Magnesium Enrichment Research Articles

Enrichment of strontium and magnesium improves the physical, mechanical and biological properties of bioactive glasses undergoing thermal treatments: New cues for biomedical applications

Bioactive glasses (BGs) have emerged as invaluable resources for bone tissue engineering due to their remarkable properties such as bioactivity, resorbability, cell compatibility, and osteoconductivity. However, these materials exhibit certain limitations when subjected to high temperatures, for their tendency to crystallize, thus leading to diminished bioactivity, reduced mechanical strength, and altered dissolution kinetics. One promising approach to counteract this problem is to reduce the alkaline element content in BGs while simultaneously adding strontium and magnesium. Building on previous studies of Bio_MS, a recently developed experimental formulation, we investigated the contributions of strontium and magnesium to the thermal, mechanical, and biological properties of various bioactive glasses, including commercially available options. Differential thermal analysis, heating microscopy, X-ray diffractometry, environmental scanning electron microscopy, measurement of the Young's modulus, simulated body fluid testing, cytotoxicity tests, cell viability, growth, adhesion and morphology were assessed through an integrated approach and compared for a complete evaluation of BGs, and of doped BGs, also undergoing thermal treatments. The results demonstrated improved thermal, mechanical and biological behaviors of the magnesium-strontium-doped BGs, thus paving the way for the development of BGs with enhanced biomedical perspectives.

Tracking fouling layer formation in membrane distillation of landfill leachate concentrate: Insights from periodic membrane autopsies

This study tracked the fouling layer formation in the operation of membrane distillation (MD) for the treatment of landfill leachate concentrate. At periodic intervals, the membrane fouling layer was autopsied by spectroscopic and compositional analyses, to provide insight into foulant evolution and interaction mechanisms. Results show that water flux declined rapidly at the beginning of MD operation as protein and sodium chloride (NaCl) preferentially attached and crystalized onto the membrane surface, respectively, to initiate the formation of fouling layer. Such decline became relatively smooth between the water recovery of 20–30% due to the interaction of humic acid with protein which slightly aggravated organic fouling and thus increased membrane surface hydrophilicity. Nevertheless, the enrichment of calcium (Ca2+) and magnesium (Mg2+) ions with further water recovery from leachate concentrate bridged organic foulants, particularly polysaccharide and humic acid, to further thicken the hydrophilic fouling layer to reduce water flux. Indeed, compositional quantification also evidenced a considerable increase in the content of humic acid and divalent cations (Ca2+ and Mg2+) in the fouling layer after a water recovery of 30%.

Geochemistry and Genesis of Magnesium Tourmalines in Jian Forsterite Jade Deposits from Ji’an County, Jilin Province, Northeast China

The Jian forsterite jade, so named because of its enrichment in end-member forsterite, is a new type of jade found in Ji’an County (Jilin Province, Northeast China). Tourmaline is discovered in Jian forsterite jade deposits and is characterized by magnesium enrichment. In this study, three types of magnesium tourmaline were identified from the pegmatite veins (type 1), the contact zone (type 2), and the tourmaline veins in jade (type 3). The results are shown by the main test methods, such as EPMA, Micro-XRF, and LA-ICP-MS. The substitutions of Fe2+−1Mg2+−1, (□Al3+)−1 (Na+Mg2+)−1, (□Al3+2)−1 (Ca2+R2+2)−1, etc. are inferred by the variations in the major element compositions. From type 1 to type 2 tourmaline, the content of Mg, Sr, and Sn gradually increases, the content of Fe, Zn, K, Mn, Sc, Ga, and Co gradually decreases, the content of Ca initially decreases and then increases, and the content of Na initially increases and then decreases. Type 3 tourmaline has significantly higher Si and Al than the first two types, and the content of the remaining elements lies between the above two types. We propose that tourmalines in Jian forsterite jade deposits are typically of hydrothermal origins and are mainly constrained by magnesium, which is related to the contact metasomatic metamorphism of pegmatite-related hydrothermal fluid with the Jian forsterite jade, and the chemical composition of tourmaline indicates the fluid characteristics of gradual serpentinization of Jian forsterite jade.

The enigmatic enrichment of potassium and magnesium in runoff and floodwater in the Negev: Do biocrusts hold the key?

Regardless of lithology and plant cover, chemical composition of floodwater in the Negev show a consistent enrichment in K+ and Mg2+ ions, which could not have been explained by the rock or clay minerals or (due to the scarcity of plants) by plant decomposition. Hypothesizing that rock-dwelling (lithobionts) or soil (loess)-dwelling biocrusts may shed light on the phenomena, we conducted sprinkling experiments in the Negev Highlands. Sprinkling was conducted on 4 types of lithobionts: cyanobacteria which inhabit the south-facing bedrock (ENC), epilithic lichens, inhabiting the inclined (EPIi) and the flat (EPIf) north-facing bedrocks, and endolithic lichens (ENL) inhabiting south-facing boulders. Additional sprinkling took place on two types of soil biocrusts, a mixed crust composed of cyanobacteria, lichens and mosses at the north-facing footslope and a cyanobacterial crust at the more xeric south-facing footslope. The runoff water (of 5 and for 4 plots for each lithobiont and soil biocrust type, respectively) was analyzed for the ionic composition of Na+, K+, Mg2+, Ca2+, NH4+, Cl−, SO42−, and NO3−, whereas HCO3− was calculated. In comparison to rainwater, all habitats (except for K+ in ENL) showed high enrichment ratios (ERs) in K+ and Mg2+, which, unlike the high ERs of the other ions (such as SO42− that may stem from gypsum dissolution), could not have been explained by the rock lithology, clay or dust composition. It is suggested that following wetting, K+, serving for osmoregulation of cells, is released by the crust organisms, being thus responsible for K+ enrichment, while chlorophyll degradation is responsible for Mg2+ enrichment. It is suggested that rock- and soil-dwelling microorganisms may explain K+ and Mg2+ enrichment in runoff and floodwater and subsequently in groundwater of the Negev, and possibly in other arid zones worldwide, affecting in turn the quality of irrigation and drinking water.

Influence of porosity network on the chemo-mechanical evolution of low-pH cementitious materials subjected to calcareous attack

This paper presents a study which aims to understand the degradation mechanisms induced in a low-pH cementitious matrix by a calcareous attack and then, to evaluate the porosity network influence on the degradation scenario. To reach these goals, three experimental campaigns were carried out in parallel. Hardened low-pH cement paste samples were made in laboratory-controlled conditions, then immersed in calcareous water containing a small amount of water. Concrete samples were then cast in industrial conditions, cured in a controlled environment, then immersed in the same experimental device. Finally, massive concrete blocks were cast and cured outside with industrial processes before immersion in the attack water. Chemo-mechanical characterizations (SEM, µCT, micro/nano-indentation) were performed to estimate the degradation state of the samples. Geochemical modelling was performed to validate experimental observations. Calcium and magnesium enrichment are the main phenomena in all cases. However, the degradation scenario changes with the curing protocol. Porosity closing is observed in samples cured in a controlled environment, whereas industrial curing conditions induce non-negligible chemical alteration due to a skin effect.

Comparison of the chemo-mechanical behavior of low-pH cement exposed to calcareous water and to argillite pore water

This paper focuses on the impact of ground water on the chemo-mechanical behavior of low-pH cementitious materials. Two kinds of ground water are considered, calcareous water and argillite pore water. A sample of low-pH cement paste was immersed for two months in each solution. Chemo-mechanical characterizations (SEM, C-14 PMMA autoradiography, nano-indentation) were performed to estimate the degradation state of the samples. Then, geochemical modelling was performed to validate experimental observations. The decalcification of C–S–H, the dissolution of ettringite and a magnesium enrichment are the main phenomena in both cases. However, we observe a larger and deeper increase of porosity when the calcareous water is in contact with the cementitious material. The chemical modifications linked to the increase of porosity tend to locally decrease the mechanical strength of the cementitious matrix.

Effect of the level of magnesium in drinking water on the state of the cardiovascular system of spontaneous hypertensive rats

INTRODUCTION. Magnesium is the second most common intracellular cation, is a cofactor for more than 300 enzymes, affects the functional state of the cardiovascular system through various mechanisms, in particular, through the action on the smooth muscle cells of the vessels, modulation of the renin-angiotensin-aldosterone system, regulation of sodium and calcium homeostasis. Therefore, maintaining a normal level of magnesium in the blood is an urgent task, and the consumption of drinking water enriched with magnesium can be considered as a method of correcting an insufficient intake of exogenous magnesium.THE AIM. The purpose of the study was determined – to evaluate the effect of drinking water with different contents of magnesium ions and a complex of magnesium with calcium on the state of the cardiovascular system of rats with genetically determined arterial hypertension. MATERIALS AND METHODS. From 6–7 weeks of age, male SHR rats received drinking water of various compositions for two months: in the first group (hCа+Mg) – with increased content of calcium and magnesium (120 mg/l Ca2+ and 45 mg/l Mg2+), the second (nCа+Mg) – drinking water normalized by mineral composition (60 mg/l Ca2+ and 25 mg/l Mg2+), in the third (hMg) – enriched Mg2+ (45 mg/l), the fourth (control) control group – St. Petersburg tap water with a low mineral content (8 mg/l Ca2+ and 3 mg/l Mg2+). WKY rats were divided into 2 groups: one group (hMg) received water enriched with Mg2+ (45 mg/l), the control WKY (control) group received water with a low mineral content (8 mg/l Ca2+ and 3 mg/l Mg2+). After 2 months, the blood pressure of rats on the tail was measured by the cuff method, the level of urea, cholesterol, total calcium, and albumin in the blood serum was analyzed, left ventricular mass index (LVMI) and myocardial mass index (MMI) were calculated. The spontaneous contractile activity of the portal vein (PV) was recorded by myography (in vitro) in isometric mode. The following were analyzed: frequency, total and maximum amplitude of phase-tonic contractions, the area under the contraction curve in 1 min, which characterizes the work performed by the vein. %). RESULTS. Enrichment of drinking water with Ca2+ and Mg2+ had a more pronounced antihypertensive effect in SHR rats compared with the hMg2+ group. In WKY rats, magnesium enrichment of water did not affect blood pressure. Modification of the mineral composition of drinking water did not affect MMI and LVMI in both SHR and WKY rats. Interlinear differences were found in the contractile activity of PV in control rats (the amplitude of PV contractions in SHR rats was greater than WKY. Consumption of water enriched with minerals decreased the amplitude of PV contractions, the largest decrease was in the hMg2+ group (in SHR, 2.6 times, in WKY, 1.5 times as compared to the control of the corresponding line). The value of the work performed by the PV in the control SHR rats was greater than in the control rats of the WKY line, and the enrichment of water with magnesium caused a decrease in the work performed by the PV only in rats SHR lines (by 55.6 %), but not for WKY. CONCLUSIONS. In rats, the consumption of drinking water enriched only with magnesium has an antihypertensive effect; however, it suppresses the spontaneous contractile activity of PV. It is advisable to use a complex of magnesium with calcium, which lowers blood pressure, but maintains an adequate level of contractile activity of the PV.

Compositional Variations of Apatite and REE-Bearing Minerals in Relation to Crystallization Trends in the Monchepluton Layered Complex (Kola Peninsula)

Abstract ––We have investigated the compositional variations of apatite (Ap) and rare-earth element (REE) minerals in the Monchepluton layered complex on the Kola Peninsula. On the basis of large sets of pertinent analytical data, we have estimated geochemical trends involving major, minor, and trace elements and studied their relation with the compositions of rock-forming silicate and oxide minerals. The variations observed in Ap differ considerably from trends reported for other layered intrusions. The composition fields of Ap are not consistent with the variations in the chemical composition of the bulk rocks and their constituent minerals, as determined along the representative cross sections of the entire complex. The compositional variations of Ap are fairly similar in all units of the complex. Chlorapatite (>6 wt.% Cl) is invariably abundant. There is no relationship between the Cl content of Ap and the degree of magnesium enrichment of the coexisting early magmatic silicates. In the F–Cl–OH diagram, broad fields of ternary solid solution are observed. There are no compositions along the Cl–F axis. The compositions of Ap are notably poor in Cl in the marginal series (the Nyud massif) and correspond to hydroxylapatite with a high content of fluorapatite component. Two composition fields of Ap are recognized in the Monchepluton complex: ≤3 wt.% and >6 wt.% Cl; there are, however, extensive overlaps. Two generations of apatite are thus implied. The first nucleated at the early stage of crystallization of H2O-bearing intercumulus melt as a result of substantial increase in the contents of P, F, Cl, and other incompatible components. The following stage of degassing of the crystallizing melt caused a decoupling of Cl and F. Fluorine remained mostly in the melt; in contrast, Cl was partitioned efficiently into an H2O-bearing fluid phase. At the early stage, the apatite incorporated combinations of hydroxylapatite and fluorapatite, with a low content of Cl. At the late stage, chlorapatite crystallized from a Cl-rich fluid, and ferrochloropargasite (4.1 wt.% Cl) formed in the Poaz massif as a result of autometasomatic alteration via reactions of this fluid with plagioclase and pyroxene. The apatite has high Sr contents (up to 4.1 wt.% SrO) in the highly magnesian cumulates of the Dunite block and the massifs of mounts Kumuzh’ya, Nittis, and Travyanaya. This enrichment illustrates the accumulation of Sr in the intercumulus melt, in which Ap was the only Sr-bearing phase in the absence or scarcity of intercumulus plagioclase. The REE contents also increased in the intercumulus melt and led to the formation of monazite-(Ce), REE-bearing Ap, and allanite-(Ce) in the remaining microvolumes of melt. Loveringite and Ap crystallized as coexisting phases in Mt. Sopcha. For the first time in a layered intrusion, an extensive range of compositions is documented in the Ce–La–Nd diagram for the REE-bearing phosphates (monazite and REE-rich apatite), which display a predominant La ↔ Nd substitution at the constant contents of Ce.

Significance of isotopic and geochemical methods to determine the evolution of inland brackish and bitter water: An example from the Zuli river in the upper reaches of the Yellow River, China

AbstractWith the increasing demand for water resources, the utilization of marginal water resources of poor‐quality has become a focus of attention. The brackish water developed in the Loess Plateau is not only salty but also famous for its ‘bitterness’. In the present work, multi‐isotope analysis (Sr, B) was combined with geochemical analysis to gain insight into the hydrogeochemical evolution and formation mechanisms of brackish water. These results demonstrate that groundwater in the headwater is influenced by carbonate weathering. After the confluence of several tributaries in the headwater, the total dissolved solids (TDS) of water is significantly increased. The dissolution of evaporates is shown to be the main source of salinity in brackish water, which also greatly affects the strontium isotopic composition of water. This includes the dissolution of Mg‐rich minerals, which is the main cause of the bitterness. Furthermore, the release of calcium from the dissolution of gypsum may induce calcite precipitation and incongruent dissolution of dolomite, which also contributes to the enrichment of magnesium. The highly fractionated boron isotopic values observed in the upstream groundwater were explained by the absorption with clay minerals. The inflow of brackish groundwater is the source of river water. Then evaporation further aggravates the salinization of river water, with water quality evolving to saline conditions in the lower reach. When the river reaches the valley plain, the 87Sr/86Sr ratios decreases significantly, which is primarily related to erosion of the riverbanks during runoff. These results indicate that water resource sustainability could be enhanced by directing focus to mitigating salinization in the source area of the catchment.

Interfacial Segregation of Alloying Elements During Dissimilar Ultrasonic Welding of AA6111 Aluminum and Ti6Al4V Titanium

Ultrasonic welding is a promising technique for joining dissimilar metals. A particular metal combination of interest to the automotive industry is aluminum-titanium. In such welds, performance is often controlled by processes at the interface, including segregation and intermetallic precipitate formation. This study used high-resolution electron microscopy to investigate this in detail. Enrichment of silicon, magnesium, and oxygen were found at ultrasonic welded aluminum/titanium interfaces; however, other alloying elements such as copper and V were not segregated. Surprisingly, in a very short welding time (1.4 seconds), ~ 4 at. pct of Si was found at the Al/Ti interface. The segregated Si distribution varied inversely with that of O and Mg. The residual oxides and the segregated Si on the Al/Ti interface may act as a barrier for Al3Ti nucleation and growth. The strong chemical attraction between Ti and Si is probably the driving force for Si segregation to the Al/Ti interface. The presence of discontinuous oxides at the Al/Ti weld interface may deteriorate the mechanical properties of the weld.

Modification of the surface layer of magnesium with 1050A aluminum alloy using electrospark deposition

This paper discusses the results of the preliminary investigations into the use of electrospark deposition (ESD) for the surface enrichment of magnesium with 1050A aluminum alloy. The experiments focused on the effects of the capacitor’s value on the surface layer microstructure. Four capacitances were considered. The modified material was analyzed at the macro and micro scales, using optical and electron scanning microscopy. The microhardness of the modified layer was also determined.

Paleoenvironmental considerations based on geochemistry and mineralogy of a Miocene lacustrine calcrete, southern Portugal

A lacustrine carbonate facies has been investigated in Middle Miocene successions of the western side of the Moura-Marmelar basin, Southern Portugal in order to evaluate paleoenvironments in which carbonates formed, by using geochemistry and mineralogy. The studied formation corresponds to a recent unearthed section of a calcrete with an homogeneous carbonate facies comprising fine, whitish, and powdery material, and the only detected difference is a slightly hardness decrease towards the top, as well as an increase of weathered rock fragments (schist). The calcrete is calcium rich, even some magnesium enrichment was observed at the middle level, which is differentiated by a general depletion of all chemical elements, particularly REE, in both the bulk and clay-size fraction. Regarding the mineralogy, calcite prevails, and dolomite is only present in the middle level of the calcrete, together with a smectite enrichment, suggesting changes to more alkaline and low drainage, lacustrine and arid to semi-arid conditions.

Assessment of groundwater quality of Ballia district, Uttar Pradesh, India, with reference to arsenic contamination using multivariate statistical analysis

A total of 22 water quality parameters were selected for the analysis of groundwater samples with reference to arsenic contamination. Samples were collected in the pre-monsoon and monsoon seasons of the year 2013. The maximum arsenic concentration in both the pre-monsoon and monsoon seasons was approximately the same, i.e., the maximum arsenic concentration being 75.60 and 74.46 µg/L in pre-monsoon and monsoon, respectively. Out of 72 collected samples, three were below the WHO guideline value of 10 µg/L for arsenic concentration. In 95.83% of the groundwater samples, the arsenic concentration was above the permissible limit. Nickel, manganese, and chromium concentrations were above the permissible limits in nearly all samples except for chromium concentration in a few pre-monsoon samples. However, the total iron concentrations in 23 samples (31.94%) were above the permissible limit. A total of six and seven principal components (PCs) were extracted using principal component analysis during the pre-monsoon and monsoon seasons, respectively, accounting for 76.25 and 78.52% of the total variation during two consecutive seasons. Correlation statistics revealed that the arsenic concentration was positively correlated with phosphate, iron, ammonium, bicarbonate, and manganese concentrations but negatively correlated with oxidation reduction potential (ORP), sulfate concentration, electrical conductivity, and total dissolved solids concentration. The negative correlation of arsenic with ORP suggested reducing conditions prevailing in the groundwater. The trilinear Piper diagram revealed calcium and magnesium enrichment of groundwater with an abundance of chloride ions but no predominance of bicarbonate ions. Thus, the groundwater fell into Ca2+ − Mg2+ − Cl− − SO42− category.

Evaluation of microstructure stability at the interfaces of Al-6061 welds fabricated using ultrasonic additive manufacturing

Ultrasonic additive manufacturing (UAM) is a solid-state additive manufacturing process that uses fundamental principles of ultrasonic welding and sequential layering of tapes to fabricate complex three-dimensional (3-D) components. One of the factors limiting the use of this technology is the poor tensile strength along the z-axis. Recent work has demonstrated the improvement of the z-axis properties after post-processing treatments. The abnormally high stability of the grains at the interface during post-weld heat treatments is, however, not yet well understood. In this work we use multiscale characterization to understand the stability of the grains during post-weld heat treatments. Aluminum alloy (6061) builds, fabricated using ultrasonic additive manufacturing, were post-weld heat treated at 180, 330 and 580 °C. The grains close to the tape interfaces are stable during post-weld heat treatments at high temperatures (i.e., 580 °C). This is in contrast to rapid grain growth that takes place in the bulk. Transmission electron microscopy and atom-probe tomography display a significant enrichment of oxygen and magnesium near the stable interfaces. Based on the detailed characterization, two mechanisms are proposed and evaluated: nonequilibrium nano-dispersed oxides impeding the grain growth due to grain boundary pinning, or grain boundary segregation of magnesium and oxygen reducing the grain boundary energy.

Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications

Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO3 ) has been successfully applied as a bone regeneration material, but hydrogel-CaCO3 composites have received less attention. Magnesium (Mg) has been used as a component of calcium phosphate biomaterials to stimulate bone-forming cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In the present study, gellan gum (GG) hydrogels were mineralized enzymatically with CaCO3 , Mg-enriched CaCO3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg5 (CO3 )4 (OH)2 .4H2 O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. The calcium:magnesium elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels with calcite or magnesian calcite promoted adhesion and growth of osteoblast-like cells. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity. In conclusion, enzymatic mineralization of GG hydrogels with CaCO3 in the form of calcite successfully reinforced hydrogels and promoted osteoblast-like cell adhesion and growth, but magnesium enrichment had no definitive positive effect. Copyright © 2017 John Wiley & Sons, Ltd.

EFFECT OF ADDITION OF CALCIUM AND MAGNESIUM IN DRINKING WATER ON STATE OF CARDIOVASCULAR SYSTEM IN SPONTANEOUSHYPERTENSIVE RATS

The aim. To assess the effect of enrichment of calcium and magnesium in drinking water on the level of arterial pressure (BP), myocardial remodeling processes, and autorhythmic contractile activity of the portal vein (PV) of spontaneously hypertensive SHR rats and control WKY rats. Material and methods . One group of SHR rats received drinking water enriched with calcium (120 mg/L) and magnesium (45 mg/L) from a 6-week-old age within 2 months. Two other groups of SHR and WKY rats received St. Petersburg tap water with a low content of Са 2+ (8 mg/L) and Mg 2+ (3 mg/L). All groups received a standard diet. At the end of the observation period, rats were assessed with blood pressure, myocardial mass index, urea level (UR), total cholesterol (Chol), total calcium (totalCa) and albumin (Alb) in blood. A contractile activity of PV was investigated by the method of myography (in vitro). The total and maximal amplitude and frequency of contractions of PV, as well as the work done by PV was determined. Results. In SHR rats, the enrichment of drinking water of Са 2+ and Mg 2+ , prevented the progressive rise BP to the level characteristic of the SHR, resulting in its stabilization at 18% lower than in the SHR of the mineral deficient group. Theincreaseinthecontent of Са 2+ and Mg 2+ in drinking water did not affect the degree of myocardial hypertrophy, as well as on the level of UR, totalCa and Alb of blood, but led to a decrease in the level of total cholesterol compared to animals that received low-mineralized water. The options of the autorhythmic contractile activity depended on the mineralization of drinking water. The addition of Са 2+ and Mg 2+ to the drinking water of SHR rats resulted in a decrease in both the amplitude of contractions of PV and the work performed by PV as compared with rats of mineral deficient groups. Conclusion. The researches have shown the important role of mineral composition of drinking water in processes of regulation of a level of arterial pressure. In spontaneously hypertensive SHR rats, the antihypertensive effect of drinking water enrichment with Са 2+ and Mg 2+ has been revealed. The increase in the intake of exogenous calcium and magnesium with water modifies the autorhythmic contractile activity of the portal vein of spontaneously hypertensive SHR rats, normalizing it to a level characteristic of normotensive WKY rats.

Influence of diffusion on the coating adhesion of zinc-magnesium thin films onto steel

Abstract In this study the zinc and magnesium diffusion in ZnMg thin PVD films is examined and linked to the crash adhesion performance of the coating-substrate system. The investigation is conducted at 175 °C because this temperature conforms to both the temperature range during production of the films and the post process steps at automotive customers. The results confirm that zinc is the faster diffusive specie and although the movement of zinc results in a phase transformation, first from magnesium into MgZn2 and later from MgZn2 into Mg2Zn11 this phase change does not seem to alter the crash adhesion performance of the coating substrate system. Additionally, the magnesium seems to diffuse along grain boundaries towards the steel substrate interface. This segregation of magnesium and the enrichment of magnesium at the interface results in a deterioration of the crash adhesion resistance. The time until the samples fail the crash adhesion test is determined by the distance the magnesium has to travel from the Mg containing layer to the steel-substrate interface.

Macroelements in the surface microlayer of water of urban ponds

Abstract Analyses were conducted concerning the accumulation of four metals representing the group of macroelements, i.e. sodium, potassium, calcium and magnesium in two ponds located in the city of Słupsk. Water samples for chemical analyses were collected from the surface microlayer using a Garrett net. At the same time subsurface water samples were collected. Concentrations of metals were determined using a mass spectrometer. Generally, amounts of sodium, potassium, calcium and magnesium were similar in surface microlayer and subsurface water. Only in the case of potassium and calcium was low enrichment observed in the surface microlayer in one pond, while the greatest extent for magnesium enrichment was observed in the spring period.

Study of Blowholes Formation and its Prevention in Nodular Iron Castings

The content of magnesium in various parts of a nodular iron casting is measured by using spectrum analyzer. The results show that the skin of castings has an enrichment of magnesium, and the inner has a gradient distribution of magnesium, not an average distribution. Discussions on the results indicate that bubbles in the liquid metal would not move upward under the action of buoyancy, but migrate toward all directions and the bubble stranded below the surface of the liquid metal form blowholes, because these bubbles can not migrate with the obstruction of oxide films and dendrites. The results of production practices show that increasing carbon equivalent in the liquid metal is helpful to avoid blowhole defects.

Mineralogical Evolution of a Claystone After Reaction With Iron Under Thermal Gradient

AbstractThe design of the repository for high-level nuclear waste (HLW) in France consists of a multiple-barrier system including steel canisters in a clay host rock. The system will undergo temperature variations in time and space, the heat source being the HLW within the canisters. The effect of a thermal gradient in space on the Fe-claystone interaction was investigated here by applying a thermal gradient (150–300°C and 80–150°C) to a mix of claystone, Fe, and an aqueous chloride solution over periods of 3 and 6 months. Following the reaction, the starting clay minerals (mostly illite and mixed-layer illite-smectite) evolved toward chlorite, Fe-serpentine, Fe-saponite, mixed-layer chlorite-smectite, or mixed-layer serpentine-smectite as a function of temperature. Iron corrosion made the medium basic and reductive. Magnesium enrichment of clay minerals was observed in the hottest part of the experiment due to Mg migration under the thermal gradient. Reaction progress was enhanced at the lowest temperatures, compared to batch experiments.