Temperature-programmed Desorption Mass Spectrometry Research Articles

Decarboxylation of p-Coumaric Acid during Pyrolysis on the Nanoceria Surface

Temperature-programmed desorption mass spectrometry (TPD MS) was used to study the pyrolysis of p-coumaric acid (pCmA) on the nanoceria surface. The interaction of pCmA with the CeO2 surface was investigated by FT-IR spectroscopy. The obtained data indicated the formation on the nanoceria surface of bidentate carboxylate complexes with chelate (Δν = 62 cm−1) and bridge structure (Δν = 146 cm−1). The thermal decomposition of pCmA over nanoceria occurred in several stages, mainly by decarboxylation. The main decomposition product is 4-vinylphenol (m/z 120). The obtained data can be useful for studying the mechanisms of catalytic thermal transformations of lignin-containing raw materials using catalysts containing cerium oxide and the development of effective technologies for the isolation of pCmA from lignin.

Self-Heating Mechanism of All-Solid-State Battery with Sulfide Electrolyte

All-solid-state batteries (ASSBs) are expected to have less safety concern than Lithium-ion batteries with organic liquid electrolyte (LIBs) because flammable liquid electrolytes are not used in ASSBs. The thermal behaviors in LIBs have widely discussed in many literatures1. However, thermal behaviors of ASSBs have not investigated much.In this study, to clarify the self-heating phenomenon of our prototype ASSB with Argyrodite-type solid electrolyte we have performed calorimetric studies and gas analyses. In the calorimetric measurement, an accelerated rate calorimetry (ARC) was used to compare the starting temperature of self-heating in ASSB to that in LIB. It was found that the self-heating of ASSB takes place at 200-300ºC which was significantly higher than that in LIB.To identify the endothermic and exothermic peaks in the calorimetric profile and to estimate the amount of heat generation in ASSB, a Calvet-type calorimeter (C600) and a differential scanning calorimeter (DSC) were used with a heating rate of 1 ℃/min under Ar atmosphere for a full cell and electrode layers of the ASSB, respectively. The exothermic peaks at 200- 300℃ for charged ASSB (at ca. 4.1 V) mostly corresponded to those for the cathode layer which was extracted from the charged ASSB. The crystal structure change of the cathode layer charged at ca. 4.1 V associated with temperature change was analyzed by X-ray diffraction (XRD) to understand the reaction mechanism. The XRD peaks for the active material and the solid electrolyte in the cathode layer were disappeared at 200-300ºC. It was suggested that the heat generation at 200- 300ºC were mainly caused by the reaction between the cathode active material and the solid electrolyte.We also analyzed the evolved gas during the heating of ASSB using a temperature-programmed desorption-mass spectrometry (TPD-MS). The detailed mechanism will be discussed on-site.AcknowledgmentsThis study was carried out in SOLiD-EV project supported by NEDO (New Energy and Industrial Technology Development Organization).References Xuning Feng, Minggao Ouyang, Xiang Liu, Languang Lu, Yong Xi, Xiangming He, Energy Storage Materials 10 (2018) 246-267.

Secondary structure of muramyl dipeptide glycoside in pristine state and immobilized on nanosilica surface

Fourier transform infrared spectroscopy (FT-IR) and temperature programmed desorption mass spectrometry (TPD-MS) data of O-glycoside MDP in pristine and immobilized on silica surface states indicate that O-glycoside MDP binds to the silica surface by means of carboxylic and NH moieties of isoglutamine. Moreover, pyrolysis of O-glycoside MDP on the silica surface proceeds through formation of additional product 3-iminopyridine-2(3H)-one, which identified in mass spectra as molecular ion with m/z 108 and its fragment ions with m/z 79, 77, 51. FTIR and TPD-MS data confirm existence of a MDP first β-turn on the silica surface resulting from the formation of a hydrogen bond between the NAc carbonyl and the L-Ala NH for MDP and its analogs, as reported previously.

PREPARATION AND CHARACTERISATION OF NEW BIOMATERIALS BASED ON CHITOSAN IODIDE WITH BIOLOGICALLY ACTIVE DYES

New composite materials were obtained based on chitosan iodide and organic dyes – methylene blue and fuchsine in fucorcin (Castellani liquid) – by using a simple synthetic procedure. The materials were characterised by scanning electron microscopy, X-ray diffraction, temperature-programmed desorption mass spectrometry, infrared spectroscopy and visible and ultraviolet light spectroscopy. The dyes in the composites were distributed uniformly and did not form separate phases. These composites could form structured porous sponges and films and therefore be used in various fields of application. The materials displayed antibacterial activity against antibiotic resistant gram-positive and gram-negative bacteria.

Catalytic Pyrolysis of Lignin Model Compounds (Pyrocatechol, Guaiacol, Vanillic and Ferulic Acids) over Nanoceria Catalyst for Biomass Conversion

Understanding the mechanisms of thermal transformations of model lignin compounds (MLC) over nanoscale catalysts is important for improving the technologic processes occurring in the pyrolytic conversion of lignocellulose biomass into biofuels and value-added chemicals. Herein, we investigate catalytic pyrolysis of MLC (pyrocatechol (P), guaiacol (G), ferulic (FA), and vanillic acids (VA)) over nanoceria using FT-IR spectroscopy, temperature-programmed desorption mass spectrometry (TPD MS), and thermogravimetric analysis (DTG/DTA/TG). FT-IR spectroscopic studies indicate that the active groups of aromatic rings of P, G, VA, and FA as well as carboxylate groups of VA and FA are involved in the interaction with nanoceria surface. We explore the general transformation mechanisms of different surface complexes and identify their decomposition products. We demonstrate that decomposition of carboxylate acid complexes occurs by decarboxylation. When FA is used as a precursor, this reaction generates 4-vinylguaiacol. Complexes of VA and FA formed through both active groups of the aromatic ring and decompose on the CeO2 surface to generate hydroxybenzene. The formation of alkylated products accompanies catalytic pyrolysis of acids due to processes of transalkylation on the surface.

Effects of composition and particle size on the surface state and degassing behavior of nickel-based superalloy powders

Surface state and degassing behavior of nickel-based superalloy powders are essential to the melting and sintering properties of additive manufacturing (AM) and powder metallurgy (PM). Superalloy powders with various compositions and particle sizes were investigated by FESEM, XPS, AES, HAADF-STEM, and temperature programmed desorption mass spectrometry (TPD-MS). The surface analysis results demonstrate that IN625, IN718, and FGH96 superalloy powders are covered by homogeneous Ni oxide/hydroxide (NiO/Ni(OH)2) layer decorated with various oxides. NiO/Ni(OH)2 layer thickness changes in the range of 5.7 nm to 9.8 nm with different powder compositions and particle sizes, while the influencing factors of thickness can be arranged in the following order (from highest to lowest) as IN625-IN718-FGH96 and (106–150 μm)-(48–106 μm)-(<48 μm) respectively. The TPD-MS results indicate that the degassing amounts significantly increase with the decrease of NiO/Ni(OH)2 layer thickness, in which the degassing behavior is partially controlled by molecular diffusion. Powders with more active metallic elements, i.e. Al and Ti, and smaller particle size possess relatively thinner oxide layer which result in lower diffusion barrier and higher degassing amounts. The investigation reveals the relationship between the surface state and degassing behavior of superalloy powders considering the differences in the composition and particle size, and gives guidance on nickel-based superalloy powder processing.

High-Resolution Lithographic Patterning with Organotin Films: Role of CO2 in Differential Dissolution Rates

Details of the chemistry enabling the patterning of organotin photoresists to single-digit-nm resolution continue to engage study. In this report, we examine the contributions of atmospheric gases to the differential dissolution rates of an n-butyltin oxide hydroxide photoresist. Cryo scanning tunneling electron microscopy (cryo-STEM) produces a micrograph of the latent image of an irradiated resist film, readily distinguishing exposed and unexposed regions. Temperature-programmed desorption mass spectrometry (TPD-MS) and cryo electron energy loss spectroscopy (cryo-EELS) show that irradiated films are depleted in carbon through desorption of butane and butene. Upon aging in air, irradiated films absorb H2O, as previously established. TPD-MS also reveals a previously unrecognized absorption of CO2, which correlates to a heightened dissolution contrast. This absorption may play an active role in determining intrinsic patterning performance and its variability based on changes in atmospheric-gas composition.

Ethanol Gas Sensing by a Zn-Terminated ZnO(0001) Bulk Single-Crystalline Substrate.

Metal oxide semiconductor gas sensors have been widely studied for the selective detection of various gases with trace concentrations. The identification of the reaction scheme governing the gas sensing response is crucial for further development; however, the mechanism of ethanol (EtOH) gas sensing by ZnO is still controversial despite being one of the most intensively studied target gas and sensing material combinations. In this work, for the first time, the detailed mechanism of EtOH sensing by ZnO is studied by using a bulk single-crystalline substrate, which has a well-defined stoichiometry and atomic arrangement, as the sensing material. The sensing response is substantial on the ZnO substrate even with a millimeter-size thickness, and it becomes larger with resistance of the substrate. The large sensing response is described in terms of the adsorption/desorption of the oxygen species on the substrate surface, namely, oxygen ionosorption. The valence state of the ionosorbed oxygen involved in EtOH sensing is identified to be O2– regardless of the temperature. The increase in the sensing response with the temperature is attributed to the enhanced oxidation rate of the EtOH molecule on the surface as analyzed by pulsed-jet temperature-programmed desorption mass spectrometry, which has been newly developed for analyzing surface reactions in simulated working conditions.

Oxidation induced cubic-tetragonal phase transformation in titanium hydride powders

We studied the effect of oxidation temperature and initial hydrogen concentration on the occurrence of cubic (δ) to tetragonal (ε) phase transformation induced by thermal oxidation of titanium hydride powders in air. X-ray diffraction analysis indicates that δ → ε transformation occurs during oxidation at 400 °C, but not at lower (300 °C) or higher (500 °C) oxidation temperatures. The relative amounts of hydrogen loss during oxidation were determined by temperature-programmed desorption mass spectrometry (TPD-MS). The findings suggest that oxygen stabilizes the tetragonal phase (ε), and that the δ/ε phase composition following oxidation depends on both oxygen and hydrogen concentrations. For high oxidation temperatures (500 °C), some degree of hydride decomposition leads to a decrease in H concentration and to destabilization of the tetragonal phase after cooling down to room temperature.

Germanium-based polyoxometalates for the adsorption-decomposition of NOx

A series of germanium-based Keggin-type polyoxometalates (POMs), including H4GeW12O40 (HGeW), H5GeW11VO40 (HGeWV), H5GeMo11VO40 (HGeMoV) and H5GeW9Mo2VO40 HGeWMoV), were first synthesized and utilized as catalysts for removal of NOx. The fourier transform infrared spectroscopy (FT-IR) and temperature-programmed desorption-mass spectroscopy (TPD-MS) characterizations were carried out to investigate the adsorption-desorption behavior and decomposition mechanism of NOx. The adsorption experiments revealed that HGeW had the highest NOx adsorption capacity up to 16.2 mg NOx per gram catalyst. Two infrared characteristic bands appeared at 2210 and 1851 cm−1 after NOx adsorption, while the latter firstly discovered over NOx-absorbed POMs could be assigned to nitrosyl radical (NO·). The regeneration of HGeW could be realized via reducing the temperature in wet atmosphere to desorb NOx. TPD-MS was conducted to investigate the decomposition behavior of NOx over HGeW and tungstophosphoric acid (HPW). O2 was firstly detected among the decomposition products, besides N2 and N2O. According to conservation calculation based on N mass, NOx removal rate of 81.5 % and N2 selectivity of 68.3 % could be achieved for HGeW. While the NOx conversion rate and N2 selectivity for HPW reached 54.1 % and 53.4 %, respectively.

Electrical resistance response of a ZnO single-crystalline substrate to trace ethanol under pulsed air jet irradiation

The pulsed jet technique was applied to measure the electrical resistance response of a Zn-terminated ZnO(0001) substrate to trace ethanol in the air to simulate the realistic working surface of a semiconductor gas sensor in a vacuum. The resistance response to the trace ethanol under the static atmospheric pressure air was well reproduced by the periodic pulsed jet technique with the optimal irradiation conditions, in which the pressure in the vicinity of the surface transiently reached 2 kPa. The behavior of the resistance upon the pulsed jet irradiation was discussed in terms of the ionosorption of oxygen. Because the background pressure was kept low enough during the pulsed jet irradiation, the reaction products during the ethanol sensing, such as acetaldehyde, has been successfully detected at the elevated temperature above 400 K by temperature programmed desorption-mass spectrometry (TPD-MS).

INFLUENCE OF FINE ADDITIVES AND SURFACTANTS ON THE STRENGTH AND PERMEABILITY DEGREE OF CONCRETE

The results of studies to determine the effect of titanium dioxide nanoparticles (nanoTiO2), finely dispersed anatase crystalline titanium dioxide (anatazTiO2) and surface-active substances (surfactants) on the compressive strength, degree of permeability and thermal stability of concrete samples are presented. Adding particles of nanotitanium, anatase titanium and surfactants up to 2 % to cement accelerates the hydration process and increases the strength of concrete, and also has a strong effect on its microstructure. As a result of the studies, it is experimentally proved that the compressive strength of concrete increases with the addition of titanium dioxide (nanoTiO2) nanoparticles by 23.2 %, finely dispersed anatase crystalline titanium dioxide (anatazTiO2) by 21.7 % to 5 % concentration by weight. In addition, the introduction of these additives reduces the permeability of concrete. This is due to a decrease in the absorption of concrete by water with the addition of nanotitanium and anatase titanium. The introduction of additives from 1 % to 5 % by weight in concrete reduces the depth of chloride penetration by 10–15 times, compared with the control. The use of temperature-programmed desorption mass spectrometry (TPD-MS) method has shown that an increase in the percentage of TiO2 nanoparticles to 5 % in concrete mixtures correlates with an increase in microporosity and dispersion level of these mixtures, which causes a shift in the peaks of intense gas evolution from the samples when heated to the side low temperatures (for example, carbon dioxide CO2). The resulting concrete samples are planned to be used for the manufacture of floors in livestock buildings. The injected additives are selected because they are not toxic substances and, in contact with the biological environment of livestock buildings (urine, feces), will not react with them

Fluorination of silylated nanosilicas using c-C4F8 radiofrequency plasma

The structure of surface layer of octafluorocyclobutane radiofrequency plasma (c-C4F8 rf-plasma) treated fumed silica—pristine and chemically modified with triethoxy-, vinyltriethoxy-, or vinyltrichlorosilane—has been studied by means of FTIR- and X-ray photoelectron spectroscopy as well as temperature-programmed desorption mass spectrometry. The surface layer structure of the silylated nanosilicas after plasma fluorination was found to be defined by the reactivity of the pre-grafted groups. It was revealed that for hydride- and vinyl-silylated silicas at facile (about 15 min) treatment the single fragments with C:F ratio close to 1:1 are attached to surface (as in the case of pristine silica fluorination), whereas a long term (about 60 min) plasma treatment leads to formation of polymeric structures at the surface. Both the nature of pre-grafted groups, capable to be involved in polymerization reaction, and their concentration effect on these polymeric structures. Thus, at surface groups concentration of about 0.5 mmol/g fluorine-enriched polymeric chains are formed, while at twice as little concentration the chains with unsaturated bonds are generated.

Synthesis and structural properties of carbon/alumina composites: Practical application in solid phase extraction of explosives

Abstract Carbon-inorganic composites belong to group of modern nanomaterials possessing high potential in many applications. Such adsorbents combine characteristics of nonpolar carbon phase and polar inorganic matrix. Both porosity and texture of composites substantially depend on applied carbon precursor, inorganic component and pyrolysis conditions. Novel carbon/alumina composites were prepared using co-polymerization of resorcinol-formaldehyde polymer with fumed Al2O3 and subsequent pyrolysis of derived materials in inert atmosphere at 800 °C. Morphological and structural characteristics of as-obtained initial polymeric and carbon-inorganic nanocomposites were studied using powder X-ray diffraction, scanning electron microscopy, Raman spectroscopy, nitrogen adsorption methods, and temperature-programmed desorption mass spectrometry. The experimental results showed that filler Al2O3 acting as catalyst has significant influence on the resorcinol-formaldehyde polycondensation reaction and further pyrolysis step, therefore affects the structure of carbon-inorganic composites that is evidenced by the changes of specific surface area and porosity. It was shown that the porosity and texture of prepared composites substantially influenced the adsorption/desorption steps of explosives from aqueous samples. The results provide new ideas on the hybrid composites synthesis as well allow one to elucidate the effect of synthesis method on the structural characteristics of materials which can be used as high quality adsorbents in water treatment.

Thermal desorption kinetics of H2O and H2 from rapidly solidified Al-Zn-Mg alloy powders

The thermal desorption of water and hydrogen from a rapidly solidified Al-Zn-Mg alloy powder was studied by means of temperature programmed desorption mass spectrometry (TPD-MS). By applying the Kissinger formalism, an activation energy of 137 ± 7 kJ/mol and a pre-exponential factor of 5.2 × 1011 s−1 were deduced for the primary broad water desorption peak, strongly conforming to the two pure phases of Al(OH)3, gibbsite and bayerite. Desorption of hydrogen is assigned to the oxidation of aluminum by water evolving during dehydration of the surface hydroxide layer upon heating. Overall, a complex mechanochemical mechanism is captured, with desorption profiles that are indicative of two types of oxidation processes: (1) fast, non-kinetic oxidation, initiated at ∼377 °C, followed by, (2) a slower, diffusion controlled oxidation event. The former may be viewed as a solid experimental evidence for the breakage of the surface oxide film, occurring at a relatively low temperature (<400 °C) during degassing. This breakage exposes either Al or other alloying elements to available water, which trigger in turn a fast oxidation reaction from which hydrogen is evolved.

Catalytic Pyrolysis of Aliphatic Carboxylic Acids into Symmetric Ketones over Ceria-Based Catalysts: Kinetics, Isotope Effect and Mechanism

Ketonization is a promising way for upgrading bio-derived carboxylic acids from pyrolysis bio-oils, waste oils, and fats to produce high value-added chemicals and biofuels. Therefore, an understanding of its mechanism can help to carry out the catalytic pyrolysis of biomass more efficiently. Here we show that temperature-programmed desorption mass spectrometry (TPD-MS) together with linear free energy relationships (LFERs) can be used to identify catalytic pyrolysis mechanisms. We report the kinetics of the catalytic pyrolysis of deuterated acetic acid and a reaction series of linear and branched fatty acids into symmetric ketones on the surfaces of ceria-based oxides. A structure–reactivity correlation between Taft’s steric substituent constants Es* and activation energies of ketonization indicates that this reaction is the sterically controlled reaction. Surface D3-n-acetates transform into deuterated acetone isotopomers with different yield, rate, E≠, and deuterium kinetic isotope effect (DKIE). The obtained values of inverse DKIE together with the structure–reactivity correlation support a concerted mechanism over ceria-based catalysts. These results demonstrate that analysis of Taft’s correlations and using simple equation for estimation of DKIE from TPD-MS data are promising approaches for the study of catalytic pyrolysis mechanisms on a semi-quantitative level.

Improvement of functional performance of concrete in livestock buildings through the use of complex admixtures

When examining concrete in livestock buildings, signs of corrosion and destruction of concrete floors and walls were found. Experimental studies have identified main critical points that directly affected concrete continuity. Excessive moisture, use of corrosive acidic or alkaline disinfectants and presence of natural excretions of animals (urine and feces) were found in livestock buildings. To solve this problem, admixtures were proposed: yellow iron oxide pigment and liquid glass which improve strength characteristics of concrete, its heat resistance and reduce penetrability. It was proved by the conducted studies that introduction into concrete of admixtures in quantities from 0.5 % to 2 % has resulted in a 2.8 times smaller depth of chloride penetration as compared to the control specimens. This was due to a decrease in water absorption by concrete when introducing iron oxide, cuprous sulphate, peracetic acid and sodium silicate which reduced pore size in samples. It was proposed as an innovation to assess thermal stability of concrete using the method of temperature-programmed desorption mass spectrometry (TPMS) based on the dependence of evolution of carbon monoxide and carbon dioxide from samples of carbonate-containing substances on the sample temperature. Microbiological studies have identified microbes of Penicillium and Fusarium species, bacteria Escherichia coli and Pseudomonas aeruginosa, which cause corrosion of concrete in livestock buildings. Numerous experiments have shown that the proposed admixtures added to the concrete (based on yellow iron oxide pigment (1.5‒2.0 wt. %), peracetic acid (0.2‒0.3 wt. %), liquid glass (2‒3 wt. %) and cuprous sulfate (0.5‒1.0 wt. %) had antimicrobial properties and thus prospects for their use in animal husbandry

In Ukrainian

The investigation of the adsorption behavior of water vapour on porous carbon matrices is still relevant because the humidity of the environment can significantly affect the adsorption capacity of the carbon adsorbents to certain substances. Furthermore, the measurements of water isotherms could also be used to analyze the pore structure of activated carbons. The correlation between the adsorption characteristics of series of activated carbon samples (Norit, NL) with similar values of the specific surface area, but different pore size distribution (different volumes of micro- and mesopores), towards water vapour and their internal structure, defined on the basis of nitrogen adsorption isotherms, as well as the chemical composition and the nature of primary adsorption centers of the surface has been researched in the study. By the methods of Thermogravimetric Analysis (TGA), Temperature-Programmed Desorption Mass Spectrometry (TPD-MS) and X-ray Photoelectron Spectroscopy (XPS) it has been determinated of quantitative and qualitative composition of the surface of investigated carbons; it has been shown that the mesoporous samples of activated carbon contain a greater total amount of surface oxygen-containing complexes than microporous samples. The adsorption and desorption branches of water adsorption isotherms for the microporous carbons come close to each other and give a plateau at high relative pressures wherein the water adsorption capacities for the microporous samples correspond to their micropore volumes determined from nitrogen adsorption isotherms. As opposed to this, a gradual rise of water uptake and the existence of wide hysteresis loops at high relative pressures are observed for the mesoporous carbons. Moreover, the maximum values of water adsorption in this case considerably exceed the micropore volumes, and are attributable to the capillary condensation in mesopores. Nevertheless, the total volumes of water uptake both for micro- and mesoporous activated carbons are significantly less than those determined from nitrogen adsorption. This could be due to a mechanism of cluster pore filling in which the water density is less than its bulk density. In addition, probably, the water can not condense in the larger mesopores.

Thermal Transformation of Caffeic Acid on the Nanoceria Surface Studied by Temperature Programmed Desorption Mass-Spectrometry, Thermogravimetric Analysis and FT–IR Spectroscopy

The studies of pyrolysis of caffeic acid (CA) and its surface complexes is important for the development of technologies of heterogeneous catalytic pyrolysis of plant- and wood- based renewable biomass components. In this work, the structure and thermal transformations of the surface complexes of CA on the surface of nanoceria were investigated using Fourier transform–infrared (FT–IR) spectroscopy, thermogravimetric analysis (TGA) and temperature-programmed desorption mass spectrometry (TPD MS). It was found that CA on the surface of cerium dioxide forms several types of complexes: bidentate carboxylates, monodentate carboxylates and complexes formed as a result of interaction with phenolic hydroxyl groups. This is due to the ability of nanosized cerium dioxide to generate basic hydroxyl groups that can deprotonate phenolic groups to form phenolates on the surface. The main pyrolysis products were identified. The possible ways of forming 3,4-dihydroxyphenylethylene, acetylene carboxylic acid, pyrocatechol and phenol from surface complexes of CA were suggested. It was established that on the nanoceria surface effectively occur the decarboxylation, decarbonylation, and dehydration reactions of the CA, which are the desirable processes in biomass conversion technologies.

Comparison of by-product gas composition by activations of activated carbon

In this study, commercial activated carbons (ACs) were upgraded by different activation methods, and the gases generated during the activations were defined and quantified. The chemical activation commonly applied for upgrading ACs uses complex reactions, involving pyrolysis, physical, and chemical reactions. The ACs based on wood materials were characterized by elemental analysis, N2 physisorption, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption mass spectrometry. The patterns and composition of the generated gases were analyzed by gas chromatography and X-ray diffraction; high-resolution scanning electron microscopy was also used to characterize the activated carbon. The AC was mostly decomposed to CO2 by pyrolysis and physical activation, while CO was mainly detected during chemical activation from the K2CO3 produced by the reactions between CO2 and K2O. The detected amounts of generated gases were differed at various KOH ratios and residence times. The highest surface area obtained in this study was 2000 m2/g at the optimum ratio of AC and KOH (1:2).