Ceramic Injection Moulding Research Articles

Improved hydrostatic piezoelectric property via incorporation of porous PZT ceramics into 1-3 type PZT-polymer composites: design to fabrication

PZT ceramic is widely used as sensors, especially in underwater applications like sound navigation and ranging(SONAR), due to its piezoelectric properties. However, single-phase PZT ceramics have poor hydrostatic piezoelectric properties, leading to the development of porous PZT and PZT-polymer composites. This study enhanced the hydrostatic figure of merit(HFOM) value by incorporating porous PZT into a 1-3 type composite. Finite element analysis and the ceramic injection molding(CIM) method were used for optimal design and fabrication. PZflex simulation tool derived the composite's piezoelectric properties, revealing that increased porosity reduced d33 and d31 but increased HFOM. The aspect ratio of PZT rods was selected by calculating the coupling factor. The fabricated composite had a higher HFOM value (4050(10-15Pa) at 12% porosity) than dense 1-3 type PZT-polymer composites. This study demonstrates the effectiveness of finite element analysis and CIM in designing high-performance piezoelectric composites, with potential for various future applications.

Evaluation of Material Extrusion Printed PEEK Mold Inserts for Usage in Ceramic Injection Molding

The rapid tooling of mold inserts for injection molding allows for very fast product development, as well as a highly customized design. For this, a combination of rapid prototyping methods with suitable polymer materials, like the high-performance thermoplastic polymer polyetheretherketone (PEEK), should be applied. As a drawback, a huge processing temperature beyond 400 °C is necessary for material extrusion (MEX)-based 3D printing; here, Fused Filament Fabrication (FFF) requires a more sophisticated printing parameter investigation. In this work, suitable MEX printing strategies, covering printing parameters like printing temperature and speed, for the realization of two different mold insert surface geometries were evaluated, and the resulting print quality was inspected. As a proof of concept, ceramic injection molding was used for replication. Under consideration of the two different test structures, the ceramic feedstock could be replicated successfully and to an acceptable quality without significant mold insert deterioration.

Characterisation and thermochemical stability analysis of 3D printed porous ceria structures fabricated via composite extrusion Modelling

Composite Extrusion Modelling (CEM) is an advanced additive manufacturing technique that enables rapid, cost-effective production of complex, customisable designs. In this study, CEM 3D printing of porous ceria structures is reported for the first time. First, the ceramic injection molding (CIM) feedstock with thermoplastic properties was prepared and optimised in terms of its rheological properties to ensure good workability for the printing process at 140–150 °C. Subsequently, the thermoplastic feedstock was used to print porous ceria structures for thermochemical splitting. The feasibility of printing various porous structures with different dimensions, geometries, and macropore sizes was investigated, and the printing parameters: extrusion multiplier (EM), extrusion temperature (ET), nozzle velocity (NV), and layer thickness (LT), were optimised to prevent clogging of the printing nozzle and to achieve homogeneous overlap of the printed layers. The optimised printing parameters for ceria structures are EM 1.3, ET 150 °C, LT ∼ 0.13 mm, and NV 50 mm/s, which were determined by multiple response optimisation process. The sintered 3D-printed bars yielded relative densities of ≥ 98 % and a total microporosity of 0.29 %, measured with a Hg porosimeter. Thermogravimetric analysis (TGA) and cyclic stability experiments were performed on the printed porous ceria structures and showed stability over 100-redox cycles.

Fabrication and mechanical characterization of biocompatible oxide ceramic parts by injection molding

In this study, we proposed a new fabrication method of artificial bone materials using Ceramic Injection Molding (CIM) and verified the mechanical properties of the fabricated compacts. Since ceramic parts can be machined in the green parts from CIM, it is possible to manufacture custom-made artificial bones that match the defective parts. The porosity of sintered compacts affected cell growth. Thus, powder loading, binder composition, and content were changed for controlling the porosity of sintered compacts. As a result, it was confirmed that porosity and mechanical properties were controlled. Bending strength slightly decreased with increasing porosity, however, it is enough for artificial bone.

Freeform injection molding of functional ceramics by hybrid additive manufacturing

Freeform Injection Molding (FIM) is a hybrid manufacturing approach where 3D-printed sacrificial polymeric molds are used for Ceramic Injection Molding (CIM). This technique offers great additive manufacturing capabilities with shape complexity and material versatility. In this paper, we present a thorough analysis of the ability of FIM to process a variety of ceramic feedstocks and evaluate samples of different geometries with increasing geometrical complexity. The materials selected are zirconia, alumina and Pb-free piezoelectrics (BaTiO 3 and (Bi, Na)TiO 3 – BaTiO 3 ). Injection molding simulations are used to optimize the processing parameters. The quality of the fabricated ceramic parts is assessed by the microstructure, macro-defects, the geometrical features of the structural ceramics and the piezoelectric performance of BaTiO 3 and (Bi, Na)TiO 3 – BaTiO 3 . The effect of green- and sintered-density, linear shrinkage (associated with sintering), and shape distortion are also discussed. • Hybrid additive manufacturing and injection molding produce 3D complex shapes • 3D-printed sacrificial molds allow molding the ceramics in freeform geometries • Photopolymer formulation results in robust printing and injection performance • Strategy to reduce defects by simulations and to adjust injection molding parameters • Sintered parts show isotropic shrinkage, no delaminations and limited shape distortion • 3D Pb-free piezoceramics preserve their piezoelectric properties

TEM Study of the Microstructure of an Alumina/Al Composite Prepared by Gas-Pressure Infiltration.

Ceramic injection moulding and gas-pressure infiltration were employed for the manufacturing of alumina/AlSi10Mg composites. Porous ceramic preforms were prepared by mixing alumina powder with a multi-binder system and injection moulding the powder polymer slurry. Then, the organic part was removed through a combination of solvent and thermal debinding, and, finally, the materials were sintered at different temperatures. Degrading the binder enabled open canals to form. The sintering process created a porous ceramic material consisting of alumina without any residual carbon content. During infiltration, the liquid metal filled the empty spaces (pores) effectively and formed a three-dimensional network of metal in the ceramic. The microstructure and properties of the manufactured materials were examined using high-resolution transmission electron microscopy, porosimetry, and bending strength testing. Microscopy observations showed that the fabricated composite materials are characterised by a percolation type of microstructure and a lack of unfilled pores. The research confirmed the diversified nature of the connection at the particle–matrix interface. It was observed that the interphase boundary was characterised by the lack of a transition zone between the components or a continuous transition zone, with the thickness not exceeding 30 nm. Thanks to their increased mechanical properties and low density, the obtained composites could be used in the automotive industry as a material for small piston rings and rods, connecting rods, or even gears.

Effect of Increased Powder-Binder Adhesion by Backbone Grafting on the Properties of Feedstocks for Ceramic Injection Molding.

The good interaction between the ceramic powder and the binder system is vital for ceramic injection molding and prevents the phase separation during processing. Due to the non-polar structure of polyolefins such as high-density polyethylene (HDPE) and the polar surface of ceramics such as zirconia, there is not appropriate adhesion between them. In this study, the effect of adding high-density polyethylene grafted with acrylic acid (AAHDPE), with high polarity and strong adhesion to the powder, on the rheological, thermal and chemical properties of polymer composites highly filled with zirconia and feedstocks was evaluated. To gain a deeper understanding of the effect of each component, formulations containing different amounts of HDPE and or AAHDPE, zirconia and paraffin wax (PW) were prepared. Attenuated total reflection spectroscopy (ATR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and rotational and capillary rheology were used for the characterization of the different formulations. The ATR analysis revealed the formation of hydrogen bonds between the hydroxyl groups on the zirconia surface and AAHDPE. The improved powder-binder adhesion in the formulations with more AAHDPE resulted in a better powder dispersion and homogeneous mixtures, as observed by SEM. DSC results revealed that the addition of AAHDPE, PW and zirconia effect the melting and crystallization temperature and crystallinity of the binder, the polymer-filled system and feedstocks. The better powder--binder adhesion and powder dispersion effectively decreased the viscosity of the highly filled polymer composites and feedstocks with AAHDPE; this showed the potential of grafted polymers as binders for ceramic injection molding.

Mechanical and tribological properties of injection molded zirconia-alumina for orthopedic implants

Ceramics have gained great attention for hip and knee arthroplasty surgical procedures due to their ability to guarantee long-life performance in patients and are considered an alternative to existing metal systems.In the present study, zirconia toughened alumina (ZTA) for orthopaedic implants has been developed by Ceramic Injection Molding (CIM) process. Microstructural, mechanical and tribological studies have been carried out to establish whether the material is suitable for the purpose. The new CIM ZTA material obtained density up to 99.4%, toughness 6.1 MPa m1/2, hardness 20 GPa, Young's modulus 320 GPa, and low coefficient of friction ranging between 0.08 and 0.13 under lubricated conditions, and between 0.11 and 0.34 in dry condition. To simulate the performance of the ZTA in vivo, i.e., the influence of material degradation on the ageing properties, accelerated hydrothermal aging was performed in vitro and good mechanical and tribological properties were confirmed for the developed ZTA.

Assessing the electrical property of carbon nanotube reinforced oxide ceramic matrix composites produced by ceramic injection moulding

Owing to its remarkable properties, multiwalled carbon nanotubes (MWCNTs) are attracting the interest for realization of sensors. The potential of MWCNTs for high temperature sensing applications was investigated by integration within reinforced aluminium oxide ceramic composite. MWCNTs up to 2 wt% were mixed with reinforced aluminum oxide ceramic composite using solution mixing method to ensure good homogeneilty of the oxide ceramic composite powders. Specimens were realized using ceramic injection moulding process (CIM) followed by debinding and sintering procedures. The topography of specimens were examined using atomic force microscopy (AFM). Electrical measurements were also carried out. The results show good demouldability at high MWCNTs concentration and homogenous distribution of the MWCNTs within the oxide ceramic matrix. AFM images illustrate the reduction of surface roughness by increasing the MWCNTs content which demonstrates the role of MWCNTs to improve the fracture resistance of the oxide ceramic matrix composite. As well, the electrical resistance of the feedstocks were reduced sharply. After sintering process, the resistance range drops enormously from M Ω to reach 12.1 Ω at low MWCNTs content; which make them suitable to be as electrode with high temperature capability. The electrical resistance temperature dependency shows a negative temperature coefficient behaviour with negligible resistance change.

Exploring the Applicability of Sinterjoining to Combine Additively Manufactured Ceramic Components

This paper examines the general applicability of sinterjoining for combining the advantages of Ceramic Injection Molding (CIM) and Additive Manufacturing (AM) as well as different AM processes. To do so, the geometric tolerance, the pre-sintering temperature and the co-sintering time are varied exemplarily on samples produced by vat photopolymerization (VPP) to minimize the force required for inserting the bodies and to maximize the degree of sintering. The results show that degrees of sintering larger 90 % can be obtained reproducibly. Thus, sinterjoining can be considered as a promising approach for combining the advantages of several ceramic manufacturing processes.

Experimental investigations on micro-EDM milling of niobium carbide-nickel based cermet using statistical and empirical techniques

Niobium Carbide (NbC) based cermet is a relatively less explored wear resistant material which has potential applications in moulds for ceramic injection moulding as well as cutting tool inserts. The NbC-Ni based cermets exhibit similar hardness as WC-Co cemented carbide but show better wear resistance and chemical stability against iron or steel. The demand for Ni bonded NbC cermets is forecasted to increase due to the rising cost of Co in conventional WC-Co cemented carbides. This poses additional challenges for existing mechanical micromachining processes such as frequent tool failure, higher tool wear and poor surface quality. Therefore, electrically conductive sintered NbC matrix cermets with a Ni binder have been developed which makes it suitable to machine them using electro discharge machining (EDM) and electrochemical machining (ECM) operations.This work presents experimental investigations using micro-EDM milling operation on NbC-Ni workpieces. A combination of empirical and statistical studies is employed to determine the suitable processing window for this material. The empirical study involves microstructural analysis and surface topography characterization using scanning electron microscopy (SEM) and confocal microscopy, respectively. The microstructural features such as micro-cracks, micro-cavities, micro-voids and micro-globules are identified and related to the major material removal mode of melting/vaporization. The statistical study involves parameter optimization and process monitoring. Material removal rate (MRR) of 0.091 mm3/min and tool wear rate (TWR) of 0.048 mm3/min can be achieved to its optimality and tracking the change in sparks frequency, shorts frequency and feed-rate enables to detect the suddenly accumulated debris. In this way, this holistic approach has been demonstrated to achieve an improvement in understanding and optimizing the machining process for novel NbC matrix cermet using micro-EDM technology.

Experimental Investigations into Machining Characteristics of Niobium Carbide Cermet with µECM / hybrid laser-µECM.

Niobium carbide (NbC) is a high hardness 1960 (HV30) cermet material which finds applications in the moulds for ceramic injection moulding as well as inserts for cutting tools. This material possesses excellent combination of hardness, toughness and thermal shock resistance. The use of nickel (Ni) binder makes it a promising material for such applications, especially in view of rising cobalt (Co) metal prices used as binder in conventional tungsten carbide (WC-Co) cermet. The tool-wear and tool-failure issues make it difficult for mechanical machining technologies to process this material, especially in the micromachining regime (< 2 mm). To address machinability challenges, electrically conductive Nb cermet has been developed inhouse with Ni as the binder material. This makes it a suitable workpiece candidate for electrochemical machining (ECM) and electrical discharge machining (EDM) processes.Therefore, experimental investigations are presented in this work to evaluate the machining characteristics of NbC cermet with micro-ECM process. Channels have been used as test-features for evaluating machinability. Furthermore, two different grades of NbC cermets have been machined to identify the effect of WC addition on the dissolution characteristics and possible passivation during ECM. A micro-second pulsed voltage source has been utilized for controlled and localized material removal. To further enhance removal mechanisms in terms of processing speed and weakening of passivating layer, the micro-ECM process has been assisted with a nano-second pulsed laser on an in-house developed hybrid machine-tool. The aim is to uniformly dissolve the NbC matrix and Ni binder with ECM process for a high integrity machined surface. The dissolution and passivation characteristics have been further analysed through a combination of current pulse acquisition and channel profile characterisation. Linear sweep voltammetry and channel machining revealed that the addition of WC has a significant impact on the stability of passive layer. Laser assistance could enhance the material removal for both the NbC grades and promote uniform dissolution, with the effect being more pronounced in the NbC grade without WC (41 % increase in average pulse peak current) due to the weaker passive film. The material dissolution was more localized in LECM of NbC grade with WC due to the strong passivation along the channel walls.

Microstructural and Physical Properties of Yttria Stabilized Zirconia (YSZ) Prepared by Ceramic Injection Moulding (CIM)

Ceramic injection moulding (CIM) is a near net shape process to produce smaller and intricate parts at a competitive cost. However, fine particle size (nano scale) used for such injection moulding process generally leads to agglomeration, higher binder content and critical dimensional shrinkage which results in defects on the sintered components. This study extensively investigates the characteristics of Yttria Stabilized Zirconia (YSZ) for CIM process. YSZ parts were moulded by CIM process that utilized a multi-component binder system using palm stearin (PS) and polyethylene (PE) in 60:40 (vol %) ratio. The powders were characterized using particle size analyzer, pycnometer density and scanning electron microscopic (SEM). The binders were characterized by the pycnometer density, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Powders loading were choosen by the critical powder volume percentage (CPVP) through oil absorption test. YSZ powder was mixed with the binders at different powder loadings ranging from 58 to 60 vol% based on CPVP. The parts were injected moulded, thermal debound, pre-sintered and sintered. The microstructure, green strength and hardness of the sintered part at different powder loadings were investigated. A large porous region was clearly observed at 58 vol% compared to 60 vol%. All samples were sintered at 1350°C, with the highest green strength and hardness were 13MPa and 357.42 HV respectively was given by the sintered part at powder loading of 60 vol.

MoSi2/Al2O3/Feldspar Composites for Injection‐Molded Ceramic Heating Elements

MoSi2 is an electrically conductive material with numerous applications mostly in high‐temperature environments. Herein, the production of MoSi2‐containing resistive heating elements by ceramic injection molding (CIM) is described. The sintered parts consist of MoSi2 particles embedded in a matrix of vitrified feldspar and Al2O3. The conductivity of sintered parts can be tuned precisely by varying the content of the conductive phase. For the development of the injection‐molding feedstock, four binder systems are evaluated. The corresponding feedstocks are injection molded into different geometries in traditional molds as well as in additively manufactured, soluble molds. For each feedstock, a debinding and sintering routine is elaborated based on thermogravimetric measurements. Higher debinding temperature leads to more oxidation of MoSi2 and less conductive samples. Therefore, the conductivity as well as density of sintered parts is used to evaluate the applicability of the feedstocks. Finally, glow tests prove that MoSi2/Al2O3/feldspar composite parts can be used as heating elements and by combining infrared temperature measurement data with computational simulations important material data such as thermal and electrical conductivity and thermal capacity can be obtained reliably.

Regional temperature control in ceramic injection moulding: An approach based on cooling rate optimisation

The injection moulding of ceramic components with uneven wall thickness presents challenges due to differential cooling rates developing in the injected parts, which cause premature solidification of the feedstock at thin features and lead to detrimental defects, worsening in components from green to sintered states. To cope with this, suitable mould thermal control approaches have to be selected and validated, as current control methods are based on the achievement of a uniform cavity surface temperature, which is not tailored to such complex geometries. In this work, a novel thermal control system is proposed, based on regional mould temperatures, implemented with the use of Peltier modules, which locally and independently heat and cool different cavity features according to their thickness. The regional temperature profiles are optimised over time with the use of a coupled Finite Element - Particle Swarm Optimisation (FE-PSO), to achieve uniform cooling rates throughout the moulded components. The performance of this approach is compared to both constant ambient mould temperature and Rapid Heat Cycle Moulding (RHCM) techniques, which instead aim at achieving uniform temperatures throughout the mould cavity surface. Results show that the novel proposed method, based on regional temperature control and uniform cooling rates, promotes the simultaneous solidification of features with a 10-times difference in surface-to-volume ratio. Due to this, in terms of components quality, the novel method brings the advantages of higher dimensional control and reduction of differential shrinkage compared to the other analysed approaches, thus increasing the capability to use injection moulding to manufacture ceramic components characterised by non-uniform wall thickness.

Development of Ceramic Items Injection Moulding Technology Using Computer Modeling

Development of Ceramic Items Injection Moulding Technology Using Computer Modeling

Debinding behaviour and sintering temperature-dependent features of coloured zirconia fabricated by ceramic injection moulding

Zirconia (ZrO2) is one of ceramic materials that has very good mechanical and chemical properties suitable for biomedical applications as well as other industrial applications. ZrO2 ceramics, in fact, has been used in orthodontic dentistry. Nowadays, ZrO2 has been played its role in decorative and jewelry purposes, such as watchcases and artificial stones. Ceramic injection moulding (CIM), a near-net shape manufacturing process that can produce small, complex-shaped components and is suitable for large volume production, is one of the best powder fabrication methods. In this work, CIM was carried out in order to form the coloured-ZrO2 specimens. Binders used in the feedstock preparation are composed mainly of polyethylene glycol (PEG) and polyvinyl butyral (PVB). A laboratory-scaled, plunger-typed injection moulding machine was used to fabricate the coloured-ZrO2 components with various sizes and shapes. Debinding was carried out by water immersion and thermal debinding. Various sintering conditions were also performed. The specimens after sintering were subjected to be characterised and tested. The results showed that the binder removal rates using water related to geometry of the specimens, surface area and volume were taken into account. Sintering temperatures played important roles on properties, microstructure as well as the appearance and shades of the coloured-ZrO2 fabricated by ceramic injection moulding.

MIM2021 Virtual Conference: Highlights from the technical program

The 2021 International Conference on Injection Molding of Metals, Ceramics and Carbides, held on February 23–25, became MPIF’s first virtual conference due to the COVID pandemic. The program included technical presentations from nine countries around the world, including two key-note presentations (already reported in the previous summary article). Studies and comparisons of binder-jetting, laser-powder bed fusion, and filament printing were included, as well as MIM and ceramic injection molding (CIM). The technical papers were interspersed with presentations from exhibitor companies and the conference sponsor, Nitrex G-M Enterprises. The virtual conference was preceded, on February 22, with what has become the traditional one-day PIM tutorial, this year presented virtually by Matthew Bulger.

Tailoring dielectric properties of cordierite-mullite ceramics through Ceramic Injection Moulding

Cordierite-mullite ceramics have been processed by Ceramic Injection Moulding (CIM) for the first time. The comparison with cordierite-mullite ceramics obtained by conventional ceramic process (CP) proves the effect of processing on the structure, microstructure, thermal and dielectric properties. CIM processing favours formation of larger content of mullite phase, a more homogeneous microstructure and reduced porosity than by conventional processed ceramics. These factors strongly condition the dielectric behaviour, which is analyzed by complex impedance formalism up to 850 °C and 1 MHz. The conduction mechanism is thermally activated and the activation energy is ~2.5 times larger in CP than in CIM ceramics. Thermal expansion coefficient is tuned by processing method, ranging from 3.9·10−6 °C−1 to 4.6·10−6 °C−1. All these findings show the strong influence of processing in cordierite-mullite ceramic composites. This work shows that tailoring composition and CIM parameters allow cordierite-mullite composites to precisely fulfill the requirements for future electronic applications.

Manufacturing porcelain components by CIM: Viability of processing different ceramic powders

Ceramic Injection Moulding (CIM) is an advanced powder processing technology launched three decades ago which has become a growing attractive alternative for new technical applications, such as thermal management and wireless charging. Porcelain-type ceramics can allow the introduction of new feedstocks into the CIM market at a competitive cost, in comparison with the conventional alumina and zirconia feedstocks. During the CIM manufacturing process, several factors related to the starting powder characteristics have an influence on the quality and properties of the final components, such as the mixing behaviour and the feedstock flow properties, as well as injection, debinding and sintering parameters. In this work, the viability of three porcelain-based powders to successfully achieve injectable mixtures for CIM is described. The mixing behaviour and the feedstocks flow behaviour as a function of its solids loading is evaluated. In this way, the ideal attributes for a CIM porcelain powder are discussed, studying the first process stages through to the production of a sintered component by injection moulding. Finally, density, hardness, bending strength and microstructural properties of the selected porcelain are investigated and a cost-efficient ceramic feedstock is suggested for aesthetic and electrical applications.