The influence of palm oil fuel ash heat treatment on the strength activity, porosity, and water absorption of cement mortar.

The current study aims to explore the impact of palm oil fuel ash (POFA) heat treatment on the strength activity, porosity, and water absorption of cement mortar. The cement mortar mixtures were typically comprising cement or cement in combination with ultrafine treated POFA (u-TPOFA) which is the final form of the treated POFA, sand, water, and a superplasticizer. Before utilizing the u-TPOFA in mortar mixtures, the treatment processes of POFA were undertaken via five steps (drying at 105 ℃, sieving, grinding, heat treatment, re-grinding) to form u-TPOFA. The heat treatment was performed at three different heating temperatures (i.e., 550 ℃, 600 ℃, and 650 ℃). The ratio on mass/mass basis of the blended ordinary Portland cement (OPC) with u-TPOFA was OPC:u-TPOFA of 70%:30%. A total of four mixtures were prepared, consisting of a plain control mixture (designated as PCM) and three mixtures containing 30% of u-TPOFA treated at three different temperatures designated as M1 "550 ℃," M2 "600 ℃," and M3 "650 ℃". The results show that the optimum mixture was M2 which achieved the highest strength activity index (SAI) of 101.84% and 107% among all mixtures at 7 days and 28 days, respectively. Meanwhile, the porosity (P%) and water absorption (Abs%) of M2 exhibited the lowest values of 9.3% and 4.5%, respectively, among all the mixtures at 28 days. This superior performance of u-TPOFA treated at 600 ℃ represented in the M2 mixture was due to the formation of more binding phases consisting of calcium silicate hydrate (C-S-H) type gel originated from a higher pozzolanic reaction and the filler effects caused by the fine u-TPOFA microparticles. These observations were further confirmed by the improved performance of the M2 mix among all the designed mixes which also exhibited better results in terms of bulk density (BD), ultrasonic pulse velocity (UPV), X-ray diffraction (XRD) as well as thermogravimetry (TGA) and field emission scanning electron microscopy (FESEM-EDX) analyses.

Effect of MgO Addition on the Mechanical and Dynamic Properties of Zirconia Toughened Alumina (ZTA) Ceramics.

Zirconia toughened alumina (ZTA) is a promising advanced ceramic material for a wide range of applications that are subjected to dynamic loading. Therefore, the investigation of dynamic compressive strength, fracture toughness and hardness is essential for ZTA ceramics. However, the relationship between these mechanical properties in ZTA has not yet been established. An example of this relationship is demonstrated using ZTA samples added with MgO prepared through conventional sintering. The microstructure and mechanical properties of ZTA composites were characterized. The hardness of ZTA composites increased for ≤0.7 wt.% MgO due to the pinning effect of MgO and decrease of the porosity in the microstructure. Oppositely, the fracture toughness of ZTA composites continuously decreased due to the size reduction of Al2O3 grains. This is the main reason of deteriorate of dynamic compressive strength more than 0.2 wt.% of MgO addition. Therefore, the SHPB test shows the improvement of the dynamic compressive strength only up to a tiny amount (0.2 wt.% of MgO addition) into ZTA ceramics.

Room temperature LPG resistive sensor based on the use of a few-layer graphene/SnO2 nanocomposite.

A nanocomposite consisting of a few layers of graphene (FLG) and tin dioxide (SnO2) was prepared by ultrasound-assisted synthesis. The uniform SnO2 nanoparticles (NPs) on the FLG were characterized by X-ray diffraction in terms of lattice and phase structure. The functional groups present in the composite were analyzed by FTIR. Electron microscopy (HR-TEM and FE-SEM) was used to study the morphology. The effect of the fraction of FLG present in the nanocomposite was investigated. Sensitivity, selectivity and reproducibility towards resistive sensing of liquid propane gas (LPG) was characterized by the I-V method. The sensor with 1% of FLG on SnO2 operated at a typical voltage of 1 V performs best in giving a rapid and sensitive response even at 27 °C. This proves that the operating temperature of such sensors can be drastically decreased which is in contrast to conventional metal oxide LPG sensors. Graphical abstract Schematic of a room temperature gas sensor for liquefied petroleum gas (LPG). It is based on the use of a few-layered graphene (1 wt%)/SnO2 nanocomposite that was deposited on an interdigitated electrode (IDEs). A sensing mechanism for LPG detection has been established.

A Review on Microdialysis Calibration Methods: the Theory and Current Related Efforts.

Microdialysis is a sampling technique first introduced in the late 1950s. Although this technique was originally designed to study endogenous compounds in animal brain, it is later modified to be used in other organs. Additionally, microdialysis is not only able to collect unbound concentration of compounds from tissue sites; this technique can also be used to deliver exogenous compounds to a designated area. Due to its versatility, microdialysis technique is widely employed in a number of areas, including biomedical research. However, for most in vivo studies, the concentration of substance obtained directly from the microdialysis technique does not accurately describe the concentration of the substance on-site. In order to relate the results collected from microdialysis to the actual in vivo condition, a calibration method is required. To date, various microdialysis calibration methods have been reported, with each method being capable to provide valuable insights of the technique itself and its applications. This paper aims to provide a critical review on various calibration methods used in microdialysis applications, inclusive of a detailed description of the microdialysis technique itself to start with. It is expected that this article shall review in detail, the various calibration methods employed, present examples of work related to each calibration method including clinical efforts, plus the advantages and disadvantages of each of the methods.

A Short Review on Copper Calcium Titanate (CCTO) Electroceramic: Synthesis, Dielectric Properties, Film Deposition, and Sensing Application.

Electroceramic calcium copper titanates (CaCu3Ti4O12, CCTO), with high dielectric permittivities (ε) of approximately 105 and 104, respectively, for single crystal and bulk materials, are produced for a number of well-established and emerging applications such as resonator, capacitor, and sensor. These applications take advantage of the unique properties achieved through the structure and properties of CCTO. This review comprehensively focuses on the primary processing routes, effect of impurity, dielectric permittivity, and deposition technique used for the processing of electroceramics along with their chemical composition and micro and nanostructures. Emphasis is given to versatile and basic approaches that allow one to control the microstructural features that ultimately determine the properties of the CCTO ceramic. Despite the intensive research in this area, none of the studies available in the literature provides all the possible relevant information about CCTO fabrication, structure, the factors influencing its dielectric properties, CCTO immobilization, and sensing applications.

Use of waste gypsum to replace natural gypsum as set retarders in portland cement.

The present study is focused on clarifying the influence of waste gypsum (WG) in replacing natural gypsum (NG) in the production of ordinary Portland cement (OPC). WG taken from slip casting moulds in a ceramic factory was formed from the hydration of plaster of paris. Clinker and 3-5wt% of WG was ground in a laboratory ball mill to produce cement waste gypsum (CMWG). The same procedure was repeated with NG to substitute WG to prepare cement natural gypsum (CMNG). The properties of NG and WG were investigated via X-ray Diffraction (XRD), X-ray fluorescence (XRF) and differential scanning calorimetry (DSC)/thermogravimetric (TG) to evaluate the properties of CMNG and CMWG. The mechanical properties of cement were tested in terms of setting time, flexural and compressive strength. The XRD result of NG revealed the presence of dihydrate while WG contained dihydrate and hemihydrate. The content of dihydrate and hemihydrates were obtained via DSC/TG, and the results showed that WG and NG contained 12.45% and 1.61% of hemihydrate, respectively. Furthermore, CMWG was found to set faster than CMNG, an average of 15.29% and 13.67% faster for the initial and final setting times, respectively. This was due to the presence of hemihydrate in WG. However, the values obtained for flexural and compressive strength were relatively the same for CMNG and CMWG. Therefore, this result provides evidence that WG can be used as an alternative material to NG in the production of OPC.