Dispersed Composites Research Articles

Photocatalytic Performance of Cementitious Composites Modified with Second-Generation Nano-TiO2 Dispersions: Influence of Composition and Granulation on NOx Purification Efficiency

This study investigated the influence of the composition of photocatalytic dispersions made with second-generation nano-TiO2 on the air purification performance of photocatalytic cementitious composites. Nine mortar series were prepared, incorporating photocatalytic dispersions of variable content of nano-TiO2, dispersing agent (superplasticizer), and hydrophobic admixture. The total mass content of nano-TiO2 in investigated mortars was kept at the same level. For investigated composites, photocatalytic removal of NOx was evaluated under simulated laboratory conditions mimicking polish autumn/winter irradiation conditions. The results indicate that within the tested range of variability, the dispersion composition significantly influenced the granulation of the dispersed nano-TiO2 particles, which in turn affected the air purification performance of the composites. A predictive model was developed to account for environmental factors potentially influencing photocatalytic performance in urban environments. The model estimated that, depending on environmental conditions and photocatalytic dispersion composition, the composite’s photocatalytic layer could remove up to 1.067 g/m2 of NO2 per year in favorable environmental conditions. Photocatalytic cementitious composites can act as environmentally beneficial composites, contributing to carbon-negative construction practices and improving urban air quality. This highlights the dual benefits of offsetting embedded carbon emissions and enhancing air purification efficiency in sustainable urban infrastructure.

HYDROPHYSICAL PROPERTIES OF HEAVY-DUTY CONCRETE WITH A COMPLEX MODIFIER FOR HYDROMELIORATIVE CONSTRUCTION

Heavy concrete is widely used as the main structural material in irrigation and drainage construction, ensuring high reliability and safety of the complexes during operation. The main quality criteria for heavy concrete are their operational characteristics. The binder was Portland cement of class CEM I 42.5N. The dispersed composition, technological and strength characteristics of cement and cement stone obtained from it were determined using sieve analysis, pycnometric method, determination of bending and compressive strength in accordance with standard methods. Natural sand was used as a fine aggregate. Granite crushed stone was used as a coarse aggregate. Water was used to mix the concrete mixture. Melflux 5581 F superplasticizer was used as a plasticizing additive. Microsilica was used as an active mineral additive. Chopped basalt fiber was chosen for dispersed reinforcement of concrete stone. To determine the efficiency of water interaction with the matrix of the developed concrete and, as a consequence, the efficiency of diffusion processes inside the matrix, affecting the destruction of the concrete stone structure and possible moisture loss during irrigation, the porosity of concrete, its water absorption and water resistance were determined. Analysis of the obtained data shows that the introduction of a complex modifier together with basalt fiber reduced the water absorption index by 57.8% compared to the control. The water resistance of the modified concrete in composition 5 increased by 4 loading stages compared to control composition 1. Improvement of hydrophysical properties of modified concrete was established: water absorption decreased by 57.8%; water resistance grade increased by 4 loading stages in comparison with the control composition. After 600 cycles of frost resistance testing, the mass loss was 1.5-1.8%, the strength decrease was 9.1%-10.2%. The proposed modification with a complex additive together with basalt fiber allows obtaining high-quality heavy concrete with improved hydrophysical properties.

EXPERIMENTAL STAND FOR STUDYING LOCAL CONDITIONS OF TRANSIENT HEAT TRANSFER

An experimental setup has been designed to study local conditions of non-stationary heat exchange during cooling of a high-temperature surface with a sprayed liquid: from nozzles of various modifications (including sprayers); water-air; steam-air; steam-water; superheated liquid; water with different concentrations of surfactants. An analysis of scientific sources has determined a research methodology that will allow the study of the influence of irrigation density, surface temperature, degree of liquid underheating, its velocity and angle of flow onto the surface, taking into account the possibility of implementing a change in the determining factors in the range of their corresponding real values ​​in natural energy and metallurgy facilities and the task of selecting a method for identifying the boundary conditions of heat exchange. We have not come across any studies of heat exchange intensity as a function of underheating of sprayed liquid – water with different concentrations of surfactants at different local irrigation densities and surface temperatures in scientific publications. Therefore, these studies, as well as the development of effective cooling systems or determination of the thermal state of objects under various external influences, are of primary importance to us. In order to implement our planned research program, in addition to developing a method for identifying the boundary conditions of heat exchange, it was necessary to solve a number of special problems associated with determining the operating parameters of the cooling medium. These include the local irrigation density and the velocity of the dispersed medium at the surface of the thermal probe. For reliable determination of local irrigation flow rate, as well as determination of the dispersed composition of drops, the pulse counting method, which has the possibility of practical implementation in our country, should be used. To determine local conditions of non-stationary heat exchange, we have developed a scheme for measuring the EMF of temperature detectors installed in the body of the rod of the thermal probe, and also selected high-speed digital recording equipment. The solution of the inverse problem of heat conduction will allow us to establish the degree of influence of practically all factors indicated as determining ones.

Assessment of polyvinylpyrrolidone vinyl acetate effect on quercetin properties in binary solid dispersion prepared by hot melt extrussion

Introduction. Flavonoids, despite their pronounced therapeutic benefits, are limitedly used in medicine as active pharmaceutical ingredients (API) owing to a complex of unsatisfactory physicochemical properties. In order to study the mentioned problem, we decided to use quercetin as model compound with extremely low water solubility and dissolution in gastrointestinal (GI) tract media. Therefore, the main idea appears to study the possibility and prospects of hot melt extrusion (HME) application for enhancement the solubility properties of quercetin in the composition of solid dispersion system (SDS) based on hydrophilic polymeric carrier (polyvinylpyrrolidone vinyl acetate, PVP/VA). Consequently, there is a necessity to select effective drug-to-polymer ratio in solid dispersion for providing better solubility and dissolution properties.Aim. Assessment of PVP/VA effect on quercetin solubility properties in binary solid dispersion prepared by HME.Materials and methods. Quercetin substance with purity 98 % was purchased from Molekula Limited, United Kingdom. PVP/VA (copolymer of polyvinylpyrrolidone with vinyl acetate in the ratio of 60 : 40, VIVAPHARM® PVP/VA 64) as carrier was procured from JRS PHARMA (JRS PHARMA GmbH & Co. KG, Germany). Quercetin SDS were prepared using micro-conical twin screw compounder HAAKE™ MiniCTW (Thermo Fisher Scientific, Germany). The obtained samples were analyzed by phase-contrast microscopy, FTIR spectroscopy and differential scanning calorimetry (DSC). Quercetin quantitative content in SDS were determined by UV-spectrophotometry.Results and discussion. The improvement of water solubility and dissolution rates of quercetin SDS in comparison with pure substance was observed for all solid dispersion compositions irrespective to drug-to-polymer ratio. Notably, with reduction of quercetin content in SDS compositions the PVP/VA contribution was increased. We found partial or even complete amorphization of API in formulations with 1 % and 5 % quercetin content, resulting in the improvement of water solubility properties, stability of solutions and increased dissolution rates in GI tract media. Water solubility of 1 % SDS relative to pure substance was enhanced by 353-fold. At the same time, the complete release of quercetin from 1 % SDS was achieved in 40 minutes in the hydrochloric acid and citrate buffer, and also quercetin dissolution of 90 % in 60 minute was observed in phosphate buffer.Conclusion. 1 % quercetin SDS based on PVP/VA appears to be the most promising for solid dosage forms development.

Siloxane-Encapsulated Perovskite Nanocrystal for Highly Stable Color-Converting Material in Displays

Perovskite Nanocrystals (PNCs) have emerged as a high-performance color-converting materials in displays because of low material cost, facile color tunability depending on size or composition, high photoluminescence quantum yield (PLQY), and very narrow emission spectra, which allow them to achieve wide color gamut. Although they exhibit high optical performance, perovskite nanocrystals (PNCs) are vulnerable to decomposition or aggregation in humid or high-temperature environments, stemming from ion migration and the development of metastable states. Stability of PNCs have been increased by various methods such as formation of an inorganic shell, Janus structures, and NC/polymer nanocomposites. However, such strategies still showed limited stability of PNCs under ambient air or in water and entail complex processes to prevent aggregation of NCs in polymer matrixes. Moreover, PNCs that are stable under harsh conditions (acid or base solutions, polar solvents, high temperature with high humidity) have not been reported. Especially methylammonium (CH3NH3 +, MA) based PNCs decay faster in the presence of moisture than do others such as formamidinium or cesium or mixed cation-based PNCs even it can be fabricated by simple process. Therefore, highly stable, and uniformly dispersed PNC composites without complex processes such as ligand-exchange and formation of an inorganic shell are desirable.Herein, we report a simple but effective materials-design approach to achieve extraordinarily long stability of crosslinked MA lead bromide (MAPbBr3) NCs in various environments (air, water, chemicals, high temperature (85 °C) with high relative humidity (85%RH) (85 °C/85%RH)) by employing sol-gel derived methacrylate-functionalized siloxane hybrid matrix. The methacrylate in the siloxane matrix induces a chemical crosslinking with unsaturated hydrocarbon in acid (oleic acid) and base (oleylamine) ligands in PNCs at a molecular scale, to form a chemically crosslinked perovskite NCs with siloxane hybrid (CPN) that prevents decomposition of MA from the perovskites and achieves homogeneous distribution of NC in the siloxane matrix. Moreover, the low concentration of moisture that diffuses through the siloxane matrix during aging can chemically heal surface defects in the NCs, and thereby reduce nonradiative recombination in CPN. As a result, CPNs showed high PLQY of ≈70% which remained for >600 d in air, water and acid or base solutions, and various polar solvents, and for >100 d under 85 °C/85%RH. We demonstrate wide color gamut and stable color-converting white LEDs and OLEDs by integration with red-emissive Cd-based QDs. Moreover, water- and chemical-persistent CPNs were successfully applied to cell proliferation which has been impossible with water-sensitive materials with toxic elements (e.g., Cd and Pb).

Non-Fluorinated Sulfonated Poly(phenylene sulfone)-Based Polymers As Membranes and Binders in Proton Exchange Membrane Fuel Cells

Sulfonated poly-phenylene-sulfone (sPPS) polymers [1,2] are emerging as a promising alternative to traditional fluorinated membranes in proton exchange membrane fuel cells (PEMFCs), offering advantages such as lower gas crossover and reduced production costs. In addition, accelerated stress tests at open circuit voltage (OCV) demonstrate that sPPS membranes exhibit superior stability compared to perfluorosulfonic acid (PFSA) membranes under extreme conditions, such as 90°C and 30% relative humidity (RH) at 50 kPa g [3], and 80°C at 100% RH and 150 kPa g . Moreover, Figure 1a highlights that sPPS membranes, when used with PFSA-bonded electrodes, slightly outperform conventional PFSA membranes in terms of performance as well as maximum power density under the tested conditions. Notably, the area-specific resistance (HFR) recorded during the polarization curve is significantly lower than that of its PFSA counterpart. This is attributed to the exceptional high conductivity of sPPS membranes and their ability to be manufactured with thicknesses < 10 µm.Our research extends their use in the catalyst layers of membrane electrode assemblies (MEAs). More specifically, we adopted two strategies to enhance the MEA performance: At the electrode architecture level, we varied the catalyst dispersion composition by adjusting the ionomer content and the nature of the solvent (see Figure 1b). At the electrochemical level, we optimized the break-in procedure. While no significant changes were observed with variations in solvent type and composition, modifications to the electrochemical break-in procedure significantly improved performance, as evidenced by an increase in the electrochemical active surface area. Figure 1c reveals that although cathodes bonded with sPPS experience initial kinetic losses at lower current densities, their performance gradually approaches that of PFSA-bonded electrodes at higher current densities. These initial kinetic losses are associated to interactions between platinum and sPPS, as identified through X-ray photoelectron spectroscopy (XPS).In conclusion, sPPS polymers hold significant potential as both membranes and binders, paving the way toward reducing dependency on fluorinated compounds for more sustainable PEMFC.

Benthic macroinvertebrate dynamics and responses to environmental factors in spring habitats of Kashmir Himalaya

ABSTRACT Understanding the dynamics of the macroinvertebrate community and the environmental influences is crucial for effective management and conservation of springs. This study examines diversity and spatio-temporal variation in macroinvertebrate assemblages across 12 spring habitats in the South Kashmir Himalayas. Macroinvertebrates were collected, sorted, identified, and enumerated from spring habitats on a seasonal basis from 2013 to 2015, and subjected to various statistical tests. Through statistical tests, significant distinctions are observed among springs and seasons. Permutational analysis of variance showed significant differences in macroinvertebrate assemblages across springs and seasons using both abundance and presence–absence data. Alpha diversity metrics depict variations in richness and Shannon’s H across springs. β-diversity evaluation reveals significant differences in macroinvertebrate assemblages across springs based on abundance and presence–absence data. So, the spring sites present homogeneity in group dispersion (composition varies similarly) while having significantly different compositions. Physicochemical factors like temperature, dissolved oxygen, sulphate, nitrate-nitrogen, and substrate heterogeneity strongly influence the assemblage. In addition, substrate heterogeneity, perennial flow, and spring size also played an important role in explaining the assemblage patterns. The present study provides important information on the impact of environmental factors on the ecological characteristics of macroinvertebrate assemblages vital for effective conservation and monitoring.

Formation of Superhydrophobic Coatings Based on Dispersion Compositions of Hexyl Methacrylate Copolymers with Glycidyl Methacrylate and Silica Nanoparticles.

In the last decade, the task of developing environmentally friendly and cost-effective methods for obtaining stable superhydrophobic coatings has become topical. In this study, we examined the effect of the concentrations of filler and polymer binder on the hydrophobic properties and surface roughness of composite coatings made from organic-aqueous compositions based on hexyl methacrylate (HMA) and glycidyl methacrylate (GMA) copolymers. Silicon dioxide nanoparticles were used as a filler. A single-stage "all-in-one" aerosol application method was used to form the coatings without additional intermediate steps for attaching the adhesive layer or texturing the substrate surface, as well as pre-modification of the surface of filler nanoparticles. As the ratio of the mass fraction of polymer binder (Wn) to filler (Wp) increases, the coatings show the lowest roll-off angles among the whole range of samples studied. Coatings with an optimal mass fraction ratio (Wn/Wp = 1.2 ÷ 1.6) of the filler to polymer binder maintained superhydrophobic properties for 24 h in contact with a drop of water in a chamber saturated with water vapor and exhibited roll-off angles of 6.1° ± 1°.

A comparison of visual and molecular methods for inferring biological communities in aquaculture enriched sediments - Impact assessment and cost-benefit analysis

Nutrients introduced to the environment by finfish aquaculture pose environmental risks, which can be mitigated by robust environmental monitoring. Biological communities in soft sediments are good indicators of aquaculture derived environmental changes. Traditionally, monitoring programs have visually surveyed macrofauna communities. However, DNA metabarcoding is a potentially more efficient alternative. We compared alpha diversity, multivariate dispersion and taxonomic composition of macrofauna communities with metabarcoding derived bacterial and eukaryote communities along an organic enrichment gradient at a salmon farm in Tasmania, Australia. Additionally, we conducted a cost-benefit analysis comparing the approaches. All methods identified indicator taxa that changed in abundance over the enrichment gradient. Macrofauna analysis was the most sensitive method for detecting changes in alpha diversity, while metabarcoding was most sensitive for multivariate dispersion. Taxonomic composition of animal communities derived from the two methods differed drastically. Metabarcoding was cheaper than macrofauna for ≥93 samples and quicker for ≥14 samples.

Enhancing thermo-physical properties of hybrid nanoparticle-infused medium temperature organic phase change materials using graphene nanoplatelets and multiwall carbon nanotubes

Phase change materials (PCMs) have emerged as an intriguing option for the storage of thermal energy because of their remarkable capacity to store latent heat. However, the practical application of these materials is hindered by their low thermal conductivity and limited photo-absorbance. For this investigation, graphene nanoplatelets (GNP) and multiwall carbon nanotubes (MWCNT) hybrid nanoparticles were disseminated in RT-54HC organic PCMs at different weight fractions. The nanoparticles were incorporated into the base PCMs using a melt blending technique. Based on the findings, one combination of GNP to MWCNT in a 0.25:0.75 ratio has shown the highest thermal conductivity, with an increase of 40% (0.28 Wm−1 K−1) compared to other hybrid combinations. This breakthrough could potentially open new avenues in the field of thermal energy storage. The chemical stability of the hybrid nanoparticle dispersed composites was assessed through FTIR analysis. In addition, the composites exhibited excellent thermal stability, maintaining their structural integrity even at temperatures as high as 300 ℃. The melting temperature of the composites also showed minimal variation. Based on the evaluation of latent heat enthalpy, the organic PCM known as base RT-54HC demonstrated a heat storage capacity of 230 J/g. However, the composites exhibited a slight decrease in latent heat with increasing nanoparticle weight fraction. In addition, the composite with added hybrid nanoparticles demonstrated an increase in optical absorbance, accompanied by a decrease in transmissibility. Therefore, the hybrid nano-enhanced composites have demonstrated enhanced thermo-physical properties, making them not only suitable but also highly promising for use in applications with mid-range melting temperatures.Graphical

Mechanical, dry sliding wear and tensile fatigue behaviour of rice hush ash–derived silicon carbide dispersed LM25 metal matrix composites

Mechanical, dry sliding wear and tensile fatigue behaviour of rice hush ash–derived silicon carbide dispersed LM25 metal matrix composites

Virtual laboratories for study technologies of environmental protection

Abstract This work is devoted to the use of virtual work for teaching bachelors in technologies of environmental protection. An analysis of publications in the field of using virtual laboratories in universities was carried out. The use of virtual laboratory work supports modern approaches to education, stimulates the learning process and creates conditions for more effective mastery of the material. The article describes an example of the development of laboratory work to determine the parameters of the dispersed composition of dust. Virtual laboratory work is developed as a web application, has a user-friendly interface, all data is saved into a database. Students can work at their own pace, repeat experiments, and adapt their approach to learning. The presented virtual laboratory is relevant to use in distance learning.

Fabrication, characterization and optimization design of flexible materials for X-ray shielding with high efficiency

In this paper, a kind of thermoplastic elastomer Polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) is used for the fabrication of W, Pb, Bi, Gd2O3, BaSO4 and Sn particles dispersed flexible composites for X-ray shielding. Through melting and blending technology, functional elements are well dispersed in the SEBS matrix even without any chemical interactions between the chemical groups of SEBS and the fillers. Based on mass attenuation coefficient rules of mixture or compound in XCOM program, X-ray shielding efficiency of the samples are predicted by mass attenuation coefficient (μm), linear attenuation coefficient (μ), half value layer (HVL) and equivalent atomic number (Zeff). It is predicted by XCOM program that three shielding levels are actually found, in which W, Pb and Bi doped samples have the strongest X-ray shielding ability, with Gd2O3, BaSO4 and Sn providing lesser effectiveness. Then, predictions of XCOM and MCNP codes are verified by the experimental measurement of shielding efficiency at X-ray tube voltages of 80 kVp and 120 kVp. Due to the different K-layer photon absorption edges of elements W and Bi, sample doped with proportion of W:Bi = 5:5 is able to achieve a complementation in the weak absorption region of 70 keV–90 keV. What is more, a layer of Gd2O3 doped sample stacked on W:Bi = 5:5 is able to greatly improve the shielding efficiency in the region of 50 keV–90 keV, indicating a more effective shielding design achieved. To sum up, based on the thermoplastic elastomer SEBS, a series of X-ray shielding functional materials with high flexibility and performance are prepared, and both theoretical and experimental results show that they could be of great potential values in the field of X-ray shielding.

Dust Pollution in Construction Sites in Point-Pattern Housing Development

Construction in cities and agglomerations is one of the main sources of air pollution in most countries in the world. Fine dust particles, PM0.5–PM10, which form as a result of construction processes, are among the most dangerous pollutants. With the increase in the volume of point-pattern housing development in cities, the task of maintaining clean air and environmental conditions becomes important. This requires research, the monitoring of dust emissions throughout the entire construction period and the development of design solutions based on the results obtained. The study examines the determination of the dispersed composition of dust generated on a construction site. A graphical representation of the dispersed composition is given by constructing integral curves on a logarithmic grid and approximating them using two-link and three-link splines. The gravimetric measurement method was used to analyze the concentration of dust in the air released during construction work near residential areas. Dust analysis at the construction site revealed significant differences in particle size that cannot be explained by statistical errors alone. The reasons for this are both working conditions and climatic factors, including humidity and wind intensity. In this regard, it is preferable to use models that take into account random processes instead of traditional deterministic methods to study the dust that shapes during construction.

Role of the novel aloe vera-based titanium dioxide bleaching gel on the strength and mineral content of the human tooth enamel with respect to age.

There has been an increased demand for dental bleaching globally irrespective of age and gender. Main drawbacks associated with conventional tooth bleaching agents have been compromised strength and mineral-content of tooth enamel which results in sensitivity, discomfort, roughness, and structure loss of human teeth. Currently, nanoparticles synthesized by green synthesis have gained popularity especially in medical and dental applications because of their versatile and beneficial nano-scaled features. Titanium dioxide nanoparticles (TiO2Nps) in this study were prepared from green ecofriendly source using the aloe vera plant extract and were then characterized via dynamic light scattering (DLS), scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), and energy dispersive X-ray (EDX), for size, shape, composition and true-phase. These TiO2 Nps were incorporated in commercial bleaching gel containing hydrogen peroxide to form a novel TiO2-bleaching gel which was used to bleach extracted anterior teeth belonging to four different age groups: 20-29 years, 30-39 years, 40-49 years and ≥50 years. These teeth were investigated for micro-hardness (Vickers microhardness tester) and mineral-content (EDX spectroscopy) including sodium, magnesium, phosphorus, calcium in an in-vitro environment both before and after bleaching. Results revealed that TiO2 Nps prepared by aloe vera plant were nanos-sized of about 37.91-49 nm, spherical shape, true anatase phase with pure titanium and oxygen in their composition. The values of Vickers micro-hardness and mineral-content (Na, Mg, P, Ca) of enamel specimens belonging to different age groups enhanced in a linear pattern before bleaching with the increase in age (p value < 0.05). There was negligible reduction observed in Vickers micro-hardness and mineral-content elements (Na, Mg, P, Ca) of all enamel specimens belonging to different ages after the bleaching (p value > 0.05). The novel TiO2-bleaching gel prepared was effective enough in preventing the declination in Vickers micro-hardness strength and mineral-content of all the enamel specimens belonging to different age groups even after the bleaching procedure which makes it a promising biomaterial.

Investigations on the dielectric properties of solution-casted B4C and PbO dispersed epoxy composites

Investigations on the dielectric properties of solution-casted B4C and PbO dispersed epoxy composites

One-pot synthesis of supported PtCox bifunctional catalysts for oxygen reduction and hydrogen evolution reactions

Hydrogen fuel cells and water electrolyzers hold significant potential for net zero emission and climate change mitigation, but their practical applications are limited by the use of the precious-metal platinum as catalysts. In this study, a one-pot method is developed for the synthesis of PtCox alloys supported on hybrid carbon materials, and it is found that the developed catalysts with reduced Pt loading can act as excellent bifunctional catalysts for both oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Morphology and composition characterizations indicate uniform dispersion and adjustable composition of PtCox alloys with the particle size of ∼3 nm on the carbon support. Among them, Pt3Co/C achieves the highest ORR performance with a high mass activity of 179.23 A/g and a specific activity of 3.15 A/m2 in acidic condition, and an extremely low overpotential of 47.6 mV at 10 mA/cm2 in alkaline media as a HER catalyst. This study presents a cost-effective approach for the development of high performance PtCox/C catalysts, and confirms their potential application in hydrogen energy technologies.

Study of dielectric properties of polymer/air plasma treated graphene oxide nanocomposites for electronic applications

In the present study we emphasized on the dielectric properties of Ethylene Vinyl Acetate (EVA) filled with untreated and plasma-treated graphene oxide (GO). The chemical fingerprints of EVA/GO were analysed using FTIR. Decreased ID/IG ratio from 2.99 to 2.75 and 1.60 to 1.16 due to exposed plasma was confirmed by Raman spectroscopy. X-ray diffraction (XRD) disclosed the decreased degree of crystallinity. Electric properties were measured by impedance analyser, dielectric constant was increased upto 11% for untreated GO dispersion and 47% for Air treated Plasma GO dispersed EVA composites. Plasma treatment further improved the exfoliated sites of GO and induced the defects, leading to optimized dielectric properties. Improved dielectric properties of EVA/GO can provide valuable insights into the potential applications in the field of electrical connectors, film capacitors, and pseudo capacitors.

Do all ceramic and composite CAD-CAM materials exhibit equal bonding properties to implant Ti-base materials? An Interfacial Fracture Toughness Study

ObjectivesTo compare the interfacial fracture toughness (IFT) with or without aging, of four different classes of CAD-CAM ceramic and composite materials bonded with self-adhesive resin cement to titanium alloy characteristic of implant abutments. MethodsHigh translucent zirconia (Katana; KAT), lithium disilicate-based glass-ceramic (IPS. emax.CAD; EMX), polymer-infiltrated ceramic network material (PICN) (Vita Enamic; ENA), and dispersed filler composite (Cerasmart 270; CER) were cut into equilateral triangular prisms and bonded to titanium prisms with identical dimensions using Panavia SA Cement Universal. The surfaces were pretreated following the manufacturers’ recommendations and developed interfacial area ratio (Sdr) of the pretreated surfaces was measured. IFT was determined using the Notchless Triangular Prism test in a water bath at 36 °C before and after thermocycling (10,000 cycles) (n = 40 samples/material). ResultsIFT of the materials ranged from 0.80 ± 0.25 to 1.10 ± 0.21 MPa.m1/2 before thermocycling and from 0.71 ± 0.24 to 1.02 ± 0.25 MPa.m1/2 after thermocycling. There was a statistical difference between IFT of CER and the two top performers in each scenario: KAT and EMX before aging, and KAT and ENA after aging. Thermocycling significantly decreased IFT of EMX. The Weibull modulus of IFT was similar for all materials and remained so after thermocycling. Sdr measurements revealed that ENA (7.60)>Ti (4.97)>CER (2.85)>KAT (1.09)=EMX (0.96). SignificanceDispersed filler CAD-CAM composite showed lower performance than the other materials. Aging only affected IFT of Li-Si glass-ceramic, whereas zirconia and PICN performed equally well, probably due to their chemical bonding potential and surface roughness respectively.

DeoxyriboNucleic acid‐enhanced carbon nanotube dispersed epoxy resin composites: Mechanical and thermal properties study

AbstractThe homogeneous dispersion of multi‐walled carbon nanotubes (MWCNTs) in a polymer matrix significantly affects the overall properties of composites. In this study, MWCNTs/epoxy (EP) composites were prepared using DeoxyriboNucleic acid (DNA) as a dispersant. The MWCNTs were uniformly dispersed in a phenalkamine curing agent and crosslinked with an epoxy resin matrix. The non‐covalent functionalization of DNA‐dispersed MWCNTs was confirmed by characterizing both the pristine and DNA‐modified MWCNTs. Additionally, the dispersion state and stability of MWCNTs in the curing agent solution were evaluated. Tensile strength and single‐lap‐shear (SLS) were employed to assess the mechanical properties of the composites. The results indicated that the DNA‐dispersed MWCNTs composites exhibited superior strength and toughness, with tensile and shear strengths of 46.81 and 19.64 MPa, respectively, at optimal ratios. These values represent increases of 68.38% and 50.96% compared to pure EP. Dynamic mechanical thermal analysis (DMTA) revealed that the energy storage modulus of DNA‐dispersed MWCNTs/EP composites increased to 2722 MPa, a 24.7% enhancement over pure EP. Furthermore, the thermal properties of the composites were thoroughly investigated. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the initial decomposition temperature of the DNA‐assisted dispersed composites rose to 330°C. The macromolecular relaxation of the EP materials occurred at higher temperatures, leading to an increased glass transition temperature.Highlights DNA was used to disperse MWCNTs in phenalkamine curing agent. MWCNTs/EP composites were made by crosslinking DNA‐dispersed MWCNTs with epoxy resin. DNA‐dispersed MWCNTs boosted tensile and lap shear strength. Thermal properties improved due to DNA‐dispersed MWCNTs, and increased the energy storage modulus of the composite.