A combinatorial sample-preparation robot system using the volumetric-weighing method

We have developed a new automatic sample-preparation robot system with use of the volumetric-weighing method. In this system, slurries, aqueous solutions, and other wet reagents are employed as starting materials and 64 (8×8) samples at the maximum are prepared on a library plate of 35 mm × 35 mm size. Volumetric-weighing and mixing of the starting materials and distributing reaction mixtures to the library plate are automatically performed by computer-controlled mechanisms with an easy-to-use programming software interface. While this robot is designed in terms of space saving and portability, it is able to equip with an atmosphere-controlled furnace to sinter the samples on the library plate. Typical preparation time for a library plate of 36 (6×6) samples is less than 40 min. This robot system is promising in enhancing throughput of wet-chemically synthesized materials researches.     

Thermal conductivities of solid and liquid phases for neopentylglycol, aminomethylpropanediol and their binary alloy

The variations of thermal conductivities of solid phases versus temperature for neopentylglycol (NPG), 2-amino-2-methyl-1,3-propanediol (AMPD) and AMPD-42.2 mol% NPG alloy were measured with a radial heat flow apparatus. From the graphs of the solid phases thermal conductivity variations versus temperature, the thermal conductivities of the solid phases at their melting temperature and temperature coefficients for same materials were also found to be 0.22±0.01, 0.45±0.02 and 0.32±0.02 W/Km and 0.0047, 0.0031 and 0.0043 K⁻¹, respectively. The thermal conductivity ratios of liquid phase to solid phase for the same materials at their melting temperature are found to be 1.07, 1.12 and 0.74 with a Bridgman type directional solidification apparatus, respectively. Thus, the thermal conductivities of liquid phases for pure NPG, pure AMPD and AMPD-42.2 mol% NPG alloy at their melting temperature were evaluated to be 0.24, 0.50 and 0.23 W/Km, respectively, by using the values of solid phase thermal conductivities and the thermal conductivity ratios of liquid phase to solid phase.     

A general and low-cost synthetic route to high-surface area metal oxides through a silica xerogel template

Porous metal oxides with a large surface area are synthesised by means of a procedure based on the templating approach. An inexpensive porous silica xerogel synthesised at moderate temperatures (∼100 °C) in order to preserve the silanol superficial groups was used as template. In a first step, the silica porosity was filled with a concentrated solution containing a metallic salt. Then, the impregnated sample was calcined in air at a temperature of 600 °C. Under these conditions, the metal oxides were synthesised within the confined space provided by the silica pores. Finally, the product was recovered after dissolution of the silica framework in 2 M NaOH solution. The materials obtained by this procedure are made up of aggregates of nanoparticles and/or 3D solid structures containing confined pores. In this work, the synthetic route proposed is illustrated by the preparation of various binary metal oxides (i.e. Fe₂O₃, Cr₂O₃, NiO, CeO₂, Mn₂O₃, Co₂O₃ and Al₂O₃). The BET surface areas measured for these materials are in the range of 100-270 m² g⁻¹. The proposed method is not restricted to the binary metal oxides. It can also be used in the preparation of other inorganic materials such as metal sulphides or mixed metal oxides.     

Complexed sol-gel synthesis of improved Pt-Ru-Os-based anode electro-catalysts for direct methanol fuel cells

A high specific surface area (SSA) Pt-Ru-Os-based anode catalyst synthesized by a novel complexed sol-gel (CSG) process shows better catalytic activity in comparison to pure equi-atomic compositions of Pt-Ru anode catalysts synthesized by similar sol-gel processes. A homogeneous amorphous gel was successfully synthesized by complexing platinum(II) acetylacetonate, ruthenium(III) acetylacetonate and osmium(III) chloride with tetramethylammonium hydroxide (TMAH) used as a complexing agent. Phase-pure Pt(Ru,Os) and Pt(Ru) solid solutions possessing high specific surface area (∼110-120 m²/g) were successfully synthesized by controlled removal of carbonaceous species present in the as-prepared precursor generated from the CSG process. This has been successfully achieved by precise thermal treatments of the precursor using controlled oxidizing atmospheres. Results indicate that the nano-crystalline Pt(Ru,Os) solid solution of nominal composition 50 at%-Pt-40 at% Ru-10 at% Os possesses good chemical homogeneity, and reveals excellent catalytic activity, thus demonstrating the potential of the novel CSG process for synthesizing high-performance Pt-Ru-Os-based catalysts for direct methanol fuel cells.     

Development of a high-throughput thermoelectric screening tool for combinatorial thin film libraries

We have developed a high-throughput thermoelectric screening tool for the study of combinatorial thin films. This tool consists of a probe to measure resistance and Seebeck coefficient on an automated translation stage. A thin film library of the (Ca_1−x−ySr_xLa_y)₃Co₄O₉ ternary system has been fabricated on a Si (1 0 0) substrate, using combinatorial pulsed laser deposition by the natural-composition-spread method. We have demonstrated successful mapping of the resistance and Seebeck coefficient of this film library. The mapping indicates that the substitution of La for Ca results in an increase of both resistance and Seebeck coefficient, and that of Sr results in a decrease of resistance. The screening tool allows us to measure 1080 data points in 6 h.     

VPO catalysts synthesized on substrates with modified activated carbons

VPO catalysts were prepared on oxidized and unoxidized activated carbons differing in initial porous structure. Carbons were oxidized under relatively soft (30% H₂O₂, 200 °C) and hard (50% H₂O₂, 350 °C) conditions. Carbon modification was carried out hydrothermally in a traditional autoclave (HTT) or a microwave reactor (MWT). The synthesis was also carried out under hydrothermal (HTS or MWS) conditions. V₂O₅ and NH₄VO₃ were used as precursors. The samples are characterized by diversified porous structure at S_BET = 732-1617 m²/g and V_por = 0.44-0.90 cm³/g, as well as various degree of VPO crystallinity. Possibility of preparation of the VPO catalysts under ecologically appropriate conditions, i.e. in aqueous solutions, was shown.     

Polyoxaethylene polypodands – powerful reduction catalysts in solid–liquid and liquid–liquid phase transfer systems

The excellent catalytic properties of polypodands, esters of inorganic acids, as phase‐transfer catalysts have been reported previously. Unfortunately, these compounds are unstable under hydrolytic conditions. A group of new, hydrolytically stable podands has been synthesized. Their complex forming abilities towards alkali metal ions have been studied. The podands studied have been used as catalysts in phase transfer catalysis conditions. The kinetics of this process has been determined. All compounds prepared have been found to complex metal ions and are a powerful catalysts in reduction of ketones by borohydrides in solid–liquid and liquid–liquid systems. Copyright © 2013 John Wiley & Sons, Ltd.     

New high-throughput material-exploration system based on combinatorial chemistry and electrostatic atomization

As a tool to facilitate future material explorations, our group has developed a new combinatorial system for the high-throughput preparation of compounds made up of more than three components. The system works in two steps: the atomization of a liquid by a high electric field followed by deposition to a grounded substrate. The combinatorial system based on this method has plural syringe pumps. The each starting materials are fed through the syringe pumps into a manifold, thoroughly mixed as they pass through the manifold, and atomized from the tip of a stainless steel nozzle onto a grounded substrate.     

Measurement of solid-liquid interfacial energy for solid Zn in the Zn-Cd eutectic system

The equilibrated grain boundary groove shapes for the Zn solid solution in Zn-Cd liquid solutions were directly observed. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient for solid Zn (Zn-15 wt.% Cd) in Zn-Cd liquid solutions has been determined to be (2.5 ± 0.1) × 10⁻⁸ Km by a direct method. The solid-liquid interfacial energy between solid Zn and Zn-Cd liquid solution has been obtained to be (165.5 ± 19.0) mJ/m² from the Gibbs-Thomson equation. The grain boundary energy for the same alloy has been determined as (317.8 ± 39.9) mJ/m². The thermal conductivities of the solid and liquid phases at the eutectic composition and temperature have also been measured.     

1064-nm laser fragmentation of thin Au and Ag flakes in acetone for highly productive pathway to stable metal nanoparticles

The laser-induced fragmentation of thin Au and Ag flakes in acetone by 1064-nm nanosecond laser (with the fluence typically ∼2 J/cm²) potentially offers a highly productive pathway to stable metal nanoparticles in liquid. Acetone serves as a superior liquid medium that keeps fine metal nanoparticles free from precipitation even in such concentrated nanoparticle solutions exceeding ∼0.1 M. Thin metal flakes have good capability to absorb the 1064-nm laser energy as efficiently as in the visible region. A part of the thus laser-heated molten flakes explosively split into submicroparticles, and some other significant part directly into fine nanoparticles. Both kinds of product particles have minor absorption cross-sections for subsequent laser pulses at 1064 nm, and thus no longer fragment further. One of the two kinds of Ag flakes studied in this work yielded fine Ag nanoparticles at a remarkable high production rate of 1.1 mg/min for the input laser power of only ∼0.65 W.     

多功能胶囊催化剂在多相催化中的应用研究进展

Capsule catalysts composed of pre-shaped core catalysts and layer zeolites have been widely used in the tandem reactions where multiple continuous reactions are combined into one process. They show excellent catalytic performance in heterogeneous catalysis, including the direct synthesis of middle isoparaffins or dimethyl ether from syngas, as compared to the conventional hybrid catalysts. The present review highlights the recent development in the design of capsule catalysts and their catalytic applications in heterogeneous catalysis. The capsule catalyst preparation methods are introduced in detail, such as hydrothermal synthesis method, dual-layer method, physically adhesive method and single crystal crystallization method. Furthermore, several new applications of capsule catalysts in heterogeneous catalytic processes are presented such as in the direct synthesis of liquefied petroleum gas from syngas, the direct synthesis of para-xylene from syngas and methane dehydroaromatization. In addition, the development in the design of multifunctional capsule catalysts is discussed, which makes the capsule catalyst not just a simple combination of two different catalysts, but has some special functions such as changing the surface hydrophobic or acid properties of the core catalysts. Finally, the future perspectives of the design and applications of capsule catalysts in heterogeneous catalysis are provided.     

Effects of nano-carbon webs on the electrochemical properties in LiFePO4/C composite

LiFePO₄/C composite is one of ways to surmount the lower electrical conductivity of LiFePO₄. In this paper, we suggest a new type of LiFePO₄/C composite in which amorphous nano-carbon webs are wrapping and connecting LiFePO₄ particles. This type of composite was obtained by adapting a new liquid-based powder preparation method, that is, all raw materials (LiFePO₄ and carbon precursor materials) were dissolved in liquid and solidified. This composite was very effective in enhancing the electrochemical properties such as capacity and rate capability. Even as high as at 400 m Ag⁻¹ current density, a capacity of about 105 m Ahg⁻¹ was obtained at 25 °C.     

Evidence of surface active sites on NaY zeolite by a model reaction

Owing to the development of a new test reaction, namely the isomerization of 1-dodecene, it becomes possible to characterize the activity of cationic zeolites under conditions close to those of industrial adsorption and separation processes (temperature around 150-200 °C and liquid phase). Indeed, 1-dodecene is highly active and still in a liquid state at 150 °C. Furthermore, by comparing the reactivity of NaY before and after treatments applied to reduce its activity ((i) passivation of the external surface by deposition of TetraEthylOrthoSiloxane (TEOS) and (ii) washing the zeolite with a basic or neutral solution), we are able to propose a nature and localization for the residual active sites of this zeolite. Indeed, the evolution of the NaY activity in their function indicates that the active sites are located both at the external and internal surfaces of NaY and that two types of sites can be described: OH groups and structure defects.     

Breakdown limits of optical multimode fibers for the application of nanosecond laser pulses at 532 nm and 1064 nm wavelength

For many applications, optical multimode fibers are used for the transmission of powerful laser radiation. High light throughput and damage resistance are desirable. Laser-induced breakdown at the end faces of fibers can limit their performance. Therefore, the determination of laser-induced damage thresholds (LIDT) at the surface of fibers is essential.Nanosecond (1064 nm and 532 nm wavelength) single-shot LIDT were measured according to the relevant standard on SiO₂ glass preforms (Suprasil F300) as basic materials of the corresponding fibers. For 10 kinds of fused silica fibers (FiberTech) with core diameters between 180 μm and 600 μm, an illumination approach utilizing a stepwise increase of the laser fluence on a single spot was used. For both wavelengths, the LIDT values (0% damage probability) obtained by means of the two methods were compared. The influence of surface preparation (polishing) on damage resistance was investigated. For equal surface finishing, a correlation between drawing speed of the fibers and their surface LIDT values was found. In addition to the surface measurements, bulk LIDT were determined for the preform material.     

Thermochromism in (Ba,Sr)-Mn oxides

Manganese based ceramic samples with composition given by the formula MeMnO₃ (Me=Ba, Sr) were prepared by solid state reaction. The preparation conditions were varied over a wide range of temperatures and the optimum sintering temperature was obtained. These materials present a change of color at low temperature (at approximately 140 K). To find the probable reason for the change of color, the materials have been characterized by various advanced techniques like X-ray diffraction (XRD), photoluminiscence, scanning and transmission electron microscopy (SEM and TEM). Studies were made at room and at low temperature. These thermochromic materials have hexagonal perovskite-like structure.     

Successive preparation of decorated zinc oxide organic sol by pulsed laser ablation and their luminescence characteristics

Nano-ZnO organic sols which were modified in situ were successively produced through focused pulsed laser ablation of ZnO target in interface of solid and flowing liquid which contained modification agents or polymer. It is found that the ZnO ethanol sol decorated by Q (8-hydroxylquinoline) radiates intense green light under ultraviolet radiation and has a broad emission band centered at 555 nm in the emission fluorescence spectrum. The influence of factors including different modification agents and their added methods, laser fluence, aging time after preparation, compositions of flowing liquid and their velocity on luminescence characteristics of nano-ZnO organic sol was characterized by TEM, UV-vis and fluorescence spectrum.     

Molecular alloys as phase change materials (MAPCM) for energy storage and thermal protection at temperatures from 70 to 85 °C

Molecular alloys, that combine a relatively high heat of melting with a suitable melting temperature adapted to the application temperature, are excellent materials for thermal protection and for thermal energy storage. Of special interest is the fact that, by making alloys of molecular materials; the range of melting can be adjusted over a range of temperatures. The present paper reports on the design of MAPCMs to be used for energy storage and thermal protection at temperatures from 70 to 85 °C. The aim is to use these materials for thermal protection in the catering sector in order to avoid proliferation of micro organisms; the minimal temperature required is higher than 65 °C. The work illustrates how some fundamental studies are helpful in choosing the right composition that is able to work at the temperature required for an application. Several molecular alloys using the n-alkanes are elaborated and characterized. The preparation of mixed crystals, their crystallographic and thermodynamic properties and stability, phase change behaviour, and their use in practical applications are reported.     

Metallo-organic decomposition derived (Ca, Sr)ZrO3 dielectric thin films on Pt coated Si substrate

Metallo-organic decomposition derived dielectric thin films of calcium zirconate doped with various concentrations of strontium ((Ca, Sr)ZrO₃) were prepared on Pt coated silicon substrate. Mainly in this paper, we present the investigations of their structural developments and present their electric and dielectric properties as well. The structural developments show that the CaZrO₃ film has amorphous structure with carbonate existing when annealed at 600 °C, while annealed at 650 °C and above, the carbonate is decomposed and those films crystallize into perovskite phase without preferred orientation. In addition, the prepared (Ca, Sr)ZrO₃ films with their Zr-O bonds affected by strontium doping are homogenous and stable as solid solutions in any concentration of strontium and all Bragg diffraction characteristics for the films shift downward with the increase in the concentration of strontium. Moreover, the electric properties show that the (Ca, Sr)ZrO₃ films have very low leakage current density and high breakdown strength; typically, the CaZrO₃ film annealed at 650 °C has the leakage current density approximately 9.5 × 10⁻⁸ A cm⁻² in the field strength of 2.6 MV cm⁻¹. Furthermore, the dielectric properties show that their dielectric constants are higher than 12.8 with very little dispersion in the frequency range from 100 Hz to 1 MHz and are independent of applied dc bias as well. The dielectric properties, in combination with the electric properties, make the materials promising candidates for high-voltage and high-reliability capacitor applications.     

Ordered mesoporous silica materials (SBA-15) with good heat-resistant magnetism

A series of highly ordered mesoporous materials (CF-SBA-15) with heat-resistant magnetism have been successfully prepared from impregnation of cobalt salt, iron salt, and citric acid with as-synthesized SBA-15. XRD and N₂ isotherms indicate that these materials have highly ordered hexagonal mesoporous symmetry and open pore systems. The measurement of magnetic property shows that these materials are ferromagnetic even if calcined at 550 °C for 10 h in air, indicating their good heat-resistant magnetism. These results would be very important for recycle and regeneration of adsorbents and catalysts in practical applications. Moreover, this method may be useful for other mesoporous materials with thermally stable magnetism from a combination of other mesoporous materials such as MCM-41 with magnetic nanoparticles of MnFe₂O₄ and NiFe₂O₄.     

Indirect laser etching of fused silica: Towards high etching rate processing

The indirect laser processing approach (LIBWE) laser-induced backside wet etching allows defined microstructuring of transparent materials at low laser fluences with high quality. The optical and the thermal properties of the solid/liquid interface determine the temperatures and therefore the etching mechanism in conjunction with the dynamic processes at the interface due to the fast heating/cooling rates. The exploration of organic liquid solvents and solutions such as 0.5 M pyrene/toluene results in low etch rates (∼20 nm/pulse). By means of liquid metals as absorber here, demonstrated for gallium (Ga), etch rates up to 600 nm/pulse can be achieved. Regardless of the high etch rates a still smooth surface similar to etching with organic liquid solutions can be observed. A comparative study of the two kinds of absorbing liquids, organic and metallic, investigates the etch rates regarding the fluence and pulse quantity. Thereby, the effect of incubation processes as result of surface modification on the etching is discussed. In contrast to pyrene/toluene solution the metallic absorber cannot decompose and consequently no decomposition products can alter the solid/liquid interface to enhance the absorption for the laser radiation. Hence, incubation can be neglected in the case of the silica/gallium interface so that this system is a suitable model to investigate the primary processes of LIBWE. To prove the proposed thermal etch mechanism an analytical temperature model based on a solution of the heat equation is derived for laser absorption at the silica/gallium interface.