Kazuhiko Kandori

The decomposition of protein molecules from a mixed-protein solution on the surface of calcium hydroxyapatite (CaHap) and Ti(IV)-doped CaHap (TiHap) particles with a Ti/(Ca + Ti) atomic ratio (X (Ti)) of 0.10 and 0.20 under UV irradiation of 365 nm in wavelength was investigated. Acidic bovine serum albumin (BSA) and basic lysozyme (LSZ) were employed as a model of pathogenic proteins. The photocatalytic activities of TiHap particles were estimated from the decomposition of BSA and LSZ from the BSA (2.5 mg/cm(3))-LSZ(1.0 mg/cm(3)) mixture under 1 mW/cm(2) UV irradiation dispersed in a 10-mL quartz tube. No change in BSA concentration by UV irradiation was observed for all the unheated original CaHap and TiHap particles without and with low photocatalytic activities, respectively. Similar results were observed for the systems that employed heat-treated particles endowed a high photocatalytic activity by heat treatment at 650 A degrees C for 1 h. On the other hand, a selective photocatalytic decomposition was observed for the LSZ, i.e., only LSZ molecules were decomposed completely from the BSA (2.5 mg/cm(3))-LSZ(1.0 mg/cm(3)) mixture by using heat-treated TiHap particles with X (Ti) = 0.10 and 0.20. This selective decomposition by TiHap particles was interpreted by higher adsorption affinity of positively charged LSZ to highly negatively charged TiHap together with low molecular weight and rigid structure of LSZ molecules.

The effects of polyvinyl alcohol (PVA) molecules on the porosity of disk-like hematite particles produced from the forced hydrolysis reaction using two kinds of PVA molecules with a well-defined molecular weight and a high degree of saponification (PVA-105 and PVA-124) were investigated. It is evident from TEM and field-emission scanning electron microscope (FE-SEM) measurements that a fraction of particles lost their spherical habit and acquired a disk-like shape by the addition of small amounts of both PVA molecules, though no difference in the particle size between the two PVA systems was observed. FE-SEM images of the particles revealed that the disk-like hematite particles are made up of small cluster particles with a diameter of approx. 5-10 nm. The disk-like particles produced a rather lower concentration for PVA-124 with a higher molecular weight than that for PVA-105 with a lower molecular weight. This fact was due to the large number of hydroxy groups in PVA-124 molecules than in PVA-105; hydroxy groups act as adsorption sites onto polynuclear (PN) primary particles and cause pronounced effects on the formation and structure of particles during the aggregation of PN particles. It was clarified from N-2 adsorption measurements at 77 K that the porosity of the hematite particles can be controlled from microporous to mesoporous by changing the concentrations of PVA-105 and PVA-124, as was classified into three groups, i.e., groups 1, 2, and 3. The control particles produced without PVA molecules, classified into group 1, showed type IV adsorption isotherms, and only the voids produced between spherical particles were detected as mesopores. On the other hand, the particles produced with small amounts of PVA produced micropores as classified in group 2. In this group, the particles produced uniform micropores after being outgassed at 100-200 A degrees C. The hematite particles produced with high concentrations of PVAs were classified into group 3. In this group, the particles after being outgassed at lower temperature produced micropores with diameters between 0.6 and 2.0 nm, though the micropores in the particles changed to mesopores after outgassing at 300 A degrees C. This mesopore formation was attributed to the elimination of the PVA-adsorbed layer by evacuation at 300 A degrees C, i.e., the large voids residing in the disk-like hematite particles make the particles mesoporous. This mesopore formation was further confirmed by adsorption experiments of C6H6(benzene) and CCl4 molecules at 298 K.

Calcium hydroxyapatite (Hap) particles were produced using a microreactor, and the relationship between the morphology of the Hap particles and the synthesis conditions using a microreactor was investigated. Sheet-like Hap particles could be produced continuously using a microreactor, whereas only rod-like Hap particles were produced by a batch method. The Ca/P atomic ratio of the Hap particles produced by microreactor processing was 1.40-1.46, which was lower than the stoichiometric value of 1.67. This result suggests that the Hap particles produced by microreactor processing were calcium-deficient. The size of the sheet-like Hap particles increased, and the length of b and c axes of the Hap particles increased as the mixing efficiency of the microreactor increased, whereas the length of a axis remained almost unchanged. The X-ray diffraction patterns revealed that the lattice constant of the c axis increased while that of the a axis decreased as the mixing efficiency of the microreactor increased and they came close to data reported in a previous study. The size and shape of Hap particles produced by microreactor processing significantly depend on the mixing efficiency of the microreactor.

To simulate the atmospheric corrosion of weathering steels, alpha-FeOOH rust particles were synthesized from acidic Fe(NO3)(3) solutions in the presence of Cu(II) at 50 degrees C. No remarkable change of crystallinity of alpha-FeOOH was observed by adding Cu(II). Increasing the added Cu(II) formed the nano-sized ferrihydrite particles and reduced the size of alpha-FeOOH particles, leading to the increase of specific surface area. The Cu(II) added in the starting solution was less easily incorporated in the particles than Fe(III). The adsorption of corrosive gasses such as H2O, CO2 and SO2 on the rust particles was inhibited by the addition of Cu(II). (C) 2012 Elsevier Ltd. All rights reserved.

The fundamental experiments on the adsorption behaviors of proteins onto photocatalyticTi(IV)-doped calcium hydroxyapatite (TiHap) particles with varied amounts of Ti(IV) ions doped (called as original particle) were examined comparing to those onto the calcium hydroxyapatite (CaHap) ones. The heat treated TiHaps and CaHap particles at 650 degrees C for 1 h were also examined (called as heat treated particle). The Ti/(Ca+Ti) atomic ratio (X-Ti) of the TiHap particles was varied between 0 and 0.20. Since the surface acidity of the particles was increased by increase in X-Ti value, the negative zeta potential (zp) of the particles was increased. All the adsorption isotherms of bovine serum albumin (BSA), myoglobin (MGB) and lysozyme (LSZ) from 1 x 10(-4) mol/dm(3) KCl solution were the pseudo-Langmuirian type. The saturated amounts of adsorbed LSZ (n(S)(LSZ)) values onto the original particles were increased with increase in the negative zp of the particles. However, the saturated amounts of adsorbed BSA (n(S)(BSA)) values were decreased by increase in the negative zp except at X-Ti = 0.05 where n(S)(BSA) value exhibited a maximum. In the case of MGB, the saturated amounts of adsorbed MGB (n(S)(MGB)) values were less dependent on the zp of the particles. These results were explained by changing the electrostatic forces between protein molecules and TiHap particles by doping Ti(IV) ions. On the other hand, n(S)(BSA), n(S)(LSZ) and n(S)(MGB) values onto the heat treated particles were larger than the original particles in each particle system, though no relationship to the X-Ti value was recognized in each protein system. This result was interpreted to the formation of beta-TCP crystal phase in both the CaHap and TiHap particles by the heat treatment. The Ca2+ ions produced by dissolution from beta-TCP phase may exert as binders between BSA and surfaces of the heat treated particles. The weak binder effects of Ca2+ and PO43- ions were observed for the adsorptions of LSZ and MGB. (C) 2012 Elsevier B.V. All rights reserved.

The photocatalytic activity of Ti(IV)-doped calcium hydroxyapatite (TiHap) particles with atomic ratio of Ti/(Ti + Ca) [X-Ti] from 0 to 0.20 prepared by a coprecipitation method, called as original particles, were examined by in situ Fourier-Transform IR (FTIR) measurement. The heat treated TiHap particles were also used after treated original particles at 650 degrees C for 1 h, called as heat treated particles. All the original particles were made up by rod-like particles with irregular size, while the heat treated particles were rounded by sintering and their sizes were enlarged in each X-Ti system. The TiHap particles were cation deficient particles with (Ca + Ti)/P atomic ratio ranging between 1.54 and 1.64. The X-Ti values of TiHap particles assayed showed approximately the dosage of Ti(IV) ions in each system. All the TiHap particles employed exhibited UV absorption below ca. 370 nm, though the UV absorption characteristics did not vary by the heat treatment. However, the pure calcium hydroxyapatite with X-Ti = 0 had no UV absorption. The IR spectra of the particles with X-Ti >= 0.05 exhibited a new large peak at 3428 cm(-1) close to the peak at 3570 cm(-1) of OH- ions together with the bands at 3654-3682 or 3673 (surface P-OH groups) and 3737 cm(-1) (surface Ti-OH groups). The deuteration method revealed that the new band at 3428 cm(-1) could be assigned to the dislocated OH- ions by substituting Ti(IV) ions. The expansion of crystal structure along with c direction by the heat treatment was identified by the unit-cell dimension obtained from the XRD patterns. It was concluded therefore that the produced dislocated OH- ions by the heat treatment induce the photocatalytic activity of TiHap particles. The strong photocatalytic activity of TiHap particles was attributed to the dislocated OH- ions because they can produce *OH radicals in the particles without water molecules by UV irradiation. Furthermore, FTIR and XRD measurements elucidated that the optimum temperature for inducing photocatalytic activity of TiHap is ca. 600 degrees C. (c) 2012 Elsevier B.V. All rights reserved.

The formation of plate-like calcium phosphate particles with slit-shaped micropores produced from the forced hydrolysis reaction of 10 mM Ca(OH)(2), 3.2 mM triphosphate(tripolyphosphate, tpp; ) and 20 mM HCl mixed solution at 100 A degrees C for 2 h were investigated. The molecular sieve effect of produced particles was also explored by using five kinds of adsorptives with various molecular diameters. The large thin plate-like particles as prepared exhibited a large and sharp peak at 2 theta = 6.929A degrees with small diffraction patterns of beta-Ca2P2O7. This characteristic peaks at 2 theta = 6.929A degrees suggested that the particles possess a layer structure with ordered basal plane and the large thin plate-like particles are made up of thin sheets. However, the large peak at 2 theta = 6.929A degrees shifted to higher 2 theta value after evacuated the particles at 50 similar to 200 A degrees C, and these characteristic peak was diminished after treated over 300 A degrees C. The interlayer distances of basal plane were estimated to be 1.280 to 0.980 nm. TG and FTIR measurements disclosed that large amounts of water molecules exist in the particles. It was also revealed that tpp molecules are not completely hydrolyzed to phosphate (orthophosphate, op; ) ions but still remain tpp and diphosphate (pyrophosphate, pp: ) ones, and are adsorbed in slit-shaped micropores. The N-2 adsorption isotherms for the particles were of Type II and they did not change significantly by changing the evacuation temperature from 25 A degrees C to 300 A degrees C. On the contrary, the amount of adsorbed H2O molecules on the particles after evacuated at 25 and 50 A degrees C steeply increased at ca. 0.3 < p/p (0) < 0.6 to provide a step-like adsorption isotherm, but it disappeared after evacuated over 75 A degrees C. From the molecular adsorption experiments employing adsorptives with different molecular diameters, it was indicated that the slit-shaped micropores possess a width less than 0.353 nm being exhibits a high selective adsorption of H2O molecules into slit-shaped ultramicropores that are accessible to H2O molecules but not to N-2 and other adsorptive ones. It was indicated that ultramicropores can be formed by the narrowing effect of residual tpp and pp ions unhydrolyzed in the slit-shaped micropores. The residual tpp and pp ions may serve for the adsorption of H2O molecules by their strong hydrogen bonding nature.

Calcium hydroxyapatite(CaHap) particles substituted five types of heavy rare earth ions (Ln: Y3+, Gd3+, Dy3+, Er3+ and Yb3+) were synthesized using a precipitation method and characterized using various means. These Ln ions strongly affected the crystal phases and the structures of the products. With increasing Ln/(Ln + Ca) in the starting solution ([X-Ln]), the length and the crystallinity of the particles first increased and then decreased. The rare earth metal-calcium hydroxyapatite (LnCaHap) solid solution particles were obtained at [X-Y] <= 0.10 for substituting Y system and at [X-Ln] <= 0.01-0.03 for substituting the other Ln systems. LnPO(4) was mixed with LnCaHap at higher [X-Ln] for all Ln systems. A series of yttrium-calcium hydroxyapatite (YCaHap) solid solutions with [X-Y] = 0-0.10 were investigated using XRD, TEM, ICP-AES, IR and TG-DTA in detail. (C) 2012 Elsevier Ltd. All rights reserved.

The effects of potassium peroxodisulfate (K₂S₂O₈) on the formation of calcium phosphate particles produced by aging Ca(OH)₂ and sodium triphosphate (sodium tripolyphosphate, Natpp: Na₅P₃O₁₀) mixed solution at 100∼160°C for 18 h were examined. Spherical and monodispersed particles were produced at low K₂S₂O₈ concentration ([K₂S₂O₈]) region ([K₂S₂O₈]≤4 mM) and their size was increased by increase in [K₂S₂O₈]. On the contrary, fine irregular particles were produced at [K₂S₂O₈]≥6 mM. The monodispersed spherical particles produced at [K₂S₂O₈]≤4 mM were amorphous, though small irregular particles produced at [K₂S₂O₈]≥6 mM were poorly crystallized calcium pyrophosphates (β-Ca₂P₂O₇). The Ca/P atomic ratios of these samples were 0.79∼0.90, fairly closed to the Ca/P atomic ratio of 1.0 for β-Ca₂P₂O₇. A high adsorption selectivity of H₂O was observed on amorphous monodispersed spherical particles. On the other hand, the β-Ca₂P₂O₇ particles with small amounts of hydrated H₂O produced at [K₂S₂O₈]≥6 mM exhibited no selective adsorption of H₂O. With increase in the aging temperature, small numbers of transparent balloon-like hollow spheres were obtained at 120∼140°C. However, the fraction of hollow spheres was less than 5%. Aging above 150°C, no balloon-like hollow sphere was precipitated but finally calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, Hap) particles with small rod-like shape could be precipitated. These Hap particles produced at 150 and 160°C did not exhibit selective adsorption of H₂O.

The present study synthesized five types of hydroxyapatite (Hap) particles containing light rare earth ions (Ln(3+): La3+, Ce3+, Pr3+, Nd3+ and Sm3+) and Ca2+ ions from aqueous solutions with different Ln/(Ln + Ca) atomic ratios ([X-Ln]) ranging from 0 to 0.15. The crystal phases of the products and their inner and surface structures were investigated by various means. Ln(3+) ions were incorporated into the CaHap crystals and formed rare earth metal-calcium hydroxyapatite (LnCaHap) solid solutions at [X-Ln] <= 0.01-0.03. A mixture of LnCaHap and LnPO(4) was formed in each Ln system at [X-Ln] > 0.01-0.03. Ln(3+) ions strongly affected the structure of the particles, although only a small quantity of Ln(3+) ions was incorporated into the Hap crystals. With increasing [X-Ln], the prepared particles first became longer and then became smaller. The crystallinity of the particles was altered, corresponding with the variation of their size. UV-vis measurements revealed that Ce-contained Hap exhibits strong UV absorption under 400 nm. (C) 2011 Elsevier B.V. All rights reserved.

The fundamental experiments on the adsorption behaviors of proteins onto photocatalytic Ti4+-doped calcium hydroxyapatite (TiHap) particles were examined comparing to those onto the calcium hydroxyapatite (CaHap) and commercially available typical titanium oxide (TiO2) photocatalyst (TKP-101). The heat treated TiHap and CaHap particles were also used after treated these particles at 650 degrees C for 1 h (abbreviated as TiHap650 and CaHap650, respectively). All the adsorption isotherms of bovine serum albumin (BSA), myoglobin (MGB) and lysozyme (LSZ) from 1 x 10(-4) mol/dm(3) KCl solution were the Langmuirian type. The saturated amounts of adsorbed BSA (n(s)(BSA)) for the CaHap650 particles was higher than that for CaHap. Similar results were observed for TiHap and TiHap650. The adsorption of LSZ exhibited the same result of BSA, while the saturated amounts of adsorbed LSZ (n(s)(LSZ)) value on the TiHap were much higher than CaHap. However, the saturated amounts of adsorbed MGB (n(s)(MGB)) are almost equal to those for the CaHap and TiHap nevertheless whether these particles were heat treated at 650 degrees C or not. The TKP-101 exhibited extremely small adsorption capacity of all proteins due to its small particle size of ca. 4 nm in diameter. The independence of the n(s)(MGB) value on the zeta potential (zp) of the particles was explained by the electrostatical neutrality of MGB molecules. On the other hand, the n(s)(LSZ) values were increased with increase in the negative zp of the particles. This fact was explained by increasing the electrostatic attractive forces between negatively charged particles and positively charged LSZ. However, the n(s)(BSA) values exhibit maxima for the heat treated TiHap650 and Ca Hap650 particles. This result was interpreted to the formation of beta-TCP crystal phase by the heat treatment. The produced Ca2+ ions by dissolution from beta-TCP phase may exert as binders between BSA and surfaces of the heat treated particles. (C) 2011 Elsevier B.V. All rights reserved.

The shape and porosity of hematite particles, produced from a forced hydrolysis reaction of acidic FeCl3 solution, were controlled by using polyethylene amine nonionic surfactants (SurfonamineA (R); 0 similar to 10 wt.%). SurfonamineA (R) possesses a nominal formula of CH3-(PEO) (x) -(PPO) (y) -NH2. Surfonamine with the highest total amine content (PEO contents were over 76 mol%, L-100) gave spherical particles, but those with lower total amine contents (L-200, L-207 and L-300) produced pseudocubic hematite particles. The pH value of the system with 10 wt.% of L-100 rose up to 8.49. With this pH rise, the diameter of the spherical particles was dramatically decreased. This fast particle formation was explained by the aggregation of very fine 6-line ferrihydrite particles produced at their high pH conditions. The uniformity of pseudocubic hematite particles produced with L-200, L-207 and L-300 were improved by increasing their concentrations. Since the pH values of these systems before aging were controlled between 2.03 and 2.35, it was presumed that the Surfonamine molecules acts as a buffer agent and attained pseudocubic particles. From the calculation of crystallite size, all the pseudocubic hematite particles were regarded as a polycrystal as well as the large spherical hematite particles produced without Surfonamine (control system). This polycrystallinity of the particles provided evidence that the particles are grown by aggregation of polynuclear (PN) primary particles. Not only the morphology but also the pore size of hematite particles was controlled from nonporous to microporous by using Surfonamines. The N-2 adsorption experiment and t-plot curve analysis revealed that the pseudocubic hematite particles have uniform micropores. The XRD, transmission electron microscope, inductively coupled plasma atomic emission spectroscopy and total organic carbon analysis measurements employed on the systems produced for pseudocubic particles elucidated that the pseudocubic crystal habit was formed by the specific adsorption of chloride ions and/or chloroferric complexes to the {012} faces, restraining the growth process through stacking of ultrafine PN particles in the direction of normal to the {012} faces but strictly restricting the growth and mutual fusion of PN ones. The uniform micropores could be produced between the PN particles. The uniform pseudocubic particles were found to be an effective photocatalytic material than the spherical particles due to their large size with uniform flat crystal faces.

The calcium hydroxyapatite Ca-10(PO4)(6)(OH)(2) (Hap) nanoparticles were prepared by using microreactor and employed these Hap nanopartices to clarify the adsorption behavior of proteins. The size of Hap particles produced by the microreactor reduced in the order of a hardness of the reaction conditions for mixing Ca(OH)(2) and H3PO4 aqueous solutions, such as flow rates of both solutions and temperature. Finally, the size of the smallest Hap nanoparticle became 2 x 15 nm(2), similar to that of BSA molecule (4 x 14 nm(2)). It is noteworthy that the smallest Hap nanoparticles still possesses rodlike shape, suggesting that particles are grown along c-axis even though the reactants mixed very rapidly in narrow channels of the microreactors. The X-ray diffraction patterns of the Hap nanoparticles revealed that the crystallinity of the materials produced by the microreactor is low. The FTIR measurement indicated that the Hap nanoparticles produced by microreactor were carbonate-substituted type B Hap, where the carbonate ions replace the phosphate ions in the crystal lattice. All the adsorption isotherms of acidic bovine serum albumin (BSA), neutral myoglobin (MGB), and basic lysozyme (LSZ) onto Hap nanoparticles from 1 x 10(-4) mol/dm(3) KCl solution were the Langmuirian type. The saturated amounts of adsorbed BSA (n(S)(BSA)) for the Hap nanoparticles produced by microreactor were decreased with decrease in the mean particle length, and finally it reduced to zero for the smallest Hap nanoparticles. Similar results were observed for the adsorption of LSZ; the saturated amounts of adsorbed LSZ (n(S)(LSZ)) also reduced to zero for the smallest Hap nanoparticles. However, in the case of MOB, the saturated mounts of adsorbed MOB (n(S)(MGB)) are also depressed with decreased in their particle size, but about half of MGB molecules still adsorbed onto the smallest Hap nanoparticles. This difference in the protein adsorption behavior was explained by the difference in the size and flexibility of three kinds of proteins. The reduction of n(S)(BSA) is due to the decrease in the fraction of C sites on the side face of each Hap nanoparticle; i.e., there is not enough area left on the nanoparticle surface to adsorb large BSA molecules even though the BSA molecules are soft and their conformations are alterable. The reduction of n(S)(LSZ) was explained by the reduction of P sites. Further, rigidity of the LSZ molecules was given another possibility of the depression of n(S)(LSZ) for the Hap nanoparticles. However, MGB molecules with small and soft structure were adsorbed on the Hap nanaoparticle surface by changing their conformation. We could control the amounts of adsorbed proteins by changing the particle size of Hap in the nanometer range and kinds of proteins. These obtained results may be useful for developing biomimetic materials for bone grafts and successful surgical devices in the biochemical field.

There exists a unique class of orthophosphates in which both the phosphorous and metal atoms are tetrahedrally coordinated by oxygen, therefore, to form metal phosphates. Various kinds of metal phosphate particles have many applications of uses in pigments, catalysis, adsorbents, and bioceramics. It is well known that calcium hydroxy apatite(Hap), a kind of calcium phosphate particles, also shows a high affinity for proteins and much attention has been focused on Hap and substituted Hap nanocrystals as sorbents. In this review, I will present (1) the preparation and characterization of monodispersed metal phosphate particles and (2) characteristics of protein adsorption onto various kinds of apatite particles based on our previous investigations.

To simulate the corrosion of galvanized steel in marine zone, beta-FeOOH was prepared by aging the FeCl(3) solutions containing ZnCl(2) and zinc rusts such as ZnO and zinc hydroxychloride (Zn(5)(OH)(8)Cl(2)center dot H(2)O:ZHC). Adding ZnCl(2), ZnO, and ZHC inhibited the crystallization and particle growth of beta-FeOOH and the inhibitory effect was in order of ZHC approximate to ZnO > ZnCl(2). The adsorption of H(2)O and CO(2) was suppressed by adding ZnCl(2), ZnO, and ZHC. These results imply that the rust formed on galvanized steel in marine environment is more compact, amorphous, and hydrophobic in nature which may lead to improve the corrosion resistance. (C) 2010 Elsevier Ltd. All rights reserved.

The shape and porosity of hematite particles, produced from a forced hydrolysis reaction of acidic FeCl(3) solution, were controlled by using Pluronics as nonionic surfactants (0-4 wt.%). Pluronics possess a nominal formula of (PEO) (x) -(PPO) (y) -(PEO) (x) . The effect of Pluronics with low hydrophilicity (PEO contents were less than 50 mol%) was small and provided spherical particles the same as that of the system without Pluronics (control system). However, Pluronics with higher hydrophilicity (PEO contents were over 50 mol%) gave ellipsoidal hematite particles. This effect on the particle morphology was enhanced by an increase in their molecular weight. On the other hand, the Pluronics possessing an opposite nominal formula [(PPO) (x) -(PEO) (y) -(PPO) (x) ] exhibited no effect on the particle shape; it only depressed phase transformation from aZ center dot-FeOOH to hematite. Not only the morphology but also the pore size of hematite particles was controlled from nonporous to mesoporous by using Pluronics. The N(2) adsorption experiment and t-plot curve analysis revealed that the hematite particles changed from mesoporous to microporous by an increase in the concentration of Pluronics. On the other hand, in the presence of very low amounts of Pluronics molecules (0.1 wt.%), nonporous hematite particles were produced via strong aggregation of PN particles by their hydrogen bonding between hydroxyl and PEO or PPO groups. The dynamic light scattering measurement for the system with Pluronics clarified the existence of polynuclear (PN) particles with a hydrodynamic particle diameter (D (a)) of ca. 40 nm after these were aged for 6 h. The size of PN particles remained constant at ca. 40 nm during aging time of 12 h similar to 3 days, but the scattering intensity was decreased. This decrease in the scattering intensity reveals that the number of PN particles is reduced by aggregation. The transmission electron microscope, inductively coupled plasma atomic emission spectroscopy, and total organic carbon analysis measurements employed on the systems produced for ellipsoidal particles elucidated that the formation of ellipsoidal hematite particles is attributed to the adsorption of Pluronics on the surfaces of PN and growing hematite particles.

The effects of addition of HCl on the formation of monodispersed spherical calcium hydroxyapatite (Hap) particles from the forced hydrolysis reaction of Ca(OH)(2)-triphosphate (tripolyphosphate, tpp. P3O105-) mixed solution were investigated The fairly uniform spherical particles were formed at concentration of HCl (abbreviated as [HCl)) of 8-12 mM. but the particles with various shapes such as very small rodlike and/or large thin platelike were produced at high [HCl] region. These fairly uniform spherical particles produced only at [HCl] = 8-12 mM where the solution exhibited almost neutral pH of 6 89-7 24 after aging The XRD patterns of the spherical particles as prepared were amorphous but they crystallized to beta-Ca2P2O7 after the calcining the samples above 600 degrees C in air. The large amounts of H2O molecules were adsorbed on all the particles after evacuating the samples at 25 degrees C though they decreased drastically after evacuating the samples above 100 degrees C, except for the particles precipitated with a high concentration of HCl ([HCl] >= 16 mM). The high selective adsorption of H2O was achieved for those amorphous spherical particles and was explained by rehydration of the particles by adsorbed H2O. The cavities formed near the cations by evacuation serve for H2O adsorption but not for N-2 The time-resolved TEM experiment revealed that polydispersed spherical particles ranging from 100-300 nm in diameter are formed after aging the solutions for 3-5 h by aggregation of the primary nanometer-sized particles, produced at the first step of the reaction within 2 11, with incorporating calcium and pyrophosphate ions. The calcium and pyrophosphate ions were further deposited on these polydispersed spherical particles and grew to fairly uniform spherical particles with ca. 600-700 am in diameter. The transparent balloonlike hollow spheres were also formed at 120-140 degrees C together with solid spheres This temperature region for producing balloonlike hollow spheres is much wider than those for the system without HCl This fact was explained by the high acidity of the present system with HCl to dissolve the inside of the solid spheres. Since the inner substances of hollow spheres to penetrate H2O molecules were dissolved, the balloonlike hollow spheres exhibited low adsorption selectivity of H2O.

In order to clarify the formation condition of zinc rusts such as layered zinc hydroxynitrate (Zn(5)(OH)(8)(NO(3))(2).2H(2)O: ZHN), ZnO particles were aged with aqueous Zn(NO(3))(2).6H(2)O solution at 6-140 degrees C for 48 h. Further, adsorption of H(2)O and CO(2) on ZHN was examined for simulating study of atmospheric corrosion of galvanized steel. The ZHN was formed at 6 C and the ZnO completely disappeared, meaning the hydrolysis of ZnO particles in aqueous Zn(NO3)(2)center dot 6H(2)O solution to recrystallize as ZHN. Increasing the aging temperature improved the crystallinity of layered structure of ZHN, showing a maximum at 85 C. The formed ZHN was hexagonal plate-like particles. The particle size was dependent of the crystallinity of layered structure of ZHN. The specific surface area of ZHN was decreased on elevating the aging temperature, showing a minimum at 85 degrees C. The adsorption of H(2)O and CO(2) was enhanced on increasing the crystallinity of layered structure of ZHN, meaning that these molecules are adsorbed not only on particle surface but also in interlayer of ZHN. These facts infer that the preferred orientation of plate-like ZHN particles leads to the formation of compact rust layer on galvanized steel and to the enhancement of corrosion resistance. (C) 2009 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

The effects of modification of calcium hydroxyapatites (Hap; Ca(10)(PO(4))(6)(OH)(2)) by trivalent metal ions (Al(III), La(III), and Fe(III)) on protein adsorption behavior were examined using bovine serum albumin (BSA; isoelectric point (iep) = 4.7 and molecular mass (M(s)) = 67 200 Da). The AI(III)-, La(III)-, and Fe(III)substituted Hap particles were prepared by the coprecipitation method with different atomic ratios, metal/(Ca + metal), abbreviated as X(metal). The particles precipitated at X(metal) = 0 (original-Hap) were rod-like and 10 x 36 nm(2) in size. The short, rod-like original-Hap particles were elongated upon adding metal ions up to X(metal) = 0.10, and the extent of the particle growth was in the order of La(III) < Al(III) << Fe(III). The crystallinity of the materials was slightly lowered by increasing X(metal) for all systems. The adsorption isotherms of BSA onto the AI(111)-, La(IIL)-, and Fe(III)-substituted Hap particles showed the Langmuirian type. The saturated amounts of adsorbed BSA (n(s)(BSA)) values were strongly dependent on X(metal) in each system. The n(s)(BSA) values for the Fe(III)-substituted Hap system were increased with an increase in X(Fe) (X(metal) value of Hap particles substituted with Fe(III)); the n(s)(BSA) value obtained at X(Fe) = 0.10 was 2.7-fold more than that for the original-Hap particle, though those for the La(III) system were decreased to ca. 1/5. On the other hand, the n(s)(BSA) values for the AI(III) system were decreased with substitution of small amounts of AI(III), showing a minimum point at X(Al) = 0.01, but they were increased again at X(Al) over 0.03. Since the concentrations of hetero metal ions dissolved from the particles exhibited extremely low values, the possibility of binder effects of trivalent cations dissolved froth the particle surface for adsorbing BSA to trivalent-ion-substituted Hap particles was excluded. The increase of n(s)(BSA) by an increase in X(Fe) was explained by elongation of mean particle length along with the production of surface hydroxo ions, such as Fe(OH)(2+) or Fe(OH)(2)(+)(,) to induce the hydrogen bond between the Fe(III)-substituted Hap surface and BSA molecules, though the number of original C sites established by Ca(II) atoms was reduced. In the case of La(III)-substituted Hap particles, the number of original C sites established by Ca(II) atoms was reduced by La(III) substitution but the mean particle length remained almost constant. Furthermore, surface hydroxo La(III) groups were absent. Therefore, the reduction of n(s)(BSA) was explained by both the unaltered mean particle length and their low surface hydrophilicity. The change of n(s)(BSA) values by X(Al) resembled that of the mean particle length. These results implied that both the mean particle length and surface hydrophilicity of AI(Ill)-, La(III)-, and Fe(I:II)-substituted Hap particles are determining factors of the adsorption amounts of BSA.

Positively charged Hap nano-crystals were prepared by using P-alanine and clarified the adsorption affinity of these surface amide functionalized Hap nano-crystals to proteins. Colloidal surface amide functionalized Hap nano-crystals were prepared by wet method in the presence of various amounts of beta-alanine by changing molar ratio of beta-alanine/Ca (beta/Ca ratio) in the solution. The rod-like nano-crystals were lengthened with addition of beta-alanine though their width did not vary; carboxyl groups of P-alanine are strongly coordinated to Ca(2+) ions exposed on ac and/or bc faces to inhibit particle growth to a- and/or b-axis directions and enhance the particle growth along to the c-axis. No difference can be recognized on the crystal structure among the synthesized Hap nano-crystals by XRD measurements. However, the large difference was recognized by TG-DTA and FTIR measurements. Those measurements revealed that R-alanine is incorporated on the Hap nano-crystal surface up to the beta/Ca ratio of 1.0, though they are absent in the nano-crystals synthesized at beta/Ca ratio >= 2.0. The zeta potential (zp) of beta-alanine-Hap nano-crystals prepared at beta/Ca = 0.4 and 1.0 of those incorporating beta-alanine exhibited positive charge at pH <= 5.9. The saturated amounts of adsorbed BSA for the positively charged beta-alanine-Hap nano-crystals were increased 2.3-2.4-fold by their electrostatic attraction force between positively charged beta-alanine-Hap nano-crystals and negatively charged BSA molecules. We were able to control the adsorption affinity of Hap nano-crystal by changing their surface charge. (C) 2009 Elsevier B.V. All rights reserved.

Calcium phosphate particles were prepared by aging a solution of dissolved Ca(OH)(2) and sodium triphosphate (sodium tripolyphosphate, Natpp: Na5P3O10) at 100-150 degrees C for 18 h in a Teflon-lined screw-capped Pyrex test tube. Large spherical and/or small aggregated spherical particles were precipitated with an extremely fast rate of reaction under 100 degrees C. The large spherical particles were amorphous and the small aggregated ones were alpha-CaNa2P2O7 center dot 4H(2)O. The former amorphous ones crystallized to beta-Ca2P2O7 after being calcined above 600 degrees C. Calcium hydroxyapatite (Ca-10(PO4)(6)(OH)(2), Hap), with rod-like and ellipsoidal or spherical aggregated shapes, was successfully produced using polyphosphates as a source of orthophosphate ions. Time resolved TEM measurement revealed that the crystallization of Hap particles takes place on the surface of tiny amorphous particles precipitated before aging. The tiny particles played the role of nuclei for Hap crystallization. The aging temperature drastically varied the particle shape under conditions for producing uniform amorphous spherical particles; solid spherical particles were produced with an aging temperature of up to 120 degrees C, whilst transparent balloon-like hollow spheres were precipitated at 125 degrees C. Finally, fully transparent balloon-like hollow spheres were produced with mere trace amounts of small rod-like particles after aging the solution above 127 degrees C. The time resolved TEM observation and ICP-AES measurements revealed that the balloon-like hollow spheres were produced by dissolving the interior of solid spherical particles after reinforcing their shell by the adsorption of unhydrolyzed tpp and/or pyrophosphate (pp) ions, which are the hydrolysis product of tpp. The balloon-like hollow spheres of calcium phosphate may have the potential use as drug delivery vehicles and have biocompatibility advantages. (C) 2009 Elsevier Ltd. All rights reserved.

The effects of heat treatment of calcium hydroxyapatite (Hap) on the protein adsorption behavior were examined using typical proteins of bovine serum albumin (BSA: isoelectric point (iep) = 4.7, molecular mass (M(s)) = 67 200 Da, acidic protein), myoglobin (MGB: iep = 7.0, M(s) = 17 800 Da, neutral protein), and lysozyme (LSZ: iep = 11.1, M(s) = 14 600 Da, basic protein). The TEM, XRD, and gas adsorption measurements ascertained that all of the Hap particles examined were highly crystallized and nonporous. The Hap single phase was continued up to the heat treatment temperature of 600 degrees C. However, after treatment above 800 degrees C in air, the beta-Ca(3)(PO(4))(2) (beta-TCP) phase slightly appeared. TG and ICP-AES measurements suggested that all of the Hap particles are Ca(2+)-deficient. Also, it was indicated from FTIR and XPS measurements that a partially dehydrated oxyhydroxyapatite (pd-OHap) was formed after treatment at high temperature. The saturated amounts of adsorbed BSA (n(s)(BSA)) did not vary on the Hap particles after heat treatment at 200 and 400 degrees C. However, n(s)(BSA) values were increased by raising the heat treatment temperature above 600 degrees C. The adsorption coverage of BSA was increased up to ca. 1.4. This adsorption coverage of BSA (theta(BSA)) over unity suggests that the BSA molecules densely adsorbed and a part of BSA molecules adsorbed as end-on type on the Hap particle surface or BSA molecules became contracted. Similar adsorption behavior was observed on the LSZ system, but the adsorption coverage of LSZ (theta(LSZ)) values are much less than theta(BSA). On the other hand, no effect of the heat treatment of Hap particles was observed on the adsorption of MGB. The increases of n(s)(BSA) and n(s)(LSZ) were explained by the increase of calcium and phosphate ions in the solutions dissolved from beta-TCP formed after heat treatment of Hap, especially treated at high temperature. The dissolved Ca(2+) and PO(4)(3-) ions may act as binders between proteins and Hap surfaces; the adsorption of Ca(2+) ions on the Hap Surface offers an adsorption site for BSA owing to its positive charge. In the case of adsorption of positively charged LSZ molecules, PO(4)(3-) ions act as a binder in an opposite way. Since the MGB molecules are neutral, no, effect of either ion was observed.

Calcium phosphate particles were prepared by aging a solution of CaCl2 and sodium triphosphate (sodium tripolyphosphate, Natpp: Na5P3O10) at 100-150 degrees C for 16h in a Teflon-lined screw-capped Pyrex test tube. The rod-like and spherical particles were precipitated lit ail extremely fast rate of reaction under 100 degrees C. The spherical particles were only produced in a very narrow region at 100 degrees C by aggregation of primary small particles. The rod-like particles were CaNa2P2O7 center dot 4H(2)O but the uniform spherical ones were amorphous and the latter ones were crystallized to beta-Ca2P2O7 after being calcined above 600 degrees C. The aging temperature drastically varied the particle shape under conditions for producing uniform spherical particles; solid spherical particles were produced up to the aging temperature of 115 degrees C but balloon-like hollow spheres were precipitated at 120 degrees C. However, large and irregular agglomerates made up of extremely small rod-like particles were precipitated after aging the Solution above 125 degrees C. TEM observation and ICP-AES measurements revealed that the balloon-like hollow spheres were produced by dissolving the interior of solid spherical particles after reinforced their shell by the adsorption of unhydrolyzed tpp. The spherical and balloon-like calcium phosphate particles with amorphous crystal form showed high selective adsorption of H2O by rehydration of Ca2+ ions by penetrated H2O molecules into the particles. In particular, the balloon-like hollow spheres or calcium phosphate may hold potential as drug delivery vehicles and have biocompatibility advantages.

The effects of anions (F-, Cl-, NO3- and Br-) on morphology and structure of hematite particles produced from a forced hydrolysis reaction of Fe(NO3)(3)-HNO3 were investigated by various means. In the case of NO3 and Br- systems, there was no significant change in particle morphology; the small spherical hematite particles with ca. 20-40 nm in diameter were produced. On the other hand, the addition of F- ions produced needle-like alpha-FeOOH particles up to 0.01 M. small rod-fike beta-FeOOH particles were formed at 0.02 M and finally the large rod-like beta-FeOOH particles were precipitated above 0.03 M. A unique effect of anions was observed on Cl- ions; the spherical hematite particles are produced up to 0.1 M and the size was increased with increase in the concentration of Cl- ions. The size of large spherical hematite particles (ca. 350 nm in diameter) produced in the Fe(NO3)(3)-HNO3 system with 0.1 M Cl- ions was analogous to that steadily attained in the FeCl3-HCl one (called as control system). It was suggested that 3.2 of the Cl/Fe molar ratio in the aging solution is an optimum condition for producing the large spherical hematite particles. The formation of large spherical hematite particles only in the Cl- system was explained by the formation of small beta-FeOOH particles as an intermediate for producing hematite ones via dissolution-reprecipitation process. The hematite particles produced from Fe(NO3)(3)-HNO3 solution were monocrystalline but those from the control system are polycrystalline. This fact describes that the system with NO3- ions provides much more condensed inner structure rather than the control system. (C) 2008 Elsevier B.V. All rights reserved.

Layered material of zinc hydroxychloride (Zn(5)(OH)(8)Cl(2) center dot H(2)O center dot ZHC), which is one of the basic zinc salts (BZS), prepared from ZnO nano-particles aged with aqueous ZnCl(2) solutions containing TiCl(4) was examined by various means. The Ti/(Ti + Zn) atomic ratio (X(Ti)) was ranged from 0 to 0.10. XRD results indicated that the diffraction intensity of ZHC was decreased with increasing X(Ti). The ZHC formed at X(Ti) = 0 is hexagonal plate particles with ca. 4 mu m in size and ca. 0.2 mu m in thickness. The particle size was reduced by doping Ti(IV) and the irregular particles were generated at X(Ti) >= 0.03. The Ti content was increased with increasing X(Ti) and Ti(IV) was more easily incorporated in the products than Zn(II). Diffuse reflection UV-vis results suggested that Ti(IV) in the products at X(Ti) <= 0.01 is tetrahedral coordination and that at X(Ti) >= 0.03 is a mixture of tetrahedral and octahedral ones. These facts prove that Ti(IV) inhibits the formation and crystal growth of ZHC. The specific surface area of Ti-doped ZHC estimated from N(2) adsorption isotherms was increased with increasing X(Ti) owing to the decrease of particle size. Contrary to the N2 adsorption, H(2)O monolayer adsorption capacity per unit surface area was reduced as X(Ti) increased. This seems that the layered structure of ZHC, which is accessible to H(2)O molecules but not to N(2) molecules, is disintegrated by incorporation of Ti(IV). Similarly, adsorption of CO(2) on ZHC was inhibited by doping Ti(IV). (C) 2008 Elsevier Ltd. All rights reserved.

Magnesium-calcium hydroxyapatite solid solution (MgCaHap) particles with different atomic Mg/(Mg + Ca) ratios (X-Mg) from 0 to 0.28 were prepared by a wet method and were used as a cation-exchanger with Cd2+ ions in solution by batch and flow methods. The amounts of Mg2+ and Ca2+ ions released into the solution from the particles and that of Cd2+ ions incorporated into the particles from the solution were determined by the batch method. The ion-exchange with Cd2+ reached an equilibrium within ca. 30 min and did not change the morphology and crystal structure of MgCaHap particles. The exchanged amount per gram exhibited a maximum at X-Mg = 0.20 depending on the specific surface area of the particles. X-Mg value of the MgCaHap particles after the ion-exchange treatment was less than that before the treatment, that is, Mg2+ ions were more easily released from the MgCaHap particles than Ca 21 ions by the treatment. The ion-exchange heat per gram and per mole of exchanged ions obtained by the flow method were increased with an increase of X-Mg, indicating that the ion-exchange heat between Mg2+ and Cd2+ is more than that between Ca2+ and Cd2+. (C) 2007 Elsevier B.V. All rights reserved.

The effects of pyrophosphate ions (PP: P2O7 4-) on the adsorption of proteins onto calcium hydroxyapatite (Hap) were examined using typical proteins of bovine serum albumin (BSA: isoelectric point (iep) = 4.7, molecular mass (Ms) = 67 200 Da, acidic protein), myoglobin (MGB: iep = 7.0, Ms = 17 800 Da, neutral protein), and lysozyme (LSZ: iep = 11.1, Ms = 14 600 Da, basic protein). The UV and CD measurements determined that both the secondary and the tertiary structures of protein molecules do not vary in the presence of PP. The adsorption of BSA was strongly depressed by the addition of PP in all the methods with changing the order of PP addition. Even if BSA was pre-adsorbed on the Hap surface, PP replaced BSA molecules by strong preferential adsorption onto Hap to reduce the amounts of adsorbed BSA. A similar effect was observed with the adsorption of MGB. On the other hand, the amount of adsorbed LSZ (nLSZ) was increased with an increase in the concentration of PP, and the nLSZ value showed a maximum point in each adsorption isotherm. This fact was explained by a compression of the electric double layer (EDL) around each LSZ molecule by PP. This compression of the EDL induced the reduction of lateral electrostatic repulsions between charged LSZ molecules on the Hap surface and enhanced the formation of closed-packed monolayers to raise the nLSZ value. However, since the number of PPs around a LSZ molecule is decreased by an increase in the LSZ concentration in each system, the thickness of the EDL may be increased. Hence, nLSZ was reduced again after the maximum point in each system. Tripolyphosphate (TPP: P3O105-) ions exhibited similar effects on the adsorption behaviors of all proteins, but a much more pronounced effect was observed on the LSZ system. TPP with a higher eletronegativity shielded the EDL more highly than PP to increase the n LSZ value. The results of the zeta potential for all the protein systems supported the modes of protein adsorption discussed. © 2008 American Chemical Society.

The shape and porosity of hematite particles formed from the forced hydrolysis of acidic FeCl3 solutions could be controlled by the use of two types of tannic acid (hydrolysable and non-hydrolysable) within the concentration range 0-2 x 10(-2) wt%. The system with hydrolysable tannic acid (AL) initially provided quite small spherical particles at concentrations up to 10(-2) wt% and finally irregular small hematite particles at 2 x 10(-2) wt%. In the system with condensed non-hydrolysable tannic acid (KT), on the other hand, the hematite particles became ellipsoidal in shape at concentrations above 10(-2) wt%. The formation of ellipsoidal particles was explained by the adsorption of KT molecules onto the growing polynuclear primary particles. TEM and XRD measurements revealed that all the hematite particles produced from FeCl3/HCl solutions with tannic acids arc polycrystalline. The rate of phase transformation from beta-FeOOH to hematite was accelerated as the concentration of AL increased, whereas no significant change was observed for the KT system. Analysis by t-plots revealed that the porosity of the hematite particles changed from mesoporous to microporous when the concentration of AL increased. In contrast, the presence of very low amounts of KT molecules (10(-5) and 10(-4) wt%) produced non-porous hematite particles via strong aggregation of polynuclear (PN) particles by hydrogen bonding between hydroxy and carboxy groups. Not only the morphology but also the pore size of hematite particles was controlled from non-porous to mesoporous by using different kinds of tannic acids.

Layered material of zinc hydroxychlorides (Zn-5(OH)(8)Cl-2 center dot nH(2)O: ZHC), which is one of the basic zinc salts (BZS), was synthesized from ZnO nano-particles aged with aqueous ZnCl2 solutions at different temperatures ranging from 6 to 140 degrees C for 48h. X-ray diffraction (XRD) results indicated that the diffraction peaks of ZnO completely disappeared by aging at 6 degrees C and the ZHC peaks were developed. By increasing the aging temperature, crystallinity of the layered structure was improved. At 6 degrees C, the ZHC particles were thin hexagonal plate particles with sizes ranging from I to 3 pm. The particle size of ZHC was independent of aging temperature. The atomic Cl/Zn ratios of all the ZHC materials were almost 0.2 less than 0.4 of the theoretical ratio, indicating that the synthetic ZHC is Cl-deficient. It seemed that half of Cl atoms in the layer were replaced with HCO $$((3)) over bar and/or OH-. The specific surface areas of ZHC estimated from N-2 adsorption isotherms were ca. 10m(2)g-1 and were independent of the aging temperature. However, the H2O monolayer adsorption capacity per unit surface area (n(w)) for all the samples was higher than that of ZnO particles, revealing the high affinity of ZHC to H2O molecules. The n(w) values were increased by reducing the crystallinity of ZHC. This enhancement of H2O adsorption selectivity was thought to be related with less-crystallized parts of the particles. (c) 2007 Elsevier Inc. All rights reserved.

Calcium phenyl phosphate (CaPP) was synthesized from a mixture of Ca(OH)(2) and phenyl phosphate (C6H5PO4H2)) in an aqueous media. XRD pattern of CaPP exhibited five diffraction peaks at 2 theta = 6.6, 13.3, 20.0, 26.8 and 33.7 degrees. The d-spacing ratio of these peaks was ca. 1: 1/2:1/3:1/4:1/5. The molar ratios of Ca/P and phenyl/P of CaPP were 1.0 and 0.92, respectively, and the chemical formula of the material was expressed as (C6H5PO4)0.92(HPO4)(0.08)Ca.1.3H(2)O, similar to that of dicalcium phosphate dihydrate (CaHPO4 center dot 2H(2)O: DCPD). These results allowed us to infer that CaPP is composed of a multilayer alternating bilayer of phenyl groups of the phosphates and DCPD-like phase. The structure of the material was essentially not altered after aging at pH 9.0-11.0 and 85 degrees C in an aqueous media. While, after aging at pH <= 8.0, the diffraction peaks of CaPP were suddenly weakened and disappeared at pH 7.0. Besides, new peaks due to calcium hydroxyapatite (Ca-10(PO4)(6)(OH)(2): Hap) appeared and their intensity was strengthened with decreasing the solution pH. TEM observation revealed that the Hap particles formed at pH 6.0 are fibrous with ca. 1.5 mu m in length and ca. 0.2 mu m in width. From these results, it is presumed that the layered CaPP was dissolved, hydrolyzed and reprecipitated to fibrous Hap particles at pH <= 8.0 and 85 degrees C in aqueous media. This phase transformation of CaPP in Hap resembled to the formation mechanism of Hap in animal organism. (C) 2006 Elsevier Ltd. All rights reserved.

The rust particles of Zn-Al-Mg alloys were synthesized from aqueous solutions dissolving ZnCl2, AlCl3, and MgCl2 at different atomic ratios of the metal ions. The crystal phase and particle morphology of the products depended on the composition of the starting solutions. The compactness of the layers of the products was estimated by measuring their air permeability. The layer of mixed metal hydroxide chloride formed at Zn:Al:Mg = 1: 1: 1 showed a highest compactness, that was ascribed to the preferred orientation of the fine plate particles. The addition of Mg(II) made plate particles smaller to give more compact layers. (c) 2007 Elsevier Ltd. All rights reserved.

Calcium hydroxyapatite (CaHap) particles with different atomic Ca/P ratios were immersed into the solutions containing Cd2+, or Pb2+ ions at 30 degrees C for different periods. The compositions of the solutions and particles before and after immersing were determined. The sorption of Cd2+ reached equilibrium within a short time of ca. 15 min without changing the morphology and crystal structure of CaHap particles. The sorption of Pb2+, continued for ca. 180 min, followed by coating of the CaHap particles with PbHap and formation of PbHap particles. The amount of incorporated Cd2+ was almost independent of the Ca/P ratio of CaHap while that of incorporated Pb2+ was decreased with the increase in Ca/P ratio. The reaction with Cd2+ took place through the surface layer dissolution of CaHap particles and recrystallization of a new layer of CdCaHap solid solution onto the particles. (c) 2006 Elsevier B.V. All rights reserved.

The specific surface area (SA) of the rusts formed by exposing various kinds of steels in different situations was determined by NZ adsorption. The SA values of the rusts increased with the increase of corrosion rate, implying that the rust layers with large SA exhibit a high resistance to corrosion. The suppression of rusting by compact rust layers was interpreted by the blockage of pores in rust layers by the adsorption and capillary condensation of water. The SA values clearly reflect the corrosion levels estimated by the external observation. It was convinced that the SA measurement is a universal quantitative technique to appraisal the protective function of rust layers. (c) 2006 Elsevier Ltd. All rights reserved.

Zinc hydroxide chloride particles of ZHC (simonkolleite, Zn-5(OH)sCl(2)center dot H2O) and layered double hydroxides (LDH, Zn-Al-Cl) were prepared by hydrolysis of ZnCl2 solutions dissolving AlCl3 at Al/Zn=0.1 and 0.6 in atomic ratio, respectively. The anion-exchange and thermal change of ZHC and LDH were investigated by XRD, TEM, FTIR, analysis of Zn, Al, and Cl and gas adsorption of N-2, H2O, and CCl4. The formed ZHC and LDH particles were hexagonal thin plates and irregularly shaped thin plates, respectively. LDH was more easily ion-exchanged with CO32- and SO42- compared to ZHC. The layered structure of LDH was damaged by the ion-exchange with SO42- but not CO32-, whereas that of ZHC was kept after the ion-exchange with both the anions. The TEM observation of the ZHC and LDH particles outgassed at different temperatures of 75-400 degrees C revealed that exfoliation takes place on outgassing ZHC at 100-150 degrees C but not occurs in LDH. ZHC showed a high H2O adsorption selectivity when outgassed below 100 degrees C, however the adsorption selectivity completely disappeared above 125 C where the exfoliation took place. On the other hand, LDH exhibited less adsorption selectivity than ZHC though the selectivity was held after outgassed at 400 degrees C. The facilitated delamination of ZHC indicates that ZHC exhibits weaker interlalyer attractive force than LDH in vacuo. (c) 2006 Elsevier B.V. All rights reserved.

To clarify the adsorption mechanism of proteins onto calcium hydroxyapatite (Hap), the present study measured adsorption (Delta H-ads) and desorption (Delta H-des) enthalpies of bovine serum albumin (BSA; isoelectric point (iep) 4.7, molecular mass (M-s) 67200 Da, acidic protein), myoglobin (MGB; iep = 7.0, M-s = 17800 Da, neutral protein), and lysozyme (LSZ; iep = 11.1, M-s = 14600 Da, basic protein) onto Hap by a flow microcalorimeter (FMC). Five kinds of large platelike particles of CaHPO4 center dot 2H(2)O (DCPD) after hydrolyzing at room temperature with different concentrations of NaOH aqueous solution ([NaOH]) for 1 h were used. DCPD converted completely to Hap after treatment at [NaOH] >= 2%, and the crystallinity of Hap was increased with an increase in [NaOH] up to 10%. The amounts of protein adsorbed (Delta n(ads)) and desorbed (Delta n(des)) were measured simultaneously by monitoring the protein concentration downstream from the FMC with a UV detector. The Delta n(ads) values were also measured statically by a batch method in each system. The Delta n(ads) values measured by the FMC and static measurements fairly agreed with each other. Results revealed that Delta DATA was decreased with an increase in [NaOH]; in other words, Delta was decreased with the improvement of Hap's crystallinity, suggesting that the BSA adsorption readily proceeded onto Hap. This fact indicated a high affinity of Hap to protein. This affinity was further recognized by Delta because its positive value was increased by increasing [NaOH]. These opposite tendencies in Delta(BSA)(ads) and Delta(BSA)(des) revealed that Hap possessed a high adsorption affinity to BSA (i.e., enthalpy facilitated protein adsorption but hindered its desorption). The fraction of BSA desorption was also decreased with an increase in [NaOH], confirming the high affinity of Hap to protein. Similar results were observed on the LSZ system, though the enthalpy values were smaller than those of BSA. In the case of neutral MGB, Delta H-ads(MGB) also exhibited results similar to those of the BSA and LSZ systems. However, due to its weak adsorption by the van der Waals force, Delta H-abs(MGB) was small and almost zero at [NaOH] >= 2%. Hence, the fraction of MGB desorption was less dependent on [NaOH].

The influence of carbodimide (CI), well known as a condensing agent for producing peptides from L-phenylalanine (L-Phe), on the formation of hematite (alpha-Fe2O3) particles through a forced hydrolysis reaction of acidic FeCl3 Solution was examined. The large ellipsoidal particles were produced together with needle-like alpha-FeOOH and fine Fe3O4 ones in the systems both with L-Phe and Cl, though the system only with C1 was not essentially changed the particle shape. Cl produced the characteristic large ellipsoidal particle accompanying the production of peptides by condensing L-Phe. This behavior was explained by the adsorption of peptides on beta-FeOOH and polynuclear (PN) particles; the adsorption of pepticles retarded the phase transformation from beta-FeCOH to hematite along with the heterogeneous aggregation of PNs, resulting the large ellipsoidal hematite particles. Cl reduced Fe3+ to Fe2+ ions during aging the solution. The decomposition of urea, by-products of peptide formation, produced two kinds of amines to raise the solution pH and provided alpha-FeOOH and Fe3O4 particles. The large ellipsoidal hematite particles exhibited large specific surface area and high mesoporosity by adsorption of peptides onto PN particles within the hematite particles. The morphology and inner structure of hematite particles were exceedingly altered by using a reaction of peptide production and this procedure is expected for a new developing method of high-quality porous materials. (c) 2006 Elsevier B.V. All rights reserved.

The artificial rusts of Zn-Fe and Zn-Ti alloys were synthesized from aqueous solutions of mixed metal chloride, sulphate, and nitrate such as ZnCl2 FeCl2, ZnSO4 Ti(SO4)(2), Zn(NO3)(2)-Fe(NO3)(3), and so forth, and were characterized by a variety of techniques. Rust particles with different compositions and morphology were formed, strongly depending on the types of anions and metal ions. Sheet particles of basic zinc chloride (simonkolleite) were generated in the ZnCl2-FeCl2 system and the plate particles of basic zinc sulphate were formed in sulphate systems. These sheet or plate particles and the nanoparticles produced in Zn-Ti systems are expected to form compact rust layers by preferred orientation and dense packing, respectively, and contribute to a high corrosion resistance of Zn alloys. (c) 2006 Elsevier Ltd. All rights reserved.

The shape, porosity, and surface hydrophilicity of hematite particles formed from a forced hydrolysis reaction of acidic FeCl3 solution were controlled by using a trace of polymers (0.001 and 0.003 wt%). The spherical particles were produced on the systems with polyvinyl alcohol (PVA) and polyaspartic acid (PAS). In the case of polyacryl amide (PAAm), slightly small spherical particles were precipitated at 0.003 wt%. However, polyacrylic acid (PAAc) and poly-gamma-glutamic acid (PGA) gave ellipsoidal particles. This morphological change on hematite particles depended on the order of functional groups of polymers as -OH <-CONH2 <-COOH <-COOH and C=O, corresponding to the order in extent of polymer molecules for complexation to Fe3+ ions and adsorption onto particle surface. Accompanying this order, the hematite particles produced were changed from less porous to microporous. On the other hand, only the system with 0.003 wt% of PAAm produced mesoporous hematite particles. Choosing the kinds of polymers also controlled the ultramicroporosity and surface hydrophilicity of the particles.