Macroscopic superlubricity of potassium hydroxide solution achieved by incorporating in-situ released graphene from friction pairs

Graphene(G),as a typical two-dimensional material,is often used as an additive for liquid lubricants.However,graphene is mostly added to liquid lubricants in a one-time manner in friction;it mainly exists in the form of multilayer agglomerated structures due to theπ–πstacking between graphene sheets,making it unable to fully exert the synergistic lubrication function.Herein,we propose a new macroscopic superlubric system of graphene/potassium hydroxide(G/KOH)solution;and the graphene additive involved is exfoliated in-situ from graphene/epoxy(G/EP)friction pair by friction,continuously providing freshly-peeled graphene into KOH solution and minimizing the adverse effects of graphene agglomeration.Moreover,the in-situ produced graphene additive has thinner thickness and better anti-aggregation ability,which provide more graphene to accommodate OH−,form more stacked sandwich structures of OH−/graphene/OH−between friction pairs(i.e.,equivalent to a moving pulley block with more wheels),and finally realize superlubricity.This study develops a new liquid superlubric system suitable for alkaline environments,and at the same time proposes a new way to gradually release graphene additives in situ,rather than adding them all at once,deepening the understanding to liquid superlubricity mechanism,and paving the experimental foundation for the practical application of macroscopic superlubricity.

Potassium hydroxide based biorefinery concepts for non-wood bioresources

The paper and paperboard production in 2016 in the world was 110.07 million tones.1 Bangladesh consumes only about 3.5~4 kg paper and board products per capita,while the developed countries consume about 300 kg/capita.Bangladesh’s consumption is also much lower than the world’s average(@50 kg/capita)and the Asia’s average(@50 kg/capita).2 To reach the world’s or Asia’s level,Bangladesh’s consumption of paper and board products needs to increase 10 folds.As forest resources are very limited in Bangladesh,alternative fibrous raw materials are required to achieve this goal.Therefore many studies have been carried out on alternative raw materials available in Bangladesh.

Development of Kaolin and Glass Fiber Reinforced Composites for Thermal Insulating Panels

In our modern world, where conserving energy is highly valued, thermal insulation panels play a crucial role in reducing heat transfer between two spaces, surfaces, or materials. They are used to enhance the energy efficiency of various industrial applications by minimizing heat loss and temperature control. These panels function as silent protectors, aiding in reducing energy consumption and making things more sustainable and better for the environment. This is where composite materials come in;they are known for their lightweight nature, high strength-to-weight ratio, and excellent thermal insulation properties and have gained significant attention. Researchers are actively engaged in various studies aimed at enhancing these materials further. This research project focuses on the development of kaolin and glass fiber-reinforced composites for thermally insulating panels, to which natural strengthening materials like corn husk and bamboo fibers are added. The aim is to create cost-effective and efficient composite materials for thermal insulation applications by incorporating these components with a binder consisting of potassium silicate, hydroxide, and distilled water. This project involves conducting compression tests, bending tests, impact tests, thermal conductivity measurements, and microscopic analysis to evaluate the mechanical and thermal properties of the developed composites. The profound impact of these engineered composites on thermal insulation panels stands to revolutionize energy conservation efforts, offering a potent avenue to minimize heat loss and enhance overall energy efficiency across an array of industrial sectors.

KOH-assisted aqueous synthesis of bimetallic metal-organic frameworks and their derived selenide composites for efficient lithium storage

To solve low efficiency,environmental pollution,and toxicity for synthesizing zeolitic imidazolate frameworks(ZIFs)in organic solvents,a KOH-assisted aqueous strategy is proposed to synthesize bimetallic ZIFs polyhedrons,which are used as precursors to prepare bimetallic selenide and N-doped carbon(NC)composites.Among them,Fe–Co–Se/NC retains the three-dimensional(3D)polyhedrons with mesoporous structure,and Fe–Co–Se nanoparticles are uniform in size and evenly distributed.When assessed as anode material for lithium-ion batteries,Fe–Co–Se/NC achieves an excellent initial specific capacity of 1165.9 m Ah·g^(-1)at 1.0 A·g^(-1),and the reversible capacity of Fe–Co–Se/NC anode is 1247.4 m Ah·g^(-1)after 550 cycles.It is attributed to that the uniform composite of bimetallic selenides and N-doped carbon can effectively tune redox active sites,the stable 3D structure of Fe–Co–Se/NCs guarantees the structural stability and wettability of the electrolyte,and the uniform distribution of Fe–Co–S nanoparticles in size esuppresses the volume expansion and accelerates the electrochemical reaction kinetics.

Electrical Characteristics of Super Capacitors Using KOH Gel

Despite aqueous electrolytes having a low cost and excellent ionic conductivity,their low withstand voltage of 1.2 V makes them problematic for battery utility because that is a very important factor in battery production.In this research,the possibility of increasing the withstand voltage while maintaining the low cost of aqueous electrolytes was investigated.In this research,the solution electrolyte was made into a viscous solid polymer electrolyte to improve the withstand voltage of the electrolyte.A solid polymer electrolyte was made from sodium polyacrylate and doped with KOH(potassium hydroxide)and pure water.The improvement of the withstand voltage was evaluated by the specific capacitance.

Removal of iron from ilmenite by KOH leaching-oxalate leaching method

Oxalic acid was used for the removal of iron from the intermediates of ilmenite leached by KOH liquor. Various parameters, such as pH, temperature, initial oxalate concentration, and illumination were investigated. Meanwhile, it was found that orthorhombic crystal Ti2O2（OH）2（C2O4）-H2O formed as the leaching proceeded. Scanning electronic microscope （SEM） images implied that the formation of Ti2O2（OH）2（C2O4）.H2O with good crystallinity proceeded through three stages. Calcining Ti2O2（OH）2（C2O4）·H2O, anatase （350℃） or mtile （550℃） type TiO2 was obtained, respectively. Element analysis found that the calcined product contained 94.9% TiO2 and 2.5% iron oxide, but only about 1600 ppm dissolvable iron oxide was left, which indicates that oxalic acid was comparatively effective on iron oxide removal from the intermediates. Finally, an improved route was proposed for the upgrading of ilmenite into mtile.

Extraction behaviours of titanium and other impurities in the decomposition process of ilmenite by highly concentrated KOH solution

To effectively utilize ilmenite and recycle KOH solution, the extraction behaviours of titanium and other associated impurities in the decomposition process of ilmenite by highly concentrated KOH solution were studied. Experiments on the extraction behaviours of tita- nium as well as other associated impurities of ilmenite such as iron, silicon, calcium, and aluminium were carried out. The effects of various parameters, including reaction temperature, KOH concentration, reaction time, alkali-to-ore mass ratio, and particle size on the extraction rate of titanium and other impurities were examined. When the finely ground ore （58-75 ~tm） reacted with KOH solution （80wt%） in an al- kali-to-ore mass ratio of 7：1 at 260~C for 60 min, almost complete extraction of titanium was achieved, while the extraction rate of aluminium was 78% and that of other impurities was less than 22%. Moreover, high purity （98.2wt%） TiO2 with the anatase structure could be gained in the purification process.

Synthesis of kalsilite from microcline powder by an alkali-hydrothermal process

The properties of aluminosilicate kalsilite have attracted the interest of researchers in chemical synthesis, ceramic industry, biofuels, etc. In this study, kalsilite was hydrothermally synthesized from microcline powder in a KOH solution. The microcline powder, rich in potassium, aluminum, and silicon, was collected from Mountain Changling in Northwestem China. The effects of temperature, time, and KOH concentration on the decomposition of microcline were investigated. The kalsilite and intermediate products were characterized by means of wet chemistry analysis, X-ray Diffraction （XRD）, infi＇ared spectrometry （IR）, 29Si magic angle spinning nuclear magnetic resonance （29Si MAS NMR）, 27A1 MAS NMR, and scanning electron microscope （SEM）. With increasing temperature, the microcline powder transforms into a metastable KAlSiO4 polymorph before transforming further into pure kalsilite. A mixture of both kalsilite and metastable KAlSiO4 polymorph is obtained when the hydrothermal reaction is carried out within 2 h; but after 2 h, kalsilite is the predominant product. The concentration of KOH, which needs to be larger than 4.3 M, is an important parameter influencing the synthesis ofkalsilite.

Preparation and modification of activated carbon for benzene adsorption by steam activation in the presence of KOH

A series of activated carbons from Taixi anthracite were prepared by steam activation in the presence of KOH and then they were modified by different methods. The regulation of porosity and the modification of surface chemistry were carried out with the aim to improve the benzene adsorption capacity of activated carbon. The influences of KOH and activation process parameters including activation temperature, activation time and steam flow rate on porosity of activated carbon were evaluated, and the effect of modification methods on surface chemistry was investigated. Also, the relationship between benzene adsorption capacity and porosity and surface chemistry was analyzed. Results show that activation temperature is the dominant factor in the activation process; the introduction of KOH into the raw material can enhance the reactivity of char in activation process, meanwhile it shows a negative effect on the porosity development, especially on the mesopore development. Results of FTIR analysis indicate that anthracite-based activated carbon with condensed aromatics and chemically inert oxygen does not present the nature to be surface modified. Besides, benzene adsorption capacity has an approximate linear relationship with surface area and in our preparation, benzene adsorption capacity and surface area of activated carbon are up to 1210 m 2 /g and 423 mg/g, respectively.

Effect of ultrasonic assisted KOH pretreatment on physiochemical characteristic and anaerobic digestion performance of wheat straw

In this study,ultrasonic field was applied during potassium hydroxide(KOH) pretreatment of wheat straw(WS).Three concentrations of KOH(2%,4%,and 6%) were tested during pretreatment.The results showed that there was a significant influence of the ultrasonic assisted KOH pretreatment(KOH(Upt)) on physiochemical characteristics of WS during pretreatment as well as on digester performance.The pretreatment time was optimized to 36 h for all KOH concentrations.The highest total volatile fatty acid(TVFA) productions(3189 mg·L^-1) from 6%KOHupt samples were observed.Similarly,the SEM analysis and FTIR observation revealed that KOH(Upt) effectively disrupted the physical morphology of WS and successful breaking of lignin and hemicellulose linkage between carboxyl groups.Moreover,the highest biogasification(555 ml·(g VS(loaded))^-1) and biomethane productions(282 ml·(g VS(loaded))^-1) from 4%KOH(Upt) digesters,with 69% of biodegradability,indicated significant availability of organic matter from KOH(Upt).The R^2 values(0.993-0.998) in Modified Gompertz Model indicated that the model was feasible to predict methane yield for this study.Similarly,the Bo values for 4%KOH(Upt)(283.30±2.74 ml·(gVS(loaded))^-1) were also in agreement to the experimental methane yield.These results suggested that ultrasonic addition during KOH pretreatment of WS can effectively increase the organic yield during pretreatment.Moreover,the increase in methane production from 4% KOH(Upt) suggested that digester performance can be improved with lower KOH concentrations using this pretreatment.

Experimental Study on Wax Protective Coating for Wet Deep Silicon Etching Processes

In order to protect the finished structures on the front side during deep silicon wet etching processes, the wax coating for double-sided etching process on the wafer is studied to separate the aforementioned structures from the strong aqueous bases. By way of heating and vacuumization, the air bubbles are expelled from the coating to extend the protection duration. The air pressure in the sealed chamber is 0.026 7 Pa, and the temperature of the heated wafer is 300℃. Two kinds of the wax are used, and the corresponding photos of the etched wafer and the protection times are given. In 75 ℃ 10 % KOH solution, the protection duration is more than 8 h.

Characterization and Comparison of Cellulose Extraction from Ginger Stalk by Two Different Chemical Treatments

Agricultural residues are important renewable biomass resources that have not received much research attention. Ginger stalk is a major agricultural waste in China.The extraction of cellulose from ginger stalk would convert this waste into a high value-added product and, simultaneously, contribute to environmental protection. This research studied the characteristics of cellulose extracted from ginger stalk by two different treatments:(i) potassium hydroxide(KOH) treatment and(ii) nitric acid-ethanol(NAE) treatment. The optimal condition for the KOH treatment was obtained, it was at 1∶30 solidto-liquid ratio(SLR) for 5 h extraction time with 14 wt% KOH. The optimal condition for the NAE treatment was as follows: 1∶40 SLR, 4 h extraction time, and a reaction temperature of 90℃. However, the cellulose obtained by NAE treatment was severely degraded than that by KOH treatment. The Fourier-transform infrared(FT-IR) spectroscopy analyses revealed that both treatments successfully dissolved the lignin and hemicellulose. Two treatments showed a higher cellulose yield, and the extracted cellulose had more crystal structure.

Compressive Strength of Metakaolin-Based Geopolymers: Influence of KOH Concentration, Temperature, Time and Relative Humidity

The influence of KOH concentration (8 and 12 M) and curing conditions as temperature (40℃ and 60℃), time (7 and 28 days) and relative humidity (85% and 95% RH), on compressive strength of metakaolin-based geopolymers (MK-based GP) was evaluated. Derived from the experimental design technique, and using a factorial design 2K with two replications in the center point, eighteen experiments were conducted. The results reveal that the best performance conditions of geopolymerization to develop a higher compressive strength of 20 MPa are 12 M KOH to 60℃ and 85% RH at 28 curing days. With these conditions, the value of relative humidity of 85%, promotes high strength compact samples, and a maximum of 42 MPa at 90 days. The results of significant, compressive design of GP showed that KOH concentration and curing relative humidity were the most important factors, followed by curing time and temperature. The GP were characterized by XRD, and their evolution on compression strength was followed by SEM.

Density and viscosity of aqueous solution of K_2CrO_4/KOH mixed electrolytes

The physicochemical properties are very important in theoretical investigation of aqueous electrolyte solution and industrial design of hydrometallurgical processes. In the green hydrometallurgical process of chromite ore with sub-molten salt medium of KOH, the ternary system of KOH+K2CrO4+H2O is essential to process control and industrial operation. In order to satisfy the needs of both fundamental research and industrial application, the dynamic viscosity (η) and density (ρ) of mixed aqueous electrolyte solution of KOH and K2CrO4 were measured over a temperature range from 15 to 60 ℃ by using Ubbelohde-type capillary viscometers and a series of densimeters, respectively. The temperature is controlled to an accuracy of ±0.01 ℃ throughout the experiment with thermostat. The dynamic viscosity and density of the ternary systems are performed as functions of chromate and hydroxide concentration and temperature. The regression equations for viscosity and density are obtained with a least-square method and the calculated values are consistent well with the experimental data. The semi-empirical equation obtained will be helpful and instructive to industrial application.

Paired interference 3-dB coupler based on SOI rib waveguides with anisotropic chemical wet etching

A 3-dB paired interference （PI） optical coupler in silicon-on-insulator （SOI） based on rib waveguides with trapezoidal cross section was designed with simulation by a modified finite-difference beam propagation method （FD-BPM） and fabricated by potassium hydroxide （KOH） anisotropic chemical wet etching. Theoretically, tolerances of width, length, and port distance are more than 1, 100, and 1 μm, respectively. Smooth interface was obtained with the propagation loss of 1.1 dB/cm at the wavelength of 1.55 μm. The coupler has a good uniformity of 0.2 dB and low excess loss of less than 2 dB.

Eco-friendly preparation of chitooligosaccharides with different degrees of deacetylation from shrimp shell waste and their effects on the germination of wheat seeds

Production of chitosan and its derivatives by traditional methods involves the excessive use of a reaction solution comprisedof sodium hydroxide and hydrochloric acid. Waste water resulting from this process has lim让ed the application of chitosanas a fertilizer as the process causes serious environmental pollution. Specifically, the resulting waste water contains highlevels of dissolved nitrogen and minerals from shrimp shells. In this study, an eco-friendly method was established to produce chitooligosaccharides (COS) with different degrees of deacetylation (DDAs) from shrimp shell waste. At a solid-tosolventratio of 1:6, the degree of demineralization was above 90% with the treatment of 30 g-L_1 H3PO4, and the degree ofdeproteinization was above 80% when treated with 30 g-L_1 KOH at 70 °C. Chitosans with different DDAs were obtainedby microwave-assisted KOH metathesis and the COS with Mw approximately 1500 Da were then prepared by oxidativedegradation. In summary, 33.73 kg H3PO4,12.77 kg, and 241.31 kg KOH were supplied during the processes of demineralization,deproteinization, and deacetylation of 100 kg shrimp shell waste, respectively. The process water was totally recycled,demonstrating that the shrimp shell could be wholly transformed into fertilize The entire process created a product withthe fractions of N:P2O5:K2O:COS = 7.94:24.44:10.72:1 &27. The test on the germination promotion of wheat seeds revealedthat the COS with 72」2% DDA significantly promoted germination. This work demonstrated the use of an eco-friendlypreparation method of COS with a specific degree of deacetylation that can be applied as a fertilizer.