Use of alumina dispersant in alumina-spinel castable: Comparison between in situ and preformed spinels

The role of alumina dispersant as a flow modifier, completely replacing fume silica, on the properties of preformed and in situ spinel-containing low cement high alumina castables was investigated with variations in spinel content and granulometry. Both 10 and 20 wt.% spinel-containing compositions were prepared using preformed spinel or magnesia in alumina castable compositions with vibratable and self-flowing consistency. The castables underwent conventional processing methods and accessed for various refractory-related parameters post-heat treatments. No glassy phase was observed in the castables upon firing. The presence of self-flowing consistency led to improved characteristics. Preformed spinel-containing compositions showed improved density, strength, hot strength, and thermal shock resistance properties, whereas slag corrosion and penetration resistances were found to be higher for in situ spinel-containing castable.     

湿式泵送喷射料的研究及其在鱼雷罐上的应用

根据鱼雷罐内衬用耐火材料的使用条件 ,结合湿法喷射技术的特点 ,对Al2 O3 -SiC -C质喷射料的粒度组成、流变性 (泵送性能 )、促凝剂对材料增稠效果、泵送性能及喷射施工的影响进行了试验研究。以临界粒度为 5mm、且 <1mm颗粒占6 0 %～ 80 % (体积分数 )的材料能够确保稳定的泵送性能 ;适当的SiO2 微粉用量可以使喷射料能在低水分、低压力下稳定泵送 ;氯化钙为促凝剂可以起到明显的促凝效果。研制的湿法喷射料在首钢 2 6 0t鱼雷罐内衬上使用后 ,鱼雷罐使用寿命由原来平均90 0次提高到目前的 14 0 0次 (仍在继续使用中 )。试验表明 ,湿法喷射浇注技术施工方便、快捷 ,回弹率≤ 5 % ,无粉尘 ,鱼雷罐使用寿命大幅度提高 ,达到预期效果。     

基质组成对Al2O3-MgO质钢包浇注料物理性能的影响

在Al_2O_3-MgO质钢包浇注料基质内引入不同配比的镁砂细粉、SiO_2微粉及预合成尖晶石细粉,固定MgO的总量约为5%(质量分数,下同),制成不同试样;研究各试样分别在400℃、800℃、1100℃、1400℃及1600℃处理3h后的物理性能以及随着温度升高而发生的物相变化。结果表明加入预合成尖晶石细粉的试样由于没有太多的膨胀反应及液相,其显气孔率、线变化率及热态抗折强度等物理性能相对较好;基质中反应生成的尖晶石、CA6以及CA6晶粒的长大会对浇注料的显气孔率及线变化率起到不利影响;基质中加入0.5%SiO_2微粉的试样,由于在高温下产生较多液相,使其在1400℃时的高温抗折强度发生明显下降,但对控制浇注料的高温膨胀还是有贡献的。     

Study on preformed and in situ spinel containing alumina castable for steel ladle: Effect of fume silica content

In the present study, the effect of fume silica content on preformed and in situ spinel containing alumina spinel castable was studied by varying fume silica content at 1 and 4 wt.%. Spinel content for preformed alumina spinel castables varied from 10 to 30 wt.% and MgO content for in situ alumina spinel castables varied from 2.8 to 8.4 wt.%, respectively, and the distribution coefficient (q value) was maintained at .21 and .29 as per Dinger and Funk model. Different castable compositions were processed as per conventional processing technique and further evaluated for densification and strength studies after heat treatment at 110, 1000, and 1550°C. Fired samples at 1550°C were further evaluated for the hot modulus of rupture study at 1400°C and phase analysis study of the matrix phase. Also, the fired samples were studied for microstructural evaluation.     

Energy efficient lightweight periclase-magnesium alumina spinel castables containing porous aggregates for the working lining of steel ladles

This study presents a new lightweight periclase-magnesium alumina spinel castable (LPSC) for the working lining of steel ladles using porous periclase-spinel aggregates to replace conventional dense magnesia aggregates. The porous periclase-spinel aggregates were produced by an in-situ decomposition technique resulting in an apparent porosity of 23.3% and a median pore size of 5.66?μm. Scanning electron microscopy revealed a better porous aggregate/matrix interface bonding in the LPSC, which significantly improved its strength and thermal shock resistance. Additionally, the higher amount of micropores of the porous aggregates in the LPSC absorbed more penetrated slag from the matrix, which enhanced the slag resistance. Thus, compared with conventional castables, the LPSC had a lower bulk density of 9.2–10.8% and a lower thermal conductivity of 18.8% (1000?°C) while at the same time a higher strength, thermal shock resistance and slag resistance was achieved.     

Preparation and application of polyaniline nanofibers: an overview

Polyaniline (PANI) nanofibers have enhanced water processibility and improved sensitivity and response time when exposed to chemical vapors, and unique advantages in other fields including electric devices and corrosion inhibition. Therefore, PANI nanofibers have attracted great interest and have potential for many commercial applications. In this paper, the advantages, formation mechanism, characteristics and factors influencing various methods for preparing PANI nanofibers are described in detail. Their conductive properties and mechanism are briefly introduced. Finally, the potential applications of PANI nanofibers are elaborated in many fields such as gas sensors, capacitors, electrode materials for cells, removal of contaminants from water, corrosion inhibition, enzyme immobilization, Schottky diodes, and so on. © 2018 Society of Chemical Industry     

钛酸铝陶瓷研究现状及其应用

钛酸铝（Al2TiO5）陶瓷具有低热膨胀、高熔点（1860℃）、优良的抗热震性等特点,被公认是制作低压铸造升液管、汽车发动机上排气阀、活塞头等对抗热震和隔热要求较高的组件最为理想的候选材料;然而其难以获得高强度产品及在一定温度范围内易分解的特点又限制了其应用。本文着重介绍了近年来材料工作者在粉料组成及粒度、添加剂、烧结温度等方面改善钛酸铝陶瓷材料性能所做的研究,并对钛酸铝材料的应用做了简要介绍。     

Bioceramic coatings on metallic implants: An overview

Metallic implants sometimes fail in orthopedic surgeries due to insufficient bio-functionality, implant-associated infections, poor osteointegration due to high inertness (Ti, Co–Cr, stainless steel alloys), and a too fast degradation rate (Mg-based alloys). Bioceramic coatings are among the most appropriate solutions for overcoming these drawbacks. After providing a picture of the history as well as the pros and cons of the different types of metallic implants, this review focuses on bioceramic coatings that can be applied on them, including metal oxides, calcium phosphates, silicates, glasses, glass-ceramics, carbon, etc. Various coating strategies and applications are described and discussed, with emphasis on a selected number of highly promising researches. The major trends and future directions in the development of bioceramic coatings are finally suggested.     

Carbon aerogels for catalysis applications: An overview

Carbon aerogels are nanostructured carbons obtained from the carbonization of organic aerogels, which are prepared from the sol-gel polycondensation of certain organic monomers. These materials have a great versatility both at the nanoscopic level in terms of their pore texture and at the macroscopic level in terms of their form. Thus, the surface area, pore volume, and pore size distribution are tuneable surface properties related to the synthesis and processing conditions, which can produce a wide spectrum of materials with unique properties. In addition, carbon aerogels can be obtained in the form of monoliths, beads, powders or thin films. All these properties make them promising materials for application in adsorption and catalysis. Metal-doped monolithic organic aerogels can be easily prepared by following three main strategies: by addition of the metal precursor to the initial mixture, by ion-exchange or by deposition of the metal precursor on the organic or the carbon aerogel by one of various methods. These metal-doped carbon aerogels have been used as catalysts and as electrodes for electrical double-layer capacitors. This article shows the preparation of metal-doped carbon aerogels, their physico-chemical surface properties and their applications as catalysts in various reactions.     

Preparation of foamed ceramics from steel slag with high calcium and iron content

In this paper, steel slag foamed ceramics were fabricated by using steel slag, kaolin, feldspar, and quartz as main raw materials, and adding SiC as high-temperature foaming agent. The effects of steel slag content and SiC particle size on porosity and mechanical properties of foamed ceramics were researched. Results indicate that when content of steel slag is 40 wt%, and particle size of SiC is 20 µm, foamed ceramics exhibited optimized properties: water absorption rate of 2.59%, total porosity of 55.91%, bulk density of 1.33 g·cm⁻³, and compressive strength of 1.21 MPa. The results show that with the increase of steel slag content, the phase composition of foamed ceramics changes, and foam process is hindered. The increase of steel slag content contributes to the formation of diopside. Fe³⁺, Fe²⁺ in liquid phase enter into diopside by solid solution, the amount of liquid phase decreases. Liquid phase mass transfer slows down, and content of SiC in liquid phase decreases, so that the porosity decreases. At the same steel slag content, different SiC particle size affects the difference between pressure inside the closed pore and surface pressure, thereby the porosity changes.     

Hybrid organosiloxane coatings containing epoxide precursors for protecting mild steel against corrosion in a saline medium

Hybrid organic–inorganic materials made from sol–gel precursors can be used as anticorrosion barriers on metal substrates. The modification of epoxy resins with silicones is an interesting approach toward the synthesis of hybrid materials that combine the advantages offered by epoxy resins with those of silicones. In this study, novel hybrid epoxy‐silicon materials were synthesized using sol–gel chemistry and subsequently functionalized with 4,4′‐methylenebis(phenyl isocyanate), incorporating urethane functionality into the final polymer. The study screened five different epoxide precursors for use in the synthesis of the new hybrid materials and optimizing their anticorrosion properties. Spectral characterization confirms the proposed chemical structures of the newly synthesized polymers. The newly developed polymers were painted on mild steel panels, thermally cured, and their thermal, surface morphological, adhesion, and anticorrosion properties were fully characterized. The new coatings were found to have excellent thermal stability and adherence properties to steel surface. The results of corrosion testing on coated steel panels following long‐term immersion in a 3.5 wt % aqueous NaCl medium revealed that the polymer prepared using the epoxide precursor bisphenol A diglycidyl ether provided the best anticorrosion protection property among the synthesized polymers. This could be attributed to the excellent integrity and crosslink density properties in addition to the lack of microdefects in the surface of this coated sample as confirmed by scanning electron microscopy analyses. The newly prepared hybrid coatings reported in this study are very promising as an alternative to toxic chromate‐based coatings. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43947.     

Sol-gel coated enamel for steel: 250 days of continuous high-temperature stability

Two types of thermally durable and heat-resistant enamel coatings were applied to steel alloys. Three-layer TiO₂-SiO₂ sol-gel films were grown by a dip-coating method on an enamelled metal alloy to maintain and protect their properties from undesired environmental impact.The enamel coatings withstood 6000 h at 600 °C, retaining their colour while staying hard and adhering firmly to the metal surface. A three-layer sol-gel coating improved the chemical resistance of the enamelled metal by 6% (0 h), 29% (3000 h), and 28% (6000 h) at 600 °C. Throughout the whole treatment at 600 °C, the enamel coatings maintained their microhardness and even increased it from 3.6 to 4.4 GPa.     

柱填充再生纤维素交联凝胶微球的制备及其力学性质的调控

再生纤维素凝胶微球是将纤维素溶液分散于连续相中,并通过一定的固化方式使分散的纤维素溶液液滴发生凝胶转变而制备的凝胶微球材料。纤维素凝胶微球具有比表面积大、亲水性好、非特异性吸附小等特点,可作为吸附剂、生物亲和载体等应用。本文以棉短绒纤维素为原料,采用乳化法（低表面活性剂用量）制备了纤维素凝胶微球。利用XRD、光学显微镜、粒径分析仪、SEM、材料力学测试仪等对纤维素微球的形貌、结构、力学性能进行了表征及测试。考察了乳化剂用量、转速、m（纤维素溶液）:m（液体石蜡）、溶液黏度以及交联剂用量等因素对纤维素微球粒径的影响。结果表明,在纤维素溶液（质量分数4%）为10 g、交联剂用量为300 μL（交联度为3%）、乳化剂用量为0.1 g、液体石蜡用量为30 g、转速为200 r/min,溶液黏度为2474 Pa·s（增黏时间为15 min）的条件下,能制备平均粒径为610 μm的纤维素微球,其中粒径范围在400~800 μm的微球收率为54.93%。另外,本研究尝试了用乙醇水溶液作为凝固浴来调节微球中纤维素链的聚集状态进而改变微球的力学性能。在上述条件制备的纤维素微球,通过无水乙醇处理的纤维素微球能够承受流速为60 mL/min产生的水压,使微球不发生形变,表现出良好的物理性能,有望于应用于血液灌流等填充柱的应用。     

Carbon nanohorn‐graphene nanoplate hybrid: An excellent electrode material for supercapacitor application

This study describes the capacitor behavior of carbon nanohorn (CNH)/graphene nanoplate (GNP) hybrid (CNGN). The well‐CNH‐decorated GNP‐plate electrode materials show high capacitance value (≈677 F/g) and can be extensively used in new generation for energy storage. In the hybrid (CNGN), two nanofillers jointly affect the capacitance behavior and increase the capacitance value of the CNGN hybrid. Homogeneous coating of CNH over the GNP plate plays an effective role to enhance the capacitance behavior of the composite. Field emission scanning electron microscopy and high‐resolution transmission electron microscopy analysis of the composite confirmed the CNH coating on the GNP plate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42118.     

矿渣-钢渣复合水泥的性能研究

试验利用矿渣和钢渣作为配制复合水泥的辅助性胶凝材料,研究了矿渣、钢渣细度和复合比例对复合水泥强度的影响,并从颗粒堆积和复合胶凝效应的角度探讨了矿渣-钢渣在复合水泥中的作用机理。试验结果表明：在矿渣与钢渣组成的复合体系中,矿渣细度决定了复合水泥的强度,矿渣越细,复合水泥强度越高;在辅助性胶凝材料掺量一定的情况下,矿渣占的比例越高,复合水泥的强度越高;在适宜的复合比例下,用矿渣和钢渣混合配制的复合水泥28d抗压强度高于纯水泥的28d抗压强度。     

Complex validation of novel mullite-based ceramic filters for microfiltration purposes

The goal of this paper is to investigate a complex validation, developed by Rauschert in Poland, of casted ceramic filters for microfiltration. For disc manufacturing, a self-developed material RaFo-MF-401e with a filtration membrane was used. The presented experiment was conducted on component, subsystem, and system levels. Component level analysis consisted of the investigation of mechanical strength, hardness, rough lifetime, and resistance against acids and alkalis. Annealing at high temperature and humidity was used to test the subsystem. The final system test was executed on the real filtration system. The final aim of the tests was to verify the filtration efficiency of a complete module (core and membrane) in a real filtration device. The filtration quality of the whole setup was very good and the particles in the permeate (filtrated solution) were smaller than 10 μm (defined as D99). Thus, the developed discs provide the expected filtration quality in the range of microfiltration.     

Expanded Core/Shell Poly(vinyl acetate)/Poly(vinyl alcohol) Particles for Embolization

An improvement to a previously published suspension polymerization process for the production of spherical core/shell PVAc/PVA particles is described. To increase the settling time of the beads in the suspension, an expansion stage was introduced. The core/shell structure was obtained through the partial hydrolysis of the PVAc. The particle density was manipulated through addition of a solvent during the suspension polymerization stage and posterior expansion of the polymer beads obtained at the end of the process. This technique allows for effective reduction of the density of the final polymer beads. The expansion stage exerts also a beneficial effect on particle drying, avoiding particle aggregation during post‐polymerization processing of the polymer beads.

     

Biotechnological Applications and Health-Promoting Properties of Flavonols: An Updated View

Flavonols are a subclass of natural flavonoids characterized by a remarkable number of biotechnological applications and health-promoting properties. They attract researchers’ attention due to many epidemiological studies supporting their usage. They are phytochemicals commonly present in our diet, being ubiquitous in the plant kingdom and, in particular, relatively very abundant in fruits and vegetables. All these aspects make flavonols candidates of choice for the valorization of products, based on the presence of a remarkable number of different chemical structures, each one characterized by specific chemical features capable of influencing biological targets inside the living organisms in very different manners. In this review, we analyzed the biochemical and physiological characteristics of flavonols focalizing our attention on the most promising compounds to shed some light on their increasing utilization in biotechnological applications in processing industries, as well as their suitable employment to improve the overall wellness of the humankind.     

An Interphase with Changing Properties and the Mechanism of Deformation in Particulate-Filled Polymers

The comparison of the results of calculations based on experimental data with those derived from a simple, two phase, elastic model proved the existence of a hard interphase in particulate-filled composites. Moreover, beside elastic properties, also other mechanical characteristics of the interphase, including yield stress, are different from those of the components. An energy analysis showed that the relationship between the yield stress of the matrix and the debonding stress determines the mechanism of deformation. Strong adhesion leads to matrix yielding, while decreased interaction leads to debonding, with a corresponding dependence of composite yield stress on filler content. Particle size, interaction and interphase properties determine the stress necessary to separate the matrix/filler interface. The thickness of the interphase depends on the strength of the interaction; a linear correlation was found between the size of the interlayer and the reversible work of adhesion.