Improving Thermal-oxidative Aging Resistance of Styrene-butadiene Rubber by Antioxidant Loaded Silica Aerogel

The antioxidant N-isopropyl-N'-phenyl-p-phenylenediamine(4010NA)was dissolved in ethanol and impregnated into silica aerogel(SAG)via vacuum-pressure cycles,yielding composite particles(A-N)with enhanced sustained-release and reinforcing capabilities.The effect of A-N on the mechanical properties and thermal-oxidative aging resistance of styrene-butadiene rubber(SBR)vulcanizates was investigated.TGA and BET assessments indicated that the loading efficiency of 4010NA in SAG reached 14.26%within ethanol's solu bility limit.Incorporating A-N into SBR vulcanizates significantly elevated tensile strength by 17.5%and elongation at break by 41.9%over those with fumed silica and free4010NA.Furthermore,A-N notably enhanced the thermal-oxidative aging resistance of SBR.After aging for 96 h at 100℃,the tensile strength and elongation at break of SBR with A-N sustained 70.09%and 58.61%of their initial values,respectively,with the retention rate of elongation at break being 62.8%higher than that of SBR with fumed silica and free antioxidant.The study revealed that A-N composite particles significantly inhibited the crosslinking in SBR's molecular chains,reducing hardening and embrittlement during later thermal-oxidative aging stages.

Evolution of mechanical properties,localized corrosion resistance and microstructure of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging

The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,intergranular corrosion test,exfoliation corrosion test,slow strain rate tensile test and electrochemical test,and the mechanism has been discussed based on microstructure examination by optical microscopy,electron back scattered diffraction,scanning electron microscopy and scanning transmission electron microscopy.The NIA treatment includes a heating stage from 40℃to 180℃with a rate of 20℃/h and a cooling stage from 180℃to 40℃with a rate of 10℃/h.The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston(GPI)zones toη'phase.During the cooling stage,the sizes ofη'phase increase with a little change in the number density,leading to a further slight increase of the hardness and strength.As NIA proceeds,the corroded morphology in the alloy changes from a layering feature to a wavy feature,the maximum corrosion depth decreases,and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.

Aging Resistance Evaluation of Aged Paper Reinforced with Different Nanocelluloses

Paper documents experience severe acidification and embrittlement.Nanocellulose is an excellent reinforcement material for paper documents owing to its compatibility and excellent mechanical strength.However,little research has been conducted on the aging resistance of nanocellulose-reinforced paper.In this study,six types of nanocelluloses were used to reinforce aged paper.The reinforcement and anti-aging performances were evaluated,and the anti-aging mechanism was further clarified.Nanocellulose with a high degree of polymerization can better enhance aged paper,and non-chemical nanocellulose also shows better anti-aging performance,such as nanocellulose prepared by mechanical or biological methods.However,nanocellulose prepared using chemical methods exhibits poor reinforcement and anti-aging performance.This is because it has a small particle size that is not beneficial for physical crosslinking with paper fibers.More importantly,the introduction of acidic or oxidizing groups on nanocellulose accelerates the acid hydrolysis and oxidation rate of paper fibers,especially nanocellulose prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation,which should not be used to protect paper documents.

How much resistance exercise is beneficial for healthy aging and longevity?

Regular physical activity(PA)promotes healthy aging,and activities aiming to increase muscular strength(i.e.,resistance exercise(RE))are important PA modalities for achieving health benefits.Previous meta-analyses demonstrated that both RE^(1) and muscular strength^(2) were associated with mortality benefits,even when RE was performed above the PA targets recommended by current guidelines^(1,3).

Effect of Organophilic Montmorillonite on Thermal-oxidative Aging Behavior of SBS Modified Bitumen Crack Filling Material

Styrene-butadiene-styrene （SBS） modified bitumen crack filling material with organophilic montmorillonite （OCFM） was prepared by melt blending. X-ray diffraction analysis shows that the interlayer spacing of organophilic montmorillonite （OMMT） in OCFM is widened and an exfoliated structure may be formed. Thermal-oxidative aging behavior of OCFM and SBS modified bitumen crack filling material （SCFM） was investigated. The experimental results indicate that the rate of thermal-oxidative aging of OCFM is much slower than that of SCFM, which can be attributed to barrier of exfoliated structure of OCFM to oxygen.

Preparation and Characterization of Lignosulfonate Intercalated Layered Double Hydroxides and Their Application in Improving Ultraviolet Aging Resistance for Bitumen

In order to develop economically anti-ultraviolet(UV) aging additives to bitumen and extend the comprehensive utilization of lignin materials, lignosulfonate(LS) was selected to intercalate into layered double hydroxides(LDHs), then the LS intercalated LDHs(LS-LDHs) were applied to improve UV aging resistance of bitumen. With the characterization of X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, chemical analysis and scanning electron microscopy(SEM), LS was successfully intercalated into the galleries of LDHs. The ultraviolet and visible(UV-vis) absorbance curves showed LS-LDHs had excellent UV absorptive ability from 200 to 400 nm. Thermogravimetry and differential scanning calorimetry(TG-DSC) indicated LS-LDHs could have a good thermal stability during the processing of bitumen. Compared with the LDHs, the LS-LDHs exhibited better performance in UV aging resistance of bitumen.

Effect of Yttrium on Aging Resistance of Zinc Alloy ZA-27

By metalloscopy,scanning electron microscope,X-ray diffraction,electron probe,salt water erosion and hot steam erosion,the microstructures and the aging resistance of zinc alloy ZA-27 with different contents of yttrium were studied. The results show that with optimum addition of yttrium in the alloy ZA-27 the fine YAl_3 phase forms. The fine YAl_3 granules can act as the condensation nuclei of α phase and the number of the α phase′s nuclei increases greatly and the growth of the nuclei comes in for restrict during the crystallization and the alloy′s grains become fine and the segregation reduces. In addition,yttrium also combines with zinc and the fine dispersion Y-Zn phase forms which improves grain boundary conditions and the alloy′s aging resistance. But when the content of yttrium is overmuch some YAl_3 granules grow to be lumpy,so the fine and close texture of the alloy′s boundaries is damaged and the proportion of the interface among the phases increase which brings a decline in the alloy′s resistance to corrosion.

Effect of Ce on the Aging of AlMgSi Alloy by Resistance Measurement

The AlMgSi wires with and without Ce were aged at temperatures 18, 30, 40, 50, 70, 100, 120 and 140 degrees C respectively after quenching from solid solution states, and their resistivity was measured in situ during aging. The results showed that the resistance of the samples aged at the temperatures given above except the one at 140 degrees C was increasing with aging time. The rate of increase was large initially and then reduced gradually. The relative resistance increases Delta R/R(0) of the samples with Ce were smaller than that without Ce under similar conditions. The result assumed to be due to reduction of the dispersion of G. P. zone by Ce.

A study on light-aging resistance of instrument panel materials and bumper materials on the automobile

The light-aging test method commonly used in the automotive industry is utilized to carry out light- aging research on automotive instrument panel （IP） materials and bumper materials. On one hand, the impacts of common light-aging test methods on aging degree of automotive component materials are reviewed; on the other hand, the light-aging resistances of different component materials are compared. The results show that, for light-aging behavior of IP materials, the aging degree of the third test method is not severer than that of the second method, but it is severer than that of the first method. The light-aging resistance of IP material A is al- most the same as that of IP material B. With reference to light-aging behavior of bumper materials, the aging de- gree of three common test methods indicates that the aging degree of the sixth test method is not severer than that of the fourth method, but it is severer than that of the fifth method. The light-aging resistance of bumper material D is superior to that of bumper material C.

Precipitation of metastable phases and its effect on electrical resistivity of Al-0.96Mg_2Si alloy during aging

The precipitation behavior and its influence on the electrical resistivity of the Al-0.96Mg2Si alloy during aging were investigated with in-situ resistivity measurement and transmission electron microscopy （TEM）. The precipitates of the peak aged alloy include both β＂ and if, but the amount ratio of β＂ to β＂ varies with the aging temperature and time increasing. The precipitates during aging at 175 ℃ are dominated by needle-like β＂ phases （including pre-β＂ phase）, the size of which increases with the time prolonging, but does not increase substantially after further aging. The evolution of electrical conductivity is directly related to such microstructural evolution. However, the hardness of the alloy stays at the peak value for a long term. When the alloy is aged at 195 ℃, the ratio of β＂ to β＇ becomes the main factor to influence relative resistivity （Ap） value. The higher the temperature is, the smaller the ratio is, and the faster the Ap value decreases. Moreover, the hardness peak drops with the decrease of the ratio. With the size and distribution parameters measured from TEM images, a semi-quantitative relationship between precipitates and the electrical resistivity was established.

Effect of Oils on SBS Modified Asphalt:Rheological Characteristics and Oxidation Aging

This study focuses on the effect of oils on rheology and oxidation aging of Styrene-Butadiene-Styrene modified asphalt(SBSMA)in the long term,after reducing one low-temperature Performance Grade(PG)of SBSMA by incorporating oils.Two oils,including corn-based bio-oil and re-refined engine oil bottom(REOB),were selected to enhance the low-temperature performance of SBSMA.All samples were subjected to Rolling Thin Film Oven(RTFO)aging and 20-h as well as 40-h Pressure Aging Vessel(PAV20 and PAV40)aging,prior to multiple stress creep recovery(MSCR),frequency sweep and Flourier transform infrared spectroscopy(FTIR)scanning.A good high-temperature performance of oil/SBS modified asphalt blends was reflected in MSCR and PG results,meanwhile non-recoverable creep compliance(Jnr)and recovery(R)were found to share a highly correlated relationship during aging progress.In addition,Glover–Rowe(G–R)parameter and phase angle master curves suggest that the improvement of cracking property mainly came from the softening effect of oils.Adding oils into SBSMA was observed to increase oxidation kinetics,but the blends with oils still exhibited better anti-oxidation aging than the base binder,mainly due to the SBS addition.Bio-oil exhibited an effect of relieving age hardening susceptibility of SBSMA.

Effect of secondary aging on microstructure and properties of cast Al-Cu-Mg alloy

To obtain better comprehensive properties of cast Al-Cu-Mg alloys,the secondary aging(T6I6)process(including initial aging,interrupted aging and re-aging stages)was optimized by an orthogonal method.The microstructures of the optimized Al-Cu-Mg alloy were observed by means of scanning electron microscopy and transmission electron microscopy,and the properties were investigated by hardness measurements,tensile tests,exfoliation corrosion tests,and intergranular corrosion tests.Results show that the S phase andθ’phase simultaneously exist in the T6I6 treated alloy.Appropriately increasing the temperature of the interrupted aging in the T6I6 process can improve the mechanical properties and corrosion resistance of Al-Cu-Mg alloy.The optimal comprehensive properties(tensile strength of 443.6 MPa,hardness of 161.6 HV)of the alloy are obtained by initial aging at 180℃for 2 h,interrupted aging at 90℃for 30 min,and re-aging at 170℃for 4 h.

锌电积用Pb-Ag阳极MnO_(2)镀膜的电化学性能

锌电积用Pb-Ag阳极存在析氧过电位高、表面铅易电化学氧化溶解,造成阴极电锌品质低等突出问题,如何减少阳极的溶铅污染并提升其催化析氧活性、降低反应能耗,成为亟待解决的难题。本文在Pb-Ag阳极表面电沉积一层均匀、致密的MnO_(2)薄膜,采用SEM、XRD和ICP等对MnO_(2)催化层的表面微观形貌、晶体结构和溶液含铅量进行分析;采用CV、LSV、EIS和Tafel等对Pb-Ag/MnO_(2)阳极的析氧催化活性和耐腐蚀性能进行分析。结果表明:在MnSO_(4)-H_(2)SO_(4)溶液中,当循环速率为200 mL/min、温度为80℃时,以4 mA/cm^(2)电沉积120 min制备的Pb-Ag/MnO_(2)镀膜电极具有最佳的催化析氧和耐蚀性能;PbAg阳极经优化镀膜后,50 mA/cm^(2)时其析氧过电位由936 mV降低为648 mV,腐蚀电流密度由7.03μA/cm^(2)降低至0.66μA/cm^(2);相较于Pb-Ag阳极,基于Pb-Ag/MnO_(2)阳极的15 d长周期电锌体系中溶铅量由0.61 mg/L降至0.29 mg/L。

Coarsening behavior of MX carbonitrides in type 347H heat-resistant austenitic steel during thermal aging

In this work, the growth kinetics of MX （M - metal, X - C/N） nanoprecipitates in type 347H austenitic steel was systematically studied. To investigate the coarsening behavior and the growth mechanism of MX carbonitrides during long-term aging, experiments were performed at 700, 800, 850, and 900℃ for different periods （1, 24, 70, and 100 h）. The precipitation behavior of carbonitrides in specimens subjected to various aging conditions was explored using carbon replicas and transmission electron microscopy （TEM） observations. The corresponding sizes ofMX carbonitrides were measured. The results demonstrates that MX carbonitrides precipitate in type 347H austenitic steel as Nb（C,N）. The coarsening rate constant is time-independent; however, an increase in aging temperature results in an increase in coarsening rate of Nb（C,N）. The coarsening process was analyzed according to the calculated diffusion activation energy of Nb（C,N）. When the aging temperature was 800-900℃, the mean activation energy was 294 kJ·mol -1, and the coarsening behavior was controlled primarily by the diffusion of Nb atoms.

Effect of aging temperature on the microstructures and mechanical properties of ZG12Cr9Mo1Co1NiVNbNB ferritic heat-resistant steel

The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant.The results show that the main precipitates during aging are Fe（Cr,Mo）23C6,V（Nb）C,and（Fe2Mo） Laves in the steel.The amounts of the precipitated phases increase during aging,and correspondingly,the morphologies of phases are similar to be round.Fe（Cr,Mo）23C6 appears along boundaries and grows with increasing temperature.In addition,it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization.The hardness and strength decrease gradually,whereas the plasticity of the steel increases.What＇s more,the hardness of this steel after creep is similar to that of other 9%-12%Cr ferritic steels.Thus,ZG12Cr9 MolColNiVNbNB can be used in the project.

电积锌用Pb-Ag/MnO_(2)涂层阳极制备及电化学性能

铅银合金(Pb-Ag)是锌电积及其它冶金工艺中应用最广泛的阳极材料。随着节能环保要求的逐渐提高,由于存在过电位低和稳定性差等缺点,Pb-Ag阳极难以适用于绿色工业体系的发展。如何提升其析氧催化活性、降低能耗并提高其耐腐蚀性能,成为亟待解决的工业难题。采用恒电流电沉积法在Pb-Ag阳极上制备了纳米二氧化锰薄膜涂层,测试了阳极的组织和电化学性能。研究表明:MnO_(2)涂层表面疏松裂纹结构不仅提高了催化活性,还促进了传质过程的进行,使得Pb-Ag/MnO_(2)阳极的析氧反应活性和稳定性均优于Pb-Ag阳极。其中,Pb-Ag/MnO_(2)阳极的析氧过电位为555 mV,塔菲尔斜率为208.5 mV/dec,优于Pb-Ag阳极的析氧过电位和塔菲尔斜率。同时,Pb-Ag/MnO_(2)阳极在长周期的电解锌实验中表现出良好的析氧反应活性和耐腐蚀性能,其槽电压比Pb-Ag阳极槽电压小0.1 V左右,能耗低于Pb-Ag阳极。

Ag/Cr_(2)AlC电接触材料的微观组织与耐电弧侵蚀性能

Ag基电接触材料被广泛应用于低压电路控制器件中,在电路中起承载、分断、闭合电流的作用。Cr_(2)AlC作为M_(n+1)AX_(n)相的典型代表之一,兼具金属和陶瓷的优良性能,有望成为Ag基电接触材料中优良的增强相。本项目采用粉末冶金法制备Ag/Cr_(2)AlC复合材料,表征其微观组织,探究其界面反应,并研究材料的物理性能和耐电弧侵蚀性能。结果表明,由于Al原子的弱结合,经烧结,Ag与Cr_(2)AlC发生明显的界面反应,生成Ag_(3)Al和Cr-C化合物。相比于生坯,Ag/Cr_(2)AlC熟坯的密度和硬度下降,分别为9.04 g/cm^(3)和(78.9±5.5)HV,且由于界面反应的发生,材料的电阻率为(141.9±0.4)×10^(-9)Ω·m。电弧侵蚀结果表明,Ag/Cr_(2)AlC材料经电弧侵蚀生成Al_(2)O_(3),Ag发生熔融喷溅,产生明显凸起,Ag/Cr_(2)AlC的质量损失为6.25%。

功能化MWCNTs/Ag对环氧涂料耐腐蚀和防污性能的影响

目的研究聚多巴胺(PDA)改性的MWCNTs/Ag复合材料(MWCNTs/Ag@PDA)对水性环氧树脂涂层结构、耐腐蚀性和防污性能的影响。方法首先制备MWCNTs/Ag复合材料,并利用聚多巴胺(PDA)对其进行改性,最后将不同的复合粉末加入水性环氧树脂中制备复合涂层,通过XRD、拉曼、XPS和SEM对不同粉末的形貌结构以及不同复合涂层的氮脆截面形貌进行分析。通过黏附力,EIS、极化以及抗三角褐指藻的防污测试对涂层的机械性、耐腐蚀性以及防污性能进行检测。结果MWCNTs成功负载纳米Ag颗粒,PDA对MWCNTs/Ag改性后,改善了MWCNTs/Ag在环氧树脂中的分散性。随着复合粉末填料的添加,涂层的黏附力升高,添加MWCNTs/Ag@PDA的复合涂层黏附力最高为4.29 MPa。在3.5%(质量分数)NaCl中浸泡28 d之后,空白涂层和添加MWCNTs/Ag的环氧涂层(MA/WEP)的耐腐蚀性能与浸泡初期相比都大幅下降,而添加MWCNTs/Ag@PDA的环氧涂层(MAP/WEP)没有变化。在三角褐指藻海水溶液中浸泡7d之后,MAP/WEP表面的海藻最少,且该涂层表面会释放Ag^(+),会破坏附着在涂层表面三角褐指藻结构的完整性,使其失活。结论PDA能够明显改善MWCNTs/Ag复合材料在环氧树脂中的分散性,且添加MWCNTs/Ag@PDA可以提升涂层的黏附力,增强涂层的耐腐蚀性能和防污性能。

添加不同含量Ga对新型SnInAg无铅焊料合金耐酸碱性的影响研究

为改进Sn-11In-1.5Ag无铅焊料合金焊料的耐蚀性,采用失重法和电化学实验研究了Sn-11In-1.5Ag-xGa(x=0,0.1,0.3,0.5,0.7,质量分数,%)焊料合金在腐蚀环境中的腐蚀行为。利用扫描电镜(SEM)观察Sn-11In-1.5Ag-xGa焊料合金的表面形貌,利用X射线衍射仪(XRD)对焊料表面的腐蚀产物进行表征。结果表明:无论是在酸性还是碱性溶液中,添加的Ga均能提高Sn-11In-1.5Ag焊料合金的耐蚀性。随Ga含量的增加,焊料的耐蚀性也随之增强。对于相同成分的焊料合金,其耐蚀性在碱性溶液中优于酸性溶液。SEM观察表明,在Sn-11In-1.5Ag合金中加入Ga可以明显减轻焊料的腐蚀程度。XRD分析表明,焊料合金在酸性和碱性溶液中的腐蚀产物均为In_(2)O_(3)。

VARIATION OF SUBSTRUCTURES OF PEARLITIC HEAT RESISTANT STEEL AFTER HIGH TEMPERATURE AGING

The observations of dislocations, substructures and other microstructural details were conducted mainly by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) for 12CrlMoV pearlitic heat-resistant steel. It is shown that during the high temperature long-term aging, the disordered and jumbled phase-transformed dislocations caused by normalized cooling are recovered and rearranged into cell substructures, and then the dislocation density is reduced gradually. Finally a low density linear dislocation configuration and a stabler dislocation network are formed and ferritic grains grow considerably.