Crystal Growth Time Research Articles

Crystallization of microlites and degassing during magma ascent: Constraints on the fluid mechanical behavior of magma during the Tenjo Eruption on Kozu Island, Japan

Bubble and crystal textures provide information with regard to the kinetics of the vesiculation and crystallization processes. They also provide insights into the fluid mechanical behavior of magma in a conduit. We performed textural (bubble and crystal) and compositional analyses of pyroclasts that were obtained from the Tenjo pyroclastic flow, which resulted on account of the eruption in 838 A.D. on Kozu Island, about 200 km south of Tokyo, Japan. Pyroclasts in one flow unit (300∼2,060 kg/m3; average density 1330 kg/m3) can be classified into three types on the basis of vesicle textures. Type I pyroclasts have small isolated spherical bubbles with higher vesicularities (67–77 vol.%) and number density (10.8–11.7 log m−3). Type II pyroclasts have vesicularities similar to type I (61–69 vol.%), but most bubbles exhibit evidences of bubble coalescence, and lower number densities than type I (8.9–9.5 log m−3). Type III pyroclasts contain highly deformed bubbles with lower vesicularities (16–34 vol.%) and number densities (8.2–9.0 log m−3). The microlite volume fraction (DRE converted) also changes consistently across type I, type II, and type III as 0.06, 0.08, and 0.10–0.15, respectively. However, the number density of the microlites remains nearly invariant in all the pyroclast types. These facts indicate that the variation in the microlite volume fraction is controlled not by the number density (i.e., nucleation process), but by the size (i.e., growth process); the growth history of each type of microlite was different. Water content determinations show that the three types of pumices have similar H2O contents (2.6±0.2 wt%). This fact implies that all three types were quenched at nearly the same depth (35±5 MPa, assuming that the magma was water-saturated) in the conduit. If the crystal sizes are limited only by growth time, a variation in this parameter can be related to the residence time, which is attributed to the flow heterogeneity in the conduit. By assuming a laminar Poiseuille-type flow, these textural observations can be explained by the difference in ascent velocity and shearing motion across the conduit, which in turn results in the differences in growth times of crystals, degrees of deformation, and bubble coalescence. Consequently, for crystals in the inner part of the conduit, the crystal growth time from nucleation to quenching is shorter than that near the conduit wall. The vesicle texture variation of bubbles in types I, II, and III results from the difference in the deformation history, implying that the effect of degassing occurred primarily towards the conduit wall.

Interaction of acid and alkali treated titanium with dynamic simulated body environment

Interaction of acid and acid+alkali treated titanium samples with simulated body fluid was studied. In case of alkali treated titanium, the dynamic arrangement of the test enabled the detection of primary calcium and phosphate ion adsorption from the solution and later apatite crystal growth (XRD). The induction time for crystal growth was 24.2±0.3 h. On acid-only treated titanium no crystal growth was detected. The calcium phosphate adsorption layer formed on the acid treated samples was detectable by XPS only, however it differed from that one formed on the acid+alkali treated samples. The adsorption layer formed on the acid+alkali treated samples contained larger amount of calcium, especially in the shortest exposure times. Charging of the apatite crystallites during the XPS measurement enabled the determination their Ca/P ratio separately from Ca/P ratio of the adsorption layers. XPS and EDS analyses indicated that the spherulitic crystallites consisted of carbonated hydroxyapatite with the Ca/P ratio close to that one of the stoichiometric hydroxyapatite. It is proposed that the adsorption layer formed spontaneously and immediately on the acid+alkali treated titanium can provide an ideal interface between the metal implant and the apatite cement line, the first structure formed by osteoblast cells during the formation of the new bone on foreign surfaces.

Influence of the superfine crystal of Li 2Ni 8O 10 as mill addition on the enamel adherence

Superfine crystal of Li 2Ni 8O 10 is made by solid reaction by controlling certain nucleation time and crystal growth time. Enamel adherence has been greatly increased by adding mill addition of the superfine powder of Li 2Ni 8O 10. Influence of the superfine powder of Li 2Ni 8O 10 as mill addition on enamel adherence has been studied by investigating chemical composition and microstructure on enamel interface with the help of scanning electron microscope (SEM) and electron microprobe. Results show that the superfine powder of Li 2Ni 8O 10 as mill addition can change the interface composition and structure, and promote interdiffusion between enamel elements and metal elements as well as the development of the interface transitional layer which results in strong adherence.

Case studies of plagioclase growth and residence times in island arc lavas from Tonga and the Lesser Antilles, and a model to reconcile discordant age information

The time scales of crystal growth and residence in magmas have received much attention because such information can constrain the physical processes involved. However, crystals and liquids can have different ages, leading to apparently contradictory information from different dating methods. Two case studies are presented from island arc lavas that highlight such dichotomies. Plagioclase crystal size distributions and U–Th–Ra isotope data are presented for lavas from Late and Metis Shoal in Tonga and from Soufriere (St. Vincent) in the Lesser Antilles. In all three lavas, mineral data yield apparent U–Th ages of 30–50 kyr yet 226Ra-excesses are preserved in both the minerals and the whole rocks. The crystal size distributions suggest crystal growth over 100s of years but also frequently indicate the presence of mixed crystal populations. Furthermore, a cumulate from Soufriere yields the same U–Th age as its host lava. On 226Ra/Ba versus time evolution diagrams, curves for melts in equilibrium with plagioclase provide apparent ages of 1700–3300 yr for Tonga but for Soufriere they are displaced below that of the whole rock. Our interpretation is that the phenocrysts from all three lavas are zoned in both composition and age. The apparent U–Th ages reflect mixtures of old cores and young rims and indicate a volume-integrated age of 10s of kyr for the time for initial crystal growth, crystal–liquid segregation, the time of storage as a cumulate plus the time spent during entrainment and growth in the new magma prior to eruption. The 226Ra-excesses were imparted to overgrowths on the old cumulate cores during entrainment by subsequent injections of new magma. Because crystal growth, segregation and entrainment can all appear to occur in 100s to a few thousand years at most, the bulk of the U–Th time scale is inferred to record storage in cumulates which are then incorporated into new magma batches. Plagioclase growth rates of 3–9×10 −13 cm s −1 would reconcile the combined Ra–Th and crystal size distribution data. Magma differentiation time scales and eruptive periodicity are one to three orders of magnitude shorter than the inferred cumulate storage times, indicating complex phenocryst–liquid behaviour beneath island arc volcanoes.

Liquid phase epitaxy of KTiOPO 4 on KTi 1− xGe xOPO 4 substrates

We have studied the liquid phase epitaxy growth of KTiOPO 4 on several faces of KTi 1− x Ge x OPO 4 substrates as a function of the crystal face, growth time and level of substitution of Ge by Ti in the substrate. The best quality films were on the {1 0 0} and {2 0 1} faces. Only slight growth steps were observed on these faces in some experiments. The lowest quality of the films was on the {1 1 0} and {0 1 1} faces and the typical defects were hillocks. The worst quality of epitaxial growth was on the {1 0 1} face and pyramidal growth was detected in all cases. There was not observed diffusion of the Ge from the substrates to the film and the maximal change in refractive indices between substrate and film was of the order of 0.01.

The Effect of a Pulse Current Supply on the Structure and Magnetic Properties of Highly Dispersed Iron

The paper examines how a pulse current supply affects the formation of highly dispersed iron powder particles. We determine the optimum current pulse frequency (104-103Hz), the ratio of the amplitude of the nucleation current to the amplitude of the crystal growth current (I n/I g = 5:25) and the optimum ratio of the nucleation time to the crystal growth time (τn/τg = 1:10). The effect of the pulsed current manifests itself in decrease in dendricity, i.e., a reduction of the particle anisotropy, and has little impact on the powder dispersity.

Kinetics of the crystal 4He growth at high overpressurizations

The growth of a helium crystal is studied within the temperature range of 0.4–1.7 K at the overpressurizations up to 15 mbar. The measurements are carried out in the opaque and optical containers. In the first case the growth rate is evaluated from the rate of pressure change inside the container during crystal growth. This yields the growth rate averaged over all crystallographic directions. In the optical container the direct filming of a crystal growth process complements the pressure measurements. At high temperatures the absolute values of the kinetic growth coefficient K for the bcc-phase are measured. For the hcp-phase, at high overpressurizations above both roughening transitions the growth rate anisotropy is observed. At high overpressurizations the point of the first roughening transition is found to shift towards lower temperature while the temperature of the second roughening transition increases. Below the second roughening transition, two growth regimes are found. The first one (normal) is typical for a crystal close to the phase equilibrium. The second regime occurs at high overpressurizations. In this case the crystal growth time decreases by two orders of the magnitude in comparison with the normal one. The phase diagram separating regions of the fast and slow growth of a 4He crystal is determined. The lifetime of the metastable state under fast kinetics is estimated.

Classical and Differential Thermal Analysis Studies of the Glass‐Ceramic Transformation in a YSiAlON Glass

Nucleation and crystallization studies were conducted on a YSiAlON glass that contained 17 equiv.% nitrogen (7.5 at.%) by using a two‐stage nucleation‐and‐growth treatment. Classical and differential thermal analysis (DTA) techniques were both used to study the crystallization process, to ensure that the optimum heat‐treatment schedule that yielded a fine microstructure and minimum residual glass was applied. The optimum nucleation and crystallization temperatures were determined from DTA traces that were recorded from isothermal heat treatments at different nucleating temperatures, ranging between Tg ‐ 40°C and Tg+ 100°C for 1 h and crystal‐growth temperatures in the range of 1170°‐1310°C for 0.5 h, respectively. The activation energy for the crystallization process was determined, based on the analysis of the variation of peak temperature at five different heating rates. Specimens heat treated in a tube furnace under nitrogen gas were subjected to microscopical investigation, and results showed variations in the volume fraction of crystalline phases and crystal size with nucleation temperature. The nucleation temperature, Tg+ 40°C (1025°C), which corresponded to the maximum volume fraction of crystalline phases and minimum crystal size, was consistent with the optimum nucleation temperature, Tg+ 35°C (1020°C), as determined from DTA. The time and temperature of nucleation and crystal growth dictated the nature and size of the crystalline phases. Properties such as hardness and density were assessed and correlated to the nucleation temperature. The influence of sample specific surface on the devitrification mechanisms was estimated, and bulk nucleation was observed to be the dominant nucleation mechanism.

Single Zircon Evaporation Thermal Ionisation Mass Spectrometry: Method and Procedures†

Zircon evaporation thermal ionisation mass spectrometry (TIMS) is used in geochronology to determine absolute 207Pb*/206Pb* ages and Th/U ratios of single zircon crystals. The process involves the breakdown of zircon (ZrSiO4) to porous baddeleyite (ZrO2) along a reaction front which progresses into the interior of the crystal. Evaporation of high quality zircons thus allows us to distinguish between crystal rim (overgrowth) and core, providing precise information about the time of magmatic crystal growth, partial dissolution, and/or metamorphic overgrowth. Derived Th/U ratios complement age data interpretation and provide valuable petrogenetic implications. A double Re-filament ion source is used. The zircon is encased in the evaporation filament and heated step-wise to 1200–1300 °C to strip off unsupported common and radiogenic Pb components. After cleaning, evaporation proceeds in temperature steps of ∼20 °C. The evaporate (SiO2, Pb, REEs, and U from the zircon and Re from the evaporation filament) of each step is deposited for 45 min on the cold ionisation filament and subsequently analysed. Lead isotopic composition is determined using a dynamic secondary electron multiplier ion counter or static Faraday cup data acquisition schemes. Lead ratios are corrected for fractionation using correction factors derived from standard measurements of a 1 ng NBS SRM 982 sample. The precision on 207Pb/206Pb ratios is <1%. Only high temperature steps (>1300 °C) with 206Pb/204Pb > 5000 are used for age calculations. The ages reported (single temperature step, multi-temperature step means) are weighted means calculated from at least 20 measured 207Pb*/206Pb* ratios with 2 standard errors of the mean. Precision of ages is strongly dependent on age range and varies between 0.1 and 10%.

Simulated growth process of single-crystal diamond at high pressure

Abstract The diffusion field of carbon is calculated for the molten metallic solvent in the temperature gradient growth system of diamond. The surface of the growing crystal gives carbon concentration on it as a part of the boundary conditions. The calculated concentration gradient on the surface produces the growth rate of the surface, which determine a new surface, a new boundary condition, for the next step calculation of the concentration distribution. The features of the calculated diffusion field can predict substantial natures of particular growth systems very well, and explain several phenomena accompanied with the growth process. The relations between the crystal weight and growth time are reproduced with different characters according to the geometry of the growth space. Quantitative agreement with observed experimental results is excellent if the process parameters are properly selected. The present simulation has revealed the existence of an important character of the growth process such as the growth rate peak, which has not been noticed so far and is considered to be related to formation of metallic inclusions in the crystal.

Degree of fatty acyl chain unsaturation in biliary lecithin dictates cholesterol nucleation and crystal growth

To clarify factors involved in the formation of cholesterol gallstones, we studied the relationship between the degree of fatty acyl chain unsaturation of biliary lecithin and bile metastability. We used supersaturated model bile solutions (molar taurocholate /lecithin/cholesterol ratio (73:19.5:7.5), total lipid concentration 9 g/dl) that contained equimolar egg yolk or soybean lecithins or a sn-1 palmitoyl, sn-2 linoleoyl phosphatidylcholine. Gel permeation Chromatographie studies showed that the vesicular cholesterol distribution and dimension were inversely related to the degree of unsaturation of the lecithin species, estimated by reverse phase, high-performance liquid chromatography. Differential interference contrast microscopy and assay of cholesterol crystal growth showed that a higher degree of fatty acyl chain unsaturation of the lecithin species was associated with a faster nucleation time and rate of crystal growth. Our results suggest that vesicular lecithins containing more unsaturated fatty acyl chains bind less tightly to cholesterol than lecithins containing predominantly saturated fatty acids, and that the biliary lecithin species dictates, in part, the nucleation and growth of cholesterol crystals in bile.

Induction time for crystal growth

Abstract An expression is derived for the induction time for crystal growth. It is shown that this induction time is not uniquely determined, and is dependent on experimental conditions. Induction time for crystal growth, unlike the induction time for nucleation, becomes unbounded if defined rigorously.

Engineering new organic crystals for nonlinear optics: from molecules to oscillator

The quest for more efficient nonlinear optical materials of increased optical quality is being spurred by the development of optical communication systems that require ultrafast broad band optical signal processing functions. Conversely, nonlinear optical phenomena enlarge traditional spectroscopic approaches to encompass more complex and informative multiphotonic pathways. In this stimulating context, organic nonlinear materials have been recognized as forefront candidates for fundamental and applied investigations involving, in a joint effort, chemists, material scientists and optical physicists. After reviewing the molecular engineering foundations of the domain, specifically with respect to an efficiency-transparency trade-off, the author concentrates on a more specific case that embodies, from the definition of the molecule all the way down to applied physics endgoals, the key concepts and methodological tools in the field. A crucial part of such study is the definition and implementation of crystal growth methods leading to the high optical quality demanded by parametric phenomena. This approach is best exemplified in the paradigmatic case of N-4-nitrophenyl-(L)-prolinol (NPP) which, after almost a decade of effort involving crystal growth and ultrafast time resolved spectroscopy, has recently reached sufficient quality to lead to optical parametric oscillation. Stable coherent tunable oscillation in the near IR from 0.9 to 1.7 mu m has thus been demonstrated for the first time in an organic molecular crystal, with specific advantages over mineral candidates, and room for further performance improvement. The author recalls in conclusion that new molecular and crystalline pathways are still opening up, such as those based on molecular nonlinearities of octupolar origin or organomineral crystals.

Crystal growth and luminescence properties of calcium- and vanadium-doped gadolinium gallium garnet

Crystal growth, optical absorption, emission spectra and fluorescence decay times of calcium- and vanadium-doped Gd 3Ga 5O 12 garnet are reported. The observed optical spectra are assigned to V 4+ ions in octahedral and tetrahedral sites. A broad red luminescence in the 600–800 nm region is shown to be due to the only octahedral V 4+ impurity ions.

Isolation and thermal characterization of high‐melting seed crystals formed during cocoa butter solidification

AbstractSeed crystals which formed during early stages of cocoa butter solidification have been isolated and determined to have extremely high melting points. The melting points of the seed crystals generally exceeded 60°C, in contrast to cocoa butter, which melts between 30–35°C. In addition, the melting point of the seed crystals decreased as a function of crystal growth time. Evidence suggests that the high‐melting seed crystal is not an additional polymorphic form of cocoa butter, but rather a distinct crystalline entity. Consequently, a unique compositional make‐up is suspected as being responsible for the elevated melting point. A technique to separate seed crystals from the molten cocoa butter mass has been developed. The procedure has been shown not to alter the thermal and compositional properties of the isolated seed crystals.

A biological macromolecule crystallization database: A basis for a crystallization strategy

A crystallization database, the Biological Macromolecule Crystallization Database, containing crystal data and the crystallization conditions for more than 1000 crystal forms of over 600 biological macromolecules, has been compiled from the scientific literature. Data for proteins, protein: protein complexes, nucleic acids, nucleic-acid: nucleic-acid complexes, protein: nucleic-acid complexes and viruses have been included. The general information catalogued for each macromolecule. The crystal data molecular weight, the subunit composition, the presence of prosthetic group(s), and the source of the macromolecule. The crystal data include the unit cell parameters, space group, crystal density, crystal habit and size, and diffraction limit and lifetime. The crystallization data consist of the crystallization method, chemical additions to the crystal growth medium, macromolecule concentration, temperature, pH, and growth time. A result of the compilation of the crystallization data was the development of a general strategy for the crystallization of soluble proteins. The strategy employs vapor diffusion experiments with the most frequently used crystallization agents and microdialysis against low ionic strength to maximize the possiblity of obtaining crystals. A detailed outline of this strategy is presented.

Crystal size distribution (CSD) in rocks and the kinetics and dynamics of crystallization II: Makaopuhi lava lake

Crystal size distribution (CSD) theory has been applied to drill core samples from Makaopuhi lava lake, Kilauea Volcano, Hawaii. Plagioclase and Fe-Ti oxide size distribution spectra were measured and population densities (n)were calculated and analyzed using a steady state crystal population balance equation: n=n0 exp(-L/Gτ). Slopes on ln(n) versus crystal size (L) plots determine the parameter Gτ, a. product of average crystal growth rate (G) and average crystal growth time (τ). The intercept is J/G where J is nucleation rate. Known temperature-depth distributions for the lava lake provide an estimate of effective growth time (τ), allowing nucleation and growth rates to be determined that are independent of any kinetic model. Plagioclase growth rates decrease with increasing crystallinity (9.9−5.4×10−11 cm/s), as do plagioclase nucleation rates (33.9−1.6×10−3/cm3 s). Ilmenite growth and nucleation rates also decrease with increasing crystallinity (4.9−3.4 ×10−10 cm/s and 15−2.2×10−3/cm3 s, respectively). Magnetite growth and nucleation rates are also estimated from the one sample collected below the magnetite liquidus (G =2.9×10−10 cm/s, J=7.6×10−2/cm3 s). Moments of the population density function were used to examine the change in crystallization rates with time. Preliminary results suggest that total crystal volume increases approximately linearly with time after ∼50% crystallization; a more complete set of samples is needed for material with <50% crystals to define the entire crystallization history. Comparisons of calculated crystallization rates with experimental data suggests that crystallization in the lava lake occurred at very small values of undercooling. This interpretation is consistent with proposed thermal models of magmatic cooling, where heat loss is balanced by latent heat production to maintain equilibrium cooling.

Urinary stone analysis

Since crystalline composition of a urinary stone is an expression of urinary chemical conditions prevalent at the time of crystal nucleation and growth, a careful analysis of the stone and identification of constituent crystals is necessary for an understanding of the disease and the initiation of a proper medical regimen for the prevention of stone recurrence. Of the number of methods available, analytical electron microscopic techniques including scanning (SEM) and transmission electron microscopy (TEM), x-ray microanalysis (XRMA), and electron diffraction (ED) are gaining in popularity.For SEM, the dried stone is fractured through the middle and small pieces representing different areas of the stone are mounted on a carbon planchet or an aluminum stub using a double sticky tape or graphite paint. The specimen is then sputter coated with silver, gold or gold/palladium; or coated with carbon. For morphological examination alone, the specimen can be coated with any of the available conducting substances, but for XRMA the specimen should either be examined uncoated or be coated with carbon, or with a substance whose peaks in the XRMA spectrum do not interfere with the peaks of the elements of interest.

鉛直過冷雲風洞中での雪結晶の浮遊成長実験

Snow crystal growth in free fall by vapor diffusion under water saturation and riming was studied up to 30 min in a supercooled cloud tunnel.The results showed that: 1) the growth rates were pronouncedly highest along a-axis at-15°C and along c-axis at-5.5°C. Each peak coincided with the growth of dendrites and needles, respectively; 2) polycrystalline snows, consisting of spatial dendrites and spatial plates, were observed very frequently below-15°C; 3) the variation of fall velocity with growth time could be expressed by two straight lines, except for the temperature zone of dendritic crystal growth, where a curve and straight lines were fitted; 4) the empirical relations between crystal fall velocity and growth time under constant temperatures were divided into two groups. In the higher fall velocity group, isometric crystals grew and were rimed; in the lower fall velocity group, shape enhancement occurred during continuing vapor diffusional growth. The crystals in the former group dropped from 700 to 800m, and those in the latter only 300 to 400m in 30 min; 5) isometric crystals grown at around-10°C changed into graupel. The growth mode was represented by three stages: vapor diffusional, transitional and graupel growths. The crystal mass was roughly proportional to t1/2, t2 and t6 in each corresponding stage. In the vapor diffusional and graupel growth stages, the particles followed Stokes' and Newton's laws of resistance, respectively.

Measurements of natural deposition and condensation-freezing ice nuclei with a continuous flow chamber

Ice nucleus concentrations in samples of city air have been determined by using a continuous flow diffusion chamber. The chamber has been set-up so that ice nuclei may be activated as they pass through regions of controlled supersaturation and temperature similar to those experienced in natural clouds. It has been found that two distinct modes of nucleation may be discerned by adjusting the flow rate through the chamber to permit a range of nucleus activation and crystal growth times. For short passage times, deposition nuclei may be activated both above and below water saturation. At longer growth times, and above water saturation, condensation-freezing nuclei have time to activate and grow. The total nucleus concentration detected is thus the sum of the two distinct types activated in these experiments. The resulting concentrations are considerably in excess of estimates obtained with a conventional filter technique and help to account for the discrepancies between observed ice nucleus and measured ice crystal concentrations in clouds.