Grain Size Of Powder Research Articles

Study of Ultimate Tensile Strength of Borosilicate Reinforced Metal Matrix Composite

Application of composite materials are increasing remarkably because of its much advantage compared to base matrix alloys properties like reduced weight, increasing strength, increasing wear resistance capacity etc. Reinforcement particles play a very important role for preparing metal matrix composite and ultimately improve its properties. In the present experiment, Al6063 designated aluminium alloy is used as matrix material and borosilicate glass powder is used as reinforcement. Specimens are prepared by stir casting method. Borosilicate glass is collected from scientific laboratory scrap to support disposal as well as recycle of the waste glass materials. In order to reduce the experimental run, the design of experiment is incorporated as per Taguchi’s L9 orthogonal array. It is observed that glass reinforcement in Al6063 aluminium alloy is compatible to form metal matrix composite. Secondly, ultimate tensile strength of the composite increases in selected combination of grain size and weight ratio of the borosilicate glass powder to the metal matrix.

Top-Down Reactive Approach for the Synthesis of Disordered ZrN Nanocrystalline Bulk Material from Solid Waste.

Transition metal nitrides possess superior mechanical, physical, and chemical properties that make them desirable materials for a broad range of applications. A prime example is zirconium nitride (ZrN), which can be obtained through different fabrication methods that require the applications of high temperature and pressure. The present work reports an interesting procedure for synthesizing disordered face centered cubic (fcc)-ZrN nanoparticles through the reactive ball milling (RBM) technique. One attractive point of this study is utilizing inexpensive solid-waste (SW) zirconium (Zr) rods as feedstock materials to fabricate ZrN nanopowders. The as-received SW Zr rods were chemically cleaned and activated, arc-melted, and then disintegrated into powders to obtain the starting Zr metal powders. The powders were charged and sealed under nitrogen gas using a pressurized milling steel vial. After 86 ks of milling, a single fcc-ZrN phase was obtained. This phase transformed into a metastable fcc-phase upon RBM for 259 ks. The disordered ZrN powders revealed good morphological characteristics of spherical shapes and ultrafine nanosize (3.5 nm). The synthetic ZrN nanopowders were consolidated through a spark plasma sintering (SPS) technique into nearly full-density (99.3% of the theoretical density for ZrN) pellets. SPS has proven to be an integral step in leading to desirable and controlled grain growth. Moreover, the sintered materials were not transformed into any other phase(s) upon consolidation at 1673 K. The results indicated that increasing the RBM time led to a significant decrease in the grain size of the ZrN powders. As a result, the microhardness of the consolidated samples was consequently improved with increasing RBM time.

A comparative study of energy harvesting performance of polymer‐piezoceramic composites fabricated with different piezoceramic constituents

Polymer-piezoceramic composites harness the flexibility of polymer and piezoelectric properties of ceramics to offer flexible piezoelectric materials for use in energy harvesting applications. Although, there is a general temptation to use piezoceramics which exhibits high piezoelectric coefficient (d33) in the fabrication of such composites, there are limitations posed by the processing conditions of the composite which eventually determines their overall performance. In the present work we have explored this aspect in detail. We fabricated composites with polyvinylidene fluoride (PVDF) as the polymer and three different piezoceramic powders namely BaTiO3 (BT), Ba(Ti0.97Sn0.03)O3 (BTS) and Sm-doped Pb (Mg1/3Nb2/3)O3-PbTiO3(Sm-PMN-PT). Our focus here is to understand the role of grain size of the ceramic powders in determining the dielectric, piezoelectric, and energy harvesting performance of the composites. To broaden the perspective, the results are compared with another analogous composite 0.59PbTiO3-0.41Bi(Zr0.5Ni0.5)O3 (PT-BNZ)-PVDF reported before. We found that, although, the dense ceramic specimen of Sm-PMN-PT exhibits exceptionally large d33, the composite with PT-BNZ exhibited the best piezoelectric and energy harvesting performance. BT, BTS and Sm-PMN-PT composites showed maximum surface power density of 6.24, 12.81 and 23.18 μW/cm2, respectively, and volume power density of 416.18, 854.1 and 1104 μW/cm3, respectively. Whereas surface power density and volume power density of PT-BNZ was 101.80 μW/cm2 and 5088.80 μW/cm3 respectively. We have also attempted to establish a correspondence between the piezoelectric response, energy harvesting performance and the poling induced domain reorientation/structural changes in the ceramic grains of the composites.

Photo and radio-luminescence properties of LuAG:Eu3+ nano crystalline powder

Nano crystalline powders of LuAG:Eu with different grain sizes were prepared by Pechini and co-precipitation methods. XRD and FTIR analyses were done. The XRD measurement confirmed the cubic structure of nano crystalline powders. The morphology and grain size of nano crystalline powders were confirmed by TEM analysis. The minimum and maximum of crystallite sizes were obtained 17 and 46 nm by the Rietveld method. The results of UV–Visible absorption analysis showed that the energy absorption value was increased for nano crystalline powder prepared at 900-1200 °C by Pichini and co-precipitation methods. The emission, excitation and quantum efficiency were investigated. The overall shape of emission and excitation spectra was not changed with increasing of nano crystalline powder size but the emission intensities were increased. Decay time was decreased with increasing the size of nano crystalline powders. The X-ray luminescence results were examined at room temperature for different currents and a constant voltage. The luminescence intensity was increased linearly with increasing the X-ray current. TL glow curves of nano crystalline powder exposed to X-rays for 2, 4 and 6 min showed two main peaks around 400 and 600 K. A glow curve deconvolution and origin software were used to calculate TL kinetic parameters.

Interaction between a falling sphere and the structure of a non-Newtonian yield-stress fluid

We present an experimental study using mixtures of aqueous superabsorbent polymers (SAP) where we systematically investigate the influence of the size of grains that make up the fluid structure on the mixture effective rheology and its domain of validity. In water, SAP powder grains can swell up to 200 times and form gel grains, dg, whose sizes (typically between 1 and 8 mm) can be controlled by choosing the size of the initial powder grains. The rheology of this mixture (water and touching grains) combines viscous, elastic and plastic aspects. Here, they are characterized using the free-fall of spheres of different densities and diameters (ds). The latter were varied between 3 and 30 mm, therefore providing a range where they become comparable to the fluid gel grains.We observe five different regimes of motion: (1) A linear regime where the sphere has a rapid and straight fall and reaches a constant terminal velocity. (2) An irregular regime where the sphere’s velocity varies around a constant value. (3) An intermittent regime where periods of no-motion and periods of irregular falls follow one another. (4) A slow fall regime where the sphere’s speed progressively decreases in a logarithmic way. (5) A no-motion regime when spheres are not heavy enough to overcome the yield stress of the mixture, or are too small compared to the grain size.The sphere trajectories in regimes (1), (2) and (3) are all following a same trend which, in the framework of a Herschel–Bulkley fluid, allows to estimate the effective yield stress σY and consistency Kv of the SAP mixtures. Both σY and Kv increase with increasing gel grain size. Regimes (2) and (3) are due to the interactions between the falling sphere and individual gel grains, i.e. the fluid structure. Moreover, the critical Yield number (Yc, which compares σY to the stress induced by the sphere’s net weight in the fluid) above which there is no motion decreases as ds∕dg becomes smaller than 2. So although the characteristic size of the fluid structure influences the magnitude of its rheological properties, the use of a Herschel–Bulkley rheology to describe the trajectories of the spheres breaks down only when the sphere diameter becomes very close to the SAP structure size.

Synthesis of biodegradable plastic from corn starch and corn husk filler with addition of glycerol as plasticizer and variation of chitosan composition

Cellulose, contained in corn husk, is one of natural polymer that can be used as filler for bioplastics. Corn starch flour (maize) as matrix and corn husk powder in different grain size as filler is then synthesized with chitosan and glycerol. The resulting bioplastics is a thin film with muddy-brown color. Alternating the corn husk powder grain size from 150 mesh to 200 mesh modifies the physical characteristics, especially mechanical properties. The most optimal bioplastics were obtained with 200 mesh grain size of corn husk powder and 0.04 % chitosan composition with tensile strength of 286.31 N/cm2, elongation of 10.19 %, Young modulus of 28.11 N/cm2 and tear resistance of 705.61 mN. There are changes in molecular structure of some functional groups as compared to the elements. Bioplastics were degraded 30–35 % for 21 days in soil, started moldy after 10 days in open air and endured for one hour in temperature 100 °C.

Ultrafine-grained Al-Mg-Zr alloy processed by shear-assisted extrusion with high thermal stability

Shear-assisted processing and extrusion (ShAPE) is used to consolidate Al-4.2Mg-1.6Zr-0.25Si-0.1Fe (wt.%) powders. The extruded alloy exhibits: (i) near-zero porosity; (ii) an attractive combination of tensile yield strength (~220 MPa), ultimate strength (330 MPa) and elongation (>20%); and (iii) excellent thermal stability at 400 °C. The ultra-fine grain size in the gas-atomized powders – created and stabilized by primary L12-Al3Zr submicron precipitates - is maintained after consolidation and subsequent exposure at 400 °C, contributing twice as much to strength as Mg in solid-solution. Electron microscopy reveals the microstructure of the L12-Al3Zr precipitates, and other precipitates (Mg2Si and Al3Fe) and dispersoids (oxides).

Effect of the environment on the morphology of Ni powder during high-energy ball milling

In high energy ball milling process, the milling environment plays an important role on tailoring the microstructure and properties of metal powder. The refining behavior regarding ball milling of Ni powder in different atmospheres (air and argon gas) is investigated in this study. We find that the Ni powder is coarsened (from 28.4 ± 0.5 μm to 38.5 ± 13.9 μm) after milling in argon gas for 16 h. By contrast, its grain size and particle size are smaller than 20 nm and 2 μm respectively after milling in air. By analyzing the morphology and the chemical composition of the milled powders, the effect of different environments, including ambient air, dry air, and ambient air with ethanol, on ball milling process was investigated. The adsorption of oxygen is believed to play a key role in the refinement of Ni powder. The results provide a new insight into the environmental effect during ball milling, and lead to a new way for refining grain size and particle size of FCC metal powders in high energy ball milling.

The Effect of Charge Grit on Impact Strength and Damping Characteristics of BN–Al Composite Materials

Abstract—The dependence of the impact strength and damping characteristics of сBN–Al composite materials on the specific surface (grain size) of cubic boron nitride powders has been investigated. The correlation between the damping characteristics of the composite material and its phase composition has been established. The dependence of the phase composition of the material on the specific surface of the powdered cBN component has been demonstrated. Composite materials with a biphasic structure and the highest density and hardness possible for this structure had the maximal impact strength.

Preparation of Nanocrystalline Fe<sub>2</sub>O<sub>3</sub> Powder by Cryomilling with Liquid Nitrogen and its Magnetic Property

Rapid preparation of nanocrystalline γ-Fe2O3 powder with superparamagnetism was realized by cryomilling commercial Fe2O3 powder using liquid nitrogen. The effects of milling temperature and duration on the grain size, phase and microstructure of the nanocrystalline Fe2O3 powder were analyzed. Magnetic property of the nanocrystalline γ-Fe2O3 powder was also tested by magnetometer at room temperature. The results demonstrate that nanocrystalline γ-Fe2O3 powder with single phase can be prepared rapidly by cryomilling with liquid nitrogen. The mean particle size of γ-Fe2O3 powder can be reduced from 300 nm to 13 nm by cryomilling at −130 °C within 3 hours. The nanocrystalline γ-Fe2O3 powder shows superparamagnetism at room temperature.

Effect of Additive Glycerol on Piezoelectric Properties of Modified Sol-Gel (Ba<sub>0.85</sub>Ca<sub>0.15</sub>)(Ti<sub>0.9</sub>Zr<sub>0.1</sub>)O<sub>3 </sub>Ceramics

Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZ) ceramics, one of the lead-free pizoelectric materials, were focused due to the environmental concern against lead. A modified BCTZ powder sol-gel fabrication process was experimentally introduced with the addition of glycerol, in order to provide an effective approach to optimize the piezoelectric response of BCTZ ceramics. The results showed that the piezoelectric properties enhanced in terms of the piezoelectric coefficient of d33, 510 pC/N and the electromechanical coupling coefficient of kp, 0.501. The enhancement in electrical properties, such as dielectric, ferroelectric and piezoelectric, could be related to the homogenous microstructure and larger grain size of BCTZ ceramic powders after the introduction of glycerol during the modified sol-gel strategy.

Comparison of Hot-deformation Behavior and Magnetic Properties between Nd-Fe-B HDDR and MQU-F Powder

Hot-deformation behavior of Nd-Fe-B HDDR powder was investigated in order to understand the difference in texturing mechanism of HDDR and MQU-F powder during hot-deformation. The composition of the HDDR powder was the same as that of MQU-F powder. However, the grain size of HDDR powder (~300 nm) was eight times larger than that of MQU-F powder (~40 nm). After being subjected to hot-pressing at 700 °C under 200 MPa in a vacuum, the grains of the magnets made from HDDR powder and MQU-F powder have globular and platelet shapes, respectively. The remanence was 12.2 kG after die-upsetting process at the strain of 0.5. And it increased up to 13 kG at the strain of 1.4 although the grains still maintained globular-like shapes. The remanence of 13 kG was almost the same as that obtained the magnet from MQU-F powder at the same deformation condition. These results indicate that the hot-deformation behavior is quite different between HDDR and MQU-F powder.

Effect of grain size of the precursor powder on the plastic deformation and the current carrying capacity of Bi-2212 wires

In the past two years, the record of current carrying capacity of Bi2Sr2CaCu2Ox (Bi-2212) wire has been broken many times by using improved powder, which shows that the precursor powder plays an important role in the preparation of Bi-2212 wire. In order to improve the quality of Bi-2212 precursor powder, this paper explored the effect of the grain size of the precursor powder on the uniformity of the plastic deformation of the wire, the grain alignment of the superconducting cores and the current carrying capacity of the wire. It was found that the plate-like large-grain precursor powder had the obvious bridging effect, which effectively prevented the Ag sheath of single-core wires from expanding freely inward, so that the single-core Bi-2212 wires with smooth Ag/oxide interface could be obtained. In addition, the precursor powder with the large plate-like grain size also had excellent slippage performance, resulting in the improving of the plastic deformation properties of multi-core wires. It could reduce the core breakage rate of multi-core Bi-2212 wire, and further improved the smoothness of Ag/oxide interface and the grain alignment of Bi-2212 cores. Under the combined action of the above two aspects, multi-core Bi-2212 wire with the uniform cores, orderly superconducting grains and low core breakage rate were prepared by large-grain precursor powder. The current carrying capacity of the final Bi-2212 wire was increased by more than 15%.

Electrical properties of Ce0.9Gd0.1O2−δ ceramics with different grain size uniformity

In this work, the effect of grain size and uniformity of the precursor powder on the electrical property of ceria based electrolytes was investigated. Gadolinia-doped ceria (GDC) samples were treated under different calcination temperatures (600 °C and 1300 °C), where their grain size and uniformity were adjusted by varying the ratio of 1300 °C powder in precursors. The phase composition, morphology and conductivities of mixed GDC samples were characterized by x-ray diffraction (XRD), scanning electron spectroscopy (SEM) and AC impedance, respectively. XRD results revealed that all GDC samples are single cubic fluorite-type structures. As the content of 1300 °C powder increased, the grain boundary conductivity first dropped markedly to the minimum at the ratio x = 5% and then basically unchanged, whereas no significant change was observed in bulk conductivity. Our study demonstrated that the ratio of the higher calcination temperature powder in the mixed precursor powder gave rise to the variation of grain size uniformity and the electrical properties of GDC samples.

Influence of Nickel Powders on Corrosion Resistance of Cold Sprayed Coatings on Al7075 Substrate

The influence of the size and structure of nickel powder grains on the corrosion resistance of nickel coatings on an Al7075 substrate in an acidic chloride solution was investigated. The Ni coating was produced by the cold spraying (CS) method. The surface and microstructure of specimens were observed by a scanning electron microscope (SEM). The corrosion test of the materials was carried out by using the electrochemical method. It has been found that the size of Ni powders has a significant effect on the corrosion resistance of nickel coatings. The porosity of nickel coatings on the Al7075 alloy increases with the increasing size of nickel powders. The corrosion rate of nickel coatings in the chloride environment decreases as the diameter of the nickel powders decreases. On the other hand, the highest corrosion resistance of nickel coatings was obtained using the Ni powders of the irregular spherical or dendritic structure. Moreover, the large particles of nickel powder cause strong residual stress (compared to small grains) in the depth of the nickel coatings.

Effect of ball milling treatment on the microstructures and properties of Cr2AlC powders and hot pressed bulk ceramics

Ball milling was used on synthesized Cr2AlC powders, and dense Cr2AlC bulk ceramics with almost pure phase were fabricated by hot pressing these ball milled Cr2AlC powders at 1300 °C for 2 h under 30 MPa. The phase compositions and the microstructures of powders and bulk ceramics were characterized. The mechanical properties and dislocation analysis of bulk ceramics were also investigated. Our results indicated that the grain size of powders became uniform and smaller after ball milling, which was also inherited in the bulk ceramics. Moreover, the mechanical properties of hot pressed Cr2AlC ceramics, including flexural strength, fracture toughness, and Vickers hardness, significantly increased by using ball milled powders treated at speed 200 rpm. The organization of hexagonal dislocation networks during hot pressing and reduction of grain size both had a positive effect on improving mechanical properties.

Industrial mass production of nanocrystalline Ce0.9Gd0.1O1.95 via a solid–liquid method using gluconic acid

Abstract To achieve industrial mass production, a simple and efficient solid–liquid method (SLM) was applied to synthesize nanocrystalline gadolinium-doped ceria (Ce 0.9 Gd 0.1 O 1.95 , GDC), using gluconic acid (GA) as a complexing agent and polyethylene glycol (PEG) as a surfactant. Unlike traditional wet-chemical methods, this method of forming metal-complex compounds does not involve heating processes, which are known to pose risks of fire and explosion. The substitution of GA for traditional citric acid (CA) reduces the corrosion of stainless-steel equipment. The effects of the varying amounts of GA and polymerization degrees of PEG were discussed. The physical properties of the precursors were characterized using thermogravimetry/differential thermal analysis (TG/DTA). The crystallinity and grain size of the GDC powders were analysed using X-ray diffractometry (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), and particle-size distribution (PSD) analyses. The results show that the GDC powder with additions of 20 wt% GA and 1 wt% PEG2000 that was sintered at 800 °C has a single phase with a particle size of around 40 nm; it is also homogenous and highly pure. In addition, the ionic conductivity of the GDC pellet that was sintered at 1450 °C for 5 h is 0.046 S/cm at 750 °C. These results indicate that this novel SLM is suitable for the mass synthesis of high-performance nanocrystalline Ce 0.9 Gd 0.1 O 1.95 powders.

Laser Surface Treatment of Sintered Stainless Steels for Wear Resistance Enhancement

In the present study, sintered austenitic stainless steel type 316L was laser surface alloyed with Inconel 625 powder by the fibre optic laser. The Inconel 625 spheroidal powder of grain size 60-150 μm was introduced by the coaxial feeding head directly to the liquid metal, during laser surface alloying. The process parameters were selected to melt and fully dissolve alloying powder into the alloyed surface. As a result of laser alloying, the porosity of sintered stainless steel was eliminated, a uniform distribution of nickel and molybdenum in the entire alloyed zone was obtained. The alloyed surface shows fully austenitic microstructure of 17%Cr, 18%Ni, 3%Mo. The superficial hardness, microhardness and surface wear resistance were significantly improved in respect to an untreated substrate material. The presented technique of laser surface alloying can be easily applied for sintered austenitic stainless steel components where selected component surfaces require an improved surface performance.

The Study on Sintering Capabilities of High Purity Metal Vanadium Powder

High purity metal vanadium powder was milled by high energy ball milling, and the grain size and morphology of vanadium powder was observed by electron probe, and the stress-strain curve was measured by CMT5305 universal testing machine for research of the mechanical property. In order to investigate the effect of sintering process on the property of product, the vanadium powder was sintered by the hot pressing sintering process and the cold isostatic pressing with vacuum sintering process respectively. The experimental results show that for the cold isostatic pressing with vacuum sintering process, the density of raw compact increases with the increase of pressing pressure. When the pressure increases to 280 MPa, the density and relative density of raw compact are 3.99 g·cm-3 and 66.94% respectively, the density and relative density of product after sintering are 5.28 g·cm-3 and 88.59% respectively. With the pressure increasing from 80 MPa to 200 MPa, the compressive strength increases significantly from 0.4 MPa to 6.0 MPa, the pressure increases to 280 MPa, the compressive strength slowly increases to 7.4 MPa. For the hot pressing sintering process, the relative density of product is higher than that of cold isostatic pressing with vacuum sintering process, and the density and relative density reach to 5.51 g·cm-3 and 92.91% respectively under 280 MPa pressure.

Microstructure and Mechanical Properties of Nanocrystalline Al-Zn-Mg-Cu Alloy Prepared by Mechanical Alloying and Spark Plasma Sintering.

In this study, Al, Zn, Mg and Cu elemental metal powders were chosen as the raw powders. The nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was prepared by mechanical alloying and spark plasma sintering. The effect of milling time on the morphology and crystal structure was investigated, as well as the microstructure and mechanical properties of the sintered samples. The results show that Zn, Mg and Cu alloy elements gradually dissolved in α-Al with the extension of ball milling time. The morphology of the ball-milled Al powder exhibited flaking, crushing and welding. When the ball milling time was 30 h, the powder particle size was 2–5 μm. The α-Al grain size was 23.2 nm. The lattice distortion was 0.156% causing by the solid solution of the metal atoms. The grain size of ball-milled powder grew during the spark plasma sintering process. The grain size of α-Al increased from 23.2 nm in the powder to 53.5 nm in the sintered sample during the sintering process after 30 h of ball milling. At the same time, the bulk alloy precipitated micron-sized Al2Cu and nano-sized MgZn2 in the α-Al crystal. With the extension of ball milling time, the compression strength, yield strength and Vickers hardness of spark plasma sintering (SPS) samples increased, while the engineering strain decreased. The compression strength, engineering strain and Vickers hardness of sintered samples prepared by 30 h milled powder were ~908 MPa, ~8.1% and ~235 HV, respectively. The high strength of the nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was attributed to fine-grained strengthening, dislocation strengthening and Orowan strengthening due to the precipitated second phase particles.