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Background: The primary hot rolling method implemented is differential speed rolling (DSR). The material is rolled and grains are strained, producing fine dynamic recrystallization (DRX) grains that improve material strength and ductility. Objective: The material introduced and under investigation in this paper is an Mg-based alloy, Mg5Zn (wt. %), whose microstructure is enhanced through a combination of heat treatments with proper temperature and holding time and subsequent plastic deformation through hot rolling to evaluate the effect on mechanical properties Methods: The method involves preheating the material to various temperatures in a range from 250ºC to 350ºC and rolling to various thickness reductions to analyze the effect of single-pass differential speed rolling (DSR) and conventional rolling (CR) on the DRX process and its influence on mechanical properties. Results: The effect of single-pass differential speed rolling (DSR) and conventional rolling (CR) on the DRX process shows that the process produces increasing amounts of finer DRX grains at higher rolling reductions, thereby improving the strength and ductility of the material. Conclusion: This investigation demonstrated that single-pass DSR can improve the mechanical properties and formability of Mg5Zn more effectively than CR in terms of grain refinement analyzed through OM, SEM, and EBSD resulting in enhanced tensile strength and ductility [1].

Earlier, various attempts to develop graphene structures using chemical and nonchemical routes were reported. Being efficient, scalable, and repeatable, 3D printing of graphene-based polymer inks and aerogels seems attractive; however, the produced structures highly rely on a binder or an ice support to stay intact. The presence of a binder or graphene oxide hinders the translation of the excellent graphene properties to the 3D structure. In this communication, we report our efforts to synthesize a 3D-shaped 3D graphene (3D2G) with good quality, desirable shape, and structure control by combining 3D printing with the atmospheric pressure chemical vapor deposition (CVD) process. Direct ink writing has been used in this work as a 3D-printing technique to print nickel powder-PLGA slurry into various shapes. The latter has been employed as a catalyst for graphene growth via CVD. Porous 3D2G with high purity was obtained after etching out the nickel substrate. The conducted micro CT and 2D Raman study of pristine 3D2G revealed important features of this new material. The interconnected porous nature of the obtained 3D2G combined with its good electrical conductivity (about 17 S/cm) and promising electrochemical properties invites applications for energy storage electrodes, where fast electron transfer and intimate contact with the active material and with the electrolyte are critically important. By changing the printing design, one can manipulate the electrical, electrochemical, and mechanical properties, including the structural porosity, without any requirement for additional doping or chemical postprocessing. The obtained binder-free 3D2G showed a very good thermal stability, tested by thermo-gravimetric analysis in air up to 500 °C. This work brings together two advanced manufacturing approaches, CVD and 3D printing, thus enabling the synthesis of high-quality, binder-free 3D2G structures with a tailored design that appeared to be suitable for multiple applications.

Understanding the structural and mechanical properties of coral skeletons is important to assess their responses to natural and anthropogenic challenges and to predict the long-term viability of hermatypic corals in a changing ocean. Here, we describe the microstructure of the critically endangered staghorn coral (Acropora cervicornis) skeleton and its mechanical properties, spectral and fluidic behavior, including uniaxial compressive strength, resistance to plastic deformation, spectral vibrational response, and flow-field analysis. We evaluated skeletons of A. cervicornis retrieved from a nursery off Broward County, Florida, USA. Optical micrographs and X-ray computed topography revealed a complex system of canals and pores that allow rapid skeletal elongation while retaining sufficient strength to withstand currents, waves, and other physical forces. Compressive loading of the aragonite skeleton resulted in complex stress–strain deformation behavior; the unique pore arrangement resisted catastrophic cracks and prevented instantaneous failure. Vickers microhardness was 3.56 ± 0.31 GPa, which is typical for soft aragonite materials yet sufficient to withstand the hydraulic pressure of ocean waves. Impressions made by the diamond indenter had almost no cracks radiating from their corners, which again demonstrated the ability of the complex skeleton microstructure to suppress crack formation and growth (e.g., from the bites of grazers). Maps of the ν1 mode Raman peak of identation surfaces showed evidence of residual strain. However, the ν1 peak’s position barely changed (from 1083.6 cm−1 outside the impression to 1083.9 cm−1 in the center), indicating weak stress sensitivity. Flow-field analysis revealed small-scale, counter-rotating vortices formed in the skeleton’s wake, which can entrain food particles within range of polyp tentacles and facilitate transport of respiratory gases and wastes. Considered together, our results demonstrate that the perforate skeleton of A. cervicornis is well-adapted to withstand physical forces normally encountered in its shallow-water habitat, but may be susceptible to anthropogenic stressors that alter its architecture.

Coral reefs provide habitat for most oceanic life forms, however, they are declining worldwide due to pollution, increased ocean temperature, diseases and other factors. In this paper, structural a...

Detailed electrical resistivity (ρ) measurements have been carried out in epitaxial TiN thin films in the temperature (T) range of 4 ≤ T ≤ 300 K in magnetic fields from 0 to 6 T. The ρ (T) data show distinct minima around 38 K, which remains unaffected by the external magnetic fields. At higher temperatures (100−300K), the ρ(T) behavior was found to be linear in agreement with classical electron-phonon interactions (∝T). Below the minima, the ρ(T) is unequivocally described by the quantum interference effect (∝ − T ). The value of the coefficient of the T term matches well with the near-universal value.

Multilayered Thin films are effective in controlling the rate of corrosion of magnesium alloys used for bio-implants applications. It’s been proven that corrosion of metallic implants can be delayed by depositing multilayered metal-oxide thin films. In this study, Mg/Al2O3 nanolaminates, along with different metal oxides, were deposited using DC and pulsed DC magnetron sputtering methods at room temperature on glass substrates. Applicability of these metal-oxide nanolaminates to corrosion control was studied by bulk volumetric degradation measurement technique using solutions such as Saline, HANKS and PBS. Mg/Al2O3 films were also studied under different flow conditions by varying flow rates and pore growth rate and degradation process are measured by time-lapsed technique on optical microscope. Effect of the oxide layer thickness, saline flow rate, total pressure, structural characteristics of oxide coatings and sputtering deposition parameters on pore density and corrosion rate was investigated. Pulsed DC magnetron sputtering enables preparation of thin films with control over pore growth and distribution. Results have shown that repeatable pore density and corrosion rate can be achieved through magnetron sputter-deposited Mg/Al2O3 nanolaminates.

Magnesium-6 wt.% aluminum (Mg-6Al) alloy plates with a 6-millimeter thickness were processed from an initial 12-millimeter thickness by differential speed rolling (DSR), with a 0.76-millimeter thickness reduction per pass using a speed ratio of 2, preheating temperature of 315 °C, and roll temperature of 265 °C. The effects of annealing temperature of 250, 275, and 300 °C with a corresponding holding time of 15 min on the microstructure, texture, and mechanical properties were investigated. Key results show that dynamic recrystallization (DRX) occurred during the roll processing, resulting in a greatly reduced grain size. In addition, the basal pole of the as-rolled plate was inclined to the rolling direction (RD) by ~20°, due to the shear strain introduced during DSR. Subsequent annealing caused grain growth, eliminated the basal pole inclination towards the RD, and slightly increased the pole intensity. Compared with the as-rolled plate, the average of the ultimate tensile strength (UTS) and the yield strength (YS) of the annealed plates decreased, while the average elongation at fracture (εf) increased. With the annealing temperature of 275 °C, the plate achieved a good combination of mechanical properties with UTS, YS, and εf being 292.1 MPa, 185.0 MPa, and 24.9%, respectively. These results suggest that post-roll annealing is an effective way to improve the mechanical response of this Mg alloy processed by DSR.

Magnesium-based alloys are being used today in various lightweight applications. The mechanical properties of magnesium-based alloys can be enhanced for such applications through a combination of annealing temperature and holding time of the magnesium-based alloy. The magnesium-based alloy under investigation in this study is Mg-5%Zn. The results of this investigation show that optimizing annealing time and temperature can achieve homogenization and enhance the mechanical properties and formability of Mg-5%Zn as seen in hardness test results for the homogenized samples.

Titanium nitride (TiN) thin films are deposited on titanium (Ti) substrates by pulsed laser deposition and radio frequency magnetron sputtering. The main goal of this research is to improve the corrosion resistance and the vibration damping performance of the Ti substrates by surface modification of the substrates with TiN thin film coatings. Electrochemical results indicate that TiN films bring about a significant improvement in the corrosion resistance of the Ti disks in phosphate buffer saline solution. It is also observed that TiN deposited at room temperature has the best corrosion efficiency in terms of lower corrosion current density and more positive corrosion potential. From the damping measurements, it is observed that the damping ratios of the TiN-coated beams are one to two orders of magnitude greater than those of uncoated ones. Additionally, the damping amplitudes of the TiN coated beams have been observed to return to zero position faster than the uncoated beam. The energy dissipation due to internal friction at the beam-coating interface and inter-lamellae interface within TiN coatings can be the mechanism responsible for reducing vibration amplitudes of TiN-coated beams.

Non-conventional differential speed and confined hot rolling methods were employed to process two binary magnesium-aluminum-alloys, Mg-xAl (x = 6 and 9 wt%), with conventional rolling being used as a comparative control. The study focused on the effect of the processing methods and parameters on the efficacy of grain refinement and texture evolution through dynamic recrystallization, and eventually on the mechanical properties of the as-processed materials. Key results are summarized as follows: (1) The grain size of the Mg–6%Al and Mg–9%Al alloy plates was greatly refined after rolling; the microstructure of the plates processed by differential speed rolling (DSR) showed greater refinement than those processed by conventional rolling (CR) or confined rolling. (2) For both alloy compositions, the as-rolled plates exhibited a strong { 0001 } basal texture, regardless of CR, DSR, or confined rolling conditions. Moreover, the basal texture intensity of the plates via DSR was lower than that of the plates processed by other rolling methods. (3) The mechanical properties were significantly improved after rolling for both alloy compositions. In particular, the anisotropy of the plates processed by DSR was reduced compared to that of the plates processed by CR. As such, our research showed that DSR holds great potential in the fabrication of bulk metal components with enhanced mechanical properties and formability.

The alignment of different carbon nanotube (CNT) structures has been studied extensively using varying techniques. Most of these techniques however do not present a true three-dimensional (3D) representation of the orientation of the material. In this work, the orientation distribution functions obtained from X-ray pole figures for different CNT structures (vertically aligned CNT arrays, randomly orientated buckypaper and horizontally aligned CNT sheets) are presented. This technique is also used to examine the effects of solvent densification and stretching on the alignment of CNT sheets. It has been demonstrated that depending on the solvent used for densification, the alignment achieved varies as the elongation is increased. The physical properties of CNT sheets are shown to depend on the alignment and solvent used for densification. The most aligned CNT sheets densified with acetone and ethanol reveal an increase in tensile strength of 140% and 58% respectively over unaligned sheets.

Multiple applications of carbon nanotubes (CNTs) require their assembly into macroscopic materials: films, sheets, and ribbons. Most of these macro-materials are flexible thin structures and need to be cut to micrometer dimensions. Laser cutting has emerged as one of the best pressure-free alternative methods, providing accuracy and uniformity. We report on the effect of laser cutting on the structural and mechanical properties of CNT sheet assemblages. Laser cutting forms a significant and deleterious amount of amorphous carbon at and near the cut edge, and this was observed by Raman spectroscopy, transmission electron microscopy, and electron energy loss spectroscopy. The damage can have adverse effects on the physical properties of CNTs and applications based on them. Laser cutting at high power was found to reduce the tensile strength of CNT sheets by as much as 75%. Nevertheless, at smaller cut widths, the mechanical properties were affected irrespective of the laser power.

In this study, the Mg-9Al% plates with a total of approximately 50% thickness reduction corresponding to 0.76mm per pass, were obtained by symmetrical and asymmetrical rolling. The effect of different annealing temperature and corresponding holding time on the microstructure and mechanical properties were investigated. Key results showed that in the as-rolled state, the plates processed by asymmetrical rolling had smaller grain size and higher hardness value and ultimate tensile strength than symmetrical rolling. After annealing treatment, the hardness value of the both plates decreased due to the internal stress released. A good combination of strength and ductility were achieved for symmetrical and asymmetrical processed plates at 350°C for 1 hour and 325°C for 1 hour, respectively, which can be attributed to the static recrystallization and weakening the basal texture. These results show that the appropriate annealing is an effective way to enhance the mechanical formability of plastic deformed Mg plates.

Mg-Zn combinatorial material libraries covering 15–85 at.% Mg were deposited on glass substrates using magnetron sputtering at room temperature. To study the phases present in the Mg-Zn combinatorial libraries the as-deposited sample was annealed at 250 °C for an hour. The composition, phase content and thickness were characterized using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and stylus profilometer respectively. The corrosion characteristics of the as-deposited and annealed combinatorial samples immersed in DPBS and PBS were evaluated using a high throughput novel optical screening technique. Corrosion maps of the combinatorial samples were generated from analysis of time lapsed images obtained from the novel optical screening technique. From the time lapsed images the corrosion rate of each composition in the combinatorial material libraries were evaluated. The results showed that compositions with Mg contents ≤40 at.% resulted in lower but similar corrosion rate for both as-deposited and annealed samples immersed in DPBS. The corrosion rate increases with increasing Mg content. Keywords: Combinatorial material libraries, Magnetron sputtering, Optical corrosion screening, Mg-Zn alloy

This paper discusses the synthesis and characterization of Al 2 O 3 /Fe and Al 2 O 3 /Ni nanocomposite thin films formed by embedding Fe or Ni nanoparticles into alumina matrix using pulsed laser deposition (PLD), RF and pulsed DC magnetron sputtering techniques. The effect of nanoparticle dispersion and temperature on the phase, structure and mechanical properties of the nanocomposite thin films were studied using grazing incidence X-ray diffraction (GIXRD), high resolution transmission electron microscopy (HRTEM) and nanoindentation respectively. The GIXRD and HRTEM studies revealed that dispersion of metal nanoparticles into alumina matrix promoted partial crystallization of Al 2 O 3 at lower temperatures. The nanoindentation results showed an increase in hardness of the nanocomposite which was dependent on temperature and the metal content. The hardness of Al 2 O 3 /Fe nanocomposite thin films was observed to be in the range of 15 GPa–29 GPa for PLD thin films, 16.5 GPa–22.5 GPa for RF magnetron sputtered thin films and 11 GPa–16 GPa for pulsed DC sputtered thin films. The nanoindentation results also showed that the hardness of Al 2 O 3 /Ni deposited by PLD ranges from 15 GPa to 28 GPa.

Nanostructured Mg/Zr multilayer films were fabricated by depositing magnesium and zirconium alternately onto a single-crystal Si substrate using magnetron sputtering. The Mg and Zr layers had equal individual layer thickness (h) which was varied from 2.5 to 100 nm. Epitaxial growth and coherent layer interface were identified for the as-deposited multilayers at all h using X-ray diffraction and scanning transmission electron microscopy techniques. The multilayers with relatively large h were highly textured along the c-axis. Columnar grains were detected in the h = 2.5 nm multilayer, accompanied with variations in crystallographic orientation. These multilayers exhibited impressive strength with the maximum value of 1.4 GPa. The flow strength increased with decreasing h when h ≥ 10 nm while the opposite trend was observed when h

Magnesium has attracted a lot of attention over the last few decades due to its light weight and potential use as biomaterial. However, the poor corrosion resistance of magnesium restricts its practical use for application where exposure to aggressive aqueous media is unavoidable. This paper describes the growth, characterization and corrosion analyses of Al2O3 and ZrO2 thin film coatings aimed at slowing down the fast degradation of Mg in saline solution. In this study, different thicknesses of Al2O3 and ZrO2 were deposited on pure magnesium (99.95%) disk using pulsed-DC reactive sputtering process. The microstructure and phase analyses were performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The corrosion protection behavior of the Al2O3 and ZrO2 coated magnesium samples immersed in 0.9 wt% NaCl solution were evaluated using electrochemical measurement techniques, such as open-circuit potential (OCP), potentiodynamic polarization (PD) and electrochemical impedance spectroscopy (EIS). The microstructural analyses showed that the Al2O3 thin film coatings have circular grains between 5 and 25 nm, while the ZrO2 coatings have bigger ellipsoidal grains. The results from the electrochemical corrosion analyses showed that the Al2O3 coated Mg disk had corrosion resistance of approximately 3 times that of ZrO2 coated Mg disk. It was also observed that increasing the thickness of the Al2O3 coating improved the corrosion resistance of the Mg disk. These results suggest that Al2O3 and ZrO2 coating can be used to effectively control the fast degradation of magnesium for medical implant applications.

The thermal stability of Mg/Ti multilayer nanofilms was investigated by examining their microstructure and nanoindentation hardness after annealing at various temperatures and time periods. The multilayers with individual layer thickness h ≥ 5 nm exhibit excellent capability of maintaining the lamellar microstructure and high strength up to 200 °C for annealing time up to 2.0 h. The annealed multilayer films with h = 2.5 nm are still highly textured but characterized with discontinuous layer interfaces, in which the transition of atomic arrangement from hexagonal close-packed (HCP) to body-centered cubic (BCC) structure was observed at columnar boundaries. The degradation of uniform lamellar microstructure is related to the decrease of hardness with annealing temperature at this size scale. A diffusion based instability mechanism was proposed for this typical HCP-based nanoscale multilayer system.

Free-standing thin carbon nanotube (CNT) sheets are challenging to handle and control for device fabrication. In this paper, we report on the inverse-ordered fabrication method from thick CNT sheets to thin free-standing CNT sheets. As proof of the concept, thin CNT sheets for a supercapacitor were fabricated from 200 thick layers. The results show that the thin CNT sheet was electrochemically stable and had enhanced capacitive performance. The smaller the number of layers is, the larger the specific capacitances we have (from 10.10 F g(-1) to 51.37 F g(-1)). Energy and power density were increased from 0.50 to 2.57 Wh kg(-1) and from 0.33 to 2.31 kW kg(-1), respectively. This simple and scalable inverse-ordered method is capable to fabricate CNT sheets in various forms, allowing fast trials on various applications.

The mechanical behavior of a lanthanum doped Mg alloy, AZXE7111, (Mg–7Al–1Zn–1Ca–1La, all in wt%) extruded at different temperatures has been investigated under both quasi-static (strain rate ~1×10 −3 s −1 ) and dynamic (strain rate ~4×10 3 s −1 ) compressive loading. Comparison has been made against the experimental results of two conventional Mg alloys, AZ91E and WE43. It was observed via transmission electron microscopy (TEM) that the nanoscale intermetallic compounds of Al 2 Ca and Al 11 La 3 , have presumably formed during the hot extrusion process. These compounds are believed to contribute significantly to the strength by reducing the grain size and acting as dislocation barriers. Additionally, twinning has been considered as the main mechanism for the higher strain hardening rate at high strain rates than that at low strain rates. It has been found that the ultimate strength of the alloy is only ~10% higher at dynamic loading rate than at quasi-static loading rate. Localized micro-shear fracture was observed and adiabatic shear mode was suggested by further examination of dynamically loaded specimens. The shear localization is further discussed in detail and it is suggested that reduced strain hardening rate is responsible for shear localization and subsequent fracture at both low and high strain rates.

We have studied semiconductor to metal transition (SMT) characteristics of VO2(011) thin films integrated epitaxially with Si(100) through NiO{001}/MgO{001}/TiN{001} buffer layers and correlated with the details of epitaxy and nature of residual stresses and strains across the VO2/NiO interface. Thin film epitaxy at both room and elevated temperatures is studied in detail by electron microscopy and in situ high-temperature X-ray diffraction techniques. The epitaxial relationship across the interface between monoclinic VO2 and NiO is determined to be (011)VO2||{100}NiO and [01¯1]VO2||[001]NiO at room temperature. The epitaxial alignment at the temperature of growth where tetragonal VO2 is stable is determined as: (110)VO2||{100}NiO and [001]VO2||[100]NiO. A cube-on-cube crystallographic alignment is established across the NiO{100}/MgO{100}/TiN{100}/Si{100} interfaces. The misfit strains across the VO2/NiO interface at the growth temperature are calculated and the mechanism of strain relaxation is discussed. The out-of-plane orientation is found to be relaxed in both monoclinic and tetragonal states of VO2. It is shown that a compressive strain of 31.65% along the [001] direction of tetragonal VO2 is fully relaxed via matching of multiple domains. However, a small tensile misfit strain of about 5% along [11¯0] direction cannot relax and remains in the lattice. This tensile residual strain leads to a compressive strain along [001] axis which, in turn, results in an SMT temperature slightly lower than that of freestanding strain-free VO2. SMT characteristics of VO2(011) epilayers are assessed where an amplitude of near five orders of magnitude, and a hysteresis of less than 3.6 °C are obtained. This study introduces VO2/NiO thin film heterostructure integrated with silicon as a promising candidate for multifunctional devices with novel characteristics where a combination of sensing, manipulation, and response functions is needed.

Formation of long-period stacking ordered (LPSO) phases can significantly improve mechanical and corrosion properties of Mg-alloys. Typically LPSO phases can be formed by quick solidification of Mg-alloys having at least two alloying elements with atomic radii higher and lower than that of Mg. Stability of LPSO phases greatly depend on amounts and ratio of alloying elements. We report formation of thin film LPSO structures produced by co-sputtering of magnesium with zinc and gadolinium having less than 10% of alloying elements. This method allows controlling the ratio of the elements in composition, deposition temperature and orientation of thin films. Pure Mg, Zn and Gd films and their alloys deposited at temperatures below 200°C have HCP Mg-based crystallographic structure with exclusively basal orientation. LPSO phases and their stacking period were detected by observation of laminar structure patterns in low-angle x-ray reflectometry scans. The study of effects of elemental composition, deposition temperature and post-annealing of room temperature-deposited films on the formation of LPSO phase showed that the co-sputtering method can be very useful and efficient for the screening of new LPSO phases without the considerable expense preparation of bulk alloy preparation.

The micro-alloying effect, mechanical properties, and plastic deformation behavior of extruded Mg-Zr alloy were investigated and characterized as a function of Zr addition, grain size, and texture. The experimental methodology used in this study was design to exploit the hot-extrusion processing parameters (in the terms of extrusion ratios and temperature) and its effect on Mg extruded alloys microstructure, texture, and mechanical properties. Microstructural observations revealed significant grain refinement through a combination of Zr addition and hot-extrusion, producing fine equiaxed grain structure with grain sizes ranging between 1–5 μm. Texture analysis and partial compression testing results showed that the initial texture of the extruded alloy gradually evolved upon compressive loading along the c-axes inducing contraction twinning creating a strong basal texture along the extrusion direction. Full tensile and compression test at room temperature showed that the combination of hot-extrusion and Zr addition can further refine the grains of the Mg alloys microstructure and enhance the texture while simultaneously enhancing the mechanical properties.

Objective. We report the study of feasibility to produce the thing bioactive coating from experimental dental cement using pulsed laser deposition (PLD) technique. Methods. The targets for PLD system (disks 30 mm in diameter × 5 mm thick) were sintered from micronized powder of set Alborg White Portland cement (WPC). The parameters for sintering process were chosen based thermo-gravimetric analysis and differential scanning calorimetry (TGA/DSC). The coatings were deposited by PLD on silicon substrates. The effect of laser power on coating crystallinity and morphology was evaluated by scanning electron microscope (SEM) and X-ray diffraction (XRD). The material transfer from target to substrate were evaluated by X-ray fluorescence (XRF) and X-ray energy dispersive spectroscopy (EDS). The bioactivity of deposited films was evaluated by ability produce the hydroxyapatite (HA) layer on a surface of specimen immersed in a simulated body fluid (Dulbecco’s Phosphate-Buffered Saline (DPBS). The formation of hydroxyapatite was confirmed by SEM, X-ray energy dispersive spectroscopy (EDS), XRD and micro-Raman spectroscopy. The formation of HA was evaluated after 1, 3, 7, 14, and 21 days of immersion. Results. This study demonstrated that White Portland cement can be used as a target material for manufacturing of bio-functional coatings. The films deposited on Si substrates have mainly amorphous structure; the crystallinity of the film can be achieved by increasing the laser power. The biological performance of deposited films was tested by HA forming ability in simulated body fluid. The HA layer was formed on a coated surface after first day of immersion.

MgZnCa and MgZnCa-RE (Rare Earth) alloys were developed for biomedical applications. Small wires of the alloys were successfully fabricated from the small rods prepared by hot-extrusion followed by multiple cold-drawing passes with intermittent annealing. It was demonstrated that addition of small amounts of rare earth (RE) elements could effectively enhance the mechanical properties of the wires. The ductility or deformability under twisting test was greatly improved by post annealing at relatively high temperatures.

Objective. The purpose of this study was to characterize and to evaluate the effect of thermal treatment on properties and bioactivity of experimental dental cement. Methods. Specimens of the dental cement (pellets 13 mm in diameter × 3 mm thick) were prepared by cold pressing of micronized powder of set Alborg White Portland cement. The thermo-gravimetric analysis and differential scanning calorimetry (TGA/DSC) were used to analyze the phase composition and determine the transition temperatures for sintering process. The effect of heat rate and dwell time on density, crystal morphologies, crystalline phases and elemental composition of cement was evaluated by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) and micro-Raman spectroscopy. The bioactivity of set and heat-treated cements was evaluated by ability produce the hydroxyapatite (HA) layer on a surface of specimen immersed in a simulated body fluid (Dulbecco’s Phosphate-Buffered Saline (DPBS). The formation of hydroxyapatite was confirmed by SEM, X-ray energy dispersive spectroscopy (EDS), XRD and and micro-Raman spectroscopy. The amount of produced HA was measured by weight method after 1, 3, 7, and 14 days of immersion. Results. The set of samples were sintered from experimental dental cement at various heating rate and dwell time. The highest density was obtained at slower heating rate and longer dwell time. The heat treatment changes the hydration phases without changing elemental composition. The heat treatment significantly improves biological performance of dental cement. The heat-treated cement produces 10 times more HA with immersion into simulated body fluid.

Composite nanofibers of biopolymers and inorganic materials have been widely explored as tissue engineering scaffolds because of their superior structural, mechanical and biological properties. In this study, magnesium ferrite (Mg-ferrite) based composite nanofibers were synthesized using an electrospinning technique. Mg-ferrite nanoparticles were first synthesized using the reverse micelle method, and then blended in a mixture of polycaprolactone (PCL), a synthetic polymer, and Aloe vera, a natural polymer, to create magnetic nanofibers by electrospinning. The morphology, structural and magnetic properties, and cellular compatibility of the magnetic nanofibers were analyzed. Mg-ferrite/PCL/Aloe vera nanofibers showed good uniformity in fiber morphology, retained their structural integrity, and displayed magnetic strength. Experimental results, using cell viability assay and scanning electron microscopy imaging showed that magnetic nanofibers supported 3T3 cell viability. We believe that the new composite nanofibrous membranes developed in this study have the ability to mimic the physical structure and function of tissue extracellular matrix, as well as provide the magnetic and soluble metal ion attributes in the scaffolds with enhanced cell attachment, and thus improve tissue regeneration.

As the need for smaller data storage devices in the market continues to grow, the study of new combinations of self-assembled magnetic nanoparticles/films is greatly needed. In this research, Fe50-Ni50 films were synthesized using a Pulsed Laser Deposition technique. The films were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM) and physical properties measurement system (PPMS). Films were deposited from Fe-Ni alloy target (50%-50% composition), deposition was conducted in vacuum, at substrate temperatures varying from liquid nitrogen temperature -196°C to 600°C. The films were annealed in a vacuum chamber at 600°C for 1 hour. The study reveals that the substrate temperature has significant effect on the structure of the films and their magnetic properties. It was shown that additional thermal treatment improved the quality of films in terms of narrow grain size distribution. Magnetic properties were also found to improve significantly after post annealing process.

We have used magnetron sputtering to deposit magnesium and titanium layers alternately onto a single-crystal silicon substrate with equal individual layer thickness (h, from 2.5 to 200 nm) to form multilayers. We have investigated the mechanical behavior of the multilayers and its dependence on h. Transmission electron microscopy and X-ray diffraction analyses suggest that the multilayers exhibit strong texture with respect to Mg (0 0 0 2) and Ti (0 0 0 2) with an epitaxial growth pattern. Two primary orientation relationships between Ti and Mg have been identified, depending on h. Instrumented nanoindentation and microcompression have been used to examine the hardness/strength and the strain rate sensitivity of the multilayers. Based on nanoindentation, we have found that the strength of these multilayers generally increases as h is decreased. The microcompression measured strength is remarkably higher than that derived from indentation. The Hall–Petch law can be used to interpret the increase in strength at relatively large h (>50 nm), while the confined layer slip model provides a better explanation for the relationship between strength and h at smaller h. We have also attempted to present an in-depth discussion about the applicability of relevant strengthening mechanisms on these hexagonal close-packed/hexagonal close-packed multilayers.

In recent times, magnesium alloys have emerged as a possible biodegradable implant material. Plasma electrolytic oxidation (PEO) has been used in the past as a useful surface treatment technique to improve wear resistance and corrosion resistance of magnesium alloys by forming protective coatings. This study focuses on the effect of electrolyte solution on the microstructural and nanomechanical behavior of PEO coatings for possible use in biodegradable implants. Microstructural characterization of the coating was carried out by X-ray diffraction (XRD), scanning electron microscopy followed by image analysis and energy dispersive X-ray spectroscopy. Furthermore, nanoindentation was used to evaluate nanohardness of the PEO coatings. The results show beneficial effects of the PEO coating to improve the hardness of the uncoated AZ31 magnesium alloy. The XRD pattern shows that the crystal structures of the film vary based on electrolyte solution and the effect that has on nanomechanical behavior. In conclusion, this article shows the possible benefit of PEO coating for biodegradable implant use.

Using transmittance electron microscopy, fluorescence and polarizing optical microscopy, optical spectroscopy, and fluorescent correlation spectroscopy, it was shown that CdSe/ZnS quantum dots coated with a specifically designed surfactant were readily dispersed in nematic liquid crystal (LC) to form stable colloids. The mixture of an alkyl phosphonate and a dendritic surfactant, where the constituent molecules contain promesogenic units, enabled the formation of thermodynamically stable colloids that were stable for at least 1 year. Stable colloids are formed due to minimization of the distortion of the LC ordering around the quantum dots.

This study aims to evaluate the wear resistance of magnesium - ceramics nano-layered thin films using atomic force microscopy technique (AFM). The magnesium - ceramics (alumina and silica) nano-layered thin films were deposited on glass substrate using DC and pulsed DC reactive magnetron sputtering process. The surface roughness and wear properties were evaluated with the single crystal diamond tip. It was observed that the surface roughness was increased with the growing of number of layers for both magnesium-ceramics films. The nano-tribology test shown a strong adhesion between Mg-ceramic layers. The results shown that alumina nanolayers more efficient to resist against wear than silica. It was also noted that magnesium-silica nanolaminates loosing wear-resistance with the increasing number of layers.

In order to enhance the phase stability of dispersions of magnetic nanoparticles (NPs) in a polymorphic liquid crystal, new ligands have been designed consisting of a terphenyl-based liquid crystalline core. The most stable dispersions were obtained with 7 nm super-paramagnetic Fe3O4 NPs decorated with the new ligands in place of 10 nm ferromagnetic CoFe2O4 spherical NPs.

It is known that theoretical considerations of fracture under loading by a spherical indenter are based on the concept of pre-existing cracks. However, nucleation and growth of the critical crack could occur during indentation, as happens during microcracking. The goal of the presented research is to develop a new concept of fracture under spherical indentation in a brittle elastic material taking into account the possibility of critical crack nucleation and growth during loading. La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) perovskite has been chosen as a polycrystalline elastic low fracture toughness ceramic to perform indentation using a tungsten carbide spherical indenter. Experimental measurements of ring crack radii for well-polished LSGM cannot be explained within the framework of the pre-existing crack hypothesis. The local risk calculated using the concept of pre-existing cracks gives a most probable range of ring crack radii that does not match the radii measured experimentally. However, the local risk calculated using the assumption of critical crack nucleation and formation during spherical indentation results in a most probable range of ring crack radii which exhibits good agreement with the experimental data.

Individual nanotubes made of carbon, boron nitride, iron, silicon, or other materials have properties such as high strength, toughness, electrical and thermal conductivity, and light weight that cannot be matched by conventional materials. Nanotubes also change their properties in response to external fields and change one type of energy into another, which are useful for design. This article explores three main steps in exploiting responsive materials based on nanotubes: nanotube synthesis, macroscale material fabrication, and incorporation into device structures for novel applications. Nanotubes are always synthesized as individual particles in the form of powders, smoke particles, or aligned forests. To be industrially important, nanotubes generally must be processed to form derivative materials such as functionalized/coated powders and forests and macroscale intermediate materials such as sheets, ribbon, and yarn. The processed nanotubes are then used to develop responsive materials and devices that are able to resist, react to, or generate energy from their environment. This article provides background information and ideas on how to develop nanotube responsive materials for everyday use.

Magnesium (Mg) is a biodegradable metal that has significant potential advantages as an implant material. In this paper, corrosion and cell culture experiments were performed to evaluate the biocompatibility of Mg. The corrosion current and potential of a Mg disk were measured in different physiological solutions including deionized (DI) water, phosphate-buffered saline (PBS), and McCoy's 5A culture medium. The corrosion currents in the PBS and in the McCoy's 5A-5% FBS media were found to be higher than in DI water, which is expected because corrosion of Mg occurs faster in a chloride solution. Weight loss, open-circuit potential, and electrochemical impedance spectroscopy measurements were also performed. The Mg specimens were also characterized using an environmental scanning electron microscope and energy-dispersive X-ray analysis (EDAX). The X-ray analysis showed that in the cell culture media a passive interfacial layer containing oxygen, chloride, phosphate, and potassium formed on the samples. U2OS cells were then co-cultured with a Mg specimen for up to one week. Cytotoxicity results of magnesium using MTT assay and visual observation through cell staining were not significantly altered by the presence of the corroding Mg sample. Further, bone tissue formation study using von Kossa and alkaline phosphatase staining indicates that Mg may be suitable as a biodegradable implant material.