Influence Of Aging Time Research Articles

Influence of ageing time on crystallization kinetics and hydroxyapatite Mimicking Silicorhenanite (β-Na2Ca4(PO4)2SiO4) phase evolution in 45S5® bioactive glass for advanced biomedical applications

Among multiple phases obtained while synthesizing bioactive glass, the phosphate-rich Silicorhenanite phase is achieved only at high temperatures. The novel outcome of this work is that sol-gel routed 45S5 bioactive glass was synthesized successfully by permutating the period of ageing and achieved the Silicorhenanite phase at 700 °C without compromising biocompatibility. The process of ‘Ostwald ripening’ was observed among the biomaterials where A24 and A72 exhibited a similar trend and A48 and A96 behaved alike. Rietveld Refinement confirms the elevation of the Silicorhenanite (β-Na2Ca4(PO4)2SiO4) phase upon increasing the ageing time over the Combeite (Na2Ca2Si3O9) phase. Since A72 exhibits compressive strain and smaller crystallite size, it lacks erythrocyte compatibility, and protein adsorption, and has an exceptionally low surface area. This study emphasizes the stability and multiple physio-chemical properties of 45S5 Bioactive glass during the ageing period, which is an imperious parameter for producing biomedically beneficial glass products, especially porous scaffolds and implant coatings.

Experimental investigation on tensile behavior of CFRP bolted joints subjected to hydrothermal aging

Abstract With the help of bolted joints to assemble a complex structure, carbon fiber reinforced polymer composite (CFRP) is widely used in various fields. However, stress concentration around holes at the bolted joints leads to a decrease in bearing capacity. Composites often result in mechanical degradation subjected to a complex hydrothermal environment. Therefore, to study the tensile behavior of CFRP bolted joints subjected to hydrothermal aging, the tensile tests are conducted carefully. The influence of aging time and temperature on tensile strength is investigated based on the response history, strain contour, and failure morphology. The failure mechanism is revealed via digital image correlation technology. Finally, the experimental results demonstrate that the bearing capacity of the structure in hydrothermal aging decreases significantly. Compared with the unaged specimens, the peak force of the specimens aged for 6 weeks at 25°C and 65°C is reduced by 22.79% and 35.63%, respectively. Under both the unaged and aged, the same bearing failure is found in the tensile tests of CFRP single-bolt single-lap joints.

Influence of Aging Time on Compressive Strength of Silica Fume Reinforced High Strength Concrete Composite

The goal of this study is to gather a High Strength Concrete (HSC) composite reinforced by silica fume and superplasticizers. Specimens are Cured by water and tested after aging time of 3, 7, 28 days. Specimens are cubes of 150 and 200 mm and 150x300mm cylinder. The aim is to get mean strength of 80- 85 MPa, and determination of physical properties of the materials used, which are basic components of the High Strength Concrete (HSC) composites. After designing mix proportions, according to design requirements some adjustments were done. Both fresh and hardened properties of the specimens were tested under standard condition (curing schemes, setting time, comp.str. etc). Compressive strength test results were gathered and compared with the requirements.

The influence of aging time and moisture content on the tensile strength of transformer bushing insulating paper

The parameter of tensile strength for transformer bushing insulating paper occupies an important position in the structural design and life evaluation of transformer bushing. In order to precisely achieve the effect of aging time and moisture content on the tensile strength of transformer bushing paper, transformer insulating paper samples with a thickness of 0.13 mm were prepared for tensile strength and dielectric strength testing under different moisture contents and aging states. The results show that the tensile strength (MPa) of insulating paper decreases linearly in the range of 0–648 h under accelerated thermal aging at 130 °C. However, there is a more serious exponential decline in the tensile strength (MPa) of insulation paper with its moisture content is boosted. The moisture content in insulation paper is the most important factor for insulation paper deterioration in oil-impregnated paper insulation equipment, which could accelerate the end of insulation service life. The value of capacitance increment ΔC of the insulation paper samples displayed closely linear growth with a moisture content from 0.5% to 5.9%. Strictly controlling the moisture content by monitoring the ΔC value of transformer insulation paper is of significance for prolonging its service life.

Influence of aging time on properties of passive film formed on chromium in 0.05 M H2SO4

Influence of aging time on properties of passive film formed on chromium in 0.05 M H2SO4

Experimental Study on Effects of Aging Time on Dry Shrinkage Cracking of Lime Soils.

The effect of aging on the internal mechanism of the dry shrinkage cracking of lime soil was studied from the perspective of macroscopic cracking phenomenon and microscopic composition change, and the reasonable aging time of lime soil was determined. Large numbers of cracks often occur in buildings constructed using lime soil, which impacts sustainable development and building environmental protection. This study explored the influence of aging time on the mechanical properties and shrinkage cracking of lime soil. The influence of aging time was evaluated using a triaxial compression test; using the dry–wet cycle, sieving, pH, and other tests, the influence of aging time on volume crack rate, expansion shrinkage rate, particle size distribution, and pH was analyzed. Scanning electron microscopy and X-ray diffraction experiments were used to analyze changes in the lime soil particle structure for different aging times and the formation of new substances. The results show that as aging time increases, the stress–strain curve of the soil softens significantly, shear strength deteriorates, and cohesion decreases. When the aging time is 6 h, the expansion rate and shrinkage rate at the center of the soil sample are the maximum. The volume fracture and expansion shrinkage rates decrease first, and then plateau with aging time, with the changes remaining stable after 72 h; these rate decreases are positively correlated with the change rate of pH. The formation of Ca(OH)2 affects the sample pH, and the changes in pH, Ca(OH)2, and CaO tend to be stable. With an increase in aging time, the proportion of particles of a size less than 0.1 mm decreases, and that of particles of size 0.1–0.5 mm increases. After 72 h of aging, the particle size proportion remains unchanged. Reasonable aging time can, thus, reduce the hydration reaction of lime, improve particle agglomeration effects, and reduce the crack development of the soil.

Influence of Aging Time at 850°C on Microstructure and Corrosion Resistance of a Cold Rolled 2205 Duplex Stainless Steel

Influence of Aging Time at 850°C on Microstructure and Corrosion Resistance of a Cold Rolled 2205 Duplex Stainless Steel

Research on the field aging gradient behavior of SBS-modified bitumen at different depths of pavement by rheological and microscopic characterization

This study investigated the aging behavior of styrene–butadienestyrene copolymer (SBS)-modified bitumen with different depth after exposure in the field. The SBS-modified bitumen after construction aging (CA), field aging for 1 year (1Y) and field aging for 5 years (5Y) was obtained and analyzed. Samples were divided into three layers (upper/middle/lower) according to depth. Dynamic shear rheometer (DSR), infrared spectroscopy (IR), bending beam rheometer (BBR) and fluorescence microscopy (FM) experiments were used to observe the trends and changes of the rheological properties and microscopic performance of SBS-modified bitumen with depth. The test results showed that in the CA stage, the SBS-modified bitumen had no aging gradient behavior in the depth direction. The SBS-modified bitumen had a gradient change with depth direction during the 1Y, but the gradient behavior had not evolved to the middle and lower layers. After 5Y the effects of deep aging behavior gradually emerged, showing a distinct gradient behavior. The molecular change characteristics of SBS modified bitumen showed obvious gradient behavior after 5Y, and the change trend was consistent with the aging trend of bitumen. Compared with the aging index of rheological properties, it was found that the most serious degree of aging was on 5Y-upper, followed by 1Y-upper, 5Y-middle and 1Y-middle. It can be seen that the influence of direct contact with aging factors on the degree of aging was greater than the influence of aging time on the depth of aging. Therefore, in the road maintenance process, only the milling surface could be considered for the restoration of the SBS modified bitumen pavement after 5 years of field aging.

Influence of Aging Time on Vertical Static Stiffness of Air Spring

To study the aging mechanism of air springs, the effect of aging time on the vertical static stiffness of an air spring was systematically analyzed by means of an accelerated aging test and finite element simulation. Accelerated aging tests were carried out on the entire air spring, rubber material, and cord material, and the vertical static stiffness and elastic moduli of the rubber and cord materials of the entire air spring were obtained with aging time. The finite element simulation model of the air spring was established. Based on the experimental data, the influences of the elastic moduli of the rubber and cord materials, aged for different times, and the cord angle on the vertical static stiffness of an air spring were simulated and analyzed, and the law of the influence of aging on the vertical static stiffness characteristics of air springs was revealed.

Influence of aging time on the corrosion behavior of 6061-T6 aluminum alloy in NaCl solution

Influence of aging time on the corrosion behavior of 6061-T6 aluminum alloy in NaCl solution

Influence of aging time, temperature and relative humidity on the sensory quality of dry-aged Belgian Blue beef

The objective of this study was to evaluate the effect of aging period (0, 3, 6 or 9 weeks), aging temperature (2 versus 6 °C at 75% relative humidity, experiment 1) and relative humidity (70 versus 90% at 2 °C, experiment 2) on the sensory traits, oxidative stability and proteolysis of Belgian Blue beef. For each experiment, eight loins (M. longissimus thoracis et lumborum) from four animals (left and right side) were assigned to one of the two treatments (n = 4). Results showed no further tenderization after three weeks of aging, whereas metmyoglobin formation and lipid oxidation increased until nine weeks of aging (P < 0.05). During the nine weeks of aging, atypical flavor, odor and flavor intensity was affected (P < 0.05). This was accompanied by an increase of small peptides and other nitrogenous compounds. Aging temperature and relative humidity had only a very limited effect on the quality traits.

Effects of aging treatment on the evolution of precipitated phase in CoCrFeNiTi0.6 high entropy alloys

In this study, the effect of aging time on the microstructure of precipitates in a face-centered cubic (FCC) CoCrFeNiTi0.6 high-entropy alloy (HEA) was investigated. The microstructure of precipitates was analyzed by SEM and TEM. The results showed that the CoCrFeNiTi0.6 alloy exhibited a typical dendritic structure, whose phase consisted of an ordered FCC solid-solution matrix (nanoscale L12-(Ni, Co)3Ti type particles) and intermetallic phases at 900 °C for different aging times. Meanwhile, the intermetallic compounds were composed of (Cr, Fe)-rich σ phases with a tetragonal structure and (Ni, Ti)-rich η phase with a long period stacking ordered (LPSO) structure. Additionally, the influence of aging time on the shape and structure of γ' precipitates was revealed. It was noticeable that the morphological transformation of nanoscale γ' precipitates evolved from an initially spheroidal to spheroidal-like shapes, following cuboidal-like shapes with flat edges, and finally, γ' precipitates with cuboidal shape were formed simultaneously with the appearance of the split with increasing aging time. Furthermore, the morphological evolution of γ' precipitates was quantitatively analyzed using a characteristic parameter's value of precipitates based on lattice misfit between the matrix and precipitates. This research would provide guidance for designing the precipitate structure in the L12-strengthened HEA and facilitate to establish the relationships between the microstructure of the precipitates and properties.

Influence of charging conditions on simulated temperature-programmed desorption for hydrogen in metals

Failures attributed to hydrogen embrittlement are a major concern for metals so a better understanding of damage micro-mechanisms and hydrogen diffusion within the metal is needed. Local concentrations depend on transport phenomena including trapping effects, which are usually characterised by a temperature-programmed desorption method often referred to as Thermal Desorption Analysis (TDA). When the hydrogen is released from the specimen during the programmed heating, some desorption peaks are observed that are commonly related to detrapping energies by means of an analytical procedure. The limitations of this approach are revisited here and gaseous hydrogen charging at high temperatures is simulated. This popular procedure enables attaining high concentrations due to the higher solubility of hydrogen at high temperatures. However, the segregation behaviour of hydrogen into traps depends on charging time and temperature. This process and the subsequent cooling alter hydrogen distribution are numerically modelled; it is found that TDA spectra are strongly affected by the charging temperature and the charging time, both for weak and strong traps. However, the influence of ageing time at room temperature after cooling and before desorption is only appreciable for weak traps.

Interfacial interactions between oleic acid and betaine molecules at decane-water interface: A study of dilational rheology

The interfacial interactions between organic acid and betaine molecules play an important role in reducing interfacial tension (IFT). To deeply detect the arrangements of organic acid and betaine molecules at the interface, the dilational rheological properties of mixed adsorption films formed by oleic acid and octadecyl carboxyl betaine (18PC) or octadecyl sulfobetaine (18PS) were investigated using drop shape analysis method at the decane-water interface. The influences of aging time, oscillation frequency and surfactants concentration were detected. The experimental results show that the properties of 18PC and 18PS adsorption film are controlled by both the fast diffusion-exchange process between the bulk and the interface and the slow re-arrangement process in the interface. 18PC film is tighter than that of 18PS because the size of carboxyl is small than sulfonyl. Oleic acid and betaine surfactants can form mixed adsorption films with less strength caused by the rapid transfer of oleic acid between the bulk and the interface, but more elastic due to the enhancement of the intermolecular interaction. In this case, the oleic acid molecules are easier to insert into the spaces between 18PS molecules on the interface, which results in a more tight mixed film than oleic acid/18PC film.

Influence of Aging Time on Microstructure and Corrosion Behavior of a Cu-Bearing 17Cr–1Si–0.5Nb Ferritic Heat-Resistant Stainless Steel

17Cr–1Si–0.5Nb–1.2Cu ferritic heat-resistant stainless steel was aged at 750 °C from 10 min to 30 h to simulate time aging and study the microstructural evolution and its effect on corrosion behavior by using optical microscopy, scanning electron microscopy, transmission electron microscopy, potentiodynamic polarization, electrochemical impedance spectroscopy, and the Mott–Schottky approach. Four types of precipitates were discovered, including ε-Cu, NbC, Fe3Nb3C, and Fe2Nb-type Laves phase. The nano-sized ε-Cu phase forms first, and its fraction follows the parabolic law change and is the largest. Compared to NbC and Fe3Nb3C particles, the coarsening of the Laves phase is the most pronounced. The aging process is divided into three parts: early-aged (0–5 h), peak-aged (5 h), and over-aged (5–30 h). However, the corrosion resistance is reduced in the early-aged stage of 0–2 h. Further extending the aging time to 30 h, the corrosion resistance is gradually improved. This change may be related to the competitive relationship between the beneficial effects of the Cu-rich phase and the harmful effects of Nb-containing particles. The dissolved Cu on the surface becomes more effective for the suppression of the anodic dissolution by the formation of ionic compounds of chlorine, thereby reducing the deterioration of corrosion resistance caused by Nb-rich precipitation.

Effect of Aging Time on Consistency Limits of Bentonites

The water contents of clay soils at liquid limit, plastic limit, and shrinkage limit are the three consistency limits and are used as fundamental index parameters for assessing the geotechnical behavior. The extensive application of highly plastic clays, such as bentonites, in the waste containment facilities and improvements in understanding of the double-porosity structure of plastic clays prompted the present work to relook into the determination of these consistency limits. The liquid limit water contents of three Indian bentonites were estimated using percussion and cone penetration tests; undrained shear strength at different clay-water interaction periods. The liquid limit water content obtained by the percussion method increased with the aging time. The variation in the liquid limit water contents with time was obtained for three different bentonites and mixtures of different percentages of sand and kaolinite. The results were analyzed based on the double-porosity hypothesis. The influence of aging time on the plastic limit and shrinkage limit was also observed. Simple linear equations were proposed to predict the equilibrium water contents at different consistency limits based on the routine testing that are valid for different plastic clays. Further, the significance of equilibrium consistency limits in understanding the soil–water characteristic relationships of the studied bentonites was presented.

CO2-induced asphaltene deposition and wettability alteration on a pore interior surface

CO2 enhanced oil recovery has a great potential to improve the rate of oil production and store carbon dioxide emission. However, CO2 injection can destabilize the asphaltene-oil colloidal system and thus favor severe asphaltene particle deposition in porous reservoir formation. These block reservoir pores and change pore wetting condition, finally damage the porous reservoir formation and significantly reduce oil production. A good understanding on CO2-induced asphaltene deposition at a pore scale is of significance for CO2-EOR processes. Few studies have directly investigated the asphaltene deposition behavior and asphaltene-induced pore wetting alteration on a pore interior surface in a confined pore. In this study, we directly measured the CO2-induced asphaltene deposition behavior on the interior surface of a single pore under high pressure and temperature. The particle size and particle size distribution of CO2-induced asphaltene deposition on pore interior surfaces were directly measured and analyzed, by considering the influences of aging time and temperature. The results indicate that long aging period and elevated temperature could favor CO2-induced asphaltene flocculation and deposition on pore interior surfaces. Finally, the pore-scale wetting alteration caused by asphaltene deposition was quantified by direct pore contact angle measurements.

Influence of Aging Time and Medium on Enclosed Mold Shear Bond Strength on Titanium

Influence of Aging Time and Medium on Enclosed Mold Shear Bond Strength on Titanium

Corona ageing characteristics of composite insulators based on orthogonal experiment

To study effects of pressure, humidity and aging time on the corona aging process, aging characteristics of silicone rubber composite insulators were researched by orthogonal tests. The test platform of adjustable pressure and humidity was constructed. TSC, SEM and FTIR tests were selected for aged samples. By the range analysis, it showed that the effect of pressure on trapped charges was related to humidity and aging time. There were more trapped charges when the humidity was higher, and the influence of humidity was more obvious along with the longer aging time at a low pressure. As the pressure increased, however, the effect of humidity on trapped charges was gradually reduced. But the influence of aging time was more significant, while aged degree of silicone rubber was deepened with increasing aging time. Furthermore, the aging state of materials was the collaboration effect of charged particles and nitric acid. Moreover, it could be seen from TSC, SEM and FTIR tests, sorting results of aging states were inconsistent. Results showed that the TSC test was comprehensively embodied the corona aging characteristics caused by physical and chemical defects. Therefore, results of TSC tests could be selected as an effective criterion for aging evaluations.

Effects of twin methyl groups insertion on the structure of templated mesoporous silica materials

In this paper, the effects of dimethyldiethoxysilane (DMDES) addition on the sol-gel process in preparation of mesoporous hybrid silicates containing twin methyl groups, were investigated. The materials were synthesized using tetraethoxysilane (TEOS) as silica source and DMDES as methyl groups precursor. All samples were prepared at low temperature in alkaline conditions using cetyltrimethylammonium bromide (CTAB) as a template. Obtained materials were characterized applying nitrogen adsorption/desorption, X-ray diffraction, HR TEM, FTIR, 29Si MAS NMR and Raman spectroscopy methods. The influence of aging time (from 5 min to 24 h) on the structure of samples containing 12% (mol/mol) of organic modifier was examined. Duration of synthesis significantly affected the material structure. The effect of added organosilicate amount (12%, 25% and 38%) on morphology and structure properties of prepared samples was also studied. The dimethylsilyl groups were successfully incorporated in wide range in the silica surface using presented short time sol-gel method.