Ppm Si Research Articles

Precipitates in Al–Cu alloys revisited: Atom-probe tomographic experiments and first-principles calculations of compositional evolution and interfacial segregation

Atom-probe tomography, transmission electron microscopy, X-ray diffraction and first-principles calculations are employed to study: (i) compositional evolution of GPII zones and θ′ precipitates; and (ii) solute segregation at α-Al/ θ′ interfaces in Al–1.7 at.% Cu (Al–4 wt.% Cu) alloys. GPII zones are observed after aging at 438 K for 8 h, whereas higher aging temperatures, 463 K for 8 h and 533 K for 4 h, reveal only θ′ precipitates. Most GPII zones and θ′ precipitates are demonstrated to be Cu-deficient at the lower two aging temperatures; only the 533 K treatment resulted in θ′ stoichiometries consistent with the expected Al 2Cu equilibrium composition. For alloys containing ∼200 at. ppm Si we find evidence of Si partitioning to GPII zones and θ′ precipitates. Significant Si segregation is observed at the coherent α-Al/ θ′ interface for aging at 533 K, resulting in an interfacial Si concentration more than 11 times greater than in the α-Al matrix. Importantly, the Si interfacial concentration undergoes a transition from a non-equilibrium delocalized profile to an equilibrium localized profile as the aging temperature is increased from 463 to 533 K. Consistent with these measurements, first-principles calculations predict a strong thermodynamic driving force favoring Si partitioning to Cu sites in θ′. Silicon segregation at, and partitioning to, θ′ precipitates results in a decrease in interfacial free energy, and concomitantly an increase in the nucleation current. Our results suggest that Si catalyzes the early stages of precipitation in these alloys, consistent with the higher precipitate number densities observed in commercial Al–Cu–Si alloys.

ChemInform Abstract: The Properties of Salt-Filled Sodalites. Part 2. Synthesis, Decomposition Reactions and Phase Transitions of Nitrate Sodalite Na8( AlSiO4)6(NO3)2.

Abstract Nitrate sodalites, Na8[AlSiO4]6(NO3)2, have been synthesized hydrothermally (570 K, 0.1 GPa) using zeolite A, sodium nitrate and 8 M NaOH. IR spectroscopy indicates clearly the enclathration of NO3− exclusively within the sodalite cages (absorption band at 1380 cm−1). 29Si-MAS-NMR confirms the alternating ordering of silicon and aluminium in the nitrate sodalite framework, according to a single peak at δ = −86.7 ppm for Si(4Al) units. From the DTA and calorimetric investigations a reversible structural phase transition has been identified for Na8[AlsiO4]6(NO3)2, starting at temperatures between 920 K (DTA) and 930 K (DSC). High temperature Guinier-Simon photographs reveal the onset of a maximal framework expansion of the nitrate sodalite at temperatures Ttr ⩾ > 920 K. The observed thermal decomposition behaviour and the corresponding evaluation of the unit-cell volume indicate special host-guest interactions due to the dynamics of the enclosed NO3−.

Anti-diabetic effects including diabetic nephropathy of anti-osteoporotic trace minerals on diabetic mice

Objective In our previous study to evaluate the effects of soluble silicon (Si) on bone metabolism, Si and coral sand (CS) as a natural Si-containing material suppressed peroxisome proliferator-activated receptor γ (PPARγ), which regulates both glucose and bone metabolism and increases adipogenesis at the expense of osteogenesis, leading to bone loss. In this study, we investigated the anti-diabetic effects of bone-seeking elements, Si and stable strontium (Sr), and CS as a natural material containing these elements using obese diabetic KKAy mice. Methods Weanling male mice were fed diets containing 1% Ca supplemented with CaCO 3 as the control and CS, and diets supplemented with 50 ppm Si or 750 ppm Sr to control diet for 56 d. The mRNA expressions related to energy expenditure in the pancreas and kidney were quantified by real-time polymerase chain reaction. Results At the end of feeding, plasma glucose, insulin, leptin, and adiponectin levels decreased significantly in three test groups, while pancreatic PPARγ and adiponectin mRNA expression levels increased significantly toward the normal level, improving the glucose sensitivity of β-cells and inducing a significant decrease in insulin expression. The renal PPARγ, PPARα, and adiponectin expression levels, histologic indices of diabetic glomerulopathy, and plasma indices of renal function were also improved significantly in the test groups. Conclusion Taken together, anti-osteoporotic trace minerals, Si and Sr, and CS containing them showed novel anti-diabetic effects of lowering blood glucose level, improving the tolerance to insulin, leptin, and adiponectin, and reducing the risk of glomerulopathy through modulation of related gene expression in the pancreas and kidney.

Roles of impurities on precipitation kinetics of dilute Al–Sc alloys

High-purity (HP) aluminum and commercial purity (CP) aluminum (major impurities: ∼250 at. ppm Si and ∼130 at. ppm Fe) are alloyed with ∼250 to ∼1100 at. ppm Sc and ∼50 at. ppm RE (RE = La, Ce, Pr, or Nd). The alloys are homogenized at 640 °C and aged at 300 °C. The precipitation kinetics, basic mechanical properties, and microstructure are studied using AC electrical conductivity, microhardness measurements, scanning electron microscopy in conjunction with energy dispersive X-ray spectroscopy, and atom-probe tomography, respectively. The Fe and RE elements form micrometer-scale diameter Al ∼3(Fe,RE) primary precipitates, which have no effect on the mechanical properties. Silicon accelerates the precipitation kinetics of nanometer-scale diameter Al 3Sc precipitates, increasing their number density, thereby resulting in higher microhardness values for CP aluminum than the HP aluminum having the same Sc concentration. Additionally, the Sc equilibrium solubility in the α-Al matrix is estimated and Orowan's strengthening mechanism is confirmed for the Al 3Sc precipitates.

Silicon alleviates salt stress, decreases malondialdehyde content and affects petal color of salt-stressed cut rose (Rosa xhybrida L.) Hot Lady

A greenhouse experiment was conducted to investigate the effects of different levels of silicon (Si) application on cut rose (Rosa xhybrida L.) ‘Hot Lady’ under two levels of salt stress. Four Si concentrations (0, 50, 100 and 150 ppm) as Si were combined with a 25 mM NaCl (EC ≈ 3.8) level in the nutrient solution supplied to the plants. Addition of Si partially maintained membrane permeability but only fully restored it to control levels in the Si50 and Si100 treatments. 150 ppm Si with or without NaCl could not alleviate or decrease cell wall damages. Inclusion of Si significantly reduced malondialdehyde content and chlorophyll content of salt-stressed plants in all treatments except that of 150 ppm. Maximum chlorophyll content was noticed when 50 ppm Si was supplied. Addition of 50 ppm Si increased the flower number in both plants grown under salinity and unstressed conditions. However, no significant difference was observed between 100 and 50 ppm Si accompanying with NaCl. Plants treated with NaCl alone showed a reduction in plant leaf area, while the reduction in plants treated with NaCl plus 50 and 100 ppm Si were like control and other unstressed plants. Key words: CIELAB, cut rose, ion leakage, malondialdehyde, salt stress, silicon.

Research Paper Silicon alleviates salt stress, decreases malondialdehyde content and affects petal color of saltstressed cut rose (Rosa xhybrida L.) ‘Hot Lady’

A greenhouse experiment was conducted to investigate the effects of different levels of silicon (Si) application on cut rose (Rosa xhybrida L.) ‘Hot Lady’ under two levels of salt stress. Four Si concentrations (0, 50, 100 and 150 ppm) as Si were combined with a 25 mM NaCl (EC
3.8) level in the nutrient solution supplied to the plants. Addition of Si partially maintained membrane permeability but only fully restored it to control levels in the Si50 and Si100 treatments. 150 ppm Si with or without NaCl could not alleviate or decrease cell wall damages. Inclusion of Si significantly reduced malondialdehyde content and chlorophyll content of salt-stressed plants in all treatments except that of 150 ppm. Maximum chlorophyll content was noticed when 50 ppm Si was supplied. Addition of 50 ppm Si increased the flower number in both plants grown under salinity and unstressed conditions. However, no significant difference was observed between 100 and 50 ppm Si accompanying with NaCl. Plants treated with NaCl alone showed a reduction in plant leaf area, while the reduction in plants treated with NaCl plus 50 and 100 ppm Si were like control and other unstressed plants.

Effects of soluble silicon compound and deep-sea water on biochemical and mechanical properties of bone and the related gene expression in mice

Silicon has been known as an essential element for bone formation. The silicon contents of sea water increase with increasing of depth: 1.8 ppm Si in deep-sea water (DW) at 612 m in depth versus 0.06 ppm in surface sea water (SW). The effects of soluble silicon (Si) and DW from which NaCl was eliminated were studied in comparison with tap water (TW) and SW in cell cultures and in animal experiments using the control strain of senescence accelerated mouse, SAMR1. Si at 10 ppm as sodium metasilicate or 10% DW in the alpha-MEM medium stimulated cellular viability, marker enzymes of osteoblast and osteoclast cell lines, and the (45)CaCl(2) uptake in those cells in comparison with the medium control. After weanling SAMR1 were maintained for 6 months on a diet containing 200 ppm Si and 39% of DW and SW, DW and Si improved bone biochemical indices such as femoral weight, mineral and collagen content, and marker enzymes of bone formation and resorption as well as mechanical properties as compared to TW. In the femoral bone marrow of SAMR1, the mRNA expression of bone morphogenetic protein-2 (BMP-2), interleukin-11 (IL-11), and runt-related transcription factor 2 (Runx 2), which stimulate osteoblast development as well as type I procollagen (COL1A1) mRNA, were significantly increased in both DW and Si groups. The expressions of both osteoprotegerin (OPG) and receptor activator of NF-kappaB ligand (RANKL) were also elevated, resulting in distinct increases of the OPG/RANKL ratio in both DW and Si groups. The results indicated that a soluble silicate and deep-sea water as its natural material stimulated cell growth in both osteoblasts and osteoclasts in cell culture and promoted bone metabolic turnover in favor of bone formation through stimulation of the related mRNA expression in animal experiments.

Effects of High Levels of Dietary Silicon on Bone Development of Growing Rats and Turkeys Fed Semi-purified Diets

Two experiments were conducted using a completely randomized design to study the effects of high levels of silicon (Si) supplementation on bone development, structure, and strength in growing rats and turkeys. Rats were supplemented at two dietary Si levels: 0 and 500 ppm; and the turkeys were supplemented at four dietary Si levels: 0, 135, 270, and 540 ppm in semi-purified diets of dextrose-albumin for rats and dextrose-casein for turkeys. The experiments lasted 8 and 4 weeks for the rats and turkeys, respectively. Physical, mechanical, and chemical parameters of bones were measured. All the physical and mechanical measures of bone size and strength were not different (P > 0.05) between treatments in rats and turkeys except the moment of inertia, which was lower (P < 0.01) in rats on the 500 ppm Si level of supplementation. There were small but consistent reductions in structural and strength parameters with Si supplementation which were not wholly due to differences in bodyweights of the rats and turkeys. Although bone mineral composition was not affected (P > 0.05) by Si supplementation, plasma magnesium (P = 0.08) in rats and plasma calcium (P < 0.05) in turkeys were reduced by high levels of Si supplementation. The antagonistic relations of high Si levels with calcium and magnesium were deemed to be the mechanisms through which high Si imposes its deleterious effects on bone size and strength.

Dissolution kinetics of a Si‐rich nanocomposite and its effect on osteoblast gene expression

Silica-calcium phosphate nanocomposite (SCPC) has recently been proposed as a novel resorbable, bioactive, and mechanically compatible template for bone reconstruction. The effect of the physicochemical properties on the surface reactivity and dissolution kinetics of SCPC immersed in simulated body fluid (SBF) was investigated and compared to that of bioactive glass (BG). Moreover, the stimulatory effect on osteoblast gene expression of SCPC was determined using quantitative real-time polymerase chain reaction (qRT-PCR), and compared to that of hydroxyapatite (HA-200). Mercury porosimetry revealed that surface areas of SCPC particles containing 10 (SCPC10), 30 (SCPC30), and 50 (SCPC50) wt % Si-content were 14-, 18-, and 32-times higher than that of BG. Inductively coupled plasma analysis showed that after 192 h of immersion, Si-rich SCPC50 exhibited controlled bulk-dissolution and released 43.1 ppm Si, which was sixfold higher than that released from BG (7.7 ppm). Moreover, SCPC50 showed a rapid Ca-uptake from SBF and developed a surface apatite layer after only 2 h, whereas a similar layer was detected on BG after 8 days of immersion under the same experimental conditions. qRT-PCR revealed that osteopontin and osteocalcin mRNA expression by osteoblast-like cells attached to Si-rich SCPC50 was significantly higher than that on HA-200 or polystyrene after 2 days in culture. This suggested a role of dissolved Si in stimulating the differentiation and mineralization of osteoblast precursor cells. The favorable physiochemical and bioactivity properties of Si-rich SCPC nanocomposite indicate that SCPC can have wide applications as a synthetic bone graft for cell delivery applications in tissue engineering.

EFFECT OF DIFFERENT NUTRITION SOLUTION PROGRAMS ON REDUCING VEGETABLES FUNGAL DISEASES TO PRODUCE HIGH QUALITY AND SAFETY VEGETABLES PRODUCTS

The effects of different nutrition solutions especially the addition of silicon (Si) and calcium (Ca) on cucumber downy mildew disease were examined. Cucumber plants grown under greenhouse were treated with nutrient solutions amended with different concentration of Si and Ca. Selected leaves inoculated with sporangia of the pathogen. Percentage of infected leaves and disease severity observed in inoculated plants were significantly reduced when nutrient solution amended with Si or Ca. Best results were obtained in nutrient solution amended with 100 ppm Si.

Consequences of Silicon Segregation on the Dielectric Properties of Sintered Alumina

The dielectric breakdown strengths of two series of sintered alumina samples of low and high impurity content (where Si is the dominant element with, respectively, 90 and 1500 ppm) and impurity level (25 ppm of Si and 12 ppm of Ti) are compared with positron lifetime measurements. The dielectric breakdown strength of sintered alumina is found higher than that of single crystal. This improvement is stronger when silicon is the only major foreign element. If, in addition to SiO2, MgO and CaO are present in substantial amounts, the improvement is lessened. This is attributed to the enhanced bulk solubility of Si. These results are discussed by calling for the potential traps for positrons and electrons that are located at grain boundaries. It is deduced that the improvement of the dielectric breakdown strength stems from the consequences of Si segregation at grain boundaries via electron trapping in shallow traps, which are likely the x '' Al • Al ) V : (3Si clusters.

Critical Anode Potential in the Chlorate Process

Anodic polarization curves on dimensionally stable anodes (DSAs) of in chlorate electrolyte bend to a higher Tafel slope at the critical potential of approximately 1.2 V vs . Operating the chlorate process above leads to increased oxygen evolution and higher potential losses. In this study the impact of different electrolyte parameters and electrolyte impurities on the risk of reaching∕exceeding was investigated. A dependency of concentration on of about was found at pH 2. An addition of to chlorate electrolyte is necessary in order to keep a high current efficiency on the cathode but was found to increase the anode potential and thereby increase the risk of exceeding at galvanostatic operation. Additions of impurities as or 100 ppm Si (added as ) resulted in increased anode potentials, but adding or HF did not have significant short-term impact on the potential. The anode potential as well as decreased with increased temperature. A high temperature is beneficial in terms of the decreased anode potential, which outweighs the negative effect of a decrease in .

Quantitative Determination of Silanol in Quartz Applying Diffuse Reflectance Infrared Fourier Transform and Chemometrics

The silanol concentration of quartz was determined by mixing 50 mg ground silica sample with 500 mg KBr followed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and chemometric data analysis. Reference samples were prepared by blending ground quartz of different silanol content. Good correlation was achieved between 10 and 240 ppm Si-OH by mass. The chemometric model's quality is characterized by a correlation coefficient of 0.965 (cross-validation) using five latent variables (factors) and a root mean square error of calibration (RMSEC) of 7 ppm. Chemometric data is compared to results from univariate data analysis. The biggest impact on the reproducibility is due to sample preparation (grinding and blending), which is dependant on the operator involved.

Perrhenate uptake by iron and aluminum oxyhydroxides: an analogue for pertechnetate incorporation in Hanford waste tank sludges.

Perrhenate (ReO4-), a nonradioactive surrogate for pertechnetate (99TcO4-), was partitioned during precipitation and aging of iron and aluminum oxyhydroxide solids from aqueous simulants of high-level nuclear waste stored at Hanford, WA. Neutralization of acidic metal nitrate solutions (Al/Fe mole ratio 0.25 and 13.5; 40 ppm Re) to a final pH > 13, followed by aging at 90 degrees C for up to 18 weeks, resulted in substantial amounts of reversibly sorbed Re (approximately 1-10 ppm). Irreversibly sorbed Re increased in the Fe-dominated system with aging, reaching a final value of approximately 83 ppb after 168 h, in a mixture of hematite with minor goethite. Irreversibly sorbed Re in the Al-dominated system generally decreased with time to approximately 30 ppb after 18 weeks in solids dominated by boehmite. Increasing the total amount of Re to 1000 ppm increased the extent of irreversible sorption. The presence of 100 ppm Si prevented transformation of and irreversible Re uptake by ferrihydrite in Fe-dominated systems. In Al-dominated systems, 200 ppm Ni prevented hematite formation but did not affect perrhenate uptake. Results suggest that 5% of the 99Tc inventory in the Hanford waste tanks may be associated with the sludges, and approximately 0.5% incorporated into the solids under oxidizing conditions.

Determination of trace amounts of Mn, Al, Si and Cr in Fe-based alloys by radio-frequency-powered glow-discharge optical emission spectrometry associated with the bias-current conduction method

In an r.f. glow-discharge plasma, a d.c. bias current can be introduced by connecting an electric circuit comprising a low-pass filter and a variable resistor. The bias current promotes the emission excitations in the plasma, leading to an improvement of the detection power in the optical-emission spectrometry. By conducting a bias current of 27 mA, the emission intensities of the atomic resonance lines were several-times larger than those obtained with conventional r.f.-powered plasmas. The detection limits for the determination of alloyed elements in Fe-based low-alloyed standard samples were estimated to be 2 ppm Mn for Mn I 403.08 nm, 2 ppm Al for Al I 396.15 nm, 7 ppm Si for Si I 288.158 nm, and 8 ppm Cr for Cr I 425.43 nm.

Isotopic composition of silicon measured by multicollector plasma source mass spectrometry in dry plasma mode

Precise Si isotopic fractionation in silica (quartz), opal (diatomite, sponges) and standards have been determined employing a Nu Instruments Plasma multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) in dry plasma mode, using a Cetac Aridus desolvating nebulization system. Variations in sample 28Si/29Si ratios are expressed as δ29Si units, which represent deviations in ‰ from the same ratio of the NBS28 standard measured using the standard-sample bracketing technique. We measured Mg isotopes in dynamic mode for adequate correction of instrumental mass bias, applying the fractionation exponential law and external normalisation. The repeatability and the internal precision on the δ29Si measurements of a 1 ppm Si solution in diluted HF/HCl is better than ±0.1‰ (±2 σ). The accuracy has been assessed by cross analyses of an in-house standard with the laser fluorination-isotope ratio mass spectrometry (IRMS). The dry plasma methodology improves the sensitivity more than ten times compared to wet plasma MC-ICP-MS and hence is of great relevance regarding environmental, biogeochemical and geological sciences where Si isotopes open up a range of new studies.

Abstracts from Other Presentations at the International Symposium on Toxins and Natural Products in Honor of Professor Anthony T. Tu

Abstracts from Other Presentations at the International Symposium on Toxins and Natural Products in Honor of Professor Anthony T. Tu

Analysis of Ferrite Powder Using Inductively Coupled Plasma Atomic Emission Spectrometry

Two kinds of ferrite powder were analyzed by inductively coupled plasma atomic emission spectrometry. High-grade Fe2O3 powder containing about 30 ppm Si and Al was analyzed directly by slurry injection while relatively impure Fe2O3 was dissolved by high-pressure acid digestion followed by matrix elimination. For slurry injection a solution containing 1% Fe2O3 powder was adjusted to pH 3 to stabilize the suspension electrostatically. Since the signal difference between a slurry and an aqueous solution for calibration was too large under the normal operating conditions of 1.1-kW forward power, the aerosol gas flow rate was optimized to minimize the difference. Relative standard deviations less than 2.6% were obtained and the results were comparable to those of acid digestion. For matrix elimination, an anion-exchange resin was used for the determination of Al, Ca, and Na and a cation-exchange resin was used for Si. The acidity of the solution prepared by high-pressure acid digestion was controlled by adding HCl for adsorption on the ion-exchange resin. The recoveries for Al, Ca, and Na were higher than 94% and that for Si was 85%.

Effect of Orientation and Purity on the Dynamic Recrystallization of Aluminum Single Crystals with Multi Glide Systems

The effects of crystal orientations and purities on the dynamic recrystallization of aluminum were investigated using constant-compression-speed testing. Three multiple-glide-orientation single crystals ([111], [100], and [110] of 99.999 mass% purity) were compressed in the temperature range from 413 to 653 K. Regular multipeak stress oscillations were generated in the three orientations above 453 K. The [111] single crystals showed a primary peak stress at the lowest strain, and the highest work hardening rate up to the primary peak stress. The effect of purities were also investigated using [111] single crystals during 533 K compression tests. Regular multipeak stress oscillations were generated in 99.999 and 99.9999 mass% aluminum while a monotonous work hardening occurred in 99.99 mass% aluminum. The comparison test using [111] single crystals with different Si content revealed that a regular multipeak stress oscillation was generated in 2 mass ppm Si while a monotonous work hardening occurred in 25 mass ppm Si. These observations demonstrated that the dynamic recrystallization of pure aluminum is controlled not only by the accumulation rate of the strain energy but also by the grain boundary mobility restricted by trace impurities.

Copper-silicon interaction studies in young, rapidly growing turkeys fed semipurified starter diets.

A 3x3 factorial experiment was conducted to study the interactions between Cu and Si in growing turkeys fed a basal dextrose-casein semipurified diet supplemented at 0, 270, and 540 ppm Si, and 2, 8, and 75 ppm Cu levels of inclusion. There were no significant (p>0.05) Cu, Si, or Cu-Si interaction effects on turkey growth. However, there were significant (p<0.05) Si effects on hemoglobin concentrations, and Cu-Si interaction effects on hematocrit and plasma Mg levels (p<0.01). Plasma Ca, P, Zn, Cu, total cholesterol, and serum alkaline phosphatase activity were not affected (p>0.05) by Cu, Si, or Cu-Si interaction. Heart and liver weights were affected (p<0.05) by the Cu-Si interaction. In general, a 8-ppm Cu supplemental level prevented cardiac hypertrophy only in the presence of 270 or 540 ppm Si inclusion in the diets. There were significant (p<0.05) Cu effects on liver Cu and Mn and heart Zn concentrations, Si effects on liver Mn levels, and Cu-Si interaction on liver Zn concentrations. Within the 0- and 270-ppm Si groups, Cu-deficient turkeys (2 ppm Cu) had higher liver Zn levels but not within the 540-ppm Si group. The Cu-Si interaction did not affect (p>0.05) concentrations of Cu in the heart and liver tissues. It is postulated that the Cu-Si interactions demonstrated in this study could have profound implications on the cardiovascular and skeletal health of birds.