Heating Ramp Rate Research Articles

Preparation of ultrahigh surface area porous carbons templated using zeolite 13X for enhanced hydrogen storage

In this report, the use of zeolite 13X as a template to generate ultrahigh surface area carbons, via a two-step process combining liquid impregnation and chemical vapour deposition is explored. The first step in the nanocasting process involves impregnation of zeolite 13X with furfuryl alcohol and the second step consists of chemical vapour deposition (CVD) of ethylene at 700°C. Zeolite-like structural ordering was achieved for zeolite templated carbons (ZTCs) prepared at variable heating ramp rates of 5, 10 or 15°C/min. The textural properties of ZTCs prepared at all heating ramp rates were comparable with small variations in which the lowest ramp rate (5°C/min) generated ZTC with highest surface area and pore volume of 3332m2/g and 1.66cm3/g respectively. The carbon materials achieved a remarkable hydrogen uptake of 7.3wt% at 20bar and 77K which is the highest ever recorded for carbon materials. This report also explores the mechanical stability of the ZTCs via compaction at up to 10t (equivalent to 740MPa) in which the compacted samples showed minimal modification and retained high hydrogen storage capacity.

Effects of synthesis parameters on zeolite templated carbon for hydrogen storage application

Templated carbon was synthesized using NH4Y-zeolite template and furfuryl alcohol as carbon precursor by carbonization method. The effects of synthesis conditions, such as carbonization temperature, dwelling time, heating ramp and flow rate of N2, on surface area and pore structure of templated carbons were investigated. The carbonization temperature was varied in range of 650–850°C and dwelling time in range of 1–4h. Physicochemical properties of zeolite and templated carbons were studied by TGA, surface area and pore analysis, XRD, SEM and FESEM techniques. The BET and micropore area increased with increasing dwelling time and were maximum at 3h at all carbonization temperatures. At 3h dwelling time, BET surface area and pore volume of templated carbons were observed to be highest at carbonization temperature of 750°C while micropore area was slightly higher at 650°C. The hydrogen storage capacity was measured by temperature programmed desorption method at atmospheric pressure and different temperatures (−100°C and −50°C). For carbons prepared by continuous heating, hydrogen storage was maximum (0.15wt.%) at −100°C and atmospheric pressure for carbon synthesized at 650°C and 3h dwelling time. The stepwise heating resulted in higher BET surface area (1886m2/g) and micropore area (1136m2/g) and increased hydrogen uptake of 0.29wt.% at −100°C was obtained for carbon synthesized at 750°C with 3h dwelling time. The storage capacity was observed to be higher for samples having higher amount of micropores and mesopores less than 6nm.

Pressureless Silver Sintering Die-Attach for SiC Power Devices

Pressureless silver sintering is an interesting die-attach technique that could overcome the reliability limitations of the power electronic devices caused by their packaging. In this paper, we study the manufacturing parameters that affect the die attach: atmosphere, drying time, heating ramp rate, sintering temperature and duration. It is found that sintering under air gives better results, but causes the substrates to oxidize. Sintering under nitrogen keeps the surfaces oxide-free, at the cost of a weaker attach.

Thermal Oxidation of Biodiesel by Pressurized Differential Scanning Calorimetry: Effects of Heating Ramp Rate

Despite its many promising characteristics as an alternative diesel fuel, the oxidative stability of biodiesel during storage is a major concern to fuel producers. Extensive degradation can affect fuel quality with respect to viscosity, acid value, cetane number, and other properties. Fuel standards in the U.S. and Europe include the induction period (IP), which is designed to ensure that good quality is maintained during storage. However, IP is measured at 110 °C to accelerate the formation of radicals and induce the oxidation reaction. This work analyzes the kinetics of thermal oxidation of biodiesel from soybean oil (SME) by non-isothermal pressurized differential scanning calorimetry (P-DSC). SME samples from four different sources were evaluated by P-DSC in static mode (zero purge gas flow) under 2000 kPa pressure. Effects of adding antioxidants to SME were also examined. Heating scans were conducted at various ramp rates (β) to determine the onset temperature (OT) of degradation. The Ozawa–Flynn–Wal...

The effect of the choice of method for determining assigned value on the assessment of performance in melting point analysis

The determination of melting point is a fundamental test in the Pharmaceutical industry, since it is one of the simplest techniques for the identification of a chemical substance. The melting point provides information on both identity and purity of a chemical substance and for that reason is a key test in the PHARMASSURE proficiency testing (PT) scheme. The PT scheme assesses participant’s determination of melting point, using chemicals of high purity and basing the assigned value on the robust consensus mean (median). In recent rounds, melting point reference standards have been provided as the test material and a reference value used as the assigned value for PT assessment. Comparison of the PT results over a number of rounds, using test materials with a wide range of melting points, shows the overall performance of the participant group is worse in rounds where a reference material and associated reference assigned value are used for performance assessment. When participants were assessed against the reference assigned value, a positive bias was observed in the participant’s results. Detailed information regarding the methodology used demonstrated that the majority of participants use the same analytical method, EU.Ph.2.2.14 (Council of Europe, Strasbourg, 2011), for the determination of melting point although this procedure allows flexibility in key methodological parameters, such as heating ramp rate, which may fail to ensure consistent performance across the group of participant laboratories.

Effect of Pt content on structure and magnetic properties of Fe100−xPtx films deposited on thermally oxidized Si substrates by rapid thermal annealing

Fe100-xPtx films with Pt contents (x) = 29–65 at.% were deposited directly onto thermally oxidized Si(100) substrate by dc magnetron sputtering. The films were then post-annealed at 700 °C for 3 min by rapid thermal annealing (RTA) at a high heating ramp rate of 100 °C/s. Experimental results show that Fe3Pt film displayed (111) preferred orientation and tended towards in-plane magnetic anisotropy when the Pt content was 29 at.%. When the Pt content was increased to 49 at.%, the FePt film inclined towards (001)-texture and perpendicular magnetic anisotropy. Its out-of-plane coercivity (Hc⊥), saturation magnetization (Ms) and out-of-plane squareness (S⊥) reached 1010 kA/m, 0.47 T and 0.8, respectively. These results reveal its significant potential as perpendicular magnetic recording media for high-density recording. Upon further increasing the Pt content to 65 at.%, the coercivity of the films decreased drastically to below 65 kA/m and tended towards in-plane magnetic anisotropy.

A rapid hard template method for the synthesis of N-doped mesoporous carbon replicated from TUD-1

A porous silica material, TUD-1, was used as the hard template to synthesize nitrogen-doped mesoporous carbon (NMC) using a modified hard template method with fewer synthesis steps, compared to the conventional method. This method starts with the formation of a triethanolamine (TEA)/TUD-1 composite, followed by direct carbonization in CH4, where TEA and CH4 are used as nitrogen (N) and carbon precursors, respectively. The direct use of the templating agent TEA as the N precursor skips the calcination step and the infiltration of another N precursor, simplifying the conventional hard template method. The obtained NMC material possesses a similar three dimensional sponge-like mesostructure to its parental TUD-1. Several characterization techniques were used to characterize textural structure, carbon yield, N content, graphitization and surface chemical composition of the resulting NMC materials. These properties can be controlled by manipulating synthesis parameters, such as carbonization temperatures, CH4 flow rate, CH4 partial pressure, heating ramp rate and the structural characteristic of the TUD-1 template. In addition, NMC with high N content (9.6at.%) was also synthesized using acetonitrile as an alternative N-containing precursor.

Non-isothermal unfolding/denaturing kinetics of egg white protein

Egg protein is an important part of our food to get protein in our daily diet, and makes this protein more important to researchers to understand its kinetic behavior to understand the energy involved in the digestion of the egg protein. Hence, the present study explores the denaturing kinetics of the protein obtained from the hen's egg white (EW) using high resolution calorimetric technique. Fresh EW was scanned for heating and cooling to see the ther- modynamics from 10 to 100 C at different heating ramp rates varying from 1 to 20 C min -1 . An endothermic peak was found on heating scan showing denaturing of protein which was found absent at the cooling indicating the absence of any residue after heating. The denature peak shifted towards higher temperature as ramp rate increases following Arrhenius behavior and shows an activated denaturing kinetics of the egg protein. This peak was also compared with the water to avoid water effects. Behavior of denaturing peak can be explained in terms of Arrhenius theory and further discussed to get the energy involved in digestion.

A Facile Synthesis of MPd (M = Co, Cu) Nanoparticles and Their Catalysis for Formic Acid Oxidation

Monodisperse CoPd nanoparticles (NPs) were synthesized and studied for catalytic formic acid (HCOOH) oxidation (FAO). The NPs were prepared by coreduction of Co(acac)(2) (acac = acetylacetonate) and PdBr(2) at 260 °C in oleylamine and trioctylphosphine, and their sizes (5-12 nm) and compositions (Co(10)Pd(90) to Co(60)Pd(40)) were controlled by heating ramp rate, metal salt concentration, or metal molar ratios. The 8 nm CoPd NPs were activated for HCOOH oxidation by a simple ethanol wash. In 0.1 M HClO(4) and 2 M HCOOH solution, their catalytic activities followed the trend of Co(50)Pd(50) > Co(60)Pd(40) > Co(10)Pd(90) > Pd. The Co(50)Pd(50) NPs had an oxidation peak at 0.4 V with a peak current density of 774 A/g(Pd). As a comparison, commercial Pd catalysts showed an oxidation peak at 0.75 V with peak current density of only 254 A/g(Pd). The synthesis procedure could also be extended to prepare CuPd NPs when Co(acac)(2) was replaced by Cu(ac)(2) (ac = acetate) in an otherwise identical condition. The CuPd NPs were less active catalysts than CoPd or even Pd for FAO in HClO(4) solution. The synthesis provides a general approach to Pd-based bimetallic NPs and will enable further investigation of Pd-based alloy NPs for electro-oxidation and other catalytic reactions.

Porous stainless steel supported magnetite crystalline membranes for hexavalent chromium removal from aqueous solutions

Magnetite (Fe 3O 4) crystalline membranes were prepared on a porous stainless steel support by a sol–gel method for the sake of hexavalent chromium [Cr (VI)] removal from aqueous solution. The impact of the fabrication parameters including concentrations of casting solutions, multiple coatings, sintering atmospheres and temperatures, as well as heating ramp rates was studied. The morphologies were characterized by scanning electron microscopy and Cr (VI) concentration was determined by spectrophotometry. Planar and continuous membrane was obtained when fired initially in air followed with N 2 and the air–nitrogen changing temperature was 400 °C. The membrane consisted of small cubic grains when the casting solution was 0.032 mol/L and the thickness was ∼5 μm. When the concentration was 0.065 mol/L, the membrane was composed of small cubic grains at the bottom and big pillar ones on the top and the thickness increased to ∼25 μm. Repeated coatings had no significant impact on the morphologies and thicknesses of the resultant membranes. When fired at 850 °C, pure magnetite membranes with clear cubic grains at the bottom and clear pillar ones on the top were obtained. Pillar grains can be obtained when sintered at a heating ramp rate of 1 °C/min. The Cr (VI) removal test exhibited an elimination efficiency of 92.5%, indicating a promising application to remove Cr (VI) from aqueous solution.

Magnetic Properties of Single-Layered Fe<sub>100-x</sub>Pt<sub>x</sub> Films by Rapid Thermal Annealing

Fe100-xPtx single-layered films with Pt contents (x) = 32~69 at.% were deposited on natural-oxidized Si(100) substrate by dc magnetron sputtering. Then the films were post-annealed at 700 °C for 3 min by a rapid thermal annealing (RTA) with a high heating ramp rate of 100 °C/sec. Experimental results show that FePt film presented (111) preferred orientation and tended to in-plane magnetic anisotropy as the content of Pt was 32 at.%. When the Pt content was increased to 55 at.%, (001)-textured FePt film was obtained and presented perpendicular magnetic anisotropy. Its out-of-plane coercivity (Hc⊥), saturation magnetization (Ms) and out-of-plane squareness (S⊥) reached to 12.7 kOe, 375 emu/cm3 and 0.8, respectively. These results reveal its significant potential as perpendicular magnetic recording media for high-density recording. Further increasing the Pt content to 69 at.%, the coercivity of FePt film was decreased drastically to below 1 kOe and tended towards in-plane magnetic anisotropy.

Granular L1 0 FePt nanocomposite films fabricated by rapid thermal annealing

Granular (FePt) 100− x –(NiO) x nanocomposite thin films with x = 0 − 42 vol% were fabricated on a natural-oxidized Si(100) substrate. It is found that both the coercivity and FePt domain size decrease with increasing NiO content for the (FePt) 100− x –(NiO) x films. When the FePt–NiO composite film with NiO content of 10.4 vol% is post-annealed at 750 °C with a high heating ramp rate of 100 °C/s, the in-plane coercivity ( H c //) and perpendicular coercivity ( H c ⊥) of the FePt films are 513 and 430 kA/m, respectively. On the other hand, we used conductive atomic force microscope (CAFM) to confirm that the NiO compound is distributed at boundary of FePt particles that will constrain the domain size of FePt and decrease the exchange coupling interactions between FePt magnetic particles.

“A Comparative Thermal Kinetic Investigation of the Fresh and Stale-Expired Protein Denaturing Transition”

Protein, in eggs, has a biological quality greater than any other natural food. The quality of the protein in eggs means that all egg protein can be used for synthesis and limits the amount burned as fuel or stored as fat. Hence, the quality of egg protein can be an important factor in weight loss and essential to understand more facts about egg proteins. In this study, a comparative thermal kinetic investigation of the fresh and stale-expired proteins was made using calorimetric technique. Three different scans as temperature scans, heating rate scans and time scans were performed using differential scanning calorimetry varying temperature range from 0 °C to 200 °C and heating ramp rates from 1 °C/min to 20 °C/min. Two protein samples were used; one obtained from a fresh egg and other from the stale-expired egg from the same batch. The denaturing transition for the stale egg protein occurred at the higher temperature with smaller enthalpy and needed a larger activation than the fresh protein. This indicates that stale-expired egg provides less energy and need more energy to be activated or burnt than the fresh egg protein. Hence, the stale protein would increase more fat and need more energy to burn if eaten in the food. Keywords: Calorimetry, fresh and stale Protein, Kinetics, Activation Energy, Denaturing transition, thermodynamics

Preparation and Magnetic Properties Studies of Granular FePt Composite Films for High-Density Magnetic Recording

Granular (FePt)100-x–(NiO)x nanocomposite thin films with x in the range of 0 – 42 vol.% were fabricated on a natural-oxidized Si(100) substrate. It is found that both the coercivity and FePt domain size decrease with increasing NiO content for the (FePt)100-x–(NiO)x films. When the FePt-NiO nanocomposite film with NiO content of 10.4 vol.% is post-annealed at 750 °C with a high heating ramp rate of 100 °C/sec, the in-plane coercivity (Hc//) and perpendicular coercivity (Hc⊥) of the FePt films are 6.4 and 5.5 kOe, respectively. On the other hand, we used conductive atomic force microscope (CAFM) to confirm that the NiO compound is distributed at grain boundary of FePt grain that will constrain the domain size of FePt and obtain isolated magnetic domains. These results indicate that NiO addition is beneficial to enhance recoding density and reduce media noise of the FePt magnetic film.

L1 0 FePt thin films with high coercivity and fine grain by rapid thermal annealing with high heating ramp rate

Iron–platinum (FePt) thin films are deposited on an oxidized Si (100) substrates followed by a rapid thermal annealing (RTA) process with various heating rates from 20 °C/s to 100 °C/s. It is found that the coercivity of the FePt films increases and the grain size decreases as the heating rate of RTA increases. As the as-deposited FePt films are annealed at 700 °C with a high heating ramp rate of 100 °C/s, the grain size of FePt films is determined to be as small as 14 nm, and its in-plane coercivity and perpendicular coercivity reached as high as 11.1 and 9.5 kOe, respectively. On the other hand, the isolated magnetic domains are observed by magnetic force microscope (MFM) at a high heating ramp rate of 100 °C/s.

“Arrhenius Approach to Study Kinetics of Fresh Egg Protein”

This study explores an interesting denaturing kinetics of fresh egg proteins following Arrhenius behavior. Fresh egg white-protein (2mg) was used in a sealed cell for scanning using calorimetric technique. Heating scans were performed from 10° C to 100° C at different heating ramp rates varying from 1 to 20° C/min. All environments were kept identical for all runs to compare parameters (temperature, enthalpy, heat energy). An endothermic peak was found on heating scan showing denaturing of protein.

The influence of precursor source and thermal parameters upon the formation of beta-phase molybdenum nitride

In the present paper the effect of the MoO 3 precursor and procedure on the synthesis of beta-phase molybdenum nitride is reported. Two different sources of MoO 3 were used, and treated under a flow of gas N 2/H 2 at 700 or 750 °C employing various heating ramp rates. All samples were characterized by XRD, SEM and their textural properties were determined by application of the BET method. The results show that, depending on the precursor, markedly different morphologies were observed, whereas both the molybdenum source and the thermal treatment, strongly influence the incorporation of nitrogen.

Kinetics of nanocolloids in the aligned domain of octylcyanobiphenyl and aerosil dispersion

In this study we explore the interesting kinetics of nanocolloids formed by the solvent dispersion method (SDM) in an aligned matrix of octylcyanobiphenyl (8CB) liquid crystals and aerosil nanoparticles. The presence of alignment changes the behaviour of the induced crystallisation (IC), and melting transition (K–SmA) observed in the aligned nanocolloidal liquid crystal samples when compared with unaligned samples. Heating‐rate‐dependent experiments were performed for the aligned and unaligned samples at various heating ramp rates varied from 20 to 1 K min−1 using a calorimetric technique. In the aligned samples, the IC transition peak shifts towards higher temperature, whereas the melting transition peak shifts towards lower temperature. The IC peak shows an increase in enthalpy whereas the melting transition shows a decrease following an Arrhenius behaviour. The presence of alignment increases the activated kinetics of the system. This behaviour can be explained in terms of molecular interaction between aligned domains of nanocolloids in the 8CB matrix which makes the material stiffer.

Probing the effect of the carbonisation process on the textural properties and morphology of mesoporous carbons

The carbonisation conditions and in particular the heating ramp rate plays an important role in determining the properties of mesoporous carbon materials prepared via either liquid impregnation (LI) or chemical vapor deposition (CVD). For LI (at final carbonization temperature of 900 °C), fast heating ramp rate (20 °C/min) results in poorly ordered mesoporous carbons, while slower heating ramp rates (5 or 1 °C/min) generate well ordered mesoporous carbons. The surface area is highest (ca. 1360 m 2/g) for carbons prepared at a ramp rate of 1 °C/min. Mesoporous carbons prepared at low heating ramp rate (1 °C/min) are virtually micropore free and exhibit only framework-confined mesoporosity. On the other hand, fast heating ramp rate generates carbons with significant microporosity (15% of surface area is associated with micropores) and some non-framework porosity (i.e., large mesopores). For CVD-derived mesoporous carbons (prepared at 1000 °C), the particle morphology changed from solid-core spheres (10 °C/min) to hollow spheres (20 °C/min) depending on the heating ramp rate. Although textural properties were comparable for CVD-derived carbons, higher levels of graphitisation were observed for fast heating ramp rates.

Kinetics of Induced Crystallization of the LC1-xSilx System

This study explores the kinetics of a new feature, called "induced crystallization (IC)", observed in an Aerosil dispersed octylcyanobiphenyl (8CB) liquid crystal system. Heating rate dependent experiments were performed using modulation differential scanning calorimetry (MDSC) at various heating ramp rates. In the presence of Aerosil nanoparticles, a well-defined exothermic peak was found as an additional feature on the heating scan before the melting transition, which was absent in the bulk 8CB; hence, we like to call it an "IC" as it is induced by Aerosil nanoparticles in the system. The system LC1-xSilx was prepared by mixing Aerosil nanoparticles in the bulk 8CB by the solvent dispersion method (SDM) where LC represents bulk 8CB and Sil represents Aerosil nanoparticles with x as the Aerosil fraction. The concentration of the Aerosil nanoparticles (x) varied from 0 to 0.2 g/cm3 in the bulk 8CB. The IC transition peak showed a temperature shift and change in the shape and size in the presence of Aerosil nanoparticles. In addition, this transition shifted significantly with different heating ramp rates following an Arrhenius behavior showing activated kinetics. The presence of Aerosil nanoparticles caused a significant increase in the enthalpy and decrease in the activation energy for the IC transition as the density of Aerosil nanoparticles increases and showed a saturation for the highest density of Aerosil nanoparticles. This behavior can be explained in terms of molecular disorder and surface molecular interaction induced by adding Aerosil nanoparticles into the bulk of 8CB liquid crystal.