EM parameter measurements were performed using a vector network analyzer (VNA) within the frequency spectrum of 2 GHz to 18 GHz. Based on the results, the ball-milled flaky CIPs showed a better capacity for absorption than the raw spherical CIPs. The electromagnetic parameters of the samples milled at 200 r/min for 12 hours and 300 r/min for 8 hours stood out significantly among all the samples. The ball-milled sample, accounting for 50% by weight, was subjected to various tests. At a thickness of 2 mm, F-CIPs showcased a minimum reflection loss peak of -1404 dB, while a 25 mm thickness yielded a maximum bandwidth (reflection loss less than -7 dB) of 843 GHz, a finding aligning with transmission line theory. Due to their flaky structure from ball milling, the CIPs were considered beneficial for microwave absorption.
A novel mesh, coated in clay, was created using a straightforward brush-coating method, eliminating the need for specialized equipment, chemicals, or intricate chemical procedures. By virtue of its superhydrophilicity and underwater superoleophobicity, the clay-coated mesh is suitable for the effective separation of various light oil/water mixtures. The mesh, coated with clay, demonstrates remarkable reusability, maintaining a 99.4% separation efficiency for kerosene and water after 30 cycles of use.
Self-compacting concrete (SCC) production costs are impacted by the inclusion of manufactured lightweight aggregates. The use of absorption water with lightweight aggregates before concrete preparation affects the accuracy of the water-cement ratio calculation. Besides that, the absorption of water degrades the bond between the aggregates and the cementing matrix. Black, vesicular volcanic rock, specifically scoria rocks (SR), is used. Implementing a changed addition order will decrease water uptake, thus making it easier to calculate the correct water content. host immune response This study's approach, which involved first preparing a rheologically-adjusted cementitious paste, then incorporating fine and coarse SR aggregates, eliminated the requirement for adding absorption water to the aggregates. This step's effect on the aggregate-cementitious matrix bond has led to an improvement in the overall strength of the lightweight SCC mix. This mix is designed for structural applications with a target 28-day compressive strength of 40 MPa. The goal of this study was realized through the creation and enhancement of diverse cementitious blends to find the best performing system. The quaternary cementitious system, optimized for low-carbon footprint concrete, incorporated silica fume, class F fly ash, and limestone dust. A comparative analysis was conducted on the rheological properties and parameters of the optimized mix, which were evaluated and contrasted against those of a standard mix formulated with normal-weight aggregates. Analysis of the results revealed that the optimized quaternary mixture displayed excellent performance in both fresh and hardened conditions. The slump flow, T50, J-ring flow, and average V-funnel flow time exhibited values spanning 790-800 mm, 378-567 seconds, 750-780 mm, and 917 seconds, respectively. Subsequently, the equilibrium density was observed to be situated within the range of 1770 to 1800 kilograms per cubic meter. After a 28-day period, the average compressive strength reached 427 MPa, along with a flexural load exceeding 2000 Newtons and a modulus of rupture at 62 MPa. Altering the order of ingredient mixing is subsequently deemed essential when using scoria aggregates to create high-quality, lightweight structural concrete. This process uniquely enables a significant improvement in the precise control of both the fresh and hardened characteristics of lightweight concrete, a level of control not feasible under conventional practices.
Various applications have seen the rise of alkali-activated slag (AAS) as a potentially sustainable alternative to ordinary Portland cement, since the latter accounted for approximately 12% of global CO2 emissions in 2020. AAS, compared to OPC, provides remarkable ecological benefits by utilizing industrial by-products to address disposal concerns, minimizing energy consumption, and reducing greenhouse gas emissions. Alongside its environmental benefits, the novel binder displays increased resistance against high temperatures and chemical attacks. Many research endeavors have emphasized the substantial difference in drying shrinkage and early-age cracking between this concrete and its OPC counterpart, with the former exhibiting higher risks. While copious research on the self-healing characteristics of OPC exists, investigation into the self-healing actions of AAS remains comparatively limited. A revolutionary product, self-healing AAS, effectively addresses the problems presented by these shortcomings. A comprehensive critical review of the self-healing mechanism of AAS and its resultant impact on the mechanical properties of AAS mortars is presented in this study. Regarding their effects, the self-healing approaches, their diverse applications, and the associated challenges for each mechanism are meticulously examined and contrasted.
This work involved the creation of Fe87Ce13-xBx (x = 5, 6, 7) metallic glass (MG) ribbons. A study was performed to ascertain the compositional correlation of glass forming ability (GFA), magnetic and magnetocaloric properties of these ternary MGs, and to uncover the relevant mechanisms. With increasing boron content, the GFA and Curie temperature (Tc) of the MG ribbons improved, culminating in a maximum magnetic entropy change (-Smpeak) of 388 J/(kg K) at 5 Tesla when x equaled 6. The three resultant data points guided the synthesis of an amorphous composite featuring a table-shaped magnetic entropy change (-Sm) profile. A relatively high average -Sm (-Smaverage ~329 J/(kg K) under 5 Tesla) is achieved over the temperature range of 2825 K to 320 K, making it a potential refrigerant candidate for high-efficiency domestic magnetic refrigeration.
The solid solution Ca9Zn1-xMnxNa(PO4)7 (x values between 0 and 10), was obtained by performing solid-phase reactions in a controlled reducing atmosphere. Activated carbon, utilized within a closed system, proved effective in producing Mn2+-doped phosphors, showcasing a simple and robust methodology. Employing powder X-ray diffraction (PXRD) and optical second-harmonic generation (SHG) methods, the crystal structure of Ca9Zn1-xMnxNa(PO4)7 was determined as the non-centrosymmetric -Ca3(PO4)2 type with a R3c space group. When stimulated by 406 nm light, the visible luminescence spectra present a substantial, red emission peak, centered at 650 nm. This band's origin is the 4T1 6A1 electron transition of Mn2+ ions, occurring within a host lattice structured like -Ca3(PO4)2. The reduction synthesis's success is substantiated by the absence of transitions attributable to Mn4+ ions. The intensity of the Mn2+ emission band within Ca9Zn1-xMnxNa(PO4)7 displays a consistent linear rise as the value of x progresses from 0.005 to 0.05. While the luminescence intensity was observed, it displayed a negative deviation specifically at x = 0.7. This observed trend is symptomatic of the impending concentration quenching. With increasing x-values, the luminescence intensity continues its upward trend, yet its rate of increase is demonstrably slowing down. PXRD analysis of samples with x = 0.02 and 0.05 indicated the presence of Mn2+ and Zn2+ ions substituting calcium ions in the M5 (octahedral) sites within the -Ca3(PO4)2 crystal structure. According to the Rietveld refinement analysis, the M5 site is exclusively occupied by manganese atoms, specifically Mn2+ and Zn2+ ions, within the 0.005 to 0.05 range. beta-granule biogenesis At x = 10, the calculated deviation of the mean interatomic distance (l) pinpointed the strongest bond length asymmetry, where l = 0.393 Å. The significant average interatomic distances characterizing Mn2+ ions in neighbouring M5 sites are the key to understanding the absence of concentration quenching in luminescence below x = 0.5.
Research into phase change materials (PCMs) and the accumulation of thermal energy in the form of latent heat during phase transitions is extremely attractive, with wide-ranging applications foreseen in both passive and active technical systems. Organic phase-change materials (PCMs), primarily paraffins, fatty acids, fatty alcohols, and polymers, constitute the largest and most significant group for low-temperature applications. A major problem with organic phase-change materials is their inflammability. The imperative task within sectors like building, battery thermal management, and protective insulation is to decrease the possibility of fires triggered by flammable phase change materials. The past decade has witnessed a plethora of studies aimed at reducing the flammability of organic phase-change materials (PCMs), preserving their thermal capabilities. The analysis in this review encompassed the principal classifications of flame retardants, PCM flame-retardation methodologies, and illustrative examples of flame-protected PCMs and their associated application sectors.
Employing NaOH activation and subsequent carbonization, activated carbons were created from avocado stones. BPTES nmr The study's textural analysis provided the following data points: specific surface area, 817-1172 m²/g; total pore volume, 0.538-0.691 cm³/g; and micropore volume, 0.259-0.375 cm³/g. A good CO2 adsorption value of 59 mmol/g, achieved at a temperature of 0°C and 1 bar, was a consequence of the well-developed microporosity, displaying selectivity over nitrogen in flue gas simulation. Nitrogen sorption at -196°C, CO2 sorption, X-ray diffraction, and SEM were employed to examine the activated carbons. The adsorption data exhibited a closer agreement with the predictions of the Sips model. For the best-performing sorbent, the isosteric heat of adsorption was evaluated. The isosteric heat of adsorption exhibited a variation, from 25 to 40 kJ/mol, in correlation with the surface coverage. A novel avenue for activated carbon production, utilizing avocado stones, yields highly microporous carbons with exceptional CO2 adsorption capabilities.