Rheological Properties Research Articles

Lube oil life prediction for heavy earth moving machinery (HEMM): A machine learning approach

Evaluating lubricant life is crucial for maintaining equipment reliability and preventing failures. Conventional methods often depend on original equipment manufacturer recommendations for lubricant changes, which may result in the premature disposal of operationally effective lubricants, leading to economic costs and degrading overall efficiency. The chemical properties of these samples are evaluated by calculating multiple parameters such as total acid number, total base number, oxidation index, soot level, and water contamination. In addition, rheological properties through viscosity index analysis and the tribological properties via friction-wear analysis are determined. In this study, an artificial neural network (ANN) (a four-layer perceptron) and an adaptive neuro-fuzzy inference system (ANFIS) are applied to predict oil conditions based on multiple calculated parameters. Performance and comparison of these advanced mathematical models are evaluated using statistical indices. Overall, the artificial intelligence (AI)-powered approach proved effective in predicting lubricant life for HEMM. Among the AI models, the ANN model demonstrated particularly strong performance, with a correlation coefficient of 0.99 compared to 0.98 for the ANFIS model. Implementing the ANN model could lead to a potential 19% reduction in current engine oil expenses, which would lower operating costs and decrease environmental impact by reducing the frequency of oil disposal.

Microemulsions and Nanoparticles: The Sustainable Future of Drilling Fluids in Oil Exploration

Objective: This study aims to contextualize the advancements in the application of nanoparticles, microemulsions, and nanoemulsions in drilling fluids, highlighting their contributions to the efficiency and sustainability of operations in the oil industry. Theoretical Framework: The research is grounded in principles of nanotechnology and fluid dynamics, analyzing the role of drilling fluids in aspects such as wellbore instability, rheological properties, filtration, and physicochemical characteristics. Method: A systematic literature review was conducted, encompassing scientific articles, conference papers, technical books, and patents. The research included both foundational and recent studies to identify trends and advancements in drilling fluid formulations. Results and Discussion: Drilling fluid formulations have evolved to address challenges such as diverse well geometries, extreme temperature and pressure gradients, and environmental regulations. The incorporation of nanoparticles into drilling fluids has demonstrated benefits such as reduced circulation losses and increased resistance to high pressures and temperatures. Nanoemulsions and microemulsions have shown reduced environmental impact compared to oil-based fluids, along with improved filtration properties, rheology, and thermal resistance compared to water-based fluids. Research Implications: The findings underscore the importance of nanoparticles and nanoemulsion and microemulsion systems for enhancing the efficiency and sustainability of drilling fluids, meeting the demand for environmentally responsible solutions. Originality/Value: This study provides a comprehensive analysis of advancements in drilling fluid formulations, emphasizing the sustainable potential of nanoparticles, nanoemulsions, and microemulsions, and reinforcing their relevance to the future of the oil industry.

Three-Dimensional Printable Magnetic Hydrogels with Adjustable Stiffness and Adhesion for Magnetic Actuation and Magnetic Hyperthermia Applications.

Stimuli-responsive hydrogels hold immense promise for biomedical applications, but conventional gelation processes often struggle to achieve the precision and complexity required for advanced functionalities such as soft robotics, targeted drug delivery, and tissue engineering. This study introduces a class of 3D-printable magnetic hydrogels with tunable stiffness, adhesion, and magnetic responsiveness, prepared through a simple and efficient "one-pot" method. This approach enables precise control over the hydrogel's mechanical properties, with an elastic modulus ranging from 43 kPa to 277 kPa, tensile strength from 93 kPa to 421 kPa, and toughness from 243 kJ/m3 to 1400 kJ/m3, achieved by modulating the concentrations of acrylamide (AM) and Fe3O4 nanoparticles. These hydrogels exhibit rapid heating under an alternating magnetic field, reaching 44.4 °C within 600 s at 15 wt%, demonstrating the potential for use in mild magnetic hyperthermia. Furthermore, the integration of Fe3O4 nanoparticles and nanoclay into the AM precursor optimizes the rheological properties and ensures high printability, enabling the fabrication of complex, high-fidelity structures through extrusion-based 3D printing. Compared to existing magnetic hydrogels, our 3D-printable platform uniquely combines adjustable mechanical properties, strong adhesion, and multifunctionality, offering enhanced capabilities for use in magnetic actuation and hyperthermia in biomedical applications. This advancement marks a significant step toward the scalable production of next-generation intelligent hydrogels for precision medicine and bioengineering.

Formulation and Evaluation of Capsaicin Transemulgel for the Treatment of Arthritis

Capsaicin (CAP)is a non-narcotic analgesic and anti-inflammatory drug used to relieve pain and inflammation associated with rheumatoid arthritis. Transemulgel is a new approach with combination emulsion and gel base having special characteristics dual controlled release for the treatment of various conditions arthritis. The present research work, a novel transemulgel with CAP (F1-F6) was formulated by using different concentration of gellan gum (GG) and xanthan gum (XG) as gelling agents with oil in water emulsion base. No significant drug-excipient interactions were observed in FT-IR studies. To evaluate various characterizations of transemulgel such as pH, spreadability, viscosity, gelation time, drug content, Invitro drug release of gel was examined in phosphate buffer pH-7.4 by Franz diffusion cell technique. The optimized transemulgel of (F5) showed pH of 5.8 ± 0.52 and viscosity of2840 ± 0.65cps. The percentage of drug content in the formulated transemulgel (F1-F6) was observed in the range of 84 to 96%w/w respectively. The optimal transemulgel spreadability was found to be 22.23 ± 0.25g·cm/s. The percentage of cumulative drug release from the formulations (F1-F3) were found to be in the range between 72.85 to 62.18% w/w and the batches (F4-F6) were observed in the range 76.85 to 70.66%w/w at the end of 6h.By considering all the investigated data while increase in concentration of GG and XG were influenced rheological properties, drug content efficiency, the Invitro drug release of transemulgel. The present investigate suggest that the CAP loaded transemulgel can be a promising topical delivery to relieve pain, inflammation and provided greater bioavailability to improve therapy. Keywords: Topical delivery, Transemulgel, Capsaicin, Xanthan gum, Gellan gum, Emulsion, Arthritis

Rheological Behavior of Gassy Marine Clay: Coupling Effects of Bubbles and Salinity

Understanding the rheological behavior of marine clay is crucial to analyzing submarine landslides and their impact on marine resource exploitation. Dispersed bubbles in marine clay (gassy clay) and electrolytes in seawater (e.g., NaCl concentration of 0.47 M) significantly impacts rheological properties. Under low ionic strength and low pore water pressure conditions, dispersed bubbles have a strengthening effect on the yield stress and the viscosity of clays. This effect turns into a weakening effect when the pore water pressure reaches 300 kPa or the ionic strength exceeds 0.18 M. It was proposed that the effect of bubbles, whether strengthening or weakening, was determined by the size of bubbles with respect to the characteristic size of the particle structure formed by clay particles. A theoretical model was developed, which reasonably captures rheological behaviors of gassy clays.

Influence of Graphene, Hydroxyapatite, and Hydroxyapatite‐Niobium Pentoxide Nanoparticles on Polycaprolactone Electrospun Fibers Mats Properties

ABSTRACTPolycaprolactone (PCL) electrospun fiber mats containing varying concentrations of graphene flakes (GF), hydroxyapatite (HAp), and hydroxyapatite with niobium pentoxide (HAp5Nb) were successfully prepared by electrospinning. These composites exhibit great potential in biomedical applications, particularly as scaffolds for bone tissue engineering. The addition of GF enhances the rheological properties of the PCL solution due to the intrinsic properties resulting from their interactions. Additionally, incorporating HAp and HAp5Nb nanoparticles increases the viscosity of PCL‐based solutions, leading to the formation of thinner fiber diameters. The GF, HAp, and HAp5Nb nanoparticles were characterized using transmission electron microscopy (TEM) and x‐ray diffractometry (XRD), while the degree of disorder and heterogeneity of GF was assessed using Raman spectroscopy. The physical and chemical properties of the electrospun fiber mats were also characterized by scanning electron microscopy (SEM), XRD, fourier‐transform infrared spectroscopy (FTIR), and contact angle measurements. The cytotoxicity of PCL‐based electrospun fiber mats containing GF, HAp, and HAp5Nb nanoparticles was evaluated using mouse fibroblasts. Results showed that cell viability with 100% extract from the fiber mats was higher than with pure PCL or Dulbecco's modified Eagle's medium DMEM control, indicating that the samples were non‐toxic and promoted cell growth. This highlights their potential as scaffolds for bone tissue engineering.

Analysis of Morphologic and Rheological Properties of Hyaluronic Acid Gel Fillers to Body Contouring and Its Clinical Correlation.

The demand for minimally invasive body contouring procedures, particularly for gluteal augmentation, has grown significantly. This study evaluates the morphologic and rheological properties of four commercially available hyaluronic acid (HA) fillers used for body contouring and explores their clinical implications. Critical parameters such as storage modulus (G'), loss modulus (G″), complex modulus (G*), and damping factor (tan δ) were measured using oscillatory rheological tests to assess each filler's elasticity, viscosity, and viscoelastic profile. Scanning Electron Microscopy (SEM) was performed to analyze the microstructure of the fillers, providing insights into their microscopic architecture. The results showed differences in mechanical properties and viscoelastic behavior among the fillers. These variations suggest that the choice of filler may need to be tailored to specific body contouring requirements. Understanding these differences is crucial for achieving the best clinical results and patient satisfaction, helping professionals select the most suitable filler for each case.

Enhancing the Rheological and Filtration Performance of Water-Based Drilling Fluids Using Silane-Coated Aluminum Oxide NPs.

For optimizing the drilling efficiency, nanoparticles (NPs) specifically nanometal oxides have been used in water-based drilling fluids (WBDF). Nano metal oxides improve the rheological and filtration characteristics of the WBDF. However, dispersion instability among pristine nano metals shrinks the performance of the nanometal oxides due to high surface energy. Therefore, this study aims to utilize silane-coated aluminum oxide NPs (S-Al2O3) as an alternative to widely used pristine aluminum oxide (P-Al2O3) in water-based drilling fluids. The S-Al2O3 NPs were synthesized using 3-aminopropyl triethoxysilane (APTES). FTIR, XRD, and SEM analyses were carried out to examine the crystalline structure and surface morphology of NPs. Moreover, the rheological and filtration properties of nanowater-based drilling fluids were investigated at low-pressure and low-temperature (LPLT) conditions. The results of experiments revealed that S-Al2O3 NPs significantly upgraded the rheological properties compared to P-Al2O3 NPs. The S-Al2O3 NPs reduced plastic viscosity from 12.6 to 9.6 cP, apparent viscosity from 34.5 to 26.5 cP, and yield point from 46.5 to 39.5 lb/100 ft2. The gel strengths (10 s and 10 min) were reduced from 44.5 to 32 lb/100 ft2 and from 77 to 59 lb/100 ft2, respectively. Furthermore, S-Al2O3 NPs enhanced the filtration performance, achieving a 26% reduction in filtrate loss and forming a thinner, more impermeable mud cake than P-Al2O3 NPs. In conclusion, the application of S-Al2O3 NPs in water-based drilling fluid was found to be effective in improving the rheological properties and controlling the filtrate loss effectively under LPLT conditions. The utilization of silane-coated NPs used in this study will open new and novel doors of research in the fields of both drilling engineering and nanotechnology.

Silicone Rheological Properties for Material Extrusion Additive Manufacturing

ABSTRACTAdditive manufacturing (AM), known as three‐dimensional (3D) printing, uses computer‐controlled materials deposition to fabricate 3D objects by selectively depositing materials, usually in a layer‐wised fashion, to build a 3D object using free‐form fabrication. Integrating silicone elastomers with AM deposition strategies has been of interest due to the important application characteristics of silicones such as excellent mechanical properties, thermal resistance, and chemical inertness. This work presents a study on the shear‐thinning properties of thermally‐curable liquid silicone feedstocks to describe ideal flow and shape‐retention properties for direct ink writing of liquid silicone rubbers. To complement the direct ink writing process developed in this work for silicone AM, flow properties of various silicone feedstocks were identified through measurement of rheological properties using the AM fluid dispenser under various pressures, supported by parallel plate oscillatory shear rheology. A systematic process for evaluating and investigating the AM performance of seven different grades of silicones is introduced. The shape retention, overhang, and dimensional accuracy of these silicones in 3D printing process have been compared and summarized. This systematic evaluation methodology can be applied for silicone material selection and printing of silicone parts with complicated architectures.

Evaluating the breadmaking potential of wholemeal flours from einkorn, emmer, and spelt grown in the Canadian prairies

AbstractBackground and ObjectivesAncient grains like einkorn, emmer, and spelt remain underutilized and underexplored, limiting their market potential. This study evaluates the chemical composition, rheology, pasting, and baking properties of spring growth habit einkorn, emmer, and spelt cultivars grown in the Canadian prairies compared to wholemeal and refined hexaploid wheat.FindingsEinkorn cultivars (CDC Aixe and CDC Marval) had inferior dough mixing properties and the lowest bread loaf volume. CDC Tatra (emmer) bread had a significantly (p < .05) higher specific volume (3.32 mL/g) than Canada Western Red Spring (CWRS) wholemeal bread.ConclusionsResults from mixing and baking indicate that emmer and spelt cultivars have the potential to be used in breadmaking applications, while einkorn cultivars with suboptimal properties need ingredient technology and process modifications to improve their functionalities.Significance and NoveltyThe study was able to identify and characterize an emmer cultivar (CDC Tatra) with excellent mixing and baking properties having the potential as a standalone flour for baking applications. This represents a significant advancement, as prior research had not recognized any emmer cultivars for their suitability in baking. Our results highlight that cultivar‐based assessment is essential in evaluating the end‐use quality of ancient grain species, thereby developing products using such underutilized grains.

Stability and Rheological Properties of Grouts with Waste Glass Powder as Cement Replacement: Influences of Content and Alkali Activator.

Effective recycling and utilization of waste glass is a critical issue that urgently needs to be addressed. This study aims to explore the feasibility of using ground waste glass powder (particle size ≤ 75 μm) as a supplementary cementitious material to partially replace cement in the preparation of low-carbon and environmentally friendly grouting materials. The research systematically evaluates the impact of waste glass powder (WGP) on the fresh properties (particularly the stability and rheological characteristics) of cement-based grouting materials under various conditions, including WGP content (0-40%), the addition of NaOH activator (Na2O content of 4%) or not, and water-solid ratio (w/s = 0.5, 0.65, 0.8, 1.0). The results indicate that, in the absence of activator, the addition of WGP generally increases the amount of free liquid exudation in the grout, reducing its stability; however, under low w/s ratios, appropriate amounts of WGP can enhance stability. When the w/s ratio is high and the WGP content is large, the grout stability decreases significantly. The addition of NaOH activator (Na2O content of 4%) significantly reduces free liquid exudation, enhancing the stability of the grout, especially when the w/s ratio is less than 1.0. Furthermore, the Herschel-Bulkley Model was experimentally validated to accurately describe the rheological behavior of waste glass-cement slurries, with all R2 values exceeding 0.99. WGP and alkaline activator have significant effects on the rheological properties of the grout. Although they do not change its flow pattern, they significantly affect shear stress and viscosity. The viscosity of the slurry is influenced by the combined effects of w/s ratio, WGP content, and alkaline activator, with complex interactions among the three. The application of these research findings in the field of grouting engineering not only contributes to significantly reducing glass waste but also promotes the production of sustainable cement-based composites, lowering carbon dioxide emissions by reducing cement usage, and thereby alleviating environmental burdens.

Probabilistic estimation of rheological properties in subduction zones using sequences of earthquakes and aseismic slip

Abstract Constraining the effective rheology of major faults contributes to improving our understanding of the physics of plate boundary deformation. Geodetic observations over the earthquake cycle are often used to estimate key rheological parameters, assuming specific laboratory-informed classes of viscous or frictional rheological models. However, differentiating between various rheological model classes using only observations of a single earthquake (coseismic and postseismic deformation) is difficult—especially in the presence of coarse spatiotemporal sampling, inherent observational noise, and non-uniqueness of the inverted properties. In this study, we present a framework to estimate key rheological parameters of a subduction zone plate interface using simulations of sequences of earthquakes and aseismic slip, constrained by pre- and postseismic surface displacement timeseries. Our simplified forward model consists of a two-dimensional subduction zone, represented by a discretized planar fault or narrow shear zone, divided into a locked, shallow region (“asperity”) experiencing periodically imposed coseismic events, and a stress-driven creeping section governed by power-law viscoelasticity or rate-dependent friction. Our inverse model fits the rheological parameters of the interface to surface displacement timeseries in a Bayesian probabilistic way. We validate that our proposed framework can successfully recover depth-dependent profiles of effective viscosity using a synthetic dataset of pre- and postseismic observations. Our first set of numerical experiments show that our framework is only mildly sensitive to uncertainties in the rupture history or assumed coseismic slip, making it robust enough to be applied to real observations of subduction zones. Our second set of tests considers the similarities of surface displacement timeseries between synthetic models that model the plate interface either as a shear zone described by power-law viscosity, or a surface described by rate-dependent friction. Here, we find that the ability to fit surface observations using functional or mechanical models assuming frictional behavior does not constitute sufficient evidence to actually infer frictional behavior at depth, as the surface expressions are virtually indistinguishable from deformation generated from models with depth-variable power-law viscous behavior. Based on our numerical experiments, we conclude that studies that aim to infer the mechanical behavior and rheological properties at depth in subduction zones should consider the surface expression from time periods representative of the entire seismic cycle. Graphical Abstract

Direct Ink Writing 3D Printing Polytetrafluoroethylene/Polydimethylsiloxane Membrane with Anisotropic Surface Wettability and Its Application in Oil-Water Separation.

Biological surfaces with physical discontinuity or chemical heterogeneity possess special wettability in the form of anisotropic wetting behavior. However, there are several challenges in designing and manufacturing samples with anisotropic wettability. This study investigates the fabrication of PTFE/PDMS grid membranes using Direct Ink Writing (DIW) 3D printing for oil-water separation applications. The ink's rheological properties were optimized, revealing that a 60% PTFE/PDMS composite exhibited the ideal shear-thinning behavior for 3D printing. Our research investigated the interplay between various printing parameters like the extrusion air pressure, layer thickness, feed rate, and printing speed, which were found to influence the filament dimensions, pore sizes, and hydrophobic properties of the grid membrane. Two distinct grid structures were analyzed for their wettability and anisotropic hydrophobic characteristics. The grid membranes achieved up to 100% oil-water separation efficiency in specific configurations. Separation efficiency was shown to be dependent on factors like intrusion pressure, grid architecture, and the number of layers. This study underscores the potential of DIW 3D printing in creating specialized surfaces with controlled wettability, particularly superhydrophobicity and anisotropy, paving the way for advanced environmental applications such as efficient oil-water separation.

AN OVERVIEW OF PREPARATION AND PROPERTIES OF NANOFLUID AS CUTTING FLUID USING VEGETABLE OIL FOR SUSTAINABLE MACHINING PROCESS

Machining processes such as turning, milling, drilling and grinding are currently required to be environmentally friendly, including cutting fluids whose function is to reduce friction, wear and corrosion. Mineral oil is a cutting fluid that is widely used in the manufacturing industry, but the problem is that it is nondegradable and the raw material has the potential to run out. Therefore, this review article aims to discuss a literature review regarding the solution to this problem, namely the use of nanofluids as cutting fluids made from vegetable oil because not much has been discussed in Indonesia. Vegetable oils are more environmentally friendly, the ingredients are abundant in nature, and have excellent lubrication properties. The characteristics of nanofluids as cutting fluids such as thermophysical, rheological and tribological properties are also explored in this review article to find out the latest research. According to the literature, it is found that the use of nano-cutting fluid made from vegetable oil can improve thermal properties and tribological performance to reduce friction and wear in the machining process due to superior cooling and lubrication to produce green manufacturing in the future.

Insights on the role of cryoprotectants in enhancing the properties of bioinks required for cryobioprinting of biological constructs

Preservation and long-term storage of readily available cell-laden tissue-engineered products are major challenges in expanding their applications in healthcare. In recent years, there has been increasing interest in the development of off-the-shelf tissue-engineered products using the cryobioprinting approach. Here, bioinks are incorporated with cryoprotective agents (CPAs) to allow the fabrication of cryopreservable tissue constructs. Although this method has shown potential in the fabrication of cryopreservable tissue-engineered products, the impact of the CPAs on the viscoelastic behavior and printability of the bioinks at cryo conditions remains unexplored. In this study, we have evaluated the influence of CPAs such as glycerol and dimethyl sulfoxide (DMSO) on the rheological properties of pre-crosslinked alginate bioinks for cryoprinting applications. DMSO-incorporated bioinks showed a reduction in viscosity and yield stress, while the addition of glycerol improved both the properties due to interactions with the calcium chloride used for pre-crosslinking. Further, tube inversion and printability experiments were performed to identify suitable concentrations and cryobioprinting conditions for bioinks containing CPAs & pre-crosslinked with CaCl2. Finally, based on the printability analysis & cell recovery results, 10% glycerol was used for cryobioprinting and preservation of cell-laden constructs at −80 °C and the viability of cells within the printed structures were evaluated after recovery. Cell viability results indicate that the addition of 10% glycerol to the pre-crosslinked bioink significantly improved cell viability compared to bioinks without CPAs, confirming the suitability of the developed bioink combination to fabricate tissue constructs for on-demand applications.Graphical abstractEffect of cryoprotectants on the viscoelastic behavior of bioinks and cell recovery in cryobioprinted tissue constructs.

The Physicochemical and Rheological Properties of Green Banana Flour-Wheat Flour Bread Substitutions.

Functional foods are currently receiving increasing popularity in diet modification. Green bananas contain far more dietary fiber (DF) and resistant starch (RS) than mature bananas. The potential for integrating these vital components into food, such as bread, has expanded. Thus, this study aimed to examine the physicochemical and rheological behavior of wheat flour dough after the addition of varying amounts of Australian, green banana flour (GBF) substitutions (5, 10, 15, 25, and 30%). Using MixoLab 2, we recorded the rheological parameters of the dough that had GBF substitutions. Additionally, the flour color ('L*', 'a*', and 'b*' value) and crumb cell structure analysis were evaluated. Although increasing the amount of GBF replacement generally improved dough quality with all banana cultivars, GBF from Cavendish and Ladyfinger showed a greater improvement than Ducasse. Improved dough mixing stability and increased viscosity, starch gelatinization, and retrogradation were all predicted to contribute to longer bread shelf life. RS content of the enriched bread increased significantly with both Ladyfinger and Ducasse (2.6%), while Ladyfinger bread had the highest DF (9.1%). With increasing GBF, L*, a*, and b* values were changed considerably with a strong linear correlation. A MATLAB analysis indicated substantial variations across samples regarding the small, medium, and total air space counts based on 10% banana flour as a standard level of addition. In conclusion, the processing properties and nutritional value of wheat flour can be enhanced by replacing specific proportions of wheat flour with green banana flour without major detrimental effects on dough processing attributes and thus highlight the possibility of utilizing GBF from different banana varieties for use in fine-tuning composite flour developments.

Synthesis, characterization, rheological properties of β-cyclodextrin-modified polyacrylamide

Synthesis, characterization, rheological properties of β-cyclodextrin-modified polyacrylamide

Comparative analysis of new-generation thermoplastic polymers: Cyclic olefin copolymer and polycarbonate urethane elastomers

In this study, the thermal, rheological, mechanical, and viscoelastic properties of two new-generation thermoplastic polymers, namely cyclic olefin copolymer (COC) and polycarbonate urethane (PCU) elastomers, were compared to those of a conventional thermoplastic elastomer, thermoplastic polyurethane (TPU). Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used for thermal examinations, while rheological, tensile, and solid-state creep tests were used for viscoelastic and mechanical analyses. The DSC results revealed that all elastomers had two different T g values, which were −23 and 7.5°C for PCU, −40 and 95°C for TPU, and 4 and 55°C for COC. Moreover, PCU had an amorphous and more compatible structure than PCU and TPU. In the DMA, it was also observed that COC melted at approximately 90°C, while PCU and TPU melted at about 155°C. In the tensile tests, it was observed that COC showed higher strength at 30°C, but it lost its strength more effectively than the other polymers with increasing temperature and exhibited similar performance to all specimens at 50°C. Finally, in the solid-state creep tests, COC exhibited the highest creep resistance at 30°C, while its creep strain increased with temperature more effectively than those of the other elastomers.

Reversible Thixotropic Rheological Properties of Graphene-Incorporated Epoxy Inks for Self-Standing 3D Printing.

As three-dimensional (3D) printing has emerged as a new manufacturing technology, the demand for high-performance 3D printable materials has increased to ensure broad applicability in various load-bearing structures. In particular, the thixotropic properties of materials, which allow them to flow under applied external forces but resist flowing otherwise, have been reported to enable rapid and high-resolution printing owing to their self-standing and easily processable characteristics. In this context, graphene nanosheets exhibit unique π-π stacking interactions between neighboring sheets, likely imparting self-standing capability to low-viscosity inks. Herein, we develop a thermally curable graphene-incorporated epoxy ink system that exhibits shear-thinning characteristics and upright standing capability owing to its high static yield stress (∼1,680 Pa). The reversible liquid-to-solid phase transition of the composite ink, absent in the pristine epoxy ink, is clearly identified by its viscoelastic properties and dynamic yield stress. This thixotropic composite ink enables the continuous filament printing of 10 stacked layers without the spreading of injected filaments. Significantly, the 3D-printed composite structure, post-thermal curing, exhibits robust structural integrity and is free from weld lines or voids at the stacked interfaces. Combined with the clearly elucidated processing-structure-property relationships of the ink system, our results highlight its potential for a wide spectrum of applications.

An Investigation of the Influence of Paste's Rheological Characteristics on the Tensile Creep of HVFAC at Early Ages.

The rheological properties of concrete paste significantly influence its tensile creep behavior. In this study, the tensile creep behavior of high-volume fly ash concrete (HVFAC) employing the same cementitious pastes was experimentally investigated, and the rheological properties of the paste containing a high volume of fly ash using the nanoindentation (NI) technique was investigated in order to explore the influence of the paste's rheological properties (such as micro-mechanical properties and microscopic creep) on the early-age tensile creep of HVFAC. The results demonstrated that the micro-strain of paste containing a high volume of fly ash (HVFA) showed a larger value than that without fly ash. As the test age extends, a decreasing trend in microscopic creep was observed which could be attributed to the growth of the content of HD C-S-H (high density C-S-H) gel. Moreover, within the same age period, the experimental data revealed that the incorporation of fly ash resulted in the reduction of the values of the creep modulus C and characteristic time τ. The effects of fly ash dosages and loading age on the creep properties of concrete was consistent with the micro-creep properties of the cementitious paste. The tensile specific creep values derived from the ZC ("ZC" are initials for the word ''self-developed" in Chinese) model based on nanoindentation data closely match those obtained from experiments.