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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The objective of this study was to determine the in vitro corrosion products that resulted from crevice corrosion of low- and high-copper dental amalgams. Specimens were potentiostatically polarized in a chloride-containing electrolyte while set against a PTFE surface to form a crevice. After 16 h, corrosion products were examined by light microscopy, SEM, EDS, and XRD. Analysis showed the presence of three previously reported products [Sn4(OH)6Cl2, SnO, and Cu2O] and a new product, CuCl, which formed on high-copper, gamma 2-free amalgams. Thermodynamic considerations show that CuCl is stable for the reported in vivo potentials of amalgam restorations and the high acidity and high chloride ion concentration associated with crevice corrosion.
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PMID:Crevice corrosion products of dental amalgam. 206 90

A single particle and four blended Cu-rich amalgam systems were immersed in 37 degrees C solutions for 1-20 months in order to determine the characterization and sequence of corrosion product formation. X-ray diffraction and SEM/EDS were used to characterize the products. The same sequence of formation occurred in all systems in Ringer's and 0.1% Ringer's solutions. The times at which each product formed varied with the brand of the amalgam and the concentration of the solution. The initial products were ZnSn(OH)6 in Zn-containing systems and SnO2 in most other systems. Cu2O formed next, followed by CuCl2 X 3Cu(OH)2. Immersion in 1% Na2S yielded only HgS on all brands. A combination of 1% Na2S and Ringer's solution yielded CaSn(OH)6 after 2 months and Cu2O at later periods. Artificial saliva resulted in a retardation of corrosion product formation and only limited amounts of a Sn-rich product could be found after 20 months. Interactions of the various components appear to alter the nature and rate of corrosion product formation on these systems and additional systematic investigations are necessary to understand the influence of these interactions on corrosion.
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PMID:Corrosion product formation sequence on Cu-rich amalgams in various solutions. 665 29

In addition to Sn-rich corrosion products found in conventional amalgams, Cu-rich amalgams also form Cu-containing corrosion products. The nature of these Cu-rich products was investigated by immersion of samples of 13 Cu-rich amalgam systems in Ringer's solution for prolonged periods. SEM/EDS and x-ray diffraction studies were used to identify the compounds formed and their morphology. Two products were identified: Cu2O, a red product, and CuCl2 . 3Cu(OH)2, a green product.
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PMID:Cu2O and CuCl2 . 3Cu(OH)2 corrosion products on copper rich dental amalgams. 705 64

Copper corrosion in the presence of orthophosphate and chlorine has indicated the formation of a protective scale containing either CuO or Cu2O depending on the pH. Furthermore, the scale forms relatively quickly, after 15 days of immersion EIS showed very little change. The scale is initially porous, but after prolonged immersion, the porous structure disappears, as evidenced by SEM. The equivalent circuit that is used to model the EIS spectra fits the data well and yields useful information on values, such as Rct, which varies from 2 to 10 kohms and Rfilm, which varies from 15 to 80 kohms when the immersion time is extended from 2 to 30 days.
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PMID:Copper corrosion kinetics and mechanisms in the presence of chlorine and orthophosphate. 1498 66

Two experiments were conducted to study effects of high-level Cu supplementation on measures of Cu status and forage utilization in beef cattle. In Exp. 1, eight steers randomly received an intraruminal bolus containing 12.5 g of CuO needles (n = 4) or no bolus (n = 4). Steers were individually offered free-choice ground limpograss (Hemarthria altissima) hay. On d 12 (Period 1) and d 33 (Period 2) steers were placed in metabolism crates, and total forage refused and feces produced were collected for 7 d. Daily samples of forage offered and refused and of feces excreted for each steer within period were analyzed for DM, ash, NDF, ADF, and CP. Liver biopsies were collected on d 0, 12, and 33. Copper oxide bolus administration resulted in greater (P < 0.03) liver Cu (DM basis) accumulation in Period 1 (556 vs. 296 mg/kg) and Period 2 (640 vs. 327 ppm). Apparent digestibilities of NDF and CP were greater (P < 0.04) for steers receiving no bolus in Period 2 (62.2 vs. 57.1% and 50.2 vs. 43.4% for NDF and CP digestibility, respectively). In Exp. 2, 24 crossbred heifers were assigned to individual pens and received a molasses-cottonseed meal supplement fortified with 0, 15, 60, or 120 ppm of supplemental Cu (Cu sulfate; six pens per treatment). All heifers were offered free-choice access to ground stargrass (Cynodon spp.) hay. Heifer BW and liver biopsies were collected on d 0, 42, and 84. Forage refusal was determined daily, and diet DM digestibility was estimated over a 21-d period beginning on d 42. Heifers consuming 120 ppm of supplemental Cu gained less (P < 0.05; 0.04 kg/d) than heifers consuming 15 (0.19 kg/d) and 60 ppm of Cu (0.22 kg/d), but their ADG did not differ from that by heifers consuming no supplemental Cu (0.14 kg/d; pooled SEM = 0.07). Heifers supplemented with 15 ppm of Cu had greater (P < 0.05) liver Cu concentrations on d 84 than those on the 0-ppm treatment and the high-Cu treatments (60 and 120 ppm). Forage intake was less (P = 0.07) by heifers receiving no supplemental Cu than by heifers on all other treatments (6.6 vs. 5.8 +/- 0.37 kg/d). Apparent forage digestibility was not affected by Cu treatment. These data suggest that high rates of Cu supplementation (Cu sulfate; > 60 ppm of total Cu) resulted in less liver Cu accumulation by beef heifers compared with heifers consuming diets supplemented with moderate dietary Cu concentrations (i.e., 15 ppm). As well, the administration of CuO boluses might depress the digestibility of forage nutrient fractions in steers.
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PMID:Effects of copper oxide bolus administration or high-level copper supplementation on forage utilization and copper status in beef cattle. 1628 29

The Cu2+ release rate of novel copper/low-density polyethylene composites as an intrauterine device material in the simulated uterine solution was investigated for 280 days. The corrosion products of these composites were identified by the X-ray diffraction method. The distributions of the copper phase and the cuprous oxide phase at different corrosion depths in the composites were measured by the internal standard method. For comparison, copper particles of two sizes were embedded in a polyethylene matrix to form composites. The average copper particle diameter of the nanocomposite was 30 nm, while that of microcomposite was 52 microm. Mechanism of Cu2+ release controlled by the nanocomposite revealed that many clusters composed of copper nanoparticles, which were observed by the field emission scanning electron microscopy in the nanocomposite, led to the formation of large amounts of Cu2O and consequently facilitated the Cu2+ steady release. A scanning electron microscope with energy dispersive X-ray microanalysis mapping technique (SEM/EDX) was employed to measure the corrosion depth and to calculate the life span of the nanocomposite. The result that the nanocomposite displayed a near zero-order release after a month of incubation indicated that the Cu2+ release behavior controlled by nanocomposite was remarkably superior to that by microcomposite.
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PMID:Cupric ion release controlled by copper/low-density polyethylene nanocomposite in simulated uterine solution. 1683 55

An optimized procedure was designed for the preparation of the microporous metal-organic framework (MOF) [Cu3(btc)2] (BTC=benzene-1,3,5-tricarboxylate). The crystalline material was characterized by X-ray diffraction, optical microscopy, SEM, X-ray photoelectron spectroscopy, N2 sorption, thermogravimetry, and IR spectroscopy of adsorbed CO. CO adsorbs on a small number of Cu2O impurities, and particularly on the free CuII coordination sites in the framework. [Cu3(btc)2] is a highly selective Lewis acid catalyst for the isomerization of terpene derivatives, such as the rearrangement of alpha-pinene oxide to campholenic aldehyde and the cyclization of citronellal to isopulegol. By using the ethylene ketal of 2-bromopropiophenone as a test substrate, it was demonstrated that the active sites in [Cu3(btc)2] are hard Lewis acids. Catalyst stability, re-usability, and heterogeneity are critically assessed.
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PMID:Probing the Lewis acidity and catalytic activity of the metal-organic framework [Cu3(btc)2] (BTC=benzene-1,3,5-tricarboxylate). 1688 Oct 30

Cuprous oxide nanocubes were successfully prepared in w/o microemulsions by gamma-irradiation in the presence of ethylene glycol (EG). Absorption spectrum, XRD, TEM, HRTEM and SEM were used to characterize the as-prepared nanoparticles. The characteristic peak of Cu2O of absorption spectra of the irradiated microemulsions red-shifts apparently with the EG increasing, showing that the as-prepared Cu2O particle size becomes larger. TEM images verify this point and indicate that Cu2O nanoparticles become uniform with the increase of EG. The results indicated that EG played an important role in the structures of cuprous oxide nanoprticles. Firstly, EG increased the viscosity of water-pools of microemulsions which affected the reactivity of hydrated electrons and finally influenced the reduction of Cu2+ and the precipitation of Cu2O. Secondly, EG reduced the rigidity of the interface of microemulsions and enhanced the mass exchange among water pools which impacted the nucleation and precipitation of Cu2O. Thirdly, EG adsorbed certain crystal faces of Cu2O and influenced the final morphology of Cu2O.
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PMID:[The effect of ethylene glycol on the morphology of Cu2O nanoparticles synthesized in w/o microemulsion by gamma-irradiation]. 1826 Mar 82

This study proposes a new method, the electrical arc discharge system, for preparing a nanocomposite fluid with the basic ingredients of Cu, Fe and O. The proposed system has the advantages of a high-power electric arc heating system, excellent stability of the electric arc, and well-developed control technology. In the fabrication process, the positive electrode uses a copper rod and the negative electrode an iron rod, and the two electrodes are processed in the insulating processing liquid. The nanocomposite fluid generated by the synthesis system is analyzed by morphological analysis, heat transfer analysis, magnetism analysis, and rheological testing. The experiment generates satisfactory results for nanocomposite fluid with an average particle diameter of 25 nm by process conditions of vacuum pressure of 30 torr, peak current of 7 A for arc discharge, breakdown voltage of 250 V and duration time of 10 micros. The experimental results showed that the nanocomposite fluid is composed of Fe, FeO, Cu, and Cu2O. SEM images show that Fe and Cu are spherical, FeO is square, and Cu2O is ovoid. For the heat transfer experiment, the experimental temperature was set at ambient temperature of 30 degrees C, the average heat transfer coefficient is 0.708 W/m oC, which is 16.3% higher than that of deionized water. The magnetism test shows that the magnetic retentivity of the fluid is 47.27 (Oe), which makes it a soft magnetic fluid.
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PMID:Preparation of nanocomposite fluid by electrical arc discharge technique. 1846 30

With H2O-polyols (glycerol, ethylene glycol and polyethylene glycol 400) mix-solvent as media in the NaCl-NaOH-NaNO3 electrolytic system, we developed a simple and efficient electrochemical route for the synthesis of Cu2O nanocrystals with different morphology. The SEM results indicated that electrolytic media and current density had a great influence on the shape of Cu2O crystals. The mono-disperse and uniform sphere Cu2O nanoparticles could be readily obtained in H2O-glycerol (or H2O-ethylene glycol) mix-solvent (1:1 volume ratio) and current density 5 mA/cm2. The sphere Cu2O nanoparticles exhibit excellent adsorption ability for organic dyes (methyl orange, fuchsin acid and methyl blue), which is obviously superior to that of the irregular shape Cu2O crystals prepared in H2O-PEG400 (polyethylene glycol 400) mix-solvent. The present work further confirmed that the adsorption ability of Cu2O crystals was related to their size and shape.
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PMID:Shape-controlled synthesis of cuprous oxide nanocrystals via the electrochemical route with H2O-polyol mix-solvent and their behaviors of adsorption. 2112 79


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