Ag/Bi2WO6 plasmonic composites with enhanced visible photocatalytic activity

Three-dimensional flower-like Bi₂WO₆ microspheres with the diameter of about 4 μm were prepared by a facile hydrothermal method using bismuth nitrate pentahydrate and sodium tungstate dihydrate as raw materials. A novel Ag-modified Bi₂WO₆ was synthesized through a simple and practical photoreduction process. The UV–vis diffuse reflectance spectra indicate that the Ag/Bi₂WO₆ samples have a significantly enhanced optical absorption in the visible light region than that of pure Bi₂WO₆ microspheres due to the surface plasmon resonance (SPR) of Ag nanoparticles on the surface of pure Bi₂WO₆. The photocatalytic activities of the as-prepared samples were evaluated by the decolorization of rhodamine B under simulated sun-light irradiation. The results reveal that the photocatalytic activities of the Ag/Bi₂WO₆ samples increase first and then decrease with increasing amount of loading Ag and the 1.0 wt% Ag-loaded Bi₂WO₆ sample exhibits the best photocatalytic activity compared with the other samples. The enhanced photocatalytic activity could be attributed to the synergistic effect of the strong SPR and the effective separation of photogenerated electrons and holes caused by Ag nanoparticles.     

Synthesis and thermal behavior of Cu/Y2W3O12 composite

Cu metal matrix composite with Y₂W₃O₁₂ as a thermal expansion compensator was fabricated by high energy ball milling followed by compaction and sintering, and its thermal properties were explored for the potential applications as heat sinks in electronic industries, high precision optics, and space structures. The volume fraction of reinforcement was varied from 40% to 70% in order to tailor the composite for the simultaneous accomplishment of low thermal expansion and high thermal conductivity. The synthesis technique was optimized by varying the parameters like milling time from 1 to 20 h and sintering temperature from 600 to 1000 °C in order to achieve densified composites. The relative density of the composites is found to be around 90% for the 10 h milled powders followed by compaction at a pressure of 700 MPa and sintering at a temperature of 1000 °C. The thermal expansion of the composites exhibits linear behavior in the temperature range 200 to 800 °C and the low coefficient of thermal expansion (CTE) is found to be for Cu–70%Y₂W₃O₁₂ composite whose value, 4.32±0.75×10⁻⁶/°C, matches with that of Si substrate. The thermal conductivities are found to increase with a decrease in the volume fraction of the reinforcement and decrease with an increase in the temperature for all the samples. The experimentally determined CTE and thermal conductivity values are found to be comparable to those predicted by the thermal expansion based Kerner and Turner model and the thermal conductivity based Maxwell model, respectively.     

Structural,morphological and up-converting luminescence characteristics of nanocrystalline Y2O3:Yb/Er powders obtained via spray pyrolysis

Sub-micronic, spherical Y₂O₃:Yb/Er particles comprising clustered nano-units (70 nm) were prepared via ultrasonic spray pyrolysis from pure nitrate precursor solutions with different Yb/Er dopant ratios. The particles were additionally thermally treated at 1100 °C for 12, 24 and 48 h. The structural and morphological characteristics of particles were studied by X-ray powder diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray analysis and specific surface area (BET) and were further correlated with their advanced optical properties. For the recorded up-conversion emissions, originating from the following Er³⁺ transitions: [²H_9/2→⁴I_15/2] in blue (407–420 nm); [²H_11/2, ⁴S_3/2→⁴I_15/2] green: 510–590 nm; and [⁴F_9/2→⁴I_15/2] in red (640–720 nm) spectral region, the corresponding lifetimes were acquired in the wide temperature range (10–300 K). The most intense green up-conversion emission with the long decay of 550 ms is recorded for Y_1.97Yb_0.02Er_0.01O₃ particles thermally treated at 1100 °C for 24 h.     

低温自反应淬熄法制备微纳米钡铁氧体空心复相陶瓷微珠吸波剂

以Fe(NO3)3-Ba(NO3)2-CO(NH2)2-酚醛树脂-硅烷偶联剂KH550为反应体系,采用低温自反应淬熄法结合热处理工艺,制备了微/纳米钡铁氧体空心复相陶瓷微珠。通过扫描电子显微镜、X射线衍射仪、透射电子显微镜、热分析及高速摄影技术测定了热处理前后微纳米钡铁氧体空心复相陶瓷微珠的形貌、结构及组成,并研究了其形成机理。结果表明:热处理前空心复相陶瓷微珠粒径为0.59至27.1μm,主要为非晶态;热处理后复相陶瓷微珠由六角晶型的Ba3Fe32O51、BaFe12O19和Ba5Fe14O26组成,且表现出片晶与固溶体相互交叉的现象。特殊的试验条件使得团聚粉粒子在火焰场中飞行过程中在受热蓄能阶段、热释放阶段、后燃烧阶段与快速凝固阶段都具有不同的反应机理,从而使得尺寸细化,具有较微米级微珠不同的本征参数。     

2,2-二(4-羟基苯基)丁烷的催化合成

以活性炭固载磷钨杂多酸为催化剂,苯酚和丁酮为原料,催化缩合了2,2-二(4-羟基苯基)丁烷(双酚B),并使用红外光谱法鉴定了产物的化学结构。通过正交试验筛选出最优反应条件,在此基础上考察了助催化剂巯基乙酸对产物收率的影响及催化剂的稳定性。最终确定的反应条件为:苯酚与丁酮摩尔比为8∶1,催化剂用量为反应物总质量的12%,助催化剂巯基乙酸与丁酮的摩尔比为0.014∶1,反应温度为130℃,反应时间为7 h,产物收率可达56.7%。     

生物质焦油成分分析及综合利用研究

生物质焦油是生物质热解和气化过程中产生的副产物,其成分非常复杂。实验对贵州省毕节市农机研究所设计的生物质气化炉所产生的生物质焦油进行了研究,选用混合溶剂(乙酸乙酯∶甲醇=5∶1)作萃取剂,采用GC/MS法对萃取物的化学成分进行了分析。结果表明,已定性的41种化合物大多为苯的衍生物,是重要的化工原料。     

高温热结构复合材料的连接技术

综述了高温热结构复合材料之间的连接技术.主要包括C/C复合材料之间采用热压炭素、反应生成SiC的连接;C/SiC复合材料的液相硅渗透连接;SiC基复合材料的钎焊连接;SiC/SiC复合材料与钨板的扩散连接等.并简介了高温热结构复合材料连接在航天及核工业上的应用.     

炭/石墨材料的成型工艺综述

由于炭/石墨材料在冶金、太阳能、核能、原子能、半导体、航空航天等领域的广泛应用,本文针对当前国内炭/石墨材料的成型方式,主要探讨挤压成型、模压成型和等静压成型,以及它们的技术特点.     

一种Ag/AgCl全固态复合式参比电极的研制

以脲醛树脂、聚乙二醇和KCl为骨架材料制备了一种Ag/AgCl全固态复合参比电极。研究了电极骨架材料组成及配比对电极性能的影响,结果发现当酚醛树脂质量分数为60%,聚乙二醇质量分数为20%,氯化钾质量分数为20%时,电极具有稳定性好、使用寿命长和温度影响小等特点。     

模温和热处理对PET/石墨复合材料导热性能的影响

从影响PET结晶度的角度出发,研究了模具温度和热处理工艺对复合材料热导率的影响,并通过DSC测试对实验结果进行了分析。结果表明:在一定温度范围内,模温升高有利于复合材料中PET结晶的完善和结晶度的提高。选用适当的温度对共混体系进行热处理可使共混材料中的热应力得到松弛,能促进聚合物分子链运动重排,共混物中PET的结晶完善、结晶度提高,提升复合材料的导热性能。