Synthesis of mesoporous silica (KCC-1) and preparation of its electrospun nanocomposites for application in microextraction of environmental pollutants

By: Ensiye Kazemi

Supervisor: Dr.Mahmood Kazemzad, Dr.Ali Aghakhani

Materials and Energy Research Center

February 2015

Abstract: In this thesis, a novel nanofibrous composite of the KCC-1/nylon 6 was prepared by the electrospinning techniques and used for adsorptive microextraction of ibuprofen from aqueous media. Fist fibrous silica nanospheres (KCC-1) were synthesized via a hydrothermal method and new solvent system and characterized successfully. The scanning electron microscopy (SEM) images showed spongy spherical morphology with uniform distribution with an average diameter around 293 nm. Synthesized KCC-1 nanospheres with a high BET specific surface area (576 m2 g-1) and BJH average pore diameter of 3.28 nm considered as a mesoporous material. Then mesoporous silica KCC-1 was modified by functional groups such as Metformin, 1- Methyl imidazole, Sulfonic acid and C8. The composite of the KCC-1/nylon 6 was fabricated by preparation of the dispersion of the nanosilica (10-50% w/w) in a solution of nylon 6 (15% w/v) in formic acid. Upon applying a high voltage the nanocomposite of KCC-1/nylon 6 was obtained. KCC-1 nanospheres were arranged in line along the nylon 6 fibers like a rosary beads. Based on the SEM images, even at higher silica content, a well distributed nanocomposite was obtained. The prepared KCC-1/nylon 6 composite showed 29% higher BET specific surface area than pure nylon 6 nanofibers and makes it a good candidate to be used as a sorbent material for environmental polutant. Finally, the nanocomposite fibers were used for the adsorptive microextraction of ibuprofen from aqueous media by TFME method. The effective parameters on the extraction and desorption including of pH, salt, extraction time and desoption solvent were optimized. The nanocomposite fibers of nylon 6/ KCC-1 modified with sulfonic acid, as the best adsorbent for ibuprofen in acidic environment, showed 20% absolute extraction efficiency for 45 min extraction time. Good dynamic linear range (50-2000 ng mL^-1) and detetion limit (20 ng mL^-1) and relative standard deviation (11%) was obtaned for the developed method. Real water sample including local tap water and bottled water showed negative result for ibuprofen in the liner range of the deveopled method.

Images from left to right:

1- SEM images and diameter distribution of KCC-1 nanospheres

2- SEM images of KCC-1/nylon6 composite nanofibers based on diferent percent of KCC-1 nanospheres: a 0, b 20, c 33, d 50 %(w/w)

Nanomaghemite synthesis and investigation of its performance as an anode in Li-ion battery

By: Mohammad Golmohammad

Supervisor: Prof. Farhad Golestanifard , Dr. Alireza Mirhabibi

Advisor: Dr. Erik Kelder

Iran University of Science and Technology

March 2016

Abstract: In this research, nano-maghemite with an average particle size of 11nm was synthesized employing design of experiment and optimization of co-precipitation method to be studied as an Li-ion battery anode. Investigation of co-precipitation parameters showed that pH and Fe3+/Fe2+ are more effective than time and temperature on particle size. For studying particle size effect on performance, nano maghemite with average particle size of 22 & 41 nm were synthesized by increasing stirring time. For investigation of morphological effect, in addition to semi-spherical particles, pseudo-needle and flaky particles with nearly same surface area (112±7 m2.g-1) were synthesized. Moreover, for understanding the effect of porosity, porous powder with specific surface area of 285 m2.g-1 was synthesized. The anode body was doctor bladed using primary powder with a binder and a conductive agent. Galvanostatic charge–discharge cycling of 11nm sample at 500 mA.g-1 current density exhibited reversible capacity of 430 mAh.g-1 which was higher than 22nm (380 mAh.g-1) and 41nm (290 mAh.g-1) samples. The reason for this increment is attributed to the higher surface area and smaller Li ion diffusion length of smaller particles. Galvanostatic charge–discharge for pseudo-needle sample showed reversible capacity of 510 mAh.g-1 which was higher than those of platelet and semi-spherical samples (470 and 430 mAh.g-1). This higher reversible capacity is due to the morphological effect and easier stress relief of volume changes during charge and discharge. Galvanostatic charge–discharge cycling of porous sample showed approximately 720 mAh.g-1 reversible capacity which is remarkably higher than other samples. The reason for this extinguished performance of the latter anode was thought to be dependent upon the role of pores in increasing the surface area and resistance against volume changes during lithium insertion/extraction. Finally, iron state in discharge cycling were investigated by X-ray diffraction pattern and X-ray photoelectron spectroscopy and the reaction of maghemite with lithium were proposed. The result of this research disclosed that increasing surface area and governing shape and size of pristine maghemite particles result in the increment of reversible capacity and cyclability which make maghemite a good candidate as an anode for Li-ion battery.

Keywords: Li-ion battery; nanomaghemite; co-precipitation method; particle morphology; reversible capacity 

Images from left to right: semi-spherical particles, pseudo-needle and flaky particles

Preparation and Investigation of Physical and Microstructural Properties of Si₃N₄/TiN Ceramic Composites

By: Celine Gharibian

Supervisor: Prof. FarhadGoelstanifard, Dr.Seyed Mohammad Mirkazemi

Iran University of Science and Technology

January 2016

Abstract: Because of their high strength, hardness and thermal stability, silicon nitride ceramics are among the most important material for structural applications.Unfortunately, the difficulties in machining and finishing of silicon nitride limit its applications. Therefore, recent developments in silicon nitride composites are focused not only on the improvements of strength and toughness, but also on different possibilities for massive production and cost reduction in manufacturing. A successful approach is to incorporate electrically conductive reinforcements into silicon nitride matrix. The incorporation of a certain content of conductive reinforcements makes the composite electrically conductive so that electrical discharge machining (EDM) can be used. TiN-reinforced silicon nitride composites has relatively high strength, low density and good electric conductivity. Si₃N₄/TiN composites have been sintered by pressureless sintering (PS), hot pressing (HP) and gas pressure sintering (GPS). The main strategy in manufacturing of Si₃N₄-TiN composites is associated with a design of the ceramics having an optimum content of TiN which distributed homogenously and provides good mechanical as well as good electrical characteristics. In the present research, titanium nitride ranging from 20 to 40 vol. % was added to silicon nitride. As sintering aids 3 wt. % Al₂O₃ and 6 wt. % Y₂O₃ were used. Pressureless sintering was done at 1650, 1700 and 1750°C. Relative density of 97.9% was achieved for the sample with 40 vol. % TiN sintered at 1750°C. This sample has the highest fracture toughness (7.1±0.3 MPa.m^1/2) and the lowest electrical resistivity (2.16×10^-6Ωm) among the other samples. Machining of this composite was successfully done by electrical discharge machining (EDM). For reaching a surface with minimum roughness after machining, a dense body required. Therefore the next attempt was prepare the composites by hot pressing at 1700°C. 99.8% of theoretical density was achieved for the sample with 40 vol. % TiN. This composite also showed remarkable mechanical properties such as bending strength, fracture toughness and hardness. Bending strength (904±81 MPa) and fracture toughness (7.3±0.7 MPa.m^1/2) increased by increasing of the amount of TiN. In contrast, hardness decreased with increasing of TiN content. The highest hardness (15.2±0.2 GPa) was achived for the sample with 20 vol. % TiN. Electrical resistivity of the sample with 40 vol. % TiN was measured 1.9×10^-5Ωm. Machining of this composite was successfully done by electrical discharge machining, as well. Investigation of surface roughness was done by profilometer.

Keywords: Silicon nitride, titanium nitride, electrical discharge machining, electrical conductivity.

Effects of Nano and Micron Sized Additives on the Properties and Microstructure of TaC-HfC System

By Farzin Arianpour

Supervisors: Prof. Farhad Golestanifard, Prof. Hamid Reza Rezaie

Iran University of Science and Technology

Advisors: Prof. Ferhat Kara, Anadolu University, Turkey, Prof. Gilbert Fantozzi, INSA Lyon University, France

January 2016

Abstract: Ultra high temperature ceramics (UHTCs) are a class of refractory ceramics showing superior stability at temperatures higher than 2500°C. They are mainly classified as borides, carbides and nitrides of transition metals of groups IV-VI of periodic table of elements. Most of the efforts in this field have focused on commonly used borides (HfB₂, ZrB₂), nitrides (ZrN, TiN), carbides (TiC, TaC) and their composites. Tantalum carbide (TaC) and hafnium carbide (HfC)  are binary compounds of metallic tantalum and hafnium with carbon which are extremely hard, brittle, refractory (melting points over 3900°C) with metallic electrical conductivity and cubic crystal structure.Binary 4:1 mole ratio TaC-HfC solid solution (Ta₄HfC₅) is considered as the most refractory material with the melting point over 4000°C and has superior physical and mechanical properties.

 In this research, Ta₄HfC₅ based samples were synthesized and consolidated using carbide materials and different amounts of nano and micron sized additives such as MoSi₂, B₄C, SiC and CNT by means of spark plasma sintering (SPS) at 2000°C. The nearly full dense monophase Ta₄HfC₅ basedspecimens were fabricated via MoSi₂ as additive with a relative density value higher than 99%. Mechanical tests revealed values of 18-19 GPa and 4-4.3 MPa.m^1/2, for average Vickers hardness and fracture toughness of the composites, respectively. Densification behavior of the samples during sintering was investigated by interpretation of SPS data. Formation of solid solution was analyzed via X-ray diffraction and scanning electron microscope (SEM). It is proposed that at the intermediate stage of sintering, mass transfer can be accelerated by liquid phase and viscous flow mechanisms. The binary TaC-HfC solid solution formation enhanced the densification process at the final stage of sintering. Also the effects of micron and nano sized SiC additives were compared in this system. It revealed that nano SiC improves the densification of the system up to more than 98% via solid state mechanism in the amounts of less than 3 wt.%. The B₄C additives also show interesting solid solution binary boride phase formation during sintering. The CNTs containing samples are investigated via Raman spectroscopy analysis showed the well survivability of CNTs during SPS sintering condition.

Effect of morphology of reinforcement phase on densification and mechanical properties of zirconium diboride based ceramic composites

By Mehdi Shahedi Asl

Supervisor: Dr. Mahdi Ghassemi Kakroudi

Advisors: Prof. Farhad Golestani-Fard, Prof. Mohammad Rezvani

University of Tabriz

April 2015

Abstract: In this research, monolithic ZrB₂ ceramics, ZrB₂-based composites reinforced with SiC (different content/particle size) as well as nano carbon (with different morphologies) reinforced ZrB₂-SiC composites were fabricated by hot pressing method under different processing conditions (sintering temperatures, dwell times and applied pressures). The project was conducted in five steps. The Taguchi methodology was employed (in steps 2-4) in order to reduce the number of experiments as well as to perform the statistical analyses and to determine the significance of each parameter of the process.

   Step 1: Effects of hot pressing temperate and SiC content on ZrB₂-based composites

   Step 2: Effects of processing parameters on monolithic ZrB₂ ceramics

   Step 3: Effects of processing parameters and SiC content on ZrB₂-based composites

   Step 4: Effects of processing parameters and SiC particle size on ZrB₂-based composites

   Step 5: Effects of morphology of nano carbon on ZrB₂-SiC composites

The results of step 1 showed that achieving a fully-dense monolithic ZrB₂ ceramic was impossible, even at 2000 °C as a relative density of 91% was obtained. This is due to the fact that the presence of oxide impurities leads to the abnormal grain growth of zirconium diboride, which inhibits the complete removal of the porosities. The addition of SiC with an efficient mixing of the starting powders had an important role as the grain growth inhibitor. By adding 30 vol% SiC, a relative density of ~100% was achieved at 2000 °C with the maximum hardness  of  21.3 GPa and the highest fracture toughness  of 4.7 MPa m^1/2. The dominant densification mechanism strongly depended on the hot pressing temperature. In addition, the various toughening mechanisms were investigated in the SiC reinforced ZrB₂-based composites.

In the steps 2-4, the maximum levels of parameters of the hot pressing process (temperature of 1850 °C, dwell time of 90 min and applied pressure of 16 MPa) were identified as the optimal hot pressing conditions. The sintering temperature was recognized as the most important parameter (with a significance of 54% on the density and a significance of 67% on the hardness) in the processing of monolithic ZrB₂ ceramics. On the other hand, the applied pressure was found to be the most influential parameter (with a significance of 62% on the density and a significance of 61% on the hardness) in the hot pressed ZrB₂-SiC composites. In addition, the optimum SiC content was determined to be 25 vol%. In ZrB₂-based composites, which were reinforced with different nano/micro-sized SiC, both the temperature (with a significance of 41% on the density and hardness) and the pressure (with a significance of 43% on the density and hardness) were identified as the important parameters. The optimum SiC particle size was 200 nm. The Taguchi predictions for the results of the optimal conditions were in a good harmony with the outcomes of the verification tests in the steps 2-4.

Adding nano carbons with different morphologies, except carbon nanotube, led to the fabrication of near fully-dense composites. The highest value of fracture toughness (7.1 MPa m^1/2), obtained in this research, belonged to the nano-graphite reinforced ZrB₂-SiC composite.

SEM micrographs of the polished surfaces with indentation crack paths of (a) ZrB₂, (b) ZrB₂-SiC, (c) ZrB₂-SiC-graphene, (d) ZrB₂-SiC-graphite, (e) ZrB₂-SiC-carbon nanotube and (f) ZrB₂-SiC-carbon black

Effect of nitride sintering aids on densification and microstructure of ZrB₂-SiC composites

By zohre ahmadi

Supervisor: Dr. M. Gassemi Kakroudi

Advisor: Dr. M. Rezvani

University of Tabriz

September 2015

Abstract: ZrB₂–SiC composites doped with 0, 1, 3 and 5 wt% SiAlON and AlN (Individually) were prepared by hot pressing (under a low pressure of 10 MPa) and pressureless sintering processes at 1900 ̊C for 2 hours. A fractographical approach was employed to investigate the effects of SiAlON and AlN addition on the densification behavior in such ceramic composites.

In the case of SiAlON, several reported chemical reactions were investigated to indicate the probable mechanisms in the progression of the sintering process and also the potential unfavorable effects of SiAlON in ZrB₂–SiC composites. On one hand, results show that the SiAlON addition promotes the densification in the hot pressed samples by the liquid phase formation, as a fully dense composite can be obtained by hot pressing of 5 wt% SiAlON doped ZrB₂–SiC composite. On the other hand, in the pressureless sintering process, more SiAlON content intensifies the formation of gasses which leads to more porosity. In both processes, investigation of fracture surfaces demonstrates the presence of thin layers of glassy phases which act as the sintering aid. The steps of densification process in both hot pressing and pressureless sintering processes were presented by a graphical model.

In the case of AlN, The results revealed that only 1 wt% AlN can aid the densification process of the hot pressed ceramic composite via the liquid phase sintering mechanism due to the formation of metakaolinite spinel. In the pressureless sintering method, adding more AlN can increase the formation of gas products which raised the amount of porosities in the final microstructure. The formation of graphite in the hot pressing process, the formation of Al₂OC in the pressureless sintering process, and the formation of BN in the both processes were disclosed by X-ray diffraction analysis.

iii

iii

Investigation of nano SiC particles on densification behavior and mechanical properties of ZrB₂-based composite

By Mehran Jaberi Zamharir

Supervisor: Dr. M. Gassemi Kakroudi

Advisor: Dr. M. Rezvani

University of Tabriz

September 2015

Abstract: ZrB2–25 vol% SiC ceramic composites were prepared by hot pressing in order to investigate the effects of processing parameters and SiC particle size (20 nm, 200 nm and 5 µm) on the densification behavior, the average ZrB2 grain size and Vickers hardness. At this study, an experimental design technique (Taguchi method) was used to specify the significance of four factors and to obtain the optimal conditions. The experimental procedure included nine tests for four parameters with three levels which were employed to optimize the process parameters. The statistical analyses recognized the hot pressing pressure and temperature as the most consequential parameters affecting the density and hardness of ZrB2–SiC composites. The SiC particle size and holding time were specified as the most effective parameters on the average ZrB2 grain size. The relative density, average ZrB2 grain size, Vickers hardness and fracture toughness of the sample, hot pressed at optimal conditions (1850 °C, 90 min, 16 MPa and 200 nm), reached about 5.36 g/cm3, 10.03 µm, ~17.1 GPa and 5.9 MPa.m1/2, respectively. The confirmation test, performed under optimum conditions, indicated that the experimental outcomes were equal with the expected values from the Taguchi prediction. Finally, the mechanisms of enhanced densification and fracture toughness of the hot pressed ZrB2–SiC ceramic composites were discussed.

An investigation into the effect of various additives on hot pressing of tantalum carbide based composites

By Firouz Rezaei Babere

Supervisor: Dr. M. Gassemi Kakroudi, Dr. M. Rezvani

University of Tabriz

September 2016

Abstract: TaC-based composites were hot pressed with addition of vanadium carbide, nano graphite and nano carbon black particles in different ratios as a sintering aid in order to improve the densification and mechanical properties such as fracture toughness and consequently thermal shock resistent. The hot pressing of the composites was carried out at of 1700, 1800, 1900 and 2000 ºC for 45 min under an uniaxial pressur of 40 MPa. The physical and mechanical properties of the composites including relative density, porosity, Vickers hardness and fracture toughness were measured. Microstructural investigation and phase analysis of the polished and fracture surfaces of the hot pressed samples were also carried out. The hot pressed composites had a homogeneous microstructure and there was no detectable impurity in the mixing process. There was a significant grain growth in the microstructure of pure TaC sample. SEM micrographs and XRD patterns of the hot pressed samples indicated the formation of a solid solution between carbides and thus formation of a single phase microstructure. By addition of nano graphite and nano carbon black particles the densification of composites improved and a relative density of 100% was achieved. Addition of hafnum carbide and vanadium carbide increased the Vickers hardness of the TaC from 15 GPa up to 23 GPa.