Novel 3-D urchin-like Ni– Co–W porous nanostructure as efficient bifunctional superhydrophilic electrocatalyst for both hydrogen and oxygen evolution reactions

Fabrication of an electrocatalyst with remarkable electrocatalytic activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important for the production of hydrogen energy. In this study, Ni–Co–W alloy urchin-like nanostructures were fabricated by binder-free and cost-effective electrochemical deposition method at different applied current densities and HER and OER electrocatalytic activity was studied. The results of this study showed that the microstructure and morphology are strongly influenced by the electrochemical deposition parameters and the best electrocatalytic properties are obtained at the electrode created at the 20 mA.cm⁻²applied current density. The optimum electrode requires −66 mV and 264 mV, respectively, for OER and HER reactions for delivering the 10 mA cm⁻² current density. The optimum electrode also showed negligible potential change after 10 h electrolysis at 100 mA cm⁻², which means remarkable electrocatalytic stability. In addition, when this electrode used as a for full water splitting, it required only 1.58 V to create a current density of 10 mA cm⁻². Such excellent electrocatalytic activity and stability can be related to the high electrochemical active surface area, being binder-free, high intrinsic electrocatalytic activity and hydrophilicity. This study introduces a simple and cost-effective method for fabricating of effective electrodes with high electrocatalytic activity.     

Hydrogen production from organic fatty acids using carbon-doped TiO2 nanoparticles under visible light irradiation

The photocatalytic production of H₂ using carbon-doped TiO₂ (CTiO₂) nanoparticles has been investigated in single or mixed systems of organic fatty acids (OFAs) under visible light irradiation, including acetic acid, propionate acid, butyric acid and lactic acid. When OFAs were applied at the same electron density (10 e-eq L^?1), the H₂ evolution rates followed the order of propionic acid > butyric acid ≈ acetic acid > lactic acid, whereas at the same molar concentration (0.5 mol L^?1), that order changed to lactic acid > acetic acid > butyric acid ≈ propionic acid. This result implied that the electron transfer efficiency differed from four OFAs, probably due to their different affinity with CTiO₂. O₂^?? and CH₃? partially contributed to OFAs degradation and H₂ production. The quantum dynamics simulations of electron transfer revealed that the dominant mechanism of H₂ production was direct electron transfer from adsorbed OFAs to CTiO₂. This work aims to pursue the synergy of solar energy utilization and conversion of OFAs into H₂.     

Enhanced photoelectrochemical performance of TiO2 through controlled Ar+ ion irradiation: A combined experimental and theoretical study

Here we demonstrate that the performance of TiO₂ electrodes for photoelectrochemical water oxidation can be effectively enhanced through oxygen vacancy doping. The ion irradiation is a simple method to introduce oxygen vacancies on the surface and into the interior of TiO₂ for making oxygen-deficient titania (TiO_2-x). The TiO_2-x thin films exhibit obvious increase in the performance of photoelectrochemical water splitting under light irradiation. The photoconversion efficiency η of the TiO_2-x photoanode is 0.5-fold higher than that of the pristine TiO₂ photoanode, which benefits from the introducing of oxygen vacancies produced by ion irradiation. While the irradiation-induced titanium vacancies act as trapping centers for charge carriers and decrease the photoelectrochemical performance of the samples. Positron annihilation spectroscopy (PAS) was used to study the type of the formed vacancies. Combining experimental with theoretical study, this study demonstrates that ion irradiation technique combing with thermal annealing could be an effective way to enhance the performance of photoanode for water splitting.     

Fabrication of ZnO/SrTiO3 nanoarrays and its photoelectrochemical performances

The ZnO/SrTiO₃ nanomaterials were fabricated by a chemical conversion hydrothermal method in order to utilize the high electron transfer rate of one-dimensional ZnO nanorods and photocatalytic activity of SrTiO₃. The technological parameters, such as TiO₂ sol concentration, TiO₂ sol dipping cycle, Sr(NO₃)₂ concentration and reaction temperature, were investigated in the synthetic process and the reaction mechanism of the ZnO/SrTiO₃ nanomaterials was proposed. A photocurrent density of 7.53 mA/cm² was obtained for the as-prepared ZnO/SrTiO₃ photocatalyst, attributed to its improved absorption spectrum and appropriate nanostructure, which indicates a potential application in photoelectrochemical water splitting.     

聚合砂浆与混凝土粘结劈拉强度的试验研究

进行了砂浆和不同强度混凝土的粘结劈拉试验,试验结果表明,聚合砂浆与混凝土之间的劈拉破坏为粘结面破坏,粘结劈拉强度随混凝土强度的增大而增大。     

玄武岩纤维混凝土冲击劈拉特性研究

利用直径100 mm的SHPB试验系统,对不同纤维体积掺量的玄武岩纤维混凝土进行平台巴西圆盘试验,研究其在冲击荷载作用下的劈裂拉伸特性。试验结果表明:BFRC的静态劈拉强度和静态抗压强度随纤维体积掺量的增大呈先增大、后减小的变化趋势;随着冲击弹速的提高,BFRC的冲击劈拉强度及冲击劈拉韧度不断增大,表现出明显的冲击强化效应;掺入玄武岩纤维可以有效提高BFRC的冲击劈拉性能,使得同一弹速下BFRC的冲击劈拉强度和冲击劈拉韧度较素混凝土普遍增大;基于本文的试验条件及配合比,玄武岩纤维的相对最优体积掺量为0.2%。     

旋轮参数对铝合金分形旋压的影响规律

铝合金分形旋压是一个复杂的多因素耦合影响的塑性成形过程,研究其旋轮参数对成形过程的影响可为相关成形参数的确定和优化设计提供理论依据。基于建立的可靠的铝合金分形旋压三维有限元模型,文章研究揭示了旋轮分形角、旋轮圆角半径、旋轮轴向进给比等旋轮参数对成形过程中的切向拉应力、周向压应力以及成形凸缘的不均匀变形程度和最终壁厚偏差的影响规律。结果表明,增大旋轮分形角,可以消除旋轮前方的金属堆积和降低成形过程中坯料开裂失效的可能性,可以使得成形凸缘的不均匀变形程度减小和成形精度降低;旋轮圆角半径的改变,对消除旋轮前方的金属堆积和降低成形过程中坯料开裂失效的可能性影响并不明显,但增大旋轮圆角半径,可以使得成形凸缘的不均匀变形程度增大和成形精度升高;旋轮轴向进给比的改变,对消除旋轮前方的金属堆积和成形凸缘的成形精度的影响并不明显,但增大旋轮轴向进给比,可以降低成形过程中坯料开裂失效的可能性,可以使得成形凸缘的不均匀变形程度减小。     

不同初始缝高比楔入劈拉试件断裂试验研究

为研究初始缝高比对混凝土断裂性能的影响,设计4组共32个不同初始缝高比的试件进行楔入劈拉试验。测定试件断裂过程中的荷载、裂缝张口位移、混凝土应变等参数的特征值及全过程曲线。以双K断裂理论为基础,计算不同初始缝髙比试件的有效裂缝长度a_c、起裂断裂韧度Kⁱⁿⁱ_IC和失稳断裂韧度K^un_IC等断裂参数。试验结果表明:有效裂缝长度a_c随缝高比的增大而增大,裂缝亚临界扩展量Δa_c随缝高比的增大而减小;起裂断裂韧度不受初始缝高比的影响,失稳断裂韧度随缝高比的减少有所增大,当a₀/D≥0.5时,为一常数。     

新老混凝土粘结强度的影响因素分析

新地第混凝土粘结是工程施工与老化病害结构修补补强中经常面临的一个问题。目前，们们对老老混凝土粘结的机理和力学性能还缺乏足够的了解，由于粘结面破坏造成的结构功能嫁化甚至工程事故也时有发生。鉴于此，在对影响新老混缔造占结强度的因素进行试验研究的基础上，采用方差分析法对有关因素进行了分析，结果表明，粘结面的处理方式、粗糙度及新混凝土的配合比对粘结强度影响较大。     

瞬间全溃溃坝波的传播、反射和绕射的数值模拟

将二维浅水方程解耦并进行空间差分分裂，应用通量限制的组合型ＴＶＤ格式，分别求解分裂后的一维双曲型方程组，针对瞬间全溃情况下溃坝波的运动问题，对溃坝波的传播、反射和绕射进行数值模似，揭示出溃坝波复杂的运动特性，为溃坝灾害性分析和防灾减提供科学依据。