Mortars for Conservation of Late 19th and Early 20th Century Buildings—Combination of Natural Cements with Air Lime

With the availability of commercial Natural cements (NC) for the conservation purposes raises a fundamental question about the compatibility between historic and repair mortars. The properties of Natural cements are dependent on the geological location of the raw material extraction and also on the production parameters, both having an impact on the final properties of the mortars produced from each distinct. Therefore, the significance of preservation of 19th and 20th century heritage and selection of the proper binder compatible with the original materials necessitate the study of existing NCs, that nowadays are produced by several manufacturers. This work provides a complex study of the mortars prepared from three NCs available in the market: Groupe Prompt Vicat, France (NCPV); Cemento Collet Marfil (NCM) and Cemento Natural Tigre (NCT), both from Spain. Various mortar sets based on individual NC containing different binder/aggregate ratios and air lime additions were analyzed after 28, 60, and 90 days of curing with the focus on their mineralogical composition (XRD), morphology (SEM), mechanical (flexural and compressive strength), and physical properties such as water absorption by capillarity, water vapor permeability, and water vapor diffusion resistance. Mortars prepared from NCPV, NCM, and NCT show distinct physical-mechanical properties with varying binder/aggregate ratio and air lime addition. This study shows that the NC variability should be taken into consideration when selecting materials for the conservation and rehabilitation of historic renders and plasters. Based on the comparison with original NC mortars, several NC mortars developed in this study show adequate properties for conservation of the buildings from late 19th and early 20th century in terms of compressive strength (>12 MPa), water absorption by capillarity (<20 kg·m⁻²·h^−0.5), water vapor permeability (<4 × 10⁻¹⁰ kg·s⁻¹·m⁻¹·Pa⁻¹), and water vapor diffusion resistance (<28) values.     

INAUGURAL ARTICLE by a Recently Elected Academy Member:In vitro evolution of horse heart myoglobin to increase peroxidase activity

Random mutagenesis and screening for enzymatic activity has been used to engineer horse heart myoglobin to enhance its intrinsic peroxidase activity. A chemically synthesized gene encoding horse heart myoglobin was subjected to successive cycles of PCR random mutagenesis. The mutated myoglobin gene was expressed in Escherichia coli LE392, and the variants were screened for peroxidase activity with a plate assay. Four cycles of mutagenesis and screening produced a series of single, double, triple, and quadruple variants with enhanced peroxidase activity. Steady-state kinetics analysis demonstrated that the quadruple variant T39I/K45D/F46L/I107F exhibits peroxidase activity significantly greater than that of the wild-type protein with k₁ (for H₂O₂ oxidation of metmyoglobin) of 1.34 × 10⁴ M⁻¹ s⁻¹ (≈25-fold that of wild-type myoglobin) and k₃ [for reducing the substrate (2, 2′-azino-di-(3-ethyl)benzthiazoline-6-sulfonic acid] of 1.4 × 10⁶ M⁻¹ s⁻¹ (1.6-fold that of wild-type myoglobin). Thermal stability of these variants as measured with circular dichroism spectroscopy demonstrated that the T_m of the quadruple variant is decreased only slightly compared with wild-type (74.1°C vs. 76.5°C). The rate constants for binding of dioxygen exhibited by the quadruple variant are identical to the those observed for wild-type myoglobin (k_on, 22.2 × 10⁻⁶ M⁻¹ s⁻¹ vs. 22.3 × 10⁻⁶ M⁻¹ s⁻¹; k_off, 24.3 s⁻¹ vs. 24.2 s⁻¹; K_O2, 0.91 × 10⁻⁶ M⁻¹ vs. 0.92 × 10⁻⁶ M⁻¹). The affinity of the quadruple variant for CO is increased slightly (k_on, 0.90 × 10⁻⁶ M⁻¹s⁻¹ vs. 0.51 × 10⁻⁶ M⁻¹s⁻¹; k_off, 5.08 s⁻¹ vs. 3.51 s⁻¹; K_CO, 1.77 × 10⁻⁷ M⁻¹ vs. 1.45 × 10⁻⁷ M⁻¹). All four substitutions are in the heme pocket and within 5 Å of the heme group.     

Evaluation of Biophysical Properties of Potential Materials for the Manufacture of Protective Garments for Preterm Infants

Preterm infants, due to immature and dysfunctional skin, have increased water loss through the skin and consequently a decreased body temperature. In order to develop protective garments for preterm infants, it is important to select materials that will protect the child against water and heat loss. The authors are currently involved in the development of protective garments for premature babies, which are similar to baby clothes and contain a membrane that is partially permeable for vapor in combination with textile materials. This article presents the study of materials intended for the production of protective garments for pre-term infants. Samples of materials were investigated to determine biophysical comfort (tests of heat resistance, vapor resistance according to PN-EN ISO 11092:2014-11 and air permeability according to PN-EN ISO 9237) and porosity, surface mass in accordance with PN-EN 12127, and thickness in accordance with PN-EN ISO 5084. In order to determine the porosity of materials and to visualize the structure, tests on computer microtomography were carried out. The mechanical properties of the tested materials and the evaluation of the total hand value were characterized; the samples were tested on the KES device. The aim of this study was to select the most suitable fabrics for protective garments for premature infants to prevent excessive heat and moisture loss from the body, which can lead to hypothermia. For laminates, the optimal results of vapor resistance and heat resistance were obtained for laminate (15 g·m⁻² PE foil + 15 g·m⁻² PP non-woven), with a level of thermal resistance of 0.0766 m²·K·W⁻¹ and vapor resistance of 188.729 m²·Pa·W⁻¹, and for laminate (15 g·m⁻² PE foil + 10 g·m⁻² PP non-woven), with a level of thermal resistance of 0.0683 m²·K·W⁻¹ and vapor resistance of 164.085 m²·Pa·W⁻¹. For knitted fabrics, knitwear single cotton 155 g·m⁻² showed the highest thermal resistance (0.0296 m²·K·W⁻¹), and knitwear interlock polyester 120 g·m⁻² showed the lowest thermal resistance (0.0179 m²·K·W⁻¹). Knitwear cotton 120 g·m⁻² had the highest water vapor resistance (8.402 m²·Pa·W⁻¹), while knitwear interlock polyester 130 g·m⁻² sample had the lowest resistance (6.356 m²·Pa·W⁻¹). Garments for premature babies should have moisture barrier properties and high thermal insulation. They should also be characterized by optimal air permeability properties. Sample two-layer laminate (15 g·m⁻² PE foil + 15 g·m⁻² PP non-woven) had the best vapor resistance and thermal insulation properties. Moreover, this sample was characterized by good air permeability and surface weight compared to the other laminate samples. During the design of garments for premature babies, it is important to reduce the surface weight to as low as possible. Among the knitted fabrics, a knitwear single cotton 120 g·m⁻² knitwear polyester interlock 120 g·m⁻² was selected for having the best THV or tactile comfort. In addition, these knits were chosen for their lower surface weight. Based on the conducted tests, two-layer laminate (15 g·m⁻² PE foil + 15 g·m⁻² PP non-woven), the knitwear single cotton 120 g·m^−2, and knitwear polyester interlock 120 g·m⁻² were selected for further research.     

Poling of Glasses Using Resistive Barrier Discharge Plasma

A technique for poling of glasses using a resistive barrier discharge plasma in the atmosphere in a gap of hundreds of microns is presented. Measurements of the polarization current, second harmonic generation, and IR spectra of poled soda-lime glass slides show that voltage sufficient to ignite plasma discharge provides efficient poling, whereas for lower voltages the poling effect is close to zero. We attributed this to the large number of hydrogen/hydronium ions generated from atmospheric water vapor by the plasma discharge in the gap, which penetrate into the glass. We also developed a simple model of poling according to Ohm’s law, analyzed the temporal dependencies of the polarization current and, basing on the model, estimated mobilities of hydrogen/hydronium and sodium ions in the glass: μ_H = (2.4 ± 0.8) × 10⁻¹⁸ m²V⁻¹s⁻¹ and μ_Na = (4.8 ± 1.8) × 10⁻¹⁵ m²V⁻¹s⁻¹. The values obtained are very close to the known literature data.     

Importance of trivalency and the eg1 configuration in the photocatalytic oxidation of water by Mn and Co oxides

Prompted by the early results on the catalytic activity of LiMn₂O₄ and related oxides in the photochemical oxidation of water, our detailed study of several manganese oxides has shown that trivalency of Mn is an important factor in determining the catalytic activity. Thus, Mn₂O₃, LaMnO₃, and MgMn₂O₄ are found to be very good catalysts with turnover frequencies of 5 × 10⁻⁴ s⁻¹, 4.8 × 10⁻⁴ s⁻¹, and 0.8 ×10⁻⁴ s⁻¹, respectively. Among the cobalt oxides, Li₂Co₂O₄ and LaCoO₃—especially the latter—exhibit excellent catalytic activity, with the turnover frequencies being 9 × 10⁻⁴ s⁻¹ and 1.4 × 10⁻³ s⁻¹, respectively. The common feature among the catalytic Mn and Co oxides is not only that Mn and Co are in the trivalent state, but Co³⁺ in the Co oxides is in the intermediate t_2g⁵e_g¹ state whereas Mn³⁺ is in the t_2g³e_g¹ state. The presence of the e_g¹ electron in these Mn and Co oxides is considered to play a crucial role in the photocatalytic properties of the oxides.     

The Effect of Heat Flux to the Fire-Technical and Chemical Properties of Spruce Wood (Picea abies L.)

The paper assesses the influence of the heat flux on spruce wood (Picea abies L.) behavior. The heat flux was performed at 15, 20, 25, and 30 kW·m⁻². The fire-technical properties, such as the mass burning rate, charring thickness, charring rate, as well as the chemical composition (contents of the extractives, lignin, cellulose, holocellulose), of wood were determined. The highest burning rate of spruce wood of 0.32%·s⁻¹ was reached at the heat flux of 30 kW·m⁻². The charring rate ranged from 1.004 mm·min⁻¹ (15 kW·m⁻²) to 2.016 mm·min⁻¹ (30 kW·m⁻²). The proposed model of the charring process of spruce wood in time and appropriate thickness as a selected parameter is applicable in validation of the results of computer fire models in the design of fire protection of wooden buildings. The decrease in the holocellulose content mostly caused by the degradation of hemicelluloses was observed during thermal loading. The biggest decrease in hemicelluloses (24.94%) was recorded in samples loaded at 30 kW·m⁻². The contents of cellulose increased due to the structural changes (carbonization and crosslinking), the content of lignin increased as well due to its higher thermal stability compared to saccharides, as well as the resulting lignin condensation.     

Effect of Nickel as Stress Factor on Phenol Biodegradation by Stenotrophomonas maltophilia KB2

This study focuses on the phenol biodegradation kinetics by Stenotrophomonas maltophilia KB2 in a nickel-contaminated medium. Initial tests proved that a nickel concentration of 33.3 mg·L⁻¹ caused a cessation of bacterial growth. The experiments were conducted in a batch bioreactor in several series: without nickel, at constant nickel concentration and at varying metal concentrations (1.67–13.33 g·m⁻³). For a constant Ni²⁺ concentration (1.67 or 3.33 g·m⁻³), a comparable bacterial growth rate was obtained regardless of the initial phenol concentration (50–300 g·m⁻³). The dependence µ = f (S₀) at constant Ni²⁺ concentration was very well described by the Monod equations. The created varying nickel concentrations experimental database was used to estimate the parameters of selected mathematical models, and the analysis included different methods of determining metal inhibition constant K_IM. Each model showed a very good fit with the experimental data (R² values were higher than 0.9). The best agreement (R² = 0.995) was achieved using a modified Andrews equation, which considers the metal influence and substrate inhibition. Therefore, kinetic equation parameters were estimated: µ_max = 1.584 h⁻¹, K_S = 185.367 g·m⁻³, K_IS = 106.137 g·m⁻³, K_IM = 1.249 g·m⁻³ and n = 1.0706.     

Microstructure Evolution,Constitutive Modelling,and Superplastic Forming of Experimental 6XXX-Type Alloys Processed with Different Thermomechanical Treatments

This study focused on the microstructural analysis, superplasticity, modeling of superplastic deformation behavior, and superplastic forming tests of the Al-Mg-Si-Cu-based alloy modified with Fe, Ni, Sc, and Zr. The effect of the thermomechanical treatment with various proportions of hot/cold rolling degrees on the secondary particle distribution and deformation behavior was studied. The increase in hot rolling degree increased the homogeneity of the particle distribution in the aluminum-based solid solution that improved superplastic properties, providing an elongation of ~470–500% at increased strain rates of (0.5–1) × 10⁻² s⁻¹. A constitutive model based on Arrhenius and Beckofen equations was used to describe and predict the superplastic flow behavior of the alloy studied. Model complex-shaped parts were processed by superplastic forming at two strain rates. The proposed strain rate of 1 × 10⁻² s⁻¹ provided a low thickness variation and a high quality of the experimental parts. The residual cavitation after superplastic forming was also large at the low strain rate of 2 × 10⁻³ s⁻¹ and significantly smaller at 1 × 10⁻² s⁻¹. Coarse Al₉FeNi particles did not stimulate the cavitation process and were effective to provide the superplasticity of alloys studied at high strain rates, whereas cavities were predominately observed near coarse Mg₂Si particles, which act as nucleation places for cavities during superplastic deformation and forming.     

Sustainable Chitosan-Dialdehyde Cellulose Nanocrystal Film

In this study, we incorporated 2,3-dialdehyde nanocrystalline cellulose (DANC) into chitosan as a reinforcing agent and manufactured biodegradable films with enhanced gas barrier properties. DANC generated via periodate oxidation of cellulose nanocrystal (CNC) was blended at various concentrations with chitosan, and bionanocomposite films were prepared via casting and characterized systematically. The results showed that DANC developed Schiff based bond with chitosan that improved its properties significantly. The addition of DANC dramatically improved the gas barrier performance of the composite film, with water vapor permeability (WVP) value decreasing from 62.94 g·mm·m⁻²·atm⁻¹·day⁻¹ to 27.97 g·mm·m⁻²·atm⁻¹·day⁻¹ and oxygen permeability (OP) value decreasing from 0.14 cm³·mm·m⁻²·day⁻¹·atm⁻¹ to 0.026 cm³·mm·m⁻²·day⁻¹·atm⁻¹. Meanwhile, the maximum decomposition temperature (Td_max) of the film increased from 286 °C to 354 °C, and the tensile strength of the film was increased from 23.60 MPa to 41.12 MPa when incorporating 25 wt.% of DANC. In addition, the chitosan/DANC (75/25, wt/wt) films exhibited superior thermal stability, gas barrier, and mechanical strength compared to the chitosan/CNC (75/25, wt/wt) film. These results confirm that the DANC and chitosan induced films with improved gas barrier, mechanical, and thermal properties for possible use in film packaging.     

Role of Air Bubble Inclusion on Polyurethane Reaction Kinetics

In this study, we investigated the influence of mixing conditions on the foaming process of water blown polyurethane (PU) foams obtained at different mixing speeds (50, 500, 1000 and 2000 rpm). In particular, the morphological evolution during the foaming process, in terms of the bubble size and bubble density, was studied via optical observations, while the effects on the reaction kinetics were monitored using in situ FTIR spectroscopy. At the slow mixing speed (50 rpm), no air bubbles were included and the early foaming process was characterized by the formation of new bubbles (CO₂ nucleation), provided by the blowing reaction. Later on, it was observed that the coalescence affected the overall foaming process, caused by the gelling reaction, which was inhibited by the indigent mixing conditions and could not withstand the bubbles expansion. As a result, a PU foam with a coarse cellular structure and an average bubble size of 173 µm was obtained. In this case, the bubbles degeneration rate, dN/dt, was −3095 bubble·cm⁻³·s⁻¹. On the contrary, at 500 rpm, air bubbles were included into the PU reaction system (aeration) and no formation of new bubbles was observed during the foaming process. After this, the air bubbles underwent growth caused by diffusion of the CO₂ provided by the blowing reaction. As the gelling reaction was not strongly depleted as in the case at 50 rpm, the coalescence less affected the bubble growth (dN/dt = −2654 bubble·cm⁻³·s⁻¹), leading to a PU foam with an average bubble size of 94 µm. For the foams obtained at 1000 and 2000 rpm, the bubble degeneration was first affected by coalescence and then by Ostwald ripening, and a finer cellular structure was observed (with average bubble sizes of 62 µm and 63 µm for 1000 rpm and 2000 rpm, respectively). During the first foaming stage, the coalescence was less predominant in the bubble growth (with dN/dt values of −1838 bubble·cm⁻³·s⁻¹ and −1601 bubble·cm⁻³·s⁻¹, respectively) compared to 50 rpm and 500 rpm. This occurrence was ascribed to the more balanced process between the bubble expansion and the PU polymerization caused by the more suitable mixing conditions. During the late foaming stage, the Ostwald ripening was only responsible for the further bubble degeneration (with dN/dt values of −89 bubble·cm⁻³·s⁻¹ and −69 bubble·cm⁻³·s⁻¹, respectively).     

Electrochemically Activated Screen-Printed Carbon Sensor Modified with Anionic Surfactant (aSPCE/SDS) for Simultaneous Determination of Paracetamol,Diclofenac and Tramadol

In this work, an electrochemically activated screen-printed carbon electrode modified with sodium dodecyl sulfate (aSPCE/SDS) was proposed for the simultaneous determination of paracetamol (PA), diclofenac (DF), and tramadol (TR). Changes of surface morphology and electrochemical behaviour of the electrode after the electrochemical activation with H₂O₂ and SDS surface modification were studied by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The influence of various parameters on the responses of the aSPCE/SDS such as pH and concentration of the buffer, SDS concentration, and techniques parameters were investigated. Using optimised conditions (E_acc. of −0.4 V, t_acc. of 120 s, ΔE_A of 150 mV, ν of 250 mV s⁻¹, and t_m of 10 ms), the aSPCE/SDS showed a good linear response in the concentration ranges of 5.0 × 10⁻⁸–2.0 × 10⁻⁵ for PA, 1.0 × 10⁻⁹–2.0 × 10⁻⁷ for DF, and 1.0 × 10⁻⁸–2.0 × 10⁻⁷ and 2.0 × 10⁻⁷–2.0 × 10⁻⁶ mol L⁻¹ for TR. The limits of detection obtained during the simultaneous determination of PA, DF, and TR are 1.49 × 10⁻⁸ mol L⁻¹, 2.10 × 10⁻¹⁰ mol L⁻¹, and 1.71 × 10⁻⁹ mol L⁻¹, respectively. The selectivity of the aSPCE/SDS was evaluated by examination of the impact of some inorganic and organic substances that are commonly present in environmental and biological samples on the responses of PA, DF, and TR. Finally, the differential pulse adsorptive stripping voltammetric (DPAdSV) procedure using the aSPCE/SDS was successfully applied for the determination of PA, DF, and TR in river water and serum samples as well as pharmaceuticals.     

Performance Evaluation of Cementless Composites with Alkali-Sulfate Activator for Field Application

This study analyzed the performance evaluation of alkali-activated composites (AAC) with an alkali-sulfate activator and determined the expected effects of applying AACs to actual sites. Results revealed that when the binder weight was increased by 100 kg/m³ at 7 days of age, the homogel strength of ordinary Portland cement (OPC) and AAC increased by 0.9 and 5.0 MPa, respectively. According to the analysis of the matrix microstructures at 7 days of age, calcium silicate hydrates (C–S–H, Ca_1.5SiO_3.5·H₂O) and ettringite (Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O) were formed in AAC, which are similar hydration products as found in OPC. Furthermore, the acid resistance analysis showed that the mass change of AAC in HCl and H₂SO₄ solutions ranged from 36.1% to 88.0%, lower than that of OPC, indicating AAC’s superior acid resistance. Moreover, the OPC and AAC binder weight ranges satisfying the target geltime (20–50 s) were estimated as 180.1–471.1 kg/m³ and 261.2–469.9 kg/m³, respectively, and the global warming potential (GWP) according to binder weight range was 102.3–257.3 kg CO₂ eq/m³ and 72.9–126.0 kg CO₂ eq/m³. Therefore, by applying AAC to actual sites, GWP is expected to be 29.5 (28.8%)–131.3 (51.0%) kg CO₂ eq/m³ less than that of OPC.     

Concrete/Glass Construction and Demolition Waste (CDW) Synergies in Ternary Eco-Cement-Paste Mineralogy

The study described sought further understanding of the synergies in a mix of CDW pozzolans, containing (calcareous and siliceous) concrete and glass waste, used to prepare ternary eco-cement paste bearing 7% of the binary blend at concrete/glass ratios of 2:1 and 1:2. The mineralogical phases in the 2-day, 28-day, and 90-day cement matrices were identified and monitored using XRF, XRD-Rietveld, SEM-EDX, FT-IR, and NMR. The findings showed that changes in the reaction kinetics in the ternary blended pastes relative to OPC pastes depended on the nature of the recycled concrete and the glass content. Adding the binary mix bearing calcareous concrete (at a ratio of 2:1) favoured ettringite, portlandite, and amorphous phase formation, whilst the blends with siliceous concrete favoured C-S-H gel formation. Monocarboaluminate was detected in the 90-day siliceous concrete and glass pastes in amounts similar to those found in the reference OPC paste.     

Electrochemically Pretreated Sensor Based on Screen-Printed Carbon Modified with Pb Nanoparticles for Determination of Testosterone

Testosterone (TST), despite its good properties, may be harmful to the human organism and the environment. Therefore, monitoring biological fluids and environmental samples is important. An electrochemically pretreated screen-printed carbon sensor modified with Pb nanoparticles (pSPCE/PbNPs) was successfully prepared and used for the determination of TST. The surface morphology and electrochemical properties of unmodified and modified sensors were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning and transmission electron microscopy (SEM and TEM), and energy-dispersive X-ray spectroscopy (EDS). Selective determinations of TST at the pSPCE/PbNPs were carried out by differential pulse adsorptive stripping voltammetry (DPAdSV, E_{Pb dep.and TST acc.} of −1.1 V, t _{Pb dep.and TST acc.} of 120 s, ΔE_A of 50 mV, ν of 175 mV s⁻¹, and t_m of 5 ms) in a solution containing 0.075 mol L⁻¹ acetate buffer of pH = 4.6 ± 0.1, and 7.5 × 10⁻⁵ mol L⁻¹ Pb(NO₃)₂. The analytical signal obtained at the potential around −1.42 V (vs. silver pseudo-reference electrode) is related to the reduction process of TST adsorbed onto the electrode surface. The use of pSPCE/PbNPs allows obtaining a very low limit of TST detection (2.2 × 10⁻¹² mol L⁻¹) and wide linear ranges of the calibration graph (1.0 × 10⁻¹¹–1.0 × 10⁻¹⁰, 1.0 × 10⁻¹⁰–2.0 × 10⁻⁹, and 2.0 × 10⁻⁹–2.0 × 10⁻⁸ mol L⁻¹). The pSPCE/PbNPs were successfully applied for the determination of TST in reference material of human urine and wastewater purified in a sewage treatment plant without preliminary preparation.     

Solid-State-Activated Sintering of ZnAl2O4 Ceramics Containing Cu3Nb2O8 with Superior Dielectric and Thermal Properties

Low-temperature co-fired ceramics (LTCCs) are dielectric materials that can be co-fired with Ag or Cu; however, conventional LTCC materials are mostly poorly thermally conductive, which is problematic and requires improvement. We focused on ZnAl₂O₄ (gahnite) as a base material. With its high thermal conductivity (~59 W·m⁻¹·K⁻¹ reported for 0.83ZnAl₂O₄–0.17TiO₂), ZnAl₂O₄ is potentially more thermally conductive than Al₂O₃ (alumina); however, it sinters densely at a moderate temperature (~1500 °C). The addition of only 4 wt.% of Cu₃Nb₂O₈ significantly lowered the sintering temperature of ZnAl₂O₄ to 910 °C, which is lower than the melting point of silver (961 °C). The sample fired at 960 °C for 384 h exhibited a relative permittivity (ε_r) of 9.2, a quality factor by resonant frequency (Q × f) value of 105,000 GHz, and a temperature coefficient of the resonant frequency (τ_f) of −56 ppm·K⁻¹. The sample exhibited a thermal conductivity of 10.1 W·m⁻¹·K⁻¹, which exceeds that of conventional LTCCs (~2–7 W·m⁻¹·K⁻¹); hence, it is a superior LTCC candidate. In addition, a mixed powder of the Cu₃Nb₂O₈ additive and ZnAl₂O₄ has a melting temperature that is not significantly different from that (~970 °C) of the pristine Cu₃Nb₂O₈ additive. The sample appears to densify in the solid state through a solid-state-activated sintering mechanism.     

Self-Template Synthesis of Nitrogen-Doped Hollow Carbon Nanospheres with Rational Mesoporosity for Efficient Supercapacitors

Rational design and economic fabrication are essential to develop carbonic electrode materials with optimized porosity for high-performance supercapacitors. Herein, nitrogen-doped hollow carbon nanospheres (NHCSs) derived from resorcinol and formaldehyde resin are successfully prepared via a self-template strategy. The porosity and heteroatoms in the carbon shell can be adjusted by purposefully introducing various dosages of ammonium ferric citrate (AFC). Under the optimum AFC dosage (30 mg), the as-prepared NHCS-30 possesses hierarchical architecture, high specific surface area up to 1987 m²·g⁻¹, an ultrahigh mesopore proportion of 98%, and moderate contents of heteroatoms, and these features endow it with a high specific capacitance of 206.5 F·g⁻¹ at 0.2 A·g⁻¹, with a good rate capability of 125 F·g⁻¹ at 20 A·g⁻¹ as well as outstanding electrochemical stability after 5000 cycles in a 6 M KOH electrolyte. Furthermore, the assembled NHCS-30 based symmetric supercapacitor delivers an energy density of 14.1 W·h·kg⁻¹ at a power density of 200 W·kg⁻¹ in a 6 M KOH electrolyte. This work provides not only an appealing model to study the effect of structural and component change on capacitance, but also general guidance to expand functionality electrode materials by the self-template method.     

External Condensation of HFE 7000 and HFE 7100 Refrigerants in Shell and Tube Heat Exchangers

The paper describes the results of experimental studies of media as an intermediary in heat exchange taking place in low volume conditions. Their properties predestine them both as a future-proof for transporting and storing heat materials. The paper concerns the current topic related to the miniaturization of cooling heat exchangers. There are many studies in the literature on the phase transition of refrigerants in the flow in pipe minichannels. However, there is a lack of studies devoted to the condensation process in a small volume on the surface of pipe minichannels. The authors proposed a design of a small heat exchanger with a shell-and-tube structure, where the refrigerant condenses on the outer surface of the pipe minichannels cooled from the inside with water. It is a response to the global trend of building highly efficient, miniaturized structures for cooling and air conditioning heat exchangers. Two future-proof, ecological replacements of the CFC refrigerants still present in the installations were used for the experimental research. These are low-pressure fluids HFE 7000 and HFE 7100. The tests were carried out in a wide range of changes in thermal-flow parameters: G = 20–700 kg·m⁻²s⁻¹, q = 3000–60,000 W·m⁻², t_s = 40–80 °C.     

High-Performance UV-Vis Light Induces Radical Photopolymerization Using Novel 2-Aminobenzothiazole-Based Photosensitizers

The popularity of using the photopolymerization reactions in various areas of science and technique is constantly gaining importance. Light-induced photopolymerization is the basic process for the production of various polymeric materials. The key role in the polymerization reaction is the photoinitiator. The huge demand for radical and cationic initiators results from the dynamic development of the medical sector, and the optoelectronic, paints, coatings, varnishes and adhesives industries. For this reason, we dealt with the subject of designing new, highly-efficient radical photoinitiators. This paper describes novel photoinitiating systems operating in UV-Vis light for radical polymerization of acrylates. The proposed photoinitiators are composed of squaraine (SQ) as a light absorber and various diphenyliodonium (Iod) salts as co-initiators. The kinetic parameters of radical polymerization of trimethylolpropane triacrylate (TMPTA), such as the degree of double bonds conversion (C_%), the rate of photopolymerization (R_p), as well as the photoinitiation index (I_p) were calculated. It was found that 2-aminobenzothiazole derivatives in the presence of iodonium salts effectively initiated the polymerization of TMPTA. The rates of polymerization were at about 2 × 10⁻² s⁻¹ and the degree of conversion of acrylate groups from 10% to 36% were observed. The values of the photoinitiating indexes for the most optimal initiator concentration, i.e., 5 × 10⁻³ M were in the range from 1 × 10⁻³ s⁻² even to above 9 × 10⁻³ s⁻². The photoinitiating efficiency of new radical initiators depends on the concentration and chemical structure of used photoinitiator. The role of squaraine-based photoinitiating systems as effective dyeing photoinitiators for radical polymerization is highlighted in this article.     

Kinetics of the Organic Compounds and Ammonium Nitrogen Electrochemical Oxidation in Landfill Leachates at Boron-Doped Diamond Anodes

Electrochemical oxidation (EO) of organic compounds and ammonium in the complex matrix of landfill leachates (LLs) was investigated using three different boron-doped diamond electrodes produced on silicon substrate (BDD/Si)(levels of boron doping [B]/[C] = 500, 10,000, and 15,000 ppm—0.5 k; 10 k, and 15 k, respectively) during 8-h tests. The LLs were collected from an old landfill in the Pomerania region (Northern Poland) and were characterized by a high concentration of N-NH₄⁺ (2069 ± 103 mg·L⁻¹), chemical oxygen demand (COD) (3608 ± 123 mg·L⁻¹), high salinity (2690 ± 70 mg Cl⁻·L⁻¹, 1353 ± 70 mg SO₄²⁻·L⁻¹), and poor biodegradability. The experiments revealed that electrochemical oxidation of LLs using BDD 0.5 k and current density (j) = 100 mA·cm⁻² was the most effective amongst those tested (C_8h/C₀: COD = 0.09 ± 0.14 mg·L⁻¹, N-NH₄⁺ = 0.39 ± 0.05 mg·L⁻¹). COD removal fits the model of pseudo-first-order reactions and N-NH₄⁺ removal in most cases follows second-order kinetics. The double increase in biodegradability index—to 0.22 ± 0.05 (BDD 0.5 k, j = 50 mA·cm⁻²) shows the potential application of EO prior biological treatment. Despite EO still being an energy consuming process, optimum conditions (COD removal > 70%) might be achieved after 4 h of treatment with an energy consumption of 200 kW·m⁻³ (BDD 0.5 k, j = 100 mA·cm⁻²).     

Effect of Polyphenylsulfone and Polysulfone Incompatibility on the Structure and Performance of Blend Membranes for Ultrafiltration

This study deals with the modification of polyphenylsulfone ultrafiltration membranes by introduction of an incompatible polymer polysulfone to the polyphenylsulfone casting solution to improve the permeability. The correlation between properties of the blend polyphenylsulfone/polysulfone solutions and porous anisotropic membranes for ultrafiltration prepared from these solutions was revealed. The blend polyphenylsulfone/polysulfone solutions were investigated using a turbidity spectrum method, optical microscopy and measurements of dynamic viscosity and turbidity. The structure of the prepared blend flat sheet membranes was studied using scanning electron microscopy. Membrane separation performance was investigated in the process of ultrafiltration of human serum albumin buffered solutions. It was found that with the introduction of polysulfone to the polyphenylsulfone casting solution in N-methyl-2-pyrrolidone the size of supramolecular particles significantly increases with the maximum at (40–60):(60:40) polyphenylsulfone:polysulfone blend ratio from 76 nm to 196–354 nm. It was shown that polyphenylsulfone/polysulfone blend solutions, unlike the solutions of pristine polymers, are two-phase systems (emulsions) with the maximum droplet size and highest degree of polydispersity at polyphenylsulfone/polysulfone blend ratios (30–60):(70–40). Pure water flux of the blend membranes passes through a maximum in the region of the most heterogeneous structure of the casting solution, which is associated with the imposition of a polymer-polymer phase separation on the non-solvent induced phase separation upon membrane preparation. The application of polyphenylsulfone/polysulfone blends as membrane-forming polymers and polyethylene glycol (M_n = 400 g·mol⁻¹) as a pore-forming agent to the casting solutions yields the formation of ultrafiltration membranes with high membrane pure water flux (270 L·m⁻²·h⁻¹ at 0.1MPa) and human serum albumin rejection of 85%.