Low temperature production of wollastonite from limestone and silica sand through solid-state reaction

AbstractWollastonite was produced using solid-state reaction from limestone and silica sand. Limestone containing a high percentage of CaO (55.10%) and silica sand with 99% SiO2 were used as starting materials. The ratios of limestone/sand used were 1:1, 2:1 and 3:1 with various firing temperatures, namely 1100, 1200, 1300, 1400 and 1450°C. The raw materials and fired products were characterised for mineral phases, chemical composition of content such as CaO, SiO2 and loss on ignition (LOI), density and microstructure. CaSiO3 with an α-phase was detected at firing temperatures as low as 1300°C, together with olivine and quartz phases, obtained from a 1:1 ratio. No α-CaSiO3 was detected for 2:1 and 3:1 ratios; only olivine and larnite phases were present. The density of the product was 2.93gcm−3, which is close to the theoretical value, with a specific surface area of 3.23m2g−1. This study shows that the Malaysian limestone and silica sand can produce good properties of wollastonite materials

Ultraviolet Sensors Based on Two-Dimensional Zinc Oxide Structures

In this chapter, we review the application of zinc oxide (ZnO) in ultraviolet (UV) sensing and emphasise on the two-dimensional (2D) ZnO structures. The synthesis of 2D ZnO structures, the morphologies, and the photoluminescence emission will be reviewed and highlighted. The performance of the UV sensors based on 2D ZnO structures is explored. The lack in the study of the 2D ZnO UV sensors might be due to the difficulties of controlling the growth of the 2D ZnO compared to the one-dimensional (1D) ZnO structures

Pengaruh teknik pengeringan yang berbeza terhadap ketumpatan, keliangan dan kebioaktifan β-wolastonit daripada batu kapur tempatan dan jerami padi

Pengaruh teknik pengeringan yang berbeza terhadap ketumpatan, keliangan dan kebioaktifan sampel β-wolastonit dikaji dan dibandingkan antara dua teknik pengeringan; kering beku pada -40°C dan di dalam inkubator pada suhu badan (36.5°C). Sampel β-wolastonit dihasilkan daripada batu kapur terkalsin dan abu jerami dengan nisbah CaO:SiO2 pada 45:55. Campuran ini diautoklaf selama 8 jam, kemudian dikeringkan dan disinter pada suhu 950°C selama 3 jam. Sampel β-wolastonit dibentuk menjadi silinder dan dikeringkan menggunakan dua teknik pengeringan iaitu kering beku pada suhu -40°C selama 12 jam dan pada suhu badan (36.5°C) selama dua hari di dalam inkubator. Kemudian, sifat ketumpatan, keliangan dan kebioaktifan sampel berbentuk silinder ini diperiksa. Didapati bahawa penggunaan teknik pengeringan kering beku menghasilkan sampel β-wolastonit yang lebih tumpat, (3.20 gcm-3) berbanding pengeringan pada suhu badan (3.03 gcm-3). Sampel yang dikering beku mempunyai bilangan liang yang lebih rendah berbanding dengan sampel yang dikeringkan pada suhu badan, masing-masing dengan 47.5% dan 53.8%. Bagi sifat kebioaktifan, selepas direndam selama 21 hari di dalam larutan SBF, didapati kalsium fosfat amorfus (ACP) dengan nisbah molar Ca/P yang berkisar antara 1.2 - 2.0 dan hidroksiapatit kurang kalsium (CDHA) dengan nisbah molar Ca/P pada 1.5 - 1.67, terhasil pada permukaan sampel β-wolastonit bagi kedua-dua teknik pengeringan

Mechanical and bioactive properties of mullite reinforced pseudowollastonite biocomposite

Bioactive composites consist of pseudowollastonite and mullite synthesized from natural resources was developed for bone implant applications. To realize such applications, a mechanical test of these composites and in vitro bioactivity in SBF solution were studied. The present paper reports pseudowollastonite synthesized from the rice husk ash and limestone reinforced with 10, 20 and 30 wt. % of mullite. Influence of sintering temperature, phase composition, morphology towards mechanical properties of various pseudowollastonite-mullite (PSW-M) composites was examined prior to the bioactivity test. It was found that pseudowollastonite with the addition of 20 wt. % of mullite sintered at 1150°C gave the best result for diametral tensile strength (DTS) and hardness with the value of 8.8 ± 0.15 MPa and 3.79 ± 0.13 GPa, respectively. The obvious increment in the mechanical strength was due to the formation of liquid phase CaAl2O3 during sintering at 1150°C. In addition, the formation of fibrous apatite (HA) layer of amorphous calcium phosphate (ACP) with Ca/P ratio 1.8 on PSW20M sample confirmed the good bioactivity of the composite

Experimental investigation of air-conditioning electrical compressor using binary TiO2–SiO2 polyol-ester nanolubricants

As electric vehicles (EVs) continue to replace conventional gasoline vehicles, maintaining thermal comfort within the car requires additional energy to operate the automotive air-conditioning (AAC) system. This work aims to optimise the electrically driven compressor (EDC) system utilising polyol-ester (POE)-based binary nanolubricants to enhance performance and minimise the size of the EV battery and AAC components. A binary nanolubricant was formulated using a two-step method of formulation. The TiO2–SiO2/POE binary nanolubricant was prepared at different volume concentrations ranging from 0.01 to 0.1 %. The experiment was conducted for the 1200–3840 rpm compressor speed with different initial refrigerant charges between 120 and 160 g. The heat absorption rose by up to 44.2 % while utilising the binary nanolubricant at a volume concentration of 0.03 %. The coefficient of performance (COP) reached its maximum value of 2.43 at a refrigerant charge of 160 g and compressor speed of 1860 rpm. Furthermore, the binary nanolubricant significantly reduced the expansion valve discharge temperature, exhibiting a substantial decrease of up to 51.6 %. The highest COP increment, up to 23.4 %, was achieved at a volume concentration of 0.03 %. Hence, it is recommended to utilise 0.03 % TiO2–SiO2/POE binary nanolubricant to achieve optimal performance in the AAC-EDC system

Pengaruh suhu sinteran terhadap kebioaktifan wolastonit daripada abu sekam padi dan batu kapur

Tujuan kajian ini adalah untuk mengenal pasti kesan rawatan suhu yang berbeza terhadap kebioaktifan wolastonit yang disintesis menggunakan teknik sol gel. Abu sekam padi dan batu kapur digunakan sebagai bahan awalan untuk menghasilkan wolastonit. Nisbah campuran kalsium oksida dan silika dioksida CaO/SiO2 ditentukan pada 55:45 dan dimasukkan ke dalam autoklaf pada suhu 135°C dengan tekanan 0.26 MPa selama 8 jam. Campuran serbuk CaO dan SiO2 tersebut disinter pada suhu yang berbeza (1150°C dan 1250°C) dan diuji sifat kebioaktifan secara rendaman dalam larutan cecair badan tersimulasi (SBF) selama 1,3,5,7 dan 14 hari secara in vitro. Sifat fizikal dan kebioaktifan wolastonit sebelum dan selepas direndam dalam larutan SBF dan beberapa pencirian telah dijalankan menggunakan teknik analisis XRD, FESEM, EDX dan FTIR. Campuran serbuk CaO-SiO2 yang telah diautoklaf dan disinter pada suhu 1250°C menghasilkan puncak tunggal pseudowolastonit. Ujian kebioaktifan menunjukkan lapisan amorfus kalsium fosfat (ACP) dengan julat nisbah Ca/P 1.9-1.51 terbentuk lebih pantas pada sampel wolastonit yang disinter pada suhu 1250°C berbanding pembentukan ACP pada sampel tersinter 1150°C

Tribology performance of polyol-ester based TiO2, SiO2, and their hybrid nanolubricants

The tribology properties of TiO2/POE, SiO2/POE and TiO2 -SiO2/POE nanolubricants were investigated for an automotive air-conditioning system with an electrically-driven compressor (EDC). A two-step preparation method was used in dispersing TiO2 and SiO2 nanoparticles into Polyol-ester (POE)-based lubricant at different volume concentrations of 0.01 to 0.1%. The coefficient of friction (COF) and wear scar diameter (WSD) were investigated using a Koehler four-ball tribo tester and microscopes. For the TiO2/POE, SiO2/POE and TiO2-SiO2/POE nanolubricants, respectively, the lowest COFs with maximum reduction were attained at 37.5%, 33.5% and 31.6% each at volume concentrations of 0.05%, 0.01% and 0.03%. The highest WSD reduction for the TiO2/POE and SiO2/POE mono nanolubricants were attained at 12.5% and 26.4%, respectively, at the same volume concentration of 0.01%. Meanwhile, the maximum reduction of WSD for the TiO2-SiO2/POE hybrid nanolubricant was reached at 12.4% at 0.03% volume concentration. As a conclusion, mono and hybrid nanolubricants with volume concentrations of less than 0.05% are suggested for use in air-conditioning systems with EDC because of their outstanding tribology performances. Further performance investigation of nanolubricants in the air-conditioning system is required to extend the present work

Electron-Beam Irradiation of the PLLA/CMS/beta-TCP Composite Nanofibers Obtained by Electrospinning

Nanofibrous materials produced by electrospinning processes have potential advantages in tissue engineering because of their biocompatibility, biodegradability, biomimetic architecture, and excellent mechanical properties. The aim of the current work is to study the influence of the electron beam on the poly L-lactide acid/ carboxy-methyl starch/beta-tricalcium phosphate (PLLA/CMS/beta-TCP) composite nanofibers for potential applications as bone-tissue scaffolds. The composite nanofibers were prepared by electrospinning in the combination of 5%v/vcarboxy-methyl starch (CMS) and 0.25 wt% of beta-TCP with the PLLA as a matrix component. The composites nanofibers were exposed under 5, 30, and 100 kGy of irradiation dose. The electron-beam irradiation showed no morphological damage to the fibers, and slight reduction in the water-contact angle and mechanical strength at the higher-irradiation doses. The chain scission was found to be a dominant effect; the higher doses of electron-beam irradiation thus increased the in vitro degradation rate of the composite nanofibers. The chemical interaction due to irradiation was indicated by the Fourier transform infrared (FTIR) spectrum and thermal behavior was investigated by a differential scanning calorimeter (DSC). The results showed that the electron-beam-induced poly L-lactide acid/carboxy-methyl starch/beta-tricalcium phosphate (PLLA/CMS/beta-TCP) composite nanofibers may have great potential for bone-tissue engineering

Photocatalytic study of two-dimensional ZnO nanopellets in the decomposition of methylene blue

We report several significant photodecomposition rates of methylene blue (MB) obtained before and after the refluxing process of own-synthesized two-dimensional (2D) zinc oxide (ZnO) nanopellets. Each photodecomposition rate of MB was found highly dependent on the weight of photocatalyst. The existing photodecomposition rate has been successfully improved to a factor of 22.0 times through refluxing process in excessive pyridine where the surface capping ligand (oleic acid) is removed from the 2D ZnO nanopellets. On the other hand, the refluxed photocatalyst (0.04 g) in this study was found to exhibit excellent recyclability up to three cycles. Furthermore, X-ray powder diffraction spectrums for the refluxed photocatatalyst, respectively, before and after three cycles of photocatalytic reactions, has generated the same patterns showing that the photocatalyst is stable and feasible to be used as an efficient photocatalyst material. Hence, these 2D ZnO nanopellets would provide a new alternative route as a highly efficient photocatalyst for wastewater treatment

Amalan Tidak Berintegriti: Remeh Tapi Salah

Kajian ini merupakan sebuah sorotan kajian mengenai integriti. Integriti merangkumi pelbagai nilai murni termasuk kesopanan, ketepatan, kebolehpercayaan, ketekunan, kemuliaan, kesederhanaan, ketinggian peribadi, jujur, ikhlas, amanah, berpegang pada janji, bercakap benar, dan pelbagai sifat positif lain. Akan tetapi, sesuatu organisasi tidak mampu mencapai kecemerlangan jika berlaku masalah dalaman yang berpunca dari integriti atau jika terdapat pengaruh luar yang tidak diselesaikan berikutan kelemahan institusi itu sendiri. Kebanyakan masalah integriti yang dibangkitkan adalah merujuk kepada hal-hal yang remeh yang sering berkait dengan bidang masing-masing, walau bagaimanapun, ia tetap salah dan perlu diperbetulkan. Oleh itu, terdapat keperluan terhadap mengenal pasti punca kelemahan pembudayaan dan penguatkuasaan integriti dalam sesuatu organisasi, khasnya dalam diri masyarakat. Hasil dari permasalahan yang berbangkit ini, dua kemungkinan telah digariskan yang bertujuan membincangkan faktor isu ini sukar menunjukkan yang ianya akan berakhir. Hasil sorotan kajian mendapati, pengetahuan dan pembudayaan tentang isu integriti dilihat menjadi kelemahan ketara dalam kegagalan pengaplikasian integriti dalam pekerjaan. Oleh itu, kefahaman tentang konsep integriti seorang kakitangan adalah perlu bagi memperlihatkan keselarasan antara kata-kata dengan perlakuan, bertindak bersandarkan kepada prinsip moral, etika dan undang-undang, serta mengutamakan kepentingan umum melebihi kehendak diri dan melakukan kerja dengan komprehensif, holistik dan relevan. Selain itu, budaya organisasi berlandaskan piawai etika yang tinggi harus menjadi penggerak dan pengaruh positif kepada amalan tingkah laku beretika dalam kalangan pekerja