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Papers by Santhosh K Matam

Journal of Colloid and Interface Science, 2015

We report a facile synthesis of superhydrophobic silica-iron oxide nanocomposites via a co-precur... more We report a facile synthesis of superhydrophobic silica-iron oxide nanocomposites via a co-precursor sol-gel process. The choice of the silica precursor (Methyltrimethoxysilane, MTMS) in combination with iron nitrate altered the pore structure dramatically. The influence of iron oxide doping on the structural properties of pristine MTMS aerogel is discussed.

ACS applied materials & interfaces, Jan 13, 2015

With growing public interest in portable electronics such as micro fuel cells, micro gas total an... more With growing public interest in portable electronics such as micro fuel cells, micro gas total analysis systems, and portable medical devices, the need for miniaturized air pumps with minimal electrical power consumption is on the rise. Thus, the development and downsizing of next-generation thermal transpiration gas pumps has been investigated intensively during the last decades. Such a system relies on a mesoporous membrane that generates a thermomolecular pressure gradient under the action of an applied temperature bias. However, the development of highly miniaturized active membrane materials with tailored porosity and optimized pumping performance remains a major challenge. Here we report a systematic study on the manufacturing of aerogel membranes using an optimized, minimal-shrinkage sol-gel process, leading to low thermal conductivity and high air conductance. This combination of properties results in superior performance for miniaturized thermomolecular air pump application...

CHIMIA International Journal for Chemistry

The phosphor CaTiO 3 :Pr 3+ was synthesized via a solid-state reaction in combination with a subs... more The phosphor CaTiO 3 :Pr 3+ was synthesized via a solid-state reaction in combination with a subsequent annealing under flowing NH 3 . Comparatively large off-center displacements of Ti in the TiO 6 octahedra were confirmed for as-synthesized CaTiO 3 :Pr 3 by XANES. Raman spectroscopy showed that the local crystal structure becomes highly symmetric when the powders are ammonolyzed at 400 °C. Rietveld refinement of powder X-ray diffraction data revealed that the samples ammonolyzed at 400 °C have the smallest lattice strain and at the same time the largest average Ti-O-Ti angles were obtained. The samples ammonolyzed at 400 °C also showed the smallest mass loss during the thermal re-oxidation in thermogravimetric analysis (TGA). Enhanced photolumincescence brightness and an improved decay curve as well as the highest reflectance were obtained for the samples ammonolyzed at 400 °C. The improved photoluminescence and afterglow by NH 3 treatment are explained as a result of the reduced ...

Journal of Alloys and Compounds, 2014

Optical Materials Express, 2013

Catalysis Today, 2015

ABSTRACT Perovskite-type oxides LaCo1−x−yPdxZnyO3±δ are studied for the methanol steam reforming ... more ABSTRACT Perovskite-type oxides LaCo1−x−yPdxZnyO3±δ are studied for the methanol steam reforming (MSR) reaction. LaCo1−x−yPdxZnyO3±δ with and without Co substitution by Pd and/or Zn are synthesized by the amorphous citrate method. The effect of substitution on the reducibility of the materials is investigated by in situ XRD and differential thermal/thermogravimetric analysis (DTA/TG) during temperature programmed reduction (TPR) with hydrogen. From this, the phase composition evolving as a function of temperature is determined. The TPR data indicate that the reducibility of the materials strongly depends on the substituent, i.e., Pd or Zn. The former increases the reducibility, while substitution by Zn decreases the reducibility. Materials containing both Pd and Zn exhibit intermediate reducibility as compared to the un-substituted LaCoO3±δ (LCO) and mono-metal substituted LaCo0.873Pd0.127O3±δ (LCPO) and LaCo0.89Zn0.11O3±δ (LCZO). In general, the metal ions in the materials are completely reduced at 590 °C, except La2O3. After reductive pre-treatment at 590 °C for 2 h, the MSR performance of the materials is evaluated between 150 and 400 °C while keeping comparable CH3OH conversion to assess the product-concentration-dependent CO2 selectivity. These results confirm that the CO2 selectivity is strongly dependent on the material composition. For example, the un-substituted LCO, LCPO and LCZO show a CO2 selectivity of around 13% at 300 °C, while it is improved to 80% on both Pd and Zn containing LaCo0.85Pd0.075Zn0.075O3±δ (LCPZO-15).

International Journal of Photoenergy, 2013

ABSTRACT Phase-pure tantalum oxynitride (β-TaON) powders were synthesized by thermal ammonolysis ... more ABSTRACT Phase-pure tantalum oxynitride (β-TaON) powders were synthesized by thermal ammonolysis of Ta2O5 powders. X-ray diffraction revealed an enlargement of the unit cell and an increase of the crystallite size with increasing ammonolysis temperature. Scanning electron microscopy showed reduced particle sizes for β-TaON synthesized at 800 and compared to the precursor oxide. With increasing nitridation temperature the Brunauer-Emmett-Teller surface area was reduced and the nitrogen content increased. UV-Vis spectroscopy showed a bandgap energy of 2.6–2.4 eV. The highest oxygen evolution rate of 220 μmol·g−1·h−1 was achieved for β-TaON synthesized at . The factors determining the photocatalytic activity of β-TaON powders were found to be the specific surface area and defects in the β-TaON.

Chemical communications (Cambridge, England), Jan 21, 2001

A titania-supported ammonium salt of 12-molybdophosphoric acid has been synthesized, and the salt... more A titania-supported ammonium salt of 12-molybdophosphoric acid has been synthesized, and the salt-support interaction, which enhanced the reaction rate, has been correlated with the activity of the catalyst in the ammoxidation of 2-methylpyrazine.

The Journal of Physical Chemistry C, 2014

ABSTRACT An empirical study of the gas solid reaction of carbon dioxide (CO2) with alanates is pr... more ABSTRACT An empirical study of the gas solid reaction of carbon dioxide (CO2) with alanates is presented. This investigation was triggered by reports of hazards related to the reaction of lithium aluminum hydride with carbon dioxide, together with the recent emergence of alanates as potential hydrogen storage materials. Furthermore, the reduction of CO2 by hydrides is an alternative to the conventional CO2 reduction employing hydrogen gas in combination with a catalyst. Experimentally this work was carried out by studying the decomposition of alanate samples in a carbon dioxide atmosphere with thermogravimetric and ex situ IR spectroscopic techniques. It is shown that alanates react with CO2 at atmospheric pressure in two distinct temperature regions, yielding methane, hydrogen gas, and metal oxides as the major products. The experimental findings allowed us to postulate a mechanism for the complex metal hydride reduction of CO2, involving alane as a highly reactive intermediate. It is suggested that nucleophilic attack of alane hydride ions onto the carbonyl carbon of CO2 leads to sequential formation of aluminum formate and methoxy species which get converted into methane and metal oxides as the final products.

Topics in Catalysis, 2011

... Kimmerle B, Grunwaldt JD, Baiker A, Glatzel P, Boye P, Ste-phan S, Schroer CG (2009) J Phys C... more ... Kimmerle B, Grunwaldt JD, Baiker A, Glatzel P, Boye P, Ste-phan S, Schroer CG (2009) J Phys Chem C 113:3037 21. Santhosh Kumar M, Aguirre MH, Weidenkaff A, Ferri D (2010) J Phys Chem C 114:9439 22. Ressler T (1998) J Synchrotron Radiat 5:118 23. ...

The Journal of Physical Chemistry C, 2011