Conventional Mechanical Method Research Articles

Pore structure optimization of electrospun PTFE nanofiber membrane and its application in membrane emulsification

Polytetrafluoroethylene (PTFE) nanofiber membranes with a kind of novel circular pore structure were fabricated in our study. Firstly, PTFE/PVA spinning solution was electrospun into precursor nanofiber membrane, during which, poly(tetrafluoroethylene-hexafluoropropylene) (FEP) aqueous dispersion was introduced by electrostatic spraying aiming to optimize the original fibrous network pore structure of electrospinning. After which, the prepared precursor nanofiber membranes were sintered, and PTFE nanofiber membranes were finally obtained. Effects of FEP contents on PTFE nanofiber membranes’ structure and performance were investigated, respectively. From the morphology observation, it was found that the PTFE nanofiber membrane’s pore structure gradually transformed from fibrous network to circular pore due to the melting of FEP resins. Owing to the excellent under-oil hydrophobicity and the uniform circular pore structure, the obtained PTFE nanofiber membranes were utilized in membrane emulsification (ME) process to prepared water in oil (W/O) emulsion. Compared with the conventional mechanical stirring method, the W/O emulsion prepared by ME process showed not only more uniform water droplet size (about 270 nm), but also more stable and higher production efficiency.

Improving thermal and mechanical properties of the alumina filled silicone rubber composite by incorporating carbon nanotubes

Carbon nanotubes (CNTs) can be used to improve the thermal and mechanical properties of composites owing to their excellent characteristics. Methyl vinyl silicone rubber matrix composites filled with alumina (Al2O3) powder and CNTs were fabricated through a conventional mechanical blending method. The effects of the mass fraction, surface modification of Al2O3 powder and the addition of CNTs on the thermal conductivity, Young's modulus and hardness of the composites were investigated. Results show that a higher mass fraction of the Al2O3 powder results in a higher thermal conductivity of the composites. When the mass fraction of Al2O3 powder is fixed, the thermal conductivity, Young's modulus and hardness of the composites are improved obviously by surface modification of Al2O3 powder and adding a small amount of CNTs. The combination of the modified Al2O3 filler and CNTs filler can synergistically enhance the interfacial interaction between the fillers and rubber matrix by the formation of better heat conduction channels and network structures in the rubber matrix, thereby improving the thermal conductivity and mechanical properties of the composites.

MoS2 Moiré Superlattice for Hydrogen Evolution Reaction

A MoS2 moire superlattice with a twisted angle of θ ≈ 7.3° via a facile method instead of a conventional mechanical stacking method is successfully fabricated. With reduced interlayer potential bar...

Toward Creating a Portable Impedance-Based Nondestructive Testing Method for Debonding Damage Detection of Composite Structures

Debonding detection of composite structures is a vital task as such damage weakens the structure leading to a failure. As adhesive bonding is a more preferable choice over the conventional mechanical fastening method, detecting debonding as early as possible could minimize the overall maintenance costs. For this reason, a vast amount of research in the nondestructive testing field is being conducted as we speak. However, most of the methods may require well-trained experts or heavy equipment. In this study, the piezoelectric (PZT) material-based method known as the electromechanical impedance technique is investigated to seek the possibility of making the technique very cheap and portable by temporarily attaching the sensor. Furthermore, ANSYS simulation studies using smaller PZT patches as small as 0.1 mm × 0.1 mm are simulated to investigate the impedance signatures acquired from the simulations. The results show the possibility of using smaller PZT patches compared to the conventional PZT sizes of 10 mm × 10 mm for a successful damage identification process.

Characteristics of direct transesterification using ultrasound on oil extracted from spent coffee grounds

Spent coffee grounds (SCG), the residue after brewing coffee beverage, is a promising biodiesel feedstock due to its high oil contents (15‒20%). However, SCG should be pretreated to reduce the high free fatty acid content, which hampers transesterification reaction. To overcome this, we explored a direct transesterification reaction of SCG using ultrasound irradiation and identified the optimal sonication parameters. A high fatty acid methyl ester (FAME) content, up to 97.2%, could be achieved with ultrasound amplitude of 99.2 <i>μ</i>m, irradiation time of 10 min, and methanol to oil ratio of 7:1 in the presence of potassium hydroxide concentration of 1.25 wt.%. In addition, we demonstrated that ultrasound irradiation is an efficient method to produce biodiesel from untreated SCG in a short time with less energy than the conventional mechanical stirring method. The physical and chemical properties of the SCG biodiesel met the requirements for an alternative fuel to the current commercial biodiesel.

Microstructures and mechanical properties of TiO2 dispersion strengthened nickel prepared using an alloying-carbonizing-oxidation-sintering process

Nickel particles containing TiO2 grains were successfully fabricated using mechanical carbonization of Ni3Ti alloy powder, followed by selective oxidation of Ni-TiC to Ni-TiO2. For comparison, Ni-TiO2 composites were prepared using a conventional mechanical alloying method. The two powders were sintered using a spark plasma sintering system at 850, 900, 950, and 1000 °C. Structural characterization was performed using X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The relative densities of all the sintered samples were up to 99.7% at all sintering temperatures. The average particle diameter, interparticle distance, and grain size of the matrix in the sintered Ni particle composites that contained TiO2 grains were finer than others at all temperatures. These results imply that the alloying-carbonizing-oxidation-sintering (ACOS) process is a very promising method for refining oxide particles of oxide-dispersion-strengthened alloys. The enhanced mechanical properties such as compression yield strength and hardness of the sintered Ni-TiO2 composite is a consequence of the refinement of oxide particles by the ACOS process.

Fabrication of high-performance graphene oxide doped PVDF/CuO/Al nanocomposites via electrospinning

In this paper, the electrospinning technique has been employed to fabricate PVDF/CuO/Al nanocomposites, where the formulation was optimized on the basis of maximizing the reaction heat with increased efficiency. The graphene oxide (GO) has also been used as both lubricant and catalyst, which is well dispersed inside the PVDF matrix by the electrospinning process as well. It has been found that the smooth PVDF nano-fibers could be fabricated with GO content of 0.5 wt%, where the Al and CuO nanoparticles are also uniformly loaded. In comparison with the n-CuO/n-Al and PVDF/CuO/Al prepared by conventional mechanical mixing method, the GO-doped PVDF/CuO/Al nanocomposites via electrospinning improved heat of reaction, density as well as anti-oxidation capability. In addition, the electrospinning technique and doping of 0.5 wt% of GO can improve the reaction efficiency of PVDF/CuO/Al nanocomposites since they contribute to dispersion of components and homogeneous structure fabrication.

Ultrasonic Assisted Transesterification of Rapeseed Oil to Biodiesel Using Nano Magnetic Catalysts

In the present work, the effect of nano magnetic catalysts on biodiesel production from rapeseed oil was investigated. The produced catalysts were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM) and BET surface area analyzer and vibrating sample magnetometer (VSM). Ultrasonic irradiation utilized just for 35 min at different molar ratio of Li/Fe3O4 and Li/ZnO–Fe3O4. The highest yield 99.8% obtained while the molar ratio of catalyst was Li/Fe3O4 = 3/1 and Li/ZnO–Fe3O4 = 3/1. The vibrating sample magnetometer demonstrated that the catalysts could easily be separated due to ferromagnetic property, even if the catalyst was regenerated and used again for esterification. The superparamagnetic behavior of particles exhibited the high yield of recovery of catalyst after three time regeneration and applying in reaction. Moreover, the results revealed that using mentioned basic nano magnetic catalyst and ultrasonic waves at 37 kHz frequency could decrease the reaction temperature and reaction time and increase biodiesel production yield comparing with conventional mechanical stirring method. The specifications of produced fatty acid methyl esters like viscosity and flash point were complied with the mentioned requirements in ASTM D6751.

Effects of Graphite Shape and Composite Fabricating Method on Mechanical Properties of Graphite/Copper Composites

To study the effects of graphite shape and the composite fabricating method on the mechanical properties of graphite/copper (Gr/Cu) composites, a copper composite using graphite flakes or graphite granules as reinforcing phases is fabricated using mechanical mixing or electroless plating method. The mechanical properties of the Gr/Cu composites are evaluated by compression tests, and the compressive strength and elongation of the Gr/Cu composites using graphite granules as a reinforcing phase are compared with those of Cu composites with graphite flakes as a reinforcing phase. The compressive yield strength or maximum strength of the Gr/Cu composites with graphite granules as a reinforcing phase is higher than that of the composites using graphite flakes as a reinforcing phase regardless of the alignment of graphite. The strength of the composite produced by the electroless plating method is higher than that of the composite material produced by the conventional mechanical mixing method regardless of the shape of the graphite. Using graphite granules as a reinforcing phase instead of graphite flakes improves the strength and elongation of the Gr/Cu composites in all directions, and reduces the difference in strength or elongation according to the direction.

Er:YAG laser application in caries removal and cavity preparation in children: a meta-analysis.

The aim of this meta-analysis was to systematically evaluate the applications of Er:YAG lasers for the removal of caries and cavity preparation in children. The meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was conducted with data extracted from seven relevant randomized controlled trials (RCTs) published from 1997 to July 2017. The data heterogeneity of each study was assessed by a Q test. We used the heterogeneity results to calculate the standard mean difference (SMD) or relative risk (RR) and 95% confidence interval (95%CI) using STATA version 10.0. The publication bias was evaluated using Begger's test. There were seven randomized controlled trials included in this study. The analysis results indicate that compared to the conventional mechanical method, more time was needed for Er:YAG laser treatment (SMD 1.945, 95%CI 0.942 to 2.948). However, the pain reported by patients was reduced with Er:YAG laser treatment (SMD - 1.013, 95%CI - 1.892 to - 0.196). There were no significant differences between the groups in the complete retention rate (RR 1.021, 95%CI 0.963 to 1.114), the marginal discoloration (RR 1.638, 95% CI 0.240 to 11.986) and the marginal adaptation (RR 1.480, 95%CI 0.257 to 8.515). In conclusion, our data indicate that the time required for Er:YAG laser treatment was longer than that for the conventional mechanical method, but there was less pain associated with the Er:YAG laser treatment. There were no significant differences in the complete retention rate, marginal discoloration, and marginal adaptation between the two groups.

Evaluation of an ultrasonic-assisted mechanical stirring technique for the synthesis of an efficient nano-photocatalyst

Photocatalysis has emerged as an efficient technique for the removal of contaminants from wastewater. In this work, conventional mechanical stirring was compared with ultrasonic-assisted mechanical stirring for the synthesis of an efficient nano-photocatalyst (Al2O3)1−x(ZnO) x Fe2O3. The photocatalytic activity of (Al2O3)1−x(ZnO) x Fe2O3 synthesized by both techniques was compared for the degradation of methyl orange dye (MO) under visible light irradiation. Important process parameters were optimized during the study and the results indicated that the photocatalyst synthesized by ultrasonic-assisted mechanical stirring was more efficient with 93.5% photocatalytic activity for the degradation of MO dye than that synthesized by using a simple mechanical stirring technique which resulted in photocatalytic activity of 83.7%. (Al2O3)0.75(ZnO)0.25Fe2O3 nano-photocatalysts synthesized by both methods were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, dynamic light scattering and BET surface area analysis. The results indicated that the particle size of the (Al2O3)0.75(ZnO)0.25Fe2O3 catalyst synthesized by ultrasonic-assisted mechanical stirring was significantly smaller and the surface area larger than the particles prepared by the conventional mechanical stirring method. A cyclic study evaluated the reusability of the photocatalyst and found minimal loss in degradation efficiency after seven cycles. The optimal photocatalyst produced in this study can degrade higher concentrations of MO with a higher efficiency using a lower or similar catalyst dose compared to other materials published in the literature.

Reactive supramolecular filler for elastomer reinforcement

A reactive amphiphile, SA1, which comprises a mercaptodecyl oleophilic tail and a β-alanine oleophobic moiety, has been introduced to serve as the building block for supramolecular filler. At least a fraction of SA1 reacts in situ during mechanically mixing and vulcanization with SBR via thiol-ene reaction. Some oxidative dimerization also concomitantly occurs to give DSA1. The chemical coupling between SA1 and SBR results in drastically improved filler domain dispersion. Short fibrous crystalline domains, which are likely composed of SA1, SA1 grafted to SBR, and DSA1, less than 10 nm in width and a few tens to one hundred nanometers in length are observed by TEM. The filler domains are evenly distributed in the SBR. In contrast, the simple filler PA1 forms large irregular aggregates on the length scale of hundreds of nanometers. The improved filler dispersion and filler-rubber interaction allow effective energy dissipation and result in significantly improved mechanical properties.A solution-mixing method proves feasible for mixing SA1 and SBR and actually has resulted in better mechanical properties than the mechanical mixing method. Since the conventional mechanical mixing method for rubber compounding is highly energy-intensive, avoidance of the mechanical mixing method is another practical advantage for the novel strategy of supramolecular reinforcement.

Thin tungsten telluride layer preparation by thermal annealing

We report a simple method to prepare a thin Tungsten Telluride (WTe2) flake with accurate thickness control, which allows preparing and studying this two dimensional material conveniently. First, the WTe2 flake, which is relatively thick due to its strong interlayer van der Waals forces, is obtained by a conventional mechanical exfoliation method. Then, the exfoliated flake is annealed at 600 °C under a constant Ar protecting flow. Raman and atomic force spectroscopy characterizations demonstrate that thermal annealing can effectively thin down the WTe2 flake and retain its original lattice structure, though its surface smoothness is slightly deteriorated. Additionally, systematical study indicates that the thinning process strongly depends on the initial thickness of the WTe2 flake before annealing: the thinning rate increases from 0.12 nm min−1 to 0.36 nm min−1 as the initial thickness increases from 10 nm to 45 nm, while the roughness of the final product also increases with the increase of its initial thickness. However, the method fails when it is applied to WTe2 flakes thicker than 100 nm, resulting in uneven or burnt surface, which is possibly caused by big cavities formed by a large amount of defects gathered at the top surface.

Pulse trawl fishing: characteristics of the electrical stimulation and the effect on behaviour and injuries of Atlantic cod (Gadus morhua)

Abstract In the North Sea flatfish fishery, electric pulse trawls have been introduced to replace the conventional mechanical method. Pulse trawls reduce the fuel consumption, reduce adverse impact on the ecosystem but cause injuries in gadoids. We describe the design and electrical properties of pulse trawls currently in use and study the behavioural response and injuries in cod exposed to electrical pulses under controlled conditions. Pulse trawls operate at an average power of 0.7 kW m−1 beam length and a duty cycle of ∼2%. The electric field is heterogeneous with highest field strength occurring close to the conductors. Cod were exposed to three different pulse types for a range of field strengths, frequencies, and duty cycles. Two size classes were tested representing cod that escape through the meshes (11–17 cm) and market-sized cod that are retained in the net (34–56 cm). Cod exposed to a field strength of ≥37 V m−1 responded by moderate-to-strong muscular contractions. Some of the large cod (n = 260) developed haemorrhages and fractures in the spine, and haemal and neural arches in the tail part of the body. The probability of injuries increased with field strength and decreased when frequency was increased from 100 to 180 Hz. None of the small cod (n = 132) were injured and all survived. The field strength at the lateral boundaries of the trawl was too low to inflict injuries in cod.

A comparative study on ultrasonic cavitation and mechanical stirring method towards efficient production of biodiesel from non-edible oils and performance testing on a CI engine

This paper presents the biodiesel production processes using low frequency ultrasonic energy (24 kHz) and conventional mechanical stirrer method. For this purpose, three different non-edible oils namely kusum, yellow oleander and bitter groundnut oil were used as the biodiesel feedstock. The experiments have been performed for molar ratio (alcohol/oil) 6:1 and 4.5:1, with three different catalyst percentages (0.5%, 0.75% and 1%) of potassium hydroxide. Further an experimental investigation has been carried out on a diesel engine with diesel and biodiesel blends [B10, B20, and B30]. The most significant conclusions are: 1) biodiesel production through ultrasound energy appears to be efficient and time saving; 2) BTE of engine slightly increases when operating on lower blends of biodiesel (up to B10) than that operating on neat diesel. It may be concluded from the experimental investigations that up to 30% of biodiesel blends can be used as a fuel in engine without modification.

Influence of microwave assisted extraction on antioxidant and antiplasmodial activities of Trichilia roka extracts

Antiplasmodial and antioxidant activities of extracts derived from Trichilia roka (Chiov) (Meliaceae) root bark were determined respectively in vitro and using two methods as well as 1,1-diphenyl-2-picrylhydrazyl radicalscavenging and β-carotene-linoleate model systems. The microwave assisted extraction extract was more effective concern antioxydant activity than the antiplasmodial activity compare to conventional mechanical agitation extraction method. Extracts obtained by microwave assisted extraction showed a high total polyphenol content of 126766 μg Equivalent of Gallic acid /g Dry Mater and a total flavonoid content of 789.22 μg Equivalent of Quercetin/g dry mater but a low antiplasmodial activity with and inhibition concentration of 48.386 μg /mL and 23.983 μg/mL for mechanical agitation extract. The evaluation of the antioxidant properties of the two extracts showed that those obtained by microwave assisted extraction shown in the 1,1-diphenyl-2-picrylhydrazyl assay and in the β-carotene bleaching test, the highest antioxidant activity respectively, with an antioxidant activity of 82.12% and with a radical-scavenging activity with inhibition percentage of 88.78%..

Effectiveness and harmfulness evaluation of graffiti cleaning by mechanical, chemical and laser procedures on granite

This paper reports the results from the comparative evaluation of the global cleaning effectiveness of four graffiti colours (red, blue, black and silver) applied on two granites with different textures and compositions. A conventional mechanical method and several chemical products were evaluated. Additionally, it was evaluated the cleaning based on laser ablation by means of a nanosecond pulsed Nd:YVO4 at a wavelength of 355nm. Optical and electronic microscopy, Fourier transformed infrared spectroscopy and spectrophotometry were applied in order to assess the cleaning effectiveness and also the harmful effects on the stones.Taking into account the graffiti extraction degree, it was found that blue, red and black colours were successfully extracted by all the evaluated methods. However, the extraction of silver colour, whose chemical composition differs from that of the other three colours, was more difficult and it was only achieved by the mechanical procedure and by several chemical products; Nd:YVO4 laser at 355nm was an ineffective procedure in removing this paint. All the cleaning methods produced damage on the granites: a roughness increase after the mechanical cleaning, chemical contamination related to some chemical procedures and melting of biotite crystals after laser cleaning. Moreover, the ability of different paints to penetrate into the rock affected the global cleaning effectiveness evaluation.

Lipase catalysed synthesis of cetyl oleate using ultrasound: Optimisation and kinetic studies

The current paper exemplifies the application of ultrasound technology to enzymatic synthesis of a cosmetic emollient ester, cetyl oleate. Fermase CALB™10000, a commercial Candida antarctica lipase B was used as a catalyst to accomplish the ultrasound supported synthesis. Multiple process parameters like reaction time, temperature, enzyme dose, alcohol to acid molar ratio, ultrasound power, frequency and speed of agitation were optimised. Maximum conversion of ∼95.96% was discerned at optimum conditions, i.e., 60°C temperature, 5% enzyme dose, 2:1 alcohol:acid ratio, 60W ultrasound power, 25kHz ultrasound frequency, 80% duty cycle and 80rpm speed of agitation after purification steps. It was observed that the reaction reached equilibrium in a short duration of 30min under the optimised conditions. This was considerably lesser than the time required for attaining equilibrium in conventional mechanical stirring method which was over 2h. Bisubstrate kinetic models like random bi–bi, ping pong bi–bi and ordered bi–bi were applied to the experimental data to determine initial rates and other kinetic parameters. Ordered bi–bi model showed the best fit with kinetic parameters, Vmax=0.029M/min/gcatalyst, KA=0.00001M, KB=4.8002M, KiA=0.00014M, KiB=3.7914M & SSE=0.00022 for enzymatic cetyl oleate synthesis under ultrasound irradiation with inhibition by both acid and alcohol at high concentrations.

Development of high performance poly (ether-ketone) composites based on novel processing technique

• Probe sonication was explored as an aid to homogenous mixing of solid lubricants in matrix. • Probe sonication proved useful in improving tribological properties, but not mechanical properties. • SEM and EDAX were used to reveal the difference in wear mechanism. Homogeneous mixing of ingredients by efficient method is necessary for desired performance of a composite. In this work, selected solid lubricants and powder of poly ether ketone (PEK) were mixed by probe-sonication method and then composites were developed incorporating short fibers during extrusion process followed by injection molding. Another batch of composites was developed by conventional mechanical powder mixing method instead of sonication. The developed composites were evaluated for physical, thermo-physical, mechanical and tribological properties (in two types of wear modes viz. adhesive and abrasive). The influence of mixing technique on all performance properties was extensively studied including SEM and EDAX studies on the surfaces of worn composites. It was concluded that the probe-sonication technique proved beneficial for improving tribological properties significantly, but not for all mechanical properties. The extent of influence depended on type of solid lubricants, fibers and operating parameters during tribo-evaluation.

Preparation of Mo2C nanoparticles dispersion-strengthened copper-based composite by EB-PVD

In this research, a nano-Mo2C particle dispersion-strengthened copper alloy was prepared by a novel method, i.e., electron beam physical vapor deposition (EB-PVD) which has advantages of simple technical process and low cost compared with the conventional mechanical alloying method. And the microstructure and properties of the material were investigated. The results show that the copper matrix is composed of columnar crystals with the average width of 7 μm, and the size of Mo2C dispersoid is 1–7 nm. The ultimate tensile strength of the material is 486 MPa, and the electrical conductivity is 82 % IACS. As the temperature increases from 293 to 573 K, the material becomes more brittle.