Slurry Formulation Research Articles

Release of Redox Additives Via Megasonic Energy for High Selectivity/Low-Stress STI CMP

The advancements in a wide array of semiconductor manufacturing processing have been pivotal for the extension of Moore’s law the Chemical Mechanical Planarization (CMP) process has become an area of focus due to the stringent surface topography requirements. CMP utilizes complex slurry formulations containing abrasive nanoparticles and additives to reduce substrate defectivity and achieve angstrom-level uniformity. One area that has gained significant attention is Shallow Trench Isolation (STI), where the modulation and control of the surface oxidation state of the ceria, specifically the Ce3+ state, is critical to TEOS removal. In the Ce3+ state, defect states (i.e., oxygen vacancies (Ovacs)) on the surface are highly electron deficient (i.e., electrophilic) and allow the nucleophilic substrate to complex. By modulating the electrophilic properties of the particle, the kinetics of surface complexations required for effective TEOS removal can be controlled. This work focuses on developing stimuli-responsive capsules that can be added to STI slurry formulations to promote the controlled release of redox-active additives that can be used to drive the oxidation state of the CeO2 nanoparticle (Ce3+/Ce4+). By encapsulating the additive in a polymeric system, the reactive properties of the slurry are limited until the additive is released. In this work, megasonic action was employed to disrupt the capsules releasing the additives on demand to facilitate the modulation of the CeO2 surface redox states. Results have shown that the addition of a controlled-release capsule with an additive resulted in the increase of Ovacs at the CeO2 surface. This led to an increase from 1800 Å/min to 3450 Å/min using a constant 2.0 W/cm2 continuous flow megasonic flux. Furthermore, the overall defectivity decreased significantly with respect to both particle contamination and surface scratching. Lastly, the nature of the polymeric capsule has been shown to enhance selectivity between TEOS and silicon nitride and preliminarily appears to be megasonic flux dependent.

Elimination of delamination cracks in ceramics manufactured using LCD stereolithography

LCD stereolithography of ceramics allows the creation of ceramic parts with unprecedented resolution for various applications from medical tooling to archeological restoration. However, the manufacturing of a delamination cracks-free sintered part using LCD stereolithography has been an arduous challenge in both industrial and academic research. This contribution is a guide for the elimination of such delamination cracks. Photo-rheology, instrumented indentation tests, UV/Vis spectrophotometry and multiple microscopy techniques were used to analyze the formation of delamination cracks and to identify their culprits. It was found that proper particle dispersion, sufficient air extraction, optimized slurry formulation, optimized printing parameters and sound design principles jointly contribute to the manufacturing of a delamination cracks-free ceramic part using LCD stereolithography. This research addresses each of the aforementioned factors, with the goal of improving the quality of ceramic parts and increasing their functionality for various applications.

Forming deviation coupling model and control method in the photopolymerization process of ceramic slurry

In the process of photocuring using ceramic slurry, the scattering of ceramic particles is widely acknowledged as the primary cause of deviations. However, when aiming to minimize scattering deviations for the production of intricate structures, it is crucial to also consider deviations resulting from resin shrinkage, an aspect that has been overlooked in previous research. This study successfully reduced scattering deviations by incorporating graphite as a light absorber. This approach enabled the evaluation and analysis of the impact of shrinkage deviations on forming deviations. Experimental results investigating deviations in size and shape across various feature structures demonstrated the substantial impact of shrinkage deviations on the final forming deviations. By combining theoretical analysis with empirical findings, this study proposes a coupled model that accounts for the combined effects of scattering deviations and shrinkage deviations. Additionally, a control method is introduced to enhance forming accuracy by compensating for scattering deviations using shrinkage deviations. Moreover, it elucidates the variation curve of forming deviations with the addition of graphite under different photocuring parameters. Ultimately, this model facilitated the enhancement of ceramic slurry formulation and photocuring process parameters, enabling the high-precision printing of intricate ceramic core molds with incorporated grids.

Progress of Dispersants for Coal Water Slurry

Dispersants, serving as an essential raw material in the formulation of coal water slurry, offer an economical and convenient solution for enhancing slurry concentration, thus stimulating significant interest in the development of novel and efficient dispersants. This paper intends to illuminate the evolution of dispersants by examining both the traditional and the newly conceived types and elaborating on their respective mechanisms of influence on slurry performance. Dispersants can be classified into anionic, cationic, amphoteric, and non-ionic types based on their dissociation properties. They can be produced by modifying either natural or synthetic products. The molecular structure of a dispersant allows for further categorization into one-dimensional, two-dimensional, or three-dimensional structure dispersants. This document succinctly outlines dispersants derived from natural products, three-dimensional structure dispersants, common anionic dispersants such as lignin and naphthalene, and amphoteric and non-ionic dispersants. Subsequently, the adsorption mechanism of dispersants, governed by either electrostatic attraction or functional group effects, is elucidated. The three mechanisms through which dispersants alter the surface properties of coal, namely the wetting dispersion effect, electrostatic repulsion effect, and steric hindrance effect, are also explained. The paper concludes with an exploration of the challenges and emerging trends in the domain of dispersants.

Roll-to-roll double side electrode processing for the development of pre-lithiated 80 F lithium-ion capacitor prototypes

Lithium-ion capacitors (LICs) show promise to help lithium-ion batteries (LIBs) and electrical double layer capacitors (EDLCs) in giving response to those applications that require an energy storage solution. However, pre-lithiation is a major challenge that needs to be tackled in order to develop efficient and long-lasting LIBs and LICs. In this work, we report for the first time the scale-up and utilization of sacrificial salts (dilithium squarate, Li2C4O4) as a pre-lithiation strategy in a LIC prototype fabricated in a pilot line. The synthesis of the sacrificial salt is scaled-up to produce 1 kg and is later incorporated in the positive electrode during the slurry formulation. After in-depth process optimization, 12 meter of a double side electrode are fabricated, achieving a high mass loading of 5.5 mg cm−2 for the HC negative electrode, and 14 mg cm−2 for the positive electrode accounting both the activated carbon and the dilithium squarate. On account of the satisfactory mechanical and electrochemical behaviour of the electrodes, multilayer pouch cell LIC prototypes are fabricated reaching 80 F each. Pre-lithiation is completed during the first ten cycles and after the required gas exhaustion, electrochemical performance of prototypes is also satisfactory. Moreover, fabricated pouch cells overcome a float test of 1600 h at 50 °C showing a capacitance retention of 84.3%. These results give clear evidence for the potential use of this strategy in real products and can foster research in the field to promote pre-lithiation by means of sacrificial salts as the final solution to the pre-lithiation step, both for LIBs and LICs.

Design and Application of a New Visible Light-Curing 3D Printing Platform

In order to solve the safety problems that exist in traditional charging technology, a new visible light-curing 3D printing platform and energetic slurry formula were designed. Within them, the formula of light-curing slurry is 60.46% EA/PUA (prepolymer), 37.21% PETA/HDDA/BA (active diluent monomer), 0.47% CQ (visible light initiator), 0.93% DMT (curing accelerator), and 0.93% additive. The curing time of visible light-curing paste is 7.5 s, the viscosity is 22 6 mPa·s, the curing hardness is 2 H, the gel rate is 96.67%, the shrinkage rate is 98.35%, and the curing depth is 9.41 mm. The optimal formulation of energetic slurry is 20% visible light-curing slurry, 57.72% AP, 15.28% Al and 7% RDX. The 3D printing energetic powder column has a smooth surface, uniform filler distribution, a flat surface, no protrusions or other defects, and good matching. The average burning rate is 1.165 mm·s−1, the combustion is stable, and the maximum burning light intensity is 2.053 cd.

Analysing the role of a bio-surfactant extracted from Colocasia esculenta (L.) Schott on the stabilization of high concentrated iron ore slurry for transportation

ABSTRACT. The transportation of minerals/ores in form of slurry through pipelines is an alternative, effective and also eco-friendly mode of transportation. Surfactants extracted from the plant sources are gaining high interest for the formulation and stabilization of high concentrated solid-water slurries. In this work, the role of a novel bio-surfactant extracted from Colocasia esculenta (L.) Schott on the stabilisation of iron ore slurry (IOS) was studied and reported first time. The collected iron ore powder (IOP) and dried IOS samples were analysed with the help of XRF, XRD, SEM and EDS analysis. The results confirmed that the surfactant molecules (present in aqueous Colocasia esculenta (L.) Schott) coated well on iron surface and forms an effective barrier between the iron ore (IO) particles. The studied rheological parameters for the slurry indicated non-Newtonian flow behaviour.
 KEY WORDS: Iron ore slurry, Colocasia esculenta (L.) Schott, XRD, SEM, rheological measurements
 Bull. Chem. Soc. Ethiop. 2023, 37(6), 1459-1470. DOI: https://dx.doi.org/10.4314/bcse.v37i6.13

Fabrication and Characterization of Freeze-Cast Tubular Solid Oxide Cells

Increasing triple phase boundaries (TPBs) and reducing gas diffusion limitation in electrodes of solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) have always been a goal for highly desirable electrochemical performance. Freeze-casting (also called ice-templating) is a promising method to produce hierarchically arranged porous ceramics with aligned and directional pores that could assist to reach such a goal. After reviewing the previous work on ceramic freeze casting, we focused on optimizing the processes to better engineer tubular supports for SOFC as well as SOEC applications. Although the optimized process does not have too many constraints on the types of ceramic materials (except particle size and surface area), we selected the commonly used 8 mol.% yttria stabilized zirconia (8YSZ)/NiO composite material set as a starting point. Cast slurry formulations, cast temperatures, slurry feeding methods and freeze-drying conditions were studied. Microstructures of the tubular parts prepared at various conditions were examined. Finally, as an example for SOFC application, the fuel cell performance was reported. Figure 1

Feasibility of Water Hyacinth Ash as an Accelerator in Cement Slurry Formulation

Cement is primarily used in drilling operations to protect the casing against the corrosive tendency of formation fluid and to support the casing with the external load on and around it. Cement slurry is formed by mixing water with Portland cement or with cement containing various essential additives as the case may be and pumping it down through to critical points in the annulus around the casing using various techniques. Class G cement is widely used in cementing jobs because it allows the use of accelerators and retarders for wide range of well depths and temperatures. Due to wait-on-cement time before commencement of drilling of the next section of the well, it is necessary to reduce the waiting time and it ripple effects on cost of drilling by introducing accelerator to the cement slurry. The chlorides of calcium, potassium and sodium are the commonly used accelerators. Water hyacinth ash have been known to contain high percentage of calcium, potassium and chlorine, these elements readily combine with water to form potassium chloride and calcium chloride of which both are used as accelerator additives in cement slurry formulation. The utilization of these compounds in water hyacinth ash as accelerator additives would be a major breakthrough in cementing jobs especially in shallow section of the wells. Locally sourced water hyacinth plants were dried and combusted in air, the ash was then activated with water and filtered. The filtrate was used to determine the thickening time of class G cement slurry and the results obtained was compared with that of inorganic calcium chloride. The thickening times at the various set temperatures for this experiment were close to the inorganic calcium chloride used. Though, the thickening time of cement slurry is dependent on temperature, the concentration of the accelerator in the slurry also affect it.. It was found out that water hyacinth ash reduces the thickening time of class G cement slurry comparatively and therefore, should be considered as accelerator additive in the formulation of oil well cement slurry for accelerating the cement setting time.

Research on the gel casting process and flexural strength of high-stability alumina ceramics

Gel casting is an advanced wet-forming method for ceramics. In this paper, Isoabm 104 is selected as the dispersant and gelation agent for gel casting. The optimization of gel casting slurry and the preparation of the green and sintered alumina bodies are investigated. TAC reduces the viscosity of the slurry significantly due to electrostatic interaction. Isopropanol alcohol and vacuum tank eliminates the slurry’s air bubbles, thus improving the density of green bodies. A staged drying process is necessary to produce smooth and defect-free green bodies. After optimization of the slurry formulation and gel casting process, alumina ceramics with a Weibull modulus of 11.1 are successfully prepared.

Two-Direction Prediction Method of Drilling Fluid Based on OS-ELM for Water Well Drilling

In this study, a drilling fluid prediction method based on an online sequential extreme learning machine (OS-ELM) is proposed, which is prepared for water well drilling on the muddy clay formation of Tarim Basin, Qinghai Province. First, we investigated the mechanism linking mix ratio to fluid performance, allowing us to employ an OS-ELM algorithm derived from the extreme learning machine. Particularly, the proposed prediction method is bidirectional to identify an appropriate slurry formulation. The forward prediction model is established to predict the fluid performance, where the mud additive contents are inputs, and the drilling fluid properties parameters are outputs. Correspondingly, the backward prediction model is established to modify the slurry formula, where differences in the drilling fluid properties are inputs and percentages of slurry additives amount are output. The simulation results show that the two-direction OS-ELM prediction model can better predict the drilling fluid properties in water well drilling.

Parameter Optimization for Printing Barium Titanate Piezoelectric Ceramics through Digital Light Processing.

Digital light processing (DLP) technology has emerged as a promising 3D printing technology with the potential for the efficient manufacturing of complex ceramic devices. However, the quality of printed products is highly dependent on various process parameters, including slurry formulation, heat treatment process, and poling process. This paper optimizes the printing process with respect to these key parameters, such as using a ceramic slurry with 75 wt% powder content. The employed degreasing heating rate is 4 °C/min, the carbon-removing heating rate is 4 °C/min, and the sintering heating rate is 2 °C/min for heat treatment of the printed green body. The resulting parts are polarized using a poling field of 10 kV/cm, a poling time of 50 min, and a poling temperature of 60 °C, which yields a piezoelectric device with a high piezoelectric constant of 211 pC/N. To demonstrate the practical application of the device, its use as a force sensor and magnetic sensor is validated.

Fabrication and Characterization of Freeze-Cast Tubular Solid Oxide Cells

Increasing triple phase boundaries (TPBs) and reducing gas diffusion limitation in electrodes of solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) have always been a goal for highly desirable electrochemical performance. Freeze-casting (also called ice-templating) is a promising method to produce hierarchically arranged porous ceramics with aligned and directional pores that could assist to reach such a goal. After reviewing the previous work on ceramic freeze-casting, we focused on optimizing the processes to better engineer tubular supports for SOFC as well as SOEC applications. Although the optimized process does not have too many constraints on the types of ceramic materials (except particle size and surface area), we selected the commonly used 8 mol.% yttria stabilized zirconia (8YSZ)/NiO composite material set as a starting point. Cast slurry formulations, cast temperatures, slurry feeding methods and freeze-drying conditions were studied. Microstructures of the tubular parts prepared at various conditions were examined. Finally, as an example for SOFC application, the fuel cell performance is reported.

Optimizing the Ceramic Slurry Formulation and Process Conditions for DSW Printing

An 3D printing is a popular additive manufacturing tool that attracts attention from many sectors and direct slurry writing (DSW) printing is a suitable technique for creating functional ceramic material. This study investigates the suitable formula with various additives and binders and the process conditions that influence DSW printing quality. To combine the unique properties of PVP and PEG binders and attapulgite, various ceramic slurry formulas of attapulgite and TiO₂mixture were prepared for direct slurry writing (DSW) printing. Establishing both qualitative and quantitative assessments on the rheological outcomes, the ceramic slurry formula, printing parameter, drying, and sintering conditions, and the binder ratio for ceramic slurries was optimized. The results showed that the most optimal ratio for ceramic slurries is with 10% PVP or 5% PEG binder and the optimal attapulgite:TiO₂ ratio is 1:1, which the slurry showed no cracking or deformation when air dried, as well as no collapse and cracking after 900 C sintering. The optimized printing parameters for attapulgite-based ceramic slurry printing layer heights of 0.8 mm, the printing pressure of 0.10 MPa, and the printing speed at 20 mm/S. XRD confirmed that TiO₂ is a rutile phase. The stable and less active rutile phase of TiO₂ as a photocatalyst is confirmed by the inhibition zone test and growth inhibition assay. SEM results further showed agglomeration of TiO₂ after high-temperature sintering. This study lays a foundation for the attapulgite application in DSW printing to take advantage of its large specific surface areas.

3D printing of doped barium-titanate using robocasting - Toward new generation lead-free piezoceramic transducers

Lead-free piezoelectric ceramics, most commonly prepared via conventional process based on a solid-state synthesis, can be used as acoustical transducers or sensors in many application fields. Particularly in some applications where specific geometries are desirable, the need of complex, time consuming, and costly operations could make conventional process inappropriate. This paper proposes an alternative solution based on additive manufacturing (AM), which is of great interest to control and shape the structure in an automatic manner. A formulation of ceramic slurry, consisting of 80%wt doped barium titanate (BT) and organic mixture, was investigated. The synthesized slurry is revealed to be compatible with the robocasting technique while maintaining good mechanical strength after debinding and sintering steps. Empirical measures together with microscopic analysis confirm high densities of the printed BT ceramics (∼ 95% after sintering), which is consistent to those obtained in literatures. To better assess the material and process performances, microstructural, dielectric and piezoelectric characterizations are conducted on both 3D printed and conventional BT ceramics. The results demonstrate that the printed samples give rise to excellent dielectric and piezoelectric properties (d33 coefficient of 260 pC/N and dielectric constant of 1800), which are very close to the values obtained by conventional method on the same composition. As only a few and recent works have been found in the literatures on such systems, this study highlights the considerable and growing potential of robocasting techniques in the field of piezoelectric ceramics. The obtained d33 coefficient is revealed as the highest value reported for printed BT doped systems.

Innovative Ceramic Forming Techniques for High-Strength, Low-Density Components

The development of high-strength, low-density ceramic components is a critical area of research in the field of material sciences and mechanical engineering, with potential applications in aerospace, automotive, and biomedical industries. In this paper, we present innovative ceramic forming techniques that enable the fabrication of high-performance ceramic components with unprecedented mechanical properties. We introduce a novel hybrid approach that combines the advantages of both additive manufacturing and traditional ceramic forming methods, such as slip casting and injection molding. By utilizing a customized ceramic slurry formulation and a modified 3D printing process, we successfully produced complex-shaped components with a uniform microstructure and enhanced mechanical properties. The resulting ceramic components exhibited a significant increase in flexural strength and fracture toughness compared to conventionally processed ceramics, while maintaining a low density. Furthermore, we conducted a comprehensive microstructural analysis using scanning electron microscopy (SEM) and X-ray diffraction (XRD) to elucidate the underlying mechanisms responsible for the improved mechanical performance. The findings of this study provide valuable insights into the potential of innovative ceramic forming techniques for the development of high-strength, low-density ceramic components, and pave the way for their widespread adoption in various engineering applications.

Waste-based biopolymer slurry for 3D printing targeting construction elements

The construction industry consumes significant quantities of mineral-based materials, thereby causing pollution and raw material depletion. To meet projected demands for new buildings, while simultaneously reducing the use of non-renewable materials and fossil-based carbon, there is therefore a strong drive to develop alternative, renewable materials to replace those currently used in this sector. In the present study, we investigate the formulation of waste-based biopolymer slurries for 3D printing as a path towards more sustainable construction elements. The printing formulation was based on xanthan gum as a binder with lignocellulosic waste fibres and particles for reinforcement. At the same time, flow properties were controlled using a combination of bio-based plasticiser (glycerol) and water. First, the amounts of water, plasticiser and waste fillers were optimised to minimise shrinkage and deformation while obtaining the best possible mechanical properties after drying. Different reinforcing fillers were investigated, and it was proven that a minor addition of inorganic material (vermiculite) could significantly improve the material’s mechanical properties during printing and in its final form after drying. Furthermore, it was shown how using calcium ions could enhance the binding effect of the xanthan gum and how combining it with an increase in binder concentration could improve the early-age strength of the printed material. The optimised formulations were proven suitable for 3D printing. The addition of vermiculite improved weathering resistance and stability during printing (shrinkage and height), which was illustrated in a bench-scale printing test. • Water-based slurries help to combine waste and bio-based materials for 3D printing at the architectural scale. • Plasticiser, water, binder and fillers were varied to achieve an optimised formulation balance between flowability and final mechanical properties. • Using calcium ions as ionic cross-linker enhances the performance of the binder, thereby improving the 3D printing performance of slurry. • The small addition of vermiculite doubles the mechanical properties of the material and improves its weathering resistance and 3D printing performance.

Surfactant induced catastrophic collapse of carbon black suspensions used in flow battery application

HypothesisCarbon black particles act as electronically conductive additives in the slurry electrodes used in electrochemical redox flow batteries. Modifying the carbon black slurry formulation with the addition of a nonionic surfactant could impart improved particle dispersion, gravitational stability, and flowability leading to better battery performance. ExperimentsCarbon black particles were dispersed in 1 M H2SO4 with volume fractions Φ = 0.01 to 0.06 and a nonionic surfactant (Triton X-100) concentration of csurf. = 0, 0.05, and 0.1 M. Particle size was characterized using microscopy and surfactant adsorption using UV–vis spectroscopy. Sedimentation kinetics was measured using a custom camera set-up that tracks the height of the settling particle bed. Rheology experiments were conducted to measure linear viscoelasticity and shear flow behavior. FindingsThe sedimentation dynamics of the slurry resembled that of a gel collapse. At short times we observed fast sedimentation associated with structural gel collapse and at long times very slow sedimentation associated with compaction of the sediment. Rheological investigations revealed that the slurry indeed behaved like colloidal gels. Addition of nonionic surfactant at α (= (csurf./cCB)) < 0.75 improved particle dispersion and increased gel elasticity. However, α> 0.75 led to a weaker gel that exhibits a fast ‘catastrophic collapse’ under gravity.

Structuring Cu/ZnO/Al2O3 catalyst for methanol synthesis: Slurry additive effect in the washcoating method

The best slurry formulation to prepare a structured catalyst for methanol synthesis reaction by washcoating method was investigated. The effect of different inorganic oxide colloids in the slurry preparation of Cu/ZnO/Al2O3 catalyst was studied: colloidal ZnO, SiO2, and Al2O3. The addition of all these colloids showed an improvement in adherence obtained on Fecralloy® monoliths, but Al2O3 exhibited the best performance. Adherence >80% was obtained with a lower amount of Al2O3 than with the other colloids. Nevertheless, the addition of these additives changes the catalytic properties of the parent catalyst. Adding a high amount of colloids decreases the copper metallic surface area which is the active phase of the methanol synthesis reaction. Moreover, the addition of Al2O3 gave rise to the dehydration of methanol to dimethyl ether (DME) due to the high acidity that Al2O3 presents. Something similar happens but to a less extent with SiO2, which present weak acidity. In contrast, the basic character of ZnO neutralizes the parent catalyst's low acidity reducing the selectivity to DME. Finally, the slurry formulation containing 10% Al2O3 exhibited the best methanol yield. Hence, a methanol synthesis structured catalyst was successfully prepared with similar activity to the powder catalyst.

Formulation and characterization of zinc slurries for zinc slurry – Air redox flow battery: A rheological approach

This study presents rheometry as an optimization tool to increase discharge performance of a zinc slurry - air redox flow battery (RFB). Incorporation of electrode suspension slurry to metal-air batteries, in which dense metal solid microparticles are suspended in a conductive fluid with the aid of gelling agents, was investigated. Electrochemical performance of zinc anode slurries was characterized in a single redox flow battery cell in discharge mode. Rheological behavior of each of the slurries is investigated and the key parameters underlying the cell performance were determined. Combined rheological and electrochemical effects were examined and an optimal PAA concentration of 0.40 wt % was found for the zinc slurry system, in which slurry stability is not compromised and conductivity is satisfactory. Furthermore, at the reported gelling agent optimal concentration, a maximum peak power density of 24 mW/cm2 is obtained from polarization curves, improving previous reported performances using the same cell configuration by a factor of 2.4. These results bring more understanding in the development of slurry-based RFBs with a rheometric approach.