Tarek Othman

This work seeks to contribute to solving the problems of inadequate artificial joint design from the mechanical perspective in total joint replacement (TJR) surgery. Ultra-high molecular weight polyethylene (UHMWPE)/hydroxyapatite (HAP) + titanium dioxide (TiO2) hybrid composites were fabricated and tested for use as artificial cartilages in the total joint prosthesis. Different amounts of TiO2 (1–10 wt%) and fixed amount of HAP (20 wt%) were dispersed in UHMWPE-based nanocomposites due to obtaining a material easy to be processed, inexpensive, with remarkable mechanical properties, and good cells interaction. The UHMWPE/HAP + TiO2 composites were prepared by using the solvent dispersing technique and twin-screw mixer, followed by hot compression molding, then mechanical testing was performed. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) are used to study the effect of the additives and the dispersion quality of the composites. The solvent dispersing technique shows better dispersion of the additives in the polymer matrix. The composites show an increase in Young's modulus, hardness, and flexural strength, by 71%, 33%, and 95% respectively concerning neat UHMWPE. The composite contains 3 wt% TiO2 showing the best enhancement percentage.

The current study aims to explore the tensile fracture mechanism and thermo-mechanical efficiency of polyamide-6 (PA6) reinforced with titanium dioxide (TiO2) and multiwalled carbon nanotubes (MWCNTs). The uniform dispersion of the MWCNTs and appreciable interfacing between PA6, TiO2, and MWCNTs were revealed in the fractography figures. The crystallization temperature and degree of crystallinity have been enhanced by the addition of nanoparticles to the PA6 matrix. Young?s modulus, tensile strength, and Charpy impact strength improved proportionally concerning reinforcement content. The essential work of fracture (EWF) method was applied to evaluate the toughening and fracture behavior of PA6 hybrid systems. Considerable improvement (+60.6%) in the EWF of PA6?TiO2?MWCNT nanocomposites was observed at 4 wt.% CNT and 2 wt.% TiO2. Limiting oxygen index (LOI) findings demonstrate that a polymer with a combination containing titanium dioxide and multiwalled carbon nanotubes has a highly substantial retardant influence. As a result, the TiO2?CNT combination acts as a synergist filler, offering versatile PA6 composite products.

A statistical optimization based on experimental work was conducted to consider ultimate tensile strength (UTS) and elongation of dissimilar joints between AA5454 and AA7075 by friction stir weld (FSW). The goal of this work is to develop a comparative study of the optimization of FSW parameters using different orthogonal arrays, i.e., L12 and L16. Four parameters correlated to softening and forging requirements (rotational speed, traverse speed, tilt angle, and plunge depth), one parameter associated with the location of base metal in the dissimilar joint, and two parameters related to an FSW tool (pin profile and Dshoulder/dpin ratio) were considered and arranged in the employed arrays. Moreover, the investigation explored the microstructure and fractography of dissimilar joints and base metals by using optical and scanning electron microscopes. The results showed that the L16OA is more accurate than L12OA for the optimization of seven parameters due to the small statistical errors. For UTS, the errors range from 0.78 to 24% for L16OA and from 27.23 to 44.14% for L12OA. For elongation, the errors run from 11 to 12.9% for L16OA and from 33.77 to 49.73% for L12OA. The accuracies of generated models range from 50 to 99.5% for L16OA and range from 30.7 to 94.9% for L12OA. Tightening the levels (narrow domain) is the main reason for switching some optimum levels between both arrays. The highest UTS obtained is 221 MPa based on the optimum levels attained from L16OA, and the highest elongation is 12.83% according to the optimum levels acquired from L12OA. Despite the deficiency of effective intermixing, the study revealed that FSW acceptably could assemble joints between AA5454 and AA7075, presenting the proficiency of FSW with welding dissimilar aluminum alloys.

The present work deals with the development of nanocomposite grease to reduce friction and wear between two contact surfaces such as the components of engine, cams, gears, and bearing. The tribological and rheological characteristics of nano grease with a new design of automated lubricant machine tests were evaluated. In this paper, a manual Reicher test machine is converted to an automatic machine by an electric actuator, which used to convert the load from manual to automatic. Calcium grease containing a different concentration of titanium dioxide and carbon nanotubes TiO2/CNTs (0.5, 1, 2, 3, 4wt. %) was successfully prepared. The tribological and rheological characteristics of the nano grease were investigated under different temperatures. The morphologies and chemical composition of the worn surface and the wear mechanisms were also discussed at different loads. X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis were used to analyze the microstructure of the nano additives and nano grease. The result shows that the optimal concentration of TiO2 /CNTs was 3wt%, which reduces the wear and coefficient of friction about 72.3 and 60 %, respectively. Furthermore, the apparent viscosity and shear stress are increased by 48.2 and 74.2 %, respectively.

The present work deals with the development of nanocomposite materials to increase the mechanical and wear properties by introducing multiwall carbon nanotube (MWCNTs) fillers into the polymer matrices. In the present study, MWCNTs with 0.2, 0.3, 0.4, and 0.5 wt% loading was mixed with PA11 pellets by using a melt mixing technique to create a family of PA11/MWCNT composites. Scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray powder diffraction (XRD) were utilized to determine the characterization of MWCNTs and the degree of dispersion of MWCNTs in the PA11. Tensile, flexural, and hardness tests have been performed in order to measure the mechanical properties such as tensile modulus, tensile strength, and elongation at fracture. The creep and creep recovery were studied using dynamic mechanical thermal analysis (DMTA). The wear behavior was investigated by using a pin-on-disk wear tester under dry sliding condition at different normal loads. The result shows that the tensile modulus and flexural modulus for PA11/MWCNT 0.5 wt% increase by 20% and 34.8%, respectively. In addition, the creep strain is increased with temperature and decreased with the MWCNT fillers which indicates an enhanced performance at short time scales. Furthermore, the wear rate for PA11/MWCNT 0.5 wt% decrease by 44% at 10 N and 22% at 5 N. Therefore, the incorporation of MWCNT fillers with PA11 has significantly enhanced the mechanical and tribological properties. Different applications in many fields can be benefited by these results as the worldwide trend is to replace steel with a reinforced polymer.

A relatively successful dissimilar joint between 1050 pure aluminum and annealed low carbon steel is achieved by using friction stir welding. Most studies of joining aluminum to steel have been performed by using low rotational speed with high traverse speed to minimize heat in weld zones and to minimize the thickness of the intermetallic compounds (IMCs). Although the minimized heat may reduce the formation of brittle IMCs but the steel side may not be strongly influenced by this heat which affects the stirring action on both sides. The novelty of this analysis is applying great generated heat by employing a combination of a low traverse speed and a high rotational speed to accomplish the joints. In this study, a high rotational speed of 1550 rpm, a low traverse speed of 17 mm/min, a tilt angle of 1°, a pin length of 1.6 mm, and a deep shoulder surface penetration of 0.2 mm on 1.9 mm sheet thickness is the best set obtained to maximize both the frictional heat and the joint strength. The theory used exhibits more stirring of steel on aluminum than previous studies. The major contribution obtained from this study is knowing a new evaluation of the effect of the thicknesses of the IMCs formed at the interface and on the nugget. It is shown that the effect of the thickness of IMCs formed has a very little impact on the joint strength of about 1.3% at a very high difference in the IMCs thickness obtained between 7.5−8 μm and 8−36 μm. The joint strength depends on how the wide intermixing of steel edge on the aluminum side creates and the size/shape of steel particles.

The removal of phenol from aqueous solution via photocatalytic degradation has been recognized as an environmentally friendly technique for generating clean water. The composite nanofibers containing PAN polymer, CNT, and TiO2 NPs were successfully prepared via electrospinning method. The prepared photocatalyst is characterized by SEM, XRD, and Raman spectroscopy. Different parameters are studied such as catalyst amount, the effect of pH, phenol concentration, photodegradation mechanism, flow rate, and stability of the composite nanofiber to evaluate the highest efficiency of the photocatalyst.

Purpose The purpose of this paper is to evaluate the influence of nanoparticles as an additive on the tribological properties of calcium grease.Design/methodology/approach The nano additives in this research are with different concentration of multi carbon nanotubes (MWCNTs) and Talc powder (1, 2, 3, 3 and 5 per cent). The ratio of MWCNTs to Talc powder is 1:1. The tribological properties of hyper MWCNTs/Talc powder to calcium grease were evaluated using a pin-on-disk wear testing. The results show that the nano additives MWCNTs/Talc to calcium grease exhibit good performance in anti-wear and friction reduction. The action mechanism was estimated through analysis of the worm surface with x-ray diffraction and transmission electron microscope.Findings The result indicates that boundary film mainly composed of MWCNT and Talc powder, and other organic compound was formed on the worm surface during the friction test. In addition, the wear rate and coefficient of friction of nanogreases have shown excellent improvement about 80.62 and 63.44 per cent, respectively, at 4 Wt.% of MWCNTs/Talc powder. Moreover, the thermal conductivity of nanogrease increased about 51.72 per cent.Originality/value This study describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

High-velocity oxygen fuel (HVOF) and flame spraying (FS) are alternative methods to thermal spraying processes to produce dense high-quality coatings. The aim of this study is to compare the microstructure and mechanical properties for HVOF and FS using a thermally sprayed bond coat NiCoCrAlY and CoNiCrAlY powders on an AISI 304 stainless steel substrate. The microstructure and composition of coatings were characterized by an X-ray Diffraction (XRD) analysis and Electron Microscopy (SEM) coupled to an Energy Dispersive Spectroscopy (EDS) detector. HVOF showed higher quality coatings compared to FS in terms of porosity and the presence of unfused particles for both employed powders. The mechanical properties and results indicated that the yield strength of the NiCoCrAlY (HVOF) coating was 1.4-folds FS, but the flexural bending modulus was almost the same. For the CoNiCrAlY powder, HVOF gave a higher yield strength and a higher flexural modulus than FS as the oxygen affinity of the CoNiCrAlY powder was lower than NiCoCrAlY given the high Co content in the former versus the latter. The results also indicated that hardness increased by about 83%, and by 58% for the NiCoCrAlY HVOF and FS coating alloys, and by 42% and 20% more for the CoNiCrAlY HVOF and FS coatings than the stainless steel substrate hardness, respectively.

In this work, Polyacrylonitrile nanofibers were enhanced by graphene oxide and zinc oxide, in terms of enhanced the photocatalytic activity and mechanical properties for the composite nanofibers. Photocatalytic degradation of two organic dyes methylene blue dye and indigo carmine dye from the simulated industrial wastewaters has been investigated under visible light irradiation. Composite nanofibers fabricated by using electrospinning technique followed by chemical cross-linking with zinc oxide. The surface sensitization and morphology changes of the fabricated composite nanofibers were studied using Fourier transform infrared spectroscopy analysis, Scanning Electron Microscopy and transmission electron microscope. Sensitized zinc oxide with graphene oxide showed higher efficiency in the degradation of MB with a 96% of degradation efficiency after 70 min and 98% for IC after merely 27 min. The optimum catalytic parameters such as initial organic dye concentration and pH were discussed. The efficacy of degradation of methylene blue dye and indigo carmine increased as initial concentration decreased. The optimal pH was around 5 where the reaction rate decreases above and under this pH value.

Friction Stir Welding (FSW) is a solid-state welding process used for welding similar and dissimilar materials. FSW is especially suitable to join Al alloys sheets, and this technique allows different material couples to be welded continuously. In this study dissimilar joints between aluminum alloy (AA5454) and aluminum alloy (AA7075) produced by friction stir welding, to optimize these parameters and determine which of them is significant by using Taguchi L16 optimization method. Seven parameters at two levels were selected in this study. The selected parameters are tool rotational speed, traverse speed, pin profile (based on taper angle), the ratio between shoulder diameter (D) and pin diameter (d) (D/d ratio), tool tilt angle, plunge depth, and base metal location (weld location)). The ultimate tensile strength (UTS) and ductility are considered as the mechanical properties of the dissimilar joints. Then, mathematical models are built for ultimate tensile strength and ductility as a function of significant parameters/interactions using response surface methodology. In addition, the microstructures of the optimum joint and the weakest joint are studied using optical microscopy. The results of this work showed that the rotational speed, traverse speed, D/d ratio and plunge depth are significant parameters in determining UTS (mean, signal to noise ratio (S/N)) at different confidence levels, but pin profile, location of base metal and tool tilt angle are insignificant parameters at any confidence levels. The traverse speed has the highest contribution to the process for UTS about 18.5% and 16.9% for S/N ratio and mean, respectively. The accuracy of the models according to the UTS is 97.6% and 99.5% for mean and S/N ratio, respectively. The maximum joint efficiency, compared to the strength of the AA5454, is 85.3%.

A novel composite nanofibers material have fabricated by using electrospinning technique followed by chemical cross-linking with zinc oxide (ZnO). The surface sensitization and morphology changes of the fabricated composite nanofibers were studied by using X-Ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM) and transmission electron microscope (TEM). The effect of operating parameters includes the amount of ZnO, initial solution PH, and hexavalent chromium concentration on adsorption were investigated. The maximum adsorption capacity was found to be 690 mg/g at pH 6, which is much higher than most of the reported adsorbents. The adsorption equilibrium reached within 25 and 180 min as the initial solution concentration increased from 10 to 300 mg/L, and the data fitted well using nonlinear pseudo first order model with determination coefficient (R2) in between 0.97 and 0.99. Adsorption isotherms correlate the data on equilibrium adsorption with different mathematical models to describe the behaviour of an adsorption process and provide valuable information for optimizing the design of an adsorption system.

This work describes the fabrication of two composite nanofibers systems containing polyacrylonitrile polymer (PAN), Multiwall carbon nanotubes (MWCNT) and Titania (TiO2) nanoparticles. Photodegradation experiments were performed to study the effect of various parameters including pH, catalyst dose, pollutant concentration and reaction time for three model compounds, methylene blue (MB), indigo carmine (IC), and ibuprofen (IBU) under visible light. Morphology and structure of the modified composite nanofibers were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA), Photoluminescence (PL) spectroscopy, Raman spectra, and X-ray Photoelectron Spectra (XPS) analyses. The photocatalytic performance was achieved in a rather short time visible light (<30 min) and under low power intensity (125 W) compared to earlier reports. Kinetics data fitted well using pseudo-first order model to describe the mechanism of photocatalytic degradation processes. The stability and flexibility of the fabricated composite nanofibers allow their application in a continuous flow system and their re-use after several cycles.

This paper introduces acoustics software for mechanical engineers and architects to aid in the early design stages or later consultations. The software uses governing equations for mechanical equipment and HVAC components in standards such as ASHARE, ASTM E477 and ARI coupled with room acoustics equations. Along the sound propagation path the noise sound pressure levels are calculated starting from the first source to the receiving point. The transmission loss of any obstacles/walls are taken into consideration to give a reliable estimation to the real values. In this paper two case studies are presented to show the efficiency of the software and verify the outputs with measurements. The sound pressure levels and noise criteria of the indoor and outdoor spaces studied showed a variation around 6.4% compared to measured values. Through this software the designer could map and manipulate the design to reach the standard or regulated noise criteria.

An effective photocatalyst obtained from composite nanofibers CA/GO fabricated by electrospinning technique followed by chemical crosslinking surface modified TiO2 nanoparticles (NPs) was used for removing the organic dyes Indigo carmine (IC) and Methylene blue (MB) from an aqueous solution under UV irradiation light. The crystalline structure and morphologies of CA–GO/TiO2–NH2 composite nanofibers were characterized by SEM, TEM, XRD, and FTIR. The prepared CA–GO/TiO2–NH2 composite nanofibers displayed significantly enhanced photocatalytic activity for photodegradation the organic dyes IC and MB under UV irradiation after 150 and 250 min respectively. The pH value of the solution was studied from 2 to 8 and obtained results showed a clear improvement of photocatalytic activity at pH 2. The results indicated that the activated CA–GO/TiO2–NH2 composite nanofibers functioned as an adsorbent for the removal of IC and MB from aqueous solutions. In addition, the results showed a high adsorption capacity remain up to 65% after five consecutive capacity cycles.