Influence of ultrasonication on the mechanical properties of Cu/Al2O3 nanocomposite thin films during electrocodeposition

To overcome the poor mechanical properties of pure Cu thin films, we performed electrocodeposition to make nanocomposite thin films by incorporating inert Al₂O₃ nanoparticles (50 nm and 300 nm in diameter). In addition, to reduce agglomeration due to their high surface energy, we used ultrasonication during the electrocodeposition. In this paper, we examined the effects of the ultrasonication on the mechanical properties of nanocomposite films with different ultrasonic energy density up to 225 W/cm². Ultrasonication during electrocodeposition efficiently reduced the agglomeration of nanoparticles and reduced the grain size of the Cu matrix. Smaller nanoparticles were more efficiently de-agglomerated by ultrasonication, which resulted in more enhanced mechanical properties in the 50 nm Al₂O₃ nanoparticle-enhanced specimens. Although the addition of nanoparticles in the Cu matrices significantly increased the hardness of the specimens, as observed in nanoindentation tests, we did not observe such an increase in tensile tests. Reducing the grain size by ultrasonication seems to be an important parameter in enhancing the overall mechanical properties of nanocomposites. Ultrasonication provided a significant increase in all mechanical properties, including elastic modulus, yield stress, ultimate tensile stress, and elongation, of all controlled Cu films.     

Conducting semi-IPN based on polyaniline and crosslinked poly(vinyl alcohol)

In the present course of investigation synthesis and properties of a series of polyaniline–PVA-based semi-IPNs are described. PVA component in a PAn–PVA composite solution/dispersion, prepared by steric stabilization mechanism, was crosslinked to give rise to the present IPN. Formaldehyde was used as the crosslinker and the IPNs were isolated in the form of flexible and free-standing films. Morphological and structural properties of the system were studied from FTIR spectra and SEM images. Different solid state properties, viz. dc conductivity at different temperatures, thermal and mechanical properties and moisture regain were also studied and a series of films with good mechanical and thermal properties were obtained.     

热挤压对不同搅拌时间制备的纳米SiCp/Mg-9Al-1Zn复合材料组织和性能的影响

通过半固态搅拌铸造和热挤压变形复合工艺制备出了质量分数为1%的纳米SiCp/Mg-9Al-1Zn镁基复合材料。研究了搅拌时间分别为10min和30min时对纳米SiCp/Mg-9Al-1Zn镁基复合材料的显微组织和力学性能的影响。结果表明,对于铸态的纳米SiCp/Mg-9Al-1Zn镁基复合材料来说,搅拌时间为30min时,基体的晶粒细化,但在晶界处析出的Mg17Al12相数量增多,网状化严重且SiC团聚增加,使得复合材料的力学性能下降。而通过热挤压后,复合材料形成了粗晶与细晶交替的组织结构。特别是对于搅拌时间为30min的复合材料,细晶区增多且纳米SiC颗粒分布更加均匀, 这就使得力学性能高于搅拌10min的挤压态的SiCp/Mg-9Al-1Zn复合材料。     

铜/银合金纳米粒子的制备及表征

研究了铜/银合金纳米粒子的制备方法,用抗坏血酸做还原剂,制备了粒径小的纳米铜粉。由于纳米铜粉的稳定性差,易氧化,为了提高其稳定性,在制备的纳米铜粉中加了少量的Ag+,在纳米铜粉表面还原制备出银纳米层覆盖于在铜上。所制备的纳米铜/银合金纳米粒子稳定性好,具有纳米粒子的效应,有望应用于印制电路的制造。该制备方法可以减少传统印制电路板制作方法的工序,节约资源,且减少对环境的污染。     

Blue-emitting yttria-stabilized tetragonal zirconia nanoparticles capped by PVA

Polycrystalline yttria-stabilized tetragonal zirconia nanoparticles having a grain size around 50-80 nm were fabricated in aqueous poly (vinyl alcohol) (PVA) solution by mechanical attrition in a planetary mill, with the PVA used as a capping agent. The surface-modified nanoparticles displayed a significant near-band-edge photoluminescence with emission band centered at 428 nm due to the good surface passivation of the nanoparticles by the PVA molecules. An enhancement of the blue emission was observed when the nanoparticles were embedded in solid PVA matrix. Elevating the temperature of the zirconia nanoparticle solution from 337.5 to 357.5 K lead to temperature quenching of the luminescence due to the decrease of emissive centers caused by desorption of PVA from the nanoparticle surface.     

兼具抗疲劳和抗菌功能的双网络水凝胶的构筑及性能

目的 解决水凝胶力学强度过低问题,同时赋予水凝胶抑菌功能,满足应用需求。方法 以离子交联的海藻酸盐为第1层网络,以化学交联的聚丙烯酰胺(PAAm)为第2层网络,借助p H缓释调节剂D–(+)–葡萄糖酸δ–内酯(GDL)制备Cu²⁺交联的海藻酸盐–聚丙烯酰胺(TG–Cu)抑菌水凝胶。利用傅里叶红外光谱(FITR)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)等手段表征双网络水凝胶的物理和化学结构。通过拉伸、压缩、Mullins测试和循环拉伸试验,研究TG–Cu水凝胶材料的力学强度和抗疲劳性能,通过细菌培养、稀释涂布平板法和活死菌荧光染色手段评价水凝胶的抑菌性能,通过ICP探究Cu²⁺的释放。结果 Cu2+交联的TG–Cu水凝胶由离子交联和化学交联的两层网络构成,具有三维网络结构。当Cu盐的添加量为每组分0.187 5 mol时,其力学性能较好,弹性模量达到22.4 kPa,断裂韧性为659.5 kJ/m³,且具有预制缺口的凝胶样品在10 000次30%应变循环加载–卸载实验后,未观察到明显的裂纹扩展。抑菌试验结果证...     

A study on the preparation of poly(vinyl alcohol) nanofibers containing silver nanoparticles

In this study, two practical methods for the facile and controlled preparation of poly(vinyl alcohol) (PVA) nanofibers containing Ag nanoparticles were investigated for use in antimicrobial applications. In the first method, PVA nanofibers containing Ag nanoparticles were successfully electrospun from PVA/silver nitrate (AgNO₃) aqueous solutions after first refluxing them. The Ag nanoparticles in the PVA/AgNO₃ aqueous solutions were generated by refluxing them. Interestingly, it was found that the Ag nanoparticles were also spontaneously generated during the electrospinning process. In the second method, Ag nanoparticles were generated by annealing the PVA nanofibers electrospun from PVA/AgNO₃ aqueous solutions. Residual Ag⁺ ions and the Ag nanoparticles generated during the electrospinning process in the PVA nanofibers were diffused and aggregated into larger Ag nanoparticles during the annealing process. All of the Ag nanoparticles were sphere shaped and evenly distributed in the PVA nanofibers prepared by the two methods.     

电弧离子镀制备 TiSiN 纳米复合涂层

目的在SiH4气氛下制备Si掺杂的TiSiN纳米复合涂层,为SiH4用于工业化TiSiN涂层生产提供依据。方法采用电弧离子镀技术,在SiH4气氛下,于单晶硅和硬质合金衬底上制备Si掺杂的TiSiN纳米复合涂层,研究SiH4流量对TiSiN涂层化学组分、微观结构、硬度和耐磨性能的影响。结果 SiH4流量对TiSiN纳米复合涂层的微观结构、硬度及摩擦系数的影响明显。随着SiH4流量的增加,TiSiN涂层由柱状晶生长的晶体结构逐渐转变为纳米晶镶嵌于非晶基体的复合结构。Si在涂层中以Si3N4非晶相存在,随着涂层中Si含量逐渐增加,TiN晶粒尺寸逐渐减小,Si3N4起到细化晶粒的作用。在42 m L/min的SiH4流量下,涂层硬度高达4100HV0.025。在对磨材料为硬质合金的条件下,TiSiN涂层摩擦系数小于0.6。结论 SiH4气氛下可以制备出Ti N纳米晶镶嵌于Si3N4非晶相结构的TiSiN纳米复合涂层,涂层的显微硬度较高。SiH4可以作为Si源用于TiSiN纳米复合涂层的工业化生产。     

Zn-Co-TiO2纳米复合镀层的光生阴极保护特性

用纳米复合电沉积技术在低碳钢表面制备了Zn-Co-TiO₂纳米复合镀层。用SEM、EDS和XRD等技术手段对样品进行了分析与表征。结果表明,镀层中TiO₂的含量约为12.63%,并均匀分散在镀层中,可以起到细化Zn-Co合金镀层晶粒的作用,并使Zn-Co合金镀层的耐蚀性能得到提高。用紫外光辅助照射电极电位监测方法研究Zn-Co-TiO₂纳米复合镀层光生阴极保护特性。结果表明,在紫外光照射下,镀层的电极电位负移,说明镀层具有光生阴极保护性能;关闭紫外光灯后,其电极电位正移,但仍低于镀层未光照前的电极电位。在400℃下氧化6 h后镀层表面生成了ZnO薄膜,其与TiO₂的协同作用可进一步提高镀层的光生阴极保护性能。     

Corrosion characteristics of copper microparticles and copper nanoparticles in distilled water

The corrosion characteristics of copper microparticles and copper nanoparticles in distilled water were investigated in this paper. The Cu²⁺ transformations of copper microparticles and copper nanoparticles in distilled water were tested by using absorbance measurement, the structures of their corrosion products were determined by using XRD and TEM techniques. The results of absorbance measurement show that the corrosion characteristics of copper nanoparticles in distilled water are quite different from that of copper microparticles. The Cu²⁺ transformations ratio of copper microparticles increases slowly with the increasing of immersion time and levels off eventually, but the Cu²⁺ transformations ratio of copper nanoparticles increases sharply with the increasing of immersion time and gets to peak rapidly, and then decreases as the immersion time increases and levels off finally. The results of XRD present that they have different corrosion products, the corrosion products of copper microparticles in distilled water are Cu and CuO, but the nanoparticles are Cu, CuO, Cu(OH,Cl)₂ · 2H₂O and Cu₂(CO₃)(OH)₂. All these differences owe to the size effect of copper particles.     

Enhancement of incorporated ferromagnetic nanoparticles content in nanocomposite electrodeposited coatings by gradient magnetic field

Electrodeposited NiCoMnP coatings incorporating ferromagnetic nanoparticles demonstrate excellent magnetic properties compared with plain metal and alloy. However, improving the weight per cent of ferromagnetic nanoparticles incorporated into nanocomposite coatings is still a challenge. In this paper, a gradient magnetic field has been applied to enhance the nanoparticles’ incorporation during composite electrodepositing. Both experimental and theoretical investigations on the effect of magnetic field on the content of nanoparticles incorporated into nanocomposite coatings were carried out. The results show that gradient magnetic field is favourable for incorporating ferromagnetic nanoparticles into coatings, and uniform or static magnetic field has almost no effect for enhancing codeposition of ferromagnetic nanoparticles into coatings. With gradient magnetic field, a maximum nanoparticles incorporation of 8·08 wt-%BaFe₁₂O₁₉ is observed in CoNiMnP–BaFe₁₂O₁₉ nanocomposite coatings deposited with a BaFe₁₂O₁₉ nanoparticles bath concentration of 40 g L^?1 at a current density of 2 A dm^?2.     

Mechanically strong conducting hydrogels with special double-network structure

Mechanically strong conducting hydrogels composed of poly(acrylamide) (PAAm) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) have been synthesized through the construction of a special double-network (sDN) structure. The novelty of the sDN hydrogels lies in the introduction of PEDOT-PSS semi-interpenetrating polymer network (semi-IPN) hydrogel as the second network. Based on the experimental results and the double-network theory, an additional strengthening effect resulting from the formation of the PEDOT clusters in a three-step fracture process is proposed. The applicability of as-prepared PAAm/PEDOT-PSS sDN hydrogels in electromechanical actuators is also briefly discussed.     

石墨烯负载纳米LaF_3复合材料的摩擦学性能

采用液相超声直接剥离法制备了石墨烯负载纳米LaF_3复合材料,用SEM、TEM对其形貌进行了表征,利用多功能往复摩擦磨损试验仪考察了石墨烯负载纳米LaF_3复合材料在纯水中的摩擦磨损性能。通过SEM、XPS分别分析了磨痕表面的形貌、典型元素的化学状态,初步探讨了石墨烯负载纳米LaF_3复合材料在纯水中的润滑机理。结果表明:纳米LaF_3均匀分布于多层石墨烯片层表面和层间,其粒径为5~50 nm;其作为纯水添加剂具有良好的减摩抗磨性能,如试验载荷10 N,添加剂浓度0.01%(质量分数)时,与纯水润滑时相比,石墨烯负载纳米LaF_3复合材料水分散体系润滑下平均摩擦系数和磨损体积分别下降34.35%和52.40%,这主要是由于复合材料在磨损表面形成的吸附膜、摩擦化学反应膜发生协同作用,改变了水的磨损机理,抑制了Fe的氧化,使得摩擦表面的摩擦磨损得到减轻。     

Mechanical and corrosion resistance properties of electrodeposited Cu–ZrO2 nanocomposites

Electrodeposited Cu–ZrO₂ nanocomposites were prepared by suspending ZrO₂ nanoparticles in an acid copper electroplating bath at pH ～1. The calculated average crystallite size of electrodeposited pure copper and Cu–ZrO₂ nanocomposites were ～32 and ～30?nm, respectively. The measured crystallite structure was fcc and the texture was (220) for both electrodeposited pure copper and Cu–ZrO₂ nanocomposites. The surface morphology and composition of electrodeposited pure copper and Cu–ZrO₂ nanocomposites were characterised by SEM with EDX analysis. The microhardness and wear resistance of the electrodeposited Cu–ZrO₂ nanocomposite was higher than that of pure copper. The corrosion resistances of electrodeposited Cu–ZrO₂ nanocomposite and pure copper were evaluated by electrochemical Tafel polarisation studies. This revealed that Cu–ZrO₂ nanocomposites have higher corrosion resistance than electrodeposited pure copper in 3.5% NaCl (w/v) solution.     

Microstructures and tribological properties of PEEK-based nanocomposite coatings incorporating inorganic fullerene-like nanoparticles

The high strength, wear resistance and high operational temperature of polyetheretherketone (PEEK) have attracted increasing interests of this material for tribological applications. The addition of solid lubricant is an effective way to further improve the tribological properties of polymeric materials. In the present work, inorganic fullerene-like tungsten disulfide (IF-WS₂) nanoparticles were incorporated into PEEK coatings with the aim of reducing the coefficient of friction (COF) and improving the wear resistance of the coatings. The microstructures of IF-WS₂/PEEK nanocomposite coatings were characterized using a combination of SEM, XRD and FTIR measurements. The thermal behaviours of the coatings were determined using differential thermal analysis (DTA). Tribological tests had also been carried out to evaluate the friction and wear behaviours of IF-WS₂/PEEK nanocomposite coatings. The results showed that significant improvement can be achieved in the tribological properties of the nanocomposite coatings by incorporating IF-WS₂ nanoparticles.     

Cu-30Ni-20Cr纳米复合镀层的高温氧化行为

采用复合电沉积法制备出新型的Cu-30Ni-20Cr纳米复合镀层．该镀层的组织结构与常规Cu-Ni-Cr三元合金不同，是由Cu-Ni基固溶体（晶粒尺寸约为60nm）和纳米Cr颗粒（平均尺寸约为28nm）组成．与相同工艺条件下制备的Cu-40Ni合金镀层相比，Cu-30Ni-20Cr纳米复合镀层在800℃空气中的氧化速率显著降低，这是由于它能迅速形成一层连续、致密的Cr2O3膜所致．对Cr颗粒在Cu-30Ni-20Cr纳米复合镀层的高温氧化过程中所起的作用进行了讨论．     

One-pot synthesis of highly stable silver nanoparticles-conducting polymer nanocomposite and its catalytic application

Herein, we report the preparation of highly stable Ag_nano–PEDOT nanocomposite by one-pot fashion in acidic condition using 3,4-ethylenedioxythiophene (EDOT) as a reductant and polystyrene sulfonate (PSS^?) as a dopant for PEDOT as well as particle stabilizer for silver nanoparticles (AgNPs). The above nanocomposite denoted as Ag_nano–PEDOT/PSS^? nanocomposite. The formation of AgNPs with concomitant EDOT oxidation was followed by UV–visible (UV–vis) spectroscopy at different time intervals. Ag_nano–PEDOT/PSS^? nanocomposite shows absorption bands at 380 and above 700 nm, which correspond to surface plasmon resonance (SPR) peak of AgNPs and oxidized PEDOT, respectively. Ag_nano–PEDOT/PSS^? nanocomposite was characterized by infrared (IR) spectroscopy, transmission electron microscopy (TEM), and XRD. TEM study reveals that AgNPs are distributed uniformly around PEDOT polymer with an average particle size diameter of 10–15 nm. In addition, Ag_nano–PEDOT/PSS^? nanocomposite was tested for the catalytic reduction of 4-nitrophenol. For comparing stability, we were also synthesized AgNPs in the absence of PSS^? (denoted as Ag_nano–PEDOT) using EDOT as reductant. UV–vis spectrum of Ag_nano–PEDOT nanocomposite revealed that AgNPs prepared in the absence of PSS^? was not stable.     

Processing, microstructure and mechanical properties of magnesium matrix nanocomposites fabricated by semisolid stirring assisted ultrasonic vibration

Particulate reinforced magnesium matrix nanocomposites were fabricated by semisolid stirring assisted ultrasonic vibration. Compared with the as-cast AZ91 alloy, the grain size of matrix alloy in the SiCp/AZ91 nanocomposite stirring for 5 min was significantly decreased due to the addition of SiC nanoparticles. SiC nanoparticles within the grains exhibited homogeneous distribution although some SiC clusters still existed along the grain boundaries in the SiCp/AZ91 nanocomposite stirring for 5 min. With increasing the stirring time, agglomerates of SiC nanoparticles located along the grain boundaries increased. The ultimate tensile strength, yield strength and elongation to fracture of the SiCp/AZ91 nanocomposite stirring for 5 min were simultaneously improved compared with the as-cast AZ91 alloy. However, the ultimate tensile strength and elongation to fracture of the SiCp/AZ91 nanocomposite decreased with increasing the stirring time.     

Corrosion properties of micro- and nanocomposite copper matrix coatings produced from a copper pyrophosphate bath under pulse current

The aim of this work was the deposition of copper matrix composites under direct and pulse current at different frequencies and the evaluation of their protective properties, in the frame of the research domain of the production of metal matrix composite coatings.The deposits were produced using copper pyrophosphate bath in which 20 g/l of either micro- (mean diameter 2 μm) or nano- (mean diameter 45 nm) SiC particles have been added. A squared current waveform was used with the frequencies 0.01, 0.1, 1, and 10 Hz for the pulse current deposition.The microstructure of all deposits, both on the top surface and in cross section, was studied by Scanning Electron Microscopy. The SiC content was evaluated by EDXs in the case of the micro-composite deposits and by Glow Discharge Optical Emission Spectroscopy for the nanocomposite ones. The protective properties were examined by potentiodynamic measurements in different corrosive environments and by salt spray exposure combined with Electrochemical Impedance Spectroscopy measurements.Both the nanoparticles incorporation and the use of pulse current lead to a noticeable grain refinement and thus to a corrosion resistance increase. The nanocomposite deposits present the highest resistance to both uniform and localized corrosion, strongly correlated to their compact structure. The micro-composite deposits produced under direct current present gaps between the particles and the copper matrix, which lower the corrosion resistance. The use of the pulse current managed to partially close these gaps and increase the corrosion resistance to values similar to those of the pure copper deposits.     

Synthesis & Characterization of PVA/STA Composite Polymer Electrolyte Membranes for Fuel Cell Application

Chemically cross-linked composite membranes consisting of poly(vinyl alcohol) (PVA) and silicotungstic acid (STA) have been prepared by solution casting and evaluated as proton-conducting polymer electrolytes. The proton conductivity of the membranes was investigated as a function of blending composition, cross-linking density, and temperature. The conductivity mechanism was investigated by using Impedance spectroscopy in the region between 40 Hz and 10 MHz. Membranes were also characterized by FTIR spectroscopy to confirm the crossl-inking reaction and differential scanning calorimetry (DSC) to assess the thermal stability. Membrane swelling decreased with increase in cross-linking density accompanied by improvement in mechanical properties. The proton conductivity of the membranes was of the order of 10⁻³ S/cm and showed similar resistance to methanol permeability as Nafion 117 under the same measurement conditions.