Excess Alkali Research Articles

Mechanisms of alkali pH-shifted colour changes in squid (Uroteuthis edulis) subjected to frozen storage

The skin discoloration of squid subjected to frozen storage negatively affects market price. In this study, various alkali treatments were investigated for effects on red granules and yellow pigments of squid skin and corresponding mechanisms were investigated at the tissue, cellular and molecular level. A significant colour improvement was observed when subjected to a pH 12 treatment, supported by decreased Δb* and increased Δa* values. Neither lower nor harsher alkali treatments than pH 12 can not obtain such results. HE staining and the UV–vis spectrum suggest that the improved red colour in skin was ascribed to the release of red pigment granules from damaged chromatophores by alkaline treatment and the release of red pigments in alkaline aqueous solutions from granules. However, based on TEM and particle size analysis, an excessive alkali treatment of pH 13 would degrade granules into smaller particles. The degradation of yellowness pigments indicated high sensitivity to alkali environments according to HPLC results. This study provides a valuable reference for improving the colour appearance of squid skin subjected to frozen storage.

Geopolymerization kinetics of steel slag activated gasification coal fly ash: A case study for amorphous-rich slags

The geopolymer processing of amorphous-rich slag required excessive soluble alkali usage severely limiting the application of geopolymer materials. In this study, industrial solid waste steel slag (SS) was introduced as alkali substitution for stimulating the potential activity of Shell gasification coal fly ash (SFA). Result shows that a 15%–20% addition of SS can reduce 14.5–23.3% NaOH consumption for the preparation of high-strength geopolymers. SS accelerates the dissolution rate of SFA promoting the early strength of geopolymer (ES) via alkalinity adjustment and reducing the wetting angle of refactoring globular particles in the slurry. The long-term strength of geopolymer (LS) is increased to 68.5 MPa with the higher devotion of SFA (67 ω%). During the geopolymerization course, Ca-rich hydrates growth are competed with the polymerization of amorphous minerals. The geopolymerization kinetics enlightens that the soluble tetrahedral SiO4 or AlO4 and hydrates in pozzolanic phase initially generated in paste then transformed to a more stable form of amorphous phase after a series of repeated processes of dissolution, homogeneous nucleation, and heterogeneous growth. This work paves a environmentally friendly way for disposing amorphous-rich slags with low activity and discloses the detailed mechanism of related geopolymerization.

Influence mechanism of alkaline environment on the hydration of hemihydrate phosphogypsum: A comparative study of various alkali

• The influence of various alkali on hydration and microstructure of HPGP was investigated. • Two opposite effects of alkali resulted by neutralization effect and ion strength effect on hydration of HPGP were observed. • Gypsum crystal morphology was significantly affected in alkaline environment except of excessive lime. • The influence effect of alkaline environment is related to its alkalinity and the impurity content in HPG. Although lime neutralization is widely recommended for raw phosphogypsum pretreatment, the influence mechanism of alkaline environment on hydration of hemihydrate phosphogypsum (HPG) is not clear. In the present paper, effect of alkaline environment created by different kinds of alkali including Mg(OH) 2 , NH 3 ·H 2 O, NaOH and Ca(OH) 2 with variable contents on hydration and microstructure of HPG were investigated. Abnormal setting and strength degradation were observed in the low-alkaline environment, while the setting time was normalized and crystal size developed in the high-alkaline environment regardless of the alkali category. Interestingly, the strength of HPG in the alkali environment only increased with excessive Ca(OH) 2 . It is verified that the formation of Ca 3 (PO 4 ) 2 from neutralization reaction in the low-alkaline environment served as retarder, and the excessive alkali beyond the threshold value of neutralization reaction played as accelerator in the high-alkaline environment, while only excessive lime particles promoted the development of gypsum crystal at c axis probably due to its absorption of Ca 3 (PO 4 ) 2 . This finding would promote the application of HPG in an alkaline environment and thus improve the utilization rate of phosphogypsum.

Synthesis and optimization of green one-part geopolymer from mine tailings and slag: Calcium carbide residue and soda residue as supplementary alkali sources

• Activated tailings acted as an alkaline activator for the one-part geopolymer production. • Waste treatment by waste: Calcium carbide residue was used as a supplementary alkali source. • Waste calcium carbide residue prompted the hydration reaction and increased the sample strength. • This study provides promising guidance for the rational and cost-effective utilization of tailings. The use of mine tailings (MTs) as the precursor for producing geopolymers is an effective way to reduce their storage and mitigate their negative effects on the environment. MTs were firstly activated through hydrothermal pretreatment in the presence of NaOH at 200 °C. Then one-part geopolymer (OPG) samples were synthesized from activated MTs and slag, and calcium carbide residue (CCR) and soda residue (SR), the solid industry wastes, were added as supplementary alkali sources to improve the strength of OPG samples. The effects of alkali sources on the setting time, fluidity, compressive strength, pH, hydration kinetics, hydration products, and microstructure of OPG samples were investigated. Both alkali sources shortened the setting time, decreased the fluidity, and increased the strength of OPG samples, and the CCR showed a more significant effect on these properties than SR. These clear differences in sample performances were associated with the pronounced mineralogical differences between SR and CCR. Compared to SR, CCR rich in Ca(OH) 2 produced a higher pH of the pore solution, which significantly promoted the slag dissolution, shortened the induction period, and accelerated the hydration process. Calcium–sodium aluminosilicate hydrate (C(N)-A S H) gel was the dominant reactant in all samples that enhanced the strength of OPG samples. More geopolymer gel was generated in CCR-doped samples and thus a much higher strength than SR-doped samples. However, the incorporation of excessive alkali sources induced the high carbonization degree of samples, and it was likely responsible for the reduction in strength.

Early properties and chemical structure analysis of alkali-activated brick geopolymer with varied alkali dosage

Alkali-activated brick powder geopolymer (BPG) was prepared by use of brick powder (BP) under the activation of sodium silicate-based activator with silicate modulus of 1.6 and alkali dosages of 2%, 4%, 6%, 8%, and the effect of alkali dosage on the early properties and reaction mechanism of BPG was studied in this paper. Results show that the BPG paste prepared with alkali dosage of 6% exhibits the best fluidity (180 mm). With increasing alkali dosage, the dissolution rate of Al from BP first increases and then decreases. The negative correlation exists between the setting time of BPG and the dissolution rate of Al from BP. The optimal compressive strength reaches 31.1 MPa at the alkali dosage of 6% after cured for 3 days (T = 70 °C, RH = 30%). Lower or excessive alkali dosage is both unfavorable to the enhancement of strength. The calorimetry, FTIR and NMR results show that the increase in alkali dosage (≤6% Na2O) improves the reaction degree, promotes the formation of network structures and increases the Al-rich structural units (Q4(3Al) and Q4(4Al)) due to the beneficial effect of alkali enhancement on dissolution of Al from BP, thereby increasing the polymerization degree of reaction products and enhancing the compressive strength of BPG. However, the higher alkali dosage (8% Na2O) impedes the further dissolution of Al and the formation of Al-rich structural units, which results in the lower reaction degree and compressive strength.

Optimizing the concentration of Na2O in alkaline activators to improve mechanical properties and reduce costs and CO2 emissions in alkali-activated mixtures

This article evaluates the influence of Na2O concentration from sodium silicate and metasilicate activators on the physical, mechanical, and chemical/mineralogical properties of blast furnace slag alkali-activated mixtures. The mixtures were prepared with Na2O dosages of 3, 4.5, 6, and 7.5%. Compressive strength results showed that the maximum values were found for the dosages of 6 and 7.5% at 28 days, while in the flexural strength, the optimal dosages were between 4.5 and 6%. Through thermogravimetry, X-ray diffraction, and infrared spectroscopy tests, it was possible to evaluate the C-S-H production, which occurred more intensely at Na2O concentrations of 6 and 7.5%. However, at the dosage of 7.5%, it was observed utilizing scanning electron microscopy that excessive cracking exerts a preponderant influence on the mechanical properties, especially on the tensile strength. Finally, an assessment of the sustainability of the mixtures was carried out by calculating the CO2 emission efficiency and costs. In this analysis, it was concluded that the mixtures with 4.5% and 6% Na2O were more efficient in these aspects. Therefore, in addition to increasing the amount of microcracks and decreasing the production of C-S-H, excess alkali increases the costs and CO2 emissions of alkali-activated materials.

An Electrochemical Study of Gold Dissolution in Thiosulfate Solution with Cobalt–Ammonia Catalysis

Alkali agents could be used to enhance the extraction of zinc from solution, but excess alkali can lead to emulsification of the solution. In this study, the redox couples of Co(III)/Co(II) could be formed based on the thermodynamic analysis, and catalyze the dissolution of gold in a cobalt–ammonia–thiosulfate system. The catalytic mechanism of cobalt–ammonia for gold dissolution in the thiosulfate solution was further proposed by the analysis of polarization curves to be that NH3 catalyzes the dissolution of gold in the anodic area, and Co(NH3)63+ catalyzes the reduction of dissolved oxygen in the cathodic area. In the dissolution of gold, the concentration of NH3, Co3+ and S2O32− increased, and the dissolution of gold increased. The apparent activation energy for gold dissolution is 41.15 kJ/mol in a temperature range of 25–40 °C, and this demonstrates that gold dissolution is chemically controlled. The SEM-EDS and XPS analyses indicate that the precipitate coating on gold surfaces is mainly S2− in CoS and S8. The decomposition of thiosulfate was also carried out in different thiosulfate solutions. Results have shown that the increase of NH3 concentration can reduce thiosulfate decomposition, while the increase of Co3+ and S2O32− concentration can accelerate thiosulfate decomposition. The apparent activation energy for thiosulfate decomposition with the temperature range of 26.6–41 °C is determined to be 22.12 kJ/mol, which shows that thiosulfate decomposition is mixed chemical-diffusion-controlled.

Оптимизация процесса омыления таллового пека методом планирования эксперимента

Sustainable recycling of wood chemical production wastes is one of the current issues of modern technology. As a by-product of the pulp and paper industry, tall oil pitch has found application as a potential source of phytosterols. Phytosterols or plant sterols are natural compounds, polycyclic alcohols structurally similar to steroids. Due to their biological activity, phytosterols are used in such areas as pharmaceutics and cosmetology, as functional products, etc., which makes them commercially attractive. This paper considers the stage of saponification of tall oil pitch, which yields free phytosterols from their esters with fatty and resin acids. A central composite design complemented by six star points was chosen to determine the combined effect of the three factors and to plan the minimum number of experiments; the response surface methodology was used to determine the optimal values of the variables. Regression models showing the impact of the basic technological factors (excess alkali, temperature and duration of saponification) on the degree of saponification of phytosterols in saponified tall oil pitch and esters in the obtained extract were developed based on the experimental data. A statistical analysis of the models was carried out. Their validity has been proved by means of analysis of variance. The experimental and predicted values closely correlated. The developed mathematical models in the regression polynomial form enable to find the optimal values of the input process variables using the Minitab software while simultaneously reaching the maximum degree of saponification (98,1 %) with the minimum value of the ether number in the extract (4 mg KOH/g): saponification temperature – 121.7 °C, process duration – 3.18 h, and excess alkali – 100 %. Thus, reliable models for predicting the degree of saponification of phytosterols and the ester number in the extract were obtained. These models can be used in industrial saponification of tall oil pitch. For citation: Korshunov A.O., Lavrenteva E.A., Lazarev M.A., Radbil’ A.B. Optimization of Tall Oil Pitch Saponification by Experimental Design. Lesnoy Zhurnal [Russian Forestry Journal], 2022, no. 1, pp. 173–187. DOI: 10.37482/0536-1036-2022-1-173-187

Rational Unraveling of Alkali Metal Concentration-Dependent Photovoltaic Performance of Halide Perovskites: Octahedron Distortion vs Surface Reconstruction.

Adding alkali metal in organic-inorganic halide perovskites effectively improves its photovoltaic performance, while excessive alkali metal incorporation would produce a detrimental effect. Through density functional theory and nonadiabatic molecular dynamics simulations, we demonstrate how and why the photogenerated carrier lifetime mutates with the increase of alkali metal concentration. A small amount of Rb doping in the lattice introduces a slight distortion of the octahedron, reducing the overlap of frontier orbitals and decreasing the nonadiabatic coupling, effectively enhancing the photogenerated carrier lifetime. In contrast, excessive Rb will introduce defect states, resulting in the low carrier lifetime by a factor of 2-3 orders of magnitude. Strikingly, the surface formamidinium (FA) cations exhibit unexpected responsibility for the carrier dynamics since its high-frequency thermal vibration strongly leads to the ultrafast hole trapping and carrier recombination. Our results provide new insight into the concentration-dependent photovoltaic performance of alkali metal cations in organic-inorganic halide perovskites.

Metakaolin-based geopolymers: Efflorescence and its effect on microstructure and mechanical properties

Efflorescence in geopolymers results from mobility of excess alkali and consequent crystallization of alkali carbonates. Efflorescence potential of various geopolymers has been reported previously but the knowledge regarding the effect of efflorescence on the microstructure and mechanical properties of geopolymers remains limited. In this work, metakaolin-based geopolymers were exposed to air, partially immersed in water, and fully immersed, to simulate different processes involved in efflorescence formation. The mechanical properties were assessed by compressive, splitting tensile and flexural strengths, and linear deformation. The microstructural features were investigated by SEM, synchrotron XRD, multinuclear MAS NMR, MIP and synchrotron X-ray microtomography. Extensive efflorescence resulted in a reduction of mechanical strength and changes in the nanostructure and microstructure, which is different from observations for Portland cement-based materials, where efflorescence is usually regarded as a surface or aesthetic problem. The understanding of the relationship between efflorescence formation, the synthesis and exposure conditions provides important insight into the manufacturing and application conditions of geopolymer related materials.

Removal of Excess Alkali from Sodium Naphthenate Solution by Electrodialysis Using Bilayer Membranes for Subsequent Conversion to Naphthenic Acids.

The processing of solutions containing sodium salts of naphthenic acids (sodium naphthenate) is in high demand due to the high value of the latter. Such solutions usually include an excessive amount of alkali and a pH of around 13. Bipolar electrodialysis can convert sodium naphthenates into naphthenic acids; however, until pH 6.5, the naphthenic acids are not released from the solution. The primary process leading to a decrease in pH is the removal of excess alkali that implies that some part of electricity is wasted. In this work, we propose a technique for the surface modification of anion-exchange membranes with sulfonated polyetheretherketone, with the formation of bilayer membranes that are resistant to poisoning by the naphthenate anions. We investigated the electrochemical properties of the obtained membranes and their efficiency in a laboratory electrodialyzer. Modified membranes have better electrical conductivity, a high current efficiency for hydroxyl ions, and a low tendency to poisoning than the commercial membrane MA-41. We propose that the primary current carrier is the hydroxyl ion in both electromembrane systems with the MA-41 and MA-41M membranes. At the same time, for the modified MA-41M membrane, the concentration of hydroxyl ions in the anion-exchanger phase is higher than in the MA-41 membrane, which leads to almost five-fold higher values of the specific permeability coefficient. The MA-41M membranes are resistant to poisoning by naphthenic acids anions during at least six cycles of processing of the sodium naphthenate solution.

Demulsification Behavior of Alkali and Organic Acid in Zinc Extraction

Alkali agents could be used to enhance the extraction of zinc from solution of high concentration, but excess alkali can sensitively lead to emulsification of the solution. In this paper, the emulsification in the extraction process, demulsification, and extraction with different additives and its action mechanism were studied. The results indicate that the associated addition of alkali and organic acid could eliminate emulsification and improve zinc extraction. The extraction ratio of zinc reached 99.61% under the conditions of 104 mL/L organic acid, 80 g/L alkali, and 40% extractant concentration. Zinc hydroxide formed from hydroxyl and zinc ion at sensitively increased pH was the cause of emulsification during extraction. Associated addition of alkali and organic acid could contribute to the control solution pH in the range of 3.0–4.0, which is lower than that of the formation of zinc hydroxide, and therefore, improve zinc extraction.

Excess soluble alkalis to prepare highly efficient MgO with relative low surface oxygen content applied in DMC synthesis

The activities of various MgO catalysts, which were prepared from different methods such as hydration synthesis, thermal decomposition, combustion, sol–gel and co-precipitation, were conducted in dimethyl carbonate (DMC) synthesis via transesterification of ethylene carbonate with methanol. MgO-P-Na2CO3-3.14 synthesized by the excess Na2CO3 precipitation compared the best catalytic activity and stability, which could be reused for seven times without obvious deactivation. The DMC yield was as high as 69.97% at 68 °C. The transesterification reaction could be separated into two steps, and the samples obtained by NaOH precipitant exhibited better ring-opening capability, while the catalysts acquired by Na2CO3 precipitant displayed superior transesterification ability. The structure-performance relationship was evaluated by multiple characterization methods. The results indicated that the as-synthesized catalyst derived from dried precursors with more crystalline magnesium carbonate was favorable for the promotion of DMC yield, and MgO-P-Na2CO3-3.14 with more Mg-O pairs, which were the active center for the transesterification of 2-hydroxyethyl methyl carbonate (HEMC) intermediate with methanol, resulted in more moderately basic sites left that was in accordance with the DMC yield variation. MgO-P-Na2CO3-3.14 with greater BET surface area and mesopore volume, relative low surface oxygen content and larger moderately basic sites amount compared the excellent activity in DMC synthesis.

High performance alkaline battery-supercapacitor hybrid device based on diffusion driven double shelled CoSn(OH)6 nanocube@∝-Ni(OH)2 core-shell nanoflower

The design and fabrication of an alkaline battery-supercapacitor hybrid (BSH) device has been proposed here introducing a hierarchically orientated double hydroxide assembly of cobalt tin hydroxide@nickel hydroxide (CoSn(OH)6@∝-Ni(OH)2) as positive (CTH@NH) and nitrogen, sulfur-doped reduced graphene oxide (NSG) as negative electrode. CTH@NH was obtained through few step time-dependant processes. Double shelled CTH nanocube arrays were obtained by excess alkali etching of intermediate nanocubes that are resulted from fast co-precipitation process at earlier stage. Subsequent growth of ∝-Ni(OH)2 nanoflake upon double shelled CTH nanocube at high pressure and temperature resulted CTH@NH. Improvised core-shell nanodimensional architecture, reduced particle size, mesoporosity and ample surface charges encourage diffusion mediated charge storage with deep flow facility of electrolyte into inner core of electrode material and thus strengthening charge storage capability and capacity which assured significant specific capacity (Cm) of ∼ 1467.24 C g−1 (specific capacitance (Cs): ∼ 2445 F g−1) in the hybrid much higher than CTH (Cm ∼ 480.96 C g−1, Cs of ∼ 801.7 F g−1) at 1 A g−1. The [CTH@NH//NSG] assembled BSH acquired CASC of ∼ 151.5 F g−1 at 1 A g−1 current density with a long term cycling stability of ∼ 95% even after 8000 successive charge-discharge cycles. The concurrent battery performance of CTH@NH along with supercapacitive output of the NSG overcomes the deficiency of specific energy of supercapacitor by providing an excellent specific energy of ∼ 53.8 Wh Kg−1 at a specific power of ∼ 800 W Kg−1 and instigates the high-performance features in the as-fabricated BSH device.

Process engineering approach to conversion of alum sludge and waste glass into zeolite LTA for water softening

This study addressed the need to better understand process engineering aspects of zeolite LTA synthesis from waste materials. In particular, concepts such as zeolite yield, recycling of mother liquor, softening performance and regeneration of calcium loaded zeolite LTA were evaluated. Zeolite LTA was made via alkaline fusion pre-activation of alum sludge and waste glass at 700 °C for 2 h; followed by hydrothermal treatment at 80 °C for 5 h. Increasing the SiO2/Al2O3 ratio of the feed mixture from 1 to 2.3 doubled the yield of zeolite LTA to 67%. Consequently, a feed mixture of composition 9.2Na2O:Al2O3:2.3SiO2:276H2O was adopted for subsequent tests. Recycling of the alkali and other dissolved species in the mother liquor improved zeolite LTA crystallinity (80 to 86 wt%) and calcium exchange capacity from 73 to 78 mg/g. Implementation of recycling depends upon the cost/benefit analysis regarding energy demand for evaporation of mother liquor relative to savings by more effectively using the excess alkali reagent. Calcium uptake on zeolite LTA was reduced when treating simulated river water (65.5 mg Ca2+/g) due to competitive ion-exchange. Regeneration of calcium loaded zeolite LTA required a NaCl solution with a molarity of at least 2 M. A notable reduction of calcium loading capacity was detected after several loading/regeneration cycles. The outlined technology proposed a feasible and scalable approach to recycling of wastes, producing a commodity, which could be successfully used locally by the water treatment plant as a water softener.

Use of active aggregates in concrete as a guarantee of expansion of raw material base and reduction of cost of products

Traditional natural materials (mainly granite and quartz) are usually used as aggregates for the manufacture of concrete products and structures. This raw material is tested, reliable and does not cause destruction during operation of structures. However, it is exhaustive and characterized by high cost. That is why it is advisable to consider the use of reactive (active) aggregates. Especially if you consider ways to eliminate alkaline corrosion. The development of alkaline concrete compositions with the use of active aggregates is the key to expanding the raw material base for the manufacture of building materials with a reduction in production costs compared to products based on traditional systems. The use of active mineral additives allows to reduce the content of free alkalis in the system, preventing the alkaline corrosion of hardened artificial stone. Simultaneously. the processes of interaction of the active siliceous component with alkalis in the cement system can be transferred from the category of destructive (such as destroying the structure of hardened stone) in constructive processes (binding these components into insoluble compounds during hydration and cement formation, without breaking its fixed structure and sealing material). Studies have shown the high efficiency of the proposed approaches for the binding of excess alkalis (more than 0.6%) and targeted synthesis of alkaline aluminosilicate-type tumors in the composition of artificial cement stone. At the same time, the issue of extending the results to control the formation of structures at different levels of concrete with the use of general construction cements requires further research, and the issue of stopping alkaline corrosion of hardened concrete has not been raised and is innovative from the point of view of domestic and world science.

Activation energies for crystallization of manganese‐doped (K,Na)NbO3 thin films deposited from a chemical solution

AbstractPotassium sodium niobate (KNN) thin films are potentially useful for energy harvesting devices and for lead‐free piezoelectric microelectromechanical systems. This work reports the activation energies for nucleation, growth and perovskite phase transformation from a 0.5% manganese‐doped KNN 2‐methoxyethanol‐based solution modified with acetylacetone and excess alkali precursors. The films were annealed in a rapid thermal processor (RTP) with a hold step at temperatures from 500 to 550°C. The activation energies for perovskite transformation and growth, determined by electron micrograph observation, were 687 ± 13 and 194 ± 10 kJ/mol. The activation energy for nucleation was 341 ± 20 kJ/mol. Based on these data, crystallization in KNN is found to be nucleation‐limited; thus, it should be possible to reduce the crystallization temperature by utilizing a seed layer which provides nucleation sites, provided the organics are removed from the film.

Study on Dielectric and charge transport behavior in alkali-treated randomly oriented Sunn Hemp Fiber Reinforced epoxy composite in connection with the microstructure of fiber

ABSTRACT The present research introduces alkalization (KOH) of Sunn Hemp (Crotalaria juncea) fiber with various alkali concentrations (5, 10, 15, and 20 wt %) and the soaking periods (2 hr, 4 hr, 6 hr, 8 hr, and 10 hr). All the composites are fabricated using the hand layout method to study dielectric properties. Dielectric constant ) and loss (tan δ) are found to be less in 10% treated composite soaked for 6 hr (10 K6) and may attribute to the decline of water affinity polar groups that result in reducing the effect of space charge polarization. The ac conductivity investigation of composites results in an increasing trend accompanied by the concentrations and soaking time, revealing the evolution of charge carriers in the amorphous phase due to excess alkali supply to the fiber. The highest and tan δ is obtained in 20 K10 composite assignable to the augmentation of polar groups by forming more amorphous components.

A review on Graphene Reinforced Composites for Ballistic applications

The review paper emphasizes mainly on the hybridization of coir fiber and spider silk with carbon fiber and different percentage compositions of graphene, with an ultimate aim as to how the strength of these hybridized composites can contribute in the fields of material and manufacturing engineering. Firstly, there is an analysis of different properties of coir, carbon fibers, graphene and spider silk. Secondly, there is an analysis of the ballistic test performed on the specimens. In this review, some very basic yet important information is collected and discussed which will help the future researchers in the preparation of hybrid composites involving graphene. Being a natural fiber, the bristle coir fibers are pre-treated with alkali (NaOH) and then acidic treatment is done to remove the excess alkali. After the fibers become neutral, permanganate treatment is done. In case of spider silk, no pre-treatment is done. These fibers are reinforced with epoxy and different weight percentage of graphene (1wt%, 2wt%, 4wt%, 6wt %). Carbon fibre is incorporated in between using conventional hand layup technique. The epoxy and graphene mixture is sonicated to make sure that a uniform and good mixture is obtained. The review facilitates to perform ballistic test on the samples as the results from this test can substantiate to deliver a vital improvement in the field of material selection for body armors.

Tailoring growth modes by excess alkali addition in magnetron sputtered potassium sodium niobate thin films

This work reports on the deposition of thin film potassium sodium niobate sputtered from equimolar and excess alkali targets, showing that the growth mode can be shifted towards recrystallized grain growth without substrate heating, while structural and electrical material properties are improved. In particular, we investigate the influence of abnormal grain growth and its attenuation in KNN thin films. This is accompanied by a comprehensive crystallographic analysis of the obtained crystal structures involving wide-range reciprocal space mapping, temperature-dependent X-ray diffraction and elemental analysis associated with the different growth modes. Moreover, we report on the phase segregation within the processed thin film discovered by scanning transmission electron microscopy, which does not show in conventional elemental analysis of the film surface. Verification of the ferroelectric properties of the films is given by piezoresponse force microscopy, which also enables a study of the ferroelectric domains.