Na2HPO4 Solution Research Articles

Bone‐bonding ability of a hydroxyapatite coated zirconia–alumina nanocomposite with a microporous surface

Using a combination of hydroxyapatite (HA) coating and microporous surface treatment, bone-bonding ability was given to composites of ceria-stabilized tetragonal zirconia and alumina (CZA), which possesses excellent mechanical and wear properties and phase stability. Four types of CZA plates (2 x 10 x 15 mm3) were prepared for this study, which were CZA with a polished surface (group 1), a microporous surface prepared by hydrofluoric acid and heat treatment (group 2), a microporous surface with a submicron HA coating prepared by alternately soaking the plate from group 2 in aqueous CaCl2/HCl and Na2HPO4 solutions (group 3), and a microporous surface with a 4-microm HA coating prepared by the biomimetic method, where the plates from group 3 were soaked in simulated body fluid (group 4). Plates were implanted into rabbit tibia, and after 4, 8, and 16 weeks, tensile testing and histological examination of the bone-implant interface were conducted. At 4 weeks, group 4 had superior bone-bonding ability compared with other implants, which was maintained at the later postimplantation times. This HA-coated CZA with a microporous surface has the possibility of clinical use as a bearing material in cementless joint prostheses or as a load-bearing bone substitute.

Preparation of α-TCP Cements from Calcium Deficient Hydroxyapatite Obtained by Hydrothermal Method

In this paper the synthesis of bioactive cement based on α-Ca3(PO4)2 (α-TCP) and calcium deficient hydroxyapatite (CDHAp), obtained by hydrothermal method from CaCl2, EDTA, NaH2PO4·12H2O and urea at 160oC, was described. According to the results of DTA, SEM, X-ray and FTIR analyses performed in this investigation, it is shown that CDHAp is transformed to β- TCP at 780oC, and to α-TCP at 1400oC. The hardening of the samples, prepared from the mixture of α-TCP and 2.5 % solution of Na2HPO4, in simulated body fluid at 37oC, was followed by the microstructure changes.

Surface Treatment of Cotton Yarn by Underwater Capillary Electrical Discharge

An alternating current (50 Hz) capillary underwater discharge in aqueous solution of NaH2PO4·2H2O is used for surface treatment of cotton yarn. The capillary discharge emits of ultraviolet radiation in the wavelength range 280–340 nm (OH band). The process of bubble generation and expansion inside the capillary results in the formation of weak shock waves. The effect on cotton yarn exposed to the discharge is quantified by a liquid wicking rate test. The treatment effect strongly depends both on the distance between plasma and cotton yarn and on the voltage. The maximum effect is observed at an applied voltage of 5.8 kV and at 1.5 mm distance to the plasma zone. Analysis of the experimental data shows that the changes in cotton yarn hydrophilicity cannot be explained solely by the locally overheated water. The nonlinear dependence of the treatment effect on the applied voltage is delivered to be due to the generation of weak shock waves in the capillary discharge.

Self-Assembly of Hierarchically Mesoporous−Macroporous Phosphated Nanocrystalline Aluminum (Oxyhydr)oxide Materials

A hierarchical structure of mesoporous−macroporous phosphated aluminum (oxyhydr)oxide (PAl) materials was prepared via a simple self-assembly process with the use of precursor aluminum sec-butoxide in a mixed solution of H3PO4 and Na2HPO4. Direct phosphation resulted in the incorporation of phosphorus into the inorganic framework of aluminum (oxyhydr)oxides by the Al−O−P bonds. The X-ray diffraction (XRD) patterns revealed that, despite slight phosphorus incorporation or phosphation, the frameworks of the as-synthesized autoclaved PAl samples remained in a crystalline phase of boehmite AlOOH-type, and their calcined products had a phase of γ-Al2O3-type. The macroporous structures are uniform, with sizes of 500−1800 nm, and the macropore walls are composed of accessible mesopores of a scaffold-like nanoparticle assembly. It is shown that the direct incorporation of phosphorus from a phosphate solution of the synthesis system can stabilize the framework of mesoporous−macroporous aluminum oxides with high surface areas and acidic properties. The present study also demonstrated that the surfactant (Brij 56) did not seem to have a direct role in the formation of macroporous structures, but significantly influenced the textural properties of the resultant PAl materials. The surface areas of surfactant-synthesized PAl exceeded 700 m2/g, which is almost two times of that of surfactantless-synthesized samples. The synthesized hierarchical PAl exhibited high thermal stability (at least 800 °C), possessing surface hydroxyl groups and acid sites, which may attract much interest for practical applications, including catalysis.

Influence of magnetic field on the properties of freshly precipitated calcium phosphate: implication in adhesion to glass surface

Static magnetic field (MF) (S–S, B = 0.1 T) effects on spontaneous precipitation of calcium phosphates from equilimolar aqueous solutions of CaCl2 and Na2HPO4, or a mixture of Na2HPO4 and NaH2PO4 solutions ([Ca] = [P] = 10−2 M) at 25°C were studied. Besides the zeta potential and pH measurements as a function of time after the solution mixing, in situ deposition of calcium phosphates on glass surface was also investigated. The deposits were photographed at 400× magnification using an optical polarizing microscope equipped with a camera. It was found that MF effects on the properties of in situ precipitated calcium phosphates appeared in terms of changes in nucleation and precipitation rates, pH and zeta potential. The largest changes in the studied parameters occurred during 20 min from the moment of nucleation and precipitation. In the first system (CaCl2 and Na2HPO4 solutions) the magnetic field increases the precipitation rate, which results in a faster pH decrease relative to the reference system. However, in the second system (CaCl2 and a mixture of Na2HPO4 and NaH2PO4 solutions) the initial pH of the slurry is lower in comparison to the above system and in the absence of the MF it decreases at a slower rate. Based on the optical microscope photographs, it was found that the MF ordered the structure of calcium phosphates crystals precipitated in both systems, but to a higher degree when the sediment was precipitated from the mixture of phosphates. From the X-ray diffractograms of the samples it can be concluded that the MF does not change the chemical composition of the precipitated mixture of calcium phosphates, although in the second system it enhances the transformation of dicalcium phosphate into octacalcium phosphate.

A facile route for preparing rhabdophane rare earth phosphate nanorods

Lanthanum orthophosphate nanorods with typical dimensions of 8 nm in diameter and 80 nm in length were prepared simply by mixing NaH2PO4 and LaCl3 aqueous solutions in an oil bath of 100 °C. Eu3+- and Ce3+-doped nanorods were also be prepared in a similar way by introducing Eu3+ and Ce3+ ions, respectively, into the reaction systems. TEM (transmission electron microscope) and XRD (X-ray diffraction) results revealed that the above-mentioned lanthanide orthophosphate nanorods possessed a rhabdophane-type structure. Compositional analysis by X-ray photoelectron spectroscopy demonstrated that LaPO4 nanorods had an anion-rich surface, which might be the main reason for their colloidal stabilities. The appearance of radiating aggregates during the early stage of the precipitation reactions and their pH dependent morphologies indicated that the formation of lanthanide orthophosphate nanorods was mainly governed by the growth nature of hexagonal LaPO4. The optical measurements indicated that LaPO4 ∶ Ce3+ with the rhabdophane structure has stronger electron–phonon coupling than monazite-type. The fluorescence quantum yield of LaPO4 ∶ Ce3+ nanorods was estimated to be 35%. In comparison with rhabdophane nanoparticles, the strongest emission of the Eu3+-doped nanorods originates from the 5D0 to 7F1 transition rather than 5D0 to 7F2. This may be attributed to the nature of the 1D structure as well as the lattice distortions in the nanorods.

Identification of a Functional Phosphatidylinositol 3,4,5-Trisphosphate Binding Site in the Epithelial Na+ Channel

Membrane phospholipids, such as phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P(3)), are signaling molecules that can directly modulate the activity of ion channels, including the epithelial Na(+) channel (ENaC). Whereas PI(3,4,5)P(3) directly activates ENaC, its binding site within the channel has not been identified. We identify here a region of gamma-mENaC just following the second trans-membrane domain (residues 569-583) important to PI(3,4,5)P(3) binding and regulation. Deletion of this track decreases activity of ENaC heterologously expressed in Chinese hamster ovary cells. K-Ras and its first effector phosphoinositide 3-OH kinase (PI3-K), as well as RhoA and its effector phosphatidylinositol 4-phosphate 5-kinase increase ENaC activity. Whereas the former, via generation of PI(3,4,5)P(3), increases ENaC open probability, the latter increases activity by increasing membrane levels of the channel. Deletion of the region just distal to the second trans-membrane domain disrupted regulation by K-Ras and PI3-K but not RhoA and phosphatidylinositol 4-phosphate 5-kinase. Moreover, PI(3,4,5)P(3) binds ENaC with deletion of the region following the second transmembrane domain disrupting this interaction and disrupting direct activation of the channel by PI(3,4,5)P(3). Mutation analysis revealed the importance of conserved positive and negative charged residues as well as bulky amino acids within this region to modulation of ENaC by PI3-K. The current results identify the region just distal to the second trans-membrane domain within gamma-mENaC as being part of a functional PI(3,4,5)P(3) binding site that directly impacts ENaC activity. Phospholipid binding to this site is probably mediated by the positively charged amino acids within this track, with negatively charged and bulky residues also influencing specificity of interactions.

Hydration characteristics of alpha-tricalcium phosphates: Comparison of preparation routes.

Alpha tricalcium phosphate ( á -TCP) cement powders were obtained by solid state reaction and milling (M1) and by precipitation from aqueous solution followed by heating (M2). The materials were hydrated to form calcium-deficient hydroxyapatite (CDHA) with a 2.5 wt% solution of Na2 HPO4 (liquid to powder ratio = 0.34 ml/g, temperature = 37.5 degrees C) and subjected to isothermal calorimetry, mechanical compression tests, X-ray powder diffraction, at various times during hydration, as well as scanning electron microscopy (SEM), laser diffraction and gas adsorption. The particle characteristics of the two powders were similar, but M2 exhibited two reaction events in the thermal power curve, while M1 showed a single event. Both reaction events were attributed to á -TCP dissolution and CDHA recipitation. The minimum in the reaction rate response of M2 was probably due to the formation of a passivating product layer. No such layer was formed on the milled M1 due to its rougher surfaces. Both preparations reached a compressive strength of 30-40 MPa after 24 hr.

Alkali ion substituted calcium phosphate cement formation from mechanically activated reactants

Potassium and sodium containing nanoapatite cements were produced from Ca2KNa(PO4)2 by prolonged high energy ball milling of the compound for up to 24 h. This mechanical treatment resulted in the decrease of the crystal size and a partial amorphisation of the cement reactant as shown by X-ray diffraction analysis and the appearance of strong exothermic peaks in differential scanning calorimetry measurements. The pH of water saturated with Ca2KNa(PO4)2 was 12.5 when the material was mechanically activated but was only 9.5 for the untreated compound suggesting an increase in solubility following milling. The cements set following mixing with a 2.5% Na2HPO4 solution in clinically acceptable times between 5-12 min and showed compressive strengths of up to 11 MPa after 24 h setting. The strong alkaline pH value of the cements may provide antimicrobial potential for an application in dentistry as pulp capping agents or cavity liners or for the treatment of infected bone sites.

Preliminary Investigation of Bone Cement Using Calcium Phosphate Glass

The mixed pastes of binary calcium phosphate glass with Ca/P ratio of 0.6 and distilled water were set after about 4 hr, while never set when calcium phosphate glass with Ca/P lower than 0.5. Their compressive strength was ranged from 16.0 to 23.3 MPa. When Na2HPO4 solution was used instead of distilled water as liquid phase, the setting time became drastically much shorter. As the mole concentration of Na2HPO4 solution increased from 0.25 M to 2 M, setting time was shortened to 35 min from almost 3 hr, but compressive strength decreased from 28.8 MPa to 13.2 MPa. At constant mole concentration, as the mass ratio of a powder to liquid ratio increased, setting time was shortened and maximum compressive strength was measured when a powder/liquid ratio was 2.5. However, no crystallized phases were detected either during setting or after complete setting. The XRD , FT-IR and SEM examinations indicated that calcium phosphate glass dissolved and then glass phase precipitated again. We concluded, therefore, that Na2HPO4 just affected the kinetics of dissolution and precipitation of CPG. The mechanism of hardening has yet to be studied.

Strengthening of Calcium Phosphate Cement by Compounding Calcium Carbonate Whiskers

The purpose of this study was to investigate how aragonite (calcium carbonate) whiskers influenced the strengthening and carbonating of alpha-tricalcium phosphate (alpha-TCP) based calcium phosphate cement. Aragonite whiskers of 0.95 microm width with an aspect ratio of 6.6 were prepared. The cement powder, alpha-TCP containing 0-50 mass% aragonite whisker, was mixed with 0.6 mol/L NaH2PO4 solution and incubated at 37 degrees C and 100% relative humidity. Diametral tensile strength (DTS) value increased significantly when appropriate amount of aragonaite whiskers was added. For example, DTS value of set cement containing 20 mass% aragonite whisker was 5.8 +/- 0.5 MPa, whereas DTS value of set cement containing no whiskers was 1.3 +/- 0.2 MPa after 1-week incubation. SEM observation revealed that the shape of the whiskers and the densification of the structure could have contributed to the strengthening of the set cement. Moreover, FTIR spectra implied that a bone-like carbonated apatite was precipitated in the cement. The results obtained in the present study revealed that the shape as well as any slight dissolution of aragonite whiskers could contribute to improving the properties of a-TCP based calcium phosphate cement.

Formation of Aluminium Oxide Film on Al Substrate by Micro-Arc-Technology in Electrolytic Solution of Sodium Hydroxide Systems

The objective of this study was to form a polycrystalline oxide film on an Al substrate in electrolytic solutions of sodium phosphate using micro-arc-technology, and to consider a mechanism for the formation of the oxide film by type of sodium phosphate. Micro-arc on the Al substrate did not occur in electrolytic solutions of Na3PO4, Na2HPO4 or NaH2PO4, which were mono-sodium phosphate, preventing micro-arc-processing. However, micro-arc-processing was possible on the Al substrate and crystalline Al2O3 films were formed in electrolytic solutions of Na4P2O7 and Na5P3O10, which were poly phosphoric acid. Micro-arc may not have occurred in the mono-phosphoric acid electrolytic solutions because the resistance value of phosphoric acid radical impurities barrier layer is small in comparison with poly phosphoric acid sodium.

DNA network structures on various solid substrates investigated by atomic force microscopy.

We have fabricated DNA network structures on glass and sapphire substrates. As a comparison, we also formed the network structure on mica substrate. For titanate strontium substrate, however, DNA network can not be obtained even if it is wet-treated by Na2HPO4 solution to make it hydrophilic. We also discuss the factors that affect the DNA networks formed on various substrates.

A potentiodynamic and SEM study of the behaviour of iron in pH 8.9‐11.0 phosphate solutions

The behaviour of iron electrodes immersed in pH 8.9‐11.0 Na2HPO4 solutions was studied by potentiodynamic measurements (cyclic voltammetry) and scanning electron microscopy (SEM). The influence of proton and phosphate content, scan rate, anodic switching potential and other devised potential/time perturbation regimes were evaluated in order to obtain an understanding of the reactions involved during the passivation process. The oxidation‐reduction peaks were analysed using a thermodynamic approach. It was possible to reveal the most important reactions coming about on the electrode surface, which comprise, initially, the formation of Fe3(PO4)2 and Fe(OH)2 at ca. −0.8 V/SCE. Subsequently, these ferrous species are further oxidized to γ‐FeOOH at ca. −0.36 V/SCE, the latter being transformed into Fe2O3 in the passive region. Depending on the pH value (11.0) and scan rate (slow), Fe3O4 is clearly present as an intermediate oxide structure between the ferrous and ferric species mentioned earlier. In addition, scan rate was discovered to play a remarkable influence on the surface morphology observed during the SEM examinations.

Amorphous α‐Tricalcium Phosphate: Preparation and Aqueous Setting Reaction

The mechanical and setting properties of calcium phosphate cements are considerably determined by the pretreatment of the constituents. In this report we show for the first time that prolonged high‐energy ball milling of α‐tricalcium phosphate (α‐TCP) led to mechanically induced phase transformation from the crystalline to the amorphous state. The amorphous material demonstrated a high reactivity such that the time for substantially complete conversion of α‐TCP to calcium‐deficient hydroxyapatite in 2.5% Na2HPO4 solution decreased from about 20 h (1 h of grinding in ethanol, 85% relative crystallinity) to 4–6 h for a material with a crystallinity of 8% (24 h of grinding). This reactivity could be attributed to an increased thermodynamic and kinetic solubility of the ground materials. Mechanically activated α‐TCP cements were produced with compressive strengths of up to 80 MPa and setting times of 5–16 min. The effect of reactant preparation and cement mixing parameters on the physical and chemical properties of mechanically activated α‐TCP cement was investigated. By comparing cements of similar porosity and degree of conversion it was demonstrated that apatite specific surface area has a strong influence on cement mechanical performance, which highlights the importance of this previously overlooked parameter in improving strength.

Pitting corrosion behavior of lead in Na2HPO4–NaNO3solutions

The pitting corrosion behavior of lead in 0.10 M Na2HPO4 solutions containing various concentrations from NaNO3 has been studied using potentiodynamic anodic polarization and SEM techniques and complemented by both X-ray and FT-IR surface analysis. Above certain critical NaNO3 concentration, the aggressive anions prevented the oxygen evolution and induce pitting on the Pb electrode surface. Pitting-initiation and pitting-growth were found to depend on the concentration of the aggressive NO−3 anions. Also, some changes in the (I–E) curves within the active, pre-passive and passive regions were recorded. These changes imply mainly the appearance of new stages and peaks. This behavior gives an indication for definite changes in the pit-characteristics, which interpreted in terms of solution composition and kinetics of its associated processes within pits.

Cyclic voltammetry and passivation behaviour of lead in Na2HPO4 solution

Abstract The electrochemical and passivation behaviour of lead electrode in 0.10 mol dm−3 Na2HPO4 solution was studied using cyclic voltammetric technique and complemented by X-ray surface analysis. The anodic half-cycle of the voltammogram exhibits active, pre-passive, passive and transpassive regions before the oxygen evolution. Passivity is due to the formation of thick porous PbO film by three-dimensional nucleation and growth on the electrode surface. The transpassive region is attributed to the electroformation of PbO2. The cathodic half-cycle shows two cathodic peaks as well as a small shoulder at the extreme negative potential just before the hydrogen evolution. The mechanism of formation of the passive film is discussed.

Dual-setting calcium phosphate cement modified with ammonium polyacrylate.

alpha-Tricalcium phosphate bone cement, as formerly designed and developed by Driessens et al., consists of a powder composed by alpha-tricalcium phosphate (alpha-TCP) and hydroxyapatite (HA) seeds, and an aqueous solution of Na2HPO4 as mixing liquid. After mixing powder and liquid, alpha-TCP dissolves into the liquid and calcium deficient hydroxyapatite (CDHA), more insoluble than the former, precipitates as an entanglement of crystals, which causes the setting and hardening of the cement. alpha-TCP bone cement offers several advantages in comparison to calcium phosphate bioceramics and acrylic bone cements as bone graft and repairing material, like perfect adaptability to the defect size and shape, osteotransductibility, and absence of thermal effect during setting. The main handicap is its low mechanical strength. Therefore, approaching its mechanical strength to that of human bone could considerably extend its applications. In the present work, an in situ polymerization system based on acrylamide (AA) and ammonium polyacrylate (PA) as liquid reducer was added to alpha-TCP cement to increase its mechanical strength. The results showed that the addition of 20 wt% of acrylamide and 1 wt% AP to the liquid increased the compressive and tensile strength of alpha-TCP bone cement by 149 and 69% (55 and 21 MPa), respectively. The improvement in mechanical strength seems to be caused by a decrease of porosity and the reinforcing effect of a polyacrylamide network coexisting with the entanglement of CDHA crystals. The studied additives do not affect the nature of the final product of the setting reaction, CDHA, but promote the reduction of its crystal size.

The Effects of S-Chitosan on the Physical Properties of Calcium Phosphate Cements

Water-soluble disodium (1→4)-2-deoxy-2-sulfoamino-β-d-glucopyranuronan (S-chitosan) was prepared from chitin by successive N-deacetylation, specific carboxylation at C-6 and sulfonation. Its structure was characterized by IR spectra and elemental analysis. The S-chitosan was added to two easily developed calcium phosphate cements (CPCs). One cement was monocalcium phosphate monohydrate (MPCM) with calcium oxide (CaO) in a 1M phosphate buffer (pH 7.4)(CPC-I); the other cement was dicalcium phosphate dihydrate (DCPD) with calcium hydroxide [Ca(OH)2] in a 1M Na2HPO4 solution (CPC-II). In vitro experiments showed that when S-chitosan where added to the liquid phases that the resulting S-chitosan containing CPCs had higher mechanical strengths and slightly prolonged setting times. The polyanion enhanced the mechanical strength of the CPCs by increasing the dissolubility of the cement start materials and binding the calcium ions strongly afterwards. An excess of the polyanion destroys the balances of the formulations of CPCs and lead to very slow setting processes or no setting at all.

Behaviour of intact and scratched phosphate coatings on zinc, zinc–nickel and mild steel in dilute sodium phosphate solution

Impedance measurements were performed at room temperature in a 0.005 M Na2HPO4 solution on steel and on electrodeposited Zn and Zn–12%Ni before and after phosphating. It was found that potential and impedance parameters (Rct and Cd) for phosphated materials attained nearly steady values within about 20 min, indicating that this solution did not cause meaningful changes in phosphate coatings and that it could therefore be used for the quality evaluation of these coatings. On scratches in phosphate coatings on Zn or Zn–12%Ni phosphate deposits rapidly formed, probably owing to enhanced dissolution of the locally exposed substrates at the nobler potentials of the coated materials. This demonstrates that damaged coatings can easily recover on Zn substrates in a non-aggressive phosphate solution. It is suggested that the formation of phosphate deposits on bare metal amidst phosphate coatings should be taken into account in the porosity determination by chemical or electrochemical methods.