Rapid solidification of Al30Si70 alloy was studied via electromagnetic levitation technique. The solidification kinetics and the morphology of the solidification front of the Si phase were analyzed in situ by using a high-speed video camera and subsequent microstructural analysis of as-solidified samples. It shows that solidification of the sample always starts from one point. After that, nucleation continues to proceed at the interface front during growth. The morphology of primary Si transforms from faceted wafer to nonfaceted equiaxed grain and the grain size decreases with increase of undercooling. At small undercooling, the growth velocity of primary Si decreases with time and the floated Si wafers have a trend to agglomerate, while at large undercooling, the nucleation rate decreases with time, which are explained by the fact that silicon content, undercooling and density at the solid–liquid interface change with time in solidification. Finally, the nucleation rate and growth velocity were discussed in combination of classical theory.

This paper describes the direct-foaming of plaster of Paris (CaSO4·½H2O) with up to 1.7 wt% of a nonionic surface-active agent to obtain highly porous, lightweight gypsum (CaSO4·2H2O) with 65–70% total porosity and a homogeneous, bimodal pore size distribution. Based on viscosity and temperature changes in the setting plaster of Paris slurry, the nonionic surfactant is seen to retard gypsum crystallization and thus extend the working time at higher water to solid ratios. The increase in viscosity during gypsum crystallization stabilizes the macropores formed during foaming. Gypsum foams of 32% density with a submicron matrix pore size, and relatively uniform macropore size of ∼100 µm were obtained. Seeding the process with 0.5 wt% 100 µm diameter gypsum particles accelerates gypsum crystallization in the presence of the nonionic surfactant and results in a more uniform, finer (92 µm) macropore structure due to less time for bubble coalescence.

In searching for a suitable semiconductor material for hydrogen production via photoelectrochemical water splitting, α-Fe2O3 received significant attention as a promising photoanode due to its band gap (∼2.1 eV), good stability, low cost, and natural occurrence. α-Fe2O3 thin films were prepared by economic and facile dip coating method and subsequently subjected to an anodic potential of 700 mV versus Ag/AgCl in 1M KOH for different anodization times (1, 10, and 900 min) under illumination. X-ray diffractometry revealed increase in crystallites size from ∼31 nm for nanoparticles in pristine state to ∼38 and 44 nm after anodization for 1 and 900 min, respectively. A clear positive correlation between anodization time and grain (particle) size was observed from field emission gun scanning electron microscopy and atomic force microscopy (AFM); longer exposure time to anodizing conditions resulted in larger grains. Grain size increased from ∼57.9 nm in pristine state to ∼153.5 nm after anodization for 900 min. A significant smoothening of the surface with increase in anodization time was evident from AFM analysis.

In this research work, planetary ball mill has been used to disperse carbon nanotubes (CNTs) in Al powders. Al-CNT nanocomposite samples have been produced using double pressing double sintering (DPDS) method. The effects of CNTs weight percent and secondary pressing and sintering on the hardness, tensile, and bending strength of Al-CNTs nanocomposites were investigated. Enhancements of about 98% in hardness, 40% in tensile strength, and 20% in bending strength of Al-CNTs nanocomposites were observed as compared with pure Al samples. Using DPDS technique increments of 2.4–16.14% in density has been obtained as compared with the nanocomposites produced by conventional sintering method. The composites were studied by scanning electron microscope and differential thermal analysis. The X-ray diffraction (XRD) was used to identify various phases if present in Al-CNTs nanocomposites.

Two kinds of Ag/ZnO electrical contact materials were fabricated by powder metallurgy method. The electrical life testing was done to investigate the arc erosion behavior of the prepared contact materials. Their properties and morphologies were characterized and discussed in detail. Results showed that Ag/ZnO(c) with coprecipitated ZnO as the second phase had better mechanical and electrical properties compared with Ag/ZnO(a) with ZnO purchased from Aladdin Industrial, Inc. Besides, some typical morphologies, such as holes, Ag or ZnO enrichment zone, Ag skeletons and bubbling area, occurred on the surface of the contacts. Especially for Ag/ZnO(c), vertically aligned ZnO nanorod arrays were detected after the life testing without any other supporting equipment. The existence of a solid solution Zn1−x Ag x O and different energy generated during arcing process were possible reasons resulting in this phenomenon. A solid–vapor–solid mechanism was put forward to analyze the phenomenon mentioned above. These evidences could also offer some valuable information desired for reducing the splashing of Ag droplet under arcing.

To develop microwave absorbing materials over X and Ku-band, M-type hexaferrites: BaCoxTixFe(12−2x)O19, with x varying from 0.0 to 1.0 in step size of 0.2, were prepared by solid state reaction route. Characterization techniques like x-ray diffraction, scanning electron micrograph and vibration sample magnetometer were used to analyze the crystalline phases, morphologies, and magnetic properties of the samples. Vector network analyzer was utilized to scrutinize the electromagnetic properties like complex permittivity, complex permeability, and microwave absorption. Results indicate the enhancement of imaginary permittivity and permeability with substitution. Absorption analysis concludes that the composition with x = 0.8 is the best single-layer microwave absorber out of all the prepared compositions with minimum reflection loss −33 dB at thickness of 3.1 mm. At the same time, the compositions x = 0.2, 0.4, 0.6, and 1.0 are combined to form double-layer absorber with absorption more than 99% in X and Ku-band.

Three isothermal sections of the Ni–Fe–Zr ternary system at 1000, 1100, and 1200 °C were experimentally determined using equilibrated ternary alloys. No ternary compound is found in this system. The obtained experimental results show that among three isothermal sections, the (γFe, Ni) phase region extends from the Ni-rich corner to the Fe-rich corner, and the solubility of Zr in the (γFe, Ni) phase is small. The phase equilibrium at 1100 °C is similar to that at 1000 °C. The Ni5Zr, Ni10Zr7, and Fe2Zr phases have solid solution composition ranges, but the Ni7Zr2, Ni21Zr8, NiZr, NiZr2, and Fe23Zr6 phases almost exhibit nearly linear compounds both at 1000 and 1100 °C. The solubilities of Fe in Ni7Zr2 phase and Ni in Fe2Zr phase are extremely large. At 1200 °C, the liquid phase of Zr-rich corner forms the continuous region from the Ni–Zr side to the Fe–Zr side. Additionally, the solubilities of Fe in Ni5Zr, NiZr phases and Ni in Fe23Zr6 phase clearly increase with increasing temperature to 1200 °C. The obtained results may provide a better understanding of microstructures and further development of the Ni–Fe–Zr alloys.

The isothermal oxidation experiments were carried out on several new γ/γ′-strengthened cobalt-base alloys Co–Al–W–4Cr–0.02X (X = La, Ce, Dy, Y) at 900 and 800 °C. Due to an appropriate content of additional elements, the change in the morphology occurred and it significantly improved the oxidation resistance compared with those without Cr, among which the one with La elements shows the best oxidation resistance. Multiple oxide layers are also formed during the oxidation process, with CoWO4 and CoAl2O4 phases in the outer layer, and Cr, Al, W, and Co (e.g., Cr2O3) in the middle layer. The inner layer consists of some Al2O3 oxides, while more protective Al2O3 oxide was formed, esp. at the temperature of 800 °C. Both Cr2O3 and Al2O3 oxides were effectively protective oxides, which can prevent the intrusion of oxygen into the alloy substrate. Moreover, a phase transformation (γ/γ′ to γ/Co3W) was observed at the interface between oxide layer and substrate.

The Manganese dioxide/reduced graphene oxide (MnO2/RGO) double-shelled hollow microsphere with an improved electrical conductivity and accessible surface area has been synthesized using the monodispersive polystyrene (PS) microsphere as a self-sacrificing template. RGO/PS core–shell microsphere was prepared through π–π stacking interaction between PS microsphere and graphene oxide sheet, and then chemical reduction using hydrazine hydrate. MnO2/RGO/PS core-shell-shell microsphere was prepared through in situ chemical redox process between KMnO4 and benzyl alcohol-anchored RGO/PS. MnO2/RGO double-shelled hollow microsphere was obtained by etching PS microsphere from MnO2/RGO/PS using tetrahydrofuran. It had a pore diameter of 560–580 nm and layer thickness of 210–270 nm. Low charge transfer resistance of 0.3006 Ω and total electrochemical impedance of 2.37 Ω caused a high specific capacitance of 450.1 F g−1 at 0.2 A g−1. The capacitance retention of 81.7% after 1000 cycles indicated good cycling capability at 5 A g−1. MnO2/RGO double-shelled hollow microsphere presented the promising application for supercapacitor electrode material.

The particle size of Fe3O4 nanoparticles is controlled using a simple oxidation–precipitation method without any surfactant. The structure, morphology and physical properties of the synthesized Fe3O4 NPs were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, and vibrating sample magnetometer. As-prepared magnetite samples exhibited spherical morphology with average diameters of 30, 70, 250, and 600 nm, respectively. Activity of the synthesized Fe3O4 NPs was evaluated for the Fenton-like reaction, using rhodamine B (RhB) as a model molecule. The results showed that catalytic activity increases with the reduced particle size. The significant higher catalytic activity of the fine Fe3O4 NPs mainly originated from the higher specific surface area, due to the increase in exposed active site number and adsorption capacity. The reusability of 30 nm Fe3O4 NPs was also investigated after three successive runs, in which the RhB degradation performances showed a slight difference with the first oxidation cycle. This investigation is of great significance for the promising application of the heterogeneous Fenton catalyst with enhanced activity in the oxidative degradation of organic pollutants.

Al-based composites reinforced with Mg–7.4%Al mechanically alloyed particles have been synthesized by hot pressing followed by hot extrusion. Microstructural characterization of the bulk samples reveals the phase transformation of the reinforced particles (Mg(Al)ss + γ-Al12Mg17) to the stable intermetallic β-Al3Mg2 phase which occurs during consolidation. The phase transformation leads to the increase of effective volume faction of the reinforcement along with strong interfacial bonding, which causes a significant increase of the strength of the composites retaining appreciable plastic deformation. The strengthening can be attributed to the reduction of ligament size and to the interface strengthening due to better interface bonding (load-transfer) between the Al-matrix and the reinforcing particles.

This paper investigates friction and wear between an electro-deposited coating and high carbon chrome steel. A ball-on-flat plate tribometer was developed, measuring tangential and normal displacements of a high carbon chrome steel ball. For the purpose of measuring displacements of a ball, laser displacement sensors were used. An electro-deposited coating was applied to a cold-rolled high strength steel plate. Displacement amplitudes of 0.2 and 1.0 mm were imposed to produce fretting and reciprocal sliding at contact. A steady-state value of the kinetic friction coefficient between an electro-deposited coating and high carbon chrome steel was found to be about 0.28. It was identified that wear volume on a coated specimen increased with the number of cycles. Correlation between the wear volume and a normal displacement of a ball was found to be linear. It was demonstrated that the proposed method is useful for understanding friction and wear of an electro-deposited coating.

Few layer graphene is attractive due to its extraordinary electronic and optical properties, which are strongly influenced by the orientation between the layers called as stacking sequence. It is challenging to synthesize high quality large size single or multi layer graphene crystals on the metal catalyst using chemical vapor deposition technique. The present work is about synthesis of few layer graphene grains on platinum foil using ambient pressure chemical together vapor deposition technique. The main focus is how the different grains coalesced and maintain the stacking sequence. Different characterization techniques are used to analyze the grains when they are in the process of merging to make a bigger grain. Scanning electron microscopy clearly shows different stacking sequences and merging of different nucleation sites of different grains. Interestingly, different stacking sequences are observed during the process of coalescence of grains. Raman spectroscopy gives accurate information about the number of layers and their stacking sequence. We observed Bernal AB and twisted layer stacking in the grains when they were combining together to grow into a bigger size. The full width at half maximum (FWHM) value of 2D Raman peaks appeared in the range of 52–69 cm−1 which shows an increase from the value of single layer graphene (30.18 cm−1) and identifies Bernal stacking in grains. For twisted stacking FWHM values lie in the range of 19–32 cm−1.

In this article, we report on the preparation of few-layered MoS2/graphene nanocomposite (MoS2/GNS-G) with enlarged interlayer distance as the lithium-ion battery anode via a facile hydrothermal method followed by glucose-assisted thermal annealing. During the synthesis, glucose serving as a small organic molecule can interlay into MoS2 nanosheets, which effectively hinder the aggregation and restacking of MoS2 during the process of heat treatment, retaining a sandwich structure of the composite. The enlarged interlayer distance (approximately 0.98 nm), along with the inserted amorphous carbon, could promote efficient lithium migration into active sites, buffer the volume change and stabilize the electrode structure effectively during the lithium insertion/extraction cycling. Electrochemical tests demonstrate that the MoS2/GNS-G delivers a high discharge capacity of 1583.0 mA h/g in the initial cycle at current density of 100 mA/g. The specific capacity remained at the relative high value of 673.5 mA h/g even at a current density of 1000 mA/g.

Hot deformation is an effective way to tackle major problems in powder metallurgy, i.e., inferior mechanical properties and low relative density. To characterize the hot deformation behavior of NiAl-based alloy manufactured by hot pressing sintering, the isothermal compression tests were performed in the deformation temperature range of 1100–1300 °C with strain rate of 0.001–1 s−1. The result indicates that calculated hot activation energy Q is 326.31 kJ/mol. The processing efficiency maps and instability maps of NiAl-based alloy were established to optimize deformation parameters on the basis of dynamic material model. They were validated through microstructure evolution. The microstructure observation revealed that fine grains, dislocation pile-up, cracks appear in high efficiency, low efficiency, and instability domains, respectively. According to effective processing window revealed by processing maps, hot forging of sintered billets was performed. The elevated temperature elongation increases from 17.86% to 74.87% after forging. The stripping feature is found on fracture surface after forging.

Diamond like carbon (DLC) films deposited using CH4 and Ar and amorphous fluorocarbon (a:C-F) films deposited using CF4 and Si2H6 as precursors were optimized for ultra-low dielectric constant applications by tuning pressure, substrate temperature, and flow rate ratio. Sixty three films belonging to three stack configurations possessed good morphology and adhesion post DLC deposition. Structural and mechanical properties with respect to film integrity, adhesion, roughness, and shrinkage rate were studied. Internal and interface stress distribution results in the increased stability of as deposited DLC–a:C-F–DLC sandwich layers in comparison to a:C-F–DLC stacks. Annealed a:C-F with DLC top coat and As deposited a:C-F are similar in bonding structure. Failure mode is buckling delamination failure with increasing severity in films with higher oxygen incorporation and can be preserved by annealing the fluorocarbon component or providing a DLC base coat. Effect of process parameters on properties relevant to integration has been determined.

A novel, simple, quick, and economic method has been developed to etch samples for characterizing the structural aspects of carbonized pitch alone and in baked anodes. Hot air is used to etch the polished carbonized pitch surface for creating its topography; followed by the characterization of the structure using scanning electron microscope. Hot air preferentially etches the carbonized pitch, which make the differentiation of carbonized pitch from the calcined coke particles possible in baked anode. After etching, lamellar parallel cracks are created and fine granular mosaics are observed on the surfaces of carbonized pitch. The structural composition in baked anode differs visibly from the pure carbonized pitch baked under the same conditions. This may be due to the effect of fine coke particles in anode on the formation of structure during baking. The etching technique permits the determination of the internal structure of carbonized pitch and its interface with coke in anode.

Microstructure evolution and tensile properties of large dimensional bulk 304 stainless steel after being rolled with different thickness reductions were characterized in detail. The results showed that the steel consisted of nano-submicro-microcrystalline austenite and nanocrystalline ferrite. Submicrocrystalline austenite was broken down with the thickness reduction, when thickness reduction was 70%, all submicrocrystalline were broken down to nanocrocrystalline, and dispersed more uniformly in the microcrystalline austenite phase in the steel, but the grain size of the nanocrystalline austenite increased to 70 nm. Tensile strength increased from 850 MPa to 965 MPa, yield strength increased from 652 MPa to 837 MPa, elongation decreased from 33% to 19%, intergranular corrosion rate decreased from 1.36 g/(m2 h) to 0.46 g/(m2 h). Strength and intergranular corrosion properties increased much. When the thickness reduction was 70%, the tensile strength, yield strength, elongation, and intergranular corrosion properties were the best in the reported value of the steel.

Segmented nanoporous WO3 is prepared via anodization with an electrolyte containing 1 M Na2SO4 and 0.07–0.7 g of NH4F. Annealing (500 °C for 1 h) was also performed to induce crystallinity in WO3. More pores (50–80 nm in diameter) and thicker porous layer were formed by increasing the amount of NH4F (400 nm for 0.3 g of NH4F). However, further increase of the NH4F amount to 0.5 and 0.7 g did not increase the porous layer thickness. Segmented nanoporous structure formation was attributed to the dissolution of anodic oxide by H+ and F− ions in the electrolyte, as well as the healing process induced by the electric field. The photocatalytic activity of the WO3 samples was evaluated through degradation of methyl orange solution. The as-anodized sample showed lower photocatalytic ability in comparison with the annealed sample because of the amorphous behavior of as-anodized WO3.

The [(BiSe)1+δ]1(VSe2)1 heterostructure was characterized structurally and electrically to determine the effects of interlayer interaction on the charge density wave (CDW) found in VSe2 and compared to previously reported [(SnSe)1.15]1(VSe2)1. Out-of-plane x-ray diffraction scans contain reflections that can be indexed as 00l reflections of a BiSe–VSe2 supercell. Structure refinement indicates that the VSe2 layer is very similar structurally to that found in [(SnSe)1.15]1(VSe2)1. Scanning transmission electron microscopy images show a turbostratically disordered layer structure and the formation of anti-phase boundaries in the BiSe bilayer. The [(BiSe)1+δ]1(VSe2)1 heterostructure is metallic with a negative Hall coefficient, in contrast to the positive Hall coefficient found for [(SnSe)1.15]1(VSe2)1. The CDW found [(SnSe)1.15]1(VSe2)1 is not present in [(BiSe)1+δ]1(VSe2)1. This work illustrates the importance of inter constituent interactions in determining the transport properties of single layer films.