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Owing to freedom of design, simplicity, and ability to handle complex structures, additive manufacturing (AM) or 3D printing of ceramics represents a promising enabling technology and has already been used to produce geometrically complex ceramic components and ceramic metamaterials. Consequently, novel applications for additively manufactured ceramics, which leverage their structural, high temperature, and chemical-resistant properties, have been proposed in areas ranging from electrical engineering and micro/nanoelectronics to chemical engineering to biology. Polymer derived ceramics (PDCs) represent a relatively new class of materials within additive manufacturing. PDCs enable the development of ceramic parts patterned via low-cost polymer 3D printing methods followed by pyrolysis in a high temperature process in which the polymer itself forms a ceramic often in the absence of any ceramic filler. PDCs have served as a feedstock for various 3D printing techniques for which a wide range of physiochemical factors can be tailored to optimize the ceramic manufacturing processes. In particular, the silicon and carbon-rich polymeric microstructure of PDCs offers a high degree of tunability and potential to achieve a closely defined combination of functional, thermomechanical, and chemical properties. In this review, we cover mechanisms underlying the design and manufacture of ceramics via 3D printing and pyrolysis of preceramic polymers, focusing on chemical formulations, printing technologies, and the mechanical performance of the ceramic network from microscale to scale. We also summarize experimental data from the literature and present qualitative and quantitative comparisons between different AM routes to provide a comprehensive review for 3D printing of PDCs and to highlight potential future research.

Abstract Natural suture structures, characterized by hard segments joined along a patterned weak interface, are found to provide unique toughening mechanisms for brittle bulk biological materials. Hierarchical ceramic sutures inspired by white‐tailed deer crania and diabolical ironclad beetle exoskeletons are developed using a biomimetic approach. Overlapping geometries unlock twin energy absorption mechanisms. Ceramics with Surlyn‐infiltrated precision laser‐cuts are fabricated using a semi‐automated and smart advanced manufacturing platform. A parametric study comprising four‐point bending, fracture toughness, and tensile tests is conducted to evaluate toughness, strength, and stiffness with geometrical interlocking in two hierarchical orders. Digital image correlation is utilized to analyze the local toughening mechanisms and failure modes in the fracture tests. For all three metrics, the panels with second‐order hierarchy outperform the anti‐trapezoidal equivalents. The ceramic sutures show up to 590%, 340%, and 700% improvements in energy absorption in the tensile, bending, and fracture tests, respectively, owing to the optimal first‐ and second‐order interlocking angles. The high‐order fractal interlocking at multiple scales and overlapping teeth are found to provide high flexibility and failure resistance, whereas progressive fracture mechanisms delay catastrophic failure by up to 50%. The concept of hierarchical suture can lead to industrially applied ceramic systems with tailored mechanical performances.

Tunable energy absorption achieved through grading of lattice structures shows high potential to be used in lightweight cellular cores for energy absorbing structures. This study investigates structurally graded and multi-material lattices consisting of plate-based octet unit cells, under quasi-static compression, to assess their energy absorption ability. Variations in the structure and material compositions of the plate-lattice structures are achieved through changing the plate thickness and through changing the filament material along the lattice in the direction of applied compressive force. The compressive stress–strain behavior reveals a near 10% increase of specific energy absorption (SEA) in the plate thickness graded designs at higher strain compared to the baseline octet lattices. The multi-material arrangements significantly modified onset location of the structure collapse. Finite element models of the structures were developed, and good agreements with experimental results were observed. Effects of varying each of the unit cell geometric parameters were analyzed, and the high sensitivity to the plate inclination angle, which resulted in greater changes to the maximum stress values and control of the overall SEA, was identified. The results demonstrate the capacity to adapt the octet lattice structure design through additive manufacturing to better suit the expected load and application.

Nanocomposite film heaters are promising for out-of-oven (OoO) and energy-efficient curing of fiber-reinforced polymer composites. However, the current techniques for manufacturing nanocomposite film heaters are intensive in terms of time and energy and require expensive resources. In this work, we present a facile and rapid approach for preparation of nanocomposite film heaters with excellent heat generation properties based on a frontally polymerizable resin system. This approach enables rapid fabrication of nanocomposite films within a few minutes and without the need for using expensive equipment, making it suitable for mass production of nanocomposite film heaters. Various characterization techniques are used to determine the morphology, composition, and mechanical properties of nanocomposite films. The electrothermal performance of nanocomposite film heaters are then evaluated under various conditions. Nanostructured heaters exhibit excellent Joule heating properties, where temperatures as high as ∼132°C can be reached within only 2 min using a low input power density of ∼2 W cm−2. Finally, a nanocomposite film heater is used for OoO curing of a small composite panel with minimal energy consumption. Using this approach, 0.1 MJ of energy is consumed during the 4-h cure cycle of a commercial prepreg system, which would otherwise require at least 40.5 MJ of energy to cure using a convection oven.

Abstract Brittleness is a major limitation of polymer-derived ceramics (PDCs). Different concentrations of three nanofillers (carbon nanotubes, Si3N4 and Al2O3 nanoparticles) were evaluated to improve both toughness and modulus of a commercial polysilazane (PSZ) PDC. The PSZs were thermally cross-linked and pyrolyzed under isostatic pressure in nitrogen. A combination of mechanical, chemical, density, and microscopy characterizations was used to determine the effects of these fillers. Si3N4 and Al2O3 nanoparticles (that were found to be active fillers) were more effective than nanotubes and improved the elastic modulus, hardness, and fracture toughness (J IC ) of the PDC by ~ 1.5 ×, ~ 3 ×, and ~ 2.5 ×, respectively. Nanotubes were also effective in maintaining the integrity of the samples during pyrolysis. The modulus and hardness of PDCs correlated positively with their apparent density; this can provide a fast way to assess future PDCs. The improvement in fracture toughness was attributed to crack deflection and bridging observed in the micro-indentation cracks in the modified PDCs. The specific toughness of the modified PDCs was 4 × higher than that of high-purity alumina, and its specific modulus reached that of commercially available technical ceramics. These PDCs can also easily take different shapes and therefore are of interest in protective armor, propulsion, thermal protection, device packaging and biomaterial systems.

Background and Aim: As a plant of the Apiaceae family, Echinophora Cinerea Boiss can grow up to 30 to 100 cm tall. The essential oil of E. cinerea contains phenolic compounds. Phenolic Compounds are one of the best sources of natural antioxidants. The present research aimed to evaluate the chemical compounds, and the antibacterial as well as antioxidant and cytotoxic activities of E. cinerea essential oil. Materials and Methods: The hydrodistillation method and gas chromatography coupling with a mass spectrometer (GC/MS) were used to prepare and identify the chemical compounds of the essential oil. The antioxidant capacity of the essential oils was evaluated by DPPH and was compared with standard antioxidants (BHT). The antibacterial test was carried out by Broth Micro Dilution, Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC) methods. These oils were evaluated and compared after 24 and 48 h to control the antibiotic. Results: The main constituents of the essential oil were combined with plant α-phellandrene (32.09), limonene (16.28), P-cymene (10.75), α-pinene (9.79), carvacrol (3.79), and β-Myrcene (2.65). IC50 for the essential oil of E. cinerea and BHT was 0.74 and 52.72 μg/ml, respectively. Strong antibacterial impacts of the essential oils belonged to Staphylococcus aureus (MIC = 0.16 μg/ml and MBC = 0.63 μg/ml. The results of inhibitory effects on tumor cell lung have shown that via increasing the concentration, the inhibitory effects of cell have increased, so that at the highest concentrations, more than 60% of tumor cells were inhibited and the IC50 was 3589.31 µg /ml. Conclusion: The present study demonstrates that Echinophora could have considerable antibacterial, antioxidant and cytotoxicity properties. The essential oil of this plant is effective against important human bacterial pathogens. It is also a determinant of nosocomial infection

Background: Nanoparticles (NPs) are colloidal systems with particles ranging from 10 to 100 nm in diameter. Because of their large surface-volume ratio, NPs are biologically active materials that could interact with biomolecules and microorganisms, enter into the cells, and affect the metabolic functions. The study aimed to biosynthesize silver nanoparticles (Ag-NPs) from Capparis spinosa fruit aqueous extract, and evaluate their Ag nanostructure characterization and antifungal activity. Materials and Methods: Capparis spinosa fruit aqueous was prepared with the percolation method. Then, silver NPs were synthesized using 0.01 M silver nitrate solution, and their formation was validated by color changing of the solution from green to dark brown . The NPs were purified using centrifugation and then dried in an oven for further analyses. Ag-NPs nanostructure characterization was determined by various techniques such as Fourier Transforms Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), and Ultraviolet-visible (UV-Vis) spectroscopy. Antifungal activity of Ag-NPs against three pathogenic fungi of Candida albicans, Candida glabrata, and Kluyveromyces marxianus was also evaluated using the microdilution method. Results: Synthesis of Ag-NPs from aqueous extract of C. spinosa fruit was done successfully. UVVis spectrum of Ag-NPs showed an absorbance peak around 420 nm, revealing Ag-NPs surface plasmon resonance (Kmax). FTIR analysis showed that functional groups correspond to plant bioactive components, promoting the formation of Ag-NPs. Furthermore, spherical uniformity of the synthesized Ag-NPs from plant extract was confirmed by SEM analysis within the 50-80 nm size range. Our results showed that the produced Ag-NPs were spherical and in a suitable form and size (50-80 nm). The biosynthesized Ag-NPs had an inhibitory effect against all tested fungi with the minimum inhibitory concentration of 2500, 5000, and 625 μg/mL and minimum bactericidal concentration of 10000, 10000, and 156.25 μg/mL for C. albicans, C. glabrata, and K. marxianus, respectively. Conclusion: According to the UV-Vis spectrum, FTIR, and SEM results, we succeeded in synthesizing Ag-NPs from C. spinosa fruit aqueous extract. This research was the first report of Ag-NPs synthesized from aqueous extract of C. spinosa fruit. Our simple, quick, and inexpensivemethod for biosynthesis of a nanoparticle, which showed antifungal activity, provides a new potential antifungal agent for therapeutic applications.

Background and Aim: Echinophora platyloba DC (Apiaceae) is a plant endemic to Kurdistan province of Iran. Aerial part of the plant is regarded as the source of natural antimicrobial agent. Materials and Methods: The aerial part of E. platyloba was extracted with hexane, dichloromethane, acetone EtOH and EtOH: H2O respectively. The extracts were individually tested against three gram-negative (Escherichia coli, Shigella flexneri, Acinetobacter baumannii) and two gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis) via agar dilution methods. Results: The best inhibitory effect was observed in ethanolic extract, which had a remarkable inhibitory effect on all bacteria especially on S. aureus. The results also indicated that dichloromethane extract showed the weakest inhibitory effect on all types of bacteria. Meanwhile, acetone extract exhibited a relatively mild inhibitory effect. Conclusion: The antimicrobial effects of E. platyloba confirmed its potential for folk use. More comprehensive investigations are recommended concerning the significant antibacterial activity of the ethanol extract of E. platyloba to determine the exact compounds responsible for observed biological activities.

Hydroxyl (OH) and amino (NH2) functionalized boron nitride nanotubes (f-BNNTs) were integrated into an epoxy resin (Epon828) to achieve improved mechanical properties. While raw BNNT-composites yielded the largest values for Young’s modulus and appeared to be well mixed, f-BNNTs were found to provide a superior combination of mechanical properties yielding improvements in strain at failure, tensile strength and toughness that were not observed using raw BNNTs. In particular, an increase of 21% in Young’s modulus is observed with 5 wt% of f-BNNT, and increases of 12, 21, and 49% are observed in tensile strength, failure strain, and toughness, respectively, with 2 wt% f-BNNT while a 34% increase in fracture toughness is observed with 3 wt% f-BNNT.

Abstract Pectin is one of the main structural components in fruits and an indigestible fiber made of d-galacturonic acid units with α (1-4) linkage. This study investigates the microbial degradation of pectin in apple waste and the production of bioactive compounds. Firstly, pectin-degrading bacteria were isolated and identified, then pectinolytic activity was assessed by DNS. The products were evaluated by TLC and LC–MS–ESI. The antioxidative effects were investigated using DPPH and anti-cancer effects and cytotoxicity were analyzed by MTT and flow cytometry. In this study two new bacterial isolates, Alcaligenes faecalis AGS3 and Paenibacillus polymyxa S4 with the pectinolytic enzyme were introduced. Structure analysis showed that the products of enzymatic degradation include unsaturated mono, di, tri, and penta galacturonic acids with 74% and 69% RSA at 40 mg/mL for A. faecalis and P. polymyxa S4, respectively. The results of anti-tumor properties on MCF-7 cells by MTT assay, for products of AGS3 and S4 at 40 mg/mL after 48 h, showed 7% and 9% survival, respectively. In the flow cytometric assessment, the compounds of AGS3 at 40 mg/mL were 100% lethal in 48 h and regarding S4 isolate caused 98% death. Cytotoxicity evaluation on L-929 cells showed no significant toxicity on living cells.