Showing papers in "Advances in Materials Science and Engineering in 2013"
TL;DR: In this article, the authors studied the synthesis of graphene oxide and graphene via a low-cost manufacturing method, which started with the chemical oxidation of commercial graphite powder into graphite oxide by modified Hummer's method, followed by the exfoliation of graphite oxides in distilled water using the ultrasound frequency from a laboratory ultrasonic bath.
Abstract: This research studied the synthesis of graphene oxide and graphene via a low-cost manufacturing method. The process started with the chemical oxidation of commercial graphite powder into graphite oxide by modified Hummer’s method, followed by the exfoliation of graphite oxide in distilled water using the ultrasound frequency from a laboratory ultrasonic bath. Finally, the oxygen functional groups on exfoliated graphite oxide or graphene oxide were eliminated by stirring in hot distilled water at 95°C, as a replacement for highly toxic and dangerously unstable hydrazine. The results assured that stirring in hot distilled water could give the product of graphene or reduced graphene oxide. The samples were characterized by FTIR, XRD, TGA, Raman spectroscopy, SEM, and TEM methods.
293 citations
TL;DR: Aerogels are highly porous structures prepared via a sol-gel process and supercritical drying technology as mentioned in this paper, and they exhibit the most remarkable physical properties, possessing lower density, thermal conductivity, refractive index, and dielectric constant than any solids.
Abstract: Aerogels are highly porous structures prepared via a sol-gel process and supercritical drying technology. Among the classes of aerogels, silica aerogel exhibits the most remarkable physical properties, possessing lower density, thermal conductivity, refractive index, and dielectric constant than any solids. Its acoustical property is such that it can absorb the sound waves reducing speed to 100 m/s compared to 332 m/s for air. However, when it comes to commercialization, the result is not as expected. It seems that mass production, particularly in the aerospace industry, has dawdled behind. This paper highlights the evolution of aerogels in general and discusses the functions and significances of silica aerogel in previous astronautical applications. Future outer-space applications have been proposed as per the current research trend. Finally, the implementation of conventional silica aerogel in aeronautics is argued with an alternative known as Maerogel.
185 citations
TL;DR: In this article, poly(lactic acid) (PLA), poly(ethylene oxide) (PEO), and poly(e-caprolactone)(PCL) were prepared at a nano-and submicron scale by solution blow spinning and electrospinning in order to compare crystalline structure and morphology developed by both processes during fiber formation.
Abstract: Nonwoven mats of poly(lactic acid) (PLA), poly(ethylene oxide) (PEO), and poly(e-caprolactone) (PCL) were prepared at a nano- and submicron scale by solution blow spinning (SBS) and electrospinning in order to compare crystalline structure and morphology developed by both processes during fiber formation. Polymer solutions were characterized by rheometry and tensiometry. Spun fibers were characterized by several analytical steps. SEM analyses showed that both solution blow spun and electrospun fibers had similar morphology. Absence of residual solvents and characteristic infrared bands in the solution blow spun fibers for PLA, PCL, and PEO was confirmed by FTIR studies. XRD diffraction patterns for solution blow spun and electrospun mats revealed some differences related to distinct mechanisms of fiber formation developed by each process. Significant differences in thermal behavior by DSC were observed between cast films of PLA, PCL, and PEO and their corresponding spun nanofibers. Furthermore, the average contact angles for spun PLA and PCL were higher than for electrospun mats, whereas it was slightly lower for PEO. When comparing electrospun and solution blow spun fibers, it was possible to verify that fiber morphology and physical properties depended both on the spinning technique and type of polymer.
148 citations
TL;DR: In this article, the main compounds are calcium, silicon, magnesium, and aluminium oxides, and calcium silicates under their various allotropic forms are the major compounds in the ladle furnace slag.
Abstract: A promising type of steel slag for applications is the ladle furnace (LF) slag, which is also known as the basic slag, the reducing slag, the white slag, and the secondary refining slag. The LF slag is a byproduct from further refining molten steel after coming out of a basic oxygen furnace (BOF) or an electric arc furnace (EAF). The use of the LF slag in further applications requires knowledge of its characteristics. The LF slag characterization in this paper has been performed using the following analytical methods: chemical analysis by energy dispersive spectrometry (EDS), mineralogical composition by X-ray diffraction (XRD), surface area properties by the Brunauer-Emmett-Teller (BET) and the Barrett-Joyner-Halenda (BJH) methods, surface chemistry by infrared absorption (FTIR) spectroscopy, and morphological analysis by scanning electron microscopy (SEM). The results showed that the main compounds are calcium, silicon, magnesium, and aluminium oxides, and calcium silicates under their various allotropic forms are the major compounds in the LF slag. Surface area properties have shown that the LF slag is a mesoporous material with relatively great BET surface area. The ladle furnace slag is a nonhazardous industrial waste because the ecotoxicity evaluation by its eluate has shown that the LF slag does not contain constituents which might in any way affect the environment harmfully.
113 citations
TL;DR: The work on cellulose fiber composites is typically strictly divided into two separated research fields depending on the fiber origin, that is, from wood and from annual plants, representing the two different industries of forest and agriculture, respectively.
Abstract: The work on cellulose fiber composites is typically strictly divided into two separated research fields depending on the fiber origin, that is, from wood and from annual plants, representing the two different industries of forest and agriculture, respectively. The present paper evaluates in parallel wood fibers and plant fibers to highlight their similarities and differences regarding their use as reinforcement in composites and to enable mutual transfer of knowledge and technology between the two research fields. The paper gives an introduction to the morphology, chemistry, and ultrastructure of the fibers, the modeling of the mechanical properties of the fibers, the fiber preforms available for manufacturing of composites, the typical mechanical properties of the composites, the modeling of the mechanical properties with focus on composites having a random fiber orientation and a non-negligible porosity content, and finally, the moisture sensitivity of the composites. The performance of wood and plant fiber composites is compared to the synthetic glass and carbon fibers conventionally used for composites, and advantages and disadvantages of the different fibers are discussed.
108 citations
TL;DR: In this article, the reliability of using the direct shear test for different clay contents and different moisture contents using an adequate shearing strain was investigated and the results showed that shear force and angle of internal friction increases with the increase of moisture content.
Abstract: The direct shear test using shear box is commonly recommended by practicing geotechnical engineers to obtain the cohesion and angle of internal friction for granular soils The clay liners involve sand as a main constituent with added clay of variable proportions This research aims at investigating the reliability of using the direct shear test for different clay contents and different moisture contents using an adequate shearing strain These factors were found to affect the bilinear trends of shear force versus horizontal displacement profile as well as vertical displacement versus horizontal displacement curves The cohesion of the mixture was found to increase consistently with the increase of clay content Increase in moisture content was found to cause a drop in both cohesion and angle of internal friction These changes are not independent of the density state of clay-sand mixtures Standard compaction properties for a range of clay-sand mixtures were investigated This work provides the general trends expected in direct shear tests for clay-sand mixtures of variable clay and moisture contents
96 citations
TL;DR: In this article, the effects of aging on the rheological and physical properties of bitumen binders were studied conducting dynamic shear rheometer test (DSR), Brookfield viscometer test, softening point test, and penetration test.
Abstract: Several road pavement distresses are related to rheological bitumen properties. Rutting and fatigue cracking are the major distresses that lead to permanent failures in pavement construction. Influence of crumb rubber modifier (CRM) on rheological properties of bitumen binder such as improvement of high and intermediate temperatures is investigated in the binder’s fatigue and rutting resistance through physical-rheological changes in this research. The bitumen binders were aged by rolling thin film oven (RTFOT) to simulate short-term aging and pressure aging vessel (PAV) to simulate long-term aging. The effects of aging on the rheological and physical properties of bitumen binders were studied conducting dynamic shear rheometer test (DSR), Brookfield viscometer test, softening point test, and penetration test. The results showed that the use of rubberised bitumen binder reduces the aging effect on physical and rheological properties of the bitumen binder as illustrated through lower aging index of viscosity, lower aging index of , and an increase in with crumb rubber modifier content increasing, indicating that the crumb rubber might improve the aging resistance of rubberised bitumen binder. In addition, the results showed that the softening point increment () and penetration aging ratio (PAR) of the rubberised bitumen binder decreased significantly due to crumb rubber modification. Furthermore, the higher crumb rubber content, the lower after PAV aging, which led to higher resistance to fatigue cracking bitumen.
83 citations
TL;DR: In this paper, the antibacterial properties and characterization of chitosan-silver nanoparticle composite materials were investigated by adding AgNO3 and NaOH solutions to chitosa solution at 95°C.
Abstract: The aim of this study is to investigate the antibacterial properties and characterization of chitosan-silver nanoparticle composite materials. Chitosan-silver nanoparticle composite material was synthesized by adding AgNO3 and NaOH solutions to chitosan solution at 95°C. Different concentrations (0,02 M, 0,04 M, and 0,06 M) of AgNO3 were used for synthesis. Chitosan-silver nanoparticle composite materials were characterized by Transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet (UV) spectrophotometer, and Fourier transform infrared (FTIR) spectrometer techniques. Escherichia coli, Acinetobacter baumannii, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Streptococcus pneumoniae were used to test the bactericidal efficiency of synthesized chitosan-Ag nanoparticle composite materials. The biological activity was determined by the minimum bacterial concentration (MBC) of the materials. Antibacterial effect of chitosan-silver nanoparticle materials was increased by increasing Ag amount of the composite materials. The presence of small amount of metal nanoparticles in the composite was enough to significantly enhance antibacterial activity as compared with pure chitosan.
82 citations
TL;DR: In this article, the authors proposed a method to test and evaluate the performance of automotive parts in the field of manufacturing and test techniques for Automobile parts, which is similar to the one we use in this paper.
Abstract: 1Key Laboratory of Manufacture and Test Techniques for Automobile Parts, Ministry of Education, Chongqing 400054, China 2Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada V6T 1Z4 3Department of Bioengineering, University of Washington, Seattle, WA 98195-5061, USA 4Department of Mechanical System Engineering, Chonnam National University, Gwangju 500757, Republic of Korea
80 citations
TL;DR: In this article, the results of the experiments undertaken to evaluate various physical and mechanical properties of hemp fibres were presented for comparison with similar properties of synthetic fibres and for assessing the suitability for use as reinforcement in composite materials.
Abstract: This paper presents the results of the experiments undertaken to evaluate various physical and mechanical properties of hemp fibres. The study of these properties is vital for comparison with similar properties of synthetic fibres and for assessing hemp fibres’ suitability for use as reinforcement in composite materials. The properties of hemp fibres were found to be good enough to be used as reinforcement in composite materials. However, the issues of relatively high moisture content of fibres, variability in fibre properties, and relatively poor fibre/matrix interfacial strength were identified as factors that can reduce the efficiency with which these fibres can be utilised.
80 citations
TL;DR: The IPN PVA/GE hydrogels showed excellent physical and mechanical Properties and showed excellent biocompatibility and good proliferation indicates that the IPN hydrogel are stable enough for various biomedical applications.
Abstract: In this work, a new approach was introduced to prepare interpenetrating polymer network PVA/GE hydrogels by cross-linking of various concentration gelatin in the presence of transglutaminase enzyme by using the freezing-thawing cycles technique. The effects of freezing-thawing cycles on the properties of morphological characterization, gel fraction, swelling, mechanical, and MTT assay were investigated. The IPN PVA/GE hydrogels showed excellent physical and mechanical Properties. MTT assay data and the fibroblasts culture also showed excellent biocompatibility and good proliferation. This indicates that the IPN hydrogels are stable enough for various biomedical applications.
TL;DR: In this paper, the effect of crumb rubber modification on the rheology of bitumen has been discussed and several techniques of chemical modification to terminal blends of CRMB have been discussed.
Abstract: Crumb rubber modification has been proven to enhance the properties of pure bitumen. This paper looks at some of the international standards for producing crumb rubber modified bitumen (CRMB) and reviews the effect of crumb rubber to the rheology of crumb rubber modified bitumen. The review shows that the rheology of CRMB depends on internal factors such as crumb rubber quantity, particle size, and pure bitumen composition, and external factors such as the mixing time, temperature, and also the modification technique. These factors govern the swelling process of crumb rubber particles that lead to the increase of viscosity of the modified bitumen. However, the mixing temperature and duration can cause rubber particles to depolymerize and subsequently cause loss of viscosity. Crumb rubber modification also improves the properties of bitumen by increasing the storage and loss modulus and enhancing the high and low temperature susceptibility. The effect of crumb rubber to aging properties of CRMB is also discussed. Finally several techniques of chemical modification to terminal blends of CRMB and the subsequent improvement to the settling property of CRMB are explained.
TL;DR: In this article, the morphological characteristics of fabricated composites were investigated by scanning electron microscopy (SEM) and optical microscopy, which revealed smooth and homogeneous texture and good dispersion of CS.
Abstract: Poly (lactic acid) (PLA)/chitosan (CS) natural polymer/epoxidised natural rubber (ENR) composites were successfully prepared through a solution casting method. The morphological characteristics of fabricated composites were investigated by scanning electron microscopy (SEM) and optical microscopy. The microstructure of PLA/ENR was significantly altered with the addition of CS. SEM analysis of composites fractured surfaces revealed smooth and homogeneous texture and good dispersion of CS. However for 15 wt% CS composites, the phase segregation and poor adhesion between the polymers were observed. Fourier transform infrared spectroscopy revealed some levels of attractive interaction between CS, PLA, and ENR in the composites. The mechanical properties of composites in terms of tensile strength and tensile modulus were significantly improved with the addition of CS into the matrix while the percent elongation at break decreased. The tensile strength increased up to 5 wt% CS loading for both PLA/CS and PLA/ENR/CS and thereafter decreased while Young’s modulus increased up to 10 wt%. However, when the CS content was increased to 15 wt%, the tensile strength and tensile modulus were slightly decreased. These improvements were attributed to good dispersion of CS at the optimum filler levels and attractive interaction between the composites components.
TL;DR: In this article, an artificial neural network model was developed to simulate the correlation between the FSLW parameters and mechanical properties, and a sensitivity analysis was performed to investigate the effect of each input parameter on the output in terms of magnitude and direction.
Abstract: Al-Mg and CuZn34 alloys were lap joined using friction stir welding while the aluminum alloy sheet was placed on the CuZn34. In addition, the mechanical properties of each sample were characterized using shear tests. Scanning electron microscopy (SEM) and X-ray diffraction analysis were used to probe chemical compositions. An artificial neural network model was developed to simulate the correlation between the Friction Stir Lap Welding (FSLW) parameters and mechanical properties. Subsequently, a sensitivity analysis was performed to investigate the effect of each input parameter on the output in terms of magnitude and direction. Four methods, namely, the “PaD” method, the “Weights” method, the “Profile” method, and the “backward stepwise” method, which can give the relative contribution and/or the contribution profile of the input factors, were compared. The PaD method, giving the most complete results, was found to be the most useful, followed by the Profile method that gave the contribution profile of the input variables.
TL;DR: In this paper, the most recent studies on the tribological behavior of polymeric materials based on synthetic fibres are summarized and compared. And the results showed that there is high potential of replacing the conventional reinforcement with the bioones.
Abstract: Many different families of polymers are used in industries and engineering applications. The demands for studying the tribological behaviour of polymers and their composites are recently increased. This article briefs the most recent studies on the tribological behaviour of polymeric materials based on synthetic fibres. It reviews several factors which control the wear and frictional characteristics of such materials, that is, additives, fibres, interfacial adhesion, tribology environment, operating parameters, and composite geometry. In addition to that, new bioreinforcement (fibre) is introduced associated with preliminary results. The results showed that there is high potential of replacing the conventional reinforcement with the bioones.
TL;DR: In this paper, the function and importance of Sn-Ag-Cu solder alloys in electronics industry and the interfacial reaction of SnAg-cu/Cu solder joint at various solder forms and solder reflow conditions are discussed.
Abstract: This paper reviews the function and importance of Sn-Ag-Cu solder alloys in electronics industry and the interfacial reaction of Sn-Ag-Cu/Cu solder joint at various solder forms and solder reflow conditions. The Sn-Ag-Cu solder alloys are examined in bulk and in thin film. It then examines the effect of soldering conditions to the formation of intermetallic compounds such as Cu substrate selection, structural phases, morphology evolution, the growth kinetics, temperature and time is also discussed. Sn-Ag-Cu lead-free solder alloys are the most promising candidate for the replacement of Sn-Pb solders in modern microelectronic technology. Sn-Ag-Cu solders could possibly be considered and adapted in miniaturization technologies. Therefore, this paper should be of great interest to a large selection of electronics interconnect materials, reliability, processes, and assembly community.
TL;DR: Sandberg et al. as mentioned in this paper presented an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: © 2013 Linn Ingunn C. Sandberg et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
TL;DR: In this paper, a biopolymer coating for plastic films was formulated based on whey protein, and its potential to replace current synthetic oxygen barrier layers used in food packaging such as ethylene vinyl alcohol copolymers (EVOH) was tested.
Abstract: A biopolymer coating for plastic films was formulated based on whey protein, and its potential to replace current synthetic oxygen barrier layers used in food packaging such as ethylene vinyl alcohol copolymers (EVOH) was tested. The whey-coating application was performed at semi-industrial scale. High barrier to oxygen with transmission rate down to ranges of 1 cm 3 (STP) m −2 d −1 bar −1 at
TL;DR: In this paper, a poly(lactic acid) (PLA)/poly(e-caprolactone) (PCL) blends were prepared via melt blending technique and GMA was added as reactive compatibilizer to improve the interfacial adhesion between immiscible phases of PLA and PCL matrices.
Abstract: Poly(lactic acid) (PLA)/poly(e-caprolactone) (PCL) blends were prepared via melt blending technique. Glycidyl methacrylate (GMA) was added as reactive compatibilizer to improve the interfacial adhesion between immiscible phases of PLA and PCL matrices. Tensile test revealed that optimum in elongation at break of approximately 327% achieved when GMA loading was up to 3wt%. Slight drop in tensile strength and tensile modulus at optimum ratio suggested that the blends were tuned to be deformable. Flexural studies showed slight drop in flexural strength and modulus when GMA wt% increases as a result of improved flexibility by finer dispersion of PCL in PLA matrix. Besides, incorporation of GMA in the blends remarkably improved the impact strength. Highest impact strength was achieved (160% compared to pure PLA/PCL blend) when GMA loading was up to 3 wt%. SEM analysis revealed improved interfacial adhesion between PLA/PCL blends in the presence of GMA. Finer dispersion and smooth surface of the specimens were noted as GMA loading increases, indicating that addition of GMA eventually improved the interfacial compatibility of the nonmiscible blend.
TL;DR: In this paper, a support vector machine (SVM) model was used to predict the splitting tensile strength of concrete from compressive strength using the available experimental data gathered from the literature.
Abstract: Compressive strength and splitting tensile strength are both important parameters that are utilized for characterization concrete mechanical properties. This paper aims to show a possible applicability of support vector machine (SVM) to predict the splitting tensile strength of concrete from compressive strength of concrete, a SVM model was built, trained, and tested using the available experimental data gathered from the literature. All of the results predicted by the SVM model are compared with results obtained from experimental data, and we found that the predicted splitting tensile strength of concrete is in good agreement with the experimental data. The splitting tensile strength results predicted by SVM are also compared to those obtained by using empirical results of the building codes and various models. These comparisons show that SVM has strong potential as a feasible tool for predicting splitting tensile strength from compressive strength.
TL;DR: In this paper, natural fiber obtained from a ladies finger plant was chemically treated separately using alkali (2% NaOH), chromium sulfate (4% ), and chromium sulphate and sodium bicarbonate(4% ).
Abstract: In present research, natural fiber obtained from ladies finger plant was chemically treated separately using alkali (2% NaOH), chromium sulfate (4% ), and chromium sulfate and sodium bicarbonate (4% ). Both raw and chemically treated fibers were subsequently characterized using mechanical (tensile), structural (Fourier transform infrared spectroscopy and scanning electron microscopy), and thermal (thermogravimetric) analysis. Fourier analysis showed the presence of (−OH) group in the ladies plant fiber. Scanning electron micrographs revealed rougher surface in case of alkali treated fiber, while thin coating layer was formed on the fiber surface during other two treatments. Tensile test on ladies finger single fiber was carried out by varying span length. The tensile strength and Young's modulus values were found to be increased after chemical treatment. For both raw and chemically treated fibers, Young's modulus increased and tensile strength decreased with increase in span length. Thermogravimetric analysis indicated the same level of thermal stability for both raw and treated ladies finger fibers.
TL;DR: In this article, a nonlocal differential constitutive relation was proposed by Eringen and a new variational framework was derived by following a consistent thermodynamic approach based on a non-local constitutive law of gradient-type.
Abstract: Various beam theories are formulated in literature using the nonlocal differential constitutive relation proposed by Eringen. A new variational framework is derived in the present paper by following a consistent thermodynamic approach based on a nonlocal constitutive law of gradient-type. Contrary to the results obtained by Eringen, the new model exhibits the nonlocality effect also for constant axial load distributions. The treatment can be adopted to get new benchmarks for numerical analyses.
TL;DR: In this article, the effect of glass composition on their crystal formations and properties was investigated, and it was found that P2O5 and CaF2 served as nucleating sites for lithium phosphate and fluorapatite to encourage heterogenous nucleation and produce a fine-grained interlocking microstructure of lithium disilicate glass ceramics.
Abstract: This work proposes four different glass formulas derived from the SiO2-Li2O-K2O-Al2O3 system to investigate the effect of glass composition on their crystal formations and properties. Glass LD1 was SiO2-Li2O-K2O-Al2O3 system with the addition of P2O5 and CaF2 as nucleating agents. In Glass LD2, a slight amount of MgO was mixed in order to increase the viscosity of the melting glass. Finally, the important factor of Si : Li ratio was increased in Glasses LD3 and LD4 with compositions otherwise the same as LD1 and LD2. The results found that P2O5 and CaF2 served as a nucleating site for lithium phosphate and fluorapatite to encourage heterogenous nucleation and produce a fine-grained interlocking microstructure of lithium disilicate glass ceramics. MgO content in this system seemed to increase the viscosity of the melting glass and thermal expansion coefficient including the chemical solubility. Increasing the Si : Li ratio in glass compositions resulted in the change of the microstructure of Li2Si2O5 crystals.
TL;DR: In this paper, the authors focused on the properties of OPF fiber and gathered mechanical properties reported by other researchers in terms of tensile and flexural properties and chemical surface modification methods to solve the interfacial bonding of fiber and polymer.
Abstract: According to environmental concerns and financial problems, natural fibers have become interesting and fascinating nowadays to be used as an industrial material and structural material for rehabilitating of structures. Oil palm empty fruit bunch fiber (OPF) is a natural fiber which is found a lot in tropical areas. Scientists have used OPF fiber with many types of resins such as epoxy, polypropylene, polyester, and phenol formaldehyde. Therefore, this paper focused on the properties of OPF fiber and gathered mechanical properties of OPF composites (OPF as reinforcement of polymer) reported by other researchers in terms of tensile and flexural properties. Furthermore, the chemical surface modification methods to solve the interfacial bonding of fiber and polymer were mentioned. In addition, the results of hybrid composites of OPF were also discussed in this paper. Meanwhile, the results of composites were compared to pure resin properties and also the stress-strain diagram and internal strain energy of composites were considered. Besides, the effects of adding OPF to other composites to make a new hybrid composite were indicated. Finally, it is clear that the use of oil palm fiber composites for structural elements for bearing loads is not recommended but the usage of OPF composites for secondary structural elements may be recommended due to future researches.
TL;DR: In this paper, the effect of adding crumb tyre rubber as an additive to SMA mixture performance properties was investigated, and the appropriate amount of the added CRM was found to be 12% by weight of bitumen.
Abstract: To prevent pavement distresses there are various solutions such as adopting new mix designs or utilisation of asphalt additives. The primary aim of this study was to investigate the effect of adding crumb tyre rubber as an additive to SMA mixture performance properties. This study investigated the essential aspects of modified asphalt mixtures in order to better understand the influence of CRM modifiers on volumetric, mechanical, and stiffness properties of SMA mixture. In this study, virgin bitumen 80/100 penetration grade was used, modified with crumb rubber (CRM) at five different modification levels, namely, 6%, 12%, 16%, and 20%, respectively, by weight of the bitumen. The appropriate amount of the added CRM was found to be 12% by weight of bitumen. This percentage results in the maximum level of stability. The resilient modulus (Mr) of modified SMA samples including different percentages of CRM was obviously higher in comparison with that of unmodified samples.
TL;DR: An overview of the history of prevailing magnesium alloys as orthopedic biodegradable materials is reported in this paper, where the effect of alloying additions along with surface treatments for corrosion protection is described.
Abstract: An overview is reported about the history of prevailing magnesium alloys as orthopedic biodegradable materials. Important features of the effect of alloying additions, along with surface treatments for corrosion protection of magnesium alloys, are described. Hydroxyapatite (HA), the promising coat deposited by different direct and electrochemical methods to tailor corrosion resistance and biocompatibility, is discussed. Surface modifications, such as microarc oxidation or anodization which lead to nanostructures fabricated to provide better adhesion for HA coatings, are presented.
TL;DR: In this article, the authors used the EDX technique to detect the presence of Ag2O and AgO at appropriate energy levels, and the morphological features obtained from SEM showed that the AgxO structures varied as the deposition time changes.
Abstract: Silver oxide thin films were deposited on glass substrates at a temperature of 50°C by chemical bath deposition technique under different deposition times using pure AgNO3 precursor and triethanolamine as the complexing agent. The chemical analysis based on EDX technique shows the presence of Ag and O at the appropriate energy levels. The morphological features obtained from SEM showed that the AgxO structures varied as the deposition time changes. The X-ray diffraction showed the peaks of Ag2O and AgO in the structure. The direct band gap and the refractive index increased as the deposition time increased and was in the range of 1.64–1.95 eV and 1.02–2.07, respectively. The values of the band gap and refractive index obtained indicate possible applications in photovoltaic and photothermal systems.
TL;DR: In this article, a thin film of silver nanoparticles for humidity sensor application was deposited by electrostatic spray deposition technique, and the influence of the deposition times on properties of films was studied.
Abstract: In this work, thin film of silver nanoparticles for humidity sensor application was deposited by electrostatic spray deposition technique. The influence of the deposition times on properties of films was studied. The crystal structures of sample films, their surface morphology, and optical properties have been investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV-VIS spectrophotometer, respectively. The crystalline structure of silver nanoparticles thin film was found in the orientation of (100) and (200) planes of cubic structure at diffraction angles 2θ = 38.2° and 44.3°, respectively. Moreover, the silver nanoparticles thin films humidity sensor was fabricated onto the interdigitated electrodes. The sensor exhibited the humidity adsorption and desorption properties. The sensing mechanisms of the device were also elucidated by complex impedance analysis.
TL;DR: In this paper, the effects of ground waste concrete (GWC) powder, coming from the attached paste/mortar, on water demand for normal consistency, setting time, fluidity, and compressive strength of cement were analyzed.
Abstract: The paste/mortar attached to the recycled aggregate decreases the quality of the aggregate and needs to be stripped. The stripped paste/mortar is roughly 20% to 50% in waste concrete, but relevant research is very limited. In this paper, the effects of ground waste concrete (GWC) powder, coming from the attached paste/mortar, on water demand for normal consistency, setting time, fluidity, and compressive strength of cement were analyzed. The results show that the 20% of GWC powder (by the mass of binder) has little effect on the above properties and can prepare C20 concrete; when the sand made by waste red clay brick (WRB) replaces 20% of river sand, the strength of the concrete is increased by 17% compared with that without WRB sand.
TL;DR: In this paper, the manufacturing steps for the realisation of biodegradable stents in AZ31 magnesium alloy were demonstrated, including laser microcutting with a Q-switched fiber laser for the generation of the stent mesh and subsequent chemical etching for the cleaning of kerf and surface finish.
Abstract: The use of magnesium-alloy stents shows promise as a less intrusive solution for the treatment of cardiovascular pathologies as a result of the high biocompatibility of the material and its intrinsic dissolution in body fluids. However, in addition to requiring innovative solutions in material choice and design, these stents also require a greater understanding of the manufacturing process to achieve the desired quality with improved productivity. The present study demonstrates the manufacturing steps for the realisation of biodegradable stents in AZ31 magnesium alloy. These steps include laser microcutting with a Q-switched fibre laser for the generation of the stent mesh and subsequent chemical etching for the cleaning of kerf and surface finish. Specifically, for the laser microcutting step, inert and reactive gas cutting conditions were compared. The effect of chemical etching on the reduction in material thickness, as well as on spatter removal, was also evaluated. Prototype stents were produced, and the material composition and surface quality were characterised. The potentialities of combining nanosecond laser microcutting and chemical etching are shown and discussed.