Search

Metal-ceramic composites such as titanium-hydroxyapatite have been extensively studied as a new generation of implant material in medical application. The powder injection moulding (PIM) process is one the viable processing method in producing the titanium-hydroxyapatite composite which offers extreme geometry part at a lower cost of production. The final powder injection moulding (PIM) product was influenced by the feedstock rheological and thermal properties that related to the binder selection and the critical solids loading. The emphasis of this study was towards the rheological and thermal properties of Ti6Al4V-hydroxyapatite composite feedstock with the powder space holder using a low-density polyethene and palm stearin binder system. The critical solids loading for 90:10 of Ti6Al4V-hydroxyapatite with 20% of the space holder was selected for capillary rheometer tests. The solids loading was obtained at 73 vol.% with optimal solids loading in the range of 2–5% below the critical solids loading which were 68, 69 and 70 vol.%. All feedstocks exhibited shear thinning behaviour, with the shear rate and viscosity values in the range of the PIM feedstock. The work in this study found that the feedstock of 68 vol.% solids loading possessed the best rheological properties with a higher flow behaviour index. [ABSTRACT FROM AUTHOR]

Abstract Titanium-ceramic composites are potential implant material candidates because of their unique mechanical properties and biocompatibility. This review focused on the latest advancement in processing of titanium-ceramic materials. Previously, titanium-ceramic incorporated using different coating techniques, i.e., plasma spraying and electrophoretic depositions, to enhance the biocompatibility of the implants. A major drawback in these coating methods is the growth of tissue at only the surface of the composite and might peel off over time. Recently, metal-ceramic composite was introduced via powder metallurgy method such as powder injection moulding. A porous structure can be obtained via powder metallurgy. Producing a porous titanium-ceramic structure would improve the mechanical properties, biocompatibility and tissue growth within the structure. Hence, further research needed to be done by considering the potential of powder injection moulding method which offer lower costs and more complex shapes for future implant. Graphical abstract Unlabelled Image Highlights • Titanium alloy • Wollastonite • Metal-ceramic composite • Plasma spray • Electrophoretic Deposition [ABSTRACT FROM AUTHOR]

The combination of metallic bio-inert material, stainless-steel 316L (SS316L) and a bio-active material, hydroxyapatite (HA) can produce a composite which has superior properties for orthopaedic applications. The main objective of this study is to investigate the effects of sintering temperature and holding time on the physical and mechanical properties of the sintered part. 50wt.% SS316L and 50wt.% HA were mixed with a binder system of palm stearin (PS) and polyethylene (PE) at 61 vol.% powder loading. Rheological properties show a pseudo-plastic behaviour of the feedstock, where viscosity decreases with increasing shear rate. The feedstock was injection moulded into a tensile bar shape while thermal debinding was carried out at 320°C and 500°C. The brown parts were sintered at 1000, 1100, 1200 and 1300°C, with three different sintering times of 1, 3 and 5 hours in the furnace. It was found that the highest sintered density measured was 95.61% of the theoretical density. In addition, the highest hardness and Young’s modulus measured were 150.45 HV and 52.61 GPa respectively, which are higher than those of human bone. The lowest percentage of carbon content was 0.022wt.% given by the sample sintered at 1300°C for 1 hour. Therefore, SS316L/HA composite with good mechanical and physical properties was successfully produced through the PIM process. [ABSTRACT FROM AUTHOR]

Solid loading and post-sintered cooling rates are two effective parameters used to control the mechanical properties of powder-injection molded parts. In the case of 316 L stainless steel (SS), these parameters also influence mechanical properties and corrosion resistance. In this study, four formulations with powder loading above and below the critical powder loading were prepared and sintered at 1325 °C in vacuum with cooling rates varying from 3 °C/min to 10 °C/min. Solid loadings above the critical loading caused reductions in final properties (i.e. mechanical properties and corrosion resistance) because of increased porosity. The high cooling rate of 10 °C/min improved the mechanical properties due to the formation of large number of grains and corrosion resistance due to formation of chromium oxide layer at the surface of PIM 316 L SS. Solid loading of 65 vol.%, sintered at 1325 °C with a cooling rate of 10 °C/min showed improvements in terms of mechanical properties and corrosion resistance compared with conventional 316 L SS. Such improvements were considered due to reduced grain sizes and formation of a chromium oxide layer on the sample surface. This study identifies the solid loading (65 vol.%) below the critical powder loading and a high post-sintered cooling rate, i.e., 10 °C/min, are suitable to achieve optimum mechanical properties and corrosion resistance in 316 L SS. The developed material may be recommended for biomedical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag decoration of GNPs by sonication assisted exfoliation and oxygen functionalization. • Ag decoration of nitrogen doped GNPs by sonication assisted exfoliation, oxygen, and nitrogen functionalization. • Enhanced mechanical properties of Ag-GNP/Cu with controlled Ag NPs attachment to GNPs. • Lower mechanical properties of Ag-N-GNP/Cu due to higher concentration of Ag NPs on GNPs. Poor wettability and weak graphene/Cu interface limit the mechanical properties' enhancement in graphene/Cu composites. This study devised an interface enhancement approach by Ag decoration of graphene nanoplatelets (Ag-GNPs) and Ag decorated nitrogen doped graphene (Ag-N-GNP) without oxide (during decoration) and carbide (during sintering) formation. Sonication was used to functionalize GNPs for decoration with Ag nanoparticles (NPs) and Cu composites (Ag-GNP/Cu and Ag-N-GNP/Cu) were fabricated using cold pressing (low-pressure) and sintering. 2-Ag-GNP/Cu (2 vol% of Ag-GNPs) and 2-Ag-N-GNP/Cu (2 vol% of Ag-N-GNPs) possessed highest sintered density. In addition, 2-Ag-GNP/Cu and 1-Ag-N-GNP/Cu showed highest microhardness and tensile strength (theoretical), respectively. Higher concentration of Ag NPs on GNPs in Ag-N-GNP (oxygen and nitrogen functionalization) showed lower mechanical properties for Ag-N-GNP/Cu compared to Ag-GNP/Cu with limited Ag NPs on GNPs (oxygen functionalization). Interface modification strategy with noble metal NPs bridging between GNP and Cu suggests controlled functionalization and noble metal NPs' attachment on GNPs for effective mechanical properties' enhancement in graphene Cu composites. [ABSTRACT FROM AUTHOR]

Component miniaturization is increasingly gaining importance in numerous microsystem technologies, including medical technology, biotechnology, and drive technology. In this study, two types of nano-sized powder, namely, metal (stainless steel 316L) and ceramic (yttria-stabilized zirconia), were used to fabricate miniature parts through micro powder injection molding. Micro parts were produced by mixing powders with a binder system, followed by injection, debinding, and sintering process. Partially water-soluble binder system with surfactant addition was used to mix with either stainless steel 316L or yttria-stabilized zirconia nanopowder to form feedstock to avoid the agglomeration of fine powder and environmentally hazardous organic binder. The polyethylene glycol loss in water was observed after a rapid removal period in the first 60 min of immersion for the micro parts. Approximately 99 % of the polymethyl methacrylate binder was removed after pyrolysis at 450 °C for 2.5 h. Sintered ceramic and metallic parts showed a relative density that is approximately 97 % of theoretical density and free of defects. Hardness of approximately 221 and 1,200 Hv was achieved for the fabricated micro parts using stainless steel 316L and yttria-stabilized zirconia powders, respectively. [ABSTRACT FROM AUTHOR]

Titanium alloy (Ti6Al4V) and hydroxyapatite (HA) are well-known materials applied in implants. Ti6Al4V shows good mechanical properties and corrosion resistance, whereas HA possesses excellent biocompatibility and bioactivity but weak mechanical properties. The combination of the Ti6Al4V and HA properties is expected to produce a superior material for bio-implants. This study aimed to analyze the feasibility of fabricating HA/Ti6Al4V composites through powder injection molding (PIM) using palm stearin as base binder. In this study, 90 wt% Ti6Al4V and 10 wt% HA were mixed with the palm stearin and polyethylene binder system. The HA/Ti6Al4V feedstock showed pseudoplastic properties, suggesting its suitability for PIM. Flexural test revealed that the strength of the sintered composite ranges from 67.12 MPa to 112.97 MPa and its Young’s modulus ranges from 39.28 GPa to 44.25 GPa. The X-ray diffraction patterns and energy-dispersive X-ray spectra of the composite showed that the HA decomposed and formed secondary phases. Isotropic porous structure was observed on the sintered sample because of HA decomposition. Results showed that the palm stearin can be used as based binder in fabricating HA/Ti6Al4V composites via PIM. The mechanical properties of the sintered composites are nearly similar to those of the human bone. In addition, the increase in weight of the sintered composite during in vitro tests indicated the nucleation and growth of the Ca–P phase, which exhibited the biocompatibility of the fabricated HA/Ti6Al4V composite. [ABSTRACT FROM AUTHOR]

Abstract: Composites consisting of Ag–Y0.25Bi0.75O1.5 (YSB) were investigated as composite cathodes for intermediate-solid oxide fuel cells. A thin film of Ag–YSB composite cathode was fabricated by using slurry painting method. The slurry of Ag–YSB composite cathodes was used to coat anode-bilayered electrolytes (NiO–SDC/SDC/YSB) at room temperature. TGA and DSC results confirmed that all the organic components in the slurry were completely decomposed at temperatures below 600°C. XRD analysis revealed the formation of a pure Ag–YSB composite cathode phase. SEM images showed the grain size increment of the Ag–YSB powder that was ascribed to the consolidation between adjacent grains, which reduced the size of the porosity as the heat treatment temperature was increased. The electrochemical performances (interfacial polarization resistance, R p) were 0.483, 0.469, 0.416, and 0.441Ωcm2 after one, two, three, and four coatings, respectively. [Copyright &y& Elsevier]

Highlights: [•] Review on physical and chemical interaction of Ti–HA at processing steps. [•] Critical criteria to be biomaterial are been summarized. [•] Critical issues in fabrication methods of Ti–HA composites. [•] Advantages and disadvantages of those fabrication methods. [ABSTRACT FROM AUTHOR]

Debinding binders in two stages is critical to maintaining the shape of injected parts; the resulting decomposition affects the strength and rigidity of a structure. This study determines the optimal debinding process on the basis of a higher binder removal rate and the production of defect-free parts. The feedstock used was a combination of alumina–zirconia powder with a binder that consists of high-density polyethylene (HDPE), paraffin wax (PW), and stearic acid (SA). During the first stage, the injected parts were immersed in an n-heptane solution at 50°C, 60°C, 65°C, and 70°C to remove PW and SA. Binder weight loss was evaluated as a function of time. In the second stage, HDPE was removed by using thermal debinding. The results show that the optimum solvent debinding process runs for 16h at 60°C. The weight loss of the binder reaches 41.1% and results in the formation of defect-free parts. The binders are degraded at approximately 550°C during thermal debinding. This degradation resulted in decomposition of nearly 96.9% of the binders. Low heating rates (1°C/min to 2°C/min) prevent defects from forming in the injected parts. [ABSTRACT FROM AUTHOR]

Zirconia-toughened alumina (ZTA) parts were fabricated by using a powder injection molding process that utilizes a multi-component binder system based on high-density polyethylene, paraffin wax, and stearic acid. The entire aspect of the manufacturing process, which includes mixing, injection molding, debinding, and sintering, were optimized in this study. ZTA powder was mixed with binders at powder loading ranging from 53vol% to 59vol%. The optimum powder loading was determined by analyzing the rheological properties and homogeneity of feedstocks. During injection molding, the temperature and injection pressure parameters were manipulated to obtain optimum density results. A two-stage debinding process (solvent and thermal) was used to remove binders in green parts. Debound parts were sintered at temperatures ranging from 1400°C to 1600°C for 2h. The shrinkage, density, and hardness of the sintered parts were measured. Results show that with homogeneous mixing, the feedstocks were transformed into pseudoplastic in less than 30min. Powder loading of 57vol% is the most optimal case for injection molding according to the power law index and flow activation energy values. The theoretical relative density reached 90.27% with defect-free parts under optimum injection temperature and pressure. The weights of the parts decreased by 82.26% during solvent debinding at 60°C, whereas the binders were completely degraded at approximately 550°C during thermal debinding. Experimental results also indicate that the shrinkage, density, and hardness reached their maximum values at a sintering temperature of 1600°C. The sintered parts were densified with approximately 98% theoretical density, hardness of 1582.4HV, and 15% shrinkage value. [ABSTRACT FROM AUTHOR]

Composite cathodes with La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF6428) and samarium-doped ceria carbonate (SDCC) were developed and investigated for solid oxide fuel cell (SOFC) applications at low operating temperatures. The LSCF–SDCC (50 wt% LSCF:50 wt% SDCC) composite cathode powders were mixed by the ball-milling technique followed by calcination at 700, 750, 800, and 850 °C for 2 h. To fabricate single SOFCs using LSCF–SDCC as the cathode, SDCC as the electrolyte, and NiO–SDCC as the anode, a single-step pressing and co-firing process was employed. The electrolyte-supported button cells were tested between 475 and 550 °C. The composite cathode exhibited well-matched TEC values with the SDCC electrolyte. Calcination at lower temperatures (700 and 750 °C) produced powders with surface areas of 10 m2 g−1–11 m2 g−1. Using LSCF–SDCC powders sintered at 700 and 750 °C to fabricate button cells resulted in power densities of 117.9 and 120.4 mW cm−2, respectively, at an operation temperature of 550 °C with the latter cathode yielding the lowest R p value. [ABSTRACT FROM AUTHOR]

Abstract: Nanoperovskite oxides, Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF), were synthesized via the co-precipitation method using Ba, Sr, Co, and Fe nitrates as precursors. Next, half cells were fabricated by painting BSCF thin film on Sm0.2Ce0.8O x (samarium doped ceria, SDC) electrolyte pellets. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS) measurements were carried out on the BSCF powders and pellets obtained after sintering at 900°C. Investigations revealed that single-phase perovskites with cubic structure was obtained in this study. The impedance spectra for BSCF/SDC/BSCF cells were measured to obtain the interfacial area specific resistances (ASR) at several operating temperatures. The lowest values of ASR were found to be 0.19Ωcm2, 0.14Ωcm2 0.10cm2, 0.09Ωcm2 and 0.07Ωcm2 at operating temperatures of 600°C, 650°C, 700°C, 750°C and 800°C, respectively. The highest conductivity was found for cells sintered at 900°C with an electrical conductivity of 153Scm−1 in air at operating temperature of 700°C. [Copyright &y& Elsevier]

Abstract: The structure and thermal properties of La0.6Sr0.4Co0.2Fe0.8O3−δ –SDC carbonate (LSCF–SDC carbonate) composite cathodes were investigated with respect to the calcination temperatures and the weight content of the samarium-doped ceria (SDC) carbonate electrolyte. The composite cathode powder has been prepared from La0.6Sr0.4Co0.2Fe0.8O3−δ and SDC carbonate powders using the high-energy ball milling technique in air at room temperature. Different powder mixtures at 30wt%, 40wt% and 50wt% of SDC carbonate were calcined at 750–900°C. The findings indicated that the structure and thermal properties of the composite cathodes were responsive to the calcination temperature and the content of SDC carbonate. The absence of any new phases as confirmed via XRD analysis demonstrated the excellent compatibility between the cathode and electrolyte materials. The particle size of the composite cathode powder was ∼0.3–0.9μm having a surface area of 4–15m2 g−1. SEM investigation revealed the presence of large particles in the resultant powders resulting from the increased calcination temperature. The composite cathode containing 50wt% SDC carbonate was found to exhibit the best thermal expansion compatibility with the electrolyte. [Copyright &y& Elsevier]

Two-component micro-powder injection molding (2C-μPIM) is a promising technique to produce bi-material micro-sized components of 3 mol% yttria-stabilized zirconia (3YSZ) and 17-4PH stainless steel (SS 17-4PH). In this research, the solvent and thermal debinding mechanisms of the green 3YSZ/SS 17-4PH micro-parts were investigated using a systematic approach. For obtaining the feedstocks, 3YSZ and SS 17-4PH powders were individually mixed with palm stearin and low-density polyethylene (LDPE) binders. This experimental work revealed that the palm stearin elimination rate in 3YSZ/SS 17-4PH micro-parts consisted of 3YSZ and SS 17-4PH feedstocks with powder loadings of 44 vol% and 69 vol%, respectively, increased with an increase in the temperature during the solvent debinding process. While a substantial amount of palm stearin was removed from the interface and other regions of the bi-material micro-component at the solvent debinding temperature of 70 °C, the joining between 3YSZ and SS 17-4PH collapsed at 80 °C. The open channels that developed in the component solvent debound at 70 °C helped to eliminate 96%–99% of the binder system in the thermal debinding stage. After the sintering, the findings signified that bi-material micro-components could be fabricated successfully through the process route of 2C-μPIM by using the feedstocks of 3YSZ and SS 17-4PH. [ABSTRACT FROM AUTHOR]

TiC 0.7 N 0.3 is widely used as a cutting tool and an abrasion-resistant material for operations requiring high wear resistance and strength. In this study, we attempted to solve one of the main issues in TiC 0.7 N 0.3; synthesis at high temperature (>1000 °C). The use of NH 4 NO 3 powder was put forward for the first time as a precursor to supply N 2 gas for synthesizing TiC 0.7 N 0.3 nanopowders at a low temperature of 180 °C. Ti, C, and NH 4 NO 3 served as feedstocks. Raw materials were mixed at different milling times (1, 5, 10, 15, and 20 h) at 300 rpm in Ar gas to avoid oxidation. XRD results revealed that no new peaks of TiC 0.7 N 0.3 appeared after milling. Prior to vacuum synthesis at 180 °C, the as-milled powders were dried at 50 °C for 1 h and shaped into cylindrical pellets under a pressure of 150 MPa. The TiC 0.7 N 0.3 peaks were distinctively present at 5–20 h except for samples milled at 1 h. Notably, activation energy decreased from 256.9 kJ/mol to 76.68 kJ/mol with prolonged milling time from 1 h to 20 h. This decrease was due to the decreased activation energy with prolonged milling time. The reaction between C and NH 4 NO 3 was found to be exothermic, which favored the release of N 2. With increased temperature caused by the exothermic reaction, the melted Ti particles reacted simultaneously with the released N 2 gas, whereas the remaining C synthesized TiC 0.7 N 0.3. [ABSTRACT FROM AUTHOR]

The interfacial interaction between graphene and Cu restricts the efficacious properties' enhancement due to poor wettability between the reinforcement and matrix. Herein, we reported an interface modification strategy by Au decoration of graphene nanoplatelets (Au-GNPs) without carbide/oxide formation. Sonication was used to induce defects in GNPs, which were then decorated with Au nanoparticles and used to fabricate a composite material with Cu (Au-GNP/Cu) via low pressure cold pressing and sintering. Sonication parameters' optimization depicted higher exfoliation of GNPs with lower defects at lower sonication amplitude and higher sonication duration which resulted in relatively monodispersed Au nanoparticles attached to the GNPs' surface. The Au-GNP/Cu composite with 1 vol% showed highest sintered density, hardness and calculated tensile strength which decreased at higher Au-GNP content. The proposed interface design with noble metal nanoparticles acting as bridges between GNP and Cu, opens new horizons for superior mechanical properties of composites. [Display omitted] • Au decoration of GNPs by sonication induced exfoliation and defect generation. • Highly exfoliated GNPs with low defects result in monodisperse Au nanoparticles' attachment. • Improved interfacial interaction between Au-GNPs and Cu without formation of carbide/oxide. • Mechanical property enhancement of Au-GNP/Cu composite. [ABSTRACT FROM AUTHOR]

Due to current trend and increasing interest towards natural based fiber products, Kenaf (Hibiscus cannabinus) fibers have been used for the developments of many products. Therefore, Kenaf fiber-reinforced composites have been widely used in engineering and industrial applications. The present work deals with the fabricating and characterization of untreated and treated kenaf/polypropylene (PP)-reinforced composites. Composites of PP reinforced with treated and untreated kenaf fibers were fabricated using the injection molding technique. Different fiber loadings of 10, 20, 30, 40, 50 wt% treated and untreated kenaf composites were also prepared. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA) were performed on the treated, untreated kenaf fibers and kenaf/PP composites. Moreover, the alkaline-treated kenaf composites exhibit better physical, morphological, and mechanical properties because of the compatibility of kenaf with PP. However, variations in tensile and flexural properties depend on treatment and kenaf fiber contents. The percentage increase in the mechanical properties of the treated kenaf/PP composites relative to that of PP was also measured. In addition, 40 wt% kenaf fiber loading resulted in higher mechanical properties. By contrast, kenaf/PP composite with 50% fiber loading was not successfully prepared because of improper mixing and the burning of kenaf fibers in the PP matrix. To conclude, 40% kenaf/PP composites with superior physical and mechanical properties may be used in variety of applications such as automotive, sports, construction, animal bedding, and mass production industries. [ABSTRACT FROM AUTHOR]

Abstract: Highly filled conductive fillers (>60vol%) for conductive polymer composites (CPCs) cause the degradation of rheological and mechanical properties. This study investigated the rheological properties of highly filled metal powder (SS316L) in a polymer matrix composite combined with carbon nanotubes (CNTs) and Graphite (G). The effects of filler concentrations and chemical functionalization on the mechanical and electrical properties of the resulting CPC were determined. Feedstocks with different concentrations were injection molded, and the molded specimens were subjected to tests of tensile strength, three-point bending, hardness, and three-point probe electrical conductivity. The feedstock of CNTs/G/SS316L can be injection molded from 28vol% polypropylene (PP). The functionalized CPC shows higher strength and elongation than as-produced CPC based on the tensile and flexural tests. The highest flexural and tensile strengths are 80 and 35MPa, respectively. The functionalized CPC also exhibits higher hardness and better electrical properties than as-produced CPC. Thus, functionalization with CNTs and Graphite enable the reinforcement and formation electrical conducting networks between metal- and carbon-based fillers within a polymer matrix. [Copyright &y& Elsevier]

Abstract: The effects of sintering temperature on the current–voltage (I–V) performance of symmetrical cells with an SDCC electrolyte composite were evaluated in this study. The SDCC electrolyte composite was prepared by mixing 80wt% SDC with 20wt% Li and Na carbonate (Li/Na ratio of 2/1) via a solid state reaction method. The resultant SDCC electrolyte composite powder was uniaxially pressed into a circular pellet and sintered at 500°C, 550°C, 600°C and 650°C for 5h. A symmetrical cell was finally fabricated by painting a conductive silver paste on both sides of the dense SDCC electrolyte composite pellet, and its I–V performance was measured using hydrogen and air as the fuel and oxidant, respectively. The phase structure and microstructure of the composite powders were investigated using an X-ray diffractometer, field emission scanning electron microscope, and transmission electron microscope. Ceramic pellets sintered at 550°C exhibited a maximum power density of 63.3mW/cm2 and an open circuit voltage of 1.14V at an operating temperature of 650°C. This study contributes to the development of SDCC electrolyte composite substrates for electrolyte-supported low-temperature SOFCs. [Copyright &y& Elsevier]

The use of kenaf fiber as a reinforcement material for polymer composites is gaining popularity, especially in the production of automotive components. The main objective of this current work is to relate the effect of alkali treatment on the single fiber itself and the composite material simultaneously. The effect of temperature condition during mechanical testing is also investigated. Composite materials with discontinuous natural kenaf fibers and epoxy resin were fabricated using a compression moulding process. The epoxy composites were reinforced with 50 wt% untreated and treated kenaf fibers. The kenaf fiber was treated with NaOH solution (6% by weight) for 24 h at room temperature. Kenaf fiber treated with NaOH treatment had a clean surface and no impurities. For the first time we can see that alkali treatment had a damaging effect on the mechanical properties of kenaf fibers itself and the treated kenaf/epoxy composites. The composite reinforced with untreated kenaf fiber and treated kenaf fiber showed increased tensile strength (72.85% and 12.97%, respectively) compared to the neat epoxy. Reinforcement of the composite with treated kenaf fiber decreased the tensile strength due to the fiber pull out and the formation of voids which weakens the adhesion between the fibers and matrix. The temperature conditions also play an important role in composites with a significant impact on the deterioration of composite materials. Treated kenaf fiber has thermal stability and is not sensitive to temperature and as a result reinforcement with treated kenaf gives a lower loss value of 76%. [ABSTRACT FROM AUTHOR]

The incorporation of kenaf fiber fillers into a polymer matrix has been pronounced in the past few decades. In this study, the effect of multiwalled carbon nanotubes (MWCNTs) with a short kenaf fiber (20 mesh) with polypropylene (PP) added was investigated. The melt blending process was performed using an internal mixer to produce polymer composites with different filler contents, while the suitability of this melt composite for the injection molding process was evaluated. Thermogravimetric analysis (TGA) was carried out to investigate the thermal stability of the raw materials. Rheological analyses were conducted by varying the temperature, load factor, and filler content. The results demonstrate a non-Newtonian pseudoplastic behavior in all samples with changed kenaf fillers (10 to 40 wt %) and MWCNT contents (1 to 4 wt %), which confirm the suitability of the feedstock for the injection molding process. The addition of MWCNTs had an immense effect on the viscosity and an enormous reduction in the feedstock flow behavior. The main contribution of this work is the comprehensive observation of the rheological characteristics of newly produced short PP/kenaf composites that were altered after MWCNT additions. This study also presented an adverse effect on the composites containing MWCNTs, indicating a hydrophilic property with improved water absorption stability and the low flammability effect of PP/kenaf/MWCNT composites. This PP/kenaf/MWCNT green composite produced through the injection molding technique has great potential to be used as car components in the automotive industry. [ABSTRACT FROM AUTHOR]

Automotive parts, including dashboards and trunk covers, are now fabricated through a compression-molding process in order to produce lightweight products and optimize fuel consumption. However, their mechanical strength is not compromised to avoid safety issues. Therefore, this study investigates kenaf-fiber-reinforced polypropylene composites using a simple combing approach to unidirectionally align kenaf fibers at 0°. The kenaf composite was found to withstand a maximal temperature of 120 °C. The tensile and flexural strengths of the aligned kenaf composites (50 and 90 MPa, respectively) were three times higher than those of the commercialized Product T (between 39 and 30.5 MPa, respectively) at a temperature range of 90 to 120 °C. These findings clearly showed that the mechanical properties of aligned kenaf fibers fabricated through the combing technique were able to withstand high operating temperatures (120 °C), and could be used as an alternative to other commercial natural-fiber products. [ABSTRACT FROM AUTHOR]

For the first time, an innovative combed technique was used for the successful preparation of untreated kenaf fibre. Subsequent to investigations, the combed strategy, provided a smooth kenaf surface with a tensile strength of 692 MPa. Although, while the water absorption was recorded as an excellent 8%, the 92° contact angle, indicated exceptional interfacial bonding, between the fibre-matrix. These results were confirmed through morphological images, which revealed the occurrence of minimal fibre breakage. Thus, the outstanding mechanical properties that come with an untreated kenaf composite, suggest a useful alternative material for automotive parts generation such as dashboard and door panel. [ABSTRACT FROM AUTHOR]

The fabrication of bi-material micro-components via two-component micro-powder injection moulding (2C-µPIM) from 3 mol% yttria-stabilised zirconia (3YSZ) and micro/nano bimodal stainless steel 316L (SS 316L) powders has received insufficient attention. Apart from this, retaining the bonding between ceramic and metal at different processing stages of 2C-µPIM is challenging. This study investigated the solvent and thermal debinding mechanisms of green bi-material micro-parts of 3YSZ and bimodal SS 316L without collapsing the ceramic/metal joining. In this research, feedstocks were prepared by integrating the powders individually with palm stearin and low-density polyethylene binders. The results demonstrated that during the solvent debinding process, the palm stearin removal rate in the bi-materials composed of 3YSZ and bimodally configured SS 316L feedstocks intensified with an increase in temperature. The establishment of interconnected pores in the solvent-debound components facilitated the thermal debinding process, which removed 99% of the binder system. Following sintering, the debound bi-materials exhibited a relative density of 95.3%. According to a study of the microstructures using field emission scanning electron microscopy, an adequate bond between 3YSZ and bimodal SS 316L was established in the micro-part after sintering. The bi-material sintered at 1350 °C had the highest hardness of 1017.4 HV along the joining region.

The micro-scale joining of two different materials using two-component micro-powder injection molding (2C-µPIM) is an intriguing technique. The formation of defects in bi-materials at different processing stages makes this technique challenging. This study presents the fabrication of defect-free bi-material micro-parts containing hydroxyapatite (HA) and 3 mol% yttria-stabilized zirconia (3YSZ) via 2C-µPIM. Critical powder volume concentrations (CPVCs) of 61.7 vol% and 47.1 vol% were obtained for the HA and 3YSZ powders, respectively. Based on the CPVCs, the optimal loadings for the HA and 3YSZ powders were selected as 60 vol% and 45 vol%, respectively. The HA and 3YSZ feedstocks were prepared by separately mixing the optimal powder contents with low-density polyethylene (LDPE) and palm stearin binders. The feedstocks displayed pseudoplastic behavior, and the lowest ranges of viscosity for the HA and 3YSZ at a temperature of 180 °C were 157.1-1392.5 Pa·s and 726.2-985.5 Pa·s, respectively. The feedstocks were injected to produce green HA/3YSZ micro-sized components. It was found that a solvent debinding temperature of 70 °C removed 60.6% of the palm stearin binder from the sample. In the thermal debinding stage, the open channels that formed in the bi-material sample's solvent debound at 70 °C and contributed to the removal of 93 to 95% of the binder system. When the debound bi-materials were sintered at 1300 °C, the highest relative density of 96.3% was obtained. The sintering operation revealed a linear shrinkage between 13 and 17% in the sintered HA/3YSZ micro-parts.

Metal injection molding (MIM) is one of the most widely used manufacturing processes worldwide as it is a cost-effective way of producing a variety of dental and orthopedic implants, surgical instruments, and other important biomedical products. Titanium (Ti) and Ti alloys are popular modern metallic materials that have revamped the biomedical sector as they have superior biocompatibility, excellent corrosion resistance, and high static and fatigue strength. This paper systematically reviews the MIM process parameters that extant studies have used to produce Ti and Ti alloy components between 2013 and 2022 for the medical industry. Moreover, the effect of sintering temperature on the mechanical properties of the MIM-processed sintered components has been reviewed and discussed. It is concluded that by appropriately selecting and implementing the processing parameters at different stages of the MIM process, defect-free Ti and Ti alloy-based biomedical components can be produced. Therefore, this present study could greatly benefit future studies that examine using MIM to develop products for biomedical applications.

In this research, we investigated the influence of the sintering temperature on the physical and mechanical properties of micro-sized bi-material components of 17-4PH stainless steel and 3 mol% yttria-stabilized zirconia fabricated using a two-component micro-powder injection molding (2C-μPIM) process. First, 17-4PH and zirconia powders were separately mixed with binders to obtain feedstocks, which were then injection-molded into the dumbbell shape, followed by the binder extraction process. Subsequently, the debound micro-specimens were subjected to sintering between 1250 °C and 1350 °C for 3 h. Per the observations of the microstructures using scanning electron microscopy (SEM), a strong bond between metal and ceramic in micro-sized 17-4PH/zirconia components was formed when the sintering temperature exceeded 1300 °C. The maximum relative density of 99% was achieved when the bi-material micro-part was sintered at 1350 °C. The linear shrinkage increased from 9.6% to 17.4% when the sintering temperature was increased from 1250 °C to 1350 °C. The highest hardness value of 1439.6 HV was achieved at 1350 °C along the bi-material bonding region. Moreover, a maximum tensile strength of 13.7 MPa was obtained at 1350 °C.