Photocatalytic oxidation activity of titanium dioxide film enhanced by Mn non-uniform doping

1 Introduction Heterogeneous photocatalysis is an effective technique for reducing the concentration of pollutants at low concentration. It has been demonstrated that almost all organics can be oxidized to generate carbon dioxide, water and simple mineral…     

Graphene as initiator/catalyst in polymerization chemistry

One of the most important applications of graphene-based materials is the formation of nanocomposite materials, where graphene in the bulk-polymer matrix transfers its properties onto the polymeric material. Control of the polymer/graphene interface by attached polymeric interlayers is essential to generate nanocomposites, thus avoiding the aggregation of graphene nanoparticles. Among all graphene materials graphene oxide (GO) and reduced graphene oxide (r-GO) can be prepared on large scales useful for mass production graphene/polymer composites. The direct use of graphene materials as both, the polymerization initiator or catalyst and additive not only diminishes the agglomeration of particles in composites but also reduces the process of composite production to one facile step, which in turn avoids further purification regarding to strong acid initiators and metal particles catalysts. Here, literature activities within the past ∼10 years using graphene-based materials either as initiator or catalyst in different polymerization reactions are reviewed.     

Electrochemical polishing of monocrystalline silicon with specific crystallographic planes

In this study, an electrolytic polishing experimental system was developed to obtain a uniform, flat-surfaced monocrystalline silicon with specific crystallographic planes. Several key factors reflecting specific electrolytic polishing on monocrystalline silicon with specific crystallographic planes were summarized. These factors, including electrolyte, conduction mode, Schottky barrier, semiconductor body resistance, and unidirectional conductivity, were analyzed comprehensively through energy spectrum analysis, theoretical modeling, and potential simulation. The effects of electrolytic polishing process were obtained, and corresponding solutions were proposed. Finally, the electrolytic polishing experiment for monocrystalline silicon with specific crystallographic planes was conducted. A uniform, flat-surfaced monocrystalline silicon with no metamorphic layer was then obtained. The flatness error of the center area was less than 0.201 µm. Furthermore, the crystallographic planes of monocrystalline silicon wafers showed no change.     

Some comments about “Comment on hardness definitions”, by J. Malzbender [J. Eur. Ceram. Soc. 23 (2003) 1355–1359]

Malzbender has suggested a model to determine hardness and elastic modulus as a function of the mechanical energies involved during tip penetration in instrumented indentations tests. However, the values obtained with these expressions are not consistent with the ones determined by the well-accepted Oliver and Pharr method. After revision, based on Malzbender's study itself, equations were rewritten and then, the obtained indentation hardness (H) for soda-lime glass was in agreement with the literature data. However, the reduced elastic modulus (E_r) was still about 20% higher than the values in the literature. Developing Malzbender's proposal by the inclusions of additional mechanical energy assumptions, a new expression for E_r is now suggested. Using the new expression, the hardness and reduced elastic modulus agreed very well with the Oliver and Pharr method.     

Study of the correlation between pitting corrosion and the component ratio of the dual phase in duplex stainless steel welds

Three duplex stainless steel weldments were produced by changing the chromium element to study the correlation between the pitting corrosion characteristics and the component ratio of the dual phase. The pit morphologies showed that metastable pits were generated at a lower pitting resistance equivalent number (PREN) phase. The secondary austenite phases seemed to serve as a path for the corrosive environment regardless of the ferrite number (FN). There is some discrepancy between the measured values (pitting potential (E_p) through polarization test) and expected values (sequence ranked by PREN of weaker phase) in 1 mol l⁻¹ NaCl solution at 60 °C.     

Effects of rare-earth oxide doping on the thermal radiation performance of HfO2 coating

In this study, the REO-HfO₂ (REO = Tb₄O₇, Gd₂O₃ and Sm₂O₃) coatings and pure HfO₂ coatings were prepared by atmospheric plasma spraying. The chemical compositions, morphologies, infrared radiation performance and thermal resistances of the coatings were systematically investigated. The experimental results showed that the Tb₄O₇-HfO₂, Gd₂O₃-HfO₂, Sm₂O₃-HfO₂ and pure HfO₂ coatings had infrared emissivity values of 0.863, 0.852, 0.854 and 0.621, respectively, at room temperature. Based on the phase analysis, the higher infrared emissivity of the REO-HfO₂ coatings could be attributed to the fact that the newly formed RE₂Hf₂O₇ (RE = Tb, Gd and Sm) phase, which had a defective fluorite-type structure, and the RE³⁺ ions enhanced the lattice absorption and electron absorption. Additionally, the Tb₄O₇-HfO₂ coating exhibited a relatively higher infrared emissivity than those of the Gd₂O₃-HfO₂ and Sm₂O₃-HfO₂ coating over the wavelength range of 1–15 μm, which was due to the relatively higher vibrational frequency of the TbO bond in RE₂Hf₂O₇ (RE = Tb, Gd and Sm) and the transformation of Tb³⁺ into Tb⁴⁺ in the Tb₄O₇-HfO₂ system. In addition, the REO-HfO₂ ceramic coatings exhibited excellent thermal resistance, which could withstand high-temperature treatment at 1600 °C for at least 50 h without undergoing a phase change and exfoliation, and the infrared emissivity at different temperatures hardly changed after thermal treatment.     

Condition multi-classification and evaluation of system degradation process using an improved support vector machine

Degradation process is a non-negligible phenomenon in system condition monitoring and reliability practices. Traditional binary-state characterization (i.e., normal and failure) on system health condition may not provide accurate information for maintenance scheduling, and the multi-state classification for degradation process is a necessary step to realize cost-effective condition based maintenance. Support vector machine (SVM) is a useful technique for system condition monitoring and fault diagnosis. However, the SVM classification accuracy of deteriorating system is usually poor, because characteristics of different degradation states may not be very distinctive. This paper presented an improved support vector machine for system degradation classification and evaluation. The core of the proposed method can be summarized as: an improved voting scheme in one-against-one SVM, and an optimization of classification process by utilizing inherent physical property of system state transition. A case study of cooling fan bearing accelerated life time test is conducted to obtain the experimental data, and a comparison before and after optimization shows that the proposed method improves the classification accuracy.     

Investigation of the effect of surface modifications on the mechanical properties of basalt fibre reinforced polymer composites

Unsaturated polyester-based polymer composites were developed by reinforcing basalt fabric into an unsaturated polyester matrix using the hand layup technique at room temperature. This study describes basalt fibre reinforced unsaturated polyester composites both with and without acid and alkali treatments of the fabrics. The objective of this investigation was to study the effect of surface modifications (NaOH & H₂SO₄) on mechanical properties, including tensile, shear and impact strengths. Variations in mechanical properties such as the tensile strength, the inter-laminar shear strength and the impact strength of various specimens were calculated using a computer-assisted universal testing machine and an Izod Impact testing machine. Scanning Electron Microscope (SEM) observations of the fracture surface of the composites showed surface modifications to the fibre and improved fibre–matrix adhesion. The result of the investigation shows that the mechanical properties of basalt fibre reinforced composites are superior to glass fibre reinforced composites. This work confirms the applicability of basalt fibre as a reinforcing agent in polymer composites.     

粉末冶金零件中孔隙的涂镀前封闭处理技术进展

阐述了粉末冶金零件中孔隙的涂镀前封闭处理技术的进展。介绍了粉末冶金的历史沿革及概念,提出、分析了粉末冶金材料在前处理过程中存在的问题,阐述了电镀或者油漆前处理之前进行材料孔隙封闭处理的重要意义,讨论了现代工业应用越来越多的粉末冶金材料的类型及产品零件。针对粉末冶金零件涂镀过程中孔隙中易残留溶液成分,导致表面涂镀层起泡、剥离等问题,介绍了目前采用的粉末冶金零件孔隙涂镀前的封闭处理方法,分析探讨了粉末冶金零件镀前用防锈水封闭处理的优势,并分析了防锈水中缓蚀剂的作用原理。防锈水中缓蚀剂等成分的渗入与扩散,对粉末冶金材料的孔隙产生化学吸附、转化及沉淀,从而封闭和填充粉末冶金材料中的孔隙,可以有效提高粉末冶金零件表面涂镀层的结合力和耐腐蚀性能。