Composite Surface Research Articles

Improvement of mechanical performance on zirconium dioxide nanoparticle synthesized magnesium alloy nano composite

With excellent mechanical properties and distinct solidification, the AZ31B series magnesium alloy has great potential for targeting engineering applications and synthesized via die casting process found a drawback on oxidation results porosity and reduced mechanical properties. Here, the magnesium alloy AZ31B series nanocomposite was synthesized with varied weight percentages of zirconium dioxide nanoparticles through a liquid metallurgy route with an applied stir speed of 200 rpm under an argon nature. With the help of a scanning electron microscope, the distribution of particles in the composite surface was found to be homogenous and void-free surface, which output results in less percentage of porosity (<1 %), and the composite contained 6 wt% ZrO2 offers superior yield strength (212 ± 3 MPa), tensile strength (278 ± 2 MPa), and impact strength of 16.4 ± 0.4 J/mm2. In addition, 8 wt% ZrO2 blended composite showed the maximum microhardness value (78.3 ± 1 HV). The best-enhanced result of NC3 (AZ31B/6 wt% ZrO2) is suggested for lightweight to high-strength structural applications.

Nitrogen-Doped Diamond-like Carbon Buffer Layer Enhances the Mechanical and Tribological Properties of Diamond-like Carbon Films Deposited on Nitrile Rubber Substrate

The poor adhesion between the DLC film and rubber restricts its application of seals. Introducing a suitable interlayer can bolster the adhesion of the coating or film. In this study, nitrogen-doped diamond-like carbon (N-DLC) emerged as the optimal intermediate layer between rubber and DLC. A series of N-DLC/DLC multilayer films were fabricated via DC magnetron sputtering on nitrile rubber (NBR) substrates, varying the substrate bias voltage (0 V, 100 V, 200 V). A scanning electron microscopy analysis revealed that the composite film surface was smoother than the DLC film alone. The results of Raman spectroscopy and X-ray photoelectron spectroscopy indicated a robust bond between nitrogen and carbon atoms in the composite film, with nitrogen facilitating the conversion of sp3C-C bonds into sp2C=C. Mechanical tests demonstrated that the N-DLC interlayer improved film adhesion and reduced the CoF of the composite film to 0.2–0.3. Specifically, the CoF of the N-DLC/DLC film prepared at 100 V was as low as 0.20, with a wear amount of 1.13 mg. Consequently, the inclusion of the N-DLC interlayer substantially enhanced the mechanical and tribological properties of DLC-coated NBR, rendering this coating highly advantageous for various applications.

Selective Cu electroplating enabled by surface patterning and enhanced conductivity of carbon fiber reinforced polymers upon air plasma etching

We demonstrate a sustainable post-processing of carbon fiber reinforced epoxy polymer (CFRP) composites by air plasma etching that permits regular electroconductive surface patterning through direct Cu galvanic metallization, in contrast to the untreated composite. Our study reveals a significant property dependence of the composite with respect to the position to the fiber/matrix composite surface and treatment. The enhancement in electrical conductivity was not compromised by the lower structural integrity of the composite, as the embedded carbon fibers remained unaffected by the air plasma etching process. The metallized Cu domains on the composite exhibit good hardness and excellent solderability potential. Thus, the electroconductive surface patterning of the composite, preceding galvanic metallization, facilitates the selective deposition of Cu layer domains. This step by step process, relying on the creation of selective electroconductive areas on the composite by plasma etching, enables galvanic metallization. Consequently, it enhances the potential for multifunctional composite applications. The feasibility of galvanic metallization brings new perspectives in selective metallization of composites by allowing the tailoring of the metal layer thickness, microstructure and selection of the metal.

Vacancy and Growth Modulation of Cobalt Hexacyanoferrate by Porous MXene for Zinc Ion Batteries

AbstractPrussian blue analogs (PBAs) featuring with 3D open framework are recognized as promising cathode candidates for Zinc‐ion batteries (ZIBs). However, challenges such as unsatisfactory active site utilization, low conductivity, and abundant structural vacancies have impeded fulfillment of their potential. In this work, a conductive in‐plane porous MXene is for the first time adopted as a multifunctional host material to enhance cobalt hexacyanoferrate (CoHCF) growth and crystallinity. Particularly, the uniform surface charges on MXene are identified to induce anisotropic and highly crystalline CoHCF, which are critical to alleviating the practical drawbacks associated with the PBAs family. Empowered by the targeted modification, the CoHCF nanotube/MXene composite realizes high surface area and low defectiveness, resulting in an impressive capacity of 197 mAh g−1 at 0.1 A g−1 and capacity retention of 95.3% over 3000 cycles at 2.0 A g−1. X‐ray spectroscopy and density functional theory (DFT) reveal that Co─C bonds in the heterostructure facilitate rapid electron/Zn‐ion transfer, enhancing Zn storage kinetics. To validate practical applicability, pouch cells incorporating Zn|CoHCF/MXene are further examined. This composition strategy, utilizing MXene as a multifunctional template, enhances the surface area, conductivity, and crystallinity of PBAs as cathodes for ZIBs, showcasing the significant potential for large‐scale energy storage applications.

The CD4 transmembrane GGXXG and juxtamembrane (C/F)CV+C motifs mediate pMHCII-specific signaling independently of CD4-LCK interactions.

CD4+ T cell activation is driven by five-module receptor complexes. The T cell receptor (TCR) is the receptor module that binds composite surfaces of peptide antigens embedded within MHCII molecules (pMHCII). It associates with three signaling modules (CD3γε, CD3δε, and CD3ζζ) to form TCR-CD3 complexes. CD4 is the coreceptor module. It reciprocally associates with TCR-CD3-pMHCII assemblies on the outside of a CD4+ T cells and with the Src kinase, LCK, on the inside. Previously, we reported that the CD4 transmembrane GGXXG and cytoplasmic juxtamembrane (C/F)CV+C motifs found in eutherian (placental mammal) CD4 have constituent residues that evolved under purifying selection (Lee et al., 2022). Expressing mutants of these motifs together in T cell hybridomas increased CD4-LCK association but reduced CD3ζ, ZAP70, and PLCγ1 phosphorylation levels, as well as IL-2 production, in response to agonist pMHCII. Because these mutants preferentially localized CD4-LCK pairs to non-raft membrane fractions, one explanation for our results was that they impaired proximal signaling by sequestering LCK away from TCR-CD3. An alternative hypothesis is that the mutations directly impacted signaling because the motifs normally play an LCK-independent role in signaling. The goal of this study was to discriminate between these possibilities. Using T cell hybridomas, our results indicate that: intracellular CD4-LCK interactions are not necessary for pMHCII-specific signal initiation; the GGXXG and (C/F)CV+C motifs are key determinants of CD4-mediated pMHCII-specific signal amplification; the GGXXG and (C/F)CV+C motifs exert their functions independently of direct CD4-LCK association. These data provide a mechanistic explanation for why residues within these motifs are under purifying selection in jawed vertebrates. The results are also important to consider for biomimetic engineering of synthetic receptors.

The CD4 transmembrane GGXXG and juxtamembrane (C/F)CV+C motifs mediate pMHCII-specific signaling independently of CD4-LCK interactions

CD4+ T cell activation is driven by five-module receptor complexes. The T cell receptor (TCR) is the receptor module that binds composite surfaces of peptide antigens embedded within MHCII molecules (pMHCII). It associates with three signaling modules (CD3γε, CD3δε, and CD3ζζ) to form TCR-CD3 complexes. CD4 is the coreceptor module. It reciprocally associates with TCR-CD3-pMHCII assemblies on the outside of a CD4+ T cells and with the Src kinase, LCK, on the inside. Previously, we reported that the CD4 transmembrane GGXXG and cytoplasmic juxtamembrane (C/F)CV+C motifs found in eutherian (placental mammal) CD4 have constituent residues that evolved under purifying selection (Lee et al., 2022). Expressing mutants of these motifs together in T cell hybridomas increased CD4-LCK association but reduced CD3ζ, ZAP70, and PLCγ1 phosphorylation levels, as well as IL-2 production, in response to agonist pMHCII. Because these mutants preferentially localized CD4-LCK pairs to non-raft membrane fractions, one explanation for our results was that they impaired proximal signaling by sequestering LCK away from TCR-CD3. An alternative hypothesis is that the mutations directly impacted signaling because the motifs normally play an LCK-independent role in signaling. The goal of this study was to discriminate between these possibilities. Using T cell hybridomas, our results indicate that: intracellular CD4-LCK interactions are not necessary for pMHCII-specific signal initiation; the GGXXG and (C/F)CV+C motifs are key determinants of CD4-mediated pMHCII-specific signal amplification; the GGXXG and (C/F)CV+C motifs exert their functions independently of direct CD4-LCK association. These data provide a mechanistic explanation for why residues within these motifs are under purifying selection in jawed vertebrates. The results are also important to consider for biomimetic engineering of synthetic receptors.

Preparation of AC/TiO2 doped N-Ce Synthesized via Microwave Irradiation for Amoxicillin Photodegradation

Activated carbon (AC) supported with titanium dioxide (TiO2) doped with nitrogen (N) and cerium (Ce), denoted as AC/TiO2 doped N-Ce was synthesized for adsorption and photodegradation of amoxicillin (AMX) antibiotic. Photocatalyst was prepared using sol-gel approach assisted by microwave irradiation.30 experiment runs were generated for photocatalyst production and optimized via Central Composite Design-Response Surface Methodology (CCD-RSM) with observation of four types of variable parameters. The experimental variables consisted of the quantities of urea (N) (𝑥𝑥𝑖𝑖: 0.02–0.20 g), amount of cerium (III) nitrate hexahydrate (Ce) (𝑥𝑥𝑗𝑗: 0.02–0.20 g), amount of AC (𝑥𝑥𝑘𝑘: 0.10 –0.50 g), and microwave power (𝑥𝑥𝑙𝑙: 600–800 W). The analysis revealed that AC/TiO2 doped N-Ce photocatalyst, which was prepared with 0.50 g AC, 0.02 g N, and 0.20 g Ce, and activated with microwave power 600 W in 15 min, achieved a 93.6% AMX removal under UV light irradiation. The photocatalyst was initially subjected to a concentration of 10 mg L-1 at 30 °Cfor a duration of 60 min.

The Mechanics of Elastomeric Sheet Reinforced With Bidirectional Fiber Mesh Subjected to Flexure on Boundaries

Abstract We investigate the concurrent three-dimensional deformations of fiber-reinforced composite sheets subjected to out-of-plane bending moments via a continuum model, where we invoke the neo-Hookean strain energy model for the matrix material of fiber-reinforced composite, and assimilate the strain energy of fiber reinforcements into the matrix material model by accounting for stretching, bending, and twisting kinematics of the fibers through the computations of the first-order and second-order gradient of deformation. Emphasis is placed on deriving the Euler equation and boundary conditions of bending moment within the framework of the variational principle and configuring composite surfaces using differential geometry. Significant attention has been given to illustrating the concurrent three-dimensional deformation of fiber composite, meshwork deformation, and fiber kinematics. The simulation results reveal that for a square fiber composite subjected to the out-of-plane bending moment, the maximum in-plane deformation of matrix material occurs along the diagonal direction of the domain while the center of the domain experiences weak in-plane deformation. Notably, the matrix material performs isotropic/anisotropic properties depending on the domain size/shape. In addition, the simulated unit fiber deformations reasonably validate the overall deformation of the network, underscoring that the deformations of the embedded fiber units govern the overall mechanical performance of the fiber meshwork. More importantly, the continuum model qualitatively provides reasonable predictions on the damage patterns of construction materials by demonstrating the kinematics of matrix material and meshwork deformation.

Dry Eye Disease Symptoms Among Glaucoma Patients at a Portuguese Hospital.

Glaucoma-related dry eye disease (DED) is often underestimated, but it is an important comorbidity affecting 40% to 59% of glaucoma patients. It may be an exacerbation of a pre-existing condition or a novel disease starting after the initiation of topical medication. The cumulative effect of medication, preservatives and excipients leads to an alteration in tear film composition and ocular surface stability. The main purpose of this investigation was to study a group of Portuguese glaucoma patients regarding the presence of DED symptoms and correlate the severity of the symptoms with the usage of different types of glaucoma topical medications. This is a cross-sectional observational study of patients diagnosed with primary and secondary open-angle glaucoma. The questionnaire Standardized Patient Evaluation of Eye Dryness (SPEED) translated to Portuguese (SPEED-Vp) was taken by patients followed in the Glaucoma Department of Unidade Local de Saúde Entre Douro e Vouga, Santa Maria da Feira, Portugal. Data was collected regarding their age, gender, type of topical medication in use as well as frequency and duration of usage. A statistical analysis was performed. A total of 75 patients answered the SPEED-Vp questionnaire. The mean age was 72 ± 7 years old. Fifty-two percent (n=39) were male, and 48% (n=36) were female patients. About 49.33% (n=37) had been on intraocular pressure (IOP)-lowering eyedrops for more than five years. About 61.43% (n=43) of patients used IOP-lowering eyedrops with preservatives. Most of the patients used prostaglandin analogs (75.71%, n=53) and beta-blockers (72.86%, n=51). SPEED score average was 2.75. About 25.33% (n=19) had no DED symptoms, 58.67% (n=44) had mild symptoms, 8% (n=6) had moderate symptoms and 8% (n=6) had severe symptoms. No statistically significant correlation was found between SPEED score and age, gender, number of eyedrop containers, number of active principles, application frequency, presence of preservatives, number of eyedrop containers with preservatives, duration of eyedrops usage or any of the medication groups. Although a high percentage of patients were on eyedrops with preservatives, this low rate of symptoms might be because patients tended to devalue these symptoms;were already on treatment with artificial tears; or have an underestimation of the sensation of dry eye due to decreased neuronal corneal nerve responses and density. These results were surprisingly positive. This might also be the result of the healthcare provider's sensibilization to this issue (early diagnosis, early prescription of artificial tears and change from preservative to preservative-free medication).

The investigation of flame-retardant fiber mats for high performance composites: flame retardancy and structure performance

The flame-retardant performance of carbon fiber reinforced composites serves as a critical metric for structural stability. Nonetheless, the prevalent methodologies for improving the flame retardancy of composites struggle to reconcile the dual objectives of flame retardancy and mechanical robustness, due in part to the constraints imposed by the conventional additive-based approach on the material interface. This study introduced a novel method involving a glass fiber mat, which was augmented with a polyurethane-based treatment integrated with flame-retardant substances, in particular ammonium polyphosphate and nickel hydroxide. This fiber mat was strategically applied to the composite surface, conferring both flame retardancy and enhanced structural resilience. The structure performance and flame retardancy of composites were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and the cone calorimeter test. Experimental comparisons with nontreated controls indicated that the innovative composites exhibited a reduction in total heat release and total smoke production by 13.7% and 18.8%, respectively. Concurrently, a notable enhancement in mechanical properties was observed, with increases of 20.9% and 23.1% for tensile and flexural strength. This well-balanced performance is attributable to the structure design, with toughened glass fiber mats to protect the composite surfaces from structural failure, and flame-retardant agent composition for combustion resistance and smoke suppression. Consequently, the proposed integrative flame-retardant structural design, enriched with specific flame-retardant treatments, offers a promising avenue for fabricating high-performance composite materials with potential utility in the aviation and aerospace sectors.

Composite PCL Scaffold With 70% β-TCP as Suitable Structure for Bone Replacement

The purpose of this work was to optimise printable polycaprolactone (PCL)/β-tricalcium phosphate (β-TCP) biomaterials with high percentages of β-TCP endowed with balanced mechanical characteristics to resemble human cancellous bone, presumably improving osteogenesis. PCL/β-TCP scaffolds were obtained from customised filaments for fused deposition modelling (FDM) 3D printing with increasing amounts of β-TCP. Samples mechanical features, surface topography and wettability were evaluated as well as cytocompatibility assays, cell adhesion and differentiation. The parameters of the newly fabricated materila were optimal for PCL/β-TCP scaffold fabrication. Composite surfaces showed higher hydrophilicity compared with the controls, and their surface roughness sharply was higher, possibly due to the presence of β-TCP. The Young's modulus of the composites was significantly higher than that of pristine PCL, indicating that the intrinsic strength of β-TCP is beneficial for enhancing the elastic modulus of the composite biomaterials. All novel composite biomaterials supported greater cellular growth and stronger osteoblastic differentiation compared with the PCL control. This project highlights the possibility to fabricat, through an FDM solvent-free approach, PCL/β-TCP scaffolds of up to 70 % concentrations of β-TCP. overcoming the current lmit of 60 % stated in the literature. The combination of 3D printing and customised biomaterials allowed production of highly personalised scaffolds with optimal mechanical and biological features resembling the natural structure and the composition of bone. This underlines the promise of such structures for innovative approaches for bone and periodontal regeneration.

Effect of process parameters on quality of alfalfa block

To address the imbalance in the supply of grass resources caused by seasonality and regional factors, it is crucial to efficiently store and transport alfalfa. Exploring suitable grass feed processing techniques contributes to the stable transportation of grass blocks and long-term storage of nutritional components. The Central Composite Design response surface design was used to design experiments, with moisture content and compressive force as the test factors. Based on the experimental results, it was found that lower moisture content and a certain compressive force were beneficial for the stability, high density, and protein storage of alfalfa blocks. The microscopic examination of alfalfa particles revealed that a certain moisture content (15%) facilitates the formation of solid bridges between particles, leading to more stable alfalfa blocks. The final optimized process parameters were moisture content of 14.3% and compressive force of 34.8 kN. Under these conditions, the density of the molded alfalfa block was 1001 kg/m3, with R-CP at 96.96%, R-EE at 67.23%, and R-CF at 114.13%.

Arsenate Adsorption from Aqueous Solutions Using Chitosan/Fe‐Nanoparticles Composite Microspheres

AbstractThe adsorption behavior and synthesis of a chitosan microsphere composite with iron nanoparticles (Ch‐Fe) for the removal of arsenates [As(V)] from aqueous solutions were investigated. First, the chitosan microspheres (Ch‐SD) were obtained using the Spray Dryer volatilization technique (SD), optimizing their particle size. Then, the iron nanoparticles (Fe‐NPs) were prepared using the microwave precipitation technique. The composite was characterized, and the arsenate adsorption parameters were determined through batch‐type experiments. Significantly fast adsorption rates were observed for both adsorbents. Besides, Ch‐Fe and Ch‐SD effectively removed arsenates over a wide pH range. The hydroxyl and amino functional groups are involved in removing arsenates. The Pseudo‐second order and the Elovich models described arsenate kinetic sorption data for Ch‐Fe and Ch‐SD, respectively. The As(V) maximum adsorption capacities were 27.46 mg/g and 29.94 mg/g for Ch‐SD and Ch‐Fe, respectively, increasing significantly at elevated temperatures. The Langmuir‐Freundlich model adequately described the isothermal data for both materials, suggesting adsorption heterogeneity. The composite's surface impregnation with Fe‐NPs enhanced the Ch‐SD adsorption properties. The SD method was suitable for obtaining the chitosan/Fe‐NPs microspheres and effectively removed As(V) from aqueous solutions.

Enhanced mechanical performance and damping behavior of CFRP composites through exfoliated MWCNT functionalization

In evaluating high-performance multiwall carbon nanotube (MWCNT) based carbon fiber composites, effective chemical functionalization of fillers for sufficient exfoliation and precise interface interactions with resin matrix are challenging to attain due to significant interlayer cohesive energy and inactive surfaces of composites. Herein, we demonstrate an effective way to produce carbon fiber-reinforced polymer (CFRP) composite with amended interfacial characteristics via incorporation of MWCNT through oxidation followed by silane functionalization with their exfoliation levels (0/48/60/72 h). The surface functional elements, morphological changes, elemental groups, quantitative information, and thermal degradation of silane functionalized MWCNTs were characterized by FESEM/HR-TEM, XRD, UV, and TG-DTA analysis, respectively. The influence of silane functionalized MWCNT reinforcement on CFRP's mechanical properties were examined using tensile, flexural, ILSS, and damping behavior was analyzed through impulse excitation technique (IET). The resulting silane-modified MWCNTs with 60 h oxidation (OAC-60) infused CFRP demonstrated significant enhancement in flexural strength (73.8%), tensile strength (58.2%), interlaminar shear strength (28.5%) compared to pure-CFRP.

Construction of Maize Threshing Model by DEM Simulation

This paper proposes a modeling method of maize in threshing. The static friction coefficient and rolling resistance coefficient of the maize grain were measured using the slope method. The maize grain stacking angle test was designed using the central composite design response surface test. A regression model was established based on the simulation results to find the best combination. The results suggested that the modeling method proposed in this paper was effective in improving the accuracy of maize grain simulation compared with previous methods. Furthermore, this paper presents a method to verify the feasibility and reliability of the maize grain cob discrete element model using the distribution of grain in the granary and the final removal rate as the verification method. The results of the actually simulated threshing test were analyzed using a Wilcoxon signed-rank test, heat map analysis, and the Spearman’s rank correlation coefficient. It was found that the DEM model of maize cob is suitable for simulating the maize threshing process. This can aid in further research on the subject.

Titanium carbide (TiC) dispersed surface on titanium based alloy (Ti-13Nb-13Zr) by in-situ laser composite surfacing and its wear performance

Ti-13Nb-13Zr is a promising titanium-based alloy for bioimplant applications due to its low Young’s modulus (80 GPa). However, it undergoes mechanical and mechano-chemical degradation after long-term application in the human body. The present study concerns the development of TiC dispersed surface on Ti-13Nb-13Zr by preplacement of graphite and subsequent melting with a continuous wave (CW) fiber-coupled diode laser using varied power (1000 W to 1400 W) and scan speed (10 mm/s to 20 mm/s). Laser composite surfacing leads to the formation of dispersion of carbide (TiC) in the beta (β) matrix. There is an improvement in microhardness from 257 VHN (for as-received) to 360–519 VHN for laser composite surfaced Ti-13Nb-13Zr and varied with process parameters. There is an increase in nanohardness value from 3.6 GPa (for as-received Ti-13Nb-13Zr) to 5.14–9.224 GPa and increased in Young’s modulus from 100 MPa (for as-received Ti-13Nb-13Zr) to 103.22–120.85 MPa due to laser composite surfacing. A significant improvement in wear resistance (5.8 times) and a decrease in coefficient of friction (COF) (2.8 times) against the WC ball in fretting wear mode was noticed. The wear mechanism has been schematically presented and discussed in details.

OBTAINING OF TiO2-SiO2-P2O5/ZnO COMPOSITES, INVESTIGATION OF THEIR PROPERTIES AND POSSIBILITY OF APPLICATION AS A BIOMATERIAL

In modern implantology composites based on various inorganic and polymeric materials are promising, which are able to provide strong adhesion with tissues in contact with the implanted material and stimulate the growth of new tissue on the implant surface. In the work macroporous cationite Tokem-250 with high selectivity to Zn2+ ions was used as a matrix, which makes it possible to use it in the development of biomaterials. Zinc has a direct stimulating effect on bone tissue formation and has antibacterial properties. For the cationite Tokem-250 based on acryl-divinylbenzene matrix the values of total exchange capacity and sorption capacity in relation to Zn2+ ion were determined. Total exchange capacity of cationite Tokem-250 is 10.35 mmol∙ekv/g, sorption capacity is 73% of the total exchange capacity and is equal to 7.58 mmol∙ekv/g. Spherical composites TiO2-SiO2-P2O5/ZnO on the basis of cationite Tokem-250 were synthesized from alcohol solutions by sol-gel method. For obtaining spherical composite the conditions of heat treatment of samples are established: drying at 60 ºC and step annealing at 150, 250, 350 ºC for 30 min at each temperature step, at 600 ºC - 6 h, at 800 ºC - 1 h. The obtained composites have the ability to precipitate and mineralize calcium-phosphates on their surface in biological media, because they have homogeneous structure with uniform distribution of elements on the surface, mesoporous structure with pore size from 5 to 12 nm and the presence of active centers (Si4+, Ti4+) on the surface of composites. The use of polyvinyl alcohol as a binder does not prevent the formation of an apatite-like layer. For citation: Tkachuk V.A., Lyutova E.S., Buzaev A.A., Borilo L.P., Spivakova L.N. Obtaining of TiO2-SiO2-P2O5/ZnO composites, investigation of their properties and possibility of application as a biomaterial. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 70-76. DOI: 10.6060/ivkkt.20246705.6953.

Nitrogen-doped carbon nano-onions/polypyrrole nanocomposite based low-cost flexible sensor for room temperature ammonia detection

One of the frontier research areas in the field of gas sensing is high-performance room temperature-based novel sensing materials, and new family of low-cost and eco-friendly carbon nanomaterials with a unique structure has attracted significant attention. In this work, we propose a novel low-cost flexible room temperature ammonia gas sensor based on nitrogen-doped carbon nano-onions/polypyrrole (NCNO-PPy) composite material mounted low-cost membrane substrate was synthesized by combining hydrothermal and in-situ chemical polymerization methods. The proposed flexible sensor revealed high sensing performance when employed as the sensing material for ammonia detection at room temperature. The NCNO-PPy ammonia sensor exhibited 17.32% response for 100 ppm ammonia concentration with a low response time of 26 s. The NCNO-PPy based flexible sensor displays high selectivity, good repeatability, and long-term durability with 1 ppm as the lower detection limit. The proposed flexible sensor also demonstrated remarkable mechanical robustness under extreme bending conditions, i.e., up to 90° bending angle and 500 bending cycles. This enhanced sensing performance can be related to the potential bonding and synergistic interaction between nitrogen-doped CNOs and PPy, the formation of defects from nitrogen doping, and the presence of high reactive sites on the surface of NCNO-PPy composites. Additionally, the computational study was performed on optimized NCNO-PPy nanocomposite for both with and without NH3 interaction. A deeper understanding of the sensing phenomena was proposed by the computation of several electronic characteristics, such as band gap, electron affinity, and ionization potential, for the optimized composite.

Effect of methyl methacrylate concentrations on surface and thermal analysis of composite polymer polymethylmethacrylates with mesogen reactive RM82

ABSTRACT This research report of the synthesis of composite polymers from liquid crystal mesogen reactive (RM82) monomers with Methyl methacrylate (MMA). The purpose of this research is analysis the effect concentration of MMA on the surface and thermal of the composite polymer PMMA-RM82. The result of the morphological analysis of composite surfaces performed by polarization optical microscopy (POM) technique showed liquid crystal textures affected composition from two monomers. SEM images show that the surface of the RM82 liquid crystal has a shape resembling fibrous and blade-like crystals with a length of up to 10 μm (micrometers). Analysis thermal showed the heat released by the PMMA-RM82 increased with the increase in MMA weight percent. This affects the rapid crystallization process of PMMA-RM82 which of concentration MMA 30%-RM82 the heat released is almost twice as much as the heat released by MMA 5%-RM82. The absence of PMMA and RM82 peaks both endothermic and exothermic in PMMA-RM82 samples indicates that polymerization has occurred and a new product has formed. Analysis structure molecule by FTIR found that the IR spectral form of each variation in the weight percent of MMA was almost the same, but there was a spectral shift that showed that polymerization had occurred in PMMA-RM82 which was characterized by a reaction to the free radical C=C bond released by the photoinitiator. XRD pattern of composite PMMA-RM82 showed the peaks formed are located at scattering angles similar to RM82 but there is a decrease in intensity as the percent weight of MMA increases.

Mechanical activation and silver supplementation as determinants of the antibacterial activity of titanium dioxide nanoparticles

Metals and metal oxides have subpar antibacterial activities compared to those of small-molecule antibiotics, yet there are hopes that with proper compositional and structural adjustments this gap might be bridged. In this study, titanium dioxide (TiO2) nanoparticles were mechanically activated and combined with particulate silver through simple reduction process elicited by UV irradiation and assisted with the ultrasound. The resulting powders in various combinations (Ag vs. no Ag, activated vs. non-activated) were characterized using a range of experimental techniques and assessed for their antibacterial activities. The preparation procedure presented in this work prevails over the disadvantages of many chemical routes, most critically by avoiding the use of toxic substances. The mechanical activation did not reduce the particle size or crystallinity of TiO2 nor did it consistently alter the bandgap, yet it enabled the doubling of the amount of silver incorporable into the material. Further, while both mechanical activation and the addition of silver in the amount not exceeding 0.5 wt% produced barely detectable structural changes in the material, they both augmented its antibacterial activity. The precursor TiO2 powder produced no inhibition zone against any of the four bacterial species tested, while the mechanical activation of TiO2 led to the formation of distinct inhibition zones against each of the four bacterial species tested. The addition of silver to activated TiO2 further widened the inhibition zones and it also imparted the antibacterial activity to non-activated TiO2. The boost in the antibacterial activity achieved by the short mechanical activation was of a similar magnitude as the boost obtained after the addition of silver. The antibacterial activity was not different for different species when no silver was added to the system. However, with the addition of silver, species selectivity was obtained, as the composites were more effective against the two Gram-negative species (Escherichia coli and Klebsiella pneumoniae) than against the two Gram-positive ones (Staphylococcus aureus and Bacillus subtilis). The antibacterial activity increased with the addition of silver in the broth assay, but it was mediocre compared to that detected in the agar assay, attesting to the poor dispersability of the powders and their best performance when the bacterial cells migrate to the composite surface than vice versa. The findings of this study give hope that with appropriate microstructural or compositional alterations, the antibacterial activity of metal oxide powders and inorganic materials in general can be made comparable to that of small-molecule antibiotics.