Chemical Tempering Research Articles

Study of the chemical tempering process in industrial porcelain tiles aiming to enhance mechanical properties and reduce thickness

Resumo Este trabalho estuda o incremento da resistência mecânica à flexão e força de ruptura de porcelanatos através da têmpera química. A troca catiônica resulta em tensões residuais de compressão na superfície do material. Foram selecionados porcelanatos técnicos (60×60 cm) com 100%, 90% e 77% da espessura padrão. Os porcelanatos foram prensados, secos e sinterizados em forno industrial. O processo de têmpera química foi realizado com uma mistura de sais de composição correspondente a 27% de nitrato de potássio (KNO3 > 99%) e 73% de fertilizante (K2O ~ 43%). O tratamento químico foi realizado a 480 ºC durante 25 min. Os resultados mostraram que as propriedades mecânicas do material atenderam à norma vigente (ABNT 10545-4 2018). Mesmo o material com 77% da espessura padrão, obteve-se um aumento de 15% na tensão de ruptura e 16% na força de ruptura. A análise de Weibull comprovou que as propriedades mecânicas foram incrementadas após a têmpera química.

Use of chemically tempered porcelain tiles in ballistic protection

A candidate for an armor material should present a lower density, a suitable ballistic performance, and low cost. Porcelain tiles might be an alternative considering their outstanding technical properties and availability. To the best of our knowledge, the use of porcelain tiles was explored for the first time as an armor material. The tests were carried out with reference and chemical-tempered samples. A chemical tempering procedure was applied to improve the impact and mechanical properties. The procedure consists of a cation exchange of sodium and potassium ions, as confirmed by chemical analysis (EDX). Mechanical properties, hardness, and flexural strength were measured. The depth of penetration (DOP) test was used to verify the ballistic protection offered by porcelain tiles. A projectile was fired into a ceramic tile backed by a semi-infinite block in the test. The residual penetration into the backing material was measured and compared to the penetration of the projectile into a monolithic block of the backing material. The test was carried out with 7.62 × 51 mm NATO-FMJ (North Atlantic Treaty Organization - Full Metal Jacket) ammunition specified for NIJ (National Institute of Justice – USA) level III body armor. After chemical tempering, the potassium concentration on the material surface increases. Chemical tempered samples showed an increase in mechanical properties and ballistic performance when compared to untreated ceramic tiles. The flexural strength was 129 ± 8 MPa for the reference material and 143 ± 14 MPa for the chemical tempered material, an increase of 10%; the hardness was HV 8.5 ± 0.9 MPa and 12.7 ± 0.5 MPa respectively, an increase of 49%; and the ballistic efficiency factor (q2) was 2.74 ± 0.72 and 3.22 ± 0.5 respectively, an increase of 17%.

Chemical modification of porcelain tile surface to optimize flexural strength and Weibull modulus through the ion exchange process

The goal of this research was to improve the ion exchange mechanism in porcelain tiles by modifying the tile surface chemically. Ion exchange, also known as chemical tempering, is a procedure for improving the mechanical qualities of porcelain tiles. So, solutions comprising alkaline and alkaline earth metals with a low ionic radius were sprayed on the surfaces of pressed unfired porcelain tiles (lithium, calcium, and magnesium). Subsequently, the porcelain tiles were sintered at the maximum densification temperature (1200 °C). The ion exchange process was carried out at 480 °C for 25 min in a eutectic mixture of molten salts with 73 wt% KNO3 and 27 wt% Ba(NO3)2. The results show that the flexural strength of the Li+/Mg+2 surface-enriched samples was 75 ± 4 MPa, representing an increase of 32% in relation to non-treated porcelain tiles and an increase of 17% in relation to the chemically tempered samples without prior modification. A significantly larger Weibull modulus (15–20) were found for the chemically modified tiles in comparison with the value for the unmodified porcelain tiles (7–8). These findings demonstrated that chemical modification of the porcelain surface can optimize the ion exchange process, resulting in increased breaking force and, as a result, flexural strength and Young's modulus. This approach can help reduce the thickness of ceramic tiles while maintaining mechanical properties. This would result in lower raw material usage and energy expenditure during production, as well as lower carbon emissions associated with the production of porcelain tiles.

Mechanical and Compositional Implications of Gallium Ion Milling on Epoxy Resin.

Focused Ion Beam (FIB) is one of the most common methods for nanodevice fabrication. However, its implications on mechanical properties of polymers have only been speculated. In the current study, we demonstrated flexural bending of FIB-milled epoxy nanobeam, examined in situ under a transmission electron microscope (TEM). Controllable displacement was applied, while real-time TEM videos were gathered to produce morphological data. EDS and EELS were used to characterize the compositions of the resultant structure, and a computational model was used, together with the quantitative results of the in situ bending, to mechanically characterize the effect of Ga+ ions irradiation. The damaged layer was measured at 30 nm, with high content of gallium (40%). Examination of the fracture revealed crack propagation within the elastic region and rapid crack growth up to fracture, attesting to enhanced brittleness. Importantly, the nanoscale epoxy exhibited a robust increase in flexural strength, associated with chemical tempering and ion-induced peening effects, stiffening the outer surface. Young’s modulus of the stiffened layer was calculated via the finite element analysis (FEA) simulation, according to the measurement of 30 nm thickness in the STEM and resulted in a modulus range of 30–100 GPa. The current findings, now established in direct measurements, pave the way to improved applications of polymers in nanoscale devices to include soft materials, such as polymer-based composites and biological samples.

Numerical and experimental study of ion exchange in porcelain tiles

AbstractRecently ion exchange, also known as chemical tempering, has been applied to strengthening of porcelain tiles based on the substitution of ions present in the material by larger ones. This paper investigates the chemical tempering in industrial porcelain tiles by the variation of process parameters such as temperature, immersion time, and chemical composition of the porcelain tile. Furthermore, a numerical simulation of the ionic diffusion process was applied. Using a design of experiments approach, the results show that the temperature and the chemical composition primarily affected the flexural strength of the tile. The largest increment obtained was 37% resulting in a porcelain tile with flexural strength of 73 MPa after chemical tempering. Through numerical simulation, it was possible to estimate a diffusion coefficient of potassium ions equal to 1.25 × 10−14 m2·s−1 into the porcelain tile microstructure. This value is about 10 times higher than the diffusion coefficient in glasses.

Thermal Shock Behavior of a Soda Lime Glass Treated by Ion Exchange

In this work, we have submitted a soda lime glass to thermochemical treatment by ion exchange in order to introduce compressive stresses in their surface. Subsequently, we studied the hot-cold thermal shock resistance of ion-exchange reinforced glass. A potassium ion from the molten salt bath replaces the sodium ion of the glass surface by a superficial diffusion process. We have determined the potassium diffusion profile by two techniques: X-ray fluorescence spectroscopy XRF and X-rays microanalysis coupled with Scattering Electronic Microscopy. In addition, for the same purpose, we used X-ray fluorescence spectroscopy. Then, we determined by micro-indentation the profile of the compressive stresses induced in the glass surface by the exchange of Na+ ions by larger ones of K+. The compressive stress profile induced by chemical tempering depends on potassium ion concentration. It reaches a maximum value of 988 MPa for a treatment done during 50 hours at 480°C. We have subjected the glass specimens treated by ion exchange to a hot-cold thermal shock technique; we realized the cooling by air jet at room temperature. The heat transfer coefficient was about 600 W/m2 °C (Biot number β = 0.3). We have determined the residual strengths of the ion exchange treated and thermal shocked specimens by a three-point bending test. The strength is improved; it passes from 90 MPa of the as received glass to 380 MPa for the chemically treated glass. We noticed that the critical temperature difference ΔTc, which caused the thermal shock fracture, depends on the glass samples states. Consequently, because of the thermochemical treatment, ΔTc has shifted to higher temperatures. Its value was 254°C for raw glass and reached 455°C for the case of reinforced glass by ion exchange at 480°C during 50 hours. The thermochemical ion exchange treatment improve the glass thermal shock resistance.

Templado químico aplicado a gres porcelánicos españoles

This work studies the application of chemical tempering process in porcelain tiles made in Spain. The chemical tempering process is largely applied to glass and its main purpose is to increase the mechanical strength of these materials. To achieve this objective, three porcelain tiles made in Spain from different suppliers were selected. The industrial pieces were cut into small specimens with dimensions of 70×17×9mm, length, width and thickness, respectively. These were then subjected to a chemical ion exchange treatment, also known as chemical tempering. The type of porcelain tile, the temperature and the time of the chemical treatment were varied according to a factorial design. The results showed a ∼55% increase in the breaking strength of one of the porcelain materials. In addition, the statistical study developed showed that the type of porcelain and the temperature of the chemical treatment were the variables that influenced the mechanical resistance to flexion of porcelain.

Self-sterilizing ormosils surfaces based on photo-synzthesized silver nanoparticles.

Medical device-related infections represent a major healthcare complication, resulting in potential risks for the patient. Antimicrobial materials comprise an attractive strategy against bacterial colonization and biofilm proliferation. However, in most cases these materials are only bacteriostatic or bactericidal, and consequently they must be used in combination with other antimicrobials in order to reach the eradication condition (no viable microorganisms). In this study, a straightforward and robust antibacterial coating based on Phosphotungstate Ormosil doped with core-shell (SiO2@TiO2) was developed using sol-gel process, chemical tempering, and Ag nanoparticle photoassisted synthesis (POrs-CS-Ag). The coating was characterized by X-ray Fluorescence Spectroscopy (XRF), Field Emission Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Microscopy (XPS). The silver free coating displays low antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, in opposition to the silver loaded ones, which are able to completely eradicate these strains. Moreover, the antimicrobial activity of these substrates remains high until three reutilization cycles, which make them a promising strategy to develop self-sterilizing materials, such as POrs-CS-Ag-impregnated fabric, POrs-CS-Ag coated indwelling metals and polymers, among other materials.

Chemical tempering of soda lime silicate glasses by ion exchange process for the improvement of surface and bulk mechanical strength

The aim of this work is improving mechanical properties of soda-lime glass by imparting compression stress on the surface through ion exchange and investigate the effect of process parameters on chemical strengthening. KNO3 salt bath was used for ionic exchange at varying temperatures and durations. Treated samples were investigated for their optical transmittance, surface potassium ionic concentrations and concentration profiles from surface to bulk using EDS and line scan EDS techniques. Effect of process temperature and time on the amount of mechanical strengthening was determined through the bending strengths (four-point), scratch resistances and indentation behaviors as micro hardness, crack formation load limit and cracking probability. Results were evaluated regarding ionic concentration variations. Transmittance decreased by 2% after the treatment. Surface potassium concentration increased with increasing temperature and was increased to become saturated in a short period. Potassium concentrations decreased from surface to bulk, and diffusion reached to deeper layers with increasing time and temperature. Ionic exchange improved micro hardness by 8–17%, threshold loads for indentation crack initiation 2–10 times, cracking probability down to 50%, strength up to 3.5–4 times and scratch resistance 2–4 times. Crack types changed between radial, median and lateral; depending on the degree of chemical tempering.

Incremento de resistencia mecánica en materiales de gres porcelánico a partir de tratamiento químico de intercambio iónico

This work provides a novel method for increasing the mechanical strength of porcelain materials. To achieve this was used a ceramic powder prepared from sodium feldspar and clay. This powder was wetted up to 8wt.% with water and pieces of rectangular section are formed by uniaxial pressing at 21MPa. The dried specimens were then sintered in a laboratory furnace (1,218°C). These specimens were subjected to a chemical ion exchange treatment in order to increase their mechanical properties, also known chemical tempering. Temperature and time were varied during chemical treatment according to a factorial design. The results showed an increase of ∼74% in breaking force of porcelain material, providing a reduction of the material thickness greater than 15%. Therefore, the process of chemical tempering can be used to increase the breaking force and consequently decreasing the thickness, saving raw materials and energy in the production process.

Chemical tempering of porcelain tiles

This work presents an innovative approach for strengthening porcelain tiles via chemical tempering, which consists in replacing cations with smaller ionic radius by similar cations with larger ionic radius. Na-containing porcelain tiles were immersed into molten KNO3 bath. A concentration profile of Na and K in the cross section of porcelain tiles to a depth of 200µm from the surface confirmed the ion exchange. Compressive stresses on the material surface were produced, leading to flexural strength of up to 54.5MPa (~74% increase) after chemical tempering at 360°C during 5.5h.

REFORZAMIENTO DE UN VIDRIO SILICO SÓDICO CÁLCICO EMPLEANDO EL PROCESO DE INTERCAMBIO IÓNICO

This work presents brittleness reduction and flexural strength increase due to composition change on a soda lime silicate (SLS) glass and further improvement was achieved by chemical tempering process. It was possible to predict and prove the effect of composition variation on the index of brittleness through Vickers indentation technique. Some glasses were subjected to ion-exchange process where flexural strength was tested. A selected composition was evaluated varying the chemical strengthening time. Also, the result of a statistical topometric analysis of fracture surface of the selected glass composition with and without ionic exchange treatment is reported.

Glass–ceramics of LAS (Li2O–Al2O3–SiO2) system enhanced by ion-exchange in KNO3 salt bath

The paper describes a low-temperature ion-exchange process on specially designed Li2O–Al2O3–SiO2 glass–ceramics (LAS). Due to thermal treatment, two main crystalline phases: lithium di-silicate and lithium alumina-silicate were obtained in glass–ceramic materials. As a result of proper time/temperature profile treatment of precursor glasses, flexural strength of final materials increased up to 300–450MPa.Crystallized samples were immersed in KNO3 molten salt, at temperatures of 400–420°C for 9 or 16h. The final materials achieved almost 100% greater mechanical resistance than glass–ceramics before ion-exchange.We claim that the process of ion-exchange improved flexural strength significantly. Furthermore, it resulted in some changes of the surface layer structure. We noticed that chemical tempering process leads to decrystallization of the multiphase LAS glass–ceramic surface layer consisting of lithium di-silicate and lithium alumina-silicate phases.

Development of mirrors made of chemically tempered glass foils for future X-ray telescopes

Thin slumped glass foils are considered good candidates for the realization of future X-ray telescopes with large effective area and high spatial resolution. However, the hot slumping process affects the glass strength, and this can be an issue during the launch of the satellite because of the high kinematical and static loads occurring during that phase. In the present work we have investigated the possible use of Gorilla glass (produced by Corning), a chemical tempered glass that, thanks to its strength characteristics, would be ideal. The un-tempered glass foils were curved by means of an innovative hot slumping technique and subsequently chemically tempered. In this paper we show that the chemical tempering process applied to Gorilla glass foils does not affect the surface micro-roughness of the mirrors. On the other end, the stress introduced by the tempering process causes a reduction in the amplitude of the longitudinal profile errors with a lateral size close to the mirror length. The effect of the overall shape changes in the final resolution performance of the glass mirrors was studied by simulating the glass foils integration with our innovative approach based on glass reinforcing ribs. The preliminary tests performed so far suggest that this approach has the potential to be applied to the X-ray telescopes of the next generation.

Effects of Ion Exchange on the Mechanical Properties of Basaltic Glass Fibers

Basaltic glass fibers with different lithium oxide (6–14 mol%) and sodium oxide (2–14 mol%) contents were prepared. The influence of Li2O and Na2O content on the process of fiber manufacturing was investigated. Addition of alkali oxides reduced the forming temperature and substantially expanded the fiber‐forming temperature ranges. The obtained thermal data from differential thermal analysis revealed a decline in glass transition temperature (Tg) of fibers against the compositional changes. The inclusion of Li2O and Na2O in the glass network led to a reduction in its thermal stability. The obtained X‐ray diffraction patterns and IR spectra of Li‐rich and Na‐rich basaltic glass fibers confirmed the formation of highly polymerized structures such as LiAl(Si2O6) and (Na,K)(AlSiO4), respectively, and relatively depolymerized silicate anions. The effects of potassium–lithium and potassium–sodium ion exchange on the mechanical properties of basaltic glass fibers were investigated. As‐received Li‐rich and Na‐rich basaltic glass fibers were ion‐exchanged in potassium nitrate for different exchange times, and their mechanical properties were measured before and after chemical tempering. The measured tensile strength and Young's modulus values of the fibers showed an increase after treatment in molten salt.

Characterization of Micrometric and Localised Residual Stresses on Amorphous Materials Using Dispersion of Surface Acoustic Waves

For amorphous materials such as glass, the fragility of the material can be limited using surface reinforcement by chemical tempering. The principle of chemical tempering consists in forming a superficial compression layer on the surface by immersing the glass in a solution of molten potassium nitrate. In this study, dispersion of surface ultrasonic waves caused by the presence of residual surface stresses was studied. The thickness and the level of the stressed cortical zones were estimated using an inverse method.

Potassium ionic exchange in glasses for mechanical property improvement

The aim of this work is to obtain information on structural modification of glass during potassium ionic exchange for mechanical reinforcement. These modifications are evaluated by two characterization methods; scanning electronic microscopy and Fourier transform infrared spectroscopy. The SEM study gives the potassium concentration profile, allows the kinetics of ionic exchange to be observed and gives access to the interdiffusion coefficient with a good concordance between theoretical and experimental concentration profiles. We have verified that the exchange is done between Na+ and K+ ions. We have coupled this SEM result to infrared spectroscopy measurements in middle and far infrared ranges and have proved that infrared spectroscopy allows the access of the structural evolution of glass near the surface after chemical tempering. The evolution of the stretching vibration of Qn modes, between 850 and 1250cm−1, shows a depolymerization of the silica network. The Gaussian positions of Qn modes evolve with the exchange time and prove that there is an increase in the rigidity of the silica network due to a compression state.

Chemical Tempering Process and Characterization of Na-Ca-Si Glass

Chemical tempered glasses were prepared using glass slides as substrate and KNO3 as melting agent by ion-exchange during 2h, 4h, 6h at 430°C,450°C and 500°C respectively. The surface composition of the glasses was analyzed by energy dispersive spectrometer (EDS), the mechanical properties and wear resistance were characterized by nanoindentation/nanoscratch tests. The results indicate that the ion- exchange method can be a good way to increase the strength and improve wear resistance of Na-Ca-Si glass. The chemical tempering has an optimal treating temperature and time.

Research on Heat Treatment Influence Factors on High-Pressure Cylinder Steel 30CrMo-M

To increase comprehensive properties of cylinder steel, high-pressure cylinder steel 30CrMo-M was developed on the basis of steel 30CrMo. Tests and researches were made on factors which influence heat treatment properties, such as chemical composition, quenching temperature, and tempering temperature. The results indicated that the 30CrMo-M steel has stable chemical composition, its strength rises with increase of carbon equivalent, and thus it has better relativity. When concentration of quenching liquid is 5%, yield ratio of the steel can be guaranteed to be low, thus safety of cylinder is improved. Tempered between 570°C~622°C, the strength of the steel is increased and plasticity rises with increase of temperature. When tempered at 570°C, inner wall structure of cylinder contains tempering martensite, the strength is high but the plasticity is low. When tempered between 610°C~615°C, temper brittleness happens very easily and toughness is on the low side. The best heat treatment technology is: quenched at 930°C with temperature holding for 40 minutes and quenching liquid concentration as 5%, tempered at 580°C with temperature kept for 90 minutes. The microstructure treated by this technology is tempered sorbite with higher strength, plasticity and toughness.

Study of edge strength of load bearing glasses

A single glass layer can be considered as safety glass if tempered or reinforced with wire mesh. When tempered glass fractures it shatters into tiny pieces with blunt edges. Heator chemically strengthened glasses can not be considered as safety glass owing to the fracture pattern (fractures in shards), unless they are laminated. Bending tests were carried out (test arrangement according to standard EN 1288-3:2000) and the bending strength of single layer tempered and float glasses were determined with use of the well-known formulas. The calculated values for surface strength with use of ultimate strain were compared to the bending strength results in the case of float and tempered glasses. The question arise: the strains measured in the centre of the pane and near the edge are equally? Strain measurements of the surface of loaded specimens – at the middle of the pane and near the edge – were also investigated. The failure of glass originates from cracks with microscopic sharp tips. In spite of the careful manufacture and handling of glass panes, impacts by sharp particles or environmental impacts can cause defects on the surface. The glass manufacture e.g. edge finishing techniques influence the glass strength and can cause flaws which can propagate during the lifetime of the glass. Defects of edge surfaces caused by different edge work techniques were shown with scanning electron microscopy. Most of the glass strengthening methods are used to introduce residual compressive stresses into the outer layers by physical or chemical tempering. The compressed resulting layer helps to close cracks initiated on the surface, can stop crack propagation and can also increase the bending strength. Recent studies [6, 14] have shown that surface strengthening can lead to substantial improvements in degradation resistance. Therefore, in outdoor conditions, when the glass surface is exposed to humidity etc., tempered or heat strengthened glass should be used.