Morphology and crystallographic phase of V–C particles formed in Fe–Cr–Ni–V–C alloys

Abstract

The morphology and crystallographic phase of V–C carbide particles formed in cast Fe–Cr–Ni–V–C alloys were investigated by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM). The combination of results obtained with these techniques revealed that cuboidal, cruciform and spherical carbide particles were formed, depending on the alloy composition, all having the cubic-VC_1?x structure (Fm-3m). Detailed TEM observations suggested that small carbide particles were initially cubic in shape and became spherical with increasing particle size. All cuboidal and spherical carbides were single crystallites with no grain boundary at any particle sizes, even after growing to 6 μm in diameter.     

Microstructure and microchemistry of silicon particles formed during electrical-discharge machining

The structure and morphology of particles representing the byproduct of electrical-discharge machining (EDM) were analyzed using transmission electron microscopy (TEM). The EDM process involved high-efficiency and high-accuracy fine boring of a single-crystal silicon ingot by high-frequency electrical spark discharges. As the silver electrode advanced, spark-discharge-melted or vaporized small particles of the silicon workpiece were produced and the particles were flushed away and collected in deionized water. Standard TEM and analytical electron microscopy (AEM) observations were carried out. Bright-field (BF) images, diffraction, and energy-dispersive X-ray spectrometry (EDXS) data were obtained to completely characterize the EDM particles. BF images indicated the presence of large silicon particles decorated by smaller silver particles originating from the electrode as the byproducts of the EDM processing. Analysis of the particle-size distribution resulted in an average silicon particle size of about 500 nm decorated by smaller silver particles of an average size of about 65 nm. EDXS spectra depicted individual silicon and silver particles with characteristic peaks that identify the elements present. Selected-area electron diffraction (SAED) pattern confirmed the presence of crystalline silicon. Finally, a set of SAED patterns, EDXS profiles, and TEM images is included that fully describe the particles' chemistry, structure, and morphology, respectively.     

Hydrothermal synthesis of zirconium oxide nanoparticles and its characterization

The paper presents the preparation and investigations of zirconium oxide (ZrO₂) nanoparticles that were synthesized by hydrothermal method. The products were characterized by means of powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-absorption spectroscopy and photoluminescence (PL) spectroscopy. The crystal structure was determined using X-ray diffraction. The morphology and the particle size were studied using (SEM) and (TEM). The spherical shaped particles were confirmed through the SEM analysis. The transmission electron microscopic analysis confirmed the formation of the nanoparticles with the particle size. The FT-IR and Raman spectrum ascertained the strong presence of ZrO₂ nanoparticles. The optical properties were obtained from UV–visible absorption spectrum and also PL emission spectrum. The dielectric constant and the dielectric loss were measured as a function of frequency and temperature.     

Synthesis of au nanoparticles at "all" pH by H2O2 reduction of HAuCl4

In this article we report the synthesis of Au nanoparticles (NPs), from HAuCl4, in the pH range of 2.9 to 11.2 using H2O2 as the reducing agent. Ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction techniques have been used to characterize the Au NPs. UV-Vis spectral observation showed that the Au NPs synthesized in acidic conditions tend to generate particles with absorption maximum around 540 nm. On the other hand the NPs generated at a pH higher than 8.0 generally have broad absorption with maxima occurring beyond 600 nm. Interestingly, TEM analysis showed that the NPs generated at pH lower than 7.0 tend to be smaller and spherical in shape, whereas the particles generated at a pH beyond 7.0 tend to be non-spherical and larger in sizes or agglomeration of small particles. Also, we speculate on the mechanisms of reduction of HAuCl4 by H2O2 under different pH conditions.     

磷酸铁包覆纳米锰酸锂的改性研究

以水热法合成的纳米MnO2为模板,合成了以棒状结构为组成单元的球状LiMn2O4纳米材料,并首次用FePO4对其进行了表面包覆改性。通过XRD、SEM、TEM、EDS等表征手段对材料的结构、形貌及组成元素进行了分析,并测试了材料的电化学性能。结果表明,经过1%(质量分数)FePO4包覆的LiMn2O4材料的电化学性能得到明显改善,在1C下首次放电比容量达128.6mAh/g,循环100次后仍保持97.3mAh/g,容量保持率为75.7%;在0.1C下充电,在0.1C、0.2C、0.5C、1C、2C、3C、4C下连续放电,放电比容量分别可达131.2mAh/g、128.0mAh/g、127.1mAh/g、126.0mAh/g、117.8mAh/g、110.9mAh/g和104.6mAh/g。     

Effect of consolidating temperature on strengthening mechanism in Fe–Cu alloy from rapidly solidified powder

Abstract

The strengthening mechanism of Fe-Cu alloy manufactured from rapidly solidified powder was investigated. Powders of Fe-Cu with copper content ranging from 0.5 to 5 wt-% were prepared by high pressure water atomisation and consolidated by groove rolling at 973, 1073 or 1273 K. Analysis by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) were carried out to evaluate the resulting structures. The microstructures were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Yield stress under tensile loading and hardness after aging were measured. The copper states in consolidated specimens were determined based on the results, and the states were correlated to the mechanical properties of the specimens. At each of the consolidating temperatures, the yield stress increased with an increase in copper content. However, the strengthening mechanism differed according to the temperature. Specimens consolidated at 973 and 1073 K were strengthened by microstructure refinement,whereas precipitation hardening was the main strengthening mechanism in specimens consolidated at 1273 K.     

Microstructure of Cu-based Amorphous Composite Coatings on AZ91D Magnesium Alloy by Laser Cladding

To improve the sliding wear resistance of AZ91D magnesium alloy,Cu-based amorphous composite coatings made of Cu47Ti34Zr11Ni8 and Cu47Ti34Zr11Ni8+20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding,respectively.SEM(scanning electron microscopy),EDS(energy dispersive X-ray spectroscopy),XRD(X-ray diffraction) and TEM(transmission electron microscopy) techniques were employed to study the phases of the coatings.The results show that the coatings mainly consist of amorphous phase a...     

Supercapacitors based on electrochemically deposited polypyrrole nanobricks

Simple and inexpensive electrodeposition method for the synthesis of polypyrrole (PPy) nanobricks has been reported. These PPy nanobricks are characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polypyrrole nanobricks exhibit amorphous nature as confirmed from XRD study. Based on SEM and TEM analysis, the formation of the spherical bunches of PPy nanobricks with average size of about 20–30 nm are inferred. The electrochemical performance of PPy electrode was evaluated by cyclic voltammetry (CV) and galvanostatic charge–discharge techniques. A high specific capacitance of 476 F·g^?1 was obtained within the potential range of ? 0.4 to 0.6 V in 0.5 M H₂SO₄ solution. Moreover, PPy electrode exhibited high discharge/charge efficiency of 89%.     

多孔球形Li2MnSiO4/C正极材料的制备及电化学性能

采用湿法球磨-喷雾干燥法制备了多孔球形锂离子电池Li2MnSiO4/C复合正极材料。X射线衍射(XRD)表明合成的Li2MnSiO4具有正交结构,属于Pmn21空间群。扫描电镜(SEM)和透射电镜(TEM)显示粉体复合材料为直径10μm左右的球形团簇,由100nm左右的颗粒堆积而成,颗粒表面包覆1层大约3nm的碳层。电化学测试表明,在0.05和0.5C倍率下,Li2MnSiO4/C样品的首次放电容量分别为153和110mAh/g,50次循环后容量分别保持80%和66%。     

Characterization of silver nanoparticles synthesized on titanium dioxide fine particles

Silver nanoparticles with a narrow size distribution were synthesized over the surface of two different commercial TiO(2) particles using a simple aqueous reduction method. The reducing agent used was NaBH(4); different molar ratios TiO(2):Ag were also used. The nanocomposites thus prepared were characterized using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), dynamic light scattering (DLS) and UV-visible (UV-vis) absorption spectroscopy; the antibacterial activity was assessed using the standard microdilution method, determining the minimum inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards. From the microscopy studies (TEM and STEM) we observed that the silver nanoparticles are homogeneously distributed over the surface of TiO(2) particles and that the TiO(2):Ag molar ratio plays an important role. We used three different TiO(2)Ag molar ratios and the size of the silver nanoparticles is 10, 20 and 80?nm, respectively. It was found that the antibacterial activity of the nanocomposites increases considerably comparing with separated silver nanoparticles and TiO(2) particles.     

Microstructure of AA2024-SiC nanostructured metal matrix composites

Nanostructured metal matrix composites (NMMCs) in large-dimension billets were fabricated by hot isostatic pressing (HIPing) of cryomilled powders consisting of AA2024 alloy reinforced by 25 wt.% SiC particles. Microstructure of the bulk nanostructured composites and cryomilled powders was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In addition, mechanical properties of the bulk nanocomposites were also addressed.     

Solvothermal synthesis of carbon nanostructure and its influence on thermal stability of poly styrene

Carbon nanostructures were synthesized via a novel solvothermal reaction between ferrocene and sulfur. Carbon nanostructures were then added to poly styrene (PS) matrix. The thermal stability behavior of PS filled with carbon nanostructures were investigated by thermogravimetric analysis (TGA). Nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, energy-dispersive X-ray (EDS) analysis and atomic force microscopy (AFM). The flame retardancy behavior of PS–carbon was studied by UL-94 analysis.     

Influences of Process Parameters on MRR Improvement in Simple and Powder-Mixed EDM of AA6061/10%SiC Composite

In the present work, aluminum alloy 6061/10%SiC composite is machined using numerical controlled Z-axis (ZNC) electrical discharge machining (EDM) process. Improvement in material removal rate (MRR) is explored using tungsten powder suspended dielectric fluid in EDM process (powder-mixed electrical discharge machining (PMEDM)). Peak current, pulse on time, pulse off time, and gap voltage are studied as process parameters. Mathematical relation between process parameters and MRR is established on basis of response surface methodology. The results obtained are further compared with MRR achieved from machining using simple EDM. The existence of tungsten particles in kerosene resulted in 48.43% improvement in MRR. The influence of tungsten powder-mixed dielectric fluid on machined surface is analyzed using scanning electron microscope and energy dispersive spectroscopy (EDS). The results revealed improvement in surface finish and reduction in recast layer thickness with PMEDM. EDS analysis reported presence of tungsten and carbon in recast layer deposited on machined surface.     

Oxidized iron nanoparticles obtained by high-power plasma cutting

A high-power industrial plasma cutting equipment was applied to carve a SAE 1010 carbon steel. The usually discarded cut material was observed by scanning electron microscopy (SEM) showing that hollow and entire microspheroidal particles were produced. The analysis with X-ray diffraction (XRD) evidenced that the composition of microparticles was FeO, Fe₂O₃ and Fe₃O₄. By transmission electron microscopy (TEM) it was found that spherical nanoparticles in the range of 2 to 150 nm in diameter were formed.     

The study on the time dependency and the stability of cobalt sulphide nanoparticles under an electron beam

We report on the synthesis and characterization of cobalt sulphide (CoS(1.097)) nanoparticles using a cobalt tetramethylthiuram disulphide complex as a single-source precursor. To study the effect of reaction time on the optical and morphological properties of the synthesized nanoparticles, aliquots from the reaction mixture were collected after different intervals of time. The absorption spectra were time dependent, with the 5 min aliquot being the most blue-shifted from bulk and the subsequent samples showing a slight shift towards the bulk. Photoluminescence of the nanoparticles showed a single emission wavelength of 341 nm, however, the peak intensity of nanoparticles decreased with reaction time. The morphology of the synthesized nanoparticles was investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution TEM (HR-TEM). Results from the SEM images showed the formation of spherical CoS(1.097) nanoparticles and the size of the observed nanoparticles increase with increasing reaction time. However, the TEM results showed a change in the morphology of the particles from spherical to wire-like. The change in morphology was thought to be induced by the high voltage electron beam and this was supported by the HR-TEM and optical results.     

八面体形状的重钼酸钠纳米晶的制备及生长机制

采用热蒸发方法,以红外烧结炉为制备仪器,在玻璃衬底上制备了空心的八面体纳米晶。利用扫描电子显微镜、X射线衍射谱、透射电子显微镜及选区电子衍射分析产物的形貌、尺寸、成分及结构,并对纳米晶的形成机理进行了探讨分析。     

Performance evaluation of Al2O3 nano powder mixed dielectric for electric discharge machining of Inconel 825

Electrical discharge machining (EDM) process is popular for machining conductive and difficult-to-cut materials, but low material removal rate (MRR) and poor surface quality are major limitations of the process. These limitations can be overcome by adding the suitable powder in the dielectric. The powder particles influence electric field intensity during the EDM process which in turn improve its performance. The size (micro to nano) and properties of the mixed powder also influence the machining efficiency. In this regard, the objective of the present work is to study the performance of EDM process for machining Inconel 825 alloy by mixing Al₂O₃ nanopowder in deionized water. The experimental investigation revealed that maximum MRR of 47?mg/min and minimum SR of 1.487?µm, which are 44 and 51% higher in comparison to conventional EDM process, respectively, can be achieved by setting optimal combinations of process parameters. To analyze these observed process behavior, pulse-train data of the spark gap were acquired. The discharge waveform identifies the less arcing phenomenon in the modified EDM process compared to conventional EDM. Further, surface-topography of the machined surface was critically examined by capturing field emission scanning electron microscopy and atomic force microscopy images.     

PEI-conjugated AuNPs as a sensing platform for arsenic (AS-III)

We have developed a simple method for synthesis of spherical gold nanoparticles (AuNPs) with enhanced surface properties. The polyethyleneimine (PEI) has good potential to minimise the size of the precursor. The UV–vis spectra of synthesised AuNPs with reducing agents (PEI) have been characterised with a peak at 530?nm. The size and shape measurement of AuNPs was confirmed by transmission electron microscopy (TEM) which shows that the mean diameter is 3.9?nm. The optimal concentration of reducing agents was found to be 1% for synthesis of AuNPs. PEI-conjugated AuNP shows binding with arsenic III (0.1?ppm) as confirmed by scanning electron microscope (SEM)/energy dispersive X-rays mapping. TEM revealed the particle shape and size. Zeta potential, zeta deviation, effective particle size, Z-average diameter, polydispersity index and electrophoretic mobility have been observed in order to understand the stability of AuNPs. The image of SEM confirmed that As (III) particles were eventually distributed in PEI-conjugated AuNPs matrix. Further, this study demonstrated that PEI-conjugated AuNPs is a sensing platform of As (III).     

Synthesis and characterization of nanocrystalline silver coating of fly ash cenosphere particles by electroless process

Electroless nanocrystalline Ag coating of fly ash cenosphere particles utilizing a Sn-Pd catalyst system is demonstrated in this article. The deposition of pure metallic nanocrystalline Ag on the fly ash cenosphere particle surface is confirmed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analysis. Under the described conditions of electroless coating, average nanocrystalline Ag-coating thickness is observed to be approximately 220 nm, using a focused ion beam technique, which is less than that observed by transmission electron microscopy (TEM) (260-360 nm). TEM observation further reveals that the Ag-coating is made up of 50 nm Ag nanocrystallites, which is comparable with the size of approximately 37 nm obtained from the XRD data. The mechanism of the electroless Ag-coating process is discussed. Ag-coated fly ash particles find applications in manufacturing conducting polymers for electromagnetic interference shielding applications.     

Biogenic silver embedded magnesium oxide nanoparticles induce the cytotoxicity in human prostate cancer cells

This work reports the synthesis, characterization, and cytotoxicity of biogenic magnesium oxide nanoparticles (MgONPs) and nanosilver embedded magnesium oxide nanoparticles (Ag-MgONPs). The formation of nanoparticles (NPs) was confirmed by the indications of color changes and precipitations. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) pattern studies showed the agglomeration colloids, porous, spherical, needle-shaped and crystal nature of MgONPs, whereas, the Ag-MgONPs was hexagonal, and spherical structured nanocrystals. Energy-dispersive X-ray fluorescence spectrometry (EDS) study indicated the existence of Ag, Mg, and O in NPs complex. The particle size analysis (PSA) revealed the mean size of 15.09?nm for Ag-MgONPs and 13.68?nm for MgONPs. Fourier transform infrared spectroscopy (FTIR) showed the peaks corresponding to amide, carboxylic acids, aromatics, alkene and esters from mycelial cell-free extract (MCFE). The absorbed and lattices oxygen of MgO was probably assigned in the formation of Ag-MgONPs as indicated by X-ray photoelectron spectroscopy (XPS). Cytotoxicity assay showed the Ag-MgONPs was stronger in inducing the prostate cancer (PC-3) cell death than the MgONPs. This work concluded that Ag-MgONPs could be potential therapeutics for cancer therapy.