New Fe82-85B13-16Si1Cu1 amorphous alloys with low B content and high B/Si content ratios were synthesized by melt spinning for developing good soft magnetic and high strength materials. The ...crystallization occurs through two stages and the first-stage onset temperature increases from 673 K to 705 K with increasing B content, while the second-stage temperature remains nearly constant. The first and second stages are due to the precipitation of the α-Fe(Si) phase with a size of about 30 nm and the decomposition of the remaining amorphous phase to α-Fe(Si)+Fe3B+Fe2B, respectively. The Fe-based alloys exhibited good soft magnetic properties both in annealed amorphous and nanocrystallized amorphous+α-Fe(Si) phases. The saturated magnetic flux density, coercivity and permeability at 1 kHz are 1.7 T, 4.92 A/m and 7100, respectively, for the annealed amorphous 14B alloy and 1.74 T, 5.62 A/m and 10100, respectively, for the nanocrystallized 13B alloy. The Vickers hardness (Hv) is 803–867 for the as-spun state and it increases with decreasing B content. The Hv increases significantly by crystallization to α-Fe+amorphous phases and reaches 997–1550 for the alloys annealed at 693–763 K just before Tx2. The ultrahigh Hv is presumably due to the combination of fine nanoscale mixed phases, high volume fraction of α-Fe(Si) without internal defects and the enrichment of B into the remaining amorphous phase. Such ultrahigh Hv has not been obtained for Fe-based amorphous and crystallized alloys before and the addition of 1%Cu is essential for the ultrahigh Hv and the amorphous phase formation for the Fe-rich 85%Fe alloy. The new Fe-based alloys are encouraging as future soft magnetic and ultrahigh strength materials with low material cost.
•New Fe82-85B13-16Si1Cu1 amorphous alloys with high B/Si ratios were synthesized.•The Bs, Hc and μ at 1 kHz are 1.74 T, 5.62 A/m and 10100 for the annealed 13%B alloy.•The Vickers hardness increases significantly by annealing and reaches 997–1550.•The addition of 1%Cu is essential for the ultrahigh hardness for the 13%B alloy.
The pressure and dependence on coastal aquifers are on the rise in many parts of the globe. These lead to overexploitation, aggravated levels of groundwater pollution, and seawater intrusion. ...Integrated analyses can create holistic insights into the quality and the vulnerability of aquifers to seawater intrusion. In this study, Mombasa North coast’s coastal aquifer was characterized by integrating multiple approaches—GALDIT overlay index, seawater intrusion groundwater quality index GQI
SWI
, total hardness, water quality index (WQI)—and the results were further explored and interpreted with geospatial analysis techniques. The study suggests that the predominant water type in areas under moderate or high vulnerabilities to seawater intrusion is the Na-Cl water type. However, similar Na-Cl water types can produce a range of total hardness from soft to hard. GQI
SWI
classification can be used to narrow down the observations from Stuyfzand’s TH-based classification system. In the aquifer studied, the results of the GALDIT overlay index, a weighted aggregation of intrinsic parameters contributing to seawater intrusion, show that 29%, 59%, and 12% of the aquifer have low, moderate, and high vulnerabilities, respectively. The GQI
SWI
analysis indicates that the groundwater is largely brackish (68%) but saline towards the southern end of the aquifer at 32%. Total hardness values indicate that 67% of the aquifer’s coverage falls under the “moderately hard” category. The geodatabase creation introduced in the study provides a template for similar studies and a baseline for future WQI and water quality monitoring. However, temporal studies on chronological timescales are recommended for sustainable management of the aquifer.
Particle impact drilling (PID) is a promising technology to enhance the rate of penetration in hard and abrasive formations. The changes to physical and mechanical properties near the crater of a ...full-size tight sandstone sample after successive impacts of a steel-particle water jet are investigated by different scales of rock physics measurements to estimate the range of the damage zone. Similar measurements are also carried out on a sample from the same formation without steel-particle water jet as a reference. The results indicate that: (i) there is a damage zone around the crater with induced cracks and pore collapse caused by the impact stress wave produced by the steel-particle water jet. The dimensionless depth of the damage zone from the crater’s surface is about 0.69 times the jet diameter (
d
0
). Within the damage zone, the dense compaction zone is just near the crater surface within a dimensionless distance of about (0.02–0.06)
d
0
, where the porosity and the permeability slightly decrease, and show significant strength decrease. (ii) The changes of the porosity and the P- and S-wave velocities after steel-particle water jet at core scale are neglectable. Compared to the reference sample, the permeability at the lateral of the crater is (4.52–30.90) times higher, while the permeability beneath the bottom of the crater is 79% lower. The uniaxial compressional strength (UCS) decreases by 15.6%–65.7%. (iii) The indentation hardness after particle jetting shows a significant decrease. The macro-indentation hardness decreases from 1.92 GPa to 1.30 GPa at core scale. Within the damage zone, the hardness and the Young’s modulus calculated from nanoindentation tests decrease with the increase of the distance to the crater’s surface. This work as a case study provides new experimental evidence of the evolution of rock damage by the impact stress of the steel-particle water jet.
Highlights
The dimensionless depth of the damage zone from the crater’s surface is about 0.69 times jet diameter.
Permeability is (4.52–30.90) times higher at the laterals of the crater.
Macro-indentation hardness and UCS decrease significantly in the damage zone.
Nanoindentation hardness decreases with its distance to the crater’s surface.
► The effects of strength and index properties of rocks on rock drillability were investigated. ► The drilling rate index (DRI) of samples were carried out. ► Decreasing linear relationships were ...found among them.
This paper examines the relationships between drilling rate index (DRI) and some mechanical properties of rocks in order to evaluate the effect of strength and indexes of rock on rock drillability. For this purpose, some index properties (in situ Schmidt rebound hardness (SRH), Shore scleroscope hardness (SSH), and point load strength (PLS)) and strength properties (uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS)) values of 32 sedimentary, igneous and metamorphic rock samples were determined. The relationships between DRI and both strength and indexes properties were evaluated using regression analysis and statistical methods. As a result, decreasing linear relationships were found between DRI and uniaxial compressive strength, Schmidt rebound hardness, Shore scleroscope hardness, diametral and axial point load strength.
The continuous galvanizing process (CGP) under high dew point temperature has been recognized as a viable technique for improving the coating quality of advanced high-strength steels (AHSS). However, ...the effect of this surface modification technique on resistance spot welding (RSW) process is not clear. The aim of this study is to investigate the role of different surface conditions and initial microstructures obtained through CGP on mechanical properties and failure behavior of resistance spot welded AHSS. It has been shown that the formation of internal oxides during the annealing and subsequent coating process reduced the heat input during RSW, resulting in smaller nugget size and consequently, lower tensile-shear peak load values. Finite element modeling (FEM) and experimental results indicated that in the case of the as-received sample, higher fusion zone/base-metal (FZ/BM) hardness ratio leads to a failure location closer to heat-affected zone (HAZ). However, the lower FZ/BM hardness ratio in the case of annealed-bare and annealed-coated specimens leads to failure location more towards FZ. It was shown that nugget size will not control the failure location during lap-shear loading but does affect nugget load-carrying capability. However, failure behavior is controlled by microstructural characteristics of different weld regions.
Transparent glass-ceramics containing nanorods are attractive for many applications. In this work, transparent aluminoborosilicate glass-ceramics containing aluminum borate nanorods are reported. ...Effects of Al2O3 and SiO2 concentrations on the thermal properties and crystallization of aluminoborosilicate glasses are studied. It is found that lithium aluminosilicate nanocrystals and Al4B2O9 nanorods are co-precipitated in glasses with Al2O3/SiO2 molar ratios of 0.29 and 0.33, and only Al4B2O9 nanorods are precipitated in glasses with Al2O3/SiO2 molar ratios of 0.375 and 0.42. Precipitation of these nanocrystalline phases leads to the enhancement in Vickers hardness. Glass-ceramics with Al2O3/SiO2 molar ratios of 0.375 and 0.42 are highly transparent in the visible region due to the small size of the Al4B2O9 nanorods precipitated inside.
•Ultra-nano-crystalline diamond (UNCD) films grown by MP–CVD system.•The hardness of the films is found to be ∼30 GPa and Young’s modulus ∼300 GPa.•The electron field emission, the turn on electric ...field, ETOE = 11 V/μm.•UNCD could be useful for flexible materials for thin film coating technology.
Ultra-nano-crystalline diamond (UNCD) thin films with average thickness ∼200 nm, were grown on n-type mirror polished silicon (100) substrates using microwave plasma enhanced chemical vapour deposition system in different gas (H2 - N2 - Ar - CH4) composition plasma atmospheres at 1200 W (2.45 GHz) and in a pressure of 120 Torr with plasma-temperature ∼475 °C. Raman spectroscopy was used for microstructural study and nano-indentation was used for Hardness/Young’s modulus study; whereas X-ray absorption near edge structure, X-ray photoelectron and ultraviolet photoemission spectroscopies were used for electronic structure of UNCD thin films. The hardness of the films is found to be ∼30 GPa, Young’s modulus ∼300 GPa and induced electron field emission, the turn on electric field, ETOE = 11 V/μm. All results show that the UNCD could be useful for different industrial semiconductor/optoelectronic devices and as flexible materials for thin film coating technology.
The epidemic of chronic kidney disease of unknown etiology (CKDu) that contributes significantly to morbidity and mortality rates among dry-zonal farming communities has become a public health ...priority in Sri Lanka. Though a large number of hypotheses were introduced as causative factors, none of them have been confirmed so far. As drinking water quality is among the most suspected causative factors for the emergence of CKDu, a detailed hydro-geochemical investigation was carried out concurrently with the population screening in the Monaragala district of Sri Lanka where high incidences of CKDu are reported. A population screening was performed selecting 46,754 people using both dipstick proteinuria test and Albumin-Creatinine Ratio (ACR). The results revealed that the disease prevalence is about 6.7 % in the district. A total of 60 groundwater samples, 30 each, were collected from CKDu-prevalent locations and control locations where there are no CKDu cases reported. The samples were analyzed to identify any possible linkage between water quality and disease prevalence. Concentrations of hardness, F−, Na+, and Mg2+ in groundwater revealed a statistically significant difference between CKDu and control wells at a confident level of p = 0.05. The study revealed that alkali (Na++K+) and alkaline earth cations (Mg2+, Ca2+, Sr2+, Ba2+) were relatively higher in drinking water sources used by CKDu patients, compared to the well waters used by healthy individuals. Nearly 87 % of the wells used by CKDu cases showed higher fluoride levels that exceed the threshold level (1.0 mg L−1). Contents of nephrotoxic trace elements such as As, Cd, and Pb were found to be comparable in both types of wells and were well below the WHO permissible levels, thus negating their prime influence on the CKDu prevalence. It is obtrusive that the elevated fluoride levels together with water hardness associated with higher Mg2+ levels have a possible relation with CKDu and may influence the disease progression.
•Geochemistry of groundwater in a CKDu hotspot was investigated as a case-control study.•Comparatively higher Mg and fluoride levels were found in affected regions.•Excess fluoride and hardness in drinking water could enhance the tubular injury.•Nephrotoxic trace elements such as As, Pb, and Cd, etc. were below the permissible levels.
Selective electron beam melting (EBM) is a layer-by-layer additive manufacturing technique that shows great promise for fabrication of medical devices and aerospace components. Before its potential ...can be fully realized, however, a comprehensive understanding of processing-microstructure-properties relationships is necessary. Titanium alloy (Ti–6Al–4V) parts were built in a newly developed, unique geometry to allow accurate investigation of the following intra-build processing parameters: energy input, orientation, and location. Microstructure evaluation (qualitative prior-β grain size, quantitative α lath thickness), tensile testing, and Vickers microhardness were performed for each specimen. For a wide range of energy input (speed factor 30–40), small differences in mechanical properties (2% change in ultimate tensile strength (UTS) and 3% change in yield strength (YS)) were measured. Vertically built parts were found to have no difference in UTS or YS compared to horizontally built parts, but the percent elongation at break (% EL) was 30% lower. The difference in % EL was attributed to a different orientation of the tensile axis for horizontal and vertical parts compared to the elongated prior-β grain and microstructural texture direction in EBM Ti–6Al–4V. Orientation within the x–y plane as well as location were found to have less than 3% effect on mechanical properties, and it is possible a second order effect of thermal mass contributed to these results.
Water plays a vital role in deteriorating stone heritage, especially those carved into vertical rock slopes. Southeast China is home to numerous limestone rock-hewn heritages, many of which showcase ...diverse deterioration patterns on their facades. Nevertheless, due to the large scale of this heritage and the limitations imposed by the principle of minimal intervention in practices, there is still a lack of practical strategies for understanding moisture distribution. Therefore, this study aims to analyse the moisture distribution of limestone rock-hewn statues via in situ detection employing a portable hygrometer and laboratory calibration based on the gravimetric method and regression analysis. The in situ determination was conducted in the Ciyunling statues niche 1 (World Heritage Site), which was hewn in the Wuyue states (942 CE). Thirty-six measuring areas were evenly planned on the niche's façade, with 20 moisture readings obtained from each measuring area. Additionally, the surface hardness of the typical area of statues was examined using a non-invasive Leeb hardness tester and Kruskal–Wallis
H
test to assess the impact of moisture on deterioration. The findings reveal that the statues' moisture content is higher than the background wall between the statues, signalling a greater potential for deterioration on the surface of the limestone statue. The primary source of moisture appears to be gaseous water in the atmosphere, which accumulates in the micropores through capillary condensation. Furthermore, the statistically significant differences in surface hardness between the chest/shoulder of statues and the root of the façade highlight the softening effect of moisture on the foundation of the limestone statues. Hence, the methodology utilised in this study serves as a viable approach for examining moisture levels and the extent of deterioration in rock-hewn heritage structures.
Highlights
Systematic in situ measurement of moisture distribution on the facades of limestone rock-hewn heritage.
A linear regression equation between limestone’s electrical resistance-based moisture content (ω
c
) and the gravimetric moisture content (ω
o
) was obtained.
The surface of the limestone statues contains more moisture signalling a greater potential for water-induced weathering.
the surface hardness of the limestone facade significantly diminishes as the height decreases according to Kruskal–Wallis
H
test.
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