Thermal Aging Conditions Research Articles

Mechanical and tribological performance of chopped basalt fiber/acrylonitrile–butadiene rubber composites

In this study, a series of basalt fiber (BF)/acrylonitrile–butadiene rubber (NBR) composites with various BF contents were prepared and evaluated. The effects of the BF content, thermal aging, and friction condition on tribological properties of the composites were the primary focus. The tribological performances of the composites were evaluated by DIN abrasion, Akron abrasion, and high‐speed block‐on‐ring tests, respectively. The results showed that with an increase in the BF content, for the DIN and Akron abrasion tests, the wear loss increased due to insufficient interactions between the BFs and the NBR matrix, whereas for the block‐on‐ring friction, both the friction coefficient and the wear loss of the composites decreased attributed to the effect of BF on transfer film formation on the polished counterpart surface. The thermal aging enhanced the wear resistance of the composites for all three friction conditions by improving the crosslinking density of the NBR matrix. POLYM. COMPOS., 40:630–637, 2019. © 2017 Society of Plastics Engineers

The growth behavior of interfacial intermetallic compound between Sn–3.5Ag–0.5Cu solder and Cu substrate under different thermal-aged conditions

The interfacial reaction, morphology, activation energies and growth behavior of interfacial intermetallic compounds (IMCs) between the Sn–3Ag–0.5Cu (in wt%) solder and Cu substrate during reflow at 280 °C for 10 min and aging at different temperatures for up to 360 h were investigated, and the growth kinetics of the interfacial Cu–Sn binary IMC layers were monitored during the isothermal aging. The results showed that the thickness of IMCs increased linearly with square root of aging time, and the diffusion coefficient related to the Cu–Sn IMC layer increased with increasing aging temperature. During aging at medium temperature (180 °C), the scallop-like Cu6Sn5 IMC layer at the SAC305/Cu interface gradually transformed into planar type with prolonged aging time. Nevertheless, in the case of high temperature (200 °C) aging, the solder/Cu6Sn5 interface became uneven because the Cu atoms came from the bulk solder would accumulate on the Cu6Sn5 IMC surface to directly thicken the existed IMC layer. Beside, the Kirkendall voids within Cu3Sn layer and the neighborhood of the Cu3Sn/Cu interface almost aggregated into continuous regions to formed micro-voids. The activation energies of the total Cu–Sn, Cu6Sn5 and Cu3Sn IMCs were obtained by plotting the diffusion constants (D) as a function of the aging temperature (1/T), and were 115.2, 122 and 98 kJ/mol, respectively.

Microstructure and properties of the space charge of LDPE under different thermal ageing conditions

Macroscopic experiment and microscopic molecular simulation were employed to study the ageing products, as well as the trap characteristic accumulation and dissipation characteristics, of the space charge of low-density polyethylene (LDPE) under different thermal ageing conditions. The obtained results indicate that carboxyl and ketone groups are generated during the ageing process of LDPE. The introduction of such groups increases the trap depth of the LDPE material from 0·98 to 1·31 eV. These deep traps enhance the accumulation but reduce the dissipation rate of space charge. Trap density increases with ageing time. Thus, the accumulation amount of space charge significantly increases, whereas the dissipation rate of space charge significantly decreases.

Effect of thermal ageing on space charge characteristics in double-layered polyester film

To understand the effect of thermal ageing mechanism on space charge formation and dissipation in double-layered polyester films (PET), the time dependence of space charge characteristics at physical interface and in the bulk of PET films have been investigated. The measurements of space charge characteristics in specimens of different thermal ageing conditions (80 and 130 °C) were conducted under different DC field strengths (polarization) and short circuit conditions (depolarization) using the Pulsed Electro Acoustic (PEA) measurement system. The influence of electric field distortion caused by the space charges on average AC breakdown strength of PET specimens was also investigated. Results indicate that the thermal ageing leads to polymer interface acts as positive charge traps at ageing temperature of 80 °C, but acts as electron traps at ageing temperature of 130 °C and provides deeper trapping level for positive charge carriers. Besides these, average breakdown strength of the composite decreases due to the electric field distortion caused by the space charges. A preliminary study of this phenomenon is given and further investigation is needed.

Combined Effect of Base Metal Dilution and Thermal Aging Conditions on the Corrosion Performance of Stainless Steel Claddings

Objectives: Present work investigates the effects of base metal dilution and the thermal aging treatment on corrosion performance and strength of stainless steel claddings, fabricated by gas metal arc welding process. Methods/Statistical Analysis: Austenitic stainless steel AISI SS 316L was selected as the cladding material and low carbon steel as substrate for the present study. Experimental conditions were selected to achieve a varying degree of dilution of the deposit. Thermal aging treatment was given to specimens at 700oC for 2 hours, 4 hours and 20 hours. The specimens were subjected to Double Loop Electrochemical Potentio Kinetic Reactivation (DLEPR), boiling nitric acid, and microhardness testing. Findings: Microhardness results of the clad deposits showed a continuous decrease in values from top of clad deposit to the base metal. However there is almost constant values of microhardness observed when it was measured along the clad deposit. Moreover the deposits with high dilution showed low microhardness values than that of low dilution clad beads. The low dilution clad deposits also performed better on testing the corrosion rate and degree of sensitization as compared to high dilution deposits. Corrosion rate measured from boiling nitric acid test showed a significant growth with increase of thermal aging time due to carbide precipitation. The corrosion rate of specimens in the as clad condition was as low as 0.19 mm/month which increased to 3.64 mm/month when sensitized for 20 hours at 700oC. Degree of sensitization (DOS) calculated by DLEPR test is more significantly affected by the thermal aging treatment. The DOS values varied from as low as 2.47 % to high as 31% for as clad and sensitized conditions respectively. Application/Improvements: The present study can beneficially be adopted for weld overlay fabrications as it suggests the processing conditions to forecast the adequate strength and corrosion performance of components in similar service conditions.

Microstructural evolution of Fe[sbnd]22%Cr model alloy under thermal ageing and ion irradiation conditions studied by atom probe tomography

Nanostructure evolution during ion irradiation of two thermally aged binary Fee22Cr alloys has been investigated using atom probe tomography. Specimens aged at 500 °C for 50 and 200 h were irradiated by 5.6 MeV Fe ions at room temperature up to fluences of 0.3 × 1015 ions/cm2 and 1 × 1015 ions/cm2. The effect of irradiation on the material nanostructure was examined at a depth of 1 μm from the irradiated surface. The analysis of Cr radial concentration functions reveals that dense α′-phase precipitates in the 200 h aged alloy become diffuse and thereby larger when subjected to irradiation. On the other hand, less Cr-enriched precipitates in the alloy aged for 50 h are less affected. The CreCr pair correlation function analysis shows that matrix inhomogeneity decreases under irradiation. Irradiation leads to a decrease in the number density of diffuse clusters, whereas in the case of well-developed precipitates it remains unchanged.

Effect of Yttrium on the Fracture Strength of the Sn-1.0Ag-0.5Cu Solder Joints

This is a preliminary investigation on the mechanical properties of Pb-free Sn-1.0Ag-0.5Cu solder joints containing 0.02 wt.% to 0.1 wt.% Y under a range of thermal aging and reflow conditions. Despite the significantly thicker intermetallic compound (IMC) formed at the solder joint, the 0.1 wt.% Y-doped joint exhibited a higher fracture strength than its baseline Sn-1.0Ag-0.5Cu counterpart under most aging and reflow conditions. This may be associated with the formation of Y-Cu IMCs formed at the interface between the solder and the Cu substrate, because the Y-Cu IMCs have recently been referred to as relatively ‘ductile’ IMCs.

Effect of Thermal Aging on Migration Characteristics of Heavy Metal in PET

Polyethylene terephthalate (PET) is usually used as food packaging materials. And the heavy metal introduced during the process of manufacture usually exists in the spaces between macromolecules as monomer form. When PET contacts with real food, some heavy metals will migrate into the food since the motion of these molecules overcomes the binding power. As a result, it does great harm to our health. In this article PET was disposed in different thermal ageing conditions in order to accelerate its aging process. Then the original and aged PET samples were tested by Different Scanning Calorimeter (DSC) to characterize its crystallinity. And migration experiments was conducted on them using 4% acetic acid (V/V) as food simulate, the heavy metal content in food simulates was detected by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), so that we can get the migration characteristics of heavy metal. The results show that different aging conditions can do harm to the structure of PET in varying degrees by changing its crystallinity and molecules arrangement. But the difference of crystallinity has no obvious effect on Sb migration characteristic of PET samples. While, the migration quantity of Sb increases significantly with the increase of migrate temperature. It will provide an important reference to the evaluation of use security and service life of PET in real usage to study the relation between heavy metal migration features and aging degree.

Migration Characteristics and Degradation Kinetics of Bisphenol A

This paper study the migration characteristics and degradation kinetics of bisphenol A using TGA - gas chromatography - mass spectrometry and found that bisphenol A polycarbonate in the thermal oxidative aging conditions of 130 °C de-gradated to bisphenol A. At the range of 0 h to 120 h, the bisphenol A content of environmental hormones increased with time. When it reached 120 h, bisphenol A environmental hormone content decreased slightly with aging time. The content of bisphenol A reached 495mg/kg when the thermal oxidative aging time was 168 h, which was decreased compared to the content of 442mg/kg at 120 h. Polycarbonate thermal decomposition kinetics study showed that the thermal decomposition of polycarbonate can be divided into three phases. The first thermal decomposition occurred at the range of 415° C to 425 ° C, the polycarbonate end groups fracture of the second stage at 493.6°C , the main fracture of the main chain rearrangement and crosslinking, and the third stage at 598.7°C, the degradation of the chain continues to decompose and the decomposition of the crosslinked carbon precursor; thermal oxidation aging of polycarbonate decreased the heat stability and promote the thermal decomposition of polycarbonate. Comparing the oxidation induction period, thermal weight loss rate and activation energy of polycarbonate before and after thermal oxidative aging, it c found that the thermal stability of the hot oxygen aging of polycarbonate is reduced.

Quasi‐Solid‐State Dye‐Sensitized Solar Cells Based on Ru(II) Polypyridine Sensitizers

AbstractThe Ru(II) polypyridine complexes SA22 and SA25 consisting of anchoring and light harvesting moieties and possessing broad light absorption spectra were used to fabricate and optimize dye‐sensitized solar cells (DSSCs). The highly efficient Z960 electrolyte was used as redox‐mediator, and the J–V characteristics and incident photon‐to‐current conversion efficiency (IPCE) data were measured. The solar cells based on these dyes and electrolyte yielded power conversion efficiencies (PCE) of 7 % using SA22 and 5 % with SA25. The higher‐performance sensitizer SA22 was selected to build solar‐cell devices, using either the high‐thermal‐stability Z946 electrolyte or a gel‐electrolyte composed of Z946 electrolyte and 2 wt % low‐molecular‐mass organogelator (LMOG) NME‐5. The quasi‐solid‐state electrolyte produced a DSSC with a PCE of 4.7 %, whereas that made using Z946 showed 5 % efficiency. The quasi‐solid‐state DSSC was sealed and a stability study was performed using accelerated thermal aging conditions at 70 °C for 7 days, by which the cell parameters (including PCE, Jsc, Voc, and FF) retained more than 90 % of their original values.

Effect of Ageing on Creep behaviour of IN 617 Nickel Base Super Alloy for Advanced USC Power Plant Applications

The goal of improving the efficiency of pulverized coal power plants has been pursued for decades. The need for greater efficiency and reduced environmental impact is pushing utilities to advanced ultra-supercritical conditions, i.e., steam condition up to 710/720 °C and 310 bar of pressure. The long-term creep strength with adequate thermal stability and environmental-resistance requirements imposed by these conditions are clearly beyond the capacity of the currently used ferritic steels and other related alloys. Nickel base alloys, such as IN617 super alloy is one of the preferred choices for steam turbine components used by fossil fuelled power generation plants. In this paper, effect of thermal ageing on creep behaviour of IN 617 nickel base super alloy were studied. Effect of thermal ageing on other mechanical properties such as tensile, yield and impact strength were also studied. Correlation between creep properties and microstructural changes, due to thermal ageing on IN 617 super alloy were also studied. Creep testing was carried out at different stress and temperatures for various thermal ageing conditions (800 and 850 °C) for different time durations and compared. The Alloy (IN 617) shows good thermal stability over long term aged condition with respect to creep strength. Less deterioration is observed in yield strength and tensile properties over long term ageing.

Thermal aging and reinforcement type effects on the tribological, thermal, thermomechanical, physical and morphological properties of poly(ether ether ketone) composites

In this study, thermal aging process was applied to glass fiber (GF) and carbon fiber (CF) reinforced poly(ether ether ketone) PEEK composites and effects of this process and reinforcement type on thermal, thermomechanical, tribological, physical and morphological properties of PEEK composites were evaluated. All the results demonstrated that a transcrystalline layer was formed between the fiber and matrix in the composites under applied thermal aging condition and this layer affected the fiber–matrix adhesion, reduced the energy dissipation in this region and improved the properties of composites. As a result of this study, it was proved that the thermal aging process is an efficient method to control the thermal, thermomechanical, tribological and physical properties of composites and these properties of composites can be improved by using this method.

Whisker growth behaviors in POSS-silanol modified Sn3.0Ag0.5Cu composite solders

Abstract As an ideal modifier, the cage-type polyhedral oligomeric silsesquioxane (POSS)-silanol creates a strong bonding with the solder without agglomeration. It has been shown that the addition of POSS-silanol improves both the mechanical performance and the solder's resistance to electromigration. This study further examined the effect of the addition of POSS-silanol on whisker growth in a Sn3.0Ag0.5Cu (SAC305) solder. The whisker growth was studied for pure SAC305 and SAC305 modified with POSS-silanol under isothermal aging and thermal cycling conditions. The results indicate that the added POSS-silanol not only reinforces the solder joint, but also inhibits whisker formation under both thermal aging and thermal cycling conditions. POSS-silanol can therefore be considered a promising modifier material which enhances the reliability of solders. During the thermal aging process, the added POSS-silanol was found to inhibit the interdiffusion of Sn and Cu atoms at the interface region, thereby preventing the formation of Cu 6 Sn 5 but promoting the conversion of Cu 6 Sn 5 into Cu 3 Sn. During the thermal cycling process, the added POSS-silanol significantly inhibited whisker formation and the deformation of the interface by stiffening the solder matrix and decreasing the driving force for whisker formation.

Reliability Performance of Palladium Coated Copper Wire in High Temperature Bake at Extreme Durations

New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C, or 1000 total hours at 175°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. Therefore, there is a need to evaluate the wire bond interconnect reliability to 2X AEC Grade 0 to assess the interconnect robustness. Palladium coated copper wire (Pd-Cu) was selected to be the wire of choice on aluminum bond pad for high reliability. Low Profile Quad Flat Pack with Exposed Pad (LQFP-EP) packages wire bonded with 20 micron Pd-Cu wire were submitted to high temperature baking (HTB) at 150°C and 175°C for 4032 and 2016 hours, respectively. This paper will discuss the results of electrical test, package deprocessing and wire pull testing, and cross-sectioning through the ball bonds to examine the welding region. Cu voiding within the bulk of the Cu ball bond, specifically close to the capillary chamfer squeezed region on top of the squashed ball, and at the ball edge interfacing with the intermetallic compound was found predominantly at 175°C bake. A trace of Sulfur was found inside the Cu corroding region. Sulfur compounds in mold compounds were examined. EFO current settings were evaluated in order to reduce the propensity to Sulfur corrosion in the Pd-Cu bond balls. Cu voiding is considered as cosmetic defect as it did not lead to electrical failures even at 2X AEC Grade 0 durations. Pd-Cu wire on aluminum bond pad forms very robust and reliable interconnect in extended thermal aging condition, including 4032 hour HTB-150°C and 2016 hour HTB-175°C, making it suitable for more demanding automotive mission profiles.

Chromium speciation methods and infrared spectroscopy for studying the chemical reactivity of lead chromate-based pigments in oil medium

Environmental factors, such as light, humidity and temperature are triggering agents for the alteration of organic and/or inorganic constituents of oil paintings. The oxidation of the organic material is favored by increasing of relative humidity and temperature, whereas processes involving changes of the oxidation states of a number of inorganic pigments (e.g., vermilion, cadmium yellows, zinc yellows, chrome yellows) are mainly activated by light-exposure.In view of the optimization of the long-term conservation and restoration strategies of paintings it is of relevant interest to establish the consequences of thermal parameters (temperature and relative humidity) on the chemical/photochemical-reactivity and the nature of the alteration products of light sensitive-pigments in oil medium.To this aim here we propose a multi-method analytical approach based on the combination of diffuse reflectance UV–Vis, FTIR, synchrotron radiation (SR)-based micro X-ray fluorescence (μ-XRF)/micro-X-ray absorption near edge structure (XANES) and electron paramagnetic resonance (EPR) spectroscopies for studying the effects of different relative humidity conditions before and after light exposure on the reactivity of a series of lead chromate-based pigments [such as PbCrO4∙PbO (monoclinic), PbCrO4 (monoclinic) and PbCr0.2S0.8O4 (orthorhombic)] in an oil medium. The investigation of paint models was also compared to that of a late 19th century historical orthorhombic PbCr0.4S0.6O4 oil paint.Diffuse reflectance UV–Vis and FTIR spectroscopies were used to obtain information associated with chromatic changes and the formation of organo-metal degradation products at the paint surface. SR-based Cr K-edge μ-XANES/μ-XRF mapping analysis and EPR spectroscopy were employed in a complementary fashion to determine the amount, nature and distribution of Cr(III) and Cr(V)-based alteration compounds within the paints with micrometric spatial resolution.Under the employed thermal aging conditions, lead(II)-carboxylates and reduced Cr-compounds (in abundance of up to about 35% at the surface) have been identified in the lead chromate-based paints. The tendency of chromates to become reduced increased with increasing moisture levels and was favored for the orthorhombic PbCr0.2S0.8O4 compounds. The redox process gave rise to the formation of Cr(V)-species in relative amount much higher than that was formed in the equivalent paint which was exposed only to light.After light-exposure of the thermally aged paints, compounds ascribable to the oxidation of the organic binder were detected for all the types of pigments. Nevertheless, the previous thermal treatment increased the tendency toward photo-reduction of only the PbCr0.2S0.8O4 pigment. For this light-sensitive compound, the thickness variation of the reduced Cr-rich (ca. 70%) photo-alteration layer with moisture levels could be ascribed to a surface passivation phenomenon that had already occurred before photochemical aging.

Effect of Thermal Aging on Microstructure and Mechanical Properties of P92 Steel

Microstructure and mechanical properties of P92 steel in the normalized and tempered, and thermal aged at 923 K for 5,000 h conditions have been investigated. Laves phase (size of ~0.160 µm) was observed in the thermal aged steel. Tensile tests were carried out at a strain rate of 3 × 10−4 s−1 and in the temperature range of 300–923 K. Both in the normalized and tempered, and thermal aged conditions, yield stress and ultimate tensile strength of the steels were found to decrease with increase in test temperatures. Tensile strengths of the thermal aged steel were decreased significantly in all test temperatures in comparison with normalized and tempered condition. Tensile strengths of thermal aged steel decreased due to sub-structure recovery and loss of solid solution strengthening from tungsten. Creep tests were conducted at 923 K in the stress range of 130–110 MPa. Lower creep rupture life has been observed in the thermal aged steel than normalized and tempered steel at higher stress level. Creep rupture life of thermal aged steel was comparable with steel in the normalized and tempered condition at lower stress levels. The presence of Laves phase precipitates in thermal aged steel has compensated the creep strength decrement due to loss of tungsten and sub-structure recovery in the steel.

Thermal aging effect on the ratcheting-fatigue behavior of Z2CND18.12N stainless steel

The uniaxial tensile and ratcheting-fatigue behaviors of the Z2CND18.12N austenitic stainless steel at room temperature were studied with different thermal aging periods (from 1h to 500h) at different thermal aging temperatures (500°C and 700°C). The thermal aging process resulted in apparent changes in the ratcheting behavior and the ratcheting-fatigue life. The precipitates under different thermal aging conditions were identified by SEM observation. Considering the deterioration of the material induced by thermal aging process, aging damage factor was introduced to predict the ratcheting-fatigue life, which resulted in good prediction for all the thermal aging conditions.

Analysis of partial discharge characteristics of natural esters as dielectric fluid for electric power apparatus applications

Petroleum based mineral oils are generally used for electric power apparatus insulation and cooling applications. Since the conventionally used mineral oils are not biodegradable and difficult to decompose, there is a need for the development of alternate vegetable based insulation oils for such applications. Formation of partial discharges plays a major role in determining the life time of liquid insulation. Reports on partial discharge characteristics of thermal aged natural ester fluids for high voltage applications are scanty. The major aim of this research work is to understand the partial discharge characteristics of natural esters as a dielectric fluid for power transformer and other electric power apparatus insulation applications. Laboratory experiments are performed as per IEC (International Electro technical Commission) test procedures in order to understand the breakdown voltage and partial discharge characteristics of vegetable oils such as corn oil and palm oil under both virgin and thermal aged conditions. This paper presents a comparative assessment of the PD characteristics of thermal aged natural ester fluids with respect to mineral oil. Time and frequency domain analysis of PD pulse at both needle-plane and rod-plane electrode configurations are studied. Statistical analysis of PD pattern is also carried out. This analysis collects the typical PD patterns from natural ester fluids in order to find its suitability for power transformer and electric power apparatus applications.

Tensile properties of Cu/Sn–58Bi/Cu soldered joints subjected to isothermal aging

The effects of isothermal aging on the tensile properties of Cu/Sn–58Bi/Cu soldered joints were investigated. Experimental results show that the scallop-shaped Cu6Sn5 and planar Cu3Sn formed at the interface between solder and Cu substrate during reflowing and aging. The thickness of the intermetallic compounds (IMCs) increased almost linearly with the square root of aging time, and aging at 120 °C yielded a much faster growth of the IMCs layer than that of samples aged at 100 °C. The IMCs growth rate constants were 6.02 × 10−18 and 1.85 × 10−18 m2 s−1 for solder joints aged at 120 and 100 °C, respectively. The tensile strength of the Sn–58Bi/Cu soldered joints decreased slightly with the increasing aging time and temperature. The failure was dominated by the mixed fracturing in both the solder and the Cu6Sn5 grains irrespective of their thermal aging conditions. However, the fracture pattern tended to transform from ductile to brittle with increasing aging time and temperature. The Bi segregation and voids were observed around the Cu/Cu3Sn interface as the long term aging at high aging temperature was carried out, which resulted in reduction of tensile strength of solder joints.

Stability of MX-type strengthening nanoprecipitates in ferritic steels under thermal aging, stress and ion irradiation

The stability of MX-type precipitates is critical to retain mechanical properties of both reduced activation ferritic–martensitic (RAFM) and conventional FM steels at elevated temperatures above ∼500°C. The stability of TaC, TaN and VN nanoprecipitates under thermal aging (600 and 700°C), creep (600°C) and ion irradiation (Fe ion, 500°C) conditions was systematically studied in this work. The statistical particle evolution in density and size was characterized using transmission electron microscopy. Nanoprecipitate stability under the studied conditions manifested differently through either dissolution, reprecipitation, growth or fragmentation, with TaC exhibiting the greatest stability followed by VN and TaN in sequence. Nanoprecipitate evolution phenomena and mechanisms and the apparent disagreement of this interpretation with published literature on the subject are discussed. These findings not only help understanding the degradation mechanisms of RAFM and conventional FM steels at elevated temperatures and under stress and irradiation, but should also prove beneficial to the development of advanced RAFM steels.