Function Of Aging Time Research Articles

On the peak strength of 7050 aluminum alloy: mechanical and corrosion resistance

This work consists of an experimental study on the ageing response and resulting properties of AA7050 plate material. New heat treatments are investigated for achieving a peak-aged temper, as a T6 temper may be said to be, that achieves yield and tensile strengths superior to those of the documented T7 treatments. For this alloy, the Standard establishes T7X tempers which were developed to obtain a very good compromise between mechanical strength and corrosion resistance. Nevertheless, for all those applications in which the environment is not considered critical for corrosion behaviour, the peak strength condition could be beneficial. In this experimental work, the authors use standard hardness testing to investigate mechanical response as a function of ageing time at several ageing temperatures, all applied immediately after solution. Upon identifying specific times and temperatures of interest, specimens aged under the selected treatments were subjected to tensile testing and intergranular corrosion testing. The results show that a single-step ageing heat treatment is able to produce a significantly high both yield and ultimate tensile strength. Moreover, the corrosion test data indicates that this new heat treatment produces corrosion resistance similar to that of the T76 heat treatment.

Evolution over time of mackinawite generated on carbon steel by the SRB metabolic activity: an in-operando Raman study

Mackinawite was biologically synthetized by immersing carbon steel coupons in artificial seawater containing Sulphate-Reducing Bacteria (SRB) for 6 months. These coupons were removed from the culture medium solution and some were stored in air while others were placed in SRB-free culture medium solution. In operando Raman spectroscopy was used to analyse all these coupons immediately after extraction from the incubation medium and nanocrystalline, well-crystallized and partially oxidized mackinawite was detected. The evolution of these corrosion products was also monitored as a function of ageing time with this technique. Nanocrystalline and well-crystallised mackinawite transformed into partially oxidised mackinawite, greigite and sulphate green rust for an ageing time between 4 and 72 h. After 120 h, maghemite, magnetite, lepidocrocite, goethite appeared on the coupons placed in SRB-free culture medium solution as opposed to those stored in air atmosphere. Greigite and sulphate green rust were not observed for Raman measurements performed in air.

Cyclic axial loads and thermal ageing of district heating pipes

Thermal ageing at elevated temperatures is the standard method to determine the service life of pre-insulated district heating pipes nowadays. However, DH pipes are also subjected to axial movements which can affect the adhesion strength between the polyurethane foam and the service pipe. This contact surface is usually exposed to the highest temperatures.In this project, DH pipes were aged at elevated temperatures and at the same time cyclic axial loads were applied. Two DH pipes were only exposed to thermal ageing at 130 and 140 °C, while two other similar pipes were also exposed to cyclic axial loads. The adhesion strength was evaluated as the function of ageing time using the RISE plug method. Any changes in the chemical structure of the PUR samples were also observed using Fourier transform infrared spectroscopy.Comparing the results in this investigation, we found that the degradation of the mechanically loaded pipes was significantly faster than the degradation observed in non-loaded pipes at the same ageing temperatures. The FTIR study revealed that cyclic mechanical loads accelerated the chemical degradation of the PUR foam during thermal ageing.This study shows how important it is to consider all influencing factors in accelerated ageing. The methods presented here should be considered as an alternative to thermal ageing at high temperatures because the combination of mechanical and thermal loads reproduces better the real operating conditions. It is even of bigger interest when energy from different sources will be connected to the fourth generation of DH networks, which can cause more temperature fluctuations.

Degradation and Stabilization of Poly(Butylene Adipate-co-Terephthalate)/Polyhydroxyalkanoate Biodegradable Mulch Films Under Different Aging Tests

The degradation and stability of biodegradable films determine the service length of mulch films in actual use. Most biodegradable polymers degrade too fast to meet the required durability of mulch films. The objective of this work is to investigate the degradation behaviors of poly(butylene adipate-co-terephthalate) (PBAT)/polyhydroxyalkanoate (PHA) blend mulch films. Several different types of stabilizers were incorporated in the biodegradable blends to provide protection for the PHA/PBAT films during thermal processing and aging on agricultural fields. The degradation process of the films was systematically studied under an Accelerated aging test (AAT) and a Soil aging test (SAT). Adding a UV stabilizer, or antioxidant to the mulch films led to significant improvement in the retention of mechanical properties of the films under both AAT and SAT. Morphological evolution of the films with or without a UV stabilizer as a function of aging times was studied by Scanning electron microscopy. The results of thermal properties and crystallinity revealed damage of crystalline structure of the films during AAT. Spectrocopic results indicated that the films underwent both hydrolysis and photodegradative chain scissions (Norrish Type I/II reactions and photo-oxidation). Two degradation mechanisms of the PBAT/PHA biodegradable mulch films were proposed.

Stability and stoichiometry of L12 Al3(Sc,Zr) dispersoids in Al-(Si)-Sc-Zr alloys

This work studies the impact of adding 0.5 wt.% Si on the formation of Al3(Sc,Zr) L12 precipitates in a lean Al-Sc-Zr alloy. Precipitation kinetics are significantly accelerated when ageing at 300 and 375 °C in the presence of Si. At 375 °C, peak hardness occurs in a few minutes and is maintained up to 200 h at 375 °C . High resolution TEM reveals the presence of very fine core-shell L12 dispersoids ~5 nm in size that remain stable for up to 200 h at 375 °C. Using high-resolution energy dispersive X-ray spectroscopy (EDX) and atom probe tomography (APT), the presence of Si and Fe is detected in the core of the dispersoids, where their content decreases as a function of ageing time. Similar Si and Fe compositions were observed inside the dispersoids for both alloys regardless of bulk Si content. Both Si and Fe are found to have preference for the Al site in the L12 structure, which is supported by density functional theory (DFT) calculations. DFT also explains the decrease of Si and Fe over time, showing that there is no thermodynamic driving force for either Si or Fe to be present in the L12. Instead Si and Fe are found to play a crucial role at the early stages of clustering, but are expelled from the particles when they stabilise into L12 structures.

Design, phase equilibria, and coarsening kinetics of a new [formula omitted] precipitation-hardened multi-principal element alloy

Multi-principal element alloys (MPEAs), with dispersed nanometric precipitates in a ductile matrix, are attracting a considerable amount of literature’s attention. Understanding the coarsening kinetics and potential properties of such alloys is crucial for future developments in the field. In the present study, we report a new precipitation-hardened multi-principal element alloy, Cr29.7Co29.7Ni35.4Al4.0Ti1.2 (at%), developed with the aid of the CALPHAD method. The alloy has a tough Cr-Co-Ni FCC matrix and nanometric L12 precipitates. After standard heat treatments, the alloy was aged at 850 °C for different aging times and the coarsening kinetics was investigated. The evolution of mechanical properties as a function of aging time was evaluated through microhardness tests. An increment of 106 HV 0.5 was observed compared to the sample in the solution-treated condition. This hardness increment was higher than that of conventional superalloys with a similar volume fraction of precipitates. Experimental data indicate that particle growth during coarsening is governed by diffusion controlling mechanism. The coarsening rate constant was lower than that of traditional wrought superalloys aged at the same temperature, indicating better thermal stability of the current MPEA. Furthermore, experimental particle size distributions show a good correlation with the curve predicted by the Lifshitz–Slyozov–Wagner (LSW) theory. Deviations and the applicability of this theory for MPEAs are discussed.

Preparation and evaluation of soft preformed particle gels for conformance control in carbonate reservoir

In this paper, we studied on the nanocomposite preformed particle gels (PPGs) for conformance control in fractured-vuggy carbonated reservoirs. The nanocomposite PPGs were synthesized via free radical polymerization, consist of acrylamide (AM), N-vinylpyrrolidone (NVP). PPGs were evaluated at 130 °C and salinity of 2.2 × 105 mg/L. Swelling ratio (Sw) and storage modulus (G′) were measured as a function of aging time. A three-stage swollen history is discovered by means of fitting the power-law relation of modulus and volume fraction. It is inferred that the deviation is caused by stress relaxation and secondary cross-link, respectively. Experimental results show that increasing the concentration of monomer, cross-linker and clay leads to a higher swelling ratio and lower modulus during the aging term. PPGs with 30 wt% monomers, NVP: AM ratio of 6:4, 0.25 wt% cross-linker and 3.0 wt% clay exhibit optimum properties for conformance control at high temperature reservoirs. The propagation and blocking efficiency of PPGs were evaluated in an ideal fracture model. The match relation of particle size and fracture width was discussed. Industrial PPGs products with various sizes were prepared. Toughness measurements and infrared spectrum (IR) show that the properties of PPGs are stable during the scale up production. Finally, the field application in Tahe oil field is briefly introduced.

Assessment of Fennel Oil Microfluidized Nanoemulsions Stabilization by Advanced Performance Xanthan Gum.

In this work, nanoemulsion-based delivery system was developed by encapsulation of fennel essential oil. A response surface methodology was used to study the influence of the processing conditions in order to obtain monomodal nanoemulsions of fennel essential oil using the microchannel homogenization technique. Results showed that it was possible to obtain nanoemulsions with very narrow monomodal distributions that were homogeneous over the whole observation period (three months) when the appropriate mechanical energy was supplied by microfluidization at 14 MPa and 12 passes. Once the optimal processing condition was established, nanoemulsions were formulated with advanced performance xanthan gum, which was used as both viscosity modifier and emulsion stabilizer. As a result, more desirable results with enhanced physical stability and rheological properties were obtained. From the study of mechanical spectra as a function of aging time, the stability of the nanoemulsions weak gels was confirmed. The mechanical spectra as a function of hydrocolloid concentration revealed that the rheological properties are marked by the biopolymer network and could be modulated depending on the amount of added gum. Therefore, this research supports the role of advanced performance xanthan gum as a stabilizer of microfluidized fennel oil-in-water nanoemulsions. In addition, the results of this research could be useful to design and formulate functional oil-in-water nanoemulsions with potential application in the food industry for the delivery of nutraceuticals and antimicrobials.

Effects of aging on the thickness of a homogeneous film fabricated using a spin coating process

The thickness of the film produced by spin coating is different from the theoretically calculated thickness based on the Newtonian fluid equation. In this study, the rotational time and rotational speed (in revolutions per minute [RPM]) were used as the control parameters, and the thickness differences between the actual and theoretical results were analyzed based on statistical analyses. Furthermore, we investigated the effects of the aging time (i.e., time after spin coating before heat treatment curing) independently from the parameters of the theoretical equation for spin coating of Newtonian fluids mentioned above. The thickness of the film formed by the spin coater within a period of 300 s was smaller than the theoretically predicted thickness at all rotation speeds irrespective of aging. Based on statistical analyses of the measured thickness values, we confirmed that rotational speeds in the range of 2000–6000 RPM within a period of 300 s did not yield thickness differences owing to aging time. However, below 1500 RPM, the thickness without aging time was smaller than the thickness with aging time. In addition, the thicknesses of the edge and center of the substrate were unequal but became uniform as the aging time increased. Additionally, the estimated thickness based on the constructed plots yielded completely different results from those predicted by the existing equation about Newtonian fluids. Based on the analyses of the thickness as a function of aging time and speed, we confirmed that the aging time—which was not accounted for in the conventional equation—was the parameter that primarily affected the thickness.

Development, characterization and modeling of mosquito repellent release from microporous devices

AbstractNanocomposite strands with mosquito repellent DEET or Icaridin incorporated in a poly(ethylene‐co‐vinyl acetate) (EVA) matrix, with either pyrogenic silica or an organoclay as a nanofiller, were prepared by a twin‐screw extrusion compounding technique. The nature and levels of the repellent and nanofiller that was used affected the material phase morphology. The repellent release was followed as a function of aging time in convection ovens set at 30 and 50°C. The experimental release data of the mosquito repellent from the microporous polymer swellable matrix strands was mathematically modeled and fitted using a range of semi‐empirical models. In the majority of case, the Korsmeyer‐Peppas power law model provided the best data fit. As expected, the wide range of internal morphologies also resulted in quite different release profiles. These models were found to be valuable as they provided insights into the mechanism of repellent release from EVA swellable matrices. It was possible to differentiate between diffusion and relaxation mechanisms. Surprisingly, strands containing nominally more than 30 wt% Icaridin showed accelerating mass loss during the initial phase, consistent with Super Case II transport. Diffusional exponents as high as 1.81 were found. Furthermore, the internal microporous region of the extruded EVA strands was covered by a surface membrane that acted a diffusion barrier that, in effect, controlled the release rate of the mosquito repellents. Some of the investigated samples exhibited release profiles that suggest that longer lasting effective release of repellents is possible than currently achieved by available commercially products.

Preparation and Evaluation of PPGs for High-Temperature Conformance Control

In this paper, the synthesis and thermal behavior of nanocomposite performed particle gels (PPGs) was investigated. The nanocomposite PPGs were synthesized via free radical polymerization at room temperature, using acrylamide (AM), N-vinylpyrrolidone (NVP) as monomers and N, N-methylenebis (acrylamide) (MBA) as crosslinker. Thermal stability evolutions were conducted by aging PPGs at 130°C and salinity of 2.2×105 mg/L for 90 days. Swelling ratio (Sw) and modulus were measured as a function of aging time. A three-stage swollen history was discovered by means of rheological experiments and swelling measurements. Eexperimental results show that increasing the concentration of monomer, crosslinker and clay leaded to higher swelling ratio and lower modulus during the aging term. PPGs prepared with 30 wt % monomers, NVP: AM ratio of 6:4, 0.25 wt % crosslinker and 3.0 wt % clay exhibited optimum properties for conformance control at high temperature reservoir condition.

The lattice parameter – composition relationship of the body centered cubic uranium-niobium alloys

In-situ time-of-flight neutron diffraction experiments were performed on uranium-niobium alloy with 6 wt% Nb to study the lattice parameter-composition relationship for the body centered cubic (bcc) alloys. Based on lattice-parameter measurements of Nb-supersaturated γs phase over the range of 450 – 790 °C, an improved Vegard's-type relationship was established for determination of Nb concentrations at elevated temperatures. Neutron diffraction data were also collected as a function of aging time over the 450 - 600 °C range when γs phase decomposed isothermally into the mixture of orthorhombic α-U and Nb-rich bcc phase, as well as at room-temperature on the alloys aged ex-situ at 500 °C up to five years. From these measurements, the average Nb concentrations in the bcc phase were determined based on the Rietveld refinements of weight fraction and mass conservation relations (lever rule). Over the 15at% – 78at% range of Nb concentrations that correspond to different experimental aging times, the lattice parameters at constant temperatures exhibit a nonlinear S-shaped variation with Nb concentration, and the associated excess volumes of mixing can be described by a subregular solution model of the Redlich–Kister type of polynomial. Over the full range of composition the S-shaped deviation from Vegard's law can be modeled using a combination of an elastic continuum model and a perturbation to the radii of the solute atoms in the solvent, suggesting that electronic interactions between solute and solvent atoms could play an important role in the compositional dependence of lattice parameter for the γ-phase U-Nb alloys. While Vegard's law is a straightforward and reasonably good approximation for the bcc solid solutions in the U-Nb system, the Nb concentrations determined from the weight fraction refinements of diffraction data provide internally consistent, mass-conserving estimates of solute redistribution for the monotectoid reaction.

Microstructural evolution and tensile properties of Fe–11Mn–10Al-1.2C medium-Mn lightweight steel

In the present study, the variations of microstructure and tensile properties were investigated as a function of aging time using a Fe–11Mn–10Al-1.2C medium-Mn lightweight steel. The 1000 °C-annealed specimen revealed an austenite matrix containing nano-sized particles of intra-granular (IG) κ-carbide and a small amount of α-ferrite. After aging at 550 °C for 3 min, pre-existing IG κ-carbide grew up rapidly and relatively coarse κ-carbide formed at the γ-austenite grain boundary (GB). With aging for 10 min, the C-depleted zones, close to the coarsened GB κ-carbide particles, were transformed to filmy grain boundary ferrite (GBF). When aging time increased to 30 min, the eutectoid reaction (γ→α+κ) occurred preferentially at the coarse particles of GB κ-carbide. The eutectoid reaction continued with increasing aging time up to 720 min, and finally the specimen had a eutectoid matrix (α+κ) with a few of α-ferrite. The annealed specimen possessed high strengths (yield strength (YS) of 1242 MPa and ultimate tensile strength (UTS) of 1314 GPa) with moderate elongation (El) of 22.2%. The YS value of aged specimens was improved to ~1.35 GPa by the growth of IG κ-carbide particles after aging for 3 min, and increased further up to ~1.54 GPa by the formation of eutectoid structure after aging for 720 min.

Effect of Aging Time on Microstructure and Mechanical Properties in a Cu-Bearing Marine Engineering Steel.

This study elucidated the structure–property relationship in a Cu-bearing marine engineering steel that was water cooled and then aged at 500 °C for 0.5–3 h. The microstructural features, tensile properties and impact properties were comparatively investigated as a function of aging time. When the aging period was increased, the Cu precipitates underwent coarsening, and a stable face-centered cubic (fcc) formation occurred. Additionally, the tensile properties were significantly improved at the expense of low temperature toughness, which can be attributed to the presence of nano-sized Cu precipitates. The increment of yield strength mainly derived from Cu precipitate–dislocation interaction strengthening effects (232 MPa for 1 h and 199 MPa for 3 h.) during aging process. Therefore, optimization of mechanical properties was achieved by controlling the parameters of aging process. The peak age hardening condition (i.e., at 500 °C for 1 h) resulted in the yield strength of 755 MPa, tensile strength of 812 MPa, elongation of 26.3% and impact energy of 78 J at −80 °C.

Predictive Framework for Modeling Changes in Asphalt Mixture Moduli with Oxidative Aging

This paper presents a predictive framework for asphalt mixture moduli as a function of aging time with two levels of sophistication. This work is built on the method currently implemented in Pavement mechanistic-empirical (ME) that uses an effective time/frequency concept based on time-aging superposition to model the effect of aging on a mixture’s modulus. Time-aging superposition implies that an asphalt mixture’s modulus mastercurves, corresponding to different aging levels, coincide when they are shifted horizontally on the log-frequency axis. This study improves the accuracy of the existing model by decoupling the time-temperature and time-aging shifts. The new framework also uses the binder dynamic shear modulus | G*| as an aging index instead of the viscosity, which is used in Pavement ME. The | G*| aging index is used to calculate an effective frequency at short-term aging (STA), which is then used in the asphalt mixture sigmoidal model to calculate the corresponding asphalt mixture modulus with aging. The pavement aging model introduced by NCHRP 09-54 predicts log | G*| at 64°C and 10 rad/s for a specific field-aged condition and pavement depth. The proposed framework can use the predicted log | G*| to predict the mixture’s corresponding dynamic modulus (| E*|) at that aging level and pavement depth. Level 1 of this framework requires characterizing the | G*| at STA and calibrating the NCHRP 09-54 pavement aging model as well as measuring the mixture | E*| at STA. Level 2 does not require any binder testing, providing relatively less accurate predictions but relieving some testing requirements.

Modeling of the properties of plasticized poly(3-hydroxybutyrate) as a function of aging time and plasticizer content

Poly(3-hydroxybutyrate) (PHB) is a biodegradable polymer synthetized by microorganisms from renewable feedstocks, and is a promising alternative for the replacement of polymers from non-renewable sources. However, this polymer undergoes physical aging, becoming brittle. The plasticization of PHB has been widely reported in the literature as a strategy for overcoming this problem. In this work, we analyze the effects of the amount of plasticizer and time on the extent of aging, by evaluating the changes in the mechanical, dynamic mechanical and thermal properties of formulations of PHB and triethyl citrate (TEC) at room temperature. Formulations with a variable mass fraction of TEC were prepared by melt extrusion, followed by the injection molding of specimens. The extent of aging of the formulations at room temperature was evaluated by analyzing specimens at a predetermined frequency for up to three months. The magnitude of the variation in their properties was larger at the beginning, and underwent exponential decay with aging time. Aging resulted in embrittlement of the formulations, the loss of the capacity to dissipate mechanical energy, and significant changes in the relaxation spectra. The effects of aging on impact resistance were more pronounced as the TEC concentration increased. The dynamic mechanical behavior suggested phase separation in formulations richer in plasticizer, induced by secondary crystallization, which expels TEC from the crystalline structure. A linear model was used to describe and to predict the effects of aging and plasticizer content on the mechanical properties of the formulations.

Positive Aging Effect of ZnO Nanoparticles Induced by Surface Stabilization.

For quantum-dot photodiodes comprising an electron-transporting layer assembled of ZnO nanoparticles, the light emitter/absorber generally exhibits enhanced optoelectronic performance after the device is shelf-aged. To understand the so-called positive aging effect, the optoelectronic properties of ZnO nanoparticles are investigated at the thin film and device level as a function of aging time. It is evidenced that the aging process is driven by a surface-stabilizing mechanism of ZnO nanoparticles, in which the active surface adsorption sites for oxygen are gradually but irreversibly stabilized, i.e.. with surface termination of HO-ZnO, leading to reduced nonradiative recombination and increased built-in potential in the adjacent photoactive layer. This work provides insight into new synthetic routes for minimizing the negative impact caused by the aging process.

Effect of ageing on the microstructural evolution in a new design of maraging steels with carbon

A new maraging steel, based on carbide precipitation, is described. Two alloys were designed namely Fe-10Mn-0.25C-2Cr-1Mo wt% (2CrMo) and Fe-10Mn-0.25C-1Cr-2Mo wt% (Cr2Mo). These compositions were chosen to achieve ultra-high strength and high tensile elongation; the former and latter are promoted through the simulatenous precipitation of Cr- and Mo-rich carbides and Mn-rich reverted austenite. The alloys were manufactured through the standard melting, casting and hot working route. Following a solution treatment at 870 °C and quench, which gave a fully martensitic structure, the alloys were aged for various times at 510 °C. The microstructure and tensile properties were investigated in detail as a function of ageing time. The microstructure observed was dominated by micron scale and nanometre scale Mn segregation which determined the local Ac3 temperature. Austenite reversion occurred in both alloys, peaking at 16 h in both cases. In the 2CrMo alloy, the reverted austenite was mainly globular in morphology due the Ac3 temperature being lower than the ageing temperature, but was acicular in the Cr2Mo with Ac3 similar to the ageing temperature of 510 °C. Moreover, acicular austenite was promoted by Mn segregation at martensite lath boundaries in Cr2Mo. In the 2CrMo steel, carbide precipitation (M3C and M7C3) occurred during heating to the ageing temperature, but the carbides gradually dissolved with further ageing. In contrast, in the Cr2Mo alloy, precipitation of carbides (M7C3 and M2C) occurred during ageing, the volume fraction of which increased with ageing time. In both alloys a TRIP effect was observed, but the extent of this was greater for the Cr2Mo alloy. The complex microstructure obtained after 16 h led to an excellent combination of strength of 1.3 GPa and elongation of 18%. Physics-based models for the microstructure in martensite, precipitation kinetics, as well as for TRIP in austenite were employed to explain and predict the individual strengthtening contributions of the microstructure to the total strength, confirming that the maximum strength-elongation relationship found after 16 h is due to an optimal combination of a slightly overaged - but still strong- martensite and 30% of reverted austenite, for increased work hardening and ductility.

Construction of complex shear modulus and phase angle master curves for aging asphalt binders

ABSTRACT Performance of asphalt concrete pavement significantly degrades during the aging of asphalt binders. The master curves of complex shear modulus and phase angle are recognised as useful tools to characterise the rheological properties of aging asphalt binders. The main shortcoming of existing master curves is that the effects of aging cannot be captured and predicted effectively. This study developed a new method to construct such aging master curves that can be extended to predict the complex shear modulus and phase angle at a wide range of aging time and temperature. The DSR tests were conducted on three different types of asphalt binders with three aging temperatures and four aging durations. The master curves of complex shear modulus and phase angle were constructed for aging asphalt binders through time-temperature-aging shift by performing both rotation and horizontal aging shift. Rotation and horizontal aging shift were determined as the function of aging time and aging temperature. Therefore, it becomes possible and convenient to construct single aging master curves at a wide range of aging temperature and aging time.

Optical oxygen sensing by MPA-capped CdTe quantum dots immobilized in mesoporous silica

Abstract A novel nanocomposite luminescent material was prepared by taking advantage of the versatile wet impregnation method for the dispersion of CdTe quantum dots (QDs) into mesoporous silica host matrix and thus providing great interaction between oxygen and QDs, with potential application in an optical oxygen sensor. The optical/spectroscopic properties of the QDs suspended in aqueous media and incorporated in mesoporous silica were evaluated as a function of aging time, temperature variation and oxygen concentration. Luminescence quenching studies were carried out for both QDs suspended in solution and loaded into the silica matrix, in the presence of varying O2 concentration. By Stern-Volmer plot analysis, obtained at different temperatures, it was possible to verify the existence of two types of emission quenching mechanisms for CdTe QDs. After aging for 120 days at room temperature, the QDs in colloidal suspension displayed a small red-shifted emission, which was interpreted as a decreased bandgap energy owing to the increase in the nanocrystal size. In contrast, the emission spectrum of CdTe QDs loaded into the mesoporous SiO2 matrix remained unchanged after aging for the same time at ambient temperature. The presented results will contribute to the discernment of oxygen quenching mechanisms and chemical stability of optical sensors based on CdTe QDs.