Journal of the Nigerian Society of Physical Sciences
The most suitable electrolyte for graphene oxide synthesis, in terms of both production eff... more The most suitable electrolyte for graphene oxide synthesis, in terms of both production efficiency and quality, using the electrochemical exfoliation technique has been investigated and reported in this study. Simultaneous anodic and cathodic graphene oxide production using ten (10) different electrolytes, including acids (H2SO4, HCl, HNO3), bases (KOH, Ca(OH)2, Mg(OH)2, NaOH), and salts (NaCl, (NH4)2SO4, K2SO4), was studied under the same experimental conditions of bias voltage, graphite nature, exfoliation time, electrolyte molarity, and post-exfoliation treatments. Assessment of the graphene oxide structures and production rates was supported using Raman spectroscopy, high-resolution scanning electron microscopy (HRSEM), and EDS (energy dispersive x-ray spectroscopy), attached to the scanning electron microscope. Analysis of the results obtained reveals that H2SO4 showed the highest graphene oxide yield (86%) but with comparably low graphene oxide quality in terms of defect...
The research investigates the effect of varying amounts of aluminium (1.05, 1.575, 2.29, 3.02 and... more The research investigates the effect of varying amounts of aluminium (1.05, 1.575, 2.29, 3.02 and 3.74 wt.%) addition and heat treatment (austempering at 300, 350, 400 oC) on the microstructure and mechanical properties of ductile cast iron alloys. The graphitizing effects of the Al alloy and varied austempering temperatures on hardness, tensile strength, and impact toughness of the ductile cast iron (DCI) were evaluated. The results of the influences of Al addition and heat treatment on the properties of the DCI determined were presented as graphical data while the microstructures were done by using a scanning electron microscope (SEM). The microstructures revealed that the addition of Al into the matrix brings about the precipitation of ferrite around the graphite nodules. The combined effects of the increase Al content and austempering temperatures produced greater hardness values on the Al-alloyed DCI samples than the as-cast sample. The hardness value for the entire sample rang...
This article reports on the structure and electronic properties of carbon-rich polysilazane polym... more This article reports on the structure and electronic properties of carbon-rich polysilazane polymer-derived silicon carbonitride (C/SiCN) corresponding to pyrolysis temperatures between 1100 and 1600 °C in an argon atmosphere. Raman spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM) and Hall measurements were used to support the structural and electronic properties characterization of the prepared C/SiCN nanocomposites. A structural analysis using Raman spectroscopy showed the evolution of sp2 hybridized carbon phase that resulted from the growth in the lateral crystallite size (La), average continuous graphene length including tortuosity (Leq) and inter-defects distance (LD) with an increase in pyrolysis temperature. The prepared C/SiCN monoliths showed a record high room temperature (RT) electrical conductivity of 9.6 S/cm for the sample prepared at 1600 °C. The electronic properties of the nanocomposites determine...
World Academy of Science, Engineering and Technology, International Journal of Materials and Metallurgical Engineering, 2015
In this research, Bond work index was used to evaluate the grinding energies of selected rock sam... more In this research, Bond work index was used to evaluate the grinding energies of selected rock samples in order to predict their use as aggregate for road pavement. Samples of granite gneiss, porphyritic granite (Location1 i.e. L1), charnockitic rock and porphyritic granite (Location2 i.e. L2) from Itaji and Ikere in Ekiti State, Akure and Itaogbolu in Ondo State respectively; all in southwestern Nigeria were tested for hardness (aggregate crushing value, ACV and aggregate impact value, AIV). The Bond work index of these samples was also determined. The Bond work index of the granite gneiss was found to be 13.72kWh/t, that of the porphyritic granite (L2) 12.76kWh/t and that of the porphyritic granite (L1) and charnockitic rock were found to be 13.64kWh/t and 17.12kWh/t respectively. In order to predict aggregate quality, Bond work index (Wi) of samples were correlated with aggregate crushing value (Xacv) and aggregate impact value (Xaiv). Hence, the Bond work index values ranging bet...
In the present study, the influence of stirring speed on the solid solution hardening of cast alu... more In the present study, the influence of stirring speed on the solid solution hardening of cast aluminium alloy leading to improvement in microhardness values have been reported. Stir casting method was used to prepare percentage compositions of Al-Cu alloys between 0 and 15 wt% Cu. Different stirring speed of 0 rev/min, 10 rev/min, 50 rev/min and 90 rev/min were used to make test sample and materials produced were characterized for hardness. Hardness values of the 0–15 wt% Cu solute addition were observed to independently increase progressively with increase in stirring speed. The increase in microhardness observed is attributed to increase in the dispersion of Cu solute in the Al solution caused by the stirring action which contributed to impeding plastic deformation in the Al lattice. The study further indicates that stirring could be a vital metallurgical processing tool to enhance hardness during alloying.
The influence of variable stirring speeds on cast aluminium-copper alloys and the resulting enhan... more The influence of variable stirring speeds on cast aluminium-copper alloys and the resulting enhancements in mechanical properties have been described in this study. Aluminium-copper (Al-Cu) alloys with 0-15 wt% Cu compositions were prepared via electro-mechanical stir casting process using various stirring speeds (0 rev/min, 10 rev/min, 50 rev/min and 90 rev/min) and the alloy materials produced were tested for microhardness and tensile strength. Increase in both wt% Cu compositions and stirring speeds were observed to have led to improvements in microhardness and tensile strength. The microstructural and mechanical characterisations also revealed that improvements in material properties recorded could be attributed to three mechanisms which are: solid solution hardening, precipitation hardening and the stirring effect.
The concentration of inorganic chemical substances released into surface water from Okaba coal de... more The concentration of inorganic chemical substances released into surface water from Okaba coal deposit were measured using spectroscopic techniques in order to assess the extent of pollution. Parameters measured (Pb, Fe, Cu, Cr, SO42-, Cl-, Mn, Zn and pH) showed that water samples within the mine area contain Pb, Fe, Cr, Cl-, Mn and Zn in concentrations beyond permissible intake limits; and the concentration of chloride measured (3000 mg/L) is capable of causing acid mine drainage (AMD). Concurrent evaluation of these inorganic substances using quantitative assessment reveal the possible presence of trace minerals like galena, sphalerite, chalcopyrite, pyrite and clay in Okaba coal deposit. Keywords— Acid mine drainage (AMD), Coal, Trace minerals, Water pollution
Corrosion cannot be completely stopped; however, the rate of corrosion can be retarded, hence the... more Corrosion cannot be completely stopped; however, the rate of corrosion can be retarded, hence the need for corrosion inhibitors. Corrosion process can be mitigated by the use of various chemical inhibitors; using green inhibitors is one of the methods used to control corrosion and still preserved the environment. The present study presents the extraction of thevetia peruviana extract using soaking method in Ethanol, and bio inhibitive properties of Thevetia peruviana fruit (TPF) extract on low carbon steel corrosion in sulphide solution. Low carbon steel samples were subjected to six sodium sulphide solution environments; five of the environments have TPF extract ranging from 10 ml to 50 ml while the 6th which served as control has no TPF extract. Weight loss experiment was carried out for 28 days and readings were taken at 4 days interval. Mechanical tests (impact test and tensile test) were also carried out on the low carbon steel samples. The results revealed that TPF extract exh...
With much amount of money the nation had invested into the extractive sector of the economy, mine... more With much amount of money the nation had invested into the extractive sector of the economy, minerals are still mined and exported out of the country for beneficiation which results into much economic losses in the mining and extractive industries. The need to reduce the huge amount of losses expended on extracting valuable metals from ores by local miners and out springing cottage industries motivates this work. This report covers the design and construction of a laboratory size leaching equipment suitable for dissolution of clean pulverised minerals in acid and alkaline media via agitation and in-situ leaching techniques in single operation system. The dissolved metals are easily recovered from the solution by other techniques. The design and fabrication is based on the fundamentals of stoichiometric calculations and chemical reactions, engineering design drawings using AUTOCAD and INVENTOR softwares, material selection and safe environmental ethics. The equipment is produced from...
In this research, grinding energy of selected rock samples collected from South West Nigeria was ... more In this research, grinding energy of selected rock samples collected from South West Nigeria was determined using comminution theory in order to evaluate suitability of rock for aggregate production. Bond Work Index (BWi), Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) of samples was characterized and correlated. The work index of the charnockitic rock, granite gneiss, porphyritic granite –labelled PG1 and porphyritic granite –labelled PG2 of samples was found to be 17.12 kWh/t, 13.72 kWh/t, 13.64 kWh/t and 12.76 kWh/t respectively. The ACV of the charnockitic rock, granite gneiss, porphyritic granite (PG1) and porphyritic granite (PG2) was determined to be 26.2 %, 27.3 %, 27.6 % and 27.8 % respectively; while the AIV of the samples, in same order, was 11.2 %, 13.2 %, 19.1 % and 18.4 % respectively. Following high correlation coefficient of 0.98% between BWi and ACV, hardness of rock materials are classified as ‘very difficult’, ‘difficult’, ‘medium’, ‘easy’ and ‘ve...
This review paper has established austempered ductile iron (ADI) as a classical material that has... more This review paper has established austempered ductile iron (ADI) as a classical material that has spectra of properties achieved by altering some processing parameters through heat treatment procedures. Concerted efforts have been made to equally explore the use of additives as additional materials to this all important alloy. The use of modifiers at ultra-fine or nano-scale level as additive to the melt prior casting has also been reviewed. However, the continuous quest for innovative approaches of upgrading the structural and mechanical characteristics of ductile irons has open up interest in the development of nanostructured and nanocomposite components in bulky iron bearing materials. This paper cross-examines few available literatures on the nanostructured ADI with the aim of adopting similar methodology in the development of nanostructured aluminium-alloyed DI and nanostructured aluminium-alloyed ADI. Emphasy is laid on reviewing the production techniques and treatment paramet...
In this study, the effects of austempering on the microstructure, mechanical properties (micro ha... more In this study, the effects of austempering on the microstructure, mechanical properties (micro hardness, impact energy and tensile strength) and corrosion behaviours of AISI 1018 low carbon steel were evaluated. The steel specimens were subjected to heat treatment by austenitizing at 830°C, maintained in this condition for 90 min before rapid cooling in a NaNO3 salt bath sustained at 300°C for isothermal transformation for additional 50 min and finally allowed to air cool to room temperature. The as-received and the austempered samples were tested for corrosion in both 0.5M aqueous acidic (HCl) and 0. 5M alkaline (NaOH) media. Microstructural investigation using scanning electron microscope (SEM) reveals transformation from ferrite/pearlite phases to bainite over the austempering process. Interestingly, significant improvements of 15.7% to 95.7% in the various mechanical properties (micro hardness, impact energy and tensile strength) and corrosion resistance in both media were obser...
In this paper, profit is maximized (or production cost is minimized) by developing an Integer pro... more In this paper, profit is maximized (or production cost is minimized) by developing an Integer programming (IP) model to determine, at a given respective unit cost, optimal numbers of outputs obtainable per production cycle (time) using public electricity generated from national grids and alternate electricity from generators subject to production output capacity or demand constraint. The results obtained showed that production cycle time has a great impact on the determination of optimal outputs for the respective conditions. Also, increase in cost of public electricity per unit product has an upper limit beyond which it has negative effect on the profitability. The results served as determinant factors for production industry in establishing the level of outputs that sustained the profitability by providing optimal cost of public electricity to operate without having any effect on the profit, at a given cycle time. Keywords— Constraint, cycle time, integer programming, optimal numb...
Aluminium alloys demonstrate exceptional properties such as high strength-weight ratio and corros... more Aluminium alloys demonstrate exceptional properties such as high strength-weight ratio and corrosion resistance are used for general engineering applications, automobile, automotives and in aerospace industries. However, they suffer some limitations as wear and creep at high temperatures. With the trending developments from nanometallurgy, diverse nano-particle compounds of mono and heterogeneous compositions have been used in reinforcing aluminium and its alloys as widely reported in the public domains. This paper reviews some of the vast literature on the enhancement of nanostructured aluminium alloys and reinforced aluminium nanocomposites. Importance is laid on the tribological and mechanical behaviours of the manufactured composites and nano-composites with respect to their production methods and applications at elevated (high) and cryogenic (low) temperatures. Keywords— Tribology; mechanical behaviours; nanostructure; aluminium alloys; nano-composites; elevated temperatures
Journal of the Nigerian Society of Physical Sciences
The most suitable electrolyte for graphene oxide synthesis, in terms of both production eff... more The most suitable electrolyte for graphene oxide synthesis, in terms of both production efficiency and quality, using the electrochemical exfoliation technique has been investigated and reported in this study. Simultaneous anodic and cathodic graphene oxide production using ten (10) different electrolytes, including acids (H2SO4, HCl, HNO3), bases (KOH, Ca(OH)2, Mg(OH)2, NaOH), and salts (NaCl, (NH4)2SO4, K2SO4), was studied under the same experimental conditions of bias voltage, graphite nature, exfoliation time, electrolyte molarity, and post-exfoliation treatments. Assessment of the graphene oxide structures and production rates was supported using Raman spectroscopy, high-resolution scanning electron microscopy (HRSEM), and EDS (energy dispersive x-ray spectroscopy), attached to the scanning electron microscope. Analysis of the results obtained reveals that H2SO4 showed the highest graphene oxide yield (86%) but with comparably low graphene oxide quality in terms of defect...
The research investigates the effect of varying amounts of aluminium (1.05, 1.575, 2.29, 3.02 and... more The research investigates the effect of varying amounts of aluminium (1.05, 1.575, 2.29, 3.02 and 3.74 wt.%) addition and heat treatment (austempering at 300, 350, 400 oC) on the microstructure and mechanical properties of ductile cast iron alloys. The graphitizing effects of the Al alloy and varied austempering temperatures on hardness, tensile strength, and impact toughness of the ductile cast iron (DCI) were evaluated. The results of the influences of Al addition and heat treatment on the properties of the DCI determined were presented as graphical data while the microstructures were done by using a scanning electron microscope (SEM). The microstructures revealed that the addition of Al into the matrix brings about the precipitation of ferrite around the graphite nodules. The combined effects of the increase Al content and austempering temperatures produced greater hardness values on the Al-alloyed DCI samples than the as-cast sample. The hardness value for the entire sample rang...
This article reports on the structure and electronic properties of carbon-rich polysilazane polym... more This article reports on the structure and electronic properties of carbon-rich polysilazane polymer-derived silicon carbonitride (C/SiCN) corresponding to pyrolysis temperatures between 1100 and 1600 °C in an argon atmosphere. Raman spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM) and Hall measurements were used to support the structural and electronic properties characterization of the prepared C/SiCN nanocomposites. A structural analysis using Raman spectroscopy showed the evolution of sp2 hybridized carbon phase that resulted from the growth in the lateral crystallite size (La), average continuous graphene length including tortuosity (Leq) and inter-defects distance (LD) with an increase in pyrolysis temperature. The prepared C/SiCN monoliths showed a record high room temperature (RT) electrical conductivity of 9.6 S/cm for the sample prepared at 1600 °C. The electronic properties of the nanocomposites determine...
World Academy of Science, Engineering and Technology, International Journal of Materials and Metallurgical Engineering, 2015
In this research, Bond work index was used to evaluate the grinding energies of selected rock sam... more In this research, Bond work index was used to evaluate the grinding energies of selected rock samples in order to predict their use as aggregate for road pavement. Samples of granite gneiss, porphyritic granite (Location1 i.e. L1), charnockitic rock and porphyritic granite (Location2 i.e. L2) from Itaji and Ikere in Ekiti State, Akure and Itaogbolu in Ondo State respectively; all in southwestern Nigeria were tested for hardness (aggregate crushing value, ACV and aggregate impact value, AIV). The Bond work index of these samples was also determined. The Bond work index of the granite gneiss was found to be 13.72kWh/t, that of the porphyritic granite (L2) 12.76kWh/t and that of the porphyritic granite (L1) and charnockitic rock were found to be 13.64kWh/t and 17.12kWh/t respectively. In order to predict aggregate quality, Bond work index (Wi) of samples were correlated with aggregate crushing value (Xacv) and aggregate impact value (Xaiv). Hence, the Bond work index values ranging bet...
In the present study, the influence of stirring speed on the solid solution hardening of cast alu... more In the present study, the influence of stirring speed on the solid solution hardening of cast aluminium alloy leading to improvement in microhardness values have been reported. Stir casting method was used to prepare percentage compositions of Al-Cu alloys between 0 and 15 wt% Cu. Different stirring speed of 0 rev/min, 10 rev/min, 50 rev/min and 90 rev/min were used to make test sample and materials produced were characterized for hardness. Hardness values of the 0–15 wt% Cu solute addition were observed to independently increase progressively with increase in stirring speed. The increase in microhardness observed is attributed to increase in the dispersion of Cu solute in the Al solution caused by the stirring action which contributed to impeding plastic deformation in the Al lattice. The study further indicates that stirring could be a vital metallurgical processing tool to enhance hardness during alloying.
The influence of variable stirring speeds on cast aluminium-copper alloys and the resulting enhan... more The influence of variable stirring speeds on cast aluminium-copper alloys and the resulting enhancements in mechanical properties have been described in this study. Aluminium-copper (Al-Cu) alloys with 0-15 wt% Cu compositions were prepared via electro-mechanical stir casting process using various stirring speeds (0 rev/min, 10 rev/min, 50 rev/min and 90 rev/min) and the alloy materials produced were tested for microhardness and tensile strength. Increase in both wt% Cu compositions and stirring speeds were observed to have led to improvements in microhardness and tensile strength. The microstructural and mechanical characterisations also revealed that improvements in material properties recorded could be attributed to three mechanisms which are: solid solution hardening, precipitation hardening and the stirring effect.
The concentration of inorganic chemical substances released into surface water from Okaba coal de... more The concentration of inorganic chemical substances released into surface water from Okaba coal deposit were measured using spectroscopic techniques in order to assess the extent of pollution. Parameters measured (Pb, Fe, Cu, Cr, SO42-, Cl-, Mn, Zn and pH) showed that water samples within the mine area contain Pb, Fe, Cr, Cl-, Mn and Zn in concentrations beyond permissible intake limits; and the concentration of chloride measured (3000 mg/L) is capable of causing acid mine drainage (AMD). Concurrent evaluation of these inorganic substances using quantitative assessment reveal the possible presence of trace minerals like galena, sphalerite, chalcopyrite, pyrite and clay in Okaba coal deposit. Keywords— Acid mine drainage (AMD), Coal, Trace minerals, Water pollution
Corrosion cannot be completely stopped; however, the rate of corrosion can be retarded, hence the... more Corrosion cannot be completely stopped; however, the rate of corrosion can be retarded, hence the need for corrosion inhibitors. Corrosion process can be mitigated by the use of various chemical inhibitors; using green inhibitors is one of the methods used to control corrosion and still preserved the environment. The present study presents the extraction of thevetia peruviana extract using soaking method in Ethanol, and bio inhibitive properties of Thevetia peruviana fruit (TPF) extract on low carbon steel corrosion in sulphide solution. Low carbon steel samples were subjected to six sodium sulphide solution environments; five of the environments have TPF extract ranging from 10 ml to 50 ml while the 6th which served as control has no TPF extract. Weight loss experiment was carried out for 28 days and readings were taken at 4 days interval. Mechanical tests (impact test and tensile test) were also carried out on the low carbon steel samples. The results revealed that TPF extract exh...
With much amount of money the nation had invested into the extractive sector of the economy, mine... more With much amount of money the nation had invested into the extractive sector of the economy, minerals are still mined and exported out of the country for beneficiation which results into much economic losses in the mining and extractive industries. The need to reduce the huge amount of losses expended on extracting valuable metals from ores by local miners and out springing cottage industries motivates this work. This report covers the design and construction of a laboratory size leaching equipment suitable for dissolution of clean pulverised minerals in acid and alkaline media via agitation and in-situ leaching techniques in single operation system. The dissolved metals are easily recovered from the solution by other techniques. The design and fabrication is based on the fundamentals of stoichiometric calculations and chemical reactions, engineering design drawings using AUTOCAD and INVENTOR softwares, material selection and safe environmental ethics. The equipment is produced from...
In this research, grinding energy of selected rock samples collected from South West Nigeria was ... more In this research, grinding energy of selected rock samples collected from South West Nigeria was determined using comminution theory in order to evaluate suitability of rock for aggregate production. Bond Work Index (BWi), Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) of samples was characterized and correlated. The work index of the charnockitic rock, granite gneiss, porphyritic granite –labelled PG1 and porphyritic granite –labelled PG2 of samples was found to be 17.12 kWh/t, 13.72 kWh/t, 13.64 kWh/t and 12.76 kWh/t respectively. The ACV of the charnockitic rock, granite gneiss, porphyritic granite (PG1) and porphyritic granite (PG2) was determined to be 26.2 %, 27.3 %, 27.6 % and 27.8 % respectively; while the AIV of the samples, in same order, was 11.2 %, 13.2 %, 19.1 % and 18.4 % respectively. Following high correlation coefficient of 0.98% between BWi and ACV, hardness of rock materials are classified as ‘very difficult’, ‘difficult’, ‘medium’, ‘easy’ and ‘ve...
This review paper has established austempered ductile iron (ADI) as a classical material that has... more This review paper has established austempered ductile iron (ADI) as a classical material that has spectra of properties achieved by altering some processing parameters through heat treatment procedures. Concerted efforts have been made to equally explore the use of additives as additional materials to this all important alloy. The use of modifiers at ultra-fine or nano-scale level as additive to the melt prior casting has also been reviewed. However, the continuous quest for innovative approaches of upgrading the structural and mechanical characteristics of ductile irons has open up interest in the development of nanostructured and nanocomposite components in bulky iron bearing materials. This paper cross-examines few available literatures on the nanostructured ADI with the aim of adopting similar methodology in the development of nanostructured aluminium-alloyed DI and nanostructured aluminium-alloyed ADI. Emphasy is laid on reviewing the production techniques and treatment paramet...
In this study, the effects of austempering on the microstructure, mechanical properties (micro ha... more In this study, the effects of austempering on the microstructure, mechanical properties (micro hardness, impact energy and tensile strength) and corrosion behaviours of AISI 1018 low carbon steel were evaluated. The steel specimens were subjected to heat treatment by austenitizing at 830°C, maintained in this condition for 90 min before rapid cooling in a NaNO3 salt bath sustained at 300°C for isothermal transformation for additional 50 min and finally allowed to air cool to room temperature. The as-received and the austempered samples were tested for corrosion in both 0.5M aqueous acidic (HCl) and 0. 5M alkaline (NaOH) media. Microstructural investigation using scanning electron microscope (SEM) reveals transformation from ferrite/pearlite phases to bainite over the austempering process. Interestingly, significant improvements of 15.7% to 95.7% in the various mechanical properties (micro hardness, impact energy and tensile strength) and corrosion resistance in both media were obser...
In this paper, profit is maximized (or production cost is minimized) by developing an Integer pro... more In this paper, profit is maximized (or production cost is minimized) by developing an Integer programming (IP) model to determine, at a given respective unit cost, optimal numbers of outputs obtainable per production cycle (time) using public electricity generated from national grids and alternate electricity from generators subject to production output capacity or demand constraint. The results obtained showed that production cycle time has a great impact on the determination of optimal outputs for the respective conditions. Also, increase in cost of public electricity per unit product has an upper limit beyond which it has negative effect on the profitability. The results served as determinant factors for production industry in establishing the level of outputs that sustained the profitability by providing optimal cost of public electricity to operate without having any effect on the profit, at a given cycle time. Keywords— Constraint, cycle time, integer programming, optimal numb...
Aluminium alloys demonstrate exceptional properties such as high strength-weight ratio and corros... more Aluminium alloys demonstrate exceptional properties such as high strength-weight ratio and corrosion resistance are used for general engineering applications, automobile, automotives and in aerospace industries. However, they suffer some limitations as wear and creep at high temperatures. With the trending developments from nanometallurgy, diverse nano-particle compounds of mono and heterogeneous compositions have been used in reinforcing aluminium and its alloys as widely reported in the public domains. This paper reviews some of the vast literature on the enhancement of nanostructured aluminium alloys and reinforced aluminium nanocomposites. Importance is laid on the tribological and mechanical behaviours of the manufactured composites and nano-composites with respect to their production methods and applications at elevated (high) and cryogenic (low) temperatures. Keywords— Tribology; mechanical behaviours; nanostructure; aluminium alloys; nano-composites; elevated temperatures
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