There is a pressing demand to prepare low-cost carbon nanotubes (CNTs) from renewable biomass resources as cheap carbon precursors and catalyst supports during chemical vapor deposition (CVD). ...Camphor and rice straw are quite an eco-friendly, renewable and low-cost carbon sources to prepare CNTs. Here, successful attempts for preparing CNTs through carbonization of hydrothermally treated rice straw using either mono-catalyst of ferrocene (RS-H/Fe) or mixed catalysts of ferrocene and nickel nitrate (RS-H/Fe-Ni) in presence of gaseous carbon source emitted from heating camphor under flowing N
2
gas were achieved. Scanning electron microscope (SEM) combined with energy-dispersive spectroscopy (EDS), transmission electron microscope (TEM), Raman spectroscopy and thermal gravimetric analysis (TGA) techniques were used to determine the morphology, surface, electronic structures and thermal stability of the produced CNTs. Different structures of CNTs were grown with outer diameters ranging from 22 nm to 66 nm. Few amounts with small outer diameters of coiled CNTs-Fe bundles were produced over carbonized rice straw with ferrocene (RS-H/Fe) through a bottom growth mechanism. Whereas considerable amounts of straight and large outer diameter of CNTs-bundles (CNTs-Fe-Ni) were formed over RS-H/Fe-Ni substrate
via
a bottom growth mechanism also. Raman spectra showed two main bands of CNTs; G-band at ∼1580 cm
−1
and D-band at 1356 cm
−1
or 1335 cm
−1
which obtained on RS-H/Fe and RS-H/Fe-Ni samples, respectively. Conclusively, the presence of Ni with ferrocene can enhance the yield, thickness and graphitization extent of the as-prepared CNTs. Therefore, conversion of available-cheap biomasses into high added-value materials such as CNTs becomes a realistic, feasible and thus reduces the cost production of CNTs.
There is a pressing demand to prepare low-cost carbon nanotubes (CNTs) from renewable biomass resources as cheap carbon precursors and catalyst supports during chemical vapor deposition (CVD).
This work presents an efficient technique to improve compressibility and thermal properties of Al–Al
2
O
3
nanocomposites. The compressibility behavior was examined by cold compaction test, and the ...thermal conductivity was calculated through the measured electrical resistivity of the prepared samples. The results showed that the addition of Al
2
O
3
to Al matrix improves the compressibility behavior of the produced nanocomposite. However, it has a negative effect on the thermal conductivity of the produced composite. Adding Al
2
O
3
hard particles accelerates the fracturing process which improves the compressibility behavior. However, it causes some agglomeration at the grain boundaries which reduce the thermal conductivity. The addition of Mg to Al–Al
2
O
3
nanocomposite improves both the compressibility behavior and the thermal conductivity. This is due to the great reduction in the particle size and the agglomeration of reinforcement particles on the grain boundaries which improve the compressibility behavior and the thermal conductivity.
In this paper, copper matrix nanocomposites reinforced by 5, 10 and 15 wt% ZrO2 particles were produced using high energy ball milling technique with different milling time. The optimum milling time ...is predicted analytically and validated experimentally. The effect of ZrO2 content on the morphology, microstructure, microhardness, compressive, electrical and wear properties of Cu-ZrO2 nanocomposites has been investigated. The results revealed that the optimum milling time to produce Cu-ZrO2 nanocomposite with homogenous distribution of reinforcement is 15 h. The compressive strength, the microhardness and wear rate of the Cu-15%ZrO2 nanocomposites are improved by 58.2%, 288% and 19.3%, respectively, compared to pure copper. However, density and electrical conductivity are negatively affected by increasing ZrO2 content. The improvement in the mechanical and wear properties comes from the large reduction of the crystallite size by increasing ZrO2, reaching 32.5, 15.2 and 11.1 nm for samples containing, 5, 10 and 15 wt% ZrO2. Moreover, the reduction in the particle size due to mechanical milling plays a critical role in the improvement of these properties.
The current study attempted to evaluate the impact of drilling parameters and delamination on the bearing strength of both neat GFRP (NG) and hybrid GFRP/aluminum (Al)-wire mesh with two various ...configurations, first with Al-mesh in the outer surface of specimen (AG) and the other with Al-mesh in the core of specimen (GA). Drilling procedure is carried out using Formula: see text 6 mm carbide twist drill with three different tip angles (90°, 120° and 135°), as well as Three different speeds and feeds (1000, 2000, and 3000 rpm) and (20, 40, and 60 mm/min), respectively. Taguchi and ANOVA analyses are used to analyze the influence of processing parameters. The findings showed that AG specimen experienced the least delamination damage. The maximum bearing strength refers to NG specimen, which is 9.6% and 8.7% more than AG and GA specimens, respectively. Drill point angle has the major effect on bearing strength for both AG and GA specimens, while for NG feed rate is of the major effect. The developed regression model displayed a high level of fitness with an average prediction error of less than 3%.
In this article, the effects of using nanometer and micrometer-sized aluminum particles in glass fiber reinforcement epoxy composites have been studied. The study evaluates the mechanical properties ...improvement with the addition of nanometer and micrometer-sized aluminum particles to glass fiber reinforcement epoxy composites. The combination of aluminum and woven glass fibers provide high potential for the modification of the epoxy matrix. The composites were produced by hand lay-up technique. The glass fiber volume fraction was kept constant at 35%, while the contents of aluminum particles were increased from 0.2 to 4 wt%. The developed composites showed enhanced tensile, flexural, hardness, wear, and impact behavior as compared to glass fiber reinforcement epoxy. An enhancement of 27% was attained in tensile strength with glass fiber reinforcement epoxy filled with 2 wt% aluminum nanoparticles; however, adding 4 wt% nanometer-sized aluminum particles showed an improvement of 114%, 116%, 21%, 52.2%, 21.4%, 76.6% in tensile elongation, toughness, tensile modulus, flexural strength, flexural strain, flexural modulus, respectively as compared to neat glass fiber reinforcement epoxy. Increasing the nanometer-sized aluminum particles in glass fiber reinforcement epoxy composites to 4 wt% reversed the improvement trend in tensile strengths, wear, and hardness. However, increasing the micrometer-sized aluminum particles to 4 wt% has shown fair improvement in all used aluminum loadings. Microscopy results showed that the aluminum particles were well dispersed in the epoxy matrix. However, a higher weight fraction of nano-aluminum in the epoxy had promoted little agglomerations.
► The copper–alumina composites were prepared by powder metallurgy (P/M) method with nano-Cu/Al2O3 powders. ► The Al2O3 content was added by 2.5, 7.5 and 12.5wt.% to the Cu matrix to detect its ...effect on thermal conductivity and thermal expansion behavior of the resultant Cu/Al2O3 nanocomposites. ► The results showed that alumina nanoparticles (30nm) were distributed in the copper matrix in a homogeneous manner. ► The measured thermal conductivity for the Cu–Al2O3 nanocomposites decreased from 384 to 78.1W/mK with increasing Al2O3 content from 0 to 12.5wt.%. ► Accordingly, the coefficient of thermal expansion (CTE) was tailored from 33×10−6 to 17.74×10−6/K, which is compatible with the CTE of semiconductors in electronic packaging applications.
Copper–alumina composites were prepared by powder metallurgy (P/M) technology. Nano-Cu/Al2O3 powders, was deoxidized from CuO/Al2O3 powders which synthesized by thermochemical technique by addition of Cu powder to an aqueous solution of aluminum nitrate. The Al2O3 content was added by 2.5, 7.5 and 12.5wt.% to the Cu matrix to detect its effect on thermal conductivity and thermal expansion behavior of the resultant Cu/Al2O3 nanocomposites. The results showed that alumina nanoparticles (30nm) were distributed in the copper matrix in a homogeneous manner. The measured thermal conductivity for the Cu–Al2O3 nanocomposites decreased from 384 to 78.1W/mK with increasing Al2O3 content from 0 to 12.5wt.%. The large variation in the thermal conductivities can be related to the microstructural characteristics of the interface between Al2O3 and the Cu-matrix. Accordingly, the coefficient of thermal expansion (CTE) was tailored from 33×10−6 to 17.74×10−6/K, which is compatible with the CTE of semiconductors in electronic packaging applications. The reduction of thermal conductivity and coefficient of thermal expansion were ascribed to the strong interface bonding in the Cu/Al2O3 nanocomposites.
In the present study, Al-4%SiC nanocomposite was manufactured with homogeneous and uniform distribution of SiC particles in Al matrix using accumulative roll bonding (ARB) technique. In addition high ...strength Al sheets were manufactured using ARB technique with the aim of comparison. Tensile test and microhardness were used to characterize the produced nanocomposite. Moreover, 3D FE model is presented to predict microhardness of the manufactured nanocomposite. The results show that at the initial stages of ARB process, particle free zones as well as particle clusters were observed in the microstructure of the nanocomposite. After 9 ARB passes, Al-4%SiC nanocomposite with uniform distribution of particles was produced. The tensile strength for ARBed Al and Al-4%SiC nanocomposite after nine passes is 3.19 and 4.09 times of the annealed Al 1050, respectively. Moreover, microhardness of ARBed Al and Al-4%SiC nanocomposite after nine passes is 3.63 and 4.76 times of the annealed Al 1050, respectively. Interestingly, the main strengthening mechanism is the grain refinement and dislocation strengthening due to rolling process, while the addition of SiC nanoparticles acts as a secondary strengthening source. Finally, the microhardness results predicted by the presented 3D FE model correlate well with the experimental results.
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•ARB technique is used to produce highly uniform Al-SiC nanocomposites.•Novel 3D FE model is presented to predict microhardness of Al-SiC nanocomposite.•Tensile strength and microhardness became 4 and 4.7 times larger than Al.•Grain refinement, dislocation strengthening are the main strengthening mechanisms.
Microstructure of Cu-Al2O3 sintered specimens produced by the three different techniques (a) DM technique, (b) MA technique and (c) MC technique. Display omitted
•Cu-Al2O3 nanocomposite is produced ...by three different techniques.•A homogeneous distribution of Al2O3 was achieved by mechanochemical technique.•The mechanical properties of the composite were determined by compression test.•A 2-D FE model was used to simulate spherical indentation experiment.•The simulation of indentation test was valid to predict hardness of nanocomposite.
Preparation of metal matrix composites with homogenously distributed reinforcement is a difficult process. The process can be even more complex when the reinforcement particles are nano-particles. In this paper, three different techniques (dry mixing, mechanical alloying and mechanochemical) were applied to produce Cu-Al2O3 nano composite with three different Al2O3 content (2.5, 7.5 and 12.5.wt.%). XRD, SEM and EDX analysis were conducted to analyse the physical and structural properties of the produced samples. Rockwell hardness test and compression test were applied to determine the mechanical properties of the produced composites. A 2D axisymmetric FE model was implemented using commercial software to predict the Rockwell hardness of the prepared samples. The results show that dry mixing and mechanical alloying techniques are valid for production of metal matrix composites with large reinforcement particle size and low reinforcement content. However, mechanochemical technique can be used to produce Cu-Al2O3 nano composite with high reinforcement weight fractions. Homogenously distributed dispersed nano alumina copper matrix can be achieved by applying mechanochemical technique and as a result, the mechanical and physical properties can be improved. The hardness predicted by the presented FE model correlates well with the experimental observation.
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•Improvement of cement kiln dust by iron slag and nanosilica.•Flooding of the cement kiln dust modified by slag and nanosilica.•Freeze-thaw durability of the cement kiln dust modified ...by slag and nanosilica.•Chemical stability of the cement kiln dust-slag-nanosilica composite immobilized radioactive waste.
Cement production and its wide applications in construction and stabilization are among the oldest technologies. Cement kiln dust is a by-product generated by cement industry with unpleasant features. Its weak integrity can be improved by mixing it with 20% of iron slag, another industrial waste generated during steel production, and a small amount of nano-additive, namely 0.1% nanosilica. This way, modified cementitious composites of improved characteristic were developed, which performed suitable for construction and waste stabilization applications.
In the present study, the novel composite material has been thoroughly examined to critically assess its performance and resistance under drastic environmental conditions that are likely to occur especially in areas exposed to severe climatic variability. The impact of flooding in water of various compositions and in strongly acidic and alkaline media was investigated. Leachability of the new composite specimens in these aqueous media and when subjected towards freezing/thawing cycles was evaluated during 90 days; especially the mechanical and chemical stability of the new composite as safe containment for radioactive 137Cs waste was studied. Compressive strength, porosity, mass change and spectroscopic investigations are the tools used in this study to check the performance of the modified cementitious composite at each condition. Although prone to deterioration after drastic freezing-thawing cycles, the new composite material displayed excellent stability under excessive flooding, and holds promise as future material of choice to immobilize and finally dispose radioactive waste in a safe and sustainable fashion.
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