Papers by Keyword: Crystallinity

Abstract: The successful implementation of fused filament fabrication (FFF) 3D printing using recycled plastics requires a deep understanding of the thermal behavior of the plastics throughout the printing process. This study investigated the influence of wall thickness of the printed sample, nozzle temperature, and cooling fan speed during 3D printing on the cooling rate, crystallinity, and tensile properties of recycled polyethylene terephthalate (rPET). The experimental process commenced with the collection of discarded rPET bottles, followed by thorough cleaning and washing to remove any adhesives and contaminants. Afterward, the bottles were cut and ground into flakes and then converted into filaments using a single-screw filament extrusion process. In-situ thermal analysis was conducted by integrating an infrared (IR) thermal camera into the 3D printing setup to monitor real-time temperature changes during the printing process. Results revealed that cooling rates increased markedly with reduced wall thickness, rising from 17.53 °C/min for the 3.6 mm wall thickness to 62.92 °C/min for the 1.2 mm wall thickness. Nozzle temperature exhibited a non-linear influence, with the highest cooling rate of 65.47 °C/min recorded at 240 °C, while enhanced cooling fan speed (100%) further accelerated cooling to 45.00 °C/min. Differential scanning calorimetry (DSC) and Raman spectroscopy confirmed that a slower cooling rate generally promoted crystallinity, which was observed in thick-walled and low-cooling speed prints. Tensile testing demonstrated a strong correlation between crystallinity and tensile performance, with ultimate tensile strength (UTS) reaching 55 MPa at 240 °C and 54.8 MPa at 25% cooling fan speed, outperforming previously reported rPET values. The use of rPET in FFF and the findings of this study contribute to the further exploration of rPET's potential in sustainable additive manufacturing practices.

Abstract: This study investigates the mechanical degradation of nylon 6,6 under tensile stress, induced by accelerated aging via ultraviolet (UV) radiation [1-3]. Specimens were fabricated and exposed to controlled UV doses, simulating outdoor weathering conditions. Tensile properties were evaluated, revealing a significant reduction in tensile strength and elongation at break with increasing UV dose. The predominant degradation mechanism was photo-oxidation, evidenced by polymer chain scission and the formation of functional groups altering the material's molecular structure[4,5]. Specimen surfaces exhibited cracks and fissures, contributing to mechanical strength loss. These findings are critical for nylon 6,6 applications in telecommunications and energy industries, where UV exposure is unavoidable. Understanding this degradation is essential for optimizing the durability and reliability of critical infrastructure. This study lays the foundation for developing advanced protective materials and coatings, enhancing the safety and efficiency of outdoor systems.

Abstract: The different characteristics of nanoparticles (NPs) are mostly determined by the sintering process. The goal of the current study is to examine how the sintering temperature affects the optical and structural characteristics of Y₂O₃ NPs made using the sol-gel method. For a competitive study, the synthesized Y₂O₃ NPs were sintered for three hours at 300, 600, and 900°C. The generated Y₂O₃ NPs were sintered for three hours at 300, 600, and 900°C in this work. Samples of Y₂O₃ NPs are designated Y1, Y2, Y3, and Y4, in that order. The cubic structure of Y₂O₃ NPs is confirmed by XRD examination, which also corresponds to JCPDS card No. 083-0927. For Y1, Y2, Y3, and Y4, the crystallite sizes were determined to be 12.58, 12.24, 12.05, and 09.16 nm, respectively. The optical characteristics, such as energy bandgap fluctuations and light absorption, were investigated using UV-Vis spectroscopy. Usually, the absorbance peak shows up between 230 and 250 nm. For Y1, Y2, Y3, and Y4, the energy band gap was determined to be 4.51, 4.40, 4.31, and 4.19 eV, respectively. The vibrational modes of the Y₂O₃ NPs are examined, which provides further evidence of phase purity and structural stability. Increased band gap, better crystallinity, and a lower percentage of oxygen atoms all help the material's mechanical and chemical durability as well as its shine, which makes it more suitable for dental ceramic applications.

Abstract: Bacterial nanocellulose (BNC) is a natural polymer gel with unique properties that are suitable for developing advanced film applications such as edible coating and packaging. However, transforming BNC gel into a suspension and applying it as a film still lacks knowledge of the condition and method since BNC film performance depends on many parameters caused by the transformation process. This work studied two important primary variables, the number of homogenization cycles and the BNC concentrations, for transforming BNC gel into aqueous suspension using a microfluidizer to homogenize nanofibers and water medium. The BNC films obtained from the suspensions were examined for their properties, i.e., morphology, crystallinity index, optical, thermal, and mechanical properties. The results explored that the number of homogenization cycles had a non-significant impact on the characteristics and properties of BNC suspension and film. A significant improvement in film properties was found when using a higher BNC concentration at 1% w/v compared with 0.5% w/v at the equivalent number of homogenization cycles (40 cycles). The degradation temperature of this film increased by 13%, and Young’s modulus and tensile strength increased more than twice compared with the 0.5% w/v sample, increasing from 0.3 to 0.7 MPa and from 9 to 19 kPa, respectively. This finding would benefit the further development of BNC film for coating and packaging applications.

Abstract: Tin oxide (SnO₂) holds significance as an n-type semiconductor metal oxide, finding diverse applications across various fields. It has optimal properties as a gas sensing material, fuel cells, batteries, and so on. The main objective of this research is to synthesize SnO₂ thin films at a low-cost, easily replicable method and study its crystallographic properties. Here, the thin film was prepared by electrodeposition using tin sulfate, tartaric acid, and potassium nitrate at 2.1 pH followed by annealing the obtained thin film at 773 K. The whole process was conducted at 300 K without any external DC. The synthesized substrate was crystallographic properties were studied using X-ray diffraction. The average crystallite grain size was evaluated to be around 19 nm with degree of crystallinity close to 48.3%. These outcomes show that the method used to create thin films was in an appropriate direction.

Abstract: Solid lubricant is an environment-friendly alternative to liquid lubricants, which can be applied in extreme environmental conditions like high temperature and pressure where liquid lubricants fail. In this work, an attempt was made to synthesize calcium fluoride, a solid lubricant material from scrap eggshell powder by using the ion exchange method. The prepared eggshell powder was treated with 40% concentric hydrofluoric acid and was manually mixed using a mortar and pestle. The synthesized CaF₂ powder was characterized by using SEM and XRD. The degree of Crystallinity was calculated from the XRD data by using Origin Pro and Excel software. The Crystallinity of the prepared CaF₂ powder was found to be 78.01%. The crystal size of the synthesized CaF₂ powder was calculated using Scherer’s formula. The crystal size was found to be between 9–22 nm ranges. The synthesized calcium fluoride XRD intensity peaks were matching exactly with the JCPDS card of the standard CaF₂ powder, confirming the presence of CaF_2.

Abstract: Ca-Mg-Zn bulk metallic glasses (BMGs) are promising biomaterials for orthopaedic applications because when they get reabsorbed, a retrieval surgery is not needed. In this study, Ca-Mg-Zn metallic glasses with different compositions, Ca_56.02Mg_20.26Zn_23.72 and Zn_50.72Mg_23.44Ca_25.84, were fabricated by induction melting followed by copper mould casting. Their degree of crystallinity was modified by annealing, obtaining exemplar specimens of fully amorphous, partially amorphous (i.e., a BMG composite (BMGC)) and fully crystalline alloys. The microstructure, thermodynamic and corrosion performance of these alloys were evaluated as well as their electrochemical behaviour. The results of polarisation tests demonstrate that the corrosion resistance of the Zn-rich alloy is markedly better than the Ca-rich BMG. Corrosion rates of these Ca-and Zn-rich alloys with different degrees of crystallinity illustrate that the corrosion behaviours of alloys strongly depend on their microstructure, which shows a positive correlation between the corrosion current density and the crystallised volume fraction of the alloy. This study aims to shed light on the impact of the amorphicity-to-crystallinity ratio on the multifunctional properties of BMGs/BMGCs, and to assess how feasible it is to fine-tune those properties by controlling the percentage of crystallinity.

Abstract: The article investigates the influence of the sintering time with constant temperature on the development of the tricalcium silicate crystallinity using the Scherrer's and Rietveld method.One suitable raw material mixture consisting of only pure CaCO₃ and SiO₂ in their specific ratio of 73.6:26.3 wt.% was selected. This raw material powder was prepared using a wet milling process in the water medium in a PULVERISETTE 6 plan mill. Based on previous research in this area, a firing temperature of 1500 °C was chosen with sintering period of 5, 10, 15 and 20 minutes in an experimental furnace with a manipulator for isothermal sintering of laboratory samples developed by Dr. Chromy. This furnace requires special sample preparation, so a procedure for their preparation was designed and optimized. Thanks to this optimization, it is possible to repeatably prepare identical pellets with the exact parameters for this type of furnace. The resulting pellet weight is 73 mg at a volumetric weight of 2,285 g·cm^-3.The results of the firings with different sintering times and constant temperatures showed that the sintering processes and mineral conversion occur very quickly, since after 5 minutes 30.81 wt.% of the mineral tricalcium silicate was identified and after 20 minutes the raw powder was converted to tricalcium silicate in a significant amount, i.e., 72.02 wt.%. At the same time, the crystallinity was monitored using Scherrer's method and after 20 minutes of sintering, the crystallite size of tricalcium silicate reached 104.889 nm. Thus, there was a relatively rapid development of the crystallinity of Alite.

Abstract: ZnO nanoparticles were successfully produced via a simple low cost hydrothermal method using different metal precursors. Zn (CH₃COO)₂), (Zn (NO₃)₂) and (ZnCl₂) were the source materials. The obtained nanoparticles were investigated by means XRD, SEM and DRS. The XRD exhibited the high crystallinity of the pure ZnO phase with hexagonal wurtzite crystalline structure for all simples excepted for ZnO synthetized from ZnCl₂ precursor. The crystallite sizes was estimated in the range of 20-37 nm. The precursor type do not affect the E_g of the nanoparticles. The bandgaps energies were between 3.21-3.22 eV. The type of precursor affect the particles morphology. SEM images revealed different morphologies. The photocatalytic activity of the synthetized ZnO NPs in comparison with that of commercial powder for the methylene blue (MB) degradation under UV irradiation, showed the appropriate activity of nanostructures obtained by Zn (NO₃)₂ and Zn (CH₃COO)₂ precursors. The first-order kinetic constant over ZnO from Zn (NO₃)₂ was 1.9, 3.7 and 1.5 times of ZnO commercial powder, ZnO from ZnCl₂ and Zn (CH₃COO)₂, respectively. The ZnO NPs from Zn (NO₃)₂ and Zn (CH₃COO)₂ precursors have the best photocatalytic degradation performance with a degradation rate of 99.3% and 96.4%, respectively. The higher photocatalytic performance was probably due to the larger crystallinity, purity phase and specific morphologies than smaller particle size effect. Thus, the synthetized ZnO nanoparticles by the soft hydrothermal process are a promising candidate for the photocatalytic purposes of dyes from waters.

Abstract: In the present study, Polylactic acid/ silicon dioxide (SiO₂)/ alumina (Al₂O₃) composite films were produced by a casting method. Thermal, morphological, optical and structural properties of obtaining samples investigated. The addition of aluminum monoxide and silicon dioxide fillers in PLA matrix increases the glass transition temperature significantly, and the Al₂O₃ and SiO₂ particles behave as good nucleating agents with PLA matrix. A homogeneous distribution of SiO₂ and Al₂O₃ particles was observed in the composite films. XRD results revealed that the addition of SiO₂ particles improved the crystallinity of PLA, knowing that the degree of crystallinity increase from 2.75% to 31.63% by adding the nucleating agents. The DSC results showed that the glass transition temperature increases by 12 °C in the composites than the pure PLA.