Crystallization of CaCO<sub>3</sub>in Water–Alcohol Mixtures: Spherulitic Growth, Polymorph Stabilization, and Morphology Change

Sand, Karina K.; Rodríguez-Blanco, Juan Diego; Makovicky, Emil; Benning, Liane G.; Stipp, S. L. S.

doi:10.1021/cg2012342

Cited by 190 publications

(219 citation statements)

References 47 publications

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“…Esse excesso acaba sendo excretado pelo leite, promovendo o aumento da instabilidade alcoólica por dois mecanismos: o primeiro é o aumento do pH, que faz a solubilidade dos sais diminuírem, aumentando as chances de precipitação na prova do álcool. O segundo fator é que maiores quantidades de HCO 3 -aumentam a concentração de CO 3 2-, possibilitando a formação de sais carbonatados com cátions (Ca 2+ , K + , Na + ), levando à precipitação de sais e, consequentemente, a maiores chances de precipitarem na prova do álcool (15) .…”

Section: Resultsunclassified

Estabilidade Do Leite Ao Álcool Ainda Pode Ser Um Indicador Confiável?

et al. 2016

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ResumoAs provas de estabilidade alcoólica e acidez Dornic ainda são amplamente utilizadas em diversos países, mensurando indiretamente a qualidade microbiológica do leite. Porém, outros fatores além da contagem de micro-organismos alteram essa relação, causando um efeito confundidor nesses testes de triagem. O objetivo deste estudo foi relacionar o pH, a contagem bacteriana total, a acidez Dornic e a porcentagem de lactose em leites estáveis e instáveis ao álcool. Foram analisadas 322 amostras de leite, sendo classificadas em ácidas, normais ou instáveis não ácidas, segundo os testes de resistência alcoólica e acidez titulável. Diferentemente de leites normais ou ácidos, não existe relação entre pH, CBT e acidez Dornic em amostras de leite que possuem instabilidade alcoólica sem acidez adquirida. Nesse tipo de leite, valores de pH entre 6,6 e 6,8 são acompanhados de contagens bacterianas mais baixas, de até 10 5 bac.mL -1 , e porcentagens de lactose mais altas, de até 4,5%. Conforme a CBT aumenta, a porcentagem de lactose ou o pH tendem a diminuir, porém não necessariamente juntos. Esse comportamento faz com que o teste do álcool não seja um indicador confiável para a qualidade do leite, devendo ser aplicado sempre em conjunto com outras provas que auxiliem no diagnóstico de acidez bacteriana e/ou resistência térmica, como titulação do ácido lático, mensuração de pH e teste da fervura. Palavras-chave: alizarol; etanol; instabilidade. AbstractThe alcoholic stability of milk is a current problem in many countries that still use the alcohol test to measure the microbiological quality of milk. Beyond microbiological acidity, many factors can also affect the alcoholic stability of milk, leading to a confounding effect in alcohol test and industrial losses. The present study aimed to evaluate the relationship between pH, bacterial count, Dornic acidity, lactose percentage and ethanol stability of milk. The samples comprised fresh raw milk from 322 dairy farms from Parana state. According to the results of the 72º ethanol test and the Dornic acidity test, the samples received the following classification: stable milk, acidic milk, or unstable milk to ethanol. There was no relationship among pH, Dornic acidity and microbiological count in samples of milk that were unstable to alcohol test. Unstable milk to ethanol has pH values ranging between 6.6-6.8 with low microbiological count (less than 10 5 cell.mL -1 ) and higher lactose percentages (up to 4.5%). As bacterial count increase, the lactose percent tends to decrease, but not necessarily together. This feature makes the alcohol test unreliable, and the use of other parameters

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Section: Resultsunclassified

Estabilidade Do Leite Ao Álcool Ainda Pode Ser Um Indicador Confiável?

et al. 2016

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“…Other methods, such as solution mixture 8,79 and hydrothermal synthesis, 88 can also produce spherulitic aragonite with different additives and thermal treatments. Aragonite spherulites synthesized from different methods, however, can have different morphologies.…”

Section: Methodsmentioning

confidence: 99%

“…7 Spherulites start forming as an aggregate of parallel acicular crystals termed "fibers", then form a "sheaf of wheat" structure, and with the growth of more fibers eventually become complete spheres. 8 In an ideal spherulite, fibers radiate from the center and contain all possible orientations within the sphere. Since the fast-growing axis in aragonite (CaCO 3 ) is the c-axis, 9 in spherulites each fiber elongation direction coincides with the crystalline c-axis.…”

mentioning

confidence: 99%

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Sun¹,

Marcus

Frazier³

et al. 2017

ACS Nano

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Coral skeletons were long assumed to have a spherulitic structure, that is, a radial distribution of acicular aragonite (CaCO 3 ) crystals with their c-axes radiating from series of points, termed centers of calcification (CoCs). This assumption was based on morphology alone, not on crystallography. Here we measure the orientation of crystals and nanocrystals and confirm that corals grow their skeletons in bundles of aragonite crystals, with their caxes and long axes oriented radially and at an angle from the CoCs, thus precisely as expected for feather-like or "plumose" spherulites. Furthermore, we find that in both synthetic and coral aragonite spherulites at the nanoscale adjacent crystals have similar but not identical orientations, thus demonstrating by direct observation that even at nanoscale the mechanism of spherulite formation is non-crystallographic branching (NCB), as predicted by theory. Finally, synthetic aragonite spherulites and coral skeletons have similar angle spreads, and angular distances of adjacent crystals, further confirming that coral skeletons are spherulites. This is important because aragonite grows anisotropically, 10 times faster along the c-axis than along the a-axis direction, and spherulites fill space with crystals growing almost exclusively along the c-axis, thus they can fill space faster than any other aragonite growth geometry, and create isotropic materials from anisotropic crystals. Greater space filling rate and isotropic mechanical behavior are key to the skeleton's supporting function and therefore to its evolutionary success. In this sense, spherulitic growth is Nature's 3D printing. KEYWORDS: Ion attachment, crystallization by particle attachment, CPA, biomineralization, PEEM, PIC-mapping, mesocrystal S pherulites are polycrystalline structures in which acicular crystals radiate from a common center and grow approximately synchronously so the final shape of a spherulite resembles a sphere. 1−7 Figure 1 shows two types of spherulites: "spherical spherulite", in which the crystal fibers start from a point, or "plumose spherulite", in which crystal fibers radiate at an angle from the line. 7 Spherulites start forming as an aggregate of parallel acicular crystals termed "fibers", then form a "sheaf of wheat" structure, and with the growth of more fibers eventually become complete spheres. 8 In an ideal spherulite, fibers radiate from the center and contain all possible orientations within the sphere. Since the fast-growing axis in aragonite (CaCO 3 ) is the c-axis, 9 in spherulites each fiber elongation direction coincides with the crystalline c-axis. 10,11 In real spherulites, biogenic 12 and synthetic, 7 the crystal orientations are not perfectly radial nor continuously varying with angle, they deviate slightly from radial and exhibit small but abrupt changes in orientation, termed "branching". In Figure 1 branching angles are smaller than 30°in direction and in crystal lattice orientation. This is distinct from crystallographic branching, which occurs in sno...

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“…Acta 2017, 90(4), 689-698 particles can be fully described with the classical growth theory. [50] Namely, in this particular case, layer-by-layer deposition of growth units (Ca 2+ and CO3 2-) on the top of the already formed crystal planes of vaterite seed, can be correlated to the measured continuous changes of their concentrations in the solution (calculated from pH changes and confirmed with chemical analyses). Thus, the growth rates, vg ≡ dc / dt, corrected for the changes of the surface area of vaterite seeds, cppt 2/3 , were plotted as a function of the supersaturation, S -1 in order to test different theoretical models.…”

Section: Crystal Growth Kineticsmentioning

confidence: 70%

Crystal Growth Mechanism of Vaterite in the Systems Containing Charged Synthetic Poly(Amino Acids)

Džakula¹,

Falini²,

Kralj³

2017

Croat. Chem. Acta

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Negatively ionisable poly-L-glutamic acid (pGlu) and poly-L-aspartic acid (pAsp), considered as analogues of the naturally occurring acidic macromolecules involved in biomineralization processes, were used as additives in the calcium carbonate precipitation systems in order to investigate their interactions with the vaterite crystallites. Poly-L-lysine (pLys), a positively ionisable poly(amino acid), was also used in order to elucidate the impact of the side chain charge. The growth kinetics of vaterite was found parabolic, indicating that the integration of growth units into the spiral step at the vaterite crystal surfaces is the rate-determining mechanism. The presence of small amounts of pGlu and pAsp inhibited the crystal growth. At the highest concentrations of both acidic macromolecules the exponential rate law was observed, which indicates the surface nucleation as the rate controlling mechanism. The addition of pLys in the range of applied concentrations did not significantly influence the crystal growth of the vaterite. Thus, the kinetic results, corroborated by morphological observations, pointed out to the significance of the negative charge of the side chains of selected polypeptides in the interfacial interactions with mineral planes.

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Crystallization of CaCO₃in Water–Alcohol Mixtures: Spherulitic Growth, Polymorph Stabilization, and Morphology Change

Cited by 190 publications

References 47 publications

Estabilidade Do Leite Ao Álcool Ainda Pode Ser Um Indicador Confiável?

Estabilidade Do Leite Ao Álcool Ainda Pode Ser Um Indicador Confiável?

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Crystal Growth Mechanism of Vaterite in the Systems Containing Charged Synthetic Poly(Amino Acids)

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Crystallization of CaCO3in Water–Alcohol Mixtures: Spherulitic Growth, Polymorph Stabilization, and Morphology Change

Cited by 190 publications

References 47 publications

Estabilidade Do Leite Ao Álcool Ainda Pode Ser Um Indicador Confiável?

Estabilidade Do Leite Ao Álcool Ainda Pode Ser Um Indicador Confiável?

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Crystal Growth Mechanism of Vaterite in the Systems Containing Charged Synthetic Poly(Amino Acids)

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Product

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Crystallization of CaCO₃in Water–Alcohol Mixtures: Spherulitic Growth, Polymorph Stabilization, and Morphology Change