微波干燥软锰矿机理研究

采用微波加热法对软锰矿进行了深度干燥,考察了微波功率、物料质量、物料原始含水率、物料粒径等对其干燥效果的影响。结果表明物料在微波干燥180 s时达到最大脱水速率,且采用微波干燥在800 s时间内可将物料脱水至3.83%;原料质量一定时,随着微波功率的增大,有利于提高物料的脱水速率;微波功率一定时,在一定范围内增大物料质量和含水率,脱水速率就越快,干燥效果越好;物料粒径并非越小越好,反而大一些粒径的物料有助于物料加速脱水过程。     

Comprehensive recovery of the components of ferritungstite base on reductive roasting with mixed sodium salts,water leaching and magnetic separation

Ferritungstite ores have great commercial value because of the huge reserve and high content of W, Mo and Fe. But their economic recovery has long been a challenge due to its complex mineralogy and heterogeneous. The current study investigated how reductive roasting of ferritungstite ores with mixed sodium salts affected the phase evolution of W, Mo and Fe through Micro-area XRD and Powder XRD, with the goal of comprehensive transformation of ferritungstite. Reductive roasting with mixed sodium salts at 800 °C transformed ferritungstite to Na₂WO₄ and magnetite (Fe₃O₄), which were easily recovered by water leaching and magnetic separation. Furthermore, a lot of pores and gaps rather than sintering or agglomeration was observed in the ore particles after roasting by SEM-EDS, which was beneficial for the water leaching of W and Mo. As a result, 96.40% of W and 96.64% of Mo were extracted after water leaching, while an iron concentrate with an Fe content of 55.65% and recovery of 83.30% was obtained after magnetic separation. These results suggested such process would be applicable to the comprehensive recovery of valuable metals from ferritungstite ores, as well as similar tungsten ores and scraps.     

Microwave dielectric properties of low-fired Li2MnO3 ceramics co-doped with LiF–TiO2

Li₂MnO₃ ceramics co-doped with 2 wt% LiF and x wt% TiO₂ (x=0, 3, 5, 7, 10) were prepared by solid-state reaction for low-temperature co-fired ceramics (LTCC) applications. The sintering temperatures of Li₂MnO₃ ceramics were successfully lowered to 925°C due to the formation of a LiF liquid phase. Their temperature stability was improved by doping with TiO₂. A typical Li₂MnO₃-2 wt% LiF-5 wt% TiO₂ sample with well-densified microstructures displayed optimum dielectric properties (ε_r=13.8, Q×f= 23,270 GHz, τ_f=1.2 ppm/°C). Such sample was compatible with Ag electrodes, which suggests suitability of the developed material for LTCC applications in wireless communication systems.     

Improved Compaction in Multilayer Capacitor Fabrication

The most common defects found in multi-layer ceramic capacitors are derived from residual porosity formed when solvents and binders are released from a ceramic green body. Without a well-controlled compaction technique, defects between sheets in the stacked body are often present, leading to lamination problems. This paper suggests alternative approaches, using compaction applied before and/or after the process of binder burnout with the intention of reducing the number of stacking-generated defects and the volume of voids formed after binder burn-out. Barium titanate tapes and stacked multilayer electroded discs have been investigated and characterised by microstructural examination and density measurement. The resulting properties are described, and the behaviour of the multi-layers discussed in terms of the microstructure and processing procedures. It is shown that the porosity content of sintered samples compacted at 300 MPa is approximately half that of samples compacted at 30 MPa when both are sintered at 1300°C for 2 h. A further improvement of densification can be achieved by a postcompaction treatment after binder burn out.     

胭脂果多糖提取工艺优化及其抗氧化活性分析

为了考察超声辅助水提法对胭脂果多糖得率的影响,本研究应用单因素实验对超声功率、超声时间、提取温度和液料比展开了研究。在此基础上,采用响应面法优化了工艺参数,并分析了胭脂果粗多糖的体外抗氧化活性。结果表明,当胭脂果多糖最佳提取工艺为超声时间6 min、超声功率97 W、提取温度86℃、提取时间150 min和液料比40 mL/g时,粗多糖得率可达12.55%±0.31%,仅低于预测值0.23%,而且其中多糖含量达到了(413.75±0.41)mg/g,说明该模型能较好地预测实际得率。胭脂果多糖对DPPH·和·OH以及总还原能力与质量浓度呈量效关系,对DPPH·和·OH的IC₅₀分别为0.0203、1.44 mg/mL。因此,响应面法优化超声辅助水提法提取胭脂果多糖工艺方便可行,得到的多糖有较好的体外抗氧化活性,可为进一步的合理开发利用提供理论依据。     

美藤果油和普洱茶籽油的主要脂肪酸组成及氧化动力学研究

采用气相色谱-质谱法测定美藤果油和普洱茶籽油的主要脂肪酸组成,并利用热重分析法(thermogravimetric analysis,TGA)测定不同升温速率下两种植物油的起始氧化温度(Ton)和氧化峰值温度(Tp),并对两种植物油的动力学参数进行求解。结果表明:美藤果油和普洱茶籽油的不饱和脂肪酸含量分别为92.89%、79.08%;随着升温速率的增加,两种植物油的Ton和Tp均随之升高。由热重分析法计算出在Ton处的活化能分别为:美藤果油123.5 kJ/mol;普洱茶籽油125.7 kJ/mol。美藤果油在Tp处的活化能是150.9 kJ/mol,普洱茶籽油是127.6 kJ/mol。总体来看,两种植物油都具有很好的热稳定性。     

Study of Cu-based Al-doped ZnO multilayer thin films with different annealing conditions

AZO/Cu/AZO multilayer thin films produced under different annealing conditions are studied in this paper, to examine the effects of atmosphere and annealing temperature on their optical and electrical properties. The multilayer thin films are prepared by simultaneous RF magnetron sputtering (for AZO) and DC magnetron sputtering (for Cu). The thin films were annealed in a vacuum or an atmosphere of oxygen at temperatures ranging from 100 to 400 °C in steps of 100 °C for 3 min. High-quality multilayer films (at Cu layer thickness of 15 nm) with resistivity of 1.99×10⁻⁵ Ω-cm and maximum optical transmittance of 76.23% were obtained at 400 °C annealing temperature in a vacuum. These results show the films to be good candidates for use as high quality electrodes in various displays applications.     

干燥方式对酸溶性钛渣干燥特性影响规律

采用热风干燥和微波干燥对酸溶性钛渣的干燥特性进行了研究,获得了微波过程中入射功率、样品质量对平均干燥速率的影响规律,并与热风干燥过程进行了对比研究。试验结果表明,在热风干燥中,平均干燥速率随温度的升高而增加,随着样品质量的增加而降低;而在微波干燥中,平均干燥速率随微波功率的增加而增加,随样品质量的增加而增加,并且微波干燥酸溶性钛渣的平均干燥速率要比热风干燥高。微波干燥酸溶性钛渣较热风干燥法具有更高的干燥速率和干燥深度,且在节能方面有着明显的优势。     

Sensitive and Selective Determination of Riboflavin in Milk and Soymilk Powder by Multi-walled Carbon Nanotubes and Ionic Liquid [BMPi]PF<Subscript>6</Subscript> Modified Electrode

A novel electrochemical method to detect riboflavin was proposed using a multi-walled carbon nanotubes and ionic liquid N-butyl-N-methyl-piperidinium hexafluorophosphate composite film modified glassy carbon electrode (MWNTs-[BMPi]PF₆/GCE). A well-defined CV behavior with a pair of sensitive and well-shaped redox peak was observed, and the response value of riboflavin at MWNTs-[BMPi]PF₆/GCE is much higher than that at MWNTs/GCE in 0.1 mol L^?1 HAc-NaAc buffer solution (pH 4.5). The electrochemical approach based on a sensitive DPV analytical signal exhibits an excellent analytical performance with a wide linear range (2.6 × 10^?8 to 1.3 × 10^?6 mol L^?1) and low detection limit (4.7 × 10^?9 mol L^?1) for the riboflavin. Moreover, the proposed method possesses a potential practical application value and can be employed for the quantitative analysis of trace riboflavin with a recovery of 95.8–102.4 % in food samples such as milk and soymilk powder.