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Effect of sintering temperature on the physical and mechanical properties of synthesized B-type carbonated hydroxyapatite (CHA) over a range of temperature in CO2 atmosphere has been investigated. The B-type CHA in nano size was synthesized at room temperature by using a direct pouring wet chemical precipitation method. The synthesized CHA powders were subsequently consolidated by sintering treatment from 800 to 1100 °C. The sintered CHA samples were evaluated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, X-ray fluorescence (XRF), carbon-hydrogen-nitrogen-sulfur-oxygen (CHNS/O) elemental analyzer, Field emission scanning electron microscopy (FESEM), and Vicker's indentation technique. The results obtained from XRD and FESEM indicated that the synthesized B-type CHA powders were nanometer in size. The crystallinity and crystallite size of the sintered CHA samples were increased due to increasing sintering temperature. The heat treatment between 800 °C and 1000 °C has resulted in coarsening and increased hardness of the sintered CHA samples. However, these properties began to deteriorate when sintering beyond 1100 °C due the formation of calcium oxide.

Ionic substituted calcium phosphates have received much attention for their use as implant materials because of their ability to mimic natural hard tissues. In this work, the properties of hydroxyapatite ceramic doped with small amounts of zinc ions (5, 10, and 15 mol%) by using a wet chemical precipitation route were studied. XRD spectra revealed that adding zinc led to the development of a biphasic mixture composed of hydroxyapatite (HA) and β-TCP phases, which affected the morphology, crystallinity, and crystallite size of the precipitates. With increasing zinc ion substitution in the HA lattices, the degree of crystallinity of the powders reduces due to the additional formation of β-TCP phase. Slender, elongated, and highly agglomerated particles were observed for all synthesized powders. However, calcination at 700 °C caused the particles to become more spherical, having diameters ranging from 30 to 37 nm. An increase in the concentration of zinc ions promoted the β-TCP phase, which ultimately altered the lattice parameters of the HA structure and suppressed the growth of particles.

Mg alloy/austenitic stainless steel (ASS) joints were produced by resistance element weld-bonding (REWB) and resistance spot weld-bonding (RSWB) techniques. Both joints consisted of two zones, namely, the adhesive zone and weld zone. The weld zone of the REWB joints was formed through a metallurgical reaction between the rivet and ASS. The microstructure of the fusion zone consisted of austenite and intercrystalline delta ferrite. The weld zone of the RSWB joints was formed via welding-brazing mechanism (involving molten Mg alloy and solid ASS), and the nugget was formed in the Mg alloy. The nugget microstructure consisted of fine columnar dendritic structure. Digital image correlation (DIC) analysis was used to study the deformation behavior and strain evolution in the loading direction during lap-shear test. The REWB and RSWB joints experienced lower degree of out-of-plane displacement, sustained higher peak load, and exhibited higher strain to failure than their conventional counterparts. However, the REWB joints exhibited superior lap-shear performance, with high energy absorption and favorable failure mode (pull out failure in the ASS sheet). Upon the failure of the adhesive zone at peak load, the load was sustained by the weld, and the final failure occurred via pullout mode in the ASS. The RSWB joints failed in a sudden manner, mainly by cohesive failure in the adhesive zone and Mg alloy nugget/ASS interface failure in the weld zone.

In the present work anorthite-TCP composite ceramics was produced for the first time by the solid-state sintering process involving the mixture of local natural materials of phosphate and kaolin. Various samples were prepared by varying the kaolin content from 47 to 57 wt%. The composite ceramics were sintered in air at various temperatures ranging from 1250 °C to 1325 °C and characterized to determine the phase present, relative density, Vickers microhardness, chemical bonding of molecules and microstructural development. In general, all the samples exhibited a hybrid structure, comprising of anorthite and β-TCP as the major phases with a concomitant minor phases such as TTCP and/or gehlinite depending on the temperature and kaolin content. In addition, increasing kaolin content and sintering temperature were found to be effective in improving the densification and hardness of the sintered body. In particular, sample containing 57 wt% kaolin exhibited excellent densification at 1300 °C and 1325 °C, achieving above 97% dense bodies and highest hardness of about 6.5 ± 0.7 GPa. Microstructural investigation revealed that a dense structure was evident for these samples due mainly to enhanced particle coalescence during the liquid phase sintering, resulting in pore elimination and grain coarsening.

This paper aims to report an aluminum–copper (Al–Cu) die-attach system as a Pb-free alternative for electronic applications. The Al–Cu die-attach system is formulated by a mixture of Al and Cu nanoparticles and a constituent of organic compounds and sintered at 380 °C ± 10 °C without any pressure application. The effects of organic additives on physical, structural, and electrical properties are investigated to understand the die-attach quality of Al–Cu nanopaste. The formation of CuAl2 phase is discovered, which confirmed the joining of Al and Cu nanoparticles in sintered nanopaste layer. Solid-state fusion of Al and Cu can be seen in scanning electron microscope (SEM) analysis. Energy dispersive X-ray (EDX) analysis demonstrates sample of 0.25-g V006A has the lowest oxygen element at 15.36%. Sample with 0.25-g organic additives exhibits the smallest crystallite size and electrical resistivity, which were 8.15 nm and $21~\mu \Omega \cdot \text {cm}$ , which is favorable for high-temperature applications.

Dissimilar lap joining of AZ31B Mg alloy to Cu-Ni coated Ti-6Al-4V was carried out by laser welding-brazing method. The effect of Cu and Ni contents on interfacial reaction and joint fracture load were analyzed. For the joint in which the Ni coating (15.36 µm) was thicker than the Cu coating (5.47 µm), thick intermetallic compound (IMC) composed of a mixture of light gray Al-Ni-Ti + Ti3Al + Ti2Ni phases mingled with dark gray Ti3Al was produced at the interface. In comparison, a mixed interfacial reaction layer consisted of Ti2Ni and Ti3Al was formed from the direct irradiation zone to the weld toe zone of the joint with comparable Ni and Cu coating thicknesses (10.78 µm Cu–9.30 µm Ni). In this case, the thickness of the mixed layer was below the critical thickness of 10 µm. For the joint in which the Cu coating is much higher than the Ni coating thickness (17.12 µm Cu–4.23 µm Ni), Ti3Al and Ti2Ni mixed reaction layer was produced at the brazed interface of direct irradiation zone, whereas, only Ti3Al phase was formed at the middle zone. At the weld toe zone, Ti2Cu uneven interfacial reaction layer was evolved. With increasing Cu and decreasing Ni coating thicknesses, the fracture load first increased and then slightly decreased, the maximum tensile-shear fracture load attained 2020 N for joints with comparable Cu and Ni coating thicknesses. This is twofold higher than that of uncoated joint. The tensile-shear investigation showed that the joint would fracture at the fusion zone when the coating thickness of Ni was comparable or higher than Cu. In contrast, interfacial failure was observed when the thickness of Cu was much higher than the Ni. For the joint with interfacial failure mode, tear ridge was observed from the fracture surface, whereas, the fusion zone fracture surfaces was noted to display a typical dimple feature. The authors would like to acknowledge the support provided by University of Malaya (Project No. GPF073A-2018 ), National Natural Science Foundation of China (Project No. 51504074 and 51875129 ) and Key Research & Development Program in Shandong Province (Grant No. 2017CXGC0811 and 2017GGX30147 ). Scopus

The current study demonstrates the simplistic approach for the synthesis of SrTiO3 nanocubes incorporated polyaniline flakes (PANI-SrTiO3) by facile in-situ oxidative polymerisation route. The synthesised nanocomposites were characterised by various spectroscopic and surface analysis techniques viz. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller analysis (BET). The electrochemical performance of the prepared nanocomposites for energy storage application was evaluated by electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV) in 1 M of KOH as an electrolyte. The electrochemical investigations demonstrate that the performance of the PANI-SrTiO3 nanocomposite in terms of rate capability was significantly higher as compared to the polyaniline flakes and SrTiO3 nanocubes. Supercapattery was fabricated by combining activated carbon and PANI-SrTiO3-250 as negative and positive electrodes respectively in order to evaluate complete device performance. It is found that fabricated supercapattery gave an energy density of 13.2 W h/kg at a power density of 299 W/kg. Additionally, the fabricated supercapattery also offered excellent stability cycle with 114% capacity retention after 4000 cycles. Moreover, the performance of PANI-SrTiO3-250 was found to be better than the other compositions.

Hydrophobic coating usually possesses a water contact angle (CA) of more than 90°. The fabrication of hydrophobic coating on the glass substrate has high potential to induce self-cleaning properties, anti-fogging and mud-repellent properties. In this study, a transparent hydrophobic self-cleaning coating with modified Polydimethylsiloxane (PDMS) has been successfully developed using 3-aminopropyltriethoxyslane (APTES). APTES has a flexible amino group for silica structuration of Polydimethylsiloxane to cross-link and form a hybrid coating system. The hydrophobic coating developed is applied onto glass plates using dip-coating method. The hydrophobicity of the coating is tested using the water contact angle (WCA) method and achieved WCA as high as 103.9°. The UV-VIS spectrometer measurement reveals that the transparency of the modified APTES/ PDMS coating is above 90% in visible region. The prepared hybrid coating also exhibits excellent self-cleaning properties in indoor and outdoor environment. In addition to that, the hybrid coating also exhibits great anti-fogging behavior where the tiny water droplets on the coated surface completely disappear after 6 min at ambient temperature.

Biopolymer electrolytes consisting of poly(vinyl alcohol) (PVA) and lithium trifluoromethanesulfonate (LiTf) were prepared by solution casting technique. The ionic conductivity of polymer electrolyte is increased about seven orders of magnitude which is from 3.53 ± 0.01 × 10−10 to 2.87 ± 0.01 × 10−3 S cm−1 at ambient temperature with the addition of 40 wt% of LiTf. All the polymer electrolytes follow Vogel–Tamman–Fulcher (VTF) relationship which is associated with free volume theory. The complexation between PVA and LiTf salt is proven by Fourier transform infrared spectroscopy (FTIR) study. The glass transition temperature (Tg) of polymer electrolyte was decreased with the addition of LiTf as shown in differential scanning calorimetry (DSC) thermogram. The potential difference of the polymer electrolyte showed wider range, up to 4.6 V, as proven in linear sweep voltammetry (LSV) study. Electric double-layer capacitor (EDLC) cell was assembled using prepared polymer electrolytes and two identical activated carbon-based electrodes and its electrochemical properties were also investigated. The specific capacitance of 0.37 F g−1 was obtained for the EDLC with the most conducting polymer electrolyte.

The state of understanding on the devastating effects of hydrothermal ageing on the properties of yttria-tetragonal zirconia polycrystal (Y-TZP) when exposed to humid environment are reviewed. The prime factors governing the ageing-induced tetragonal to monoclinic phase transformation include the tetragonal grain size, sintering techniques particularly two-step sintering, microwave sintering and electric field assisted sintering, and yttria content are discussed. In addition, the beneficial effects of sintering additives or dopants in promoting sintering as well as suppressing the ageing-induced monoclinic formation are also deliberated. Selective dopants and co-dopants such as copper oxide, alumina, iron oxide and magnesium oxide were found to be beneficial in suppressing hydrothermal ageing in zirconia. Other important boundary conditions to be considered when evaluating the ageing behaviour of Y-TZP includes the ageing environment i.e. temperature, medium and applied pressure which were discovered to have an impact on the rate of phase transformation. Furthermore, the effects of ageing-induced monoclinic formation on the surface topography and mechanical properties of Y-TZP are reviewed. This review indicated that the ageing of Y-TZP can be rather intricate as there are many combinatory factors that needs to be tailored in order to develop an ageing-resistant zirconia without compromising on the transformation toughening effect and other properties.

AZ31B and Ti-6Al-4V were lap welded using laser welding-brazing technique with and without Ni, Cu, and Cu-Ni coatings under similar welding conditions. The effect of the coatings on the appearance, microstructural evolution, and mechanical properties of the joint was studied. For the uncoated joint, only Ti3Al phase formed along the entire brazed interface. In comparison, Ti3Al phase was observed at direct irradiation and middle regions, whereas, Ti2Cu phase was produced at the weld toe region of Cu-added joint. For Ni- and Cu-Ni-coated joints, Ti2Ni mingled with Ti3Al interfacial reaction products evolved from the direct irradiation region to the weld toe region. Interestingly, the thickness of Cu-Ni joint mixed reaction layer was less than the critical thickness of 10 μm. The Cu-Ni-coated joint sustained the highest tensile shear fracture load of 2014 N (which was about 100% higher than that of the uncoated joint), followed by the Ni- and Cu-added joints with 1795 N and 1680 N, respectively. The fracture mode of the uncoated and Cu-added joints was interfacial failure, whereas, FZ fracture with typical dimple feature was observed for both Ni and Cu-Ni joints.

The effect of various amounts of copper oxide (CuO) up to 1 wt% on the densification behaviour and mechanical properties of 3 mol% yttria-tetragonal zirconia polycrystal (Y-TZP) were studied by using microwave (MW) sintering method. The MW sintering was performed at temperatures between 1100 ?C and 1400 ?C, with a heating rate of 30 ?C/min. and holding time of 5 min. The beneficial effect of MW in enhancing densification was also compared for the undoped and 0.2 wt% CuO-doped Y-TZP when subjected to conventional sintering (CS) method. The results showed that significant enhancement in the relative density and Vickers hardness were observed for the undoped Y-TZP when MW-sintered between 1100 ?C and 1250 ?C. It was revealed that the 0.2 wt% CuO-doped Y-TZP and MW sintered at 1250?1300 ?C could attain ? 99.8% of theoretical density, Vickers hardness of about 14.4 GPa, fracture toughness of 7.8 MPam1/2 and exhibited fine equiaxed tetragonal grain size of below 0.25 ?m. In contrast, the addition of 1 wt% CuO was detrimental and the samples exhibited about 50% monoclinic phase upon sintering coupled with poor bulk density and mechanical properties. The study also revealed that the addition of 0.2 wt% CuO and subjected to conventional sintering produced similar densification as that obtained for microwave sintering, thus indicating that the dopant played a more significant role than the sintering method. The authors thank University of Malaya for the financial support (PPP Grant No. PG091-2015A ) in carrying out this research. Scopus

The utmost priority in reducing the usage of ordinary Portland cement (OPC) while replicating the cementitious properties by utilizing industrial by-products in construction materials is seriously undertaken by many researchers. The technology of geopolymerization that utilizes materials and activator solution to form geopolymer matrix could lead to alleviate some of the issues related to OPC based concrete. Numerous experiments have established that geopolymer concrete has higher compressive strength, higher acid resistivity and lower shrinkage than ordinary concrete. This review article focusses on the microstructure analyses of the geopolymer specimens and comparison of geopolymers with various binders. The review analysis of various binders used and their microstructural investigations reveal that different molarity of sodium hydroxide or phosphoric acid solution, liquid-to-binder ratio, curing temperature and duration yield geopolymers of diverse properties. Most of the geopolymer products revealed a wide hump in the XRD analysis due to the amorphous structure of aluminosilicate. Investigation of MIP and Micro CT reveals that aged geopolymer has a denser matrix arrangement and produce high compressive strength. Geopolymerization prevents interconnectivity of micropores due to the formation of denser matrix of geopolymer gel. Generally, the use of 12M of sodium hydroxide solution, low liquid-to-binder ratio of about 0.4 and curing temperature at approximately 70 °C for at least 24 h produced high strength geopolymers. The binders mixed with lower sodium silicate to sodium hydroxide mass ratio of 2.0–2.5 tend to react more efficiently.

A closed-form solution for stress intensity factors (SIFs) of a semi-elliptical surface crack in round bars subjected to torsional loading using the dual boundary element method are presented in this paper. The SIFs of surface cracks having different crack aspect ratios and inclination angles were calculated using the numerical software BEASY. In general, the results revealed that the Mode III SIF was strongly affected by both the crack size and crack shape whereas that crack aspect ratio had the greatest influence on the SIFs regardless of the fracture modes.

Solid polymer electrolyte (SPE) based on fumed silica nanoparticles as nanofillers, hydroxylethyl cellulose (HEC) as host polymer, magnesium trifluoromethanesulfonate salt and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid is prepared by solution casting technique. The ionic conductivity, interactions of adsorbed ions on the host polymer, structural crystallinity and thermal stability are evaluated by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Ionic conductivity studies at room temperature reveals that the SPE with 2 wt. % of fumed silica nanoparticles gives the highest conductivity compared to its counterpart. The XRD and FTIR studies confirm the dissolution of salt, ionic liquid and successful incorporation of fumed silica nanoparticles with host polymer. In order to examine the performance of SPEs, electric double-layer capacitor (EDLC) are fabricated by using activated carbon electrodes. EDLC studies demonstrate that SPE incorporated with 2 wt. % fumed silica nanoparticles gives high specific capacitance (25.0 F/g) at a scan rate of 5 mV/s compared to SPE without fumed silica. Additionally, it is able to withstand 71.3% of capacitance from its initial capacitance value over 1600 cycles at a current density of 0.4 A/g.

In recent years, there is an increased in used of titanium alloys for some parts of mass-produced automobiles and aerospace. However, titanium alloys are characterized by difficult machinability, high melting temperature, high strength, low thermal conductivity, and high reactivity to oxygen, which overshadowed conventional manufacturing processes. To this end, there is a pressing need for more efficient technologies for the manufacture of low-cost titanium structures. Over the years, several joining techniques have been considered for fabrication of titanium alloys. Nevertheless, laser beam welding presents a viable option for welding of titanium due its versatility, high specific heat input, and flexibility. To date, under optimum processing conditions, the strength of the laser-welded titanium alloys can be close to the original material; however, there are still some processing problems such as lower elongation and corrosion resistance coupled with inferior fatigue properties. In this document, the laser beam welding of similar and dissimilar titanium alloys is reviewed, focusing on the influence of the processing parameters, microstructure-property relationship, metallurgical defects, and possible remedies.

In this study, the effect of seed-recrystallization on the Ag deposition onto silica sphere surfaces has been investigated. It was found that increasing the seed-recrystallization cycles resulted in higher atomic deposition at ca. 84% coverage of silica surfaces with the same mole ratio of Ag precursor characterized by the Ag/Si atomic ratio obtained by XPS analyses. The addition of straight-chain palm oil derived fatty alcohols (PODFA) in the sol-gel prior to seed-recrystallization aided the deposition of Ag. Thus, PODFA play the role of nonsurfactant surface modification agent to produce Ag-silica nanocomposite. Structural analyses showed that the resulting Ag nanocrystallines having a face centre cubic structure and particle size of 5–20 nm were deposited homogeneously on silica spheres. Chemical state analyses from XPS indicated that the increasing number of seed repetition process increased the seeding of Ag nanoparticles on silica surface with the same molar of Ag atoms. XPS spectra at O1s orbital elucidated that the binding energy of three oxides components were determined at ca. 533.8 eV (Si-O-H), 532.8 eV (Si-O-Si) and 530.8 eV (Si-O-Ag), respectively. The high sensitivity of surface plasmon resonance observed in the nanocomposites prepared in this study are useful in optical applications.

No empirical solution for the stress intensity factors (SIFs) of a surface crack in a solid cylinder under torsion was reported in literature. In this paper, empirical solutions for Modes I, II, and III stress intensity factors of a semi-elliptical surface crack in a solid cylinder under pure torsion are proposed. The dual boundary element method (DBEM) based software was used to generate the SIFs for different crack size, crack aspect ratio, and different inclination angles. Next, the solutions for the SIFs were produced through a systematic curve fitting approach.

Calcium phosphate coatings produced on the surface of Ti6Al4V by plasma electrolytic oxidation (PEO) using different concentrations of hydroxyapatite (HA) in a 0.12 M Na3PO4 (NAP) electrolyte solution was investigated. It was found that the amount of calcium phosphate particles infiltrated into the coating layer as well as the thickness and the surface roughness of the coating increased with increasing HA concentration. The porosity of the ceramic coatings indicated an inverse relationship with the concentration of HA particles dispersed in the NAP solution. The result also demonstrates that higher scratch adhesive strength was achieved using 1.5 g/L HA solution, producing a critical load of 2099 mN, while 0 g/L HA only produced a critical load of 1247 mN. The adhesion becomes independent of thickness when the concentration of HA exceeds 1.5 g/L. The failure of the coating was characterized by large periodic hemispherical chipping, while intermittent delamination was noticed with the coating embedded with HA particles. This study demonstrate the viability of using PEO to produce a thin layer of HA ceramic coating on Ti6Al4V suitable for biomedical applications.

With exponentially increasing copper alloys consumption globally, the automatization, high efficiency, and quality improvement of the copper joining process become inevitable in modern industrial production. In this context, laser welding presents a particular suitability for joining of copper alloys because of its high precision, high-energy concentration, and rapid processing potentials. Studies have shown that laser welding of copper has two principal challenges. Namely, the high laser power required due to the low laser beam absorptivity and high thermal conductivity of copper, and the low process stability. Interestingly, with the recent laser technology improvements, the tremendous laser power required will eventually be solved. Although some achievements were obtained in previous studies, the problem of spattering and high porosity associated with low process stability still exist. In this review, the effect of the most significant laser welding processing parameters on the joint’s performances were systematically examined; the microstructure, mechanical, and electrical properties and metallurgical defects of copper laser welds were discussed. Furthermore, laser welding of copper to other metals particularly copper to steel and copper to aluminum dissimilar alloys in terms of structure and properties relationships were also discussed.

With the growing demand for vehicle weight reduction and the increased application of multimaterial design, it is imperative to address the challenges of welding dissimilar light alloys. This paper presents a review on laser welding of Al/Mg, Al/Ti, and Mg/Ti alloys, with focus on the techniques used to suppress the formation of brittle intermetallic compounds (IMCs) and improve joining mechanism. For Al/Mg joints, studies have shown that the use of structural adhesives, the use of interlayers such as Ce, Ni, Ti, and Fe foils and Zn-Al filler metals, and hybrid adhesive-interlayers could suppress the formation of brittle IMCs and improve joint strength. The formation of brittle IMCs during laser welding of Al/Ti alloys could be minimized by offsetting the laser beam at an appropriate distance towards either the Al or Ti alloy, the use of split-beam laser with appropriate joint design, the use of high welding speed, improving the laser energy distribution, and the use of V-groove with Al-Si filler metals. For Mg/Ti alloys, offsetting the laser beam at an appropriate distance towards the Mg alloy, the use of AZ series Mg alloy-based filler wires, and coating the Ti alloy with Ni were found to facilitate the joint formation and improve the joint strength.

An AZ31 Mg alloy and 316L austenitic stainless steel (ASS) were joined via resistance spot welding (RSW) and resistance element welding (REW). The RSW joints were found to be produced through welding-brazing mode, in which the Mg alloy melted and spread on the solid steel, forming a nugget only in the Mg alloy. The microstructure of the nugget consisted of columnar dendritic structure, indicating that columnar-to-equiaxed transition was interrupted. Shrinkage porosity and cracking were also observed in the RSW nugget. In contrast, a two-zone nugget was formed during REW, consisting of a peripheral nugget on the ASS side and the main nugget. Compared with the RSW joints, the REW joints were obtained at lower welding currents, and they exhibited superior mechanical performance, with 63% higher peak load and 9 times higher energy absorption. Irrespective of the welding current, the RSW joints failed in interfacial failure mode, while the failure mode of the REW joints transited from interfacial to pull out with increased welding current.

The main problem of landfill leachate is its diverse composition comprising many persistent organic pollutants which must be removed before being discharge into the environment. This study investigated the treatment of raw landfill leachate using electrocoagulation process. An electrocoagulation system was designed with iron as both the anode and cathode. The effects of inter-electrode distance, initial pH and electrolyte concentration on colour and COD removals were investigated. All these factors were found to have significant effects on the colour removal. On the other hand, electrolyte concentration was the most significant parameter affecting the COD removal. Numerical optimization was also conducted to obtain the optimum process performance. Under optimum conditions (initial pH: 7.73, inter-electrode distance: 1.16 cm, and electrolyte concentration (NaCl): 2.00 g/L), the process could remove up to 82.7% colour and 45.1% COD. The process can be applied as a pre-treatment for raw leachates before applying other appropriate treatment technologies.

Hybrid polymeric based nanocomposite coating systems (NCs) were fabricated by solution intercalation method with the use of epoxy (E) and polydimethylsiloxane (PDMS) as the host hybrid polymeric matrix and different weight ratio of SiO2 nanoparticles, ranging from 2 wt. % to 8 wt. %, as the reinforcing agents. The effects of introducing PDMS as a modifier to epoxy resin, as well as, the influence of embedding SiO2 nanoparticles within the developed matrix were evaluated via utilizing X-ray diffraction (XRD), contact angle measurements (CA), field emission scanning electron microscope (FESEM), and electrochemical impedance spectroscopy (EIS). XRD and FESEM results revealed the good dispersion of the nanoparticles within the polymeric matrix and confirmed the efficiency of the solution intercalation method. CA findings confirmed the achievement of hydrophobic surface after modifying epoxy resin with PDMS with CA value at 96° for epoxy-PDMS coating system (ES 0). Also CA results indicated the ability of SiO2 nanoparticles to participate in developing more hydrophobic surface as CA value up to 132° was achieved with utilizing 6 wt% SiO2 loading ratio. The results obtained from EIS studies revealed that the coating system with 2 wt% had the best anticorrosion performance and have demonstrated an intact behavior over all the immersion period without any sign of coating damage or degradation.

With the aim of replacing liquid electrolytes in dye sensitized solar cells (DSSCs) due to the evident issues the system has, we have prepared and optimized gel polymer electrolytes (GPEs) consisting of poly(methyl methacrylate-co-methacrylic) acid, P(MMA-co-MAA), sodium iodide (NaI), iodine (I 2 ), ethylene carbonate (EC), propylene carbonate (PC) with a novel lab-made ionic liquid N -butyl-6-methylquinolinium bis(trifluoromethylsulfonyl)imide [C 4 mquin][NTf 2 ]. Synthesized via metathesis following an alkylation, the quinolinium based ionic liquid has a yield of 87%. The highest ionic conductivity obtained for this system is 2.26 × 10 −3 S cm −1 at room temperature for the GPE at 25 wt.% of [C 4 mquin][NTf 2 ]. XRD and FTIR studies have been done to confirm the formation of complexes of the materials. With a standard DSSC arrangement of glass/FTO/TiO 2 /N719dye/electrolyte/Pt/FTO/glass, the co-polymer based conducting electrolyte displayed power conversion efficiency of 5.67% with a maximum short circuit current density (J sc ) of 15.32 mA cm −2 , open circuit voltage (V oc ) of 0.62 V and fill factor of 59% at 25 wt.% of [C 4 mquin][NTf 2 ] under AM 1.5 (100 mW cm −2 ) illumination. The Nyquist plot and Bode plot studies have been done in order to understand the electrochemical properties of the GPE based DSSCs.

Bovine hydroxyapatite, a widely used scaffold in tissue engineering, is sintered at varied temperatures (600 °C, 700 °C, 750 °C, 800 °C, 900 °C and 1000 °C) and was evaluated for its osseo-integration potential with human bone marrow derived mesenchymal stromal cells. The cell attachment, distribution, morphology, and osteogenic marker assays were analysed. SEM analysis on day 11 revealed the porous structure and well-defined equiaxed HAp grain morphology and its affinity for cell attachment. While confocal microscopy showed viable cells on all samples, the proliferation assay indicated that cells in monolayer is significantly higher on day 11 and 15 than the scaffold (p

Composites containing cobalt oxide (Co3O4) nanocubes integrated with multiwall carbon nanotubes (MWCNT) were synthesized by a hydrothermal route. The fractions of MWCNTs in the composite were varied from 4, 8, 12, 16 and 20 wt.%, and the resulting materials are denoted as C1, C2, C3, C4 and C5, respectively. The formation of products with high structural crystallinity was confirmed by X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. A morphological study by field emission scanning electron microscopy and high resolution transmission electron microscopy showed the successful integration of Co3O4 nanocubes to the MWCNTs with an average particle size of ∼32 nm. The surface of a glassy carbon electrode (GCE) was modified with the nanocomposites in order to evaluate the electrochemical performance of the nanocomposites. Cyclic voltammetry showed that the C4-modified GCE displays best performance in terms of oxidation potential and peak current in comparison to that of a bare GCE, Co3O4 nanocubes, or GCEs modified with C1, C2, C3 or C5. The detection limit (at an S/N ratio of 3) is 0.176 nM by using chronoamperometry, and the linear range is between 1 and 20 μM.

This paper aims to report on the formation of neodymium oxide by thermal oxidation of sputtered metallic Nd thin film deposited on Si substrate. Sputtered Nd thin film on Si substrate followed by thermal oxidation in O2 ambient at a fixed duration of 15 min for various temperatures (500–1100 °C) has been investigated systematically. The structural and chemical properties of the formed thin films were evaluated by X-ray diffraction analysis, Fourier transform infrared analysis, Raman analysis and high resolution transmission electron microscopy analysis. It was found that cubic phase of Nd2O3 film was formed along with orthorhombic phase of Nd2Si2O7 and multiple phases of SiO2 which consists of monoclinic, tetragonal, and hexagonal phases. Based on the electrical results, sample thermally oxidized at 900 °C revealed the highest electrical breakdown field of 5.26 MV/cm at the lowest leakage current density of 2.19 × 10− 6 A/cm2 together with lowest Q eff and average interface trap density. This is attributed to the lowest Nd-silicate content, the largest SiO2 and the smallest Nd2Si2O7 crystallite size, and highest barrier height.

Poly(1-vinylpyrrolidone-co-vinyl acetate)-based quasi-solid polymer electrolytes doped with potassium iodide are prepared. The highest room temperature ionic conductivity of 1.72 mS cm−1 is obtained. The dielectric studies are performed to understand the ion conduction mechanism. Fourier transform infrared study has been performed to understand complexation of the poly(1-vinylpyrrolidone-co-vinyl acetate)-based quasi-solid polymer electrolytes. The best power energy conversion efficiency (η) obtained is 2.94% with short circuit current density (Jsc) of 8.05 mA cm−2, open circuit voltage (Voc) of 0.58 V, and fill factor of 63% under standard light intensity of 100 mW cm−2 irradiation.

Bulk copper and Cu-7.0Ni-9.3Sn-6.3P (in wt %) filler alloys were brazed by microwave hybrid heating (MHH) and the results were compared with brazing using conventional furnace heating. Characterizations of the brazed joint were investigated through field emission scanning electron microscope, X-ray diffraction, shear strength test and Vicker's microhardness test. It was observed that microwave heating decreased to 94 % of total processing time compared to conventional heating. Metallurgical study showed the formation of the alpha-copper, copper phosphide and nickel phosphide intermetallics at the joint interface for both heating methods. The reaction layer thickness of microwave brazed joint was three times thinner compared to the conventionally brazed joint. The optimum shear strength of the microwave brazed joints was found to be 108.8 MPa while it was 16 % higher for the samples brazed using the conventional method. The failures of the microwave brazed joints showed a brittle cleavage structure while a mixed cleavage structure with tearing regions was observed for the conventionally brazed joints.

The effect of flyash (FA) additions of 0.05 wt% to 1 wt% on yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), sintered in air at temperatures ranging from 1250°C to 1500°C, was examined. The bulk density, Young’s modulus, Vickers hardness and fracture toughness for each addition were determined while ageing behaviour were observed by subjecting them to superheated steam at 180°C/10 bar in an autoclave for 24 hours. Additions of FA, particularly of 0.05 wt% and 0.1 wt%, were found to be beneficial in aiding densification and increasing Young’s modulus beyond 200 GPa for sintering temperatures up to 1350°C. A common trend was observed for the Vickers hardness of all additions including undoped; hardness continues to rise from 1250°C and peaked at 1350°C before gradually decreasing as the sintering temperature increases further. No pronounced effect of flyash was seen on the fracture toughness of all samples. The ageing resistance of Y-TZP improved with addition of FA resulting in relatively lower amount of ageing-induced tetragonal to monoclinic phase transformation exhibited by doped samples compared to the undoped.

In this study, a new analytical solution by the recursive method for evaluating stresses/displacements in multilayered hollow cylinder under thermo-mechanical loading was developed. The results for temperature distribution, displacements and stresses obtained by using the proposed solution were shown to be in good agreement with the FEM results. The proposed analytical solution was also found to produce more accurate results than those by the analytical solution reported in literature.

The effect of varying amounts (up to 1 wt%) of graphene oxide (GO), on the densification behaviour of yttria–stabilised tetragonal zirconia (Y-TZP) was investigated. Green bodies were prepared and sintered in air atmosphere over the temperature range of 1200 °C to 1500 °C. Sintered samples were then evaluated to determine bulk density, Vickers's Hardness, fracture toughness, phase stability and grain size. Furthermore, the samples were subjected to hydrothermal ageing in superheated steam at 180 °C/10 bar for up to 200 h to evaluate the ageing-induced tetragonal to monoclinic phase transformation. The results showed that the addition of GO was beneficial in improving densification and mechanical properties of Y-TZP ceramic, particularly at low sintering temperatures. A high hardness of 14.3 GPa and fracture toughness of 5.6 MPa m 1/2 were recorded for GO-doped Y-TZP sintered at 1300 °C and 1400 °C, respectively. Despite the improvement in the sintering properties, the addition of GO was not effective in suppressing the ageing-induced monoclinic phase formation for samples sintered above 1300 °C.

The effect of pressureless sintering on the properties of magnesium orthosilicate-hydroxyapatite (MO-HA) ceramic has been studied. The amount of MO composition in the green body was varied from 10 wt% to 50 wt% through mechanical ball milling and was subsequently sintered at varying temperatures in air atmosphere from 1000 °C to 1300 °C for 2 h. The magnesium orthosilicate phase was stable during sintering but the hydroxyapatite phase decomposed to tricalcium phosphate. The MO-HA composites generally exhibited lower mechanical properties across all the investigated composition. Nevertheless, a high fracture toughness of 2.5 MPam 1/2 was recorded for sintered body that contained 20 wt% MO. This finding indicates the potential of this ceramic composite to be used for biomedical applications.

The effect of conventional sintering from 1300 to 1550 °C on the properties of 1 mol% ceria-doped scandia stabilized zirconia was investigated. In addition, the influence of rapid sintering via microwave technique at low temperature regimes of 1300 °C and 1350 °C for 15 min on the properties of this zirconia was evaluated. It was found that both sintering methods yielded highly dense samples with minimum relative density of 97.5%. Phase analysis by X-ray diffraction revealed the presences of only cubic phase in all sintered samples. All sintered pellets possessed high Vickers hardness (13–14.6 GPa) and fracture toughness (~3 MPam 1/2 ). Microstructural examination by using the scanning electron microscope revealed that the grain size varied from 2.9 to 9.8 µm for the conventional-sintered samples. In comparison, the grain size of the microwave-sintered zirconia was maintained below 2 µm. Electrochemical Impedance Spectroscopy study showed that both the bulk and grain boundary resistivity of the zirconia decreases with increasing test temperature regardless of sintering methods. However, the grain boundary resistivity of the microwave-sintered samples was higher than the conventional-sintered ceramic at 600 °C and reduced significantly at 800 °C thus resulting in the enhancement of electrical conduction.

A novel ternary composite consisting of cobalt oxide (Co3O4) nanoparticles (NPs) grown on multiwalled carbon nanotubes (MWCNTs) and mixed with gold (Au) NPs is synthesized by a single step hydrothermal route. Initially, density functional theory (DFT) simulations were carried out to model the aggregation of Co3O4 NPs and validated further with experimental results. To circumvent this issue, MWCNTs with gold NPs were introduced, which significantly reduced the particle aggregation. Standard three electrode cell studies revealed that the Co3O4/Au@MWCNT composite possesses an excellent energy density, rate capability and very good cyclic stability compared to unsupported Co3O4 or the binary Co3O4@MWCNT. The promising electrochemical performance compared to the single Co3O4 or the binary Co3O4@MWCNT materials is assigned to the synergetic effects of MWCNTs and Au to disaggregate the Co3O4 NPs and to enhance the overall conductivity, respectively. In order to get insight into the evaluation of the performance, two electrode devices were assembled employing activated carbon as a negative electrode and the Co3O4/Au@MWCNT composite as a positive electrode material. The two electrode supercapattery device demonstrated splendid cycling stability with a retention value of 91.90% in 1 M KOH for over 3500 cycles. Additionally, it exhibited an excellent energy density of 18.80 W h kg−1 at a power density of 302.00 W kg−1. These encouraging outcomes can be associated with the distinctive morphology, outstanding conductive networks, increased electroactive sites, and emergence of strong networking of Co3O4, MWCNT and Au in the ternary composite.

A fiber laser welding-brazing procedure has been developed for joining AZ31B magnesium alloy to Cu-Ni coated Ti-6Al-4V titanium sheet using AZ92D filler wire. The effect of the interlayer arrangements (AZ31B/Ni-Cu/Ti-6Al-4V and AZ31B/Cu-Ni/Ti-6Al-4V) on appearance, interfacial reaction and mechanical properties were investigated at different heat input. It was found that the feasibility of this process depends strongly on the pre-existing Cu-Ni layer on the Ti surface that promotes wetting of the AZ92 filler. Within the range of 1200-1600 W, defect free joints in both interlayer arrangements. Depending on the interlayer arrangements chosen, different reactions layers formed inside the joint region. Nevertheless, at optimum heat input (1400 W), Ti2Ni mingled with Ti3Al interfacial reaction products was produced along the fusion zone (FZ)-Ti brazed interface in both interlayer arrangements. The tensile-shear fracture load of the joints produced at the optimum laser power reached a maximum value of 2016.5 N for AZ31B/Ni-Cu/Ti-6Al-4V and 2014.6 N for AZ31B/Cu-Ni/Ti-6Al-4V, representing an efficiency of 71% compared to AZ31B alloy. Under suitable heat input, the joints failed at the fusion zone of the AZ31B base metal. In contrast, incomplete brazing or large volume of intermetallics at the brazed interface resulted in interfacial failure at lower/higher heat input. This work was financially supported by University of Malaya (Grant No. GPF073A-2018 ), National Natural Science Foundation of China (Grant. No. 51504074 and 51875129 ) and Key Research & Development Program in Shandong Province (Grant No. 2017CXGC0811 and 2017GGX30147 ). Scopus

This technical note demonstrates the use of tetrahedral meshing for modelling a slanted semi-elliptical surface crack at a solid cylinder by finite element method (FEM). For a relatively small ratio of the crack depth over cylinder diameter, Modes I and II (in-plane) stress intensity factors (SIFs) at the corner points by FEM were observed to be in good agreements with those by the dual boundary element method (DBEM). Effect of the crack aspect ratio, crack size and loading mode on the corner point singularity was noted. The tearing loading mode was found to promote a greater corner point singularity.

The growth of portable technologies and electrical automotive industry has led to the development of supercapattery, as one of the options in the electrochemical energy storage system. In this work, nanocomposite of polyaniline-metal phosphate (comprising nickel phosphate-silver phosphate (Ni3(PO4)2-Ag3PO4) nanocomposite) was synthesized by two-step route; a combination of sonochemical-calcination method, followed by the physical blending method. Structural and morphology studies reveal that crystalline Ag3PO4 which were decorated on amorphous Ni3(PO4)2 were supported by semi-crystalline PANI nanofibers. The electrochemical performance studies show the resultant PANI-Ni3(PO4)2-Ag3PO4 exhibited significantly improved rate capability from 32% (Ni3(PO4)2) to 73% with a maximum specific capacity of 677 C/g. The origin of the outstanding performance shown by PANI-Ni3(PO4)2-Ag3PO4 was due to the synergistic effect produced by the conductive platform provided by PANI, redox behavior of Ni3(PO4)2 and extended channels provided by Ag3PO4. In order to evaluate the real-time performance of PANI-Ni3(PO4)2-Ag3PO4, supercapattery devices were fabricated in a configuration of PANI-Ni3(PO4)2-Ag3PO4//activated carbon (AC), Ni3(PO4)2-Ag3PO4//AC and Ni3(PO4)2//AC. PANI-Ni3(PO4)2-Ag3PO4//AC produced a superior performance by providing specific energy of 38.9 Wh/kg at 400 W/kg compared to its counterpart devices. Moreover, the life cycle test of PANI-Ni3(PO4)2-Ag3PO4//AC demonstrated high stability which lost only 12% of its initial capacity after 5000 cycles.

This paper presents a review on the resistance spot welding (RSW) of Al/Al alloys, Al alloys/steel, Al/Mg alloys, and Al/Ti alloys, with focus on structure, properties, and performance relationships. It also includes weld bonding, effect of welding parameters on joint quality, main metallurgical defects in Al spot welds, and electrode degradation. The high contact resistance, induced by the presence of oxide layer on the surface of Al alloys, and the need for application of high welding current during RSW of Al alloys result in rapid electrode tip wear and inconsistency in weld quality. Studies have shown that cleaning the oxide layer, sliding of a few microns between sheets, enhancing the electrode force, and the application of a low-current pre-heating can significantly reduce the contact resistance and improve joint quality. For Al/steel dissimilar RSW, the technique of resistance element welding, the use of optimized electrode morphology, the technique of RSW with cover plates, and the use of interlayers such as Al-Mg, AlSi12, and AlCu28 alloys were found to suppress the formation of brittle intermetallic compounds (IMC) and improve the joint quality. The employment of pure Ni foil, Au-coated Ni foil, Sn-coated steel, and Zn-coated steel interlayers was also found to restrict the formation of brittle IMCs during RSW of Al/Mg alloys. Furthermore, the techniques of RSW with cover plates and RSW under the influence of electromagnetic stirring effect were found to improve the weldability of Al/Ti dissimilar alloys.

In this work, the effect of microwave sintering on the properties of 1 mol% ceria-doped scandia stabilized zirconia (10Sc1CeSZ) was investigated. The sintering was carried out at temperatures 1300 °C and 1350 °C for 15 min using a 2.45 GHz microwave furnace. The sintering behavior of the microwave sintered ceramics was compared with that obtained via the conventional sintering at temperatures ranging from 1300 °C to 1550 °C with 2 h holding time. It was found that both sintering processes yielded highly dense samples with minimum density of 98% theoretical value. Phase analysis by X-ray diffraction revealed the presences of only cubic phase in all sintered samples. All sintered pellets possessed high Vickers hardness (13–14.6 GPa) and fracture toughness (∼3 MPa m 1/2 ). Microstructural examination by using the scanning electron microscope showed that the grain size varied from 2.9 to 9.8 μm for the conventional sintered samples whereas the grain size of the microwave sintered ceramics was below 2 μm. Electrochemical Impedance Spectroscopy study recorded the maximum ionic conductivity of 0.280 S/cm at 800 °C for the conventional-sintered sample at 1550 °C whereas a high value of 0.314 S/cm was measured for the microwave-sintered sample at 1350 °C.

The effect of microwave sintering on the densification of forsterite ceramic was investigated. Forsterite powder was prepared via solid-state reaction method with the application of attrition milling and heat treatment. The forsterite compacts were microwave sintered at 1100 °C to 1250 °C with 30 min holding and a ramping rate of 50 °C/min. The samples were then characterized in terms of phase stability, relative density and microstructure evaluation. This work revealed that microwave sintering is beneficial in producing dense forsterite at lower sintering temperature with shorted operating hour (< 1 hr). Highest relative density of 87.9% was successfully obtained at 1250 °C with estimated grain size of lesser than 1 μm as compared to conventional sintering.

Electrochemical anodisation is a well-received method in the complementary metal-oxide-semiconductor field as it is advantageous; best performed at room temperature which translates into being more affordable and a simple alternative to form nano-structured oxide films for different metals. The quintessential parameters involved allow numerous formations of metal oxide films according to desired morphology and thickness. Therefore, this paper aims to review the effects of anodising parameters such as applied voltage, concentration, temperature, time, current density and post-anodisation annealing among them.

In this study, the effect of microstructural evolution of TiO2 nanotubular arrays on wettability and optical properties was investigated. Pure titanium was deposited on silica glass by PVD magnetron sputtering technique. The Ti coated substrates were anodized in an electrolyte containing NH4F/glycerol. The structures of the ordered anodic TiO2 nanotubes (ATNs) as long as 175 nm were studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The result shows a sharp peak in the optical absorbance spectra around the band gap energy, 3.49–3.42 eV for annealed and non-annealed respectively. The thermal process induced growth of the grain size, which influence on the density of particles and the index of refraction. Furthermore, the wettability tests' result displays that the contact angle of intact substrate (θ = 74.7°) was decreased to 31.4° and 17.4° after anodization for amorphous and heat treated (450 °C) ANTs coated substrate, respectively.

In this research, Cu3.21Bi4.79S9 was synthesized from Cu, Bi and S powders using ball milling. The effects of ball milling duration and the process control agent, i.e. ethanol, on the formation of Cu3.21Bi4.79S9 were investigated. The thermal stability of Cu3.21Bi4.79S9 was also studied using a Differential Scanning Calorimeter (DSC) in combination with X-ray diffraction (XRD) analysis. It was observed that the addition of ethanol shows a significant effect on the refinement of the particle size of the milled powder. However, ethanol showed a negative effect on the formation of single phase Cu3.21Bi4.79S9 during ball milling. Cu3.21Bi4.79S9 was found in the milled powder after milling for 5 h without using ethanol, whilst the presence of secondary phases such as Bi2S3 and Cu2S were also detected. All these secondary phases were disappeared after milling for 15 h. Prolonged milling duration did not produce any change in the phases. Minimum particle size of the milled powder was achieved around 0.251 μm after milling for 25 h. The XRD and DSC results showed that Cu3.21Bi4.79S9 is thermally stable up to 230 °C.

The microwave assisted pyrolysis of oil palm fiber (OPF) for production of hydrogen rich gas was experimentally investigated by considering different reaction parameters. Five different OPF sample sizes (i.e., lengths less than 1 mm, 1–3 mm, 4–6 mm, 7–9 mm and 10–12 mm), microwave power ranging from 400 W to 900 W, reaction temperatures ranging from 450 °C to 700 °C and N 2 flow rates ranging 200–1200 cm 3 min −1 were tested. The hydrogen and the total gas yield from all process parameters have been reported. The microwave assisted pyrolysis was carried out by using a microwave reactor which has a capacity of providing 2450 ± 25 MHz microwave frequency. It has been found that the use of a smaller OPF particle sizes, a higher microwave power, a higher reaction temperature and a higher N 2 flow rates significantly yields more H 2 rich gas. The char produced at the maximum hydrogen yield process parameter was considered for TGA and SEM analyses and the results shows a potential use for the soil fertilization.

Nanocrystalline hydroxyapatite derived from eggshell (HA-Es) was successfully prepared via a direct solid-state sintering method. The process involved mixing calcined eggshell powder and dicalcium hydrogen phosphate di-hydrate followed by a heat treatment at 800 °C. The resulting flower-like HA-Es powder was sintered at various temperatures ranging from 1050 °C to 1350 °C for 2 h in air atmosphere. The material was characterized to determine the thermal stability and the effect of sintering on the microstructure as well as properties of the resulting HA derived from eggshell. The results showed that sintering beyond 1250 °C resulted in the HA phase decomposition to tricalcium phosphate and tetra-calcium phosphate. However, these secondary phases did not disrupted the densification process as the samples exhibited densities above 98% when sintered at 1300–1350 °C. A maximum fracture toughness of 1.51 MPam 1/2 was measured for HA-ES sample sintered at 1250 °C with a concomitant small grain size, below 1 µm coupled with high hardness of 5.62 GPa and high relative density of 98% being measured. The study also revealed that the relative density and grain size played a significant role in governing the properties of the HA-Es samples.

We demonstrated the effect of ZnO (different wt%)-coated LiMnPO4-based cathode materials for electrochemical lithium ion batteries. ZnO-coated LiMnPO4 cathode materials were prepared by the sol-gel method. X-ray diffraction (XRD) analysis indicates that there is no change in structure caused by ZnO coating, and field emission scanning electron microscopy (FESEM) images depict the closely packed particles. Galvanostatic charge-discharge tests show the ZnO-coated LiMnPO4 sample has an enhanced electrochemical performance as compared to pristine LiMnPO4. The 2 wt% of ZnO-based LiMnPO4 exhibited maximum discharge capacity of 102.2 mAh g−1 than pristine LiMnPO4 (86.2 mAh g−1) and 1 wt% of ZnO-based LiMnPO4 (96.3 mAh g−1). The maximum cyclic stability of 96.3 % was observed in 2 wt% of ZnO-based LiMnPO4 up to 100 cycles. This work exhibited a promising way to develop a surface-modified LiMnPO4 using ZnO for enhanced electrochemical performance in device application.