Sodium Silicate Binder Research Articles

Effect of Additives on Heat Hardened Inorganic Solid Foundry Binder

AbstractRenewed interest in inorganic binders for sand molding has also intensified research on different forms of it. In this study, solid inorganic sodium silicate binder was tested with different additives to see how these affected the silica mold quality. The five additives used were: glucose, sucrose, boric acid, aluminum oxide and iron(III)oxide powders. The mold quality was assessed through tests like bending strength, tensile strength, hot distortion, wear resistance, gas evolution and collapsibility tests. In addition, SEM imaging was done on some select mold fracture samples. In the end, a casting trial was carried out followed by a surface roughness and defects analysis. A reduction in mold strength was noticed with glucose and boric acid, while collapsibility was improved by glucose, sucrose and boric acid additives. Casting trials have shown the best surface finish to be obtained with sucrose additive. All the casts in general showed some penetration; however, repeat casts have proven that altering some casting parameters could result in casts with excellent surface finish using solid silicates.

INFLUENCE OF BINDERS, MIX PROPORTIONS, AND FABRICATION METHOD ON THE CHARACTERISTICS OF FLY ASH AGGREGATE

In this paper, two types of lightweight fly ash (FA) aggregates: cold bonded fly ash (CFA) and sintered fly ash (SFA) aggregates were prepared through the cold bonding and sintering method. During the pelletization process, different ratios of binders to fly ash were used, i.e., 10:90, 15:85, 17:83, and 20:80 with a set amount of water. Cement, metakaolin, sodium silicate, urea-formaldehyde resin, bentonite powder, and phenol-formaldehyde resin were employed as binders. A comparative study on physicochemical, mechanical, phase identification, microstructure, and optical analysis of CFA and SFA was performed. The results showed that CFA (an alkali binder) had a higher water absorption (WA) value of 9,50 % with a crushing strength (CS) value of 6,30 MPa than SFA (sodium silicate binder) with a CS value of 5,80 MPa and a WA value of 10,28 %. Experimental observations also demonstrated that the leaching ability of SFA was considerably lower than that of CFA. Most notably, SFA can be used as a substitute for construction material and structural applications along with solving FA waste disposal and related problems to a considerable extent.

Preparation of h‐BN microspheres for nanocomposites with high through‐plane thermal conductivity

AbstractIn recent times, electronics have been increasingly minimized, and hence, heat dissipation has become essential. Owing to its high thermal conductivity and superior electrical insulation, hexagonal‐boron nitride (h‐BN) has been regarded as an appropriate ceramic material to increase the thermal conductivity of polymer nanocomposites for effective heat dissipation. However, the poor through‐plane thermal conductivity of h‐BN severely restricts its practical uses, and it is favorable for heat to radiates in the in‐plane direction. In this study, densified spherical h‐BN (sph‐BN) microspheres, composed of as‐synthesized nano‐sized h‐BN (nano‐BN), were manufactured by a spray‐drying process with variations in organic and/or inorganic binders followed by sintering. After incorporating various sph‐BN particles as fillers into polydimethylsiloxane (PDMS), the through‐plane thermal conductivity of composites embedded with sph‐BN, assisted by a sodium silicate binder, enhanced the highest through‐plane and in‐plane thermal conductivities. The composites exhibited high thermal isotropy (through‐plane thermal conductivity/in‐plane thermal conductivity: ) of 0.77. The out‐of‐plane thermal conductivity of the composites was remarkably enhanced by over 2000% compared with pristine PDMS, which can be attributed to the synergy combined with the synthesis of the densified spherical BN initiated by nano‐BN, sintering, and the application of inorganic binders. This study proposes a simple method to prepare polymer composites with h‐BN that exhibit high through‐plane thermal conductivity and are promising materials for heat removal in electronics.

Study on Laser Selective Curing Additive Manufacturing of Foamed Structural Ceramics

An additive manufacturing method for ceramic materials with internally formed foaming structure was proposed in this paper with the adoption of ceramic powder and sodium silicate binder to prepare sizing agent. The forming process on each layer consists of three basic processes, including spreading, freezing and laser scanning. Foaming structure arises due to the foaming effect of the frozen sodium silicate caused by laser gasification. After 3D printing, the support material in frozen state will be removed when it has been melt in water. Then finally the green ceramic parts internally filled with foaming structures will come into being. Experimental results show that the laser parameters, the content of ceramic, the scanning spacing and other factors affect the interior appearance of the green part. At the scanning speed of 100 mm·s-1, laser power of 20 W, and 0.3 mm scanning spacing, the ceramic parts are processed with a slurry with 50% solid content. The support materials in the deep fine structure can be quickly removed without mechanical damage or swelling in the water. This new process can be used to process thermal insulation ceramic parts.

Softening of sand mixtures on a liquid-glass binder as a result of thermal-oxidative destruction of a combined carbon-containing additive. Part 1

The chemical and physical processes that occur during high-temperature heating of carbon-containing additives are studied in order to develop an effective composition, whose components destruction will lead to a violation of the integrity of the binder film and a decrease in the residual strength of liquid-glass mixtures, and hence an improvement in the knock-out of molds and cores in the conditions of obtaining castings from alloys of ferrous metals. Carboncontaining materials used in foundry production, the destruction of which proceeds in different temperature ranges, have been studied. The methods of thermogravimetric and differential thermal analyzes have been used to study the processes that tale place with materials under study when heated to temperatures comparable to the actual operating conditions of casting cores in direct contact with liquid and solidifying metal in the mold. As a result of the analysis of the considered carbon-containing materials, the temperature intervals of destruction were revealed, which made it possible to predict their effect on the structure of sodium silicate (binder) on the refractory filler and the residual strength of mixtures in order to improve the knock-out of steel castings. Obtaining high-quality casting molds and cores depends on the technological, hydraulic and mechanical characteristics of the mixture, therefore, additional studies were carried out, the results of which revealed the compliance of the determined properties of the studied samples with the requirements for molding and core sand mixtures on a liquid-glass binder.

Comparison of Compressive Strength of Fly Ash Bonded Flue Dust Briquettes with that of Briquettes made with Bentonite, Sodium Silicate, Lime, Starch, Pitch, Molasses and Dextrin Binder

Comparison of Compressive Strength of Fly Ash Bonded Flue Dust Briquettes with that of Briquettes made with Bentonite, Sodium Silicate, Lime, Starch, Pitch, Molasses and Dextrin Binder

Performance evaluation on engineering properties of sodium silicate binder as a precursor material for the development of cement-free concrete

In emerging economies, huge stocks of industrial wastes are dumped in open landfills. Such wastes serve as a source for environmental pollution. Some of these materials such as Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBFS), Rice Husk Ash (RHA), and Palm Oil Fuel Shell Ash (POFA) can be used as binder materials to produce concrete mix. Aim of the study is to effectively utilize the Municipal Solid Waste (Sodium Silicate Waste (SSW)) powder as a partial replacement for FA in the development of Geopolymer Concrete (GPC). GPC requires heat curing for the attainment of early age strength. The development of GPC under heat curing conditions is a hard process in practice. To overcome such circumstances, an attempt was made to develop the GPC under ambient curing conditions with the aid of SSW. The influence of SSW on strength gain and microstructural characteristics of GPC is investigated. Mechanical properties of GPC such as compressive strength, tensile strength, and flexural strength are reported and discussed. This study focuses on the assessment of mechanical and microstructure characterization of eco-efficient GPC developed with SSW. The required optimum quantity of binder, alkali activator, alkaline liquid to binder ratio and aggregates was determined by appropriate trials. Following the properties of SSW, it is realistic to substitute up to 50% of SSW as the resulting binder mix falls within the requirements of the analyzed mix. Increase in the percentage of SSW decreases the fresh properties of GPC, such as setting time and workability; mix with 50% SSW exhibited the lowest initial and final setting time i.e., 77% and 81% than the control mix. Contrastingly, inclusion of SSW content enhances the mechanical properties of the mix. 12SSW50 mix produces the maximum compressive, tensile and flexural strength of 40.16 MPa, 2.8 MPa, and 4.18 MPa, respectively. Mix with 8 M concentration comprising 50% SSW possess higher cost efficiency than the mix with higher alkaline content. The main significance of this research work is, SSW can be used as a precursor material as an alternative for cementitious binder with better efficiency in terms of strength, microstructure, and sustainability. Therefore, GPC produced with SSW is an eco-friendly and sustainable building material. Effective use of waste materials such as fly ash and SSW for the development of GPC is another major research focus in the proposed investigation.

Effect of Compound Additives on the Adhesive Performance of Sodium Silicate Binder for Core-making

Effect of Compound Additives on the Adhesive Performance of Sodium Silicate Binder for Core-making

Effect of sodium silicate binder on the performance of ceramic coatings on copper prepared by the slurry method

Low melting point metals, such as copper, are often used as high-temperature cooling equipments and endure harsh environments during operations. This usually leads to reduced service life and reliability. To address this problem, a protective coating was prepared on copper via a slurry method. However, due to the low melting point of copper, solid-state sintering was applied. Therefore, during this process, the defects generated in the ceramic coating could affect the performance of the coating. To reduce the defects, a series of ceramic coating samples using sodium silicate water glass (SSWG) as the binder were prepared, changing the SSWG-to-aggregate mass ratio (SAMR) for each sample. The results showed that they were all related to the SAMR, and there was an optimal SAMR with minimum defects and favourable performance. The non-optimized SAMR lead to more internal defects, that is, microfractures and pores in the coating, resulting to a decline in the coating performance. By identifying the types of defects and quantifying them, the relationship between the SSWG and the generation of defects was studied, and the effect of the defects on the performance of the ceramic coating was analysed in detail. The research presented in this paper provides a method for the improvement of ceramic coatings by optimising the key factors that is the SAMR in solid-state sintering. The effect of thermal stress on the formation of microfracture defects during the sintering was investigated by experiments and simulation. It is found that with increase of sintering temperature, the thermal stress inside the coating increases gradually, resulting in more generation of microfracture defects inside the coating. The inhibition effect of SSWG on thermal stress during the sintering process was verified.

Investigation on characteristic and formation mechanism of porosity defects of Al–Li alloys prepared by sand casting

Porosity defects and interfacial reaction are very serious problems in sand casting Al–Li alloy, which greatly affect the quality of castings. In this work, the characteristic and formation mechanism of the porosity defects in the sand casting Al–Li alloys were systematically investigated by scanning electron microscopy, transmission electron microscopy, energy spectrometry, and inductively coupled plasma mass spectrometry, in order to provide a theoretical basis for the prevention and control of the pore defects in the sand casting Al–Li alloys. The results found that the Al–Li alloys prepared by metal mold and graphite mold as casting molds had almost no pore defects and interfacial reaction layers, with the porosities of 5.81% and 5.05%, respectively, while the sand casting Al–Li alloys with furan resin, phenolic resin, and sodium silicate binder as binders all had serious pore defects and interfacial reaction layers, with the porosity of 15.67%, sharply weakening the mechanical properties of the Al–Li alloy casting. The types of the pore defects were mainly reactive pores and intrusive pores, and the interface reaction layer was mainly composed of LiAlO2 and C–H–O organics. The formation mechanism of the pore defects in the sand casting Al–Li alloys was caused by the reaction between Li and the hydroxyl groups in the binder of the sand mold to generate a large amount of hydrogen, which intruded into the melt or was sucked into the melt.

Effect of Silica Nanoparticle Dispersion on Flexural Strength of Sand Mold with Sodium Silicate Binder

Sodium silicate solutions are used as an eco-friendly binder in the casting process. However, the strength of sand molds using the sodium silicate solutions is reduced because of their low humidity resistance. In this study, silica nanoparticles were added to a sodium silicate solution with a constant SiO2/Na2O ratio to improve the humidity resistance of the inorganic binder. The effects of the dissolution times and particle size of the silica on the flexural strength of the molds was also investigated. The physiochemical properties of the inorganic binders were characterized by viscometer, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Sand molds for the flexural strength test were prepared by mixing artificial sand and inorganic binders. The addition of silica nanoparticles reduced the viscosity and water evaporation rate of the inorganic binders and improved the humidity resistance of the molds due to an increase in the SiO2/Na2O ratio. The flexural strength of the molds increased as the size of the silica nanoparticles increased, due to formation of discrete silica aggregates with high surface area. However, as the dissolution times of the silica nanoparticles increased, the strength of the molds decreased due to an enhanced Q2/Q3 ratio. Therefore, we suggest that the addition of silica nanoparticles will improve the humidity resistance of molds, and that varying the particle size and dissolution time of the silica nanoparticles affects the strength of the molds.

The effect of flux composition on tensile strength of re-engineered E308H-16 electrode

A stainless steel flux for manual metal arc welding (MMAW) has been developed. The coated electrode is a rutile electrode whose basic components are titanium (IV) oxide and stainless steel powder. Some of the other components were substituted; the more popular but expensive potassium silicate binder was replaced with readily available sodium silicate binder. For the binder to perform effectively, it was enriched with potassium carbonate, which was sourced locally from palm bunch. Cellulose, a good gas former was replaced with starch, which was gotten from cassava. The components were sieved into 75 µm particle size. The experimental design was set up using Central Composite Design in Design Expert software. The design varied the percentage composition of calcium carbonate, binder, titanium (IV) oxide, silicon (IV) oxide, and stainless steel powder. Twenty-six (26) test samples were produced using the central composite design tool of the design expert software and tested for tensile strength. The experimental results were analyzed and optimized using Response Surface Methodology and Validated using the ANOVA tool of the Design Expert software. An optimal composition of 10% CaCO3, 13% Binder, 13% Titanium oxide, 12% silicon (IV) oxide, and 36% stainless steel powder were obtained to give a corresponding 539.7 N/mm2 tensile strength.

Technogenic resources of ferrous metallurgy and their complex processing in the conditions of JSC Uzmetkombinat

The article deals with the involvement of accumulated and formed technogenic formations in the form of steel-making slag and dust-like waste from ferrosilicon production into processing, in order to obtain additional valuable components from industrial waste. To isolate them, various methods of hydraulic classifi cation, jigging, enrichment have been investigated, and gravitational enrichment on a concentration table is recognized as the most optimal. The possibilities of using technogenic waste of aspiration dust from the production of ferroalloys – microsilica containing at least 85% amorphous silica in its composition – can be used for the production of sodium silicate binder (liquid glass) by the autoclave method. The resulting material can be used as an import-substituting raw material in the production technology of manual arc welding electrodes.

Properties of the glass formed from ground glass cullet via sintering

Recycled glass cullet was sintered from green compacts with 0.5 and 1% by weight respectively of organic binders added: polyvinyl alcohol (PVA), and sodium silicate (Na2SiO3). Typically, glass is recycled by melting, requiring large amounts of energy from fossil fuels adding to greenhouse emissions. Disc shaped compacts with a 13 mm diameter, formed by uniaxial pressing, were sintered at temperature of 680, 700, and 720 °C for 60 min. The recycled material with 1 wt% sodium silicate binder sintered at 700 °C has the highest tensile strength; more important, in the range of regular soda-lime glass, suggesting a greenhouse gas reduction using this sintering process.

An Application of Analytical Hierarchy Process in Selection of Coating Material Composition in Lost Foam Casting Process

In modern industrial era, the dimensional accuracy and surface finish are two major criteria in the selection of casting process. To achieve this paradise, lost foam casting is one of the casting processes. In this casting process, the shell is made by removal of expandable polystyrene or foam pattern with the application of heat. During the foam decomposition process, many problems have been generated such as bending, expansion, distending and crack of the shell. These problems may be eliminated by selecting the optimum ratio of coating materials. In this research work, zircon and aluminium silicate refractory coating materials with sodium silicate binder have been used with different composition and prepared the four test samples from them. For selection of best shell material composition, analytical hierarchy process is used.

An assessment of pyrite thin-film cathode characteristics for thermal batteries by the doctor blade coating method

Abstract Using FeS2 (pyrite) as an active material for cathodes in the thermal battery has received much more attention due to its abundant natural resources, cheapness, and excellent efficiency. Nevertheless, scientists take a large internal resistance issue of the FeS2 cathodes into urgent consideration, decreasing the electrochemical efficiency of typical Li–Si/FeS2 thermal batteries. In this study, we surveyed the effect of binders, thin-film thicknesses, and the addition of conductive carbonaceous additives such as carbon black (CB), super P (SP) and activated carbon (AC) on the FeS2 thin film cathode fabrication by applying the blade coating method. To obtain the FeS2 homogeneous slurry, we utilized the ball-milling process to reduce the FeS2 particle size from 8.7 μm to 0.9 μm. Subsequently, the FeS2 thin film with different thicknesses, expected to elevate mass loading causing higher capacity of thermal batteries, by means of the doctor blade was successfully fabricated from the homogeneous slurry comprising ball-milled FeS2 active material, polyvinylidene fluoride (PVDF) binder or sodium silicate (Na2SiO3) binder, accompanied with conductive carbonaceous additive; even without conductive carbonaceous additive, thin films were still capable of being produced. Among these samples, the thin-film type, mass loading from 1.4 to 3.6 mg/cm2 (corresponding to the doctor blade thicknesses in a range of 150–300 μm), manufactured from the slurry consisting of 80 wt% of ball-milled FeS2, 15 wt% of conductive carbonaceous additive (CB/SP/AC), and 5 wt% of PVDF binder will promisingly contribute to increasing electrochemical efficiency of thermal batteries, possibly on account of high mechanical durability.

The Optimization of the Properties of Sodium Silicate Bonded Ceramic Sand by Nano-Oxide Particles and Ultrasonication

In this paper, the nanoparticles (NPs) of magnesium oxide (nano-MgO) and silicon dioxide (nano-SiO2) and ultrasonication on the properties of sodium silicate bonded sand (SSBS) were studied, and the quantity of NPs and ultrasonication time in their interaction with sodium silicate binder were optimized by orthogonal experiment. This research was conducted with sodium silicate as a part of two-component (sodium silicate–silica fume) binder system to be used for heat-cured sodium silicate bonded ceramic sands. The results of experiment indicated that the addition of NPs and ultrasonication promoted the continuity and density of the bonding bridge of sand samples, the optimal quantity of nano-MgO and nano-SiO2 was 1.5% and 1.0% of sodium silicate binder, the optimal ultrasonication time was 15min, hot strength (σ0), 4-h tensile strength (σ4h) and 24-h tensile strength (σ24h) of modified sand samples increased by 11%, 25% and 27%, and the residual strength (σ800oC) decreased by 28%. The different linear expansion coefficients between nano-MgO, the new phase Na2Si3O7 and the sodium silicate system caused many cracks on the bonding bridge in the process of heating at 800°C and cooling, which resulted in the reduction of the residual strength of SSBS.

Study of adhesion properties and mechanism of sodium silicate binder reinforced with silicate fume

In this study, the effect of different amounts of silica fume additive on the bonding strength of sodium silicate binder, over time, was studied. It has been concluded that silica fume can improve the bonding strength and humidity resistance of sodium silicate bonded sand. The microscopic morphology of the adhesive film was examined by scanning electron microscopy, and the functional group changes of the polymerised adhesive were analysed by Fourier-transform infrared (FT-IR) spectroscopy. In addition, the hardening mechanism, between the sodium silicate binder and silica fume on the sand surface, and the hydration reaction mechanism, after polymerisation, were investigated using first-principles calculations in the CASTEP program based on density functional theory (DFT). It was found that silica fume enhances the binding energy of the binder by enhancing the degree of polymerisation, while subsequent hydration of the hardened binder is a spontaneous reaction. After the sodium silicate binder hardens, the water molecules are adsorbed by unpolymerised –OH and Na+; these water molecules destroy the -Si-O-Si bonds to depolymerise the sodium silicate bonded network. This research provides important theoretical support for improving or even eliminating the hygroscopic properties of sodium-silicate-bonded sand during casting.

Experimental study on silica sand using bottom ash on metal casting

Nowadays the disposal of bottom ash and fly ash are the major problem in industries. These wastes become pollutants to the environment and induce hazardous effects to human beings. So these wastes (ash) are replaced or reclaimed to other economical applications. This paper mainly deals with thermal power plant bottom ash. Their property includes volume of expansion, compressive strength, cohesiveness and refractoriness. The initial process includes that ash is mixed with silica sand by using binders to prepare the mould. Later the preparation of mould is to be introduced which undergoes several test like sieve test, sand hardness test. By using mould the casting is prepared and the physical property of the finished casting is tested under SEM, XRD. Finally the castings are produced using moulding sand mixed with 20 wt% of bottom ash and different binders (bentonite and sodium silicate binder). It was found that castings prepared by sodium silicate binder have high impact strength and hardness value compared with bentonite binder.

Wet regeneration of waste artificial sand used in sand casting using chemical solutions

Natural sand and organic binders have been the main materials used in sand casting. However, inorganic binders are used in novel casting technologies, and research on artificial sand as a substitute of natural sand has been conducted. Herein, the wet regeneration of waste artificial sand was performed using a sodium silicate binder. Acidic, neutral, and basic solutions were used for wet regeneration. The effects of binder removal and reusability of the regenerated sand were investigated by comparing the characteristics and strengths of the artificial and regenerated sand. It was demonstrated that the basic solution effectively removed the binder from the surface of the waste artificial sand. The Si-O-Si bond cleavage in the binder occurred due to the high concentration of hydroxide ions in the basic solution. The strength of the regenerated sand treated with the basic solution and that of the artificial sand were similar. Moreover, the strengths of regenerated sands treated with the acidic or neutral solutions were lower than that of artificial sand due to the presence of residual binder. These results indicated that the basic solution was suitable for removing the sodium silicate binder. The quality of the regenerated sand was similar to that of artificial sand.