Optimized CVD production of CNT-based nanohybrids by Taguchi robust design

Taguchi's robust design method is for the first time employed to optimize many aspects of the production of nanohybrids based on C nanotubes by iron-catalyzed chemical vapor deposition in i-C4H10 + H2 atmosphere. By analyzing the outcomes of the catalytic process in terms of selectivity, carbon yield, purity and crystalline arrangement of the hybrid-forming nanotubes, the influence is ranked of the following parameters: synthesis temperature (500-700 degrees C), support material (alumina, magnesia or sodium-exchanged montmorillonite), calcination- (450-750 degrees C) and reduction-(500-700 degrees C) temperatures of the 15 wt% Fe-catalyst. In the experiments initially performed for this purpose, the growth process had, on average, scarce selectivity (2 in a scale 1-5) and poor yield (130 wt%); carbonaceous deposits exhibited unsatisfactory graphitization degree (Raman D/G intensity ratio > 1.5) and contained large amounts of metal impurities (14 wt%) and amorphous carbon (5 wt%). The indications emerging from Taguchi approach to the process optimization are critically examined. The experimental conditions chosen for carrying out test experiments allow achieving excellent selectivity (5) or large yield (760 wt%), hybrids with well-graphitized nanotubes (D/G intensity ratio < 0.6), nearly free of metallic (0.3 wt%) or amorphous (0.4 wt%) inclusions, with consequent possibility of satisfying the different requisites that the specific application to be addressed may require.     

Optimization of carbon fibre production using the Taguchi method

Since the variation of carbon fibre mechanical properties is very large, the Taguchi method was used to produce carbon fibre in a pilot plant, and to improve the properties of carbon fibre. Due to the production conditions of the Taguchi method, the tensile strength, modulus and breaking elongation of carbon fibre are increased by about 20, 13 and 26%, respectively.     

Optimization of pickling and annealing parameters in cold rolling using the Taguchi method

In this study, the optimum values of pickling and annealing parameters in cold rolling were obtained by using the Taguchi method. The materials taken from the hot rolling mill were subjected to pickling with different pickling times (3 min, 4 min, 5 min) parameters and then cold rolled. After this process, annealing was carried out with different annealing temperatures (700 °C, 750 °C, 800 °C), annealing times (5 min, 7.5 min, 10 min) in order to eliminate the cold working hardness. After these processes, sheet materials were subjected to skin-pass rolling, which is the last step of the rolling process. Optimum conditions are minimum rolling force measured from the load cell positioned on the work rolls. In this direction, S/N ratios with objective function “smaller is better” and were calculated and the optimum levels of the parameters were determined as 3 min pickling time, 750 °C annealing temperature and 10 min annealing time. In line with the findings obtained from the analysis of variance, it was determined that the most important parameter was the annealing time with a rate of 48.99 %. Confirmation experiments were carried out and it was concluded that the optimization was valid.     

Optimization of sol-gel technique for coating of metallic substrates by hydroxyapatite using the Taguchi method

In this study, the Taguchi method of design of experiment (DOE) was used to optimize the hydroxyapatite (HA) coatings on various metallic substrates deposited by sol-gel dip-coating technique. The experimental design consisted of five factors including substrate material (A), surface preparation of substrate (B), dipping/withdrawal speed (C), number of layers (D), and calcination temperature (E) with three levels of each factor. An orthogonal array of L₁₈ type with mixed levels of the control factors was utilized. The image processing of the micrographs of the coatings was conducted to determine the percentage of coated area (PCA). Chemical and phase composition of HA coatings were studied by XRD, FT-IR, SEM, and EDS techniques. The analysis of variance (ANOVA) indicated that the PCA of HA coatings was significantly affected by the calcination temperature. The optimum conditions from signal-to-noise (S/N) ratio analysis were A: pure Ti, B: polishing and etching for 24 h, C: 50 cm min^?1, D: 1, and E: 300 °C. In the confirmation experiment using the optimum conditions, the HA coating with high PCA of 98.5 % was obtained.     

Optimization of counter flow Ranque–Hilsch vortex tube performance using Taguchi method

This study discusses the application of Taguchi method in assessing maximum temperature gradient for the Ranque–Hilsch counter flow vortex tube performance. The experiments were planned based on Taguchi's L27 orthogonal array with each trial performed under different conditions of inlet pressure, nozzle number and fluid type. Signal-to-noise ratio (S/N) analysis, analysis of variance (ANOVA) and regression analysis were carried out in order to determine the effects of process parameters and optimal factor settings. Finally, confirmation tests verified that Taguchi method achieved optimization of counter flow Ranque–Hilsch vortex tube performance with sufficient accuracy.     

Cloud point extraction for determination of Diazinon: Optimization of the effective parameters using Taguchi method

Since Diazinon is one of the organophosphorous compounds which are harmful for human organisms, a simple, sensitive and accurate testing method for extraction and determination of this pesticide is mandatory. In this project, Cloud Point Extraction (CPE) method was developed for determination of Diazinon in aqueous samples. CTAB (cetyl trimethyl ammonium bromide) was used as cationic surfactant to extract and preconcentrate of Diazinon at the same time and the extracted Diazinon was determined by UV spectrophotometery. Taguchi L₉ array was employed for design of experiments to investigate influences of surfactant concentration, salt concentration, temperature and incubation time as effective parameters. According to the analysis of variance (ANOVA) results, the most effective parameter of the process is incubation time. The results show that a surfactant concentration of 10^− 5% (w/v), an incubation time of 30 min, a KI concentration of 10^− 6 mol L^− 1 and a temperature of 35 °C are the best operating conditions. Also, the linear calibration graph in the range of 0.02-24 ng ml^− 1 of Diazinon with r = 0.999 was obtained. The limit of detection (LOD) was 0.02 ng ml^− 1 and relative standard deviation (RSD) for 15 ng ml^− 1 of Diazinon was 0.76%.     

基于田口方法齿圈压板精冲模具参数优化

在精密冲裁过程中,精冲模具结构参数和板料的摩擦系数显著影响精冲剪切面质量.采用有限元模拟和田口方法,对齿圈压板精冲模具精冲H62黄铜板料过程中凹模圆角半径、V形齿齿高、V形齿齿边距和板料摩擦系数对剪切面撕裂比的影响进行了研究.结果表明:参数按照减小撕裂比能力由大到小排序依次是凹模圆角半径,V形齿齿高,板料-模具摩擦系数和V形齿齿边距.研究发现:采用优化参数可显著减小剪切面上撕裂比,撕裂比最大减小24.8%,并可抑制凹模刃口附近微裂纹萌生,使剪切带内裂纹由凸模单向扩展至凹模刃口,避免裂纹的双向扩展-贯通导致较大撕裂比剪切面的出现.     

Influence of co-catalyst on growth of carbon nanotubes using alcohol catalytic CVD method

This paper describes the influence of a co-catalyst on growth of carbon nanotubes (CNTs) by alcohol catalytic chemical vapour deposition (ACCVD) method. Silicon wafers covered with thermal oxide or polycrystalline diamond thin film were used as substrates. Ni thin film supported with Al, Cu or Ti was used as a catalyst. The films were deposited by pulsed laser deposition technique. Comparison of the various types of the co-catalyst (Al, Cu, Ti) leads to the conclusion that Cu co-catalyst is suitable for producing very thin single wall carbon nanotubes (SWCNTs) and combination of Al and Ni provide a good condition to the catalytic growth of CNTs. In addition, we observed also the influence of the various diffusion barriers (thermal oxide and polycrystalline diamond) on growth of CNTs. Prepared samples were analysed by Raman spectroscopy (RS) and scanning electron microscopy (SEM).     

Optimization of microstructural and mechanical properties of friction stir welding using the cellular automaton and Taguchi method

In this study, microstructural and mechanical properties of friction stir welding (FSW) of AA1100 is optimized using Taguchi L9 orthogonal design of experiments. First, in order to study the microstructural properties of the weld, microstructure evolution of the weld zone is simulated with the cellular automaton (CA) method coupling the modified Laasraoui–Jonas (LJ) model. Then, the microstructural simulation results were validated by obtained experimental results. Good agreements between the simulation and the experimental results were observed. Then, tensile and hardness test were done to investigate the mechanical properties of the weld. The design parameters considered in the experiment were rotational speed, traverse speed, and shoulder diameter. The optimum process parameters were determined with reference to grain size (GS), ultimate tensile strength (UTS) and hardness. The predicted optimal value of grain size, ultimate tensile strength and hardness was validated by conducting the confirmation test using optimum parameters. Analysis of variance was done in order to determine the most dominant factors in friction stir welding.     

Sisal-glass fiber hybrid biocomposite: Optimization of injection molding parameters using Taguchi method for reducing shrinkage

The current work presents an application of Taguchi method to optimize injection molding (IM) process parameters of sisal-glass fiber hybrid biocomposite. Six parameters that influence flow and cross-flow shrinkage such as injection pressure, melt temperature, mold temperature, holding pressure, cooling time and holding time were selected as variables and two hybrid biocomposites were used with different content of sisal (SF) and glass fiber (GF); SF20GF10 and SF10GF20. For the experimental design, L18 orthogonal array with a mixed-level design and signal-to-noise (S/N) of smaller-the-better was used. Optimal combination IM parameters were determined and the significant variables were identified using ANOVA. Optimized flow and cross-flow shrinkage values for SF20GF10 were 0.53% and 0.85% and the values for SF10GF20 were 0.47% and 0.88% respectively. Comparison was made with the shrinkage requirements of an automotive material specification suggesting that hybrid biocomposites with optimized IM parameters meet the dimensional requirements of automotive parts.     

Optimization of ultrasonic machining for fabricating square holes using the Taguchi methods

Abstract

One of the solutions for making quality molded plastic products is to adopt post-machining to avoid the warpage problem. Considering many traditional and non-traditional machining techniques, we have suggested that ultrasonic machining may be suitable for fabricating square holes in plastics. Because many factors are involved in ultrasonic machining, the objective of this research was to find the optimal conditions for ultrasonic machining by the Taguchi methods. The plastic material utilized in the study was PMMA, and there were two quality characteristics adopted for the experiment. One was the area deviation percentage (ADP) of square holes created by ultrasonic machining, and the other was the average thrust force during the machining process. Four factors, which were tool material, tool type, abrasive, and feed rate were considered in the experiment. The optimal conditions for ultrasonic machining to minimize ADPs and to reduce the average thrust force, respectively, are reported in the paper. These conditions can be applied to machine PMMA using ultrasonic machining in future applications.     

Optimization of field emission properties of carbon nanotubes by Taguchi method

It is the purpose of this study to evaluate the field emission property of carbon nanotubes (CNTs) prepared by microwave plasma-enhanced chemical vapor deposition (MPCVD) method. Nickel layer of 5 nm in thickness on 20-nm thickness titanium nitride film was transformed into discrete islands after hydrogen plasma pretreatment. CNTs were then grown up on Ni-coated areas by MPCVD. Through the practice of Taguchi method, superior CNT films with very low emission onset electric field, about 0.7 V/μm (at J = 10 μA/cm²), are attained without post-deposition treatment. It is found that microwave power has the most important influence on the field emission characteristics of CNT films. The increase of methane flow ratio will downgrade the degree of graphitization of CNT and thus its field emission characteristics. Scanning electron microscope and transmission electron microscopy (TEM) observation and energy dispersive X-ray spectrometer analysis reveal that CNT growth by MPCVD is based on tip-growth mechanism. TEM micrographs validate the hollow, bamboo-like structure of the multi-walled CNTs.     

Investigations on the drilling process of unreinforced and reinforced polyamides using Taguchi method

The reinforced plastic materials have been widely used to manufacture several machine parts due to their lightweight and superior specific strength/modulus compared to the metallic materials. This paper investigates the use of Taguchi’s method in order to identify the best drilling setup of glass reinforced polyamide. Experimental study on PA6 and PA66GF30 composites was conducted using three carbide drills (K20) with different geometries. The effect of tool geometry, spindle speed and feed rate factors on the thrust force, hole mean diameter and circularity error were analyzed. The results revealed the quality of the holes can be improved by proper selection of cutting parameters.     

Optimization of process parameters for ultrasonic drilling of advanced engineering ceramics using the Taguchi approach

The effect of process parameters on the cutting ratio (ratio of material removal rate to tool wear rate) for ultrasonic drilling of alumina-based ceramics using silicon carbide abrasive was studied. The parameters considered were workpiece material, tool material, grit size of the abrasive, power rating, and slurry concentration. Taguchi’s optimization approach was used to obtain the optimal parameters. The significant parameters were identified and their effects on cutting ratio were studied. The results obtained were validated by conducting confirmation experiments.     

Synthesis of vertically aligned boron nitride nanosheets using CVD method

Boron nitride nanosheets (BNNSs) protruding from boron nitride (BN) films were synthesized on silicon substrates by chemical vapor deposition technique from a gas mixture of BCl₃–NH₃–H₂–N₂. Parts of the as-grown nanosheets were vertically aligned on the BN films. The morphology and structure of the synthesized BNNSs were characterized by scanning electron microscopy, transmission electron microscopy, and Fourier transformation infrared spectroscopy. The chemical composition was studied by energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Cathodoluminescence spectra revealed that the product emitted strong UV light with a broad band ranging from 250 to 400 nm. Field-emission characteristic of the product shows a low turn-on field of 6.5 V μm^?1.     

Design of retrodiffraction gratings for polarization-insensitive and polarization-sensitive characteristics by using the Taguchi method

We present the design of retrodiffraction gratings that utilize total internal reflection (TIR) in a lamellar configuration to achieve high performance for both TE and TM polarized light and polarization-sensitive performance for gratings behaving as polarizer filters; the design was based on rigorous coupled wave analysis (RCWA) and the Taguchi method. The components can thus be fabricated from a single dielectric material and do not have to be coated with a metallic or dielectric film layer to enhance the reflectance. The effects of the structural and optical parameters of lamellar gratings were investigated, and the TIR gratings in a lamellar configuration were structurally and optically optimized in terms of the signal-to-noise ratio (S/N) and a statistical analysis of variance (ANOVA) of the refractive index, grating period, filling factor, and grating depth as control factors and the estimated efficiency by RCWA as a noise factor. For more accurate robustness, a two-step optimization process was used for each purpose. For TIR gratings designed to perform similarly for TE and TM incident polarization, the -1st-order efficiencies were estimated to be up to 92.0% and 88.5% for TE and TM polarization, respectively. Also, for the TIR gratings designed to achieve polarization-sensitive performance when behaving as a polarizer filters, the -1st-order diffraction efficiencies for TE and TM polarization were estimated to be up to 95.5% and 2.7%, respectively. From these analysis results, it was confirmed that the Taguchi method shows feasibility for an optimization approach to a technique for designing optical devices.     

Failure detection and optimization of sugar mill boiler using FMEA and Taguchi method

Sugar industry plays an important role in economic development of country. Cogeneration is an important source of income for sugar industries. Boiler is one of the essential components used in cogeneration process. Unscheduled boiler outages in sugar mills are major problem resulting loss of production. The boiler may be failed due to number of reasons; some of the reasons such as mechanical failure, electrical failure and temperature sensors failure. This paper describes the failures of the fuel feeding system frequently occurred in the cogeneration boiler and gives the solution to rectify these failures by using three important tools, namely, cause and effect diagram, Failure Mode and Effect Analysis and Taguchi method.     

Improving dimensional accuracy of Fused Deposition Modelling processed part using grey Taguchi method

This paper presents experimental investigations on influence of important process parameters viz., layer thickness, part orientation, raster angle, air gap and raster width along with their interactions on dimensional accuracy of Fused Deposition Modelling (FDM) processed ABSP400 (acrylonitrile-butadine-styrene) part. It is observed that shrinkage is dominant along length and width direction of built part. But, positive deviation from the required value is observed in the thickness direction. Optimum parameters setting to minimize percentage change in length, width and thickness of standard test specimen have been found out using Taguchi’s parameter design. Experimental results indicate that optimal factor settings for each performance characteristic are different. Therefore, all the three responses are expressed in a single response called grey relational grade. Finally, grey Taguchi method is adopted to obtain optimum level of process parameters to minimize percentage change in length, width and thickness simultaneously. The FDM process is highly complex one and hardly any theoretical model exist for the prediction purpose. The process parameters influence the responses in a highly non-linear manner. Therefore, prediction of overall dimensional accuracy is made based on artificial neural network (ANN).     

Optimizing preparation of the TiO2 thin film reactor using the Taguchi method

In this study, titanium dioxide thin film was prepared using the modified chemical vapor deposition. The parameters employed to control the preparation of the catalyst include the temperature of water bath, the Ti(OC₃H₇)₄/H₂O ratio, the flow rate of carrier gas, the oxidation temperature, the oxidation time, the calcination temperature, the rotating speed of furnace, and the speed of geared motor. The orthogonal arrays in the design of experimental method proposed by Taguchi were adopted to conduct the multiple-factor experiment. The conversion rate of salicylic acid in the aqueous or heterogeneous phase photocatalysis experiment was employed to identify the optimal conditions for assembly. The results indicated that a higher conversion ratio of the organic substance could be achieved under catalytic oxidation temperature of 400 °C, calcination temperature of 550 °C, and spraying speed of 30 rpm and the optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm⁻² on salicylic acid at concentration of 250 mg L⁻¹ by both agitation and aeration processes (dissolved oxygen level = 8.2 mg O₂ L⁻¹) at pH 5, which could achieve optimal hydroxyl radical yield of 5.1 × 10⁻¹⁷ M.