@article{25906, abstract = {{A composite material of copper oxide (CuO) dispersed in the nanopores of KIT-6 silica (SiO2) is used as a dosimetric sensor for the detection of hydrogen sulfide (H2S) gas in low parts per milion concentrations. The sensor principle is based on the reversible chemical conversion of CuO to CuS, which guarantees a high selectivity, and on the corresponding percolation-induced change in electronic conductance.}}, author = {{Paul, Andrej and Weinberger, Christian and Tiemann, Michael and Wagner, Thorsten}}, issn = {{2574-0970}}, journal = {{ACS Applied Nano Materials}}, pages = {{3335--3338}}, title = {{{Copper Oxide/Silica Nanocomposites for Selective and Stable H2S Gas Detection}}}, doi = {{10.1021/acsanm.9b01004}}, year = {{2019}}, } @inproceedings{25641, abstract = {{Langzeitfestigkeit von Schweißungen aus PP unter Berücksichtigung der Morphologie}}, author = {{Schöppner, Volker and Wübbeke, Andrea and Paul, Andre and Tiemann, Michael and Fitze, F. and Austermeier, Laura and Chen, M. and Jakob, F. and Heim, H.-P. and Wu, T. and Niendorf, T. and Röhricht, M-L. and Schmidt, M.}}, booktitle = {{Werkstoffwoche (2019)}}, location = {{Dresden (Deutschland)}}, title = {{{Langzeitfestigkeit von Schweißungen aus PP unter Berücksichtigung der Morphologie}}}, year = {{2019}}, } @article{41524, author = {{Engelkemeier, Katja and Lindner, Jörg K N and Bürger, Julius and Vaupel, Kathrin and Hartmann, Marc and Tiemann, Michael and Hoyer, Kay-Peter and Schaper, Mirko}}, issn = {{0957-4484}}, journal = {{Nanotechnology}}, keywords = {{Electrical and Electronic Engineering, Mechanical Engineering, Mechanics of Materials, General Materials Science, General Chemistry, Bioengineering}}, number = {{9}}, publisher = {{IOP Publishing}}, title = {{{Nano-architectural complexity of zinc oxide nanowall hollow microspheres and their structural properties}}}, doi = {{10.1088/1361-6528/ab55bc}}, volume = {{31}}, year = {{2019}}, } @article{22541, abstract = {{Monodisperse micron-sized silica particle monolayers deposited onto plasma-grown SiOx-ultra-thin films have been used as reference systems to investigate wetting, water adsorption and capillary bridge formation as a function of silica surface functionalization. 1H,1H, 2H,2H perfluorooctyltriethoxysil (FOTS) monolayers, have been deposited on the respective surfaces by means of chemical vapor deposition resulting in macroscopically low energy surfaces. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) reflection absorption spectroscopy confirmed the monolayer formation. Water adsorption isotherms were studied by a combination of in-situ FTIR reflection spectroscopy and quartz crystal microbalance (QCM) while macroscopic wetting was analysed by contact angle measurements. The comparative data evaluation indicates that the macroscopic wetting behaviour was changed as expected, however, that water nanodroplets formed both at intrinsic defects of the FOTS monolayer and at the FOTS/SiOx interface. Capillary bridges of liquid water are dominantly formed in the confined particle contact areas and between surface asperities on the particles. The comparison of wetting, adsorption and capillary bridge formation shows that the hydrophobization of porous materials by organosilane monolayers leads to the formation of morphology dependent nanoscopic defects that act as sites for preferential capillary bridge formation.}}, author = {{Giner, Ignacio and Torun, Boray and Han, Yan and Duderija, Belma and Meinderink, Dennis and Orive, Alejandro González and de los Arcos de Pedro, Maria Teresa and Weinberger, Christian and Tiemann, Michael and Schmid, Hans-Joachim and Grundmeier, Guido}}, issn = {{0169-4332}}, journal = {{Applied Surface Science}}, pages = {{873--879}}, title = {{{Water adsorption and capillary bridge formation on silica micro-particle layers modified with perfluorinated organosilane monolayers}}}, doi = {{10.1016/j.apsusc.2018.12.221}}, year = {{2019}}, } @article{25912, abstract = {{It is possible to infiltrate a guest species selectively in one pore system of bimodal mesoporous CMK-5 carbon by an optimized nanocasting procedure. The selective filling has a drastic impact on the low-angle X-ray diffraction pattern of this novel class of materials. The structures of CMK-5, CMK-5 composite materials (sulfur and SnO2 as guest species), and CMK-3 carbon were simulated to investigate the influence of the pore filling with different guest species on the diffraction pattern and compared with experimental results. Additionally, the impact of structural defects is taken into account. The nature of the guest species strongly influences the relative intensity of the diffraction peaks. It turns out that the diffraction patterns of sulfur-carbon composite materials are nearly identical as those of CMK-3 carbon, which is attributed to a similar electron density of carbon and sulfur. Thus, sulfur is an ideal guest species to investigate the selective pore filling in CMK-5 carbon.}}, author = {{Weinberger, Christian and Hartmann, Marc and Ren, Sai and Sandberg, Thomas and Smått, Jan-Henrik and Tiemann, Michael}}, issn = {{1387-1811}}, journal = {{Microporous and Mesoporous Materials}}, pages = {{24--31}}, title = {{{Selective pore filling of mesoporous CMK-5 carbon studied by XRD: Comparison between theoretical simulations and experimental results}}}, doi = {{10.1016/j.micromeso.2018.02.035}}, year = {{2018}}, } @article{25910, abstract = {{We describe the synthesis of mesoporous Al2O3 and MgO layers on silicon wafer substrates by using poly(dimethylacrylamide) hydrogels as porogenic matrices. Hydrogel films are prepared by spreading the polymer through spin-coating, followed by photo-cross-linking and anchoring to the substrate surface. The metal oxides are obtained by swelling the hydrogels in the respective metal nitrate solutions and subsequent thermal conversion. Combustion of the hydrogel results in mesoporous metal oxide layers with thicknesses in the μm range and high specific surface areas up to 558 m2∙g−1. Materials are characterized by SEM, FIB ablation, EDX, and Kr physisorption porosimetry.}}, author = {{Chen, Zimei and Kuckling, Dirk and Tiemann, Michael}}, issn = {{2079-4991}}, journal = {{Nanomaterials}}, title = {{{Porous Aluminum Oxide and Magnesium Oxide Films Using Organic Hydrogels as Structure Matrices}}}, doi = {{10.3390/nano8040186}}, year = {{2018}}, } @article{25913, abstract = {{Ordered mesoporous CMK-5 carbon exhibits two distinct pore systems that can be modified individually. This work demonstrates how one of the pore systems can be selectively filled with elemental sulfur, while the other pore system remains empty. The resulting sulfur–carbon composite material with high residual porosity can be used as the cathode material in lithium–sulfur battery cells. We present a systematic investigation of the loading of CMK-5 carbon with variable relative amounts of sulfur and compare the results to the preparation of SnO2 (as well as TiO2, Mn2O3/Mn3O4, NiO) nanoparticle-loaded CMK-5 carbon.}}, author = {{Weinberger, Christian and Ren, Sai and Hartmann, Marc and Wagner, Thorsten and Karaman, Didem. Ş. and Rosenholm, Jessica M. and Tiemann, Michael}}, issn = {{2574-0970}}, journal = {{ACS Applied Nano Materials}}, pages = {{455--462}}, title = {{{Bimodal Mesoporous CMK-5 Carbon: Selective Pore Filling with Sulfur and SnO2 for Lithium Battery Electrodes}}}, doi = {{10.1021/acsanm.7b00307}}, year = {{2018}}, } @article{25909, abstract = {{Organic polymer-hydrogels are known to be capable of directing the nucleation and growth of inorganic materials, such as silica, metal oxides, apatite or metal chalcogenides. This approach can be exploited in the synthesis of materials that exhibit defined nanoporosity. When the organic polymer-based hydrogel is incorporated in the inorganic product, a composite is formed from which the organic component may be selectively removed, yielding nanopores in the inorganic product. Such porogenic impact resembles the concept of using soft or hard templates for porous materials. This micro-review provides a survey of select examples from the literature.}}, author = {{Weinberger, Christian and Kuckling, Dirk and Tiemann, Michael}}, issn = {{2310-2861}}, journal = {{Gels}}, title = {{{Hydrogels as Porogens for Nanoporous Inorganic Materials}}}, doi = {{10.3390/gels4040083}}, year = {{2018}}, } @article{25911, abstract = {{Different types of reduced graphene oxide and graphene oxide particles have been studied regarding their influence on the curing behaviour of epoxy-amine resins. Especially the specific surface area of reduced graphene oxide was selectively influenced by controlled drying of the material. The different types of reduced graphene oxide particles were used to produce epoxy-amine composites that significantly change their curing behaviour and mechanical properties. A variety of surface areas and compositions were prepared by combination of a fast heating rate and different drying methods. The combination of freeze drying with a fast heating rate leads to a large specific surface area of 680 m2/g. The morphologies of the particles were observed by scanning electron microscope and the BET surface area was measured with nitrogen-physisorption. The exfoliation quality was measured by XRD. The generated graphene oxide and thermally reduced graphene oxide particles were mixed with epoxy-amine resin. The curing behaviour was studied with rheological and differential scanning calorimetry (DSC) measurements. We observed that different surface functionalities lowers the Glass transition temperature and the gel time of an epoxy-amine curing system. In addition, we found that generated graphene oxide acts as flexibilizer. An increase of the deformation from 2.5 mm to 3.1 mm was measured by Erichsen Cupping Test.}}, author = {{Wolk, Andreas and Rosenthal, Marta and Weiß, Julia and Voigt, Markus and Wesendahl, Jan-Niklas and Hartmann, Marc and Grundmeier, Guido and Wilhelm, Rene and Meschut, Gerson and Tiemann, Michael and Bremser, Wolfgang}}, issn = {{0300-9440}}, journal = {{Progress in Organic Coatings}}, pages = {{280--289}}, title = {{{Graphene oxide as flexibilizer for epoxy amine resins}}}, doi = {{10.1016/j.porgcoat.2018.05.028}}, year = {{2018}}, } @article{25916, abstract = {{

We determine ozone decomposition on indium oxide by utilizing the gas transducing properties of hierarchically porous monoliths.

}}, author = {{Klawinski, Danielle and Weinberger, Christian and Klaus, Dominik and Smått, Jan-Henrik and Tiemann, Michael and Wagner, Thorsten}}, issn = {{1463-9076}}, journal = {{Physical Chemistry Chemical Physics}}, pages = {{10326--10332}}, title = {{{Kinetics of ozone decomposition in porous In2O3 monoliths}}}, doi = {{10.1039/c6cp08874k}}, year = {{2017}}, } @article{25915, abstract = {{Dimethylacrylamide-based hydrogels were utilized as porogenic matrices in the synthesis of mesoporous aluminum oxide (γ-Al2O3) with specific BET surface areas up to 360 m2 g–1. Polymers with molecular mass in the range 12000–35000 g mol–1 were synthesized from dimethylacrylamide and various comonomers by free-radical polymerization. Photo-cross-linking of the polymers and impregnation with aluminum nitrate [Al(NO3)3] was carried out in a single step, followed by formation of Al(OH)3/AlO(OH) and subsequent calcination. Calcination led to the formation of mesoporous Al2O3 and simultaneous combustion of the hydrogel. The structural properties of the products were characterized by powder XRD, N2 physisorption analysis, Hg intrusion porosimetry, and thermogravimetric analysis.}}, author = {{Weinberger, Christian and Chen, Zimei and Birnbaum, Wolfgang and Kuckling, Dirk and Tiemann, Michael}}, issn = {{1434-1948}}, journal = {{European Journal of Inorganic Chemistry}}, pages = {{1026--1031}}, title = {{{Photo-Cross-Linked Polydimethylacrylamide Hydrogels as Porogens for Mesoporous Alumina}}}, doi = {{10.1002/ejic.201601364}}, year = {{2017}}, } @article{25914, abstract = {{Dimethylacrylamide-based hydrogels were utilized as porogenic matrices in the synthesis of mesoporous aluminum oxide (γ-Al2O3) with specific BET surface areas up to 360 m2 g–1. Polymers with molecular mass in the range 12000–35000 g mol–1 were synthesized from dimethylacrylamide and various comonomers by free-radical polymerization. Photo-cross-linking of the polymers and impregnation with aluminum nitrate [Al(NO3)3] was carried out in a single step, followed by formation of Al(OH)3/AlO(OH) and subsequent calcination. Calcination led to the formation of mesoporous Al2O3 and simultaneous combustion of the hydrogel. The structural properties of the products were characterized by powder XRD, N2 physisorption analysis, Hg intrusion porosimetry, and thermogravimetric analysis.}}, author = {{Chen, Zimei and Weinberger, Christian and Tiemann, Michael and Kuckling, Dirk}}, issn = {{2227-9717}}, journal = {{Processes}}, title = {{{Organic Polymers as Porogenic Structure Matrices for Mesoporous Alumina and Magnesia}}}, doi = {{10.3390/pr5040070}}, year = {{2017}}, } @article{25919, abstract = {{The sorption properties of mixed-linker CAU-10 type metal organic frameworks (MOFs), [Al(OH)(1,3-BDC-X)n(1,3-BDC-SO3H)m] with 1,3-BDC = 1,3-benzenedicarboxyliate, X = H, NO2 or OH, 0.76 ≤ n ≤ 0.89 and 0.11 ≤ m ≤ 0.24, can be varied by surface modification through variation of the respective linker molecules. It is thus possible to design surface-modified CAU-10 type MOFs with variable affinity and accessibility of the pores for water vapour. When used as a dielectric in a capacitor, the MOF material will change its permittivity depending on the amount of physisorbed water; this is the working principle of capacitive humidity sensors. Three different mixed-linker compounds with CAU-10 structure are compared regarding their water sorption and impedance characteristics. A setup was developed allowing the characterization of the MOF samples under exposure to different relative humidity values in air by impedance spectroscopy. Interpretation of the results by means of standard models shows that the MOFs are qualified for functional layers of capacitive humidity sensors. Since the prepared MOFs are more temperature-stable than many commonly used polymers they offer the potential to build a new generation of high-temperature (up to 350 °C) humidity sensors.}}, author = {{Weiss, Alexander and Reimer, Nele and Stock, Norbert and Tiemann, Michael and Wagner, Thorsten}}, issn = {{1387-1811}}, journal = {{Microporous and Mesoporous Materials}}, pages = {{39--43}}, title = {{{Screening of mixed-linker CAU-10 MOF materials for humidity sensing by impedance spectroscopy}}}, doi = {{10.1016/j.micromeso.2015.08.020}}, year = {{2016}}, } @article{25917, abstract = {{Ordered, bimodal mesoporous CMK-5 carbon is prepared by using mesoporous SBA-15 silica as a structural mold. The carbon material is chemically modified by oxidative treatment with acidic persulfate solution. This leads to the creation of oxygen-containing functionalities at the pore walls of the carbon (up to 13 wt% oxygen), as confirmed by IR spectroscopy. The oxidative treatment is carried out before removal of the silica mold which ensures that only one of the two distinct modes of mesopores (namely, the intra-tubular pores) is affected; the other mode (inter-tubular pores) is protected from oxidation by the presence of the silica mold. This is proven by water vapor physisorption analysis. The oxidatively treated (intra-tubular) pores are significantly more polar and, hence, better wettable than the untreated (inter-tubular) pores.}}, author = {{Weinberger, Christian and Cao, X. and Tiemann, Michael}}, issn = {{2050-7488}}, journal = {{Journal of Materials Chemistry A}}, pages = {{18426--18431}}, title = {{{Selective surface modification in bimodal mesoporous CMK-5 carbon}}}, doi = {{10.1039/c6ta07772b}}, year = {{2016}}, } @article{25918, abstract = {{Characterization and application of (meso)porous materials often require information about the density of the respective samples. For example, the BET surface area is, by definition, normalized to the sample mass; hence, any comparison between samples of different composition needs to take into account their respective densities. Literature data on the densities of porous materials are scarce. Frequently, only bulk-phase densities are available which sometimes differ from those of porous samples, especially for amorphous systems, such as silica or carbon. The apparent density, i.e. the density of the sample excluding the gas-accessible pore volume, is typically determined by helium gas pycnometry utilizing specialized pycnometers. We demonstrate how to obtain the same data from standard N2 physisorption measurements as part of the regular measurement routine. We evaluate the method by reference measurements utilizing a non-porous reference sample (glass rod) to confirm the validity of the method. Then we present results on apparent density measurements of several mesoporous silica materials (MCM-41, MCM-48, SBA-15, KIT-6), mesoporous carbon (CMK-3, -5, -8, -9), and a variety of mesoporous metal oxides obtained by nanocasting.}}, author = {{Weinberger, Christian and Vetter, Simon and Tiemann, Michael and Wagner, Thorsten}}, issn = {{1387-1811}}, journal = {{Microporous and Mesoporous Materials}}, pages = {{53--57}}, title = {{{Assessment of the density of (meso)porous materials from standard volumetric physisorption data}}}, doi = {{10.1016/j.micromeso.2015.10.027}}, year = {{2016}}, } @article{25940, abstract = {{Metal–organic frameworks (MOFs) are crystalline microporous materials with tunable chemical and physical properties. By combining various metal clusters with different interconnecting organic linkers, the pore structure, crystallinity, as well as the surface properties can be modified. In the present work, modification of the organic linker molecules is utilized to synthesize CAU-10 type MOFs with variable affinity of the pore surface to water. In principle, this should influence the accessibility of the pores for water vapor and therefore offer a tool to control its sorption properties. For a deeper understanding we studied the water sorption characteristics and compared the results to the conductive and dielectric properties studied by impedance spectroscopy. Spectra in a wide frequency range from 1 mHz to 1 MHz were recorded. Data analysis is performed using the Havriliak–Negami model. The MOFs are also tested as sensitive layers for capacitive humidity sensing by correlating the change in permittivity of the materials with the amount of physisorbed water. Such an MOF-based sensor was tested with respect to environmental monitoring and compared to a commonly used commercial humidity sensor.}}, author = {{Weiss, Alexander and Reimer, Nele and Stock, Norbert and Tiemann, Michael and Wagner, Thorsten}}, issn = {{1463-9076}}, journal = {{Physical Chemistry Chemical Physics}}, pages = {{21634--21642}}, title = {{{Surface-modified CAU-10 MOF materials as humidity sensors: impedance spectroscopic study on water uptake}}}, doi = {{10.1039/c5cp01988e}}, year = {{2015}}, } @article{25939, abstract = {{A variety of metal nitrates were filled into the pores of an ordered mesoporous CMK-3 carbon matrix by solution-based impregnation. Thermal conversion of the metal nitrates into the respective metal oxides, and subsequent removal of the carbon matrix by thermal combustion, provides a versatile means to prepare mesoporous metal oxides (so-called nanocasting). This study aims to monitor the thermally induced processes by thermogravimetric analysis (TGA), coupled with mass ion detection (MS). The highly dispersed metal nitrates in the pores of the carbon matrix tend to react to the respective metal oxides at lower temperature than reported in the literature for pure, i.e., carbon-free, metal nitrates. The subsequent thermal combustion of the CMK-3 carbon matrix also occurs at lower temperature, which is explained by a catalytic effect of the metal oxides present in the pores. This catalytic effect is particularly strong for oxides of redox active metals, such as transition group VII and VIII metals (Mn, Fe, Co, Ni), Cu, and Ce.}}, author = {{Weinberger, Christian and Roggenbuck, Jan and Hanss, Jan and Tiemann, Michael}}, issn = {{2079-4991}}, journal = {{Nanomaterials}}, pages = {{1431--1441}}, title = {{{Synthesis of Mesoporous Metal Oxides by Structure Replication: Thermal Analysis of Metal Nitrates in Porous Carbon Matrices}}}, doi = {{10.3390/nano5031431}}, year = {{2015}}, } @article{25941, abstract = {{Ordered mesoporous In2O3 particles of variable size synthesized by the nanocasting method are used for preparation of resistive gas-sensing layers. Light activation by a LED (blue light, 460 nm) permits room-temperature ozone sensing. Apart from differences in base-line resistance in sensing layers containing small (diameter approx. 170 nm) or large particles (approx. 870 nm), differences in the response amplitude and response time constant are also observed. Signal stabilization is achieved faster for small particles. In addition, sensors show a particle size-dependent reaction threshold for low ozone concentration. Larger particles show negligible response to 50 ppb ozone whereas a significant response is observed for the small-particle sensors. A simple model based on geometrical properties and formation of depletion layers explaining the observed behavior is presented.}}, author = {{Klaus, Dominik and Klawinski, Danielle and Amrehn, Sabrina and Tiemann, Michael and Wagner, Thorsten}}, issn = {{0925-4005}}, journal = {{Sensors and Actuators B: Chemical}}, pages = {{181--185}}, title = {{{Light-activated resistive ozone sensing at room temperature utilizing nanoporous In2O3 particles: Influence of particle size}}}, doi = {{10.1016/j.snb.2014.09.021}}, year = {{2015}}, } @article{25942, abstract = {{Cobalt oxide spinel (Co3O4) with an ordered nanostructure is used as a resistive gas sensor for carbon monoxide (CO) in low ppm concentrations. The operating temperature has a strong impact on the concentration-dependent sensing behavior. At lower temperature (473 K) the sensor response is governed mainly by surface coverage with CO and/or CO2, whereas at higher temperature (563 K) oxygen diffusion in the crystal lattice of Co3O4 strongly affects the sensing behavior.}}, author = {{Vetter, S. and Haffer, S. and Wagner, T. and Tiemann, Michael}}, issn = {{0925-4005}}, journal = {{Sensors and Actuators B: Chemical}}, pages = {{133--138}}, title = {{{Nanostructured Co3O4 as a CO gas sensor: Temperature-dependent behavior}}}, doi = {{10.1016/j.snb.2014.09.025}}, year = {{2015}}, } @article{25945, abstract = {{Catalysis plays a central role in many fields of life, e.g., in biochemical processes, to reduce energy costs and resources in chemical industry and to decrease or even avoid environmental pollution and in energy management. Porous alumina (Al2O3) is an essential material in various applications, especially as a support material for catalysts. It is often prepared by nanocasting using porous carbon materials that serve as rigid structure matrices. In this work, an alternative way to synthesize mesoporous Al2O3 by using hydrogels as porogenic material is presented. Hydrogels can easily be patterned by light and used to imprint their structure onto alumina opening a new approach to fabricate patterned Al2O3. The hydrogels used in this work are based on poly(dimethylacrylamide) and were photo-chemically cross-linked. Followed by a nanocasting process, mesoporous alumina samples were synthesized and characterized by N2 physisorption and X-ray diffraction. The cross-linker amount in the polymer network was varied and the influence on the properties of the Al2O3 is analyzed.}}, author = {{Birnbaum, Wolfgang and Weinberger, Christian and Schill, Verena and Haffer, Stefanie and Tiemann, Michael and Kuckling, Dirk}}, issn = {{0303-402X}}, journal = {{Colloid and Polymer Science}}, pages = {{3055--3060}}, title = {{{Synthesis of mesoporous alumina through photo cross-linked poly(dimethylacrylamide) hydrogels}}}, doi = {{10.1007/s00396-014-3379-5}}, year = {{2014}}, }