Higher Hardness Values Research Articles

Structure elucidation {single X-ray crystal diffraction studies, Hirshfeld surface analysis, DFT} and antibacterial studies of 1,2-benzothiazine metal complexes

The 2-benzyl-4‑hydroxy-1,1-dioxo-1,2-benzothiazine-3-carboxylic acid methyl ester i.e., ligand 1 was utilized to synthesize Mn(II) 2, Co(II) 3, Ni(II) 4, Cu(II) 5 and Zn(II) 6 derived metal complexes in mild basic conditions. The structural investigation was carried out by UV–vis, FT-IR, NMR spectroscopy, CHN analysis, conductivity measurement, ESI-MS analysis and magnetic susceptibility techniques. The X-ray diffraction analysis confirmed the octahedral and distorted square pyramidal geometries of the cobalt and copper complexes. The ligand 1 coordinated with metal centres through enolic oxygen atoms of the thiazine ring and ester group while methanol coordinated with metal center via oxygen atom. The Hirshfeld surface analysis (HSA) was utilized to determine the intermolecular interactions. In support of the experimental data, DFT studies were also performed for the cobalt and copper complexes. The NBO analysis resulted in the large stabilization values 11.91 and 12.35 kcal/mol for the cobalt and copper complexes. The global reactivity indicated the higher values of hardness and the large values of FMO analysis which support the higher stability of the metal complexes. The synthesized compounds were also evaluated against six bacterial strains to check their antibacterial potential. It was observed from results that highest activity was depicted by copper complex 5 against B. subtilis and the zone of inhibition is 23.4 ± 0.6 mm which is comparable to ampicillin (standard drug).

Making Composite Materials from Unsaturated Polyester and Coconut Fiber Judging from Mechanical Properties

Making combined materials that consist of unsaturated polyester and coconut fiber is the target of this research. The samples were tested by tensile and hardness tests before and after warm-up, and obtained by the result was that the trend value of hardness of unsaturated polyester+coconut fiber experienced proportional degradation with the addition of the composition of coconut fiber. The composition of 3% coconut fiber+97% unsaturated polyester has the highest hardness value, reaching 46,7 kg/mm2, and downhill becomes 43,1 kgf/mm2 moment heated at a temperature of 500C for 1 hour. Analog to the tensile test, 3% coconut fiber + 97% unsaturated polyester composition has the highest ultimate tensile strength and yield point. Adding fiber can boost the elasticity modulus, but the warm-up treatment causes the expansion of coconut fiber. The result is that the value of the tensile and hardness of the polyblend will go downhill.

Formation Mechanisms and Crack Propagation Behaviors of White Etching Layers and Brown Etching Layers on Raceways of Failure Bearings

White etching layers (WELs) and brown etching layers (BELs), formed on the upper layer of bearing raceways generally lead to surface crack initiation and propagation and significantly affect the stable operation of precision bearings. In this study, the microstructure features of WELs and BELs from two failure bearings have been characterized and analyzed. The BEL mainly consists of quenched martensite with higher hardness values. The bainite simultaneously exists at the boundary of the BEL/matrix. Owing to the relative roll and slip, temperature increases and rapid decreases are the main formation mechanisms of the BEL in this study (thermal-induced effect). The WEL can be only found on one sample, and elongated and coarse grains are found in this region. It can be speculated that the WEL may originate from the surface region temperature increasing again and then slowly decreasing. Cracks can initiate at the boundaries of the WEL/BEL/matrix. The crack propagation behaviors are significantly affected by the properties of the WEL and BEL microstructure. It is difficult for the cracks to propagate from a softer WEL into a harder BEL. Thus, the depth of cracks in the WEL is shallower. However, because of the brittle nature of quenched martensite in the BEL, cracks can easily propagate downward under contact stress. Thus, the depth of cracks can exceed 100 μm easily. The formation mechanisms of the WEL/BEL and crack propagation behaviors have been further proved and discussed in this study.

Impact and Compression Behavior of Habesha Moringa/Bamboo Fiber Reinforced Epoxy Composites

ABSTRACT Nowadays, synthetic fiber composites are in decline because of their high initial cost and detrimental impact on the environment. The main aim of this work is to develop natural fiber composite materials that are made from moringa and bamboo fibers by using the hand lay-up method by maintaining a constant 40 vol.% of epoxy content. Both the natural composites were treated with NaOH and also compared with their hybrid composite. The mechanical properties, such as compression, hardness, impact, tensile, flexural properties were investigated. Additionally, thermo gravimetric analysis of composites was also carried out. The biggest boost in compressive strength was seen in bamboo with 60% volume, with improvements ranging from a pure resin value of 13.06 to 68.43% compared to moringa 60% and 30–30% moringa-bamboo. The maximum rise in impact strength was recorded by BM-30/30 at 21J. In addition to this, the highest hardness value was observed by moringa-reinforced composites (MM-60) and noted to be around 40.83 HV. Tensile and flexural properties of all the composites reveal improvement as compared with neat epoxy composites. Bamboo exhibits a considerable improvement in thermal stability as compared with other compositions. Scanning electron micrographs were used to analyze the structure-property correlations.

Synthesis, spectral, DFT, and antibacterial studies of Nickel(II) and Cobalt(II) complexes with aminoantipyrine based Schiff base ligands

Schiff base complexes are a class of molecules that have sparked a great deal of attention due to their interesting chemical and physical properties, as well as their diverse applicability in a variety of scientific fields. Schiff bases and aminoantipyrine derivatives are continuously being investigated, despite their widespread use as medicines and bioactive compounds. In this study, we present the synthesis of new Ni(II) and Co(II) Schiff base complexes [M(L1-5)2Cl2] using the following ligands: 1,5-dimethyl-2-phenyl-4-((3,4,5-trimethoxy-benzylidene)amino)-1H-pyrazol-3(2H)-one (L1), 4-((4-methoxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (L2), 4-((3,4-dimethoxy-benzyli-dene)amino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (L3), 4-((1-([1,1′-biphenyl]-4-yl)ethyli-dene)amino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (L4), 4-((4-hydroxy-3-methoxy-benzylidene)amino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (L5), derived from aminoantipyrine. Various approaches, including UV, IR, NMR (1H, 13C), DFT analyses, and molar conductance measurement, have been employed to characterise freshly synthesised compounds. The antimicrobial screening results indicate that the anti-bacterial activities of the metal complexes are more active than the free ligands. All the synthesized compounds were found to be active against both Gram positive and Gram negative bacteria. Compound [Ni(L4)2Cl2] was found to show best activity. According to the reactivity parameter factors, compound Co(L2)2Cl2 has a higher value of hardness (η = 1.677 eV) and a lower value of softness (σ = 0.596 eV), It suggests that compound [Co(L2)2Cl2] is less reactive and more stable.

Increased Hardness Value of Medium Manganese Steel Through Double Tempering, Hot Rolling, and Variation of Cooling Media

Research has been conducted to enhance the hardness value of medium manganese steel through a heat treatment. Initially, this process begins with austenization at a temperature of 900°C, followed by tempering at 650°C and double tempering at 600°C, with each stage lasting 30 minutes. Subsequently, each stage concludes with a hot rolling process, after which air or water cools the material. As a result of these processes, the hardness tests revealed an increase in the hardness of medium manganese steel, reaching up to 389.70 BHN with a tensile strength of 827 MPa, which was notably achieved through air cooling. This significant increase in hardness is attributed to the emergence of the martensite phase and the presence of a large number of carbides, which are more evenly distributed after the double-tempering process. Additionally, small amounts of carbides were observed in the austenite matrix. Upon examination of the SEM fractography results, it was revealed that the fracture was mixed, with a cleavage area slightly larger than the dimple area. This observation suggests that despite its high hardness value, the sample retains good toughness.

Explosion Cracking Analysis of Sulfur Resistance Induction Heat Bend Pipe

The explosion cracking reason on induction heat bend pipe was analyzed through macroscopic analysis, chemical composition analysis, mechanical properties testing, metallographic analysis, scanning electron microscopy and XRD. The results showed that the chemical composition, tensile test, Vickers hardness results of the straight section of the bent pipe met the requirements of the technical specifications, and the metallographic structure of the straight section of the bent pipe was pearlite and ferrite. The Charpy impact test in the neutral zone of the bend section had a low shear fracture ratio, and the Vickers hardness test results were on the high side. The metallographic structure was granular bainite. The fracture surface of the failed bent pipe exhibited brittle fracture characteristics on the macro level. The metallographic analysis and hardness test results of the crack source area showed that the fracture surface had typical intergranular propagation characteristics and high hardness values. Energy spectrum analysis of the crack source area revealed the presence of S element. The XRD analysis of the product on the inner wall of the pipe contained sulfides. The comprehensive results indicated that the failed bend pipe undergoes stress corrosion and initiates corrosion cracks on the surface under the combined action of operating pressure, additional bending stress, residual stress, etc. in a sulfide corrosive medium, the cracks continued to propagate along the grain boundaries and ultimately caused the bend pipe to explode.

Fabrication of multi-walled carbon nanotube/polycaprolactone scaffolds for possible application in tissue engineering

Flexible scaffolds made of polycaprolactone (PCL), and multi-walled carbon nanotubes (MWCNTs) were created and chemically verified through RAMAN. The most suitable coupling percentages for PCL were 1%, 3%, and 5% MWCNT. The scaffolds were very stable with high hardness values (10–12 GPa). The PCL/MWCNT 5% scaffold was the most flexible and least resistant, with adequate porosity, pore size, and interconnectivity for cell anchoring. Moreover, the scaffold exhibited low cytotoxicity with a cell viability of 90%. These flexible PCL/MWCNT scaffolds were developed to support tissue engineering by providing a mechanical response with flexibility and elasticity like the surrounding tissue.

The effect of chemical composition and heat parameter on Nano-sized precipitate dispersion characterization in ODS steels

Oxide dispersion strengthened (ODS) supersaturated solid solution alloy powders with different Y/Ti atomic ratios were formed by mechanical alloying (MA) method and then heat treated under different conditions. The morphology, phase composition, and particle size distribution were researched. The precipitate distribution densities and hardness values of alloy powders after heat treatment were measured at the same time by the SAXS method and hard tester. The results show that the morphology of MA alloy powders is irregular in shape and only a small amount of MA alloy powders is bigger than 30 μm. During the MA process, alloy elements are solid solutions in the matrix. The work-harden effect of alloy powders formed in the MA process would be eliminated during the heat treatment process. The chemical composition and heat treatment parameters are crucial effects on nano-sized precipitate distribution characterization in ODS steels. The ODS sample with a Y/Ti atomic ratio of 0.99 has the highest distribution density of oxide precipitates at 1.89×1022/m3 resulting in the highest hardness value during the heat treatment process. The sample with a Y/Ti atomic ratio of 0.42 has the highest distribution density of nanoclusters 7.32×1023/m3.

Analysis of Mechanical Properties and Microstructure of Aluminum and Copper Sheet Welding Using Friction Stir Spot Welding Method

Welding aluminum and copper materials using friction stir spot welding (FSSW) is widely practiced. Although strong enough, it still produces keyhole and shoulder marks, which are quite large due to the large shoulder and pin sizes. This study investigates the joining of aluminum and copper panels using the FSSW technique using smaller shoulders and pins in different shoulder shapes. The study began by cutting aluminum and copper panels 150 mm long, 50 mm wide, and 5 mm thick. The joining process was carried out at rotational speeds of 900, 1200, and 1500 rpm with tools with several variations in pin length. Pin lengths of 0, 5, and 7 mm with pin diameters made the same at 5 mm, shoulder diameter 20 mm. The connection was observed for macrostructure, microstructure, and hardness. Different tool geometries have the potential to be applied in FSSW joints, especially for sheets. The highest hardness value is found in Cu-Cu material welding, with an average hardness value of 101.63 HVN in the stir zone area. The lowest hardness value is located in the base metal of aluminum material, with an average hardness value of 48.37 HVN.

EXPERIMENTAL STUDY THE MECHANICAL PROPERTIES OF GMAW WELDING RESULTS ON S355J2+N MATERIAL WITH POST WELD HEAT TREATMENT (PWHT)

Assembly underframe trains are a connecting process part-part into a system that has a unified function, the process of which uses GMAW-type welding. From the welding results, there is potential for the formation of residual stress which is a problem in this research, so it is minimized using the method Post Weld Heat Treatment (PWHT) thermal. The research aims to determine and analyze the effect of PWHT on the mechanical properties and microstructure of low-carbon steel type S355J2+N resulting from GMAW welding. The research method uses experiments with PWHT temperatures at 450 °C, 750 °C, and non-PWHT to find out the mechanical properties of materials, use the tensile test and micro-Vickers hardness test. Meanwhile, to determine the microstructure formed is used micro examination. The test results, were compared between the welding material with PWHT and the welding material non-PWHT. The results of the research are that the largest tensile strength value of 576 MPa was produced in the material using PWHT at a temperature of 450 °C, the largest elongation of 34.85% was produced in the material with a PWHT temperature of 750 °C, and the highest hardness value was 207.44 HV in the material non-PWHT. The conclusion of the research shows that with increasing PWHT temperature, the hardness and tensile strength values of the material decrease, and there is an increase in the ductility value of the material which is influenced by changes in the dominance of ferrite and pearlite in the material.

Reduced fat and sugar cakes developed by protein/polysaccharide/licorice extract ternary gel-like foams

Reduced sugar and fat products are increasingly in demand due to the link between excessive consumption of these substances and chronic noncommunicable diseases. Therefore, this study aimed to produce a low-calorie cake by replacing sugar and fat with whey protein isolate/sodium alginate/licorice extract ternary foam at three substitution levels of 0 %, 25 %, and 50 %. As the amount of foam used as a replacement increased, there were marked decreases in batter viscosity (5.29–2.64 Pa s) and density (1.13–0.88 g cm−3), as well as in the cake's fat (8.91–4.73 g/100 g), carbohydrate (67.92–47.09 g/100 g), specific volume (3.13–1.76 mL g−1), calories (371.37–252.57 kcal/100 g), and porosity (10.25–5.05 %). On the other hand, moisture and water activity increased significantly (p < 0.05) with the increase of foam replacement. In terms of crust color, a* decreased while L* and b* increased remarkably. The cake samples with 0 % and 50 % substitution levels had the lowest and highest values for hardness (0.76 vs. 2.38 N), cohesiveness, and chewiness, respectively. The sensory evaluation results showed that the sample with a 25 % substitution level was more similar to the control sample. This suggests that foam can be used as a substitute for sugar and fat to produce a healthier product.

Effect of milling time on microstructure and hardness of AA7075-15 wt% SiC-1 wt% MWCNT nanocomposite

In this study, the effect of ball milling on microstructure and hardness of Al7075 - 15 wt% SiC - 1 wt% MWCNT nanocomposite was investigated as a function of milling time up to 20 h. Mechanically alloyed powders were consolidated by cold pressing followed by sintering at 560°C for 1 h in an argon atmosphere. The structural characterization of nanocomposites was conducted by a X-ray diffractometer (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and grain size analyses. The hardness of samples was measured by using Wolpert Wilson-400 micro-hardness testing equipment comprising of a Vickers indenter. The structural defects of pristine and milled MWCNTs were calculated by using defect and carbon intensity ratio (ID/IG) resulted from Raman spectroscopy. The results indicate that after ball milling, the grain size decreases depending on the milling time, the intermetallic Al4C3 phase is formed as a result of the reaction between the matrix and the MWCNT particles, and the MWCNT structure is destroyed. The finest grain size and highest hardness values were obtained as 483 nm and 134 HV, respectively, after 15 h of grinding.

Effects of temperature and strain rate on the deformation microstructure and hardness of Al–Zn eutectoid damping alloy

Abstract The effects of temperature and strain rate on the deformation microstructure and hardness of Al–Zn eutectoid damping alloy was systematically investigated. The results show that the deformed alloy is mainly composed of eutectoid structure with η-Zn distributing on α-Al matrix. There are two forms of η-Zn particles in the eutectoid structure of the deformed alloy. The first type of η-Zn particles (η-ZnI) have relatively large sizes and display irregular morphology; another type of η-Zn particles (η-ZnII) have relatively small sizes and are characterized by dispersion distribution. There exist predominant η-ZnI particles at lower temperature and higher strain rate while dominant η-ZnII particles at higher temperature and lower strain rate. The hardness of the Al–Zn eutectoid damping alloy shows an overall rising trend with increase in temperature and decrease in strain rate. In particular, the highest hardness values (up to 113.07 HB) are obtained at 648 K/0.01 s−1.

Low‐temperature sintered (Ti, Zr, Nb, Ta, Mo)C ceramics with improved hardness and toughness by using CrN as sintering additive

AbstractCurrently, previous studies of low‐temperature sintering of high‐entropy carbide ceramics (HECCs) have followed the traditional approach to use the low‐melting‐point metals, such as Co, Ni, and so forth, as sintering additives. However, metallic binders can cause adverse impacts on hardness of HECCs. This study reported an innovation processing method for low‐temperature sintering of HECCs, which involved the use of various contents of CrN as sintering additive and spark plasma sintering at 1600°C to obtain dense HECCs. In comparison to the grain size of pure (Ti, Zr, Nb, Ta, Mo)C bulk sintered at 2000°C (3.29 ± 1.02 μm), the grain size of samples with the addition of 5–15 wt.% CrN sintered at 1600°C was significantly smaller, ranging from 0.32 to 0.48 μm. By using only 5 wt.% CrN, dense (Ti, Zr, Nb, Ta, Mo)C ceramics with a high hardness value of 26.73 ± 0.43 GPa could be obtained. Furthermore, increasing the amount of CrN to 15 wt.% resulted in a fracture toughness of 3.78 ± 0.10 MPa·m1/2. It is anticipated that the (Ti, Zr, Nb, Ta, Mo)C ceramic with an ideally combined hardness and toughness can be achieved at low sintering temperatures by the proper control of CrN content.

A brief study of electrical and biological properties of BNT6BT/ZnO-HA Composite

The discovery of the piezoelectric properties of natural bone and their influence on bone growth within scaffolds has spurred researchers to investigate a range of bio-piezoelectric composite materials. By exploring these materials, researchers aim to better understand how piezoelectricity can be harnessed to promote bone growth and tissue regeneration, potentially leading to new breakthroughs in the field of regenerative medicine. In this study, the piezoelectric material, Bi0.5Na0.5TiO3-0.6BaTiO3/nano ZnO (BNT6BT/ZnO) and the biological hydroxyapatite (HA) were separately synthesized using the sol-gel method. The composite samples consisting of BNT6BT/ZnO and HA were fabricated using isostatic cold pressing. The composition and phase structure were studied using the X-ray diffraction (XRD) analysis, and the scanning electron microscopy (SEM) was used to study the microstructure and morphology. The presence of different phases and the distribution of elements were examined using EDAX elemental analysis and its corresponding maps. Among the composite samples the one containing 10 wt% HA (BNT6BT/ZnO-10HA) possessed the best dielectric properties. The Vickers hardness measurements showed that the addition of HA to the piezoelectric phase BNT6BT/ZnO results in higher hardness values, which expects to increase the fracture toughness of HA due to the higher elastic modulus to hardness ratio (E/H) of composite samples compared to pure HA. The in vitro bioactivity of the samples was tested in simulated body fluid (SBF) solution and the cell culture analysis was performed to examine the biocompatibility of the samples. Accordingly, apatite was deposited on the surface of the samples and all of the composite samples were bioactive. Furthermore, the BNT6BT/ZnO-10HA sample containing the largest amount of deposit showed the highest optical density (OD) in the MTT test.

Influence of Salting on Physicochemical and Sensory Parameters of Blue-Veined Cheeses

Salting influences microbial growth, enzymatic activity, and biochemical reactions during ripening, thus contributing to the final quality of cheese. The aim of this study was to evaluate the influence of different salting methods (dry salting at 12, 24, and 48 h; salting in brine; and salting of partially drained curd, before moulding) on the chemical (moisture and salt content), physicochemical (pH, titratable acidity, and water activity), and sensory characteristics (texture profile analysis, colour, and sensory attributes) of industrial blue-veined cheese. Dry-salted cheeses had lower moisture content and water activity, and higher salt/moisture content and acidity than those salted in brine and in the partially drained curd. Dry-salted cheeses were also characterised by higher values for hardness, fracturability, and instrumental gumminess. Dry-salted cheeses showed differences only in the red/green colour component (a*), with the cheeses salted in the partially drained curd being less greenish. All cheeses scored high (around 7) in the tasters’ overall impression, with the dry-salted cheeses at 12 and 24 h showing optimal growth and distribution of mould, as well as better flavour and texture.

Hardness Test Analysis on ST 37 Steel Plate Material and Aluminum Using the Brinell Test Method

One of the most frequently used methods of material testing is hardness testing. The aim of conducting research on material hardness is to determine the hardness value of the material specimens tested, namely ST 37 steel plate and aluminum plate. The test method is to use the Brinell hardness test where the values ​​obtained during testing are from the force load, indenter diameter and pressure trace diameter and the pressure time that has been determined. By using testing tools such as hardness tester, mechanical caliper, indenter, flat file, stopwatch. And the materials used are ST 37 steel plate, aluminum plate and sandpaper. From the test results obtained we can calculate the Brinell hardness value of the test material. The value from the calculation of test data where the highest hardness value using the Brinell method (BHN) for ST 37 steel plate material is 256.992. Meanwhile, the highest hardness value using the Brinell method (BHN) for aluminum plate material is 55,182.

High entropy Fe–Mn–Ni–Co–Al–C alloys from an industrial steel

High entropy alloys (multiprinciple element alloys) were produced by dilution of the base component in a Fe–Mn–Al–C alloy. The studied Fe–Mn–Ni–Al–C and Fe–Mn–Ni–Co–Al–C alloys were treated thermally and mechanically. These alloys were studied by X-ray diffractometry and electron microscopy, while mechanical properties were tested by mechanical loading. A dual-phase cF4 and cP2 structure was formed. The alloys showed high-hardness values and high-strain hardening ability but when hot rolled exhibited precipitation of carbides. These alloys are considered to be model alloys for the development of future high-entropy alloys based on industrial steels.

The role of carbon addition on properties of boron carbide- silicon carbide composites

In this research, composites were produced by mixing boron carbide (B4C) and silicon carbide (SiC) with varying amounts of carbon (C) and densifying them via spark plasma sintering at 1950 °C for 5 min. The effects of different C contents on the properties of the composites were observed. Density, elastic modulus, microstructure, Vickers hardness, and fracture toughness were evaluated. It has been observed that the oxygen content of starting powders should be matched with the added C content to obtain high density and desirable mechanical properties. The highest density, elastic modulus, and hardness values were obtained in samples containing 1.5 wt% C. The highest elastic modulus was obtained in the 10 wt% B4C–SiC-1.5 wt% C sample, at 451 GPa. The highest hardness value was 32.85 GPa, corresponding to the sample containing 90 wt% B4C–SiC-1.5 wt% C. The highest fracture toughness value was attained by the sample containing 10 wt% B4C–SiC-2.5 wt% C, at 2.87 MPa m1/2. Lastly, the composite samples showed transgranular fracture behavior.