Consolidated Material Research Articles

Evaluation the effectiveness of hydroxyapatite HA NPs/g-C3N4 hybrid nanocomposites embedded in B72/B44 matrix on the physical and mechanical properties of archaeological stucco

Purpose This study aims to provide an efficient nanocomposite that might be used to protect deteriorated archaeological stucco. Design/methodology/approach The current experimental study evaluates the effectiveness of the hydroxyapatite nanoparticles (HA NPs) added to graphite carbon nitride (g-C3N4) and mixed with Paraloid (B-72) (B-44) in acetone in consolidating samples. The physicochemical properties of the as-prepared nanopowders have been investigated using Fourier transform infrared (FT-IR). This study involves monitoring the transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform changes in consolidated samples after exposure to various conditions by using the digital microscope and scanning electron microscopy to identify the appearance of the consolidated stucco samples after applying the selected nanocomposites and after their artificial aging procedures. Color change is measured using a colorimeter, and comparisons are made between samples before and after aging. Physical and mechanical properties are determined, and the contact angle is measured to measure hydrophobicity rate. Findings The obtained results indicate that HA/g-C3N4 hybrid nanocomposites with a composition of HA 0.5%/g-C3N4 1%/B-72 3% and HA 0.5%/g-C3N4 1%/B-44 3% achieved the best consolidating results among the proposed mixtures for stucco samples, where the percentage of weight loss was 0.77 with B-72, 0.53 with B-44. Surface identification and characterization of hydroxyapatite HA NPs/g-C3N4 hybrid nanocomposites embedded in B72/B44matrix were carried out using Scanning Electron Microscopy coupled with energy-dispersive x-ray spectroscopy (SEM–EDX). Originality/value This study provides important findings from the analytical procedures used to evaluate the consolidation materials used in this study. The findings are beneficial for the preservation of archaeological stucco. The investigation findings revealed that the most favorable outcomes were obtained from HA/g-C3N4 hybrid nanocomposites containing HA 0.5%, g-C3N4 1% and B-72 3%, as well as HA 0.5%, g-C3N4 1% and B-44 3%. Consequently, it is advised to use this nanocomposite to consolidate archaeological stucco, thus establishing a promising initial stride toward conserving archaeological stucco for future research endeavors. This study introduces a new nanocomposite material (HA NPs/G-C3N4) that can be used to protect and improve archaeological plaster. This is very important for preserving cultural heritage. The incorporation of nanotechnology improves the material’s physical and mechanical qualities. The research uses various characterization techniques (including TEM, XRD and FT-IR) to meticulously analyze the physicochemical properties of the nanocomposite material and assess its efficacy in practical applications through artificial aging experiments, offering novel insights and methodologies for future cultural relic preservation studies.

Cellulose consolidated with polyethylene glycol: The nanoscale mechanisms revealed by hybrid Monte Carlo/molecular dynamics modeling

Polyethylene glycol (PEG) consolidation treatment is a widely used conservation strategy for wooden culture relics. However, the consolidation mechanism of PEG is still open to interpretation. PEG-cellulose, the representative component of wood cell wall, interactions are governed by various coupled multi-scale mechanisms which require nano-scale investigation. In this study, a hybrid molecular dynamics and grand canonical Monte Carlo (MD/GCMC) simulation combined with rule of mixture (RoM) analyses are employed to reveal the underlying mechanisms of PEG-induced consolidation. We found that PEG200 reduces moisture adsorption and swelling at museological conditions, confirming its consolidation effect. At high PEG content, a crossover behavior is identified at humid conditions (RH > 80) where excessive sorption and swelling are observed surpassing the untreated sample. The molecular modeling results are found to be consistent with experimental observations. Furthermore, the structural and mechanical properties of the hydrated samples are assessed by examining the porosity distribution, mechanical properties, and hydrogen bonding network. Results indicate mechanical softening induced by PEG treatment. A modified mixture model is proposed based on molecular modeling results that incorporate sorption and swelling coupling, porosity filling and mechanical softening behaviors. Two key mechanisms are identified explaining the consolidation effect of PEG: first, the PEG fills the porosities of amorphous structure thus diminishing sorption sites; second, the polymer structure prohibits PEG from further swelling thus constraining water sorption. The model and theoretical framework can serve as a guide for the design of novel consolidant materials by identifying the key molecular features of an ideal consolidant.

Effect of chemical consolidation on physico-mechanical properties of porous coral reef limestone

Porous coral reef limestone (CRL) is characterized by the low strength and developed pore structure, so improving its physico-mechanical properties is important for marine engineering construction work. Chemically consolidated porous CRL was prepared by taking a non-granular chemical grout (sodium silicate) as the main consolidation material. Then, the chemical consolidation effect was evaluated from two aspects (both the physical and mechanical properties) by conducting computed tomography (CT) scanning and quasi-static uniaxial compression tests. The results indicate that the consolidation material can fill the pores in the CRL, which reduces the porosity of specimens by more than 50%. In addition, the peak strength under quasi-static compression is increased by about 20%. The fragments decrease at failure, and fracture plane slip and crack opening are inhibited. Finally, influences of the special banded shape of consolidation material retained in the specimens on the failure process and failure mode of specimens were investigated. The chemical consolidation mechanism of porous CRL was revealed by combining with the scanning electron microscope (SEM) images. Research results indicate that the non-granular chemical material (sodium silicate) improves the physico-mechanical properties of porous CRL. The research provides reference for the foundation treatment in coral reefs and the design of consolidation schemes for surrounding rocks of underground spaces in marine engineering operations.

Mechanical property testing and damage assessment of the regenerated rock mass with very weakly bonded cement

The regenerated rock mass is a bearing structure formed by natural compaction in a hollow area, and the investigation of its optimal consolidation material and consolidation parameters is the key to improving the supporting effect and bearing stability of roadways. The effects of consolidation materials and parameters on the stability of the regenerative rock mass were studied using laboratory tests, numerical simulations, and theoretical analyses. Acoustic emission was used to monitor the variation characteristics of energy and ringing count during the process of rock mass failure, and the bonding interface area of the extremely weak cementation regeneration structure was tested by electron microscope scanning. The results show that there is a quadratic function relationship between the water–cement ratio of different cementing materials and the bond strength of the recycled rock mass; the regenerative rock mass with superfine cement exhibited the highest compressive strength and the largest cumulative energy of acoustic emission. This shows that it has the strongest bearing capacity, the highest elastic performance, the most stable micro-fracture development, and the best cementation effect, followed by ordinary cement, gypsum, and laterite. The scanning test showed that the regenerated structure had more internal pores, a loose structure, and poor cementation. Three-dimensional scanning modeling of four representative broken rock blocks was carried out, and the simulation verified that the regenerated structure had macroscopic “X”-shaped shear failure characteristics. The numerical simulation also verified three forms of rupture in the regenerative structure detected by electron microscopy scanning. Exploring the mechanism of action of the regenerative rock mass in the goaf provides a certain reference value for the stability control of the regenerated rock mass roadway.

A MAS-NMR analysis of 29Si, 27Al and 1H on the temperature's impact on geopolymer grouts derived from argillite and metakaolin

This study investigates how the curing temperature can enhance the reactivity of poorly reactive aluminosilicate source for geopolymer synthesis using a structural approach. The studied geopolymers are based on different aluminosilicate sources, a metakaolin and argillite, under varying curing temperatures (20 and 80°C). The impact of curing temperature on the reactivity of the two aluminosilicate sources and on the resulting consolidated materials was highlighted using pH value measurements, X-ray diffraction (XRD), and MAS-NMR for silicon (29Si), aluminum (27Al), and hydrogen (1H) nucleus. Metakaolin-based samples exhibited stable pH values, unvaried amorphous content, and structural consistency whatever the curing temperature. In contrast, argillite-based samples showed a significant drop in pH values (from 13 to 12) and a rise of amorphous content when cured at 80°C, indicating a reactivity change with temperatures. This was corroborated with MAS-NMR analysis, that highlighted a dissolution of the associated minerals such as illite and smectite. It was evidenced the presence of the geopolymer phase Q4(2Al) and Q4(3Al), in addition to two other networks based on silicon (Q4(1Al) and Q4(0Al)), and on aluminum Q4(4Al). The 1H MAS-NMR corroborated this finding by an increase of the bounded water (the band at 4.8 ppm) in the geopolymer network. All these data underline how temperature influences the reactivity of geopolymer materials, especially argillite-based samples by enhancing the dissolution of associated minerals (illite muscovite and smectite).

Creative Problem Solving and Communication in Entrepreneurship

This abstract introduces a plug and play set of materials designed for teachers to use as flipped learning tasks in the context of proposal writing and persuasive presentations. These materials were developed based on interview videos featuring young local entrepreneurs, who provided valuable insights and perspectives into the importance of research, creative problem solving, communication and language skills. PolyU students in discipline-specific subjects engage in project-based learning, where they write proposals and deliver persuasive presentations based on their unique understanding and ideas within their respective disciplines. Given the constraints of a tight 13-week schedule, flipped discovery and consolidation materials based on the interview videos have been developed, covering a range of topics related to research, proposal writing, and presentation skills. This submission centers around two plug-and-play sets: Creative Problem Solving and Communication, which can be seamlessly integrated into existing teaching and learning materials as flipped warmer and consolidation activities. Students have expressed in focus group interviews how these materials have made their learning experience more authentic and transferable. By incorporating relatable real-world examples and practical insights, these plug-and-play sets offer teachers a convenient and effective way to introduce engaging warm-up activities into their existing materials. Students are guided to reflect on their research process, creative problem-solving skills and communication skills which are essential for successfully communicating their discipline knowledge and ideas in proposal writing and persuasive presentations.

Multifunctional Nanocomposites in B4C-Tic-Tib2-Sic-BN-Al2O3-Sialon-C Carbon Fiber System for Armor Fillets, Turbine Discs and Wings, High-Temperature Wear Resistant Nodes

Goal - to receive on first stage β - SIALON containing nanocomposites by reactive sintering method at 14000C, with nitrogen pro-cess from origin composition in TiC-BN-SiC-B4C-Si-Al-Al2O3 (nanopowder) system. By using this method of synthesis, it became possible to receive nanocomposites with different percentages of β - SIALON. Our task was to study the phase composition of re-ceived consolidated materials in the TiC-TiB2-BN-SiC-B4C-β-SiAlON-Al2O3 (nanopowder-400nm.) system. Method. The obtained mass was grounded in an attritor and the consolidated composite was obtained by hot pressing at 16200C during 40 minutes, with glass perlite (Armenia) dope 2 mass%, delaying at final temperature for 8 min, under 30 MPa pressure and vacuum – 10-3 Pa. Perlite from Aragatc contained 96 mas. % glass. To study the phase composition of the composites, we conducted an X-ray structural analysis on the DRON-3 device. And to study the microstructure, we conducted research on an optical microscope -AC100 and a raster electron microscope “Nanolab 7” of the company "OPTON”. The values of the electrical parameters of the studied composites were calculated on the basis of the ob-tained "lgp- t" dependence. We have studied mechanical properties. Result. In TiC-TiB2-BN-SiC-B4C- β-SiAlON-Al2O3 – C Carbon Fiber system we obtained nanocomposites with high mechanical proper-ties. The advantage of this method is that compounds, which are newly formed thanks to interaction going on at thermal treat-ment: Si3N4, Si, AlN are active, which contributes to β-SiALON formation at relatively low temperature, at 1300-13500C. It is evi-dent that inculcation of ALN in crystal skeleton of ß-Si3N4 is easier since at this temperature interval crystal skeleton of Si3N4 is still in the process of formation. ß-SiAlON was formed at 14500C. Part of boron carbide was transformed into boron nitride in ni-trogen environment and in titanium diboride, which in the case of both composites is in small quantities. Conclusion. The phase composition of the obtained composite provides high physical-technical and performance properties of these nanocomposites. Compression strength-2198 MPa, Bending strength-271 MPa, Thermal expansion coefficient a20-700-3.8 10-6 0C.

Unveiling Crucial Chemical Processing Parameters Influencing the Performance of Solution-Processed Inorganic Thermoelectric Materials.

Production of thermoelectric materials from solution-processed particles involves the synthesis of particles, their purification and densification into pelletized material. Chemical changes that occur during each one of these steps render them performance determining. Particularly the purification steps, bypassed in conventional solid-state synthesis, are the cause for large discrepancies among similar solution-processed materials. In present work, the investigation focuses on a water-based surfactant free solution synthesis of SnSe, a highly relevant thermoelectric material. We show and rationalize that the number of leaching steps, purification solvent, annealing, and annealing atmosphere have significant influence on the Sn : Se ratio and impurity content in the powder. Such compositional changes that are undetectable by conventional characterization techniques lead to distinct consolidated materials with different types and concentration of defects. Additionally, the profound effect on their transport properties is demonstrated. We emphasize that understanding the chemistry and identifying key chemical species and their role throughout the process is paramount for optimizing material performance. Furthermore, we aim to demonstrate the necessity of comprehensive reporting of these steps as a standard practice to ensure material reproducibility.

Unveiling Crucial Chemical Processing Parameters Influencing the Performance of Solution‐Processed Inorganic Thermoelectric Materials

AbstractProduction of thermoelectric materials from solution‐processed particles involves the synthesis of particles, their purification and densification into pelletized material. Chemical changes that occur during each one of these steps render them performance determining. Particularly the purification steps, bypassed in conventional solid‐state synthesis, are the cause for large discrepancies among similar solution‐processed materials. In present work, the investigation focuses on a water‐based surfactant free solution synthesis of SnSe, a highly relevant thermoelectric material. We show and rationalize that the number of leaching steps, purification solvent, annealing, and annealing atmosphere have significant influence on the Sn : Se ratio and impurity content in the powder. Such compositional changes that are undetectable by conventional characterization techniques lead to distinct consolidated materials with different types and concentration of defects. Additionally, the profound effect on their transport properties is demonstrated. We emphasize that understanding the chemistry and identifying key chemical species and their role throughout the process is paramount for optimizing material performance. Furthermore, we aim to demonstrate the necessity of comprehensive reporting of these steps as a standard practice to ensure material reproducibility.

Preparation of a Consolidation Material of Organosilica-Modified Acrylate Emulsion for Earthen Sites and the Evaluation of Its Effectiveness

In this paper, a new consolidation material for earthen sites with silicone-modified acrylic emulsion was synthesized and applied to the consolidation test of soil samples of the site. The effectiveness was tested through the properties of soil samples on the changes in weight, color, permeability test, air permeability, hydrolysis resistance, water resistance, and salt resistance. The results show that the samples treated with the new material have an outstanding effect on hydrolysis resistance, water resistance, and salt resistance without the change in color and gas permeability. After being soaked in Na2SO4 and sodium chloride solution for half a month, the reinforced soil sample did not crack, and it could undergo 15 days of water resistance test and five cycles of sodium sulfate resistance.

Direct consolidation of an oxide dispersion strengthened alloy by hot rotary swaging

AbstractSteels strengthened by alloying elements and precipitates typically maintain their enhanced properties up to the ferrite‐austenite transformation. However, oxide dispersion strengthened ferritic steels are creep resistant even at much higher temperatures given by dispersions of nanosized oxides. To ensure homogeneous dispersion of the oxides, powder metallurgy is used for preparation of the original material. The presented study investigates the effects of direct consolidation of powder of ferritic steel strengthened with yttrium oxide nanoparticles. The powders were mechanically alloyed and sealed into evacuated steel containers, which were subjected to gradual hot consolidation via the industrially applicable intensive plastic deformation method of rotary swaging. Investigations assessing the effects of several reduction ratios showed that the direct consolidation of the oxide dispersion strengthened steel was successful – in the macroscale – at the swaging ratio of 1.03; the quality of consolidation further increased with increasing swaging ratio. At the swaging ratio of 1.83, the consolidated bulk material featured ultra‐fine grains characterized with high angle grain boundaries, homogeneous dispersion of oxide precipitates, and the average Vickers microhardness of 706.6 HV 1.

Enhancing the functional properties and performance of paper via cellulose nanocrystals and funori loaded onto ZnO NPs

Purpose This paper aims to investigate the ability of traditional biopolymers, such as funori or the nanoscale form of cellulose nanocrystals, to consolidate fragile paper and preserve it for as long as possible. Design/methodology/approach Degraded papers dating back two centuries were separated into paper samples for consolidation processes. Funori – a marine spleen – was used as a traditional consolidation material and a mixture with ZnO NPs compared with modern materials, such as cellulose nanocrystals. The samples were aged for 25 years, examinations and analyses were performed using scanning electron microscopy and color change was assessed using the CIELAB system, X-ray diffraction and Fourier-transform infrared spectroscopy. Findings According to the results, using traditional materials to consolidate damage, such as funori, after aging resulted in glossiness on the surface, a color change and increased water content and oxidation. Furthermore, samples treated with a mixture of ZnO NPs and funori revealed that the mixture improved the sample properties and increased the degree of crystallization. Cellulose nanocrystals improved the surface, filled gaps, formed bridges between the fibers and acted as a protector from aging effects. Originality/value This paper highlights the ability of nanomaterials to enhance the properties of materials as additives and treat the paper manuscripts from weaknesses.

Simulation, Structural, Thermal and Mechanical Properties of the FeTiTaVW High Entropy Alloy

Developing new materials to be applied in extreme environments is an opportunity and a challenge for the future. High entropy alloys are new materials that seem promising approaches to work in nuclear fusion reactors. In this work, FeTaTiVW high entropy alloys were developed and characterized with Molecular Dynamic and Hybrid Molecular Dynamic Monte Carlo simulations. The simulation results show that phase separation originates a lower potential energy per atom and a high level of segregation compared to those of a uniform solid solution. Moreover, the experimental diffractogram of the milled powder shows the formation of a body-centred cubic-type structure and the presence of TiO2. In addition, the microstructure of the consolidated material evidenced three phases: W-rich, Ti-rich, and a phase with all the elements. This phase separation observed in the microstructure agrees with the Hybrid Molecular Dynamic Monte Carlo simulation. Moreover, the consolidated material’s thermal conductivity and specific heat are almost constant from 25 °C to 1000 °C, and linear expansion increases with increasing temperature. On the other hand, specific heat and thermal expansion values are in between CuCrZr and W values (materials chosen for the reactor walls). The FeTaTiVW high entropy alloy evidences a ductile behaviour at 1000 °C. Therefore, the promising thermal properties of this system can be attributed to the multiple phases and systems with different compositions of the same elements, which is exciting for future developments.

Consolidation materials used with illuminated and non-illuminated paper manuscripts and historical leather bindings: a review

Purpose This study aims to focus on the main materials used in consolidation processes of illuminated paper manuscripts and leather binding. Design/methodology/approach For each material, chemical structure, chemical composition, molecular formula, solubility, advantages, disadvantages and its role in treatment process are presented. Findings This study concluded that carboxy methyl cellulose, hydroxy propyl cellulose, methyl cellulose, cellulose acetate, nanocrystalline cellulose, funori, sturgeon glue, poly vinyl alcohol, chitosan, chitosan nanoparticles (NPs), gelatin, aquazol, paraloid B72 and hydroxyapatite NPs were the most common and important materials used for the consolidation of illuminated paper manuscripts. For the leather bindings, hydroxy propyl cellulose, polyethylene glycol, oligomeric melamine-formaldehyde resin, acrylic wax SC6000, pliantex, paraloid B67 and B72, silicone oil and collagen NPs are the most consolidants used. Originality/value Illuminated paper manuscripts with leather binding are considered one of the most important objects in libraries, museums and storehouses. The uncontrolled conditions and other deterioration factors inside the libraries and storehouses lead to degradation of these artifacts. The brittleness, fragility and weakness are considered the most common deterioration aspects of illuminated paper manuscripts and leather binding. Therefore, the consolidation process became vital and important to solve this problem. This study presents the main materials used for consolidation process of illuminated paper manuscripts and leather bindings.

Efficacy of polyacrylate latex nanodispersions as consolidation agents in porous sandstones evaluated by synchrotron X-ray computed microtomography

This research describes the effects of two innovative aqueous polyacrylate polymers on the microstructure of porous stone materials. Such latex nanodispersions have been designed (with and without fluorination) as consolidation agents and tested on two types of sandstone, namely, Prague (Mšené) and Obernkirchen, largely used as building materials for valuable Cultural Heritage objects. Quantitative description of the polymer distribution within the specimens was obtained noninvasively by adopting synchrotron radiation computed microtomography. The propagation-based phase-contrast mode was adopted to test its effectiveness in enabling the recognition of the polymers in the two matrices, which is usually hampered by their low attenuation coefficient for X-rays. Quantitative image analysis revealed significant dissimilarities in total porosity, specific surface area of pores, connectivity density and fractal dimension as a consequence of the consolidation treatments. For instance, about 7% and 3% lower porosity values were found in the consolidated Prague and Obernkirchen sandstones, respectively, with the distribution shifted towards smaller pores. Furthermore, the simulation of water transport, based on the retrieved pore network, evidenced a decrease in water permeability and diffusivity of more than one order of magnitude in the treated samples; the effect was more pronounced along the direction of penetration of the consolidating agent. Overall, both latexes exhibited similar film-forming and pore-filling abilities. In general, the results highlighted the high potential of synchrotron-based 3D X-ray imaging for the quantitative assessments of the porous microstructure of consolidated building materials.

Use of carboxymethyl cellulose, Klucel G, gum Arabic and zinc oxide nanoparticles nanocomposite as strength agents for inked papyrus

Purpose The purpose of this study is to detect the effect of some natural cellulosic polymers in their nano forms with the addition of zinc oxide nanoparticles on restoring the lost mechanical strength of degraded papyrus without any harmful effects on the inks. Design/methodology/approach In the current study, the USB digital microscopy, scanning electron microscope, measurement of mechanical properties (tensile and elongation), pH measurement, color change and infrared spectroscopy were undertaken for the samples before and after treatment and aging. Findings In the current study, the USB digital microscopy, scanning electron microscope, measurement of mechanical properties (tensile and elongation), pH measurement, color change and infrared spectroscopy were undertaken for the samples before and after treatment and aging. Originality/value The effect of strengthening materials was studied on cellulose and carbon ink, which makes this study closer to reality as the manuscript is the consistent structure of cellulose and inks, whereas most of the literature stated the impact of consolidation materials on the strengthening the cellulosic supports without attention to their impact on inks.

Enhancing the Electrical and Photoelectrical Efficacy with the Synergistic SrO–ZnO Nano‐Heterosystem

Development of the sustainable materials for consolidation of the energy sustainability needs special emphasis in the current era of the increasing energy demand. In compliance with this, present investigation reports first investigation on the amended sustainable production conjugated with the microwave process of the strontium oxide (SrO) and zinc oxid (ZnO) forming SrO–ZnO nanoscale heterostructure. The band gap of the prepared green nanomaterial was tuned reducing it from 5.8 to 3.6 eV upon the formation of the nanocomposite. With the mixed cubic and hexagonal phase, these particles have average crystallite size of 66.4 nm and irregular shape. The electro‐catalytic assays have expressed the bifunctional role of the SrO–ZnO towards generation of the oxygen and hydrogen. However, it has an excellent hydrogen production capacity with the lower overpotential of 126 mV and Tafel slopes 123.6 mV dec−1. In addition, this nanomaterial has also exhibited superior electrochemical charge storage for batter applications with the unit capacity of 541.7 mAH g−1 and Rs = 0.4 Ω, reflecting facilitated diffusion at the interface. In terms of photovoltaic applications, SrO–ZnO nanocomposite has effectively passivated the perovskite solar cells by improving efficiency from 7.2% to 15.1%. Such an improved performance is associated with the chemical synergism.

Электроимпульсное плазменное спекание прозрачной керамики из алюмомагниевой шпинели с повышенным фактором формы

Magnesium aluminate spinel is a promising material for optical application. It can be used as transparent armor, spacecraft windows, scanners, optical elements in night vision systems, as well as a base (matrix) for scintillation and laser materials. The wide range of practical applications of MgAl2O4 ceramics is due to the complex of its unique properties. The research is aimed to creating transparent ceramic materials with an increased shape factor, relevant and of high practical importance. In the presented work, a comprehensive characterization of the commercial nanopowder of magnesium aluminate spinel is completed. Its main structural features are defined. Rheological properties of nanopowder in the process of its compression and thermal consolidation are investigated on the basis of the provisions of the mechanistic pressing model by approximating experimental data of compaction during spark plasma sintering with a dimensionless logarithmic equation, the graphical representation of which allows us to evaluate the possibility of achieving a non-porous state of the consolidated material and optimize the modes of spark plasma sintering. Shown, that the structure of the sealing surface and the search for the optimal way to increase pressure and temperature during spark pulse plasma sintering on this surface can be used to optimize the consolidation modes of transparent ceramics. Verified discrete element modeling of the processes of packing and consolidation of particles of magnesium aluminate spinel nanopowder has been performed. Model and field experiments have shown that the revealed combination of temperature (1300 °C) and static pressure (100 MPa) is sufficient to obtain a porous ceramic structure and does not lead to excessive recrystallization. It is shown that transparent ceramics based on magnesium aluminate spinel with an increased shape factor can be produced by spark plasma sintering at temperature of 1300 °C and static pressure of 100 MPa. The optical and mechanical properties of the manufactured transparent ceramics are comparable to their analogues. The light transmission of samples reaches 41% of the visible spectrum and 64% in the infrared spectrum, the Vickers microhardness value is 15.6±0.5 GPa, crack resistance is 4.4±0.4 MPa·m1/2, compressive strength is 1.37±0.23 GPa, Poisson's ratio is 0.26±0.01, Young's modulus - 278±6 GPa, shear modulus - 110±2 GPa.

Temporary Consolidation of Marine Artifact Based on Polyvinyl Alcohol/Tannic Acid Reversible Hydrogel.

Underwater artefacts are vulnerable to damage and loss of archaeological information during the extraction process. To solve this problem, it is necessary to apply temporary consolidation materials to fix the position of marine artifacts. A cross-linked network hydrogel composed of polyvinyl alcohol (PVA), tannic acid (TA), borax, and calcium chloride has been created. Four hydrogels with varying concentrations of tannic acid were selected to evaluate the effect. The hydrogel exhibited exceptional strength, high adhesion, easy removal, and minimal residue. The PVA/TA hydrogel and epoxy resin were combined to extract waterlogged wooden artifacts and marine archaeological ceramics from a 0.4 m deep tank. This experiment demonstrates the feasibility of using hydrogel for the extraction of marine artifacts.

The mosaic tesserae in the industrial Byzantine wine press, Yavne, Israel: A natural unusually hard chalk or a chemically transformed chalk?

Many of the surfaces of a large industrial scale wine press from the Byzantine period in Yavne, Israel, are covered in mosaic tesserae. These surfaces are part of the grape presses, storage pools, fermentation pools and also the walkways between these structures. The calcitic tesserae resemble limestone in color, texture and fracture properties. We were therefore surprised to discover that they are more disordered at the atomic level than consolidated limestone and in fact they are as disordered as porous and friable chalk. In addition SEM examination of fracture surfaces reveals abundant nannofossils, mostly coccoliths and foraminifera; properties that are also reminiscent of chalk. The nanofossil identifications shows that the tesserae are from the Middle Eocene, and this includes the chalky Maresha Formation that outcrops about 15kms from the site. SEM examination of polished surfaces shows that the larger pores of tesserae are lined with euhedral calcite crystals. Vickers hardness measurements show that the tesserae are much harder than chalk, and are comparable to limestone. There are two scenarios for explaining these seemingly contradictory observations. One scenario is that a chalky limestone geological formation with all these properties exists somewhere in the Mediterranean region and is the source of the raw material for the tesserae. The second scenario is that the Byzantine constructors of the wine press transformed a chalk into a harder and more consolidated material. Chalk transformation processes akin to plaster formation can be excluded based on the analyses of the stable carbon isotopic compositions of the tesserae, as well as their 14C concentrations. A chemical transformation using a weak acid that would only affect the calcite in the vicinity of the accessible pores, and leave the bulk of the chalk and its microfossils in a good state of preservation, is conceivable. In fact a by-product of producing wine is vinegar and the acetic acid of the vinegar could conceivably have been used for this purpose. If indeed a chemical transformation of soft chalk into a hard durable material was used, this would represent a “lost” technology that might even be useful in present times.