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21.
《Ceramics International》2022,48(15):21951-21960
A high surface area is one of desired properties for yttria-zirconia (Y2O3–ZrO2) ceramic materials given their catalytic applications. The objective of this study is to develop high-surface-area Y2O3–ZrO2 materials by silicon (Si) modification and investigate the role of Si. Si-modified yttrium-zirconium hydroxides were prepared via a one-step precipitation process and calcined at 800 or 950 °C to form Si-modified Y2O3–ZrO2 (denoted as SiO2–Y2O3–ZrO2) materials containing 0-20 wt% Si as SiO2. These hydroxides or materials were characterized by 29Si NMR, XPS, TG-DSC, XRD, UV Raman, TEM, and N2 physisorption measurements. Si species uniformly distributed in the hydroxides tended to be enriched on the material surface at high temperatures. These Si species dominated by the silicates blocked the migration of Y and Zr atoms, which resisted the crystallite growth of Y2O3–ZrO2 components and reduced their crystallite size. Therefore, the SiO2–Y2O3–ZrO2 possessed a surface area of 59-112 m2/g after calcination at 950 °C for 9 h, which was significantly higher than that of the Y2O3–ZrO2 (23 m2/g). This study may stimulate ideas for developing high-surface-area crystalline ceramic materials calcined at high temperatures. 相似文献
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通过馏分切割、温和加氢相结合对中低温煤焦油进行精制处理,精制后的原料采用分级热聚制备中间相炭微球。考察了精制处理条件对原料性质、中间相炭微球宏观外貌及微晶结构的影响。采用FTIR、GC-MS、族组成、元素分析对原料进行表征,采用SEM、XRD对中间相炭微球进行表征。结果表明:中低温煤焦油中300~430℃馏分油是制备中间相炭微球的较佳馏分。300~430℃馏分油中正庚烷可溶物(HS)质量分数高达84.76%,吡啶不溶物(PI)质量分数低至0.23%,杂原子含量低,芳烃化合物的环数为2~4环。300~430℃馏分油在TH=350℃、p=8MPa、t=1.5h、剂油比1∶40(质量比)的条件下温和加氢得到的精制原料,经420℃热聚6h得制备的中间相炭微球宏观外貌、微晶结构较好。中低温煤焦油基炭微球的粒径范围为5~15μm,小球表面光滑,微观结构为地球仪型,经1450℃高温煅烧后,石墨化度达到12.33%。 相似文献
24.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文
25.
化学转化膜是金属表面主要的处理方法之一,具备良好的附着力和耐蚀性,能为铝合金提供一定的临时防护。传统的六价铬酸盐化学转化膜在日渐严苛的环保压力下已经逐渐淘汰,取而代之的是近几年发展迅猛的三价铬及无铬锆基化学转化膜。铝合金可分为铸造铝合金和变形铝合金,按照所含主要合金元素和热处理状态可分为若干个系列和型号。本文选取几种典型的变形铝合金,综述了不同铝合金微观组织对转化膜成膜过程的影响,化学转化液添加剂、预处理和后处理工艺对转化膜性能的调控及作用机理,以及几种典型商业钝化剂在变形铝合金表面的应用。总结了目前变形铝合金表面锆基化学转化膜仍面临的问题和发展趋势,未来化学转化膜需在满足新型铝合金发展要求的基础上,通过不同有机、无机添加剂以及外场作用对转化膜的成膜均一性、完整性进行调控,以提高转化膜的综合性能。 相似文献
26.
27.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
28.
Molecular structure and granule morphology of native and heat‐moisture‐treated pinhão starch 下载免费PDF全文
Vania Z. Pinto Khalid Moomand Nathan L. Vanier Rosana Colussi Franciene A. Villanova Elessandra R. Zavareze Loong‐Tak Lim Alvaro R. G. Dias 《International Journal of Food Science & Technology》2015,50(2):282-289
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications. 相似文献
29.
Sundaram Vickram Karunakaran Rohini Subramanian Srinivasan David Nancy Veenakumari Kumar Archana Krishnan Anbarasu Palanivelu Jeyanthi Sundaram Thanigaivel Govindarajan Gulothungan Nanmaran Rajendiran Padmalayam Sadanandan Srikumar 《International journal of molecular sciences》2021,22(4)
Zinc (Zn), the second-most necessary trace element, is abundant in the human body. The human body lacks the capacity to store Zn; hence, the dietary intake of Zn is essential for various functions and metabolism. The uptake of Zn during its transport through the body is important for proper development of the three major accessory sex glands: the testis, epididymis, and prostate. It plays key roles in the initial stages of germ cell development and spermatogenesis, sperm cell development and maturation, ejaculation, liquefaction, the binding of spermatozoa and prostasomes, capacitation, and fertilization. The prostate releases more Zn into the seminal plasma during ejaculation, and it plays a significant role in sperm release and motility. During the maternal, labor, perinatal, and neonatal periods, the part of Zn is vital. The average dietary intake of Zn is in the range of 8–12 mg/day in developing countries during the maternal period. Globally, the dietary intake of Zn varies for pregnant and lactating mothers, but the average Zn intake is in the range of 9.6–11.2 mg/day. The absence of Zn and the consequences of this have been discussed using critical evidence. The events and functions of Zn related to successful fertilization have been summarized in detail. Briefly, our current review emphasizes the role of Zn at each stage of human reproduction, from the spermatogenesis process to childbirth. The role of Zn and its supplementation in in vitro fertilization (IVF) opens opportunities for future studies on reproductive biology. 相似文献
30.
活塞环在内燃机中有着支撑、密闭、储油、导热的作用,内燃机活塞环制备材料应该具备优良的加工性能、耐高温、耐腐蚀、导热性好且具有良好的强韧性,较好的与气缸材料表面的磨合性能。球墨铸铁和专用钢材已经成为制备内燃机活塞环的基础材料,目前国内外采用多种表面处理技术比如:镀铬、氮化、PVD与CVD镀膜、喷钼、喷涂陶瓷层等表面处理工艺进行表面改性,提高内燃机活塞环的使用寿命和使用性能。需要不断研究和开发新的内燃机活塞环的表面处理技术来满足实际生产和应用中内燃机越来越高的要求。 相似文献