Sharif Hussein Sharif Zein

Calcium phosphate-based composites as injectable bone substitute materials.

A major weakness of current orthopedic implant materials, for instance sintered hydroxyapatite (HA), is that they exist as a hardened form, requiring the surgeon to fit the surgical site around an implant to the desired shape. This can cause an increase in bone loss, trauma to the surrounding tissue, and longer surgical time. A convenient alternative to harden bone filling materials are injectable bone substitutes (IBS). In this article, recent progress in the development and application of calcium phosphate (CP)-based composites use as IBS is reviewed. CP materials have been used widely for bone replacement because of their similarity to the mineral component of bone. The main limitation of bulk CP materials is their brittle nature and poor mechanical properties. There is significant effort to reinforce or improve the mechanical properties and injectability of calcium phosphate cement (CPC) and this review resumes different alternatives presented in this specialized literature.

A review on carbon nanotubes in an environmental protection and green engineering perspective

Recent developments in nanotechnologies have helped to benchmark carbon nanotubes (CNTs) as one of the most studied nanomaterials. By taking advantages of CNTs extraordinary physical, chemical and electronic properties, a wide variety of applications has been proposed in various engineering fields. In this short review, the contribution of CNTs is addressed in terms of sustainable environment and green technologies perspective, such as waste water treatment, air pollution monitoring, biotechnologies, renewable energy technologies, supercapacitors and green nanocomposites. Consideration of CNTs for large scale application from the aspect of cost and potential hazards are also discussed. Based on the literature studied, CNTs pose a great potential as a promising material for application in various environmental fields.

MULTIWALLED CARBON NANOTUBES BASED NANOCOMPOSITES FOR SUPERCAPACITORS: A REVIEW OF ELECTRODE MATERIALS

Electrode materials are the most important factors to verify the properties of the electrochemical supercapacitor. In this paper, the storage principles and characteristics of electrode materials, including carbon-based materials, transition metal oxides and conducting polymers for supercapacitors are depicted in detail. Other factors such as electrode separator and electrolyte are briefly investigated. Recently, several works are conducted on application of multiwalled carbon nanotubes (MWCNTs) and MWCNTs-based electrode materials for supercapacitors. MWCNTs serve in experimental supercapacitor electrode materials result in specific capacitance (SC) value as high as 135 Fg-1. Addition of pseudocapacitive materials such as transition metal oxides and conducting polymers in the MWCNTs results in electrochemical performance improvement (higher capacitance and conductivity). The nanocomposites of MWCNTs and pseudocapacitive materials are the most promising electrode materials for supercapacitors because of their good electrical conductivity, low cost and high mass density.

Production of high purity multi-walled carbon nanotubes from catalytic decomposition of methane

Removing all the impurities in the carbon nanotubes is essential due to the unique characteristic of purified carbon nanotubes applications such as electronic devices, hydrogen storage, tools in nanotechnology, polymer reinforcement, fuel cells, sensors and actuators. However, the removal of some catalysts is very difficult. Carbon nanotubes, which were used for purification, were synthesized using Ni/TiO2 catalyst. The main impurity of the assynthesized carbon nanotubes that needs to be removed was the catalyst used to synthesized carbon nanotubes. In order to purify this carbon nanotube, nitric acid treatment followed by oxidation either chemical or thermal method has been used and the results have been compared. Acid treatment followed by thermal oxidation was more effective than acid treatment followed by chemical oxidation. The process again was compared with thermal oxidation followed by acid treatment. It was found that the thermal oxidation followed by acid treatment gave better result than acid treatment followed by thermal oxidation. The efficiency of oxidation followed by nitric or sulfuric acid treatment followed by re-oxidation also were tested and found that this method has successfully removed most of the impurities. The purity of the oxidation followed by sulfuric acid treatment then re-oxidation gave carbon nanotube with purity as high as 99.9 wt%. The percentage of the carbon nanotubes purity was obtained from Thermal Gravimetric Analysis (TGA) while the structure and morphology of carbon nanotubes were characterized using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). TEM and SEM showed that the structure of the carbon nanotubes was not damage after purification using oxidation followed by sulfuric acid treatment and then re-oxidation.

Carbon Nanotubes Applications: Solar and Fuel Cells, Hydrogen Storage, Lithium Batteries, Supercapacitors, Nanocomposites, Gas, Pathogens, Dyes, Heavy Metals and Pesticides

Energy and environment are major global issues inducing environmental pollution. Energy generation from conventional fossil fuels has been identified as the main culprit of environmental degradation from global warming effects, in addition to environmental pollution which arises from rapid industrialization and agricultural development. In order to address these issues, nanotechnology plays an essential role in revolutionizing the applications for energy conversion and storage, environmental monitoring, as well as green engineering of environmental friendly materials. Carbon nanotubes and their hybrid nanocomposites have received immense research attention for their potential applications in various fields due to their unique structural, electronic, and mechanical properties. Here, we review the applications of carbon nanotubes (i) in energy conversion and storage as in solar cells, fuel cells, hydrogen storage, lithium ion batteries, and electrochemical supercapacitors, (ii) in environmental monitoring and wastewater treatment as in the detection and removal of gas pollutants, pathogens, dyes, heavy metals, and pesticides, and (iii) in green nanocomposite design. Integration of carbon nanotubes in solar cells and fuel cells has increased the energy conversion efficiency of these energy conversion applications, which serve as the future sustainable energy sources. Carbon nanotubes doped with metal hydrides show high hydrogen storage capacity of around 6 wt% as a potential hydrogen storage medium. Carbon nanotubes nanocomposites have exhibited high energy capacity in lithium ion batteries and high specific capacitance in electrochemical supercapacitors, in addition to excellent cycle stability. High sensitivity and selectivity towards the detection of environmental pollutants is demonstrated by carbon nanotubes based sensors, as well as the anticipated potentials of carbon nanotubes as adsorbent to remove environmental pollutants, which show high adsorption capacity and good regeneration capability. Carbon nanotubes are employed as reinforcement material in green nanocomposites, which is advantageous in supplying the desired properties, in addition to the biodegradability. This paper presents an overview of the advantages imparted by carbon nanotubes in electrochemical devices of energy applications and green nanocomposites, as well as nanosensor and adsorbent for environmental protection.

MnO2-FILLED MULTIWALLED CARBON NANOTUBE/POLYANILINE NANOCOMPOSITES: EFFECT OF LOADING ON THE CONDUCTION PROPERTIES AND ITS PERCOLATION THRESHOLD

This paper reports the synthesis and characterization of ternary nanocomposites consisting of polyaniline (PANI), multiwalled carbon nanotubes (MWCNTs) and manganese dioxide (MnO2) at different MWCNT–MnO2 loadings. The composite electrical percolation threshold is investigated as well. The in situ nanocomposites were characterized by UV-visible, Fourier transform and Raman spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, and electrical conductivity measurements. The conductivity of the nanocomposite reached up to 78.79 Scm-1 with 50 wt.% addition of MWCNT–MnO2 with good conduction stability and reversibility. The percolation threshold of this nanocomposite was achieved at 0.5 wt.%. Using the scaling law of the percolation theory, it was found that the theoretical conductivity of the nanocomposite exhibited an exponential factor, (t) of 1.38 instead of the universal t value of 2.

Hydroxyapatite nanoparticles: Electrospinning and calcination of hydroxyapatite/polyvinyl butyral nanofibers and growth kinetics†

Electrospinning of hydroxyapatite (HA)/polyvinyl butyral solution resulted in the formation of fibers with average diameter of 937-1440 nm. These fibers were converted into HA nanoparticles with size <100 nm after undergoing calcination treatment at 600°C. The diameter of the fiber was found to be influenced by applied voltage and spinning distance. The injection flowrate did not affect the diameter significantly. The electrospinning method successfully reduced the commercial HA particle size in the range of 400-1100 nm into <100 nm. The dispersion of the finally calcined HA nanoparticles was improved significantly after anionic sodium dodecyl sulfate surfactant was introduced. The experimental data of HA growth kinetics were subjected to the integral method of analysis, and the rate law of the reaction was found to follow the first order reaction.

EFFECT OF PARA-HYDROXYBENZENE SULFONIC ACID ON THE PROPERTIES OF EX SITU PREPARED POLYANILINE/MULTIWALLED CARBON NANOTUBES–MnO2

New ex situ polyaniline (PANI)/MnO2-filled multiwalled carbon nanotubes (MWCNTs) nanocomposites using para-hydroxybenzene sulfonic acid (PHBSA) as a dopant and linker exhibit enhanced electrical conductivity and interfacial interaction. Strong and enhanced interfacial interaction was observed on the surfaces of the filled carbon nanotubes and PANI. Transmission electron microscope (TEM) demonstrated clearly the improved bonding at the interface compared to the nanocomposite without PHBSA.

Screening of metal oxide catalysts for carbon nanotubes and hydrogen production via catalytic decomposition of methane

A number of catalysts prepared from transition metals such as copper (Cu), iron (Fe), nickel (Ni), cobalt (Co) and manganese (Mn) on TiO 2 support were tested for the decomposition of methane into hydrogen and carbon. These catalysts were used in the experiments without any pretreatment. The experimental results show that the activities of the metal-TiO 2 catalysts decreased in the order of NiO/TiO 2 > CoO/TiO 2 > MnO x /TiO 2 ≃ FeO/TiO 2 ≃ CuO/TiO 2 . NiO/TiO 2 catalyst exhibited extremely high initial activity in the decomposition of methane. The optimum NiO doping on TiO 2 for the decomposition of methane were obtained at 20mol% NiO. The effective promoters for the catalyst was investigated using 15mol%M/20mol%NiO/Ti02 catalysts (where M = MnO x , FeO, CoO and CuO). 15mol%MnO x /20mol%NiO/TiO 2 was found to be an effective bimetallic catalyst for the catalytic decomposition of methane into hydrogen and carbon, giving higher catalytic activity, attractive carbon nanotube formed as well as longer catalytic lifetime.

HIGHLY EFFICIENT HYBRID SUPERCAPACITOR MATERIAL FROM NICKEL-MANGANESE OXIDES/MWCNTs/PEDOT NANOCOMPOSITE

A novel ternary nanocomposite of nickel-manganese oxides/multi-walled carbon nanotubes (NMO/MWCNTs) coated with poly (3,4-ethylenedioxythiophene)(PEDOT) was prepared by chemical oxidation method. The filling of NMO particles inside MWCNTs and the uniform coating of NMO/MWCNTs with PEDOT intensified the capacitive behavior of MWCNTs. The lowest IR drop (0.1 V) and highest specific capacitance (SC) values of 526.55 F/g of NMO/MWCNTs/PEDOT imply it as highly efficient hybrid supercapacitor materials in 6 M KOH electrolyte.