Advanced Materials Research Vol. 1179

Abstract: A modified natural zeolite will be used as a catalyst in the isomerization process of glucose to fructose. It is modified by inserting Fe into its pores with the impregnation method so that the active site of the catalyst is formed as part of the isomerization process. This study aimed to make a catalyst from Fe-impregnated natural zeolite and determine its catalytic performance under various pH, temperature, and isomerization time conditions. The zeolite was activated using 6M H₂SO₄ and 0.5M KMnO₄. The zeolite impregnation process was carried out using 1% (%w/v) FeCl₃.6H₂O solution with a ratio of (1:8) and continued with calcination at 500°C for 4 hours. The Fe-zeolite catalyst was characterized to determine the degree of crystallinity and crystal form, functional groups of its constituent compounds, and surface area. The isomerization process was carried out as a substrate of 10% glucose solution and 1 g of Fe-zeolite catalyst at various temperatures of 40, 50, and 60°C; pH 5, 7, and 9; a sampling time of every 15 minutes for 1 hour. The best fructose yield from the isomerization process was at a reaction temperature of 60°C, pH 5, and 45 min with a yield of 0.837%. It concluded that the Fe-Zeolite catalyst did not give a significant effect on the glucose isomerization process. It is expected that other researchers conduct similar research with different types of metal impregnated to give better results on the glucose isomerization process.

Abstract: Nanoencapsulation technology has been used in food and pharmaceutical applications to increase bioactive chemical functioning and stability against external influences. To develop a cost-effective encapsulating procedure, additional optimization is required. This study employed response surface methodology (RSM) to optimize the encapsulation of anthocyanin-rich extract from black rice bran. The extract was encapsulated through pre-gelation and polyelectrolyte complex formation processes. Box-Behnken design was employed to determine the optimum conditions for the encapsulation process with the following process variables: chitosan concentration, pH, and CaCl₂ concentration. Chemical characteristics, surface morphology, and particle size were used to describe the resultant capsules, which were then subjected to phytochemical analysis. The optimal encapsulation conditions for anthocyanin were 6.30 mg/mL chitosan, pH 5.5, and 36 mM CaCl_2, with a 51.20 % encapsulation efficiency. The developed anthocyanin-loaded nanocapsule has a high TPC (3.87 mg GAE/g) and potent antioxidant activity (5.69 mg TE/g). SEM images revealed a smooth surface area and spherical particles that clumped together, with an average particle size of 94.70 nm. FTIR analysis corroborates the well-incorporation of anthocyanin into the nanocapsules. The encapsulation process of anthocyanin-rich extract from black rice bran was successfully optimized via RSM.

Abstract: In the field of fuel cell technology, the development of cost-effective catalysts is crucial for the commercialization of Alkaline Membrane Fuel Cells (AMFCs). Platinum (Pt) has traditionally been employed as the catalyst in AMFCs, but its high cost poses a major barrier to widespread adoption. In this study, a new catalyst material was developed by incorporating Manganese Dioxide (α-MnO₂) into Carbon Nanotubes (CNTs) using hydrothermal synthesis techniques. The synthesized catalyst was characterized using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), and its electrocatalytic activity was evaluated through Linear Sweep Voltammetry (LSV) and CV through Rotating Disc Electrode (RDE) experiments. The results showed that the α-MnO₂-CNT composite displayed strong durability in the alkaline environment and high electrocatalytic activity for oxygen reduction reaction (ORR). The LSV measurements revealed a current density of -4.1 mA/cm² and an overpotential of -0.3V relative to Standard Calomel Electrode (SCE) in a 0.1M KOH electrolyte. Additionally, the α-MnO₂-CNT composite displayed high methanol tolerance and long-term stability compared to commercial Pt/C catalysts. This study demonstrates that the use of α-MnO₂-CNT as a cost-effective alternative to Pt has the potential to facilitate the commercialization of AMFC technology.

Abstract: We report on an approach for the in-situ synthesis (chemical method based) of SnO-SnO₂ nanocomposites followed by characterisation (including morphological, chemical, structural and optical) and investigation of the electrical properties of the nanocomposites with reference to the as-synthesized SnO₂ nanoparticles. Compared to spherical SnO₂ particles, the SnO phase is found existing in the form of sheet like morphology. It has been found that through controlling of the Sn:OH precursor ratio is effective for the achievement of SnO phase. Compared to the pristine SnO₂ nanoparticles, the current-voltage (I-V) characteristics of the nanocomposites show the p-n junction characteristics. The observation of rectification ratio 2.05 indicates the excellent rectifying property of the nanocomposites due to the presence of p-type SnO phase. Further, exploration of the I-V characteristics has revealed the dominance of space-charge limited current transport mechanism for the nanocomposites sample. The lattice defects are discovered to be the cause of the transport mechanism in the nanocomposites sample.

Abstract: Aiming at the shortcomings of large volume, high cost and long detection cycle of traditional solid propellant aging detection methods, a solid propellant aging detection method based on impedance spectroscopy is proposed. Firstly, the internal impedance of the solid propellant changes after aging, and a portable solid propellant impedance spectrum acquisition system based on impedance spectroscopy is designed based on the principle of electrochemical impedance spectroscopy, and the real and imaginary parts of the impedance spectrum are obtained. Secondly, in order to reduce the data dimension of the classification algorithm, the KPCA (Nuclear Principal Component Analysis) feature extraction algorithm is used to extract the impedance spectrum features of the solid propellant. Then, according to the impedance spectrum characteristics, the BP neural network is used for classification training, and the correspondence between the impedance spectrum and the aging time is obtained. Finally, the feasibility and effectiveness of the proposed method are verified on the physical platform, and the results show that the proposed method has the advantages of high precision and accurate classification, and can effectively predict the aging degree of solid propellant.

Abstract: Solid-state diffusion bonding effectively joins dissimilar materials, even with varying metallurgical properties and melting points. In this study, a Cu/Ni joint was produced at a bonding temperature of 950°C for 60 minutes under a vacuum. The microstructural and mechanical properties of the bonding interface were evaluated using scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), microhardness tests, and X-ray diffraction (XRD). It was found that the EDS point scan analysis revealed the formation of a solid solution of Cu-Ni at the bonding interface. Since Cu-Ni exhibit complete solubility with each other, no intermetallic compounds (IMCs) were formed. The microhardness indicated that the bonding interface had a microhardness of 20% and 54% higher than the base metals (BM) of Ni and Cu, respectively.

Abstract: As a post treatment, thermal remelting is an effective method to eliminate pores and establish a metallurgical bonding for thermal sprayed coatings. However, it is rather difficult to obtain simultaneously high corrosion and wear resistance, since additional energy input usually leads to more homogeneous microstructure in coatings, which deteriorates mechanical hardness. In this work, flame remelting has been imposed to high velocity oxygen-fuel sprayed self-flux NiCrBSi coatings. The remelting effects on microstructure were characterized in terms of porosity and phase analysis. The microhardness, wear resistance and corrosive behaviors were compared among substrate steel, as-sprayed and as-remelted coatings. Results show that the lamellar boundaries and internal defects in the as-sprayed coatings have been eliminated by remelting. The coating porosity has substantially reduced from 7.36% to 0.75%, and a metallurgical bonding at the coating/substrate interface has been formed. Comparing with the as-sprayed coatings, the microhardness of the remelted coatings increases about 21% and the wear weight loss reduces about 42%. By flame remelting, the wear mechanism changes from furrow and abrasive wear to micro-cutting and local fracture. The remelted coatings have also exhibited better corrosion resistance by means of salt spraying and potentiodynamic tests.

Abstract: Most of the bottles manufactured with PET polymer (polyethylene terephthalate) are used in beverage packaging and, after use, are turned into garbage, causing environmental problems. The concept of recycling and reuse of these materials for use in civil construction can become an interesting solution for the reduction of urban solid waste that would be destined to the formation of large volumes in sanitary landfills. Seeking to minimize this problem, this work used discarded PET bottles, ground into fibers, to prepare a concrete-based composite. The behavior of concrete composites with the addition of PET fibers in different compositions 7.5 kg/m³, 10 kg/m³ and 12.5 kg/m³ was evaluated. The choice of these concentrations aimed to study the addition of a reasonable amount of PET, characterizing greater reuse of a recycled material, seeking to provide a reinforcement effect in the cementitious matrix. The samples were subjected to mechanical tests of axial compression and diametral compression in a duly calibrated hydraulic press. For the axial compression test, the composite with 10 kg/m³ showed better mechanical performance. Probably at this content, the fibers were better distributed in the concrete for axial compression, resisting more to the fracture point, surpassing the composite of 12.5 kg/m³ by 24% in resistance to compression. For the axial compression test, the composite with 10 kg/m³ showed better mechanical performance, because in this composition there was an ideal amount for the homogenization of the PET fibers in the concrete, achieving a greater reinforcement effect. For the permeability test, the composites prepared with higher percentages of PET showed a lower percentage of permeability (44% lower than the content of 7.5 kg/m³), absorbing less water in this composition, in an axial position. This can be attributed to the fact that the distributed PET fibers act as an impermeable barrier, offering greater resistance to water absorption in the material.

Abstract: To increase cohesiveness, toughness, impermeability, and adhesion strength in cementitious materials like mortars and concrete, vinyl acetate ethylene (VAE) copolymer redispersible powder (RDP) is used. However, due to numerous variety of material, choosing an original performing RDP is challenging. The goal of this study is to assess the bond strength to concrete surfaces of various redispersible polymer-modified cementitious coatings under various accelerated settings. The outcomes showed that the RDP backbone composition has a significant influence on the coatings' adhesion strength. Methyl methacrylate (MMA) and Vinyl chloride (VC) present as comonomers in RDP exhibit outstanding thermal stability and boost tensile adhesion strength by 41% and 21%, respectively, in comparison to other RDPs. According to SEM studies, the VC- RDP stimulates the formation of fibrous ettringite, producing a uniform and cohesive microstructure.

Abstract: This study investigates the influence of cow bone powder (CBP) on consistency and compaction characteristics of lime-stabilized soil. Twelve soil samples were collected from four routes connecting Ado-Ekiti. Index and compaction tests were performed on the natural and stabilized samples. The soil samples were classified according to AASHTO groups and eventually restructured into four (4) groups: A-6, A-7-6, A-4, and A-7-5. They were named samples A, B, C, and D respectively. The oxide compositions of the samples were determined. Lime was blended with soils at proportions of 0, 2, 4, 6, 8,10 %, and the optimal lime content (Lime_Opt) was obtained. The Lime_Opt + soil mixture was mixed with 2, 4, 6, 8,10 % of CBP. The Soil + LimeOpt + CBP mixtures were subjected to consistency limits and compaction tests. Plasticity index (PI) of soils A, B, C, and D was 14.19, 21.06, 11.64, and 14.19 % respectively, while the MDD was 1640, 1730, 1630, and 1631 kg/m³. Soil A, B, C, and D + Lime_Opt all had reduced PIs of 7.68, 16.40, 5.04, and 12.05%, respectively. For the MDD of soil + LimeOpt mixtures, 1789, 1920, 1906, and 1898 kg/m³ were also found for Samples A, B, C, and D. Soil + LimeOpt + CBP showed that both the PI (from 0.6 to 81.7%) and MDD (from 0.1 to 14.6%) improved. On the other hand, the addition of lime to soils A, B, C, and D showed that 8% lime content offered the optimal CBR performance. Further addition of CBP to the soil + Lime_Opt mixtures equally improved both the soaked and unsoaked CBR of soils A, B, C, and D predominantly with 6% CBP addition offering the peak performance. This suggests that CBP is viable and can save cost, mitigate environmental hazards, and complement lime. Strength and durability evaluation of the ternary mixture is however recommended.