Effect of Doping Element and Electrolyte’s pH on the Properties of Hydroxyapatite Coatings Obtained by Pulsed Galvanostatic Technique

Hydroxyapatite (HAp) is the most widely used calcium phosphate as a coating on metal implants due to its biocompatibility and bioactivity. The aim of this research is to evaluate the effect of the pH’s electrolyte and doping element on the morphology, roughness, chemical, and phasic composition of hydroxyapatite-based coatings obtained by pulsed galvanostatic electrochemical deposition. As doping elements, both Sr and Ag were selected due to their good osseoinductive character and antibacterial effect, respectively. The electrolytes were prepared at pH 4 and 5, in which specific concentrations of Sr, Ag, and Sr + Ag were added. In terms of morphology, all coatings consist in ribbon-like crystals, which at pH 5 appear to be a little larger. Addition of Sr did not affect the morphology of HAp, while Ag addition has led to the formation of flower-like crystals agglomeration. When both doping elements were added, the flowers like agglomerations caused by the Ag have diminished, indicating the competition between Sr and Ag. X-Ray Diffraction analysis has highlighted that Sr and/or Ag have successfully substituted the Ca in the HAp structure. Moreover, at higher pH, the crystallinity of all HAp coatings was enhanced. Thus, it can be said that the electrolyte’s pH enhances to some extent the properties of HAp-based coatings, while the addition of Sr and/or Ag does not negatively impact the obtained features of HAp, indicating that by using pulsed galvanostatic electrochemical deposition, materials with tunable features dictated by the function of the coated medical device can be designed.

Karakteristik Fisik, Total Padatan dan Hedonik Velva Nangka dengan Penambahan Gum Arab Sebagai Penstabil

Velva nangka (VN) merupakan ekstensifikasi usaha pengolahan nangka sebagai hidangan pencuci mulut beku yang disukai. VN yang berkualitas menggunakan bahan penstabil yaitu kombinasi Carboxyl Methil Celullose (CMC) dan Gum Arab (GA). Penelitian ini bertujuan untuk mengetahui pengaruh penambahan GA sebagai bahan penstabil tunggal terhadap karakteristik fisik (overrun dan waktu pelelehan), total padatan dan hedonik VN. GA dengan variasi konsentrasi 0; 0,25; 0,5; 0,75; dan 1% terhadap total adonan digunakan sebagai penstabil pada pembuatan VN. Penambahan GA berpengaruh nyata pada karakteristik fisik dan total padatan serta hedonik tekstur namun tidak mempengaruhi rasa dan aroma VN. VN dengan penstabil GA 1% mempunyai overrun terendah (P<0,05) sedangkan GA >0,25-1% menghasilkan VN dengan waktu pelelehan lebih lama dan total padatan lebih tinggi (P<0,05). Penambahan GA >0,5-1% menghasilkan VN dengan tekstur yang makin disukai (P<0,05). Penambahan penstabil GA lebih dari 0,25% dalam adonan mampu menghasilkan VN berkualitas baik ditinjau dari karakteristik fisik dan total padatan dengan tekstur yang disukai.Kata kunci: Gum arab; nangka; penstabil; velva Characteristic of Physicals, Total Solids and Hedonik of Jackfruit Velva with Addition of Arabic Gum as StabilizerABSTRACTJackfruit velva (JV) is a business extensification of the jackfruit processing as a preferred frozen dessert. Good quality JV used a stabilizer such as combination of Carboxyl Methyl Cellullose (CMC) and Arabic Gum (AG). This study aimed to get more insight the effect of AG addition as a single stabilizer to the physical characteristics (overrun and melting time), total solids and hedonic JV. AG in various concentration of 0; 0.25; 0.5; 0.75; and 1% of the total dough was used as a stabilizer in the JV manufacture. The addition of AG significantly affected the physical characteristic, total solids and texture hedonic without any effect on the flavor and aroma of JV. JV with 1% AG stabilizer had the lowest overrun (P<0.05) while >0.25-1% AG resulted in JV with longer melting time and higher total solids (P<0.05). The addition of >0.5-1% AG resulted JV more favorable texture (P<0.05). The addition of more than 0.25% AG stabilizer in the dough was able to produce good quality JV in the aspects of physical characteristics and total solids with a preferred texture.Keywords: Arabic gum; jackfruit; stabilizer; velva

Effect of Ag Addition on the Gas-Sensing Properties of Nanostructured Resistive-Based Gas Sensors: An Overview

Nanostructured semiconducting metal oxides (SMOs) are among the most popular sensing materials for integration into resistive-type gas sensors owing to their low costs and high sensing performances. SMOs can be decorated or doped with noble metals to further enhance their gas sensing properties. Ag is one of the cheapest noble metals, and it is extensively used in the decoration or doping of SMOs to boost the overall gas-sensing performances of SMOs. In this review, we discussed the impact of Ag addition on the gas-sensing properties of nanostructured resistive-based gas sensors. Ag-decorated or -doped SMOs often exhibit better responsivities/selectivities at low sensing temperatures and shorter response times than those of their pristine counterparts. Herein, the focus was on the detection mechanism of SMO-based gas sensors in the presence of Ag. This review can provide insights for research on SMO-based gas sensors.