Plate-like Shape Research Articles

Rheological properties of plate-like shape carbonyl iron particles compositions based magnetorheological grease in oscillatory mode

This paper investigates dynamic viscoelastic properties of magnetorheological (MR) grease with different fractions of plate-like Carbonyl Iron (CI) particles (MRGP). The plate-like CI particles were prepared through milling process. Subsequently, three types of MRGP was developed by dispersing 30 to 70 wt% of plate-like CI particles into grease using mechanical stirrer. The rheological test was performed using oscillatory shear rheometer under flux density influence of 0 to 0.7T and strain amplitude ranging from 0.001 to 10% at constant temperature of 25°C. The experimental results show that the storage and loss moduli of the MRGP is dependent on the fractions of the plate-like CI particles. The enhancement in the MR effect in the plate-like CI particles based MR grease is observed due to the anisotropy shape which leads to the strong inter-particle configuration and chain formations.

Anionic polyelectrolytes in titanosilicate molecular sieve synthesis towards simultaneously accomplishing low production cost and high catalytic activity.

Assisted by an anionic polyelectrolyte of poly(acrylic acid) (PAA), high-performance titanium silicalite-1 (TS-1) could be facilely synthesized at very low usage of expensive organic templates (tetrapropylammonium hydroxide). The presence of PAA helped to incorporate more active Ti species into the TS-1 framework and change the morphology to a plate-like shape, which was beneficial to molecular diffusion among its micropores to access the Ti active sites. Therefore, TS-1 synthesized with PAA showed much higher catalytic activity than that synthesized using the traditional synthesis without polyelectrolytes, and only a 30% usage amount of organic template was used. Moreover, this ultra-cheap catalyst also displayed a better catalytic activity than commercial TS-1 synthesized via a series of complicated preparation processes including alkene epoxidation with hydrogen peroxide as a green oxidant.

Investigation of the effect of various parameters on the amount and morphology of nano-laminate MAX phase in Cf-C-SiC-Ti3SiC2 composite

This research focuses on investigating the synthesis of nano-laminate Ti3SiC2 and evaluates the effect of various parameters such as the amount and size of TiC, residual silicon, aluminum additive and annealing duration on the amount and morphology of MAX phase in Cf-C-SiC-Ti3SiC2 composite fabricated by LSI method. The infiltration process conducted at a temperature of 1500°C for 30min and then the samples were annealed at 1350°C. The phase composition and microstructure of the samples were analyzed by X-ray diffraction (XRD) technique and were observed by scanning electron microscopy (SEM), respectively. The results showed that by changing the TiC/polymer precursor ratio and TiC particles size, MAX phase content varied from 0 to 31vol%. The highest amount of MAX phase (31vol%) was synthesized in the sample which contains 0.13g Al, a TiC/polymer precursor ratio of 4, TiC grain size of 2–3μm and an annealing duration of 1.5h. Removal of aluminum and presence of residual silicon led to the reduction of the MAX phase content down to 19vol%. Microstructure observations indicated that MAX phases have been synthesized in the plate-like shape and equiaxial grains. They also revealed that the average distance between the layers, the average size of basal planes ({002}) and the average size of Ti3SiC2 in Z axis are dependent on the amount of residual silicon, the size of TiC particles and the existence of the aluminum in the initial composition.

Refractive index and temperature sensing in anisotropic silver nanostructures with stable photo-physical properties

In this report, we have demonstrated the refractive index and temperature-sensing abilities of polyvinylpyrrolidone (PVP)-protected silver nanostructures of triangular, connected and plate-like shapes. Interestingly, these nanostructures even after 2 and ½ years of syntheses showed plasmonic-sensing ability of temperature in the temperature range of 283–333 K. Also, refractive index (R.I.) sensing has been demonstrated in the aged samples and obtained the highest R.I. sensitivity of 306 nm/RIU in one of the sample. The synthesized samples have been kept in dark (inside desiccators) intentionally for the extended period of 2 and ½ years after synthesis and monitored intermittently their UV–Vis absorption and photoluminescence (PL) emission characteristics to check the functionally of the aged silver nanostructures. It has been found the samples remain well dispersed in different solvents and can forbid agglomeration even in 0.25 M NaCl solution. We have also demonstrated here fabrication of a flexible and transparent thin film of the synthesized samples in polyvinyl alcohol (PVA) matrix and investigated its low power continuous-wave (CW) nonlinear optical properties using spatial self-phase modulation (SSPM) technique. The nonlinear refractive index (n 2) value of the film has been determined to be 5.6 × 10− 6 cm2/W at the He–Ne laser wavelength of 632.8 nm. In this report we have demonstrated temperature and R.I. sensing and also it has been demonstrated that the synthesized samples remain functional even after 2 and ½ years of synthesis. Also, samples may find potential applications in nonlinear optical phase modulation devices.

Effects of Ni and Cu additions on microstructures, mechanical properties and wear resistances of ultra-coarse grained WC–6Co cemented carbides

Ultra-coarse grained WC–6Co cemented carbides with 1.2wt% (Ni and/or Cu) additions were investigated and compared with a focus on microstructure, mechanical properties and wear resistance using scanning electron microscope, X-ray diffraction, mechanical properties tests and wear test. The results reveal that Ni and/or Cu play a definite role in inhibiting the growth of WC grain and stabilizing fcc-Co. Moreover, Cu exhibits a stronger inhibition effect on the WC grain growth compared to Ni. In addition, Ni promotes WC grains to evolve towards the plate-like shape, while Cu retards the evolution of WC grains from round shape to facetted shape. Therefore, the addition of 1.2wt% Ni can improve simultaneously hardness and fracture toughness, resulting in an approximate 50% improvement in wear resistance. However, Cu is proven to improve hardness at the expense of fracture toughness, and deteriorate wear resistance. Instead of Cu, in this regard, Ni is a promising addition to strength ultra-coarse grained WC–Co cemented carbides used for rock-drilling applications.

Hydrothermal synthesis of SnQ (Q = Te, Se, S) and their thermoelectric properties

Lead-free IV–VI semiconductors SnQ (Q = Te, Se, S) are deemed as promising thermoelectric (TE) materials. In this work, we designed a hydrothermal route to selectively synthesize single phase SnTe, SnSe and SnS nanopowders. For all three samples, the phase structure were characterized by x-ray diffraction, SnTe particles with octahedron structure and SnSe/SnS particles with plate-like shape were observed by field emission scanning electron microscopy and transmission electron microscopy, the formation mechanism was discussed in detail. Then, SnTe, SnSe and SnS nanopowders were densified by spark plasma sintering for investigating TE properties. It was noticed that SnSe and SnS exhibited remarkably anisotropy in both electrical and thermal properties attributed to the layered crystal structure. The highest ZT values 0.79 at 873 K, 0.21 at 773 K, and 0.13 at 773 K were achieved for SnTe, SnSe and SnS bulk samples, respectively.

Synthesis and visible-light-induced sacrificial photocatalytic water oxidation of quinary oxynitride BaNb0.5Ta0.5O2N crystals

Quinary oxynitride BaNb0.5Ta0.5O2N crystals were fabricated through the partial nitridation and acidification of the KCl flux grown Ba5Nb2Ta2O15 crystals. The parameters of both the solute concentrations and cooling rates are optimized for the KCl flux growth of the larger Ba5Nb2Ta2O15 crystals with clearer crystal habits. Here, the optimal Ba5Nb2Ta2O15 crystals mainly have a hexagonal plate-like shape. After the partial nitridation and acidification, the porous BaNb0.5Ta0.5O2N crystals maintained the crystal shape of the oxide precursor and had a single-crystalline nature. For the Ba5Nb2Ta2O15 crystals, the wavelength of the absorption edge was about 707 nm. Especially, the CoOx-loaded BaNb0.5Ta0.5O2N photocatalyst demonstrated the comparatively high amount of O2 gas (150.7 μmol) during the 5 h visible-light-induced sacrificial water oxidation half-reaction, which might be achieved due to the high crystallinity and visible-light absorption property.

X-ray powder diffraction data for acetamidinium formate C3H8N2O2, elimination of preferred orientation effect

X-ray powder diffraction data, unit-cell parameters, and space group for acetamidinium formate, C3H8N2O2, are reported [a = 6.4564(5) Å, c = 13.021 (3) Å, unit-cell volume V = 542.8(3) Å3, M.p. = 215(1)°C, ρc = 1.274 g.cm−3, ρm = 1.269 g.cm−3, Z = 4, and space group P43212]. The front-loaded technique got sample with strong preferred orientation because of plate-like shape of crystallites, so the capillary packing was used for final powder data collection. All measured lines were indexed and are consistent with the P43212 space group. No detectable impurities were observed.

Atomically Dispersed (AD)Fe-N-C Oxygen Reduction Catalysts for Polymer Electrolyte Membrane Fuel Cells

Atomically dispersed (AD)Fe-N-C catalysts are the ultimate goal towards achieving Fe catalyst size reduction. Such catalysts are expected to have unique properties that can be exploited for the purpose of developing highly active and durable oxygen reduction reaction (ORR) catalysts. The biggest challenge during the fabrication of atomically dispersed catalysts is to prevent clustering of atoms on the support during synthesis. In this work we address this challenge by employing metal organic frameworks (MOFs) as the structural precursor for (AD)Fe-N-C catalysts. Specifically, we (i) synthesize Fe-containing MOFs (Fe-MOFs) followed by (ii) heat treatment of the Fe-MOFs to produce (AD)Fe-N-C catalysts. The heat treatment converts Fe-MOFs to N-doped carbons, with the Fe atoms contained in the MOF being uniformly distributed on the N-doped carbons without observable agglomeration. In the approach used, maintaining the initial morphology of MOFs after the heat treatment step is key to taking advantage of the MOF structural features. In a preliminary experiment, we synthesized an Fe-containing nano platelet-shaped MOF support and heat-treated it at 1000 °C in an oxygen-free atmosphere to obtain atomically dispersed Fe atoms anchored on N-doped carbon nano-plates, (AD)Fe-N-Cnano-plates. Figure 1a (high angle annular dark field scanning transmission electron microscopy (STEM) images)demonstrates that the initial plate-like shape of the MOF, which is typically 30-50 nm wide and up to hundreds of nm long, is successfully maintained during the heat treatment at 1000 °C. Microporosity within the nano-plates is generated during the heat treatment, assuring high accessibility to the Fe atoms within the catalyst. The nitrogen content in the nano-plates measured by X-ray photoelectron spectroscopy is ca. 5 at.%. X-ray diffraction (XRD) confirms the absence of crystalline particles in (AD)Fe-N-Cnano-plates,, e.g., Fe-rich particles in particular. As shown in Figure 1b, aberration-corrected (AC)-STEM clearly indicates that all of the Fe is atomically dispersed over the N-doped carbon nano-plates (individual white dots in the image). No Fe-rich clusters or particles are observed, corroborating successful synthesis of atomically dispersed Fe-N-Cnano-plates catalysts. Electrochemical and fuel cell performance data will be presented attesting to high ORR activity of the (AD)Fe-N-Cnano-plates catalysts. Figure 1

Influences of CuO addition on sintering, microstructural characteristics and microwave dielectric properties of 0.6Nd[(Zn0.7Co0.3)0.5Ti0.5]O3–0.4(Na0.5Nd0.5)TiO3 ceramics

Abstract 0.6Nd[(Zn 0.7 Co 0.3 ) 0.5 Ti 0.5 ]O 3 –0.4(Na 0.5 Nd 0.5 )TiO 3 (NZCT–NNT) ceramics with different amounts of CuO were prepared through a traditional ceramic technique. The influences of CuO addition on the sintering, microstructural characteristics and microwave dielectric properties of the NZCT–NNT ceramics were studied in detail. Acting as a sintering aid, CuO addition improved the sinterability and promoted the densification of the NZCT–NNT ceramics due to the production of a liquid phase. The sintering temperature of the NZCT–NNT ceramics was successfully reduced from 1410 °C to 1250 °C. The addition of CuO resulted in a change in the grain shape of the NZCT–NNT ceramics, ranging from a plate-like layered shape to a round–like shape. Additionally, CuO addition adjusted the temperature coefficient of resonant frequency (τ f ) toward near–zero without inducing an obvious deterioration in the dielectric constant (e r ) and the quality factor ( Q × f ) of the NZCT–NNT ceramics. After being sintered at 1250 °C for 3 h, the NZCT–NNT ceramics to which 2.0 wt% CuO was added exhibited optimized microwave dielectric properties of e r = 48.56, Q × f = 46,420 GHz, and τ f = + 1.3 ppm/°C. The CuO–doped NZCT–NNT ceramics could find the potential commercial applications in microwave components that require low sintering temperatures.

Synthesis and characterization of monolithic ZnAl2O4 spinel with well-defined hierarchical pore structures via a sol-gel route

Hierarchically porous ZnAl2O4 spinel monolith derived from ionic precursors has been successfully prepared via the sol-gel route accompanied by phase separation in the presence of poly (ethylene oxide) (PEO) and propylene oxide (PO). Appropriate amounts of PEO as a phase-separation inducer and PO as a gelation mediator allow the formation of the xerogel with bicontinuous macrostructure and a monolithic shape. The macropore size of the resultant dried gel is mainly distributed in the range of 0.2–1 μm, and the whole porosity is about 65%. The dried gel is constructed by crystalline ZnAl hydrotalcite, becoming amorphous after heat-treated at 300–500 °C in air, and is further transformed into single phase ZnAl2O4 spinel with plate-like shape at 600 °C. The macroporous structure is well maintained while the porosity increases to 75% and the surface area rises to 109 m2 g−1 after heat-treatment.

Directional solidification of a Sn-0.2Ni solder alloy in water-cooled copper and steel molds: Related effects on the matrix micromorphology, nature of intermetallics and tensile properties

The present investigation is focused on, firstly, performing transient directional solidification experiments with a Sn-0.2 wt.% Ni solder alloy using two different substrates as mold sheets separating the alloy casting from the cooling fluid: copper and low carbon steel. Secondly, the examination of the obtained microstructures is carried out highlighting not only the micromorphology aspects of the formed β-Sn phase but also the nature and the shape of the intermetallic compounds (IMCs) developed. The purpose of this research work is to verify the influences that different substrate materials may have on the alloy solidification kinetics, resultant microstructures and tensile properties of the Sn-0.2 wt.%Ni solder. The microstructure characteristics may be correlated with thermal solidification parameters such as the eutectic cooling rate and eutectic growth rate along with a qualitative evaluation of Fe and Cu dissolutions into the alloy. The results display that the dissolution of Cu into the Sn-Ni alloy provided the prevalent growth of the (Cu,Ni)6Sn5 fiber-like eutectic phase along the length of the casting. Other than, the Cu-containing Sn-Ni alloy allowed the growth of high-velocity β-Sn cells only for very high cooling rates, associated with positions closer to the bottom of the alloy casting. Farther positions are characterized by a complex growth of β-Sn dendrites. On the other hand, for the alloy solidified against the steel mold, a predominance of the non-equilibrium NiSn4 eutectic phase with plate-like shape has been identified by SEM/EDS and XRD. In this case, the predominant growth of β-Sn cells associated with the presence of the plates of the NiSn4 IMC allowed lower tensile strength and higher ductility to be attained.

Synthesis of Uniform Barium Ferrite Powders by Co-Precipitation Method

The uniform hexagonal barium ferrite powders were synthesized by co-precipitation method using metal chloride. The effects of the amount of hexadecyltrimethyl ammonium bromide (CTAB), the water bath and calcination temperature on the phase formation, microstructure and density of barium ferrites were systematically investigated. The results showed that the formation of uniform hexagonal barium ferrite powders was significantly influenced by the amount of CTAB and the water bath could lead to the larger grain size and density. The SEM demonstrated that the BaFe12O19 powders had plate-like shape with crystallite sizes varing from 150 to 200 nm. When the amount of CTAB was 0.2g/100ml and the calcination temperature was 850 °C, the barium ferrite powders were uniform which indicated that the amount of surfactant and calcination temperature were very optimum.

Superconductivity and its enhancement under high pressure in “F-free” single crystals of CeOBiS2

“F-free” CeOBiS2 single crystals have successfully grown, thoroughly eliminating a concern about F-contamination by using a high-purity CsCl flux. The obtained crystals have a plate-like shape with a size of 1.0–3.0 mm in the well-developed plane. Single crystal X-ray structural analysis clearly revealed that the CeOBiS2 crystallizes with a space group P4/nmm (with lattice parameters of a = 4.0189 (6) Å, c = 13.573 (2) Å). The bond valence sum estimation and X-ray photoelectron spectroscopy analysis showed that the chemical state of Ce was in the mixed valence of Ce3+ and Ce4+. The single crystals show superconductivity with zero resistivity at ∼1.3 K. This is the first conclusive evidence of superconductivity driven by Ce valence fluctuation in surely non-doped CeOBiS2. The superconducting transition temperature was enhanced up to ∼3.8 K by applying hydrostatic pressure.

Growth and superconducting properties of Cd-doped La(O,F)BiS2 single crystals

Cd-doped La(O,F)BiS2 single crystals were grown using a CsCl/KCl flux. The grown crystals have a plate-like shape with ~1–2mm square size in a well-developed ab-plane. The Cd doping in the crystals was successfully characterized by single crystal X-ray diffraction and electron probe microanalysis techniques. The superconductivity of La(O,F)BiS2 was gradually suppressed with Cd doping. The superconducting transition temperature with zero resistivity of La(O0.54F0.46)(Bi0.92Cd0.08)S2 was 2.3K. The Cd doping does not change the superconducting anisotropy so much, albeit the considerable suppression of Tc.

Magnetic and optical properties of Cu1−xFexO nanosheets prepared by the hydrothermal method

Cu1−xFexO (x = 0, 0.025, 0.05, 0.075, and 0.1) nanosheets can be sucessfully prepared by hydrothermal method at 160 °C for 3 h in a solution of 0.5 M KOH. X–ray diffraction results indicated a monoclinic phase of crystalline CuO nanosheets. Crystallite sizes and lattice constants were determined by Rietveld refinements of the X–ray diffraction peaks. The crystallite sizes significantly decreased from 28.46 to 21.71 nm with the increase of Fe content. Scanning electron microscopy and transmission electron microscopy revealed the plate-like shapes with the estimated width and length in the range of 50–170 and 100–275 nm, respectively. The optical band gaps (E g) studied by ultraviolet-visible spectroscopy are found to decrease from 3.625 eV for undoped sample to 3.430 eV in Fe–doped CuO sample of x = 0.1. The magnetic properties of samples studied by vibrating sample magnetometry indicated a paramagnetic behavior for CuO nanosheets and ferromagnetic behavior in Fe–doped CuO nanostructures with the magnetization strongly depended on the Fe content. The ferromagnetism of Fe-doped samples was discussed base on the F-center exchange mechanism via oxygen vacancy defects. This figure shows the magnetization of Fe doped CuO nanosheets synthesized at 160 °C for 3 h in 0.5 M KOH with SEM micrograph, showing the plate-like morphology. It can be seen in this figure that ferromagnetic behavior of CuO nanosheets can be induced by doping with Fe ion. Moreover, the optical band gaps of Fe-doped CuO nanosheets decrease with the increase of Fe content, suggesting that Fe-doped CuO nanosheets may be applied as photocatalytic materials. Ferromagnetism is proposed to be originated from the coupling of Fe3+ with the oxygen vacancy promoted in the samples.

Structural, dielectric and optical analysis of Li1.1−yNb0.9-3yTi0.1+4yO3 M-phase solid solutions

Abstract The present paper reports the structural, dielectric and optical analysis of the M-phase Li1.1−yNb0.9-3yTi0.1+4yO3 (y=0.00, 0.045, 0.09, 0.11, 0.135) solid solutions in the Li2O–Nb2O5–TiO2 ternary system prepared by conventional solid state reaction method. High density (relative density>91%) ceramics were obtained by sintering the solid solutions at 1100 °C. XRD spectra revealed these ceramics to exhibit hexagonal structure and the superstructure formation was observed for higher Ti content (≥28 mol%) samples. Plate-like shape and closely packed grains were formed with low porosity (≤10%). Particle size was obtained in the range of 392–235 nm using TEM images. Relative permittivity changed from 46 to 31 while temperature coefficient of resonant frequency ranged from −93.5 to 57.5 at 1 MHz frequency. The maximum photoluminous intensity of 203.13 for the emission peak at 453 nm (blue emission) was observed for the sample y=0.00.

The Study of Microstructure and Magnetic Properties of La3+ doped W-Type Hexagonal Ferrites Sr1−x La x Co2Fe16O27

The W-type hexagonal ferrites with the composition Sr1−xLaxCo2Fe16O27 (0 ≤ x ≤ 0.35) magnetic powders were synthesized by the solid state method. The phase constituents, micro-morphology, and magnetic properties of the particles were investigated by x-ray diffraction (XRD), a scanning electron microscope, and a vibrating sample magnetometer. The single phase was observed in the W-type ferrites with different La content from XRD. The micro-morphology of the particles exhibits the hexagonal plate-like shape, and the particles are distributed homogeneously of W-type ferrites with different La content. The coercivity (Hc) of the particles increases with the increase of La content (x), while the saturation magnetization (Ms) of the particles first increases with x from 0 to 0.15, and then begins to decrease when x continues to increase.

High strength Mg-Zn-Y alloys reinforced synergistically by Mg12ZnY phase and Mg3Zn3Y2 particle

Eight Mg100-x-yZnxYy (at.%, x = 2–7.2, y = 4–7) alloys with atomic ratios of Y/Zn = 0.75–2 were designed and prepared by rapidly solidified powder metallurgy technology. The atomized powders with the Y/Zn atomic ratios larger than 1 contain α-Mg dendrite and network-like X-Mg12ZnY compound, but those with the Y/Zn atomic ratios of 1 and 0.75 have W-Mg3Zn3Y2 particle besides the above two phases. After hot extrusion, network-like Mg12ZnY phase was changed into acicular and plate-like shape. These as-extruded alloys exhibit excellent mechanical properties at room and elevated temperature. Especially, the ultimate tensile strength of as-extruded Mg86Zn7Y7 alloy reaches up to 541 MPa at room temperature and 297 MPa at 250 °C. HRTEM study reveals that Mg12ZnY phase is composed of 18R LPSO structures. These sub-micrometer Mg3Zn3Y2 particles bring about dispersion strengthening to Mg12ZnY phases, resulting in a synergistic strengthening of Mg12ZnY phase and Mg3Zn3Y2 particle in the alloy which has the Y/Zn atomic ratio equal to or larger than 1. Therefore, the excellent mechanical properties of Mg86Zn7Y7 alloy are attributed to the second phase strengthening of LPSO phase and synergistic strengthening of Mg12ZnY phase and Mg3Zn3Y2 particle.

The Performance of Geotextile Materials Used for Filtration and Separation in Different Structures as an Important Part of Geotextiles Requirements

Currently, a water discharge coefficient as an important feature of geotextile materials that affects their filtration capacity in a frozen condition is not included in the geotextiles material specifications. The higher the water discharge coefficient of geotextile materials is, the less ice they contain when frozen. The necessary requirements and corresponding mathematical relations for choosing the appropriate geotextile materials are presented in this study. Geotextile materials used as separating layers in a railway formation should meet the same requirement.The effective diameter of the geotextile material pores (cells) was obtained by sieving through it the fine-grained quartz sand of pre-determined grain-size composition. Nevertheless, as microscopic research showed, particles produced due to the ballast abrasion and bridging (colmating) of the geotextile material have a plate-like shape. Consequently, the curve of their granulometric composition differs from that of the quartz sand.Based on the experimental data, the criteria for the required mathematically calculated filtration flow diameter have been established to ensure that geotextile materials are not colmated during their designed life span. The theoretical, field and laboratory research conducted permitted to formulate the propositions on making amendments to the requirements and their modification boundaries depending on the area of geotextile materials application.