Crystal growth in Bi–Sr–Ca–Cu–O system

We report growth of Bi₂Sr₂CaCu₂O_8+δ single crystals with dimensions of 6×2×0.03 mm³ using a melt and growth technique. The oxygen content is determined to be δ≈0.13 by iodometric titration. The crystal is shown to be homogeneous and close to stoichiometric cation ratio. The superconducting temperature with a sharp transition width (10–90% level) of 6–8 K was determined to be T_c=92 K from resistivity and dc susceptibility measurements. The predominant impurity phase is a Cu-free crystal, whose composition is identified as Bi₁₀Sr₁₁Ca₅O_x. The crystal structure of Bi₁₀Sr₁₁Ca₅O_x is monoclinic with a=11.108(1) Å, b=5.9487(1) Å; c=19.838 (3) Åand β=101.5° (P2_1/c space group).     

Matrix-type effect on the magnetotransport properties of Ni–AlO and Ni–NbO composite systems

The effect of the insulating-matrix material on the electronic and magnetic properties of nanocomposites is investigated in the Ni_x(Al₂O₃)_100–x metal–insulator system and the Ni_x(Nb₂O₅)_100–x metal–semiconductor system. It is established that the characteristics of composites determined by electron transport through the matrix (the electrical resistivity, the position of the electrical percolation threshold, the magnetoresistance effect) depend on the material type. Replacement of the matrix from Al₂O₃ to Nb₂O₅ results in a decrease in the electrical resistivity by two–three orders of magnitude, a decrease in the magnetic resistivity by more than an order of magnitude, and in displacement of the percolation threshold from 40 to 30 at % of Ni. In this case, the magnetic properties of the composites are independent of the type of matrix: the concentration of the magnetic percolation threshold is identical in the two systems (~45 at % of Ni), and the coercive force of the samples occurring beyond the percolation threshold is close in magnitude (5–8 and 12–18 Oe) in the Ni_x(Nb₂O₅)_100–x and Ni_x(Al₂O₃)_100–x composites, respectively.     

Interface Reaction Between Electroless Ni–Sn–P Metallization and Lead-Free Sn–3.5Ag Solder with Suppressed Ni3P Formation

The voids formed in the Ni₃P layer during reaction between Sn-based solders and electroless Ni–P metallization is an important cause of rapid degradation of solder joint reliability. In this study, to suppress formation of the Ni₃P phase, an electrolessly plated Ni–Sn–P alloy (6–7 wt.% P and 19–21 wt.% Sn) was developed to replace Ni–P. The interfacial microstructure of electroless Ni–Sn–P/Sn–3.5Ag solder joints was investigated after reflow and solid-state aging. For comparison, the interfacial reaction in electroless Ni–P/Sn–3.5Ag solder joints under the same reflow and aging conditions was studied. It was found that the Ni–Sn–P metallization is consumed much more slowly than the Ni–P metallization during soldering. After prolonged reaction, no Ni₃P or voids are observed under SEM at the Ni–Sn–P/Sn–3.5Ag interface. Two main intermetallic compounds, Ni₃Sn₄ and Ni₁₃Sn₈P₃, are formed during the soldering reaction. The reason for Ni₃P phase suppression and the overall mechanisms of reaction at the Ni–Sn–P/Sn–3.5Ag interface are discussed.     

IMC Growth at the Interface of Sn–2.0Ag–2.5Zn Solder Joints with Cu,Ni, and Ni–W Substrates

Growth of intermetallic compounds (IMC) at the interface of Sn–2.0Ag–2.5Zn solder joints with Cu, Ni, and Ni–W substrates have been investigated. For the Cu substrate, a Cu₅Zn₈ IMC layer with Ag₃Sn particles on top was observed at the interface; this acted as a barrier layer preventing further growth of Cu–Sn IMC. For the Ni substrate, a thin Ni₃Sn₄ film was observed between the solder and the Ni layer; the thickness of the film increased slowly and steadily with aging. For the Ni–W substrate, a thin Ni₃Sn₄ film was observed between the solder and Ni–W layer. During the aging process a thin layer of the Ni–W substrate was transformed into a bright layer, and the thickness of bright layer increased with aging.     

Interfacial reactions of Sn–58Bi and Sn–0.7Cu lead-free solders with Alloy 42 substrate

Eutectic Sn–58 wt%Bi (SB) and Sn–0.7 wt%Cu (SC) lead-free solders reacting with Alloy 42 substrates were investigated at 240, 270, 300, and 330 °C for various reaction times. The FeSn₂ phase was the only phase formed at the solder/Alloy 42 interface for all couples. However, this FeSn₂ phase had two different microstructures. The intermetallic compound (IMC) morphology near the solder/Alloy 42 interface was dense with a tiny microstructure after reflowing at 240 °C. Massive spalling FeSn₂ phases with large and platy grain were observed in the solder matrix. When the reflow temperature was increased the IMC morphology assumed bulk or cylindrical shape with no spalling IMCs observed at the solder/Alloy 42 interface. The IMC thickness increased with increasing reaction temperature and time. Both SB/Alloy 42 and SC/Alloy 42 couples presented a diffusion controlled growth mechanism in. The activation energies for SB/Alloy 42 and SC/Alloy 42 couples were 86.2 and 103.4 kJ/mol, respectively.     

Effects of Cu on the interfacial reactions between Sn–8Zn–3Bi–xCu solders and Cu substrate

The microstructure, thermal property, and interfacial reaction with Cu substrate of Sn–8Zn–3Bi–xCu (x = 0, 0.5, 1) lead-free solders were investigated in this work. Cu–Zn intermetallics formed in the solder matrix and the melting temperature increases slightly with Cu addition. After soldering at 250 °C for 90 s, a flat Cu₅Zn₈ layer and a scallop CuZn₅ layer formed at the interfaces of all samples. The CuZn₅ intermetallic compound (IMC) transformed to Cu₅Zn₈ IMC with longer reaction time due to the diffusion of Cu atoms from Cu substrate. The interfacial IMC layer grew thicker with the reaction time following a parabolic law which suggested the interfacial reactions were diffusion controlled. The calculation results show that the activation energy of IMC growth for Cu-containing solders is larger than that of Sn–8Zn–3Bi solder, which demonstrated that a small amount of Cu addition to the solder can effectively suppressed the growth of the interfacial IMC.     

Impact of Ni concentration on the intermetallic compound formation and brittle fracture strength of Sn–Cu–Ni (SCN) lead-free solder joints

Cu₆Sn₅ and Cu₃Sn are common intermetallic compounds (IMCs) found in Sn–Ag–Cu (SAC) lead-free solder joints with OSP pad finish. People typically attributed the brittle failure to excessive growth of IMCs at the interface between the solder joint and the copper pad. However, the respective role of Cu₆Sn₅ and Cu₃Sn played in the interfacial fracture still remains unclear. In the present study, various amounts of Ni were doped in the Sn–Cu based solder. The different effects of Ni concentration on the growth rate of (Cu, Ni)₆Sn₅/Cu₆Sn₅ and Cu₃Sn were characterized and compared. The results of characterization were used to evaluate different growth rates of (Cu, Ni)₆Sn₅ and Cu₃Sn under thermal aging. The thicknesses of (Cu, Ni)₆Sn₅/Cu₆Sn₅ and Cu₃Sn after different thermal aging periods were measured. High speed ball pull/shear tests were also performed. The correlation between interfacial fracture strength and IMC layer thicknesses was established.     

微量Ag、Bi、Ni对无铅微焊点固-液界面扩散的影响

为了获得微量元素Ag、Bi、Ni对无铅微焊点固-液界面扩散行为的影响规律,以低银无铅微焊点Cu/SAC0705+Bi+Ni/Cu为主要研究对象,并与Cu/SAC0705/Cu及高银钎料Cu/SAC305/Cu进行对比。研究了三种成分焊点固-液扩散后界面IMC的生长演变行为,并分析了Ag、Bi、Ni对微焊点固-液扩散的影响。研究结果表明:钎料中微量元素Ag、Bi、Ni添加可细化界面IMC晶粒,对提高界面强度有利。长时间的固-液时效过程中,界面IMC的生长速率主要取决于界面IMC的晶粒尺寸。Cu/SAC0705+Bi+Ni/Cu焊点界面IMC晶粒尺寸最小,界面IMC生长速率最大,为11.74μm/h。Cu/SAC0705/Cu焊点界面IMC晶粒尺寸最大,界面IMC生长速率最慢,其数值为1.24μm/h。     

Cruciform Pattern of Ni5Zn21 Formed in Interfacial Reactions Between Ni and Sn–Zn Solders

A unique cruciform pattern was observed for the Ni₅Zn₂₁ phase formed in both liquid-state and solid-state interfacial reactions between rectangular Ni substrate and both Sn–9 wt.%Zn and Sn–80 wt.%Zn. In these reactions, the Ni₅Zn₂₁ layers were uniformly formed at the interfaces. However, the Ni₅Zn₂₁ layer ruptured near the edges of the rectangular Ni substrate and the reaction layers were discontinuous. The cruciform pattern was closely correlated with linear growth of the Ni₅Zn₂₁ phase and the tensile stress generated because of the edge geometry. The liquid-state reaction between Sn–9 wt.%Zn and Ni resulted in a crescent shape at the edges because Ni₅Zn₂₁ growth was enhanced, owing to its linear growth. Most importantly, cruciform pattern formation also occurred in the solid-state reactions between Sn–Zn and Ni. In the liquid-state reaction between Sn–80 wt.%Zn and Ni, a porous structure and unusually fast growth at the acute-angled corner were observed. The reactions between Cu and Sn–9 wt.%Zn and Sn–80 wt.%Zn were also studied. For these, in contrast, parabolic growth was observed. The reaction layer was uniformly formed at the corners of the Cu substrate, leading to complete coverage.     

Microstructure,shear strength,and nanoindentation property of electroplated Sn–Bi micro-bumps

In order to investigate the microstructure and mechanical properties of small sized Sn–Bi bump, the eutectic Sn–Bi bumps with a diameter of 25 μm and a height of less than 20 μm after reflow were fabricated by electroplating and reflow. The reflow temperature of the Sn–Bi bumps was 170 °C, and the reflow times were varied from 5 to 20 min. The experimental results showed that a eutectic Sn–Bi composition was obtained by plating at a current density of 30 mA/cm² for 15 min. The average height and diameter of the bumps reflowed for 5 min were 16.1 ± 0.7 μm and 25.2 ± 0.7 μm, respectively. The microstructure of the reflowed bumps consisted of Sn- and Bi-rich phases. The thickness of the IMC of Cu₆Sn₅ increased from 1.17 to 2.25 μm with increasing reflow time from 5 to 20 min. The shear strength of the reflowed Sn–Bi bump increased with increasing reflow time, and reached approximately 11 gf at 15 and 20 min. The elastic modulus and hardness of eutectic Sn–Bi bump by nanoindentation were 53.5 and 0.43 GPa. Those of Cu₆Sn₅ were found to be 121.1 and 6.67 GPa.     

Effect of Nonlinearity of the Phonon Spectrum on the Thermal Conductivity of Nanostructured Materials Based on Bi–Sb–Te

A theoretical investigation of the lattice thermal conductivity of nanostructured materials based on Bi–Sb–Te is presented. The calculations were based on relaxation time approximation and took into account both the real phonon spectra, obtained from first-principles by use of density functional theory, and the anisotropy of phonon relaxation time. Phonon relaxation time data were determined from experimental values of the lattice thermal conductivity. The decrease of the thermal conductivity caused by the nanostructure was compared with results from calculations based on the linear Debye approach. Estimation showed that phonon boundary scattering can lead to a 55% decrease of thermal conductivity for a grain size of ~20 nm in the Debye approximation. Taking the nonlinearity of the acoustic phonon spectrum into account leads to a 20% larger decrease of the thermal conductivity because of boundary scattering. The reason is that consideration of the real phonon spectrum increases the relative contribution to thermal conductivity of acoustic phonons with low frequencies that are scattered more strongly at nanograin boundaries. Similarly, estimation of lattice thermal conductivity reduction as a result of phonon scattering by nanoinclusions gave an 8% larger decrease when the real phonon spectrum was used rather than the linear Debye approximation. For such a substantial decrease of lattice thermal conductivity, the effect of the optical phonons was estimated; it was shown that optical phonons can reduce the change of thermal conductivity as a result of grain boundary scattering by no more than 10%. Finally, the minimum lattice thermal conductivity was estimated to be 0.07 W/m K because of acoustic modes (0.09 W/m K in the Debye approach) and 0.14 W/m K when the contribution of optical modes was also taken into consideration.     

13～14 nm区类Ni氙跃迁X光激光器研究

1 引言目前正积极研究13~14nm区真空紫外激光振荡的可能性，因为在该波长区发展了反射率达到60%的多层膜反射镜的制造方法[1~3]。该区较强激光可用于微光刻、X射线显微术和生物技术等。最近几年正在探讨建立真空紫外激光器的新实验途径。例如，研究了在脉宽0.9~10 ns、能量~0.7 J的Nd∶YAG激光抽运的所谓气体-喷团靶内1~22 nm区的强辐射[4]。这种“光火花等离子体”源早在70年代初讨论过[5]。目前它是为了在1~5nm区产生激光辐射的、形成不压缩、不消蚀等离子体的有前途的装置[6]。P.V.Nickles等人提出了混合抽运源：毛细管放电形成类Ne…     

Ni电极X8R多层陶瓷电容器的制备及性能

采用具有抗还原性的X8R瓷粉、镍内电极浆料和柔性导电端头浆料为原料,制备了Ni电极X8R多层陶瓷电容器(MLCC),研究了烧结升温速率以及柔性导电端头浆料对所制MLCC性能的影响。结果表明:最佳烧结升温速率为2℃/min,制备的Ni电极X8R-MLCC在-55～+150℃范围内,容量变化率≤±15%,电性能优良,可靠性高,适用于汽车电子等高温应用领域。     

Sb、Bi、Ni元素对Sn基无铅焊点电迁移可靠性的影响北大核心CSCD

智能汽车的高集成化发展,使得组装焊点尺寸减小,对焊点抗电迁移服役可靠性的要求提高。目前用于汽车电子的三元系焊料SnAgCu无法满足日益严苛的服役环境,而多元合金化焊料是最有潜力的解决方案之一。通过差示扫描量热法、润湿性实验以及电子背散射衍射仪、扫描电子显微镜、能谱仪等表征手段,系统研究了添加Ni、Sb、Bi元素对SnAgCu焊料的焊接性能和电迁移可靠性的影响。结果表明:添加Ni、Sb、Bi元素降低了SnAgCu焊料的熔点和过冷度,改善了焊料的润湿性。在高电流密度载荷作用下,这些元素的引入可以有效地缓解焊点电迁移行为,进而提高焊点的服役可靠性。     

Nanosilver-Promoted Trimetallic Ni–Co–Mn Perovskite Fluorides for Advanced Aqueous Supercabatteries with Pseudocapacitive Multielectrons Phase Conversion Mechanisms

Aqueous supercapacitors (ASCs) and batteries (ABs) have drawn great attention as promising energy storage devices. However, the key issues of limited energy density of ASCs and inferior power density/poor cycling life of ABs discourage their further application. Herein, a new concept of advanced aqueous supercabatteries (ASCBs) realized by nanosilver-promoted trimetallic Ni–Co–Mn perovskite fluorides (K_1.0Ni_0.4Co_0.2Mn_0.4F_3.2 (KNCMF-10^#)/Ag(37%), denoted as 10^#/Ag(37%)) electrode materials is proposed, integrating with the respective superior specific power/cycling behavior and energy density of ASCs and ABs. A pseudocapacitance-dominated multielectrons phase conversion mechanism of the 10^#/Ag(37%) electrode materials can be deduced by ex situ characterizations and electrochemical techniques. The constructed ASCBs by matching 10^#/Ag(37%) cathode with activated carbon (AC)/Bi(17%) anode achieve great energy density without sacrifice of power density and cycling life in wide temperatures, benefiting from the synergistic energy storage superiority of ASCs and ABs containing capacitive, pseudocapacitive, and Faradaic response in electrochemical processes. Overall, this work highlights the new idea of nano-Ag-promoted trimetallic Ni–Co–Mn perovskite fluorides with a pseudocapacitive multielectrons phase conversion mechanism as a new pop star for advanced ASCBs, showing a great significance in the context of designing advanced electrode materials and in-depth understanding of their complicated charge storage mechanisms for aqueous electrochemical energy storage systems.     

Ni3N–CeO2 Heterostructure Bifunctional Catalysts for Electrochemical Water Splitting

Developing low-cost and high-efficient bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is greatly significant for water electrolysis. Here, Ni₃N-CeO₂/NF heterostructure is synthesized on the nickel foam, and it exhibits excellent HER and OER performance. As a result, the water electrolyzer based on Ni₃N-CeO₂/NF bifunctional catalyst only needs 1.515 V@10 mA cm⁻², significantly better than that of Pt/C||IrO₂ catalysts. In situ characterizations unveil that CeO₂ plays completely different roles in HER and OER processes. In situ infrared spectroscopy and density functional theory calculations indicate that the introduction of CeO₂ can optimizes the structure of interface water, and the synergistic effect of Ni₃N and CeO₂ improve the HER activity significantly, while the in situ Raman spectra reveal that CeO₂ accelerates the reconstruction of O_V (oxygen vacancy)-rich NiOOH for boosting OER. This study clearly unlocks the different catalytic mechanisms of CeO₂ for boosting the HER and OER activity of Ni₃N for water splitting, which provides the useful guidance for designing the high-performance bifunctional catalysts for water splitting.     

Sn/Bi合金电镀

概述了 Sn-Bi 合金镀液,可以获得均匀致密、可焊性和耐热性良好的 Sn-Bi 合金镀层,适用于印制板等电子部品的可焊性镀层。