Elevated Temperatures Research Articles

Efficacy of sutimlimab for cold agglutinin disease in a patient on chronic hemodialysis.

Reports of cold agglutinin disease (CAD), an autoimmune hemolytic anemia, in dialysis patients are limited. Recently, sutimlimab for CAD was covered by insurance. Herein, we report a case in which sutimlimab was effective in the treatment of CAD in a patient undergoing hemodialysis (HD). The patient was a 73year-old Japanese man with an 11year history of HD for diabetic nephropathy. He was admitted to our hospital for examination and treatment of erythropoiesis-stimulating agent (ESA)-induced hyporesponsive anemia and fatigue, which was present in the previous year October to March when temperatures were cooler. The patient was diagnosed with hemolytic anemia based on decreased hemoglobin levels, elevated reticulocyte count, elevated lactate dehydrogenase levels, and decreased haptoglobin levels. Furthermore, he was diagnosed with CAD based on a positive direct antiglobulin test for C3 and cold agglutinin tests. The patient did not respond well to an elevated dialysate temperature or rituximab therapy. After initiating sutimlimab treatment, an increase in the hemoglobin level was observed despite a decrease in temperature, and his fatigue disappeared. Anemia in hemodialysis patients is generally renal; however, some ESA resistance exists, which may be due to hemolytic anemia. In this case, the use of sutimlimab was effective in controlling hemolytic anemia due to CAD.

Enhancing the electrochemical properties of biopolymer composites using starch‐graphene nanoplatelets

AbstractThe study presents the ideal distribution of graphene nanoplatelets (GNP) within the thermoplastic starch (TPS) matrix significantly elevated the thermal and electrical conductivities, as well as the electrochemical efficiency of the biocomposites. Additionally, the incorporation of GNP resulted in an increased thermal stability for the TPS, as indicated by the elevated temperatures required for maximum degradation. The biocomposites exhibited a self‐aligned layered structure, creating conductive pathways and enhancing electron conduction. An electrical conductivity increased as the concentration of GNP increased, with the highest conductivity observed on the top and bottom surface with the value of 4.23 × 10−7 S/m and 3.92 × 10−6 S/m when 12 wt% of GNP was added. The presence of hydroxyl groups in TPS facilitated the formation of hydrogen bonds with GNP, preventing GNP from stacking and forming a more uniform conductive network within the film. The addition of 15 wt% GNP also improved the capacitive performance of the TPS matrix, as evidenced by higher current responses and larger quasi‐rectangular areas in the cyclic voltammetry curves compared to neat TPS. The Nyquist plots which are illustrated impedance data showed that the TPS film with 12 wt% GNP exhibits the smallest semicircle, indicating the highest conductivity which is suggested that GNP improves charge transfer compared to pure TPS.Highlights Optimal dispersion of GNP enhanced the biocomposite's properties. The electrical conductivity increases with the GNP content until 12 wt%. TPS/GNP self‐aligned layered improved conduction and capacitive behavior. GNP improved thermal stability by restricting polymer chain movement. Electrochemical impedance shows improved properties of TPS/GNP.

Thermal performance of MK/FA geopolymers: Unveiling the role of FA, equivalent Na2O and modulus

This paper investigates the thermal stability of metakaolin/fly ash (MK/FA) based geopolymers at elevated temperature of 500℃ and 800℃. The thermal stability of geopolymers is evaluated from the following aspects: apparent morphology, residual compressive strength, volumetric shrinkage, and microstructure. The results show that the incorporation of FA contributes to the reduction of specimen cracking while the increasing of equivalent Na2O leads to severe cracking. After experiencing 800°C, the compressive strength of all specimens remains above 70 % of that at room temperature, and the specimen with high equivalent Na2O exhibits higher compressive strength. The XRD and FTIR results indicate that the chemical component of most specimens remains stable at elevated temperatures without decomposition and formation of new crystalline phases. However, the MK/FA based geopolymer exhibit considerable volume shrinkage at elevated temperatures. The shrinkage ranges from 3.2 % to 4.9 % at 500°C and 5.1–14.2 % at 800°C for different specimens. The increase of equivalent Na2O from 8 % to 16 % results in a 174.8 % increase of shrinkage. Overall, MK/FA based geopolymers exhibit convincing thermal performance, and the specimens exhibit higher residual compressive strength and chemical stability after exposure to elevated temperatures.

Investigation of the static constitutive relationship of rubberized self-compacting concrete after high-temperature exposure

Rubber self-compacting concrete (RSCC), recognized as an environmentally friendly material, possesses excellent resistance to impact. However, the inclusion of rubber particles significantly decreases its compressive strength. This study investigated the compressive properties of RSCC with rubber particles substituting for fine aggregate volume percentages of 0 %, 10 %, 20 %, and 30 % after exposure at 25, 300, 600, and 900 °C for 3 h. The interface conditions among the rubber particles and the mortar were examined using scanning electron microscopy (SEM). The findings reveal that: (1) Both the compressive strength and the modulus of elasticity of RSCC exhibit a pronounced decline as the exposure elevates, with the maximum reduction reaching 84.25 % and 89.42 % respectively (where the substitution percentage of rubber particles is 30 %), compared to values at room temperature. Conversely, the peak strain exhibited an increase of 130.41 % (with the substitution percentage of rubber particles being 30 %). (2) As the substitution percentage of rubber particles increases, the decline in RSCC's compressive strength and elastic modulus after cooling at elevated temperatures is less noticeable than at room temperature, and the peak strain of RSCC exhibits negligible increase after being subjected to high temperatures. (3) Prediction equations and constitutive models for the compressive strength and peak strain of RSCC post-high temperature exposure are proposed in light of the experimental data. The comparison shows an obvious connection between the experimental outcomes and the predictive results.

The Effect of Radiation Intensity on the Performance of Direct-Expansion Solar PVT Heat Pump Systems

The objective of this study was to investigate the impact of solar radiation intensity on the performance of direct-expansion solar PVT heat pump systems. To this end, an experimental setup was constructed for direct-expansion photovoltaic (PVT) solar heat pump water heating systems and photovoltaic (PV) power generation systems. The system performance and main parameters were analyzed and discussed under different solar radiation intensities. The winter experiments in southern China revealed that the exhaust temperature of the heat pump unit varied considerably under clear conditions, while the back temperature remained stable, fluctuating between approximately −13.5 °C and 24 °C. In contrast, the power generation of PVT panels increased with the increase in radiation intensity, from 78.33 W to 122.68 W, for an increase of 56.6%. Furthermore, the total electricity generation of the PVT panels was higher than that of PV panels, with an increase of 8.7–8.3%. Nevertheless, discrepancies between experimental and theoretical data were observed, particularly under overcast conditions, where the back panel temperature error was pronounced. Additionally, the system exhibited enhanced stability at elevated temperatures in comparable environments, accompanied by an improvement in the system’s coefficient of performance (COP) by 5.67%.

Climate Change impact on Weeds and Herbicide Efficacy

Climate change is the change in statistical distribution of weather pattern that lasts for an extended period of time. There are several components of these climate changes occurring globally that includes uneven rainfall, droughts, floods, warming of atmosphere etc. These are the most important challenges influencing natural ecosystems, agricultural productivity and food security. Climate change is not only influencing crop plants and forests directly but can also impact the pests of these crops. Weeds respond to climate change by changing the duration of their life cycles, population dynamics and shift to new habitats and become a potential competitor to crop plants thereby reducing the production and productivity of crops. Elevated temperature and elevated CO2 level in the environment interfere with herbicide activity, which affects the herbicide absorption, translocation and thereby reduces the efficacy of the applied herbicide. Weeds’ resistance to herbicides may probably increase due to further aggressive growth of weeds in future climate conditions, which can cause a decline in the efficacy of routinely used herbicides.

Comparative analysis of cultivated and wild olive genotypes to salinity and drought stress.

The Mediterranean region's harsh conditions, characterized by low rainfall, high solar radiation, and elevated temperatures, pose challenges for vegetation, particularly in the face of climate change. Cultivated olive (Olea europaea subsp. europaea var. europaea) holds historical and economic significance as one of the oldest crops in the Mediterranean. Due to their high germplasm diversity and greater flowering abundance compared to the offspring of cultivated olives, wild olives (Olea europaea subsp. europaea var. sylvestris) could be utilized for selecting new olive cultivars capable of adapting to a changing climate. This research aimed to compare the effects of salt and drought stress on wild and cultivated genotypes by analyzing morphological, physiological, and biochemical parameters. Results showed that shoot length, shoot dry mass, and leaf area are key drought stress indicators in wild olive trees. The results indicated the olive trees more susceptible to salinity stress had lower Na+ and Cl- concentrations in their leaves and took longer to stabilize salt ion levels. Decreased K+ content in roots across all treatments indicated a general stress response. The uptake of Ca2+ appears to be the most energy-efficient response of olive trees to short-term salinity and drought. In contrast to proline and malondialdehyde, trends in superoxide dismutase activity suggest that it is a reliable indicator of salinity and drought stress. Regarding olive adaptability to salinity stress, promising results obtained with two wild olive genotypes merit their further physiological study.

Investigation of the Temperature Coefficients of Perovskite Solar Cells for Application in High-Temperature Environments.

Perovskite solar cells are actively investigated for their potential as highly efficient and cost-effective photovoltaic devices. However, a significant challenge in their practical application is enhancing their durability. Particularly, these cells are expected to be subjected to heating by sunlight in real-world operating environments. Therefore, high-temperature durability and device operation under such conditions are critical. Our study aims to improve the durability of perovskite solar cells for practical applications by examining their temperature coefficients at elevated temperatures using MA-free compositions. We assessed these coefficients and investigated their correlation with the ideality factor, revealing that carrier recombination markedly affects the temperature behavior of these cells. Our methodology involves simple J-V measurements to evaluate device degradation at high temperatures, paving the way for further research to enhance device performance in such environments.

Engineering and microstructural properties of environmentally friendly alkali-activated composites containing clinker aggregate: heat-curing regime and elevated-temperature effect

The common wisdom in the literature about clinker aggregate (CA) is that it improves the performance properties of mortar or concrete to some extent. The current study, in this context, investigated the physical characteristics and mechanical performances of alkali-activated composites (AACs) made entirely with CA. The CA was used in three particle sizes of 0–2 mm (named No.10), 2–4 mm (named No.5), and 4–8 mm (named medium). To examine the impact of the fine CA-size fraction on the characteristics of AAC, No.10 CA was partially replaced by No.5 CA up to 50%, while the content of the medium CA was kept constant in all AAC mixtures. Moreover, to evaluate the influence of the 8-h curing temperature on the performance of the AACs, different temperature-based curing strategies (ambient, 45, and 75 °C) were applied to the AACs. In the production of AACs, granulated blast furnace slag was employed as an aluminosilicate-rich raw material, and a sodium silicate and sodium hydroxide combination was used as an alkaline activator. Physical properties (flowability, water absorption, capillary water absorption, and dry unit weight), and 8-h strength performances (flexural and compressive) were determined. Furthermore, to monitor the influence of high temperatures on the characteristics of the AAC, the mixtures were exposed to elevated temperatures (200, 500, and 800 °C). In SEM image analysis, it was determined that spherical CSH gels were formed in the heat-cured AACs. It has been observed that the geopolymerization products decompose in AACs exposed to 800 °C. To evaluate statistically the experimental results, a multi-factor analysis of variance (ANOVA) was also applied. The results revealed that increasing the coarser fine aggregate fraction led to higher water absorption and apparent porosity capacities and lower unit weight. Besides, strength performance was improved by applying a heat-curing strategy to the AAC, whereas a decrease was observed by increasing the No.5 CA fraction. There was a remarkable reduction in compressive strength and considerable loss of mass when the AAC mixes were exposed to high temperatures.

Effect of thermal ageing on fatigue crack growth behaviour of forged alloy 617M at elevated temperatures

ABSTRACT Fatigue crack growth (FCG) studies have been conducted on compact tension specimens of alloy 617M for as-received and aged for 1000, 5000 and 10,000 h at 710°C. Effects of thermal ageing on FCG behaviour of alloy 617M forged has been characterised at 27°C, 650°C, 710°C and 750°C. Results reveal that threshold stress intensity factor ( Δ K th ) decreases as temperature increases upto 710°C and then increases at 750°C for all the ageing conditions except for 1000 h aged. The Δ K th value also decreases with an increase in ageing time till 5000 h, but at 10,000 h a reverse trend is observed. The influence of thermal ageing and temperature reflects major deviations for Paris constant (C) and exponent (m). Additionally, thermal ageing and temperature influences on FCG, the effects of dynamic strain ageing, Cr-rich carbides and γ’-phase precipitations have been discussed and corroborated with fractographic and microstructural changes.

Microstructure and Mechanical Properties of Mg-Al-La-Mn Composites Reinforced by AlN Particles.

The Mg-Al-RE series heat-resistant magnesium alloys are applied in automotive engine and transmission system components due to their high-temperature performance. However, after serving at a high temperature for a long time, the Al11RE3 phase coarsened and even decomposed, while the Mg17Al12 phase grew and dissolved, which limits the service temperature of Mg-Al-RE series heat-resistant magnesium alloys to a maximum of 175 °C. In this study, a new preparation method for in situ AlN particles was presented. The AlN/Mg-4Al-4La-0.3Mn composites were prepared by a master alloy and casting method. The effects of various contents of AlN (0.5-3.0 wt.%) on the microstructure and mechanical properties of the Mg-4Al-4La-0.3Mn (AE44) alloy at room (25 °C) and high temperatures (150-250 °C) were investigated. Microstructure analysis revealed that the inclusion of AlN led to a reduction in both the grain size and second phase size in the AE44 alloy, while also improving the distribution of the second phase. The average grain size, Al11La3 phase, Al2La phase, and Al3La phase of the 2.0 wt.% AlN/AE44 composite were 135.7, 9.6, 1.9, and 12.6 μm, respectively, which were significantly lower than those of the AE44 matrix alloy (179.8, 12.6, 3.3, 17.8 μm). The refinement was attributed to the ability of AlN particles to serve as heterogeneous nucleation cores for α-Mg and, at the same time, impede the growth of the solid-liquid interface, eventually leading to grain refinement. With the increase in the AlN content, the mechanical properties of composites initially exhibited an increase at both room and high temperatures, followed by a subsequent decrease. When the AlN content was 2.0 wt.%, the composite exhibited optimal strength and plasticity matching. At room temperature, the TYS, UTS, and EL values of the 2.0 wt.% Mg-4Al-4La-0.3Mn composite were 96 MPa, 175 MPa, and 7.0%, respectively, which were increased by 26 MPa, 27 MPa, and 0.7% when compared with the base alloy. The TYS of the 2.0 wt.% Mg-4Al-4La-0.3Mn composite at 150 °C, 200 °C, and 250 °C were 17 MPa, 14 MPa, and 22 MPa higher than those of the matrix alloy, respectively. The main strengthening mechanisms were second phase strengthening, load transfer strengthening, and thermal mismatch strengthening. At elevated temperatures, AlN particles effectively pinned the grain boundaries, inhibiting their migration, and hindered dislocation climbing, resulting in excellent mechanical properties of the composites at high temperatures. This study contributes to the advancement of in situ AlN particle preparation methods and the exploration of effects of AlN on the properties and microstructure of Mg-Al-RE alloys at high temperatures (150-250 °C).

Experimental study on concentrated light photothermal catalytic glycerol for hydrogen production using a novel linear concentrated light flow reactor

Developing a suitable scale-up photothermal reactor is important for the application of solar photothermal catalytic hydrogen(H2) production from biomass. Herein, Ru nanoparticles loaded on TiO2 were used as photocatalysts to catalyze hydrogen production from glycerol. A novel linear concentrated light flow reactor (LCLFR) was designed and installed. The effects of concentrated light intensity and thermal energy were investigated on the hydrogen production performance of LCLFR. The optical performance of the reactor was evaluated using Monte Carlo ray tracing method and experimentally validated. The spectral absorption and the photothermal conversion properties of Ru/TiO2 photocatalysts in the LCLFR were analyzed with different concentration light intensity. The results showed that both concentrated light and temperature could significantly enhance the hydrogen production performance of glycerol catalyzed by Ru/TiO2. Notably, the promotion of hydrogen production rates by concentrated light becomes stronger at elevated temperatures.

The Impact of Long-Term (4 Months) Exposure to Low pH and Elevated Temperature on the Growth Rate of Gold Mollies’ (Poecilia Sphenops) Larvae

Researchers in the marine ecosystem have documented the significant impacts that anthropogenic ocean acidification has on marine organisms. These include olfactory abilities in fish, impaired behavioral as well as physiological changes, including anti-predatory response leading to consequences in population dynamics and community structure. In this research, we endeavored to investigate and compare the growth rate of the gold mollies (Poecialia sphenops) larvae under a low pH of 5 water temperature of 28 O C, and a pH of 6.9 at a water temperature of 26 O conditions. The mollies larvae were weighed for four months (August, September, October, and November) and the data collected was analyzed using the Statistical Package for Social Sciences (IBM SPSS). The analysis was a multivariate test for a more complete examination of data by looking at independent variables and their relationship to one another. There was no statistically significant difference in the growth rate in August (p-value 0.969) and September (p-value 0.286) between the larvae in aquarium A (experimental) and those in aquarium D (control) at the beginning of the experiment. But there was a statistically significant difference in the third (3) month (October) P-value = 0.007 and in the fourth month (4) (November) P-value = 0.004. The low pH of 5 impacted the growth rate of the Poecilia sphenops larvae while those in the control aquarium pH of 6.9 seemed to have not been affected and grew well.

Low- and elevated-temperature constitutive model of cold-formed titanium-clad bimetallic steel sections

An experiment was conducted to study the mechanical properties of the flat and corner portions of cold-formed TCBS sections at low and elevated temperatures. The predetermined temperatures were set at −80 °C, −40 °C, 20 °C, 200 °C, 300 °C, 400 °C, and 500 °C. The failure modes, stress-strain curves, and key mechanical parameters of TCBS flat and corner couple specimens at different temperatures were obtained based on test results. The TCBS flat and corner specimens failed in ductile mode. The stress-strain curves of the TCBS flat and corner specimens at different temperatures did not show a yield plateau. The strength properties of TCBS flat and corner specimens at low temperatures obviously increased. The strength properties of the TCBS flat and corner specimens generally decreased with increasing elevated temperature. The cold-forming process increased and decreased the strength and ductile properties of TCBS at different temperatures, respectively. Additionally, the mechanical property reduction factors of TCBS flat and corner specimens at different temperatures were compared with those of various structural steels. Moreover, the applicability of the reduction factors for yield strength and elastic modulus provided in current codes was assessed for TCBS flat and corner specimens. Furthermore, the prediction equations of mechanical parameters and constitutive models were proposed for the TCBS flat and corner couple specimens at different temperatures, which provided a basis for designing TCBS structures in low- and elevated-temperature conditions.

Effect of Expanded Glass Lightweight Aggregate on the Performance of Geopolymer Mortar at Elevated Temperatures

AbstractThe greenhouse gas emissions associated with conventional concrete as a result of the cement industry have prompted scientists to search for eco-friendly alternatives. Among these promising alternatives is geopolymer concrete or mortar. This work studies the impact of using polyvinyl alcohol (PVA) fibers and lightweight expanded glass (EG) aggregate on the mechanical behaviour of lightweight geopolymer mortar (LWGM) at various temperatures (room temperature, 250 °C, and 500 °C). EG was utilized to partially replace the sand by 10 and 20%. Limited studies dealt with geopolymer mortar based on such composition at high temperatures. The geopolymer mortar was created using slag as the main precursor activated by a mixed solution of sodium hydroxide and sodium silicate. Various combinations were produced, and their behaviour was observed at room and high temperatures. Several tests such as workability, compressive and flexural strengths, density, stress-strain relationship, load-displacement behaviour, and uniaxial tensile strength were performed. The findings of the study indicate that the density and compressive strength of geopolymer mortar reduced with increasing the replacement level by the EG. However, the utilization of 10% EG can produce a lightweight mortar with a compressive strength of 17.9 at 28 days. Moreover, the use of 1% PVA significantly improves the mechanical performance. Furthermore, the mechanical characteristics of the materials were considerably altered when subjected to extreme temperatures of 500 °C as observed from experimental data.

Nursing Care in Prevention of Post-Operative Pulmonary Complications among High-Risk Hospitalized Patients: A Case Study Design

Introduction: Post-operative pulmonary complications (PPCs) such as pneumonia, atelectasis, and respiratory failure significantly impact surgical outcomes, especially among high-risk patients with pre-existing respiratory conditions, advanced age, or those undergoing major surgeries. Effective prevention of PPCs is critical for improving patient outcomes. Nursing care plays a pivotal role in this prevention through early mobilization, respiratory exercises, proper positioning, and vigilant monitoring.Objectives :This study investigates the effectiveness of nursing care in preventing PPCs among high-risk hospitalized patients.Methods: A descriptive case study design was used, involving 15 patients from a multispecialty hospital in Trivandrum who met the inclusion criteria of having more than four risk factors for PPCs and consented to participate. Data collection tools included demographic variables, clinical manifestation checklists, risk factors for PPCs, and an individualized nursing care plan. Over six weeks, patients were selected through convenience sampling and a 24-hour nursing care plan was implemented. Descriptive statistics were used for data analysis. Results: The study sample consisted predominantly of elderly patients (73.3% aged above 60 years), with males constituting 66.7%. Significant risk factors included smoking history (66.7%) and elevated BMI (53.3%). All surgeries were performed under general anesthesia, with 60% lasting over 3-4 hours. Nursing interventions included deep breathing and coughing exercises, frequent position changes, early ambulation, use of an incentive spirometer, prophylactic antibiotics, and strict aseptic techniques. Most severe PPC symptoms were absent; however, mild symptoms like elevated temperature and cough were observed in 20% of patients. Discussion: The results indicate that the comprehensive nursing care strategies effectively prevented most significant PPCs. The absence of severe symptoms suggests the success of interventions such as early mobilization and respiratory exercises. The occurrence of mild symptoms in some patients highlights the need for ongoing refinement of nursing protocols. Conclusion: Effective nursing care significantly reduces PPC incidence in high-risk postoperative patients. This study supports the development of best practice guidelines for nursing care, emphasizing individualized care plans to improve patient outcomes and ensure high-quality healthcare services.

The effect of temperature on mechanical properties of calcium silicate hydrate enhanced by graphene oxide and graphene via molecular simulation study

With the advancement of the construction industry, there is a growing demand for cement materials with enhanced high-temperature resistance. This study utilizes reactive molecular dynamics to investigate the impact of elevated temperatures on the mechanical properties of graphene cement-based materials and the underlying mechanisms. The findings suggest that graphene nanosheets (GN) and graphene oxide (GO) can stabilize the structure of calcium silicate hydrate (C-S-H). Moreover, high temperatures can disrupt the H-bond network in composite structures, but the addition of GO can mitigate this effect. Additionally, elevated temperatures can influence the strength of relevant chemical bonds within the composite structure, leading to degradation in tensile strength and Young's modulus. Nevertheless, the incorporation of GO can enhance the mechanical properties of C-S-H at high temperatures. Conversely, the effect of GN on reducing the tensile strength of C-S-H is not significant and may even decrease the stiffness of C-S-H.

Investigation of the Influence of NiBSi/NiCrBSi Coatings Applied by Flame Spraying with Simultaneous Fusing on the Substrate Material

The aim of this research is to investigate the influence of nickel alloy type from the same group, the parameters of flame spraying, as well as the preparation of the substrate and the heat treatments of the substrate on the microstructure of the coating/substrate system. Due to the possibility of applying nickel alloys in corrective maintenance of tools used on elevated working temperatures, hot work tool steel X38CrMoV5-1 was selected as a substrate material. The investigation of the microstructure of the coating/substrate system was carried out according to the factorial design of experiment, where the input factors were varied on two levels. The factors that were varied are: Ni based self-fluxing alloys - NiCrBSi and NiBSi; distance of the burner from the workpiece - small (6 mm) and large (20 mm); preparation of the substrate - roughened and non roughened and the heat treatments of the substrate - soft annealed and tempered condition. Ni-based self-fluxing alloys were applied on samples (12,5 × 25 × 25 mm) by flame spraying with simultaneous fusing process. Analysis of the microstructures of the coating/substrate system was carried out on the Leica DM 2500M light microscope. After the conducted analysis the paper concluded that by spraying the selected coatings onto the X38CrMoV5-1 tool steel base, poor quality coatings are obtained, due to the appearance of cracks (NiCrBSi) or separation of the coating from the substrate (NiBSi). This is attributed to the formation of martensitic structure of the substrate after spraying and the presence of residual stresses.

Internally cooled tools: An eco-friendly approach to wear reduction in AISI 304 stainless steel machining

Austenitic stainless steel 304 is widely used in various applications due to its mechanical strength, toughness, and, most importantly, its corrosion resistance. However, machining this material presents significant challenges, primarily due to its high tendency for work hardening and generation of elevated temperatures. In the cutting process, this temperature rise can result in premature tool wear, leading to a reduction in their lifespan. To address these issues, cutting fluids are typically applied. Although this component offers advantages, it also contributes to environmental pollution, health risks, and significant costs, including disposal.Therefore, this study introduces an Internally Cooled Tool (ICT) method aimed at reducing the heat generated during machining. In this study, an analysis of tool life and wear was conducted to evaluate the effectiveness of ICTs compared to conventional machining methods during the turning of austenitic stainless steel 304 using double-coated tools (AlCrN on TiAlN, PVD (Physical Vapor Deposition)). Additionally, the use of ICTs in combination with lubrication (hybrid machining Minimum Quantity Lubrication (MQL) + ICT) was also investigated. The study covered five machining atmospheres (ICT, ICT + MQL, dry, wet, MQL). Cutting conditions were kept constant, including cutting speed (vc = 400 m/min), feed rate (f = 0.1 mm/rev), and depth of cut (ap = 0.5 mm). Scanning electron microscopy (SEM) analyses were conducted to examine the wear mechanisms and types present in each condition, along with statistical tests such as analysis of variance and Tukey tests to validate the experiments. The results indicated that ICTs (ICT and ICT + MQL) showed a longer tool life compared to dry machining and MQL techniques, while the wet machining method did not demonstrate significance compared to this technique. The observed wear mechanisms included abrasion, adhesion, and diffusion, with abrasion being the predominant mechanism. In summary, it was found that the durability of the inserts was directly related to coating adhesion, as coating detachment quickly led to the end of the insert's lifespan.

Micropillar compression of single-crystal single-phase (Co, Cu, Mg, Ni, Zn)O

Bulk, polycrystalline (Co, Cu, Mg, Ni, Zn)O was synthesized using solid-state sintering. Micropillars were prepared and mechanically deformed along three crystallographic orientations: (001), (101), and (111). Pillars (001) and (111) cracked, while Pillar (101) remained intact. Pillars (001) and (101) exhibited activated slip systems, confirmed by a large stress drop, and the presence of slip bands, respectively. Schmid factor (SF) analysis was performed to examine the effect of grain orientations on dislocation activity and slip behavior. SF values range from 0 to 0.5, with non-zero values indicating potential for slip. Six slip systems exist in the (Co, Cu, Mg, Ni, Zn)O rock salt crystal structure: 1/2⟨110⟩11¯0. For the (001) orientation, four slip systems are potentially active (SF = 0.5). For the (101) orientation, there are four potentially active slip systems (SF = 0.25). For the (111) orientation, no potentially active slips systems exist (SF = 0). Dislocation structures, which were observed post-compression via transmission electron microscopy, demonstrated variations in size, number, and distribution across the pillar, depending on micropillar orientation. Entangled dislocations created misorientation in Pillar (001), which led to the possible formation of subgrains, while singular dislocations were observed in Pillar (101), and a lack of dislocations was observed in Pillar (111). Zener–Stroh type dislocation entanglement-mediated cracking is the proposed cause of the transgranular-type cracks in Pillar (001). The possible subgrain formation, or lack of formation, respectively, caused intergranular-type cracks to additionally form in Pillar (001), while Pillar (111) only exhibited transgranular-type brittle fracture. In combination, these findings highlight the importance of dislocation activity, without the need for elevated temperature, and grain orientation in controlling the mechanical deformation response in single-phase (Co, Cu, Mg, Ni, Zn)O.