Additive manufacturing (AM) is a crucial development area for high temperature, inorganic and ceramic materials which, using conventional methods, are difficult to process into complex shapes. In particular, carbon/carbon (C/C) composites produced using AM techniques are underexplored compared to other ceramics and ceramic matrix composites. This work investigated and optimized the development of phenolic resin/carbon fiber inks for the material extrusion technique of direct ink writing (DIW) to form C/C composites. Utilizing recent advances in the material extrusion of ceramics, namely the DIW preceramic polymers and preceramic polymer-based suspensions or slurries, we were able to create C/C composites. AM processes can be used to obtain complex geometries and material extrusion processes also facilitate the alignment of high aspect ratio fillers, like carbon fiber, which affects material properties like strength or stiffness. Formulation of material extrusion inks from phenolic resole resin, pitch-based milled carbon fiber as a reinforcement, and a low-density carbon black filler is reported herein. The effects of carbon fiber content and filler, which was used to obtain a printable rheology and appreciable yield stress are discussed in the context of printability.
Abstract Recent advances in large‐scale additive manufacturing (AM) with polymer‐based composites have enabled efficient production of high‐performance materials. Cellulose nanomaterials (CNMs) have emerged as bio‐based feedstocks due to their exceptional strength and sustainability. However, challenges such as hornification and poor dispersion in polymer matrices still limit large‐scale CNM–polymer composite manufacturing, requiring novel strategies. This review outlines an approach starting with atomic‐level simulations to link molecular composition to key parameters like bulk density, viscosity, and modulus. These simulations provide data for finite element analysis (FEA), which informs large‐scale experiments and reduces the need for extensive trials. The strategy explores how atomic interactions impact the morphology, adhesion, and mechanical properties of CNM‐based composites in AM processes. The review also discusses current developments in AM, along with predictions of mechanical and thermal properties for structural applications, packaging, flexible electronics, and hydrogel scaffolds. By integrating experimental findings with molecular dynamics (MD) simulations and finite element modeling (FEM), valuable insights for material design, process optimization, and performance enhancement in CNM‐based AM are provided to address ongoing challenges.
Abstract Engineering curricula have begun to provide opportunities for inclusive and diverse learning. The National Science Foundation (NSF) Integrative Graduate Education and Research Traineeship (IGERT) Program: Global Traineeship in Sustainable Electronics” is an example of one such initiative. The program brought together s an interdisciplinary group of students to study the environmental, economic, and societal aspects of the global electronics lifecycle. The IGERT was designed as a two-year training program with a two-week international trip to India as a key event in the educational experience with an international experience trip in India. There were three cohorts altogether, but the dynamics of each group were substantially different. In the final IGERT cohort, for instance, the students demonstrated a notably high degree of self-motivation and group cohesion. This third cohort actively sought additional experiences outside the original planned courses and trips. Assuming the final IGERT cohort exhibited a higher level of motivation, the aim of this work is to glean insight into what and how specific curriculum design may promote the learning experiences in which students take initiative beyond the scope of the program, especially in interdisciplinary fields. We identified four factors that might influence the experiential learning within a framework incorporating the self-determination theory (SDT) and the expectancyvalue model: the factors considered are value, relatedness, competence, and autonomy. Utilizing a non-experimental approach, we surveyed the last cohort to identify when and why they felt or failed to feel motivated during the program and what curriculum modules were most valuable for their learning experiences. We found that all four factors (value, relatedness, competence, and autonomy) grew throughout the program. In particular, the international workshop in India marks the point when students started to see shared values with their peers; the self-organized seminar course marks the point when students developed the feeling of autonomy. The most valuable aspects of the program were ranked to be international field trips, peers, and team projects. For the latter two aspects, defined in this work as the group dynamic, the most important factors for building a sense of community are group pro-activity, cohesiveness, and attitude.
The main objective of this study was to examine the impact of cellulose nanocrystals (CNCs) in advanced waterborne wood coatings such as polycarbonate urethane (PCU) and hybrid alkyd varnish (HAV) in terms of coating performance, mechanical properties, optical properties, and water permeation and uptake properties. The influence of CNCs on the overall quality of the various waterborne wood coatings was investigated by incorporating different percentages of CNCs. Varying CNC content in coating formulations showed that CNCs are effective for waterborne wood coatings; CNCs offer both higher scratch and impact resistance as compared to neat coatings and have a significant reduction in water vapor permeation through a film with little increase in water vapor uptake at high concentrations. It was observed that the CNC darkened and reduced gloss in the coatings and viscosified the dispersion. These research findings suggest that CNCs are well-dispersed at lower concentrations, but at high concentrations, agglomeration occurred. Thus, while CNCs can give better mechanical and permeation performances at contents of up to 5 wt %, at 1 wt % CNCs can still provide modest scratch and chip resistance improvement without loss of optical properties (gloss and color) while retaining a similar water uptake. Overall, it can be concluded that CNCs have the potential to be used as a reinforcement filler in high-performance waterborne wood coatings.
In nature, cellulose nanofibers form hierarchical structures across multiple length scales to achieve high-performance properties and different functionalities. Cellulose nanofibers, which are separated from plants or synthesized biologically, are being extensively investigated and processed into different materials owing to their good properties. The alignment of cellulose nanofibers is reported to significantly influence the performance of cellulose nanofiber-based materials. The alignment of cellulose nanofibers can bridge the nanoscale and macroscale, bringing enhanced nanoscale properties to high-performance macroscale materials. However, compared with extensive reviews on the alignment of cellulose nanocrystals, reviews focusing on cellulose nanofibers are seldom reported, possibly because of the challenge of aligning cellulose nanofibers. In this review, the alignment of cellulose nanofibers, including cellulose nanofibrils and bacterial cellulose, is extensively discussed from different aspects of the driving force, evaluation, strategies, properties, and applications. Future perspectives on challenges and opportunities in cellulose nanofiber alignment are also briefly highlighted.
