Effect of Accelerated Aging Temperature under Artificial Seawater on the Properties of Carbon Fiber/Epoxy Composites and the Erosion Mechanism

In order to explore the effect of artificial accelerated aging temperature on the performance of carbon fiber/epoxy resin composites,we used artificial seawater as the aging medium,designed the aging environment of seawater at different temperatures under normal pressure,and studied the aging behavior of carbon fiber/epoxy composites.The infrared spectroscopy results show that,with the increase of aging temperature,the degree of hydrolysis of the composite is greater.At the same time,after 250 days of aging of artificial seawater at regular temperature,40 and 60 ℃,the moisture absorption rates of composite materials were 0.45%,0.63%,and 1.05%,and the retention rates of interlaminar shear strength were 91%,78%,and 62%,respectively.It is shown that the temperature of the aging environment has a significant impact on the hygroscopic behavior and mechanical properties of the composite,that is,the higher the temperature,the faster the moisture absorption of the composite,and the faster the decay of the mechanical properties of the composite.

Microstructure evolution and nitrides precipitation in in-situ Ti_2 AlN/TiAl composites during isothermal aging at 900°C

Microstructures of Ti2AlN/TiAl composites prepared by in-situ method were characterized in in-situ and aging treatment conditions and the nitride precipitation was investigated in Ti2AlN/TiAl composites aged at 900 ℃ for 24 h after being heat treated at 1400 ℃ for 0.5 h. The in-situ composites consist of γ＋α2 lamellar colonies, equiaxed y grains and Ti2AlN reinforcements. Matrix with nearly fully lamellar structure formed after solution and subsequently aging treatment. With the increase of Ti2AlN content, the nearly fully lamellar structure becomes instable for the aged composites. According to TEM study, fine Ti2AlN precipitates are found to distribute at the grain boundaries of lamellar colony. Needle-like Ti3AlN precipitates arrange in line with growing axis parallel to [001] direction of the γ-TiAl matrix and another needle-like Ti3AlN precipitates with lager size distribute at the dislocations. Key words：

Ni-Ag双原子团簇催化甲烷干法重整反应的理论研究

甲烷干重整制合成气是将温室气体转换为合成气的有效途径,兼具环境效益和经济效益.本文采用密度泛函理论方法对Ni-Ag双原子团簇催化甲烷干重整反应的体系进行理论研究,对势能面上各驻点进行了全几何参数优化,通过频率分析确认了过渡态,并通过内禀反应坐标方法进行了验证,得出各基元反应的能量最低路径.研究结果对于理解在Ni上引入第二种金属Ag形成双原子团簇催化甲烷干法重整的理论研究有一定的意义,并为下一步实验研究提供理论基础.

Microstructural characterization and mechanical properties of friction surfaced AA2024-Ag composites

The effects of Ag on the microstructure, mechanical properties, and electrical conductivity of AA2024 aluminum alloy coating were investigated. It was fabricated by friction surfacing as an additive manufacturing process. To carry out this investigation, Ag was added by 5.3, 10.6, and 16.0 wt.% to an AA2024 consumable rod by inserting holes in it. It was found that due to the strengthening by solid solution and the formation of precipitates and intermetallic containing Ag, the driving force for grain growth is reduced and consequently the grain size of the coating is decreased. After artificial aging heat treatment, the electrical conductivities of the coatings containing 0 and 16.0 wt.% Ag are increased by 4.15%(IACS) and decreased by 2.15%(IACS), respectively. While considering a linear relationship, it can be proposed that for a 1 wt.% Ag increase, the strength and hardness of the coating will be increased by 1.8% and 1.0%, respectively. It was established that the effect of Al6(Cu,Ag)Mg4 precipitate formation on strengthening is greater than that of Ag-rich intermetallic.

Interfacial reactions between Sn-2.5Ag-2.0Ni solder and electroless Ni(P) deposited on SiC_p/Al composites

A novel Sn-2.5Ag-2.0Ni alloy was used for soldering SiCp/Al composites substrate deposited with electroless Ni(5%P) (mass fraction)and Ni(10%P)(mass fraction)layers.It is observed that variation of P contents in the electroless Ni(P)layer results in different types of microstructures of SnAgNi/Ni(P)solder joint.The morphology of Ni3Sn4 intermetallic compounds(IMCs)formed between the solder and Ni(10%P)layer is observed to be needle-like and this shape provides high speed diffusion channels for Ni to diffuse into solder that culminates in high growth rate of Ni3Sn4.The diffusion of Ni into solder furthermore results in the formation of Kirkendall voids at the interface of Ni(P)layer and SiCp/Al composites substrate.It is observed that solder reliability is degraded by the formation of Ni2SnP,P rich Ni layer and Kirkendall voids.The compact Ni3Sn4 IMC layer in Ni(5%P)solder joint prevents Ni element from diffusing into solder,resulting in a low growth rate of Ni3Sn4 layer.Meanwhile,the formation of Ni2SnP that significantly affects the reliability of solder joints is suppressed by the low P content Ni(5%P)layer.Thus,shear strength of Ni(5%P) solder joint is concluded to be higher than that of Ni(10%P)solder joint.Growth of Ni3Sn4 IMC layer and formation of crack are accounted to be the major sources of the failure of Ni(5%P)solder joint.

Magnetic Wakame-Based Biochar/Ni Composites with Enhanced Adsorption Performance for Diesel

In this study,the magnetic wakame biochar/Ni composites were prepared with three activating reagents of H_(3)PO_(4),ZnCl_(2) and KOH by one-step pyrolysis activation,characterized by BET,SEM,TEM,FI-IR,XRD,Raman,and elemental analyzer,and their adsorption performance for diesel were also analyzed.The results showed that wakame biochar/Ni composites had larger specific surface area,abundant porous structure,and various reactive groups,rendering its enhancement of adsorption efficiency.The adsorption experiments indicated that the maximum adsorption capacities for diesel using WBPA 0.5,WBHZ 0.5 and WBPH 0.5 were 4.11,8.83,and 13.47 g/g,respectively.The Langmuir model was more suitable for the adsorption isotherms process,and the Pseudo-second-order model could better describe the adsorption kinetic experimental.And the magnetic wakame biochar/Ni composites presented good stability and recyclability.This study provides a novel pattern for the high-value utilization of wakame,having huge potential in the treatment of oily wastewater.

Influence of thermomechanical processing on the structure and properties of Cu-Ag alloy in situ composites

The influences of the thermomechanical processing, including the solidification conditions, the cold deformation and the intermediate annealing treatment, on the structure and properties of the Cu-10Ag alloy in situ composite were studied in this paper. The cast structure and the structural changes in the cold deformation and intermediate annealing process were observed. The properties including the ultimate tensile strength (UTS) and the electrical conductivity were determined. A two-stage strain strengthening effect for the Cu-10Ag alloy in situ filamentary composite was observed. The factors influencing the UTS and conductivity were discussed. The solidification conditions in the range of 10-1000 K/s cooling rates and the intermediate heat treatment showed obviously influence on the structure and properties on the Cu-10Ag alloy in situ filamentary composite. The typical properties of the Cu-Ag alloy in situ filamentary composites through thermomechanical processing were reported.

Influence of Microstructure Refinement on Strain Strengthening Effect of Cu-Ag Alloy in situ Filamentary Composites

The Cu-10Ag and Cu-10Ag-RE （RE=Ce, Y） alloys in situ filamentary composites were prepared. The relationships of the ultimate tensile strengths （UTS） and microstructure changes of the composites were studied. With increasing of the true strain η, the sizes of the Ag filaments in the composites reduce according to a negative exponential function of η:d=d0·exp（-0.228η）, and the UTS of the composites increase also according to a exponential function of η, σ Cu/Ag=σ 0（Cu）+[k Cu/Agd0 -1/2]exp（η/3）, here d0 is a coefficient related to the original size of Ag phase. The strain strengthening follows a two-stage strengthening effect. The strengthening mechanisms are related to changes of microstructure in the deformation process. At the low true strain stage, the strengthening is mainly caused by the working hardening controlled by dislocation increasing; at the high true strain stage, the strengthening is mainly caused by the super-fine Ag filaments and the large coherent interfaces between the Ag filaments and Cu matrix. The trace RE additions and the rapid solidification obviously refine scales of the Ag filament of the composites, and therefore obviously increased the strain strengthening rate. The microstructure refinement of the composites, especially the refinement of Ag filament, is the main reason of the high strain strengthening effect in Cu-Ag alloy in situ filamentary composites.

Ternary Ag/AgCl/BiOIO_3 composites for enhanced visible-light-driven photocatalysis

Ternary Ag/AgC l/BiO IO3 composite photocatalysts are prepared by a facile method. Enhanced visible-light absorption and charge carrier separation are achieved after the introduction of Ag/AgC l particles into BiO IO3 systems,as revealed by ultraviolet-visible diffuse-reflectance spectrometry,photocurrent response and electrochemical impedance spectroscopy. The Ag/AgC l/BiO IO3 composites are applied to the visible-light photocatalytic oxidization of NO in air and exhibit an enhanced activity for NO removal in comparison with Ag/AgC l and pure BiO IO3. A possible photocatalytic mechanism for Ag/AgC l/BiO IO3 is proposed,which is related to the surface plasmon resonance effects of Ag metal and the effective carrier separation ability of BiO IO3. This work provides insight into the design and preparation of BiO IO3-based materials with enhanced visible-light photocatalysis ability.

WC-Ni_3Al-B composites prepared through Ni+Al elemental powder route

In order to develop the liquid phase sintering process of WC-Ni3Al-B composites,the preparation process of WC＋Ni3Al prealloyed powder by reaction synthesis of carbonyl Ni,analytical purity Al and coarse WC powders was investigated.DSC and XRD were adopted to study the procedure of phase transformation for the 3Ni＋Al and 70%WC＋（3Ni＋Al） mixed powders in temperature ranges of 550-1200 °C and 25-1400 °C,respectively.The results demonstrate that the formation mechanism of Ni3Al depends on the reaction temperature.Besides WC phase,there exist Ni2Al3,NiAl and Ni3Al intermetallics in the powder mixture after heat treatment at 200-660 °C,while only NiAl and Ni3Al exist at 660-1100 °C.Homogeneous WC＋Ni3Al powder mixture can be obtained in the temperature range of 1100-1200 °C.The WC-30%（Ni3Al-B） composites prepared from the mixed powders by conventional powder metallurgy technology show nearly full density and the shape of WC is round.WC-30%（Ni3Al-B） composites exhibit higher hardness of 9.7 GPa,inferior bending strength of 1800 MPa and similar fracture toughness of 18 MPa-m1/2 compared with commercial cemented carbides YGR45（WC-30%（Co-Ni-Cr））.

Microstructures,mechanical and oxidation behaviors of C/C composites modified by NiAl alloy

Carbon/carbon composites modified by NiAl alloy were prepared using vacuum reactive melt infiltration methods with NiAl and titanium mixed powders as raw materials. The microstructures were investigated by scanning electron microscopy. The fracture behavior, infiltration and oxidation mechanism were further discussed. The results indicated that NiAl alloy exhibited good wettability on the C/C preform because a TiC reaction layer formed at the interface. Multi-layer（PyC/TiC/NiAl＋TiC） coating evenly and compactly distributed on the surface of the carbon fiber in tubular form. The penetration depth of molten NiAl alloys depended on the reaction between the PyC and titanium. The impact fracture was inclined to along the interface between the NiAl permeability layer and C/C matrix. Al_2TiO_5 and TiO_2 formed on the surface, while the interior multi-layer tubular structure partially remained after oxidation at 1773 K for 30 min.

化学镀Ni-P/Sn2.5Ag0.7Cu0.1RE微连接焊点热时效过程组织与性能

为探究化学镀Ni-P无铅焊点在热时效作用下的组织与性能,采用化学镀方法在T2紫铜表面制备Ni-P层,使用Sn_(2.5)Ag_(0.7)Cu_(0.1)RE钎料通过回流焊方法制备化学镀Ni-P无铅焊点。结果表明:微焊点Ni-P/钎缝过渡区域金属间化合物(IMC)初始组织为呈块状的(Ni,Cu)_(3)Sn_(4),平均厚度为1.5μm。在180℃条件下时效100 h过程中,微焊点Ni-P/钎缝过渡区(Ni,Cu)_(3)Sn_(4)IMC形貌逐渐转变为层状并增厚至3.3μm,微焊点剪切断裂位置由钎缝处向Ni-Sn-P/IMC交界处转移,断裂方式由韧性断裂转变为脆性断裂,相应微焊点的推剪力由初始的16 N下降11.9%。

含Ag@Ni核壳结构粉体镍基复合涂层的多循环高温摩擦学性能

为了抑制Ag的扩散,采用化学镀方法制备Ag@Ni核壳结构粉体,并利用大气等离子喷涂技术制备NiCrAlY-Mo-Ag@Ni涂层,详细研究核壳结构设计对涂层在高温循环工况下的力学及摩擦学性能的影响。研究结果表明:Ag的核壳结构设计可以提高镍基涂层中Ag与NiCrAlY的界面结合强度,进而显著提高复合涂层的硬度。Ni覆层有效地抑制了Ag在高温摩擦过程中的扩散与耗散。800℃时NiCrAlY-Mo-Ag@Ni涂层的摩擦因数仅为0.25,磨损率仅为1×10^(-5)mm^(3)/(N·m),显著低于NiCrAlY-Mo-Ag涂层。同时,Ag的核壳结构设计使得涂层在高温多循环工况下始终保持良好的自润滑性和耐磨性。

基于ICP的Ar等离子体干法刻蚀Ti/Ni/Ag薄膜

在电感耦合等离子体(ICP)刻蚀工艺中,选择合适的刻蚀条件对Ti/Ni/Ag薄膜的刻蚀至关重要。使用氩气(Ar)作为刻蚀气体,研究了射频偏压功率、气体体积流量、腔体压强、刻蚀时间等多个参数对功率芯片背面Ti/Ni/Ag薄膜刻蚀深度的影响,并优化刻蚀工艺参数。实验结果表明,调节射频偏压功率和Ar体积流量可以显著影响刻蚀速率,进而对薄膜的微结构进行有效调控。通过优化工艺参数,在射频偏压功率300 W、Ar体积流量40 cm^(3)/min、腔体压强1.2 Pa、刻蚀时间50 min下,芯片Ti/Ni/Ag薄膜的刻蚀深度达到283.25μm,有效提升了刻蚀效率和刻蚀精度。

Ag-Ni/KCC-1的制备及其在草酸二甲酯加氢制乙醇酸甲酯中的催化性能

针对草酸二甲酯(DMO)加氢制备乙醇酸甲酯(MG)反应中,银(Ag)基催化剂成本较高、催化性能不稳定等问题,为降低成本并提高催化性能,以水热合成法制备的树枝状纤维形二氧化硅纳米球(KCC-1)为载体,采用等体积浸渍法制备Ag/KCC-1、Ag-Ni/KCC-1负载型催化剂。考察了Ag的较优负载量及总负载量不变时,Ag与镍(Ni)较佳的质量比。结果表明,Ag/KCC-1催化剂中,不同Ag负载量的催化剂,其结构和催化性能均有所不同,Ag负载量(质量分数)为15%时,性能较好;Ag-Ni/KCC-1催化剂中,适量Ni的引入对催化剂的结构和催化性能均有明显提高,当Ag和Ni的负载量分别为12%和3%时,催化性能较佳,与单组分负载的Ag/KCC-1催化剂相比,DMO转化率由90.37%提高至96.75%,MG转化率由90.77%提高至92.48%,MG收率由82.04%提高至89.47%。

Effects of intermediate Ni layer on mechanical properties of Al–Cu layered composites fabricated through cold roll bonding

Layered composites have attracted considerable interest in the recent literature on metal composites. Their mechanical properties depend on the quality of the bonding provided by the intermediate layers. In this study, we analyzed the mechanical properties and bond strengths provided by the nickel layer with respect to its thickness and nature(either powder or coating). The results suggest that bond strength decreases with an increase in the content of nickel powder. At 0.3 vol% of nickel coating, we found the nature of nickel to be less efficient in terms of bond strength. A different picture arose when the content of nickel was increased and the bond strength increased in nickel coated samples. In addition, the results demonstrate that mechanical properties such as bend strength are strongly dependent on bond strength.

TiC-Maraging stainless steel composite:microstructure, mechanical and wear properties

Particulate TiC reinforced 17-4PH and 465 maraging stainless steel matrix composites were processed by conventional powder metallurgy （P/M）. TiC-maraging stainless steel composites with theoretical density 〉97% were produced using conventional P/M. The microstructure, and mechanical and wear properties of the composites were evaluated. The microstructure of the composites consisted of （core-rim structure） spherical and semi-spherical TiC particles depending on the wettability of the matrix with TiC particles. In TiC-maraging stainless steel composites, 465 stainless steel binder phase showed good wettability with TiC particles. Some microcracks appeared in the composites, indicating the presence of tensile stresses in the composites produced during sintering. The typical properties, hardness, and bend strength were reported for the composites. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was at- tributed to the aging reaction in maraging stainless steel. The specific wear behavior of the composites strongly depends on the content of TiC particles and their interparticle spacing, and on the heat treatment of the maraging stainless steel.

Ag-Ni-La_(2)Sn_(2)O_(7)复合材料在不同气氛中的耐电弧烧蚀性能及机理

采用化学共沉淀法制备了La_(2)Sn_(2)O_(7)粉末,并使用真空热压烧结法制备出Ag-Ni-La_(2)Sn_(2)O_(7)(85∶12∶3)复合材料。分别在空气、N_(2)和SF_(6)气氛中对Ag-Ni-La_(2)Sn_(2)O_(7)复合材料进行电弧烧蚀实验,通过热场发射扫描电镜(SEM)和三维激光共聚焦扫描显微镜(3D LSCM)对复合材料烧蚀后的表面形貌进行分析,使用能谱仪(EDS)和X射线光电子能谱(XPS)对烧蚀后的样品成分进行分析。分析了Ag-Ni-La_(2)Sn_(2)O_(7)复合材料在不同气氛中的电弧烧蚀行为及机理。结果表明:Ag-Ni-La_(2)Sn_(2)O_(7)复合材料在空气和N_(2)气氛中烧蚀区域面积大、表面起伏小,在SF_(6)气氛中烧蚀区域面积显著缩小,伴随的是表面起伏程度增大。在空气气氛中电弧烧蚀后金属元素均被氧化,生成Ag_(2)O、NiO、La_(2)O_(3)和SnO_(2),在N_(2)气氛中由于O~(2-)不足,电弧烧蚀后生成La_(2)O_(3)、NiO和部分SnO_(2),剩余部分Sn和Ag保持金属态,在SF_(6)气氛中电弧烧蚀后金属元素被氟化,生成AgF、NiF_(2)、LaF_(3)和SnF_(4)。

Wetting of molten Sn-3.5Ag-0.5Cu on Ni-P(-SiC) coatings deposited on high volume faction SiC/Al composite

The wetting of molten Sn-3.5Ag-0.5Cu alloy on the Ni-P(-SiC)coated SiCp/Al substrates was investigated by electroless Ni plating process,and the microstructures of the coating and the interfacial behavior of wetting systems were analyzed.The SiC particles are evenly distributed in the coating and enveloped with Ni.No reaction layer is observed at the coating/SiCp/Al composite interfaces.The contact angle increases from^19°with the Ni-P coating to 29°,43°and 113°with the corresponding Ni-P-3SiC,Ni-P-6SiC and Ni-P-9SiC coatings,respectively.An interaction layer containing Cu,Ni,Sn and P forms at the Sn-Ag-Cu/Ni-P-(0,3,6)SiC coated SiCp/Al interfaces,and the Cu-Ni-Sn and Ni-Sn-P phases are detected in the interaction layer.Moreover,the molten Sn-Ag-Cu can penetrate into the Ni-P(-SiC)coatings through the Ni-P/SiC interface and dissolve them to contact the SiCp/Al substrate.

Sn和Ni对过冷Ag-28.1Cu共晶合金凝固组织的影响

为了揭示在共晶相中具有不同固溶度的Sn和Ni元素对过冷共晶凝固组织的影响和作用机理,使用熔融玻璃净化和循环过热相结合的方法制备了过冷Ag-28.1Cu-xM(x=0%0.5%、1%,质量分数;M=Sn,Ni)共晶合金试样,分析了第3组元Sn和Ni对过冷Ag-Cu共晶合金凝固组织的影响。结果表明添加Sn元素不会改变宏观组织的分区特征,微观组织中出现反常共晶增多和粗化的现象,并具有随机的取向分布。凝固过程中Sn会形成垂直于固-液界面的浓度梯度,造成胞状界面失稳形成树枝状,但仍能够维持耦合共晶生长。而添加Ni元素会使宏观组织的分区特征消失,微观组织中则出现了单相枝晶,且表现出单一取向分布,原因是第3组元Ni平行于固-液界面扩散,使共晶合金生长方式从耦合生长转变为离异生长。