Chemical bond characteristics and infrared reflectivity spectrum of a novel microwave dielectric ceramic CaIn2O4 with near-zero τf

Orthorhombic-structured CaIn₂O₄ ceramics with a space group Pca2₁ were synthesized via a solid-state reaction method. A high relative density (95.6 %) and excellent microwave dielectric properties (ε_r ～11.28, Qf = 74,200 GHz, τ_f ～ ?4.6 ppm/°C) were obtained when the ceramics were sintered at 1375 °C for 6 h. The dielectric properties were investigated on the basis of the Phillips–Van Vechten–Levine chemical bond theory. Results indicated that the dielectric properties were mainly determined by the InO bonds in the CaIn₂O₄ ceramics. These bonds contributed more (74.65 %) to the dielectric constant than the CaO bonds (25.35 %). Furthermore, the intrinsic dielectric properties of the CaIn₂O₄ ceramics were investigated via infrared reflectivity spectroscopy. The extrapolated microwave dielectric properties were ε_r ～10.12 and Qf = 112,200 GHz. Results indicated that ion polarization is the main contributor to the dielectric constant in microwave frequency ranges.     

Effects of Sr2+ substitution on the crystal structure,Raman spectra,bond valence and microwave dielectric properties of Ba3-xSrx(VO4)2 solid solutions

The effects of Sr²⁺ substitution for Ba²⁺ on microwave dielectric properties and crystal structure of Ba_3-xSr_x(VO₄)₂ (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr²⁺ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (∑_r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τ_f value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with ∑_r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τ_f = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B₂O₃ as sintering additive for the representative Sr₃V₂O₈ (SVO) ceramic and only 1 wt.% B₂O₃ addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication.     

缸套材质工艺的改进

针对缸套耐磨性差、寿命短的现象,对其进行了全面的热处理分析研究.并通过对缸套材质工艺的改进,使其使用寿命提高了10倍以上.     

金属切削加工喷雾冷却方法

通过对喷雾冷却原理的探索,找到了喷雾冷却适用的场合及方法,同时对冷却介质的消耗量进行计算。通过试验和测试,掌握几种喷雾器的优点,有效地提高了工作效率。实验证明:应用的喷雾冷却方法切实有效,充分说明了喷雾冷却在实际生产中的可行性和可操作性。     

白云铁矿富钾板岩综合利用途径的研究

文章阐述了白云鄂博铁矿富钾板岩的几种综合利用的途径,分别探讨了碳酸钠、石灰石烧结法和湿法的酸碱分离方法,以此达到富钾板岩综合利用的目的.     

电涡流传感器在汽轮发电机组的应用及标定

简述电涡流传感器的工作原理,着重介绍了电涡流传感器的标定方法以及正确的安装方法,从维护的角度,指出安装使用时应该注意的问题及故障处理办法.     

FFH泵送免振掺合料在工程中的应用

介绍了FFH混凝土掺合料最新专利产品，并对其在泵送混凝土，大体积混凝土，抗渗混凝土上的应用技术及质量效果作了阐述，经分析取得了良好的技术质量效果和明显的经济效益。     

甘肃敦煌雅丹国家地质公园总体规划

总体规划充分尊重地质演化的自然特征和属性,综合科普教育和旅游观光的要求,进行合理布局.对于未来公园建设中可能出现的不利因素也进行了分析,并提出对策.对于如何发展敦煌的区域旅游提出了合理的建议.     

大学图书馆迷人的砖墙立面

位于东田纳西州州立大学校园中的Charies C.Sherrod图书馆，可供约12000名学生使用。这座占地面积约为54万m^3的建筑物共有四层，如此广阔的空间容纳了超过800000册的藏书，以及私人自习室、计算机室，教师办公室等许多其他的附属设施，在图书馆的这些办公室和附属设施中，     

浅析防水混凝土基础漏水问题

对造成混凝土蜂窝、孔洞、麻面渗漏水、施工缝漏水、裂缝渗漏水、预埋件部位渗漏水的原因进行了分析,提出相应的预防措施,并对低混凝土的入模温度、浇灌速度、保温保湿养护措施等方面进行了阐述,以保证工程质量。