Hybrid Powder Research Articles

Mechanical Properties and Thermal Conductivity of Epoxy Composites Containing Aluminum-Exfoliated Graphite Nanoplatelets Hybrid Powder

Epoxy/aluminum-exfoliated graphite nanoplatelet (Al-xGnP) composites were prepared. Prior to the preparation of the composite, two types of Al-xGnP hybrid powder were prepared, one is fully inserted xGnP in aluminum (Al) flake and the other is partially inserted xGnP in Al flake, which were confirmed by TEM images. The thermal conductivities of the epoxy composites increased monotonically with the filler content and the partially and fully inserted epoxy/Al-xGnP composites showed almost 2–3 times higher than those of epoxy/xGnP and epoxy/Al composites. Especially, partially inserted epoxy/Al-xGnP composite showed the highest values of thermal conductivity at the same filler concentration because of the network bridge between Al flakes. The tensile and flexural moduli of the fully inserted epoxy/Al-xGnP showed the highest value in all areas of the filler content because of the good dispersion quality but the tensile and flexural strengths of all epoxy composites decreased with the filler content due to the increase of weak interface between epoxy matrix and the filler.

H13/Ni/WC混合粉末梯度熔覆层的激光熔覆制备及耐磨性研究

H13/Ni/WC混合粉末梯度熔覆层的激光熔覆制备及耐磨性研究

TiO2/rGO/Cu2O ternary hybrid for high-performance photoelectrochemical applications

In this paper, TiO2 was hybridized with Cu2O and reduced graphene oxide (rGO) in order to increase the light absorption range and improve the photoelectrochemical (PEC) activity of TiO2. The TiO2 powder (P25) was added to an aqueous GO colloidal solution, and then heated in an autoclave to attain the binary TiO2/rGO hybrid. The ternary hetero-nanostructure was achieved through the growth of Cu2O nanoparticles on the TiO2/rGO hybrid by a chemical bath deposition process. The characteristics of TiO2/rGO/Cu2O hybrid powders were investigated through XRD, SEM, TEM, HRTEM, EDS, Raman spectroscopy, FT-IR, PL, and UV–Vis/DRS techniques. The PEC behavior of the ternary hybrid electrode was examined using linear sweep voltammetry, amperometry, and electrochemical impedance spectroscopy tests. The results reveal that TiO2 nanoparticles are well placed on the rGO nanoplatelets while Cu2O nanoparticles are distributed on the binary hybrid. With the addition of Cu2O and rGO, the band-gap energy of TiO2 is reduced from 3.3 eV to 2.72 eV. The PEC test results indicate that the photoelectrochemical activity of the TiO2/rGO/Cu2O ternary hybrid is much higher than that of the bare TiO2 or the TiO2/rGO binary hybrid. The mechanisms responsible for the enhanced PEC behavior of the TiO2/rGO/Cu2O ternary hybrid are discussed in detail.

Investigating the impact of a selective laser melting process on Ti6Al4V alloy hybrid powders with spherical and irregular shapes

ABSTRACT A hybrid powder of Ti6Al4V, which consists of 50 wt% plasma atomised (PA) spherical and 50 wt% hydride-dehydride (HDH) irregular-shaped powder with a flowability of 36.5 s, is projected as the raw materials in this research. In addition, Ti6Al4V (Gr.23) plasma atomised 100 wt% spherical powder was used as the reference powder with a flowability of 28 s to facilitate the tensile property discussion. It was found that the powder flowability is the crucial parameter governing the tensile properties of fabricated specimens. It was shown that the decrease in powder flowability (36.5 s) resulted in increases in susceptibility to the formation of a lack of fusion defects with dropped tensile properties. The microstructure of the fabricated Ti6Al4V alloy features the formation of prior β grain boundaries and an alpha prime (α′) martensite. Furthermore, no intermetallic aluminide phase (Ti3Al) precipitations in grain boundaries were detected through energy-dispersive X-ray spectroscopy analysis.

Investigation of using recycled powder from the preparation of recycled aggregate as a supplementary cementitious material

Considerable amounts of hybrid powder are produced when recycled aggregate is being prepared. An economic and environmental-friendly method of treatment is to take this recycled hybrid powder (RHP) as a sort of supplementary cementitious material for concrete and mortar. However, the application of RHP requires a deep understanding of its capacity and limitations, which relies on the clarity of properties possessed by the single powder contained in it. Therefore, in this study, the properties of recycled concrete powder (RCP) and recycled brick powder (RBP) as well as the impact of their incorporation on the mortar properties were investigated. The results showed that RBP had a lower negative impact on the workability of mortar than RCP due to its lower specific surface area and porosity. The water requirement ratios of RBPs and RCPs with different levels of fineness varied from 103 to 105% and from 110 to 114%, respectively. The activity indexes of RBPs reached the range between 82 and 87% at 90 days as a result of the pozzolanic effect, while those of RCPs varied from 72 to 78%. Moreover, RBP exhibited an excellent contribution to the flexural strength, which was ascribed to its favourable interfacial bonding with cement paste. Mercury intrusion porosimetry analysis also indicated that the addition of RBP led to a refined pore structure by reducing the average pore diameter. Notably, an improved shrinkage resistance was achieved by the incorporation of high-fineness RBP. A detrimental RCP particle-cement paste interfacial zone was observed in RCP-containing mortars, which was speculated to be an important reason for the appreciable decline in mechanical and durability-related properties.

Mechanical and tribological characterization of self-lubricating Mg-SiC-Gr hybrid metal matrix composite (MMC) fabricated via mechanical alloying

Abstract This study deals with the fabrication and tribo-mechanical characterization of magnesium (Mg)-silicon carbide (SiC)- graphite (Gr) hybrid metal matrix composites (MMCs). The hybrid MMCs were fabricated by a mechanical alloying process and their mechanical and tribological properties were investigated as well as compared with those of the base material and the Mg-Gr composite. The morphology analysis of the constituent powders and the hybrid powder mixture was conducted through SEM, EDX and XRD. The microstructure of the sintered MMCs showed a uniform distribution of the reinforcement on the matrix. The developed hybrid MMCs exhibited greater mechanical properties when compared to the base material and the Mg-Gr composite. The tribological characterization of the fabricated hybrid MMCs was studied using the pin-on-disc tribometer under dry sliding conditions. The hybrid MMC composed of 5%Gr and 10%SiC (Mg+5%Gr+10%SiC) demonstrates 92% low wear rate and 53% low friction coefficient than the matrix Mg. Therefore, this hybrid MMC can be a potential candidate to develop components used in the tribological operation.

Process−microstructure−properties relationship in Al−CNTs−Al2O3 nanocomposites manufactured by hybrid powder metallurgy and microwave sintering process

Abstract Al−2CNTs−xAl2O3 nanocomposites were manufactured by a hybrid powder metallurgy and microwave sintering process. The correlation between process-induced microstructural features and the material properties including physical and mechanical properties as well as ultrasonic parameters was measured. It was found that physical properties including densification and physical dimensional changes were closely associated with the morphology and particle size of nanocomposite powders. The maximum density was obtained by extensive particle refinement at milling time longer than 8 h and Al2O3 content of 10 wt.%. Mechanical properties were controlled by Al2O3 content, dispersion of nano reinforcements and grain size. The optimum hardness and strength properties were achieved through incorporation of 10 wt.% Al2O3 and homogenous dispersion of CNTs and Al2O3 nanoparticles (NPs) at 12 h of milling which resulted in the formation of high density of dislocations and extensive grain size refinement. Also both longitudinal and shear velocities and attenuation increase linearly by increasing Al2O3 content and milling time. The variation of ultrasonic velocity and attenuation was attributed to the degree of dispersion of CNTs and Al2O3 and also less inter-particle spacing in the matrix. The larger Al2O3 content and more homogenous dispersion of CNTs and Al2O3 NPs at longer milling time exerted higher velocity and attenuation of ultrasonic wave.

Synthesis and Structural Properties of Hybrid Powder Materials Based on Colloidal Silica and Silver Iodide

This paper considers approaches to the preparation of potential reagents for precipitation enhancement processes. New reagents have the form of hybrid powder materials produced via physical attachment of silver iodide crystals to colloidal silica particles. In our work, hybrid powder is thought of as a combination of an inert matrix (colloidal silica) and a modifier (silver iodide as an active reagent). We demonstrate that the way in which composite powders are synthesized influences the phase state of the modifier. We have studied structural characteristics of the synthesized powder materials. The results demonstrate that increasing the percentage of silica in the composition of the powders leads to predominant formation of the hexagonal crystalline phase of silver iodide.

Sequential co-precipitation as a convenient preparation method of anticorrosive hybrid calcium phosphate/calcium silicate powder pigments

Hybrid powder pigments based on calcium phosphates and Ca-exchange silicates (CPS) were prepared via a sequential co-precipitation method. Chemical composition of CPS and reference pigments (calcium phosphates (CP) and calcium silicates (CS)) was investigated in relation to molar ratio of substrates and pH value of reaction medium. Steel corrosion inhibition efficiency (η) for the pigments was evaluated using electrochemical noise (EN), polarization resistance (POL) and Tafel (TAF) techniques. XRD and FT-IR data indicated that CPS are mixtures of the relevant CP and CS pigments. The EN, POL and TAF data revealed a sinusoidal relation between η and P:Si molar ratio in the substrates (at pH = 8.5 or 11). The best anticorrosive features were observed for CPS prepared at Si molar excess (pH = 8.5) (ηEN = 99%, ηPOL = 73% and ηTAF = 85%). Probably, the synergistic effect was resulted by a specific content and molar ratio of Ca, P2O5 and Si in the CPS-based electrolytes.

Modeling surface chemistry and adsorption behavior of biomimetic chitosan/silica hybrid materials

Chitosan/silica hybrid powders, obtained by the sol-gel method (pH 6, 7, 8) are studied for proposing surface chemical models and rationalizing their behaviour as adsorbents. The chitosan and silica exposed groups in dried powders and their protonation state are inferred. Solid-state 29Si-NMR, XPS, zeta potential experiments and DFT computational calculations reveal the synthesis pH history of each sample. These details, summarized in surface models, are validated by copper adsorption: The pH 8 sample exhibits the highest hydrophilic and negative character, due to the deprotonated free silanol and neutral amine groups. These favor higher copper adsorption efficiency (30.4%) and loading capacity (0.077 mg Cu(II)/m2), through SiO−-Cu(II) electrostatic interactions and [Cu-(NH2)x]2+ complexation. For lower synthesis-pH samples, the neutral silanol and protonated amine populations increase, and the net surface charge becomes positive. This reduces the copper adsorption through electrostatic repulsions. The protonated amine and deprotonated silanol groups are the main responsible of electrokinetic surface response of materials prepared at lower and higher pH, respectively. The complexation is also involved in copper interactions, especially in surfaces populated by neutral amines. In conclusion, this work helps to understand the pH-dependent surface activity of chitosan/hybrid materials, being helpful for their further functionalization and applications.

Nucleation and growth of brushite crystals on the graphene sheets applicable in bone cement

Since recent research indicates that the addition of graphene increases the mechanical and biological properties of calcium phosphates simultaneously, graphene oxide (GO) was used in this research to enhance the properties of brushite cement. The main objective of this study is to investigate the mechanism of nucleation and growth of brushite crystals on GO sheets. Calcium nitrate tetrahydrate and diammonium hydrogenphosphate were used as calcium and phosphate precursors. The brushite chemical precipitation method on graphene sheets was used in this study and computer-assisted modeling was used to understand the process. The results of this study showed that the hybrid powders contained brushite and GO. Brushite crystals were grown after nucleation in proportion to the three main planes containing (020), (121¯), and (141). The final particles were plate shaped. The results of setting time tests showed that increasing the GO% decreases the setting time and this trend continues with an increasing amount of GO. The results of the mechanical evaluation showed that increasing the GO by up to 2% increased the mechanical properties and more than that decreased the mechanical properties.

Simulation of convective MHD flow with inclusion of hybrid powders

In the present research, outputs of numerical modeling of hybrid nanomaterial flow structure and thermal behavior were investigated and in-house code was implemented for simulation. Radiation terms and Lorentz force terms were included in mathematical model. Outputs demonstrate the flow structure and isotherm style with altering important parameters. Dependence of variables on Nu values was summarized in a new formula. More intensive convection should be accomplished with growth of buoyancy force and permeability. More smooth separation from the hot surface can appear with rise in permeability. Besides, it is worth mentioning that augmenting Da leads to easier nanopowder migration and thinner boundary layer generation.

Improve the dielectric property and breakdown strength of composites by cladding a polymer/BaTiO3 composite layer around carbon nanotubes

This work offers a strategy for combining ceramic and conductive fillers to produce composites with high dielectric properties and breakdown strength through a novel core@shell structure. First, we successfully attached barium titanate (BT) nanoparticles to the surface of multi-walled carbon nanotubes (MWCNTs) by sol-gel method. Hyperbranched aromatic polyamide (HB-Pa) was grafted from the surface of BT-attached MWCNTs via in suit polymerization to obtain HB-Pa/BT composite-coated MWCNTs (H-B@CNTs). After the hybrid powders were compounded with epoxy resin (EP), composites with high dielectric properties were prepared. The H-B@CNTs/EP composite exhibited a dielectric constant of 110, a dielectric loss of 0.28 (1 kHz) and a breakdown strength of 6.7 kV/mm at 20 wt % MWCNTs content. The results indicated that we could tailor the dielectric properties of composites by adjusting the amount of BT nanoparticles on the surface of MWCNTs. In addition, HB-Pa played multiple roles in this system: (i) preventing BT nanoparticles from falling off the surface of MWCNTs; (ii) increasing the dispersibility and interaction of fillers in the polymer matrix; (iii) preventing MWCNTs from overlapping one another to form a conductive network to effectively improve the breakdown strength of composites.

Effect of radiative source term on the behavior of nanomaterial with considering Lorentz forces

An in-house FORTRAN code was developed to analyze the hybrid powders migration within a porous domain which was in appearance of Lorentz force. The permeable 2D enclosure was full of nanomaterial, and properties were selected via empirical formulas. Results indicate that positive impact on Nuave can be obtained with rise of permeability which is related to greater temperature gradient. Also, similar impact exists for buoyancy force which shows the greater convective flow with rise of Ra. Reduction in temperature gradient with rise of Ha makes the convective flow to reduce.

Mechanical synthesis of agglomerated aluminum-based hybrid powders containing nano- and microsized filler

This paper reports on the obtained an agglomerated hybrid powder for gas-dynamic spraying based on an aluminum alloy with dispersion-strengthened by nano- and microsized particles by mechanical synthesis in a planetary mill in two stages. Based on the results of scanning electron microscopy, a model for the formation of hybrid powder particles is proposed. The influence of the micro-dimensional filler concentration on the powder particle size distribution is considered. The structural-phase composition of the powder is characterized by X-ray phase analysis.

Advanced Coatings by Thermal Spray Processes

Coatings are pivotal in combating problems of premature component degradation in aggressive industrial environments and constitute a strategic area for continued development. Thermal spray (TS) coatings offer distinct advantages by combining versatility, cost-effectiveness, and the ability to coat complex geometries without constraints of other in-chamber processes. Consequently, TS techniques like high-velocity oxy-fuel (HVOF) and atmospheric plasma spray (APS) are industrially well-accepted. However, they have reached limits of their capabilities while expectations from coatings progressively increase in pursuit of enhanced efficiency and productivity. Two emerging TS variants, namely high-velocity air-fuel (HVAF) and liquid feedstock thermal spraying, offer attractive pathways to realize high-performance surfaces superior to those hitherto achievable. Supersonic HVAF spraying provides highly adherent coatings with negligible porosity and its low processing temperature also ensures insignificant thermal ‘damage’ (oxidation, decarburization, etc.) to the starting material. On the other hand, liquid feedstock derived TS coatings, deposited using suspensions of fine particles (100 nm–5 µm) or solution precursors, permits the production of coatings with novel microstructures and diverse application-specific architectures. The possibility of hybrid processing, combining liquid and powder feedstock, provides further opportunities to fine tune the properties of functional surfaces. These new approaches are discussed along with some illustrative examples.

Preparation of reduced graphene oxide/hydroxyapatite nanocomposite and evaluation of graphene sheets/hydroxyapatite interface

In this investigation, reduced graphene oxide/hydroxyapatite (rGO/HA) hybrid powders have been synthesized using hydrogen gas injection into hydrothermal autoclave. The powders were then consolidated with spark plasma sintering. The results showed that this method of synthesis caused the obtained powders to have high crystallinity. Microscopic analysis confirmed the presence of rGO sheets with folding and wrinkling in the nanocomposite and indicated that various crystalline planes such as (002) and (300) played a role in the growth of hydroxyapatite crystals. The results of interface analysis (HA||rGO) showed that the HA is coherently connected by its (300)-planes with the surface of the rGO sheets and this coherency is accomplished in the rGO cross-section with the (002) planes of HA. The hardness and the Young's modulus of the composite samples were 5.9–6.6 GPa and 132–146 GPa respectively.

Application of electrostatic powder coating on wood composite panels using a cooling method. Part 1: Investigation of water intake, abrasion, scratch resistance, and adhesion strength,

Powder coating is environmentally friendly and safe in terms of human health and is used especially on home appliances and in the automotive sector. Because of these advantages, recent studies have expanded work on the application of powder coating on non-conductive surfaces. Within the scope of this research, low temperature curing (120 °C to 130 °C) was applied on wood-based composite panels of medium-density fiberboard (MDF), particleboard, and plywood to facilitate conductivity. Epoxy, polyester, and hybrid (epoxy-polyester) types of powder paint and water-based liquid paint (control group) were applied to the surface of materials. Panels coated with the powder coatings were compared to the panels coated with the water-soluble acrylic resin coating. The prepared samples were analyzed for performance properties. The best results for thickness swelling, water absorption, adhesive strength, abrasion, and scratch resistance were found for the plywood coated with water-based liquid paint, MDF coated with polyester-based powder paint, plywood coated with hybrid powder paint, particleboard coated with hybrid powder paint, and plywood coated with epoxy powder paint, respectively.

Study on thermal and erosive wear behaviour of hard powders filled glass-epoxy composite

The effect of hybrid powder fillers (WC + Ta/NbC) on thermal response and erosion wear resistance of woven glass fiber reinforced-epoxy composites has been studied. Vacuum assisted resin transfer moulding (VARTM) method was used to fabricate a set of GE composite specimen. Erosion wear test was carried out using alumina erodent, impinging at 40 m/s velocity, from a distance of 10 mm, at ambient and above glass transition temperatures. The rate of erosion was assessed at impingement angles 30°, 60° and 90°. The thermal stability of the composite samples and their response to heat was analysed by using thermal analysis methods TGA and DSC. The erosion wear mechanism of the composites was established by inspecting the eroded surface with the help of scanning electron microscopy.

Fabrication of gelatin/hydroxyapatite/3D-graphene scaffolds by a hydrogel 3D-printing method

In this study, we demonstrate the fabrication of three-dimensional reduced graphene oxide/hydroxyapatite (HA)/Gelatin scaffolds by employing two steps, including a hydrothermal autoclave with hydrogen gas injection to synthesize three-dimensional graphene (3DG)/HA powders and a hydrogel 3D-printing method to fabricate the scaffolds. Evaluations were performed separately for synthesized powders and fabricated scaffolds, which included field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, Raman spectroscopy, and instrumented compression experiments. The powders characterization results showed that the nanostructured hybrid powders were successfully synthesized. The graphene sheets were stacked in 3D and the HA nanorods were attached on the surface of the graphene. Interface analysis showed that the two phases (HA/Graphene) are connected coherently and various preferential directions played a role in the growth of hydroxyapatite crystals. Characterization of the scaffolds showed that the addition of HA and graphene/HA powders resulted in smaller pores and higher dimensional accuracy of the fabricated scaffolds. Mechanical evaluation showed that the addition of HA (0.3 gr) increased the mechanical properties of the scaffolds. Also, increasing the small amount of graphene (0.0045 gr) made the mechanical properties much higher than that of pure HA.