Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 7.124
Filtrar
1.
J Environ Sci (China) ; 140: 46-58, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38331514

RESUMO

Reducing CO2 emissions of the iron and steel industry, a typical heavy CO2-emitting sector, is the only way that must be passed to achieve the 'dual-carbon' goal, especially in China. In previous studies, however, it is still unknown what is the difference between blast furnace-basic oxygen furnace (BF-BOF), scrap-electric furnace (scrap-EF) and hydrogen metallurgy process. The quantitative research on the key factors affecting CO2 emissions is insufficient. There is also a lack of research on the prediction of CO2 emissions by adjusting industrial structure. Based on material flow analysis, this study establishes carbon flow diagrams of three processes, and then analyze the key factors affecting CO2 emissions. CO2 emissions of the iron and steel industry in the future is predicted by adjusting industrial structure. The results show that: (1) The CO2 emissions of BF-BOF, scrap-EF and hydrogen metallurgy process in a site are 1417.26, 542.93 and 1166.52 kg, respectively. (2) By increasing pellet ratio in blast furnace, scrap ratio in electric furnace, etc., can effectively reduce CO2 emissions. (3) Reducing the crude steel output is the most effective CO2 reduction measure. There is still 5.15 × 108-6.17 × 108 tons of CO2 that needs to be reduced by additional measures.


Assuntos
Poluentes Atmosféricos , Ferro , Poluentes Atmosféricos/análise , Dióxido de Carbono/análise , Aço , Carbono , Metalurgia , Hidrogênio
2.
J Mech Behav Biomed Mater ; 152: 106466, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38387120

RESUMO

Ti-15Mo/HA composite was prepared by powder metallurgy, and the influence of Hydroxyapatite (HA) on the microstructure, tribological behavior and in vitro biocompatibility was studied by comparison with TC4. The results show that the Ti-15Mo/HA composite consists of increased α-Ti, decreased ß-Ti and a variety of ceramic phases (CaTiO3, Ca3(PO4)2, CaO, etc.) with the increase of HA content. The friction coefficient and wear rate of Ti-15Mo/HA composite is apparently lower than those of TC4 due to solid solution strengthening of Mo in Ti and dispersion strengthening of ceramic phases. Ti-15Mo/5HA displays more excellent wear resistance than the other composite. TC4 alloy is dominated by adhesive wear, however, Ti-15Mo alloy is a combination of adhesive wear and abrasive wear. Ti-15Mo/HA composite is mainly subjected to abrasive wear, together with adhesive wear. The viability and the number of mouse osteoblasts in Ti-15Mo/5HA extract are higher than that of Ti-15Mo. The morphology of the osteoblasts is clear and full, and the growth and proliferation are satisfactory with the increased cell pseudopodia with the culture time. The Ti-15Mo/HA composite displays good wear resistance and biocompatibility, and accordingly has a potential application in bone repair materials.


Assuntos
Cerâmica , Titânio , Animais , Camundongos , Pós , Titânio/farmacologia , Durapatita , Metalurgia
3.
J Environ Manage ; 352: 120051, 2024 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-38262282

RESUMO

With the rapid growth of the metallurgical industry, there is a significant increase in the production of metallurgical slags. The waste slags pose significant challenges for their disposal because of complex compositions, low utilization rates, and environmental toxicity. One promising approach is to utilize metallurgical slags as catalysts for treatment of refractory organic pollutants in wastewater through advanced oxidation processes (AOPs), achieving the objective of "treating waste with waste". This work provides a literature review of the source, production, and chemical composition of metallurgical slags, including steel slag, copper slag, electrolytic manganese residue, and red mud. It emphasizes the modification methods of metallurgical slags as catalysts and the application in AOPs for degradation of refractory organic pollutants. The reaction conditions, catalytic performance, and degradation mechanisms of organic pollutants using metallurgical slags are summarized. Studies have proved the feasibility of using metallurgical slags as catalysts for removing various pollutants by AOPs. The catalytic performance was significantly influenced by slags-derived catalysts, catalyst modification, and process factors. Future research should focus on addressing the safety and stability of catalysts, developing green and efficient modification methods, enhancing degradation efficiency, and implementing large-scale treatment of real wastewater. This work offers insights into the resource utilization of metallurgical slags and pollutant degradation in wastewater.


Assuntos
Poluentes Ambientais , Poluentes Químicos da Água , Águas Residuárias , Cobre , Substâncias Perigosas , Metalurgia , Oxirredução , Poluentes Químicos da Água/análise
4.
Waste Manag ; 175: 121-132, 2024 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-38194797

RESUMO

Kish graphite is a typical byproduct of steel production, and its enrichment and purification are essential prerequisites for its high value and comprehensive utilization. To solve the problem of recovery and application of difficult-to-treat kish graphite with a small particle size obtained from metallurgical dust, kish graphite in blast furnace tapping yard dust was effectively enriched and purified by a comprehensive flotation-acid leaching treatment process in this study. The influence of the flotation agents on the flotation process was explored. The results showed that the optimized flotation agent dosage was 500.0 g·t-1 (collector) and 120.0 g·t-1 (frother), respectively. Based on the optimized flotation scheme, a graphite concentrate (FG) with 79.12 % carbon content and 93.5 % carbon recovery was obtained. After the leaching treatment with a HCl-HF mixed acid solution, the carbon content of the graphite concentrate increased to 95.55 %. The ID/IG value of the graphite concentrate was 0.145, and the average lattice spacing was approximately 0.3354 nm. The SEM results showed that the leaching-treated graphite concentrate (AFG) had a loose, fragment-like structure. When used as an anode material for lithium-ion batteries, The AFG still provided a high reversible capacity of âˆ¼370 mAh·g-1 and excellent coulombic efficiency of 99.6 % after 350 cycles. In addition, an industrial-grade recycling and utilization path for kish graphite based on a circular supply chain strategy was proposed. The results of this study may serve as a conceptual basis for the recovery and application of kish graphite from metallurgical dust.


Assuntos
Grafite , Carbono , Poeira , Fontes de Energia Elétrica , Metalurgia
5.
J Biomed Mater Res B Appl Biomater ; 112(1): e35338, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37846459

RESUMO

Titanium and its alloys are used to make dental implants because of its low density, high strength, and corrosion resistance. This paper describes the development of a potential biomaterial Ti-10Nb by powder metallurgy utilizing four different compaction pressures and analyses its microstructural, physical, mechanical, electrochemical, biological, and tribological behavior under various situations. The alloys were fabricated using four different compaction pressures, that is, 600, 650, 700, and 750 MPa, and sintered in a vacuum atmosphere at 1000°C for 1.5 h. The density of the samples was measured using Archimedes principle. X-ray diffraction and scanning electron microscopy equipped with energy dispersive spectroscopy were used to investigate the phase composition and microstructure, and a profilometer was used to examine the surface roughness of various samples. Vickers hardness tester was used to evaluate hardness, and a universal testing machine was used for compression testing. Corrosion and wear behavior were examined using a potentiostat and a Bio-Tribometer, respectively. This Ti-10Nb alloys consist of α + ß phase, and have 16% highest porosity in sample compacted at 600 MPa. The samples compacted at 750 MPa achieved highest hardness, yield strength, compressive strength, and elastic modulus of 450 ± 29.72 HV, 718.22 ± 16.37 MPa, 1543.59 ± 24.37 MPa, and 41.27 ± 3.29 GPa, respectively. In addition, it also possesses highest corrosion and wear resistance with lowest icorr of 0.3954 ± 0.008 µA/cm2 and wear volume of (31.25 ± 0.206) × 10-3 mm3 . These results indicate that the developed alloys have a variety of desirable properties, including high hardness, adequate compressive strength, good corrosion and wear resistance, apatite-forming capability, and a low elastic modulus, which is advantageous for avoiding stress shielding. Therefore, it may be recommended to use it as a dental implant material.


Assuntos
Ligas , Titânio , Ligas/química , Titânio/química , Pós , Materiais Biocompatíveis , Corrosão , Metalurgia , Teste de Materiais
6.
Int J Environ Health Res ; 34(2): 1044-1052, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36970880

RESUMO

The incidence of DNA damage from exposure to specific types of metalworking fluids has been reported. In this research, size-selective permissible limits to prevent genotoxic damage in A549 cell lines exposed to two types of mineral oil were estimated for the first time using a benchmark dose approach and extrapolated to workers. The comet assay was performed based on Olive and Banath protocol to determine DNA damage. Then, the Benchmark Dose, the 95% lower bound confidence limit BMD, and the 95% upper-bound confidence limit BMD were determined using continuous response data. Finally, the four Benchmark Dose levels reported in the A549 cell line were extrapolated to the human population in occupational settings in two phases. This study showed when determining the permissible limits, the type used or unused, the type of injury, the organ affected in the body and the size of the particles should also be considered.


Assuntos
Poluentes Ocupacionais do Ar , Exposição Ocupacional , Humanos , Exposição Ocupacional/análise , Óleo Mineral/toxicidade , Metalurgia , Dano ao DNA
7.
Int Arch Occup Environ Health ; 97(1): 57-64, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38070038

RESUMO

OBJECTIVE: The relationship between metalworking fluids (MWFs) and nonalcoholic fatty liver disease (NAFLD) has not been previously explored. We aim to investigate the relationship between occupational exposure to MWFs and the prevalence of NAFLD and to determine the cumulative exposure threshold per day. METHODS: In 2020, 2079 employees were selected randomly from one computer numerical control machining factory in Wuxi for a questionnaire survey, and occupational health examinations were conducted at the affiliated branch of Wuxi Eighth People's Hospital. MWF samples were collected within the factory using the National Institute for Occupational Safety and Health (NIOSH) 5524 method. NAFLD was defined as having a hepatic steatosis index (HSI) ≥ 36 without significant alcohol consumption. The relationship between NAFLD and MWFs was analyzed using logistic regression, and the daily exposure threshold was calculated using R software. RESULTS: MWF exposure was found to be a risk factor for NAFLD in exposed workers compared to the non-exposed group. The OR for NAFLD in workers exposed to MWFs compared to controls was 1.42 (95% CI: 1.04-1.95). An increased risk of NAFLD was shown to be associated with an increasing dose. The daily exposure dose threshold to MWFs was found to be 6.54 mg/m3 (OR = 2.09, 95% CI: 1.24-3.52). CONCLUSION: An association between occupational exposure to MWFs and NAFLD was found. As the concentration of exposure rose, the prevalence of NAFLD was also escalated.


Assuntos
Poluentes Ocupacionais do Ar , Hepatopatia Gordurosa não Alcoólica , Exposição Ocupacional , Humanos , Poluentes Ocupacionais do Ar/análise , Hepatopatia Gordurosa não Alcoólica/epidemiologia , Hepatopatia Gordurosa não Alcoólica/induzido quimicamente , Metalurgia , Exposição Ocupacional/análise , Fatores de Risco
9.
J Environ Manage ; 350: 119649, 2024 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-38007928

RESUMO

A profound green transformation of China's heavy industrial aggregation regions is required to conquer severe air pollution, and fulfill carbon peak pledge. Here, to clarify the coordinated mechanism and an optimal roadmap for the reduction of CO2 and gaseous pollutants, we integrated input-output modelling, system dynamics, and multi-objective programming to construct a CO2 and gaseous pollutants synergistic reduction model initially; investigated incentive approaches from 2020 to 2035; Hebei, with the largest steel production in China, was adopted as a demonstrative region. Results revealed that intensive dual control of efficiency and structure in energy and industry can accelerate achieving carbon peak in 2029. In optimal case, CO2 emission intensity can reach a 75.2% reduction compared to 2020, and gaseous pollutants continue decline simultaneously (SO2 and NOx can drop by 63% and 48%); and the synergistic reduction level is expected to improve. Thus, vigorously develop decoupling between economy-air pollution-carbon reduction in Hebei. As opposed to efficiency improvement, structural adjustments were demonstrated to be more effective than short-term efficiency improvements. In addition, the estimated development potential of traditional heavy industries such as steel and petrochemicals is limited, whereas the equipment manufacturing industry, closely linked to traditional industries, is expected to continue its development. Furthermore, although in the electrification process, coal consumption is still needed because of its indispensable role in the production process of heavy industries. The results can facilitate policy-making for heavy industrial aggregation areas' green transformation in shaping policies and actions with clear objectives, effective measures, and sound coordination.


Assuntos
Poluentes Atmosféricos , Poluentes Ambientais , Poluentes Atmosféricos/análise , Dióxido de Carbono/análise , Gases , China , Metalurgia , Carbono , Aço
10.
Environ Geochem Health ; 46(1): 12, 2023 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-38147164

RESUMO

To conduct a precise health risk assessment of heavy metals (HMs) in soil, it is imperative to ascertain the primary sources of potential health risks. In this study, we conducted comprehensive measurements of HMs, specifically focusing on the accumulation of Cu, Cd, Sb, Zn, and Pb in local soil, which may pose threats to environmental quality. To achieve our objective, we employed a method that combines positive matrix factorization with a health risk assessment model to quantify the health risks associated with specific sources. The results obtained from the geo-accumulation index indicate that the majority of HMs found in the local soil are influenced by anthropogenic activities. Among these sources, local industrial-related activities contributed the largest proportion of HMs to the soil at 34.7%, followed by natural sources at 28.7%, mining and metallurgy-related activities at 28.2%, and traffic-related activities at 8.40%. Although the non-carcinogenic and carcinogenic risks associated with individual HMs were found to be below safety thresholds, the cumulative health risks stemming from total HMs exceeded safety limits for children. Moreover, the unacceptable health risks for children originating from industrial-related activities, natural sources, and mining and metallurgy-related activities were primarily concentrated in proximity to mining sites and industrial areas within the local region. This investigation furnishes valuable insights that can aid governmental authorities in formulating precise control policies to mitigate health threats posed by soils in polymetallic mining areas.


Assuntos
Metalurgia , Metais Pesados , Criança , Humanos , China , Metais Pesados/toxicidade , Medição de Risco , Solo
11.
PLoS One ; 18(12): e0294569, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38113240

RESUMO

Metalwork was a major technological innovation that displaced stone-tool technologies and transformed human society and the environment. However, our understanding of these processes remains partial. In this paper, we approach the stone-to-metal transition from a novel angle-the presence of flint knapping at metal production sites. Drawing on excavations at the Late Bronze and Iron Age copper smelting sites in Timna Valley, Israel, we demonstrate that systematic production of expedient stone tools was integral to these sites' industrial operations, placing it at the heart of the very same metal circulation networks that were presumably responsible for its displacement. The observations from Timna, coupled with evidence for the use of chipped stone technology in other early Iron Age metallurgical contexts, support the hypothesis that it was probably both the high accessibility of iron and its qualities that put an end to the stone tool industry. Copper and bronze could not easily fulfill the function of the ad hoc stone tools and were not used to replace stone tools even if they were available and accessible.


Assuntos
Arqueologia , Cobre , Humanos , Israel , Tecnologia , Metalurgia
12.
Environ Sci Pollut Res Int ; 30(57): 119627-119653, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37962753

RESUMO

Metallurgy is pivotal for societal progress, yet it yields wastewater laden with hazardous compounds. Adhering to stringent environmental mandates, the scientific and industrial sectors are actively researching resilient treatment and disposal solutions for metallurgical effluents. The primary origins of organic pollutants within the metallurgical sector include processes such as coke quenching, steel rolling, solvent extraction, and electroplating. This article provides a detailed analysis of strategies for treating steel industry waste in wastewater treatment. Recent advancements in membrane technologies, adsorption, and various other processes for removing hazardous pollutants from steel industrial wastewater are comprehensively reviewed. The literature review reveals that advanced oxidation processes (AOPs) demonstrate superior effectiveness in eliminating persistent contaminants. However, the major challenges to their industrial-scale implementation are their cost and scalability. Additionally, it was discovered that employing a series of biological reactors instead of single-step biological processes enhances command over microbial communities and operating variables, thus boosting the efficacy of the treatment mechanism (e.g., achieving a chemical oxygen demand (COD) elimination rate of over 90%). This review seeks to conduct an in-depth examination of the current state of treating metallurgical wastewater, with a particular emphasis on strategies for pollutant removal. These pollutants exhibit distinct features influenced by the technologies and workflows unique to their respective processes, including factors such as their composition, physicochemical properties, and concentrations. Therefore, it is of utmost importance for customized treatment and disposal approaches, which are the central focus of this review. In this context, we will explore these methods, highlighting their advantages and characteristics.


Assuntos
Águas Residuárias , Poluentes Químicos da Água , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Resíduos Industriais/análise , Metalurgia , Aço
13.
PLoS One ; 18(10): e0289771, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37856549

RESUMO

This paper discusses the use of "legacy data" in research on Roman Period iron smelting in the territory of the Przeworsk Culture in Magna Germania. The dataset includes results of 240 analyses of smelting slag and iron ores chemistry. A majority of these analyses were conducted in the 1950s-1980s. The quality of these data is far below present-day standards. Only major elements were reported, analytical methods were often not specified (although optical emission spectroscopy and wet chemical analyses can be assumed in such cases) and information on detection limits, precision and accuracy of the results is missing. In spite of this, a Principal Component Analysis-Agglomerative Hierarchical Clustering treatment successfully isolated observations from the three main iron smelting regions of the Przeworsk Culture (the Holy Cross Mountains, Masovia and Silesia). These results to a degree confirm a theory proposed in the 1960s by J. Piaskowski, according to whom it was possible to distinguish iron produced in the Holy Cross Mountains from the iron produced elsewhere in the territory of what is now Poland on the basis of metal characteristics. These findings will pave the way to the ongoing research project on the Przeworsk Culture metallurgy. It is also argued that, apart from a search for new methods in iron provenance studies, more attention should be paid to results of earlier analyses and to a compilation of legacy databases. The other result is an open and flexible Agglomerative Hierarchical Clustering R code to examine discrimination between production areas and to propose artefact provenance patterns in a convenient interactive way using the R development environment.


Assuntos
Ferro , Metais , Ferro/química , Metalurgia , Polônia , Artefatos
15.
Sci Rep ; 13(1): 14954, 2023 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-37737292

RESUMO

Since February 2022, the full-scale war in Ukraine has been strongly affecting society and economy in Ukraine and beyond. Satellite observations are crucial tools to objectively monitor and assess the impacts of the war. We combine satellite-based tropospheric nitrogen dioxide (NO2) and carbon dioxide (CO2) observations to detect and characterize changes in human activities, as both are linked to fossil fuel combustion processes. We show significantly reduced NO2 levels over the major Ukrainian cities, power plants and industrial areas: the NO2 concentrations in the second quarter of 2022 were 15-46% lower than the same quarter during the reference period 2018-2021, which is well below the typical year-to-year variability (5-15%). In the Ukrainian capital Kyiv, the NO2 tropospheric column monthly average in April 2022 was almost 60% smaller than 2019 and 2021, and about 40% smaller than 2020 (the period mostly affected by the COVID-19 restrictions). Such a decrease is consistent with the essential reduction in population and corresponding emissions from the transport and commercial/residential sectors over the major Ukrainian cities. The NO2 reductions observed in the industrial regions of eastern Ukraine reflect the decline in the Ukrainian industrial production during the war (40-50% lower than in 2021), especially from the metallurgic and chemical industry, which also led to a decrease in power demand and corresponding electricity production by thermal power plants (which was 35% lower in 2022 compared to 2021). Satellite observations of land properties and thermal anomalies indicate an anomalous distribution of fire detections along the front line, which are attributable to shelling or other intentional fires, rather than the typical homogeneously distributed fires related to crop harvesting. The results provide timely insights into the impacts of the ongoing war on the Ukrainian society and illustrate how the synergic use of satellite observations from multiple platforms can be useful in monitoring significant societal changes. Satellite-based observations can mitigate the lack of monitoring capability during war and conflicts and enable the fast assessment of sudden changes in air pollutants and other relevant parameters.


Assuntos
COVID-19 , Humanos , COVID-19/epidemiologia , Dióxido de Nitrogênio , Ucrânia , Metalurgia , Fatores Socioeconômicos
16.
Int Endod J ; 56(11): 1412-1428, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37698946

RESUMO

AIM: To compare the design, metallurgy, and mechanical properties of four heat-treated reciprocating instruments coupled with the evaluation of the irrigation flow using an in silico model. METHODOLOGY: New EdgeOne Fire Primary, Easy-File Flex Regular 25, WaveOne Gold Primary and Reciproc Blue R25 instruments (n = 124) were initially evaluated regarding their design through stereomicroscopy, scanning electron microscopy and 3D surface scanning. In addition, energy-dispersive X-ray spectroscopy was utilized to determine their elemental composition, and differential scanning calorimetry tests to evaluate their phase transformation temperatures. Their mechanical performance was further assessed through torsional and bending tests. Using scans obtained from a real tooth and the instruments, a computational fluid dynamics assessment was conducted to determine the irrigation flow pattern, apical pressure, and wall shear stress in simulated canal preparation. Mood's median and One-way anova post hoc Tukey tests were used for statistical comparisons (α = 5%). RESULTS: Reciproc Blue exhibited a superior number of blades (n = 8), whereas EdgeOne Fire had the highest overall volume (4.38 mm3 ) and surface area (32.32 mm2 ). At the 3-mm axial level, EdgeOne Fire displayed the lowest core diameter (0.13 mm), while Reciproc Blue had the highest (0.16 mm). All blades were symmetrical, and the tips of the instruments were non-active but differed from each other. The most irregular surfaces were observed in EdgeOne Fire and Easy-File Flex. All instruments were manufactured from nickel-titanium alloys and exhibited distinct phase transformation temperatures. WaveOne Gold and Reciproc Blue demonstrated the highest maximum torque values (1.87 and 1.62 N cm, respectively), while the lowest was observed on EdgeOne Fire (1.21 N cm) (p < .05). The most flexible (p < .05) were EdgeOne Fire (angle of rotation: 602.6°; maximum bending load: 251.4 g.f) and Reciproc Blue (533.2° and 235.6 g.f). There were no significant differences observed in the irrigation flow among the four domains generated by the tested instruments. CONCLUSIONS: Despite observing variations in the design, phase transformation temperatures, and in the torsional and bending test outcomes among the four heat-treated reciprocating instruments, no significant differences were found in the irrigation flow pattern among the different groups in the simulated root canal preparations.


Assuntos
Instrumentos Odontológicos , Temperatura Alta , Desenho de Equipamento , Estresse Mecânico , Preparo de Canal Radicular , Titânio/química , Metalurgia , Ouro , Teste de Materiais
17.
Int Endod J ; 56(10): 1301-1315, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37594701

RESUMO

AIM: To assess the influence of a flat-side design on the geometry, metallurgy, mechanical performance and shaping ability of a novel nickel-titanium rotary instrument. METHODOLOGY: Sixty-five new 25-mm flat-side rotary instruments (size 25, taper 0.04) and their nonflat-side prototypes (n = 65) were assessed for major deformations and examined regarding macroscopic and microscopic design, determination of nickel and titanium elements ratio, measurement of phase transformation temperature and evaluation of mechanical performance parameters including time/cycles to fracture, maximum torque, angle of rotation, maximum bending and buckling strengths and cutting ability. Additionally, unprepared canal areas, volume of hard tissue debris and percentage reduction of dentine thickness were calculated for each tested instrument after preparing mesial canals of mandibular molars (n = 12), using micro-CT imaging. Statistical analyses were performed using the U-Mann-Whitney test and independent Student t-test (α = 5%). RESULTS: The number of spirals (n = 8) and blade direction (clockwise) were similar between both flat and nonflat instruments, whilst the helical angles were equivalent (⁓25°). Flat-instruments showed inconsistencies in the homogeneity of the gold colour on the flat-side surface, blade discontinuity, and incomplete and variable S-shaped cross-sections. The titanium-to-nickel ratios were equivalent, but significant differences in the R-phase finish and austenitic start phase transformation temperatures were observed between the flat and nonflat-side instruments. The flat-side instruments demonstrated superior cutting ability compared to the nonflat instruments, as well as, significantly lower values for time to fracture, rotation to fracture and maximum torque to fracture (p < .001). No statistical difference was observed between tested instruments regarding angle of rotation (p = .437), maximum bending (p = .152) and buckling load (p = .411). Preparation protocols using flat and nonflat instruments did not show any statistically significant differences (p > .05). All flat-side instruments exhibited deformation after shaping procedures. CONCLUSIONS: The flat-side instrument showcased enhanced cutting ability compared to its nonflat counterpart. However, it exhibited inferior performance in terms of time, rotation and maximum torque to fracture, along with distinct phase transformation temperatures. No differences were observed in the titanium-to-nickel ratios, angle of rotation, maximum bending, buckling load, preparation time, percentage of untouched canal walls, volume of hard tissue debris and percentage reduction of dentine thickness.


Assuntos
Níquel , Titânio , Humanos , Cavidade Pulpar , Metalurgia , Dente Molar
18.
Environ Sci Process Impacts ; 25(9): 1491-1504, 2023 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-37584085

RESUMO

Exposures to metals from industrial emissions can pose important health risks. The Chester-Trainer-Marcus Hook area of southeastern Pennsylvania is home to multiple petrochemical plants, a refinery, and a waste incinerator, most abutting socio-economically disadvantaged residential communities. Existing information on fenceline community exposures is based on monitoring data with low temporal and spatial resolution and EPA models that incorporate industry self-reporting. During a 3 week sampling campaign in September 2021, size-resolved particulate matter (PM) metals concentrations were obtained at a fixed site in Chester and on-line mobile aerosol measurements were conducted around Chester-Trainer-Marcus Hook. Fixed-site arsenic, lead, antimony, cobalt, and manganese concentrations in total PM were higher (p < 0.001) than EPA model estimates, and arsenic, lead, and cadmium were predominantly observed in fine PM (<2.5 µm), the PM fraction which can penetrate deeply into the lungs. Hazard index analysis suggests adverse effects are not expected from exposures at the observed levels; however, additional chemical exposures, PM size fraction, and non-chemical stressors should be considered in future studies for accurate assessment of risk. Fixed-site MOUDI and nearby mobile aerosol measurements were moderately correlated (r ≥ 0.5) for aluminum, potassium and selenium. Source apportionment analyses suggested the presence of four major emissions sources (sea salt, mineral dust, general combustion, and non-exhaust vehicle emissions) in the study area. Elevated levels of combustion-related elements of health concern (e.g., arsenic, cadmium, antimony, and vanadium) were observed near the waste incinerator and other industrial facilities by mobile monitoring, as well as in residential-zoned areas in Chester. These results suggest potential co-exposures to harmful atmospheric metal/metalloids in communities surrounding the Chester-Trainer-Marcus Hook industrial area at levels that may exceed previous estimates from EPA modeling.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Arsênio , Metais Pesados , Selênio , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Monitoramento Ambiental/métodos , Antimônio/análise , Arsênio/análise , Cádmio/análise , Material Particulado/análise , Poeira/análise , Selênio/análise , Vanádio/análise , Aerossóis/análise , Metalurgia , Metais Pesados/análise
19.
Sci Rep ; 13(1): 10669, 2023 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-37393379

RESUMO

Orbital friction stir welding (FSW) has been applied to clad pipes, which is certainly of interest to the oil and gas industry. In this context, an FSW system capable of performing sound joints in one pass with full tool penetration was developed. Orbital FSW was executed in 6 mm thick API X65 PSL2 steel clad pipes with 3 mm thick Inconel 625 using a polycrystalline cubic boron nitride (pcBN) tool. The metallurgical and mechanical properties of the joints were investigated. Sound joints with axial forces of 45-50 kN, tool rotational speeds of 400-500 rpm, and a welding speed of 2 mm/s were obtained, illustrating that the developed system can perform FSW joints without volumetric defects.


Assuntos
Soldagem , Estudos de Viabilidade , Fricção , Metalurgia , Som
20.
J Environ Manage ; 345: 118650, 2023 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-37499416

RESUMO

Low-grade kaolin is the largest emissions of industrial solid waste that is difficult to dispose of and pollutes the environment seriously. From the perspective of harmless and complete resource utilization, we proposed a novel strategy that combines the wet leaching under mild conditions and physical beneficiation for the facile and low-cost high-valued utilization of low-grade kaolin that involves high-efficiency recovery of aluminum (Al), silicon (Si), and titanium (Ti). The key to successful implementation of this method lies in the new discovery that the residual SiO2 after Al extraction of kaolinite by acid leaching under specific conditions could be rapidly dissolved in dilute NaOH solution at room temperature 25 °C. This highly reactive SiO2 challenges the conventional notions of various silica species are usually chemically stable. By adjusting the key technical parameters of the thermal activation-acid leaching process, the selective and efficient extraction of Al2O3 from low-grade kaolin was realized. The acid leaching residue was then subjected to selective recovery of SiO2 by alkaline leaching at 25 °C to obtain high-quality sodium silicate. Finally, the alkali leaching residue as titanium coarse concentrate was separated by centrifugal concentrator to obtain artificial rutile (TiO2 >91.06%). The key mechanism for the formation of the highly reactive silica was also systematically studied and confirmed.


Assuntos
Caulim , Resíduos Sólidos , Dióxido de Silício , Titânio , Alumínio , Metalurgia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...