Series Of Composites Research Articles

Long-term and efficient treatment of shale gas flowback wastewater by the novel double SEP@Fe-Mn/RGO composite membranes method

The long-term and efficient treatment of shale gas wastewater is an inevitable tendency. This study employed the SEP@Fe-Mn/RGO composite membrane series for the membrane separation treatment of shale gas wastewater. Different proportions and different function of SEP@Fe-Mn/RGO composite membranes were obtained through the method of electrostatic self-assembly. This study researched the “Trade-off” issue of membranes separation through the analysis，resulting in membranes that best meets the separation requirements for shale gas wastewater. After two membrane separation, The oil-water separation efficiency (COD 2040 mg/L and TOC 487.14 mg/L) of shale gas wastewater was >99.3 %. The removal rate of the main salt component (Na2SO4) reached 83.56 %, and the removal rate of major heavy metal ions (Fe3+, Cr3+, Ba2+) was above 60 %. Because of the continuous generation of in-situ bubbles by the reaction of MnO2 with H2O2, and Fenton reactions on the membrane, which further accelerated the separation of pollutants. In a variety of harsh water environments, this membrane series remained stable within 12 h. Simple to prepare, cost-effective, low in energy consumption, and environmentally friendly, which makes it promising for wide applications in the field of petroleum water treatment.

One-pot synthesis of cerium-organic framework@carbon black composites for simultaneous detection of dopamine, uric acid, and acetaminophen

Accurate identification of dopamine (DA), uric acid (UA), and acetaminophen (APAP) is critical to safeguarding human health. However, their simultaneous detection is still challenging due to their similar oxidation potentials. In this work, a series of new composites based on cerium-organic framework (Ce-MOF) and carbon black (CB) were constructed by one-pot method at room temperature. The introduction of CB can significantly affect the conductivity and specific surface area of the composites. The optimal composite Ce-MOF-COOH/CB0.4 can identify DA, UA, and APAP simultaneously with low detection limit of 0.030, 0.045, and 0.057 μM and wide detection range of 2.5–310.0, 3.0–305.0, and 2.5–617.0 μM, respectively. Furthermore, density-functional theory (DFT) calculation was performed to explore the influence of functional groups (-NH2 or –COOH) on the sensing performance. It was found that the introduced functional groups can obviously enhance the host-guest interactions through the formation of strong hydrogen bonds, which is beneficial for promoting sensing performance. In addition, the constructed electrode could also detect DA, UA, and APAP in real samples, which indicated its potential for practical applications. This study provides a feasible approach to utilize MOFs as electrochemical sensors for simultaneously detection of biomolecules.

Geochemical proxies for deep-sea temperature and nutrient content in cold-water bamboo corals

The impact of warming, acidification, and deoxygenation on deep-sea environments is a growing concern. Historical records are sparse, particularly at high latitudes, making climate change projections challenging. Indirect proxies, such as trace element composition of marine carbonates, such as coral skeletons, can offer an alternative method to fill data gaps but have not been realised. Here, using Laser Ablation Triple-Quadrupole Inductively Coupled Plasma Mass Spectrometry (LA-QQQ-ICP-MS), we examined micrometre-scale element variation within and between individual colonies of the bamboo coral Keratoisis sp. obtained from the Eastern Canadian Arctic. These data are used to assess the influence of biological variability on geochemical tracers for reconstructing past environmental conditions (temperature: Mg/Ca, Li/Mg, Sr/Ca, Ba/Ca, U/Ca; [Ba]SW: Ba/Ca). We place these data into context, based on a survey of literature data, using refined calibrations for high-Mg calcitic Octocorals. We find reproducible (2σ relative coefficient of variation) values of Mg/Ca (3%) and Ba/Ca (6%) along the radial growth axis of all colonies and internodes of Keratoisis sp., indicating that these signals are likely suitable for environmental reconstructions. After revising the available multi-taxa calibrations for Mg/Ca (0.316 ± 0.026 °C/mmol/mol, R2 = 0.87, p < 0.001) and Ba/Ca ([Ba/Ca μmol/mol] = 0.148 ± 0.005 [BaSW nmol/kg], R2 = 0.97, p < 0.001), we show that vital effects within and among Keratoisis sp. colonies strongly influence reconstructed temperature and [Ba]SW, but this can be somewhat mitigated by combining multiple internode transects from one colony into a single composite series. Despite the ontogenetic variability, all colonies reveal a gradual deep-water cooling trend since the early 21st century and synchronised, multi-year spikes in Ba/Ca (and hence [Ba]SW) that suggest substantial and coherent barium inputs to the seafloor. Our study confirms the reliability of Mg/Ca and Ba/Ca proxies in high-Mg bamboo corals for detecting multi-annual temperature and seawater barium variations in cold-water environments, but further investigation into micro-scale element behaviour influenced by biotic processes in these corals is needed to enhance confidence in reconstructions at finer spatial and temporal resolutions. We conclude that employing empirical calibrations based on multi-taxa approaches can increase the certainty of capturing regional changes in the environment more accurately than a single species calibration, while leveraging multiple element series to account for biological-induced variability improves single colony reconstructions.

Investigating Thermal Decomposition Kinetics and Thermodynamic Parameters of Hydroxyl-Terminated Polybutadiene-based Energetic Composite

Background: Hydroxyl-Terminated Polybutadiene (HTPB)-based energetic compositions have been developed for enhanced blast energetic composite, composite rocket propellant formulations, metal cutting, demolition, welding and explosive reactive armour in civil and military applications. The types and choice of curing agents are crucial in enhancing the mechanical and structural integrity of the binder. To understand the stability and safety of energetic composites for potential applications, it is necessary to understand the thermal decomposition kinetics and thermodynamic parameters clearly. Objective: The main objective is to study the decomposition kinetic and thermodynamic parameters of energetic composites cured by different curing agents. Methods: A series of energetic composites based on HMX (1,3,5,7-tetranitro-1,3,5,7- tetrazocane) and HTPB-based binder system cured with various curing agents were prepared by the cast cured method. The curatives, namely MDI (4,4’-methylene diphenyl diisocyanate), IPDI (isophorone diisocyanate), TDI (toluene dissocyanate) and TMDI (2,2,4-trimethylhexamethylene diisocyanate) were used. The thermal analysis method was employed to investigate the thermal decomposition characteristics, which are closely associated with the thermal stability and safety considerations during handling, processing, and storage. The kinetic parameters for thermal decomposition reactions were studied by employing the Flynn-Wall-Ozawa method. The thermodynamic parameters of the activation enthalpy, activation Gibbs energy free and activation entropy of all energetic composites were also determined by the theory of activated complex. Results: The thermogravimetric results show that the thermal stability is almost similar for all composites cured with the different types of curing agents. The average activation energy of the energetic composites cured with IPDI, MDI, TMDI and TDI was 207.5, 237.3, 243.3 and 187.6 kJ/mol, respectively. The thermodynamic parameters for the thermal decomposition process show that they are generally thermodynamically stable and non-spontaneous. Scanning electron microscope (SEM) micrographs of all the samples clearly indicate that HMX crystals are well embedded in the polymer matrices. result: The thermogravimetric results show that the thermal stability and thermal decomposition behaviour do not change significantly by varying the type of the curing agent in the HTPB-based binder. The SEM micrographs of all the samples clearly indicate that HMX crystals are well embedded in the polymer matrices. The averaged activation energy for the HMX/HTPB/MDI, HMX/HTPB/IPDI, HMX/HTPB/TDI and HMX/HTPB/TMDI samples obtained from FO method was 237.3, 207.5, 187.6 and 243.3 kJ/mol, respectively. The thermodynamic parameters including the activation enthalpy, activation Gibbs free energy and activation entropy for the thermal decomposition process show that they are generally thermodynamically stable and non-spathaceous. Conclusion: The thermal stability of all energetic composites is almost constant. The activation energy of the prepared energetic composites is significantly varied with varying the type of curing agents in the HTPB-based binder system. The thermodynamic parameters indicate that composites possess superior stability and thermal safety. The SEM micrographs indicate that HMX crystals of prepared composites are embedded in the polymer matrix.

Effective formaldehyde elimination over pyrolusite-manganite hybrid catalysts promoted by Keggin acid decoration: Tungsten doping and chemically adsorbed active oxygen

A series of pyrolusite-manganite composites with five levels of phosphotungstic acid additions (HPWxMn, x indicating the added mass of phosphotungstic acid) were applied in the catalytic oxidation of 330–350 mg/m3 formaldehyde under ambient conditions. Different techniques were used to characterize the pristine composite and the best-performed HPW0.2Mn catalyst. Compared to the effects of hydrogen (replacing a small part of structural K+ ions) and phosphorus (not detected in the HPW0.2Mn catalyst) elements in phosphotungstic acid, the doping of tungsten would prefer to occur via forming W-O-Mn species, which significantly altered the crystallite growth and induced numerous defects. As to formaldehyde degradation, the best 91% conversion and 72% CO2 yield were achieved on HPW0.2Mn. The uniqueness of tungsten doping on boosting formaldehyde oxidation was expounded from the angles of intimate elemental interaction (XPS), redox behavior and molecular O2 activation (CO-TPR, UV-Vis DRS and O2-TPD). The incorporation of tungsten led to higher surface Mn3+ concentration, higher content of surface oxygen vacancies, better low-temperature reducibility and abounding chemically adsorbed oxygen species (They were proposed to be the dominant oxidants for formaldehyde oxidation in this study), which were well correlated with the sequence of catalytic activity. Finally, possible reaction pathways were examined by coupling the characterizations of used catalysts.

A formaldehyde gas sensor based on Ag-decorated ZnCo2O4/FF composite

Cobalt-containing spinel oxides are highly active materials for gas sensing and have shown promise in various applications. In this study, we prepared a series of gas-sensitive composites by doping Ag into ZnCo2O4/Phenylalanine dipeptide (ZCO/FF) and investigated their gas sensitivity to formaldehyde. The experiments showed that the response of ZCO/FF-3 wt%Ag to 20 ppm formaldehyde was 23 at an optimum operating temperature of 175 °C. Further experimental data show that the sensor has excellent selectivity and stability. These results provide basic knowledge for the practical use of spinel oxide gas sensors.

Gamma radiation shielding efficiency of some different ceramic composites: A comparative study

The development of a non-toxic, and low-cost material that offers good shielding against harmful ionizing radiation is highly demanded. This work offers a strategy for combining ceramic composites and carbon nanotubes to produce composites with desirable radiation shielding properties. First, we successfully prepared barium titanate (BT) ceramic by sol-gel auto-combustion method. Then, a series of CERAM-1, CERAM-2, and CERAM-3 ceramic composites were formed by inserting into BT different types of ferrite and carbon nanotubes. The crystal structural analysis indicated that all ceramic composites crystallized into a cubic structure. The crystallite sizes of the final products were calculated and were found to be 30.8 nm, 25.4 nm, 35.9 nm, and 33.1 nm for pure BT, CERAM-1, CERAM-2, and CERAM-3, respectively. The gamma radiation shielding parameters were experimentally examined at four energies ranging from low to high energy radiation. At 0.06 MeV, the ceramics have the greatest linear attenuation coefficient (LAC) values, ranging from 31.760 to 29.683 cm−1. The results showed that CERAM-1 has the greatest LAC values at 0.060 and 0.662 MeV, which indicated that CERAM-1 is the most effective shield to its advantage over the other ceramic samples at low and middle energies. Based on the obtained results, it can be concluded that various prepared ceramics can be useful for low-energy radiation protective applications.

Toughened bulk high-entropy diborides with high hardness and enhanced oxidation resistance via SiC whiskers

The fracture toughness and oxidation resistance are crucial factors affecting the practical applications of high-entropy diboride ceramics (HEBs). In this study, silicon carbide whiskers (SiCw) were introduced as a reinforcement for HEBs for the first time. To achieve a uniform dispersion of SiCw within the HEB powders, a combination of simultaneous ultrasonic dispersion, mechanical agitation, and freeze-drying technology was employed. Consequently, a series of composites, (Hf0.2Zr0.2Ta0.2V0.2Nb0.2)B2-nSiCw (n = 0–20 vol%), were densified by spark plasma sintering. The effect of SiCw on the microstructure and mechanical properties of the HEBs were studied, as well as the toughening mechanism involved. The results revealed that the introduction of SiCw led to grain-size refinement in (Hf0.2Zr0.2Ta0.2V0.2Nb0.2)B2, along with significant improvements in relative density, hardness, fracture toughness, and oxidation resistance. The relative density, hardness and fracture-toughness of (Hf0.2Zr0.2Ta0.2V0.2Nb0.2)B2-SiCw composites exhibited an initial increase followed by a decrease with increasing SiCw content. Specifically, the (Hf0.2Zr0.2Ta0.2V0.2Nb0.2)B2–15 vol% SiCw composite simultaneously obtained the highest hardness of 25.6 GPa and fracture-toughness of 4.8 MPa·m1/2, representing a 26% improvement compared to (Hf0.2Zr0.2Ta0.2V0.2Nb0.2)B2 ceramics.

Some algebraic questions about the Reed-Muller code

Let Rq(r,n) denote the rth order Reed-Muller code of length qn over Fq. We consider two algebraic questions about the Reed-Muller code. Let Hq(r,n)=Rq(r,n)/Rq(r−1,n). (1) When q=2, it is known that there is a “duality” between the actions of GL(n,F2) on H2(r,n) and on H2(r′,n), where r+r′=n. The result is false for a general q. However, we find that a slightly modified duality statement still holds when q is a prime or r<charFq. (2) Let F(Fqn,Fq) denote the Fq-algebra of all functions from Fqn to Fq. It is known that when q is a prime, the Reed-Muller codes {0}=Rq(−1,n)⊂Rq(0,n)⊂⋯⊂Rq(n(q−1),n)=F(Fqn,Fq) are the only AGL(n,Fq)-submodules of F(Fqn,Fq). In particular, Hq(r,n) is an irreducible GL(n,Fq)-module when q is a prime. For a general q, Hq(r,n) is not necessarily irreducible. We determine all its submodules and the factors in its composition series. The factors of the composition series of Hq(r,n) provide an explicit family of irreducible representations of GL(n,Fq) over Fq.

Inclusions in Placer Pt-Fe Alloy Nuggets, Northwest Ecuador: Evolution of a Ural-Alaskan Type PGE Mineralizing System (Cr-Spinel, IPGE, Sulfarsenides, and Cu-Depleted PGM)

Abstract A Cu- and Rh-enriched magmatic ore system is defined by abundant PGM (platinum group mineral) inclusions in forty-four Pt-Fe alloy nuggets from the Camumbi River gold placer, northwest Ecuador. Isoferroplatinum is depleted in Rh, Os, and Ru compared with native platinum, suggesting most crystallized after Os-(Ir) alloy, laurite, and some Rh-PGM. Two Pt-Fe alloy nuggets have zoned hydrothermal alteration rinds, and an UM (unnamed mineral) is (Rh,Pd)4As3. Our previous work shows that silicate glass inclusions define a fractionated co-magmatic compositional series related to primitive hydrous ferrobasalt, and trace element chemistry matches their Late Cretaceous accreted volcanic arc terrane. Here we report exceptional Cr-spinel (Ural-Alaskan type) inclusions coexisting with primitive ferrobasaltic glass crystallized at highest T. Laurite inclusions also indicate high T and S saturation of early melt. Os-(Ir) inclusions are Ru-depleted while two discrete Ir-enriched osmium crystals have remarkable, extreme Ru enrichment and depletion, confirming crystallization before and after laurite. Laurite and osmium inclusions in one Pt-Fe alloy reflect concomitant crystallization and fluctuating low fS2 melt conditions. In experimental primitive Cu-bearing Pt-Pd-S-(As) melt (cf. exsolved from primitive basalt), first Cu-PGM-sulfide crystallization generates a Cu-depleted, Pt-Pd-As-(S) residual melt. At lower T immiscible melts Pt-As-(S) and later Pd-As-(S) crystallize distinctive PGM. We report analogous natural multiphase PGM inclusion assemblages in separate isoferroplatinum nuggets: (1) zoned sulfarsenides, sperrylite, and genkinite, with rare resorbed cognate xenocrystic cooperite (captured from primary sulfide melt) define a high T, Pt-enriched sub-system [Pt &amp;gt; Rh(Pd,Ir,Ru)As,S ≫ Sb,Bi] and (2) zoned sulfarsenides, arsenopalladinite, sperrylite, törnroosite, and gold define a lower T, fractionated Pd-enriched sub-system [(Pd &amp;gt; Rh ≃ Pt &amp;gt; Ir &amp;gt; Au)As,S &amp;gt; Te ≫ Sb,Bi]. The previously undocumented natural S-rich sperrylite (formerly “platarsite”) solid solution series and later crystallized irarsite series are discriminated in terms of Pt-Ir-Rh. Both trends fractionate toward increasing Rh (hollingworthite). The discrete PGM assemblage, sperrylite-telluropalladinite (with exsolved palladium and electrum) defines an IPGE-depleted Pd &amp;gt; Pt(Au &amp;gt; Ag)As ≥ Te ≥ Sb sub-system and records extreme fractionation. Cu-bearing multiphase PGM inclusions (some coexisting with silicate glass) derived from the fraction of Cu-bearing exsolved Pt-Pd-S-(As) melt will be reported separately.

Tunable structure and linear viscoelastic properties of poly(glycerol adipate urethane)-based elastomeric composites for tissue regeneration

Elastomeric biocomposites based on poly(glycerol adipate urethane) and hydroxyapatite were fabricated for tissue regeneration. The poly(glycerol adipate urethane) (PGAU) elastomeric composite matrices were obtained by chemical crosslinking of the poly(glycerol adipate) prepolymer (pPGA) with diisocyanate derivative of L-lysine. Two series of composites varying in the amount of L-lysine diisocyanate ethyl ester (LDI) used as a crosslinking agent were manufactured. As a ceramic filler both unmodified and L-lysine surface-modified hydroxyapatite (HAP) particles were used. The novelty of our research consists in the manufactured elastomeric materials and characterization of their linear viscoelastic (LVE) properties. The LVE properties of the composites were investigated by means of dynamic thermomechanical analysis. Frequency sweep and amplitude sweep measurements were performed in shear mode. The influence of the crosslinking agent (LDI) amount, HAP content and surface modification of HAP on the LVE properties of the composites was determined based on the analysis of the master curves of storage (G′) and loss (G″) moduli and of tanδ of the composites. Depending on the amount of LDI, HAP and surface modification, the materials differ in the values of rubber elasticity plateau modulus (G0) and G′ and G″ determined at selected shear frequencies and at the glassy state. G0 ranges from 278 kPa to 3.98 MPa, G′ in the glassy state is within the range of 219 MPa–459 MPa. The G0 values of the PGAU-based composites are within the stiffness range of soft tissue. In view of the choice of HAP as the ceramic component and the G0 values, elastomeric composites have the potential to be used as filling materials in small bone defects (due to their mechanical similarity to osteoid) as well as materials for cartilage tissue regeneration.

Broadband near infrared emission of Er3+ ions doped fluorophosphate glasses for solid state laser applications

A series of glass compositions (P2O5 + Bi2O3 + Na2CO3 + SrF2 + xEr2O3) with different concentrations of erbium ions (Er3+) was synthesized using the melt quenching method and the samples were subjected to thorough characterization to explore their optical and structural properties. In order to ascertain the amorphous nature of the glass and acquire a deeper understanding of its chemical bonding, conventional methods of characterization, such as X-ray diffraction and Fourier transform infrared spectroscopy, were utilized. The Judd-Ofelt intensity parameters were computed using the absorption spectra of glasses doped with Er3+, providing vital information about the local environment and coordination of Er3+ ions in the glass matrix. Using the Judd-Ofelt intensity parameters and emission spectra to calculate the radiative parameters like total radiative transition probability (AT), radiative lifetime (τR) and radiative branching ratios for 4I13/2 → 4I15/2 transition. The McCumber theory is used to study absorption and emission cross-section for 4I13/2 → 4I15/2 transition. Prepared the PBNSEr05 glass sample suitable candidates for 1.53 μm solid state laser applications.

Water-soluble Polypyrrole-Polybis(4-oxy benzene sulfonic acid)phosphazene Composites and Investigation of Their Performance as Cathode Binder in Li-ion Batteries.

Current electric storage systems eagerly focus on high-power and energy-dense Lithium-ion batteries to cope with increasing energy storage demands. Since cathode materials are one of the bottlenecks of these batteries, there is much interest in layered lithium-rich manganese oxide-based (LLMO) cathodes which can develop this technology. However, Initial Coulombic Efficiency (ICE) loss, poor rate performance and cycling instability issues are still persistent as problems to be solved for these materials. Recent research shows that water-soluble binders are effective in improving the performance of LLMO materials. Herein, we describe the synthesis, characterisation, and application of a series of water-soluble composites as a binder for LLMO cathodes. The PPy is introduced as part of the binder to improve the electronic conductivity and two different oxidants and various PPy to PSAP ratios were used to optimise the final properties. The electrochemical performance and morphology of the cathodes before and after cycling were investigated and compared with the conventional PVDF binder. The LLMO-2c electrode showed excellent charge-discharge performance, especially at 5 C and 10 C rates, and high cycling stability at 0.2 C whilst maintaining a final capacity of 184 mAh/g after 200 cycles, which is equal to 89.3 % capacity retention.

Photoelectrothermocatalytic reduction of CO2 to glycol via CdIn2S4-N/C hollow heterostructure mimicking plant cell

A series of novel semiconductor composites of CdIn2S4-N/C, in which CdIn2S4 is grown on hollow nitrogen-doped carbon spheres to mimic plant cells, were designed and applied to photoelectrothermocatalytic reduction of CO2. Our results reveal that the unique hollow structure and photothermal properties of N/C contribute to excellent performance of catalyst in CO2 reduction. Specifically, the optimal catalyst of CdIn2S4-N/C-2–800 demonstrates an outstanding catalytic activity with a formation rate of 168.5 µM h−1 cm−2 for carbon-based products and an electron selectivity for C2 products of 66.9 %. DFT calculations demonstrate that pyridine N and pyrrole N can reduce the energy barrier during CO2 reduction. Two important species of *=C=O and OC-COH* were detected by operando IR spectra and suggested to be key intermediates to C2 products via a carbene (*=C=O) coupling mechanism. CdIn2S4-N/C provides thermoelectrons and active sites like in the membrane of plant to enhance the probability of C-C coupling.

Leveraging gauge networks and strategic discharge measurements to aid the development of continuous streamflow records

Abstract. Quantifying continuous discharge can be difficult, especially for nascent monitoring efforts, due to the challenges of establishing gauging locations, sensor protocols, and installations. Some continuous discharge series generated by the National Ecological Observatory Network (NEON) during its pre- and early-operational phases (2015–present) are marked by anomalies related to sensor drift, gauge movement, and incomplete rating curves. Here, we investigate the potential to estimate continuous discharge when discrete streamflow measurements are available at the site of interest. Using field-measured discharge as truth, we reconstructed continuous discharge for all 27 NEON stream gauges via linear regression on nearby donor gauges and/or prediction from neural networks trained on a large corpus of established gauge data. Reconstructions achieved median efficiencies of 0.83 (Nash–Sutcliffe, or NSE) and 0.81 (Kling–Gupta, or KGE) across all sites and improved KGE at 11 sites versus published data, with linear regression generally outperforming deep learning approaches due to the use of target site data for model fitting rather than evaluation only. Estimates from this analysis inform ∼199 site-months of missing data in the official record, and can be used jointly with NEON data to enhance the descriptive and predictive value of NEON's stream data products. We provide 5 min composite discharge series for each site that combine the best estimates across modeling approaches and NEON's published data. The success of this effort demonstrates the potential to establish “virtual gauges”, sites at which continuous streamflow can be accurately estimated from discrete measurements, by transferring information from nearby donor gauges and/or large collections of training data.

Manju Varghese and Shery Fernandez

P. S. Das [Sivaramakrishna Das, P. Fuzzy groups and level subgroups. {\it J. Math. Anal. Appl.} {\bf 84} (1981), no. 1, 264--269.] proved that the level subgroups of any fuzzy subgroup of a finite group form a chain. In this paper we extend it to modules and showed that the level submodules of a fuzzy module also form a chain. With the help of these results we introduced fuzzy noetherian module for noetherian modules. Some results are proved for level submodules of any fuzzy module of modules with composition series.

Образ советского детства как условие самоидентификации героя в зрелых поэмах Л. Рубинштейна

The article is devoted to the analysis of structural, compositional and figurative series of the “catalog” poems “The Appearance of a Hero” (1986), “Mama Washed the Frame” (1987), “This Is Me” (1995) by Lev Rubinstein, which made up his most representative collection “Regular Writing” (1996). The research was undertaken in order to comprehend not only the formal features of Rubinstein’s poems, which modern criticism most often turned to, but also the content and semantic layer of the poet’s “card” texts. The authors of the article differentiate the main ideological and figurative dominants of Rubinstein’s mature poems, identify the existential spaces of the characters contoured in the text, trace the maturation of the persona’s own idea of the world and himself. In particular, the authors consider the motif of the hero’s self-identification, his self-determination in the atmosphere of memories of childhood, of the Soviet past, which is an end-to-end motif for all the analyzed poems. The scientific novelty of the research lies in the fact that it is the first to examine various aspects of the hero’s self-determination within the framework of Rubinstein’s conceptualist poems, to reveal axiological perspectives of the persona’s memories of the Soviet past, the country and himself. As a result, it is proved that Rubinstein’s catalog texts, declared by conceptualists as “meaningless”, are permeated not only with semantic, but also with nostalgic motifs.

Enhanced Thermal Conductivity of High-Density Polyethylene Composites with Hybrid Fillers of Flaky and Spherical Boron Nitride Particles.

The synergistic effect between different fillers plays a crucial role in determining the performance of composites. In this work, spherical boron nitride (BN) and flaky BN are used as hybrid fillers to improve the thermal conductivity (TC) of high-density polyethylene (HDPE) composites. A series of HDPE composites were prepared by adjusting the mass ratio (1:0, 4:1, 2:1, 1:1, 1:2, 1:4, and 0:1) of spherical BN and flaky BN. The SEM results indicate that the spherical BN (with a particle size of 3 μm) effectively filled the gaps between the flaky BN (with a particle size of 30 μm), leading to the formation of more continuous heat conduction paths with the composite. Remarkably, when the mass ratio of spherical BN to flaky BN was set to 1:4 (with a total BN filling amount of 30 wt%), the TC of the composite could reach up to 1.648 Wm-1K-1, which is obviously higher than that of the composite containing a single filler, realizing the synergistic effect of the hybrid fillers. In addition, the synergistic effect of fillers also affects the thermal stability and crystallization behavior of composites. This work is of great significance for optimizing the application of hybrid BN fillers in the field of thermal management.

Impact of composite modes on electrochemical properties of Fe3O4/CNTs for Li-ion storage

Transition metal oxides (TMOs, e.g., Fe3O4) with high theoretical capacity hold tremendous potential in the field of lithium-ion batteries. Unfortunately, TMOs still suffer from the significant volume expansion and low intrinsic electronic conductivity, which results in irreversible structural collapse, uncontrollable particle aggregation, and sluggish electrochemical reaction kinetics, leading to bad rate performance and cycling stability. Combining TMOs with carbon has become the most effective approach to address the aforementioned issues. However, the interaction mechanism between TMOs and carbon influencing on electrochemical properties has not yet been thoroughly explored and widely recognized. Herein, we proposed a simple and controllable method to synthesize a series of Fe3O4 composites, i.e., Fe3O4 combined with carbon nanotubes (CNTs), via different composite modes, i.e., mixing, embedding and encapsulation. The mixing one exhibits the highest initial capacity but the poorest cycling stability. Encapsulating Fe3O4 into the cavities of CNTs effectively mitigates the volume expansion of Fe3O4, thereby achieving satisfactory rate performance. The embedded composite produces ultrafine Fe3O4 particles within the walls of CNTs, which not only enhances the dispersion of Fe3O4, but also provides an efficient pathway for electronic transport. The electrode based on the embedded composite mode demonstrates excellent cycling stability and an acceptable reversible capacity of 683.7 mAh/g at 1 A/g after 100 cycles. The relationship between structure and electrochemical properties of Fe3O4/CNTs composites is elaborated, which provides universal aspect for future design of high-energy–density lithium-ion batteries.

Synthesis of a novel clay/polyacrylic acid-tannic acid hydrogel composite for efficient removal of crystal violet dye with low swelling and high adsorption performance

Hydrogels are versatile materials with numerous applications; however, their potential in water treatment is hindered by their tendency to exhibit high swelling, degradation, and excessive water absorption. In this study, a hydrogel composed of natural clay, polyacrylic acid (PAA), and tannic acid (TA) was prepared with varying ratios of TA to control swelling ratio, reduce degradation and enhance adsorption efficiency for removal of cationic dye-contaminated wastewater. The effect of the TA ratio on the physical, chemical, and adsorption properties of prepared hydrogel (clay/PAA-TA) was studied by preparing a series of hydrogel composites and characterizing them using various techniques. The swelling ratio of pure PAA hydrogels was 7061%, but by incorporating TA into the polymer mixture, the swelling ratio decreased to less than 500%, with the lowest observed swelling of 250% occurring at a 5% tannic acid. In adsorption studies, the target pollutant was crystal violet dye (CV) and the pH effect, time effect, temperature and initial dye concentration for the adsorption CV dye were investigated using batch adsorption parameters. Adsorption studies showed that using 5% of TA is the optimal ratio to achieve the highest adsorption capacity of the prepared clay/PAA-TA to uptake CV dye. With an adsorption capacity of 444.5 mg/g, the Langmuir-Freundlich model suited the adsorption isotherm. The adsorption kinetics were best explained by the pseudo-first-order model. The results of thermodynamic studies indicated that the adsorption was spontaneous, favorable, and endothermic.