等离子体化学气相沉积法制备氮化碳薄膜的研究

试图制备某一方面性能超过现有材料的新一代材料,一直是材料科学的一个发展方向。人们知道金刚石是硬度材料之王,然而美国Soienoe等报道:从经验模型和量子力学从头计算出发,预估碳氮之间的假想的共价化合物β-C_3N_4若能制备出来,它将是一种硬度接近或超过金刚石的超硬材料。同时从组成、结构和价键特点可以预测碳氮化合物的薄膜材料将会具有良好的绝缘掩蔽性能和异常高的热传导性能,因而将成为新一代的半导体或光、电器件的介质膜材料。     

关于发表科技论文的若干问题

 今年1月11日,中国科学报发表《1991年我国科技论文分析结果》,其中公布了在国际、国内发表论文数量多的个人名单.本刊主编吴水清致函他们中物理学专业作者,表示祝贺,并提出若干问题请他们解答.现根据本刊收到回信的顺序分期刊载,各位读者有什么问题和看法也欢迎发表.     

常微分方程若干周期解存在定理

我们考虑如下微分系统:其中X∈R~n,f关于(t,X)连续且保证解的存在唯一性,f(t+T,X)=f(t.X)(T>0) 再考虑(1)的特例(2):     

STRESS ANALYSIS IN CUBIC BORON NITRIDE FILMS BY X-RAY DIFFRACTION USING sin2 ψ METHOD

The boron nitride (BN) films containing cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) were prepared by radio frequency a ssisted thermal filament chemical vapor deposition. The stress and strain in BN films were investigated by X-ray diffraction analysis using the sin² ψ method. The results showed that both c-BN and h-BN in the same film have similar values of elastic strain, however, the compressive stress in c-BN is much greater than that in h-BN for the same film. Both stress and strain gradually decre ased with the increase of substrate temperature (T_s). The effective stress in the films calculated by the effective stress model increased with the increase of T_s. Furthermore, the dependence of effective stress in the films on T_s was also investigated.     

An Elastic Interaction Model of Vortices

Soliton theory plays an important role in nonlinear physics. The elastic interaction among solitons is one of the most important properties for integrable systems. In this Letter, an elastic vortex interaction model is proposed. It is found that the momenta, vortex momenta and the energies of every one vortex and the interaction energies of every two vortices are conserved.     

变系数KdV方程和变系数MKdV方程的无穷多守恒律

本文利用Miura方法研究具有三个任意函数的变系数KdV方程和变系数MKdV方程的无穷多守恒律,结果表明:守恒密度仅与一个任意函数有关,并且与常系数KdV(和MKdV)方程的守恒密度有完全类似的结构,另两个任意函数仅包含于相应的流密度中。 关键词：     

La0.8Sr0.2Mn1-xNixO3微波吸收特性

采用溶胶-凝胶法制备La0.8Sr0.2Mn1-xNixO3(y=0.12,0.14),用X射线,扫描电镜对样品结构和形貌进行了表征,用HP8722型矢量网络分析仪测定样品2~18 GHz损耗角正切及微波吸收特性曲线,发现y=0.14,样品厚度2.0 mm,吸收峰值达到了14 dB,10 dB以上吸收带宽达到了3.5 GHz。对该材料的电磁损耗机理进行了研究,发现在频率12.08 GHz附近有突变发生,2~12.08 GHz频段损耗主要以介电损耗为主,12.08~18 GHz频段损耗是以磁损耗为主。