Розробка мобільної технології ремонту низьковуглецевих стальних труб низького та високого тиску методом пайки низькотемпературними припоями

Розроблено технологію безвогневого ремонту дефектів конструкцій з низьковуглецевих сталей шляхом пайки низькотемпературними припоями. Розроблено та заявлено новий склад легкоплавкого припою на базі олова з домішками міді та вісмуту. Припій оптимально поєднує властивості рідкоплинності, корозійної стійкості, міцності та адгезійної міцності. Технологію пайки сталей низькотемпературними припоями із застосуванням високочастотного генератора електричного струму доведено до стану практичного застосування.Разработана технология безогневого ремонта дефектов конструкций из низкоуглеродистых сталей путем пайки низкотемпературными припоями. Разработан и заявлен новый состав легкоплавкого припоя на базе олова, с добавками меди и висмута. Припой оптимально объединяет свойства жидкотекучести, коррозионной стой кости, прочности и адгезионной прочности. Технологию пайки сталей низкотемпературными припоями с применением высокочастотного генератора электрического тока доведено до состояния практического применения.The technology of out fire defects repair in low carbon steel constructions by soldering with low- temperature solders is developed. The new fusible tin rich solder composition containing copper and bismuth additives is developed and declared. The solder has optimum properties of liquid stream, corrosion resistance, durability and adhesion strength. The low carbon steel soldering technology with application of high-frequency electric current generator is carried to practical application

High-throughput optimization of nitroxide mediated radical polymerizations as basis for the synthesis of temperature-responsive copolymers

The development of controlled radical polymn. techniques, namely atom transfer radical polymn. (ATRP), reversible addn. fragmentation transfer (RAFT) and nitroxide mediated radical polymn. (NMP), have opened up unprecedented possibilities for the synthesis of well-defined macromol. architectures with a large no. of different monomers. In addn., well-defined polymers with LCST behavior have wound widespread interest for a use as -smart' responsive materials. Here we report our automated parallel investigations on the NMP of 2 hydroxypropylacrylate (HPA), N,N-dimethylacrylamide (DMA) and N-acryloyl morpholine (Amor) using BlocBuilder- nitroxide and addnl. free SG-1 nitroxide. The high-throughput approach allowed fast optimization of the polymn. procedure for solvent, temp. and concn. of free nitroxide. In addn., the optimal polymn. conditions were applied for the synthesis of systematical libraries of well-defined statistical copolymers based on HPA and DMA or Amor. The effect of monomer compn. on the thermal properties and thermoresponsiveness of the copolymers was studied in detail. [on SciFinder (R)

Entrance size analysis of silica materials with cagelike poer structure by thermoporometry

Ordered mesoporous materials offer many potential applications in catalysis, chromatography, and drug delivery. If the pores form cages rather than straight channels, the entrance size to these cages is a crucial parameter but notoriously difficult to asses. For example, classical physisorption techniques are limited by forced closure of the hysteresis loop. Here we apply thermoporometry by differential scanning calorimetry (DSC) of confined water to quantify the entrance sizes in a series of mesoporous silica materials with cagelike pore structure, i.e. SBA-16 and FDU-12. With DSC, entrance sizes of materials with cages of up to 15 nm were determined which could not be assessed by nitrogen physisorption and were validated by argon physisorption at 77 K. For cage sizes exceeding 15 nm, entrance sizes were quantified by thermoporometry that were inaccessible by either of the physisorption techniques. In addition, the size distribution of the widest-entrance path toward the cages was determined by applying a step-equilibration method with DSC, providing essential structural information beyond the limits of physisorption with N2 or Ar at 77 K. We show that thermoporometry extends the range of classical physisorption techniques and is a powerful tool for the determination of entrance sizes in mesoporous materials

Freeze-drying for controlled nanoparticle distribution in Co/SiO 2 Fischer–Tropsch catalysts

Controlling the nanoparticle distribution over a support is considered essential to arrive at more stable catalysts. By developing a novel freeze drying method, the nanoparticle distribution was successfully manipulated for the preparation of Co/SiO2 Fischer-Tropsch catalysts using a commercial silica-gel support. After loading the precursor via a solution impregnation or melt infiltration, differential scanning calorimetry was used to study the phase behavior of the confined cobalt nitrate precursor phases to ascertain suitable freeze-drying conditions. When a conventional drying treatment was utilized, catalysts showed inhomogeneous cobalt distributions, with 6 – 8 nm nanoparticles grouped in clusters of up to 400 nm. In contrast, by utilizing freeze-drying starting at liquid nitrogen temperatures, homogeneous distributions of 4 – 7 nm nanoparticles were obtained. Raising the temperature at which the freeze drying process takes place resulted in either uniform or strongly nonuniform nanoparticle distributions, depending on the specific conditions and precursor loading method. After reduction, all catalysts showed high activity for the Fischer- Tropsch reaction at 1 bar. The catalysts thus synthesized form an excellent platform for future studies of the stability under industrially relevant Fischer-Tropsch conditions

Entrance size analysis of silica materials with cagelike poer structure by thermoporometry

Ordered mesoporous materials offer many potential applications in catalysis, chromatography, and drug delivery. If the pores form cages rather than straight channels, the entrance size to these cages is a crucial parameter but notoriously difficult to asses. For example, classical physisorption techniques are limited by forced closure of the hysteresis loop. Here we apply thermoporometry by differential scanning calorimetry (DSC) of confined water to quantify the entrance sizes in a series of mesoporous silica materials with cagelike pore structure, i.e. SBA-16 and FDU-12. With DSC, entrance sizes of materials with cages of up to 15 nm were determined which could not be assessed by nitrogen physisorption and were validated by argon physisorption at 77 K. For cage sizes exceeding 15 nm, entrance sizes were quantified by thermoporometry that were inaccessible by either of the physisorption techniques. In addition, the size distribution of the widest-entrance path toward the cages was determined by applying a step-equilibration method with DSC, providing essential structural information beyond the limits of physisorption with N2 or Ar at 77 K. We show that thermoporometry extends the range of classical physisorption techniques and is a powerful tool for the determination of entrance sizes in mesoporous materials

Tuning the viscosity of halogen free bulk heterojunction inks for inkjet printed organic solar cells

For the solution processing of organic photovoltaics on an industrial scale, the exclusion of halogenated solvents is a necessity. However, the limited solubility of most semiconducting polymer/fullerene blends in non-halogenated solvents results in ink formulations with low viscosities which poses limitations to the use of roll-to-roll compatible deposition processes, such as inkjet printing. We propose to add polystyrene as a rheological modifier to increase the viscosity of bulk heterojunction (BHJ) non-halogenated inks. The printing and performance of P3HT/PCBM photoactive layer inks are characterized as a function of polystyrene concentration and three different molecular weights. Addition of 1 wt% polystyrene provided a near two-fold gain in viscosity, with the largest viscosity gains coming from the polymer with the highest molecular weight. However, this coincided with greater viscoelastic behavior, which reduced the jetting performance of the inks. Differences in solvent compatibility of the polystyrene/P3HT/PCBM ternary blend resulted in phase separation upon layer drying, whereby polystyrene segregated to the layer-air interface to form an isolated domain or network like topology. Nevertheless, a 1.7-fold increase in dynamic viscosity was obtained for devices with printed BHJ layers containing polystyrene at the expense of a 20% reduction in OPV performance. The improved viscosity and good printing behavior achieved with small additions of polystyrene demonstrates its potential to overcome the limited viscosity resulting from typical non-halogenated ink formulations for semiconducting polymers. These results offer a step forward to the industrialization of inkjet printing as an effective deposition technique for functional layers of organic electronics

Fundamentals of Melt infiltration for the Preparation of Supported Metal Catalysts.The Case of Co/SiO2 Fischer-Tropsch Synthesis

We explored melt infiltration of mesoporous silica supports to prepare supported metal catalysts with high loadings and controllable particle sizes. Melting of Co(NO3)2 ·6H2O in the presence of silica supports was studied in situ with differential scanning calorimetry. The melting point depression of the intraporous phase was used to quantify the degree of pore loading after infiltration. Maximum pore-fillings corresponded to 70-80% of filled pore volume, if the intraporous phase was considered to be crystalline Co(NO3)2 ·6H2O. However, diffraction was absent in XRD both from the ordered mesopores at low scattering angles and from crystalline cobalt nitrate phases at high angles. Hence, an amorphous, lower density, intraporous Co(NO3)2 ·6H2O phase was proposed to fill the pores completely. Equilibration at 60 °C in a closed vessel was essential for successful melt infiltration. In an open crucible, dehydration of the precursor prior to infiltration inhibited homogeneous filling of support particles. The dispersion and distribution of Co3O4 after calcination could be controlled using the same toolbox as for preparation via solution impregnation: confinement and the calcination gas atmosphere. Using ordered mesoporous silica supports as well as an industrial silica gel support, catalysts with Co metal loadings in the range of 10-22 wt % were prepared. The Co3O4 crystallite sizes ranged from 4 to 10 nm and scaled with the support pore diameters. By calcination in N2, pluglike nanoparticles were obtained that formed aggregates over several pore widths, while calcination in 1% NO/N2 led to the formation of smaller individual nanoparticles. After reduction, the Co/SiO2 catalysts showed high activity for the Fischer-Tropsch synthesis, illustrating the applicability of melt infiltration for supported catalyst preparation

Quantitative Assessment of Pore Blockage in Supported Catalysts: Comparing Differential Scanning Calorimetry and Physisorption

Mesoporous materials are commonly used as supports for a guest phase, such as catalytically active transition metal nanoparticles. N2 physisorption at 77 K is the standard technique to characterize mesoporosity; however, it is not always suitable to assess pore blockage caused by the guest phase. Here we report on the qualitative and quantitative assessment of pore blockage comparing N2 physisorption with two alternative techniques: differential scanning calorimetry (DSC) of the freezing and melting of confined water and physisorption of Ar at 77 K. A set of well-defined model catalyst nanostructures with varying degrees of pore blockage was synthesized using ordered mesoporous supports and different nanoparticle sizes. Pore blockage was detected with sorption techniques by analyzing the delayed gas desorption. For the first time we report the analysis of nanoparticle induced constrictions with DSC by studying the delayed freezing of water in the constricted pores. Both DSC and argon sorption provided information which cannot be accessed by standard N2 physisorption. Therefore, both techniques are advocated for the analysis of complex porous structures

Impregnation of mesoporous silica for catalyst preparation studied with differential scanning calorimetry

Aqueous impregnation of mesoporous silica as a first step in catalyst preparation was studied to investigate the distribution of the metal-precursor solution over the support. The degree of pore-filling after impregnation was determined using the freezing point depression of confined liquids. A separate bulk melting transition observed with differential scanning calorimetry in combination with TGA and N2-physisorption allowed rigorous quantification of the extent of pore-filling of the support. The micro- and mesoporous volumes of different mesoporous silica were filled up to 90−100% with water. With KCl solution, at maximum 75−85% of the pores were filled. However, the total pore-filling reached 85−90% when the estimated volume of physisorbed water was included. As a case study for catalyst preparation, silica supports were also impregnated with an aqueous Ni(NO3)2 solution. Generally, the solution occupied up to 80−90% of the pore volume, similar to the pore-filling with KCl. This study shows that ordered mesoporous silica, as well as silica-gel, are filled spontaneously and largely with aqueous solutions by capillary forces. Just up to 10% empty pores are expected to be present after a so-called incipient wetness impregnation. Therefore, a largely uniform distribution of the metal precursor over the support is achieved by aqueous impregnation

Study of Nanoconfined Phases for the Rational Synthesis of Supported Catalysts

Catalysts are indispensable for modern day society since they are used in the production of transportation fuels, chemicals and materials. Understanding the structure-activity relation for a catalytic system allows the formulation of catalyst structure specifications that optimizes activity, selectivity and stability. For supported catalysts, size and shape of the catalytic nanoparticles and their distribution over the support are of paramount importance to achieve the desired catalytic properties. Nevertheless, catalyst preparation has long been considered an art rather than a science. In this work, catalyst preparation is rationalized from the phase behavior of the precursor salt or salt solution and is mainly performed within the framework of silica supported cobalt catalysts for Fischer-Tropsch synthesis. The Fischer-Tropsch synthesis involves the conversion of CO and H2 gas into longer chain hydrocarbons to produce transportation fuels and lubricants from feedstock other than crude oil, e.g. natural gas, coal or biomass. Therefore, this process has a high industrial and economic relevance. Supported cobalt catalysts require a controlled preparation method as there is an optimum cobalt nanoparticle size of ~6 nm. Furthermore, high metal loadings are needed to obtain high activity of the supported catalysts. At the same time, the nanoparticles should be distributed uniformly over the support such that their nearest neighbor distance is maximized and deactivation due to the coalescence of nanoparticles (sintering) is minimized. Finally, due the large scale of the applications, a convenient preparation method producing little waste is desired. Impregnation and drying is such a convenient preparation method and is commonly applied in industry and academia. However, it suffers from a lack of control over the nanoparticle dispersion and distribution, especially when using low cost transition metal nitrate salts with a high solubility in water. In this thesis we aim to acquire fundamental insight into this preparation method to reach the ultimate goal: equally-sized and maximally-spaced nanoparticles. First, pore filling with the precursor solution and salt by impregnation or melt infiltration, respectively was confirmed using differential scanning calorimetry and the depressed melting points of the confined phases as compared to the extraporous phases. Using transmission electron microscopy the distribution of the solution over the pores of the support was visualized after impregnation and after drying. This showed that freeze-drying led to a homogeneous distribution of the salt and subsequently to a more homogeneous nanoparticle distribution in the final catalys