热处理对铅锡青铜耐腐蚀性能的影响

利用传统浇铸技术铸造含15%Sn的Cu-Sn-Pb青铜合金。经不同温度热处理及未经热处理的样品在酸性含Cl-环境中进行腐蚀试验,用金相和XRD分析两者的耐腐蚀性能。结果表明:经过热处理后,其内部的晶间组织结构发生改变,δ相分解或减少,α相再结晶。选择合适的热处理温度可以增强青铜的耐腐蚀能力,达到控制"粉状锈"的效果。

青铜合金成分与粉状锈的生成

铸造不同成分的铅锡青铜合金块，在相同条件下人为地对它们进行腐蚀．分析结果表明：锡含量高于２０％的青铜块不易生成粉状锈，锡含量在１０％左右的青铜块最易生成粉状锈．

Intermetallics and phase relations of Mg-Zn-Ce alloys at 400 ℃

The crystal structures,compositions and phase relations of the intermetallics of Mg-Zn-Ce system in the Mg-rich corner at 400 ℃ were identified through equilibrium alloy method.For Mg-Zn-Ce system,there is a linear ternary compound（T phase）,whose chemical formula is（Mg1-xZnx）11Ce.The range of Zn content in T phase is from 9.6% to 43.6%（molar fraction）.The crystal structure of T phase is C-centered orthorhombic lattice with lattice parameters of a=0.96-1.029 nm,b=1.115-1.204 nm,c=0.940-1.015 nm.And the lattice parameters of T phase are decreasing a little with increasing Zn content.According to the results of composition and crystal structure,the maximal solubility of Zn in Mg12Ce is about 7.8%（molar fraction）,and the chemical formula of the solid solution can be identified as（Mg1-xZnx）12Ce.The isothermal section of Mg-Zn-Ce system in Mg-rich corner at 400 ℃ was constructed.

Characteristic atom occupation patterns of Au_3Cu,AuCu_3,AuCuI and AuCuII based on experimental data of disordered alloys

The potential energies, volumes and electronic structures of characteristic atoms coordinated by neighboring configurations were obtained from the experimental heats of formation and lattice parameters of disordered Au1-xCux alloys. From characteristic atom occupation （CAO） patterns of L12-Au3Cu, L12-AuCu3 and Llo-AuCu compounds, their electronic structures, volumetric and energetic properties were calculated. The CAO pattern of Johasson-Linde（J-L） model shows that the transition AuCuI→AuCulI is an exothermic and volume contraction reaction, which is opposite from experimental phenomena. According to CAO pattern of Guymont-Feutelais-Legendre（G-F-L） model, the AuCulI cell consists of two periodic antidirection （PAD） AuCuI regions and two PAD boundary regions. The equations derived from CAO pattern of G-F-L model can be used to calculate energetic properties, volumetric properties and ordering degrees of the PAD AuCuI region and PAD boundary region, as well as corresponding average properties of the AuCulI phase. The results are consistent with experimental phenomena.

A High Speed IGBT Based on Dynamic Controlled Anode-Short

IGBT with high switching speed is described based on the dynamic controlled anode- short,which incorpo- rates a normally- on,p- MOSFET controlled by the anode voltage indirectly.This device works just as normal when it is in on- state since the channel of the p- MOSFET is pinched- off.During the course of turning off,the channel of the p- MOSFET will prevent the injection of m inorities and introduce an extra access for the carriers to flow to the anode directly,which m akes the IGBT reach its off- state in a shorter time.The simulation results prove that the new structure can reduce the turn- off time by m ore than75 % compared with the normal one under the same break- down voltage and on- state perform ance.Only two more resistors are needed when using this structure,and the re- quirement of the drive circuits is just the sam e as normal.

Influence of quench transfer time on microstructure and mechanical properties of 7055 aluminum alloy

The influence of quench transfer time on the microstructure and mechanical properties of 7055 aluminum alloy with and without zirconium was investigated by tensile properties test,optical microscopy,scanning electron microscopy and transmission electron microscopy.For the Zr-free alloy,the strength increases to the highest value at 20 s with transfer time,and then decreases slightly.The elongation decreases slowly with transfer time within 20 s,and more rapidly after 20 s.For the Zr-containing alloy,prolonging transfer time within 20 s results in slight decrease in the strength and elongation,and rapid drop of which is observed after 20 s.For the Zr-free alloy,prolonging transfer time can increase the percentage of intergranular fracture,which is mainly caused by wide grain boundary precipitate free zone.The failure mode of the Zr-containing alloy is modified from the predominant transgranular void growth and intergranular fracture to transgranular shear and intergranular fracture with increase in the transfer time,which is attributed to the wider grain boundary precipitate free zone and coarse equilibrium η phases in the matrix.

The Calculation of Parameters for DNA Kinetic Structure Based on Monte-Carlo Multiple Integrals

Based on protein-DNA complex crystal structural data in up-to-date Nucleic Acid Database,the related parameters of DNA Kinetic Structure were investigated by Monte-Carlo Multiple Integrals on the base of modified DNA structure statistical mechanical model,and time complexity and precision were analyzed on the calculated results.

Characterization of microstructural length scales in directionally solidified Sn-36%Ni peritectic alloy

Sn-36%Ni peritectie alloys were directionally solidified at different growth rates under a constant temperature gradient （20 K/mm）, the dependences of microstructural characteristic length scales on the growth rate were investigated. Experimental results are presented, including primary and higher order dendrite arm spacings 21, 22, 23 and dendrite tip radius R of primary NisSn2 phase. Comparisons between the theoretical predictions and the experimental results show that, for the primary dendrites, 21=335.882v-0.21, which is in agreement with the Kurz-Fisher model; for the secondary dendrites, λ2=44.957v-0.277, which is consistent with the Bouchard-Kirkaldy model; for the tertiary dendrites, λ3=40.512v-0.274; for the dendrite tip radius, R=22.7v-0.36. The experimental results also show that the 21/22 changes greatly with increasing growth rate while the 21/23 has no significant change, indicating that tertiary dendrite arms have a more similar growth characteristics to primary dendrites compared with secondary dendrites. The λ1/R ranges from 2 to 2.3 with the increase of growth rate. Key words： Sn-Ni alloy; directional solidification; dendrite arm spacing; dendrite tip radius

2024 aluminum alloy ultrahigh-strength sheet due to two-level nanostructuring under cryorolling and heat treatment

The effect of rolling to a total effective strain of 2 at the liquid nitrogen temperature and subsequent natural and artificial aging on the structure and service properties of the pre-quenched hot-pressed 2024 aluminum alloy was investigated.Using optical and electron microscopy,and X-ray analysis,it was found that the cryorolling did not qualitatively change the type of the initial coarse-fibered microstructure,but produced a well-developed nanocell substructure inside fibers.Further aging led to decomposition of the preliminary supersaturated and work-hardened aluminum solid solution and precipitation of strengthening phases in the statically recovered and/or recrystallized matrix.As a result,the rolled and naturally aged alloy demonstrated the yield and ultimate tensile strengths(YS=590 MPa,UTS=640 MPа)much higher than those in the pressed andТ6-heat treated alloy at equal elongation to failure(El^6%).Artificial aging at a temperature less than conventional T6 route could provide the extra alloy strengthening and the unique balance of mechanical properties,involving enhanced strength(YS=610 MPa,UTS=665 MPа)and ductility(El^10%),and good static crack resistance(the specific works for crack formation and growth were 42 and 18 k J/m^2,respectively)and corrosion resistance(the intensity and depth of intercrystalline corrosion were 23%and 50μm,respectively).

Revising Space Groups from Simulated SHELXfcf Structure Factors. More Examples of Incorrect Space Groups, an Example of a Chemically-Incorrect Structure and the Special Case of Pgl to PRevisions

The structure factors of any crystal structure can be simulated from its atomic coordinates (and temperature factors) in a SHELXL-97 run on a dummy hkl in which only the scale factor is refined. The squares of the structure factors are retrieved from the fcf, and such simulated data are used in the revision of the space groups of several incorrectly-refined crystal structures. Two cases, a P1 to P1 revision and a chemically-incorrect structure that is refined in a correct space group, are discussed.

Cooperative Dynamics in Lattice-Embedded Scale-Free Networks

We investigate cooperative behaviors of lattice-embedded scale-free networking agents in the prisoner'sdilemma game model by employing two initial strategy distribution mechanisms,which are specific distribution to themost connected sites (hubs) and random distribution.Our study indicates that the game dynamics crucially dependson the underlying spatial network structure with different strategy distribution mechanism.The cooperators' specificdistribution contributes to an enhanced level of cooperation in the system compared with random one,and cooperationis robust to cooperators' specific distribution but fragile to defectors' specific distribution.Especially,unlike the specificcase,increasing heterogeneity of network does not always favor the emergence of cooperation under random mechanism.Furthermore,we study the geographical effects and find that the graphically constrained network structure tends toimprove the evolution of cooperation in random case and in specific one for a large temptation to defect.

Synthesis of (3aS,6aR)-1,3-Dibenzyl-tetrahydro-1H- thieno[3,4-d]-imidazole-2(3H)-one-4-ylidenepentanoic Acid and Characterization of Its Crystal

The intermediate of d-biotin, (3aS,6aR)-1,3-dibenzyltetrahydro-1H-thieno[3,4- d]-imidazole-2(3H)-one-4-ylidenepentanoil acid was synthesized from (3aS,6aR)-1,3-dibenzylte- trahyro-4H-thieno[3,4-d]-imidazole-2,4(1H)-dione by using the Grignard reaction. The structure of 3 was characterized by IR, 1H NMR and MS, and the absolute configuration was further confirmed by X-ray crystal structure analysis. Compound 3 crystallizes in monoclinic, space group P21 with a = 11.030(2), b = 7.783(2), c = 12.797(2) , b = 93.44(1)o, Z = 2, Mr = 422.53 (C24H26N2O3S), V = 1096.3(6) 3, = 0.177 mm-1, Dc = 1.280 g/cm3, F(000) = 448 and T = 293(2) K. The final R = 0.0737 and Rw = 0.1974 for 1009 observed reflections with I >2s(I).

Synthesis and Crystal Structure of 2,2-Pentamethylene-1,2,3,4-tetrahydroquinazolin-4-one

The title compound 2,2-pentamethylene-1,2,3,4-tetrahydroquinazolin-4-one is of monoclinic, space group P21/n with a = 10.387(1), b = 10.954(2), c = 10.827(2) ? b = 110.77(1), C13H16N2O, Mr = 216.28, Z = 4, V = 1151.8(4) 3, Dc = 1.247 g/cm3, m(MoKa) = 0.080 mm-1, F(000) = 464, R = 0.0499 and wR = 0.1217 for 1575 observed reflections (I > 2s(I)). X-ray analysis reveals that the pyrimidine and cyclohexane rings adopt half-chair and chair configurations, respectively. In addition, there exists an intermolecular hydrogen bond (N(1)H(1)…O) in the product molecule.

Er_3(Fe,Co,M)_(29)化合物(M=Cr,V,Ti,Mn,Ga,Nb)的结构与磁性

合成了Er3Fe29-x-yCoxMy化合物(M=Cr,V,Ti,Mn,Ga,Nb)并用x射线衍射和磁测量等手段研究了它们的结构和磁性.发现Fe基Er3(Fe,M)29化合物结晶成哑铃对Fe-Fe无序替代的Th2Ni17型结构(P63/mmc空间群)而不能形成Nd3(Fe,Ti)29型结构,因此其化学式也可以用Er2-n(Fe,M)17+2n(n=0.2)表示.当Er3Fe29化合物中部分Fe原子被M原子所取代时,其居里温度均有一定程度的提高.所有Er3(Fe,M)29化合物在室温均为易面型各向异性.当Er3(Fe,M)29(M=Cr,V)中的部分Fe原子被Co原子取代且Co原子数与Fe原子数达到一定比值时,得到一个单斜结构的新相.磁测量表明Er3Fe19.5Co6V3.5在室温可能为单轴各向异性,在162K出现自旋重取向,其各向异性由易轴型变为易面型.在5K下于难磁化方向磁化时观察到一个一级磁化过程(FOMP).

Aggregation-induced emission and thermally activated delayed fluorescence of 2,6-diaminobenzophenones

Exploration of novel organic luminophores that exhibit thermally activated delayed fluorescence(TADF) in the aggregated state is very crucial for advance of delayed luminescence-based applications such as time-gated bio-sensing and temperature sensing.We report herein that synthesis, photophysical properties, molecular and crystal structures, and theoretical calculations of 2,6-bis(diarylamino)benzophenones. Absorption spectra in solution and calculations using density functional theory(DFT) method revealed that the optical excitation took place through intramolecular charge-transfer from one diarylamino moiety to an aroyl group. While the benzophenones did not luminesce in solution, the solids of the benzophenones emitted green light with moderate-to-good quantum yields. Thus, the benzophenones exhibit aggregation-induced emission. Based on the lifetime measurement, the green emission of the solids was found to include TADF. The emergence of the TADF is supported by the small energy gap between the excited singlet and triplet states, which was estimated by time-dependent DFT calculations. Thin films of poly(methyl methacrylate) doped by the benzophenones also showed green prompt and delayed fluorescence whose lifetimes were in the order of microseconds. Linear correlation between logarithm value of TADF lifetime and temperature was observed with the benzophenone in powder, suggesting that the benzophenones can serve as molecular thermometers workable under aqueous conditions.

Ultrafast quasiparticle dynamics in spin-density-wave LaOFeAs single crystal

Ultrafast quasiparticle dynamics of single crystalline LaOFeAs were investigated by pump-probe measurement.The compound experiences structural and spin-density-wave(SDW)phase transitions at 150 K(TS1)and 130 K(TS2),respectively.The relaxation time of quasiparticles was somewhat temperature independent at high temperature but exhibited a sharp upturn at TS1and reached the maximum at approximately TS2.The remarkable slowing down of quasiparticle relaxation time is caused by the formation of energy gap.By employing the Rothwarf-Taylor model analysis,we found that there should be already energy gaps opening just below the structural transition.The magnitude of SDW gap was identified to be 72 meV.