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.     

Ferroelectric,Ferromagnetic, and Magnetoelectric Properties of Multiferroic Ni0.5Zn0.5Fe2O4–BaTiO3 Composite Ceramics

Lead-free multiferroic composite ceramics xNi_0.5Zn_0.5Fe₂O₄–(1 ? x)BaTiO₃ (x = 0.2, 0.5, 0.8) with a 0–3-type connection structure have been prepared by a traditional ceramic process. The cubic spinel Ni_0.5Zn_0.5Fe₂O₄ phase and the tetragonal perovskite BaTiO₃ phase were confirmed by x-ray diffraction. The effect of Ni_0.5Zn_0.5Fe₂O₄ ferrite content on ferroelectric and ferromagnetic behavior, and the magnetoelectric coupling effect of the composite ceramics is discussed. With increasing Ni_0.5Zn_0.5Fe₂O₄ ferrite content, the saturation magnetization of the composite ceramic increased and the saturation polarization decreased. The magnetoelectric coupling response voltage was observed to decrease rapidly for samples with x = 0.2, then 0.5, then 0.8. The highest magnetoelectric coupling response voltage, measured for 0.2Ni_0.5Zn_0.5Fe₂O₄–0.8BaTiO₃, was 150 μV, which corresponds to a maximum magnetoelectric coupling voltage coefficient of 109 μV/cm Oe. When x = 0.5, the maximum magnetoelectric response voltage is only 8 μV, and when x = 0.8, no magnetoelectric response voltage is detected because of very large leakage current of the 0.8Ni_0.5Zn_0.5Fe₂O₄–0.2BaTiO₃ composite ceramic.     

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.     

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.     

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.     

电子探针分析中Ni,Co,Mo,Nb,Zr及其氧化物的价态分析

一、分析原理:用强度比分析价态是基于原子的外壳层价电子状态的改变引起谱线强度相应的变化。Ni,Co的M_5,N_1电子和Mo,Nb,Zr的N_4,N_5,O_1电子是价电子。Kα_(1,2),Lα_(1),Lβ_1,Lβ_2和Lγ_1谱线分别产生于K—L_(2,3),L_3—M_5,L_2—M_4,L_3—N_5和L_2—N_4跃迁,因此可预见上述元素有关谱线强度比的价态效应。二、实验与结果:在JSM—35C扫描电镜和波谱仪(WDS),可编程序探针自动分析器(MiCRO—PM)上测定Ni和NiO,Co和CoO,Co_3O_4,Mo和MoO_3,Nb和Nb_2oO_5,Zr和ZrO_2在15和20或25kV下的谱线强度。测量强度经ZAF修正分别还原为纯“离子”强度,以统一比较的基准。结果见表1,2。     

控制镀Ni层厚度,提高微波管制管水平

电真空器件中常用的不锈钢、纯铁、可伐等材料在氢气炉中焊接,需电镀一层Ni作为保护层,不同材料焊接温度不同,所需最佳镀Ni层的厚度也不同,找出最佳镀Ni层厚度,经常监测与检测,可提高焊接质量及制管成品率.     

A low drive voltage,transparent, metal-free n–i–p electrophosphorescent light emitting diode

We demonstrate a transparent, inverted, electrophosphorescent n–i–p organic light emitting diode (OLED) exhibiting a luminance of 500 cd/m² at 3.1 V, and with a luminous power efficiency of 23 lm/W when light emitted from both top and bottom surfaces is summed. We find that 10% more light is emitted from the top surface; hence a power efficiency of 12 lm/W is obtained for a device viewed through the top, transparent contact. This device, with applications to head-up and displays employing n-type Si driver circuitry, has significantly higher power efficiency and lower drive voltage than undoped fluorescent inverted OLEDs. Efficient injection of both electrons and holes is made possible by controlled n- and p-doping of the transport layers with high doping levels. The light emitting region is protected from ITO sputtering damage by a 210 nm thick p-doped hole transport layer. The transparency of the device at the peak OLED emission wavelength of 510 nm is (80 ± 5)%.     

Lattice strains and magnetic properties evolution of Ni doped rod-like cobalt–manganese ferrite

Co_0.5Mn_0.5–xNi_xFe₂O₄ (0.0≤x≤0.3) precursor is obtained by solvothermal method at 160 °C in glycol–water. Cubic Co_0.5Mn_0.5–xNi_xFe₂O₄ is obtained by calcining the precursor from 600 °C to 800 °C in air. The precursor and its calcined products are characterized by thermogravimetry and differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. A high-crystallized rod-like Co_0.5Mn_0.5–xNi_xFe₂O₄ with a cubic structure is obtained when the precursor is calcined at 800 °C in air for 2 h. Lattice parameters decrease with the increase of Ni²⁺ addition amount. The magnetic properties of Co_0.5Mn_0.5–xNi_xFe₂O₄ depend on Ni²⁺ doped amount and calcination temperature. Co_0.5Mn_0.3Ni_0.2Fe₂O₄ obtained at 800 °C has the highest specific saturation magnetization value, 63.51 emu/g. However, Co_0.5Mn_0.3Ni_0.2Fe₂O₄ obtained at 600 °C has the highest coercivity value, 1204.02 Oe.     

Optical and mechanical properties of C,Si, Ge,and 3C–SiC determined by first-principles theory using Heyd–Scuseria–Ernzerhof functional

Accurately calculating the band gap and electronic state density distribution of crystals is significant in determining optical properties. First-principles calculations were based on the projector-augmented-wave method with the Perdew–Burke–Ernzerhof generalized gradient approximation functional, pure density functional theory (DFT) and Heyd–Scuseria–Ernzerhof (HSE) hybrid functional. Such calculations account for the lattice parameters, electronic structure, optical properties, and mechanical properties of materials, which include the diamond-C and zinc blende structure of Si, Ge, and 3C–SiC in this study. The results obtained with HSE calculations is more accurate than that of the pure DFT calculations, and consistent with previous experimental values. The band structure and density of states of Si, Ge, and 3C–SiC indicate that these materials are indirect band gap materials. Based on HSE calculation, the band gap of Si and 3C–SiC is in accordance with previous experimental values. The imaginary part of the analytical dielectric function, the refractive index, and the adsorption coefficient also matches previous experimental values. A corresponding relationship exists among the peak of the imaginary part of the analytical dielectric function, the refractive index, and the adsorption coefficient. The optical properties have a direct relationship with the distribution of the crystal band gap and electronic state density. The materials exhibit brittleness. Although 3C–SiC is not as hard and stiff as diamond, it is a better semiconductor than Si and Ge. The mechanical anisotropy of the four materials is inconspicuous. The anisotropy of diamond-C in terms of its Young's modulus is extremely inconspicuous.     

ECSCRM 96, Heraklion,Crete, Greece 6–9 October 1996

The first European Conference on Silicon Carbide and Related Materials (ECSCRM 96) followed about a year after the International Conference in Kyoto, Japan (ICSCRM '95), a tough act to follow indeed with 400 participants. Nevertheless with more than 140 participants and 92 accepted presentations ECSCRIM'96 was at the same levels as ICSCRM '91 and was another indication that SiC and GaN-related fields are among the hottest topics in compound semiconductor research.     

Comparison of 3C–SiC, 6H–SiC and 4H–SiC MESFETs performances

A comparative analysis of the main DC and microwave performances of MESFETs made of the commercially available silicon carbide polytypes 3C–SiC, 6H–SiC and 4H–SiC is presented. In this purpose, we have developed an analytical model that takes into account the basic material properties such as field dependent mobility, critical electric field, ionization grade of impurities, and saturation of the charge carrier velocity. For a better precision in appreciating device characteristics in the case of a short gate device, the influences of the gate length and parasitic elements of the structure, e.g. source and drain resistances, are considered too. Cut-off frequency f_T, the corresponding output power P_m and the thermal stability are also evaluated and compared with the available experimental data, revealing the specific electrical performances of MESFETs, when any of the three polytypes is used in device fabrication.     

Low temperature fabrication of Ni–P metallic patterns on ITO substrates utilizing inkjet printing

A low temperature process to fabricate high resolution metallic lines on indium tin oxide (ITO) substrates using inkjet printing and subsequent electroless plating is described in this study. In this method, a thermo-sensitive (styrene-co-NIPAAm)/Pd (St-co-NIPAAm/Pd) nanoparticle-based ink was printed onto ITO substrates to create patterned catalytic sites, where nickel is subsequently deposited by electroless plating to form metal lines with desired width and conductivity. The inkjet printing variables such as droplet spacing and printing voltage, as well as the Ni electroless deposition variables such as deposition time and temperature were systematically investigated to obtain the optimum parameters. The adhesion of the deposited Ni–P coating to the ITO substrate was evaluated by a scotch tape test method. Optical microscope observation shows that a continuous pattern was formed with a printing voltage of 37 V and a droplet spacing of 50 μm. The irritating coffee ring effect was significantly suppressed by raising the substrate temperature to 50 °C and increasing the electroless plating temperature to 75 °C. High-resolution conductive metal lines can be easily and successfully fabricated using our method, which shows good potential for preparing the metallic lines as front or back electrodes in solar cells.     

Effect of Isothermal Aging on the Long-Term Reliability of Fine-Pitch Sn–Ag–Cu and Sn–Ag Solder Interconnects With and Without Board-Side Ni Surface Finish

The combined effects on long-term reliability of isothermal aging and chemically balanced or unbalanced surface finish have been investigated for fine-pitch ball grid array packages with Sn–3.0Ag–0.5Cu (SAC305) (wt.%) and Sn–3.5Ag (SnAg) (wt.%) solder ball interconnects. Two different printed circuit board surface finishes were selected to compare the effects of chemically balanced and unbalanced structure interconnects with and without board-side Ni surface finish. NiAu/solder/Cu and NiAu/solder/NiAu interconnects were isothermally aged and thermally cycled to evaluate long-term thermal fatigue reliability. Weibull plots of the combined effects of each aging condition and each surface finish revealed lifetime for NiAu/SAC305/Cu was reduced by approximately 40% by aging at 150°C; less degradation was observed for NiAu/SAC305/NiAu. Further reduction of characteristic life-cycle number was observed for NiAu/SnAg/NiAu joints. Microstructure was studied, focusing on its evolution near the board and package-side interfaces. Different mechanisms of aging were apparent under the different joint configurations. Their effects on the fatigue life of solder joints are discussed.