等离子蚀刻挠性PI基材制作悬空引线及其参数优化

悬空引线的制作是挠性印制线路板制作的难点之一,需要在基材的某些区域蚀刻掉PI（聚酰亚胺）基材来满足设计的要求。目前采用的在基材上开窗口的方法有机械冲切、数控铣、化学试剂蚀刻法和等离子蚀刻法等。其中,等离子蚀刻法加工精度高、操作简便、清洁环保,但由于运行成本相对较高使其生产应用受到了限制。本文通过正交设计试验优化等离子蚀刻PI的参数,以达到充分利用气体、缩短等离子蚀刻时间的目的,从而大大降低等离子蚀刻过程的成本。并最终完成悬空引线的制作。     

用于排架结构的铅剪切阻尼器试验及数值分析

为进一步促进铅阻尼器在工程中的应用,针对常见的排架结构,研制了一种铅剪切阻尼器,通过低周往复加载试验,逐个分析阻尼材料铅的有效剪切面积、受剪区厚度、剪切截面形式、加载位移幅值、加载频率、加载次数等因素对阻尼器耗能性能的影响。试验结果表明,设计的阻尼器的阻尼力—位移滞回曲线饱满,耗能性能良好,符合双线性力学模型,并对试验中两个典型型号的阻尼器进行了数值模拟分析,通过对比数模值和试验值,证明了数值计算模型的实用性,为阻尼器在结构体系中的减震应用奠定了基础。     

Zinc diffusion and extractability as affected by zinc carrier and soil chemical properties

This work was carried out to evaluate the effect of soil chemical properties, Zn carrier and time elapsed after fertilizer application on the diffusion and extractability of Zn. A soil block technique was used to study zinc diffusion and DTPA extractability from ZnEDTA and ZnSO₄ fertilizers in three soils that varied in texture, CaCO₃ content, organic matter content, and pH using Zn⁶⁵ tracer. ZnEDTA diffused readily in all soils, moving 20–25 mm from the fertilizer layer after three days. The rate of Zn diffusion and the extractability of Zn, however, varied among the soils and were lowest in Baha soil with the highest clay content, organic matter, and CEC despite its lower pH. The high pH and CaCO₃ content in Dirab soil did not restrict the diffusion or reduce the extractability of ZnEDTA in this soil. On the other hand, the diffusion of Zn from ZnSO₄ fertilizer was largely restricted in all soils and was confined to 5 mm from the fertilizer layer after 13 d. The extractability of ZnSO₄ fertilizer was largely affected by soil pH and CaCO₃ content and was lowest in Dirab calcareous soil. Organic matter amendment at 5% (as alfalfa) considerably reduced the diffusion and the extractability of ZnSO₄ in both Dirab calcareous and Bakyria noncalcareous soils. The application of 1% (w/w) elemental S reduced soil pH and increased Zn diffusion from ZnSO₄ fertilizer in Bakyria soil but had slight effect on Dirab calcareous soil.     

Thermodynamic Theory of Single-Crystal Lead Titanate with Consideration of Elastic Boundary Conditions

A phenomenological free-energy function including the effects of elastic boundary conditions was presented and used to investigate the single-domain, single-crystal properties of the ferroelectric perovskite, PbTiO₃. In particular, the effects of tensile and compressive hydrostatic stress on the spontaneous polarization, Curie point, dielectric susceptibility, and piezoelectric property coefficients were examined. The calculated shift of the Curie point with hydrostatic stress, along with the entropy and enthalpy of the ferroelectric-paraelectric phase transition, was found to be in good agreement with experimental measurements. The isothermal variation of the relative dielectric susceptibility and piezoelectric coefficients with hydrostatic stress exhibited the expected behavior near the ferroelectric-paraelectric phase transition.     

Farbication of Optically Transparent Lead Magnesium Niobate Polycrystalline Ceramics Using Hot Isostatic Pressing

The physical, dielectric, and optical properties of hot isostatically pressed lead magnesium niobate polycrystalline ceramics modified with 1/2 mol% La₂O₃, Pb_{1–3/2 x} La _x □ _{x /2}-(Mg_1/3Nb_2/3)O₃, have been investigated. Methods used to characterize the ceramics included determination of the dielectric permittivity, optical transmittance, and refractive index dispersion. The materials exhibited relaxor ferroelectric type behavior with a peak dielectric constant K > 14000 and average T _c ∼−35°C. Various sintering, hot isostatic pressing, and annealing conditions were examined to produce highly dense and optically transparent materials. Through the use of hot isostatic pressing, densities more than 99.5% theoretical and transmittance greater than 50% at 633-nm wavelength were obtained. Hot isostatic pressing technique appears to be a good alternative to hot uniaxial pressing without the associated problem of PbO volatility, reactivity with the pressure vessel, and geometrical constraints.     

Thermally Stimulated Polarization and Depolarization in Halogen-Containing Lead Silicate Glasses

Thermally stimulated polarization and depolarization current (TSPC/TSDC) measurements were made on lead halide silicate glasses having compositions (65 − x )PbO· x PbX₂·35SiO₂ where x = 0, 0.1, 2, 10 and X = F, CI, Br, and I. The addition of halogen ions to lead silicate glasses gives rise to a new high-temperature TSDC peak in the vicinity of the peak previously observed in binary lead silicate glasses. The integrated area of the new peak is dependent on the amount and type of halogen ion present in the glass and does not saturate in the temperature range of our measurements. This new peak is attributed to space charge polarization of halogen ions.     

Ordering Behavior of Lead Magnesium Niobate Ceramics with A-Site Substitution

The ordering behavior of lanthanum-modified lead magnesium niobate ceramics was investigated over a wide range of lanthanum content (from 0 to 50 at.%). The ordering of magnesium and niobium ions in the B site was examined by X-ray diffraction, and the superlattice reflection was associated with the A(B'_1/2B"_1/2)O₃-type partial ordering structure. Moreover, the ordering degree increased pronouncedly with respect to lanthanum content of the sample and almost reached unity at [La] = 50 at.%. Finally, a comparison of the ordering behavior was performed among several lead magnesium niobate (PMN) samples with different A-site substitutional ions. The mechanism used to enhance the ordering of PMN by A-site substitution is then described by the effect of high valence.     

Fabrication of High-Curie-Point Barium-Lead Titanate PTCR Ceramics

High-Curie-point semiconducting barium-lead titanate positive temperature coefficient of resistivity (PTCR) ceramics of composition Ba_0.897Pb_0.1La_0.003TiO₃ and Ba_0.5Pb_0.5La_0.003TiO₃ were prepared. The starting powders were synthesized by reacting commercial BaTiO₃, PbO, and TiO₂. To avoid the nonstoichiometry due to the volatilization of Pb during the sintering process, a lead atmosphere sintering approach with PbTiO₃ as packing powder was used. The samples being fabricated by this method show a PTCR effect of 3 to 4.5 orders of magnitude above the Curie point. The curie points were about 180°C for Ba_0.897Pb_0.1La_0.003TiO₃ and about 360°C for Ba_0.497Pb_0.5La_0.003TiO₃.     

Bi2—xPbxSr2Ca2Cu3Oy系高Tc超导体相变的研究

用DSC研究了高T_e超导体B_(2-r)Pb_rSr_2Ca_2Cu_sO_v(x=0,0.2,0.4,0.6)从室温至600℃范围内的相变。在320℃和440℃附近有二个吸热蜂,每一个峰对应一个相变过程。440℃附近的相变是不可递的,其原子激活能为1.37eV,是由高T_e相向低T_e相的转变。而320℃附近的相变则与超结构的形成有关。