From Molecules to Devices: Insights into Electronic and Optical Properties of Pyridine-Derived Compounds Using Density Functional Theory Calculations.

In this study, we delve into the electronic structure, spectroscopic, and optical properties of five benzo derivatives of pyridine, namely, 5-(4-chlorophenyl)-2-fluoropyridine (1), 2-fluoro-5-(4-fluorophenyl)pyridine (2), 4-(2-fluoropyridin-5-yl)phenol (3), 5-(2,3-dichlorophenyl)-2-fluoropyridine (4), and 5-(5-bromo-2-methoxyphenyl)-2-fluoropyridine (5). Utilizing quantum chemical density functional theory calculations at the B3LYP and Perdew-Burke-Ernzerhof levels of theory combined with the 6-311G(d,p) and 6-311++G(d,p) basis sets, we investigated the electronic and optical characteristics of these compounds. Band structure calculations were conducted for their crystalline structures, revealing a direct band gap varying from 3.018 to 3.558 eV, with the valence band maximum and conduction band minimum located at the G point in the Brillouin zone. The optical properties were analyzed, including the dielectric functions, reflectivity, and refractive index. Notably, reflectivity was found to be minimal in the photon energy range of 0.0-3.0 eV, and the static refractive index, n(0), ranged from 1.55 to 1.70. The research also involved assessing the reactivity of the compounds through calculation of the frontier orbital energy gaps (ΔE), indicating a significant charge transfer and high reactivity. Additionally, we performed frequency analysis to unveil the Fourier-transform infrared spectra of compounds 1-5 at room temperature. Molecular electrostatic potential surfaces of the optimized structures were employed to map the electrophilic and nucleophilic regions of the compounds. This investigation provides a comprehensive understanding of the electronic and optical properties of these pyridine derivatives, shedding light on their potential applications in optoelectronics.

Effect of Spatter Behavior on Mechanical Properties and Surface Roughness of Printed Parts during PBF-LM of 316L.

The spatter generated by the interaction between laser and powder during Powder Bed Fusion-Laser Melting (PBF-LM) can significantly affect the quality of printed parts. A high-speed camera is used to observe the dynamic process of spatter's behavior under different layer thickness and laser powers during the printing process, and to analyze the printed samples' surface roughness, microstructure, and mechanical properties. In terms of spatter image processing, employing an optical flow approach to track and quantify the number of spatters efficiently eliminates statistical redundancy and improves statistical correctness. It is found that under the same laser power, the number of spatters produced by the laser scan direction with the gas flow (LSD-W) is more than that by the laser scan direction against the gas flow (LSD-A), and the number of spatters produced increases with the increase of laser power. Analyzing the mechanical properties and surface roughness of the printed samples under different process parameters quantitatively reveals that differences in the spatter amount generated under different process parameters in the PBF-LM process is not the determining factor affecting the difference in tensile strength of printed parts. During LSD-W, the number of spatters generated at laser power of 170 W and layer thickness of 0.03 mm is 87, and the tensile strength of the printed sample is 618 MPa. During LSD-W, the number of spatters generated at laser power of 320 W and layer thickness of 0.05 mm is 211, and the tensile strength of the printed sample is 680 MPa. Instead, spatter generation has a more direct impact on the surface roughness of printed parts. The layer thickness is 0.03 mm, the laser power is 170 W, and (Ra = 2.372 µm) is the surface roughness of the sample. The layer thickness is 0.05 mm, the laser power is 320 W, and (Ra = 8.163 µm) is the surface roughness of the sample.

Polymer Composites in 3D/4D Printing: Materials, Advances, and Prospects.

Additive manufacturing (AM), commonly referred to as 3D printing, has revolutionized the manufacturing landscape by enabling the intricate layer-by-layer construction of three-dimensional objects. In contrast to traditional methods relying on molds and tools, AM provides the flexibility to fabricate diverse components directly from digital models without the need for physical alterations to machinery. Four-dimensional printing is a revolutionary extension of 3D printing that introduces the dimension of time, enabling dynamic transformations in printed structures over predetermined periods. This comprehensive review focuses on polymeric materials in 3D printing, exploring their versatile processing capabilities, environmental adaptability, and applications across thermoplastics, thermosetting materials, elastomers, polymer composites, shape memory polymers (SMPs), including liquid crystal elastomer (LCE), and self-healing polymers for 4D printing. This review also examines recent advancements in microvascular and encapsulation self-healing mechanisms, explores the potential of supramolecular polymers, and highlights the latest progress in hybrid printing using polymer-metal and polymer-ceramic composites. Finally, this paper offers insights into potential challenges faced in the additive manufacturing of polymer composites and suggests avenues for future research in this dynamic and rapidly evolving field.

The Laser Selective Sintering Controlled Forming of Flexible TPMS Structures.

Sports equipment crafted from flexible mechanical metamaterials offers advantages due to its lightweight, comfort, and energy absorption, enhancing athletes' well-being and optimizing their competitive performance. The utilization of metamaterials in sports gear like insoles, protective equipment, and helmets has garnered increasing attention. In comparison to traditional truss and honeycomb metamaterials, the triply periodic minimal surface lattice structure stands out due to its parametric design capabilities, enabling controllable performance. Furthermore, the use of flexible materials empowers this structure to endure significant deformation while boasting a higher energy absorption capacity. Consequently, this study first introduces a parametric method based on the modeling equation of the triply periodic minimal surface structure and homogenization theory simulation. Experimental results demonstrate the efficacy of this method in designing triply periodic minimal surface lattice structures with a controllable and adjustable elastic modulus. Subsequently, the uniform flexible triply periodic minimal surface lattice structure is fabricated using laser selective sintering thermoplastic polyurethane technology. Compression tests and finite element simulations analyze the hyperelastic response characteristics, including the element type, deformation behavior, elastic modulus, and energy absorption performance, elucidating the stress-strain curve of the flexible lattice structure. Upon analyzing the compressive mechanical properties of the uniform flexible triply periodic minimal surface structure, it is evident that the structure's geometric shape and volume fraction predominantly influence its mechanical properties. Consequently, we delve into the advantages of gradient and hybrid lattice structure designs concerning their elasticity, energy absorption, and shock absorption.

Advancing nitrate reduction to ammonia: insights into mechanism, activity control, and catalyst design over Pt nanoparticle-based ZrO2.

The reduction of nitrogen oxides (NOx) to NH3, or N2 represents a crucial step in mitigating atmospheric NO3 and NO2 emissions, a significant contributor to air pollution. Among these reduction products, ammonia (NH3) holds particular significance due to its utility in nitrogen-based fertilizers and its versatile applications in various industrial processes. Platinum-based catalysts have exhibited promise in enhancing the rate and selectivity of these reduction reactions. In this study, we employ density functional theory (DFT) calculations to explore the catalytic potential of Pt nanoparticle (PtNP)-supported ZrO2 for the conversion of NO3 to NH3. The most favorable pathway for the NO3 reduction to NH3 follows a sequence, that is, NO3 → NO2 → NO → ONH → ONH2/HNOH → NH2/NH → NH2 → NH3, culminating in the production of valuable ammonia. The introduction of low-state Fe and Co dopants into the ZrO2 support reduces energy barriers for the most challenging rate-determining hydrogenation step in NOx reduction to NH3, demonstrating significant improvements in catalytic activity. The incorporation of dopants into the ZrO2 support results in a depletion of electron density within the Pt cocatalyst resulting in enhanced hydrogen transfer efficiency during the hydrogenation process. This study aims to provide insights into the catalytic activity of platinum-based ZrO2 catalysts and will help design new high-performance catalysts for the reduction of atmospheric pollutants and for energy applications.

Promising New Horizons in Medicine: Medical Advancements with Nanocomposite Manufacturing via 3D Printing.

Three-dimensional printing technology has fundamentally revolutionized the product development processes in several industries. Three-dimensional printing enables the creation of tailored prostheses and other medical equipment, anatomical models for surgical planning and training, and even innovative means of directly giving drugs to patients. Polymers and their composites have found broad usage in the healthcare business due to their many beneficial properties. As a result, the application of 3D printing technology in the medical area has transformed the design and manufacturing of medical devices and prosthetics. Polymers and their composites have become attractive materials in this industry because of their unique mechanical, thermal, electrical, and optical qualities. This review article presents a comprehensive analysis of the current state-of-the-art applications of polymer and its composites in the medical field using 3D printing technology. It covers the latest research developments in the design and manufacturing of patient-specific medical devices, prostheses, and anatomical models for surgical planning and training. The article also discusses the use of 3D printing technology for drug delivery systems (DDS) and tissue engineering. Various 3D printing techniques, such as stereolithography, fused deposition modeling (FDM), and selective laser sintering (SLS), are reviewed, along with their benefits and drawbacks. Legal and regulatory issues related to the use of 3D printing technology in the medical field are also addressed. The article concludes with an outlook on the future potential of polymer and its composites in 3D printing technology for the medical field. The research findings indicate that 3D printing technology has enormous potential to revolutionize the development and manufacture of medical devices, leading to improved patient outcomes and better healthcare services.

Quenching and Tempering-Dependent Evolution on the Microstructure and Mechanical Performance Based on a Laser Additively Manufactured 12CrNi2 Alloy Steel.

For exploring an effective heat treatment schedule to enhance the strength-plasticity balance of the ferrite-austenite 12CrNi2 alloy steel additively manufactured by directed energy deposition (DED), 12CrNi2 was heat-treated with deliberately designed direct quenching (DQ) and cyclic quenching (CQ), respectively, and the differently quenched steels were then tempered at a temperature from 200 °C to 500 °C. It was found that the CQ, in contrast to the DQ, led the 12CrNi2 to have significantly increased tensile strength without losing its plasticity, based on the introduction of fine-grained lath martensite and the {112}<111>-type nanotwins. The nanotwins were completely degenerated after the 200 °C tempering. This led the CQ-treated steel to decrease in not only its tensile strength, but also its plasticity. In addition, an interesting phenomenon observed was that the DQ-induced laths and rod-like precipitates, and the tempering-induced laths and rod-like precipitates were all prone to be generated along the {112} planes of the martensitic crystal (α-Fe), which were exactly fitted with the {112}-type crystalline orientation of the long or short nanotwins in the CQ-induced martensite. The quenching-tempering-induced generation of the {112}-orientated laths and rod-like precipitates was explicated in connection with the {112}<111>-type long or short nanotwins in the CQ-induced lath martensite.

3D Printing of Flexible Mechanical Metamaterials: Synergistic Design of Process and Geometric Parameters.

Mechanical metamaterials with ultralight and ultrastrong mechanical properties are extensively employed in various industrial sectors, with three-periodic minimal surface (TPMS) structures gaining significant research attention due to their symmetry, equation-driven characteristics, and exceptional mechanical properties. Compared to traditional lattice structures, TPMS structures exhibit superior mechanical performance. The mechanical properties of TPMS structures depend on the base material, structural porosity (volume fraction), and wall thickness. Hard rigid lattice structures such as Gyroid, diamond, and primitive exhibit outstanding performance in terms of elastic modulus, energy absorption, heat dissipation, and heat transfer. Flexible TPMS lattice structures, on the other hand, offer higher elasticity and recoverable large deformations, drawing attention for use in applications such as seat cushions and helmet impact-absorbing layers. Conventional fabrication methods often fail to guarantee the quality of TPMS structure samples, and additive manufacturing technology provides a new avenue. Selective laser sintering (SLS) has successfully been used to process various materials. However, due to the layer-by-layer manufacturing process, it cannot eliminate the anisotropy caused by interlayer bonding, which impacts the mechanical properties of 3D-printed parts. This paper introduces a process data-driven optimization design approach for TPMS structure geometry by adjusting volume fraction gradients to overcome the elastic anisotropy of 3D-printed isotropic lattice structures. Experimental validation and analysis are conducted using TPMS structures fabricated using TPU material via SLS. Furthermore, the advantages of volume fraction gradient-designed TPMS structures in functions such as energy absorption and heat dissipation are explored.

On the Evolution of Additive Manufacturing (3D/4D Printing) Technologies: Materials, Applications, and Challenges.

The scientific community is and has constantly been working to innovate and improve the available technologies in our use. In that effort, three-dimensional (3D) printing was developed that can construct 3D objects from a digital file. Three-dimensional printing, also known as additive manufacturing (AM), has seen tremendous growth over the last three decades, and in the last five years, its application has widened significantly. Three-dimensional printing technology has the potential to fill the gaps left by the limitations of the current manufacturing technologies, and it has further become exciting with the addition of a time dimension giving rise to the concept of four-dimensional (4D) printing, which essentially means that the structures created by 4D printing undergo a transformation over time under the influence of internal or external stimuli. The created objects are able to adapt to changing environmental variables such as moisture, temperature, light, pH value, etc. Since their introduction, 3D and 4D printing technologies have extensively been used in the healthcare, aerospace, construction, and fashion industries. Although 3D printing has a highly promising future, there are still a number of challenges that must be solved before the technology can advance. In this paper, we reviewed the recent advances in 3D and 4D printing technologies, the available and potential materials for use, and their current and potential future applications. The current and potential role of 3D printing in the imperative fight against COVID-19 is also discussed. Moreover, the major challenges and developments in overcoming those challenges are addressed. This document provides a cutting-edge review of the materials, applications, and challenges in 3D and 4D printing technologies.

Influence of Exposure Period and Angle Alteration on the Flexural Resilience and Mechanical Attributes of Photosensitive Resin.

Despite the large number of studies addressing the effect of acrylic resin polymerization concerning flexural properties, limited research has been conducted on the manufacturing impact on a polymer's mechanical properties. Photosensitive resinous materials are used in various engineering applications where they may be exposed to multiple detrimental environments during their lifetime. Therefore, there is a need to understand the impact of an environment on the service life of resins. Thus, flexural tests were conducted to study the effects of exposure time and angle on the flexural strength of resins. Herein, the main objective was to explore the strength, stability, and flexural durability of photosensitive resin (EPIC-2000ST) fabricated at different exposure times (E) and angle deviation varying from 0° to 85° with a 5° increment. The samples in circular rings were manufactured and divided into five groups according to their exposure time (E): 10 s, 20 s, 30 s, 40 s, and 50 s. In each exposure time, we designed rings via SolidWorks software and experimentally fabricated at different oblique angles (OA) varying from 0° to 85° with a 5° increment during each fabrication, i.e., OA = 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, and 85°. Flexural strength was evaluated using a three-point bending test. Optical electron microscopy was used to examines the samples' exterior, interior, and ruptured surfaces. Our experimental analysis shows that flexural strength was significantly enhanced by increasing exposure time and at higher oblique angles. However, at lower angles and less exposure time, mechanical flexural resilience declines.

Enhanced Dielectric Energy Storage Performance of 0.45Na0.5Bi0.5TiO3-0.55Sr0.7Bi0.2TiO3/AlN 0-3 Type Lead-Free Composite Ceramics.

Na0.5Bi0.5TiO3 (NBT) ceramic is the promising dielectric material for energy storage devices due to its high maximum polarizability and temperature stability. However, its low breakdown strength limits its application. Here, we prepared 0-3 type composite 0.45Na0.5Bi0.5TiO3-0.55Sr0.7Bi0.2TiO3/x wt % AlN (NBT-SBT/xAlN) to increase the breakdown strength. The effects of the various AlN contents on the phase composition, microstructures, dielectric, and energy storage properties of NBT-SBT were systematically discussed. The result showed that the enhanced energy storage properties were obtained by introducing AlN particles. The NBT-SBT/6AlN composite ceramics showed a high breakdown strength of 360 kV/cm, large energy density of 5.53 J/cm3, and energy efficiency of 90%. Meanwhile, the excellent frequency (10-500 Hz) and temperature stability (25-125 °C) were exhibited with the fluctuation of energy storage within 9% and energy efficiency more than 87%, suggesting that the 0-3 composite NBT-SBT/xAlN is a candidate dielectric material for the dielectric energy storage.

Biomechanical Evaluation and Preliminary Clinical Results of Anterolateral Screw Fixation for Oblique Lumbar Interbody Fusion Surgery.

BACKGROUND: The most common complication of oblique lumbar interbody fusion (OLIF) is endplate fracture/subsidence. The aim of this study was to evaluate biomechanical stability in patients undergoing OLIF surgery with anterolateral screw fixation (ASF). METHODS: Based on a previously validated model technique, L4-L5 functional surgical models corresponding to the ASF and bilateral pedicle screw fixation (BPSF) methods were created. Finite element models were developed to compare the biomechanics of the ASF and BPSF groups. We retrospectively analyzed 18 patients with lumbar degenerative diseases who underwent OLIF with ASF in Shenzhen Hospital of Southern Medical University from April 2020 to April 2021. Intraoperative and postoperative complications were observed. RESULTS: Compared with the BPSF model, the maximum stresses of the L4 inferior endplate and L5 superior endplate were greatly increased in the ASF model. The contact surface between the vertebrae and screw (CSVS) in the ASF model produced nearly 100% more stress than the BPSF model at all moments. In clinical practice, after a 12-month follow-up, 7 adverse events were observed, including 3 cases of left thigh pain/numbness, 3 cases of cage subsidence, and 1 case of screw loosening. CONCLUSIONS: OLIF surgery with ASF could not reduce the maximum stresses on the endplate and CSVS, which may be a potential risk factor for cage subsidence and screw loosening.

Lead-Free BF-BT Ceramics With Ultrahigh Curie Temperature for Piezoelectric Accelerometer.

Piezoelectric ceramics have been widely used in high precision sensors such as vibration detection, but piezoelectric accelerometers in high-temperature applications are very rare. We prepared ( 1- x ) BiFeO3- x BaTiO3-0.0035MnO2-0.001Li2CO3(BF- x BT) ceramics by a solid state approach, and investigated the effect of BT content( x ) on the phase structure, microstructure, dielectric properties, ferroelectric properties, piezoelectric properties, temperature stability, and especially the sensitivity of the piezoelectric accelerometer. The crystal structure of the sample is pure perovskite structure with the MPB (R and P phases) locating in a composition range of 0.28 ≤ x ≤ 0.32 for BF-xBT ceramics, and the single R phase exist at . When x = 0.30, the ceramic presents both high Curie temperature and d33 . Notably, the sensitivity of BF-0.30BT piezoelectric accelerometer reaches the highest value of about 40 pC/g and shows an excellent stability until 400 °C, indicating that this material is a promising candidate for high-temperature piezoelectric accelerometer applications.

Surface silanization and grafting reaction of nano-silver loaded zirconium phosphate and properties strengthen in 3D-printable dental base composites.

In this work, surface modification of nano silver-loaded zirconium phosphate (6S-NP3) were obtained from simultaneous silanization of γ-methacryloxypropyltrimethoxysilane (MPS) and grafting reaction of methyl methacrylate (MMA), and then mixed with denture base resin (E-Denture) to prepare denture base composites using 3D printer printing. FT-IR spectra confirmed that surface silanization and grafting reaction had occurred and MPS and MMA were successfully anchored on the surface of 6S-NP3. XRD results demonstrated that surface modification had occurred on the surface of hexagonal lattice. The average diameter data indicated that the surface modification decreased the average diameter of nanoparticles. The water contact angle (WCA) was found increasing as the surface modification. SEM images illustrated that the dispersion and compatibility of nanoparticles in denture base composite materials had improved. The results of mechanical properties presented that composites with the addition of P-6S-NP3 nanoparticles achieved higher flexural strength, flexural modulus and impact strength. The data of antibacterial activities revealed that composites had exhibited good antibacterial activities against either S. aureus or E. coli and the latter showed better antibacterial efficacy than the former.

TiO2 and PEEK Reinforced 3D Printing PMMA Composite Resin for Dental Denture Base Applications.

The future of manufacturing applications in three-dimensional (3D) printing depends on the improvement and the development of materials suitable for 3D printing technology. This study aims to develop an applicable and convenient protocol for light-curing resin used in 3D industry, which could enhance antibacterial and mechanical properties of polymethyl methacrylate (PMMA) resin through the combination of nano-fillers of surface modified titanium dioxide (TiO2) and micro-fillers of polyetheretherketone (PEEK). PMMA-based composite resins with various additions of TiO2 and PEEK were prepared and submitted to characterizations including mechanical properties, distribution of the fillers (TiO2 or/and PEEK) on the fractured surface, cytotoxicity, antibacterial activity, and blood compatibility assessment. These results indicated that the reinforced composite resins of PMMA (TiO2-1%-PEEK-1%) possessed the most optimized properties compared to the other groups. In addition, we found the addition of 1% of TiO2 would be an effective amount to enhance both mechanical and antibacterial properties for PMMA composite resin. Furthermore, the model printed by PMMA (TiO2-1%-PEEK-1%) composite resin showed a smooth surface and a precise resolution, indicating this functional dental restoration material would be a suitable light-curing resin in 3D industry.

A Study of 3D-Printable Reinforced Composite Resin: PMMA Modified with Silver Nanoparticles Loaded Cellulose Nanocrystal.

With the rapid application of light-curing 3D printing technology, the demand for high-performance polymer resins is increasing. Existing light-curable resins often have drawbacks limiting their clinical applications. This study aims to develop a new type of polymethyl methacrylate (PMMA) composite resins with enhanced mechanical properties, high antibacterial activities and excellent biocompatibilities. A series of reinforced composite resins were prepared by mechanically mixing PMMA with modified cellulose nanocrystals (CNCs), which were coated with polydopamine and decorated by silver nanoparticles (AgNPs) via Tollen reaction. The morphology of CNCs-Ag was observed by transmission electron microscopy and the formation of AgNPs on CNCs was confirmed by X-Ray photoelectron spectroscopy analyses. Functional groups in PMMA-CNCs-Ag composites were verified by Fourier Transform infrared spectroscopy (FTIR) spectroscopy. The mechanical assessment and scanning electron microscopy analysis suggested that the evenly distributed CNCs-AgNPs composite effectively improve mechanical properties of PMMA resin. Cytotoxicity assay and antibacterial activity tests indicated excellent biocompatibility and high antibacterial activities. Furthermore, PMMA with CNCs-AgNPs of 0.1 wt.% (PMMA-CNCs-AgNPs-0.1) possessed the most desirable mechanical properties owing to the homogeneous distribution of AgNPs throughout the resin matrix. This specific composite resin can be used as a functional dental restoration material with potential of other medical applications.

Estimation of the tensile modulus of polymer carbon nanotube nanocomposites containing filler networks and interphase regions by development of the Kolarik model.

In this paper, the Kolarik model for the tensile modulus of co-continuous blends based on cross-orthogonal skeleton structures is simplified and developed for polymer/carbon nanotube (CNT) nanocomposites assuming continuous CNT networks in the polymer matrix and the reinforcing and percolating efficiencies of the interphase. For this purpose, the Ouali model for the modulus of nanocomposites above the percolation threshold is linked with the Kolarik model and the interphase percolation is considered with the excluded volume of the nanoparticles. In addition, the simplified Kolarik model is developed with the interphase as a new phase surrounding the nanofiller. A good agreement between the experimental data and the predictions is observed in the samples containing interphases and filler networks, while the developed model cannot estimate the modulus in the absence of interphases and network structures. The developed model demonstrates the effects of all the parameters on the modulus. The interphase parameters more significantly affect the modulus compared to the concentration and modulus of the filler, demonstrating the importance of the interphase properties.

Synthesis, characterization and osteogenesis of phosphorylated methacrylamide chitosan hydrogels.

Phosphorylated biopolymers can induce mineralization, mimic the process of natural bone formation, and have the potential as scaffolds for bone tissue engineering. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a low cytotoxicity phosphorus source, is mainly applied in vascularization and promoting blood compatibility and has been less researched for bone repair. In this study, phosphorylated methacrylamide chitosan (PMAC) hydrogel was prepared by mixing methacrylamide chitosan (MAC) and different mass of MPC with photoinitiator under UV irradiation. A series characterization tests showed that PMAC hydrogels were successful prepared and had a pretty good mineralization ability. Moreover, human fetal osteoblastic (hFOB) cells cultured on PMAC hydrogels exhibited not only highly viability but also the enhanced ALP activity and calcium deposition. The PMAC hydrogels have great potential in bone tissue engineering applications.