Recent findings on the production of quantum dots from various carbon sources shed light on their advantages such as sustainability, low toxicity and cost, and one-step synthesis over their heavy-metal counterpart. This paper focused on developing and analyzing the production of carbon quantum dots from glycerol via hydrothermal carbonization and conjugated with Tetraethylenepentamine (TEPA). A 23 full factorial experimental design was applied considering factors: the compositional ratio of TEPA (A), time of exposure (B), and temperature of reaction (C). Statistical analyses revealed experimental factors A and B; and interactions of AB and AC had statistically significant effects on the response variable, quantum yield (QY). Factor C as the main effect was not significant but was included in the statistical model to maintain hierarchy and integrity. Coded and actual statistical models were presented here.

Additive Manufacturing (AM) has been in the manufacturing industry for more than a decade. It has aided in producing several intricate objects for several purposes. One of the most used techniques in AM is fused deposition modeling (FDM) wherein a plastic filament is heated to its melting point and deposited layer by layer in a build plate to form a 3D model. Acrylonitrile butadiene styrene (ABS) is one of the commonly used filaments because of its relatively good impact resistance and toughness, and workability in 3D printing various structures. The gyroid structure is a self-supporting structure that has a good strength-to-weight ratio. The compressive strength of single and multiple-layered structures of ABS gyroid lattice structure with different line widths, infill densities, and wall counts was observed. A 0.35 line width with an infill density of 25% and wall count of 3 has a compressive strength of 11.94 MPa, material consumption of 1.87 grams, and printing time of 14 min which makes it the most efficient design for single-layered structures. Among three-layered structures, the combination of infill densities of 25% and 35% is the most efficient with 0.45 line width and 3 walls. It has a compressive strength of 15.87 MPa, printing time of 13 min, and material consumption of 2.3 grams. Nowadays, there are limited research articles on AM of a single structure with gradual varying densities as well as the effect of lesser-known printing parameters on the mechanical properties of AM parts. This study aims to aid future research by providing data on single and functionally graded structures with different line widths and wall counts. With the information from this study, future researchers and designers can further optimize printing parameters to make an efficient design that is light and has sufficient mechanical strength to serve a specific function.

Mechanical properties and failure behavior of 3D printed poly (lactic) acid (PLA) reinforced with varying loadings of nano-alumina (Al2O3) (0, 2.5, 5.0, and 10.0 wt.%) were investigated through simulation using a finite element analysis (FEA)-based software. Tensile test specimens were 3D printed via fused deposition modeling (FDM) technique and underwent actual testing. The mechanical properties determined were then used as parameters for the FEA simulation to achieve prediction accuracy. Specifically, this study utilized MSC Patran and Nastran software to simulate the tensile test on the modeled test specimen with tetrahedron mesh. The finite element model was verified by comparing the simulated values with the results of actual experimental testing. Upon calculation, the average percentage differences for the tensile strength, elastic modulus, and displacement were 5.86%, 12.07%, and 10.57%, respectively. Although percentage differences were obtained, using FEA as an initial analysis for the prediction of mechanical properties and failure behavior could serve as a solution for better design and materials optimization.

Incorporation of nanoparticles in Polylactic Acid (PLA) for additive manufacturing is explored to alter the material property to suit its intended application. In this study, PLA is reinforced with multi-walled carbon nanotubes (MWCNT) using two-roll mill for fused deposition modeling (FDM) additive manufacturing. The chemical composition, thermal behavior, electrical, and antibacterial properties of the PLA/MWCNT nanocomposite were investigated. The Fourier transform infrared spectroscopy (FTIR) analysis showed the physical interaction of MWCNT to the PLA matrix. The x-ray diffraction analysis (XRD) data showed that increasing the MWCNT percentage increases the amorphous region and intensity, indicating the nucleating effect of MWCNT on PLA. Differential scanning calorimetry (DSC) analysis showed a decrease in the glass transition and melting temperatures compared to pure PLA by up to 9.36°C and 23.25°C, respectively, while introducing cold crystallization with the addition of MWCNT. The two point-probe resistance measurement showed a decreasing trend in the resistance of the composite which indicates an increase in conductivity as the the amount of MWCNT is increased. The analysis of disk diffusion test concluded that no bacterial growth of Escherichia coli and Staphylococcus aureus happened underneath the sample. Furthermore, the nanocomposite was successfuly extruded into a filament and test samples were 3D printed using FDM. The PLA/MWCNT produced are suitable for the production of a multifunctional filament with improved electrical, thermal and antimicrobial properties for different fused deposition modelling (FDM) additive manufacturing increasing the probable applications and competitiveness of this promising market niche.

The emergence of COVID-19 raised awareness in hygiene practices and reminded us of the harm that microbes bring to our health. Incorporating antibacterial agents in polymeric materials would allow us to combat lingering bacteria on surfaces that we often use. The utilization of composite filaments with antibacterial activity would allow us to employ better precautions in reducing contact with harmful bacteria. Antibacterial acrylonitrile‐butadiene‐styrene (ABS) nanocomposites were prepared by incorporating silver zirconium phosphate (AgZrP) nanoparticles via twin screw extruder. The ABS/AgZrP nanocomposite filament with 5 wt % and 20 wt% of AgZrP were synthesized and characterized with Differential scanning calorimetry (DSC), Thermogravimetric Analysis (TGA), X-ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FTIR). DSC and XRD data denote an increase in the presence of crystalline regions as the AgZrP content is increased. TGA data indicate that the addition of AgZrP has no effect on the thermal stability of the material. FTIR data indicate a decrease in transmission at higher AgZrP loading. The decreasing trend in tensile properties of the 3D-printed neat and AgZrP-filled ABS may have been due to particle agglomeration acting as stress concentrators. Antibacterial activity assessment via disk diffusion test showed a zone of inhibition within the sample indicating that there is no bacterial growth both for Escherichia coli and Staphylococcus aureus.

The study involves the use of high density polyethylene (HDPE) as a filament for 3D printing. Considering the warpage and adhesion problem of HDPE on the build plate during 3D printing, this was addressed through the incorporation of wood flour compatibilized with styrene-ethylene-butylene-styrene grafted maleic anhydride (SEBS-gMAH). The composite wood-HDPE (cHDPE) was studied to observe warpage changes. Using different SEBS, heat bed parameters and identification of the suitable print heat beds for HDPE was conducted. Results from the mechanical testing show that the compressive strength and elastic force of virgin HDPE (vHDPE) increases with infill percentage, while the same properties for cHDPE increases up to 50% infill density/percentage then decreases as it approaches 100% infill percentage. Digital microscopy imaging shows that poor layer adhesion initiated the poor compressive performance of cHDPE. Warp studies reveal that wood flour significantly decreases warping of HDPE by 42.88% at 50% infill density. While different SEBS brands show similar effectiveness as heat beds in reducing warping of HDPE during printing.

Additive manufacturing can be utilized to harness developments in polymer research. This study aims to investigate the effect of Philippine halloysite on poly(lactic acid) (PLA) filament for 3D printing using Fused Deposition Modeling (FDM). PLA-based filaments with halloysite powders were prepared by melt-compounding using a twin-screw extruder. The chemical composition and morphology of the halloysite powder was determined using XRD and SEM, respectively. Composite filament with 3% halloysite (PLA/HSC) was developed and characterized. The thermal properties of pure PLA and PLA/HSC were measured using DSC and TGA. CAD files for XRD analysis and tensile tests were generated using SolidWorks computer software (Dassault Systemes). Printability of pure PLA and the composite filament was observed by using Ultimaker S5 3D printer. The effect on chemical composition and mechanical performance of the 3D printed specimens was evaluated using XRD and UTM, respectively. XRD result confirmed the presence of dehydrated halloysite clay mineral. SEM image revealed the spherical morphology of the halloysite powder with average particle size of 72.472 nm. DSC analysis showed that incorporation of halloysite powder filaments had slightly decreased the glass transition of pure PLA matrix. This could be attributed to the enhanced mobility of polymeric chains by plasticization. Moreover, the melting temperature of PLA/HSC composite has slightly higher value than pure PLA filament owing to increased crystallinity imparted by the halloysite particles. With high stability of halloysite at elevated temperatures, the thermal stability of PLA/HSC filament was also enhanced. Mechanical performance of pure PLA was also improved with addition of halloysite. The tensile strength and elastic modulus of pure PLA matrix increased by 180.32% and 143.96%, respectively which could be due to the formation of hydrogen bonds between PLA matrix and halloysite particles. Digital micrographs of the fractured surface reveal that tensile pieces predominantly ruptured by brittle fracture.

Additive Manufacturing (AM) is revolutionizing the manufacturing industry as various AM technologies continue to mature and more AM-compatible materials are being developed. Polyether ether ketone (PEEK) is one of the promising materials at the forefront of this technological revolution as efforts to enhance its application as a 3D-printing material are continuously being pursued. In this study, the effect of printing parameters on the void content of 3D-printed PEEK was examined using a non-destructive method, X-ray micro computed tomography (X-ray micro-CT). Of the fused filament fabrication (FFF) parameters considered, higher nozzle temperature and printing speed were seen to promote an increase in void content while higher build plate temperature reduces it. Void content has a direct effect on the mechanical and other properties of the manufactured material and therefore provides a link between the printing parameters and the expected mechanical performance of these materials. This study also highlights the importance of choosing the right printing parameters to ensure the quality of the manufactured PEEK.