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Two commercial grade silicon nitride ceramics (Honeywell GS44 and Kyocera SN235) were exposed to an oil ash to evaluate the long-term corrosion/oxidation resistance in a simulated diesel engine environment. The exposure condition was at 850 °C for 1000 h in air. Subsequently, the exposed specimens were tested in flexure for strength degradation at room temperature and 850 °C at stressing rates of 30 MPa/s and 0.003 MPa/s in air, respectively. A similar set of specimens not exposed to the oil ash was also tested in flexure for purpose of comparison. Little change in strength was measured after 1000 h exposure in the oil ash environment. Also, the values of Weibull modulus obtained for all of the exposed silicon nitride materials were similar to those with the unexposed specimens whose strength were obtained under the same conditions. However, both exposed and unexposed GS44 specimens exhibited a low fatigue exponent, suggesting a susceptibility to slow crack growth at test temperature. In addition, detailed SEM/EDAX analyses indicated that no oil ash elements (e.g., Zn, Ca, P, Na, and S) were detected beneath a thin layer in the surface; thus, there were no changes in the chemistry of the secondary phase(s) within the bulk. These elements were detected only in a region about 1–3 μm below the exposed surface, but no apparent changes in microstructure observed. Results of mechanical properties and microstructural characterizations indicated that these candidate silicon nitride materials exhibited excellent corrosion/oxidation resistance in the simulated diesel engine environment and, based on their excellent mechanical strengths, would be ideal candidates for diesel engine exhaust valve applications. [ABSTRACT FROM AUTHOR]

The microstructure, compressive properties and in vitro degradation behavior of as-cast Mg alloys with high Zn or Ca content were investigated. The results showed that the addition of Ca (1 wt%) to Mg–5Zn or Zn (1 wt%) to Mg–5Ca changed the shape, distribution, volume fraction and the type of second phase. When 1 wt% Ca was added to Mg–5Zn alloy, the second phase changed from Mg7Zn3 to Ca2Mg6Zn3 phase and it was distributed from granular formation to a continuous network structure. While the second phase was changed from Mg2Ca in Mg–5Ca alloy to the coexistence of Mg2Ca(Zn) and slight Ca2Mg6Zn3 phase in Mg–5Ca–1Zn alloy. The second phase exhibited a continuous network distribution in both of Mg–5Ca and Mg–5Ca–1Zn alloys, but the width of Mg2Ca(Zn) phase was reduced obviously after adding 1 wt% Zn to Mg–5Ca alloy. The compressive test revealed that Zn element was contributed to the promotion of ultimate compressive strength and fracture elongation, while Ca element was beneficial for improving the yield strength of Mg alloys. The immersion test proved that the weight loss of Mg–5Zn–1Ca was the highest, followed by Mg–5Zn, Mg–5Ca and Mg–5Ca–1Zn alloy. The Mg–5Zn-based alloys suffered severe pitting, while Mg–5Ca-based alloy exhibited a relatively uniform corrosion. The Ca addition accelerated the corrosion of Mg–5Zn alloy due to the expansion of potential difference between second phase and Mg matrix, while Zn addition reduced the micro-galvanic corrosion of Mg–5Ca alloy due to the lowest potential difference between Mg2Ca(Zn) phase and Mg matrix. [ABSTRACT FROM AUTHOR]

Twin-roll cast magnesium has a fine-grained microstructure and exhibits relatively high strength and ductility. However, hydrogen-induced embrittlement in magnesium alloys can limit the mechanical properties substantially and can lead to sudden and unpredictable failure. In this study, embrittlement is determined by means of slow strain rate tests (SSRT) and instrumental indentation tests (IIT). The latter enables analysis of embrittlement under the suppression of crack propagation mechanisms and surface influences (e.g. notch effects due to pitting) and is a new technique for the investigation of hydrogen embrittlement (HE). In this study, the influence of immersion time and elastic deformation on the HE of twin-roll cast and heat-treated magnesium sheets (AZ31) was analysed. Distilled water and two NaCl solutions (0.05 and 0.5 wt%) served as analysing media. It is shown that both influencing factors significantly affect the rate and the degree of HE. Relatively short immersion in distilled water led to a substantial decrease in strain and an increase in brittleness, even without external mechanical loading. In contrast, strength was not affected by immersion in water and the resulting HE. In comparison to immersion in distilled water, immersion in sodium chloride solution led to a total loss of plasticity and a decrease in strength during SSRT without a distinct increase in embrittlement during IIT. Analysis by X-ray diffractometry did not determine a detectable amount of magnesium hydrides in the embrittled AZ31 structure. [ABSTRACT FROM AUTHOR]

In this study, we investigated the thermodynamics and experimental performance of Al, Zr, and Ce species under anode and cathode gas conditions in Li/K carbonate at 650 °C. Among the Al, Zr, and Ce species investigated, we found that lithium aluminate (LiAlO), lithium zirconate (LiZrO), and cerium/ceria oxide (CeO) were the most stable materials. Experimentally, we performed immersion tests in molten (Li/K)CO at 650 °C to evaluate the phase and microstructure stabilities of these materials. The γ-LiAlO phase transformation, determined using X-ray diffractometry, was dependent on the immersion time. We performed similar measurements for α-LiAlO, LiZrO, and CeO materials in molten Li/K carbonate at 650 °C. From immersion tests, the presence of the α-LiAlO phase revealed that phase transformation of γ-LiAlO occurs in Li/K carbonate melts under cathode gas atmospheres; in contrast, no phase transformation was evident after immersion of the pure α-LiAlO phase in molten carbonate for 5,000 h. Furthermore, we found that LiZrO and CeO were stable phases after immersion in molten carbonate at 650 °C, under both anode and cathode gas atmospheres, for more than 5,000 h. [ABSTRACT FROM AUTHOR]

The microstructure, corrosion behavior and corrosive film formation of as-extruded Mg–2Zn–0.4Mn–0.1Sr–xGd alloys (x = 0, 0.5, 1 and 2 wt%) in Hank's solution were studied. Microstructure was investigated by scanning electron microscopy (SEM), scanning Kelvin probe force microscopy (SKPFM), X-ray photoelectron spectroscopy (XPS). Corrosion behavior was evaluated by immersion and electrochemical tests. The microstructural observations indicated that the addition of 0.5–2 wt% Gd led to the formation of Mg3Zn3Gd2 phase and grain refinement. SKPFM results showed that the Gd-rich (Mg3Zn3Gd2) phase was nobler than the α-Mg matrix in Gd-containing alloys and formed micro-galvanic corrosion. The alloy with 0.5–1 wt% Gd addition had better corrosion resistance and displayed uniform corrosion behavior than that Gd-free alloy. However, excessive Gd addition (2 wt%) decreased the corrosion rate and caused severe localized corrosion due to massive cathode Gd-rich particles. Combined with mechanical properties and corrosion resistance, the alloy with 1 wt% Gd exhibited a potential for degradable implant applications. The obtained superior corrosion resistance was due to the refined microstructure and the compactness of Gd-containing corrosion products film. In addition, a systematic discussion of corrosion behavior and corrosion film formation was provided by means of schematic illustration. [ABSTRACT FROM AUTHOR]

Magnesium-based alloys presented great potential for biodegradable implant materials. However, the poor mechanical properties and high corrosion rate blocked its extensive application. In this study, a new biodegradable Mg–Zn–Y–Gd–Zr alloy was fabricated and extruded. The microstructure, corrosion morphologies and corrosion products film of the as-cast, homogenized and as-extruded alloys were characterized by optical micrographs, scanning electron microscopy, X-ray diffraction and laser scanning confocal microscopy. Moreover, the corrosion mechanisms of the as-cast and as-extruded alloys were proposed, and the influencing factors of corrosion properties were discussed. The electrochemical test, immersion tests and corrosion morphologies demonstrated that the as-extruded alloy exhibited favorable corrosion properties. The as-cast and homogenized alloys displayed localized corrosion mode, and the as-extruded alloy displayed uniform corrosion mode. The Volta potential of the Mg3(Y,Gd)2Zn3 phase relative to Mg matrix was measured by using Kelvin probe force microscopy. [ABSTRACT FROM AUTHOR]

The effect of copper addition in the microstructure of sol–gel titanium oxide (TiO2) supported on anodic aluminum oxide (AAO) membranes is reported. Two deposition methods based on immersion and flow techniques were used for the coating of the porous AAO membrane. Copper-free membranes were studied as a function of different ratios of H+/Ti, H2O/Ti, selecting the most appropriate for the sensitization with copper. For copper-doped TiO2 arrays, the presence of copper causes the reduction of grain size and enhances titania deposition inside the AAO pores, although no clear tendency with copper content was found. The formation of copper-doped titania nanotubes was validated after dissolving the AAO membranes, finding a deposition-dependent stability in the Cu-doped materials. Titania and Cu-doped titania nanotubes analyzed as colloidal solutions show band gaps substantially shifted to the red in comparison to the direct band gap of near-spherical colloidal materials. These arrays are important for photocatalysis and for the development of third generation photovoltaic devices. [ABSTRACT FROM AUTHOR]

In this study, the corrosion behavior of Mg–5Al alloys with different quantities of calcium was investigated by DC and AC polarization and immersion tests. The alloys’ microstructure was investigated by optical microscopy and SEM with EDS. It was found that increasing the Ca content from 0.9 to 1.8 wt% improves the corrosion resistance of the alloy; the corrosion resistance of the alloy with 1.8 wt% Ca equals that of the base Mg–5Al alloy. Ca addition causes a reduction of the average grain size, which increases corrosion resistance as the precipitates located at grain boundaries are more continuous and act as a barrier to the advance of corrosion. The precipitates located at grain boundaries contain Al and Ca and are much less cathodic than the β phase, thus making the microgalvanic effect in the specimen less effective. [ABSTRACT FROM AUTHOR]

Localized oxidation and corrosion behavior of a nickel-titanium (NiTi) shape memory alloy (SMA) was investigated via static immersion experiments in a simulated body fluid solution. Detailed electron microscopy examinations on the sample surfaces revealed preferential formation of local oxide particles around dislocation networks, which constitute high-energy zones. Moreover, various intermediate phases were detected in addition to the parent NiTi phase around dislocation networks. These are also areas with enhanced diffusion, which promotes Ni release. These findings emphasize the significant role of fine microstructural features, such as dislocation networks, on the oxidation and Ni release, and thus, the biocompatibility of the NiTi SMAs. [ABSTRACT FROM AUTHOR]

The influence of grain boundaries and fine precipitation on the corrosion behavior was investigated in two model aluminum-lithium alloys, namely (in wt%) Al-1.6Li (lithium in a solid solution) and Al-2.3Li (lithium in the form of AlLi precipitation), subjected to three different severe plastic deformation (SPD) treatments which refined the microstructure of the alloys to the ultrafine grain size. The SPD techniques used in the experiments were equal channel angular pressing (ECAP), hydrostatic extrusion (HE), and extrusion-torsion (ET). The corrosion behavior was examined using a potentiodynamic polarization test, electrochemical impedance spectroscopy, and an immersion test followed by a SEM surface analysis. The electrochemical tests were conducted in a 0.1 M NaSO solution added with 100 ppm of Cl. The immersion tests (48 h) were performed in a 3.5% NaCl solution at room temperature. The results indicate that the pitting potential, pit number, and stability of the passive layer formed on the surface of the substrates undergo changes depending on the average grain size and the presence of precipitation or its lack. The corrosion resistance, examined in the solution mentioned above, appears to increase with decreasing average grain size. The ET method gave the microstructure with the lowest corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, the effects of calcium (Ca) and yttrium (Y) on the microstructure, mechanical properties, corrosion behaviour and biocompatibility of magnesium (Mg) alloys, i.e. Mg- xCa ( x = 0.5, 1.0, 2.0, 5.0, 10.0, 15.0 and 20.0%, wt%, hereafter) and Mg-1Ca-1Y, were investigated. Optical microscopy, X-ray diffractometry (XRD), compressive and Vickers hardness testing were used for the characterisation and evaluation of the microstructure and mechanical properties. The in vitro cytotoxicity of the alloys was assessed using osteoblast-like SaOS2 cells. The corrosion behaviour of these alloys was evaluated by soaking the alloys in simulated body fluid (SBF) and modified minimum essential medium (MMEM) at 37 °C in a humidified atmosphere with 5% CO. Results indicated that the increase of the Ca content enhances the compressive strength, elastic modulus and hardness of the Mg-Ca alloys, but deteriorates the ductility, corrosion resistance and biocompatibility of the Mg-Ca alloys. The Y addition leads to an increase in the ductility; but a decrease in the compressive strength, hardness, corrosion resistance and biocompatibility of the Mg-1Ca-1Y alloy when compared to the Mg-1Ca alloy. Solutions of SBF and MMEM with the immersion of Mg- xCa and Mg-1Ca-1Y alloys show strong alkalisation. Our research results indicate that Mg- xCa alloys with Ca additions less than 1.0 wt% exhibited good biocompatibility, low corrosion rate as well as appropriate elastic modulus and strength; whilst the Y is not a proper element for Mg alloys for biomedical application due to its negative effects to the corrosion resistance and biocompatibility. [ABSTRACT FROM AUTHOR]

An excimer laser (KrF) operating at a wavelength of 248 nm was used to modify the surface microstructure of 7075-T651 aluminium alloy. The aim was to improve both the corrosion resistance and the pitting corrosion fatigue resistance of the alloy by means of laser surface melting (LSM). The microstructure and the phases of the modified surface structure were analysed, and the corrosion behaviour of the untreated and the laser-treated specimens were evaluated by immersion test. The fatigue resistance of the 7075 alloy has been presented in the form of S/N curves. A microscopical examination and the transmission electron microscopy (TEM) study revealed that LSM caused a reduction both in number and size of constituent particles and a refinement of the grain structure within the laser melted zone. As a result, the corrosion resistance of the aluminium alloy was improved. There was a significant reduction in the number of corrosion pits and shallow attack occurred. The fatigue test results showed that under dry fatigue conditions, the total fatigue life of the laser treated specimens, in which the crack initiation period is of considerable significance, was lower than that of the untreated specimens. However, after shot peening, the fatigue life of the laser treated specimens was recovered. This was primarily attributed to the elimination of surface defects, but also be in part, due to the introduction of compressive residual stresses in the surface layer of the specimen. The fatigue resistance of the shot peened laser-treated specimens, tested in 3.5 wt% NaCl solution with 48 hrs prior immersion, was greater than the untreated specimens with an increase of two orders of magnitude in fatigue life. This was primarily due to the elimination of surface defects and the reduction of corrosion pits. [ABSTRACT FROM AUTHOR]

The influence of the microstructural characteristics on the mechanical and hydrogen embrittlement properties of 1800 MPa grade hot-stamped 22MnB5 steel was experimentally investigated using samples processed under various hot-stamping conditions, i.e., different heating temperatures and strain levels. The tensile strength increased with increasing hot-stamping temperature up to approximately 920 °C and subsequently decreased owing to the increasing sizes of the lath martensite and prior austenite phases. Some degree of internal strain was introduced into the 22MnB5 steel specimen during hot stamping at 920 °C, which led to a slightly higher hardness although no clear microstructural change was observed. The severity of hydrogen embrittlement of the hot-stamped 22MnB5 steel samples was investigated after immersion in a NH4SCN solution, and the degree of hydrogen embrittlement was found to be directly associated with the amount of hydrogen that penetrated into the grain boundary and lath martensite boundary. The high-strength 22MnB5 steel with a very small lath martensite phase exhibited severe hydrogen embrittlement due to the large amount of hydrogen in the sample, and the high internal strain (or high dislocation density) could lead to accelerated hydrogen embrittlement. Severe hydrogen embrittlement occurred upon charging with more than approximately 0.8 ppm hydrogen. Based on the obtained results, models are proposed for the hydrogen embrittlement characteristics of hot-stamped 22MnB5 steel. [ABSTRACT FROM AUTHOR]

Fabrication of polymer scaffolds via various preparation procedures generally leads to creation of different morphologies, microstructure and properties. In this work, porous nanocomposite scaffolds of poly(ε-caprolactone) filled with different quantities of ZnO nanoparticles (0.5-5 wt%) were prepared by thermally induced phase separation (TIPS), using freeze-extraction method for solvent removal. The aim of this research was to investigate the influence of the fabrication procedure and the ZnO loadings on the PCL thermal, morphological and bioactivity properties. The TIPS procedure was confirmed to induce significantly high degree of crystallinity (up to 81%) in all investigated scaffolds, besides the nucleation capacity of the nanofiller. The in vitro bioactivity and biodegradability were tested by immersing produced scaffolds in standard simulated body fluid (SBF) for different periods of time (15 and 30 days). Scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction were used to assess the variations in scaffolds after their incubation in SBF. No bioactivity was identified for 15 days of immersion, while the mineralization process was confirmed in all investigated scaffolds for the incubated period of 30 days. Thermogravimetric analysis was used to quantify the mineralization properties, confirming best mineralization properties in scaffolds containing lower contents of ZnO nanofiller (0.5 and 1 wt%). [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) is an effective welding technique to realize the joining of dissimilar aluminum alloys. The microstructural heterogeneities induced by FSW across the joints could have curial implication for the corrosion performance of the joints. In this research, the microstructure and localized corrosion behavior of shoulder interface zone (SIZ), vortex zone (VZ), bottom zone (BZ) and bottom interface zone (BIZ) in the stir zone (SZ) of dissimilar FSW AA2024/AA7075 joint was systematically investigated through detailed microstructural characterization and relevant corrosion tests. The results indicated that plentiful of Cu-rich constituent particles are formed on AA2024 side and the areas near the interface on both sides, and corrosion originates from these regions. Grain size has little influence on corrosion behavior of the SZ, while the local regions with higher stored energy are more sensitive and liable to corrosion. The sequence of mixing degree of materials in the four regions of the SZ is: BZ > VZ > SIZ > BIZ, which is in contrast to the order of corrosion rate. Galvanic corrosion is detected in the SIZ and BIZ, and sufficient mixing of materials significantly weakens the galvanic corrosion, resulting in higher corrosion resistance in the BZ. [ABSTRACT FROM AUTHOR]

Zinc-nanodiamond (ND) composite is proposed as a novel biodegradable implant material due to its desirable corrosion, mechanical, and biocompatible properties. In this research, the microstructure, corrosion behavior, and mechanical properties of Zn-ND composites were investigated for the first time as a potential implant material in biomedical applications. Powder metallurgy manufacturing processes were used and different sintering conditions were studied. Grain size increased with increasing sintering temperature and longer sintering time. Corrosion resistance was improved 61.0, 65.9, and 70.7 % for 1, 2.5, and 5 % ND compared with pure Zn. Compression and hardness tests were performed to determine the mechanical properties. In the compression tests, Zn-1ND showed the highest Young's modulus, with 10.95 and 27.32 % more than pure Zn and Zn-5ND. Pure Zn had the highest compressive strength, 11.8 and 29.5 % higher than Zn-1ND and Zn-2.5ND. Zn-1ND and Zn-2.5ND are 55.2 and 68.9 % lower in hardness compared with pure Zn (HV = 27). Compression-molded zinc with low concentrations of nanodiamond offers a promising combination of strength and low corrosion rate, and with strength approaching cortical bone and higher than most biological tissues. [ABSTRACT FROM AUTHOR]

Electroless Ni-P/electroless Pd/immersion Au (ENEPIG) with ultra-thin Ni-P deposit serve as a potential replacement of traditional ENEPIG surface finish because of its superior electrical performance in flip chip solder joints interconnection. However, the interfacial reaction and mechanical reliability of solder joints in ENEPIG with ultra-thin Ni-P layer is not yet well evaluated. In this study, we investigated the characteristic microstructure of interfacial intermetallic compounds and high-speed impact responses of Sn-3.0Ag-0.5Cu/ENEPIG attachments with 4.8, 0.3, and 0.05 μm Ni-P deposit. ENEPIG with Ni-P layer of 0.3 μm exhibited the eutectic structure dispreading in the solder alloys and layer-type P-rich IMCs at solder/metallization interface, while there was (Cu,Ni)Sn precipitation in the solder but no P-rich IMCs layer formed in ENEPIG with 0.05 μm Ni-P layer. Slower interfacial reaction rate in ENEPIG with 0.3 μm Ni-P layer was attributed to the effect of electroless Ni-P diffusion barrier layer, which would further provide better impact resistivity than that of ENEPIG with 0.05 μm Ni-P deposit. Moreover, breach in P-rich IMCs and underneath (Cu,Ni)Sn patch were observed in ENEPIG with 0.3 μm Ni-P layer. The growth mechanism was closely related to the Ni diffusion from surface finish and element redistribution. [ABSTRACT FROM AUTHOR]

In this study, the application of severe plastic deformation technology to biomedical titanium alloys with stress-induced martensitic transformation (SIMT) was investigated. Through the use of X-ray diffraction analysis, transmission electron microscopy analysis, and tensile testing, the influence of multi-axial compression (MAC) processing on the microstructure evolution and properties of the Ti-27Nb-2Mo-2Zr-2Sn alloy was evaluated. The findings demonstrated that a combination of SIMT and MAC could result in significant grain refinement. MAC technology enabled the generation of β grains smaller than 100 nm in the Ti-27Nb-2Mo-2Zr-2Sn alloy. Effective grain refinement was found to be closely associated with the evolution of stress-induced α″ martensitic phases. Furthermore, after MAC processing, the strength of the alloy increased due to the increased levels of dislocation density and grain refinement. Conversely, the reduction in the elastic modulus resulted from the dissolution of nonthermal ω phases and α″ martensitic phases. In addition, the high-density dislocation and β/α″ interface introduced by MAC pretreatment greatly accelerated the aging precipitation process at 550 °C. Notably, the Ti-27Nb-2Mo-2Zr-2Sn alloy exhibited an improved tensile strength to elastic modulus ratio (18.9 × 10−3) and a suitable corrosion resistance after 6 MAC processing cycles, highlighting its potential for future application as an orthopedic implant material. [ABSTRACT FROM AUTHOR]

In this study, the microstructure, texture, and mechanical properties of Mg–4Zn–1Mn–xCa (x = 0, 0.2, 0.5, wt%) alloys are studied. The thin-walled micro-tubes of Mg–4Zn–1Mn–xCa (x = 0, 0.2, wt%) alloy are fabricated by hot extrusion, and the microstructure and corrosion behaviors of micro-tubes are investigated. The results show that the addition of trace Ca caused the microstructure of Mg–4Zn–1Mn–xCa alloys to become finer, while resulting in a significant basal texture owing to the increased volume fraction of unrecrystallized grains. Notably, the addition of 0.2Ca enhanced the yield strength (YS) by 30.3%. Then, Mg alloy micro-tubes with an outer diameter of 3.2 mm, inner diameter of 2.4 mm, and a wall thickness of 0.4 mm are successfully produced. Besides, the hardness of micro-tubes with 0.2Ca addition (72.3Hv) is higher significantly than that without Ca addition (62.9Hv), and the grain size is much finer. An electrochemical test demonstrated that the corrosion resistance of micro-tubes shows an improvement with the addition of 0.2Ca. These findings indicated that it is feasible to fabricate a biodegradable Mg stent with grain superfine Mg–4Zn–1Mn–0.2Ca alloy billet. [ABSTRACT FROM AUTHOR]

This paper presents the effects of aqueous processing of WC-Co powders on their sinterability and mechanical properties. WC-Co powders have been milled in aqueous media (distilled water + corrosion inhibitor). The as-milled samples have been compacted and sintered in vacuum at 1380 °C. The investigations performed on the two components, carbide and binder, reveal different oxidation behaviour in water, with a further effect on the properties of the sintered product. The decrease of the saturation magnetisation of the compacts corroborated with the microstructure reveals the oxidation of the samples milled for a longer duration. The magnetic properties, hardness and microstructure suggest that the used corrosion inhibitor is effective for short milling durations. [ABSTRACT FROM AUTHOR]

Polymer–clay nanocomposites are the most remarkable nanomaterials of the current decade with broad range of applications, because they attempt a great competence to impart outstanding properties when compared to pure polymers even at a very less percentage of nanofiller inclusion. Montmorillonite, vermiculite, halloysite, sepiolite, laponite, bentonite, and attapulgite are the dominant classes of clay used as reinforcement in polymer–clay nanocomposites. Clay is easily accessible, easily processed, inexpensive, and non-toxic, and clay nanocomposites have seen significant commercial interest due to improvements in processing. Clay nanocomposites show distinctive properties of outstanding thermal stability, enhanced flame retardancy, high dimensional stability, decreased gas permeability, and enhanced anticorrosive and improved mechanical properties. This review reveals the polymer-based nanocomposites reinforced with halloysite nanotubes, for high-performance promising applications. The qualities of the nanofiller can be changed by chemically modifying exterior surface and interior lumen. Chemical alteration of the halloysite nanotube surface, in particular, results in nanoarchitecture with targeted affinity through functionalization of the outer surface and potential for drug transport through functionalization of the nanotube lumen. The various functionalization techniques of altering the nanofillers to allow interaction with polymers are discussed. The significance of filler dispersion in the polymeric matrix is also featured. The consequences of functionalized nanofillers on the microstructure and morphology, mechanical strength, thermal stability, drug encapsulation and sustained release abilities, and flame retardancy as well as barrier properties can be summarized. Subsequently, the challenges, key problems, future prospects, and feasible mechanism for polymeric clay nanocomposites are also reviewed. [ABSTRACT FROM AUTHOR]

The effects of supersonic particle bombardment (SFPB) on the microstructure, microhardness and wear property of Ti6Al4V alloy prepared by laser metal deposition (LMD) were investigated in this paper. The electrochemical corrosion behaviors of the LMDed Ti6Al4V alloy samples before and after SFPB treatment in 3.5% NaCl solution were measured. The results showed that a gradient severe deformation layer of ~ 350 μm thickness was formed with refined equiaxed grains oriented in various directions on the surface of LMDed Ti6Al4V alloy after SFPB treatment. The microhardness of the deformation layer was significantly increased due to the plastic deformation, grain refinement, dislocations and deformation twins increment. After SFPB treatment, the LMDed Ti6Al4V exhibited higher wear resistance which is about 55.6% decrease in wear loss than that of the untreated sample. Moreover, the corrosion resistance and corrosion rate of the SFPB-treated samples in 3.5% NaCl solution improved due to the finer hexagonal grains and high density of grain boundary in the severe deformation layer. [ABSTRACT FROM AUTHOR]

Arc discharge plasma nitriding (ADPN) of stainless steel was achieved using the thermionic electrons generated from column arc discharge to ionize the working gas to form a high-energy plasma. The column arc current is a key influential factor in the ADPN technique. AISI 420 martensite stainless steel (420 SS) was nitrided at a low temperature of ~ 440 °C to improve its mechanical properties and corrosion resistance using a highly efficient low-pressure ADPN technique. The arc plasma was generated by applying arc currents ranging from 100 to 130 A. The results of arc currents on the microstructure, mechanical characteristics, tribological properties, and corrosion performance of treated layers were investigated. The results revealed that the nitrided layers are primarily composed of expanded martensite (αN), Fe4N and Fe2-3 N, and a high arc current leads to the formation of a compound layer composed of Fe2-3 N and Fe4N. The surface microhardness and wear resistance of 420 SS were greatly improved following ADPN compared with conventional plasma nitriding. The samples treated at the higher arc current have a thicker nitrided layer and a tough surface with a higher fraction of Fe2-3 N, which shows the best wear and corrosion performance. [ABSTRACT FROM AUTHOR]

The present study aims to evaluate and compare the effect of 5 vol.% TiC or WC addition on densification, phase stability, microstructure, mechanical properties, thermal residual stress and reciprocating wear behaviour of spark plasma-sintered ZrB2-20 vol.% SiC composite. ZrB2–20SiC–5TiC (vol.%) composite attains 99.6% mean sintered density even at 1700 °C, while WC containing composites (ZrB2–20SiC–2.5TiC–2.5WC and ZrB2–20SiC–5WC, vol.%) necessitates a sintering temperature of 1800 °C for > 98% densification. Phase and microstructure analyses confirm that respective incorporation of TiC and WC leads to in situ formation of (Zr,Ti)B2 and (Zr,W)B2 solid solution in the sintered composite. Elastic modulus and thermal expansion coefficients of the composites have been estimated utilizing well-established analytical models. The thermal residual stress of the sintered composites is determined analytically utilizing Taya's model and Hsueh's model and compared with residual stress of SiC reinforcement determined by Raman spectroscopy. Nano-indentation analysis confirms that the minimum resistance to deformation and maximum plasticity index are observed in ZrB2–20SiC–2.5TiC–2.5WC composite due to its relatively low elastic modulus. The maximum Vickers hardness is observed in ZrB2–20SiC–2.5TiC–2.5WC composite, whereas an excellent combination of indentation toughness and indentation modulus is found in ZrB2–20SiC–5WC. Owing to relatively high fracture toughness exponent and low brittleness index, ZrB2–20SiC–5WC composite records the minimum wear volume and wear rate in linear reciprocating wear test. [ABSTRACT FROM AUTHOR]

Uniform corrosion and stress corrosion cracking (SCC) of high-strength low-alloy steels with different microstructures in marine environment were investigated. The results show that microstructures (granular bainite, granular bainite and ferrite and tempered sorbite) significantly affect the uniform corrosion rate and SCC susceptibility, but the order of the effect of the microstructures on the two kinds of corrosion is different. Microstructures change the γ-FeOOH proportion of the rust layer, which determines the protection performance and corrosion rate. Hydrogen embrittlement, one of SCC mechanisms, is highly related to the microstructures, i.e., the dislocation density, high-angle grain boundary proportion and Taylor factor value. [ABSTRACT FROM AUTHOR]

WC–15Co–0.95Cr cemented carbide with various carbon content was fabricated via sintering hot isostatic pressing. The influences of carbon content on the microstructure, magnetic and mechanical properties, as well as corrosion behavior, were systematically investigated. The results show that the increases in carbon contribute to WC grain growth. (Cr, W)Cx phase would precipitate at the interface while excessive carbon is added. The coercive force and Vickers hardness gradually decreased with carbon content added, while the transverse rupture strength initially increased and then decreased. The higher carbon content cemented carbide exhibits inferior corrosion resistance in the sodium sulfate solution. The poor corrosion resistance of higher carbon content cemented carbide primarily ascribes to the precipitation of Cr-rich phase, which gave rise to the lack of Cr elements in the Co binder phase. [ABSTRACT FROM AUTHOR]

Shape memory alloys (SMAs) exhibit unique properties, including the ability to restore their original shape by temperature variations. One of the grand challenges of the aerospace industry is to develop SMAs with transformation temperatures above 100 ºC with high thermal conductivity. This study focuses on the effects of heat treatments on the microstructure, thermal and electrical conductivities of the Ni50.9Ti29.6Hf19.5 SMA that features good combination between transformation temperatures and physical properties desirable for aerospace applications, such as actuators. We found that heat treatments at 550 °C or 700 °C for 3 or 50 h affect the microstructure significantly, leading to formation of nanometer-size Hf-rich precipitates. As a result, the Martensite-to-Austenite phase transformation temperature is shifted from 100 °C up to 205 °C. Moreover, these heat treatments affect the electrical and thermal conductivities. The maximum room-temperature values of both thermal and electrical conductivities were recorded after heat treatment at 700 ºC for 3 h and are as high as κ = 13.1 ± 0.4 W m - 1 K - 1 and σ = (9 ± 0.27) × 10 3 S cm - 1 , respectively. The correlation between transformation temperature, microstructure, and thermal and electrical conductivities provides us with useful knowledge required for high temperature SMA design. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) have attracted more and more attention in recent years because of their renewable, clean energy and high-cost performance. Polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA) were expected to be used in the preparation of LIB separator due to their excellent comprehensive properties. In this work, a series of PVDF/PMMA LIB separators were prepared by thermally-induced phase separation (TIPS), which is a simple method of fabricating microporous films. In order to improve the comprehensive performance, SiO2 was adopted to modify the composite films with various filling proportions by solution method. Results of DSC and XRD tests showed that SiO2 nanoparticles could significantly reduce the crystallinity of the films, but hardly changed the morphology of PVDF. With an increase in SiO2 content, both porosity and electrolyte uptake rate for the composite films increased, but an excessive loading of SiO2 tended to agglomerate inside the films. The porosity and electrolyte uptake rate for composite film containing 3% SiO2 were found to be the highest. As SiO2 loading increased, both first charge–discharge capacity and efficiency of the composite films were enhanced with the discharge cycle stability enhanced simultaneously. When 3% SiO2 was incorporated, the PVDF/PMMA/SiO2 composite film displayed the best comprehensive performance of the battery among all film samples examined. This study presents a facile way of manufacturing LIB separators with relatively ideal overall battery performance. [ABSTRACT FROM AUTHOR]

The article presents the details of a process for the preparation of single fiber composite microdroplets for use in interfacial shear strength fiber push-out testing of fiber-matrix composites. Topics include the immersion of carbon fiber specimens in resin solutions, the effects of various experimental conditions on droplet size, and the observation of resin droplet microstructure with optical and scanning electron microscopy.

Designing tissue engineering scaffolds with the required mechanical properties and favourable microstructure to promote cell attachment, growth and new tissue formation is one of the key challenges facing the tissue engineering field. An important class of scaffolds for bone tissue engineering is based on bioceramics and bioactive glasses, including: hydroxyapatite, bioactive glass (e.g. Bioglass®), alumina, TiO2 and calcium phosphates. The primary disadvantage of these materials is their low resistance to fracture under loads and their high brittleness. These drawbacks are exacerbated by the fact that optimal scaffolds must be highly porous (>90% porosity). Several approaches are being explored to enhance the structural integrity, fracture strength and toughness of bioceramic scaffolds. This paper reviews recent proposed approaches based on developing bioactive composites by introducing polymer coatings or by forming interpenetrating polymer-bioceramic microstructures which mimic the composite structure of bone. Several systems are analysed and scaffold fabrication processes, microstructure development and mechanical properties are discussed. The analysis of the literature suggests that the scaffolds reviewed here might represent the optimal solution and be the scaffolds of choice for bone regeneration strategies. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate corrosion protection properties of Ce conversion coating on the graphite fiber-reinforced aluminum matrix (Gr(f)/Al) composite surface by electrochemical measurements, and microstructure of the Ce conversion coating was studied by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). It is found that the coating covers the whole surface of Gr(f)/Al composites as oxidized islands, since there are some micro-cracks on the coating. The Ce conversion coating consists of Ce-rich nano-particles, and the contact sites between particles have some porosity. The porosity is not obvious during initial deposition, however, as deposition time prolonged development apparently. Moreover, some severe cracks may appear during the drying process, since evaporation of water molecules would cause shrinkage and large stress is induced. In addition, pretreatment of surface has an effect on the formation of cracks. Ce conversion coating has the composition of Ce3+ and Ce4+. Deposition of Ce-rich coating on Gr(f)/Al composite surfaces shifts the polarization curves toward lower current density values. Electrochemical impedance spectroscopy (EIS) data show that Ce conversion coating improved corrosion resistance as compared with samples that have no coating. [ABSTRACT FROM AUTHOR]

The through-thickness heterogeneous microstructure of thick-section high strength steels is responsible for the significant scatter of properties along the thickness. In this study, in order to identify the critical microstructural features in the fracture behaviour and allow for design optimisation and prediction of structural failure, the through-thickness microstructure of thick-section steels was extensively characterised and quantified. For this purpose, samples were extracted from the top quarter and middle thickness positions, and a combination of techniques including chemical composition analysis, dilatometry, and microscopy was used. The hardness variation through the thickness was analysed via micro-Vickers measurements and the local hardness variation in the middle section was studied via nanoindentation. The middle section presented larger prior austenite grain (PAG) sizes and larger sizes and area fraction of inclusions than the top section. Additionally, cubic inclusions were observed distributed as clusters in the middle, sometimes decorating PAG boundaries. Defects associated with the cubic inclusions or the interface between the matrix and the circular and cubic inclusions were observed in the mid-thickness. Moreover, the middle section presented long interfaces with the most significant hardness gradients due to the presence of hard centreline segregation bands. Hence, the microstructural and nanoindentation analyses indicated the middle section as the most likely area to have the lowest fracture toughness and, therefore, the most unfavourable section for fracture performance of the investigated S690QL high strength steel. The detrimental effect of the middle section was confirmed via CTOD tests where the middle presents lower fracture toughness than the top section. [ABSTRACT FROM AUTHOR]

In this study, the effects of different Sc + Zr compound addition on the tensile properties, impact toughness, stress corrosion cracking (SCC) properties, polarization curves, electrochemical impedance spectroscopy (EIS), and pitting corrosion (PC) of Al–Zn–Mg alloys are investigated. The results show that the Sc + Zr co-addition significantly inhibits the recrystallization behavior, refines the grain structure, and improves the tensile properties and impact toughness of the studied alloys. In fact, 0.43 wt% Sc + Zr-containing alloy achieves the maximum tensile properties, the tensile strength and yield strength are increased by 60.4 and 71.5 MPa, respectively. The impact toughness of 0.30 wt% Sc + Zr-containing alloy is 36.5 J/cm2, which is increased by 6.4 J/cm2. The Sc + Zr co-addition significantly reduces the SCC sensitivity, increases the charge transfer resistance, decreases the corrosion current density, and improves the PC resistance of Al–Zn–Mg alloys. The results of the strengthening model show that the main strength mechanism of Al–Zn–Mg alloys is precipitation strengthening of conventional η′ phases. The high toughness and corrosion resistance of alloys with Sc + Zr co-addition associated with the recrystallization resistance and the grain structures yielded by coherent Al3ScxZr1-x particles. [ABSTRACT FROM AUTHOR]

As part of the separation by froth flotation of PVC and PET from waste bottles before recycling, the adsorption mechanism of a lignosulphonate used to selectively render one of the plastics hydrophilic has been studied. As the 'rest' method is not sufficiently sensitive for this purpose, X-ray Photoelectron Spectroscopy analysis was conducted. A method of calculating the surface coverage of both plastics by the reagent is proposed based on the fact that the lignosulphonate contains sulphur whereas PVC and PET do not. The results show that a greater quantity of lignosulphonate adsorbs on PET than PVC, leading to a higher surface coverage of LS on PET. The surface coverage values are a function of the lignosulphonate macromolecular configuration. For the sphere and film configurations hypothetised, the surface coverage values remain less than 1, which is consistent with the patchy adsorption assumed in the calculations. [ABSTRACT FROM AUTHOR]

The influence of MoS2–Al2O3 nanofluid as a functional lubricant on the microstructure and corrosion resistance of hot-rolled steel surface was studied. Because of the excellent lubrication performance of the nanofluid, the rolled surface quality improved with a 18.2% and 69.5% reduction in surface roughness and oxide scale thickness, respectively, when compared with the base-fluid without nanoparticles. The further microstructure characterization determined that the grain size, local misorientation and deformed grain fraction of the steel decreased significantly. A diffusion layer of Al2O3, FeS and FeMo4S6 was found in the outer oxide layer of rolled surface. Closely arranged Al2O3 grains inhibited the oxidation of steel strips that the oxidation activation energy was increased by about 14.5%. Through density functional theory (DFT) calculation, the formation of FeS and FeMo4S6 was attributed to the migration of Mo and S atoms from MoS2 into the Fe lattice through substitutional and interstitial diffusion, respectively, with the energy barrier of 0.84 eV and 0.54 eV. Finally, the protection of diffusion layer, reduction in surface defects, and alleviation of residual stress and deformation resulted in the enhancement of corrosion resistance. This study provides a possible route to achieve surface enhancement during the hot rolling process. [ABSTRACT FROM AUTHOR]

The understanding of rapid solidification behaviour, e.g. the undercooling versus growth velocity relationship, is crucial for tailoring microstructures and properties in metal alloys. In most rapid solidification processes, such as additive manufacturing (AM), in situ investigation of rapid solidification behaviour is missing because of the lack of accurate measurement of the cooling rate and nucleation undercooling. In the present study, rapid solidification of single micro-sized Al-Si12 (mass%) particles of various diameters has been investigated via differential fast scanning calorimetry employing controllable cooling rates from 100 to 90,000 K s−1 relevant for AM. Based on nucleation undercooling and on microstructure analysis of rapidly solidified single powder particles under controlled cooling rates, two different heterogeneous nucleation mechanisms of the primary α-Al phase are proposed. Surface heterogeneous nucleation dominates for particles with diameter smaller than 23 μm. For particles with diameter larger than 23 μm, the nucleation of the primary α-Al phase changes from surface to bulk heterogeneous nucleation with increasing cooling rate. The results indicate that at large undercoolings (> 95 K) and high cooling rates (> 10,000 K s−1), rapid solidification of single particle can yield a microstructure similar to that formed in AM. The present work not only proposes new insight into rapid solidification processes, but also provides a theoretical foundation for further understanding of microstructures and properties in additively manufactured materials. [ABSTRACT FROM AUTHOR]

As-extruded Mg-1.8Zn-0.5Zr-xGd alloys are thoroughly investigated for their microstructure, mechanical properties and degradation behavior in a wide range of minor Gd alloying (0 ≤ x ≤ 2.5 wt%). These alloys show complete dynamic recrystallization when the extrusion ratio and extrusion temperature are 7.7 and 350 °C, respectively. The resultant grain size decreases with the increase in Gd content until its stabilization. Of many observed second phases in these alloys, one type of second phase mainly consists of the granular (Mg, Zn)3Gd phase, the volume of which gradually increases with the increase in Gd content. The other precipitated nanoscale (Mg, Zn)3Gd second phase shows a coherent interfacial relationship with the alloy matrix. At Gd greater than 1.0wt%, a fraction of the insoluble second phase shows transformation into black paralleled strips, which are noted to be distributed along the extrusion direction. The mechanical characteristics of these alloys show optimal performances at x = 1.5 wt%, while decreasing (increasing) trend for 1.5 < x ≤ 2.5 (0 < x ≤ 1.5). Together with the best corrosion resistance at x = 1.0 wt%, these alloys show increment in the corrosion resistance first and then weakens with the increase in Gd content. This study reveals an optimized scale for minor Gd alloying toward the optimal mechanical properties and corrosion resistance of extruded Mg-Zn-Zr alloys, and hopefully beneficial in biomedical applications. [ABSTRACT FROM AUTHOR]

In this study, graphite/copper composites were prepared by microwave sintering. The microstructure and properties of the composites were characterized. The effects of different sintering temperatures on the properties of the composites were studied, and the differences between microwave sintering and conventional sintering composites were compared. The results show that after microwave sintering, the grain size of the copper matrix is refined and the graphite/copper interface is improved, and the distribution of graphite over the matrix becomes more uniform. Compared with conventional sintering, the properties of microwave-sintered samples have been further improved. Besides, with the increase in sintering temperature, the density, hardness, electrical conductivity and thermal conductivity of the composite have been improved, and some properties have become anisotropic obviously. Thus, the electrical conductivity and thermal conductivity along the direction of graphite sheet are higher than those perpendicular to the sheet. [ABSTRACT FROM AUTHOR]

A diffusion-barrier-contained Hf-doped (Ni,Pt)Al coating was prepared by firstly composite electroplating and then aluminising. The TEM study of the microstructure showed that Hf serves as a solid solution in (Ni,Pt)Al lattice and forms HfO2 in the Hf-rich zone. This HfO2 is formed in situ during aluminisation under low oxygen pressure. It acts as a diffusion barrier to prevent the inter-diffusion during cyclic oxidation. In comparison with (Ni,Pt)Al coating, the oxide scale on Hf-dope (Ni,Pt)Al is more adherent. Moreover, the surface rumpling extent is much relieved due to slower Al depletion rate and higher creep resistance by Hf addition. [ABSTRACT FROM AUTHOR]

The intergranular corrosion (IGC) behavior of an extruded 6005A alloy profile with the coexisting of peripheral coarse grain (PCG) structure and partial recrystallized grain (PRG) structure was investigated by using an accelerated corrosion test, electrochemical impedance spectroscopy and a quasi in situ examination of IGC process. PCG structure was found to have a unique IGC behavior that pitting corrosion and subsequent IGC are less severe and will not be transformed into intragranular corrosion as they were found in PRG structure. Microstructure characterization reveals that the microstructural differences in grain boundary precipitates, primary α-AlFeMnSi intermetallic particles and grain characteristic between PCG structure and PRG structure are the reason for these phenomena. Further analysis indicates that the grain boundaries decorated with more AlFeMnSi particles and Q phase precipitates are more sensitive to corrosion, where Q phase precipitates are the primary cathodes and the most important factor affecting IGC; AlFeMnSi particles are supposed to initiate pitting corrosion since they are dissolved as anodes in the early stage of corrosion. With the development of corrosion, they are transformed into cathodes and become the bridges of IGC propagation by connecting the Q phase precipitates at grain boundary. In addition, grain characteristic was also found to have great effects on IGC. With the decrease in grain size and the increase in the frequency of high-angle grain boundaries and the dislocation density, corrosion becomes more severe and more likely to be transformed into intragranular corrosion. [ABSTRACT FROM AUTHOR]

FeCoCrNiAlMox (x = 0, 0.25, 0.5, 0.75, 1.0, molar ratio) alloy coatings were prepared on 2Cr13 steel substrates by wide-beam laser cladding, aiming to investigate the effects of different Mo addition amounts on the microstructure, phase composition, microhardness, and corrosion resistance of the coatings. The results show that all the coatings are of good quality without cracks or pores. Due to the dilution of the substrate, the actual composition of the coatings deviates from the designed composition to different degrees. The main constituent phase of different coatings was body-centered cubic solid solutions, which does not change with increasing Mo content. The middle part of the Mo0, Mo0.75, and Mo1.0 coatings consists of columnar crystal and Cr-rich needle-like precipitates, but the middle part of Mo0.25 and Mo0.5 coatings has a typical dendrite structure. There is not much difference in the alloy composition between dendrite and interdendrite, and the hardness and corrosion resistance of Mo0.25 and Mo0.5 coatings are basically the same. Among the coatings investigated in our study, the Mo1.0 coating has the greatest hardness and best corrosion resistance in 0.5 mol/L HCl solution. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are 2D ionic lamellar nanomaterials, which attract increasing interest for applications in different fields. This paper shows that their morphology is strongly affected by the microstructure of the substrate on which they grow. Zn–Al LDHs were grown in the same conditions on Al substrates with different microstructural features obtained from cold-rolled sheets by annealing at 265 °C for increasing soaking time up to 1 h. LDH morphology was then investigated through scanning electron microscopy observations. The homogeneous distribution of petals on the substrate surface mainly depends on grain size distribution. A bimodal grain size distribution in the substrate leads to the formation of petal clusters and a not complete covering of the surface. In the case of grains of large size the nucleation sites are the dislocations forming the walls of the cells, while owing to their low density, the dislocations inside the grains are not a relevant factor in determining the LDH morphology. [ABSTRACT FROM AUTHOR]

This work explores high-speed impact of fully age-hardened 15-5 PH stainless steel with itself at average impact speed of 682 m/s and impact angles ranging from 8° to 28°. It was assumed that higher angles corresponded with higher shear stresses at impact point. Microstructural examination indicated more pronounced shear-induced features at higher angles, such as nanoscale elongated grains and adiabatic shear bands. Interfacial waves, a feature associated with impact welding, were most prominent at 12° and 16°. White etching layers (WELs), a constituent formed by rapid heating and cooling at impact, were found along the impact interface and most prominently at the front and back vortices of the interfacial waves. WELs (along the interface) were softer than base materials due to overaging, whereas materials surrounding the interface were harder than base materials due to grain refinement. Numerical simulations based on smoothed particle hydrodynamics method were employed to predict the local temperature and strain distributions which supported microstructural findings. Thus, through high-speed impact experiments carried out at different angles along with advanced microscopy and numerical simulations, this work helped reveal the microstructural response of 15-5 PH stainless steel in a range of dynamic shear conditions. [ABSTRACT FROM AUTHOR]

A series of blend membranes based on sulfonated poly(arylene ether phosphine oxide)s (sPEPOF) and poly(vinylidene fluoride) (PVDF) were prepared and studied. The miscibility and thermal properties of blend membranes were evaluated. The morphologies were investigated by atomic force microscope. The results demonstrated that the blend membranes exhibited good compatibility and high thermal stability. The microstructures of blend membranes could be adjusted by introducing hydrophobic PVDF, thus improving the properties of membranes. Additionally, a suitable content of PVDF was in favor of promoting proton conductivity, oxidative stability, restraining water swelling, and methanol permeability. For example, the blend membrane containing 5% weight content of PVDF displayed a proton conductivity of 0.135 S cm−1, which was higher than those of the pristine sPEPOF membrane (0.124 S cm−1) and Nafion 117 (0.114 S cm−1) at 80 °C and 100% relative humidity. Meanwhile, it showed a lower swelling than that of Nafion 117, and its methanol permeability was about one-fortieth that of Nafion 117. Besides, the oxidative stability was also remarkably improved compared to the pristine sPEPOF membrane. Therefore, the achieved blend membranes exhibited excellent application prospect. [ABSTRACT FROM AUTHOR]

We present an in-depth characterisation of shells from two bivalve species with crossed lamellar microstructure, namely Tridacna gigas and Fulvia tenuicostata. High-resolution scanning electron microscopy and confocal microscopy imaging reveal a fine structure of nanogranular particles that are inorganic-bioorganic nanocomposites for both shells. In F. tenuicostata, inorganic-organic components are arranged in a polycrystalline fibre-like fabric. T. gigas consists of up to four hierarchical lamellar structural orders and the second-order lamellae consist of elongated nanometre-sized laths. The inorganic matrix is intimately intergrown with the total amount of organic matter (1.8 and 1.5 wt%), and the composition of the shell macromolecules is variable between the two calcareous biominerals. This work shows for the first time the presence of polysaccharide-based compounds that could be essential for the construction of bio-organics as well as many prominent protein bands, glycoproteins and/or glycosaminoglycans of unknown sizes far above 260 kDa in bivalve shells with crossed lamellar microstructure. Chitosan (deacetylated chitin) with apparent molecular weights from 18 to 110 kDa for T. gigas and from 12 kDa till above 110 kDa for F. tenuicostata are detected in gel electrophoresis after Calcofluor staining. In each of the shell extracts, the infrared spectroscopy shows polysaccharides, proteins and lipids. Our findings from two crossed lamellar shells representing two genera of Mollusca: Cardiidae indicate that chitin-protein complexes and lipid-lipoproteins are not restricted only to bivalves with nacroprismatic shells. [ABSTRACT FROM AUTHOR]

Fabrication of biomimetic laminated polypropylene/graphene powder (PP/GP) nanocomposites by template method to form the highly structured micropillars with submicron villi on top is presented in this work. Microstructures on PP surfaces are stretched and warped by the considerable force between the PP material and microcavities in the template during demolding, changing from micropillars to micropyramids. With the addition of 9% GP, the surface adhesive force is reduced from ~ 571 to ~ 215 μN on smooth surfaces and is almost as weak as ~ 4 μN on microstructured PP/GP surfaces, contributing to the successful demolding of microstructures from microcavities. The droplet of less than 10 μL would rather adhere to the syringe needle than the microstructured PP/GP surface. Apparently, the microstructured PP/GP surface with an extremely small roll-off angle of ~ 0.5° is slippery and superhydrophobic, exhibiting lotus effect. With the ability to work under a water pressure of up to 1500 Pa, the microstructured PP/GP surface exhibits a high-efficiency self-cleaning performance by a combination of droplet bouncing and rolling behaviors. The submicron villi forming on the top of PP/GP micropillars are caused by a mild stretch. This phenomenon might be attributed to a weak adhesion between PP/GP nanocomposites and the microcavities during demolding, facilitating the formation of the sufficiently robust Cassie-Baxter state. After a 1000 mm abrasion length, the newly formed tapering microfibers increase the roughness on the top of the micropillars and help the worn microstructured surface transform to the sticky superhydrophobicity, i.e., petal effect. [ABSTRACT FROM AUTHOR]

The interfacial transition zone (ITZ) between an aggregate and a cement matrix is known to be the weakest component of concrete; hence, its microstructure is the key factor determining its performance in terms of permeability. The objectives of this study are to strengthen the ITZ and reduce the permeability of concrete using nano-silica, and explore its improvement features under different water-to-cement ratios (W/Cs) between 0.3 and 0.5. An innovative testing and characterization methodology is adopted to quantitatively evaluate the properties of the ITZ. The results indicate that nano-silica can reduce both the width and formation of abrasion cracks in the ITZ. Further, the role of nano-silica is especially effective when the W/C of concrete is reduced. Small hydration products growing on the surface of the aggregate and cement matrix of nano-concrete with a reduced W/C can overlap each other and effectively fill the gap, resulting in enhanced densification of the ITZ by the nano-silica at reduced W/C ratios. Further, the enhancement rate of the anti-permeability of concrete also becomes significant. It can be concluded that nano-silica can effectively improve the performance of concretes, especially those with reduced W/C. [ABSTRACT FROM AUTHOR]