Temperature Ramp Rate Research Articles

A novel method for preparing CuAlO 2 thin films and the film properties

Single-phase CuAlO 2 thin films have been successfully prepared by rapid thermal reaction of a Cu 2O/sapphire structure. Second phases, such as CuAl 2O 4, could be formed if there were any chance to transform Cu 2O into CuO. Therefore, the annealing ambient, the reaction temperature and the temperature ramp rate are crucial for the formation of CuAlO 2. An Al 2O 3 cap layer is necessary to prevent the formation of Cu 2O droplets when the sample is heated to a temperature above 1000 °C and turned into a liquid state. The optical bandgap of a CuAlO 2 film with monocrystalline structure was determined to be 3.75 eV. The electrical properties related to the oxygen diffusion in and out of the films are reported.

Microfluidic Chips for Detecting the t(4;14) Translocation and Monitoring Disease during Treatment Using Reverse Transcriptase-Polymerase Chain Reaction Analysis of IgH-MMSET Hybrid Transcripts

Diagnosis platforms incorporating low-cost microfluidic chips enable sensitive, rapid, and accurate genetic analysis that could facilitate customized therapies tailored to match the vulnerabilities of any types of cancer. Using ex vivo cancer cells, we have detected the unique molecular signature and a chromosomal translocation in multiple myeloma. Multiple myeloma is characterized by IgH rearrangements and translocations that enable unequivocal identification of malignant cells, detected here with integrated microfluidic chips incorporating genetic amplification via reverse transcriptase-polymerase chain reaction and capillary electrophoresis. On microfluidic chips, we demonstrated accurate and versatile detection of molecular signatures in individual cancer cells, with value for monitoring response to therapy, detecting residual cancer cells that mediate relapse, and evaluating prognosis. Thus, testing for two clinically important molecular biomarkers, the IgH VDJ signature and hybrid transcripts signaling the t(4;14) chro-mosomal translocation, with predictive value in diagnosis, treatment decisions, and monitoring has been efficiently implemented on a miniaturized microfluidic system.

Temperature-Programmed GC Using Silicon Microfabricated Columns with Integrated Heaters and Temperature Sensors

Columns were fabricated in silicon substrates by deep reactive-ion etching. The channels were sealed with a glass wafer anodically bonded to the silicon surface. Heaters and temperature sensors were fabricated on the back side of each column chip. A microcontroller-based temperature controller was used with a PC for temperature programming. Temperature programming, with channel lengths of 3.0 and 0.25 m, is described. The 3.0-m-long channel was fabricated on a 3.2 cmx3.2 cm chip. Four columns were fabricated on a standard 4-in. silicon wafer. The 0.25-m-long channel was fabricated on a 1.1 cmx1.1 cm chip, and approximately 40 columns could be fabricated on a 4-in. wafer. All columns were coated with a nonpolar poly(dimethylsiloxanes) stationary phase. A static coating procedure was employed. The 3.0-m-long column generated about 12000 theoretical plates, and the 0.25-m-long channel generated about 1000 plates at optimal carrier gas velocity. Linear temperature ramps as high as 1000 degrees C/min when temperature programmed from 30 to 200 degrees C were obtained with the shorter column. With the 0.25-m-long column, normal alkanes from n-C5 through n-C15 were eluted in less than 12 s using a temperature ramp rate of 1000 degrees C/min. Temperature uniformity over the column chip surface was measured with infrared imaging. A variation of about 2 degrees C was obtained for the 3.0-m-long channel. Retention time reproducibility with temperature programming typically ranged from +/-0.15% to +/-1.5%. Design of the columns and the temperature controller are discussed. Performance data are presented for the different columns lengths.

Thermal Fatigue of SnPb and SAC Resistor Joints: Analysis of Stress-Strain as a Function of Cycle Parameters

Accelerated thermal cycling (ATC) has been widely used in the microelectronics industry for reliability assessment. The relative effects of thermal cycling parameters (temperature range, dwell time, and ramp rate) and the failure mechanisms they induce have been the subject of many studies; however, uncertainty remains, particularly regarding the role of a very high ramp rate such as encountered in a thermal shock chamber. In the present research, thermomechanical finite-element (FE) models were used to analyze the stress/strain response of a resistor test vehicle during ATC testing under three accelerated test conditions: two ramp rates (14 degC/min and 95 degC/min) and two temperature ranges (DeltaT=0degC-100degC and -40degC-125degC), denoted 14-100 (ramp rate-temperature range), 95-100, and 95-165. The temperature gradients through the thickness of the assemblies were measured during the ATC test with the high ramp rate and were used to create an FE model that included transient stresses and strains. The effect of the transient temperature gradients during thermal shock was found to be negligible in these resistor joints. The FE models were then used to simulate the above three ATC test conditions with either SnPb or Pb-free (SAC) solders and were compared with previously published thermal fatigue lives for this resistor test vehicle. For both SnPb and SAC resistors, the maximum total solder strains (sum of elastic, plastic, and creep) and strain energy dissipation per cycle predicted by the FE models in the 95-165 test condition were much greater than those in either the 14-100 or 95-100 test conditions, which produced almost identical strains and energy dissipation. In all cases, the strain energy density dissipation per cycle due to creep was much larger than that due to plastic deformation. The trend of these results was in accordance with the ATC tests, which showed that the thermal cycling lives decreased in the same order for both the SAC and SnPb solders; i.e., the fatigue life decreased as the predicted total strain increased

Rapid Analysis of Benzoylecgonine in Urine by Fast Gas Chromatography-Mass Spectrometry

A novel fast gas chromatography-mass spectrometry (FGC-MS) analytical method for benzoylecgonine (BZE) has been developed to improve the efficiency of specimen analysis without diminishing the reliability of metabolite identification and quantification. Urine specimens were spiked with deuterated internal standard (BZE-d8), subjected to solid-phase extraction, and derivatized with pentafluoropropionic anhydride (PFPA) and pentafluoropropanol (PFPOH). The pentafluoropropyl ester derivative of BZE was identified and quantified using both a standard GC-MS method and the newly developed FGC-MS method. Shorter GC analyte retention times were made possible in the FGC-MS method by employing a 220-volt GC oven controller, which allowed an increased temperature ramp rate. The FGC-MS method was linear between 25 and 10,000 ng/mL of BZE yielding a correlation coefficient of 0.9994. The intra-assay precision of a 100 ng/mL BZE standard (n=15) yielded an average concentration of 99.7 ng/mL and a coefficient of variation of 1.2%. The interassay precision of 21 sets of 50, 100, and 125 ng/mL BZE controls was found to be acceptable, with coefficients of variation less than 2.4%. No interference was observed when the FGC-MS method was challenged with cocaine, ecgonine, ecgonine methyl ester, and nine other drugs of abuse. Analysis of presumptively positive specimens (n=146) by both analytical methods yielded comparable results with a correlation coefficient of 0.996. The FGC-MS method, when compared with a standard GC-MS method, reduces total assay time by approximately 50% while demonstrating comparable reliability.

Thermodynamics of Activated Phase Transitions of 8CB: DSC and MC Calorimetry

The present paper reports the heating rate effect on the phase transitions of a pure liquid crystal octylcyanobiphenyl (8CB) with use of Differential Scanning Calorimetry (DSC) and Modulation Calorimetry (MC) techniques. The DSC runs were taken at various temperature ramp rates from 20 to 0.5 K/min for heating and cooling scans. Well-defined endothermic/exothermic peaks were found at the melting/crystallization, smectic-A to nematic (SmA-N), and nematic to isotropic (N-I) transitions on heating/cooling scans, respectively. All transitions shift in temperature significantly with different ramp rates. The temperature shift of C(p) peaks between heating and cooling scans indicates the order of the transitions. In addition, all transitions follow an Arrhenius behavior. The activation energy of a transition increases as the total energy involved in the transition decreases. The respective enthalpy and entropy change of each transition provides information on the Gibbs free energy. The significance of the results is discussed in terms of the order of transitions. A comparative analysis of MC and DSC techniques highlights the significance of the two techniques. MC is a practicable tool for observing the phase dynamics whereas DSC is a good tool for studying the rate kinematics of the transitions.

A comprehensive characterization of photoelectron resonance capture ionization aerosol mass spectrometry for the quantitative and qualitative analysis of organic particulate matter

Photoelectron resonance capture ionization (PERCI), when coupled with thermal vaporization aerosol mass spectrometry (AMS) is found to be an excellent ionization method for the identification of particle-bound organics. While the qualitative analytical advantages of PERCI have been demonstrated previously, a comprehensive characterization of PERCI-AMS, which will be of paramount importance in developing the method to perform reliable quantitative measurements, is discussed here. A detailed analysis, based on photoelectron, gas phase, and particle phase measurements, of the behavior and limitations of PERCI-AMS is given. The performance of PERCI-AMS is affected by: delayed time between anion formation and extraction for mass spectral analysis, relative positioning of the vaporization probe (VP) and photoelectrode (PE), laser intensity, analyte pressure in the ionization region, particle matrix, and vaporization temperature ramping rate. Gas phase detection limits are found to be on the order of 10 7–10 9 cm −3 and particle phase detection limits for individual compounds are found to be on the order of 10 −8–10 −7 g of total sampled mass. An additional level of analyte selectivity is gained with the vapor pressure dependent desorption of deposited particles, achieved with ramped thermal vaporization. The major limitation of the thermal vaporization PERCI-AMS is the low duty cycle of the measurement, stemming from the pulsed nature of PERCI. Finally, prospects for improvements in detection limits as high as 3–4 orders of magnitude by adaptation of pulsed IR laser desorption to the system are discussed.

The Effect of Catalytic Washcoat Geometry on Light-off in Monolith Reactors

This paper presents the results of a series of simulations of the light-off of carbon monoxide in excess oxygen in a single channel monolith reactor. The catalytic washcoat geometry is tested for its effect on the light-off position and shape. The simulations used a combination of two and three-dimensional modelling with non-linear oxidation kinetics. Different temperature ramp rates were employed. It is seen that the shape of the washcoat has an influence on the shape of the light-off curve, especially for high values of gas hourly space velocity and larger temperature ramp rates. The washcoat geometry that gives the fastest rise to complete conversion is the one that is the most non-uniform in shape; that is, the one that has thin sections.

An investigation of the skin/core bond in honeycomb sandwich structures using statistical experimentation techniques

Experimental design has been used to investigate the effect of processing parameters on the peel strength of Nomex honeycomb core/carbon fibre-epoxy prepreg skin sandwich panels, manufactured by vacuum bagging. The four processing parameters considered were: (i) consolidation pressure; (ii) temperature cure cycle; (iii) temperature ramp rate and (iv) vacuum pressure application time. Each parameter was considered at three levels. It was found that (ii) was the dominant parameter. Panels manufactured under the optimum combination of processing parameters gave a mean peel strength more than twice that of the worst panels. Qualitative microscopy has associated the higher peel strengths with larger, regular shaped adhesive fillets between honeycomb cell walls and skin laminate.

Peak pattern variations related to comprehensive two-dimensional gas chromatography acquisition

Identifying compounds of interest for peaks in data generated by comprehensive two-dimensional gas chromatography (GC × GC) is a critical analytical task. Manually identifying compounds is tedious and time-consuming. An alternative is to use pattern matching. Pattern matching identifies compounds by matching previously observed patterns with known peaks to newly observed patterns with unidentified peaks. The fundamental difficulty of pattern matching comes from peak pattern distortions that are caused by differences in data acquisition conditions. This paper investigates peak pattern variations related to varying oven temperature ramp rate and inlet gas pressure and evaluates two types of affine transformations for matching peak patterns. The experimental results suggest that, over the experimental ranges, the changes in temperature ramp rate generate non-linear pattern variations and changes in gas pressure generate nearly linear pattern variations. The results indicate the affine transformations can largely remove the pattern variations and can be used for applications such as pattern matching and normalizing retention times to retention indices.

Effect of annealing temperature ramp rate on bubble formation in helium-implanted silicon

We have implanted He3 into Si(100) at 1.0MeV ion energy and to fluences ranging between 2×1015 and 2×1016cm−2, followed by annealing at 700°C. Heating ramp rates have been systematically varied over more than two decades (0.3°C∕sto100°C∕s) at each fluence. The retention of He3 is measured through the He3(d,p)He4 nuclear reaction yield. We show that gas retention can be varied by more than an order of magnitude even while the other anneal parameters—anneal temperature and anneal time—are maintained constant. Cross-sectional scanning electron micrographs confirm the presence of planetarylike cavity structures at a depth closely matching that calculated for the damage peak.

Tensile properties of bcc Nb–Al supersaturated solid solution embedded in a Nb matrix to be transformed toA15-type Nb3Al filaments

The mechanical Cu-cladding method is favourable to incorporate stabilizerinto the rapid-heating, quenching and transformation (RHQT) processedNb3Al conductor for NMR insert coil uses, because an appropriatemechanical deformation of bcc Nb–Al supersaturated solid solution(Nb(Al)ss) is effective in transforming it in a short time, making the resultant superconducting propertieslarge and insensitive to the temperature ramp rate during transformation annealing. Inorder to examine the drawability of a Cu-clad stabilized conductor with rectangular diesthat might be effective in finishing the conductor with a precision dimension, which wouldeventually be a key to homogenizing the magnetic field of NMR magnet, the tensile loadingtest at room temperature was performed for Cu-clad conductors. For comparison, thetensile properties of as-quenched wires and round-to-round deformed bare wires werealso examined. A fracture elongation reached as much as 11% for as-quenchedNb/Nb(Al)ss composites, but only 3.5% for Cu-clad conductors. Effects of pre-annealing on tensile properties werealso studied. Ductility does not seem to deteriorate after pre-annealing at temperatures less than500 °C, but thepre-annealing at 600 °C apparently reduces the elongation. Pre-annealing did not improve the drawability ofCu-clad stabilized conductor with rectangular dies.

Startup Strategy for Operating a Solid Oxide Fuel Cell Based on Transient Analyses

In this paper, conservations of charge, mass, and energy are implemented to establish the basic relationship between voltage and current as well as the mathematical model for investigating the transient behavior of a planar SOFC. Typical response time and temperature ramp rate of the SOFC under steady operating conditions are calculated first and ascend with increasing current density. Furthermore, transient behavior is investigated by setting a series of step functions of current density to simulate various startup operating modes. To avoid the temperature ramp rate being too high during the startup period, stepwise increment of the current density seems to be more suitable. For example, the three-step increment series of 300 mA/cm2, 500 mA/cm2 and 640 mA/cm2 would result in a temperature ramp rate complied with a given specification, e.g., less than 5°C per minute, while the total response time is in a moderate range as well.

Performing microchannel temperature cycling reactions using reciprocating reagent shuttling along a radial temperature gradient

This study develops a novel temperature cycling strategy for executing temperature cycling reactions in laser-etched poly(methylmethacrylate) (PMMA) microfluidic chips. The developed microfluidic chip is circular in shape and is clamped in contact with a circular ITO heater chip of an equivalent diameter. Both chips are fabricated using an economic and versatile laser scribing process. Using this arrangement, a self-sustained radial temperature gradient is generated within the microfluidic chip without the need to thermally isolate the different temperature zones. This study demonstrates the temperature cycling capabilities of the reported microfluidic device by a polymerase chain reaction (PCR) process using ribulose 1,5-bisphosphate carboxylase large subunit (rbcL) gene as a template. The temperature ramping rate of the sample inside the microchannel is determined from the spectral change of a thermochromic liquid crystal (TLC) solution pumped into the channel. The present results confirm that a rapid thermal cycling effect is achieved despite the low thermal conductivity of the PMMA substrate. Using IR thermometry, it is found that the radial temperature gradient of the chip is approximately 2 degrees C mm(-1). The simple system presented in this study has considerable potential for miniaturizing complex integrated reactions requiring different cycling parameters.

Impact of crystallization manner of the buffer layer on the crystalline quality of GaN epitaxial layers on GaAs (1 1 1)A substrate

We studied experimentally the crystallization of a low-temperature (LT)-GaN buffer layer and its effect on the subsequent crystalline quality of the GaN epitaxial layer. The degree of crystallization was sensitive to the thickness and the temperature ramp rate of the GaN buffer layer. When the LT-GaN buffer layer was more than 100 nm thick, there was relatively little crystallization of the buffer layer and subsequently poor crystalline quality of the GaN epitaxial layer. The optimum crystallization condition for the GaN buffer layer just prior to high-temperature growth was found when the single-crystal regions in the GaN buffer layer occupied a volume 40% as large as the randomly aligned matrix. We could reduce the threading dislocation density in the GaN epitaxial layer by inserting the LT-GaN buffer layers in periodically. To explain this result, we propose a mechanism by which the periodic layer reduces the density of threading dislocations.

Genotyping by dynamic heating of monolayered beads on a microheated surface

A miniaturized bead-based dynamic allele-specific hybridization (DASH) approach for single-nucleotide polymorphism analysis is presented. Chips with integrated heater and temperature sensors for open-surface DNA analysis were microfabricated. Microcontact printing using a poly(dimethylsiloxane) (PDMS) stamp was employed to create monolayers of immobilized beads on the surface of the chip. This chip allows fast, well-controllable temperature ramping. The temperature distribution was homogeneous over the entire heater area. All three possible variants of an SNP site of a synthesized oligonucleotide were accurately scored using the bead-based DASH approach. Our assay has a nonoptimized temperature ramping rate of 4 degrees C-6 degrees C/min compared to earlier reported values of 2 degrees C-3 degrees C/min, thereby reducing the total analysis time by a factor of 2. Reliable DASH measurement data from areas as small as 12 x 13 microm was achieved. Our bead-based DASH approach has enabled a dramatic volume reduction and is a step towards developing a cost-effective high-throughput DASH method on arrays of single beads.

Trade-off between thickness and temperature ramping rate of GaN buffer layer studied for high quality GaN growth on GaAs (1 1 1)A substrate

The correlation between crystallization of low-temperature (LT) GaN buffer layer and crystalline quality of subsequently grown thick GaN layer at high-temperature on GaAs (1 1 1)A substrate has been investigated. During heating of LT-GaN buffer layer to 1000°C, the degree of crystallization highly depended on the thickness and the temperature ramping rate of GaN buffer layers. When the LT-GaN buffer layer was less than 40-nm-thick or temperature ramping rate was low, excess crystallization and/or agglomeration of the buffer layer occurred, which resulted in a poor crystalline quality of the GaN epitaxial layer subsequently grown on it. On the other hand, when the thickness of LT-GaN buffer layer exceeded 100 nm, there was relatively little agglomeration of buffer layer, which also resulted in poor crystalline quality of the subsequently grown GaN. To grow high-quality GaN layer at high-temperature, optimum crystallization condition for GaN buffer layer just prior to high-temperature growth was found to be as follows: single crystallites region in the GaN buffer layer occupied a volume 40% as large as the randomly aligned matrix. The trade-off between thickness and temperature ramping rate of GaN buffer layer clearly indicates that the degree of crystallization of the GaN buffer layer is an important parameter for achieving high-quality GaN growth at high-temperature.

Mechanistic study of organic template removal from ZSM-5 precursors

The decomposition mechanism of tetrapropylammonium (TPA +) template cations in several commercial ZSM-5 precursors was studied by temperature-programmed desorption/oxidation using a mass spectrometer (TPD/TPO-MS). Different oxygen concentrations, gas flow rates and temperature ramp rates were examined to understand the effects of these factors on the organic template decomposition. The TPA + template decomposition pattern is strongly dependent on the SiO 2/Al 2O 3 molar ratio (SAR) and the oxygen concentration. The TPA + template cations may be associated with three different sites depending on the SAR: Lewis acid sites (surface Al–O −), Brønsted acid sites (framework Al–O −), and weakly acidic SiO − sites. The thermal decomposition of TPA + templates at different sites produced different products, including water, ammonia, propylene, ethylene, methane, and n- and iso-propylamines. However, no significant heavy volatile compounds were detected, suggesting that secondary reactions (e.g., oligomerization of olefins) were extremely limited and negligible in a fixed-bed micro-reactor used for TPD/TPO. The TPD-MS results suggest that the thermal decomposition mechanism on Lewis acid sites is possibly a free radical type of reaction, while on Brønsted acid sites and SiO − sites, the decomposition undergoes both Hoffman elimination reaction and a radical type of reaction. The presence of oxygen significantly lowered the TPA + decomposition temperature, which is also a function of oxygen concentration. The knowledge about the template decomposition pattern and the composition of the evolved volatiles obtained by the TPD/TPO-MS technique may be used to develop ideal organic template removal procedures for zeolites.

Influence of temperature on the modulus of elasticity (MOE) of Pinus sylvestris L.

Abstract The influence of temperature on the modulus of elasticity (MOE) and on the flexural stiffness of Pinus sylvestris L. was determined under temperature conditions ranging from 25 to 300°C for samples with a water content of about 6.0%. The experiments were carried out on microsamples, with a thermomechanical analyser, in isothermal conditions and under temperature ramping rates. The behaviour of the curves of the MOE is explained by wood drying and by the behaviour of the wood polymers as a function of temperature. The results obtained by thermomechanical analysis were validated by the results obtained by centre-point bending tests on small scale samples, which therefore allows for its use in modelling the behaviour of timber structures during a fire.

Fabrication and characterization of diamond AFM probe integrated with PZT thin film sensor and actuator

In order to develop a diamond probe with a piezoelectric sensor and actuator for atomic force microscope (AFM), we fabricated lead zirconate titanate (PZT) thin film on a diamond thin film substrate and examined its piezoelectric properties. The PZT thin film was sputtered at room temperature and then annealed to obtain a perovskite structure. After rapid thermal annealing at temperature ramp rate of more than 10 °C/s and at temperatures of more than 500 °C in a nitrogen (N 2) ambient, the PZT thin film fabricated on flat Si substrates showed high piezoelectric constant, d 31, of about −90 pC/N, as well as in an oxygen (O 2) ambient. On diamond thin film substrates, the value of piezoelectric constant was as low as about −20 pC/N due to rough surface of the diamond film. After a poling treatment, however, its piezoelectric constant improved to about −65 pC/N. For realization of a PZT sensor and actuator on a diamond cantilever, the PZT thin film was also successfully patterned by reactive ion etching (RIE) in sulfur hexafluoride (SF 6) plasma using a platinum (Pt) upper electrode layer as an etching mask without any damage on the diamond layer. Based on the fabrication and patterning of PZT thin film together with microfabrication techniques of diamond film formed by chemical vapor deposition (CVD), we demonstrate the diamond AFM probe of 150 μm in length, 50 μm in width, and 5 μm in thickness with a PZT sensor and actuator of 1 μm in thickness. The resolution of image sensing and actuation force were estimated to be about 0.4 nm at a resolution of charge measurement of 1×10 −15 C, and 17 μN at an applied voltage of 8 V, respectively.