等离子体改性海绵铁活化过硫酸盐处理含酚废水

采用低温等离子体技术对海绵铁表面进行改性,并将其用于活化过硫酸盐（PS）处理含酚废水。通过氮气等温吸附（BET）、X射线衍射（XRD）和扫描电子显微镜（SEM）等手段对改性前后的海绵铁进行表征分析。以苯酚为目标污染物,通过静态实验考察催化剂投加量、催化剂/PS摩尔比、pH和苯酚初始浓度对等离子体改性海绵铁活化PS处理含酚废水的影响。结果表明,改性后的海绵铁比表面积、孔容及孔径均有增大,活化PS能力显著提高;在最佳反应条件（等离子改性海绵铁的投加量为0.4g/L,催化剂/PS摩尔比为1∶15,溶液pH为2,苯酚的初始浓度为250mg/L）下,苯酚的去除率可达95%;反应过程符合二级反应动力学,主要是硫酸根自由基和羟基自由基起氧化作用。等离子体技术改性海绵铁活化过硫酸钠可有效去除水中苯酚,为实际含酚废水的处理提供一些思路。     

Thermoelectric properties of the textured Bi1.9Gd0.1Te3 compounds spark-plasma-sintered at various temperatures

Elemental composition, crystal and grain structures, specific electrical resistivity, Seebeck coefficient, thermal conductivity, and thermoelectric figure-of-merit of n-type grained Bi_1.9Gd_0.1Te₃ compounds, spark-plasma-sintered at T_S = 690, 720, 750, 780 and 810 K, have been studied. All the samples are highly textured along the 001 direction parallel to the pressing direction. The average grain size measured along the pressing direction is much less as compared to the average grain size measured in the perpendicular direction. A strong anisotropy in the transport properties measured along directions parallel and perpendicular to the pressing direction was found within the 290 ÷ 630 K interval. Electrical resistivity decreases and thermal conductivity increases for parallel orientation as compared to these properties for perpendicular orientation. The T_S - effect on thermoelectric figure-of-merit of textured Bi_1.9Gd_0.1Te₃ compounds has been found and analyzed. Highest thermoelectric figure-of-merit (∼0.75) was observed for sample with T_S = 750 K at perpendicular orientation.     

Mechanical properties and microstructure of Yb2SiO5 environmental barrier coatings under isothermal heat treatment

Yb₂SiO₅ (ytterbium monosilicate) top coatings and Si bond coat layer were deposited by air plasma spray method as a protection layer on SiC substrates for environmental barrier coatings (EBCs) application. The Yb₂SiO₅-coated specimens were subjected to isothermal heat treatment at 1400 °C on air for 0, 1, 10, and 50 h. The Yb₂SiO₅ phase of the top coat layer reacted with Si from the bonding layer and O₂ from atmosphere formed to the Yb₂Si₂O₇ phase upon heat treatment at 1400 °C. The oxygen penetrated into the cracks to form SiO₂ phase of thermally grown oxide (TGO) in the bond coat and the interface of specimens during heat treatment. Horizontal cracks were also observed, due to a mismatch of the coefficient of thermal expansion (CTE) between the top coat and bond coat. The isothermal heat treatment improves the hardness and elastic modulus of Yb₂SiO₅ coatings; however, these properties in the Si bond coat were a little bit decreased.     

Growth Performance,Carcass Characteristics,Fatty Acid Composition,and Blood Biochemical Parameters of Lamb Fed Diet with the Addition of Lingonberry Leaves and Oak Bark

The aim of the study is to determine the effect of natural additives supplemented to the lamb diet on lamb performance, fatty acid (FA) composition of edible parts of lambs, and biochemical plasma indices. The study is carried out on 18 male lambs, allocated to three groups in a randomized complete block design. Control animals (CON) are fed a basic diet, while the experimental lambs additionally receive lingonberry leaves (VVI) or oak bark (QUE) (10 g d^?1), as a different source of tannins. Supplementing lambs with the VVI diet decreases fat content in the longissimus dorsi muscle (MLD). The VVI diet decreases monounsaturated fatty acid (MUFA) concentration (including C18:1 cis‐9) in the MLD, increases the proportion of C16:0, C16:1, C17:1, and C22:6 n‐3 in the semitendinosus muscle, as well as increases the n‐6/n‐3 ratio and thrombogenic index in the liver. The addition of QUE to lamb diets decreases C17:1 concentration and increases the content of C18:1 trans‐11 in the MLD. Tannins‐enriched diets increase low density lipoprotein concentrations in the blood plasma. The VVI diet increases the activity of alkaline phosphatase, while QUE supplementation decreases gamma‐glutamyl transferase activity in blood plasma. Modifications of FA composition in lamb tissues may suggest an indirect effect of tannins on FA ruminal biohydrogenation. Practical Applications: The use of VVI and QUE in lamb nutrition as natural resources is of a great interest to scientists. The present study shows that primarily VVI addition to lamb diets affects the quality of meat, due to higher proportion of catechin than QUE. Decreased concentration of fat, as well as increased proportion of C22:6 n‐3 and desirable fatty acids (including MUFA, polyunsaturated fatty acid, C18:0) after VVI supplementation increases health‐promoting properties of lamb meat and is related to humans. However, the presence of biologically active substances (tannins) in the examined additives makes it necessary to further research and discover their full potential in many areas.     

Evaluation of alumina reinforced oil fly ash composites prepared by spark plasma sintering

The thermomechanical behavior of micro/nano-alumina (Al₂O₃) ceramics reinforced with 1-5 wt.% of acid-treated oil fly ash (OFA) was investigated. Composites were sintered using spark plasma sintering (SPS) technique at a temperature of 1400°C by applying a constant uniaxial pressure of 50 MPa. It was evaluated that the fracture toughness of micro- and nanosized composites improved in contrast with the monolithic alumina. Highest fracture toughness value of 4.85 MPam^1/2 was measured for the nanosized composite reinforced with 5 wt.% OFA. The thermal conductivity of the composites (nano-/microsized) decreased with the increase in temperature. However, the addition of OFA (1-5 wt.%) in nanosized alumina enhanced the thermal conductivity at an evaluated temperature. Furthermore, a minimum thermal expansion value of 6.17 ppm*K⁻¹ was measured for nanosized Al₂O₃/5 wt.% OFA composite. Microstructural characterization of Al₂O₃-OFA composites was done by x-ray diffraction and Raman spectroscopy. Oil fly ash particles were seen to be well dispersed within the alumina matrix. Moreover, the comparative analysis of the nano-/microsized Al₂O₃/OFA composites shows that the mechanical and thermal properties were improved in nanosized alumina composites.     

高频氢等离子体增强还原制备超细铜粉

利用高频感应热氢等离子体强化还原制备超细铜粉,考察了加料速率、还原氢气流量、氢气分布位置、反应区空间、冷却温度等因素对铜粉颗粒性能的影响,对制备的铜粉颗粒进行氧含量、XRD晶体结构、松装密度、粒度分布和比表面积的表征。结果表明,优化的工艺条件为反应区内径100 mm,加料速率4 g/min,淬火气氩气气量500 L/h,氢气气量500 L/h并通入少量载气,由氢等离子电离产生的氢自由基可强化反应实现瞬时还原,不仅可控制铜粉形貌,还能有效控制铜粉颗粒大小;利用该方法制备出粒径分布100?200 nm、分散性好的超细球形铜粉颗粒。该方法操作简便、产品纯度高、气氛可控、对环境污染小。     

喷涂功率对YSZ涂层的力学性能和抗铝硅熔体腐蚀性能的影响

热浸镀Al–Si合金涂层是一种有效的现代钢铁防腐涂层,但熔融Al–Si合金腐蚀已成为热浸镀Al–Si合金生产线沉没辊及其备件亟待解决的关键问题之一。本工作采用大气等离子喷涂技术制备Y2O3部分稳定ZrO2(YSZ)/NiCrAlY防护涂层,研究了喷涂功率对YSZ涂层组织和力学性能的影响和涂层在700℃下Al–Si熔体中的腐蚀行为。结果表明,YSZ涂层是由板条和层间柱状晶粒组成的典型层状结构,随着喷涂功率从37 kW增至46 kW,层间柱状结晶呈长大趋势;YSZ涂层主要由t-ZrO2相和少量m-ZrO2相组成,喷涂功率对涂层相组成无明显影响;喷涂功率为40 kW的YSZ涂层具有较高的显微硬度642.4 HV0.3和结合强度62 MPa。此外,当带有涂层的样品在700℃的Al–Si熔液中腐蚀240 h后,YSZ涂层与高温Al–Si熔液之间的界面没有反应层生成,同时Al–Si合金熔液中的Al和Si元素也未渗透进YSZ涂层内部,表明YSZ/NiCrAlY防护涂层有效地将Al–Si合金熔体阻挡在涂层表面。     

Role of MgO on densification and mechanical properties in spark plasma sintered Os0.9Re0.1B2 ceramic

To promote the densification and therefore the mechanical properties of boride-based ceramics, MgO was added as sintering aid into Os_0.9Re_0.1B₂ powders for densification by using spark plasma sintering (SPS). The Os_0.9Re_0.1B₂ powders were synthesized by mechanochemical method from powder mixture of Os, Re and amorphous B. The role of MgO on densification, phase composition, microstructure and mechanical properties (hardness, fracture toughness and wear behavior) were studied by using X-ray diffraction (XRD), scanning electron microscope (SEM) with energy-dispersive spectroscopy (EDS), micro indentation and ball-on-disk tribometer. The results show that, with the introduction of MgO as sintering aid, the relative density of the Os_0.9Re_0.1B₂ ceramic samples increased. When the MgO content reached 9 wt%, the as-sintered sample is almost fully dense. No obvious regularity was found from the samples with the addition of different content of MgO. Vickers hardness values of the samples with 0, 3 wt% and 9 wt% MgO are found to be very close with each other within the experimental error (~30 GPa), while the sample with the addition of 6 wt% MgO exhibits the highest hardness of ~35 GPa. The fracture toughness of the samples is decreased slightly with the addition of MgO. The friction coefficient and wear rate of the sample with the addition of 6 wt% MgO was also found to be the lowest among all samples, which indicate best wear resistance. As a whole, with the addition content of 6 wt% MgO, the Os_0.9Re_0.1B₂ ceramic sample performs relatively excellent mechanical properties among four groups of samples.     

Evolution mechanism of the microstructure and mechanical properties of plasma-sprayed yttria-stabilized hafnia thermal barrier coating at 1400 °C

Yttria stabilized hafnia (Hf_0.84Y_0.16O_1.92, YSH16) coatings were sprayed by atmospheric plasma spraying (APS). The effects of thermal aging at 1400 °C on the microstructures, mechanical properties and thermal conductivity of the coatings were studied. The results show that the as-sprayed coating was composed of the cubic phase, and the nano-sized monoclinic (M) phase was precipitated in the annealed coating. The presence of M phase effectively constrained the sintering of the coating due to its superior sintering-resistance. The Young's modulus kept at a nearly same level of ~78 GPa even after annealing, and the coating annealed for 6 h yielded a maximum value of hardness but revealed a declining tendency in the Vicker's hardness with prolonged sintering time. The thermal conductivity increased from 0.8-0.95 W m^-1 K^-1 at as-sprayed state to 1.6 W m^-1 K^-1 after annealing at 1400 °C for 96 h. The dual-phase coating is promising to serve at temperatures above 1400 °C due to its excellent thermal stability and mechanical properties.     

Microstructural evaluation and thermal oxidation behaviors of YSZ/NiCoCrAlYTa coatings deposited by different thermal techniques

In this paper, two coating techniques, the high velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques, were used to deposit a bond coat of NiCoCrAlYTa on the Inconel 625 substrate, followed by applying a topcoat of yttria-stabilized zirconia (YSZ). The samples were preoxidized in an argon-controlled furnace at a temperature of 1000 °C for 12 and 24 h to characterize the microstructure of a thermally grown oxide (TGO) using the two coating techniques. The most suitable preoxidized samples were further tested for isothermal oxidation at 1000 °C for up to 120 h, and a hot corrosion test was performed at 1000 °C for up to 52 h or until spalling occurred. As-sprayed and oxidized samples prepared with different coating techniques were evaluated in terms of their microstructure using different characterization methods, such as field emission scanning electron microscopy (FESEM), variable pressure scanning electron microscopy (VPSEM), energy dispersive X-ray spectroscopy (EDS) equipped with energy dispersive X-ray and X-ray diffraction (XRD) analyses. In addition, the mechanical properties of these samples were evaluated using adhesion tests. The results show that the YSZ/NiCoCrAlYTa coating applied with the HVOF technique forms a more thin and continuous layer of TGO than that obtained when applying a YSZ/NiCoCrAlYTa coating using the APS technique, indicating that a severe brittle oxidation interface exists between the two layers. The results also indicate that the mechanical strength obtained from the adhesion test of the coated samples is observably affected by the oxidation behaviors obtained with the different deposition techniques chosen.