Titanium and its alloys have long been used as implant materials due to their outstanding mechanical properties and apparent biocompatibility.Despite this,the search for better alloys has continued to be active by res...Titanium and its alloys have long been used as implant materials due to their outstanding mechanical properties and apparent biocompatibility.Despite this,the search for better alloys has continued to be active by researchers and industries alike,as there are still pressing issues that require attention.These include(1)a large mismatch in the elastic modulus of the implant material,which causes a stress shielding problem;(2)the release of harmful ions from Ti alloys after long-term use;(3)a low bioactivity of the Ti alloy surface,which prolongs the healing process.More research has been directed toward finding new generation Ti alloys composed of more biocompatible phases and modifying the surface of Ti alloys from naturally bio-inert to bioactive in order to circumvent the problems.This review examines recent work reported on the fabrication of Ti alloys,and based on the survey,major characteristics highlighted the importance of elastic modulus and the use of non-toxic metal elements to improve biocompatibility.In terms of surface modification of Ti alloys,numerous studies have found that a nano-scaled surface oxide layer grown on the surface is always beneficial to improving the bioactivity of Ti alloys for rapid recovery after implantation.This comprehensive review focuses on the appropriate phase and composition for new Ti alloys intended for use as biomedical implants,emphasizing both fabrication and surface modification methods.展开更多
Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current,pulse frequency and pulse duration that meets the AWS D17.1 specifications for aero...Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current,pulse frequency and pulse duration that meets the AWS D17.1 specifications for aerospace industry.The microstructure and mechanical properties of the weldments were also investigated.Relationships between the parameters and weld bead geometry were found.High quality weld joints without solidification crack that met AWS D17.1 requirements were obtained at(I)high pulse energy(25 J)and high average peak power(4.2 kW)and(II)low pulse energy(17.6 J)and low average peak power(2.8 kW).The weld joint formed at lower heat energy input exhibited finer dendritic grain structure.Mg vapourisation and hard phase compound(Al0.5Fe3Si0.5)formation decreased in the weld joint formed at lower heat energy input.Consequently,the tensile strength of the weldment formed at lower heat energy input(168 MPa)is by a factor of 1.15 higher but showed^29%decrease in hardness(111 HV0.1)at the joint when being compared with the weldment formed at higher heat energy input.Appropriate parameters selection is critical to obtaining 0.6 mm-thick AA5052-H32 pulse laser weld joints that meet AWS D17.1 requirements for aircraft structures.展开更多
The syntheses of nanosized carbonated hydroxyapatite （CHA） were performed by comparing dropwise and direct pouring of acetone solution of Ca（NO3）2·4H2O into mixture of （NH4）2HPO4 and NH4HCO3 at room tempera...The syntheses of nanosized carbonated hydroxyapatite （CHA） were performed by comparing dropwise and direct pouring of acetone solution of Ca（NO3）2·4H2O into mixture of （NH4）2HPO4 and NH4HCO3 at room temperature controlled at pH 11. Direct pouring method was later applied to study the increment of carbonate content in syntheses. The as-synthesized powders were characterized by various characterization techniques. The crystallographic results of the produced powders were obtained from X-ray diffraction analysis, whilst the carbonate content in the produced powders was determined by the CHNS/O elemental analyzer. Fourier transform infrared analysis confirmed that the CHA powders formed were B-type. Field emission scanning electron microscopy revealed that the powders were highly agglomerated in nanosized range and hence energy filtered transmission electron microscopy was employed to show elongated particles which decreased with increasing carbonate content.展开更多
Magnesium-based biomaterials have recently gained great attention as promising candidates for the new generation of biodegradable implants.This study investigated the mechanical performance and biodegradation behaviou...Magnesium-based biomaterials have recently gained great attention as promising candidates for the new generation of biodegradable implants.This study investigated the mechanical performance and biodegradation behaviour of magnesium-zinc/hydroxyapatite(Mg-Zn/HA)composites fabricated by different powder mixing techniques.A single step mixing process involved mechanical alloying or mechanical milling techniques,while double step processing involved a combination of both mechanical alloying and mechanical milling.Optimum mechanical properties of the composite were observed when the powders were prepared using single step processing via mechanical alloying technique.However,Mg-Zn/HA composite fabricated through single step processing via mechanical milling technique was found to have the most desirable low degradation rate coupled with highest bioactivity.The composite achieved the lowest degradation rate of 0.039×10^−3 mm/year as measured by immersion test and 0.0230 mm/year as measured by electrochemical polarization.Ca:P ratio of the composite also slightly more than enough to aid the initial bone mineralization,that is 1:1.76,as the required Ca:P ratio for initial bone mineralization is between 1:1 and 1:1.67.展开更多
The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet(UV)resistance of zinc oxide-functionalized halloysite nanotubes(HNT–ZnO).The HNT–ZnO was synthesized using a facile solvent...The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet(UV)resistance of zinc oxide-functionalized halloysite nanotubes(HNT–ZnO).The HNT–ZnO was synthesized using a facile solvent-free route.The properties of the HNT–ZnO nanofillers were characterized using zeta-potential measurement,X-ray diffraction(XRD),field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),and thermogravimetric analysis(TGA).The immobilization of ZnO nanoparticles onto HNT is feasible even at the lowest mass ratio of HNT/ZnO.The TGA results indicate that the thermal stability of the HNT–ZnO nanofillers is higher than that of the HNT.Furthermore,UV?Vis diffuse reflectance spectroscopy(UV-DRS)results show that the HNT–ZnO achieve a total reflectance as high as approximately 87.5%in the UV region,as compare with 66.9%for the HNT.In summary,the immobilization of ZnO onto HNT is a viable approach for increasing the thermal stability and improving the UV shielding of HNT.展开更多
Over the past decade,the interest in aluminum composites reinforced with carbon nanotubes has grown significantly.Studies have been carried out to overcome problems with uniform dispersion,interfacial bonding,void for...Over the past decade,the interest in aluminum composites reinforced with carbon nanotubes has grown significantly.Studies have been carried out to overcome problems with uniform dispersion,interfacial bonding,void formation and carbide formation of the composites.In the present work,multi-wall carbon nanotubes(MWCNTs) aluminum composites were produced.High-energy ball milling with the aim at developing well-dispersed MWCNTs Al composites was followed by cold compaction,sintering,and hot extrusion at 500 ℃.Different amounts of stearic acid as processing control agent(PCA) is used in order to minimize cold welding of the Al particles,and to produce finer particles.Differential scanning calorimetry(DSC),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray diffraction(XRD) were employed to analyze the MWCNTs,the aluminum powder,and the composites’ microstructural behavior.The hardness and tensile properties of the composites are also evaluated.The results showed 500% increase in yield stress after the addition of 1 wt% MWCNTs in Al-MWCNTs based composite.The ball-milling time of 4 h is found to be sufficient as excessive milling time destroys a vast number of MWCNTs.展开更多
The influence of La_(2)O_(3)inclusion(0-3 wt%)on the micro structure,phase formation and mechanical properties of zirconia toughed alumina(ZTA)added with 5.0 wt%CeO_(2)was investigated.ZTA CeO_(2)composites were sinte...The influence of La_(2)O_(3)inclusion(0-3 wt%)on the micro structure,phase formation and mechanical properties of zirconia toughed alumina(ZTA)added with 5.0 wt%CeO_(2)was investigated.ZTA CeO_(2)composites were sintered at 1600℃for 4 h.The microstructure,phase formation,density,fracture toughness and hardness properties were characterised through FESEM,Microscopy Image Analysis Software and XRD diffractometer,Archimedes principle and Vickers indentation technique,respectively.The XRD,image processing and FESEM reveal the existence of LaAl_(11)O_(18).The addition of La_(2)O_(3)incites the sintering,microstructure refinement,densification of ZTA-CeO_(2)matrix and phase transformation.Hence,the hardness of ZTA-CeO_(2)ceramics is increased rapidly based on refinement of Al_(2)O_(3)grains,densification of ZTA-CeO_(2)composites and porosity reduction.It is observed that the fracture toughness is enhanced through in situ formation of elongated LaAl_(11)O_(18)grains.The addition of 0.7 wt%La_(2)O_(3)culminated in the achievement of the optimum findings for density(4.41 g/cm^(3)),porosity(0.46%),hardness(1792 HV)and fracture toughness(8.8 MPa·m^(1/2)).Nevertheless,excess La_(2)O_(3)is proven to be detrimental as it displays poor mechanical properties due to the poor compactness of numerous LaAl_(11)O_(18)grains,coarsening of Al_(2)O_(3)grains and decline in density.展开更多
Biphasic calcium phosphate (BCP) consisting of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) was successfully synthesized by new hydrothermal route using β-TCP as precursor. The X-ray diffraction analysis ...Biphasic calcium phosphate (BCP) consisting of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) was successfully synthesized by new hydrothermal route using β-TCP as precursor. The X-ray diffraction analysis of as-synthesized powder indicated that β-TCP had been transformed into HA phase and amount of HA formed gradually increased with prolonged time. The results revealed that the recent technique may be able to control the composition of the obtained BCP which would influence the bioresorbability. Porous body of BCP was prepared by impregnation of polymeric sponge template with the slurry of the powder followed by sintering. The X-ray diffraction of porous product revealed that the composition of β-TCP increased after sintering indicating that HA had been decomposed. Porous BCP obtained from the recent technique possessed both macro and micropores structure which are useful for rapid tissue formation. Besides, the recent porous fabrication technique yielded porous BCP which preserved the sponge template morphology, enabling it to fabricate porous material with controlled pores structure.展开更多
Magnetic skyrmions emerge when the energy of ferromagnetic exchange interaction promoting parallel alignment of spins enters in competition with energies favoring non-collinear alignment of spins such as Dzy aloshinsk...Magnetic skyrmions emerge when the energy of ferromagnetic exchange interaction promoting parallel alignment of spins enters in competition with energies favoring non-collinear alignment of spins such as Dzy aloshinskii-Moriya interaction(DMI),long-rang dipole-dipole interaction(DDI),or higher-order exchange interactions.We perform an unbiased Monte Carlo simulation to study the DMI-based skyrmion nucleation and stabilization on the surface of magnetic nanotubular monolayer controlled by tuning constants of DDI(g) and next-nearest-neighbor antiferromagnetic exchange interaction(j') with appropriate balance.Without g and j',the loosely distributed skyrmions initially nucleate on the surface of nanotube approaching to the magnetic field(h) direction with increasing h in the intermediate range.Then,the skyrmion size,shape,density,distribution and crystal structure,as well as its driven field range,are tailored by g and j'.This work demonstrates the skyrmion nucleation mechanisms in three-dimensional magnetic nanostructures with curvature effect and multiple interactions,serving as a benchmark for a guide to experimentalists for preparation of samples in magnetic skyrmion states.展开更多
Biodegradable Mg-Zn alloy was synthesized using mechanical alloying where a statistical model was developed using fractional factorial design to predict elastic modulus and mass loss of the bulk alloy.The effects of m...Biodegradable Mg-Zn alloy was synthesized using mechanical alloying where a statistical model was developed using fractional factorial design to predict elastic modulus and mass loss of the bulk alloy.The effects of mechanical alloying parameters(i.e.,milling time,milling speed,ball-to-powder mass ratio and Zn content)and their interactions were investigated involving 4 numerical factors with 2 replicates,thus 16 runs of two-level fractional factorial design.Results of analysis of variance(ANOVA),regression analysis and R2 test indicated good accuracy of the model.The statistical model determined that the elastic modulus of biodegradable Mg-Zn alloy was between 40.18 and 47.88 GPa,which was improved and resembled that of natural bone(30-57 GPa).Corrosion resistance(mass loss of pure Mg,33.74 mg)was enhanced with addition of 3%-10%Zn(between 9.32 and 15.38 mg).The most significant independent variable was Zn content,and only the interaction of milling time and ball-to-powder mass ratio was significant as P-value was less than 0.05.Interestingly,mechanical properties(represented by elastic modulus)and corrosion resistance(represented by mass loss)of biodegradable Mg-Zn alloy can be statistically predicted according to the developed models.展开更多
Microplastics are emerging micropollutants in water threatening aquatic and land organisms.The microplastic–water system is complicated due to the multiple constituents in the water system and the minuscule size of t...Microplastics are emerging micropollutants in water threatening aquatic and land organisms.The microplastic–water system is complicated due to the multiple constituents in the water system and the minuscule size of the plastic waste.Although typical plastic-based materials are inert,the behavior of fragmented plastics is arbitrary and indefinite.When exposed to erratic water environments with the presence of organic and synthetic impurities,pH,temperature,and salt,microplastic surfaces may be potentially active and generate charges in water.These phenomena determine microplastics in water as a colloidal system.The classical Derjaguin Landau Verwey and Overbeek(DLVO)theory can be used to identify the microplastic surface behavior in water.The modification of microplastic surfaces eventually determines the overall interactions between microplastics and other constituents in water.Moreover,the geometry of microplastics and additives present in microcontaminants play a crucial role in their net interactions.Hence,multiple microplastic removal techniques,such as coagulation,filtration,and air flotation,can be developed to address the issue.In many cases,a combination of these methods may be needed to achieve the overall procedure in water treatment plants or generic water systems.Selection of an appropriate microplastic removal technique is crucial and should be based on the water environment and intended water use to ensure its safety.展开更多
In this work, thermosetting resin, epoxy and fibre loading were used in optimizing the strength at which ABS/epoxy coated kenaf fibre (EKF) composites would perform apparently during mechanical stress. Kenaf bast fibr...In this work, thermosetting resin, epoxy and fibre loading were used in optimizing the strength at which ABS/epoxy coated kenaf fibre (EKF) composites would perform apparently during mechanical stress. Kenaf bast fibres were resin coated before incorporated into engineering thermoplastic ABS at its processing temperature (230°C), cured in-situ at internal mixer and later compression moulded at 210°C under 65 kg/cm2pressure. The results showed the optimum level of tensile strength with thermoset and fibre loading as well as increase in strong interfacial bonding while the hardness values increased with increasing thermosetting and fibre contents. Both the tensile and flexural modulus apparently increased as the fibre contents increased.展开更多
Fabrication of full-density W-brass composites is very difficult to achieve because of evaporation of zinc, insolubility of W and brass and compacts expansion. In this study, to achieve full-density W-brass composites...Fabrication of full-density W-brass composites is very difficult to achieve because of evaporation of zinc, insolubility of W and brass and compacts expansion. In this study, to achieve full-density W-brass composites, mechanical alloying (MA) and activated sintering process were utilized. Mechanical coating of W with Ni using high energy planetary ball mill was carried out. The milling was divided into two stages: to alloy and modify the surface of W with Ni for enhanced activation. The microstructure of the milled powders and sintered compacts, elemental composition and phases present were studied by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) respectively. As-received powder compacts was also sintered under the same condition for comparison purpose. The effects of milling time on the microstructure, sinterability and the hardness of the composites were investigated. It was observed that the samples produced from 8 h milled powder had the highest relative sintered density (98% TD) and microhardness (234 Hv). On the other hand, the samples from the as-received powders expanded and had a relative sintered density of (67% TD) and microhardness as low as 24 Hv. The significance of this study is the possibility of producing W-brass composites as a cheaper alternative to W-Cu composites.展开更多
The modification of asphalt binder with natural rubber latex(NR)significantly improves the rutting and fatigue resistance of asphalt mixtures.However,NR-modified binder is prone to low workability and wettability due ...The modification of asphalt binder with natural rubber latex(NR)significantly improves the rutting and fatigue resistance of asphalt mixtures.However,NR-modified binder is prone to low workability and wettability due to its high viscosity.Therefore,this research focuses on examining the influences of silane and wax-based additives on the wettability of natural rubber-modified binders and the binder-aggregates adhesion performances.In this study,experimental and analytical approaches were used.The contact angles of asphalt binder were measured using a goniometer through the sessile drop method with three solvents:deionised water,formamide,and glycerol.The Cþþalgorithm was adopted to compute the surface free energy(SFE)elements of the asphalt binder.Analytical methods were employed to analyse the results based on the Young-Dupre equation,followed by linear regression to establish a correlation between the compatibility ratio(CR)and the SFE components.The results inferred that modified asphalt binders with additives possessed improved moisture resistance,wherein dry work adhesion values were less than 210 mJ/m^(2)under granite interfaces,whereas the limestone interface exhibited higher dry adhesion values of 340 mJ/m^(2)and below.Similar performance results were observed under wet adhesion conditions;with granite wet adhesive values observed below 120 mJ/m^(2),while limestone wet adhesion values were ascertained below 180 mJ/m^(2)for all tested samples and conditions.According to the spread–ability coefficient results,the limestone interface has greater spread-ability than granite interfaces.Meanwhile,compatibility ratio values indicated better compatibility of 1.9 or higher for tested samples under granite interfaces,whereas compatibility values of 1.7 and below were observed under limestone interfaces.展开更多
The filler-bitumen interaction mechanism is one of the most essential phases for comprehending the asphalt mixture's performance.However,despite numerous studies,in-depth knowledge of filler-bitumen reciprocity at...The filler-bitumen interaction mechanism is one of the most essential phases for comprehending the asphalt mixture's performance.However,despite numerous studies,in-depth knowledge of filler-bitumen reciprocity at a microscale level is yet to be ascertained.The goal of this research is to gain a better understanding of the fillerbitumen microscale interaction in terms of the synergy and coaction between the physicochemical and rheological performance of mastics due to filler inclusions.The rheological properties of two sustainable mastics,dolomite powder(DP)and lime kiln dust(LKD),together with a neat PEN 60/70 binder,were analysed based on a temperature sweep at elevated temperature conditions.Meanwhile,frequency sweep and multiple stress creep recovery(MSCR)tests were also conducted at pavement serviceability temperature using the dynamic shear rheometer(DSR).Physicochemical tests using a scanning electron microscope(SEM)and energy dispersive X-rays(EDX)were conducted to analyse the impact of parameters such as particle shape,grain size,texture,and chemical compositions.The DSR test results showcased how the incorporation of fillers in asphalt binder considerably improved the performance of the binder in terms of rutting and fatigue.Likewise,its strain and nonrecoverable compliance parameters were substantially reduced at higher filler and binder concentrations.Physical filler attributes of low rigden voids(R.V),high fineness modulus(FM),and high specific surface area(SSA)led to greater interfacial stiffness and elasticity in LKD mastics compared to DP mastics at different loading frequencies and temperature levels.The SEM/EDX results also indicated that the elemental calcium and carbon composition of each filler component,together with its grain morphology,strongly influenced its rheological performance.展开更多
The immobilization of catalysts on supporting substrates for the removal of organic pollutants is a crucial strategy for mitigating catalyst loss during wastewater treatment.This study presented a rapid and cost-effec...The immobilization of catalysts on supporting substrates for the removal of organic pollutants is a crucial strategy for mitigating catalyst loss during wastewater treatment.This study presented a rapid and cost-effective direct heating method for synthesizing MnO_(2) nanoflowers on coil substrates for the removal of organic pollutants.Traditional methods often require high power,expensive equipment,and long synthesis times.In contrast,the direct heating approach successfully synthesized MnO_(2) nanoflowers in just 10 min with a heating power of approximately 40 W·h after the heating power and duration were optimized.These nanoflowers effectively degraded 99%Rhodamine B in 60 min with consistent repeatability.The catalytic mechanisms are attributed to crystal defects in MnO_(2),which generate electrons to produce H_(2)O_(2).Mn6(2+)ions in the acidic solution further dissociate H_(2)O_(2) molecules into hydroxyl radicals(·OH).The high efficiency of this synthesis method and the excellent reusability of MnO_(2) nanoflowers highlight their potential as a promising solution for the development of supporting MnO_(2) catalysts for organic dye removal applications.展开更多
Objective This study aimed to evaluate the potential of a collagen-coated,3D-printed tracheal scaffold(3D-TechTra)integrated with human umbilical cord mesenchymal stem cells(hUC-MSCs)for tracheal tissue regeneration.M...Objective This study aimed to evaluate the potential of a collagen-coated,3D-printed tracheal scaffold(3D-TechTra)integrated with human umbilical cord mesenchymal stem cells(hUC-MSCs)for tracheal tissue regeneration.Methods The thermoplastic polyurethane/polylactic acid(TPU/PLA)scaffold was engineered to optimize mechanical properties and biocompatibility,with the goal of mimicking the structural and tensile characteristics of native tracheal tissue.Subsequently,preclinical experiments were conducted using rabbit models:the performance of the collagen-coated TPU/PLA scaffold with hUC-MSCs was compared with that of uncoated scaffolds and collagen-only scaffolds.In vitro tests were also performed to assess the adhesion,proliferation,and differentiation of hUC-MSCs on the scaffold.For in vivo evaluation,multiple analytical methods were employed,including immunohistological analysis(to detect glycosaminoglycan deposition and extracellular matrix remodeling),radiographic and endoscopic evaluations(to assess tracheal contour and airway obstruction),and survival analysis(to monitor animal outcomes and systemic toxicity).Results In vitro,hUC-MSCs successfully adhered to and proliferated on the TPU/PLA scaffold,and differentiated into adipogenic,osteogenic,and chondrogenic lineages,which supported the potential for tissue-specific regeneration;in vivo,compared with uncoated or collagen-only scaffolds,the collagen-coated TPU/PLA scaffold integrated with hUC-MSCs exhibited enhanced integration with host tissues,superior biocompatibility,and reduced tracheal stenosis,while also preserving airway patency,alleviating inflammation,and facilitating epithelial regeneration,smooth muscle formation,and vascularization.Immunohistological analysis further revealed significant glycosaminoglycan deposition and extracellular matrix remodeling in the hUC-MSC-treated group,and radiographic and endoscopic evaluations confirmed preserved tracheal contour and reduced airway obstruction;additionally,survival analysis showed significantly improved outcomes in animals treated with the collagen-coated TPU/PLA scaffold containing hUC-MSCs,with no systemic toxicity observed.Conclusions This study demonstrated the synergistic potential of TPU/PLA scaffolds,collagen coatings,and hUC-MSCs,providing valuable evidence for advancing the application of these components in tracheal tissue engineering.展开更多
Twist morphing （TM） is a practical control technique in micro air vehicle （MAV） flight. However, TM wing has a lower aerodynamic efficiency （CL/CD） compared to membrane and rigid wing. This is due to massive dra...Twist morphing （TM） is a practical control technique in micro air vehicle （MAV） flight. However, TM wing has a lower aerodynamic efficiency （CL/CD） compared to membrane and rigid wing. This is due to massive drag penalty created on TM wing, which had overwhelmed the succes- sive increase in its lift generation. Therefore, further CL/CDmax optimization on TM wing is needed to obtain the optimal condition for the morphing wing configuration. In this paper, two-way fluid- structure interaction （FSI） simulation and wind tunnel testing method are used to solve and study the basic wing aerodynamic performance over （non-optimal） TM, membrane and rigid wings. Then, a multifidelity data metamodel based design optimization （MBDO） process is adopted based on the Ansys-DesignXplorer frameworks. In the adaptive MBDO process, Kriging metamodel is used to construct the final multifidelity CL/CD responses by utilizing 23 multi-fidelity sample points from the FSI simulation and experimental data. The optimization results show that the optimal TM wing configuration is able to produce better CL/CDmax magnitude by at least 2% than the non-optimal TM wings. The flow structure formation reveals that low TV strength on the optimal TM wing induces low CD generation which in turn improves its overall CL/CDmax performance.展开更多
Ceramic parts usually experience dynamic load in armor applications. Therefore, studying the dynamic behaviors of ceramics is important. Limited data are available on the dynamic behaviors of ceramics; thus, it is hel...Ceramic parts usually experience dynamic load in armor applications. Therefore, studying the dynamic behaviors of ceramics is important. Limited data are available on the dynamic behaviors of ceramics; thus, it is helpful to predict the dynamic strength of ceramics on the basis of their mechanical properties. In this paper, the addition of SrCO3 into zirconia-toughened alumina（ZTA） was demonstrated to improve the fracture toughness of ZTA due to the formation of the SrAl12O19（SA6） phase. The porosity of ZTA was found to be increased by the addition of SrCO3. These newly formed pores served as the nucleation sites of cracks under dynamic load; these cracks eventually coalesced to form damaged zones in the samples. Although the KIC values of the samples were improved, the dynamic strength was not enhanced because of the increase in porosity; in fact, the dynamic strength of ZTA ceramics decreased with the addition of SrCO3.展开更多
基金funded by the Malaysian Ministry of Higher Education under the Fundamental Research Grant Scheme(Project Code FRGS/1/2018/TK05/USM/01/5)the first author is supported financially by a scholarship from Universiti Sains Malaysia(USM Fellowship)。
文摘Titanium and its alloys have long been used as implant materials due to their outstanding mechanical properties and apparent biocompatibility.Despite this,the search for better alloys has continued to be active by researchers and industries alike,as there are still pressing issues that require attention.These include(1)a large mismatch in the elastic modulus of the implant material,which causes a stress shielding problem;(2)the release of harmful ions from Ti alloys after long-term use;(3)a low bioactivity of the Ti alloy surface,which prolongs the healing process.More research has been directed toward finding new generation Ti alloys composed of more biocompatible phases and modifying the surface of Ti alloys from naturally bio-inert to bioactive in order to circumvent the problems.This review examines recent work reported on the fabrication of Ti alloys,and based on the survey,major characteristics highlighted the importance of elastic modulus and the use of non-toxic metal elements to improve biocompatibility.In terms of surface modification of Ti alloys,numerous studies have found that a nano-scaled surface oxide layer grown on the surface is always beneficial to improving the bioactivity of Ti alloys for rapid recovery after implantation.This comprehensive review focuses on the appropriate phase and composition for new Ti alloys intended for use as biomedical implants,emphasizing both fabrication and surface modification methods.
基金the funding (UniversityIndustry Engagement Grant)support provided by the Universiti Sains Malaysia under the Teaching Fellowship Scheme
文摘Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current,pulse frequency and pulse duration that meets the AWS D17.1 specifications for aerospace industry.The microstructure and mechanical properties of the weldments were also investigated.Relationships between the parameters and weld bead geometry were found.High quality weld joints without solidification crack that met AWS D17.1 requirements were obtained at(I)high pulse energy(25 J)and high average peak power(4.2 kW)and(II)low pulse energy(17.6 J)and low average peak power(2.8 kW).The weld joint formed at lower heat energy input exhibited finer dendritic grain structure.Mg vapourisation and hard phase compound(Al0.5Fe3Si0.5)formation decreased in the weld joint formed at lower heat energy input.Consequently,the tensile strength of the weldment formed at lower heat energy input(168 MPa)is by a factor of 1.15 higher but showed^29%decrease in hardness(111 HV0.1)at the joint when being compared with the weldment formed at higher heat energy input.Appropriate parameters selection is critical to obtaining 0.6 mm-thick AA5052-H32 pulse laser weld joints that meet AWS D17.1 requirements for aircraft structures.
基金Universiti Sains Malaysia for the USM FellowshipUSM-RU-PGRS(8033006)for the financial support
文摘The syntheses of nanosized carbonated hydroxyapatite （CHA） were performed by comparing dropwise and direct pouring of acetone solution of Ca（NO3）2·4H2O into mixture of （NH4）2HPO4 and NH4HCO3 at room temperature controlled at pH 11. Direct pouring method was later applied to study the increment of carbonate content in syntheses. The as-synthesized powders were characterized by various characterization techniques. The crystallographic results of the produced powders were obtained from X-ray diffraction analysis, whilst the carbonate content in the produced powders was determined by the CHNS/O elemental analyzer. Fourier transform infrared analysis confirmed that the CHA powders formed were B-type. Field emission scanning electron microscopy revealed that the powders were highly agglomerated in nanosized range and hence energy filtered transmission electron microscopy was employed to show elongated particles which decreased with increasing carbonate content.
基金The authors would like thank to Universiti Sains Malaysia for FRGS Grant No.203/PBAHAN/6071386 and financial scholarship from Ministry of Higher Education of Malaysia.
文摘Magnesium-based biomaterials have recently gained great attention as promising candidates for the new generation of biodegradable implants.This study investigated the mechanical performance and biodegradation behaviour of magnesium-zinc/hydroxyapatite(Mg-Zn/HA)composites fabricated by different powder mixing techniques.A single step mixing process involved mechanical alloying or mechanical milling techniques,while double step processing involved a combination of both mechanical alloying and mechanical milling.Optimum mechanical properties of the composite were observed when the powders were prepared using single step processing via mechanical alloying technique.However,Mg-Zn/HA composite fabricated through single step processing via mechanical milling technique was found to have the most desirable low degradation rate coupled with highest bioactivity.The composite achieved the lowest degradation rate of 0.039×10^−3 mm/year as measured by immersion test and 0.0230 mm/year as measured by electrochemical polarization.Ca:P ratio of the composite also slightly more than enough to aid the initial bone mineralization,that is 1:1.76,as the required Ca:P ratio for initial bone mineralization is between 1:1 and 1:1.67.
基金Universiti Sains Malaysia for Bridging Fund(grant No.304.PBAHAN.6316090)
文摘The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet(UV)resistance of zinc oxide-functionalized halloysite nanotubes(HNT–ZnO).The HNT–ZnO was synthesized using a facile solvent-free route.The properties of the HNT–ZnO nanofillers were characterized using zeta-potential measurement,X-ray diffraction(XRD),field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),and thermogravimetric analysis(TGA).The immobilization of ZnO nanoparticles onto HNT is feasible even at the lowest mass ratio of HNT/ZnO.The TGA results indicate that the thermal stability of the HNT–ZnO nanofillers is higher than that of the HNT.Furthermore,UV?Vis diffuse reflectance spectroscopy(UV-DRS)results show that the HNT–ZnO achieve a total reflectance as high as approximately 87.5%in the UV region,as compare with 66.9%for the HNT.In summary,the immobilization of ZnO onto HNT is a viable approach for increasing the thermal stability and improving the UV shielding of HNT.
文摘Over the past decade,the interest in aluminum composites reinforced with carbon nanotubes has grown significantly.Studies have been carried out to overcome problems with uniform dispersion,interfacial bonding,void formation and carbide formation of the composites.In the present work,multi-wall carbon nanotubes(MWCNTs) aluminum composites were produced.High-energy ball milling with the aim at developing well-dispersed MWCNTs Al composites was followed by cold compaction,sintering,and hot extrusion at 500 ℃.Different amounts of stearic acid as processing control agent(PCA) is used in order to minimize cold welding of the Al particles,and to produce finer particles.Differential scanning calorimetry(DSC),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray diffraction(XRD) were employed to analyze the MWCNTs,the aluminum powder,and the composites’ microstructural behavior.The hardness and tensile properties of the composites are also evaluated.The results showed 500% increase in yield stress after the addition of 1 wt% MWCNTs in Al-MWCNTs based composite.The ball-milling time of 4 h is found to be sufficient as excessive milling time destroys a vast number of MWCNTs.
基金financially supported by research university grantUniversiti Sains Malaysia RUI 1001/PBAHAN/811212teaching fellow scheme USM.9/25 Jld.ⅩⅢ。
文摘The influence of La_(2)O_(3)inclusion(0-3 wt%)on the micro structure,phase formation and mechanical properties of zirconia toughed alumina(ZTA)added with 5.0 wt%CeO_(2)was investigated.ZTA CeO_(2)composites were sintered at 1600℃for 4 h.The microstructure,phase formation,density,fracture toughness and hardness properties were characterised through FESEM,Microscopy Image Analysis Software and XRD diffractometer,Archimedes principle and Vickers indentation technique,respectively.The XRD,image processing and FESEM reveal the existence of LaAl_(11)O_(18).The addition of La_(2)O_(3)incites the sintering,microstructure refinement,densification of ZTA-CeO_(2)matrix and phase transformation.Hence,the hardness of ZTA-CeO_(2)ceramics is increased rapidly based on refinement of Al_(2)O_(3)grains,densification of ZTA-CeO_(2)composites and porosity reduction.It is observed that the fracture toughness is enhanced through in situ formation of elongated LaAl_(11)O_(18)grains.The addition of 0.7 wt%La_(2)O_(3)culminated in the achievement of the optimum findings for density(4.41 g/cm^(3)),porosity(0.46%),hardness(1792 HV)and fracture toughness(8.8 MPa·m^(1/2)).Nevertheless,excess La_(2)O_(3)is proven to be detrimental as it displays poor mechanical properties due to the poor compactness of numerous LaAl_(11)O_(18)grains,coarsening of Al_(2)O_(3)grains and decline in density.
文摘Biphasic calcium phosphate (BCP) consisting of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) was successfully synthesized by new hydrothermal route using β-TCP as precursor. The X-ray diffraction analysis of as-synthesized powder indicated that β-TCP had been transformed into HA phase and amount of HA formed gradually increased with prolonged time. The results revealed that the recent technique may be able to control the composition of the obtained BCP which would influence the bioresorbability. Porous body of BCP was prepared by impregnation of polymeric sponge template with the slurry of the powder followed by sintering. The X-ray diffraction of porous product revealed that the composition of β-TCP increased after sintering indicating that HA had been decomposed. Porous BCP obtained from the recent technique possessed both macro and micropores structure which are useful for rapid tissue formation. Besides, the recent porous fabrication technique yielded porous BCP which preserved the sponge template morphology, enabling it to fabricate porous material with controlled pores structure.
基金financially supported by the Key Program of National Natural Science Foundation of China-Regional Innovation and Development Joint Fund (No.U22A20117)the Natural Science Foundation of Liaoning Province (No.2022-MS108)the Fundamental Research Funds for Central Universities (No.N2205015)。
文摘Magnetic skyrmions emerge when the energy of ferromagnetic exchange interaction promoting parallel alignment of spins enters in competition with energies favoring non-collinear alignment of spins such as Dzy aloshinskii-Moriya interaction(DMI),long-rang dipole-dipole interaction(DDI),or higher-order exchange interactions.We perform an unbiased Monte Carlo simulation to study the DMI-based skyrmion nucleation and stabilization on the surface of magnetic nanotubular monolayer controlled by tuning constants of DDI(g) and next-nearest-neighbor antiferromagnetic exchange interaction(j') with appropriate balance.Without g and j',the loosely distributed skyrmions initially nucleate on the surface of nanotube approaching to the magnetic field(h) direction with increasing h in the intermediate range.Then,the skyrmion size,shape,density,distribution and crystal structure,as well as its driven field range,are tailored by g and j'.This work demonstrates the skyrmion nucleation mechanisms in three-dimensional magnetic nanostructures with curvature effect and multiple interactions,serving as a benchmark for a guide to experimentalists for preparation of samples in magnetic skyrmion states.
基金supported by the Universiti Sains Malaysia RU-PRGS (No. 8046026)Universiti Sains Malaysia FRGS by Ministry of High Education, Malaysia (No. 6071304)
文摘Biodegradable Mg-Zn alloy was synthesized using mechanical alloying where a statistical model was developed using fractional factorial design to predict elastic modulus and mass loss of the bulk alloy.The effects of mechanical alloying parameters(i.e.,milling time,milling speed,ball-to-powder mass ratio and Zn content)and their interactions were investigated involving 4 numerical factors with 2 replicates,thus 16 runs of two-level fractional factorial design.Results of analysis of variance(ANOVA),regression analysis and R2 test indicated good accuracy of the model.The statistical model determined that the elastic modulus of biodegradable Mg-Zn alloy was between 40.18 and 47.88 GPa,which was improved and resembled that of natural bone(30-57 GPa).Corrosion resistance(mass loss of pure Mg,33.74 mg)was enhanced with addition of 3%-10%Zn(between 9.32 and 15.38 mg).The most significant independent variable was Zn content,and only the interaction of milling time and ball-to-powder mass ratio was significant as P-value was less than 0.05.Interestingly,mechanical properties(represented by elastic modulus)and corrosion resistance(represented by mass loss)of biodegradable Mg-Zn alloy can be statistically predicted according to the developed models.
基金supported by the Universiti Sains Malaysia Apex Era Research Grant(Grant No.1001.PBAHAN.881008).
文摘Microplastics are emerging micropollutants in water threatening aquatic and land organisms.The microplastic–water system is complicated due to the multiple constituents in the water system and the minuscule size of the plastic waste.Although typical plastic-based materials are inert,the behavior of fragmented plastics is arbitrary and indefinite.When exposed to erratic water environments with the presence of organic and synthetic impurities,pH,temperature,and salt,microplastic surfaces may be potentially active and generate charges in water.These phenomena determine microplastics in water as a colloidal system.The classical Derjaguin Landau Verwey and Overbeek(DLVO)theory can be used to identify the microplastic surface behavior in water.The modification of microplastic surfaces eventually determines the overall interactions between microplastics and other constituents in water.Moreover,the geometry of microplastics and additives present in microcontaminants play a crucial role in their net interactions.Hence,multiple microplastic removal techniques,such as coagulation,filtration,and air flotation,can be developed to address the issue.In many cases,a combination of these methods may be needed to achieve the overall procedure in water treatment plants or generic water systems.Selection of an appropriate microplastic removal technique is crucial and should be based on the water environment and intended water use to ensure its safety.
文摘In this work, thermosetting resin, epoxy and fibre loading were used in optimizing the strength at which ABS/epoxy coated kenaf fibre (EKF) composites would perform apparently during mechanical stress. Kenaf bast fibres were resin coated before incorporated into engineering thermoplastic ABS at its processing temperature (230°C), cured in-situ at internal mixer and later compression moulded at 210°C under 65 kg/cm2pressure. The results showed the optimum level of tensile strength with thermoset and fibre loading as well as increase in strong interfacial bonding while the hardness values increased with increasing thermosetting and fibre contents. Both the tensile and flexural modulus apparently increased as the fibre contents increased.
文摘Fabrication of full-density W-brass composites is very difficult to achieve because of evaporation of zinc, insolubility of W and brass and compacts expansion. In this study, to achieve full-density W-brass composites, mechanical alloying (MA) and activated sintering process were utilized. Mechanical coating of W with Ni using high energy planetary ball mill was carried out. The milling was divided into two stages: to alloy and modify the surface of W with Ni for enhanced activation. The microstructure of the milled powders and sintered compacts, elemental composition and phases present were studied by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) respectively. As-received powder compacts was also sintered under the same condition for comparison purpose. The effects of milling time on the microstructure, sinterability and the hardness of the composites were investigated. It was observed that the samples produced from 8 h milled powder had the highest relative sintered density (98% TD) and microhardness (234 Hv). On the other hand, the samples from the as-received powders expanded and had a relative sintered density of (67% TD) and microhardness as low as 24 Hv. The significance of this study is the possibility of producing W-brass composites as a cheaper alternative to W-Cu composites.
基金The authors sincerely acknowledge the Ministry of Higher Education,Malaysia for the Fundamental Research Grant Scheme with Project Code:FRGS/1/2021/TK01/USM/02/1 that enabled them to conduct this research work.Special thanks to material suppliers for extending their support.The authors also express their appreciation to the technicians of the Highway Engineering Laboratory and Materials Engineering Laboratory at Universiti Sains Malaysia for their help.
文摘The modification of asphalt binder with natural rubber latex(NR)significantly improves the rutting and fatigue resistance of asphalt mixtures.However,NR-modified binder is prone to low workability and wettability due to its high viscosity.Therefore,this research focuses on examining the influences of silane and wax-based additives on the wettability of natural rubber-modified binders and the binder-aggregates adhesion performances.In this study,experimental and analytical approaches were used.The contact angles of asphalt binder were measured using a goniometer through the sessile drop method with three solvents:deionised water,formamide,and glycerol.The Cþþalgorithm was adopted to compute the surface free energy(SFE)elements of the asphalt binder.Analytical methods were employed to analyse the results based on the Young-Dupre equation,followed by linear regression to establish a correlation between the compatibility ratio(CR)and the SFE components.The results inferred that modified asphalt binders with additives possessed improved moisture resistance,wherein dry work adhesion values were less than 210 mJ/m^(2)under granite interfaces,whereas the limestone interface exhibited higher dry adhesion values of 340 mJ/m^(2)and below.Similar performance results were observed under wet adhesion conditions;with granite wet adhesive values observed below 120 mJ/m^(2),while limestone wet adhesion values were ascertained below 180 mJ/m^(2)for all tested samples and conditions.According to the spread–ability coefficient results,the limestone interface has greater spread-ability than granite interfaces.Meanwhile,compatibility ratio values indicated better compatibility of 1.9 or higher for tested samples under granite interfaces,whereas compatibility values of 1.7 and below were observed under limestone interfaces.
文摘The filler-bitumen interaction mechanism is one of the most essential phases for comprehending the asphalt mixture's performance.However,despite numerous studies,in-depth knowledge of filler-bitumen reciprocity at a microscale level is yet to be ascertained.The goal of this research is to gain a better understanding of the fillerbitumen microscale interaction in terms of the synergy and coaction between the physicochemical and rheological performance of mastics due to filler inclusions.The rheological properties of two sustainable mastics,dolomite powder(DP)and lime kiln dust(LKD),together with a neat PEN 60/70 binder,were analysed based on a temperature sweep at elevated temperature conditions.Meanwhile,frequency sweep and multiple stress creep recovery(MSCR)tests were also conducted at pavement serviceability temperature using the dynamic shear rheometer(DSR).Physicochemical tests using a scanning electron microscope(SEM)and energy dispersive X-rays(EDX)were conducted to analyse the impact of parameters such as particle shape,grain size,texture,and chemical compositions.The DSR test results showcased how the incorporation of fillers in asphalt binder considerably improved the performance of the binder in terms of rutting and fatigue.Likewise,its strain and nonrecoverable compliance parameters were substantially reduced at higher filler and binder concentrations.Physical filler attributes of low rigden voids(R.V),high fineness modulus(FM),and high specific surface area(SSA)led to greater interfacial stiffness and elasticity in LKD mastics compared to DP mastics at different loading frequencies and temperature levels.The SEM/EDX results also indicated that the elemental calcium and carbon composition of each filler component,together with its grain morphology,strongly influenced its rheological performance.
基金supported by Ministry of Higher Education,Malaysia,through the Fundamental Research Grant Scheme(FRGS)(Grant No.FRGS/1/2020/TK0/USM/02/27)。
文摘The immobilization of catalysts on supporting substrates for the removal of organic pollutants is a crucial strategy for mitigating catalyst loss during wastewater treatment.This study presented a rapid and cost-effective direct heating method for synthesizing MnO_(2) nanoflowers on coil substrates for the removal of organic pollutants.Traditional methods often require high power,expensive equipment,and long synthesis times.In contrast,the direct heating approach successfully synthesized MnO_(2) nanoflowers in just 10 min with a heating power of approximately 40 W·h after the heating power and duration were optimized.These nanoflowers effectively degraded 99%Rhodamine B in 60 min with consistent repeatability.The catalytic mechanisms are attributed to crystal defects in MnO_(2),which generate electrons to produce H_(2)O_(2).Mn6(2+)ions in the acidic solution further dissociate H_(2)O_(2) molecules into hydroxyl radicals(·OH).The high efficiency of this synthesis method and the excellent reusability of MnO_(2) nanoflowers highlight their potential as a promising solution for the development of supporting MnO_(2) catalysts for organic dye removal applications.
基金funded by the Ministry of Higher Education Malaysia for the Prototype Research Grant Scheme(PRGS)with Project Code PRGS/1/2021/SKK07/USM/02/1.
文摘Objective This study aimed to evaluate the potential of a collagen-coated,3D-printed tracheal scaffold(3D-TechTra)integrated with human umbilical cord mesenchymal stem cells(hUC-MSCs)for tracheal tissue regeneration.Methods The thermoplastic polyurethane/polylactic acid(TPU/PLA)scaffold was engineered to optimize mechanical properties and biocompatibility,with the goal of mimicking the structural and tensile characteristics of native tracheal tissue.Subsequently,preclinical experiments were conducted using rabbit models:the performance of the collagen-coated TPU/PLA scaffold with hUC-MSCs was compared with that of uncoated scaffolds and collagen-only scaffolds.In vitro tests were also performed to assess the adhesion,proliferation,and differentiation of hUC-MSCs on the scaffold.For in vivo evaluation,multiple analytical methods were employed,including immunohistological analysis(to detect glycosaminoglycan deposition and extracellular matrix remodeling),radiographic and endoscopic evaluations(to assess tracheal contour and airway obstruction),and survival analysis(to monitor animal outcomes and systemic toxicity).Results In vitro,hUC-MSCs successfully adhered to and proliferated on the TPU/PLA scaffold,and differentiated into adipogenic,osteogenic,and chondrogenic lineages,which supported the potential for tissue-specific regeneration;in vivo,compared with uncoated or collagen-only scaffolds,the collagen-coated TPU/PLA scaffold integrated with hUC-MSCs exhibited enhanced integration with host tissues,superior biocompatibility,and reduced tracheal stenosis,while also preserving airway patency,alleviating inflammation,and facilitating epithelial regeneration,smooth muscle formation,and vascularization.Immunohistological analysis further revealed significant glycosaminoglycan deposition and extracellular matrix remodeling in the hUC-MSC-treated group,and radiographic and endoscopic evaluations confirmed preserved tracheal contour and reduced airway obstruction;additionally,survival analysis showed significantly improved outcomes in animals treated with the collagen-coated TPU/PLA scaffold containing hUC-MSCs,with no systemic toxicity observed.Conclusions This study demonstrated the synergistic potential of TPU/PLA scaffolds,collagen coatings,and hUC-MSCs,providing valuable evidence for advancing the application of these components in tracheal tissue engineering.
基金the Government of Malaysia via the sponsorship by the Ministry of Education under the IPTA Academic Training Schemethe Malaysia Ministry of Higher Education’s Fundamental Research Grant Scheme (FRGS) (No. 600-RMI/FRGS 5/3 (22/2012))
文摘Twist morphing （TM） is a practical control technique in micro air vehicle （MAV） flight. However, TM wing has a lower aerodynamic efficiency （CL/CD） compared to membrane and rigid wing. This is due to massive drag penalty created on TM wing, which had overwhelmed the succes- sive increase in its lift generation. Therefore, further CL/CDmax optimization on TM wing is needed to obtain the optimal condition for the morphing wing configuration. In this paper, two-way fluid- structure interaction （FSI） simulation and wind tunnel testing method are used to solve and study the basic wing aerodynamic performance over （non-optimal） TM, membrane and rigid wings. Then, a multifidelity data metamodel based design optimization （MBDO） process is adopted based on the Ansys-DesignXplorer frameworks. In the adaptive MBDO process, Kriging metamodel is used to construct the final multifidelity CL/CD responses by utilizing 23 multi-fidelity sample points from the FSI simulation and experimental data. The optimization results show that the optimal TM wing configuration is able to produce better CL/CDmax magnitude by at least 2% than the non-optimal TM wings. The flow structure formation reveals that low TV strength on the optimal TM wing induces low CD generation which in turn improves its overall CL/CDmax performance.
基金supported by research university grant (RU) of 1001/PBAHAN/811212 from Universiti Sains Malaysia
文摘Ceramic parts usually experience dynamic load in armor applications. Therefore, studying the dynamic behaviors of ceramics is important. Limited data are available on the dynamic behaviors of ceramics; thus, it is helpful to predict the dynamic strength of ceramics on the basis of their mechanical properties. In this paper, the addition of SrCO3 into zirconia-toughened alumina（ZTA） was demonstrated to improve the fracture toughness of ZTA due to the formation of the SrAl12O19（SA6） phase. The porosity of ZTA was found to be increased by the addition of SrCO3. These newly formed pores served as the nucleation sites of cracks under dynamic load; these cracks eventually coalesced to form damaged zones in the samples. Although the KIC values of the samples were improved, the dynamic strength was not enhanced because of the increase in porosity; in fact, the dynamic strength of ZTA ceramics decreased with the addition of SrCO3.
