微波热裂解-KOH活化制备杏壳活性炭及其对甲基橙的吸附性能

以陇东地区生物质废弃物杏壳为原料,采用微波热裂解-KOH活化联合法制备活性炭,研究了微波功率和时间,活化过程中KOH溶液的浓度、用量、浸渍时间、加热活化温度和时间对活性炭吸附性能的影响;以甲基橙为染料模拟印染废水,研究了甲基橙初始浓度、振荡吸附时间和活性炭用量对吸附效果的影响。结果表明:微波功率800W,热裂解30min,生物炭的收率为56%;KOH溶液的浓度为25%,碱/炭为2.5∶1,活化温度800℃,加热活化1.5h,所制备活性炭的碘吸附值为1332mg/g,比表面积为1223m2/g,总孔体积为0.68cm3/g,活性炭的得率为32.7%;甲基橙浓度为250mg/g,振荡吸附240min,活性炭用量为每100mL甲基橙溶液0.15g时,甲基橙去除率高达99.78%;吸附过程符合准二级动力学方程。     

微波辐射制备吸油烟复合材料及其吸附油烟性能

用微波辐射的方法制备吸油烟无纺布复合材料,讨论了微波辐照时间、合成温度、单体配比和交联剂用量对吸油烟复合材料的吸油烟性能的影响。研究结果表明,当采用微波辐照时间15min、合成反应温度为85℃、100份质量的单体(m(DMA)∶m(EHMA)=7∶3)、0.5份质量的交联剂EGDMA和5份质量的引发剂BPO,在此条件下制得吸油烟复合材料的吸油烟率最佳。与常规制备方法相比,微波辐射制备吸油烟复合材料的反应时间可由6h缩短至15min,而且其吸油烟性能也有明显的提高。     

Morphology,thermal and mechanical properties of PVC/MMT nanocomposites prepared by solution blending and solution blending + melt compounding

Two types of montmorillonite (MMT), natural sodium montmorillonite (Na-MMT) and organically modified montmorillonite (OMMT), in different amounts of 1, 2, 5, 10 and 25 phr (parts per hundred resin), were dispersed in rigid poly (vinyl chloride) by two different methods: solution blending and solution blending + melt compounding. The effects on morphology, thermal and mechanical properties of the PVC/MMT nanocomposites were studied by varying the amount of Na-MMT and OMMT in both methods. SEM and XRD analysis revealed that possible intercalated and exfoliated structures were obtained in all of the PVC/MMT nanocomposites. Thermogravimetric analysis revealed that PVC/Na-MMT nanocomposites have better thermal stability than PVC/OMMT nanocomposites and PVC. In general, PVC/MMT nanocomposites prepared by solution blending + melt compounding revealed improved thermal properties compared to PVC/MMT nanocomposites prepared by solution blending. Vicat tests revealed a significant decrease in Vicat softening temperature of PVC/MMT nanocomposites prepared by solution blending + melt compounding compared to unfilled PVC.     

Preparation and characterization of poly(methyl methacrylate)-clay nanocomposites via melt intercalation: Effect of organoclay on thermal, mechanical and flammability properties

The PMMA nanocomposites were prepared by melt processing method. The influence of organoclay loading on extent of intercalation, thermal, mechanical and flammability properties of poly(methyl methacrylate) (PMMA)-clay nanocomposites were studied. Three different organoclay modifiers with varying hydrophobicity (single tallow vs. ditallow) were investigated. The nanocomposites were characterized by using wide angle X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. The intercalation of polymer chain within the silicate galleries was confirmed by WAXD and TEM. Mechanical properties such as tensile modulus (E), tensile strength, percentage elongation at break and impact strength were determined for nanocomposites at various clay loadings. Overall thermal stability of nanocomposites increased by 16-17 °C. The enhancement in T_g of nanocomposite is merely by 2-4 °C. The incorporation of maleic anhydride as compatibilizer further enhanced all the properties indicating improved interface between PMMA and clay. The flammability characteristics were studied by determining the rate of burning and LOI.     

微波干燥法制备纳米TiO2光催化剂及其催化性能研究

以钛酸丁酯为前驱物,离子液体1-丁基-3-甲基咪唑四氟硼酸盐为模板剂,采用溶胶-凝胶法及微波干燥法制备了纳米TiO2光催化剂。通过XRD、SEM及BET对光催化剂进行结构表征,以甲基橙溶液为模拟污染物,太阳光为光源,评价了其光催化活性,考察了模板剂及微波干燥条件对纳米TiO2光催化剂活性的影响。结果表明,采用离子液体作为模板剂,微波干燥条件下制备的TiO2光催化剂活性明显高于普通溶胶-凝胶法制备的TiO2光催化剂,光照3h甲基橙溶液降解率可达到95%。     

The characterizations of rheological,electrokinetical and structural properties of ODTABr/MMT and HDTABr/MMT organoclays

In the present paper, we have investigated as a function of surfactant concentration the rheological (yield value, plastic viscosity) and electrokinetic (mobility, zeta potential) properties of montmorillonite (MMT) dispersions. The influence of surfactants (Octadeccyltrimethylammonium bromide, ODTABr and Hexadecyltrimethylammonium bromide, HDTABr) on dispersions of Na-activated bentonite was evaluated by rheological and electrokinetic measurements, and X-ray diffraction (XRD) studies. The interactions between clay minerals and surfactants in water-based Na-activated MMT dispersions (2 wt.%) were examined in detail using rheologic parameters, such as viscosity, yield point, apparent and plastic viscosity, hysteresis area, and electrokinetic parameters of mobility and zeta potentials, and XRD also analyses helped to determine swelling properties of d-spacings. MMT and organoclay dispersions showed Bingham Plastic flow behavior. The zeta potential measurements displayed that the surfactant molecules hold on the clay particle surfaces and the XRD analyses displayed that they get into the basal layers.     

Rapid,High‐Temperature,In Situ Microwave Synthesis of Bulk Nanocatalysts

Carbon‐black‐supported nanoparticles (CNPs) have attracted considerable attention for their intriguing catalytic properties and promising applications. The traditional liquid synthesis of CNPs commonly involves demanding operation conditions and complex pre‐ or post‐treatments, which are time consuming and energy inefficient. Herein, a rapid, scalable, and universal strategy is reported to synthesize highly dispersed metal nanoparticles embedded in a carbon matrix via microwave irradiation of carbon black with preloaded precursors. By optimizing the amount of carbon black, the microwave absorption is dramatically improved while the thermal dissipation is effectively controlled, leading to a rapid temperature increase in carbon black, ramping to 1270 K in just 6 s. The whole synthesis process requires no capping agents or surfactants, nor tedious pre‐ or post‐treatments of carbon black, showing tremendous potential for mass production. As a proof of concept, the synthesis of ultrafine Ru nanoparticles (≈2.57 nm) uniformly embedded in carbon black using this microwave heating technique is demonstrated, which displays remarkable electrocatalytic performance when used as the cathode in a Li–O₂ battery. This microwave heating method can be extended to the synthesis of other nanoparticles, thereby providing a general methodology for the mass production of carbon‐supported catalytic nanoparticles.     

Synthesis and characterization of pyrite (FeS2) using microwave irradiation

A procedure using microwave irradiation was studied to develop a fast and reliable method for synthesizing pyrite. Pyrite was successfully synthesized within a few minutes via reaction of ferric iron and hydrogen sulfide under the influence of irradiation by a conventional microwave oven. The SEM-EDX study revealed that the nucleation and growth of pyrite occurred on the surface of elemental sulfur, where polysulfides are available. Compared to conventional heating, using microwave energy results in rapid (<1 min) formation of smaller particulates of pyrite. Higher levels of microwave power can form pyrite even faster, but faster reaction can lead to the formation of pyrite with defects.     

Dielectric properties of montmorillonite clay filled poly(vinyl alcohol)/poly(ethylene oxide) blend nanocomposites

Organic–inorganic nanocomposites of poly(vinyl alcohol) (PVA)–poly(ethylene oxide) (PEO) blend filled with montmorillonite (MMT) nanoclay up to 10 wt.% concentration were synthesized by aqueous solution-cast technique. The complex dielectric function, electrical conductivity, electric modulus and impedance spectra of the nanocomposites were measured in the frequency range 20 Hz–1 MHz at ambient temperature. A direct correlation was observed between the real part of dielectric function and the mean relaxation time of the polymer chain segmental dynamics, with the exfoliated and intercalated MMT clay structures, and the extent of miscibility between PVA and PEO due to hydrogen bonded bridging through exfoliated MMT clay nanosheets. The large increase of dielectric relaxation time revealed that the dispersed exfoliated nanoscale MMT clay in the polymers blend matrix produces a large hindrance to the polymer chain dynamics. Results confirm that the real part of dielectric function of the nanocomposites can be tailored by varying amount of MMT clay filler for their use as nanodielectric materials in the microelectronic technology.     

Preparation,characterization and photocatalytic activities of holmium-doped titanium dioxide nanoparticles

Holmium-doped TiO₂ nanoparticles with high photocatalytic activities were prepared by sol–gel method and characterized by X-ray diffraction, transmission electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, and surface area measurement by nitrogen adsorption in this study. Experimental results indicated holmium doping could increase the surface area of TiO₂ nanoparticles, and inhibit the growth of crystalline size and the anatase-to-rutile phase transformation. The results of photodegrading methyl orange showed holmium doping improved the photocatalytic activity of TiO₂, and the reasons could be attributed to the synergetic effects of large surface areas, small crystallite size, lattice distortion and more charge imbalance of holmium-doped TiO₂. In our experiment, the optimal doped amount was 0.3 mol.% for the maximum photocatalytic degradation ratio when holmium-doped TiO₂ was calcined at 500 °C, and the optimal calcined temperature was 600 °C when the doped amount was 0.5 mol.%.     

A new approach to joining of bulk copper using microwave energy

Metallurgical joining of high thermal conductivity materials like copper has been technically challenging. This paper illustrates a novel method for joining of bulk metallic materials through microwave heating. Joining of copper in bulk form has been carried out using microwave energy in a multimode applicator at 2.45 GHz and 900 W. Charcoal was used as susceptor material to facilitate microwave hybrid heating (MHH). Copper in coin and plate forms have been successfully joined through microwave heating within 900 s of exposure time. A sandwich layer of copper powder with approximately 0.5 mm thickness was introduced between the two candidate surfaces. Near complete melting of the powder particles in the sandwich layer does take place during the microwave exposure leading to metallurgical bonding of the bulk surfaces. Characterisation of the joints has been carried out through microstructure study, elemental analysis, phase analysis, microhardness survey, porosity measurement and tensile strength testing. X-ray diffraction (XRD) pattern indicates that some copper powder particles got transformed into copper oxides. XRD analysis also reveals that the dominant orientation (3 1 1) in starting copper powder got transformed into a preferential orientation (1 1 1) in the joint. A dense uniform microstructure with good metallurgical bonds between the sandwich layer and the interface was obtained. The hardness of the joint area was observed to be 78 ± 7 Hv, while the porosity in the joint was observed to be 1.92%. Strength character of the copper joints shows approximately 29.21% elongation with an average ultimate tensile strength of 164.4 MPa.     

Surface properties of activated carbon treated by cold plasma heating

To modify the surface properties of activated carbon powders, we have applied the cold plasma treatment method. The cold plasma was used to be generated in the evacuated reactor vessel by 2.45 GHz microwave irradiation. In this paper, changes of surface properties such as distribution of acidic functional groups and roughness morphology were examined. By the cold plasma treatment, activated carbons with large specific surface area of ca. 2000 m²/g or more could be prepared in a minute. The amount of every gaseous organic compound adsorbed on the unit gram of treated activated carbons was more increased that on the unit gram of untreated carbons. Especially, the adsorbed amount of carbon disulfide was remarkably increased even if it was compared by the amount per unit surface area. These results suggest that the surface property of the sample was modified by the plasma treatment. It became apparent by observing SEM photographs that dust and impure particles in macropores of activated carbons were far more reduced by the plasma treatment than by the conventional heating in an electric furnace under vacuum. In addition, a bubble-like surface morphology of the sample was observed by AEM measurement. The amount of acidic functional groups at the surface was determined by using the Boehm's titration method. Consequently, the increase of lactone groups and the decrease of carboxyl groups were also observed.     

Preparation of the acidic PVA/MMT nanocomposite polymer membrane for the direct methanol fuel cell (DMFC)

A novel nanocomposite polymer electrolyte membrane composed of PVA polymer matrix and nanosized Montmorillonite (MMT) filler, was prepared by a solution casting method. The characteristic properties of the PVA/MMT nanocomposite polymer membrane were investigated using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), atomic force microscopy (AFM), micro-Raman spectroscopy, and the AC impedance method. The PVA polymer directly blended with nanosized MMT filler (2-20 wt.%) showed good ionic conductivity, thermal, and mechanical properties. The highest ionic conductivity value for the acidic PVA/10 wt.%MMT nanocomposite polymer membrane was around 0.0368 S cm^− 1 at 30 °C. The methanol permeability (P) value was 3-4 × 10^− 6 cm² s^− 1. It was revealed that the addition of nanosized MMT fillers into the PVA matrix could markedly improve the electrochemical properties of the PVA/MMT nanocomposite membrane. In fact, the PVA/MMT nanocomposite polymer membrane appears to be a good candidate for the DMFC applications.     

Development of microwave assisted zeolite–water adsorption heat pump

A microwave assisted zeolite–water adsorption heat pump system was designed, manufactured and investigated experimentally. The influence of operation time of microwave oven on performance of the adsorption heat pump was studied. The performance criteria: coefficient of performance, specific cooling power and volumetric cooing power, were calculated for the designed and tested adsorption heat pump system. The regeneration of adsorbent bed was achieved very rapidly (35 min) by using microwave heating system. The poor thermal conductivity of adsorbent did not affect the periods of isosteric heating and isobaric desorption processes.     

Photo-reductive decolorization of an azo dye by natural sphalerite: Case study of a new type of visible light-sensitized photocatalyst

Natural sphalerite, which represents a new class of mineral-based catalyst, was characterized and investigated for photo-reduction of an azo dye methyl orange (MO) under visible light. After 2 h of visible light irradiation, a complete decolorization of the MO solution was achieved. The degradation rate was related to the pH conditions. Spectra from FT-IR analysis indicate an initial adsorption of MO to sphalerite via its sulfonate group. Further reduction of the adsorbed MO by sphalerite under light irradiation led to the destruction of the azo structure, as indicated by the results from UV–vis, FT-IR and ESI-MS analyses. The visible light-induced photocatalytic reductive activity of natural sphalerite was mainly attributed to the distribution of foreign metal atoms in its crystal lattice, which reduces the intrinsic bandgap of sphalerite and also broadens its spectra responding range. In addition, the high conduction band potential of natural sphalerite may also enhance the photo-reduction of MO.     

微波辅助聚氯乙烯-苯酚之间的Friedel-Crafts接枝反应及对聚氯乙烯热稳定性的影响

在四氢呋喃溶液中通过微波辐照实现了聚氯乙烯(PVC)与苯酚的Friedel-Crafts接枝反应;通过紫外分光光度法表征了PVC-g-苯酚接枝物的接枝率,考察了加热方式、反应温度、催化剂用量及反应时间对接枝反应的影响,并通过红外光谱表征了接枝物的结构;通过刚果红试验、热重分析研究了接枝苯酚对PVC热稳定性的影响。结果表明,相同反应时间,水浴加热接枝率仅为0.1,而微波辐照接枝率可达2.12,其优化工艺条件为无水AlCl_3的用量为PVC质量的8%,反应时间30 min,反应温度为65℃;接枝样品的刚果红试验热稳定时间为6 min46 s,比空白PVC延长了3 min,在空气气氛和氮气气氛中的热降解第一阶段活化能比空白PVC分别提高11.2 kJ/mol和13.8 kJ/mol,而在第二和第三阶段,接枝样品的活化能反而低于空白PVC。证明苯酚取代了容易导致PVC降解的活性氯,抑制了PVC热降解的第一阶段,即脱HCl反应,提高了PVC的热稳定性。     

Rapid synthesis of TiO2 hollow nanostructures with crystallized walls by using CuO as template and microwave heating

In this paper, TiO₂ hollow nanostructures with anatase walls have been rapidly fabricated by using CuO as template and microwave heating. These TiO₂ hollow nanostructures have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Experimental results showed that the TiO₂ shell transformed from amorphous to anatase phase in 3 min, induced by the hot CuO core under microwave irradiation. The diameter of TiO₂ hollow nanostructures is about 50-80 nm, and the length is about 200-300 nm. The thickness of the shell is about 3 nm. This method is promising to be used to synthesize other nanomaterials with a hollow nanostructure.     

微波与水浴加热条件下对沸石分子筛吸附量的对比研究

为了研究微波作用对沸石分子筛吸附的影响与特点,采用静态吸附容量法,对比研究了微波与水浴两种加热条件下沸石分子筛的吸附量.实验结果表明:在相同的加热温度下,与水浴加热相比,微波加热能够快速加热分子筛,极大地缩短了加热时间;在相同的温度与压力条件下,与水浴加热相比,微波作用下分子筛吸附量总是更低.这表明微波加热沸石分子筛,...     

Characterization and photocatalytic activity of Bi3TiNbO9 nanocrystallines synthesized by sol-gel process

Nanocrystalline Bi₃TiNbO₉ powders were synthesized by a sol-gel process, based on a colloid solution of bismuth acetate, titanium butoxide and niobium ethoxide. X-ray diffraction analysis revealed that pure Aurivillius phase of Bi₃TiNbO₉ could be prepared at a calcination temperature of 500 °C. By using scanning electron microscopy and gas adsorption method, the morphology and the specific surface area of the powders were examined. The photophysical properties of Bi₃TiNbO₉ were investigated by means of the UV-visible diffuse reflectance spectrum, from which a band gap ∼3.2 eV was empirically calculated. The as-prepared Bi₃TiNbO₉ powders were applied in the photodegradation of organic contaminant for the first time, and they showed effective photocatalytic activity for the complete decomposition of methyl orange under UV light irradiation.     

Electrophoretic effects of the adsorption of anionic surfactants to poly(dimethylsiloxane)-coated capillaries

Poly(dimethylsiloxane) (PDMS) is one of the most convenient materials to construct capillary electrophoresis microchips. Even though PDMS has many advantages, its use is often limited by its hydrophobicity. Although it is well-known that the surface properties of PDMS can be modified by anionic surfactants, very little is known regarding the driving forces or the electrophoretic consequences of the adsorption of anionic surfactants. In this work, the adsorption of alkyl surfactants on PDMS was studied by performing electroosmotic flow (microEOF) measurements. In order to mimic the behavior of PDMS microchannels, fused-silica capillaries were coated with PDMS and used for the microEOF measurements. This approach allowed using standard CE instrumentation and provided significant advantages over similar experiments performed on microchips. The change in the microEOF in the presence of surfactants was correlated to the surfactant adsorbed amount which, plotted versus surfactant concentration, gives an adsorption isotherm. The adsorption isotherms were obtained using alkyl surfactants with different chain lengths and head groups. According to our results, the interaction of alkyl surfactants with the PDMS surface is determined by a combination of hydrophobic and electrostatic interactions, where the former is more significant than the latter. The affinity of each surfactant for the PDMS surface was calculated by fitting the adsorption profiles with a Langmuir equation and, in the case of single-charged surfactants, correlated to the corresponding cmc value.