Abstract: Dehydrated sugar solutions were used as models of thermal behavior of amorphous foods, and of the effect of temperature, moisture content and time on physical state of such foods. The transition temperatures determined were glass transition (Tg), crystallization (Tcr) and melting (Tm) which all decreased with increasing moisture. Tg of a sucrose/ fructose model had a slightly lower value than the empirical “sticky point,” at all moisture contents studied. Crystallization of sucrose was delayed by addition of fructose or starch. Crystallization above Tg was time-dependent, and the relaxation time of this process followed the WLF equation.

Abstract: Annealing of initially amorphous FeCuNbSiB alloys at temperatures above their crystallization temperature leads to an ultrafine grain structure of α-FeSi with average grain sizes down to D ≈ 10 nm and random texture. Owing to the nanocrystalline structure the magneto-crystalline anisotropy is randomly averaged out by exchange interaction. Moreover magnetostriction decreases on crystallization owing to the formation of α-FeSi. As a consequence the material reveals excellent soft magnetic properties.

Abstract: The crystallization of amorphous Si induced by Al during heat treatment has been investigated by cross section and plan view transmission electron microscopy. The lowest temperature of Al induced crystallization of amorphous Si was found to be 440 K. The crystallization temperature, however, depends on the thickness of Al layers in layered structures and on the concentration of Al in co‐deposited layers below 1‐nm‐layer thickness and 15 at.% of Al concentration, respectively. Al‐induced crystallization in layered structures starts at the Al/amorphous Si interfaces and is located close to them. The amount of crystallized Si depends on the quantity of Al and on the temperature and increases with them. The mechanism of crystallization involves intermixing of Al with Si and the formation of an alloy of high metal concentration in the amorphous/crystalline interface. When the formation of this alloy is not assured due to low Al concentration, then crystallization does not start or the process of crystallization stops. In Al induced crystallization the nucleation of polycrystalline Si grains rather than their crystal growth is affected.

Abstract: Series Editors' Preface. Preface. Introduction. Phase diagrams of the Me^O2O-P^O2O^O5(As^O2O^O5)-(H,D)^O2O systems in the crystallization region of mono-substituted salts: The [N(H,D)^O4]^O 2O-P^O2O^O5-(H,D)^O2O system. The K^O 2O-P^O2O^O5-(H,D)^O2O system. The Rb^O2O-P^O2O^O5-(H,D)^O2O system. The Cs^O2O-P^O2O^O5-(H,D)^O2O system. The Cs^O2O-As^O2O^O5-(H,D)^O2O system. Liquidus surface of phase diagrams. Isotope effects. Mechanism and kinetics of crystallization: Research technique. Surface morphology of growing faces. The dislocation spiral. The main characteristics of dislocation growth. The effect of impurities. The stability of the growing surface. Growing single crystals: Methods of creating supersaturation. The stability of supersaturated solutions. Achievement of the kinetic growth mode. Problems of crystal quality. References. Subject index.

Abstract: A review of the recent literature on crystallization of the commercial sugars (fructose, glucose, lactose, and sucrose) is presented. Topics include: NUCLEATION--The formation of the crystalline phase from supersaturated solutions can occur by either a spontaneous or a forced nucleation mechanism. Recent work on the mechanisms, kinetics, and impact of both heterogeneous and secondary (contact) nucleation is discussed. GROWTH--Recent studies on the mechanisms and kinetics of crystal growth will be reviewed. This discussion includes work on the growth rate dispersion exhibited by these sugars. EFFECTS OF IMPURITIES AND ADDITIVES--The presence of impurities and additives (including mixed sugar systems) affects both the nucleation and growth steps. A discussion of the recent work in this area is included. Emphasis is placed on the relationship between these crystallization phenomena and the solution structure for comparison purposes.

Abstract: A new method to prepare nanocrystalline alloys was developed by means of crystallization from amorphous alloys. By using this method, a Ni-P alloy with 9 nm crystallites was synthesized. The structure and grain sizes of the alloy were examined by means of x-ray diffraction, transmission electron microscopy, and high resolution electron microscopy. Specific heat capacity and thermal expansion coefficient of the nanocrystalline Ni-P alloy prepared by this method were found to be greater than those of the coarse-grained crystalline alloy by 12.3% and 56.2%, respectively. A new micromechanism for nanometer-sized crystallites formation is discussed.

Abstract: Impinging fluid jet streams are used in a continuous crystallization process to achieve high intensity micromixing of fluids so as to form a homogeneous composition prior to the start of nucleation. This process permits direct crystallization of high surface area particles of high purity and stability.

Abstract: It is shown that the structure and morphology of syndiotactic polypropylene depend very sensitively and in a unique wanner on the temperature of crystallization. Moreover, as the temperature of crystallization is lowered, edge-on lamellae of isotactic polypropylene grow at the lateral sides of the syndiotactic laths through a specific epitaxial relationship

Abstract: The influence on the crystallization of molecular weight at a fixed co-unit content as well as that of co-unit content at a fixed molecular weight was studied for hydrogenated polybutadienes anf for an ethylene-hexene copolymer. The most general features of the crystallization process are found to be very similar to those of homopolymers. Some important exceptions are found: the isotherms do not superpose one with the other; deviations from the Avrami equation occur at low levels of crystallinity; relatively low levels of crystallinity can be attained after long-time crystallization.

Abstract: The formation of ultrafine microstructures by crystallization of metal-metalloid glasses was investigated by means of electron microscopy as well as in situ time-resolved X-ray diffraction. The results can be understood on the basis of nucleation and growth theories, taking into account the effect of recalescence during massive crystallization and the differences in the mode of crystallization and the diffusivity. In a polymorphic crystallizing Fe66Ni10B24 glass the finest microstructure can be achieved by annealing at temperatures significantly below the “nose” of the TTT diagram; the finest grain size can be calculated and observed to be in the range of about 0.1 μm. In glassy Fe73.4Cu1Nb3.1Si13.4B9.1 (FINEMENT) the combination of a reduced growth rate due to the niobium content as well as with increasing size of the primary crystals and an accelerated nucleation rate due to the copper additions allows the formation of extremely fine-grained microstructures in primary crystallizing metal-metalloid glasses at temperatures above the glass transition.

Abstract: The recognition of a three-way correlation between magmatic SiO2 content, critical crystallinity, and the size (magnitude) of crystal fractionation-generated composition gaps in calc-alkaline magmatic systems suggests an important control of magmatic critical crystallinity on the formation of such composition gaps. To explain this correlation, it is proposed that fractionation-generated composition gaps are caused by: (1) simultaneous interior (i.e. non-substrate) crystallization and vigorous chamberwide convection which leads to progessive crystal suspension; (2) cessation of convection when the percentage of suspended crystals reaches the critical crystallinity of the magma, and; (3) eventual buoyancy-driven crystal-liquid segregation producing a discrete body of fractionated magma which is separated from the initial magma by a composition gap. This mechanism implies that many, if not most magma bodies are characterized by interior crystallization and vigorous convection, conditions which are not universally agreed upon at present. Given that such conditions characterize natural magma bodies, fractional crystallization through crystal settling in low-velocity boundary layers should be an important mechanism of fractional crystallization. In a crystallizing and convecting body of magma, composition gap formation should represent one endmember of a complete spectrum of possible evolutionary paths governed by the relative rates of crystal settling and crystal retention. As a given volcanic plumbing system matures with time, average settling/retention ratios within individual magma bodies should increase due to higher average wall-rock temperatures. It follows that, within a given volcanic center, early-stage volcanism should be more likely to display fractionation-generated composition gaps than later-stage volcanism. Such a temporal evolution has been documented at at least two Aleutian calc-alkaline volcanic centers.

Abstract: DTA is presently used to characterize the nucleation and crystallization processes of the Na2O-2CaO-3SiO2 glass. A nucleation rate-temperaturelike curve is obtained by plotting either the reciprocal of the temperature corresponding to the crystallization peak maximum, or the height of the crystallization peak, as a function of nucleation temperature. The nucleation-temperature range for this glass composition, 550-650 C, and the maximum nucleation temperature of 600 + or - 5 C, are found to be in excellent agreement with those associated with the classical nucleation technique, followed by isothermal crystallization. It is noted that when most of the nucleation occurs during the DTA measurements, a modified Kissinger equation must be used to calculate the crystallization energy.

Abstract: All but one of polypropylene (PP) fractions with different isotacticities exhibit a regime III/II transition in their linear crystal growth rate data at a supercooling of about 48 K. At high supercoolings, two new crystal growth regions are observed for these PP fractions with low isotacticities. These crystallization regions are isotacticity dependent, which could be due to a disordered α-crystal form and cross-hatched branching. Crystal morphology changes, in particular, the cross-hatching phenomenon, with crystallization conditions and isotacticity have been observed

Abstract: Transmission electron microscopy and electron diffraction have been used to determine the structure, orientation and morphology of CaCO3 crystals at the early stages of growth under compressed Langmuir monolayers of stearic acid [CH3(CH2)16CO2H] and octadecylamine [CH3(CH2)17NH+3]. At [Ca]≈ 9 mmol dm–3, elongated plate-like calcite single crystals of narrow particle size distribution were nucleated under fully compressed stearate monolayers. The crystals were elongated along the c axis and oriented with a {1text-decoration:overline10} face parallel to the monolayer/solution interface. Subsequent development of the crystals resulted in rhombohedral outgrowth into the bulk solution. Calcite crystals nucleated under partially compressed monolayers showed the same crystal chemical properties but had a more uniform size population. Nucleation under octadecylamine monolayers resulted in disc-shaped vaterite single crystals of narrow particle size distribution. Two types of disc were observed: (a) circular/hexagonal crystals oriented with their c axis perpendicular to the monolayer, and (b) oval-shaped crystals oriented with their a axis perpendicular to the monolayer. Changes in monolayer surface pressure did not influence these properties. The preferred orientation of calcite can be rationalized in terms of geometric and stereochemical matching between the carboxylate headgroups and the ions in the {1text-decoration:overline10} crystal face. There is no geometric match for vaterite but a stereochemical relationship exists on stearate monolayers with respect to the (00.1) face. For octadecylamine monolayers, bidentate binding of HCO–3 may be important in determining the preferential orientation of nuclei formed at the organic surface.

Abstract: Amorphous sucrose showed typical thermal transitions of amorphous materials. The temperatures of those transitions, glass transition, crystallization and melting, decreased with increasing moisture content. The glass transition temperature of dry amorphous sucrose at 57°C was decreased to -46°C as the sucrose was plasticized with excess water. That value remained constant due to maximal freeze-concentration with 72-73% sucrose in the unfrozen matrix which showed ice melting at -34°C. Concentrated solutions may become supercooled resulting in partial freeze-concentration with resultant lowering of glass transition temperature.

Abstract: Suspensions of colloidal particles execute Brownian motion and thus exhibit thermodynamic properties analogous to those of molecular systems. Hard-sphere colloidal silica suspensions undergo a disorder–order transition, i.e. freezing or crystallization, at high volume fractions. In suspensions of small particles the slow sedimentation permits the transition to occur at the bottom where the bulk of the crystalline sediment is formed by one-dimensional crystallization, as illustrated with photographs and scanning electron microscopy. X-Ray tomography measurements reveal a volume fraction discontinuity coincident with the observed crystal boundary occurring between the sediment and hindered setting region of the Kynch theory. Larger particles, however, form amorphous sediments because their rate of accumulation at the bottom exceeds the maximum crystal growth rate, in accord with classical kinetic theory. This theory is paired with Kynch's kinematic theory using an experimental sedimentation coefficient to interpret observations of settling suspensions.

Abstract: DTA and both isothermal and nonisothermal DSC techniques are presently used to investigate the crystallization kinetics of a 40 (mol) percent Li2O-60 percent SiO2 glass as a function of glass powder particle size, the use of either alumina or Pt as the crucible material, the use of N, O, or Ar atmospheres, and surface pretreatments of the glass powder with deionized water, HCl, or HF. Neither the furnace atmosphere nor the crucible material had a significant effect on activation energy, frequency factor, or Avrami exponent. Washings of the glass with the three different fluids decreased the crystallization temperature by 25 to 30 C.