铝锂合金被认为是在航空航天领域中实现飞行器轻量化的理想结构材料之一.采用高功率光纤激光器焊接1.76 mm厚的2198-T851铝锂合金,研究填充ER4047焊丝时激光功率、焊接速率和送丝速率对焊接热裂纹和焊缝组织的影响,以及最优焊接工艺下焊接接头的显微组织与力学性能.结果表明,当激光功率为4 kW,焊接速率为4 m/min,送丝速率为4 m/min时,填充ER4047焊丝焊接可获得成形良好且无宏观裂纹缺陷的焊接接头.接头的平均抗拉强度为342MPa,拉伸断裂后接头断裂强度达到母材的65.4％,熔合区为薄弱部位.

The inversion behaviors of atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitors are studied by various surface treatments and postdeposition annealing using different gases. By using the combination of wet sulfide and dry trimethyl aluminum surface treatment along with pure hydrogen annealing, a strong inversion capacitance-voltage (C-V) response is observed, indicating a remarkable reduction in interface trap state density (Dit) at lower half-part of In0.53Ga0.47As band gap. This low Dit was confirmed by the temperature independent C-V stretch-out and horizontal C-V curves. The x-ray photoelectron spectroscopy spectra further confirm the effectiveness of hydrogen annealing on the reduction of native oxides.

The photoluminescence (PL) of high quality GaN epitaxial layer grown by MOCVD was investigated for various excitation power and temperatures from 8.3 to 300K. The PL at 8.3 K and with relatively low excitation power of GaN film grown on c-plane sapphire by using MOCVD shows clearly free-exciton A, B and exciton A bound to neutral donors (D°X) at 3.502 eV, 3.509 eV, and 3.496 eV, respectively. The full width at half maximum (FWHM) and binding energy of exciton A of the high quality GaN film were evaluated as small as 3.7 meV and 27.9 ± 0.5 meV, respectively. In addition, PL and Raman scattering of GaN films grown on r-plane sapphire and (111) Si substrates by using MOCVD were examined. The residual stress effect was detected in all films.

The diffusional reaction between titanium and zirconia was carried out isothermally at 1550°C in argon. The distinct reaction layers in the reaction‐affected zone between Ti and ZrO2 were investigated using analytical scanning electron microscopy, analytical transmission electron microscopy, and electron probe microanalyses. In the metal side, there existed five reaction layers in a sequence of α‐Ti(O), Ti2ZrO+α‐Ti(O, Zr), Ti2ZrO+α‐Ti(O, Zr)+β′‐Ti (O, Zr), α‐Ti (O, Zr)+β′‐Ti (O, Zr), and β′‐Ti (Zr, O) after cooling. In the zirconia side, two reaction layers were found: near the original interface, β′‐Ti coexisted with fine spherical c‐ZrO2−x and Chinese‐script‐like c‐ZrO2−x, which dissolved a significant amount of Y2O3 in solid solution; further away from the original interface, the coarsened intergranular α‐Zr was excluded from metastable ZrO2−x, resulting in the lenticular t‐ZrO2−x and ordered c‐ZrO2−x. An attempt was made to determine and propose the microstructural evolution and formation mechanism of the reaction layers between titanium and zirconia isothermally annealed at 1550°C.

A diffusion couple of 3 mol% Y2O3-ZrO2 and titanium was isothermally annealed in argon at temperatures between 1100 degrees and 1550 degrees C. The phases and microstructure in the ceramic side were investigated using scanning electron microscopy and transmission electron microscopy, both attached to an energy-dispersive spectrometer. After annealing at 1100 degrees C/6 h, zirconia grains did not grow conspicuously and evolved only traces of oxygen, resulting in t-ZrO2-x but not alpha-Zr. At temperatures above 1300 degrees C, a significant amount of oxygen evolved from zirconia, reducing the O/Zr ratio, such that alpha-Zr was excluded from t-ZrO2-x during cooling, yielding a higher O/Zr ratio (approximate to 2). When held at 1550 degrees C/6 h, zirconia grains grew rapidly. The alpha-Zr was segregated on grain boundaries during cooling by the exsolution of zirconium from ZrO2-x, while twinned t'-ZrO2-x or lenticular t-ZrO2-x, which was embedded in ordered c-ZrO2-x, was found. The ordered c-ZrO2-x was identified by the 1/5 {113} superlattice reflections of its electron diffraction patterns.

Hot‐pressed 3 mol% Y2O3 partially stabilized ZrO2 was reacted with titanium at 1550°C/30 min. The interface was characterized by analytical transmission microscopy (transmission electron microscopy/energy‐dispersive spectroscopy). The lamellar and the spherical Ti2ZrO as well as the orthorhombic β′‐Ti were found to exist in the titanium side after cooling down to room temperature. The crystal structures of the lamellar and the spherical Ti2ZrO were orthorhombic and hexagonal, respectively. On heating, the dissolution of a large amount of zirconium and oxygen into titanium gave rise to the metastably supersaturated disordered α‐Ti(Zr, O) solid solution where two different Ti2ZrO phases subsequently precipitated, while the β‐Ti coexisting with α‐Ti at high temperatures was transformed to the orthorhombic β′‐Ti during cooling. The spherical hexagonal Ti2ZrO was an ordered structure, with Zr and O occupying substitutional and interstitial sites, respectively. The orientation relations between α‐Ti and the lamellae orthorhombic Ti2ZrO were determined to be [0001]α‐Ti//[110]Ti2ZrO and (1010)α‐Ti//(110)Ti2ZrO; meanwhile, those between the α‐Ti and the spherical hexagonal Ti2ZrO were [0001]α‐Ti//[0001]Ti2rO and (1010)α‐Ti//(1010)Ti2ZrO.

In this paper, a (1200,720) LDPC decoder based on an irregular parity check matrix is presented. For achieving higher chip density and less critical path delay, the proposed architecture features a data reordering such that only one specific data bus exists between message memories and computational units. Moreover, the LDPC decoder can also process two different codewords concurrently to increase throughput and datapath efficiency. After chip implementation, a 3.33Gb/s data rate is achieved with 8 decoding iterations in the 21.23mm/sup 2/ 0.18/spl mu/m silicon area. The other 0.13/spl mu/m chip with the 10.24mm/sup 2/ core can further reach a 5.92Gb/s data rate under 1.02V supply.