# Optimizing the Performance of Window Frames: A Comprehensive Review of Materials in China
## 3 Improvement Methods and Sustainability Assessment
### Metal
Optimization of window frame geometry, material modifications, and cavity filling can effectively enhance the thermal performance of window frames [115; 116; 117]. Thermal break structures are often employed for insulation. The main feature of thermal break aluminum is the incorporation of one or multiple thermal insulation \"breaks\" made of insulating materials (typically plastics or thermoplastic materials) within the framework of aluminum alloy. This thermal break structure isolates the interior and exterior aluminum materials, reducing heat conduction and improving insulation performance [114; 118]. * Laboratory tests Accurate and reliable design formulas are a prerequisite for ensuring structural safety. Over the past few decades, scholars have undertaken numerous research projects involving experimental, numerical, and analytical studies on various structural aluminum alloys. [PERSON] et al. [18] discussed the reported experimental, numerical, and analytical studies on different structural aluminum alloys, providing a comprehensive review of the research. They also explored the applicability of international design codes to structural aluminum alloys to address knowledge gaps. Fire safety is a major concern in the design of aluminum alloy structures [119; 120]. In the event of a fire, the temperature of aluminum \begin{table}
\begin{tabular}{c c c} \hline \hline
**Technologies** & **Principle** & **Characteristics** \\ \hline \multirow{3}{*}{ anodization} & In the electrolyte, aluminum alloy is used as the & Forms thin (5–20 μm) to thick (60–200 μm) oxide \\  & anode, and a current is applied to generate an & films, dense with high hardness, strong adhesion, and remarkable corrosion resistance. \\  & oxide film on its surface. & \\ \hline \multirow{3}{*}{ chemical oxidation} & Placing an aluminum alloy in an oxidation & \multirow{3}{*}{Simple operation, low cost, film thickness ranging from 0.5 to 4 μm.} \\  & solution at a certain temperature allows & \\  & aluminum atoms to undergo oxidation reactions & \\  & in the solution, forming a dense oxide film on & \\  & the surface & \\ \hline \multirow{3}{*}{ spraying} & The spray material is heated by a heat source to a & Preparation is versatile, widely applicable for \\  & molten or semi-molten state, then accelerated to & spray materials such as metals, alloys, or \\  & impact and deposit on the substrate surface, & non-metallic materials, with coatings exhibiting \\  & where it cools and forms a coating & \\ \hline \multirow{3}{*}{ laser cladding technology} & Using a high-energy laser beam to melt powder & \multirow{3}{*}{Obtaining coatings with special protective} \\  & coatings onto the substrate surface, forming a & properties, tightly bonded to the substrate, with \\  & dense cladding layer & controllable thickness of the cladding layer and \\ \hline \multirow{3}{*}{ Nano-coating} & \multirow{3}{*}{Involves creating nanoscale films on the surface} & The nano-coating is dense, uniform, and smooth, \\  & of aluminum alloys & enhancing both corrosion resistance and wear \\ \cline{1-1}  & & resistance. It also meets the dimensional \\ \cline{1-1}  & & requirements of high-precision components. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Coating technologies for metal window (adapted from [113]). alloy materials can rapidly rise, significantly reducing material strength [121]. The performance of materials in a fire can be determined through experiments, including steady-state and transient tests [122; 123]. In addition, digital simulation and analysis represented by finite elements have been widely used in the structural design of aluminum windows; computational modeling of any newly proposed section saves on all three fronts: cost, time, and effort.