Exotic Materials Research Articles

Chemical Design of Spin Frustration to Realize Topological Spin Glasses.

Patterning spins to generate collective behavior is at the core of condensed matter physics. Physicists develop techniques, including the fabrication of magnetic nanostructures and precision layering of materials specifically to engender frustrated lattices. As chemists, we can access such exotic materials through targeted chemical synthesis and create new lattice types by chemical design. Here, we introduce a new approach to induce magnetic frustration on a modified honeycomb lattice through a competition of alternating antiferromagnetic (AFM) and ferromagnetic (FM) nearest-neighbor interactions. By subtly modulating these two types of interactions through facile synthetic modifications, we created two systems: (1) a topological spin glass and (2) a frustrated spin-canted magnet with low-temperature exchange bias. To design this unconventional magnetic lattice, we used a metal-organic framework (MOF) platform, Ni3(pymca)3X3 (NipymcaX where pymca = pyrimidine-2-carboxylato and X = Cl, Br). We isolated two MOFs, NipymcaCl and NipymcaBr, featuring canted Ni2+-based moments. Despite this similarity, differences in the single-ion anisotropies of the Ni2+ spins result in distinct magnetic properties for each material. NipymcaCl is a topological spin glass, while NipymcaBr is a rare frustrated magnet with low-temperature exchange bias. Density functional theory calculations and Monte Carlo simulations on the NipymcaX lattice support the presence of magnetic frustration as a result of alternating AFM and FM interactions. Our calculations enabled us to determine the ground-state spin configuration and the distribution of spin-spin correlations relative to paradigmatic kagomé and triangular lattices. This modified honeycomb lattice is similar to the electronic Kekulé-O phase in graphene and provides a highly tunable platform to realize unconventional spin physics.

A CONTEXTUALIZED ARCHAEOLOGICAL PENDANT TO NEPHRITIC JADE IN THE AMAZON: A POSSIBLE LINK TO CARIBBEAN PEOPLE

“Green stone” ornaments from archaeological sites, also known as Muiraquitã, typically a frog-shaped pendant, found throughout Amazonia and the Caribbean, have been known since the 19th century; and were believed to have been carved in jade, an Amazonia exotic raw material supposed to have come from East Asia. The knowledge of the provenience and production of these artifacts is crucial for testing and improving explanatory models on the movement of people and artifacts, as well as on the complexity and entanglement of social networks’ interactions. It was only in the 2000s that Lima da Costa and colleagues were able to show that muiraquitã artifacts were composed by different minerals and the ones closest to jade were tremolite and/or tremolite-actinolite, that are found in the Amazon region. Despite advances in physical/chemistry characterizations of the “Green stone” ornaments, the vast majority have been on artifacts without any archaeological context. We present here the analysis of a pendant excavated from Monte Dourado 1 archaeological site, located in northwest of Pará state, northern Amazonia, near the border with French Guiana and Suriname. The pendant, found within a funerary context, associated with Koriabo ceramics and anthropogenic dark earth, is constituted by nephritic jade or tremolite-type jade; raw material that do occur in the Amazon region. The lack of other lithic artifacts usually associated with the chaîne opératoire for the manufacture of pedants might be an indication that these ornaments were being produced potentially in the Caribbean region. The detailed physical/chemistry characterization of archaeologically contextualized “Green stone” ornaments is crucial for creating a benchmark for these types of artifacts in order to better understand and improve our knowledge about the historical paths taken by pre-colonial societies in the Amazon e Caribbean regions.

Application of AlTiBN Coating for Machining of Exotic Materials

Application of AlTiBN Coating for Machining of Exotic Materials

Crystallization-Based Modification of Ammonium Perchlorate Heat Release.

Composite propellants use the decomposition of crystalline oxidizers, such as ammonium perchlorate (AP), to produce oxidizing species that can combust with fuels. Controlled crystal microstructure must be leveraged to tailor reactivity to minimize the use of exotic energetic materials. This work uses meniscus-guided coating (MGC) to fabricate films of AP with a high degree of control over the AP crystal microstructure. Exploring a wide range of crystallization parameters resulted in film thickness ranging from 200 nm to 14 μm, particle size ranging from 18 to 110 μm, variable preferential orientation with respect to the substrate, and relative defect density ranging from 2.74 × 105 to 6.78 × 105 μm-3. Increasing coating blade speed and substrate temperature within the MGC process shifts the preferential orientation of the AP crystals from predominantly exhibiting (002) and (210) crystal planes parallel to the substrate to (200)/(011) crystal planes parallel to the substrate. This shift in orientation is accompanied by an increase in defect density, which is shown to increase the heat release from the low-temperature decomposition regime and decrease the heat release from the high temperature regime. These results demonstrate the ability to use recrystallization, defect density control, and orientation control to tune the heat release profiles of energetic materials to augment propellant performance.

Surface Doping and Dual Nature of the Band Gap in Excitonic Insulator Ta2NiSe5.

Excitons in semiconductors and molecules are widely utilized in photovoltaics and optoelectronics, and high-temperature coherent quantum states of excitons can be realized in artificial electron-hole bilayers and an exotic material of an excitonic insulator (EI). Here, we investigate the band gap evolution of a putative high-temperature EI Ta2NiSe5 upon surface doing by alkali adsorbates with angle-resolved photoemission and density functional theory (DFT) calculations. The conduction band of Ta2NiSe5 is filled by the charge transfer from alkali adsorbates, and the band gap decreases drastically upon the increase of metallic electron density. Our DFT calculation, however, reveals that there exist both structural and excitonic contributions to the band gap tuned. While electron doping reduces the band gap substantially, it alone is not enough to close the band gap. In contrast, the structural distortion induced by the alkali adsorbate plays a critical role in the gap closure. This work indicates a combined electronic and structural nature for the EI phase of the present system and the complexity of surface doping beyond charge transfer.

Predicting exciton binding energies from ground-state properties

We systematically investigate the correlations between exciton binding energies and various easily calculated ground-state properties (“predictors”) that have been proposed to correlate with them. We do so for 51 bulk compounds, ranging from simple binary semiconductors to more exotic materials such as noble gas solids, perovskites, and layered systems and show that using only a few easily calculable parameters, a broadly applicable clustering of materials according to their exciton binding energies is possible. While no single one of the proposed parameters satisfactorily predicts the exciton binding energy, a combination of several parameters that enter the Wannier-Mott model or characterize the nature of the valence band and the ionicity of the compound allows a reliable automated clustering of exciton binding energies. The results allow an efficient estimation of the importance of excitonic effects without the need for expensive many-body perturbation theory calculations or other advanced numerically demanding approaches. Published by the American Physical Society 2024

(Energy Technology Division Research Award) New Materials vs. Reaction Engineering in Anion Exchange Membrane Fuel Cells

In recent years, the desire to design, create and/or discover advanced functional nanomaterials has changed the way that faculty members and graduate students approach engineering research. Though materials can (and likely will) make a significant impact on most technologies, the truth is that in most disciplines, materials with highly complex structures remain on the fringes of realistic deployment. In some cases, even when so-called “advanced” materials are discovered there are significant difficulties in transitioning them from ex-situ tests to the real reacting environment. Therefore, we must be careful to understand that material chemistry and structure are only two variables in an extremely complex system and often times there are other fundamental (e.g. electronic mobility, thermodynamic barriers, diffusivity) and engineering (porosity, concentration, temperature) properties that drive behavior in such environments. Additionally, there are systems where materials are being sought without a clear understanding of what is truly limiting performance and durability or the properties that are required of a real engineered system to operate effectively.Anion exchange membrane fuel cells (AEMFCs) are an example system where the literature is littered with exotic materials that claim to improve activity and stability (presumed as performance and durability in real devices). However, it will be shown that for several years, such new materials had limited success (if any) in advancing performance and durability. This talk will summarize ~five years of work in AEMFCs where the performance and durability of AEMFCs were improved significantly without any new materials – just using traditional chemical engineering principles for reactor engineering. Only later – once device operation was well understood and controlled – were new materials helpful. On the operational side, the main discussion point will be the transport of water. On the materials side, new membranes and catalysts will be discussed. The talk will end with perspectives on transitioning AEMFCs to more realistic operating environments, including the mitigation of effects from CO2.

Multi-attribute optimization of eco-manufacturing based criteria in CNC manufacturing systems using an evolutionary algorithm

Manufacturing technology has evolved over the years with the development of CNC manufacturing systems, flexible manufacturing, rapid prototyping, smart manufacturing etc Simultaneously, the development of new and exotic materials to match specific requirements has shaped new problems in manufacturing. The materials developed thus far require special tools, lubricating agents, and extra-care in machining without compromising the quality. Further the study of carbon emissions in manufacturing sector has also gained unusual spotlight in view of their deleterious effect on the ecological balance. The manufacturing systems have to be consequently designed and developed, such that they generate minimal quantity of emissions without forfeiting the prime objectives of quality and tool morphology. The present work is principally intended to analyse the effect of cutting parameters on the emission rate of greenhouse gases, tool wear and work-piece temperature concurrently. These studies are accomplished in both dry and wet conditions on computer numerical control machining system. The machining process involved plain facing of a Ti-6Al-4V hardened material. The experimental studies are realized using both single point and multi-point cutting tools and are supplemented with the application of Multi-Objective Genetic Algorithm (MOGA). The MOGA generated set of pareto-fronts for the four machining conditions were subjected to VIKOR, TOPSIS and LINMAP decision making approaches to arrive at the optimum values of decision variables. The optimum cutting parameters obtained in single point cutting tool machining in dry conditions are speed (873.2 rpm), feed (0.199 mm rev−1) and depth of cut (0.25 mm), while the corresponding values of responses are tool wear (67.19 μm), work-piece temperature (39.36 °C) and carbon emission (0.138 Kg-CO2). The equivalent values for multi-point cutting were determined as 899.8 rpm, 0.195 mm rev−1 and 0.25 mm, while the responses for these optimal conditions are 69.92 μm, 39.48 °C and 0.137 Kg-CO2 in that order.

Statuary Qualities of White and Black Göktepe Identified in the Hispanic Valdetorres de Jarama Marble Collection

This paper focuses on the role of the most common mineralogical techniques applied to the identification of the different statuary qualities in white, grey, and black Göktepe marble. For this purpose, the case of a Roman sculpture marble collection from the rural villa of Valdetorres de Jarama (central Iberia), dating to the 4th century AD, is presented. The mythological statuary, combining white, grey, and black marbles, is one of the most outstanding marble collections in the Aphrodisian style found in Hispania. The analytical results (achieved through Petrography, Cathodoluminescence, C and O isotopes, and Sr and Mn concentration) support the identification of two varieties of “black” Göktepe, traditionally referred to as bigio morato and bigio antico, as well as the best statuary quality of white Göktepe. In addition, the analytical identification of other Asiatic marbles in the Valdetorres collection, a white coarse-grain originally from the quarries of Aphrodisias city, and one small piece identified as Carian red from Iasos, corroborates the already suggested strong connection existing between artists and the stone material they chose for their works. Finally, the identification carried out on the marble of the bases that served as seats for the sculptures is noteworthy, as it is a white marble of lower quality whose analytical characteristics are consistent with the Microasiatic marble of Denizli. The use of these exotic and exceptional raw materials confirms the taste for luxury and decorative richness in Late Antique Hispanic rural villae and contributes to a better understanding of the distribution of Aphrodisian production and trade networks with the Western Roman provinces.

How EVs Can Escape the Rare Earth Trap: Promising Experimental Motors are Using Exotic Materials and Ingenious Configurations

How EVs Can Escape the Rare Earth Trap: Promising Experimental Motors are Using Exotic Materials and Ingenious Configurations

Lithic production and the use of siliceous raw material in the Neolithic of Istria, Croatia

This article contains the results of the lithic analysis of assemblages from the Neolithic sites of Kargadur and Vižula in southern Istria, Croatia. The assemblages have been analysed in terms of reduction strategies and typology, with a special focus on raw material analysis and petrographic analysis. During the Early Neolithic, and especially the Middle Neolithic, raw materials circulated the Istrian peninsula, as evidenced by the presence of obsidian and other non-local (exogenous) chert at several sites. Obsidian is certainly an exotic material in this region, and items found at Kargadur come from the Aeolian islands. With these results we have tried to gain a better understanding of lithic production of the period, the approach of the Neolithic people to raw materials and the scope of the distribution network of high-quality chert.

Unconventional superconductivity in chiral molecule-TaS2 hybrid superlattices.

Chiral superconductors, a unique class of unconventional superconductors in which the complex superconducting order parameter winds clockwise or anticlockwise in the momentum space1, represent a topologically non-trivial system with intrinsic time-reversal symmetry breaking (TRSB) and direct implications for topological quantum computing2,3. Intrinsic chiral superconductors are extremely rare, with only a few arguable examples, including UTe2, UPt3 and Sr2RuO4 (refs. 4-7). It has been suggested that chiral superconductivity may exist in non-centrosymmetric superconductors8,9, although such non-centrosymmetry is uncommon in typical solid-state superconductors. Alternatively, chiral molecules with neither mirror nor inversion symmetry have been widely investigated. We suggest that an incorporation of chiral molecules into conventional superconductor lattices could introduce non-centrosymmetry and help realize chiral superconductivity10. Here we explore unconventional superconductivity in chiral molecule intercalated TaS2 hybrid superlattices. Our studies reveal an exceptionally large in-plane upper critical field Bc2,|| well beyond the Pauli paramagnetic limit, a robust π-phase shift in Little-Parks measurements and a field-free superconducting diode effect (SDE). These experimental signatures of unconventional superconductivity suggest that the intriguing interplay between crystalline atomic layers and the self-assembled chiral molecular layers may lead to exotic topological materials. Our study highlights that the hybrid superlattices could lay a versatile path to artificial quantum materials by combining a vast library of layered crystals of rich physical properties with the nearly infinite variations of molecules of designable structural motifs and functional groups11.

Gd substitution induced incommensurate antiferromagnetism in B20 noncentrosymmetric CoSi

Rare-earth element Gd doped CoSi, Co 1−x Gd x Si (x = 0.01), is investigated using x-ray diffraction and magnetization. It crystallizes in B20 cubic structure with lattice parameter of a = 4.4429 Å. The alloy exhibits two antiferromagnetic transitions AFM-I at 38.44 K and AFM-II at 21.87 K followed by an upturn of magnetization below Tut = 9.79 K as illustrated through the temperature-magnetic field T-H phase diagram. AFM-I state is incommensurate. AFM-II state is weakly correlated as inferred from field-induced transition to AFM-I state. Further, AFM-I state is reported to transform to ferromagnetic state in high magnetic fields. The present study stimulates an approach to derive novel and exotic magnetic materials by substituting rare-earth in transition metal monosilicides.

Elemental differentiation and isotopic fractionation during space weathering of Chang’E-5 lunar soil

To investigate the chemical variation during space weathering of young mare basalts, here we report elemental, radiogenic Sr-Nd and stable Fe-Mg-Ca isotopic data of Chang’E-5 sieved soils and breccias. From the coarse fraction to the fine one, the sieved soils display increasing Al2O3 (10.34 wt%–13.36 wt%) and Sr (248 ppm–307 ppm) but decreasing FeO (23.50 wt%–20.22 wt%), MgO (6.88 wt%–5.78 wt%), FeO/Al2O3 (2.27–1.51) and MgO/Al2O3 (0.67–0.43). The contents of rare earth elements (except Eu) and high field strength trace elements do not vary with particle size but correlate with P2O5 contents. Given the limited contribution from contamination by meteorites and exotic materials ejected far away from the landing site, these elemental variations can be explained by differential comminution and distribution behaviors of plagioclase and mesostasis phases. These sieved soils yield a Sm-Nd isochron age (1.84 ± 0.83 Ga) comparable to that of basaltic clasts obtained by U-Pb dating (∼2.0 Ga). However, their Rb-Sr isotopic system is disturbed as indicated by their relatively homogeneous 87Sr/86Sr (0.701425–0.701592) despite variable Rb/Sr (0.017–0.028). These results suggest the Sm-Nd isotopic system is more robust to impact disturbance during space weathering compared to the Rb-Sr isotopic system. Given that the bulk soil still plots on the 2.03 Ga Rb-Sr reference isochron from the pristine plagioclases in CE-5 basalts, this disturbance did not affect the Rb-Sr isotopic system on the bulk scale. The CE-5 bulk soil has higher Mg# (33.6), 87Rb/86Sr (0.06) and present-day 87Sr/86Sr (0.701542) than the mean composition of reported basaltic clasts (Mg#: ∼28; 87Rb/86Sr: ∼0.038; 87Sr/86Sr: ∼0.700941), possibly implying that the bedrocks in CE-5 landing site consist of multiple magma pulses. The δ56Fe (0.122 ± 0.002 ‰ to 0.199 ± 0.008 ‰) and δ26Mg (−0.204 ± 0.016 ‰ to −0.109 ± 0.006 ‰) of sieved CE-5 soils increase with decreasing particle sizes but their δ44/42Ca (0.38 ± 0.04 ‰ to 0.44 ± 0.02 ‰) are relatively homogeneous. Mass balance modelling indicates that differential comminution has limited influence on the Fe-Mg-Ca stable isotopic compositions. We further dismiss the role of solar-wind sputtering, as Ca and Mg are more susceptible to sputtering and thus would be expected to show larger isotope fractionations compared to Fe, which is inconsistent with the observations. Free evaporation may explain the elevated δ56Fe and δ26Mg in fine fractions at given very limited depletion in FeO and MgO. The observed positive correlation between δ56Fe and δ26Mg, however, is much steeper than the slope expected for free evaporation, indicating also other mechanisms (e.g., Fe-Mg inter-diffusion). Since the CE-5 soil has a unique composition compared with Apollo and Luna soils, the chemical differentiation identified in this study provides new insights for establishing a connection between the chemistry and reflectance spectral properties of lunar soil. Our combined Fe-Mg-Ca isotopic study also provides a paradigm to distinguish the role of solar-wind sputtering and impact evaporation, and shows that the inter-particle diffusion process may be an important mechanism for the isotope fractionation among lunar soil components.

Anisotropic stellar evolution and exotic matter

In this paper, we discuss the stability of isotropic pressure conditions for a spherically symmetric dissipative fluid distribution in the framework of f(G,T) gravity. We consider the fluid to be composed of seen and exotic matter particles. The Gauss Bonnet terms represent exotic matter particles. For the physical significance of the pressure isotropy conditions, we transform the system into the hydrostatic equilibrium approximation. We observe the presence of shear, dissipative fluxes, energy density inhomogeneities, and prominently, the exotic matter tends to abandon isotropy leading to pressure anisotropy. It is found that exotic matter and dissipation are major factors that induce matter anisotropy in the evolving stellar system. In order to discuss the physical significance of the stellar model in f(G,T) gravity, the behaviour of stellar structure is explored according to the observational data of a compact star 4U1820 − 30. It is found that f(G,T) terms indicating the exotic material in the stellar model plays a vital role in governing the dynamics of the evolution. To strengthen the results, we also incorporate some arguments by choosing an axially symmetric case.

Higher‐Order Topological Corner States in a Specially Distorted Photonic Kagome Lattice

AbstractKagome lattices have garnered significant interest over the decades due to their rich physics and implications for exotic superconductors and topological materials. In particular, the so‐called “breathing Kagome lattice” (BKL) is often used as a prototypical model to understand higher‐order topological insulators. Here it is demonstrated that higher‐order corner states exist in a specially distorted Kagome lattice, resembling the “Inverse Hexagram” lattice distortion originally introduced in the study of charge density waves in Kagome metals. Importantly, it is found that such an Inverse Hexagram‐like Kagome lattice with C6 rotational symmetry hosts two types of in‐gap corner states, in contrast to a flat‐cutting BKL of C3 symmetry that supports only one type of corner state under the tight‐binding condition. It is shown that the nontrivial corner states exhibit a fractional corner anomaly, revealing the feature of higher‐order topology. Using laser‐written waveguide lattices as a photonic platform, these two types of corner states are experimentally observed, along with a direct comparison with the corner excitation at their trivial counterparts. Experimental observations are further corroborated by numerical simulations and stability analysis under random perturbation. These results may prove relevant and applicable to similar phenomena in other Kagome platforms beyond photonics.

Soft sol–gel combustion synthesis: A potential route for functional nanocomposites of copper-based mixed valent oxides and cermet

The high reaction rate in the sol–gel combustion synthesis (SCS) often restricts precise control over the composition of mixed valent oxides in a single step. The current study overcomes this limitation by employing melamine—that forms a hydrogel with Cu(II)—as a novel fuel in the combustion synthesis. As opposed to the conventional SCS approach, the current synthesis occurs in a mild and controlled way under oxygen-lean conditions,wherein at and above 300 °C of calcination, a red-hot coke is found to form and persist for hours and hence termed as ‘soft sol–gel combustion synthesis’ (SSCS). Such a controlled synthesis is shown to be pivotal in obtaining a copper-based mixed-valent oxide/cermet nanocomposite system, comprising tunable levels of g-C3N4, in a single step. The phase compositions of the nanocomposites are modulated by varying calcination parameters like temperature and duration. These nanocomposites are thoroughly characterized for their microstructural, morphological, elemental, bandgap, and optical properties.Unique compositions are synthesized from the blend of Cu(II)–melamine complex gel with ZIF-8, in which formulations comprising different proportions of ZnO, CuO, Cu2O, metallic Cu and g-C3N4 have been obtained. Such multicomponent formulations post ball-milling exhibit notable photocatalytic activity in degrading organic pollutants and show high antibacterial efficacy against Escherichia coli under dark-light dual-mode conditions. Additionally, the SSCS approach has also been demonstrated for its versatility by synthesizing nickel-based cermet, which opens up numerous avenues for developing exotic material compositions for diverse applications in the realms of energy and environment.

Unveiling a Family of Dimerized Quantum Magnets, Conventional Antiferromagnets, and Nonmagnets in Ternary Metal Borides.

Dimerized quantum magnets are exotic crystalline materials where Bose-Einstein condensation of magnetic excitations can happen. However, known dimerized quantum magnets are limited to only a few oxides and halides. Here, we unveil 9 dimerized quantum magnets and 11 conventional antiferromagnets in ternary metal borides MTB4 (M = Sc, Y, La, Ce, Lu, Mg, Ca, and Al; T = V, Cr, Mn, Fe, Co, and Ni), where T atoms are arranged in structural dimers. Quantum magnetism in these compounds is dominated by strong antiferromagnetic (AFM) interactions between Cr (Cr and Mn for M = Mg and Ca) atoms within the dimers, with much weaker interactions between the dimers. These systems are proposed to be close to a quantum critical point between a disordered singlet spin-dimer phase, with a spin gap, and the ordered conventional Néel AFM phase. They greatly enrich the materials inventory that allows investigations of the spin-gap phase. Conventional antiferromagnetism in these compounds is dominated by ferromagnetic Mn (Fe for M = Mg and Ca) interactions within the dimers. The predicted stable and nonmagnetic (NM) YFeB4 phase is synthesized and characterized, providing a scarce candidate to study Fe dimers and Fe ladders in borides. The identified quantum, conventional, and NM systems provide a platform with abundant possibilities to tune the magnetic exchange coupling by doping and study the unconventional quantum phase transition and conventional magnetic transitions. This work opens new avenues for studying novel magnetism in borides arising from spin dimers and establishes a theoretical workflow for future searches for dimerized quantum magnets in other families of materials.

The Potential of Spot Size Control in Shaping the Thickness Distribution in Ultrashort Laser Deposition.

The availability of new-generation femtosecond lasers capable of delivering pulses with energies in the hundreds of mJ, or even in the joules range, has called for a revision of the effect of scaling spot size on the material distribution within the plasma plume. Employing a state-of-the-art Szatmári-type hybrid dye-excimer laser system emitting 248 nm pulses with a maximum energy of 20 mJ and duration of 600 fs, copper films were grown in the classical pulsed laser deposition geometry. The exceptionally clean temporal profile of the laser pulses yielded a femtosecond component of 4.18 ± 0.19 mJ, accompanied by a 0.22 ± 0.01 mJ ASE pedestal on the target surface. While varying the spot sizes, the plasma plume consistently exhibited an extremely forward-peaked distribution. Deposition rates, defined as peak thickness per number of pulses, ranged from 0.030 to 0.114 nm/pulse, with a gradual narrowing of the thickness distribution as the spot area increased from 0.085 to 1.01 mm2 while keeping the pulse energy constant. The material distribution on the silicon substrates was characterized using the f(Θ) = AcoskΘ + (1 - A)cospΘ formalism, revealing exponents characterizing the forward-peaked component of the thickness profile of the film material along the axes, ranging from k = 15 up to exceptionally high values exceeding 50, as the spot area increased. Consequently, spot size control and outstanding beam quality ensured that majority of the ablated material was confined to the central region of the plume, indicating the potential of PLD (pulsed laser deposition) for highly efficient localized deposition of exotic materials.

APPLICATION OF HYDROGELS FOR WATER SHUTOFF TREATMENTS. Message No. 2

The article analyzes the use of hydrogels with nanoparticle additives for well water shutoff, as well as the development of a mathematical apparatus for hydrodynamic modeling of water shutoff operations. One of the most significant trends in the development of gel forming compounds for well water shutoff in the last 10 years has been the use of nanocomposites. The base polymers for nanocomposites used for water shutoff operations are either synthetic or biopolymer origin. The article highlights the novelty and prospects of using nanoparticles in sealing compositions. Various nanocomponent additives are used to increase the success of the use of hydrogel polymer systems in order to limit water inflow and expand the scope of their application in complicated reservoir conditions. These include carbon and mineral nanoparticles, which increase the stability and strength of crosslinked gels in formation conditions.In this paper, we consider the optimization of the repair and insulation operations design using gels for well water shutoff using mathematical modeling, which helps to justify the volume of hydrogel injection and calculate the necessary pressure gradients at which the sealing screen remains stable. The paramount importance of determining the source of well flooding is emphasized, depending on which the processing design is already being built, and appropriate materials are selected; trends in the development of repair and insulation operations at the present stage are traced. Based on the results of the implementation of the proposed model by numerical methods, the authors constructed diagrams of the stability of the waterproofing screen depending on the fracture width, screen size, gel injection rate and reservoir permeability. The technique proposed in the work allows to correctly select and optimize the technological parameters of the operation to maintain the stability of the screen in specific geological conditions.Mathematical modeling allows us to strictly justify the volume of injection of the gel screen, increase the technological and economic efficiency of the process, and in large fields — to rank wells according to the priority of processing. Oilfield practice in various regions of the country fully confirms the main conclusions made in this review article. Preliminary mathematical modeling and the introduction of microdispersions into gel formulations can significantly increase the efficiency of water shutoff operations. The next step in the development of water insulation technologies is the use of nanodispersions, which look very promising in laboratory modeling and are no longer exotic materials with unrealistic cost.