Thermally assisted electron beam induced deposition can result in an improvement of the purity of nano-scale depositions. Six commonly used organic precursors were examined: W(CO)(6), TEOS (tetraethylorthosilicate), MeCpPtMe(3), Co(CO)(3)NO, Co(2)(CO)(8), and Me(2)Auacac. The last two precursors were also tested on two different instruments to confirm reproducibility of the results. The influence of the substrate temperature on the composition of the deposition has been quantified systematically in the temperature range 25-360 °C. It has been shown that most purities improve when applying an elevated temperature, while the shape of the deposition remains intact. The purity improvement is achieved at the cost of a lower deposition yield. The amount of improvement is different for each precursor. Within the maximum temperature range of 360 °C, the best improvement was found for W(CO)(6): from 36.7 at.% at 25 °C to 59.2 at.% at 280 °C. For both cobalt precursors an additional transition region between patterned electron beam induced deposition (EBID) and thermal thin film growth has been identified. In this region seeded growth occurs with strongly increased growth rates.
The development of advanced hybrid materials based on polymers from biorenewable sources and mineral nanoparticles is currently of high importance. In this paper, we applied softwood kraft lignins for the synthesis of lignin/SiO2 nanostructured composites. We described the peculiarities of composites formation in the sol-gel process through the incorporation of the lignin into a silica network during the hydrolysis of tetraethoxysilane (TEOS). The initial activation of lignins was achieved by means of a Mannich reaction with 3-aminopropyltriethoxysilane (APTES). In the study, we present a detailed investigation of the physicochemical characteristics of initial kraft lignins and modified lignins on each step of the synthesis. Thus, 2D-NMR, 31P-NMR, size-exclusion chromatography (SEC) and dynamic light scattering (DLS) were applied to analyze the characteristics of pristine lignins and lignins in dioxan:water solutions. X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) were used to confirm the formation of the lignin–silica network and characterize the surface and bulk structures of the obtained hybrids. Termogravimetric analysis (TGA) in nitrogen and air atmosphere were applied to a detailed investigation of the thermal properties of pristine lignins and lignins on each step of modification. SEM confirmed the nanostructure of the obtained composites. As was demonstrated, the activation of lignin is crucial for the sol-gel formation of a silica network in order to create novel hybrid materials from lignins and alkoxysilanes (e.g., TEOS). It was concluded that the structure of the lignin had an impact on its reactivity during the activation reaction, and consequently affected the properties of the final hybrid materials.
A new method of direct, rapid nano- to micro-scale patterning of high purity cobalt is presented. The method utilizes a combination of electron beam induced deposition (EBID) and seeded growth at elevated temperatures below the temperature of spontaneous thermal decomposition. Dicobalt octacarbonyl Co₂(CO)₈ is used as the precursor and carbon as a seed layer. Seeded deposition is carried out in the substrate temperature range from 55 to 75 °C. Deposition yield is significantly higher than conventional EBID and magnetotransport measurements indicate that resistivity, 22 µΩ cm, and saturation magnetization, 1.55 T, are much closer to the corresponding values for bulk Co than those for standard EBID.
Industrial production of low-charge microfibrillated cellulose (MFC) typically results in wide fibril size distributions. This polydispersity influences viscosity, overall colloidal stability, and rheological properties of MFC suspensions and gels in aqueous systems. In this work, a systematic rheological analysis is performed for industrially prepared MFC and fractions of different size distributions. Gel formation and flow characteristics (e.g., shear-thinning) of each fraction are examined under neutral and acidic conditions and compared with the unfractionated MFC suspension. The effects of size, aspect ratio, and surface charge on the rheology of semi-dilute MFC suspensions are discussed. The results demonstrate that particle size and aspect ratio distribution control the viscoelasticity and shear-thinning properties of MFC suspensions. An increased fraction of small diameter nanofibrils, by ex situ addition of the fine particles with high aspect ratio or removal of the coarsest particles (with lower aspect ratio) by fractionation, significantly enhances the storage modulus and the yield stress of the complex mixture, compared to the properties of the coarser fractions. New insights are also reported on the tailoring of the rheology of highly polydisperse fibrillar mixtures, where the rheological contributions of each fraction are discussed. Graphic