Experimental Determination of Phase Equilibria in the Na2O-SiO2-WO3 System

The present study investigated phase equilibria in the Na2O-SiO2-WO3 system experimentally using high-temperature equilibration, quenching, and electron probe X-ray microanalysis (EPMA). New thermodynamic information on the Na2O-SiO2-WO3 system was derived based on the newly obtained experimental results and data from the literature. The primary phase fields of sodium metasilicate, sodium disilicate, and tridymite were determined along with the isotherms at 1073, 1173, and 1273 K. The solubilities of WO3 in SiO2, Na2Si2O5, and Na2SiO3, and the solubility of SiO2 in Na2WO4 were accurately measured using EPMA. Comparisons between the existing and newly constructed phase diagram were carried out and the differences are discussed. The phase equilibrium data will be beneficial to the future development of sustainable tungsten industries and thermodynamic modelling in WO3 related systems.

Laser-induced optical nonlinearity in a Li-rich glass

The selective crystallization of a photosensibilized lithium silicate glass after a light emitting diode (280 nm) and a nanosecond laser (355 nm) UV irradiation and subsequent heat treatment was studied. Using a focused beam of the laser allows successive drawing regions in which the formation of silver nanoparticles after 500°C heat treatment of the glass co-doped with silver and cerium ions takes place. It is shown that this treatment is a necessary step for the growth of sodium metasilicate crystals under the second thermal treatment of the glass at 600 °C, while these regions demonstrate second optical harmonic generation of 1064 nm nanosecond laser radiation.

Influence of Graphene Nanoplatelets on the Compressive and Split Tensile Strengths of Geopolymer Concrete

Geopolymer is now a more advanced alternative to cement and available substitute for OPC while graphene nanoplatelets (GnP) are new nanomaterials with extraordinary properties that can enhance and improve the strength of cementitious materials. Although graphene reinforced concrete has intriguing potential, its implementation in construction requires better knowledge of the impact of GnP on the properties of concrete related to durability. Studies on the compressive and tensile strength performance of geopolymer concrete (GPC) containing GnP are needed. The present study investigated the influence of reinforcing GPC with varying percentages of GnP on the compressive and split tensile strengths of GPC. The addition of GnP ranged from 0.0%, 0.25% and 0.5% by weight of total binder. It has been observed that the addition of GnP increased the compressive strength by 30% and the tensile strength by 22% in comparison to a reference sample with a specified composition of fly ash and sodium metasilicate. In addition, the effect of GnP on enhancing the compressive strength of the geopolymer was shown to diminish as the amount of sodium metasilicate increased.

Strength, Shrinkage and Early Age Characteristics of One-Part Alkali-Activated Binders with High-Calcium Industrial Wastes, Solid Reagents and Fibers

Alkali-activated binders (AABs) are developed using a dry mixing method under ambient curing incorporating powder-form reagents/activators and industrial waste-based supplementary cementitious materials (SCMs) as precursors. The effects of binary and ternary combinations/proportions of SCMs, two types of powder-form reagents, fundamental chemical ratios (SiO2/Al2O3, Na2O/SiO2, CaO/SiO2, and Na2O/Al2O3), and incorporation of polyvinyl alcohol (PVA) fibers on fresh state and hardened characteristics of 16 AABs were investigated to assess their performance for finding suitable mix compositions. The mix composed of ternary SCM combination (25% fly-ash class C, 35% fly-ash class F, and 40% ground granulated blast furnace slag) with multi-component reagent combination (calcium hydroxide and sodium metasilicate = 1:2.5) was found to be the most optimum binder considering all properties with a 56 day compressive strength of 54 MPa. The addition of 2% v/v PVA fibers to binder compositions did not significantly impact the compressive strengths. However, it facilitated mitigating shrinkage/expansion strains through micro-confinement in both binary and ternary binders. This research bolsters the feasibility of producing ambient cured powder-based cement-free binders and fiber-reinforced, strain-hardening composites incorporating binary/ternary combinations of SCMs with desired fresh and hardened properties.

Basic Properties of fly Ash/Slag -Concrete Slurry Waste Geopolymer Activated by Sodium Carbonate and Different Silicon Sources

As a kind of granular waste with complex composition and alkali corrosiveness, concrete slurry waste (CSW) has severe recycling limitations in the ordinary Portland cement (OPC). Considering this, a new type of geopolymer, prepared by granulated blast furnace slag/fly ash, concrete slurry waste, and powdered activators (sodium carbonate and different silicon sources including sodium metasilicate pentahydrate and silica fume), was adopted to conduct a comparative study with the OPC counterpart. In this study, the homogenized CSW was mixed in the OPC and geopolymer with a constant ratio of 50 wt%, respectively. Then the properties were studied in terms of the flowability, setting times, mechanical strengths, and microstructures. The results showed that better flowability (200 mm) could be achieved in the obtained geopolymer than in the OPC reference group (95 mm) by increasing the powdered activators. The setting time of the OPC was significantly shortened due to the addition of CSW. The strengths of geopolymer were supported by the produced C-A-S-H and carbonates, with less chemically bonded water than the hydration products in the reference group. The dominant size of pores in the hardened geopolymer was much smaller than that in the OPC group which was 80 nm. Silica fume could be the alternate of the sodium metasilicate pentahydrate and had an insignificant negative impact on the fresh and hardened properties and microstructures of the geopolymer when the incorporation rate was within 5%.

JUSTIFICATION OF OPTIMAL PARAMETERS OF THE PROCESS OF CHEMISORPTION PURIFICATION OF CORN OIL WITH A SOLUTION OF SODIUM SILICATE

Для обоснования оптимальных параметров хемосорбционной очистки нерафинированного кукурузного масла, обеспечивающих получение продукта с допустимыми показателями качества, проведен ряд экспериментов. Объектом исследования было нерафинированное кукурузное масло, полученное двукратным прессованием из кукурузного зародыша, произведенного мокрым способом отделения, со следующими показателями: кислотное число 4,2 мг КОН/г, массовая доля фосфорсодержащих веществ 1,65% в пересчете на стеароолеолецитин, перекисное число 4,7 ммоль активного кислорода/кг, цветное число 60 мг йода, массовая доля влаги и летучих веществ до 0,2%. В качестве реагента применяли водный раствор метасиликата натрия заданной концентрации с силикатным модулем 1. Исследования проводили на лабораторной установке, которая включала реакционную емкость рабочим объемом 500 мл с динамическим смесителем, обеспечивающим преимущественно смешанную циркуляцию потоков жидкой фазы при перемешивании с частотой вращения от 25 с–1 до 50 с–1, лабораторный автотрансформатор, перистальтический насос подачи раствора типа InLab и емкость для водного раствора реагента. На основании спланированных экспериментальных исследований получены адекватные экспериментально-статистические модели для расчета содержания мыла в получаемом кукурузном масле и его выхода в зависимости от исследованных параметров процесса. Установлено, что оптимальные параметры процесса хемосорбционной очистки – температура 40°С, дозировка метасиликата натрия 22 г/кг и его концентрация 55% при изменении критерия Рейнольдса мешалки в интервале от 4000 до 12000 обеспечивают получение кукурузного масла с установленными показателям качества. To substantiate the optimal parameters of chemisorption purification of unrefined corn oil, ensuring the production of a product with acceptable quality indicators, a number of experiments were conducted. The object of the study was unrefined corn oil obtained by double pressing from corn germ produced by wet separation, with the following indicators: acid number 4,2 mg KOH/g, mass fraction of phosphorus-containing substances 1,65% in terms of stearoleolecithin, peroxide number 4,7 mmol of active oxygen/kg, color number 60 mg of iodine, mass fraction of moisture and volatile substances up to 0,2%. An aqueous solution of sodium metasilicate of a given concentration with a silicate modulus of 1 was used as the reagent. The studies were carried out on a laboratory installation that includes a reaction tank with a working volume of 500 ml with a dynamic mixer that provides mainly mixed circulation of liquid phase flows during mixing with a rotation speed from 25 s–1to 50 s–1, a laboratory autotransformer, a peristaltic solution supply pump of the InLab type and a container for an aqueous solution of the reagent. Based on the planned experimental studies, adequate experimental and statistical models were obtained for calculating the soap content in the resulting corn oil and its yield, depending on the studied process parameters. It was found that the optimal parameters of the chemisorption purification process - the temperature of 40°C, the dosage of sodium metasilicate 22 g/kg and its concentration of 55% when changing the Reynolds criterion of the agitator in the range from 4000 to 12000 provide corn oil with the established quality indicators.

Hydrophobic Lightweight Cement with Thermal Shock Resistance and Thermal Insulating Properties for Energy-Storage Geothermal Well Systems

This study assessed the possibility of using polymethylhydrosiloxane (PMHS)-treated fly ash cenospheres (FCS) for formulating a thermally insulating and thermal shock (TS)-resistant cementitious blend with calcium aluminate cement. To prevent FCS degradation in an alkaline cement environment at high temperatures, the cenospheres were pre-treated with sodium metasilicate to form silanol and aluminol groups on their surface. These groups participated in a dehydrogenation reaction with the functional ≡Si–H groups within PMHS with the formation of siloxane oxygen-linked M-FCS (M: Al or Si). At high hydrothermal temperatures of 175 and 250 °C, some Si–O–Si and SiCH3 bonds ruptured, causing depolymerization of the polymer at the FCS surface and hydroxylation of the raptured sites with the formation of silanol groups. Repolymerization through self-condensation between the silanol groups followed, resulting in the transformation of siloxane to low crosslinked silicon-like polymer as a repolymerization-induced product (RIP) without carbon. The RIP provided adequate protection of FCS from pozzolanic reactions (PR), which was confirmed by the decline in zeolites as the products of PR of FCS. Cements with PMHS-treated FCS withstood both hydrothermal and thermal temperature of 250 °C in TS tests, and they also showed improved compressive strength, toughness, and water repellency as well as decreased thermal conductivity. The lubricating properties of PMHS increased the fluidity of lightweight slurries.

Silicon In the Growth of Rice Seedlings Pretreated with Dietholate and Subjected to Cold Stress

Silicon (Si) is an enzyme stimulator that can promote signaling for the production of antioxidant compounds, important in cellular detoxification of excess ROS accumulated during stress. The aim of the study was to evaluate the effects of Si on post-germination rice seeds in the mitigation of cold stress combined with stress induced by seed treatment with the dietholate protector. The experimental design was fully randomized with three replicates and a 3x2x2x4x2 factorial arrangement: three temperatures (5, 10 and 20 °C), two cultivars (IRGA 424 RI and Guri INTA CL), two seed pretreatments (with and without dietholate), four rates of Si (0; 4.0; 8.0 and 16 mg.L-1) and two sources of Si (sodium and potassium metasilicate). Seed pretreatment with dietholate reduced shoot and radicle length, especially at the lower temperatures of 5 and 10 °C. Sodium metasilicate as the source of Si was more efficient in boosting shoot and radicle length, both with and without pretreatment, regardless of temperature. Si was found to attenuate low-temperature stress and the impairment of shoot and radicle growth in rice seedlings grown from seeds pretreated with dietholate.

Mechanical and Fresh Properties of Multi-Binder Geopolymer Mortars Incorporating Recycled Rubber Particles

This paper examines the performance of multi-binder conventional geopolymer mixes (GCMs) with relatively high early strength, achieved through curing at ambient temperature. Mixes incorporating ground granulated blast-furnace slag (GGBS), fly ash (FA) and microsilica (MS) and sodium metasilicate anhydrous, were assessed in terms of workability, mechanical properties and embodied carbon. A cement mortar was also prepared for the sake of comparison. The best performing GCM was then used as a reference for rubberised geopolymer mixes (RuGM) in which the mineral aggregates were replaced by recycled rubber particles in proportions up to 30% by volume. Experimental results were combined with embodied carbon estimations in a multi-criteria assessment to evaluate the performance of each material. A mix with a 75/25 GGBS-to-FA ratio, in which 5% MS was added, had the best performance in terms of strength, workability, water absorption and environmental impact. The compressive strength was above 50 MPa, similar to that of the cement mortar. The latter had significantly higher embodied carbon, with factors ranging between 3.48 to 4.20, compared with the CGM mixes. The presence of rubber particles reduced the mechanical properties of RuGM proportionally with the rubber amount, but had similar workability and embodied carbon to CGMs. Finally, a strength degradation model is validated against the tests from this paper and literature to estimate the compressive strength of RuGM, providing reliable predictions over a wide range of rubber contents.

Obtaining a nanosized silica-humic preparation and its initial approbation

The recent decades have witnessed a significant development and implementation of nanotechnology, including in various branches of agriculture. There is an active search for ways to obtain preparations for plant growing with nanoparticles that can be more rapidly involved in the metabolic processes of plants. This article aims to obtain a nanosized silica-humic preparation and its approbation on potato plants. As a source of humic substances, a liquid humic preparation BoGum (developed by the All-Russian Research Institute of Reclaimed Lands) was used, as a source of silicon – sodium metasilicate. Ultrasonic dispersion method was used for achieving the nanoscale of the samples. A silicon source was introduced in an amount of 0.1% (of SiO2) into BoGum, followed by the application of ultrasonic action for 5, 10, 15 and 20 minutes. The analysis of the obtained samples using a 90 Plus/MAS particle size analyzer has shown that with increasing dispersion time, the effective particle diameter changed insignificantly. At the same time, a redistribution of particles was noted: when the samples were exposed for 20 minutes, the number of smaller particles increased. After 5 minutes of treatment, the range of particle distribution was 115±13–830±23 nm, after 20 minutes of exposure, the particle diameter fell into two regions: 81±8–120±10 and 280±4–470±18 nm. Ultrasonic action contributed to the retention of the stable state of aggregation of the obtained preparation, larger microbiological activity and larger content of humic acid in comparison with the silica-humic preparation, obtained without the application of an ultrasound. The new nanosized silica-humic preparation has been tested on potato plants. Treatment of tubers before planting, followed by foliar spraying of vegetative plants, has contributed to an increase in potato yield by 18.7%. Changes were noted in the content of mono- and polysilicic acids in the soil, as well as the accumulation of silicon in the tops of potatoes when using silicahumic preparations by 0.96% of absolute dry mass on average.