Now showing 1 - 10 of 23
  • Publication
    Effectiveness of dimple microtextured copper substrate on performance of Sn-0.7Cu solder alloy
    ( 2022)
    Siti Faqihah Roduan
    ;
    ; ;
    Nurul Aida Husna Mohd Mahayuddin
    ;
    ;
    Aiman Bin Mohd Halil
    ;
    Amira Qistina Syamimi Zaifuddin
    ;
    Mahadzir Ishak Muhammad
    ;
    Andrei Victor Sandu
    ;
    Mădălina Simona Baltatu
    ;
    Petrica Vizureanu
    This paper elucidates the influence of dimple-microtextured copper substrate on the performance of Sn-0.7Cu solder alloy. A dimple with a diameter of 50 µm was produced by varying the dimple depth using different laser scanning repetitions, while the dimple spacing was fixed for each sample at 100 µm. The dimple-microtextured copper substrate was joined with Sn-0.7Cu solder alloy using the reflow soldering process. The solder joints’ wettability, microstructure, and growth of its intermetallic compound (IMC) layer were analysed to determine the influence of the dimple-microtextured copper substrate on the performance of the Sn-0.7Cu solder alloy. It was observed that increasing laser scan repetitions increased the dimples’ depth, resulting in higher surface roughness. In terms of soldering performance, it was seen that the solder joints’ average contact angle decreased with increasing dimple depth, while the average IMC thickness increased as the dimple depth increased. The copper element was more evenly distributed for the dimple-micro-textured copper substrate than its non-textured counterpart.
  • Publication
    Effect of kaolin geopolymer ceramics addition on the microstructure and shear strength of Sn-3.0Ag-0.5Cu solder joints during multiple reflow
    ( 2022)
    Nur Syahirah Mohamad Zaimi
    ;
    ; ; ;
    Andrei Victor Sandu
    ;
    Petrica Vizureanu
    ;
    Mohd Izrul Izwan Ramli
    ;
    Kazuhiro Nogita
    ;
    Hideyuki Yasuda
    ;
    Ioan Gabriel Sandu
    Solder interconnection in three-dimensional (3D) electronic packaging is required to undergo multiple reflow cycles of the soldering process. This paper elucidates the effects of multiple reflow cycles on the solder joints of Sn-3.0Ag-0.5Cu (SAC305) lead (Pb)-free solder with the addition of 1.0 wt.% kaolin geopolymer ceramics (KGC). The samples were fabricated using powder metallurgy with the hybrid microwave sintering method. Apart from using conventional cross-sectioned microstructure imaging, advanced synchrotron real-time in situ imaging was used to observe primary IMC formation in SAC305-KGC solder joints subjected to multiple reflow soldering. The addition of KGC particles in SAC305 suppressed the Cu6Sn5 IMC’s growth as primary and interfacial layers, improving the shear strength after multiple reflow soldering. The growth rate constant for the interfacial Cu6Sn5 IMC was also calculated in this study. The average growth rate of the primary Cu6Sn5 IMCs decreased from 49 µm/s in SAC305 to 38 µm/s with the addition of KGC particles. As a result, the average solidified length in the SAC305-KGC is shorter than SAC305 for multiple reflow soldering. It was also observed that with KGC additions, the growth direction of the primary Cu6Sn5 IMC in SAC305 changed from one growth to two growth directions. The observed results can be attributed to the presence of KGC particles both at grains of interfacial Cu6Sn5 IMCs and at the surface of primary Cu6Sn5 IMC.
  • Publication
    Contribution of interfacial bonding towards geopolymers properties in geopolymers reinforced fibers: a review
    ( 2022)
    Muhd Hafizuddin Yazid
    ;
    ; ;
    Marcin Nabiałek
    ;
    ; ;
    Marwan Kheimi
    ;
    Andrei Victor Sandu
    ;
    Adam Rylski
    ;
    Bartłomiej Jeż
    There is a burgeoning interest in the development of geopolymers as sustainable construction materials and incombustible inorganic polymers. However, geopolymers show quasi-brittle behavior. To overcome this weakness, hundreds of researchers have focused on the development, characterization, and implementation of geopolymer-reinforced fibers for a wide range of applications for light geopolymers concrete. This paper discusses the rapidly developing geopolymer-reinforced fibers, focusing on material and geometrical properties, numerical simulation, and the effect of fibers on the geopolymers. In the section on the effect of fibers on the geopolymers, a comparison between single and hybrid fibers will show the compressive strength and toughness of each type of fiber. It is proposed that interfacial bonding between matrix and fibers is important to obtain better results, and interfacial bonding between matrix and fiber depends on the type of material surface contact area, such as being hydrophobic or hydrophilic, as well as the softness or roughness of the surface.
  • Publication
    The influence of sintering temperature on the pore structure of an Alkali-Activated Kaolin-Based Geopolymer Ceramic
    ( 2022)
    Mohd Izrul Izwan Ramli
    ;
    ; ;
    Ikmal Hakem Aziz
    ;
    Tan Chi Ying
    ;
    Noor Fifinatasha Shahedan
    ;
    Winfried Kockelmann
    ;
    Anna Fedrigo
    ;
    Andrei Victor Sandu
    ;
    Petrica Vizureanu
    ;
    Jitrin Chaiprapa
    ;
    Dumitru Doru Burduhos Nergis
    Geopolymer materials are used as construction materials due to their lower carbon dioxide (CO2) emissions compared with conventional cementitious materials. An example of a geopolymer material is alkali-activated kaolin, which is a viable alternative for producing high-strength ceramics. Producing high-performing kaolin ceramics using the conventional method requires a high processing temperature (over 1200 °C). However, properties such as pore size and distribution are affected at high sintering temperatures. Therefore, knowledge regarding the sintering process and related pore structures on alkali-activated kaolin geopolymer ceramic is crucial for optimizing the properties of the aforementioned materials. Pore size was analyzed using neutron tomography, while pore distribution was observed using synchrotron micro-XRF. This study elucidated the pore structure of alkali-activated kaolin at various sintering temperatures. The experiments showed the presence of open pores and closed pores in alkali-activated kaolin geopolymer ceramic samples. The distributions of the main elements within the geopolymer ceramic edifice were found with Si and Al maps, allowing for the identification of the kaolin geopolymer. The results also confirmed that increasing the sintering temperature to 1100 °C resulted in the alkali-activated kaolin geopolymer ceramic samples having large pores, with an average size of ~80 µm3 and a layered porosity distribution.
  • Publication
    Metakaolin/sludge based geopolymer adsorbent on high removal efficiency of Cu2+
    ( 2022)
    Pilomeena Arokiasamy
    ;
    ; ;
    Mohd Remy Rozainy Mohd Arif Zainol
    ;
    ;
    Marwan Kheimi
    ;
    Andrei Victor Sandu
    ;
    Petrica Vizureanu
    ;
    Rafiza Abdul Razak
    ;
    Activated carbon (AC) has received a lot of interest from researchers for the removal of heavy metals from wastewater due to its abundant porous structure. However, it was found unable to meet the required adsorption capacity due to its amorphous structure which restricts the fundamental studies and structural optimization for improved removal performance. In addition, AC is not applicable in large scale wastewater treatment due its expensive synthesis and difficulty in regeneration. Thus, the researchers are paying more attention in synthesis of low cost geopolymer based adsorbent for heavy metal removal due its excellent immobilization effect. However, limited studies have focused on the synthesis of geopolymer based adsorbent for heavy metal adsorption by utilizing industrial sludge. Thus, the aim of this research was to develop metakaolin (MK) based geopolymer adsorbent with incorporation of two types of industrial sludge (S1 and S3) that could be employed as an adsorbent for removing copper (Cu²⁺) from aqueous solution through the adsorption process. The effects of varied solid to liquid ratio (S/L) on the synthesis of metakaolin/sludge based geopolymer adsorbent and the removal efficiency of Cu²⁺ by the synthesis adsorbent were studied. The raw materials and synthesized geopolymer were characterized by using x-ray fluorescence (XRF), x-ray diffraction (XRD), scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and micro XRF. The concentration of Cu²⁺ before and after adsorption was determined by atomic absorption spectroscopy (AAS) and the removal efficiency was calculated. The experimental data indicated that the synthesized geopolymer at low S/L ratio has achieved the highest removal efficiency of Cu²⁺ about 99.62% and 99.37% at 25%:75% of MK/S1 and 25%:75% of MK/S3 respectively compared to pure MK based geopolymer with 98.56%. The best S/L ratio for MK/S1 and MK/S3 is 0.6 at which the reaction between the alkaline activator and the aluminosilicate materials has improved and enhanced the geopolymerization process. Finally, this work clearly indicated that industrial sludge can be utilized in developing low-cost adsorbent with high removal efficiency
  • Publication
    Effect of Ni on the suppression of sn whisker formation in Sn-0.7Cu solder joint
    ( 2021) ; ;
    Andrei Victor Sandu
    ;
    ; ;
    Noor Zaimah Mohd Mokhtar
    ;
    Jitrin Chaiprapa
    The evolution of internal compressive stress from the intermetallic compound (IMC) Cu6Sn5 growth is commonly acknowledged as the key inducement initiating the nucleation and growth of tin (Sn) whisker. This study investigates the effect of Sn-0.7Cu-0.05Ni on the nucleation and growth of Sn whisker under continuous mechanical stress induced. The Sn-0.7Cu-0.05Ni solder joint has a noticeable effect of suppression by diminishing the susceptibility of nucleation and growth of Sn whisker. By using a synchrotron micro X-ray fluorescence (µ-XRF) spectroscopy, it was found that a small amount of Ni alters the microstructure of Cu6Sn5 to form a (Cu,Ni)6Sn5 intermetallic layer. The morphology structure of the (Cu,Ni)6Sn5 interfacial intermetallic layer and Sn whisker growth were investigated by scanning electron microscope (SEM) in secondary and backscattered electron imaging mode, which showed that there is a strong correlation between the formation of Sn whisker and the composition of solder alloy. The thickness of the (Cu,Ni)6Sn5 IMC interfacial layer was relatively thinner and more refined, with a continuous fine scallop-shaped IMC interfacial layer, and consequently enhanced a greater incubation period for the nucleation and growth of the Sn whisker. These verification outcomes proposes a scientifically foundation to mitigate Sn whisker growth in lead-free solder joint.
  • Publication
    Mechanical performance, microstructure, and porosity evolution of fly ash geopolymer after ten years of curing age
    ( 2023)
    Ikmal Hakem A. Aziz
    ;
    ; ; ; ;
    Jitrin Chaiprapa
    ;
    Catleya Rojviriya
    ;
    Petrica Vizureanu
    ;
    Andrei Victor Sandu
    ;
    ; ;
    This paper elucidates the mechanical performance, microstructure, and porosity evolution of fly ash geopolymer after 10 years of curing age. Given their wide range of applications, understanding the microstructure of geopolymers is critical for their long-term use. The outcome of fly ash geopolymer on mechanical performance and microstructural characteristics was compared between 28 days of curing (FA28D) and after 10 years of curing age (FA10Y) at similar mixing designs. The results of this work reveal that the FA10Y has a beneficial effect on strength development and denser microstructure compared to FA28D. The total porosity of FA10Y was also lower than FA28D due to the anorthite formation resulting in the compacted matrix. After 10 years of curing age, the 3D pore distribution showed a considerable decrease in the range of 5–30 µm with the formation of isolated and intergranular holes.
  • Publication
    Influence of 1.5 wt.% Bi on the microstructure, hardness, and shear strength of Sn-0.7Cu solder joints after isothermal annealing
    ( 2021)
    Mohd Izrul Izwan Ramli
    ;
    ;
    Andrei Victor Sandu
    ;
    Siti Farahnabilah Muhd Amli
    ;
    ; ; ;
    Petrica Vizureanu
    ;
    Adam Rylski
    ;
    Jitrin Chaiprapa
    ;
    Marcin Nabialek
    This manuscript reports the isothermal annealing effect on the mechanical and microstructure characteristics of Sn-0.7Cu-1.5Bi solder joints. A detailed microstructure observation was carried out, including measuring the activation energy of the intermetallic compound (IMC) layer of the solder joints. Additionally, the synchrotron µX-ray fluorescence (XRF) method was adopted to precisely explore the elemental distribution in the joints. Results indicated that the Cu6Sn5 and Cu3Sn intermetallic layers thickness at the solder/Cu interface rises with annealing time at a rate of 0.042 µm/h for Sn-0.7Cu and 0.037 µm/h for Sn-0.7Cu-1.5Bi. The IMC growth’s activation energy during annealing is 48.96 kJ mol-1 for Sn-0.7Cu, while adding Bi into Sn-0.7Cu solder increased the activation energy to 55.76 kJ mol−1. The µ-XRF shows a lower Cu concentration level in Sn-0.7Cu-1.5Bi, where the Bi element was well dispersed in the β-Sn area as a result of the solid solution mechanism. The shape of the IMC layer also reconstructs from a scallop shape to a planar shape after the annealing process. The Sn-0.7Cu hardness and shear strength increased significantly with 1.5 wt.% Bi addition in reflowed and after isothermal annealing conditions.
  • Publication
    Performance of Sn-3.0Ag-0.5Cu somposite solder with kaolin geopolymer ceramic reinforcement on microstructure and mechanical properties under isothermal ageing
    ( 2021)
    Nur Syahirah Mohamad Zaimi
    ;
    ;
    Andrei Victor Sandu
    ;
    ; ; ;
    Petrica Vizureanu
    ;
    Mohd Izrul Izwan Ramli
    ;
    This paper elucidates the effect of isothermal ageing at temperature of 85 °C, 125 °C and 150 °C for 100, 500 and 1000 h on Sn-3.0Ag-0.5Cu (SAC305) lead-free solder with the addition of 1 wt% kaolin geopolymer ceramic (KGC) reinforcement particles. SAC305-KGC composite solders were fabricated through powder metallurgy using a hybrid microwave sintering method and reflowed on copper substrate printed circuit board with an organic solderability preservative surface finish. The results revealed that, the addition of KGC was beneficial in improving the total thickness of interfacial intermetallic compound (IMC) layer. At higher isothermal ageing of 150 °C and 1000 h, the IMC layer in SAC305-KGC composite solder was towards a planar-type morphology. Moreover, the growth of total interfacial IMC layer and Cu3Sn layer during isothermal ageing was found to be controlled by bulk diffusion and grain-boundary process, respectively. The activation energy possessed by SAC305-KGC composite solder for total interfacial IMC layer and Cu3Sn IMC was 74 kJ/mol and 104 kJ/mol, respectively. Based on a lap shear test, the shear strength of SAC305-KGC composite solder exhibited higher shear strength than non-reinforced SAC305 solder. Meanwhile, the solder joints failure mode after shear testing was a combination of brittle and ductile modes at higher ageing temperature and time for SAC305-KGC composite solder.
  • Publication
    Recent developments in steelmaking industry and potential alkali activated based steel waste: A comprehensive review
    ( 2022)
    Ikmal Hakem Aziz
    ;
    ; ; ;
    Long Yuan Li
    ;
    Andrei Victor Sandu
    ;
    Petrica Vizureanu
    ;
    Ovidiu Nemes
    ;
    Shaik Numan Mahdi
    The steel industry is responsible for one-third of all global industrial CO2 emissions, putting pressure on the industry to shift forward towards more environmentally friendly production methods. The metallurgical industry is under enormous pressure to reduce CO2 emissions as a result of growing environmental concerns about global warming. The reduction in CO2 emissions is normally fulfilled by recycling steel waste into alkali-activated cement. Numerous types of steel waste have been produced via three main production routes, including blast furnace, electric arc furnace, and basic oxygen furnace. To date, all of the steel waste has been incorporated into alkali activation system to enhance the properties. This review focuses on the current developments over the last ten years in the steelmaking industry. This work also summarizes the utilization of steel waste for improving cement properties through an alkali activation system. Finally, this work presents some future research opportunities with regard to the potential of steel waste to be utilized as an alkali-activated material.