Volume Fraction Of Powder Research Articles

Effect of Laser Shock Peening on Fatigue Stress Concentration of Polyester Reinforced by Al-Micro Powder Composites

Laser shock peening is a widely common process for materials treatment and typically used for fatigue strength enhancement especially for metals. In this paper, its effect on polymeric composite materials studied experimentally. Unsaturated polyester was used as a matrix in order to composites preparation and Aluminum powder as fillers. A Hand lay-up technique has been used for composites making. Composites with three volume fractions of Aluminum powder were prepared (2.5%, 5%, and 7.5%). Fatigue specimens as a standard and with (1mm) semi-circular notch are prepared for testing. The fatigue test was performed at room temperature and stress ratio (R=-1). Laser shock peening with two levels of energy have been applied (1Joule, and 2Joule). The results showed an increase in the endurance strength of the notch for 7.5% volume fraction especially at 1J laser energy by about 26.7056% compared with the un-treatment notched state, which in turn reduced the fatigue stress concentration by about 21.0508% compared with standard fatigue stress concentration. On the other hand, the presence of notch effect on endurance strength was increased after laser treatment of composites with 2.5% volume fraction and the reduced was by about 39.698% at 2J laser energy.

Comparison in characteristic and atomization behavior of metallic powders produced by plasma rotating electrode process

In this study, characteristics of powder for additive manufacturing from three typical alloys Ti-6Al-4V, 316-steel and Co-29Cr-6Mo produced by plasma rotating electrode process (PREP) at 4 rotation speeds are compared in details. The results indicate that for a given rotation speed, alloy with higher ratio of surface tension and density (γρ) is capable of producing powder with larger particle size and narrower particle size distribution δ (D90-D10). The formation mechanism of the satellite and irregular particle produced by PREP are discussed in detail. The satellite powder is confirmed to be formed by collisions between two particles, and the volume fraction of the satellite powder is lower in the alloy with higher (γρ) and high thermal conductivity. The formation of irregular powder is possibly related to the peeling of liquid film, which is strongly dependent on the thermal conductivity of alloy.

Enhanced thermal conductivity of diamond/copper composite fabricated through doping with rare-earth oxide Sc2O3

Diamond/copper composite has been considered as one of the next generation thermal management materials. Interfacial modification is an essential means of ameliorating interface wettability and bonding of diamond/copper composite for improving its thermal conductivity. In the present work, Diamond/copper composite was manufactured by using spark plasma sintering (SPS) technology with 60% volume fraction of diamond mixed with 40% volume fraction of copper power, chromium powder (0.7 wt%) and scandium oxide powder (0.21 wt%). A series of material analysis methods were used to characterize the microstructure, interfacial layer, phase compositions and distributions of Diamond/copper composite. The total and partial electron density of states (DOS) for Diamond-Cr-Sc2O3 interfacial model was investigated by means of first-principles calculations from CASTEP modules. The results showed Sc2O3 made a 5–20 nm well-arranged and uniformly distributed interfacial chromium carbide layer in the interface region, which played a critical role in increasing the amount of reactive interfacial bonding and decreasing defect. The addition of Sc2O3 brought the increasing number of heat transfer carriers at the interface and made the interface energy system more stable. The obtained diamond/copper composite exhibited that the wettability between diamond particles and copper was effectively improved. The thermal conductivity of diamond/copper is 872 W/(m·K) and the possible reasons for doping rare-earths Sc2O3 to improve the thermal conductivity were discussed.

Analysis and Experimental Study on Rheological Performances of Magnetorheological Fluids

Silicone-based Magnetorheological Fluids (MRFs) were prepared with 10% volume fraction of carbonyl iron powder. Rheometer Physica MCR 301 was used to test the rheological performances of MRFs.The experimental results show Bingham model and Casson model could well describe rheological behaviors of MRFs. Shear stress of MRFs increases but apparent viscosity is significantly decreased and tends to be stable with the increase of shear rate in the presence of magnetic field. The results also show that MRFs are shear thinning fluids. The dependence of shear stress on magnetic field was tested under the condition of constant shear rate and increasing magnetic field, shear stress of MRFs increases remarkably.

The effect of powder addition manner and volume fraction of reinforcement on tribological behavior of Al7075/B4C surface composite produced by friction stir processing

Al7075/B4C surface composites were fabricated by friction stir processing using four passes. The B4C powders were added into the prepared grooves with 1 and 2 mm width at the surface of Al7075 alloy in two different manners. In the first one, the B4C powders were added prior to the four consecutive passes in one stage. In the second manner, the powders were added in two stages, prior to the first pass and following the second one. The microstructural evaluations showed that the increase in the volume fraction of reinforcement significantly reduced the matrix grain size. Meanwhile, the reinforcement had a more homogeneous and uniform distribution in the samples processed through four consecutive passes. The maximum hardness and wear resistance was achieved in the one-stage powder-added samples, containing higher volume fraction of the reinforcement. A direct relationship was observed between the wear resistance and the composite layer hardness. The wear mechanism in the Al7075 substrate and the non-reinforced friction stir processed sample was the delamination of unstable aluminum oxide tribolayer. However, in the composite samples, a mechanically mixed layer, containing aluminum, chromium, and iron mixed oxides was formed along with B4C on the worn surface. In the two-stage powder-added samples, containing lower amounts of reinforcement, the detachment of mechanically mixed layer resulted in three-body abrasive wear condition and high friction coefficient. However, the most stable mechanically mixed layer was formed on the surface of the one-stage powder-added sample containing higher amounts of B4C.

Analytical modeling of part porosity in metal additive manufacturing

Porosity is a frequently observed defect in metal additive manufacturing due to the large thermal gradients caused by the repeated rapid melting and solidification. This work presents a physics-based model to predict the part porosity in powder bed metal additive manufacturing (PBMAM) per given process parameters, materials properties, powder size distribution. The molten pool dimensions were first calculated by a closed-form temperature solution considering the laser heat input and part boundary heat loss. The porosity evolution was calculated by subtracting the volume fraction of the preprocessed powder bed void from the postprocessed porosity. The volume fractions of powder and void in packed powder bed were calculated by advancing front approach (AFA) and image analysis considering powder size variation and statistical distribution. The porosity model was developed based on the correlation between molten pool dimensions and porosity evolution using regression analysis. Experimental validation of porosity values under different process conditions was included in PBMAM of Ti6Al4V. A close agreement was observed upon validation. Different from the previous statistical model, the presented model was developed based on the physical relationship between thermal behaviors porosity formation, which leads to an improved prediction accuracy with a small number of calibration data. Moreover, the short computational time of the closed-form temperature solution allows a fast porosity prediction for various processing window.

Modelling the hydromechanical behaviour of expansive granular mixtures upon hydration

Bentonite pellet-powder mixtures are candidate sealing materials in radioactive waste disposal concepts. The mixture is installed in galleries in dry state as a granular material. The material is progressively hydrated by the pore water of the host rock and becomes homogeneous. Before homogenisation, the granular structure controls the material behaviour. In the present work, a modelling approach able to address particular features of pellet-powder mixtures is introduced. Two domains are considered: i) granular, and ii) homogeneous. The material behaviour before homogenisation is studied through Discrete Element Method (DEM) simulations. Constitutive laws for the granular state are proposed from DEM results. The behaviour of the homogenised material is described by a modified Barcelona Basic Model (BBM). Transition from granular to homogeneous states depends on suction and relative volume fractions of pellets and powder. Swelling pressure tests performed in the laboratory are satisfactorily simulated using this approach.

Mechanical Characterization with Morphological Analysis of Dry Flower Waste Bio Filler Reinforced Epoxy Composite

Dry flower waste powder is incorporated in the Epoxy resin matrix to study the effect of the bio filler in Epoxy composites. Composite Specimens were prepared by using different volume fractions (0.4, 0.8, 0.12, 0.16, 0.20 v/v) of Dry flower waste bio powder in the Epoxy resin by hand layup method. Experiments were conducted to evaluate the mechanical properties such as Tensile Properties, Flexural properties and Impact strength of the epoxy composite. The results indicated that the bio filler had significant influence on the tensile and flexural modulus whereas tensile and flexural strength and impact strength of the composite are not significantly affected by the addition of the filler. Better mechanical properties were obtained at 12% v/v of Dry flower waste bio powder. Morphological properties were examined using the SEM images of tensile fractured specimen.

Dielectric and pyroelectric properties of thick and thin film relaxor-ceramic/PVDF-TrFE composites

In the present work 0–3 composites of Relaxor-Ceramic/PVDF-TRFE with different volume fractions of ceramic powder are processed using solution deposition techniques. Free standing thick films of up to 100 µm thickness were fabricated via the doctor blade method while thin films of up to 10 µm thickness were deposited on silicon wafers using spin coating.The microstructure was investigated via scanning electron microscopy. Effects of the volume fraction of the ceramic on the phase transition were studied in a wide temperature range using DSC. The dielectric properties were investigated as a function of temperature via impedance analysis. Finally low and high frequency pyroelectric properties were obtained.It is shown that homogeneous films with a homogeneous distribution of ceramic particles can be obtained using appropriate solvents for both the polymer and the powder. The DSC measurements show that with increasing powder volume fraction the phase transition temperature in general slightly decreases. The dielectric constant increases with increasing ceramic volume fraction whereby the values do not agree with those calculated based on 0–3 connectivity. Relaxation effects of the composites are also reported. Pyroelectric measurements show a good response of the composite with figure of merits comparable to that of PZT films.

Effect of Powder Shape and Size on Rheological, Thermal, and Segregation Properties of Low-Pressure Powder Injection Molding Feedstocks

Optimization of molding parameters at different filling stages requires that the characteristics of low-viscosity feedstocks must be properly known. In this study, the influence of the particle size (3, 7, and 12 μm) and powder morphology (gas- and water-atomized) was quantified using different feedstock formulations based on a 17-4 PH stainless steel powder, all combined with the same binder system. The specific heat capacity, viscosity, and segregation levels were assessed using a differential scanning calorimeter, a rotational rheometer, and a thermogravimetric analyzer, respectively. It was then shown that the feedstock prepared with the gas-atomized powder exhibits a higher specific heat capacity value when compared to a water-atomized powder (i.e., Cp varying from 0.6 to 0.3 J/g K, respectively). It was also shown that the feedstock viscosity profiles and the intensity of segregation both depend significantly on the powder shape and size used in the feedstock formulation. For short processing times (e.g., < 1 min spent in molten state), a feedstock formulated with coarse gas-atomized powder can be considered to be the best candidate for an injection process because its viscosity and segregation potential are relatively low (with a viscosity varying from 0.5 to 2 Pa s, and a volume fraction of powder close to 60 vol.%). Following this, the moldability index was used to predict that coarser water-atomized powder (i.e., 12 versus 7 μm) will not have a significant effect on the molding properties, and can be seen as a potential means of decreasing shrinkage during sintering without impacting the injection properties. For very long processing times, the magnitude of segregation remains insignificant for feedstock formulated with fine powder (i.e., a volume fraction of powder remaining close to 60 vol.%). However, this important gain (i.e., no segregation) comes with a significant increase in viscosity varying from 2 to 10 Pa s, resulting in a decrease in the molding properties.

Evaluation of hardness and impact strength of aluminium alloy (LM6)–soda–lime composite

ABSTRACT Aluminium is one of the lightweight materials which is the principal necessity in many applications worldwide and is less luxurious than other light metals such as titanium and magnesium. With the increasing requirements of strength and toughness of aluminium castings, there is a huge demand to improve the mechanical properties of available aluminium alloys. It had been noticed and scientifically proved that when reinforced with other materials, properties of aluminium alloys will get enhanced. In this research work, an investigation was performed on cast-ability, microstructure and mechanical properties (hardness and impact strength) of a composite with LM6 alloy (Al–11.6% Si) as the matrix, and varying sizes and volume fractions of glass powder as the reinforcement. In this work, Al–Si metal matrix composites with soda–lime glass powder as reinforcement were produced using stir casting technique. Composites were produced with varying percentage of glass (1.5–4.5% by weight) as reinforcing particles. Commercially, available LM6 alloy (Al–11.6% Si) was selected as the matrix material. The composite produced has superior mechanical properties and it has been observed that the mechanical properties are improving with increase in the percentage of glass powder. The best distribution of glass in the matrix was when 3% glass of 125 µm particle size was reinforced. The microstructures of the developed LM6–glass composite were studied using optical microscopy. This work was part of the feasibility study performed as part of a new product development in armoured protection equipment by Mobile Land Systems LLC, South Africa.

Thermal decomposition behavior and modeling of PMN-PZT ceramic feedstock with varying binder compositions

The thermal debinding process is one of the most crucial steps in powder injection molding because it consumes a great deal of the processing time and may introduce defects into the component. To enhance production efficiency and increase defect avoidance, debinding conditions including maximum temperature, heating rate, and holding time should be determined based on the analysis of thermal decomposition behavior. The thermal decomposition behavior of lead magnesium niobate-lead zirconate titanate (PMN-PZT) ceramic feedstock with varying binder compositions was investigated in this paper using experimental analysis and modeling. In this study, the powder volume fraction in the feedstock was fixed at 45 vol% in order to isolate the effects of binder composition on thermal decomposition behavior. Each feedstock was divided into three groups depending on the variation in the filler binder (first), the backbone binder (second), and the entire binder system (third), respectively. Thermal decomposition behaviors for the feedstocks were analyzed by thermogravimetric analysis experiments at heating rates of 2, 5, and 10 °C min−1. All of the TGA graphs showed two sigmoidal curves due to the difference in the molecular weights of the binders. The apparent activation energy for binder decomposition was calculated based on the Kissinger approach. A remarkable change in activation energy was derived from the variation in the entire binder system. Based on the acquired decomposition parameters, master decomposition curve was constructed and verified experimentally in order to provide a predictive design tool for identifying optimal debinding conditions based on the intrinsic kinetics of binder pyrolysis.

The dimensional effect of MgTiO3 ceramic filler on the microwave dielectric properties of PTFE/MgTiO3 composite with ultra-low dielectric loss

PTFE matrix loaded with different volume fractions of MgTiO3 ceramic powder with particle sizes of around 5 μm and 15 μm (abbreviated as MT-5 and MT-15, respectively) was prepared. The microstructure, microwave dielectric properties and thermal properties of the composites were studied by scanning electron microscope, vector network analyzer and thermal dilatometer. The results show that PTFE/MT-15 composite exhibits higher relative density and better dielectric properties than the PTFE/MT-5 composite, since the former with coarse particles possesses lower surface energy to weaken the particle agglomeration effect. Even at 40% filler volume fraction, the ultra-low dielectric loss of PTFE/MT-15 composite can be maintained in the order of 10− 4 at 10 GHz. Different models are used to predict the dielectric constant of the composites. Among which, the effective medium theory shows the least deviation from the experimental results. PTFE matrix filled with 40V% MT-15 ceramic powder shows excellent microwave dielectric properties: er = 5.5, tanδ = 2.7 × 10− 4 (at 10 GHz), which may be a promising material in electronic packaging field.

Numerical analysis on gas-solid mixing in ceramic dry granulation room with baffles

In order to investigate the influence of baffles on the mixing effect of particles during ceramic dry granulation process.Air-particles interaction was analyzed by euler gas-solid two phases flow model, the granulation area was simplified.The three dimensional physical model of particles mixing process was constructed, granulation room rotary motion was simulated by sliding grid method and multiple reference frame method, turbulent motion was analyzed by modified RNG discrete model. The influence of different baffles on particles mixing was investigated according to the volume fraction distribution and velocity field, changed the position of the baffle can increase the blending effect by about 22%.The results showed: when there were no baffles, wall baffles and middle baffles in the granulation room, the average volume fraction of powder was about 0.22, 0.18 and 0.26 respectively. The average speed of powder was about 0.6m/s, 0.9m/s and 0.4m/s respectively. The wall baffle made the powder have significant axial movement, the experimental data showed: when granulation room had wall baffles, the content of active particles accounted for about 73%. It is helpful to improve the understanding of gas-solid two phase flow field in ceramic drying granulation room and provide some theoretical guidance for the design and optimization of the baffle.

Effect of Hydrocolloids on Rheological Properties and Printability of Vegetable Inks for 3D Food Printing.

In food ink systems in which the particles are dispersed in a hydrocolloid matrix, the source of the particles and the particle content are the main factors affecting the printability and rheological properties of the system. In this study, different contents (10% and 30% w/w) of vegetable (broccoli, spinach, or carrot) powders were added to hydrocolloid matrices with different hydration properties, and their influence on the printability and rheological properties was investigated. At low powder contents (10%), slight differences in the printability and rheological values were observed between the different vegetable sources in all hydrocolloids. When the powder content was increased to 30%, the hydrocolloid with the lowest water hydration capacity, hydroxypropyl methylcellulose, showed the greatest differences in rheology and printability when different vegetable sources were used. Xanthan gum, with its higher water hydration capacity, inhibited the swelling of the particles, thus minimizing the increase in the rheological values at high volume fractions of powder and reducing the differences in printability between different vegetable sources. Confocal laser scanning microscopy analysis of the vegetable inks showed that xanthan gum inhibited swelling of the particles regardless of the vegetable powder source. The mixtures using xanthan gum could be smoothly extruded from the nozzle due to their low extruded hardness (2.96 ± 0.23 to 3.46 ± 0.16 kg), and the resulting objects showed high resolution without collapse over time. PRACTICAL APPLICATION: The powder-based texturization technology introduced in this study provides a standardized method of preparing food ink that can be universally applied to all food materials that can be powdered. In addition, the present invention can be applied to a 3D printing technique in which a powder and a hydrocolloid matrix are independently stored and mixed immediately before printing. This technique can minimize the inherent rheological differences between formulations with different food sources and compositions.

3D printing of NdFeB bonded magnets with SrFe12O19 addition

Rectangular, square, ring and horseshoe-shaped NdFeB bonded magnets with SrFe12O19 addition have been prepared by additive manufacturing, also known as 3D printing. The prepared NdFeB slurries with ferrite addition were deposited to form shaped parts using a 3D printer. Highly loaded pseudo-plastic printing slurries were employed to print bonded magnets with 98% of theoretical density. In the printed magnets with 20 wt.% strontium ferrite (SrFe12O19), good dimensional accuracy and surface quality were obtained with a relatively low surface roughness of ∼6 μm. In addition, good coalescence without obvious defects or pores was observed, and the ultimate tensile strength was 12 MPa. The magnetic properties of the hybrid magnets decreased with the increase of SrFe12O19 content due to a lower volume fraction of the NdFeB powder and lower magnetic performance of the SrFe12O19 powder. Nevertheless, the coercivity temperature coefficient β increased from −0.4%/°C to −0.2%/°C with the SrFe12O19 content increase to 20 wt.%, indicating better thermal stability of hybrid magnets. The proposed method of fabricating NdFeB bonded magnets significantly reduces the manufacturing cost of complex-shaped magnets, enables efficient utilization of rear earth elements and broadens elevated operating temperature applications.

Fabrication and Evaluation of Composite Magnetic Core Using Iron-Based Amorphous Alloy Powder With Different Particle Size Distributions

The authors proposed the iron-based metal composite bulk magnetic core for high efficient and lightweight MHz switching DC–DC converter using SiC/GaN power devices. Although the iron-based metal composite bulk magnetic core exhibited a lower core loss than that of Ni-Zn ferrite in MHz frequency band, its relative permeability was low around 10. In this paper, in order to increase the permeability of such composite magnetic core with low core loss, we investigated an effect of mixing amorphous alloy powder having different particle size distributions. This method estimated increasing volume fraction of amorphous alloy powder and decreasing the demagnetization field of the composite magnetic core. From the experimental results, the composite magnetic core with an optimal mixing ratio of 2.4 $\mu \text{m}$ and 12.8 $\mu \text{m}$ median diameter Fe-based amorphous alloy (Fe-AMO) powders exhibited a relative permeability of 20.5 which was 2.4 times higher than that of composite magnetic core using 2.4 $\mu \text{m}$ median diameter Fe-AMO powders. And its core loss was 555 kW/m3 at 1 MHz in frequency and under 20 mT in maximum flux density.

Stiffness to Weight Ratio of Various Mechanical and Thermal Loaded Hyper Composite Plate Structures

In this study, several models of the rocket fins were made of hyper composite materials (with two or more reinforced materials) with different volume fractions of components used to produce isotropic composite plate structures. The reinforcement of polyester resin material was done in two ways, with fibre reinforcement and powder reinforcement. The types of fibresthat used were chopped glass fibre and chopped carbon fibre, and the type of powder used was carbon powder. A concentrated load was applied to the models in the form of a cantilever plate. The effect of adding carbon powder on the stiffness to weight ratio and the effect of temperature on this stiffness to weight ratio were studied and discussed. It was observed that hybridization improves the properties of composite materials at certainspecific volume fractions of carbon powder. The best percentage of improvement of the value of stiffness was69.87% in a specimenmade of 50% polyester, 30% glass fibres, and 20% carbon powderin terms of models reinforced with glass fibres, while for models reinforced with carbon fibres, it was 79.94% in the model made of 60% polyester, 30% carbon fibre, and 10% carbon powder. In addition, the results showed that an increase in temperature leads to a decrease in the stiffness to weight ratio for all models. The smallest effect of temperature on the stiffness to weight ratio was shown in the sample composed of 50% polyester, 30% glass fibres, and 20% carbon powder, at 45.83% for the models reinforced with chopped glass fibres, and in the model made of 60% polyester, 20% carbon fibres, and 20% carbon powder at 57.54% for models reinforced with carbon fibres.

Porous Titanium Fabricated by a Combination of Vacuum Distillation and Sintering Process

As a new type of material combined with special structure and function, the porous titanium was prepared through vacuum distillation and sintering process, by which the titanium powder was used as raw material, magnesium particles and its powder as space holder, anhydrous ethanol as binder. The porosity of porous titanium obtained by this method is between 35% and 75% and its opening ratio runs up to 95%. The experimental result showed that magnesium existed in the compacted precursor was evaporated rapidly in vacuum when temperature reached 750°C and removed completely within 20 minutes. The suitable sintering temperature was between 1050°C and 1250°C, but the porosity of porous titanium decreased from 76.2% to 61.3% with temperature elevated. The precursor uniformity was improved by addition of anhydrous ethanol and its formability and density was also done by addition of magnesium powder. The relative density of precursor increased from 82% to 98% with magnesium powder volume fraction varied from 30 vol.% to 80 vol.%.

Powder distribution on powder injection moulding of ceramic green compacts using thermogravimetric analysis and differential scanning calorimetry

Powder-binder separation during injection moulding causes defects such as cracking, warpage or anisotropic shrinkage during firing. In this paper, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) have been previously used to analyse powder distribution within the green body for metal injection moulding are used for ceramics. TGA and DSC are used to characterize the mass loss and heat of fusion of the binder system, silicon nitride feedstock and test-bars. TGA can measure the volume fraction of powder in green parts directly with 1.76vol% difference from nominal volume fraction and variations up to 0.177vol%. The DSC empirical model predicted volume fraction of powder in green parts with 1.76vol% difference from nominal volume fraction and variations up to 1.710vol%. Using rule of mixture, it over predicted volume fraction of powder in green parts by 6.78vol% from nominal volume fraction and with variations up to 2.510vol%.