full-flow penetration tests were performed at five international well-characterized soft clay test sites to assess the use of full-flow penetrometers to estimate undrained shear strength. Field vane shear data were used as the reference undrained strength. Statistical analyses of strength factors indicates that full-flow penetrometers provide an estimate of undrained shear strength at a similar level of reliability compared to the piezocone. Relationships for estimating the strength factor and soil sensitivity using only full-flow penetrometer data obtained during initial penetration and extraction are developed. A strong dependence of the strength factor on sensitivity was identified and can be used for the estimation of undrained strength. The effectiveness and use of the developed correlations are demonstrated through their application at an additional test site.     

绿色技术

国际信息显示协会首次在研讨会上组织了专门的会议来探讨显示产业中的绿色技术,会议内容包括新型低功耗技术、显示器制造的绿色技术、低功耗电子纸和其它双稳态显示器、节电设备设计以及有源矩阵设备中的绿色技术。     

电源模块的电磁干扰设计

电源设计中即使是普通的直流到直流开关转换器的设计都会出现一系列问题,尤其在高功率电源设计中更是如此。除功能性考虑以外,工程师必须保证设计的鲁棒性,以符合成本目标要求以及热性能和空间限制,当然同时还要保证设计的进度。     

SAG mill system diagnosis using multivariate process variable analysis

Semi‐autogenous grinding (SAG) of ore plays a critical role in a mineral processing plant. In SAG operations, abnormal conditions, such as overload or insufficient ore holdup, often result in inefficient production and unstable operation. It is, therefore, essential to monitor the process using effective technology so that abnormal or faulty conditions can be detected and addressed in a timely manner. In this study, investigation is focused on applying multivariate analysis in the monitoring and diagnosing of an industrial SAG operation. The results show that principal component analysis provides an effective methodology for on‐line monitoring and diagnosis. The detection and removal of faulty conditions will help to provide stable and cost‐efficient operation.     

Application of a novel microwave plasma treatment for the sintering of nickel oxide coatings for use in dye-sensitized solar cells

In this study the use of microwave plasma sintering of nickel oxide (NiO_x) particles for use as p-type photoelectrode coatings in dye-sensitized solar cells (DSSCs) is investigated. NiO_x was chosen as the photocathode for this application due to its stability, wide band gap and p-type nature. For high light conversion efficiency DSSCs require a mesoporous structure exhibiting a high surface area. This can be achieved by sintering particles of NiO_x onto a conductive substrate. In this study the use of both 2.45 GHz microwave plasma and conventional furnace sintering were compared for the sintering of the NiO_x particles. Coatings 1 to 2.5 μm thick were obtained from the sintered particles (mean particle size of 50 nm) on 3 mm thick fluorine-doped tin oxide (FTO) coated glass substrates. Both the furnace and microwave plasma sintering treatments were carried out at ~ 450 °C over a 5 min period. Dye sensitization was carried out using Erythrosin B and the UV–vis absorption spectra of the NiO_x coatings were compared. A 44% increase in the level of dye adsorption was obtained for the microwave plasma sintered samples as compared to that obtained through furnace treatments. While the photovoltaic performance of the DSSC fabricated using the microwave plasma treated NiO_x coatings exhibited a tenfold increase in the conversion efficiency in comparison to the furnace treated samples. This enhanced performance was associated with the difference in the mesoporous structure of the sintered NiO_x coatings.     

CXS chemical dry vacuum pump brings smart vacuum to the process industry

Dry vacuum pumps are now well established around the world as an efficient, reliable option for demanding chemical processing industry applications. Chemical processors are placing new demands on the market, driving an emerging trend for vacuum to be seen as a utility; highly reliable, flexible, and available on demand in a ′plug and pump′ system that requires minimum set up and maintenance. CXS dry vacuum pump systems from Edwards have been in operation worldwide for several years now, and are providing ′utilitarian′ high performing, highly controllable vacuum equipment allowing processors to minimise running costs and reduce environmental performance.     

Conversion of amorphous TiO2 coatings into their crystalline form using a novel microwave plasma treatment

Crystalline titanium dioxide (TiO₂) coatings have been widely used in photo-electrochemical solar cell applications. In this study, TiO₂ and carbon-doped TiO₂ coatings were deposited onto unheated titanium and silicon wafer substrates using a DC closed-field magnetron sputtering system. The resultant coatings had an amorphous structure and a post-deposition heat treatment is required to convert this amorphous structure into the photoactive crystalline phase(s) of TiO₂. This study investigates the use of a microwave plasma heat treatment as a means of achieving this crystalline conversion. The treatment involved placing the sputtered coatings into a 2.45 GHz microwave-induced nitrogen plasma where they were heated to approximately 550 °C. It was observed that for treatment times as short as 1 min, the 0.25-μm thick coatings were converted into the anatase crystalline phase of TiO₂. The coatings were further transformed into the rutile crystalline phase after treatments at higher temperatures. The doping of TiO₂ with carbon was found to result in a reduction in this phase transformation temperature, with higher level of doping (up to 5.8% in this study) leading to lower anatase-to-rutile transition temperature. The photoactivity performance of both doped and un-doped coatings heat-treated using both furnace and microwave plasma was compared. The carbon-doped TiO₂ exhibited a 29% increase in photocurrent density compared to that observed for the un-doped coating. Comparing carbon-doped coatings heat-treated using the furnace and microwave plasma, it was observed that the latter yielded a 19% increase in photocurrent density. This enhanced performance may be correlated to the differences in the coatings' surface morphology and band gap energy, both of which influence the coatings' photoabsorption efficiency.