Morphology Of Samples Research Articles

A Novel Nano-Spherical Tip for Improving Precision in Elastic Modulus Measurements of Polymer Materials via Atomic Force Microscopy.

Micro-nano-scale mechanical properties are vital for engineering and biological materials. The elastic modulus is generally measured by processing the force-indentation curves obtained by atomic force microscopy (AFM). However, the measurement precision is largely affected by tip shape, tip wear, sample morphology, and the contact model. In such research, it has been found that the radius of the sharp tip increases due to wear during contact scanning, affecting elastic modulus calculations. For flat-ended tips, it is difficult to identify the contact condition, leading to inaccurate results. Our research team has invented a nano-spherical tip, obtained by implanting focused helium ions into a silicon microcantilever, causing it to expand into a silicon nanosphere. This nano-spherical tip has the advantages of sub-micro size and a smooth spherical surface. Comparative tests of the elastic modulus measurement were conducted on polytetrafluoroethylene (PTFE) and polypropylene (PP) using these three tips. Overall, the experimental results show that our nano-spherical tip with a consistent tip radius, symmetrical geometric shape, and resistance to wear and contamination can improve precision in elastic modulus measurements of polymer materials.

Magnetorheological and magnetic actuation behaviour of solvent cast 4D printed styrene-ethylene-butylene-styrene block copolymer based magnetorheological elastomeric materials

In this work styrene-ethylene-butylene-styrene (SEBS) block copolymer based smart magnetorheological elastomeric (MREs) materials have been additively manufactured using solvent-cast 4D Printing (SC-4DP) technique. The effect of carbonyl iron powder (CIP) content on the particle distribution, particle–matrix adhesion, surface and layer morphology of the 4D Printed MRE sample was investigated. CIP particles were observed to be well embedded and dispersed up to 60 wt% content. However, at higher CIP content the tendency of the particles to agglomerate increased significantly. Furthermore, samples with CIP content ≥70 wt% showed poor particle–matrix adhesion and possessed inter-layer coalescence defects. Investigations were also performed to evaluate the magnetic properties of MREs at room temperature. Magnetorheological behaviour was studied to evaluate the effect of varying magnetic field on dynamic viscoelastic properties. Magnetorheological effect increased from ∼79 % to ∼211 % with an increase in CIP content. However, the particle–matrix adhesion also significantly affected the magnetorheological effect for higher CIP content samples. Magnetic actuation capability of flexible MRE samples was evaluated for gripper-based application. SC-4D Printed flexible grippers were able to successfully grip, lift, and drop both the soft deformable and rigid freeform profile objects in different media (air and sodium hydroxide solution) suggesting suitability for remotely actuated gripper-based applications.

Impact of graphite on tribo‐mechanical, structural, and thermal behaviors of polyoxymethylene copolymer/glass fiber hybrid composites via Taguchi optimization

AbstractUnique hybrid thermoplastic composites based on polyoxymethylene copolymer (POM C), 10 wt.% glass fiber (GF) and graphite (Grt) filler at 1, 3, and 5 wt.% were developed using injection molding technique. According to the Taguchi L16 orthogonal array, present experiments were carried out with the aim of determining the coefficient of friction (COF) and specific wear rate (SWR) under a range of loads (namely, 5, 10, 20, and 30 N), sliding speeds (namely, 200, 400, 600, and 800 rpm), and run times (namely, 15, 30, 45, and 60 min) with varying wt.% of Grt (namely, 1, 3, and 5 wt.%) throughout the experiment. Analysis of variance (ANOVA) was used to evaluate the most significant factors that affect the output functions (viz., COF and SWR). The findings demonstrated that POM C/10GF composites' tribo‐mechanical, structural, and thermal properties were considerably improved upon by including Grt. Various microscopical methods were also employed to study the wear mechanisms of the composites and the surface morphology of the worn samples. The POM C/10GF with a 3 wt.% of Grt exhibited superior tribological properties owing to its enhanced interfacial bonding characteristics, resulting to increased wear resistance.Highlights Injection molded POM C/10GF hybrid composites with 1, 3, and 5 wt.% graphite (Grt) Structural, thermal, chemical, tribo‐mechanical and microstructural studies Design of experiment with variable loads, times, speeds, and Grt compositions COF and specific wear resistance as response Optimization of hybrid composite composition using Taguchi L16 orthogonal array

PEDOT: PSS Doped Activated Biochar as a Novel Composite Material for Photocatalytic and Efficient Energy Storage Application

Herein, we report the synthesis of activated biochar from green algae and the effect of its doping on the structural, photocatalytic, and energy storage properties of PEDOT-PSS. The morphology of pure and doped samples was investigated with Fourier Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM), Brunauer–Emmett–Teller (BET) analysis, and thermogravimetric analysis (TGA). AFM results for PEDOT-PSS@6wt.% of BC indicate that the calculated average peak height, particle size, and roughness were 283 nm, 136 nm, and 71 nm, respectively. Adding biochar to PEDOT-PSS significantly improved the thermal stability of PEDOT-PSS up to 550 °C. The novel photocatalyst PEDOT-PSS@6wt.% BC improved photocatalytic performance by approximately 17% in Methylene Blue (MB) dye removal. The electrochemical performance in terms of supercapacitors for the synthesized samples was investigated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), specific capacitance, stability, and electrochemical impedance spectra (EIS). PEDOT-PSS@6wt.% of BC as a novel electrode material in supercapacitors exhibits an initial specific capacitance of 1300 Fg−1. Moreover, the PEDOT-PSS@6wt.% of BC electrode shows excellent stability up to 1000 cycles of operation. The EIS studies suggest the presence of charge transfer resistance. Considering the economical biosynthesis and multifunctional features, the PEDOT-PSS@6wt.% of BC could potentially be used as a photocatalyst to remove organic dyes and supercapacitors in energy storage applications.

Microstructural evolution and formation of defect complexes in diamond films by nitrogen-containing plasma

Abstract The morphology and crystalline quality of polycrystalline diamond samples were studied by systematically varying the flowrate of nitrogen gas in the microwave plasma. A slight improvement in both crystallite size and crystalline quality is observed for a low concentration of 0.5 sccm nitrogen. With a further increase in nitrogen concentration, diamond switches from micro-crystalline (MCD) to nanocrystalline (NCD) with a nitrogen flow of 2.5 sccm (10% of methane concentration). The surface roughness of the sample is found to depend strongly on the crystallite size of the sample. Extensive spectroscopic studies have been done to understand the presence and formation of different defect complexes in diamond. The presence of nitrogen-containing defect complexes has been studied thoroughly and their concentration has been found to be limited by the solubility limit rather than the availability of reactants in the gas environment. In contrast, the effect these complexes have on the strain of the diamond film is found to be negligible. Optical emission spectroscopy (OES) of the plasma reveals the presence of C2 dimers as well as C-N radicals. However, they have little role in modifying diamond grain morphology or crystalline quality.

Exploring the influence of ultrasonic peening treatment at ambient and cryogenic conditions on the surface characteristics and fatigue life of austenitic stainless steel 304L

This study investigates the impact of Ultrasonic Peening Treatment (UPT) at room temperature (Troom) and cryogenic temperature (Tcryo) on phase transformation, surface morphology, and fatigue life of stainless steel 304L samples. Finite element simulations were developed to analyze the effects of different material models and the pin's vertical velocity on residual stress, martensite volume fraction (ξ), and surface deformation. The numerical results of residual stress and ξ were consistent with experimental measurements obtained via X-ray diffraction. Significant compressive residual stress and martensite volume fraction were induced in the subsurface of the specimens following UPT at both temperatures. Various UPT process parameters, including static load, the pin's horizontal velocity, the number of treatments, and lubrication conditions, were experimentally explored for their effects on surface morphology and hardness. Indentation hardness revealed values of 621 HV for samples treated at Tcryo and 489 HV for those treated at Troom, compared to 286 HV for untreated specimens. Furthermore, UPT reduced surface roughness by approximately 88 % for a mechanically polished surface and over 93 % for a rough surface. Investigating conditions leading to potential damage and defects during the process was also undertaken. Fractography of the fracture surfaces and fatigue analysis revealed that the fatigue life of UPT-treated samples at Troom and Tcryo increased by 63 % and 45 %, respectively, compared to untreated specimens.

Sm3+ activated Ba3LaNa(PO4)3F fluorophosphate phosphor: Synthesis, characterization and their photoluminescence investigation for warm WLEDs

In this present research report, the series of Ba3LaNa(PO4)3Fphosphor doped with Sm3+ was successfully synthesized by using a high-temperature solid-state reaction method. The phase purity was examined using X-ray diffraction (XRD), which confirmed a pure phase of prepared material after sintering the sample at 700 °C. Fourier transform infrared (FT-IR) spectra showed absorption bands corresponding to the stretching and vibrational modes of PO4 in phosphate. Scanning electron microscopy (SEM) images displayed the morphology of sample and agglomerated structure of micron-sized particles. Photoluminescence excitation (PLE) and emission spectra of the Ba3LaNa(PO4)3F: Sm3+ phosphors were studied. When excited with near-UV light, the phosphor showed three prominent peaks at 567, 604, and 643 nm. The emission spectra for different concentrations of Sm3+ ions were also measured to find the optimal dopant concentration. The highest intensity was observed at a 2.0 mol% concentration of Sm3+ ions at 604 nmwith concentration quenching occurring beyond this point. The CIE chromaticity coordinates for the different concentration phosphor were located in the orange-red region, indicating its characteristic light emission. So therefore, these results suggested that the synthesized reddish-orange light-emitting Ba3LaNa(PO4)3F: Sm3+prepared phosphor is promising for applications in white light-emitting diodes (WLEDs).

The Influence of Grain Size on Microstructure Evolution in CeO2 under Xenon Ion Irradiation.

Large-grained UO2 is considered a potential accident-tolerant fuel (ATF) due to its superior fission gas retention capabilities. Irradiation experiments for cerium dioxide (CeO2), used as a surrogate fuel, is a common approach for evaluating the performance of UO2. In this work, spark plasma sintered CeO2 pellets with varying grain sizes (145 nm, 353 nm, and 101 μm) and a relative density greater than 93.83% were irradiated with 4 MeV Xe ions at a fluence of 2 × 1015 ions/cm2 at room temperature, followed by annealing at 600 °C for 3 h. Microstructure, including dislocation loops and bubble morphology of the irradiated samples, has been characterized. The average size of dislocation loops increases with increasing grain size. Large-sized dislocation loops are absent near the grain boundary because the boundary absorbs surrounding defects and prevents the dislocation loops from coalescing and expanding. The distribution of bubbles within the grain is uniform, whereas the large-sized and irregularly shaped xenon bubbles observed in the small grain exhibit pipe diffusion along the grain boundaries. The bubble diameter in the large-grained pellet is the smallest. As the grain size increases, the volumetric swelling of the irradiated pellets decreases while the areal density of Xe bubbles increases. Elemental segregation, which tends to occur at dislocation loops and grain boundaries, has been analyzed. Large-grained CeO2 pellet with lower-density grain boundaries exhibits better resistance to volumetric swelling and elemental segregation, suggesting that large-grained UO2 pellets could serve as a potential ATF.

Mechanical and shrinkage properties of cellulose nanocrystal modified alkali-activated fly ash/slag pastes

Alkali-activated materials based on fly ash (FA) and ground granulated blast furnace slag (GGBFS) offer lower carbon footprints but face challenges like low tensile strength and shrinkage susceptibility. This research explores the potential of cellulose nanocrystals (CNC) as additives to enhance the mechanical and shrinkage properties of alkali-activated fly ash/slag (AAFS) pastes to advance sustainable construction materials. A comprehensive examination is conducted on the impact of different contents of CNC (0.05 %, 0.1 %, 0.2 %, and 0.3 % by mass of FA + GGBFS) on the properties of AAFS pastes with two different alkaline activator contents (4 % and 8 % by mass of FA + GGBFS). It is found that incorporating 0.3 % CNC into AAFS pastes respectively improves the 28-day compressive and flexural strengths by 18.54 % and 60.87 % (8 % alkaline activator) and by 16.99 % and 50.12 % (4 % alkaline activator), and reduces the autogenous shrinkage and drying shrinkage by 26.42 % and 50.32 % (8 % alkaline activator) and by 11.74 % and 22.05 % (4 % alkaline activator). Also, the flexural/compressive strength ratio of AAFS pastes is increased with increasing CNC content. The microstructural analysis shows increased hydration product formation and a smoother, more compact morphology in CNC-modified samples, which together with water retention and distribution effect and nano-reinforcing effect of CNC explains the improvements in mechanical properties and volume stability. The research findings highlight the great potential of CNC as a reinforcing agent for sustainable construction materials, aligning with the demand from industries for eco-friendly alternatives to traditional cementitious materials.

CFRTP single-lap adhesive bonding and its mechanical performance enhanced by laser surface treatment: Finite element simulation and experimental validation

The outstanding mechanical properties of carbon fiber reinforced thermoplastic polymer (CFRTP) have led to its widespread application in many industrial sectors. In response to the engineering challenge of repairing large non-critical CFRTP structural components in situ, an infrared fiber laser surface cleaning technology is proposed to treat the bonding interface and enhance the tensile strength of polypropylene (PP)-based CFRTP single-lap bonded joints. Specifically, through single-factor and orthogonal experiments, the impact of different process parameters on the properties of the bonded joints was identified first. Then, online temperature monitoring was performed to elucidate the laser treatment mechanism of the CFRTP sample interface. Surface morphology of the laser-treated samples further indicates that when the temperature of the sample surface surpasses the resin decomposition temperature with extended holding time, the resin could be removed from the surface more thoroughly. Additionally, a novel three-dimensional woven finite element (FE) model, accounting for anisotropic heat transfer, was established to predict the surface temperature and cleaning quality of CFRTP. The FE model incorporates the anisotropic heat transfer characteristics of carbon fibers, thus accurately simulating the heat transfer behaviors between carbon fibers and the resin matrix. The laser ablation mechanism is elucidated by examining the surface ablation morphologies and peak surface temperatures. A comparison between experimental results and FE simulations demonstrated a notable coherence in the trend of surface morphology variations, with discrepancies in peak surface temperatures ranging from 3.29 % to 24.63 %. The experimental tests proved that the shear strength of single-lap bonded joints reaches its maximum value when the laser power is 35 W, the scanning speed is 2500 mm/s, and the number of scans is four. The enhancement of the mechanical properties of bonded joints can be attributed to the improved wettability and higher surface free energy of the laser-treated samples.

Mesoscopic simulation of concrete drying shrinkage with hydration kinetics

Shrinkage-induced cracking significantly impacts the durability of mass concrete structures. Quantitatively evaluating drying shrinkage of concrete proves challenging due to the time-consuming experiments and overlooked microstructure changes during the hydration process. To address this concern, this study initially characterized the long-term hydration products and microstructure of low-heat Portland cement (LHPC) through microstructural experiments. Subsequently, a novel high-resolution mesoscale framework is developed to investigate the drying shrinkage with hydration kinetics. High-resolution models consist of realistic-shaped aggregates are validated by the aggregate morphology and gradation parameters of core sample from mass concrete. Concurrently, the quantitative effects of internal and external factors on LHPC drying shrinkage are explored. Results indicated that LHPC possesses a denser microstructure, lower porosity, higher carbonation resistance, and 20% lower drying shrinkage compared to moderate-heat Portland cement, suggesting promising applications. Furthermore, experimental and computational findings suggested that increasing aggregate volume, controlling aggregate morphology, and adjusting curing time and humidity could be employed to reduce and manage drying shrinkage, ensuring concrete structure durability.

Reliable determination of polymeric carbon nitride wettability: A standardized sessile drop method for pressed-tablet samples

The wettability of polymeric carbon nitride (PCN) is an important surface chemical factor affecting its catalytic and separation performance. However, due to the amphipathic characteristics of hydrophilic/lipophilic and porous powder properties, the contact angle (CA) of PCN measured by the common sessile drop method will be interfered by the substrate, resulting in randomness of the results. Herein, the pristine PCNs obtained by thermal polycondensation of different precursors in air or nitrogen atmosphere were used as the wettability research object. The CA of the PCNs was measured by a modified sessile drop method after the traditional powders were replaced by pressed-tablet samples. The influence of sample mass and applied pressure on specific surface area, pore volume, surface morphology and CA of the pressed-tablet samples was investigated carefully, and the optimal experimental conditions were determined. When the sample mass was 0.15 g and the applied pressure was 10 MPa, the measured water CA of PCNs was between 27 ∼ 34°, and the diiodomethane CA is between 24 ∼ 29°. The measurement results showed considerable stability and reproducibility. This improved CA measurement method provides a simple and standardized way to accurately explore the surface chemistry of PCN, and has the potential to be applied to other hydrophilic and/or oleophilic porous powder materials.

An experimental investigation on the influence of pore foaming agent particle size on cell morphology, hydrophobicity, and acoustic performance of open cell poly (vinylidene fluoride) polymeric foams

Abstract Globally, the development of porous structured materials has been receiving incredible responses for various high-performance engineering applications. Piezoelectric cellular foams have recently attracted the attention of researchers to emerging applications of acoustic sensors, low-frequency hydrophones, and energy-harvesting devices. As pore morphology is closely related to the shape and the size of the pore-foaming agent, it is necessary to address the influence of particle size of the foaming agent on cell morphology to expand their application area. Hence, this research article establishes the impact of particle size of pore foaming agents on pore morphology, hydrophobicity, and acoustic characteristics of open-cell polyvinylidene fluoride (PVDF) based piezoelectric cellular composites. Open-cell PVDF cellular composites have been fabricated using the template removal method with sodium chloride (NaCl) as a sacrificial templating agent in three different particle sizes: larger, medium, and finer. Based on the experimental results, it can be stated that the particle size of the templating agents dramatically influences the pore morphology, hydrophobicity, and acoustics performance of the PVDF foam samples. The PVDF foams possessing medium pore size have exhibited a maximum sound absorption coefficient of 0.89 at a frequency range of 1,000–1,500 Hz, indicating that PVDF foams have great potential for noise-controlling applications.

Novel CdFe2O4 nanoparticles facile synthesis and their applications towards practical ammonia detection: an effect of annealing

Cadmium ferrite (CdFe2O4) nanoparticles were synthesized via a simple co-precipitation method, and the effect of annealing temperature over the prepared samples’ structural, morphological, and optical properties was analyzed by varying the temperatures 700, 800, and 900 °C. The x-ray diffraction (XRD) studies revealed that the prepared samples are highly crystalline in nature and belong to a cubic spinel crystal structure, and the crystallite size increases from 32 to 59 nm with respect to the increasing temperature. The surface morphology of the ferrite samples showed the uniformly distributed highly agglomerated particles with larger voids for the ferrite nanoparticles annealed at 900 °C. Optical properties of the prepared CdFe2O4 samples were carried out by diffused reflectance spectroscopy (DRS) and the optical band gap of the samples were found to be 2.57, 2.55 and 2.53 eV. The Vibrating sample magnetometer (VSM) studies at room temperature showcased that the nanoparticle samples possess ferromagnetic behavior, and the magnetization (Ms), Coercivity (Hc), and Retentivity (Mr) values were found to be 27.5 × 10−3 emu g−1, 237.60 Oe, and 1976 × 10−6 emu/g for the CdFe2O4 sample annealed at 900 °C. The gas sensing studies were carried out with the presence of target gas ammonia, and its significant sensing parameters such as gas responsivity (S%), rise time, and recovery times were determined, and these values of CdFe2O4 samples annealed at 900 °C were observed to be 1610%, 7.1 s, and 2.2 s. Our findings strongly suggest that the CdFe2O4 samples annealed at 900 °C hold significant promise as a multifunctional material, particularly in gas-sensing applications. This potential opens an exciting avenue for further research and development.

Ni doped carbon-based composites derived from waste cigarette polypropylene filter rod with electromagnetic wave absorption performance

Abstract Polypropylene is widely used in the plastics industry, especially in the tobacco industry, served as cigarette filters to reduce tar and harm. However, it’s difficult to degrade these polypropylene plastics and suitable methods for recycling and reuse is urgent. This research proposes an efficient method for the reuse of polypropylene cigarette filters by mixing waste polypropylene filters with nickel source in different proportions, followed by a facile calcination treatment to prepare nickel-modified carbon-based composite materials with excellent microwave absorption properties. Morphology and magnetic properties of as-prepared samples were analyzed via XRD, SEM, and VSM, exhibiting an increase in carbon content with raising nickel content. Nickel ion anchored on polypropylene fiber may facilitate better fixation of carbon chains during the polypropylene decomposition process. Among the as-prepared samples, CN2 exhibited superior microwave absorption performance, with an optimal absorption peak of -26.76 dB at 7.97 GHz when matched with a given thickness of 4.3 mm, and an effective absorption bandwidth of 3.64 GHz (8.04 GHz to 11.68 GHz) with a matching thickness of 3.5 mm, covering the X band. Therefore, the as-prepared microwave absorbers provides a feasible solution for the recycling and reuse of polypropylene filters, aligning with the tobacco industry requirements for green and sustainable development.

UV-enhanced Mg:MOF-ZnO sensor for n-butanol gas detection at a lower operating temperature

In this study, a novel UV-enhanced Mg-doped MOF-ZnO sensor was investigated for its efficient detection of n-butanol gas at lower temperatures. The composite samples were prepared by the co-precipitation method with the appropriate component ratio. The structure, morphology, and optical properties of the as-prepared samples were systematically analyzed through XRD, SEM, TEM, BET, XPS, and UV–vis characterizations. The gas-sensitive performances based on the pristine MOF-ZnO and Mg-doped MOF-ZnO sensor series with the doping levels of 1 %, 3 %, 5 %, and 7 % (wt%) were comprehensively evaluated by adopting the gas-sensitive system. Among them, the 3 % Mg:MOF-ZnO sensor has given prominence to the largest specific surface area and highest oxygen vacancy concentration demonstrating the most excellent gas-sensing performance. Furthermore, with the aid of UV excitation, the 3 % Mg:MOF-ZnO sensor had achieved the enhanced response value of 2049 that was 4.44 times higher than that of pristine MOF-ZnO to 100 of ppm n-butanol at a low temperature of 246 °C, additionally presented out the superior reproducibility with speedy response/recovery time (12/22 s), the theoretical detection limit as low as 200 ppb, as well as the excellent long-term stability and selectivity for n-butanol. This study offers a promising strategy for the well-development of high-performance n-butanol sensors.

Effect of post-processing treatments on surface roughness and mechanical properties of laser powder bed fusion of Ti–6Al–4V

This study focuses on enhancing the surface characteristics of Ti–6Al–4V alloy fabricated through laser powder bed fusion (LPBF), a prominent additive manufacturing technique. The primary objective is to assess the impact of post-processing surface treatments on the surface roughness, microstructure, and mechanical properties of LPBF Ti–6Al–4V. As-built specimens with fully dense structures underwent sandblasting (SB), chemical etching (CE), and a combination of sandblasting and chemical etching (SB + CE). The investigation reveals significant variation in the surface morphology of as-built samples, primarily influenced by factors such as spattered particles, powder adhesion, and the stair-step effect. In the as-built condition, the down-skin exhibited the highest particle adhesion, covering 11.9 % of the surface. Sandblasting proved particularly effective in removing adhered particles, reducing surface roughness to 5.1 μm from an initial value of 17.8 μm for the down-skin surface. Furthermore, combining sandblasting and chemical etching was more effective than chemical etching alone in achieving uniform surface profiles. Tensile testing indicated that while the ultimate tensile strength remained unchanged, the strain at break significantly improved from 4.8 % to 11.5 %, representing a noticeable increase in ductility in post-processed samples compared to as-built conditions. These findings underscore the influence of post-processing treatments in mitigating surface roughness and enhancing ductility without compromising mechanical strength.

Enhancement of Q-Switched Erbium-Doped Fibre Laser Performance using Graphene Oxide-Calcium Oxide Thin Film Saturable Absorbers

This paper presents an experiment utilizing calcium oxide (CaO) from the cuttlefish bone combined with graphene oxide (GO) to create a graphene oxide-calcium oxide (GO-CaO) based saturable absorber (SA) for Q-switched erbium-doped fibre lasers. The experiment aims to investigate the impact of calcium oxide when added to graphene oxide to form the SA thin film. The laser performance of both types of SA was compared, considering their input pump power, repetition rate, pulse width, and output power. The results indicated that the graphene oxide – calcium oxide SA thin film provided the best output power and the lowest threshold input pump power at 10.76 µW and 53.12 mW, respectively. In the characterization, UV-Vis spectroscopy was utilized to determine the number of discrete wavelengths in UV or visible light that the materials absorbed or transmitted. The UV-Vis results indicated that the graphene oxide thin film exhibited an absorbance value of 0.049 AU and a transmittance value of 89.25 % at a wavelength of 1565 nm. In comparison, the GO-CaO SA thin film displayed an absorbance value of 0.037 AU and a transmittance value of 91.89 % at the same wavelength. Raman spectroscopy was also conducted to provide details about the chemical structure and crystallinity of the thin film samples. The results showed high-intensity peaks for the GO thin film at wavenumbers of 1353.74 cm-1 and 1609.85 cm-1, and for GO – CaO thin film at wavenumbers of 1358.56 cm-1 and 1612.18 cm-1. Additionally, SEM was utilized to study the morphology of the thin film samples. Based on the characterization and laser performance results, it was concluded that the addition of calcium oxide to graphene oxide enhances the properties of the SA thin film, leading to improved laser performance due to its higher thermal conductivity.

Solid State Additive Manufacturing of Thermoset Composites.

Softening and subsequent deformation are significant challenges in additive manufacturing of thermal-curable thermosets. This study proposes an approach to address these issues, involving the preparation of thermosetting composite powders with distinct curing temperatures, the utilization of cold spray additive manufacturing (CSAM) for sample fabrication, and the implementation of stepwise curing for each component. To validate the feasibility of this approach, two single-component thermosetting powders P1 and P2 and their composite powder C were subjected to CSAM and stepwise curing. From the sample morphology observation and deposition/curing mechanism investigation based on thermomechanical analysis and differential scanning calorimetry, it is found that severe plastic deformation occurs during the CSAM process, accompanied by heat generation, leading to local melting to promote a good bond at the contact surface of the particles and form small pores. During the progressive curing, the samples printed using C demonstrate superior deformation resistance compared with those using P1 and P2, and the curing time is reduced from 16.7 h to 1.5 h, due to the sequential curing reactions of P1 and P2 components in composite C, allowing the uncured P2 and cured P1 to alternately remain solid for providing structural support and minimizing deformation.

Small Punch Testing of a Ti6Al4V Titanium Alloy and Simulations under Different Stress Triaxialities.

The mechanical properties of local materials subjected to various stress triaxialities were investigated via self-designed small punch tests and corresponding simulations, which were tailored to the geometry and notch forms of the samples. The finite element model was developed on the basis of the actual test method. After verifying the accuracy of the simulation, the stress, strain, and void volume fraction distributions of the Ti6Al4V titanium alloy under different stress states were compared and analyzed. The results indicate that the mechanical properties of the local material significantly differ during downward pressing depending on the geometric shape. A three-dimensional tensile stress state was observed in the center area, where the void volume fraction was greater than the fracture void volume fraction. The fracture morphology of the samples further confirmed the presence of different stress states. Specifically, the fracture morphology of the globular head samples (with or without U-shaped notches) predominantly featured dimples. Modifying the specimen's geometry effectively increased stress triaxiality, facilitating the determination of the material's constitutive relationship under varying stress states.