Measurement Of Density Changes Research Articles

Neutron irradiation-induced dimensional changes in MEMS glass substrates

A study is made of radiation-induced expansion/compaction in Pyrex® (Corning 7740) and Hoya SD-2® glasses, which are used as substrates for MEMS devices. Glass samples were irradiated with a neutron fluence composed primarily of thermal neutrons, and a flotation technique was employed to measure the resulting density changes in the glass. Transport of Ions in Matter (TRIM) calculations were performed to relate fast (∼1MeV) neutron atomic displacement damage to that of boron thermal neutron capture events, and measured density changes in the glass samples were thus proportionally attributed to thermal and fast neutron fluences. Pyrex was shown to compact at a rate of (in Δρ/ρ per n/cm2) 8.14×10−20 (thermal) and 1.79×10−20 (fast). The corresponding results for Hoya SD-2 were 2.21×10−21 and 1.71×10−21, respectively. On a displacement per atom (dpa) basis, the compaction of the Pyrex was an order of magnitude greater than that of the Hoya SD-2. Our results are the first reported measurement of irridiation-induced densification in Hoya SD-2. The compaction of Pyrex agreed with a previous study. Hoya SD-2 is of considerable importance to MEMS, owing to its close thermal expansivity match to silicon from 25 to 500°C.

Activation of KCI Cotransport by Urea Induces Dehydration in Both Sickle and Normal Reticulocytes.

KCl Cotransport (KCC) is highly expressed in sickle red blood cells (SS RBC) and recent data have demonstrated its abnormal response to cell swelling and acid pH. We showed that the final MCHC achieved by SS reticulocytes upon activation of KCC by these stimuli was higher than that of normal (AA) reticulocytes (Joiner et al, Blood, in Press). Here we report studies examining the sensitivity of KCC to activation by urea at concentrations present in the kidney and the effect of urea stimulation of KCC on reticulocyte MCHC. KCC fluxes were assayed as Rb uptake over 20 min in isotonic saline solutions buffered with HEPES to pH 7.4 (37°C) containing 0.1 mM ouabain, and 0.01 mM bumetanide, with 27 mM RbCl replacing equimolar NaCl. Under these conditions > 95 % of Rb uptake was Cl-dependent (assessed by sulfamate replacement of Cl). The maximal volume-stimulated KCC flux (VSmax KCC) was measured for each sample in cells swollen isotonically to MCHC < 27 gm/dl (nystatin method). Urea (100 to 1000 mM) increased osmolality of buffers, but did not alter initial MCHC. MCHC of reticulocytes (detected by flow cytometry) was tracked by measuring density changes on calibrated OPTIprep® gradients. Cl-dependent, ouabain- and bumetanide-insensitive Rb influx in both AA and SS RBC was increased by urea, reaching a plateau at 1000 mM urea that was similar to VSmax KCC. SS RBC were more sensitive to urea stimulation than AA RBC: 50% VSSmax KCC was achieved at 330 mM urea in SS RBC vs 550 mM in AA RBC. This effect was sulfhydryl dependent: exposure to the reducing agent dithiothreitol (preincubation for 30 min at 37°C with 10 mM DTT, then 1 mM in flux media) normalized the response to urea in SS RBC, with no effect in AA RBC. When swollen to MCHC 30 gm/dl, SS and AA retics exhibited Regulatory Volume Decrease (RVD) which increased MCHC. RVD in both AA and SS retics was abolished by incubation in sulfamate media, indicating mediation by KCC. As previously reported, final MCHC achieved after two hours incubation by SS retics was greater than AA retics (see Table, Control).Final Reticulocyte MCHC, gm/dl [mean (SD), n = 3]AASSp (AA vs SS)Control31.9 (0.7)34.7 (1.20.03Urea35.3 (0.5)37.8 (0.3)0.002p (Control vs Urea)0.0050.03Urea (600 mM) enhanced RVD in both AA retics and SS retics. Sulfhydryl reduction with DTT had no effect on urea-stimulated RVD in SS reticulocytes. RVD stimulated by urea was complete within 60 minutes, and was irreversible: additional incubation without urea did not lower MCHC. The partially dehydrating effect of brief (10 min) exposure to urea was also irreversible, and was cumulative: cells exposed to two 10 min exposures to high urea (600 mM), separated by 10 min at a low, non-stimulating concentration of urea (100 mM), yielded the same MCHC as a continuous 20 min exposure. These data demonstrate that urea, at concentrations found in the renal medulla, is a powerful stimulant of KCC and intiates a striking RVD in reticulocytes. To the extent that intermittent stimulation of KCC by urea in the kidney occurs in vivo, this could contribute an exaggerated RVD resulting in dehydration of SS reticulocytes.

Ultrasonic Velocity Technique for Nondestructive Quantification of Elastic Moduli Degradation during Creep in Silicon Nitride

The ultrasonic velocity technique was used for nondestructive quantification of creep damage during interrupted tensile creep tests at 1400°C in an advanced silicon nitride to investigate the possibilities of this technique for creep damage monitoring in ceramic components. The longitudinal and shear wave velocities, Poisson's ratio, and Young's, shear, and bulk moduli linearly decreased with strain. Precise density change measurements indicated a linear relationship with a coefficient of proportionality of 0.69 between the volume fraction of cavities and tensile strain. Cavitation was identified as the main creep mechanism in the studied silicon nitride and the reason for ultrasonic velocity and elastic moduli degradation. The measurement of just the longitudinal wave velocity changes was found to be sufficient for quantification of cavitation during creep. The capability of the ultrasonic velocity technique for simple, sensitive, and reliable nondestructive monitoring of creep damage during intermittent creep was demonstrated in silicon nitride.

Length and density changes of amorphous Pd 40Cu 30Ni 10P 20 alloys due to structural relaxation

The density changes of bulk amorphous Pd 40Cu 30Ni 10P 20 due to structural relaxation under isothermal heat treatment were measured using the buoyancy method. The corresponding length changes of amorphous Pd 40Cu 30Ni 10P 20 ribbons applying non-isothermal heat treatment are determined applying dilatometry. The measured density changes Δ ρ( T=const., t)/ ρ o as a function of isothermal heat treatment increase close to the glass transition up to 0.18%. The measured density changes as a function of temperature and time are furthermore reversible. The experimental data validate the model predictions of the free volume model for length and density changes of amorphous alloys due to structural relaxation applying isothermal and non-isothermal heat treatment.

Instrumented Indentation and Ultrasonic Velocity Techniques for the Evaluation of Creep Cavitation in Silicon Nitride

Instrumented indentation and ultrasonic wave velocity techniques combined with precise density change measurements and transmission electron microscopy (TEM) were used to investigate the changes of elastic moduli in silicon nitride after tensile deformation up to 3%. Linear dependencies on strain were also found for the degradation of the indentation modulus, longitudinal and transverse ultrasonic wave velocities, Young's, shear and bulk moduli and Poisson's ratio. The results obtained by indentation technique and ultrasonic method were essentially identical. TEM observation confirmed that multigrain junction cavities were responsible for the density changes and the elastic moduli degradation. The density changes were linearly proportional to tensile strain with the slope of 0.75. Thus, cavitation is the dominant creep mechanism in silicon nitride studied. Instrumented indentation and ultrasound velocity techniques are suitable for non-destructive monitoring of creep damage accumulation in ceramic components.

Buoyancy-induced mixing during wash and elution steps in expanded bed adsorption.

Buoyancy-induced mixing occurs during expanded bed adsorption processes when the feed stream entering the bottom of the system has a lower density than that of the fluid above it. In the absence of a headspace, mixing in the expanded bed can be modeled as a single, well-mixed vessel, with first-order dynamics. In the presence of a headspace, the system exhibits second-order dynamics for the densities typically encountered in protein chromatography, and can be modeled as two well-mixed vessels (the expanded bed and the headspace) arranged in series. In this paper, the mixing dynamics of the expanded bed are described and a mathematical model of the system is presented. Experimental measurements of density changes during the dilution of sucrose and salt solutions in a STREAMLINE 25 column are presented. These show excellent agreement with predictions using the model. A number of strategies for wash and elution in expanded mode, both in the presence and absence of headspace, are discussed.

Ozone Concentration Effects on the Dark Fade of Inkjet Photographic Prints

ANSI Standard IT9.9-1996 is commonly recommended for predicting dark storage print life for color photographic materials. This methodology focuses primarily on measurement of density changes that occur as a function of temperature at 50% &#xB1; 3% relative humidity (Arrhenius methodology). An additional factor in the dark stability of inkjet photographic prints is the presence of ozone. Current practical tests utilize a relatively high concentration (5 ppm) of ozone for short periods of time at ambient temperatures to predict what might occur for longer exposures at lower concentrations. However, ambient ozone levels are typically well under 0.1 ppm (100 ppb). The objective of this paper is to explore the effect of ozone concentration on inkjet photographic prints produced with commercially available desktop inkjet printers. The primary focus will be on current dye-based inks printed onto both porous and non-porous photo-quality papers. We will examine the reciprocity relationship between ozone concentration and the duration of exposure to ozone.

Multichannel interferometer system for the helically symmetric experiment

A multichannel millimeter-wave interferometer system has been designed, fabricated and installed on the helically symmetric experiment (HSX), located at the University of Wisconsin, Madison. The interferometer system will view the plasma cross section along nine adjacent chords with 1.5 cm spacing. With this arrangement, coverage will span from the low-field side plasma scrape-off layer to well past the magnetic axis. For the plasma densities anticipated on HSX, a solid-state source operating at 288 GHz will be utilized. At this frequency refraction will be manageable, being less than the channel spacing. The source will be bias-tuned and modulated with a sawtooth wave form at 750 kHz in order to generate the intermediate frequency necessary for the heterodyne detection scheme. The signals will be measured using Schottky-diode corner-cube mixers. The interferometer will have sensitivity nedl≈8×1011 cm−2, being able to measure density changes &amp;lt;1%. Initially, the phase will be evaluated using analog electronics with bandwidth &amp;lt;10 kHz providing real-time line-integrated output. A digital phase comparator scheme will also be implemented whereby the measured wave forms are directly digitized and the phase evaluated using a software-based algorithm. This will increase the time response up to the modulation frequency of 750 kHz. Improved time response will permit measurement of high-frequency density fluctuations along with “fast changes in” the equilibrium profile.

Neutron Irradiation-Induced Dimensional Changes in MEMS Glass Substrates

AbstractA study is made of radiation-induced expansion/compaction in Pyrex and Hoya SD-2 glasses, which are used as substrates for MEMS devices. Glass samples were irradiated with a neutron fluence composed primarily of thermal neutrons, and a flotation technique was employed to measure the resulting density changes in the glass. Transport of Ions in Matter (TRIM) calculations were performed to relate fast (∼1 MeV) neutron atomic displacement damage to that of boron thermal neutron capture events, and measured density changes in the glass samples were thus proportionally attributed to thermal and fast neutron fluences. The trend for strain with thermal neutron fluence (n/cm2) was found to be a linear compaction of -2.8×10−20 for Pyrex and -1.0×10−21 for Hoya SD-2. For fast neutron fluence, the trend for strain was also linear: -6.1×10−21for Pyrex and -7.9×10−22 for Hoya SD-2. The measured radiation-induced compaction of Pyrex is found to agree with that of previous studies. To our knowledge, this work represents the first study of compaction in Hoya SD-2 with neutron fluence. Hoya SD-2 is of considerable importance to MEMS, owing to its close thermal expansivity match to silicon from 25-500 C.

Response of dynamically compacted tungsten to high fluence neutron irradiation at 423–600°C in FFTF

When pure tungsten produced by dynamic compaction at 95.3% theoretical density was irradiated in FFTF at temperatures of 423–600°C and neutron doses as high as 14.4 × 10 22 n cm −2 ( E > 0.1 MeV), it densified 2–3% and became very brittle. The brittle behavior resulted in failure at grain surfaces and appears not to be related to neutron-induced transmutation or segregation of transmutants. Based on density change measurements, it can be concluded that significant cavity formation did not occur at these high neutron exposures.

Mechanism of carbon combustion: Relative influence of adsorption, desorption, and boundary layer diffusion as a function of pressure

These results show that common, pressure-independent coefficients can be used to predict oxygen-carbon reaction rates. Accurate agreement with experiment requires determination of the (Thiele) second effectiveness factor (ε) which at this time can only be done by analysis of the experimental measurements of density changes with burn-off. This identifies prediction of the dependence of ε on pressure as a future theoretical target. Independent evaluation of the terms governing the combustion show that, at the higher temperatures, adsorption has significant influence at atmospheric pressure, but its importance drops rapidly, to minor or insignificant, as pressure increases. Overall, the results show that, partly on account of offsetting effects of changes of ε with pressure, governing the degree of internal penetration of the reaction, the influence of pressure on the reaction rate is second order or less.

Microstructural examination of commercial ferritic alloys at 200 dpa

Microstructures and density change measurements are reported for martensitic commercial steels HT-9 and modified 9Cr1Mo (T91) and oxide dispersion strengthened ferritic alloys MA956 and MA957 following irradiation in the FFTF/MOTA at 420°C to 200 dpa. Swelling as determined by density change remains below 2% for all conditions. Microstructures are found to be stable except in recrystallized grains of MA957, which are fabrication artifacts, with only minor swelling in the martensitic steels and α′ precipitation in alloys with 12% or more chromium. These results further demonstrate the high swelling resistance and microstructural stability of the ferritic alloy class.

Void swelling resistance of phosphorus-modified austenitic stainless steels during HFIR irradiation at 300–500°C to 57 dpa

The austenitic stainless steel prime candidate alloy (PCA) is a Ti-modified alloy (14Cr16Ni) developed for void swelling resistance at 400–600°C by the US Fusion Reactor Materials (FMR) program. During irradiation in the High Flux Isotope Reactor (HFIR) to 34 and 57 dpa (70–75 appm He/dpa) at 300–600°C, th e PCA (and the closely related D9 type alloy) has been shown to be highly susceptible to void swelling at 500°C. Generally such alloys show good void swelling resistance to higher doses during irradiation in fast-breeder reactors (FBRs, 0.5–1 appm He/dpa) in the 20–25% cold-worked (CW) condition. New multiply-stabilized, phosphorus-modified PCA alloys have been developed, with specific amounts and combinations of minor alloy elements added for improved MC formation and stability characteristics during irradiation. After HFIR irradiation at 300–500°C to 34–57 dpa, the multiply-stabilized, phosphorus-modified PCA and phosphorus-modified D9 alloy showed better swelling resistance (by density-change measurements) than similar alloys without phosphorus, particularly at 500°C. Microstructural studies after 34 dpa at 500°C showed that void swelling resistance in the multiply-stabilized, phosphorus-modified PCA alloys was directly related to the formation of ultrafine dispersions of MC precipitates during HFIR irradiation.

Void swelling in copper and copper alloys irradiated with fission neutrons

Specimens of pure copper and copper alloys (Cu5Ni, CuCrZr) were irradiated with fission neutrons. Radiation damage microstructures were determined by transmission electron microscopy (TEM). The change in volume due to irradiation was obtained by density change measurements. The void nucleation and growth are found to be significantly affected by the presence of 5% Ni; the effects observed in the present experiments are directly opposite to the findings reported earlier on the Cu-5% Ni alloy irradiated with 1 MeV electrons. The swelling is found to be significantly reduced in CuCrZr alloy. The implications of these results are discussed in terms of spectrum and rate effects.

A microstructural explanation for irradiation embrittlement of V-15Cr-5Ti

In order to explain severe degradation of mechanical properties, specimens of V-15Cr-5Ti have been examined by transmission electron microscopy following irradiation at 600°C to 14 dpa in FFTF. Specimens irradiated at 420 and 520°C were also examined to confirm density change measurements that indicated swelling levels as high as 2.5%. Following irradiation at 600°C, a complex microstructure was found that included a perfect dislocation network of line segments and loops, faulted loops, a high density of black spot damage and a high density of rod-shaped precipitates. Heat-to-heat variations did not appear to significantly alter these microstructural features; instead the density of large blocky precipitates, believed to be TiO 2, was found to have increased with increasing oxygen content. Only two of the specimens irradiated at 600°C contained voids, whereas none of the specimens irradiated at 420 or 520°C contained voids. Therefore, swelling as measured by density change is probably due to phase instability in these specimen conditions, and the hardening and irradiation embrittlement that has been observed can be explained by the microstructural development. Phase stability appears to be an important criterion in the design of vanadium alloys for fusion applications.

Quantitative Radiographic Measurement of Dentinal Lesions

The purpose of this investigation was the comparison of the precision and accuracy of two reference ramp techniques for the quantification of radiographic density changes in teeth. Radiographs (65 kVp, 10 ma, 1 s, and intra-oral ultraspeed film) of transverse sections from extracted permanent human molars were made before and after dentinal lesions were created. Each radiograph contained the image of a tooth section and the aluminum reference ramp. Method A used the image of the ramp on both the before- and after-lesion radiographs, and method B used the image of the ramp only on the before-lesion radiograph. Three groups of lesions (0.525-mm diameter, n = 11; 0.675-mm diameter, n = 9; and the 0.525-mm holes enlarged to 0.675 mm) were measured radiographically by each technique and by direct planimetry of the lesions. Radiographic method B produced results in close agreement with the planimetric measurements. Method B differentiated (p less than 0.05) between groups that had a mean planimetric size difference of 0.10 mm (equivalent to a change in density difference of 0.6%). These density change measurements are in absolute units of mm of aluminum that can be compared between lesions and between samples. This technique may prove useful for the quantification of changes in mineral density of caries lesions detectable in longitudinal radiographic records.

Resinter testing in relation to in-pile densification

There are two ways to predict dimensional behaviour during irradiation: 1. (i) quantitative analysis of the density and pore structure and model calculation, and 2. (ii) thermal resinter testing and application of a predicting correlation between measured density changes and in-pile densification. This paper gives a comparison between predicted in-pile densification and actual densification as determined by post-irradiation examination. A mechanistic model for thermal and fission-induced densification was applied. It was shown that the model predictions and the experimental results agreed well. Thus it was possible to derive a relation for the out-pile simulation of in-reactor behaviour which is applicable in quality control practice. However, long resintering periods are necessary for the simulation of high burnup.

Formability of sheet metal with heterogeneous damage

During sheet metal forming operations, internal damage occurs as a result of nucleation, growth and coalescence of cavities around particles, inclusions or second phase. In this work, this phenomenon is experimentally studied by relative density change measurements and scanning electron microscope observations in a dual-phase steel sheet. It is observed that the distribution of cavities is not homogeneous. A model of plastic flow localization is proposed taking account of a non-uniform void distribution. The results show a substantial reduction in the formability of the sheet as well as anisotropic effects due to the heterogeneous distribution of voids.

密度変化測定によるCr-Mo-V鋼のクリープ損傷評価

密度変化測定によるCr-Mo-V鋼のクリープ損傷評価

Damage in sheet metal forming—I. Physical behavior

It is well established that ductile fracture occurs by nucleation, growth and coalescence of voids generally associated with particles. However, volume damage is present in the material at the first stage of the plastic deformation and, therefore, has an influence on the plastic behavior of the material. Metallographical observations and relative density change measurements show that there exists two main damage mechanisms: either decohesion at the particle-matrix interface or failure of the particles. In both cases, an analysis of the evolution of damage is performed and a model is proposed. A general law of void growth according to the strain and strain path is then established for both damage mechanisms.