Nanostructured Thin Films via Self‐Assembly of Block Copolymers

Thin films of incompatible block copolymers self‐assemble into highly regular supramolecular structures with characteristic dimensions in the 10–100 nm regime. There is increasing interest in controlling the resulting structures and utilizing them, for instance in the area of nanotechnology. So far, research has concentrated mainly on exploiting the melt structure of diblock copolymers. Recent work on block copolymer solutions and more complex co‐ and terpolymer architectures has revealed a rich variety of novel thin‐film structures, some of which exhibit high complexity and order. In addition, by use of mean field dynamic density functional theory along with well‐controlled experiments, the fundamentals of thin film structure formation have been elucidated. We highlight some aspects of these studies and point to future directions in this lively field of materials science.     

Fabrication of platinum thin films for ultra-high electrocatalytic hydrogen evolution reaction

While the noble metals (e.g., platinum, (Pt)) remain the benchmark electrocatalyst for the hydrogen evolution reaction (HER), their mass production require a reduced metal loading and faster fabrication protocols. The aim of the present work is to prepare Pt thin films by simple and fast fabrication technique, and to evaluate their performance for HER. The thin films of Pt are grown on two substrates, namely titanium foil (Ti) and nickel foam (NF), using a single step aerosol assisted chemical vapor deposition (AACVD) method. The film deposition time are varied from 20 to 60 min. Microscopic analyses suggest a gradual evolution of the films into percolated and/or porous nanostructures, a feature that remains highly desired to allow the maximum access of active sites. The performance of the as-prepared electrodes is evaluated by monitoring the HER in acidic electrolyte. The Pt film on nickel foam (Pt/NF) exhibits better electrical conductivity and smaller charge transfer resistance, while the film deposited on the Ti foil (Pt/Ti) demonstrates superior catalytic activity per active sites. The as-prepared Pt/Ti and Pt/NF electrodes produce 10 mA cm⁻² at overpotential of 28 mV and 26 mV, respectively, better in performance than commercial Pt/C electrode (~39 mV), set a new bench mark electrocatalyst for the HER.     

Comparing the reinforcement capacity of welded steel mesh and a thin spray-on liner using large scale laboratory tests

Steel mesh is used as a passive skin confinement medium to supplement the active support provided by rock bolts for roof and rib control in underground coal mines. Thin spray-on liners (TSL) are believed to have the potential to take the place of steel mesh as the skin confinement medium in underground mines. To confirm this belief, large scale laboratory experiments were conducted to compare the behaviour of welded steel mesh and a TSL, when used in conjunction with rock bolts, in reinforcing strata with weak bedding planes and strata prone to guttering, two common rock conditions which exist in coal mines. It was found that while the peak load taken by the simulated rock mass with weak bedding planes acting as the control sample (no skin confinement) was 2494 kN, the corresponding value of the sample with 5 mm thick TSL reinforcement reached 2856 kN. The peak load of the steel mesh reinforced sample was only 2321 kN, but this was attributed to the fact that one of the rock bolts broke during the test. The TSL reinforced sample had a similar post-yield behaviour as the steel mesh reinforced one. The results of the large scale guttering test indicated that a TSL is better than steel mesh in restricting rock movement and thus inhibiting the formation of gutters in the roof.     

浅埋薄基岩煤层快速推进工作面矿压显现规律研究

基于神东矿区1-2#煤层的赋存条件和开采技术条件,采用FLAC3D数值模拟方法,研究浅埋薄基岩回采工作面快速推进过程中的矿压显现规律,为工作面支架阻力确定和岩层控制提供依据。结果表明,随着推进速度的增加,顶板压力呈现减小趋势;推进速度越快,工作面前方应力集中程度越高,峰值应力距工作面距离越小,应力集中影响范围呈减小趋势;推进速度不同时煤层上部的薄基岩和厚松散层破断都直接波及地表,地表下沉量明显高于相同条件下的正常采深煤层工作面;浅埋采场上覆松散层变形移动过程中难以形成承载结构,荷载估算时不能采用传统的普氏压力拱理论。