Decomposition Of Stearic Acid Research Articles

Water Speciation and Storage Capacity of Olivine under the Reduced Fluid—Peridotite Interaction

The key features of the interaction between peridotites of the continental lithospheric mantle and reduced hydrocarbon-rich fluids have been studied in experiments conducted at 5.5 GPa and 1200 °C. Under this interaction, the original harzburgite undergoes recrystallization while the composition of the fluid changes from CH4-H2O to H2O-rich with a small amount of CO2. The oxygen fugacity in the experiments varied from the iron-wustite (IW) to enstatite-magnesite-olivine-graphite/diamond (EMOG) buffers. Olivines recrystallized in the interaction between harzburgite and a fluid generated by the decomposition of stearic acid contain inclusions composed of graphite and methane with traces of ethane and hydrogen. The water content of such olivines slightly exceeds that of the original harzburgite. Redox metasomatism, which involves the oxidation of hydrocarbons in the fluid by reaction with magnesite-bearing peridotite, leads to the appearance of additional OH absorption bands in the infrared spectra of olivines. The water content of olivine in this case increases by approximately two times, reaching 160–180 wt. ppm. When hydrocarbons are oxidized by interaction with hematite-bearing peridotite, olivine captures Ca-Mg-Fe carbonates, which are products of carbonate melt quenching. This oxidative metasomatism is characterized by the appearance of specific OH absorption bands and a significant increase in the total water content in olivine of up to 500–600 wt. ppm. These findings contribute to the development of criteria for reconstructing metasomatic transformations in mantle rocks based on the infrared spectra and water content of olivines.

Carbon isotopic composition of solid carbon and C–H–O fluid produced through the decomposition of stearic acid under HP-HT condition

ABSTRACT We estimated δ13C of the C–H–O fluid produced by the decomposition of stearic acid at high-pressure and high-temperature conditions (10 and 17 GPa, 800–1600°C) from δ13C of the solid carbon products and the initial stearic acid. The δ13C of the stearic acid and the recovered graphite/diamond were −28.0‰ and −27.08 to −29.35‰, respectively. Then, the δ13C of the coexisting C–H–O fluid was estimated to be −26.3 to −29.2‰ based on the stoichiometry of the decomposition reaction C18H36O2 → 10C + 8CH4 + 2H2O. In the studied P-T-t conditions, carbon isotope fractionation through the stearic acid decomposition is as small as < 3‰. This means that the δ13C of the C–H–O fluid is almost identical to that of the initial stearic acid and can be a useful tracer of carbon source for diamond forming reaction such as in fluid/carbonate systems.

MOF-Derived Co3O4 Nanoparticles Catalyzing Hydrothermal Deoxygenation of Fatty Acids for Alkane Production

Designing economical and nonprecious catalysts with a catalytic performance as good as that of noble metals is of great importance in future renewable bioenergy production. In this study, the metal–organic framework (MOF) was applied as a precursor template to synthesize Co3O4 nanoparticles with a carbon matrix shell (denoted as M-Co3O4). To select the synthesized optimal catalyst, stearic acid was chosen as the model reactant. The effects of catalyst dosage, methanol dosage, water dosage, temperature, and reaction time on catalytic efficiency were examined. Under the designed condition, M-Co3O4 exhibited high catalytic performance and the catalyst showed higher conversion of stearic acid (98.7%) and selectivity toward C8–C18 alkanes (92.2%) in comparison with Pt/C (95.8% conversion and 93.2% selectivity toward C8–C18). Furthermore, a series of characterization techniques such as scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption isotherms (Brunauer–Emmett–Teller (BET) method), and thermogravimetric analysis (TGA) was applied to investigate the physicochemical properties of the catalysts. Finally, we proposed that decarbonization (deCO) could be the presumably mechanistic pathway for the production of C8–C18 alkanes from the decomposition of stearic acid.

Pyrolysis behavior and kinetic analysis of waste polypropylene-based complex for cable filler

To better understand the thermochemical conversion for the pyrolysis recycling of cable waste, the pyrolysis kinetics of the typical cable filler was investigated in detail. Thermogravimetric experiments were conducted at different heating rates ranging from 5 °C/min−1 to 40 °C/min−1. Three degradation stages were observed in the process of pyrolysis. The influence of air on the superposition of the first two peaks was also identified. The activation energy at different heating rates was calculated using three commonly used model-free methods. A three-component reaction scheme was proposed to describe the whole degradation process. The first one was associated with the stearic acid decomposition, the second was dominated by the polypropylene decomposition, while the third was attributed to the calcium carbonate decomposition. The created reaction model combined with an optimization algorithm was applied to determine the kinetic parameters. The values of activation energy estimated by this method were in accordance with those by isoconversional methods, which verified the accuracy of the parameter calculation by the optimization algorithm. The predicted results based on the optimized parameters agreed well with the experimental data. Finally, the whole kinetics process was deconstructed into three independent reactions corresponding to all reactants and products.

Properties of poly(titanium oxide)-containing polymeric materials exhibiting UV-induced superhydrophilicity under simulated climate test conditions

Optically transparent organic-inorganic terpolymers containing nanostructured poly (titanium oxide) (PTO or (≡TiO)n) in polymeric matrixes of poly (hydroxiethylmethacrylate) (pHEMA) and its copolymers with acrylonitrile (AN), 2-ethylhexyleacrylate, buthylmethacrylate, vinylbuthyl ether and exhibiting UV-induced reversible surface hydrophilization had been subjected by climatic tests in the Q-SUN Xe-2 light weathering chamber, which simulates the exposure of the material under ambient conditions for 20 months of its operation. Adhesion, physical-mechanical and thermal-physical properties of PTO-containing materials had studied before and after climatic testing. The materials retain the capacity for the one-electron transition Ti4+ + e‾ ⇆ Ti3+ under UV-irradiation after environmental testing, resulting in both photochromic properties and reversible surface hydrophilization. The photocatalytic activity of materials in stearic acid decomposition at terpolymer's surface of composition [(≡TiO)n]: [HEMA]: [AN] = 1:5:1 had proven.

Formation mechanism of superhydrophobicity of stainless steel by laser-assisted decomposition of stearic acid and its corrosion resistance

Superhydrophobic surfaces have attracted extensive attention over the past decade, primarily due to their self-cleaning, corrosion resistance and anti-bacterial abilities. However, it is still a challenge to prepare superhydrophobic surfaces with good chemical stability, low cost, environmental friendliness, and suitable for large-scale production applications. In this paper, a hybrid laser-chemical method to prepare superhydrophobic micro-patterns on 316L stainless steel were put forward, which combined laser ablation and laser assisted chemical decomposition of stearic acid (C17H35COOH). Experiments show that under the laser power of 10 W, the frequency of 150 kHz, the speed of 20 mm/s, and the mesh spacing of 75 μm, the best superhydrophobicity with a static contact angle of 153.9° can be obtained. The fundamental mechanism of laser-chemical method is the increase of the non-polar CC(H) bond of specimen by laser assisted hydrodeoxygenation reaction of stearic acid. Moreover, unlike laser ablation-stearic acid coated specimen, the specimen prepared by laser-chemical method can maintain superhydrophobicity after 10 min of ultrasonic cleaning. The electrochemical corrosion experiments shows that the hybrid laser-chemical method can manufacture superhydrophobic specimens with better chemical durability and corrosion resistance.

Microwave pyrolysis of biomass for low-oxygen bio-oil: Mechanisms of CO2-assisted in-situ deoxygenation

This work used CO2 as a co-reaction gas to realize in-situ deoxygenation of the bio-oil produced from microwave pyrolysis of biomass, and the mechanisms were thoroughly analyzed. Results showed that the bio-oil obtained at 550 °C (N2 atmosphere) had the highest yield of 29.24 wt% with the higher heating value (HHV) of 20.27 MJ/kg. The introduction of CO2 atmosphere reduced the oxygen content of the bio-oil by 12.68 wt% and increased the HHV by 26.43%. The oxygen mass balances demonstrated that the oil-O decreased by 31.45%, and the gas-O increased by 29.28% at CO2 atmosphere. The specific components in the bio-oil and pyrolytic gas were characterized. Furans in the bio-oil could react homogeneously with CO2 to generate CO at CO2 atmosphere, which was the main route to realize in-situ deoxygenation of the bio-oil. Meanwhile, stearic acid was selected as a model compound of the bio-oil to verify the action mechanisms of CO2 atmosphere. CO2 inhibited the decomposition of stearic acid to reduce the polycyclic aromatic hydrocarbons (PAHs) content in the bio-oil and promoted the generation of alkenes and CO. This study provides a novel perspective for the production of low-oxygen and high-quality bio-oil from biomass using CO2 reaction atmosphere.

Porous Ni-Cr-Mo-Cu alloys fabricated by elemental powder reactive synthesis

Fabrication of porous Ni-Cr-Mo-Cu alloys is available through Ni, Cr, Mo and Cu elemental powder reactive synthesis at the sintering temperature of 1150 °C. The pore structures, including swelling behavior, open porosity, pore size and viscous permeability of the porous Ni-Cr-Mo-Cu alloys are systematically investigated. The results revealed that the parameters of pore structure firstly increased, and then decreased with the increase of the sintering temperature. When the sintering temperature rose to 1000 °C, the volume expansion, open porosity and viscous permeability of porous Ni-Cr-Mo-Cu alloys reached the peak value of 8.0%, 41.6% and 17.2 μm2, respectively. In addition, it was confirmed that the pore structure evolution was based on three stages, that is, in the low temperature section before stearic acid decomposition, the formation of pores was initiated by the volatilization of pore-forming agent and the interstitial pores of green compact; when the temperature was lower than 1083 °C, the increase of open porosity was mainly due to the Kirkendall effect caused by solid partial diffusion; while, when the temperature is within the range of 1083 ∼ 1150 °C, the shrinkage behavior at high temperature and a small amount of metal solution formed by the unreacted Cu led to decrease in pore structure parameters.

Fabrication of robust and versatile superhydrophobic coating by two-step spray method: An experimental and molecular dynamics simulation study

The low mechanical durability of superhydrophobic surfaces has been considered as a serious limitation to develop these unique coatings in industrial applications. Despite the promising results, the main challenges are related to the fabrication of stable and practical superhydrophobic coatings with proper adhesion using the facile approaches. In the present study, the superhydrophobic surface was fabricated using the two-step spray method with a WCA of 160°. At the first step of this method, the hydrophobic resin was sprayed as an adhesive layer. Then, at the next step, the stearic acid-modified Alumina nanoparticles were sprayed on the adhesive layer. Important coating parameters such as stability of spray suspension and thermal stability of coating were investigated. The results showed that the decreasing agglomeration rate of particles during the spraying enhances the more uniform distribution and hydrophobicity of the layer. Besides, increasing the temperature, especially after 250 °C, reduced the roughness and hydrophobicity of the layers due to the decomposition of stearic acid. Meanwhile, molecular dynamics (MD) simulation was applied to investigate the adsorption of stearic acid on the Alumina surface along with its interaction with water molecules. The results can propose the effective mechanism of suspension stability and thermal stability on the growth and formation of coatings. Also, the findings of this study can help to fabricate superhydrophobic coatings on various substrates using the two-step spray method with wear resistance.

Nano-polycrystalline diamond synthesized through the decomposition of stearic acid

ABSTRACTHere we report a novel route for synthesizing nano-polycrystalline diamond (NPD) using stearic acid (C18H36O2) as a starting material under high pressure and high temperature. The obtained NPD shows a transparent dark-yellowish color similar to the standard NPD synthesized from graphite and consists of extremely fine diamond grains (∼10 nm). The temperature required for the present synthesis of pure transparent NPD is as low as 1000°C at 13 and 17 GPa, which is surprisingly lower than that for conventional NPD synthesis (1800–2000°C). The amorphous-like, extremely poorly crystalline graphite produced by the thermal decomposition of stearic acid likely provides preferential nucleation sites for diamond and significantly lower the activation energy. The removal of volatile components such as H2O generated through the decomposition from the system is a key to obtain pore-free transparent NPD. Magnesite, MgCO3 and periclase, MgO can be used as an efficient H2O remover through the hydration reaction.

Use of ion-assisted sputtering technique for producing photocatalytic titanium dioxide thin films: Influence of thermal treatments on structural and activity properties based on the decomposition of stearic acid

Titanium dioxide thin films were deposited by the reactive ion-assisted sputtering method from titanium targets at various partial pressures and deposition parameters. The films were deposited onto substrates at temperatures ranging from room-temperature conditions to 722 K. A selection of thin films was post-deposited annealed at temperatures up to 972 K for 10 min and characterized by micro-Raman spectroscopy and scanning electron microscopy (SEM) and subsequently analysed to assess their photocatalytic activity. Micro-Raman characterization revealed that the as-deposited films had either predominant amorphous, rutile-like structures, anatase-like structures or anatase-rutile mixed structures. The thin films deposited with a high substrate temperature and with energy assistance from the ion source tended to be amorphous, while films deposited on a hot substrate without ion energy assistance tended to have a mixed crystalline phase. On subsequent annealing the amorphous films changed to a rutile structure at temperatures above 672 K, while mixed anatase-rutile films changed to predominant rutile structures only after thermal treatments above 872 K. Thus, this study has revealed an astonishing persistence of the anatase-rutile mixed phase at very high temperatures and showed the possible existence of a key transition temperature at 672 K, where it was possible to see a transformation from amorphous or mixed phase to a rutile or dominant rutile mixed phase. Photocatalytic tests were undertaken by using a novel method consisting of observing the degradation of a film of stearic acid by the thin films under artificial UV radiation. Of the films investigated those with anatase-rutile mixed phases showed the greatest photoactivity. This work was essential in the understanding of the correlation between growth deposition conditions, phase transitions and photocatalytic activity. This set of experiments demonstrated that titania made under a highly oxidizing atmosphere, with no temperature applied on the substrate during fabrication and using an ion sputtering method, is a useful and valuable novel method for creating active TiO2 thin films.

Visible light active photocatalytic C-doped titanium dioxide films deposited via reactive pulsed DC magnetron co-sputtering: Properties and photocatalytic activity

Doping of TiO2 with carbon is known to be an efficient method of enhancing visible light photocatalytic activity. The present work describes the deposition of carbon-doped titania coatings deposited by reactive magnetron co-sputtering of Ti and C targets. Undoped titania coatings were produced under similar deposition conditions for comparison purposes. Following deposition, all coatings were annealed in air at 873 K for 30 min to develop the required crystalline structure; and then analysed with EDS, XRD, AFM, XPS and UV–visible spectrophotometry. A number of tests, including methylene blue and stearic acid decomposition tests, and photo-induced hydrophilicity measurements, were employed for the assessment of the photocatalytic properties of the C-doped and un-doped titanium dioxide coatings under UV and visible light irradiation. It was found that carbon-doped titania coatings significantly outperformed undoped titania when using both visible and UV irradiation. Similar trends were observed for other properties. While excessive carbon doping has been shown to have a negative effect on the photocatalytic properties of the titanium dioxide, overall, carbon doping via reactive co-sputtering has been confirmed as an efficient method of photocatalytic property enhancement. This is due to a narrowing of the bandgap and to extended lifetimes of the photo-generated charge carriers.

Deposition of Visible Light-Active C-Doped Titania Films via Magnetron Sputtering Using CO₂ as a Source of Carbon.

Doping of titanium dioxide with p-block elements is typically described as an efficient pathway for the enhancement of photocatalytic activity. However, the properties of the doped titania films depend greatly on the production method, source of doping, type of substrate, etc. The present work describes the use of pulsed direct current (pDC) magnetron sputtering for the deposition of carbon-doped titania coatings, using CO2 as the source of carbon; ratios of O2/CO2 were varied through variations of CO2 flow rates and oxygen flow control setpoints. Additionally, undoped Titanium dioxide (TiO2) coatings were prepared under identical deposition conditions for comparison purposes. Coatings were post-deposition annealed at 873 K and analysed with scanning electron microscopy (SEM), X-ray diffreaction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The photocatalytic properties of the thin films were evaluated under ultraviolet (UV) and visible light irradiation using methylene blue and stearic acid decomposition tests. Photoinduced hydrophilicity was assessed through measurements of the water contact angle under UV and visible light irradiation. It was found that, though C-doping resulted in improved dye degradation compared to undoped TiO2, the UV-induced photoactivity of Carbon-doped (C-doped) photocatalysts was lower for both model pollutants used.

Effects of Ag on the photocatalytic activity of multiple layer TiO2 films

This work reports effective activated multiple layers Ag-TiO2 films and Ag-TiO2/Ag films via a solgel and direct coating approach. Scanning electron microscopy and transmission electronic microscope are performed to characterize the morphology. The roles of metallic Ag on TiO2 films for photodegradation stearic acid are explained by UV–vis spectroscopy and photoluminescence spectroscopy. The photocatalytic activity of Ag-TiO2 films for stearic acid decomposition is 5 times higher than that of pure TiO2 films. Different Ag-TiO2/Ag films have almost the same activity of photodegradation stearic acid. The strong surface plasmon resonance effect of Ag makes TiO2 absorb more visible light. The separation effect of photogenerated electron–hole pairs could be increased by doping a small amount of Ag. For more Ag amount in Ag film, there will likely be an equilibrium between the separation of electron–hole pairs and the recombination of them.

Synthesis of Vanadium-Vanadium Carbide in-situ nanocomposites by high energy ball milling and spark plasma sintering

In the present work, Vanadium-Vanadium Carbide (V-V2C) in-situ nanocomposites were synthesized by mechanically milling vanadium powders with 0.5 wt.% stearic acid. Milled powders were consolidated using spark plasma sintering at 1150, 1250 and 1350°C for 10 min. Phase and morphology of the milled powders were studied using X-ray diffraction and scanning electron microscopy. X-ray diffraction analysis of 10 h milled powder shows the evolution of amorphous phase. Energy dispersive X-ray spectroscopy studies on milled powder shows the presence of carbon, which could be due to the decomposition of stearic acid during milling. Degree of crystallinity of milled powder was confirmed using the selective area electron diffraction pattern. X-ray diffraction analysis of sintered samples indicate sharp peaks from vanadium and vanadium carbide (V2C), endorsing amorphous to nanocrystalline transformation. Micro-hardness value of sintered samples increases with increasing sintering temperature.

Photocatalytic Properties of TiO2 Thin Films Modified with Ag and Pt Nanoparticles Deposited by Gas Flow Sputtering.

In this work, a gas flow sputtering (GFS) process which allows the production and deposition of metal nanoparticles (NPs) in a vacuum environment is described. Aim of the study is to prove the potential of this technology for the fabrication of new TiO2 films with enhanced photocatalytic properties. For this purpose, Ag and Pt NPs have been produced and deposited on photocatalytic float glass coated with TiO2 thin films by magnetron sputtering. The influence of the process parameters and of the metal amount on the final properties of the particles (quantity, size, size distribution, oxidation state etc.,) was widely investigated. Moreover, the effect of the NPs on the photocatalytic activity of the resulting materials was evaluated for the case of the decomposition of stearic acid (SA) during UV-A irradiation. The reduction of the water contact angle (WCA) during the irradiation period was measured in order to test the photo-induced super-hydrophilicity (PSH).

Growth mechanism and photocatalytic performance of double-walled and bamboo-type TiO2nanotube arrays

Double-walled and bamboo-type TiO2 nanotube arrays on titanium can be grown by a self-organized electrochemical anodization in viscous organic electrolytes. In order to better understand the growth process of this novel structure, anodized samples under alternating voltage (AV) conditions at different stages were systematically studied. Field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy were used to investigate the morphology, structure, and crystalline and chemical components of the resulting TiO2 nanotubes. Meanwhile, the corresponding current versus time curves were recorded to monitor the process. Based on the results obtained, the possible formation mechanism of these novel nanotubes was explored. It was noted that the formation of double-walled and bamboo-type structure has a close relationship with the current density and ion-diffusion gradient inside the TiO2 nanotubes. In our experiment, the double-walled and bamboo-type TiO2 nanotube arrays can be repeatedly and successfully synthesized via AV anodization. In addition, the solar-light induced photocatalytic decomposition of stearic acid of the nanotube arrays obtained was presented. Double-walled and bamboo-type TiO2 nanotube arrays showed higher efficiencies than those based on smooth-walled nanotubes with the same tube length because of enhanced specific surface area.

Debinding Mechanisms in Thermoplastic processing of a Ba0.5Sr0.5Co0.8Fe0.2O3−δ- Stearic Acid-Polystyrene Mixture

In the present study, we address the interaction between a thermoplastic binder system and Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) (BSCF) during thermal treatment of the thermoplastic feedstock. BSCF powder was coated with different amounts of stearic acid (SA) acting as a surfactant. Oxygen release from the uncoated BSCF surface changes the decomposition of polystyrene (PS) in inert atmospheres from a pyrolytic to a thermoxidative mechanism, thereby decreasing the break-down temperature and the activation energy. In mixtures with coated BSCF powder, the decomposition products of SA carbonatize the BSCF surface, which inhibits oxygen release. Mass spectrometry of the breakdown products indicates that the decomposition of SA in the presence of BSCF also modifies the decomposition pathway of PS. The influence of BSCF on the polymer decomposition reaction in air is not as strong. Oxygen diffusion seems to be responsible for the differences to pure PS in reaction rates and the activation energies.

Solar-Light Photoamperometric and Photocatalytic Properties of Quasi-transparent TiO2 Nanoporous Thin Films

Transparent photocatalytic surfaces are of ever increasing importance for many applications on self-cleaning windows and tiles in everyday applications. Here, we report the formation and photocatalytic testing of a quasi-transparent thin and nanoporous titania films deposited on glass plates. Sputtered Ti thin films were anodized in fluoride-ion-containing neutral electrolytes to form optically semitransparent nanoporous films, which transformed to be completely transparent after thermal annealing. The nanoporous films were studied at different stages, such as before and after anodization, as well as after thermal annealing using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis and Raman spectroscopy. It was observed that anodization at 20 V of high-temperature deposited titanium films resulted in regular nanopore films with pore diameters of 30 nm. Structural investigations on the transparent nanopore arrays reveal the presence of anatase phase TiO(2) even after annealing at 500 °C, which was confirmed by XRD and Raman spectroscopy measurements. The solar-light induced photocatalytic decomposition of stearic acid and photoconductivity characteristics of these nanoporous thin films are also presented.

Transparent visible light activated C–N–F-codoped TiO 2 films for self-cleaning applications

The current work reports a potential technology for fabricating visible light activated doped TiO 2 coatings for self-cleaning applications. Transparent C–N–F-codoped TiO 2 films with enhanced visible light photocatalytic activity and non-light activated superwettability were successfully prepared by a simple layer-by-layer dip-coating method using TiO 2 sol and NH 4F methanol solution as precursors. The current coating method prevents the reactions of F − ions with the glass substrate and hence resulting in a uniform and transparent coating. It also creates TiO 2 coating with high surface roughness without an additional pore-inducing agent and generates non-irradiated superhydrophilic surface. Contact angles of the C–N–F-codoped TiO 2 films were 2.3–3.1° in the absence of any illumination and they rose slowly in the dark (<1.8° in 30 days). The C–N–F-codoped TiO 2 films showed strong visible-light absorption and enhanced photocatalytic activity for stearic acid decomposition under visible light irradiation, which was 5 times higher than that of C-doped TiO 2 film. Our DFT calculations also showed that increasing N:F doping ratio leads to band gap narrowing of TiO 2.